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Compared to a variety of mechanical vectoring nozzles, fluidic vectoring nozzles possess more research value nowadays. The dual throat nozzle is gradually developing into an outstanding technology to handle supersonic and hypersonic aircraft deflections. Three-dimensional, steady, compressible, and viscous flows in rectangular dual throat nozzles are numerically investigated by resolving Reynolds-averaged Navier-Stokes equations and shear stress transport k-omega turbulence model. Computational fluid dynamics results are verified against the existing experimental data, where a good consistency is gained. The impacts of nozzle pressure ratio, injection-to-mainstream momentum flux ratio, and setup angle of the slot injector on the systemic performance are examined. Useful conclusions are summarized for engineering designers. Firstly, pitching angles decline along with an increasing nozzle pressure ratio, while systemic thrust ratio and thrust efficiency increase. Secondly, thrust vector angles enlarge with an increase of the injection-to-mainstream momentum flux ratio, whereas both systemic thrust ratio and thrust efficiency decay. Finally, the setup angle of the slot injector impacts the systemic performance remarkably. Although the pitching angle for the setup angle of 120° is highest, comprehensive characteristics in terms of systemic thrust efficiency and systemic thrust ratio for the setup angle of 150° are more excellent.

Public health policy decisions in the United States have resulted in 62.4% of the population having access to fluoridated water. The purpose of this study was to examine the association between community water fluoridation and osteosarcoma. A secondary data analysis was performed with data collected from 2 separate but linked studies. Patients for phase 1 and phase 2 were selected from US hospitals via a matched case-control study design. For both phases, cases included patients diagnosed with osteosarcoma, and controls were patients diagnosed with other bone tumors or nonneoplastic conditions. In phase 1, cases ( n = 209) and controls ( n = 440) were patients of record in the participating orthopedic departments from 1989 to 1993. In phase 2, cases ( n = 108) and controls ( n = 296) were incident patients who were identified and treated by orthopedic physicians from 1994 to 2000. This analysis included all patients who met eligibility criteria on whom we had complete data on covariates, exposures, and outcome. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% CIs for the association of community water fluoridation with osteosarcoma. A modestly significant interaction existed between fluoridation living status and bottled water use ( P = 0.047). The adjusted OR for osteosarcoma and ever having lived in a fluoridated area for nonbottled water drinkers was 0.51 (95% CI, 0.31 to 0.84; P = 0.008). In the same comparison, the adjusted OR for bottled water drinkers was 1.86 (95% CI, 0.54 to 6.41; P = 0.326). Findings from this study demonstrated that community water fluoridation is not associated with an increased risk for osteosarcoma.

Wear mechanisms of three Ag–Cu eutectic alloy samples cooled at different rates from the melt have been investigated by friction force microscopy. The eutectic phase exhibits a lamellar structure where the interlamellar thickness decreases with increasing cooling rate. The hardness of the samples decreases with decreasing thickness of the lamellae. In the low normal force regime (Fn ≤ 1000 nN) friction is governed by shearing and the relevant contact area can be well described by the Johnson–Kendal–Roberts model. At higher normal force values, the surface is worn, and friction can be described by the ploughing friction coefficient. A ploughing friction coefficient is determined, which is positively correlated with the hardness of the Ag–Cu eutectic alloy samples cooled at different rates, while the wear volume negatively correlates with the hardness.

In mammalian cells, the bulky DNA adducts caused by ultraviolet radiation are mainly repaired via the nucleotide excision repair (NER) pathway; some defects in this pathway lead to a genetic disorder known as xeroderma pigmentosum (XP). Ribosomal protein S3 (rpS3), a constituent of the 40S ribosomal subunit, is a multi-functional protein with various extra-ribosomal functions, including a role in the cellular stress response and DNA repair-related activities. We report that rpS3 associates with transcription factor IIH (TFIIH) via an interaction with the xeroderma pigmentosum complementation group D (XPD) protein and complements its function in the NER pathway. For optimal repair of UV-induced duplex DNA lesions, the strong helicase activity of the TFIIH complex is required for unwinding damaged DNA around the lesion. Here, we show that XP-D cells overexpressing rpS3 showed markedly increased resistance to UV radiation through XPD and rpS3 interaction. Additionally, the knockdown of rpS3 caused reduced NER efficiency in HeLa cells and the overexpression of rpS3 partially restored helicase activity of the TFIIH complex of XP-D cells in vitro. We also present data suggesting that rpS3 is involved in post-excision processing in NER, assisting TFIIH in expediting the repair process by increasing its turnover rate when DNA is damaged. We propose that rpS3 is an accessory protein of the NER pathway and its recruitment to the repair machinery augments repair efficiency upon UV damage by enhancing XPD helicase function and increasing its turnover rate.

Nano- and microelectromechanical systems (NEMS and MEMS) are interesting as switches for next-generation computing electronics. Unfortunately, repeated switching causes the formation of gunk known as $t\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}b\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}y\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r$ in the junction, which spoils device performance. To understand the mechanism behind this phenomenon at the intersection of physics, chemistry, and electronics, the authors use density functional theory to study the switching of a RuO${}_{2}$ NEMS in the presence of benzene. Tribopolymer formation involves a chain reaction of an oxidized biphenyl-like structure, with abstraction of surface oxygen, leading to strongly chemisorbed species that continue to polymerize.

Measurements of differential t (t) over bar production cross sections are presented in the single-lepton decay channel, as a function of a number of kinematic event variables. The measurements are performed with proton-proton collision data at root s = 13 TeV, collected by the CMS experiment at the LHC during 2016, with an integrated luminosity of 35.9 fb(-1). The data are compared to a variety of state-of-the-art leading-order and next-to-leading order t (t) over bar simulations.

Chronic facial paralysis induces degenerative facial muscle changes on the involved side, thus, making the individual seem as older than their actual age. Furthermore, contralateral facial hypertrophy aggravates facial asymmetry. A thread-lifting procedure has been used widely for correction of a drooping or wrinkled face due to the aging process. In addition, botulinum toxin injection can be used to reduce facial hypertrophy. The aim of study was to evaluate the effectiveness of thread lifting with botulinum toxin injection for chronic facial paralysis. A total 34 of patients with chronic facial paralysis were enrolled from March to October 2014. Thread lifting for elevating loose facial muscles on the ipsilateral side and botulinum toxin A for controlling the facial muscle hypertrophy on the contralateral side were conducted. Facial function was evaluated using the Sunnybrook grading system and dynamic facial asymmetry ratios 1 year after treatment. All 34 patients displayed improved facial symmetry and showed improvement in Sunnybrook scores (37.4 vs. 83.3) and dynamic facial asymmetry ratios (0.58 vs 0.92). Of the 34 patients, 28 (82.4%) reported being satisfied with treatment. The application of subdermal suspension with a reabsorbable thread in conjunction with botulinum toxin A to optimize facial rejuvenation of the contralateral side constitutes an effective and safe procedure for face lifting and rejuvenation of a drooping face as a result of long-lasting facial paralysis.

Using the spark plasma sintering (SPS) process, Al 4 SiC 4 powder was synthesized at a temperature 550 °C lower and for one-sixth of the holding time compared with the conventional heating method. The extrusion of molten raw powder and the temperature overshoot could be prevented by modifying the mold. The increase in maximum applicable temperature for powder synthesis was another benefit of the new mold. The synthesis temperature and time decreased with increasing size of the mold as a result of the effect of high current during SPS.

Single Stage To Orbit (SSTO) missions which require its engines to be operated at varying back pressure conditions, use engines operate at high combustion chamber pressures (more than 100bar) with moderate area ratios (AR 70~80). This ensures that the exhaust jet flows full during most part of the operational regimes by optimal expansion at each altitude. Aero-spike nozzle is a kind of altitude adaptation nozzle where requirement of high combustion chamber pressures can be avoided as the flow is adapted to the outside conditions by the virtue of the nozzle configuration. However, the thrust prediction using the conventional thrust equations remains to be a challenge as the nozzle plume shapes vary with the back pressure conditions. In the present work, the performance evaluation of a new aero-spike nozzle is being carried out. Computational studies are carried out to predict the thrust generated by the aero-spike nozzle in varying back pressure conditions which requires the unsteady pressure boundary conditions in the computational domain. Schlieren pictures are taken to validate the computational results. It is found that the flow in the aero-spike nozzle is mainly affected by the base wall pressure variation. The aerospike nozzle exhibits maximum performance in the properly expanded flow regime due to the open wake formation.

A new analysis technique for the composition measurement of mixed nuclear material by using a ssion neutron multiplicity distribution is proposed on the basis of the fact that the ssion neutron multiplicity distribution of each isotope has its own characteristics. The feasibility study for identifying a single isotope and determining the composition of a mixed material has been carried out using the Monte Carlo simulation method. The neutron counter system is simulated with the MCNPX code. In the single isotope case, the measured neutron multiplicity distributions result in over 1.0% dierence from that of each individual isotope using the following six isotopes simulated: 238 Pu, 240 Pu, 242 Pu, 242 Cm, 244 Cm, 252 Cf. In the mixed nuclear material case, the mixed materials of 239 Pu and 244 Cm isotopes are simulated with various mixing ratios. The neutron multiplicity distributions for the mixture of 239 Pu and 244 Cm are distinguishable when the mass mixing ratio of 244 Cm to 239 Pu is less than 10 8 and the composition of the mixture is measured by 1.0% relative

Summary Fusobacterium nucleatum plays a pivotal role in dental plaque biofilm formation and is known to be involved in chronic inflammatory systemic disease. However, limited knowledge of F. nucleatum genes expressed in vivo interferes with our understanding of pathogenesis. In this study, we identified F. nucleatum genes induced in vivo using in-vivo-induced antigen technology (IVIAT). Among 30,000 recombinant clones screened, 87 reacted reproducibly with pooled sera from 10 patients with periodontitis. The clones encoded for 32 different proteins, of which 28 could be assigned to their functions, which were categorized in translation, transcription, transport, energy metabolism, cell envelope, cellular process, fatty acid and phospholipid metabolism, transposition, cofactor biosynthesis, amino acid biosynthesis, and DNA replication. Putative virulence factors detected were ABC transporter, butyrate-acetoacetate CoA-transferase, hemin receptor, hemolysin, hemolysin-related protein, LysR family transcriptional regulator, serine protease, and transposase. Analysis of immune responses to the in-vivo-induced (ivi) antigens in five patients demonstrated that most were reactive to these proteins, confirming results with pooled sera. IVIAT-identified F. nucleatum genes in this study may accelerate the elucidation of F. nucleatum-mediated molecular pathogenesis.

Sodium tungsten oxide nanobundles are synthesized by acid precipitation method with the ammonium tungstate and sodium hydroxide. The crystal structure, morphology and optical properties of the sodium tungsten oxide (NaxWO3, x = 0.33, 0.5, 0.75, and 1.0) nanobundles are analyzed by X-ray diffraction, field-emission scanning electron microscopy, and UV-visible spectroscopy, respectively.

Transonic flow around a symmetric disc butterfly valve is associated with the appearance of shock waves on valve surfaces. In this case, the interaction between shock waves and boundary layers becomes complex and thus generates the flow-induced aerodynamic instability. In the transonic or supersonic flow where vapour is contained in the main flow, the rapid expansion of the flow may give rise to non-equilibrium condensation. In the present study, the effect of non-equilibrium condensation of moist air on the shock-induced flow field oscillation around a butterfly valve was investigated numerically. The results showed that in cases with non-equilibrium condensation, the flow field aerodynamic instabilities such as root mean square of pressure oscillation and shock-induced oscillation frequency are reduced significantly compared with those without the non-equilibrium condensation. Moreover, the total pressure loss increases and the vortex shedding frequency is reduced with non-equilibrium condensation.

A critical nozzle is used to measure the mass flowrate of gas. It is well known that the coefficient of discharge of the flow in a critical nozzle is a single function of the Reynolds number, in which the discharge coefficient approaches unity as the Reynolds number increases. However, it has recently been reported that at very high Reynolds numbers, which correspond to high-pressure supply conditions, the discharge coefficient exceeds unity. This impractical value in the discharge coefficient is vaguely inferred to be due to real gas effects. The purpose of the present study is to investigate high-pressure hydrogen gas flow through a critical nozzle. A computational analysis has been carried out to simulate a critical nozzle flow with real gas effects. Redlich—Kwong's equation of state is incorporated into the axisymmetric, compressible Navier—Stokes equations to account for the inter-molecular forces and molecular volume of hydrogen. The computational results show that the critical pressure ratio and the discharge coefficient for ideal gas assumptions are significantly different from those of the real gas, as the Reynolds number exceeds a certain value. It is also known that the real gas effects appear largely in terms of the compressibility factor and the specific heat ratio, and these become more remarkable as the pressure of hydrogen increases.

We have compared the KOrea Multi-Purpose SATellite-1 (KOMPSAT-1) drag derived density with the MSISE model (NRLMSISE-00 and MSISE-90) density during strong solar and/or geomagnetic activities. It is well known that there are two major mechanisms to induce satellite drag caused by atmospheric density enhancement: the heating by solar EUV radiation and joule heating associated with local geomagnetic current enhancements during geomagnetic storms. For this work we select five events dominated by the radiation effect and/or the geomagnetic effect. For these events we compared the satellite drag derived density with the MSISE model density. The major results can be summarized as follows. (1) The density predicted from the MSISE models during radiation dominated periods are comparable to the drag derived density but the MSISE model density during strong geomagnetic storms is significantly underestimated when the MSISE model density is compared to the drag derived density, by about two times for the NRLMSISE-00 model. (2) The ratios of the KOMPSAT-1 (around 685 km) drag derived density to the MSISE model density during a strong geomagnetic storm are abruptly enhanced (up to a factor of about 8 for the MSISE-90 model and about 3 for the NRLMSISE-00 model), which are much larger than previous estimates from low altitude (around 400 km) satellites. (3) There is a possible correlation between daily drag enhancement and daily Dst variation. We note that there is a remarkable difference in daily drag enhancement although solar and geomagnetic activities are quite similar to each other. We suggest that such a difference should be explained by the accumulation of solar radiation effect depending on solar activity cycle.

Adetailed picture of the internal flow during the starting transient of high-performance solid rocket motors (SRMs) is of topical interest for several reasons in addition to the motor performance itself [1–12]. Despite the fact that many of the existing models could predict the internal flow features of certain classes of SRMs, none of these models could capture the unusual starting transient flow features such as pressure overshoot and pressure-rise rate often observed during the initial phase of operation of the dual-thrust motors (DTMs) [1]. Ikawa and Laspesa [8] reported that during the first launching of the space shuttle from the Eastern Test Range, the launch vehicle experienced the propagations of a strongly impulsive compression wave. This wave was induced by the SRM ignition and was emanating from the large SRM duct openings. The analysis further showed that the compression wave created by ignition of the main grain was the cause of the ignition overpressure on the launch pad [9]. Alestra et al. [10] reported that Ariene 5 launcher experienced overpressure load during the liftoff phase. The overpressure is composed of the ignition overpressure, which emanates from the launch pad, and the duct overpressure, which emanates from the launch ducts. Of late, Sanal Kumar et al. [1,2] reported that abnormal high-pressure overshoot in certain class of DTMs during the startup transient is due to the formation of shock waves because of the fluid-throat effect, which has received considerable attention in the scientific community. This manuscript is the continuation of the previous connected note for establishing the intrinsic flow physics pertinent to internal flow choking in inert simulators of dual-thrust motors [1]. Note that the illustration of ignition pressure spike is deliberately set aside in this note for explaining the intrinsic flow physics pertinent to internal flow choking without complications arising from the propellant combustion.

We examine the atmospheric drag on the low earth-orbiting satellite, KOMPSAT-1 in a sun-synchronous orbit at ~685-km altitude starting in 1999, during a 3-month (October-December) period in 2003. This 3-month interval includes the October 29-30 and November 20 magnetic superstorms and weak to moderate storms. We observed that the daily KOMPSAT-1 drag acceleration transiently responses to transient storm-time disturbances. That is, there is an one-to-one correspondence between the KOMPSAT-1 drag accelerations and the storm events. We find that the drag acceleration correlates strongly with the level of geomagnetic disturbance. This indicates that the trajectory of KOMPSAT-1 is significantly perturbed during extremely disturbed intervals because of atmospheric density increase. The main contributor to the density increase is Joule heating associated with the geomagnetic activity rather than the solar EUV radiation, as reported by previous studies. We suggest that understanding how the upper atmosphere responses to the geomagnetic-associated heating is important to predict space weather impacts on low earth-orbiting satellites.

Human cathepsin K, a cysteine proteinase of the papain family, has been recognized as a potential drug target for the treatment of osteoporosis. The predominant expression of cathepsin K in osteoclasts has rendered the enzyme into a major target for the development of novel antiresorptive drugs. Now, we report the pharmacological properties of OST-4077 [furan-2-carboxylic acid (1-{1-[4-fluoro-2-(2-oxo-pyrrolidin-1-yl)-phenyl]-3-oxo-piperidin-4-ylcarbamoyl}-cyclohexyl)-amide] as a novel selective cathepsin K inhibitor. Human and rat cathepsin K were inhibited in vitro by OST-4077 with the IC50 values of 11 and 427 nM, respectively. OST-4077 suppressed bone resorption induced by rabbit osteoclasts (IC50, 37 nM) but did not affect bone mineralization or cellular alkaline phosphatase activity in MC3T3-E1 cells. Parathyroid hormone-induced bone resorption was inhibited in a dose-dependent manner in thyroparathyroidectomized rats gavaged with a single dose of OST-4077 (ED50, 69 mg/kg). When given orally twice daily for 4 weeks to 3-month-old ovariectomized (OVX) rats, OST-4077 dose-dependently prevented bone loss, as monitored by bone densitometry, ash content, and urinary excretion of deoxypyridinoline. No change in serum osteocalcin in the OVX rats by OST-4077 suggested that bone formation might not be affected by the agent. In summary, OST-4077 selectively inhibited bone resorbing activities of osteoclasts and prevented bone loss induced by estrogen deficiency but did not affect bone formation. OST-4077, an orally active selective human cathepsin K inhibitor, may have the therapeutic potential for the treatment of diseases characterized by excessive bone loss including osteoporosis.

The present study addresses experimental results to investigate the effect of nozzle inlet configuration on under-expanded swirling jets, which is generated by a convergent nozzle with four tangential inlets at the supply chamber. Several different types of plugs and needles, which can be regarded as a means to measure the nozzle inlet pressure or temperature, are employed to change the nozzle supply chamber. The jet supply pressure at the tangential inlets is varied to obtain the swirling jets ranging from a moderately under-expanded to a strongly under-expanded flow at the exit of nozzle. The under-expanded swirling jet flows are specified by the impact pressure measurements and visualized using the shadowgraph optical method. The results show that the major features of the under-expanded swirling jet are considerably influenced by the detailed configuration of the nozzle inlet chamber.

We investigated the magnetic and structural properties of TiO 2 rutile single- and codoped with Fe and Co prepared by a solid state reaction method. The concentrations of each dopant was varied from 0 to 5%. Most of the samples were ferromagnetic at room temperature. When Co or Fe was single-doped to 3%, only weak room temperature ferromagnetism was observed. But when 1% of Fe or Co was additionally co-doped, magnetic moment per magnetic ion, remnant magnetization, and coercivity were significantly enhanced compared to the single-doped case, and this behavior was observed up to 5% co-doping. The structural study showed the TiO 2 rutile phase for all of the samples with second phases of Fe 2 TiO 5 and/or CoTiO 3 depending on the contents of Co and Fe, but no indication of Co or Fe metallic cluster was found. The micro composition analysis showed the linear correlation between Co and Fe concentrations, which is a result of enhanced incorporation of magnetic ions into TiO 2 host when co-doped. The Mosbauer spectrum showed that the value of the hyperfine field is about 1.5 times as large as that of α-Fe indicating that the Fe impurities substituted into Ti atoms instead of forming iron clusters.

For technological reasons many high-performance solid rocket motors are made from segmented propellant grains with non-uniform port geometry. In this paper parametric studies have been carried out to examine the geometric dependence of transient flow features in solid rockets with non-uniform ports. Numerical computations have been carried out in an inert simulator of solid propellant rocket motor with the aid of a standard k-ω turbulence model. It was seen that the damping of the temperature fluctuation is faster in solid rocket with convergent port than with divergent port geometry. We inferred that the damping of the flow fluctuations using the port geometry is a meaningful objective for the suppression and control of the instability and/or pressure/thrust oscillations during the starting transient of solid rockets.

The present study addresses a computational result of unsteady gas flow through a critical nozzle. The axisymmetric unsteady compressible Navier-Stokes equations are solved using a finite volume method that makes use of the second-order upwind scheme for spatial derivatives and the multi-stage Runge-Kutta integral scheme for time derivatives. The steady solutions of the governing equation system are validated with the previous experimental data to ensure that the present computational method is valid to predict the critical nozzle flows. In order to simulate the effects of back-pressure fluctuations on the critical nozzle flows, an excited pressure oscillation with an amplitude and frequency is assumed downstream of the exit of the critical nozzle. The results obtained show that, for low Reynolds numbers, the unsteady effects of the pressure fluctuations can propagate upstream of the throat of the critical nozzle, thus giving rise to the applicable fluctuations in mass flow rate through the critical nozzle, while, for high Reynolds numbers, the pressure signals occurring at the exit of the critical nozzle do not propagate upstream beyond the nozzle throat. For a low Reynolds number, it is found that the sonic line near the throat of the critical nozzle markedly fluctuates with time, providing an important mechanism for pressure signals to propagate upstream of the nozzle throat, even in choked flow conditions. The present study is the first investigation to clarify the unsteady effects on the critical nozzle flows.

We have investigated the effects of high temperature annealing on the physical and electrical properties of multilayered high-k gate oxide [HfSixOy/HfO2/intermixed-layer(IL)/ZrO2/intermixed-layer(IL)/HfO2] in metal-oxide-semiconductor device. The multilayered high-k films were formed after oxidizing the Hf/Zr/Hf films deposited directly on the Si substrate. The subsequent N2 annealing at high temperature (⩾ 700 °C) not only results in the polycrystallization of the multilayered high-k films, but also causes the diffusion of Zr. The latter transforms the HfSixOy/HfO2/IL/ZrO2/IL/HfO2 film into the Zr-doped HfO2 film, and improves electrical properties in general. However, the thin SiOx interfacial layer starts to form if annealing temperature increases over 700 °C, deteriorating the equivalent oxide thickness.

We have investigated the effects of annealing temperature on the physical and electrical properties of the HfSixOy/HfO2 thin film for high-k gate oxides in a metal-oxide-semiconductor device. The oxidation and subsequent postoxidation N2 annealing at 500 °C of Hf deposited directly on the Si substrate results in the HfSixOy/HfO2 stack layer with excellent electrical properties. For instance, we observe a negligible hysteresis window, an excellent equivalent oxide thickness (1.2 nm), and a low leakage current density (⩽4×10−5 A/cm2 at 2 V after compensating the flatband voltage shift). However, the formation of an interfacial SiOx layer enhances as annealing temperature increases. Based on current observation, we suggest that annealing temperature must be carefully controlled to obtain the excellent electrical properties of HfO2/HfSixOy high-k gate oxides.

We studied the structural and magnetic properties of Ti1−xCoxO2 powder samples synthesized by the sol–gel method. In order to study the post annealing effect on the magnetic properties, the same precursor was annealed at 770 K for 5 h in air and in the pressure of 10−6 Torr. In the case of samples annealed in vacuum, enhanced ferromagnetism was observed at room temperature, while only paramagnetic behavior was observed in samples annealed in air. Moreover, the magnetization of the vacuum-annealed sample sharply decreased around 650 K while measuring in air, but such decrease in the magnetization was almost absent while measuring in He gas up to 750 K. The structural studies showed dominant anatase and minor rutile phases in vacuum-annealed samples, while an additional nonmagnetic CoTiO3 phase was observed in air-annealed samples. We attribute the enhanced magnetization in the vacuum-annealed sample to the oxygen deficiency which prevents the formation of non-magnetic CoTiO3 complexes. It is also possible that the reduced oxygen environment can promote the clustering of Co-rich clusters as evidenced by transmission electron microscopy in samples of x = 0.1, thus giving rise to an enhanced ferromagnetic behaviour. However, no direct observation of Co clusters in samples for x ≤ 0.05 was made. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A shock wave discharged from a tube leads to an impulsive noise that is similar to a sonic boom. The impulsive noise has often been a major factor in deterioration of the performance of flow devices and has hazardous effects on human beings. The objective of the current work is to develop a new technique for the control of the impulsive wave. Experiments using a simple shock tube were carried out to investigate the effect of a cavity/helical vane system on the magnitude of an impulsive wave. The results showed that the magnitude of the impulsive wave was influenced by the detailed configuration of the helical vane inside the cavity which was installed at the exit of a tube. The results of the tests with and without the helical vane were compared to validate the effectiveness of the present control technique. The experimental data showed that the present cavity/helical vane system reduced the peak pressure of the impulsive wave up to about 50 per cent, compared with a straight tube, and was suitable for alleviating the magnitude of the impulsive wave.

The present study addresses experimental investigations of the near-field flow structures of an underexpanded sonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the underexpanded free jets. The interactions between the secondary swirl and primary underexpanded jets are quantified by a fine pitot impact and static pressure measurements and are visualized using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary underexpanded jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary underexpanded jets, compared with the secondary stream of no swirl. The results show that the presence of an annular swirl stream causes the Mach disc to move further downstream, with an increased diameter, and remarkably reduces the fluctuations of the impact pressures in the underexpanded sonic dual coaxial jet, compared with the case of the secondary annular stream with no swirl.

When a plane shock wave reflects from a concave wall or when a curved shock wave reflects from a straight wall, it is focused at a certain location, resulting in extremely high local pressure and temperature. This focusing is due to a non-linear phenomenon of a shock wave. This focusing phenomenon has been extensively applied in a variety of engineering and medical areas. In the current study, the focusing phenomenon of a weak shock wave over a reflector is numerically investigated using a computational fluid dynamics (CFD) method. The total variation diminishing (TVD) scheme is used to solve the unsteady, two-dimensional, compressible, Euler equations. The Mach number of the incident shock wave is changed in the range from 1.1 to 1.5. Several different types of reflectors are employed to investigate the effect of the reflector on the focusing phenomenon of the weak shock wave. The focusing characteristics of the shock wave are investigated in terms of peak pressure, gas dynamic and geometrical foci. The results obtained are compared with previous experiment results that are available. The results show that the peak pressure of shock wave focusing and its location strongly depend on the Mach number of the incident shock wave and the reflector geometry. The location of the gas dynamic focus is always shorter than that of the geometrical one. This tendency is more remarkable as the incident shock wave becomes stronger. The present computations predict the experimental results with a very good accuracy.

The critical nozzle is defined as a device to measure the mass flow with only the nozzle supply conditions making use of the flow choking phenomenon at the nozzle throat. The discharge coefficient and critical pressure ratio of the gas flow through the critical nozzle are strongly dependent on the Reynolds number, based on the diameter of the nozzle throat and nozzle supply conditions. Recently a critical nozzle with a small diameter has been extensively used to measure mass flow in a variety of industrial fields. For low Reynolds numbers, prediction of the discharge coefficient and critical pressure is very important since the viscous effects near walls significantly affect the mass flow through the critical nozzle, which is associated with working gas consumption and operation conditions of the critical nozzle. In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through the critical nozzle. In order to investigate the effect of the working gas and turbulence model on the discharge coefficient, several kinds of gases and several turbulence models are employed. The Reynolds number effects are investigated with several nozzles with different throat diameters. The diffuser angle is varied in order to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the standard k-ε turbulence model with the standard wall function gives the best prediction of the discharge coefficient. The discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that the diffuser angle affects the critical pressure ratio.

The present paper describes experimental and numerical investigations of a new boundary condition at an open end of a tube, in which a weak shock wave is discharged towards the surroundings. Experimental and computational investigations were performed on a simple shock tube with and without baffle plates. A numerical calculation was carried out for an unsteady, axisymmetric, inviscid, compressible flow. The size of baffle plate was varied in order to understand its effect on the reflection of the weak shock wave from the open end of the tube. With and without a baffle plate, the results of the experiment were in good agreement with those of numerical calculations. The results showed that an open end correction is subject to the presence of a baffle plate at the open end. An improved empirical equation for the reflection of the weak shock wave from the open end of a duct with and without a baffle plate was developed.

The propagation of the impulsive wave discharged from the inclined exit of a tube is investigated using a shock tube experiment and by numerical computations. The pressure histories and wavefront geometries of the impulsive wave propagating outside the exits of the tube with several different configurations are analysed for the range of an initial shock wave Mach number between 1.1 and 1.4. In the shock tube experiments, the impulsive waves are visualized by a Schlieren optical system for the purpose of validation of computational work. Computations using the two-dimensional, unsteady, compressible, Euler equations are carried out to represent the experimental impulsive waves. The results obtained show that the inclination angle of the tube exit reduces the magnitude of the impulsive wave and affects the wavefront geometry of the impulsive wave. It is also found that the propagation direction and magnitude of the impulsive wave depend on the Mach number of the initial shock wave, while the impulsive waveform does not significantly vary with the Mach number of the initial shock wave. The computed results obtained predict the experimental ones with quite good accuracy.

An experimental study has been performed to investigate boiling mechanism and to estimate critical heat removal rate from a critical power through a hemispherical narrow gap using distilled water and Freon R-113. The distilled water data on the critical heat removal rate were compared with the R-113 data. The experimental results on the critical heat removal rate were also compared with the existing correlations, developed in flat plate, annuli, and spherical gaps. The test results have shown that a CCFL (Counter Current Flow Limitation) brings about local dryout and finally global dryout in the hemispherical gap thickness of 0.5, 1.0, and 2.0 mm. The boiling mechanism in a hemispherical gap thickness of 5.0 mm is the combination of the CCFL and the pool boiling condition. An increase in gap thickness of 10.0 mm leads to the pool boiling condition rather than the CCFL. Increases in the gap thickness and pressure lead to increase in critical heat removal rate, but the pressure effect on the critical heat removal rate was found to be much milder than the predictions by flat plate and annuli gaps. The measured critical heat removal rate using the R-113 in hemispherical narrow gap thickness of 1.0 and 2.0 mm are 51.5%, 44.5% lower than that using the distilled water due to the lower boiling point and the bubble size, which is different from the pool boiling condition of approximately 14.8%. The measured critical heat removal rate using the R-113 in a gap thickness of 5 mm is 21.6% lower than that using distilled water, which approaches to the pool boiling condition.

The impulse wave, which is usually generated by a shock wave discharge from the exit of a pipe, almost always leads to undesirable noise and vibration problems. The present study addresses experimental and computational work of the impulse wave discharged from the exit of two kinds of right-angle pipe bends, which are attached to the open end of a simple shock tube. The weak normal shock wave with its magnitude of Mach number from 1·02 to 1·20 is employed to obtain the impulse wave propagating outside the exit of the pipe bends. A Schlieren optical system is employed to visualize the impulse wave discharged from the exit of the pipe bends at an instant. The experimental data of the magnitude of the impulse wave and its propagation directivity are analyzed to characterize the impulse waves discharged from the exit of the pipe bends and compared with those discharged from a straight pipe. Computational analysis using the unsteady, inviscid, compressible equations is complemented to represent the major features of the impulse wave obtained from the shock tube experiments. Computational results well predict the experimented dynamic behaviors of the impulse wave. The results obtained show that a right-angle miter bend considerably reduces the magnitude of the impulse wave and its directivity toward to the pipe axis, compared with the straight pipe. It is believed that the right-angle miter bend pipe can play one role of a passive control against the impulse wave.

The impulse wave is made by the weak normal shock discharge from an open end of a shock tube. In order to understand the dynamic characteristics of the impulse wave impinging upon a flat plate, experiments are performed over the shock Mach number range from 1·01 to 1·20. A flat plate is placed downstream, normal to the axis of the shock tube, to simulate the impulse wave impingement on an object. The distance between the exit of the shock tube and flat plate is changed. The baffle plate is installed at the exit of the shock tube. The sizes of the baffle plate and impinging flat plate are varied to investigate the magnitude of the impulse wave impinging upon the flat plate. Computational analysis is applied to model the flow field subject to unsteady, axisymmetric, inviscid, compressible, equations. Computational results well predict the experimented dynamic behavior of the impinging impulse wave. The impulse wave impinging upon the flat plate has a sharp peak of very short rising time and its magnitude decreases with distance from the center of the flat plate. The magnitude of the impulse wave impinging upon the flat plate can be predicted by the empirical equations that are developed in the present study.

Railway train aerodynamic problems are closely associated with the flows occurring around train. Much effort to speed up the train system has to date been paid on the improvement of electric motor power rather than understanding the flow around the train. This has led to larger energy losses and performance deterioration of the train system, since the flows around train are more disturbed due to turbulence of the increased speed of the train, and consequently the flow energies are converted to aerodynamic drag, noise and vibrations. With the speed-up of train, many engineering problems which have been neglected at low train speeds, are being raised with regard to aerodynamic noise and vibrations, impulse forces occurring as two trains intersect each other, impulse wave at the exit of tunnel, ear discomfort of passengers inside train, etc. These are of major limitation factors to the speed-up of train system. The present review addresses the state of the art on the aerodynamic and aeroacoustic problems of high-speed railway train and highlights proper control strategies to alleviate undesirable aerodynamic problems of high-speed railway train system.

KAERI (Korea Atomic Energy Research Institute) has been studing the pyroprocess since 1997. For a demonstration of the pyroprocess, KAERI developed two facilities, the ACPF (Advanced spent fuel Conditioning Process Facility) and PRIDE (PyRoprocess-Integrated inactive DEmonstration facility), by 2012. From 2013, KAERI has been studying a pre-conceptual design of the ESPF (Engineering-Scale Pyroprocess Facility). In this paper, the safety evaluation methods and results for these three facilities are described.

The present paper describes experimental and computational work to augment the magnitude of the impulsive wave generated at the exit of a pipe. An experiment was performed using a simple shock tube with an open end, and numerical calculations were carried out to solve the unsteady, axisymmetric, inviscid, compressible governing equations that represent the experimental flowfield. The control strategy applied was to alter the exit geometry of a straight tube to a sudden enlargement tube and a flare tube. The effects of the configurations of the tube exit on the magnitude of the impulsive wave were investigated over the range of weak shock Mach numbers from 1.01 to 1.10. Various types of geometric parameter were explored for the configurations of the tube exit. The results obtained were compared with those of the straight tube tests. The numerical result predicted the magnitude of the experimented impulsive waves with a good accuracy. The present passive control technique enabled the magnitude of the impulsive wave to be augmented by about 24 per cent, compared with that of the straight tube with no control.