A note on global output regulation of nonlinear systems in the output feedback form

This note shows how the adaptive control method developed recently for nonlinearly parameterized systems can be used to solve the problem of global output regulation, for nonlinear systems in the so-called output-feedback form with unknown parameters and exogenous signals belonging to a compact set whose bound is also unknown.     

Dynamical modeling and experimental validation of a micro-speaker with corrugated diaphragm for mobile phones

As the design trend of modern cellular phones evolves to be miniaturization and versatile sound in quality, the electro-mechanical components including the micro-speaker are essential toward size reduction and broad frequency range of sound. To reduce size, a diaphragm type micro-speaker is commonly employed in industry, while to broaden the sound frequency range corrugations on the diaphragm are adopted. The corrugations are generally capable of leading to fairly flat response over a broad range since diaphragm stiffness is decreased in axial direction. To confirm the aforementioned capability, the modeling on a corrugated diaphragm is performed first using finite element method (FEM) to obtain the associated dynamic equations in terms of modal coordinates; then the equations are next combined with the magneto-electrical model of the voice coil motor (VCM) that is attached to the bottom side of the diaphragm. Finally, the acoustic effects of the air inertia on the diaphragm and vents of the outer case are modeled using basic acoustic theories. Assembling all derived system equations and solving them, the frequency response of the micro-speaker in sound pressure level (SPL) can be simulated. It shows that the diaphragm corrugation in fact helps flatten the SPL response of the micro-speaker (especially in high frequency range) to lessen sound distortion. Furthermore, the corrugation angle approximately below 45° is favored over other angles or flatter SPL response. Experiments are also conducted to verify the theoretical findings.     

对油田企业建设和执行内部控制体系的思考

内部控制是一个由企业董事会、管理层和其他员工实施的,为实现企业经营的效果和效率目标、财务报告的可靠性目标和舍规性目标提供合理保证的过程。有效地建设以及有力地执行内控制度,对石油企业发展过程中有效地避免风险的发生起着非常重要的作用。但是,由于种种原因,油田企业目前的内部控制体系还不成熟,还存在着一些建设上的不足和执行上的不力。同时,企业员工普遍对内部控制还存在着一些认识误区,这就要求我们必须努力学习内控知识,加强内控知识培训,充分调动企业全体员工建设和雏护内部控制体系的积极性和自觉性,使得内控可以真正发挥其防范风险的作用。     

Inhibition of natural killer cell cytotoxicity by cell growth-related molecules

Certain MHC class I molecules on target cells are known to inhibit the cytotoxic action of NK cells. By using monoclonal antibody (mAb) Cho-1, we have found inhibitory non-MHC class I cell surface molecules that are noncovalently-associated with 200 kDa and 40 kDa antigens. Poly I-C-induced rat NK cells were not cytotoxic to rat fetus-derived fibroblast WFB cell line. In contrast, NK cells were cytotoxic to H-ras oncogene-induced transformants of WFB, W14 and W31. FACS analysis indicated that mAb Cho-1 reacts with WFB, but not with W14 and W31 cells. Thus, this antigen may disappear concomitantly with cell growth and transformation. Cho-1 antigens were also expressed on other NK-resistant lines, such as mouse BALB3T3 fibroblast, EL-4 lymphoma and human fibroblast HEPM. However, they were not expressed on NK-sensitive mouse YAC-1 and H-ras transformant (Brash) of BALB3T3 cells. Furthermore, treatment of target cells with IFN-gamma clearly induced the cell surface expression of Cho-1 antigens, and conferred a resistance to NK cytolysis on target cells. These data strongly suggest that Cho-1 antigen expression may correlate with target cell susceptibility to NK cells. Indeed, treatment of NK-resistant WFB as well as HEPM cells with F(ab')2 fragments of mAb Cho-1 resulted in the acquisition of susceptibility to NK cytolysis. Cho-1 antigens may be novel molecules that regulate the NK resistance of cells.     

Experimental studies of high frequency jet ventilation improved by enhancing expiratory turbulence

A 43-year-old male and a 39-year-old male presented with multiple pituitary adenomas with two distinct histological types. The first patient who had multiple endocrine neoplasia type 1 had developed acromegaly due to a growth hormone-releasing hormone (GHRH)-producing pancreatic tumor. Both plasma GHRH and growth hormone (GH) levels decreased to normal after resection of the pancreatic tumor. However, the plasma GH level gradually increased again and magnetic resonance imaging revealed pituitary adenoma formation. Histological examination revealed two different histological types of pituitary adenoma: GH cell adenoma and null cell adenoma. The second patient, with no such genetic condition, had a non-functioning pituitary adenoma. Histological examination revealed two different histological types of silent GH cell adenoma and silent gonadotroph adenoma. Careful histological examination is required to exclude the possibility of multiple pituitary adenomas.     

Reliability-estimation and stopping-rules for software testing,based on repeated appearances of bugs

Software-testing (debugging) is one of the most important components in software development. An important question in the debugging process is, when to stop. The choice is usually based on one of two decision criteria: (1) when the reliability has reached a given threshold, and (2) when the gain in reliability cannot justify the testing cost. Various stopping rules and software reliability models are compared by their ability to deal with these two criteria. Two new stopping rules, initiated by theoretical study of the optimal stopping rule based on cost, are more stable than other rules for a large variety of bug structures. The 1-step-ahead stopping rules based on the Musa et. al. basic execution and logarithmic Poisson models, as well as the stopping rule by Dalal and Mallows (1990), work well for software with many relatively small bugs (bugs with very low occurrence rates). The comparison was done by simulation     

BID: a novel BH3 domain-only death agonist

The BCL-2 family of proteins consists of both antagonists (e.g., BCL-2) and agonists (e.g., BAX) that regulate apoptosis and compete through dimerization. The BH1 and BH2 domains of BCL-2 are required to heterodimerize with BAX and to repress cell death; conversely, the BH3 domain of BAX is required to heterodimerize with BCL-2 and to promote cell death. To extend this pathway, we used interactive cloning to identify Bid, which encodes a novel death agonist that heterodimerizes with either agonists (BAX) or antagonists (BCL-2). BID possesses only the BH3 domain, lacks a carboxy-terminal signal-anchor segment, and is found in both cytosolic and membrane locations. BID counters the protective effect of BCL-2. Moreover, expression of BID, without another death stimulus, induces ICE-like proteases and apoptosis. Mutagenesis revealed that an intact BH3 domain of BID was required to bind the BH1 domain of either BCL-2 or BAX. A BH3 mutant of BID that still heterodimerized with BCL-2 failed to promote apoptosis, dissociating these activities. In contrast, the only BID BH3 mutant that retained death promoting activity interacted with BAX, but not BCL-2. This BH3-only molecule supports BH3 as a death domain and favors a model in which BID represents a death ligand for the membrane-bound receptor BAX.     

Laser welding of Al55-Zn coated steel sheet

A study has been made of the procedures used for the lap and butt welding of 0.62 and 1.16 mm thickness steel sheets coated with Al55-Zn alloy, using laser-beam technology. The main problems arise in lap welding as a result of zinc evaporation from the coating. The vapour pressures of this element lead to cratering and blistering of the welds which are visible from the external surface and imply severe weld defects. An efficient solution to this problem consists in leaving a gap between the internal faces, thus allowing the zinc vapours to escape. Excessive gaps, however, lead to the molten metal collapse and to lack of penetration. In the present work, acceptable results were obtained with a maximum interface separation of 0.1 mm. This allows excellent continuity of the joints, without cracks, pores or non-metallic inclusions and with moderate hardnesses, thus demonstrating the good laser weldability of the coated material. A difficulty arises, however, in relation to the coating in zones close to the weld. In these high-temperature zones the coating is lost, and in the immediately adjacent areas the coating microstructure and phases are altered, as was shown by scanning electron microscope analyses.     

岩石高速冲击实验的最新进展

根据１９８３～１９９０年国际联机检索资料，说明了近１０年来有关ＳＨＰＢ（ＳＨＢ）研究的最新发展，并提出了我国有关ＳＨＰＢ研究的几点建议。