Correlation between the rock mass properties and maximum horizontal stress:A case study of overcoring stress measurements

Understanding the mechanical properties of the lithologies is crucial to accurately determine the horizontal stress magnitude.To investigate the correlation between the rock mass properties and maximum horizontal stress,the three-dimensional(3D)stress tensors at 89 measuring points determined using an improved overcoring technique in nine mines in China were adopted,a newly defined characteristic parameter C_(ERP)was proposed as an indicator for evaluating the structural properties of rock masses,and a fuzzy relation matrix was established using the information distribution method.The results indicate that both the vertical stress and horizontal stress exhibit a good linear growth relationship with depth.There is no remarkable correlation between the elastic modulus,Poisson's ratio and depth,and the distribution of data points is scattered and messy.Moreover,there is no obvious relationship between the rock quality designation(RQD)and depth.The maximum horizontal stress σ_(H) is a function of rock properties,showing a certain linear relationship with the C_(ERP)at the same depth.In addition,the overall change trend of σ_(H) determined by the established fuzzy identification method is to increase with the increase of C_(ERP).The fuzzy identification method also demonstrates a relatively detailed local relationship betweenσ_H and C_(ERP),and the predicted curve rises in a fluctuating way,which is in accord well with the measured stress data.

Violent collisions can reveal hexadecapole deformation of nuclei

A new observable in heavy ion collision experiments was identified to be sensitive to the hexadecapole deformation of the colliding nuclei.Such deformation is difficult to measure in traditional nuclear electric transition measurements,as it is often overwhelmed by the nuclear quadrupole deformation.This opens the door to gain new insight into nuclear structure with experiments that were designed to study hot and dense nuclear matter.

A Rigidity Measurement of Pseudo-Rapidity Spectrum of Produced Particles in High Energy Nucleus-Nucleus Collisions

A new concept,rigidity of pseudo-rapidity spectrum,is extended into the study of the multiplicity fluctuations in high energy nucleus-nucleus interactions.In using the novel method to analyze the data of l6O-Em at 14.6,60,and 200A GeV,and ^(32)S-Em at 200A GeV,it is found that the rigidity of pseudo-rapidity spectrum in the central domain of pseudo-rapidity might be a mixture of Poisson type and Wigner one.

A MEASUREMENT ON ENERGY-POOLING COLLISION CROSS SECTION IN Mg

The energy-pooling collision cross section for the transfer from 3s3p^(1)P to 3s4s^(3)S of Mg has been determined by measuring the relative intensity of the fluorescence at 5184Åand 2852Å.The average cross section is(3.1±40%)×10^(-15)cm^(2).By considering the influence of radiation trapping and other uncertain effects,the absolute uncertainty of our measurement is within one order of magnitude.

Measurement of Absolute Atomic Collision Cross Section with Helium Using^(87)Rb Atoms Confined in Magneto-Optic and Magnetic Traps

We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using^(87)Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap.The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences.The collision cross sections as a function of trap depth for helium gas are obtained.These findings are significant for extracting the information about the different cross sections when the trap depth is changed.

Investigating the elliptic anisotropy of identified particles in p-Pb collisions with a multi-phase transport model

The elliptic azimuthal anisotropy coefficient(v_(2))of the identified particles at midrapidity(|η|<0.8)was investigated in p-Pb collisions at√s_(NN)=5.02 TeV using a multi-phase transport model(AMPT).The calculations of differential v_(2)based on the advanced flow extraction method of light flavor hadrons(pions,kaons,protons,andΛ)in small collision systems were extended to a wider transverse momentum(p_(T))range of up to 8 GeV/c for the first time.The string-melting version of the AMPT model provides a good description of the measured p_(T)-differential v_(2)of the mesons but exhibits a slight deviation from the baryon v_(2).In addition,we observed the features of mass ordering at low p_(T)and the approximate number-of-constituentquark(NCQ)scaling at intermediate p_(T).Moreover,we demonstrate that hadronic rescattering does not have a significant impact on v_(2)in p-Pb collisions for different centrality selections,whereas partonic scattering dominates in generating the elliptic anisotropy of the final particles.This study provides further insight into the origin of collective-like behavior in small collision systems and has referential value for future measurements of azimuthal anisotropy.

Electromagnetic fields in ultra-peripheral relativistic heavy-ion collisions

Ultra-peripheral heavy-ion collisions(UPCs)offer unique opportunities to study processes under strong electromagnetic fields.In these collisions,highly charged fast-moving ions carry strong electromagnetic fields that can be effectively treated as photon fluxes.The exchange of photons can induce photonuclear and two-photon interactions and excite ions.This excitation of the ions results in Coulomb dissociation with the emission of photons,neutrons,and other particles.Additionally,the electromagnetic fields generated by the ions can be sufficiently strong to enforce mutual interactions between the two colliding ions.Consequently,the two colliding ions experience an electromagnetic force that pushes them in opposite directions,causing a back-to-back correlation in the emitted neutrons.Using a Monte Carlo simulation,we qualitatively demonstrate that the above electromagnetic effect is large enough to be observed in UPCs,which would provide a clear means to study strong electromagnetic fields and their effects.

Shock Tube Measurement of Ethylene Ignition Delay Time and Molecular Collision Theory Analysis

In this study, 75% and 96% argon diluent conditions were selected to determine the ig- nition delay time of stoichiometric mixture of C2Ha/O2/Ar within a range of pressures （1.3-：3.0 arm） and temperatures （1092-1743 K）. Results showed a logarithmic linear rela- tionship of the ignition delay time with the reciprocal of temperatures. Under both two diluent conditions, ignition delay time decreased with increased temperature. By multiple linear regression analysis, the ignition delay correlation was deduced. According to this correlation, the calculated ignition delay time in 96% diluent was found to be nearly five times that in 75% diluent. To explain this discrepancy, the hard-sphere collision theory was adopted, and the collision numbers of ethylene to oxygen were calculated. The total collision numbers of ethylene to oxygen were 5.99×10^30 s^-1cm^-3 in 75% diluent and 1.53×10^29 s^-1cm^-3 in 96% diluent （about 40 times that in 75% diluent）. According to the discrepancy between ignition delay time and collision numbers, viz. 5 times corresponds to 40 times, the steric factor can

A portable instrument for measurement of atmospheric O_(x) and NO_(2) based on cavity ring-down spectroscopy

Atmospheric O_(x)(nitrogen dioxide(NO_(2))+ozone(O_(3)))can better reflect the local and regional change character-istics of oxidants compared to O_(3)alone,so obtaining O_(x)accurately and rapidly is the basis for evaluating the O_(3)production rate.Furthermore,O_(x)has proved to be a more representative indicator and can serve as a reflection of pollution prevention efficacy.A portable instrument for measuring atmospheric O_(x)and NO_(2)based on cavity ring-down spectroscopy(O_(x)/NO_(2)-CRDS)was developed in this work.The NO_(2)concentration is accurately mea-sured according to its absorption characteristic at 407.86 nm.Ambient O_(3)is converted into NO_(2)by chemical titration of high concentrations of nitrogen oxide(NO),and the O_(3)conversion efficiencies obtained are nearly 99%.The detection limit of the O_(x)/NO_(2)-CRDS system for O_(x)is 0.024 ppbv(0.1 s),and the overall uncertainty of the instrument is±6%.Moreover,the Kalman filtering technique was applied to improve the measurement accuracy of O_(x)/NO_(2)-CRDS.The system was applied in a comprehensive field observation campaign at Hefei Sci-ence Island from 26 to 30 September 2022,and the time concentration series and change characteristics of O_(x)and NO_(2)were obtained for five days.The measured O_(x)concentrations were compared with those of two com-mercial instruments,and the consistency was good(R^(2)=0.98),indicating that this system can be deployed to accurately and rapidly obtain the concentrations of atmospheric O_(x)and NO_(2).It will be a useful tool for assessing the atmospheric oxidation capacity and controlling O_(3)pollution.

Measurement of Electron Density and Ion Collision Frequency with Dual Assisted Grounded Electrode DBD in Atmospheric Pressure Helium Plasma Jet

The properties of a helium atmospheric-pressure plasma jet（APPJ）are diagnosed with a dual assisted grounded electrode dielectric barrier discharge device.In the glow discharge,we captured the current waveforms at the positions of the three grounded rings.From the current waveforms,the time delay between the adjacent positions of the rings is employed to calculate the plasma bullet velocity of the helium APPJ.Moreover,the electron density is deduced from a model combining with the time delay and current intensity,which is about 10^（11）cm^（-3）.In addition,The ion-neutral particles collision frequency in the radial direction is calculated from the current phase difference between two rings,which is on the order of 10~7 Hz.The results are helpful for understanding the basic properties of APPJs.

Measurement of the Low-Energy Rb+-Rb Total Collision Rate in an Ion-Neutral Hybrid Trap

An ion-neutral hybrid trap is built to study low-energy ion-atom collisions. The ion-neutral hybrid trap is combined with two spatially concentric traps: a linear Paul trap for the ionic species and a magneto-optical trap (MOT) for the neutral species. The total ion-atom collision rate coefficient k(ia) between Rb-87 atoms and optically dark Rb-87(+) ions is measured by monitoring the reduction of the steady-state MOT atoms by sequentially introducing various mechanisms, namely photoionization and ion-atom collisions. In contrast to other experiments, a concise experimental procedure is devised to obtain the loss rates of the MOT atoms due to photoionization and ion-atom collisions in one experimental cycle, and then the collision rate k(ia) of cold Rb-87 atoms with Rb-87(+) ions is deduced to 0.94(+/- 0.24) x 10(-13) m(3)/s with T-i = 3770(+/- 100) K measured by the time of flight of the ion signal. The measurements show good agreement with the collision rate derived from the Langevin model.

Measurement of Collision Conditions in Magnetic Pulse Welding Processes

MPW （magnetic pulse welding） is a solid state joining technology that allows for the generation of strong metallic bonds, even between dissimilar metals. Due to the absence of external heat, critical intermetallic phases can largely be avoided. In this process, Lorentz forces are utilized for the rapid acceleration of at least one of the two metallic joining partners leading to the controlled high velocity impact between them. The measurement of the collision conditions and their targeted manipulation are the key factors of a successful process development. Optical measuring techniques are preferred, since they are not influenced by the prevalent strong magnetic field in the vicinity of the working coil. In this paper, the characteristic high velocity impact flash during MPW was monitored and evaluated using phototransistors in order to measure the time of the impact. The results are in good accordance with the established PDV （photon Doppler velocimetry） and show a good repeatability. Furthermore, the collision front velocity was investigated using adapted part geometries within a series of tests. This velocity component is one of the key parameters in MPW; its value decreases along the weld zone. With the help of this newly introduced measurement tool, the magnetic pressure distribution or the joining geometry can be adjusted more effectively.

Training for Vessel Collision Prevention:Circumstances and Causes of Near-Miss Incidents

Among the near-miss incidents related to the operation of training ship of the JMETS(Japan Agency of Maritime Education and Training for Seafarers),three characteristic cases were analyzed,extracting their circumstances and near-miss factors.Based on the results of these analyses,measures to prevent vessel collisions were studied,from which we proposed collision prevention training.The training entails(1)lookout training,(2)navigation planning training,(3)resource management training,and(4)false assumption prevention training.In future research,we aim to verify the effectiveness of the proposed training,improve the training’s effectiveness,and contribute to the development of effective anti-collision support devices.

Multi-USV Formation Collision Avoidance via Deep Reinforcement Learning and COLREGs

Dear Editor,This letter focuses on the collision avoidance for a multi-unmanned surface vehicle(multi-USV)system.A novel multi-USV collision avoidance(MUCA)algorithm is proposed.Firstly,in order to get a more reasonable collision avoidance policy,reward functions are constructed according to international regulations for preventing collisions at sea(COLREGS)and USV dynamics.

Collisionless shock acceleration of protons in a plasma slab produced in a gas jet by the collision of two laser-driven hydrodynamic shockwaves

We have recently proposed a new technique of plasma tailoring by laser-driven hydrodynamic shockwaves generated on both sides of a gas jet[Marquès et al.,Phys.Plasmas 28,023103(2021)].In a continuation of this numerical work,we study experimentally the influence of the tailoring on proton acceleration driven by a high-intensity picosecond laser in three cases:without tailoring,by tailoring only the entrance side of the picosecond laser,and by tailoring both sides of the gas jet.Without tailoring,the acceleration is transverse to the laser axis,with a low-energy exponential spectrum,produced by Coulomb explosion.When the front side of the gas jet is tailored,a forward acceleration appears,which is significantly enhanced when both the front and back sides of the plasma are tailored.This forward acceleration produces higher-energy protons,with a peaked spectrum,and is in good agreement with the mechanism of collisionless shock acceleration(CSA).The spatiotemporal evolution of the plasma profile is characterized by optical shadowgraphy of a probe beam.The refraction and absorption of this beam are simulated by post-processing 3D hydrodynamic simulations of the plasma tailoring.Comparison with the experimental results allows estimation of the thickness and near-critical density of the plasma slab produced by tailoring both sides of the gas jet.These parameters are in good agreement with those required for CSA.

Production of the X(4014)as the Spin-2 Partner of X(3872)in e^(+)e^(-)Collisions

In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associatedwith the shallow isoscalar D*D* bound state and as such is an excellent candidate for the spin-2 partner of the X(3872)with the quantum numbers J^(PC)=2^(++)conventionally named X_(2).

Influence of sampling on three-dimensional surface shape measurement

In order to accurately measure an object’s three-dimensional surface shape,the influence of sampling on it was studied.First,on the basis of deriving spectra expressions through the Fourier transform,the generation of CCD pixels was analyzed,and its expression was given.Then,based on the discrete expression of deformation fringes obtained after sampling,its Fourier spectrum expression was derived,resulting in an infinitely repeated"spectra island"in the frequency domain.Finally,on the basis of using a low-pass filter to remove high-order harmonic components and retaining only one fundamental frequency component,the inverse Fourier transform was used to reconstruct the signal strength.A method of reducing the sampling interval,i.e.,reducing the number of sampling points per fringe,was proposed to increase the ratio between the sampling frequency and the fundamental frequency of the grating.This was done to reconstruct the object’s surface shape more accurately under the condition of m>4.The basic principle was verified through simulation and experiment.In the simulation,the sampling intervals were 8 pixels,4 pixels,2 pixels,and 1 pixel,the maximum absolute error values obtained in the last three situations were 88.80%,38.38%,and 31.50%in the first situation,respectively,and the corresponding average absolute error values are 71.84%,43.27%,and 32.26%.It is demonstrated that the smaller the sampling interval,the better the recovery effect.Taking the same four sampling intervals in the experiment as in the simulation can also lead to the same conclusions.The simulated and experimental results show that reducing the sampling interval can improve the accuracy of object surface shape measurement and achieve better reconstruction results.

Impact of initial fluctuations and nuclear deformations in isobar collisions

Relativistic isobar^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zrcollisions have revealed intricate differences in their nuclear size and shape,inspiring unconventional studies of nuclear structure using relativistic heavy ion collisions.In this study,we investigate the relative differences in the mean multiplicityR_(<Nch>)and the secondR_(ε2)and third-order eccentricityR_(ε3)between isobar collisions using initial state Glauber models.It is found that initial fluctuations and nuclear deformations have negligible effects on R_(<Nch>)in most central collisions,while both are important for the R_(ε2)and R_(ε3),the degree of which is sensitive to the underlying nucleonic or sub-nucleonic degree of freedom.These features,compared to real data,may probe the particle production mechanism and the physics underlying nuclear structure.

Bunch-length measurement at a bunch-by-bunch rate based on time–frequency-domain joint analysis techniques and its application

This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings.This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters,such as bunch length and synchronous phase.The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz.The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s,and the single-shot sampling data buffer covered thousands of turns.The bunch-length and synchronous phase information were extracted via offline calculations using Python scripts.The calibration coefficient of the system was determined using a commercial streak camera.Moreover,this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility(SSRF),and longitudinal instabilities were observed during the single-bunch accumulation process at Hefei Light Source(HLS).For Gaussian-distribution bunches,the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps,and the bunch-length uncertainty was better than 1 ps.The dynamic range exceeded 10 ms.This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.

Imaging the initial condition of heavy-ion collisions and nuclear structure across the nuclide chart

High-energy nuclear collisions encompass three key stages:the structure of the colliding nuclei,informed by low-energy nuclear physics,the initial condition,leading to the formation of quark-gluon plasma(QGP),and the hydrodynamic expansion and hadronization of the QGP,leading to fnal-state hadron distributions that are observed experimentally.Recent advances in both experimental and theoretical methods have ushered in a precision era of heavy-ion collisions,enabling an increasingly accurate understanding of these stages.However,most approaches involve simultaneously determining both QGP properties and initial conditions from a single collision system,creating complexity due to the coupled contributions of these stages to the fnal-state observables.To avoid this,we propose leveraging established knowledge of low-energy nuclear structures and hydrodynamic observables to independently constrain the QGP's initial condition.By conducting comparative studies of collisions involving isobar-like nuclei—species with similar mass numbers but diferent ground-state geometries—we can disentangle the initial condition's impacts from the QGP properties.This approach not only refnes our understanding of the initial stages of the collisions but also turns high-energy nuclear experiments into a precision tool for imaging nuclear structures,ofering insights that complement traditional low-energy approaches.Opportunities for carrying out such comparative experiments at the Large Hadron Collider and other facilities could signifcantly advance both highenergy and low-energy nuclear physics.Additionally,this approach has implications for the future electron-ion collider.While the possibilities are extensive,we focus on selected proposals that could beneft both the high-energy and low-energy nuclear physics communities.Originally prepared as input for the long-range plan of U.S.nuclear physics,this white paper refects the status as of September 2022,with a brief update on developments since then.