• Journal of Biosystems Engineering
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• 제25권5호
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• pp.379-384
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• 2000

In order to use the natural thermal energy as much as possible for greenhouse heating, the air-air heat pump system involved PCM(phase change material) latent heat storage system was composed, and three types of greenhouse heating system(greenhouse system, greenhouse-PCM latent heat storage system, greenhouse-PCM latent heat storage-heat pump system) were recomposed from the greenhouse heating units to analyze the heating characteristics. The results could be concluded as follows; 1) In the greenhouse heated by the heat pump under the solar radiation of 406.39W/$m^2$, the maximum PCM temperature in the latent heat storage system was 24$^{\circ}C$ and the accumulated thermal energy stored in PCM mass of 816kg during the daytime was 100,320kJ. In the greenhouse without heat pump under the maximum solar radiation of 452.83W/$m^2$, the maximum PCM temperature in the latent heat storage system was 22$^{\circ}C$ and the accumulated thermal energy stored during the daytime was 52.250kJ. 2) In the greenhouse-PCM system without heat pump the heat stored in soil layers from the surface to 30cm of the soil depth was 450㎉/$m^2$. 3) In all of the greenhouse heating systems, the difference between the air temperature in greenhouse and the ambient temperature was about 20~23$^{\circ}C$ in the daytime. In the greenhouse without heat pump and PCM latent heat storage system the difference between the ambient temperature and the air temperature in the greenhouse was about 6~7$^{\circ}C$ in the nighttime, in the greenhouse with only PCM latent heat storage system the temperature difference about 7~13$^{\circ}C$ in the nighttime and in the greenhouse with the heat pump and PCM latent heat storage system about 9~14$^{\circ}C$ in the nighttime.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.827-830
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• 2006

With recent advanced in portable electric devices, wireless sensor, MEMS and bio-Mechanics device, the new typed power supply, not conventional battery but self-powered energy source is needed. Particularly, the system that harvests from their environments are interests for use in self powered devices. For very low powered devices, environmental energy may be enough to use power source. In the generality of cases, these energy harvesting systems are used in the piezoelectric materials as mechanisms to convert mechanical vibration energy into electric energy. Through the piezoelectric materials, the ambient vibration energy could be used to prolong the power supply or in the ideal case provide endless energy f9r the devices. Therefore, the piezoelectric power harvesting cantilever beam is developed. Also, the output voltage and power are predicted in this study. We also discuss the developing system of the piezoelectric energy scavenger. An experimental verification of the model is also performed to ensure its accuracy.

• International Journal of Automotive Technology
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• 제7권4호
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• pp.493-500
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• 2006

Investigation on the fuel adhering on a wall was carried out experimentally to clarify the characteristics of impinging diesel sprays. Diesel sprays were injected into a high-pressure chamber of cold state and impinged to a wall having various impingement distances and ambient pressures. Photographs of both the fuel film and the post-impingement spray were taken through a transparent wall. Adhered fuel mass on a wall was measured by means of dividing into two types of fuel state: the fuel film itself; and sparsely adhered fuel droplets. Adhering fuel ratio was predicted and further the distribution of fuel mass for impinging diesel spray was analyzed as a function of time. As result, with an increase of the ambient pressure, both the maximum fuel film diameter and the adhered fuel ratio decreased. Based on some assumptions, the adhering fuel mass increased rapidly until the fuel film diameter approached the maximum value, and then increased comparatively gradually.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.147-156
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• 2007

This study offers a design procedure of optimum cable damper for multi-mode vibration control with nonlinear damper and also investigate the relation between mode and amplitude dependency. The proposed multi-mode damping index, which is defined as a energy loss ratio of cable potential, is a main component of optimization problem of optimum nonlinear damper. In order to include the amplitude dependency of nonlinear damper, it is assumed to exist three kinds of multi-mode patterns such as ambient vibration, support excitation and rain-win induced vibration. The optimum damper exponent depends on amplitude patterns. In case of ambient vibration, optimum factor is less than 0.5. In case of support excitation or rain-wind induced vibration is between 0.5 and 1.0. In this study, the effects of cable sag and inclination angle are included in the asymptotic design equation of damped cable structures.

• Smart Structures and Systems
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• 제11권1호
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• pp.123-134
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• 2013

Identifying structural modal parameters, especially those modes within high frequency range, from ambient data is still a challenging problem due to various kinds of uncertainty involved in vibration measurements. A procedure applying an ensemble empirical mode decomposition (EEMD) method is proposed for accurate and robust structural modal identification. In the proposed method, the EEMD process is first implemented to decompose the original ambient data to a set of intrinsic mode functions (IMFs), which are zero-mean time series with energy in narrow frequency bands. Subsequently, a Sub-PolyMAX method is performed in narrow frequency bands by using IMFs as primary data for structural modal identification. The merit of the proposed method is that it performs structural identification in narrow frequency bands (take IMFs as primary data), unlike the traditional method in the whole frequency space (take original measurements as primary data), thus it produces more accurate identification results. A numerical example and a multiple-span continuous steel bridge have been investigated to verify the effectiveness of the proposed method.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 추계학술발표대회 논문집
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• pp.48-52
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• 2008

The photovoltaic modules are affected by heat. The hotter the PV module, the lower the power output, then the life time will be short. If the cell temperature rises above a certain limit the encapsulating materials can be damaged, and this will degrade the performance of the PV module. This paper presents that the PV module temperature can be estimated by using thermal analysis programs, and demonstrates the thermal characteristics of the PV module.

• KIEAE Journal
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• 제4권3호
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• pp.87-94
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• 2004

The purpose of this study is to improve thermal environment of telecommunication equipment rooms that hold TDX-10, TDX-100, 5ESS-2000, PCM of the latest telecommunication equipment. Analysis program is used the commercial CFD code, Star-CD and DOE-2.1E. The result has been compared by the energy consumption and the temperature contour at the 1 m height of room for each case. Different methods such as the relocation of the existing air-conditioner, the inflow of the ambient air into room, the installation of the forced fan and the cooling system equipment of the duct-connection type have been used to test for improvement of thermal environment. The analysis shows that most efficient method is the inflow of the ambient air into room but auxiliary equipment should be needed to prevent the local thermal spot.

• 천문학회지
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• 제29권spc1호
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• pp.253-254
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• 1996

To understand the dynamical structures of stellar wind bubble, one and two-dimensional calculations has been performed. Using FCT Code with cooling effects and assuming constant mass loss rate and ambient medium density, we could divide stellar winds into the regime of slow and fast winds. The slow wind driven bubble shows initially radiative and becomes partially radiative bubble in which shocked stellar wind zone is still adiabatic. In contrast., the fast wind driven bubble shows initially fully adiabatic and becomes adiabatic bubbles with radiative outer shell. We also determine analytically the onset of thin-shell formation time in case of fast wind driven bubble with power-law energy injection and ambient density structure. We solve the line transfer problem with numerical results in order to calculate line profile of [OIII] forbidden line.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.827-832
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• 2009

Exergy is the amount of reversible work obtainable when some matter is brought to a state of thermodynamic equilibrium with ambient. This exergy is availability or useful work induced from carnot cycle, and this can calculate the irreversible loss work which occurs within any thermal or power cycle. The exergy ratio is the value of exergy divided by enthalpy of ambient reference, where the quality of energy or enthalpy in substances is evaluated by exergy ratio. Exergy is very important in optimal design method of thermal system or each component, and the value of exergy at given state is calculated by equation. Here, designer can easily understand and find the value of enthalpy because enthalpy is graphically drawn in chart, however exergy did not. In this paper, exergy and exergy ratio of air were drawn on temperature-entropy chart, and we wish to this chart is a help to design, analysis and education.

• 한국소음진동공학회논문집
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• 제17권9호
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• pp.785-796
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• 2007

This study offers a design procedure of optimum cable damper for multi-mode vibration control with nonlinear damper and also investigates the relation between mode and amplitude dependency. The proposed multi-mode damping index, which is defined as a potential energy loss ratio of cable vibration, is a main component of optimization problem of optimum nonlinear damper. In order to include the amplitude dependency of nonlinear damper, three types of multi-mode patterns such as ambient vibration, support excitation and rain-wind induced vibration are assumed. The optimum damper exponent depends on amplitude patterns. In case of ambient vibration, optimum factor is less than 0.5 and in case of support excitation or rain-wind induced vibration it is between 0.5 and 1.0.