Background: Recently, multileaf collimators (MLC) have become an important part of any LINAC collimation system because they reduce the treatment planning time and improve the conformity. Important factors that affect MLCs collimation performance are leaves material composition and their thickness. Objective: In this study, we investigate main dosimetric parameters of a typical MLC including dose in the buildup point, physical penumbra as well as average and end leaf leakages. Effects of the leaves geometry and density on these parameters are evaluated. Materials and Methods: In this analytical study, calculations were performed by using phase space data for Varian ix just above MLC and BEAMnrc/ DOSXYZnrc for SSD=100cm and in a water phantom. Results: Based on the results, a new MLC with improved dosimetric parameters is proposed. The physical penumbra for proposed MLC is 4. 7mm was compared to 5. 16 mm for Millennium 120 leaf. Average leakage in our design is reduced to 1. 16% compared to 1. 73% for Millennium 120 leaf, the end leaf leakage suggested design also reduced to 4. 86% compared to 7. 26% for Millennium 120 leaf. Conclusion: The results show that the proposed MLC could improve the dosimetric parameters and conformity of treatment planning.

The acceleration process starts with the evaluation and selection of startups. Identification of the criteria used in the evaluation and selection process is important on the one hand for Accelerators, and on the other hand, for the admission of applicants in acceleration periods. This study has been used mixed method to identify the criteria for evaluating opportunities in Accelerators. In this regard, first, by systematically reviewing articles related to Accelerators, as well as interviewing the experts, the evaluation criteria from three dimensions of the problem-solution, the entrepreneurial team and the accelerator were derived. Then, by analyzing the collected questionnaires completed by directors and trainers of active Iranian Accelerators, opportunity assessment criteria and reasons for non-acceptance of opportunity were examined using SPSS software. The results of factor analysis show that Accelerators use 11 criteria to evaluate the quadruple risks of market, technology, agency and capital. Clustering the importance of evaluation criteria for Accelerators shows that evaluation approaches can be divided into two groups of team-oriented and market-oriented evaluation

Cost and safety are two most important factors involved in the design of civil engineering systems and structures. Thus, the optimal design of structure dimensions is of big importance in order to reduce the cost of construction while meeting the safety requirement and the design constraints. Up to now several algorithms have been developed and used for optimization of different civil engineering problems. One of these algorithms is the Particle Swarm Optimization (PSO) which is a swarm intelligence based algorithm inspired by the social behavior of animals such as fish schooling and bird flocking to solve continuous problems. In this paper, an optimization model is developed for the optimal design of flood control systems which contain both detention dam and bottom outlet. The proposed model uses the powerful PSO algorithm as the search engine and The "Transport Module" of "SWMM" as the hydraulic analyzer of the system. The applicability of the model to solve real world problem is verified by the optimal design of of South Pars flood control system which contains both detention dam and bottom outlet. The results show that the proposed optimization model can considerably reduce the total costs of flood control systems.

Background: Nowadays, advanced radiotherapy equipment includes algorithms to calculate dose. The verification of the calculated doses is important to achieve accurate results. Mostly homogeneous dosimetric phantoms are available commercially which do not mimic the actual patient anatomy; therefore, an indigenous heterogeneous pelvic phantom mimicking actual human pelvic region has been used to verify the doses calculated by different algorithms. Objective: This study aims to compare the planed dose using different algorithms with measured dose using an indigenous heterogeneous pelvic phantom. Material and Methods: In this experimental study, various three dimensional conformal radiotherapy (3D-CRT) plans were made using different doses calculated by algorithms. The plans were delivered by medical linear accelerator and doses were measured by ion chamber placed in the indigenous pelvic phantom. Planned and measured doses were compared with together and analyzed. Results: The relative electron densities of different parts in the pelvic phantom were found to be in good agreement with that of actual pelvic parts, including bladder, rectum, fats and bones. The highest percentage deviations between planned and measured dose were calculated in the single field for Superposition algorithm (3. 09%) and single field with 45˚ wedge for Superposition (3. 04%). The least percentage deviation was calculated in the opposite field for Convolution which was-0. 08%. The results were within the range of ± 5% as recommended by International Commission on Radiation Units and Measurement. Conclusion: The cost-effective indigenous heterogeneous pelvic phantom has the density pattern similar to the actual pelvic region; thus, it can be used for routine patient-specific quality assurance.

Background: Intensity Modulated Radiation Therapy (IMRT) technique is an advanced method of radiotherapy leading into the development of Flattening Filter-Free (FFF) medical linear Accelerators (Linacs). Monte Carlo simulation has been a standard method for calculation of Particle transport due to precise geometry and material specifications. Objective: This study is to obtain the design optimization of Flattening Filter Free (FFF) for 6 MV Linac machine. Material and Methods: In this simulating study, EGSnrc user code was used to simulate Particles emitted from head of linac 6MV Varian to achieve the most suitable filter in FFF linac design. Monte Carlo simulation results of the PDD and profile, on the 10 × 10 cm2 field, were compared with the measurements. Differences in small profile beams from Monte Carlo simulation were also evaluated between FF and FFF linac. Results: The spectrum on Monte Carlo simulation in isocenter was compared with Treatment Planning System (TPS) for each filter variation. The slight differences of average spectrum are simulated using 2 mm copper filter and FakeBeam with-1. 52 ± 3. 82% and-3. 13 ± 3. 61%. Whereas, for PDD and profiles, each variation has an average difference of 7. 10 ± 0. 70% and-5. 99 ± 1. 39%. Conclusion: FakeBeam filter is a proper filter for the use of linac design 6MV Varian. It is necessary to decrease the kinetic energy of electrons to perform MC simulations on FFF linac.

Increasing population and food demand, disproportionate cultivation and annual production of various agricultural products with market needs and low productivity of the agricultural sector and the loss of water and soil resources have made it necessary to determine and implement the country's optimal cropping pattern. In this study, due to the limitations and problems of classical methods in order to reduce processing time and improve the quality of solutions, the Multi-Objective Chaotic Particle Swarm Optimization was used to determine the optimal cultivation pattern of Sistan plain in optimal conditions and deficit irrigation. The results of the Multi-Objective Chaotic Particle Swarm Optimization for the dominant cultures in the region showed that the current cropping pattern of the region is not optimal and with the implementation of the proposed model, the profit per unit area under cultivation will increase. The results of application of deficit irrigation during different growing periods of wheat, barley, alfalfa, sorghum, watermelon and grapes showed that applying deficit irrigation in this plain is not a good strategy and therefore only a full irrigation strategy is recommended. The results of sensitivity analysis of the model showed that at low prices, farmers reaction is less and at higher prices more reaction to price changes and with increasing prices, the program efficiency is lower.

Background: With the advent of Intensity Modulated Radiotherapy (IMRT) and recently, Volumetric Modulated Arc Therapy (VMAT), treatment planning using Flattening Filter Free (FFF) beams can meet all of the energy requirements in radiation therapy clinics. Manufacturers of linear Accelerators no longer need to install a flattening filter (FF) in gantry head. This study aims to provide evidence of the superiority of FFF to FF through both dosimetric measurements and clinical treatment plans. Materials and Methods: A 50×50×50cm3 water phantom was created in the RayStation treatment planning system (TPS) for dosimetry comparisons. Flat beam profiles were generated using FFF beam through an optimization process for 10×10 to 30×30cm2 field sizes. Next, a comparison of treatment plans was made using 21 Head and Neck and 14 Lung/Mediastinum treatment sites using 6MV and 6MV-FFF beams. Results: Using FFF beams, profiles with flatness and symmetry identical to or better than those of the flattened beams were produced. At the very edge of the optimized plans for FFF beams, horns had the highest gamma index deviation <1. 5% of the normalized dose. For clinical plans evaluated, most of the mean doses to organs-atrisk (OAR) volumes receiving 5% to 30% of the prescription dose were reduced with FFF beams. Conclusion: These results indicate the feasibility of delivering flat beams with FFF quality and producing treatment plans with equal or higher qualities in PTV coverage while achieving better sparing of OAR which will allow escalation of target dose if desired. Plus, removing FF will simplify the gantry head and reduces quality assurance and machine maintenance efforts.

Various amounts of dicyandiamide (Dicy), two grades of epoxy resins, i.e. Epiran 06 and Epikote 828, and three different Accelerators including benzyl dimethyl amine (BDMA), 3-(4-chlorophenyl)-1, 1-dimethyl urea (Monuron) and 2-methyl imidazole (Im) were used in curing of Dicy/epoxy resin system. Both of the used epoxy resins were based on diglycidyl ether of bisphenol A (DGEBA). The effects of type and concentration of Accelerators on curing behavior were studied by differential scanning calorimetry (DSC) method in dynamic or non-isothermal mode. The optimum concentration of Dicy for curing of epoxy resins was obtained based on the glass transition temperature of the cured epoxy/Dicy formulations. The maximum glass transition temperature of 139oC was obtained at the stoichiometric ratio of Dicy to epoxy of 0.65. The results showed that BDMA has a broader curing peak in DSC and starts the cure reaction earlier than the others. However, Monuron has a narrow curing reaction peak with good cure latency. The tensile properties of Dicy-cured Epiran 06 and Epikote 828 epoxy resins reinforced with chopped strand mat showed that these two epoxy resins have similar mechanical properties. For composites based on the Epiran 06 and Epikote 828 reinforced with 40 wt % glass chopped strand mat, tensile strength and modulus were 156 and 153.4 MPa and 11.6 and 12.4 GPa, respectively.

Aims: This study is aimed at developing a university-based incubators taking into account Accelerators. The university-based incubators are one of the key elements of sustainable entrepreneurial ecosystems, which act as the entrepreneurship ombudsman. Improving the model’ s incubators would foster innovation and commercialization of research. Methods: This study, using a qualitative approach based on Grounded theory, was conducted through the theoretical sampling and data gathering from among 18 academic entrepreneurs who could benefited from acceleration centers services, incubators managers and experts, accredited managers and experts in Accelerators as well as experts in the field of research concepts. Also, the data were analyzed using interview tools during three common coding steps in the Glaser approach. Conclusion: The findings show that the acceleration characteristics in the incubator model are determined by the indicators identified in this study as center features. Accelerator-based incubators need to use strategies such as modeling successful international examples, validating ideas and business, accessing to the Internet to achieve their goals. Finally, the results indicate the impact of environmental contexts and such as stakeholders. Applying the resulting model can lead to various outcomes such as promoting the interests of academic entrepreneurs, creating jobs, transferring knowledge and technology, creating sustainable business, creating new businesses and social benefits.

Accelerators are a relatively new type of institutions which support entrepreneurial ecosystem across the world that rapidly grows and they offer the necessary services to startups in the early stages of their development. The emergence of this phenomenon has opened up a new path in front of the entrepreneurs and in a short period of time, the startups have developed very quickly. Identifying success factors of Accelerators can minimize failure of the startups. The determinants of success in the field of biotechnology Accelerators, has shaped the main question of this research. After reviewing literature, interviewing with managers and experts in the field of biotechnology, twenty factors have been identified. After designing the questionnaire and distributing it among selected statistical sample, by using Binomial test, the important success factors have been identified. Some factors such as strategic intent of accelerator for development and teams’ support, teams’ investigaton criteria of ideas and capabilities, presented services to the teams, training programs, accessibility to market, customer and investor networks through and after the accelerating program.