Analysis of Inner-Scale Effect on Atmosphere Scintillation for Infrared Laser Beam Propagating on Earth-Space Paths

On Earth-space paths, based on ITU-R C _n ² (h) model, by means of a modification of the Rytov method that incorporates an amplitude spatial frequency filter function under strong fluctuation conditions, considering atmospheric turbulence inner-scale, an expression is developed for the scintillation index of a visible or a near and middle infrared laser beam wave that is valid under moderate to strong irradiance fluctuations. The quantitative analyses of scintillation index are done by this analytic model for laser Gaussian collimated beam wave at visible or near and middle infrared wave band. The results agree with theoretic analysis scintillation. This scintillation model can be converted into a Gaussian beam wave model with finite inner-scale on horizontal sight paths of invariable C _n ².     

Architectural Control of Hierarchical Nanobelt Superstructures in Catanionic Reverse Micelles

BaXO₄ (X = Mo, W) nanobelts and a variety of hierarchical superstructures assembled from the nanobelts have been synthesized in a catanionic reverse‐micelle system. The effects of various factors, such as the mixing ratio (r) between the anionic and cationic surfactants, the temperature, and the presence of polymeric additives, on the formation of the nanobelts and their hierarchical assembly have been examined in detail. In particular, r has been shown to be powerful in modulating the formation and assembly of the BaMoO₄ and BaWO₄ nanobelts. Architectural control of the penniform nanobelt superstructures has been readily achieved by changing the experimental parameters. A plausible two‐stage growth mechanism has been proposed for the formation of penniform BaXO₄ nanobelt superstructures in catanionic reverse micelles.     

The Infrared Ray Transport Model of Finite Size Flat Beam in Tissue

The infrared ray propagation model of finite size flat beam in biological tissue is set up. Gaussian beams and circularly flat beams were compared. The model is simulated with Monte Carlo method, and the influence of parameters of biological tissue and properties is analyzed. The potential application of the model is demonstrate by estimating the absorption and transport-corrected scattering coefficients from reflectance measured from intact tissue.     

Luminescence Properties of Aminobenzanthrones and Their Application as Host Emitters in Organic Light‐Emitting Devices

A series of aminobenzanthrone derivatives, possessing a keto and an amino group on the aromatic ring, are synthesized and their photoluminescence (PL) and electroluminescence (EL) properties are studied in detail. These compounds emit strongly in solution and in the solid state, with the emission maxima in the range of 528–668 nm resulting from charge‐transfer transitions from the amino group to the keto moiety. The emission wavelength depends greatly on the polarity of the solvent. A red shift of nearly 100 nm is observed from n‐hexane to dichloromethane for each of these compounds. The PL quantum yields of these molecules also depend tremendously on the solvent. The values are between 88 and 70 % in n‐hexane and decrease as the polarity of the solvent increases. The single‐crystal X‐ray diffraction data reveal that the aminobenzanthrone planes of these molecules stack in the crystals in an antiparallel head‐to‐tail fashion. This strong dipole–dipole interaction accounts for the observed red‐shifted emissions of the aminobenzanthrone molecules in powders and in films relative to those in nonpolar solvents. Electroluminescent devices using aminobenzanthrone derivatives as the host emitters or dopants emit orange to red light in the range 590–645 nm. High brightness, current efficiency, and power efficiency are observed for some of these devices. For example, the device using N‐(4‐t‐butylphenyl)‐N‐biphenyl‐3‐benzanthronylamine as the emitter gives saturated red light with a current efficiency of 1.82 cd A^–1, brightness of 11 253 cd m^–2, and Commission Internationale de l'Éclairage (CIE) coordinates of (0.64,0.36); the device using N‐(2‐naphthyl)‐N‐phenyl‐3‐benzanthronylamine as the emitter gives orange–red light with a current efficiency of 3.52 cd A^–1, brightness of 25 000 cd m^–2, and CIE coordinates of (0.61,0.38).     

Cu/Ta/SiO_2/Si多层结构的纳米压痕研究

利用磁控溅射方法在Si衬底上沉积钽层以及铜层,并利用纳米压痕技术对Cu/Ta/SiO_2/Si多层膜结构进行了硬度和弹性模量的表征,研究发现多层膜结构的硬度随着薄膜厚度的增加而降低,然而弹性模量与膜厚之间并没有这样的关系。利用聚焦离子束（FIB）工艺将纳米压痕区域剖开,并通过透射电子显微镜（TEM）表征发现在纳米压痕过后,钽以及二氧化硅界面有了明显的分层现象,这一点表明层与层之间较弱的键合在相对大的负荷下遭到了破坏。     

Intermetallic reactions in a Sn-20In-2.8Ag solder ball-grid-array package with Au/Ni/Cu pads

The intermetallic compounds formed during the reflow and aging of Sn-20In-2.8Ag ball-grid-array (BGA) packages are investigated. After reflow, a large number of cubic-shaped AuIn₂ intermetallics accompanied by Ag₂In precipitates appear in the solder matrix, while a Ni(Sn_0.72Ni_0.28)₂ intermetallic layer is formed at the solder/pad interface. With further aging at 100°C, many voids can be observed in the solder matrix and at the solder/pad interface. The continuous distribution of voids at the interface of specimens after prolonged aging at 100°C causes their bonding strength to decrease from 5.03 N (as reflowed) to about 3.50 N. Aging at 150°C induces many column-shaped (Cu_0.74Ni_0.26)₆(Sn_0.92In_0.08)₅ intermetallic compounds to grow rapidly and expand from the solder/pad interface into the solder matrix. The high microhardness of these intermetallic columns causes the bonding strength of the Sn-20In-2.8Ag BGA solder joints to increase to 5.68 N after aging at 150°C for 500 h.     

基于Monte Carlo方法的任意概率密度随机数字信号发生器设计

在信号处理和计算机微观模拟的过程中,经常要构造具有特定概率密度的随机数发生器.采用常规方法实现难度较大且不具普遍性,本文根据Monte Carlo方法基本原理和随机信号的数字特征给出一种任意概率密度随机数发生器的设计方法及核心源代码.实验证明该方法简单高效、通用性好.     

基于互信息的MIMO雷达通信一体化系统的性能分析

该文讨论共存式多输入多输出(Multiple-input multiple-output,MIMO)雷达通信一体化系统的性能.雷达端和通信端采用合作的方式共享信息,使得一体化系统的通信端可以利用雷达信号来辅助完成通信任务,而雷达端则可利用被动的通信信号来完成雷达任务.该文推导合作情况下共存一体化MIMO系统的雷达互信息...     

Structural and optical properties of AIN sputtering deposited on sapphire substrates with various orientations

AIN thin films were deposited on c-,a-and r-plane sapphire substrates by the magnetron sputtering technique.The in-fluence of high-temperature thermal annealing (HTTA) on the structural,optical properties as well as surface stoichiometry were comprehensively investigated.The significant narrowing of the (0002) diffraction peak to as low as 68 arcsec of AIN after HTTA implies a reduction of tilt component inside the AIN thin films,and consequently much-reduced dislocation densities.This is also supported by the appearance of E2(high) Raman peak and better Al-N stoichiometry after HTTA.Furthermore,the in-creased absorption edge after HTTA suggests a reduction of point defects acting as the absorption centers.It is concluded that HTTA is a universal post-treatment technique in improving the crystalline quality of sputtered AIN regardless of sapphire orienta-tion.     

Self‐Assembled In‐Plane Growth of Mg2SiO4 Nanowires on Si Substrates Catalyzed by Au Nanoparticles

In‐plane growth of Mg₂SiO₄ nanowires on Si substrates is achieved by using a vapor transport method with Au nanoparticles as catalyst. The self‐assembly of the as‐grown nanowires shows dependence on the substrate orientation, i.e., they are along one, two, and three particular directions on Si (110), (100), and (111) substrates, respectively. Detailed electron microscopy studies suggest that the Si substrates participate in the formation of Mg₂SiO₄, and the epitaxial growth of the nanowires is confined along the Si <110> directions. This synthesis route is quite reliable, and the dimensions of the Mg₂SiO₄ nanowires can be well controlled by the experiment parameters. Furthermore, using these nanowires, a lithography‐free method is demonstrated to fabricate nanowalls on Si substrates by controlled chemical etching. The Au nanoparticle catalyzed in‐plane epitaxial growth of the Mg₂SiO₄ nanowires hinges on the intimate interactions between substrates, nanoparticles, and nanowires, and our study may help to advance the developments of novel nanomaterials and functional nanodevices.