Effects of alumina on the crystallization behavior, densification and dielectric properties of BaO–ZnO–SrO–CaO–Nd2O3–TiO2–B2O3–SiO2 glass–ceramics

The alumina addition effects on the crystallization, sintering behaviors and dielectric properties of BaO–ZnO–SrO–CaO–Nd₂O₃–TiO₂–B₂O₃–SiO₂ (Ba–Zn–Sr–Ca–Nd–Ti–B–Si) glass powder were investigated using the differential thermal analyzer (DTA), thermo-mechanical analyzer (TMA), X-ray diffractometer (XRD). The results showed that the addition of alumina powder into Ba–Zn–Sr–Ca–Nd–Ti–B–Si glass changed the crystallization sequence from Nd₂Ti₄O₁₁–Nd_0.66TiO₃ to Nd₂Ti₃O_8.7–Nd₂Ti₂O₇–Nd₂Ti₄O₁₁and increased the densification activation energy due to the dissolution of Al³⁺ ions into the glass structure. Fully densified 30 vol.% alumina-added Ba–Zn–Sr–Ca–Nd–Ti–B–Si glass can be obtained via glass viscous flow before the second and third crystalline phases, Nd₂Ti₂O₇ and Nd₂Ti₄O₁₁crystallization. The 30 vol.% alumina-added Ba–Zn–Sr–Ca–Nd–Ti–B–Si glass–ceramics sintered at 900 °C exhibited a high dielectric constant of 17 and a quality factor of about 820, which provided a promising candidate for LTCC applications.     

Thermal Behavior and Phase Transformation of TiO2 Nanocrystallites Prepared by a Coprecipitation Route

TiO₂ freeze-dried precursor powders were synthesized using a coprecipitation route that includes titanium tetrachloride (TiCl₄) as initial material prepared at 348 K (75 °C) and pH 7. Differential scanning calorimetry/thermogravimetry (DSC/TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) and high resolution TEM were utilized to characterize the thermal behavior and phase transformation of the TiO₂ freeze-dried precursor powders after calcination. The main compound of the TiO₂ freeze-dried precursor powders was TiO₂·H₂O based on a TG analysis conducted at a heating rate of 20 K (20 °C)/min. The anatase TiO₂ (a-TiO₂) first appeared at 473 K (200 °C), then from a-TiO₂ transformed to rutile TiO₂ (r-TiO₂) at 773 K (500 °C). The activation energy of a-TiO₂ formation from TiO₂ freeze-dried precursor powders was 242.4 ± 33.9 kJ/mol, whereas, the activation energy of phase transformation from a-TiO₂ to r-TiO₂ was 267.5 ± 19.1 kJ/mol. The crystallite size of a-TiO₂ grew from 3.5 to 23.2 nm when raising the calcination temperature from 473 K to 873 K (200 °C to 600 °C). In addition, the crystallite size of r-TiO₂ increased from 17.4 to 48.1 nm when calcination temperature increased from 773 K to 1073 K (500 °C to 800 °C).     

A lightweight,self‐adaptive lock gate designation scheme for data collection in long‐thin wireless sensor networks

Constrained by the physical environments, the long‐thin topology has recently been promoted for many practical deployments of wireless sensor networks (WSNs). In general, a long‐thin topology is composed of a number of long branches of sensor nodes, where along a branch each sensor node has only one potential parent node toward the sink node. Although data aggregation may alleviate excessive packet contention, the maximum payload size of a packet and the dynamically changing traffic loads may severely affect the amount of sensor readings that may be collected along a long branch of sensor nodes. In addition, many practical applications of long‐thin WSNs demand the exact sensor readings at each location along the deployment areas for monitoring and analysis purposes, so sensor readings may not be aggregated when they are collected. This paper proposes a lightweight, self‐adaptive scheme that designates multiple collection nodes, termed lock gates, along a long‐thin network to collect sensor readings sent from their respective upstream sensor nodes. The self‐adaptive lock gate designation scheme balances between the responsiveness and the congestion of data collection while mitigating the funneling effect. The scheme also dynamically adapts the designation of lock gates to accommodate the time‐varying sensor reading generation rates of different sensor nodes. A testbed of 100 Jennic sensor nodes is developed to demonstrate the effectiveness of the proposed lock gate designation scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

The phase transformation and crystallization kinetics of (1 − x)Li2O–xNa2O–Al2O3–4SiO2 glasses

The phase transformation and crystallization kinetics of (1 − x)Li₂O–xNa₂O–Al₂O₃–4SiO₂ glasses have been studied by using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED) analysis. The crystallization temperature at the exothermic peak increases from 1171 to 1212 K when the Na₂O content increases from 0 to 0.6 mol. The crystalline phase is composed of spodumene crystallization when the Na₂O content increases from 0 to 0.6 mol. The activation energy of spodumene crystallization decreases from 444.0 ± 22.2 to 284.0 ± 10.8 kJ mol⁻¹ when the Na₂O content increases from 0 to 0.4 mol. Moreover, the activation energy increases from 284.0 ± 10.8 to 446.0 ± 23.2 kJ mol⁻¹ when the Na₂O content increases from 0.4 to 0.6 mol. The crystallization parameters m and n approach 2, indicating that the surface nucleation and two-dimensional growth are dominant in (1 − x)Li₂O–xNa₂O–Al₂O₃–4SiO₂ glasses.     

Efficient algorithms to create and maintain balanced and threaded binary search trees

The algorithm proposed by Chang and lyengar to perfectly balance binary search trees has been modified to not only balance but also thread binary search trees. Threads are constructed in the same sequence as normal pointers during the balancing process. No extra workspace is necessary, and the running time is also linear for the modified algorithm. Such produced tree structure has minimal average path length for fast information retrieval, and threads to facilitate more flexible and efficient traversing schemes. Maintenance and manipulation of the data structure are discussed and relevant algorithms given.     

The mechanism of plantar unloading in total contact casts: implications for design and clinical use

Although the total contact cast (TCC) has been shown to be an extremely effective treatment for the healing of plantar ulcers in diabetic patients, little is known about the biomechanics of its action. In this study, plantar pressure and ground reaction force measurements were obtained from over 750 foot contacts as five subjects with known elevated plantar forefoot pressures walked barefoot, in a padded cast shoe, and a TCC. Peak plantar pressures in the forefoot were markedly reduced in the cast compared with both barefoot and shoe walking (reductions of 75% and 86% respectively, P < 0.05). Peak plantar pressures in the heel were not, however, significantly different between the shoe and the TCC, and the longer duration of heel loading resulted in an impulse that was more than twice as great in the cast compared with the shoe (P < 0.05). An analysis of load distribution indicated that the mechanisms by which the TCC achieves forefoot unloading are (1) transfer of approximately 30% of the load from the leg directly to the cast wall, (2) greater proportionate load sharing by the heel, and (3) removal of a load-bearing surface from the metatarsal heads because of the "cavity" created by the soft foam covering the forefoot. These results point out some of the "essential design features" of the TCC (which are different from what had been previously supposed), support the use of the TCC for healing plantar ulcers in the forefoot, but raise questions about its utility in the healing of plantar ulcers on the heel.     

Radio characteristics evaluation tests of an experimental 3G WCDMA system in Taiwan suburban environments

Abstract

An experimental study on the radio characteristics of a 3G WCDMA system in a Taiwan suburban environment was conducted. This paper presents the results of handover behaviors. The examinations and performance evaluation are based on the measured E_b /I ₀, mobile system transmitting power, bit‐error‐rate and frame‐error‐rate statistic distributions with respect to the time variations, which corresponds to different measurement locations, under individual and independent but appropriate design of experiment procedures. The corresponding radio characteristics are analyzed and evaluated according to the measured data.     

Tripartite dynamic competition and equilibrium analysis on global television market

This study intends to investigate the tripartite competition among CRT, LCD and PDP TV by means of the quarterly shipments of 30- to 45-in. TV. The Lotka–Volterra competition diffusion model has been adopted to conduct the empirical analysis with the Lyapunov function to carry out equilibrium and stability. The results indicate that adopting this model can lead to good performance. The price dropping of LCD TV is greater than that of CRT and PDP TV. The severe dropping in the price of LCD TV leads to its higher growth rates. With respect to the equilibrium and stability analysis, PDP and LCD TV will coexist in the TV market and reach a stable equilibrium, while CRT TV will disappear from the 30- to 45 in. TV market.     

A study of user experiences mediated by nomadic web content in a museum

Abstract How should nomadic web content be designed to improve and transform user experiences in a hands‐on museum? In this study, 15 users were studied while using an electronic guidebook designed to augment user experiences via wireless technologies at the Exploratorium, an interactive science museum. Several recurring themes emerged from the analysis, such as users' sense of isolation and users' attempts to make a seamless transition between real‐place and virtual contexts. This paper shares a preliminary framework for organising user interactions with handheld devices, user experiences based on interviews and insights regarding the role of nomadic web content.