Simulation of high-performance memory allocators

For the last 30 years, a large variety of memory allocators have been proposed. Since performance, memory usage and energy consumption of each memory allocator differs, software engineers often face difficult choices in selecting the most suitable approach for their applications. To this end, custom allocators are developed from scratch, which is a difficult and error-prone process. This issue has special impact in the field of portable consumer embedded systems, that must execute a limited amount of multimedia applications, demanding high performance and extensive memory usage at a low energy consumption. This paper presents a flexible and efficient simulator to study Dynamic Memory Managers (DMMs), a composition of one or more memory allocators. This novel approach allows programmers to simulate custom and general DMMs, which can be composed without incurring any additional runtime overhead or additional programming cost. We show that this infrastructure simplifies DMM construction, mainly because the target application does not need to be compiled every time a new DMM must be evaluated and because we propose a structured method to search and build DMMs in an object-oriented fashion. Within a search procedure, the system designer can choose the “best” allocator by simulation for a particular target application and embedded system. In our evaluation, we show that our scheme delivers better performance, less memory usage and less energy consumption than single memory allocators.     

Viewing experience optimization based on adaptive requesting window adjustment in peer-to-peer media streaming

In the last few years, great achievements have been made in the field of peer-to-peer (P2P) streaming system. In mesh-based P2P streaming system, retrieving data from multiple parents simultaneously improves resilience of the streaming service. However, it also brings in playback lags. To improve users’ viewing experiences, we should consider both playback lags and resilience of the streaming service. However, it seems there is a natural trade-off between these two goals. In this paper we propose a viewing experience optimization algorithm which adjusts the position of the requesting window adaptively based on different requesting strategies. The novelty of the proposed method is that it utilizes heterogeneous real-time demands for different genres of videos, and can adjust requesting strategies adaptively. Under the condition of guaranteeing basic QoS (Quality of Service), the algorithm achieves a balance between playback lags and resilience. Finally, experiment results show the satisfactory performance of the proposed method.     

Comparative analysis of power variables in high performance embedded and x86 architectures using GNU/Linux

In this work a comparative analysis of typical power variables is made using several hardware architectures and GNU/Linux software. Voltage and current data are simulated for an industrial device, comparing the performance of x86 and ARM in order to demonstrate the technical feasibility of using embedded hardware to manage high volumes of interesting data in the study of power quality systems.Voltage, current, active power, reactive power and harmonic distortion (both voltage and current) were obtained with simulated data provided by MATLAB and using Discrete Fourier Transform (DFT) implementations like Fast Fourier Transform (FFT) and libraries like FFTW and KISS FFT.All the software used in our work was open source, running Linux behind them. Results show the feasibility of using high performance embedded systems to develop advanced tasks in analyzing power signals.     

A lossless ECG data compression technique using ASCII character encoding

A software based lossless ECG compression algorithm is developed here. The algorithm is written in the C-platform. The algorithm has applied to various ECG data of all the 12 leads taken from PTB diagnostic ECG database (PTB-DB). Here, a difference array has been generated from the corresponding input ECG data and this is multiplied by a large number to convert the number of arrays into integers. Then those integers are grouped in both forward and reverse direction, out of which few are treated differently. Grouping has been done in such a way that every grouped number resides under valid ASCII value. Then all the grouped numbers along with sign bit and other necessary information are converted into their corresponding ASCII characters. The reconstruction algorithm has also been developed in using the reversed logic and it has been observed that data is reconstructed with almost negligible difference as compared with the original (PRD 0.023%).     

A secure energy-efficient m-banking application for mobile devices

Mobile banking is one of the emerging services in telecommunications due to the explosive increase in the number of mobile customers around the world. Solutions for mobile banking are varied, ranging from the use of Wireless Transport Layer Security, Security Socket Layer, or application-layer based options. Whereas security at the transport layer is a good choice for e-banking, using it in a mobile device presents several disadvantages such as high energy consumption. In this work, we present a secure energy-efficient m-banking solution for mobile devices. We propose an application-layer protocol whose message formats and message exchanges are designed to reduce time processing, bandwidth use, and energy consumption. Through experimentation, we demonstrate that our secure solution reduces power and energy consumption in more than 30% compared to a secure web-access from the mobile device.     

The changing face of adaptive control: The use of multiple models

Adaptive systems that continuously monitor their own performance and adjust their control strategies to improve it, have been studied for over 50 years. The theory of such systems is now commonly referred to as classical adaptive control. Such control is now well established and is found to be satisfactory when the uncertainty in the system to be controlled (i.e. the plant) is small.During the past 15 years several attempts were made to extend this general methodology to systems with large uncertainties, by using multiple models to identify the plant. Among these, two general methods based on “switching” and “switching and tuning” have emerged as the leading contenders. Recently, a radically different approach was proposed by the authors (Han & Narendra, 2010b), in which the multiple models are used to play a significantly larger role in the decision making process, resulting in substantial improvement in performance.In this paper, which is tutorial in nature, the three methods based on multiple models are critically examined. At the same time, alternative methods using fixed and adaptive models are also proposed. In all cases, detailed simulation studies of adaptation in different environments are presented. Theoretical explanations are given, where available, for the wide spectrum of performances observed in the simulation studies.     

An efficient diversity-driven selective forwarding approach for replicated data queries in wireless sensor networks

This study considers a wireless sensor network (WSN) designed to track specified objects of interest such as bird-calls, insect-images, and so forth. An assumption is made that the sensors in the WSN are capable of analyzing and identifying detected objects and are pre-loaded with the features of the tracked objects before they are deployed. The features associated with the tracked objects are referred to as “model tuples”. When a sensor subsequently detects an object, it extract features from the detected object and then compares it with the tuples stored in its memory in order to determine whether or not the detected object is the tracked object. Since the sensors have only limited memory and storage space, it is impossible to store all the tuples on a single sensor. Furthermore, the sensors are battery operated, and thus the stored tuples are irretrievably lost once the sensor’s energy resources have been consumed. As a result, the network no longer has a complete knowledge of all the tracked information. Accordingly, the present study proposes four tuple dispatching schemes for distributing the tracked information amongst the sensors in such a way as to mitigate the effects of sensor energy depletion, namely sequential dispatching, sequential dispatching with overlap, fixed distance dispatching, and balanced incomplete block dispatching. In addition, an efficient diversity-driven selective forwarding scheme is proposed to resolve the problem where the detected object fails to match the tuples held at the local sensor. In the approach, the local sensor applies the correlation between the sensor identifier and the indexes of the tuples stored at the various sensors to deliver the feature of the object along the paths with the highest diversity. The simulation presents a series of experimental results to benchmark the performance of the proposed forwarding approach for each of the dispatching schemes against that of a blind flooding approach.     

Ten years of cryomagnetic W7-X test facility construction and operation

The construction, commissioning, and operation phases of the W7-X cryomagnetic test facility in CEA Saclay lasted ten years. The large diversity of equipments called, specialties involved and problems solved attest the expertise that was required to operate the test facility and test the coils. Nearly one hundred cryogenic tests were performed on the seventy W7-X coils, at a rate always increasing, using two cryostats each holding two coils.This paper presents the test facility and its operation first, the cryogenic difficulties that were confronted with their solutions, the electro-magnetic difficulties encountered along with corrective actions, and finally the instrumentation and data acquisition aspects.     

从婚恋主题看女性意识

社会政治、经济的发展以及教育程度都影响着女性的人生观、价值观及婚恋观的变化。女性的家庭地位、婚恋选择也因女性意识的改变和个人素养的提高而逐步改变。从婚姻中的女性权利、女性对财富的争取和对事业的追求、对人生价值的体现四个方面探究了女性意识、女性家庭以及社会角色的变化。