General Nakagami approximation for sum of Ricean interferers

The statistical distribution of the sum of interfering signals at the receiving end of a wireless system is important to effect theoretical evaluation of its performances. The authors show that the sum of generic, narrow-band, Ricean interferers can be approximated by a single Nakagami interferer. A theoretical insight about this fact is given and some simulated results are shown to confirm the result     

Partially systematic rate-compatible punctured SCCCs

In this letter, we propose and compare some new rate-compatible serially concatenated convolutional code (SCCC) families. To obtain them, inner coded bits only are punctured. However, and this is the novelty proposed in the letter, the puncturing is not limited to inner parity bits, but extended also to inner systematic bits, thus obtaining high rate SCCCs (i.e., beyond the outer code rate). The two main applications of this technique are its use in hybrid Automatic-Repeat-reQuest/Forward-Error Correction (ARQ/FEC) schemes and to achieve unequal error protection (UEP) of an information sequence.     

Filler Debonding in Particulate-Filled Composites

The decrease in Young's modulus after mechanically loading particulate-filled composites serves as a measure of the fraction of debonded filler particles.

For composites based on plasticized rubber and fine ammonium perchlorate these effects have been studied for various stresses and for both varying amounts and particle sizes of the filler.

It was found that debonding filler particles during loading is strongly dependent both on the filler concentration and the particle size. Composites with small particles are characterized by higher stresses at which debonding takes place. The effects observed are supposed to be connected with different conditions of the stress distribution depending on the filler particle size and amount. Another reason is the varying fraction of the interphase zone formed at the filler-matrix boundary.     

Adhesion of Polymer Blends. I. Phenomenological Model

A phenomenological model based on the Takayanagi approach is proposed to describe the adhesion of polymer blends to a solid support. The model consists of three elements corresponding to two components of the blend and a solid surface. The conditions for failure of the adhesion joints at the interface between the solid surface and the polymer blend are found to depend on the blend composition and the moduli and adhesion joint strength of each component to the solid.     

Evaluation of copper(II)-pyruvaldehyde bis (N-4-methylthiosemicarbazone) for tissue blood flow measurement using a trapped tracer model

PURPOSE: Adolescent childbearing is twice as common among Native Americans as among all US races combined. Despite this, little is written about the psychosocial context or prenatal care of pregnant Native American adolescents. The objective of this study was to explore the reactions and prenatal care of Navajo and Apache adolescents delivering infants at Shiprock Indian Hospital, New Mexico, between January and March 1991, and Whiteriver Indian Hospital, Arizona, between May and June 1991. METHODS: Of the 25 eligible adolescents aged 19 years and younger, 15 Navajo and 5 Apache participants were interviewed within 24 hours of delivery. The interview consisted of 121 questions divided into 5 areas: sociodemographics, personal and family reactions to the pregnancy, knowledge and attitudes toward prenatal care, barriers to care, and ways to improve access to care. RESULTS: The mean age was 17.4 +/- 1.1, 6 were married, and 13 were primiparous. According to the Maternal Health Services Index, 5 adolescents received adequate, 13 intermediate, and 2 inadequate prenatal care. During the pregnancy, 3 adolescents used tobacco, 3 used alcohol, and none admitted to other drugs. Although only 1 adolescent planned the pregnancy, 15 were not using contraception when they became pregnant. In exploring reactions to the pregnancy, 13 adolescents were afraid to tell their families and 4 concealed the pregnancy until confronted. During the pregnancy, 7 adolescents described loneliness and 6 expressed suicidal ideation. Although over half reported no barriers to obtaining prenatal care, barriers that were noted by the remainder included transportation, family problems, and missing school. CONCLUSION: We conclude that pregnancy among many American Indian adolescents is unplanned and characterized by uncertainty and fear of disclosure, resembling the reactions to pregnancy of other adolescent populations. Furthermore, despite universal access to health services, many American Indian adolescents continue to experience barriers to care and receive intermediate or inadequate prenatal care. These preliminary findings suggest further research may help clarify how adolescent reactions to pregnancy and knowledge of prenatal care affect health care utilization.     

Effect of Alternating Bending on the Structure and Mechanical Properties of Tough-Pitch Copper

Metal Science and Heat Treatment - The structure and mechanical properties of tough-pitch copper are studied after alternating elastoplastic deformation (bending). It is shown that alternating...     

An adaptive fuzzy logic system for the compensation of nonlinear distortion in wireless power amplifiers

Neural Computing and Applications - Computational intelligent systems are becoming an increasingly attractive solution for power amplifier (PA) behavioural modelling, due to their excellent...     

Effect of elastomeric additives on fabrication and properties of filled fiber materials formed from polymer solutions

We have studied the effect of elastomer additives on the properties of spin dopes for obtaining filled fiber materials by aerodynamic spinning from polymer solutions. We have obtained laboratory samples of materials with different polyurethane content. We have analyzed the results of physicomechanical, sorption, and physical tests of these materials. We show that modification of filled fiber materials by introducing elastomeric additives has only an insignificant negative impact on the sorption properties and markedly improves their physicomechanical characteristics.     

Adhesion of Polymer Blends. I. Phenomenological Model

A phenomenological model based on the Takayanagi approach is proposed to describe the adhesion of polymer blends to a solid support. The model consists of three elements corresponding to two components of the blend and a solid surface. The conditions for failure of the adhesion joints at the interface between the solid surface and the polymer blend are found to depend on the blend composition and the moduli and adhesion joint strength of each component to the solid.