增效射孔中火药装药的实验研究

文章介绍了一种增效射孔弹模拟靶试验装置。并用该装置测得了在装药量相同的情况下,增面燃烧火药,减面燃烧火药以及复合装药的枪内压力时间曲线。同时讨论了在装药量变化时,枪内压力时间曲线的变化。     

Si基Si3N4/SiO2双层驻极体薄膜的电荷储存稳定性和电荷输运特性

非晶态二氧化硅（ＳｉＯ２）具有优良的驻极体性质,可制成微型化、集民经和机敏化的高灵敏度的传感器。但是,热氧化ＳｉＯ２驻极体膜的高压应力引起微结构变形,对薄膜储电特性形成复杂的影响。利用氮化硅薄膜的高张应力研究成氮化硅／二氧化硅Ｓｉ３Ｎ４／ＳｉＯ２）双层膜,可使其内应力相互补偿。本文讨论了双怪膜驻极体的电荷储存稳定性及电荷输运特性。实验结果表明,Ｓｉ３Ｎ４／ＳｉＯ２双层膜系统的电荷寿命比ＳｉＯ２驻极     

Effect of Si substrate on ethanol gas sensing properties of ZnO films

We prepared ZnO/n-Si heterojunctions by depositing ZnO films on n-Si substrates with different resistivities by radio-frequency magnetron sputtering. The microstructure of ZnO film was analyzed by X-ray diffraction and scanning electron microscopy. The current-voltage characteristics and ethanol gas sensing properties of the junctions were investigated at room temperature. It is found that optimization of n-Si substrate resistivity is critical to enhance the ethanol gas sensitivity of ZnO/n-Si heterojunction. The ZnO/n-Si heterojunction with n-Si substrate of 2-3 Ω cm exhibits the best ethanol gas sensing property. The junction shows the sensitivity of 29.41% to 0.24 g/L ethanol gas under + 0.52 V forward bias voltage.     

Mid-infrared materials and devices on a Si platform for optical sensing

In this article, we review our recent work on mid-infrared (mid-IR) photonic materials and devices fabricated on silicon for on-chip sensing applications. Pedestal waveguides based on silicon are demonstrated as broadband mid-IR sensors. Our low-loss mid-IR directional couplers demonstrated in SiN_x waveguides are useful in differential sensing applications. Photonic crystal cavities and microdisk resonators based on chalcogenide glasses for high sensitivity are also demonstrated as effective mid-IR sensors. Polymer-based functionalization layers, to enhance the sensitivity and selectivity of our sensor devices, are also presented. We discuss the design of mid-IR chalcogenide waveguides integrated with polycrystalline PbTe detectors on a monolithic silicon platform for optical sensing, wherein the use of a low-index spacer layer enables the evanescent coupling of mid-IR light from the waveguides to the detector. Finally, we show the successful fabrication processing of our first prototype mid-IR waveguide-integrated detectors.     

Two-dimensional position sensing Si detectors: Current and charge pulse characteristics

The current and charge pulse characteristics of two-dimensional position sensing Si detectors (PSDs) employing resistive charge division have been measured by making use of pulsed photon systems. The detectors studied are discrete two-dimensional PSDs where individual gold and orthogonal aluminum strips are deposited on the front and back surfaces, respectively, of the silicon wafer. Resistive charge division is accomplished by two external resistor networks. Detector fabrication and the pulsed photon systems are described. The anomalous currents (i.e., polarity reversal with time) exhibited by these detectors, which we reported earlier, have been studied and their time characteristics determined. Calculations based on a simplified model of the detector predict these anomalous currents, and the results of the calculations are compared with measurements. The currents characteristic of two-dimensional detectors have measured time durations considerably longer than those measured for equivalent one-dimensional detectors. Further, the anomalous currents result in ballistic deficits which are greater than unity, an effect entirely absent for one-dimensional detectors. For detectors having fixed area and thickness, the requirement that these detectors exhibit near distortion-free position response for heavy ions in the presence of intense background fluxes (i.e., protons) imposes strong restrictions on the total resistance of the external resistor networks, which are discussed.     

Charge Density Wave and Superconducting Properties in Single Crystals of Lu5Ir4Si10

We measured the electrical resistivity from 2 K up to 900 K on high quality single crystals of Lu₅Ir₄Si₁₀. A clear thermal hysteresis was found at the onset of the Charge Density Wave (CDW), evidencing the first-order nature of the transition. When tantalum is included in the compound, the CDW is destroyed and the superconducting critical temperature is enhanced. Finally, we present specific heat and magnetic penetration depth in the Meissner state. We show that the superconducting properties are very close to a weak coupling BCS superconductor.     

Charge trapping phenomena of tetraethylorthosilicate thin film containing Si nanocrystals synthesized by solid-state reaction

In this work, we report on the fabrication of tetraethylorthosilicate (TEOS) thin dielectric film containing silicon nanocrystals (Si nc), synthesized by solid-state reaction, in a capacitor structure. A metal-insulator-semi-conductor (MIS) capacitor, with 28?nm thick Si nc in a TEOS thin film, has been fabricated. For this MIS, both electron and hole trapping in the Si nc are possible, depending on the polarity of the bias voltage. A V(FB) shift greater than 1?V can be experienced by a bias voltage of 16?V applied to the metal electrode for 1?s. Though there is no top control oxide, the discharge time for 10% of charges can be up to 4480?s when it is biased at 16?V for 1?s. It is further demonstrated that charging and discharging mechanisms are due to the Si nc rather than the TEOS oxide defects. This form of Si nc in a TEOS thin film capacitor provides the possibility of memory applications at low cost.     

Si基多孔 SiO2薄膜驻极体电荷储存稳定性

通过控制溶胶－凝胶（sol-gel)工艺条件,利用相应条件下样品的红外光谱,等温表面电位衰减,开路热刺激放电电流谱等,考虑了Si基多孔SiO2薄膜驻极体体内沉积的空间电荷的储存稳定性,分析了各种工艺参数与薄膜驻极体性质之间的联系。实验结果表明,反应物中水含量对簿膜驻极体的电荷储存稳定性及陷阱分布有一定的影响;烧结温度和时间对电荷的储存稳定性的影响较大。     

恒栅流负电晕充电的Si基SiO2驻极体的电荷稳定性

本文讨论了在不同充电参数条件下的恒恒流电晕充电的Ｓｉ基ＳｉＯ２薄膜驻极体的空间电荷储存稳定性,并和栅控恒压电晕充电的结果进行了比较。利用电容－电压（Ｃ－Ｖ）分析技术确定了空间电荷重心的漂移,并利用等温表面电位衰减测量,开路热刺激放电实验及Ｃ－Ｖ分析技术讨论了Ｓｉ基ＳｉＯ２薄膜驻极体的空间电荷储存和输动特性。     

Charge transport and ammonia sensing properties of flexible polypyrrole nanosheets grown at air–liquid interface

Flexible polypyrrole nanosheets (thickness ∼150 nm) grown at the air–liquid interface have been investigated for charge transport and NH₃ sensing application. Polypyrrole nanosheets films exhibited a uniform and dense morphology. Temperature dependent charge transport measurements revealed that the PPy films obey Mott's 3-D variable range hopping mechanism. The mobility values calculated using temperature dependent current voltage characteristics indicated them to obey Arrhenius behaviour. These films exhibited a reversible response towards NH₃ at room temperature. The sensor exhibited a sensitivity of ∼12% with a typical response and recovery times of 240 s and 50 min, respectively towards 50 ppm of NH₃. Raman studies indicated that there is an increase in the antisymmetrical C–N stretching upon exposure to higher concentration of NH₃ (500 ppm) and could be assigned to the interaction of NH₃ with the carbon backbone of PPy film. Our results clearly emphasize that these flexible PPy films could be used to realize flexible sensors.     

Assembly of ligand-stripped nanocrystals into precisely controlled mesoporous architectures

The properties of mesoporous materials hinge on control of their composition, pore dimensions, wall thickness, and the size and shape of the crystallite building units. We create ordered mesoporous materials in which all of these parameters are independently controlled. Different sizes (from 4.5 to 8 nm) and shapes (spheres and rods) of ligand-stripped nanocrystals are assembled using the same structure-directing block copolymers, which contain a tethering domain designed to adsorb to their naked surfaces. Material compositions range from metal oxides (Sn-doped In(2)O(3) or ITO, CeO(2), TiO(2)) to metal fluorides (Yb,Er-doped NaYF(4)) and metals (FePt). The incorporation of new types of nanocrystals into mesoporous architectures can lead to enhanced performance. For example, TiO(2) nanorod-based materials withstand >1000 electrochemical cycles without significant degradation.     

Backscattering enhancement of light by nanoparticles positioned in localized optical intensity peaks

We report what we believe to be a novel backscattering phenomenon associated with localized optical intensity peaks (spanning as little as 43 nm) arising at the shadow-side surfaces of plane-wave-illuminated dielectric microcylinders of noncircular cross sections. Namely, for nanometer-scale dielectric particles positioned within the localized intensity peaks, their backscattering of visible light is enhanced by several orders of magnitude relative to the case of isolated nanoparticles (i.e., Rayleigh scattering). The positions of the localized intensity peaks can be quickly scanned along the microcylinder surface by changing either the incident wavelength or angle. This combination of giant backscattering enhancement of nanoparticles and ease and rapidity of scanning may present advantages relative to the use of fragile, mechanically scanned, near-field probes. Potential applications include visible-light detection, characterization, and manipulation of nanoparticles.     

Wave-optical simulation of hard-x-ray nanofocusing by precisely figured elliptical mirrors

Computer simulations of nanofocusing by elliptical mirrors are presented wherein the diffraction and propagation of coherent hard x rays are predicted using wave-optical calculations. Surface height data acquired via microstitching interferometry were used to calculate the complex pupil function of a mirror, taking into account the Fresnel reflectivity and treating the surface topography as an aberration to a perfect elliptical mirror. The reflected wave-field amplitude and phase downstream of the mirror were obtained by numerically evaluating the Fresnel-Kirchhoff diffraction integral. Simulated intensity profiles and contours (isophotes) around the focal plane are presented for coherent illumination by a 15 keV point source, which indicate nearly diffraction-limited focusing at the 40 nm level. The effect of high spatial frequency microroughness on nanofocusing was investigated by low-pass filtering the Fourier spectrum of the residual height profile. Simulations using the filtered metrology data confirmed that roughness length scales shorter than 0.1 mm have a minor effect on the focal spot size and intensity.     

分层装药对杆式射流的影响分析

为了研究分层装药结构的内、外层炸药材料、装药厚度对杆式射流成型的影响,利用True Grid和LSDYNA软件对不同工况下杆式射流的成型进行数值模拟。仿真结果表明:分层装药对杆式射流的影响与内、外层装药的爆速差△D和厚度比d_1/d_2有关,当d_1/d_24.4时,装药的爆速差△D对射流的增益效果成正相关;当4.4d_1/d_28.0时,分层装药对射流无明显影响;当d_1/d_28.8时,爆速差△D与射流的增益效果呈负相关。总体上,分层装药结构对射流形态、整体动能和头、尾速度有优化增益作用,且优化和增益效果与内、外层装药的厚度比及材料有关,合理的装药材料以及装药比例能够有效提高杆式射流的毁伤效能。     

Differential precisely controllable piezoresonant absolute pressure transducer with a manifold increase in sensitivity

A new system is developed for a multiple increase change in the output of transducer frequency that leads to an increase in its sensitivity. The system does not disturb the vacuum and it makes it possible to perform precise micrometric control of absolute pressure. Deceased. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 34–37, December, 2005.     

Electrostatic fields of an infinite medium containing arbitrarily positioned coated cylinders

We propose a framework for evaluation of the electrostatic fields in an unbounded isotropic medium containing a number of arbitrarily dispersed circular cylinders or coated cylinders subjected to a remotely prescribed potential field. The cylinders or coated cylinders could be at most cylindrically orthotropic, and may have different radii with different conductivities. The approach is based on a multipole expansion formalism, together with a construction of consistency conditions and translation operators. This main procedure is inspired from an ingenious concept of the classic work of Lord Rayleigh [1], in which the effective conductivity of a periodic array of circular disks or spheres is considered. In the present formulation, we expand the potential field versus various local coordinates with origins positioned at the inclusions’ centers. The key step is to link the potential data with the outer applied field, which is accomplished by the use of Green’s second identity in the matrix domain. We show that the coefficients of field expansions are governed by an infinite set of linear algebraic equations. Numerical results are presented for a few different configurations. We have verified our numerical solutions for a simplified configuration with those obtained from the bipolar coordinate transformation.