김호영 교수

Jumping on water is a unique locomotion mode found in semi-aquatic arthropods, such as water striders. To reproduce this feat in a surface tension-dominant jumping robot, we elucidated the hydrodynamics involved and applied them to develop a bio-inspired impulsive mechanism that maximizes momentum transfer to water. We found that water striders rotate the curved tips of their legs inward at a relatively low descending velocity with a force just below that required to break the water surface (144

Water striders are water-walking insects that can jump upwards from the water surface. Quick jumps allow striders to avoid sudden dangers such as predators' attacks, and therefore their jumping is expected to be shaped by natural selection for optimal performance. Related species with different morphological constraints could require different jumping mechanics to successfully avoid predation. Here we show that jumping striders tune their leg rotation speed to reach the maximum jumping speed tha

This paper describes the locomotion of a water jumping robot which emulates the ability of the water strider and the fishing spider to jump on the water surface. While previous studies of the robots mimicking aquatic arthropods were focused on recreating their horizontal skating motions, here we aim to achieve a vertical jumping motion. The robot jumps by pushing the water surface with rapidly released legs which were initially bent. The motion is triggered with a latch driven by the shape memor

Jumping out of water is a phenomenon exhibited by a variety of aquatic and semi-aquatic animals. Yet, there is no common groundwork that clarifies the physical constraints required to jump out of water. In this study, we elucidate the physical conditions required for an animal to jump out of water. More than 100 jumps are analysed over five taxonomic groups. By balancing the power produced by animals with drag-induced dissipation, we expect that maximum jumping height, H, scales with body length

Production of fresh water based on a renewable energy source is one of the most important global challenges for mankind due to ever-accelerating climate changes. Solar thermal evaporation shows promise for overcoming the water scarcity problem by utilizing solar energy, the most abundant and clean energy source. To enhance the performance of solar evaporators, interfacial solar evaporators have been introduced, which harness solar energy onto the water surface. To enable energy conversion and wa

This paper deals with interactions of the wakes of two flapping wings on aerodynamic characteristics in hover. With dynamically scaled-up robotic wings installed in a water tank, the effects of both the shape of motion profiles and the mean flapping angle of the wings (the average location of the wings with respect to pivots) were investigated. For the zero mean flapping angle case, the interaction commonly reduced aerodynamic force production regardless of the shape of motion profiles. A leadin

Insect hovering is one of the most fascinating acrobatic flight modes in nature, and its aerodynamics has been intensively studied, mainly through computational approaches. While the numerical analyses have revealed detailed vortical structures around flapping wings and resulting forces for specific hovering conditions, theoretical understanding of a simple unified mechanism enabling the insects to be airborne is still incomplete. Here, we construct a scaling law for the lift of hovering insects

Nanostructured transparent glass surfaces with self-cleaning and anti-fogging properties were fabricated using a non-lithographic, anisotropic etching technique. The superhydrophilic glass surface was achieved by nanostructuring pre-deposited SiO 2 film in a glow discharge chamber. For superhydrophobicity, the surface energy of the nanostructured glass was lowered by treatment with 1H,1H,2H,2Hperfluorooctyl trichlorosilane. The self-cleaning and anti-fogging behavior was compared for glasses wit

본 연구는 국내 노인인구에 적합한 언어학습검사를 개발하고 검사의 신뢰도와 타당도를 검증하여 그 활용 가능성을 확인하고자 하였다. 이를 위해 국내 노인들에게 친숙한 세 의미범주로부터 친숙성, 발음 용이성과 심상형성 용이성을 바탕으로 난이도를 조정한 9개의 단어 자극을 선정하여 노인용 언어학습검사(Elderly Verbal Learning Test; EVLT)를 개발하였다. 검사의 타당도를 검증하기 위해 55세 이상의 정상 장노년 피검자 273명과 알츠하이머성 치매로 진단받은 25명의 환자를 대상으로 검사를 실시하였다. EVLT 측정치들은 K-DRS의 기억 소검사, 이야기 회상 검사 등 기존의 다른 일화적 기억 측정치들과 유의미한 상관을 보였다. 반면, 시공간폭 바로따라하기 검사와는 유의한 상관을 보이지 않아 수렴 및 변별 타당도가 확인되었다. 요인 분석 결과, EVLT는 모두 6개의 구성요인을 가지는 것으로 확인되었는데, 이는 보편적인 성인의 기억 구조와 함께 국내 노인집단 고유의 기

This paper introduces an experimental device which can measure accurate aerodynamic forces without support interference in wide experimental region for wind tunnel test of micro aerial vehicles (MAVs). A stereo pattern recognition (SPR) method was introduced to a magnetic suspension and balance system (MSBS), which can eliminate support interference by levitating the experimental model, to establish wider experimental region; thereby MSBS-SPR integrated system was developed. The SPR method is no

Nature's flyers adopt deviating motion when they fly, however, the effect of deviating motion on the aerodynamics of flapping wings is not yet clearly understood. In this study, the aerodynamic characteristics of figure-of-eight deviating motion were investigated by comparing the aerodynamic force obtained from an experiment and the quasi-steady (QS) model in wide ranges of both the pitch and deviation amplitude. A flapping-wing robotic manipulator with a one-ton water tank was used in the exper

북미에서 가장 많이 사용되고 있는 대표적인 치매 평가 도구 중 하나인 Dementia Rating Scale(DRS)은 90년대 말 우리나라에서도 한국판 치매 평가 검사(Korean-Dementia Rating Scale, K-DRS)로 재표준화 되어 국내 치매 환자를 진단하고 병리적 경과를 측정하는데 사용되어 왔다. K-DRS의 신뢰도와 타당도는 선행연구들을 통해 입증되었으며, 규준은 두 개의 연령 수준과 두 개의 교육연한 수준으로 세분화되어 제시됨으로써 4개의 규준이 결과를 해석하는데 사용되고 있다. 그러나 규준이 확립된 후 10년이 지난 현 시점에서 검사의 정확한 해석을 위해서는 국내 노인 인구의 변화된 특성을 보다 잘 대변할 수 있는 개정된 규준이 요구되었다. 본 연구는 국내 지역사회에 거주하는 만 50~89세의 정상 노인 인구들(N=785)을 대상으로 실시되었다. 검사 수행에 영향을 미치는 인구 통계학적 요인의 효과를 분석한 결과 교육과 연령이 유의미한 주요 요인으로 작용하

The imbibition of wetting liquids in porous media takes place on length scales spanning several orders of magnitude, in phenomena ranging from landslide due to heavy rainfall in geophysics to stiction of nanopatterns in semiconductor manufacturing. We review the current theoretical understanding of the dynamics of liquid infiltration that are driven by capillary forces and resisted by viscous friction. Physical principles that govern the flows in smooth channels and porous media, either with or

We propose an optimal cold sink temperature for thermoelectric dehumidifiers based on theoretical and experimental investigations. We show that the optimal condition is such that the latent heat absorption rate per unit power supplied to the dehumidifier is maximized. In consideration of the cooling ability of Peltier pellet and the heat exchange characteristics of the cold sink, we estimate the condensation rate as a function of the cold sink temperature. The theoretical predictions are compare