• Title/Summary/Keyword: 시간 안정성 분석

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The Difference in Tear Film Stability between Normal and Dry Eyes by Wearing Clear and Circle Contact Lenses made of the Same Materials (동일 재질의 투명 및 써클콘택트렌즈 착용 시 정상안과 건성안의 눈물막 안정성 차이)

  • Lee, Sehee;Park, Mijung;Kim, So Ra
    • Journal of Korean Ophthalmic Optics Society
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    • v.21 no.1
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    • pp.11-21
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    • 2016
  • Purpose: The aim of this study was to analyze the difference in tear film stability according to the wearing time when wearing clear and circle soft contact lens(circle lens) made of same material. Methods: The clear and circle contact lenses of hilafilcon B and nelfilcon A materials were respectively applied on the subjects classified as normal and dry eyes depending on their tear volume, and their tear film stability was investigated by measuring the non-invasive tear film break-up times, lens centration and the first appearing area of tear breakup after 30 mins and 6 hrs of lens wearing. Results: Non-invasive tear film breakup time significantly reduced with increase of the wearing time for normal and dry eyes when wearing clear and circle contact lenses. The starting ratio of tear film break-up was higher at the peripheral area of clear and circle lenses in all two different materials, and higher at the peripheral area of dry eyes than normal eyes. Starting ratio of tear film break-up was higher at the peripheral area of nelfilcon A lenses compared with hilafilcon B lenses, however, its change with the increase of wearing time showed a different aspect. The number of tear film break-up per unit area when wearing circle lenses of nelfilcon A increased at the central area with the wearing time while its number was higher at the peripheral area when wearing circle lenses of hilafilcon B. The centration of clear lenses made of two materials was closer to pupil compared to circle lenses with the increase of wearing time, however, a larger decentration was shown in dry eyes compared with normal eyes. Conclusions: The research revealed that an effect on tear film stability may be changed by clear lenses as well as circle lenses with coloring process according to the increase of wearing time, and the factors affecting on tear film stability may also vary depending on lens materials. Thus, the appropriate lenses should be selected by the consideration of lens material as well as coloring method/dyes according to the wearers' habit such as daily wearing time and wearing period when trying to wear clear and circle lenses.

Numerical Investigation on the Stability of Reinforced Earth Wall during Rainfall (강우시 보강토 옹벽의 안정성에 관한 수치 해석 연구)

  • Yoo, Chung-Sik;Kim, Sun-Bin;Han, Joon-Yeon
    • Journal of the Korean Geotechnical Society
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    • v.24 no.12
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    • pp.23-32
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    • 2008
  • This paper presents the results of numerical investigation on the stability of reinforced earth wall during rainfall. A series of limit-equilibrium based slope stability analyses within the framework of unsaturated shear strength, coupled with transient seepage analyses, were conducted with due consideration of rainfall characteristics in Korea. It is shown that the factor of safety of the reinforced wall during rainfall decreases with time due to decreases in the suction in the reinforced as well as retained zones. Also revealed is that the decrease in the factor of safety depends not only on the backfill soil type but also on the rainfall characteristics. Practical implications of the findings were discussed.

A Study on Stability evaluation in the freezing/thawing process of urine specimen analytes (소변 검체 분석물질의 냉/해동 과정 안정성 평가 연구)

  • Kim, Min Kyung;Kim, Sung Wook;Hwang, You Seong;Oh, Eunha
    • Journal of the Korean Applied Science and Technology
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    • v.39 no.1
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    • pp.52-62
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    • 2022
  • The purpose of this study was to find a way to improve the stability and quality of urinalysis by checking the changes in the measurement values of representative clinical chemistry test items according to the repeated freezing and thawing before the urine test and the thawing process. All subjects were 10 healthy males, and the freeze and thaw stability test was performed using their urine samples. In the case of micro-albumin and amylase, there was no statistical significance at 37℃ with time, but at 42℃ and 60℃, there was a statistically significant change in the results with time. There were statistically significant changes in BUN, creatinine, uric acid, and glucose. As a result of long-term stability, after 7 days, glucose mutation increased and amylase decreased at 60℃. In the case of glucose and amylase, there was a statistically significant change in the results over time. To obtain accurate test results, accurate standardization of urinalysis including appropriate collection, storage, and storage methods of urine samples is required and systematic study of conditions for securing stability for each biomaterial is required.

A Study on Verification of Patch File Integrity (패치 파일 무결성 검증에 관한 연구)

  • An, Jeongmin;Won, Yoojae
    • Proceedings of the Korea Information Processing Society Conference
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    • 2016.10a
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    • pp.232-233
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    • 2016
  • 패치 관리 시스템은 패치 서버에 속한 에이전트들의 보안 패치를 배포 및 관리하는 시스템이다. 에이전트에서의 보안사고로 인한 큰 피해를 막기 위해, 패치 관리 시스템은 패치 파일의 무결성 및 안정성을 고려해야 한다. 소프트웨어 벤더는 모든 패치 에이전트 환경에 대해 패치 호환성을 고려할 수 없기 때문에 충돌로 인한 패치 적용 실패 시 충돌 원인 분석이 필요하다. 기존의 패치 관리 시스템은 테스트 환경에서 수동으로 패치 파일에 대한 무결성을 검증하고 있다. 본 논문에서는 파일 변화 모니터링을 통해 패치 테스트 및 적용 과정을 자동화하고, 변경 파일 정보를 통해 호환성 충돌 문제에 대한 분석 시간을 단축하는 방법을 제시한다.

A Study on Improving Reliability of Benefit Estimation Based on User Equilibrium Traffic Assignment Results (이용자 균형 통행배정 결과를 이용한 편익추정의 안정성 제고방안 연구)

  • Kim, Jae-Yeong;Son, Ui-Yeong
    • Journal of Korean Society of Transportation
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    • v.25 no.6
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    • pp.19-31
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    • 2007
  • When estimating the benefits from an investment project in the transportation sector, errors caused by many factors may exist. This study focuses on user equilibrium traffic assignment methods and stopping criteria. According to previous studies, when using a user equilibrium assignment model, the benefits of travel time savings can be effected by the relative gap value. As the stopping criteria decreases, the time needed for traffic assignment increases, so that lowering the criteria cannot be the best solution. Therefore, an effort is necessary to reduce this change rate and thus improve reliability. This paper considers three methods: reducing the links subject to benefit calculation, extracting sub-area O/D tables and networks, and applying the mean value of successive traffic assignment results. The results of the analysis show that the method using the mean value of five results is more proper than the other methods. Using the sub-area analysis method, if the study area is small the benefits of a project might be over- or under-estimated. This paper used a nationwide O/D table and network at peak time as a case study. The resulting patterns can differ according to basic data to be used in analysis. So further analysis using the data from metropolitan areas are needed.

Fault Tree Analysis based on State-Transition Model (상태 전이 모델 기반 결함 트리 분석)

  • Chung, In-Sang
    • The Journal of the Korea Contents Association
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    • v.11 no.10
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    • pp.49-58
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    • 2011
  • Fault Tree Analysis(FTA) builds fault trees to perform safety analysis of systems. However, building fault trees depends on domain knowledge and expertize on target systems and consumes lots of time and efforts. In this paper, we propose a technique that builds fault trees systematically based on state-transition models which are software design artifacts. For the end, this paper identifies conditions that should be satisfied to guarantee safety of state-transition models and develop templates for fault tree construction. This paper also describes the results of appling the proposed method to railway crossing control system.

Numerical simulation of local scour around porous type fish reef (다공성 인공어초의 국부세굴 특성 분석 수치모형실험)

  • Yoon, Jae Seon;Lee, Ji-Hun;Shin, Choong Hun;Ha, Taemin
    • Proceedings of the Korea Water Resources Association Conference
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    • 2019.05a
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    • pp.233-233
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    • 2019
  • 본 연구에서는 3형식 다공성 인공어초의 국부세굴 발생에 따른 인공어초의 안정성 검토를 위하여 3차원 수치모형인 FLOW-3D의 Sediment 모듈을 적용하여 분석을 실시하였다. 실험파랑 설정을 위하여 인공어초 설치 예정지인 서해 대상해역(대청도, 연평도 인근)의 100년 빈도 설계파랑을 적용하였으며, Bretschneider-Mitsuyasu 스펙트럼 기법을 통하여 파랑을 재현하였다. 원형상격자 조건은 최대 0.1m~2.0m에 해당하며, 수치모형실험 해석 시간을 고려하여 입사파랑의 진행방향으로 인공어초의 1/2 폭에 해당하는 X축(190개), Y축(80개), Z축(110~180개) 영역에 대한 격자조건 설정하고 분석을 실시하였다. 분석은 인공어초 하중에 따른 동적 거동을 반영하는 FSI(Flood Structure Interaction)기법을 적용하였으며, 분석결과 인공어초 구조물 하단의 돌출부분에서 세굴발생이 확인되었으며, 최대세굴심은 3형식 인공어초의 규격 및 단위체적당 중량이 클수록 높게 발생하였다.

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Automatic Calibration of the Storage-Function Rainfall-Runoff Model Using an Optimization Technique (최적화 기법에 의한 저류함수 유출 모델의 자동 보정)

  • Yun, Jae-Heung;Go, Seok-Gu;Kim, Yang-Il
    • Proceedings of the Korea Water Resources Association Conference
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    • 1991.07a
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    • pp.88-101
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    • 1991
  • 충주댐 및 소양강댐 유역에 대해 현재 한국수자원공사에서 개발 사용되고 있는 저류함수 유출모형에 최적화 기법을 적용하여 모형을 효율적으로 자동보정 하기위함이 본 연구의 목적이다. 최적화 기법으로는 다양한 조건하에서도 해의 안정성이 Gradient-Based 방법보다 우수한 직접 탐색법(Direct Search Method)의 하나인 Pattern-Search법으로 선정하였으며 목적함수로는 산정된 유출과 관측치의 편차의 제곱에 대한 누계치로 정의하였다. 합성유입량(Synthetic Inflow)을 이용한 민감도 분석에 의해 매개변수 5개(유역 저류상수 및 지체시간, 포화우량, 하도의 지체시간)를 결정변수로 선정하였다. 또한 실시간 모형의 보정을 위하여 최적화 모형의 수렴조건을 분석한 결과 P-S 법의 증분 감소횟수 2회가 합리적으로 나타났다. 본 모형을 충주댐 및 소양강댐의 과거 홍수사상에 대해 적용하였으며 댐지점에서 전체유역을 일괄 보정하는 방법과 댐 상류 수위국을 기준으로 나눈 중유역별로 일괄 보정하는 방법을 채택하여 분석하였다. 실시간 보정된 모형의 예측기능을 시험한 결과 상당한 오차발생의 여지가 충분하며 중유역별 매개변수의 보정은 대유역 일괄보정에 비해 예측에 따른 오차를 줄일 수 있는 방법의 하나이다. 또한 최적화 기법에 의한 매개변수의 자동 보정은 시행착오에 의한 수동보정의 경우보다 시간 및 노력면에서 효율적이며 보다 신뢰성 있는 보정을 실시 할 수 있다.

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New Synthesis of Sestamibi and Comparison of Stability of Its Formulation (Sestamibi의 신규합성과 제제화에 따른 안정성 비교)

  • Son, Mi-Won;Lim, Joong-In;Chang, Young-Soo;Jung, Mi-Young;Jeong, Lak-Shin;Kim, Soon-Hoe;Kim, Won-Bae;Jeong, Jae-Min
    • The Korean Journal of Nuclear Medicine
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    • v.35 no.5
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    • pp.334-341
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    • 2001
  • Purpose: Ascorbic acid us known to act as an antioxidant. Therefore, it can be used in increasing the efficiency of radiochemical labeling of Technetium-99m setamibi by inhibition of oxidation of $Sn^{2+}$ at low concentration. We intended to estimate the efficiency of radiochemical labeling and the stability of the newly formed formulation when ascorbic acid was added to a commercial kit. Materials and Methods: Synthesis of sestamibi was performed according to Dong-A's patent procedure (No.10-2001-0012877). First, we undertook a study to evaluate the efficiency of radiochemical labeling of sestamibi containing ascorbic acid. The stability of the vials was assessed using either $7.5{\mu}g\;or\;75{\mu}g$ of ascorbic acid, added to commercial vials under the accelerated condition(Temp : $40^{\circ}C{\pm}2^{\circ}C$, Relative humidity : $75{\pm}5%$). Results: Sestamibi was synthesized in overall 35-40% yield over 5 steps from a commercially available methallyl chloride as a starling material. When ascorbic acid was added, the efficiency of radiochemical labeling was maintained compared to the vial with no ascorbic acid. The accelerated test showed that the addition of ascorbic acid inhibited the oxidation of $Sn^{2+}$ ion by antioxidation mechanism. Also, the efficiency of radiochemical labeling of this vial after 9 months was nearly the same as the starting point. Therefore, the storage period of the kit is likely to be extended. Taken together, it suggests that the addition of ascorbic acid as a stabilizer is desirable. Conclusion: To increase the stability of a sestamibi cold kit, it is desirable to add ascorbic acid as a stabilizer to the commercial formulation.

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Copula Function Based Multivariate Flood Frequency Analysis (Copula 함수를 이용한 다변량 홍수 빈도해석)

  • Kim, Min ji;Ryou, Min-Suk;Kwon, Hyun-Han
    • Proceedings of the Korea Water Resources Association Conference
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    • 2017.05a
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    • pp.82-82
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    • 2017
  • 최근 기후변화로 인해 전 세계적으로 과거와 다른 이상홍수 발생이 빈번하게 발생하여 오래된 수공구조물인 댐, 저수지 붕괴가 우려되는 실정이다. 수공구조물의 수문학적인 안정성을 고려하지 않은 상황에서 댐 붕괴 홍수나 돌발홍수로 발생한 피해는 인명, 재산 및 환경 피해의 정도가 매우 크므로 피해가 발생하기 이전인 수공구조물 설계 시 홍수위험도 평가를 통해 안정성을 확보하는 것이 필요하다. 본 연구에서는 홍수사상의 다양한 변량들의 특성을 고려한 빈도해석을 위하여 Copula 함수를 이용한 다변량 빈도해석 기법을 개발하였다. 즉, 기존 홍수위험도 분석에서 주로 사용되는 첨두홍수량 뿐만 아니라, 홍수지속시간, 홍수체적 등을 고려한 이변량 또는 삼변량 홍수 빈도해석을 수행하고, 기존 홍수위험도와 비교 검토를 수행하고자 한다. 매개변수의 불확실성을 고려하기 위하여 매개변수 추정은 Bayesian 기법을 활용하였다.

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