The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth condi...The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth conditions on E2 (TO), E1 (TO) and A1 (LO) phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2 (TO) modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2 (TO) mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 (longitudinal optical plasma coupling (LOPC)) mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1 (LOPC) mode in 4H-SiC.展开更多
[Objective] The study aimed at selecting the predominant strains being able to degrade kerosene and studying its best growth conditions. [Method] Choosing kerosene as the only carbon source, we selected and separated ...[Objective] The study aimed at selecting the predominant strains being able to degrade kerosene and studying its best growth conditions. [Method] Choosing kerosene as the only carbon source, we selected and separated the predominant strains being able to degrade kerosene from the contaminated soil near petrochemical plants, and then optimized the grow conditions of the bacteria. [Result] The best conditions for the bacteria growth were determined as follows, that is, temperature was 30 ℃, pH=7, salinity was 2.5%, and the rotational speed of the thermostatic shake was 190 r/min. Under the optimal conditions, the degradation rate of kerosene by the bacteria cultured for three days reached 42.6%. [Conclusion] The research could provide scientific references for the restoration of polluted soil by kerosene.展开更多
Let Ω be a bounded domain with smooth boundary Ω in R~n. We consider the following eigenvalue problem for systems of elliptic equations under the natural growth conditions
In this paper we give a priori estimates for the maximum modulus of generalizedsolulions of the quasilinear elliplic equations irith anisotropic growth condition.
This paper deals with the extinction of weak solutions of the initial and boundary value problem for ut = div((|u|σ + d0)| u|^p(x)-2 u). When the exponent belongs to different intervals, the solution has ...This paper deals with the extinction of weak solutions of the initial and boundary value problem for ut = div((|u|σ + d0)| u|^p(x)-2 u). When the exponent belongs to different intervals, the solution has different singularity (vanishing in finite time).展开更多
The Buyeo Royal Tomb No. 1 is an ancient tomb built in the late 6<sup>th</sup> and early 7<sup>th</sup> century. The four walls of the main room have murals of four guardian deities, and the ce...The Buyeo Royal Tomb No. 1 is an ancient tomb built in the late 6<sup>th</sup> and early 7<sup>th</sup> century. The four walls of the main room have murals of four guardian deities, and the ceiling has murals of lotus and cloud patterns. This study assessed the optimal growth conditions of two fungal (Fusarium oxysporum, Mortierella sp.) and four bacterial (Bacillus cereus, Cupriavidus campinensis, Streptomyces avidinii, Streptomyces cirratus) strains isolated from the Tomb No. 1, along with their effects on the painting layer. The two fungi showed optimal growth at 20°C - 30°C under both nutrient and non-nutrient conditions. These strains did not decompose or discolor the three pigments (cinnabar, hematite, oyster shell white);however, M. sp. showed slight decomposition of the media (starch paste, sea weed). The four bacterial strains showed the most active growth at 20°C - 25°C under nutrient conditions and did not grow under non-nutrient conditions. These bacteria commonly degraded animal glue and sea weed components. In addition, S. cirratus degraded starch. The genus Streptomyces discolored the pigment medium to brown and black, suggesting a possible risk of discoloration of the murals. The current environment in Tomb No. 1 was sufficient for microorganism growth, and the presence of strains such as soil bacteria and actinomycetes on the mural surface may damage the murals. The findings of this study could be helpful for preserving mural tombs against biological damage caused by microorganisms that are already present or may be present in the tombs in the future. These findings also provide guidelines for comprehensive conservation management.展开更多
In this paper, we get the existence of a weak solution of the following inhomogeneous quasilinear elliptic equation with critical growth conditions: where N≥2, f(x,u)~|u|<sup>m-1</sup>e<sup>b|u|&...In this paper, we get the existence of a weak solution of the following inhomogeneous quasilinear elliptic equation with critical growth conditions: where N≥2, f(x,u)~|u|<sup>m-1</sup>e<sup>b|u|<sup>γ</sup></sup>at +∞, with γ=N/N-1, m≥1, b】0.展开更多
In this paper, we investigate the interior regularity including the local boundedness and the interior HSlder continuity of weak solutions for parabolic equations of the p(x, t)-Laplacian type. We improve the Moser ...In this paper, we investigate the interior regularity including the local boundedness and the interior HSlder continuity of weak solutions for parabolic equations of the p(x, t)-Laplacian type. We improve the Moser iteration technique and generalize the known results for the elliptic problem to the corresponding parabolic problem.展开更多
A class of quasilinear elliptic variational inequalities with double degenerate is discussed in this paper. We extend the Keldys-Fichera boundary value problem and the first boundary problem of degenerate elliptic equ...A class of quasilinear elliptic variational inequalities with double degenerate is discussed in this paper. We extend the Keldys-Fichera boundary value problem and the first boundary problem of degenerate elliptic equation to the variationalinequalities. We establish the existence and uniqueness of the weak solution of ocrresspending problem under nonstandard growth conditions.展开更多
Ground-based platform systems provide a good tool for monitoring and managing crop conditions in precision agriculture applications and have been widely used for monitoring crop conditions.To develop an unmanned groun...Ground-based platform systems provide a good tool for monitoring and managing crop conditions in precision agriculture applications and have been widely used for monitoring crop conditions.To develop an unmanned ground vehicle system(UGVS)based multi-sensors and test the feasibility of this system for monitoring rice conditions,an UGVS was developed to collect real-time rice condition information including NDVI values,reflectance measurements and crop canopy temperature in this study.Major components of the integrated system are GreenSeeker R100 system,hyper-spectroradiometer and infrared temperature sensor.The leaf area index(LAI)was measured by the CGMD302 Spectrometer.The Independent Samples T-Test method and the one way ANOVA method were used to determine the best spectral indices and analyze the relationship between the vegetation indices and rice LAI.It was found that the two best spectral indices for estimating LAI were NDVI(860 nm and 750 nm)with the correlation coefficient(R^(2))at 0.745 and RVI(853 nm and 751 nm)with the R^(2)at 0.724.The results show the UGVS can support multi-source information acquisition and is useful for crop management and precision agriculture applications.展开更多
Habanero pepper(Capsicum chinense Jacq.)is a crop of economic relevance in the Peninsula of Yucatan.Its fruits have a high level of capsaicinoids compared to peppers grown in other regions of the world,which gives the...Habanero pepper(Capsicum chinense Jacq.)is a crop of economic relevance in the Peninsula of Yucatan.Its fruits have a high level of capsaicinoids compared to peppers grown in other regions of the world,which gives them industrial importance.Soil is an important factor that affects pepper development,nutritional quality,and capsaicinoid content.However,the effect of soil type on fruit development and capsaicinoid metabolism has been little understood.This work aimed to compare the effect of soils with contrasting characteristics,black soil(BS)and red soil(RS),on the expression of genes related to the development of fruits,and capsaicinoid synthesis using a transcriptomic analysis of the habanero pepper fruits.Plants growing in RS had bigger fruits and higher expression of genes related to floral development,fruit abscission,and softening which suggests that RS stimulates fruit development from early stages until maturation stages.Fruits from plants growing in BS had enrichment in metabolic pathways related to growth,sugars,and photosynthesis.Besides,these fruits had higher capsaicinoid accumulation at 25 days post-anthesis,and higher expression of genes related to the branched-chain amino acids metabolism(ketol-acid reductisomerase KARI),pentose phosphate pathway and production of NADPH(glucose-6-phosphate-1-dehydrogenase G6PDH),and proteasome and vesicular traffic in cells(26S proteasome regulatory subunit T4 RPT4),which suggest that BS is better in the early stimulation of pathways related to the nutritional quality and capsaicinoid metabolism in the fruits.展开更多
In this article, the authors consider the nonlinear elliptic systems under the natural growth condition. They use a new method introduced by Duzaar and Grotowski, for proving partial regularity for weak solutions, bas...In this article, the authors consider the nonlinear elliptic systems under the natural growth condition. They use a new method introduced by Duzaar and Grotowski, for proving partial regularity for weak solutions, based on a generalization of the technique of harmonic approximation. And directly establish the optimal Holder exponent for the derivative of a weak solution.展开更多
The sown area of winter wheat in the Huang-Huai-Hai(HHH) Plain accounts for over 65% of the total sown area of winter wheat in China. Thus, it is important to monitor the winter wheat growth condition and reveal the...The sown area of winter wheat in the Huang-Huai-Hai(HHH) Plain accounts for over 65% of the total sown area of winter wheat in China. Thus, it is important to monitor the winter wheat growth condition and reveal the main factors that influence its dynamics. This study assessed the winter wheat growth condition based on remote sensing data, and investigated the correlations between different grades of winter wheat growth and major meteorological factors corresponding. First, winter wheat growth condition from sowing until maturity stage during 2011–2012 were assessed based on moderate-resolution imaging spectroradiometer(MODIS) normalized difference vegetation index(NDVI) time-series dataset. Next, correlation analysis and geographical information system(GIS) spatial analysis methods were used to analyze the lag correlations between different grades of winter wheat growth in each phenophase and the meteorological factors that corresponded to the phenophases. The results showed that the winter wheat growth conditions varied over time and space in the study area. Irrespective of the grades of winter wheat growth, the correlation coefficients between the winter wheat growth condition and the cumulative precipitation were higher than zero lag(synchronous precipitation) and one lag(pre-phenophase precipitation) based on the average values of seven phenophases. This showed that the cumulative precipitation during the entire growing season had a greater effect on winter wheat growth than the synchronous precipitation and the pre-phenophase precipitation. The effects of temperature on winter wheat growth varied according to different grades of winter wheat growth based on the average values of seven phenophases. Winter wheat with a better-than-average growth condition had a stronger correlation with synchronous temperature, winter wheat with a normal growth condition had a stronger correlation with the cumulative temperature, and winter wheat with a worse-than-average growth condition had a stronger correlation with the pre-phenophase temperature. This study may facilitate a better understanding of the quantitative correlations between different grades of crop growth and meteorological factors, and the adjustment of field management measures to ensure a high crop yield.展开更多
The InGaAs/InAIAs/InP high electron mobility transistor (HEM:F) structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and grow...The InGaAs/InAIAs/InP high electron mobility transistor (HEM:F) structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si ^-doping concentration (Nd) is about 5.0 x 1012 cm-2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission elec- tron microscopy. An InGaAs/InAiAs/InP HEMT device with a gate length of lOOnm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT = 249 GHa and fmax 〉 400 GHz.展开更多
In this article,we consider interior regularity for weak solutions to nonlinear elliptic systems of divergence type with Dini continuous coefficients under natural growth condition for the case 1〈m〈 2.All estimates ...In this article,we consider interior regularity for weak solutions to nonlinear elliptic systems of divergence type with Dini continuous coefficients under natural growth condition for the case 1〈m〈 2.All estimates in the case of m≥2 is no longer suitable,and we can’t obtain the Caccioppoli’s second inequality by using these techniques developed in the case of m≥2.But the Caccioppoli’s second inequality is the key to use A-harmonic approximation method.Thus,we adopt another technique introduced by Acerbi and Fcsco to overcome the difficulty and we also overcome those difficulties due to Dini condition.And then we apply the A-harmonic approximation method to prove partial regularity of weak solutions.展开更多
Inorganic nonlinear optical crystal GdGa 4O(BO 3) 3(GdCOB) possesses moderate NLO efficient (1.3pm/V) ,high damage threshold(>1GW/cm 2),and wide transmission wave band(320-2700nm).In addition,it is chemically stabl...Inorganic nonlinear optical crystal GdGa 4O(BO 3) 3(GdCOB) possesses moderate NLO efficient (1.3pm/V) ,high damage threshold(>1GW/cm 2),and wide transmission wave band(320-2700nm).In addition,it is chemically stable,nonhygroscopic and easy to process,which makes GdCOB a promising practical NLO material for frequency conversion.Crack free single crystals of GdCOB with large size have been grown using the vertical Bridgman method for the first time.Stoichiometric amounts of starting materials 4N pure Gd 3O 3,H 3BO 3(or B 3O 3)and 3N pure CaCO 3 were mixed and preheated at 1100℃,then encapsulated in a Pt crucible with a single crystal seed.Thickness of the crucible we chose was within the range of 0.1—0.6mm.After thorough melting of the raw materials and partial melting of the seed(obtained by spontaneous nucleation),the crucible descended at a rate of <0.8mm/h.The vertical temperature gradient at the growth interface in the BR furnace was about 30—40℃/cm,and the temperature profile was kept symmetrical.Typical size of the GdCOB crystal without macroscopic defects obtained in this way was 25mm in diameter and 60mm in length.Due to the small temperature gradient in growth and the cooling process similar to the anneal after growth,cracking problem which was often met in pulling techniques was overcome efficiently.展开更多
The paper develops exponential stability of the analytic solution and convergence in probability of the numerical method for highly nonlinear hybrid stochastic pantograph equation. The classical linear growth conditio...The paper develops exponential stability of the analytic solution and convergence in probability of the numerical method for highly nonlinear hybrid stochastic pantograph equation. The classical linear growth condition is replaced by polynomial growth conditions, under which there exists a unique global solution and the solution is almost surely exponentially stable. On the basis of a series of lemmas, the paper establishes a new criterion on convergence in probability of the Euler-Maruyama approximate solution. The criterion is very general so that many highly nonlinear stochastic pantograph equations can obey these conditions. A highly nonlinear example is provided to illustrate the main theory.展开更多
Background: The aim of this study was to construct a nationwide stand age model by using National Forest Inventory(NFI) data and nationwide airborne laser scanning(ALS) data. In plantation forestry, age is usually kno...Background: The aim of this study was to construct a nationwide stand age model by using National Forest Inventory(NFI) data and nationwide airborne laser scanning(ALS) data. In plantation forestry, age is usually known.While this is not the case in boreal managed forests, age is still seldom predicted in forest management inventories.Measuring age accurately in situ is also very laborious. On the other hand, tree age is one of the accurately measured sample tree attributes in NFI field data. Many countries also have a nationwide coverage of airborne laser scanning(ALS) data. In this study, we merged these data sources and constructed a nationwide, area-based model for stand age.Results: While constructing the model, we omitted old forests from the data, since the correlation between ALS height metrics and stand age diminished at stands with age > 100 years. Additionally, the effect of growth conditions was considerable, so we also utilized different geographical and NFI variables such as site fertility and soil type in the modeling. The resultant nationwide model for the stand age of managed forests yielded a root mean square error(RMSE) of about 14 years. The model could be improved further by additional forest structure variables, but such information may not be available in practice.Conclusions: The results showed that the prediction of stand age by ALS, geographical and NFI information was challenging, but stil possible with moderate success. This study is an example of the joint use of NFI and nationwide ALS data and re-use of NFI data in research.展开更多
Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to ...Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to p-GaN are investigated. It is confirmed that the specific contact resistivity can be lowered nearly two orders by optimizing the growth conditions of compound contact layer. When the flow rate ratio between Mg and Ga gas sources of p++-InGaN layer is 10.6% and the thickness of p++-InGaN layer is 3 nm, the lowest specific contact resistivity of 3.98× 10-5 Ω cm2 is achieved. In addition, the experimental results indicate that the specific contact resistivity can be further lowered to 1.07 × 10-7Ω.cm2 by optimizing the alloying annealing temperature to 520 ℃.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 61176085,11474365 and 61377055the Department of Education of Guangdong Province under Grant No gjhz1103the Open-Project Program of the State Key laboratory of Opto-Electronic Material and Technologies of Sun Yatsen University
文摘The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth conditions on E2 (TO), E1 (TO) and A1 (LO) phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2 (TO) modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2 (TO) mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 (longitudinal optical plasma coupling (LOPC)) mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1 (LOPC) mode in 4H-SiC.
基金Supported by National Key Technology R&D Program of China (2010BAD03B01)
文摘[Objective] The study aimed at selecting the predominant strains being able to degrade kerosene and studying its best growth conditions. [Method] Choosing kerosene as the only carbon source, we selected and separated the predominant strains being able to degrade kerosene from the contaminated soil near petrochemical plants, and then optimized the grow conditions of the bacteria. [Result] The best conditions for the bacteria growth were determined as follows, that is, temperature was 30 ℃, pH=7, salinity was 2.5%, and the rotational speed of the thermostatic shake was 190 r/min. Under the optimal conditions, the degradation rate of kerosene by the bacteria cultured for three days reached 42.6%. [Conclusion] The research could provide scientific references for the restoration of polluted soil by kerosene.
文摘Let Ω be a bounded domain with smooth boundary Ω in R~n. We consider the following eigenvalue problem for systems of elliptic equations under the natural growth conditions
基金This work is supported by the Youth Foundation, NSFC.
文摘In this paper, we get the existence result of the nontrivial weak solution (λ, u) of the following eigenvalue problem with natural growth conditions.
文摘In this paper we give a priori estimates for the maximum modulus of generalizedsolulions of the quasilinear elliplic equations irith anisotropic growth condition.
基金Partially supported by the NSF(11271154)of China the 985 program of Jilin University
文摘This paper deals with the extinction of weak solutions of the initial and boundary value problem for ut = div((|u|σ + d0)| u|^p(x)-2 u). When the exponent belongs to different intervals, the solution has different singularity (vanishing in finite time).
文摘The Buyeo Royal Tomb No. 1 is an ancient tomb built in the late 6<sup>th</sup> and early 7<sup>th</sup> century. The four walls of the main room have murals of four guardian deities, and the ceiling has murals of lotus and cloud patterns. This study assessed the optimal growth conditions of two fungal (Fusarium oxysporum, Mortierella sp.) and four bacterial (Bacillus cereus, Cupriavidus campinensis, Streptomyces avidinii, Streptomyces cirratus) strains isolated from the Tomb No. 1, along with their effects on the painting layer. The two fungi showed optimal growth at 20°C - 30°C under both nutrient and non-nutrient conditions. These strains did not decompose or discolor the three pigments (cinnabar, hematite, oyster shell white);however, M. sp. showed slight decomposition of the media (starch paste, sea weed). The four bacterial strains showed the most active growth at 20°C - 25°C under nutrient conditions and did not grow under non-nutrient conditions. These bacteria commonly degraded animal glue and sea weed components. In addition, S. cirratus degraded starch. The genus Streptomyces discolored the pigment medium to brown and black, suggesting a possible risk of discoloration of the murals. The current environment in Tomb No. 1 was sufficient for microorganism growth, and the presence of strains such as soil bacteria and actinomycetes on the mural surface may damage the murals. The findings of this study could be helpful for preserving mural tombs against biological damage caused by microorganisms that are already present or may be present in the tombs in the future. These findings also provide guidelines for comprehensive conservation management.
基金Supported by the Youth FoundationNatural Science Foundation, People's Republic of China.
文摘In this paper, we get the existence of a weak solution of the following inhomogeneous quasilinear elliptic equation with critical growth conditions: where N≥2, f(x,u)~|u|<sup>m-1</sup>e<sup>b|u|<sup>γ</sup></sup>at +∞, with γ=N/N-1, m≥1, b】0.
文摘In this paper, we investigate the interior regularity including the local boundedness and the interior HSlder continuity of weak solutions for parabolic equations of the p(x, t)-Laplacian type. We improve the Moser iteration technique and generalize the known results for the elliptic problem to the corresponding parabolic problem.
文摘A class of quasilinear elliptic variational inequalities with double degenerate is discussed in this paper. We extend the Keldys-Fichera boundary value problem and the first boundary problem of degenerate elliptic equation to the variationalinequalities. We establish the existence and uniqueness of the weak solution of ocrresspending problem under nonstandard growth conditions.
文摘Ground-based platform systems provide a good tool for monitoring and managing crop conditions in precision agriculture applications and have been widely used for monitoring crop conditions.To develop an unmanned ground vehicle system(UGVS)based multi-sensors and test the feasibility of this system for monitoring rice conditions,an UGVS was developed to collect real-time rice condition information including NDVI values,reflectance measurements and crop canopy temperature in this study.Major components of the integrated system are GreenSeeker R100 system,hyper-spectroradiometer and infrared temperature sensor.The leaf area index(LAI)was measured by the CGMD302 Spectrometer.The Independent Samples T-Test method and the one way ANOVA method were used to determine the best spectral indices and analyze the relationship between the vegetation indices and rice LAI.It was found that the two best spectral indices for estimating LAI were NDVI(860 nm and 750 nm)with the correlation coefficient(R^(2))at 0.745 and RVI(853 nm and 751 nm)with the R^(2)at 0.724.The results show the UGVS can support multi-source information acquisition and is useful for crop management and precision agriculture applications.
文摘Habanero pepper(Capsicum chinense Jacq.)is a crop of economic relevance in the Peninsula of Yucatan.Its fruits have a high level of capsaicinoids compared to peppers grown in other regions of the world,which gives them industrial importance.Soil is an important factor that affects pepper development,nutritional quality,and capsaicinoid content.However,the effect of soil type on fruit development and capsaicinoid metabolism has been little understood.This work aimed to compare the effect of soils with contrasting characteristics,black soil(BS)and red soil(RS),on the expression of genes related to the development of fruits,and capsaicinoid synthesis using a transcriptomic analysis of the habanero pepper fruits.Plants growing in RS had bigger fruits and higher expression of genes related to floral development,fruit abscission,and softening which suggests that RS stimulates fruit development from early stages until maturation stages.Fruits from plants growing in BS had enrichment in metabolic pathways related to growth,sugars,and photosynthesis.Besides,these fruits had higher capsaicinoid accumulation at 25 days post-anthesis,and higher expression of genes related to the branched-chain amino acids metabolism(ketol-acid reductisomerase KARI),pentose phosphate pathway and production of NADPH(glucose-6-phosphate-1-dehydrogenase G6PDH),and proteasome and vesicular traffic in cells(26S proteasome regulatory subunit T4 RPT4),which suggest that BS is better in the early stimulation of pathways related to the nutritional quality and capsaicinoid metabolism in the fruits.
基金Supported by NSF of China(10531020)the Program of 985 Innovation Engieering on Information in Xiamen University(2004-2007).
文摘In this article, the authors consider the nonlinear elliptic systems under the natural growth condition. They use a new method introduced by Duzaar and Grotowski, for proving partial regularity for weak solutions, based on a generalization of the technique of harmonic approximation. And directly establish the optimal Holder exponent for the derivative of a weak solution.
基金financially supported by the National Nonprofit Institute Research Grant of Chinese Academy of Agricultural Sciences(IARRP-2015-8)the European Union seventh framework"MODEXTREME"(modelling vegetation response to extreme events)programme(613817)
文摘The sown area of winter wheat in the Huang-Huai-Hai(HHH) Plain accounts for over 65% of the total sown area of winter wheat in China. Thus, it is important to monitor the winter wheat growth condition and reveal the main factors that influence its dynamics. This study assessed the winter wheat growth condition based on remote sensing data, and investigated the correlations between different grades of winter wheat growth and major meteorological factors corresponding. First, winter wheat growth condition from sowing until maturity stage during 2011–2012 were assessed based on moderate-resolution imaging spectroradiometer(MODIS) normalized difference vegetation index(NDVI) time-series dataset. Next, correlation analysis and geographical information system(GIS) spatial analysis methods were used to analyze the lag correlations between different grades of winter wheat growth in each phenophase and the meteorological factors that corresponded to the phenophases. The results showed that the winter wheat growth conditions varied over time and space in the study area. Irrespective of the grades of winter wheat growth, the correlation coefficients between the winter wheat growth condition and the cumulative precipitation were higher than zero lag(synchronous precipitation) and one lag(pre-phenophase precipitation) based on the average values of seven phenophases. This showed that the cumulative precipitation during the entire growing season had a greater effect on winter wheat growth than the synchronous precipitation and the pre-phenophase precipitation. The effects of temperature on winter wheat growth varied according to different grades of winter wheat growth based on the average values of seven phenophases. Winter wheat with a better-than-average growth condition had a stronger correlation with synchronous temperature, winter wheat with a normal growth condition had a stronger correlation with the cumulative temperature, and winter wheat with a worse-than-average growth condition had a stronger correlation with the pre-phenophase temperature. This study may facilitate a better understanding of the quantitative correlations between different grades of crop growth and meteorological factors, and the adjustment of field management measures to ensure a high crop yield.
基金Supported by the National Natural Science Foundation of China under Grant No 61434006
文摘The InGaAs/InAIAs/InP high electron mobility transistor (HEM:F) structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si ^-doping concentration (Nd) is about 5.0 x 1012 cm-2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission elec- tron microscopy. An InGaAs/InAiAs/InP HEMT device with a gate length of lOOnm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT = 249 GHa and fmax 〉 400 GHz.
基金Supported by National Natural Science Foundation of China (10976026)the Education Department of Fujian Province (JK2009045)
文摘In this article,we consider interior regularity for weak solutions to nonlinear elliptic systems of divergence type with Dini continuous coefficients under natural growth condition for the case 1〈m〈 2.All estimates in the case of m≥2 is no longer suitable,and we can’t obtain the Caccioppoli’s second inequality by using these techniques developed in the case of m≥2.But the Caccioppoli’s second inequality is the key to use A-harmonic approximation method.Thus,we adopt another technique introduced by Acerbi and Fcsco to overcome the difficulty and we also overcome those difficulties due to Dini condition.And then we apply the A-harmonic approximation method to prove partial regularity of weak solutions.
文摘Inorganic nonlinear optical crystal GdGa 4O(BO 3) 3(GdCOB) possesses moderate NLO efficient (1.3pm/V) ,high damage threshold(>1GW/cm 2),and wide transmission wave band(320-2700nm).In addition,it is chemically stable,nonhygroscopic and easy to process,which makes GdCOB a promising practical NLO material for frequency conversion.Crack free single crystals of GdCOB with large size have been grown using the vertical Bridgman method for the first time.Stoichiometric amounts of starting materials 4N pure Gd 3O 3,H 3BO 3(or B 3O 3)and 3N pure CaCO 3 were mixed and preheated at 1100℃,then encapsulated in a Pt crucible with a single crystal seed.Thickness of the crucible we chose was within the range of 0.1—0.6mm.After thorough melting of the raw materials and partial melting of the seed(obtained by spontaneous nucleation),the crucible descended at a rate of <0.8mm/h.The vertical temperature gradient at the growth interface in the BR furnace was about 30—40℃/cm,and the temperature profile was kept symmetrical.Typical size of the GdCOB crystal without macroscopic defects obtained in this way was 25mm in diameter and 60mm in length.Due to the small temperature gradient in growth and the cooling process similar to the anneal after growth,cracking problem which was often met in pulling techniques was overcome efficiently.
基金support from the National Natural Science Foundation of China(70871046,71171091,71191091)Fundamental Research Funds for the Central Universities(2011QN167)
文摘The paper develops exponential stability of the analytic solution and convergence in probability of the numerical method for highly nonlinear hybrid stochastic pantograph equation. The classical linear growth condition is replaced by polynomial growth conditions, under which there exists a unique global solution and the solution is almost surely exponentially stable. On the basis of a series of lemmas, the paper establishes a new criterion on convergence in probability of the Euler-Maruyama approximate solution. The criterion is very general so that many highly nonlinear stochastic pantograph equations can obey these conditions. A highly nonlinear example is provided to illustrate the main theory.
基金funded by the University of Eastern Finland and Natural Resource Institute Finland。
文摘Background: The aim of this study was to construct a nationwide stand age model by using National Forest Inventory(NFI) data and nationwide airborne laser scanning(ALS) data. In plantation forestry, age is usually known.While this is not the case in boreal managed forests, age is still seldom predicted in forest management inventories.Measuring age accurately in situ is also very laborious. On the other hand, tree age is one of the accurately measured sample tree attributes in NFI field data. Many countries also have a nationwide coverage of airborne laser scanning(ALS) data. In this study, we merged these data sources and constructed a nationwide, area-based model for stand age.Results: While constructing the model, we omitted old forests from the data, since the correlation between ALS height metrics and stand age diminished at stands with age > 100 years. Additionally, the effect of growth conditions was considerable, so we also utilized different geographical and NFI variables such as site fertility and soil type in the modeling. The resultant nationwide model for the stand age of managed forests yielded a root mean square error(RMSE) of about 14 years. The model could be improved further by additional forest structure variables, but such information may not be available in practice.Conclusions: The results showed that the prediction of stand age by ALS, geographical and NFI information was challenging, but stil possible with moderate success. This study is an example of the joint use of NFI and nationwide ALS data and re-use of NFI data in research.
基金support by the National Natural Science Foundation of China(Grant Nos.61474110,61377020,61376089,61223005,and 61176126)the National Science Fund for Distinguished Young Scholars,China(Grant No.60925017)
文摘Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to p-GaN are investigated. It is confirmed that the specific contact resistivity can be lowered nearly two orders by optimizing the growth conditions of compound contact layer. When the flow rate ratio between Mg and Ga gas sources of p++-InGaN layer is 10.6% and the thickness of p++-InGaN layer is 3 nm, the lowest specific contact resistivity of 3.98× 10-5 Ω cm2 is achieved. In addition, the experimental results indicate that the specific contact resistivity can be further lowered to 1.07 × 10-7Ω.cm2 by optimizing the alloying annealing temperature to 520 ℃.