Prototype experiments were carried out on the explosion-proof performance of the RC blast wall.The mass of TNT detonated in the experiments is 5 kg and 20 kg respectively.The shock wave overpressure was tested in diff...Prototype experiments were carried out on the explosion-proof performance of the RC blast wall.The mass of TNT detonated in the experiments is 5 kg and 20 kg respectively.The shock wave overpressure was tested in different regions.The above experiments were numerically simulated,and the simulated shock wave overpressure waveforms were compared with that tested and given by CONWEP program.The results show that the numerically simulated waveform is slightly different from the test waveform,but similar to CONWEP waveform.Through dimensional analysis and numerical simulation under different working conditions,the equation for the attenuation rate of the diffraction overpressure behind the blast wall was obtained.According to the corresponding standards,the degree of casualties and the damage degree of the brick concrete building at a certain distance behind the wall can be determined when parameters are set.The above results can provide a reference for the design and construction of the reinforced concrete blast wall.展开更多
In recent years,explosion shock wave has been considered as a signature injury of the current military conflicts.Although strong shock wave is lethal to the human body,weak shock wave can cause many more lasting conse...In recent years,explosion shock wave has been considered as a signature injury of the current military conflicts.Although strong shock wave is lethal to the human body,weak shock wave can cause many more lasting consequences.To investigate the protection ability and characteristics of flexible materials and structures under weak shock wave loading,the blast wave produced by TNT explosive is loaded on the polyurethane foam with the density of 200.0 kg/m3(F-200)and 400.0 kg/m3(F-400),polyurea with the density of 1100.0 kg/m^(3)(P-1100)and structures composed of the two materials,which are intended for individual protection.Experimental results indicate that the shock wave is attenuated to weak pressure disturbance after interacting with the flexible materials which are not damaged.The shock wave protective capability of single-layer materials is dependent on their thickness,density and microscopic characteristics.The overpressure,maximum pressure rise rate and impulse of transmitted wave decrease exponentially with increase in sample thickness.For the same thickness,F-400 provides better protective capability than F-200 while P-1100 shows the best protective capability among the three materials.In this study,as the materials are not destroyed,F-200 with a thickness more than10.0 mm,F-400 with a thickness more than 4.0 mm,and P-1100 with a thickness more than 1.0 mm can attenuate the overpressure amplitude more than 90.0%.Further,multi-layer flexible composites are designed.Different layer layouts of designed structures and layer thickness of the single-layer materials can affect the protective performance.Within the research range,the structure in which polyurea is placed on the impact side shows the optimal shock wave protective performance,and the thicknesses of polyurea and polyurethane foam are 1.0 mm and 4.0 mm respectively.The overpressure attenuation rate reached maximum value of 93.3%and impulse attenuation capacity of this structure are better than those of single-layer polyurea and polyurethane foam with higher areal density.展开更多
Porous materials are widely used in the field of protection because of their excellent energy absorption characteristics.In this work,a series of polyurethane microscopic models are established and the effect of poros...Porous materials are widely used in the field of protection because of their excellent energy absorption characteristics.In this work,a series of polyurethane microscopic models are established and the effect of porosity on the shock waves is studied with classical molecular dynamics simulations.Firstly,shock Hugoniot relations for different porosities are obtained,which compare well with the experimental data.The pores collapse and form local stress wave,which results in the complex multi-wave structure of the shock wave.The microstructure analysis shows that the local stress increases and the local velocity decreases gradually during the process of pore collapse to complete compaction.Finally,it leads to stress relaxation and velocity homogenization.The shock stress peaks can be fitted with two exponential functions,and the amplitude of attenuation coefficient decreases with the increase of density.Besides,the pore collapse under shock or non-shock are discussed by the entropy increase rate of the system.The energy is dissipated mainly through the multiple interactions of the waves under shock.The energy is dissipated mainly by the friction between atoms under non-shock.展开更多
The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of th...The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle jet.Specifically,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of vortices.In this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving body.We designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving body.We also considered models without a constrained track for the sake of comparison.The results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the muzzle.Because the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric characteristics.This in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been identical.The results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving body.The work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch system.It also sheds light on the technical bottlenecks that need to be considered to recover high-value warheads.展开更多
There are great differences in the distribution characteristics of shock waves produced by ammunition explosions at different altitudes.At present,there are many studies on plain explosion shock waves,but there are fe...There are great differences in the distribution characteristics of shock waves produced by ammunition explosions at different altitudes.At present,there are many studies on plain explosion shock waves,but there are few studies on the distribution characteristics of plateau explosion shock waves,and there is still a lack of complete analysis and evaluation methods.This paper compares and analyzes shock wave overpressure data at different altitudes,obtains the attenuation effect of different altitudes on the shock wave propagation process and proposes a calculation formula for shock wave overpressure considering the effect of altitude.The data analysis results show that at the same TNT equivalent and the same distance from the measuring point,the shock wave overpressure at high altitude is lower than that at low altitude.With the increase in the explosion center distance of the measuring point,the peak attenuation rate of the shock wave overpressure at high altitudes is smaller than that at low altitudes,and the peak attenuation rate of the shock wave overpressure at high altitudes gradually intensifies with increasing proportional distance.The average error between the shock wave overpressure and measured shock wave overpressure in a high-altitude environment obtained by using the above calculation formula is 11.1389%.Therefore,this method can effectively predict explosion shock wave overpressure in plateau environments and provides an effective calculation method for practical engineering tests.展开更多
BACKGROUND Active myofascial trigger points(TrPs)often occur in the upper region of the upper trapezius(UT)muscle.These TrPs can be a significant source of neck,shoulder,and upper back pain and headaches.These TrPs an...BACKGROUND Active myofascial trigger points(TrPs)often occur in the upper region of the upper trapezius(UT)muscle.These TrPs can be a significant source of neck,shoulder,and upper back pain and headaches.These TrPs and their related pain and disability can adversely affect an individual’s everyday routine functioning,work-related productivity,and general quality of life.AIM To investigate the effects of instrument assisted soft tissue mobilization(IASTM)vs extracorporeal shock wave therapy(ESWT)on the TrPs of the UT muscle.METHODS A randomized,single-blind,comparative clinical study was conducted at the Medical Center of the Egyptian Railway Station in Cairo.Forty patients(28 females and 12 males),aged between 20-years-old and 40-years-old,with active myofascial TrPs in the UT muscle were randomly assigned to two equal groups(A and B).Group A received IASTM,while group B received ESWT.Each group was treated twice weekly for 2 weeks.Both groups received muscle energy technique for the UT muscle.Patients were evaluated twice(pre-and posttreatment)for pain intensity using the visual analogue scale and for pain pressure threshold(PPT)using a pressure algometer.RESULTS Comparing the pre-and post-treatment mean values for all variables for group A,there were significant differences in pain intensity for TrP1 and TrP2(P=0.0001)and PPT for TrP1(P=0.0002)and TrP2(P=0.0001).Also,for group B,there were significant differences between the pre-and post-treatment pain intensity for TrP1 and TrP2 and PPT for TrP1 and TrP2(P=0.0001).There were no significant differences between the two groups in the post-treatment mean values of pain intensity for TrP1(P=0.9)and TrP2(P=0.76)and PPT for TrP1(P=0.09)and for TrP2(P=0.91).CONCLUSION IASTM and ESWT are effective methods for improving pain and PPT in patients with UT muscle TrPs.There is no significant difference between either treatment method.展开更多
In this paper,we study the shock waves for a mixed-type system from chemotaxis.We are concerned with the jump conditions for the left state which is located in the elliptical region and the right state in the hyperbol...In this paper,we study the shock waves for a mixed-type system from chemotaxis.We are concerned with the jump conditions for the left state which is located in the elliptical region and the right state in the hyperbolic region.Under the generalized entropy conditions,we find that there are different shock wave structures for different parameters.To guarantee the uniqueness of the solutions,we obtain the admissible shock waves which satisfy the generalized entropy condition in both parameters.Finally,we construct the Riemann solutions in some solvable regions.展开更多
Energy output and heating effects are essential for vapor-liquid fuel/air cloud detonation in the fuel-air explosive(FAE) applications or explosion accidents. The purpose of this study is to examine the dynamic large-...Energy output and heating effects are essential for vapor-liquid fuel/air cloud detonation in the fuel-air explosive(FAE) applications or explosion accidents. The purpose of this study is to examine the dynamic large-size flame behavior, shock wave propagation law, and instantaneous thermal field generated by unconfined vapor-liquid propylene oxide(PO)/air cloud detonation. Based on computational fluid dynamics(CFD) and combustion theory, a numerical simulation is used to study the detonation process of a PO/air cloud produced by a double-event fuel-air explosive(DEFAE) of 2.16 kg. The large-scale flame behavior is characterized. The flame initially spreads radially and laterally in a wing shape. Subsequently,the developed flame increases with a larger aspect ratio. Moreover, the propagation laws of shock waves at different heights are discussed. The peak pressure of 1.3 m height level with a stepwise decline is obviously different from that of the ground with an amplitude of reversed ’N’ shape. In the vast majority of the first 6.9 m, the destructive effect of the shock wave near the ground is greater than that of the shock wave at 1.3 m height. Furthermore, the dynamic instantaneous isothermal field is demonstrated.The scaling relationship of various isotherms in the instantaneous thermal field with the flame and initial cloud is summarized. The comprehensive numerical model used in this study can be applied to determine the overpressure and temperature distribution in the entire fuel/air cloud detonation field,providing guidance for assessing the extent of damage caused by DEFAE detonation.展开更多
Shock tube experiments were carried out to investigate dynamic behavior of Ultra-high hardness(UHH)steel and Aluminium(Al) sheets of 0.8 mm thickness at 0.55, 0.9 and 1.18 MPa peak-over pressure.Experimental results s...Shock tube experiments were carried out to investigate dynamic behavior of Ultra-high hardness(UHH)steel and Aluminium(Al) sheets of 0.8 mm thickness at 0.55, 0.9 and 1.18 MPa peak-over pressure.Experimental results showed that center point deflection increases with an increase in peak-over pressure for Al sheets. However, UHH steel sheets showed negligible deformation when loaded at low peak-over pressures and showed sudden brittle failure at high peak-over pressures. Similar results were obtained by quasi-static testing, UHH steel failed abruptly while Al showed ductile behavior. Results from literature indicate that to protect structures against shock loading it is necessary that they dissipate energy via plastic deformation. The Al sheets were shown to deform plastically both in quasi-static and shock loading. Thus, hardness along with ductility is required to dissipate supersonic shock waves.展开更多
This paper is concerned with an ideal polytropic model of non-viscous and heatconductive gas in a one-dimensional half space. We focus our attention on the outflow problem when the flow velocity on the boundary is neg...This paper is concerned with an ideal polytropic model of non-viscous and heatconductive gas in a one-dimensional half space. We focus our attention on the outflow problem when the flow velocity on the boundary is negative and we prove the stability of the viscous shock wave and its superposition with the boundary layer under some smallness conditions.Our waves occur in the subsonic area. The intrinsic properties of our system are more challenging in mathematical analysis, however, in the subsonic area, the lack of a boundary condition on the density provides us with a special manner for defining the shift for the viscous shock wave, and helps us to construct the asymptotic profiles successfully. New weighted energy estimates are introduced and the perturbations on the boundary are handled by some subtle estimates.展开更多
BACKGROUND Approximately 65%-78%of patients with a spinal cord injury(SCI)develop any symptom of spasticity.The aim of this study was to investigate the tolerability and short-term effects of radial extracorporeal sho...BACKGROUND Approximately 65%-78%of patients with a spinal cord injury(SCI)develop any symptom of spasticity.The aim of this study was to investigate the tolerability and short-term effects of radial extracorporeal shock wave therapy(r ESWT)on plantar flexor spasticity in a patient with incomplete SCI.CASE SUMMARY An 18-year-old man with an incomplete SCI completed five sessions of r ESWT.The primary outcomes were the changes in ankle-passive range of motion(APROM)and passive resistive force to ankle dorsiflexion.The outcomes were assessed at baseline(T0),immediately after treatment(T1)and 1 wk after the end of treatment(T2).The A-PROM increased by 15 degrees at T1 and 25 degrees at T2 compared with T0.The passive resistive force to ankle dorsiflexion at low velocity decreased by 33%at T1 and 55%at T2 in the gastrocnemius muscle and by 41%at T1 and 39%at T2 in the soleus muscle compared with T0.At high velocity,it also decreased by 44%at T1 and 30%at T2 in the gastrocnemius muscle compared with T0.However,in the soleus muscle,the change was minor,with a decrease of 12%at T1 and increased by 39%at T2 compared with T0.CONCLUSION In this patient,the findings showed that r ESWT combined with conventional therapy was well-tolerated and could be effective in improving A-PROM and passive resistive force to ankle dorsiflexion in the short-term.Further randomized controlled clinical trials with longer period of follow-up are necessary to confirm the results obtained in patients with SCI.展开更多
Double pulsed-laser-ablation is a promising method to prepare nanoparticle composites. The backward movement of the plume after the collision with counter-propagating shock wave has been observed in experiments. In th...Double pulsed-laser-ablation is a promising method to prepare nanoparticle composites. The backward movement of the plume after the collision with counter-propagating shock wave has been observed in experiments. In the present study, collision dynamics of the oppositely injected Si and Ge jets into a He background gas was numerically calculated as a simulation for double pulsed-laser-ablation. The experimentally observed backward movement was reproduced. The effect of distance between two jet exits on the distance of backward movement of the jet, B<sub>L</sub>, after the collision with the counter-propagating shock front was calculated to discuss the collision dynamics and to optimize the target distance for the experiment. We found that B<sub>L </sub>does not decrease monotonically with increasing distance between two jet exits, but has a maximum value at a certain distance. This behavior is discussed by calculating the expansion dynamics of an individual jet. Shock wave grows with time at the initial stage of the jet expansion and then attenuates;the density just behind the shock front for individual jet has a maximum value at a certain time and position. B<sub>L</sub> has a maximum value when the densities just behind the shock fronts for the individual jets have maximum values. This result is important for designing the appropriate distance between the two jet exits, i.e., the distance between the targets of double pulsed-laser-ablation.展开更多
AIM To compare the efficacy of a session of extracorporeal shock wave lithotripsy(ESWL) before endoscopic retrograde cholangiopancreatography(ERCP) vs ERCP only for problematic and large common bile duct(CBD) stones.M...AIM To compare the efficacy of a session of extracorporeal shock wave lithotripsy(ESWL) before endoscopic retrograde cholangiopancreatography(ERCP) vs ERCP only for problematic and large common bile duct(CBD) stones.METHODS Adult patients with CBD stones for whom initial ERCP was unsuccessful because of the large size of CBD stones were identified. The patients were randomized into two groups,an "ESWL + ERCP group" and an "ERCP-only" group. For ESWL + ERCP cases,ESWL was performed prior to ERCP. Clearance of the CBD,complications related to the ESWL/ERCP procedure,frequency of mechanical lithotripsy use and duration of the ERCP procedure were evaluated in both groups.RESULTS There was no significant difference in baseline characteristics between the two groups. A session of ESWL before ERCP compared with ERCP only resulted in similar outcomes in terms of successful stone removal within the first treatment session(74.2% vs 71.0%,P = 0.135),but a higher clearance rate within the second treatment session(84.4% vs 51.6%,P = 0.018) and total stone clearance(96.0% vs 86.0%,P = 0.029). Moreover,ESWL prior to ERCP not only reduced ERCP procedure time(43 ± 21 min vs 59 ± 28 min,P = 0.034) and the rate of mechanical lithotripsy use(20% vs 30%,P = 0.025),but also raised the clearance rate of extremely large stones(80.0% vs 40.0%,P = 0.016). Post-ERCP complications were similar for the two groups.CONCLUSION Based on the higher rate of successful stone removal and minimal complications,ESWL prior to ERCP appears to be a safe and effective treatment for the endoscopic removal of problematic and large CBD stones.展开更多
Metal sheet plastic deformation or forming is gener at ed through a mechanical pressure or a thermal variation. These pressure variatio ns or thermal variations can be created by a variety of means such as press form ...Metal sheet plastic deformation or forming is gener at ed through a mechanical pressure or a thermal variation. These pressure variatio ns or thermal variations can be created by a variety of means such as press form ing, hydroforming, imploding detonation and so on. According to the magnitude of the strain rates all these forming methods can be divided into quasi-static fo rming and dynamical forming. Up to now there are no reports of forming methods w ith the strain rates above 10 5sec -1, even though the exploding forming. In this article, we work on a dynamic super-speed forming method driven by lase r shock waves and advanced a novel concept of laser shock forming. The initial o bservation of the laser shock forming is done through a bugle testing with speci mens of SUS430 sheet metal, using a neodymium-glass laser of pulse energy 10J～ 3 0J and duration of 20 ns (FWHM). The investigation revealed that the plastic de formation during the laser shock forming is characterized as ultrahigh strain ra te up to 10 7sec -1. We indicate that plastic deformation increases nonlin early when the energy density of the laser varies. By investigating the hardness and residual stress of the surfaces, we conclude that laser shock forming is a combination technique of laser shock strengthening and metal forming for introdu cing a strain harden and a compressive residual stress on the surface of the wor k-piece, and the treated surface by laser shock forming has good properties in fatigue and corrosion resistance. This technique can achieve forming wit h or without mould.展开更多
For over 35 years shock wave lithotripsy has proven to be an effective,safe and truly minimally invasive option for the treatment of nephrolithiasis.Various technical factors as well as patient selection can impact th...For over 35 years shock wave lithotripsy has proven to be an effective,safe and truly minimally invasive option for the treatment of nephrolithiasis.Various technical factors as well as patient selection can impact the success of the procedure.We used published work focusing on outcomes of shock wave lithotripsy,risk of complications,and strategies for improving stone fragmentation to create this review.Multiple patient and technical factors have been found to impact success of treatment.Skin to stone distance,stone density and composition,size and location of the stone within the urinary system all influence stone free rates.A slower rate with a gradual increasing voltage,precise targeting,proper coupling will improve stone fragmentation and decrease risk of complications.The selection of appropriate patients through a shared decision making process and attention to the technical factors that improve stone free rates is key to providing an effective treatment and patient satisfaction.展开更多
BACKGROUND One of the most common complications following surgery for midshaft clavicle fracture is nonunion/delayed union.Extracorporeal shock wave therapy(ESWT)is an alternative to promote new bone formation without...BACKGROUND One of the most common complications following surgery for midshaft clavicle fracture is nonunion/delayed union.Extracorporeal shock wave therapy(ESWT)is an alternative to promote new bone formation without surgical complications.To date,no literature has reported low-intensity ESWT(LI-ESWT)in delayed union of midshaft clavicle fracture.CASE SUMMARY We reported a 66-year-old Chinese amateur cyclist with clavicle delayed union treated with 10 sessions of LI-ESWT(radial,0.057 mJ/mm^(2),3 Hz,3000 shocks).No anesthetics were applied,and no side effects occurred.At the 4 mo and 7 mo follow-ups,the patient achieved clinical and radiographical recovery,respectively.CONCLUSION In conclusion,our findings indicated that LI-ESWT could be a good option for treating midshaft clavicular delayed union.展开更多
The present study focuses on the mitigation of shock wave using novel geometric passages in the flow field.The strategy is to produce multiple shock reflections and diffractions in the passage with minimum flow obstru...The present study focuses on the mitigation of shock wave using novel geometric passages in the flow field.The strategy is to produce multiple shock reflections and diffractions in the passage with minimum flow obstruction,which in turn is expected to reduce the shock wave strength at the target location.In the present study the interaction of a plane shock front(generated from a shock tube)with various geometric designs such as,1)zig-zag geometric passage,2)staggered cylindrical obstructions and 3)zigzag passage with cylindrical obstructions have been investigated using computational technique.It is seen from the numerical simulation that,among the various designs,the maximum shock attenuation is produced by the zig-zag passage with cylindrical obstructions which is then followed by zig-zag passage and staggered cylindrical obstructions.A comprehensive investigation on the shock wave reflection and diffraction phenomena happening in the proposed complex passages have also been carried out.In the new zig-zag design,the initial shock wave undergoes shock wave reflection and diffraction process which swaps alternatively as the shock front moves from one turn to the other turn.This cyclic shock reflection and diffraction process helps in diffusing the shock wave energy with practically no obstruction to the flow field.It is found that by combining the shock attenuation ability of zig-zag passage(using shock reflection and diffraction)with the shock attenuation ability of cylindrical blocks(by flow obstruction),a drastic attenuation in shock strength can be achieved with moderate level of flow blocking.展开更多
To investigate the shock wave characteristics of RDX-based aluminized explosives,air blast tests were conducted for measuring the parameters of 10 kg aluminized explosives which contained 0-40% aluminum.The results sh...To investigate the shock wave characteristics of RDX-based aluminized explosives,air blast tests were conducted for measuring the parameters of 10 kg aluminized explosives which contained 0-40% aluminum.The results showed that with the increasing of aluminum content,the overpressures and impulses increase at first and then decrease within 7 m or 5 m,which reached the maximum when aluminum content was 20% or 30%.Power exponential formulas are used to fit the shock wave parameters vs scaled distance,where an equal weight of TNT is used to calculate the scaled distance.The overpressures of HL0 and TNT in tested locations not only conform to the similar law,but also conform to the same attenuation law after gaining the scaled distances of equal TNT mass.The pre-exponential factors of overpressure and impulse,k_p and k_I,decrease along with the increasing of Al content and keep the same pace as the calculated P_(CJ).The attenuation coefficients a_P and aIincrease a_t first and decrease later with the increasing of aluminum content,and they reached the maximal values with30% Al containing,which keeps the same pace as the calculated Q_V.展开更多
A novel third-order optimized symmetric weighted essentially non-oscillatory(WENO-OS3)scheme is used to simulate the hypersonic shock wave/boundary layer interactions.Firstly,the scheme is presented with the achieveme...A novel third-order optimized symmetric weighted essentially non-oscillatory(WENO-OS3)scheme is used to simulate the hypersonic shock wave/boundary layer interactions.Firstly,the scheme is presented with the achievement of low dissipation in smooth region and robust shock-capturing capabilities in discontinuities.The Maxwell slip boundary conditions are employed to consider the rarefied effect near the surface.Secondly,several validating tests are given to show the good resolution of the WENO-OS3 scheme and the feasibility of the Maxwell slip boundary conditions.Finally,hypersonic flows around the hollow cylinder truncated flare(HCTF)and the25°/55°sharp double cone are studied.Discussions are made on the characteristics of the hypersonic shock wave/boundary layer interactions with and without the consideration of the slip effect.The results indicate that the scheme has a good capability in predicting heat transfer with a high resolution for describing fluid structures.With the slip boundary conditions,the separation region at the corner is smaller and the prediction is more accurate than that with no-slip boundary conditions.展开更多
Objectives:To compare the efficacy of tamsulosin versus tamsulosin plus tadalafil in achieving clearance of fragments after shock wave lithotripsy(SWL)to treat renal calculi.Methods:Between January 2016 to December 20...Objectives:To compare the efficacy of tamsulosin versus tamsulosin plus tadalafil in achieving clearance of fragments after shock wave lithotripsy(SWL)to treat renal calculi.Methods:Between January 2016 to December 2017,140 patients with solitary,non-branched,non-lower calyceal renal calculus and measuring less than 20 mm and treated with SWL were randomized to tamsulosin(group A)or tamsulosin plus tadalafil(group B).Therapy was given for a period of 4 weeks.Stone clearance rate,analgesic requirement,occurrence of steinstrasse,need for auxiliary procedures(endoscopic treatment),and adverse effects of drugs were recorded.Results:The overall clearance rate was 72.5%(50/69)in the group A and 90.1%(64/71)in the group B(pZ0.007).For stones up to 12 mm,the difference in the clearance rate was significant(pZ0.039)while it was not so for stones larger than 12 mm(pZ0.151).There was no statistically significant difference between the two groups with regards to analgesic requirement(pZ0.94),occurrence of steinstrasse(pZ0.101),need for auxiliary procedures(pZ0.76),and adverse effects of the drugs(pZ0.148).Conclusion:Our study shows that adjunctive medical expulsive therapy with tamsulosin and tadalafil achieves better clearance rate than tadalafil alone in patients receiving SWL for renal stones.展开更多
基金funded by Key R&D Projects in Hubei Province (Grant No.2020BCA084)Innovative Group Project of Hubei Natural Science Foundation (Grant No.2020CFA043)。
文摘Prototype experiments were carried out on the explosion-proof performance of the RC blast wall.The mass of TNT detonated in the experiments is 5 kg and 20 kg respectively.The shock wave overpressure was tested in different regions.The above experiments were numerically simulated,and the simulated shock wave overpressure waveforms were compared with that tested and given by CONWEP program.The results show that the numerically simulated waveform is slightly different from the test waveform,but similar to CONWEP waveform.Through dimensional analysis and numerical simulation under different working conditions,the equation for the attenuation rate of the diffraction overpressure behind the blast wall was obtained.According to the corresponding standards,the degree of casualties and the damage degree of the brick concrete building at a certain distance behind the wall can be determined when parameters are set.The above results can provide a reference for the design and construction of the reinforced concrete blast wall.
基金supported by the National Natural Science Foundation of China(Grant Nos.12221002,12102233)。
文摘In recent years,explosion shock wave has been considered as a signature injury of the current military conflicts.Although strong shock wave is lethal to the human body,weak shock wave can cause many more lasting consequences.To investigate the protection ability and characteristics of flexible materials and structures under weak shock wave loading,the blast wave produced by TNT explosive is loaded on the polyurethane foam with the density of 200.0 kg/m3(F-200)and 400.0 kg/m3(F-400),polyurea with the density of 1100.0 kg/m^(3)(P-1100)and structures composed of the two materials,which are intended for individual protection.Experimental results indicate that the shock wave is attenuated to weak pressure disturbance after interacting with the flexible materials which are not damaged.The shock wave protective capability of single-layer materials is dependent on their thickness,density and microscopic characteristics.The overpressure,maximum pressure rise rate and impulse of transmitted wave decrease exponentially with increase in sample thickness.For the same thickness,F-400 provides better protective capability than F-200 while P-1100 shows the best protective capability among the three materials.In this study,as the materials are not destroyed,F-200 with a thickness more than10.0 mm,F-400 with a thickness more than 4.0 mm,and P-1100 with a thickness more than 1.0 mm can attenuate the overpressure amplitude more than 90.0%.Further,multi-layer flexible composites are designed.Different layer layouts of designed structures and layer thickness of the single-layer materials can affect the protective performance.Within the research range,the structure in which polyurea is placed on the impact side shows the optimal shock wave protective performance,and the thicknesses of polyurea and polyurethane foam are 1.0 mm and 4.0 mm respectively.The overpressure attenuation rate reached maximum value of 93.3%and impulse attenuation capacity of this structure are better than those of single-layer polyurea and polyurethane foam with higher areal density.
基金financial support from National Natural Science Foundation of China(Grant No.12172325)。
文摘Porous materials are widely used in the field of protection because of their excellent energy absorption characteristics.In this work,a series of polyurethane microscopic models are established and the effect of porosity on the shock waves is studied with classical molecular dynamics simulations.Firstly,shock Hugoniot relations for different porosities are obtained,which compare well with the experimental data.The pores collapse and form local stress wave,which results in the complex multi-wave structure of the shock wave.The microstructure analysis shows that the local stress increases and the local velocity decreases gradually during the process of pore collapse to complete compaction.Finally,it leads to stress relaxation and velocity homogenization.The shock stress peaks can be fitted with two exponential functions,and the amplitude of attenuation coefficient decreases with the increase of density.Besides,the pore collapse under shock or non-shock are discussed by the entropy increase rate of the system.The energy is dissipated mainly through the multiple interactions of the waves under shock.The energy is dissipated mainly by the friction between atoms under non-shock.
文摘The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle jet.Specifically,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of vortices.In this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving body.We designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving body.We also considered models without a constrained track for the sake of comparison.The results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the muzzle.Because the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric characteristics.This in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been identical.The results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving body.The work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch system.It also sheds light on the technical bottlenecks that need to be considered to recover high-value warheads.
文摘There are great differences in the distribution characteristics of shock waves produced by ammunition explosions at different altitudes.At present,there are many studies on plain explosion shock waves,but there are few studies on the distribution characteristics of plateau explosion shock waves,and there is still a lack of complete analysis and evaluation methods.This paper compares and analyzes shock wave overpressure data at different altitudes,obtains the attenuation effect of different altitudes on the shock wave propagation process and proposes a calculation formula for shock wave overpressure considering the effect of altitude.The data analysis results show that at the same TNT equivalent and the same distance from the measuring point,the shock wave overpressure at high altitude is lower than that at low altitude.With the increase in the explosion center distance of the measuring point,the peak attenuation rate of the shock wave overpressure at high altitudes is smaller than that at low altitudes,and the peak attenuation rate of the shock wave overpressure at high altitudes gradually intensifies with increasing proportional distance.The average error between the shock wave overpressure and measured shock wave overpressure in a high-altitude environment obtained by using the above calculation formula is 11.1389%.Therefore,this method can effectively predict explosion shock wave overpressure in plateau environments and provides an effective calculation method for practical engineering tests.
文摘BACKGROUND Active myofascial trigger points(TrPs)often occur in the upper region of the upper trapezius(UT)muscle.These TrPs can be a significant source of neck,shoulder,and upper back pain and headaches.These TrPs and their related pain and disability can adversely affect an individual’s everyday routine functioning,work-related productivity,and general quality of life.AIM To investigate the effects of instrument assisted soft tissue mobilization(IASTM)vs extracorporeal shock wave therapy(ESWT)on the TrPs of the UT muscle.METHODS A randomized,single-blind,comparative clinical study was conducted at the Medical Center of the Egyptian Railway Station in Cairo.Forty patients(28 females and 12 males),aged between 20-years-old and 40-years-old,with active myofascial TrPs in the UT muscle were randomly assigned to two equal groups(A and B).Group A received IASTM,while group B received ESWT.Each group was treated twice weekly for 2 weeks.Both groups received muscle energy technique for the UT muscle.Patients were evaluated twice(pre-and posttreatment)for pain intensity using the visual analogue scale and for pain pressure threshold(PPT)using a pressure algometer.RESULTS Comparing the pre-and post-treatment mean values for all variables for group A,there were significant differences in pain intensity for TrP1 and TrP2(P=0.0001)and PPT for TrP1(P=0.0002)and TrP2(P=0.0001).Also,for group B,there were significant differences between the pre-and post-treatment pain intensity for TrP1 and TrP2 and PPT for TrP1 and TrP2(P=0.0001).There were no significant differences between the two groups in the post-treatment mean values of pain intensity for TrP1(P=0.9)and TrP2(P=0.76)and PPT for TrP1(P=0.09)and for TrP2(P=0.91).CONCLUSION IASTM and ESWT are effective methods for improving pain and PPT in patients with UT muscle TrPs.There is no significant difference between either treatment method.
基金the National Natural Science Foundation of China(11771442)。
文摘In this paper,we study the shock waves for a mixed-type system from chemotaxis.We are concerned with the jump conditions for the left state which is located in the elliptical region and the right state in the hyperbolic region.Under the generalized entropy conditions,we find that there are different shock wave structures for different parameters.To guarantee the uniqueness of the solutions,we obtain the admissible shock waves which satisfy the generalized entropy condition in both parameters.Finally,we construct the Riemann solutions in some solvable regions.
基金supported by the National Natural Science Foundation of China ( Grant No. 11972089)。
文摘Energy output and heating effects are essential for vapor-liquid fuel/air cloud detonation in the fuel-air explosive(FAE) applications or explosion accidents. The purpose of this study is to examine the dynamic large-size flame behavior, shock wave propagation law, and instantaneous thermal field generated by unconfined vapor-liquid propylene oxide(PO)/air cloud detonation. Based on computational fluid dynamics(CFD) and combustion theory, a numerical simulation is used to study the detonation process of a PO/air cloud produced by a double-event fuel-air explosive(DEFAE) of 2.16 kg. The large-scale flame behavior is characterized. The flame initially spreads radially and laterally in a wing shape. Subsequently,the developed flame increases with a larger aspect ratio. Moreover, the propagation laws of shock waves at different heights are discussed. The peak pressure of 1.3 m height level with a stepwise decline is obviously different from that of the ground with an amplitude of reversed ’N’ shape. In the vast majority of the first 6.9 m, the destructive effect of the shock wave near the ground is greater than that of the shock wave at 1.3 m height. Furthermore, the dynamic instantaneous isothermal field is demonstrated.The scaling relationship of various isotherms in the instantaneous thermal field with the flame and initial cloud is summarized. The comprehensive numerical model used in this study can be applied to determine the overpressure and temperature distribution in the entire fuel/air cloud detonation field,providing guidance for assessing the extent of damage caused by DEFAE detonation.
文摘Shock tube experiments were carried out to investigate dynamic behavior of Ultra-high hardness(UHH)steel and Aluminium(Al) sheets of 0.8 mm thickness at 0.55, 0.9 and 1.18 MPa peak-over pressure.Experimental results showed that center point deflection increases with an increase in peak-over pressure for Al sheets. However, UHH steel sheets showed negligible deformation when loaded at low peak-over pressures and showed sudden brittle failure at high peak-over pressures. Similar results were obtained by quasi-static testing, UHH steel failed abruptly while Al showed ductile behavior. Results from literature indicate that to protect structures against shock loading it is necessary that they dissipate energy via plastic deformation. The Al sheets were shown to deform plastically both in quasi-static and shock loading. Thus, hardness along with ductility is required to dissipate supersonic shock waves.
基金the Natural Science Foundation of China(11871388)。
文摘This paper is concerned with an ideal polytropic model of non-viscous and heatconductive gas in a one-dimensional half space. We focus our attention on the outflow problem when the flow velocity on the boundary is negative and we prove the stability of the viscous shock wave and its superposition with the boundary layer under some smallness conditions.Our waves occur in the subsonic area. The intrinsic properties of our system are more challenging in mathematical analysis, however, in the subsonic area, the lack of a boundary condition on the density provides us with a special manner for defining the shift for the viscous shock wave, and helps us to construct the asymptotic profiles successfully. New weighted energy estimates are introduced and the perturbations on the boundary are handled by some subtle estimates.
基金Supported by BTL Industries Ltd.Prague,Czech Republic。
文摘BACKGROUND Approximately 65%-78%of patients with a spinal cord injury(SCI)develop any symptom of spasticity.The aim of this study was to investigate the tolerability and short-term effects of radial extracorporeal shock wave therapy(r ESWT)on plantar flexor spasticity in a patient with incomplete SCI.CASE SUMMARY An 18-year-old man with an incomplete SCI completed five sessions of r ESWT.The primary outcomes were the changes in ankle-passive range of motion(APROM)and passive resistive force to ankle dorsiflexion.The outcomes were assessed at baseline(T0),immediately after treatment(T1)and 1 wk after the end of treatment(T2).The A-PROM increased by 15 degrees at T1 and 25 degrees at T2 compared with T0.The passive resistive force to ankle dorsiflexion at low velocity decreased by 33%at T1 and 55%at T2 in the gastrocnemius muscle and by 41%at T1 and 39%at T2 in the soleus muscle compared with T0.At high velocity,it also decreased by 44%at T1 and 30%at T2 in the gastrocnemius muscle compared with T0.However,in the soleus muscle,the change was minor,with a decrease of 12%at T1 and increased by 39%at T2 compared with T0.CONCLUSION In this patient,the findings showed that r ESWT combined with conventional therapy was well-tolerated and could be effective in improving A-PROM and passive resistive force to ankle dorsiflexion in the short-term.Further randomized controlled clinical trials with longer period of follow-up are necessary to confirm the results obtained in patients with SCI.
文摘Double pulsed-laser-ablation is a promising method to prepare nanoparticle composites. The backward movement of the plume after the collision with counter-propagating shock wave has been observed in experiments. In the present study, collision dynamics of the oppositely injected Si and Ge jets into a He background gas was numerically calculated as a simulation for double pulsed-laser-ablation. The experimentally observed backward movement was reproduced. The effect of distance between two jet exits on the distance of backward movement of the jet, B<sub>L</sub>, after the collision with the counter-propagating shock front was calculated to discuss the collision dynamics and to optimize the target distance for the experiment. We found that B<sub>L </sub>does not decrease monotonically with increasing distance between two jet exits, but has a maximum value at a certain distance. This behavior is discussed by calculating the expansion dynamics of an individual jet. Shock wave grows with time at the initial stage of the jet expansion and then attenuates;the density just behind the shock front for individual jet has a maximum value at a certain time and position. B<sub>L</sub> has a maximum value when the densities just behind the shock fronts for the individual jets have maximum values. This result is important for designing the appropriate distance between the two jet exits, i.e., the distance between the targets of double pulsed-laser-ablation.
文摘AIM To compare the efficacy of a session of extracorporeal shock wave lithotripsy(ESWL) before endoscopic retrograde cholangiopancreatography(ERCP) vs ERCP only for problematic and large common bile duct(CBD) stones.METHODS Adult patients with CBD stones for whom initial ERCP was unsuccessful because of the large size of CBD stones were identified. The patients were randomized into two groups,an "ESWL + ERCP group" and an "ERCP-only" group. For ESWL + ERCP cases,ESWL was performed prior to ERCP. Clearance of the CBD,complications related to the ESWL/ERCP procedure,frequency of mechanical lithotripsy use and duration of the ERCP procedure were evaluated in both groups.RESULTS There was no significant difference in baseline characteristics between the two groups. A session of ESWL before ERCP compared with ERCP only resulted in similar outcomes in terms of successful stone removal within the first treatment session(74.2% vs 71.0%,P = 0.135),but a higher clearance rate within the second treatment session(84.4% vs 51.6%,P = 0.018) and total stone clearance(96.0% vs 86.0%,P = 0.029). Moreover,ESWL prior to ERCP not only reduced ERCP procedure time(43 ± 21 min vs 59 ± 28 min,P = 0.034) and the rate of mechanical lithotripsy use(20% vs 30%,P = 0.025),but also raised the clearance rate of extremely large stones(80.0% vs 40.0%,P = 0.016). Post-ERCP complications were similar for the two groups.CONCLUSION Based on the higher rate of successful stone removal and minimal complications,ESWL prior to ERCP appears to be a safe and effective treatment for the endoscopic removal of problematic and large CBD stones.
文摘Metal sheet plastic deformation or forming is gener at ed through a mechanical pressure or a thermal variation. These pressure variatio ns or thermal variations can be created by a variety of means such as press form ing, hydroforming, imploding detonation and so on. According to the magnitude of the strain rates all these forming methods can be divided into quasi-static fo rming and dynamical forming. Up to now there are no reports of forming methods w ith the strain rates above 10 5sec -1, even though the exploding forming. In this article, we work on a dynamic super-speed forming method driven by lase r shock waves and advanced a novel concept of laser shock forming. The initial o bservation of the laser shock forming is done through a bugle testing with speci mens of SUS430 sheet metal, using a neodymium-glass laser of pulse energy 10J～ 3 0J and duration of 20 ns (FWHM). The investigation revealed that the plastic de formation during the laser shock forming is characterized as ultrahigh strain ra te up to 10 7sec -1. We indicate that plastic deformation increases nonlin early when the energy density of the laser varies. By investigating the hardness and residual stress of the surfaces, we conclude that laser shock forming is a combination technique of laser shock strengthening and metal forming for introdu cing a strain harden and a compressive residual stress on the surface of the wor k-piece, and the treated surface by laser shock forming has good properties in fatigue and corrosion resistance. This technique can achieve forming wit h or without mould.
文摘For over 35 years shock wave lithotripsy has proven to be an effective,safe and truly minimally invasive option for the treatment of nephrolithiasis.Various technical factors as well as patient selection can impact the success of the procedure.We used published work focusing on outcomes of shock wave lithotripsy,risk of complications,and strategies for improving stone fragmentation to create this review.Multiple patient and technical factors have been found to impact success of treatment.Skin to stone distance,stone density and composition,size and location of the stone within the urinary system all influence stone free rates.A slower rate with a gradual increasing voltage,precise targeting,proper coupling will improve stone fragmentation and decrease risk of complications.The selection of appropriate patients through a shared decision making process and attention to the technical factors that improve stone free rates is key to providing an effective treatment and patient satisfaction.
基金Supported by Beijing Municipal Natural Science Foundation,No.7212117.
文摘BACKGROUND One of the most common complications following surgery for midshaft clavicle fracture is nonunion/delayed union.Extracorporeal shock wave therapy(ESWT)is an alternative to promote new bone formation without surgical complications.To date,no literature has reported low-intensity ESWT(LI-ESWT)in delayed union of midshaft clavicle fracture.CASE SUMMARY We reported a 66-year-old Chinese amateur cyclist with clavicle delayed union treated with 10 sessions of LI-ESWT(radial,0.057 mJ/mm^(2),3 Hz,3000 shocks).No anesthetics were applied,and no side effects occurred.At the 4 mo and 7 mo follow-ups,the patient achieved clinical and radiographical recovery,respectively.CONCLUSION In conclusion,our findings indicated that LI-ESWT could be a good option for treating midshaft clavicular delayed union.
文摘The present study focuses on the mitigation of shock wave using novel geometric passages in the flow field.The strategy is to produce multiple shock reflections and diffractions in the passage with minimum flow obstruction,which in turn is expected to reduce the shock wave strength at the target location.In the present study the interaction of a plane shock front(generated from a shock tube)with various geometric designs such as,1)zig-zag geometric passage,2)staggered cylindrical obstructions and 3)zigzag passage with cylindrical obstructions have been investigated using computational technique.It is seen from the numerical simulation that,among the various designs,the maximum shock attenuation is produced by the zig-zag passage with cylindrical obstructions which is then followed by zig-zag passage and staggered cylindrical obstructions.A comprehensive investigation on the shock wave reflection and diffraction phenomena happening in the proposed complex passages have also been carried out.In the new zig-zag design,the initial shock wave undergoes shock wave reflection and diffraction process which swaps alternatively as the shock front moves from one turn to the other turn.This cyclic shock reflection and diffraction process helps in diffusing the shock wave energy with practically no obstruction to the flow field.It is found that by combining the shock attenuation ability of zig-zag passage(using shock reflection and diffraction)with the shock attenuation ability of cylindrical blocks(by flow obstruction),a drastic attenuation in shock strength can be achieved with moderate level of flow blocking.
文摘To investigate the shock wave characteristics of RDX-based aluminized explosives,air blast tests were conducted for measuring the parameters of 10 kg aluminized explosives which contained 0-40% aluminum.The results showed that with the increasing of aluminum content,the overpressures and impulses increase at first and then decrease within 7 m or 5 m,which reached the maximum when aluminum content was 20% or 30%.Power exponential formulas are used to fit the shock wave parameters vs scaled distance,where an equal weight of TNT is used to calculate the scaled distance.The overpressures of HL0 and TNT in tested locations not only conform to the similar law,but also conform to the same attenuation law after gaining the scaled distances of equal TNT mass.The pre-exponential factors of overpressure and impulse,k_p and k_I,decrease along with the increasing of Al content and keep the same pace as the calculated P_(CJ).The attenuation coefficients a_P and aIincrease a_t first and decrease later with the increasing of aluminum content,and they reached the maximal values with30% Al containing,which keeps the same pace as the calculated Q_V.
基金supported by the National Key Basic Research and Development Program (No.2014CB744100)
文摘A novel third-order optimized symmetric weighted essentially non-oscillatory(WENO-OS3)scheme is used to simulate the hypersonic shock wave/boundary layer interactions.Firstly,the scheme is presented with the achievement of low dissipation in smooth region and robust shock-capturing capabilities in discontinuities.The Maxwell slip boundary conditions are employed to consider the rarefied effect near the surface.Secondly,several validating tests are given to show the good resolution of the WENO-OS3 scheme and the feasibility of the Maxwell slip boundary conditions.Finally,hypersonic flows around the hollow cylinder truncated flare(HCTF)and the25°/55°sharp double cone are studied.Discussions are made on the characteristics of the hypersonic shock wave/boundary layer interactions with and without the consideration of the slip effect.The results indicate that the scheme has a good capability in predicting heat transfer with a high resolution for describing fluid structures.With the slip boundary conditions,the separation region at the corner is smaller and the prediction is more accurate than that with no-slip boundary conditions.
文摘Objectives:To compare the efficacy of tamsulosin versus tamsulosin plus tadalafil in achieving clearance of fragments after shock wave lithotripsy(SWL)to treat renal calculi.Methods:Between January 2016 to December 2017,140 patients with solitary,non-branched,non-lower calyceal renal calculus and measuring less than 20 mm and treated with SWL were randomized to tamsulosin(group A)or tamsulosin plus tadalafil(group B).Therapy was given for a period of 4 weeks.Stone clearance rate,analgesic requirement,occurrence of steinstrasse,need for auxiliary procedures(endoscopic treatment),and adverse effects of drugs were recorded.Results:The overall clearance rate was 72.5%(50/69)in the group A and 90.1%(64/71)in the group B(pZ0.007).For stones up to 12 mm,the difference in the clearance rate was significant(pZ0.039)while it was not so for stones larger than 12 mm(pZ0.151).There was no statistically significant difference between the two groups with regards to analgesic requirement(pZ0.94),occurrence of steinstrasse(pZ0.101),need for auxiliary procedures(pZ0.76),and adverse effects of the drugs(pZ0.148).Conclusion:Our study shows that adjunctive medical expulsive therapy with tamsulosin and tadalafil achieves better clearance rate than tadalafil alone in patients receiving SWL for renal stones.
