Prediction of zonal and total discharges in smooth straight prismatic compound channels using regression modeling

Experimental results are presented concerning the zonal and total discharge distribution and characteristics in a compound channel cross-section comprising one rectangular main channel and two symmetrical floodplains. The discharges in the main channel, floodplains, and total compound channel are found to be highly correlated to several dimensionless parameters defined using the compound channel cross-section geometry. Multi-variable regression analysis was utilized for developing predictive models that can estimate the main channel, floodplains and total discharges as a function of four different dimensionless parameters. The developed models to predict the zonal and total discharges in compound channels are found to be highly significant according to several major statistics including the model standard error, coefficient of determination (R²), and F-statistic. The developed multi-variable regression-based models are also tested for validity using available experimental data. Several statistical tests applicable to the analysis of residuals have indicated the effectiveness of the developed predictive models.     

Stability of combustion waves in the Zeldovich–Liñán model

In this paper we investigate the stability of the premixed combustion waves in the Zeldovich–Liñán model in the adiabatic limit in two spatial dimensions. It is shown that either wave or cellular instabilities emerge for the Lewis number for fuel greater or smaller than one respectively. On the Lewis number for fuel vs activation energy parameter plane, the critical parameter curve for wave (cellular) instability is a monotonically decaying (increasing) function, which tends to one for large values of activation energies and grows infinitely (vanishes) as the activation energy is decreased to some critical value (zero). Decreasing the recombination parameter, which corresponds to the relation between the characteristic times of the branching and recombination reactions, makes the combustion waves more stable by increasing the region of parameter values for stable traveling wave solutions. Increasing the ambient temperature is demonstrated to have similar stabilizing effect on combustion waves. The effect of the varying the Lewis number for radicals is shown to be more complex and depends on the regime of recombination. It is demonstrated that as the critical parameter values for the onset of instability are crossed, either pulsating or cellular two-dimensional solutions emerge. The properties of these solutions are studied. A comparison of the results of this paper with known data from the literature for deflagration of hydrogen–oxygen mixtures is made.     

The effect of tape casting operational parameters on the quality of adjacently graded ceramic film

For small length tape casting of ceramic slurries varying green film thickness is often a problem. To optimise this, the following parameters were investigated: single blade, double blade, using a pump system and a modelled speed change mode have been analysed. Advantages and limitations of every method are described here. The tape casting experiments were built to be generic in order to allow the control of various processing conditions.From these results, the single-blade technique was chosen for a study of side-by-side tape casting. The influence of the geometric parameters of partitioning the casting tank into chambers, on the quality of graded tape was studied. Tape casting experiments at different speeds and partition tongue lengths in combination with rheological tests revealed that high casting speeds and absence of the partition under the blade are detrimental to the formation of the smooth well-controlled interface between the co-cast slurries, required for most of applications.     

Crystal growth of LiF/LiYF4 eutectic crystals and their luminescent properties

Undoped and 0.5 mol% Ce-doped LiF–LiYF₄ eutectic crystals were grown by the micro-pulling-down method at different growth rates. The SEM images of all the eutectic crystals showed LiF with rod-like structure in the LiYF₄ matrix. The diameter of the rod phase systematically decreased with the increase of the growth rate. The radioluminescence spectra of cerium doped crystal under alpha-ray excitation showed emission peak at 325 nm related to Ce³⁺ 5d-4f transition. The white part in the cathodoluminescence image is considered to be due to Ce³⁺ ion in LiYF₄ phase, according to the scanning electron microscopy (SEM) image in the same region.     

Syngas methanation for substitute natural gas over Ni–Mg/Al2O3 catalyst in fixed and fluidized bed reactors

A comparative study was conducted for laboratory syngas methanation over a self-made Ni–Mg/Al₂O₃ catalyst to demonstrate the technical advantages of fluidized bed over fixed bed reactor. At different reaction temperatures, gas velocities and pressures, the CO conversion and selectivity to CH₄ in fluidized bed were shown to be higher than in fixed bed, and much closer to the thermodynamic equilibriums. The spent catalysts from fluidized bed methanation had distinctively low and easy-oxidizing deposited carbon in comparison with that from fixed bed. The results were attributed to the bigger effective catalytic surface, better heat and mass transfer in fluidized bed reactor.     

Chinese yam polysaccharide enhances growth performance and cellular immune response in weanling rats

BACKGROUND: In order to develop a novel dietary additive for potential application in domestic animals and humans, a fraction of Chinese yam polysaccharide (CYP) was prepared and a study was conducted to determine the effects of dietary supplementation with CYP on the immune response and growth performance in weanling rats. RESULTS: Dietary supplementation with CYP increased the average daily feed intake and average daily gain but decreased the feed/gain ratio overall compared with the non‐supplemented group. CYP also significantly increased the serum contents of interleukin‐2 and tumour necrosis factor and the proliferation activity of peripheral lymphocytes but decreased the serum contents of low‐density lipoprotein, total cholesterol and triglyceride compared with the non‐supplemented group. CONCLUSION: The increase in cellular immunity in CYP‐supplemented weanling rats confers an important protective role in the non‐specific defence against infections. This herbal polysaccharide, as a natural green dietary additive for promoting the immune response and healthy growth, may offer an effective alternative to antibiotics for weanling animals. Copyright © 2009 Society of Chemical Industry     

Highly transparent AlON ceramics sintered from powder synthesized by carbothermal reduction nitridation

Aluminum oxynitride (AlON) powders were synthesized by the carbothermal reduction and nitridation process using commercial γ-Al₂O₃ and carbon black powders as starting materials. And AlON transparent ceramics were fabricated by pressureless sintering under nitrogen atmosphere. The effects of ball milling time on morphology and particle size distribution of the AlON powders, as well as the microstructure and optical property of AlON transparent ceramics were investigated. It is found that single-phase AlON powder was obtained by calcining the γ-Al₂O₃/C mixture at 1550 °C for 1 h and a following heat treatment at 1750 °C for 2 h. The AlON powder ball milled for 24 h showed smaller particles and narrower particle size distribution compared with the 12 h one, which was benefit for the improvement of optical property of AlON transparent ceramics. With the sintering aids of 0.25 wt% MgO and 0.04 wt% Y₂O₃, highly transparent AlON ceramics with in-line transmittance above 80% from visible to infrared range were obtained through pressureless sintering at 1850 °C for 6 h.     

金沙遗址出土铜片的加工工艺研究

采用X射线荧光仪、金相显微镜和扫描电镜等现代检测手段，分析金沙遗址出土铜片的元索成分和金相组织。探讨其加工工艺。结果表明，铜片为高温热锻成形。其热锻温度范围在500～700℃之间，符合现代金属学原理。铜片表面的树形纹饰是用预先制作的树模在铜片上压印而成。这一研究结果对进一步了解成都平原的青铜加工技术有重要意义。     

High-throughput optimization and fabrication of Bi2Te2.7Se0.3-based artificially tilted multilayer thermoelectric devices

Artificially tilted multilayer thermoelectric devices (ATMTDs) have attracted growing attention due to their ease in miniaturization and high flexibility in device design. However, most of these devices are inefficient due to the lack of effective strategy to optimize their material matching and geometrical configurations. Herein, a high-throughput optimization approach is employed to screen high-performance Bi₂Te_2.7Se_0.3-based ATMTDs from a material genome database covering 230 kinds of candidates. 14 kinds of ATMTDs are found to have ZT_zx,max values exceeding 0.3 and tilt angles greater than 15°. Bi_0.1Sb_1.9Te₃/Bi₂Te_2.7Se_0.3 ATMTD is screened out and fabricated because of its excellent transverse figure of merit, large tilt angle, and good interface compatibility. Consequently, transverse figure of merit over 0.3, thermal sensitivity greater than 0.11 mV·K^?1, and power density up to 1.1 kW·m^?2 are recorded in Bi_0.1Sb_1.9Te₃/Bi₂Te_2.7Se_0.3 ATMTD. This indicates that ATMTDs have great potential for application in the fields of temperature detection and power generation.     

Fabrication of Aluminum Oxynitride (γ‐AlON) Transparent Ceramics with Modified Gelcasting

Transparent aluminum oxynitride (AlON) ceramics have been prepared through aqueous gelcasting forming technique starting from the raw materials of single phase AlON powders. The powder was specially treated for anti‐hydrolysis in ethanol before the shaping technique. The surface‐treated AlON powders could then be dispersed in an aqueous‐organic solution to prepare stable slurries containing 35 vol% solids loading. The obtained stable slurries were subsequently casted, calcined, and pressureless sintered at 1950°C for 8 h in nitrogen atmosphere. High transparent AlON ceramics with an average grain size of 112 μm and the in‐line transmittance of 81% at wavelength 1100 nm have been obtained.