Solving the uncapacitated multi-facility Weber problem by vector quantization and self-organizing maps

The uncapacitated multi-facility Weber problem is concerned with locating m facilities in the Euclidean plane and allocating the demands of n customers to these facilities with the minimum total transportation cost. This is a non-convex optimization problem and difficult to solve exactly. As a consequence, efficient and accurate heuristic solution procedures are needed. The problem has different types based on the distance function used to model the distance between the facilities and customers. We concentrate on the rectilinear and Euclidean problems and propose new vector quantization and self-organizing map algorithms. They incorporate the properties of the distance function to their update rules, which makes them different from the existing two neural network methods that use rather ad hoc squared Euclidean metric in their updates even though the problem is originally stated in terms of the rectilinear and Euclidean distances. Computational results on benchmark instances indicate that the new methods are better than the existing ones, both in terms of the solution quality and computation time.     

A location–allocation heuristic for the capacitated multi-facility Weber problem with probabilistic customer locations

The capacitated multi-facility Weber problem is concerned with locating m facilities in the Euclidean plane, and allocating their capacities 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 non-convex optimization problem and difficult to solve. In this work, we focus on a probabilistic extension and consider the situation where the customer locations are randomly distributed according to a bivariate distribution. We first present a mathematical programming formulation, which is even more difficult than its deterministic version. We then propose an alternate location–allocation local search heuristic generalizing the ideas used originally for the deterministic problem. In its original form, the applicability of the heuristic depends on the calculation of the expected distances between the facilities and customers, which can be done for only very few distance and probability density function combinations. We therefore propose approximation methods which make the method applicable for any distance function and bivariate location distribution.     

A novel technique for the identification of the surface plasmon in eels

In this work we report on angle-resolved Electron Energy Loss Spectroscopy (EELS) with grazing-emergent electrons, which has been used to enhance considerably the surface sensitivity of EELS and thus distinguish between surface and bulk-related loss features. Surface plasmon losses for Ni (001) are clearly identified at 7 eV and 14 eV. Also, a new interpretation is suggested for a loss peak observed at 10 eV.     

Rhodium catalyzed reaction of internal alkynes with organoborons under CO atmosphere: a product tunable reaction

Alkynes react with organoborons under a CO atmosphere in the presence of a rhodium(I) catalyst to afford mainly 5-aryl-2(5H)-furanones, α,β-unsaturated ketones, and indanones. The product selectivity can be tuned by modifying the reaction conditions.     

Reactions of pentachloro-2-nitrobutadiene with some aliphatic and heterocyclic thiols and a crystallographic study

In this study, S-, S,S- and S,O-substituted novel nitrodiene compounds were synthesized. Cyclization products were formed when difunctional nucleophiles were used. The stereoisomerism of a heterocyclic nitrodiene is discussed with the help of XRD studies. The structures of all compounds were characterized by spectroscopic methods (FT-IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, MS) and microanalysis.     

Thiocyanate separation by imprinted polymeric systems

Novel polymers for the specific recognition of thiocyanate ion (SCN) have been prepared by template polymerization of SCN with chitosan-Zn(II), the N-(2-aminoethyl)-3-aminopropyl-trimethoxysilan-Zn(II) complex, epichlorohydrin, and tetraethoxysilane. After removal of SCN, the imprinted beads have been used for solid-phase extraction of SCN from aqueous solutions. Optimised conditions for SCN separation are reported with respect to sample pH for the quantitative preconcentration and desorption. Competitive adsorption of fluoride and phosphate has been investigated and selectivity coefficients are given for these ions with respect to SCN.     

Variable neighbourhood search heuristics for the probabilistic multi-source Weber problem

The Multi-source Weber Problem (MWP) is concerned with locating m facilities in the Euclidean plane, and allocating these facilities 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 non-convex optimization problem and difficult to solve. In this work, we focus on a probabilistic extension and consider the situation where customer locations are randomly distributed according to a bivariate distribution. We first present a mathematical programming formulation for the probabilistic MWP called the PMWP. For its solution, we propose two heuristics based on variable neighbourhood search (VNS). Computational results obtained on a number of test instances show that the VNS heuristics improve the performance of a probabilistic alternate location-allocation heuristic referred to as PALA. In its original form, the applicability of the new heuristics depends on the existence of a closed-form expression for the expected distances between facilities and customers. Unfortunately, such an expression exists only for a few distance function and probability distribution combinations. We therefore use two approximation methods for the expected distances, which make the VNS heuristics applicable for any distance function and bivariate distribution of customer locations.     

Effect of hyamine on electrochemical behaviour of brass alloy in HNO3 solution

The electrochemical behaviours of a brass alloy in 0.1 M nitric acid, including the hyamine inhibitor with concentrations between 2.5 × 10^?4 M and 1.0 × 10^?5 M, were studied. For this purpose, potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), linear polarisation resistance (LPR) techniques, and flame atomic absorption spectroscopy (FAAS) were utilised. The inhibitor molecules adsorbed on the brass surface were calculated to be in good agreement with the Langmuir adsorption isotherm and the standard free enthalpy of adsorption (??G _ads ^° ). Hyamine effectively improved the corrosion inhibition of brass and acted as a mixed-type inhibitor on alloy surfaces. The surface morphology of the alloy was also clarified by optical microscopic and SEM techniques. A theoretical study of the corrosion inhibition efficiency of hyamine molecule was carried out using density functional theory (DFT) at the B3LYP/6-311G(d,p) basis set level.     

Radiolabeling, quality control and kit formulation of a new 99mTc-labeled antibiotic: 99mTc-doxycycline hyclate

Since radiolabeled antibiotics specifically bind to the bacterial components they are promising radiopharmaceuticals for the precise diagnosis and detection of infectious lesions. Doxycycline hyclate (DOX) was chosen to investigate as a new radiolabeled antibacterial agent since its bacteriostatic activity against a wide variety of microorganisms. The aim of the present study is to develop simple and easy formulation of DOX with ^99mTc ready to use kit. ^99mTc-DOX was developed and standardized under varying conditions of reducing and antioxidant agent concentration, pH, radioactivity dose and reducing agent type. Labeling studies were performed by changing the selected parameters one by one and optimum labeling conditions were determined. After observing the conditions for maximum labeling efficiency and stability, lyophilized freeze dry kits were prepared accordingly. Radiochemical purity was determined with RTLC and RHPLC which was found more than >95 %. Two different freeze dry kits were formulated with optimum labeling conditions. The improved kits were found stable up to 6 months.