• Computers and Concrete
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• 제33권2호
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• pp.217-240
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• 2024

The purpose of this study is to propose new hysteretic characteristics of medium- to low-rise RC structures controlled by both shear and flexure. Through previous study, the dual lateral force-resisting system composed of shear and flexural failure members has a new failure mechanism that cooperates to enhance the flexural capacity of the flexural failure member even after the failure of the shear member, and the existing theoretical equation significantly underestimates the ultimate strength. In this study, the residual lateral strength mechanism of the dual lateral force-resisting system was analyzed, and, as a result, an equation for estimating the residual flexural strength of each shear-failure member was proposed. The residual flexural strength of each shear-failure member was verified in comparison with the structural testing results obtained in previous study, and the proposed residual flexural strength equation for shear-failure members was tested for reliability using FEA, and its applicable range was also determined. In addition, restoring-force characteristics for evaluating the seismic performance of the dual lateral force-resisting system (nonlinear dynamic analysis), reflecting the proposed residual flexural strength equation, were proposed. Finally, the validity of the restoring-force characteristics of RC buildings equipped with the dual lateral force-resisting system proposed in the present study was verified by performing pseudo-dynamic testing and nonlinear dynamic analysis based on the proposed restoring-force characteristics. Based on this comparative analysis, the applicability of the proposed restoring-force characteristics was verified.

• 한국통신학회논문지
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• 제37B권12호
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• pp.1174-1185
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• 2012

본 논문은 무선메쉬네트워크 환경에서 패킷의 지연 보장을 위한 호 접속 제어 방안을 제안하였다. 각 노드에서 클래스별 가용 대역폭을 구하여 지연 성능을 예측하고 이를 기반으로 호 접속 허용 여부를 결정짓는다. 새로운 트래픽 증가로 인해 영향 받는 모든 노드들을 호 접속 제어에 반영하여 기존 트래픽의 지연 성능이 보전되도록 하였다. 그 과정에서 추가적인 메시지 교환 없이 간섭 노드들의 가용 대역폭을 효과적으로 관측하는 방안을 제시하였다. 클래스 간의 차별화된 지연 제어는 큐잉 정책으로 수용하여 MAC 동작을 간결하게 하였다. 컴퓨터 시뮬레이션을 이용하여 제안된 방식의 타당성을 확인하였다. 새로운 호 추가에 따르는 지연 예상이 적절하게 이루어짐을 확인하였고, 호 접속 제어 기능으로 지연 성능이 보장되는 것을 보였다.

• 대한조선학회논문집
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• 제55권4호
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• pp.350-360
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• 2018

Analysis of ship's manoeuverability in shallow water is an important task from the perspective of the vessels' navigational safety. Since the number of ships operated in restricted water has increased due to the enlargement of vessels and ships represent different characteristics of the manoeuverability when operated in shallow and deep water, it is significant to evaluate ship manoeuverability at initial design stage. At the initial stage of design, the estimation of manoeuverability is generally performed with hydrodynamic coefficients estimated based on empirical formula. However, the accuracy of estimating hydrodynamic coefficients by the empirical formula in shallow water is poor compared to that in deep water. Therefore, the error in the estimation of manoeuverability increases in shallow water. In this study, CFD is proposed to improve the accuracy of manoeuverability in shallow water at the initial design stage and hydrodynamic coefficients were obtained based on PMM test in shallow water. Furthermore, the ship manoeuverability was estimated both the proposed strategy and the empirical formula. At last, validity of the proposed strategy using CFD for the estimation of manoeuverability was confirmed by comparison with the manoeuverability estimation results from model test.

• 한국강구조학회 논문집
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• 제19권3호
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• pp.313-321
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• 2007

본 연구에서는 공용 중인 현수교에서 측량된 데이터를 이용하여 현수교의 형상오차 원인을 추정하는 방법을 제시하였다. 주케이블의 여러 점에서 측량된 데이터와 설계시의 형상과의 차이를 형상오차로 정의하고, 현수교의 형상오차 원인으로 보강형 자중의 변동과 지반의 크리프로 인한 앵커리지 기초의 변형으로 가정하였다. 보강형 자중의 변동 및 앵커리지 기초의 변형에 대한 현수교 구조계의 영향행렬을 이용하여 주케이블의 형상오차를 유발한 자중의 변동량 및 기초의 변형량을 추정하였다. 공용 중인 광안대교를 대상으로 본 기법의 타당성을 검토한 후 실제 측량 데이터를 이용하여 동 교량의 형상오차 원인 분석에 적용하였다.

• 한국농공학회지
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• 제44권5호
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• pp.96-105
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• 2002

As an useful water purification system for non-point source pollution in rural watersheds, interests in constructed wetlands are growing at home and abroad. It is well known that constructed wetlands are easily installed, no special managemental needs, and more flexible at fluctuating influent loads. They have a capacity for purification against nutrient materials such as phosphorus and nitrogen causing eutrophication of lentic water bodies. The Constructed Wetland Design Model (CWDM), developed through this study is consisted mainly of Database System, Runoff-discharge Prediction Submodel, Water Quality Prediction Submodel, and Area Assessment Submodel. The Database System includes data of watershed, discharge, water quality, pollution source, and design factors for the constructed wetland. It supplies data when predicting water quality and calculating the required areas of constructed wetlands. For the assessment of design flow, the GWLF (Generalized Watershed Loading Function) is used, and for water quality prediction in streams estimating influent pollutant load, Water Quality Prediction Submodel, that is a submodel of DSS-WQMRA model developed by previous works is amended. The calculation of the required areas of constructed wetlands is achieved using effluent target concentrations and area calculation equations that developed from the monitoring results in the United States. The CWDM is applied to Bokha watershed to appraise its application by assessing design flow and predicting water quality. Its application is performed through two calculations: one is to achieve each target effluent concentrations of BOD, SS, T-N and T-P, the other is to achieve overall target effluent concentrations. To prove the validity of the model, a comparison of unit removal rates between the calculated one from this study and the monitoring result from existing wetlands in Korea, Japan and United States was made. As a result, the CWDM could be very useful design tool for the constructed wetland in rural watersheds and for the non-point source pollution management.

• 한국통신학회논문지
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• 제35권3C호
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• pp.295-301
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• 2010

본 논문에서는 프로펠러를 사용한 전자관악기를 위한 취구의 모델링 방법을 제안한다. 이 방법은 프로펠러의 각속도에 의한 바람의 세기를 계산을 빠르게 하도록 풍속계의 방식을 이용한 것이다. 풍속계의 경우에, 바람의 세기가 프로펠러의 각속도에 비례한다는 속성을 이용하여 바람의 세기를 계산한다. 하지만, 프로펠러의 각속도로부터 기대하는 바람의 세기가 계산되기까지 과도시간이 있기 때문에, 바람의 세기와 프로펠러의 각속도는 일대일대응이 아니다. 이 문제를 개선하기 위하여, 풍속계를 선형 시스템으로 해석하여, 그 시스템의 임펄스 응답과 프로펠러의 각속도를 디컨벌루션하여 바람의 세기를 추정한다. 실험으로 제안된 시스템의 타당성을 입증하기 위하여, 모터와 프로펠러, 엔코더로 구성된 취구 모델을 디자인하였다. 이 방법으로 바람의 세기를 추정한 결과는 이 시스템이 기존의 풍속계의 방법 보다 8배 빠른 시스템을 보여주었다.

• 한국광학회지
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• 제17권5호
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• pp.420-429
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• 2006

곡률, 두께, 굴절률 오차와 같은 광축대칭 오차요인들 때문에 상면이 이동하는 디지털 카메라용 줌렌즈 광학계에서 보상자를 이동시켜서 상면을 고정시키는 조건을 가우스 괄호법을 이용하여 유도하였다. 그리고 줌렌즈 광학계의 일반적인 세 가지 형태(3군, 4군, 5군 줌렌즈)를 사용하여 이 조건의 타당성을 검증하였다. 이러한 줌렌즈 형태에서 각 면의 곡률, 두께, 굴절률 등을 공차 내에서 Monte Carlo 방법에 따라 임의로 변화시켰을 때, 보상자의 이동량의 분포가 정규분포를 이루는 것을 확인하였다. 그리고 이로부터 공정능력을 계산하여 보상자의 최대 이동량에서 이에 따른 불량률을 이론적으로 예측하는 방법을 제시하였다.

• Wind and Structures
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• 제37권6호
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• pp.445-460
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• 2023

Accurate estimation of modal parameters (i.e., natural frequency, damping ratio) of tall buildings is of great importance to their structural design, structural health monitoring, vibration control, and state assessment. Based on the combination of variational mode decomposition, smoothed discrete energy separation algorithm-1, and Half-cycle energy operator (VMD-SH), this paper presents a method for structural modal parameter estimation. The variational mode decomposition is proved to be effective and reliable for decomposing the mixed-signal with low frequencies and damping ratios, and the validity of both smoothed discrete energy separation algorithm-1 and Half-cycle energy operator in the modal identification of a single modal system is verified. By incorporating these techniques, the VMD-SH method is able to accurately identify and extract the various modes present in a signal, providing improved insights into its underlying structure and behavior. Subsequently, a numerical study of a four-story frame structure is conducted using the Newmark-β method, and it is found that the relative errors of natural frequency and damping ratio estimated by the presented method are much smaller than those by traditional methods, validating the effectiveness and accuracy of the combined method for the modal identification of the multi-modal system. Furthermore, the presented method is employed to estimate modal parameters of a full-scale tall building utilizing acceleration responses. The identified results verify the applicability and accuracy of the presented VMD-SH method in field measurements. The study demonstrates the effectiveness and robustness of the proposed VMD-SH method in accurately estimating modal parameters of tall buildings from acceleration response data.

• 대한기계학회논문집A
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• 제36권2호
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• pp.223-230
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• 2012

취성이 큰 재료의 강도는 일반적으로 정규분포 또는 와이블분포로 설명되어 왔으나 감마분포도적합할 수 있다. 재료의 파손이 가해진 응력의 연속된 값 중 가장 큰 값에 좌우된다면 극치분포를 적용하는 것이 합당하다. 본 논문에서는 재료강도가 감마분포를 따르며 극치분포하는 응력이 작용할 경우 응력-강도 간섭이론에 기반하여 신뢰도 계산식을 제시하였으며, 확률분포 파라미터별 신뢰도와 안전율 및 변동계수와의 관계를 통하여 신뢰도 계산식의 유효성을 입증하였다. 안전율과 변동계수에 기반한 신뢰도 예측방법으로 목표 신뢰도가 설정되었을 때 최소한 요구되는 안전율과 최대로 허용되는 응력의 변동계수를 예측할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.634-645
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• 2014

VoIP (Voice over Internet Protocol) is a technology of transmitting and receiving voice and data over the Internet network. As the telecommunication industry is moving toward All-IP environment with growth of broadband Internet, the technology is becoming more important. Although the early VoIP services failed to gain popularity because of problems such as low QoS (Quality of Service) and inability to receive calls as the phone number could not be assigned, they are currently established as the alternative service to the conventional wired telephone due to low costs and active marketing by carriers. However, VoIP is vulnerable to eavesdropping and DDoS (Distributed Denial of Service) attack due to its nature of using the Internet. To counter the VoIP security threats efficiently, it is necessary to develop the criterion or the model for estimating the information security level of VoIP service providers. In this study, we developed reasonable security indicators through questionnaire study and statistical approach. To achieve this, we made use of 50 items from VoIP security checklists and verified the suitability and validity of the assessed items through Multiple Regression Analysis (MRA) using SPSS 18.0. As a result, we drew 23 indicators and calculate the weight of each indicators using Analytic Hierarchy Process (AHP). The proposed indicators in this study will provide feasible and reliable data to the individual and enterprise VoIP users as well as the reference data for VoIP service providers to establish the information security policy.