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- 저자 : Shizhong Xu (검색결과 4 건)
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Shizhong Xu,Xiong Wang,Guangxu Yang,Jing Ren,Sheng Wang 한국통신학회 2020 Journal of communications and networks Vol.22 No.2
Distributed in-network cloud architecture is a promisingsolution to efficiently host next generation internet-of-things (IoT)services. With the rapid increase of IoT devices and applications,the backhaul or backbone networks, which transmit IoT trafficto various in-network clouds, will experience a predicted explosionin the volume of carried traffic. To guarantee the QoS of IoTcloud services and improve the network performance, it is crucialfor network operator to implement efficient routing optimizationstrategies for IoT traffic. As a promising networking paradigm,software-defined networking (SDN) has flexible and programmablecontrol capability for fine-grained flows. The emergence of SDNpaves a way for implementing high-performance routing optimizationin networks. In SDN networks, the routing strategies are realizedthrough flow rules, which are usually stored in TCAM withvery limited capacity. However, the number of IoT flows are enormous. Thus, in this paper, we address the routing optimizationproblem in SDN-based IoT with TCAM capacity constraint. Wefirst formulate the problem as a mixed integer linear programmingproblem and prove the problem is NP-hard. Then to solve theproblem efficiently, we propose several approximate algorithms,which solve the problem in two stages. In the first stage, the algorithmscalculate the routing strategies for flows without consideringthe TCAM capacity constraint. To meet the TCAM capacityconstraint, the algorithms using different strategies to adjust thepaths of some flows in the second stage. Extensive simulations areconducted on both real ISP and synthetic topologies to evaluate theperformance of the algorithms. The simulation results verify thatthe algorithms can achieve promising load balancing performancein SDN-based IoT, where the capacity of TCAM in SDN switches isvery limited.
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A Unifi ed Theory for Distortion Analysis of Thin-Walled Hollow Sections
Xun Xu,Huawen Ye,De-Yi Zhang,Shizhong Qiang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3
A novel unifi ed theory for distortion analysis of thin-walled hollow section has been proposed based on the Hellinger– Reissner variational principle to account for distortional shear deformation eff ects. Based on the proposed theory, a fi nite segment model has been developed and the method for determining the distortion functions of the cross-section has been proposed. The rationality of approaches for determining distortional shear stress has been analysed and it is concluded that Bredt’s pure distortion does not exist in the single-cell hollow section. Comparisons and analyses have been performed between the proposed theoretical model and the existing four groups of theories in distortion analysis of thin-walled hollow section. Eff ects of distortional warping shear stress on the shear deformation has been investigated and the results indicate that the distortional shear deformation eff ect results in a decrease of the distortional warping stresses and shear stresses but an increase of the transverse bending stresses. The numerical study indicates that the distortional shear deformation eff ects can be ignored and the fi rst derivative of the distortion angle can be employed as the distortional warping function for the conventional hollow sections of bridge structures.
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Yunlai Zhao,Shizhong Zhang,Hongwei Zhao,Guang’ai Sun,Yao Xu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
Understanding the phase transformation and failure mechanism of NiTi shape memory alloys under variable environments of high and low temperatures is critical to the establishment of constitutive properties and to the realization of controllable design. Information regarding the correlation between the phase transformation and deformation can be obtained by in situ neutron scattering measurements. Therefore, a variable temperature mechanical loading device is designed, which can be used for mechanical loading and in situ neutron scattering measurements in a variable temperature environment. Specifically, the device can achieve precise temperature control with a temperature change from -55 °C to 200 °C in a protective atmosphere. The rated load in the axial direction is 6 kN, and the maximum displacement of the unilateral grip is larger than 30 mm. In situ neutron scattering measurements can be performed through neutron windows, and the strain can be measured by digital image correlation technology. Moreover, the force sensor is calibrated to improve test precision. Through an evaluation of temperature uncertainty, the temperature measurement performance is estimated. Tensile tests of the NiTi alloy at variable temperatures are carried out, and preliminary results are given. The four deformation stages of the NiTi alloy can be seen from the stressstrain curve, which corresponds to the existing results. This demonstrates that the designed variable temperature mechanical loading device can supply the testing demands. The device provides a new way to study the relationship between the phase transformation and mechanical properties of NiTi shape memory alloys at variable temperatures.
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Extraction of bioethanol from fermented sweet sorghum bagasse by batch distillation
Guangming Li,Jihong Li,Shizhong Li,Xu Zu,Lei Zhang,Lisong Qi,Weiliang Xu 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.1
Extraction of bioethanol, a potential alternative to fossil fuel in the transport industry, from sweet sorghum stems [Sorghum bicolor (L.) Moench] using solid-state fermentation (SSF) technology has become a popular research topic worldwide. Because SSF technology can directly convert fermentable sugars into target products without juice squeezing and water input, this method can potentially reduce energy and water consumption. However, ethanol extraction from fermented sweet sorghum bagasse requires further investigation. We used batch solid-state distillation to investigate the optimal operating parameters in a distillation column (diameter, 400 mm) via a single-factor experiment. Results showed that the optimal steam flow rate and loading height were 8-10 kg·h−1 and 700-1,000 mm, respectively. Under optimal conditions, an energy consumption of 3.82 tons of steam per ton of ethanol and distillate concentration of 60.9% (v/v) were obtained. The pseudo-first-order rate equation was used to describe the distillation kinetics, and good correlations were obtained. Therefore, solid-state distillation can be effectively used to extract ethanol from fermented sweet sorghum bagasse.
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