The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform
Jae Hong Park - One of the best experts on this subject based on the ideXlab platform.
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fabrication of a multi walled carbon nanotube deposited glass fiber air Filter for the enhancement of nano and submicron aerosol particle filtration and additional antibacterial efficacy
Science of The Total Environment, 2011Co-Authors: Ki Young Yoon, Hyungjoo Na, Jungho Hwang, Jae Hong Park, Young Hun YoonAbstract:We grew multi-walled carbon nanotubes (MWCNTs) on a glass fiber air Filter using thermal chemical vapor deposition (CVD) after the Filter was catalytically activated with a spark discharge. After the CNT deposition, filtration and antibacterial Tests were performed with the Filters. Potassium chloride (KCl) particles (< 1 μm) were used as the Test aerosol particles, and their number concentration was measured using a scanning mobility particle sizer. Antibacterial Tests were performed using the colony counting method, and Escherichia coli (E. coli) was used as the Test bacteria. The results showed that the CNT deposition increased the filtration efficiency of nano and submicron-sized particles, but did not increase the pressure drop across the Filter. When a pristine glass fiber Filter that had no CNTs was used, the particle filtration efficiencies at particle sizes under 30 nm and near 500 nm were 48.5% and 46.8%, respectively. However, the efficiencies increased to 64.3% and 60.2%, respectively, when the CNT-deposited Filter was used. The reduction in the number of viable cells was determined by counting the colony forming units (CFU) of each Test Filter after contact with the cells. The pristine glass fiber Filter was used as a control, and 83.7% of the E. coli were inactivated on the CNT-deposited Filter.
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characteristics of submicron sized aerosol filtration and pressure drop of an electret Filter installed in an air diffuser in a residential apartment unit
Aerosol and Air Quality Research, 2011Co-Authors: Jae Hong Park, Yeekyeong Jung, Sunghwan Yi, Jungho HwangAbstract:We investigated submicron-sized aerosol filtration and the pressure drop of an electret Filter called a “Flimmer Filter.” The fibers of the Filter are aligned parallel to the direction of the airflow, unlike conventional fibrous Filters or conventional electret Filters. Lab-scale Tests were performed first in a laboratory duct system for submicron particle removal efficiency and pressure drop of the Filter. Then, Field Tests were conducted in an apartment home using two portable aerosol spectrometers and with a Flimmer Filter installed at the terminal of a duct within a mechanical ventilation system. The removal efficiencies at the face velocity of 1.0 m/s for 0.4 μm and 0.6 μm were 52% and 65%, respectively. The removal efficiency for PM1.0 was about 51%. Through an adapted mass balance model, indoor particle concentrations both in number and mass were predicted. The predicted results for the temporal variations of 0.4 and 0.6 μm sized particle, and PM1.0 correlated well with the results obtained from the field Tests. When the face velocity was 1.0 m/s, which is the nominal operating condition of the Test Filter, the pressure drop was 11.5 Pa, which is relatively lower than the pressure drops of other conventional fibrous Filters or conventional electret Filters having the same filtration efficiency.
Jungho Hwang - One of the best experts on this subject based on the ideXlab platform.
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fabrication of a multi walled carbon nanotube deposited glass fiber air Filter for the enhancement of nano and submicron aerosol particle filtration and additional antibacterial efficacy
Science of The Total Environment, 2011Co-Authors: Ki Young Yoon, Hyungjoo Na, Jungho Hwang, Jae Hong Park, Young Hun YoonAbstract:We grew multi-walled carbon nanotubes (MWCNTs) on a glass fiber air Filter using thermal chemical vapor deposition (CVD) after the Filter was catalytically activated with a spark discharge. After the CNT deposition, filtration and antibacterial Tests were performed with the Filters. Potassium chloride (KCl) particles (< 1 μm) were used as the Test aerosol particles, and their number concentration was measured using a scanning mobility particle sizer. Antibacterial Tests were performed using the colony counting method, and Escherichia coli (E. coli) was used as the Test bacteria. The results showed that the CNT deposition increased the filtration efficiency of nano and submicron-sized particles, but did not increase the pressure drop across the Filter. When a pristine glass fiber Filter that had no CNTs was used, the particle filtration efficiencies at particle sizes under 30 nm and near 500 nm were 48.5% and 46.8%, respectively. However, the efficiencies increased to 64.3% and 60.2%, respectively, when the CNT-deposited Filter was used. The reduction in the number of viable cells was determined by counting the colony forming units (CFU) of each Test Filter after contact with the cells. The pristine glass fiber Filter was used as a control, and 83.7% of the E. coli were inactivated on the CNT-deposited Filter.
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characteristics of submicron sized aerosol filtration and pressure drop of an electret Filter installed in an air diffuser in a residential apartment unit
Aerosol and Air Quality Research, 2011Co-Authors: Jae Hong Park, Yeekyeong Jung, Sunghwan Yi, Jungho HwangAbstract:We investigated submicron-sized aerosol filtration and the pressure drop of an electret Filter called a “Flimmer Filter.” The fibers of the Filter are aligned parallel to the direction of the airflow, unlike conventional fibrous Filters or conventional electret Filters. Lab-scale Tests were performed first in a laboratory duct system for submicron particle removal efficiency and pressure drop of the Filter. Then, Field Tests were conducted in an apartment home using two portable aerosol spectrometers and with a Flimmer Filter installed at the terminal of a duct within a mechanical ventilation system. The removal efficiencies at the face velocity of 1.0 m/s for 0.4 μm and 0.6 μm were 52% and 65%, respectively. The removal efficiency for PM1.0 was about 51%. Through an adapted mass balance model, indoor particle concentrations both in number and mass were predicted. The predicted results for the temporal variations of 0.4 and 0.6 μm sized particle, and PM1.0 correlated well with the results obtained from the field Tests. When the face velocity was 1.0 m/s, which is the nominal operating condition of the Test Filter, the pressure drop was 11.5 Pa, which is relatively lower than the pressure drops of other conventional fibrous Filters or conventional electret Filters having the same filtration efficiency.
S Moinian - One of the best experts on this subject based on the ideXlab platform.
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high q inductors for wireless applications in a complementary silicon bipolar process
IEEE Journal of Solid-state Circuits, 1996Co-Authors: K B Ashby, I A Koullias, W C Finley, J J Bastek, S MoinianAbstract:Rectangular spiral inductors with Q's over 12 have been built in a high-speed complementary bipolar process and characterized for use in wireless applications. An accurate broadband model for the inductors has been developed, and a Test Filter and mixer have been built to verify the performance of the inductors and the accuracy of the model.
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High Q inductors for wireless applications in a complementary silicon bipolar process
Proceedings of IEEE Bipolar BiCMOS Circuits and Technology Meeting, 1994Co-Authors: K B Ashby, W C Finley, J J Bastek, S Moinian, I A KoulliasAbstract:Rectangular spiral inductors with Q's as high as 12 have been built in a high-speed complementary bipolar process and characterized for use in wireless applications. An accurate broadband model has been developed for the inductors, and a Test Filter and mixer have been built to verify the performance of the inductors and the accuracy of the model.
Marc B Parlange - One of the best experts on this subject based on the ideXlab platform.
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a scale dependent lagrangian dynamic model for large eddy simulation of complex turbulent flows
Physics of Fluids, 2005Co-Authors: Elie Bouzeid, Charles Meneveau, Marc B ParlangeAbstract:A scale-dependent dynamic subgrid model based on Lagrangian time averaging is proposed and Tested in large eddy simulations (LES) of high-Reynolds number boundary layer flows over homogeneous and heterogeneous rough surfaces. The model is based on the Lagrangian dynamic Smagorinsky model in which required averages are accumulated in time, following fluid trajectories of the resolved velocity field. The model allows for scale dependence of the coefficient by including a second Test-Filtering operation to determine how the coefficient changes as a function of scale. The model also uses the empirical observation that when scale dependence occurs (such as when the Filter scale approaches the limits of the inertial range), the classic dynamic model yields the coefficient value appropriate for the Test-Filter scale. Validation Tests in LES of high Reynolds number, rough wall, boundary layer flow are performed at various resolutions. Results are compared with other eddy-viscosity subgrid-scale models. Unlike the...
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Field Experimental Study of Dynamic Smagorinsky Models in the Atmospheric Surface Layer.
Journal of the Atmospheric Sciences, 2004Co-Authors: Jan Kleissl, Marc B Parlange, Charles MeneveauAbstract:An analysis of dynamic Smagorinsky models is performed based on the Horizontal Array Turbulence Study (HATS) dataset. In the experiment, two vertically separated horizontal arrays of 14 three-dimensional sonic anemometers were placed in the atmospheric surface layer. Subgrid-scale (SGS) and resolved quantities are derived from 2D Filtering at a Filter scaleD and differentiation of Filtered velocity fields. In a previous study the Smagorinsky coefficient was computed directly from these data and found to depend on atmospheric (D) cs stability and height above the ground. The present study examines the scale-invariant dynamic model of Germano et al. and the scale-dependent dynamic model of Porte ´-Agel et al. and Tests their accuracy in predicting and (D) cs its dependencies on stability and height above the ground. The Germano identity uses a Test Filter at aD (in this study a 5 1.75 is used). The coefficient is derived from various data Test-Filtered at this scale assuming that the Smagorinsky coefficient is scale invariant. The results show that the scale-invariant dynamic model severely underpredicts the coefficient and its trends whenever D is similar to, or larger than, the large-scale limit of the inertial range (typically the smaller of the height above the ground z or the Obukhov length L). The scaledependent dynamic model uses a second Test Filter at scale a 2D to deduce dependence of on the Filtering (D) cs scale. This model gives excellent predictions of and its dependence upon stability and height. (D) cs
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a scale dependent dynamic model for large eddy simulation application to a neutral atmospheric boundary layer
Journal of Fluid Mechanics, 2000Co-Authors: Fernando Porteagel, Charles Meneveau, Marc B ParlangeAbstract:A scale-dependent dynamic subgrid-scale model for large-eddy simulation of turbulent flows is proposed. Unlike the traditional dynamic model, it does not rely on the assumption that the model coefficient is scale invariant. The model is based on a second Test-Filtering operation which allows us to determine from the simulation how the coefficient varies with scale. The scale-dependent model is Tested in simulations of a neutral atmospheric boundary layer. In this application, near the ground the grid scale is by necessity comparable to the local integral scale (of the order of the distance to the wall). With the grid scale and/or the Test-Filter scale being outside the inertial range, scale invariance is broken. The results are compared with those from (a) the traditional Smagorinsky model that requires specification of the coefficient and of a wall damping function, and (b) the standard dynamic model that assumes scale invariance of the coefficient. In the near-surface region the traditional Smagorinsky and standard dynamic models are too dissipative and not dissipative enough, respectively. Simulations with the scale-dependent dynamic model yield the expected trends of the coefficient as a function of scale and give improved predictions of velocity spectra at different heights from the ground. Consistent with the improved dissipation characteristics, the scale-dependent model also yields improved mean velocity profiles.
K B Ashby - One of the best experts on this subject based on the ideXlab platform.
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high q inductors for wireless applications in a complementary silicon bipolar process
IEEE Journal of Solid-state Circuits, 1996Co-Authors: K B Ashby, I A Koullias, W C Finley, J J Bastek, S MoinianAbstract:Rectangular spiral inductors with Q's over 12 have been built in a high-speed complementary bipolar process and characterized for use in wireless applications. An accurate broadband model for the inductors has been developed, and a Test Filter and mixer have been built to verify the performance of the inductors and the accuracy of the model.
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High Q inductors for wireless applications in a complementary silicon bipolar process
Proceedings of IEEE Bipolar BiCMOS Circuits and Technology Meeting, 1994Co-Authors: K B Ashby, W C Finley, J J Bastek, S Moinian, I A KoulliasAbstract:Rectangular spiral inductors with Q's as high as 12 have been built in a high-speed complementary bipolar process and characterized for use in wireless applications. An accurate broadband model has been developed for the inductors, and a Test Filter and mixer have been built to verify the performance of the inductors and the accuracy of the model.