Henan University of Technology

About: Henan University of Technology is a education organization based out in Zhengzhou, China. It is known for research contribution in the topics: Catalysis & Starch. The organization has 7648 authors who have published 6503 publications receiving 73067 citations. The organization is also known as: Hénán Gōngyè Dàxué.

Duty-cycle-aware minimum-energy multicasting in wireless sensor networks

Abstract: In duty-cycled wireless sensor networks, the nodes switch between active and dormant states, and each node may determine its active/dormant schedule independently. This complicates the Minimum-Energy Multicasting (MEM) problem, which was primarily studied in always-active wireless ad hoc networks. In this paper, we study the duty-cycle-aware MEM problem in wireless sensor networks both for one-to-many multicasting and for all-to-all multicasting. In the case of one-to-many multicasting, we present a formalization of the Minimum-Energy Multicast Tree Construction and Scheduling (MEMTCS) problem. We prove that the MEMTCS problem is NP-hard, and it is unlikely to have an approximation algorithm with a performance ratio of (1 - 0(1)) ln Δ, where Δ is the maximum node degree in a network. We propose a polynomial-time approximation algorithm for the MEMTCS problem with a performance ratio of O (H(Δ + 1)), where H(·) is the harmonic number. In the case of all-to-all multicasting, we prove that the Minimum-Energy Multicast Backbone Construction and Scheduling (MEMBCS) problem is also NP-hard and present an approximation algorithm for it, which has the same approximation ratio as that of the proposed algorithm for the MEMTCS problem. We also provide a distributed implementation of our algorithms, as well as a simple but efficient collision-free scheduling scheme to avoid packet loss. Finally, we perform extensive simulations, and the results demonstrate that our algorithms significantly outperform other known algorithms in terms of the total transmission energy cost, without sacrificing much of the delay performance.

Attitude-Rate Measurement and Control Integration Using Magnetically Suspended Control and Sensitive Gyroscopes

Abstract: To achieve the high-accuracy and high-bandwidth attitude-rate measurement and control integration of spacecraft, a novel method based on a magnetically suspended control and sensitive gyroscope (MSCSG) configuration is proposed in this paper. MSCSGs are employed as both actuators and attitude-rate sensors. First, the structure and principle of a MSCSG is given and its modeling is established. Second, the attitude-rate measurement method based on a four-cross configuration is proposed. The corresponding attitude decoupling control law of spacecraft and the steering law of the MSCSGs have been further designed. Compared with the traditional attitude-rate measurement methods, the proposed one entirely preserves the inertial coupling moment items and cross-coupling moment items in the resolution of attitude rate by making full use of the dynamic information of the configuration. Thus, the measurement precision can be greatly improved, and the traditional tension between the accuracy and bandwidth can be well alleviated. The proposed method also enlarges greatly the attitude control bandwidth by the microgimbal moment, providing a new method for high-frequency vibration suppression. Semiphysical simulation results demonstrate the correctness and superiority of the proposed method.

Ba–ZnO catalysts for soybean oil transesterification

Abstract: The transesterification of soybean oil to biodiesel using Ba–ZnO as a solid catalyst was investigated. The Ba–ZnO sample with loading of 2.5 mmol/g Ba on ZnO and being calcined at 873 K for 5 h, was found to be the optimum catalyst, which could exhibit the highest basicity and the best catalytic activity for the reaction. When the transesterification reaction was carried out at reflux of methanol (338 K), with a 12:1 molar ratio of methanol to oil and a catalyst amount of 6 wt.%, the conversion of soybean oil was 95.8%. Furthermore, XRD, XPS, DTA–TG and the Hammett indicator method were employed for the catalyst characterizations, and the relation between the catalytic efficiency and the basicity of the catalysts was also discussed.