Resource Allocation for Relay-Aided Cooperative Systems Based on Multi-Objective Optimization

( Runze Wu ),( Jiajia Zhu ),( Hailin Hu ),( Yanhua He ),( Liangrui Tang ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.5

This paper studies resource allocation schemes for the relay-aided cooperative system consisting of multiple source-destination pairs and decode-forward (DF) relays. Specially, relaying selection, multisubcarrier pairing and assignment, and power allocation are investigated jointly. We consider a combinatorial optimization problem on quality of experience (QoE) and energy consumption based on relay-aided cooperative system. For providing better QoE and lower energy consumption we formulate a multi-objective optimization problem to maximize the total mean opinion score (MOS) value and minimize the total power consumption. To this end, we employ the nondominated sorting genetic algorithm version II (NSGA-II) and obtain sets of Pareto optimal solutions. Specially, two formulas are devised for the optimal solutions of the multi-objective optimization problems with and without a service priority constraint. Moreover, simulation results show that the proposed schemes are superior to the existing ones.

Studies on Axial Tensile Loading Capacity of CHS T-joints Reinforced with External Stiffening Rings

Shanshan Huang,Lei Zhu,Hailin Sun,Miao Wang,Xi Chen 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.3

To analyze the eff ects of stiff ening external rings on the brace axial tension capacity of circular hollow section T-joints (CHST), loading experiments and fi nite element model analysis were utilized. Three groups of full-scale specimens (reinforced and unreinforced T-joints) of diff erent brace-to-chord diameter ratios were tested under tension to validate the strengthening eff ect (Three unreinforced specimens were previously tested and the other three reinforced samples were newly completed). The experimental equipment and parameters are described in detail. Load–ovalization and load–displacement curves in addition to the failure modes were analyzed. It is concluded that the ultimate strength and initial stiff ness are signifi cantly enhanced for the reinforced CHS joints compared to the unreinforced specimens. SHELL181 elements were utilized in the fi nite element analysis to accurately simulate the loading capacity with and without external stiff ening rings of the joints, within 10% error.

Experimental and Numerical Investigation of Axial Tensile Strength of CHS X-Joints Reinforced with External Stiffening Rings

Lei Zhao,Lei Zhu,Hailin Sun,Lu Yang,Xi Chen 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.3

To study the reinforcement eff ect of the external stiff ening ring reinforced and unreinforced X-joints having a circular hollow section subjected to brace tensile load, an experimental and computer-simulated research has been done. Six full-scale X-joints are examined in this study: three reinforced specimens and three corresponding unreinforced ones. The test specimens cover diff erent brace to chord diameters ratios ( β ) of 0.25, 0.51, and 0.73. The experimental facilities and detailed parameters are presented. The experimental results including failure modes, load–displacement curves, and ultimate capacity are analyzed and compared. Two failure modes, weld failure and chord plastifi cation, are observed in the tests. The test results reveal an ultimate load enhancement in the reinforced joints by approximately 50% in comparison with the unreinforced joints and an initial stiff ness increase of 248.1% for the β of 0.25 and approximately 49–76% for the β of 0.51 and 0.73. A fi nite element model using shell elements is developed, which accurately predicts the static performance of the X-joints subjected to brace tensile load with and without external stiff ening rings.

A Novel Structural Optimization Method and a Case Study Based on a CHS X-Joint

Xingqi Liu,Weitong Yi,Hailin Sun,Lei Zhu,Xi Chen 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.4

In this paper, a new structural optimization method, “percentage structure optimization”, is presented. This method is obtained by using fi nite element method (FEM) to reduce a specifi c proportion of the stress ineffi cient element reduction, which is called the "structural optimization percentage index". In addition, an evaluation index of the optimized structure, “economic benefi t index”, is introduced. Compared with the existing structural optimization methods, the optimization process is smoother and the results are more controllable. Moreover, the method of evaluating the optimization results through the “economic benefi t index” pays more attention to the economic benefi ts of the project, and can achieve the balance between the minimization of material and the detention of bearing capacity to maximize the economic benefi ts. On the basis of the existing experiment, using ANSYS 17.0 software, two Circular Hollow Sections (CHS) X-joints are optimized by "structural optimization percentage index" of 5, 10 and 15%, and "economic benefi t index" is adopted as the judgment condition of the optimization results. The results show that the method can not only guarantee the bearing capacity, but also save materials as much as possible, and verify the reliability of the new structural optimization method.

Fabrication of recyclable UiO-66-NH2/PVDF hybrid fibrous membrane for Cr(VI) removal in wastewater

Fan Yu,Liusha Cen,Caihong Lei,Feichao Zhu,Lan Zhou,Hailin Zhu,Bin Yu 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.123 No.-

Efficient and recyclable water treatment technology plays a vital role in practical application of Cr(Ⅵ)removal. Zr-based metal–organic framework (UiO-66-NH2) is widely used in wastewater treatmentdue to its water stability. Powdery UiO-66-NH2 has disadvantages of easy aggregation, reclamation difficultyand secondary pollution. In this work, UiO-66-NH2 was successfully loaded on electrospunpolyvinylidene fluoride (PVDF) fibers by in-situ growth to achieve efficient adsorption and photoreductionof Cr(Ⅵ). Grooved surface of PVDF fibers and truncated octahedron shape of UiO-66-NH2 ensuredthe loading uniformity and firmness. The loading rate and size of UiO-66-NH2 crystals increased withthe amount of trifluoroacetic acid (TFA) in the preparation process. Meantime, the introduction of TFAin synthesis was conducive to the separation efficiency of photogenerated carries. When the additionamount of TFA was 5 ml, UiO-PVDF-3 with loading rate of 44.8% exhibited best Cr(VI) adsorption andphotocatalysis performance. For the pure adsorption process, the adsorption capacity of UiO-PVDF-3 at90 min was 3.76 mg/cm2, and the corresponding removal rate was 95.8%. When visible light was applied,the Cr(VI) removal rate for UiO-PVDF-3 reached to about 95.0% at 45 min. Furthermore, regenerationexperiments showed UiO-PVDF-3 had excellent adsorption and photocatalysis reusability. Based on thismethod, synthesized UiO-66-NH2/PVDF hybrid membrane as a bifunctional material for adsorption andphotocatalysis realizes the reuse of UiO-66-NH2 crystals conveniently and avoids secondary pollutionduring Cr(VI) wastewater treatment.

Lowering Error Floor of LDPC Codes Using an Improved Parallel WBF Algorithm

Kexiang Ma,Yongzhao Li,Caizhi Zhu,Hailin Zhang,Yuming Zhang 한국전자통신연구원 2014 ETRI Journal Vol.36 No.1

In weighted bit-flipping-based algorithms for low-densityparity-check (LDPC) codes, due to the existence ofoverconfident incorrectly received bits, the metric values of thecorresponding bits will always be wrong in the decodingprocess. Since these bits cannot be flipped, decoding failureresults. To solve this problem, an improved parallel weightedbit flipping algorithm is proposed. Specifically, a reliabilitysaturationstrategy is adopted to increase the flippingprobability of the overconfident incorrectly received bits. Simulation results show that the error floor of LDPC codes isgreatly lowered.

Bearing Capacity of Steel Square Tubular Column I-Shaped Beam Joints Connected by New Elliptical One-Sided Bolts

Weitong Yi,Lingxiao Zuo,Tianxi Chen,Mei Wang,Hailin Sun,Lei Zhu,Xi Chen 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.6

A new elliptical one-sided bolt was applied for connection of the steel square tubular column and the I-shaped beam joint. This new bolt is simple in structure and easy to install. Besides, as the bolt head and bolt hole are both elliptical, the new one is quite diff erent from the traditional circular bolts lacking bending performance studies of the joint. Therefore, experiments and fi nite element analysis on ultimate bearing capacity of the joint were conducted, monotonic static loading of six joint specimens were tested, and the moment-rotation curves were obtained in this study. The eff ects of various factors such as axial load ratio and bolt size on bearing capacity were analyzed. Finite element simulation was carried out, and it fi tted tests well. Both tests and simulation showed that failure mode of joints is fi rstly yielding at the endplate. The larger the bolt size, the better the joint ultimate bearing capacity can be enhanced. The M16 group indicated a pattern that the larger axial load on column, the less of ultimate bearing capacity of the joint. However, the M20 group comes to a diff erent pattern which contradicts the assumption, thus further studies are needed in this regard.

Fabrication of ZIF-8/TiO2 electrospinning nanofibers for synergistic photodegradation in dyeing wastewater

Liusha Cen,Tao Tang,Fan Yu,Han Wu,Chengcai Li,Hailin Zhu,Yuhai Guo 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.126 No.-

Semiconductormetal–organic framework (MOF) hybrid photocatalysts become a significant material totreating dyeing wastewater recently. Zinc-based metal–organic framework (ZIF-8) stands out amongnumerous photocatalysts for its stability and simplicity to prepare. In this work, the gourd-shaped ZIF-8/TiO2 nanocomposites are prepared in situ on anatase TiO2 by precursor method, and then ZIF-8/TiO2nanocomposites is supported on PVDF electrospinning nanofibers by blending method to form ZIF-8/TiO2 nanofibers (ZIF-8/TiO2 NFs). We compare the degradation ability of Rhodamine B by ZIF-8/TiO2NFs with different mass ratios and load rates. When the mass ratio of ZIF-8 to TiO2 is 2:1 and the loadingrate is 10%, the photocatalytic degradation efficiency of ZIF-8/TiO2 NFs reached 95.4%, and the degradationremained as high as 88.7% after cycling five times. The characterization results showed that ZIF-8 andTiO2 are connected by N Ti O chemical bond, which narrows the band gap and rebars the recombinationof the electron-hole pairs. The synergistic action of ZIF-8 and TiO2 largely improves the photocatalyticcapacity of ZIF-8/TiO2 NFs.

QoE-aware Energy Efficiency Maximization Based Joint User Access Selection and Power Allocation for Heterogeneous Network

( Shiyu Ji ),( Liangrui Tang ),( Chen Xu ),( Shimo Du ),( Jiajia Zhu ),( Hailin Hu ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.10

In future, since the user experience plays a more and more important role in the development of today’s communication systems, quality of experience (QoE) becomes a widely used metric, which reflects the subjective experience of end users for wireless service. In addition, the energy efficiency is an increasingly important problem with the explosive growth in the amount of wireless terminals and nodes. Hence, a QoE-aware energy efficiency maximization based joint user access selection and power allocation approach is proposed to solve the problem. We transform the joint allocation process to an optimization of energy efficiency by establishing an energy efficiency model, and then the optimization problem is solved by chaotic clone immune algorithm (CCIA). Numerical simulation results indicate that the proposed algorithm can efficiently and reliably improve the QoE and ensure high energy efficiency of networks.