Second-order spin-wave instability in Mn-Zn2Y planar hexagonal ferrites

The letter describes some measurements of the decline of the main resonance under 2nd-order pumping in an Mn-Zn2Y single-crystal hexagonal ferrite biased in the easy plane. Measurements were carried out with the r.f. field in the easy plane and also with the r.f. field perpendicular to it. The ratio of the two responses in the linear region is e02, which is the ratio of the susceptibilities for the two excitations. The ratio of the two r.f. threshold fields is also approximately e. Here e02 is the uniform-mode ellipticity. For the samples used, the critical r.f. threshold field was 41A/m in the easy plane and the spinwave linewidth was 565A/m.     

多中继协作通信系统容量分析及中继选择协作分集策略

本文针对多中继辅助通信系统,将系统建模为一个两跳通信链路,并进行了系统容量分析。针对两种特殊情况:用户端接收噪声方差远小于中继端接收噪声方差和中继端接收噪声方差远小于用户端接收噪声方差的情况,本文具体给出了系统传输容量上限与协作中继个数之间的关系。基于容量的分析,本文设计了两种中继选择策略。在第一种情况下,根据中继与用户间的信道特征值对多路数据流分别选取不同的中继子信道进行传输;在第二种情况下,选择一个信道条件最好的中继完成多路数据流的并行传输。仿真分析表明,不同的信道环境需要选择不同的中继选择策略。      

Berechnungsmethoden zur Ermittlung der Schutzstrecke bei U- und Stadtbahnen

One essential component of project planning of train control system plants is the design and calculation of the protective route. At first, definitions of the most important terms are explained. There are three different calculation methods depending on the regard of the slope of the track system as well as on the train mass representable. The simplest method only considers the maximum slope before the signal and the danger point. The second method considers the slope of the track in the form of stairs. The gradient method is presented as a third method. The regard of the inclination gradient occurs here in the form of a twofold averaging. On the one hand the mean value in the form of an integral is formed via the train length. On the other hand averaging occurs in the form of an integral via the braking distance. The middle inclination value found in this way is inserted in the iterative process for the determination of the protective route.     

基于图连通密度的海面漂浮小目标检测

海面漂浮小目标由于其能量弱,一直是海面目标检测的重难点。传统基于统计模型的漂浮小目标检测算法借助回波能量进行检测,没有利用数据频域幅度间的关联性,导致检测性能受损。该文借助图的处理方式,首先利用回波数据脉冲间频域幅度的关联性计算连通密度,生成邻接矩阵,接着将邻接矩阵转换为拉普拉斯矩阵,提取拉普拉斯矩阵的最大特征值作为检测特征,提出了一种基于图的连通密度的海面漂浮小目标检测算法。通过对实测的全相参的X波段 (IPIX)雷达数据进行连通密度的分析,发现海杂波构成的图比较稠密,而海面漂浮小目标构成的图比较稀疏,故通过连通密度构成的图可以有效地检测海杂波中的漂浮小目标。进一步地,通过与对比算法实验分析发现,该文所提基于图的连通密度的检测算法检测性能明显优越。     

基于运放退饱和的电阻炉温度控制系统设计

为了实现电阻炉的快速升温及温度控制,采用运放退饱和的方法,当电阻炉温度未达到设定值时,运放饱和输出,所控制的驱动电路输出脉冲的占空比最大,IGBT近似全导通,电炉加热功率最大,温度快速上升;当温度达到设定值时,运放开始退饱和,输出电压逐渐减小,从而减小驱动电路输出脉冲的占空比,IGBT导通时间变短,电炉加热功率减小,实现温度控制.通过Multisim软件仿真及硬件电路测试,验证了本设计的可行性.该温度控制系统具有升温速度快、易于操作、滞后性较低的优点.     

基于红外测温的柜内元件热故障的反问题识别

结合红外辐射理论分别建立了控制柜内部单个和多个元件同时过热时对壳体内表面的红外辐射模型,得到了壳体内表面总的热流密度分布,并针对受热壳体建立二维热传导模型。基于对壳体表面红外成像测温,运用L-M算法进行了导热反问题模拟研究,对控制柜内部单个和多个元件的发热温度和方位进行了识别,最后分析了测量误差对计算结果的影响。结果发现运用L-M算法对单个和多个故障元件的发热温度和方位进行分开反演求解和同时进行反演计算时,都取得了较好效果,求解精度较高。测量误差对发热温度的反演计算结果影响更大。     

An approach in the life cycle cost of integrated logistic support

In this paper an approach in the L.C.C. of I.L.S. is presented. Beginning with the three state Markov model of each equipment of the system and by considering the problem of the scheduling of preventive maintenance, the optimum interval between inspections of equipment-system is determined. Then the total cost of the I.L.S. is calculated for both the contractor and the customer.     

Adaptive Cooperative Spectrum Sharing Based on Fairness and Total Profit in Cognitive Radio Networks

A cooperative model is presented to enable sharing of the spectrum with secondary users. Compared with the optimal model and competitive model, the cooperative model could reach the maximum total profit for secondary users with better fairness. The cooperative model is built based on the Nash equilibrium. Then a conceding factor is introduced so that the total spectrum required from secondary users will decrease. It also results in a decrease in cost which the primary user charges to the secondary users. The optimum solution, which is the maximum total profit for the secondary users, is called the collusion state. It is possible that secondary users may leave the collusion state to pursue the maximum of individual profit. The stability of the algorithm is discussed by introducing a vindictive factor to inhabit the motive of deviation. In practice, the number of secondary users may change. Adaptive methods have been used to deal with the changing number of secondary users. Both the total profit and fairness are considered in the spectrum allocating. The shared spectrum is 11.3893 with a total profit of 65.2378 in the competitive model. In the cooperative model, the shared spectrum is 8.5856 with the total profit of 73.4963. The numerical results reveal the effectiveness of the cooperative model.     

一种宽1dB增益带宽全介质Fresnel透镜天线

高增益和宽1dB增益带宽天线具有重要意义。文中提出一种E 波段全介质菲涅尔(Fresnel)波带透镜 天线,它包括一个菲涅尔波带透镜以及一个作为馈源的喇叭天线。透镜对电场进行操控,使穿过透镜的电磁波相位变 化满足需求,从而使透镜口径面处的电场分布更加均匀。与传统菲涅尔透镜的焦点电场相比,本透镜在焦点处的电场 值约提高了1. 6~3. 0 V,说明透镜的聚焦特性提高,从而实现更高的增益和带宽。该透镜天线的口径为72 mm,整体剖 面高度仅为52. 47 mm,焦径比为0. 66。透镜采用3D 打印技术进行加工,降低了加工成本。与传统菲涅尔透镜相比,实 测结果表明,该透镜天线在70 GHz 峰值增益达到了27. 5 dBi,1 dB 增益带宽34. 2% (63~89 GHz),占总带宽85. 53%。     

电磁窗桁架阻挡比对天线口径场影响分析

基于感应电流率理论, 提出了将阻挡面积与口径场分布相结合的阻挡比计算方法, 修正了传统算法存在的入射场分布不均匀问题, 分析了金属桁架电磁窗中金属桁杆的散射效应, 研究了桁架阻挡比在特定天线口径场分布下对天线传输特性的影响, 以卡塞格伦天线为例计算了平行极化波入射桁杆阵列时的插入损耗, 并将计算结果与FEKO软件中矩量法仿真结果进行了对比验证.结果表明:考虑天线口径场的阻挡比算法相比传统算法在计算精度上有了较大提高, 最大误差不超过0.1 dB; 金属桁架电磁窗的插入损耗不仅受阻挡面积与感应电流率的影响, 还与天线口径场能流密度分布有关; 减小阻挡比, 是设计低损耗电磁窗的有效途径.     

内置负载开缝腔体谐振效应抑制方法研究

开缝腔体谐振特性放大了进入腔内的耦合能量,对内部电子设备构成严重威胁。文中建立内含金属 隔板、吸波体等负载的圆柱腔体模型,提出了在隔板上涂覆吸波材料以抑制谐振的新方式,研究了吸波体电磁特性 对谐振的影响。结果表明:隔板越靠近腔体前壁放置、板间距越大,对内部场影响越小,谐振点出现位置越接近空腔 固有模式;谐振点处屏蔽效能(Shielding Efficiency, SE)的提升是隔板和吸波材料综合作用的结果,隔板可迫使谐振 点迁移,吸波材料能改善谐振特性,并且涂覆磁性吸波材料性能更优;在隔板双面涂敷吸波材料抑制高次谐振效果 更好;适当增加隔板上涂覆材料厚度或提高材料相对磁导率,都能实现和全腔内壁涂覆相同的谐振抑制效果,效费 比也更高;场强分布因传播模式不同而不同,强电场区应放置电性吸波体才有效。     

Al膜的微孔阵列湿法腐蚀技术研究

微通道板(Microchannel Plate,MCP)是像增强器中实现电子倍增的关键器件。以硅为基体制备的微通道板相对于传统的微通道板在性能方面有很大的提高。在对硅进行反应离子深刻蚀(DRIE)前,需要对充当掩蔽层的金属铝膜进行湿法腐蚀。对于掩模图形为孔径10 m、孔间距5 m的大面阵的微孔阵列,在腐蚀过程中,微孔孔径较小导致溶液对流困难且反应生成物H2极易吸附在反应界面上,影响反应物质的输送和化学反应的进行。如果腐蚀参数不合适,阵列式微孔图形会出现随机腐蚀、不完全腐蚀、过腐蚀等现象。通过加入表面活性剂,减小溶液中表面应力,可以促使反应物H2排出。同时通过逐一控制变量,研究了腐蚀液浓度、腐蚀液温度和腐蚀时间对腐蚀结果的影响。结果表明,腐蚀速率与腐蚀液浓度、腐蚀液温度成正比。通过参数优化,得到了最佳的腐蚀参数。此时图形完整,尺寸准确,解决了微孔阵列的图形化问题。     

Fast Interframe mode decision algorithm based on mode mapping and MB activity for MPEG-2 to H.264/AVC transcoding

Recently the latest video coding standard H.264/AVC is widely used for the mobile and low bitrate video codec in the various multimedia terminals. On the other hand, the MPEG-2 MP@HL codec has become the center of digital video contents since it is the standard codec for the Digital TV (DTV). To provide the bridge between the contents in MPEG-2 and mobile terminals, the transcoding of MPEG-2 contents into H.264/AVC format is an inevitable technology in the digital video market. The main bottleneck in the process lies in the computational complexity. In H.264/AVC, the variable block size (VBS) mode decision (MD) is used in the Interframe for the improved performance in the motion compensated prediction. For the macroblock (MB) which cannot be accurately predicted with one motion vector (MV), it is partitioned into smaller blocks and predicted with different MVs. In addition, SKIP and Intra modes are also permitted in the Interframe MD of H.264/AVC to further ameliorate the encoding performance. With the VBS MD technology, the Inter prediction accuracy can be improved significantly. However, the incidental side-effect is the high computational complexity. In this paper, we propose a fast Interframe MD algorithm for MPEG-2 to H.264/AVC transcoding. The relationships between SKIP and Intra modes are detected at first to map these two kinds of modes directly from MPEG-2 to H.264/AVC. And then the MB activity will be scaled by the residual DCT energy obtained from the MPEG-2 decoding process to estimate the block sizes of the MB mode for H.264/AVC Interframe MD. In our proposed method, the original redundant candidate modes can be eliminated effectively, resulting in the reduction of the computational complexity. It can reduce about 85% Rate-to-Distortion Cost (RDCost) computing and 45% entire processing time compared with the well-known cascaded transcoder while maintaining the video quality.     

电子束曝光机传输片机械手研制

以前的传输片机械手由于采用双浮动滑板结构来实现各个状态的定位,长时间使用易导致机械磨损、弹簧应力疲劳等,出现机械手碰撞片夹或抓不到片等现象,难以实现高精度、高可靠性的定位。研究中的传输片机械手采用卡尔登直线运动机构配合两根导向动轴以达到长期运行的稳定性及可靠性,克服了原传输片机构存在的上述问题,且动作过程有所简化,机构体积大大缩小,动作可靠性和准确度显著提高。介绍了传输片机械手的功能、组成及其结构设计,叙述了传输片机械手的动作原理和系统控制流程。     

均匀随机媒质中传播的波——有不同波数的m-n阶矩方程的解

在研究随机媒质中传播的波的一些有关问题时,常常需要求解波的矩方程。具有不同波数的m-n阶矩方程是一个抛物近似的偏微分波动方程。本文应用格林函数方法将偏微分方程变为积分方程,并用迭代法求得了该积分方程的解。同时,又应用接连散射的方法求解了具有不同波数的m-n阶矩方程,两种方法所得的结果完全相同。文中对解的物理含义作了说明,并讨论了用于波传播研究中的一些问题。     

Weighted average indoor positioning algorithm that uses LEDs and image sensors

We propose a weighted average indoor positioning algorithm, which is an improved version of the M.S. Rahman’s algorithm, for the calculation of unknown positions in a visible light communication system consisting of light-emitting diodes (LEDs) and image sensors. The algorithm considers the LED illumination intensity as a key factor, and the generalized Lambert illumination model is adopted to estimate the LED illumination intensity of each pixel in the images obtained at the sensors. The LED illumination intensity is normalized as a weighting factor, following the determination of the center position of the LED image. Simulations showed that the average signal-to-noise ratio in our positioning system was 19.3 dB. The simulation results also showed that the root mean square positioning error was reduced from 6.6 to 3.7 cm when the resolution of the image sensor was 3000 pixels per cm, which is comparable to the error in the widely used M.S. Rahman’s algorithm. The distance between the centers of the lenses and the focal lengths of the lenses also affects the positioning error. After the simulations, the relationship between the positioning error and the lens distance or focal length is deduced. It is observed that this algorithm has lesser positioning errors than the M.S. Rahman’s algorithm.     

谐振式光纤陀螺调相检测分析

谐振式光纤陀螺（R—FOG）是新一代惯性旋转传感器的代表。在陀螺系统中，信号检测系统占有非常重要的地位，其检测精度的大小直接影响陀螺的分辨率，而解调曲线的优化能够进一步提高检测系统的灵敏度。利用贝塞尔函数展开和光波场叠加的方法分析了谐振式光纤陀螺调相检测系统解调输出信号与谐振频率偏差之间的关系，系统采用的是带有铌酸锂相位调制器的相位谱检测技术。根据解调输出信号的解析表达式，通过数值计算，分析了解调曲线的变化规律，得到了施加在铌酸锂相位调制器上调制波形的最佳调制系数和相应的最佳调制频率范围，并进一步用实验系统验证了上述分析结果。     

双包层光纤芯径与位置影响吸收效率的研究

为了提高双包层光纤结构中泵浦光耦合进纤芯的效率,文章首先探索了常折射率内包层光纤中芯径与内包层尺寸比对吸收效率的影响.然后对端泵入射光进行建模,研究了纤芯偏心距的优化.数值模拟结果表明,当偏心距为R-r时,即纤芯位于内包层边缘时,吸收效率最高.文章还阐述了渐变折射率内包层对耦合效率的影响.     

Mechanism of Thermally Biological Effects of the Millimeter Waves and Its Properties

We think that the thermally biological effects of millimeter waves are caused by the thermal motions of water molecules in the living systems, according to experimental fact that the millimeter waves can heat water, and the skin effect on the surface of the biological tissues arising from the millimeter waves. For clarifying this idea we studied the states and features of the liquid water and calculated the rotational energy-spectra of water molecules in the living systems by quantum mechanics. In fact, there is a large number of water which are polarized and have certain dipole moments in the living systems. This shows that the millimeter waves can interact with the water molecules. Through calculation of quantum rotational energy-spectra of the water molecules, we can confirm that the water molecules can absorb the millimeter waves with certain wavelength to generate the rotations of water molecules according to the principle of resonant absorption. One mechanism of the thermally biological effect of the millimeter waves is just a result produced by disorderly thermal-motions of the water molecules which are transformed from their rotation energy caused by the millimeter waves. Owing to the fact that water has a lot of biological functions and plays an important role in the living activity. Thus the heating waters by the millimeter waves can cause a lot of biological effects and phenomena in the living systems. Another mechanism of the thermally biological effect of the millimeter waves is caused by the Joule-Lenz heat arising from the skin effect of the millimeter waves in the skin layers of human beings and animals and membranes of cells which can facilitate the blood circulation in them. We finally study this effect. PACSnumbers: 87.50.Hj; 05.70.Ce; 87.15.He; 65.50.tm.     

激光跟踪中目标卫星表面BRDF对回波信号的影响

通过双向反射分布函数(BRDF)公式,模拟了空间激光主动照明跟踪中,相同材料、不同粗糙度下卫星表面的BRDF,得出了随着卫星表面材料粗糙度的增加,镜面反射分量越小,漫反射分量越大,双向反射分布散射角越宽,接收到的回波信号对方向的敏感性减小。同时模拟了入射角度对卫星表面BRDF的影响,得出了照明光束小角度入射、接收信号方向与照明光束方向一致时,镜面反射分量的增加增强了反馈信号,当大角度入射时,反馈信号急剧减小。当入射角大于34°时,通过卫星表面BRDF计算得到的最小接收功率,比之前把卫星目标看成朗伯体,通过激光雷达公式计算得到的最小接收功率小。得出了增加照明光束的发射功率为原来的5倍,或者增大接收口径为原来的2.5倍,可以消除大入射角度带来的接收功率的减小,使得系统有4倍的功率余量。