Motion State of Fuel within Shell in Projection Acceleration Process

The fuel-air explosive (FAE) warheads are charged with the liquid-solid mixture fuel. The fuel is different 'om conventional solid explosives in physical and mechanical properties. The mass centre of the charged fuel changes during projecting the projectile. In this study, a method to calculate the mass centre change of the charged fuel is suggested and the  influence of this change on the projectile motion state in the projection process is discussed. The results show that in projection, the fuel mass centre varies with the projection acceleration and the deformation characteristics of the mixture fuel. The higher is the acceleration, the larger is the displacement of the mass centre. This displacement also increases with the compressibility of the fuel. It constitutes an influence on the state of motion for the whole projectile in the projection process, whose calculation approach is also proposed. The result provides a theoretical basis for the design of the FAE weapons

Critical Ignition Temperature of Fuel-air Explosive

The charge of fuel-air explosive (FAE) warhead usually is solid-liquid mixed fuel. The solid component is aluminium powder. To meet the demand of FAE weapon usage and storage safety, in the mixed-fuel medium, there must be gaps where adiabatic compression occurs during launchin-e overloading- of warhead. Adiabatic compression makes the temperature of the mediumin the gaps to rise. High temperature can cause dxplosion of the mixed fuel during launching acceleration of the warhead, which is very dangerous. Because the fuel is a multicomponentmixture, the critical ignitioh temperature can't be determined only by one component. Through experiment, the critical ignition temperature of the mixed fuel is attained, and the changingregularity of the pressure following the temperature is shown in this paper

Effect of Explosive Sources on the Elastic Wave Field of Explosions in Soils

A seismic wave is essentially an elastic wave, which propagates in the soil medium, with the strength of initial elastic wave being created by an explosion source that has a significant effect on seismic wave energy. In order to explore the explosive energy effect on output characteristics of the elastic wave field, four explosives with different work capacity (i.e., TNT, 8701, composition B and THL) were used to study the effects of elastic wave pressure and rise time of stress wave to the peak value of explosions in soils. All the experimental data was measured under the same geological conditions using a self-designed pressure measuring system. This study was based on the analysis of the initial pressure of elastic waves from the energy output characteristics of the explosives. The results show that this system is feasible for underground pressure tests, and the addition of aluminum powder increases the pressure of elastic waves and energy release of explosions in soils. The explosive used as a seismic energy source in petroleum and gas exploration should have properties of high explosion heat and low volume of explosion gas products.Defence Science Journal, 2013, 63(4), pp.376-380, DOI:http://dx.doi.org/10.14429/dsj.63.277

cyclo-Tetra­kis{μ-2,2′-dimethyl-1,1′-[2,2-bis­(bromo­meth­yl)propane-1,3-di­yl]di(1H-benzimidazole)-κ2 N 3:N 3′}tetra­kis­[bromidocopper(I)]

The title compound, [Cu4Br4(C21H22Br2N4)4], features a macrocyclic Cu4 L 4 ring system in which each CuI atom is coordinated by one bromide ion and two N atoms from two 2,2′-dimethyl-1,1′-[2,2-bis­(bromo­meth­yl)propane-1,3-di­yl]di(1H-benzimidazole) (L) ligands in a distorted trigonal–planar geometry. The L ligands adopt either a cis or trans configuration. The asymmetric unit contains one half-mol­ecule with the center of the macrocycle located on a crystallographic center of inversion. Each bromide ion binds to a CuI atom in a terminal mode and is oriented outside the ring. The macrocycles are inter­connected into a two-dimensional network by π–π inter­actions between benzimid­azole groups from different rings [centroid–centroid distance = 3.803 (5) Å

Progress in Research and Application of Insect-resistant Packaging for Grain Storage

Stored grain is extremely vulnerable to the storage insects during storage and processing. At present, chemical control is still the main method for controlling stored grain insects. However, the increasing resistance of insects caused by long-term use of chemical control raises unprecedented challenges. Insect-repellent packaging, as a traditional and emerging physical insect prevention method, has increasingly attracted widespread attention among people. The types and characteristics of food packaging materials, the types and application of insect-repellent packaging, the research and evaluating methods of insect-repellent packaging at home and abroad, and the problems existing in the practical application of insect-repellent packaging were reviewed, and the development trend of insect-repellent packaging was prospected, so as to provide reference information for the scientific and efficient use of insect-repellent packaging, development of new insect-repellent packaging to control stored grain insects in the future

Structural mechanism for bacterial oxidation of oceanic trimethylamine into trimethylamine N -oxide

Trimethylamine (TMA) and trimethylamine N-oxide (TMAO) are widespread in the ocean and are important nitrogen source for bacteria. TMA monooxygenase (Tmm), a bacterial flavin-containing monooxygenase (FMO), is found widespread in marine bacteria and is responsible for converting TMA to TMAO. However, the molecular mechanism of TMA oxygenation by Tmm has not been explained. Here, we determined the crystal structures of two reaction intermediates of a marine bacterial Tmm (RnTmm) and elucidated the catalytic mechanism of TMA oxidation by RnTmm. The catalytic process of Tmm consists of a reductive half-reaction and an oxidative half-reaction. In the reductive half-reaction, FAD is reduced and a C4a-hydroperoxyflavin intermediate forms. In the oxidative half-reaction, this intermediate attracts TMA through electronic interactions. After TMA binding, NADP+ bends and interacts with D317, shutting off the entrance to create a protected micro-environment for catalysis and exposing C4a-hydroperoxyflavin to TMA for oxidation. Sequence analysis suggests that the proposed catalytic mechanism is common for bacterial Tmms. These findings reveal the catalytic process of TMA oxidation by marine bacterial Tmm and first show that NADP+ undergoes a conformational change in the oxidative half-reaction of FMOs