Development of a high-repetition-rate lumped-inductance kicker magnet prototype for the beam switchyard of SHINE

The Shanghai high-repetition-rate X-ray free-electron laser and extreme light facility(SHINE)operates at a maximum repetition rate of 1 MHz.Kicker magnets are key components that distribute electron bunches into three different undulator lines in a bunch-by-bunch mode.The kicker field width must be less than the time interval between bunches.A lumpedinductance kicker prototype was developed using a vacuum chamber with a single-turn coil.The full magnetic field strength was 0.005 T.This paper presents the requirements,design considerations,design parameters,magnetic field calculations,and measurements of the kicker magnets.The relevant experimental results are also presented.The pulse width of the magnetic field was approximately 600 ns,and the maximum operation repetition rate was 1 MHz.The developed kicker satisfies the requirements for the SHINE project.Finally,numerous recommendations for the future optimization of kicker magnets are provided.

Experimental and numerical study on dynamic mechanical behaviors of shale under true triaxial compression at high strain rate

High-energy gas fracturing of shale is a novel,high efficacy and eco-friendly mining technique,which is a typical dynamic perturbing behavior.To effectively extract shale gas,it is important to understand the dynamic mechanical properties of shale.Dynamic experiments on shale subjected to true triaxial compression at different strain rates are first conducted in this research.The dynamic stress-strain curves,peak strain,peak stress and failure modes of shale are investigated.The results of the study indicate that the intermediate principal stress and the minor principal stress have the significant influence on the dynamic mechanical behaviors,although this effect decreases as the strain rate increases.The characteristics of compression-shear failure primarily occur in shale subjected to triaxial compression at high strain rates,which distinguishes it from the fragmentation characteristics observed in shale under dynamic uniaxial compression.Additionally,a numerical three-dimensional Split Hopkinson Pressure Bar(3D-SHPB),which is established by coupling PFC3D and FLAC3D methods,is validated to replicate the laboratory characteristics of shale.The dynamic mechanical characteristics of shale subjected to different confining stresses are systematically investigated by the coupling PFC3D and FLAC3D method.The numerical results are in good agreement with the experimental data.

Preparation and performance evaluation of the slickwater using novel polymeric drag reducing agent with high temperature and shear resistance ability

Slickwater fracturing fluids are widely used in the development of unconventional oil and gas resources due to the advantages of low cost,low formation damage and high drag reduction performance.However,their performance is severely affected at high temperatures.Drag reducing agent is the key to determine the drag reducing performance of slickwater.In this work,in order to further improve the temperature resistance of slickwater,a temperature-resistant polymeric drag reducing agent(PDRA)was synthesized and used as the basis for preparing the temperature-resistant slickwater.The slickwater system was prepared with the compositions of 0.2 wt%PDRA,0.05 wt%drainage aid nonylphenol polyoxyethylene ether phosphate(NPEP)and 0.5 wt%anti-expansion agent polyepichlorohydrindimethylamine(PDM).The drag reduction ability,rheology properties,temperature and shear resistance ability,and core damage property of slickwater were systematically studied and evaluated.In contrast to on-site drag reducing agent(DRA)and HPAM,the temperature-resistant slickwater demonstrates enhanced drag reduction efficacy at 90℃,exhibiting superior temperature and shear resistance ability.Notably,the drag reduction retention rate for the slickwater achieved an impressive 90.52%after a 30-min shearing period.Additionally,the core damage is only 5.53%.We expect that this study can broaden the application of slickwater in high-temperature reservoirs and provide a theoretical basis for field applications.

Supercritical-hydrothermal accelerated solid state reaction route for synthesis of LiMn_2O_4 cathode material for high-power Li-ion batteries

Synthesis of the spinel structure lithium manganese oxide （LiMn2O4） by supercritical hydrothermal （SH） accelerated solid state reaction （SSR） route was studied. The impacts of the reaction pressure, reaction temperature and reaction time of SH route, and the calcination temperature of SSR route on the purity, particle morphology and electrochemical properties of the prepared LiMn2O4 materials were studied. The experimental results show that after 15 min reaction in SH route at 400 ℃ and 30 MPa, the reaction time of SSR could be significantly decreased, e.g. down to 3 h with the formation temperature of 800 ℃, compared with the conventional solid state reaction method. The prepared LiMn2O4 material exhibits good crystallinity, uniform size distribution and good electrochemical performance, and has an initial specific capacity of 120 mA.h/g at a rate of 0.1C （1C=148 mA/g） and a good rate capability at high rates, even up to 50C.

Development of a Novel Parallel-spool Pilot Operated High-pressure Solenoid Valve with High Flow Rate and High Speed

High-pressure solenoid valve with high flow rate and high speed is a key component in an underwater driving system.However,traditional single spool pilot operated valve cannot meet the demands of both high flow rate and high speed simultaneously.A new structure for a high pressure solenoid valve is needed to meet the demand of the underwater driving system.A novel parallel-spool pilot operated high-pressure solenoid valve is proposed to overcome the drawback of the current single spool design.Mathematical models of the opening process and flow rate of the valve are established.Opening response time of the valve is subdivided into 4 parts to analyze the properties of the opening response.Corresponding formulas to solve 4 parts of the response time are derived.Key factors that influence the opening response time are analyzed.According to the mathematical model of the valve,a simulation of the opening process is carried out by MATLAB.Parameters are chosen based on theoretical analysis to design the test prototype of the new type of valve.Opening response time of the designed valve is tested by verifying response of the current in the coil and displacement of the main valve spool.The experimental results are in agreement with the simulated results,therefore the validity of the theoretical analysis is verified.Experimental opening response time of the valve is 48.3 ms at working pressure of 10 MPa.The flow capacity test shows that the largest effective area is 126 mm2 and the largest air flow rate is 2320 L/s.According to the result of the load driving test,the valve can meet the demands of the driving system.The proposed valve with parallel spools provides a new method for the design of a high-pressure valve with fast response and large flow rate.

Enhanced Anion-Derived Inorganic-Dominated Solid Electrolyte Interphases for High-Rate and Stable Sodium Storage

It is highly desirable for the promising sodium storage possessing high rate and long stable capability,which are mainly hindered by the unstable yet conventional solvent-derived organic-rich solid electrolyte interphases.Herein,an electrolyte solvation chemistry is elaborately manipulated to produce an enhanced anion-derived and inorganic components-dominated solid electrolyte interphases by introducing a low permittivity(4.33)bis(2,2,2-trifluoroethyl)ether diluent into the sodium bis(trifluoromethylsulfonyl)imidedimethoxyethane-based high concentration electrolyte to obtain a localized high concentration electrolyte.The bis(2,2,2-trifluoroethyl)ether breaks the balance of original cation solvation structure and tends to interact with Na^(+)-coordinated dimethoxyethane solvent rather than Na^(+)in high concentration electrolyte,leaving an enhanced Coulombic interaction between Na^(+)and(FSO_(2))_(2)N^(-),and more(FSO_(2))_(2)N^(-)can enter the Na^(+)solvation shell,forming a further increased number of Na^(+)-(FSO_(2))_(2)N^(-)-dimethoxyethane clusters(from 82.0%for high concentration electrolyte to 94.3%for localized high concentration electrolyte)at a low salt dosage.The preferential reduction of this(FSO_(2))_(2)N^(-)-enriched clusters rather than the dimethoxyethane-dominated Na^(+)solvation structure produces an enhanced anion-derived and inorganic components-dominated solid electrolyte interphases.The reversible charge storage process of Na is decoupled by operando Raman along with a shift of D and G peaks.Benefiting from the enhanced anion-derived electrode-electrolyte interface,the commercial hard carbon anode in localized high concentration electrolyte shows a well rate capability(5 A g^(−1),70 mAh g^(−1)),cycle performance and stability(85%of initial capacity after 700 cycles)in comparison to that of high concentration electrolyte(68%)and low concentration electrolyte(only 5%after 400 cycles),indicative of uniqueness and superiorities towards stable Na storage.

Fiber coupled high count-rate single-photon generated from InAs quantum dots

In this work,we achieve high count-rate single-photon output in single-mode(SM)optical fiber.Epitaxial and dilute InAs/GaAs quantum dots(QDs)are embedded in a GaAs/AlGaAs distributed Bragg reflector(DBR)with a micro-pillar cavity,so as to improve their light emission extraction in the vertical direction,thereby enhancing the optical SM fiber’s collection capabil-ity(numerical aperture:0.13).By tuning the temperature precisely to make the quantum dot exciton emission resonant to the micro-pillar cavity mode(Q~1800),we achieve a fiber-output single-photon count rate as high as 4.73×10^(6) counts per second,with the second-order auto-correlation g2(0)remaining at 0.08.

Development of miniaturized SAF-LIBS with high repetition rate acousto-optic gating for quantitative analysis

The self-absorption effect in laser-induced breakdown spectroscopy(LIBS)reduces the accuracy of quantitative measurement results.The self-absorption-free LIBS(SAF-LIBS)has been proved to directly capture the optically thin plasma spectra by setting an appropriate exposure time.In this work,a novel SAF-LIBS technique with high repetition rate acousto-optic gating is developed,in which an acousto-optic modulator is used as the shutter to diffract the optically thin fluorescence,and a high repetition rate laser is used to produce quasi-continuous plasmas to enhance the integral spectral intensity,so that the CCD spectrometer can replace an intensified CCD(ICCD)and echelle spectrometer in SAF-LIBS.Experimental results show that the average absolute prediction error of aluminum is reduced to 0.18%,which is equivalent to that of traditional SAF-LIBS.This technique not only effectively shields continuous background radiation and broadened spectral lines in optically thick plasma,but also has advantages of miniaturization,low cost,convenience and reliability.

An Analysis of Amazon’s High Turnover Rate

Amazon’s internal and external environments were analyzed using PEST and SWOT models.Taking into account of relevant literature on strategic human resource management(SHRM)and models like the Harvard model and the human resource management/industrial relation(HRM/IR)model,the reasons for Amazon’s employee high turnover rate were analyzed.In this paper,several solutions to this issue are indicated,including improving incentive policies and organizing training.At the end of this paper,my personal experiences and the lessons learned throughout the course are summarized.

Flow behavior and microstructure of ZK60 magnesium alloy compressed at high strain rate

Flow behavior and microstructure of a homogenized ZK60 magnesium alloy were investigated during compression in the temperature range of 250-400 ℃ and the strain rate range of 0.1-50 s^-1. The results showed that dynamic recrystallization （DRX） developed mainly at grain boundaries at lower strain rate （0.1-1 s^-1）, while in the case of higher strain rate （10-50 s^-1）, DRX occurred extensively both at twins and grain boundaries at all temperature range, especially at temperature lower than 350 ℃, which resulted in a more homogeneous microstructure than that under other deformation conditions. The DRX extent determines the hot workability of the workpiece, therefore, hot deformation at the strain rate of 10-50 s^-1 and in the temperature range of 250-350 ℃ was desirable for ZK60 alloy. Twin induced DRX during high strain rate compression included three steps. Firstly, twins with high dislocation subdivided the initial grain, then dislocation arrays subdivided the twins into subgrains, and after that DRX took place with a further increase of strain.

HIGH STRAIN RATE SU PERPLASTICITY IN SiCp REINFORCED AZ31 MAGNESIUM MATRIX COMPOSITE

Superplasticity of AZ 31 magnesium matrix composites reinforced with 10 vol% SiC（2 μm） particulate i s investigated at temperature range from 365℃ to 565℃ and strain rate from 2.0 8×10-3 to 5.21×10-1 s-1. The maximum total elongation of 228 % is obtained at a strain rate of 2.08×10-1 s-1. The strain rate se nsitivity exponent （m） higher than 0.3, is observed when the strain rate is high er than 10-1 s-1 at 525℃. Increasing the test temperature to 540℃, the maximum total elongation exceeding 195% is achieved at a higher strain rate of 5.21×10-1 s-1 than that at 525℃. SiC in AZ31/SiCp composite ca n fine the matrix grain size. Filament is observed on the fracture surface of th e specimens showing superplasticity.

Breeding and Utilization of Japonicalinous CMS Line Chunjiang 19A with Wide Compatibility and High Outcrossing Rate

[Objective] To breed and utilize the japonicalinous cytoplasmic male sterile （CMS） line Chunjiang 19A with wide compatibility and high outcrossing rate. [Method] Cbunjiang 16A was used as the female parent to cross with Indica-Japonica crossing material B125, which was used as male parent. Backcross breeding was contin- ued for consecutive generations to breed the CMS lines with wide compatibility and high outcrossing rate. [Result] Chunjiang 19A is a late medium Japonica CMS line with good fertility stability. The proportion of sterile plants and pollen abortion rates are 100% and the Cheng＇s index is 14. It is the japonicalinous CMS line with early flowering, partial stigma exsertion, high outcrossing rate, wide compatibility, high re- sistance to stripe disease and good combining ability. The hybrid rice combinations originated from Chunjiang 19A have strong tUlering ability, dominant heterosis, high resistance to stripe disease, great yield potential and good color change at mature stage. [Conclusion] The successful breeding of Chunjiang 19A laid good foundation for the breeding of Japonica hybrid rice and Indica-Japonica hybrid rice combinations with high seed production and dominant heterosis, showing a promising application prospect.

Studies of an event-building algorithm of the readout system for the twin TPCs in HFRS

The High-energy Fragment Separator(HFRS),which is currently under construction,is a leading international radioactive beam device.Multiple sets of position-sensitive twin time projection chamber(TPC)detectors are distributed on HFRS for particle identification and beam monitoring.The twin TPCs'readout electronics system operates in a trigger-less mode due to its high counting rate,leading to a challenge of handling large amounts of data.To address this problem,we introduced an event-building algorithm.This algorithm employs a hierarchical processing strategy to compress data during transmission and aggregation.In addition,it reconstructs twin TPCs'events online and stores only the reconstructed particle information,which significantly reduces the burden on data transmission and storage resources.Simulation studies demonstrated that the algorithm accurately matches twin TPCs'events and reduces more than 98%of the data volume at a counting rate of 500 kHz/channel.

Challenges and opportunities in the production of magnesium parts by directed energy deposition processes

Mg-alloys have gained considerable attention in recent years for their outstanding properties such as lightweight,high specific strength,and corrosion resistance,making them attractive for applications in medical,aerospace,automotive,and other transport industries.However,their widespread application is hindered by their low formability at room temperature due to limited slip systems.Cast Mg-alloys have low mechanical properties due to the presence of casting defects such as porosity and anisotropy in addition to the high scrap.While casting methods benefit from established process optimization techniques for these problems,additive manufacturing methods are increasingly replacing casting methods in Mg alloys as they provide more precise control over the microstructure and allow specific grain orientations,potentially enabling easier optimization of anisotropy properties in certain applications.Although metal additive manufacturing(MAM)technology also results in some manufacturing defects such as inhomogeneous microstructural evolution and porosity and additively manufactured Mg alloy parts exhibit lower properties than the wrought parts,they in general exhibit superior properties than the cast counterparts.Thus,MAM is a promising technique to produce Mg alloy parts.Directed energy deposition processes,particularly wire arc directed energy deposition(WA-DED),have emerged as an advantageous additive manufacturing(AM)technique for metallic materials including magnesium alloys,offering advantages such as high deposition rates,improved material efficiency,and reduced production costs compared to subtractive processes.However,the inherent challenges associated with magnesium,such as its high reactivity and susceptibility to oxidation,pose unique hurdles in the application of this technology.This review paper delves into the progress made in the application of DED technology to Mg-alloys,its challenges,and prospects.Furthermore,the predominant imperfections,notably inhomogeneous microstructure evolution and porosity,observed in Mg-alloy components manufactured through DED are discussed.Additionally,the preventive measures implemented to counteract the formation of these defects are explored.

Extra-Axial Anaplastic Pleomorphic Xanthoastrocytoma Mimicking Meningioma: A Case Report with Literature Review

Background: A number of meningeal neoplastic lesions may radiologically and clinically simulate meningioma, include hemangiopericytomas, solitary fibrous tumors, schwannomas, hematolymphoid lesions, metastases, and others very rarely, also may clinically mimic meningiomas. Case Description: We present the case of A 28-year-old male patient, with no notable medical history, who presented with worsening headaches for 3 months, imbalance, and visual deficits, An initial MRI revealed extra-axial lesion involving the right Parieto-occipital, The tumor was hypointense on T1-weighted MR images, hyperintense signals on T2-weightedMR images, and heterogeneously enhanced suggestive of a meningioma, total resection was achieved, and the histopathological analysis confirmed the diagnosis of an angioblastic meningioma. However, 15 months later, the patient presented with the same initial visual complaints. A subsequent MRI showed lesion recurrence, leading to a second surgical intervention. The histopathological analysis confirmed the diagnosis of an anaplastic xanthoastrocytoma. Conclusion: This represents an unusual location for an anaplastic pleomorphic xanthoastrocytoma, which should broaden the differential diagnosis of extra-axial lesions.

Dynamic tensile properties and microstructural evolution of extruded EW75 magnesium alloy at high strain rates

The dynamic tensile properties and microstructural evolution of an extruded EW75 magnesium alloy deformed at ambient temperature and different high strain rates(from 1000 to 3000 s^(-1))along extrusion direction(ED)were investigated by Split Hopkinson Tension Bar(SHTB).The corresponding deformation mechanisms,texture evolution and microstructure changes were analyzed by optical microscope(OM),electron backscatter diffraction(EBSD)and transmission electron microscope(TEM).The results show that the extruded EW75 magnesium alloy along ED exhibits a conventional positive strain rate sensitivity that the dynamic flow stresses increase with in creasing strain rate.Texture measurements show that after dynamic tension,the initial weak texture of extruded EW75 magnesium alloy tansforms to a relatively strong<10-10>//ED texture with increasing strain rates.The microstructural analysis demonstrates that dislocation motion are main deformatin mode to accommodate dynamic tensile deformation at high strain rates.In addition,the interactions of dislocation-dislocation and dislocation-second phase lead to the in crease of flow stress and strain hardening with increasing strain rate.

Study on High Rate Discharge Performance and Mechanism of AB_5 Type Hydrogen Storage Alloys

The effects of surface treatment, particle size distribution,rare earth composition and B additive on the high rate discharge performance of hydrogen storage alloys were investigated. It is found that the activity, discharge capacity and high rate dischargeability of the alloys are improved after physical and chemical modification as a result of the increase of the surface area and formation of the electrocatalysis layers, which increase both the electrochemical reaction rate on the alloy surface and H diffusion rate in the alloy bulk. It is also found that both the over-coarse and over-fine particle size increase the contact resistance of the electrode, resulting in a decrease of discharge capacity, deterioration of high rate dischargeability and lower discharge plateau. In another word, a suitable particle size distribution can enhance the alloy activity, discharge capacity and high rate dischargeability. In addition, the high rate dischargeability is enhanced by increasing La content and decreasing Ce content of the alloy composition because of enlargement of the unit cell volume and the improvement of the surface activity. Moreover, B additive resultes in the formation of the second phase, and makes the alloys easier pulverization, which greatly improves the activity, discharge capacity and high rate dischargeability.

Feasibility and Diagnostic Accuracy for Assessment of Coronary Artery Stenosis of Prospectively Electrocardiogram-gated High-pitch Spiral Acquisition Mode Dual-source CT Coronary Angiography in Patients with Relatively Higher Heart Rates: in Comparison wit

Objective To prospectively investigate the diagnostic accuracy for coronary artery stenosis of prospectively electrocardiogram-triggered spiral acquisition mode (high pitch mode) dual-source computed tomography coronary angiography (CTCA) in patients with relatively higher heart rates (HR) compared with catheter coronary angiography (CCA). Methods Forty-seven consecutive patients with relatively higher HR (>65 and <100 bpm) (20 male, 27 female; age 55±10 years) who both underwent dual-source CTCA and CCA were prospectively included in this study. All patients were performed CTCA using high pitch mode setting at 20%-30% of the R-R interval for the image acquisition. All coronary segments were evaluated by two blinded and independent observers with regard to image quality on a three-point scale (1: excellent to 3: non-diagnostic) and for the presence of significant coronary stenoses (defined as diameter narrowing exceeding 50%). Considered CCA as the standard of reference, the sensitivity, specificity, positive predictive value and negative predictive value were calculated. Radiation dose values were calculated using the dose-length product. Results Image quality was rated as being score 1 in 92.4% of segments, score 2 in 6.1% of segmentsand score 3 in 1.5% of segments. The average image quality score per segment was 1.064±0.306. The HR variability of patients with image score 1, 2 and 3 were 2.29±1.06 bpm, 5.17±1.37 bpm, 8.88±1.53 bpm, respectively. The average HR variability of patients with different image scores were significantly different (F=170.402, P=0.001). The sensitivity, specificity, positive and negative predictive values were 92.6%, 97.0%, 87.6%, 98.3%, respectively, per segment and 90.0%, 95.2%, 85.3%, 96.9%, respectively, per vessel and 100%, 63.6%, 90.0%, 100%, respectively, per patient. The effective radiation dose was on average 0.86±0.16 mSv. Conclusion In patients with HR more than 65 bpm and below 100 bpm without cardiac arrhythmia, the prospectively electrocardiogram-gated high-pitch spiral acquisition mode with image acquired timing set at 20%-30% of the R-R interval provides a high diagnostic accuracy for the assessment of coronary stenoses combined with a 1.5% of non-diagnostic coronary segments and a radiation dose below 1 mSv.

High strain rate compressive strength behavior of cemented paste backfill using split Hopkinson pressure bar

The stability of cemented paste backfill(CPB)is threatened by dynamic disturbance,but the conventional low strain rate laboratory pressure test has difficulty achieving this research purpose.Therefore,a split Hopkinson pressure bar(SHPB)was utilized to investigate the high strain rate compressive behavior of CPB with dynamic loads of 0.4,0.8,and 1.2 MPa.And the failure modes were determined by macro and micro analysis.CPB with different cement-to-tailings ratios,solid mass concentrations,and curing ages was prepared to conduct the SHPB test.The results showed that increasing the cement content,tailings content,and curing age can improve the dynamic compressive strength and elastic modulus.Under an impact load,a higher strain rate can lead to larger increasing times of the dynamic compressive strength when compared with static loading.And the dynamic compressive strength of CPB has an exponential correlation with the strain rate.The macroscopic failure modes indicated that CPB is more seriously damaged under dynamic loading.The local damage was enhanced,and fine cracks were formed in the interior of the CPB.This is because the CPB cannot dissipate the energy of the high strain rate stress wave in a short loading period.

3D hierarchically porous NiO/Graphene hybrid paper anode for long-life and high rate cycling flexible Li-ion batteries

With the rapid emergence of wearable devices, flexible lithium-ion batteries(LIBs) are much more needed than ever. Free-standing graphene-based composite paper electrodes with various active materials have appealed wide applications in flexible LIBs. However, due to the prone-to-restacking feature of graphene layers, a long cycle life at high current densities is rather difficult to be achieved. Herein, a unique threedimensional(3D) hierarchically porous NiO micro-flowers/graphene paper(fNiO/GP) electrode is successfully fabricated. The resulting fNiO/GP electrode shows superior long-term cycling stability at high rates(e.g., storage capacity of 359 mAh/g after 600 cycles at a high current density of 1 A/g). The facile 3D porous structure combines both the advantages of the graphene that is highly conductive and flexible to ensure rapid electrons/ions transfer and buffer the volume expansion of NiO during charge/discharge,and of the micro-sized NiO flowers that induces hierarchical between-layer pores ranging from nanomicro meters to promote the penetration of the electrolyte and prevent the re-stacking of graphene layers. Such structural design will inspire future manufacture of a wide range of active materials/graphene composite electrodes for high performance flexible LIBs.