The Role of Mirror Dichroic in Tandem Solar Cell GaAs/Si

The good choice of the mirror dichroic between two solar cells was key to the development of the first two-terminal monolithic, multi-junction solar cell. In this paper describes a simulation for mirror dichroic between the first cell (GaAs) and second cell (Si ). In the simulation, Spectrum of the mirror Issued to first cell is changed the 0.3 ?m to0.6 ?m and the rest of the spectrum turns to the second cell. the By varying the mirror dichroic was demonstrate in the form of current-voltage(I-V) characteristics and quantum efficiency (QE). Keywords: multi-junction, mirror dichroic, quantum efficiency

Effect of Temperature on the AlGaAs/GaAs Tandem Solar Cell for Concentrator Photovoltaic Performances

Multijunction solar cells for concentrator photovoltaic (CPV) systems have attracted increasing attention in recent years for their very high conversion efficiencies. But there is a problem in this type of solar cells (CPV) is to increase the temperature if it has been augmenting the concentration ratio. In this paper, we studied the effect of the concentration photovoltaic in a high-efficiency double-junction devices solar cell on temperature solar cell and its impact on the photocurrent, the efficiency and open circuit voltage. In this study, the top cell is made of AlGaAs (1.73 eV) while the bottom cell is made of GaAs (1.42 eV) between them a tunnel junction

Effect of plastic fins on a traditional solar still's efficiency

Solar distillation is a relatively straightforward and environmental method. It is used in many countries and especially in isolated areas to treat polluted water. In this context, two similar solar stills of 50 x 50 cm were used in the same climatic conditions in order to test the influence of plastic fins on the performance of this device. The results show that there is a negative effect on the output of the distiller with a rate of 8.8 %. So this way is not recommended for researchers in this field

A wireless system for monitoring leakage current in electrical substation equipment

In this paper, the design and the development of a remote system for continuous monitoring of leakage currents and ground currents in high voltage electrical substations are proposed. Based on wireless local area network technology, the system can be used to monitor continuously a variety of plants within the substation and has low power consumption with inbuilt overvoltage protection. It consists of a transmitter module equipped with a data acquisition (DAQ) system connected to leakage current and voltage sensors, and a receiver module connected to a remote controller for data processing and storage. The principle of operation and the characteristics of the various components of the system are described. Validation tests have been used to verify its performance in three different test situations: A) laboratory monitoring of the leakage current and voltage of a distribution surge arrester; B) laboratory measurement of the leakage current of an outdoor insulator; and C) field monitoring of the earth current and potential rise of high-voltage tower. The measured results are in close agreement with those recorded directly through a DAQ card with fiber-optic and coaxial cable connected systems. Data processing is carried out at the receiving end so that the monitored parameter is displayed continuously or at specified time intervals. The operation of the system has been tested and proved resilient under high-frequency interference signals such as those generated by corona and surface discharges

Thermal state of electronic assemblies applied to smart building equipped with QFN64 device subjected to natural convection

The performance and reliability of electronic components and assemblies strongly depend on their thermal state. The knowledge of the temperature distribution throughout the assembly is therefore an essential element to ensure their correct operation. This is the main objective of this work that examines the case of a conventional assembly equipped with a quad flat nonlead QFN64 subjected to free convection. This active electronic package is welded on a PCBwhich may be inclined by an angle varying between 0° and 90° (horizontal and vertical positions respectively) and generates during its operation a high power ranging from 0.1 to 1W.Thermoregulation of the assembly is ensured by natural convection, given its many well known advantages in this engineering field. Accurate relationships are proposed to determine the temperature on different areas of the device and the PCB. They are determined by means of a 3D numerical survey based on the finite volume method confirmed by measurements on an actual installation. These relationships allow reliability improvement of these electronicassemblies widely used in many engineering fields, as computing industry, mobile telephony, home automation, automotive, embarked electronics and smart building considered in this survey. The present survey complements a recent study which quantifies the natural convective heat transfer on the considered electronic assembly equipped with the QFN64 device, for thesame power range and angle of inclination

Multi-Antenna Data-Driven Eavesdropping Attacks and Symbol-Level Precoding Countermeasures

In this work, we consider secure communications in wireless multi-user (MU) multiple-input single-output (MISO) systems with channel coding in the presence of a multi-antenna eavesdropper (Eve). In this setting, we exploit machine learning (ML) tools to design soft and hard decoding schemes by using precoded pilot symbols as training data. In this context, we propose ML frameworks for decoders that allow an Eve to determine the transmitted message with high accuracy. We thereby show that MU-MISO systems are vulnerable to such eavesdropping attacks even when relatively secure transmission techniques are employed, such as symbol-level precoding (SLP). To counteract this attack, we propose two novel SLP-based schemes that increase the bit-error rate at Eve by impeding the learning process. We design these two security-enhanced schemes to meet different requirements regarding complexity, security, and power consumption. Simulation results validate both the ML-based eavesdropping attacks as well as the countermeasures, and show that the gain in security is achieved without affecting the decoding performance at the intended users.Comment: Submitted to the IEEE Transactions on Information Forensics and Securit

Enhancement of natural convection for improvement of Trombe wall performance. An experimental study

This experimental work shows that the natural convective heat transfer in the active enclosure of a conventional Trombe wall assembly is enhanced by the interposition of transparent and vertical partitions. Quantification of the average Nusselt number corresponding to both versions with and without partitions was carried out by means of a 1/5 scale assembly. The glass cover is maintained isothermal at cold temperature while the active wall generates a variable heat flux simulating the incident solar radiation. The distance between the two active and parallel walls is variable. Four ratios between this distance and the height of the wall are considered, associated with a wide range of Rayleigh number reaching 4.1×109. An error calculation is carried out for all the processed configurations, taking into account the experimental uncertainties of the measured physical parameters. The maximum error found on the average Nusselt number is low, of about 5%. Measurements made by means of an interstitial medium without partitions are consistent with the results of other work carried out by experimental and numerical approaches in specific ranges of Rayleigh number. This study reveals the partitions effectiveness, since the natural convective heat transfer's increase lies between 10.0% and 14.4% according to the considered configuration. Correlations are proposed in the present work in order to calculate the average natural convective Nusselt number for the conventional Trombe wall without partitions and for its improved version, for any aspect ratio and in the whole range of the considered Rayleigh number. They contribute to the optimization of the thermal design of this interesting assembly

The intercontinental schizophrenia outpatient health outcomes (IC-SOHO) study: baseline clinical and functional characteristics and antipsychotic use patterns in the North Africa and Middle Eastern (AMEA) region: original article

Objective: To describe the baseline findings of the Intercontinental Schizophrenia Outpatient Health Outcomes (IC-SOHO) study in the North Africa and Middle Eastern sub-region (AMEA-SOHO) Method: The IC-SOHO study is an ongoing prospective, three-year, non-interventional observational study of schizophrenia treatment, clinical characteristics and mental health services utilization in two North African and two Middle Eastern countries. The study population consists of non-hospitalised patients who had initiated treatment with or changed to a new antipsychotic. Results: The baseline findings of the IC-SOHO study (AMEA Subset) appear to reflect clinical practice in Turkey, Saudi Arabia, Egypt and Algeria (N=1, 398). Overall, the patients were moderately to markedly ill and either overweight (46%) or obese (8%) when they entered the study. Functionally, the majority of patients were not involved in social activities, could not care for themselves and were unemployed. Substance and alcohol dependency/abuse was not a problem in this study population. At baseline the majority of patients were treated with typical antipsychotics (oral and depot); and anticholinergics were the most commonly prescribed concomitant medication. Sexual side effects were most frequently reported among the surveyed adverse events. Overall compliance/adherence to medication was good. Conclusion: The baseline IC-SOHO data highlighted various clinical and functional characteristics and antipsychotic use patterns in a group of outpatients with schizophrenia in a naturalistic setting. Once completed, the IC-SOHO study will add further to this knowledge base. SA Psychiatry Rev. Vol.7(3) 2004: 27-3

Les pel·lícules del mes de febrer

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