r. ansari
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Decision Support System for Analyzing Key Performance Indicators in Construction Projects ManagementMany factors play a role in the life cycle of construction industry projects, focusing on human resources and relationships as the main axis of business development. Thus, the conflict of interests between the stakeholders in the construction industry projects is a clear and challenging problem. The increased number of stakeholders in the project complicates human relationships and, consequently, increases the possible conflicts. The conflicts may result in claims if not resolved. The success of construction projects and their cost and time management can be affected by the poor management of claims. Therefore, this research aims to take a significant step to improve the efficiency of projects by identifying and ranking the causes of claims and analyzing their effects on key efficiency indicators. Firstly, causes of claim are collected according to experts’ opinions and literature and classified based on key efficiency indicators using the integrated analytic hierarchy process-technique for order preference by similarity to ideal solution (AHP-TOPSIS) technique. According to findings, delays with a proximity coefficient of 0.728 are the most significant factors in making claims with a great effect on the key efficiency indicators of the construction project. The changes in most construction projects are ranked in second place, followed by acceleration command, extra work, changing workshop conditions, and contractual ambiguities. The present study results may reduce the challenges in managing the construction industry claims and ensure the successful completion of projects.Keywords: Construction, Claim Management, Performance Management, Decision support system
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Dynamic vibration absorbers (DVAs) play an important role in the energy dissipation of a vibrating system. Undesirable vibrations of structures can be reduced by using the absorbers. This paper investigates the effect of an attached energy sink on the energy dissipation of a simply supported beam subjected to harmonic excitation. The aim is to design an optimal linear energy sink (LES) and a nonlinear energy sink (NES) and then compare them with each other. Each absorber includes a spring, a mass, and a damper. For each absorber, the optimum mass, stiffness, and damping coefficients are obtained in order to minimize the beam’s maximum amplitude at the resonant frequencies. The optimization problem is minimizing the maximum amplitude of the beam subjected to an arbitrary harmonic force excitation. For consideration of the effects of rotary inertia and shear deformation, the Timoshenko beam theory is used. The mathematical model of beam with DVA is verified by using the ANSYS WORKBENCH software. Finally, by considering the uncertainty on the DVA parameters it was observed that the LES is more robust than the NES.Keywords: Dynamic Vibration Absorber, Timoshenko beam, Optimization, Uncertainty, Robustness
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زمینه و هدف
با توجه به وجود صنایعی مانند فولاد زنگ نزن، حضور یون نیکل (II) در آب ها و پساب ها در غلظت های بالا گزارش شده است. بنابراین، حذف یون نیکل (II) از پساب ها و محیط زیست امری ضروری به شمار می آید. در این پژوهش نانوذرات اکسید آهن (III) به عنوان جاذب برای حذف یون نیکل (II) از آب در یک سیستم تعادلی منقطع مورد مطالعه قرار گرفت.
روش بررسیجهت مشخصه یابی ساختاری نمونه از تکنیک های FT-IR، SEMو XRDاستفاده شد. برای تعیین شرایط بهینه جذب، اثر پارامترهای مهم از قبیل: pH، زمان تماس، وزن جاذب و غلظت اولیه مورد بررسی قرار گرفت. همچنین، مطالعه ترمودینامیکی (تغییرات انرژی آزاد استاندارد گیبس، آنتالپی و آنتروپی)، مطالعات ایزوترمی (ظرفیت جذب) و مطالعات سینتیکی (تاثیرپذیری جاذب با زمان) بررسی گردید.
یافته هانتایج نشان داد که جاذب مغناطیسی مذکور، دارای بالاترین راندمان حذف آلاینده نیکل (II) در pH برابر 7، زمان تماس min 60، مقدار جاذب mg 200 و بالاترین غلظت قابل حذف mg/L 400 است.
نتیجه گیریبا مطالعات ترمودینامیکی مشخص گردید که واکنش گرماگیر بوده و خودبه خودی بودن فرایند جذب، با عامل آنتروپی کنترل می شود (J/mol.K 165/7+ ΔS°=و KJ/mol 2/7-(ΔG°= . برای درک بهتر مکانیزم جذب، از معادلات سینتیک شبه درجه اول و دوم استفاده شد. سپس جهت تعیین ظرفیت جذب، ایزوترم های جذبی لانگمویر و فروندلیچ بررسی گردید و مطابقت خوب نتایج با مدل فروندلیچ و ظرفیت جذب برابر با mg/g 43/5 به دست آمد که بیانگر ظرفیت جذب بالای جاذب و چند لایه بودن آن است.
کلید واژگان: نانوذرات اکسید آهن (III)، نیکل (II)، ایزوترم، ترمودینامیک، سینتیکBackground and ObjectiveDue to the existence of industries such as stainless steel, the presence of nickel (II) ions in water and wastewater has been reported at high concentrations. Removal of nickel (II) ions from wastewater and the environment are of primary importance. In this study, iron (III) oxide nanoparticles were studied as an adsorbent for removal of Ni (II) ions from water in the batch equilibrium system.
Materials and MethodsFT-IR, SEM and XRD techniques were used to characterize the structure of the sample. To determine the optimum adsorption, the effect of important parameters such as pH, contact time, adsorbent weight and initial concentration were investigated. Also, thermodynamic study (Gibbs standard energy variations, enthalpy and entropy), isothermal studies (absorption capacity) and kinetic studies (absorbent effect with time) were investigated.
ResultsThe results showed that the magnetic adsorbent had the highest removal efficiency of nickel (II) at pH 7, contact time 60 min, adsorbent dosage of 200 mg, and maximum removable concentration of 400 mg/L.
ConclusionWith thermodynamic studies, it was determined that the reaction was endothermic and the spontaneous process was controlled using the entropy factor (ΔG°=-2.7 KJ/mol, ΔS°=+165.17 J/mol.K). In order to better understand the mechanism of adsorption, kinetics studies were carried out using the pseudo-first-order and pseudo-second-order models. Then, Langmuir and Freundlich adsorption isotherms were investigated to determine the adsorption capacity, and it was found that the adsorption data were well fitted to Freundlich model and the maximum adsorption capacity was 43.5 mg/g, which indicated high adsorption capacity and its multi-layers.Then, Langmuir and Freundlich adsorption isotherms were investigated and it was found that the adsorption data were well fitted to Freundlich model and maximum adsorption capacity (qmax=43.5 mg/g) was obtained which indicates good adsorption capacity of adsorbent and its multi-layers.
Keywords: Iron (III) oxide nanoparticles, Ni (II), Isotherm, Thermodynamics, Kinetics -
تحلیل امواج فشاری یکی از روش های موثر برای بررسی دقیق تر سیستم هاست. در تحقیق پیش رو، امواج آکوستیک منتشر شده به واسطه ی نفوذ گاز در ستون عمودی واکاوی شده است. فیزیک جریان گذرای دوفازی سه بعدی، برپایه ی روش حجم مایعات (V O F) شبیه سازی شده و برای محاسبه ی دقیق نوسانات فشاری حاصل از ورود گاز، از مدل آشفتگی L E S و روش بازسازی سطح مشترک H R I C استفاده شده است. منابع صوتی با نمونه برداری نوسانات فشاری از دیواره ی نفوذ و صفحه ی مجازی در جریان، توسط معادلات F W H استخراج شده و این منابع در لحظات جدا شدن و تشکیل حباب ها بررسی و با کمک معادله انتقال موج در دریافت کننده ها تعیین شده است. همچنین با کمک تبدیل فوریه(F F T) داده ها از میدان زمان به میدان فرکانس منتقل و با ثبت کمیت های آکوستیکی، تحلیل های طیفی ازجمله بررسی فرکانس جدا شدن حباب انجام شده است. شایان ذکر است با نمایش استقلال از شبکه، نتایج با داده های تجربی صحت سنجی شده است.
کلید واژگان: جریان دوفازی، امواج آکوستیک، آنالوژی لایت هیل، انتشار نویزTwo-phase flow systems analysis data are rear and cause major problems as efficient prediction in operation and control of the system or delay in identifying system parameters behavior.Analysis of the pressure waves through transient conditions can be an effective method to achieve precise results.In the present article, the bubble formation was studied using computational fluid dynamics (CFD) and the acoustic finite element method (FEM). The simulation conducted to obtain the aerodynamic noises generated by initiation and separation of bubbles in a vertical column. A Transient three-dimensional model is developed based on VOF method for tracking interface of two phases and large eddy simulation (LES) for an accurate calculation of pressure fluctuations. The model is simulated with the aid of the commercial software ANSYS FLUENT based on the finite volume method. To obtain convergence the implicit body force treatment is taken into account PISO algorithm is used to calculate a consistent result between velocity and pressure field. Pressure is discretized with PRESTO scheme. The RANS solution is used to calculate the initial flow field. In this case momentum is discretized with the second order upwind scheme and the geometric reconstruction scheme has been used as the volume fraction discretization scheme.Due to the importance of interface tracking in sound sources recognition and the problems which occur during adding LES model in the simulation, different interface reconstruction methods has been compared. High Resolution Interface Capturing scheme (HRIC) is selected as the best method.The Fofwcs Williams and Hawking (FWH) equation is used as an extension of the classical Lighthill aerodynamic acoustics for predicting far field noises. Sound sources are extracted by taking samples of pressure fluctuations from Wall penetration and virtual plane that is defined parallel to flow. These sources are investigated in the moment of separation and formation of bubble. In this paper are concluded that the largest fluctuation occur during necking of bubbles, while the smallest bubble produced the biggest peak in acoustic fluctuation curves.Besides time analysis, the pressure fluctuation is transferred from time domain to frequency by Fourier transform method and spectral analysis is performed on the data. The spectral analysis are compared to experimental results to better understand the effects of turbulence models, flow rate and methods of taking sample on the acoustic frequency response. The spectra of the filtered acoustic data (at airflow rate of 240 lit/min) shows a peak at about 40 Hz and is shown frequency response increases by the decrement of flow rate in bubbly flow. In this research frequency merge of two bubbles is demonstrated at 800 Hz and frequency response is used to estimate the bubble size.
Keywords: Two-phase flow, acoustic waves, lighthill analogy, noise emissions -
The multi-scale finite element method is used to study the vibrational characteristics of polymer matrix reinforced by single-walled silicon carbide nanotubes. For this purpose, the nanoscale finite element method is employed to simulate the nanotubes at the nanoscale. While, the polymer is considered as a continuum at the larger scale. The polymer nanotube interphase is simulated by spring elements. The natural frequencies of nanocomposites with different nanotube volume percentages are computed. Besides, the influences of nanotube geometrical parameters on the vibrational characteristics of the nanocomposites are evaluated. It is shown that reinforcing polymer matrix by single-walled silicon carbide nanotubes leads to increasing the natural frequency compared to neat resin. Increasing the length of the nanotubes at the same diameter results in increasing the difference between the frequencies of nanocomposite and pure polymer. Besides, it is observed that clamped-free nanocomposites experience a larger increase in the presence of the nanotubes than clamped-clamped nanotube reinforced polymers.Keywords: Finite element method, Vibrational behavior, Single-walled silicon carbide nanotube, Polymer matrix, Nanocomposites
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Objectives:
This study aimed at evaluating the trends in hypertension prevalence and control during the last decade.
Methods:
We drew upon four independent cross-sectional population surveys conducted in 1992, 1996, 1999 and 2001 in Isfahan, Iran.
Results:
The prevalence of hypertension had a downward trend from 31.8% in 1992 to 17.5% in 2001.the,mean systolic (SBP)and diastolic blood pressure (DBP) decreased in both. sexes.the mean SBP decreased from 142.24 to 116.8 mmHg in men and from 143.07 to113.7 mmHg in women.Regarding DBP, this decrease was from 92.5 to 73.8mmHg in men and from 92.2 to 72.8 mmHg in women (P<0.05). The proportion of , hypertensives who were aware of their condition increased from 46.2% to 50.1%. (P<0.05), and the proportion of hypertensive subjects with adequately controlled blood pressure increased from 2.8% to 12% (P<0.05).
Conclusion:
Hypertension care has improved significantly during the last decade, which is probably the result of the implementation of different population-based national plans
Keywords: HYPERTENSION. BLOOD PRESSURE. AWARENESS. CONTROLLED HYPERTENSION -
Between 1993-1996 seventy-three consecutive patients (33 M, 40 F, mean age 35.4) with newly diagnosed achalasia underwent one or more pneumatic dilatations with the Rigiflex balloon using a protocol of graded dilatation with a fixed inflation pressure of 10 psi and constant duration of 30 seconds for all patients without using fluoroscopy. Using Vantrappen's classification for assessment of response, excellent or good results were considered as cure and fair or poor results as failure. Duration of symptoms and the amount of weight loss before dilatation averaged 5.2 years and 10 kg, respectively. In 62 patients one, in 5 patients two, and in 4 patients three dilatations were performed. Dilatation failed in one patient because of previous surgery and was followed by perforation in one patient (1.4%) and bleeding in another patient (1.4%). Follow up period averaged 20 months (range 6-38 months) with a cure rate of 90% (57 excellent, 9 good) and failure rate of 6.8% (3 fair, 2 poor). We conclude that graded pneumatic dilatation without fluoroscopy is a safe and very effective treatment for achalasia with 90% of patients having a sustained response lasting at least for an average of 20 months.
Keywords: Achalasia, pneumatic dilatation, fluoroscopy, esophageal perforation -
سابقه و هدف
کولیت اولسروز مقاوم به کورتیکوستروئید از جمله مشکلات درمانی در بیماری های التهابی روده است. مطالعات متعدد در این مورد نشان داده است که پیش از درمان جراحی استفاده از سیکلوسپرین وریدی در حملات شدید ممکن است موثر واقع شود. اما در درمان موارد مقاوم که از همان ابتدا از سیکلوسپرین خوراکی استفاده شده باشد، تجربه کمتری وجود دارد. در این مطالعه اثربخشی و عوارض سیکلوسپرین در حملات شدید کولیت اولسروز مورد ارزیابی قرار گرفته است.
مواد و روش هاچهار بیمارکولیت اولسروز که بر اساس معیارهای Truelove Witts مبتلا به حمله شدید و مقاوم به استروئید بودند و 2 بیمار کولیت اولسروزی که وابسته به استروئید بودند و در آنها بیماری به صورت کامل کنترل نشده بود مورد مطالعه قرار گرفتند. 2 بیمار سیکلوسپرین خوراکی با دوز پایین (mg/kg 5 £ روزانه) دریافت داشتند. 4 بیمار از ابتدا سیکلوسپرین خوراکی به همان میزان دریافت داشتند. متوسط مدت مداوا 3/15 هفته بوده است. پاسخ به درمان براساس تعداد دفعات اجابت مزاج، رکتوراژی و مشاهدات کلونوسکوپی ارزیابی گردید.سنجش سطح خونی سیکلوسپرین در هفته های اول، دوم، چهارم، ششم، هشتم، دهم، چهاردهم و هجدهم به عمل آمد. تمامی بیماران همزمان کورتیکواستروئید، سولفاسالازین (یا 5-ASA) و پنج بیمار آزاتیوپرین (یا 6MP) دریافت می کردند.
نتایجپس از مصرف سیکلوسپرین وریدی، در 2 بیمار، از شدت بیماری کاسته شد اما در مجموع از 6 بیمار که تحت مداوا با سیکلوسپرین خوراکی با دوز پایین قرار گرفتند. تنها در 1 مورد بهبودی به دست آمد. بر اساس آنالیز آماری در بیماران هیچگونه بهبودی واضح در متوسط امتیاز متغیرها به دست نیامد. نهایتا پس از 18 هفته 3 نفر کولکتومی شدند و 2 نفر پاسخ قابل توجه نداشتند. در 4 بیمار عوارض جانبی ظاهر شد که شامل سینوزیت، ریزش مو، پرموئی، هیپرپلازی لثه، کاهش شدید لیبیدو و افزایش کراتی نین هر کدام در یک بیمار و ترمور در 2 بیمار بوده است.
استنتاجدر تجربه محدود فوق، دوز پایین سیکلوسپرین در کنترل کولیت اولسروز مقاوم به درمان استاندارد بی تاثیر و با عوارض جانبی قابل توجه همراه بوده است.
کلید واژگان: کولیت اولسروز مقاوم به درمان، سیکلوسپرین، مشاهدات کلونوسکوپیBackground and
PurposeTreatment of refractory ulcerative colitis (ÜÇ) is a problem in the intestinal tract diseases. Different researches have shown that intravenous administration of cyclosporine before surgical operation can be effective. But less is known about the oral administration of cyclosporine given at the onset of the treatment of refractory ÜÇ. Ïn this study effectiveness and side effects of cyclosporine have been evaluated in the severe case of ÜÇ.
Materials And MethodsFour cases of ÜÇ. at severe attack, conformed on the basis of Truelove and wilk criteria were found resistant to steroids, and two patients were dependent to steroids whose disease was not controlled completely and were under our investigation. Two patients received intravenous cyclosporine 4 mg/kg daily for two days and followed by low does of (≤ 5mg/kg daily) oral administration of cyclosporine. The same low doses of oral cyclosporine were administered in four patients at the onset of treatment. Mean duration of treatment was 15.5 weeks. Response to treatment was evaluated on the basis of frequency of defecation, rectorhalgia and colonoscopic appearance. Blood level of cyclosporine in the, 9, 4, 6, 8, 10, 14 and 18 weeks was measured. Âll the patients simultaneously received corticosteroides sulfasulazin 5-ÂSÂ, and patients received Âzathioprine (6MP).
ResultsThe severiarity of disease was decreased after intravenous administration of cyclosporine within 2 months, but one of all six patients was recovered after the administration of low dose of oral cyclosporine. Ôn the basis of statistical analysis there was no apparent recovery in the mean score of variants. Finally after 18 weeks three patients were colectomy, and there was no significant response in 2 patients. Ïn four patients there was side effects of sinusitis, gum hyperplasy severe reduction of libido and increase in keratinin in one patient, tremor was observed in 2 patients. Çonclusion: Ïn our limited experience,low doses of cyclosporine in controlled standard refractory ÜÇ was not effective and was followed by side effects.
Keywords: Refractory ulcerative colitis, Çyclosporine, Çolonoscopy appearance
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