An online technique for monitoring the insulation condition of AC machine stator windings

A novel online technique for monitoring the insulation condition of ac machine stator windings is proposed in this paper. The concept is to measure the differential leakage currents of each phase winding from the terminal box in a noninvasive manner to assess the insulation condition during motor operation. The conventional differential CTs used for phase fault protection can be replaced with high performance current sensors to measure the leakage current with higher accuracy. Indicators for insulation condition such as the capacitance and dissipation factor are calculated based on the measurements to provide a low cost solution for online insulation condition assessment. A simplified online insulation system model is derived for analysis and interpretation of the measured data. Experimental results on a 15-hp induction motor under simulated insulation degradation conditions show that the proposed technique is a very sensitive method capable of detecting incipient signs of insulation degradation.     

Evaluation of recursive queries with extended rules in deductivedatabases

In order to extend the expressive power of deductive databases, a formula that can have existential quantifiers in prenex normal form in a restricted way is defined as an extended rule. With the extended rule, we can easily define a virtual view that requires a division operation of relational algebra to evaluate. The paper addresses a recursive query evaluation where at least one formula in a recursive rule set is of an extended rule. We investigate transformable recursions as well as four cases of non-transformable recursions of transitive-closure-like and linear type. The work reveals that occurrence of an existentially quantified variable in the extended recursive body predicate might dramatically limit the level of recursive search. In particular, the number of iterations to answer extended queries can be determined, independently of database contents     

Nicalon-fibre-reinforced silicon-carbide composites via polymer solution infiltration and chemical vapour infiltration

A new, faster process was developed for the fabrication of Nicalon-fibre-reinforced SiC composites by combining polymer solution infiltration (PSI) and chemical vapour infiltration (CVI). The process led to the near-net-shape fabrication of fibre-reinforced ceramic-matrix composites and reduced infiltration time. Typical flexural strength and fracture toughness of these composites were 296 MPa and 10.9 MPa m^1/2 at room temperature (RT) and 252 MPa and 9.6 MPa m^1/2 at 1000 °C, respectively. The composites exhibited load-carrying capability after crack initiation.     

正交试验法于优选白瓷坯料配方中的应用

对长石、石英、龙岩土、莱阳土４种因素各取４个水平，用正交表Ｌ１６（４５）安排１６个试验，分析了这１６个试验产品的吸水率、白度、热稳定性与每种因素各水平之间的关系．得出了白瓷坯料的最佳配方。其中，长石１９，石英２１，龙岩土２１．莱阳土０．     

Performance of TZCD-MBOK watermarking scheme in T-DMB systems

Recently, watermarking based data transmission techniques using terrestrial digital TV signal have been proposed since they are also cost-free and can overcome the limitations of GPS. However, in the previous watermarking based methods, the detection accuracy is low and additional data rate is too low. Thus, we propose the throughput enhancement method by employing the TZCD-MBOK watermarking technique in T-DMB system. By applying the proposed scheme to T-DMB, it allows additional data transmission for disaster broadcasting and improves efficiency of data transmission in shadow region and indoor to mobile environment through watermarking spread code. From the simulation results, we confirm the proposed watermarking scheme affected on the existing T-DMB signal. Moreover, it was also confirmed that the system capacity increases as the power of additional watermarking signal rose. The results of the paper can be applied to wireless multimedia digital broadcasting systems.     

Power- and time-aware buffer cache management for real-time embedded databases

Due to the explosive increases of data from both the cyber and physical worlds, the demand for database support in embedded systems is increasing. Databases for embedded systems, or embedded databases, are expected to provide timely in situ data services under various resource constraints, such as limited energy. However, traditional buffer cache management schemes, in which the primary goal is to minimize the number of I/O operations, is problematic since they do not consider the constraints of modern embedded devices such as limited energy and distinctive underlying storage. In particular, due to asymmetric read/write characteristics of flash memory-based storage of modern embedded devices, minimum buffer cache misses neither coincide with minimum power consumption nor minimum I/O deadline misses. In this paper we propose a novel power- and time-aware buffer cache management scheme for embedded databases. A novel multi-dimensional feedback control architecture is proposed and the characteristics of underlying storage of modern embedded devices is exploited for the simultaneous support of the desired I/O power consumption and the I/O deadline miss ratio. We have shown through an extensive simulation that our approach satisfies both power and timing requirements in I/O operations under a variety of workloads while consuming significantly smaller buffer space than baseline approaches.     

Signal tracking method of GNSS receivers for spinning vehicles

A signal tracking method of GNSS receivers for spinning vehicles is proposed in order to eliminate the influence of spinning to the GNSS signal of a vehicle. In the proposed method, a rotation tracking loop is added into the carrier tracking loop of a conventional GNSS receiver. The proposed method was verified through computer simulations and an experiment for live GPS signals. The results show that the proposed method gives an accurate tracking performance.