Electrical Resistance Tomography의 영상복원 기법의 비교

김호찬,부창진,이윤준,Kim, Ho-Chan,Boo, Chang-Jin,Lee, Yoon-Joon 한국조명전기설비학회 2005 조명·전기설비학회논문지 Vol.19 No.3

Electrical resistance tomography(ERT)는 적절하게 설계된 전류를 대지 지하에 주입하여 이에 따른 인가전압을 대지 경계에서 측정한 후 이를 근거로 ERT의 영상복원 알고리즘에서 대지 지하의 대지저항률 분포를 얻고 대지 지하에 뭍힌 물체를 크기와 위치, 그리고 저항률에 대한 특성을 파악할 수 있는 기술이다. 본 논문에서는 ERT의 영상복원 기법으로 Gauss-Newton, TLS와 SIRT 방법들을 살펴본다. 컴퓨터 시뮬레이션을 통해 TLS 방법을 이용한 ERT 영상복원의 성능이 Gauss-Newton와 SIRT방법에 의해 얻어진 결과보다 향상되는 것을 보이도록 한다. Electrical resistance tomography(ERT) maps resistivity values of the soil subsurface and characterizes buried objects. The characterization includes location, size and resistivity of buried objects. In this paper, Gauss-Newton, truncated least squares(TLS) and simultaneous iterative reconstruction technique(SIRT) methods are presented for the solution of the ERT image reconstruction. Computer simulations show that the spatial resolution of the reconstructed images by the TLS approach is improved as compared to those obtained by the Gauss-Newton and SIRT method.

방사선 치료중인 암환자의 임상적 특징과 정신과 장애의 관련성

김호찬,문창우,박시성,Kim, Ho-Chan,Moon, Chang-Woo,Park, Si-Sung 한국정신신체의학회 1999 정신신체의학 Vol.7 No.1

연구목적 : 암환자에서는 암의 임상적 특성이나, 치료방법에 따라 다양한 심리적인 문제들이 발생한다. 특히 방사선 치료는 다른 방법의 치료를 받는 환자들에서 볼 수 없는 다른 심리적 반응을 보이는 경우가 많으며, 정서적 고통과 갈등이 가중될 수 있다. 이에 저자들은 방사선 치료중인 암환자들에게는 어떠한 정신과 장애가 발생하는지 알아보고, 정신과 질환이 암과 관련된 다양한 임상적 특성과 어떠한 연관성을 지니는지 알아보고자 본 연구를 시행하였다. 방법 : 방사선 치료를 위해 치료방사선과에 입원한 암환자 47명을 대상으로 하여. DSM-IV 진단기준에 따라 정신과 장애를 평가하고, 환자들의 인구학적 자료, 암의 부위, 이환기간, 재발횟수 등의 임상적 특성, 암환자의 암에 대한 인지여부, 치료결과에 대한 기대 등의 요인과 정신과 장애의 관련성을 살펴보았다. 결과 : 1) 21 명(44.7%)의 환자가 정신과 장애를 가지고 있었다. 적응장애가 14명(66.7%)으로 가장 많았고, 다음은 5명(23.8%)의 환자에서 동반된 주요 우울장애였다. 2) 성별, 연령, 학력, 결혼상태, 종교 등의 인구학적 변인과 정선과적 장애와의 관련성은 통계적 유의성을 보이지 않았다. 3) 암의 부위별로는 골반부에 위치하는 암이 22명(46.8%)으로 가장 많았으며, 암의 부위, 이환기간과 정신과 장애와의 유의한 관련성은 없었다. 4) 암의 재발에 있어 재발의 증거가 없는 경우에 비해 재발한 경우 통계적으로 유의하게 정신과 장애의 이환율이 높았다. 5) 암의 인지여부와 정신과 장애는 통계적으로 유의한 연관은 없었다. 6) 치료결과에 대한 기대와 관련하여, 방사선 치료가 단지 보조적인 것으로 생각하는 군이 방사선치료에 의해 완치될 것으로 생각하는 군에 비해 통계적으로 유의하게 정신과 장애의 이환율이 높았다. Objects : Cancer patients receiving radiotherapy have many psychological problems. Those problems depend on clinical factors of cancer and the characteristics of patients. This study was designed to estimate the morbidity of psychiatric disorder and to investigate the relationship between psychiatric disorders and clinical variables. Methods : The subjects were 47 patients who had been treated by radiotherapy. Psychiatric disorder was diagnosed according to DSM-IV. The authors assessed the relation between psychiatric disorder and demographic features, clinical features of cancer such as site, duration, frequency of recurrence of cancer, and patients' awareness of disease and expectation of outcome of radiotherapy. Results : 21 patients(44.7%) had a psychiatric disorder. The most common psychiatric disorder were adjustment disorder(66.7%), and the next major depressive disorder(23.8%). There was a significant positive relationship between psychiatric disorder and recurrence of cancer, patients' expectation of poor outcome after radiotherapy. Psychiatric morbidity was significantly low in those who had no evidence of recurrence and who considered radiation treatment as curative. However, site and duration of cancer, patients' awareness about serious illness were not related with psychiatric disorder. Conclusion : Psychiatric disorders are common among cancer patients on radiotherapy. Further clinical attention and effective treatment of psychiatric complication in cancer patients are needed not only for reducing symptoms but for better adjustment.

부품방향의 선정을 통한 광조형물의 후가공면적 최소화

김호찬,이석희,Kim, Ho-Chan,Lee, Seok-Hee 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11

The surfaces of prototypes become rough due to the stair-stepping which is the inevitable phenomenon in the Rapid Prototypes are not used only for the verification of feature. The grinding, coating, or the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. The solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. the solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the regions for post-processing. the factors to cause the surface roughness and their effects are analyzed through the experiments. Software modules are developed to predict the surface roughness of each face in the prototyping with the result. An experimental compensation method is developed to apply the modules to various RP equipments, materials and build styles. The build direction is searched with use of genetic algorithm to maximize the total areas of the surface of which roughness is better than the user-defined value.

시뮬레이티드 어닐링을 이용한 전기임픽던스단층촬영법의 영상복원

김호찬,부창진,이윤준,Kim Ho-Chan,Boo Chang-Jin,Lee Yoon-Joon 대한전기학회 2003 전기학회논문지 D Vol.52 No.2

In electrical impedance tomography(EIT), various image reconstruction algorithms have been used in order to compute the internal resistivity distribution of the unknown object with its electric potential data at the boundary. Mathematically the EIT image reconstruction algorithm is a nonlinear ill-posed inverse problem. This paper presents a simulated annealing technique as a statistical reconstruction algorithm for the solution of the static EIT inverse problem. Computer simulations with the 32 channels synthetic data show that the spatial resolution of reconstructed images by the proposed scheme is improved as compared to that of the mNR algorithm or genetic algorithm at the expense of increased computational burden.

Multi-Jet Modeling 3차원 프린트를 위한 표면거칠기와 제작시간의 저감을 위한 모델 분할제작

김호찬,이인탁,이경창,이석,이석희,Kim, Ho-Chan,Lee, In-Tak,Lee, Kyung-Chang,Lee, Suk,Lee, Seok-Hee 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.5

3D printers are widely used to verify the designs in the early stage of product development, and are required to have short build time. However, the build time is still too long for a quick design review for engineers. This research focuses on how to split the prototype in order to reduce the build time and improve surface roughness. In order to verify the feasibility of prototype splitting, the build time and the roughness have been experimentally measured for various parts and build orientations. Based on the experimental results an expert system was developed for splitting the original CAD mod el by using an efficient splitting method. It can recommend a splitting plane based on build time, surface roughness and the number of divided parts. It is shown that the model splitting reduces the build time significantly and improves surface quality wit bout rough surfaces where the support was removed.

미세입자 분사가공을 위한 3 차원 임의형상 모재용 마스크 모델링

김호찬(Ho Chan Kim),이인환(In Hwan Lee),고태조(Tae Jo Ko) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.8

Micro-abrasive Jet Machining is one of the new technology which enables micro-scale machining on the surface of high brittle materials. In this technology it is very important to fabricate a mask that prevents excessive abrasives not to machine un-intend surface. Our previous work introduced the micro-stereolithography technology for the mask fabrication. And is good to not only planar material but also for non-planar materials. But the technology requires a 3 dimensional mask CAD model which is perfectly matched with the surface topology of parent material as an input. Therefore there is strong need to develop an automated modeling technology which produce adequate 3D mask CAD model in fast and simple way. This paper introduces a fast and simple mask modeling algorithm which represents geometry of models in voxel. Input of the modeling system is 2D pattern image, 3D CAD model of parent material and machining parameters for Micro-abrasive Jet Machining. And the output is CAD model of 3D mask which reflects machining parameters and geometry of the parent material. Finally the suggested algorithm is implemented as software and verified by some test cases.

선삭가공으로 제작되는 나사형상의 3차원 파라메터릭 모델

김호찬(Ho-Chan Kim),고태조(Tae-Jo Ko) 한국기계가공학회 2012 한국기계가공학회지 Vol.11 No.6

Geometry of a screw fabricated by a turning process determined by the shape of the tool, feed rate of the tool and rotation speed of the spindle. Therefore, computing the exact geometry of the screw is very important to perform a simulation on machining or an evaluation of the workpice quality. In this paper, a new mathematical geometry model of the 3 dimensional screw is fabricated by turning process introduced for the exact geometry computation. Becasue model has a parametric formulation, it is easy to process for a CAD geometry or apply for a machining simulation. Also, it can be applied to process planning because it gives precise machined geometry on whole the 3 dimensional surface of the screw. This paper introduces a new parametric model of a geometry for screw fabricated by turning process. As an application, a simulation software for the 3 dimensional screw surface is developed and evaluated for several manufacturing parameters.

Lyapunov 행렬방정식의 역해를 이용한 선형 이산시스템의 공분산제어

김호찬(Ho-Chan Kim),최종호(Chong-Ho Choi),김상현(Sang-Hyun Kim) 대한전기학회 1998 대한전기학회 학술대회 논문집 Vol.1998 No.7

유전 알고리즘을 이용한 전기 임피던스 단층촬영법의 영상복원

김호찬(Ho Chan Kim),문동춘(Dong Chun Moon),김민찬(Min Chan Kim),김신(Sin Kim),이윤준(Yoon Joon Lee) 제어로봇시스템학회 2003 제어·로봇·시스템학회 논문지 Vol.9 No.1

분산형 제품개발 시스템의 구축을 위한 SOAP의 활용

김호찬(Ho-Chan Kim),안대건(Dae-Keon Ahn),이석희(Seok-Hee Lee) 한국자동차공학회 2003 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-

Better understanding and sharing information are getting important to manage interdisciplinary product development team in a globally-distributed company. This study propose a solution to implement RPD(Rapid Product Development) system, focusing on rapid production process, for better understanding between development team members in different place and easy sharing of product information. The system developed by this research shows that SOAP(Simple Object Access Protocol) operates in distributed environment more efficiently than other RPC(Remote Procedure Call) techniques and it does not respond sensitively to firewall. And SOAP is an excellent RPC and messaging technique to exchange structured data. Procedures developed with use of SOAP are worked together with web, and users can use remote services as an application program in their computer.