• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2001년도 The Seoul International Simulation Conference
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• pp.440-443
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• 2001

As inter-network traffics grows rapidly, the router systems as a network component becomes to be capable of not only wire-speed packet processing but also plentiful programmability for quality services. A network processor technology is widely used to achieve such capabilities in the high-end router. Although providing two such capabilities, the network processor can't support a deep packet processing at nominal wire-speed. Considering QoS may result in performance degradation of processing packet. In order to achieve foster processing, one chipset of network processor is occasionally not enough. Using more than one urges to consider a problem that is, for instance, an out-of-order delivery of packets. This problem can be serious in some applications such as voice over IP and video services, which assume that packets arrive in order. It is required to develop an effective packet processing mechanism leer using more than one network processors in parallel in one linecard unit of the router system. Simulation analysis is also needed for verifying the mechanism. We propose the packet processing mechanism consisting of more than two NPs in parallel. In this mechanism, we use a load-balancing algorithm that distributes the packet traffic load evenly and keeps the sequence, and then verify the algorithm with simulation analysis. As a simulation tool, we use DEVSim++, which is a DEVS formalism-based hierarchical discrete-event simulation environment developed by KAIST. In this paper, we are going to show not only applicability of the DEVS formalism to hardware modeling and simulation but also predictability of performance of the load balancer when implemented with FPGA.

• Composites Research
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• 제13권6호
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• pp.39-46
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• 2000

방전가공은 공구와 공작물 사이의 얇은 간극에 전류를 방전시켜 금속을 가공하는 방법이다. 방전 와이어 가공은 전도성 와이어를 사용하는 방전가공의 특수한 예로서, 펀치나 금형제조에 널리 이용되고 있다. 와이어 방전가공에서 와이어는 와이어 가이드 및 외팔보로서 지지되어 있다. 최근 생산성의 증가추세와 더불어 와이어의 이송속도가 증가함에 따라 외팔보의 진동 등으로 인한 기계 정밀도의 저하가 우려된다. 본 논문에서는 정, 동특성이 우수한 방전가공기용 복합재료 외팔보를 설계, 제작하였다. 끼워맞춤길이와 보강 적층수의 변화에 따른 정, 동특성의 변화를 살펴보기 위하여 시편을 제작하여 하중실험을 수행하였다. 또한 유한요소 해석을 수행하여 하중실험의 결과와 상호 비교하였다. 시편실험의 결과로부터 방전가공기용 복합재료 외팔보를 설계, 제작하여 기존의 금속 외팔보와 그 성능을 상호 비교하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제3권1호
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• pp.27-36
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• 2011

In the proposed paper numerical calculations are carried out using two versions of a three-dimensional, timedomain panel method developed by the group of Prof. P. Sclavounos at MIT, i.e. the linear code SWAN2, enabling optionally the use of the instantaneous non-linear Froude-Krylov and hydrostatic forces and the fully non-linear SWAN4. The analytical results are compared with experimental results for three hull forms with increasing geometrical complexity, the Series 60, a reefer vessel with stern bulb and a modern fast ROPAX hull form with hollow bottom in the stern region. The details of the geometrical modeling of the hull forms are discussed. In addition, since SWAN4 does not support transom sterns, only the two versions of SWAN2 were evaluated over experimental results for the parent hull form of the NTUA double-chine, wide-transom, high-speed monohull series. The effect of speed on the numerical predictions was investigated. It is concluded that both versions of SWAN2 the linear and the one with the non-linear Froude-Krylov and hydrostatic forces provide a more robust tool for prediction of the dynamic response of the vessels than the non-linear SWAN4 code. In general, their results are close to what was expected on the basis of experience. Furthermore, the use of the option of non-linear Froude-Krylov and hydrostatic forces is beneficial for the accuracy of the predictions. The content of the paper is based on the Diploma thesis of the second author, supervised by the first one and further refined by the third one.

• 한국인터넷방송통신학회논문지
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• 제20권4호
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• pp.1-6
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• 2020

본 논문에서는 효율적인 AES 암호화를 위한 곱셈역원 연산기인 S-Box 설계를 제안한다. 제안한 방법은 먼저, 합성체 기반의 개선된 S-Box 모듈을 설계하고, 다단 파이프라인(multi-stage pipeline) 구조의 S-Box의 성능을 평가한다. 제안하는 S-Box 모듈에서의 곱셈역원 연산은 조합 논리로 구성되기 때문에 하드웨어 부담이 감소되고 처리 속도가 개선된다. 논리합성을 통하여 3-단 파이프라인 구조의 S-Box 의 경우, 기존 방법과의 연산속도 비교에서 약 28% 정도 개선됨을 보인다. 본 논문에서 제안한 개선된 S-Box는 Verilog-HDL을 사용하여 혼합 레벨에서 모델링을 행하였으며, Xilinx ISE 14.7툴을 사용하여 Spartan 3s1500l FPGA 상에서 합성을 수행하였다. 그리고 타이밍 시뮬레이션(ModelSim PE 10.3 사용)을 통하여 설계된 S-Box가 정상적으로 동작함을 확인하였다.

• Ocean Systems Engineering
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• 제7권2호
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• pp.143-155
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• 2017

For complex flexible structures such as nets, the determination of drag forces and its deformation is a challenging task. The accurate prediction of loads on cages is one of the key steps in designing fish farm facilities. The basic physics with a simple cage, can be addressed by the use of experimental studies. However, to design more complex cage system for various environmental conditions, a reliable numerical simulation tool is essential. In this work, the current load on a cage is calculated using a Morison-force model applied at instantaneous positions of equivalent-net modeling. Variations of solidity ratio ($S_n$) of the net and current speed are considered. An equivalent array of cylinders is built to represent the physical netting. Based on the systematic comparisons between the published experimental data for Raschel nets and the current numerical simulations, carried out using the commercial software OrcaFlex, a new formulation for $C_d$ values, used in the equivalent-net model, is presented. The similar approach can also be applied to other netting materials following the same procedure. In case of high solidity ratio and current speed, the hybrid model defines $C_d$ as a function of Re (Reynolds number) and $S_n$ to better represent the corresponding weak diffraction effects. Otherwise, the conventional $C_d$ values depending only on Re can be used with including shielding effects for downstream elements. This new methodology significantly improves the agreement between numerical and experimental data.

• Journal of Preventive Medicine and Public Health
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• 제28권4호
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• pp.765-771
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• 1995

치과용 핸드피스에서 발산하는 고주파수의 진동에 의한 일시적 진동감각역치 변화를 관찰하고자 치과위생병 28명을 대상으로 34,000rpm의 low-speed handpiece를 진동기구로 사용하였다. 진동에 폭로시키기 전과 후, 치과의사가 스케일링시 취하는 작업자세에 5분간 폭로시킨 후의 진동감각역치를 청력계기의 골전도진동기를 사용하여 250 Hz에서 그들이 주로 사용하는 손의 제2지두수에서 측정한 결과, 각각 $23.5{\pm}3.5dB,\;30.8{\pm}4.2dB,\;23.7{\pm}4.6dB$로 진동에 5분간 폭로시킨 후의 역치가 폭로 전에 비해 7.3dB의 유의한 증가가 있었다(p<0.001). 진동폭로 전후의 차이에 따른 분포를 보면, 10 dB 내외로 증가한 사람이 71.4%로 대부분이었고 16 dB의 증가가 가장 높았다. 진동 폭로 전의 진동감각역치와 신장, 체중, 체질량 지수와의 상관관계는 각각의 상관계수가 0.0360, -0.1657, -0.2641로 통계적 유의성은 없었으며, 흡연에 따른 차이도 흡연군(N=20)과 비흡연군(N=8)의 진동감 각역치가 각각 23.1 dB, 24.6 dB로 그 차이 가 없었다. 본 연구 결과로 볼 때 핸드피스와 같은 고주파-진동기구를 사용하는 치과의사 및 치과위생사에게서 진동감각역치의 변화가 예상되며, 말초신경병증의 원인이 될 수 있는 작업자세에 의한 장기간의 영향 및 아말감 충전시 사용하는 수은의 영향에 대해서도 연구가 필요할 것으로 생각된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.427-434
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• 2011

This paper is focused on application of recursive least squares method to estimate rail irregularities from the acceleration measurement on an axle-box or a bogie for the rail condition monitoring with in-service high-speed trains. Generally, the rail condition was monitored by a special railway inspection vehicle but the monitoring method needs an expensive measurement system. A monitoring method using accelerometers on an axle-box or a bogie was already proposed in the previous study, and the displacement was successfully estimated from the acceleration data by using Kalman and frequency selective band-pass filters. However, it was found that the displacement included not only the rail irregularities but also phase delay of the applied filters, and effect of suspension of the bogie and conicity of the wheel. To identify the rail irregularities from the estimated displacement, a compensation filter method is proposed. The compensation filters are derived by using recursive least squares method with the estimated displacement as input and the measured rail irregularity as output. The estimated rail irregularities are compared with the true rail irregularity data from the rail inspection system. From the comparison, the proposed method is a useful tool for the measurement of lateral and vertical rail irregularity.

• Archives of Plastic Surgery
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• 제46권6호
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• pp.603-607
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• 2019

During a full-thickness skin graft procedure, the thickness of the harvested donor skin is adjusted based on the location of the recipient site and the judgment of the surgeon. Conventionally, the thickness of the harvested skin is roughly adjusted using surgical instruments such as scalpels and scissors. However, this method is not only time-consuming, but also requires effort to obtain both the desired thickness of the harvested skin and a smooth surface of that skin. Moreover, there is a possibility of skin perforation. Hence, the authors devised a method of adjusting harvested skin thickness using the Versajet Hydrosurgery System. The Versajet device is a handheld hydrosurgical tool that delivers a high-speed jet stream of saline solution, which enables the precise debridement of tissue. This method makes it easier and faster for the surgeon to obtain the desired thickness of harvested skin. In addition, by obtaining a smooth surface and an even thickness of harvested donor skin, this technique may lead to improved graft viability.

• 한국CDE학회논문집
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• 제18권2호
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• pp.148-154
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• 2013

Han-ok (the Korean traditional house) is famous for its beauty and healthful aspects. However, its construction cost is too high because of the manual process of parts such as rafter, timber, etc. These days, many people want to build a modernized Korean traditional house at a low cost. In order to do so, the rafter machining process is required to be automatized using a CNC machine. It is also observed that, generally the timber does not have a uniform shape. Therefore, it is also needed to examine the timber shape before starting its processing. This paper presents the concept design of the rafter processing CNC machine, and a 3D laser scanning system. The laser scanner is developed to acquire 3D details of the timber shape. Furthermore, the results of simulated experiments are presented to investigate surface roughness during the machining process of the timber. Since cutting parameters largely influence on surface roughness and cusps formation, it is needed to achieve optimal machining parameters. Several experiments were carried out changing cutting parameters such as cutting tool diameter, feed-rate, and spindle speed.

• Smart Structures and Systems
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• 제15권2호
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• pp.283-297
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• 2015

Jacket-type offshore structures are always exposed to severe environmental conditions such as salt, high speed of current, wave, and wind compared with other onshore structures. In spite of the importance of maintaining the structural integrity for an offshore structure, there are few cases to apply a structural health monitoring (SHM) system in practice. The impedance-based SHM is a kind of local SHM techniques and to date, numerous techniques and algorithms have been proposed for local SHM of real-scale structures. However, it still requires a significant challenge for practical applications to compensate unknown environmental effects and to extract only damage features from impedance signals. In this study, the impedance-based SHM was carried out on a 1/20-scaled model of an Uldolmok current power plant structure in Korea under changes in temperature and transverse loadings. Principal component analysis (PCA)-based approach was applied with a conventional damage index to eliminate environmental changes by removing principal components sensitive to them. Experimental results showed that the proposed approach is an effective tool for long-term SHM under significant environmental changes.