一类非线性广义强阻尼时滞扰动Sine-Gordon方程初值问题

本文讨论了一类非线性广义Sine-Gordon扰动方程,基于渐近理论得到对应方程的时滞初值问题并求出渐近解析解．首先,利用Fourier变换方法得出外部解．其次,按时滞变量展开扰动函数,再根据摄动方法和理论求出强阻尼时滞扰动广义Sine-Gordon方程初值问题的的渐近解．根据本文的理论和方法得到的渐近解是解析的表示式,能够进行解析运算,从而可得到相关的物理量的性状,扩大了问题的讨论范围．     

Inducing synthesis of CdS nanotubes by PTFE template

Using PTFE membrane as structure-directing template, the CdS nanotubes with the internal diameter of 100–130 nm, the wall thickness of 15–18 nm, and the length of about 1.4 μm were inductively synthesized.     

高蛋白饮用型纯益生菌发酵乳的研制

以鲜牛乳和浓缩牛奶蛋白为主要原料,以酸度和感官评价为评价指标,通过单因素试验和正交试验确定高蛋白饮用型纯益生菌发酵乳的最佳发酵工艺条件。结果表明,高蛋白饮用型纯益生菌发酵乳的最佳发酵工艺条件为浓缩牛奶蛋白添加量6.0%,发酵剂接种量2.0%、发酵温度43 ℃、二次无菌均质压力4 MPa。在此优化条件下,制得的高蛋白饮用型纯益生菌发酵乳感官评分达到89分,酸度129.1 °T,口感清爽顺滑,组织状态良好,理化及微生物指标均符合国家相关标准。     

UPLC-MS/MS法测定乳制品中的氯霉素类药物

建立超高效液相色谱-串联质谱(UPLC-MS/MS)法测定乳与乳制品中氯霉素、甲砜霉素和氟苯尼考的检测方法。样品经乙腈及乙酸乙酯提取、正己烷脱脂、C18柱净化后,通过超高效液相色谱-质谱联用仪进行检测,内标法定量。各标准溶液在0.1～10μg/L范围内呈线性相关(r=0.999),不同基质样品中添加回收率为75%～114%,检出限为0.1μg/kg。结果表明,该方法是一种准确测定乳与乳制品中氯霉素、甲砜霉素和氟苯尼考的检测方法。     

酪蛋白水解方法及水解产物功能性的研究进展

牛奶是婴幼儿喂养时母乳的主要替代品,酪蛋白是牛奶中的主要蛋白质。由于母乳和牛奶中酪蛋白成分存在差异,使得婴幼儿在使用牛奶时出现病症。本文从酪蛋白水解方法和水解产物的功能性等角度,针对其相关的国内外研究进展进行了综述。     

酸奶保存期内风味物质与风味变化研究

研究成品酸奶在4℃冷藏条件下主要风味物质的变化,包括羰基化合物乙醛、双乙酰以及挥发酸和酸性物质,同时考察酸奶的感官品评分数。结果显示,酸奶的主要风味化合物含量均呈增加趋势,且增长速度先快后慢。当乙醛与双乙酰含量的比例在0.56～0.80之间时,酸奶的风味比较协调。风味物质和风味评分分数的相关分析证明,酸奶中的各风味化合物相关性显著,且对酸奶的风味强度和风味协调性均有不同程度的影响。     

An assembly precision analysis method based on a general part digital twin model

Assembly precision analysis is one of the fundamental technologies used for controlling the assembly quality of products. Existing assembly precision analysis methods focus on identifying the assembly deviation caused by manufacturing errors of parts. They place less emphasis on the influencing factors in the assembly process, which significantly affect the reliability of the analytical results. Additionally, the lack of assembly knowledge for part models leads to a low efficiency of the assembly simulation. To address these problems, this paper presents an assembly precision analysis method based on a general part digital twin model (PDTM). The proposed PDTM integrates multi-source heterogeneous geometric models and maps assembly information from assembly semantics to geometry elements, allowing automatic assembly positioning of parts and improving the efficiency of assembly simulation. In addition to the manufacturing errors, the assembly-positioning error and mating-surface deformation are considered to quantify the impact on the key characteristics of the assembled product. Based on the real mating status simulation for the mating surfaces, the uncertainty of assembly positioning in an actual assembly is simulated by combining the small displacement torsor (SDT) theory and the Monte Carlo method. Furthermore, the mating-surface deformation can be superposed to the result of the assembly-gap calculation, improving the reliability of the analytical results. Finally, a prototype system and a case study involving a load-sensitive multi-way valve assembly process are introduced to demonstrate the applicability of the proposed method.     

Calibration of laser beam direction for optical coordinate measuring system

For the purpose of measuring free form surfaces of some key parts in the aviation field accurately and effectively, such as blades, a non-contact optical coordinate measuring system is set up in the paper. A laser displacement sensor is mounted on the Z axis of a CMM via a turntable and adjusted to the suitable orientation according to the shape of the target surface. The combination of optical sensor and CMM can reach the full potential of them both. To enable the laser sensor to perform measurement in every direction, a calibration method used to determine the laser beam direction based on a standard sphere is proposed, the principle of which is analyzed in detail in the paper. In the calibration procedure, the sensor moves at an equal step along X, Y and Z axes respectively and then equation sets are established to calculate the unit direction vector of the line which the laser beam is on. In the process of solving the unknown quantities, a new parameter substitution method is applied. Finally, a gauging block and a sphere with known size are used to verify the method. As the experimental results show, the measuring errors in several directions are all smaller than 0.05 mm, which manifests that the calibration method proposed can meet the requirements of reverse engineering.     

基于快速成形的仿生骨建模技术

通过案例介绍了一种仿生骨模型重建方法。首先在CAD软件中读取DICOM格式的医学断层数据．通过调整阈值提取需要重建的骨骼．在PC机上重建出仿生骨的三维模型，转化成快速成形需要的文件格式，最后利用快速成形技术获取实物模型。