Discrete approximation heuristics for the capacitated continuous location–allocation problem with probabilistic customer locations

The capacitated continuous location–allocation problem, also called capacitated multisource Weber problem (CMWP), is concerned with locating m facilities in the Euclidean plane, and allocating their capacity to n customers at minimum total cost. The deterministic version of the problem, which assumes that customer locations and demands are known with certainty, is a nonconvex optimization problem. In this work, we focus on a probabilistic extension referred to as the probabilistic CMWP (PCMWP), and consider the situation in which customer locations are randomly distributed according to a bivariate probability distribution. We first formulate the discrete approximation of the problem as a mixed-integer linear programming model in which facilities can be located on a set of candidate points. Then we present three heuristics to solve the problem. Since optimal solutions cannot be found, we assess the performance of the heuristics using the results obtained by an alternate location–allocation heuristic that is originally developed for the deterministic version of the problem and tailored by us for the PCMWP. The new heuristics depend on the evaluation of the expected distances between facilities and customers, which is possible only for a few number of distance function and probability distribution combinations. We therefore propose approximation methods which make the heuristics applicable for any distance function and probability distribution of customer coordinates.     

Design and Hardware-in-the-Loop Integration of a UAV Microavionics System in a Manned–Unmanned Joint Airspace Flight Network Simulator

One of the challenges for manned-unmanned air vehicles flying in joint airspace is the need to develop customized but scalable algorithms and hardware that will allow safe and efficient operations. In this work, we present the design of a bus-backboned UAV microavionics system and the hardware-in-the-loop integration of this unit within a joint flight network simulator. The microavionics system is structured around the Controller Area Network and Ethernet bus data backbone. The system is designed to be cross-compatible across our experimental mini-helicopters, aircrafts and ground vehicles, and it is tailored to allow autonomous navigation and control for a variety of different research test cases. The expandable architecture allows not only scalability, but also flexibility to test manned-unmanned fleet cooperative algorithm designs at both hardware and software layer deployed on bus integrated flight management computers. The flight simulator is used for joint simulation of virtual manned and unmanned vehicles within a common airspace. This allows extensive hardware-in-the-loop testing capability of customized devices and algorithms in realistic test cases that require manned and unmanned vehicle coordinated flight trajectory planning.     

Production of graphene layer by liquid-phase exfoliation with low sonication power and sonication time from synthesized expanded graphite

Multi-layer graphene was produced through synthesized expanded graphite (EG) liquid exfoliation using organic solvent. Hexagonal graphite (HG) was used as a starting material. HG was mixed with an acidic mixture, dried, rand subjected to thermal treatment. After this process, EG was obtained. This obtained EG was sonicated for 1 h via an ultrasonic homogenizer by blending an organic solvent. Samples were subjected to SEM, TEM, FTIR, and UV-Vis/NIR spectroscopy investigations. After the investigations, it was shown that nano-size graphene sheets were obtained.     

Shear strength estimation of plastic clays with statistical and neural approaches

Because shear strength parameters highly influence the bearing capacity of soils, several researchers have carried out large number of experimental and theoretical studies aimed at understanding soil strength behaviors. Within this context, the determination of correlations between soil index properties and shear strength parameters for specific soil types is possible. The aim of this study is to observe the performance of statistical and artificial neural network (ANN)-based methods on establishing correlations between index properties and shear strength parameters of normally consolidated plastic clays. To collect modeling data, consolidated-undrained triaxial tests were performed on normally consolidated plastic clays obtained from the same region. Additionally, detailed statistical analyses were conducted on the test data. Results indicate that the ANN-based model is superior in determining the relationships between index properties and shear strength parameters. However, in order to get appropriate outcomes, specific care must be dedicated when applying ANN-based correlation models.     

Capturing Knowledge in Construction Projects: Knowledge Platform for Contractors

Managing knowledge effectively is critical to the survival and advance of a company, especially in project-based industries such as construction. However, capturing knowledge in construction projects is a tedious task, as knowledge is usually experience based, tacit, and hard to pass on to others. In this study, a survey was carried out among eight leading Turkish construction contractors that are operating within the international construction market. The specific objectives of this survey are to find out how the tacit and explicit knowledge are captured, stored, shared, and used in forthcoming projects, as well as major drivers and barriers for knowledge management. Based on the survey, it was determined that most of these firms do not have a knowledge management strategy and a systematic way of capturing and storing tacit knowledge. A conceptual framework is proposed to formalize the knowledge-capturing process within construction companies. To demonstrate how the conceptual framework can be implemented in practice, a Web-based system, namely, Knowledge Platform for Contractors (KPfC) is presented. It is hypothesized that KPfC can be used to manage both tacit and explicit knowledge effectively in construction projects.     

Some Physical Properties of Heat-Treated Hornbeam (Carpinus betulus L.) Wood

Thermal treatment of wood alters its structure due to degradation of wood polymers (cellulose, hemicellulose, and lignin), so the physical properties of wood are either improved or worsen. In this study, the effect of thermal treatment on density, equilibrium moisture content (EMC), and color of hornbeam wood was investigated. The color and density (air-dry and oven-dry density) were determined for the control and heat-treated samples, as well as their equilibrium moisture content at relative humidities of 35, 50, 65, 80, and 95%. The data showed that thermal treatment resulted mainly in darkening of the wood and the reduction of its density and EMC. It was found that the treatment temperature had a much more significant impact on color changes than the duration of the treatment. Generally, heat-treated wood color becomes darker than nontreated wood, so it can be used as decorative material. Because the EMC is lower, the heat-treated wood can be used in saunas and pool sides. Also, heat-treated wood can be used in outdoor applications because of lower density.     

The effect of cutting parameters and cutting tools on machining performance of carbon graphite material

Abstract

The present study focuses on the effects of cutting speed, feed rate and cutting tool material on the machining performance of carbon graphite material. Polycrystalline Diamond (PCD) cutting tools are used in machining experiments and its performance is compared with the tungsten carbide (WC) and Cubic Boron Nitride (CBN) tools. Machining performance criteria such as flank and nose wear and resulting surface topography and roughness of machined parts were studied. This study illustrates that feed rate and cutting tool material play a dominant role in the progressive wear of the cutting tool. The highest feed rate and cutting speed profoundly reduce the tool wear progression. The surface roughness and topography of specimens are remarkably influenced from the tool wear. Major differences are found in the wear mechanisms of PCD and WC and CBN cutting tools.     

The fate of two Listeria monocytogenes serotypes in "cig kofte" at different storage temperatures

Cig kofte is a traditional Turkish food prepared from minced beef, bulgur, onions, garlic and varieties of spices. It is generally consumed within a few hours. However, leftovers can be kept in refrigerator or in room temperature up to 24h until they are consumed. In this study, survival and growth of two Listeria monocytogenes serotypes were investigated in cig kofte during the storage. For this purpose, the prepared samples were separately contaminated with serotypes 1/2b or 4b of L. monocytogenes at the level of 10(4)CFU/g and stored at 4°C and 21°C. L. monocytogenes colonies were counted at the beginning, 3rd, 6th, 12th and 24th hours of the storage. At 4°C, L. monocytogenes 4b significantly increased (P<0.05) from 4.12 to 5.49log(10)CFU/g but L. monocytogenes 1/2b remained constant (P>0.05) during the storage period. At 21°C, both L. monocytogenes 1/2b and 4b increased significantly (P<0.05) from 4.56 to 5.16log(10)CFU/g and from 4.23 to 5.65log(10)CFU/g, respectively. The physicochemical and microbiological characteristics of the cig kofte did not inhibit the growths of L. monocytogenes serotypes during the storage. These results indicated that L. monocytogenes was able to survive and grow in cig kofte at the both storage temperatures of 4°C and 21°C and cig kofte seemed to be a suitable medium for this pathogen.     

Moisture Diffusivity in Rice Components During Absorption and Desorption

Moisture diffusivity values of different rice kernel components, namely endosperm, bran and husk, are required to solve mathematical models describing absorption and desorption processes. In addition to the rice variety and temperature, the moisture diffusivity also depends on its instantaneous moisture content or water activity (a_w) and whether rice is absorbing or desorbing moisture. This research was undertaken to determine moisture diffusivity values of rough rice components in different a_w ranges during absorption and desorption. Experiments were performed to measure sorption rates of different rice forms, including white rice, brown rice, and rough rice kernels. Mathematical models were developed to predict their moisture distribution during moisture sorption processes. These models were solved by finite element method using Comsol Multiphysics® simulation program. Moisture diffusivity values of different rice components were calculated and found to be different during absorption and desorption. Diffusivity of rice endosperm was higher during desorption than absorption at a_w higher than 0.20 and increased with an increase in a_w in 0.20–0.80 a_w range. Diffusivity of bran remained almost the same with a_w while diffusivity of husk decreased with an increase in a_w. Results obtained in this research demonstrated that the moisture diffusivity of different rice components varies significantly with the change in water activity or moisture and should be accounted in the mathematical models.