Self-adaptation of mobile systems driven by the Common Variability Language

The execution context in which pervasive systems or mobile computing run changes continually. Hence, applications for these systems require support for self-adaptation to the continual context changes. Most of the approaches for self-adaptive systems implement a reconfiguration service that receives as input the list of all possible configurations and the plans to switch between them. In this paper we present an alternative approach for the automatic generation of application configurations and the reconfiguration plans at runtime. With our approach, the generated configurations are optimal as regards different criteria, such as functionality or resource consumption (e.g. battery or memory). This is achieved by: (1) modelling architectural variability at design-time using the Common Variability Language (CVL), and (2) using a genetic algorithm that finds nearly-optimal configurations at run-time using the information provided by the variability model. We also specify a case study and we use it to evaluate our approach, showing that it is efficient and suitable for devices with scarce resources.     

DynMAC: A resistant MAC protocol to coexistence in wireless sensor networks

The growth of mobile and ubiquitous computing has increased the demand for wireless communications, which in turn raises interference levels and spectrum pollution, causing problems of network coexistence. The coexistence assurance between these devices and wireless sensor networks is a big challenge. This paper proposes a new medium access protocol, DynMAC (Dynamic MAC), which uses mechanisms of dynamic channel reconfiguration, recovery from lost links and reconfiguration of transmission parameters based on the properties of the cognitive radios, to deal with this problem. Simulations and experiments using a real WSN testbed, were performed to validate our protocol. Results show that the proposed mechanisms solve the WSN configuration problems, in noisy and interference environments, and enable the coexistence with different networks and devices operating in the same frequency spectrum, while maintaining application requirements in critical deployment scenarios.     

Mathematical representation of radiality constraint in distribution system reconfiguration problem

Distribution systems are most commonly operated in a radial configuration for a number of reasons. In order to impose radiality constraint in the optimal network reconfiguration problem, an efficient algorithm is introduced in this paper based on graph theory. The paper shows that the normally followed methods of imposing radiality constraint within a mixed-integer programming formulation of the reconfiguration problem may not be sufficient. The minimum-loss network reconfiguration problem is formulated using different ways to impose radiality constraint. It is shown, through simulations, that the formulated problem using the proposed method for representing radiality constraint can be solved more efficiently, as opposed to the previously proposed formulations. This results in up to 30% reduction in CPU time for the test systems used in this study.     

An interpretative structural modeling based network reconfiguration strategy for power systems

The network reconfiguration is an important stage of restoring a power system after a complete blackout or a local outage. Reasonable planning of the network reconfiguration procedure is essential for rapidly restoring the power system concerned. An approach for evaluating the importance of a line is first proposed based on the line contraction concept. Then, the interpretative structural modeling (ISM) is employed to analyze the relationship among the factors having impacts on the network reconfiguration. The security and speediness of restoring generating units are considered with priority, and a method is next proposed to select the generating unit to be restored by maximizing the restoration benefit with both the generation capacity of the restored generating unit and the importance of the line in the restoration path considered. Both the start-up sequence of generating units and the related restoration paths are optimized together in the proposed method, and in this way the shortcomings of separately solving these two issues in the existing methods are avoided. Finally, the New England 10-unit 39-bus power system and the Guangdong power system in South China are employed to demonstrate the basic features of the proposed method.     

Fault‐tolerant control of distributed systems by information pattern reconfiguration

Given a fault‐tolerance strategy and a distributed control system, the set of recoverable faults depends on the information pattern that is implemented. This paper shows that fault‐tolerance can be achieved, when possible, by the reconfiguration of the information pattern. A necessary and sufficient recoverability condition is provided, and sub‐optimal solutions are developed for actuator and sensor faults under system reconfiguration. Copyright © 2014 John Wiley & Sons, Ltd.     

Boron doping induced electronic reconfiguration of Fe-Nx sites in N-doped carbon matrix for efficient oxygen reduction reaction in both alkaline and acidic media

Developing non-precious metal-based catalysts as the substitution of precious catalysts (Pt/C) in oxygen reduction reaction (ORR) is crucial for energy devices. Herein, a template and organic solvent-free method was adopted to synthesize Fe, B, and N doped nanoflake-like carbon materials (Fe/B/N–C) by pyrolysis of monoclinic ZIF-8 coated with iron precursors and boric acid. Benefiting from introducing B into Fe–N–C, the regulated electron cloud density of Fe-N_x sites enhance the charge transfer and promotes the ORR process. The as-synthesized Fe/B/N–C electrocatalyst shows excellent ORR activity of a half-wave potential (0.90 V vs 0.87 V of Pt/C), together with superior long-term stability (95.5% current density retention after 27 h) in alkaline media and is even comparable to the commercial Pt/C catalyst (with a half-wave potential of 0.74 V vs 0.82 V of Pt/C) in an acidic electrolyte. A Zn-air battery assembled with Fe/B/N–C as ORR catalyst delivers a higher open-circuit potential (1.47 V), specific capacity (759.9 mA h g^?1_Zn at 10 mA cm^?2), peak power density (62 mW cm^?2), as well as excellent durability (5 mA cm^?2 for more than 160 h) compared to those with commercial Pt/C. This work provides an effective strategy to construct B doped Fe–N–C materials as nonprecious ORR catalyst. Theoretical calculations indicate that introduction of B could induce Fe-N_x species electronic configuration and is favorable for activation of OH1 intermediates to promote ORR process.     

Cross-fertilization for routine reconfiguration in IT-enabled organizational transformation

Routine reconfiguration is a key challenge for IT-enabled organizational transformation projects. However, how to successfully reconfigure existing routines remains unclear. This case study explores how to achieve routine reconfiguration in IT-enabled organizational transformation and suggests that routine reconfiguration can be achieved through the cross-fertilization of business domain knowledge. We identified a process model of cross-fertilization of business domain knowledge, which essentially incorporates three key processes (i.e., knowledge combination, reflection, and experimentation) and indicates that cross-fertilization can bring changes to all three types of trajectory components. The theoretical and practical implications of this study are also discussed.     

浅析重型板式给矿机的调偏

本文对重型板式给矿机经常出现的故障即跑编的危害性进行了分析，并且对尖山铁矿重型板式给矿机的调偏机构进行了较为有效的研究．     

一种减少落煤管堵塞的技术方法

煤粉含水量高、刮板给煤机的落煤管夹角角度大,造成给煤系统落煤管堵煤,严重时造成给煤输送设备跳闸,影响锅炉的正常运行,通过对落煤管改造、拆除旋转给料阀、加装管壁吹扫风等,有效降低落煤管堵煤次数。