Integrated mathematical optimisation approach for the tower crane hook routing problem to satisfy material demand requests on-site

Optimising decisions around the location and operation of tower cranes can improve the workflow in construction projects. Traditionally, the location and allocation problems involved in tower crane operations in the literature have been solved separately from the assignment of material supply points to demand points and the scheduling of the crane’s activity sequence across supply and demand points on a construction site. To address the gap, this paper proposes a binary integer programming problem, where location of the tower crane, allocation of supply points to material-demanding regions, and routing of hook of the crane based on activity sequencing of the hook across supply and material-demanding regions on site are optimised. The novelty in this work is in the way the crane’s activity scheduling is modelled via mathematical programming, based on routing the hook movement to meet material demand, through minimising tower crane operating costs. A realistic case study is solved to assess the validity of the model. The model is contrasted with results obtained from other solving algorithms commonly adopted in the literature, along with a solution proposed by an experienced practitioner. Results indicate that all instances can be solved when compared to other meta-heuristics that fail to achieve an optimum solution. Compared to the solution proposed by the practitioner, the results of the proposed model achieve a 46% improvement in objective function value. Planners should optimise decisions related to the location of the crane, the crane’s hook movement to meet service requests, and supply points’ locations and assignment to material-demanding regions simultaneously for effective crane operations.     

Selective determination of urea using urease immobilized on ZnO nanowires

Well-aligned zinc oxide (ZnO) nanowire arrays were fabricated on gold-coated plastic substrates using a low-temperature aqueous chemical growth (ACG) method. The ZnO nanowire arrays with 50–130 nm diameters and ∼1 μm in lengths were used in an enzyme-based urea sensor through immobilization of the enzyme urease that was found to be sensitive to urea concentrations from 0.1 mM to 100 mM. Two linear sensitivity regions were observed when the electrochemical responses (EMF) of the sensors were plotted vs. the logarithmic concentration range of urea from 0.1 mM to 100 mM. The proposed sensor showed a sensitivity of 52.8 mV/decade for 0.1–40 mM urea and a fast response time less than 4 s was achieved with good selectivity, reproducibility and negligible response to common interferents such as ascorbic acid and uric acid, glucose, K⁺ and Na⁺ ions.     

A mathematical model and a computer tool for the Tower of Hanoi and Tower of London puzzles

We propose a mathematical model for the Towers of Hanoi and London based on state graphs. The analysis of this model allows to address questions like equivalence of puzzles, difficulty of tasks and optimality of solutions using topological, metric and symmetry properties of the corresponding graphs.The mathematical model serves as a base for a computer program to administer tower puzzles in a variety of psychological test situations. It is suitable for bedside use and is equipped with numerous devices for post-processing of recorded data. Among these features is the graphical representation of the projection of the path taken by a test person onto the state graph.     

基于JSSE的汉诺塔游戏设计与实现

对汉诺塔游戏问题进行了研究,发现了对汉诺塔游戏用递归算法实现符合问题逻辑结构。设计了基于JSSE的递归算法实现了手动移盘和自动移盘的游戏功能。     

The road to intelligence

It is argued that robotic platforms are the way forward towards building intelligent systems, where multiple sensors and manipulation are used for cognitive processes. It is also argued that the cue for developing the right architecture for such a system is human language.     

木素-UF胶粘剂的研制

本文介绍了一种木素－UF胶粘剂的制造方法，并分析了木素羟甲基化、过程pH值、尿素加料次数及木素加量对胶粘剂性能的影响。     

500m3钢筋砼水塔承载力及动态刚度实例分析

针对一钢筋混凝土水塔实例,通过现场静态、动态参数测试,分析了钢筋混凝土水塔的承载能力及动态刚度,作出了科学诊断。     

尿素施肥量对土壤微生物和酶活性的影响

不同肥料用量对土壤生物学过程的影响研究是肥域(际)土壤生态学研究的重要内容之一。本试验采用室内模拟培养试验,研究了不同尿素施肥量对潮土微生物数量和酶活性的影响。结果表明:放线菌和霉菌对尿素施肥量比较敏感,B(肥土比1:1500)施肥量就可以明显降低它们的数量,分别比不施肥(A)下降45.5%和32.2%。硝化细菌在D(肥土比1:400)施肥量时数量最大,之后随施肥量增加而下降,反硝化细菌随施肥量增加直线下降。土壤酶活性均在E(肥土比1:200)施肥量时发生明显变化,脲酶、中性磷酸酶和蔗糖酶活性急剧下降。     

Improved electrocatalytic kinetics of nickel hydroxide nanoparticles on Vulcan XC-72R carbon black towards alkaline urea oxidation reaction

Nickel hydroxide nanoparticles were fabricated on Vulcan XC-72R carbon black using various reducing agents through assisted microwave polyol process. The formed electrocatalysts using sodium borohydride [Ni(OH)₂/C–NB], ethylene glycol [Ni(OH)₂/C–EG] and a mixture of them [Ni(OH)₂/C–EGNB] displayed an electrocatalytic activity towards urea oxidation in NaOH solution. The oxidation peak potential and current density values were greatly influenced by the employed reducing agent. Lower onset and peak potential values were measured at Ni(OH)₂/C–EGNB, while Ni(OH)₂/C–EG exhibited the highest oxidation current density during urea oxidation reaction. Electroactive surface area measurements revealed that the number of available active sites for the oxidation reaction was arranged in an ascending order as Ni(OH)₂/C–NB < Ni(OH)₂/C–EGNB < Ni(OH)₂/C–EG. The diffusion coefficient of urea molecules at Ni(OH)₂/C–EG and Ni(OH)₂/C–EGNB was 14.69 and 5.90 times higher than that at Ni(OH)₂/C–NB. Stable performance was measured at all studied electrocatalysts over prolonged operation suggesting their valuable application as efficient anode materials in direct urea oxidation fuel cells.     

Maximum Spreading of Urea Water Solution during Drop Impingement

Droplet impingement of urea water solution (UWS) is a common source for liquid film and solid deposits formed in the tailpipe of diesel engines. In order to better understand and predict wetting phenomena on the tailpipe wall, this study focuses on droplet spreading dynamics of urea water solution. Impingement of single droplets is investigated under defined conditions by high‐speed imaging using shadowgraphy technique. The experimental studies are complemented by numerical simulations with a phase‐field method. Computational results are in good agreement with experimental data for the advancing phase of spreading and the maximum and terminal spreading radius, whereas for the receding phase notable differences occur. For the maximum spreading radius, an empirical correlation derived for glycerol‐water‐ethanol mixtures is found to be valid for millimeter‐sized UWS droplets as well. A numerical simulation for a much smaller droplet however indicates that this correlation is not valid for the tiny droplets of UWS sprays in technical applications.