Design of NRAs having higher aperture opening ratio and autocorrelation compression ratio by means of a global optimization method

When noises considerations are made, nonredundant arrays (NRAs) are endowed with many advantages which other arrays e.g., uniformly redundant arrays (URAs) do not possess in applications of coded aperture imaging. However, lower aperture opening ratio limits the applications of NRA in practice. In this paper, we present a computer searching method based on a global optimization algorithm named DIRECT to design NRAs. Compared with the existing NRAs e.g., Golay's NRAs, which are well known and widely used in various applications, NRAs found by our method have higher aperture opening ratio and auto correlation compression ratio. These advantages make our aperture arrays be very useful for practical applications especially for which of aperture size are limited. Here, we also present some aperture arrays we found. These aperture arrays have an interesting property that they belong to both NRA and URA. (C) 2006 Elsevier GmbH. All rights reserved.

光照和不同形态氮营养盐供应对坛紫菜硝酸还原酶活性的影响

为了探讨光照、NO3--N和NH4+-N对坛紫菜(Porphyra haitanensis)硝酸还原酶活性(NRA)的影响,在光照和黑暗条件下分别对坛紫菜叶状体进行氮(N)饥饿→氮(N)加富和N加富→N饥饿处理,并测定NRA的变化。结果表明:在N饥饿→N加富过程中,光照下NRA比黑暗中要高;NO3--N的加富能提高NRA,且在光照下比黑暗中NRA达到最大值的时间要短;而NH4+-N与NO3--N共同对N饥饿藻体加富时NRA没有明显变化,并与NH4+-N单独加富无显著差异。另外,对于N加富→N饥饿的处理,在

Hydrogen behavior in GaN epilayers grown by NH3-MBE

Hydrogen behavior in unintentionally doped GaN epilayers on sapphire substrates grown by NH3-MBE is investigated. Firstly, we find by using nuclear reaction analysis (NRA) that with increasing hydrogen concentration the background electron concentration increases, which suggests that there exists a hydrogen-related donor in undoped GaN, Secondly, Fourier transform infrared (FTIR) absorption and X-ray photoelectron spectroscopy (XPS) reveal Further that hydrogen atom is bound to nitrogen atom in GaN with a local vibrational mode at about 3211 cm(-1) Hence, it is presumed that the hydrogen-related complex Ga. . .H-N is a hydrogen-related donor candidate partly responsible for high n-type background commonly observed in GaN films. Finally, Raman spectroscopy results of the epilayers show that ill addition to the expected compressive biaxial strain, in some cases GaN films suffer from serious tensile biaxial strain. This anomalous behavior has been well interpreted in terms of interstitial hydrogen lattice dilation. (C) 2001 Elsevier Science B.V. All rights reserved.

Hydrogen-dependent lattice dilation in GaN

Using Raman spectroscopy we have analysed the strain status of GaN films grown on sapphire substrates by NH3 source molecular beam epitaxy (MBE). In addition to the expected compressive biaxial strain, in some cases GaN films grown on c-face sapphire substrates suffer from serious tensile biaxial strain. This anomalous behaviour has been well interpreted in terms of interstitial hydrogen-dependent lattice dilation. The hydrogen concentration in the films is measured by nuclear reaction analysis (NRA). With increasing hydrogen incorporation, the residual compressive biaxial strain is first further relaxed, and then turns into tensile strain when the hydrogen contaminant exceeds a critical concentration. The hydrogen incorporation during the growth process is found to be growth-rate dependent, and is supposed to be strain driven. We believe that the strain-induced interstitial incorporation is another way for strain relaxation during heteroepitaxy, besides the two currently well known mechanisms: formation of dislocations and growth front roughening.

Influence of rapid thermal annealing on the optical properties of gallium nitride grown by gas-source molecular-beam epitaxy

Raman scattering, photoluminescence (PL), and nuclear reaction analysis (MA) have been employed to investigate the effects of rapid thermal annealing (RTA) on GaN films grown on sapphire (0001) substrates by gas-source molecular-beam epitaxy, The Raman spectra showed the presence of the E-2 (high) mode of GaN and shift of this mode from 572 to 568 cm(-1) caused by annealing. The results showed that RTA has a significant effect on the strain relaxation caused by the lattice and thermal expansion misfit between the GaN epilayer and the substrate. The PL peak exhibited a blueshift in its energy position and a decrease in the full width at half maximum after annealing, indicating an improvement in the optical quality of the film. Furthermore, a green luminescence appeared after annealing and increased in intensity with increasing annealing time. This effect was attributed to H concentration variation in the GaN film, which was measured by NRA. A high H concentration exists in as-grown GaN, which can neutralize the deep level, and the H-bonded complex dissociates during RTA, This leads to the appearance of a luminescent peak in the PL spectrum. (C) 1998 American Institute of Physics.

Hydrogen behavior in GaN epilayers grown by NH3-MBE

Hydrogen behavior in unintentionally doped GaN epilayers on sapphire substrates grown by NH3-MBE is investigated. Firstly, we find by using nuclear reaction analysis (NRA) that with increasing hydrogen concentration the background electron concentration increases, which suggests that there exists a hydrogen-related donor in undoped GaN, Secondly, Fourier transform infrared (FTIR) absorption and X-ray photoelectron spectroscopy (XPS) reveal Further that hydrogen atom is bound to nitrogen atom in GaN with a local vibrational mode at about 3211 cm(-1) Hence, it is presumed that the hydrogen-related complex Ga. . .H-N is a hydrogen-related donor candidate partly responsible for high n-type background commonly observed in GaN films. Finally, Raman spectroscopy results of the epilayers show that ill addition to the expected compressive biaxial strain, in some cases GaN films suffer from serious tensile biaxial strain. This anomalous behavior has been well interpreted in terms of interstitial hydrogen lattice dilation. (C) 2001 Elsevier Science B.V. All rights reserved.

N~+离子注入GCr15轴承钢和钝铁的温度效应

本文研究在不同注入温度(50 ℃ - 350 ℃)下的~+N离子注入GCr15 (1at%C, 1.5at%Cr, 0.3at%Mn, 0.2at%Si)轴承刚和纯铁(99.99at%Fe)，注入剂量：5 * 10~(17) N~+·cm~(-2)。运用~(14)N(d,d_1)~(12)C带电粒子核反应(NRA)测量氮的总保留量及深度公布；内转换电子穆斯堡乐谱(CEMS)测定铁的化学态，并用x射线衍射分析进一步加以验证；最后用磨损实验检验磨损效果，寻找对研究的两种材料的一个最佳注入温度。对GCr15钢，低温（小于100 ℃）注入比350 ℃注入更有利于提高钢的耐磨性，这是由于50 ℃注入，氮间隙原子浓度高，且形成了Fe_2N相。高于150 ℃注入时，N~+离子前移，N~+离子保留量下降，Fe_2N相消失，而Fe_2N相的产生对提高耐磨性起重要作用。对纯铁，50 ℃注入时也形成了ε－Fe_2N相，在高于150 ℃注入时，此相消失，半生新相γ－Fe_4N。但在350 ℃时，GCr15钢与纯铁都形成了Fe_3O_4相，这对改性是极为不利的，所以建议，对GCr15钢和纯铁，不宜在350 ℃时注入

不同用量腐植酸复合肥在辣椒上的施用效应及其防衰增产机理研究

以辣椒为供试作物进行盆栽试验 ,对不同用量腐植酸复合肥在辣椒上的施用效应及其防衰增产机理进行研究 .结果表明 ,不同肥料用量对辣椒体内各种生理活动均有明显影响 ,并最终影响产量 ,且与无机复合肥相比 ,腐植酸复合肥表现了明显的优势 .NRA随施肥量的增加而提高 ,但变化速率逐渐下降 ;SOD活性在施肥量低于 0 .2g·kg-1时 ,随施肥量的增加显著提高 ,但当施肥量超过 0 .2g·kg-1后 ,SOD活性开始显著降低 ;对POD活性的影响与对NR活性的影响趋势基本一致 ,但当施肥量超过 0 .3g·kg-1时 ,无机肥处理的POD活性显著提高 ,而HA复合肥处理的POD活性变化则始终较平缓 ;对辣椒叶片蒸腾速率的影响与对SOD活性的影响趋势是一致的 .施肥量与辣椒产量之间呈显著二次曲线相关 ,HA复合肥最高产量施肥量 (纯养分量 )为 0 .2 7g·kg-1,每盆最高产量为 16 5 .2 2 g .