DETERIORATIVE KINETICS OF BAKER'S YEAST DURING THERMAL DRYING

An attempt was made to determine the kinetic model, which describes the degradation of activity and viability during thermal drying of baker's yeast. The pellels of baker's yeast were dried under a variety of conditions using a laboratory scale VFB dryer to generate a broad database. The data used in determining the parameters for the kinetic model, such as the average moisture content, temperature as well as the relative activity and viability of baker's yeast were measured under dynamic procedure. The extensive data from the experiments under variety conditions enable the model to predict the quality retention of baker's yeast in a rather wide range during thermal drying, The interpretation procedure of raw data was described in detail.     

Enhanced visible light photocatalytic activity of QDS modified Bi2WO6 nanostructures

Bi₂WO₆ (BWO) nanostructures with QDS dispersed on single crystalline nanosheets were successfully prepared by a facile solvothermal method. The product possessed large surface area of 60 m²/g and exhibited excellent visible light absorption with a blue shift from 2.54 eV to 2.75 eV. The photocatalytic efficiency of the sample was six times that of nanoparticles assembled BWO nanostructures and three times that of nanoplates assembled BWO nanostructures. The photocatalytic mechanism for degradation of dyes over QDS modified BWO nanostructures was discussed, which revealed the important role of QDS in the generation, migration and consumption of the photogenerated electrons and holes.     

Investigation of solid particle number measurement: Existence and nature of sub-23 nm particles under PMP methodology

A Particle Measurement Program (PMP) compliant system, an AVL advanced particle counter (APC) and an alternative volatile particle removal system, a catalytic stripper (CS) were evaluated and compared for measuring solid particle number (PN) emissions. The evaluations and comparisons were conducted using sulfuric acid and hydrocarbon particles as model volatile particles in laboratory tests, and diluted exhaust from a diesel particle filter (DPF)-equipped heavy-duty diesel vehicle operated on a heavy-duty chassis dynamometer under steady speed conditions at two different engine loads. For the laboratory test, both the APC and CS removed more than 99% of the volatile particles in terms of PN when using aerosols composed of pure sulfuric acid or hydrocarbons. When using laboratory test aerosols consisting of mixtures of sulfuric acid and hydrocarbons more than 99% of the particles were removed by the APC but the surviving particles were no longer entirely volatile, 12–14% were solid. For the chassis dynamometer test, PN emissions between 3 and 10 nm downstream the APC were ∼2 and 7 times higher than the PN emissions of particles above 10 nm at the 74% and 26% engine load, respectively. At the 26% engine load, PN level of the 3–10 nm particles downstream the APC were significantly higher than that in the dilution tunnel, demonstrating that the APC was making 3–10 nm particles. The PN emission of 3–10 nm particles downstream the APC was related to the heating temperature of the APC evaporation tube, suggesting these particles are artifacts formed by renucleation of semivolatiles. Considerably fewer particles between 3 to 10 nm were seen downstream of the CS for both engine loads due mainly to removal of semivolatile material by the catalytic substrates, although some of this difference could be attributed to diffusion and thermophoretic losses. The findings of this study imply that improvement of the current PMP protocol would be necessary if the PMP were to be used in other applications where the PN emissions of particles below 23 nm are important.     

Effect of the deposition parameters on the voiding propensity of solder joints with Cu electroplated in a Hull cell

A quantitative study of the impact of key Cu plating parameters on the voiding propensity of solder joints with Cu electroplated in a commercially available plating solution (CAPS) is performed first on 0.3 cm² Cu rotating disk electrode. It is shown that similar to samples plated in a generic plating solution (GPS) containing bis(3-sulfopropyl) disulfide, polyethylene glycol, and Cl⁻ ions, void-prone samples are deposited predominantly at higher overpotentials, in the range from positive to −0.20 V. In the second part, a Hull cell with 46 cm² cathode is used to scale up the voiding study in both, GPS and CAPS. It is demonstrated that plating conditions could be chosen in a way to generate both, void-prone and void-proof Cu on the same cathode panel. Thus, the controlled voiding propensity illustrated for the first time in a prototype of industrial Cu plating helps in realizing the sporadic nature of the voiding phenomenon.     

Counterion Interaction and Association in Metal-Oxide Cluster Macroanionic Solutions and the Consequent Self-Assembly

The interaction between large metal-oxide polyanions and their counterions is unique. Owing to their size disparity, there is a moderate ion-pairing effect and loose distribution of counterions around macroions, which leads to the unique solution behavior and the self-assembly of the macroions in polar solvents, and the counterion exchange capability around macroions. Furthermore, the macroion–counterion interaction also affects the catalytic behavior of the polyoxometalate (POM) clusters. Replacement of functionalized cations helps to modify the POM anions through static charge attraction. At the same time, the strong POM–counterion interaction can also lead to counterion-dependent synthesis. Recent developments on theoretical simulations help to understand this interaction at the molecular scale. This review summarizes the chronological progress of the exploration of macroion–counterion interaction (both theoretically and experimentally) and its impact on related research fields.     

用激光扫描法自动测量齿轮接触斑点

齿轮接触斑点可以作为评价齿轮承载能力的一项重要指标．迄今为上，接触斑点的测量仅限于目视观察，所以精度很低．本文介绍一种全新的、基于激光扫描的接触斑点自动测量装置。并对该装置的测量原理作了简要讨论。     

不锈钢散热器芯体真空钎焊工艺研究

针对散热器芯体产品进行了钎料选择和真空钎焊工艺研究，提出采用粘带钎料的生产方案和真空钎焊工艺参数，经小批量生产，各种试验，试车，证明本项目研究的钎焊工艺是成功的。     

Cathodoluminescence study of crystalline quality of (Al, In, Ga)N heterostructures

Wurtzite InGaN/GaN and AlGaN/GaN heterostructures grown by metal organic vapor phase epitaxy were studied using cathodoluminescence (CL) combined with secondary electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The surface morphology of samples containing InGaN layers is dominated by three types of defects: mesa-like hexagonal structures, hexagonal pyramids and micropipes. At the positions of pyramids the whole epilayer is thicker than at defect free positions, while at the positions of micropipes the whole epilayer is much thinner. The luminescence efficiency as well as the emission wavelength are influenced by these defects. In SL structures an increasing SL period thickness in the growth direction was observed. Panchromatic CL images show intensity inhomogeneity in both InGaN/GaN and AlGaN/GaN heterostructure, which are related to local variations of the interface quality. In AlGaN/GaN SQW structures a broad deep-level luminescence band at around 543 nm was observed, which is generally absent in InGaN/GaN heterostructures. This deep-level emission is strongly enhanced in defect positions.