• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.822-826
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• 2008

A linkage mechanism is a device to convert an input motion into a desired output motion. Traditional linkage mechanism designs are based on trial and error approaches so that size or shape changes of an original mechanism often result in improper results. In order to resolve these problems, an improved automatic mechanism synthesis method that determines the linkage type and dimensions by using an optimization method during the synthesis process has been proposed. For the synthesis, a planar linkage is modeled as a set of rigid blocks connected by zero-length translational springs with variable stiffness. In this study, the sizes of rigid blocks were also treated as design variables for more general linkage synthesis. The values of spring stiffness and the size of rigid block yielding a desired output motion at the end-effecter are found by using an optimization method.

• Computers and Concrete
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• 제21권5호
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• pp.593-605
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• 2018

A nonlinear finite element modeling approach is developed to assess the behavior of a dowel bar embedded on a single concrete block substrate, subjected to monotonic loading. In this approach, a discrete representation of the steel reinforcing bar is considered, using beam finite elements with nonlinear material behavior. The bar is connected to the concrete embedment through nonlinear Winkler spring elements. This modeling approach can only be used if a new constitutive model is developed for the spring elements, to simulate the deformability and strength of the concrete substrate. To define this constitutive model, an extensive literature review was conducted, as well as 3 experimental tests, in order to select the experimental data which can be used in the calibration of the model. Based on this data, an empirical model was established to predict the global dowel response, for a wide range of bar diameters and concrete strengths. This empirical model provided the information needed for calibration of the nonlinear Winkler spring model, valid for dowel displacements up to 4 mm. This new constitutive model is composed by 5 stages, in order to reproduce the concrete substrate response.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1479-1490
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• 2000

The design process of the motor driven tilt/telescopic steering column is established by axiomatic design approach in conceptual design stage. By selecting independent design variables for improvin g performance of the steering system, each detailed design can be carried out independently. In the detailed design, the safety in crash environment and vibration reduction are considered. An occupant analysis code SAFE(Safety Analysis For occupant crash Environment) is utilized to simulate the body block test. Segments, contact ellipsoids and spring-damper elements are used to model the steering column in SAFE. The model is verified by the result of the body block test. After the model is validated, the energy absorbing components are designed using an orthogonal array. Occupant analyses are performed for the cases of the orthogonal array. Final design is determined for the minimum occupant injury. For vibrational analysis, a finite element model of the steering column is defined for the modal analysis. The model is validated by the vibration experiment. Size and shape variables are selected for the optimization process. An optimization is conducted to minimize the weight subjected to various constraints.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.144-155
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• 1999

An occupant analysis code SAFE (Safety Analysis For occupant crash Environment) is utilized to simulate and improve the crash performance of an energy absorbing steering system. The safety standard FMVSS 203 is simulated and used for design evaluations . Segments and contact elliposids are utilized to model the bod blocks and the components of the steering system with SAFE. Spring-damper elements and force-deflection characteristics are utilized to model the energy absorbing components such as the plate and the polyacetal molding. The plate absorbs the impact energy through tensile deformation . Whereas, the polyacetal molding absorbs the impact energy through compression. the body block test is carried out to validate tie simulation model, and real component tests are performed to extract the force-deflection curves . After the model is validated , the parameter study is carried out to evaluate the crash performance of the energy absorbing components. A performance measure is defined for the parameter study. Using the results of the parameter study and managing the orthogonal arrays, optimum design values of energy absorbing components are determined to minize the occupant injury.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권4호
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• pp.1246-1262
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• 2021

Recent studies have demonstrated the strong ability of deep convolutional neural networks (CNNs) to significantly boost the performance in single image super-resolution (SISR). The key concern is how to efficiently recover and utilize diverse information frequencies across multiple network layers, which is crucial to satisfying super-resolution image reconstructions. Hence, previous work made great efforts to potently incorporate hierarchical frequencies through various sophisticated architectures. Nevertheless, economical SISR also requires a capable structure design to balance between restoration accuracy and computational complexity, which is still a challenge for existing techniques. In this paper, we tackle this problem by proposing a competent architecture called Enhanced U-Net Network (EUN), which can yield ready-to-use features in miscellaneous frequencies and combine them comprehensively. In particular, the proposed building block for EUN is enhanced from U-Net, which can extract abundant information via multiple skip concatenations. The network configuration allows the pipeline to propagate information from lower layers to higher ones. Meanwhile, the block itself is committed to growing quite deep in layers, which empowers different types of information to spring from a single block. Furthermore, due to its strong advantage in distilling effective information, promising results are guaranteed with comparatively fewer filters. Comprehensive experiments manifest our model can achieve favorable performance over that of state-of-the-art methods, especially in terms of computational efficiency.

• 수산해양기술연구
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• 제58권1호
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• pp.19-31
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• 2022

Damages by jellyfish are occurring frequently around the world. Among them, accidents caused by jellyfish stings are serious enough to cause death. So we designed a jellyfish blocking net and analyzed its stability to prevent sting caused by jellyfish entering the beach. To this end, the dynamic behavior of the jellyfish blocking net according to the current speed (0.25-1.0 m/s) and the net type (50, 100 and 150 mm) on the upper part of the blocking net was modeled using the mass spring model. As a result of simulations for the model, the horizontal tension (horizontal component of the mooring tension) of the mooring line increased with the decrease in the mesh size on the upper part of the blocking net at all current speeds, but exceeded the holding force at high tides faster than 0.5 m/s and exceeded the holding force at all current speeds at low tide. Therefore, the jellyfish blocking nets showed poor stability overall. The depth of the float line had a little difference according to the upper mesh size and increased lineary proportional to the current speed. However, the float line sank too much to block the incoming jellyfish. These analysis results helped us find ways to improve the stability of the jellyfish blocking net, such as adjusting the length of the mooring line and improving the holding power. Therefore, it is expected that this technology will be applied us various underwater structures to discover the weaknesses of the structures and contribute to increasing the stability in the future.

• 한국자동차공학회논문집
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• 제3권1호
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• pp.33-44
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• 1995

As the occupant safety receives more attention from automobile industries. protection systems have been developed quite well. Developed protection systems must be evaluated through real tests in crash environment Since the real tests are extremely expensive. computer simulations are replaced for some prediction of the real test In the computer simulation. it is very crucial to express the real environment precisely in the modeling precess. The energy absorbing(EA) steering system has a very important rote in vehicle crashes because the occupant can hit the system directly. In this study. the EA steering system is modeled precisely. analyzed for the safely and designed by an optimization technology. First. the EA steering system is disassembled by parts and modeled by segments and joints. The segments are modeled by rigid bodies in motion and they have resistances in contact. Spring-damper elements and force-deflection curves are utilized to represent the joints. The body block test is cal lied out to validate. the modeling. When the test results are not enough for the detailed modeling. the differences between tests and simulations are minimized to calculate unknown parameters using optimization. The established model is applied to a crash simulation of a full-car model and tuned again. After the modeling is finished. components of the steering system are designed by an optimization algorithm. In the optimization process. the compound injury of a driver is defined and minimized to determine the chracteristics of the components. The second. order approximation algorithm has been adopted for the optimization.

• 드라이브 ㆍ 컨트롤
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• 제12권3호
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• pp.52-59
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• 2015

An electro hydraulic poppet valve (EHPV) and a variable orifice poppet are assembled in a single block, which is referred to as a RHINO but is also generally called a pilot-operated flow control valve. In this study, we analyzed the structure and the operating principle for a RHINO applied in a 21-ton electric excavator system. The RHINO was experimentally tested to measure the dynamic responses and the pressure energy loss. In this test, we investigated the variation in the conductance coefficient according to the increase in the supply pressure under a constant current and a variation in the flow rate according to the increase in the current. Then, the geometrical shapes and the spring stiffness of the RHINO were considered to develop an analysis model. The characteristics (current-force and hysteresis) for the solenoid based on the experimental data were reflected in the analysis model that was developed, and the reliability of the analysis model was also verified by comparing the experimental and analytical results. The developed model is thus considered to be reliable for use in a wide range of applications, including optimum design, sensitivity analysis, parameter tuning, etc.

• 한국해안해양공학회지
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• 제16권4
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• pp.224-232
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• 2004

지난 20여년간 다양한 공사가 시행된 금강하구에서 퇴적으로 인한 수로매몰을 분석하기 위하여 1988년부터 2000년까지 매 2년 간격으로 7가지 경우에 대해 단계별로 수치수동역학모형을 적용한 후측실험이 실시되어 바닥마찰응력의 변화와 상관된 퇴적율 평가가 실시되었다. 금강하구둑 건설로 최대마찰응력장이 약 $1-2N/m^2$ 에서 $0.2-0.6N/m^2$크게 줄어들고, 특히 1994년 금강하구둑의 수문 폐쇄 이후에 장항수로에서는 해저마찰응력이 한계마찰응력으로 제시된 $0.4N/m^2$ 이하로 급감하면서 퇴적환경으로 전이되고 있는 것으로 분석되었다. 하구둑건설은 금강 상류로 전파되는 조석에너지를 차단함으로써 조석수동역학의 급격한 변화를 초래하고 하구둑 전면에 퇴적환경이 급속도로 진행되는 직접적인 원인을 제공하고 있는 것으로 추론되었다. 소형어선의 통행지장을 겪는 장항수로의 매몰평가는 평균대조 조석을 적용하여 분석한 결과 기존에 비해 20% 이상 통행지장을 받는 것으로 평가되었다.

• 한국토양비료학회지
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• 제21권4호
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• pp.386-408
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• 1988

본(本) 연구(硏究)는 배추를 대상(對象)으로 1986년(年)부터 1986년(年)까지 6년간 Lysimeter시험(試驗)과 포장시험(圃場試驗)을 통하여 기상자료(氣象資料)로 부터 생육시기별(生育時期別) 증발산량(蒸發散量)과 수량(收量)을 추정(推定)하는 모형(模型)을 개발(開發)할 목적(目的)으로 실시(實施)하였다. Lysimeter 시험(試驗)에서는 잠재증발산량(潛在蒸發散量)과 최대증발산량(最大蒸發散量)을 측정(測定)하였고, 관개포장시험(灌漑圃場試驗)에서는 시기별(時期別) 토양수분(土壤水分)을 측정(測定)하여 실증발산량(實蒸發散量)을 계산(計算)하고 수량(收量)을 조사(調査)하였다. 시험(試驗)을 통(通)하여 얻어진 성적(成績)과 기상자료(氣象資料)의 상호관계(相互關係)를 다각적(多角的)으로 비교(比較)하여 증발산량(蒸發散量)과 수량추정모형(收量推定模型)을 설정(設定)하고 검정(檢定)한 결과(結果)는 다음과 같다. 1. 잠재증발산(潛在蒸發散)의 5년간(年間) 측정치(測定値)의 평균치(平均値)는 4월초순(月初旬) 2.38mm/day 에서 시일(時日)이 경과(經過)함에 따라 점점(漸漸) 증가(增加)되어 6월중순(月中旬)에 3.98로 최고치(最高値)를 보이고 다시 감소(減少)되어 11월중순(月中旬)에는 1.06으로 떨어졌다. 기존(旣存) 공식(公式)에 의한 잠재증발산추정치(潛在蒸發散推定値)는 실측치(實測値)에 비(比)하여 Penman법(法), Radiation법(法), Blaney-Criddle법(法)은 과다(過多)하게 추정(推定)되고, Pan evaporation법(法)은 과소(過少)하게 추정(推定)되는 경향을 보였다. 추정치(推定値)와 실측치간(實測値間)에는 전체적(全體的)으로 보아 고도(高度)의 유의(有意)한 상관(相關)이 있었으나, Blaney-Criddle법(法)은 7, 8월(月)에 상관(相關)이 없다는 것이 특이(特異)하였다. 2. 기상요인중(氣象要因中) 잠재증발산량실측치(潛在蒸發散量實測値)와 유의(有意)한 상관(相關)이 있는 것은 기온(氣溫), 대기포차(大氣飽差), 일조시수(日照時數), 일사량(日射量), Pan증발량(蒸發量)이었으며, 이들 요인(要因)을 고려(考慮)한 다중회귀식(多重回歸式)은 PET산정식(算定式)으로 활용(活用)이 가능(可能)하였다. 잠재증발산량(潛在蒸發散量) 추정모형(推定模型)으로서는 Pan 증발량(蒸發量)(Eo)을 사용(使用)한 회귀식(回歸式)이 가장 간편(簡便)하고 정확(正確)하였다. PET= 0.712 + 0.705 Eo 3. 잠재증발산량(潛在蒸發散量)에 대한 최대증발량(最大蒸發量)(ETm)의 비(比)로 정의(定義)된 작물계수(作物係數)(Kc)는 배추생육초기(生育初期)에 0.5~0.7 범위(範圍)이었으며, 생육중기(生育中期)부터는 0.9~1.2범위(範圍)로 유지(維持)되었다. 작물계수(作物係數)는 생육진도(生育進度)(G ; 0~1.0)의 2차함수(次函數)로부터 추정(推定)할 수 있었다. 봄배추 : $$Kc=0.598+0.959G-0.501G^2$$ 가을배추 : $$Kc=0.402+1.887G-1.432G^2$$ 4. 최대증발산량(最大蒸發散量)에 대(對)한 실증발산량(實蒸發散量)의 비(比)로 정의(定義)된 토양수분계수(土壤水分係數)(Kf)는 근권(根圈)의 유효수분률(有效水分率)(f)이 임계치(臨界値)(fp)이상(以上)에서는 1.0 수준(水準)으로 유지(維持)되다가 그 이하(以下) 에서는 f에 따라 직선적(直線的)으로 감소(減少)되었다. Kc와 f와의 관계(關係)에 있어서 fp와 직선함수(直線函數)의 기울기는 재배시기(栽培時期)와 PET에 따라 각각 다르게 나타났다. Kf=1.0, if $$f{\geq}fp$$ $$Kf=a+b{\cdot}f$$, if f＜fp 5. 층위별(層位別) 토양수분함량(土壤水分含量)으로부더 근권(根圈)의 물보유량변화(保有量變化)(${\Delta}S$) 계산(計算)에 있어서 모관수(毛管水)의 상승(上昇)과 배수량(排水量)은 무시(無視)할 정도(程度)로 적었다. 침투량(浸透量)(I)이 있을때 표토(表土) 5cm에 보유(保有)되었다가 증발(蒸發)되어 버리는 물량(量)(Es)은 실증발산(實蒸發散) 추정한형(推定漢型)에서 별도로 고여(考濾)되어야 하며, Es는 근권(根圈)의 유효수분율(有效水分率)로부터 추정(推定)된 표사(表士) 5cm에서 증발가능(蒸發可能)한 최대(最大) 물량(Esm)과 I을 비교(比較)하여 결정(決定)할 수 있었다. Es = I if I < Esm Es = Esm if < Esm 380 6. 실증발산최(實蒸發散最)(ETa) 추정모형(推定模型)은 물수지식(收支式)에 근거(根據)하여, 모관수(毛管水)의 상하이동양(上下移動量)은 무시(無視)하고 잠재증발산양(潛在蒸發散量)(PET), Kc, Kf, Es를 고려(考慮)하여 아래식(式)으로 설정(設定)되었다. $$ETa=PET{\cdot}Kc{\cdot}Kf+Es$$ 7.배추의 상대수양(相對收量)(Y/Ym) 추정모형(推定模型)은 재배기간중(栽培期間中)의 ETa의 대수함수(對數函數)의 형태(形態)로 설정(設定)되었다. $$Y/Ym=a+b{\cdot}{\ell}n(ETa)$$ 봄배추 : a=0.07, b =0.73 가을배추 : a=0.37, b =0.66 8. 설정(設定)된 모형(模型)에 의해 추정(推定)된 실증발산양(實蒸發散量)과 상대수양(相對收量)을 실측치(實測値)와 비교(比較)하여 본 결과(結果), 실증발산추정치(實蒸發散推定値)의 평균편차(平均偏差)는 봄배추에서는 0.29mm/day, 가을배추에서는 0.19mm/day이었으며, 상대수양추정치(相對收量推定値)의 평균편차(平均偏差)는 봄배추에서는 0.14, 가을배추에서는 0.09이었다. 9. 모형설정(模型設定)이 완료(完了)된 이후(以後) 별도(別途)로 3작기(作期)에 대(對)한 실측치(實測値)와 추정치간(推定値間)의 편차(偏差)도 모형설정기간(模型設定期間)의 것보다 오히려 더 적게 나오는 경향(傾向)을 보였다. 따라서 본추정모형(本推定模型)은 실제(實際) 활용가치(活用價値)가 있다고 판단(判斷)된다.