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Effect of compressibility on the hypervelocity penetration

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Acta Mechanica Sinica 2018年第1期34卷 82-98页

作者： W.j.Song X.W.Chen P.Chen Department of Mechanics and Engineering Science College of Engineering Peking University Advanced Research Institute for Multidisciplinary Science Beijing Institute of Technology The State Key Lab of Explosion Science and Technology Beijing Institute of Technology Centre for Applied Physics and Technology (CAPT) Peking University

We further consider the effect of rod strength by employing the compressible penetration model to study the effect of compressibility on hypervelocity ***, we define different instances of penetration efficiency in various modified models and compare these penetration efficiencies to identify the effects of different factors in the compressible model. To systematically discuss the effect of compressibility in different metallic rod-target combinations, we construct three cases, i.e., the penetrations by the more compressible rod into the less compressible target, rod into the analogously compressible target, and the less compressible rod into the more compressible target. The effects of volumetric strain, internal energy, and strength on the penetration efficiency are analyzed simultaneously. It indicates that the compressibility of the rod and target increases the pressure at the rod/target interface. The more compressible rod/target has larger volumetric strain and higher internal energy. Both the larger volumetric strain and higher strength enhance the penetration or anti-penetration ability. On the other hand, the higher internal energy weakens the penetration or anti-penetration ability. The two trends conflict, but the volumetric strain dominates in the variation of the penetration efficiency, which would not approach the hydrodynamic limit if the rod and target are not analogously compressible. However, if the compressibility of the rod and target is analogous, it has little effect on the penetration efficiency.

关键词： Compressibility Hypervelocity penetration Equation of state(EOS) Shockwave Bernoulli equation

Measurement of the Third-Order Nonlinear Optical Coefficient of ZnO Crystals by Using ICCD-Z-Scan

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Chinese Physics Letters 2004年第7期21卷 1356-1358页

作者： jIAGuang-Ming ZHANGGui-Zhong XIANGWang-Hua j.B.Ketterson CollegeofPrecisionInstrumentandOptoelectronicsEngineering TianjinUniversityTianjin300072 KeyLaboratoryofOptoelectronicsInformationandTechnicalScience(MinistryofEducation) Tianjin300072 DepartmentofPhysicsandAstronomy NorthwesternUniversityEvanstonIL60208USA

We present an image-intensified charge-coupled-device (ICCD) version of Z-scan by employing an ICCD detector and fixing the sample at the beam waist, and a measurement of the third-order nonlinear optical coefficient of single crystal zinc oxide (ZnO). The χ(3) value of −9.1×10−15cm2/W measured is in agreement with the published result. Our Z-scan configuration of placing sample at beam waist and collecting the whole wavefront by an ICCD detector is simple and can be deployed in cryogenic research where the sample cannot be Z-scanned.

关键词： Zinc oxide

FTIR Studies on NO Adsorption on [Co+Mg(Sr)] /ZSM-5

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Chemical Research in Chinese Universities 2002年第4期18卷 389-392页

作者： LEE C. W. CHONG P. j. KRICT Taejon 305-606 KoreaKRICT Taejon 305-606 Korea

The adsorption of NO on /ZSM-5 zeolites with different contents was studied by means of FTIR spectroscopy. The dominant NO species adsorbed on /ZSM-5 was found to be in a dinitrosyl form, as demonstrated by the IR bands at 1 813 and 1 896 cm -1. NO was adsorbed in a mononitrosyl form as shown in the region of 1 937-1 939 cm -1 as a minor species. Samples /ZSM-5 showed a new band near 1 858 cm -1(w) attributable to the species of Co_3O_4-NO. It was found that zeolite /ZSM-5 exhibits superior performance characteristics for SCR of NO molecules, and is promising as a useful catalyst. The typical catalyst /ZSM-5 for SCR resulted from the collaboration of the metal alkalinity and the ionic radius of the metal(such as Mg or Sr).

关键词： Infrared spectroscopy Nitric oxide Adsorption Mononitrosyl Dinitrosyl Cobalt oxide

A Hybrid Artificial Intelligence Model for Skin Cancer Diagnosis

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Computer Systems Science & Engineering 2021年第5期37卷 233-245页

作者： V.Vidya Lakshmi j.S.Leena jasmine Research Scholar Anna UniversityChennaiTamil Nadu600025India Velammal Engineering college ChennaiTamil Nadu600066India

Melanoma or skin cancer is the most dangerous and deadliest *** the incidence and mortality rate of skin cancer increases worldwide,an automated skin cancer detection/classification system is required for early detection and prevention of skin *** this study,a Hybrid Artificial Intelligence Model(HAIM)is designed for skin cancer *** uses diverse multi-directional representation systems for feature extraction and an efficient Exponentially Weighted and Heaped Multi-Layer Perceptron(EWHMLP)for the *** the wavelet transform is a powerful tool for signal and image processing,it is unable to detect the intermediate dimensional structures of a medical *** the proposed HAIM uses Curvelet(CurT),Contourlet(ConT)and Shearlet(SheT)transforms as feature extraction *** MLP is very flexible and well suitable for the classification problem,the learning of weights is a challenging ***,the optimization process does not converge,and the model may not be *** overcome these drawbacks,EWHMLP is *** show that the combined qualities of each transform in a hybrid approach provides an accuracy of 98.33%in a multi-class approach on PH2 database.

关键词： Skin cancer multi-directional systems curvelet contourlet shearlet multi-layer perceptron

Approximate Eigensolutions of the Deformed Woods-Saxon Potential via AIM

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Chinese Physics Letters 2013年第2期30卷 32-36页

作者： Sameer M.Ikhdair Babatunde j.Falaye Majid Hamzavi Department of Physics Faculty of ScienceAn-Najah National UniversityNablusWest BankPalestine Department of Physics Near East University922022 NicosiaNorthern CyprusTurkey Theoretical Physics Section Department of PhysicsUniversity of IlorinP.M.B.1515IlorinNigeria Department of Science and Engineering Abhar BranchIslamic Azad UniversityAbharIran

Using the Pekeris approximation,the Schrödinger equation is solved for the nuclear deformed Woods-Saxon potential within the framework of the asymptotic iteration *** energy levels are worked out and the corresponding... 详细信息

关键词： function. method. Saxon

Three-dimensional steep wave impact on a vertical cylinder

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journal of Hydrodynamics 2016年第4期28卷 523-533页

作者： Ioannis K.CHATjIGEORGIOU Alexander A.KOROBKIN Mark j.COOKER School of Mathematics University of East Anglia School of Naval Architecture and Marine Engineering National Technical University of Athens

In the present study we investigate the 3-D hydrodynamic slamming problem on a vertical cylinder due to the impact of a steep wave that is moving with a steady *** linear theory of the velocity potential is employed by assuming inviscid,incompressible fluid and irrotational *** the problem is set in 3-D space,the employment of the Wagner condition is *** set of equations we pose,is presented as a mixed boundary value problem for Laplace＇s equation in *** from the mixedtype of boundary conditions,the problem is complicated by considering that the region of wetted surface of the cylinder is a set whose boundary depends on the vertical coordinate on the cylinder up to the *** make some simple assumptions at the start but otherwise we proceed *** find closed-form relations for the hydrodynamic variables,namely the time dependent potential,the pressure impulse,the shape of the wave front（from the contact point to beyond the cylinder） and the slamming force.

关键词： cylinder hydrodynamic incompressible steep Wagner employment otherwise coordinate analytically assumptions

A NOVEL THEORY OF EFFECTIVE MECHANICAL PROPERTIES OF CLOSED-CELL FOAM MATERIALS

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Acta Mechanica Solida Sinica 2013年第6期26卷 559-569页

作者： Yuli Ma Xianyue Su R.Pyrz j.Ch.Rauhe The State Key Laboratory for Turbulence and Complex Systems (LTCS) and Department of Mechanics and Aerospace Engineering College of EngineeringPeking University Chinalco Research Institute of Science and Technology Department of Mechanical and Manufacturing Engineering Aalborg University

In this paper a new theory of effective mechanical properties of foam materials is proposed. A cell volume distribution coefficient is introduced to modify the original Gibson-Ashby equations of effective mechanical properties of foam materials. The constants that influence the effective modulus are replaced by the coeff^cient. Based on the modified distribution coefficient, the yield stress is also recalculated. Using X-ray microtomography, the internal structures of dif- ferent samples of polypropylene-nanoclay foam are obtained. The cell volume distributions of these samples are derived from the experiment by image analysis and the fitting curves are plot- ted. The distribution coefficient is acquired using the parameters from the theoretical model of the distribution curves. The results of the improved theory are compared with the experimental values and show good fitting quality. It was found that the precision of the improved theory is high and the cell volume distribution has an impact on the effective mechanical properties that would lead to the optimization of the synthesis procedure.

关键词： closed-cell foam cell volume distribution distribution coefficient Young's modulus yield stress distribution function

Simplified seismic performance assessment and implications for seismic design

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Earthquake Engineering and Engineering Vibration 2014年第S1期13卷 95-122页

作者： Timothy j.Sullivan David P.Welch Gian Michele Calvi University of Pavia Department of Civil Engineering & ArchitecturePavia 27100Italy European Centre for Training and Research in Earthquake Engineering Pavia 27100Italy UME School ROSE ProgrammeIUSS Pavia PhD candidate IUSS Pavia Professor

The last decade or so has seen the development of refined performance-based earthquake engineering(PBEE) approaches that now provide a framework for estimation of a range of important decision variables,such as repair costs,repair time and number of casualties. This paper reviews current tools for PBEE,including the PACT software,and examines the possibility of extending the innovative displacement-based assessment approach as a simplified structural analysis option for performance assessment. Details of the displacement-based s+eismic assessment method are reviewed and a simple means of quickly assessing multiple hazard levels is proposed. Furthermore,proposals for a simple definition of collapse fragility and relations between equivalent single-degree-of-freedom characteristics and multi-degree-of-freedom story drift and floor acceleration demands are discussed,highlighting needs for future research. To illustrate the potential of the methodology,performance measures obtained from the simplified method are compared with those computed using the results of incremental dynamic analyses within the PEER performance-based earthquake engineering framework,applied to a benchmark building. The comparison illustrates that the simplified method could be a very effective conceptual seismic design tool. The advantages and disadvantages of the simplified approach are discussed and potential implications of advanced seismic performance assessments for conceptual seismic design are highlighted through examination of different case study scenarios including different structural configurations.

关键词： performance-based earthquake engineering displacement-based assessment seismic assessment

Assessing the Effectiveness of Strategies in US Birth Cohort Screening for Hepatitis C Infection

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journal of Clinical and Translational Hepatology 2020年第1期8卷 25-41页

作者： Cynthia j.Tsay joseph K.Lim Department of Internal Medicine Yale University School of MedicineNew HavenCTUSA Yale Liver Center Section of Digestive DiseasesYale University School of MedicineNew HavenCTUSA

Chronic hepatitis C infection in the USA is a highly morbid condition and current guidelines recommend one-time screening among the birth cohort(1945-1965).Understand-ing strategies to optimize screening can help inform future hepatitis C virus(HCV)screening guidelines.A focused literature search was performed using PubMed and manual abstract review from major hepatology conferences over the past 2 *** search strategy involved using Medical Subject Headings terms for hepatitis C,screening,birth cohort,baby boomers,and *** review was limited to data from the USA.A total of 327 articles were identified and 36 abstracts were included,with studies published between *** including clinician education,electronic medical record alerts,reflex HCV RNA testing,point-of-care testing,multisite(outpatient,inpatient,emergency department,endoscopy suite)initiatives,direct patient solicitation,and utilization of non-physician providers have increased HCV screening ***,broad imple-mentation remains less than *** include lack of patient acceptance to screening and engagement in the HCV care *** Veterans Affairs Healthcare System has achieved higher birth cohort screening rates through an integrated approach requiring high-level engagement by leadership and institutional *** strategies for increasing birth cohort screening have been successful,but overall rates of HCV screening remain *** strat-egies can inform public health efforts to implement emerging national recommendations for expansion of HCV screening to all *** age 18 or older.

关键词： Hepatitis C Epidemiology HCV antibody Screening Birth cohort Baby boomers Care cascade Electronic medical records