• 한국지구과학회지
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• 제30권5호
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• pp.529-549
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• 2009

In 2007, just after the recession of the Changma, anomalously long rainy period (from July 30 to August 15) occurred in Korea. To identify the cause of the sustained rainy period, we performed synoptic analysis and the associated air motions. The behavior of each air parcel trajectory associated with atmospheric motion was then investigated. As a result, three particular phenomena occurring at latitudes lower than $40^{\circ}N$ were discovered. First, a mass of relatively cold air, referred to as E, made a deep intrusion from $20^{\circ}N$ to $60^{\circ}N$. Second, this intrusion was accompanied by another mass of air called dE. It was colder and drier than E and originated from the mid-troposphere over the tropical ocean. Third, dE and E rotated clockwise three times over a period of 17 days over the Northwestern Pacific and blocked the westerly waves imbedded in the zonal flow from propagating. Two additional phenomena were observed at latitudes higher than $40^{\circ}N$. First, the cold core system, while approaching from the west with low geopotential values at its center, was stagnated over Shanxi China. It enhanced the northward intrusion of dE and E, and then diminished. The subsequent low system showed similar evolution as the first one. Second, a warm core anticyclone was formed over Lake Baikal, blocking the westerlies for 13 days and contributed to the persistent northward incursion of warm moist air. Moreover, a horizontally extended intrusion of upper level clouds from the tropics to $50^{\circ}N$, which may be interpreted as a tropical plume, was found around the end of the period (from August 12 to 15, 2007) with successive tropical nights over Korea.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.253-256
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• 2003

65마력급 UAV용 초소형 터보샤프트 엔진의 코어를 55lbf급 터보제트 형식으로 개조 개발하였다. 터보샤프트 엔진의 동력발생기와 동일한 유량 특성을 갖는 배기 노즐을 부착함으로써 코어 엔진은 완제 엔진과 완전히 동일한 기계적, 공력적 특성을 보유하고 있다. 엔진 출력은 축 마력 대신 비교적 계측이 용이한 추력으로 나오기 때문에 터보샤프트 엔진의 성능과 수명을 좌우하는 코어의 검증 시험 용도로 매우 유용하다. 뿐만 아니라 코어 엔진은 그 자체로 하나의 터보제트엔진으로 추력이 필요한 소형 비행체의 추진기관으로 직접적인 활용이 가능하다.

• 전자통신동향분석
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• 제38권3호
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• pp.1-10
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• 2023

In this study, the status of global advanced air mobility (AAM) was investigated to derive information and communications technologies (ICTs) that should be prepared according to directions of domestic AAM development. AAM is an urban air traffic system for moving from city to city by electric vertical take-off and landing or personal aircraft. It is expected to establish a three-dimensional air traffic system that can solve ground traffic congestion caused by the rapid global urbanization. With the full-scale commercialization of AAM solutions, high-density air traffic is expected, and with the advent of the personal air vehicle (PAV), the flight space usage is expected to expand. Therefore, it is necessary to develop a safe AAM service through early research on core ICTs for autonomous flight.

• 한국분무공학회지
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• 제6권1호
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• pp.9-17
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• 2001

The effect of air entrainment in twin-fluid spray structure is investigated experimentally by varing the amount of itemizing air. The air entrainment is expected to affect on droplet size and velocity, droplet number density, turbulent kinetic energy and vorticity. PDA(Phase Doppler Anemometer) and PIV(Particle Image Velocimetry) system are used to measure those important factors in analyzing spray structure. The results show that spray structure consists of three distinctive regions ; the atomizing region near nozzle, characterizing strong convective effect, the central core region where droplets are accelerated, and the spray sheath region where droplets are decelerated due to air entrainment. The local air entrainment rate is largest near nozzle, characterizing strong turbulent kinetic energy and vorticity but deceases along axial distance.

• 한국초전도ㆍ저온공학회논문지
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• 제22권2호
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• pp.38-43
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• 2020

This paper presents comparative research on characteristics of air-cored and iron-cored high-temperature superconductor (HTS) field winding synchronous motors. The 100 kW air-cored model is designed analytically by Spatial Harmonic Method, and based on this model, the iron-cored model having the same output power is designed for comparison. Due to the substantial difference of permeability property between air and iron-core, there is a difference of magnetic field magnitude and angle with respect to the HTS tape c-axis, resulting in a different critical current of the field winding considering the anisotropic property of HTS tape. For a detailed comparison between two models, the following key motor characteristics are calculated through the Finite Element Method (FEM) simulation: 1) critical current; 2) HTS wire length; and 3) torque characteristics. From the simulation results, it can be confirmed that the critical current value of the iron-cored model increases by 33 %. Also, in the case of the superconducting wire consumption, those of the iron-cored and air-cored models are 95.3 m and 815.6 m, respectively. So the wire usage can be reduced to about 88 % by using iron core. However, in terms of torque characteristics, the torque ripple of the iron-cored model is about twice as large as that of the air-cored model, which may be a disadvantage on vibration and acoustic noise.

• JSTS:Journal of Semiconductor Technology and Science
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• 제12권3호
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• pp.297-312
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• 2012

For future multi-core processors, 3D integration is regarded as one of the most promising techniques since it improves performance and reduces power consumption by decreasing global wire length. However, 3D integration causes serious thermal problems since the closer proximity of heat generating dies makes existing thermal hotspots more severe. Conventional air cooling schemes are not enough for 3D multi-core processors due to the limit of the heat dissipation capability. Without more efficient cooling methods such as liquid cooling, the performance of 3D multi-core processors should be degraded by dynamic thermal management. In this paper, we examine the architectural impact of cooling methods on the 3D multi-core processor to find potential benefits of liquid cooling. We first investigate the thermal behavior and compare the performance of two different cooling schemes. We also evaluate the leakage power consumption and lifetime reliability depending on the temperature in the 3D multi-core processor.

• 한국전기전자재료학회논문지
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• 제22권12호
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• pp.1073-1077
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• 2009

The iron core, which comprises the superconducting fault current limiter (SFCL) using magnetic coupling of coils, can be operated in the saturation region, especially at the initial fault period. This operation of the iron core in the saturation region deteriorates the fault current limiting operation of the SFCL. To solve the saturation problem of the SFCL using magnetic coupling of coils, the iron core with two magnetic paths, which has an air-gap in one of them, was adopted. In this paper, the hysteresis characteristics of SFCL using magnetic coupling of coils, which were wound in the iron core with two magnetic paths, were analyzed. Through comparative analysis on the hysteresis characteristics of the iron core comprising SFCL, the hysteresis characteristics of the iron core with two magnetic paths were confirmed to be kept in the non-saturation region during the fault period and thus, the effective fault current limiting operation of the SFCL using the magnetic coupling of coils could be performed.

• 과학교육연구지
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• 제44권2호
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• pp.183-196
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• 2020

본 연구는 예비 과학교사들을 대상으로 아두이노를 활용한 STEAM 프로그램을 적용하여 융합인재 핵심 역량에 어떠한 변화가 있는지 살펴보았다. 아두이노를 활용한 STEAM 프로그램은 STEAM과 아두이노, 그리고 SW 교육에 대한 이론적 배경의 학습, 상황 제시, 창의적 설계, 감성적 체험, 그리고 평가 단계로 구성되며, 각 단계에서 아두이노를 활용할 수 있도록 구성하였다. 예비 과학교사들은 '미세먼지'를 주제로 아두이노를 활용한 STEAM 프로그램을 경험하였다. 예비교사들은 상황제시 단계에서 미세먼지란 무엇인지, 그리고 미세먼지의 심각성에 대해 학습한 후 미세먼지 측정기의 원리에 대해 살펴보았다. 창의적 설계 단계에서는 공기청정기를 제작하기 위해 설계도를 고안하였으며, 이때 아두이노를 활용하여 미세먼지 측정기 제작을 위한 방안을 구상할 수 있도록 하였다. 다음으로 감성적 체험 단계에서는 공기 청정기를 제작하고, 아두이노를 활용하여 미세먼지 측정기를 제작하도록 하였다. 마지막 평가 단계에서는 제작한 공기청정기를 작동하여 미세먼지 측정기를 활용하여 미세먼지 농도를 측정하여 평가할 수 있도록 하였다. 예비교사들은 아두이노를 활용한 STEAM 프로그램 경험 후 의사소통 역량, 문제 해결 역량, 정보수집 역량, 논리분석적 사고 역량, 창의적 역량이 향상되었다. 또한, 예비교사들은 프로그램 경험 후 예비교사들은 아두이노를 활용한 STEAM 수업의 학교 현장에서의 활용 가능성에 대해 과학적 탐구능력 함양, 협동심과 소통능력 향상, 문제해결력과 창의적 사고력 활용을 언급하였다. 또한 이들은 STEAM 프로그램에 아두이노를 접목하여 활용함으로써 소프트웨어적 지식과 능력을 기를 수 있을 것이라고 하였다.

• 한국전문물리치료학회지
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• 제17권1호
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• pp.17-25
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• 2010

The aim of this study was to investigate the effect of supporting surface instability to trunk and lower extremity muscle activities during bridging exercise combined with core-stabilization exercise. Thirty young healthy adults (15 males and 15 females) voluntarily participated in this study. Each subject was asked to perform bridging exercise combined with core-stabilization exercise on three different supporting surfaces (stable ground surface, the wooden balancing board, and the air cushion). The muscle activities were measured using surface electromyography (EMG) during performing exercise. To test statistical significance, one-way ANOVA with repeated measures was used with the significance level of .05. The findings of this study are summarized as follows. (1) There were significant differences in muscle activities on internal oblique, external oblique, gluteus medius, semitendinosus, biceps femoris, medial gastrocnemius and lateral gastrocnemius during exercise (p<.05). (2) The biceps femoris and lateral gastrocnemius showed significantly higher muscle activity on the wooden balancing board rather than on the ground, and semitendinosus, biceps femoris, medial gastrocnemius and lateral gastrocnemius showed significantly higher muscle activity on the air cushion rather than on the ground (p<.05). Therefore, it is concluded that muscle activities in the trunk and the lower limbs during bridging exercise combined with core-stabilization exercise was affected with instability of supporting surface. Further researches are needed to investigate the long term effect of bridging exercise on muscle activity with patient group.

• 한국주거학회논문집
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• 제16권4호
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• pp.37-44
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• 2005

The purpose of this study is to analyze the typological characteristics of super high-rise housings in Hong Kong. The results are as follows; 1) Most of the plan types of the residential building in Hong Kong are tower types and they show lots of curves on the external resident blocks so that each resident families can face maximum open air. 2) Each residential unit is arranged symmetrically and systematically around the central core. 3) The most of core types are central core types which are usually planned to place void light well to improve lighting and ventilation. 4) Rooms are arranged in line from entrance to kitchen, to living & dinning room, and finally bedroom and bathroom. Dinning area is arranged together with living area. 5) At least, more than two sides of the each unit were facing the open air; one side is for the view from a bedroom or a livingroom, the other side is for the ventilation of a kitchen or a bathroom.