The detection efficiency study of NaI(Tl) scintillation detector with the different numbers of SiPMs

Wang Bao,Zhang Xiongjie,Wang Qingshan,Wang Dongyang,Li Dong,Xiahou Mingdong,Zhou Pengfei,Ye Hao,Hu Bin,Zhang Lijiao 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.7

SiPMs are generally coupled into whole columns in gamma energy spectrum measurement, but the relationship between the distribution of whole SiPM columns and the energy resolution of the measured energy spectra is rarely reported. In this work, ∅ 3 3 inch NaI scintillator is placed on an 8 8 SiPM array, and the energy resolution of the 137Cs peak at 662 keV corresponding to the g-ray is selected as a reference. Each SiPM is switched to explore the influence of the number of SiPM arrays, distribution position, and reflective layer on the energy resolution of SiPMs. Results show that without coupling, the energy resolution is greatly improved when the number of SiPMs ranges from 4 to 32. However, after 32 slices (the area covered by SiPMs relative to the scintillator reaches 25.9%), the improvement in energy resolution and total pulse count is not obvious. In addition, the position of SiPMs relative to the scintillator does not exert much impact on the energy resolution. Results also indicate that by adding a reflective film (ESR), the energy resolution of the tested group increases by 10.38% on average. This work can provide a reference for the design and application of miniaturized SiPM gamma spectrometers

Distortional buckling of I-steel concrete composite beams in negative moment area

Wangbao Zhou,Shujin Li,Zhi Huang,Lizhong Jiang 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.1

The predominant type of buckling that I-steel concrete composite beams experience in the negative moment area is distortional buckling. The key factors that affect distortional buckling are the torsional and lateral restraints by the bottom flange. This study thoroughly investigates the equivalent lateral and torsional restraint stiffnesses of the bottom flange of an I-steel concrete composite beam under negative moments. The results show a coupling effect between the applied forces and the lateral and torsional restraint stiffnesses of the bottom flange. A formula is proposed to calculate the critical buckling stress of the I-steel concrete composite beams under negative moments by considering the lateral and torsional restraint stiffnesses of the bottom flange. The proposed method is shown to better predict the critical bending moment of the I-steel composite beams. This article introduces an improved method to calculate the elastic foundation beams, which takes into account the lateral and torsional restraint stiffnesses of the bottom flange and considers the coupling effect between them. The results show a close match in results from the calculation method proposed in this paper and the ANSYS finite element method, which validates the proposed calculation method. The proposed calculation method provides a theoretical basis for further research on distortional buckling and the ultimate resistance of I-steel concrete composite beams under a variable axial force.

Distortional buckling calculation method of steel-concrete composite box beam in negative moment area

Wangbao Zhou,Shujin Li,Lizhong Jiang,Zhi Huang 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.5

'Distortional buckling&' is one of the predominant buckling types that may occur in a steel-concrete composite box beam (SCCBB) under a negative moment. The key factors, which affect the buckling modes, are the torsional and lateral restraints of the bottom plate of a SCCBB. Therefore, this article investigates the equivalent lateral and torsional restraint rigidity of the bottom plate of a SCCBB under a negative moment; the results of which show a linear coupling relationship between the applied forces and the lateral and/or torsional restraint stiffness, which are not depended on the cross-sectional properties of a SCCBB completely. The mathematical formulas for calculating the lateral and torsional restraint rigidity of the bottom plate can be used to estimate: (1) the critical distortional buckling stress of SCCBBs under a negative moment; and (2) the critical distortional moment of SCCBBs. This article develops an improved calculation method for SCCBBs on an elastic foundation, which takes into account the coupling effect between the applied forces and the lateral and/or torsional restraint rigidity of the bottom plate. This article analyzes the accuracy of the following calculation methods by using 24 examples of SCCBBs: (1) the conventional energy method; (2) the improved calculation method, as it has been derived in this article; and (3) the ANSYS finite element method. The results verify that the improved calculation method, as it has been proved in this article, is more accurate and reliable than that of the current energy method, which has been noted in the references.

Flexural natural vibration characteristics of composite beam considering shear deformation and interface slip

Wangbao Zhou,Lizhong Jiang,Zhi Huang,Shujin Li 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.5

Based on Hamilton's principle, the flexural vibration differential equations and boundary conditions of the steel-concrete composite beam (SCCB) with comprehensive consideration of the influences of the shear deformation, interface slip and longitudinal inertia of motion were derived. The analytical natural frequencies of flexural vibration were compared with available results previously observed by the experiments, the results calculated by the FE model and the other similar beam theories available in the open literatures. The comparison results showed that, the calculation results of the analytical and Timoshenko models had a good agreement with the results of the experimental test and FE model. Finally, the influences of shear deformation and interface slip on the flexural natural frequencies of the SCCB were discussed. The shear deformation effect increases with the increase of the mode orders of flexural natural vibration, and the flexural natural frequencies of the higher mode orders ignoring the influence of shear deformations effect would be overestimated. The interface slip effect decrease with the increase of the mode orders of flexural natural vibration, and the influence of the interface slip effect on flexural natural frequencies of the low mode orders is significant. The influence of the degree of shear connection on shear deformation effect is insignificant, and the low order modes of flexural natural vibration are mainly composed of the rotational displacement of cross sections.

A novel smooth switching control strategy for multiple photovoltaic converters in DC microgrids

Qinjin Zhang,Wangbao Hu,Yancheng Liu,Hanwen Zhang,Honglai Wang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.2

With the photovoltaic (PV) penetration rate increasing in PV-storage-based DC microgrids, the conventional PV controller with only the maximum power point tracking (MPPT) control function can hardly meet the needs of the coordinated operation. The PV converter should operate at the MPPT or the constant voltage droop (CVD) mode according to the load demand. Two sets of relatively independent control loops are used to control the two modes. Inevitably, bus voltage and PV output power fluctuations are caused in the process of mode switching. This paper proposes a novel smooth switching control strategy for the smooth transition of multiple PV converters between MPPT and CVD modes. When combined with the PV array output characteristic curve, the value of dp/di is selected as the control variable. By tracking different dp/di command values, the PV converter can realize the control of the MPPT mode, the CVD mode, and smooth switching between the two modes. The MPPT and CVD modes are unified in the sense of using the same control loop, which avoids control loop switching during the PV mode switching. Finally, the effectiveness of the novel smooth switching control strategy is verified by the simulation and hardware in loop (HIL) experimental tests.

An analytical solution to the vibration characteristics for continuous girder bridge-track coupling system and its application

Yulin Feng,Lizhong Jiang,Wangbao Zhou,Yuntai Zhang,Xiang Liu 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.5

To study the vibration characteristics of a high-speed railway continuous girder bridge-track coupling system (HSRCBT), a coupling vibration analysis model of an m-span continuous girder bridge-subgrade-track system with n-span approach bridge was established. The model was based on the energy and its variational method, where both the interlaminar slip and shear deformation effects were considered. In addition, the free vibration equations and natural boundary conditions of the HSRCBT were derived. Further, according to the coordination principle of deformation and mechanics, an analytical method for calculating the natural vibration frequencies of the HSRCBT was obtained. Three typical bridge-subgrade-track coupling systems of high-speed railway were taken and the results of finite element analysis were compared to those of the analytical method. The errors between the simulation results and calculated values of the analytical method were less than 3%, thus verifying the analytical method proposed in this paper. Finally, the analytical method was used to investigate the influence of the number of the approach bridge spans and the interlaminar stiffness on the natural vibration characteristics of the HSRCBT based on the degree of sensitivity. The results suggest the approach bridges have a critical number of spans and in general, the precision requirements of the analysis could be met by using 6-span approach bridges. The interlaminar vertical compressive stiffness has very little influence on the low-order natural vibration frequency of HSRCBT, but does have a significant influence on higher-order natural vibration frequency. As the interlaminar vertical compressive stiffness increases, the degree of sensitivity to interlaminar stiffness of each of the HSRCBT natural vibration characteristics decrease and gradually approach zero.

Improved Analytical Method to Investigate the Dynamic Characteristics of Composite Box Beam with Corrugated Webs

Yulin Feng,Lizhong Jiang,Wangbao Zhou 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1

This study establishes an improved analytical method (IAM) to investigate the dynamic characteristics of composite box beam with corrugated webs (CBBCW), and the IAM has comprehensively considered the eff ects of several factors, such as the shear lag, interfacial slip, shear deformation and rotational inertia of CBBCW in combination with the characteristics of CBBCW. Further, based on the Hamilton principle, the vibration diff erential equation and boundary conditions for CBBCW have been deduced. Finally, an IAM for calculating the dynamic characteristics of CBBCW was proposed. Based on the IAM developed in this study, the natural frequencies of multiple CBBCW cases with diff erent spans, shear connection degrees and boundary conditions have been calculated. The results calculated by the IAM have been compared with those calculated by the fi nite element method and by the general beam theory. The comparison verifi es the eff ectiveness of the IAM and obtains some conclusions that are meaningful to engineering design, i.e. the shear lag eff ect of CBBCW increases with increasing shear connection degree and also increases with increasing order of the vibration mode, the shear lag eff ect of the CBBCW is up to 6.2% in the fi rst fi ve orders of the vibration modes and the eff ect cannot be ignored. In the fi rst- and second-order vibration modes of the CBBCW cases, the maximum interface slip eff ect of CBBCW is 28.42% and therefore cannot be ignored. On the other hand, the shear lag eff ect of CBBCW is usually lower than those of ordinary composite box beam with the same web thickness.

Post-earthquake track irregularity spectrum of high-speed railways continuous girder bridge

Yulin Feng,Lizhong Jiang,Wangbao Zhou,Mengcheng Chen 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.3

To study the track irregularity spectrum for CRTS II ballastless track continuous girder bridge for high-speed railway (CBTCGB) after the action of earthquake, a line-bridge integration seismic calculation model was established. By considering the randomness of structural parameters and ground motion, large amounts of samples were analyzed for additional track irregularity caused by factors such as earthquake-induced damage and earthquake-induced void of key components between the layers of track-bridge system. Using improved Blackman-Turkey method and Levenberg- Marquardt algorithm, the earthquake damaged CBTCGB track irregularity spectrum, track irregularity spectrogram, and a fitting formula for track irregularity spectrum after the action of near-field earthquake were obtained, and the calculation results obtained from the fitting formula and CBTCGB numerical model were compared. The results indicate that the probability sampling distribution of ground motion and structural parameters selected according to “binning method” can effectively reflect the randomness of ground motion and structural parameters. The track irregularity spectrum line forms can be roughly divided into three ranges, namely, high-frequency, medium-frequency, and low-frequency waveband. The tracks suffer more track irregularity diseases with high-frequency after earthquake, which is necessary to conduct tracking analysis. It is rational to use a three-segment power function for the fitting of track irregularity spectrum after the action of earthquake.

Analysis on natural vibration characteristics of steel-concrete composite truss beam

Lizhong Jiang,Yulin Feng,Wangbao Zhou,Binbin He 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.1

In order to study the natural vibration characteristics of steel-concrete composite truss beam (SCCTB), the influence of multiple factors such as interface slip, shear deformation and moment of inertia are considered. Afterwards, based on the Hamilton principle the vibration control differential equation and natural boundary conditions of SCCTB are deduced. By solving SCCTB differential equations of vibration control, an analytical calculation method is proposed for analyzing the natural vibration characteristics of SCCTB. The natural frequencies of SCCTBs with different degrees of shear connection and effective lengths are calculated by using the analytical method, and the results are compared against those obtained from ANSYS finite element numerical calculation method. The results show that the analytical method considering the influence factors such as interface slip, shear deformation and moment of inertia are in good agreement with those obtained from ANSYS finite element numerical calculation method. This evidences the correctness of the analytical method and show that the method proposed exhibits improvement over the previously developed theories for the natural vibration characteristics of SCCTB. Finally, based on the analytical method, the influence factors of SCCTB natural vibration characteristics are analyzed. The results indicate that the influence of interface slip stiffness on SCCTB's natural frequency is more than 10% and therefore cannot be neglected. Moreover, shear deformation has an effect of more than 35% on SCCTB’s natural frequency and the effect cannot be ignored either in this case too.

An analytical solution to the mapping relationship between bridge structures vertical deformation and rail deformation of high-speed railway

Yulin Feng,Lizhong Jiang,Wangbao Zhou,Zhipeng Lai,Xilin Chai 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.2

This paper describes a study of the mapping relationship between the vertical deformation of bridge structures and rail deformation of high-speed railway, taking the interlayer interactions of the bridge subgrade CRTS II ballastless slab track system (HSRBST) into account. The differential equations and natural boundary conditions of the mapping relationship between the vertical deformation of bridge structures and rail deformation were deduced according to the principle of stationary potential energy. Then an analytical model for such relationship was proposed. Both the analytical method proposed in this paper and the finite element numerical method were used to calculate the rail deformations under three typical deformations of bridge structures and the evolution of rail geometry under these circumstances was analyzed. It was shown that numerical and analytical calculation results are well agreed with each other, demonstrating the effectiveness of the analytical model proposed in this paper. The mapping coefficient between bridge structure deformation and rail deformation showed a nonlinear increase with increasing amplitude of the bridge structure deformation. The rail deformation showed an obvious "following feature"; with the increase of bridge span and fastener stiffness, the curve of rail deformation became gentler, the track irregularity wavelength became longer, and the performance of the rail at following the bridge structure deformation was stronger.