基于FPGA的高速电光选通系统设计

介绍了一种获取高速调制电信号的新方法－基于FPGA的高速电光选通系统.此系统分为选通脉冲和高压调控两个模块.选通脉冲模块由高速信号放大、FPGA延时、可控延迟传输线三个部分组成.利用FPGA高密度、高可靠性、可反复擦写和可以现场编程、灵活调制的特点,将整个系统的主要控制部分集成在FPGA中,并将延时分为数字延时和模拟延时两部分.然后利用FPGA实现数字延时,可控延时线实现模拟延时.经试验检测,高压部分可以产生重复频率1 Hz~1 kHz,步进1 Hz,延时范围为0~1 μs,步进为1 ns,幅度为8 000 V,前沿和后沿小于10 ns,抖动小于1 ns的高压矩形电脉冲,从而满足各种电光调制系统中的需要.     

Operation of thin-film gated SOI lateral PIN photodetectors with gate voltage applied and intrinsic length variation

This paper describes the operation principle of thin-film gated SOI lateral PIN photodetectors, and an analytical model of depletion voltage is presented and validated by two-dimensional Atlas simulations. With gate voltage applied to achieve fully depleted (FD) condition in intrinsic region, the variation of intrinsic length (L_i) on photocurrent and dark current characteristics, sensitivity, and speed is addressed. With L_i between 1 and 10 μm, the simulated results predict internal quantum efficiency (QI) in excess of 95% even near 100% at a 400 nm wavelength. Also, QI can yield over 87% for the long channels. Under FD condition, the total −3 dB frequency value can achieve 16 GHz (19 GHz) for L_i = 1  and 4.1 GHz (6.2 GHz) for L_i = 2 μm with V_K = 1.0 V (2.0 V). And a high ratio of more than 10⁷ between illuminated and dark currents can be yielded for all detectors realized in 0.18 μm SOI CMOS technology.     

TEOS-based low-pressure chemical vapor deposition for gate oxides in 4H–SiC MOSFETs using nitric oxide post-deposition annealing

The use of SiO₂/4H–SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) can be problematic due to high interface state density (D_it) and low field-effect mobility (μ_fe). Here, we present a tetra-ethyl-ortho-silicate (TEOS)-based low-pressure chemical vapor deposition (LPCVD) method for fabricating the gate oxide of 4H–SiC MOSFETs using nitric oxide post-deposition annealing. SiO₂/4H–SiC MOS capacitors and MOSFETs were fabricated using conventional wet and TEOS oxides. The measured effective oxide charge density (Q_eff) and D_it of the TEOS-based LPCVD SiO₂/4H–SiC MOS capacitor with nitridation were 4.27 × 10¹¹ cm⁻² and 2.99 × 10¹¹ cm⁻²eV⁻¹, respectively. We propose that the oxide breakdown field and barrier height were dependent on the effective Q_eff. The measured μ_fe values of the SiO₂/4H–SiC MOSFETs with wet and TEOS oxides after nitridation were, respectively, 11.0 and 17.8 cm²/V due to the stable nitrided interface between SiO₂ and 4H–SiC. The proposed gate stack is suitable for 4H–SiC power MOSFETs.     

Prediction of financial distress: An empirical study of listed Chinese companies using data mining

The deterioration in profitability of listed companies not only threatens the interests of the enterprise and internal staff, but also makes investors face significant financial loss. It is important to establish an effective early warning system for prediction of financial crisis for better corporate governance. This paper studies the phenomenon of financial distress for 107 Chinese companies that received the label ‘special treatment’ from 2001 to 2008 by the Shanghai Stock Exchange and the Shenzhen Stock Exchange. We use data mining techniques to build financial distress warning models based on 31 financial indicators and three different time windows by comparing these 107 firms to a control group of firms. We observe that the performance of neural networks is more accurate than other classifiers, such as decision trees and support vector machines, as well as an ensemble of multiple classifiers combined using majority voting. An important contribution of the paper is to discover that financial indicators, such as net profit margin of total assets, return on total assets, earnings per share, and cash flow per share, play an important role in prediction of deterioration in profitability. This paper provides a suitable method for prediction of financial distress for listed companies in China.     

Correlated majority model

We extend the bichromatic majority model by including (one-dimensional isotropic) correlations and numerically discuss, through Monte Carlo simulations, the simple, 1/3, and 2/3 majority rules. We calculate, as functions of the concentration and correlation degree, the mean finite cluster size, and the order parameterm as well as their respective critical exponents and. We find1 regardless of the correlation degree or the type of majority. Also, a supplementary divergence of is observed at the>0 borderline.     

Three-state majority-vote model on square lattice

Here, a non-equilibrium model with two states (−1,+1) and a noise q on simple square lattices proposed for M.J. Oliveira (1992) following the conjecture of up-down symmetry of Grinstein and colleagues (1985) is studied and generalized. This model is well-known, today, as the majority-vote model. They showed, through Monte Carlo simulations, that their obtained results fall into the universality class of the equilibrium Ising model on a square lattice. In this work, we generalize the majority-vote model for a version with three states, now including the zero state, (−1,0,+1) in two dimensions. Using Monte Carlo simulations, we showed that our model falls into the universality class of the spin-1 (−1,0,+1) and spin-1/2 Ising model and also agree with majority-vote model proposed for M.J. Oliveira (1992). The exponent ratio obtained for our model was γ/ν=1.77(3), β/ν=0.121(5), and 1/ν=1.03(5). The critical noise obtained and the fourth-order cumulant were q_c=0.106(5) and U^∗=0.62(3).     

Effect of post-deposition annealing on structural and electrical properties of high-k HoTiO3 gate dielectrics

In this article, the authors developed a high-k HoTiO₃ gate dielectric deposited on Si (1 0 0) through reactive cosputtering. They found that the HoTiO₃ dielectrics annealed at 800 °C exhibited excellent electrical properties such as high capacitance value, small density of interface state, almost no hysteresis voltage, and low leakage current. This phenomenon is attributed to the decrease in intrinsic defect (related to oxygen vacancy) due to a rather well-crystallized HoTiO₃ structure and composition observed by X-ray diffraction, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy, respectively.     

Stereotype formation as trait aggregation

We propose an aggregation model which explains stereotype formation under the attribution hypothesis. We show, under very mild axioms, that an observer can be thought of perceiving a group in terms of her subjective opinion about the representativeness of subgroups, as well as a possible prejudice she might have.     

Continuity properties of majority rule with intermediate preferences

This paper shows that certain conditions which have previously been shown (by Grandmont) to be sufficient for a society's majority rule relation to be transitive or acyclic are also sufficient for the map from distributions of voter preferences to indices identified with their majority rule relations to be continuous. Applications of this result to societies with certain classical assumptions on preferences reveal that, in such societies, the map from distributions of voter preferences to their majority rule equilibria is also continuous.     

Majority judgment over a convex candidate space

Most voting methods can only deal with a finite number of candidates. In practice, there are important voting applications where the candidate space is continuous. We describe a new voting method by extending the Majority Judgment voting and ranking method to handle a continuous candidate space which is modeled as a convex set. We characterize the structure of the winner determination problem and present a practical iterative voting procedure for finding a (or the) winner when voter preferences are unknown.