牛顿冷却定律适用范围的探讨

从实验上对牛顿冷却定律的适用范围进行了测量和分析，得到了一个牛顿冷却定律适用范围的具体结论。     

Nonexistence in power and gamma density regression, sum of nonnegative terms

When we use the power function α(c x)^b and gamma density αx^be^-cx to fit the data by the least squares method, we have to address the question of existence. The closure of the set of each type of these functions defined on a finite domain is determined. We derive a way to determine the closure of a sum of nonnegative functions if the closures of the summands are available.     

从能量的角度讨论两体碰撞问题

从能量角度导出了两体对心碰撞的能量损失公式,重新讨论了恢复系数的物理意义．     

带有机器准备时间且允许重排的在线排序

本文中, 我们考虑了带有机器准备时间且允许重排的两台平行机在线排序问题. 其目标为极小化最大完工时间. 我们研究了两种不同的模型, 并分别给出了最好可能的算法.     

A Unified Approach to Phytosiderophore Natural Products

This work reports on the concise total synthesis of eight natural products of the mugineic acid and avenic acid families (phytosiderophores). An innovative „east-to-west“ assembly of the trimeric products resulted in a high degree of divergence enabling the formation of the final products in just 10 or 11 steps each with a minimum of overall synthetic effort. Chiral pool starting materials (l -malic acid, threonines) were employed for the outer building blocks while the middle building blocks were accessed by diastereo- and enantioselective methods. A highlight of this work consists in the straightforward preparation of epimeric hydroxyazetidine amino acids, useful building blocks on their own, enabling the first synthesis of 3’’-hydroxymugineic acid and 3’’-hydroxy-2’-deoxymugineic acid.     

Determination of metal ions extracted by DTPA in a soil treated with effluent using an Hg-electroplated-Pt microelectrode

Determinations of Cu, Fe, Mn and Zn were performed in an oxisol soil treated with effluent originated from a biodigester septic cesspool. The extracts were obtained from a DTPA/TEA (pH 7.3) solution and analysed by electroanalytical methodologies using square wave anodic stripping voltammetry (SWASV) for the analysis of Cu, Mn and Zn and square wave voltammetry (SWV) for Fe analysis, both of them with a thin mercury film microelectrode (ME-Hg). DTPA (diethylenetriaminepentaacetic acid) complexes with Cu, Mn and Fe show electroactivity in the potentials range close to the ones for the free ions in solution, but the Zn complex did not show any electroactivity at the potential range analysed. SWASV/ME-Hg and SWV/ME-Hg results were in good agreement (r² = 0.996) with the flame atomic absorption spectroscopy (FAAS) analyses, demonstrating that electroanalytical methodologies can be used for micronutrient determinations in soil extracts without serious interferences of the matrix components. Some characteristics of the complex formed between DTPA-metals are explored by EPR experiments.     

Innovative Formulations of Phosphate Glasses as Controlled-Release Fertilizers to Improve Tomato Crop Growth,Yield and Fruit Quality

Three phosphate glass compositions, VF1, VF2, and VF3, containing macro and micronutrients with different [K₂O/(CaO+MgO)] ratio, were formulated to be used as controlled release fertilizers for tomato crop, depending on their chemical durability in water and their propriety with respect to the standards of controlled-release fertilizers. This study investigated the influence of [K₂O/(CaO+MgO)] ratio variation on glass properties. For this, the elaborated glasses have undergone a chemical characterization using inductively coupled plasma atomic emission spectroscopy, a thermal characterization using differential thermal analysis, a physicochemical characterization based on density and molar volume measurements, and a structural characterization using Raman spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. In addition, the chemical durability was determined by measuring the percentage of weight loss and the pH. Results revealed that the glass structure and composition have the mean role in controlling the release of nutrients in water. By increasing [K₂O/(CaO+MgO)] ratio, the dissolution rates of the glasses increased due to the shrinking in the rate of crosslinking between phosphate chains, accompanied with a diminution in transition and crystallization temperatures, and an increase in the molar volume. An agronomic valorization of VF1 and VF2 glass fertilizers, which showed dissolution profiles adequate to the criteria of controlled-release fertilizers, was carried out to evaluate their efficiency on tomato crops. These glass fertilizers improved soil mineral content and tomato performances in comparison to the control and NPK treatments with the distinction of VF2. The results highlight the effectiveness of these smart fertilizers toward their potential large-scale application to improve crop production and quality for high nutritional value foods.     

Kinetics of thermal decomposition of some nitrophosphate fertilizers with micronutrients in isothermal conditions

The thermal behavior under isothermal conditions of some ammonia nitrate, ammonia phosphates and calcium phosphates mixtures with added micronutrients was studied. In order to establish the variation of activation energy (E) vs. conversion (α), the TG data were interpolated with spline functions, followed by numeric derivation. Using the so determined reaction rate the Friedman differential-isoconversional method was applied. A dependence of the activation energy vs. conversion was observed, meaning a many-step reaction. Therefore a procedure based on the compensation effect (and suggested by Budrugeac and Segal) was applied.     

一种满足有效样本量固定的放回抽样方法

相比不放回抽样,放回抽样的实施比较简单,操作性强,但缺点在于单元可能被重复抽到,抽出的有效样本量小于等于样本量,不是固定的。本文应用逆抽样的原理,设计了一种放回抽样方法,满足有效样本量固定,并且估计量的性质优良。     

太阳电池中光电转换的有效能

本文提出了光量子在光电转换中的能昔效率的表示方法,给出了太阳电池光电转换的理论效率极限,以及太阳电池的理论最佳带隙和最佳截止波长,最后,讨论了光电转换的驱动力,分析了光电跃迁的有效能的不可逆损失和熵增,给出了太阳电池中激发电子的有效能的表达式.