Main Charge Research Articles

The Study of the Electrical Properties of Anisotropic Semiconductors in the Laboratory Workshop of the University Course in Physics

The purpose of the article is to develop a theoretically and experimentally substantiated specific laboratory work for studying the anisotropy of the electrical properties of semiconductors within the framework of the curricula of higher educational institutions, for such areas of training as “Physics”, “Technical Physics”, “Radiophysics” and “Electronics and Nanoelectronics”. The relevance of the problem is due to the desire of domestic electronics for technological sovereignty and high requirements for the training of qualified personnel for the production of structures of solid-state functional electronics. Based on the solution of the boundary electrodynamic problem, an expression is obtained for the electric potential in the region of a thin rectangular semiconductor sample with a tensor character of conductivity. The results of this work is the development of an original laboratory setup for the demonstration and practical study of the anisotropy of the electrical properties of semiconductor crystals. The proposed technique makes it possible to determine the main electrokinetic parameters of an anisotropic semiconductor – specific conductivity, concentration and Hall mobility of the main charge carriers. A schematic diagram of the installation and formulas for calculating the errors of the measured quantities are proposed. The results obtained may also be of scientific interest in the study of anisotropic semiconductor materials in laboratory conditions.

Experimental investigation of the bonding of sulfur in highly reduced silicate glasses and melts

Elucidating the role of sulfur on the structure of silicate glasses and melts at elevated pressures and temperatures is important for understanding transport properties, such as electrical conductivity and viscosity, of magma oceans and mantle-derived melts. These properties are fundamental for modeling the evolution of terrestrial planets and moons. Despite several investigations of sulfur speciation in glasses, questions remain regarding the effect of S on complex glasses at highly reducing conditions relevant to Mercury. Glasses were synthetized with compositions representative of the Northern Volcanic Plains of Mercury and containing quantities of S up to 5 wt%. Multiple spectroscopic methods and microprobe analyses were employed to probe the glasses, including in situ impedance spectroscopy at 2- and 4-GPa pressures and temperatures up to 1740 K using a multi-anvil press, 29Si NMR spectroscopy, and Raman spectroscopy. Electrical activation energies (Ea) in the glassy state range from 0.56 to 1.10 eV, in agreement with sodium as the main charge carrier. The electrical measurements indicate that sulfide improves Na+ transport and may overcome a known impeding effect of the divalent cation Ca2+. The glass transition temperature lies between 700 and 750 K, and for temperatures up to 970 K Ea decreases (0.35–0.68 eV) and the conductivities of the samples converge (∼5–8 × 10−3 S/m). At Tquench, the melt fraction is 50–70% and melt conductivity varies from 0.7 to 2.2 S/m, with the sample containing 5 wt% S the most conductive among the set. 29Si NMR spectra reveal that a high fraction of S bonds with Si in these complex glasses, a characteristic that has not been recognized previously. Raman spectra and maps reveal regions rich in Ca–S or Mg–S bonds. The evidence of sulfide interactions with both Si and Ca/Mg suggest that alkaline earth sulfides can be considered weak network modifiers in these glasses, under highly reduced conditions.

Research on Simulation Model of Unexploded Ordnance Destruction Based on Sniping Method

To evaluate the ability of the sniping method to destroy unexploded ordnance, a simulation model of bullet impact on 38mm stun grenades was established with the SPH-FEM coupling method. The destruction process of unexploded ordnance and residual velocity and direction of the bullet were analyzed at different conditions of impact positions and velocities. The results show that axial or radial top position impact of unexploded ordnance can completely separate primary explosive and main charge, which is more thorough than radial middle and bottom position impact; When shooting at a distance of 50m-250m, unexploded ordnance can be effectively destroyed, with little difference in velocity attenuation. However, after penetrating unexploded ordnance, the flight direction of the bullet will change by 1 ° to 7 °. In conclusion, the simulation model can effectively calculate the process of ordnance destruction and the flight of the bullet; the sniping method prioritizes the use of axial or radial top propellant position impact; The impact bullet has a deviation in flight direction, and it is necessary to take good safety measures in the shooting range to avoid ricocheting out of the field.

Ultracapacitor as selectable energy buffer in electric vehicle application

A method of ultracapacitor integration with a regenerative braking system for use in electric drive trains is presented in this paper. An ultracapacitor (UC) is an intermediary to store and provide energy on the DC bus in certain scenarios, such as during acceleration and regenerative braking. UC is used to avoid direct inrush loading on the battery, which the electric drive system may cause. The energy from UC is injected into the DC bus in compliment to the battery, for which a dedicated power source switch called the “Main Charge Controller” (MCC) is responsible. The charge discharge of UC is done through a bidirectional buck-boost converter (BDBBC). The use of UC to offload high energy demand from the battery and store energy recovered during regenerative braking helps improve the vehicle's life and per-charge range. The stored energy in UC can be obtained from the battery at the start. UC can also be charged at the time of charging. The design and the presented control are ideal for lightweight electric vehicles. The system uses a 39.9 kJ ultracapacitor, formed from market-available 50F 2.7 V units in a 52S configuration, storage, and a 6kWh battery. The simulated vehicle in battery only case provides a minimum of 154 km range in rough conditions, in best case scenario it provides a 200 km range. The proposed design provides an increased extended range compared to simple battery-based regenerative braking, in the case of this work the hybrid solution provides an addition of more than 30 km of additional range compared to a battery-only solution which is simulated for all the same conditions except without the addition of the UC and its control and handling system, resulting in a total range of 230 km. The speed control response achieved by the user is also very fast. Electric Vehicles have range limitations due to storage technology which is a high entry barrier for consumers looking for reliable vehicles without range anxiety, as storage technology progresses adoption will become easier. This work is an attempt at using hybrid storage and selective use of it, for improved range and sharper speed response. However, this work does not explore the aging of the storage components due to increased operational load and thermal stresses or application to alternate battery chemistries. This work is primarily focused on the vehicles that use lithium-based batteries.

Device for measuring the Seebeck coeffi cient of thermoelectric materials in the temperature range 300–800 K

The problem of identifying patterns that are associated with the features of the structure and phase composition of new thermoelectric materials obtained by self-propagating high-temperature synthesis is considered. A measuring device has been developed to determine the Seebeck coefficient (thermoelectric motive force) of thermoelectric materials in the temperature range of 300–800 K in argon, air or vacuum. The design of the measuring device is described in detail, the capabilities of the device and the measurement error (less than 5 %) are discussed. The thermoelectromotive force of reference nickel samples in the temperature range of 300–800 K in an argon medium was measured by a differential method. Negative values of the Seebeck coefficient of the nickel sample were obtained throughout the studied temperature range, which indicates the predominance of electrons as the main charge carriers in the sample material. At room temperature, the measured value of the Seebeck coefficient is –19.05 mkV/K and decreases to a value of –25.71 mkV/K with an increase in temperature to 515 K. With a further increase in temperature to 640 K, the Seebeck coefficient monotonically increases to a value of –19.60 mkV/K. At temperatures above 640 K, the Seebeck coefficient continuously decreases and at 824 K reaches a value of –24.12 mkV/K. The Curie point is 644 K. The obtained values of the Seebeck coefficient for nickel in the temperature range 300–800 K are comparable with the data given in the literature. When calculating the Seebeck coefficient of the material, equations are used using the Seebeck coefficient values for the positive and negative thermocouple paths, which eliminates the need for additional measuring probes and contacts to measure the thermoelectric voltage on the sample. The set-up can also be used to make electrical resistance measurements using the standard 4-point method.

Oxide ion conductivity in doped bismuth gallate mullite type oxide, Bi2Ga4O9

Mullite-phase bismuth gallate (Bi2Ga4O9) was successfully synthesized with partial substitution of bismuth with alkaline-earth cation, Mg2+, Ca2+, Sr2+, and Ba2+. The effect of this substitution on the electrical conductivity was investigated. In this study, substitution with Ca2+ of Bi site was further studied for increasing the ionic conductivity as well as the phase stability in reducing atmospheres. Substitution with Ca2+ was found to be the most effective and with 12.5 mol% of Ca2+ as the optimized doping amount. Conductivity and stability in reducing atmospheres was increased down to pO2 ≤ 10−19 atm while keeping the conductivity of σ = 2.6 × 10−2 S·cm−1 at 973 K largely independent of oxygen partial pressure. Oxygen permeation analysis estimates 76% of theoretical oxygen permeation rate at 973 K suggesting main charge carrier is oxide ion. Partial electronic conductivity was measured with the ion blocking method. Oxide ion conductivity is dominated over wide pO2 range excepting for hole conduction at high pO2. Density functional theory (DFT) analysis on oxide ion diffusion route suggests oxygen hoping through lattice vacancy is main pathway for oxide ion conductivity in this doped Bi2Ga4O9. Despite the low oxide ion conductivity in Mullite-phase oxide, it was found that Ca doped Bi2Ga4O9 shows good oxide ion conductivity over wide pO2 range.

Characterization of art materials and degradation processes in the exterior wall paintings of the main church of Rila Monastery, Bulgaria

The present study focused on the characterization of the art materials and the degradation processes in the exterior (exonarthex) mural paintings of the main church of the Nativity of the Virgin in Rila monastery, Bulgaria, which is believed to be the last large-scale example of Eastern Orthodox wall painting. For the first time the art materials used to create a unique and colourful polychrome decoration of the outer gallery and the possible degradation products, caused by atmospheric influence - permanent exposure to open air and moisture - were revealed by a multi-technique approach. The mineral pigments were identified by means of attenuated total reflectance Fourier transform infrared (ATR-FTIR), micro-Raman spectroscopy, scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The natural yellow, red ochre, and green earth pigments, as well as some synthetic ones such as ultramarine and vermillion, were found in stable condition. Minium and emerald green pigments showed chemical transformations due to adverse environmental conditions which lead to chromatic changes of wall paintings. Black discolouration occurred due to the conversion of orange minium to black plattnerite (PbO2) and white discolouration – due to its transformation to white lead carbon oxide (PbCO3). The copper acetoarsenite (Cu(CH3COO)2.3Cu(AsO2)2) in the emerald green pigment showed partial transformation to arsen-containing mineral phases clinoclase and lindackerite, which fortunately did not affect much the colour appearance. Gypsum and calcium oxalate were found in the majority of the microsamples as decay products. Analysis of the binders by enzyme-linked immunosorbent assay (ELISA) implied the use of the Orthodox Church post-Byzantine egg-tempera technique. The registered Ca metal oxalates in accordance with ELISA results suggested binder chemical degradation induced by external factors. Most of the used painting materials are close to the those found in other Eastern Orthodox Byzantine and post-Byzantine monuments which indicates that the wall painting decoration of the main church of Rila monastery continues the post-Byzantine traditions. On the other hand, the study showed that the exonarthex wall paintings of the main charge of Rila monastery bear some new features as the religious artists supplemented the colourful scheme by emerald green as a new pigment and replaced smalt by the brighter synthetic ultramarine.

Numerical study of the effects of excess air ratio on passive pre-chamber jet performance and ignition mechanism

Pre-chamber (PC) ignition is a promising lean-burn technology to improve the efficiency of spark ignition (SI) engines while achieving ultra-low NOx emissions. However, the significant effects of the excess air ratio (λ) on the PC jet performance and ignition mechanism were still not fully unraveled. The current study numerically investigated the jet characteristics and combustion behaviors of a narrow-throat PC with two rows of orifices on a passive PC engine fueled with methane. The numerical model was validated extensively by the pressure, heat release rate, and natural flame luminosity (NFL) imaging of the PC flame jet. A detailed comparison of the NFL images of the jets and the simulated flame iso-faces presented excellent matching in the flame jet penetration and propagation process. The results reveal that the λ = 0.9 case has the best jet performance, but it doesn’t lead in every jet characteristic. For instance, the jet temperature is highest under λ = 1.0, and OH concentration is most under λ = 1.1. The transition from cold jet to flame jet produces noticeable jet non-uniformity, which is reported for the first time. This observation can be remarked as a more accurate indication of the initiation of pre-chamber flame jet discharge. The asymmetrical mixture inflow from the main chamber produces asymmetrical turbulent kinetic energy (TKE) and temperature distributions; these result in different flame propagation in the PC, jet non-uniformity, and varied stages of jet discharge. The upper jets are quenched in every case because of the much higher TKE, while the lower jets don’t present quenching when the λ ranges from 0.9 to 1.3; especially, the λ = 1.1 case has the best ignition performance for its most OH radicals. The “jet ignition regime”, in which flame quenching takes place, results in highly non-uniform flame propagation and low flame propagation speed. The ultra-rich case shows more signs of jet ignition and thus exhibits worse jet performance than the lean cases. This study uncovers the mechanisms and the optimal λ value for the pre-chamber ignition of the main chamber charge, providing valuable guidance for PC design.

Active and passive prechamber assisted engine combustion: simultaneous 50kHz formaldehyde PLIF and OH* visualization

Prechamber-assisted internal combustion engines allow lean limit extension by replacing the spark plug with multiple, high-temperature, radical-rich jets that entrain and ignite the main chamber charge. This work reports the first investigation of active ultra-lean, active rich, and passive prechamber assisted prechamber engine operation (with a fixed prechamber geometry) through 50 kHz cycle-resolved measurements of formaldehyde planar laser-induced fluorescence (PLIF) and OH* imaging in a heavy-duty optical engine operating at 1200 rpm. The third harmonic of a burst mode laser (355 nm) provided the excitation source for formaldehyde PLIF, and a high-speed CMOS camera collected the fluorescence signal from the side window of the engine. Bottom-view imaging of OH* chemiluminescence was achieved using an intensified high-speed camera. The high-speed image sequence of the prechamber jet formaldehyde layer and OH* captures the main chamber heat release stages and the interaction between the moving piston and the prechamber jet. The prechamber-assisted combustion process in the main chamber could be segmented into three phases: initial jet, jet wall interaction, and Post Jet Combustion. The first two phases differ between active and passive operations owing to the global lambda, while the last phases mostly remain flame propagation driven. Jet wall interaction leading to mixing and vortical transport across the main chamber is pivotal in main chamber heat release rate shaping. The study reports the dynamics and evolution of main chamber combustion in detailed time-resolved setups.

Influence of Quantum Effects on Dielectric Relaxation in Functional Electrical and Electric Energy Elements Based on Proton Semiconductors and Dielectrics

Using the quasi-classical kinetic theory of dielectric relaxation, in addition to existing methods, fundamental mathematical expressions are built, which make it possible to more strictly consider the effects of the main charge carriers’ (protons’) tunneling on the numerical values of the molecular parameters (activation energy, equilibrium concentration) of protons in HBC. The formulas for calculating the statistically averaged non-stationary quantum transparency of a parabolic potential barrier for protons have been modernized by more stringent consideration of the effects of corrections caused by an external electric field. For the model of a double-symmetric potential well, a generalized nonlinear solution of the quasi-classical kinetic equation of dielectric relaxation in HBC was built. The phenomenological Bucci-Rive formula for thermally stimulated depolarization current density (TSDC) was first investigated, taking into account quantum transparency, for the case of a parabolic potential barrier. The choice of the parabolic shape of the potential barrier allowed, at a theoretical level, for the mathematical model of relaxation polarization to be brought closer to the conditions of the real spatial structure of the crystal potential field, in comparison with the rectangular potential barrier model. It has been found that quantum effects due to proton tunnel transitions significantly affect the mechanism of thermally stimulated depolarization currents in HBC, over a wide temperature range (50–550 K) and external field parameters (0.1–1 MV/m). Generalized solutions of the nonlinear kinetic equation, recorded considering the effects of field parameters on proton tunnel transitions, made it possible to significantly approximate the theoretical values of activation energies, equilibrium concentrations of protons and amplitudes of the theoretical maxima of the current density of thermally stimulated depolarization, according to their experimental values in the field of low-temperature (50–100 K) and high-temperature (350–550 K) maxima of TSDC density in HBC. For the first time, precision measurements of TSDC temperature spectra were carried out for chalcanthite crystals. The effects of alloying impurities concentrations and crystal calcination temperatures on the parameters of experimental maxima in the TSDC spectrum of chalcanthite were established. A physical mechanism of the quantum tunnel motion of protons in HBC with a complex crystal structure (crystalline hydrates, layered silicates, ferroelectric HBC (KDP, DKDP)) is described. The patterns found in this article indicate a fairly high degree of applied scientific significance for the obtained theoretical results, allowing for the further development of electrophysics and optoelectronics of heterogeneous structures (MIS, MSM) based on proton semiconductors and dielectrics (PSD) and their composites.

Poloidal impurity asymmetries, flow and neoclassical transport in pedestals in the plateau and banana regimes

Charge exchange recombination spectroscopy (CXRS) measures the radial electric field in the pedestal by measuring the impurity density, temperature and flow. Combined outboard and inboard CXRS measurements allow poloidal variations that arise due to the poloidal variation of the magnetic field to be determined. At present, impurity neoclassical pedestal models avoid the complications of treating finite poloidal gyroradius effects by assuming the impurity charge number is large compared with the main ion charge number. These models are extended slightly by retaining the impurity radial pressure gradient to demonstrate that no substantial effect occurs due to impurity diamagnetic effects. More importantly, the neoclassical model is significantly extended to obtain a more comprehensive treatment of the main ions in the plateau and banana regimes. A parallel impurity momentum equation is derived that is consistent with previous results in the banana regime and reduces to the proper large aspect ratio form required in the plateau regime. The implications for interpreting the CXRS measurements are discussed by writing all results in terms of the gradient drive and poloidal flow.

Trends in costs, reimbursements, and surgeon payments for cervical disc arthroplasty cost of care from 2009 to 2019.

The use of cervical disc arthroplasty (CDA) continues to increase in the Medicare population. As healthcare costs continue to rise, payors have begun to implement bundled payment structures for spine surgery. While Medicare has steadily decreased reimbursements for cervical fusions, Medicare reimbursements for CDA have not been studied. The purpose of this study was to assess trends in 1) hospital costs and reimbursement, 2) physician reimbursement, and 3) potential cost drivers for CDA in a Medicare population. This is a retrospective longitudinal study of CDA in Medicare patients. The Medicare Provider Analysis and Review Limited Data Sets for 2009, 2014, and 2019 were used for this study. Patients undergoing elective CDA were included. Corresponding Inpatient Prospective Payment System files were used to calculate cost through cost-to-charge ratios. Physician fees were obtained from the Medicare Physician Fee Schedule Look-Up Tool. All financial data were adjusted for inflation to 2019 values based on the Consumer Price Index for All Urban Consumers. Demographic, comorbidity, surgical, and hospital trends were assessed. Trends in revenue center-level charges were also assessed. Adjusted for inflation, from 2009 to 2019, mean total hospital charges for elective CDA increased from $64,609 ± $45,787 to $111,874 ± $78,611 (73% increase, p < 0.001) and the mean total cost for index hospital admission increased from $19,665 ± $13,414 to $24,682 ± $13,818 (26% increase, p < 0.001). Over the same period, Medicare reimbursement increased from a mean of $11,154 ± $11,684 to $12,879 ± $13,613 (15% increase, p = 0.003), while total reimbursement increased from a mean of $15,005 ± $15,684 to $15,547 ± $15,829 (4% increase, p = 0.040). The mean hospital profit decreased from -$4076 ± $14,041 to -$9023 ± $16,084 (-121%, p < 0.001). Surgeon reimbursement for CDA decreased from a mean of $1850 ± $165 (2009) to $1722 ± $138 (2019) (7% decrease, p < 0.001). On multivariate analysis, increasing year of surgery (p < 0.001), increasing age (p = 0.001), increasing length of stay (p < 0.001), rural hospital setting (p = 0.027), and hospital geography (p < 0.001) were independently associated with cost of care. Medical/surgical supplies and operating room charges increased 71.6% (p < 0.001) and 98.5% (p < 0.001) and accounted for 41.1%-42.5% and 30.6%-35.1% of total charges, respectively. From 2009 to 2019, costs of care for elective inpatient CDA increased disproportionately to reimbursement. Hospitals operated at increasing losses and surgeon reimbursement decreased. Cost of care was independently associated with year of surgery, increasing age, length of stay, hospital setting, and hospital geography. The main charge drivers were medical/surgical supplies and operating room charges. These results may have implications for the future financial feasibility of inpatient CDA for Medicare patients and targets to improve the value of CDA. Further study is necessary to provide fair reimbursement for CDA in Medicare patients and prevent financially based bias against use of CDA in Medicare patients.

Utilization of Recycled Egg Carton Pulp for Nitrocellulose as an Accelerant in Briquette Production.

Nitrocellulose (NC) is a conservative material that is used in a variety of applications, such as coating agents, biodegradable plastics, and propellant main charge. Nitrocellulose raw materials are easily obtained from lignocellulose sources, most notably cotton and wood pulp. The egg carton, a recycled paper waste designed for packaging and transporting eggs, is used in this study to make nitrocellulose in pulp form. The effects of different nitration durations (40, 50, and 60 min) from egg carton pulp bleached with various KOH concentrations (0.6 M, 1.0 M, and 1.5 M) on NC properties were evaluated. The accelerant properties of the NC of nitration time in 50 min were studied in a rice husk charcoal briquette. Rice husk charcoal briquettes are made in various ratios with nitrocellulose as an accelerant (97:3, 96:4, and 95:5). The NC was characterized using Fourier transform infrared (IR) spectroscopy and thermogravimetric (TG) analysis. 1.0 M of bleached egg carton pulp has the highest cellulose content (86.94%) with the presence of crystalline structure of cellulose at peak 1430 cm-1 after the bleaching process. Meanwhile, different nitration times revealed that 50 min had the highest nitrogen content (7.97%) with a 1.23 degree of substitution (DS) value. Based on its TG analysis, NC 50 has met the requirements for use as an accelerant for briquettes, with an onset temperature of 91.60 °C and a weight loss of 62.60%. Infrared at peak 1640 cm-1 confirmed the presence of NO2 groups in nitrocellulose successfully formed by nitration. After the addition of nitrocellulose, the calorific value of the briquette increased from 13.54% to 15.47%. Fixed carbon and volatile matter showed the same pattern. The combustion of nitrocellulose-briquette has also been demonstrated by Td10% of degradation, which degraded between 310 and 345 °C.

ПОДВИЖНОСТЬ НОСИТЕЛЕЙ ЗАРЯДА ВДОЛЬ ГРАНИЦЫ РАЗДЕЛА ПОЛИМЕР/ПОЛИМЕР

Organic thin-film transistors are increasingly being used in various electronic devices, successfully replacing transistors on silicon and other traditional semiconductors. The advantages of such electronic devices are particularly noticeable in the development of flexible electronic devices. However, one of the intractable problems of organic devices is the low mobility of charge carriers, often not exceeding 10-3 cm2/Vs. Obviously, this significantly limits the scope of their application. In this paper, a new approach to the formation of a transport layer in an organic field-effect transistor is proposed. This approach is based on the use of anomalous transport properties occurring along the interface of two dielectrics. Along such a boundary, a layer of quasi-two-dimensional electron gas with abnormally large values of conductivity and mobility of charge carriers can occur. In this regard, polymer heterostructures representing a field-effect transistor with a transport layer made in the form of an interface between two films of an unconjugated (dielectric) polymer, polydiphenylene phthalide, were investigated in this work. Along such a boundary, a layer of quasi-two-dimensional electron gas with abnormally large values of conductivity and mobility of charge carriers can occur. In this regard, polymer heterostructures representing a field-effect transistor with a transport layer made in the form of an interface between two films of an unconjugated (dielectric) polymer, polydiphenylene phthalide, were investigated in this work. The paper describes the technology of creating a multielectrode device. Polymer films were made by centrifugation from a polymer solution in cyclohexanone. The metal electrodes were manufactured by thermal deposition in vacuum. Measurements of the electrophysical characteristics of an organic field-effect transistor have been carried out. It is established that the main charge carrier along the interface are electrons. Estimates of the mobility of charge carriers were carried out using two different techniques. At zero potential at the gate, an injection model of currents limited by a volumetric charge was used. In the presence of a potential on the gate, the mobility assessment was made within the framework of the field effect model. Comparison of the obtained estimates showed satisfactory agreement of the mobility values. From this fact, it was concluded that it is possible to use an injection model to estimate the mobility of charge carriers when they move along the polymer/polymer interface.

Experiment and instantaneous driving simulation of explosion dispersion process of central tube for submunition

In order to study the influence of explosion dispersion of submunition on the dispersion velocity and pressure characteristics of subunits, the experimental study of explosive dispersion of the central tube was carried out when the explosives with low detonation velocity were applied in central tube as the main charge. In addition, the explosion dispersion test process was recorded by high-speed photography. RDX-based aluminized explosive samples with low detonation velocity were prepared and tested, and the low detonation velocity performance changes under different charge diameters and densities were obtained. Based on the explosive dispersion test of the central tube of the submunition, the physical model and three-dimensional axisymmetric finite element model of the central tube, subunit and aluminium alloy shell with prefabricated grooves are established. The fluid-structure coupling calculation method is used to simulate the explosive dispersion process. The simulation results are compared with the test results, and the pressure distribution characteristics of the subunit and the variation law of the dispersion velocity are analyzed. The effectiveness of the engineering calculation method of JWL equation model parameters is verified. The results show that using RDX based aluminized low detonation velocity explosive as the main charge of the central tube structure can achieve the design goal of the explosive dispersion for submunition, and the explosion dispersion model of submunition can accurately describe the dispersion characteristics of the subunit. The research results can be used to guide the structural design of submunition warhead.

Numerical Simulation of Hypervelocity Launch Process of Cased Telescoped Ammunition Armor-piercing Projectile

In order to study the interior ballistic characteristics of cased telescoped ammunition (CTA) armor-piercing projectile in the hypervelocity launch process, in this paper, based on the secondary ignition and propellant combustion technology, the zero-dimensional internal ballistic model of CTA is established. At the same time, in order to improve the lightweight of CTA and the energy utilization rate of the launch process, combustible cartridge materials are applied to the structure of cased telescoped ammunition. Numerical simulation of 105 mm CTA grenade shooting experiment has verified its correctness. On this basis, the internal ballistic process of 105 mm CTA armor-piercing projectile with semi-combustible cartridge is predicted and analyzed. When main charge propellant weight is 6 kg, the maximum pressure is 569.5 MPa and the muzzle velocity can reach 1702 m/s.

Synthesis of Low-Crystalline MnO2/MXene Composites for Capacitive Deionization with Efficient Desalination Capacity

MXene has drawn widespread attention as a potential material for electrode use in capacitive deionization (CDI). However, the applications of MXene are limited by its property of low electrical capacity. Herein, a MnO2/MXene composite was firstly evaluated in a capacitive deionization system, in which the MnO2 acts as intercalation-type pseudocapacitive electrodes to enhance the electrical capacity, and MXene provides an electron conduction highway network that improves the charge transfer of the MnO2. The result showed that the low-crystallinity MnO2 with irregular particles was well-distributed on the surface of the MXene. The desalination capacity of 30.5 mg·g−1 is achieved at a voltage window of 1.2 V, which was higher than that of the reported pure MXene and MnO2. The electrical double-layer (EDL) capacitive and the diffusion-controlled processes are the main charge storage mechanisms, and the EDL contribution provides 50.3% to the total capacitance. This result suggests a promising direction for further applying a MnO2/MXene composite in CDI.

Synthesis, structure determination, NBO analysis and vibrational/electronic spectroscopic study of Iron(II) Bis(diethyldithiocarbamate) [Fe(DDTC)2

This work deals with the synthesis, computational molecular modeling, and vibrational/electronic spectroscopic analysis of the coordination complex [Fe(DDTC)2]. The complex was synthesized according to the guidelines provided by the graphical method. The optimization of the molecular structure was performed using Density Functional Theory with the exchange functional B3LYP and basis set 6–311G(d,p). The experimental FT-IR and Raman spectra of the complex were recorded in the range of 4000–0 cm−1 to correlate them with the calculated spectra. Most of the DFT calculated frequencies agreed with the experimental results, and complete vibrational assignments (including metal-ligand) were made. To investigate the internal electronic mobility of the complex, we performed natural bond orbital analysis (NBO), which provided information regarding intramolecular charge transfer interactions resulting from the overlapping of bonding and antibonding orbitals. The NBO analysis also provided information about the electronic distribution between the HOMO and LUMO orbitals due to charge transfers. We found that the NBO analysis provided the main charge transfers between donor and acceptor atoms, and the HOMO-LUMO energy gap revealed that the complex has high kinetic stability. We also correlated the calculated and experimental UV–Vis spectra to investigate the configurations of several excited states of the complex that involve intra-ligand transitions. The charge transfer and d-d (Laporte Forbidden) bands were assigned. The results also corroborate the existence of several Ligand to Metal Charge Transfer (LMCT) and Metal to Ligand Charge Transfer (MLCT) transitions, as well as d-d transitions. We found that the experimental vibrational spectra agreed with the theoretical ones.

An investigation on the microscale detonation transmission performance of HMX-based explosive ink

ABSTRACT To investigate the effect of Octogen (HMX) in the application of microscale explosive transfer sequence charges. In this paper, we designed and formulated four kinds of explosive inks with different solid contents using submicron HMX as the main explosive and polyvinyl alcohol (PVA) aqueous solution / fluorocarbon resin (FEVE) ethyl acetate solution emulsion as the binder system, studied the effect of solid content on the rheological properties of explosive inks, conducted micro loading studies using a direct ink writing molding platform, The morphology, safety performance and explosion transmission performance of the microscale printed molding samples were tested and analyzed. The results show that the ink containing 90 wt.% HMX explosive has the largest n value, has good printability, smooth surface of the molded sample, consistent, uniform particle dispersion inside the line; HMX crystalline type is still β type; critical impact energy and critical friction of the printed sample compared to the raw HMX increased by 114% and 100% respectively, critical impact energy compared to CL-20-based explosive ink printed sample increased by 67%, indicating that the printed samples have a high safety under the Mechanical Sensitivity. The detonation velocity of the printed sample is 6902 m·s−1 at a charge cross-section size of 1 mm × 1 mm. The critical detonation thickness of the printed sample is 1 × 0.095 mm, Can be stable under the corner of not more than 120 ° detonation.The results of the study show that HMX as the main charge can improve the wide applicability of direct-written explosive ink.

Trajectories of principal stresses after plastic deformation

Improving research efficiency of mechanical stresses in metals can be achieved by studying and taking into account the fields of the trajectories of the main stresses (isostats), which qualitatively characterize the stress state. The purpose of the work was to determine the possibility of detecting the isostates in a St3 steel sample, following its plastic deformation. The methodology is based on the magnetoelastic method, manifested by the dependence of magnetic permeability of ferromagnetic materials upon mechanical stresses, acting in them. The method is implemented using the IMN-4M monophase magnetoelastic meter of mechanical stress: the base of the device gage is 5 mm, the angle meter error is ± 2°. The sample is a plate with dimensions of 150 x 150 x 4 mm. Coordinate grids with 10 x 10 mm cells were applied to its front and back surfaces. Using the IMN-4M device, we measured the values of tilt angles for tangents to principal stress trajectories in all nodes, then we created isostates by consecutive adjustment of the direction and radius of curvature for a raised curve. The plastic deformation of a plate was performed by shooting small lead pellets with kinetic energy of 1916 J. The maximum plate curvature in the impact zone of main charge equaled 7 mm. After a shot, the measurements were repeated in the same nodes of coordinate grids, and the isostates were plotted again. The experiment has shown that: the magnetoelastic method makes it possible to detect the isostates even after plastic deformation; the trajectories are present both on front and back surfaces of the deformed plate; isotropic points and parallel isostates are available in fields, formed by the shot. Izotropic zones were formed on front and back surfaces, in which isostates can not be plotted due to random orientation of tangents. The "disturbances" of fields with disruption of regular trajectory flows were detected. The results of the work may be useful for researchers and technical engineers, engaged in the study of elastic and plastic deformations.