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Heterogeneous numerical modelling for the auto thermal reforming of crude glycerol in a fixed bed reactor

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chinese Journal of chemical Engineering 2022年第2期35卷 261-268页

作者： jason Williams Hussameldin Ibrahim Nima Karimi Kelvin Tsun Wai ng clean Energy Technologies Research Institute Process Systems EngineeringFaculty of Engineering and Applied ScienceUniversity of ReginaRegina SK S4S 0A2Canada Environmental Systems Engineering Faculty of Engineering and Applied ScienceUniversity of ReginaRegina SK S4S 0A2Canada

A mathematical model for the catalytic autothermal reforming(ATR)reaction of synthetic crude glycerol to hydrogen in a fixed bed tubular reactor(FBTR)and over an in-house developed metal oxide catalyst is presented in this *** heterogeneous model equations account for a two-phase system of solid catalyst and bulk feed ***,the ATR of crude glycerol reaction scheme and intrinsic kinetic rate model over an active,selective,and stable nickel-based catalyst were integrated in the developed ***,the model was validated using experimental data generated in our labs for the ATR of synthetic crude *** modelling results adequately described the detailed gas product composition and distribution,temperature profiles,and conversion propagation in the axial direction of the fixed bed reactor over a wide range of reaction temperature(773–923 K)and mass-time(12.71–158.23 g cat·min·(mol c)^(-1)).The crude glycerol conversion predicted with the model showing a close resemblance to those obtained experimentally with an average absolute deviation(AAD)of less than 8%.The maximum crude glycerol conversion and hydrogen yield were found to be 92%and 3 mol hydrogen/mol crude glycerol,***,the gas product concentration profile in the reactor was adequately described(90%)accuracy with a hydrogen concentration of 39%(volume).

关键词： Hydrogen crude glycerol Autothermal reforming Numerical analysis Fixed-bed reactor

Zinc-oxide/PDMS-clad tapered fiber saturable absorber for passively mode-locked erbium-doped fiber laser

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chinese Physics B 2021年第5期30卷 384-389页

作者： F D Muhammad S A S Husin E K ng K y Lau c A c Abdullah M A Mahdi Department of Physics Faculty of ScienceUniversiti Putra Malaysia43400 UPM SerdangSelangorMalaysia Wireless and Photonics Networks Research centre Faculty of EngineeringUniversiti Putra Malaysia43400 UPM SerdangSelangorMalaysia Department of Electronics and Nanoengineering Tietotie 3Aalto University02150 EspooFinland

We propose and demonstrate a passively mode-locked erbium-doped fiber laser(EDFL)based on zinc-oxide/polydimethylsiloxane(ZnO/PDMS)saturable absorber(SA)that evanescently interacts with the light on a tapered *** ZnO/PDMS composite is coated on the whole surface of the tapered fiber to guarantee the maximum efficiency of the SA device,with a measured insertion loss of 0.87 dB and a modulation depth of 6.4%.The proposed laser can generate soliton mode-locking operation at a threshold power of 33.07 *** generated output pulse yields a repetition rate and pulse width of 9.77 MHz and 1.03 ps,*** results indicate that the proposed ZnO/PDMS-clad tapered fiber could be useful as an efficient,compatible,and low-cost SA device for ultrafast laser applications.

关键词： zinc-oxide saturable absorber tapered fiber mode-locked fiber laser

On business cycle forecasting

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Frontiers of Business Research in china 2020年第3期14卷 324-349页

作者： Huiwen Lai Eric c.y.ng School of Accounting and Finance Faculty of BusinessHong Kong Polytechnic UniversityHong KongChina Department of Economics Hong Kong University of Science and TechnologyHong KongChina

We develop a recession forecasting framework using a less restrictive target variable and more flexible and inclusive specification than those used in the *** target variable captures the occurrence of a recession within a given future period rather than at a specific future point in time(widely used in the literature).The modeling specification combines an autoregressive Logit model capturing the autocorrelation of business cycles,a dynamic factor model encompassing many economic and financial variables,and a mixed data sampling regression incorporating common factors with mixed sampling *** model gene rates significantly more accurate forecasts for *** with smaller forecast errors and stronger early signals for the turning points of business cycles than those gene rated by existing models.

关键词： Recession forecasting Business cycle Autoregressive Logit Dynamic factor Mixed data sampling(MIDAS)regression

clinically relevant factors associated with quantitative optical coherence tomography angiography metrics in deep capillary plexus in patients with diabetes

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Eye and Vision 2020年第1期7卷 64-74页

作者： Fang yao Tang Erica O.chan Zihan Sun Raymond Wong Jerry Lok Simon Szeto jason c.chan Alexander Lam clement c.Tham Danny S.ng carol y.cheung Department of Ophthalmology and Visual Sciences The Chinese University of Hong KongHong Kong Special Administrative RegionKowloonChina Hong Kong Eye Hospital Hong Kong Special Administrative RegionKowloonChina cUHK Eye centre Hong Kong Eye Hospital147K Argyle StreetKlnKowloonHong KongChina

Background:To test clinically relevant factors associated with quantitative artifact-free deep capillary plexus(DcP)metrics in patients with diabetes mellitus(DM).Methods:563 eligible eyes(221 with no diabetic retinopathy[DR],135 with mild DR,130 with moderate DR,and 77 with severe DR)from 334 subjects underwent optical coherence tomography-angiography(OcT-A)with a swept-source OcT(Triton DRI-OcT,Topcon,Inc.,Tokyo,Japan).Strict criteria were applied to exclude from analysis those DcP images with artifacts and of poor quality,including projection artifacts,motion artifacts,blurriness,signal loss,B-scan segmentation error,or low-quality score.A customized MATLAB program was then used to quantify DcP morphology from the artifact-free DcP images by calculating three metrics:foveal avascular zone(FAZ),vessel density(VD),and fractal dimension(FD).Results:166(29.5%)eyes were excluded after quality control,leaving in the analysis 397 eyes(170 with no DR,101 with mild DR,90 with moderate DR,36 with severe DR)from 250 *** the multiple regression models,larger FAZ area was associated with more severe DR(β=0.687;p=0.037),shorter axial length(AL)(β=−0.171;p=0.003),thinner subfoveal choroid thickness(β=−0.122;p=0.031),and lower body mass index(BMI)(β=−0.090;p=0.047).Lower VD was associated with more severe DR(β=−0.842;p=0.001),shorter AL(β=0.107;p=0.039),and poorer visual acuity(VA)(β=−0.133;p=0.021).Lower FD was associated with more severe DR(β=−0.891;pconclusions:Quantitative artifact-free DcP metrics are associated with VA,DR severity,AL,subfoveal choroidal thickness,age,and BMI in diabetic *** effects of ocular and systemic factors should be considered for meaningful interpretations of DcP changes in DM patients.

关键词： Optical coherence tomography angiography Diabetic retinopathy Deep capillary plexus Visual acuity

Accurate ab initio Predictions of Ionization Energies and Heats of Formation for cyclopropenylidene, Propargylene and Propadienylidene

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chinese Journal of chemical Physics 2006年第1期19卷 29-38页

作者： K. c. Lau c. y. ng James Franck Institute and Department of chemistry University of Chicago Chicago 60637 USA Department of chemistry University of california Davis One Shields Avenue Davis California95616 USA

The ionization energies （IEs） of cyclopropenylidene （c-c3H2）, propargylene （HcccH） and propadienylidene （H2ccc） have been computed using the ccSD（T）/cBS method, which involves the approxixnation to the complete basis set （cBS） limit at the coupled cluster level with single and double excitations plus quasi-perturbative triple excitation effect （ccSD（T））. The zero-point vibrational energy correction, the core-valence electronic correction, the scalar relativistic effect and the high level correction beyond the ccSD（T） excitations have also been made in these calculations. The ccSD（T）/cBS values for the IN（c-c3H2） and IE（HcccH） of 9.164, 8.987 eV are in good agreement with the experimental values of （9.15±0.03） and （8.96±0.04） eV. The ccSD（T）/cBS calculations yield the IE values of 10.477 and 10.388 eV for the ionization transitions H2ccc→H2ccc^＋（^2A1, c2v） and H2ccc→H2ccc＋（^2A＇, cs）, respectively. On the basis of the Franek-condon factor consideration, the IE of （10.43±0.02） eV determined in the previous single-photon ionization experiment most likely corresponds to the ionization threshold for the H2ccc→H2ccc^＋（^2A1, c2v） transition. Although the precision of the experimental IN measurements fpr c-c3H2, HcccH, and H2ccc is insufficient to pin down the accuracy of the theoretical calculations to better than ±30 meV, the excellent agreement between the experimental and theoretical IE values observed in the present study indicates that the ccSD（T）/cBS calculations together with high-order correlation corrections are capable of yielding reliable IE predictions for simple hydrocarbon carbenes and bi-radicals. We have also reported the heats of formation at 0 K （△H^of0） and 298 K （△H^of298）for c-c3H2/c-c3H2^＋, HcccH/HcccH^＋, and H2ccc/H2ccc^＋, The available experimental △H^of0 and △H^of298 values for c-c3H2/c c3H2^＋, HcccH/HcccH^＋ are found to be in good accord with the ccSD（T）/cBS predictions after taking into account the experimental uncertainties.

关键词： Ab intio Ionization energy Heat of formation c-c3H2 HcccH H2ccc

State-to-state Photoionization Dynamics of Vanadium Nitride by Two-color Laser Photoionization and Photoelectron Methods

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chinese Journal of chemical Physics 2013年第6期26卷 669-678,I0003页

作者： Huang Huang Zhi-hong Luo yih chung chang Kai-chung Lau c. y. ng Department of chemistry University of California Davis CA 95616 USA Department of Biology and chemistry Oty University of Hone Kong Kowloon Hone Kong China

We have conducted a two-color visible-ultraviolet （VIS-UV） resonance-enhanced laser pho- toionization and pulsed field ionization-photoelectron （PFI-PE） study of gaseous vana- dium mononitride （VN） in the total energy range of 56900-59020 cm-1. The VN molecules were selectively excited to single rotational levels of the intermediate VN（D3H0, v＇=0） state by using a VIS dye laser prior to photoionization by employing a UV laser. This two-color scheme allows the measurements of rovibronically selected and re- solved PFI-PE spectra for the VN＋（X2A; v＋=0, 1, and 2） ion vibrational bands. By simulating the rotationally resolved PFI-PE spectra, J＋=3/2 is determined to be the lowest rotational level of the ground electronic state, indicating that the symmetry of the ground VN＋ electronic state is 2A3/2. The analysis of the PFI-PE spectra for VN＋ also yields accurate values for the adiabatic ionization energy for the formation of VN＋（X2A3/2）, IE（VN）=56909.5＋0.8 cm-1 （7.05588±0.00010 eV）, the vibrational fre- quency wc＋=1068.0±0.8 cm-1, the anharmonicity constant wc＋Xe＋=5.8±0.8 cm-1, the rotational constants Be＋=0.6563±0.0005 cm-1 and ae＋=0.0069±0.0004 cm-1, and the equi-librium bond length, re＋=1.529A, for VN＋（X2A3/2）; along with the rotational constants Bc＋=0.6578i0.0028 cm-1 and a＋=0.0085±0.0028 cm-1, and the equilibrium bond length re＋=1.527A for VN＋（X2As/2）, and the spin-orbit coupling constant A=153.3±0.8 cm-1 for VN＋（X2/k5/2,3/2）. The highly precise energetic and spectroscopic data obtained in the present study are valuable for benchmarking the predictions based on state-of-the-art ab initio quantum calculations.

关键词： Vanadium nitride Vanadium nitride cation Photoionization dynamics Two- color photoionization Pulsed field ionization-photoelectron Ionization energy Bond disso- ciation energy

Molecular Dynamics Simulation of Behaviours of Non-Polar Droplets Merging and Interactions with Hydrophobic Surfaces

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Journal of Bionic Engineering 2008年第4期5卷 271-281页

作者： y.y. yan c.y. Ji School of the Built Environment University of Nottingham Nottingham NG7 2RD UK

This paper presents a molecular dynamics simulation of the behaviours of non-polar droplets merging and also the fluid molecules interacting with a hydrophobic surface. Such behaviours and transport phenomena are popular in general microchannel flow boiling and two-phase flow. The droplets are assumed to be composed of Lennards-Jones type molecules. Periodic boundary conditions are applied in three coordinate directions of a 3-D system, where there exist two liquid droplets and their vapour. The two droplets merge when they come within the prescribed small distance. The merging of two droplets apart from each other at different initial distances is tested and the possible larger （or critical） non-dimensional distance, in which droplets merging can occur, is discussed. The evolution of the merging process is simulated numerically by employing the Molecular Dynamics （MD） method. For interactions with hydrophobic solid wall, a system with fluid confined between two walls is used to study the wetting phenomena of fluid and solid wall. The results are compared with those of hydrophilic wall to show the unique characteristics of hydrophobic interactions by microscopic methods.

关键词： molecular dynamics simulation mist flow droplets merging hydrophobic wetting

AUTHENTIcATED SyMMETRIc-KEy ESTABLISHMENT FOR MEDIcAL BODy SENSOR NETWORKS

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Journal of Electronics(china) 2007年第3期24卷 421-427页

作者： Bao Shudi Poon carmen c.y. Shen Lianfeng Zha.ng yuanting National Mobile communications Research Laboratory Southeast University Nanjing 210096 China Joint Research centre for Biomedical Engineering The Chinese University of Hong Kong N.T. Hong Kong

This study concerns security issues of the emerging Wireless Body Sensor Network (WBSN) formed by biomedical sensors worn on or implanted in the human body for mobile healthcare appli-cations. A novel authenticated symmetric-key establishment scheme is proposed for WBSN,which fully exploits the physiological features obtained by network entities via the body channel available in WBSN but not other wireless networks. The self-defined Intrinsic Shared Secret (ISS) is used to replace the pre-deployment of secrets among network entities,which thus eliminates centralized services or au-thorities essential in existing protocols,and resolves the key transport problem in the pure symmet-ric-key cryptosystem for WBSN as well. The security properties of the proposed scheme are demon-strated in terms of its attack complexity and the types of attacks it can resist. Besides,the scheme can be implemented under a light-weight way in WBSN systems. Due to the importance of the ISS concept,the analysis on using false acceptance/false rejection method to evaluate the performance of ISS for its usage in the scheme is also demonstrated.

关键词： Wireless Body Sensor Network (WBSN) Network security Authenticated key estab-lishment Physiological feature

Synthesis, crystal and Molecular Structure and Biological Activity of Dimethyl Trans-3-(2-bromophenyl)-2-methylisoxazolidine-4,5-dicarboxylate

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chinese Journal of Structural chemistry 2012年第9期31卷 1251-1262页

作者： yÜKSEKTEPE Çigdem ÖZKAN Hamdi yAVUZ Serkan yANMAZ Volkan DISLI Ali BÜyÜKGÜngÖR Orhan Department of Physics Faculty of ScienceCankiri Karatekin University Department of chemistry Faculty of ScienceCankiri Karatekin University Department of chemistry Faculty of Arts and SciencesGazi University Department of Physics Faculty of Arts and SciencesOndokuz Mayis University

The compound of dimethyl trans-3-（2-bromophenyl）-2-methylisoxazolidine-4,5-dicarboxylate has been synthesized and characterized by IR, 1H-NMR, 13c-NMR, 2D-NMR （cOSy, NOESy, HMQc, HMBc） and UV-vis. spectroscopy techniques and single-crystal X-ray diffraction （XRD）. The biological activities of the title compound have been investigated in detail. The new compound crystallizes in monoclinic, space group c2/c with a = 26.9263（10）, b = 7.0970（2）, c = 19.8554（7）？, and β = 126.630（2）. In addition to the single crystal structure, the molecular geometry, vibrational frequencies, chemical shifts, molecular electrostatic potential and frontier molecular orbital analysis of the title compound in the ground state have been calculated by Density Functional Theory （DFT） method.

关键词： ab initio calculations isoxazolidine spectroscopy X-ray structure determination