• Smart Structures and Systems
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• 제4권6호
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• pp.809-828
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• 2008

Real-time hybrid testing is an attractive method to evaluate the response of structures under earthquake loads. The method is a variation of the pseudodynamic testing technique in which the experiment is executed in real time, thus allowing investigation of structural systems with time-dependent components. Real-time hybrid testing is challenging because it requires performance of all calculations, application of displacements, and acquisition of measured forces, within a very small increment of time. Furthermore, unless appropriate compensation for time delays and actuator time lag is implemented, stability problems are likely to occur during the experiment. This paper presents an approach for real-time hybrid testing in which time delay/lag compensation is implemented using model-based response prediction. The efficacy of the proposed strategy is verified by conducting substructure real-time hybrid testing of a steel frame under earthquake loads. For the initial set of experiments, a specimen with linear-elastic behavior is used. Experimental results agree well with the analytical solution and show that the proposed approach and testing system are capable of achieving a time-scale expansion factor of one (i.e., real time). Additionally, the proposed method allows accurate testing of structures with larger frequencies than when using conventional time delay compensation methods, thus extending the capabilities of the real-time hybrid testing technique. The method is then used to test a structure with a rate-dependent energy dissipation device, a magnetorheological damper. Results show good agreement with the predicted responses, demonstrating the effectiveness of the method to test rate-dependent components.

• 한국화재소방학회논문지
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• 제19권4호
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• pp.37-41
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• 2005

본 연구에서는 미분무수 소화시스템의 변압기에 대한 냉각성능을 기술한다. 재발화를 방지하기 위한 냉각성능은 변압기의 철심으로부터 절연유에 전달되어 축적된 열에너지를 효과적으로 소산시키는 것을 의미한다. 철심이 매우 무겁기 때문에 축소 규모의 변압기를 이용하여 실험을 수행하였고, 이 결과로부터 냉각시간을 결정하기 위하여 상사해석을 수행하였다. 해석 및 실험을 통한 상사법칙으로부터 재발화 방지를 위한 미분무수 소화시스템의 소화시간은 약 12시간으로 나타났다.

• 한국소음진동공학회논문집
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• 제21권9호
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• pp.805-812
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• 2011

This study investigated the characteristics of heavy-weight floor impact sounds of box-frame type structure using 1:10 scale model. Ten types of floor structures(bare slabs and floating floors) were evaluated in terms of dynamic stiffness and loss factor. Floor vibrations and radiated sounds generated by simulated impact source were also measured. The results showed that the bakelite was appropriate for simulating concrete slab in the 1:10 scale model, and surface velocity and sound pressure level of concrete slab measured from the scale model showed similar tendencies with the results from in-situ in frequency domain. It was also found that dynamic behaviors of layered floor structures in the 1:10 scale model were similar to those in a real scale. Therefore, the use of 1:10 scale model would be useful for evaluating the heavy-weight floor impact sound insulation of layered floor structures when the frequency-dependent dynamic properties of each material are known.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권10호
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• pp.4060-4079
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• 2020

Blur is an important type of image distortion. How to evaluate the quality of blurred image accurately and efficiently is a research hotspot in the field of image processing in recent years. Inspired by the multi-scale perceptual characteristics of the human visual system (HVS), this paper presents a no-reference image blur/sharpness assessment method based on multi-scale local features in the spatial domain. First, considering various content has different sensitivity to blur distortion, the image is divided into smooth, edge, and texture regions in blocks. Then, the Gaussian scale space of the image is constructed, and the categorized contrast features between the original image and the Gaussian scale space images are calculated to express the blur degree of different image contents. To simulate the impact of viewing distance on blur distortion, the distribution characteristics of local maximum gradient of multi-resolution images were also calculated in the spatial domain. Finally, the image blur assessment model is obtained by fusing all features and learning the mapping from features to quality scores by support vector regression (SVR). Performance of the proposed method is evaluated on four synthetically blurred databases and one real blurred database. The experimental results demonstrate that our method can produce quality scores more consistent with subjective evaluations than other methods, especially for real burred images.

• 한국산학기술학회논문지
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• 제8권3호
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• pp.563-568
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• 2007

본 논문에서는 EVRC 시스템에 사용되어지는 실근 방식의 계산량 감소 알고리즘을 치안한다. 실근 방법에서는 다항식에서의 근을 구하여 LSP로 변환하는 과정이 필요하다. 그러나, 근을 구하는 과정에서 주파수 대역을 순차적으로 검색하므로 계산시간이 많이 소요된다. LSP 파라미터의 중요한 특징은 대부분의 계수가 특정 주파수 대역에 주로 분포한다는 것이다. 그러므로, 본 논문에서는 실근 방식에서의 계산시간을 줄이기 위하여 1KHz 대역까지는 선형적이고 1KHz 대역 이상에서는 로그 스케일인 멜 스케일을 사용하였다. 실근 방식과 제안한 방법을 비교하기 위하여 두 가지를 측정하였다. 첫째, 제안한 방법에서의 LSP 파라미터의 값과 실근방식에서의 LSP 파라미터 값을 비교하였다. 둘째, 계산 시간 감소율을 측정하였다. 실험결과, LSP 파라미터의 값은 변화하지 않았으며 계산량은 약 48% 정도 감소하였다.

• 한국통신학회논문지
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• 제25권10B호
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• pp.1675-1689
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• 2000

We present CReMeS a CORBA-compliant design and implementation of a new real-time communication service. It provides for efficient predictable and scalable communication between information producers and consumers. The CReMeS architecture is based on MidART's Real-Time Channel-based Reflective Memory (RT-CRM) abstraction. This architecture supports the separation of QoS specification between producer and consumer of data and employs a user-level scheduling scheme for communicating real-time tasks. These help us achieve end-to-end predictability and allows our service to scale. The CReMeS architecture provides a CORBA interface to applications and demands no changes to the ORB layer and the language mapping layer. Thus it can run on non real-time Off-The-Shelf ORBs enables applications on these ORBs to have scalable and end-to-end predictable asynchronous communication facility. In addition an application designer can select whether to use an out-of-band channel or the ORB GIOP/IIOP for data communication. This permits a trade-off between performance predictability and reliability. Experimental results demonstrate that our architecture can achieve better performance and predictability than a real-time implementation of the CORBA Even Service when the out-of-band channel is employed for data communication it delivers better predictability with comparable performance when the ORB GIOP/IIOP is used.

• 한국산학기술학회논문지
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• 제17권9호
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• pp.34-44
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• 2016

본 연구는 소하천을 대상으로 홍수로 인한 교량에서의 유송잡물 집적을 방지하기 위한 저감시설에 대한 실험연구이다. 일반적으로 소하천은 태풍 및 집중호우 시 유송잡물에 의한 구조물 피해가 빈번하게 발생하고 있으나 이러한 피해에 대한 저감대책은 전무한 실정이다. 국외에서는 유송잡물로 집적으로 인한 피해저감시설로 수직분리대방식, 말뚝시설방식, 스위퍼 방식에 대해 소개하고 있다. 이에 본 연구에서는 유송잡물 저감시설 중 스위퍼를 대상으로 실규모 집적실험을 통해 저감능력을 검토하고자 하였다. 스위퍼는 교각전면부에 설치하여 자력회전을 통해 유송잡물을 우회시켜 교각에 유송잡물이 집적되지 않게 만드는 시설이다. 실규모 실험을 위해 소교량 모형을 실물크기로 제작하였으며, 유송잡물 길이와 흐름조건에 따라 스위퍼 설치 전 후 집적실험을 통해 저감능력을 검토하였다. 실험결과 유송잡물의 길이가 길어지거나 유속이 적을 경우 집적률이 높게 나타나는 것으로 나타났다. 스위퍼 설치에서 따른 유송잡물의 집적률은 스위퍼 설치 전에 비해 최소 55%에서 최대 88%의 유송잡물 집적률이 저감되는 것으로 확인되었다. 이러한 결과로 판단할 때 유송잡물 잠재능력이 높은 소하천에 스위퍼를 설치할 경우 유송잡물 집적으로 인한 교량의 안정성 확보 측면에서 유리할 것으로 판단된다.

• Smart Structures and Systems
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• 제16권6호
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• pp.1003-1021
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• 2015

MR dampers have been proposed for the control of cable vibration of cable-stayed bridge in recent years due to their high performance and low energy consumption. However, the highly nonlinear feature of MR dampers makes them difficult to be designed with efficient semi-active control algorithms. Simulation study has previously been carried out on the cable-MR damper system using a semi-active control algorithm derived based on the universal design curve of dampers and a bilinear mechanical model of the MR damper. This paper aims to verify the effectiveness of the MR damper for mitigating cable vibration through a full-scale experimental test, using the same semi-active control strategy as in the simulation study. A long stay cable fabricated for a real bridge was set-up with the MR damper installed. The cable was excited under both free and forced vibrations. Different test scenarios were considered where the MR damper was tuned as passive damper with minimum or maximum input current, or the input current of the damper was changed according to the proposed semi-active control algorithm. The effectiveness of the MR damper for controlling the cable vibration was assessed through computing the damping ratio of the cable for free vibration and the root mean square value of acceleration of the cable for forced vibration.

• Wind and Structures
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• 제11권4호
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• pp.291-302
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• 2008

Three-dimensional engineering simulations of momentum-driven tornado-like vortices are conducted to investigate the flow dynamics dependency on swirl ratio and the possible relation with real tornado Fujita scales. Numerical results are benchmarked against the laboratory experimental results of Baker (1981) for a fixed swirl ratio: S = 0.28. The simulations are then extended for higher swirl ratios up to S = 2 and the variation of the velocity and pressure flow fields are observed. The flow evolves from the formation of a laminar vortex at low swirl ratio to turbulent vortex breakdown, followed by the vortex touch down at higher swirls. The high swirl ratios results are further matched with full scale data from the Spencer, South Dakota F4 tornado of May 30, 1998 (Sarkar, et al. 2005) and approximate velocity and length scales are determined.

• 한국실내디자인학회:학술대회논문집
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• 한국실내디자인학회 2007년도 춘계학술대회 논문집
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• pp.75-76
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• 2007

Recently with increasing interest in the natural science history education, a lot of natural science museums have been developed in various locations. This project is located in one of the biggest Paleozoic site, Taebak Kangwon-do. This kind museum has had important rolls in terms of education for student, destination for traveling and reservation of important holdover of the old ages. To do those kind of parts, this project has been designed with concepts and themes like; i. being organized with story telling structure with theme "secret of life and earth from Taebak" ii. combining experiences between outdoor experimental search for the real fossils and indoor educational interactions with real size model and moving films. iii. designing with strong identities of Paleozoic era. For the design identities the outer appearance was designed with motive of trilbites in an abstract way and inside was finished with exposed concrete and various size of moving films projected to walls and floor to emphasize real scale experience of the old ages.