Evolution of molecular structure of TATB under shock loading from transient Raman spectroscopic technique

By combination of the transient Raman spectroscopic measurement and the density functional theoretical calculations,the structural evolution and stability of TATB under shock compression was investigated.Due to the improvement in synchronization control between two-stage light gas gun and the transient Raman spectra acquisition,as well as the sample preparation,the Raman peak of the N-O mode of TATB was firstly observed under shock pressure up to 13.6 GPa,noticeably higher than the upper limit of 8.5 GPa reported in available literatures.By taking into account of the continuous shift of the main peak and other observed Raman peaks,we did not distinguish any structural transition or any new species.Moreover,both the present Raman spectra and the time-resolved radiation of TATB during shock loading showed that TATB exhibits higher chemical stability than previous declaration.To reveal the detailed structural response and evolution of TATB under compression,the density functional theoretical calculations were conducted,and it was found that the pressure make N-O bond lengths shorter,nitro bond angles larger,and intermolecular and intra-molecular hydrogen bond interactions enhanced.The observed red shift of Raman peak was ascribed to the abnormal enhancement of H-bound effect on the scissor vibration mode of the nitro group.

Simplified design of rock cavern concrete lining to resist shock loading

A simplified method was proposed for the design of concrete lining in underground rock cavern/tunnel against shock loading. The loading may result from the detonation of explosives on ground surface or ground penetration projectiles exploding adjacent to the cavern/tunnel. The resulting problem necessitates the solution of the dynamics of a beam loaded by a transient pressure uniformly distributed over the span. According to mechanical characteristics of the system with rock bolt and shotcrete, a dynamic support design method based on equivalent single degree of freedom （SDOF） was put forward. The SDOF method was applied to obtaining the maximum displacement at the mid-span of the beam, which is often the controlling factor in the blast-resistant design. In the formulation of the problem, the proposed method combines the phenomena of spalling and structural dynamics theory. An example is provided to demonstrate the applicability of this simplified method.

Spall in Aluminium with Helium Bubbles under Laser Shock Loading

The spallation behaviors of Al＋0.2wt% ^10B targets and neutron irradiated Al＋0.2wt% ^10B targets with 5nm radius helium bubble subjected to direct laser ablation are presented. It is found that the spall strength increases significantly with the tensile strain rate, and the helium bubble or boron inclusions in aluminum reduces the spall strength of materials by 34%. However, slight difference is observed in the spall strength of unirradiated samples compared with the irradiated sample with helium bubbles.

Phase Transformations in ZrO_2 after Shock Loading

The effects of shock loading on the morphology,grain growth during heating and phase transforma- tion of ZrO_2 have been investigated.It is shown that shock loading may be efficiently used to modify submicron ceramic powders with nanocrystalline structure.After shock loading,the critical diameter of ZrO_2 particles transformed from tetragonal to monoclinic decreased due to stored strain energy. Annealing of powders resulted in reversible transformation to the tetragonal without considerable grain growth up to 1200℃.

Plasticity and melting characteristics of metal Al with Ti-cluster under shock loading

Impurity agglomeration has a significant influence on shock response of metal materials.In this paper,the mechanism of Ti-clusters in metal Al under shock loading is investigated by non-equilibrium molecular dynamics simulations.Our results show that the Ti-cluster has obvious effects on the dislocation initiation and melting of bulk Al.First,the Ti clusters induces the strain concentrate and leads the dislocations to be initiated from the interface of Ti cluster.Second,dislocation distribution from the Ti-cluster model results in a formation of a grid-like structure,while the dislocation density is reduced compared with that from the perfect Al model.Third,the critical shock velocity of dislocation from the Ti-cluster model is lower than from perfect Al model.Furthermore,it is also found that the temperature near the interface of Ti-cluster is100 K–150 K higher than in the other areas,which means that Ti-cluster interface melts earlier than the bulk area.

Stress Analysis of Printed Circuit Board with Different Thickness and Composite Materials Under Shock Loading

In this study,the deformation and stress distribution of printed circuit board(PCB)with different thickness and composite materials under a shock loading were analyzed by the finite element analysis.The standard 8-layer PCB subjected to a shock loading 1500 g was evaluated first.Moreover,the finite element models of the PCB with different thickness by stacking various number of layers were discussed.In addition to changing thickness,the core material of PCB was replaced from woven E-glass/epoxy to woven carbon fiber/epoxy for structural enhancement.The non-linear material property of copper foil was considered in the analysis.The results indicated that a thicker PCB has lower stress in the copper foil in PCBs under the shock loading.The stress difference between the thicker PCB(2.6 mm)and thinner PCB(0.6 mm)is around 5%.Using woven carbon fiber/epoxy as core material could lower the stress of copper foil around 6.6%under the shock loading 1500 g for the PCB with 0.6 mm thickness.On the other hand,the stress level is under the failure strength of PCBs with carbon fiber/epoxy core layers and thickness 2.6 mm when the peak acceleration changes from 1500 g to 5000 g.This study could provide a reference for the design and proper applications of the PCB with different thickness and composite materials.

Dynamic strength behavior of a Zr-based bulk metallic glass under shock loading

Dynamic strength behavior of Zr51Ti5NiloCu25A19 bulk metallic glass （BMG） up to 66 GPa was investigated in a series of plate impact shock-release and shock-reload experiments. Particle velocity profiles measured at the sample/LiF window interface were used to estimate the shear stress, shear modulus, and yield stress in shocked BMG. Beyond confirm- ing the previously reported strain-softening of shear stress during the shock loading process for BMGs, it is also shown that the softened Zr-BMG still has a high shear modulus and can support large yield stress when released or reloaded from the shocked state, and both the shear modulus and the yield stress appear as strain-hardening behaviors. The work provides a much clearer picture of the strength behavior of BMGs under shock loading, which is useful to comprehensively understand the plastic deformation mechanisms of BMGs.

Robustness of anammox granular sludge treating low-strength sewage under various shock loadings:Microbial mechanism and little N2O emission

With the increasing application of anammox for the treatment of high-strength industrial wastewater,application of anammox in municipal sewage has been gaining more attention.Sludge granulation in particular enhances the enrichment and retention of anammox bacteria in municipal sewage treatment systems.However,the performance of granular sludge under continuous and varying hydraulic loading shock remains little understood.In this study,the robustness of anammox granular sludge in treating lowstrength municipal sewage under various shock loadings was investigated.Results showed that an upflow anaerobic sludge blanket(UASB)reactor with anammox granules performed well,with anammox specific activity up to 0.28 kg N/kg VSS/day and anti-loading shock capability up to 187.2 L/day during the 8-month testing period.The accumulation rate of N2O(<0.01 kg N/kg VSS/day)in the liquid phase was seven times higher than that of the gas phase,which could be mainly attributed to the incomplete denitrification and insufficient carbon source.However,only a small part of the produced N2O escaped into the atmosphere.High-throughput sequencing and molecular ecological network analyses also identified the bacterial diversity and community structure,indicating the potential resistance against loading shock.The composition and structural analyses showed that polysaccharides were an important functional component in the tightly bound extracellular polymeric substances(TB-EPS),which was the major EPS layer of anammox granules.Scanning electron microscopy(SEM)also showed that the gaps in between the anammoxclusters in the granules inhibit the flotation of the sludge and ensure efficient settling and retention of anammox granules.

Experimental Study on the Dynamic Mechanical Properties of Reinforced Concrete under Shock Loading

A simple experimental method was introduced to study the mechanical properties of reinforced concrete under shock loading. The one-stage light gas gun was used to test the me- chanical properties of reinforced concrete with different reinforcement ratios under various impact velocities. Three Mn-Cu piezoresistive pressure gauges embedded in the target were used to record the voltage-time signals, from which the stress-strain curves of reinforced concrete were obtained using Lagrangian analysis. Experimental results indicated that the load-bearing capacities of re- inforced concrete increased greatly with the impact velocity and the reinforcement ratio. The peak stress of the shock wave decreased exponentially with the propagation distance.

Dynamic response and damage evolution of Zr-based bulk metallic glass under shock loading

Dynamic response and damage evolution of Zr_(70)Cu_(13)Ni_(9.8)Al_(3.6)Nb_(3.4)Y_(0.2) bulk metallic glass(Zr-based BMG)under impact pressure ranging from 4.03 GPa to 27.22 GPa were studied.The Hugoniot Elastic Limit(HEL)and the spalling Strength(σ_(sp))were measured as 7.09 GPa and 2.28 GPa,and the curve of impact velocity(D)and particle velocity(u)were also obtained.Under the strain rate of~10^(5)s^(-1),local crystallization phenomenon was observed.As increasing the impact pressure,the failure mode of Zr-based BMG changed from spallation to fragmentation caused by the combination of spalling cracks and longitudinal cracks.Cone-cup structures were also observed in the internal spalling zone via nano-CT characterization.When increasing the impact pressure,the thickness of Zr-based BMG increased after impact and the remelting and cladding layers were also observed on the fracture surfaces.The fragments of the specimen were welded after impact due to the high temperature remelting,which causes plastic deformation of Zr-based BMG under shock loading.

Influence of structural factors on the strength properties of aluminum alloys under shock wave loading

The results of measurements of the strength characteristics-Hugoniot elastic limit and spall strength of aluminum and aluminum alloys in different structural states under shock wave loading are presented.Single-crystals and polycrystalline technical grade aluminumА1013 and aluminum alloysА2024,АА6063Т6,А1421,A7,А7075,А3003,A5083,АА1070 in the initial coarse-grained state and ultrafine-grained or nanocrystalline structural state were investigated.The refinement of the grain structure was carried out by different methods of severe plastic deformation such as Equal Chanel Angular Pressing,Dynamic Channel Angular Pressing,High-Pressure Torsion and Accumulative Roll-Bonding.The strength characteristics of shock-loaded samples in different structural states were obtained from the analysis of the evolution of the free surface velocity histories recorded by means of laser Doppler velocimeter VISAR.The strain rates before spall fracture of the samples were in the range of 10^(4)-10^(5 )s^(-1),the maximum pressure of shock compression did not exceed 7 GPa.The results of these studies clearly demonstrate the influence of structural factors on the resistance to high-rate deformation and dynamic fracture,and it is much less than under the static and quasi-static loading.

Investigation on the Shock Response of Vitreous Carbon

The dynamic response of vitreous carbon to uniaxial strain loading has been investigated by means of the plate impact experiments. The two x cut shorted quartz gauges assembled with impactor and target were used to obtain the wave speeds in material and the stress histories at the sample gauge interface. The wave speed and stress histories were analyzed to determine the peak state in the sample. For compressive stress up to 4 0 GPa, the wave profiles were observed to be simple and steady, the uniaxial strain response is essentially nonlinear elastic, and no inelastic deformation has been found. All the experiment results indicate that the Hugoniot curve of vitreous carbon is concave downward just like that of fused silicon. There is no shock wave but the compressed wave propagating in the impacted samples.

Performance of a double-layer BAF using zeolite and ceramic as media under ammonium shock load condition

An experiment was carried out to investigate the anti-ammonium shock load capacity of a biological aerated filter （BAF） composed of a double-layer bed. This bed was made up of a top layer of ceramic and a bottom layer of zeolite. The experiment shows that the anti-ammonium shock load process can be divided into two processes： adsorption and release. In the adsorption process, the total removal efficiency of ammonia nitrogen by zeolite and ceramic was 94%. In the release process, the ammonia nitrogen concentration increased significantly and then gradually returned to the normal level four hours after the shock load. The results indicated that the double-layer BAF had a high level of adaptability to the short-term ammonium shock load and long-term operation. The main factors influencing the dynamic process of ammonia nitrogen adsorption were the filter bed height, ammonia nitrogen concentration of influent, and flow rate. The bed depth service time （BDST） model was used to predict the relationship between the filter bed height and breakthrough time at different flow rates, and the results are reliable.

Effect of Salinity Variations on the Performance of Activated Sludge System

To investigate the influence of salinity variations on the performance of activated sludge systems, treating domestic wastewater. Methods The completely mixed reactor was used and operated in a batch-wise mode. The activated sludge taken from the Gaobeidian Wastewater Treatment Plant was used as a seeding sludge. Total organic carbon (TOC), oxygen uptake rate (OUR) and suspended solids (SS) were used as parameters to characterize the performance of the treatment systems. TOC was measured using a TOC-analyzer (TOC-5000, Japan). The OUR value was measured with a dissolved oxygen meter (YSI model-58). SS was measured gravimetrically. Results The TOC removal efficiency and the OUR value of activated sludge were not deteriorated when the NaCl shock concentration was less than 0.5 g/L. However, when the NaCl shock concentrations were up to 10g/L and 20 g/L, the OUR of activated sludge was reduced by 35% and TOC removal efficiency was dropped by 30%, compared with the control experiment without NaCl shock loading. Conclusion The effect of NaCl shock loading on the activated sludge wastewater treatment system is dependant upon the NaCl concentrations and the degree of influence can be inferred through the change of substrate utilization rate at different shock NaCl loadings.

Study of velocity effects on parachute inflation performance based on fluid-structure interaction method

The inflation of a five-ring cone parachute with the airflow velocity of 18 m/s is studied based on the simplified arbitrary Lagrange Euler （SALE）/fluid-structure interaction （FSI） method. The numerical results of the canopy shape, stability, opening load, and drag area are obtained, and they are well consistent with the experimental data gained from wind tunnel tests. The method is then used to simulate the opening process under different velocities. It is found that the first load shock affected by the velocity often occurs at the end of the initial inflation stage. For the first time, the phenomena that the inflation distance proportion coefficient increases and the dynamic load coefficient decreases, respectively, with the increase in the velocity are revealed. The above proposed method is competent to solve the large deformation problem without empirial coefficients, and can collect more space-time details of fluid-structure-motion information when it is compared with the traditional method.

Soil-Structure Interaction Effects on Dynamic Behaviour of Transmission Line Towers

As inferred from earthquake engineering literature,considering soil structure interaction(SSI)effects is important in evaluating the response of transmission line towers(TLT)to dynamic loads such as impulse loads.The proposed study investigates the dynamic effects of SSI on TLT behavior.Linear and non-linearmodels are studied.In the linearmodel,the soil is represented by complex impedances,dependent of dynamic frequency,determined from numerical simulations.The nonlinearmodel considers the soil non-linear behavior in its material constitutive law and foundation uplift in a non-linear time history analysis.The simplified structure behavior of a typical lattice transmission tower is assessed.The analysis of frequency and time domain are followed through varying soil stiffness and damping values.Three different shock durations are investigated.The soil-structure system with equivalent dynamic properties is determined.The behaviors achieved utilizing a rigid and a flexible base for the structures is compared to estimate the impact of taking SSI into account in the calculation.The current mainstream approach in structural engineering,emphasizing the importance of the SSI effect,is illustrated using an example where the SSI effect could be detrimental to the structure.Furthermore,the non-linear analysis results are analyzed to show the linear approach’s limitations in the event of grand deformations.

Development and Control Strategy of Subsea All-Electric Actuators

The development of subsea all-electric Christmas trees is an area of focus in the offshore oil industry worldwide.The main difficulties are associated with the development and control strategies for subsea all-electric actuators,which are the most criti-cal components of subsea Christmas trees.A single-motor-level fuzzy PID control with an integrated working condition detection mod-ule and a three-motor redundant-level deviation strategy with coupled joint synchronous control were proposed in this paper to real-ize the real time determination of algorithm parameters according to the working conditions,solve the rapid redistribution problems,and maintain the fast speed of the servo motor of the subsea all-electric tree valve actuator.A synchronous control electrical system was built,tested,and verified through simulation analysis.Test results show that the two redundant servo motors can still control the all-electric valve actuator and provide good synchronization control capabilities despite the failure of one servo motor,and the verti-cal and horizontal vibration values of the system are within reasonable ranges.The synchronous control strategy can be applied to the synchronous control problem of subsea all-electric production systems,which is of considerable importance for the development of subsea all-electric production systems.

Rgwo performances of submerged membrane bioreactor treating brewery wastewater: A laboratory study

Performances of submerged membrane bioreactor （SMBR） treating brewery wastewater were investigated in this study. With little variation of COD：TN：TP ratio （100：5：1） in influent, SMBR showed high removal efficiency （ 〉 90% ） for both COD and NH4^＋ - N, and it also showed a strong resistive ability for shock organics loading rate, evidenced by no obvious fluctuation for COD in the effluent when the organics loading rate suddenly increased from 0. 27 g/（ gMLSS · d） to 0. 54 g/（ gMLSS · d）. Comparatively different with the COD removal, TN and TP removal showed a strong correlation with the growth stage of the sludge in SMBR. When the sludge was in the multiplication stage, about 45% of TN was removed and an average removal efficiency of 30% for TP was also observed. However, when the activated sludge was in the steady stage, the removal efficiency for TN decreased to about 30% , whereas, the removal efficiency for TP was very low, and sometimes even below zero. The results of GC/MS indicated that the residual organic matters in the effluent were mainly alkyl hydrocarbon with high molecular weight, and coupling with the results of electroseopic scanning, it is speculated that biomass formed at external and internal membrane fibers played an important role for the removal of small organics.

The response of structure and nitrogen removal function of the biofilm on submerged macrophytes to high ammonium in constructed wetlands

The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands(CWs).The effects of high ammonium shocks on submerged macrophytes and epiphytic biofilms on the leaves of submerged macrophytes in CWs were rarely mentioned in previous studies.In this paper,the 16S rRNA sequencing method was used to investigate the variation of the microbial communities in biofilms on the leaves of Vallisneria natans plants while the growth characteristics of V.natans plants were measured at different initial ammonium concentrations.The results demonstrated that the total chlorophyll and soluble sugar synthesis of V.natans plants decreased by 51.45%and 57.16%,respectively,and malondialdehyde content increased threefold after8 days if the initial NH_(4)^(+)-N concentration was more than 5 mg/L.Algal density,bacterial quantity,dissolved oxygen,and pH increased with high ammonium shocks.The average removal efficiencies of total nitrogen and NH_(4)^(+)-N reached 73.26%and 83.94%,respectively.The heat map and relative abundance analysis represented that the relative abundances of phyla Proteobacteria,Cyanobacteria,and Bacteroidetes increased.The numbers of autotrophic nitrifiers and heterotrophic nitrification aerobic denitrification(HNAD)bacteria expanded in biofilms.In particular,HNAD bacteria of Flavobacterium,Hydrogenophaga,Acidovorax,Acinetobacter,Pseudomonas,Aeromonas,and Azospira had higher abundances than autotrophic nitrifiers because there were organic matters secreted from declining leaves of V.natans plants.The analysis of the nitrogen metabolic pathway showed aerobic denitrification was the main nitrogen removal pathway.Thus,the nitrification and denitrification bacterial communities increased in epiphytic biofilms on submerged macrophytes in constructed wetlands while submerged macrophytes declined under ammonium shock loading.

Performance of biotrickling filters for hydrogen sulfide removal under starvation and shock loads conditions

In the industrial operation of biotrickling filters for hydrogen sulfide(H2S) removal,shock loads or starvation was common due to process variations or equipment malfunctions.In this study,effects of starvation and shock loads on the performance of biotrickling filters for H2S removal were investigated.Four experiments were conducted to evaluate the changes of biomass and viable bacteria numbers in the biotrickling filters during a 24-d starvation.Compared to biomass,viable bacteria numbers decreased significantly during the starvation,especially when airflow was maintained in the absence of spray liquid.During the subsequent re-acclimation,all the bioreactors could resume high removal efficiencies within 4 d regardless of the previous starvation conditions.The results show that the re-acclimation time,in the case of biotrickling filters for H2S removal,is mainly controlled by viable H2S oxidizing bacteria numbers.On the other hand,the biotrickling filters can protect against shock loads in inlet fluctuating H2S concentration after resuming normal operation.When the biotrickling filters were supplied with H2S at an input of lower than 1700 mg/m3,their removal efficiencies were nearly 98% regardless of previous H2S input.