MULTIPLE SOLUTIONS OF IMPULSIVE BOUNDARY VALUE PROBLEMS ON THE HALF-LINE

Liu, Xiyu,Yan, Baoqiang 한국전산응용수학회 1998 Journal of applied mathematics & informatics Vol.5 No.1

Existence results of multiple solutions are obtained un-der suitable conditions for impulsive integrodifferential boundary value problems on the half-line which may be singular at the boundary.

Ultra-Low Cyclic Fatigue Fracture of Q235B and Q345B Steels and Their Butt Welded Joints

Xiyue Liu,Yidu Bu,Yuanqing Wang,Yang Guan 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.2

Earthquake-induced fractures in steel structures are characterised by high-strain low-cycle conditions. In order to investigate the ultra-low cyclic fatigue fracture of steel welded joints under earthquakes, two most commonly used structural steels (Q235B and Q345B) and the corresponding welds were studied by experiments and numerical analysis in this paper. Specimens were extracted from the base material, the weld metal and the heat aff ected zone to investigate the behaviour in diff erent parts of the welded joint. Eighteen smooth round bars were tested under large strain amplitudes, the hysteretic properties, damage degradation characteristics and failure process were analyzed. Constitutive model named Chaboche model was calibrated to describe the cyclic hardening behaviour of these materials. Seventy-two notched round bars with three diff erent notch sizes and two loading protocols were tested to study the fracture behaviour of diff erent materials at different stress triaxialities and diff erent strain amplitudes. Two micromechanical fracture models: cyclic void growth model and degraded signifi cant plastic strain model were calibrated based on the test results. The micromechanical models and Chaboche model were incorporated into numerical simulations by software ABAQUS with subroutine VUMAT to predict the materials fracture. The results show that the failure process under cyclic loads is opposite to that of monotone loads. The dissipation capacity of Q345B is superior to that of Q235B. The fracture resistance deteriorate more in the weld zone under the same loading conditions. The validated models can be used to eff ectively and accurately evaluate the fracture in steel welded connections under ULCF conditions.

Investigation of the Fracture Behavior of High-Strength Structural Steel and Welds based on Micromechanical Models

Liu XiYue,Yang Jia,Wang YuanQing,Ye YiCong,Li JinGuang,Sun Tong 한국강구조학회 2024 International Journal of Steel Structures Vol.24 No.4

To investigate the fracture initiation mechanisms and establish the relationship between the ductile fracture mechanism and macro stress–strain for high-strength structural steel, the mechanical response and fracture behavior of Q460C steel and its butt welds were studied via tests, numerical analysis and scanning electron microscopy (SEM) in this paper. The mechanical properties of high-strength steel (HSS) under diff erent stress triaxialities were studied by uniaxial tensile tests on standard specimens and notched round rods. The fi nite element model is set up according to the characteristic length which is based on SEM observations. By combining experimental results and numerical simulations, the constitutive model and fracture prediction model were established. The relationship between the ductile fracture mechanism and the macro stress strain was obtained. The toughness parameters of the micromechanical model of Q460C steel and its welded joints were compared with those of Q345 steel and seven other types of structural steel from the United States and Japan. The results show that the characteristic length of the crack tip is the key factor aff ecting the accuracy of predicting fracture toughness under a large stress–strain gradient. The toughness predicted by the model is in good agreement with the traditional fracture toughness test results when taking the average value. The experimental results and fi nite element analysis verifi ed the eff ectiveness of the VGM and SMCS micromechanical models in predicting the fracture toughness of Q460C steel and its welded joints, which can provide a theoretical basis and practical guidance for the anti-fracture design and application of HSS structures.

Anti-Reactive Jamming Technology Based on Jamming Utilization

Xin Liu,Mingcong Zeng,Yarong Liu,Mei Wang,Xiyu Song 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.10

Since the existing anti-jamming methods, including intelligent methods, have difficulty against high-speed reactive jamming, we studied a new methodology for jamming utilization instead of avoiding jamming. Different from the existing jamming utilization techniques that harvest energy from the jamming signal as a power supply, our proposed method can take the jamming signal as a favorable factor for frequency detection. Specifically, we design an intelligent differential frequency hopping communication framework (IDFH), which contains two stages of training and communication. We first adopt supervised learning to get the jamming rule during the training stage when the synchronizing sequence is sent. And then, we utilize the jamming rule to improve the frequency detection during the communication stage when the real payload is sent. Simulation results show that the proposed method successfully combated high-speed reactive jamming with different parameters. And the communication performance increases as the power of the jamming signal increase, hence the jamming signal can help users communicate in a low signal-to-noise ratio (SNR) environment.

Graphene quantum dots decorated 3D transitional metal (Fe, Co) oxide graphene nanoribbons for oxygen reduction reaction

Xiyu Zhao,Changrui Lu,Jing Li,Caiyun Liu,Cheng Cao,Tianli Wu 한국탄소학회 2023 Carbon Letters Vol.33 No.1

In this paper, we presented a hybrid composite of graphene quantum dots (GQDs)-modified three-dimensional graphene nanoribbons (3D GNRs) composite linked by Fe3O4 and CoO nanoparticles through reflux and ultrasonic treatment with GQDs, denoted as 3D GQDs-Fe3O4/CoO@GNRs (3D GFCG). In this hybrid, the 3D GNRs framework strengthened the electrical conductivity and the synergistic effects between GQDs and 3D GFCG enhanced the oxygen reduction reaction (ORR) activity of the nanocomposite. The results imply that decorating GQDs with other electro-catalysts is an effective strategy to synergistically improve their ORR activity.

Efficient Method to Include Joint Zones of Chord Members in Finite Element Model of Tubular Transmission Tower at Linear Elastic Stage

Haifeng Liu,Junke Han,Zhenmao Sun,Jingbo Yang,Fengli Yang,Xiyu Xu 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.4

To include the effects of the joint zones efficiently, firstly a chord member considering the joint zones is seen as a combination of three beams with different sections and its element stiffness matrix is derived; Secondly, based on the statistically geometrical properties of the joint zones and chord members in service, the coefficients in the element stiffness matrix of the varied section beam element related to the moments and shear forces greatly increase more than 70%, while the coefficients related to axial forces only increase less than 2%. Therefore, along with the other two inherent mechanical properties of member structures, it is essential to include the effects of the joint zones. Finally, the results by the finite element models where the chord members and the joint zones are simulated by four methods are compared, which proves the efficiency and the accuracy of the varied section beam element.

Dynamic Response of High Strength Steel Beams Subjected to Explosion Induced Blast Load

Xinchang Feng,Xiyue Liu,Zhiyang He,Shuxin Bai,Shun Li,Yu Tang 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.6

A series of anti-explosion tests were performed on H-type high strength steels (Q460JSC and HQ600) and ordinary steels (Q345B) to address the problem of anti-explosion in the technical application of high strength steel. The dynamic behavior of steel beams during explosion and the propagation of shock waves were analyzed. The effects of proportionate distance, steel strength, high-span ratio, section shapes were investigated. The finite element software (ANSYS/LS-DYNA) was used to analyze the anti-explosion performance of high strength steel beams. The finite element models which adopted modified Johnson–Cook constitutive model and damage criterion were validated by comparing with the experimental results. The influence factors of anti-explosion performance of high strength steel were explored by numerical simulation as well. The results reveal that under near-explosion conditions, the peak values of overpressure predicted by empirical formulas are often less than the experimental outcomes. As the scaled distance reduces, the damage to the steel beam increases, making it more prone to local fracture. By decreasing the scaled distance, increasing the high-span ratio, and strengthening the constraint of H-type steel beam, the deformation and damage of steel beams can reduce. The results provide an effective basis to evaluate the safety of high strength steel beams applied in practical engineering when subjected to explosion.

Fertility and prognosis assessment between bleomycin/etoposide/cisplatin and paclitaxel/carboplatin chemotherapy regimens in the conservative treatment of malignant ovarian germ cell tumors: a multicenter and retrospective study

Ran Chu,Penglin Liu,Jingying Chen,Xiaodong Cheng,Kezhen Li,Yanci Che,Jianliu Wang,Li Li,Xi Zhang,Shu Yao,Li Song,Ying Zhao,Changzhen Huang,Ying Xue,Xiyu Pan,Junting Li,Zhongshao Chen,Jie Jiang,Beihua 대한부인종양학회 2023 Journal of Gynecologic Oncology Vol.34 No.2

Objective: To evaluate the impact of bleomycin/etoposide/cisplatin (BEP) and paclitaxel/carboplatin (PC) chemotherapy regimens on the fertility and prognostic outcomes in malignant ovarian germ cell tumor (MOGCT) patients who underwent fertility-sparing surgery (FSS). Methods: A propensity score matching algorithm was performed between the BEP and PC groups. The χ2 test and the Kaplan-Meier method were used to compare the fertility outcome, disease-free survival (DFS) and overall survival (OS). The Cox proportional hazards regression analysis was used to identify risk factor of DFS. Results: We included 213 patients, 185 (86.9%) underwent BEP chemotherapy, and 28 (13.1%) underwent PC chemotherapy. The median age was 22 years (range, 8–44 years), and the median follow-up period was 63 months (range, 2–191 months). Fifty-one (29.3%) patients had a pregnancy plan, and 35 (85.4%) delivered successfully. In the before and after propensity score matching cohorts, there were no significant differences in spontaneous abortion, selective termination of pregnancy, during-pregnancy status, and live birth between the BEP and PC groups (p>0.05). Fourteen (6.6%) patients experienced recurrence, including 11 (5.9%) in the BEP group and 3 (10.7%) in the PC group. Four (1.9%) patients in the BEP group died. Kaplan-Meier analysis revealed no significant differences in DFS (p=0.328) and OS (p=0.446) between the BEP and PC groups, and the same survival results were observed in the after matching cohort. Conclusion: The PC regimen is as safe as the BEP regimen for MOGCT patients with fertility preservation treatment, and no differences were observed in fertility and clinical prognosis.

Robust, fatigue resistant, self-healing and antifreeze ionic conductive supramolecular hydrogels for wearable flexible sensors

Jia Yang,Qiong Kang,Bin Zhang,Xiyu Tian,Shuzheng Liu,Gang Qin,Qiang Chen 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

Ionic conductive hydrogel-based sensors have been capturing growing attention in various areas, but stillcannot satisfy the operating requirements of next generation wearable electronics. Herein, inspired bybiosystems, we demonstrate ionic conductive supramolecular hydrogels with simple one-step methodbased on salting-out effect and multiple hydrogen bond interactions. The supramolecular hydrogels exhibithigh toughness and strength, quick self-recovery, high sensitive sensing performance as well as goodself-healing, fatigue and frost resistances in mechanical and sensing properties, and can monitor largeand subtle movements and physiological activities of the human body sensitively, quickly and stably. Thus, it provides a convenient and promising way to obtain stretchable sensors of excellent comprehensiveproperties, which have tremendous application potential as wearable electronic devices in harshenvironments.

Fault analysis of CNC equipment based on DEMATEL/ISM/ANP

Sun Shuguang,Zhou Wenjie,Zhang Meng,Liu Xiyu,Mou Xiaowan 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.8

To make a reasonable reliability improvement strategy for CNC equipment, it is necessary to clearly understand the fault relation characteristics and the weak links of reliability. While the fault complexity of CNC equipment makes the fault relation characteristics unclear, it is very difficult to determine the weak link of reliability. Therefore, a fault analysis method for CNC equipment based on decision-making and trial evaluation laboratory (DEMATEL)/ interpretive structure modeling (ISM)/analytic network process (ANP) is proposed in this study to describe the relationship between CNC equipment faults accurately and identify reliability weaknesses. First, the fault mechanism was analyzed by the fault phenomenon, and the fault factors of the CNC equipment were identified in view of the system. Second, DEMATEL/ISM/ ANP method was adopted to integrate the interaction direction and intensity between the failure factors, hierarchical structure of the factors, and their relative importance, and a hierarchical network structure model for CNC equipment fault factors was built. Finally, according to the analysis results of the aforementioned model, the fault factors of the CNC equipment were divided into drive, link, dependence, and independent fault factors, and the identification of the weak link of reliability was completed. Results show that the proposed method can quantify the fault factors of the CNC equipment and clearly identify the main direction of its reliability improvement.