• Journal of Wetlands Research
• /
• v.18 no.4
• /
• pp.357-362
• /
• 2016

Improvement of the solid-liquid separation efficiency in the secondary sedimentation tank of the biological treatment process, is known to be increasing effectiveness of the overall system operation. Sewage treatment plant effluent SS is composed of most organic substances. In order to reduce the SS component in the secondary sedimentation tank discharge, fine SS components constituting the heterogeneous should be increased by its own aggregation (self flocculation), so that can be deleted through their precipitation. So, it is improved through using the installation of double rectification wall in this secondary tank. In case, sewage is rapidly increased due to the daily change of the influent water, it was confirmed that suspended solids caused by the impact load are processed stably. Therefore, there is a need for a facility installation which can be its own aggregation for reduction suspended solids in secondary sedimentation tank.

• Journal of rehabilitation welfare engineering & assistive technology
• /
• v.8 no.4
• /
• pp.283-289
• /
• 2014

This paper presents a design and optimization of the fully-active transfemoral prosthesis leg system. As it has one degree of freedom in knee joint, this prosthesis leg can imitate the human's gait. The weight of system, which makes the users more comfortable due to less tiredness, and the knee joint torque to rise stability of the system are major factors of prosthesis leg system. Thus the mechanism of prosthesis changes from 3-linkage type to geared type. The sensorized foot is also designed to effectively determine human's gait by measuring deformation of the foot during gait. Topology optimization is carried out for the sensorized foot to remove its unnecessary weight. The safety of optimized foot is verified by carrying out finite element analysis.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.5 no.5
• /
• pp.459-466
• /
• 2000

A new control method for precision robust speed control of a PMSM(Permanent Magnet Synchronous Motor) using load torque observer is presented. Using this system, we can more precisely evacuate of vestibular function. Until now a rotating chair system, so called 2D-stimulator, which has vertical rotate axis is used to make dizziness. However, an inclined rotating chair system witch is called 3D-stimulator is needed to obtain the precise dizziness data. This 3D-stimulator include unbalanced load caused by unbalanced center of mass. In this case, new compensation method is considered to obtain robust speed control using load torque observer. To reduce the effect of this disturbance, we can use dead-beat observer that has high gain. The application of the load to torque observer is published in for position control. However, there is a problem of using speed information such as amplifying effect of noise. Therefore, we can reduce a noise effect by moving average process. The experimental results are depicted in this paper to show the effect of this proposed algorithm.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.9
• /
• pp.983-989
• /
• 2014

In this paper, a new active noise control method was proposed to decrease a weight of car, and to increase a fuel efficiency and to provide passengers' comfort and calmness, instead of a passive noise control method such as sound absorbing and insulating materials. The proposed method is an enhanced active noise controller operating by a bidirectional control algorithm. The algorithm is simple to implement and available to analyze mathematically with nearly equivalent complexity of computation. Through simulations for engine noises of a car, the proposed controller was verified that its performances of time and frequency domain were superior to those of both feedforward and feedback controllers, and it had better capability of controlling the noises when the impulsive disturbance was flow in and the response of secondary path was varied.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.3
• /
• pp.1241-1246
• /
• 2014

Take-out robots used for handling of the plastic parts manufactured with the injection mold are usually the gantry type that consists of long and thin links. In this study, we want to evaluate the safety of the take-out Robot structure through finite element analysis. The take-out Robot is automated robot to transport from one location to another in the molded article. The take-out Robot structure has a 380 kilogram weight, a 1300mm width, a 670.5mm depth and a 670mm height. It confirms the equivalent stress and the deformation of the load and its own weight through weight analysis. It looks for the natural frequency of the take-out robot through modal analysis. It confirms the acceleration, the normal stress and the deformation about the natural frequency of the take-out robot through response analysis. Also It repeats the analysis by changing the structure of the take-out robot, to confirm the results and it is determined whether the safety of the structure. These analysis results are effectively used to reduce the vibration of the take-out robot.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2017.05a
• /
• pp.136-136
• /
• 2017

화학제염 기술은 산화제, 환원제, 금속이온, 무기산등이 혼합되어 있는 화학용액을 사용하여 원전기기 계통 내부에 생성된 고방사능 준위의 산화막과 오염물질을 제거하는 기술이다. 원전의 해체 및 유지보수에 있어 방사능 피복저감을 위한 필수적인 기술이다. 현재 원전 해체 산업은 잠재성이 높은 고부가가치 창출 산업으로 주목을 받고 있다. 원전 보유국의 경우, 기존 상용 제염기술과는 차별성 있는 제염기술을 확보하고자 노력하고 있다. 기존의 공정과 비교하여 공정비용 및 시간을 감소시킬 수 있어야 할 뿐만 아니라, 화학용액에 의한 원전 계통 금속 부품의 부식 및 손상을 최소화해야 한다. 금속 부품이 화학약품에 의한 부식손상을 받는다면 금속 부품의 수명 및 재활용 가치가 감소하기 때문에, 화학제염 기술 적용에 있어 용액에 대한 재료의 건전성 평가가 사전에 필히 이루어져야 한다. 본 연구에서는 원전 냉각재 펌프용 재료로 주로 사용되는 Stainless 304강을 시험편으로 선정하여, 화학제염 시험공정 3가지에 대한 부식손상 특성을 규명하였다. 산화공정은 과망간산($HMnO_4$) 용액을 공통으로 사용하였으며, 산화공정 종료 후 환원공정은 각 시험공정에 따라 시험공정 1은 옥살산($H_2C_2O_4$) 2000ppm, 시험공정 2는 옥살산($H_2C_2O_4$)1500ppm + 시트르산($H_8C_6O_7$)500ppm, 그리고 시험공정 3은 옥살산($H_2C_2O_4$) 3000ppm 용액을 각각 투입하여 수행하였다. 산화, 환원공정을 1Cycle로 하여, 각 시험공정 별로 총 5Cycle을 실시하였다. 각 시험공정 Cycle종료 후 시험편을 취외하여 무게감량측정, SEM(Scanning electron microscope) 분석, 3D현미경분석 그리고 타펠분극 실험을 실시하였다. 각 분석결과를 토대로 하여, Stainless 304강에 대한 화학제염 시 모델별 시험공정에 따른 부식특성을 규명하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.6
• /
• pp.595-602
• /
• 2016

An automotive wheel bearing is important part that translates rotating motion and bears vehicle weight. Recently, in accordance with the demands for $CO_2$ emission reduction and fuel economy regulation, the requirements for the weight reduction and miniaturization of vehicles has increased. Therefore, life evaluation technology of the bearings has increased in necessity. Since the bearing life is affected by many parameters such as bearing geometry, bearing specifications, and vehicle specifications, it is difficult to predict. In this paper, the bearing life was tested by varying the applied load and rotation speed and comparing them with the basic rating life and modified rating life that were suggested in ISO standards. From the results, it was found that there was a difference between the test life and theoretical life and modified rating life than basic rating life was to be relatively well predicted by test life.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.112-112
• /
• 2018

알루미늄 합금은 내구성과 내식성이 우수한 경량 재료이다. 그 중 Al-Mg계 5083 Al 합금은 가공성 및 용접성이 우수하여 선체 재료로 널리 이용되고 있다. 이는 선체 중량의 경량화로 인해, 연료비 절감과 빠른 선속 등 다양한 이점을 지니기 때문이다. 그러나 선박의 고속화에 따라 선체에 가해지는 유체충격이 증가하고, 압력 저하에 기인하여 캐비테이션-침식 손상이 증가할 뿐만 아니라, 염소이온이 존재하는 해수환경에서는 침식과 부식의 시너지효과로 인하여 재료의 손상이 더욱 가속화된다. 이에 대한 다양한 방지책들이 제안되고 있으나, 강한 충격압을 동반한 캐비테이션 침식-부식 복합 손상 환경에서는 다소 한계가 있다. 따라서 본 연구에서는 알루미늄 5083에 대하여 캐비테이션 환경 하에서 일정 전위를 인가하며 침식-부식 손상이 최소화 되는 전위 구간을 규명하고자 하였다. 먼저, 분극 실험을 선행하여 재료의 전기화학적 거동을 파악 한 후 적용 전위구간을 선정하여, 해당 전위를 인가한 상태에서 캐비테이션 실험을 실시하였다. 전기화학적 분극실험과 캐비테이션-전기화학 복합 실험은 $25^{\circ}C$의 해수 하에서 실시하였으며, 시험편의 노출면적은 $3.24cm^2$으로 하였다. 분극 실험은 개로전위로부터 +3 V까지 2 mV/s의 분극속도로 전위를 인가하였고, 기준전극으로 Ag/AgCl, 대극으로 백금전극을 사용하였다. 캐비테이션-전기화학 복합 실험은 정전위를 인가한 상태에서 대향형 진동법으로 진동수 20 kHz, 진폭 $30{\mu}m$ 진동을 20분간 가하였으며, 혼팁과 시험편 사이의 거리는 1 mm로 일정하게 유지하였다. 실험 후 표면 손상의 정량적 분석을 위해 인가된 전위별 전류밀도를 비교하고, 무게감소량을 측정하였으며, 손상경향 파악을 위하여 3D광학현미경과 주사전자현미경(SEM)을 통해 표면을 분석하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.8
• /
• pp.661-669
• /
• 2021

A mechanical stiffener has been mainly applied on a PCB to secure fatigue life of a solder joint of an electronic components in spaceborne electronics by minimizing bending displacement of the PCB. However, it causes an increase of mass and volume of the electronics. The high damping PCB implemented by multi-layered viscoelastic tapes of a previous research was effective for assuring the fatigue life of the solder joint, but it also has a limitation to decrease accommodation efficiency for the components on the PCB. In this study, we proposed high damping PCB with a multi-layered superelastic shape memory alloy stiffener for spatialminimized, light-weighted, high-integrated structure design of the electronics. To investigate the basic characteristics of the proposed PCB, a static load test, a free vibration test were performed. Then, the high damping characteristic and the design effectiveness of the PCB were validated through a random vibration test.

• Composites Research
• /
• v.32 no.1
• /
• pp.45-49
• /
• 2019

Fiber reinforced composites fabricated by the resin film infusion (RFI) process, which is one of the outof-autoclave process, have the advantage of significantly reducing the processing cost in large structures while having excellent mechanical properties and uniform impregnation of the resin. In this study, we applied RFI carbon fiber composites to unmanned aerial vehicle structures to improve structural safety and achieve weight reduction. The tensile test results showed that the strength was 46% higher than that of generic T300 grade plain weave carbon fiber composites. As a result of the layup design and finite element analysis of the composite wing structure using the above material properties, the wing tip deflection is decreased by 31%, the structural safety factor is increased by 28% and the weight of the entire structure can be reduced by more than 10% compared to the reference model using glass fiber composite material.