multiple linear regression
در نشریات گروه علوم انسانی-
Transactions on Quantitative Finance and Beyond, Volume:1 Issue: 2, Summer and Autumn 2024, PP 195 -202
Management is an effective and goal-oriented process that guides an organization. This guidance involves five sequential functions: planning, organizing, leading, coordinating, and controlling and evaluating. The fundamental knowledge of management, or the management process, has been present even in ancient civilizations such as those of the Iranians, Egyptians, Sumerians, and others. In Islamic civilization, we have had grand and civilizational management systems. Today, the successful implementation of an HSE (Health, Safety, and Environment) management system depends on the participation of all employees. Given that job satisfaction can influence employee performance, this study aims to model the relationship between job satisfaction and the HSE performance of Pars Oil and Gas Company employees. The statistical population of this research consists of all employees of Pars Oil and Gas Company (N = 5300). Using Cochran's formula and simple random sampling, 360 employees were selected as the sample. The data collection tool was a questionnaire, and to ensure its validity, the opinions of several university faculty members were used. Cronbach's alpha coefficient was applied to confirm the reliability, yielding values of 0.79 for job satisfaction and 0.83 for HSE performance. The results indicate a positive and significant relationship between job satisfaction and HSE performance (P-value < 0.01). The regression results show that, in two steps, the indices of job nature and security and safety, which had the highest impact on HSE performance, were included in the analysis. In the first step, the job nature index explains 59% of the variance in the response variable (HSE performance), and in the second step, with the inclusion of the security and safety index, this figure increases to 63%.
Keywords: Job Satisfaction, Multiple Linear Regression, HSE Performance -
این پژوهش با هدف بررسی تاثیر کیفیت رابطه معلم-دانش آموز و کیفیت محیط آموزشی بر اشتیاق تحصیلی دانش آموزان دبستانی در شهر تهران انجام شد. در این راستا، رابطه بین این دو عامل با میزان اشتیاق تحصیلی دانش آموزان مورد بررسی قرار گرفت تا نقش هر یک از آن ها در بهبود انگیزه و مشارکت تحصیلی مشخص شود. این مطالعه به روش مقطعی و بر روی 250 دانش آموز دبستانی در تهران انجام شد. نمونه گیری به روش تصادفی خوشه ای صورت گرفت. ابزار گردآوری داده ها شامل پرسشنامه اشتیاق تحصیلی، مقیاس رابطه معلم-دانش آموز، و پرسشنامه کیفیت محیط آموزشی بود. برای تحلیل داده ها از نرم افزار SPSS-27 استفاده شد. همبستگی پیرسون برای بررسی رابطه بین متغیرها و رگرسیون خطی چندگانه برای پیش بینی اشتیاق تحصیلی بر اساس متغیرهای مستقل به کار رفت. نتایج نشان داد که کیفیت رابطه معلم-دانش آموز (r = 0.45, p < 0.01) و کیفیت محیط آموزشی (r = 0.41, p < 0.01) هر دو به طور معناداری با اشتیاق تحصیلی دانش آموزان مرتبط هستند. تحلیل رگرسیون خطی چندگانه نشان داد که این دو متغیر مستقل توانایی پیش بینی 28 درصد از واریانس اشتیاق تحصیلی را دارند (R² = 0.28, p < 0.001). همچنین، هر دو متغیر به طور معناداری اشتیاق تحصیلی دانش آموزان را پیش بینی کردند. این پژوهش نشان داد که کیفیت رابطه معلم-دانش آموز و کیفیت محیط آموزشی نقش مهمی در افزایش اشتیاق تحصیلی دانش آموزان دارند. بهبود این دو عامل می تواند به طور موثری انگیزه و مشارکت تحصیلی دانش آموزان را ارتقا دهد. نتایج این مطالعه می تواند به سیاست گذاران و مدیران آموزشی در طراحی برنامه های موثر برای بهبود کیفیت آموزش و افزایش انگیزه تحصیلی دانش آموزان کمک کند
کلید واژگان: کیفیت رابطه معلم-دانش آموز، کیفیت محیط آموزشی، اشتیاق تحصیلی، دانش آموزان دبستانی، رگرسیون خطی چندگانهThis study aimed to examine the impact of teacher-student relationship quality and the quality of the educational environment on the academic engagement of elementary students in Tehran. The study sought to explore the relationship between these factors and students' academic engagement to understand their role in enhancing motivation and participation in learning. This cross-sectional study was conducted on 250 elementary students in Tehran. The sample was selected through cluster random sampling. Data collection tools included the Student Engagement Questionnaire, the Teacher-Student Relationship Scale, and the Classroom Environment Scale. Data were analyzed using SPSS-27. Pearson correlation was used to assess the relationships between variables, and multiple linear regression was employed to predict academic engagement based on the independent variables. The results indicated that both teacher-student relationship quality (r = 0.45, p < 0.01) and educational environment quality (r = 0.41, p < 0.01) were significantly correlated with students' academic engagement. Multiple linear regression analysis revealed that these two independent variables explained 28% of the variance in academic engagement (R² = 0.28, p < 0.001). Both variables were significant predictors of students' academic engagement. This study demonstrated that the quality of the teacher-student relationship and the educational environment play critical roles in enhancing students' academic engagement. Improving these factors can effectively boost students' motivation and participation in learning. The findings can assist policymakers and educational administrators in designing effective programs to improve the quality of education and increase students' academic motivation.
Keywords: Teacher-Student Relationship Quality, Educational Environment Quality, Academic Engagement, Elementary Students, Multiple Linear Regression -
در سالهای اخیر، در ادبیات مالی، توجه روز افزونی به سطح نگهداشت وجه نقد شرکت ها شده است. لذا؛ پیش بینی برای تعیین سطح بهینه نگهداشت وجه نقد اهمیت دارد. در این پژوهش با استفاده از روش های خطی و غیرخطی و 13 متغیر ورودی تاثیر گذار میزان وجه نقد در 103 شرکت پذیرفته شده در بورس اوراق بهادار ایران طی سال های 1392 تا 1400 پیش بینی شده است. روش های به کار رفته شامل رگرسیون خطی چندگانه (MLR) ، نزدیکترین k همسایه (KNN) ، ماشین بردار پشتیبان (SVM) و شبکه های عصبی چند لایه (MLNN) برای پیش بینی استفاده شده است. نتایج نشان می دهد که روش سنتی رگرسیون خطی چندگانه در پیش بینی وجه نقد موفق عمل نکرده اند ولی الگوریتم های یادگیری ماشین با دقت 99/0 برتر بوده اند. متغیرهای سود هر سهم، نسبت داراییهای جاری به بدهیهای جاری و نسبت بدهی کوتاه مدت به کل دارایی ها تاثیر گذاری بیشتری در همه الگوریتم ها داشته اند. بنابراین، مدیران می توانند از الگوریتم های پیشرفته یادگیری ماشین جهت پیش بینی میزان وجه نقد آینده شرکت ها بهره بگیرند.
کلید واژگان: پیش بینی، رگرسیون خطی چندگانه، نگهداشت وجه نقد، الگوریتم های یادگیری ماشینIn recent years, in the financial literature, more attention has been paid to the level of cash holding of companies. So; Forecasting is important to determine the optimal level of cash holding. In this research, using linear and non-linear methods and 13 influential input variables, the amount of cash in 103 companies admitted to the Iran Stock Exchange during the years 2013 to 2021 has been predicted. The methods used include multiple linear regression (MLR), k nearest neighbor (KNN), support vector machine (SVM) and multi-layer neural networks (MLNN) for prediction. The results show that the traditional method of multiple linear regression has not been successful in predicting cash, but machine learning algorithms have been superior with an accuracy of 0.99. The variables of profit per share, the ratio of current assets to current liabilities and the ratio of short-term debt to total assets have had a greater impact in all algorithms. Therefore, managers can use advanced machine learning algorithms to predict the future cash flow of companies.
Keywords: Forecasting, Cash Holdings, Multiple Linear Regression, Machine LearningAlgorithms -
امروزه با پیشرفت فن آوری سنجش از دور، به منظور دسترسی آسان تر محققین به متغیرهای آب و هوایی، توسعه محصولات ماهواره ای دما و بارش نسبت به تحلیل باندهای مختلف تصاویر ماهواره ای، کاربرد بیشتری دارد. این محصولات با استفاده از تصاویر ماهواره ای به تخمین متغیرهای دما و بارش در نقاط فاقد داده می پردازد و معمولا با خطا همراه بوده و نیاز به واسنجی دارند. در این پژوهش کارایی محصولات دما و بارش ماهواره TRMM در استان مازندران بررسی شد و در نهایت یک مدل رگرسیون چندگانه برای تخمین دقیق دما و بارش با ترکیب محصولات ماهواره ای TRMM و عوارض زمینی، ارائه شد. به همین منظور از 25 ایستگاه هواشناسی و 48 تصویر ماهانه و سالانه دما و بارش ماهواره TRMM در دو سال 2014 و 2017 استفاده شد. نتایج نشان داد همبستگی داده های واقعی دما و بارش با محصولات ماهواره ای، طول جغرافیایی و ارتفاع در اکثر ماه ها در سطح 5 درصد معنی دار است ولی بنظر عرض جغرافیایی تاثیر معنی دار بر نوسانات دما ندارد. تحلیل شاخص های خطا نشان داد دمای ماهواره TRMM مقدار دما را کمتر از داده های واقعی برآورد می کند. همچنین محصولات بارش ماهواره ای TRMM دارای خطای بالایی بوده، بطوریکه میزان بیش برآورد یاکم برآورد این ماهواره به بیش از 150 میلی متر در سال می رسد. امادر این پژوهش با استفاده از روش اصلاحی پیشنهادی، برآورد دما ماهواره TRMMا تا 80 درصد کاهش و مقدار خطای تخمین دمای سالانه ا از 3 درجه سانتی گراد به کمتر از 1 درجه و خطای تخمین بارش ماهواره ی TRMM ا حدود 25 تا 40 درصد کاهش یافت. بررسی نقشه های هم دما و هم بارش سالانه ترسیم شده با روش پیشنهادی، بیانگر درک دقیق تر نقشه های بدست آمده از نوسانات فضایی دما و بارش نسبت به محصولات دما و بارش ماهواره TRMM است.
کلید واژگان: متغیرهای کمکی، محصولات ماهواره ای، خطای اریبی، مازندران، رگرسیون خطی چندگانهIntroductionAccurate spatial estimation of Precipitation and temperature is very important in hydrological models. Despite the development of automatic meteorological stations in recent years, obtaining reliable climate data in data-deficient areas is still a big challenge. Spatial estimation of climatic data is mainly done by geostatistical methods and satellite images. Nowadays, satellite products are widely accepted in the preparation of climatic maps. These products use satellite images to estimate temperature and rainfall data in points without data, and usually the provided data is accompanied by errors and needs to be recalibrated. It seems that the combination of covariates and satellite products can be effective in increasing the accuracy of climatic maps, especially in areas with complex topography such as Mazandaran province.
Materials and MethodsIn this research, the accuracy of temperature and rainfall products of TRMM satellite was evaluated in Mazandaran province and the possibility of combining them with land features of latitude, longitude and elevation in the form of regression model was investigated. In this regard, the monthly rainfall data of 21 meteorological stations and 48 monthly and 4 annual images of TRMM products in 2014 and 2017 were used. The evaluation indicators are root mean square error (RMSE), mean bias error (MBE), mean absolute percent error (MAPE). Also, the annual temperature and rainfall maps of the province were drawn by satellite products and modified method.
Results and DiscussionThe results showed that the TRMM products have a huge bias error, so that the amount of annual rainfall bias in some years reaches more than 180 mm per year. About the temperature products the underestimation error is more than 2 Celsius degrees. The correlation coefficients of land features and temperature and precipitation data in most of the months provided acceptable results and were significant in 95% confidence level. In general, the relationship between monthly temperature and, latitude and TRMM products was significantly positive in all the investigated months. in the case of altitude, the relationship was negative and strong. But the relationship between temperature and longitude was a little weaker than other covariates. Regarding the precipitation variable, satellite products have a positive and significant relationship in all the investigated months, and the altitude has a negative effect on precipitation data except in the spring months, but the latitude has a positive relationship in the cold months and in the warm months has almost a negative relationship, and no specific seasonal trend was found in the case of longitude. Also, the correlation coefficients of TRMM products with temperature and precipitation data was significant in 100 and 77% of the months, respectively. Investigating the possibility of combining the TRMM products with the latitude, longitude and altitude in a form of regression equation to estimate temperature and precipitation data showed that the hybrid method increased the accuracy of satellite productions, impressively and the error of rainfall and temperature products reduced by about 30% and 70%, respectively. But as expected, the spatial estimation error of precipitation data was higher than temperature in all investigated months. The annual rainfall maps of Mazandaran for the years 2014 and 2017 shows the higher accuracy of the hybrid methods compared to satellite products. So that it shows well the rainy area of the west coastline and also depicts the meridional and altitudinal gradients of precipitation in the Mazandaran province as well. Examining the annual isothermal maps showed that the drawn map with the correction method has a significant difference with the temperature product of the TRMM satellite and has well highlighted the ring of cold areas of Alborz Mountain range and the foothills of Damavand and Alam-Kouh peaks. Also, the modified map has correctly distinguished the temperate coasts of the southern Caspian Sea from the Middle Band and Upper Band regions. In addition, the higher temperature of eastern half of Mazandaran compared to the western half has shown well.
ConclusionThe results of the present research showed that the TRMM temperature and rainfall products alone do not have proper accuracy in the spatial estimation of climate data and have a large bias error, but their combination as a covariate, along with Longitude, latitude and altitude in a regression equation, improved the accuracy of temperature and rainfall maps, and can be used as a new post-processing method in modification of satellite products.
Keywords: Covariates, satellite products, Bias error, Mazandaran, Multiple linear regression -
کاربرد رگرسیون چندگانه در مدل سازی الگوی برق مصرفی ایستگاه های آتش نشانی با هدف بهینه سازی و اصلاح الگوی مصرف (مطالعه موردی : سازمان آتش نشانی و خدمات ایمنی شهر مشهد)پیش بینی مناسب مصرف برق جزء مهمترین پارامترها در برنامه ریزی برای یک سیستم میباشد. یکی از متداول ترین ابزارها برای انجام پیش بینی، روش های مبتنی بر رگرسیون میباشد . در این تحقیق با استفاده از مدل رگرسیون خطی چندگانه به پیش بینی مصرف انرژی برق در ایستگاه های آتش نشانی مشهد پرداخته شده است. جامعه آماری تحقیق حاضر ایستگاه های سازمان آتش نشانی مشهد می باشند که 45 ایستگاه به عنوان نمونه آماری انتخاب گردیدند. جهت تحلیل داده های تحقیق از روش های آماری همبستگی پیرسون و رگرسیون استفاده گردید. نتایج تحقیق نشان می دهد که بین سه متغیر مستقل تعداد نیرو آتش نشان مستقر در ایستگاه ، مساحت ایستگاه و تعداد خودرو آتش نشانی با متغیر وابسته میزان برق مصرفی سالیانه ایستگاه همبستگی قوی و مستقیمی وجود دارد. درنهایت با استفاده از مدل رگرسیون چندگانه الگویی برای محاسبه میزان برق مصرفی سالیانه بر اساس متغیرهای مستقل ذکر شده بدست آمد . به جهت تایید مدل بدست آمده، با استفاده از تحلیل رگرسیون ریج نشان داده شد که علیرغم وجود هم خطی شدید بین متغیرهای مستقل ، در برآورد ضرایب مدل رگرسیون چندگانه تاثیری نداشته و ضرایب مدل رگرسیون ریج بسیار نزدیک و برابر با ضرایب رگرسیون چندگانه معمولی بدست آمده است .
از نتایج این تحقیق می توان در پیش بینی میزان بودجه هزینه ای سالیانه برق مصرفی ایستگاه های آتش نشانی و نیز به جهت بهینه سازی و اصلاح الگوی مصرف و مدیریت ایستگاه هایی که بیشتر از نرم استاندارد مصرف برق دارند ، استفاده نمود .کلید واژگان: رگرسیون ریج، رگرسیون چندگانه خطی، ضریب همبستگی، برق مصرفی، ایستگاه آتش نشانیThe application of multiple regression in modeling the electricity consumption pattern of fire stations with the aim of optimizing the consumption patternProper prediction of electricity consumption is one of the most important parameters in planning for a system. One of the most common tools for forecasting is regression-based methods. In this research, using the multiple linear regression model, the prediction of electricity consumption in Mashhad fire stations has been discussed. The statistical population of the current research is the stations of the Mashhad Fire Department, of which 45 stations were selected as a statistical sample.
Pearson correlation and regression statistical methods were used to analyze the research data. The results of the research show that there is a strong and direct correlation between the three independent variables of the number of firemen stationed at the station, the area of the station and the number of fire trucks with the dependent variable of the station's annual electricity consumption. Finally, by using the multiple regression model, a model was obtained to calculate the annual electricity consumption based on the mentioned independent variables.
In order to confirm the obtained model, it was shown by using ridge regression analysis that despite the presence of strong collinearity between independent variables, it did not affect the estimation of coefficients of the multiple regression model and the coefficients of the ridge regression model were very close and equal to the normal multiple regression coefficients.
The results of this research can be used to predict the amount of the annual budget of electricity consumed by fire stations and to optimize and modify the consumption pattern.Keywords: Ridge regression, multiple linear regression, correlation coefficient, electricity consumption, fire station -
بررسی اثرات گردشگری تجاری بر ساختارهای اقتصادی، اجتماعی و کالبدی شهرها (نمونه موردی: منطقه آزاد ارس)
هدف این پژوهش بررسی اثرات گردشگری تجاری بر ساختارهای اقتصادی، اجتماعی و کالبدی شهرها در منطقه آزاد ارس است. روش تحقیق پژوهش حاضر از نظر هدف کاربردی و از نظر روش توصیفی تحلیلی و علی مقایسه ای است. در بخش نخست با استفاده از آزمون t تک نمونه ای میانگین هر یک از گویه ها محاسبه شد. سپس با توجه به بازخورد پاسخ کارشناسان، برای تحلیل میزان اثرگذاری ابعاد و آزمون فرضیه های پژوهش از آزمون رگرسیون خطی چندگانه استفاده شد. نتایج این پژوهش نشان می دهد که میانگین هریک از ابعاد گردشگری تجاری (4.35)، اقتصادی (3.92)، اجتماعی (3.72) و کالبدی (3.31) از مقدار متوسط نظری (3) بالاتر می باشد. به دلیل مثبت بودن تفاوت میانگین کلی هریک از ابعاد، می توان ذکر کرد که گردشگری تجاری بر ساختارهای موجود مورد مطالعه اثرگذار می باشد. نتایج آزمون همبستگی نشان می دهد میان گردشگری تجاری با ابعاد سه گانه پژوهش همگی معنادار و مثبت بودهاند. همچنین آزمون رگرسیون خطی چندگانه نشان می دهد که رابطه ی محکمی بین اثرات گردشگری تجاری و ساختارهای موجود وجود دارد (R=0.99). درمجموع ساختارهای سه گانه توانستند 0.69 درصد از میزان تغییر واریانس در گردشگری تجاری را پیش بینی کنند.F(9,63)= 35.08 p
کلید واژگان: گردشگری تجاری، ساختارهای اقتصادی، اجتماعی و کالبدی، رگرسیون خطی چندگانه، منطقه آزادThe purpose of this study is to investigate the effects of commercial tourism on the economic, social and physical structures of cities in the Aras Free Zone. The research method of the present study is applied in terms of purpose and comparative in terms of descriptive-analytical and causal methods. In the first part, the mean of each item was calculated using a single sample t-test. Then, according to the feedback of experts, multiple linear regression test was used to analyze the effect of dimensions and test the research hypotheses. The results of this study show that the average of each of the dimensions of commercial (4.35), economic (3.92), social (3.72) and physical (3.31) tourism is higher than the theoretical average (3). Due to the positive difference in the overall average of each dimension, it can be said that business tourism affects the existing structures under study. The results of the correlation test show that between business tourism and the three dimensions of research have all been significant and positive. Multiple linear regression tests also show that there is a strong relationship between the effects of commercial tourism and existing structures (R = 0.99). In total, the three structures were able to predict 0.69% of the variance in commercial tourism (F (9,63) = 35.08 p
Keywords: Business Tourism, Economic, Social, Physical Structures, Multiple linear regression, Aras Free Zone -
تحقیق حاضر، با هدف ارایه شاخص دورسنجی کیفیت آب به کمک فناوری سنجش از دور صورت گرفته است. در این پژوهش ابتدا با توجه به شرایط منطقه، مطالعه منابع علمی و دسترسی به داده های ماهواره ای پارامتر های فلزات سنگین، یون های محلول، دمای آب، کلروفیلa و pH انتخاب شد. سپس توسط بررسی منابع و مقایسه بین عملکرد سنجنده های مختلف، محصول کد 02 و 09 سنجنده مودیس و تصاویر سطح دوم یک کیلومتر کلروفیل aو دمای آب سنجنده مودیس تهیه و آماده سازی شد. همچنین اطلاعات میدانی آبهای بندرعسلویه همزمان با تصویربرداری ماهواره آکوا و ترا، در ماه اوت سال 2014 تهیه گردید. سپس رابطه میان مقادیر اندازه گیری شده و مقادیر بازتابش تصاویر ماهواره ای، به صورت مدلهای خطی بررسی شد و ضریب تعیین بین 59/0 تا 94/0 از مدلها به دست آمد. در ادامه تصاویر سنجنده مودیس بین سالهای 2015 تا 2017 تهیه و مدلهای به دست آمده بر روی آنها اعمال گردید. سپس لایه ها برای بیان میزان مطلوبیت هر ناحیه با استفاده از منطق فازی استانداردسازی شد. همچنین سری های زمانی داده های دمای آب از سال 2003 تا 2017 تهیه و برای هر ماه مقادیر میانگین پیکسلی محاسبه شد و برهمان اساس تغییرات این پارامتر استانداردسازی شد. در نهایت شاخصی کارآمد جهت بررسی کیفیت آبهای ساحلی به کمک سری های زمانی داده های دورسنجی ارایه گردید و آبهای بندرعسلویه پهنه بندی شد. نتایج نشان داد کیفیت آب از سالهای 2015 تا 2017 از وضعیت ضعیف به وضعیت بسیار ضعیف تغییر پیدا کرده است. براساس نتایج این پژوهش با توسعه شاخص پیشنهادی در مطالعات آتی بررسی مداوم پایش زیست محیطی امکان پذیر خواهد بود.
کلید واژگان: سنجنده مودیس، منطق فازی، پهنه بندی آبهای ساحلی، شاخص دورسنجی کیفیت آب، رگرسیون خطی چندگانهThis study was conducted with the aim of providing a remotely sensed water quality index in Assaluyeh port using remote sensing technology. so, according to the region conditions, studying of scientific resources and access to satellite data, the parameters of heavy metals, dissolved ions, SST, chlorophyll-a and pH were selected. Then, by reviewing sources, the product MYD091km, MYD021km, MOD021km, MOD091km and level2 images of chlorophyll-a and SST of MODIS sensor were used after preprocessing operations. Also In-situ data were collected Simultaneously with the capture of satellite images in August 2014. Then, the relationships between the water quality parameters and MODIS data, with (R2) from 0.59 to 0.94 and (RMSE) from 0.07 to 0.1 were obtained. Next the images of the MODIS sensor from 2015 to 2017 were prepared and the models were applied to them, then the layers were standardized by fuzzy logic. Also time series of SST data from 2003 to 2017 were prepared and for each month the average pixel values were calculated and based on this, from 2015 to 2017, the variation of this parameter was standardized. Finally, an effective index for assessing the quality of coastal waters was provided by time series of satellite images and the waters of Assaluyeh port were zoned. The results showed that the water quality in 2015 and 2016 has shifted from poor to very poor status in 2017. Based on the results, with the development of a proposed index, in future studies a continuous assessment of environmental monitoring is possible.
Keywords: MODIS Sensor, Fuzzy logic, Coastal water zoning, Remotely Sensed Water Quality Index, Multiple Linear Regression -
در این مطالعه اثر تغییر اقلیم بر فنولوژی (مرحله گل دهی) و عملکرد گندم در غرب و شمال غرب کشور بررسی شده است. ابتدا رخداد تغییر اقلیم برای دوره پایه (2018-1988) در منطقه با استفاده از دو آزمون من-کندال و Estimator slopsen's ارزیابی شد نتایج نشان داد که در غرب و شمال غرب کشور متوسط دمای سالانه دارای روند افزایشی به میزان 2 درجه سانتی گراد، و همچنین متوسط بارندگی ها سالانه دارای روند کاهشی به میزان 38 درصد می باشد. در ادامه هم با کوچک مقیاس سازی آماری داده های خروجی مدل CCSM4 به وسیله نرم افزار LARS WG ، پارامترهای اقلیمی بیشینه دما، کمینه دما و بارندگی منطقه تحت سناریوی RCP4.5 در افق سال های 2019 تا 2039 شبیه سازی شد. سپس پیش بینی طول مرحله گل دهی و میزان عملکرد با استفاده از مدل رگرسیون چندگانه خطی بدست آمد انتخاب مدل براساس شاخص R-Square بود که شاخص(R-Square) یا ضریب تبیین مدل برای پیش بینی عملکرد 83 ٪ بوده و ضریب تبیین (R-Square) مدل برای پیش بینی فنولوژی 94 ٪ بود. یافته ها نشان داد که در غرب و شمال غرب کشور دوره آتی، متوسط درجه حرارت در تمامی ماه های سال افزایشی بین 5/2 تا 5/3 درجه سانتیگراد تا پایان سال 2039 خواهد داشت. همچنین تحت شرایط تغییر اقلیم در آینده طول مرحله گل دهی 18 روز کوتاه تر خواهد شد و عملکرد دانه گندم 35 درصد افزایش خواهد یافت.
کلید واژگان: تغییر اقلیم، رگرسیون چندگانه خطی، فنولوژی، عملکرد، گندمIntroduction:
Climate change will affect all sectors of the economy to some extent, but the agricultural sector may be the most sensitive and most vulnerable part because agricultural products are highly dependent on climate resources, And according to scientific evidence, future climate change, especially the combined effects of elevated temperatures and elevated atmospheric CO2 concentrations, will have a significant impact on crops (droughts, floods, frosts) on crops( Chiottioud ,1995). The general effects of climate change on crop development vary depending on the plant and study area (Rawlins, 1991), and commenting on the response of different species to climate change requires case studies.
Materials and Methodsarea of study The study area includes west and northwest of the country Uncovering Climate Change in Past Times Climatic data of maximum temperature, minimum temperature, 30-year historical rainfall (1988-2008) were obtained from 23 stations in the west and northwest of the country And Using two nonparametric tests Mann-Kendall and Estimator slop sen, the trend of precipitation and temperature changes was investigated in order to detect climate change phenomenon in the region. Generating climate scenarios in future periods To assess future climate change in the west and northwest of the country, the CCSM4 general circulation model under RCP4.5 scenario is one of a number of new RCP emission scenarios that the Climate Change Intervention Board will develop in its Fifth Assessment Report (AR5) as representative of the linesVarious concentrations of greenhouse gases have been used Predictive model of wheat phenology and yield unctional and phenological data for three years (90-93) with 40 climatic parameters (Table 2) from seven stations (Zanjan, Arak, Sararood, Maragheh, Ghamloo, Ardabil and Orumieh) containing performance and phenology data Was prepared Then, using these data, performance and phenology in the baseline and future period were predicted through simple linear regression, multiple regression. The results consisted of 20 regression models The best model was selected based on R-squard index using RMSE.
Results and discussionFebruary, March, September, and the year are at 99 percent confidence levels, while January, June, July and August are at 95 percent confidence levels. As well as total rainfall, both the upward and downward trends have a significant and decreasing trend at 95% confidence level only in January and March. Changes in temperature and rainfall in the coming period The results of climate change assessment at each of the stations in the future climate show that the mean maximum temperature in the future climate has increased at 14 stations compared to the previous climate and decreased at the other stations. The mean minimum temperature in the future climate has increased in all the stations except for Ghamloo and Sanandaj stations compared to the previous climate. Average temperature also increased at all stations except Ahar, Zarineh, Sarab and Ghomloo stations in all stations compared to past climates Average mean precipitation in all stations excluding sarpolzahab station in future climates It increases with the past climate Impact of Climate Change on Phenology nder the climate change, the length of the flowering stage of the wheat in the future climate will be shorter than in the previous climate, so that the flowering stage length in all the studied stations with the exception of Zarrineh station in the next period (2039-2018 ) Is shorter than the average long-term flowering stage of wheat. he mean flowering stage duration in the basal climate is 136 days, whereas the mean flowering stage duration in the future climate is 118 days, ie the average flowering stage duration in the future climate is 18 days short. Increasingly, the shortening of the flowering stage in future climates is due to the increase in average temperature in May and April and average maximum temperature in December. Impact of Climate Change on PerformanceUnder climate change, wheat grain yields will increase in future climates than in the past, so that at all stations with the exception of Mahabad station, wheat grain yield is higher than the long-term average in the past. verage wheat yield in the past climate was 1863.3 kg / ha but in the future climate it would be 2529.9 kg / ha. Wheat yields are up 35 percent due to the favorable future climate in the region.
Conclusiontudies show that precipitation in the west and northwest region of the country during the past period has been decreasing and the temperature is increasing in most months of the year. And in the coming period the temperature in all months of the year until the end of 2039 shows an increase of 2.5 to 3.5 ° C. The flowering period is also 136 days for the previous period but 118 days for the next period shortening of flowering stage of wheat plant is due to increase in average temperature in May and April and average maximum temperature in December as well as increase in precipitation in December and February. Comparison of wheat grain yields of the current and past periods showed that wheat grain yields will increase by 35% in the future, due to the increase in average March and April temperatures and average January and March minimum temperatures. It also saw an increase in the average precipitation of February and March in the next period compared to the previous period.
Keywords: climate change, Multiple linear regression, Phenology, Yield, Wheat -
امروزه شناسایی فاکتورهای موثر بر آتش سوزی جنگل ها از اهمیت بسیار بالایی برخوردار است زیرا سالانه مساحت زیادی از جنگل های جهان بر اثر آتش سوزی نابود می شوند و تکرار این اتفاق در بلندمدت می تواند خسارات جبران ناپذیری بر زمین و ساکنین آن وارد کند. با شناسایی این فاکتورها می توانیم زمان ها و نقاط دارای ریسک بالای آتش سوزی را شناسایی نماییم و با وضع قوانین و سیاست های مدیریتی کارآمد، آموزش به مردم و نظارت بیشتر در جهت مقابله با عوامل محرک آتش برآییم. در این تحقیق سعی شده است فاکتورهای موثر بر آتش سوزی های جنگل گلستان شناسایی شود و برای این منظور از سه روش رگرسیون خطی چندگانه، رگرسیون لجستیک و رگرسیون اسپلاین تطبیقی چندمتغیره در ترکیب با الگوریتم ژنتیک استفاده شد. نتایج این تحقیق نشان داد که هر دو دسته فاکتورهای بیوفیزیکی و انسانی در آتش سوزی های منطقه مورد مطالعه دارای تاثیر هستند. از این میان تنها فاکتورهای حداقل دما و حداکثر سرعت باد در هر سه حالت موثر شناخته شدند. روش رگرسیون اسپلاین تطبیقی چندمتغیره در مقایسه با دو روش دیگر عملکرد بهتری از خود نشان داد. مقدار RMSE نرمال شده این سه روش برابر 0/4291 برای رگرسیون خطی چندگانه، 0/9416 برای رگرسیون لجستیک و 0/1757 برای رگرسیون اسپلاین تطبیقی چندمتغیره و مقدار R2 آن ها نیز به ترتیب برابر 0/9862، 0/9912 و 0/9886 به دست آمد.
کلید واژگان: آتش سوزی جنگل، رگرسیون اسپلاین تطبیقی چندمتغیره، رگرسیون خطی چندگانه، رگرسیون لجستیک، الگوریتم ژنتیکIntroductionNowadays, Determining the effective factors on fire is so important, because the plenty areas of forests around the world are destroyed annually by fire and recurrence of that in the long term can irreparably damage to the earth and its inhabitants. It helps us to identify most dangerous locations and times in forest fire. Hence, we can prevent many of driving factors of forest fire by law enforcement, efficient forest management policies and more supervision. In the current study, we identified the effective factors on the fire in Golestan forest through integration of three different methods including multiple linear regression, logistic regression and multivariate adaptive regression spline with Genetic Algorithm.
Study Area
Golestan Province is in the North of Iran and 18% of it is covered by forests. Golestan Province is a touristic province and several roads pass through its forests and according to statistical records, most of the occurred fires were in proximity of these roads. Our study area is located in 36°53′-37°25′N and 55°5′- 55°50′E and its area is about 3719.5 km2. We selected this area, because includes the most of fires have been occurred in Golestan Province in recent years.Materials and MethodsA big fire was occurred on 12 December, 2010 in our study area and we used it as the dependent variable. The actual burnt area and some other data, such as Digital Elevation Model (DEM), the roads network, the rivers, the land uses, and soil types in the area were provided from Golestan Province Department of Natural Resources. Also, geographic coordination of the synoptic weather stations near the area and their data, including maximum, minimum, and mean temperature; total rainfall, as well as maximum wind speed and azimuth in December 2010 were obtained from National Meteorological Organization of Iran.
The land use and soil layers were in scale of 1:100000 and the roads and the rivers layers were in 1:5000 and all of them were provided in 2006. The region DEM is generated from topographic maps of Iran National Cartographic Center in scale of 1:25000 with positional resolution of 30m and we produced the slope and the aspect layers from it in ArcGIS software with the same resolution. The roads and the rivers were in vector format, hence, we used the Euclidean Distance analysis to generate rasters that each cell of them shows the distance from the nearest road or river.
At first we had 5 weather stations, which is very few for GWR. In this regard, we generated 1000 random points in the area and interpolated data to these points using Ordinary Kriging method with exponential semivariogram model in 30m resolution in ArcGIS software.
The multiple linear regression (MLR) model is the generalization of simple linear regression that is modeling the linear relation between one dependent variable and some independent variables. The general formula of MLR is seen below: (1)The unknown coefficients are obtained using least squares adjustment as follows: (2)The logistic regression (LR) model is a nonlinear model for determination of the relation between a binary dependent variable and some independent variables. If we use the values of 0 and 1 for non-fire and fire points respectively, then the probability that a point be a fire point is obtained by Eq. (3): (3)If the number of parameters is insignificant compared to the observations, then we use the unconditional maximum likelihood estimation shown by Eq. (4) to compute the unknown coefficients of this model. (4)The multivariate adaptive regression spline (MARS) model is a flexible non-parametric model that requires no assumption about the relation between the dependent andindependent variables. Hence it has a high ability in determination of complex nonlinear relations among the variables. The general formula of MARS is seen below: (5) is the m’th basic function that is obtained by Eq. (6): (6)These basic functions are chosen in such a way that leads to minimum RMSE of model.
We use the genetic algorithem (GA) with the fitness function of the normalized RMSE to select the optimum combination of effective factors on forest fire.Results and DiscussionIn this paper we study the dependence of the forest fire to 14 factors shown in table 1, in the study area. Our results are shown in figures 1 to 3.
ConclusionThis research shows that both of the biophysical and anthropogenic factors have significant effects on forest fire in our study area. Just two factors were identified as impressive factors in all three cases including the minimum temperature and the maximum speed of wind. This study concluded to the NRMSE=0.4291 and R2=0.9862 for the multiple linear regression, NRMSE=0.9416 and R2=0.9912 for the logistic regression and NRMSE=0.1757 and R2=0.9886 for the multivariate adaptive regression spline and totally the multivariate adaptive regression spline method showed a better performance in comparison to the other two methods.
Keywords: Forest fire, Multivariate Adaptive Regression Spline, Multiple Linear Regression, Logistic Regression, Genetic Algorithm -
مجله راهور، پیاپی 29 (تابستان 1398)، صص 45 -68
با توجه به استفاده فراوان از سرعت گیر و سرعت کاه ها به عنوان ابزارهای آرام سازی در راه های کشور خصوصا در استان های شمالی (به علت دسترسی های زیاد، تداخل نقش های اجتماعی و جابه جایی راه و تفاوت زیاد سرعت وسایل نقلیه با سرعت مجاز تعیین شده)، در این پژوهش، بررسی اثربخشی این اقدامات در کاهش سرعت مدنظر قرار گرفته است. این مطالعه به تعیین ارتباط بین مشخصات هندسی سرعت کاه ها و سرعت وسایل نقلیه در 90 سرعت کاه نصب شده در نواحی مختلف از راه های واقع در شرق استان مازندران پرداخته است. ازآنجایی که نمونه موردبررسی شامل انواع سرعت کاه ها اعم از قوسی و تخت بود و در راه هایی با رده های مختلف عملکردی اجرا شد، برای بررسی بهتر، سرعت کاه ها دسته بندی شدند و به طور جداگانه مشخصات هندسی هرکدام مشخص و سرعت وسایل نقلیه در پیرامونشان برداشت شد. سرعت وسایل نقلیه در چند نقطه قبل، رو و بعد از سرعت کاه با استفاده از دوربین سرعت سنج ثبت شد و ابعاد هریک از سرعت کاه ها با استفاده از دوربین توتال استیشن به صورت دقیق برداشت شد. درنهایت با استفاده از مدل رگرسیون خطی، داده ها در نرم افزار SPSS موردارزیابی قرار گرفته و عوامل اصلی تاثیرگذار روی کاهش سرعت وسایل نقلیه به همراه مدل رگرسیونی برآورد کاهش آن ارائه گردید. با توجه به اینکه تعداد سرعت کاه های موردمطالعه زیاد بوده است، نتایج این پژوهش نشان داد که برای طراحی و اجرای سرعت کاه ها در سرعت های عبور و سرعت های هدف مختلف می توان از این مدل ها استفاده نمود تا اثربخشی سرعت کاه ها در کاهش سرعت و پروفیل سرعت در فاصله های مختلف از سرعت کاه ها را با سطح اطمینان بالایی موردارزیابی قرار داد.
کلید واژگان: آرام سازی فیزیکی ترافیک، سرعت کاه، مدل سازی سرعت، رگرسیون چندگانه خطیIn this study, the effectiveness of these measures in reduction of vehicles speed has been considered, considering the extensive use of speed humps and humps as physical traffic calming measures in Iran, especially in the northern provinces (due to high accesses, interference of social roles and displacement of road, and the significant difference between speed of vehicles and speed limit). This study was carried out to determine the relationship between geometric characteristics of humps and vehicles speed in 90 different areas of roads in eastern part of Mazandaran province. Since the studied sample consisted of all types of humps, including arches and beds and they performed in different functional classes of roads, they were categorized for better examination and Separately, each geometric feature was identified. and the speed of vehicles were determined individually around them. The speed of the vehicle was recorded at a few points before, on the humps and then it was recorded using a speedometer camera , and their dimensions were surveyed accurately by using the Total Station camera. Finally , data was evaluated using linear regression model in SPSS software and has been presented the main factors affecting vehicle speed reduction and models related to speed reduction. Considering the high number of selected humps in the study, the results of this research showed that it is possible to use these models to design and implement humps for passage speed and different specific speeds; in addition, these models could evaluate the effectiveness of the humps in speed reduction, and determine the speed profile at different distances from the humps in a high level of confidence.
Keywords: physical traffic calming measures, speed humps, speed modeling, multiple linear regression -
پژوهش در مورد انتظارات و ترجیحات کاری نسل هزاره به عنوان نسل جوان نیروی کار، فراهم کننده بینشی است که شکل دهی سیاست های جذب و نگه داری متناسب با این نسل را برای مدیران تسهیل می کند. بر این اساس، پژوهش حاضر با بررسی سیستماتیک نتایج تحقیقات کیفی در این حوزه، لیستی از انتظارات کاری این نسل را ارائه و سپس با استفاده از روش آنتروپی شانون ترتیب اهمیت آنان را مشخص کرد. این پژوهش از نظر هدف، توصیفی و از نظر نوع استفاده کاربردی است. جامعه آماری پژوهش، شامل 68 مقاله و پایان نامه کیفی معتبر بود که تعداد 21 مورد با استفاده از روش قضاوتی وارد فرایند فراترکیب شد. جهت سنجش میزان توافق بین دو رتبه دهنده از شاخص کاپا و جهت سنجش روایی نتایج از شاخص CVI استفاده شد و بدین ترتیب روایی و پایایی مورد تصدیق قرار گرفت. نتایج نشان داد که به ترتیب، توازن بین کار و زندگی، فرصت برای رشد و توسعه حرفه ای در کار، وجود محیط کاری سرگرم کننده و لذت بخش، برخورداری از زمان کاری منعطف، بر عهده داشتن وظایف چالشی، کار تیمی، محیط کار حمایتی، برخورداری از حقوق و مزایای بیشتر و کار معنی دار ازجمله مهم ترین انتظارات کاری نسل هزاره هستند.
کلید واژگان: فضیلت سازمانی، عوامل درون سازمانی، عوامل برون سازمانی، بیمارستان های دولتی شهر تبریز، رگرسیون خطی چندگانهInvestigating work expectations and preferences of Millennium Generation as a young generation of labor, provides an insight that facilitates the formation of Millennium’s appropriate attraction and maintenance policies for managers. Accordingly, the present study, by systematically reviewing the results of qualitative researches in this area, presented a list of work expectations of this generation and then determined the importance of them by using the Shannon entropy method. This research is descriptive in terms of purpose and is practical in terms of its type. The statistical population of the study consisted of 68 qualitative papers in which 21 cases were entered into meta-synthesis process by using the judgment method. In order to measure the agreement between the two raters, the Cohen's kappa coefficient was used and the CVI index was utilized to assess the validity of the results. Therefore, validity and reliability were confirmed. The results showed that respectively balance between work and life, the opportunity for professional development in work, the existence of a fun and enjoyable working environment, having flexible working hours, challenging job, teamwork, and supportive work environment, more salary and benefits and meaningful job are among the most important work expectations for millennial generation.
Keywords: Organizational virtuousness, Intra-organizational factors, Extra-organizational factors, Tabriz state hospitals, Multiple linear regression -
پیشبینی مقدار مصرف برق، با توجه به شرایط آبوهوایی، میتواند در تنظیم استراتژی های تولید و توزیع آن نقش مهمی ایفا کند. هدف از این پژوهش، بررسی رابطه بین متغیرهای آبوهوایی با مصرف برق و پیشبینی مصرف برق تحت تاثیر پدیده تغییر اقلیم در منطقه غرب کشور است. به این منظور، رابطه بین متغیرهای آبوهوایی و مصرف برق در سیزده ایستگاه منطقه در دوره 28ساله (1987-2014) با استفاده از معادلات رگرسیونی چندگانه مدلسازی شد. در صورت معناداربودن مدلها، براساس داده های آبوهوایی مدل CCSM4، مصرف برق در ایستگاه ها طی دوره زمانی 2021-2080 تحت دو سناریوی RCP4.5 و RCP8.5 برآورد شد. نتایج نشان داد درجه- روزهای سرمایشی و گرمایشی و رطوبت نسبی بیشترین تاثیر معنیدار را در افزایش مصرف برق دارند. میانگین دماهای حداقل و حداکثر در منطقه در دوره آتی (2012-2080) به طور متوسط تحت سناریوی RCP4.5 بهترتیب 95/1 و 01/2 و تحت سناریویRCP8.5بهترتیب46/3 و 81/3درجه سانتیگراد افزایش خواهد یافت. ازاین رو،میزان مصرف برق در دوره گرم سال براساس سناریوی RCP4.5 در حدود 80درصد و براساس سناریوی RCP8.5 در حدود 150درصد افزایش خواهد یافت. بیشترین میزان افزایش مربوط به ایستگاه های گرمسیری غرب منطقه و کمترین آن مربوط به ایستگاه های سردسیر کوهستانی است.کلید واژگان: رگرسیون خطی چندگانه، غرب ایران، متغیرهای آبوهوایی، مدلهای گردش عمومی جو، مصرف برقExtended Abstract Introduction Electric energy has no storage capacity on a large scale. Considering the importance of this energy in various programs and increasing its consumption in the context of global warming, its future consumption forecast in the energy sector policy will be of significant importance. Therefore, awareness of the variables affecting electricity consumption and the impact of each of them will enable policy makers to make more precise planning and prediction of electricity consumption in the coming years. Therefore, accurate estimation of the amount of consumption with regard to climatic conditions can play an important role in the economic use of electrical energy. The purpose of this research is to investigate the relationship between climatic variables with electricity consumption and prediction of electricity consumption under the influence of climate change in western Iran. Materials and Methods The region studied in this research is western Iran, including provinces of Kermanshah, Kurdistan, Hamedan, Ilam and Lorestan. This region has a variety of climates due to its location on the path of hot and cold air masses and mid-latitude cyclones. The data used in this study are: 1- meteorological data of 13 stations in the region over a 28-year period (1987 to 2014), including minimum temperature, maximum temperature, relative humidity, wind speed, sunshine hours and rainfall, 2- data on monthly electricity consumption during the corresponding period, 3- minimum temperature, maximum temperature and relative humidity data simulated by CCSM4 General Circulation Model. To calculate the heating and cooling requirements, Heating Degree Days (HDD) and Cooling Degree Days (CDD) values were calculated using the minimum and maximum temperature data. First, the relationship between climatic variables and electricity consumption at stations was modeled using multiple regression equations. In the case of significant models based on the data of the CCSM4 model, the electricity consumption at the stations during the period 2080-2080 was estimated under two scenarios RCP4.5 and RCP8.5. Future climate scenarios were then downscaled using the "change factor" method. To verify the downscaled data, the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Coefficient of Determination (R2) were used. Results and Discussion At all stations, the CDD have a direct and significant relationship with electricity consumption, due to the high consumption of air conditioning/cooling equipment in summer. But the relationship between the HDD and electricity consumption is weaker than the CDD; because in winter, less electricity is used to heat the environment. Especially in warm stations such as Ilam, Dehloran and Sarpole-Zahab, the relationship between the HDD and electricity consumption is not substantially significant. At these stations, during the cold season due to the mildness and shortness of the cold, there is little need for electrical equipment for heating purposes. In contrast, in these three stations, humidity has a significant and inverse relationship with electricity consumption. Other climatic parameters have no significant relationship with electricity consumption. The mean maximum and minimum temperatures in the region in the future period (2021-2080) will increase on average under the RCP4.5 scenario by 1.95ºC and 2.01ºC respectively, and under the RCP8.5 scenario by 3.46ºC and 3.81ºC. Therefore, electricity consumption at all stations in the upcoming period (2021-2080) will increase compared to the past period, and this increase will be much higher in the warm period of the year. The average increase in consumption during the warm period at the stations under the two scenarios will be 80% and 150% respectively. Particularly warm stations in the west of the region, such as Dehloran, Sarpole-Zahab and Ilam in the warm-season months (6 months, from May to October) will experience the highest increase in electricity consumption under two scenarios, of about 110% and 210%, respectively. The lowest increase in demand for electricity in the upcoming period is related to the relatively cold stations of Hamedan, Sanandaj, Saqez and Bijar. Because of the mountainous nature, the high altitude and the longer cold period, the main need of these stations is heating, a significant part of which is supplied by natural gas. This clearly has little dependence on electricity. But in any case during the warm period of these stations, which is shorter, and lasts for 4 months (June to September), the increase in consumption is lower than in warm stations and under the two scenarios, would be about 60% And 110%, respectively. Other stations like Khorramabad, Kermanshah, Kangavar, Boroujerd and Islamabad will have an intermediate level of consumption. However, it should be noted that regardless of the increase, electricity supply for larger and more populous cities such as Kermanshah and Hamedan will be more important than warm cities. There is not much increase in consumption in cold-period months at any warm and cold station. Conclusion Since a significant part of the electricity consumption in the region is due to the use of conditioning/cooling equipment, any change in temperature during the warm period will be effective in increasing or decreasing the use of those equipment, and consequently, increasing power consumption. Considering the significant increase in the temperature of the region during the 2021-2080 period under the two scenarios used, it is necessary to take appropriate strategies to deal with the drastic increase in electricity consumption in the future, especially during the warm period of the year.Keywords: Multiple Linear Regression, West of Iran, Climatic Variables, Electricity Consumption, General Circulation Models
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جنگل ها از مهم ترین منابع طبیعی و اکولوژیکی در کره زمین و از ارکان مهم توسعه پایدار در هر کشوری به حساب می آیند. آتش سوزی هر سال حدود 5500 هکتار از جنگل ها را در ایران از بین می برد. در این تحقیق با استفاده از داده های آتش سوزی سازمان جنگل ها در تلفیق با داده های سنجنده MODIS بین سال های 91 تا 96 نقاط آتش شناسایی شدند. ازآنجا که بیش از 75 درصد آتش سوزی ها در فصل گرم سال یعنی سه ماه تیر، مرداد و شهریور اتفاق افتاده بود، از داده های این سه ماه برای مدل سازی استفاده شد. پارامترهای موثر در وقوع آتش سوزی ارزیابی و پارامترهای وابسته حذف شدند. سپس دو روش رگرسیون چندگانه خطی و رگرسیون انطباقی چندمتغیره اسپیلاین برای پیش بینی ریسک وقوع آتش سوزی بررسی شدند. برای ارزیابی از چند پارامتر مهم شامل جذر میانگین مربعات خطاها، ضریب تعیین R2، درصد برآورد درست نقاط آتش و غیرآتش و توزیع خطا استفاده شد. نتایج نشان داد که روش رگرسیون انطباقی چندمتغیره اسپیلاین با داشتن خطای میانگین مربعات باقی مانده ها داده های آموزشی برابر با 0/1628، R2 داده های آموزشی برابر با 8932/0، درصد پیش بینی درست نقاط آتش آزمایشی نزدیک به 94 درصد، درصد پیش بینی درست نقاط غیرآتش آزمایشی نزدیک به 88 درصد و توزیع مناسب تر خطا عملکرد بهتری نسبت به روش دیگر دارد. این امر در واقع نشان دهنده مدل سازی دقیق تر یک روش محلی در مقایسه با یک روش غیرمحلی است. به همین دلیل نقشه ریسک تهیه شده با رگرسیون انطباقی چندمتغیره اسپیلاین اعتمادپذیری بیشتری از روش دیگر دارد. در نهایت با استفاده از نقشه ریسک این روش مناطق پرریسک شناسایی شدند. ویژگی این مناطق شامل فاصله کم تا مناطق مسکونی و راه، دارای خاک غنی از مواد عالی، دمای به نسبت زیاد و ارتفاع کم بود.
کلید واژگان: آتش سوزی جنگل، رگرسیون انطباقی چندمتغیره اسپیلاین (MARS)، رگرسیون چندگانه خطی(MLR)، نقشه ریسک آتش سوزیForest areas are among the most important natural and ecological resources on the Earth and are considered as one of the main pillars of sustainable development in any country. Fires ruins almost 5500 hectares of Iran’s forests yearly. In this research, firstly, the fire points were identified using the fire data of Forest Organization in combination with MODIS sensor data between 2012 and 2017. Due to the fact that more than 75% of fires were happened in the hot season of the year (June, July, and August), the data of the three months was used for modeling. Then, the effective parameters in fire occurring were evaluated and the dependent parameters were removed. Accordingly, two methods, including multiple linear regression and multivariate adaptive regression spline were studied to predict the fire risk. Some important parameters including the root-mean-square error (RMSE), R2, the correct estimation percentage of fire and non-fire points, and error distribution were used to evaluate. After modeling, it was found that the multivariate adaptive regression spline has better performance—where its RMSE of test data was 0.1628, its R2 of test data was 0.893, and its correct estimation percentage of test fire points and test non-fire points was near 94% and 88% respectively, as well as its error distribution was better than the other method. This actually shows that modeling with a local method is very better than modeling with a global method. Therefore, the risk map resulted by multivariate adaptive regression spline has better reliability compared to those of the other method. Finally, the high-risk areas were recognized using the risk map of this method. The traits of these areas were a short distance to residential areas and roads, having rich soil with organic materials, relatively high temperature, and low height.
IntroductionIn 2000, a convention was established in the United Nations to improve the quality of human life in which the principles of the Millennium Development Goals were adopted. One of these goals was to ensure the stability of the environment and natural resources. In the contemporary world, the value of forests is about 120 billion dollars and the livelihood of almost 9.1 people is dependent on forest (in)directly.
According to the opinion of global experts including FAO, if the forest cover of a country is less than 25% of that country’s area, that country is in critical condition in terms of the human environment. Almost 190000 hectares of Iranian forests have been ruined by fire in a 28-year period. Forest fire not only changes the natural ecosystem and ruins many plant and animal species of a region, but also makes other destructive effects like air pollution, respiratory problems, soil erosion, increased flowing surface waters, increased acidity of soil, decreased fertility, tourism industry losses, manufacturing industry and economy losses, and even climate change.
Immediate and accurate detection of the fire location and the ability to determine the effective parameters on it, as well as the detection of the areas with high-risk of fire is among the main concerns of environmental protection and disaster management. We can prevent the fire by training people, making effective regulations and management policies, and increased monitoring to deal with fire triggers. Moreover, in the case of fire occurrence, we must take necessary actions like deploying fire-fighting equipment near hazardous areas and making easy access to these areas. In fact, nowadays, the increasing importance of protecting the forests and natural resources has led to change the focus from crisis management to risk management.MethodologyThe modeling was not possible without non-fire points. Accordingly, at the beginning, some points are randomly selected in the whole area with a certain distance from the fire points and are identified as non-fire points. To implement the methods in MATLAB programming environment, firstly, the parameters used in the modeling are extracted using the maps of these parameters for fire and non-fire points. These parameters are used as inputs in each of these methods.
Constantly, 70% of the selected data were used as the training data and 30% of them were used as the test data. Initially, the multivariate linear regression and then the multivariate adaptive regression spline were used for modeling. The steps of the research implementation are shown in Figure (1).
After implementation of the modeling, the evaluation parameters of each method were provided to compare. Then, the risk map of the area was provided using trial points and Inverse Distance Weighting (IDW) and by employing 12 lateral points for each method (Figures 2 and 3). The points with a high risk were extracted from the resulted map. Then, the main traits of these points are considered as the traits of high-risk points.
Fig. 1. The steps of the research implementation
Fig. 2. Fire risk map provided using the MLR method on test data
Fig. 3. Fire risk map provided using the MARS method on test dataDiscussion and Results
After removing the dependent parameters from the effective parameters on the fire, the optimal effective parameters are presented in Table (1). These parameters are divided into three groups including climate, ground physical, and human parameters.
The modeling of fire risk was done by two methods. In the training and testing data section, the RMSE and R2 are presented in Table (2) for multivariate adaptive regression spline and multivariate linear regression methods, respectively. The results achieved by the training data section indicate that the training procedure is more accurate (R2 closer to 1) and with less error (less RMSE) in the multivariate adaptive regression spline than those achieved by the multivariate linear regression method. The appropriate amount of evaluation parameters for test data shows that the model does not experience over-fitting in these methods.
Table 1. Effective parameters on fire occurrence in the case-study area
In the linear regression method, the two parameters of the correct estimation percentage of fire points and non-fire points have a low value, hence, the worst possible scenario has happened and the risk map has the least amount of reliability. In the multivariate adaptive regression spline, the fire and non-fire points are simultaneously estimated with a high accuracy. This makes the risk map provided by the multivariate adaptive regression method becomes to be more reliable.
As seen in the results, the risk map provided by the multivariate adaptive regression spline method has a very higher reliability compared to the risk map provided by multivariate linear regression method. Hence, the risk map resulted by the first method was used to determine the features of the areas with a high risk of fire (Figure 4).
Since the fire risk has a normal distribution, the areas which satisfy Equation (1) are among the 2.5% of the areas that have the most fire risk.
(1)
where is the average, is the standard deviation, and R is the fire risk. The main features of the mentioned areas can be used as the important tools for decision making. The extraction of high-risk areas is done in ArcGIS environment. Statistical analysis of effective parameters’ features in these areas shows some key points. These features include low distance from the residential regions (less than 2 km), low distance from the road (less than 2 km), having mollisol, relatively high average temperature (more than , and low height (less than 50 m).
Fig. 4. High risk map provided using the MARS method on test dataConclusionsThis research attempted to identify the optimal method for modeling of fire points risk using climate, ground physical, and human parameters. Therefore, an accurate local method (MARS) was used along with a non-local method (MLR).
In the test data and the training data sections, the MARS method had the lowest RMSE and a value closer to 1. The outputs showed that the MARS method had a more accurate performance in the estimation of the fire and non-fire points compared to the MLR method. This indicated the high reliability of the MARS method. After determining the optimal method for the modeling of the area’s fire occurrence, the points of the area with high risk of fire were detected. After doing a statistical analysis it was found that these points have some fundamental features including low distance from the residential regions (less than 2 km), low distance from the road (less than 2 km), having mollisol, relatively high average temperature (more than and low height (less than 50 m).Keywords: Forest Fire, Multiple Linear Regression, Multivariate Adaptive Regression Spline, Risk Map -
با توجه به اهمیت و نقش طلا به عنوان ابزاری برای سرمایه گذاری، بخصوص در کشوهای درحال توسعه، روش های مختلفی برای پیش بینی بازده آتی طلا استفاده شده است. ازاین رو، هدف اصلی از پژوهش حاضر پیش بینی بازده روزانه قرارداد آتی سکه طلا در بورس کالای ایران با استفاده از مدل آرچ و شبکه عصبی است. برای این منظور، از داده-های روزانه 20 قرارداد آتی سکه طلا برای دوره زمانی تیرماه 1392 تا شهریورماه 1395 که به روش «تعدیل به عقب» پیوسته شده اند، به کار گرفته شد. همچنین پس از بررسی نتایج تحقیقات پیشین از بازده قیمتی دلار، بازده قیمتی سکه طلا و بازده قیمتی طلای جهانی به عنوان متغیرهای موثر بر بازده قرارداد آتی سکه طلا استفاده شد. علاوه بر این، دقت پیش بینی این مدل ها با استفاده از معیارهای میانگین مربعات خطا، ریشه میانگین مربعات خطا، میانگین قدر مطلق خطا و ضریب تعیین ارزیابی شد. نتایج پژوهش نشان داد در دوره موردبررسی، شبکه عصبی در مقایسه با مدل آرچ در پیش بینی برون نمونه بهتر عمل کرده است؛ اما بر مبنای نتایج آزمون تی زوجی، دقت پیش بینی دو مدل ازنظر آماری تفاوت معناداری نداشته است.کلید واژگان: پیش بینی بازده، قرارداد آتی سکه طلا، شبکه عصبی، مدل آرچ، مدل رگرسیون خطی چندگانهGiven the importance and role of gold as a tool for investing, especially in developing countries, various approaches have been used to predict gold future returns. Hence, the main purpose of the present study is prediction the daily return of gold coin future contract by using multilayer feed-forward neural network and auto-regressive conditional heteroskedasticity (ARCH) models in Iran mercantile exchange. For this purpose, the daily data on 20 the gold coin futures contracts for periods July 2014 to September 2016 which has been continued using the method “back-adjusted”, is used. Also, after investigating results of previous studies, dollar price return, gold coin price return and global gold price return have been used as effecting variables on gold coin future contracts return. In addition, Predictive accuracy the neural network and the ARCH models were evaluated using root mean squared error (RMSE), mean squared error (MSE), mean absolute error (MAE) and coefficient of determination (R2). The results showed that in the period under review, the neural network model performs better than the ARCH model in the prediction out of sample. But based on the results of the paired t-test, the prediction accuracy of the two models hasn’t been the statistically significant difference.Keywords: Forecasting of return, Gold coin future contract, Neural network, ARCH model, Multiple linear regression
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