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1

Dynamic Test and Analysis of Strength of Bamboo Curtain Plywood Based on Free Vibration Modal Method

Gu Xiaoyu, Zhou Aijin, Adjei Patrick, Zhang Rongzhuo, Zhou Yuhao, Wang Zheng

Drewno : prace naukowe, doniesienia, komunikaty

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2023

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Vol. 66, nr 212

Art. no. 176766

EN

Bamboo curtain plywood is made of equal-thickness slotted bamboo slivers as its constituent units and is formed into boards with high pressure. In this paper, rectangular plates, beam specimens, and two sizes of square plates were tested to determine the elastic modulus and shear modulus of bamboo curtain plywood quickly, easily, and accurately. The free square board torsional vibration method was used to test the shear modulus of the square plates. The dynamic test results were also verified by means of the static four-point bending method. The main conclusions show that the dynamic elastic modulus, shear modulus and Poisson's ratio of this bamboo curtain plywood are 0.7 GPa, 1300 MPa and 0.12, respectively. The values of the elastic constants of these bamboo curtain plywood specimens measured by dynamic and static methods are consistent, and this dynamic test method has the advantages of fast, easy, good repeatability and high accuracy.

2

Columnar Dendrite Morphology and Solute Concentration of GH3039 Nickel-Based Superalloys during Wire and Laser Additive Manufacturing: Insights from Phase Field Simulations

Zong Nanfu, Wang Zheng, Liu Yang, Liang Xinghong, Jing Tao

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 1

387--393

EN

Wire and laser additive manufacturing (WLAM) can produce outstanding mechanical properties of GH3039 nickel-based superalloys. A quantitative rapid phase field model with solute trapping kinetics has been developed during the rapid solidification process, where a range of process conditions are considered in terms of thermal gradients and pulling speeds. Intergranular hot cracking is found to occur at boundaries of tilted columnar dendrite in the GH3039 nickel-based superalloys. The simulations demonstrate that the phase field model considering the interface deflection can represent the dendrite growth during additive manufacturing more realistically. With the aid of numerical simulations, it is determined that dendrite growth morphologies transform from symmetrical columnar dendrite to tilted columnar dendrite as the interface crystallographic deflection is increased, while increasing the deflection angle can lead to uneven composition of material matrix, especially at the columnar dendrite interface. Solute concentrations at the columnar dendrite interface tend to promote hot cracking in additively manufactured Ni-based superalloy.

3

Dynamics of plant litter storage in a subtropical forest headwater stream during the rainy season

Hu Wanrong, Wu Fuzhong, Ni Xiangyin, Peng Yan, Wang Zheng, Zhao Zemin, Wang Yuan, Yue Kai

Polish Journal of Ecology

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2022

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vol. 70, nr 4

129--141

EN

Plant litter is not only the major source of carbon (C) and nutrients for heterotrophic organisms in forest headwater streams, but also an important component of stream C storage. The dynamics of stream litter storage (i.e., the standing stock) are thus closely related to forest C fluxes, but has not been well assessed in the literature. To fill this gap, we investigated the monthly dynamics of plant litter storages at 17 reaches of a subtropical headwater stream from stream source to mouth during the rainy season (from March to August) of 2021. We found that (1), across sampling reaches, the mean litter storages of leaves, twigs (< 1 cm in diameter), fine woody debris (FWD, < 10 cm in diameter), reproductive parts (flowers and/or fruits), and barks in the stream during the rainy season were 25.6, 11.9, 16.7, 0.3, and 0.6 g/m2, respectively, and the storage peak of total litter was in May, while the storage peaks at most of the sampling reaches were in April and May; (2) litter storage, especially leaf litter, at the stream source reach (i.e., reach 1) was significantly higher than those in the other reaches, and riparian forest type affected the storages of twig and FWD litter, with higher values in reaches with broad-leaved than mixed riparian forests; and (3) stream physicochemical characteristics, especially channel gradient, channel width, and water discharge and alkalinity, had significant effects on litter storage, but their effects varied among different litter types. Overall, our study clearly assessed the dynamics of plant litter storages in a headwater stream of subtropical forests, which will help us to better understand the role of headwater streams in forest carbon storage and cycling.

4

Attapulgite suspension filter material for biological aerated filter to remove CODMn and ammonia nitrogen in micropolluted drinking water source

Xu Kai, Wang Jiahao, Li Jiacheng, Wang Zijie, Lin Zizeng, Wang Zheng

Environment Protection Engineering

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2020

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Vol. 46, nr 4

21--40

EN

An attapulgite suspended (AS) filter material was successfully prepared and used in combination with biological aerated filter (BAF) to pretreat excess organic matter and ammonia nitrogen in micropolluted water. The AS filter material was of low density and floated on the water surface, which is beneficial to optimize the hydraulic conditions. Through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) It was found that the surface of the filter material was uneven, the pores were deep. When the hydraulic load is 4 m/h and the gas to water volume ratio is 2:1, the removal rates of permanganate index (CODMn) and ammonia nitrogen by ASBAF are up to 57.49 and 88.11%, respectively, and the effluent quality meets relevant standards. After backwashing, the pollutants removal rate will return to stable filtration after two hours. A short-term shutdown of the reactor has little effect on the processing performance of ASBAF, but a long-term shutdown will greatly affect the removal rate of CODMn. The complete organic matter degradation model can well fit the experimental effluent water quality.

5

Fault Diagnosis of Sensors for T-type Three-Level Inverter-fed Dual Three-Phase Permanent Magnet Synchronous Motor Drives

Wang Xueqing, Wang Zheng, Wang Wei, Cheng Ming

Power Electronics and Drives

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2019

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Vol. 4 (39)

165--176

EN

To improve the reliability of motor system, this paper investigates the sensor fault diagnosis methods for T-type inverter-fed dual three-phase permanent magnet synchronous motor (PMSM) drives. Generally, a T-type three-level inverter-fed dual three-phase motor drive utilizes four phase-current sensors, two direct current (DC)-link voltage sensors and one speed sensor. A series of diagnostic methods have been comprehensively proposed for the three types of sensor faults. Both the sudden error change and gradual error change of sensor faults are considered. Firstly, the diagnosis of speed sensor fault was achieved by monitoring the error between the rotating speed of stator flux and the value from speed sensor. Secondly, the large high-frequency voltage ripple of voltage difference between the estimated voltage and the reference voltage was used to identify the voltage sensor faults, and the faulty voltage sensor was determined according to the deviation of voltage difference. Thirdly, the abnormal current amplitude on harmonic subspace was adopted to identify the current sensor faults, and the faulty current sensor was located by distinguishing the current trajectory on harmonic subspace. The experiments have been taken on a laboratory prototype to verify the effectiveness of the proposed fault diagnosis schemes.

6

Secure Data Aggregation Mechanism based on Constrained Supervision for Wireless Sensor Network

Wang Yubo, Li Liang, Ao Chen, Zhang Puning, Wang Zheng, Zhao Xinyang

International Journal of Electronics and Telecommunications

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2019

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Vol. 65, No. 2

259--266

EN

The data aggregation process of wireless sensor networks faces serious security problems. In order to defend the internal attacks launched by captured nodes and ensure the reliability of data aggregation, a secure data aggregation mechanism based on constrained supervision is proposed for wireless sensor network, which uses the advanced LEACH clustering method to select cluster heads. Then the cluster heads supervise the behaviors of cluster members and evaluate the trust values of nodes according to the communication behavior, data quality and residual energy. Then the node with the highest trust value is selected as the supervisor node to audit the cluster head and reject nodes with low trust values. Results show that the proposed mechanism can effectively identify the unreliable nodes, guarantee the system security and prolong the network life time.