Feasibility of Photon-counting K-edge Imaging in X-ray and Computed Tomographic Systems: Monte Carlo Simulation Studies

이승완,김희중,최유나,조효민,이영진,류현주 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.4

Conventional X-ray systems and X-ray computed tomography (CT) systems, which use detectors operated in the integrating mode, are not able to reflect spectral information because the detector output is proportional to the energy fluence integrated over the whole spectrum. Photon-counting detectors have been considered as alternative devices. These detectors can measure the photon energy deposited by each event and improve the image quality. In this study, we investigated the feasibility of K-edge imaging using a photon-counting detector and evaluated the capability of material decomposition in X-ray images. The geometries of X-ray imaging systems equipped with cadmium telluride (CdTe) detectors and phantoms consisting of different materials were designed using Geant4 Application for Tomographic Emission (GATE) version 6.0. To observe the effect of a discontinuity in the attenuation due to the K-edge of a high atomic number material, we chose the energy windows to be one below and one above the K-edge absorption energy of the target material. The contrast-to-noise ratios (CNRs) of the target materials were increased at selective energy levels above the K-edge absorption energy because the attenuation is more dramatically increased at energies above the K-edge absorption energy of the material than at energies below that. The CNRs for the target materials in the K-edge image were proportional to the material concentration. The results of this study show that K-edge imaging can be carried out in conventional X-ray systems and X-ray CT systems using CdTe photon-counting detectors and that the target materials can be separated from background materials by using K-edge imaging. The photon-counting detector has potential to provide improved image quality, and this study will be used as a basis for future studies on photon-counting X-ray imaging.

군 조직과 회계담당자의 특성이 국방회계정보의 발생액에 미치는 영향

이승완,윤병섭 한국기업경영학회 2015 기업경영연구 Vol.22 No.5

The aim of this study is to investigate whether the effects of military organizational and accountant’s characteristics on total accruals, quality, of accounting information. Especially, using the financial statements of ministry of national defense, this paper is based on the empirical approach. Governmental financial statements based on accrual and double-entry accounting system have disclosed since fiscal year 2011. The governmental financial statements including financial position, financial operations, the net asset change statement, and notes. The biggest difference between the governmental and the general corporate accounting standard is the structure of the national financial statements of public information users two weeks spending of appropriations areas of concern and a point was made around the cost of each program. This study executes this empirical analysis using a data set containing virtually sub corp of army, air force and navy for the period 2008-2014. As a result of analyzing the relationship between the organization and accrual characteristics are as follows: First, at a statistically significant level of negative forces between the scale and total accruals - it was relevant to the negative coefficient. It is interpreted that the larger the bag size can be higher the quality of accounting information in accordance with the political cost hypothesis. Second, if you have a relatively Welfare Center showed that increasing the size of accruals. This means that the more units to take advantage of them held the Welfare Hall to apply accounting standards can relatively be lower accruals to steam the quality of accounting information. Results of analysis of the relationship between military personnel of the properties and accruals accounting are as follows. First, the size of the accruals up to the more high rank bags of bottles and financial officers observed a phenomenon that is relatively small. The higher the rank the greater professionalism of accounting judgment on the interpretation and application of the defense process accounting standards as a result that suggests that maintained a conservative stance. Second, working between career and accruals negative (-) the relevance of the observed. This work experience is further the professional degree for a conservative accounting approach and attitude to accounting because of high and this can be interpreted as a factor that may act to increase the quality of accounting information. The result of this study is to provide policy implications for the workforce of the group financial footing and treasurer for the organization and enhance the usability of accounting information defense. 본 연구의 목적은 군 조직의 특성과 회계담당자의 특성이 국방회계정보의 품질에 미치는 영향을 분석하는데 있다. 본 연구는 국방회계 재무제표를 생산하는 육・해・공 단위부대급을 대상으로 발생주의・복식부기 회계제도를 도입한 2009년부터 2014년까지 6년 동안의 표본 604개를 분석했다. 군 조직특성과 발생액 사이 관련성을 분석한 결과는 다음과 같다. 첫째, 부대규모와 총발생액 사이 유의한 음(-)의 관련성이 있음을 발견했다. 이는 부대규모가 클수록 정치비용가설에 따라 회계정보의 품질이 높아질 수 있음을 시사한다. 둘째, 복지회관을 보유한 경우 상대적으로 발생액의 크기가 증가함을 밝혔다. 이는 기업회계기준을 적용하는 복지회관을 보유한 부대일수록 이를 활용하여 발생액을 증가시킬 수 있어 상대적으로 회계정보의 품질이 낮아질 수 있음을 의미한다. 다음으로 군 회계담당자의 특성과 발생액 사이 관련성을 분석한 결과는 다음과 같다. 첫째, 재정병과 간부의 최고계급이 높은 부대일수록 발생액의 크기가 상대적으로 작아지는 현상이 관찰되었다. 계급이 높을수록 회계업무의 전문성이 높아 국방회계기준의 적용과 해석과정에서 보수주의적 입장을 견지한다는 것을 시사하는 결과로 판단된다. 둘째, 근무경력과 발생액간에 음(-)의 관련성이 관찰되었다. 이는 근무경력이 길수록 회계업무에 대한 전문성 정도가 높기 때문에 회계처리 등에 대해 보수주의적 태도로 접근하고 이는 회계정보의 질을 높이는 요인으로 작용할 수 있다는 것으로 해석할 수 있다. 이러한 연구의 결과는 국방회계정보의 유용성을 높이기 위한 군 회계조직 및 회계담당자에 대한 편제와 인력운영에 관한 정책적 시사점을 제공하고 있다.

API X70 라인파이프 강재의 변형 시효 특성에 미치는 미세조직의 영향

이승완,임인혁,황병철,Lee, Seung-Wan,Im, In-Hyuk,Hwang, Byoungchul 한국재료학회 2018 한국재료학회지 Vol.28 No.12

This study deals with the effect of microstructure factors on the strain aging properties of API X70 pipeline steels with different microstructure fractions and grain sizes. The grain size and microstructure fraction of the API pipeline steels are analyzed by optical and scanning electron microscopy and electron backscatter diffraction analysis. Tensile tests before and after 1 % pre-strain and thermal aging treatment are conducted to simulate pipe forming and coating processes. All the steels are composed mostly of polygonal ferrite, acicular ferrite, granular bainite, and bainitic ferrite. After 1 % pre-strain and thermal aging treatment, the tensile test results reveal that yield strength, tensile strength and yield ratio increase, while uniform elongation decreases with an increasing thermal aging temperature. The increment of yield and tensile strengths are affected by the fraction of bainitic ferrite with high dislocation density because the mobility of dislocations is inhibited by interaction between interstitial atoms and dislocations in bainitic ferrite. On the other hand, the variation of yield ratio and uniform elongation is the smallest in the steel with the largest grain size because of the decrease in the grain boundary area for dislocation pile-ups and the presence of many dislocations inside large grains after 1 % pre-strain.

극저온용 오스테나이트계 고망간강의 인장 및 충격 특성에 미치는 C, Mn, Al 첨가의 영향

이승완,황병철,Lee, Seung-Wan,Hwang, Byoungchul 한국재료학회 2019 한국재료학회지 Vol.29 No.3

The effect of C, Mn, and Al additions on the tensile and Charpy impact properties of austenitic high-manganese steels for cryogenic applications is investigated in terms of the deformation mechanism dependent on stacking fault energy and austenite stability. The addition of the alloying elements usually increases the stacking fault energy, which is calculated using a modified thermodynamic model. Although the yield strength of austenitic high-manganese steels is increased by the addition of the alloying elements, the tensile strength is significantly affected by the deformation mechanism associated with stacking fault energy because of grain size refinement caused by deformation twinning and mobile dislocations generated during deformation-induced martensite transformation. None of the austenitic high-manganese steels exhibit clear ductile-brittle transition behavior, but their absorbed energy gradually decreases with lowering test temperature, regardless of the alloying elements. However, the combined addition of Mn and Al to the austenitic high-manganese steels suppresses the decrease in absorbed energy with a decreasing temperature by enhancing austenite stability.

물리적 인자의 변화에 따른 다양한 구성물질의 하운스필드 단위 평가 및 응용

이승완,김희중,김태호,조소정,이창래,Lee, Seung-Wan,Kim, Hee-Joung,Kim, Tae-Ho,Jo, So-Jeong,Lee, Chang-Lae 한국의학물리학회 2009 의학물리 Vol.20 No.3

This study aims to evaluate CT (Computed Tomography) characteristics through the estimation of HU (Hounsfield Unit) and the corresponding variations using coefficient of variation values for various materials as a function of physical factor. HU values for various materials with varying densities as a function of physical factor were measured using MDCT (Siemens SOMATOM Sensation 4, Germany). The results showed that the HU values were decreased and increased as a function of kVp and material density, respectively. Especially, the HU values for bone and iodine at 140 kVp were 32% and 42% smaller than those at 80 kVp, respectively. In case of iodine, the HU values also decreased and increased as a function of kVp and concentration, respectively. While the HU values were fixed as a function of mAs. The decreased ratio of HU values between 80 keV and 140 keV was different at various concentration and maximum difference was shown as 1.73 at 3% concentration. These results indicated that it may be possible to separate composition of materials, e.g. iodine and bone, using single source CT. The results showed that dual energy techniques using single source CT can be applied to material separation and expand CT imaging techniques to other practical applications.

Quantification of Breast Composition by Using a Dual-energy Technique with a Photon-counting Detector: Monte Carlo Simulation Studies

이승완,최유나,김희중 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.2

Photon-counting detectors with energy-discrimination capabilities are able to reduce radiationdose and suppress noise compared with conventional detectors for X-ray imaging. These detectorsare suitable for spectral X-ray imaging because they can measure the energy of each photonand provide spectral information. One potential application of photon-counting detectors withenergy-discrimination capabilities is the quantification of breast composition by using dual-energytechniques. In this study, we implemented quantitative breast imaging with dual-energy techniquesby using Monte Carlo simulations. An X-ray imaging system was simulated with a photon-countingdetector based on cadmium zinc telluride and a micro-focus X-ray tube. In order to decompose threematerials with two spectral measurements, we applied an additional constraint that the sum of thevolumes of each material be equivalent to the volume of the mixture. Inverse fitting functions withthe least-squares estimation were used to obtain fitting coefficients and calculate volume fractionsfor each material. The results showed that the degree of decomposition for the composition includedin the mixtures varied with the type of composition and the inverse fitting function. High-orderfitting functions increased the quantitative accuracy, but the uncertainty of the decomposed imageswas increased for high-order fitting functions. This study demonstrates that it is possible to quantifybreast composition by using dual-energy techniques and photon-counting detectors without anadditional exposure and that the decomposed images should be evaluated by considering both theiruncertainties and quantitative accuracies.

청각피질유발반응을 이용한 중추청각시스템의 노화반응 연구

이승완,나원도,한우재,김진숙 한국노년학회 2017 한국노년학회 학술발표논문집 Vol.2017 No.3

Evaluation of Dose Reduction and Image Quality in Pediatric Multi-detector CT

이승완,김희중,Dae-Hong Kim,Chang-Lae Lee 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.1

The number of CT (computed tomography) examinations in the diagnosis field has increased, and X-ray exposure to patients has also continued to increase. As the number of CT examinations is increasing in the general population, the number of pediatric CT examinations is rapidly increasing as well. The radiation dose from CT for pediatric patients remains a major concern because the risk related to ionizing radiations is higher in children than in adults. The purpose of this study was to evaluate radiation dose, image noise, and image contrast as a function of tube voltage (kVp) and tube current (mAs) in different phantoms, which were intended to simulate abdominal size, and to provide guidance on dose reduction on the basis of patient dimensions, as well as technical parameters. In this study, MDCT (multi-detector computed tomography) was used as an X-ray generator, and PMMA (polymethylmethacrylate) phantoms were used in all experiments. PMMA phantom diameters were 10 cm, 16 cm, and 32 cm corresponding to newborn, age 5, and adult abdominal sizes, respectively. To evaluate radiation dose, the CTDIw (weighted CT dose index) was calculated from the CTDI measured using ion chamber, and to evaluate image quality, image noise and image contrast were measured from a scanned image. Finally, the CNRD (dose-weighted contrast-to-noise ratio) was calculated from the radiation dose, image noise, and image contrast to optimize the technical factors. The radiation dose increased as a function of kVp and mAs and decreased as a function of the phantom diameter. Especially, for increasing tube voltage from 80 to 140 kVp, there were 395.08% and 448.27% increases in radiation dose for 10 cm and 32 cm PMMA phantoms, respectively. The image noise decreased as a function of kVp and mAs and increased as a function of the phantom diameter. And, the image contrast decreased as a function of kVp and phantom diameter and remained fixed as a function of mAs. The values of the CNRD were maximum at 80 kVp for all three phantoms. The results of this study show that it is possible to reduce radiation dose and maintain image quality through the use of lower technical factors (kVp and mAs) for small-sized phantom corresponding to pediatric patients and to provide guidance on radiation dose reduction on the basis of the patient’s dimensions.

전산화단층촬영의 발전 및 전망

이승완 대한전자공학회 2017 전자공학회지 Vol.44 No.3

조직규모, 회계인력, 회계환경 특성이 국방회계정보의 유용성에 미치는 영향

이승완,윤병섭 한국회계정보학회 2017 회계정보연구 Vol.35 No.1

본 연구는 국방부 산하 육군·해군·공군의 예하 단위부대에서 산출한 재무제표상의 회계정보를 활용하여 조직규모, 회계인력, 회계환경 특성이 국방회계정보의 품질을 대용하는 총발생액과 비배분원가에 미치는 영향을 분석하였다. 2009년부터 2014년까지 6년 동안 국방회계 재무제표를 생산하는 육군·해군·공군의 단위부대급 총표본 604부대-연도를 분석하였다. 본 연구 결과는 다음과 같다. 첫째, 군 조직규모의 특성을 부대의 자산규모와 자산성장성으로 구분하여 분석한 결과, 부대 자산규모가 클수록 총발생액이 감소하였으며, 비배분원가의 크기가 감소하고 있음을 발견하였다. 이러한 결과는 부대규모가 클수록 정치비용효과가 크게 작용하고 세부적이고 정교한 원가배분기준을 마련해 적용하는 것으로 여겨진다. 둘째, 군 회계업무를 담당하는 재정병과 간부의 특성은 회계정보의 품질이나 유용성 등에 영향을 미치는 것으로 나타났다. 재정병과 간부의 계급이 높을수록 군 회계업무 경력이나 전문성이 높아 보수주의적 입장에서 회계처리를 하고 공통원가 배분기준을 마련한다고 판단된다. 셋째, 부대 내 참모부별 회계정보 활용수준이 높을수록 보수적 태도를 견지해 회계처리 하고 있음을 발견하였다. 이는 해당 참모부가 정교하고 세분화한 원가배분기준을 마련해 적용할 가능성이 높고 비배분원가 비중을 낮추는 것으로 보인다. 본 연구의 정책적 시사점은 다음과 같다. 첫째, 군 회계정보의 품질을 유지하거나 개선할 수 있는 제도적 장치를 마련함이 필요하다. 회계업무담당자의 회계처리에 따라 재정운영이나 재정상태가 달라짐은 그 만큼 회계정보의 안정성이나 품질의 신뢰성을 훼손할 수 있기 때문에 합리적 회계처리가 이루어질 수 있도록 지침이나 가이드라인과 같은 제도적 장치를 마련해야 한다. 둘째, 정교하고 세분화한 군 원가배분기준을 합리적이고 타당성 있게 마련할 필요가 있다. 소비집단이라고 할 수 있는 국방조직은 수익보다 비용이나 원가 중심의 재무제표를 산출한다. 직접원가보다 공통원가(또는 결합원가)의 비중이 높으면 정교하고 세분화한 원가배분기준을 마련하여 원가분석이나 비용분석에 필요한 신뢰성 있는 자료를 제공해야 한다. 이를 통해 성과중심의 효율적 예산편성을 가능하게 해야 한다. 셋째, 발생주의·복식부기 국방회계를 도입한 이후 군은 각 자원관리부대의 운영성과와 재정상태에 관한 정보를 산출하고 있다. 이러한 회계정보는 부대 운영에 필요한 경제적 의사결정과정에 활용하지만 회계정보의 활용도가 기대만큼 크지 않은 게 현실이다. 따라서 고품질의 회계정보를 활용한 부대 운영의 사례를 발굴하고 이에 대한 가이드라인을 제시할 필요가 있다. 넷째, 국방 회계업무를 담당하고 있는 재정병과 병력들이 발생주의·복식부기 회계정보를 산출하고 있다. 재정병과 병력들을 지휘하는 각급부대 지휘관이 회계정보 이해력을 높일 수 있는 방안을 모색할 필요가 있다. 군 조직의 운영에 회계정보를 활용하기 위해서는 보병, 포병, 기갑 등 전투병과 간부들이 회계정보를 이해할 수 있도록 각종 보수교육과정에 회계교과목을 편성할 필요성이 있다. The purpose of this study is to investigate the effects of organizational size, accounting manpower, accounting environment, etc. on the total accruals and non-allocation cost, which substitute the quality of defense accounting information, by using the accounting information on financial statements calculated by the units of the army, navy and air force. A total of 604 units at each level of the army, navy, and air force, which produce the financial accounting statements from 2009 to 2014, were analyzed on a year-on-year basis. The results of this study are as follows. First, as a result of analyzing the characteristics of military organization size by asset size and asset growth ability of the unit, the larger the size of the unit’s asset is, the smaller the total accruals are and the less the non-allocation cost is. These results suggest that the larger the size of the unit is, the greater the effect of the political cost is and the more detailed and sophisticated cost allocation criteria are applied. Second, the characteristics of the cadres in the financial branch in charge of military accounting affect the quality and usefulness of accounting information. The higher the rank of fiscal officers is, the higher the experience and expertise in the military accounting business are. Therefore, it can be interpreted as accounting for relatively conservative stance and applying cost allocation criteria for common costs. The number of commanders in fiscal is similar to the results of the variables in the highest class. Third, I found that the higher the level of utilization of accounting information by staff is, the more conservative attitude is maintained to process accounting. This implies that the staffs are more likely to apply more sophisticated and detailed cost allocation criteria and reduce the proportion of non-allocation costs. The political implications of this study are as follows. First, it is necessary to establish an institutional device to maintain or improve the quality of military accounting information. The fact that the financial management and the financial status are changed according to the accounting process of the accounting staff in charge can cause the reliability of the accounting information to be deteriorated in terms of stability and quality. Therefore, institutional arrangements such as guidelines should be made so that institutionally conservative accounting can be done. Second, it is required to establish elaborate and detailed cost allocation standards for military cost accounting system. Defense organization, so-called consumer group, produces financial statements based on expense or production cost rather than revenue. Especially, since the share of common cost . or combined cost) is higher than direct cost, rational and valid allocation standards should be made, so reliable data should be calculated for production cost analysis and expense analysis. This will enable effective compilation of budget oriented performance. Third, since the accrual basis of accounting and double-entry bookkeeping were introduced, information about operation result and financial condition of each unit has been produced. These accounting information are used in the economic decision making process required for the unit operation, but the utilization of accounting information is not as large as expected. Therefore, it is necessary to develop a case study on the use of accounting information and to provide guidelines for it. Fourth, the military forces in charge of defense accounting are calculating the accrual basis of accounting and double-entry bookkeeping information, so it is necessary to seek ways to improve the understanding of these accounting information by unit commanders at each level. In order to utilize accounting information in the operation of military organizations, it is necessary to organize accounting courses in various curriculums such as infantry, artillery, armor, etc. to enable sold...