Si-Sb-Te materials for phase change memory applications

Si-Sb-Te materials including Te-rich Si?Sb?Te? and Si(x)Sb?Te? with different Si contents have been systemically studied with the aim of finding the most suitable Si-Sb-Te composition for phase change random access memory (PCRAM) use. Si(x)Sb?Te? shows better thermal stability than Ge?Sb?Te? or Si?Sb?Te? in that Si(x)Sb?Te? does not have serious Te separation under high annealing temperature. As Si content increases, the data retention ability of Si(x)Sb?Te? improves. The 10 years retention temperature for Si?Sb?Te? film is ~393 K, which meets the long-term data storage requirements of automotive electronics. In addition, Si richer Si(x)Sb?Te? films also show improvement on thickness change upon annealing and adhesion on SiO? substrate compared to those of Ge?Sb?Te? or Si?Sb?Te? films. However, the electrical performance of PCRAM cells based on Si(x)Sb?Te? films with x > 3.5 becomes worse in terms of stable and long-term operations. Si(x)Sb?Te? materials with 3 < x < 3.5 are proved to be suitable for PCRAM use to ensure good overall performance.     

Induced albumin secretion from HepG2 spheroids prepared using poly(ethylene glycol) derivative with oleyl groups

We developed a poly(ethylene glycol) (PEG) derivative with oleyl groups, so-called “cell adhesive”, for the promotion of human hepatocellular carcinoma HepG2 cell spheroids. Our approach was based on crosslinking of the cell membrane with a cell adhesive via a hydrophobic interaction. A cell adhesive, PEG derivative with hydrophobic oleyl groups at both ends was synthesized and characterized. HepG2 spheroids formed when the adhesive was added to cell suspensions. The size of the spheroids increased with time in culture. In addition, Ammonia elimination of HepG2 spheroid with cell adhesive was 3.4 times higher than that without cell adhesive. Furthermore, albumin secretion from HeG2 spheroids grown with the cell adhesive for 7 days was 3.3 times that from HepG2 spheroids grown without cell adhesive. Fluorescence microscopy showed greater albumin staining in spheroids grown with cell adhesive compared with spheroids grown without adhesive. This cell adhesive may be useful not only for single type of cells but also for multi types of cells to form artificial organs. This cell adhesive will be a key material for liver tissue engineering when it will apply to primary hepatocytes.     

Analysis and simulation of a solar water pump for lift irrigation

A solar water pump for lift irrigation, which was shown to be economically viable, was proposed by Rao and Rao [5]. A “modified pump” is suggested, which is suitable for village water supply. The thermodynamic analysis of the pumps is presented. Though the solar water pump is intended to be operated with flat-plate collectors, it is analysed whether the pump could be run more efficiently when coupled with concentrating collectors. The analysis is also applicable for bellow actuated solar water pumps.Preliminary experimental studies showed that the heat losses are 2–3 times the theoretical energy requirement and the losses to the water tank shell accounted for a major part of the total heat losses. To reduce these losses, it is proposed that the inner surface of the water tank shell be lined with a resin bonded cork insulation. A method to evaluate the heat losses to the shell with insulation by solving the unsteady state heat conduction equation for a composite cylindrical body with time varying convective boundary conditions is presented. The heat losses are reduced to 5–15 per cent of the theoretical energy requirement with the use of the internal insulation. The major problem encountered in operating the pump was the inadequate condensation of the working fluid, which resulted in failure of the suction of water into the water tank. To ensure proper suction of water, the conditions to be maintained are analysed. The presence of water vapor and air in the spent vapor has to be taken into consideration while designing the condenser.An algorithm to evaluate the year round performance of the water-cooled pump for any location, given the lift and collector area, is presented. The cost of the water-cooled pump is compared with the costs of other types of solar water pumps and it is shown that the pump under consideration costs several times less than the other ones. The conditions at which the pump will be economical vis-a-vis diesel and electrical pumps are presented.     

Domestic fuel energy consumption in an Indian urban ecosystem

Berhampur is one of the oldest and biggest towns of Orissa State where 93% of people earn their living from non-primary economic activities. The fuel consumption structure reveals an element of rural bias since the domestic sector derives 49% of its energy used for cooking and heating from biomass sources. Firewood is the only fuel used by all income groups and almost all occupations. Other traditional fuels such as dungcake, agricultural waste and leaf litter are used in the town with different degrees of dominance in various occupation groups and income classes. The inequality of income distribution is reflected in the fuel consumption structure of the rich and poor with greater dependence on non-biomass in the high income group and biomass in the low income group. Family size is an important determinant of biomass fuel use. For the urban poor, there is a relationship between income and fuel consumption. There exists scope for enlarging the biomass base by utilising the available bio-wastes and developing a green belt around the town. This requires some rural features in the urban area using new technologies.     

Estimation of the thickness of the lower convective layer of solar ponds

In solar ponds, the lower convective layer plays a dual role. It provides a means for the extraction of energy from the pond. It acts also as an in-built seasonal energy store. The ground beneath the pond acts as an additional energy store. To enhance the ground energy storage, a method was earlier proposed by the authors employing trapezoidal-shaped trenches at the bottom of the pond. A rigorous method is presented for the determination of the thickness of the lower convective layer in the case of a flatbottomed pond and the trench depth for a pond with trapezoidal trenches. The energy storage to be provided depends on the magnitude and the pattern of energy extraction. For a constant extraction rate, the required thickness of the lower convective layer or the trench depth increases with an increase in the rate. For a sinusoidal extraction pattern, the thickness or depth increases with an increase in the phase lag of the extraction pattern from the insolation and exhibits a minimum for the amplitude of the extraction pattern for phase lags less than about 95 days. The results also indicate that, for a given heat load (total energy extracted in a year), there exists an area for which the cost of the pond and the associated system for energy utilization is a minimum.     

SEP calculations for coherent M‐ary FSK in different fading channels with MRC diversity

In this paper, the authors derive symbol error probability (SEP) expressions for coherent M‐ary frequency shift keying (MFSK) modulation schemes in multipath fading channels. The multipath or small‐scale fading process is assumed to be slow and frequency non‐selective. In addition, the channel is also subjected to the usual degradation caused by the additive white Gaussian noise (AWGN). Different small‐scale fading statistics such as Rayleigh, Rician (Nakagami‐n), Hoyt (Nakagami‐q), and Nakagami‐m have been considered to portray diverse wireless environments. Further, to mitigate fading effects through space diversity, the receiver front‐end is assumed to be equipped with multiple antennas. Independent and identically distributed (IID) as well as uncorrelated signal replicas received through all these antennas are combined with a linear combiner before successive demodulation. As the detection is coherent in nature and thus involves phase estimation, optimum phase‐coherent combining algorithms, such as predetection maximal ratio combining (MRC), may be used without any added complexity to the receiver. In the current text, utilizing the alternate expressions for integer powers (1≤n≤4) of Gaussian Q function, SEP values of coherent MFSK are obtained through moment generating function (MGF) approach for all the fading models (with or without MRC diversity) described above. The derived end expressions are composed of finite range integrals, which can be numerically computed with ease, dispenses with the need of individual expressions for different M, and gives exact values up to M=5. When the constellation size becomes bigger (M≥6), the same SEP expressions provide a quite realistic approximation, much tighter than the bounds found in previous literatures. Error probabilities are graphically displayed for each fading model with different values of constellation size M, diversity order L, and for corresponding fading parameters (K, q, or m). To validate the proposed approximation method extensive Monte‐Carlo simulations were also performed, which show a close match with the analytical results deduced in the paper. Both these theoretical and simulation results offer valuable insight to assess the efficacy of relatively less studied coherent MFSK in the context of the optimum modulation choice in wireless communication. Copyright © 2010 John Wiley & Sons, Ltd.     

CB125摩托车噪声辐射源识别及控制研究

本文介绍了声强测试的基本原理和声强测试技术在CB25摩托车噪声控制中的应用，利用CF—6400声强测试分析系统对该摩托车进行主要噪声辐射源识别，快速、准确地找到其主要噪声源。通过有针对性地采取降噪措施，使该车行驶噪声显著降低。     

应用于3.3kV IGBT的线性渐变掺杂结终端扩展的设计与优化

本文将线性渐变掺杂结终端扩展（LG-JTE）技术用于3.3kV IGBT并进行了试验验证。和采用多次光刻和离子注入传统结终端扩展技术不同,LG-JTE只用一张注入窗口宽度随与主结的距离线性变化的掩膜版。结合仿真设计了采用LG-JTE的IGBT,并在国内工艺平台上成功流片,其测试耐压达到3.7kV,接近理想的平行平面情形的耐压。     

External cavity tunable quantum cascade lasers and their applications to trace gas monitoring

Since the first quantum cascade laser (QCL) was demonstrated approximately 16 years ago, we have witnessed an explosion of interesting developments in QCL technology and QCL-based trace gas sensors. QCLs operate in the mid-IR region (3-24?μm) and can directly access the rotational vibrational bands of most molecular species and, therefore, are ideally suited for trace gas detection with high specificity and sensitivity. These sensors have applications in a wide range of fields, including environmental monitoring, atmospheric chemistry, medical diagnostics, homeland security, detection of explosive compounds, and industrial process control, to name a few. Tunable external cavity (EC)-QCLs in particular offer narrow linewidths, wide ranges of tunability, and stable power outputs, which open up new possibilities for sensor development. These features allow for the simultaneous detection of multiple species and the study of large molecules, free radicals, ions, and reaction kinetics. In this article, we review the current status of EC-QCLs and sensor developments based on them and speculate on possible future developments.     

Investigation of phase transition behaviors of the nitrogen-doped Sb-rich Si-Sb-Te films for phase-change memory

The phase transformation properties of the nitrogen-doped Sb-rich Si-Sb-Te films were investigated in detail. It was found that the addition of N atoms into the Si-Sb-Te films increases the temperature for phase transition from the amorphous phase to a stable hexagonal structure and enhances the sheet resistance of the films following grain refinement. The surface topography of the crystalline films was improved by doping nitrogen atoms. The activation energy for crystallization of the films was increased from 1.84 to 2.89 eV with the increased nitrogen content from 0 to 21 at.%, which promises an improved thermal stability. A prolonged data lifetime up to 10 years at 149.4 °C was realized. From the device performance point of view, the N-doped Si-Sb-Te film with a moderate nitrogen content was preferable for the phase-change memory applications due to its advantage of higher reliability.