一种新颖的求解离散Gabor展开对偶窗的方法

本文给出了一种新颖的简捷的求解离散Gabor展开最佳对偶窗的方法．首先推导了离散Gabor展开的公式，给出了连续Gabor展开和离散Gabor展开间的关系．最后利用连续展开和离散展开间的关系给出了一求解离散Gabor展开最佳对偶窗的表达式及实例．     

Nitrone spin-traps block calcium channels and induce pulmonary artery relaxation independent of free radicals

Free radicals react with nitrones to form stable nitroxides which can be identified by ESR spectroscopy. Unfortunately, little is known regarding the pharmacological properties of these compounds. In this study, three commonly used nitrones, 5,5-dimethylpyrroline-N-oxide (DMPO), alpha-phenyl-tert-butylnitrone (PBN), and alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (POBN), were found to induce relaxation of preconstricted isolated rat pulmonary artery rings. Additional experiments with PBN indicated that vasorelaxation could not be attributed to production of endothelial derived factors, prostaglandins, or free radicals. Patch-clamp techniques revealed reversible calcium channel blockade with PBN at a concentration below that needed to detect free radicals. Calcium channel blockade probably accounts for the vasorelaxation observed in the isolated ring preparations described here, and should be considered when using nitrone spin-traps both in in vivo and clinical studies.     

混合集成电路激光功能调值技术

本文提出了激光功能微调技术在高精度混合集成电路上的应用，讨论了关键技术问题，并以实例具体说明。该技术的应用为研制高精度混合集成电路开辟了新途径。     

努力攀登科技高峰 为把石化工业建成支柱产业多做贡献

概述中国石化总公司成立以来所取得的重大科技成果。     

The preparation and magnetic properties of Fe-Ag granular solid using a sol-gel method

The Fe-Ag granular metal solid samples with 10% and 30% weight iron have been successfully fabricated using a sol-gel method, which are characterized by X-ray diffraction and transmission electron micrography. The average diameters of iron particles are from about a few nanometres to a few tens of nanometres controlled by the reducing temperature. The evolution of magnetic properties and microstructure during heat treating are described in detail and explained by using the superparamagnetism, single domain and multi domain theories. The magnetic anisotropy of the Fe-Ag granular solid is studied by using the law of approach to saturation. It is found that the magnetic anisotropy constant is in the order of 10⁵ J m^–3 which is higher than the value of the bulk iron and increases with the increase of reducing temperature.     

Curvilinear fatigue crack reliability analysis by stochastic boundary element method

In this paper, the stochastic boundary element method, which combines the mixed boundary integral equations method explored in Reference 1 with the first-order reliability method, is developed to study probabilistic fatigue crack growth. Due to the high degree of complexity and non-linearity of the response, direct differentiation coupied with the response-surface method is employed to determine the response gradient. Three random processes, the mode I and mode II. stress intensity factors and the crack direction angle, are included in the expression of the response gradient. The sensitivity of these random processes is determined using a first-order response model. An iteration scheme based on the HL-RF method² is applied to locate the most probable failure point on the limit-state surface. The accuracy and efficiency of the stochastic boundary element method are evaluated by comparing the cumulative distribution function of the fatigue life obtained with Monte Carlo simulation. The reliability index and the corresponding probability of failure are calculated for a fatigue crack growth problem with randomness in the crack geometry, defect geometry, fatigue parameters and external loads. The response sensitivity of each primary random variable at the design point is determined to show its role in the fatigue failure. The variation of each primary random variable at the design point with the change of probability of failure is also presented in numerical examples.     

The geometry effects for stress intensity factor of sandwich specimen for measuring interfacial fracture toughness

The interfacial stress intensity factors for three types of sandwich specimens: the single edge crack tensile specimen, the three point bend specimen and the four point shear specimen were obtained by the finite element analysis and compared with the asymptotic solutions. The results show that the geometric effect for mode II specimen is larger than mode I specimen. The limit curves for geometry factor equal to 1.05 were obtained to indicate the usable range of validity of the asymptotic solution.     

机器人离散滑模变结构—PI控制器

本文采用离散滑模变结构控制方法，针对机器人提出了一种滑模变结构——ＰＩ控制方案，给出了该控制方案滑模存在条件及控制器设计方案。该控制器将离散滑模变结构控制和ＰＩ控制两者的优点有机地结合起来，理论分析和仿真结果表明该控制器能使机器人在各种复杂非线性动力学情况下具有良好的性能指标。这种控制器输出切换小，可以投入应用。     

A Study of the Specific Heats of the Compounds in the Sm_2O_3-BaO-CuO System

By means of X-ray diffraction and adiabatic scanning calorimeter,the specific heatsof five compounds in the Sm_2O_3-BaO--CuO system,such as Sm_2BaO_4,Sm_2CuO_4,BaCuO_4,Sm_2BaCuO_5,SmBa_2Cu_3O_(7-x),from -150℃ to 800℃ have been measured.It is found that the specific heats ofthese compounds increase smoothly with the increase of temperature.