对数平均值的极小积问题

考虑一类含参数对数平均值的极小积问题。利用对数平均值不等式，问题转述为不含对数的参数规划问题。作为它们的应用，如果涉及的函数均为线性齐次、约束集为凸多面体（无论有界或无界），则必存在最优解并且可以在其极点处实现。     

ICU病人褥疮的预防和护理

褥疮是临床常见的并发症之一,因ICU病人大多为长期卧床病人,患病率更高。文章通过对文献资料和临床实践的分析,对褥疮的预防与护理进行综述,并提出提高ICU病人褥疮的预防与护理水平的方法。     

Is the polydispersity exponent of the hyperbranched polymers the 3/2 or 5/2？

Dendrimers and hyperbranched polymers have re- ceived much attention in recent decade due to their novel physical and chemical properties, such as multi- ple end groups, high solubility, and reduced viscosities relative to their linear counterparts, and h…     

一类复合系统稳定性分析

考虑一类复合系统的稳定性问题，得到类似于线性规划的结果。     

氨活塞式双级制冷压缩机轴功率和单位轴功率制冷量的计算

根据生产厂家[2]提供的产品样本和A．C．Cleland[3]提出的制冷剂热力学参数快速求值的方法，采用计算机绘制活塞式双级制冷压缩机在实际工况下的轴功率和单位轴功率制冷量变化曲线，计算和拟合出双级制冷压缩机轴功率数学模型，为实现制冷系统节能提供理论依据。     

K系数—双波长标准加入法测定镀镍溶液中的钴含量

提出了一种Ｋ系数－双波长标准加入法，应用于镀镍溶液中钴的测定。通过加入掩蔽剂氨三乙酸（ＮＴＡ），使得Ｎｉ（Ⅱ）与５－Ｂｒ－ＰＡＤＡＰ形成的配合物的吸光度显著降低，而相对应的Ｃｏ（Ⅱ）配合物的吸光度基本不变，提高了在大量Ｎｉ（Ⅱ）存在下测定Ｃｏ（Ⅱ）的准确度。     

Low-cost solid FeS lubricant as a possible alternative to MoS<Subscript>2</Subscript> for producing Fe-based friction materials

Three reaction systems of MoS₂-Fe, FeS-Fe, and FeS-Fe-Mo were designed to investigate the use of FeS as an alternative to MoS₂ for producing Fe-based friction materials. Samples were prepared by powder metallurgy, and their phase compositions, microstructures, mechanical properties, and friction performance were characterized. The results showed that MoS₂ reacts with the matrix to produce iron-sulfides and Mo when sintered at 1050℃. Iron-sulfides produced in the MoS₂-Fe system were distributed uniformly and continuously in the matrix, leading to optimal mechanical properties and the lowest coefficient of friction among the systems studied. The lubricity observed was hypothesized to originate from the iron-sulfides produced. The FeS-Fe-Mo system showed a phase composition, porosity, and density similar to those of the MoS₂-Fe system, but an uneven distribution of iron-sulfides and Mo in this system resulted in less-optimal mechanical properties. Finally, the FeS-Fe system showed the poorest mechanical properties among the systems studied because of the lack of Mo reinforcement. In friction tests, the formation of a sulfide layer contributed to a decrease in coefficient of friction (COF) in all of the samples.