Reliability-based design optimization with cooperation between support vector machine and particle swarm optimization

Reliability-based design optimization (RBDO) is concerned with designing an engineering system to minimize a cost function subject to the reliability requirement that failure probability should not exceed a threshold. Conventional RBDO methods are less than satisfactory in dealing with discrete design parameters and complex limit state functions (nonlinear and non-differentiable). Methods that are flexible enough to address the concerns above, however, come at a high computational cost. To enhance computational efficiency without sacrificing model flexibility, we propose a new RBDO framework: PS2, which combines Particle Swarm Optimization (PSO), Support Vector Machine (SVM), and Subset Simulation (SS). SS can efficiently estimate small failure probabilities, based on which SVM is adopted to evaluate the reliability of candidate solutions using binary classification. PSO is employed to solve the discrete optimization problem. Primary emphasis is placed upon the cooperation between SVM and PSO. The cooperation is mutually beneficial since the SVM classifier helps PSO evaluate the feasibility of solutions with high efficiency while the optimal solutions obtained by PSO assist in retraining the SVM classifier to attain better accuracy. The PS2 framework is implemented to find the optimal design of a ten-bar truss, whose component sizes are selected from a commercial standard. The reliability constraints are non-differentiable with two failure modes: yield stress and buckling stress. The interactive process between PSO and SVM contributes greatly to the success of the PS2 framework. It is shown that in various trials the PS2 framework consistently outperforms both the double-loop and single-loop approaches in terms of computational efficiency, solution quality, and model flexibility.     

On-line rule matching for event prediction

The prediction of future events has great importance in many applications. The prediction is based on episode rules which are composed of events and two time constraints which require all the events in the episode rule and in the predicate of the rule to occur in a time interval, respectively. In an event stream, a sequence of events which matches the predicate of the rule satisfying the specified time constraint is called an occurrence of the predicate. After finding the occurrence, the consequent event which will occur in a time interval can be predicted. However, the time intervals computed from some occurrences for predicting the event can be contained in the time intervals computed from other occurrence and become redundant. As a result, how to design an efficient and effective event predictor in a stream environment is challenging. In this paper, an effective scheme is proposed to avoid matching the predicate events corresponding to redundant time intervals for prediction. Based on the scheme, we respectively consider two methodologies, forward retrieval and backward retrieval, for the efficient matching of predicate events over event streams. The approach based on forward retrieval construct a queue structure to incrementally maintain parts of the matched results as events arrive, and thus it avoids backward scans of the event stream. On the other hand, the approach based on backward retrieval maintains the recently arrived events in a tree structure. The matching of predicate events is triggered by identifiable events and achieved by an efficient retrieval on the tree structure, which avoids exhaustive scans of the arrived events. By running a series of experiments, we show that each of the proposed approaches has its advantages on particular data distributions and parameter settings.     

Cereal and nonfat milk support muscle recovery following exercise

Background  

This study compared the effects of ingesting cereal and nonfat milk (Cereal) and a carbohydrate-electrolyte sports drink (Drink) immediately following endurance exercise on muscle glycogen synthesis and the phosphorylation state of proteins controlling protein synthesis: Akt, mTOR, rpS6 and eIF4E.     

In Vitro Study of Transdermal Nicotine Delivery: Influence of Rate-Controlling Membranes and Adhesives

The objective of this study was to evaluate the influence of a rate-controlling membrane and adhesive on the in vitro permeation of nicotine. The physicochemical properties of the adhesive, including adhesion and rheology (viscosity), were also detected. Higher permeability of nicotine was observed through a hydrophilic membrane than through a hydrophobic membrane. Natural rubber and silicone were used as the adhesive bases, respectively. The silicone adhesive showed the highest adhesion among all adhesive formulations. To increase the adhesion of natural rubber, a tackifier (polyisoprene) and a secondary tackifier (terpene polymer; Px 1150®) were incorporated into the formulations to achieve acceptable adhesion. The nicotine permeation through silicone adhesive and three natural rubber adhesives with the secondary tackifier (2%, 4%, and 6% Px 1150) was close to that from a commercially available patch (Habitrol®), although the loading amount of nicotine was not the same. A longer lag time during the in vitro permeation study of nicotine was required for the adhesives prepared in our laboratory than for the commercially available patch.     

Updating real-time reliability of instrumented systems with stochastic simulation

In this research, a new method is proposed to update real-time reliability based on data recorded by instruments and sensors installed on a system. The method is founded on Bayesian analysis and subset simulation and is capable of estimating the functional relationship between the real-time failure probability and the monitoring value. It is shown that as long as the monitoring data can be reasonably deduced into a single index, this relationship can be obtained; moreover, it can be obtained prior to the monitoring process. Three examples of civil engineering systems are used to demonstrate the new method. This new method may be applied to safety monitoring of in-construction civil systems and monitoring of existing civil systems.     

Efficient frequent sequence mining by a dynamic strategy switching algorithm

Mining frequent sequences in large databases has been an important research topic. The main challenge of mining frequent sequences is the high processing cost due to the large amount of data. In this paper, we propose a novel strategy to find all the frequent sequences without having to compute the support counts of non-frequent sequences. The previous works prune candidate sequences based on the frequent sequences with shorter lengths, while our strategy prunes candidate sequences according to the non-frequent sequences with the same lengths. As a result, our strategy can cooperate with the previous works to achieve a better performance. We then identify three major strategies used in the previous works and combine them with our strategy into an efficient algorithm. The novelty of our algorithm lies in its ability to dynamically switch from a previous strategy to our new strategy in the mining process for a better performance. Experiment results show that our algorithm outperforms the previous ones under various parameter settings. This paper is a major-value added version of the following paper: D. Y. Chiu, Y. H. Wu, A. L. P. Chen, “An Efficient Algorithm for Mining Frequent Sequences by a New Strategy without Support Counting,” Proceedings of IEEE Data Engineering Conference, pp. 375–386, 2004.     

Modeling of ad-hoc and infrastructure dual mode mobile networks

1 Introduction Existing mobile telephone networks utilize fixed base stations (BSs) as infrastructure to populate a ser- vice area, in which a mobile station (MS) communi- cates with a BS via a radio interface[1～3]. To increase network capability, several studies[4,5] have integrated an ad hoc communication mode with an infrastructure communication mode for cellular systems. In the ad hoc mode, MSs are allowed to communicate with each other without consuming any BS radio channels. Fig.1 i…     

Modeling and Coordinate Control of Circulating Currents in Parallel Three-Phase Boost Rectifiers

In this paper, definition of the circulating currents of multiphase paralleled converters is first presented, and the circulating-current-generating mechanism is clearly explained. Thus, based on this definition, an averaged model of the circulating current is proposed. It is seen from this model that the circulating current consists of not only the zero-sequence but also the nonzero-sequence components. The governing differential equation also shows explicitly the relation between the circulating currents and the affecting factors such as different pulse width-modulation strategies. With this understanding, a simple coordinate control is then presented to reduce the circulating current. The phenomenon of the intrinsic circulating current is also explained. Furthermore, a prototype system is constructed, and the proposed control is implemented using TMS320F2812 DSP. Both simulation and experimental results verify the validity of the proposed theory and control     

The effect of mixed-solvent and terpenes on percutaneous absorption of meloxicam gel

The purpose of the present study was to develop the meloxicam transdermal dosage form. The response surface methodology was used to obtain an appropriate mixed-solvent system of pH-7.4 buffer and ethanol for preparing meloxicam hydrogel. The enhancement effects of terpenes on drug precautious absorption were evaluated via in vitro and in vivo study. The result showed that the solubility of meloxicam was dependent on the pH value of buffer solution. The mixed-solvent system of pH-7.4 buffer and ethanol had a synergistic effect on the increase of drug solubility. The highest solubility was obtained in the ratio of 50/50 pH 7.4 buffer/ethanol. A series of terpenes were used as enhancer for improving the penetration rate of meloxicam. The penetration rates were significantly increased by about 70-593 fold and the lag times were shortened from 7.92 to 0.17 hr by enhancer incorporation. Among these terpenes, menthol showed the greatest effect. In vivo penetration study, the AUC(48h) was increased by about 1.7 fold by the addition of 5% menthol as enhancer.