Temperature dependant structural and electrical properties of ZnO nanowire networks

In this paper, we report a successful growth of zinc oxide nanowire networks by simple thermal evaporation process using metallic zinc powder in the presence of oxygen. The morphological investigations of the synthesized nanowire networks are conducted by using field emission scanning electron microscopy (FESEM) which reveals that the grown products are in high-density over the whole substrate surface and possessing nanowire networks like structures. The structural and compositional properties of the grown nanowire networks are analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), respectively which confirm that the synthesized products are well-crystalline, with wurtzite hexagonal phase ZnO. The as-grown ZnO nanowire networks grown on silicon substrate are utilized to fabricate n-ZnO/p-Si heterojunction diode and presented in this paper. The I-V characteristics of the fabricated heterojunction diode at different temperatures (77 K-477 K) are also investigated. High values of quality factor, which are obtained from this study, indicate a non-ideal behavior of the fabricated device. The mean barrier height of -0.84 eV is also estimated and presented in this paper.     

On Estimating a Constant Stress Life Test Model Using Time-Censored Data from the Linear Failure Rate Distribution

Strength of Materials - In this paper, a constant stress partially accelerated life test model is considered and investigated using type-I censored data from the linear failure rate distribution....     

Congenital diaphragmatic hernia: experience with preoperative stabilization and delayed surgery without ECMO and inhaled nitric oxide

Despite many advances in the management of congenital diaphragmatic hernia (CDH), the condition carries a mortality rate of 40-50% usually consequent to pulmonary hypoplasia and/or persistent pulmonary hypertension. Several centers have reported improved survival with preoperative stabilization and delayed surgery, which is now an accepted method of management. This is a retrospective analysis of all neonates with respiratory distress at birth due to CDH who were treated at our institution with neither extracorporeal membrane oxygenation nor nitric oxide being used. The medical records of all neonates with CDH and respiratory distress at birth who were treated at this institution from August 1, 1992 through March 1, 1997 were reviewed. There were 21 patients, 11 male and 10 female. There were 17 full-term and 4 premature infants; two premature infants at 30 and 34 weeks' gestation were not resuscitated because of severe associated congenital anomalies. Surgery was performed from 5 to 144 hr (mean 45 hr) in 18 infants. One infant died during preoperative stabilization from severe pulmonary hypoplasia and pulmonary hypertension and one infant died postoperatively from the same conditions. Seventeen of 19 infants (89.5%) survived and were discharged home. Three infants (17.6%) who failed to thrive due to severe gastroesophageal reflux (GER) required fundoplication. Eleven infants (64.7%) who had sepsis proven by blood culture responded satisfactorily to appropriate antibiotics. Preoperative stabilization and delayed surgery has been a satisfactory form of management in our series. The significant complication was sepsis, which must be addressed.     

Stable Wollastonite-Cuspidine Glass-Ceramic Using Inexpensive Raw Materials

Transparent glasses within the K₂O-CaO-SiO₂-F composition were prepared. The influence of CaF₂, TiO_2, Li₂O, Li₂O-TiO₂ and CeO₂ additions on the crystallization of the parent glass has been investigated. Crystallization process gave wollastonite and cuspidine as the major phases whereas; xontolite and traces of miserite were developed as subordinate ones. Wollastonite was developed alone in the temperature range of 800 °C-1100 °C in Li₂O-containing the base glass. Wollastonite and cuspidine were stable in the 800-1100 °C range in Li₂O+TiO₂-containing samples and within the 900 °C-1100 °C range in CaF₂ and CeO₂ containing samples. The microstructure of the Li₂O-containing glass-ceramic showed an interlocked needle in nano-scale wollastonite crystals, while fibrous textures were developed in all other crystallized samples at 1000 °C. The thermal expansion coefficient value of the crystallized samples was between 7.596 to 8.708 X10 ^?6 °C^?1 (20-500 °C) and the higher values reflect the increase of crystallization content of cuspidine and even the traces of miserite. This glass-ceramic is thought to be important in dental laboratories.     

Hollow fibers for seawater desalination from blends of PVDF with different molecular weights: Morphology,properties and VMD performance

In this work, different PVDF grades were used for producing hollow fibers for application in seawater desalination by membrane distillation (MD). In particular, PVDF Solef^® homopolymers, with increasing molecular weight and different crystallinity, were used, also in blend, for preparing polymeric dopes. The effect of PVDF molecular weight on the dope viscosity was investigated. Then, a group of six polymeric dopes, having the same additive composition and the same viscosity (about 7000 mPa s), but containing different PVDF types was selected. Spinning experiments were carried out under the same conditions to highlight the effect of PVDF type on the produced hollow fibers’ morphology and properties. It was evidenced that polymer concentration plays a major role in determining the final membrane morphology; in particular, the formation of macrovoids is more affected by polymer concentration than dope viscosity. Fibers’ mechanical properties, porosity and pore size were found to be also strongly affected by polymer concentration. Finally, the produced hollow fibers were tested in a membrane distillation unit working under vacuum (VMD). Tests were carried out both feeding pure water and synthetic seawater. It was found that VMD performance, both in terms of flux (J) and solute separation factor (α), being connected to fibers’ morphology and porosity, is also clearly dependent on polymer concentration.     

Adapting k-means for supervised clustering

k-means is traditionally viewed as an algorithm for the unsupervised clustering of a heterogeneous population into a number of more homogeneous groups of objects. However, it is not necessarily guaranteed to group the same types (classes) of objects together. In such cases, some supervision is needed to partition objects which have the same label into one cluster. This paper demonstrates how the popular k-means clustering algorithm can be profitably modified to be used as a classifier algorithm. The output field itself cannot be used in the clustering but it is used in developing a suitable metric defined on other fields. The proposed algorithm combines Simulated Annealing with the modified k-means algorithm. We apply the proposed algorithm to real data sets, and compare the output of the resultant classifier to that of C4.5.     

Crystal plasticity simulations using discrete Fourier transforms

In this paper, we explore efficient representation of all of the functions central to crystal plasticity simulations in their complete respective domains using discrete Fourier transforms (DFTs). This new DFT approach allows for compact representation and fast retrieval of crystal plasticity solutions for a crystal of any orientation subjected to any deformation mode. The approach has been successfully applied to a rigid–viscoplastic Taylor-type model for face-centered cubic polycrystals. It is observed that the novel approach described herein is able to speed up the conventional crystal plasticity computations by two orders of magnitude. Details of this approach are described and validated in this paper through a few example case studies.     

A new technique of cancelation of the MOSFET leakage currents and parasitic capacitances

The paper presents a new topological technique to be used with MOSFET's to appreciably minimize their channel and drain leakage currents (by a factor of 4) and parasitic capacitances (about 10 times smaller). It also enhances the channel inversion rate due to the channel potential distribution and leads consequently to greater device-switching speeds (10 times greater). This technique will allow a smaller device to device separation without fearing from any proximity effects. It is based on the creation of a transverse lateral field which is oriented so as to keep the channel electrons within its potential-well and to reduce the channel to substrate depletion layer width. A detailed study and characterization of the new technique is comprised.     

Study of transient heat transfer in laminar flow of a non-newtonian fluid over a flat plate

Unsteady state heat transfer in laminar flow of a non-Newtonian fluid flowing over a flat plate is investigated. Effect of Prandtl number and the viscosity index on the transient is also studied. The steady state temperature profile obtained from the model agrees with the published results.     

Adhesion of cast metal alloy and lithium disilicate copings luted to different core build-up materials with self-adhesive resin cement

This study evaluated the shear bond strength of two coping materials (non-nickel chrome-based cast alloy and lithium disilicate ceramic (IPS Empress) to four different core foundation materials (resin composite, cast metal alloy, lithium disilicate, and dentin), luted with adhesive resin cement (RelyX Unicem). Specimens (N = 56) were fabricated and divided into eight groups (n = 7 per group). Each coping material was luted with self-adhesive resin cement (RelyX Unicem) to the core materials. Bond strength was measured in a Universal Testing Machine (0.5 mm/min). Data were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey’s HSD tests (alpha = 0.05). Both core (p = 0.000) and coping material type (p = 0.000) significantly affected the mean bond strength (MPa) values. Interaction terms were also significant (p = 0.001). The highest bond strength results were obtained when lithium disilicate was bonded to lithium disilicate (21.48) with the resin cement tested. Lithium disilicate in general presented the highest bond results when bonded to all core materials tested (16.55–21.38) except dentin (3.56). Both cast alloy (2.9) and lithium disilicate (3.56) presented the lowest bond results on dentin followed by cast-alloy-cast alloy combination (3.82).