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A unified formulation of optimal guidance-to-collision law for accelerating and decelerating targets

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Chinese Journal of Aeronautics 2022年第7期35卷 40-54页

作者： Young-Won KIM Boseok KIM Chang-hun lee Shaoming HE Department of Aerospace Engineering Korea Advanced Institute of Science and TechnologyDaejeon 34141Republic of Korea School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

This paper provides a unified formulation of optimal guidance-to-collision law for a target with an arbitrary acceleration or *** collision course for general target acceleration or deceleration is first determined from the engagement geometry in conjunction with the nonlinear engagement kinematics in the proposed *** heading error defined in the collision course is then adopted as a variable to be nullified for accomplishing the intercept *** proposed guidance law is derived based on the heading error dynamics and the optimal error dynamics to ensure optimality and finite-time *** illustrative examples,the proposed guidance command for a constant target acceleration and a target deceleration in the form of a quadratic function of speed are ***,the time-to-go prediction method is suggested for implementing the proposed *** characteristics of the proposed guidance command are analytically investigated to provide insight into the proposed *** key benefits of the proposed method lie in not producing unnecessary guidance commands near a target compared to other methods and ensuring optimality in guidance command even in the nonlinear engagement ***,numerical simulations are performed to validate the proposed method and to show our findings.

关键词： Guidance-to-collision law Optimal guidance Optimal error dynamics Target acceleration or deceleration Unified formulation

Controlling a lithium surface with an alkyl halide nucleophile exchange

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Journal of Energy Chemistry 2021年第11期30卷 617-626,I0015页

作者： Jung-hun lee Thuy Hoai Linh Vuong Soo Min Hwang Jae-hun Kim Young-Jun Kim SKKU Advanced Institute of Nanotechnology(SAINT) Sungkyunkwan UniversitySuwon 16419Republic of Korea Department of Nano Engineering Sungkyunkwan UniversitySuwon 16419Republic of Korea School of Materials Science and Engineering Kookmin UniversitySeoul 02707Republic of Korea

Despite its high theoretical energy density, lithium metal faces huge challenges in its implementation as an anode for Li secondary batteries because of its uncontrollable dendritic growth and large volume change during plating/stripping processes. These geometric changes cause degradation in a cell’s cycle life and performance and can lead to short-circuits and explosions. Here, we report a new approach to producing a LiF-rich phase on the lithium anode surface by employing a “bi-phase” separator. We fabricated it by coating polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) onto a cellulose separator. The coverage of coating was adjusted by varying its concentration in the coating solution. The combination of cellulose and PVDF-HFP produced a LiF-rich solid-electrolyte interphase layer on the Li metal surface via an alkyl halide nucleophile exchange in contact with the bi-phase separator during plating. Symmetric cell tests show that the bi-phase separator extends the cycle life by more than 300 h, with overpotentials of less than 100 mV under plating/stripping at 2 mA cm^(−2) for a capacity of 2 mAh cm^(−2). The formation mechanism of the LiF-rich phase is suggested from spectroscopic analyses.

关键词： Li metal anode PVDF-HFP Cellulose LiF Phase inversion

Optimal three-dimensional impact time guidance with seeker’s field-of-view constraint

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Chinese Journal of Aeronautics 2021年第2期34卷 240-251页

作者： Shaoming HE Chang-hun lee Hyo-Sang SHIN Antonios TSOURDOS School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Department of Aerospace Engineering Korea Advanced Institute of Science and TechnologyDaejeon 34141Republic of Korea School of Aerospace Transport and ManufacturingCranfield UniversityCranfiehMK43 OALUnited Kingdom

This paper proposes a new three-dimensional optimal guidance law for impact time control with seeker’s Field-of-View(FOV) constraint to intercept a stationary target. The proposed guidance law is devised in conjunction with the concept of biased Proportional Navigation Guidance(PNG). The guidance law developed leverages a nonlinear function to ensure the boundedness of velocity lead angle to cater to the seeker’s FOV limit. It is proven that the impact time error is nullified in a finite-time under the proposed method. Additionally, the optimality of the biased command is theoretically analyzed. Numerical simulations confirm the superiority of the proposed method and validate the analytic findings.

关键词： Applied optimal control Field-of-view constraint Impact time control Missile guidance Optimal error dynamics

Stability for Leipholz’s Type of Laminated Box Columns with Nonsymmetric Lay-Ups on Elastic Foundation

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Advances in Applied Mathematics and Mechanics 2015年第2期7卷 158-179页

作者： nam-Il Kim Jaehong lee Department of Architectural Engineering Sejong University98 Kunja DongKwangjin KuSeoul 143-747Korea

The stability behavior of the Leipholz’s type of laminated box columns with nonsymmetric lay-ups resting on elastic foundation is investigated using theﬁnite el-ement *** on the kinematic assumptions consistent with the Vlasov beam theory,a formal engineering approach of the mechanics of the laminated box column-s with symmetric and nonsymmetric lay-ups is *** extended Hamilton’s principle is employed to obtain the elastic stiffness and mass matrices,the Rayleigh damping and elastic foundation matrices,the geometric stiffness matrix due to dis-tributed axial force,and the load correction stiffness matrix accounting for the uni-formly distributed nonconservative *** evaluation procedures for the critical values of divergence andﬂutter loads with/without internal and external damping ef-fects are brieﬂy *** examples are carried out to validate the present theory with respect to the previously published ***,the inﬂuences of theﬁber angle change and damping on the divergence andﬂutter loads of the laminated box columns are parametrically investigated.

关键词： Leipholz column laminate stability divergence ﬂutter ﬁnite element analysis

Methane Emission from Rice Fields:Necessity for Molecular Approach for Mitigation

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Rice science 2024年第2期31卷 159-178页

作者： Sujeevan RAJENDRAN Hyeonseo PARK Jiyoung KIM Soon Ju PARK Dongjin SHIN Jong-Hee lee Young hun SONG nam-Chon PAEK Chul Min KIM Department of Horticulture Industry Wonkwang UniversityIksan 54538Korea Plant Molecular Biology and Biotechnology Research Center Gyeongsang National UniversityJinju 52828Korea Department of Southern Area Crop Science National Institute of Crop ScienceMiryang 50424Korea Department of Agricultural Biotechnology Seoul National UniversitySeoul 08826Korea Department of Plant Science Plant Genomics and Breeding InstituteResearch Institute of Agriculture and Life SciencesSeoul National UniversitySeoul 08826Korea

Anthropogenic methane emissions are a leading cause of the increase in global averagetemperatures,often referred to as global *** soils play a significant role in methaneproduction,where the anaerobic conditions promote the production of methane by *** fields contribute a considerable portion of agricultural methane emissions,as riceplants provide both factors that enhance and limit methane *** plants harbor both methaneproducingand methane-oxidizing *** from rice roots provide source for methaneproduction,while oxygen delivered from the root aerenchyma enhances methane *** haveshown that the diversity of these microorganisms depends on rice cultivars with some genes characterizedas harboring specific groups of microorganisms related to methane ***,there is still aneed for research to determine the balance between methane production and oxidation,as rice plantspossess the ability to regulate net methane *** agronomical practices,such as fertilizerand water management,have been employed to mitigate methane ***,studiescorrelating agronomic and chemical management of methane with productivity are ***,evidences for breeding low-methane-emitting rice varieties are scattered largely due to the absence ofcoordinated breeding *** has indicated that phenotypic characteristics,such as rootbiomass,shoot architecture,and aerenchyma,are highly correlated with methane *** reviewdiscusses available studies that involve the correlation between plant characteristics and *** emphasizes the necessity and importance of breeding low-methane-emitting rice varieties inaddition to existing agronomic,biological,and chemical *** review also delves into the idealphenotypic and physiological characteristics of low-methane-emitting rice and potential breeding techniques,drawing from studies conducted

关键词： methane emission rice breeding aerenchyma greenhouse gas radial oxygen loss

Hybrid windshield-glass heater for commercial vehicles fabricated via enhanced electrostatic interactions among a substrate, silver nanowires, and an over-coating layer

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Nano Research 2015年第6期8卷 1882-1892页

作者： Sae Mi lee Ji hun lee Sora Bak Keunsik lee Yang Li Hyoyoung lee 2066 Seoburo Jangan-gu Center for Smart Molecular Memory Department of Chemistry Sungkyunkwan University Suwon 440-746 Republic of Korea 2066 Seoburo Jangan-gu Center for Smart Molecular Memory Department of Energy Science Sungkyunkwan University Suwon 440-746 Republic of Korea 2066 Seoburo Jangan-gu Center for Smart Molecular Memory SKKU Advanced Institute of Nano Technology (SAINT) Sungkyunkwan University Suwon 440-746 Republic of Korea

We introduce a transparent windshield-glass heater produced via transparent electrodes using silver nanowire （AgNW） networks for conventional use in the automobile industry. A high-quality conducting hybrid film is deposited on a plasma-treated glass substrate by spraying AgNWs, immersing the sprayed product in positively charged adhesive polymer solution, and then spraying negatively charged graphene oxide （GO） and a silane layer as an over-coating layer （OCL）.The results of heating tests conducted after adhesion tests show that the sheet resistance changes with the application of polymer glue. Surprisingly, the transmittance of the film with the GO OCL is higher than that of the film without the GO OCL. Heating and defrosting tests are carefully conducted via infrared （IR） monitoring. Adhesive-polymer-treated and GO-protected AgNW transparent glass heaters exhibit the best performance with low sheet resistance; thus, through strong electrostatic interaction among the substrate, adhesive layer, and OCL, our AgNW hybrid glass heater can reach the target temperature with a standard vehicle voltage of 12 V in a short period of time.

关键词： transparentwindshield-glass heater silver nanowires heating glass adhesive polymers material science

Acheivement of Nano-Scale SiGe Layer with Discrete Ge Mole Fraction Profile Using Batch-Type HVCVD

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Journal of Rare Earths 2004年第Z2期22卷 178-182页

作者： Gon-sub lee Tae-hun Shim Jea-gun Park Advanced Semiconductor Material and Device Development Center Hanyang UniversitySeoul 133-791Korea Advanced Semiconductor Material and Device Development CenterHanyang UniversitySeoul 133-791Korea Advanced Semiconductor Material and Device Development CenterHanyang UniversitySeoul 133-791Korea

The strained Si grown on the relaxed SiGe-on-insulator C-MOSFET's is a promising device for the future system LSI devices with the design rule of sub-micron. The achievement of the discrete Ge mole fraction in the SiGe layer is a key engineering in low-temperature SiGe epitaxial growth using HVCVD. The pre-flow of GeH4 gas enhanced the Ge mole fraction and SiGe layer thickness. In addition, the Ge mole fraction and SiGe layer thickness increases with the gas ratio of GeH4/SiH4 + GeH4, process temperature, and gas flow time. However, the haze was produced if the Ge mole fraction is above 22wt%. The discrete-like Ge mole fraction with 22 wt% in 10 nm SiGe layer was obtained by the pre-flow of GeH4 for 10 s, the mixture gas ratio of GeH4/SiH4 + GeH4 of 67%, and the gas flow time for 150 s at the process temperature of 550 C.

关键词： strained Si nano scale SiGe layer Ge mole fraction HVCVD gas flow boat-out time

Dragging 3D printing technique controls pore sizes of tissue engineered blood vessels to induce spontaneous cellular assembly

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Bioactive Materials 2024年第1期31卷 590-602页

作者： hun-Jin Jeong Hyoryung nam Jae-Seok Kim Sungkeon Cho Hyun-Ha Park Young-Sam Cho Hyungkook Jeon Jinah Jang Seung-Jae lee Department of Mechanical Engineering Wonkwang University54538IksanRepublic of Korea Department of Convergence IT Engineering Pohang University of Science and Technology37673PohangGyeongbukRepublic of Korea Department of Mechanical and Design Engineering Wonkwang University54538IksanRepublic of Korea Department of Mechanical Engineering Pohang University of Science and Technology37673PohangGyeongbukRepublic of Korea School of Interdisciplinary Bioscience and Bioengineering Pohang University of Science and Technology37673PohangGyeongbukRepublic of Korea Institute of Convergence Science Yonsei University03722SeoulRepublic of Korea Regenerative Engineering Laboratory Columbia University630W 168th STNew York10032USA Department of Manufacturing Systems and Design Engineering Seoul National University of Science and Technology01811SeoulRepublic of Korea

To date,several off-the-shelf products such as artificial blood vessel grafts have been reported and clinically tested for small diameter vessel(SDV)***,conventional artificial blood vessel grafts lack endothelium and,thus,are not ideal for SDV transplantation as they can cause *** addition,a suc-cessful artificial blood vessel graft for SDV must have sufficient mechanical properties to withstand various external ***,we developed a spontaneous cellular assembly SDV(S-SDV)that develops without additional *** improving the dragging 3D printing technique,SDV constructs with free-form,multilayers and controllable pore size can be fabricated at ***,The S-SDV filled in the natural poly-mer bioink containing human umbilical vein endothelial cells(HUVECs)and human aorta smooth muscle cells(HAoSMCs).The endothelium can be induced by migration and self-assembly of endothelial cells through pores of the SDV *** antiplatelet adhesion of the formed endothelium on the luminal surface was also *** addition,this S-SDV had sufficient mechanical properties(burst pressure,suture retention,leakage test)for *** believe that the S-SDV could address the challenges of conventional SDVs:notably,endothelial formation and mechanical *** particular,the S-SDV can be designed simply as a free-form structure with a desired pore *** endothelial formation through the pore is easy even in free-form con-structs,it is expected to be useful for endothelial formation in vascular structures with branch or curve shapes,and in other tubular tissues such as the esophagus.

关键词： Small diameter vessel Dragging 3D printing Pore control Spontaneous cellular assembly

Graphene-based saturable absorber and mode-locked laser behaviors under gamma-ray radiation

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Photonics Research 2019年第7期7卷 57-62页

作者： Dohyun Kim nam hun Park Hyunju lee Jaegoan lee Dong-Il Yeom Jungwon Kim School of Mechanical and Aerospace Engineering Korea Advanced Institute of Science and Technology (KAIST)Daejeon 34141South Korea Department of Energy Systems Research & Department of Physics Ajou UniversitySuwon 16499South Korea

We investigate optical and electrical behaviors of a graphene saturable absorber (SA) and mode-locking performance of a graphene-SA-based mode-locked Er fiber laser in gamma-ray radiation. When irradiated up to 4.8 kGy at ~ 100 Gy/hr dose rate, the overall nonlinear transmittance in transverse electric mode was increased, while maintaining modulation depth to >10%. The corresponding *** loss was reduced at a 1.2-dB/kGy rate. In the electrical properties, the charge carrier mobility was reduced, and the Dirac voltage shift was increased to positive under gamma-ray radiation. The radiation-induced optical and electrical changes turned out to be almost recovered after a few days. In addition, we confirmed that the graphene-SA-based laser showed stable CW mode-locking operation while the inserted graphene SA was irradiated for 2-kGy at a 45-Gy/hr dose rate, which corresponds to >40 years of operation in low Earth orbit *** the best of our knowledge, this is the first evaluation of graphene SAs and graphene-SA-based mode-locked lasers in gamma-ray radiation, and the measured results confirm the high potential of graphene SAs and graphene-SA-based lasers in various outer-space environments as well as other radiation environments, including particle accelerators and radiationbased medical instruments.

关键词： absorber modelocked laser accelerators