• 대한전기학회논문지
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• 제39권8호
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• pp.868-874
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• 1990

A singular value approach is presented in order to determine the number of multiple sinusoids from the finite noisy data. Simulations are conducted for Akaike's information criterion (AIC), Rissanen's shortest data description (MDL) and a singular value approach, for various examples with different SNR's and methods of estimating frequencies. And then the performances are compared. Simulation results that the singular value approach is superior to AIC and MDL for FBLP, HOYW and covariance matrix based methods are investigated. The approach with contribute to the frequency estimation of multiple sinusoids from the finite noisy data. Furthermore, this will be applied to the DSPs of communication and bio-medical engineering.

• Journal of Korean Neurosurgical Society
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• 제47권5호
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• pp.332-337
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• 2010

Objective : Although a transradial angiography is accepted as the gold standard for cardiovascular procedures, cerebral angiography has been performed via transfemoral approach in most institutions. The purpose of this study is to present our experience concerning the feasibility, efficacy, and safety of a transradial approach to cerebral angiography as an alternative to a transfemoral approach. Methods : Between February 2007 and October 2009, a total of 1,240 cerebral angiographies were performed via a transradial approach in a single center. The right radial approach was used as an initial access route. The procedure continued only after the ulnar artery was proven to provide satisfactory collateral perfusion according to two tests (a modified Allen's test and forearm angiography). Results : The procedural success rate was 94.8% with a mean duration of 28 minutes. All supra-aortic vessels were successfully catheterized with a success rate of 100%. The success rates of selective catheterization to the right vertebral artery, right internal carotid artery, left internal carotid artery, and left vertebral artery were 96.1%, 98.6%, 82.6% and 52.2%, respectively. The procedure was performed more than twice in 73 patients (5.9%), including up to 4 times in 2 patients. The radial artery occlusion was found in 4 patients (5.4%) on follow-up cerebral angiography, but no ischemic symptoms were observed in any of the cases. Conclusion : This study suggests that cerebral angiography using a transradial approach can be performed with minimal risk of morbidity. In particular, this procedure might be useful for follow-up angiographies and place less stress on patients.

• 한국해양공학회지
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• 제17권2호
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• pp.34-39
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• 2003

Recent deepwater offshore structures in the Gulf of Mexico utilize butt welded tubular joints. Application of a welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical, as the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimation of the fatigue behavior of these tubular members in the design stage is generally condrcted by using S-N curves, as specified in the codeds and standards. Applying the stress concentration factor of the welded structure to the S-N approach often results in a very conservative assessment, because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fatigue life analysis using fracture mechanics has been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. Still, there is inconsistency when designing tubular joints using a conventional S-N approach and when specifying weld flaw acceptance criteria using fracture mechanics approach. This study developed fatigue curves that are consistent with both the S-N approach and the fracture mechanics approach. Accounting for non-uniform stress distribution and threshold stress intensity factor were key parameters in relating both approaches. A series of S-N curves, generated from the fracture mechanics approach, were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02 ). The new curves for tubular joint agree very well with the experimental results. The comparison also indicated the degree of conservatism built into the API X design curve.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제6권1호
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• pp.69-74
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• 2003

Recent deepwater offshore structures in the Gulf of Mexico utilize butt welded tubular joints. Application of a welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical, as the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimation of the fatigue behavior of these tubular members in the design stage is generally conducted by using S-N curves, as specified in the codes and standards. Applying the stress concentration factor of the welded structure to the S-N approach often results in a very conservative assessment, because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fatigue life analysis using fracture mechanics has been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. Still, there is inconsistency when designing tubular joints using a conventional S-N approach and when specifying weld flaw acceptance criteria using fracture mechanics approach. This study developed fatigue curves that are consistent with both the S-N approach and the fracture mechanics approach. Accounting for non-uniform stress distribution and threshold stress intensity factor were key parameters in relating both approaches. A series of S-N curves, generated from the fracture mechanics approach, were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02). The new curves for tubular joint agree very well with the experimental results. The comparison also indicated the degree of conservatism built into the API X design curve.

• Journal of the Korean Data and Information Science Society
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• 제15권4호
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• pp.957-963
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• 2004

A new agreement measure for multivariate interval data by different sets of raters is proposed. The proposed approach builds on Um's multivariate extension of Cohen's kappa. The proposed measure is compared with corresponding earlier measures based on Berry and Mielke's approach and Janson and Olsson approach, respectively. Application of the proposed measure is exemplified using hypothetical data set.

• Korean Journal of Radiology
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• 제23권9호
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• pp.901-910
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• 2022

Objective: This study aimed to assess the technical feasibility, efficacy, and safety of the safe triangular working zone (STWZ) approach applied in percutaneous vertebroplasty (PV) for spinal metastases involving the posterior part of the vertebral body. Materials and Methods: We prospectively enrolled 87 patients who underwent PV for spinal metastasis involving the posterior part of the vertebral body, with or without the STWZ approach, from January 2019 to April 2022. Forty-nine patients (27 females and 22 males; mean age ± standard deviation [SD], 57.2 ± 11.6 years; age range, 31-76 years) were included in group A (with STWZ approach), accounting for 54 vertebrae. Thirty-eight patients (18 females and 20 males; 59.1 ± 10.9 years; 29-81 years) were included in group B (without STWZ approach), accounting for 57 vertebrae. Patient demographics, procedure-related variables, and pain relief as assessed using the visual analog scale (VAS) were collected at different time points. Tumor recurrence in the vertebrae after PV was analyzed using Kaplan-Meier curves. Results: The STWZ approach was successful from T1 to L5 without severe complications. Cement filling was satisfactory in 47/54 (87.0%) and 25/57 (43.9%) vertebrae in groups A and B, respectively (p < 0.001). Cement leakage was not significantly different between groups A and B (p = 1.000). Mean VAS score ± SD before and 1 week and 1, 3, 6, 9, and 12 months after PV were 7.6 ± 1.8, 4.2 ± 2.0, 2.7 ± 1.9, 1.9 ± 1.5, 1.7 ± 1.4, 1.7 ± 1.1, and 1.6 ± 1.3, respectively, in group A and 7.2 ± 1.7, 4.0 ± 1.3, 3.4 ± 1.6, 2.4 ± 1.2, 1.8 ± 1.0, 1.4 ± 0.5, and 1.7 ± 0.9, respectively, in group B. Kaplan-Meier analysis showed a lower tumor recurrence rate in group A than in group B (p = 0.001). Conclusion: The STWZ approach may represent a new, safe, alternative/auxiliary approach to target the posterior part of the vertebral body in the PV for spinal metastases.

• 지식경영연구
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• 제21권1호
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• pp.27-40
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• 2020

Response surface methodology (RSM) empirically studies the relationship between a response variable and input variables in the product or process development phase. The ultimate goal of RSM is to find an optimal condition of the input variables that optimizes (maximizes or minimizes) the response variable. RSM can be seen as a knowledge management tool in terms of creating and utilizing data, information, and knowledge about a product production and service operations. In the field of product or process development, most real-world problems often involve a simultaneous consideration of multiple response variables. This is called a multiple response surface (MRS) problem. Various approaches have been proposed for MRS optimization, which can be classified into loss function approach, priority-based approach, desirability function approach, process capability approach, and probability-based approach. In particular, the loss function approach is divided into univariate and multivariate approaches at large. This paper focuses on the univariate approach. The univariate approach first obtains the mean square error (MSE) for individual response variables. Then, it aggregates the MSE's into a single objective function. It is common to employ the weighted sum or the Tchebycheff metric for aggregation. Finally, it finds an optimal condition of the input variables that minimizes the objective function. When aggregating, the relative weights on the MSE's should be taken into account. However, there are few studies on how to determine the weights systematically. In this study, we propose an interactive procedure to determine the weights through considering a decision maker's preference. The proposed method is illustrated by the 'colloidal gas aphrons' problem, which is a typical MRS problem. We also discuss the extension of the proposed method to the weighted MSE (WMSE).

• 농촌지도와개발
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• 제21권3호
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• pp.181-213
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• 2014

본 연구는 최근 우리나라 ODA의 양적 성장이 이루어지고 있는 가운데 농업분야 ODA 질적 제고를 위해 우량사업 발굴을 위한 접근법에 대해 분석하였다. 이 분석은 국제사회의 ODA 발전 패러다임, 우리나라 ODA 발전 방향 및 농업분야 ODA 사업 발굴에 있어서의 구조 절차 내용상의 문제점을 기초로 이루어졌다. 분석 결과 전략에 근거한 접근(Strategy Approach), 비교우위에 기초한 접근(Comparative Advantage Approach), 파트너십에 기초한 접근(Partnership Approach), 공여주체간 협의에 기초한 접근(Networking Approach), 모델화 접근(Modeling Approach) 등 5가지 접근법이 도출되었다. 각각의 접근법이 유기적으로 연계되어 적용될 경우 우량사업 발굴 가능성이 더욱 높아지고, 결국에는 사업의 효과성 제고로 이어질 것이다. 본고에서는 이러한 접근법을 적용하여 맞춤형 ODA 사업을 발굴한 KAPEX 프로그램 사례를 소개하였다.

• 한국인터넷방송통신학회논문지
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• 제12권4호
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• pp.119-130
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• 2012

최근 들어 소프트웨어 시스템은 점차적으로 복잡해지고 있으며, 고객(customer)은 보다 빠른 개발을 요구하고 있다. 전통적인(traditional) 순차적 접근법 (Sequential Approach)으로는 이러한 압력에 효과적으로 대처할 수 없어 대안으로 반복적 접근법 (Iterative Approach)이 적용되고 있다. 대표적인 반복적 접근법으로는 래쇼날의 단일화된 프로세스 (Rational Unified Process, RUP)가 있다. 그러나 RUP의 표준화된 수행방법은 단계, 반복과 활동들을 모두 순차적으로 수행하는 형태이다. 그 결과, 하나의 반복에서 수행된 하나의 활동은 다음 반복의 해당 활동이 수행될 때까지 기다려야 하는 인력낭비 현상이 발생한다. RUP를 수행하는 방법으로는 선형 접근법, 순차적 접근법, 중첩된 반복 접근법과 Time-boxed 반복 접근법이 제안되었다. 그러나 이들 방법은 인력낭비 현상 또는 적용시 프로젝트 관리의 어려움이라는 문제점을 갖고 있다. 본 논문은 활동들을 동시에 수행하는 방법을 제안하였다. 동시개발 접근법은 인력 낭비 현상을 방지할 수 있으며, 프로젝트 관리의 어려움도 해결할 수 있는 장점을 갖고 있다.

• 조명전기설비학회논문지
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• 제27권1호
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• pp.68-75
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• 2013

This paper presents a scheme to improve transient stability using Newton's Approach for generation rescheduling. For a given contingency, the energy margin and sensitivities are computed. The bigger energy margin sensitivity of generator is, the more the generation of the generator effects to the transient stability. According to energy margin sensitivity, the control variables of generation rescheduling are selected. The fuel cost function is used as objective function to reallocate power generation. The results are compared to the results of time simulation to show its the effectiveness.