Predictive formulas for different measures of cheese yield using milk composition from individual goat samples

The objective of this study was to develop formulas based on milk composition of individual goat samples for predicting cheese yield (%CY) traits (fresh curd, milk solids, and water retained in the curd). The specific aims were to assess and quantify (1) the contribution of major milk components (fat, protein, and casein) and udder health indicators (lactose, somatic cell count, pH, and bacterial count) on %CY traits (fresh curd, milk solids, and water retained in the curd); (2) the cheese-making method; and (3) goat breed effects on prediction accuracy of the %CY formulas. The %CY traits were analyzed in duplicate from 600 goats, using an individual laboratory cheese-making procedure (9-MilCA method; 9 mL of milk per observation) for a total of 1,200 observations. Goats were reared in 36 herds and belonged to 6 breeds (Saanen, Murciano-Granadina, Camosciata delle Alpi, Maltese, Sarda, and Sarda Primitiva). Fresh %CY (%CY_CURD), total solids (%CY_SOLIDS), and water retained (%CY_WATER) in the curd were used as response variables. Single and multiple linear regression models were tested via different combinations of standard milk components (fat, protein, casein) and indirect udder health indicators (UHI; lactose, somatic cell count, pH, and bacterial count). The 2 %CY observations within animal were averaged, and a cross-validation (CrV) scheme was adopted, in which 80% of observations were randomly assigned to the calibration (CAL) set and 20% to the validation (VAL) set. The procedure was repeated 10 times to account for sampling variability. Further, the model presenting the best prediction accuracy in CrV (i.e., comprehensive formula) was used in a secondary analysis to assess the accuracy of the %CY predictive formulas as part of the laboratory cheese-making procedure (within-animal validation, WAV), in which the first %CY observation within animal was assigned to CAL, and the second to the VAL set. Finally, a stratified CrV (SCrV) was adopted to assess the %CY traits prediction accuracy across goat breeds, again using the best model, in which 5 breeds were included in CAL and the remaining one in the VAL set. Fitting statistics of the formulas were assessed by coefficient of determination of validation (R²_VAL) and the root mean square error of validation (RMSE_VAL). In CrV, the formula with the best prediction accuracy for all %CY traits included fat, casein, and UHI (R²_VAL = 0.65, 0.96, and 0.23 for %CY_CURD, %CY_SOLIDS, and %CY_WATER, respectively). The WAV procedure showed R²_VAL higher than those obtained in CrV, evidencing a low effect of the 9-MilCA method and, indirectly, its high repeatability. In the SCrV, large differences for %CY_CURD and %CY_WATER among breeds evidenced that the breed is a fundamental factor to consider in %CY predictive formulas. These results may be useful to monitor milk composition and quantify the influence of milk traits in the composite selection indices of specific breeds, and for the direct genetic improvement of cheese production.     

箱形横梁的水压爆破拆除

某电影院大厅内钢筋混凝土箱形横梁长25m,断面尺寸1 6m×2 4m,用水压爆破拆除。通过梁的受力分析得知,为避免横梁的挠度过大,在吊梁拆除后必须另补支撑,以确保水压爆破正常进行。文中对水压爆破炸药用量的计算公式进行了比较和简评。在参考计算结果和考虑厅内环境的基础上,并结合以往水压爆破工程的经验,确定了合理、有效的药量,保证了主体结构的绝对安全。     

Comparison of approaches to the numerical modelling of pure metals solidification using the control volume method

The thermal processes proceeding in the casting-mould system are analysed. Solidification process can be described in the different ways. One of them consists in the application of the Fourier–Kirchhoff equation in which the source function controlling the phase change is introduced. In this paper, two approaches to the modelling of pure metals solidification, i.e. the solidification proceeding at the constant temperature and in the artificially introduced interval of temperature are considered. Numerical model used at the stage of computations is constructed using the Control Volume Method in which the principle of conservation of energy (taking also into account the release of latent heat of solidification) is applied to each control volume ensuring the correctness of the model. The use of Voronoi/Thiessen tessellation to the discretization of the casting-mould system can accurately reproduce the shape of each sub-domain. In the final part of the paper, the examples of computations are shown.     

Minimization of the Theoretical Error of Input Parameters for a Vapor Permeation Apparatus

All input experimental errors for membrane flux determination were analyzed. The overall error in pressure did not largely influence the determination of membrane flux. The main contribution to errors was ascribed to flow meters and membrane thickness. The choice of an optimal operational range for input parameters led to elimination of at least 2/3 of the theoretical relative error for subsequent evaluation of the permeability of individual species. This is especially valuable for low‐permeable membranes, whereas a very low relative theoretical error can be obtained in the case of highly permeable materials.     

Experimental and theoretical approaches for electrical,magnetic, micromechanical,and structural characterization of BSCCO ceramic superconductors

This study investigates how the preparation and re-pelletization of BSCCO ceramic superconductors affects their structural, magnetic, electrical, and mechanical properties. Samples were prepared using conventional methods including the dry solid state (SS) reaction and wet ammonium nitrate (AN) precipitation, with three variations prepared for each technique. The fabricated samples were then characterized with X-ray powder diffraction (XRD) and scanning electron microscopy. The density, resistance vs. temperature characteristics, AC susceptibility vs. temperature characteristics, and magnetic hysteresis properties were measured. In addition, Vicker's microhardness was measured and revealed that all six samples exhibit the reverse indentation size effect (RISE). Microhardness modeling was also conducted. Calculations with Meyer's law, the Hays and Kendall model, and the proportional sample resistance model indicate that the samples are far from the plateau region, whereas the indentation-induced cracking model was consistent with the experimental results. The elastic modulus, Young's modulus, yield strength, and brittleness index were also calculated for each sample.     

Zinc doped Fe2O3 for boosting Electrocatalytic Nitrogen Fixation to ammonia under mild conditions

Artificial nitrogen fixation is emerging as a promising approach for synthesis of ammonia at mild conditions. Inspired by biological nitrogen fixation based on bacteria containing iron, zinc doped Fe₂O₃ nanoparticles are proposed as an efficient and earth abundant electrocatalyst for converting N₂ to NH₃. In neutral media, it achieves a maximum Faradaic efficiency (FE) of 10.4% and a large NH₃ yield rate of 15.1 μg h^?1 mg^?1_cat. at ?0.5 V vs. reversible hydrogen electrode. This catalyst also exhibits excellent selectivity and stability. Theoretical calculations suggest the reaction follows the associative enzymatic mechanism and it has a barrier of as low as 0.68 eV.     

深海采矿扬矿硬管纵向振动的解析分析

深海采矿系统中，扬矿管纵向振动是影响扬矿管寿命的主要因素。本文对带有泵组及中间仓的阶梯式扬矿管的纵向振动进行了建模，并用解析方法对方程进行求解，通过计算机的模拟计算，分析了扬矿管纵向振动稳态响应的特性。     

我国上游法尾矿坝理论研究及工程实践综述

上游法尾矿坝是我国尾矿坝的主要坝型,其安全问题非常重要．本文综述了我国上游法尾矿坝在筑坝、渗流、排渗、地震反应、管理、监测以及环境影响方面的理论研究及工程实践,并着重介绍了大石河尾矿坝的研究成果,给出了基于渗流的上游法尾矿坝研究的几个建议。这些内容对指导上游法尾矿坝设计以及中后期管理,有较大的参考价值。     

GPS用于单航线航空摄影测量加密的可行性研究

精度是表征平差系统各未知数求解质量的绝对数字指标之一，本文采用一组带ＧＰＳ导航数据的实际航摄资料，通过平差计算出精度矩阵Ｑｘｘ的数值，然后分析了单航线ＧＰＳ辅助光束法平差的质量。在此基础上，经与区域网ＧＰＳ辅助光束法平差的精度相比较，对ＧＰＳ用于单航线航空摄影测量加密的可行性进行了探讨并提出了相应的作业方法。