• Journal of Advanced Navigation Technology
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• v.9 no.1
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• pp.28-33
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• 2005

In this paper, we developed the algorithm to control longitudinal and lateral motion of UAV(Unmanned Aerial Vehicle) with Infrared heat sensors and GPS(Global Positioning System) receiver. UAV was controlled to be flown horizontally and also turned coordinately maintaining the constant altitude. Accomplishing the flight test of UAV sevral times, we were able to develope low price controller to control bank angle for lateral motion, and also pitch angle and altitude for longitudinal motion simultaneously.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1581-1588
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• 2010

Most digital cameras use a single image sensor with Color Filter Array(CFA) for the advantage of costs and speed. The various color interpolation(demosaicing) algorithms are researched to reconstruct a full representation of the image. In this paper, we proposed a method of demosaicing about using weighted directional filter for vertical, horizontal, and diagonal direction edge. The method considered the efficiency of hardware resources for hardware implementation. The performance of proposed method was confirmed by comparing the conventional method in experiments using 24 Kodak test images. The proposed method was designed by Verilog HDL and was verified by using Virtex4 FPGA boards and CMOS Image Sensor.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.561-568
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• 2020

A performance analysis was conducted according to changes in inflow velocity and the tip speed ratio of a portable horizontal-axis hydro turbine that can be used for marine leisure sports and outdoor activities by using the commercial computational fluid dynamics software ANSYS CFX. By using the analysis result and flow field analysis, the design was reviewed and the performance of the device was confirmed. In addition, data necessary to improve the performance of the hydro turbine were acquired by performing an additional performance analysis according to the variable blade pitch angle. The results among the numerical analysis cases show that the highest performance at all inflow velocities and blade pitch angles if achieved at a tip speed ratio of 4. The output power was found to be 30 W even under some conditions below the design flow rate. Among the numerical analysis cases, the highest output power (~ 85 W) and power coefficient (~ 0.30) were observed at an inlet flow rate of 1.5 m/s, a blade pitch angle of 3°, and a tip speed ratio of 4.

• The korean journal of orthodontics
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• v.27 no.3 s.62
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• pp.373-389
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• 1997

The purpose of this stdudy was to evaluate the effect of maxillary protraction and the relapse of hard and soft tissue after maxillary protraction. For this study 29 patients who were treated with maxillary protractor and labiolingual archwire were selected. Their mean age was 9 years 4 months and mean treatment period was 8.5 months. Lateral cephalograms were taken at pretreatment, immediately after treatment and one to three months after removal of the maxillary protractor. They were traced on skeletodental and soft tissue structures based on Burstone's analysis and analyzed by Quick-Ceph Image Digitizing System(ORTHODONTIC PROCESSING). The mean and standard deviation between pretreatment and posttreatment and between posttreatment and retention period for each cephalometric variable were calculated. Student t-test was used to determine the statistical significance of the changes in each variable. Correlation coefficients between hard tissue and soft tissue were used to determine interrelationship. The results were as follows. 1. After maxillayy protraction, the maxilla and maxillary dentition moved antero-inferiorly, the mandibld and mandibular dentition moved postero-interiorly and palatal plane rotated antero-superiorly by $0.59^{\circ}$. 2. After maxillary protraction, the soft tissue of upper lip moved antero-interiorly with the movement of hard tissue but the antero-posterior position of lower lip was stable in spite of the change of hard tissue. The thickness of upper lip was decreased and that of lower lip was increased after maxillary Protraction. 3. During the retention period, the position of jaws was relatively stable but upper and lower anterior teeth and antero-superiorly rotated palatal plane relapsed to original position. 4. During the retention period, the soft tissue of lips was stable antero-posteriorly and moved mote inferiorly than posttreatment. 5. The correlation coefficients between the postion of upper and lower incisal edge and that position of lips were high, especially in horizontal change.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.4
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• pp.435-442
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• 1995

The abalone shell (Haliotis) is one of the most important resources for the coastal fisheries and it is popular as an aquacultural species. Proper cultivating grounds for mid-term nursery of abalone spats are required before releasing them. It is difficult for us to find good enough aquacultural grounds to rear abalone spats to 20"30mm of shell length. Therefore, we need to study a practical and effective new type of aquacultural device for the nursing of abalone spats by using open sea areas. We can find this kind of studies from 'Marine aya No. 1' of Japan, Though they focused on the easy operation, safe working and low operating cost, it involves so much initial cost that it is difficult for us to justify such expenditure. However, with a modified small buoy system, this submersible facility needs only a horizontal frame to fulfill its essential function and the vortical part can be removed. The working boat equipped with a pump can operate this facility to keep it submerged or floated. This paper deals with the possibility of this submersible fishery facility for the mid term nursing of abalone spats in the open sea. A small version of this system to ensure low initial cost is suggested and wave and current forces were calculated for the estimation of the weight of the mooring anchor.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.533-540
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• 2012

Rubber laminated bearings with lead core are highly affected by changes in temperature because key materials which are rubber and lead have temperature dependencies. In this study, two full scale LRB(D800, S=5) are manufactured and temperature dependency tests on shear properties are accomplished. The shear properties at the 3rd cycle are used at $-10^{\circ}C$, $0^{\circ}C$, $10^{\circ}C$, $20^{\circ}C$, $30^{\circ}C$, $40^{\circ}C$ respectively. The double shear configuration, simultaneously testing two pieces, is applied for compression shear test in order to minimize the friction effects due to the test machine, described in ISO 22762-1:2010. Characteristic strength, post-yield stiffness, effective stiffness, equivalent damping ratio are estimated and presented coefficient due to the temperature changes.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.100-100
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• 2017

2016년부터 중국에 수출한 진공포장 쌀이 진공이 풀려 중국 현지 소비자들에게 품질에 대한 신뢰저하로 외면 받아 판매에 어려움을 겪었다. 진공풀림 원인은 주로 포장재의 모양, 과열 열접착 및 운송 중 부주의 등을 들 수가 있다. 따라서 본 연구에서는 쌀 진공포장 후 진공 풀림현상이 발생되는 원인을 분석하고, 진공포장에 적절한 포장재 및 취급조건에 대해 구명하여, 중국 쌀 수출 시 품질신뢰도 및 경쟁력 제고로 쌀 수출 확대를 위해 진공 포장재, 진공포장기술 및 운송 취급 방법을 제시하고자 하였다. 미곡종합처리장에서 사용하고 있는 플라스틱 필름 포장재의 적합 여부를 살펴보기 위하여 산소투과도 및 투습도를 산소투과도 측정장치(OX-Tran Model 2/61, Mocon, USA), 투습도 측정장치(Permatran-W Model 3/33, Mocon, USA)를 이용하여 측정하였다. 적정 열접착 온도를 구명하기 위하여 열접착 작업시간 간격 3, 5, 10초 3수준으로 하고 가열시간을 0.2초~2초까지 9수준으로 설정하여 포장필름을 열접착한 후 접착상태를 조사하였다. 진공 포장된 쌀을 골판지상자에 2차 포장하여 운송할 때 진공풀림 현상이 발생 여부를 조사하기 위해 가상 운송시험을 진동시험 장치를 이용하여 수직 및 수평으로 진동시험을 수행하였으며, 또한 취급조건에 따라 진공풀림을 조사하기 위하여 골판지 상자단위, 비닐포장 단위로 50, 70, 90cm 높이에서 낙하 시험을 하고 진공풀림여부를 조사하였다. 유통 중인 쌀 진공 포장재는 나이론(nylon)+선형저밀도폴리에틸렌(LLDPE) 복합필름으로 산소투과도가 $30{\sim}70cc/m^2{\cdot}day$, 투습도가 $2{\sim}4.5g/m^2{\cdot}day$로 산소투과도 및 투습도가 충분히 낮아 진공포장재로 적합했으며, 적정 열접착온도 조건은 $130{\sim}150^{\circ}C$에서 1~1.5초가량 가열해야 되는 것으로 조사되었다. 진동시험 및 낙하시험결과, 골판지박스 포장 시 완충재를 사이에 넣은 경우 진골풀림이 적었고, 상자단위나 비닐포장단위 모두 가능한 50cm보다 높은 곳에서 낙하충격을 받지 않도록 취급해야 할 것으로 판단되었다.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.74-74
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• 2011

본 연구에서는 중앙경간 54m, 교폭 4m의 사장교형식의 보도교로 측경간은 계단으로 이루어진 1경간 케이블교량을 대상으로 보행하중에 의한 수직진동을 제어하기 위해 제진장치(TMD)를 적용하기로 하고 실물 TMD의 설계 및 제작 그리고 설치 및 제어성능실험을 수행하였다. 우선 사장교형식의 교량. 그리고 1경간 교량이라는 점에서 상대적으로 감쇠율이 낮을 것으로 예측되었고 또한 54m의 경간장이 보행자가 가진 주파수에 근접한 고유진동수를 나타낼 것으로 사료되어 Eurocode 2 part 2(EC5-2)의 규준에 따라 1인 및 다수 보행하중에 의한 보도교의 발생가속도를 산출하였다. 이 경우 최대가속도는 다수의 보행자가 연속적으로 진행할 때 발생하였으며, 수직방향의 가속도가 사용성기준을 초과하는 것으로 나타났다. 또한 구조해석프로그램에 의한 고유치 해석결과, 보행하중의 주파수대역내에 진동모드가 존재하는 것으로 나타났다. 따라서 본 교량의 설계단계에 있어서 보행진동을 제어하기 위하여 유지관리가 용이한 수동형의 동조질량감쇠장치(Tuned Mass Damper)를 적용하기로 하였으며 TMD의 설계에서는 TMD의 제어목표를 만족시킬 수 있는 TMD의 가동질량(moving mass)을 우선적으로 결정하였고, 이로부터 Den Hartog의 제안식에 따라 TMD의 고유진동수비, 유효감쇠비를 산정하였다. 산정된 변수들을 이용하여 설계된 TMD는 현장설치 및 튜닝의 편의성을 고려하여 수평 외팔보형식으로 설계, 제작되었으며 제작된 TMD의 경우 회전축에 대해 질량, 스프링, 댐퍼의 중심거리를 조정함으로써 TMD의 진동수, 강성, 감쇠력을 상대적으로 매우 용이하게 조절할 수 있으며, 조정범위 또한 광범위하여 일반 TMD에 비해 현장설치시 대상구조물에 동조시키기가 용이하며, 작동시 마찰감쇠가 거의 없다는 장점이 있다. 현장설치전에 제작된 TMD를 대상으로 자유진동 시험을 통하여 질량의 중심거리, 스프링 크기 그리고 댐퍼의 설치유무를 각각 변화시키며 TMD의 자유진동 데이터를 취득하였다. 각각의 시험에서 얻어진 데이터로부터 스펙트럼해석을 통하여 고유진동수를 구하였고, 자유진동 파형으로 부터 감쇠비를 구하였다. TMD는 일반적으로 제어모드의 변형형상이 가장 큰 곳에 설치되었을 때 최대의 제진효과를 발휘할 수 있다. 그러나 현장여건상 설치가 불가능하거나 미관을 해치는 경우에는 가능한 범위 내에서 TMD 제어효율이 가장 크게 발휘할 수 있는 곳을 선택하여야 한다. 본 보도교의 경우, 중앙경간 중심부에서 가장 큰 모드변형형상을 나타내지만, 보도교의 상판 연결부 등에 따른 TMD 시공문제로 인하여 TMD 설치위치는 교량 중앙에서 양 방향으로 1.25m 떨어진 곳에 대칭으로 총 2기를 설치하기로 하였다. 일반적으로 TMD의 모든 설계변수는 구조물의 설계단계에서 수행된 구조해석결과에 근거하여 설정하므로 완공된 구조물, 즉 실제보도교의 동적특성을 계측하여 정확하게 진동수를 튜닝하여야 한다. 구조해석에 의한 보도교의 수직방향(TMD 작동방향) 고유진동수는 1.5225 Hz이며, 감쇠비는 규준에 의하여 0.6 %로 가정하였다. 그러나 이 값들은 구조해석모델 및 재료적 특성과 시공상의 오차에 의하여 실제와 다를 수 있으므로 현장계측에 의한 확인이 요구된다. 또한 TMD의 제진효율이 설계시의 목표대로 확보되었는지도 확인해야 하므로 현장튜닝 및 성능시험을 실시하였다. 보도교의 가진은 사전에 실시한 상시 미진동계측결과를 토대로 2Hz를 목표로 하여 인력가진실험을 수행하였고, 탁월진동 주파수는 1.9896Hz로 나타나 구조해석결과와 오차가 있음을 알 수 있다. 가진실험결과를 토대로 TMD의 진동수를 최적진동수비로 튜닝하고 인력가진 실험을 다시 실시하여 TMD의 진동제어성능을 검토하였다. TMD 튜닝 전, 후의 보도교 감쇠비를 비교한 결과, TMD를 설치함으로써 약 4.218%의 감쇠비 증가가 있음을 알 수 있다.

• Particle and aerosol research
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• v.13 no.3
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• pp.111-118
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• 2017

Electrohydrodynamic (EHD) printing with the aid of strong electric fields can generate and pattern droplets that are smaller than droplets by other printing technologies. Conventional EHD printing has created two-dimensional (2D) patterns by moving its nozzle or a substrate in X and Y directions. In this study, we aimed to develop an EHD system that can create 2D patterns using a multielectrode array (MEA) without moving a nozzle or substrate. In particular, printing ink mixtures of biodegradable polymers and model dyes was patterned on a thin film made of another biodegradable polymer. Without movement of a nozzle and substrate, stable 2D patterning of minimum $6{\mu}m$ size over a range of about 1 mm away from the nozzle position was achieved by MEA control only. We also demonstrated the possibility of denser 2D pattering of the ink mixtures by moving a target substrate relative to MEA position.

• Tunnel and Underground Space
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• v.32 no.3
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• pp.219-230
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• 2022

The Geo-Reservoir Experimental Analogue Technology (GREAT) cell was designed to recreate the thermal-hydro-mechanical conditions of deep subsurface in the laboratory. This apparatus can generate a polyaxial stress field using lateral loading elements, which rotate around the longitudinal axis of a sample and is capable of performing a fluid flow test for samples containing fractures. In the present study, numerical simulations were carried out for triaxial compression tests using the GREAT cell and the mechanical behavior of samples under different conditions of lateral loading was investigated. We simulated an actual case, in which triaxial compression tests were conducted for a polymer sample without fractures, and compared the results between the numerical analysis and experiment. The surface strain (circumferential strain) of the sample was analyzed for equal and non-equal horizontal confining pressures. The results of the comparison showed a good consistency. Additionally, for synthetic cases with a fracture, we investigated the effect of the friction and type of fracture surface on the deformation behavior.