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Search Results: 1 - 10 of 321911 matches for " Cheng J "
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A Novel Wind Energy Conversion System with Storage for Spillage Recovery  [PDF]
J. Cheng, F. Choobineh
Journal of Power and Energy Engineering (JPEE) , 2015, DOI: 10.4236/jpee.2015.37006
Abstract:

This paper proposes a new system configuration for integrating a compressed air energy storage system with a conventional wind turbine. The proposed system recycles the mechanical spillage of blades and stores it for later electricity generation with assistance from a rotary vane machine. The configuration and operational policy is explained, and a comparative case study shows that the proposed system recovers investment costs through savings on electricity procurement and revenue through power export.?

Influence of carbon nanotube length on toxicity to zebrafish embryos
Cheng J, Cheng SH
International Journal of Nanomedicine , 2012, DOI: http://dx.doi.org/10.2147/IJN.S30459
Abstract: fluence of carbon nanotube length on toxicity to zebrafish embryos Original Research (2384) Total Article Views Authors: Cheng J, Cheng SH Published Date July 2012 Volume 2012:7 Pages 3731 - 3739 DOI: http://dx.doi.org/10.2147/IJN.S30459 Received: 01 February 2012 Accepted: 27 March 2012 Published: 20 July 2012 Jinping Cheng,1,2 Shuk Han Cheng1 1Department of Biology and Chemistry, City University of Hong Kong, Hong Kong; 2State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, China Abstract: There is currently a large difference of opinion in nanotoxicology studies of nanomaterials. There is concern about why some studies have indicated that there is strong toxicity, while others have not. In this study, the length of carbon nanotubes greatly affected their toxicity in zebrafish embryos. Multiwalled carbon nanotubes (MWCNTs) were sonicated in a nitric acid solution for 24 hours and 48 hours. The modified MWCNTs were tested in early developing zebrafish embryo. MWCNTs prepared with the longer sonication time resulted in severe developmental toxicity; however, the shorter sonication time did not induce any obvious toxicity in the tested developing zebrafish embryos. The cellular and molecular changes of the affected zebrafish embryos were studied and the observed phenotypes scored. This study suggests that length plays an important role in the in vivo toxicity of functionalized CNTs. This study will help in furthering the understanding on current differences in toxicity studies of nanomaterials.
Black-body radiation shift of the Ga$^{+}$ clock transition
Yongjun Cheng,J. Mitroy
Physics , 2013, DOI: 10.1088/0953-4075/46/18/185004
Abstract: The blackbody radiation shift of the Ga$^+$ $4s^2 \ ^1S^e_0 \to 4s4p \ ^3P^o_0$ clock transition is computed to be $-$$0.0140 \pm 0.0048$ Hz at 300 K. The small shift is consistent with the blackbody shifts of the clock transitions of other group III ions which are of a similar size. The polarizabilities of the Ga$^+$ $4s^2 \ ^1S^e_0$, $4s4p \ ^3P^o_0$, and $4s4p \ ^1P^o_1$ states were computed using the configuration interaction method with an underlying semi-empirical core potential. A byproduct of the analysis involved large scale calculations of the low lying spectrum and oscillator strengths of the Ga$^{2+}$ ion.
Comment on "Spin-split two-dimensional electron gas perturbed by intense terahertz laser field"
J. L. Cheng
Physics , 2004,
Abstract: We show that the time-dependent wavefunctions which serve as basis of the whole paper of Xu [Phys. Rev. B {\bf 70}, 193301 (2004)] are incorrect and point out the right ones.
Blackbody radiation shift of B$^+$ clock transition
Yongjun Cheng,J. Mitroy
Physics , 2012, DOI: 10.1103/PhysRevA.86.052505
Abstract: A calculation of the blackbody radiation shift of the B$^+$ clock transition is performed. The polarizabilities of the B$^+$ $2s^2$ $^1$S$^e$, $2s2p$ $^1$P$^o$, and $2s2p$ $^3$P$^o$ states are computed using the configuration interaction method with an underlying semi-empirical core potential. The recommended dipole polarizabilities are 9.64(3) $a_0^3$, 7.78(3) $a_0^3$ and 16.55(5) $a_0^3$ respectively. The derived frequency shift for the $2s^2$ $^1$S$^e$ $\to$ $2s2p$ $^3$P$^o_0$ transition at 300 K is 0.0160(5) Hz. The dipole polarizabilities agree with an earlier relativistic calculation (Safronova {\em et al.} Phys. Rev. Lett. {\bf 107} 143006 (2011)) to better than 0.2%. Quadrupole and octupole polarizabilities and non-adiabatic multipole polarizabilities are also reported.
AIS-BN: An Adaptive Importance Sampling Algorithm for Evidential Reasoning in Large Bayesian Networks
J. Cheng,M. J. Druzdzel
Computer Science , 2011, DOI: 10.1613/jair.764
Abstract: Stochastic sampling algorithms, while an attractive alternative to exact algorithms in very large Bayesian network models, have been observed to perform poorly in evidential reasoning with extremely unlikely evidence. To address this problem, we propose an adaptive importance sampling algorithm, AIS-BN, that shows promising convergence rates even under extreme conditions and seems to outperform the existing sampling algorithms consistently. Three sources of this performance improvement are (1) two heuristics for initialization of the importance function that are based on the theoretical properties of importance sampling in finite-dimensional integrals and the structural advantages of Bayesian networks, (2) a smooth learning method for the importance function, and (3) a dynamic weighting function for combining samples from different stages of the algorithm. We tested the performance of the AIS-BN algorithm along with two state of the art general purpose sampling algorithms, likelihood weighting (Fung and Chang, 1989; Shachter and Peot, 1989) and self-importance sampling (Shachter and Peot, 1989). We used in our tests three large real Bayesian network models available to the scientific community: the CPCS network (Pradhan et al., 1994), the PathFinder network (Heckerman, Horvitz, and Nathwani, 1990), and the ANDES network (Conati, Gertner, VanLehn, and Druzdzel, 1997), with evidence as unlikely as 10^-41. While the AIS-BN algorithm always performed better than the other two algorithms, in the majority of the test cases it achieved orders of magnitude improvement in precision of the results. Improvement in speed given a desired precision is even more dramatic, although we are unable to report numerical results here, as the other algorithms almost never achieved the precision reached even by the first few iterations of the AIS-BN algorithm.
Development and evaluation of pH-responsive single-walled carbon nanotube-doxorubicin complexes in cancer cells
Gu YJ, Cheng J, Jin J, Cheng SH, Wong WT
International Journal of Nanomedicine , 2011, DOI: http://dx.doi.org/10.2147/IJN.S25162
Abstract: pment and evaluation of pH-responsive single-walled carbon nanotube-doxorubicin complexes in cancer cells Original Research (4241) Total Article Views Authors: Gu YJ, Cheng J, Jin J, Cheng SH, Wong WT Published Date November 2011 Volume 2011:6 Pages 2889 - 2898 DOI: http://dx.doi.org/10.2147/IJN.S25162 Yan-Juan Gu1,2,*, Jinping Cheng2,*, Jiefu Jin3, Shuk Han Cheng2, Wing-Tak Wong1 1Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, 2Department of Biology and Chemistry, The City University of Hong Kong, 3Department of Chemistry, The University of Hong Kong, Hong Kong, China *These authors contributed equally to this work Abstract: Single-walled carbon nanotubes (SWNTs) have been identified as an efficient drug carrier. Here a controlled drug-delivery system based on SWNTs coated with doxorubicin (DOX) through hydrazone bonds was developed, because the hydrazone bond is more sensitive to tumor microenvironments than other covalent linkers. The SWNTs were firstly stabilized with polyethylene glycol (H2N-PEG-NH2). Hydrazinobenzoic acid (HBA) was then covalently attached on SWNTs via carbodiimide-activated coupling reaction to form hydrazine-modified SWNTs. The anticancer drug DOX was conjugated to the HBA segments of SWNT using hydrazine as the linker. The resulting hydrazone bonds formed between the DOX molecules and the HBA segments of SWNTs are acid cleavable, thereby providing a strong pH-responsive drug release, which may facilitate effective DOX release near the acidic tumor microenvironment and thus reduce its overall systemic toxicity. The DOX-loaded SWNTs were efficiently taken up by HepG2 tumor cells, and DOX was released intracellularly, as revealed by MTT assay and confocal microscope observations. Compared with SWNT-DOX conjugate formed by supramolecular interaction, the SWNT-HBA-DOX featured high weight loading and prolonged release of DOX, and thus improved its cytotoxicity against cancer cells. This study suggests that while SWNTs have great potential as a drug carrier, the efficient formulation strategy requires further study.
Development and evaluation of pH-responsive single-walled carbon nanotube-doxorubicin complexes in cancer cells
Gu YJ,Cheng J,Jin J,Cheng SH
International Journal of Nanomedicine , 2011,
Abstract: Yan-Juan Gu1,2,*, Jinping Cheng2,*, Jiefu Jin3, Shuk Han Cheng2, Wing-Tak Wong11Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, 2Department of Biology and Chemistry, The City University of Hong Kong, 3Department of Chemistry, The University of Hong Kong, Hong Kong, China*These authors contributed equally to this workAbstract: Single-walled carbon nanotubes (SWNTs) have been identified as an efficient drug carrier. Here a controlled drug-delivery system based on SWNTs coated with doxorubicin (DOX) through hydrazone bonds was developed, because the hydrazone bond is more sensitive to tumor microenvironments than other covalent linkers. The SWNTs were firstly stabilized with polyethylene glycol (H2N-PEG-NH2). Hydrazinobenzoic acid (HBA) was then covalently attached on SWNTs via carbodiimide-activated coupling reaction to form hydrazine-modified SWNTs. The anticancer drug DOX was conjugated to the HBA segments of SWNT using hydrazine as the linker. The resulting hydrazone bonds formed between the DOX molecules and the HBA segments of SWNTs are acid cleavable, thereby providing a strong pH-responsive drug release, which may facilitate effective DOX release near the acidic tumor microenvironment and thus reduce its overall systemic toxicity. The DOX-loaded SWNTs were efficiently taken up by HepG2 tumor cells, and DOX was released intracellularly, as revealed by MTT assay and confocal microscope observations. Compared with SWNT-DOX conjugate formed by supramolecular interaction, the SWNT-HBA-DOX featured high weight loading and prolonged release of DOX, and thus improved its cytotoxicity against cancer cells. This study suggests that while SWNTs have great potential as a drug carrier, the efficient formulation strategy requires further study.Keywords: carbon nanotubes, drug delivery, controlled release, SWNTs
Spin relaxation in $n$-type ZnO quantum wells
C. Lü,J. L. Cheng
Physics , 2009, DOI: 10.1088/0268-1242/24/11/115010
Abstract: We perform an investigation on the spin relaxation for $n$-type ZnO (0001) quantum wells by numerically solving the kinetic spin Bloch equations with all the relevant scattering explicitly included. We show the temperature and electron density dependence of the spin relaxation time under various conditions such as impurity density, well width, and external electric field. We find a peak in the temperature dependence of the spin relaxation time at low impurity density. This peak can survive even at 100 K, much higher than the prediction and measurement value in GaAs. There also exhibits a peak in the electron density dependence at low temperature. These two peaks originate from the nonmonotonic temperature and electron density dependence of the Coulomb scattering. The spin relaxation time can reach the order of nanosecond at low temperature and high impurity density.
Vacuum polarization calculations for hydrogenlike and alkalilike ions
J. Sapirstein,K. T. Cheng
Physics , 2003, DOI: 10.1103/PhysRevA.68.042111
Abstract: Complete vacuum polarization calculations incorporating finite nuclear size are presented for hydrogenic ions with principal quantum numbers n=1-5. Lithiumlike, sodiumlike, and copperlike ions are also treated starting with Kohn-Sham potentials, and including first-order screening corrections. In both cases dominant Uehling terms are calculated with high accuracy, and smaller Wichmann- Kroll terms are obtained using numerical electron Green's functions.
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