Effects of circumferential pick spacing on boom type roadheader cutting head performance

Effects of equal and unequal circumferential pick spacing on the performance of boom type roadheaders having cylindrical cutting heads are investigated. For this purpose, two experimental cutting heads with equal and unequal circumferential spacing are designed and manufactured. The cutting head with unequal circumferential spacing is specifically designed to prevent tool-holder overlap at the nose section. Manufacturing difficulties associated with equal circumferential pick spacing due to tool-holder overlap are discussed with solid modeling and practical applications. The heads are tested at Park Cayirhan Coal Mine in Turkey and their cutting performances are analysed. Although better cutting performance for equal circumferential spacing are predicted by force–balance analysis, in situ measurements of instantaneous (net) traversing speed and cutting rate, pick consumption rate and machine vibration show that no significant difference exists between the performances of the two cutting heads.     

Thermal Radiative Properties of Xonotlite Insulation Material

Introduction Xonotlite-type calcium silicate (6CaO?6SiO2?H2O) is synthesized porous insulation material by hydrothermal processing with quartz powder and limestone as the raw material (with CaO/ SiO2≈1:1). Compared with fire- retardant fibre, xonotlite has more excellent insulating performance, such as low thermal conductivity, environment friendly, high intension, and wide applying temperature range, which has been emphasized in recent years by many scholars and widely used in many indu…     

Inference for pth‐order random coefficient integer‐valued autoregressive processes

Abstract. A pth‐order random coefficient integer‐valued autoregressive [RCINAR(p)] model is proposed for count data. Stationarity and ergodicity properties are established. Maximum likelihood, conditional least squares, modified quasi‐likelihood and generalized method of moments are used to estimate the model parameters. Asymptotic properties of the estimators are derived. Simulation results on the comparison of the estimators are reported. The models are applied to two real data sets.     

2，6-萘二甲酸二甲酯在有机溶剂中溶解度的测定与关联

Solubility of dimethyl-2,6-naphthalene dicarboxylate in acetic acid, N,N-dimethylfonnamide, N,N-dimethyl acetamide, dimethyl sulphoxide, and N-methyl-2-ketopyrrolidine were determined using a dynamic method. The measured systems were correlated by UNIFAC group contribution method. A new main group （aromatic ester, ACCOO） was defined to express the activity coefficients of the aromatic ester. New interaction parameters of the ACCOO group were expressed as the first-order function of temperature and were determined from the experimental data. The calculated results for the new interaction parameters were satisfactory. The measured systems were also correlated with the Wilson and 2-h models, and the results were compared with those of the UNIFAC model.     

Temperature dependence of kinetics and diffusion coefficients for ferrocene/ferricenium in ammonium-imide ionic liquids

The electrochemical behavior of ferrocene (Fc) and ferricenium (Fc⁺) was investigated by cyclic voltammetry with convolutional and semi-differential electroanalyses in the temperature range 298-373 K in the hydrophobic room temperature ionic liquid systems consisting of bis(trifluoromethanesulfone)imide anion with quaternary ammonium cation. The experimental results indicated that the redox reaction of Fc/Fc⁺ was reversible in this ionic liquid and the charge-transfer rate constant (k⁰) has been obtained. Mass transport towards the electrode is a simple diffusion process and the diffusion coefficient (D) for Fc/Fc⁺ has been also calculated. These results indicated that the k⁰ and D increased with increasing temperature in ionic liquids. The validity of the Arrhenius law was verified by investigating the temperature dependences of k⁰ and D.     

Simultaneous HPLC quantification of total cholesterol,tocopherols and β-carotene in Barrosã-PDO veal

A simple, rapid and sensitive procedure for the simultaneous determination of total cholesterol, tocopherols and β-carotene in meat is described. The method involves a direct saponification of the meat, a single n-hexane extraction and the analysis of the extracted compounds by normal-phase HPLC, using fluorescence (tocopherols) and UV–Vis photodiode array (cholesterol and β-carotene) detections in tandem. Rates of recovery of spiked meat samples were 93% for cholesterol, 83–86% for (α-, β- and -γ) tocopherols and 89% for β-carotene. Repeatabilities were high (CV < 6%) for all determined compounds, except for δ-tocopherol. This tocopherol, which is not usually present in meat, showed a much lower recovery percentage (73%) and repeatability (12.8%). This methodology was applied for the quantification of total cholesterol, tocopherols and β-carotene in three muscles (longissimus thoracis, longissimus lumborum and semitendinosus) of the Portuguese traditional Barrosã-PDO veal, obtained from autochthonous calves fed extensively during summer (with the least abundant green pastures) and slaughtered in early autumn (October). Barrosã-PDO veal showed median contents of total cholesterol (0.50–0.56 mg/g) and, depending on the analysed muscle, moderate to high contents of α-tocopherol (3.3–3.9 μg/g) and β-carotene (0.07–0.09 μg/g), suggesting an high sensorial and hygienic quality.     

Q195冷轧板材轧制困难原因分析

针对部分Q195冷轧板材存在轧制困难的现象，进行了现场检验与分析。带状组织、混晶现象严重导致变形强化系数偏高是造成轧制困难的主要原因。     

Water and salt permeability of reinforcement polymer‐gel composite membrane

The charged mosaic polymer membrane (CMM) without reinforcement and the composite charged mosaic polymer membrane (CCMM) with reinforcement were investigated in terms of salt and water transport (permeability). The composite charged mosaic polymer membrane (CCMM) with reinforcement showed a unique transport behavior such as preferential material transport L_p and ω. Water permeability coefficient, L_p and salt permeability coefficient, ω were estimated by taking account of active layer thickness of composite polymer gel. The L_p and ω values of CCMM with reinforcement were larger than those of CMM without reinforcement. On the other hand, the reflection coefficient of CCMM, σ, showed negative value, which suggested preferential material transport to solvent transport. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Water absorption properties of phosphate glass fiber‐reinforced poly‐ϵ‐caprolactone composites for craniofacial bone repair

The moisture uptake of polymers and composites has increasing significance where these materials are specified for invasive, long‐term medical applications. Here we analyze mass gain and the ensuing degradation mechanisms in phosphate glass fiber reinforced poly‐?‐caprolactone laminates. Specimens were manufactured using in situ polymerization of ?‐caprolactone around a bed of phosphate glass fibers. The latter were sized with 3‐aminopropyltriethoxysilane to control the rate of modulus degradation. Fiber content was the main variable in the study, and it was found that the moisture diffusion coefficient increased significantly with increasing fiber volume fraction. Diffusion, plasticization, and leaching of constituents appear to be the dominant aspects of the process over these short‐term tests. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

基于基尼系数的Web社区稳定性度量

Web社区是互联网中自组织程度较高的部分,它不是一个孤立系统,而是一个耗散系统,很多时候涨落无法耗散摔,导致社区运行不稳定.基尼系数可以用来衡量Web社区稳定性,通过基尼系数的简易计算公式计算社区内部成员积分或者其它参数,可以得出Web社区稳定性的度量.该度量对于研究和利用Web社区具有重要参考意义.