Energy efficient scheduling for downlink elastic traffic in wireless networks

In wireless networks, maximizing throughput and minimizing energy consumption are two conflicting objectives. For elastic traffic, it is the total completion time, not the delay constraint of a single packet or the short‐term throughput requirement, that directly affects the quality‐of‐service (QoS). At the same time, the energy consumption should be minimized in order to prolong the battery lifetime of the mobile station (MS). In this paper, we propose energy efficient schedulers that consider throughput and energy saving simultaneously. Through extensive simulations, we compare the proposed schemes with the conventional scheme where a mobile terminal stays awake until all the pending packets are completely serviced. The simulation results show that our schemes outperform the conventional one in terms of utility, i.e., user satisfaction, which is defined as inversely proportional to the multiplication of weighted service completion time and energy consumption. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of Nanoparticles on Electron and Thermoelectric Transport

Recent experimental results have shown that adding nanoparticles inside a bulk material can enhance the thermoelectric performance by reducing the thermal conductivity and increasing the Seebeck coefficient. In this paper we investigate electron scattering from nanoparticles using different models. We compare the results of the Born approximation to that of the partial-wave method for a single nanoparticle scattering. The partial-wave method is more accurate for particle sizes in the 1 nm to 5 nm range where the point scattering approximation is not valid. The two methods can have different predictions for the thermoelectric properties such as the electrical conductivity and the Seebeck coefficient. To include a random distribution of nanoparticles, we consider an effective medium for the electron scattering using the coherent potential approximation. We compare various theoretical results with the experimental data obtained with ErAs nanoparticles in an InGaAlAs matrix. Reasonably good agreement is found between the measured and theoretical electrical conductivity and Seebeck data in the 300 K to 850 K temperature range.     

CDMA Mobile System Overview: Introduction,Background, and System Concepts

The CDMA Mobile System (CMS) has been developed by Electronics and Telecommunications Research Institute (ETRI) and fieldtested for commercial ser- vice deployment in Korea. The project was started in 1989 and completed in 1995 with the CMS commercial test. During the course of development, there had been active technical cooperation with Qualcomm, Inc. and Korean manufacturers. The CMS adopted the basic CDMA concepts conforming to Korean CDMA system which was derived from IS-95. The CMS functions are allocated to subsystems by considering efficiency and expandability. The CMS consists of mobile stations and the infrastructure which is composed of base stations, mobile exchanges and home location register/authentication center. The commercial field tests performed both in Taejon and Seoul have indicated that the CMS capacity is 10 to 15 times larger than that of AMPS. This paper overviews the development history, system characteristics, architecture and test results.     

Carbon Nanotube Penetration Through Fiberglass and Electret Respirator Filter and Nuclepore Filter Media: Experiments and Models

Three different respirator filter media (two electrets and one fiberglass) were challenged with monodisperse multi-walled carbon nanotubes (MWCNTs) of mobility diameters 20–500 nm at 5.3 and 10.6 cm s^?1 face velocities. The penetration data were compared with that of sphere-like NaCl particles. The MWCNT penetrations were generally lower than those of NaCl at both face velocities in all three filters. However, the MWCNTs had a slightly higher penetration than the NaCl in the fiberglass filter at 10.6 cm s^?1 face velocity when their mobility diameters were lower than 50 nm and the alignment effect was expected to occur. Results from the scanning electron microscopic (SEM) analysis supported the hypothesis of the alignment effect, which showed that the MWCNTs tend to be straighter or with higher aspect-ratios at the mobility sizes less than 100 nm, leading them more readily to align with the flow. Therefore, caution should be exercised when respirators are used against the MWCNTs with the mobility diameters less than 100 nm. The single fiber theory predicted the penetration of both particles in the fiberglass filters well for the particles with below 100 nm mobility diameters but discrepancies occurred beyond 100 nm. The theory still predicted the NaCl penetration through the electret filters well for the sizes below 100 nm but only predicted the MWCNT penetration well for ～20–30 nm. The Nuclepore filter and the corresponding capillary tube model were adopted to study the mechanical deposition mechanisms of MWCNTs. The model was found to predict MWCNT penetration very well when the effective length of the MWCNT was taken into account.

Copyright 2014 American Association for Aerosol Research     

Protecting aluminum alloy from particle-impact ignition with an Al2O3 film

Bare aluminum alloy is compared to soft-anodized aluminum alloy (oxide film thickness 5 μm, 10 μm, 20 μm, or 50 μm) for susceptibility to ignition by supersonic particle impact in pure oxygen. The particle diameter ranged from 1600 μm to 2000 μm, temperature ranged from 220 K to 672 K and oxygen pressure was 27.6 MPa. The event of ignition was recorded on video tape. The results of ignition frequency are reported as a Logistic Regression Model over the variable space. In addition, the impact process was simulated using the computer code ZEUS to identify ignition temperatures and ignition sites as well as to qualitatively describe the mechanism of protection offered by the soft-anodized oxide film. Significant improvement against particle-impact ignition was achieved through the use of the anodized oxide film.     

Contention based scheduling for femtocell access points in a densely deployed network environment

The proliferation of new data intensive devices has caused an enormous burden on wireless systems. A femtocell network is a promising new technology developed to meet these demands. Since each femtocell network consists of uncoordinated subnetworks that work independently, the interference between subnetworks can result in a significant degradation of the overall network capacity. In this paper, we address the interference problem between uncoordinated femtocell access points (FAPs) and propose a distributed FAP scheduling scheme in a densely deployed femtocell network where FAPs interfere with each other. In contrast to previous works that have focused on dynamic power and frequency management, our approach focuses on time sharing through FAP contention. Depending on the outcome of contention, our method selects a winning FAP to be the sole user of the next time frame. The approach operates in a fully distributed manner with help from mobile nodes (MNs). To implement this scheme, we develop a new synchronous frame structure, which uses special common control channels. Through simulations, we observe that the proposed scheme doubles the network capacity compared to the legacy non-contending scheme, and could serve as the basis for future standards on femtocell networks.     

Osteochondromalike parosteal osteosarcoma: a report of six cases of a new entity

OBJECTIVE: Our purpose was to describe a rare juxtacortical bone sarcoma with deceptively benign, osteochondromalike histologic characteristics. We present criteria by which this low-grade malignant neoplasm can be distinguished from other benign and malignant surface lesions of bone with particular emphasis on the imaging features. MATERIALS AND METHODS: Six cases of a low-grade, chondroossifying parosteal sarcoma of bone were reviewed. Patients included four males and two females 11 months to 66 years old. Histologic findings from initial tumors and from recurrent tumors were reviewed. Two musculoskeletal radiologists analyzed the imaging studies, which included plain films, CT scans, MR images, and a bone scan. RESULTS: Histologically, the lesions were characterized by a thin layer of proliferating, periosteally derived spindle cells overlying a thin, low-grade malignant cartilage cap that underwent calcification, neovascularization, and conversion into benign bone and marrow fat. These lesions were unique in that the malignant elements were only at their periphery. All six cases were initially misdiagnosed as benign lesions on pathologic evaluation. In each patient, imaging revealed a "pasted-on" ossified surface lesion with an intact underlying cortex and no medullary involvement. In three cases, recurrent tumors had histologic appearances consistent with conventional parosteal osteosarcoma. Dedifferentiation, metastases, and death occurred in one of these three cases. CONCLUSION: To our knowledge, this surface lesion of bone has not been specifically described. Whether this tumor constitutes a distinct entity or is a specialized variant of parosteal osteosarcoma is unclear. Precise radiologic-pathologic correlation is essential for appropriate diagnosis and management.