Actively recharged single photon counting avalanche photodiode integrated in an industrial CMOS process

An actively recharged single photon counting avalanche photodiode (SPAD) is integrated in a conventional CMOS process. A fast recharge through a low impedance path leads to a dead time lower than 10 ns. This outstanding feature allows one to work with pulse repetition rate up to 100 MHz in time correlated single photon counting based experiments. Biased 2.5 V above its breakdown voltage, the 30 μm² sensitive area photodiode has a maximum detection probability of about 20% at λ=440 nm and up to 5% in the visible part of the spectrum. At this bias condition, the dark count rate is as low as 60 Hz at room temperature, making a cooling of the microsystem unnecessary. The AR-SPAD exhibits no afterpulsing phenomenon revealing the maturity of the CMOS process used. The timing resolution of the AR-SPAD is less than 50 ps. For applications where the photons can be focused on the detector with an objective, the AR-SPAD is highly competitive with commercially available single photon counter. Furthermore, CMOS integration opens the way to arrays fabrication as well as co-integration of additional functions to develop smart optical sensors.     

A Computer Method to Model the Dose Distribution of High Energy Photon Grid Therapy in Three Dimensions

High energy photon grid therapy is the application of multiple circular divergent photon beams to the palliative care of patients. The photon beams are defined by cylindrical holes in a large attenuator placed in the path of an open radiation beam. We have developed a computer method to model the three-dimensional dose distribution of high energy photon grid therapy. The semiempirical method requires the measured data from a single cylindrical hole of the size to be modeled. For a given hole diameter, any arbitrary geometry can be calculated. This information is important when investigating the clinical implications of grid therapy for patient care.     

The Beam Radiance Estimate for Volumetric Photon Mapping

We present a new method for efficiently simulating the scattering of light within participating media. Using a theoretical reformulation of volumetric photon mapping, we develop a novel photon gathering technique for participating media. Traditional volumetric photon mapping samples the in‐scattered radiance at numerous points along the length of a single ray by performing costly range queries within the photon map. Our technique replaces these multiple point‐queries with a single beam‐query, which explicitly gathers all photons along the length of an entire ray. These photons are used to estimate the accumulated in‐scattered radiance arriving from a particular direction and need to be gathered only once per ray. Our method handles both fixed and adaptive kernels, is faster than regular volumetric photon mapping, and produces images with less noise.     

Mutual information expansion for studying the role of correlations in population codes: how important are autocorrelations?

The role of correlations in the activity of neural populations responding to a set of stimuli can be studied within an information theory framework. Regardless of whether one approaches the problem from an encoding or decoding perspective, the main measures used to study the role of correlations can be derived from a common source: the expansion of the mutual information. Two main formalisms of mutual information expansion have been proposed: the series expansion and the exact breakdown. Here we clarify that these two formalisms have a different representation of autocorrelations, so that even when the total information estimated differs by less than 1%, individual terms can diverge. More precisely, the series expansion explicitly evaluates the informational contribution of autocorrelations in the count of spikes, that is, count autocorrelations, whereas the exact breakdown does not. We propose a new formalism of mutual information expansion, the Poisson exact breakdown, which introduces Poisson equivalents in order to explicitly evaluate the informational contribution of count autocorrelations with no approximation involved. Because several widely employed manipulations of spike trains, most notably binning and pooling, alter the structure of count autocorrelations, the new formalism can provide a useful general framework for studying the role of correlations in population codes.     

Control loop diagnosis with ambiguous historical operating modes: Part 1. A proportional parametrization approach

Control-loop performance assessment methods have been evolving over the past two decades, with many different monitor algorithms being used to single out specific problems and determine the operating mode. However, a change in operating mode may affect multiple monitors, resulting in the possibility of conflicting assessments. Data-driven Bayesian methods were previously proposed which use multiple monitors to yield probabilistic assessments; however, training data for Bayesian methods requires complete knowledge of underlying operational modes. This paper proposes an approach based on proportionality parameters θ to address the problem of incomplete mode information in the training data; values in θ can be used to fill in missing information, and by varying θ one can determine the boundaries on a probabilistic diagnosis. Two diagnostic approaches are considered: the first type is direct probability approach, which can only be applied when historical data on the operation mode is sufficient and representative. The second type is the likelihood approach which can be applied to more general cases, including when the historical data is too limited to adequately represent mode frequency. In order to represent mode frequency, the likelihood approach takes into account prior probabilities of operating modes. The proposed methods are evaluated in two simulated chemical processes.     

基于分集接收的单光子探测技术

单光子三维探测技术因为在微弱信号目标的光学探测方面的独特优势，在空间目标探测、空中目标侦查、远距离预警探测等方面有重要应用，近年来获得了广泛关注。对主动扫描成像的单光子探测系统，为扩展作用距离和提高扫描速度，接收口径和接收视场角不断增大。但对高集成的盖革APD型的单光子探测器，大接收口径和大接收视场带来背景噪声光子数量的增大，这会导致探测器频繁进入死区，给扫描图像带来大量盲点。针对此问题，提出和通过仿真证明了，利用多镜头分集接收和联合单光子信息处理，可实现对单光子探测器死区时间抑制，进而有效提高系统探测概率，降低扫描图像的盲点数量，并通过试验系统进行了验证。     

Efficient entanglement concentration for quantum dot and optical microcavities systems

A recent paper (Chuan Wang in Phys Rev A 86:012323, 2012) discussed an entanglement concentration protocol (ECP) for partially entangled electrons using a quantum dot and microcavity coupled system. In his paper, each two-electron spin system in a partially entangled state can be concentrated with the assistance of an ancillary quantum dot and a single photon. In this paper, we will present an efficient ECP for such entangled electrons with the help of only one single photon. Compared with the protocol of Wang, the most significant advantage is that during the whole ECP, the single photon only needs to pass through one microcavity which will increase the total success probability if the cavity is imperfect. The whole protocol can be repeated to get a higher success probability. With the feasible technology, this protocol may be useful in current long-distance quantum communications.     

Scheduling jobs and maintenance activities subject to job-dependent machine deteriorations

This paper considers machine scheduling that integrates machine deterioration caused by jobs and, consequently, maintenance activities. The maintenance state of the machine is represented by a maintenance level which drops by a certain, possibly job-dependent amount while jobs are processed. A maintenance level of less than zero is associated with the machine’s breakdown and is therefore forbidden. Hence, maintenance activities that raise the maintenance level may become necessary and have to be scheduled additionally. We consider the objective to minimize the makespan throughout the paper. For the single machine case, we provide a linear-time approximation algorithm with worst-case a bound of 5/4, and comment on how an FPTAS from previous literature can be employed to apply to our problem. Due to problem similarity, these results also apply to the minimum subset sum problem, and the 5/4 linear-time approximation algorithm is an improvement over the 5/4 quadratic-time approximation algorithm of Güntzer and Jungnickel. For the general problem with multiple machines, we provide approximability results, two fast heuristics, an approximation algorithm with an instance-dependent approximation factor and a computational study evaluating the heuristics.     

无线传感器网络分簇路由的能量有效性研究

无线传感器网络中的节点以簇的方式进行路由时,簇成员可使用单跳或多跳通信模式将感知数据包发送至簇头。该文以簇内成员节点的最大能耗作为评价指标,研究了单跳和多跳的能量有效性,得出了通信模式的选择取决于通道衰减系数的结论。考虑到单纯的单跳或多跳模式会引起网络能耗不均衡,提出了簇成员节点以一定概率在单跳和多跳间切换的混合通信模式。以典型的网络参数进行仿真,验证了混合通信模式在能量有效性和能耗均衡分配方面的优势。     

A single chip multi-channel surface plasmon resonance imaging system

A single chip, multi-channel surface plasmon resonance (SPR) imaging system has been developed. The equipment has no moving parts and uses a single sensor chip on which multiple channels can be incorporated. A light emitting diode is used as a photon source while a CCD camera forms the detector. The optical configuration has been designed to achieve a uniform illumination of the sample over a fixed area with a range of incident angles. A calibration test using sucrose solutions shows that the sensitivity of the equipment is 4.3×10⁻⁴ refractive index units per pixel line-pair. The use of the system for simultaneous interrogation of different polyelectrolyte thin films, formed by the electrostatic layer-by-layer deposition method, is demonstrated. A reversible pH-dependent response for these organic layers is also reported.     

Elementary quantum gates in different bases

We introduce transformation matrix connecting sets of the displaced states with different displacement amplitudes. Arbitrary pure one-mode state can be represented in new basis of the displaced number (Fock) states (\(\alpha \)-representation) by multiplying the transposed transformation matrix on a column vector of initial state. Analytical expressions of the \(\alpha \)-representation of superposition of vacuum and single photon and two-mode squeezed vacuum are obtained. On the basis of the developed mathematical formalism, we consider the mechanism of interaction between qubits which is based on their displaced properties. Superposed coherent states deterministically displace target state on equal modulo but opposite on sign values. Registration of the single photon in auxiliary mode (probabilistic operation) results in constructive interference and gives birth to entangled hybrid state corresponding to outcome of elementary quantum gates. The method requires minimal number of resource and works in realistic scenario.     

Parallel bandwidth characteristics calculations for thin avalanche photodiodes on a SGI Origin 2000 supercomputer

An important factor for high‐speed optical communication is the availability of ultrafast and low‐noise photodetectors. Among the semiconductor photodetectors that are commonly used in today's long‐haul and metro‐area fiber‐optic systems, avalanche photodiodes (APDs) are often preferred over p‐i‐n photodiodes due to their internal gain, which significantly improves the receiver sensitivity and alleviates the need for optical pre‐amplification. Unfortunately, the random nature of the very process of carrier impact ionization, which generates the gain, is inherently noisy and results in fluctuations not only in the gain but also in the time response. Recently, a theory characterizing the autocorrelation function of APDs has been developed by us which incorporates the dead‐space effect, an effect that is very significant in thin, high‐performance APDs. The research extends the time‐domain analysis of the dead‐space multiplication model to compute the autocorrelation function of the APD impulse response. However, the computation requires a large amount of memory space and is very time consuming. In this research, we describe our experiences in parallelizing the code in MPI and OpenMP using CAPTools. Several array partitioning schemes and scheduling policies are implemented and tested. Our results show that the code is scalable up to 64 processors on a SGI Origin 2000 machine and has small average errors. Copyright © 2004 John Wiley & Sons, Ltd.     

印染行业不可靠生产系统生产控制模型

基于印染行业自身特性,建立了适合于该行业特点的不可靠生产系统的生产控制模型。该模型不但考虑了生产设备时有故障和修复事件的发生,而且也把由于生产系统操作条件及生产原料属性的波动造成合格产品呈随机分布的情况纳入模型框架,其中当不同产品间生产切换时,所需切换时间及切换费用也被引入模型,并假设此时设备的故障过程为Markov过程。结合单设备单产品情况,给出了其最优生产控制策略。为实现印染行业生产的优化控制及建立完善的MES系统提供了理论支持。     

T-bulge-shaped quantum router

The transport properties of a single photon scattered by a two-level system (TLS) in a T-bulge-shaped waveguide have been studied, which is made of two coupled-resonator waveguides (CRWs), an infinite CRW and a semi-infinite CRW with \(N-1\) FP cavities below the node. The spontaneous emission of the TLS directs single photons from one CRW to the other. The \(N-1\) FP cavities effect the extreme point’s value and location of the propagation coefficient and incident energy curve.     

Restitution curves and the stability of reentry in three-dimensional simulations of cardiac tissue

Recent studies have shown that cardiac antiarrhythmic drugs may actually increase mortality in certain instances. Due to the failure of the premise that an increased refractory period alone is sufficient to provide protection, it has been posited that the slope of the action potential duration (APD) restitution curve is a critical factor in the deterioration of tachycardia into fibrillation suggesting another avenue to explore in developing new antiarrhythmic drugs. This paper examines the relationship between APD restitution curves and the breakdown of stable reentry into fibrillation in a three dimensional model of a slab of cardiac tissue. The Luo-Rudy I model was used to describe the ionic current. Three different methods were used to measure the restitution curve: the standard protocol, the dynamic protocol and that measured directly, the natural restitution curve. The effects of altering conductances and time constants controlling the individual ionic currents on restitution and breakdown were determined. Manouevres which decreased action potential duration decreased the slope of the restitution curve. Consequently, reducing the slope of the restitution curve led to scroll waves which were more stable, taking longer time to break up. The restitution curves as measured by each of the different methods differed from each other as did restitution curves computed from two-dimensional sheets of tissue. Restitution curves produced by the standard and dynamic protocols defined an envelope in which the natural restitution curve was found to lie. From single cell experiments one could not determine whether the activity would break up by examining the peak slope of the restitution curve or the region of the slope above one, although the latter tended to correlate better with the simulated activity. This result suggests that the medium plays an important role in determining what behaviour gets expressed. Finally, the best route for preventing the breakdown of tachycardia into fibrillation would be to increase the kinetics of the slow inward current since it decreases the APD the least.     

供热系统集中器的智能控制终端设计与实现

为了解决目前城市供热系统主控中心单一控制方式造成的工作量大、控制不稳定、上传数据延迟等问题,提出了一种以楼栋集中器为控制对象的智能控制终端.该终端主要由中央处理器、IC卡读写模块、万年历时钟模块、数据存储比对模块、短信提醒模块、声光提醒模块组成.采用集散控制方式,把供热系统主控中心的单一控制权分散到每个楼栋,用户持IC卡到主控中心充值购热,然后在居民楼的控制终端刷卡来控制自家热量的使用状态,实现了供热管理的集中操作、分散控制、分级管理和灵活组态.     

Single‐cell‐gap transflective liquid‐crystal display and the use of photoalignment technology

Abstract— In this paper, transflective liquid‐crystal‐display (LCD) technology will be reviewed, and several new single‐cell‐gap transflective LCD configurations are proposed. Photoalignment technology is studied especially for transflective‐LCD applications. In order to realize the optimal performance of the display as well as a matched transmittance/reflectance voltage curve (TVC/RVC) for the transflective configurations, two different single‐cell‐gap transflective‐LCD approaches will be discussed. The first one is the dual‐mode single‐cell‐gap approach, in which different liquid‐crystal modes are applied to the transmissive and reflective subpixels of the transflective LCD. The other approach is the single‐mode s ingle‐cell‐gap approach, in which an in‐cell retardation film is applied to adjust the performance and TVC/RVC matching of a transflective LCD. Photoalignment technology is used to fabricate the dual‐mode liquid‐crystal cell in the first approach and also the in‐cell retardation film in the second approach. Prototypes of the proposed configurations have been fabricated, which show good performance and a matched TVC/RVC.     

嵌入式实时控制系统硬件可靠性及应用研究

嵌入式实时控制系统硬件故障是造成系统失效的主要原因之一,针对此问题,首先定义嵌入式实时控制系统硬件体系结构;然后分析嵌入式实时控制系统的可用性和失效模式,并对单个IP硬核和嵌入式实时控制系统硬件应用Markov链建立了可靠性模型;最后用所建立的模型,对嵌入式联锁控制器硬件进行了可靠度计算和分析。通过计算可知,所建立的可靠性模型能够描述嵌入式实时控制系统硬件的状态变迁,并能定量预测和分析其可靠度,模型具有一定的实用价值。     

计算机显卡常见故障与检修分析

我们知道,在很多情况下,电脑出现无法显示的故障并不是直接由显示硬件损坏所造成的,一些故障可以自己动手排除。本文为此根据介绍了与显卡有关的常见故障给出了现象、分析及其检修方法。     

An optical design for reflective color STN‐LCDs

In reflective color STN‐LCDs, it is necessary to achieve achromatic representation in single‐polarizer STN‐LCD modes. We propose an optimization method for the optical components of single‐polarizer STN‐LCD modes in order to achieve achromatic representation. By applying this method, it is shown that a contrast ratio of more than 20 can be achieved in the normally black (NB) mode. Furthermore, we prove that the normally white (NW) mode can be realized as well as an NB mode which is usually used in current reflective color STN‐LCDs. Comparing the viewing‐angle characteristics of the NW and NB modes, it was found that those of the NW mode are better than those of the NB mode. Particularly, high reflectance can be realized even at larger viewing angles in the NW mode.