Exceeding probability analysis for rail of high-speed railway under seismic excitations

Purpose–The smoothness of the high-speed railway(HSR)on the bridge may exceed the allowable standard when an earthquake causes vibrations for HSR bridges,which may threaten the safety of running trains.Indeed,few studies have evaluated the exceeding probability of rail displacement exceeding the allowable standard.The purposes of this article are to provide a method for investigating the exceeding probability of the rail displacement of HSRs under seismic excitation and to calculate the exceeding probability.Design/methodology/approach–In order to investigate the exceeding probability of the rail displacement under different seismic excitations,the workflow of analyzing the smoothness of the rail based on incremental dynamic analysis(IDA)is proposed,and the intensity measure and limit state for the exceeding probability analysis of HSRs are defined.Then a finite element model(FEM)of an assumed HSR track-bridge system is constructed,which comprises a five-span simply-supported girder bridge supporting a finite length CRTS II ballastless track.Under different seismic excitations,the seismic displacement response of the rail is calculated;the character of the rail displacement is analyzed;and the exceeding probability of the rail vertical displacement exceeding the allowable standard(2mm)is investigated.Findings–The results show that:(1)The bridge-abutment joint position may form a step-like under seismic excitation,threatening the running safety of high-speed trains under seismic excitations,and the rail displacements at mid-span positions are bigger than that at other positions on the bridge.(2)The exceeding probability of rail displacement is up to about 44%when PGA 50.01g,which is the level-five risk probability and can be described as’very likely to happen’.(3)The exceeding probability of the rail at the mid-span positions is bigger than that above other positions of the bridge,and the mid-span positions of the track-bridge system above the bridge may be the most hazardous area for the running safety of trains under seismic excitation when high-speed trains run on bridges.Originality/value–The work extends the seismic hazardous analysis of HSRs and would lead to a better understanding of the exceeding probability for the rail of HSRs under seismic excitations and better references for the alert of the HSR operation.

Generating Proton Beams Exceeding 10 MeV Using High Contrast 60TW Laser

A prototype of a laser driven proton accelerator is built at Peking University. Protons exceeding IOMeV are accelerated from micrometer-thick aluminum targets irradiated by tightly focused laser pulse with 1.8 J energy and 30fs duration. The beam energy spectrum and charge distribution are measured by a Thomson parabola spectrometer and radiochromic fihn stacks. The sensitivity of proton cut-off energy to the focusing of the laser beam, the pulse duration, and the foil thickness are systematically investigated in the experiments. Stable proton beams have been produced with an optimized parameter set, providing a cornerstone for the future applications of laser accelerated protons.

China's Power Generating Capacity Exceeding 200 GW

Shi Dazhen, Minister of the Power Industry, has announced that China’s power Construction had developed to a new level, exceeding 200 GW. He said that China’s power generating capacity reached 100 GW in 1987 and 199.9 GW at the end of last year. As another two 60,000 kilowatts of power generation units went into operation in March, this year, power generating capacity reaches 200 GW in only seven years. Such a construction scale and

Exceeding Expectations

As the escalating trade dispute between China and the United States casts a shadow over the world＇s two largest economies andthe global economy at large, the much an ticipated Chinese economic figures for the first half of the year offer some certainty of China＇s economic resilience and sustainability.

Hole transport layer-free inverted perovskite solar cells with power conversion efficiency exceeding 25%and much improved stability

Organic-inorganic hybrid perovskites possess a unique combination of excellent electronic and photoelectrochemical properties that can be readily tailored by partial or complete substitution of their constituent elements owing to their nonclose packing anion lattice[1,2].Perovskite solar cells(PSCs)employing hybrid perovskites as an active layer have seen rapid improvements and have achieved high power conversion efficiencies(PCEs)now exceeding 25%[2].

Is it worth already in the first step exceeding the 3-g protein limit for the oral food challenge for food protein-induced enterocolitis syndrome?

To the editor:Food protein-induced enterocolitis syndrome(FPIES)is a non-immunoglobulin E-mediated food allergy that is characterized by repetitive vomiting within 1-4 h of eating the trigger food and may be associated with lethargy,pallor,and diarrhea.The diagnosis is in most cases anamnestic.1 In a few cases,it is necessary to perform the oral food challenge(OFC).

Harnessing the power of pericytes and hypoxia-inducible factor-1 to modulate stroke outcome

The human brain has exceedingly high metabolic demands.The cerebral vasculature has the critical task of providing sufficient blood supply to meet this demand.The sudden interruption of blood flow to the brain,as observed during ischemic stroke,results in acute neurological injury with devastating consequences-a high rate of adult disability and death.Ischemic stroke is thus a vascular disorder with a dramatic neurological impact.There is an urgent need for more effective disease management to combat stroke as current treatment paradigms,focusing on vascular recanalization and neuroprotection,have only limited clinical success.Since accumulating data suggests successful long-term neuroprotection is unlikely to be achievable without a functional microvascular network,strategies that reduce endothelial dysfunction could be indispensable.Encouragingly,very recent evidence highlighted herein suggests protecting the humble pericyte may be a new approach to reaching this goal.

Current Status and Prospects of China’s Natural Gas Industry

In 2023,China’s natural gas sector experienced robust growth in both supply and demand dynamics,as consumption regained an upward trend,reaching 394.53 billion m3,reflecting a 7.6%year-on-year surge.Domestic gas production and reserves persistently progressed,hitting a production volume of 228.84 billion m3 and achieving a seven-year consecutive increment exceeding 10 billion m^(3).After an initial sharp decline,imported natural gas rebounded to record growth;the combined import volume of pipeline gas and LNG climbed to 163.92 billion m^(3),a notable 11.3%rise compared to the previous year.As China’s policies for stable economic growth are further entrenched in 2024,the macroeconomic recovery is anticipated to continue.Bolstered by the dual-carbon strategy and the transformative policies targeting high-energy-consuming industries,the natural gas market is expected to sustain its rapid expansion,with estimated growth in demand ranging between 5.8%and 7.1%.

SCIENCE AND TECHNOLOGY

Deep-Earth Borehole Drilling Project Achieves 10,000-Meter Milestone China has achieved a significant breakthrough in deep-Earth exploration with the drilling of a superdeep borehole in Xinjiang Uygur Autonomous Region exceeding the 10,000-meter mark,making it the deepest vertical well in Asia,even though the project as a whole is not yet completed.Amid the continuous humming of the drilling rig,the number on an electronic screen in the command center reached the milestone of 10,000 meters at 2:48 p.m.on March 4.More than 100 workers on site,who had eagerly anticipated this moment,erupted into cheers.Located in the hinterland of the Taklimakan Desert in the Tarim Basin,Shenditake 1 is a scientific exploratory borehole with a designed depth of 11,100 meters.In addition to searching for oil and gas resources,it is also tasked with pursuits such as exploring the evolution of Earth.

In Brief

The annual oil and gas output of Fuman Oilfield,China's largest ultra-deep oilfield,exceeded 4 million tons,On December 29,2023,the annual oil and gas production of Fuman Oilfield,China's largest ultra-deep oilfield,exceeded 4 million tons,reaching a new peak of 4.036 million tons.This marks another new advancement in the large-scale and efficient development of ultra-deep and complex oil and gas reservoirs in CNPC Tarim Oilfield,creating a new growth pole for increasing reserves and production of crude oil in China.Fuman Oilfield is the oilfield with the largest number of ultra-deep wells of over 8,000 meters in China,and more than 110 wells have a depth exceeding 8,o00 meters and are defined as Underground Everest".In 2019,the annual oil and gas production of Fuman Oilfield increased from 20,000 tons at the beginning of development to 1.08 million tons.

Exciton diffusion exceeding 1μm:run,exciton,run!

Exciton diffusion lengths reaching the micrometer length scale have long been desired in solution-processed semiconductors but have remained unattainable using conventional materials to date.Now halide perovskite nanocrystal films show unprecedented exciton migration with diffusion lengths approaching 1μm owing to the efficient combination of radiative and nonradiative energy transfer.

Probability Distribution Characteristics of Strong Nonlinear Waves Under Typhoon Conditions in the Northern South China Sea

The generation and propagation mechanism of strong nonlinear waves in the South China Sea is an essential research area.In this study,the third-generation wave model WAVEWATCH III is employed to simulate wave fields under extreme sea states.The model,integrating the ST6 source term,is validated against observed data,demonstrating its credibility.The spatial distribution of the occurrence probability of strong nonlinear waves during typhoons is shown,and the waves in the straits and the northeastern part of the South China Sea show strong nonlinear characteristics.The high-order spectral model HOS-ocean is employed to simulate the random wave surface series beneath five different platform areas.The waves during the typhoon exhibit strong nonlinear characteristics,and freak waves exist.The space-varying probability model is established to describe the short-term probability distribution of nonlinear wave series.The exceedance probability distributions of the wave surface beneath different platform areas are compared and analyzed.The results show that with an increase in the platform area,the probability of a strong nonlinear wave beneath the platform increases.

THE MEASUREMENT OF OXYGEN ISOTOPE COMPOSITION OF EXCEEDING MICRO-WATER——CAPILLARY CO_2-H_2O ROOM TEMPERATURE EQUILIBRIUM METHOD

We first established a method utilizing the oxygen isotope equilibration between water vapor and CO2 gas catalyzed by a hot platinum filament at 1300°C for analysing oxygen isotope composition in China in 1982. It is especially suitable for simultaneously analysing H-O isotope composition of microliter water extracted from fluid inclusion according to our exoerience. The minimum ouantitv of water for this method is 2 μl. The water contents

The Chinese Economy Starts the Year Off Strong with Overall Stability Exceeding Expectations

In the first quarter of 2019, despite complex and daunting conditions both at home and abroad, China continued to uphold the core principle of progress amidst stability. We remained committed to the new development philosophy, resolutely promoted high-quality growth by focusing on furthering structural reform on the supply side, and continued to fight the three critical battles against potential risks, poverty, and pollution. Thanks to these efforts, ChinaJs economic performance has maintained overall stability and exceeded expectations.

Machine-learning-assisted Investigation into the Relationship between the Built Environment,Behavior,and Physical Health of the Elderly in China

Due to an increasing life expectancy and decreasing fertility rate,China officially entered a stage of increased ageing in 2011[1].According to China’s seventh national census,2019,the country’s overall population was 1.44 billion,and this included eighteen per cent of people over 60(13.5%of people exceeding 65 years old).

Spin Transport Properties of MnBi_(2)Te_(4)-Based Magnetic Tunnel Junctions

The van der Waals heterojunctions,stacking of different two-dimensional materials,have opened unprecedented opportunities to explore new physics and device concepts.Here,combining the density functional theory with non-equilibrium Green’s function technique,we systematically investigate the spin-polarized transport properties of van der Waals magnetic tunnel junctions(MTJs),Cu/MnBi_(2)Te_(4)/MnBi_(2)Te_(4)/Cu and Cu/MnBi_(2)Te_(4)/hBN/n·MnBi_(2)Te_(4)/Cu(n=1,2,3).It is found that the maximum tunnel magnetoresistance of Cu/MnBi_(2)Te_(4)/hBN/3·MnBi_(2)Te_(4)/Cu MTJs can reach 162.6%,exceeding the system with only a single layer MnBi_(2)Te_(4).More interestingly,our results indicate that Cu/MnBi_(2)Te_(4)/h-BN/n·MnBi_(2)Te_(4)/Cu(n=2,3)MTJs can realize the switching function,while Cu/MnBi_(2)Te_(4)/h-BN/3·MnBi_(2)Te_(4)/Cu MTJs exhibit the negative differential resistance.The Cu/MnBi_(2)Te_(4)/h-BN/3·MnBi_(2)Te_(4)/Cu in the parallel state shows a spin injection efficiency of more than 83.3%.Our theoretical findings of the transport properties will shed light on the possible experimental studies of MnBi_(2)Te_(4)-based van der Waals magnetic tunneling junctions.

乘势而上:中国斡旋沙特伊朗复交及其影响

On March 10,2023,China,Saudi Arabia and Iran issued a trilateral joint statement in Beijing,in which Saudi Arabia and Iran agreed to resume their diplomatic relations and reopen their embassies and missions within a period not exceeding two months.The Saudi-Iran confrontation has been one of the most intractable regional conflicts in the Middle East.The announcement of the two countries to restore their diplomatic ties resulted from the interplay of several favorable factors and is expected to set off a series of positive developments that might de-escalate many regional hotspot issues in Yemen,Syria,Iraq,and Lebanon.

SCIENCE AND TECHNOLOGY

Chinese Telescope LAMOST Reaches New Milestone in Spectral Data The Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) has become the world’s first sky survey telescope to release more than 22 million spectra,said the National Astronomical Observatories under the Chinese Academy of Sciences (NAOC).

高精度钠热管固定点炉及其等温特性

介绍了中国计量科学研究院新研制的两台高精度钠热管固定点炉(SHPF-1、SHPF-2),并测量了其垂直温场.当这两台钠热管固定点炉的炉温分别控制在比铝凝固点低约2℃、3℃时,铝点容器温度计阱底部150 mm范围内温场均匀性分别为15 mK和11 mK,并与国外同类的钠热管固定点炉的技术指标进行比较.此外,分析了影响固定点炉等温性能的因素. Abstract： Two sodium heat-pipe fixed point furnaces (SHPF-1, SHPF-2) developed at the National Institute of Metrology (NIM) are described, and their vertical temperature uniformities are measured. When the temperatures of the these two furnaces are controlled about 2 ℃ and 3 ℃ respectively, below the freezing point of the aluminum, the largest temperature differences did not exceed 15 mK and 11 mK in a distance about 150mm along the reentrant well of the aluminum point cell, respectively. These temperature uniformities are compared with those of foreign similar sodium heat pipe furnaces. Additionally, factors influencing isothermal characteristics of fixed point furnaces are analyzed.

Discussion on the influence of truncation of ground motion residual distribution on probabilistic seismic hazard assessment

Recent studies on assessment of a very low annual probability of exceeding （APE） ground motions, 10-4 or less, have highlighted the importance of the upper bound of ground motions when very low probability results are acquired. The truncation level adopted in probabilistic seismic hazard analysis （PSHA） should be determined by an aleatory uncertainty model （i.e., distribution model） of ground motions and the possible maximum and minimum ground motion values of a specific earthquake. However, at the present time, it is impossible to establish the upper bound model for ground motions based on the source characteristics and/or ground motion propagation. McGuire suggested a truncation level be fixed at a number of = 6, or the distribution of residuals be truncated in such a manner that site intensity cannot be greater than the epicenter intensity. This study aims to find a reasonable and feasible truncation level to be used in PSHA when the physical mechanism is not available to find the extreme ground motion. A mathematical analysis of the influence of the truncation level on PSHA, case studies of sites in different seismotectonic settings, and a distribution analysis of ground motion residuals are conducted in this study. It is concluded that = 4 is the minimum acceptable value for engineering applications for APEs within 0.002 to 10-4, and for low APEs, such as 10-5 and 10-6, the value of should be no less than 5 in most regions of China.