基于DVD双光束多层数据存储系统的设计及仿真

为了实现三维光信息存储的实用化, 在三维光盘存储实验系统的基础上, 改进、设计出了一种可用于三维数据存储的单侧读写光学头。对光学头进行了光学和控制系统的设计, 利用专门设计的耦合分光棱镜进行光束耦合和分离; 采用双音圈电机控制透镜的方式实现数据的选层; 进行了聚焦伺服系统的建模和仿真。结果表明双光束焦点同步误差保持在±3μm之内。     

一种增益可控音频前置放大器电路的设计

设计了一种基于0.5μm CMOS工艺的增益可控音频前置放大器电路。该电路采用直流音量控制方式控制前置放大器的增益,进而实现整体音频放大器的音量控制。外部输入的直流模拟电压经过片内模数转换器转换成数字控制信号,控制前置放大器的输入电阻与反馈电阻的比值,从而实现前置放大器的增益控制。该放大器能够实现32档的音量控制范围,增益从-50 dB变化到25 dB,电路版图面积为1.2 mm×0.8 mm。     

Vocal Fold Vibration and Phonation Start in Aspirated, Unaspirated, and Staccato Onset

Objectives/Hypotheses

Singers learn to produce well-controlled tone onsets by accurate synchronization of glottal adduction and buildup of subglottal pressure. Spectrographic analyses have shown that the higher spectrum partials are present also at the vowel onset in classically trained singers’ performances. Such partials are produced by a sharp discontinuity in the waveform of the transglottal airflow, presumably produced by vocal fold collision.

Study Design

After hearing a prompt series of a triad pattern, six singer subjects sang the same triad pattern on the vowel /i/ (1) preceded by an aspirated /p/, (2) preceded by an unaspirated /p/, and (3) without any preceding consonant in staccato.

Methods

Using high-speed imaging we examined the initiation of vocal fold vibration in aspirated and unaspirated productions of the consonant /p/ as well as in the staccato tones.

Results

The number vibrations failing to produce vocal fold collision were significantly higher in the aspirated /p/ than in the unaspirated /p/ and in the staccato tones. High frequency ripple in the audio waveform was significantly delayed in the aspirated /p/.

Conclusions

Initiation of vocal fold collision and the appearance of high-frequency ripple in the vowel /i/ are slightly delayed in aspirated productions of a preceding consonant /p/.     

Double threshold behaviour of I－V characteristics of CoSi2/Si Schottky contacts

The forward current－voltage (I－V) characteristics of polycrystalline CoSi₂/n-Si(100) Schottky contacts have been measured in a wide temperature range. At low temperatures (≤200K), a plateau-like section is observed in the I－V characteristics around 10^-4A·cm^-2. The current in the small bias region significantly exceeds that expected by the model based on thermionic emission (TE) and a Gaussian distribution of Schottky barrier height (SBH). Such a double threshold behaviour can be explained by the barrier height inhomogeneity, i.e. at low temperatures the current through some patches with low SBH dominates at small bias region. With increasing bias voltage, the Ohmic effect becomes important and the current through the whole junction area exceeds the patch current, thus resulting in a plateau-like section in the I－V curves at moderate bias. For the polycrystalline CoSi₂/Si contacts studied in this paper, the apparent ideality factor of the patch current is much larger than that calculated from the TE model taking the pinch-off effect into account. This suggests that the current flowing through these patches is of the tunnelling type, rather than the thermionic emission type. The experimental I－V characteristics can be fitted reasonably well in the whole temperature region using the model based on tunnelling and pinch-off.     

基于LXI的飞机音频管理系统检测系统研究

飞机音频管理系统检测中一方面要模拟、测量与之存在交联的来自机载导航和通信设备的信号,且测试项目、信号种类和数量繁多;另一方面,还要控制和监视专用试验平台模拟机载运行环境以便音频管理系统故障复现,因此基于LXI总线的自动测试系统构建方案成为最佳选择。在软件开发中,通过分析被测对象的测试需求和测试过程,提出面向对象的模块化软件开发方法,大大提高了软件复用性和开发效率。实践证明,采用LXI总线提高了自动测试系统的可靠性,缩短了航修公司的维修时问,降低了维修成本,提高了维修效率。     

基于Android平台和WiFi传控的多功能机顶盒设计

按照数字电视市场对机顶盒的使用需求,分析了市场上常见的机顶盒的优劣,提出一种基于Android平台和采用WiFi进行数据传输与控制的机顶盒设计方案,以满足用户的使用需求。工程实测表明,基于该方案的机顶盒成本经济、可靠性高,功能强,达到设计的预期目的。     

音频功放环路频率响应的测试

音频功放的稳定性是由环路频率响应的增益与相位曲线决定的。在设计时可以通过仿真软件分析,在实际测试时由于测试误差和动态范围的限制很难得到准确的结果。本文以AB类音频功放为例,介绍了一种采用网络分析仪的增益和相位端口,测试环路频率响应的方法。     

Exact solutions for nonlinear Schr?dinger equation in phase space: applications to Bose－Einstein condensate

The stationary-state nonlinear Schr?dinger equation, which models the dilute-gas Bose－Einstein condensate, is introduced within the framework of the quantum phase-space representation established by Torres-Vega and Frederick. The exact solutions of equation are obtained in the phase space, by means of the wave-mechanics method. The eigenfunctions in position and momentum spaces are obtained through the ‘Fourier-like' projection transformation from the phase space eigenfunctions. The eigenfunction with a hypersecant part is discussed as an example.     

Ground state properties of a Bose－Einstein condensate confined in an anharmonic external potential

In light of the interference experiment of Bose－Einstein condensates, we present an anharmonic external potential model to study ground state properties of Bose－Einstein condensates. The ground state energy and the chemical potential have been analytically obtained, which are lower than those in harmonic trap. Additionally, it is found that the anharmonic strength of the external potential has an important effect on density and velocity distributions of the ground state for the Thomas－Fermi model.