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Adaptive Tracking Controller Design for Welding Mobile Manipulator with Unknown Parameters
Sang-Bong Kim,Tan-Tung Phan,Nak-Soon Choi,Hak-Kyeong Kim 한국해양공학회 2009 韓國海洋工學會誌 Vol.23 No.2
This paper presents an adaptive tracking control method for a welding mobile manipulator with several unknown parameters such as the last length of the manipulator, the wheel radius and the distance from the center to the wheel. The mobile manipulator consisted of the manipulator and the mobile-platform. Kinematic modelings for the manipulator and the mobile-platform with several unknown parameters were produced. The tracking error vectors for the manipulator and the mobile-platform were defined. These adaptive controllers were designed based on the Lyapunov function to guarantee the stability of the whole system when the mobile manipulator performs a welding task. Update laws were also designed to estimate the unknown dimensional parameters. To implement the designed controllers, a control system integrated with PIC16F877 microporcessors and a TMS320C32 DSP was developed. Simulation and experimental results are presented to show the effectiveness of the proposed controller.
The Impact of Freight Forwarder Service Failure Factors on Service Recovery Effort
Nak-hyun Kim(김낙현),Myung-shin Ha(하명신),Sung-kwang Choi(최성광) 한국국제상학회 2018 國際商學 Vol.33 No.3
Ⅰ. 서론 Ⅱ. 선행연구 Ⅲ. 연구모형 및 연구가설 Ⅳ. 실증분석 Ⅴ. 결론 참고문헌 복합운송주선인과 화주의 관계에서 발생하는 다양한 서비스 실패 요인을 파악하고, 서비스 실패 요인이 서비스 회복노력에 어떠한 영향을 미치는가를 규명하는데 그 목적을 두고 있다. 이를 통해 복합운송주선인의 서비스 실패에 따른 회복을 위해 화주의 부정적인 반응을 효과적으로 처리해 줄 수 있는 서비스 회복전략을 체계화하고, 화주와의 관계성 강화 및 신규고객 창출을 위한 실무적 시사점을 제공할 수 있을 것이다. 본 연구의 결과를 구체적으로 살펴보면 첫째, 인적 요인에 의한 서비스 실패, 규정적 요인에 의한 서비스 실패, 기본적 요인에 의한 서비스 실패가 발생한 경우 심리적 회복노력이 효과적인 것으로 나타났으며, 둘째, 인적 요인에 의한 서비스 실패, 기본적 요인에 의한 서비스 실패, 환경적 요인에 의한 서비스 실패가 발생한 경우에는 물질적 회복노력이 효과적인 것으로 나타났다. 물류서비스 제공 기업은 서비스 실패에 대해 즉각적인 인정, 피해에 대한 공감, 사과, 회복할 수 있다는 믿음 제공 등의 심리적 회복노력이나, 서비스의 재제공, 보상, 비용 할인, 부가 서비스 제공 등과 같은 물질적 보상이 제공되어야만 화주기업의 실망이나 불만족이 회복될 수 있으며, 적절한 회복노력은 불만족의 회복을 넘어 서비스 재이용율을 높이는 데도 기여할 수 있다.
First Report of Powdery Mildew Caused by Erysiphe cruciferarum on Arabidopsis thaliana in Korea
Choi, Hyong-Woo,Choi, Young-Jun,Kim, Dae-Sung,Hwang, In-Sun,Choi, Du-Seok,Kim, Nak-Hyun,Lee, Dong-Hyuk,Shin, Hyeon-Dong,Nam, Jae-Sung,Hwang, Byung-Kook The Korean Society of Plant Pathology 2009 Plant Pathology Journal Vol.25 No.1
In November 2008, typical powdery mildew symptoms were observed on leaves of Arabidopsis thaliana ecotype Col-0 plants in a growth room under controlled laboratory conditions at Korea University, Seoul. The disease was characterized by the appearance of white powder-like fungal growth on the surface of infected leaves. As the disease progressed, infected leaves exhibited chlorotic or necrotic brown lesions, and leaf distortion and senescence. Conidiophores of the causal fungus were hyaline, unbranched, 3-4 celled, cylindrical, and $80-115{\times}6-9{\mu}m$ in size. Singly produced conidia (pseudoidium type) were hyaline, oblong to cylindrical or oval in shape, and $26-55{\times}15-20{\mu}m$ in size with a length/width ratio of average 3, angular/rectangular wrinkling of outer wall and no distinct fibrosin bodies. Appressoria on the hyphae were multi-lobed. These structures are typical of the powdery mildew Oidium subgenus Pseudoidium, anamorph of the genus Erysiphe. The measurements of the fungal structures coincided with those of Erysiphe cruciferarum. The phylogenetic analysis using ITS rDNA sequences revealed that the causal fungus Erysiphe sp. KUS-F23994 is identical to E. cruciferarum. The isolated fungus incited powdery mildew symptoms on the inoculated Arabidopsis leaves, which proved Koch's postulates. Taken all data together, we first report the occurrence of powdery mildew disease of A. thaliana caused by Erysiphe cruciferarum in Korea.
Optimization of Material Properties for Coherent Behavior across Multi-resolution Cloth Models
( Nak-jun Sung ),( Shane Transue ),( Minsang Kim ),( Yoo-joo Choi ),( Min-hyung Choi ),( Min Hong ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.8
This paper introduces a scheme for optimizing the material properties of mass-spring systems of different resolutions to provide coherent behavior for reduced level-of-detail in MSS(Mass-Spring System) meshes. The global optimal material coefficients are derived to match the behavior of provided reference mesh. The proposed method also gives us insight into levels of reduction that we can achieve in the systematic behavioral coherency among the different resolution of MSS meshes. We obtain visually acceptable coherent behaviors for cloth models based on our proposed error metric and identify that this method can significantly reduce the resolution levels of simulated objects. In addition, we have confirmed coherent behaviors with different resolutions through various experimental validation tests. We analyzed spring force estimations through triangular Barycentric coordinates based from the reference MSS that uses a Gaussian kernel based distribution. Experimental results show that the displacement difference ratio of the node positions is less than 10% even if the number of nodes of MSS<sup>sim</sup> decreases by more than 50% compared with MSS<sup>ref</sup>. Therefore, we believe that it can be applied to various fields that are requiring the real-time simulation technology such as VR, AR, surgical simulation, mobile game, and numerous other application domains.
Nak-Sun Choi,Giwoo Jeung,Sang Sik Jung,Chang-Seob Yang,Hyun-Ju Chung,Dong-Hun Kim IEEE 2012 IEEE transactions on magnetics Vol.48 No.2
<P>This paper presents an efficient methodology for optimizing degaussing coil currents in ships to minimize the anomaly of underwater magnetic fields due to the hull magnetization induced under the Earth's magnetic field. To achieve this, first, the shielding effect of the hull on the underwater fields is thoroughly examined. Then, for a fast search of optimum degaussing currents, a sensitivity formula of an objective function with respect to the magnetomotive force is adopted. The feature of the proposed method is that it does not require any numerical field analyses to assess an objective function during optimization process providing experimental field data for each coil are given. The validity and effectiveness of the method has been tested with a model ship.</P>
Groundwater Flow Modeling in a Block-Scale Fractured Rocks considering the Fractured Zones
Nak-Youl Ko,Sung-Hoon Ji,Yong-Kwon Koh,Jon-Won Choi 한국방사성폐기물학회 2010 방사성폐기물학회지 Vol.8 No.2
핀란드 Okiluoto 섬 중앙부에 방사성폐기물 처분장으로 예정된 부지에서 블록 규모 지하수 유동 모의를 수행하였다. 현장에 설치된 심부 관측공에서 관찰된 단열대에 관한 자료를 이용하여 단열망을 구성하였다. 이 단열망을 이용하여 3차원 유한 요소 격자망의 수리전도도장를 생성하고, 이를 지하수 유동 모의에 이용하였다. 현장에서 이루어진 양수시험 전과 후에 심부 관측공에서 측정된 수위와 구간별 유입, 유출량을 이용하여 시추공과 교차하는 단열대의 투수량계수와 부지의 함양률을 조절하며 지하수 유동 모형을 보정하였다. 양수 시험 전과 후를 순차적으로 보정해가며 모의한 결과, 보정된 지하수 유동 모형으로 계산한 지하수위는 관측 자료와 비교적 일치하지만, 관측공에서의 지하수 유입, 유출량은 상당한 차이를 보이는 구간도 있는 것으로 확인되었다. 이런 불일치는 지하수 유동로가 될 수 있는 구조가 지하수 유동 모의를 위한 개념모형에 충분히 반영되지 않아 생기는 것으로 생각되며, 이에 배경단열과 같은 국지적인 유동로 구조가 개념모형에 반영되어야 할 것으로 판단되었다.
Effect of Gamma Irradiation on the Structural and Physiological Properties of Silk Fibroin
Nak-Yun Sung,Eui-Baek Byun,Sun-Kyu Kwon,Jae-Hun Kim,Beom-Seok Song,Jong-il Choi,Jin-Kyu Kim,Yohan Yoon,Myung-Woo Byun,Mee-Ree Kim,Hong-Sun Yook,Ju-Woon Lee 한국식품과학회 2009 Food Science and Biotechnology Vol.18 No.1
This study was conducted to examine the changes in the molecular structure and physiological activities of silk fibroin by gamma irradiation. The results of gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the molecular weight of fibroin was increased depending upon the irradiation dose. Secondary structure of fibroin determined by using circular dichroism revealed that the ratio of α-helix was increased up to 10 kGy and then decreased depending upon the irradiation dose. Whereas, the ratio of β-sheet, β-turn, and random coil were decreased and then increased with an alteration in the α-helix secondary conformation. The 2.2-diphenyl-1-picryl-hydrazil (DPPH) radical scavenging activity of fibroin was increased by gamma irradiation at 5 kGy, but was decreased above 10 kGy depending upon the irradiation dose. Also, the inhibition activities of tyrosinase and melanin synthesis of fibroin were increased by gamma irradiation. These results indicated that gamma irradiation could be used as an efficient method to make fibroin more suitable for the development of functional foods and cosmetics.