两台进口600MW汽轮发电机防止定子绕组端部损坏的技术改造措施

两台日本进口的600MW大型汽轮发电机,投产之前发现设备质量存在问题,定子绕组端部共振特性试验结果不满足订货合同,为此我们对相关的发电机定子绕组端部振动问题进行了深入研究,为保证设备能够长期安全稳定运行,我们与日方共同在发电机上采取了一些必要的技术改造措施.本文介绍了技术改造的经过和实际效果.     

Hilbert transform based FBP algorithm for fan-beam CT full and partial scans

This paper presents a new type of filtered backprojection (FBP) algorithm for fan-beam full- and partial-scans. The filtering is shift-invariant with respect to the angular variable. The backprojection does not include position-dependent weights through the Hilbert transform and the one-dimensional transformation between the fan- and parallel-beam coordinates. The strong symmetry of the filtered projections directly leads to an exact reconstruction for partial data. The use of the Hilbert transform avoids the approximation introduced by the nonuniform cutoff frequency required in the ramp filter-based FBP algorithm. Variance analysis indicates that the algorithm might lead to a better uniformity of resolution and noise in the reconstructed image. Numerical simulations are provided to evaluate the algorithm with noise-free and noisy projections. Our simulation results indicate that the algorithm does have better stability over the ramp-filter-based FBP and circular harmonic reconstruction algorithms. This may help improve the image quality for in place computed tomography scanners with single-row detectors.     

Cell Membrane Camouflaged Hollow Prussian Blue Nanoparticles for Synergistic Photothermal‐/Chemotherapy of Cancer

Nanodrug‐based cancer therapy has been actively developed in the past decades. The main challenges faced by nanodrugs include poor drug loading capacity, rapid clearance from blood circulation, and low antitumor efficiency with high risk of recurrence. In this work, red blood cell (RBC) membrane camouflaged hollow mesoporous Prussian blue nanoparticles (HMPB@RBC NPs) are fabricated for combination therapy of cancer. The stability, immune evading capacity, and blood retention time of HMPB@RBC NPs are significantly enhanced compared with those of bare HMPB NPs. Doxorubicin (DOX), as a model drug is encapsulated within HMPB@RBC NPs with loading capacity up to 130% in weight. In addition, DOX loaded HMPB@RBC NPs show pH‐/photoresponsive release. The in vivo studies demonstrate the outstanding performance of DOX@HMPB@RBC NPs in synergistic photothermal‐/chemotherapy of cancer.     

On energy efficiency of geographic opportunistic routing in lossy multihop wireless networks

Geographic opportunistic routing (GOR) is an emerging technique that can improve energy efficiency in lossy multihop wireless networks. GOR makes local routing decision by using nodes?? location information, and exploits the broadcast nature and spatial diversity of the wireless medium to improve the packet forwarding reliability. In this paper, our goal is to fully understand the principles and tradeoffs in GOR, thus provide insightful analysis and guidance to the design of more efficient routing protocols in multihop wireless networks. We propose a local metric, one-hop energy efficiency (OEE), to balance the packet advancement, reliability and energy consumption in GOR. We identify and prove important properties about GOR on selecting and prioritizing the forwarding candidates in order to maximize the expected packet advancement. Leveraging the proved properties, we then propose two localized candidate selection algorithms with O(N ³) running time to determine the forwarding candidate set that maximizes OEE, where N is the number of available next-hop neighbors. Through extensive simulations, we show that GOR applying OEE achieves better energy efficiency than the existing geographic routing and blind opportunistic routing schemes under different node densities and packet sizes.     

Ⅴ/Ⅲ比和生长温度对RF-MBE InN表面形貌的影响

由于生长InN所需平衡氮气压较高,而且InN分解温度比较低,因此在生长InN时In原子很容易在表面聚集形成In滴,使InN外延膜的表面形貌变差,影响InN外延膜质量的提高.通过研究Ⅴ/Ⅲ比和生长温度对RFMBE生长InN外延膜表面形貌的影响,发现Ⅴ/Ⅲ比和生长温度对InN外延膜表面In滴的量有重要影响.通过选择合适的Ⅴ/Ⅲ比和生长温度,得到了表面平整光亮、无In滴的InN外延膜.     

Delamination‐Free Functional Graphene Surface by Multiscale,Conformal Wrinkling

Obtaining a delamination‐free wrinkled functional graphene surface in layered systems is an interesting challenge because the interface is usually too weak to withstand interfacial stress mismatch, which can trigger mechanical instability. In this paper, a general strategy is proposed toward addressing the delamination limitation imposed by fabricating conformal graphene wrinkles with bilayer systems of poly(methyl methacrylate) (PMMA) and polydimethylsiloxane (PDMS). To improve the interfacial strength, a postcuring transfer process is introduced to form a gradient interface layer without interfacial liquid between the PMMA and PDMS by entanglement of polymer chains during high‐temperature curing. Compared to the conventional wet transfer of graphene,the transfer method can greatly enhance the interfacial strength. The chemical and mechanical mechanisms underlying the enhancement are revealed both experimentally and theoretically in terms of the transition from the buckled‐induced delamination state to the delamination‐free wrinkled state. Moreover, the light diffraction behaviors of multiscale graphene wrinkles are initially demonstrated to be an interesting continuous pattern induced by overlapping. The delamination‐free conformal wrinkled functional graphene surface can provide valuable insight and design guidelines for the fundamental problems of deformed graphene and its applications in flexible functional devices.     

分解区域方法在涡流检测仿真中的应用

随着现代制造业的发展,涡流检测仿真问题日渐复杂。传统的单一求解区域方法的运用遇到瓶颈,而分解区域方法将复杂的单一区域上的求解转化为较简单的若干个子区域上的求解,克服了传统方法遇到的困难。该文主要介绍分解区域方法在涡流检测仿真中的应用。     

锰(Ⅱ)化合物对二氧化锰结构及电化学性能的影响

采用氧化还原水热法合成二氧化锰。研究了在氧化剂及反应温度等条件相同的情况下,不同反应时间和还原剂对二氧化锰晶型及电化学性能的影响。通过对产物进行XRD分析发现,还原剂为MnSO4时,仅生成单相α-MnO2;而在Mn(NO3)2和MnCl2溶液中,随着反应时间由2～24 h增加到48 h,产物由含有γ-MnO2的α-MnO2转变为单相β-MnO2。对反应时间为12 h生成的二氧化锰进行了循环充放电测试。结果显示,在Mn(NO3)2和MnCl2溶液中生成的含有γ-MnO2的α-MnO2,其初次放电容量分别为203和186.3 mA.h/g,均比在MnSO4溶液中生成的单相α-MnO2的容量140 mA.h/g高;7次循环充放电后,在Mn(NO3)2,MnCl2和MnSO4溶液中生成的MnO2的容量分别保持在初次放电容量的51%,54%和49%。     

微片激光器线性调频技术的研究

提出一种激光线性调频方法。在微片激光器谐振腔中插入电光晶体,利用电光晶体的线性电光效应,通过对外加电场的控制,可以得到线性调频的激光信号。采用该方法,可获得较高的调制频率和较大的调制范围,能够满足激光雷达和测距仪的要求,而且外加电路实现简单、易控制。     

Construction of low-density parity-check codes by superposition

This paper presents a superposition method for constructing low-density parity-check (LDPC) codes. Several classes of structured LDPC codes are constructed. Codes in these classes perform well with iterative decoding, and their Tanner graphs have girth at least six.