• Earthquakes and Structures
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• 제6권1호
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• pp.111-125
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• 2014

Multiple level performance of seismically isolated elevated storage tank isolated with multi-phase friction pendulum bearing is investigated under totally 60 records developed for multiple level seismic hazard analysis (SLE, DBE and MCE). Mathematical formulations involving complex time history analysis have been proposed for analysis of typical storage tank by multi-phase friction pendulum bearing. Multi-phase friction pendulum bearing represent a new generation of adaptive friction isolation system to control super-structure demand in different hazard levels. This isolator incorporates four concave surfaces and three independent pendulum mechanisms. Pendulum stages can be set to address specific response criteria for moderate, severe and very severe events. The advantages of a Triple Pendulum Bearing for seismic isolation of elevated storage tanks are explored. To study seismic performance of isolated elevated storage tank with multi-phase friction pendulum, analytical simulations were performed with different friction coefficients, pendulum radii and slider displacement capacities.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.177-186
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• 2000

An improved multi-level（IML) optimization algorithm using automatic differentiation (AD) for multi-objective optimum design of framed structures is proposed in this paper. In order to optimize the steel frames under seismic load, two main objective functions need to be considered for minimizing the structural weight and maximizing the strain energy. For the efficiency of the proposed algorithm, multi-level optimization techniques using decomposition method that separately utilizes both system-level and element-level optimizations and an artificial constraint deletion technique are incorporated in the algorithm. And also to save the numerical efforts, an efficient reanalysis technique through approximated structural responses such as moments, frequencies, and strain energy with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by AD that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. The efficiency and robustness of the IML algorithm, compared with a plain multi-level (PML) algorithm, is successfully demonstrated in the numerical examples.

• 한국통신학회논문지
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• 제26권11A호
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• pp.1864-1871
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• 2001

본 논문에서는 Multi-level PAM신호 방식을 사용하는 디지털 통신 시스템에 적합한 새로운 심볼 타이밍 복원알고리즘을 제시한다. 새로이 제안한 심볼 타이밍 복원 방식은 매 심볼 주기마다 다양한 신호레벨로 변하는 표본화된 심볼들의 변화량을 중간 샘플과 결정된 심볼들로 구한 기울기로 보상하여 타이밍 에러 함수를 추출한다. 종래의 심볼 타이밍 복원 방법들은 Multi-level PAM 신호에서는 충분한 성능을 발휘하지 못하였으나, 새로 제안된 방식은 QPSK뿐만 아니라 Multi-level PAM 신호에서도 적용 가능한 방식이다. 제안된 방식의 성능분석을 위하여 유도한 타이밍 에러함수의 분산 및 5-curve에서의 타이밍 에러 특성은 기존의 방식인 Gardner 방식과 Gardner방식을 수정한 방식과 비교한 바 성능이 더 우수함을 분석하였다.

• 전자공학회논문지A
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• 제32A권9호
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• pp.1167-1176
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• 1995

This paper suggests a method for optimal power assignment of the satellite transponder input carriers in the Multi-level & Multi-bandwidth system. The interference and the noise effects analyzed for the optimal power assignment are intermodulation product caused by the nonlinear transponder characteristics, adjacent channel interference, co-channel interference, and thermal noise in the satellite link. The Fletcher- Powell algorithm is used to determine the optimal input carrier power. The performance criteria for optimal power assignment is classified into 4 categories according to the CNR of destination receiver earth station to meet the requirement for various satellite link environment. We have performed mathematical analysis of objective functions and their derivatives for use in the Fletcher-Powell algorithm, and presented various simulation results based on mathematical analysis. Since the satellite link, it is meaningful to model and analyze these effects in a unified manner and present the method for optimal power assignment of transponder input carriers.

• 한국자동차공학회논문집
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• 제8권2호
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• pp.138-150
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• 2000

This study is concerned with computerized multi-level substructuring methods and stress analysis of coil springs. The purpose of substructuring methods is to reduce computing time and capacity of computer memory by multiple level reduction of the degrees of freedom in large size problems which are modeled by three dimensional continuum finite elements. In this paper, a super element has been developed for stress analysis of coil springs. The spring super element developed has been examined with tension and torsion simulation of cylindrical bars for demonstrating its validity. The result shows that the super element enhances the computing efficiency while it does not affect the accuracy of the results and it is ready for application to the coil spring analysis.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권7호
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• pp.352-360
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• 2003

This paper deals with a simple method in order to analyze and compare the harmonic characteristics in the multi-level inverter. Generally, the magnitude of harmonic components becomes different according to the multi-carrier Pulse Width Modulation(PWM) techniques, the modulation index($M_i$) and the switching frequency The previous papers analyzed the harmonic characteristics from the viewpoint of the space voltage vector. Hence, the calculation of the harmonic vector becomes more difficult and complex in 4-level or over 5-level. However, the proposed method has reduced an amount of calculation and simplified the process of it, using the relationship between the reference voltage and the output phase voltage to the load neutral point. It is applied to the 5-level cascade inverter and the harmonic characteristics for each multi-carrier PWM technique are compared through the simulation.

• 전력전자학회논문지
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• 제17권4호
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• pp.291-297
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• 2012

Recently, Switching devices become cheaper, depending on the multi-level inverters are considered as the power-conversion systems for high-power and power-quality demanding applications. The multi-level inverters can reduce the THD(Total Harmonic Distortion) as the output which is similar sinusoidal waveform by synthesizing several capacitor DC voltages. However it has some disadvantages such as increased number of components, complex PWM control method. Therefore, this paper is proposed the new multi-level inverter topology using an new H-bridge output stage with a bidirectional auxiliary switch. The proposed topology is the 4-level 3-phase PWM inverter with less switching part than conventional multi-level inverters and reactive power control possible. In order to understand the new multi-level inverter, topology analysis and switching patterns and modes according to the current loop are described in this paper. The proposed multi-level inverter topology is validated through PSIM simulation and the experimental results are provided from a prototype.

• 보건행정학회지
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• 제25권1호
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• pp.31-39
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• 2015

Background: The purpose of this study is comparison of the results between regression and multi-level analysis to find out factors influencing outcome indicators (in-hospital death, length of stay, and medical charges) of stroke patients. Methods: By using patient sample data of Health Insurance Review & Assessment Service, patients admitted with stroke were selected as survey target and 15,864 patients and 762 hospitals were surveyed. Results: For the results of existing regression analysis and multi-level analysis, models were assessed through model suitability index value and as a result, the value of results of multi-level analysis decreased compared to the results of regression, showing it is a better model. Conclusion: Factors influencing in-hospital death of stroke patients were analyzed and as a result, intra-class correlation (ICC) was 13.6%. In factors influencing length of stay, ICC was 11.4%, and medical charges, ICC was 17.7%. It was found that factors influencing the outcome indicators of stroke patients may vary in every hospital. This study could carry out more accurate analysis than existing research findings through analysis of reflecting structure at patient level and hospital level factors and analysis on random effect.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.115-124
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• 2000

An efficient multi-level (EML) optimization algorithm using discrete variables of framed structures is proposed in this paper. For the efficiency of the proposed algorithm multi-level optimization techniques using a decomposition method that separates both system-level and element-level are incorporated in the algorithm In the system-level, to save the numerical efforts an efficient reanalysis technique through approximated structural responses such as moments and frequencies with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by automatic differentiation (AD) that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. In the element-level, to use AISC W-sections a section search algorithm is introduced. The efficiency and robustness of the EML algorithm, compared with a conventional multi-level (CML) algorithm and single-level genetic algorithm is successfully demonstrated in the numerical examples.

• Journal of Preventive Medicine and Public Health
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• 제55권2호
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• pp.153-163
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• 2022

Objectives: This study divided the factors that affect participation in health screenings into individual, household, and regional levels and conducted a multi-level analysis to identify the factors related to participation in health screenings. Methods: Participants from the 2017 Community Health Survey were classified into 2 groups (under 40 and 40 or older). A multi-level logistic regression analysis was conducted to identify the factors that affected participation in health screenings. Results: The screening rate of the participants was 69.7%, and it was higher among participants aged 40 and older (80.3%) than it was among participants younger than 40 (49.8%). At the individual level, the factors that influenced participation in health screenings included age, economic activity, smoking status, physician-diagnosed hypertension, and a moderate or high physical activity level. At the household level, the odds ratio of participation in health screenings was high for participants who lived in single-person households, lived with a spouse, earned a high monthly household income, and were not beneficiaries of national basic livelihood security. At the regional level, the odds ratio at the 95% confidence interval level of participation in health screenings was high for participants who had trust in the local community and lived in an area with a proportionally high social welfare budget. Conclusions: This study analyzed nationalwide data and confirmed that individual, household, and regional characteristics affected participation in health screenings. Therefore, policies that prioritize the improvement of regional level factors and especially household level factors are likely to be the most effective for improving the screening rate.