• Steel and Composite Structures
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• 제50권3호
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• pp.347-362
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• 2024

Controlling vibrations and noise in steel box girders is important for reducing noise pollution and avoiding discomfort to residents of dwellings along bridges. The fundamental approach to solving this problem involves first identifying the main path of transmission of the vibration energy and then cutting it off by using targeted measures. However, this requires an investigation of the characteristics of flow of vibration energy in the steel box girder, whereas most studies in the area have focused on analyzing its single-point frequency response and overall vibrations. To solve this problem, this study examines the transmission of vibrations through the segments of a steel box girder when it is subjected to harmonic loads through structural intensity analysis based on standard finite element software and a post-processing code created by the authors. We identified several frequencies that dominated the vibrations of the steel box girder as well as the factors that influenced their emergence. We also assessed the contributions of a variety of vibrational waves to power flow, and the results showed that bending waves were dominant in the top plate and in-plane waves in the vertical plate of the girder. Finally, we analyzed the effects of commonly used stiffened structures and steel-concrete composite structures on the flow of vibration energy in the girder, and verified their positive impacts on energy regionalization. In addition to providing an efficient tool for the relevant analyses, the work here informs research on optimizing steel box girders to reduce vibrations and noise in them.

• International Journal of Railway
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• 제2권4호
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• pp.139-146
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• 2009

Vehicle braking in non-electrified rail systems wastes energy. Advanced flywheel technology presents a way to capture and reuse this braking energy to improve vehicle efficiency and so reduce the operating costs and environmental impact of diesel trains. This paper highlights the suitability of flywheels for rail vehicle applications, and proposes a novel mechanical transmission system to apply regenerative braking using a flywheel energy storage device. A computational model is used to illustrate the operation and potential benefits of the energy storage system.

• 전기학회논문지P
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• 제67권2호
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• pp.112-118
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• 2018

In recent years, decentralized power have been increasing due to environmental problems, liberalization of electricity markets and technological developments. These changes have led to the evolution of power generation, transmission, and distribution into discrete sectors and the division of integrated power systems. Therefore, studies are underway to efficiently supply power and reduce losses to each sector's demand. This is a major concern for system planners and operators, as it accounts for a relatively high proportion of total power, with a transmission and distribution loss of 4-6%. Therefore, this paper analyzes the status of loss management based on the current transmission and distribution loss rate of each country and transmission loss management cases of each national power company, and proposes a loss rate prediction algorithm according to the long-term transmission system plan. The proposed algorithm predicts the demand-based long-term evolution and the loss rate of the grid to which the transmission plan is applied.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.960-965
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• 2014

Transmission loss of specimen is calculated by measuring energy of incident and transmission and using reverberant room of large size. But normal measurement of transmission loss has trouble because it is actually demanded that large area and specimen of certain size is satisfied with condition of diffused sound field. Especially, in case of mechanical component, interested frequency band is mid-frequency band between 500 ~ 2k Hz, and it is used to be available to minimize a reverberation chamber under conditions satisfying acoustic one because production of specimen for transmission loss measurement has limit. But, as in semi-reverberation room, it is difficult to satisfy condition of diffuse sound field and modification factor is applied to complement that. Correction factor when measuring transmission loss using semi-reverberation chamber is required accuracy because it works as main factor determining reliability of reuslts on transmission loss. In this study, it is analyzed that an effect on correction factor based on varying materials and sizes of specimens in order to deduction of it. Also It is confirmed that applied by elicited correction factor with actual railway vehicle's floor has reliability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2098-2117
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• 2012

This paper jointly investigates the bandwidth allocation, transmission strategy and relay positions for two-way transmission aware cellular networks with network coding (NC). Our goal is to minimize the transmission power of mobile terminals (MTs). Consider a cellular system, where multiple MTs exchange information with their common base station, firstly, we propose an efficient bandwidth allocation method and then give a transmission strategy for each MT to determine whether to use relay stations (RSs) for its two-way transmission with the BS or not. To further improve the system performance, the optimal positions of RSs are also jointly discussed. A GA-based algorithm is presented to obtain the optimum positions for RSs. Besides, the impacts of frequency reuse on MT's transmission power and system spectral efficiency (SE) under different number of relays are also discussed in our work. Numerical results show that the proposed NC aware scheme can extend MTs' battery life at least 6% more than traditional method.

• 한국소음진동공학회논문집
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• 제22권8호
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• pp.777-783
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• 2012

진동 인텐시티는 진동시스템에서 진동원의 위치를 찾는데 사용되어 왔다. 벡터 표현법 사용에 의해 파워흐름의 원인과 진동에너지 전달경로가 밝혀질 수 있다. 그러나, 판과 같은 구조물의 넓은 면적으로 인해 벡터 가시화를 사용하여 명확한 전달경로를 알아낼 수 없었다. 실험적으로 큰 면적의 물체에서는 측정점의 수가 늘어나게 된다. 이것은 측정에 많은 시간이 요구된다. 이번 연구에서는 FEM과 실험에 의한 모든 면에서 파워흐름 전달경로를 분명하게 가리키기 위해 유선 표현법이 사용되었다. 진동 인텐시티 전달경로를 분명하게 향상시키기 위해 실험과 FEM으로부터의 유선 표현을 비교하였다. 또한 FEM과 실험의 개선된 전달경로 가시화를 기존의 벡터표현과 비교하였다. 이 유선 가시화는 큰 표면을 갖는 판과 같은 구조물에 대해 진동원과 상세한 에너지 전달경로를 확인하는데 유용하다. 그 뿐만 아니라, 이 가시화 방법은 실험과 FEM 해석에 대해 많은 측정점을 필요로 하지 않는다.

• 한국컴퓨터정보학회논문지
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• 제16권4호
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• pp.119-126
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• 2011

지그비 네트워크는 비콘 전송 방식을 사용하는 경우 지그비 기기들은 코디네이터의 전송 범위 제약을 받고, 비콘 전송 방식을 사용하지 않는 경우는 지그비 기기들이 특정 시간에만 동작하고 나머지는 sleep 모드로 전환하는 에너지 절약 방법을 적용하기 쉽지 않다. 본 논문에서는 비콘 전송 방식을 사용하지 않고 특정 전송 시간을 지정해 주는 활성화 슬롯할당 방법을 제안한다. 지그비의 분산 주소 할당 기법을 기반으로 하며 코디네이터의 전송범위 제약을 받지 않아 확장성을 지원해준다. 본 논문에서는 활성화 슬롯의 구조와 활성화 슬롯을 할당해주는 순서에 대해 설명하고 이를 지그비 기기들의 동작 방식에 대해 기술한다. 모의실험을 통하여 제안한 방식을 검증하고 성능 평가를 보인다. 제안 방안은 산업 자동화와 환경 감시 등의 큰 규모의 네트워크에 유용하게 활용될 수 있다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제16권11호
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• pp.1081-1085
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• 2010

무선 센서 네트워크에서는 전송파워 제어를 이용하여 전력소비를 줄이고 채널간의 간섭을 줄일 수 있다. 무선 링크의 품질은 시간 및 공간적인 상황에 따라 변화하기 때문에 링크의 실패가 빈번하다. 기존의 전송파워 제어 기법은 링크 품질 변화에 적응할 수 있도록 주기적으로 이웃 노드와 비컨 패킷을 주고 받아 동적으로 전송파워를 조절하도록 하였다. 하지만 전송파워를 조절하는 주기에 따라서 링크 품질의 변화에 적용하는 시간과 트래픽 및 에너지 오버헤드에 영향을 줄 수 있다. 본 논문에서는 링크의 품질변화에 따른 동적인 전송파워 제어 기법과 전송파워 제어 주기를 변경하는 기법을 제안한다. 이를 통하여 링크가 불안정할 때에는 전송파워 제어 주기를 감소시켜 민첩하게 링크 품질을 유지하며, 링크가 안정할 때는 전송파워 제어 주기를 증가시켜 이에 따른 프로토콜의 오버헤드를 줄이고자 하였다.

• 조명전기설비학회논문지
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• 제29권1호
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• pp.86-93
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• 2015

Globally, wind power development is experiencing dramatic growth and wind power penetration levels are increasing. Wind generation is highly variable in time and space and it doesn't guarantee the system reliability and secure system operation. As wind power capacity becomes a significant portion of total generation capacity, the reliability assessment for wind power are therefore needed. At present, this operational reliability assessment is focusing on a generation adequacy perspective and does not consider transmission reliability issues. In this paper, we propose the critical transmission operating constraint prediction(CTOCP) system with high wind power penetration to enhance transmission reliability.

• 한국정밀공학회지
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• 제31권4호
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• pp.343-351
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• 2014

Washing machines designed to clean laundry have been more widely used at home as they reduce household labor and boost the quality of life. Technological advances and better standards of life increase demand for laundry washing performance. Energy efficiency regulations and consumer demand for the larger trend, washing machine makers should be done in performance studies to reduce power, and water consumption and the load on power transmission devices. In this study, performance of a fully automatic washing machine with unconstrained transmission is analyzed through experiment and CFD simulation. It is found that the interaction between laundry and transmission change the washing behavior and affect washing performance with regard to the degree of freedom. The results obtained in this study can be used in developing new washing machine transmissions and make them more robust.