Modeling and Optimization of a Novel Micro-Opto-Xray Imaging Lens

Micro-Electro-Opto-Mechanical-Systems or MOEMS have potential applications inter alia in biomedical research. For instance, studies of the Bystander Effect require controlled irradiation of biological cells with focused X-rays to reveal the mechanisms occurring. X-ray focusing may be achieved using an adaptive optic micro-lens in which focusing is entirely reflective and therefore compatible with broad band illumination, an improvement over diffractive systems such as zone plates. Such a micro-lens can be microfabricated in the form of a bent-cantilever beam made from two dissimilar materials (polyimide and gold) in a thermal bimorph configuration, actuated with a micro heater. The parallel horizontal slots on the beam provide the transmission and focusing functions, while the heater provides control of the focal length through variation of the beam’s curvature. This novel system has been named 1D-MOXI (Micro-Opto-X-ray Imaging) and a basic system has already been made and tested thermo-mechanically. The present work focuses on details of the geometry of the deformed slotted micro-beam lens element under thermally derived strain, using finite element analysis, and suggests an optimized MOEMS design, giving prescribed curvature of the lens through changing the number and the dimensions of the slots. The study reveals the localized stress and the small deviations of the micro-lens behavior from that of perfect spherical geometry. The focal length variation with temperature is compared with the experimental values and those predicted by an analytical model

The effect of actual currency rate on total productivity of factors of production of industrial sector of Iran

The aim of the present research is to study the effect of actual currency rate on total productivity of factors of production in industrial sector of Iran. In other words. the effect of the actual currency rate on total productivity of factors of production in industrial sector of Iran was studied by using econometric method of OLS (ordinary least squares)  during 1974- 2006. On this basis, the effects of the actual rate of foreign currency, the openness rate of economy, foreign investment, private and public investment on total productivity of factors of production in the industrial sector of our country were analyzed and studied. In order to calculate total productivity of factors of production Divisia method has been used. The estimation outcome and model estimation indicate that there is a significant and reverse relationship between actual currency rate and economic openness degree with total productivity of factors of production in long-term. The results of this estimation indicate that, due to the dependency of the industry and economy of Iran to imported intermediate and capital goods having modern technologies, which are in turn the results of the R & D activities of developed countries; therefore, with an increase in actual currency rate the investment rate decreases due to capital goods becoming more expensive that this follows with a decrease in total productivity of factors of production. Also, the relationship between the openness rate of economy and total productivity of factors of production indicate that, due to the existence of some weaknesses and problems in Iran’s structures and especially in social structures, there is an increase in openness rate of economy resulting in a decrease in total productivity of factors of production of the industrial sector

The effect of actual currency rate on total productivity of factors of production of industrial sector of Iran

The aim of the present research is to study the effect of actual currency rate on total productivity of factors of production in industrial sector of Iran. In other words. the effect of the actual currency rate on total productivity of factors of production in industrial sector of Iran was studied by using econometric method of OLS (ordinary least squares)  during 1974- 2006. On this basis, the effects of the actual rate of foreign currency, the openness rate of economy, foreign investment, private and public investment on total productivity of factors of production in the industrial sector of our country were analyzed and studied. In order to calculate total productivity of factors of production Divisia method has been used. The estimation outcome and model estimation indicate that there is a significant and reverse relationship between actual currency rate and economic openness degree with total productivity of factors of production in long-term. The results of this estimation indicate that, due to the dependency of the industry and economy of Iran to imported intermediate and capital goods having modern technologies, which are in turn the results of the R & D activities of developed countries; therefore, with an increase in actual currency rate the investment rate decreases due to capital goods becoming more expensive that this follows with a decrease in total productivity of factors of production. Also, the relationship between the openness rate of economy and total productivity of factors of production indicate that, due to the existence of some weaknesses and problems in Iran’s structures and especially in social structures, there is an increase in openness rate of economy resulting in a decrease in total productivity of factors of production of the industrial sector

Optimization Model for Maintenance Planning of Loading Equipment in Open Pit Mines

Maintenance plays a significant role in operating costs in the mining industry. Improving this matter controls maintenance costs and enhances productivity and production effectively. Shovels are one of the most widely used loading machines in non-continuous activities. Thus, evaluating and optimizing their availability is one of the essential solutions to achieving high productivity and cost reduction. This paper presents a mathematical programming model to maximize availability and minimize the total expected costs. We programmed the proposed nonlinear planning model using the Symbiotic Organisms Search (SOS) meta-heuristic algorithm in Matlab software. It determines the optimal maintenance intervals for different parts of the shovel. The maintenance benefit analysis approach selects various maintenance activities in optimal maintenance intervals. The model is implemented in a practical case study, Chadormalu Iron Mine, to evaluate its performance. The failure distribution matches the Weibull distribution function. The computational results show the efficiency of the presented approach

The investigation of relationship between binocular vision status and migraine headaches

زمینه و هدف: با توجه به نتایج ضد و نقیض در مورد ارتباط بین سردردهای میگرنی و اختلالات دید دوچشمی، این مطالعه با هدف تعیین ارتباط بین برخی از پارامترهای دید دو چشمی با میگرن انجام شد. روش بررسی: در این مطالعه مورد- شاهدی، 30 نفر بیمار میگرنی که معیارهای ورود به مطالعه را داشتند به همراه 30 نفر بدون سردرد میگرنی مورد مطالعه قرار گرفتند. ابتدا بیماران با استفاده از پرسشنامه استاندارد سردرد غربال شده و تایید نهایی توسط نورولو‍‍‍‍‍‍‍‍‍‍‍‍ژیست انجام شد. عیوب انکساری به روش رتینوسکوپی تعیین و سپس نقطه نزدیک تقارب، تقارب پرشی، استریوپسیس، ذخایر فیوژنی، انحراف دور و نزدیک در دو گروه تعیین شد. داده ها با استفاده از آزمون های من- ویتنی و رگرسیون لجستیک تک متغیره و چندگانه تحلیل شد. یافته ها: میانگین استریوپسیس در گروه مورد و شاهد به ترتیب 82/33±17/154 و 1/26±0/49 ثانیه بر کمان بود و به ترتیب در گروه مورد و شاهد میانگین فوریای نزدیک 72/6±3/8 و 85/2±5/6، ذخایر فیوژنی مثبت دور 76/2± 7/10 و 07/5±07/6، ذخایر فیوژنی منفی دور 7/4±2/18 و 37/7±0/11، ذخایر فیوژنی مثبت نزدیک 49/4±5/16 و 72/8±97/13 و ذخایر فیوژنی منفی نزدیک 22/5±7/22 و 25/9±67/14 پریزیوم دیوپتر بود. متوسط متغیرهای فوق و تقارب پرشی در دو گروه تفاوت معنی داری داشت (05/0>P) ولی متوسط سایر متغیرها در دو گروه معنی دار نبود. در رگرسیون لجستیک چندگانه فقط تقارب پرشی، تقارب فیوژنی مثبت در دور و نزدیک در مدل باقی ماند (05/0

Method to improve catalyst layer model for modelling proton exchange membrane fuel cell

Correctly describing oxygen reduction within the cathode catalyst layer (CL) in modelling proton exchange membrane fuel cell is an important issue remaining unresolved. In this paper we show how to derive an agglomerate model for calculating oxygen reactions by describing dissolved oxygen in the agglomerates using two independent random processes. The first one is the probability that an oxygen molecule, which dissolves in the ionomer film on the agglomerate surface, moves into and then remains in the agglomerates; the second one is the probability of the molecule being consumed in reactions. The first probability depends on CL structure and can be directly calculated; the second one is derived by assuming that the oxygen reduction is first-order kinetic. It is found that the distribution functions of the first process can be fitted to a generalised gamma distribution function, which enables us to derive an analytical agglomerate model. We also expend the model to include oxygen dissolution in the ionomer film, and apply it to simulate cathode electrodes. The results reveal that the resistance to oxygen diffusion in ionomer film and agglomerate in modern CL is minor, and that the main potential loss is due to oxygen dissolution in the ionomer film

Modelling water intrusion and oxygen diffusion in a reconstructed microporous layer of PEM fuel cells

The hydrophobic microporous layer (MPL) in PEM fuel cell improves water management but reduces oxygen transport. We investigate these conflict impacts using nanotomography and pore-scale modelling. The binary image of a MPL is acquired using FIB/SEM tomography. The water produced at the cathode is assumed to condense in the catalyst layer (CL), and then builds up a pressure before moving into the MPL. Water distribution in the MPL is calculated from its pore geometry, and oxygen transport through it is simulated using pore-scale models considering both bulk and Knudsen diffusions. The simulated oxygen concentration and flux at all voxels are volumetrically averaged to calculate the effective diffusion coefficients. For water flow, we found that when the MPL is too hydrophobic, water is unable to move through it and must find alternative exits. For oxygen diffusion, we found that the interaction of the bulk and Knudsen diffusions at pore scale creates an extra resistance after the volumetric average, and that the conventional dusty model substantially overestimates the effective diffusion coefficient