低迟滞PMN-PT叠层型驱动器件的制备

研究了PMN-PT电致应变陶瓷材料的铌铁矿法制备及其电致应变性能,以及该陶瓷膜叠层型驱动器件的制备条件及性能.结果表明,0.94PMN-0.06PT陶瓷的应变迟滞最小;利用压延法可以提高叠层陶瓷膜的密度等特性;叠层型驱动器件的成型压力、预烧和烧结阶段的压力分别为200和0.01 MPa时,驱动器件的应变迟滞小于百分之一,并且驱动特性优异.

飞机叠层结构预联接工艺优化

为有效消除叠层件之间由于制造误差、定位误差、钻削力等因素产生的初始间隙和制孔间隙,提出预联接工艺优化方法,预联接件的紧固作用可有效消除叠层间隙,抑制毛刺生长.通过建立蒙皮和边梁之间的预联接有限元简化模型,在不考虑压紧力的情况下,研究不同预联接件数量、安装位置以及预紧力条件下的叠层残余间隙和制孔间隙,给出最优预联接工艺方案,通过机器人自动化制孔系统进行实验,验证了该优化方案的正确性和有效性.实验结果表明,随着预紧力的增大,叠层毛刺尺寸先明显减小后小幅增大,较优的预联接件数量和安装位置可优化叠层件的接触刚度,有效减小毛刺尺寸.

Laterally Electrostatically Driven Poly 3C-SiC Folded-Beam Resonant Microstructures

Micromachined comb-drive electrostatic resonators with folded-cantilever beams were designed and fabricated. A combination of Rayleigh＇s method and finite-element analysis was used to calculate the resonant frequency drift as we adjusted the device geometry and material parameters. Three micromachined lateral resonant resonators with different beam widths were fabricated. Their resonant frequencies were experimentally measured to be 64.5,147.2, and 255.5kHz, respectively, which are in good agreement with the simulated resonant frequency. It is shown that an improved frequency performance could be obtained on the poly 3C-SiC based device structural material systems with high Young＇s modulus.

从切筋成形废品分析模具设计

通过对切筋成形设备的生产观察与产品失效分析,对其切筋成形模具用料、寿命对比,提出半导体行业提高切筋成形模具设计的合理化建议。

流致振动电磁测量装置的研究

流致振动其本质是一个固液耦合问题 ,数学处理十分复杂 ,这里介绍一种电磁测量方法。由于测量中 ,探测器和流体管道不存在相对运动和影响流场的问题 。

Common reflection surface stack using dip decomposition for rugged surface topography

We present an extension of the Common Reflection Surface （CRS） stack that provides support for an arbitrary top surface topography. CRS stacking can be applied to the original prestack data without the need for any elevation statics. The CRS-stacked zero- offset section can be corrected （redatumed） to a given planar level by kinematic wave field attributes. The seismic processing results indicate that the CRS stacked section for rugged surface topography is better than the conventional stacked section for S/N ratio and better continuity of reflection events. Considering the multiple paths of zero-offset rays, the method deals with reflection information coming from different dips and performs the stack using the method of dip decomposition, which improves the kinematic and dynamic character of CRS stacked sections.

An effective denoising strategy for wave equation migration based on propagation angles

We present an effective denoising strategy for two-way wave equation migration. Three dominant artifact types are analyzed and eliminated by an optimized imaging condition. We discuss a previously unsolved beam-like artifact, which is probably caused by the cross-correlation of downward transmitting and upward scattering waves from both the source and receiver side of a single seismic shot. This artifact has relatively strong cross- correlation but carries no useful information from reflectors. The beam-like artifact widely exists in pre-stack imaging and has approximately the same amplitude as useful seismic signals. In most cases, coherent artifacts in the image are caused by directionally propagating energy. Based on propagation angles obtained by wavefield gradients, we identify the artifact energy and subtract its contribution in the imaging condition. By this process most artifacts can be accurately eliminated, including direct wave artifacts, scattering artifacts, and beam- like artifacts. This method is independent of the wavefield propagator and is easy to adapt to almost all current wave equation migration methods if needed. As this method deals with the physical artifact origins, little damage is caused to the seismic signal. Extra k-domain filtering can additionally enhance the stacking result image quality. This method succeeds in the super-wide-angle one-way migration and we can expect its success in other two-way wave equation migrations and especially in reverse time migration.

The Law of the Iterated Logarithm for the Sums of φ-Mixing Sequences with Duple Suffixes

Hu Shuhe gets a sufficient condition on the law of the iterated logarithm for the sums of φ-mixing sequences with duple suffixes. This paper greatly improves his condition.

Elimination of boundary effect for laminated overburden model in pillar stability analysis

The laminated overburden model(La Model)has been widely used for pillar design and stability analysis.As a boundary element program,the La Model program is sensitive to the boundary condition,which should be considered before creating the model.To eliminate the boundary effect in a La Model pillar stability analysis,a suitable boundary buffer zone is needed around the model edge.The radius of influence(R)and the abutment load extent(D)are two major factors that affect the stresses and displacements calculated in LaM odel.To determine the optimum buffer zone extent,a database of case histories was analyzed using the La Model program.Values for R and D were varied until a buffer zone having negligible influence on the pillar stability factor(SF)of the active mining zone(AMZ)was determined.

Effect of the Chemical Mutagens Sodium Azide on Plant Regeneration of Two Tomato Cultivars under Salinity Stress Condition in vitro

The study was carried out to induce variations and stimulate callus induction, plant regeneration from different explants of two tomato （Lycopersicon esculentum Mill.） cultivars Trescantos and super Regina by using tissue culture technique and Sodium azide as a chemical mutagens at concentrations （0.0, 2.0 and 4.0） mM under salinity stress condition at the levels（3.0, 6.0 and 9.0） dS/m. Different plant growth regulators were tested for their potentials in callus induction. The results revealed that treated seeds with SA （sodium azide） at concentration （2.0） mM increased seed germination percentage, seedling height and root length as compare to control treatment. While （4.0） mM concentration cause a reduction in all parameters mentioned above. Concerning to callus induction both cultivars showed a different response against different tested media with varying concentrations of plant growth regulators and despite their variable response to all tested media a combination of （2.0） mg from Kinetin （KIN） and lndol acetic acid （IAA） was found to be the most effective as compare to other treatments. Moreover, when callus transferred to a stressed media the variation was observed in explants fresh weight, and high reduction with the increment of salt level were recorded. Similarly the regeneration efficiency from stressed callus were observed at the level 3.0 and 6.0 dS/m while 9.0 dS/m the callus failed to regenerate plants for all three explants of both tomato cultivars.

A preliminary experimental validation of superposition strategy in thermal management of integrated circuit with multiple hot-spots

Thermal management is a key issue in the integrated circuit(IC)design.In this paper,the superposition strategy was experimentally validated using a modeling IC device,which was fabricated by laboratory-level microfabrication technique.Metal thin film resistors on the top of dielectric layer were used to analogize the multiple hot-spots in the modeling IC device.The measured temperature rise with multiple hot-spots agrees well with the predictions given by the superposition calculations.With the help of the superposition strategy,thermal management of IC device can be significantly simplified by decomposing the system into sub-systems and optimizing each part individually.The influence coefficients in the superposition strategy extracted from the experimental measurement offer the IC designers a useful engineering tool to facility the thermal optimization and evaluate the thermal performance of IC devices.

The principle of compromise in competition: exploring stability condition of protein folding

Thermodynamic hypothesis and kinetic stabil- ity are currently used to understand protein folding. The former assumes that free energy minimum is the exclusive dominant mechanism in most cases, while the latter shows that some proteins have even lower free energy in inter- mediate states and their native states are kinetically trapped in the higher free energy region. This article explores the stability condition of protein structures on the basis of our study of complex chemical systems. We believe that sep- arating one from another is not reasonable since they should be coupled, and protein structures should be dom- inated by at least two mechanisms resulting in different characteristic states. It is concluded that： （1） Structures of proteins are dynamic, showing multiple characteristic states emerging alternately and each dominated by a respective mechanism. （2） Compromise in competition of multiple dominant mechanisms might be the key to understanding the stability of protein structures. （3） The dynamic process of protein folding should be depicted through the time series of both its energetic and structural changes, which is much meaningful and applicable than the free energy landscape.

Paleo-redox conditions across the Permian-Triassic boundary in shallow carbonate platform of the Nanpanjiang Basin, South China

Ocean anoxia has been widely implicated in the Permian-Triassic extinction. However, the duration and distribution of the ocean anoxia remains controversial. In this study, the detailed redox changes across the Permian-Triassic boundary （PTB） in the shallow platform interior at Great Bank of Guizhou （GBG） has been reconstructed based on the high-resolution microfossil composition and multiple paleo-redox proxies. The shallow platform is characterized by low sulfur （total sulfur （TS） and pyrite sulfur （Spy）） concentrations, low Spy/TOC ratios, and low DOP values before the mass extinction, representing oxic conditions well. Following the mass extinction, the shift of multiple geochemical proxies, including high Spy/TOC ratios and DOP values, indicates dysoxic-anoxic conditions in shallow ocean. Furthermore, we reconstruct the transition of the redox conditions of Nanpanjiang Basin： the intense volcanic eruptions, which release huge COz and SO2 before the mass extinction, provoke the temperature rising and the collapse of terrestrial ecosystem. As a result, the increased weathering influx causes the carbon iso- topic negative excursion and the expansion of the ocean oxygen minimum zone （OMZ）. When the OMZ expanded into the photic zone, the episodic H2S release events enhance the pyrite burial at Dajiang section. Thus, intense volcanic eruptions, temperature increase, and oceanic hypoxia together lead to the PTB extinction. Recent studies show high temperature might be the key mechanism of the PTB extinction. In addition, this study confirms that the microbialites were formed in the dysoxic- anoxic shallow water.

An air-stable supported Cu(?) catalyst for azide-alkyne click polymerization

An air-stable supported Cu(I) catalyst, Cu I@PS-Phen, was designed and synthesized. Cu I@PS-Phen can efficiently catalyze the click polymerization of diynes a and diazides b to produce soluble and thermally stable polytriazoles with high molecular weights(Mw up to 30800), and low copper residue content(down to 190 ppm) in high yields(up to 94.2%) under mild reaction conditions without the exclusion of oxygen.

The large increase of δ^(13)C_(carb)-depth gradient and the end-Permian mass extinction

Carbonate carbon isotope （δ^13Ccarb） has received considerable attention in the Permian-Triassic transition for its rapid negative shift coinciding with the great end-Permian mass extinction event. The mechanism has long been debated for such a c~ δ^13Ccarb negative excursion through the end-Permian crisis and subsequent large perturbations in the entire Early Triassic. A δ^13Ccarb depth gradient is observed at the Permian-Triassic boundary sections of different water-depths, i.e., the Yangou, Meishan, and Shangsi sections, and such a large δ^13Ccarb-depth gradient near the end-Permian mass extinction horizon is believed to result from a stratified Paleotethys Ocean with widespread anoxic/euxinic deep water. The evolution of δ^13Ccarb-depth gradient com- bined with paleontological and geochemical data suggests that abundant cyanobacteria and vigorous biological pump in the immediate aftermath of the end-Permian extinction would be the main cause of the large δ^13Ccarb-depth gradient, and the enhanced continental weathering with the mass extinction on land provides a mass amount of nutriment for the flourishing cyanobacteria. Photic zone anoxia/euxinia from the onset of chemocline upward excursion might be the direct cause for the mass extinction whereas the instability of chemocline in the stratified Early Triassic ocean would be the reason for the delayed and involuted biotic recovery.