• Journal of the Korean Data and Information Science Society
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• 제17권1호
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• pp.141-147
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• 2006

BOK-X12-ARIMA has been developed by the Bank of Korea in order to accomodate special features such as lunar effect, labor day and election effect which are intrinsic in Korean seasonal time series. Irregular component resulting from BOK-X12-ARIMA is usually treated as white noise time series. If this shows dependency structure, it may be advisable to incorporate dependency in irregular component into prediction. This article illustrates how to refine point forecast using dependency structure in irregular component.

• 한국해안해양공학회지
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• 제15권1호
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• pp.11-20
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• 2003

본 논문에서는 규칙파 모델을 이용하여 유공케이슨 방파제로부터의 불규칙파의 반사를 계산하는 몇 가지 방법들을 검토한다. 첫 번째 방법은 불규칙파를 파고 및 주기가 각각 불규칙파의 제곱평균제곱근 파고 및 유의주기와 같은 규칙파로 근사하는 것이다. 두 번째는 불규칙파 스펙트럼의 각 주파수 성분에 대하여 규칙파 모델을 반복적으로 사용하는 것이다. 파의 주기는 성분파의 주파수에 따라 결정되며, 모든 주파수에 대해서 제곱평균제곱근 파고를 사용한다. 세 번째 방법은 두 번째 방법과 같으나, 각 성분파의 에너지에 해당하는 파고를 사용한다. 이전 연구자들의 실험 결과와 비교해 본 결과, 두 번째 방법이 가장 타당하며, 주파수 평균 반사율과 반사파 스펙트럼 모두 실험치와 양호한 일치를 보였다.

• 수산해양기술연구
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• 제34권2호
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• pp.165-173
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• 1998

When an automatic course-keeping is concerned, as is quite popular in modem navigation, the closed-loop steering system consists of autopilot device, power unit (or telemotor unit), steering gear, magnetic or gyro compass and ship dynamics. In order to estimate automatic steering system of ships in open seas. we need to know the characteristics of each component of the system, and also to know the characteristics of disturbance to ship dynamics. In this paper, I provide calculation method of imposing irregular disturbance to autopilot navigation system of the ship in open seas, and also show calculation examples about fishing boat. The disturbance consists of the irregular wave and the fluctuating component of wind. Finally, The disturbances are calculated in terms of equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.205-208
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• 2002

Numerous studies have been performed to develop an analytical model that can predict the reflection of regular or irregular waves from a perforated-wall caisson breakwater. Though such irregular wave models as Suh et at. (2001) become available, regular wave models are still in extensive use because of their simplicity. In the present study, using the regular wave model of Fuggazza and Natale(1992), the reflection of irregular waves from a perforated-wall caisson breakwater was calculated in several different methods. First, the regular wave model was re-validated by the hydraulic model tests. Though the model somewhat over-predicted the reflection coefficients at larger values and under-predicted them at smaller values, overall agreement was pretty good between calculation and measurement. Then, the regular wave model was applied to calculate the irregular wave reflection in the experiments of Suh et at.(2001) and Bennett et al. (1992). In applying the regular wave model to irregular wave reflection, several different methods were used. The results showed that it is the most reasonable to use the regular wave model repeatedly for each frequency component of the irregular wave specuum with the root-mean-squared wave height for all the frequencies .

• Earthquakes and Structures
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• 제16권5호
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• pp.575-588
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• 2019

Seismic design method based on bearing capacity has been widely adopted in building codes around the world, however, damage and collapse state of structure under strong earthquake can not be reflected accurately. This paper aims to present a deformation-based seismic design method based on the research of RC component deformation index limit, which combines with the feature of Chinese building codes. In the proposed method, building performance is divided into five levels and components are classified into three types according to their importance. Five specific design approaches, namely, "Elastic Design", "Unyielding Design", "Limit Design", "Minimum Section Design" and "Deformation Assessment", are defined and used in different scenarios to prove whether the seismic performance objectives are attained. For the components which exhibit ductile failure, deformation of components under strong earthquake are obtained quantitatively in order to identify the damage state of the components. For the components which present brittle shear failure, their performance is guaranteed by bearing capacity. As a case study, seismic design of an extremely irregular twin-tower high rise building was carried out according to the proposed method. The results evidenced that the damage and anti-collapse ability of structure were estimated and controlled by both deformation and bearing capacity.

• 한국항해학회지
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• 제25권4호
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• pp.407-415
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• 2001

In the present study, irregular disturbances to ship dynamics is proposed, where irregular disturbances implying irregular wave and the fluctuating component of wind for the evaluation of automatic steering system of ship in following seas. Prediction method based on the principle of linear superposition. Irregular wave disturbances in following seas is calculated by frequency variation method. The mathematical model of each element of an automatic steering system is derived, which takes account of a few non-linear mechanisms. PD(Proportional-Derivative) controller and low-pass filter with a weather adjustment are adopted to modelling the characteristics of an autopilot. Performance index is introduced from the viewpoint of energy saving, which derived from the concept of energy loss on ship propulsion. Finally, the present methods are applied to two typical types of ship ; an ore carrier and a fishing boat. The various effects of control constants of autopilot on propulsive energy loss are investigated

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1995년도 춘계학술발표회 논문집
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• pp.65-92
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• 1995

The final aim of our research project is a study on assessment of automatic steering system of ships in open seas. In order to achieve this aim we need to know the characteristics of each component of the system and also to know the characteristics of disturbance to ship dynamcis. In this paper we provide calculation method of irregular disturbance to ships in autopilot navigation in open seas and also show calculation examples about two kinds of ship ore carrier and fishing boat. The disturbance consists of irregular wave and random wind, The disturbance is calculated as equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated. Further investigation concerning to performance index of autopilot system and energy loss related to automatic course keeping will be dealt with in another paper,

• 한국항해학회지
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• 제19권2호
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• pp.1-12
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• 1995

The final aim of our research project is a study on assessment of automatic steering system of ships in open seas. In order to achieve this aim, we need to know the characteristics of each component of the system, and also to know the characteristics of disturbance to ship dynamics. In this paper, we provide calculation method of irregular disturbance to ships in autopilot navigation in open seas, and also show calculation examples about two kinds of ship, ore carrier and fishing boat. The disturbance consists of irregular wave and random wind. The disturbance is calculated as equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated. Further investigation concerning to performance index of autopilot system and energy loss related to automatic course keeping, will be dealt with in another paper.

• 한국해안해양공학회지
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• 제4권2호
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• pp.72-82
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• 1992

현지 해안에서 발생하는 해빈류를 정확히 예측하기 위해서는, 해빈류의 기인력인 다방향불 규칙파낭에 의해서 발생하는 방사응력(radiation stress)에 대해서 충분히 파악해 둘 필요가 있다. 본 연구에서는, 이차원수리실험에 있어서 단일성분파, 이성분합성 파, Bretschneider-광역형의 불규칙파를 발생시켜서, 그들의 천수쇄파변형에 따른 전파특성에 대해서 고찰하고, 불규칙파의 천수쇄파변형을 해석할 경우 가정되어지는 3가지 방법, 즉 (1) 파별해석법, (2) 성분파법, (3) 대표파법의 적용성에 대해서 檢討했다. 파별해석법에 대해서는, zero-down cross 법에 의해, 파별해석되어진 불규칙파의 전파특성으로서, 통계파(최대파, 1/3유의파, rms파 등) 및 시계열중의 임의 특정의 개개파의 파고 및 주기의 천수변화라고 하는 관점으로부터 검토했다. 또한, 성분파법에 대해서는 Spectrum 해석에 의해, 입력신호인 기본주파수성분파 및 천수비파변형에 따라 증가하는 간섭주파수 성분파에 대한 파속 및 파고의 천수변형이라고 하는 관점으로부터 그 타당성에 대해서 검토했다.

• 한국해안해양공학회지
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• 제13권2호
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• pp.158-168
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• 2001

불규칙파의 방향분산과 부분쇄파의 정도 높게 고려하기 위해 광각 포물형 근사식을 이용하는 수치모형이 수립되었다. 이 수치모형은 불규칙파를 여러 개의 단일주기의 규칙파로 분해한 다음, 각 성분파를 동시계산하여 중첩함으로써 합성파고를 구한다. 불규칙파의 부분쇄파를 고려하기 위해 합성파고를 이용하여 쇄파에 의한 에너지 감쇠량을 산정한다. 기존의 불규칙파 수리실험 결과와 비교하여 수립된 수치모형의 정확성을 검사한 바, 비쇄파의 경우 규칙파와 불규칙파 모두에 대해 상당한 정확도가 있음이 확인되었으나, 쇄파 발생 시에는 수치모형의 정도가 크게 저하됨을 발견하였으며, 그 이유에 대한 분석을 제시하였다.