• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2583-2588
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• 2008

In the present experimental study, the regime limit and pressure drop of dry-plug flow (dry wall condition at the gas portions of plug flow) in round mini-channels has been investigated. The air-water mixture was flowed through the round mini-channels made of Teflon, where the tube diameters ranged from 1.26 to 2.06 mm. For the present experimental range, with decreasing of the tube diameter, the transition between the plug and slug flows (wet and dry) happened at the higher gas superficial velocity region, which were in good agreement with the previous flow pattern maps tested. On the other hand, the transition between the wet- and dry-plug flows was little affected by the change of the tube diameter. In the pressure drop of dry-plug flows, among the correlations tested, the Lee and Lee's (2008) correlation best fitted the measured pressure drop data within the mean deviation of 10% for the present experimental range.

• 디지털융복합연구
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• 제19권2호
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• pp.481-488
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• 2021

본 연구의 목적은 농구동호인의 만성발목관절불안정성(CAI)에 따른 한발착지패턴의 변화를 확인하고 비교분석하고자 하였다. 현재 부산광역시에서 레크레이션 농구경기에 참여하고 있는 농구동호인 30명을 대상으로 국제발목협회에서 제공하는 CAI 표준 선정기준에따라 CAI집단 21명과 CON집단 9명으로 분류하였다. 한발착지패턴을 측정하기 위해 초기접촉 시점 및 무릎관절 최대 굽힘 시점에서 하지정렬과 관절 움직임을 측정하고 초기접촉 시점, 발꿈치접촉 시점 및 무릎관절 최대 굽힘 시점에서 앞정강근, 긴종아리근, 안쪽장딴지근 및 중간볼기근의 활성도를 측정하였다. 그 결과, 집단 간 단일 다리 드롭랜딩 시 하지정렬과 하지 근활성도는 유의한 차이를 보이지 않았다. 이런 결과는, CAI에 따라 한발착지패턴과 근활성도에 유의한 차이가 없다는 것을 보여주었다. 추후 연구에서는 CAI를 세부적으로 구분하고 경기포지션을 고려하여 움직임의 특성 및 기능적 요구의 차이를 반영해야 할 것으로 생각된다.

• 전기학회논문지P
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• 제65권1호
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• pp.57-65
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• 2016

This paper was analyzed the characteristics of piezoelectric inkjet print head using finite element method(FEM). It showed the bending node driving of piezoelectric and relation theory principle consider piezoelectric material characteristics and ink characteristics. From such result we were had the piezoelectric head design and manufacture. It got a this head characteristics through experiment, we confirmed that proper voltage control is possible to through ink drop control experiment of piezoelectric print head. This paper was obtained the suitable ink jetting characteristics that manufacture the control circuit and piezoelectric inkjet print head. This practice product was applied to improvement of PCB electric circuit pattern by etching resist ink that PCB manufactured to complex process over traditional 6 stages can be simpled to 1 stage by inkjet printing technology.

• 한국화재소방학회논문지
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• 제27권2호
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• pp.54-61
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• 2013

항공기에 의한 산불공중진화는 지상진화 보다 진화의 효과성이 좋다. 따라서 공중진화는 산불의 대형화를 방지하는데 중요하다. 미국에서는 고정익항공기 및 회전익항공기(헬리콥터)가 합동으로 공중진화를 하나 우리나라는 회전익항공기만을 이용하고 있다. 따라서 헬리콥터에 의한 공중진화의 효과성에 대한 연구가 필요하다. 공중진화의 효과성은 투하되는 물의 분포형태와 범위에 따라서 결정된다. 따라서 본 연구는 산림청에서 운용하는 S-64E, Ka-32T, AS350B2의 3개 기종으로 물투하 실험을 실시하여 유효 분포형태와 범위를 도출하였다. 이 연구 결과로 조종사들이 공중진화의 효과성을 증대시키는데 기여하고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3440-3445
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• 2007

For proton exchange membrane fuel cell, it is very important to design the flow channel on separation plate optimally to maximize the current density at same electrochemical reaction surface and reduce the concentration polarization occurred at high current density. In this paper, three dimensional computation model including anode and cathode domain together was developed to examine effects of flow patterns and operation conditions such as humidity and operating temperature on performance of fuel cell. Results show that voltage at counter flow condition is higher than that at coflow condition in parallel and interdigitated flow pattern. And fuel cell with interdigitated flow pattern which has better mass transport by convection flow through gas diffusion layer has higher performance than with parallel flow pattern but its pressure drop is increased such that the trade off between performance and pressure drop should be considered for selection of flow pattern of fuel cell.

• 한국재료학회지
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• 제15권1호
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• pp.54-60
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• 2005

Recently a lots of problems have observed in high densified and high integrated electronic components. One of them is ion migration phenomena, which induce the electrical short of electrical circuit. ion migration phenomena has been observed in the field of exposing the specific environment and using for a long tin e. This study was evaluated the generation time of ion migration and was investigated properly test method through water drop test and high temperature high humidity test. Also we observed direct causes and confirmed generation mechanism of dendritic growth as we reproduced the ion migration phenomena. We utilized PCB(printed circuit board) having a comb pattern as follows 0.5, 1.0, 2.0 mm pattern distance. Cu, SnPb and Au were electroplated on the comb pattern. 6.5 V and 15 V were applied in the comb pattern and then we measured the electrical short time causing by ion migration. In these results, we examined a difference of ion migration time depending on pattern materials, applied voltage and pattern spacing of PCB conductor.

• 한국운동역학회지
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• 제31권1호
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• pp.64-71
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• 2021

Objective: This study investigated the different in isokinetic peak strength of the knee joint, and kinetics and kinematics in drop landing pattern of lower limb between the patellofemoral pain syndrome (PFPS) patients and normal. Method: 30 adult females were divided into the PFPS (age: 23.13±2.77 yrs; height: 160.97±3.79 cm, weight: 51.19±4.86 kg) and normal group (age: 22.80±2.54 yrs, height: 164.40±5.77 cm, weight: 56.14±8.16 kg), with 15 subjects in each group. To examine the knee isokinetic peak strength, kinematics and kinetics in peak vertical ground reaction force during drop landing. Results: The knee peak torque (Nm) and relative strength (%) were significantly weaker PFPS group than normal group. In addition, PFPS group had significantly greater hip flexion angle (°) than normal group. Moreover, normal group had significantly greater moment of hip abduction, hip internal rotation, and left ankle eversion than PFPS group, and PFPS group had significantly greater moment of knee internal rotation. Finally, there was significant differences between the groups at anteroposterior center of pressure. Conclusion: The PFPS patients had weakened knee strength, and which can result in an unstable landing pattern and cause of more stress in the knee joints despite to effort of reduce vertical ground reaction force.

• 한국분무공학회지
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• 제1권2호
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• pp.57-65
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• 1996

Breakup models are evaluated using the experimental drop trajectory ill this study. The experimental conditions corespond to Weber # 56, 260, 463. Computations are carried out using a modified KIVA-II program with 2 different breakup submodel(TAB and Wave breakup model) and dynamic drag model which the drag coefficient changes dynamically with distortion parameter. Results show that computation with wave breakup model represents the experimental drop trajectory better than that with TAB submodel. And result with wave breakup model shows similar breakup pattern to experimental breakup process. It is thought that in wave breakup model the small drops are shed from the parent drop throughout parcel lifetime such thai this modelling represents the real breakup process well.

• 한국운동역학회지
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• 제16권2호
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• pp.25-35
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• 2006

The purpose of this study was to investigate the shock attenuation mechanisms while varying the loads in a backpack during drop landing. Ten subjects (age: $22.8{\pm}3.6$, height: $173.5{\pm}4.3$, weight: $70.4{\pm}5.2$) performed drop landing under five varying loads (0, 5kg. 10kg. 20kg. 30kg). By employing two cameras (Sony VX2100) the following kinematic variables (phase time, joint rotational angle and velocity of ankle, knee and hip) were calculated by applying 2D motion analysis. Additional data, i.e. max vertical ground force (VGRF) and acceleration, was acquired by using two AMTI Force plates and a Noraxon Inline Accelerometer Sensor. Through analysing the power spectrum density (PSD), drop landing patterns were classified into four groups and each group was discovered to have a different shock attenuation mechanism. The first pattern that appeared at landing was that the right leg absorbed most of the shock attenuation. The second pattern to appear was that subject quickly transferred the load from the right leg to the left leg as quickly as possible. Thus, this illustrated that two shock attenuation mechanisms occurred during drop landing under varying load conditions.

• 대한의용생체공학회:의공학회지
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• 제23권1호
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• pp.27-32
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• 2002

본 연구에서는 혈관내 혈액 흐름의 압력손실을 최소화하여야 하는 제한 인자를 만족하는 새로운 막형 인공폐에서 액체흐름경향과 중공사 개수에 대한 압력손실 영향을 고찰하고자 하였다 막형 인공폐는 380 $\mu m$의 중공사 외경과 600 mm의 축 방향 길이를 갖는 수 백 개의 중공사로 이루어진 다발이다 중공사 다발은 8가지로 변화시켰으며 흐름은 펌프를 이용하여 조절하였다 혈액대용물질로 글리세롤 용액과 물을 사용하여 압력손실을 측정하였으며 동일한 흐름 경향을 각 중공사들에서 얻었다. 700개의 중공사로 이루어진 막형 인공 폐의 외부 압력손실은 13-16 mmHg이었으며 중공사 개수의 감소에 따른 마찰계수는 중공사와 액체와의 효과적인 접촉이 일어나므로 증가되었다.