Preparation of natural brucite nanofibers by the dispersion method

The preparation of natural brucite nanofibers through dispersion by the wet process is described. The test results indicate that brucite fibers can be well dispersed by using sodium dioctyl sulfosuccinate (OT) as the dispersant at a dispersant/fiber mass ratio of 0.15:1, dispersing for 30 min at a water/solid mass ratio of 20:1. The prepared nanofibers were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). It is shown that the prepared single brucite nanofiber is around 30 nm in diameter and the talus of the nonsingle brucite nanofibers is about 50-150 nm in diameter. Natural brucite mineral fibers were treated by the dispersion method to obtain nanomaterials. These fibers have significant advantages over artificial nanofibers both in yield and in cost.     

Fatigue life prediction of Package-on-Package stacking assembly under random vibration loading

This paper presents a general methodology to predict the fatigue life of the Package-on-Package (PoP) under random vibration loading by means of vibration tests and finite element (FE) simulation. The behavior of the critical solder joints of the PoP under vibration loading was accurately described by FE model using ANSYS software and confirmed by modal analysis and linear sweep tests. The stress-life (S-N) curve of the PoP solder joints was obtained by the sinusoidal fatigue vibration tests and FE simulations to characterize the fatigue properties of the PoP under vibration. The comparison of the S-N curves of the SAC305 solder joints in different structures indicates the S-N curve of the SAC305 solder joints depends on the package structure. With the same fatigue cycles, the stress levels for the current 3D package is the smallest compared with the other 2D package due to the stacked structure of the PoP. Spectrum analysis for the random vibration tests was performed by the FE simulations to acquire the stress response power spectral density (PSD) of the critical solder joint. A specific frequency domain approach based on the Palmgren-Miner's rule was established to predict the fatigue life of the PoP under random vibration. Results show that simulated fatigue life matches well with the random vibration test results, which implies that this approach could be a potential method for the predication of fatigue life of the 3D packaging under random vibration.     

大容量地热有机朗肯循环发电机组配置研究

地热发电是地热能利用的最重要方式之一,目前我国地热发电装机容量较小,技术发展缓慢,未能满足可再生能源多样化、平衡发展的要求。以某地热电站二期项目为例,通过对地热资源品质分析,建立大容量有机工质朗肯循环发电系统模型,对发电机组配置进行研究,并对系统性能进行预测分析。当室外温度为0℃时,机组可满负荷17.6 MW运行,室外温度小于0℃时,最高发电功率可达19 MW以上。     

基于对数正态分布的电缆状态评估方法研究

为了了解电缆在长时间使用后的健康状况,通过对数正态分布和Weibull分布两种分布函数来进行电缆状态的评估。先假定电缆的介电损耗与局部放电数据符合两种分布,借助于Matlab数值模拟软件对某供电公司近几年通过振荡波试验检测积累的老化数据进行了拟合,并对两种拟合结果进行了对比分析。结果证明,对数正态分布更符合电缆老化参数的分布。设定了电缆状态的三个级别,通过建立状态评估模型,并使用该模型完成对某供电公司10 kV电缆的状态评估。研究成果有助于及时了解电缆在运行过程中的状态变化,并提出对应的检修计划。     

空心电抗器温升试验调压异常及涌流现象的分析

分析了空心电抗器温升试验调压过程中的异常现象,提出了试验过程中应注意的事项和抑制合闸时产生涌流的措施。     

基于云模型和关联分析法的电力营销目标市场模糊评价

提出了基于云模型和关联分析法的电力营销目标市场模糊评价方法,采用云模型关联分析法获得指标的权重信息,不但消除了人为的主观因素,而且同时考虑到了不确定性中的模糊性和随机性。通过实例证明该方法结果更加接近实际,为确定电力营销目标市场提供了一种简单可行的方法。     

Experimental analysis of Sn-3.0Ag-0.5Cu solder joint board-level drop/vibration impact failure models after thermal/isothermal cycling

Sn-3.0Ag-0.5Cu board-level lead-free solder joint drop (1000g, 1 ms)/vibration (15g, 25–35 Hz) reliability after thermal (− 40–125 °C, 1000 cycle)/isothermal (150 °C, 500 h) cycling was reported in this study. The failure performance of solder joint and testing life were analyzed under design six testing conditions (1. Single drop impact, 2. Order thermal cycling and drop impact, 3. Order isothermal cycling and drop impact, 4. Single vibration 5. Order thermal cycling and vibration 6. Order isothermal cycling and vibration). The results revealed that the pre-cracks initiation during thermal cycling do not affect the solder joint drop impact reliability, but decrease the vibration reliability. The formation of voids weaken both drop and vibration reliability of solder joint. After thermal cycling, the crack initiated from β-Sn near IMC layer, and continued propagation through the same path when under second in order vibration impact. But propagation path turn to IMC layer when under second in order drop impact. The drop life increases from 41 times to 49 times, and vibration life decrease from 77 min to 45 min. After isothermal cycling, the formation of voids let the cracks occurred at IMC layer under second in order no matter drop impact or vibration. The drop and vibration life is 19 times and 62 min respectively.     

智能用电非侵入式负荷监测系统研究

能源互联网对智能电网的数据交互与信息挖掘提出了更高的要求。非侵入式负荷监测技术能够挖掘用户用电负荷状态信息,在智能用电领域受到日益广泛的重视。针对现有非侵入式负荷监测系统只能解决用户端负荷数据挖掘,难以实现电网与用户的双向交互及用户信息深度挖掘等问题,提出智能用电非侵入式负荷监测系统及其技术架构设计,并从信息通信、负荷识别和数据挖掘等方面分析论述该系统的实现与应用技术方案。     

Fretting fatigue behavior of SUS304 stainless steel under pressurized hot water

Fretting fatigue behavior of the sensitized SUS304 stainless steel under a pressurized hot water at 7.3 MPa and 288 °C was investigated. The tests were carried out under a contact pressure of 100 MPa and a frequency of 20 Hz. From the experimental result, combined effect of pressurized hot water and localized high tangential stress due to fretting resulted in nucleation of intergranular crack along the outer edge of contact region at lower stress amplitudes, while a fretting fatigue crack was nucleated at the highest tangential force point independently from these intergranular cracks at higher stress amplitudes. No intergranular crack nucleation was observed for fretting fatigue at the same temperature in air. The higher stress ratio reduced the fatigue strength, where the crack tip was exposed more in corrosive environment due to the high mean stress compared to the lower stress ratio.     

In-field detection of multiple pathogenic bacteria in food products using a portable fluorescent biosensing system

Foodborne diseases caused by pathogenic bacteria have increasingly become a major public health issue worldwide. Rapid, simple, and accurate detection methods are urgently needed for in-field screening of bacterial pathogens. In our previous work, rapid detection methodologies have been established based on fluorescent nanobiosensors for simultaneous separation and detection of multiple foodborne pathogenic bacteria. In this research, a portable fluorescent biosensing system was designed and built and further assessed for in-field detection of three main types of bacterial pathogens that have been associated with the outbreaks of foodborne illness. Using the developed fluorescent nanobiosensor coupled with nanobead-based immunomagnetic separation, we conducted blind tests with the portable device to simultaneously detect E. coli O157:H7, L. monocytogenes, and S. Typhimurium in different food products in three cities selected from three big agricultural provinces in China. Specificity tests showed low interference of this multiplex biosensor from non-targets in food samples. The detection could be done from sampling to results within 60 min. Limits of detections of this method for E. coli O157:H7, L. monocytogenes, and S. Typhimurium were determined to be 10², 10³, and 10³ CFU/mL in lettuce, shrimp, and ground beef, respectively. Recovery tests were also investigated and this method was evaluated to be accurate comparing with the gold standard culturing method. Therefore, it is feasible for this portable fluorescence biosensing system to be used in rapid and in-field screening of multiple foodborne pathogenic bacteria in foods, such as vegetables, livestock meat, and sea food. And together with fluorescent nanobiosensors, it provides a promising alternative tool to traditional culturing method, or even conventional ELISA and PCR based methods.