Abstract:The irreversible electroporation technique has demonstrated remarkable efficacy in tumor treatment. Recent studies indicate that combining high-voltage nanosecond pulses with low-voltage microsecond pulses can significantly improve ablation effectiveness. To address this, this paper proposes a novel topology for a synergistic pulse generator, consisting of two Marx circuits utilizing insulated-gate bipolar transistors(IGBT) and metal-oxide-semiconductor field-effect transistors(MOSFETs) as main switching devices. By flexibly controlling these switches, the generator can produce a synergistic pulse sequence comprising high-voltage nanosecond pulses and low-voltage microsecond pulses. This study explores the generator’s operating principle, circuit simulation, and prototype development. The resulting all-solid-state synergistic pulse generator features flexible and adjustable parameters, leveraging semiconductor switches for improved performance. Its functionality is evaluated using a 100 Ω resistance load, yielding the following pulse characteristics: nanosecond pulses with voltage amplitudes of 0 kV to 15 kV and pulse widths of 200 ns to 1 μs, and microsecond pulses with voltage amplitudes of 0 kV to 5 kV and pulse widths of 10 μs to 100 μs. These parameters meet the experimental requirements for synergistic pulsing in tumor ablation.

Abstract:Multichip insulated gate bipolar transistor(IGBT) modules are widely used in high-power converters, where condition monitoring plays a crucial role in improving the reliability of power equipment. This paper proposes a fault detection method for identifying partial chip failures in multichip IGBT modules by analyzing variations in turn-on delay time. First, the influence of chip failure on the turn-on process is analyzed, establishing the relationship between chip failure and turn-on delay. Based on this relationship, a fault monitoring method is developed to correlate turn-on delay with the number of failed chips. The effectiveness of the proposed method is verified by experimental testing. The results show that this method is significant for improving the operational reliability of power converters.

Abstract:Accurately determining the daily theoretical line loss rate in low-voltage distribution networks is challenging, making it difficult to quantitatively assess its fluctuation range. To address this issue, this paper proposes a probabilistic analysis method for evaluating the daily theoretical line loss rate in low-voltage distribution networks. First, the actual three-phase four-wire connection of the low-voltage distribution network is considered, and it is assumed that the random models of three-phase voltage, distributed power output, and the three-phase active and reactive power of the distribution transformer on the low-voltage side are known and simulated. Then, source-load correlation is incorporated, and Latin hypercube sampling, combined with the equal probability transform principle and rank correlation, is employed. Finally, using the Monte Carlo simulation method, the probabilistic distribution of power flow and the daily theoretical line loss rate is calculated by the Newton injection current method, taking three-phase unbalance into account. This approach provides a decision-making basis for reducing losses in low voltage distribution networks. Experimental data from the Hengshan Garden low-voltage distribution network validate the effectiveness of the proposed method.

Abstract:Data aggregation is a key technology in smart grid communication, enabling efficient collection of essential data while optimizing energy usage. However, the large-scale deployment of smart meters raises significant privacy concerns, as it may expose users’ lifestyle habits. To address this issue, this paper proposes an efficient and privacy-preserving data aggregation(EPPDA) scheme for IoT-enabled smart grid, leveraging smart contracts. First, a four-layer blockchain-based architecture is introduced to facilitate secure data aggregation. At the collection layer, the Boneh-Goh-Nissim system is improved to better suit privacy protection scenarios in smart grids. At the platform layer, blockchain’s tamper-proof features are utilized for secure storage and efficient querying of aggregated data. Performance analysis indicates that the proposed EPPDA satisfies key privacy requirements of smart grid systems. Finally, experimental results show that the proposed EPPDA reduces computational and communication costs while improving overall system efficiency.

Abstract:Overhead transmission lines are a fundamental means of electric energy transmission within power systems, playing a crucial role in supporting national strategies of “West-to-East Power Transmission” and the “Dual Carbon” initiative. As a key component of overhead transmission lines, conductor performance directly influences power transmission capacity. To meet the growing demand for high-quality energy delivery and to adapt to complex outdoor environments, ongoing innovations and optimizations in the material composition and structural design of overhead transmission line conductors have been pursued. This paper provides a comprehensive review of the types, operational parameters, and applications of overhead transmission line conductors both domestically and internationally. It analyzes the technical shortcomings and challenges associated with various conductor types and presents a comparative analysis of domestic and international standards for overhead conductors. Additionally, the paper examines the practical application of different conductor types in domestic transmission line projects. Finally, it summarizes the current status and challenges of overhead transmission line conductors and outlines future technological development directions and trends in this field.

Abstract:Understanding the seepage and failure characteristics of rough fractured rock masses under thermal-hydro-mechanical(THM) coupling is crucial for exploring temperature field distribution in hydrothermal high ground temperature tunnels during construction. This study investigates the failure modes and seepage-heat transfer characteristics of sandstone through laboratory THM triaxial loading tests and multi-physical field coupling numerical simulation, considering various initial rock temperatures (25 °C, 50 °C and 75 °C) and fracture roughness coefficients (JRC). The main findings are as follows: 1) Under THM coupling, the stress-strain curves and failure modes of intact and fractured sandstones are basically consistent. The stress-strain curves exhibit 5 distinct stages: initial compaction stage, elastic deformation stage, stable crack propagation stage, rapid crack propagation stage, and post-peak stress stage. The variation pattern of permeability strain curves correspond to those of stress-strain curves. 2) Prefabricated fractures reduce the sandstone’s peak strength by about 7%. The duration of the post-peak stage decreases with the increase of JRC value, shifting failure behavior from ductile to brittle. The fracture surface angle increases with JRC, and rougher fractures are more prone to shear failure originating from the extreme points of sine curve. 3) The permeability of the fractured specimen first decreases to its minimum value during the initial loading stage, and after 2 growth stages, the permeability reaches its maximum value. In the early stage, seepage primarily occurs through the rock matrix and prefabricated fractures, while in the later stage, the expansion of prefabricated and newly developed cracks significantly broadens seepage channels, with permeability growth rates approximately 3 times higher than that of the early stage. 4) Temperature elevation significantly affects the initial and minimum permeability values but has a limited effect on the strength characteristics of the sample.

Abstract:To study the hysteretic behavior of a new kind of high-performance steel produced by HBIS(Hebei-Iron-and-Steel), three beam-column joints with different connection forms were designed and tested under quasi-static loading conditions. The experimental results show that the “taper weakened” joint exhibits fully developed ductility and excellent energy dissipation capacity, while the “composite” joint shows significantly improved seismic performance. Based on the test results, a trilinear restoring force model considering stiffness degradation was established, with the skeleton curve fitted to key experimental feature points.The hysteretic curve expression was derived using an exponential differential equation. The reconstructed model achieved an analytic error within 10%, effectively capturing the hysteretic response of the jonts.

Abstract:A discrete interfacial bonding element(BS1) was developed using the User Element (UEL) interface in ABAQUS, ant it’s capable of automatically calculating element length based on a specified bond-slip relationship. Numerical simulations of beam-cast-in-place column subassemblages were carried out using the simplified Eligehausen bond-slip constitutive model. The results were consistent with experimental data. The BS1 element demonstrated a 25% improvement in computational efficiency due to its automatic length calculating feature. A total of 30 finite element models of PC beam-column subassemblages were established for multi-parameter analysis, considering variables such as the thickness of the cast-in-place layer, the slab width of T-composite beams, and the direction of load application. Results show that subassemblages with 90° hooked bars and headed bars exhibit nearly equivalent bearing capacities, though the ductility index differs by 12% , favoring the 90° hooked bar. The slab width specified in Chinese design codes proved more reliable for bearing capacity performance than those in foreign codes. Furthermore, changes in load directions result in a 12% variation of bearing capacity and a 55% difference in deformation capacity, highlighting the need for further investigation. This study provides valuable insights and reliable references for the numerical analysis of prefabricated concrete structures considering bond-slip effects.

Abstract:Existing researches on the crack propagation mechanisms in composite pavement often focus on materials, but do not emphasize structure. There are many simulation methods, but they are difficult to reflect actual working conditions. To solve these problems, this study conducts an in-depth investigation on the fatigue crack propagation behavior of non-linear damage in composite pavements. Using damage mechanics theory, residual strength theory, accelerated loading tests, and Python algorithms, a comprehensive simulation of the mechanical behavior of cement concrete slab joint load transfer was conducted. A cycle fatigue damage-fracture simulation system was established using the DLOAD subroutine, UMAT subroutine, UDMGINI subroutine, and XFEM main program. This system reveals the degradation patterns 4 key indexes under cyclic loading: reflection crack propagation rate, internal material damage, residual strength, and pavement deflection. The results show that fatigue damage accumulates with the increase of loading cycles, leading to a gradual decline in residual strength, with the damage accumulation rate closely linked to the extent of residual strength reduction. Under axle loads of 100 kN, 160 kN, and 220 kN, the crack propagation phase accounts for 43.94%, 35.34%, and 28.82% of the pavement’s full life cycle, respectively. For vehicle speeds of 40 km/h, 60 km/h, and 100 km/h, the crack propagation phase comprises 46.83%, 43.94%, and 43.13% of the pavement’s life cycle, respectively. Overloading significantly impacts pavement stability, accelerating fatigue damage and reducing service life.

Abstract:To improve the structural rigidity of multi-tower cable-stayed bridges, a novel crossed cable arrangement is proposed. By deriving and analyzing the restraint stiffness formula of the middle tower’s crossed cables, the optimal position for maximum restraining stiffness was investigated, leading to the proposal of an asymmetrical cable arrangement. Finite element models of three-tower and four-tower cable-stayed bridges were established, accounting for cable sag effects and large structural displacements. The influence of the asymmetrical cable arrangement on tower-beam deformation and tower forces was analyzed. Results show that when the height-to-span ratio of the multi-tower cable-stayed bridge ranges from 0.2 to 0.3, the optimal position for the crossed cables is approximately 0.7 to 0.76 times the span length form the middle tower. Compared to the traditional symmetrical arrangement, the asymmetrical configuration reduces the horizontal displacement at the top of the middle tower by 10.8% and 11.9%, and decreases the mid-span deflection under uniform load by 3.3% and 0.2% for the three-tower and four-tower cable-stayed bridges, respectively. Additionally, the first-order vertical bending frequency of the main girder increases by 3.5% and 6.4%, while the bottom bending moment of the middle tower decreases by 14.1% and 8.1%. These findings demonstrate that the asymmetrical arrangement significantly improves the restraining effect of crossed cables on the middle tower, increases overall structural rigidity, and improves the load-bearing performance of the middle tower.