New frequency/voltage converters for ac-electrogravimetric measurements based on fast quartz crystal microbalance

A better understanding of the mechanisms located at the solid/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the only difference is the determination of mass changes given by the quartz crystal microbalance rather than current changes following sine wave modulations of the applied potential. This function appears very well adapted to characterize ionic exchanges at the electrochemical interface. Frequency/voltage converters are the key devices in translating the microbalance frequency response in terms of a continuous voltage change. The latter allows the transfer function to be obtained via a frequency response analyzer. Different converters were tested in this work in order to improve the performances of the experimental setup.     

Quasi-parallel grippers for the concentric handling of cylindrical workpieces

The majority of workpieces found in industry have cylindrical shapes. The design of jaws to enable the concentric handling of these workpieces by grippers with quasi-parallel jaw-closure is investigated. The jaws are given specially-shaped profiles resembling the Greek letter v. The basic equations defining such profiles are given along with an analysis of the geometrical parameters which govern the jaw dimensions. The rules for selecting the parameters to achieve compact jaw designs are enshrined in a computer program which implements these rules. By this means, optimal jaw profiles from specifications of workpiece and gripper dimensions can be determined. Sample computer outputs illustrate the effectiveness of the method.     

Tribochemical interactions of Si-doped DLC film against steel in sliding contact

This study concerns the effects of tribochemical interactions at the interface of Si-DLC (silicon-doped diamond-like carbon) film and steel ball in sliding contact on tribological properties of the film. The Si-DLC film was over-coated on pure DLC coating by radio frequency plasma-assisted chemical vapor deposition (r.f. PACVD) with different Si concentration. Friction tests against steel ball using a reciprocating type tribotester were performed in ambient environment. X-Ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) were used to study the chemical characteristics and elemental composition of the films and mating balls after tests. Results showed a darkgray film consisting of carbon, oxygen and silicon on the worn steel ball surface with different thickness. On the contrary, such film was not observed on the surface of the ball slid against pure DLC coating. The oxidation of Si-DLC surface and steel ball was also found at particular regions of contact area. This demonstrates that tribochemical interactions occurred at the contact area of Si-DLC and steel ball during sliding to form a tribofilm (so called transfer film) on the ball specimen. While the pure DLC coating exhibited high coefficient of friction (∼0.06), the Si-DLC film showed a significant lower coefficient of friction (∼0.022) with the presence of tribofilm on mating ball surface. However, the Si-DLC film possesses a very high wear rate in comparison with the pure DLC. It was found that the tribochemical interactions strongly affected tribological properties of the Si-DLC film in sliding against steel.     

Quadratic Discriminant Analysis Based Ensemble Machine Learning Models for Groundwater Potential Modeling and Mapping

In this study, the AdaBoost, MultiBoost and RealAdaBoost methods were combined with the Quadratic Discriminant Analysis method to develop three new GIS-based Machine Learning ensemble models, i.e., ABQDA, MBQDA, and RABQDA for groundwater potential mapping in the Dak Nong Province, Vietnam. In total, 227 groundwater wells and 12 conditioning factors (infiltration, rainfall, river density, topographic wetness index, sediment transport index, stream power index, elevation, aspect, curvature, slope, soil, and land use) were used for this study. Performance of the models was evaluated using the Area Under the Receiver Operating Characteristics Curve AUC (AUC) and several other performance metrics. The results showed that the ABQDA model that achieved AUC?=?0.741 was superior to the other models in producing an accurate map of groundwater potential for the Dak Nong Province. The models and potential maps produced here can help policymakers and water resources managers to preserve an optimal exploit from these vital resources.

     

Solving the quorumcast routing problem by constraint programming

The quorumcast routing problem is a generalization of multicasting which arises in many distributed applications. It consists of finding a minimum cost tree that spans the source node r and at least q out of m specified nodes on a given undirected weighted graph. This paper proposes a complete and an incomplete approach, both based on the same Constraint Programming (CP) model, but with two different specific search heuristics based on shortest paths. Experimental results show the efficiency of the two proposed approaches. Our complete approach (CP model + complete search) is better than the state of the art complete algorithm and our incomplete approach (CP model + incomplete search) is better than the state of the art incomplete algorithm. Moreover, the proposed complete search is better than the standard First-Fail search in the same CP model.     

S-CLONE: Socially-aware data replication for social networks

Online social networking has become one of the most important forms of today’s communication. While an online social network can be attractive for many socially interesting features, its competitive edge will diminish if it is not able to keep pace with increasing user activities. Deploying more servers is an intuitive way to make the system scale, but for the best performance one needs to determine where best to put the data, whether replication is needed, and, if so, how. This paper is focused on replication; specifically, we propose S-CLONE, a socially-aware data replication scheme which can significantly improve a social network’s efficiency by taking into account social relationships of its data. S-CLONE’s performance is substantiated in our evaluation study.     

Some viscoelastic wave equations

The authors study the problem of existence, uniqueness and asymptotic behavior for t of (weak or strong) solutions of equations in the form% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiGc9yrFr0xXdbba91rFfpec8Eeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqGaaO% abaeqabaGaamyDamaaBaaaleaacaWG0bGaamiDaaqabaGccqGHsisl% cqaH7oaBcqqHuoarcaWG1bWaaSbaaSqaaiaadshaaeqaaOGaeyOeI0% YaaabCaeaacqGHciITcaGGVaGaeyOaIyRaamiEamaaBaaaleaacaWG% Pbaabeaakiabeo8aZnaaBaaaleaacaWGPbaabeaakiaacIcacaWG1b% WaaSbaaSqaaiaadIhadaWgaaadbaGaamyAaaqabaaaleqaaOGaaiyk% aiabgUcaRaWcbaGaamyAaiabg2da9iaaigdaaeaacaWGobaaniabgg% HiLdGccaWGMbGaaiikaiaadwhacaGGSaGaamyDamaaBaaaleaacaWG% 0baabeaakiaacMcacaqGGaGaeyypa0Jaaeiiaiaaicdaaeaaaeaaae% aaaeaacqaH7oaBcaqGGaGaeyyzImRaaeiiaiaaicdacaqGGaGaaiik% aiaadIhacaGGSaGaamiDaiaacMcacqGHiiIZcqGHPoWvcaqGGaGaae% iEaiaabccacaGGOaGaaGimaiaacYcacaWGubGaaiykaaqaaaqaaaqa% aaqaaiabgM6axjaabccacaqG9aGaaeiiaiaabggacaqGGaGaaeizai% aab+gacaqGTbGaaeyyaiaabMgacaqGUbGaaeiiaiaabMgacaqGUbGa% aeiiaiabl2riHoaaCaaaleqabaGaamOBaaaakiaacYcaaaaa!879A!\[\begin{array}{l}u_{tt} - \lambda \Delta u_t - \sum\limits_{i = 1}^N {\partial /\partial x_i \sigma _i (u_{x_i } ) + } f(u,u_t ){\rm{ }} = {\rm{ }}0 \\\\\\\\\lambda {\rm{ }} \ge {\rm{ }}0{\rm{ }}(x,t) \in \Omega {\rm{ x }}(0,T) \\\\\\\\\Omega {\rm{ = a domain in }}^n , \\\end{array}\]with various boundary and initial conditions on u(x, t). The case >0 corresponds to a nonlinear Voigt model (for nonlinear). The case =0, N=1 and f(u, u ₁ )=|u ₁ | sgn u ₁ , 0<<1 with nonhomogeneous boundary conditions corresponds to the motion of a linearly elastic rod in a nonlinearly viscous medium. The method followed is the Galerkin method.

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Résumé En suivant la méthode de Gaberkin, les auteurs ont étudié le problème de l'existence, de l'unicité et du comportement asymptotique lorsque t des solutions des équations d'état des ondes visco-élastiques, pour diverses conditions initiales et aux limites de U (x, t). On analyse les cas auxquels correspondent des valeurs positives (modèle non linéaire de Voigt) ou nulle du paramètre, ce dernier cas étant représentatif du mouvement d'un barreau élastique linéaire dans un milieu visqueux non linéaire, monyennant l'adoption de diverses conditions aux limites.

     

Phenolic Compounds of Cereals and Their Antioxidant Capacity

Phenolic compounds play an important role in health benefits because of their highly antioxidant capacity. In this review, total phenolic contents (TPCs), phenolic acid profile and antioxidant capacity of the extracted from wheat, corn, rice, barley, sorghum, rye, oat, and millet, which have been recently reported, are summarized. The review shows clearly that cereals contain a number of phytochemicals including phenolics, flavonoids, anthocyanins, etc. The phytochemicals of cereals significantly exhibit antioxidant activity as measured by trolox equivalent antioxidant capacity (TEAC), 2,2-diphenyl-1-picrylhydrazyl radical scavenging, reducing power, oxygen radical absorbance capacity (ORAC), inhibition of oxidation of human low-density lipoprotein (LDL) cholesterol and DNA, Rancimat, inhibition of photochemilumenescence (PCL), and iron(II) chelation activity. Thus, the consumption of whole grains is considered to have significantly health benefits in prevention from chronic diseases such as cardiovascular disease, diabetes, and cancer because of the contribution of phenolic compounds existed. In addition, the extracts from cereal brans are considered to be used as a source of natural antioxidants.     

Investigation of the decomplexation of polyamide/CaCl2 complex toward a green,nondestructive recovery of polyamide from textile waste

The ‘circular economy’ concept envisages deriving the maximum value out of resources and reducing waste to a minimum. In textiles, that includes the recovery of fiber materials out of used clothing and reusing them in the construction of new clothes. Processes such as mechanical separation, depolymerization treatment, and selective dissolutions of individual polymers are applied. We investigate the approach of selective nondestructive dissolution and recovery of polyamide fiber from mixed textile waste by using the solvent system CaCl₂/ethanol/water (CEW) based on complexation and decomplexation of polyamide (PA). The results show that PA is precipitated and decomplexed by simple addition of water and a substantial amount of previously incorporated calcium by complexation, is removed. The recovered polyamide shows properties similar to pristine polyamide. Investigation on a mixed textile waste model of polyamide/wool demonstrates that CEW treatment can successfully separate different fiber materials. The nondestructive approach in dissolving PA using CEW, clearly shows the benefit, that PA fiber can be separated by controlled complexation/decomplexation without degradation, thus avoiding the repolymerization step. Furthermore, the solvent system is made of abundantly available materials that are inexpensive and used widely in industrial-scale operations. Thus, the concept will make significant contribution to a green textile recycling approach.