n. fallah

Due to the environmental pollution caused by the production and consumption of cement, the demand for new and environmentally friendly methods to improve and strengthen the soil is increasing. In addition, reinforcing the soil with steel fibers improves the mechanical properties, including the formability and bearing capacity of the soil. The purpose of this research is to evaluate the effect of zeolite on the behavior of cemented sand soil reinforced with steel fibers. In the following, the unconfined compressive strength (UCS) test was used to check the compressive strength, and the flexural strength (FT) test was used to check the flexural. It should be mentioned that to improve the soil from cement in the amount of 5% by weight, zeolite in the amount of 0, 25, 50, 75 and 100% was used instead of cement, as well as steel fibers in the amount of 2% and random distribution in the curing of 28-day. In the results of unconfined compressive strength tests, the best replacement percentage of zeolite instead of cement in sandy soil was 25%, which initiated an increase in unconfined compressive strength and an increase in the failure strain of the sample. In the results of flexural strength tests, 25% of zeolite to replace cement in sandy soil affected the greatest increase in flexural strength and increased soft behavior. In addition, with the addition of steel fibers, the samples endured much more displacements than those without fibers.

According to their functions, the media can provide the ground for the participation of more people in the society in sports activities, especially for teenagers and young people. The purpose of this research is to provide a model for improving the quality of media programs in order to attract teenagers and young people to participate in sports and physical activity. This research has been done with the fundamental purpose and grounded theory method (systematic model of Strauss and Corbin) and with a qualitative approach. Also, the data has been collected in the field. The statistical population of this research includes experts familiar with the media, sports participants, sports media and psychologists of adolescents and young people, as well as researchers, university professors and people involved in sports media, public relations managers of sports organizations and some young and adolescent athletes. It has been mentioned that 25 people have been selected by targeted sampling method. In data analysis for open, central and selective coding, the qualitative approach of grounded theory was used and open coding was done by analyzing the interviews. The model for improving the quality of media programs in order to attract teenagers and young people to participate in sports and physical activity is based on causal conditions (human resource, organizational cooperation and organizational structure) and taking into account extractive strategies (media content, programming, planning and evaluation) which is affected by background conditions (infrastructure and cultural) and intervening conditions (economic and legal political factors), consequences such as sports development, health improvement and social effects can be observed. Specialized programming with special attention to the benefits of physical activity, the sports needs of teenagers and young people, the facilities and equipment available in sports centers, etc. can improve the quality of media programs and help attract different groups, especially teenagers and young people, to sports.

This article proposes a new approach for identifying damage in structures through model updating. The approach is based on principal component analysis (PCA) of strain-based power spectral density (PSD) data. The proposed method detects damage, identifies damage location, and quantifies damage severity using an innovative sensitivity equation of strain-based data on a least square optimization. The data is obtained from incomplete measured structural responses, and the approach utilizes frequency domain data where changes in stiffness matrix of elements model damage. One of the crucial components for successful model updating is evaluating an accurate sensitivity relation. Highly sensitive structural indices such as PSD data require a valid sensitivity relation to yield satisfactory results. The PCA technique provides an advantage by transforming PSD data to PCs with the most significant changes and ignoring PCs that correspond to low changes caused by measurement errors. The presented approach embeds the PCA of incomplete PSD data and measured strain data for a damaged structure into a mathematical formulation to obtain an appropriate sensitivity equation. To prevent weakening the sensitivity equation, the proposed formulation does not employ derivatives of the PCs. The proposed method is applied to two steel structures, a 2-D truss and a 2-D two-story two-bay frame, to demonstrate its performance as a strong damage identification algorithm, even in the presence of measurement errors. Comparative observations indicate that the results obtained by the provided sensitivity equation and strain-based PSD data are more appropriate than the results of other strain-based methods such as PCA-FRF or using only PSD data.

The diagnosis of the location of structural damage and its extent after an earthquake using numerical methods is one of the ongoing research topics. After the occurrence of damage in a structure and a reduction in its stiffness, the dynamic characteristics of the structure change, and therefore, assessing the changes in its dynamic characteristics can be used as an indicator for detecting damage. In this article, an advanced technique called Direct Stiffness Calculation (DSC) and a new damage index based on flexural stiffness variations (SVI) are utilized for damage detection in structures. Initially, the proposed technique is examined on a steel beam with known specifications. Then, a reinforced concrete moment frame is modeled, and after extracting its dynamic characteristics, it is subjected to a pushover analysis to create a damage scenario without direct intervention. Based on the analysis results, the plastic hinge formation location at both ends of the beam is selected as the probable location of damage in the floor. By using the modal information of the damaged structure and calculating the SVI in the beams of the floors, it is determined that this index can accurately and significantly distinguish the location of damage only by knowing the first mode of the structure and with sufficient magnification compared to other points. Furthermore, the results demonstrate that with this method, it is possible to accurately determine the location of damage even without knowing the dynamic characteristics of the intact structure and solely with the information of the damaged structure.

Earthquakes cause a lot of damage to structures. A quantitative estimate of the amount of damage to the structure always seems quite necessary after an earthquake. For this purpose, seismic damage indices have been introduced as dimensionless quantities that can report the extent of damage using various criteria. This quantitative assessment can help make decisions about the process of improving, repairing, and strengthening structures. This paper presented a new stiffness-based damage index with simple formulation by performing pushover analysis on existing concrete models and applying the results. Using the capacity curve obtained from the pushover analysis output, this index can provide a quantitative estimate of the amount of damage to the entire structure. To validate the results, damage estimation was also performed using several reliable models such as the Park-Ang model and then compared with the proposed index results. Then, a series of theoretical suggestions were presented to address the existing weaknesses, which were implemented, and new results were obtained. Finally, the implemented reform proposals led to an improvement in the performance of the proposed index, resulting in excellent accuracy due to the simple computational process compared to the complex implementation of the Park & Ang index.

In this study, the effects of using rubber ash on the mechanical properties of plain concrete were experimentally investigated. The main purpose of this study was to determine the proper fraction of rubber ash to be utilized in concrete by investigating the mechanical properties of concrete such as elasticity modulus, compressive strength, tensile strength, bending strength, and fresh concrete slump. Four different fractions of rubber ash (2.5, 5, 7.5 and 10% of cement weight) were added to the concrete mixture. Based on the results achieved from the tests conducted on the specimens, it could be deduced that adding rubber ash to concrete considerably increased compressive and bending strength and reduced the slump flow. It also increased tensile strength and elasticity modulus at a lower level.

Diarrheal strains of Escherichia coli (DEC) are common pathogens that cause acute intestinal diseases in humans through the consumption of contaminated food. The present study was conducted on 240 samples including strudel, pizza, sandwiches, and salad. E. coli was isolated by conventional culture tests and confirmed by PCR (using uidA gene). Out of 240 samples, 123 isolates (51.25%) were found positive as E. coli. Amongst 103 isolates (42.9%) contained no pathogenic genes. 11 isolates (4.6%) were identified as EPEC, 5 isolates (2%) as EHEC, 2 isolates (0.8%) as EAEC. ETEC and EIEC were not detected in any of the samples. Due to the contamination of ready-to-eat food samples with intestinal pathogenic pathotypes, continuous monitoring of the field of ready-to-eat food is suggested.

Due to cyclic nature of applied pressure on engineering structures like airplane fuselages, storage tanks, and ship hulls, members evolving the through crack, results in the sudden failure; so-called as fatigue fracture. Investigation of this type of fracture is an important issue for a successful design of these structures. On the other hand, the finite volume method (FVM) as a well-known method in the computational mechanics, is found as a powerful method for the bending analysis of beams and plates, with no matter of thickness varies from very thin to moderately thick beams and plates. Usually in this method, according to the classic approximation of the field variables, the displacement at a favorite point on the face of control volume is approximated linearly in terms of displacement of cell centers adjacent to that face. However, accuracy of the approximation can be increased by using of the higher-order approximation techniques like Moving Least Squares (MLS) approximation which is well suited in the mesh free methods. In this research the MLS approximation is used in the finite volume method, and the Reissner plate with a through-the-thickness crack (through crack) is analyzed for the computation of the stress intensity factors (SIFs) at the crack tip. First, the influence of the size of support domain as one of the key parameter of the MLS approximation is investigated. By using of the obtained value of the support domain size, the SIF values of several benchmark cracked plates are calculated. The obtained results compared with the values obtained by the other analytical and numerical methods presented in literature where good agreement can be seen. These comparisons indicate the capability of the presented FVM for studying of the cracked plates. Furthermore, the size of support domain found in this research can be considered as the convenient values for the FVM analysis of cracked plate in the future researches.

Nails can act as a protective, defensive and beauty cover of the phalanges. The dermatologic disorders as well as the systemic diseases and trauma can produce change in the nails. Normal variations of nails are important to recognize and distinguish from nail diseases. There is not enough information about the prevalence of nail disorders in children. In this study, we have determined the prevalence of leukonychia, pitting and koilonychia in Tehran elementary schools. Examinations were conducted among 1902 elementary students and leukonychia in 16.9%, pitting in 2.1% and koilonychia in 1.8% were found. There was no difference in the overall frequency of the nail disorders between males and females. The prevalence of leukonychia and pitting was more frequent in the 5th grade than first grade and in 11th educational area of the education ministry. There was not any important relation between the nail disorders and dermatologic disorders or systemic diseases, trauma may be the most important factor in these nail disorders. As regards to the importance of diagnosing the hypochromic anemia and cystine deficiency, we suggest a scientific research about koilonychia and those disorders.