Preparation and Characterization of BaxSr1-x, TiO3 Thin Films by a Sol-Gel Technique

Barium strontium titanate, (Ba_x,Sr_1-x TiO₃, thin films of various compositions were prepared by a sol-gel method. Solutions consisting of acetate powders and titanium IV isopropoxide in a mixture of acetic acid and ethylene glycol were spin-coated onto silicon and platinum-coated silicon substrates. Processing parameters were optimized to develop stable solutions which yielded films with relatively low crystallization temperatures. It was determined that ethylene glycol was a necessary component of the solution to increase stability to precipitation and to decrease the crystallization temperature of the films. The grain size of the films varied with annealing temperature and atmosphere and directly affected the dielectric properties. A dielectric constant of 400 and a dissipation factor of 0.04 were measured at 1 kHz for (Ba_0.8,Sr_0.2) TiO₃ films heated to 700°C for 1 h with a thickness of approximately 400 nm. Films of this composition maintained low leakage current densities for extended time periods when measured at an applied field of 75 kV/cm.     

Spin-Based Quantum Dot Quantum Computing in Silicon

The spins of localized electrons in silicon are strong candidates for quantum information processing because of their extremely long coherence times and the integrability of Si within the present microelectronics infrastructure. This paper reviews a strategy for fabricating single electron spin qubits in gated quantum dots in Si/SiGe heterostructures. We discuss the pros and cons of using silicon, present recent advances, and outline challenges. PACS: 03.67.Pp, 03.67.Lx, 85.35.Be, 73.21.La     

Review of phenotypic diversity formulations for diagnostic tool

Practitioners often rely on search results to learn about the performance of a particular optimizer as applied to a real-world problem. However, even the best fitness measure is often not precise enough to reveal the behavior of the optimizer's added features or the nature of the interactions among its parameters. This makes customization of an efficient search method a rather difficult task.The aim of this paper is to propose a diagnostic tool to help determine the impact of parameter setting by monitoring the exploration/exploitation balance (EEB) of the search process, as this constitutes a key characteristic of any population-based optimizer. It is common practice to evaluate the EEB through a diversity measure. For any diagnostic tool developed to perform this function, it will be critical to be able to certify its reliability. To achieve this, the performance of the selected measure needs to be assessed, and the EEB framework must be able to accommodate any landscape structure. We show that to devise a diagnostic tool, the EEB must be viewed from an orthogonal perspective, which means that two diversity measures need to be involved: one for the exploration axis, and one for the exploitation axis. Exploration is best described by a genotypic diversity measure (GDM), while exploitation is better represented by a phenotypic convergence measure (PCM). Our paper includes a complete review of PCM formulations, and compares nearly all the published PCMs over a validation framework involving six test cases that offer controlled fitness distribution. This simple framework makes it possible to portray the underlying behavior of phenotypic formulations based on three established requirements: monotonicity in fitness varieties, twinning, and monotonicity in distance. We prove that these requirements are sufficient to identify phenotypic formulation weaknesses, and, from this conclusion, we propose a new PCM, which, once validated, is shown to comply with all the above-mentioned requirements. We then compare these phenotypic formulations over three specially designed fitness landscapes, and, finally, the new phenotypic formulation is combined with a genotypic formulation to form the foundation of the EEB diagnostic tool. The value of such a tool is substantiated through a comparison of the behaviors of various genetic operators and parameters.     

Total anomalous pulmonary venous connection in neonates and young infants: repair in the current era

Total anomalous pulmonary venous connection has been one of the more challenging congenital heart defects in newborns and young infants despite improvements in surgical technique, cardiac anesthesia, neonatal myocardial preservation, and postoperative care. Since 1981, 30 patients with total anomalous pulmonary venous connection have undergone primary total correction. Mean age at operation was 28 +/- 6 days and mean weight, 3.3 +/- 0.7 kg. Essential features of the surgical approach in these small patients included early surgical intervention, profound hypothermia with total circulatory arrest, cardioplegic myocardial preservation, and a wide posterior anastomosis. Operative mortality was 13% +/- 6%. All four deaths were in patients having emergency operation within 24 hours of the surgical consult and requiring ventilator support preoperatively. The mean follow-up is 47 +/- 7 months. There have been two late deaths, and the 7-year survival rate is 79% +/- 8%. There have been two reoperations, and 91% +/- 6% of the patients are reoperation free at 7 years. Only 1 of the 24 surviving patients is symptomatic. Growth in survivors is closely monitored. The height growth percentile is less than 5% in 15% +/- 8% of survivors and the weight growth percentile, less than 5% in 17 +/- 8%. During the past decade, with a consistent surgical approach to neonates and infants with total anomalous pulmonary venous connection, it has been possible to achieve low early mortality, low attrition, and excellent late results.     

Synthesis of Some Polymer Models of Potentially Biologically Active Compounds

2-(p-Styryl)-4-carboxyquinoline (vinyl cincophen), its 6-methyl and 6,7-benzo derivatives, p-formylstyryl thiosemicarbazone, and p-vinyl-DL-threo-β-phenylserine were synthesized and polymerized.     

Nonrigid geometric metrology using generalized numerical inspection fixtures

Freeform surfaces have become an integral part of the automobile and aerospace industries. The parts with a very thin wall in proportion to their size are referred to as nonrigid (or flexible) parts. Generally, for the geometric inspection of such flexible parts, special inspection fixtures, in combination with coordinate measuring systems (CMM), are used because these parts may have different shapes in a free state from the design model due to dimensional and geometric variations, gravity loads and residual strains. A general procedure to eliminate the use of inspection fixtures will be developed. Presented methodology is based on the fact that the interpoint geodesic distance between any two points of a shape remains unchangeable during isometric deformation. This study elaborates on the theory and general methods for the metrology of nonrigid parts. We will merge existing technologies in metric and computational geometry, statistics, and finite element method to develop a general approach to the geometrical inspection of nonrigid parts.     

Shear Lag and Effective Breadth in Rectangular Plates with Material Orthotropy. Part 2: Typical Results of Parametric Studies

In this, the second of a two-part series of articles on boundary-shear solutions applied to the phenomenon of shear lag in orthotropic rectangular plates, the salient results of parametric studies conducted on this problem are presented and discussed.     

Single Fourier series solutions for rectangular plates under in-plane forces, with particular reference to the basic problem of colinear compression. Part 1: Closed-form solution and convergence study

This paper considers certain types of classical plane-stress problems, concentrating on their solutions by means of the simple, although usually approximate, single Fourier series technique. While this approach is well known, no systematic studies based on it seem to have been carried out in the past. Such a study is presently undertaken with reference to the problem of a colinearly compressed rectangular plate so as to reach some conclusions regarding (ordinary) convergence rates for stresses, as well as to investigate possible ways of improving convergence. In addition, a truly closed-form solution for the single Fourier series technique is given (thus bypassing the need to repeatedly solve systems of equations) which encompasses completely arbitrary normal and/or shear loading along two opposite edges. In a follow-up paper (Tahan et al., Thin Walled Structures 17(1) (1993)), the present findings will be used to conduct an investigation of the stress distribution in a plate subject to colinear compression.     

Contents

With deregulation and the privatization processes in progress, there were high expectations that the private sector would invest in generation and transmission, but this did not occur. The shortage of generation was exacerbated by drought conditions that deteriorated reservoir levels. These circumstances led to an increase of the risk of an energy shortage. Plans are now being implemented that take measures to assure a proper balance of generation and consumption in the near and long-term future.