• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.361-366
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• 2000

The machinability of Ti-6Al-4V titanium alloy and tool wear behavior when machining Ti-6Al-4V titanium alloy was studied to understand the machining characteristics. this material is one of the strong candidate materials present and future aerospace or medical applications. Nowadays their usage has already been broaden to everyday's commercial applications such as golf club heads, finger rings and many decorative items. Anticipating the general use of this material and development of the titanium alloys in domestic facilities, the review and the study of the machining parameters for those alloys are deemed necessary. this study is concentrated to the machining parameters of the Ti-6Al-4V alloy due to their dominant position in the production of titanium alloys.

• 한국안전학회지
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• 제14권1호
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• pp.141-149
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• 1999

At present time, industrial accidents statistics are used as the basic data of the policy to prevent industrial accidents and the plan to applicate the industrial accident insurance. But this statistical data is not sufficient for the effective safety management because it is the expression of the itemized distribution and the frequency for the whole cases. This study tried to correlational analysis for each causes by defining investigational items as their accident parameters. The correlational analysis, between the unsafe action and status and their relational causes, was performed to analyze the occurrence causes of industrial accident. And to assume the severity of accident, the correlativity and independency between causes and direct causes which are defined hospital days subordinate parameter were analyzed. In addition, this study expressed numerically the effectiveness of subordinate parameters depended on the level of independent parameter by presenting the predictive model between dependent parameter and independent parameter, which have the categorical parameter, through the Logit analysis method.

• 한국공작기계학회논문집
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• 제10권6호
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• pp.29-35
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• 2001

The cutting characteristics of Ti-6Al-4V alloy and total wear when machining Ti-6Al-4V alloy was studied to understand the machining characteristics. This material is one of the strong candidate materials present and future aerospace or met ical applications. Nowadays their usage has already been broaden to commercial applications such as golf club head, finger rings and many decorative items. Anticipating the general use of this material and development of the titanium alloy in domestic facilities, the review and the study of the machining parameters far those alloys are deemed necessary. This study is concentrated to the machining parameters of the Ti-6Al-4V alloy due to their dominant position in the production of tita mum alloys.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.422-429
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• 2003

A comparative study was performed for a suspension bridge to grasp the possible differences in seismic responses evaluated by several analytical methods. The items mainly investigated are the linear vs. nonlinear response the response spectrum method vs. the linear dynamic analysis method and the damping ratio and it's implementation into analysis procedures. According to the numerical example, it is found that the seismic responses are considerably affected by the damping-related parameters even though slight differences are shown depending on the response quantities md the exciting directions. On the other hand, it is also confirmed that the seismic responses are less affected by the analysis method-related parameters such as the response spectrum method vs. the linear dynamic analysis method, and the linear and nonlinear analysis method. The response spectrum method is expected to give conservative results for the examined bridge, provided that the design response spectrum in the Korean Highway Design Specification is modified according to the proper damping ratio.

• Journal of Information Processing Systems
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• 제15권5호
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• pp.1082-1095
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• 2019

Camera calibration is an important part of machine vision and close-range photogrammetry. Since current calibration methods fail to obtain ideal internal and external camera parameters with limited computing resources on mobile terminals efficiently, this paper proposes an improved fast camera calibration method for mobile terminals. Based on traditional camera calibration method, the new method introduces two-order radial distortion and tangential distortion models to establish the camera model with nonlinear distortion items. Meanwhile, the nonlinear least square L-M algorithm is used to optimize parameters iteration, the new method can quickly obtain high-precise internal and external camera parameters. The experimental results show that the new method improves the efficiency and precision of camera calibration. Terminals simulation experiment on PC indicates that the time consuming of parameter iteration reduced from 0.220 seconds to 0.063 seconds (0.234 seconds on mobile terminals) and the average reprojection error reduced from 0.25 pixel to 0.15 pixel. Therefore, the new method is an ideal mobile terminals camera calibration method which can expand the application range of 3D reconstruction and close-range photogrammetry technology on mobile terminals.

• Imaging Science in Dentistry
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• 제47권2호
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• pp.87-92
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• 2017

Purpose: The aim of this study was to determine whether the panoramic mandibular index (PMI) is useful for assessing bone mineral density. We also analyzed the potential correlations between PMI parameters and patient age. Materials and Methods: Four observers measured the PMI of both sides of the mental foramen using a picture archiving and communication system and images in the Digital Imaging and Communications in Medicine format. They studied 300 panoramic radiographic images of patients belonging to the following age groups: 40-49 years, 50-59 years, 60-69 years, 70-79 years, and 80-89 years. The observers were allowed to zoom in or out and to adjust the contrast of the images. Further, they were instructed to record the reasons for any measurements that could not be made. Then, we conducted a reliability analysis of the measured PMI and assessed the correlations between different patient age groups and the 3 parameters used for determining the PMI from the available data. Results: Among the 600 data items collected, 23 items were considered unmeasurable by at least 1 observer for the following 4 reasons: postoperative state, lesion, unidentified mental foramen, and alveolar bone loss. The intraobserver reproducibility of the measurable data was 0.611-0.752. The mandibular cortical width (MCW) decreased significantly as patient age increased. Conclusion: PMI had limited usability when the margin of the mental foramen was not clear. In contrast, MCW, a parameter used for determining the PMI, had fewer drawbacks than the PMI with respect to bone mineral density measurements and exhibited a significant correlation with patient age.

• Journal of Nutrition and Health
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• 제29권3호
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• pp.251-259
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• 1996

The validity of the energy data of the starch-foods and seaweeds in Korean food composition tables has been suspected due to possible differences in their chemical compositions from those of western food ingredients. Energy conversion parameters being used currently in nutrition has been derived in countries where food items re quite different from ours. This study was undertaken to determine the metabolizable energy of starch-foods and seaweeds by the method selected in preexperiment20). Cooked starch foods and seaweeds were freeze-dried and fed to Sprague Dawley rat with 200∼300g body weight to measure apparent metabolizable energy (AME) values and nitrogen-corrected AME (AMEn) values for four days after three days of preliminary period for adaptation to the diets. The AME and AMEn values of the wheat noodle were 4554.6, 4584.7, the Starch Vermicelli, 3763.4, 3855.7, the Ra myon, 4916.9, 4876.0, the Buckwheat noodle, 4469.7, 4442.0kcal/kg dry matter, the Potato, 4514.6, 4520.0 and those of the Bread, 3256.9, 3582.6, 3260.5, kcal/kg dry matter, respectively. Those of Sea tangle were 1437.3, 1631.3 and of Laver, 3126.6, 3171.3kcal/kg dry matter, resectively. When the AME values of the starch-foods and seaweeds measureed in present study were compared with energy values calculated by various conversion parameters such as Atwater's Rubner's, Sochun's and FAO's, there appeared dramatic differences indicating that for many of the food items, the latter energy values by conversion factors are hardly acceptable. These data also suggest that the existing energy conversion factors are not applicable to seaweeds and a further study is needed to obtain specific factors for the conversion to biological energy from the chemical composition of seaweeds.

• 정보학연구
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• 제2권2호
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• pp.235-250
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• 1999

디지털 VLSI 소자 테스트는 소자 규격서에 정의 된 파라메터들을 최악의 환경 상태에서 소자가 설계된 기능들이 모두 동작하는 지를 보증하는 것이다. 통신용 VLSI 소자의 고집적화에 따른 제품의 신뢰성을 향상하는 것이 VLSI 소자 테스트에서 중요한 고려사항이 된다. 통신용 소자의 신뢰성 향상을 위해서 테스트 파라메터들이 증가되고 테스트 시간이 늘어난다. 데스트 종류는 크게 펑션 데스트, DC 파라메터 테스트 및 AC 파라메터 테스트로 나눌 수 있다 소자의 특성과 신뢰성을 분석하는 기존의 데스트 항목들 중에는 핀간 단락 또는 핀간 누설저항을 테스트하는 항목들이 없다. 본 논문은 핀간 현상을 모델링하고 현재의 DC 파라메터 테스트 방법을 수정하고 새로운 핀간 DC 파라메터들을 테스트하는 방법을 제안한다. 실제로 제품 테스트를 통해 테스트 방법의 수정과 추가에 따른 제품 테스트의 신뢰성 향상을 확인하였다.

• 한국지반공학회논문집
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• 제18권6호
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• pp.43-59
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• 2002

본 연구에서는 국내에서 이용되고 있는 지하구조물 누수에 대한 지수공법과 재료에 대하여 이론적 고찰 및 실험을 실시하고 현장적용 자료의 수집을 통한 통계적인 분석.고찰을 통하여 지하구조물의 누수유형별 지수공법 선정을 위한 시스템을 구축하고자 하였다. 선정시스템의 구성은 데이터베이스 5개의 대구분과 73개 항목의 세분화된 체크리스트를 이용하여 다양한 현장 조건을 고려한 설문조사를 토대로 4개로 대분된 위계성 등급에 따른 26개의 주요 선정인자를 설정하였다. 지수공법 데이터베이스는 국내에 적용실적이 많은 10개의 공법으로 이루어졌다. 설계조건 데이터베이스에서는 10개의 지수공법에 대한 적용범위와 설계조건에 대한 자료를 제공한다. 연구결과에 의한 시스템은 선정인자 데이터베이스와 지수공법 데이터베이스 그리고 설계조건 데이터베이스에 의한 관계형 데이터베이스로 구성되었다. 본 선정시스템의 현장적용 결과, 설계단계에 적용할 경우 지수공법 선정을 위한 시간 단축과 지수공법 선정시의 오류를 감소시킬 수 있었다. 또한 시공단계에 적용할 경우에는 설계단계에서 선정된 지수공법을 현장조건에 따라 재확인함으로써 지수공법의 타당성 분석을 할 수 있고 향후 유지관리에도 활용될 수 있을 것으로 기대된다.

• Advances in aircraft and spacecraft science
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• 제7권1호
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• pp.79-90
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• 2020

The dynamic coupling between shaker and test-article has been investigated by recent research through the so called Virtual Shaker Testing (VST) approach. Basically a VST model includes the mathematical models of the test-item, of the shaker body, of the seismic mass and the facility vibration control algorithm. The subsequent coupled dynamic simulation even if more complex than the classical hard-mounted sine test-prediction, is a closer representation of the reality and is expected to be more accurate. One of the most remarkable benefits of VST is the accurate quantification of the frequency down-shift (with respect to the hard-mounted value), typically affecting the first lateral resonance of heavy test-items, like medium or large size Spacecraft (S/Cs), once mounted on the shaker. In this work, starting from previous successful VST experiences, the parameters having impact on the frequency shift are identified and discussed one by one. A simplified analytical system is thus defined to propose an efficient and effective way of calculating the lower bound frequency shift through a simple equation. Such equation can be useful to correct the S/C lateral natural frequency measured during the test, in order to remove the contribution attributable to the shaker in use. The so-corrected frequency value becomes relevant when verifying the compliance of the S/C w.r.t. the frequency requirement from the Launcher Authority. Moreover, it allows to perform a consistent post-test correlation of the first lateral natural frequency of S/C FE model.