• ETRI Journal
• /
• 제42권5호
• /
• pp.658-668
• /
• 2020

In edge computing, most procedures, including data collection, data processing, and service provision, are handled at edge nodes and not in the central cloud. This decreases the processing burden on the central cloud, enabling fast responses to end-device service requests in addition to reducing bandwidth consumption. However, edge nodes have restricted computing, storage, and energy resources to support computation-intensive tasks such as processing deep neural network (DNN) inference. In this study, we analyze the effect of models with single and multiple local exits on DNN inference in an edge-computing environment. Our test results show that a single-exit model performs better with respect to the number of local exited samples, inference accuracy, and inference latency than a multi-exit model at all exit points. These results signify that higher accuracy can be achieved with less computation when a single-exit model is adopted. In edge computing infrastructure, it is therefore more efficient to adopt a DNN model with only one or a few exit points to provide a fast and reliable inference service.

• Structural Engineering and Mechanics
• /
• 제17권5호
• /
• pp.611-626
• /
• 2004

On the basis of a structural analysis of radial gate (i.e. Tainter gate), the current paper focuses on weight minimization according to the location of the arms on a radial gate. In spite of its economical significance, there are hardly any previous studies on the optimum design of radial gate. Accordingly, the present study identifies the optimum position of the support point for a radial gate that guarantees the minimum weight satisfying the strength constraint conditions. This study also identifies the optimum position for 2 or 3 radial arms with a convex cylindrical skin plate relative to a given radius of the skin plate curvature, pivot point, water depth, ice pressure, etc. These optimum designs are then compared with previously constructed radial gates. Local genetic and hybrid-type genetic algorithms are used as the optimum tools to reduce the computing time and enhance the accuracy. The results indicate that the weights of the optimized radial gates are appreciably lower than those of previously constructed gates.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.2381-2384
• /
• 2008

The heat exchange between the Borehole Heat Exchanger(BHE) and the surrounding ground depends directly on ground thermal conductivity k at the certain site. The k is thus a key parameter in designing BHE and coupled geothermal heat pump systems. Currently, although a thermal hydraulic Response Test(TRT) is mostly used in practice, the thermal hydraulic TRT needs additional power and is generally time-consuming. A new, simple wireless probe for hi-speed k determination was introduced in this paper. This technique using a wireless probe is less time-consuming and requires no external source of energy for measurement and predicts local thermal properties by measuring soil temperatures along the depth. Measured temperature data along the depth was analyzed. As a result, the electronic wireless probe can replace the conventional hydraulic TRT method after carrying out the additional research on a lot of local heat flow, etc.

• Structural Engineering and Mechanics
• /
• 제40권5호
• /
• pp.719-743
• /
• 2011

A hybrid damage monitoring scheme using parallel acceleration-impedance approaches is proposed to detect girder damage and support damage in steel plate-girder bridges which are under ambient train-induced excitations. The hybrid scheme consists of three phases: global and local damage monitoring in parallel manner, damage occurrence alarming and local damage identification, and detailed damage estimation. In the first phase, damage occurrence in a structure is globally monitored by changes in vibration features and, at the same moment, damage occurrence in local critical members is monitored by changes in impedance features. In the second phase, the occurrence of damage is alarmed and the type of damage is locally identified by recognizing patterns of vibration and impedance features. In the final phase, the location and severity of the locally identified damage are estimated by using modal strain energy-based damage index methods. The feasibility of the proposed scheme is evaluated on a steel plate-girder bridge model which was experimentally tested under model train-induced excitations. Acceleration responses and electro-mechanical impedance signatures were measured for several damage scenarios of girder damage and support damage.

• Steel and Composite Structures
• /
• 제35권3호
• /
• pp.405-413
• /
• 2020

Current study on the buckling analysis of steel plate in composite structures normally focuses on applying finite element method to derive the buckling stress. However, it is time consuming, computationally complicated and tedious for general use in design by civil engineers. Therefore, in this study an analytical study is conducted to predict the buckling behavior of steel plates in composite structures. Hand calculation method was proposed based on energy principle. Novel buckling shapes with biquadratic functions along both loaded and unloaded direction were proposed to satisfy the boundary condition. Explicit solutions for predicting the critical local buckling stress of steel plate is obtained based on the Rayleigh-Ritz approach. The obtained results are compared with both experimental and numerical data. Good agreement has been achieved. Furthermore, the influences of key factors such as aspect ratio, width to thickness ratio, and elastic restraint stiffness on the local buckling performance are comprehensively discussed.

• Journal of Power Electronics
• /
• 제14권4호
• /
• pp.733-741
• /
• 2014

The integration of photovoltaic (PV) energy sources into DC grid has gained considerable attention because of its enhanced conversion efficiency with reduced number of power conversion stages. During the integration process, a local control unit is normally included with every power conversion stage of the PV source to accomplish the process of maximum power point tracking. A centralized monitoring and supervisory control unit is required for monitoring, power management, and protection of the entire system. Therefore, we propose a field-programmable gate array (FPGA) based centralized control unit that integrates all local controllers with the centralized monitoring unit. The main focus of this study is on the process of integrating many local control units into a single central unit. In this paper, we present design and optimization procedures for the hardware implementation of FPGA architecture. Furthermore, we propose a transient analysis and control design methodology with consideration of the nonlinear characteristics of the PV source. Hardware experiment results verify the efficiency of the central control unit and controller design.

• 한국군사과학기술학회지
• /
• 제13권5호
• /
• pp.875-885
• /
• 2010

Recently, the role of Ubiquitous Sensor Network(USN) has been considered to be essential for supporting the near future Network Centric Warfare(NCW) and Tactical Information Communication Network(TICN). In this paper, we explore a set of data storage methods(external storage, local storage and data storage) and query processing methods in WSN. In particular, we focus on analyzing a novel data structure for supporting the local storage method, named the partial ordered tree(POT). The main idea behind POT is that sensor readings are usually correlated with the physical spatial domain. With the help of POT, only a small portion of sensor nodes participate in query processing tasks, and thus network lifetime is greatly increased. Through a series of simulation experiments, we demonstrate that the POT based local storage method clearly outperforms the existing data storage methods in terms of the energy-efficiency, which directly affects the network lifetime, for processing exact match queries, range queries and top-k queries.

• 대한기계학회논문집A
• /
• 제26권4호
• /
• pp.731-738
• /
• 2002

To understand failure behavior of pipe thinned by flow accelerated corrosion, in this study, the pipe failure tests were performed on 102mm-Sch.80 carbon steel pipe with various local wall thinning shapes, and the failure mode, load carrying capacity, and deformability were investigated. The tests were conducted under loading conditions of 4-points bending and internal pressure. The experimental results showed that the failure mode of thinned pipe depended on magnitude of internal pressure and thinning length as well as loading direction and thinning depth and angle. The variation in load carrying capacity and deformability of thinned pipe with thinning length was determined by stress type appled to the thinning area and circumferential thinning angle. Also, the effect of internal pressure on failure behavior was dependent on failure mode of thinned pipe, and it promoted crack occurrence and mitigated local buckling at thinned area.

• 한국통신학회논문지
• /
• 제35권8C호
• /
• pp.713-719
• /
• 2010

협력 스펙트럼 감지 방식은 페이딩이 존재하는 환경에서 1차 사용자의 활동 유무를 알아내는 효과적인 방식으로 알려져 있다. 지금까지 협력 스펙트럼 감지에 관해 이루어진 대부분의 연구는 2차 사용자가 내린 국부 스펙트럼 감지 결정들이 통계적으로 서로 독립이라는 가정에 기초한 것이다. 그러나 실제 환경에서는 이러한 전제가 성립하지 않을 수 있다. 이 논문에서는 지역적으로 이웃한 2차 사용자의 국부 스펙트럼 감지 결정들 사이에 동일한 상관도가 존재하고, 이웃하지 않은 경우에는 통계적으로 독립인 인지 무선 네트워크를 대상으로 하여, AND 규칙과 OR 규칙을 사용하는 협력 스펙트럼 감지 방식의 성능을 분석하였다. 분석 결과, 상관 정도가 강할 때 AND 방식이 OR 방식에 비해 우수한 성능을 나타냄을 확인할 수 있었다.

• Proceedings of the National Institute of Ecology of the Republic of Korea
• /
• 제3권2호
• /
• pp.122-128
• /
• 2022

To present the spatial variation of fish assemblages in the Geum River in Korea, the concept of beta diversity (β-diversity) estimates based on the variance of the community data table was applied. Fish communities and environmental variables were collected from 13 sampling sites along the in mid-low reaches of the River. We calculated the β-diversity and local contribution to beta diversity (LCBD) values at each site depending on the two types of data, 'occurrence' with Jaccard and Sørensen dissimilarity coefficients, and 'abundance' with Hellinger distance. Multivariate and correlation analyses were also performed to determine the relationships between LCBD and other variables, such as community indices and physicochemical and hydrological factors. The β-diversity values of fish communities in the River were estimated as 0.218 and 0.145 for occurrence data table with Jaccard and Sørensen respectively, and 0.268 for abundance data. Similar patterns of LCBD along the sampling sites were detected in two dissimilarity measurements of occurrence table, and LCBD values with abundance data were slightly different. The LCBD values are strongly correlated with community indices, and also suitable for indicating the uniqueness of fish assemblages. However, further research is needed to determine the LCBD value as an indicator of environmental variability.