Angular measurement of acoustic reflection coefficient for substrate materials and layered structures by V(z) technique

An experimental method to evaluate the acoustic reflection coefficient as a function of the incident angle R(θ) for substrate materials or layered structures is presented. By measuring the acoustic material signature V(z) using a highly focused acoustic lens or transducer at normal incidence, the reflection coefficient R(θ) can be reconstructed from the FFT of the complex V(z) signal (amplitude and phase of the echo). This technique has a great simplicity for the experimental procedure of R(θ) measurement. It overcomes the disadvantages of the conventional method where the finite-aperture plane beam reduces the angular precision and causes the unexpected non-specular reflection at critical incident angles. Results are given for different substrate materials, single plates and a three-layered bonded joint, and are compared to theoretical predictions.     

多元有理函数域F（z）上的RLC网络的可约性`可断性及能控性

本文将ＲＬＣ电网络的第一支路上的物理参量都视为独立参量，于是网络成了这些参量的有理函数域Ｆ（ｚ）上的网络；介绍了网络的可约性和可断性的概念和结论：讨论了网络在域Ｆ（ｚ）上的能控性。     

Behavior of endothelial cells on micro-patterned titanium oxide fabricated by plasma immersion ion implantation and deposition and plasma etching

Titanium oxide films synthesized by plasma immersion ion implantation and deposition (PIII&D) were micro-patterned using argon plasma etching. Wells containing organized arrays of square holes of different depths separated by gaps of 25 μm were produced on the surface of the titanium oxide by etching for 30, 60, 90, and 120 min. The surface wettability and tension of the samples were evaluated. Human umbilical vein endothelial (HUVE) cells were cultured on both smooth and patterned surfaces. The effects of surface micro-patterning on the behavior of the HUVE cells were investigated. Our results show that the titanium oxide prepared by PIII&D has good cyto-compatibility and the micro-patterns influence both the surface energy and cell behavior. Our results demonstrate the feasibility of using micro-patterned surfaces to modulate HUVE cell behavior.     

Studying optical and nonlinear optical properties of synthesized azo dyes doped in polymer and liquid crystal using birefringence and Z‐ scan techniques

The authors report the effect of the structure of new synthesized photo‐responsive azo dyes, based on N‐benzyl‐N‐ethyl‐aniline on their optical and nonlinear optical properties, when doped in polymer and liquid crystal (LC) hosts. Anisotropic response of dyes doped with polymer polymethyl methacrylate is studied using photo‐induced birefringence experiment and the optical nonlinearity of dyes doped in LC 5CB is measured using z‐scan technique. A correlation is established between dipole moment and optical/nonlinear optical response, which makes it possible to develop molecular design strategies to create structures with suitable anisotropic response and nonlinearity in various host systems for different applications. It is also shown how very little change in the structure of the dye may cause severe changes in the dipole moment and its nonlinear response. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Vertically aligned Mn-doped zinc oxide nanorods by hybrid wet chemical route

Mn-doped zinc oxide (Mn:ZnO) nanorods were synthesized by incorporating manganese in aligned ZnO nanorods. For this, Mn was evaporated onto ZnO nanorods and the composite structure was subjected to rapid thermal annealing. The nanorods were preferentially oriented in (0 0 2) direction as indicated by the XRD measurement. Optical band gap was seen to decrease with increasing amount of Mn incorporation. XPS studies indicated that incorporated Mn was in Mn²⁺ and Mn⁴⁺ states. Mn²⁺ atomic concentration was found to be larger than Mn⁴⁺ concentration in all the samples. The Raman spectra of the Mn:ZnO nanorods indicated the presence of the characteristic peak at ∼438 cm⁻¹ for high frequency branch of E₂ mode of ZnO. The PL peak at ∼376 nm (∼3.29 eV) was ascribed to the band edge luminescence while the peak at ∼394 nm (∼3.15 eV) was assigned to the donor bound exciton (D^oX) and free exciton transition related to Mn²⁺ states.     

Phenolic profiles of andean mashua (Tropaeolum tuberosum Ruíz & Pavón) tubers: Identification by HPLC-DAD and evaluation of their antioxidant activity

Qualitative high performance liquid chromatography with diode array detection (HPLC-DAD) was performed to characterize non-anthocyanin phenolic compounds in three different coloured mashua genotypes. The ORAC antioxidant activity contribution in the tubers related to the type of phenolic compounds present was also evaluated. Phenolic compounds were analysed by separating them into four main fractions: fraction I obtained by means of a liquid–liquid partition with ethyl acetate and fractions II, III and IV obtained by elution on a Sephadex LH-20 column. Fraction I revealed the presence of gallic acid, gallocatechin, procyanidin B₂ and epigallocatechin. Other phenolic compounds such as hydroxycinnamic and hydroxybenzoic acid derivatives, rutin and/or myricetin derivatives were also present in fraction I. Fraction II was mainly composed of epicatechin, hydroxycinnamic and hydroxybenzoic acid derivatives. Fraction III presented mainly anthocyanins for the purple coloured mashua tubers and rutin, hydroxycinnamic acid and hydroxybenzoic acid derivatives for the yellow coloured genotype. Fraction IV was composed of proanthocyanidins. Alkaline and acid hydrolysis of the different fractions revealed the presence of gallocatechin, epicatechin, p-coumaric acid, o-coumaric acid, cinnamic acid, protocatechuic acid, rutin and quercetin as the main phenolic moieties present. The proanthocyanidin fractions were the major contributors to the ORAC antioxidant activity of the mashua tubers for two of the three genotypes (34.7–39.2%). The results obtained in the present study confirm that mashua tubers constitute a promising source of antioxidant phenolics and could potentially be considered as a functional food with beneficial health effects.     

一种基于时间域的实用单侧电量故障测距方法

【摘要】 分析了现时广泛应用的基于频域的正弦稳态故障测距方法的不足，指出其对网 络运行参数过分依赖，介绍了一种不需知道网络运行参数的时域法，同时，利 用频域法的优点对其假设条件进行修正，将时域与频域两种方法的优越性有机 地结合起来。该方法最少只需四个采样点就可构造出一个简单的关于故障距离 的非线性方程组，易于在微机自动化装置上实现。该方法被成功地应用于一种 故障录波分析装置。     

蓄电池电量监测新技术

为了准确了解以蓄电池为动力的电动汽车所用电池的剩余电量,在分析目前一些电池剩余电量计算方法的基础上,提出了一种利用阻抗跟踪技术的单芯片监测电池剩余电量方案。在实际设计中采用了TI公司的bq20280芯片,它能够在电池整个寿命周期内以高达99%的精确度计算电池组的剩余电量。在电池组处于静止状态时,通过在相应的温度下关联电池组的空载电压和充电状态可以分析出准确的电荷状态。     

Antiferromagnetic manganite La1/3Ca2/3MnO3 as barrier material in superconductor/insulator/ferromagnet tunnel junctions

Current transport through thin antiferromagnetic (AF) barriers of the perovskita manganite La_1/3Ca_2/3MnO₃ (LCMO) was studied with respect to its dependence on temperature and voltage. Planar-type La_2/3Ca_1/3MnO₃(~ 80 nm)/La_1/3Ca_2/3MnO₃(~ 7 nm)/YBa₂Cu₃O_7 − δ(~ 100 nm) heterojunctions were used as basic structures. The current-voltage (I-V) measurements were carried out on test junctions with a standard area of 20 × 40 µm² in a four-terminal configuration. In spite of the carefully controlled growth conditions, barriers with the same nominal thickness showed different electrical behavior varying from elastic tunneling to Mott variable range hopping (VRH) via localized states. The different transport characteristics seem to be related to intrinsic difference in microstructure as the average surface roughness of the constituent layers may already be larger than the thickness of the barrier itself.     

Electrochemical deposition of octacalcium phosphate micro-fiber/chitosan composite coatings on titanium substrates

Calcium phosphate/chitosan composites have been extensively studied as bone substitutes, tissue engineering scaffolds, or bone cements. In the present study, we have prepared octacalcium phosphate (OCP) micro-fiber/chitosan composite coatings through an electrochemical deposition method. OCP coatings with microporous structure, which are woven by micro-fibers with 20-30 μm in length and 0.1-1 μm in width, have a good ability to incorporate chitosan. This novel OCP micro-fiber/chitosan composite coating could have broad applications in the biomedical engineering.