• Title/Summary/Keyword: Dissipation rate

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HEATING OF SUNSPOT CHROMOSPHERES BY SLOW-MODE ACOUSTIC SHOCK WAVES

  • Lee, Myung-Gyoon;Yun, Hong-Sik
    • Journal of The Korean Astronomical Society
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    • v.18 no.1
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    • pp.15-31
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    • 1985
  • Making use of the arbitrary shock theory developed by Ulmschneider (1967, 1971) and Ulmschneider and Kalkofen (1978), we have calculated the dissipation rates of upward-travelling slow-mode acoustic shock waves in umbral chromospheres for two umbral chromosphere models, a plateau model by Avrett (1981) and a gradient model by Yun and Beebe (1984). The computed shock dissipation rates are compared with the radiative cooling rate given by Avrett (1981). The results show that the slow-mode acoustic shock waves with a period of about 20 second can heat the low umbral chromospheres travelling with a mechanical energy flux of $2.6{\times}10^6\;erg/cm^2s$ at a height of $300{\sim}400km$ above the temperature minimum region.

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Character of PWM DC-DC Converter for Conduction Loss Reduction and Efficiency Rise (전도손실 저감 및 효율 상승을 위한 PWM DC-DC 컨버터의 특성)

  • Kim, M.Y.;Kim, H.J.;Kim, C.Y.;Lyu, J.Y.;Kim, S.W.
    • Proceedings of the KIEE Conference
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    • 2007.11c
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    • pp.125-127
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    • 2007
  • Presented increase and so on of switch stress and switching dissipation and EMI that is happened in general PWM converter and in this study to solve problem the resonance energy return to life rate and new active snubber PWM converter because do maximization. Active snubber PWM converter that try adds auxiliary switch and resonance capacitor, diode to existing converter under all switching conditions turn on/off Minimised switching dissipation that occur. Reduced harmonic components absorbing station recovery electric current that happen to snubber diode inserting diode and resistance. And decreased peak current that is happened in auxiliary switch arranging resonance capacitor and inductor properly, Certified effect that efficiency rises about 2.5[%] more than existent PWM converter in rated load through an experiment.

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A Study on Nonlinear Rocking Vibration Characteristics of Rigid Block (In the Case of Sliding Occurrence) (강체 블록의 비선형 로킹진동특성에 관한 연구 (미끄럼이 있는 경우))

  • 정만용;김정호;김선규;나기대;양인영
    • Journal of the Korean Society of Safety
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    • v.15 no.1
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    • pp.1-10
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    • 2000
  • This paper deals with rocking response behavior of rigid block structure subjected to horizontal excitation. A strict consideration of impact and sliding between the block and base is essential to investigate the rocking vibration characteristics because the rocking behavior were greatly influenced by the impact and sliding motion. Therefore, not only restitution coefficient between the block and base but also the energy dissipation rate which is associated with sliding motion, and the static and kinetic friction coefficient between those should be included in the modeling of rocking system. The analytic program was developed to be able to simulate the experimental responses of the block subjected to horizontal sinusoidal excitations. By using this program, rocking responses were numerically calculated by the nonlinear equations for rocking system. From the response simulation and rocking vibration experiment, the following results were obtained. The rocking responses are affected by the impact motion due to energy dissipation and friction and provide very complex behavior. The toppling condition of the block is also influenced by the impact motion and sliding motion.

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Entropy analysis in a cilia transport of nanofluid under the influence of magnetic field

  • Abrar, Muhammad N.;Haq, Rizwan Ul;Awais, Muhammad;Rashid, Irfan
    • Nuclear Engineering and Technology
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    • v.49 no.8
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    • pp.1680-1688
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    • 2017
  • In this study, analysis is performed on entropy generation during cilia transport of water based titanium dioxide nanoparticles in the presence of viscous dissipation. Moreover, thermal heat flux is considered at the surface of a channel with ciliated walls. Mathematical formulation is constructed in the form of nonlinear partial differential equations. Making use of suitable variables, the set of partial differential equations is reduced to coupled nonlinear ordinary differential equations. Closed form exact solutions are obtained for velocity, temperature, and pressure gradient. Graphical illustrations for emerging flow parameters, such as Hartmann number (Ha), Brinkmann number (Br), radiation parameter (Rn), and flow rate, have been prepared in order to capture the physical behavior of these parameters. The main goal (i.e., the minimizing of entropy generation) of the second law of thermodynamics can be achieved by decreasing the magnitude of Br, Ha and ${\Lambda}$ parameters.

A Power-Efficient CMOS Adaptive Biasing Operational Transconductance Amplifier

  • Torfifard, Jafar;A'ain, Abu Khari Bin
    • ETRI Journal
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    • v.35 no.2
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    • pp.226-233
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    • 2013
  • This paper presents a two-stage power-efficient class-AB operational transconductance amplifier (OTA) based on an adaptive biasing circuit suited to low-power dissipation and low-voltage operation. The OTA shows significant improvements in driving capability and power dissipation owing to the novel adaptive biasing circuit. The OTA dissipates only $0.4{\mu}W$ from a supply voltage of ${\pm}0.6V$ and exhibits excellent high driving, which results in a slew rate improvement of more than 250 times that of the conventional class-AB amplifier. The design is fabricated using $0.18-{\mu}m$ CMOS technology.

Battery Equalization Method for Parallel-connected Cells Using Dynamic Resistance Technique

  • La, Phuong-Ha;Choi, Sung-Jin
    • Proceedings of the KIPE Conference
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    • 2018.11a
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    • pp.36-38
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    • 2018
  • As the battery capacity requirement increases, battery cells are connected in a parallel configuration. However, the sharing current of each battery cell becomes unequal due to the imbalance between cell's impedance which results the mismatched states of charge (SOC). The conventional fixed-resistance balancing methods have a limitation in battery equalization performance and system efficiency. This paper proposes a battery equalization method based on dynamic resistance technique, which can improve equalization performance and reduce the loss dissipation. Based on the SOC rate of parallel connected battery cells, the switches in the equalization circuit are controlled to change the equivalent series impedance of the parallel branch, which regulates the current flow to maximize SOC utilization. To verify the method, operations of 4 parallel-connected 18650 Li-ion battery cells with 3.7V-2.6Ah individually are simulated on Matlab/Simulink. The results show that the SOCs are balanced within 1% difference with less power dissipation over the conventional method.

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Improvement of Compressor-Cooling Efficiency Based on Ribs (리브를 활용한 압축기 냉각 효율 향상에 관한 연구)

  • Hwang, Il Sun;Lee, Young Lim
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.20 no.6
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    • pp.70-75
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    • 2021
  • Recently, several efforts have been made to improve the thermal efficiency of a refrigerant compressor. In this study, we attempted to improve energy efficiency ratio (EER) performance by reducing the superheat of the linear compressor. To this end, heat generated inside the compressor must be effectively dissipated. Therefore, heat dissipation was improved by processing ribs in the gap-flow region generated owing to the vibration of the compressor body. The results showed that the convective heat transfer coefficient becomes significantly high when ribs are used, increasing the heat dissipation rate. This helps improve EER by reducing the superheat of the compressor.

The effects of thermo-mechanical behavior of living tissues under thermal loading without energy dispassion

  • Ibrahim Abbas;M. Saif AlDien;Mawahib Elamin;Alaa El-Bary
    • Coupled systems mechanics
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    • v.13 no.1
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    • pp.61-72
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    • 2024
  • This study seeks to develop analytical solutions for the biothermoelastic model without accounting for energy dissipation. These solutions are then applied to estimate the temperature changes induced by external heating sources by integrating relevant empirical data characterizing the biological tissue of interest. The distributions of temperature, displacement, and strain were obtained by utilizing the eigenvalues approach with the Laplace transforms and numerical inverse transforms method. The impacts of the rate of blood perfusion and the metabolic activity parameter on thermoelastic behaviors were discussed specifically. The temperature, displacement, and thermal strain results are visually represented through graphical representations.

Residue Dissipation Patterns of Indoxacarb and Pymetrozine in Broccoli under Greenhouse Conditions (시설재배 브로콜리 중 Indoxacarb 및 Pymetrozine의 잔류 소실특성)

  • Yang, Seung-Hyun;Lee, Jae-In;Choi, Hoon
    • Korean Journal of Environmental Agriculture
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    • v.39 no.1
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    • pp.75-82
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    • 2020
  • BACKGROUND: This study was carried out to establish pre-harvest residue limits (PHRLs) of indoxacarb and pymetrozine in broccoli under greenhouse conditions, based on dissipation patterns and biological half-lives of pesticides during 10 days after application. METHODS AND RESULTS: The field studies were conducted in two different greenhouse, located in Chungju-si (Field 1) and Gunsan-si (Field 2). Samples were collected at 0, 1, 2, 3, 5, 7 and 10 days after spraying pesticide suspension. The analytical methods for indoxacarb and pymetrozine using HPLC-DAD were validated by recoveries ranging of 94.3-105.4% and 81.8-96.0%, respectively, and MLOQ (Method Limit of Quantification) of 0.05 mg/kg. Biological half-lives of indoxacarb and pymetrozine were 2.9 and 3.2-3.8 days in broccoli, respectively. The lower 95% confidence intervals of dissipation rate constant of indoxacarb were determined as 0.1508 (Field 1) and 0.2017 (Field 2), whereas those of pymetrozine were calculated as 0.1489 (Field 1) and 0.1577 (Field 2). CONCLUSION: The significant differences were not observed between the dissipation rates of indoxacarb and pymetrozine in broccoli. The major factor affecting residue dissipation was the dilution effect by fast growth. The PHRLs for 10 days prior to harvest were recommended as 30.06 (Field 1) and 18.07 (Field 2) mg/kg for indoxacarb, and 4.84 (Field 1) and 4.43 (Field 2) mg/kg for pymetrozine, respectively.

A High Data Rate, High Output Power 60 GHz OOK Modulator in 90 nm CMOS

  • Byeon, Chul Woo;Park, Chul Soon
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.17 no.3
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    • pp.341-346
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    • 2017
  • In this paper, we present a 60 GHz on-off keying (OOK) modulator in a 90 nm CMOS. The modulator employs a current-reuse technique and a switching modulation for low DC power dissipation, high on/off isolation, and high data rate. The measured gain of the modulator, on/off isolation, and output 1-dB compression point is 9.1 dB, 24.3 dB, and 5.1 dBm, respectively, at 60 GHz. The modulator consumes power consumption of 18 mW, and is capable of handling data rates of 8 Gb/s at bit error rate of less than $10^{-6}$ for $231^{-1}$ PRBS over a distance of 10-cm with an OOK receiver module.