Implementation Effect of Farmland Protection in Urumqi-Changji Economic Zone,China

A multi-level evaluation index system is established with farmland protection as the target layer,farmland quantity,farmland quality andfarmland sustainable development as the criterion layer.And the index layer includes the quantity change of farmland,per capita farmland area,multiple cropping index,total grain yield,unit grain yield,per capita grain security coefficient,and unit machinery dynamical input.Both expert eval-uation method and factor analysis method are used to determine the weight of index.According to the data in farmland area,grain yield and eco-nomic development in Urumqi-Changji Economic Zone in the years 1996-2007,a comprehensive evaluation model of intensive farmland use inUrumqi-Changji Economic Zone is established after data standardization.The overall implementation effect of farmland protection policy is ana-lyzed by integrating the farmland quantity,farmland quality and sustainable development.Result shows that implementation effect of farmland pro-tection shows an upward trend in general in Urumqi-Changji Economic Zone in the years 1996-2007,with a fluctuation in the years 2000-2003and a stable rising phase from 2004 till now.The maximum value is 0.779 in the year 2007;the minimum value is 0.242 in the year 1996;and themean value in the years 1996-2007 is 0.454.Farmland protection at first strictly controls the farmland quantity,then pays attention to farmlandquality,and finally focuses on the sustainable use of farmland.

An improved design for Al Ga N solar-blind avalanche photodiodes with enhanced avalanche ionization

To enhance the avalanche ionization, we designed a new separate absorption and multiplication AlGaN solarblind avalanche photodiode （APD） by using a high/low-Al-content AlGaN heterostructure as the multiplication region instead of the conventional AlGaN homogeneous layer. The calculated results show that the designed APD with Al0.3Ga0.7N/Al0.45Ga0.55N heterostructure multiplication region exhibits a 60% higher gain than the conventional APD and a smaller avalanche breakdown voltage due to the use of the low-Al-content Al0.3Ga0.7N which has about a six times higher hole ionization coefficient than the high-Al-content Al0.45Ga0.55N. Meanwhile, the designed APD still remains a good solar-blind characteristic by introducing a quarter-wave A1GaN/A1N distributed Bragg reflectors structure at the bottom of the device.

Negative transconductance effect in p-GaN gate AlGaN/GaN HEMTs by traps in unintentionally doped GaN buffer layer

We investigate the negative transconductance effect in p-GaN gate AlGaN/GaN high-electron-mobility transistor(HEMT) associated with traps in the unintentionally doped GaN buffer layer. We find that a negative transconductance effect occurs with increasing the trap concentration and capture cross section when calculating transfer characteristics.The electron tunneling through AlGaN barrier and the reduced electric field discrepancy between drain side and gate side induced by traps are reasonably explained by analyzing the band diagrams, output characteristics, and the electric field strength of the channel of the devices under different trap concentrations and capture cross sections.

Characteristics of an Indium-Rich InGaN p-n Junction Grown on a Strain-Relaxed InGaN Buffer Layer

An indium-rich InGaN p-n junction is grown on a strain-relaxed InGaN buffer layer.The results show that the n-InGaN is grown coherently on the buffer layer but the p-InGaN layer exhibits a partial strain relaxation.The fabricated InGaN p-n junction has a low reverse leakage current density on the order of 10^(-8)A/cm^(2)within the measured voltage range,and exhibits a wide spectral response due to the presence of band tail states or deep level states which origin from indium composition fluctuation or various defects.The measured peak responsivity at 438 nm is 31 mA/W at zero bias and reaches 118 mA/W at 3 V reverse bias.In addition,the Raman spectra of the p-and n-type InGaN alloys are also analyzed.

High-Gain N-Face AlGaN Solar-Blind Avalanche Photodiodes Using a Heterostructure as Separate Absorption and Multiplication Regions

It is well known that -nitride semiconductors can generate the magnitude of MV/cm polarization electric field which is comparable with their ionization electric fields. To take full advantage of the polarization electric field, we design an N-face AlGaN solar-blind avalanche photodiode (APD) with an Al0.45Ga0.55N/Al0.3Ga0.7N heterostructure as separate absorption and multiplication (SAM) regions. The simulation results show that the N-face APDs are more beneficial to improving the avalanche gain and reducing the avalanche breakdown voltage compared with the Ga-face APDs due to the effect of the polarization electric field. Furthermore, the Al0.45Ga0.55N/Al0.3Ga0.7N heterostructure SAM regions used in APDs instead of homogeneous Al0.45Ga0.55N SAM structure can increase significantly avalanche gain because of the increased hole ionization coefficient by using the relatively low Al-content AlGaN in the multiplication region. Meanwhile, a quarter-wave AlGaN/AlN distributed Bragg reflector structure at the bottom of the device is designed to remain a solar-blind characteristic of the heterostructure SAM-APDs.

Dissolution and recrystallization of perovskite induced by N-methyl-2-pyrrolidone in a closed steam annealing method

High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone(NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH_3NH_3PbI_3 perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.

Design and Research of Efficient Adaptive Spray Plant Protection UAV

When the plant protection UAV is spraying on plants, the operator usually performs visual inspection on the vertical distance between the UAV and the plant to adjust the spray height to complete the application. Visual inspection by human eyes is easy to cause the error of spray deposition and deposition density. In order to improve the full utilization of drugs and the spraying efficiency of plant protection UAV, an efficient adaptive spray plant protection UAV was designed, and the vertical distance from the UAV to the plant was collected by ultrasonic wave. Meantime, the plant density was detected in real time, and the flight attitude of plant protection UAV and application rate of spray nozzle were automatically adjusted. The experimental results showed that the designed highly efficient adaptive spray plant protection UAV had fast response speed, precise spray location and less drug loss.

Convergence of a Sinusoidal Series with an Infinite Integral

In this paper, we study the relationship between the convergence of the sinusoidal series and the infinity integrals (any real number α ∈[0,1], parameter p > 0). First of all, we study the convergence of the series (any real number α ∈[0,1], parameter p > 0), mainly using the estimation property of the order to obtain that the series diverges when 0 p ≤1-α, the series converges conditionally when 1-α p ≤1, and the series converges absolutely when p >1. In the next part, we study the convergence state of the infinite integral (any real number α ∈[0,1], parameter p > 0), and get that when 0 p ≤1-α, the infinite integral diverges;when 1-α p ≤1, the infinite integral conditionally converges;when p >1, the infinite integral absolutely converges. Comparison of the conclusions of the above theorem, it is not difficult to derive the theorem: the level of and the infinity integral with the convergence of the state (any real number α ∈[0,1], the parameter p >0), thus promoting the textbook of the two with the convergence of the state requires the function of the general term or the product of the function must be monotonically decreasing conditions.

Analysis of Person Deictic Expressions in Advertising Discourse

The aim for this research is to analyze the person deictic expressions in advertising English and to find out their characteristics and possible functions.Advertising has become a very specialized activity in modern times.During the period of development,advertising has performed its own language style,which is quite different from other types of languages.The proper interpretation and use of the language is dependent on its specific situation or context.Person deixis puts the text in a specific situation;the selection of person deixis not only can reflect the physical distance but also indicate the psychological distance between the advertiser and the public.Three categories of person deictic expressions in the advertisements are analyzed to find out frequency of appearance.Statistical results show that more first person and second person pronouns like I,we,and you are used than third person pronouns he,she,they and it,among which the second person pronouns take up the highest rank.On the basis of the frequency of person deictic expressions,this study finds that through the proper use of the person deictic expressions,the advertiser can attract a large number of people in an interactive communication and at the same time,make the advertisement become more cordial,thus greatly shorten the psychological distance between the advertiser and the audience.

Properties of CdTe nanocrystalline thin films grown on different substrates by low temperature sputtering

CdTe nanocrystalline thin films have been prepared on glass, Si and Al2O3 substrates by radio-frequency magnetron sputtering at liquid nitrogen temperature. The crystal structure and morphology of the films were charac-terized by X-ray diffraction （XRD） and field-emission scanning electron microscopy （FESEM）. The XRD examinations revealed that CdTe films on glass and Si had a better crystal quality and higher preferential orientation along the （111） plane than the Al2O3. FESEM observations revealed a continuous and dense morphology of CdTe films on glass and Si substrates. Optical properties of nanocrystalline CdTe films deposited on glass substrates for different deposited times were studied.