THE INFLUENCE OF EXTRUSION DIE ANGLE DURING THE HOT EXTRUSION PROCESS OF AL ALLOYS

One of the most important parameters for the hot extrusion process effecting the deformation force, material flow, microstructural and mechanical properties of the extruded material is the Extrusion Die Angle (EDA). In this investigation, the effects of EDA on load, material flow and microstructure of hot extruded commercially pure aluminum has been studied. The Finite element simulation were carried out using Deform 3D. Finite element modeling shows that the values of the equivalent plastic strain and its distribution, flow material and deformation forces depend extremely on deformation temperature, reduction and EDA. To estimate the reliability of the numerical analysis, the FE model was validated using experimental results. The results showed that the lowest extrusion force occurs in an optimum die angle for each reduction. Optimum EDA obtained 16, 18 and 23 degrees at reductions of 50%, 60% and 70%, respectively. Also, material flow, inhomogeneity of microstructure and the equivalent plastic strain increases with increasing of EDA

Thermal Behavior of Double Skin Buildings

Most energy losses will be made by skins, so offering optimized solution helps in energy saving. Glass as outdoor skin is considered the weakest part of building from energy loss viewpoint. Therefore a solution should be found to minimize energy losses in building meanwhile providing natural light. Double skin facades as a suitable solution for achieving this goal are considerable. Buildings with double skin façade can have better function than normal skin façade. So, this article is focused on thermal function of different forms of these buildings. This article by studying behavior of different forms intends to analyze the effect of general form of building on thermal function of double skin façade and attempt to categorized different situations so that recognize situations and conditions which may tangle classic behavior of double skin facades. Research method is quasi-experimental. Statistical population includes studying features of 10 building forms. The result of this analytical approach indicates classic function of double skins changes with change of general form of building. Keywords: energy saving, double skin facades, thermal behavior, building form

Influence processing parameters of FDM 3D printer on the mechanical properties of ABS Parts

250-2573D printing has been a type of additive manufacturing (AM) that creates parts by adding or printing thin layers of material on top of each other using computer-aided design (CAD) models. Fused deposition modeling (FDM) is a 3D printing process that produces parts by heating, extruding, and depositing the thermoplastic polymers. FDM-fabricated products have been becoming increasingly popular in various industries such as medical, electronics, automobile, pharmaceutical, etc. This study has been carried out on a set of standard samples out of acrylonitrile butadiene styrene (ABS) which have been produced using the FDM process. A comprehensive mechanical property evaluation has been performed to determine the influence of the infill density and layer thickness of ABS (FDM-fabricated) on the ultimate tensile strength, elastic modulus, yield strength, fracture strain, and toughness (energy absorption) using a tensile test. From the result analysis, it has been found that infill density and layer thickness haveimportant effects on the tensile properties. The behavior investigation of ABS-filament freeform fabrication has shown that infill density of 100% and a layer height of 0.1 mm achieve optimized process parameters values

Proposing a criteria-based assessment pattern for architectural design studios

Background and Objective:Architecture education is one of the most important issues in the development of architecture. In this decade, universities and colleges are increasingly committed to effective assessment of students to improve students' learning, and not just giving them a grade. The importance of examining this issue is that the assessment methods for architectural education systems that are based on design and studio, need more research than other fields. In the field of architectural design, unlike other fields students do not take part in written, descriptive, or multiple choice tests, and it is much more difficult to turn what architecture students offer into a score in comparison to other disciplines. One of the important pillars of education is evaluation. The crit is the most common assessment method and having feedback in architecture. In research on the crit, little attention was paid to the sense and reception of students from the process of evaluation, while being recognized as one of the greatest student's dissatisfaction. The purpose of this research is to understand the students' viewpoints about the current methods of the crit, in addition of studying student designing capability, evaluate the design and process, in a way to judge architectural projects to improve the quality of arbitration and education in this field, شnd provides model for the correct measurement and judgment method, based on goals and design process, relying on criteria which are based on educational objectives. Methods: In this research, 40 undergraduate and postgraduate students at Sure university school of architecture were selected through cluster sampling as focus groups, and experts has been used to weight the criteria by AHP method. Findings: Among them, critical explanation with weight of 38% is more important, after that the development of the chosen idea with 21%, the concept and design solution, with 17% & 14% eventually the final design with 10% is the least important of the five criteria. Conclusion: In order to evaluate the architectural design based on the students' opinion and the previous methods of evaluation, a model was proposed. The proposed pattern correctly plays all four roles of evaluation - feedback, motivator, guide, evaluation-communication. With this model, students are graded based on the quality of their work and this have nothing to do with the performance of other students; and therefore there is no comparison between students. At the same time, because a number is presented in the end, the rank of the student is determined among the other students, while each person's work is compared to his own. In this model, the criteria are defined and prioritized based on the objectives of the course. The proposed model can provide strategies for practitioners of architecture education, such as lecturers and students to enhance their learning   ===================================================================================== COPYRIGHTS  ©2019 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.  ====================================================================================

Influence processing parameters of FDM 3D printer on the mechanical properties of ABS parts

3D printing has been a type of additive manufacturing (AM) that creates parts by adding or printing thin layers of material on top of each other using computer-aided design (CAD) models. Fused deposition modeling (FDM) is a 3D printing process that produces parts by heating, extruding, and depositing the thermoplastic polymers. FDM-fabricated products have been becoming increasingly popular in various industries such as medical, electronics, automobile, pharmaceutical, etc. This study has been carried out on a set of standard samples out of acrylonitrile butadiene styrene (ABS) which have been produced using the FDM process. A comprehensive mechanical property evaluation has been performed to determine the influence of the infill density and layer thickness of ABS (FDM-fabricated) on the ultimate tensile strength, elastic modulus, yield strength, fracture strain, and toughness (energy absorption) using a tensile test. From the result analysis, it has been found that infill density and layer thickness haveimportant effects on the tensile properties. The behavior investigation of ABS-filament freeform fabrication has shown that infill density of 100% and a layer height of 0.1 mm achieve optimized process parameters values

Izolati streptokoka grupe B u mokraći i njihova antimikrobna osjetljivost u skupini iranskih žena: učestalost i sezonske razlike

Streptococcus agalactiae is one of the uropathogens responsible for urinary tract infections (UTI ) in children, pregnant women, and elderly people with chronic underlying diseases. This study was performed to determine the prevalence of urinary tract isolates of group B streptococci (GBS) in a group of females referred to a referral University Hospital in Iran. In this retrospective cross-sectional study, urine analysis and urine culture results of all female subjects referred to the laboratory of the Rasoul-e-Akram Hospital, Tehran, Iran in 2010 were reviewed. Bacteriuria, colony count, pyuria and demographic data of patients were also evaluated. In this study, 10,256 females were investigated; 2061 (20.1%) of them had positive urine cultures. GBS was the isolated microorganism in 184 (8.92%) cases, yielding a prevalence of 1.79% in total study population. The mean age of subjects with positive GBS cultures was 48.24}18.8 years, with a higher prevalence recorded in the 51-60 and 21-30 age groups. The highest rates of cultures positive for GBS were seen in December and January. GBS was found to be sensitive to the following antibiotics: cephalothin (100%), norfloxacin (96.9%), ampicillin (96%), nitrofurantoin (95.5%), and vancomycin (95%). In this study, GBS showed greatest resistance to tetracycline (81.6%) and co-trimoxazole (68.9%). In conclusion, the prevalence of GBS in females with suspected UTI is relatively low; however, attention to the age and susceptibility pattern of antibiotic treatment for UTI caused by this microorganism is necessary.Streptococcus agalactiae je jedan od uropatogena odgovornih za infekcije mokraćnog sustava kod djece, trudnica i starijih osoba s kroničnim osnovnim bolestima. Cilj ove studije bio je utvrditi učestalost izolata streptokoka grupe B u mokraćnom sustavu skupine žena upućenih u referentnu Sveučilišnu bolnicu u Iranu. U ovoj retrospektivnoj studiji obrađeni su rezultati analize mokraće i kulture mokraće svih ženskih osoba upućenih u laboratorij Bolnice Rasoul-e-Akram u Teheranu, Iran tijekom 2010. godine. Obrađeni su i podaci o bakteriuriji, broju kolonija, piuriji, te demografski podaci svih bolesnica. Od ukupno 10.256 ispitanih žena pozitivna kultura mokraće utvrđena je u 2061 (20,1%) žene. Streptokok grupe B bio je izolirani mikroorganizam u 184 (8,92%) slučajeva, dok je njegova ukupna učestalost u čitavoj ispitivanoj populaciji bila 1,79%. Srednja dob žena s pozitivnom kulturom streptokoka grupe B bila je 48,24}18,8 godina, s većom učestalošću u dobnim skupinama od 51-60 i 21-30 godina. Najviše stope pozitivnih kultura streptokoka grupe B zabilježene su u prosincu i siječnju, a mikroorganizam je pokazao osjetljivost na slijedeće antibiotike: cefalotin (100%), norfloksacin (96,9%), ampicilin (96%), nitrofurantoin (95,5%) i vankomicin (95%). U ovoj studiji je streptokok grupe B pokazao najveću otpornost na tetraciklin (81,6%) i kotrimoksazol (68,9%). Zaključuje se kako je učestalost streptokoka grupe B kod žena sa sumnjom na infekciju mokraćnog sustava relativno niska, međutim, pozornost treba posvetiti dobi bolesnice i profilu osjetljivosti antibiotske terapije za infekciju mokraćnog sustava uzrokovanu ovim mikroorganizmom