基于DM642的视频音频监控系统设计

为实现视频音频数据的实时采集传输,提出了一种基于DM642的视频音频监控系统的设计方案。硬件上,利用DM642丰富的外设资源,完成了视频输入、输出模块,音频输入输出模块和以太网接口模块的设计。软件上,基于DSP/BIOS实时操作系统,实现对视频音频数据的管理和控制,并构建Web服务器,用户可通过浏览器访问系统,实现远程监控。测试结果表明,该系统性能稳定,符合设计要求。     

基于无速率码的遥感数据自适应传输技术

基于自适应编码调制的遥感数据传输方案实现了传输速率阶梯式换挡,但未能充分利用链路余量。为进一步提高遥感卫星数据传输过程中的频谱效率,提出了基于无速率码的遥感数据自适应传输技术。将无速率码与QPSK、8PSK、16QAM、64QAM调制方式结合,通过设定译码成功概率阈值得到离散信噪比下的最佳译码开销和最佳码率值。采用多项式拟合求得卫星过境期间码率值的变化情况,进而得到有效数据率变化曲线,实现了遥感卫星过境时段内有效数据率随仰角的无缝切换。通过求解有效数据率曲线的积分值,得到了采用联合译码算法的Raptor码在4种方案下的传输数据量。分析结果表明,与第二代数字卫星电视广播标准（DVB-S2）中的自适应编码调制方案相比,所提出的传输方案使传输数据量提高了10.29%~27.65%,且在信噪比低至-5 dB的情况下也可以进行数据自适应传输。     

特大地震灾害现场医疗救援的组织与实施

采用固相反应制备了(Bi1.975Li0.025)(Zn2/3Nb4/3-xSnx)O7陶瓷,研究了Sn4+取代Nb5+对BLZNS陶瓷介电性能的影响.结果表明,当替代量x≤0.4时,相结构保持单一的单斜焦绿石相.介电损耗温度特性出现了明显的弛豫现象,运用缺陷偶极子模型分析了该现象.x为0.05、0.15、0.30和0.40时,样品的介电损耗峰值温度为78℃、7℃、36℃、83℃,比较了介电弛豫温区移动的差异及分析介电弛豫现象的不对称.     

基于2.32μm TDL的CO吸收光谱参数测量北大核心CSCD

采用2.32μm的可调谐二极管激光器(TDL)测量了一氧化碳(CO)气体v(0→2)振动带R转动带从R(4)至R(12)9条谱线在N_(2)为背景气下的碰撞展宽系数,且与HITRAN数据库对比并给出了谱线展宽系数随转动量子数的变化关系。本文通过采用WM-DAS方法提高实验信噪比,在不同压力(1~100 kPa)下采用Voigt(VP),Rautian(RP),Galatry(GP)和Speed-dependent Voigt(SDVP)模型对实验测量吸收率进行拟合并探究各类线型不同参数随压力的变化关系。本文还以R(10)谱线为例测量了该谱线在He,N_(2)和Ar为背景气下的碰撞展宽系数和压力频移系数,并探究了Dicke收敛系数和速度依赖性系数随压力变化的非线性关系,且通过定义残差-吸收峰值比,分析了不同背景气下R(10)谱线的收敛效应。最后,本文结合该波长范围内CO谱线的吸收强度、展宽特性和抗H_(2)O分子光谱干扰能力,推荐R(6)和R(10)两条谱线用于工业现场测量CO浓度。     

氟金云母衬底上C_(60)薄膜的光学性质

用热壁外延法在氟金云母衬底上生长出了高质量 C6 0 薄膜 ,用原子力显微镜观察了样品的表面形貌 .测量并分析了不同厚度 C6 0 薄膜的紫外 -可见吸收光谱 .由测量的透射及反射光谱 ,经计算得到了吸收系数与入射光子能量的关系 .利用结晶半导体的带间跃迁理论 ,对禁戒的带间直接跃迁 hu→ t1 u和电偶极允许的带间直接跃迁 hu→ t1 g的带隙分别进行了计算     

含水木材热解和着火试验研究

在自行研制的火灾固体可燃物热解和着火早期特性试验台上,针对建筑装潢中常用的水曲柳木材进行热解和着火特性试验。辐射热流选择20～70kW／m^2。试验结果表明,水分对木材的热解和着火特性影响很大。相同的辐射热流下,随着含水率的增加,木材的着火时间延长;辐射热流强度对木材的热解和着火也有很大影响,随着外加辐射热流的增加,木材的着火时间逐渐缩短。提出一个考虑水分影响的木材热解模型,通过模型计算的木材表面温度和失重与试验结果对比,两者吻合较好。     

Critical Heat Flux (CHF) Correlations for Subcooled Water Flow Boiling at High Pressure and High Heat Flux

The subcooled water flow boiling is beneficial for removing the high heat flux from the divertor in the fusion reactor,for which an accurate critical heat flux(CHF)correlation is necessary.Up to now,there are many CHF correlations mentioned for subcooled water flow boiling in the open literatures.However,the CHF correlations’accuracies for the prediction of subcooled water flow boiling are not satisfactory at high heat flux and high pressure for reactor divertor.The present paper compiled 1356 CHF experimental data points from 15 independent open literatures and evaluated 10 existing CHF correlations in subcooled water flow boiling.From the evaluation,the W-2 CHF correlation performs best for the experimental CHF data in all existing critical heat flux correlations.However,the predicted mean absolute error(MAE)of the W-2 correlation is not very ideal for all database and the MAE of the W-2 correlation is from 30%to 50%for some database.In order to enhance the CHF prediction accuracy in subcooled water flow boiling at high heat flux and high pressure,the present paper developed a new CHF correlation.Compared with other existing CHF correlations,the new CHF correlation greatly enhances the prediction accuracy over a broad range of pressures and heat fluxes which are desired in the cooling of high heat flux devices,such as those in the fusion reactor divertor.The validation results show that the new correlation has a MAE of 10.05%and a root mean squared error(RMSE)of 16.61%,predicting 68.1%of the entire database within±10%and 81.5%within±15%.The MAE of the new CHF correlation is 7.4%less than that of the best existing one(W-2 correlation),further confirming its superior prediction accuracy and reliability.Besides,the new CHF correlation works well not only for a uniform power profile but also for a non-uniform power profile in subcooled water flow boiling at high pressure and high heat flux.     

Experimental Investigation on the Effect of Blending Ethanol on Combustion Characteristic and Idle Performance in a Gasoline Rotary Engine

Rotary engine is an ideal electric vehicle range extender.However,the combustion chamber of rotary engine is very narrow and long at the top dead center,which is detrimental to fuel combustion performance.In order to improve its economic and emission performance,this paper built an ethanol/gasoline dual-fuel rotary engine test bench,and the combustion and emission performance of gasoline rotary engine under five ethanol blending ratios were studied.The experimental results showed that,when the fuel pulse width is not adjusted,since the calorific value of ethanol is lower than that of gasoline and the latent heat of vaporization of ethanol is higher than that of gasoline,the addition of ethanol in gasoline lowers the peak pressure.When the ethanol blending ratio reaches 30 vol%,the pressure curve shows a distinct double peak.Under the theoretical air-fuel ratio condition,mixing ethanol in gasoline increases the heat release rate,shortens the combustion duration while prolonging delay period.After blending ethanol,HC,CO and NO_x emissions have been reduced under various operating conditions.Excessive ethanol blending ratio increases NO_x emissions and increases cycle variation coefficient.When the ethanol blending ratio is 15 vol%,it has better power ability while maintaining low cycle variation coefficient and emissions.     

基于空洞U-Net网络的乳腺细胞图像分割算法

乳腺细胞的准确分割是乳腺组织切片图像病理分析的关键环节,对乳腺癌的诊治具有重要价值.针对乳腺细胞图像分割中细胞边界不清晰、分割准确率低的问题,提出一种基于空洞U-Net网络的乳腺细胞图像分割算法.在U-Net网络中引入空洞卷积增大卷积层感受野,获得包含更多乳腺细胞边缘信息的特征图,在卷积层和池化层间增加实例归一化层,提...     

西南菌种站部分酿酒增香酵母产酯性能初探

酯类是白酒中的主要香气成分,本文主要介绍西南菌种站保存的部分酿酒增香酵母在不同发酵培养条件下的产酯能力。试验对7株产酯酵母进行3种培养基、3种培养时间的多配方处理发酵,采用皂化法测定总酯。实验结果表明,菌株SICC 2．644与SICC2．645产酯水平较高,分别达到230．2mg／100mL和171．2mg／100mL;大部分菌株于麦芽汁发酵培养能获得较为理想的产酯测试效果。