Response spectra for nuclear structures on rock sites considering the near-fault directivity effect

Near-fault ground motions, potentially with large amplitude and typical velocity pulses, may significantly impact the performance of a wide range of structures. The current study is aimed at evaluating the safety implications of the near-fault effect on nuclear power plant facilities designed according to the Chinese code. To this end, a set of near- fault ground motions at rock sites with typical forward-directivity effect is examined with special emphasis on several key parameters and response spectra. Spectral comparison of the selected records with the Chinese and other code design spectra was conducted. The bi-normalized response spectra in terms of different comer periods are utilized to derive nuclear design spectra. It is concluded that nuclear design spectra on rock sites derived from typical rupture directivity records are significantly influenced both by the earthquake magnitude and the rupture distance. The nuclear design spectra specified in the code needs to be adjusted to reflect the near-fault directivity effect of large earthquakes.

Rupture directivity and hanging wall effect in near field strong ground motion simulation

A random synthesis procedure based on finite fault model is adopted for near field strong ground motion simulation in this paper. The fault plane of the source is divided into a number of sub-sources, the whole moment magnitude is also divided into more sub-events. The Fourier spectrum of ground motion caused by a sub-event in given sub-source, then can be derived by means of taking the point source spectrum, attenuation with distance, energy dissipation, and near surface effect, into account. A time history is synthesized from this amplitude spectrum and a random phase spectrum, and being combined with an envelope function. The ground motion is worked out by superposition of all time histories from each sub-event in each sub-source, with time lags determining by the differences between the triggering times of sub-events and distances of the sub-sources. From the example of simulations at 21 near field points in a scenario earthquake with 4 dip angles of the fault plane, it is illustrated that the procedure can describe the rupture directivity and hanging wall effect very well. To validate the procedure, the response spectra and time histories recorded at three near fault stations MCN, LV3 and PCD during the Northridge earthquake in 1994, are compared with the simulated ones.

Reproducing fling-step and forward directivity at near source site using of multi-objective particle swarm optimization and multi taper

This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the differences between the response spectra and multi-tapered power spectral delsilies corresponding to the recorded and simulated wavelbrms. The multi-taper method is used to reduce the spectral leakage that is inherent in the Fourier rams formed form ofwavelbrms, ieading to a reduction of variance in power spectral amplitudes, thus permitting the calibration of the two sets of data. The technique is implemented using the 1998-Fandoqa （lran） earthquake data and the results are compared with the actual observed data. Additionally, a comparison is made with a SAR interfcrometry study leading to fair agreement with the reported dislocation along the main fault. The simulation procedure and results are discussed and assessed concluding that, although the technique may be associated with uncertainties, it can still be used to reproduce wavelbnns at near source sites that include permanent dislocation, and can be used for seismic pertbrmance evaluation of structures in the region under study.

Design of a High Power Directional Coupler with High Directivity Used in the LHCD Launcher for EAST

A high power waveguide directional coupler was designed to measure the transmitted power and reflected power in the 4.6 GHz LHCD （lower hybrid current drive） launcher for the EAST tokamak. The design principle of the coupler is assessed. Further analysis is performed by CST （computer simulating test） and Ansoft HFSS （high frequency structure simulator） software and the optimal structural parameter is obtained. In addition, finite element code ANSYS is used to determine the temperature distribution in the coupler conductively cooled by forced water. The test results of a directional coupler manufactured according to the design are close to what is expected.

Effect of seismic super-shear rupture on the directivity of ground motion acceleration

The effect of seismic super-shear rupture on the directivity of ground motions using simulated accelerations of a vertical strike-slip fault model is the topic of this study. The discrete wave number/finite element method was adopted to calculate the ground motion in the horizontal layered half space. An analysis of peak ground acceleration （PGA） indicates that similar to the sub-shear situation, directivity also exists in the super-shear situation. However, there are some differences as tbllows： （1） The PGA of the fault-normal component decreases with super-shear velocity, and the areas that were significantly affected by directivity in the PGA field changed from a cone-shaped region in the forward direction in a sub-shear situation to a limited near-fault region in a super-shear situation. （2） The PGA of the fault-parallel and vertical component is not as sensitive as the fault-normal component to the increasing super-shear velocity. （3） The PGA of the fault-normal component is not always greater than the fault-parallel component when the rupture velocity exceeds the shear wave velocity.

Rupture directivity effect on strong ground motion during the 12 May 2008 M_(W)7.9 Wenchuan earthquake

We focus here on the rupture directivity effect on the spatial distribution and attenuation characteristics of near-field ground motions during the 2008 MW7.9 Wenchuan earthquake.We examine the difference between the observed ground motions in and opposite the rupture directions and compare them with Next Generation Attenuation-West2(NGA-West2)ground motion prediction models.The isochrone directivity predictor is used to quantify the band-limited nature of the rupture directivity effect on strong ground motion.Our results show that the observed peak ground velocity(PGV)and spectral accelerations of periods of 1.0 s and longer are significantly amplified in the rupture direction,but de-amplified in the opposite direction affected by rupture directivity effect of this event.In contrast,the effect of rupture directivity on the observed peak ground acceleration(PGA)and periods of shorter than 1.0 s are relatively weak.The rupture directivity of this event shows clear period dependent and band limited characteristics with the strongest effect occurring around the period of 7.5 s.

Effects of hanging wall and forward directivity in the 1999 Chi-Chi earthquake on inelastic displacement response of structures

The characteristics of the inelastic response of structures affected by hanging wall and forward directivity in the 1999 Chi-Chi earthquake are investigated. Inelastic displacement ratios （IDRs） for ground motions impacted by these nearfield effects are evaluated and comprehensively compared to far-field ground motions. In addition, the inelastic displacement responses to hanging wall and footwall ground motions are compared. It is concluded that the inelastic displacement response is significantly affected in the short period range by hanging wall and in the long period range by footwall. Although high peak ground acceleration was observed at hanging wall stations, the IDRs for structures on hanging wall sites are only larger than footwall sites in the very long period range. Forward directivity effects result in larger IDRs for periods longer than about 0.5s. Adopting statistical relationships for IDRs established using far-field ground motions may lead to either overestimation or underestimation in the seismic evaluation of existing structures located in near-field regions, depending on their fundamental vibration periods.

DIRECTIVITY OPTIMIZATION OF CURVED SURFACE DIPOLE ANTENNAS

Based on the calculation of the characteristic parameters by moment method, the curved surface dipoles are optimized by an optimization method, the maximum directivities of some V-curved and Gauss-curved surface dipoles are given.

Seismic hazard assessment of Tehran,Iran with emphasis on near-fault rupture directivity effects

Many destructive earthquakes happened in Tehran, Iran in the last centuries. The existence of active faults like the North Tehran is the main cause of seismicity in this city. According to past investigations, it is estimated that in the scenario of activation of the North Tehran fault, many structures in Tehran will collapse. Therefore, it is necessary to incorporate the near field rupture directivity effects of this fault into the seismic hazard assessment of important sites in Tehran. In this study, using calculations coded in MATLAB, Probabilistic Seismic Hazard Analysis （PSHA） is conducted for an important site in Tehran. Following that, deaggregation technique is performed on PSHA and the contribution of seis- mic scenarios to hazard is obtained in the range of distance and magnitude. After identifying the North Tehran fault as the most hazardous source affecting the site in 10000-year return period, rupture directivity effects of this fault is incorporated into the seismic hazard assessment using Somerville et al. （1997） model with broadband approach and Shahi and Baker （2011） model with narrowband approach. The results show that the narrowband approach caused a 27% increase in the peak of response spectrum in 10000-year return period compared with the conventional PSHA. Therefore, it is necessary to incorporate the near fault rupture directivity effects into the higher levels of seismic hazard assessment attributed to important sites.

Directivity effect of unloading bedding coal induced fracture evolution and its application

In the coal mining process, the gas contained in the coalbed is one source of the most serious accident hazards. Stress releasing from the coal deposit is the main controlling factor that leads to such accidents.Based on the bedding of coal samples, the gas permeability well describes the evolution of fracture, so the paper carries out research on the permeability properties of coal under different unloading directions.The research obtains that when the stress unloading direction is perpendicular to bedding, more penetrating fractures and bedding fractures occur, and the permeability significantly increases. Although the axial stress reduced, the confining pressure makes the permeability of the bedding plane fracture exist under constant. The permeability obtained when the unloading direction was perpendicular to the bedding is 52 times larger than that when it is parallel to the bedding. The results show that the efficiency of gas drainage is impacted by the relative direction of gas drainage drilling in relation to the bedding orientations. The maximum amount of gas extraction when drilling is perpendicular to the bedding is 1.3 times than that when drilling is oblique to the bedding, and 1.75 times than that when drilling is parallel to the bedding.

The influence of reflections from the train body and the ground on the sound radiation from a railway rail

Purpose – The vibration of the rails is a significant source of railway rolling noise, often forming the dominantcomponent of noise in the important frequency region between 400 and 2000 Hz. The purpose of the paper is toinvestigate the influence of the ground profile and the presence of the train body on the sound radiation fromthe rail.Design/methodology/approach – Two-dimensional boundary element calculations are used, in which therail vibration is the source. The ground profile and various different shapes of train body are introduced in themodel, and results are observed in terms of sound power and sound pressure. Comparisons are also made withvibro-acoustic measurements performed with and without a train present.Findings – The sound radiated by the rail in the absence of the train body is strongly attenuated by shieldingdue to the ballast shoulder. When the train body is present, the sound from the vertical rail motion is reflectedback down toward the track where it is partly absorbed by the ballast. Nevertheless, the sound pressure at thetrackside is increased by typically 0–5 dB. For the lateral vibration of the rail, the effects are much smaller. Oncethe sound power is known, the sound pressure with the train present can be approximated reasonably well withsimple line source directivities.Originality/value – Numerical models used to predict the sound radiation from railway rails have generallyneglected the influence of the ground profile and reflections from the underside of the train body on the soundpower and directivity of the rail. These effects are studied in a systematic way including comparisons with measurements.

Cell reprogramming therapy for Parkinson’s disease

Parkinson’s disease is typically characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta.Many studies have been performed based on the supplementation of lost dopaminergic neurons to treat Parkinson’s disease.The initial strategy for cell replacement therapy used human fetal ventral midbrain and human embryonic stem cells to treat Parkinson’s disease,which could substantially alleviate the symptoms of Parkinson’s disease in clinical practice.However,ethical issues and tumor formation were limitations of its clinical application.Induced pluripotent stem cells can be acquired without sacrificing human embryos,which eliminates the huge ethical barriers of human stem cell therapy.Another widely considered neuronal regeneration strategy is to directly reprogram fibroblasts and astrocytes into neurons,without the need for intermediate proliferation states,thus avoiding issues of immune rejection and tumor formation.Both induced pluripotent stem cells and direct reprogramming of lineage cells have shown promising results in the treatment of Parkinson’s disease.However,there are also ethical concerns and the risk of tumor formation that need to be addressed.This review highlights the current application status of cell reprogramming in the treatment of Parkinson’s disease,focusing on the use of induced pluripotent stem cells in cell replacement therapy,including preclinical animal models and progress in clinical research.The review also discusses the advancements in direct reprogramming of lineage cells in the treatment of Parkinson’s disease,as well as the controversy surrounding in vivo reprogramming.These findings suggest that cell reprogramming may hold great promise as a potential strategy for treating Parkinson’s disease.

Complication rates after direct anterior vs posterior approach for hip hemiarthroplasty in elderly individuals with femoral neck fractures

BACKGROUND Dislocation rates after hemiarthroplasty reportedly vary from 1%to 17%.This serious complication is associated with increased morbidity and mortality rates.Approaches to this surgery are still debated,with no consensus regarding the superiority of any single approach.AIM To compare early postoperative complications after implementing the direct anterior and posterior approaches(PL)for hip hemiarthroplasty after femoral neck fractures.METHODS This is a comparative,retrospective,single-center cohort study conducted at a university hospital.Between March 2008 and December 2018,273 patients(a total of 280 hips)underwent bipolar hemiarthroplasties(n=280)for displaced femoral neck fractures using either the PL(n=171)or the minimally invasive direct anterior approach(DAA)(n=109).The choice of approach was related to the surgeons’practices;the implant types were similar and unrelated to the approach.Dislocation rates and other complications were reviewed after a minimum followup of 6 mo.RESULTS Both treatment groups had similarly aged patients(mean age:82 years),sex ratios,patient body mass indexes,and patient comorbidities.Surgical data(surgery delay time,operative time,and blood loss volume)did not differ significantly between the groups.The 30 d mortality rate was higher in the PL group(9.9%)than in the DAA group(3.7%),but the difference was not statistically significant(P=0.052).Among the one-month survivors,a significantly higher rate of dislocation was observed in the PL group(14/154;9.1%)than in the DAA group(0/105;0%)(P=0.002).Of the 14 patients with dislocation,8 underwent revision surgery for recurrent instability(posterior group),and one of them had 2 additional procedures due to a deep infection.The rate of other complications(e.g.,perioperative and early postoperative periprosthetic fractures and infection-related complications)did not differ significantly between the groups.CONCLUSION These findings suggest that the DAA to bipolar hemiarthroplasty for patients with femoral neck fractures is associated with a lower dislocation rate(<1%)than the PL.

Progress,challenges,and prospects of spent lithium-ion batteries recycling:A review

The recycling and reutilization of spent lithium-ion batteries(LIBs)have become an important measure to alleviate problems like resource scarcity and environmental pollution.Although some progress has been made,battery recycling technology still faces challenges in terms of efficiency,effectiveness and environmental sustainability.This review aims to systematically review and analyze the current status of spent LIB recycling,and conduct a detailed comparison and evaluation of different recycling processes.In addition,this review introduces emerging recycling techniques,including deep eutectic solvents,molten salt roasting,and direct regeneration,with the intent of enhancing recycling efficiency and diminishing environmental repercussions.Furthermore,to increase the added value of recycled materials,this review proposes the concept of upgrading recycled materials into high value-added functional materials,such as catalysts,adsorbents,and graphene.Through life cycle assessment,the paper also explores the economic and environmental impacts of current battery recycling and highlights the importance that future recycling technologies should achieve a balance between recycling efficiency,economics and environmental benefits.Finally,this review outlines the opportunities and challenges of recycling key materials for next-generation batteries,and proposes relevant policy recommendations to promote the green and sustainable development of batteries,circular economy,and ecological civilization.

Anisotropic time-dependent behaviors of shale under direct shearing and associated empirical creep models

Understanding the anisotropic creep behaviors of shale under direct shearing is a challenging issue.In this context,we conducted shear-creep and steady-creep tests on shale with five bedding orientations (i.e.0°,30°,45°,60°,and 90°),under multiple levels of direct shearing for the first time.The results show that the anisotropic creep of shale exhibits a significant stress-dependent behavior.Under a low shear stress,the creep compliance of shale increases linearly with the logarithm of time at all bedding orientations,and the increase depends on the bedding orientation and creep time.Under high shear stress conditions,the creep compliance of shale is minimal when the bedding orientation is 0°,and the steady-creep rate of shale increases significantly with increasing bedding orientations of 30°,45°,60°,and 90°.The stress-strain values corresponding to the inception of the accelerated creep stage show an increasing and then decreasing trend with the bedding orientation.A semilogarithmic model that could reflect the stress dependence of the steady-creep rate while considering the hardening and damage process is proposed.The model minimizes the deviation of the calculated steady-state creep rate from the observed value and reveals the behavior of the bedding orientation's influence on the steady-creep rate.The applicability of the five classical empirical creep models is quantitatively evaluated.It shows that the logarithmic model can well explain the experimental creep strain and creep rate,and it can accurately predict long-term shear creep deformation.Based on an improved logarithmic model,the variations in creep parameters with shear stress and bedding orientations are discussed.With abovementioned findings,a mathematical method for constructing an anisotropic shear creep model of shale is proposed,which can characterize the nonlinear dependence of the anisotropic shear creep behavior of shale on the bedding orientation.

Review on laser directed energy deposited aluminum alloys

Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.

Intrahepatic portal venous systems in adult patients with cavernous transformation of portal vein: Imaging features and a new classification

Background: Cavernous transformation of the portal vein(CTPV) due to portal vein obstruction is a rare vascular anomaly defined as the formation of multiple collateral vessels in the hepatic hilum. This study aimed to investigate the imaging features of intrahepatic portal vein in adult patients with CTPV and establish the relationship between the manifestations of intrahepatic portal vein and the progression of CTPV. Methods: We retrospectively analyzed 14 CTPV patients in Beijing Tsinghua Changgung Hospital. All patients underwent both direct portal venography(DPV) and computed tomography angiography(CTA) to reveal the manifestations of the portal venous system. The vessels measured included the left portal vein(LPV), right portal vein(RPV), main portal vein(MPV) and the portal vein bifurcation(PVB). Results: Nine males and 5 females, with a median age of 40.5 years, were included in the study. No significant difference was found in the diameters of the LPV or RPV measured by DPV and CTA. The visualization in terms of LPV, RPV and PVB measured by DPV was higher than that by CTA. There was a significant association between LPV/RPV and PVB/MPV in term of visibility revealed with DPV( P = 0.01), while this association was not observed with CTA. According to the imaging features of the portal vein measured by DPV, CTPV was classified into three categories to facilitate the diagnosis and treatment. Conclusions: DPV was more accurate than CTA for revealing the course of the intrahepatic portal vein in patients with CTPV. The classification of CTPV, that originated from the imaging features of the portal vein revealed by DPV, may provide a new perspective for the diagnosis and treatment of CTPV.

Influences of prolate spheroidal baffle of sound diffraction on spatial directivity of acoustic vector sensor

The directivity of acoustic vector sensor (AVS) will be distorted by the sound diffraction of the AVS carrier. In this paper,the scattering of a plane acoustic wave from a prolate spheroid baffle is considered. At first,the sound diffraction of prolate spheroidal baffle is established,then the mathematical expressions of sound pressure field and particle vibration velocity field of sound diffraction are derived and the characteristic of the directivity of pressure and velocity of sound diffraction field at different frequencies and distances is analyzed. The directivity of AVS is determined by the amplitude and phase difference of diffraction wave and incident wave,which possesses a close relationship with frequency and incident angle. Finally,the calculated results are compared with the experimental results.

A particle-resolved heat-particle-fluid coupling model by DEM-IMB-LBM

Multifield coupling is frequently encountered and also an active area of research in geotechnical engineering.In this work,a particle-resolved direct numerical simulation(PR-DNS)technique is extended to simulate particle-fluid interaction problems involving heat transfer at the grain level.In this extended technique,an immersed moving boundary(IMB)scheme is used to couple the discrete element method(DEM)and lattice Boltzmann method(LBM),while a recently proposed Dirichlet-type thermal boundary condition is also adapted to account for heat transfer between fluid phase and solid particles.The resulting DEM-IBM-LBM model is robust to simulate moving curved boundaries with constant temperature in thermal flows.To facilitate the understanding and implementation of this coupled model for non-isothermal problems,a complete list is given for the conversion of relevant physical variables to lattice units.Then,benchmark tests,including a single-particle sedimentation and a two-particle drafting-kissing-tumbling(DKT)simulation with heat transfer,are carried out to validate the accuracy of our coupled technique.To further investigate the role of heat transfer in particle-laden flows,two multiple-particle problems with heat transfer are performed.Numerical examples demonstrate that the proposed coupling model is a promising high-resolution approach for simulating the heat-particle-fluid coupling at the grain level.

Physical and mechanical properties and microstructures of submarine soils in the Yellow Sea

In recent years,the exploration of seabed has been intensified,but the submarine soils of silt and sand in the Yellow Sea area have not been well investigated so far.In this study,the physical and mechanical properties of silt and sand from the Yellow Sea were measured using a direct shear apparatus and their microstructures were observed using a scanning electron microscope.The test results suggest that the shear strength of silt and sand increases linearly with the increase of normal stress.Based on the direct shear test,the scanning electron microscope was used to observe the section surface of sand.It is observed that the section surface becomes rough,with many“V”‐shaped cracks.Many particles appear on the surface of the silt structure and tend to be disintegrated.The X‐ray diffraction experiment reveals that the sand and silt have different compositions.The shear strength of sand is slightly greater than that of silt under high stress,which is related to the shape of soil particles and the mineral composition.These results can be a reference for further study of other soils in the Yellow Sea;meanwhile,they can serve as soil parameters for the stability and durability analyses of offshore infrastructure construction.