Time-frequency spectral estimation of speech

In recent years there has been a growing interest amongst the speech research community into the use of spectral estimators which circumvent the traditional quasi-stationary assumption and provide greater time-frequency (t-f) resolution than conventional spectral estimators, such as the short time Fourier power spectrum (STFPS). One distribution in particular, the Wigner distribution (WD), has attracted considerable interest. However, experimental studies have indicated that, despite its improved t-f resolution, employing the WD as the front end of speech recognition system actually reduces recognition performance; only by explicitly re-introducing t-f smoothing into the WD are recognition rates improved. In this paper we provide an explanation for these findings. By treating the spectral estimation problem as one of optimization of a bias variance trade off, we show why additional t-f smoothing improves recognition rates, despite reducing the t-f resolution of the spectral estimator. A practical adaptive smoothing algorithm is presented, whicy attempts to match the degree of smoothing introduced into the WD with the time varying quasi-stationary regions within the speech waveform. The recognition performance of the resulting adaptively smoothed estimator is found to be comparable to that of conventional filterbank estimators, yet the average temporal sampling rate of the resulting spectral vectors is reduced by around a factor of 10. © 1992.

A CMOS analogue predistortion circuit for wideband optical fibre links

The laser is a major source of nonlinearity for optical fibre communication systems. In this paper, we propose a CMOS analogue predistortion circuit to reduce laser nonlinearity for wideband optical fibre links. The circuit uses a nonlinearity having the inverse transfer characteristic of the directly modulated vertical cavity surface emitting laser (VCSEL). It is shown by post-layout simulation that the predistortion circuit shows 12dBm improvement in the optical fibre system. The optical fibre transmitter front-end with predistortion lineariser is being fabricated using the austriamicrosystems (AMS) 0.3 5μm CMOS technology.

Addressing the cognitive and social influence inhibitors during the ideation stages of technology roadmapping workshops

Technology roadmapping workshops are essentially a social mechanism for exploring, creating, shaping and implementing ideas. The front-end of a roadmapping session is based on brainstorming in order to tap into the group's diverse knowledge. The aim of this idea stimulation activity is to capture and share as many perspectives as possible across the full scope of the area of interest. The premise to such group brainstorming is that the sharing and exchange of ideas leads to cognitive stimulation resulting in a greater overall group idea generation performance in terms of the number, variety and originality of ideas. However, it must be recognized that the ideation stage in a roadmapping workshop is a complex psychosocial phenomenon with underlying cognitive and social processes. Thus, there are downsides to group interactions and these must be addressed in order to fully benefit from the power of a roadmapping workshop. This paper will highlight and discuss the key cognitive and social inhibitors involved. These include: production blocking, evaluation apprehension, free riding/social loafing, low norm setting/matching. Facilitation actions and process adjustments to counter such negative factors will be identified so as to provide a psychosocial basis for improving the running of roadmapping workshops. © 2009 PICMET.

Constrained discriminative mapping transforms for unsupervised speaker adaptation

Discriminative mapping transforms (DMTs) is an approach to robustly adding discriminative training to unsupervised linear adaptation transforms. In unsupervised adaptation DMTs are more robust to unreliable transcriptions than directly estimating adaptation transforms in a discriminative fashion. They were previously proposed for use with MLLR transforms with the associated need to explicitly transform the model parameters. In this work the DMT is extended to CMLLR transforms. As these operate in the feature space, it is only necessary to apply a different linear transform at the front-end rather than modifying the model parameters. This is useful for rapidly changing speakers/environments. The performance of DMTs with CMLLR was evaluated on the WSJ 20k task. Experimental results show that DMTs based on constrained linear transforms yield 3% to 6% relative gain over MLE transforms in unsupervised speaker adaptation. © 2011 IEEE.

Low-cost PCB-integrated 10-Gb/s optical transceiver built with a novel integration method

A novel integration method for the production of cost-effective optoelectronic printed circuit boards (OE PCBs) is presented. The proposed integration method allows fabrication of OE PCBs with manufacturing processes common to the electronics industry while enabling direct attachment of electronic components onto the board with solder reflow processes as well as board assembly with automated pick-and-place tools. The OE PCB design is based on the use of polymer multimode waveguides, end-fired optical coupling schemes, and simple electro-optic connectors, eliminating the need for additional optical components in the optical layer, such as micro-mirrors and micro-lenses. A proof-of-concept low-cost optical transceiver produced with the proposed integration method is presented. This transceiver is fabricated on a low-cost FR4 substrate, comprises a polymer Y-splitter together with the electronic circuitry of the transmitter and receiver modules and achieves error-free 10-Gb/s bidirectional data transmission. Theoretical studies on the optical coupling efficiencies and alignment tolerances achieved with the employed end-fired coupling schemes are presented while experimental results on the optical transmission characteristics, frequency response, and data transmission performance of the integrated optical links are reported. The demonstrated optoelectronic unit can be used as a front-end optical network unit in short-reach datacommunication links. © 2011-2012 IEEE.

Tandem system adaptation using multiple linear feature transforms

Adaptation to speaker and environment changes is an essential part of current automatic speech recognition (ASR) systems. In recent years the use of multi-layer percpetrons (MLPs) has become increasingly common in ASR systems. A standard approach to handling speaker differences when using MLPs is to apply a global speaker-specific constrained MLLR (CMLLR) transform to the features prior to training or using the MLP. This paper considers the situation when there are both speaker and channel, communication link, differences in the data. A more powerful transform, front-end CMLLR (FE-CMLLR), is applied to the inputs to the MLP to represent the channel differences. Though global, these FE-CMLLR transforms vary from time-instance to time-instance. Experiments on a channel distorted dialect Arabic conversational speech recognition task indicates the usefulness of adapting MLP features using both CMLLR and FE-CMLLR transforms. © 2013 IEEE.

支持JSR286规范的Portlet协作框架的设计与实现

Portlet是具有用户界面的可与用户多次交互的Web组件。随着Portal和Portlet在企业中的广泛应用，仅仅将各种应用和数据通过Portlet集成到Portal中已经不能满足用户的需求。用户希望这些应用之间能够相互协作，以利用现有应用组建新的业务流程。Portlet协作是指两个或多个Portlet进行信息交换并使用这些信息的能力。目前协作功能的实现方式可以分为两种：基于后端(back-end)的实现方式与基于前端(front-end)的实现方式。在这两种协作实现方式的基础上，本文提出了两种Portlet协作框架。 本文提出一种基于事件的Portlet前端协作模型，通过引入此模型，解决了Portlet前端协作中客户端与服务器端无法交互的困难，使协作动作由客户端和服务器端共同完成。基于此模型提供给开发者一种可扩展的协作框架，利用JavaScript技术使得协作的Portlet在客户端“相知”，协作的行为在客户端触发，Portlet获得协作数据后使用Ajax技术请求服务器端的资源，服务器端使用JSR286规范定义的资源服务接口响应用户的请求，进而动态更新界面。 当前的Portlet后端协作方式依赖于特定的Portal产品，针对这点不足，本文在JSR286规范定义的事件及共享渲染参数协作机制基础上，实现了一个Portlet后端协作框架。在该框架中协作服务使用消息队列保存待处理的消息，Portlet 容器作为中介实现发布事件的Portlet和订阅事件的Portlet之间松散耦合。Portlet监听协作事件，事件触发后调用事件协作服务发布事件，为了提高协作的并发性，事件协作服务使用多线程处理协作事件。该协作框架与JSR286规范兼容，具有良好的可移植性。 本文对这两种Portlet协作框架进行了实现，并将其应用于中科院软件所自主开发的门户产品OncePortal中。本文重构了OncePortal系统，给出了框架的体系结构与系统接口，描述了框架的各功能模块，并详细讨论了Portlet协作框架中的关键技术，包括事件协作流程的描述、事件处理过程、多级事件流等。

Multi-strip MRPCs for FOPI

During the last years FOPI has developed a new ToF system as an upgrade of the existing detector based on Multi-strip Multi-gap Resistive Plate Chambers (MMRPCs). The intention is to increase the charged Kaon identification up to a laboratory momentum of 1 GeV/c and to enhance the azimuthal detector granularity. The new ToF barrel has an active area of 5 m(2) with 2400 individual strips (900 x 1.6 mm(2)) [A. Schuttauf, et al., Nucl. Phys. B 158 (2006) 52] which are read out on both sides by a custom designed electronics [M. Ciobanu, et al., IEEE Trans. Nucl. Sci. NS-54 (4) (2007) 1201; K. Koch, et al., IEEE Trans. Nucl. Sci. NS-52(3) (2005) 745]. To reach the envisaged goal a time resolution of 100 ps is needed, at a flight path of 1-1.3 m. Due to the rare production of the K- at SIS energies the efficiency of the MMRPCs has to be above 95%. We report on measurements with the detectors and electronics from the mass production line. For this purpose we used a proton beam at 2.0 and 1.25 GeV, at rates between 0.1 and 5 kHz/cm(2) to determine the timing, efficiency and rate capability of the MMRPCs

A low noise charge sensitive preamplifier with switch control feedback resistance

In this paper, the design and analysis of a new low noise charge sensitive preamplifier for silicon strip, Si(Li), CdZnTe and CsI detectors etc. with switch control feedback resistance were described, the entire system to be built using the CMOS transistors. The circuit configuration of the CSP proposed in this paper can be adopted to develop CMOS-based Application Specific Integrated Circuit further for Front End Electronics of read-out system of nuclear physics, particle physics and astrophysics research, etc. This work is an implemented design that we succeed after a simulation to obtain a rise time less than 3ns, the output resistance less than 94 Omega and the linearity almost good.

The Compact Pulsed Hadron Source: A Design Perspective

During the past. decades, large-scale national neutron sources have been developed in Asia, Europe, and North America. Complementing such efforts, compact hadron beam complexes and neutron sources intended to serve primarily universities and industrial institutes have been proposed, and some have recently been established. Responding to the demand in China for pulsed neutron/proton-beam platforms that are dedicated to fundamental and applied research for users in multiple disciplines from materials characterization to hadron therapy and radiography to accelerator-driven sub-critical reactor systems (ADS) for nuclear waste transmutation, we have initiated the construction of a compact, yet expandable, accelerator complex-the Compact Pulsed Hadron Source (CPHS). It consists of an accelerator front-end (a high-intensity ion source, a 3-MeV radio-frequency quadrupole linac (RFQ), and a 13-MeV drift-tube linac (DTL)), a neutron target station (a beryllium target with solid methane and room-temperature water moderators/reflector), and experimental stations for neutron imaging/radiography, small-angle scattering, and proton irradiation. In the future, the CPHS may also serve as an injector to a ring for proton therapy and radiography or as the front end to an ADS test facility. In this paper, we describe the design of the CPHS technical systems and its intended operation.

中子墙探测器前端电子学研究

随着国家大科学工程兰州重离子加速器冷却储存环(HIRFL-CSR)建成，CSRm实验探测系统也正在建设当中。CSRm实验探测系统由外靶系统和内靶系统构成。外靶系统主要有γ探测器、多丝漂移室（MWDC）、ToF墙(ToF Wall)、中子墙（Neutron Wall）等探测器组成，主要用于核物理研究。其中，用于探测中子的中子墙探测器是外靶系统中的一个重要组成部分，它有252个探测单元，每一个探测器单元都要求既有很好的能量分辨，也要有很好的时间分辨，同时还要求数据获取率达到每秒几千个事件。对于这样先进的探测器和大型实验探测系统采用传统的电子学仪器和方法已经无法构成读出电子学系统，建造与之相配的读出电子学系统是极为重要的和亟待解决的工作。为此，我们设计研发适合于中子墙探测器这样的大型闪烁体探测器的前端电子学读出系统。包括三大部分：16道电荷幅度转换电路（QAC），16道时间幅度转换电路（TAC）和有效信号判断电路。本论文的主要内容如下：在第一章绪论中，介绍了论文课题的出发点以及课题的意义，并对课题的背景进行了介绍。第二章介绍我们所自行设计的中子墙探测器的特点、结构。分析了中子墙探测器的输出信号的特点以及对后续前端电子学读出系统的要求。第三章是本论文两大核心部分之一，是本论文的创新点所在。主要介绍了我们电荷幅度转换的新方法，结合通常的QAC电路方法和具体的实际情况，我们自行提出了一种新的QAC电路，包括以下几个部分：差分输入电路、电流分割、上下恒流源、门控电流积分器。我们的创新点在于，我们用上下恒流源分别代替了通常QAC中作为电流分配的电流镜像和作为电流基准的电阻，这样一来更容易得到比较稳定的偏置电流，从而能够得到更高的转换精度。第四章是本论文的另外一个核心部分，首先我们论述了核电子学时间测量的几种方法，在对它们进行对比后，结合中子墙的实际特点，我们确定了采用起停型的TAC方法。然后介绍了TAC的原理，以及具体的电路结构。第五章主要的内容是对我们整个电路的逻辑电路进行了详细的介绍，它包括16道QAC和16道TAC的积分控制信号和泄放控制信号的产生电路以及有效信号判断电路。详细论述了这些逻辑关系以及如何在CPLD实现，并且给出了仿真结果。第六章详细讨论了我们在设计PCB板时遇到的问题及其解决方法。第七章介绍了多路QAC和多路TAC主要指标及其测试方法、步骤、结果并给出了误差分析。在总结部分我们回顾了我们整个工作的过程，介绍了论文的主要成果和创新点以及对于整个CSR工程的意义。本论文的创新点： 1、提出了一种新型的QAC电路。 2、将16道QAC和16道TAC以及有效信号判断电路集成在一个插件中提高了电路的集成度，并为最终集成在一片ASIC芯片中打下坚实的基础。 3、用可编程逻辑器件代替ECL器件来构建逻辑电路，降低了功耗和成本并提高了系统的可靠性

HIRFL-CSR束流位置监测系统的前端电子学研究

国家大科学工程兰州重离子加速器冷却储存环(HIRFL-CSR)已经建成，在CSR调试过程中各系统均要保证加速器稳定运行，而束流诊断系统的稳定可靠运行对顺利完成调试任务具有重要意义。系统可测得束流的能量、强度、位置、相位、剖面和发射度等参数。对这些参数的准确测量是实现CSR稳定运行和各部分之间匹配的必要手段。而束流参数一般都是通过采集可由计算机处理的电信号，并经过合理的分析得到的。因此对前端电子学系统的研究必不可少。本论文将围绕HIRFL-CSR束流诊断系统的子系统——束流位置监测系统的前端电子学设计来展开。由于我所冷却储存环的束流强度弱（最低100nA），现场的噪声和干扰较大，束流监测系统探测单元的输出信号很容易被噪声淹没，所以设计一个合适的前端电子学电路十分必要，而且需要采用一些特殊的微弱信号检测方法。通过对微弱信号检测方法的研究和学习，我们先后采用了两种处理方法，对淹没于噪声中的微弱信号幅值进行检测。第一种方法是基于宽带放大和峰值保持电路来完成对信号峰值的检测；第二种方法是基于外差式技术与锁定放大方法来实现信号峰值的检测。本论文对这两种处理方法和所涉及到的电子学电路原理进行了详细的阐述。论文的主要内容如下：第一章主要针对课题的研究背景来展开。简单介绍了HIRFL-CSR工程，及其束流诊断系统，最后结合束流诊断系统的子系统—束流位置检测系统的前端电子学电路，提出了微弱信号检测方法。第二章介绍了微弱信号检测技术，重点分析了噪声的种类和抑制噪声的处理方法。第三章对我们在束流位置检测系统的前端电子学电路中，采用的第一种处理方法—基于宽带方式的处理方法，作了详细的介绍。主要包括下面几个单元电路： 高阻输入形式和低阻输入形式的低噪声宽带放大器、高速窄脉冲信号峰值保持电路，慢前沿信号峰值保持电路。第四章对我们在束流位置检测系统的前端电子学电路中，采用的第二种处理方法—基于窄带方式的处理方法，作了详细的介绍。重点分析了外差式锁定放大电路中的频率合成器、频谱搬移电路和低通滤波电路。第五章围绕巴特沃思型滤波器的设计展开。主要介绍了低通、高通和带通三种滤波器的理论计算，并作了相应的功能仿真。第六章针对我们涉及到的所有电路的PCB设计，作了相关的分析和总结。第七章对外差式锁定放大电路的实验室参数测试方法、步骤和偏差分析作了详细的介绍。第八章对总结回顾了几年来科研学习所取得的阶段性成果，并对今后的工作方向做了一个简单的计划

CSR实验探测装置前端电子学的研究

随着国家大科学工程兰州重离子加速器冷却储存环（HIRFL－CSR）的建成， HIRFL－CSR实验探测装置也在建设中。它主要由CSR外靶实验装置和CSRe上的配套实验装置组成，具有高通道数，高探测效率，高能量分辨，高时间分辨和高位置分辨等特点；将实现奇异核性质及奇异核反应研究，核物质的同位旋效应研究等物理目标。如此先进的大型实验探测系统对前端电子学提出了高密度、高集成度，低功耗和良好的长期稳定性等多方面的严格要求，传统的插件化的NIM 和CAMAC 电子学对此已无能为力，因此建造与之相配的读出电子学和数据获取系统成为一个重要的课题和任务。基于这个出发点，论文从发展髙性能多路小型化前端电路和基于先进ASIC芯片的前端电子学系统两个方面进行研究，讨论了我们在这两种电路研究方面采用的新思路和新方法。论文在发展髙性能多路小型化前端电路方面，阐述了一种用于时间分析的宽带放大电路的设计与实现。电路采用超低噪声的集成运放，解决了如何降低噪声的问题；同时引入2阶贝塞尔滤波器加反向求和电路，有效抑制直流漂移，使快放具有良好的直流稳定性和增益稳定性。基于先进ASIC芯片的前端电子学系统的研究是论文的重点。它着重解决了近代核与粒子物理实验中越来越突出的多路多道需求和高性能指标要求。论文首先介绍了一种处于国际先进水平的ASIC芯片的内部结构；随后详细论述了系统的硬件设计和软件开发；最后对系统进行了调试和性能分析。实验室调试结果说明系统已能够适应物理实验的要求，并为最终建立一个完整的满足性能要求的前端电子学系统打下了坚实的基础

电荷测量与时序逻辑电路的研究

中国科学院近代物理研究所大科学工程HIRFL-CSR（Heavy Ion Research Facility at LanZhou-Cooling Storage Ring兰州重离子冷却储存环）已建成并处于调试和验收阶段，实验探测系统也正在建设当中。CSRm实验探测系统由外靶系统和内靶系统构成，主要用于核物理实验研究。CSRm TOF测量系统是现阶段CSRm实验探测系统的主要任务之一。 针对CSRm TOF测量系统电荷测量部分，论文阐述了一种采用前端ASIC-SFE16（Saclay Front End 16）芯片实现电荷测量的新型方法。它替代了采用分立元件和电子学插件构建系统的传统方法，着重解决了近代核物理实验中越来越突出的多路多道需求和高性能指标要求。根据我所多丝漂移室探测器的实际情况，我们设计了基于ASIC芯片的电荷测量前端电路板，结合中国科技大学的时间测量数字获取板，我们初步完成了对系统软硬件的测试，给出的实验室性能测试指标，为其在实验探测系统中的应用奠定了坚实的基础。 同时为了选出测量中的有用事例，需要进行事例判选，因此我们研制了多路延迟/脉宽调节时序逻辑电路，主要功能是针对提供的多路逻辑时序信号进行延迟和脉宽调节，支持NIM负信号输入和输出。 文中最后一部分论述了根据在调试过程中出现的实际问题所提出的解决方法，主要是针对电路的可靠性设计和噪声的处理