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Null Controllability of Some Degenerate Wave Equations

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Journal of Systems Science & Complexity 2017年第5期30卷 1027-1041页

作者： Zhang Muming gao hang School of Mathematics and Statistics Northeast Normal UniversityChangchun 130024China.

This paper is devoted to a study of the null controllability problems for one-dimensional linear degenerate wave equations through a boundary controller. First, the well-posedness of linear degenerate wave equations is discussed. Then the null controllability of some degenerate wave equations is established, when a control acts on the non-degenerate boundary. Different from the known controllability results in the case that a control acts on the degenerate boundary, any initial value in state space is controllable in this case. Also, an explicit expression for the controllability time is given. Furthermore, a counterexample on the controllability is given for some other degenerate wave equations.

关键词： Controllability degenerate wave equation Fourier expansion observability.

MECHANICAL-ELECTRIC COUPLING DYNAMICAL CHARACTERISTICS OF AN ULTRA-HIGH SPEED GRINDING MOTORIZED SPINDLE SYSTEM

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Chinese Journal of Mechanical Engineering 2008年第5期21卷 34-40页

作者： LUE Lang XIONG Wanli gao hang National Engineering Research Center for High Efficiency Grinding Hunan University Changsha 410082 China College of Mechanical Engineering Dalian University of Technology Dalian 116011. China

On the basis of the traditional mechanical model of a grinding wheel rotor and the mechanical-electric coupling model with ideal sinusoidal supply, taking high-frequency converting current of inverter power switches into further consideration, a modified mechanical-electric coupling model is created. The created model consists of an inverter, a motorized spindle, a grinding wheel and grinding loads. Some typical non-stationary processes of the grinding system with two different supplies, including the starting, the speed rising and the break in grinding loads, are compared by making use of the created model. One supply is an ideal sinusoidal voltage source, the other is an inverter. The theoretical analysis of the high-order harmonic is also compared with the experimental result. The material strategy of suppressing high-order harmonic mechanical-electric coupling vibration by optimizing inverter operating parameters is proposed.

关键词： Ultra-high speed grinding Motorized spindle Mechanical-electric coupling Vibration Suppression

Experimental study on high-efficiency polishing for potassium dihydrogen phosphate (KDP) crystal by using two-phase air-water fluid

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Frontiers of Mechanical Engineering 2020年第2期15卷 294-302页

作者： Ziyuan LIU hang gao Dongming GUO Key Laboratory for Precision and Non-Traditional Machining Technology of Ministry of Education Dalian University of TechnologyDalian 116024China

A high-efficiency polishing approach using two-phase air–water fluid(TAWF)is proposed to avoid surface contamination and solve the inefficiency of previous water-dissolution polishing techniques for potassium dihydrogen phosphate(KDP)*** the proposed method,controllable deliquescence is implemented without any chemical *** product of deliquescence is then removed by a polishing pad to achieve surface *** mechanism underlying TAWF polishing is analyzed,a special device is built to polish the KDP crystal,and the effect of relative humidity(RH)on polishing performance is *** relationship between key parameters of polishing and surface planarization is also *** show that the polishing performance is improved with increasing ***,precisely controlling the RH is extremely difficult during TAWF *** deliquescence can easily be disrupted once the RH fluctuates,which therefore needs to be restricted to a low level to avoid its influence on deliquescence *** material removal of TAWF polishing is mainly attributed to the synergistic effect of deliquescence and the polishing *** polishing pressure and revolution rate remarkably reduce the life of the polishing pad and the surface quality of the KDP *** polishing using IC-1000 and TEC-168S increase the machining efficiency by 150%,and a smooth surface with a root mean square surface roughness of 5.5 nm is obtained.

关键词： potassium dihydrogen phosphate(KDP)crystal controllable deliquescence two-phase air–water fluid high-efficiency polishing material removal

Facial Fabrication of Biomimetic Water Pinning Microstructures on Polyethylene Surfaces with Robust Superhydrophobic Wetting State

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Journal of Bionic Engineering 2020年第4期17卷 644-651页

作者： Yuzhu Li hang gao Yunhai Ma Donghui Chen School of Mechatronics Engineering Shenyang Aerospace UniversityShenyang 110136China Key Laboratory of Fundamental Science for National Defense of Aeronautical Digital Manufacturing Process Shenyang 110136China Key Laboratory for Bionic Engineering Ministry of EducationJilin UniversityChangchun 130022China

Applying hot-embossing technology,a simple and cost-effective method for the fabrication of microstructured High Density Polyethylene(HDPE)surfaces with a robust superhydrophobic wetting state is ***-meshes and micro-grooves in the flexible template are filled by the PE melt in the hot embossing ***,a two-stage microstructure on the PE film surface is *** PE film exhibits a contact angle of 151.8°±2°and roll-offangle of>90~when a 5μL water droplet is dropped on its *** pinning ability on the surface is figured out and roll-off angles are as a quadratic function of specified water droplet ***,a 356μN water pinng force appears on the HDPE film due to the solid-vapor composite interface on its ***,self-cleaning and immersion tests reveal that the HDPE surface with micro-pillars exhibit robust Cassie impregnating wetting state against external *** proposed method for facial fabrication ofmicrostructured surfaces is an appropriate candidate for the development of droplet manipulation and functional biomimetic polymer surfaces.

关键词： water pinning hot-embossing Cassie impregnating self-cleaning microstructure

Machining the Integral Impeller and Blisk of Aero-Engines:A Review of Surface Finishing and Strengthening Technologies

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Chinese Journal of Mechanical Engineering 2017年第3期30卷 528-543页

作者： Youzhi Fu hang gao Xuanping Wang Dongming Guo key laboratory for precision and non-traditional machining technology of ministry of education dalian university of technologyDalian 116024China

The integral impeller and blisk of an aero-engine are high performance parts with complex structure and made of difficult-to-cut materials. The blade surfaces of the integral impeller and blisk are functional surfaces for power transmission, and their surface integrity has signif- icant effects on the aerodynamic efficiency and service life of an aero-engine. Thus, it is indispensable to finish and strengthen the blades before use. This paper presents a comprehensive literature review of studies on finishing and strengthening technologies for the impeller and blisk of aero-engines. The review includes independent and inte- grated finishing and strengthening technologies and dis- cusses advanced rotational abrasive flow machining with back-pressure used for finishing the integral impeller and blisk. A brief assessment of future research problems and directions is also presented.

关键词： Integral impeller and blisk Aero-engine Surface integrity Surface finishing Surface strengthening

Effect of mechanical anisotropy on material removal rate and surface quality during polishing CdZnTe wafers

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Rare Metals 2011年第4期30卷 381-386页

作者： LI Yan JIE Wanqi KANG Renke gao hang State Key laboratory of Solidification Processing Northwestern Polytechnical University Xi＇an 710072 China Key Laboratory for Precision and Non-Traditional Machining Technology （Ministry of Education of China） Dalian University of Technology Dalian 116024 China

The mechanical characters of CdZnTe crystal were investigated by nanoscratch tests, and the effects of mechanical anisotropy on the material removal rate and surface quality were studied by polishing tests. There is a peak of frictional coefficient at the early stage of scratch, and increasing the vertical force will result in the increase of peak value correspondingly. The fluctuation phenomenon of frictional coefficient is generated at high vertical force. The lateral forces show the apparent twofold and threefold symmetries on （110） and （111） planes, respectively. To obtain high surface quality, low polishing pressure and hard direction （〈 T10 〉 directions on （110） plane and 〈 112 〉 directions on （111） plane） should be selected, and to achieve high material removal rate, high polishing pressure and soft direction （〈001〉 directions on （110） plane and 〈 121 〉 directions on （111） plane） should be selected.

关键词： cadmium compounds single crystals nanoscratch tests frictional coefficient material removal rate surface quality anisotropy

Micro water dissolution machining principle and its application in ultra-precision processing of KDP optical crystal

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Science China(Technological Sciences) 2015年第11期58卷 1877-1883页

作者： gao hang WANG Xu TENG XiaoJi GUO DongMing Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education Dalian University of Technology

In this paper, a micro water dissolution machining （MWDM） principle is proposed for machining potassium dihydrogen phosphate （KDP） crystal using water-in-oil micro-emulsion as an abrasive-free polishing fluid. In addition, two instances of the application of this principle to ultra-precision machining of KDP crystals are presented. Computer-controlled optical surfacing （CCOS） and diamond wire cutting （DWC） process were carried out according to the MWDM principle. In the case of the CCOS technology, it is found that the micro-waviness was removed completely by following the MWDM principle. The surface undulation decreased from 40 nm to less than 10 nm, and the surface root-mean-square （rms） roughness obviously reduced from 8.147 to 2.660 nm. In the case of the DWC process, the surface rms roughness reduced from 8.012 to 2.391 gm, and the cutting efficiency was improved. These results indicate that the MWDM principle can efficiently improve the machining quality of KDP optical crystal and has a great potential to machine water-soluble materials.

关键词： potassium dihydrogen phosphate (KDP) crystal micro water dissolution machining (MWDM) principle ultra-precision machining surface root-mean-square (rms) roughness

L^p and L~∞ Norm Estimates of the Cost of the Controllability for Heat Equations

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Acta Mathematica Sinica,English Series 2009年第8期25卷 1305-1324页

作者： Pei Dong LEI Xu LIU hang gao School of Mathematics & Statistics Northeast Normal University Changchun 130024 P. R. China

This paper is concerned with the bound of the cost of approximate controllability and null controllability of heat equations, i.e., the minimal Lp norm and L∞ norm of a control needed to control the system approximately or a control needed to steer the state of the system to zero. The methods we use combine observability inequalities, energy estimates for heat equations and the dual theory.

关键词： approximate controllability null controllability cost of the controllability observability inequality

KSHV strategies for host dsDNA sensing machinery

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Virologica Sinica 2016年第6期31卷 466-471页

作者： hang gao Yanyan Song Chengrong Liu Qiming Liang Department of Nephrology The Second Hospital of Jilin University Changchun 130041 China

The innate immune system utilizes pattern recognition receptors cyclic GMP-AMP synthase(cGAS)to sense cytosolic double-stranded(ds) DNA and initiate type 1 interferon signaling and autophagy pathway, which collaborate to limit pathogen infections as well as alarm the adaptive immune response. The genomes of herpesviruses are large dsDNA, which represent a major class of pathogen signatures recognized by cellular DNA sensor cGAS. However, to successfully establish the persistent infection, herpesviruses have evolved their viral genes to modulate different aspects of host immune signaling. This review summarizes the evasion strategies of host cGAS DNA sensing pathway by Kaposi's Sarcoma-associated Herpesvirus(KSHV) and their contributions to KSHV life cycles.

关键词： dsDNA interferon innate autophagy signaling modulate pathogen alarm initiate contributions