基于随机活动工期的多模式现金流均衡项目调度优化

承包商在项目执行过程中的现金流均衡是保证项目成功的关键因素。本文研究基于随机活动工期的多模式现金流均衡项目调度问题,旨是在项目工期及鲁棒性阈值约束下合理安排活动执行模式与开始时间,实现承包商现金流均衡。本文通过构建整数规划优化模型对研究问题进行刻画,随后设计模拟退火算法进行求解,最后进行案例分析。结果表明:鲁棒性阈值虽然可以保证基准进度的稳定性,但是提高鲁棒性阈值水平反而不利于承包商的现金流均衡,该值过高时甚至得不到可行解。本文研究可为随机活动工期背景下承包商的现金流控制提供定量化决策支持。     

Requirements in mathematics textbooks: a five-dimensional analysis of textbook exercises and examples

Mathematics textbooks play a very important role in mathematics education and textbook tasks are used by students for practice to a large extent. Since the nature of the tasks may influence the way students think it is important that the textbooks provide a balance of a variety of tasks. The analyses of the requirements in textbook tasks contain the usual dimensions of content, cognitive demands, question type and contextual features. The aim of this study is to embed a new fifth dimension into the framework: mathematical activities. This addresses the question of what a student should do in a particular textbook task: to represent, to compute, to interpret or to use argumentation. The analysis encompassed more than 22,000 tasks from the most commonly used Croatian mathematics textbooks in the 6th, 7th and 8th grade. The results show that the textbooks do not provide a full range of task types. There is an emphasis on computation, while argumentation and interpretation activities, reflective thinking and open answer tasks are underrepresented. The study revealed that incorporating mathematical activities into the multidimensional framework of textbook tasks may help to better understand the opportunities to learn which are afforded students by using mathematics textbooks.     

SINGLE MACHINE SCHEDULING WITH CONTROLLABLE PROCESSING TIMES AND COMPRESSION COSTS （PART I：EQUAL TIMES AND COSTS）

Most papers in scheduling research have treated individual job processing times as fixed parameters. However, in many practical situations, a manager may control processing time by realloeating resources. In this paper, authors consider a machine scheduling problemwith controllable processing times. In the first part of this paper, a special case where the pro-cessing times and compression costs are uniform among jobs is discussed. Theoretical results are derived that aid in developing an O（n^2) algorithm to slove the problem optimally. In the second part of this paper, authors generalize the discussion to general case, An effective heuristic to the genera/ problem will be presented.     

高压与加热协同处理对牛肌肉中蛋白酶活性的影响

在不同温度(20～60℃)和压力(0.1～600 MPa)下处理20 min,对牛肌肉中蛋白酶活性的影响进行了研究.结果显示:室温下,随着处理压力的增加,酶的活力显著下降,而压力达400 MPa及以上时,酶的活力则没有明显变化,同时在pH值为3和7.5时酶的活性几乎完全丧失.200 MPa以下的压力处理使肌肉中游离氨基...     

Synthesis,Structural Investigations,and In Vitro/In Silico Bioactivities of Flavonoid Substituted Biguanide: A Novel Schiff Base and Its Diorganotin (IV) Complexes

Quercetin is one of the most powerful bioactive dietary flavonoids. The in vivo biological study of quercetin is extremely difficult due to its very low solubility. However, diorganotin complexes of quercetin are more useful when contrasted with quercetin due to increased solubility. In the present study, quercetin, substituted biguanide synthesized in the form of Schiff base and its di-alkyl/aryl tin (IV) complexes were obtained by condensing Schiff base with respective di-alkyl/aryl tin (IV) dichloride. Advanced analytical techniques were used for structural elucidation. The results of biological screening against Gram-positive/Gram-negative bacteria and fungi showed that these diorganotin (IV) derivatives act as potent antimicrobial agents. The in silico investigation with dihydropteroate (DHPS) disclosed a large ligand–receptor interaction and revealed a strong relationship between the natural exercises and computational molecular docking results.     

The Synthesis of Neodymium Complexes with Polymers Containing Thiol and Sulphoxide and Their Catalytic Activities

Introduction Polymers containing thiol and sulphoxide which have active—SH and—SO groups respectively, have wide application to biological, pharmaceutical, industrial and other chemical field and—SH and—SO groups are easy to form complexes with metals, so they have aroused an increasing interest of many authors. A large number of functional resins and corresponding metal complexes have been synthesized.     

A copper(II) complex with 2-(2′-pyridyl)benzimidazole and l-arginine: synthesis,structure, antibacterial activities,and DNA interaction

A Cu(II) complex with 2-(2′-pyridyl)benzimidazole and l-arginine has been synthesized and investigated by elemental analysis, molar conductivity, IR, UV/vis, and X-ray diffraction. The complex crystallizes in the triclinic space group P1 with six molecules in a unit cell of dimensions a?=?10.6397(5)?Å, b?=?19.2178(8)?Å, c?=?20.0387(9)?Å, α?=?75.3670(10)°, β?=?79.4670(10)°, γ?=?87.4470(10)°, V?=?3897.6(3)?ų, R ₁?=?0.0408, and wR ₂?=?0.0502. The complex contains six crystallographically independent complexes, Cu1, Cu2, Cu3, Cu4, Cu5, and Cu6, which have a distorted square-pyramidal geometry. The complex was screened for its in vitro antibacterial activities against two Gram-positive (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative (Escherichia coli and Salmonella) micro-organisms. The complex exhibited good antibacterial activities against the micro-organisms compared with HPB and Cu(ClO₄)₂. Interaction of the complex with DNA was studied by electronic absorption spectroscopy, fluorescence spectroscopy, circular dichroic spectroscopy, viscosity measurements, and agarose gel electrophoresis. Results suggest that the complex could bind to CT-DNA via partial intercalation, and cleave the plasmid DNA with involvement of hydroxyl radicals, and probably singlet oxygen-like copper-oxo species in the presence of ascorbate.     

Synthesis,characterization, biological activities,crystal structure and DNA binding of organotin(IV) 5-chlorosalicylates

New organotin(IV) carboxylates, R₂SnL₂ (R=n-Bu: 1), R₂Sn(Cl)L (R=n-Bu: 2), and R₃SnL (R=Me: 3; n-Bu: 4; Ph: 5) have been synthesized by stirring 5-chloro-2-hydroxybenzoic acid HL with KOH and R₂SnCl₂ (R=n-Bu)/R₃SnCl (R=Me, n-Bu, Ph) in methanol at room temperature. The complexes along with ligand have been characterized by FTIR, (¹H, ¹³C) NMR, EI-MS, and single-crystal XRD crystallography. FTIR data indicated bidentate coordination of carboxylate. NMR data suggested six- or five-coordinate geometry of organotin(IV) carboxylates. Single-crystal XRD of 1 demonstrated skew-trapezoidal geometry around the tin center, with the basal plane occupied by four oxygens and the two butyl groups lying in distorted axial position. Complexes 1, 2, and 5 exhibited interaction with SS-DNA (salmon sperm) and suggests intercalating mode of binding. The complexes displayed significant antimicrobial activities against bacterial and fungal strains as compared to free ligand. The hemolytic activity of the complexes was lower compared to Triton-X 100 (positive control, 100% lysis) and higher than phosphate-buffered saline (negative control, 0% lysis). Complex 4 was the most potent inhibitor of bacterial/fungal growth.