Electrodeposited Cu2ZnSnSe4 thin film solar cell with 7% power conversion efficiency

High performance Cu₂ZnSnSe₄ (CZTSe) photovoltaic materials were synthesized by electrodeposition of metal stack precursors followed by selenization. A champion solar cell with 7.0% efficiency is demonstrated. This is the highest efficiency among all of the CZTSe solar cells prepared from electrodeposited metallic precursors reported to‐date. Device parameters are discussed from the perspective of material microstructure and composition in order to improve performance. In addition, a high performance electrodeposited CZTS (S only) solar cell was demonstrated and its device characteristics were compared against the CZTSe (Se only) cell. Using secondary ion mass spectrometry for the analysis of the chemical composition of the absorber layer, a higher concentration of oxygen in the electrodeposited absorber is thought to be the root cause of the lower performance of the electrodeposited CZTS or CZTSe solar cells with respect to a solar cell fabricated by evaporation. The grain boundary areas of Sn‐rich composition are thought to be responsible for the lower shunt resistance commonly observed in CZTSe devices. We measured the longest minority carrier lifetime of 18 ns among all reported kesterite devices. This work builds a good baseline for obtaining higher efficiency earth‐abundant solar cells, while it highlights electrodepositon as a low cost and feasible method for earth‐abundant thin film solar cell fabrication. Copyright © 2013 John Wiley & Sons, Ltd.     

OPTIMUM STEAM INJECTION STRATEGIES FOR NATURALLY FRACTURED RESERVOIRS

ABSTRACT

This study aims to identify the effective parameters on matrix oil recovery and the efficiency of this process while there is a continuous flow of steam in fracture. Single matrix system is studied first. The critical injection rate is defined for laboratory scale simulation for different matrix properties. It is observed that there is a critical injection rate optimizing the process and the critical injection rate for an efficient matrix oil recovery is defined for different matrix sizes and matrix heat transfer coefficients.

In the second part of the study, similar analysis is performed to investigate the effect of injection rate on the oil recovery for field scale. Critical rate concept is evaluated for different number of horizontal fractures and steam qualities. Finally, the economics of steam injection in the field scale is studied. The optimum injection strategies determined by the adjustment of injection rates are discussed based on the fracture properties such as density and permeability. The approach and results can be used in further studies to analyze the efficiency of thermal applications and to obtain correlations for steam injection performances in naturally fractured reservoirs.     

Bond strength of polymer lightweight aggregate concrete

Bond strength, physical, and mechanical properties of lightweight PC were investigated with inclusion of pumice lightweight aggregate in maximum size of 12 mm. As binder material, epoxy resin‐based polymer was used with its hardener. The binder to aggregate ratio was 30% by weight. In addition, steel fibers were added to lightweight PC mixtures in ratio of 0, 0.5, and 1%. After lightweight PC mixture was prepared, it was poured in the molds with different type of steel‐bars in size of 100 × 100 × 100 mm³. The steel‐bars centered in the cubic molds, and they were in size of Ø12, Ø14, and Ø16. The specimens were cured at 60°C for 2 h. On the hardened polymer lightweight concrete (PLC), pull‐out test for bond strength and compressive strength tests were performed. Moreover, ultrasonic pulse velocity, water absorption by weight, specific porosity, and density experiments were carried out. The relation between physical and mechanical properties showed that PLCs become more durable when using ratio of steel fibers. POLYM. COMPOS., 34:2125–2132, 2013. © 2013 Society of Plastics Engineers     

Plasticity models for concrete material based on different criteria including Bresler–Pister

The purpose of this study is to investigate nonlinear behavior of reinforced concrete (RC) structures with the plasticity modeling. For this aim, a nonlinear finite element analysis program is coded in MATLAB. This program contains several yield criteria and stress–strain relationship for compression and tension behavior of concrete. In this paper, the well-known criteria, Drucker–Prager, von Mises, and Mohr Coulomb, and a new criterion-Bresler–Pister are taken into account. The elastic–perfectly plastic and Saenz stress–strain relationships in compression and tension stiffening in tension behavior of concrete are used with four different yield criteria mentioned above. The proposed models are in good agreement with the experimental and analytical results taken from the literature. It is concluded that the coded program, the proposed models, and Bresler–Pister criterion can be effectively used in nonlinear analysis of reinforced concrete beams.     

Thermal,electrical, mechanical and fluidity properties of polyester-reinforced concrete composites

Polyester particles in concrete are preferred because they provide thermal, chemical and water resistance. In this study, thermal conductivity, electrical resistivity, mechanical strength and water resistance properties of concretes containing polyester granules such as flame-retardant polyester, cationic dyeable polyester and polyester with a low melting point-filled concrete have been analyzed using a full factorial design via Minitab^® version 17. The effect of the most influential factors on thermal conductivity of polyester aggregate reinforced concrete composite has been determined as an interaction between the cationic dyeable and low-melt–point polyester. This mixture is suitable for production of thermal insulating concrete. Moreover, it is concluded that cationic dyeable polyester is the highest corrosion- and water-resistant product among the polyesters used in this study. The recovery rate of 33.94% in the thermal conductivity and 214.89% in the electrical resistivity of polyester-reinforced concrete composites has been obtained with a 28-day compressive strength loss of 41.94% according to the reference concrete in the full factorial design application. These results indicate that the polyester-reinforced concrete composites are quite effective in achieving thermal and corrosion resistance concrete but with noticeable compressive strength loss.     

Synthesis and comparison of crosslinked peptide nanoparticles based on diphenylalanine derivatives

Self‐assembly is a mechanism that creates novel nanomaterials with amplified properties but with stability challenges. In this report, highly stable and biocompatible anionic zwitterionic diphenylalanine nanoparticles (ZFFNPs), which are novel for the literature, are demonstrated. ZFF was crosslinked with glutaraldehyde (GA) and self‐assembled into nanoparticles in a self‐assembly mechanism like that for diphenylalaninamide nanoparticles (FFANPs). Also, ZFFNPs were compared with FFANPs in aspects of morphology, surface charge, stability, and cytotoxicity. ZFFNPs demonstrate a spherical morphology and homogenicity like FFANPs, but while ZFFNPs have negative surface groups (carboxyl), FFANPs contain polar surface groups (amide). While ZFFNPs exhibit a high stability in extremely acidic environments (pH 3–5), AFFNPs show stability in a wide pH range (pH 4–10). Both NPs are nontoxic and biocompatible. These novel anionic ZFFNPs have great promise for potential utilization in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45930.     

Broadband analogue predistortion using a distortion generator based on two-stage RF mixer topology

An analogue predistorter using a distortion generator based on a two-stage radio frequency mixer topology is presented. The proposed distortion generator achieves fundamental signal cancellation without using a signal cancellation loop or a resonant circuit, thus it generates an error signal that predominantly consists of unwanted intermodulation distortion (IMD). Measurements are performed using multi-tones, WLAN- and Terrestrial Trunked Radio (TETRA)-modulated signals. Distortion generator provides high levels of IMD and achieves more than 40 dB fundamental signal cancellation across a bandwidth of 120 MHz. A proof-of-concept predistorter was constructed to validate the usefulness of the proposed distortion generator, which achieves up to 15 dB suppression of IMD and adjacent channel power ratio at the output of a power amplifier. Distortion generator and predistorter gave similar results at multiple frequencies between 920 MHz and 2 GHz, with different test signals having bandwidths ranging from 25 kHz to 120 MHz.     

Satisfying agent goals by executing different task semantics: HTN, OWL-S or plug one yourself

In this paper, we propose a plan execution architecture which supports different task semantics. This way, each goal that is identified during the deliberation cycle of an agent can be satisfied through tasks defined in different semantics. The capability of supporting different task semantics provides two main advantages. The first advantage is the reuse of legacy artifacts within agent plans. The second advantage is simplifying the adaptation of an agent architecture to different standards of a business organization. In order to integrate various task semantics within a plan execution architecture, we have used a smoothly revised version of a previously articulated workflow model into which different task semantics would be reduced before execution. We have integrated hierarchical task network and OWL-S semantics into our plan execution architecture to test the strength of it in terms of support for executing different task semantics in an agent architecture. We think that such a plan execution architecture will contribute to the industrialization of agent architectures.     

Fuzzy expert system for land reallocation in land consolidation

One of the most important steps of land consolidation projects is land reallocation studies. In Turkey, reallocation studies carried out in the scope of land consolidation projects are made according to farmer preferences (interviews). In addition to interview-based land reallocation model, mathematical models have been used in the previous optimization studies for reallocation procedure. Recently, fuzzy logic method, which is capable of modeling human mindset and used when other forms of mathematical models cannot be developed, has also been applied to the field of geomatic engineering, as well as in other engineering branches.This study examined the applicability of a fuzzy logic method at the reallocation stage of land consolidation study, where development of an accurate mathematical model was not possible. The results obtained from the fuzzy logic-based land reallocation model were compared with those obtained from the interview-based land reallocation model. Farmers were surveyed to determine which land reallocation model they preferred. The results indicate that 80.5% of the participant landholdings were satisfied with the fuzzy logic-based reallocation land model, while 50% were with the interview-based land reallocation model.