• 대한기계학회논문집 C: 기술과 교육
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• 제1권1호
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• pp.69-73
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• 2013

역삼투막을 이용한 해수담수화 공정에서 발생되는 농축수의 최소방류 및 회수율 극대화를 위한 공정으로 전기투석을 이용한 농축수의 이차 농축기술 연구를 수행하였다. 실험방법은 정전압운전 방식을 채용하였으며, 농축/탈염조의 용량비율, 전압별 변화 및 전해질을 농축수로 활용시 등에 대한 검토를 수행하였다. 사용한 막은 다가이온막을 채용하였으며, 전력효율을 최소화하며, 농축수의 농도를 극대화 및 탈염수의 농도를 최소화할 수 있는 조건 도출을 목표로 삼았다. 실험결과 농축/탈염조의 비율은 1대 5의 비율이, 전압의 경우 12V로 전해질의 경우 농축수를 이용시에도 효율에는 큰 차이가 발생하지 않았다. 이와 같은 실험조건에서 도출된 최적조건으로는 탈염수의 총용존고형물 농도가 5.32g/l, 이차 농축수의 염도는 17.07%이며 전력량은 탈염수 톤당 16.74kWh로 나타났다.

• 한국유기농업학회지
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• 제11권1호
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• pp.79-88
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• 2003

본 연구는 찰옥수수의 무경운 재배의 가능성을 구명하고자 5개의 찰옥수수 교잡종을 공시하여 경운 재배와 무경운재배에서 풋이삭수량, 종실구량, 및 주요형질의 반응을 조사하였으며 그 결과는 다음과 같다. 1. 경운 구에 비하여 무경운구에서는 출현율이 4％ 정도 낮았고, 출웅일수와 출사일수가 다소 빨랐으며, 생육초기와 후기의 초장은 길었다. 2. 이삭길이 및 수량구성요소는 경운구와 무경운구의 차이가 없었으나, 교잡종간에는 유의성이 있었다. 3. 무경운구의 풋이삭수량과 종실수량은 경운구와 차이를 보이지 않아 무경운재배의 가능성을 나타내었다. 4. 출웅일수, 출사일수, 초장, 이삭길이는 풋이삭수량 및 종실수량과 상관관계를 나타내었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.164-164
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• 2013

Among multicomponent nanostructures, hybrid nanocatalysts consisting of metal nanoparticle-semiconductor junctions offer an interesting platform to study the role of metal-oxide interfaces and hot electron flows in heterogeneous catalysis. In this study, we report that hot carriers generated upon photon absorption significantly impact the catalytic activity of CO oxidation. We found that Pt-CdSe-Pt nanodumbbells exhibited a higher turnover frequency by a factor of two during irradiation by light with energy higher than the bandgap of CdSe, while the turnover rate on bare Pt nanoparticles didn't depend on light irradiation. We also found that Pt nanoparticles deposited on a GaN substrate under light irradiation exhibit changes in catalytic activity of CO oxidation that depends on the type of doping of the GaN. We suppose that hot electrons are generated upon the absorption of photons by the semiconducting nanorods or substrates, whereafter the hot electrons are injected into the Pt nanoparticles, resulting in the change in catalytic activity. We discuss the possible mechanism for how hot carrier flows generated during light irradiation affect the catalytic activity of CO oxidation.

• 전기학회논문지
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• 제62권8호
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• pp.1080-1089
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• 2013

Interior Permanent Magnet Synchronous Machines (IPMSMs) with rare earth magnet are widely used in electric vehicles and hybrid electric vehicles. IPMSMs having high efficiency, high torque, and a wide speed range are employed in propulsion system. And the rotor in an IPMSM is generally made of a rare earth magnet to achieve a large energy product and high torque. This paper discusses issues regarding design and performance of IPMSMs using different factors of BH magnetic characteristic. It is necessary to choose factors of magnetic material according to permanent magnet shape in rotor for high performance. Response Surface Methodology (RSM) is selected to obtain factors of magnetic material according to variety of rotor shapes. The RSM is a collection of mathematical and statistical techniques useful for the analysis of problems in which a response of interest in influenced by several variables and the objective is to optimize response. Therefore, it is necessary to analyze the torque characteristics of an IPMSM having magnet BH hysteresis curve with different rotor shape. Factors of residual flux density (Br) factor and intrinsic coercive force (Hc) are important parameters in RSM for rotor shape. The rotor shapes for IPMSMs having magnet BH characteristic were investigated using the RSM, and three shapes were analyzed in detail using FEA. The results lead to design consequence of IPMSMs in the various rare earth magnet materials.

• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.209-220
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• 1998

The stability problem of steady motion of a rigid body with multi-elastic appendages and multi-liquid-filled cavities, in the presence of no external forces or torque, is considered in this paper. The flexible appendages are modeled as the clamped -free-free-free rectangular plates, or/and as the discrete mass- spring sub-system. The motion of liquid in every single ellipsoidal cavity is modeled as the uniform vortex motion with a finite number of degrees of freedom. Assuming that stationary holonomic constraints imposed on the body allow its rotation about a spatially fixed axis, the equation of motion for such a systematic configuration can be very complex. It consists of a set of ordinary differential equations for the motion of the rigid body, the uniform rotation of the contained liquids, the motion of discrete elastic parts, and a set of partial differential equations for the elastic appendages supplemented by appropriate initial and boundary conditions. In addition, for such a hybrid system, under suitable assumptions, their equations of motion have four types of first integrals, i.e., energy and area, Helmholtz' constancy of liquid - vortexes, and the constant of the Poisson equation of motion. Chetaev's effective method for constructing Liapunov functions in the form of a set of first integrals of the equations of the perturbed motion is employed to investigate the sufficient stability conditions of steady motions of the complete system in the sense of Liapunov, i.e., with respect to the variables determining the motion of the solid body and to some quantities which define integrally the motion of flexible appendages. These sufficient conditions take into account the vortexes of the contained liquids, the vibration of the flexible components, and coupling among the liquid-elasticity solid.

• 제어로봇시스템학회논문지
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• 제19권7호
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• pp.646-652
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• 2013

EU's Galileo project is a market-based GNSS (Global Navigation Satellite System) that is under development. It is expected that Galileo will provide the positioning services based on new technologies in 2020s. Because Galileo E1 signal for OS (Open Service) shares the same center frequency with GPS L1 C/A signal, CBOC (Composite Binary Offset Carrier) modulation scheme is used in the E1 signal to guarantee interoperability between two systems. With E1 signal consisting of a data channel and a pilot channel at the same frequency band, there exist several options in designing signal acquisition for Assisted-Galileo receivers. Furthermore, compared to SNR worksheet of Assisted-GPS, some factors should be examined in Assisted-Galileo due to different correlation profile and code length of E1 signal. This paper presents SNR worksheets of Galileo E1 signals in E1-B and E1-C channel. Three implementation losses that are quite different from GPS are mainly analyzed in establishing SNR worksheets. In the worksheet, hybrid long integration of 1.5s is considered to acquire weak signal less than -150dBm. Simulation results show that the final SNR of E1-B signal with -150dBm is 19.4dB and that of E1-C signal is 25.2dB. Comparison of relative computation shows that E1-B channel is more profitable to acquire the strongest signal in weak signal environment. With information from the first satellite signal acquisition, fast acquisition of the weak signal around -155dBm can be performed with E1-C signal in the subsequent satellites.

• 대한간호학회지
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• 제36권5호
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• pp.782-791
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• 2006

Purpose: The purpose of this study was to conceptualize and clarify a concept of "preparatory grief" in terminal cancer patients. Method: A hybrid model of concept development was applied to develop a concept of preparatory grief, which included a field study carried out in Busan, Korea. Participants of this study were 8 cancer patients. Results: On the basis of our literature, research and clinical experience, the concept of preparatory grief emerged as a complex phenomenon playing an important role in five areas; physical, emotional, interpersonal, religious, and transcendental dimensions. Two new attributes were defined through a field phase; trust of the post-mortal world and a serene state of mind. Indicators reflected attitudes of sadness, worry, regret, capability to adapt and hope. The results of preparatory grief were loss of energy and interest, emotional chaos, contemplation, taciturnity and restoration. Conclusions : Differentiating among preparatory grief and other symptoms in cancer patients is essential because of therapeutic implications. Understanding preparatory grief is necessary in order to manage cancer patients for promoting quality of life so that its application may have a positive impact on the patient's life.

• 한국추진공학회지
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• 제21권5호
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• pp.10-18
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• 2017

알루미늄 입자들이 함유된 고폭약의 비정상 데토네이션 전파속도에 대하여 수치 해석을 수행하였다. 알루미늄 입자의 점화와 연소는 고폭약에 비해 상대적으로 긴 시간이 요구되기 때문에, 알루미늄 입자연소에 의한 에너지 발산은 고폭약의 데토네이션 후방에서 이루어진다. 이러한 비정상 데토네이션에 대한 수치해석은 기체상과 균일하게 분포된 고체 입자와의 질량, 운동량, 에너지 교환을 다루는 이종매질 이론을 이용한다. 알루미늄 입자가 함유된 고폭약의 데토네이션 전파에 대한 수치 해석은 폭약 HMX에 대하여 수행되었으며, 5~25%의 알루미늄 함량과 0.5, 7, $15{\mu}m$의 알루미늄 입자크기에 대한 수치 해석 결과와 실험 결과를 비교하여 검증하였다.

• 대한기계학회논문집B
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• 제40권6호
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• pp.403-408
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• 2016

리튬 이온 배터리는 높은 에너지 밀도와 안정적인 충전/방전 특성을 내재하고 있어 하이드리드 및 전기자동차에 보편적으로 사용된다. 리튬 이온 배터리의 효율은 배터리 자체의 온도 특성에 직접적인 영향을 받으므로, 열을 효율적으로 냉각하는 기술이 요구된다. 본 논문에서는 수냉식 배터리 냉각 시스템의 냉각 성능과 펌프 소모동력에 관한 전산유체해석을 수행하였다. 이를 위해 배터리 셀의 냉각수 유량 및 냉각 채널의 특성에 따른 냉각 성능을 수치적으로 예측하였다. 이를 바탕으로 250개 배터리 셀을 기준으로 유량 및 차압에 의한 소모동력을 계산하였다. 이러한 연구는 차세대 하이브리드 및 전기자동차의 시간에 따른 배터리의 온도 변화 및 충/방전 효율 최적화 기술에 적용할 수 있는 기초 연구로 활용될 수 있을 것으로 기대된다.

• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.488-499
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• 2016

We present a design and optical simulation of a cost-effective hybrid daylighting/LED system composed of mixing sunlight and light-emitting diode (LED) illumination powered by renewable solar energy for indoor lighting. In this approach, the sunlight collected by the concentrator is split into visible and non-visible rays by a beam splitter. The proposed sunlight collector consists of a Fresnel lens array. The non-visible rays are absorbed by the solar photovoltaic devices to provide electrical power for the LEDs. The visible rays passing through the beam splitters are coupled to a stepped thickness waveguide (STW) by tilted mirrors and confined by total internal reflection (TIR). LEDs are integrated at the end of the STW to improve the lighting quality. LEDs’ light and sunlight are mixed in the waveguide and they are coupled into an optical fiber bundle for indoor illumination. An optical sensor and lighting control system are used to control the LED light flow to ensure that the total output flux for indoor lighting is a fixed value when the sunlight is inadequate. The daylighting capacity was modeled and simulated with a commercial ray tracing software (Lighttools^TM). Results show that the system can achieve 63.8% optical efficiency at geometrical concentration ratio of 630. A required accuracy of sun tracking system achieved more than ±0.5^o . Therefore, our results provide an important breakthrough for the commercialization of large scale optical fiber daylighting systems that are faced with challenges related to high costs.