Role of polymeric matrices in improving wear resistance of irradiated FRP composites

The present paper reports the effect of different resin matrices on the abrasive wear behaviour of woven fabric composites based on them. Three different resin systems and a common glass fibre reinforcement were used in the present study. It was found that polymer composites based on the epoxy resin system show maximum wear resistance. This has been attributed to the fact that fibre-matrix interfacial bonding is very strong between the glass fibres and epoxide resin. The bonding resists composite failure and improves on irradiation.     

FUNGIBILITY OF MATCHING CONDITIONAL GRANTS TO LOCAL GOVERNMENTS

Abstract. This article finds that about 31 cents of every dollar of matching conditional grants to upper-tier municipalities in Ontario, Canada were converted into fungible resources during the period 1977–1992. As a result these grants did not stimulate local economic activities, as desired by the donor. In particular, the expenditure response to these grants is reduced by almost 25 percent due to fungibility. The implied fungibility ratio is also found to vary across municipalities and service categories. Fungibility of grants is 15 percent higher in the transportation sector than in the health sector and in both sectors the estimated ratio is lower than the corresponding ratio based on U.S. data. It is further found that a municipality, with a regional structure, larger size, and lower proportion of statutory expenditure, tends to convert larger amounts of grants into fungible resources than others.     

Computer-aided optimal design of a polar-based template digitizer-NC contouring system—II. Dynamic analysis

This paper presents the computer-aided optimal design of a template digitizer-NC contouring system which utilizes a set of polar coordinates. The system can operate both as a copying machine or as a numerical control (NC) machine. Part I of the paper describes the proposed system and its salient features. It also analyzes the contouring error due to the incremental approximation of the contour. This error is dependent on the relative location of the contour pole from the machine pole. An objective function relating the area error to the position of the contour is derived and an optimization procedure to minimize this error is outlined. Test results of an attempt to locate the poles of three test contours for minimum error are then presented.     

Sampling Errors in the Estimation of Peak Wind-Induced Internal Forces in Low-Rise Structures

Peak values in time histories of wind effects may be obtained by using the entire information inherent in the time series of the wind effect, a method entailing the estimation of the probability distribution of the peak through the application of the classical Rice procedure extended for non-Gaussian time histories. We present estimates of the sampling errors inherent in this method. These are needed for structural reliability calculations and for decisions on the requisite length of wind tunnel pressure records, especially for database-assisted design. If based on the analysis of 1-h-long records generated by Monte Carlo simulation, typical sampling errors in the estimation of peaks of time histories corresponding to windstorms of 1-h duration are about 5%. If based on 30- or 20-min records, they are about 1.5 times or twice as large, respectively. Consideration of the sampling errors in reliability calculations entails an estimated increase in the requisite safety margins with respect to wind loading of roughly 2, 3, and 5% if 1-h, 30-min, or 20-min records are used, respectively.     

Wind speed estimation uncertainties: effects of climatological and micrometeorological parameters

To achieve structures that are risk-consistent, structural reliability methods must be used that account for uncertainties with respect to the relevant parameters affecting the estimation of wind effects. In this paper, we obtain measures of uncertainties in the estimation of the wind speeds upwind of structures. These uncertainties are due to incomplete knowledge with respect to the relevant extreme climatological and micrometeorological parameters. Advances in wind engineering and improvements in computational capabilities now make it possible to improve upon earlier estimates available in the literature. The work presented in this paper is a phase of a broader NIST project aimed at developing user-friendly software for the estimation of probabilities of failure of low-rise structures subjected to wind loads.     

Influence of silicoating,etching and heated glaze treatment on the surface of Y-TZP and its impact on bonding with veneering ceramic

The study aimed to investigate the influence of surface treatments of Y-TZP on its topography and their impact on shear bond strength (SBS) of Y-TZP to veneering porcelain. Thirty-four zirconia cubes (Cercon) (10 × 10 × 10 mm³) were divided randomly into 3 groups (n = 11) according to the different surface treatments, Silica Coating (SC); Hot Solution Etching (HE); and Heat Treatment after porcelain glaze and powder application (GP). Porcelain application (IPs e.max) was performed after surface treatment using a standardized technique. Porcelain application (Ceramco-3) was also performed on 10 metal cubes (I BOND 2) as controls (MC). Specimens were subjected to thermocycling (5–55 °C, 20,000 cycles) followed by SBS testing in a universal testing machine. Surface topography was assessed by scanning electron microscopy and surface roughness (Image J). SC developed significantly higher SBS (42.10 ± 5.84 MPa) of Y-TZP to veneering ceramics compared to treatment by HE (24.0 ± 6.4 MPa), GP (23.30 ± 4.72), and the MC (29.3 ± 5.4 MPa) control (p < 0.05). SBS among HE, GP and MC specimens was comparable (p > 0.05). Y-TZP specimens treated with SC and HE showed high surface roughness compared to GP. Silicoating of Y-TZP prior to veneering can potentially reduce the high failure rates of zirconia-based restorations by enhancing the chemical bond between the core and the veneer materials.     

Use of social network sites among depressed adolescents

Social network sites (SNSs) are relatively new phenomena, and the relationship between SNSs and psychopathology remains unclear. The purpose of this study was to evaluate the type of SNSs depressed adolescents use and the incidence of depressive disclosure on SNSs among them. The study was designed to be cross-sectional. The sample consisted of 53 adolescents diagnosed with depressive disorder, as confirmed by K-SADS-PL, and 55 non-depressed adolescents. The Children’s Depression Inventory, Social Anxiety Scale and Social Network Use Questionnaire were administered. The primary finding was that the amount of time spent on the Internet and on SNSs was significantly higher among depressed adolescents than non-depressed adolescents. Additionally, depressed adolescents reported significantly higher disclosure of anhedonia, worthlessness, guilt, loss of concentration, irritability and thoughts of suicide on SNSs. The intensity of the depression sharing was significantly higher in the depressed group. Depressed young people use social networks to express their symptoms. Adolescents’ disclosure on social networks may be able to guide relatives, friends and mental health professionals.     

Neuro-heuristic computational intelligence for solving nonlinear pantograph systems

We present a neuro-heuristic computing platform for finding the solution for initial value problems (IVPs) of nonlinear pantograph systems based on functional differential equations (P-FDEs) of different orders. In this scheme, the strengths of feed-forward artificial neural networks (ANNs), the evolutionary computing technique mainly based on genetic algorithms (GAs), and the interior-point technique (IPT) are exploited. Two types of mathematical models of the systems are constructed with the help of ANNs by defining an unsupervised error with and without exactly satisfying the initial conditions. The design parameters of ANN models are optimized with a hybrid approach GA–IPT, where GA is used as a tool for effective global search, and IPT is incorporated for rapid local convergence. The proposed scheme is tested on three different types of IVPs of P-FDE with orders 1–3. The correctness of the scheme is established by comparison with the existing exact solutions. The accuracy and convergence of the proposed scheme are further validated through a large number of numerical experiments by taking different numbers of neurons in ANN models.     

Fabrication of Nanoporous Alumina Ultrafiltration Membrane with Tunable Pore Size Using Block Copolymer Templates

Control over nanopore size and 3D structure is necessary to advance membrane performance in ubiquitous separation devices. Here, inorganic nanoporous membranes are fabricated by combining the assembly of cylinder‐forming poly(styrene‐block‐methyl methacrylate) (PS‐b‐PMMA) block copolymer and sequential infiltration synthesis (SIS). A key advance relates to the use of PMMA majority block copolymer films and the optimization of thermal annealing temperature and substrate chemistry to achieve through‐film vertical PS cylinders. The resulting morphology allows for direct fabrication of nanoporous AlO_x by selective growth of Al₂O₃ in the PMMA matrix during the SIS process, followed by polymer removal using oxygen plasma. Control over the pore diameter is achieved by varying the number of Al₂O₃ growth cycles, leading to pore size reduction from 21 to 16 nm. 3D characterization, using scanning transmission electron microscopy tomography, reveals that the AlO_x channels are continuous through the film and have a gradual increase in pore size with depth. Finally, the ultrafiltration performance of the fabricated AlO_x membrane for protein separation as a function of protein size and charge is demonstrated.     

Prediction of surface tension of naphtha reformate using UNIFAC

The surface tension of naphtha reformate cuts (60?170°C) were predicted using a modified UNIFAC group contribution method. The naphtha was distilled into eleven cuts of 10°C intervals to obtain narrow boiling range cuts. The surface tensions were determined in the temperature range 10?50°C and were compared with predicted values. A standard deviation of 5.9% was found using this method, versus 3.7% when the corresponding states method was used over the temperature range of 60?170°C. However, for the higher temperature range of 140?170°C, this method gave a standard deviation of 2.9% versus 7.6% for the other method.