N2分子二聚物在352.3 nm处增益特性研究

利用微波放电激励高纯氮,并采用放大自发辐射法,研究了不同微波激励功率和不同N₂气压条件下N₂分子二聚物352.3nm辐射的增益特性。给出了沿放电管轴线N₂分子二聚物352.3nm辐射的小信号增益系数随微波激励功率和充入放电管N₂气压变化的规律。研究结果表明当微波功率大于100W时,充入N₂气压在330~1 800Pa范围内,N₂分子二聚物在352.3nm处存在受激辐射特性。当微波功率为500W,充入放电管的N₂气压为1 100Pa时,N₂分子二聚物352.3nm辐射的小信号增益系数最大为1.08%cm^-1。另外,还给出了N₂分子二聚物352.3nm辐射增益沿放电管径向分布情况。 N₂分子二聚物352.3nm辐射的增益系数在放电管中心最小,接近管壁时最大。     

吉林省光学学会1991年年会论文摘要

铌酸钆(GdNbO₄)的结构是畸变的白钨矿结构,单斜晶系.稀土离子处在 C₂对称格位上,因此⁵D₀→⁷F₁(或⁷F₀-⁵D₁)跃迁应该是三重(2J+1)劈裂.实际观察到⁵D₀→⁷F₁(j=1,2,3)跃迁荧光谱线数目是与基质晶格的完整性和热振动有关.⁶D₀→⁷F₂电偶极跃迁(611nm)荧光强度与激发波长有关.     

全固态连续波555 nm黄-绿光激光器

报道了全固态连续波555 nm黄-绿光激光器,黄-绿激光分别由Nd:YAG和Nd:YVO₄晶体的946 nm和1342 nm谱线非线性和频产生,两条谱线各自晶体对应的能级跃迁分别为⁴F_3/2-⁴I_9/2和⁴F_3/2-⁴I13/2。实验中采用复合折叠腔结构,利用LBOI类临界位相匹配进行腔内和频,当注入到Nd∶YAG和Nd:YVO₄晶体的泵浦功率分别为12 W和8 W时,获得542 mW的TEM₀₀连续波555 nm黄-绿激光输出,4 h功率稳定度优于±3.7％。实验结果表明,采用Nd:YAG和Nd:YVO₄两种激光晶体进行腔内和频是获得黄-绿激光的高效方法,并可以应用到其它两种激光晶体进行腔内非线性和频,获得更多不同波长的激光输出。     

基于区域分割的自适应反锐化掩模算法

针对线性反锐化掩模法的缺点,提出一种基于区域分割的自适应反锐化掩模法,利用像素局部方差将输入图像划分为平滑区、中等对比度区和高对比度区,根据像素(x,y)所属的区域类型,自适应确定其局部灰阶变化率增益系数α(x,y)及期望的输出局部灰阶变化率H_d(x,y),并导出增强系数K(x,y)。对一幅胸片图像进行处理,并与其它几种反锐化掩模法的处理结果进行比较,结果显示该方法获得较好的边缘增强效果,且有较强的噪声抑制能力。     

基于铯里德堡原子的太赫兹探测能级机理

为了更深入地探索基于铯里德堡原子的太赫兹新探测技术，通过仿真模拟研究了在四能级里德堡原子模型下，其原子跃迁后的辐射寿命以及不同跃迁模式下（S_1/2→P_3/2、D_5/2→P_1/2、D_5/2→P_3/2）的系统散粒噪声限制灵敏度。仿真结果表明，原子跃迁后的辐射寿命会随着其能级主量子数的增大而增加；且在模型3种跃迁模式中，S_1/2→P_3/2的原子辐射寿命较其他两种跃迁模式短。对于散粒噪声限制灵敏度方面，探究发现D_5/2→P_1/2的跃迁模式下灵敏度数值最小，即该跃迁模式下系统的探测灵敏度最高。该结论为基于里德堡原子太赫兹探测技术提供了参考，使其对生物、材料领域的微弱信号的探测奠定了基础。     

全固态589 nm复合腔连续波和频激光器

给出了一种复合腔结构和频激光器,用2台激光二极管阵列(LDA)经过光纤耦合分别单独端面抽运Nd:YVO₄和Nd:YAG晶体,其中Nd:YVO₄和Nd:YAG晶体所选择的能级跃迁分别为⁴F_3/2-⁴I_11/2和⁴F_3/2-⁴I_13/2,其对应激光跃迁波长分别为1 064 nm和1 319 nm,两基频激光束分别在两个子谐振腔中振荡,在其交叠区利用KTP II类临界相位匹配(CPM)进行腔内和频,获得了589 nm的和频激光。当抽运功率为8 W/14 W时获得了340 mW连续波TEM₀₀黄激光输出。光束质量因子M²<1.2,激光输出功率噪声低,4 h功率不稳定度小于±3％。该复合腔结构是实现LDA泵浦589 nm全固态黄光激光器一种有效的和频方法。     

稀土掺杂钙钛矿型氟化物晶体生长及其光谱

用Bridgman-Stockbarger法长出了Eu²⁺:KMgF₃和LiBaF₃单晶。用区熔法长出Re:LiBaF₃(Re=Ce³⁺,Tb³⁺,Eu²⁺)晶体。X光衍射分析表明由相图得到的原料比BaF₂:LiF=40:60(mol%)时生长的是多晶,因为,最开始析出的是BaF₂。对掺杂晶体进行了光谱研究。氮分子激光器泵浦的Eu²⁺:KMgF₃荧光光谱显示了多中心结构。     

弧矢聚焦双晶单色器聚焦误差分析

简单介绍了弧矢聚焦单色仪的分光原理及结构原理,分析了同步辐射弧矢聚焦双晶单色器实际转轴偏离理想转轴ΔS及晶面偏离与导轨的理想夹角Δα对出射光高度的影响,并对弧矢聚焦晶体压弯半径的压弯精度Δh对实验站聚焦光斑展宽的作用进行了理论推导.当ΔS≤31μm、Δα≤1′,就可以确保出射光线高度误差Δh≤25μm;当对称压弯第二晶体所需微位移器的行程≥1mm、精度≤1.25μm时,可满足聚焦光斑的展宽≤0.5mm要求,且当压弯半径R的弯曲精度在ΔR≤0.75%R的范围内不需对晶体压弯.     

高平均功率腔内和频蓝光Nd:YAG激光器

高平均功率蓝光激光是当前固体激光技术研究热点之一。尽管通过Nd³⁺的⁴F_3/2→⁴I_9/2态谱线倍频可获得瓦级蓝光输出,然而其准三能级物理特性严重限制其更高功率输出。研究了Nd³⁺离子⁴F_3/2→⁴I_13/2态1.3 μm谱线腔内三倍频产生高平均功率蓝光激光,获得4.3 W蓝光激光输出,重复频率3.5 kHz,脉冲宽度150±10 ns,光束质量M²因子约为5±1。研究表明:Nd∶YAG晶体1.3 μm多谱线振荡是制约实验结果的重要因素,若克服多谱线振荡问题,有望获得10 W级蓝光激光输出。     

红外折射率精密测试方法的研究

本文阐述了应用最小偏向角法及自准直法测定红外波段折射率的基本原理。并较详细地讨论了最小偏向角的定位问题,探索了用逐渐逼近的光电接收方法测定最小偏向角的规律。对两种方法做了比较。实验装置由 GSJ-A 型数字测角仪加红外反射系统构成。叙述了消除杂光方面所做的工作,保证了测试精度的提高。文中列举了对0.935微米,1.014微米、1.129微米、1.3622微米、1.5295微米、1.7012微米波长测得的晶体材料(CaF₂)、红外光学玻璃(N-344)、普通光学玻璃(Lak₂)及铝酸盐红外材料的折射率典型数据,并对测试结果进行了分析和讨论。本方法获得了±2×10^-2的测试精度,与国外相比已达到了同量级的精度。     

Recent advances in insect olfaction, specifically regarding the morphology and sensory physiology of antennal sensilla of the female sphinx moth Manduca sexta.

The antennal flagellum of female Manduca sexta bears eight sensillum types: two trichoid, two basiconic, one auriculate, two coeloconic, and one styliform complex sensilla. The first type of trichoid sensillum averages 34 microm in length and is innervated by two sensory cells. The second type averages 26 microm in length and is innervated by either one or three sensory cells. The first type of basiconic sensillum averages 22 microm in length, while the second type averages 15 microm in length. Both types are innervated by three bipolar sensory cells. The auriculate sensillum averages 4 microm in length and is innervated by two bipolar sensory cells. The coeloconic type-A and type-B both average 2 microm in length. The former type is innervated by five bipolar sensory cells, while the latter type, by three bipolar sensory cells. The styliform complex sensillum occurs singly on each annulus and averages 38-40 microm in length. It is formed by several contiguous sensilla. Each unit is innervated by three bipolar sensory cells. A total of 2,216 sensilla were found on a single annulus (annulus 21) of the flagellum. Electrophysiological responses from type-A trichoid sensilla to a large panel of volatile odorants revealed three different subsets of olfactory receptor cells (ORCs). Two subsets responded strongly to only a narrow range of odorants, while the third responded strongly to a broad range of odorants. Anterograde labeling of ORCs from type-A trichoid sensilla revealed that their axons projected mainly to two large female glomeruli of the antennal lobe.     

Surface quality investigation of turbine blade steels for turning process

The quality of surface or surface finish is the widely used index of product quality and it is also critical in functional behavior of the products like turbine blades, especially when they are in contact with other medium or the materials. This paper presents the surface quality evaluation of turbine blade steels (ST 174PH, ST 12TE and ST T1/13W) for different combination of cutting parameters viz. speed, feed and depth of cut in a CNC turning process. The response surface method (RSM) is devised in design of experiments and 20 experiments per material are conducted in surface quality evaluation and analysis. The results are analyzed using ANOVA and different graphical methods like contour plot and 3D surface graphs. The reasons for the highest surface roughness of ST 174PH material are analyzed using metallurgical perspective. The regression equations for predicting the surface roughness of the materials are formulated in terms of cutting parameters based on experimental results and are verified using confirmatory experiments.     

基于Pumplinx的螺杆泵性能优化仿真研究

为了得到螺杆泵转子直径与定子导程对泵性能的影响规律,基于Pumplinx软件对橡胶定子单头单螺杆泵进行非稳态数值计算求解,在此基础上探究了不同压差条件下无量纲参数T/D对螺杆泵流量、水力效率以及轴向力的影响进行分析并基于此进行性能优化。结果显示,随着T/D的增大,泵流量增加,轴向力基本保持不变,而水力效率先增大后减小,其最优值出现在T/D=4.5时;螺杆泵定子转子啮合区域的泄漏较为明显,且随着T/D的增大泄漏量增多。因此为了得到更高的效率,T/D宜优化至4.5;为了得到更大流量的同时不牺牲效率,T/D宜优化至5.4。此外,数值计算与试验结果较为一致,偏差不超过3.5%,表明该螺杆泵仿真方法具有参考价值。     

Electron beam damage of behenic acid films

The rate of fading of electron diffraction patterns of behenic acid monolayer crystals as well as multilayer crystals was measured at 100 kV at room temperature to investigate the dependence of beam damage on specimen thickness. The diffracted intensities for monolayers and double layers decreased nearly exponentially with electron exposure; however, the intensities for multilayers were unchanged during initial electron exposures, often increased temporarily and then decreased with electron exposure. The critical dose, D_e, defined as the dose at which the diffracted intensity falls to 1/e of its initial value, was 1.0 electrons/Ų for the monolayers, 1.8 electrons/Ų for the double layers and more for multilayers. These results lead to the conclusion that D_e for behenic acid increases nearly linearly with specimen thickness in the range of about 25–100 Å for dose rate of 0.1–2 electrons/Ų min.     

Salvage procedures for trochanteric femoral fractures after internal fixation failure: biomechanical comparison of a plate fixator and the dynamic condylar screw

The aim of this study was the biomechanical evaluation of the reversed less invasive stabilization system (LISS) internal fixation as a joint-preserving salvage procedure for trochanteric fractures. Five LISS plates and five dynamic condylar screws (DCS) were tested using synthetic femora (Sawbones) with an osteotomy model similar to a type-A2.3 pertrochanteric fracture. The constructs were subjected to axial loading up to 1000 N for five cycles. Then, the force was continuously increased until fixation failure. For the evaluation of the biomechanical behaviour, the stiffness levels were recorded and the osteotomy gap displacement was mapped three-dimensionally. The average stiffness for the constructs with LISS plates was 412 N/mm (with a standard deviation (SD) of 103N/mm) and 572N/mm (SD of 116 N/mm) for the DCS constructs (p=0.051). Local displacement at the osteotomy gap did not yield any significant differences. The LISS constructs failed at a mean axial compression of 2103N (SD of 519N) and the DCS constructs at a mean of 2572N (SD of 372N) (p=0.14). It is concluded that the LISS plate offers a reliable fixation alternative for salvage procedures.     

低基液氨质量分数对卡琳娜循环系统(kcs-34)理论循环效率的影响

为探究卡琳娜循环系统(kcs-34)的热源进出口温度及质量流量均不发生变化的情况下,低基液氨质量分数a(<0.66)的变化对系统理论循环效率η的影响。通过改变蒸发器工质侧进口温度T8和富氨蒸气氨质量分数b,得出系统理论循环效率η与低基液氨质量分数a之间的关系。结果表明,在b不变的情况下,随着T8的增大,系统最大理论循环效率ηmax增大,a的取值区间呈减小趋势;在T8不变的情况下,随着b的增大,系统最大理论循环效率ηmax增大,系统最大理论循环效率ηmax对应的a值也逐渐增大,并且a的取值区间也呈增大趋势,同时,当T8保持不变并且a＜0.36时,系统理论循环效率η会随着b的增大而减小,而当a＞0.4时,系统理论循环效率η则会随着b的增大而增大。     

Temperature Dependences in the Tomlinson/Prandtl Model for Atomic Sliding Friction

The temperature dependence of the Tomlinson/Prandtl model for nanoscale sliding friction is analyzed by considering the properties of the initial and final states between which the tip can move, as well as the energy barrier between them, for various sliding regimes defined by the value of the corrugation factor γ. When γ < 1, the friction force tends to zero, defining a so-called superlubricious regime. The most commonly observed behavior is found for γ > 4.603, where the friction force increases monotonically with increasing sliding velocity up to a critical value equal to the value of F ^* (lateral force at T = 0) and monotonically decreases with temperature from F ^* at T = 0. However, completely different behavior is found when 1 < γ < 4.603. The temperature dependence of the lateral force in this regime is investigated using Monte Carlo simulations. The friction force still tends to F ^* as T approaches 0 K, but in contrast to the behavior found when γ > 4.603, the friction force increases with increasing temperature from F ^* , reaches a maximum value, and then decreases monotonically as the temperature rises further. Such behavior has been observed in atomic force microscopy friction measurements.     

Comparison of intensity distributions in tomograms from BF TEM, ADF STEM, HAADF STEM, and calculated tilt series

The three-dimensional (3D) morphology of a nanometer-sized object can be obtained using electron tomography. Variations in composition or density of the object cause variations in the reconstructed intensity. When imaging homogeneous objects, variations in reconstructed intensity are caused by the imaging technique, imaging conditions, and reconstruction. In this paper, we describe data acquisition, image processing, and 3D reconstruction to obtain and compare tomograms of magnetite crystals from bright field (BF) transmission electron microscopy (TEM), annular dark-field (ADF) scanning transmission electron microscopy (STEM), and high-angle annular dark field (HAADF) STEM tilt series. We use histograms, which plot the number of volume elements (voxels) at a given intensity vs. the intensity, to measure and quantitatively compare intensity distributions among different tomograms. In combination with numerical simulations, we determine the influence of maximum tilt angle, tilt increment, contrast changes with tilt (diffraction contrast), and the signal-to-noise ratio (SNR) as well as the choice of the reconstruction approach (weighted backprojection (WB) and sequential iterative reconstruction technique (SIRT)) on the histogram. We conclude that because ADF and HAADF STEM techniques are less affected by diffraction, and because they have a higher SNR than BF TEM, they are better suited for tomography of nanometer-sized crystals.     

Comparison of intensity distributions in tomograms from BF TEM,ADF STEM,HAADF STEM,and calculated tilt series

The three-dimensional (3D) morphology of a nanometer-sized object can be obtained using electron tomography. Variations in composition or density of the object cause variations in the reconstructed intensity. When imaging homogeneous objects, variations in reconstructed intensity are caused by the imaging technique, imaging conditions, and reconstruction. In this paper, we describe data acquisition, image processing, and 3D reconstruction to obtain and compare tomograms of magnetite crystals from bright field (BF) transmission electron microscopy (TEM), annular dark-field (ADF) scanning transmission electron microscopy (STEM), and high-angle annular dark field (HAADF) STEM tilt series. We use histograms, which plot the number of volume elements (voxels) at a given intensity vs. the intensity, to measure and quantitatively compare intensity distributions among different tomograms. In combination with numerical simulations, we determine the influence of maximum tilt angle, tilt increment, contrast changes with tilt (diffraction contrast), and the signal-to-noise ratio (SNR) as well as the choice of the reconstruction approach (weighted backprojection (WB) and sequential iterative reconstruction technique (SIRT)) on the histogram. We conclude that because ADF and HAADF STEM techniques are less affected by diffraction, and because they have a higher SNR than BF TEM, they are better suited for tomography of nanometer-sized crystals.     

Equipment and procedure for measuring physicochemical properties of hygroscopic crystals

The equipment and procedure for measuring different characteristics of hygroscopic crystals in a temperature interval from −100 to +100°C is described. A glass vacuum cuvette is placed into a massive metal vessel, the temperature of which may be varied over wide limits. The measured temperature dependence of permittivity ɛ in the phase transition area of strongly hygroscopic crystals of ammonium pyroselenite (NH₄)₂Se₂O₅ and (ND₄)₂Se₂O₅ at about room temperature is given. Original Russian Text ? O.I. Nasluzova, A.G. Lundin, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 3, pp. 135–137.