When a high‐speed train approaches the insulated phase‐splitting section embedded between neighbouring power supply arms, the vacuum circuit breaker (VCB) installed on trains must be disconnected to ...maintain the traction power supply system as a no‐load condition for completing phase‐switching action, as the train passes through the phase‐splitting section depending on its inertia. However, when operating VCBs, the arc is easily triggered between the mobile contacts inside, accompanied by an overvoltage impulse. Herein, to explore the generating mechanism of inrush current and operational overvoltage, a model describing the ‘substation‐catenary‐train’ traction power supply system is launched based on an equivalent circuit modelling technique. Through the analysis of the transient VCB operational process, the phase of catenary voltage is directly related to the characteristics of the VCB switching‐on overvoltage, as the traction current's phase angle is relevant to the amplitude‐frequency characteristics of the VCB switching‐off overvoltage. Inrush current as a noteworthy element is related to the traction transformer's remanence. The automatic phase‐switching technique is utilised to suppress both operational overvoltage and inrush current, as the optimal combination of VCB switching‐on and switching‐off phases considering the balance between overvoltage and inrush current is achieved based on the particle swarm algorithm.
Accurate prediction of lithium ion (li-ion) battery capacity is of great significance to battery health status management. In this paper, the different discharge time corresponding to the equal ...voltage interval is taken as the health factor. Three highly correlated health factors are extracted from the battery discharge curve, and the Back Propagation neural network (BPNN) optimized by a genetic algorithm (GA) is used to estimate the battery capacity accurately and quickly. Firstly, health factors related highly to battery capacity from the battery cycle life test are extracted, and the selected health factors are analyzed using the Spearman correlation coefficient and Pearson correlation coefficient. Secondly, this paper analyzes the prediction effect of different combinations of selected health factors using BPNN optimized by a genetic algorithm. Then, to verify the superiority of the proposed optimization algorithm, different optimization algorithms are used to adjust and optimize the parameters of BPNN automatically, and the experimental data are used for comparative analysis. Finally, the GA-BP is compared with other common battery capacity prediction methods. The results show that the GA-BP neural network prediction model can accurately and effectively predict the capacity of li-ion battery when using selected health factors.
As the unique power-discharging channel for high-speed trains, the 'train-rail' mobile coupling grounding system plays a vital role in sending the traction power back to the terrestrial substations, ...through the electrical contact between the rotating wheel and the steel rail. The whole system is composed of two kinds of grounding modes: working grounding is in charge of draining the traction power into the rail track; the protective grounding provides the reference grounding potential for the vehicle-mounted equipment. Different from the fixed terrestrial grounding technique normally implemented in power system, when the relative motion occurs between the train and the rail, both the 'catenary-to-train' and 'train-to-ground' impedances vary transiently, which may lead to the current flowing through each grounding wheel varying unpredictably. Herein, the 'catenary-train-rail' mobile coupling grounding model was built based on the equivalent circuit modeling technique for evaluating the transiently-varying tendency of the grounding impedances and currents flowing through each grounding wheel. To cope with different operational conditions, the adjustable grounding impedance methodology is firstly proposed for adapting the unpredictable variation of the grounding impedance, when the relative motion occurs between the train and the rail. Ultimately, the validity of the novel grounding system applying the adjustable grounding impedance technology is verified under different operational conditions, with the consideration of both TB current and voltage.
When a high-speed train approaches an insulated split-phase section embedded between neighboring power supply arms carrying powers with different phases, the vehicle-mounted vacuum circuit breaker ...(VCB) needs to be switched off to avoid short-circuit fault during the phase-changing procedure. At the moment of switching the VCB contacts, the arc is triggered easily, accompanying with overvoltage impulse. As the core of the whole system, the traction transformer frequently suffers the invasion of the overvoltage impulse, which possibly causes partial discharge or breakdown accidents. To evaluate the impact of overvoltage on the transformer, it is essential to observe the overvoltage distribution at different positions in the transformer. As an equivalent circuit (EC) model of the traction transformer involving the spatially distributed capacitance is built based on the improved capacitor network methodology (ICNM), the partial discharge risk in the transformer has been assessed. Ultimately, the multiphysics coupling models based on the finite-element method (FEM) have been launched to observe the specific distribution of the multiphysics field for verifying the validity of an EC model based on ICNM. These works lay the theoretical foundation for guiding the design of insulation and the thermal dissipation settings of the traction transformer, considering the threat brought from impulse.
The mobile distributed grounding system plays an irreplaceable role in discharging power for intercity trains, including two types of grounding settings (GSs): the working GS provides the pathway for ...discharging the traction current; the protective GS provides the reference grounding potential for the vehicle-mounted equipment. As both working and protective GSs share the rail as the common current-releasing pathway, the traction current released by working GSs might return the carriage through the adjacent protective GSs, forming as the train body (TB) current which threatens the vehicle-mounted electrical equipment. Herein, an equivalent circuit of the mobile distributed grounding system is built to analyze the TB current. For evaluating the influence brought by TB current on the vehicle-mounted equipment, a 3D finite element (FEM) geometry is launched, meanwhile the comparison of the multi-physical distributions is undertaken when applying different grounding layouts, with the emphasis of the highlighted region containing critical devices.
To obtain the relationship between use of installment tensioning technology and the bearing capacity of prestressed concrete beams, tensile and cyclic loading tests are conducted on five rectangular ...prestressed concreted specimens. Two types of prestressed tensioning methods are adopted in the tests, one uses installment tensioning technology to tension beams on days 4, 12, and 8, 12, respectively, and the other adopts the conventional method to tension the beam on day 28 only. The age of concrete, number of times tensioned, and the prestress value of early tensioning are considered in tests. Results show that use of installment tensioning technology has no effect on the bending failure pattern of prestressed concrete beams, but it reduces prestress loss and increases crack and yield loads.
In this paper, the influential design thctors of wide-shallow composite bucket foundation for 3 MW off- shore wind turbine are systematically studied by numerical simulation. The results show that ...the bucket diameter is larger than 27 m in generak and the range of 7--12 m is appropriate for cylinder height. In particular the bucket foun- dation with diameter of 30 m and cylinder height of 10 m is suitable for most soils. Under ultimate loads, the bucket diameter and elasticity modulus of soil have major effects on the deibrmability of bucket foundation, while the influ- ence of friction coefficient between the bucket and soil is relatively slight.
A series of model experiments of bucket foundations concerning suction installation and negative pressureconsolidation in saturated silt were carried out in a cube steel bin at Tianjin University. ...The experimental resultsshow that the silt inside the bucket has been strengthened by negative pressure, and the strengthening effectdecreases with the increase of the distance from the bucket. A three-dimensional numerical model of the experimentswas built by means of finite element software ABAQUS with fluid-solid coupling method. The results showthat the bearing capacity of the silt inside the bucket foundation increases significantly at the former stage of negativepressure consolidation, while the increasing trend slows down over time. The rotation centers of the bucketfoundation and the inner soil region tend to be closer to each other based on the consolidation. The bearing capacityof the bucket foundation is improved effectively with the increase of soil strength. The effects of negative pressureconsolidation on the bearing capacity of bucket foundation were also illustrated by an actual offshore wind powerproject case.
Key message
Major and environmentally stable QTL for flag leaf-related traits in wheat were identified and validated across ten environments using six populations with different genetic backgrounds.
...Flag leaf size and posture are two important factors of “ideotype” in wheat. Despite numerous studies on genetic analysis of flag leaf size including flag leaf length (FLL), width (FLW), area (FLA) and the ratio of length/width (FLR), few have focused on flag leaf posture including flag leaf angle (FLANG), opening angle (FLOA) and bend angle (FLBA). Further, the numbers of major, environmentally stable and verified genetic loci for flag leaf-related traits are limited. In this study, QTL for FLL, FLW, FLA, FLR, FLANG, FLOA and FLBA were identified based on a recombinant inbred line population together with values from up to ten different environments. Totally, eight major and stably expressed QTL were identified. Three co-located chromosomal intervals for seven major QTL were identified. The five major QTL
QFll.sicau
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5B.3
and
QFll.sicau
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2D.3
for FLL,
QFlr.sicau
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5B
for FLR,
QFlw.sicau
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2D
for FLW and
QFla.sicau
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2D
for FLA were successfully validated by the tightly linked Kompetitive Allele Specific PCR (KASP) markers in the other five populations with different genetic backgrounds. A few genes related to leaf growth and development in intervals for these major QTL were predicated. Significant relationships between flag leaf- and yield-related traits were evidenced by analyses of Pearson correlations, conditional QTL and genetic mapping. Taken together, these results provide valuable information for understanding flag leaf size and posture of “ideotype” as well as fine mapping and breeding utilization of promising loci in bread wheat.
The NLRP3 inflammasome, a sensor for a variety of pathogen- and host-derived threats, consists of the adaptor ASC (Apoptosis-associated Speck-like protein containing a Caspase Activation and ...Recruitment Domain (CARD)), pro-caspase-1, and NLRP3 (NOD-Like Receptor family Pyrin domain containing 3). NLRP3-induced neuroinflammation is implicated in the pathogenesis and progression of eye diseases, but it remains unclear whether activation of NLRP3 inflammasome contributes to retinal ganglion cell (RGC) death. Here we examined NLRP3-induced neuroinflammation and RGC survival following partial optic nerve crush (pONC) injury. We showed that NLRP3 was up-regulated in retinal microglial cells following pONC, propagating from the injury site to the optic nerve head and finally the entire retina within one day. Activation of NLRP3-ASC inflammasome led to the up-regulation of caspase-1 and a proinflammatory cytokine, interleukin-1β (IL-1β). In NLRP3 knockout mice, up-regulation of ASC, caspase-1, and IL-1β were all reduced, and, importantly, RGC and axon loss was substantially delayed following pONC injury. The average survival time of RGCs in NLRP3 knockout mice was about one week longer than for control animals. Taken together, our study demonstrated that ablating the NLRP3 gene significantly reduced neuroinflammation and delayed RGC loss after optic nerve crush injury.
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