Temperature of a photovoltaic module under the influence of different environmental conditions – experimental investigation

The climate changes affect photovoltaic (PV) module temperature significantly. The module temperature is one of the most important factors that influence the PV module efficiency and a deep analysis of PV module temperature will aid in better understanding of the environmental influences on the PV module performance. The module temperature depends on many parameters such as solar radiation, ambient temperature, air humidity, speed and direction of the wind, PV module orientation, dust and sand deposition on PV module, and PV module materials. An experimental research was conducted to investigate the effect of these factors on the PV module temperature in the Renewable Energy Laboratory of the Graduate University of Advanced Technology in Iran. The results of this study highlighted that the deposited dust over the PV module surface increases the module temperature and this consequently decreases the PV module power. It was also revealed that a combination of the temperature increase and the incident solar radiation decrease due to the dust deposition over the PV module enhances significantly the module power reduction.     

Microstructural scale effects in the nonlinear elastic response of bio-inspired wavy multilayers undergoing finite deformation

Materials with wavy microstructures span disciplinary boundaries, yet relatively little systematic work has been done to characterize their thermo-mechanical response. Motivated by recent work on the elastic–plastic response of wavy periodic multilayers, and the discovered layer thickness effect in the post-yield domain, we extend our finite-volume based homogenization theory in order to investigate the effect of microstructural refinement, as well as geometric and material parameters, in this class of periodic materials in the finite-deformation domain. Micromechanical analysis of a model wavy multilayered system which mimics certain biological tissues quantifies the importance of layer thickness, and hence the microstructural bending stiffness, on the stiffening stress–stretch response. The role of the matrix phase in the unfolding process is also highlighted. The results provide insight into the design of materials intended to mimic the response of a certain class of biological tissues with stiffening characteristics such as chordae tendineae.     

An integrated analytic network process with mixed-integer non-linear programming to supplier selection and order allocation

As the global business environment changed, much more commercial and technological competitions evolved in this environment. Consequently, more attention is devoted to the business partners including suppliers. In this paper, supplier selection with order allocation problem is addressed for strategic items with respect to the materials’ characteristics as well as what has been mostly considered in the literature, suppliers’ characteristics. The proposed model comprises an analytic network process (ANP) sub-model to qualify suppliers and filter-suitable candidates among the available ones. Additionally, the ANP sub-model is applied to evaluate suppliers regarding their qualitative attributes which cannot be modeled with mathematical tools properly. Moreover, a mixed-integer non-linear sub-model is presented to simultaneously allocate order quantities to the chosen suppliers. The model is customized to the strategic items by introducing supplier switching cost which is a notable cost component for products. Finally, experimental results and sensitivity analyses are presented to validate the proposed model.     

A multi-objective decision-making process of supplier selection and order allocation for multi-period scheduling in an electronic market

Supplier selection is a multi-criteria problem which includes both tangible and intangible factors. In these problems when suppliers have capacity or other different constraints, two questions persist: which suppliers are the best and how much should be purchased from a selected supplier? Here, we propose an integrated approach of analytic hierarchy process (AHP), Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS), and multi-objective nonlinear programming to consider both tangible and intangible factors in choosing the best suppliers and define the optimum quantities among selected suppliers to maximize the total value of purchasing and minimize the budget, total penalized earliness and tardiness, and defect rate. The priorities are calculated for each supplier by use of AHP. TOPSIS is applied to rank the suppliers. Finally, using the obtained weights, the optimal quantities of order to the suppliers are clarified in multi-period horizon. An application study presents the validity and efficiency of the proposed model. Moreover, a performance analysis has been worked out on the numerical example to investigate the capability and effectiveness of the results.     

Modeling and nonlinear analysis of a micro-switch under electrostatic and piezoelectric excitations with curvature and piezoelectric nonlinearities

In this paper, a comprehensive model of a micro-switch with both electrostatic and piezoelectric excitations, which accounts for the nonlinearities due to inertia, curvature, electrostatic forces and piezoelectric actuator is presented to demonstrate the mechanical characteristics of such a micro-system. Dynamic equations of this model are derived by the Lagrange method. Static analysis of this model is performed with five modes through the Galerkin method. The micro-switch beam is assumed as an elastic Euler-Bernoulli beam with clamped-free end conditions. The electrostatic actuation results are compared with other existing experimental and numerical results. Whereas the major drawback of electrostatically actuated micro-switches is the high driving voltage, using the piezoelectric actuator in these systems can provide less driving voltage and control the pull-in voltage. The study demonstrates that when the ratio of electrostatic actuation distance to length of micro-switch is small, the nonlinear piezoelectric term has a significant effect on the pull-in phenomenon. There are three ways to influence the design and control of the mechanical characteristics of this micro-switch: the softening effect due to electrostatic actuation, the hardening effect due to piezoelectric actuation, and varying the length and thickness of the piezoelectric actuator.     

Numerical simulation of two phase refrigerant flow through non-adiabatic capillary tubes using drift flux model

Journal of Mechanical Science and Technology - This research presents a drift flux model to simulate steady state refrigerant flow through horizontal lateral straight capillary tube-suction line...     

Fabrication of resistive CO gas sensor based on SnO2 nanopowders via low frequency AC electrophoretic deposition

A resistive CO gas sensor has been fabricated using AC electrophoretic deposition (ACEPD) technique. SnO₂ thick films are deposited by applying low frequency (0.01–1,000 Hz) AC electric field to a stable suspension of SnO₂ nanoparticles in acetyl acetone. A carbon film base electrode is used as deposit substrate. Effect of CO gas exposure on conductivity of the SnO₂ film at 300 °C is investigated. Results show that the sensor is sensitive and its response is repeatable. This work shows that ACEPD can be used as an easy and cheap technique for fabrication of electronic devices such as ceramic gas sensors.     

Preparation and characterization of indium zinc oxide thin films by electron beam evaporation technique

In this work, the preparation of In₂O₃-ZnO thin films by electron beam evaporation technique on glass substrates is reported. Optical and electrical properties of these films were investigated. The effect of dopant amount and annealing temperature on the optical and electrical properties of In₂O₃-ZnO thin films was also studied. Different amount of ZnO was used as dopant and the films were annealed at different temperature. The results showed that the most crystalline, transparent and uniform films with lowest resistivity were obtained using 25 wt% of ZnO annealed at 500 °C.     

A Photographic Encoder Applied to an Optical Processor Using Speckle Techniques

Abstract

An artificial screen has been constructed to encode spatial information of simple transparent objects. The constructed encoder is composed of a matrix of small strips, photographed several times on a high resolution film to obtain strips of nearly ten times the average grain size of natural speckles. A second encoder has been constructed by recording a natural speckle pattern on a photographic plate which has gone through a continuous shift during the time of exposure in a specific direction, forming an elongated speckle pattern. A comparison between the results obtained using the two encoders has been presented.     

The thermal stability of nanocrystalline cartridge brass and the effect of zirconium additions

The thermal stability of nanocrystalline cartridge brass (Cu–30 at.% Zn) and brass–Zr alloys were investigated. The alloys were produced by cryogenic ball milling and subsequently heat treated to a maximum temperature of 800 °C. The grain size of pure brass was found to be relatively stable in comparison to pure copper, and a high hardness was retained up to 600 °C. When 1 at.% zirconium was alloyed with the brass, the grain size was stabilized near 100 nm even at 800 °C. At the highest temperature, hardness was retained above 2.5 GPa for 1 and 5 at.% zirconium alloys, but the pure brass softened significantly. The stabilization is believed to be dominated by Zn–Zr interactions as a second phase of these two was observed in X-ray diffraction and transmission electron microscopy. Thermodynamic modeling indicates a zero grain boundary energy may be achieved depending on the mixing enthalpy value used (i.e., calculated vs. experimental) under ideal conditions, but microstructural features such as twinning and second phase particles are thought to be the dominant stabilization mechanism. Zr worked well in stabilizing the brass in the nanocrystalline state to nearly 90 % of its melting temperature.