Limits of Increasing the Penetration of Shaped‐Charge Jets by Pulsed Thermal Action on Shaped‐Charge Liners

The effect of preheating of liners on the penetration capability of shaped charges is considered theoretically. It is shown that for a plastically fractured shapedcharge jet, preheating of the liner generally increases the effective jet length and shapedcharge jet penetration. Restrictions on the parameters of preheating of shapedcharge liners due to the possible thermal initiation of the explosive are established. It is noted that excessive weakening of a shapedcharge jet can lead to transition from plastic to volume fracture with a corresponding decrease in shapedcharge jet penetration. The ultimate possibilities of the thermal method for increasing the penetration capability of shaped charges are estimated. Calculation results are compared with available experimental data.     

Mechanisms of Iron Activation on Fe-Containing Zeolites and the Charge of α-Oxygen

According to previous Mössbauer data [1] -sites formation at the activation of Fe-containing zeolites is accompanied by irreversible self-reduction of the iron, proceeding without participation of an external reducing agent. Reduced Fe²⁺ ions are inert to O₂ but are reversibly oxidized to Fe³⁺ by N₂O, generating the -oxygen species, O, which provide selective oxidation of hydrocarbons.In this work, the mechanism of -sites formation was studied via quantitative measurement of the dioxygen amount desorbed into the gas phase at the step of self-reduction. A prominent role of the zeolite matrix chemical composition has been revealed. For example, with zeolites of Al–Si composition (FeZSM-5 and Fe-), heating to 900 °C in a closed vacuum space leads to irreversible evolution of O₂, which is accompanied by the immediate formation of -sites. Similar heating of B–Si and Ti–Si zeolites also leads to dioxygen evolution; however, this evolution is reversible and is not accompanied by formation of -sites. Activation of these zeolites occurs only in the presence of water vapor. Stoichiometric measurements showed that in terms of charge one regular O^2- ion, removed at the activation, is equivalent to two -oxygen atoms. So, -oxygen is identified as an ion-radical species O ^-., whose unique oxidation properties still distinguish it from the generally observed O^-. radicals.The mechanism of -sites formation is proposed, in which the process of strong chemical stabilization of reduced Fe²⁺ atoms in the zeolite structure is a key step, making impossible the reoxidation of the iron with O₂.     

Possibilities of Controlling the Shaped–Charge Effect by Electromagnetic Actions

This paper deals with electromagnetic actions that allow one to control the shaped–charge effect at different stages of shaped–charge operation. A decrease in penetration of the shaped–charge jet is attained by passage of a powerful electric current pulse through it, production of an axial magnetic field in the shaped–charge liner immediately before shot, and production of a magnetic field in the conducting target material that is transverse to the direction of jet propagation. The action on a jet by low–frequency and high–frequency longitudinal magnetic fields and mild current action are directed toward increasing the penetration capability of a shaped–charge jet by increasing its ultimate elongation. Results of experimental and theoretical studies of different versions of electromagnetic actions are analyzed, and the associated physical effects are considered.     

Phase Compositions of Coatings Applied to Titanium Targets by Means of Shaped‐Charge Jets

Coatings containing titanium carbides of the cubic and hexagonal modifications were applied to titanium targets by a shapedcharge explosion. In the experiments, a conical liner with a cone angle of 30° made from a mixture of fine powders of boron and ammonium nitrate were used. A quantitative Xray phase analysis of various segments of the coating was performed. The values of the unit cell parameters indicate the formation of complex phases. In some regions of the target, the microhardness reaches 3800 kg/mm².     

Surface of a Titanium Target After Interaction with Shaped‐Charge Jet Particles

Coatings containing WC_1-x and W₂C_1-x tungsten carbides were produced on titanium targets by a shapedcharge explosion. The experiment used conical liners with a cone angle of 30° manufactured from a mixture of fine powders of tungsten, graphite, and ammonium nitrate. A comparative quantitative xray analysis of the top and bottom layers of the coating was performed. For the phase WC_1-x in the bottom layer, the value of the cubic unit cell parameter falls outside the range known in the literature. Microhardness in different segments of the target was studied.     

Charge–discharge characteristics of polythiopheneas a cathode active material in a rechargeable battery

Polythiophene films were electrochemically deposited on glassy carbon substrates under potentiostatic control and used as cathode active material together with a Zn anode in a rechargeable battery with propylene carbonate, Zn(ClO4)2, LiClO4 electrolyte. Charge–discharge characteristics were studied. The average discharge voltage of the polythiophene/Zn cell was 1.25V. In the low current density region (i.e. 10–50Acm–2) the cycling coulombic efficiency was above 95%, but in the fast charge–discharge region, where current densities were 0.1–0.5mAcm–2, the coulombic efficiency decreased to 55% with increasing discharge rate. Additionally, it was found that the cyclic coulombic efficiency was a function of the charging depth.     

Layers Produced by Entrapment of a Shaped‐Charge Jet in a Titanium Target

An xray diffraction study was performed of layers produced on titanium targets by a shapedcharge explosion. Mixtures of fine powders of graphite and ammonium nitrate in different proportions were used as liners. The phase compositions of the central and peripheral zones of the target were shown to be different. The unitcell parameters of the detected crystalline phases and sample microhardness were measured.     

Experimental Study of Laser Initiation of a Light-Sensitive Explosive Charge over a ≈1000 mm2Surface

Combustion, Explosion, and Shock Waves - This paper presents the results of a study of the initiation of explosive transformation of flat charges 40 mm in diameter and 5 mm thick,...     

The Effect of Number of Porphyrin Polymer Units on Bandgap for ππ* Conjugation and Charge Transfer System Based on Simulation

This paper discusses the effect of number of units on bandgap for conjugation versus charge transfer system by using a conjugated polymer ([Zn])_n and an unconjugated planar push–pull one (AQ–[Zn])_n built upon 2,3-anthraquinone and bis(ethynyl)zinc(II)porphyrin. They are supported by DFT and TDDFT calculations, along with some experimental data. The position of the Q-bands is highly adjustable due to the presence of the twisted conformations in ([Zn])_n chain.     

Ion–Aerosol Flux Coefficients and the Steady-State Charge Distribution of Aerosols in a Bipolar Ion Environment

Fuchs’ theory, as corrected by Hoppel and Frick, is widely used to compute flux coefficients of ions to aerosol particles and the resultant charge distribution. We have identified approximations made in previous works that limit the theory's accuracy. Hoppel and Frick used two characteristic speeds or kinetic energies to calculate the flux coefficients of ions to aerosol particles in lieu of an average of the flux coefficients over the Maxwell–Boltzmann distribution of ion speeds. In the present work, we show that this approximation artificially reduces the number of multiply charged particles. Ion capture may be enhanced by three-body trapping, a process wherein an ion has a collision with a neutral gas molecule and loses sufficient kinetic energy to be captured by the particle. The gas kinetic theory approach to three-body trapping has been refined to better account for the collision between the ion and a neutral gas molecule within the potential presented by the particle. Approximations to the calculation of energy losses and the probability of ion capture have been relaxed. The possibility that an image charge may be induced on the ion as well as on the particle is allowed. While the previous work was limited to electrically conductive particles, both the ion and the particle are allowed to have any dielectric constant in the present work, and the finite size of the ions is taken into account when calculating minimum capture radii for the ion–particle interactions. The resulting ion flux coefficients differ from previous results both in the low nanometer regime and in the continuum regime. We explore the influence of key parameters on the charge distribution, including dielectric constant, temperature, and pressure, to understand how operating conditions may affect the interpretation of differential mobility analyzer measurements of particle size distributions. Finally, an empirical expression for the new charge distribution is given to facilitate rapid calculations.

© 2013 American Association for Aerosol Research     

Charge–discharge performance of Cr-substituted V-based hydrogen storage alloy negative electrodes for use in nickel-metal hydride batteries

To improve the charge–discharge cycle durability of a TiV_2.1Ni_0.3 alloy negative electrode with a discharge capacity of ～470 mAh g^?1, the vanadium constituent was partially substituted with chromium. The TiV_2.1?xCr_xNi_0.3 (x = 0.1–0.4) alloys, which were prepared by arc-melting, were composed of two phases, similar to the TiV_2.1Ni_0.3 alloy. Each constituent was distributed in both phases, and the V and Cr content in the primary phase was higher than that in the secondary phase, although the Ti and Ni content was higher in the secondary phase. The maximum discharge capacity for the TiV_2.1?xCr_xNi_0.3 (x = 0.1–0.4) negative electrodes showed a slight decrease as the x value increased, and their cycle durability was significantly improved due to the effective suppression of the dissolution of V. In particular, the loss of discharge capacity per cycle for the TiV_1.7Cr_0.4Ni_0.3 negative electrode was about one-tenth that for the TiV_2.1Ni_0.3 negative electrode. The high-rate dischargeability (HRD) was also greatly improved by increasing the Cr content. At 200 mA g^?1 the variations of the HRD and the charge transfer resistance (R_ct) with the Cr content were similar, while at 400 mA g^?1 the change in the HRD at a lower Cr content was markedly different from the change in R_ct. Moreover, at a lower Cr content the potential at a 50% degree of discharge stagnated at specific discharge currents over 200 mA g^?1. These results strongly suggest that hydrogen diffusion in the primary phase served as the main hydrogen reservoir.     

On the Charge Carrier Concentration in Sodium–Calcium Aluminophosphate Glasses

The dc and ac conductivities of the xNa₂O–(35 – x)CaO–7.5Al₂O₃–57.5P₂O₅glasses (mol %) with x= 0–35 are studied in the frequency range from 20 Hz to 1 MHz at different temperatures. It is found that the dc conductivity strongly depends on xonly for glasses with x 10. For glasses with x 5, the dc conductivity is virtually composition independent. The dependence of the ac conductivity plotted on the log(()/_dc) vs. log(/_dc) coordinates is analyzed. The ac conductivity represented in these coordinates depends on xonly for glasses with x 5, in which the dc conductivity does not depend on x. For glasses with xin the range from 10 to 35, all the isotherms of the ac conductivity closely coincide with each other. This result is discussed in the framework of two hypotheses: (1) the conductivity () is determined by the dynamic polarization (of the Maxwell–Wagner type at low frequencies) of the material due to spatial fluctuations of the density of paths providing the migration of sodium ions and (2) the concentration of charge carriers is independent of x.     

Charge–discharge curves and discharge capacities of LiNi1−yCoyO2 synthesized from lithium carbonate and nickel and cobalt oxides

LiNi_1?yCo_yO₂ (y=0.1, 0.3, and 0.5) were synthesized by a solid-state reaction method at 800 °C and 850 °C using Li₂CO₃, NiO, and Co₃O₄ as the starting materials. The electrochemical properties of the synthesized LiNi_1?yCo_yO₂ were then investigated. For samples with the same composition, the particles synthesized at 850 °C were larger than those synthesized at 800 °C. The particles of all the samples synthesized at 850 °C were larger than those synthesized at 800 °C. LiNi_0.5Co_0.5O₂ synthesized at 850 °C had the largest first discharge capacity (159 mA h/g), followed in order by LiNi_0.7Co_0.3O₂ synthesized at 800 °C (158 mA h/g) and LiNi_0.9Co_0.1O₂ synthesized at 850 °C (151 mA h/g). LiNi_0.9Co_0.1O₂ synthesized at 850 °C had the best cycling performance with discharge capacities of 151 mA h/g at n=1 and 156 mA h/g at n=5.     

FeCl3-Catalyzed C(sp3)−H Heteroarylation Enabled by Photoinduced Ligand-to-Metal Charge Transfer

Herein, we report a strategy for pyrimidination of inert alkanes via synergistic visible light-driven redox reaction and FeCl₃ catalysis. This transformation involves C−H activation by a chlorine radical generated during the iron-promoted ligand-to-metal charge transfer process, triggering subsequent C−H pyrimidination. The substrates and catalysts are inexpensive and readily available, while the reaction conditions and procedures are simple without the need for external oxidants. This work provides a practical approach for synthesizing pyrimidine derivatives with high structural diversity.     

How Does DNA Compaction Favor Chiral Selectivity with Cationic Species? Higher Selectivity with Lower Cationic Charge

A single-molecule study on giant DNA compaction by enantiomeric dications and tetracations demonstrates that strong chiral discrimination in DNA compaction is manifested only if the positive charge on enantiomeric multications is relatively low. The increase in cationicity of the chiral compaction agent inevitably leads to an increase in nonspecific electrostatic interactions and quenching of chiral discrimination in the DNA-folding phase transition.     

Hopping Mechanism of Charge Transfer in the Thin Layers of a Ge<Subscript>28.5</Subscript>Рb<Subscript>15</Subscript>S<Subscript>56.5</Subscript> Vitreous System

The results of the study of the charge transfer processes in the thin layers of a Ge_28.5Рb₁₅S_56.5 vitreous system are presented. The power-law dependence of the conductivity on frequency and a decrease in the value of the exponent s with increasing temperature are found. The charge transfer is a thermally activated process and two areas on the temperature dependence of conductivity are present. The activation energies of these areas are Е₁ = 0.20 ± 0.01 and Е₂ = 0.50 ± 0.01 eV, respectively. The obtained results are explained within the scope of the correlated barrier hopping (CBH) model of the hopping conductivity in disordered systems. The main microparameters of the system, namely, the density of the localized state (N), hopping length (R_ω), and the maximal value of the height of the potential barrier (W_M), are calculated.     

Could a Lower Toll-like Receptor (TLR) and NF-κB Activation Due to a Changed Charge Distribution in the Spike Protein Be the Reason for the Lower Pathogenicity of Omicron?

The novel SARS-CoV-2 Omicron variant B.1.1.529, which emerged in late 2021, is currently active worldwide, replacing other variants, including the Delta variant, due to an enormously increased infectivity. Multiple substitutions and deletions in the N-terminal domain (NTD) and the receptor binding domain (RBD) in the spike protein collaborate with the observed increased infectivity and evasion from therapeutic monoclonal antibodies and vaccine-induced neutralizing antibodies after primary/secondary immunization. In contrast, although three mutations near the S1/S2 furin cleavage site were predicted to favor cleavage, observed cleavage efficacy is substantially lower than in the Delta variant and also lower compared to the wild-type virus correlating with significantly lower TMPRSS2-dependent replication in the lungs, and lower cellular syncytium formation. In contrast, the Omicron variant shows high TMPRSS2-independent replication in the upper airway organs, but lower pathogenicity in animal studies and clinics. Based on recent data, we present here a hypothesis proposing that the changed charge distribution in the Omicron’s spike protein could lead to lower activation of Toll-like receptors (TLRs) in innate immune cells, resulting in lower NF-κB activation, furin expression, and viral replication in the lungs, and lower immune hyper-activation.     

Synthesis of Unsaturated Polyester Resin—Effect of Sequence of Addition of Reactants

Abstract

Unsaturated polyesters were synthesized in the laboratory by the condensation of maleic anhydride and phthalic anhydride with propylene glycol. The condensate obtained was mixed with styrene monomer to get an unsaturated polyester resin formulation. The properties of the polyester resin synthesized were found to be affected by the synthesis parameters. In this study, the effect of sequence of addition of reactants on the properties of resin was investigated. Properties such as tensile strength, tensile modulus, elongation at break, toughness, impact strength, surface hardness, abrasion resistance, and water absorption were evaluated after curing the resin. Propylene glycol necessary for esterification of both the anhydride fractions was initially reacted with phthalic anhydride. Later, the esterification was completed by reaction with maleic anhydride. This sequence of addition of reactants was found to give the best mechanical properties among all possible methods of reactant addition. Moreover, it was found that this sequence of addition of reactants gives the shortest reaction time.     

Mechanism of the Initial Stage of Thermal Decomposition of Nitroguanidine

A theoretical and experimental study of the thermal decomposition of nitroguanidine(NQ) has been carried out. Various thermolysis channels were studied by quantum chemistry methods at the CCSD(or DLPNO-CCSD) level using the aug-cc-pVDZ basis set. It is shown that the lowest activation enthalpies(170—180kJ/mol) are characteristic of the reactions of NO₂ abstraction from the initial NQ and the reaction channel with the transfer of oxygen from the nitro group to carbon in the limiting st...