Distance spectrum analysis of space-time trellis-coded Modulations in quasi-static Rayleigh-fading channels

In this correspondence, we propose an algorithm for computing the distance spectrum of a space-time trellis code achieving maximal diversity gain in quasi-static fading channels. We further present a state reduction technique for trellis codes that can reduce the complexity of the distance spectrum computation. We provide numerical results supporting the empirical evidence that a truncated union bound obtained from the distance spectrum provides an accurate characterization of the relative performance ordering of different space-time trellis codes and, therefore, it offers a tool for better space-time trellis code design.     

Outage Capacity of Spatially Correlated Multipath Fading Channels

In this paper, we study the effect of the scattering environment on the capacity of a single carrier linear modulation used in a multipath, multiple antenna channel. The work incorporates detailed 3D geometric channel models to assess the effect of spatial correlation. The analysis techniques, based on the pioneering work of Hirt and Massey (1988), provide a method to evaluate outage capacity. Channels that are derivatives of the ETSI standard hilly terrain and typical urban are considered in detail. The results quantify the loss of capacity produced by higher spatial correlation. When comparing signals of different bandwidth, wideband systems produce more diversity due to better temporal resolution. Surprisingly, narrowband systems gain some diversity back by being less susceptible to loss of diversity from spatial correlation     

A randomized trial of three diabetes registry implementation strategies in a community internal medicine practice

BACKGROUND: Disease registries are powerful tools with the potential to transform the way chronic diseases are managed. To date, however, little work has been done to determine how to optimize the implementation of a chronic disease registry in practice. METHODS: Twenty-nine physicians and their nurse teams in a large community internal medicine practice participated in this 6-month prospective randomized trial in 2000. Teams were assigned to one of three implementation strategies using information from a diabetes registry. Process and outcome measures for diabetes management were analyzed. Process measures included the percentage of patients completing glycosylated hemoglobin (Hgb) testing within 6 months and low-density lipoprotein (LDL) testing within 12 months. Outcome measures included the percentage of patients with a glycosylated Hgb > 9.3% (equivalent to a HgbA1c > 8.0%), the percentage of patients with an LDL cholesterol > 130 mg/dl, and the percentage of patients with controlled blood pressure, defined as < 130/85 millimeters of mercury. Mean change in LDL and glycosylated Hgb values was also measured. RESULTS: Teams randomized to an intervention strategy that included direct letters to patients showed significant improvement across a number of measures. The improvement was most apparent among patients without recent testing or with poorly controlled disease. The two interventions that did not include direct patient letters resulted in limited improvement. DISCUSSION: Disease registries can be used to improve outcomes in the management of diabetes and other chronic diseases. Better outcomes were seen in patients who received letters based on registry-generated data. This strategy should be included as part of a comprehensive chronic disease management plan. Further refinements in the use of registries should result in further incremental improvement.     

Conical Boron Nitride Nanorods Synthesized Via the Ball-Milling and Annealing Method

A boron nitride (BN) nanostructure, conical BN nanorod, has been synthesized in a large quantity on Si substrates for the first time via the ball-milling and annealing method. Nitridation of milled boron carbide (B₄C) powders was performed in nitrogen gas at 1300°C on the surface of the substrates to form the BN nanorods. The highly crystallized nanorods consist of conical BN basal layers stacked along the nanorod axis. Ball milling of the B₄C powders can significantly enhance the nitridation of the powders and thus facilitate the formation of nanorods during the annealing process.     

Unitary peak power reduction in multiple transmit antennas

This paper proposes a new peak-to-average power ratio (PAPR) reduction scheme in multiple transmit antenna environments. Instead of applying individual PAPR reduction on each antenna, a joint PAPR reduction technique is proposed. By applying a relevant unitary rotation over the transmit antennas, overall PAPR of the multiple transmit antenna system is reduced. This scheme does not require any side information to decode the signal in the receiver, enabling throughput-lossless PAPR reduction. Furthermore, there is no increase in the complexity of the receiver.     

Least-energy path planning and oscillation analysis of robotic manipulator using direct collocation with nonlinear programming

ABSTRACT

Direct collocation is a method that converts a two-point boundary-value problem into a nonlinear programming problem by approximating the state variables and controls into parameters. It has been broadly used in studies of space and orbital mechanics yet has been rarely applied in the fields of robotics. This study builds up a mathematical model of a five-linked manipulator arm. Gradually reducing the upper and lower bounds of the five joint actuator outputs, this paper explores the variations in the least-energy cost function and the final time. Special attention has been focused on whether restrictions would ever arouse any un-anticipated oscillation in the joints. The numerical results show some irony. Excessively restricting the upper and lower output bounds of actuators does not actually gain traction in minimizing the cost index. On the contrary, the value of the cost index is increased by 41.77% from 924.87 to 1310.44 for a tunnel case whose radius is 1.5 m. The simulation cautions that unwanted frequency of oscillation begins to surface due to this wishful restricting. This paper demonstrates how Direct Collocation with Nonlinear Programming can be successfully applied to solve robotic path planning problems. It also cautions the users and designers of the manipulator about the unwanted frequency drift so that the users and designers can amend it before the oscillation builds up.     

Sensitivity and teaching by dysphoric and nondysphoric women in structured versus unstructured situations.

This study compared the sensitivity and teaching strategies of dysphoric and nondysphoric women working with unfamiliar 5- and 6-year-olds. Interactions of 20 dysphoric and 20 nondysphoric mothers and an unfamiliar child were observed during 2 classification tasks and 3 unstructured activities staged as breaks. Nondysphoric women were more sensitive to children's level of understanding than dysphoric women and were more likely to use a variety of teaching strategies. Dyads with nondysphoric women were also more likely to share decision making than dyads with dysphoric women. These differences between dysphoric and nondysphoric women were significant only in the structured classification tasks. The findings indicate that in some situations dysphoric and nondysphoric women vary in their sensitivity to children's cues and in the teaching strategies they use with children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Soft-output demodulator in space-time-coded continuous phase modulation

Space-time coding has shown great promise for digital transmission in wireless communication links, especially when the channel response is known at the receiver. Space time coding combined with continuous phase modulation (CPM) can offer better tradeoffs in bandwidth and power efficiency. Because of the memory inherent in CPM, channel estimation is often harder than for linear modulations. We present an adaptive soft algorithm that performs joint channel estimation and data detection for space-time CPM systems. Properly designed pilot symbols are inserted at the very beginning to give good initial estimates of the channels. This soft receiver is further applied to the interleaved space-time CPM system to yield better performance with moderate complexity through iterative processing. Simulation results show that the receiver can often achieve near-coherent performance in quasistatic fading as well as in time-varying fading.