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Two-dimensional oblique detonation waves (ODWs) induced by finite wedges in a stoichiometric hydrogen–air mixture have been investigated numerically based on reactive Euler equations with a detailed chemical reaction model. The main zone affected by the expansion wave emanating from the turning point of a wedge is the flowfield downstream of the intersection point of the oblique shock wave (OSW) and the expansion wave. The ODW would be reduced to Chapman–Jouguet (CJ) detonation or decoupled combustion downstream. Three combustion regimes, detonation, decoupled combustion, and no ignition, were observed successively, as the wedge length decreases. It is found that the location of the intersection point is a key parameter for the detonation initiation. When the intersection point is located upstream of the ODW transition point, the expansion wave may quench ODW. Then, the critical wedge length is obtained by theoretical analysis of wave structures and the initiation criterion of ODWs for finite wedges is proposed. When the wedge length is greater than the critical wedge length, ODWs can be initiated. On the contrary, the initiation of ODWs do not occur. For wedge lengths small enough, no ignition occurs. Previously proposed criteria that use the induction length are also examined and compared with the present critical wedge length criterion in this study, and the latter is proven to achieve better results.

In this study, we clarified the effect of plate mounted between two wires in electric arc spraying by performing both Computational Fluid Dynamics (CFD) and observation using a high-speed camera. By placing a plate between the wires, it was revealed that expansion waves were generated on both sides of the plate, which affected the refinement of the molten particles. Furthermore, it was revealed that the magnitude of the expansion wave generated by changing the position and size of the plate changed, and the larger the expansion wave, the finer the molten particle became.

During a range expansion, deleterious mutations can “surf” on the colonisation front. The resultant decrease in fitness is known as expansion load. An Allee effect is known to reduce the loss of genetic diversity of expanding populations, by changing the nature of the expansion from “pulled” to “pushed”. We study the impact of an Allee effect on the formation of an expansion load with a new model, in which individuals have the genetic structure of a Muller’s ratchet. A key feature of Muller’s ratchet is that the population fatally accumulates deleterious mutations due to the stochastic loss of the fittest individuals, an event called a click of the ratchet. We observe fast clicks of the ratchet at the colonization front owing to small population size, followed by a slow fitness recovery due to migration of fit individuals from the bulk of the population, leading to a transient expansion load. For large population size, we are able to derive quantitative features of the expansion wave, such as the wave speed and the frequency of individuals carrying a given number of mutations. Using simulations, we show that the presence of an Allee effect reduces the rate at which clicks occur at the front, and thus reduces the expansion load.

The flow field which results from an expansion wave entering a cavity from an upstream tube, and the focusing effect which occurs, is investigated. Different cavity geometries, different expansion wave pressure ratios and different expansion wave widths are explored. As the expansion wave propagates into the cavity it induces flow in the opposite direction and back down the walls. The flow experiences compression as it flows out back into the tube because of the concave surface of the cavity it encounters. This can result in the formation of shock waves which can propagate back up into the cavity. Very low pressure and temperature regions can develop because of the focusing action of the expansion. A convenient way of generating an expansion wave numerically and/or experimentally is in a shock tube. This consists of a tube divided into two compartments, one at high pressure and one at low pressure separated by a frangible diaphragm. On bursting the diaphragm, a shock wave travels in one direction and an expansion in the other towards the cavity. Whilst ideal boundary conditions can be imposed in numerical simulation laboratory experiments are complicated by the diaphragm being curved and having a finite opening time. The effect of an initially curved diaphragm is briefly considered. The expansion wave pressure ratio was altered by changing the initial pressure ratio across the diaphragm. For an initially high pressure ratio, supersonic flow can occur behind the trailing edge of the expansion wave which has a marked influence on the flow. The width of the wave is dependent on the distance of the diaphragm from the cavity and also has a significant influence on the flow. As the width of the wave increases and the density gradient decreases, focusing effects becomes significantly weaker. Correspondence between experiment and simulation is examined.

The open circuit underwater breathing apparatus can be a one or two-stage regulator used in scuba diving or a two-stage regulator used in surface supplied installations. These installations are proper in underwater sites at small depth. The pneumatic circuit of a two-stage regulator is composed mainly of a first stage regulator mounted on the air cylinders and a second stage carried by the diver in his mouth. The two regulators are linked together by a medium pressure hose. The circuit opens when the depression created by the diver’s inhalation, in the second stage body, reaches a certain value. The second stage opening causes a transient movement, namely an expansion wave that propagates through the medium pressure hose to the first stage regulator. The first stage regulator opens and the air in the cylinders is allowed to flow to the diver. The longer the hose, the greater the duration of the expansion wave propagation. Investigations on the wave propagation offer data on the inspiration unsteady motion duration which influences the respiratory effort of the diver.

This paper reports an experimental result of expansion wave and cavitation bubble generation by underwater shock wave reflection at the interface for understanding of shock wave interaction phenomena related to the mechanism of shock wave human tissue damage. Underwater shock wave was generated by detonating a micro-explosive (silver azide pellet). The process of underwater shock wave reflection at the interface, expansion wave and cavitation bubble generation were visualized by shadowgraph method and recorded by an ultra-high-speed framing camera at high spatiotemporal resolution. The pressure time history near the interface in water was measured simultaneously by a needle hydrophone. High-speed shadowgraph sequential images show that a compression wave (shock wave) was reflected from a thin interface plate (Polystyrene, acrylic, Teflon, thickness of t=0.5 mm), and expansion wave was then generated in water by reflection from the air. In addition, a cavitation bubble was created behind the expansion wave. The simultaneously measured pressure history also shows that an expansion wave propagated behind shock wave. The negative peak pressure of expansion wave in the case of a thin plate shock wave interaction was larger than that in water surface interaction.

This contribution explores emerging features of social relations of production as expressed through the contract farming system in Zimbabwe. It seeks to link earlier research on plantation-based outgrower schemes in tea and sugar that were on a modest scale, to contemporary contract farming in tobacco and cotton that has expanded to a relatively large scale in the post-land reform period. The article questions whether the current expansion wave is a qualitatively new process or a variant of ‘old wine in new bottles’ in terms of relations between growers and large capital. Some themes for research are then outlined potentially to address emerging pertinent issues arising out of contemporary contract farming arrangements.

Objectives The arrival of Neolithic farmers in Europe was the source of major cultural and genetic transitions. Neolithic settlers brought a new set of maternal lineages (mitochondrial DNA), recently well-characterized on the continental road, from the Balkans to West Germany (Rhine River). In the present study, the first mitochondrial DNA data from groups associated with this continental expansion wave located west of the Rhine River has been provided and their genetic affinities with contemporary groups have been discussed. Material and methods The mitochondrial DNA analysis of 27 human remains originating from Obernai (5,000–4,400 cal. BC), a necropolis located in French Alsace Region and attributed to Grossgartach, Planig–Friedberg, and Roessen cultures was conducted. Results and discussion Among the 27 individuals studied, 15 HVR-I sequences and 17 mitochondrial haplogroups could be determined. The analysis of the Obernai gene pool clearly confirmed the genetic homogeneity of Linearbandkeramik (LBK) groups on both sides of the Rhine River. Notably, one N1a sequence found in Obernai is shared with LBK farmers from Central Europe, including one individual from the Flomborn site located approximately 200 km north-east of Obernai. On the whole, data gathered so far showed major genetic influence of the Danubian wave from Transdanubia to Atlantic French Coast, going by Alsace Region. However, the genetic influence of descendants from the Mediterranean Neolithic expansion and the significant hunter-gatherer admixture detected further west in the Paris Basin were not perceived in the Obernai necropolis. Conclusions Genetic homogeneity and continuity within LBK groups can be proposed on both sides of the Rhine River for the middle Neolithic groups. Nevertheless, mitochondrial data gathered so far for Neolithic groups from the entire extant French Territory clearly point out the complexity and the variability of Neolithic communities interactions that is worthy of further investigation.

The prompt oblique detonation wave (PODW) sustained by a finite-length wedge is investigated by numerical simulation. The numerical results show that it is possible to stabilize a PODW on a finite-length wedge shorter than the induction length of the mixture behind the inert shock by numerically imposing a premature initiation of combustion in the initial flow field. The fully coupled and the partially coupled PODWs are observed in the numerical results. For the fully coupled PODW, the upstream facing transverse waves (UF TW) are swept downstream and consequently a fully coupled PODW can persist. For the partially coupled PODW, the UF TWs propagate upstream and the downstream facing transverse waves are weakened by the expansion wave emanating from the corner. As a result, a partially coupled PODW forms. Further, it is found that the stability of the partially coupled PODW is weak. The configuration of the partially coupled PODW can be altered by local explosions occurring downstream.

Anatolia and the Near East have long been recognized as the epicenter of the Neolithic expansion through archaeological evidence. Recent archaeogenetic studies on Neolithic European human remains have shown that the Neolithic expansion in Europe was driven westward and northward by migration from a supposed Near Eastern origin [1-5]. However, this expansion and the establishment of numerous culture complexes in the Aegean and Balkans did not occur until 8,500 before present (BP), over 2,000 years after the initial settlements in the Neolithic core area [6-9]. We present ancient genome-wide sequence data from 6,700-year-old human remains excavated from a Neolithic context in Kumtepe, located in northwestern Anatolia near the well-known (and younger) site Troy [10]. Kumtepe is one of the settlements that emerged around 7,000 BP, after the initial expansion wave brought Neolithic practices to Europe. We show that this individual displays genetic similarities to the early European Neolithic gene pool and modern-day Sardinians, as well as a genetic affinity to modern-day populations from the Near East and the Caucasus. Furthermore, modern-day Anatolians carry signatures of several admixture events from different populations that have diluted this early Neolithic farmer component, explaining why modern-day Sardinian populations, instead of modern-day Anatolian populations, are genetically more similar to the people that drove the Neolithic expansion into Europe. Anatolia's central geographic location appears to have served as a connecting point, allowing a complex contact network with other areas of the Near East and Europe throughout, and after, the Neolithic.

Oblique detonation waves (ODWs) have attracted increasing attention in recent years due to their potential application to air-breathing hypersonic propulsion. Most of the previous studies on them were based on a semi-infinite wedge, considering the ODW itself but ignoring its interaction with geometric confinement. In this study, the ODWs based on bended tunnel geometry had been studied with a detailed hydrogen–air chemical reaction model. An expansion wave was introduced by the bended upper-wall, and then interacted with the original ODW surface, resulting in a series of complicated wave configurations along different positions of the upper expansion wave. When the expansion wave was induced far upstream before the original ODW surface, the ODW surface would be partially decoupled. And if the expansion wave has located downstream enough, the reflection of the ODW surface on the wall would induce an unsteady ODW. However, a modest distance between the ODW and expansion wave created a structure that had never been reported before. This novel structure was found to be combined by two high-temperature regions, one was from the original ODW reaction zone while the other append near the upper wall after the turning point. The new high-temperature region was found to be overlapped by a recirculation region, suggesting a balance between flow and heat release.

The oblique detonation wave (ODW) triggered by a semi-infinite cowl or wedge has been widely studied, but the effects of finite-length cowls require further clarification to enhance their applicability. Based on two-dimensional inviscid Euler equations and a two-step induction–reaction model, two structures with smooth and abrupt transitions are simulated, and their interactions with the cowl-induced expansion wave are investigated. The expansion waves located downstream and far away from the initiation zone do not affect the macroscopic structures of the ODW. However, when the expansion waves move upstream, the structures evolve into a decoupled shock and a reactive front. Alongside findings from previous studies, these results indicate that the initiation mechanism, rather than the transition type, determines the near-quenching evolution of the structure. Moreover, given the same parameter settings for the chemical and inflow gas dynamics, these numerical results show that the abrupt transition evolves into a smooth transition under an expansion wave disturbance. This demonstrates that the local wave interaction plays a key role in the ODW structures.

Experimental study on premixed fuel–air mixture venting explosion process with various gas volume concentrations and vent sizes was conducted in a 20 L cylinder vessel. The results showed that both overpressure dynamic process and flame evolution process could be divided into 4 stages, including 2 positive and 2 negative overpressure peaks. Specifically, the 1st and 2nd positive overpressure peaks were respectively induced by flame venting and external explosion, while the 1st and 2nd negative overpressure peaks were respectively caused by expansion wave after the external explosion and external large-scale vortex. Both the overpressure and flame parameters were related to initial gas volume concentrations. As the gas volume concentration increased from 1.00% to 2.99%, both the positive overpressure peaks, flame velocity and flame propagation distance presented a first increasing and then decreasing trend, but the negative overpressure peaks and the time corresponding to each overpressure peak presented a first decreasing and then increasing trend. Moreover, as the vent coefficient Kv increased from 1.16 to 10.44, the maximum positive overpressure peaks increased from 2.32 to 60.54 mbar, and the maximum axial flame velocity increased from 9.21 m·s−1 to 53.85 m·s−1. However, as the Kv increased, the minimum negative overpressure peak and the maximum radial flame velocity changed non-monotonically.

In the present study, 87 unrelated individuals from the Marquesas Archipelago in French Polynesia were typed using mtDNA, Y-chromosome and autosomal (STRs) markers and compared to key target populations from Island South East Asia (ISEA), Taiwan, and West and East Polynesia to investigate their genetic relationships. The Marquesas, located at the eastern-most fringes of the Austronesian expansion, offer a unique opportunity to examine the effects of a protracted population expansion wave on population structure. We explore the contribution of Melanesian, Asian and European heritage to the Marquesan islands of Nuku-Hiva, Hiva-Oa and Tahuata. Overall, the Marquesas Islands are genetically homogeneous. In the Marquesan Archipelago all of the mtDNA haplogroups are of Austronesian origin belonging to the B4a1 subhaplogroup as the region marks the end of a west to east decreasing cline of Melanesian mtDNA starting with the West Polynesian population of Tonga. Genetic discrepancies are less pronounced between the Marquesan and Society islands, and among the Marquesan islands. Interestingly, a number of Melanesian, Polynesian and European Y-chromosome haplogroups exhibit very different distribution between the Marquesan islands of Nuku Hiva and Hiva Oa, likely resulting from drift, differential migration involving various source populations and/or unique trading routes.

平成29年度衝撃波シンポジウム (2018年3月7日-9日. 東北大学片平さくらホール ）仙台市, 宮城県, (2018年3月7日-9日. 宇宙航空研究開発機構角田宇宙センター ）角田市, 宮城県, Symposium on Shock Waves in Japan, FY2017 (March 7-9, 2018. Sakura Hall), Sendai, Miyagi, (March 7-9, 2018. Kakuda Space Center, Japan Aerospace Exploration Agency (JAXA)(KSPC)), Kakuda, Miyagi, 資料番号: SA6000119019, レポート番号: 1A4-4【若】

平成28年度衝撃波シンポジウム (2017年3月8日-10日. ヴェルクよこすか 横須賀市立勤労福祉会館）横須賀市, 神奈川県, Symposium on Shock Waves in Japan, FY2016 (March 8-10, 2017. Werk Yokosuka), Kanagawa, Japan, 資料番号: SA6000084034, レポート番号: 1C1-2

平成28年度衝撃波シンポジウム (2017年3月8日-10日. ヴェルクよこすか 横須賀市立勤労福祉会館）横須賀市, 神奈川県, Symposium on Shock Waves in Japan, FY2016 (March 8-10, 2017. Werk Yokosuka), Kanagawa, Japan, 資料番号: SA6000084050, レポート番号: 1D1-2【若】

There has been a large amount of work done on the shock wave and boundary layer interaction (SWBLI) as reported by Babinski [1]. In some cases, there is a tendency for the shock to induce separation. In adiabatic and non-reactive flow, the only source of entropy rise is viscosity. The SWBLI is of interest as it establishes a trend. The trend for expansion wave/boundary layer interaction (EWBLI) will have SWBLI as a benchmark, for comparison.

Previous research on wave focusing has concentrated on shock wave cavity flows [1]. Expansion wave cavity flows have not been investigated before. This paper looks at the flow resulting from an expansion wave entering a cylindrical cavity. Initially numerical simulations were run with the assumption of a plane diaphragm, however after experimental testing it was found that an investigation of the effect of a curved diaphragm also needed to be done. An expansion wave is a pressure wave which causes the fluid it travels through to decrease in pressure. As expansions cause a decrease in pressure they tend to flatten out (decrease in gradient) as they travel through a fluid. This makes them difficult to visualise as generally they are associated with weak gradients [2]. The interaction between shock and expansion waves has been investigated, as has the diffraction of an expansion wave around a corner [3].

The results of experiments on shock-wave loading of materials distinguished by a negative slope of the melting curve are reported. An anomalous situation is possible, when the material is melted by a shock wave and then a fast transition to the solid phase takes place in the expansion wave. The newly formed phase should be a nanostructural formation of the given element. Experiments confirmed the existence of the transition from the liquid to the solid phase of the nanostructural modification.

In the present work the problem of detonation wave formation in a shock tube was considered in one-dimensional formulation. The Monte Carlo non-stationary method of statistical simulation (MCNMSS), also known as DSMC, was used for simulation. The method automatically takes into account all details of mass and heat transfer. At an initial moment, the low-pressure channel (LPC) of the shock tube was filled with gas A while the high-pressure chamber (HPC) was filled with gas C. The cross-sections of the HPC and LPC, as well as the temperatures of gases A and C were equal to each other. At the beginning of the simulation the ratio of pressures in the HPC and LPC was equal to 100. It was assumed that chemical reactions $$\mathrm{{A}}+\mathrm{{M}} \rightarrow \mathrm{{B}}+\mathrm{{M}}$$ ( $$\mathrm{{M}}=\mathrm{{A}},\, \mathrm{{B}}$$ and $$\mathrm{{C}}$$ ) took place. The ratio of molecular masses of gases $$\mathrm{{A}},\, \mathrm{{B}}$$ and $$\mathrm{{C}}$$ was taken as 20:20:1. Different reaction thresholds were considered. For the case of a low reaction threshold, the velocity of the resulting detonation wave was found to be higher than the Chapman–Jouguet velocity. A region with constant values of flow parameters inside product was observed. An increase of the reaction threshold led to disappearance of this region and gave rise to something similar to an expansion wave, with peaks of flow parameters at the leading part of the detonation wave. The values of these peaks were found to be constant in time. The velocity of the detonation wave became appreciably lower than the Chapman–Jouguet velocity. Further increase of the reaction threshold led to disappearance of detonation. The reactions $$\mathrm{{A}}+\mathrm{{B}} \rightarrow \mathrm{{B}}+\mathrm{{B}}$$ and $$\mathrm{{A}}+\mathrm{{C}}\rightarrow \mathrm{{B}}+\mathrm{{C}}$$ turned out to be very important for initiation of detonation.

The organic Rankine cycle (ORC) favorably operates at low temperature. It differs significantly from the steam Rankine cycle in fluid enthalpy drop during expansion and reaction to change in condensation temperature. In current method for ORC-based energy conversion the expander leaving loss is generally neglected. Shortcomings of this method are outlined in this paper. Theoretical analysis of the expander leaving loss varying with the condensation temperature, evaporation temperature, and inlet pressure is first performed. Experimental test is subsequently carried out. The results indicate that unlike in the steam Rankine cycle, the leaving loss in the ORC on using R123 or R245fa increases by about 10 times as the condensation temperature changes from 30 to 0 °C, and is comparable with the enthalpy drop. With an inlet temperature of about 97 °C and a deviation of about 20 °C from the design condensation temperature, the ratio of the leaving loss to the enthalpy drop is about 10.4%. Besides, variation in the leaving loss may lead to expansion wave or shock wave inside the expander. The leaving loss becomes an important factor and should be included to determine the ORC year-round performance.

平成27年度衝撃波シンポジウム (2016年3月7日-9日. 熊本大学 黒髪南地区）熊本市, 熊本県, Symposium on Shock Waves in Japan, FY2015 (March 7-9, 2016. Kumamoto University), Kurokami Chuo-ku, Kumamoto, Japan, 資料番号: SA6000049117, レポート番号: P-05

平成27年度衝撃波シンポジウム (2016年3月7日-9日. 熊本大学 黒髪南地区）熊本市, 熊本県, Symposium on Shock Waves in Japan, FY2015 (March 7-9, 2016. Kumamoto University), Kurokami Chuo-ku, Kumamoto, Japan, 資料番号: SA6000049119, レポート番号: P-07【若】

平成27年度衝撃波シンポジウム (2016年3月7日-9日. 熊本大学 黒髪南地区）熊本市, 熊本県, Symposium on Shock Waves in Japan, FY2015 (March 7-9, 2016. Kumamoto University), Kurokami Chuo-ku, Kumamoto, Japan, 資料番号: SA6000049091, レポート番号: 3A2-1

In the recent decades southern European cities experienced morphological changes and a demographic transition towards zero (or negative) growth and aging. Population dynamics shifted from the impressive growth of the post-industrial period into recent de-concentration processes determining the spillover of commercial and residential settlements across the surrounding rural areas. Based on long-term demographic data, the present study hypothesizes that urban expansion did not follow a one-way linear path from compactness to dispersion while reflecting differentiated growth patterns based on the specific socioeconomic context at the local scale. Along a sufficiently long time period non-linear expansion waves alternating settlement densification and scattering are expected to be found especially in complex urban contexts such as those developed in the Mediterranean region. This hypothesis was tested for a paradigmatic case study in southern Europe (Athens, Greece) using demographic data covering 160 years (1848–2011). Urban growth in Athens was assessed through the analysis of long-term census data made available on a district level. These data provide information on the spatial distribution of resident population and characterize distinct expansion waves according to the dominant socioeconomic context. Results of the study were discussed in the light of the debate on future development of the Mediterranean cities and the (changing) economic relations with the surrounding region.

Pressure waves are generated and propagate in tunnel when train enters a tunnel with high speed. Compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as expansion wave. While expansion wave due to the entry of train tail propagates along the tunnel and is reflected at tunnel exit as compression wave. These pressure waves are repeatedly propagated and reflected at tunnel entrance and exit. Severe pressure change per second causes ear-discomfort for passengers in cabin and micro pressure wave around tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnel qualitatively and quantitatively, because pressure change rate is considered as one of major design parameters for an optimal tunnel cross sectional area and the repeated fatigue force on car body. In this study, we developed the characteristics method analysis based on fixed mesh system and compared with the results of real train test. The results of simulation agreed with that of experiment.

Interaction of a single chemically active bubble in water with acoustic waves is numerically studied within the framework of the model of a two-dimensional unsteady flow of an ideal compressible medium. The boundaries between the phases are explicitly identified. It is demonstrated that bubble explosion initiation can be determined by the character of bubble deformation. Nonsphericity of deformation and jet formation lead to an explosion even if the bubble does not collapse. The possibility of the bubble explosion in an expansion wave, transfer of detonation from one bubble to another, and, thus, emergence of bubble detonation is demonstrated.

When a train travels through tunnel at a high speed, large pressure variations are produced on the train surface by pressure waves. In particular, when an express train travels through a narrow tunnel at a speed higher than that of a conventional train, more severe pressure variations can occur and cause passengers ear discomfort. This paper presents a very simple and effective reduction method of the large pressure variation for a narrow conventional tunnel. When a compression wave and an expansion wave are superposed, the pressure variation can be greatly reduced. Using this phenomenon, this study proposes the construction of a dummy tunnel duct which superposes the pressure waves and reduces the large pressure variation. Using the proposed method, the construction cost is much lower compared to other methods because the dummy tunnel duct can be constructed at the entrance or at the exit of an existing tunnel with a simple tunnel shape. To investigate the change in the maximum pressure difference and pressure variation ratio with the application of a dummy tunnel duct, full-scale tests and numerical analyses were conducted. The results showed that the maximum pressure changes and pressure variation ratio are significantly reduced by a short dummy tunnel duct. From these results, the dummy tunnel duct is expected to be a very economical and practical solution to passenger ear discomfort problems for express trains traveling through conventional narrow tunnels.

In this paper, we consider an initial-boundary value problem for the Korteweg-de Vries equation on the positive quarter-plane. The normalised Korteweg-de Vries equation considered is given by u τ + uu x + u xxx = 0, 0 0, where x and τ represent dimensionless distance and time, respectively. In particular, we consider the case when the initial and boundary conditions are given by u(x, 0) = u i for 0 0, respectively. Here, the initial value u i > 0 and we restrict attention to values of the boundary value, u b , for which u b 0, u b 0, u b = 0) and (u i > 0, 0 < u b < u i ). In each case, the method of matched asymptotic coordinate expansions is used to obtain the large-τ asymptotic structure of the solution to this problem, which exhibits the formation of an expansion wave solution.

Based on the experiment, the important influence of the pipe with abnormal structure on gas explosion propagation characteristics is analyzed. The results show that gas explosion propagation at the turning point is a process of interaction of pressure wave, flame and complicated flow field. The overpressure of pressure wave and flame transmission velocity are rapidly accelerated and the pipe wall at the turning point is seriously destroyed. The angle of bend has a great influence on the gas explosion propagation characteristics, i.e. there is a different degree of change in both flame velocity and pressure wave overpressure value when gas explosion propagates through bend with different angles. The bend not only increases the turbulent flow of combustion area that accelerates the reaction and velocity, but also enlarges the resistance and heat transmission to the pipe wall. At the same time, the expansion wave at the turning point restrains the gas explosion propagation. The influence of bend on gas explosion propagation characteristics is determined by the combined impact of inhibitor factors and motivation factor. Experiment research and theory analysis indicate that gas explosion propagation characteristics in bend pipe are obviously different from that in straight pipe. So in the mine exploitation, the bend roadways should be decreased as few as possible, and preventive measures should be taken in order to diminish the loss caused by gas explosion. The research results will play an important role in the guidance of preventing gas explosion from occurring and alleviating the damage in coal mine.

The biolistic approach of DNA/drug delivery was applied to deliver liquid DNA into living cells. The liquid DNA to be delivered was deposited as a drop on a thin aluminum foil and the posterior surface of the foil was ablated using an Nd:YAG laser. The ablation launched a shock wave through the foil. A part of this shock wave was transmitted to the drop, and a part was reflected back into the foil as an expansion wave. The wave motions caused the drug droplet to accelerate and acquire a sufficiently high velocity in the forward direction. A part of the propelled DNA droplet, on impacting the surface of a soft, living target, entered the target cells, accomplishing the drug delivery. The technique was tested on E-coli bacteria by delivering a plasmid DNA pUC119 into the bacterial cells. A few bacterial colonies could be transformed by this method of DNA delivery.

The properties of diverse difference schemes of gas dynamics (nonconservative, conservative, and completely conservative) were studied with reference to the example of the classical problem of a piston. It is shown that in the case in which the piston is pulled out of a gas with the formation of an expansion wave, the application of schemes without a sufficient stability margin can lead to the appearance of discontinuities in the form of expansion shock waves. The explanation of this effect and possible ways for eliminating it are proposed

It is suggested to employ detonation waves for the processing of gas suspensions. Computational experiment is used for assessing the possibility of processing particles by detonation waves. The structure of detonation wave and its impact on solid particles are numerically calculated. The combined impact made by detonation wave and expansion wave on a particle is studied. The investigation results are used to demonstrate the possibility of processing particles in detonation tubes.

The shock wave transmitted at the speed that exceeds speed of sound generates the expansion wave by the density difference. The expansion wave causes negative pressure on the density difference side. And it causes the high-speed destruction phenomenon that is called “the spalling destruction”. This phenomenon is caused also on the surface of the cell wall of the plant. The cell of the plant has the cell wall to maintain the shape. This is a big difference between the animal cell and the plant cell. That is, the plant has all big density differences in the cell structure. Therefore, the spalling destruction on the surface of the cell wall can spread to the entire cell tissue of the plant by the shock wave. It is possible to apply it to the extraction of the cytoplasm etc. by the cell wall destruction by using this phenomenon. The mechanism to which walls of the plant cells are destroyed by the shock wave is described in the experiment and the comparison with the scanning electron microscope photograph in this research.

This paper presents numerical simulations for the interaction of an expansion wave with an incident shock wave of the opposite family, the specific aim being to study the resultant reflection of the now-perturbed shock wave from a solid surface. This problem is considered in the context of an incident flow entering a parallel duct, a situation that commonly arises in a range of flow-turning problems including supersonic intake flows. Once the incident shock conditions are such that Mach reflection must occur, it is shown that stabilization of a simple Mach reflection is only possible for a narrow range of Mach numbers and that this depends sensitively on the relative streamwise positioning of the origins of the shock wave and the expansion wave.

The model, which hit a mountain (technogenic earthquakes) - is presented as a way out of the shock wave at the inner wall of the shaft. This raises the unloading wave, stretching, moving backward (deep wall) direction. Shock wave accompanied by the movement of the medium in the propagation direction of the shock waves at a speed considerably less than that of the wave. The totality of phenomena occurring on the inner surface of the mine, leads to the release of coal dust and methane dissolved in the coal, which is the cause of the explosion.

平成26年度衝撃波シンポジウム (2015年3月9日-11日. 群馬県伊香保温泉 ホテル天坊）渋川市, 群馬県, Symposium on Shock Waves in Japan, FY2014 (March 9-11, 2015. Hotel Tenbo), Shibukawa, Gunma, Japan, 資料番号: SA6000038061, レポート番号: 2B2-4

In the past, much attention was given to the diffraction of a shock wave over various geometries; extensively explored through experimentation and simulation [1, 2], and by many others

The authors present results of determination of sound velocities in explosion products (EP) of HMX-based explosive overcompressed up to the pressures of 50–85 GPa by overtaking unloading method. The radiowave and optical methods are used to record the time when a front of overcompressed detonation wave in investigated sample of high explosive (HE) is overtaken by expansion wave, which propagates from the back surface of impactor with sound velocity. The data on sound velocities, which were independently obtained by two different methods, were in agreement. The methods with use of radiointerferometer and indicator liquid are rather effective for determination of sound velocities in overcompresed EP and for investigation of parameters at the Jouget point of various HEs, which are required for calibration of their equations of state (EOS).

In shock tubes, driver and driven section are usually separated by a diaphragm, which produces nearly ideal shock waves due to its instant rapture. However, known disadvantages of diaphragms motivate the investigation of diaphragmless shock tubes. One of these concepts is to replace a diaphram by a rapidly opening piston.

Numerical computation of differential equations usually needs some discretization of the original equation. The discretization is called discrete (or discretized) model, while the original differential equation is called continuous model. The properties of both models are expected to be of exact coincidence, but there is always some inconsistency between them. In such a situation, we need to know the inconsistency in order to understand what a result of numerical computation means. Otherwise we might misunderstand it to regard a specific behavior of numerical solution coming from the property of discrete model but not from that of continuous one as a part of behavior of the original equation's solution. Here we show some trial to analyze the numerical instability that occurs in numerical calculation of shock waves, where occurs a typical example of inconsistency between the continuous and discrete models., 資料番号: AA0063154027, レポート番号: JAXA-SP-06-010

Development of Balloon-based Operation Vehicle (BOV) is currently in progress for the first flight scheduled in 2006. A vehicle in a wing-body configuration will be lifted by a high-altitude balloon and dropped. Various types of onboard experiments such as a microgravity experiment and a demonstration of a supersonic engine are planned during flights for the second, third and fourth flights. The aerodynamics load and characteristics of BOVs have been obtained by the CFD simulations as well as by the wind tunnel testing in ISAS. In this paper, the numerical simulations for BOV are presented and the results showed that the interaction between the wings, body and engine increases for transonic flow with high angle of attack., 資料番号: AA0049212034, レポート番号: JAXA-SP-05-017