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At the present time, it is of major significance to study the solid-liquid-gas three-phase coupling relationship of coal, water, and gas in deep-mining stopes in order to prevent and control coal and gas outbursts in high-gas mines. In this study, the influence rules of water on the mechanical characteristics of coal, as well as gas diffusion and migration processes, was examined by combining theoretical analysis and laboratory testing procedures. The results showed that with increases in water content, the mechanical characteristics of coal bodies presented change trends of first increasing and then decreasing. In this study, it was found that the water content levels which corresponded to the maximum shear strength of the coal in the No. 8 coal seam in the study area had ranged between 6.77% and 11.9%, and the water content level corresponding to the extreme point was 8.66%. It was observed that under different water content conditions, the gas desorption speeds of the coal bodies gradually decreased over time. The gas desorption speeds rapidly decreased during the initial desorption stage and then gradually decreased over time. Furthermore, under the different water content conditions, the amount of gas desorption in the coal bodies was observed to gradually increase over time, with the initial desorption amounts displaying rapid increases. Then, with the passage of time, the increase speeds of the gas desorption amount gradually decreased and finally tended to remain at a stable value. It was found that with the increases in water content, the desorption speeds, initial desorption speeds, and desorption amount of gas in the coal bodies continuously decreased. In other words, the water content levels in the coal bodies were negatively correlated with the gas desorption speeds and desorption amounts of the coal bodies. In addition, the gas desorption speeds, initial desorption speeds, and desorption amounts were observed to change more sharply with the increases in water content. The results of this research hold important guiding significance for the improvement of the understanding of the mechanical properties of high-gas coal seams and the implementation of effective gas control measures.

Warranty claims forecasting plays an increasingly important role not only for preparing financial plans but also for optimizing warranty policy and improving after-sale services. In the case of new products, an important feature is that the new generation of products often has a close connection with the previous generations of products it replaces. Thus, the warranty claims data of the previous generations of products can be used for extracting reliability information of new products. In this context, we propose a warranty claims forecasting model considering usage rate for new products sold with a two-dimensional warranty. The accelerate failure time model is introduced to investigate the effect of usage rate on product degradation. The non-homogeneous Poisson process is used to model failure counts of repairable products and the constrained maximum likelihood estimation method is used to estimate model parameters. The results of data experiments based on both simulation and real data collected from an automobile manufacturer in China show that the proposed model considering the varying usage rate outperforms the traditional models in forecasting the number of warranty claims.

Offering appropriate preventive maintenance strategy has an effective impact on achieving higher customer satisfaction. This article presents a flexible preventive maintenance strategy, where customers are grouped into two groups according to their usage rates, and then different preventive maintenance programs are applied to different types of customers. The product follows a two-dimensional failure process and the preventive maintenance cost is shared between the manufacturer and customer on a pro rata basis. The manufacturer’s warranty cost is minimized by jointly optimizing the pro rata proportion of the preventive maintenance cost, the preventive maintenance number and the corresponding preventive maintenance levels. Numerical experiments are presented to illustrate the effectiveness of the proposed approach. Results prove that the flexible preventive maintenance strategy outperforms the conventional unified preventive maintenance strategy in terms of total warranty cost. Besides, some managerial suggestions are also given to provide guidance of implementing the proposed preventive maintenance strategy.

Understanding the field reliability of a sold product is crucial to both managers and engineers for monitoring product quality and improving warranty service design. When practitioners model warran...

Warranties are prevalent in the market. The manufacturer of products sold with warranties often faces a problem of balancing a trade-off between warranty cost and boosted demand by warranties when ...

Design of experiments has received much attention in the context of reliability improvement. Many engineers and researchers are considering how to use designed experiments to improve the reliability of products and processes. This work illustrates a 12-run Plackett-Burman design and its analysis to improve the reliability of a diamond drill bit. A detailed description and execution of the design are provided including how to choose the factors and determine the number of experimental factors. In addition, the results of the real-world experiment are presented and the predicted performance from statistical model fitting is verified by part of a confirmation experiment. The experimental data show that the recommended factor settings substantially improved the reliability of the diamond drill bits.

Telemedicine with mobile communications is a new research area aimed at providing highly flexible medical services that are not possible with standard telephony. In this article, a teleconference system via mobile Internet connections for homecare service is presented. An important purpose of this system is the realization of real time communication between the service station (experts) and the service providers (nurses) in mobile conditions. The following functions are realized via mobile internet connections: 1) a communication control platform for data transmission and process management; 2) whiteboard function to share image and draw free lines; 3) voice transmission between service station and service providers; 4) system management including data maintenance and database access. In this system, still images and voice data are transmitted in real time between service providers (patient's home site) and service managers (station site). This study is a new trial to support homecare service with mobile telecommunication technology.

A human identification method using electrocardiogram (ECG) is presented based on Bayes' theorem. A data base containing 502 ECG recordings are used for development and evaluation. Each ECG recording is divided into two segments: a segment for training, and a segment for performance evaluation. The ECG features are extracted from both the training dataset and the test dataset for model development and identification. Principal component analysis is used to reduce the dimension of feature variables. Classification method based Bayes' theorem are deduced. Results of experiments confirmed that the classification based on Bayes' theorem achieved better accuracy than the exiting method based on the Mahalanobis' distance.

A teleconference system via mobile Internet connections is developed for homecare services. An important purpose of such a system is the realization of real time instruction from a service station (doctors) to service providers (nurses) in mobile conditions. In this paper, we present a whiteboard system as an interactive communication platform between the station site and home site. The following four features of this system are summarized: 1) two distinct layers including image layer and memo layer are used to save mouse motions; 2) a snapshot from USB camera presents medical images or illustrations to all participants' computers in a teleconference; 3) the synchronization of any data and operations (such as displaying an image, drawing a line, and so on) within all participants' computers; 4) a realization via mobile Internet connections, where communication abilities are limited.

We propose an optical domain pilot-aided carrier phase recovery (PA-CPR) scheme used in a single-carrier Nyquist system. A comprehensive mathematical description of the proposed PA-CPR scheme is presented. Optimal parameters for the system are obtained through optimizations. Furthermore, we propose the two-stage PA-CPR algorithm combinations which use the maximum likelihood or constellation transformation phase estimation as the second stage just after the pilot phase compensation. We also make the evaluation and comparison of the linewidth tolerance performances among the proposed two-stage PA-CPR algorithm combinations and other typical CPR algorithms in a 28-Gbaud Nyquist polarization-division multiplexed (PDM)-16QAM optical communication system. The calculation results show that the proposed two-stage PA-CPR algorithm combinations, which have lower complexities, show better performances than others.

We propose an optically generated pilot tone aided carrier phase recovery scheme in dual-carrier Nyquist-mQAM systems. Both side channels can be compensated using one pilot, providing a high linewidth tolerance with small complexity.