基于W77E58的多路数据采集系统的设计与实现

为了对实际信号进行监测,设计了以W77E58微控制器为核心的多路数据采集系统,介绍了系统总体结构,阐明了模拟量采集的硬件和软件设计方法,给出了具体的电路图和软件程序,经实际测试表明,该系统具有采集精度高、功耗低、抗干扰能力强、通用性好的特点。     

Effect of ultraviolet‐B irradiation on antioxidative properties of aqueous extracts from shiitake (Lentinus edodes) mushrooms

Antioxidant properties of aqueous extracts from Lentinus edodes treated with UV‐B irradiation were examined in vitro systems including DPPH, ABTS and oxygen radical absorbance capacity (ORAC) assays and in riboflavin‐photosensitised oil‐in‐water (O/W) emulsions. Changes in total phenolics, total flavonoids and vitamin C were also analysed. Lentinus edodes receiving 25 kJ m^?2 UV‐B treatment showed high radical scavenging ability based on DPPH and ABTS assays compared with samples with 0, 50 and 75 kJ m^?2, while those with 50 kJ m^?2 had higher antioxidant capacities than other samples from ORAC assays. Samples with 25 kJ m^?2 UV treatment had significantly 7.1% higher total phenolic content, 12.0% higher total flavonoid content and 8.0% higher vitamin C content than UV‐B‐untreated sample (P < 0.05), respectively. In O/W emulsions under riboflavin photosensitisation, 25 and 50 kJ m^?2 UV treatment significantly increased the oxidative stability compared with other samples based on headspace oxygen content and lipid hydroperoxide analyses (P < 0.05). Aqueous extracts of UV‐B‐treated mushrooms possessed enhanced antioxidant properties compared with untreated mushrooms.     

Thermodynamic investigation of phase equilibria on the (W,Mo)C-(Co,Ni) cemented carbides

The C-Co-Mo-W and C-Mo-Ni-W quaternary systems have been critically evaluated by means of the CALPHAD approach, in which the Co-Mo-W system was readjusted to ensure the model consistency. The thermodynamic models of Gibbs energies for individual phases in the ternary and quaternary systems are described, including substitutional solution model, sublattice model and linear compound model. The modeling covers the whole temperature and composition ranges, and a set of self-consistent thermodynamic parameters for the C-Co-Mo-W and C-Mo-Ni-W quaternary systems is obtained. According to the comprehensive comparisons between the reported and calculated phase diagram data, the reliable equilibria information is satisfactorily accounted for by the modeling. Based on the present work together with the previously reported assessments of binary, ternary and quaternary sub-systems, a thermodynamic database for the C-Co-Mo-Ni-W quinary system is constructed and applied to calculate the sintering region phase equilibria of the (W,Mo)C-(Co,Ni) cemented carbides.     

A Method of Estimating Variance Components in Unbalanced Designs

Another method of estimating variance components in the unbalanced case is presented for a general model with unbalanced population structure and unequal variances over the population. The method utilizes unweighted means and can be shown to give unbiased estimates when the numbers of observations are sampled and certain to be > 1. When the design is balanced the estimators coincide with the usual anova-estimators. The construction of estimators is exemplified for four situations with factors crossed and nested in different ways.     

Design of a low-density wood-cement particleboard for interior wall finish

Gypsum boards form a very large part of the building walls and ceilings finishing market. However, they have poor screw-withdrawal resistance, low hardness and are highly sensitive to moisture. The objective of this study was to determine whether it is possible to make wood-cement particleboards of the same density as gypsum boards while avoiding these drawbacks.Wood-cement particleboards were made by pouring the wood-cement paste in a mould. This was made possible by adding a viscosity modifying mixture to the mixing water and a set accelerating mixture to improve wood/cement compatibility. The mechanical properties and surface quality of the wood-cement particleboards were improved by using, on the board surfaces, paper sheets that were the same as those used on gypsum boards.The average specific gravity of the wood-cement particleboards was the same as gypsum boards, at 0.7. The average bending modulus of rupture obtained for the wood-cement particleboards was 10 MPa in the finishing paper principal direction and 5 MPa in the other direction compared to 5.5 MPa and 1.6 MPa respectively for gypsum boards. The average screw-withdrawal resistance of wood-cement particleboards was 570 N, that is, 1.7 times higher than for gypsum boards.     

Formulation of Insulin-Loaded Polymeric Nanoparticles Using Response Surface Methodology

The objective of this work was to formulate new oral insulin-loaded nanoparticules using the response surface methodology. The insulin nanoparticles were prepared by a water-in-oil-in-water emulsification and evaporation method. The polymers used for the encapsulation were blends of biodegradable poly-epsilon-caprolactone (PCL) and of positively-charged, nonbiodegradable polymer (Eudragis RS®). A central composite design has been built to investigate the effects of three controlled variables: ratio of polymers (PCL/RS ratio), volume, and pH of the aqueous solution of polyvinyl alcohol. The nanoparticles were characterized by measuring the amount of entrapped insulin, the particle size, the polydispersity of the obtained particles, the zeta potential, and the amount of insulin released after 7 hours. A second-order model was evaluated by multiple regression and was statistically tested for each of the studied controlled variable. The obtained polynomials proved efficient to localize an optimal operating area highlighted by the use of three-dimensional response surfaces and their corresponding isoresponse curves. An interesting formulation given by the models was selected, prepared, and evaluated. The corresponding quantity of entrapped insulin was 25 IU per 100 mg of polymer, and the particle size was 350 nm with a polydispersity of 0.21. The quantity of released insulin was 4.8 IU per 100 mg of polymer after 7 hours and the zeta potential was + 44 mV. All these collected values were in perfect accordance with values estimated by the models. Finally, the results suggested that PCL/RS 50/50 nanoparticles might represent a promising formulation for oral delivery of insulin.     

‘s Gravesande's Appropriation of Newton's Natural Philosophy,Part II: Methodological Issues

It has been suggested in the literature that, although Willem Jacob ‘s Gravesande occasionally treated Newton's doctrines in a selective manner, he was nevertheless an unremitting follower of Newton's methodology. As part of a reassessment of ‘s Gravesande's Newtonianism, I argue that, although ‘s Gravesande took over key terms of Newton's methodological canon, his methodological ideas are upon close scrutiny quite different from and occasionally even incongruent with Newton's views on the matter.     

Room temperature tensile deformation behavior of a Ni-based superalloy with high W content

K416B Ni-based superalloy with high W content has good high temperature properties and low cost, which has a great development potential. To investigate the room temperature tensile property and the deformation feature of K416B superalloy, tensile testing at room temperature was carried out, and optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the deformation and damage mechanisms. Results show that the main room temperature tensile deformation features of the K416B nickel-based superalloy are dislocations slipping in the matrix and shearing into γ′ phase. The <110> super-dislocations shearing into γ′ phase can form the anti-phase boundary two coupled (a/2)<110> partial-dislocations or decompose into the configuration of two (a/3)<112> partial dislocations plus stacking fault. In the later stage of tensile testing, the slip-lines with different orientations are activated in the grain, causing the stress concentration in the regions of block carbide or the porosity, and cracks initiate and propagate along these regions.

     

金属W中辐照缺陷的产生、演化与热回复机制

金属W是核聚变反应堆中面向等离子体部件的主要候选材料。服役期间,钨部件需要承受高温、高通量聚变反应中子轰击带来的辐照级联损伤。这些损伤主要表现为高浓度的点缺陷及团簇。它们与氢氦等离子体、嬗变反应的多种产物相互作用,导致辐照硬化、韧脆转变温度升高、导热能力下降等问题。本文围绕金属W的辐照级联损伤,基于显微缺陷实验表征与材料多尺度模拟计算,系统总结了辐照缺陷的产生、演化与热回复行为及作用机制。这些信息反映了材料中辐照缺陷特征的统计规律,构成定量描述微观损伤组织随时间尺度与空间尺度变化的依据,有利于钨部件性能的预测、服役可靠性评价以及未来新型材料部件的研发。