Strong shock propagation for the finite-source circular blast in a confined domain

The circular explosion wave produced by the abrupt discharge of gas from a high-temperature heat source serves as a crucial model for addressing explosion phenomena in compressible flow.The reflection of the primary shock and its propagation within a confined domain are studied both theoretically and numerically in this research.Under the assumption of strong shock,the scaling law governing propagation of the main shock is proposed.The dimensionless frequency of reflected shock propagation is associated with the confined distance.The numerical simulation for the circular explosion problem in a confined domain is performed for validation.Under the influence of confinement,the principal shock wave systematically undergoes reflection within the domain until it weakens,leading to the non-monotonic attenuation of kinetic energy in the explosion fireball and periodic oscillations of the fireball volume with a certain frequency.The simulation results indicate that the frequency of kinetic energy attenuation and the volume oscillation of the explosive fireball align consistently with the scaling law.

70 Gbps PAM-4850-nm oxide-confined VCSEL without equalization and pre-emphasis

Directly modulated 850-nm vertical-cavity surface-emitting lasers(VCSELs)with the advantages of low cost,high modulation speed,good reliability,and low power consumption,are the key sources in the optical interconnects with multimode fibers for the supercomputers,data centers,and machine learning applications[1−3].Typically,non-return-tozero(NRZ)modulation format is used.

Multiscale confinement nitridation in molybdenum carbide for efficient hydrogen production

The molybdenum carbide(Mo_(2)C)has been regarded as one of the most cost-efficient and stable electrocatalyst for the hydrogen evolution reaction(HER)by the virtue of its Pt-like electronic structures.However,the inherent limitation of high density of empty valence band significantly reduces its catalytic reactivity by reason of strong hydrogen desorption resistance.Herein,we propose a multiscale confinement synthesis method to design the nitrogen-rich Mo_(2)C for modulating the band structure via decomposing the pre-coordination bonded polymer in a pressure-tight tube sealing system.Pre-bonded c/N-Mo in the coordination precursor constructs a micro-confinement space,enabling the homogeneous nitrogenization in-situ happened during the formation of Mo_(2)C.Simultaneously,the evolved gases from the precursor decomposition in tube sealing system establish a macro-confinement environment,preventing the lattice N escape and further endowing a continuous nitridation.Combining the multiscale confinement effects,the nitrogen-rich Mo2C displays as high as 25%N-Mo concentration in carbide lattice,leading to a satisfactory band structure.Accordingly,the constructed nitrogen-rich Mo_(2)C reveals an adorable catalytic activity for HER in both alkaline and acid solution.It is anticipated that the multiscale confinement synthesis strategy presents guideline for the rational design of electrocatalysts and beyond.

Influence of Confined Concrete Models on the Seismic Response of RC Frames

In this study, the influence of confined concrete models on the response of reinforced concrete structures is investigatedat member and global system levels. The commonly encountered concrete models such as Modified Kent-Park, Saatçioğlu-Razvi, and Mander are considered. Two moment-resisting frames designed according to thepre-modern code are taken into consideration to reflect the example of an RC moment-resisting frame in thecurrent building stock. The building is in an earthquake-prone zone located on Z3 Soil Type. The inelasticresponse of the building frame is modelled by considering the plastic hinges formed on each beam and columnelement for different concrete classes and stirrups spacings. The models are subjected to non-linear static analyses.The differences between confined concrete models are comparatively investigated at both reinforced concretemember and system levels. Based on the results of the comparative analysis, it is revealed that the column behaviouris mostly influenced by the choice of model, due to axial loads and confinement effects, while the beams areless affected, and also it is observed that the differences exhibited in the moment-curvature response of columncross-sections do not significantly affect the overall behaviour of the global system. This highlights the critical roleof model selection relative to the concrete strength and stirrup spacing of the member.

Mechanical properties and influence mechanism of confined concrete arches in high-stress tunnels

Deep underground projects(e.g., coal mines), are often faced with complex conditions such as high stress and extremely soft rock. The strength and rigidity of the traditional support system are often insufficient,which makes it difficult to meet the requirements of ground control under complex conditions. As a new support form with high strength and rigidity, the confined concrete arch plays an important role in controlling the rock deformation under complex conditions. The section shape of the tunnel has an important impact on the mechanical properties and design of the support system. However, studies on the mechanical properties and influence mechanism of the new confined concrete arch are rarely reported. To this end, the mechanical properties of traditional U-shaped steel and new confined concrete arches are compared and comparative tests on arches of circular and straight-leg semicircular shapes in deep tunnels are conducted. A large mechanical testing system for underground engineering support structure is developed. The mechanical properties and influence mechanism of confined concrete arches with different section shapes under different loading modes and cross-section parameters are systematically studied. Test results show that the bearing capacity of the confined concrete arch is 2.10 times that of the U-shaped steel arch, and the bearing capacity of the circular confined concrete arch is 2.27 times that of the straight-leg semicircular arch. Among the various influencing factors and their engineering parameters,the lateral stress coefficient has the greatest impact on the bearing capacity of the confined concrete arch,followed by the steel pipe wall thickness, steel strength, and core concrete strength. Subsequently, the economic index of bearing capacity and cost is established, and the optimization design method for the confined concrete arch is proposed. Finally, this design method is applied to a high-stress tunnel under complex conditions, and the deformation of the surrounding rock is effectively controlled.

Summary of the 10th Conference on Magnetically Confined Fusion Theory and Simulation(CMCFTS)

This paper gives a summary of the organization and the presentations delivered at the 10th Conference on Magnetically Confined Fusion Theory and Simulation(CMCFTS)held in Zhuhai,China,from 28th to 31st October 2022.The conference focused on the latest progress in the research of the magnetic confined fusion plasma theory and simulations,as well as the largescale numerical simulation techniques developed in recent years.This conference is held both online and offline,with about 110 domestic participants from 18 institutes participating in the live conference,and the statistical data from the live broadcast platform indicated that the online conference attracted over 20000 views per day.A summary of the conference is given,and the history of the CMCFTS is presented.A brief introduction to the poster section is also included in this paper.

Bacterial turbulence in gradient confinement

We investigate a novel form of non-uniform living turbulence at an extremely low Reynolds number using a bacterial suspension confined within a sessile droplet. This turbulence differs from homogeneous active turbulences in two or threedimensional geometries. The heterogeneity arises from a gradient of bacterial activity due to oxygen depletion along the droplet’s radial direction. Motile bacteria inject energy at individual scales, resulting in local anisotropic energy fluctuations that collectively give rise to isotropic turbulence. We find that the total kinetic energy and enstrophy decrease as distance from the drop contact line increases, due to the weakening of bacterial activity caused by oxygen depletion. While the balance between kinetic energy and enstrophy establishes a characteristic vortex scale depending on the contact angle of the sessile drop. The energy spectrum exhibits diverse scaling behaviors at large wavenumber, ranging from k-1/5to k-1,depending on the geometric confinement. Our findings demonstrate how spatial regulation of turbulence can be achieved by tuning the activity of driving units, offering insights into the dynamic behavior of living systems and the potential for controlling turbulence through gradient confinements.

Experimental study of density gradient-driven micro-instabilities and the confinement degradation during H-mode in EAST

A broadband(BB)mode is observed by collective Thomson scattering diagnostics in repeatable shots of EAST and analyzed for the first time.This BB mode usually grows during L–H transitions,featuring a BB quasi-coherent mode with increasing frequency.During H-mode operations,it is characterized by steady-state BB in the high-frequency range(f~200–2000 k Hz),at the electron scale(k_(θ)ρ_(s)=1–2),mainly driven by the density gradient,and is sensitive to the value ofηein the region of interest(ρ=0.4–0.8),wherehe=(R/L_(Te))/(R/L_(ne))is the ratio of the normalized electron temperature gradient and density gradient,and the regionρ=0.4–0.8 usually has a relatively low collisionality(v_(eff)<5).The frequency of BB is found to be dependent on the electron temperature and density gradient,which is a typical feature of electron-driven turbulence.A negative correlation between the energy confinement and the intensity of the BB turbulence during H-mode has been found,which indicates a strong electron thermal transport induced by the BB turbulence.The BB significantly decreases the electron temperature and causes flatter electron temperature profiles in the region of interest(ρ=0.4–0.8),thus makingηedecrease and the BB destabilize further.These characteristics of BB are related to the theoretical density gradient-driven trapped electron mode.It should be noted that this mode is not observed by other diagnostics in EAST,and shows very different features to the coherent modes in the edge.

Anion type-dependent confinement effect on glass transitions of solutions of LiTFSI and LiFSI

We present findings on the effect of nanometer-sized silica-based pores on the glass transition of aqueous solutions of lithium bis(trifluoromethane)sulfonimide(LiTFSI)and lithium difluorosulfimide(LiFSI),respectively.Our experimental results demonstrate a clear dependence of the confinement effect on the anion type,particularly for water-rich solutions,in which the precipitation of crystalized ice under cooling process induces the formation of freeze-concentrated phase confined between pore wall and core ice.As this liquid layer becomes thinner,the freeze-concentrated phase experiences glass transition at increasingly higher temperatures in solutions of LiTFSI.However,differently,for solutions of LiFSI and LiCl,this secondary confinement has a negligible effect on the glass transition of solutions confined wherein.These different behaviors emphasize the obvious difference in the dynamic properties’response of LiTFSI and LiFSI solutions to spatial confinement and particularly to the presence of the hydrophilic pore wall.

Ethylene purification in a metal–organic framework over a wide temperature range via pore confinement

The separation of C2H4from C_(2)H_(6)/C_(2)H_(4)mixture is of great importance but difficult and energy intensive. Adsorptive separation provides an alternative approach to ameliorate this situation. Here, we report a microporous metal–organic framework(MOF) BUT-315-a as a C_(2)H_(6)-selective adsorbent for the separation of C2H6/C2H4gas mixture. BUT-315-a combines good IAST selectivity of 2.35 with high C_(2)H_(6)uptake of 97.5 cm^(3)g^(-1), giving superior high separation potential ΔQ(2226 mmol L^(-1)) for equimolar C_(2)H_(6)/C_(2)H_(4) at 298 K. Impressively, such excellent performance can be preserved at higher temperatures of 313 and 323 K to accommodate industrial conditions. Efficient dynamic separation performance of BUT-315-a has been demonstrated by column breakthrough experiments under varied temperatures and gas ratios. Theoretical calculations further reveal multiple synergistic interactions between C_(2)H_(6) and the framework. This work highlights a new benchmark material for C_(2)H_(6)/C_(2)H_(4)separation and provides guidance for designing adsorbent for separation applications.

Liquid–liquid phase transition in confined liquid titanium

We report the layering and liquid–liquid phase transition of liquid titanium confined between two parallel panel walls.Abnormal changes in the volume and the potential energy confirm the existence of the liquid–liquid phase transition of the liquid titanium. The typical feature of the liquid–liquid phase transition is layering, which is induced by the slit size,pressure and temperature. We highlight the fact that the slit size and pressure will determine the number of layers. In addition, with the change in the slit size, the density of the confined liquid expresses a fluctuating law. The phase diagram of the layering transition is drawn to clearly understand the layering. This study provides insights into the liquid–liquid phase transition of liquid metal in a confined space.

Single-Molecule Confinement Induced Intrinsic Multi-Electron Redox-Activity to Enhance Supercapacitor Performance

Aggregation of polyoxometalates(POM)is largely responsible for the reduced performance of POM-based energy-storage systems.To address this challenge,here,the precise confinement of single Keggin-type POM molecule in a porous carbon(PC)of unimodal super-micropore(micro-PC)is realized.Such precise single-molecule confinement enables sufficient activity center exposure and maximum electron-transfer from micro-PC to POM,which well stabilizes the electron-accepting molecules and thoroughly activates its inherent multi-electron redox-activity.In particular,the redox-activities and electron-accepting properties of the confined POM molecule are revealed to be super-micropore pore size-dependent by experiment and spectroscopy as well as theoretical calculation.Meanwhile,the molecularly dispersed POM molecules confined steadily in the“cage”of micro-PC exhibit unprecedented large-negative-potential stability and multiple-peak redox-activity at an ultra-low loading of~11.4 wt%.As a result,the fabricated solid-state supercapacitor achieves a remarkable areal capacitance,ultrahigh energy and power density of 443 mF cm^(-2),0.12 mWh cm^(-2)and 21.1 mW cm^(-2),respectively.This work establishes a novel strategy for the precise confinement of single POM molecule,providing a versatile approach to inducing the intrinsic activity of POMs for advanced energy-storage systems.

Implosion Plasma Driven Fusion Pellet of Inertial Confinement(A Short Memorandum)

The implosion plasma drive fusion pellet of inertial confinement is a concept related to nuclear fusion,a process in which atomic nuclei combine to form heavier nuclei,releasing a large amount of energy in the process.The implosion plasma drive fusion pellet is a potential fuel source for achieving controlled nuclear fusion.ICF(inertial confinement fusion)is a technique used to achieve fusion by compressing a small target containing fusion fuel to extremely high densities and temperatures using lasers or other methods.The implosion plasma drive fusion pellet concept involves using a small pellet of deuterium and tritium(two isotopes of hydrogen)as fusion fuel,and then rapidly heating and compressing it using a pulsed power system.The implosion process creates a high-pressure plasma that ignites the fusion reactions,releasing energy in the form of neutrons and charged particles.The resulting energy can be captured and used for power generation.This technology is still in the experimental stage,and significant research and development is required to make it commercially viable.However,it has the potential to provide a virtually limitless source of clean energy with no greenhouse gas emissions or long-term radioactive waste.Be that as it may,ICF has to get exact control of the implosion process,mitigate insecurities,and create modern materials and advances to resist the extraordinary conditions of the combined response.

Confinement-induced modulation of elastic properties of nano-confined fluids in slit pore

Based on statistical mechanics for classical fluids, the general expressions for the elastic moduli of inhomogeneous fluid are derived and expressed as functionals of density functions. Within the framework of classical density functional theory, the bulk modulus of confined argon in slit pore is calculated under different conditions. The effects of vapor pressure, temperature, and pore width on modulus are calculated and investigated. Obvious confinement-induced effect has been observed in the confined argon. In addition, the solvation pressure dependence of the bulk modulus is also investigated,and the results suggest that the Tait–Murnaghan equation is still valid for the confined fluids.

Manifestation of Color Confinement in the YY Model for Atomic Nuclei

In this paper, a manifestation of the well-known color confinement from the QCD (quantum chromodynamics) in the newly developed YY model for the atomic nucleus is presented. There is a wonderful correspondence between the structural requirements from the YY model and some elementary properties of the color dynamics from QCD. The open questions in the YY model, namely the holding forces for triple nodes and for pairing space links, are exactly covered by the three-color compensation or by the paired color anti-color balance. We will see what colors and anti-colors do mean in the YY model, how up quarks and down quarks get assigned a color or anti-color. We will discover some relationships between gluon-based interactions as described in the standard model and pairing space links in the YY model.

Rock-breaking mechanism and experimental analysis of confined blasting of borehole surrounding rock

The rock-breaking mechanism and effect of confined blasting were analysed by blasting and impact dynamic mechanics, fluid dynamic mechanics, fracture mechanics as well as blasting experiment. The results showed that the fracturing of surrounding rock in confined blasting condition is the result of coaction of rock pre-cracking by shock wave and stress wave and the continuing expanding crackenhancement of confined medium, and the model of crack development of borehole surrounding rock in confined blasting condition was established. This study acquired the damage range of surrounding rock under the action of shock wave and stress wave, as well as the crack development characteristics of surrounding rock after the wedge-in confined medium into the crack space. Deep-hole confined blasting experiment on large rock showed that the high-efficient utilisation of in-hole explosive was achieved and the safety of rock blasting operation was ensured. Safe static rock-breaking under the action of high-efficient explosive blasting was achieved as well as the unification of super dynamic load of explosive blasting and static rock-breaking of water medium.

Synthesis of Nanosized NaY Zeolite by Confined Space Method

Nanosized NaY crystals have been prepared from metakaolin and sodium silicate by confined space synthesis with starch additive. It is found that the product has a narrow crystal size distribution (50-100 nm), high Si/Al ratio (Si/Al=4.6-6.1), high surface area (1090 m2/g) and the average diameter of nanosized NaY (75 nm) synthesized is 30 nm, it is smaller than that of without starch additive.

Manipulation of confined structure in alcohol-permselective pervaporation membranes

Alcohol-permselectivity pervaporation has been arousing increasingly more attention in bioalcohol production due to the advantages of environmental friendliness, low energy consumption and easy coupling with fermentation process. With the intrinsic feature of larger molecules preferentially permeating and the consequent inferiority in selective diffusion, the development of alcohol-permselective membrane is relatively retarded compared with water-permselective membrane. This review presents the prevalent membrane materials utilized for alcohol-permselective pervaporation and emphatically expatiates the representative and important developments in the past five years from the aspect of tuning confined structure in membranes. In particular, the diverse structure tuning methods are described with the classifications of physical structure and chemical structure. The corresponding structure-performance relationships in alcohol-permselective pervaporation membranes are also analyzed to identify the objective of structure optimization. Furthermore, the tentative perspective on the possible future directions of alcohol-permselective pervaporation membrane is briefly presented.

Enhanced hydrogen evolution reaction over molybdenum carbide nanoparticles confined inside single-walled carbon nanotubes

Carbon nanotubes(CNTs) have shown as unique nanoreactors to tune the catalytic activity of confined nano-catalysts. Here we report that the catalytic performance of molybdenum carbide nanoparticles(MoC_x NPs) for the hydrogen evolution reaction(HER) process can be enhanced by encapsulation within single-walled carbon nanotubes(SWNTs) with a diameter of 1–2 nm. The catalyst with MoC_x NPs located on the interior surface of SWNTs(MoCx@SWNTs) exhibits a lower onset over-potential and a smaller Tafel slope than the one with MoC_x NPs attached on the exterior surface(MoCx/SWNTs). This is likely attributed to the much smaller particle size and the more reduced states of the confined MoC_x NPs, as well as the larger specific surface area of MoCx@SWNTs compared with Mo Cx/SWNTs. In addition, the electronic structure of the confined MoC_x NPs might be modified by the confinement effects of SWNTs, and hence the adsorption free energy of H atoms on the confined MoC_x NPs, which could also contribute to their higher performance. These results suggest that the SWNTs can be further explored for constructing novel catalysts with beneficial catalytic performance.