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Self-Driving Algorithm and Location Estimation Method forSmall Environmental Monitoring Robot in Underground Mines

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Computer Modeling in Engineering & Sciences 2021年第6期127卷 943-964页

作者： Heonmoo Kim Yosoon choi Department of Energy Resources Engineering Pukyong National UniversityBusan48513Korea

In underground mine environments where various hazards exist,such as tunnel collapse,toxic gases,the application of autonomous robots can improve the stability of exploration and efficiently perform repetitive exploratory *** this study,we developed a small autonomous driving robot for unmanned environmental monitoring in underground *** developed autonomous driving robot controls the steering according to the distance to the tunnel wall measured using the light detection and ranging sensor mounted on the robot to estimate its location by simultaneously considering the measured values of the inertial measurement unit and encoder *** addition,the robot autonomously drives through the underground mine and performs environmental monitoring using the temperature/humidity,gas,and particle sensors mounted on the *** a result of testing the performance of the developed robot at an amethyst mine in Korea,the robot was found to be able to autonomously drive through tunnel sections with∼28 m length,∼2.5 m height,and∼3 m width *** average error of location estimation was approximately 0.16 *** environmental monitoring sensors,temperature of 15–17◦C,humidity of 42%–43%,oxygen concentration of 15.6%–15.7%,and particle concentration of 0.008–0.38 mg/m3 were measured in the experimental area,and no harmful gases were *** addition,an environmental monitoring map could be created using the measured values of the robot’s location coordinates and environmental factors recorded during autonomous driving.

关键词： Underground mine environmental monitoring autonomous driving geographic information system

An optimized framework for degree distribution in LT codes based on power law

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Journal of Central South University 2013年第10期20卷 2693-2699页

作者： Asim Muhammad choi GoangSeog Department of Information and Communication Engineering Chosun University

LT codes are practical realization of digital fountain codes, which provides the concept of rateless coding. In this scheme, encoded symbols are generated infinitely from k information symbols. Decoder uses only(1+α)k number of encoded symbols to recover the original information. The degree distribution function in the LT codes helps to generate a random graph also referred as tanner graph. The artifact of tanner graph is responsible for computational complexity and overhead in the LT codes. Intuitively, a well designed degree distribution can be used for an efficient implementation of LT codes. The degree distribution function is studied as a function of power law, and LT codes are classified into two different categories: SFLT and RLT codes. Also, two different degree distributions are proposed and analyzed for SFLT codes which guarantee optimal performance in terms of computational complexity and overhead.

关键词： fountain codes degree distribution overhead computational complexity power law

Iwasawa Theory of Quadratic Twists of X0（49）

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Acta Mathematica Sinica,English Series 2018年第1期34卷 19-28页

作者： Junhwa choi John COATES Department of Mathematics POSTECH Emmanuel College Cambridge University

The field K ---- Q（x/-AT） is the only imaginary quadratic field with class number 1, in which the prime 2 splits, and we fix one of the primes p of K lying above 2. The modular elliptic curve X0 （49） has complex multiplication by the maximal order O of K, and we let E be the twist of Xo （49） by the quadratic extension K（v/M）/K, where M is any square free element of O with M -- i mod 4 and （M, 7） = 1. In the present note, we use surprisingly simple algebraic arguments to prove a sharp estimate for the rank of the MordeII-Weil group modulo torsion of E over the field F∞=k（Ep∞ ）, where Epic denotes the group of p∞-division points on E. Moreover, writing B for the twist of X0（49） by K（C/ET）/K, our Iwasawa-theoretic arguments also show that the weak form of the conjecture of Birch and Swinnerton-Dyer implies the non-vanishing at s =1 of the complex L-series of B over every finite layer of the unique Z2-extension of K unramified outside p. We hope to give a proof of this last non-vanishing assertion in a subsequent paper.

关键词： Birch-Swinnerton-Dyer conjecture elliptic curves Iwasawa theory

Grade-4 commercially pure titanium with ultrahigh strength achieved by twinning-induced grain refinement through cryogenic deformation

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Journal of Materials Science & Technology 2021年第7期66卷 193-201页

作者： Seong-Woo choi Jae Sukjeong Jong Woo Won Jae Keun Hong Yoon Suk choi Titanium Department.Korea Institute of Materials Science Changwon51508Republic of Korea School of Materials Science and Engineering Pusan National UniversityPusan.46241Republic of Korea Materials and Manufacturing Development Team Doosan Heavy Industries and ConstructionChangwon51711Republic of Korea

The yield strength of commercially pure(CP) Ti of ASTM grade 4, the strongest among all the CP-Ti grades, is too low for structural applications that require high-strength materials. Here, we demonstrate the strengthening of grade-4 CP Ti by cryogenic-temperature rolling(CTR), which enables deformation twinning in grade-4 CP Ti to achieve twinning-induced grain refinement. CTR activated {11.22} twinning and {10.12} twinning, which are the most common twinning systems in pure Ti, whereas room-temperature rolling(RTR) did not activate any twinning system. CTR with imposing an area reduction of just 30% significantly increased the yield strength of the CP Ti to 946 MPa, which is not achievable through typical processes performed at or above room temperature and is comparable to that of commercial Ti-6 Al-4 V. The significant increase in strength was due to microstructural strengthening caused by twinning-induced grain refinement, combined with dislocation accumulation. In contrast to RTR, CTR greatly increased the stress concentration at grain boundaries(GBs), which caused the unusual activation of twinning in the grade-4 CP Ti by facilitating twin nucleation at GBs. The stress concentration increased because CTR activated the slip to a lesser extent compared to RTR, thereby reducing the strain compatibility between neighboring grains. These results will contribute to development of ultrahigh-strength CP Ti and may thereby extend its use to structural applications that require high-strength materials.

关键词： Titanium Twinning Cryogenic deformation Grain refinement Tensile properties

The geometry of the moduli space of one-dimensional sheaves

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Science China Mathematics 2015年第3期58卷 487-500页

作者： choi Jinwon CHUNG Kiryong School of Mathematics Korea Institute for Advanced Study

Let Md be the moduli space of stable sheaves on P2with Hilbert polynomial dm+*** this paper,we determine the effective and the nef cone of the space Md by natural geometric *** idea is to use the wall-crossing on the space of Bridgeland stability conditions and to compute the intersection numbers of divisors with curves by using the Grothendieck-Riemann-Roch *** also present the stable base locus decomposition of the space *** a byproduct,we obtain the Betti numbers of the moduli spaces,which confirm the prediction in physics.

关键词： effective cone nef cone birational morphism determinant line bundle Bridgeland wall-crossing

Effect of Artemisia species on cellular proliferation and apoptosis in human breast cancer cells via estrogen receptor-related pathway

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Journal of Traditional Chinese Medicine 2013年第5期33卷 658-663页

作者： Eunjeong choi Gunhee Kim Plant Resources Research Institute Duksung Women's University

OBJECTIVE:To investigate the mechanism underlying the anticancer effect of Artemisia species through the inhibition of cell growth and induction of apoptosis in breast carcinoma ***:To evaluate the anticancer activity of methanol extracts of eight Artemisia species(Artemisia stolonifera,Artemisia selengensis,Artemisia japonica,Artemisia Montana,Artemisia capillaris,Artemisia sylvatica,Artemisia keiskeana,and Artemisia scoparia),we first investigated the proliferation of estrogen receptor(ER)-positive MCF-7breast carcinoma cells exposed to 5 or 200 g/mL for72 *** induction was assessed by an Annexin V binding assay in cells exposed to extracts at a high concentration(200 g/mL).To verify the mechanism of apoptosis,ER expression and its related signaling was investigated using an immunoblot assay under the same ***:MCF-7 cells showed the strongest antiproliferative response to the tested ***-er,a biphasic effect was observed:the extracts inhibited proliferation at high concentrations whereas they stimulated it at low *** expression was similarly modulated by the ***,all of the extracts induced apoptosis at a high concentration(200 g/mL).Compared to the control level,exposure to the extracts resulted in a remarkable increase in the shift of cell ***:The present study suggests that the tested Artemisia species exerted their anticancer effects through the induction of apoptosis via an ER-related pathway.

关键词： Artemisia Breast neoplasms Bcl-2gene Cyclin D1 Estrogen receptor

Study of Partial Coefficients for Design of Semicircular Breakwaters

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China Ocean Engineering 2010年第1期24卷 29-40页

作者：郄禄文 Byung Ho choi College of Civil Engineering Hebei University Department of Civil and Environmental Engineering Sungkyunkwan University300 Chunchun-dongJangan-GuSuwon

In the present study, the reliability design of semicircular breakwater is based on the verification of the rules defined by standard specifications, where partial coefficients are introduced to ensure safety. The reliability of the semicircular breakwaters has been analyzed by using the Hasofer-Lind method to determine the reliability index of structure that has correlated loads, utilizing the long-term observed wave data at a given place. The relation curve between reliability index and safety factor in the traditional design method, as well as the relationships between reliability index and partial coefficients, have been obtained. This paper proposes values of partial coefficients for the design expression of semicircular breakwaters in the cases of anti-sliding and anti-overturning.

关键词： partial coefftcient reliability index correlated variables semicircular breakwater

Laser-assisted deposition of Cu bumps for microelectronic packaging

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中国有色金属学会会刊：英文版 2012年第S3期22卷 683-687页

作者： Won-Seok choi Joohan KIM Department of Nano IT Fusion Program Seoul National University of Science and Technology Department of Mechanical and Automotive Engineering Seoul National University of Science and Technology

Cu bump was transferred using a focused laser pulse for microelectronic *** Nd:YAG laser pulse (maximum energy of 500 mJ;wavelength of 1064 nm;fluences of 0.4-2.1 kJ/cm2) was irradiated on a sacrificial absorption layer with copper *** focused laser beam induced plasma between the semi-transparent donor slide and the sacrificial layer,causing a shock *** shock wave pressure pushed the Cu layer and transferred material to deposit a bump on substrate.A beam-shaper was used to produce uniform pressure at the interface to reduce fragmentation of the transferred material on the *** calculated shock wave pressure with respect to laser fluence was 1-3 GPa.A Cu bump of diameter of 200 μm was successfully deposited at laser fluence of 0.6 kJ/cm *** pressure control at the sacrificial layer using a laser pulse was critical to produce a bump with less *** technique can be applied to forming Cu bump for an interconnecting process in electronics.

关键词： laser induced forward transfer bump deposition Nd:YAG pulsed laser micro system packaging beam shaping

Investigation of ZrO2 nanoparticles concentration and processing time effect on the localized PEO coatings formed on AZ91 alloy

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Journal of Magnesium and Alloys 2019年第4期7卷 555-565页

作者： Zeeshan Ur Rehman Dongjin choi School of Materials Science and Engineering Hongik UniversitySejongRepublic of Korea

AZ91 Mg alloy was treated through a new localized PEO(Plasma Electrolytic Oxidation)coating approach,using electrolyte solutions with varying ZrO2 nanoparticles concentration(2-8 g/L)and processing *** increase in the ZrO2 concentration,several microstructural changes were observed including;formation of cluster-type structure,damage to the inner layers(∼30 min)and sealing of *** analysis of the final coatings was carried out using potentiodynamic polarization,electrochemical impedance spectroscopy and post-corrosion *** was explored that highest corrosion resistance(Rp∼81.17 kΩcm^2)of the coatings was obtained for ZrO2∼2 g/***,higher concentration of the ZrO2 nanoparticles caused weak crystalline coating structure,due to unstable and lower intensity discharges,thus failed to offer high corrosion resistance performance.

关键词： Magnesium alloy PEO coating ZrO2 Corrosion Nanoparticles addition