간 역동적 검사에서 Compressed Sensing을 이용한 Double Arterial Phase 기법 적용 시 최적 Acceleration Factor에 대한 고찰

지소영 대한자기공명기술학회 2019 대한자기공명기술학회지 Vol.29 No.2

목 적:간 역동적 검사 시 호흡이 불규칙하거나 호기 후 정지의 어려움을 갖는 환자의 경우 영상의 질이 저하된다. 이 문제점을 해결하기 위해서 GRAPPA, CAIPIRHINA, Compressed Sensing 기법을 사용하여 호흡 정지 시간을 단축하고 있다. 본 연구에서는 acceleration factor 8, 9, 10을 적용한 CS 기법과 초기 동맥기와 동맥기를 동시에 얻을 수 있는 Double arterial phase 기법을 사용하여 VIBE 영상을 얻어 비교함으로써 최적 acceleration factor 값과 phase를 평가해보고자 한다. 대상 및 방법:2019년 8월 19일부터 9월 20일까지 본원에서 간 MRI 검사를 시행한 환자 15명을 대상(남자 10명 여자 5명 64±12.6세)으로 단일 호흡 정지 동안 2번 측정되는 double phase image를 사용할 때, acceleration factor를 각각8, 9, 10으로 변화를 주고 다른 변수들은 같게 하여 실험을 진행하였다. 획득한 acceleration factor 값과 phase가 다른 각 영상의 SNR, CNR을 측정하여 정량적 평가를 진행하고, 정성적 영상평가와 호흡 정지 시간의 변화를 비교하였다. 결 과:같은 phase에서 acceleration factor의 값이 9, 10, 8 순으로 SNR이 높았으며, acceleration factor가 8, 10일 경우 SNR이 phase 1보다 phase 2가 높았고, acceleration factor가 9일 경우에는 phase 1가 더 높았다. phase 1의CNR은 acceleration factor 9, 8, 10 순으로 높았고, phase 2에서의 CNR은 acceleration factor 9, 10, 8 순으로 높았다. acceleration factor가 8, 9인 경우는 phase 1의 CNR이 높았고, 10인 경우 phase 2의 CNR이 높았다. 결 론:본 연구의 실험결과를 종합하였을 때 acceleration factor 9를 적용한 double phase image 중 Phase 1에서 가장 높은 SNR과 CNR을 확인할 수 있었다. 또한, 호흡 정지시간 역시 acceleration factor 8 대비 acceleration factor 9에서는 13% 감소하고, acceleration factor 10에서는 20% 감소한 효과를 얻었다. CS 기법을 사용한 간의 역동적 Double Phase 검사 시 영상의 질의 변화에 큰 유의함이 없는 상태로 acceleration factor를 조절하여 호흡 정지시간을 줄이고,2개의 영상 중 선택하여 임상적으로 활용할 수 있다고 생각한다. Purpose:In Liver MRI dynamic scan, the image quality would be lowered if the patients have a difficulty in holding a breath or breathe irregularly. GRAPPA, CAIPIRHINA, and Compressed Sensing(CS) are applied to conventional VIBE sequence for shortening the breath-hold time in order to improve the image quality. In this study, we investigate the optimal acceleration factor and phase of CS applied Double arterial phase VIBE images which are conventionally used to get early arterial phase and arterial phase in a single breath hold. Materials and Methods:15 patients consisted of 10 males and 5 females took Liver MRI examination from August 19th to September 20th. CS techniques is applied to conventional VIBE sequence which is dominantly used in a dynamic scan. This CS applied VIBE sequence is measured two times in a single breath-hold and it is also controlled by acceleration factor from 8 to 10. After acquiring images, SNR, CNR, and scan time are quantitatively evaluated, and then these images were evaluated using 4points qualitative assessment by Radiological technologists. Results:In the same phase, SNR and CNR of the ACC 9 are higher than those of ACC 8 and ACC 10. When acceleration factor is set as 9, SNR and CNR of Phase 1(P1) is higher than those of Phase 2 (P2). According to the results, CS VIBE sequence whose acceleration factor is 9 has a shorter scan time which is 13% decreased compared to CS VIBE sequence whose acceleration factor is 8. Moreover, the first phase of double phase CS VIBE image whose acceleration factor is 9 has not only the highest SNR and CNR but also an acceptable image quality. Conclusion:The first phase image with acceleration factor 9 has the highest SNR and CNR compared to the other images which has a different acceleration factor and phase. It has also shorter scan time than acceleration factor 8. As a result, the double arterial phase image which has optimal CS acceleration factor, short scan time and acceptable visual image quality, can be considered as a clinical Liver dynamic scan sequence. Moreover, the double arterial phase image has two types of phase that the operator is possible to chose one image which has more valuable information and good quality. Thus, it could be applied to the patients who have a difficulty in breath hold, or breathe irregularly.

브레이크 고장데이터 분석을 통한 가속인자 및 가속계수 결정에 관한 연구

김나연,심현수,김용수 한국신뢰성학회 2019 신뢰성응용연구 Vol.19 No.4

Purpose: Fault data on automobile brakes are applied to reliability and statistical analysis methods to derive the brake acceleration factor and acceleration factor for automobiles. Based on these results, a brake acceleration life test design is proposed. Methods: The factors influencing brake failure are derived from literature review. The wear data are extracted by two-mixture Weibull distribution analysis based on three levels of failure data to determine if the factor affects the failure of brake parts. The extracted wear data are analyzed to confirm the acceleration and determine the acceleration factor and the acceleration factor. Results: Acceleration life tests can be designed from existing vehicle brake life tests by reflecting the derived acceleration factors and acceleration factors. Conclusion: With the reduction in the proposed testing time compared with the existing one, a more reliable design can be achieved. The proposed analytical process can be useful in deriving the acceleration factor for the design of an accelerated life test for non-brake car parts.

AHP를 활용한 액셀러레이터와 투자유치 성공 스타트업, 유치희망 스타트업의 투자결정요인 관점 차이 연구

심규진,최세현,유지연 한국엔터테인먼트산업학회 2023 한국엔터테인먼트산업학회논문지 Vol.17 No.8

The biggest difficulty faced by startups is to secure funds, for which private investment institutions play an important role along with government support. The key is to secure funds from accelerators that provide mentoring and educational programs to startups in addition to equity investment. However, it is not easy for content startups to attract investments and maintain their survival at the local level. Most previous studies have investigated the supporting effects of accelerators or investment decision factors for startups from an investor's viewpoint. In contrast, research on content startups is extremely limited, and the ones that compared and analyzed differences from accelerators’ perspectives are in high shortage. Therefore, this study examines the viewpoints in which accelerators considered investing into content startups and actually made the investment, and investigates differences in perceptions between content startups that succeeded in attracting investment and ones that did not. For these purposes, this study conducted a survey with investment firms and content startups located in the Southeastern parts of Korea and examined the relative importance of investment decision factors with an AHP analysis. The finding shows that accelerators placed the greatest importance on “entrepreneurs (teams)" among the top investment decision factors. Startups that attracted an investment also placed the biggest importance on “entrepreneurs (teams)” while startups hoping to attract an investment did on "the market." Among the bottom factors, accelerators, startups that attracted an investment, and startups hoping to attract an investment considered “industry expertise," ”reliability," and “market size and growth potential," respectively, as the most important factor. The finding implies that content startups need to further reinforce their internal factors, including “entrepreneurs (teams)" at the local level to succeed in their initial investment. Furthermore, the finding will contribute to accelerators in order to increase their competence in identifying content startups and selecting the ones to invest in within the Southeastern parts of Korea.

기업혁신요인이 기업혁신성과에 미치는 영향 연구 : 혁신촉진요인(High, Low 수준)과 혁신저해요인(High, Low 수준)의 집단별 차이 분석

지용빈(Yong-Bin Ji),서영욱(Young Wook Seo) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.4

기업은 지속적인 성장과 경쟁우위 확보를 위해 기술개발 관련 적극적인 혁신 활동을 하고 있다. 이러한 기업혁신활동이 기업혁신성과에 미치는 요인은 여러 가지가 있지만, 기업의 이러한 혁신 활동이 항상 긍정적인 영향을 미치는 것은 아니다. 이에 본 연구에서는 기업혁신요인 중 혁신촉진요인과 혁신저해요인을 중심으로 혁신성과에 미치는 효과를 분석하였다. 연구모형은 2016년 기술혁신조사(STEPI)에 응답한 2,081개 국내 제조기업을 분석하였고, 신뢰도, 타당성 및 로지스틱 회귀분석을 위해 SPSS 25.0이 사용되었다. 결과는 다음과 같다. 첫째, 혁신 활동은 제품혁신성과와 공정혁신성과에 긍정적인 영향을 미치며, 정부지원은 반대의 결과를 나타냈다. 둘째, 기술 협력은 혁신촉진 및 저해요인과 상관없이 제품혁신성과에 긍정적인 영향을 나타냈다. 셋째, 혁신 활동은 혁신촉진 및 저해요인과 상관없이 공정혁신성과에 긍정적인 영향을 나타냈다. 본 연구는 기술적 혁신에 한정된 기존 선행연구들과는 달리 혁신촉진요인과 혁신저해요인에 대한 기업들의 태도를 구분하여 그에 따라 집단별로 혁신 성과가 어떻게 달라지는지를 중심으로 수행하였기 때문에 혁신의 실패와 위험부담을 낮출 수 있는 기업혁신전략을 수립하는데 기여할 것으로 기대된다. Enterprise is focused on R&D innovative activities in order to achieve sustainable growth & secure competitive advantage. There are many factors that influence enterprise innovation performance, but enterprise innovation activities do not always have a positive effect. Therefore, this study analyzed the effects of on innovation performance, focusing on innovation acceleration factors and innovation hindrance factors. The research model analyzed 2,081 national manufacturing enterprises that responded to the 2016 Korean Innovation Survey (STEPI). SPSS 25.0 was used to perform reliability, feasibility, and logistic regression analysis. The results are as follows. First, innovation activities have positive effects on enterprise product and process innovation performance. On the other hand, government support had the opposite results. Second, the collaboration of technology showed a positive effect on product innovation performance, independent of innovation acceleration and hindrance factors. Third, innovation activities showed a positive effect on process innovation performance, regardless of the innovation acceleration and hindrance factors. Unlike prior studies limited to technological innovation, this study analyzed the attitudes of enterprises toward innovation acceleration and hindrance factors. This study is expected to contribute to establishing a strategy for reducing the failure and risk of innovation due to its findings on how innovation performance varies by groups.

비정규분포 풍속에 따른 피크팩터에 관한 연구

김한솔,김주원,윤성기 한국풍공학회 2015 한국풍공학회지 Vol.19 No.4

Lately damage caused by typhoons and regional squall has been increasing. In addition, the construction of high-rise buildings in metropolitan and coastal cities is increasing. In the case of high-rise buildings when the typhoon occurred, acceleration of the building increases. The vibration of the building is directly related to serviceability problems of residents. The serviceability of the building is determined by the maximum acceleration of the building. Country-specific peak factor estimating equations, necessary to calculate the maximum acceleration of the structure, are assuming that wind speed is a gaussian distribution. However, typhoon and strong winds, etc. that have a direct impact on serviceability, are almost non-gaussian distribution. Eventually country-specific codes are calculating the maximum acceleration which does not reflect the typhoon and strong winds. The study was conducted over a number of comparison of maximum acceleration applied peak factor. Peak factor is divided into two, country-specific peak factor estimating equations and peak factor using fifty wind speed data of weather center. As a result, the study presents need to reflect wind speed of non-gaussian distribution in peak factor estimating equations of code. 최근 태풍의 크기가 커지면서 태풍과 지역적 돌풍에 의한 피해가 증가하고 있으며, 또한 수도권과 해안도시를 중심으로 초고층건물의 건설이 증가하고 있다. 초고층건물의 경우 태풍 발생 시 건축물의 변위뿐 아니라 가속도가 증가하며 건축물의 진동이 큰 문제가 되며 이는 거주자의 사용성 문제로 직결된다. 건축물의 사용성은 건축물의 최대가속도로 판단하며, 최대가속도를 산정하는데 필요한 국가별 코드에 따른 피크팩터는 풍속이 정규분포라 가정하여 산정한 값이다. 그러나 사용성에 직접적인 영향을 주는 태풍과 강풍 등은 비정규분포인 경우가 대부분이기 때문에, 결국 국가별 코드에서는 태풍과 강풍의 영향을 반영하지 않은 건축물의 최대가속도산정 방법을 제시하고 있는 것이라 할 수 있다. 본 논문에서는 기상청에서 제공하는 서울 등 10개 지역의 2010년부터 2014년까지 5개년의 총 50개의 풍속 자료를 이용해 산정한 피크팩터를 적용하여 계산한 건축물의 최대가속도와 국가별 코드를 적용한 최대가속도의 비교분석을 통한 연구를 진행하였고, 그 결과 국가별 피크팩터 산정식에 비정규분포의 풍속을 반영할 필요에 대하여 자료를 제시하고 있다.

전자제품용 컴프레서의 가속열화시험에 관한 연구

이후진(Hoo-Jin Lee),윤원영(Won Young Yun) 한국신뢰성학회 2010 신뢰성응용연구 Vol.10 No.1

In this paper, an accelerated degradation test procedure for an electronic appliance compressor is proposed. We investigate the amount of wear of the compressor and consider several factors as accelerating factors. Finally we select the operating pressure as a main accelerating factor. The test condition of accelerated degradation test is determined. The modified accelerating test reduces the test time in design phase by using the suggested accelerating factor.

The Stromal Overexpression of Decay Accelerating Factor (DAF/CD55) Correlates with Poor Clinical Outcome in Colorectal Cancer Patients

백태화,김주헌,박미자,이혜경,손현진,순현기,김창남,고제명,강동욱 대한병리학회 2011 Journal of Pathology and Translational Medicine Vol.45 No.5

Background: Decay accelerating factor (DAF/CD55), regulates the complement system by accelerating decay of the C3 convertase, has been described in several malignancies, however, the clinicopathologic significance of CD55 and its receptor CD97 has not been fully investigated. We examined the expression patterns of both CD55 and CD97 and their association with clinicopathologic parameters in colorectal cancers (CRCs). Methods: Expression patterns of CD55 and CD97 in the stroma and tumor cells at tumor center and invasive front were examined in 130 CRCs, and their significance was statistically evaluated. Results: CD55-high stroma was correlated with tumor border (p=0.006) and invasion depth (p=0.013). CD55-high tumor cells at tumor center and invasive front were correlated with histologic grade, and CD55-high tumor cells at invasive front with tumor, node and metastasis (TNM) stage (p<0.05). CD97-high stroma was correlated with lymph node metastasis (p=0.016) and TNM stage (p=0.030). CD97-high tumor cells at tumor center and invasive front were correlated with tumor size and CD97-high tumor cells at tumor center with tumor border (p<0.05). Patients with CD55-high stroma showed poor overall and recurrence-free survival (p<0.05) in univariate analysis, and were independently associated with short recurrence-free survival (p=0.025) in multivariate analysis. Conclusions: Stromal CD55 overexpression would be an indicator of adverse clinical outcome and a useful prognostic factor.

Analysis of an Unsteadily Propagating Crack under Mode Ⅰ and Ⅱ Loading

Kwang Ho Lee,Gap Su Ban 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.3

Stress and displacement fields for an unsteadily propagating crack under mode I and II loading are developed through an asymptotic analysis. Dynamic equilibrium equations for the unsteady state are developed and the solution to the displacement fields and the stress fields for a crack propagating with high crack tip acceleration, deceleration and rapidly varying stress intensity factor. The influence of transients on the higher order terms of the stress fields are explicitly revealed. Using these stress components, isochromatic fringes around the propagating crack are generated for different crack speeds, crack tip accelerations and the time rate of change of stress intensity factor, and the effects of the transients on these fringes are discussed. The effects of the transients on the dynamic stress intensity factor are discussed when a crack propagates with high acceleration and deceleration. The effect of transient on the time rate of change of dynamic stress intensity factor below Rayleigh wave speed in an infinite body is also studied.

이원배치법을 이용한 공기압 실린더의 가속수명시험에 관한 연구

강보식(Bo-Sik KANG),김형의(Hyoung-Eui KIM),유영철(Yung-Chul YOO) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

In this study, we researched how to estimate life-stress relationship and acceleration factor through performing accelerated life test and analyzing it. The purpose of this study is to predict life of pneumatic cylinder within short time which is widely used in automation manufacturing line. In design of accelerated life test, we selected operating pressure and load that have the most influence on main failure mode of pneumatic cylinder as accelerated factor. We used two-way factorial design for arranging of test condition to accelerated factor and accelerated level.

면진구조의 응답가속도 감소효과를 고려한 상부구조의 설계전단력 저감계수

천하오(Chen, Hao),오상훈(Oh, Sang-Hoon) 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.7

The structural damage caused by earthquake to the upper structure of seismic base-isolated system can be suppressed effectively because it is designed to concentrate the input energy on the seismic isolation floor. Further, the response acceleration of seismic base-isolated system can be greatly reduced compared to the seismic structure because of the long period, which means that the design shear force of the seismic base-isolated system can be reduced appropriately. However, when the design shear force is determined to be reduced, the design stiffness will decrease, and the response acceleration will increase oppositely. Therefore, for finding the extent to which the design shear force of the upper structure can be reduced, this paper considered the seismic base-isolated structure as the analytical model and proposed the design shear force reduction factor of the base-isolated structure through the dynamic response analysis, while considering the decrement effect of response acceleration. The research result shows that the response acceleration of the isolated the upper structure can be reduced by 50%~70% of the seismic structure under the same design conditions, and the design shear force can be reduced by up to 40%. By increasing the design stiffness over to 1.8 times of the original design value, the design shear force can be reduced to the same extent as the response acceleration can be reduced compared to the seismic structure.