Investigation of the Transition State in the Wear of Polyphenylene Sulfide Sliding Against Steel

The effect of sliding variables, including counterface roughness, sliding speed, and contact pressure, on the run-in state of wear and friction was studied. Sliding was performed in the pin-on-disk configuration with a polyphenylene sulfide (PPS) pin resting on the flat steel counterface. Some experiments were also run to study the effect of air cooling and heating. Optical microscopy and scanning electron microscopy were used to study the shape and size of the wear debris, worn pin surface, and the transfer film formed on steel counterfaces. It was found that friction and wear in the run-in state were significantly affected by the sliding variables studied and their influence was closely related to the development of a transfer film during the run-in state. If the transfer film developed during initial sliding, the coefficient of friction increased and wear rate decreased. The wear rate in the run-in state increased with the increase in initial counterface roughness and there was an optimal counterface roughness of 0.06 m Ra for minimum steady state wear rate. A higher applied load led to a higher wear rate in the run-in state but that was not the case with steady state wear rate.     

Project Oriented Problem Based Learning: A Wireless Sensor Network Perspective

Every nation rely on latest engineering technologies to foster in today’s technological era. Wireless Sensor Networks (WSNs) is one of the latest emerging technologies being the center of interest of today’s researchers. All the researchers work hard to produce quick deliverables through Research and Development (RandD) and by applying different learning pedagogues. Currently, the learning pedagogues in Engineering RandD are Project Based Learning and Problem Based Learning (PBL). Based on these pedagogues, this paper propose and implements a hybrid pedagogy called Project Oriented PBL (PO-PBL) which is time effective and result oriented learning pedagogy. It has resulted in providing impetus to RandD in WSNs. Further the proposed pedagogy is divided into two paradigms namely PO-PBL Macro Model and PO-PBL Micro Model. We observed that PO-PBL Macro Model results in optimal number of deliverables in time restricted manner over large scale. Moreover, we have also implemented PO-PBL Micro Model, compared it with PO-PBL Macro Model and propose PO-PBL Micro Model as basis for designing self-learning algorithm for WSNs devices.     

Use of low CaO unprocessed steel slag in concrete as fine aggregate

Steel slag, which is produced locally in great amounts, has a negative impact on the environment when disposed. Local steel slag has a low CaO content and has no pozzolanic activity.In this research, local unprocessed steel slag is introduced in concrete mixes. Various mixes with compressive strength ranging from 25 to 45 MPa are studied. The slag is used as fine aggregate replacing the sand in the mixes, partly or totally. Ratios of 0%, 15%, 30%, 50% and 100% are used.Depending on the grade of concrete, the compressive strength is improved when steel slag is used for low sand replacement ratios (up to 30%).When optimum values are used, the 28-day tensile strength of concrete is improved by 1.4–2.4 times and the compressive strength is improved by 1.1–1.3 times depending on the replacement ratio and the grade of concrete. The best results are obtained for replacement ratios of 30–50% for tensile strength and 15–30% for compressive strength.Therefore, the use of steel slag in concrete would enhance the strength of concrete, especially tensile strength, provided the correct ratio is used.     

Use of basalt in asphalt concrete mixes

One of the main reasons behind the appearance of early distresses in Jordan roads and the low surface skid resistance is the use of marginal quality limestone aggregate. Large quantities of good quality basalt are available in the Northeastern parts of Jordan. In this research, the possibility of improving the properties of local asphalt concrete mixes by replacing different portions of the normally used limestone aggregate by basalt was investigated. The replacement included total replacement of the limestone by basalt, replacing the coarse aggregate, and replacing the fine aggregate. Results showed that the optimal mix was the mix that had basalt coarse aggregate and limestone fine aggregate. In order to overcome the stripping potential of the optimal mix, 20% of the filler portion of the aggregate, material smaller than 0.075 mm, was replaced by lime. The optimal mix showed superiority, over the tested mixes, in all the evaluated properties, which were Marshall Stability, indirect tensile strength, stripping resistance, resilient modulus, dynamic creep, fatigue, and rutting.     

Compositional and structural analysis of RF magnetron sputtered La3+-modified PZT thin films

In the present work, we report the preparation of lanthanum-modified lead zirconate titanate (PLZT) thin films in pure perovskite phase by RF magnetron sputtering. For this purpose, a 3-in. diameter target of PLZT (8/60/40) was prepared by conventional solid-state reaction route. The chemical composition of PLZT target was determined using gravimetric analysis followed by UV–vis and flame atomic absorption spectrometry. Various deposition parameters such as target-to-substrate spacing, deposition temperature, post-deposition annealing temperature and time have been optimized to obtain PLZT films in pure perovskite phase. The films prepared in pure argon at 100 W RF power without external substrate heating exhibited pure perovskite phase after rapid thermal annealing (RTA) as confirmed by X-ray diffraction (XRD). Compositional analysis of the PLZT film was performed by secondary ion mass spectroscopy (SIMS) using PLZT target as standard sample. Depth profile of the film shows very good stoichiometric uniformity of all elements of PLZT.     

Optimization Models for Layout and Pipe Design for Storm Sewer Systems

Optimization models are developed for simultaneously determining the pipe layout and the pipe design for storm sewer systems. The pipe design process includes computation of commercial diameters, slopes, and crown elevations for the storm sewer pipes. The optimization models aim to minimize the total costs of the layout and the pipe design for most of system elements. The optimization models are formulated as a 0–1 Integer Nonlinear Programming problem and solved using the General Algebraic Modeling System without the use of heuristic models which were characteristic of all previous models for the simultaneous determine of the pipe layout and pipe design of sewer networks. The models are based upon two different optimization approaches: (1) considers one or more commercial diameters of pipe connecting two manholes and (2) considers only one commercial diameter in a pipe connecting two manholes. The commercial diameters, pipe slopes, crown elevations, and total costs of the storm sewer system were compared for the two approaches using an example that illustrates the savings in cost by allowing multiple pipe sizes. The two new optimization modeling approaches developed herein can simultaneously determine the minimum cost pipe design (commercial diameters, slopes, and crown elevations) and pipe layout of storm sewer systems and satisfy all design constraints.

     

Phytoplankton primary production, chlorophyll-a and nutrient concentrations in the water column of mountainous Lake Phewa, Nepal

The seasonal patterns of phytoplankton primary production, chlorophyll‐a concentration, cell number and several other limnological variables in Lake Phewa, located in the active monsoon zone in Central Himalaya, Nepal, were studied for a year beginning in April 2001. During the study period, the gross primary production and chlorophyll‐a concentrations were relatively low during the monsoon season. The phytoplankton cell number, represented by 24 genera, also fluctuated seasonally, but tended to increase in the pre‐ and post‐monsoon period. These results suggest that the monsoon plays a crucial role in the primary production and phytoplankton dynamics for Lake Phewa. Among the phytoplankton species, Microcystis aeruginosa, a representative species for eutrophic lakes, was the dominant phytoplankton. At the same time, however, it is clear that the lake is not yet heavily eutrophic. The present study suggests that the exchange of lake water during the monsoon season contributes to maintaining the health of the lake against further degradation. Nevertheless, the silt carried in the monsoon rain run‐off from the lake's catchment area suggests increasingly serious degradation problems for this small mountainous lake.     

Strain hardening equation and the prediction of tensile strength of rolled polymers

A number of thermoplastic polymers were tested in tension to investigate their strain hardening behavior. A strain hardening equation has been proposed in terms of the true stress, true strain and two constants σ_o and m. The three material constants, viz. σ_o m and the true fracture strain, are shown to be adequate to describe completely the material's nonlinear viscoelastic or the so-called “plastic” behavior. The true stress-strain data for the polymers rolled to varying amounts of cold-work fits the strain hardening plot of the unrolled material. The same strain hardening equation, therefore, applies to rolled materials as well. The procedure for predicting the tensile strength of rolled materials is given.     

Computationally efficient 2D beamspace matrix pencil method for direction of arrival estimation

In this paper, we propose a new 2-dimensional beamspace matrix pencil (2D BMP) method for direction of arrival (DOA) estimation of plane wave signals using a uniform rectangular array (URA). Based on some a priori information about DOA, the proposed method transforms the complex signal subspace in 2D matrix pencil (2D MP) method [Y. Hua, Estimating two-dimensional frequencies by matrix enhancement and matrix pencil, IEEE Trans. Signal Process. 40 (9) (1992) 2267–2280] into a real and reduced dimensional beamspace using the discrete Fourier transform (DFT) matrix transformation. Consequently, the computational complexity is reduced (several times) in comparison with 2D MP method. Computer simulations are provided to show that 2D BMP method gives comparable performance in terms of average mean square error of the estimated DOA with lesser floating point operations as compared to the existing (MP) methods.