bluuebunny/crossref_metadata_2025_split huggingface dataset:
Could compact stars in globular clusters constrain dark matter?
Authors: Garani Raghuveer , Raj Nirmal , Reynoso-Cordova Javier 
Published: July 2023

Abstract
The dark matter content of globular clusters, highly compact gravity-bound stellar systems, is unknown.
It is also generally unknowable, due to their mass-to-light ratios typically ranging between 1-3 in solar units, accommodating a dynamical mass of dark matter at best comparable to the stellar mass.
That said, recent claims in the literature assume densities of dark matter around 1000 GeV/cm3 to set constraints on its capture and annihilation in white dwarfs residing in the globular cluster M4, and to study a number of other effects of dark matter on compact stars.
Motivated by these studies, we use measurements of stellar kinematics and luminosities in M4 to look for a dark matter component via a spherical Jeans analysis; we find no evidence for it, and set the first empirical limits on M4's dark matter distribution.
Our density upper limits, a few × 104 GeV/cm3 at 1 parsec from the center of M4, do not negate the claims (nor confirm them), but do preclude the use of M4 for setting limits on non-annihilating dark matter kinetically heating white dwarfs, which require at least 105 GeV/cm3 densities.
The non-robust nature of globular clusters as dynamical systems, combined with evidence showing that they may originate from molecular gas clouds in the absence of dark matter, make them unsuitable as laboratories to unveil dark matter's microscopic nature in current or planned observations.
Effect of gas mixture pressure on detection sensitivity of molecular iodine in the atmosphere by laser-fluorescent method using a copper vapor laser (578.2 nm)
Authors: Kireev S V , Kondrashov A A , Shnyrev S L , Suganeev S V 
Published: July 2023

Abstract
The paper reports on the calculation studies of the influence of the pressure of the analyzed gas mixture on the measuring sensitivity of the concentrations of 127I2, 127I129I and 129I2 in atmospheric air by the laser-fluorescence method using a copper vapor laser with a wavelength of 578.2 nm as a fluorescence excitation source. It is shown that for each of these iodine molecules there are pressures at which the highest fluorescence intensity is achieved, which correspond to the best detection sensitivity of the molecules. The results obtained can be used in the development of methods for real-time detection of molecular iodine in the atmosphere.
Bidirectional hierarchical quantum teleportation based on an eight-qubit entangled state
Authors: Yang Benchao 
Published: July 2023

Abstract
This article proposes an asymmetric bidirectional hierarchical quantum teleportation protocol, which is based on a quantum channel composed of a maximum of eight-qubit entangled state. With this method, Alice can transmit an unknown single-qubit state to Bob, meanwhile, Bob can transmit an arbitrary unknown two-qubit quantum state to Alice. As a sender with high authority, Bob can send any unknown two-qubit quantum state to Alice only under the sole control of the controller Charlie; Alice, as a sender with low-level permissions, if Bob intends to receive the unknown single-qubit quantum state sent by Alice, he must get the permission and assistance of Charlie and David to complete the communication.
The effect of ambient temperature fluctuations on the output frequency instability of the fiber femtosecond frequency comb
Authors: Filonov A A , Kuznetsov S A , Pivtsov V S , Farnosov S A , Isaeva Y G , Chepurov S V , Koliada N A 
Published: July 2023

Abstract
A study of the influence of temperature fluctuations of individual blocks of a fiber femtosecond frequency comb (FFC) generator and of the entire system as a whole on its output radio frequencies has been carried out. A two-circuit system for thermal stabilization of the air inside the FFC housing was implemented. An additional system for thermal stabilization of the transport fiber, which is included in the measurement scheme (outside the FFC), was implemented. A significant temperature effect on the measured output frequencies of the FFS is shown. Thanks to all the thermal stabilization systems, it has been shown that the instability of the developed fiber FFC introduced into its output microwave frequencies (in addition to the instability of the reference optical standard) is no worse than 2 × 10−16 per 1000 s.
On the microscopic shell-model version of the Bohr-Mottelson collective model
Authors: Ganev H. G. 
Published: July 2023

Abstract
The recently proposed microscopic shell-model version of the Bohr-Mottelson (BM) collective model is considered in more detail in the coordinate representation. The latter possesses a clear and transparent physical meaning, which reveals several features of the new version of the collective model missed in the previous formulation. The relationship to the original BM model is considered, along with the relationships between the different limiting submodels of the microscopic version of the BM model, which closely resemble the relationships of the original Wilets-Jean and rotor models. The kinematically correct many-particle wave functions of the microscopic version of the BM model, conserving the experimentally observed integrals of motion, are shown to consist of collective irrotational-flow and intrinsic components

in accordance with the original BM unified model. The general BM Hamiltonian is obtained as a contraction limit of the microscopic many-particle nuclear Hamiltonian, or, alternatively, by restricting the latter to the scalar

irreducible collective space.
Spatially repeatable components from ultrafast ultrasound are associated with motor unit activity in human isometric contractions
*
Authors: Rohlén Robin , Carbonaro Marco , Cerone Giacinto L , Meiburger Kristen M , Botter Alberto , Grönlund Christer 
Published: July 2023

Abstract

Objective. Ultrafast ultrasound (UUS) imaging has been used to detect intramuscular mechanical dynamics associated with single motor units (MUs). Detecting MUs from ultrasound sequences requires decomposing a velocity field into components, each consisting of an image and a signal. These components can be associated with putative MU activity or spurious movements (noise). The differentiation between putative MUs and noise has been accomplished by comparing the signals with MU firings obtained from needle electromyography (EMG). Here, we examined whether the repeatability of the images over brief time intervals can serve as a criterion for distinguishing putative MUs from noise in low-force isometric contractions. Approach. UUS images and high-density surface EMG (HDsEMG) were recorded simultaneously from 99 MUs in the biceps brachii of five healthy subjects. The MUs identified through HDsEMG decomposition were used as a reference to assess the outcomes of the ultrasound-based components. For each contraction, velocity sequences from the same eight-second ultrasound recording were separated into consecutive two-second epochs and decomposed. To evaluate the repeatability of components’ images across epochs, we calculated the Jaccard similarity coefficient (JSC). JSC compares the similarity between two images providing values between 0 and 1. Finally, the association between the components and the MUs from HDsEMG was assessed. Main results. All the MU-matched components had JSC > 0.38, indicating they were repeatable and accounted for about one-third of the HDsEMG-detected MUs (1.8 ± 1.6 matches over 4.9 ± 1.8 MUs). The repeatable components (JSC > 0.38) represented 14% of the total components (6.5 ± 3.3 components). These findings align with our hypothesis that intra-sequence repeatability can differentiate putative MUs from noise and can be used for data reduction. Significance. This study provides the foundation for developing stand-alone methods to identify MU in UUS sequences and towards real-time imaging of MUs. These methods are relevant for studying muscle neuromechanics and designing novel neural interfaces.
The effect of gas injection location on a lithium vapor box divertor in NSTX-U
Authors: Emdee E.D. , Goldston R.J. 
Published: July 2023

Abstract
The lithium vapor box divertor is a proposed divertor design that will minimize contamination of the upstream plasma in a fusion device, while also ensuring protection of the target. In this design lithium is evaporated near the target by high temperature lithium surfaces, dissipating the plasma heat flux. The lithium vapor box has been predicted via the fluid-kinetic code scrape off layer plasma simulator (SOLPS-ITER) to achieve low (

n

L
i

/

n

e

∼

0.05) upstream concentrations of lithium and low target heat fluxes. Here we compare two choices of deuterium gas puff location using SOLPS-ITER, the private flux region (PFR) and the common flux region (CFR), and find significant differences in the contamination level required to reach an acceptable target heat flux (defined here as q

tar

max

⩽

10 MW m−2). Deuterium gas puffing from the PFR is seen to better reduce upstream lithium contamination. The difference in puffing location is seen to cause changes in the upstream flow of lithium ions. The PFR puff, having better access to the separatrix, can better reduce the upstream-directed flow of lithium near the separatrix which is the primary source of contamination due to a large thermal force in this region. Puffing from the CFR, partially due to inefficacy at reducing separatrix lithium flow, has higher lithium concentration within the plasma. Solutions that reduce the heat flux to below 10 MW m−2 have a range of lithium concentrations between

n

L
i

/

n

e

∼

0.01–0.12 depending on puff intensity, location, evaporator temperature and recycling at the various plasma facing components. The efficacy of the puffs is tested for sensitivity to deuterium recycling coefficient at the target, evaporators, and main chamber walls. A CFR located puff is found to be more dependent on the recycling coefficients used than a PFR located puff. regardless of the set of recycling coefficients chosen, PFR puffing achieves lower lithium contamination than CFR puffing for a given heat flux.
Simulation-based Fatigue Life Analysis of Polyimide Film in Afterburner Fuel Distributor
Authors: Ban Jinlei , Zhao Zhihui , Huang Sen , Han Yongjian , Zhou Zhenhua , Wang Fei , Zhou Weixuan 
Published: July 2023

Abstract
Aiming at the problem of premature failure of organic material polyimide film in the afterburner fuel distributor of a turbofan engine, the material parameters of polyimide film and the temperature and the fluctuation amplitude of the film during use were obtained based on previous investigation. The finite element simulation model of polyimide film was established in ANSYS software to study the Mises stress distribution and weak area distribution of the film when the film fails in the form of fracture. Based on the fatigue life calculation theory of probabilistic fracture mechanics, the fatigue life cycle times and their variation rules of the film under different reliability were obtained. The results show that there is stress concentration in the film, and the stress con-centration and weak area of the film occur at the outer edge of the film clamping. The fatigue life cycle times of the film under different reliability are calculated, and the fatigue life cycle times decrease with the increase of reliability.
Computational Fluid Dynamics of Useful Grinding Fluid Flow and Sensitivity Analysis of Grinding Parameters
Authors: Sharma Vivek , Ghosh Amitava 
Published: July 2023

Abstract
In the grinding process, a high speed rotating grinding wheel develops a stiff air barrier around it. This air barrier restricts the flow of incoming grinding fluid through a nozzle jet into the grinding zone, and this leads to a considerable amount of grinding fluid being wasted. An insufficient amount of grinding fluid from the nozzle jet not reaching the grinding wheel-workpiece contact zone will result in many defects in the workpiece as well as in the grinding wheel. In this paper, a unique method of air scraper is modelled and simulated in order to impinge the grinding fluid maximum through a thick boundary layer around the periphery of the rotating grinding wheel and the effect of grinding parameters are analyzed and Ugff rate equation established using Box Behnken Design method.
QFD/TRIZ Based Mechanical Structure Design of Elderly Walker
Authors: Wang Zongsheng , Zhang Baoyi 
Published: July 2023

Abstract
To ensure the safety of the elderly and to provide a convenient and comfortable travel experience, elderly walkers are widely used. The Quality Function Deployment (QFD)/Teoriya Resheniya Izobretatelskikh Zadatch (TRIZ) integrated model is constructed and the specific implementation process is given by starting from the mechanical structure of the product. Firstly, the design requirements of the existing structure of the product are obtained from the elderly users by interview, and the requirements are classified into three categories: walking state, stationary state, and handling state from the state of the elderly travel. Then, on the basis of the requirements, a characteristic House of Quality (HOQ) for walkers suitable for the elderly was constructed, and the relationship matrix inside the HOQ was further analyzed to integrate and eliminate the characteristics of different products. Finally, the negative correlation characteristic problem in the autocorrelation matrix of the quality roof is extracted, and after transforming it into TRIZ problem, the product characteristic conflict in the design stage is eliminated by using TRIZ theory. Through the combination of the two methods, the objective requirement acquisition and the scientific design positioning in the design research stage are ensured. This study verifies the feasibility of the integrated model applied to elderly walkers through specific design practices.
Design of a New Bulletproof Structure and Simulation of Stiffness and Strength of the Whole Shelter
Authors: Wang Shengdong , Shen Yanyou , Zhou Chi 
Published: July 2023

Abstract
In order to improve the battlefield survivability of military equipment and personnel, more and more research institutions have conducted research on the bulletproof performance of equipment. This paper analyzes the advantages and disadvantages of several main bulletproof materials and their applicable environments, and briefly analyzes the damage performance of typical antiradiation missile warhead fragments. On this basis, a new type of hanging bullet proof structure is designed, which can be used to protect the warhead fragments of anti radiation missile. Using ANSYS simulation software, the stiffness and strength of the whole cabin under hoisting conditions are simulated.
Development and Validation of an in-House Direct Simulation Monte Carlo Code for Supersonic Rarefied Gas Microflows
Authors: Hew J K J , Boswell R W 
Published: July 2023

Abstract
An in-house Direct Simulation Monte Carlo (DSMC) code has been developed using an object-oriented interface for the purpose of eventually modelling gas and plasma microflows in micromechanical systems, by coupling it with an existing Particle-In-Cell (PIC) solver. The code is validated with canonical flow problems such as the micro-Couette and micro-Poiseuille flows. Since the emphasis is on supersonic and highly compressible flows, we perform validation studies of our algorithm for high velocity and Mach number cases, as compared to known analytical or semi-analytical profiles via asymptotic Bhatnagar-Gross-Krook (BGK) and Chapman-Enskog theory. Reasonably good agreement is found for all the test cases, which indicates the reliability of the present algorithm for modelling supersonic rarefied gas flows. Our results have implications for future validation studies of DSMC codes, where concrete quantitative theoretical and experimental comparisons across different flow configurations are required.
Experimental Investigation of Novel Liquid Flow Measurement by Using Thermoelectric Module
Authors: Oncha-ek P , Prasongsil C , Saitong N , Saimala W , Rungruang C , Leephakpreeda T 
Published: July 2023

Abstract
This paper presents an experimental investigation of liquid flow measurement by using a thermoelectric module. The measuring principle is based on the Seebeck effect of the thermoelectric module and the energy balance of convective heat transfer between the liquid flow and the thermoelectric module during implementation. The experimental studies confirm the viability of the thermoelectric module in determining the flow rates of water. In experiments, the results show that the determined flow rates by using the thermoelectric module are close to the actual flow rates of water with a coefficient of determination R2 of 0.9965. In addition to the straightforward measuring principle, low-cost material, no limitation of fluid types as well as directions of flows in a pipe, and no requirement of electrical power source make the thermoelectric module noteworthy as a sensor material in developing liquid flow meters.
AI Intelligent Detection Technology of Metal Hose for Rocket Engine
Authors: Chen Chong Kun 
Published: July 2023

Abstract
Endoscope is an important method for defect detection of metal hose used in rocket engine. Due to the traditional endoscopic detection technology is dependent on manual and low detection efficiency, this paper introduces Ai Image recognition technology to detect inner surface defects of metal hose. Aiming at the problem that most of the defects on the inner wall of the bellows of metal hose are small in scale and easy to be misjudged, a method of post-processing and rechecking of the bellows defect detection model is proposed, it is used to strengthen the defect detection model of the inner wall of the bellows of the metal hose for rocket engine. In this paper, based on the block classification network, the defect detection of the captured image of bellows is carried out, and the defect detection results of n*n blocks are output, then the metal hose defects are classified by using the bi fine-grained classification network with small structure, and the final n*n multi-class detection results are obtained. The results show that the engine and model of Ai Algorithm reduce the rate of missed detection and false detection, and improve the reliability of endoscope detection.
Analysis of an Abnormal Secondary Voltage Accident of Capacitive Voltage Transformer
Authors: Ouyang Zeyu , Chen Jiasheng , Zhu Silin , Dai Jiyulei 
Published: July 2023

Abstract
Capacitive Voltage Transformer (CVT) is an important measurement and protection equipment in power system, which has the characteristics of high electrical strength, large insulation margin and reliable operation. During the operation of CVT, its upper and lower capacitors, compensation reactors, lightning rods and other components often have faults. The faults of CVT can be found in time by judging the secondary voltage value. In this paper, an abnormal secondary voltage fault of CVT is introduced. Combined with test and disassembly analysis, it is determined that the fault is caused by breakdown of capacitor unit. Through fault simulation, this paper studies the typical CVT faults and the change law of secondary voltage, and puts forward the threshold of the secondary voltage abnormal alarm of CVT, providing important reference for CVT online monitoring.
Design and Analysis of a Vertical Electric Ducted Fan for Unmanned Aerial Vehicles
Authors: Shiau Y R , Fang J , Huang Y C 
Published: July 2023

Abstract
Several types of multirotor unmanned aerial vehicles (UAVs) are widely used in various industrial activities. UAVs with electric ducted fans (EDFs) have been developed to mitigate the risks associated with rotary blades, which are installed on the exterior structure of conventional UAVs and exposed to the ambient environment. Particularly, vertical EDFs have become a focus in the field of UAV design because they require less space for the flow channel compared with horizontal EDFs. In this study, a vertical EDF UAV model was developed. Structural and flow field analysis was performed in Ansys software to determine the optimal design configuration. The results confirmed that the designed model facilitated smooth air flow with favorable inlet and outlet velocity. The vehicle structure required minor adjustment to reduce the frequency of occurrence of vortices. Overall, this study made two research contributions. First, an EDF UAV model was developed to mitigate the risk of rotary blades being exposed to the ambient environment. Second, a vertical EDF system was proposed to reduce the flow channel space and maintain the outlet velocity, thereby improving the takeoff, landing, and thrust performance of UAVs.
Application of Impact Elastic Wave Method in Nondestructive Testing Technology
Authors: Feng Shaojie , Liu Chaoran 
Published: July 2023

Abstract
This paper summarizes the research status of nondestructive testing technology of building structures, focuses on the technical principles and characteristics of the first wave phase inversion method and the impact elastic wave method, and on this basis, the nondestructive detector based on the first wave phase reversal and impact elastic wave were used to conduct experimental research on cracks, materials, defects and thickness of the test block. The results show that the first wave phase inversion has low requirements for the test environment, and the test results are affected by the water, dust, steel reinforcement and signal attenuation inside the crack, which have a tendency to be shallow compared with the actual value. The first wave of defect location, size and other results are consistent with the actual situation, which verifies the good reliability of the nondestructive testing technology based on impact elastic wave.
A large area 100-channel PICOSEC Micromegas detector with time resolution at the 20 ps level
Authors: Utrobicic A. , Angelis Y. , Bortfeldt J. , Brunbauer F. , Chatzianagnostou E. , Dehmelt K. , Fanourakis G. , Floethner K.J. , Gallinaro M. , Garcia F. , Garg P. , Giomataris I. , Gnanvo K. , Gustavsson T. , Iguaz F.J. , Janssens D. , Kallitsopoulou A. , Kovacic M. , Legou P. , Lisowska M. , Liu J. , Lupberger M. , Maniatis I. , Meng Y. , Muller H. , Oliveri E. , Orlandini G. , Papaevangelou T. , Pomorski M. , Ropelewski L. , Sampsonidis D. , Scharenberg L. , Schneider T. , Sohl L. , van Stenis M. , Tsipolitis Y. , Tzamarias S.E. , Veenhof R. , Wang X. , White S. , Zhang Z. , Zhou Y. 
Published: July 2023

AbstractThe PICOSEC Micromegas precise timing detector is based on a Cherenkov radiator coupled to a photocathode operating in a semi-transparent mode and a Micromegas amplification structure. The first proof of concept single-channel prototype was able to achieve a time resolution below 25 ps. One of the crucial aspects in the development of precise timing gaseous detectors applicable in high-energy physics experiments is a modular design that enables large area coverage. The first 19-channel multi-pad prototype with an active area of approximately 10 cm2suffered from degraded timing resolution due to the non-uniformity of the preamplification gap thickness. A new 100 cm2detector module with 100 channels based on a rigid hybrid ceramic/FR4 Micromegas board for improved drift gap uniformity was developed. Initial measurements with 80 GeV/c muons showed improvements in timing response over the measured pads and a time resolution below 25 ps. More recent measurements with a thinner drift gap detector module and newly developed RF pulse amplifiers show that the pad centre resolution can be enhanced to the level of 17 ps. This work will present the development of the detector from structural simulations, design, and beam test commissioning with a focus on the timing performance of a thinner drift gap detector module in combination with new electronics using an automated timing scan method.