Dense State Research Articles

Altered the structural, morphological and optical properties of SbSe thin films through swift heavy ion irradiation

Chalcogenide based phase change materials are gaining attention due to their ability to exhibit expeditious and reversible structural transition from amorphous to crystalline phase. This work included the effect of swift heavy silver (Ag9+) ion-irradiation (120 MeV), at various fluences (5E11, 1E12, 5E12 and 1E13 ions/cm2) on the structural, optical and morphological properties of pristine and annealed (250 ° C) SbSe thin films. The pristine films undergo a structural transition from amorphous to crystalline upon annealing and from crystalline to amorphous upon irradiation of annealed films. Structural transition caused by annealing and ion-irradiation resulted in a drastic change in morphology and optical properties. The annealed films exhibited less transmission than the pristine and irradiated films, which increased with increase in ion-irradiation fluences because of phase transition. After irradiation, the optical band decreased for pristine thin films, because the forbidden gap defect concentration has increased, but increased after irradiating the annealed thin films that may be due to annealing out of dense localized defect states. The significant optical contrast upon phase transition in near infrared region can be utilized for different optoelectronic applications.

Angular correlation of the two gamma rays produced in the thermal neutron capture on gadolinium-155 and gadolinium-157

Abstract The ANNRI-Gd collaboration studied in detail the single γ-ray spectrum produced from the thermal neutron capture on 155Gd and 157Gd in our previous publications. Gadolinium targets were exposed to a neutron beam provided by the Japan Spallation Neutron Source (JSNS) in J-PARC, Japan. In the present analysis, one new additional coaxial germanium crystal was used in combination with the 14 germanium crystals in the cluster detectors to study the angular correlation of the two γ rays emitted in the same neutron capture. We present for the first time angular correlation functions for two γ rays produced during the electromagnetic cascade transitions in the (n, γ) reactions on 155Gd and 157Gd. As expected, we observe mild angular correlations for the strong, but rare transitions from the resonance state to the two energy levels of known spin-parities. Contrariwise, we observe negligibly small angular correlations for arbitrary pairs of two γ rays produced in the majority of cascade transitions from the resonance state to the dense continuum states.

Effects of membrane compliance on the normal-scale triaxial cyclic liquefaction test results of saturated coral sand

Correctly evaluating the membrane penetration and compliance effects in the element liquefaction test of saturated coral sand is important for test result applications. Therefore, the penetration volume measurement and triaxial cyclic liquefaction testing of saturated coral sand and quartz sand samples with the same grading and relative density were conducted for relatively loose and dense states, and the liquefaction resistance test results before and after membrane compliance correction were analyzed. The results showed that under the same conditions, the influence of the penetration and compliance of coral sand samples was more significant than that of the quartz sand samples. The general practice of ignoring the effect of membrane compliance in normal-scale triaxial tests is inapplicable in coral sand tests and will result in relatively unsafe analysis results.

Fetal brain activity and the free energy principle.

To study whether the free energy principle can explain fetal brain activity and the existence of fetal consciousness via a chaotic dimension derived using artificial intelligence. In this observational study, we used a four-dimensional ultrasound technique obtained to collect images of fetal faces from pregnancies at 27-37weeks of gestation, between February and December 2021. We developed an artificial intelligence classifier that recognizes fetal facial expressions, which are thought to relate to fetal brain activity. We then applied the classifier to video files of facial images to generate each expression category's probabilities. We calculated the chaotic dimensions from the probability lists, and we created and investigated the free energy principle's mathematical model that was assumed to be linked to the chaotic dimension. We used a Mann-Whitney test, linear regression test, and one-way analysis of variance for statistical analysis. The chaotic dimension revealed that the fetus haddense and sparse states of brain activity, which fluctuated at a statistically significant level. The chaotic dimension and free energy were larger in the sparse state than in the dense state. The fluctuating free energy suggests consciousness seemed to exist in the fetus after 27weeks.

Constitutive model for simulating the mechanical behaviour of rock under triaxial cyclic loading

To simulate the cyclic behaviour of rock comprehensively, relevant mechanical features were analysed sufficiently, including the massing effect, ratcheting effect, Kaiser effect and Felicity effect. A constitutive body was proposed based on the deformation mechanism and implemented by strain increment method. This body comprised three elements (elastic element Ee, plastic element Ep and friction element Ef), in which Ee and Ep were connected in series, and Ef was connected with them in parallel. Two kinds of triaxial cyclic loading experiments were conducted to determine the constitutive laws of these elements and the Poisson’s ratios of Ee and Ep; moreover, the simulation effect was validated against the experimental data. Results showed that the tangential modulus of Ee was nonlinear due to damage development and variation of particle dense state, the backwards movement of the yield surface involving Ep during reloading induced the ratcheting effect and Felicity effect, and the opposite role of Ef during loading and unloading caused the massing effect. The constitutive laws of Ee and Ep could be expressed by quadratic polynomial function and logistic equation, respectively; the Poisson’s ratio variations in Ee and Ep with axial plastic strain could be expressed by linear function and exponential function, respectively.

Efficient Band-Edge Emission from Indirect Bandgap Semiconductor Quantum Dots upon Shell Engineering

Environmentally friendly colloidal quantum dots (QDs) of groups III-V are in high demand for next-generation high-performance light-emitting devices for display and lighting, yet many of them (e.g., GaP) suffer from inefficient band-edge emission due to the indirect bandgap nature of their parent materials. Herein, we theoretically demonstrate that efficient band-edge emission can be activated at a critical tensile strain γc enabled by the capping shell when forming a core/shell architecture. Before γc is reached, the emission edge is dominated by dense low-intensity exciton states with a vanishing oscillator strength and a long radiative lifetime. After γc is crossed, the emission edge is dominated by high-intensity bright exciton states with a large oscillator strength and a radiative lifetime that is shorter by a few orders of magnitude. This work provides a novel strategy for realizing efficient band-edge emission of indirect semiconductor QDs via shell engineering, which is potentially implemented employing the well-established colloidal QD synthesis technique.

Degraded Ballast Stiffness Characterization Using Bender Element Field Sensor and PANDA® Penetrometer

The progressive degradation of railway ballast over time increases the degree of ballast fouling and poses significant drainability concerns leading to frequent maintenance activities. To avoid such issues, an effective and continuous characterization of the physical properties of the ballast layer is deemed necessary. This paper introduces the combined use of a bender element (BE) piezoelectric field sensor and a PANDA® dynamic cone penetrometer for periodic evaluations of ballast condition over the traffic use. To simulate various levels of ballast degradation, box tests were conducted using a dolomitic ballast material compacted in a laboratory-sized testbed with fouling indices ranging from zero to 39%. BE sensor pairs were embedded in the ballast layer to calculate the small strain modulus behavior of the ballast assessed through shear wave velocity measurements under different confinement conditions. Strength profiles of the ballast at different fouling levels were also measured using the PANDA® penetrometer. Experimental findings from both test methods indicate the existence of a dense state of ballast linked to a certain fouling index that maximized stiffness and strength characteristics of the tested ballast in dry condition. Accordingly, the potential use of BE field sensors embedded within in-service ballasted track coupled with periodic penetration testing can be a viable approach to evaluate ballast layer degradation. Various void packing conditions associated with ballast fouling levels can be linked to important ballast layer modulus and strength behavior. Further, such smart sensing of ballasted track behavior can provide long-term performance monitoring solutions for ballast cleaning and maintenance scheduling.

Metallic water: Transient state under ultrafast electronic excitation.

The modern means of controlled irradiation by femtosecond lasers or swift heavy ion beams can transiently produce such energy densities in samples that reach collective electronic excitation levels of the warm dense matter state, where the potential energy of interaction of the particles is comparable to their kinetic energies (temperatures of a few eV). Such massive electronic excitation severely alters the interatomic potentials, producing unusual nonequilibrium states of matter and different chemistry. We employ density functional theory and tight binding molecular dynamics formalisms to study the response of bulk water to ultrafast excitation of its electrons. After a certain threshold electronic temperature, the water becomes electronically conducting via the collapse of its bandgap. At high doses, it is accompanied by nonthermal acceleration of ions to a temperature of a few thousand Kelvins within sub-100fs timescales. We identify the interplay of this nonthermal mechanism with the electron-ion coupling, enhancing the electron-to-ions energy transfer. Various chemically active fragments are formed from the disintegrating water molecules, depending on the deposited dose.

Green Processing of Neat Poly(lactic acid) Using Carbon Dioxide under Elevated Pressure for Preparation of Advanced Materials: A Review (2012-2022).

This review provides a concise overview of up-to-date developments in the processing of neat poly(lactic acid) (PLA), improvement in its properties, and preparation of advanced materials using a green medium (CO2 under elevated pressure). Pressurized CO2 in the dense and supercritical state is a superior alternative medium to organic solvents, as it is easily available, fully recyclable, has easily tunable properties, and can be completely removed from the final material without post-processing steps. This review summarizes the state of the art on PLA drying, impregnation, foaming, and particle generation by the employment of dense and supercritical CO2 for the development of new materials. An analysis of the effect of processing methods on the final material properties was focused on neat PLA and PLA with an addition of natural bioactive components. It was demonstrated that CO2-assisted processes enable the control of PLA properties, reduce operating times, and require less energy compared to conventional ones. The described environmentally friendly processing techniques and the versatility of PLA were employed for the preparation of foams, aerogels, scaffolds, microparticles, and nanoparticles, as well as bioactive materials. These PLA-based materials can find application in tissue engineering, drug delivery, active food packaging, compostable packaging, wastewater treatment, or thermal insulation, among others.

Compression of gaseous hydrogen into warm dense states up to 95 GPa using multishock compression technique

The thermodynamic properties of warm dense hydrogen, such as the equation of state (EOS) and sound velocity, affect our understanding of the evolution and interior structures of gas giant planets. However, for this low-$Z$ gas, obtaining the EOS and sound velocity experimentally under relevant planetary conditions is challenging because the extremely warm states are difficult to reach, characterize, and interrogate. Here, the multishock compression technique is used to generate the thermodynamic states of warm dense hydrogen. This provides a dynamic loading from shock adiabatic to quasi-isentropic compressions, covering wide pressure and density ranges of 0.02--95 GPa and $0.01--0.64 \mathrm{g}/{\mathrm{cm}}^{3}$, which enables us to determine the EOS and infer the high-pressure sound velocities of warm dense hydrogen relevant to planetary interiors. The data obtained in this way are comprehensively compared with several important theoretical models for astrophysics applications. The present experiments provide desirable principal- and off-Hugoniot states for revisiting the thermodynamic space of existing experimental data. These observations and thermodynamic states may be important in guiding future theoretical developments and constructing interior structure models for gas giant planets.

Descriptive Parameters and Its Hysteresis of the Group Separation and Recombination in Bicycle Points Races: Leader’s Velocity and Speed Difference between Leader and Main Group

This study examined the descriptive parameters for separation and recombination processes in a cycling points race. The candidate descriptive parameters were the speed of the leading cyclist and the main group and the difference between their time and speed. We focused on the transition between the four states of peloton configuration (dense state, stretched state, divided state, and escape and dense state) defined by previous studies that occur during the points race. As a result, it was found that the distribution of the leader’s velocity and the speed difference significantly differed when the groups were separated and recombined compared to when the state did not change. It was also examined whether the separation and recombination processes had a phenomenon such as a hysteresis depending on the present state. Regarding the leader velocity and the speed difference between the leader and the main group, the state of the group was not uniquely determined by the speed difference, and the influence of the speed difference for separation or recombination depended on the state; that is, there was asymmetry in separation and recombination in a points race. These suggest that the cyclists need the ability to choose an appropriate speed and distance from other cyclists depending on the situation.

The Effect of the Nonplastic Fines on the Cyclic Resistance of the Saturated Sand-Fines Mixtures

A series of undrained cyclic triaxial tests were carried out to study the nonplastic fines on the cyclic behaviour of saturated sand-fines mixtures. The influences of the fines content (FC), global void ratio (e), and relative density (Dr) were considered. The results show that the cyclic resistance ratio (CRR) of the mixtures firstly decreases and then increases, finally stabilizing with increasing FC when the samples are prepared at a constant Dr. The CRR reaches its minimum when the FC is 20%. However, the CRR decreases and then increases with increasing FC when the samples are prepared at a constant e. The CRR reaches its minimum when the FC is at 30%. The CRR of the mixtures increases with increasing Dr when the FC is given. A single Dr or e cannot describe the dense state of the mixture effectively. A new index, Dr/e, is proposed in this study to describe the dense state of the mixtures. A semiempirical model is proposed to evaluate the CRR of the mixtures using the parameters of Dr/e and FC of the mixture based on the back analysis method. The applicability of the model is verified by the test data from this study and other scholars. In addition, the parameters of Dr/e and FC of the mixture can be obtained from basic geotechnical tests, which is convenient for the application of the model.

The performance of laterally loaded piles in layered sandy soils under variable degree of saturation

This paper investigates the capacity of a single laterally loaded pile in single- and multi-layered sandy soils under dry, unsaturated and saturated conditions for a wide range of void ratios. Two Linear ariable Differential Transformers (LVDT) were employed to measure lateral displacements. For unsaturated tests, on one layer and two layered sandy soils, suction was controlled using the hanging column technique. Two different suction levels were applied to the soils. The results demonstrated that, the capacity of a single laterally loaded pile in single- and multi-layered sandy soils, under unsaturated conditions, were greater than those in dry and saturated conditions for loose, medium and dense states. Comparison between experimental data for unsaturated tests and several proposed mathematical expressions in the literature for calculating the capacity of a single laterally loaded pile in sandy soils showed a significantly good fit between measured and predicted values of the capacity of the piles where Bishop’s stress is used in the expressions instead of effective stress, confirming the importance of inclusion of suction and degree of saturation in mathematical models when unsaturated conditions of soils were investigated.

A two-particle approach for dry high density-ratio granular collapse

We report on the role of density ratio for granular column collapse experimentally and numerically by demonstrating the fundamental changes using a two-particle approach. The influence of the density ratio for the different profile arrangements on the velocity distribution, interface, and energy transition is described using the Moving Particle Semi-Implicit method (MPS). A constitutive equation utilizing the granular material strength is formulated using the elasto-viscoplastic model under the μ ( I ) rheology framework by replacing the frictional coefficient with the internal friction angle. The dense state of the granular materials results in a linear relationship between the length scale and inertia constant, which makes the shear strength the driving parameter. Experimental data are compared with numerical simulation for granular collapse with varying density profile configurations to validate the method. We found that the density ratio does not influence the velocity and free surface profile. The interface is maintained similarly to a single-phased granular flow except for erosive configurations where a penetrating regime is evident. The rate at which the granular kinetic energy transforms to the potential energy when the lower density material is on top and at the left of the higher granular materials is similar compared to other profile arrangements. The results demonstrated that the density ratio for different profile arrangements could significantly influence the deformation of the granular materials depending on the particle arrangements. The numerical investigation for the granular column collapse agrees well with experimental studies. Collapse mechanisms of varying density ratio configuration. • Flow dynamics and energy evolution in density ratio granular column collapse. • Replacement of the μ (I) rheology model parameters with the material strength parameters. • Effective phase-change for high-density ratio for single and two-phase granular flow. • Relationship between the inertia constant and wave front. • The meshfree particle method, MPS, shows excellent agreement with the experiment.

Simultaneous Analysis of Midrapidity pT Spectra of Identified Particle Species in Pb + Pb Collisions at snn = 2.76 TeV Using Tsallis Distribution with Transverse Flow

The midrapidity transverse momentum distributions of the charged pions, kaons, protons, and antiprotons in ten groups of centrality of Pb + Pb collisions at snn = 2.76 TeV, measured by the ALICE Collaboration, have been analyzed successfully using both thermodynamically consistent and non-consistent Tsallis distribution functions with transverse flow. The collision centrality dependencies of the extracted parameters of two kinds of Tsallis functions with transverse flow have been investigated. The significantly different behavior (growth rates) of ⟨βT⟩ in regions ⟨Npart⟩ < 71 and ⟨Npart⟩ > 71 with the temperature T0 becoming constant in region ⟨Npart⟩ > 71 has been observed. This could indicate that ⟨Npart⟩ = 71 ± 5 (corresponding to ⟨dNch/dη⟩ = 205 ± 15) is a threshold border value of collision centrality for crossover phase transition from the dense hadronic state to the QGP state (or a mixed state of QGP and hadrons) in Pb + Pb collisions at snn = 2.76 TeV. This conjecture is supported further by the observed, significantly different correlations between T0 and ⟨βT⟩ parameters in the corresponding ⟨βT⟩ < 0.44 and ⟨βT⟩ > 0.44 ranges. The strong positive linear correlation between non-extensivity parameter q for pions and kaons, between q for pions and (anti)protons, and between q for kaons and (anti)protons has been obtained. The parameter q for all studied particle species has proven to be strongly anticorrelated with the average transverse flow velocity, ⟨βT⟩. Quite a large positive linear correlation has been obtained between the q of the studied particle species and temperature parameter T0. Analysis of q versus ⟨Npart⟩ dependencies for the studied particle species suggests that the highly thermalized and equilibrated QGP is produced in central Pb + Pb collisions at snn = 2.76 TeV with ⟨Npart⟩ > 160.

Derivation and verification of multilevel particle packing model for Ultra-High Performance Concrete (UHPC): Modelling and experiments

This paper aims to address the conflict between gap gradation and continuous particle packing for the precise design of ultra-high performance concrete (UHPC). More exactly, a new multilevel particle packing model is proposed by deriving the modified Anderson and Andreasen (MAA) equation. The key parameters of the model are determined by Box-Behnken design method. On this basis, the dense packing states of powder and aggregate segments are achieved, and the accurate ratio of two segments are confirmed. Thus, the optimal mix proportion of UHPC matrix can be calculated. Moreover, some novel viewpoints on the development of dense particle packing theory are presented in this study, including the derivation of multilevel particle packing model with n times of gap gradation and the discussion of general mix design procedure that unifies gap gradation and continuous packing, which could further improve the design theory of UHPC composites.

Dense Local Triplet States and Steric Shielding of a Multi‐Resonance TADF Emitter Enable High‐Performance Deep‐Blue OLEDs (Adv. Mater. 50/2022)

Dense Local Triplet States and Steric Shielding of a Multi‐Resonance TADF Emitter Enable High‐Performance Deep‐Blue OLEDs (Adv. Mater. 50/2022)

Liquefaction Characteristics of Sandy Soil Distributed in Wind Power Farms, Soc Trang Province, Vietnam

Wind power has been widely utilized and has become a safe and renewable energy source in many countries. In Vietnam, many wind power farms have been built in coastal provinces such as Soc Trang, Bac Lieu, Ninh Thuan, Binh Thuan, Ca Mau, Vung Tau, and the Central Highlands. For onshore wind power farms, the dynamic loads generated from wind and the operation of the turbine will act on soil ground and affect the long-term strength and liquefaction potential of soil, especially for sandy soil. Thus, it is necessary to investigate the potential for liquefaction of the sandy soil layer in wind power farms. In this study, the liquefaction potential of sand distributed in onshore wind power farms in Soc Trang province, Vietnam was evaluated using the undrained cyclic triaxial test. The sand specimens were remolded using dry pluviation and moist tamping methods to simulate the field density. The analysis of test results showed that the very fine sand with a loose state distributed at the depth of less than or equal to 11.5 m could be liquefied under the testing conditions. While the fine sand specimens with a dense to very dense state distributed deeper than 30 m were not liquefied under testing conditions. However, for these specimens, the pore water ratio could be increased by 11.3 to 18.6% and this increase can lead to a decrease in soil strength.

Effect of oxides composition on the mechanical properties of non‐sintered spherical filters from waste steel slag

AbstractNon‐sintered spherical filters (NSSFs) from the waste steel slag for bottom filtration process are regarded as promising materials for sustainable development with economical benefits due to saving natural resource pebbles. To further optimize the preparation process, the influence mechanism of the main oxides on characteristics are comprehensively examined in this work. CaO in the raw materials makes it easier to release active components from the resulting glass body structure, while the expansion stress of Ca(OH)2 crystals precipitated under highly basic circumstances needs special consideration. SiO2 can positively contribute to the properties due to its adequate participation in the hydration reaction and the micro‐aggregate effect. Al3+ tends to combine and form a stable tetrahedral structure, which is conducive to liquid viscosity and the hindrance of hydration reaction of the active substance. Under the 6% mass ratio of MgO, NSSFs exhibit relatively excellent in physical properties. Specifically, the stimulation and promotion effect of MgO on hydration reaction is superior to the negative effect of excessive product Mg(OH)2 on expansion stress. Fe2O3 particles convert the structure in NSSFs to a dense state by the filling effect and serving as nucleation sites to promote the formation of hydration products.

Dense Local Triplet States and Steric Shielding of a Multi-Resonance TADF Emitter Enable High-Performance Deep-Blue OLEDs.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) molecules based on boron and nitrogen atoms are emerging as next-generation blue emitters for organic light-emitting diodes (OLEDs) due to their narrow emission spectra and triplet harvesting properties. However, intermolecular aggregation stemming from the planar structure of typical MR-TADF molecules that leads to concentration quenching and broadened spectra limits the utilization of the full potential of MR-TADF emitters. Herein, a deep-blue MR-TADF emitter, pBP-DABNA-Me, is developed to suppress intermolecular interactions effectively. Furthermore, photophysical investigation and theoretical calculations reveal that adding biphenyl moieties to the core body creates dense local triplet states in the vicinity of S1 and T1 energetically, letting the emitter harvest excitons efficiently. OLEDs based on pBP-DABNA-Me show a high external quantum efficiency (EQE) of 23.4% and a pure-blue emission with a Commission Internationale de L'Eclairage (CIE) coordinate of (0.132, 0.092), which are maintained even at a high doping concentration of 100wt%. Furthermore, by incorporating a conventional TADF sensitizer, deep-blue OLEDs with a CIE value of (0.133, 0.109) and an extremely high EQE of 30.1% are realized. These findings provide insight into design strategies for developing efficient deep-blue MR-TADF emitters with fast triplet upconversion and suppressed self-aggregation.