Tradeoff between utility and lifetime in energy-constrained wireless sensor networks

We study the tradeoff between network utility and network lifetime using a cross-layer optimization approach. The tradeoff model in this paper is based on the framework of layering as optimization decomposition. Our tradeoff model is the first one that incorporates time slots allocation into this framework. By using Lagrangian dual decomposition method, we decompose the tradeoff model into two subproblems： routing problem at network layer and resource allocation problem at medium access control （MAC） layer. The interfaces between the layers are precisely the dual variables. A partially distributed algorithm is proposed to solve the nonlinear, convex, and separable tradeoff model. Numerical simulation results are presented to support our algorithm.

GRU-Based Fault Diagnosis Method for Ball Mill

Recently, the fault diagnosis of the ball mill mostly depends on the experience of workers, which brings about a lot of uncertainty for fault diagnosis. In addition, the cost of labor is getting higher, so that the research of ball mill fault diagnosis based on machine learning has become increasingly valuable. The current fault diagnosis methods are mostly judging based on instantaneous data, which makes it difficult to reflect the ball mill indicators and the occurrence of time-related correlation(such as hysteresis effect). This paper presents a ball mill fault diagnosis method based on Gate Recursion Unit(GRU),which analyzes the fault data in the form of time series and compares with other common methods such as neural network, Autoencoder and Long Short-Term Memory(LSTM). After comparison,it is concluded that the fault diagnosis method based on GRU ball mill has the lowest error rate as 4.85%.

Optimal replicator factor control in wireless sensor networks

For TDMA MAC protocols in wireless sensor networks (WSNs), redundancy and retransmission are two important methods to provide high end-to-end transmission reliability. Since reliable transmissions will lead to more energy consumption, there exists an intrinsic tradeoff between transmission reliability and energy efficiency. For each link, we name the number of its reserved time slots in each MAC superframe as a replicator factor. In the following paper, we propose a reliability-lifetime tradeoff framework (RLTF) for WSNs to study replicator factor control problem. First, for the redundancy TDMA MAC, we formulate replicator factor control problem as convex programming. By the gradient projection method, we develop a fully distributed algorithm to solve the convex programming. Second, for the retransmission TDMA MAC, we set the retransmission upper bound for each link according to the optimal replicator factors under the redundancy MAC and compute the total communication overhead for the retransmission MAC. Finally, we compare the communication overhead of these two MAC protocols under different channel conditions.