First-principles study of transport properties of endohedral Li@C20 metallofullerene

Yi-Peng An,Chuan-Lu Yang,Mei-Shan Wang,Xiao-Guang Ma,De-Hua Wang 한국물리학회 2010 Current Applied Physics Vol.10 No.1

The transport properties of the endohedral Li@C20 metallofullerene are studied using density functional non-equilibrium Green’s function method. The equilibrium conductance of Li@C20 metallofullerene becomes larger than that of the empty C20 fullerene molecule. The I.V curve under low-bias voltage shows the characteristic of metallic behavior; another, the novel negative differential resistance behavior is also observed. It is found that the doping effect of Li atom significantly changes the transport properties of C20 fullerene.

Slender RC columns strengthened with combined CFRP and steel jacket under axial load

Yi-Yan Lu,Shan Li,Na Li,Tian-yan Ou 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.5

This paper presents an experimental study on the effectiveness of simultaneous application of carbon fiber-reinforced polymer (CFRP) and steel jacket in strengthening slender reinforced concrete (RC) column. The columns were 200 mm square cross section with lengths ranging from 1600 to 3000 mm. Ten columns were tested under axial load. The effects of the strengthening technique, slenderness ratio, cross-section area of steel angle and CFRP layer number were examined in terms of axial load-axial strain curve, CFRP strain, steel strip strain and steel angle strain. The experiments indicate that strengthening RC columns with combined CFRP and steel jacket is effective in enhancing the load capacity, ductility and energy dissipation capacity of RC column. Based on the existing models for RC columns strengthened with CFRP and with steel jacket, a design formula considering a slenderness reduction factor is proposed to predict the load capacity of the RC columns strengthened with combined CFRP and steel jacket. The predictions agree well with the experimental results.

Effect of the Outer Diameter on the Behavior of Square RC Columns Strengthened with Self-Compacting Concrete Filled Circular Steel Tube

Yi-Yan Lu,Zhenzhen Liu,Shan Li,Xiaobo Zhao 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3

This paper aimed to investigate the optimum outer diameter of square RC columns strengthened with self-compacting concrete fi lled circular steel tube. An experiment of twelve strengthened RC columns (SRC) and two referential RC columns subjected to axial load was presented. The variables considered in the test were the confi nement index and the diameter of the strengthened section. The experimental results showed that, with the same confi nement index, the material strength utilization of SRC columns dropped with the increasing of strengthened section diameter. There existed an optimum outer diameter to take full use of material strength. With the outer diameter below the optimum value, the material strength utilization increased with increasing confi nement index. As the outer diameter beyond the optimum one, the material strength utilization decreased with improving confi nement index.

Eccentric strength and design of RC columns strengthened with SCC filled steel tubes

Yi-Yan Lu,Hong-Jun Liang,Shan Li,Na Li 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.4

Self-compacting Concrete Filled steel Tubes (SCFT), which combines the advantages of steel and concrete materials, can be applied to strengthen the RC columns. In order to investigate the eccentric loading behavior of the strengthened columns, this paper presents an experimental and numerical investigation on them. The experimental results showed that the use of SCFT is interesting since the ductility and the bearing capacity of the RC columns are greatly improved. And the performance of strengthened columns is significantly affected by four parameters: column section type (circular and square), wall thickness of the steel tube, designed strength grade of strengthening concrete and initial eccentricity. In the numerical program, a generic fiber element model which takes in account the effect of confinement is developed to predict the behavior of the strengthened columns subjected to eccentric loading. After the fiber element analysis was verified against experimental results, a simple design formula based on the model is proposed to calculate the ultimate eccentric strength. Calibration of the calculated results against the test results shows that the design formula closely estimates the ultimate capacities of the eccentrically compressed strengthened columns by 5%.

Axial behavior of RC columns strengthened with SCC filled square steel tubes

Yi-Yan Lu,Hong-Jun Liang,Shan Li,Na Li 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.3

Self-compacting Concrete (SCC) Filled Square steel Tubes (SCFST) was used to strengthen square RC columns. To establish the efficiency of this strengthening method, 17 columns were tested under axial compression loading including 3 RC columns without any strengthening (WRC), 1 RC column strengthened with concrete jacket (CRC), 13 RC columns strengthened with self-compacting concrete filled square steel tubes (SRC). The experimental results showed that the use of SCFST is interesting since the ductility and the bearing capacity of the RC columns are greatly improved. The improvement ratio is significantly affected by the nominal wall thickness of steel tubes (<i>t</i>), the strength grade of strengthening concrete (C), and the length-to-width ratio (L /B) of the specimens. In order to quantitatively analyze the effect of these test parameters on axial loading behavior of the SRC columns, three performance indices, enhancement ratio (ER), ductility index (DI), and confinement ratio (CR), were used. The strength of the SRC columns obtained from the experiments was then employed to verify the proposed mode referring to the relevant codes. It was found that codes DBJ13-51 could relatively predict the strength of the SRC columns accurately, and codes AIJ and BS5400 were relatively conservative.

Durability of CFRP Strengthened Steel Plates Under Wet and Dry Cycles

Shan Li,Jiyue Hu,Yi-Yan Lu,Hong-Jun Liang 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.2

This paper presents tensile test results of CFRP strengthened steel plates (CS) after wet and dry corrosion. The number of cycle times and strengthened schemes were investigated. The results showed that the CS specimens, subjected to wet–dry corrosion, behaved in a more brittle manner and appeared massive CFRP and adhesive rupturing coincided with the failure. As the wet–dry cycle increasing, the yield strength and ultimate strength of CS strengthened specimens decreased signifi - cantly, while the stiff ness before and beyond yield strength degraded slightly. Furthermore, the yield strength and ultimate strength of double-sided specimens subjected to wet–dry cycles were higher than those of one-sided specimens. Finally, analytical formulas considering wet–dry corrosion were proposed to predict elastic modulus, yield strength, tangent modulus, ultimate strength of CS specimens subjected to wet–dry cycles, respectively. The calculated results were in good agreement with experimental values.

Operation start time and long-term outcome of hepatocellular carcinoma after curative hepatic resection

Qiang Lu,Qing-Shan Li,Wei Zhang,Kang Liu,Tao Li,Jia-Wei Yu,Yi Lv,Xu-Feng Zhang 대한외과학회 2020 Annals of Surgical Treatment and Research(ASRT) Vol.99 No.1

Purpose: The objective of the current study was to examine the potential effects of surgery start times (morning vs. afternoon) on the long-term prognosis of patients after hepatic resection (HR) for hepatocellular carcinoma (HCC). Methods: All eligible patients were divided into 2 groups according to the start time of surgery: group M (morning surgery, 8 AM–1 PM) and group A (afternoon surgery, 1 PM–6 PM). Clinicopathologic and surgical parameters, as well as oncologic outcomes were compared between the 2 groups. Results: In total, 231 patients were included in the study. There was no difference in age, body mass index, comorbidities, tumor size, tumor location, tumor stages, surgical procedures, or surgical margin between morning and afternoon surgery (all P > 0.05). In contrast, patients in group M experienced longer operation duration than those in group A (median, 240 minutes vs. 195 minutes, P = 0.004). However, no differences of overall survival were observed between morning and afternoon surgery groups in the whole cohort or stratified by surgical margin (all P > 0.05). Conclusion: Surgery start times during the work day have no measurable influence on patient outcome following curative HR for HCC, indicating good self-regulation and professional judgment of surgeons for progressive fatigue during surgery

Impedance Identification Using Tactile Sensing and Its Adaptation for an Underactuated Gripper Manipulation

Zhong-Yi Chu,Shao-Bo Yan,Jian Hu,Shan Lu 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.2

Underactuated gripper has a broad application in the field of space robot and industrial robot because of its better shape-adaptation. However, because of the underactuated characteristics, it is a great challenge to accurately obtain the displacement of the contact point between the finger and grasped object, which makes it difficult to control the gripper grasp stably, especially the environmental parameters are unknown. This paper develops the identification of the unknown environmental parameters using a tactile array sensor based on the recursive leastsquares (RLS) method. The unknown environments are described as linear systems with unknown dynamics, and the environmental parameters are identified using the measured contact force and the derived displacement of the contact point which is obtained through the underactuated gripper dynamics. Meanwhile, an impedance adaptive control is presented to match the variability of the environment parameters, and the desired impedance model is imposed to the underactuated gripper to achieve stable grasp. A cost function that measures the contact force, velocity and displacement error is defined, and the critical impedance parameters are found to minimize it. At last, a co-simulation of ADAMS and MATLAB for an underactuated gripper grasp is implemented to show the feasibility of environmental parameters identification and its adaptive method.

Statistical-based evaluation of design codes for circular concrete-filled steel tube columns

Na Li,Yi-Yan Lu,Shan Li,Hong-Jun Liang 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.2

This study addresses the load capacity prediction of circular concrete-filled steel tube (CFST) columns under axial compression using current design codes. Design methods given in the Chinese code CECS 28:2012 (2012), American code AISC 360-10 (2010) and EC4 (2004) are presented and described briefly. A wide range of experimental data of 353 CFST columns is used to evaluate the applicability of CECS 28:2012 in calculating the strength of circular CFST columns. AISC 360-10 and EC4 (2004) are also compared with the test results. The comparisons indicate that all three codes give conservative predictions for both short and long CFST columns. The effects of concrete strength, steel strength and diameter-to-thickness ratio on the accuracy of prediction according to CECS 28:2012 are discussed, which indicate a possibility of extending the limitations on the material strengths and diameter-to-thickness ratio to higher values. A revised equation for slenderness reduction factor in CECS 28:2012 is given.

Eccentrically compressive behaviour of RC square short columns reinforced with a new composite method

Fan Zhang,Yi-Yan Lu,Shan Li,Wenlong Zhang 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.1

A new composite reinforced method, namely self-compacting concrete filled circular CFRP-steel jacketing, was proposed in this paper. Experimental tests on eight RC square short columns reinforced with the new composite reinforced method and four RC square short columns reinforced with CFS jackets were conducted to investigate their eccentrically compressive behaviour. Nine reinforced columns were subjected to eccentrically compressive loading, while three reinforced columns were subjected to axial compressive loading as reference. The parameters investigated herein were the eccentricity of the compressive loading and the layer of CFRP. Subsequently, the failure mode, ultimate load, deformation and strain of these reinforced columns were discussed. Their failure modes included the excessive bending deformation, serious buckling of steel jackets, crush of concrete and fracture of CFRP. Moreover, these reinforced columns exhibited a ductile failure globally. Both the eccentricity of the compressive loading and the layer of CFRP had a significant effect on the eccentrically compressive behaviour of reinforced columns. Finally, formulae for the evaluation of the ultimate load of reinforced columns were proposed. The theoretical formulae based on the ultimate equilibrium theory provided an effective, acceptable and safe method for designers to calculate the ultimate load of reinforced columns under eccentrically compressive loading.