Effects of particle size of reactant on characteristics of combustion synthesis of TiC-Fe cermet

Four Ti-C-Fe powder mixtures, with a same molar ratio but a different particle size, were used for a combustion synthesis of TiC-Fe cermet to investigate effects of the particle size on the characteristics of the combustion synthesis. The results showed that the mixture with the finer Ti powder gave out a higher combustion temperature, a higher reaction velocity, a higher product density, a layer-shaped pore, and a greater size of TiC particles whether the Fe powder was finer or coarser. While in the case of the coarser Ti powder used, a small amount of residual phase remained in the product, and what is more interesting that the mixture with the finer Fe powder gave out a lower reaction velocity than that by the mixture with the coarser Fe powder. These effects were successfully explained with the previously proposed mechanisms of the combustion synthesis of TiC-Fe, and the mechanisms were proved to be valid thereby.     

A method of numerical solution of one-dimensional stefan problems of two types

A one-dimensional conjugate problem of heat transfer with phase transitions of two types (with interfaces of two phases and with a two-phase zone) is solved by a finite difference method based on the general initial heat conduction equation written with the Dirac delta function. A calculating scheme is developed using a nonuniform spatial net with floating nodes and the method of oppositely directed pivots.Nizhnii Novgorod Polytechnic Institute. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No. 3, pp. 332–340, September, 1993.     

Modeling of processes of failure of laminated composite materials

The article explains the essence of the mathematical method with which processes of failure of composite materials can be modeled with the aid of a computer. The strength characteristics of laminated material Cr-V are calculated on the basis of the physicomechanical and structural properties with a view to their statistical scatter.Translated from Problemy Prochnosti, No. 2, pp. 88–91, February, 1990.     

Experimental investigation of a variant of the theory of elastoplastic deformation of metals under complex loading

The article presents analytical approximations of two scalar functionals of the ternary relation of the theory of elastoplastic processes containing, in addition to the function of simple loading, four constants of plasticity of the material which are determined from experiments with bilinear strain paths with an orthogonal corner. It also presents the results of a comparison with the data of experiments with complex loading along variegated two- and three-dimensional strain paths that make it possible to assume the applicability of the suggested defining equations for describing processes of a single (with possible unloading) arbitrarily complex loading of initially isotropic strain-hardening materials.Translated from Problemy Prochnosti, No. 12, pp. 48–53, December, 1990.     

用多聚-L-赖氨酸活化生物芯片玻璃片基的研究

采用红外光谱、紫外光谱和扫描电镜等多种分析手段研究了以多聚－L－赖氨酸（P－L－L）为活化试剂时载碳片的活化过程，讨论了NaOH溶液预处理以及P－L－L浓度和浸泡时间等因素对玻璃片基活化效果的影响。结果表明，多聚－L－赖氨酸与载玻片表面发生联接，其联接量与NaOH预处理条件以及P－L－L的浓度和浸泡时间等因素有关。在本实验条件下，先经24h的NaOH(25%)预处理，再于10％的多聚－L－赖氨酸溶液中浸泡2h，可得到较为理想的活化效果。     

Circle of least confusion of a spherical reflector

A simple, tractable equation is provided for determining the size and location of the circle of least confusion of a concave spherical reflector. This method is exact for the object at infinity and with wave effects neglected. Designers of large radius Arecibo-like telescopes, both radio and optical, with symmetrical, spherical primaries should find the method useful. The mathematical results are valid for apertures with an angle of incidence up to 45 degrees. Comparisons of the location of the disk of least confusion with longitudinal spherical aberration and the radius of the disk with transverse spherical aberration are presented.     

挥发萘回用对萘系高效减水剂性能的影响

萘系高效减水剂合成过程中回收的挥发萘颜色较深,与工业萘相比纯度降低近3%。使用掺有挥发萘合成的萘系高效减水剂配制水泥净浆,研究表明,随着挥发萘掺入量的增加,净浆初始流动度减小,经时损失增大;混凝土试验表明,随着挥发萘掺入量的增加,萘系高效减水剂的减水率降低,增强作用减弱。因此,在挥发萘回用过程中,掺量不宜过大,最好不要超过5%。     

A comparison of the cyclic durability,ease of disassembly,repair, and reuse of parts of wooden chair frames

Simple, statically-determinate wooden chair frames constructed with seven types of joints were subjected to cyclic front to back load tests to determine joint durability, chair reparability, and parts' reuse. Knockdown joints, namely, screw, bed bolts (with dowel nuts), pinned round mortise and tenon, and pinned rectangular mortise and tenon joints; and glued joints, namely, dowel, round mortise and tenon, and rectangular mortise and tenon joints were included in the study. Glued round and rectangular mortise and tenon joints had the highest levels of cyclic load durability whereas bed bolts had the least. Chairs constructed with knockdown joints were easiest to repair, whereas chairs constructed with glued joints were the most difficult to repair. Parts' recovery with rectangular mortise and tenon joints was high when tenons were replaced with inserted tenons. Likewise, recovery was high with dowel joints since the failed dowels were replaced with larger dowels. Parts' recovery with metal knockdown fasteners was low because of side rail splitting; however, parts' recovery with pinned round and rectangular mortise and tenon joints was high.     

自贡西山公园山脊地形的场地效应分析

利用自贡地形影响台阵在2008年汶川地震中获得的主震强震记录,采用水平 /垂直谱比法（HVSR）对该山脊地形场地对地震动的放大效应进行了分析,并探讨了所获记录结果的可靠性;采用显式有限元－有限差分法结合局部透射人工边界的二维场地影响分析模型与方法,模拟了该场地的地震动响应。对模拟结果与HVSR法分析结果进行对比分析,表明数值模拟结果与观测记录分析结果具有较好的一致性,利用数值计算方法建立的简单二维分析模型基本上可以反映山脊地形对地震动的影响。     

Measurement of the Effect of Thermal Noise on the Amplitude of Oscillation of a Maser Oscillator

Experimental verification of the effect of thermal noise on the oscillation amplitude of a maser is described. Two different masers are considered, the H maser with an homogeneous atomic line and the Rb maser with an inhomogeneous line. The effect is characterized by the spectral density of the relative amplitude fluctuations and this parameter is measured with a conventional superheterodyne AM receiver for various maser saturation factors. Experimental results show good agreement with theoretical predicted values. At high saturation factors, a peak appears with a maximum at a frequency close to the Rabi frequency. Observed values at high Fourier frequencies allow a measurement of the atomic power by the knowledge of the absolute temperature of the cavity and the prediction of the oscillator short-term frequency stability. Furthermore, the effect on amplitude and on frequency noise of an external feedback loop used to increase the cavity quality factor is discussed.     

双层药型罩内罩开槽对EFP形成尾翼的影响？

为了研究内层药型罩周向对称开槽对爆炸成型弹丸（ EFP）形成尾翼的影响,利用LS-DYNA显示动力分析有限元程序,采用Lagrange算法,对双层药型罩聚能装药的成型过程进行数值模拟。对不同开槽参数的数值模拟结果进行对比分析,选择数值模拟最佳结果进行试验验证。数值模拟与试验研究所得结论基本吻合。结果表明：内层药型罩周向对称开槽结构能够形成带尾翼的串联EFP。当L/Da ＝0.20、W/Da ＝0.05时（ Da 为装药直径,L为开槽长度、W为开槽宽度）,前后EFP长径比最大,带尾翼的串联EFP的成型效果最佳。     

最优地挑选若干个伪硬币

用一台理想设备在最少的测试次数中,从n个硬币中挑选出m个不同的伪硬币。在该文中,我们通过分析鉴别m个不同的伪硬币中的理想设备基本模型的结果,得到了在最坏的情况下的一个确定的测试过程,我们证明这个测试过程是一个最优分组测试过程。对于n个硬币中的m个相同伪硬币,给出了鉴别n个硬币中m个相同伪硬币的两个最优分组测试过程。     

涂布两种施胶剂对抄制纸板物理性能的影响

目的对涂布氧化淀粉胶纸板、聚乙烯醇胶纸板和未涂布纸板的耐破强度、戳穿强度、挺度、防水防潮性等物理性能进行研究。方法实验选用表面施胶的方法来增强纸板的物理性能。通过抄制不同定量的化学机械浆和化学浆纸板,在纸板表面涂布相同体积的氧化淀粉胶和聚乙烯醇胶,测试纸板的物理性能。结果在相同温度、相对湿度条件下涂布施胶剂的纸板,其耐破强度、戳穿强度、挺度和防水防潮性要优于未涂布纸板;涂布聚乙烯醇的纸板其耐破强度、戳穿强度和防水防潮性要优于涂布氧化淀粉胶的纸板,涂布氧化淀粉胶的纸板挺度要优于涂布聚乙烯醇胶的纸板。结论涂布施胶剂后纸板的物理性能均有所提高,涂布聚乙烯醇胶的纸板强度较强,涂布氧化淀粉胶的纸板韧性较好。     

Hf栅极栅电子发射的研究

栅发射在栅控行波管及速调管中是较为普遍的现象,为了降低栅发射,通常采用高功函数金属作为栅极或在栅极表面沉积高功函数物质或沉积能与蒸散到栅极上的活性物质反应形成高功函数化合物的金属。本文直接采用纯金属Hf作为栅极,与普通Mo栅极对比,研究了Hf栅极在模拟电子管中管子激活前、阴极激活后栅发射的情况,并对氧化物阴极加速寿命中栅发射情况进行测试分析。结果表明:在阴极激活前后及寿命过程中,纯Hf栅极具有较小的栅发射电流。     

现代中国包装文化的属性

阐述了现代中国包装文化的属性:传统风格与现代意识的共存,民族化与世界性的互补,多元化与个性追求的结合等;并提出有关现代包装设计趋向。     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Aspects of the theory of graphene

Following a brief review of the device-friendly features of graphene, recent work on its Green's functions with and without a normal magnetic field are discussed, for an infinite graphene sheet and also for a quantum dot, with analyses of the Landau-quantized energy spectra of the sheet and dot. The random phase approximation dielectric response of graphene is reviewed and discussed in connection with the van der Waals interactions of a graphene sheet with atoms/molecules and with a second graphene sheet in a double layer. Energy-loss spectroscopy for a graphene sheet subject to both parallel and perpendicular particle probes of its dynamic, non-local response properties are also treated. Furthermore, we discuss recent work on the coupling of a graphene plasmon and a surface plasmon, yielding a collective plasma mode that is linear in wavenumber. Finally, we discuss the unusual aspects of graphene conduction and recent work on diffusive charge transport in graphene, in both the DC and AC regimes.     

不同氟碳涂层在武汉地区老化行为的比较研究

在武汉地区对两种不同氟含量的氟碳树脂涂层进行户外曝晒试验,并对曝晒1 a后的试样进行盐雾试验,使用红外吸收光谱法检测涂层的特征基团变化,用常规方法检测光泽度及结合强度.同时,通过对结合强度变化数据的拟合,分析了氟碳涂层中含氟分子链降解及结构变化的规律.结果表明,相同曝晒时间下,含氟量低的氟碳涂层老化较含氟量高的严重,且含氟量低的氟碳涂层的耐蚀性能和结合强度随曝晒时间下降较快.     

Influence of different types of water on strength, porosity and hydric parameters of metakaolin admixtured cement

The present research deals with strength, porosity and hydric behavior of metakaolin cement admixtured with different types of water. The hydration of ordinary Portland cement in the presence of 0%, 10%, 20% and 30% metakaolin treated with distilled, ground and sea water with the water to cement ratio of 0.4 was studied. The experimental results on setting time, strength, porosity and hydric parameters are reported. The results show that, metakaolin percentage increases in strength with a decrease in porosity. The observed results are discussed with SEM micrographs. Further, sea water accelerates the cement hydration at the early stages but retards it in the latter stages of hydration.     

滑移系统自由振动的停滞区

综合分析了线性、渐硬和渐软恢复力滑移系统自由振动的停滞区,给出了三种滑移系统停滞区的解析解;论证了解的连续性和随系统参数变化的规律性。结果表明:滑移系统的停滞区在系统参数的整个取值范围内处处连续;随摩擦系统单调增加,而随系统的线性与非线性恢复力参数单调减小;相对于线性恢复力滑移系统,弹簧的软化至多可使停滞区增加50%;渐软恢复力参数有一个下限,低于此限的软化系统没有停滞区。