E-BAMA vs. RAMA [multiple access protocols]

The article presents a performance comparison of two random access protocols for wireless mobile signaling in which a single channel is dedicated to the signaling function, enhanced beacon assisted multiple access (E-BAMA) and resource auction multiple access (RAMA). Data traffic is transported separately on a set of orthogonal channels. The beacon assisted multiple access (BAMA) protocol was first presented as a method of providing mobility management functions, e.g., handover, while minimizing the processing burden placed on the mobile. In BAMA, throughout the duration of its call, an active user repeatedly and quasi-periodically broadcasts a beacon containing its ID using the Aloha protocol. Quasi-periodicity prevents a pair of users from repeatedly colliding with each other. When a base successfully receives the beacon and assigns a channel, it uses a separate downstream channel to send to the mobile an acknowledgement that contains the number of the assigned channel. The BAMA protocol includes a scheme to maintain lists of active mobiles in nearby cells and to exchange periodically these lists among the base-stations. The authors evaluate the capacity and delay performance of E-BAMA and RAMA. Then, they present a numerical comparison of the parameters. Finally, the results are summarized qualitatively. Some additional derivation is included in the appendix     

Magnetic properties of proximity-induced superconducting copper and silver

The magnetic properties of micrometer thick, proximity-induced superconductors have been investigated in the temperature range 5×10^–4 T _CNS T _CNS . HereT _CNS is the transition temperature of the NS proximity system. By means of ac susceptibility measurements and dc magnetization curves in copper and silver, we have determined the breakdown fieldH _b , the supercooled fieldH _sc and the superheated fieldH _sh , as functions of temperature and normal metal thicknessd _N . Precise magnetization curves of specimens withd _N <15 µm at the lowest temperatures gave the screening length as function of the field H. From these data, the spatial dependence of the local critical fieldH _c (x) and of the induced order parameter _N (x) in theN side were derived in the case _N (x)>k _B T and xK _N ^–1 . HereK _N ^–1 is the Cooper pair penetration length, andx the distance form the SN interface.     

A theoretical perspective on social agency

In interacting with artificial social agents, novel forms of sociality between humans and machines emerge. The theme of Social Agency between humans and robots is of emerging importance. In this paper key theoretical issues are discussed in a preliminary exploration of the concept. We try to understand what Social Agency is and how it is created by, negotiated with, and attributed to artificial agents. This is done in particular considering socially situated robots and by exploring how people recognize and accept social agents. The interplay between humans and agents is investigated through dynamics of interpretation, signification and attribution. The ultimate goal of this research is to explore the challenges and opportunities brought by the design of socially intelligent agents.

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Signaling system performance evaluation for personal communications

A key measure of wireless network performance is the amount of signaling information needed to deliver calls to mobile users. Estimates of the signaling system loading are widely available in recent literature. However, in all of the available publications the results are heavily dependent upon assumptions about user density, velocity, cell sizes, and other quantities related to the system and users. This paper presents a methodology to evaluate the signaling system loading that can produce general results that are independent of these assumptions. The technique relies upon the definition of an index of mobility which aggregates several key quantities in a single measure. With this index as the independent variable, graphical results reveal the behavior of a system. This paper evaluates three protocols: GSM Pan-European Cellular, IS-41 North American Cellular, and Bellcore's PCS Access Service for Networks. The method is general and can be easily applied to a new system     

Signaling traffic volume generated by mobile and personalcommunications

The authors develop a framework for evaluating the signaling load in a wireless network. Using bounds and approximations, we find that the key parameter to estimate is the number of location updates between two calls. The results are dependent upon the choice of protocols, but are independent of the traffic parameters relating user calling behavior and mobility. We use the framework to draw general conclusions about signaling load, as well as to compare the signaling loads for the European and North American systems and demonstrate the impact of architectural tradeoffs. We also describe the message flows for the major contributors to the signaling load that are defined in the GSM system     

Adjoint sensitivity analysis and optimization of hysteretic dynamic systems with nonlinear viscous dampers

In this paper we discuss the adjoint sensitivity analysis and optimization of hysteretic systems equipped with nonlinear viscous dampers and subjected to transient excitation. The viscous dampers are modeled via the Maxwell model, considering at the same time the stiffening and the damping contribution of the dampers. The time-history analysis adopted for the evaluation of the response of the systems relies on the Newmark-β time integration scheme. In particular, the dynamic equilibrium in each time-step is achieved by means of the Newton-Raphson and the Runge-Kutta methods. The sensitivity of the system response is calculated with the adjoint variable method. In particular, the discretize-then-differentiate approach is adopted for calculating consistently the sensitivity of the system. The importance and the generality of the sensitivity analysis discussed herein is demonstrated in two numerical applications: the retrofitting of a structure subject to seismic excitation, and the design of a quarter-car suspension system. The MATLAB code for the sensitivity analysis considered in the first application is provided as “Supplementary Material”.     

Embedding reading comprehension training in content-area instruction.

This study evaluated the effectiveness of comprehension training embedded in a program that taught science content to 2nd graders. The program included instruction about the structure of compare-contrast expository text, emphasizing clue words, generic questions, graphic organizers, and the close analysis of well-structured text exemplars. This program was compared with a program that focused on the science content but included no compare-contrast training as well as with a no-instruction control. Regular classroom teachers (14 from 4 schools), randomly assigned to treatment, provided the instruction; 215 students (7-8 years old) participated. The study replicated acquisition and transfer effects found in an earlier study, that is, transfer to compare-contrast text with content related and unrelated to the instructional content (with no loss in the amount of science content acquired). The program also led to better performance on written and oral response measures and on 1 of the 2 measures involving authentic (less well-structured) compare-contrast text. These findings support and extend previous findings that explicit instruction in comprehension is effective as early as the primary-grade level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)