Phosphorus release characteristics of different trophic lake sediments under simulative disturbing conditions

The effect of simulative disturbing on phosphorus (P) release characteristics and the differences of the P buffering capacity of different trophic lake sediments were investigated. The magnitudes of the dissolved total phosphorus (DTP), soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) released from the studied sediments increased with the increasing of disturbing intensity. The equilibrium time of the DTP release from the heavily polluted sediments was approximately 16 h, and that from the slightly polluted sediments was 8h. This may be related to the difference of P forms in the different trophic sediments. About 30% of the DTP released from Wuli Lake and Yue Lake was from DOP, about 60% and 50%, respectively, was from Gonghu Lake and East Taihu Lake. DOP was the important fraction of DTP released. The effect of disturbing on P release was related to both disturbing intensity and sediment pollution level. After the disturbing stop, the DTP, SRP and DOP concentrations in the overlying water of the different sediments decreased rapidly within 3, 10 and 3h, respectively, then gradually reached equilibrium at different time for the sediments with different pollution level. The different trophic lake sediments had different P buffering capacity, P buffering capacity of the slightly polluted sediments was lower at the initial lower SRP concentrations and was higher at the initial higher than that of the heavily polluted sediments.     

氮气气体辅助注射控制台的技术改造

介绍气体辅助注射控制台的组成及工作原理。针对其在实际应用中出现的阀体受到污染而频繁拆装产生的系统精度误差等问题,通过对生产工艺的分析,结合实际,提出注气阶段和回气阶段气体回路分离的技术改造方案和建议,使气路经过改造后从根本上提高和改善了阀体的控制精度,从而提高了生产效率和产能。     

交流电场作用下铝硅共晶合金凝固组织和力学性能的变化

电场下的凝固是控制金属凝固组织和制造具有特殊性能新型材料的一种新途径。研究交流电场对Al-Si共晶合金凝固组织的影响,以及对其力学性能的影响。通过试验分析Al-Si共晶合金Si的形貌、Si相间距、Si片的线长度、抗拉强度和硬度。试验结果表明:在Al-Si共晶合金凝固过程中施加交流电场,Al-Si共晶合金的凝固组织得到细化;共晶Si质点增加,共晶Si由原来的针片状演化成细小的针状,合金力学性能得到了改善;在通入适当数值的电流后Al-Si共晶合金能够获得最佳的抗拉强度和硬度。     

高速公路行程时间可靠性的小波密度估计

针对传统参数估计方法依赖于事先对总体分布假设的情况,在概率分布簇不确定的前提下,提出一种基于小波密度估计的高速公路行程时间可靠性建模方法.以西安市绕城高速为例,构建了小波密度估计的高速公路行程时间可靠性.实证结果表明,基于小波密度估计的高速公路行程时间分布函数明显优于其他方法.同时探讨了电子不停车收费系统对高速公路行程时间可靠性的影响.     

Measuring the component overlapping in the Gaussian mixture model

The ability of a clustering algorithm to deal with overlapping clusters is a major indicator of its efficiency. However, the phenomenon of cluster overlapping is still not mathematically well characterized, especially in multivariate cases. In this paper, we are interested in the overlap phenomenon between Gaussian clusters, since the Gaussian mixture is a fundamental data distribution model suitable for many clustering algorithms. We introduce the novel concept of the ridge curve and establish a theory on the degree of overlap between two components. Based on this theory, we develop an algorithm for calculating the overlap rate. As an example, we use this algorithm to calculate the overlap rates between the classes in the IRIS data set and clear up some of the confusion as to the true number of classes in the data set. We investigate factors that affect the value of the overlap rate, and show how the theory can be used to generate “truthed data” as well as to measure the overlap rate between a given pair of clusters or components in a mixture. Finally, we show an example of application of the theory to evaluate the well known clustering algorithms.     

汽车安全带卷簧扭矩测试系统软件的设计与实现

扭矩性能是汽车安全带卷簧最重要性能之一;为了准确,直观测试汽车安全带卷簧的扭矩性能,应用MFC文档视图技术开发汽车安全带卷簧扭矩测试系统软件;软件基于VC6.0开发环境,采用多线程技术实现了数据采集与控制模块;利用MFC类库开发了数据波形与监测交互模块,应用COM技术开发了数据报表模块,结合卷簧扭矩测试硬件对软件功能作了测试;结果表明,测试精度符合要求,达到0.001 N·m;开发的软件满足汽车安全带卷簧扭矩测试的要求,具有较高的测试精度,较好的交互功能和一定的应用前景.     

QPSK中频全数字解调器的研究与FPGA实现

基于QPSK调制方式的高效率、低误码率、频谱性能好等特点,本文采用可编程逻辑器件CycloneⅡEP2C70F896C6N成功地实现了QPSK全数字解调的电路的设计。分别在MATLAB软件和Quartus Ⅱ9.0软件中进行了解调器中的核心模块的设计和仿真,同时在各个模块仿真成功的情况下,对整体电路进行了仿真。输入端的信号都为20MHz的中频已调信号,最后准确解调出基带信号。通过比较Quartus II仿真结果和MATLAB仿真结果,解调出来的结果是一致的,这也说明了所设计的解调模块是正确的。在信噪比为10dB时,误码率达到10-3,显然电路的设计能够达到要求的性能指标。     

电磁炉上盖注塑模具设计

分析了电磁炉上盖塑件的结构工艺特点。为了优化模具结构,减少塑件缺陷,采用Moldflow软件对其进行了最佳浇口位置、填充、翘曲变形等模拟分析。以模拟结果为依据,设计了轮辐式侧浇口注塑模,介绍了模具结构及工作过程。采用此模具结构实现了从注射到塑件落料的半自动化生产模,具结构合理生,产效率较高。     

中间高温回火工艺对15MnNi4MoA渗碳钢微观组织及性能的影响

研究了15MnNi4MoA钢渗碳后的热处理工艺对其微观组织及性能的影响。设计了3种不同的渗碳后热处理工艺:淬火+低温回火、一次高温回火+淬火+低温回火、两次高温回火+淬火+低温回火,并对热处理后的力学性能及微观组织进行了对比和分析。通过扫描电镜对3种不同热处理后的显微组织和冲击断口形貌进行了观察。同时,对不同热处理工艺的试样进行了维氏硬度和常温冲击吸收能量(U型缺口)检测。结果表明,经3种不同的热处理后,试样的微观组织差异不大,均为马氏体+残留奥氏体组织。其中,经两次高温回火处理所得到的试样,马氏体组织更加细小,力学性能更加突出,心部硬度降低至358 HV,表面硬度提高到664 HV,常温冲击吸收能量达到143 J。     

强震区断裂活动与大型滑坡关系研究

 活动断裂带与大型滑坡之间的关系一直是人们关注的热点问题。通过汶川Ms8.0级地震活动断裂和大型滑坡调查,阐述龙门山活动断裂带大型滑坡形成的地质背景,总结活动断裂带大型地震滑坡的分布特征、形态特征、启动特征和分段特征及其相关影响因素。基于野外调查资料,以龙门山中央断裂带谢家店子滑坡为例,采用离散元方法模拟分析滑坡的启动和快速运移过程,提出高速远程滑坡的致灾后果决定于启动方式、飞行路径和堆积特征3个方面。本项研究对于认识断裂活动与大型滑坡之间的关系以及滑坡成灾后果预测具有重要的指导作用。