• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.587-592
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• 2009

Heat transfer model and energy dissipation rate were investigated to examine the heat transfer mechanism in bubble columns with continuous operation. The energy dissipation rate($E_D$) obtained from the unsteady state heat transfer model based on the surface renewal theory was significantly small, comparing with the hydrodynamic energy dissipation rate($P_v$) calculated from the overall hydrodynamic energy balance based on the behaviors and holdups of gas and liquid phases in the column. It was found from these results that the energy dissipation rate based on the surface renewal theory is independent of the hydrodynamic energy dissipation rate obtained from the overall hydrodynamic energy balance in the bubble column, in considering their mechanism. The different two energy dissipation rates were correlated in terms of operating variables within this experimental conditions, respectively.

• Earthquakes and Structures
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• v.5 no.6
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• pp.657-678
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• 2013

For economical earthquake resistant design of cable-stayed bridge tower, the use of energy dissipation systems for the earthquake protection of steel structures represents an alternative seismic design method where the tower structure could be constructed to dissipate a large amount of earthquake input energy through inelastic deformations in certain positions, which could be easily retrofitted after damage. The design of energy dissipation systems for bridges could be achieved as the result of two conflicting requirements: no damage under serviceability limit state load condition and maximum dissipation under ultimate limit state load condition. A new concept for cable-stayed bridge tower seismic design that incorporates sacrificial link scheme of low yield point steel horizontal beam is introduced to enable the tower frame structure to remain elastic under large seismic excitation. A nonlinear dynamic analysis for the tower model with the proposed energy dissipation systems is carried out and compared to the response obtained for the tower with its original configuration. The improvement in seismic performance of the tower with supplemental passive energy dissipation system has been measured in terms of the reduction achieved in different response quantities. Obtained results show that the proposed energy dissipation system of low yield point steel seismic link could strongly enhance the seismic performance of the tower structure where the tower and the overall bridge demands are significantly reduced. Low yield point steel seismic link effectively reduces the damage of main structural members under earthquake loading as seismic link yield level decreases due their exceptional behavior as well as its ability to undergo early plastic deformations achieving the concentration of inelastic deformation at tower horizontal beam.

• Korean Journal of Environmental Agriculture
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• v.37 no.2
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• pp.97-103
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• 2018

BACKGROUND: Dissipation of acetamiprid and thiamethoxam in greenhouse grown chard samples was evaluated at 5 intervals including the pre-harvest interval after application. This study was conducted to determine the residue levels, the biological half-lives and dissipation rate of acetamiprid and thiamethoxam in chard under controlled conditions. METHODS AND RESULTS: Acetamiprid and thiamethoxam were applied in accordance with good agricultural practices for chard. Chard samples were collected at 0, 1, 2, 3, 5, 7, 10 and 14 days after application. Quantitaion was performed by HPLC-DAD system with C18 column. Limit of quantification (LOQ) of acetamiprid and thiamethoxam were both 0.02 mg/kg for chard. The recovery of acetamiprid and thiamethoxam were 77.8~107.5% and 94.3~108.6% at two concentration levels. The half-lives of pesticide dissipation in chard for two fields were 11.9 and 8.2 days for acetamiprid and 3.6 and 3.3 days for thiamethoxam respectively. The dissipation rate of acetamiprid and thiamethoxam were estimated according to the statistics method with a 95% confidence. CONCLUSION: Dissipation of acetamiprid and thiamethoxam in chard were determined under greenhouse. The concentration of acetamiprid and thiamethoxam in chards at 0 days after application were below specified by Korean MRL. Dissipation rate constant will be useful to set the pre-harvest residue limit for public health and consumer protection.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.45-49
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• 2008

Polyethylene is widely used as the insulator for power cable. To investigate the conduction mechanism for power cable insulation under ac high field, it is very important to acquire the dissipation current under actual running field. Recently, we have developed the unique system, which make possible to observe the nonlinear dissipation current waveform. In this system, to observe the nonlinear properties with high accuracy, capacitive current component is canceled by using inverse capacitive current signal instead of using the bridge circuit for canceling it. We have already reported that the dissipation currents of $40\;{\mu}m$ thick LDPE film at 10 kV/mm and over 140 Hz, it starts to show nonlinearity and odd number's harmonics were getting large. To investigate the conduction mechanis ms in this region, especially space charge effect, various kinds of estimation, such as time variations of instantaneous resistivity for one cycle, FFT spectra of dissipation current waveforms and so on, has been examined. As the results of these estimations, it was found that the dissipation current will depend on not only the instantaneous value of electric field but also the time differential of applied electric field due to taking a balance between applied field and internal field. Furthermore, two large peaks of dissipation current for each half cycle were observed under certain condition. In this paper, to clarify the reason why it shows two peaks for each half cycle, the film thickness dependences of dissipation current waveforms were observed by using the three different thickness LDPE films.

• Structural Engineering and Mechanics
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• v.9 no.3
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• pp.241-256
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• 2000

The major sources of energy dissipation in steel frames with partially restrained (PR) connections are evaluated. Available experimental results are used to verify the mathematical model used in this study. The verified model is then used to quantify the energy dissipation in PR connections due to hysteretic behavior, due to viscous damping and at plastic hinges if they are formed. Observations are made for two load conditions: a sinusoidal load applied at the top of the frame, and a sinusoidal ground acceleration applied at the base of the frame representing a seismic loading condition. This analytical study confirms the general behavior, observed during experimental investigations, that PR connections reduce the overall stiffness of frames, but add a major source of energy dissipation. As the connections become stiffer, the contribution of PR connections in dissipating energy becomes less significant. A connection with a T ratio (representing its stiffness) of at least 0.9 should not be considered as fully restrained as is commonly assumed, since the energy dissipation characteristics are different. The flexibility of PR connections alters the fundamental frequency of the frame. Depending on the situation, it may bring the frame closer to or further from the resonance condition. If the frame approaches the resonance condition, the effect of damping is expected to be very important. However, if the frame moves away from the resonance condition, the energy dissipation at the PR connections is expected to be significant with an increase in the deformation of the frame, particularly for low damping values. For low damping values, the dissipation of energy at plastic hinges is comparable to that due to viscous damping, and increases as the frame approaches failure. For the range of parameters considered in this study, the energy dissipations at the PR connections and at the plastic hinges are of the same order of magnitude. The study quantitatively confirms the general observations made in experimental investigations for steel frames with PR connections; however, proper consideration of the stiffness of PR connections and other dynamic properties is essential in predicting the dynamic behavior.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.120-127
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• 1998

An Elliptic model for calculating the combined refraction/diffraction of monochromatic linear waves is developed, including a term which allows for the dissipation of wave energy. Conjugate gradient method is employed as a solution technique. Wave height variations are calculated for localized circular and rectangular dissipation areas. It is shown that the numerical results agree very well with analytical solution in the case of circular damping region. The localized dissipation area creates a shadow region of low wave energy and the recovery of wave height by diffraction occurs very slowly with distance behind the damping region.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.297-305
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• 2002

As advanced earthquake analysis/design methods such as the nonlinear static analysis are developed, it is required to estimate precisely the cyclic behavior of reinforced concrete members that is characterized by strength, deformability, and capacity of energy dissipation. However, currently, estimation of energy dissipation depends on empirical equations that are not sufficiently accurate, or experiment and sophisticated numerical analysis which are difficult to use in practice. In the present study, nonlinear finite element analysis was performed to investigate the behavioral characteristics of flexure-dominant RC members under cyclic load. The effects of axial force, arrangement of reinforcing bars, and reinforcement ratio on the cyclic behavior were studied. Based on the investigation, a simplified method to estimate the capacity of energy dissipation was proposed, and it was verified by the comparison with the finite element analyses and experiments. The proposed method can estimate the energy dissipation of RC members more precisely than currently used empirical equations, and it is easily applicable in practice.

• Journal of Industrial Technology
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• v.10
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• pp.69-72
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• 1990

In this paper the numerical method for the study of wave reflection from and transmission through submerged permeable breakwaters using the boundary element method is developed. The numerical analysis technique is based on the wave pressure function instead of velocity potential because it is difficult to define the velocity potential in the each region arising the energy dissipation. Also, the non-linear energy dissipation within the submerged porous structure is simulated by introducing the linear dissipation coefficient and the tag mass coefficient equivalent to the non-linear energy dissipation. For the validity of this analysis technique, the numerical results obtained by the present boundary element method are compared with those obtained by the other computation method. Good agreements are obtained and so the validity of the present numerical analysis technique is proved.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.1
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• pp.112-121
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• 2020

In this work energy and entransy characteristics of heat exchangers are analyzed for 12 different flow arrangements of heat exchangers. The dimensionless parameters are number of entransy dissipation (Ng), number of entransy dissipation-based thermal resistance (Nr), and entransy dissipation-based effectiveness of heat-exchanger (εg). The dimensionless parameters are expressed analytically in terms of the effectiveness of heat exchanger (ε), heat capacity ratio (c), and number of transfer unit (N) for optimal performance of heat exchangers. Results showed that the dimensionless parameters based on the entransy dissipation can be useful concepts for optimal design of heat exchangers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.224-234
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• 1997

It was demonstrated earlier that for laminar, isothermal flow of the lubricant in long journal bearings, inertia has negligible effect on the load carrying capacity and influences only the stability characteristics of the bearing. The question in the present paper is: 'will these conclusions of the isothermal theory remain valid in the presence of significant dissipation, or will lubricant inertia and dissipation interact non-linearly to bring about qualitative changes in bearing performance\ulcorner' The results obtained here assert that the effect of lubricant inertia on load carrying capacity remains negligible, irrespective of the rate of dissipation. The stability of the bearing is, however, affected by lubricant inertia. These results, although obtained here for long bearings with Sommerfeld and Gumbel boundary conditions, are believed to be applicable to practical bearing operations and affirm that bearing load may be calculated from classical, i. e., non-inertial theory.