• Structural Engineering and Mechanics
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• 제82권4호
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• pp.517-542
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• 2022

The effect of mean angle of wind attack on the flutter critical wind speed of two generic bridge deck cross-sections, viz, one closed box type streamlined section (deck-1) and closed box trapezoidal bluff type section with extended flanges/overhangs (deck-2) type of section have been studied using Computational Fluid Dynamics (CFD) based forced vibration simulation method. Owing to the importance of the effect of the amplitude of forcing oscillation on the flutter onset, its effect on the flutter derivatives and flutter onset have been studied, especially at non-zero mean angles of wind attack. The flutter derivatives obtained have been used to evaluate flutter critical wind speeds and flutter index of the deck sections at non-zero mean angles of wind attack studied and the same have been validated with those based on experimental results reported in literature. The value of amplitude of forcing oscillation in torsional degree of freedom for CFD based simulations is suggested to be in the range of 0.5° to 2°, especially for bluff bridge deck sections. Early onset of flutter from numerical simulations, thereby conservative estimate of occurrence of instability has been observed from numerical simulations in case of bluff bridge deck section. The study aids in gaining confidence and the extent of applicability of CFD during early stages of bridge design, especially towards carrying out studies on mean incident wind effects.

• Wind and Structures
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• 제36권6호
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• pp.423-434
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• 2023

Aerodynamic force coefficients are generally obtained from traditional wind tunnel tests or computational fluid dynamics (CFD). Unfortunately, the techniques mentioned above can sometimes be cumbersome because of the cost involved, such as the computational cost and the use of heavy equipment, to name only two examples. This study proposed to build a deep neural network model to predict the aerodynamic force coefficients based on data collected from CFD simulations to overcome these drawbacks. Therefore, a series of CFD simulations were conducted using different geometric parameters to obtain the aerodynamic force coefficients, validated with wind tunnel tests. The results obtained from CFD simulations were used to create a dataset to train a multilayer perceptron artificial neural network (ANN) model. The models were obtained using three optimization algorithms: scaled conjugate gradient (SCG), Bayesian regularization (BR), and Levenberg-Marquardt algorithms (LM). Furthermore, the performance of each neural network was verified using two performance metrics, including the mean square error and the R-squared coefficient of determination. Finally, the ANN model proved to be highly accurate in predicting the force coefficients of similar bridge sections, thus circumventing the computational burden associated with CFD simulation and the cost of traditional wind tunnel tests.

• 디지털융복합연구
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• 제16권12호
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• pp.571-577
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• 2018

자전거 이용자가 안경 및 선글라스를 쓴 상태에서 마스크를 착용 할 때 여러 가지 불편함을 호소한다. 본 논문은 이러한 불편함을 보완하여 자전거 라이더들에게 필요한 일회용 미세먼지 마스크를 개발하는데 그 목적이 있다. 미세먼지 마스크의 특성상 일회성 정전기 발생 섬유와 마스크의 형태적 문제로 연구범위를 제한하고 기존 미세먼지 마스크를 간결한 제작공정으로 디자인한다. 이렇게 개발된 일회용 미세먼지 마스크는 세로방향 접힘으로 입 앞 마스크 내 공간을 충분히 확보하였고 거친 숨에도 입에 닿지 않게 접힘 부위형태가 유지 되게 하여 답답함을 최소화 하였다. 코지지대에 유선형 스폰지를 부착하고 안면 볼 부위를 일반마스크 보다 2.5cm 정도의 확장하여 측면 밀착성을 높였다. 또한 기존에 없던 일회용 미세먼지 스카프 마스크를 제작하여 안면과 목 부위 자외선을 차단하고 밀착성 높은 미세먼지 마스크를 개발하였다.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.644-652
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• 2018

본 논문은 제품 교체 주기가 비교적 짧고 정기적인 IT 제품의 조립 공정 맞춤형 그리퍼 개념 설계에 관한 내용을 담고 있다. 제조 현장에서 쓰이는 그리퍼는 대부분 1~2 자유도로 간단하게 구성되고 한 번에 다양한 물체가 아닌 정해진 것만 다룬다. 또한 가격이 중요한 비중을 차지한다. 만약 공정에 적합한 그리퍼를 빠르고 쉽게 개발 할 수 있다면 제품 및 공정의 잦은 변경에 따른 자동화의 어려움을 일부 해소할 것으로 기대한다. 연구에 필요한 조립 공정은 재조사의 기밀인 관계로 공정 분석 진행 절차와 방법을 정의하고 기술하였다. 공리적 설계를 이용해 테블릿 PC 조립을 위한 그리퍼의 기능 요구와 설계 파라미터를 도출하였다. 이러한 파라미터를 결정함으로써 그리퍼의 개념 설계가 이루어질 수 있도록 설계 방법을 제안하였다. 타당성 검토를 위해 특정 공정을 선택하고 그리퍼 설계 진행 과정을 예재로 기술하였다. 그리퍼 설계 지침에 관한 연구가 있지만 고려 사항이 너무 일반적이고 아이디어 도출의 자유도가 높은 문제가 있다. 본 논문은 제품 및 자동화 시장이 활성화 된 IT 제품의 조립 공정을 바탕으로 그리퍼의 기능을 정의하였다. 이를 통해 물체를 잡는 것에 그치지 않고 조립 과정을 반영한 설계를 목표로 하였다.

• 한국농촌건축학회논문집
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• 제14권4호
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• pp.1-9
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• 2012

Recently, the central and local government support various improvement projects on existing public buildings and areas. Improving public use and environment of these areas is adequate because financial condition of local city is not enough to build new infrastructures. As one of the projects, Geochang-Eup(Geochang-Gun, Gyeongnam Province) is selected as the project site since most of the public buildings and areas of the city are located close each other in downtown but not streamlined in function and use nor easily accessible. The purpose of this study is to analyze the causes of decline in local city and to present strategies to vitalize the city through improving environment of public areas. And we analyzed the problems by discussion with local officer, field investigation on the site and paper survey. The analysis shows that public infrastructures are grouped by function: administration, education, life support, culture, health, etc, but not well-connected, easily accessible, adequately located, various in use nor enough in quantity. This study summarized the problems into five categories: Access&Linkage, Safe&Comfort, Identity&Image, Usage&Activity and Ownership&Management and proposes strategy in three phases. The first phase is to improve functions and design of public places per each area: more consistent design on public buildings, better civil facilities and better accessibility to public areas. The second is to vitalize of the areas and to improve efficiency in use through linking each other physically and sharing uses. The third is to encourage citizen's participation and by developing civil programs to streamline public areas each other.

• 한국산학기술학회논문지
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• 제21권5호
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• pp.103-110
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• 2020

수중 로봇의 가장 기본 성능이라 할 수 있는 동적 성능인 유영속도와 동적 효율 향상을 위해 수중생물을 모사한 로봇들이 주로 연구되고 있다. 그중에서 생체모사 소프트 로봇은 유연한 꼬리지느러미를 적용함으로써 높은 자유도를 구현할 수 있다. 다만, 유연한 구동부의 효율을 높이기 위해서는 구동 주파수에 맞추어 꼬리지느러미의 강성이 바뀌어야 한다. 따라서, 연구를 통해 새로운 형태의 가변강성 메커니즘을 구현하고, 이를 연구 과정에서 검증하였다. 본 연구에서는 실제 돌고래의 해부도에서 영감을 얻어, 가변강성 메커니즘을 적용한 돌고래 로봇을 새로이 설계하고 제작하는 과정을 기술하였다. 실제 돌고래의 척추 모양을 모사하여, 절삭과 적층형 공정으로 가변강성 구동부를 제작하였다. 로봇 돌고래를 구동하기 위한 텐던도 실제 돌고래의 텐던 위치를 고려하여 배치하였으며, 추가로 강성 변화를 위한 텐던을 설치하였다. 돌고래의 유선형 외형을 모사하여 로봇 돌고래를 제작하였고, 강성 변화에 따른 로봇 돌고래의 유영속도를 측정하였다. 동일한 구동 주파수에 꼬리지느러미 구동부의 강성을 변화시켰을 때, 로봇 돌고래의 유영속도의 차이가 약 1.24배, 추력으로는 약 1.5배 변화하였다.

• 복식
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• 제57권3호
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• pp.90-107
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• 2007

Modernization movement has affected classical operas. Today, classical operas are often re-interpreted from the modern perspective and played differently only with the storyline maintained. Also, operas are increasingly performed outside traditional theaters as the boundaries between stage and audience become less obvious. Accordingly, stage costumes are being differently designed than before. New attempts are being made to look costumes in a harmony with increasingly streamlined stage machinery. This helps increase public attention on operas, consequently promoting the opera industry. This study examines modernization of opera costumes. For this study, the author worked as one of costume design staff for "Faust," which was played in Sungnam Art Center from November 24, 2005 to November 27, 2005 in commemoration of the opening of the center. The following outcomes of the crowd are drawn from this study. A variety of splendid pink dresses, ribbons, dolls, hand mirror, and hair bands were used to express haughty girls with "Princess Syndrome." Fashion models, the envy of all woman, wore fashionable clothes including luxury dresses, fur-coats, high heels, purses, and hats, Models also had big shopping bags and gift boxes to symbolize shopping lovers in a modern society. Gay men wore tight leather trousers and vest and sleeves shirts with deeply cut neckline to express their preference for feminie style. their clothes were splendid colors that normally women liked such as gold, purple, light green, scarlet, and silver. Soldiers were in combat uniform representing their participation in the war. In particular, clothes stained with dirt, iron helmet, crutches, and canteens were used to vividly express soldiers coming back home from the war. Modern opera costumes now help reduce the time and space between stage and audience, improve economic efficiency, and meet the audience's needs for various style.

• 한국실내디자인학회논문집
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• 제15권4호
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• pp.21-28
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• 2006

To promote environmentally responsible architectural practice, many nations have established their own green building rating system. Among other criteria, recently the indoor environmental quality section has been paid great attention due to Sick Building Syndrome, as this believed to caused by polluted indoor environment. In this context, indoor environmental quality is one of very important sections of each green building rating system and closely related to the very happiness of building users. The goal of this research is to compare and analyze the indoor environmental sections of three green building rating systems, GBCC, LEED v2.1, and BREEAM Office 2005, and find a direction for the improvement of GBCC. First, the three rating systems are analyzed in general to compare the importance of indoor environmental factors in each system. Second, the indoor environmental factors are reclassified within related sub-categories for the comparable analysis. Finally, based upon the comparable analysis, directions for the improvement of GBCC are as follows: 1. GBCC's h4r Environment Section needs to clarify its VOCs criteria based upon types of finish materials. 2. Sound Environment Section's noise control criteria needs to be revised based upon types of building usages and application method. 3. An indoor lighting related section needs to be included in GBCC, as even though light is the one of the most important factors in indoor environment, it has not been included in GBCC yet. 4. The sub-section of Confortable Indoor Environment Section related to the resting space and the universal accessibility are not in accord with the goal of green building rating system. These items need to be dealt within general building codes. 5. The rating evaluation structure and process need to be streamlined.

• Smart Structures and Systems
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• 제15권3호
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• pp.769-785
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• 2015

Although timber structures have been extensively used in underground temporary supporting system, their actual performance is poorly understood, resulting in potentially conservative and over-engineered design. In this paper, a novel wireless sensor technology, SmartPlank, is introduced to monitor the field performance of timber structures during underground construction. It consists of a wooden beam equipped with a streamlined wireless sensor node, two thin foil strain gauges and two temperature sensors, which enables to measure the strain and temperature at two sides of the beam, and to transmit this information in real-time over an IPv6 (6LowPan) multi-hop wireless mesh network and Internet. Four SmartPlanks were deployed at the London Underground's Tottenham Court Road (TCR) station redevelopment site during the Stair 14 excavation, together with seven relay nodes and a gateway. The monitoring started from August 2013, and will last for one and a half years until the Central Line possession in 2015. This paper reports both the short-term and long-term performances of the monitored timber structures. The grouting effect on the short-term performance of timber structures is highlighted; the grout injection process creates a large downward pressure on the top surface of the SmartPlank. The short and long term earth pressures applied to the monitored structures are estimated from the measured strains, and the estimated values are compared to the design loads.

• 한국해양공학회지
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• 제35권6호
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• pp.434-445
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• 2021

This paper proposes an optimal design method for an unmanned underwater vehicle (UUV) platform to overcome strong current. First, to minimize the hydrodynamic drag components in water, the vehicle is designed to have a streamlined disc shape, which help maintaining horizontal motion (zero roll and pitch angles posture) while overcoming external current. To this end, four vertical thrusters are symmetrically mounted outside of the platform to stabilize the vehicle's horizontal motion. In the horizontal plane, four horizontal thrusters are symmetrically mounted outside of the disc, and each of them has the same forward and reverse thrust performances. With these four thrusters, a specific thrust vector control (TVC) method is proposed, and for external current in any direction, four horizontal thrusters are controlled to generate a vectored thrust force to encounter the current while minimizing the vehicle's rotation and maintaining its heading. However, for the numerical simulations, the vehicle's hydrodynamic coefficients related to the horizontal plane are derived based on both theoretical and empirically derived formulas. In addition to the simulation, experimental studies in both the water tank and circulating water channel are performed to verify the vehicle's various final performances, including its ability to overcome strong current.