Microstructure and properties of silicon carbide whisker reinforced zirconium diboride ultra-high temperature ceramics

Hot-pressed zirconium diboride (ZrB₂) matrix composites containing 0–30 vol% silicon carbide (SiC) whiskers have been investigated to determine the effect of composition (i.e. amount of SiC whiskers) on the microstructure, mechanical properties and thermal properties. With increasing SiC whisker volume contents, the flexural strength and fracture toughness of the composites were improved compared to those of monolithic ZrB₂. Flexural strength increased from 629 MPa for pure ZrB₂ to 767 MPa for ZrB₂–30 vol%SiCw. Likewise, fracture toughness ranged from 5.4 to 7.1 MPa m^1/2 over the same composition range. Specific heat capacity increased with SiC whisker addition, while thermal diffusivity and thermal conductivity decreased slightly with the increase of SiC whisker content.     

Approximate solution of the Fredholm integral equation of the first kind in a reproducing kernel Hilbert space

An approach for solving Fredholm integral equations of the first kind is proposed for in a reproducing kernel Hilbert space (RKHS). The interest in this problem is strongly motivated by applications to actual prospecting. In many applications one is puzzled by an ill-posed problem in space C[a,b] or L²[a,b], namely, measurements of the experimental data can result in unbounded errors of solutions of the equation. In this work, the representation of solutions for Fredholm integral equations of the first kind is obtained if there are solutions and the stability of solutions is discussed in RKHS. At the same time, a conclusion is obtained that approximate solutions are also stable with respect to _∞ or _L² in RKHS. A numerical experiment shows that the method given in the work is valid.     

Rapid solidification processing in molten salts chemistry: X-ray analysis of deeply undercooled cryolite-alumina melts

Rapid solidification processing (cooling rate from the interval 10⁵–10⁶ K s⁻¹) was used to prepare deeply undercooled cryolite-alumina melts. Such prepared samples were analyzed by the XRD method. Besides cryolite, XRD patterns belonging to ι-Al₂O₃ were recorded. The influence of annealing on the XRD patterns of deeply undercooled melts was also investigated.     

The electrochemical behavior of N-n-undecyl-N''-(sodium-p-amino-benzenesulfonate)thiourea and its interaction with bovine serum albumin

In pH 5.5 phosphate buffer solution,N-n-undecyl-N'-(sodium-p-amino-benzenesulfonate)thiourea(UPT)produced a pair of redox peaks on the bare glassy carbon electrode.At the multi-walled carbon nanotube(MWNT)modified electrode,the electrochemical behavior of UPT enhanced greatly.In the presence of bovine serum albumin (BSA),the peak currents of UPT decreased linearly due to the formation of a super-molecular complex.This method was successfully applied to the determination of BSA in a bovine serum sample.     

Typical Microstructures of Chinese Medicines with X-Ray Microscopy in Phase Contrast

Due to the low absorption contrast of plant tissues, traditional x-ray radiography has not been included in the microscopic techniques used in the identification of traditional Chinese medicines （TCMs）. With the development of x-ray phase contrast imaging （XPCI） in recent years, weakly absorbing materials could also be imaged by x- rays. Here we investigate microstructures of TCMs utilizing XPCI based on a nano-focus x-ray tube. The results demonstrated that XPCI is capable of revealing the microstructures of TCMs used as judging criteria in the identification of TCMs. The major advantages of the new method are nondestructivity, no special demand for sample preparation and suitability for thick samples.     

金属氧化物半导体场效应管热载流子退化的1/fγ噪声相关性研究

研究了金属氧化物半导体(MOS)器件在高、中、低三种栅压应力下的热载流子退化效应及其1/fγ噪声特性.基于Si/SiO2界面缺陷氧化层陷阱和界面陷阱的形成理论,结合MOS器件1/f噪声产生机制,并用双声子发射模型模拟了栅氧化层缺陷波函数与器件沟道自由载流子波函数及其相互作用产生能级跃迁、交换载流子的具体过程.建立了热载流子效应、材料缺陷与电参量、噪声之间的统一物理模型.还提出了用噪声参数Sfγ表征高、中、低三种栅应力下金属氧化物半导体场效应管抗热载流子损伤能力的方法.根据热载流子对噪声影响的物理机制设计了实验并验证这个模型.实验结果与模型符合良好.     

Banach空间上线性算子的伪条件数

设X和Y是两个Banach空间,用[X,Y]表示由X到Y上的所有有界线性算子全体之集,若算子A∈[X,Y]是可逆的,通常我们把A的条件K(A)定义为:若算子A∈[Y,X],存在广义逆,文献[1]中给出了A(关于A~ 的)伪条件数的概念。记A的伪条件数为,其定义为:显然,当A可逆时,1980年,匡蛟(员力灬)又对可逆算子引进了w—条件数的概念,对一     

Nanotubes Made from Deeply Undercooled Cryolite/Alumina Melts

The rapid‐solidification processing (by a cooling rate of 10⁵–10⁶ K/s) was used for the preparation of deeply undercooled cryolite/alumina (Na₃AlF₆/Al₂O₃) melts. We found a mass of nanotubes on the surface of these undercooled melts. The nanotubes were preferentially located on the defect places of the surface with the following approximate dimensions: base≈100×100 nm, length≈1000 nm. The solidified samples with the nanotubes on the surface were analyzed by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), and infrared spectroscopy (IR).     

A Glass/PDMS Hybrid Microfluidic Chip Embedded with Integrated Electrodes for Contactless Conductivity Detection

A new glass/PDMS hybrid chip for contactless conductivity detection is reported. This chip consists of a glass substrate with microchannels and a PDMS cover sheet embedded with a small integrated electrode plate. In the region of detection, electrodes are insulated from the microchannel by a formed PDMS membrane about 100 μm in thickness. Without any modification, this glass/PDMS chip is suitable for contactless conductivity detection with good properties, such as excellent heat-dissipation, stable electroosmotic flow, high separation efficiency, satisfactory sensitivity, simple construction and high degree of integration. Its feasibility and performance had been demonstrated by analyzing inorganic ions and amino acids in mixtures, and alkaloids in traditional Chinese medicine. The limits of detection reached micromole per liter (μmol L⁻¹) levels. This microchip could be promising for mass production due to its stability, reproducibility, ease of fabrication and low cost.

     

Ergodic dynamics of the coupled quasigeostrophic-flow-energy-balance system

The authors consider a mathematical model for the coupled atmosphere-ocean system, namely, the coupled quasigeostrophic-flow-energy-balance model. This model consists of the large-scale quasigeostrophic oceanic flow model and the transport equation for oceanic temperature, coupled with an atmospheric energy-balance model. After reformulating this coupled model as a random dynamical system (cocycle property), it is shown that the coupled quasigeostrophic-energy balance fluid system has a random attractor, and under further conditions on the physical data and the covariance of the noise, the system is ergodic, namely, for any observable of the coupled atmosphere-ocean flows, its time average approximates the statistical ensemble average, as long as the time interval is sufficiently long. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 12, No. 6, pp. 67–84, 2006.