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A Finite Difference Scheme for Blow-Up Solutions of Nonlinear Wave Equations

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Numerical Mathematics(Theory,Methods and Applications) 2010年第4期3卷 475-498页

作者： Chien-Hong cho Research Institute for Mathematical Sciences Kyoto UniversityKyoto 606-8502Japan Department of Mathematics National Chung Cheng UniversityMin-HsiungChia-Yi 621Taiwan

We consider a finite difference scheme for a nonlinear wave equation, whose solutions may lose their smoothness in finite time, i.e., blow up in finite time. In order to numerically reproduce blow-up solutions, we propose a rule for a time-stepping,which is a variant of what was successfully used in the case of nonlinear parabolic equations. A numerical blow-up time is defined and is proved to converge, under a certain hypothesis, to the real blow-up time as the grid size tends to zero.

关键词： Finite difference method nonlinear wave equation blow-up

Mechanical behavior and properties of fiber reinforced ceramic matrix composites for high temperature use

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航空动力学报 2007年第4期22卷 594-601页

作者： chongdu cho Qiang Pan Sangkyo Lee Department of Mechanical Engineering Inha University Mechanical Engineering Graduate School Inha University

Ceramics can keep their mechanical characteristics up to 2 000℃ or *** this paper,A model to predict ultimate strength of continuous fiber-reinforced brittle matrix composites is developed.A statistical theory for the strength of a uni-axially fiber-reinforced brittle matrix composite is *** a semi-empirical frictional heating method for estimating in-situ interfacial shear in fiber-reinforced ceramic matrix composites was *** uneven fiber packing variation as well as uneven micro-damage during fatigue can be expected to have effects on the composites:generation of frictional heating,thermal gradients,and residual stresses around local fiber *** study examined those engineering interests by the finite element method.

关键词：高温纤维增强型陶瓷基复合材料机械性能有限元航空推进系统

Electrochemical Characteristics in Seawater for Cold Thermal Spray-Coated Al-Mg Alloy Layer

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Acta Metallurgica Sinica(English Letters) 2016年第8期29卷 727-734页

作者： Il-cho Park Seong-Jong Kim Division of Marine Engineering Mokpo National Maritime University

For corrosion protection of carbon steel in a marine environment,cold arc thermal spray coating was applied to the surface with Al and Al-Mg alloy *** surface hardness of Al and Al-Mg thermal spray coatings increased with Mg *** the various electrochemical experiments were carried out to evaluate corrosion damage characteristics of the thermal spray coating *** Al and Al-Mg thermal spray coating layers presented negative potentials compared to carbon steel in corrosion potential *** an anodic polarization experiment revealed a tendency of activation polarization with no ***,the corrosion damage of the thermal spray coating layer in galvanostatic experiment was observed mainly at the defect area,and the Al-3Mg thermal spray coating layer presented less surface damages than *** addition,the Al-3Mg thermal spray coating layer showed the lowest corrosion rate while having a sufficient driving voltage for cathodic corrosion ***,it is an optimal thermal spray material for sacrificial anode.

关键词： Corrosion protection Carbon steel Arc thermal spray coating Al-Mg alloy Marine environment

Importance of nutrient availability for soluble microbial products formation during a famine period of activated sludge:Evidence from multiple analyses

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Journal of Environmental Sciences 2019年第10期31卷 112-121页

作者： Tahir Maqbool Jinwoo cho Jin Hur Department of Environment and Energy Sejong University

Much remains unknown about compositional variations in soluble microbial products(SMP)with the shift of the substrate condition from a feast to a famine phase in biological treatment *** study demonstrated that the formation of SMP could be suppressed by up to 75%during the famine phase with the addition of essential *** contrast,presence of electron acceptor did not play any significant role during the stress condition,showing the similar amounts of SMP(r=0.98,p0.95).The fluorescence excitation-emission matrix coupled with parallel factor analysis(EEM-PARAFAC)revealed the presence of four different fluorescent components,including two protein-like(C1 and C4),fulvic-like(C2),and humic-like(C3)components,in the SMP and bEPS formed at different *** C1 and C4 showed increasing trends(R^2>0.95)with the length of starvation in the bioreactors without essential *** availability was found to be a key factor to quench the production of large-sized *** study provides a wealth of information on operation conditions of activated sludge treatment systems to minimize large sized SMP molecules(particularly proteins),which typically exert many environmental concerns to effluent organic matter quality.

关键词： Soluble microbial products Nutrient availability EEM-PARAFAC SEC-OCD-OND Famine phase

Strong internal resonance in a nonlinear, asymmetric microbeam resonator

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Microsystems & Nanoengineering 2021年第1期7卷 117-131页

作者： Keivan Asadi Junghoon Yeom Hanna cho Department of Mechanical and Aerospace Engineering The Ohio State UniversityColumbusOH 43210USA Department of Mechanical Engineering Michigan State UniversityEast LansingMI 48824USA

Exploiting nonlinear characteristics in micro/nanosystems has been a subject of increasing interest in the last *** others,vigorous intermodal coupling through internal resonance(IR)has drawn much attention because it can suggest new strategies to steer energy within a micro/nanomechanical ***,a challenge in utilizing IR in practical applications is imposing the required frequency commensurability between vibrational modes of a nonlinear micro/***,we experimentally and analytically investigate the 1:2 and 2:1 IR in a clamped–clamped beam resonator to provide insights into the detailed mechanism of *** is demonstrated that the intermodal coupling between the second and third flexural modes in an asymmetric structure(e.g.,nonprismatic beam)provides an optimal condition to easily implement a strong IR with high energy transfer to the internally resonated *** this case,the quadratic coupling between these flexural modes,originating from the stretching effect,is the dominant nonlinear mechanism over other types of geometric *** design strategies proposed in this paper can be integrated into a typical micro/nanoelectromechanical system(M/NEMS)via a simple modification of the geometric parameters of resonators,and thus,we expect this study to stimulate further research and boost paradigm-shifting applications exploring the various benefits of IR in micro/nanosystems.

关键词： nonlinear asymmetric clamped

Aerial multi-spectral AI-based detection system for unexploded ordnance

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Defence Technology（防务技术） 2023年第9期27卷 24-37页

作者： Seungwan cho Jungmok Ma Oleg A.Yakimenko Republic of Korea Army Republic of Korea/Defense Acquisition Program Administration47Gwanmun-roGwacheon-siGyeonggi-do13809Republic of Korea Department of Defense Science Korea National Defense University1040Republic of Korea Hwangsanbul-ro Yangchon-myeonNonsan-siChungcheongnam-do33021Republic of Korea Department of Systems Engineering Naval Postgraduate SchoolUSA 1 University Circle MontereyCA93943USA

Unexploded ordnance(UXO)poses a threat to soldiers operating in mission areas,but current UXO detection systems do not necessarily provide the required safety and efficiency to protect soldiers from this *** technological advancements in artificial intelligence(AI)and small unmanned aerial systems(sUAS)present an opportunity to explore a novel concept for UXO *** new UXO detection system proposed in this study takes advantage of employing an AI-trained multi-spectral(MS)sensor on *** paper explores feasibility of AI-based UXO detection using sUAS equipped with a single(visible)spectrum(SS)or MS digital electro-optical(EO)***,it describes the design of the Deep Learning Convolutional Neural Network for UXO detection,the development of an AI-based algorithm for reliable UXO detection,and also provides a comparison of performance of the proposed system based on SS and MS sensor imagery.

关键词： Unexploded ordnance(UXO) Multispectral imaging Small unmanned aerial systems(sUAS) Object detection Deep learning convolutional neural network(DLCNN)

Nanomechanical Characterization of Bone Quality Depending on Tissue Age via Bimodal Atomic Force Microscopy

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Nanomanufacturing and Metrology 2023年第4期6卷 24-34页

作者： Jinha Kwon Hanna cho Department of Mechanical and Aerospace Engineering The Ohio State UniversityColumbusOH 43210USA

Characterization of bone quality during the healing process is crucial for successful implantation procedures and patient *** this study,a bone implant specimen that underwent a 4-week healing period was *** atomic force microscopy(AFM)was employed to simultaneously obtain the morphology and elastic modulus maps of the newly formed and pre-existing bone regions within the *** indicate that the new bone matrix possessed lower miner-alization levels and presented larger,uneven mineral grains,exhibiting the attributes of a woven *** the other hand,the old bone matrix exhibited a more uniform and mineralized structure,which is characteristic of lamellar *** new bone had a lower overall elastic modulus than the old *** AFM further confrmed that the new bone displayed three regions comprising unmineralized,partially mineralized,and fully matured sections,which indicate a turbulent change in its ***,the old bone exhibited two sections comprising partially mineralized and matured bone parts,which denote the fnal phase of *** study provides valuable insights into the morphological and nanome-chanical diferences between the old and new bone matrixes and presents a novel approach to investigate bone quality at diferent phases of the bone-healing process.

关键词： Bone quality Atomic force microscopy Bimodal AFM Nanomechanical characterization Bone tissue age Woven bone Lamellar bone

Ever-changing endoscopic treatment for early gastric cancer:Yesterday-today-tomorrow

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World Journal of Gastroenterology 2014年第37期20卷 13273-13283页

作者： Mi-Young Kim Jun-Hyung cho Joo Young cho Digestive Disease Center Soonchunhyang University Hospital

Endoscopic resection has been an optimal treatment for selected patients with early gastric cancer(EGC) based on advances in endoscopic instruments and techniques. As endoscopic submucosal dissection(ESD) has been widely used for treatment of EGC along with expanding ESD indication, concerns have been asked to achieve curative resection for EGC while guaranteeing precise prediction of lymph node metastasis(LNM). Recently, new techniques including ESD or endoscopic full-thickness resection combined with sentinel node navigation enable minimal tumor resection and a laparoscopic lymphadenectomy in cases of EGC with high risk of LNM. This review covers the development and challenges of endoscopic treatment for EGC. Moreover, a new microscopic imaging and endoscopic techniques for precise endoscopic diagnosis and minimally invasive treatment of EGC are introduced.

关键词： Endoscopic resection Early gastric cancer Confocal laser endomicroscopy Sentinel node navigation Hybrid natural orifice transluminal endoscopic surgery

Simple black holes with anisotropic fluid

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Chinese Physics C 2019年第2期43卷 125-131页

作者： Inyong cho Hyeong-Chan Kim School of Liberal Arts Seoul National University of Science and Technology School of Liberal Arts and Sciences Korea National University of Transportation

We study a spherically symmetric spacetime made of an anisotropic fluid whose radial equation-of-state is given by p_1=-ρ. This case allows analytic solutions and is a good example for studying the static configuration of a black hole plus matter. For a given equation-of-state parameter w_2 = p_2/ρ for angular directions, we find the exact solutions of the Einstein equation described by two parameters. We classify the solutions into six types based on the behavior of the metric function. Depending on the parameters, the solutions can have event and cosmological horizons. One of the solution types corresponds to a generalization of the Reissner-Nordstr(o|¨)m black hole, the thermodynamic properties for which are obtained in a simple form. The solutions are stable under radial perturbations.

关键词： black hole exact solution general relativity