This paper describe the theoretical consideration, experimental results and applications of diffusion tube, used for preparing the calibration standard of organic vapours. This dynamic procedure entirely eliminates th...This paper describe the theoretical consideration, experimental results and applications of diffusion tube, used for preparing the calibration standard of organic vapours. This dynamic procedure entirely eliminates the adsorption effect, which is important in static procedures. Its concentration range is wider than that of the permeation tube. The diffusion tube technique is therefore a very accurate, simple and easy-to-make device. It is quite useful in the determination of organic pollutants existing in the environment.展开更多
Short term repeated exposure of 1-chloroacetophenone (CN) vapours at a concentration of 0.153 mg per litre for 15 minutes daily on 10 consecuitve days in Swiss albino male mice resulted in increased mortality to Liste...Short term repeated exposure of 1-chloroacetophenone (CN) vapours at a concentration of 0.153 mg per litre for 15 minutes daily on 10 consecuitve days in Swiss albino male mice resulted in increased mortality to Listeria monocytogenes. Significantly elevated bacterial growth was observed in the spleen and liver of the CN exposed animals. The increased bacterial count in these organs was evident within 4-6 days post challenge as compared to vehicle exposed infected and unexposed infected animals. Increased susceptibility to infection has been considered to be the function of immune alteration due to cumulative short term effects ofCN vapour inhalation. This may be attributed to immunotoxic effects of CN on Tcells mediated macrophage functions.展开更多
Theoretical investigation of nitrogen-silver arc transport properties and an arc plasma model in stationary state have studied at low temperature i.e. between 3500 K and 13,000 K at atmospheric pressure. Results showe...Theoretical investigation of nitrogen-silver arc transport properties and an arc plasma model in stationary state have studied at low temperature i.e. between 3500 K and 13,000 K at atmospheric pressure. Results showed that the presence of small amounts of metal vapours, which have low ionization potential such as silver, modify the plasma characteristics. The solution of Elenbaas-Heller gives us some information about the effect of metal vapours emitted from electrode on the characteristics of the arc column. We concluded that a small fraction of metal vapours in the arc column modify the electric field, current and the axial temperature.展开更多
Natural gas is widely regarded as an efficient,relatively clean,and economically viable energy source.Its safe operation and continuous supply through pipeline infrastructure has led to its prominence in the energy se...Natural gas is widely regarded as an efficient,relatively clean,and economically viable energy source.Its safe operation and continuous supply through pipeline infrastructure has led to its prominence in the energy sector.Methanol plays an important role in the natural gas industry,typically serving as a solvent or hydrate inhibitor.Therefore,the accurate estimation of thermodynamic properties for methane/methanol binary is extremely important to optimise the operating parameter,maximise the dehydration effect,and reduce the cost.As the Helmholtz energy equation of state is expected to offer high accuracy in predicting the vapour-liquid equilibrium of methane/methanol binary,four reducing parameters were derived based on collected experimental data.Additionally,the sensitivities of various reducing parameter combinations were simultaneously investigated.The results demonstrated a strong agreement between predicted fractions and experimental data,with the UMADs(uncertainty-weighted mean absolute deviation)of 3.484 and 0.665 for liquid and vapour phases,respectively.Meanwhile,it is deemed“very likely”,“likely”,and“unlikely”to achieve acceptable prediction for 3-parameter optimisation,2-parameter optimisation and,1-parameter optimisation,respectively.展开更多
Organosilicone thin films were prepared through plasma polymerization(pp)in a plasma enhance chemical vapour deposition(PECVD)system,utilizing hexamethyldisilazane(HMDSN)as a monomer precursor,at varying distances(25 ...Organosilicone thin films were prepared through plasma polymerization(pp)in a plasma enhance chemical vapour deposition(PECVD)system,utilizing hexamethyldisilazane(HMDSN)as a monomer precursor,at varying distances(25 mm,35 mm,45 mm,55 mm,and 65 mm)from the plasma source to the substrate.Research has examined how the distance between the substrate and plasma source impacts the properties of thin films,including their thickness,surface morphology,and photoluminescence(PL).It was discovered that as the distance increased,both film thickness and PL intensity also increased.Additionally,the film was observed to be more uniform and smoother when deposited 45 mm below the plasma source.展开更多
Stomatal conductance was found to change from steady-state to a slate of oscillations during daytime when vapour pressure deficit (VPD) increased to a value of 1 kPa in Glycyrrhiza inflata Batalin grown under the cond...Stomatal conductance was found to change from steady-state to a slate of oscillations during daytime when vapour pressure deficit (VPD) increased to a value of 1 kPa in Glycyrrhiza inflata Batalin grown under the conditions of arid desert in north-west China. The injected metabolic inhibitors (NaN3 or carbonyl cyanide-m-chlorophenyl-hydrazone (CCCP)) slightly reduced the stomatal conductance but did not significantly decrease the intensity of stomatal oscillations (amplitude/average). The oscillation intensity was found to he significantly correlated with VPD and root resistance, but not with the respiration rate. There might exist a minimum threshold of VPD (0.8 kPa) and root resistance (1/4 relative value) that induced stomatal oscillations. These results suggested that stomatal oscillations induced by atmospheric drought stress and root resistance were mainly a type of hydropassive movement.展开更多
The monthly variation,temporal-spatial distribution,transportation characteristics of vapour field at middle and lower atmosphere and their effects on drought in Beijing,Tianjin and Hebei districts were studied,which ...The monthly variation,temporal-spatial distribution,transportation characteristics of vapour field at middle and lower atmosphere and their effects on drought in Beijing,Tianjin and Hebei districts were studied,which have a guiding significance on predicting climate and arranging agricultural production in the district.展开更多
From June 18th to June 19th of 2009,Heilongjiang Province was hit by the regional rainstorm rarely paralleled in history.According to the findings based upon the conventional observation data,the precipitation occurre...From June 18th to June 19th of 2009,Heilongjiang Province was hit by the regional rainstorm rarely paralleled in history.According to the findings based upon the conventional observation data,the precipitation occurred under the double-blocking situation of Ural Mountains and the Sea of Okhotsk.The main influencing systems were the upper vortex and northward low-pressure that came from Hetao area,accompanied by the delivery of high and low level jet stream.The results showed that the evolvement of blocking high,transfer of water vapor and configuration of high and low level jet stream were the key factors resulting in the rainfall process.展开更多
Aim To study the relationship between the substrate temperature and the morphology and properties of GaN. Methods\ Applying the hydride chemical vapor deposition method, GaN films were deposited on different kinds of...Aim To study the relationship between the substrate temperature and the morphology and properties of GaN. Methods\ Applying the hydride chemical vapor deposition method, GaN films were deposited on different kinds of substrates, including sapphire, Si(111),Si(100),GaAs and GaP(111) both on the P face and the Ga face. The growth was performed at low temperatures of below 700℃. XRD, Hall measurement, cathodoluminescence (CL) and atomic force microscopy (AFM) were used to characterise the film properties. Results\ It was found that the temperature and the nature of substrate materials influence the layer morphology. Conclusion\ The analysis shows that no apparent relationship exists between the optical properties and layer morphology.展开更多
Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integra...Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integrated circuits.When used a s the material for LEDs and LDs,GaN has high transforming efficiencies and its d evice s have a long using lifetime of up to 10000 hours,several decuple times longer t han that of conventional light emitting diodes.As a semiconductor material for b lue/green light sources,GaN is non replaceable.It will have important applications in li g ht emitting devices,optical communication systems,compact disk(CD)players,full c olor copying devices,full color printers,high distinguishing laser printers,gr ea t screen full color displaying devices,and super thin TV displaying devices etc . In recent years,GaN has been the focus and hotspot of semiconductor industries,a nd its devices have a shining place in light emitting and laser industries. We synthesized GaN nanowires by a chemical vapor deposition (CVD)method.The nano wires have diameters from 20 nm to 60 nm,and the maximum length is up to 100 μ m .Following figure is the scanning electron microscopy (SEM)image of the as synt hesized GaN nanowires.展开更多
This paper analyzes the possibility of applying binary nonazeotropic refrigerants in the jet refrigeration cycle. The thermodynamic cycle performance of two kinds of working pairs (R30/R142b, R30/R124) are calculated ...This paper analyzes the possibility of applying binary nonazeotropic refrigerants in the jet refrigeration cycle. The thermodynamic cycle performance of two kinds of working pairs (R30/R142b, R30/R124) are calculated using the EOS of PR equation of state, and the results are discussed. The theoretical calculations indicate that refrigerating quality can be improved if the binary mixtures evaporate just in the low temperature region. The character of the rejecter to compress two phase medium supports the possibility of this kind of cycle.展开更多
Statistical expression of vapour pressure equations of metals is derived from the Debye model.The statistical distribution of T_(-p) ensemble is presented in an in-elab- orate mode and the partition function is define...Statistical expression of vapour pressure equations of metals is derived from the Debye model.The statistical distribution of T_(-p) ensemble is presented in an in-elab- orate mode and the partition function is defined.The vapour pressure of eleven metals have been calculated with the Debye equation and compared with those given by the E- instein equation and empirical equation.Comparison of results of calculation from dif- ferent methods show their evident accordance within the same orders of magnitude.展开更多
Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated cir...Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated circuits.Recent progress in th in film crystal technique has realized the output of blue semiconductor lasers w i th a lifetime of over 10000 hours under continuous wave operation at room tempe r ature.So far GaN and its ternary indium and aluminum alloys are grown almost uni v ersally on foreign substrates with varying lattice mismatches.The mismatch undou btedly results in a significant dislocation density in the grown films.Hence it is necessary to grow single crystal GaN to be used as substrates for improvement of laser diodes.On the other hand,low dimensional GaN materials such as nanocry stalline powder,nanocrystal assembled bulk(nanophase) and nano wires are very u seful in both fundamental mesoscopic research and future development of GaN nano devices.Here we report our main recent progresses on the crystal growth of GaN a nd the preparation of its low dimensional materials.展开更多
In this paper, a back propagation artificial neural network （BP-ANN） model is presented for the simultaneous estimation of vapour liquid equilibria （VLE） of four binary systems viz chlorodifluoromethan-carbondioxi...In this paper, a back propagation artificial neural network （BP-ANN） model is presented for the simultaneous estimation of vapour liquid equilibria （VLE） of four binary systems viz chlorodifluoromethan-carbondioxide, trifluoromethan-carbondioxide, carbondisulfied-trifluoromethan and carbondisulfied-chlorodifluoromethan. VLE data of the systems were taken from the literature for wide ranges of temperature （222.04-343.23K） and pressure （0.105 to 7.46MPa）. BP-ANN trained by the Levenberg-Marquardt algorithm in the MATLAB neural network toolbox was used for building and optimizing the model. It is shown that the established model could estimate the VLE with satisfactory precision and accuracy for the four systems with the root mean square error in the range of 0.054-0.119. Predictions using BP-ANN were compared with the conventional Redlich-Kwang-Soave （RKS） equation of state, suggesting that BP-ANN has better ability in estimation as compared with the RKS equation （the root mean square error in the range of 0.115-0.1546）.展开更多
NiA1 intermetallic compounds attract increas- ing attention for high-temperature applications due to their combination of excellent properties, especially as metallic protective coatings on superalloys or as bond coat...NiA1 intermetallic compounds attract increas- ing attention for high-temperature applications due to their combination of excellent properties, especially as metallic protective coatings on superalloys or as bond coats in thermal barrier coatings （TBCs）. Oxidation behaviour of the β-NiA1Hf coatings prepared by electron beam physical vapour deposition （EB-PVD） was investigated at 1100 ℃ for short time and 100h in 20% 02＋Ar and 15 % H20 ＋ Ar, respectively. The results of mass changes re- veal that the addition of minor reactive element Hf sig- nificantly improves the cyclic oxidation resistance of the 13- NiA1 coatings in both dry and humid atmospheres. During the initial oxidation stage, water vapour retards the phase transformation from 0-A1203 to a-A1203. Moreover, com- pared with the case in dry atmosphere, water vapour sig- nificantly reduces the surface roughness of the oxide scales formed on EB-PVD β-NiA1Hf coatings after 100 h cyclic oxidation, which corresponds with the difference of surface morphologies of the oxide scales.展开更多
The coefficient of selective reflection at oblique incidence from two-level atoms confined between two dielectric walls is calculated in this paper. It is found to be related to the transient behaviour of atoms after ...The coefficient of selective reflection at oblique incidence from two-level atoms confined between two dielectric walls is calculated in this paper. It is found to be related to the transient behaviour of atoms after colliding with the wall and the distribution of the field inside the vapour corresponds to L/λ, with L the thickness of the film and λ the incident wavelength. We find that the sub-Doppler structure is manifest both for normal incidence and small angle oblique incidence, It is feasible to detect the real part of selective reflection in several cases that have not been achieved before.展开更多
We demonstrate a new approach to tune the electrical properties of graphene and functionalized graphene. Graphene was synthesized using thermal chemical vapour deposition(TCVD) method on copper foil using precursor ga...We demonstrate a new approach to tune the electrical properties of graphene and functionalized graphene. Graphene was synthesized using thermal chemical vapour deposition(TCVD) method on copper foil using precursor gas acetylene and co-catalyst H2 gas. TCVD assisted graphene was successfully transferred onto a silicon wafer. Transferred graphene sheet was then functionalized to prepare graphene oxide(GO) and reduced graphene oxide(rGO). Different surface charge carbon nanoparticles, e.g. carbon nanoparticle with net positive charge and carbon nanoparticle with net negative charge were then immobilized on transferred graphene and functionalized graphene sheets. The functionalized graphene and charge mobilized functionalized graphene were characterized by Uv–vis spectroscopy,Fourier transformed infrared spectroscopy, scanning electron microscopy, and Raman spectroscopy. After immobilization of carbon nanomaterials, the ac electrical conductivity was found to increase due to enhancement of the surface charge, electron density, and mobility. It was observed that negative surface charge immobilized graphene and functionalized graphene show higher conductivity. Thus, the electrical property of graphene and functionalized graphene can be tuned by surface modification with different surface charge carbon nanomaterials.展开更多
Thermodynamic study was carried out on the reaction EuCl_(3(s))+(v/2)Al_2Cl_(6(g))= EuAl_vCl_((3v)+3(g))byquenching experiments within 6 3 8 ～ 7 6 2 K and 0 . 0 3 ～ 0 . 1 4 MPa . The results suggested that theEuAl_3...Thermodynamic study was carried out on the reaction EuCl_(3(s))+(v/2)Al_2Cl_(6(g))= EuAl_vCl_((3v)+3(g))byquenching experiments within 6 3 8 ～ 7 6 2 K and 0 . 0 3 ～ 0 . 1 4 MPa . The results suggested that theEuAl_3Cl_(12(g)) complex was the predormnant species. The equilibrium constants of the reaction were measured. The reaction enthalpy and entropy derived from the measurements were and展开更多
Theory and evidence indicate that trees and other vegetation influence the atmospheric water-cycle in various ways.These influences are more important, more complex, and more poorly characterised than is widely realis...Theory and evidence indicate that trees and other vegetation influence the atmospheric water-cycle in various ways.These influences are more important, more complex, and more poorly characterised than is widely realised.While there is little doubt that changes in tree cover will impact the water-cycle, the wider consequences remain difficult to predict as the underlying relationships and processes remain poorly characterised. Nonetheless, as forests are vulnerable to human activities, these linked aspects of the water-cycle are also at risk and the potential consequences of large scale forest loss are severe. Here, for non-specialist readers, I review our knowledge of the links between vegetation-cover and climate with a focus on forests and rain(precipitation). I highlight advances, uncertainties and research opportunities. There are significant shortcomings in our understanding of the atmospheric hydrological cycle and of its representation in climate models. A better understanding of the role of vegetation and tree-cover wil reduce some of these shortcomings. I outline and il ustrate various research themes where these advances may be found.These themes include the biology of evaporation, aerosols and atmospheric motion, as well as the processes that determine monsoons and diurnal precipitation cycles. A novel theory—the ‘biotic pump’—suggests that evaporation and condensation can exert a major influence over atmospheric dynamics. This theory explains how high rainfall can be maintained within those continental land-masses that are sufficiently forested. Feedbacks within many of these processes can result in non-linear behaviours and the potential for dramatic changes as a result of forest loss(or gain): for example, switching from a wet to a dry local climate(or visa-versa). Much remains unknown and multiple research disciplines are needed to address this: forest scientists and other biologists have a major role to play.New ideas, methods and data offer opportunities to improve understanding. Expect surprises.展开更多
文摘This paper describe the theoretical consideration, experimental results and applications of diffusion tube, used for preparing the calibration standard of organic vapours. This dynamic procedure entirely eliminates the adsorption effect, which is important in static procedures. Its concentration range is wider than that of the permeation tube. The diffusion tube technique is therefore a very accurate, simple and easy-to-make device. It is quite useful in the determination of organic pollutants existing in the environment.
文摘Short term repeated exposure of 1-chloroacetophenone (CN) vapours at a concentration of 0.153 mg per litre for 15 minutes daily on 10 consecuitve days in Swiss albino male mice resulted in increased mortality to Listeria monocytogenes. Significantly elevated bacterial growth was observed in the spleen and liver of the CN exposed animals. The increased bacterial count in these organs was evident within 4-6 days post challenge as compared to vehicle exposed infected and unexposed infected animals. Increased susceptibility to infection has been considered to be the function of immune alteration due to cumulative short term effects ofCN vapour inhalation. This may be attributed to immunotoxic effects of CN on Tcells mediated macrophage functions.
文摘Theoretical investigation of nitrogen-silver arc transport properties and an arc plasma model in stationary state have studied at low temperature i.e. between 3500 K and 13,000 K at atmospheric pressure. Results showed that the presence of small amounts of metal vapours, which have low ionization potential such as silver, modify the plasma characteristics. The solution of Elenbaas-Heller gives us some information about the effect of metal vapours emitted from electrode on the characteristics of the arc column. We concluded that a small fraction of metal vapours in the arc column modify the electric field, current and the axial temperature.
基金supported financially by the National Natural Science Foundation of China(52202434)the National Natural Science Foundation of Ningbo(2023J275).
文摘Natural gas is widely regarded as an efficient,relatively clean,and economically viable energy source.Its safe operation and continuous supply through pipeline infrastructure has led to its prominence in the energy sector.Methanol plays an important role in the natural gas industry,typically serving as a solvent or hydrate inhibitor.Therefore,the accurate estimation of thermodynamic properties for methane/methanol binary is extremely important to optimise the operating parameter,maximise the dehydration effect,and reduce the cost.As the Helmholtz energy equation of state is expected to offer high accuracy in predicting the vapour-liquid equilibrium of methane/methanol binary,four reducing parameters were derived based on collected experimental data.Additionally,the sensitivities of various reducing parameter combinations were simultaneously investigated.The results demonstrated a strong agreement between predicted fractions and experimental data,with the UMADs(uncertainty-weighted mean absolute deviation)of 3.484 and 0.665 for liquid and vapour phases,respectively.Meanwhile,it is deemed“very likely”,“likely”,and“unlikely”to achieve acceptable prediction for 3-parameter optimisation,2-parameter optimisation and,1-parameter optimisation,respectively.
基金the AECS for its financial support of this study
文摘Organosilicone thin films were prepared through plasma polymerization(pp)in a plasma enhance chemical vapour deposition(PECVD)system,utilizing hexamethyldisilazane(HMDSN)as a monomer precursor,at varying distances(25 mm,35 mm,45 mm,55 mm,and 65 mm)from the plasma source to the substrate.Research has examined how the distance between the substrate and plasma source impacts the properties of thin films,including their thickness,surface morphology,and photoluminescence(PL).It was discovered that as the distance increased,both film thickness and PL intensity also increased.Additionally,the film was observed to be more uniform and smoother when deposited 45 mm below the plasma source.
文摘Stomatal conductance was found to change from steady-state to a slate of oscillations during daytime when vapour pressure deficit (VPD) increased to a value of 1 kPa in Glycyrrhiza inflata Batalin grown under the conditions of arid desert in north-west China. The injected metabolic inhibitors (NaN3 or carbonyl cyanide-m-chlorophenyl-hydrazone (CCCP)) slightly reduced the stomatal conductance but did not significantly decrease the intensity of stomatal oscillations (amplitude/average). The oscillation intensity was found to he significantly correlated with VPD and root resistance, but not with the respiration rate. There might exist a minimum threshold of VPD (0.8 kPa) and root resistance (1/4 relative value) that induced stomatal oscillations. These results suggested that stomatal oscillations induced by atmospheric drought stress and root resistance were mainly a type of hydropassive movement.
基金Supported by National Natural Sciences Foundations of China(40875032 and 40875002)Talents Culture Foundations of Beijing City (20051D0200802)~~
文摘The monthly variation,temporal-spatial distribution,transportation characteristics of vapour field at middle and lower atmosphere and their effects on drought in Beijing,Tianjin and Hebei districts were studied,which have a guiding significance on predicting climate and arranging agricultural production in the district.
文摘From June 18th to June 19th of 2009,Heilongjiang Province was hit by the regional rainstorm rarely paralleled in history.According to the findings based upon the conventional observation data,the precipitation occurred under the double-blocking situation of Ural Mountains and the Sea of Okhotsk.The main influencing systems were the upper vortex and northward low-pressure that came from Hetao area,accompanied by the delivery of high and low level jet stream.The results showed that the evolvement of blocking high,transfer of water vapor and configuration of high and low level jet stream were the key factors resulting in the rainfall process.
文摘Aim To study the relationship between the substrate temperature and the morphology and properties of GaN. Methods\ Applying the hydride chemical vapor deposition method, GaN films were deposited on different kinds of substrates, including sapphire, Si(111),Si(100),GaAs and GaP(111) both on the P face and the Ga face. The growth was performed at low temperatures of below 700℃. XRD, Hall measurement, cathodoluminescence (CL) and atomic force microscopy (AFM) were used to characterise the film properties. Results\ It was found that the temperature and the nature of substrate materials influence the layer morphology. Conclusion\ The analysis shows that no apparent relationship exists between the optical properties and layer morphology.
文摘Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integrated circuits.When used a s the material for LEDs and LDs,GaN has high transforming efficiencies and its d evice s have a long using lifetime of up to 10000 hours,several decuple times longer t han that of conventional light emitting diodes.As a semiconductor material for b lue/green light sources,GaN is non replaceable.It will have important applications in li g ht emitting devices,optical communication systems,compact disk(CD)players,full c olor copying devices,full color printers,high distinguishing laser printers,gr ea t screen full color displaying devices,and super thin TV displaying devices etc . In recent years,GaN has been the focus and hotspot of semiconductor industries,a nd its devices have a shining place in light emitting and laser industries. We synthesized GaN nanowires by a chemical vapor deposition (CVD)method.The nano wires have diameters from 20 nm to 60 nm,and the maximum length is up to 100 μ m .Following figure is the scanning electron microscopy (SEM)image of the as synt hesized GaN nanowires.
文摘This paper analyzes the possibility of applying binary nonazeotropic refrigerants in the jet refrigeration cycle. The thermodynamic cycle performance of two kinds of working pairs (R30/R142b, R30/R124) are calculated using the EOS of PR equation of state, and the results are discussed. The theoretical calculations indicate that refrigerating quality can be improved if the binary mixtures evaporate just in the low temperature region. The character of the rejecter to compress two phase medium supports the possibility of this kind of cycle.
文摘Statistical expression of vapour pressure equations of metals is derived from the Debye model.The statistical distribution of T_(-p) ensemble is presented in an in-elab- orate mode and the partition function is defined.The vapour pressure of eleven metals have been calculated with the Debye equation and compared with those given by the E- instein equation and empirical equation.Comparison of results of calculation from dif- ferent methods show their evident accordance within the same orders of magnitude.
文摘Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated circuits.Recent progress in th in film crystal technique has realized the output of blue semiconductor lasers w i th a lifetime of over 10000 hours under continuous wave operation at room tempe r ature.So far GaN and its ternary indium and aluminum alloys are grown almost uni v ersally on foreign substrates with varying lattice mismatches.The mismatch undou btedly results in a significant dislocation density in the grown films.Hence it is necessary to grow single crystal GaN to be used as substrates for improvement of laser diodes.On the other hand,low dimensional GaN materials such as nanocry stalline powder,nanocrystal assembled bulk(nanophase) and nano wires are very u seful in both fundamental mesoscopic research and future development of GaN nano devices.Here we report our main recent progresses on the crystal growth of GaN a nd the preparation of its low dimensional materials.
文摘In this paper, a back propagation artificial neural network （BP-ANN） model is presented for the simultaneous estimation of vapour liquid equilibria （VLE） of four binary systems viz chlorodifluoromethan-carbondioxide, trifluoromethan-carbondioxide, carbondisulfied-trifluoromethan and carbondisulfied-chlorodifluoromethan. VLE data of the systems were taken from the literature for wide ranges of temperature （222.04-343.23K） and pressure （0.105 to 7.46MPa）. BP-ANN trained by the Levenberg-Marquardt algorithm in the MATLAB neural network toolbox was used for building and optimizing the model. It is shown that the established model could estimate the VLE with satisfactory precision and accuracy for the four systems with the root mean square error in the range of 0.054-0.119. Predictions using BP-ANN were compared with the conventional Redlich-Kwang-Soave （RKS） equation of state, suggesting that BP-ANN has better ability in estimation as compared with the RKS equation （the root mean square error in the range of 0.115-0.1546）.
基金financially supported by the National Natural Science Foundations of China(Nos.51071013 and 5120100)Natural Basic Research Program of China(Nos.2010CB631200 and 2012CB625100)
文摘NiA1 intermetallic compounds attract increas- ing attention for high-temperature applications due to their combination of excellent properties, especially as metallic protective coatings on superalloys or as bond coats in thermal barrier coatings （TBCs）. Oxidation behaviour of the β-NiA1Hf coatings prepared by electron beam physical vapour deposition （EB-PVD） was investigated at 1100 ℃ for short time and 100h in 20% 02＋Ar and 15 % H20 ＋ Ar, respectively. The results of mass changes re- veal that the addition of minor reactive element Hf sig- nificantly improves the cyclic oxidation resistance of the 13- NiA1 coatings in both dry and humid atmospheres. During the initial oxidation stage, water vapour retards the phase transformation from 0-A1203 to a-A1203. Moreover, com- pared with the case in dry atmosphere, water vapour sig- nificantly reduces the surface roughness of the oxide scales formed on EB-PVD β-NiA1Hf coatings after 100 h cyclic oxidation, which corresponds with the difference of surface morphologies of the oxide scales.
基金Project supported by Science Foundation of Ningxia Higher Education of China （Grant No 2005153）.
文摘The coefficient of selective reflection at oblique incidence from two-level atoms confined between two dielectric walls is calculated in this paper. It is found to be related to the transient behaviour of atoms after colliding with the wall and the distribution of the field inside the vapour corresponds to L/λ, with L the thickness of the film and λ the incident wavelength. We find that the sub-Doppler structure is manifest both for normal incidence and small angle oblique incidence, It is feasible to detect the real part of selective reflection in several cases that have not been achieved before.
基金the Science and Engineering Research Board(SERB),New Delhi,for project grant SB/S1/PC-69/2012the Board of Research in Nuclear Sciences(BRNS),Mumbai,Grant No.34/14/20/2014-BRNSSERB,New Delhi,for fellowship
文摘We demonstrate a new approach to tune the electrical properties of graphene and functionalized graphene. Graphene was synthesized using thermal chemical vapour deposition(TCVD) method on copper foil using precursor gas acetylene and co-catalyst H2 gas. TCVD assisted graphene was successfully transferred onto a silicon wafer. Transferred graphene sheet was then functionalized to prepare graphene oxide(GO) and reduced graphene oxide(rGO). Different surface charge carbon nanoparticles, e.g. carbon nanoparticle with net positive charge and carbon nanoparticle with net negative charge were then immobilized on transferred graphene and functionalized graphene sheets. The functionalized graphene and charge mobilized functionalized graphene were characterized by Uv–vis spectroscopy,Fourier transformed infrared spectroscopy, scanning electron microscopy, and Raman spectroscopy. After immobilization of carbon nanomaterials, the ac electrical conductivity was found to increase due to enhancement of the surface charge, electron density, and mobility. It was observed that negative surface charge immobilized graphene and functionalized graphene show higher conductivity. Thus, the electrical property of graphene and functionalized graphene can be tuned by surface modification with different surface charge carbon nanomaterials.
文摘Thermodynamic study was carried out on the reaction EuCl_(3(s))+(v/2)Al_2Cl_(6(g))= EuAl_vCl_((3v)+3(g))byquenching experiments within 6 3 8 ～ 7 6 2 K and 0 . 0 3 ～ 0 . 1 4 MPa . The results suggested that theEuAl_3Cl_(12(g)) complex was the predormnant species. The equilibrium constants of the reaction were measured. The reaction enthalpy and entropy derived from the measurements were and
基金the value of participation in the Australian Research Council projects under grants DP160102107 and LP130100498benefitted from the meeting in Leuven,Belgium in 2015 where his participation was funded by We Forest and the Center for International Forest Researchfrom the meeting in Wageningen,Netherlands,also in 2015,where his participation was funded by Tropenbos
文摘Theory and evidence indicate that trees and other vegetation influence the atmospheric water-cycle in various ways.These influences are more important, more complex, and more poorly characterised than is widely realised.While there is little doubt that changes in tree cover will impact the water-cycle, the wider consequences remain difficult to predict as the underlying relationships and processes remain poorly characterised. Nonetheless, as forests are vulnerable to human activities, these linked aspects of the water-cycle are also at risk and the potential consequences of large scale forest loss are severe. Here, for non-specialist readers, I review our knowledge of the links between vegetation-cover and climate with a focus on forests and rain(precipitation). I highlight advances, uncertainties and research opportunities. There are significant shortcomings in our understanding of the atmospheric hydrological cycle and of its representation in climate models. A better understanding of the role of vegetation and tree-cover wil reduce some of these shortcomings. I outline and il ustrate various research themes where these advances may be found.These themes include the biology of evaporation, aerosols and atmospheric motion, as well as the processes that determine monsoons and diurnal precipitation cycles. A novel theory—the ‘biotic pump’—suggests that evaporation and condensation can exert a major influence over atmospheric dynamics. This theory explains how high rainfall can be maintained within those continental land-masses that are sufficiently forested. Feedbacks within many of these processes can result in non-linear behaviours and the potential for dramatic changes as a result of forest loss(or gain): for example, switching from a wet to a dry local climate(or visa-versa). Much remains unknown and multiple research disciplines are needed to address this: forest scientists and other biologists have a major role to play.New ideas, methods and data offer opportunities to improve understanding. Expect surprises.
