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Photovoltaic performance of bulk heterojunction organic solar cell based on poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were investigated. The active layer is a spin coated organic blend of a p material (P3HT) and an n-material from the fullerene derivative PCBM; it is sandwiched between electrodes ITO-PEDOT/PSS and Al/LiF as back-contact. Modeling of organic bulk heterojunction solar cells is complicated because of various internal mechanisms involved. Two models have been suggested, namely an effective medium model and a network model. We applied an effective medium model where the main assumption is the p–n nanostructure is treated as one single effective semiconductor layer, and parameters in this configuration are fed into a standard solar cell device simulator, called SCAPS. In this model, other non-carrier related properties, such as the refractive index n, the dielectric constant ε and the absorption constant α are influenced by both p–n materials and used as input parameters. The power conversion efficiency of 3.88% with short circuit current density of 20.61 mA/cm², open circuit voltage of 0.39 V and fill factor of 48% were obtained. Finally, factors which could limit cell conversion efficiency are discussed.

In the present investigation, a three dimensional steady flow field model inside crystallizer system of a thin slab steel continuous caster is presented using real geometrical dimension starting from the inlet port of the nozzle. The nozzle flow was modeled considering the minimum casting defects. In addition, a new numerical model is developed for a thin slab casting mold. The velocity of the liquid from the inlet and outlet of the nozzle was considered as the boundary condition. The liquid flow field was computed with main concern on the velocities exiting the nozzle ports for the flow in the liquid pool. It was shown that the fluid pattern in the liquid pool has four main fluid rings including two fluid rings provided by the outer fluid coming from the bottom outlets into the liquid pool and two small fluid rings prepared by the fluid coming from the upper inlets into the liquid pool. The flow pattern agrees well with real measurements obtained by water model. The pool simulation shows asymmetries between two sides of the flow, mainly in the lower recirculation zone. The predictions of slag/liquid interface at the top side of the nozzle and its fluctuations show good agreement with the experimental results. The maximum upward wave flow occurred because of the liquid contact to the upper ports. Hence, a maximum upward flow wave was defined to prevent any unsteady state at the highest casting speed and lowest submergence depth.

The influence of the thermal residual stress and reinforcement geometry on the creep behavior of a composite disc has been analyzed in this paper. The creep analysis in a rotating disc made of Al-SiC (particle/whisker) composite having hyperbolically varying thickness has been carried out using anisotropic Hoffman yield criterion and results obtained are compared with those using Hill's criterion ignoring difference in yield stresses. The steady state creep behavior has been described by Sherby's creep law. The creep parameters characterizing difference in yield stresses have been used from the available experimental results in literature. It is observed that the stresses are not much affected by the presence of thermal residual stress, while thermal residual stress introduces significant change in the strain rates in an anisotropic rotating disc. Secondly, it is noticed that the steady state creep rates in whisker reinforced disc with/without residual stress are observed to be significantly lower than those observed in particle reinforced disc with/without residual stress. It is concluded that the presence of residual stress in an anisotropic disc with varying thickness needs attention for designing a disc.

In this paper, an effort has been made to study the effect of anisotropy on the steady state creep behavior in the functionally graded material disc with hyperbolic thickness made of Al-SiC (particle). The content of silicon carbide particles in the disc is assumed to decrease linearly from the inner to the outer radius of the disc. The creep behavior of the disc under stresses developing due to rotation at 15,000 rpm has been determined by Sherby's law. The creep parameters of the FGM disc vary along the radial distance due to varying composition and this variation has been estimated by regression fit of the available experimental data. The creep response of rotating disc is expressed by a threshold stress with value of stress exponent as 8. The study reveals that the anisotropy has a significant effect on the steady state creep response of rotating FGM disc. Thus, the care to introduce anisotropy should be taken for the safe design of the rotating FGM disc with hyperbolic thickness.

An analysis of the equations used for modeling thermal arsenic diffusion in silicon has been carried out. It was shown that for arsenic diffusion governed by the vacancy-impurity pairs and the pairs formed due to interaction of impurity atoms with silicon self-interstitials in a neutral charge state, the doping process can be described by the Fick’s second law equation with a single effective diffusion coefficient which takes into account two impurity flows arising due to interaction of arsenic atoms with vacancies and silicon self-interstitials, respectively. Arsenic concentration profiles calculated with the use of the effective diffusivity agree well with experimental data if the maximal impurity concentration is near the intrinsic carrier concentration. On the other hand, for higher impurity concentrations a certain deviation in the local regions of arsenic distribution is observed. The difference from the experiment can occur due to the incorrect use of effective diffusivity for the description of two different impurity flows or due to the formation of nonuniform distributions of neutral vacancies and neutral self-interstitials in heavily doped silicon layers. We also suppose that the migration of nonequilibrium arsenic interstitial atoms makes a significant contribution to the formation of a low concentration region on thermal arsenic diffusion.

A model of interstitial impurity migration is proposed which explains the redistribution of ion-implanted boron in low-temperature annealing of nonamorphized silicon layers. It is supposed that nonequilibrium boron interstitials are generated either in the course of ion implantation or at the initial stage of thermal treatment and that they migrate inward and to the surface of a semiconductor in the basic stage of annealing. It is shown that the form of the “tail” in the boron profile with the logarithmic concentration axis changes from a straight line if the average lifetime of impurity interstitials is substantially shorter than the annealing duration to that bending upwards for increasing lifetime.

The calculated impurity concentration profiles are in excellent agreement with the experimental data describing the redistribution of implanted boron for low-temperature annealing at 750${}^{\circ }$C for 1h and at 800${}^{\circ }$C for 35min. Simultaneously, the experimental phenomenon of incomplete electrical activation of boron atoms in the “tail” region is naturally explained.

The prediction of Young’s modulus properties of a hybrid composite using micromechanical models based on the geometrical characteristics and individual constituent properties of materials is a challenging task for the researchers. In this work, the micromechanical and experimental approaches are used to evaluate the hybrid effect on the Young’s modulus properties of continuous banana and palmyra fiber-reinforced epoxy composites. In computational modeling, a square unit cell is employed by using ANSYS to study the effect of the fiber weight percentage and weight ratio over Young’s modulus properties along the longitudinal and transverse direction. The effectiveness of the numerical predictions is evaluated by comparing with the experimental results and analytical micromechanical models (Rule of hybrid Mixture, Halpin–Tsai (HT), and Lewis and Nielsen). In the experimental approach, the hybrid composites were fabricated with the continuous banana and palmyra fibers reinforced with epoxy by varying the fiber percentages (10%, 20%, 30% and 40%) and weight ratios (1:1, 1:3, and 3:1). The micromechanical approaches show that Young’s modulus of the hybrid composites is consistently increased with the fiber percentages. The longitudinal Young’s modulus obtained by the Lewis and Nielsen equation gave good agreement with numerical and experimental results. On the other hand, the experimental transverse Young’s modulus gave a better fit with the inverse rule of hybrid mixture as compared with other analytical model predictions.

“What do you want to be when you grow up?” is a common question posed to children, and answers such as firefighter, policeman, athlete, doctor, or teacher are probably just as common. Some, like Oliver Sacks, recall an early fascination with metals, the periodic table, and chemical reactions that planted the seeds for the later pursuit of the natural sciences or medicine (neurology in his case). We are familiar with memories of chemists that include their first chemistry set, followed by complaints by parents over strange smells and close calls due to particularly exothermic reactions. For others, including myself, a future in research remained more obscure until a later period in adolescence or perhaps even the undergraduate years. Rather than seeking out a field, the field finds you. In actuality, teachers and mentors with expertise in and enthusiasm for a field exert a force that charts a path toward scientific research throughout life. Here, I stress the importance of terrific teachers and mentors from high school onwards to the undergraduate, Ph.D., and postdoc years for setting me on a track (and on occasion preventing me from derailing) to research in structural chemistry and molecular mechanism using crystallography as the main tool.

Environmentally responsible and minimal natural variation in electric power generation has been a goal of researchers for several decades. With the establishment of the electrical power generation potential from microalgae’s photosynthesis, several researchers revealed interesting microbial fuel cell configurations to improve the output of electrical parameters. However, little work is done to understand the electrical charge collected from photosynthesis. This article proposes a fuel cell-based electrochemical modeling of the micro-photosynthetic power cell. The model is developed, excluding significant analytical assumptions at stationary conditions. Due to the complexity of modeling the electron release from photosynthesis, the electron release reactions are substituted with a simpler redox coupler of similar electric potential to that of photosynthesis. The micro-photosynthetic power cell revealed that the electron collection rate does not directly correlate to the photosynthesis electron chain. It might remain constant for a specific electrical load. The peak power is obtained at a different operating loading than the internal resistance of the device. The experimental open circuit voltage ($\sim$0.96V) and the peak power ($\sim$0.18mW) are predicted accurately by this modeling approach. The results show that the fill factor remains constant with respect to several effective electrode surface areas. Based on this theoretical modeling, we believe that with optimized algal physiological state and micro-photosynthetic power cell’s effective surface area, this micro-photosynthetic power cell will be useful for application in low-power applications.

A new modeling and parameter extraction methodology to represent the parasitic effects associated with shielded test structures is presented in this paper. This methodology allows to accurately account for the undesired effects introduced by the test fixture when measuring on-wafer devices at high frequencies. Since the proposed models are based on the physical effects associated with the structure, the obtained parameters allow the identification of the most important parasitic components, which lead to potential measurement uncertainty when characterizing high-frequency devices. The proposed methodology is applied to structures fabricated on different metal levels in order to point out the advantages and disadvantages in each case. The validity of the modeling and characterization methodology is verified by achieving excellent agreement between simulations and experimental data up to 50 GHz.