| 1. |
- Jia, He, et al.
(author)
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Optimization and economic analysis of distributed photovoltaic-energy storage system under dynamic electricity price
- 2021
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In: Taiyangneng Xuebao/Acta Energiae Solaris Sinica. - 0254-0096. ; 42:5, s. 187-193
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Journal article (peer-reviewed)abstract
- This paper investigated the influence of different dynamic electricity pricing schemes, energy storage capacity and unit capacity cost on the economics of PV-storage systems. The energy storage control stratety of improving the photovoltaic micro-grid self-consumption was adopted in this study. Taking an office building in Changsha as an example, the dynamic planning method was used to solve the system's best operating strategy and calculated the system' life cycle economy and PV self-consumption rate. The results showed that the system profitable area was increased by 87% for every 41.5% increase of dynamic electricity price. Moreover, the impact of energy storage capacity on system economics is greater than unit cost. The increase of dynamic electricity price is beneficial to increase the self-consumption of photovoltaic power generation, and the storage capacity and unit cost dominate the self-consumption of photovoltaic energy in different intervals.
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| 2. |
- Lu, Yichen, et al.
(author)
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Analytical Method of Traffic Conflict at Urban Road Intersections Based on Risk Region
- 2021
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In: Tongji Daxue Xuebao/Journal of Tongji University. - 0253-374X. ; 49:7, s. 941-948
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Journal article (peer-reviewed)abstract
- A two-stage method of traffic conflict analysis was proposed based on risk region. By using the inD dataset, traffic conflicts were recognized with the calculation of time to risk region(tTTR), and then the degree of traffic conflict risk was judged by risk region duration. Compared with the method based on time-to-collision(tTTC), the proposed method can not only identify rear-end conflicts and crossing conflicts more effectively, but also characterize the degree of traffic conflict risk at different times.
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| 3. |
- Wang, Benxin, 1991, et al.
(author)
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Fracture characteristics and the damage constitutive model of 3D printing undulating joint samples based on DIC
- 2022
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In: Gongcheng Kexue Xuebao/Chinese Journal of Engineering. - 2095-9389. ; 44:12, s. 2029-2039
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Journal article (peer-reviewed)abstract
- Due to the influence of geological structures, various forms of joint structural planes are present in rock mass engineering. The undulating structural planes, such as a torsional fold surface, are unique geological structures. These structures affect the stability of rock masses and cause potential hazards to rock mass engineering. Because of their shape complexity, the research on the fracture and damage constitutive law of rock mass with undulating joints is not thoroughly conducted. Undulating joints with various dip angles were fabricated using three-dimensional printing technology. The uniaxial compression test and digital image correlation (DIC) technology were used to study the mechanical and fracture characteristics of undulating joint specimens. Based on the principle of fracture mechanics, an idea was proposed to use the DIC displacement field for solving the stress intensity factor (SIF: type one KI and type two KII) at the joint tips and to study the damage constitutive law. The results show that the upper limit of undulating joint damage to specimens is determined with 46.6% through the minimum strength analysis. The sensitivity of uniaxial strength to a joint dip angle of undulating joint specimen is greater than that of a straight joint specimen. The fracture initiation occurs near peak stress. The fracture process can be divided into the initiation and synchronous penetration of microcracks on the fracture path. Additionally, the fracture mode shows a combination of multiple tension and shear fractures. The SIF increases with loading at the prepeak stage, and the cracks propagate in shear fracture at the joint left and right tips in the postpeak stage because KII>KI under the same stress. The undulating joint damage to the specimen with the dip angle is in a sinusoidal curve form. The relationships between the total damage coupled by joint and load with strain are all “S” curves.
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| 4. |
- Wu, Hao Yu, et al.
(author)
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Transient response analysis of tension-leg-platformfloating offshore wind turbine under tendon failure conditions
- 2020
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In: Zhejiang Daxue Xuebao (Gongxue Ban)/Journal of Zhejiang University (Engineering Science Edition. - 1008-973X. ; 54:11, s. 2196-2203
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Journal article (peer-reviewed)abstract
- The mooring load calculation module of the fully coupled dynamic simulation software FAST was recompiled, and the transient response of a tension-leg-platform floating offshore wind turbine (FOWT) named WindStar TLP system under tendon failure was numerically simulated using a time domain method, in terms of the coupled system of wind turbine, tension-leg-type support platform and tendons. The transient response of the key parameters, i.e., platform motions, nacelle accelerations and tensions in the remaining tendons under different wave directions in 50-year extreme condition were investigated. Results show that the transient response of platform motions, nacelle accelerations and tendon tensions under tendon failure are significant. The transient response of FOWT with the broken tendon in back waves is greater than that with the broken tendon in head waves. And when the broken tendon in back waves is aligned with the wave, the transient response of FOWT is the maximum. The safety factor for tendon system under tendon failure in 50-year extreme condition meets the requirements of specification constituted by American Bureau of Shipping (ABS), which verifies the survivability of this tension-leg-type FOWT.
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| 5. |
- Yuan, Ying Kuo, et al.
(author)
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Applications of graphene transistor optimized fabrication process in monolithic integrated driving gallium nitride micro-light-emitting diode
- 2021
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In: Wuli Xuebao/Acta Physica Sinica. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 70:19
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Journal article (peer-reviewed)abstract
- In the information display field, micro-light-emitting diodes (micro-LEDs) possess high potentials and they are expected to lead the direction of developing the next-generation new display technologies. Their display performances are superior to those produced by the currently prevailing liquid crystal and organic light-emitting diode based technologies. However, the micro-LED pixels and their driving circuits are often fabricated on different wafers, which implies that the so-called mass transfer seems to be inevitable, thus facing an obvious bottleneck. In this paper, the emerging graphene field effect transistors are used as the driving elements and integrated onto the GaN micro-LEDs, which is because the pixels and drivers are prepared directly on the same wafer, the technical problem of mass transfer is fundamentally bypassed. Furthermore, in traditional lithographic process, the ultraviolet photoresist directly contacts the graphene, which introduces severe carrier doping, thereby leading to deteriorated graphene transistor properties. This, not surprisingly, further translates into lower performances of the integrated devices. In the present work, proposed is a technique in which the polymethyl methacrylate (PMMA) thin films act as both the protection layers and the interlayers when optimizing the graphene field effect transistor processing. The PMMA layers are sandwiched between the graphene and the ultraviolet photoresist, which is a brand new device fabrication process. First, the new process is tested in discrete graphene field effect transistors. Compared with those devices that are processed without the PMMA protection thin films, the graphene devices fabricated with the new technology typically show their Dirac point at a gate voltage (Vg) deviation from Vg = 0, that is, 22 V lower than their counterparts. In addition, an increase in the carrier mobility of 32% is also observed. Finally, after applying the newly developed fabrication process to the pixel-and-driver integrated devices, it is found that their performances are improved significantly. With this new technique, the ultraviolet photoresist no longer directly contacts the sensitive graphene channel because of the PMMA protection. The doping effect and the performance dropping are dramatically reduced. The technique is facile and cheap, and it is also applicable to two-dimensional materials besides graphene, such as MoS2 and h-BN. It is hoped that it is of some value for device engineers working in this field.
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| 6. |
- Zhang, Di, et al.
(author)
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Modeling of ship navigation risk field for the icebreaker escort operations based on an artificial potential field
- 2024
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In: Harbin Gongcheng Daxue Xuebao/Journal of Harbin Engineering University. - 1006-7043. ; 45:1, s. 119-128
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Journal article (peer-reviewed)abstract
- To assess the risk of a ship colliding and getting stuck in ice accidents, this study aims to analyze and quantify the ship navigation risk for icebreaker escort operations concerning the mutual relationship between the icebreaker and the assisted ship following the icebreaker and that between the assisted ship and sea ice. We propose a concept and model of a ship navigation risk field under an icebreaker escort operation based on an artificial potential field, including the icebreaker and sea ice risk fields. The icebreaker risk field quantifies the collision risk level between the icebreaker and the assisted ship, while the sea ice risk field quantifies the level of collision risk between the assisted ship and sea ice. The model can calculate the safe following distance between the icebreaker and the assisted ship. Finally, based on the marshaling navigation data of the TianYou ship in the Arctic, 2018, a ship navigation risk field model for an icebreaker escort operation is constructed for simulation verification. Results show that the proposed model is feasible and practical, which can theoretically support safety research following the distance between the icebreaker and the assisted ship under the icebreaker escort operation.
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| 7. |
- Zhang, Yijie, et al.
(author)
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Error Analysis and Correction of Relative Permittivity Measured by Three-electrode System
- 2018
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In: Gaoya Dianqi/High Voltage Apparatus. - 1001-1609. ; 54:6, s. 24-31,37
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Journal article (peer-reviewed)abstract
- To improve the accuracy of the measured relative permittivity based on three-electrode system, a three-dimensional model for relative permittivity measurement is established and solved with consideration of real electrode system’s material properties and dimension by means of the finite element analysis software Comsol for multiple physical fields. In view of the nearly rotational symmetry of the electrodes system, the model is simplified to two-dimensional one to reduce computation amount. Comparison of the computation results between the 3D and 2D models verifies the reliability of the latter. Subsequently, the potential, electric field and surface charge distributions are obtained, and the error of the relative permittivity calculated by the method in a standard is calculated. The influences of sample’s thickness, relative permittivity and area (radius) on the accuracy of the calculated relative permittivity are systematically investigated, and the key factors influencing the accuracy are determined. Employing the 2D model with the sample’s thickness ranging from 0.2 to 10 mm and relative permittivity ranging from 1 to 100, the errors of relative permittivity are obtained, which are all less than zero. The relationship among sample thickness, measured relative permittivity and real value of relative permittivity is obtained, and the 2D interpolation method is used to correct the measured relative permittivity. In addition, the proposed correction method is validated by simulation and is applied to relative permittivity measurement of an insulating material.
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| 8. |
- Chen, Xiangrong, 1982, et al.
(author)
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Study on conducting characteristics of electrical trees in cross-linked polyethylene cable insulation
- 2012
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In: Wuli Xuebao/Acta Physica Sinica. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 61:8, s. Art. no. 087701-
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Journal article (peer-reviewed)abstract
- The conducting characteristics of two typical electrical trees in cross-linked polyethylene (XLPE) cable insulation are studied by a combination of optical microscopy observation, partial discharge measurement and con-focal Raman spectroscopy analysis. Although they are grown under similar conditions, these two trees display very different shapes. One is a typical branch-pine tree grown at 9 kV, and the other is a branch tree grown at 11 kV. The growth and the partial discharge regularities show obvious differences. The disordered graphitic carbon is condensed in the main tree channels of the branch-pine tree. From the relative intensity of the graphitic carbon G band to D band, the graphitic domain is estimated to be about 8 nm in size. The tree channel resistance per unit length is less than 10 Ω· μm-1, which is sufficient to prevent the partial discharge from developing within the tree structure. The branch-pine tree shows the features of the conducting tree. The fluorescence background is observed in the channels of branch tree, which shows the existence of the products of the material degradation, but no disordered graphitic carbon is observed in these tree channels. These tree channels display obvious non-conducting characteristics, which is not sufficient to prevent the continuous effect of the partial discharges. Finally, a single channel growth model is proposed for the conducting and non-conducting trees grown in XLPE cable insulation. Based on the equivalent circuit theory, the growth mechanisms of the two trees with different conducting characteristics in XLPE cable insulation are discussed.
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| 9. |
- Xiao, Sen, et al.
(author)
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Analysis of chest injury in frontal impact via finite element modelling based on biomechanical experiment
- 2017
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In: Lixue Xuebao/Chinese Journal of Theoretical and Applied Mechanics. - 0459-1879. ; 49:1, s. 191-201
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Journal article (peer-reviewed)abstract
- The usage of the seatbelt as a part of the vehicle protection system has immensely promoted occupant safety. However, recent accident investigation shows that it is necessary to increase the chest injury protective e_ciency in frontal impact condition. This study aims to investigate the influence of seatbelt system design variables on occupant chest injury related physical parameters at varying impact conditions, especially concerning with the chest deflection and distribution of rib stress/strain. The study is conducted by using human body FE model in combination with post mortem human subjects tests. An FE model of the belted occupant is therefore established by using a baseline human body FE model (GHBMC), which is validated according to detailed experimental data regarding kinematics, seatbelt force and chest deflection. A parameter study is implemented in terms of seatbelt position, seatbelt angle and impact speed to determine the influence of seatbelt utilization on occupant thoracic injury in frontal impact. The results show that the influence of seatbelt position on chest deflection and distribution of rib stress/strain is greater than that of the seatbelt angle. Meanwhile, the trends of chest deflections are the same with the trends of the rib stress/strain responses while the changes of seatbelt design variables. This study provides a virtual test method on investigation of the chest injury biomechanics related to the seatbelt design variables. Furthermore, the results from this study of chest injury mechanism will also provide a reference for optimizing of the occupant restraint system. © 2017, Editorial Office of Chinese Journal of Theoretical and Applied Mechanics. All right reserved.
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| 10. |
- Fu, L., et al.
(author)
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Wear mechanism of Cr 3 C 2 /Ni 3 Al composites showing excellent wear resistance
- 2019
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In: Gongcheng Kexue Xuebao/Chinese Journal of Engineering. - 2095-9389. ; 41:1, s. 117-123
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Journal article (peer-reviewed)abstract
- The Ni 3 Al intermetallic compound is considered an excellent wear-resistant material. The addition of Cr 3 C 2 particles can further improve the wear resistance of Ni 3 Al-based alloys. In order to elucidate the wear mechanism of Cr 3 C 2 /Ni 3 Al composites improved by the Cr 3 C 2 strengthening phase, Ni 3 Al-alloy and Cr 3 C 2 /Ni 3 Al composites were prepared by the hot isostatic pressing process in this study. The mechanical properties and wear resistance of each phase in the Ni 3 Al-alloy and Cr 3 C 2 /Ni 3 Al composites were investigated using a nano-indentation instrument and a pin-on-disk friction and wear tester, respectively. The worn surface morphologies and the hardness of the subsurface layer under the worn surfaces of the Ni 3 Al-alloy and Cr 3 C 2 /Ni 3 Al composites were determined by a scanning electron microscopy (SEM) and a nano-indentation instrument. The results indicate that the hardness of the matrix phase in the Cr 3 C 2 /Ni 3 Al composites is significantly improved by the addition of Cr 3 C 2 particles. The nano-hardness and the elastic modulus of each phase in the Cr 3 C 2 /Ni 3 Al composites gradually increase from matrix phase through diffusion phase to hard core phase. The mechanical properties between the matrix, diffusion, and hard core phases in the Cr 3 C 2 /Ni 3 Al composites present a gradient transition. This kind of structure distribution is good for enhancing the wear resistance of Cr 3 C 2 /Ni 3 Al composite materials. As for friction and wear conditions in this study, abrasive wear was the dominant wear mechanism, which occurred on the surfaces of the Ni 3 Al-alloy and Cr 3 C 2 /Ni 3 Al composites. The Cr 3 C 2 /Ni 3 Al composites showed a good wear resistant property. The carbide-strengthening phase can block up the cutting action of the wear debris, reduce the interaction between the wear materials, and decrease the thickness of the subsurface layer and the size of the wear debris, resulting in improved wear resistance of Cr 3 C 2 /Ni 3 Al composites.
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