Temperature-Aware Task Allocation and Scheduling for Embedded Multiprocessor Systems-on-Chip (MPSoC) Design

Temperature affects not only the performance but also the power, reliability, and cost of the embedded system. This paper proposes a temperature-aware task allocation and scheduling algorithm for MPSoC embedded systems. Thermal-aware heuristics are developed, and a temperature-aware floorplanning tool is used to reduce the peak temperature and achieve a thermally even distribution while meeting real time constraints. The paper investigates both power-aware and thermal-aware approaches to the task allocation and scheduling. The experimental results show that the thermal-aware approach outperforms the power-aware schemes in terms of maximal and average temperature reductions. To the best of our knowledge, this is the first MPSoC task allocation and scheduling algorithm that takes temperature into consideration.

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Managing context data for diverse operating spaces

Context-aware computing is an exciting paradigm in which applications perceive and react to changing environments in an unattended manner. To enable behavioral adaptation, a context-aware application must dynamically acquire context data from different operating spaces in the real world, such as homes, shops and persons. Motivated by the sheer number and diversity of operating spaces, we propose a scalable context data management system in this paper to facilitate data acquisition from these spaces. In our system, we design a gateway framework for all operating spaces and develop matching algorithms to integrate the local context schemas of operating spaces into a global set of domain schemas upon which SQL-based context queries can be issued from applications. The system organizes the operating space gateways as peers in semantic overlay networks and employs distributed query processing techniques over these overlays. Evaluation results on a prototype implementation demonstrate the effectiveness of our system design.     

A flip-chip packaged 80-nm In0.7Ga0.3As MHEMT for millimeter-wave low-noise applications

In this paper, we present a flip-chip 80-nm In_0.7Ga_0.3As MHEMT device on an alumina (Al₂O₃) substrate with very little decay on device RF performance up to 60 GHz. After package, the device exhibited high I_DS = 435 mA/mm at V_DS = 1.5 V, high g_m = 930 mS/mm at V_DS = 1.3 V, the measured gain was 7.5 dB and the minimum noise figure (NF_min) was 2.5 dB at 60 GHz. As compared to the bare chip, the packaged device exhibited very small degradation in performance. The result shows that with proper design of the matching circuits and packaging materials, the flip-chip technology can be used for discrete low noise FET package up to millimeter-wave range.     

The effect of call admission policies on the system benefit of CDMA communication networks

Previous studies of call admission control (CAC) in mobile communication networks focused on call blocking and call dropping mechanisms. However, achieving global optimization of the system benefit is a complicated process. In this paper, we propose a benefit optimization model that accommodates as many users as possible, while simultaneously maintaining system-wide quality of service (QoS) in terms of admission control. To clarify the CAC concept, we construct a framework of CAC policies, derive associated interference models based on the framework, and then investigate the effects of the policies on the system benefit. In addition, to solve the complicated integer programming problem, we adopt the Lagrangean relaxation approach, and employ Lagrangean multipliers to perform sensitivity analysis of several parameters. The contribution of this study is twofold: the novel problem formulation and the improvement in the system benefit. The computational results demonstrate that the system accrues more benefit as new traffic is loaded and the number of users increases. Meanwhile, the sensitivity analysis shows that proper assignment of the strength of power-controlled signals is a key factor in the global optimization of the system benefit.     

Fault Detection of Linear Guide Preload of a Positioning Stage with Vibration–Acoustic Analysis

The vibration analysis method has been widely used to detect faults in the components of a machine. For a linear positioning stage, its vibration characteristics are closely related to and affected by the preload of linear guides. To clarify the meaning of the vibration signals coming out from an abnormal machine, in this study we aimed to investigate the influence of a faulty linear guide on the vibration and acoustic characteristics of a positioning stage through experimental and finite element modeling approaches. Experimental measurements indicate that stages equipped with abnormal or damaged linear guides indeed exhibit different vibration behavior compared to stages with intact guides. According to finite element analysis, the variation in vibration characteristics can be attributed to the changes in the structural stiffness of linear guides because of rolling ball defects. This phenomenon was also found in the acoustic characteristics measured for stages under various preloaded conditions, providing further correlations between the variations in acoustic characteristics and changes in structural stiffness. The present results clearly show that faulty conditions of linear guides can be effectively detected by means of monitoring the vibration and acoustic characteristics of the stage.     

Heterogeneous Structure Design to Strengthen Carbon-Containing CoCrFeNi High Entropy Alloy

A carbon-containing CoCrFeNi high entropy alloy (HEA) with heterogeneous structures was obtained through thermome-chanical treatments,which induced concurrent recrystallization and carbide precipitation in the alloy.A combination of high yield strength (556 MPa) and large uniform elongation (45％) was achieved in the investigated alloy.The enhancement of the strength is attributed to the combined effects of grain refinement,precipitation strengthening and microstructural het-erogeneity.Our work demonstrated that the heterogeneity design could be realized by thermomechanical processes,which provided a practical strategy for producing HEAs with high performance.