Online help-seeking in communities of practice: Modeling the acceptance of conceptual artifacts

Interactive online help systems are considered to be a fruitful supplement to traditional IT helpdesks, which are often overloaded. They often comprise user-generated FAQ collections playing the role of technology-based conceptual artifacts. Two main questions arise: how the conceptual artifacts should be used, and which factors influence their acceptance in a community of practice (CoP). Firstly, this paper offers a theoretical frame and a usage scenario for technology-based conceptual artifacts against the theoretical background of the academic help-seeking and CoP approach. Each of the two approaches is extensively covered by psychological and educational research literature, however their combination is not yet sufficiently investigated. Secondly, the paper proposes a research model explaining the acceptance of conceptual artifacts. The model includes users' expectations toward the artifact, perceived social influence and users' roles in the CoP as predictors of artifact use intention and actual usage. A correlational study conducted in an academic software users' CoP and involving structural equations modeling validates the model, suggesting thus a research line that is worth further pursuing. For educational practice, the study suggests three ways of supporting knowledge sharing in CoPs, i.e. use of technology-based conceptual artifacts, roles and division of labor, and purposeful communication in CoPs.     

Two-axis flexure hinges with axially-collocated and symmetric notches

The paper introduces a new class of two-axis flexure hinges with axially-collocated and symmetric notches as an alternative to the existing flexure designs with serially-disposed notches. A generic formulation is developed in terms of the geometric curves defining the two notches which includes assessing the capacity of rotation, precision of rotation, sensitivity to parasitic effects, stress values, motion efficiency and shearing effects by means of compliance factors. Closed-form compliance equations are derived for a two-axis flexure hinge that is defined by two non-identical parabolic profiles. The analytical model predictions are confirmed by finite element data. A numerical comparison is made of the parabolic flexure with a constant rectangular cross-section flexure hinge in terms of several performance criteria.     

Liquid crystalline polymers, 9. Synthesis and thermal behavior of some oligomers containing a diethyletheric spacer

Polyethers based on bis(2-chloroethyl) ether and various bisphenols were obtained using a phase transfer catalysis technique in a liquid/liquid system. 4,4′-Dihydroxyazobenzene, 4,4′-dihydroxybiphenyl, bisphenol A, 2,7-dihydroxynaphthalene and 4,4′-dihydroxydiphenyl) sulfide were used. Only the polymers with azobenzene and biphenyl units exhibited mesophases, since the others have semi-crystalline or amorphous structures. The polymers were characterized by ¹H NMR, DSC and optical microscopy in polarized light. The molecular weights of the samples were low, situated in the oligomeric domain. The various transfer rates of the bisphenols from the aqueous to the organic phase, in some cases, led to very different copolymerization ratios as compared to the feed ratios. The LC polymers exhibited monotropic mesophases, probably for conformational reasons. A comparison between similar polyether structures containing the diethyletheric spacer and an oxetanic one was effectuated.     

The effect of poly[styrene‐b‐(ethylene‐co‐butylene)‐ b‐styrene] on dielectric,thermal, and morphological characteristics of polypropylene/silica nanocomposites

The effect of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) copolymer on the thermal and dielectric properties of polypropylene (PP)—nanosilica (NS) composites in relation with morphological aspects revealed by atomic force microscopy (AFM) was investigated in this article. SEBS hindered the crystallization process of PP in PP/NS composites, leading to a smaller degree of crystallinity and lower perfection of crystalline structure. Broader lamellar thickness distribution was obtained in nanocomposites containing SEBS. Almost two times higher dielectric loss as compared to PP reference and two relaxation processes were detected in ε_r ^′′(f) curves of nanocomposites. The first peak, in the same frequency domain as for the references, was assigned to α‐relaxation of polymer components together with interfacial polarization. The relaxation time follows the Arrhenius law with an activation energy of 80–90 kJ/mol. For the second process, the temperature dependence of the relaxation times obeyed the VFT equation. The dielectric changes following the incorporation of SEBS support its tendency to hinder the motional processes in PP, in accordance with DSC results. A smooth transition from a phase rich in SEBS to one containing mainly PP was detected in the AFM image of the composite with the larger amount of SEBS, emphasizing the good compatibility at the PP/SEBS interface. POLYM. ENG. SCI., 53:2081–2092, 2013. © 2013 Society of Plastics Engineers     

Assessment of the availability of agricultural and forest residues for bioenergy production in Romania

This paper provides a resource-based assessment of availability of biomass resources for energy production in Romania, at NUTS-3 level. The estimation of available biomass includes the residues generated from crop production, pruning of vineyards and orchards, forestry operations and wood processing. The estimation of crop residue availability considers several site-specific factors such as crop yields, multi-annual yield variation, environmental constraints and competitive uses. The evaluation of agricultural residues was based on specific residue to product ratios, depending on crop type and crop yield. An estimate of pruning residues is proposed, based on current orchard and vineyard areas and specific ratios of residues. Woody biomass considers forest and forestry residues (including firewood) and wood processing by-products, taking into account the type and share of the unused part of the tree biomass and technical and economic aspects, including availability and competitive use. The amount of agricultural and forest residues available for bioenergy in Romania was estimated at 228.1 PJ on average, of which 137.1 PJ was from annual crop residues, 17.3 PJ residues from permanent crops and 73.7 PJ/year from forestry residues, firewood and wood processing by-products. The biomass availability shows large annual and spatial variations, between 135.6 and 320.0 PJ, due to the variation in crop production and forestry operations. This variation, which is even larger at the NUTS-3 level, if not properly considered may result in shortages in biomass supply in some years, when biomass is available in a lower amount than the average.     

Revival by automation of induction generator for distributed power systems, in Romanian academic research

The paper approaches the half-century history and the main research results of the academic staff and researchers from “Politehnica” University of Timisoara (Universitatea “Politehnica” Timisoara—UPT) and their collaboration with the academic, research and production environment concerning the use of induction machine as power supply in microhydro plants and windmills in particular; from among these collaborators we mention: The Romanian Academy—Timisoara Branch, The Institute for Automation IPA—Timisoara Branch, The Research and Modernization Institute for Energetics ICEMENERG Bucharest, The National Institute for Heat Engines INMT Bucharest, The Machine Construction Works UCMR—Resita, “Electroputere” Works—Craiova and “Electromotor” Works—Timisoara.The paper aims at presenting the original research results at UPT against the background of general research from all over the world focused on revival the induction generator by automation.     

Optical emission studies of the gas phase during the silicon suboxide deposition by reactive r.f. magnetron-sputtering

Silicon oxide (a-SiO) is one of the most used silicon-based materials in optoelectronic and microelectronic technology. It is well-known that the electronic properties are linked to the material structure, which depends on the deposition technique and on the details of the deposition. Silicon suboxide (a-SiO_x 0 < x < 2) layers were prepared by r.f. magnetron-sputtering from a polycrystalline silicon target in a well defined oxidation environment.Optical Emission Spectroscopy (OES) was employed to study the plasma used in SiO_x depositions. Theoretical calculations performed in the frame of electron impact excitation mechanism for argon and atomic oxygen corroborated with electron impact dissociation of the molecular oxygen have shown the strong influence of the electron temperature on the rate coefficients of photons' production.Correlation functions between the OES signals assigned to silicon and oxygen atoms from plasma (gas phase) and the SiO_x layer composition (infrared and energy dispersive X-ray investigated) have been found. Based on these functions, the OES plasma monitoring is proposed as a tool to control in-situ and in direct time the SiO_x layer composition.     

Influence of octyl substituted octakis(dimethylsiloxy)octasilsesquioxane on the morphology and thermal and mechanical properties of low density polyethylene

Low density polyethylene (LDPE) was melt blended with octyl substituted octakis(dimethylsiloxy)octasilsesquioxane (AS8) prepared in high yield by hydrosilylation of octene with octakis(hydrodimethylsiloxy)octasilsesquioxane. Two procedures were used to incorporate AS8 into LDPE at nanolevel and their efficiency was investigated by X‐ray diffraction (XRD), scanning electron microscopy, atomic force microscopy (AFM), differential scanning calorimetry, thermogravimetry and mechanical characterization. A slight increase of crystallite mean dimensions was observed by XRD in both types of LDPE‐AS8 composites compared with neat LDPE. Better AS8 dispersion was observed by AFM in the composite prepared by the first procedure and the increase of both tensile strength and elongation at break in this composite confirmed the nanolevel dispersion and interface improvement in this case. AS8 influence in the final stages of polyethylene fracture was illustrated by AFM of elongated tensile specimens and a new mechanism of AS8 action was suggested. An interesting behavior consisting of simultaneous improvement of elastic modulus, strength and ductility was detected in the low range of polyhedral oligomeric silsesquioxane concentration in LDPE (0.5 wt%). © 2013 Society of Chemical Industry     

Component-based analysis of embedded control applications

The widespread use of embedded systems requires the creation of industrial software technology that will make it possible to engineer systems being correct by construction. That can be achieved through the use of validated (trusted) components, verification of design models, and automatic configuration of applications from validated design models and trusted components. This design philosophy has been instrumental for developing COMDES—a component-based framework for distributed embedded control systems. A COMDES application is conceived as a network of embedded actors that are configured from instances of reusable, executable components—function blocks (FBs). System actors operate in accordance with a timed multitasking model of computation, whereby I/O signals are exchanged with the controlled plant at precisely specified time instants, resulting in the elimination of I/O jitter. The paper presents an analysis technique that can be used to validate COMDES design models in SIMULINK. It is based on a transformation of the COMDES design model into a SIMULINK analysis model, which preserves the functional and timing behaviour of the application. This technique has been employed to develop a feasible (light-weight) analysis method based on runtime observers. The latter are conceived as special-purpose actors running in parallel with the application actors, while checking system properties specified in Linear Temporal Logic. Observers are configured from reusable FBs that can be exported to SIMULINK in the same way as application components, making it possible to analyze system properties via simulation. The discussion is illustrated with an industrial case study—a Medical Ventilator Control System, which has been used to validate the developed design and analysis methods.     

Impact evaluation of the polarization diversity over the LTE transmission mode one

The article focuses on the design, measurement, and simulation of a new Long Term Evolution (LTE) downlink mode in which the polarization diversity replaces the spatial diversity at the user equipment (UE). The proposed system enables the analysis of the circularly polarized (CP) antenna over the multipath SISO channel. The purpose of the article is to design a compact LTE SISO system capable of providing comparable performance to the one with spatial diversity (SIMO 1 × 2). In this respect, the entire process is described from antenna designing and measurements to the final stage of integration and simulation. The results indicate the necessity of taking into account the effect of the polarization diversity to keep up the data rate for the small LTE devices when spatial diversity is not an option. The new system proves valuable to evolve toward new downlink modes suitable especially for tiny devices yet capable of achieving high data rates. The article envisages some new processing stages at the UEs as well as at the base station (eNodeB) for CP usage. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:547–558, 2016.