薄材多点成形中回弹的预测

多点成形技术是三维曲面板类件柔性成形的新技术.在薄板边多点成形中,回弹是一个必须解决的问题.论文中采用显-隐式算法分析了板材厚度、曲率半径对柱面、球面等典型曲面的多点成形回弹的影响,得到了回弹趋势和回弹分布规律,这些结果对多点成形技术具有一定的参考价值.     

基于多点成形的颅骨钛板假体数字化制造技术

基于多点成形技术,提出了一种全新的用于颅骨缺损修补的钛板假体数字化制造技术.首先,从病人患处的CT数据集中重构颅骨三角网格模型.然后,采样该三角网格模型获得代表性散乱点集,使用薄板样条插值技术重建得到钛板假体表面形状模型.最后,将该表面模型传递给多点成形CAD/CAM系统控制多点压力机最终成形出所需的钛板假体.得益于多点成形和计算机辅助设计技术的紧密融和,该技术能够显著缩短钛板假体的制造周期,同时大大提高假体与患处的贴合精度.目前,应用该技术已完成近10例,可以初步证实其可行性及效率.     

冷弯成型力研究

在研究冷弯变形过渡区基础上，按照成型过程中成型辊施加于坯料上的力所做的功与坯料在该道次中实现规定的几何形状产生变形所消耗的功相等的原理，建立了计算冷弯成型力的理论表达式。通过现场实例证实了理论计算结果与实测数据吻合良好，相对误差均在３０％以内。     

Joint multi-user space time block coding and beamforming via convolutional weighting

A convolutional weighting （CW） scheme applied to a half-wavelength spacing array was proposed for multi-user system to joint STBC （space time block ceding） and beam forming （BF）. The transmitting beam is equivalent to the product of two sub-beams. One is used to realize interference suppression, while the other is employed to form a couple of uncorrelated channels from base station （BS） to the desited user （to meet the requirement of STBC） and to maximize SINR （signal-to-interference-plus noise ratio） at the desired receiver. As an optimum combination of STBC and beam forming, the proposed scheme can achieve both full diversity order of STBC and array gain of BF. Meanwhile, it can also effec- tively restrain multi-user interference by nulling. Simulation results show that the proposed scheme can significantly improve the BER （Bit Error Rate） performance and enhance system capacity as compared with the conventional eigen-beamforming （EBF） technique applied to a half-wavelength spacing array.     

钛合金网板多点成形起皱缺陷的数值模拟

采用动态显式有限元软件,针对不同厚度、不同曲率半径的带孔网板和无孔板球形面的无压边多点成形过程进行了数值模拟.模拟结果表明,在相同的成形条件下,带孔网板成形球形件时不易起皱,成形效果较好.分析表明,带孔网板成形时不易起皱的原因是网孔吸收了部分金属变形,从而减小了网板起皱的趋势.通过模拟得到了带孔网板和无孔板成形球面件时不起皱成形极限与板厚的关系曲线.实验结果表明,模拟结果与实验结果吻合良好,且满足与不起皱成形极限图的对应关系.     

带柔性附件的充液飞行器姿态动力学与控制

研究了流-刚-弹耦合飞行器系统的姿态动力学、稳定性与控制问题,给出了组成系统的每部分控制律,证明了在此控制律下系统可达到姿态定位和受控系统指数渐近稳定.     

Independent inactivation of MPF and cytostatic factor (Mos) upon fertilization of Xenopus eggs.

In vertebrates, mature eggs are arrested at the second meiotic metaphase by the cytostatic factor (CSF), now known to be the c-mos proto-oncogene product (Mos). Fertilization or egg activation triggers a transient increase in the cytoplasmic free calcium and releases the meiotic arrest by inactivating maturation/mitosis-promoting factor (MPF). CSF or Mos, which is also inactivated by the calcium transient, seems to stabilize MPF in mature eggs and CSF-injected embryos. Thus, it was assumed that CSF inactivation is the primary cause of MPF inactivation on meiotic release. We have directly compared the degradation kinetics of CSF (Mos) and MPF during meiotic release, using the same batch of Xenopus eggs. We report here that, at the molecular level, cyclin subunits of MPF are degraded before Mos is degraded and, at the physiological level, that MPF activity is inactivated before CSF activity during activation of Xenopus eggs. These results, in conjunction with circumstantial evidence, support the novel view that a calcium transient on fertilization induces a CSF-independent pathway for MPF inactivation, whereas CSF inactivation during meiotic release serves only to allow the fertilized egg to enter mitosis.     

求解LGP模型的MPF法的完善与证明

本文完善了文献[1]提出的解线性目标规划模型的“量化优先因子法”(简称MPF法)，给出MPF法的理论证明，最后通过实例进一步说明MPF法的算法．     

高原公路线形对驾驶员肌电特性影响试验分析

为了解高原公路线形对驾驶员肌电特性影响,寻求提高行车安全途径以及今后道路线形设计参考依据。通过在新疆帕米尔高原G314路段进行驾驶员行车试验,利用生物反馈仪提取受测驾驶员肌电信号,利用频域分析方法选取平均功率频率(MPF)作为测评指标,定量分析其在海拔与道路线形影响下的变化规律,同时建立关系模型。分析结果表明:驾驶员颈部MPF会随着海拔的升高而减小;平曲线半径逐渐减小的路段上,驾驶员颈部MPF会减小,而纵坡度变化对MPF的影响并不显著;线形组合值增大会导致驾驶员颈部MPF减小;海拔与线形组合值共同影响下,驾驶员颈部MPF变化明显,海拔越高、线形组合值越大,驾驶员颈部MPF越小。     

基于分布式无味边缘粒子滤波的同步定位与地图构建

针对复杂环境下同步定位与地图构建(SLAM)中分布式粒子滤波算法存在计算量大、粒子退化严重的问题,在分布式算法的基础上结合无味粒子滤波和边缘化算法,提出了一种基于分布式无味边缘粒子滤波的算法.该算法依据分布式思想将系统分解为多个仅包含部分状态量的子系统,各子系统均采用无味粒子滤波算法进行状态估计,通过边缘化算法优化无味粒子滤波算法的边缘分布函数,主滤波器融合各子滤波器的数据计算最终结果,克服了滤波精度低、计算复杂度高的问题.最后,通过仿真试验证明改进的分布式边缘粒子滤波算法能够抑制粒子退化现象,具有较好的实时性和滤波精度,是解决SLAM的新的有效方法.     

Dephosphorylation and activation of Xenopus p34cdc2 protein kinase during the cell cycle

Genetic studies in the fission yeast Schizosaccharomyces pombe have established that a critical element required for the G2----M-phase transition in the cell cycle is encoded by the cdc2+ gene. The product of this gene is a serine/threonine protein kinase, designated p34cdc, that is highly conserved functionally from yeast to man2 and has a relative molecular mass of 34,000 (34 K). Purified maturation-promoting factor (MPF) is a complex of p34cdc2 and a 45K substrate that appears in late G2 phase and is sufficient to drive cells into mitosis. This factor has been identified in all eukaryotic cells, and in vitro histone H1 is the preferred substrate for phosphorylation. The increase in the activity of H1 kinase in M-phase is associated with a large increase in total cell protein phosphorylation which is believed to be a consequence of MPF activation. We show here that the H1 kinase activity of p34cdc2 oscillates during the cell cycle in Xenopus, and maximal activity correlates with the dephosphorylated state of p34cdc2. Direct inactivation of MPF in vitro is accompanied by phosphorylation of p34cdc2 and reduction of its protein kinase activity.     

新型气动穿孔机的机理分析

现有的气动穿孔机已能完成预期的施工任务,但其耗气量和冲击频率等性能参数还有待于进一步的提高,为此,介绍一种新型的气动穿孔机,并对其进行理论分析,结果表明它比现有的穿孔机在这两方面的性能有较大的提高。     

Meiotic initiation by the mos protein in Xenopus.

When fully grown Xenopus oocytes are stimulated by progesterone, a period of protein synthesis is necessary for maturation. Synthesis of the mos proto-oncogene product, pp39mos, is necessary for the activation of M-phase promoting factor (MPF) in meiosis I. On the basis that mos is translated de novo on hormonal stimulation of Xenopus oocytes and that injecting mos RNA into oocytes induces their maturation, we have proposed that the mos protein is a candidate initiator of oocyte maturation, needed to trigger the conversion of precursor MPF into its active form. To determine whether mos is the only protein required for initiating maturation, we have produced a soluble, active recombinant mos protein and injected it into Xenopus oocytes. We report here that in the absence of protein synthesis that mos protein efficiently induces germinal vesicle breakdown and the activation of MPF. The oocytes, however, do not proceed into meiosis II. Thus, the mos protein fulfills the requirements of an initiator protein, but the synthesis of one or more additional proteins may be necessary to complete oocyte maturation.     

DBF技术在雷达接收系统中的应用

介绍DBF体制雷达的特点和经常运用的关键技术,对接收系统的原理、组成、各部分的特点及实现方法作了详细的说明,着重介绍了中频直接采样技术的原理和数字波形产生技术在该接收系统中的应用,并给出了试验结果.     

不同强度快速伸膝运动对股四头肌肌电图平均功率频率和输出功率的影响

为研究不同强度快速伸膝运动对股四头肌群表面肌电信号（surface electromyography,s EMG）的平均功率频率（mean power frequency,MPF）下降率和伸膝平均输出功率下降率的影响及相关性,探讨了动态肌肉运动的中枢控制理论,以17名男性大学生为研究对象,让他们下肢负荷分别为105.8,140.9,176.4 kg时,以最快速度完成30次蹬踏运动.采集股四头肌s EMG信号和每次动作时间、距离,考察了3种负荷对股四头肌（外侧）、股四头肌（内侧）和股直肌MPF及输出功率的影响.结果显示：不同强度快速伸膝运动下股四头肌s EMG信号MPF随次数而下降,与以往静态研究相一致;MPF下降斜率没有差异;平均输出功率下降斜率有差异,在短时爆发力运动中,3个负荷输出功率分别呈现上升、不变和下降的趋势.     

Function and interaction of maturation-promoting factor and mitogen-activated protein kinase during meiotic maturation and fertilization of oocyte

Mitogen-activated protein kinase (MAP kinase) cascade and maturation-promoting factor (MPF) play very important roles during meiotic maturation and fertilization of oocyte. Interaction between MAP kinase and MPF influences meiotic maturation and fertilization of oocyte throughout the animal kingdom, including stimulation of germinal vesicle breakdown (GVBD), suppression of DNA replication, control of meiotic chromosome segregation, maintenance of metaphase II arrest, and resumption and completion of second meiosis. This review focuses on the function and interaction of MAP kinase and MPF during meiotic maturation and fertilization of oocyte.     

二阶系统的复特征根对其鲁棒H∞ 控制性能的影响

针对具有复特征根的二阶线性系统的鲁棒H_∞控制性能进行了研究,特别是探讨了虚部特征根对H_∞性能的作用,揭示了当特征根的实部固定不变的情况下,特征根的虚部增加到一定程度就会对H_∞性能不起作用,进而针对给定的系统矩阵,在H_∞性能的框架下分析了特征根实部和虚部之间的比例关系.同时,比照经典二阶系统的部分成果,探讨了经典二阶系统的阻尼比系数选取范围与H_∞性能框架下复特征根参数之间的对照关系,进而从时域的角度给出了阻尼比参数选取的一种合理解释,并形成时频交互综合分析,为极点配置控制理论中的期望极点的选取提供一种理论参考.     

基于信息熵的系统诊断参数交互推理选择方法

介绍了一种多输入，多输出系统的故障诊断参数选择方法，该方法经可观参数集的信息熵为标准，进行启发性诊断参数集的划分，先以系统状态决定的启发性诊断参数子集作为驱动数据，实施正向推理，缩小目标集合，再以故障目标集合为对象，进行反向推理以确定最终故障集合；最后将故障集合的元素所对应的可测诊断参数作为系统的诊断参数进行测量，该方法构成了诊断型专家系统的一子部分。     

板料成形数值模拟的过程研究

讨论了板料成形数值模拟方法的一般步骤及零件工作参数的确定方法.应用DYNAFORM软件分析了底壳件的成形过程,预测了零件可能产生起皱和破裂的部位,提出了消除和减少起皱及破裂的工艺改进措施.     

快速跳频多址信号的检测

对码分多址(CDMA)信号的检测常会遇到使用相同载波频率的系统用户的干扰(信道内干扰),或是遇到使用相近频率的用户的干扰(信道间干扰),提出了采用两阶段检测器,这个检测器并不复杂,但能消除大部分的信道内干扰和部分的信道间干扰。