Optimal code rates for concatenated codes on a PR4-equalizedmagnetic recording channel

At some nominal recording density, the read signal in digital magnetic recording resembles a Class IV partial response (PR4) signal and, hence, may be equalized to the PR4 shape with relatively little noise enhancement. When coding is added, for a fixed user density, the recording density must increase as a result of coding overhead, and the read signal will resemble PR4 to a lesser extent. Equalization to PR4 in this case will produce excessive noise enhancement. Thus, coding overhead (or rate) must be selected for optimum tradeoff between code strength and noise enhancement. Toward this end, we provide results for high-rate concatenated codes, assuming a Lorentzian recording channel model. In addition to examining optimal code rates, we compare parallel and serial concatenated code performance on the PR4 channel     

Quasi-Reduced-State Soft-Output Viterbi Detector for Magnetic Recording Read Channel

Reduced-state trellis detection with decision feedback is widely used to reduce the energy consumption of trellis detectors, particularly for soft-output trellis detectors that are energy-hungry by nature. However, the decision feedback tends to increase the circuit critical path and, more important, makes it difficult to apply some well-proven high-speed trellis detector design techniques such as bit-level pipelining. This paper presents a method, referred to as quasi-reduced-state trellis detection, to tackle such speed bottlenecks. The basic idea is to simply obviate the use of decision feedback by mapping only the data storage block of the trellis detector onto a reduced-state trellis and keeping the trellis state metric computation on the original full-state trellis. This makes sense because the data storage block tends to dominate the overall energy consumption while the decision feedback is due to the reduced-state trellis metric computation. Therefore, it is intuitive that such quasi-reduced-state detectors may largely maintain the energy saving potentials of reduced-state trellis detection without being subject to decision-feedback-induced speed bottlenecks. We demonstrated the effectiveness of this proposed design method by using soft-output Viterbi algorithm (SOVA) detection for a magnetic recording read channel as a test vehicle.     

Quasi-Cyclic LDPC Codes for the Magnetic Recording Channel: Code Design and VLSI Implementation

By implementing a field-programmable gate array (FPGA)-based simulator, we investigate the performance of randomly constructed high-rate quasi-cyclic (QC) low-density parity-check (LDPC) codes for the magnetic recording channel at very low block sector error rates. On the basis of extensive simulations, we conjecture guidelines for designing randomly constructed high-rate regular QC-LDPC codes with low error floor for the magnetic recording channel. Experimental results show that our high-rate regular QC-LDPC codes do not suffer from error floor, at least at block error rates of 10^-9, and can realize significant coding gains over Reed-Solomon codes that are used in current practice. Furthermore, we develop a QC-LDPC decoder hardware architecture that is well suited to achieving high decoding throughput. Finally, to evaluate the implementation feasibility of LDPC codes for the magnetic recording channel, using 0.13 mum standard cell and memory libraries, we designed a read channel signal processing datapath consisting of a parallel max-log-MAP detector and a QC-LDPC decoder, which can achieve a throughput up to 1.8 Gb/s     

莱斯信道下大规模MIMO系统混合模数转换器的随机向量量化方案

针对大规模MIMO系统用配置单精度模数转换器(ADC)来降低系统能耗会导致系统损失部分性能的问题,提出了一种莱斯信道下大规模MIMO系统的采用混合ADC的随机向量量化(RVQ)改进方案。该方案在频分双工模式下,首先在基站端采用高分辨率ADC和低分辨率ADC混合的接收方案处理信号,使接收的导频信号和有用信号具有较高的转换精度;系统对导频信号进行信道估计后,再对信道状态信息(CSI)进行RVQ处理,以此减小系统的反馈开销;最后运用最小均方误差(MMSE)信号检测算法减轻由量化误差引起的的用户间干扰,从而达到降低能耗并减小系统性能损失的目的。实验结果表明,这种改进的RVQ方案能在降低系统能耗的基础上有效减小系统容量损失,并使其和速率接近传统的高分辨率ADC接收方案。     

铸造多晶硅制备技术的研究进展

近年来,由于低成本、低耗能和少污染的优势,铸造多晶硅成为主要的光伏材料之一,越来越受到人们的广泛关注.系统论述了太阳能级多晶硅制备技术的研究进展,重点介绍了目前铸造多晶硅制备技术,如浇注法(Ingot casting)、定向凝固法及电磁感应加热连续铸造法(EMCP).另外,着重阐述了铸造多晶硅中磷和硼的提纯、多晶硅晶粒组织中晶界和位错的形成与控制以及定向凝固的数值模拟技术,讨论了铸造多晶硅材料的研究现状和存在的问题,展望了今后的发展方向.     

Low-loss, silicon integrated, aluminum nitride photonic circuits and their use for electro-optic signal processing

Photonic miniaturization requires seamless integration of linear and nonlinear optical components to achieve passive and active functions simultaneously. Among the available material systems, silicon photonics holds immense promise for optical signal processing and on-chip optical networks. However, silicon is limited to wavelengths above 1.1 μm and does not provide the desired lowest order optical nonlinearity for active signal processing. Here we report the integration of aluminum nitride (AlN) films on silicon substrates to bring active functionalities to chip-scale photonics. Using CMOS-compatible sputtered thin films we fabricate AlN-on-insulator waveguides that exhibit low propagation loss (0.6 dB/cm). Exploiting AlN's inherent Pockels effect we demonstrate electro-optic modulation up to 4.5 Gb/s with very low energy consumption (down to 10 fJ/bit). The ultrawide transparency window of AlN devices also enables high speed modulation at visible wavelengths. Our low cost, wideband, carrier-free photonic circuits hold promise for ultralow power and high-speed signal processing at the microprocessor chip level.     

Cresst-II: dark matter search with scintillating absorbers

In the CRESST-II experiment, scintillating CaWO₄ crystals are used as absorbers for direct weakly interacting massive particles (WIMP) detection. Nuclear recoils can be discriminated against electron recoils by measuring phonons and scintillation light simultaneously. The absorber crystal and the silicon light detector are read out by tungsten superconducting phase transition thermometers. Results on the sensitivity of the phonon and the light channel, radiopurity, the scintillation properties of CaWO₄, and on the WIMP sensitivity are presented.     

单用户毫米波大规模MIMO系统的混合预编码方案设计

对MIMO通信系统的数字预编码方法进行了深入分析,指出单用户毫米波大规模MIMO系统和传统全数字预编码方案所用射频(RF)链路数量过大致使系统实现成本大和能量消耗较高,并针对这种情况,提出了一种在系统收发两端分别采用混合预编码器和混合合成器的混合预编码方案。该方案首先通过迭代算法设计模拟预编码矩阵,并且根据信道矩阵与模拟预编码矩阵作用生成的等效信道矩阵设计数字预编码矩阵,然后根据混合预编码器设计混合合成器,从而使系统频谱效率最大化。该方案与传统全数字预编码及现有混合预编码方案的仿真比较结果表明,该方案有效降低了系统实现成本和能量消耗,且性能优于现有的混合预编码方案,与传统全数字预编码方案相比,性能非常接近。     

A silicon composite thermal and ionization X-ray detector

We have made a combination calorimetric and ionization X-ray detector by attaching a silicon p-i-n diode to a monolithic silicon microcalorimeter. Applying a bias to the diode enhanced the thermal signal, and with a reverse bias of 25 V we achieved a detection threshold of 8 eV, based upon energy scaling of the standard deviation of the baseline noise. We were able to measure a charge signal in the absence of applied bias on the diode, demonstrating that the junction potential is sufficient to drift the ionized charges to the contacts. A fraction of the electron-hole pairs created became trapped, manifested by excess broadening in the measured thermal signal and by using the variation of the thermal signal magnitude with reverse bias to fit for the fraction of charge that is trapped. The ability to collect charge without an applied bias is necessary to produce high resolution combination thermal and ionization detectors.     

Practical equalizer for a perpendicular magnetic disk

We have developed a readback equalizer for a perpendicular magnetic disk with a commercial anisotropic magnetoresistive head for use with a PR4ML read channel with 8-9 coding. The transfer function of the perpendicular magnetic disk, derived by Fourier analysis, has a phase lag of 90/spl deg/ from that of the longitudinal magnetic disk. We defined the parameters of the equalizer by simulation. The equalized readback signal nearly satisfied Nyquist's first criterion. Using resistor-capacitor circuits that correspond to the simulated function, we obtained a byte-error rate of below 10/sup -7/. Comparing the effect of incorporating PR4 or PR1 as part of the equalizer, we observed that PR4 gave a lower bit-error rate than PR1. Thus, PR4 is an effective detection method for a perpendicular magnetic disk. It is suitable not only for longitudinal magnetic disks, but also for perpendicular magnetic disks.     

Coding and Modulation for LMDS and Analysis of the LMDS Channel

Local Multipoint Distribution Service (LMDS) has the potential to become a viable alternative to coaxial cable, fiber and other wired and wireless technologies providing “last mile” communication services. A major obstacle, however, is the high equipment cost. While for example cable modems supporting two-way services are available for $200 to $300, LMDS modem providing similar services will cost over $1000. The major cost driver of LMDS equipment is the radio frequency (RF) unit, as Ka-band technology still is quite expensive. The modem design must minimize the overall architecture cost, and low-cost modems requiring an expensive architecture should not be used. The channel characteristics of LMDS systems are very different from those of fiber, coaxial cable, and lower frequency wireless links, major channel impairments being non-linear high power amplifier (HPA), high phase noise and high co-channel interference. Modems should therefore be developed specifically for LMDS systems. This report deals with the choice of coding and modulation schemes, the LMDS channel, and how the channel impairments should be overcome by digital signal processing algorithms.     

Silicon nanostructured layers for improvement of silicon solar cells' efficiency: A promising perspective

The photovoltaics industry is dominated by silicon solar cells technology mainly because of the low manufacturing cost. However, these solar cells show an important limiting factor on conversion efficiency due to the inefficient absorption of high energy photons as a consequence of the indirect bandgap structure of bulk silicon. In this article, we discuss about different possibilities to improve the efficiency of solar cells and we propose the use of silicon nanostructured layers to achieve this goal. We present the fabrication methods as well as the characterization results of two kinds of layers which can be used for solar cells' efficiency improvement, namely non-stoichiometric silica layers (SiO_x) and non-stoichiometric silicon nitride layers (SiN_x). We demonstrate that the photoluminescence (PL) properties and/or the increased photocurrent (PC) signal at high-energy photon could be used to improve this efficiency. Finally, the major asset of these methods lies in their possibility to be incorporated to the solar cell processing for an insignificant cost.     

民宿无人值守智能管理系统设计与实现

在民宿的运营成本中,人力成本与能源成本所占份额较大。为了在降低成本和减少能源损耗的同时增加收益,设计了一款民宿无人值守智能管理系统。基于数据挖掘技术,利用爬虫程序获取了大量民宿运营数据,为辅助民宿商户决策提供参考;使用无线RFID（radio frequency identification,射频识别）技术,通过读写器读取对应标签的RSSI（received signal strength indicator,接受信号强度指示器）值来检测人体位置的变化情况,使得入住管理和退房管理更加高效;通过STM32控制模块控制照明灯、窗帘和空调等的驱动电路以实现自动控光、自动控温等功能,或通过智能触控面板手动控制智能家居设备。结果表明：结合SVM（support vector machine,支持向量机）算法,RFID检测系统可准确检测到房间内人员的变化情况,其准确率达到99.25%,具有较高的实用价值。研究显示,该智能管理系统可实现民宿的无人值守管理,既降低了人力成本又减少了能源损耗,为响应国家智能用电服务的乡村振兴战略奠定了基础。     

Iterative processing of ultrasonic measurements to characterize flaws in critical optical components

Real-time nondestructive evaluation is crucial for the safety and maintenance of critical optics in high energy, laser physics experiments. Fluence levels in short pulse, high-energy lasers can produce pits and cracks in the surfaces of the laser's optical components. These flaws in the optical glass can adversely affect the production of the laser light, or even result in a catastrophic failure of the optical component itself. Consequently, the detection, localization, and characterization of these flaws is critical. This paper describes the novel application of several signal and image-processing techniques that detect, localize, and characterize flaws in optical components. These techniques are embedded into an optic scanning system to automatically identify and report on the condition of the vacuum windows used in high fluence laser systems. These techniques exploit measurements made from two orthogonal acoustic arrays mounted on adjacent edges of the optic. After preprocessing the raw channel measurement data from two orthogonal, narrow beamwidth, transducer arrays, a two-dimensional (2-D) power image is created. A physics-based 2-D matched filter is then developed for detecting and localization. An iterative solution to sequentially search the resulting image to extract and characterize the flaws is discussed.     

Study on the removal process of phosphorus from silicon by electron beam melting

According to the traditional metallurgical theory, the evaporation process of phosphorus and silicon during silicon refining by electron beam melting (EBM) is discussed and a theoretical model is established to obtain the loss rate of silicon, the removal efficiency of phosphorus and the corresponding energy consumption. The results show that phosphorus can be removed from silicon melt efficiently and quickly by EBM. There is a one-to-one correspondence between the loss of silicon and the removal efficiency of phosphorus, indicating that they have obvious effect on each other, whereas the EB power has little influence on the loss rate of silicon. If the EB power is increased from 9 kW to 21 kW, the melting time can be shortened by 68%, the loss of silicon increased by only 0.1% and the energy consumption decreased by 25%. Based on the theoretical and experimental results, a high-power EBM method is considered to be a better way for the removal of phosphorus with high efficiency and low energy consumption under such experiment conditions.     

High-efficiency ordered silicon nano-conical-frustum array solar cells by self-powered parallel electron lithography

Nanostructured silicon thin film solar cells are promising, due to the strongly enhanced light trapping, high carrier collection efficiency, and potential low cost. Ordered nanostructure arrays, with large-area controllable spacing, orientation, and size, are critical for reliable light-trapping and high-efficiency solar cells. Available top-down lithography approaches to fabricate large-area ordered nanostructure arrays are challenging due to the requirement of both high lithography resolution and high throughput. Here, a novel ordered silicon nano-conical-frustum array structure, exhibiting an impressive absorbance of 99% (upper bound) over wavelengths 400-1100 nm by a thickness of only 5 μm, is realized by our recently reported technique self-powered parallel electron lithography that has high-throughput and sub-35-nm high resolution. Moreover, high-efficiency (up to 10.8%) solar cells are demonstrated, using these ordered ultrathin silicon nano-conical-frustum arrays. These related fabrication techniques can also be transferred to low-cost substrate solar energy harvesting device applications.     

Silicon nanoribbons for electrical detection of biomolecules

Direct electrical detection of biomolecules at high sensitivity has recently been demonstrated using semiconductor nanowires. Here we demonstrate that semiconductor nanoribbons, in this case, a thin sheet of silicon on an oxidized silicon substrate, can approach the same sensitivity extending below the picomolar concentration regime in the biotin/streptavidin case. This corresponds to less than approximately 20 analyte molecules bound to receptors on the nanoribbon surface. The micrometer-size lateral dimensions of the nanoribbon enable optical lithography to be used, resulting in a simple and high-yield fabrication process. Electrical characterization of the nanoribbons is complemented by computer simulations showing enhanced sensitivity for thin ribbons. Finally, we demonstrate that the device can be operated both in inversion as well as in accumulation mode and the measured differences in detection sensitivity are explained in terms of the distance between the channel and the receptor coated surface with respect to the Debye screening length. The nanoribbon approach opens up for large scale CMOS fabrication of highly sensitive biomolecule sensor chips for potential use in medicine and biotechnology.     

A single active nanoelectromechanical tuning fork front-end radio-frequency receiver

Nanoelectromechanical systems (NEMS) offer the potential to revolutionize fundamental methods employed for signal processing in today's telecommunication systems, owing to their spectral purity and the prospect of integration with existing technology. In this work we present a novel, front-end receiver topology based on a single device silicon nanoelectromechanical mixer-filter. The operation is demonstrated by using the signal amplification in a field effect transistor (FET) merged into a tuning fork resonator. The combination of both a transistor and a mechanical element into a hybrid unit enables on-chip functionality and performance previously unachievable in silicon. Signal mixing, filtering and demodulation are experimentally demonstrated at very high frequencies (?>?100?MHz), maintaining a high quality factor of Q?=?800 and stable operation at near ambient pressure (0.1?atm) and room temperature (T?=?300?K). The results show that, ultimately miniaturized, silicon NEMS can be utilized to realize multi-band, single-chip receiver systems based on NEMS mixer-filter arrays with reduced system complexity and power consumption.     

Reverse-phase versus sandwich antibody microarray, technical comparison from a clinical perspective

Protein microarrays are powerful tools to quantify and characterize proteins in multiplex assays. They have great potential within clinical diagnostics and prognostics, as they minimize consumption of both analyte and biological sample. Assays that do not require labeling of the biological specimen, henceforth called label-free, are vital for ease of clinical sample processing. Here, we evaluate two label-free techniques, reverse-phase and sandwich antibody assays, using microarrays on high-performance porous silicon surfaces and fluorescence detection. In view of increasing interest in reverse microarrays, this paper focuses on analytical sensitivity of the reverse assays compared to the more complex but highly sensitive sandwich assay. Sensitivity, linear range, and reproducibility of the two assays were compared using prostate-specific antigen (PSA) in buffer. The sandwich assay displayed 5 orders of magnitude lower detection limit (0.7 ng/mL) compared to the reverse assay (70 microg/mL). PSA at 50 nM (1.5 microg/mL) in cell lysates was detected by the sandwich assay but not by the reverse assay, demonstrating again a far lower detection limit for sandwich microarrays. In independent assay runs of PSA spiked in female serum, the sandwich assay had good linearity (R2 > 0.99) and reproducibility (coefficient of variation < or =15%), and the detection limit could be improved to 0.14 ng/mL. Without further signal amplification, the sandwich assay would be our choice for PSA analysis of clinical samples using a microarray technology platform.     

Performance Analysis of Multi-Channel CR Enabled IoT Network with Better Energy Harvesting

Wireless Sensor Networks (WSNs) can be termed as an auto-configured and infrastructure-less wireless networks to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure and motion etc. WSNs may comprise thousands of Internet of Things (IoT) devices to sense and collect data from its surrounding, process the data and take an automated and mechanized decision. On the other side the proliferation of these devices will soon cause radio spectrum shortage. So, to facilitate these networks, we integrate Cognitive Radio (CR) functionality in these networks. CR can sense the unutilized spectrum of licensed users and then use these empty bands when required. In order to keep the IoT nodes functional all time, continuous energy is required. For this reason the energy harvested techniques are preferred in IoT networks. Mainly it is preferred to harvest Radio Frequency (RF) energy in the network. In this paper a region based multi-channel architecture is proposed. In which the coverage area of primary node is divided as Energy Harvesting Region and Communication Region. The Secondary User (SU) that are the licensed user is IoT enabled with Cognitive Radio (CR) techniques so we call it CR-enabled IoT node/device and is encouraged to harvest energy by utilizing radio frequency energy. To harvest energy efficiently and to reduce the energy consumption during sensing, the concept of overlapping region is given that supports to sense multiple channels simultaneously and help the SU to find best channel for transmitting data or to harvest energy from the ideal channel. From the experimental analysis, it is proved that SU can harvest more energy in overlapping region and this architecture proves to consume less energy during data transmission as compared to single channel. We also show that channel load can be highly reduced and channel utilization is proved to be more proficient. Thus, this proves the proposed architecture cost-effective and energy-efficient.