检索结果-南通市图书馆

Graphene-based Q-switched pulsed fiber laser in a linear configuration

在线全文

学校读者我要写书评

暂无评论

Chinese Optics Letters 2012年第4期10卷 36-39页

作者： y.k.yap Richard M.De La Rue C.H.Pua S.W.Harun H.Ahmad Photonics Research Centre Department of PhysicsFaculty of ScienceUniversity of MalayaKuala LumpurMalaysia Department of Electrical Engineering Faculty of EngineeringUniversity of MalayaKuala LumpurMalaysia

A pulsed laser system is realized with graphene employed as a *** graphene is exfoliated from its solution using an optical deposition and the optical tweezer effect.A fiber ferrule that already has the graphene deposited on it is inserted into an erbium-ytterbium laser（EyL）system with linear cavity *** successfully demonstrate a pulsed EyL with a pulse duration of approximately 5.9μs and a repetition rate of 20.0 kHz.

关键词： mode FWHM kHz Figure

在线全文

学校读者我要写书评

暂无评论

产生高功率UV光硼酸盐晶体的可靠性改进

人工晶体学报 2000年第S1期29卷 11-页

作者： y.k.yap, M.yoshimura, y.Mori, T.Sasaki (Department of Electrical Engineering,Osaka University,2 1 yamadaoka,Suita,Osaka 565 0871,Japan) (TEL +81 6 6879 7707,FAX +81 6 6879 7708)

All solid state UV lasers have been in demand for various industrial and medical applications because of the convenient operation procedure and cost effectiveness as alternative to corrosive gas based excimer *** performance of such lasers seems to depend on the capability and reliability of UV frequency *** the third decade,CsLiB 6O 10 (CLBO)and Gd xy 1 x Ca 4O(BO 3) 3 (GdyCOB)were developed by the authors *** is the most effective nonlinear optical crystal to generate high power fourth and fifth harmonics of Nd∶yAG *** is the first material which can achieve noncritical phase matching (NCPM) condition for THG of Nd∶yAG *** NCPM condition is advantageous owing to its large angular acceptance and the elimination of walk off between fundamental and harmonic *** the other hand,reliability is very importmat for actual application of these ***,we will present about techniques to improve durability of NLO crystals for high power UV light *** instance,we found that removal of surface polishing compound by means of ion beam etching can imrpove surface durability of ***,we will discussed about photo induced damages in GdyCOB and its solution.

关键词： nonlinear optical crystal borate crystal UV frequency converter

Promotional Effect of Bismuth as Dopant in Bi-Doped Vanadyl Pyrophosphate Catalysts for Selective Oxidation of n-Butane to Maleic Anhydride

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2006年第4期15卷 297-302页

作者： y.H.Taufiq-yap y.kamiya k.P.Tan Department of Chemistry Universiti Putra Malaysia43400 UPM SerdangSelangorMalaysia Graduate School of Environmental Earth Science Hokkaido UniversitySapporo 060-0810Japan

Bismuth-promoted （1% and 3%） vanadyl pyrophosphate catalysts were prepared by refluxing Bi（NO3）4.5H2O and VOPO4.2H2O in isobutanol. The incorporation of Bi into the catalysts lattice increased the surface area and lowered the overall V oxidation state. Profiles of temperature programmed reduction （TPR） in H2 show a significant shift of the maxima of major reduction peaks to lower temperatures for the Bi-promoted catalysts. A new peak was also observed at the low temperature region for the catalyst with 3% of Bi dopant. The addition of Bi also increased the total amount of oxygen removed from the catalysts. The reduction pattern and reactivity information provide fundamental insight into the catalytic properties of the catalysts. Bi-promoted catalysts were found to be highly active （71% and 81% conversion for 1% and 3% Bi promoted catalysts, respectively, at 703 k）, as compared to the unpromoted material （47% conversion）. The higher activity of the Bi-promoted catalysts is due to that these catalysts possess highly active and labile lattice oxygen. The better catalytic performance can also be attributed to the larger surface area.

关键词： bismuth promoter vanadyl pyrophosphate n-butane oxidation

n-Butane Oxidation over γ-Al_2O_3 Supported Vanadium Phosphate Catalysts

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2007年第3期16卷 266-272页

作者： y.H.Taufiq-yap L.k.Leong R.Irmawati Putra Laboratory for Catalysis Science and Technology Department of ChemistryFaculty of ScienceUniversiti Putra Malaysia43400 UPM SerdangSelangorMalaysia Department of Bioscience and Chemistry Faculty of Engineering and ScienceUniversiti Tunku Abdul RahmanJalan Genting Kelang53300 SetapakKuala LumpurMalaysia

Four vanadium phosphate catalysts supported on γ-A1203 （20 wt%） were synthesized via wetness impregnation of VOHPO4.0.5H2O precursor and calcined for different durations （6, 10, 30 and 75 h） at 673 k in a reaction flow of n-butane/air mixture. The samples calcined for 6 and 10 h produced only a single phase of （VO）2P2O7. However, the VOPO4 phase （β-VOPO4） was detected and became more prominent with only a minor pyrophosphate peaks were found after 30 h of calcination. All these pyrophosphate peaks disappeared after 75 h of calcination. The formation of V^5＋ phase was also observed in the SEM micrographs. The redox properties and the nature of oxidants of the catalysts employed in this study were investigated by H2-TPR analysis. Selective oxidation of n-butane to maleic anhydride （MA） over these catalysts shows that the percentage of n-butane conversion decreases with the transformation of the catalysts from V^4＋ to V^5＋ phases. An appropriate ratio of V^5＋/V^4＋ can enhance the performance of the VPO catalyst. However, a higher amount of V^5＋ and its associated oxygen species are responsible to promote the MA selectivity.

关键词： n-butane oxidation VPO alumina maleic anhydride

Evolution of hepatitis B management in kidney transplantation

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2014年第2期20卷 468-474页

作者： Desmond y H yap Tak Mao Chan Division of Nephrology Department of MedicineQueen Mary Hospitalthe University of Hong Kong

Chronic hepatitis B virus(HBV)infection adversely influences the clinical outcomes of renal transplant recipients owing to increased hepatic *** of HBV infection in kidney transplant recipients presents a challenge to clinicians,especially in endemic *** precipitates renal allograft *** with lamivudine,the first oral nucleoside analogue available,resulted in effective viral suppression,reduced liver-related complications,and improved patient survival so that medium-term data showed comparable patient survival rates between hepatitis B surface antigen-positive and HBsAg-negative kidney transplant recipients in the era of effective antiviral *** has replaced lamivudine as first-line therapy for treatment-na?ve subjects in view of the propensity for drug resistance with the *** of HBV infection in kidney transplant patients needs to take into consideration the nephrotoxicity of nucleoside/tide analogues such as adefovir and *** of HBV-related complications in kidney transplant recipients starts much earlier prior to transplantation,with vaccination of patients with chronic kidney disease and donor-recipient matching with regard to HBV *** addition to anti-viral treatment,patients with chronic HBV infection must have regular surveillance for liver cancer and assessment for the development of cirrhosis.

关键词： Hepatitis B kidney transplantation

Mechanosynthesis and mechanochemical treatment of bismuth-doped vanadium phosphorus oxide catalysts for the partial oxidation of n-butane to maleic anhydride

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2008年第3期17卷 232-237页

作者： y. H. Taufiq-yap y.C. Wong y. kamiya W.J. Tang Putra Center for Catalysis Science and Technology Department of Chemistry Faculty of Science Universiti Putra Malaysia 43400 UPM Serdang Selangor Darul Ehsan Malaysia Graduate School of Environmental Science Hokkaido Universit3 Sapporo 060-0810 Japan

Three Bi-doped vanadyl pyrophosphate catalysts were prepared via dihydrate route （VPD method）, which consisted of different preparation methods including mechanosynthesis, mechanochemical treatment, and the conventional reflux method. The catalysts produced by the above three methods were characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, and temperature programmed reduction （TPR）. Catalytic evaluation for the partial oxidation of n-butane to maleic anhydride （MA） was also carried out. The XRD patterns of all the Bi-doped catalysts showed the main peaks of pyrophosphate phase. Lower intensity peaks were observed for the mechanochemically treated Bi-doped catalyst （VPDBiMill） with two additional small peaks corresponding to the presence of a small amount of V5＋ phase. The TPR profiles showed that the highest amount of active oxygen species, i.e, V4＋–O- pair, responsible for n-butane activation, was removed from VPDBiMill. Furthermore, from the catalytic test results, the graph of selectivity to MA as a function of the conversion of n-butane demonstrated that VPDBiMill was the most selective catalyst. This suggests that the mechanochemical treatment of vanadium phosphate catalyst （VPDBiMill） is a potential method to improve the catalytic properties for the partial oxidation of n-butane to maleic anhydride.

关键词： mechanosynthesis mechanochemical treatment bismuth vanadyl pyrophosphate

Synthesis of self-assembled nanorod vanadium oxide bundles by sonochemical treatment

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2009年第3期18卷 312-318页

作者： y.H.Taufiq-yap y.C.Wong Z.Zainal M.Z.Hussein Centre of Excellence for Catalysis Science and Technology Faculty of ScienceUniversiti Putra Malaysia Department of Chemistry Faculty of ScienceUniversiti Putra Malaysia

Self-assembled nanorod of vanadium oxide bundles were synthesized by treating bulk V2O5 with high intensity sonochemical technique. The synthesized materials were characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM）, transmission electron microscope （TEM） and temperature-programmed reduction （TPR） in H2. Catalytic behaviour of the materials over anaerobic n-butane oxidation was studied through temperature-programmed reaction （TPRn）. Catalytic evaluation of the sonochemical treated V2O5 products was also studied on microreactor. XRD patterns of all the vanadium samples were perfectly indexed to V2O5. The morphologies of the nanorod vanadium oxides as shown in SEM and TEM depended on the duration of the ultrasound irradiation. Prolonging the ultrasound irradiation duration resulted in materials with uniform, well defined shapes and surface structures and smaller size of nanorod vanadium oxide bundles. H2-TPR profiles showed that larger amount of oxygen species were removed from the nanorod V2O5 compared to the bulk. Furthermore, the nanorod vanadium oxide bundles, which were produced after 90, 120 and 180 min of sonochemical treatment, showed an additional reduction peak at lower temperature （-850 k）, suggesting the presence of some highly active oxygen species. TPRn in n-butane/He over these materials showed that the nanorod V2O5 with highly active oxygen species showed markedly higher activity than the bulk material, which was further proven by catalytic oxidation of n-butane.

关键词： nanorod vanadium oxide sonochemical treatment butane oxidation

Effect of tellurium promoter on vanadium phosphate catalyst for partial oxidation of n-butane

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2011年第6期20卷 635-638页

作者： y.H.Taufiq-yap S.Nor Asrina G.J.Hutchings N.F.Dummer J.k.Bartley Centre of Excellence for Catalysis Science and Technology Faculty of ScienceUniversiti Putra Malaysia Department of Chemistry Faculty of ScienceUniversiti Putra Malaysia Cardiff Catalysis Institute School of ChemistryCardiff University

Te-promoted （1%） vanadium phosphate catalyst （VPDTe） was prepared via VOPO4·2H2O by calcining its precursor VOHPO4·0.5H2O in a flow of n-butane/*** catalyst has resulted a higher existence of V5＋ phase with V5＋/V4＋ ratio of *** micrographs show that Te addition altered the arrangement of the platelets from ＂rose-like＂ clusters to layer with irregular *** addition has also markedly lowered the reduction activation energies of the vanadium phosphate catalyst as revealed by TPR *** amount of active oxygen species associated with V4＋ phase of the Te promoted catalyst was significantly higher than those of the unpromoted *** observations suggest that high mobility and availability of reactive oxygen species contributed to the enhancement of n-butane conversion up to 80% at 673 k,while only 47% over unpromoted catalyst （2400 h^-1,1.7% n-butane in air）.

关键词： vanadium phosphate tellurium promoter butane oxidation

Effect of Cr and Co Promoters Addition on Vanadium Phosphate Catalysts for Mild Oxidation of n-Butane

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2006年第2期15卷 144-148页

作者： yun Hin Taufiq-yap Putra Laboratory for Catalysis and Technology Department of ChemistryFaculty of ScienceUniversiti Putra Malaysia43400 UPM SerdangSelangorMalaysia

In this study, Cr and Co promoted, as well as unpromoted vanadium phosphate （VPO） catalysts were synthesized by the reaction of V2O5 and o-H3PO4 in organic medium followed by calcination in n-butane/air environment at 673 k. The physico-chemical properties and the catalytic behavior were affected by the addition of Cr and Co dopants. H2-TPR was used to investigate the nature of oxidants in the unpromoted and promoted catalysts. The results showed that both the Cr and Co promoters remarkably lowered the temperature of the reduction peak associated with V^5＋. The amount of oxygen species originated from the active phase, V^4＋, removed was significantly increased for Co and Cr-promoted catalysts. Both Cr and Co dopants improve strongly the n-butane conversion without sacrificing the MA selectivity. A good correlation was observed between the amount of oxygen species removed from V^4＋ phase and the activity for n-butane oxidation to maleic anhydride. This suggested that V^4＋-O was the center for the activation of n-butane.

关键词： n-butane oxidation VPO promoter maleic anhydride TPR