South Carolina southeast high speed rail corridor improvement study

DOT National Transportation Integrated Search

2001-02-01

The Southeast Rail Corridor was originally designated as a high-speed corridor in Section 1010 of the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991. More specifically, it involved the high-speed grade-crossing improvement program o...

Cavitation induced by high speed impact of a solid surface on a liquid jet

NASA Astrophysics Data System (ADS)

Farhat, Mohamed; Tinguely, Marc; Rouvinez, Mathieu

2009-11-01

A solid surface may suffer from severe erosion if it impacts a liquid jet at high speed. The physics behind the erosion process remains unclear. In the present study, we have investigated the impact of a gun bullet on a laminar water jet with the help of a high speed camera. The bullet has a flat front and 11 mm diameter, which is half of jet diameter. The impact speed was varied between 200 and 500 ms-1. Immediately after the impact, a systematic shock wave and high speed jetting were observed. As the compression waves reflect on the jet boundary, a spectacular number of vapour cavities are generated within the jet. Depending on the bullet velocity, these cavities may grow and collapse violently on the bullet surface with a risk of cavitation erosion. We strongly believe that this transient cavitation is the main cause of erosion observed in many industrial applications such as Pelton turbines.

Fast and accurate: high-speed metrological large-range AFM for surface and nanometrology

NASA Astrophysics Data System (ADS)

Dai, Gaoliang; Koenders, Ludger; Fluegge, Jens; Hemmleb, Matthias

2018-05-01

Low measurement speed remains a major shortcoming of the scanning probe microscopic technique. It not only leads to a low measurement throughput, but a significant measurement drift over the long measurement time needed (up to hours or even days). To overcome this challenge, PTB, the national metrology institute of Germany, has developed a high-speed metrological large-range atomic force microscope (HS Met. LR-AFM) capable of measuring speeds up to 1 mm s‑1. This paper has introduced the design concept in detail. After modelling scanning probe microscopic measurements, our results suggest that the signal spectrum of the surface to be measured is the spatial spectrum of the surface scaled by the scanning speed. The higher the scanning speed , the broader the spectrum to be measured. To realise an accurate HS Met. LR-AFM, our solution is to combine different stages/sensors synchronously in measurements, which provide a much larger spectrum area for high-speed measurement capability. Two application examples have been demonstrated. The first is a new concept called reference areal surface metrology. Using the developed HS Met. LR-AFM, surfaces are measured accurately and traceably at a speed of 500 µm s‑1 and the results are applied as a reference 3D data map of the surfaces. By correlating the reference 3D data sets and 3D data sets of tools under calibration, which are measured at the same surface, it has the potential to comprehensively characterise the tools, for instance, the spectrum properties of the tools. The investigation results of two commercial confocal microscopes are demonstrated, indicating very promising results. The second example is the calibration of a kind of 3D nano standard, which has spatially distributed landmarks, i.e. special unique features defined by 3D-coordinates. Experimental investigations confirmed that the calibration accuracy is maintained at a measurement speed of 100 µm s‑1, which improves the calibration efficiency by a factor of 10.

High-speed microjet generation using laser-induced vapor bubbles

NASA Astrophysics Data System (ADS)

Oudalov, Nikolai; Tagawa, Yoshiyuki; Peters, Ivo; Visser, Claas-Willem; van der Meer, Devaraj; Prosperetti, Andrea; Sun, Chao; Lohse, Detlef

2011-11-01

The generation and evolution of microjets are studied both experimentally and numerically. The jets are generated by focusing a laser pulse into a microscopic capillary tube (~50 μm) filled with water-based red dye. A vapor bubble is created instantly after shooting the laser (<1 μs), sending out a shockwave towards the curved free surface at which the high-speed microjet forms. The process of jet formation is captured using high-speed recordings at 1.0 × 106 fps. The velocity of the microjets can reach speeds of ~850 m/s while maintaining a very sharp geometry. The high-speed recordings enable us to study the effect of several parameters on the jet velocity, e.g. the absorbed energy and the distance between the laser spot and the free surface.The results show a clear dependence on these variables, even for supersonic speeds. Comparisons with numerical simulations confirm the nature of these dependencies.

High-speed ethanol micro-droplet impact on a solid surface

NASA Astrophysics Data System (ADS)

Fujita, Yuta; Kiyama, Akihito; Tagawa, Yoshiyuki

2016-11-01

Recently, droplet impact draws great attention in the fluid mechanics. In previous work, micro-droplet impact on a solid surface at velocities up to 100 m s-1 was studied. However the study was only on water micro-droplets. In this study, we experimentally investigate high-speed impact of ethanol micro-droplets in order to confirm the feature about maximum spreading radius with another liquid. A droplet is generated from a laser-induced high-speed liquid jet. The diameter of droplets is around 80 μm and the velocity is larger than 30 m s-1. The surface tension of ethanol is 22.4 mNm-1 and density is 789 kgm-3. Weber number ranges We >1000. By using a high-speed camera, we investigate the deformation of droplets as a function of Weber number. This work was supported by JSPS KAKENHI Grant Number JP26709007.

Surface topography and roughness of high-speed milled AlMn1Cu

NASA Astrophysics Data System (ADS)

Wang, Zhenhua; Yuan, Juntang; Yin, Zengbin; Hu, Xiaoqiu

2016-10-01

The aluminum alloy AlMn1Cu has been broadly applied for functional parts production because of its good properties. But few researches about the machining mechanism and the surface roughness were reported. The high-speed milling experiments are carried out in order to improve the machining quality and reveal the machining mechanism. The typical topography features of machined surface are observed by scan electron microscope(SEM). The results show that the milled surface topography is mainly characterized by the plastic shearing deformation surface and material piling zone. The material flows plastically along the end cutting edge of the flat-end milling tool and meanwhile is extruded by the end cutting edge, resulting in that materials partly adhere to the machined surface and form the material piling zone. As the depth of cut and the feed per tooth increase, the plastic flow of materials is strengthened and the machined surface becomes rougher. However, as the cutting speed increases, the plastic flow of materials is weakened and the milled surface becomes smoother. The cutting parameters (e.g. cutting speed, feed per tooth and depth of cut) influencing the surface roughness are analyzed. It can be concluded that the roughness of the machined surface formed by the end cutting edge is less than that by the cylindrical cutting edge when a cylindrical flat-end mill tool is used for milling. The proposed research provides the typical topography features of machined surface of the anti-rust aluminum alloy AlMn1Cu in high speed milling.

Airfoil shape for flight at subsonic speeds

DOEpatents

Whitcomb, Richard T.

1976-01-01

An airfoil having an upper surface shaped to control flow accelerations and pressure distribution over the upper surface and to prevent separation of the boundary layer due to shock wave formulation at high subsonic speeds well above the critical Mach number. A highly cambered trailing edge section improves overall airfoil lifting efficiency.

Surface friction alters the agility of a small Australian marsupial.

PubMed

Wheatley, Rebecca; Clemente, Christofer J; Niehaus, Amanda C; Fisher, Diana O; Wilson, Robbie S

2018-04-23

Movement speed can underpin an animal's probability of success in ecological tasks. Prey often use agility to outmanoeuvre predators; however, faster speeds increase inertia and reduce agility. Agility is also constrained by grip, as the foot must have sufficient friction with the ground to apply the forces required for turning. Consequently, ground surface should affect optimum turning speed. We tested the speed-agility trade-off in buff-footed antechinus ( Antechinus mysticus ) on two different surfaces. Antechinus used slower turning speeds over smaller turning radii on both surfaces, as predicted by the speed-agility trade-off. Slipping was 64% more likely on the low-friction surface, and had a higher probability of occurring the faster the antechinus were running before the turn. However, antechinus compensated for differences in surface friction by using slower pre-turn speeds as their amount of experience on the low-friction surface increased, which consequently reduced their probability of slipping. Conversely, on the high-friction surface, antechinus used faster pre-turn speeds in later trials, which had no effect on their probability of slipping. Overall, antechinus used larger turning radii (0.733±0.062 versus 0.576±0.051 m) and slower pre-turn (1.595±0.058 versus 2.174±0.050 m s -1 ) and turning speeds (1.649±0.061 versus 2.01±0.054 m s -1 ) on the low-friction surface. Our results demonstrate the interactive effect of surface friction and the speed-agility trade-off on speed choice. To predict wild animals' movement speeds, future studies should examine the interactions between biomechanical trade-offs and terrain, and quantify the costs of motor mistakes in different ecological activities. © 2018. Published by The Company of Biologists Ltd.

Effect of High-speed Milling tool path strategies on the surface roughness of Stavax ESR mold insert machining

NASA Astrophysics Data System (ADS)

Mebrahitom, A.; Rizuan, D.; Azmir, M.; Nassif, M.

2016-02-01

High speed milling is one of the recent technologies used to produce mould inserts due to the need for high surface finish. It is a faster machining process where it uses a small side step and a small down step combined with very high spindle speed and feed rate. In order to effectively use the HSM capabilities, optimizing the tool path strategies and machining parameters is an important issue. In this paper, six different tool path strategies have been investigated on the surface finish and machining time of a rectangular cavities of ESR Stavax material. CAD/CAM application of CATIA V5 machining module for pocket milling of the cavities was used for process planning.

The machined surface of magnesium AZ31 after rotary turning at air cooling condition

NASA Astrophysics Data System (ADS)

Akhyar, G.; Purnomo, B.; Hamni, A.; Harun, S.; Burhanuddin, Y.

2018-04-01

Magnesium is a lightweight metal that is widely used as an alternative to iron and steel. Magnesium has been applied in the automotive industry to reduce the weight of a component, but the machining process has the disadvantage that magnesium is highly flammable because it has a low flash point. High temperature can cause the cutting tool wear and contributes to the quality of the surface roughness. The purpose of this study is to obtain the value of surface roughness and implement methods of rotary cutting tool and air cooling output vortex tube cooler to minimize the surface roughness values. Machining parameters that is turning using rotary cutting tool at speed the workpiece of (Vw) 50, 120, 160 m/min, cutting speed of rotary tool of (Vt) 25, 50, 75 m/min, feed rate of (f) 0.1, 0.15, 0.2 mm/rev, and depth of cut of 0.3 mm. Type of tool used is a carbide tool diameter of 16 mm and air cooling pressure of 6 bar. The results show the average value of the lowest surface roughness on the speed the workpiece of 80 m/min, cutting speed of rotary tool of 50 m/min, feed rate of 0.2 mm/rev, and depth of cut of 0.3 mm. While the average value of the highest surface roughness on the speed the workpiece of 160 m/min, cutting speed of rotary tool of 50 m/min, feed rate of 0.2 mm/rev, and depth of cut of 0.3 mm. The influence of machining parameters concluded the higher the speed of the workpiece the surface roughness value higher. Otherwise the higher cutting speed of rotary tool then the lower the surface roughness value. The observation on the surface of the rotary tool, it was found that no uniform tool wear which causes non-uniform surface roughness. The use of rotary cutting tool contributing to lower surface roughness values generated.

Flying fish accelerate at 5 G to leap from the water surface

NASA Astrophysics Data System (ADS)

Yang, Patricia; Phonekeo, Sulisay; Xu, Ke; Chang, Shui-Kai; Hu, David

2013-11-01

Flying fish can both swim underwater and glide in air. Transitioning from swimming to gliding requires penetration of the air-water interface, or breaking the ``surface tension barrier,'' a formidable task for juvenile flying fish measuring 1 to 5 cm in length. In this experimental investigation, we use high-speed videography to characterize the kinematics of juvenile flying fish as they leap from the water surface. During this process, which lasts 0.05 seconds, flying fish achieve body accelerations of 5 times earth's gravity and gliding speeds of 1.3 m/s, an order of magnitude higher than their steady swimming speed. We rationalize this anomalously high speed on the basis of the hydrodynamic and surface tension forces and torques experienced by the fish. Specifically, leaping fish experience skin friction forces only on the submerged part of their body, permitting them to achieve much higher speeds than in steady underwater swimming. We also perform experiments using a towed flying fish mimc to determine optimality of various parameters in this process, including body angle and start position with respect to the water surface.

High-speed optical 3D sensing and its applications

NASA Astrophysics Data System (ADS)

Watanabe, Yoshihiro

2016-12-01

This paper reviews high-speed optical 3D sensing technologies for obtaining the 3D shape of a target using a camera. The focusing speed is from 100 to 1000 fps, exceeding normal camera frame rates, which are typically 30 fps. In particular, contactless, active, and real-time systems are introduced. Also, three example applications of this type of sensing technology are introduced, including surface reconstruction from time-sequential depth images, high-speed 3D user interaction, and high-speed digital archiving.

Forecasting Cool Season Daily Peak Winds at Kennedy Space Center and Cape Canaveral Air Force Station

NASA Technical Reports Server (NTRS)

Barrett, Joe, III; Short, David; Roeder, William

2008-01-01

The expected peak wind speed for the day is an important element in the daily 24-Hour and Weekly Planning Forecasts issued by the 45th Weather Squadron (45 WS) for planning operations at Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). The morning outlook for peak speeds also begins the warning decision process for gusts ^ 35 kt, ^ 50 kt, and ^ 60 kt from the surface to 300 ft. The 45 WS forecasters have indicated that peak wind speeds are a challenging parameter to forecast during the cool season (October-April). The 45 WS requested that the Applied Meteorology Unit (AMU) develop a tool to help them forecast the speed and timing of the daily peak and average wind, from the surface to 300 ft on KSC/CCAFS during the cool season. The tool must only use data available by 1200 UTC to support the issue time of the Planning Forecasts. Based on observations from the KSC/CCAFS wind tower network, surface observations from the Shuttle Landing Facility (SLF), and CCAFS upper-air soundings from the cool season months of October 2002 to February 2007, the AMU created multiple linear regression equations to predict the timing and speed of the daily peak wind speed, as well as the background average wind speed. Several possible predictors were evaluated, including persistence, the temperature inversion depth, strength, and wind speed at the top of the inversion, wind gust factor (ratio of peak wind speed to average wind speed), synoptic weather pattern, occurrence of precipitation at the SLF, and strongest wind in the lowest 3000 ft, 4000 ft, or 5000 ft. Six synoptic patterns were identified: 1) surface high near or over FL, 2) surface high north or east of FL, 3) surface high south or west of FL, 4) surface front approaching FL, 5) surface front across central FL, and 6) surface front across south FL. The following six predictors were selected: 1) inversion depth, 2) inversion strength, 3) wind gust factor, 4) synoptic weather pattern, 5) occurrence of precipitation at the SLF, and 6) strongest wind in the lowest 3000 ft. The forecast tool was developed as a graphical user interface with Microsoft Excel to help the forecaster enter the variables, and run the appropriate regression equations. Based on the forecaster's input and regression equations, a forecast of the day's peak and average wind is generated and displayed. The application also outputs the probability that the peak wind speed will be ^ 35 kt, 50 kt, and 60 kt.

High-speed Raman-encoded molecular imaging of freshly excised tissue surfaces with topically applied SERRS nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Yu "Winston"; Yang, Qian; Kang, Soyoung; Wall, Matthew A.; Liu, Jonathan T. C.

2018-04-01

Surface-enhanced Raman scattering (SERS) nanoparticles (NPs) are increasingly being engineered for a variety of disease-detection and treatment applications. For example, we have previously developed a fiber-optic Raman-encoded molecular imaging (REMI) system for spectral imaging of biomarker-targeted SERS NPs topically applied on tissue surfaces to identify residual tumors at surgical margins. Although accurate tumor detection was achieved, the commercial SERS NPs used in our previous studies lacked the signal strength to enable high-speed imaging with high pixel counts (large fields of view and/or high spatial resolution), which limits their use for certain time-constrained clinical applications. As a solution, we explored the use of surface-enhanced resonant Raman scattering (SERRS) NPs to enhance imaging speeds. The SERRS NPs were synthesized de novo, and then conjugated to HER2 antibodies to achieve high binding affinity, as validated by flow cytometry. Under identical tissue-staining and imaging conditions, the targeted SERRS NPs enabled reliable identification of HER2-overexpressed tumor xenografts with 50-fold-enhanced imaging speed compared with our standard targeted SERS NPs. This enables our REMI system to image tissue surfaces at a rate of 150 cm2 per minute at a spatial resolution of 0.5 mm.

An oilspill trajectory analysis model with a variable wind deflection angle

USGS Publications Warehouse

Samuels, W.B.; Huang, N.E.; Amstutz, D.E.

1982-01-01

The oilspill trajectory movement algorithm consists of a vector sum of the surface drift component due to wind and the surface current component. In the U.S. Geological Survey oilspill trajectory analysis model, the surface drift component is assumed to be 3.5% of the wind speed and is rotated 20 degrees clockwise to account for Coriolis effects in the Northern Hemisphere. Field and laboratory data suggest, however, that the deflection angle of the surface drift current can be highly variable. An empirical formula, based on field observations and theoretical arguments relating wind speed to deflection angle, was used to calculate a new deflection angle at each time step in the model. Comparisons of oilspill contact probabilities to coastal areas calculated for constant and variable deflection angles showed that the model is insensitive to this changing angle at low wind speeds. At high wind speeds, some statistically significant differences in contact probabilities did appear. ?? 1982.

Computational Model for Impact-Resisting Critical Thickness of High-Speed Machine Outer Protective Plate

NASA Astrophysics Data System (ADS)

Wu, Huaying; Wang, Li Zhong; Wang, Yantao; Yuan, Xiaolei

2018-05-01

The blade or surface grinding blade of the hypervelocity grinding wheel may be damaged due to too high rotation rate of the spindle of the machine and then fly out. Its speed as a projectile may severely endanger the field persons. Critical thickness model of the protective plate of the high-speed machine is studied in this paper. For easy analysis, the shapes of the possible impact objects flying from the high-speed machine are simplified as sharp-nose model, ball-nose model and flat-nose model. Whose front ending shape to represent point, line and surface contacting. Impact analysis based on J-C model is performed for the low-carbon steel plate with different thicknesses in this paper. One critical thickness computational model for the protective plate of high-speed machine is established according to the damage characteristics of the thin plate to get relation among plate thickness and mass, shape and size and impact speed of impact object. The air cannon is used for impact test. The model accuracy is validated. This model can guide identification of the thickness of single-layer outer protective plate of a high-speed machine.

Surface morphology study in high speed milling of soda lime glass

NASA Astrophysics Data System (ADS)

Konneh, Mohamed; Bagum, Mst. Nasima; Ali, Mohammad Yeakub; Amin, A. K. M. Nurul

2018-05-01

Soda lime glass has a wide range of applications in optical, bio-medical and semi-conductor industries. It is undeniably a challenging task to produce micro finish surface on an amorphous brittle solid like soda lime glass due to its low fracture toughness. In order to obtain such a finish surface, ductile machining has been exploited, as this usually cause's plastic flow which control crack propagation. At sub-micro scale cutting parameters, researchers achieved nano finish surface in micro milling operation using coated tool. However it is possible to enhance the rate of material removal (RMR) of soda lime glass at flexible cutting condition. High speed cutting at micro meter level, extend of thermal softening might be prominent than the strain gradient strengthening. The purpose of this study was to explore the effects of high cutting speed end milling parameters on the surface texture of soda lime glass using uncoated carbide tool. The spindle speed, depth of cut and feed rate were varied from 20,000 to 40,000 rpm, 10 to 30 mm/min and 30 to 50 µm respectively. Mathematical model of roughness has been developed using Response Surface Methodology (RSM). Experimental verification confirmed that surface roughness (Ra) 0.38 µm is possible to achieve at increased RMR, 4.71 mm3/min.

High speed propeller acoustics and aerodynamics - A boundary element approach

NASA Technical Reports Server (NTRS)

Farassat, F.; Myers, M. K.; Dunn, M. H.

1989-01-01

The Boundary Element Method (BEM) is applied in this paper to the problems of acoustics and aerodynamics of high speed propellers. The underlying theory is described based on the linearized Ffowcs Williams-Hawkings equation. The surface pressure on the blade is assumed unknown in the aerodynamic problem. It is obtained by solving a singular integral equation. The acoustic problem is then solved by moving the field point inside the fluid medium and evaluating some surface and line integrals. Thus the BEM provides a powerful technique in calculation of high speed propeller aerodynamics and acoustics.

Experimental Study in Taguchi Method on Surface Quality Predication of HSM

NASA Astrophysics Data System (ADS)

Ji, Yan; Li, Yueen

2018-05-01

Based on the study of ball milling mechanism and machining surface formation mechanism, the formation of high speed ball-end milling surface is a time-varying and cumulative Thermos-mechanical coupling process. The nature of this problem is that the uneven stress field and temperature field affect the machined surface Process, the performance of the processing parameters in the processing interaction in the elastic-plastic materials produced by the elastic recovery and plastic deformation. The surface quality of machining surface is characterized by multivariable nonlinear system. It is still an indispensable and effective method to study the surface quality of high speed ball milling by experiments.

Dualcavitating Hydrofoil Structures.

DTIC Science & Technology

The invention is directed to hydrofoil structures for efficient operation over a wide speed range from subcavitating to supercavitating operation. A...structures by providing a supercavitating profile shape in the lower surface to achieve a supercavitating condition at high speeds and that overcomes...problems associated with low speed operation of prior art supercavitating hydrofoil structures by providing an upper surface that combines with the lower

Dual Cavitating Hydrofoil Structures for Multi-Speed Applications.

DTIC Science & Technology

A hydrofoil structures for efficient operation over a wide speed range from subcavitating to supercavitating operation is provided. The...dualcavitating hydrofoil overcomes cavitation problems associated with high speed operation of prior art subcavitating hydrofoils by providing a supercavitating ...profile shape in the lower surface to achieve a supercavitating condition at high speeds and overcomes performance related problems associated with low

Study on the surface constitute properties of high-speed end milling aluminum alloy

NASA Astrophysics Data System (ADS)

Huang, Xiaoming; Li, Hongwei; Yumeng, Ma

2017-09-01

The physical and mechanical properties of the metal surface will change after the metal cutting processing. The comprehensive study of the influence of machining parameters on surface constitute properties are necessary. A high-speed milling experiment by means of orthogonal method with four factors was conducted for aluminum alloy7050-T7451. The surface constitutive properties of the Al-Alloy surface were measured using SSM-B4000TM stress-strain microprobe system. Based on all the load-depth curves obtained, the characteristics parameters such as strain hardening exponent n and yield strength σy of the milling surface are calculated. The effect of cutting speed, feed rate, and width and depth of cut on n and σy was investigated using the ANOVA techniques. The affecting degree of milling parameters on n and σy was v>fz> ap < ae. The influence of milling parameters on n and σ y was described and discussed.

Recent recovery of surface wind speed after decadal decrease: a focus on South Korea

NASA Astrophysics Data System (ADS)

Kim, JongChun; Paik, Kyungrock

2015-09-01

We investigate the multi-decadal variability of observed surface wind speed around South Korea. It is found that surface wind speed exhibits decreasing trend from mid-1950s until 2003, which is similar with the trends reported for other parts of the world. However, the decreasing trend ceases and becomes unclear since then. It is revealed that decreasing wind speed until 2003 is strongly associated with the decreasing trend of the spatial variance in both atmospheric pressure and air temperature across the East Asia for the same period. On the contrary, break of decreasing trend in surface wind speed since 2003 is associated with increasing spatial variance in surface temperature over the East Asia. Ground observation shows that surface wind speed and air temperature exhibit highly negative correlations for both summer and winter prior to 2003. However, since 2003, the correlations differ between seasons. We suggest that mechanisms behind the recent wind speed trend are different between summer and winter. This is on the basis of an interesting finding that air temperature has decreased while surface temperature has increased during winter months since 2003. We hypothesize that such contrasting temperature trends indicate more frequent movement of external cold air mass into the region since 2003. We also hypothesize that increasing summer wind speed is driven by intrusion of warm air mass into the region which is witnessed via increasing spatial variance in surface temperature across East Asia and the fact that both air and surface temperature rise together.

Digital holographic interferometry for characterizing deformable mirrors in aero-optics

NASA Astrophysics Data System (ADS)

Trolinger, James D.; Hess, Cecil F.; Razavi, Payam; Furlong, Cosme

2016-08-01

Measuring and understanding the transient behavior of a surface with high spatial and temporal resolution are required in many areas of science. This paper describes the development and application of a high-speed, high-dynamic range, digital holographic interferometer for high-speed surface contouring with fractional wavelength precision and high-spatial resolution. The specific application under investigation here is to characterize deformable mirrors (DM) employed in aero-optics. The developed instrument was shown capable of contouring a deformable mirror with extremely high-resolution at frequencies exceeding 40 kHz. We demonstrated two different procedures for characterizing the mechanical response of a surface to a wide variety of input forces, one that employs a high-speed digital camera and a second that employs a low-speed, low-cost digital camera. The latter is achieved by cycling the DM actuators with a step input, producing a transient that typically lasts up to a millisecond before reaching equilibrium. Recordings are made at increasing times after the DM initiation from zero to equilibrium to analyze the transient. Because the wave functions are stored and reconstructable, they can be compared with each other to produce contours including absolute, difference, and velocity. High-speed digital cameras recorded the wave functions during a single transient at rates exceeding 40 kHz. We concluded that either method is fully capable of characterizing a typical DM to the extent required by aero-optical engineers.

Low-reflectance laser-induced surface nanostructures created with a picosecond laser

NASA Astrophysics Data System (ADS)

Sarbada, Shashank; Huang, Zhifeng; Shin, Yung C.; Ruan, Xiulin

2016-04-01

Using high-speed picosecond laser pulse irradiation, low-reflectance laser-induced periodic surface structures (LIPSS) have been created on polycrystalline silicon. The effects of laser fluence, scan speed, overlapping ratio and polarization angle on the formation of LIPSS are reported. The anti-reflective properties of periodic structures are discussed, and the ideal LIPSS for low surface reflectance is presented. A decrease of 35.7 % in average reflectance of the silicon wafer was achieved over the wavelength range of 400-860 nm when it was textured with LIPSS at high scan speeds of 4000 mm/s. Experimental results of broadband reflectance of silicon wafers textured with LIPSS have been compared with finite difference time domain simulations and are in good agreement, showing high predictability in reflectance values for different structures. The effects of changing the LIPSS profile, fill factor and valley depth on the surface reflectance were also analyzed through simulations.

Effect of Blade-surface Finish on Performance of a Single-stage Axial-flow Compressor

NASA Technical Reports Server (NTRS)

Moses, Jason J; Serovy, George, K

1951-01-01

A set of modified NACA 5509-34 rotor and stator blades was investigated with rough-machine, hand-filed, and highly polished surface finishes over a range of weight flows at six equivalent tip speeds from 672 to 1092 feet per second to determine the effect of blade-surface finish on the performance of a single-stage axial-flow compressor. Surface-finish effects decreased with increasing compressor speed and with decreasing flow at a given speed. In general, finishing blade surfaces below the roughness that may be considered aerodynamically smooth on the basis of an admissible-roughness formula will have no effect on compressor performance.

Experimental investigation of the cornering characteristics of 18 by 5.5, type 7, aircraft tires with different tread patterns

NASA Technical Reports Server (NTRS)

Dreher, R. C.; Tanner, J. A.

1974-01-01

The characteristics, which include the cornering-force and drag-force friction coefficients and self-alining torque, were obtained on dry, damp, and flooded runway surfaces over a range of yaw angles from 0 deg to 12 deg and at ground speeds from approximately 5 to 90 knots. The results indicate that a tread pattern with pinholes in the ribs reduces the tire cornering capability at high yaw angles on a damp surface but improves cornering on a dry surface. A tread pattern which has transverse grooves across the entire width of the tread improves the tire cornering performance slightly at high speeds on the flooded runway surface. The cornering capability of all the tires is degraded at high ground speeds by thin film lubrication and/or tire hydroplaning effects. Alterations to the conventional tread pattern provide only marginal improvements in the tire cornering capability which suggests that runway surface treatments may be a more effective way of improving aircraft ground performance during wet operations.

Visualization of Projectile Flying at High Speed in Dusty Atmosphere

NASA Astrophysics Data System (ADS)

Masaki, Chihiro; Watanabe, Yasumasa; Suzuki, Kojiro

2017-10-01

Considering a spacecraft that encounters particle-laden environment, such as dust particles flying up over the regolith by the jet of the landing thruster, high-speed flight of a projectile in such environment was experimentally simulated by using the ballistic range. At high-speed collision of particles on the projectile surface, they may be reflected with cracking into smaller pieces. On the other hand, the projectile surface will be damaged by the collision. To obtain the fundamental characteristics of such complicated phenomena, a projectile was launched at the velocity up to 400 m/s and the collective behaviour of particles around projectile was observed by the high-speed camera. To eliminate the effect of the gas-particle interaction and to focus on only the effect of the interaction between the particles and the projectile's surface, the test chamber pressure was evacuated down to 30 Pa. The particles about 400μm diameter were scattered and formed a sheet of particles in the test chamber by using two-dimensional funnel with a narrow slit. The projectile was launched into the particle sheet in the tangential direction, and the high-speed camera captured both projectile and particle motions. From the movie, the interaction between the projectile and particle sheet was clarified.

THRUST BEARING

DOEpatents

Heller, P.R.

1958-09-16

A thrust bearing suitable for use with a rotor or blower that is to rotate about a vertical axis is descrihed. A centrifagal jack is provided so thnt the device may opernte on one hearing at starting and lower speeds, and transfer the load to another bearing at higher speeds. A low viscosity fluid is used to lubricate the higher speed operation bearing, in connection with broad hearing -surfaces, the ability to withstand great loads, and a relatively high friction loss, as contraated to the lower speed operatio;n bearing which will withstand only light thrust loads but is sufficiently frictionfree to avoid bearing seizure during slow speed or startup operation. An axially aligned shaft pin provides the bearing surface for low rotational speeds, but at higher speed, weights operating against spring tension withdraw nthe shaft pin into the bearing proper and the rotor shaft comes in contact with the large bearing surfaces.

A Study of Supersonic Surface Sources: The Ffowcs Williams-Hawkings Equation and the Kirchhoff Formula

NASA Technical Reports Server (NTRS)

Farassat, F.; Brentner, Kenneth S.; Dunn, M. H.

2004-01-01

In this paper we address the mathematical problem of noise generation from high speed moving surfaces. The problem we are solving is the linear wave equation with sources on a moving surface. The Ffowcs Williams-Hawkings (FW-H) equation as well as the govern- ing equation for deriving the Kirchhoff formula for moving surfaces are both this type of partial differential equation. We give a new exact solution of this problem here in closed form which is valid for subsonic and supersonic motion of the surface but it is particularly suitable for supersonically moving surfaces. This new solution is the simplest of all high speed formulations of Langley and is denoted formulation 4 following the tradition of numbering of our major results for the prediction of the noise of rotating blades. We show that for a smooth surface moving at supersonic speed, our solution has only removable singularities. Thus it can be used for numerical work.

Investigation on Effect of Material Hardness in High Speed CNC End Milling Process.

PubMed

Dhandapani, N V; Thangarasu, V S; Sureshkannan, G

2015-01-01

This research paper analyzes the effects of material properties on surface roughness, material removal rate, and tool wear on high speed CNC end milling process with various ferrous and nonferrous materials. The challenge of material specific decision on the process parameters of spindle speed, feed rate, depth of cut, coolant flow rate, cutting tool material, and type of coating for the cutting tool for required quality and quantity of production is addressed. Generally, decision made by the operator on floor is based on suggested values of the tool manufacturer or by trial and error method. This paper describes effect of various parameters on the surface roughness characteristics of the precision machining part. The prediction method suggested is based on various experimental analysis of parameters in different compositions of input conditions which would benefit the industry on standardization of high speed CNC end milling processes. The results show a basis for selection of parameters to get better results of surface roughness values as predicted by the case study results.

Investigation on Effect of Material Hardness in High Speed CNC End Milling Process

PubMed Central

Dhandapani, N. V.; Thangarasu, V. S.; Sureshkannan, G.

2015-01-01

This research paper analyzes the effects of material properties on surface roughness, material removal rate, and tool wear on high speed CNC end milling process with various ferrous and nonferrous materials. The challenge of material specific decision on the process parameters of spindle speed, feed rate, depth of cut, coolant flow rate, cutting tool material, and type of coating for the cutting tool for required quality and quantity of production is addressed. Generally, decision made by the operator on floor is based on suggested values of the tool manufacturer or by trial and error method. This paper describes effect of various parameters on the surface roughness characteristics of the precision machining part. The prediction method suggested is based on various experimental analysis of parameters in different compositions of input conditions which would benefit the industry on standardization of high speed CNC end milling processes. The results show a basis for selection of parameters to get better results of surface roughness values as predicted by the case study results. PMID:26881267

Molecular dynamic simulations of the high-speed copper nanoparticles collision with the aluminum surface

NASA Astrophysics Data System (ADS)

Pogorelko, V. V.; Mayer, A. E.

2016-11-01

With the use of the molecular dynamic simulations, we investigated the effect of the high-speed (500 m/s, 1000 m/s) copper nanoparticle impact on the mechanical properties of an aluminum surface. Dislocation analysis shows that a large number of dislocations are formed in the impact area; the total length of dislocations is determined not only by the speed and size of the incoming copper nanoparticle (kinetic energy of the nanoparticle), but by a temperature of the system as well. The dislocations occupy the whole area of the aluminum single crystal at high kinetic energy of the nanoparticle. With the decrease of the nanoparticle kinetic energy, the dislocation structures are formed in the near-surface layer; formation of the dislocation loops takes place. Temperature rise of the system (aluminum substrate + nanoparticle) reduces the total dislocation length in the single crystal of aluminum; there is deeper penetration of the copper atoms in the aluminum at high temperatures. Average energy of the nanoparticles and room temperature of the system are optimal for production of high-quality layers of copper on the aluminum surface.

Investigation of transient temperature's influence on damage of high-speed sliding electrical contact rail surface

NASA Astrophysics Data System (ADS)

Zhang, Yuyan; Sun, Shasha; Guo, Quanli; Yang, Degong; Sun, Dongtao

2016-11-01

In the high speed sliding electrical contact with large current, the temperature of contact area rises quickly under the coupling action of the friction heating, the Joule heating and electric arc heating. The rising temperature seriously affects the conductivity of the components and the yield strength of materials, as well affects the contact state and lead to damage, so as to shorten the service life of the contact elements. Therefore, there is vital significance to measure the temperature accurately and investigate the temperature effect on damage of rail surface. Aiming at the problem of components damage in high speed sliding electrical contact, the transient heat effect on the contact surface was explored and its influence and regularity on the sliding components damage was obtained. A kind of real-time temperature measurement method on rail surface of high speed sliding electrical contact is proposed. Under the condition of 2.5 kA current load, based on the principle of infrared radiation non-contact temperature sensor was used to measure the rail temperature. The dynamic distribution of temperature field was obtained through the simulation analysis, further, the connection between temperature changes and the rail surface damage morphology, the damage volume was analyzed and established. Finally, the method to reduce rail damage and improve the life of components by changing the temperature field was discussed.

Acceleration ramps along high operating speed roadways.

DOT National Transportation Integrated Search

2010-11-01

Until recently, guidelines for the geometric design of acceleration lanes used for the : successful merge of an entering vehicle into a high-speed surface transportation system : through-traffic lane have been based upon concepts and vehicle characte...

Rapid road repair vehicle

DOEpatents

Mara, Leo M.

1998-01-01

Disclosed is a rapid road repair vehicle capable of moving over a surface to be repaired at near normal posted traffic speeds to scan for and find an the high rate of speed, imperfections in the pavement surface, prepare the surface imperfection for repair by air pressure and vacuum cleaning, applying a correct amount of the correct patching material to effect the repair, smooth the resulting repaired surface, and catalog the location and quality of the repairs for maintenance records of the road surface. The rapid road repair vehicle can repair surface imperfections at lower cost, improved quality, at a higher rate of speed than was was heretofor possible, with significantly reduced exposure to safety and health hazards associated with this kind of road repair activities in the past.

Rapid road repair vehicle

DOEpatents

Mara, L.M.

1998-05-05

Disclosed is a rapid road repair vehicle capable of moving over a surface to be repaired at near normal posted traffic speeds to scan for and find at the high rate of speed, imperfections in the pavement surface, prepare the surface imperfection for repair by air pressure and vacuum cleaning, applying a correct amount of the correct patching material to effect the repair, smooth the resulting repaired surface, and catalog the location and quality of the repairs for maintenance records of the road surface. The rapid road repair vehicle can repair surface imperfections at lower cost, improved quality, at a higher rate of speed than was not heretofor possible, with significantly reduced exposure to safety and health hazards associated with this kind of road repair activities in the past. 2 figs.

High-Speed Scanning Interferometer Using CMOS Image Sensor and FPGA Based on Multifrequency Phase-Tracking Detection

NASA Technical Reports Server (NTRS)

Ohara, Tetsuo

2012-01-01

A sub-aperture stitching optical interferometer can provide a cost-effective solution for an in situ metrology tool for large optics; however, the currently available technologies are not suitable for high-speed and real-time continuous scan. NanoWave s SPPE (Scanning Probe Position Encoder) has been proven to exhibit excellent stability and sub-nanometer precision with a large dynamic range. This same technology can transform many optical interferometers into real-time subnanometer precision tools with only minor modification. The proposed field-programmable gate array (FPGA) signal processing concept, coupled with a new-generation, high-speed, mega-pixel CMOS (complementary metal-oxide semiconductor) image sensor, enables high speed (>1 m/s) and real-time continuous surface profiling that is insensitive to variation of pixel sensitivity and/or optical transmission/reflection. This is especially useful for large optics surface profiling.

Slide system for machine tools

DOEpatents

Douglass, S.S.; Green, W.L.

1980-06-12

The present invention relates to a machine tool which permits the machining of nonaxisymmetric surfaces on a workpiece while rotating the workpiece about a central axis of rotation. The machine tool comprises a conventional two-slide system (X-Y) with one of these slides being provided with a relatively short travel high-speed auxiliary slide which carries the material-removing tool. The auxiliary slide is synchronized with the spindle speed and the position of the other two slides and provides a high-speed reciprocating motion required for the displacement of the cutting tool for generating a nonaxisymmetric surface at a selected location on the workpiece.

Slide system for machine tools

DOEpatents

Douglass, Spivey S.; Green, Walter L.

1982-01-01

The present invention relates to a machine tool which permits the machining of nonaxisymmetric surfaces on a workpiece while rotating the workpiece about a central axis of rotation. The machine tool comprises a conventional two-slide system (X-Y) with one of these slides being provided with a relatively short travel high-speed auxiliary slide which carries the material-removing tool. The auxiliary slide is synchronized with the spindle speed and the position of the other two slides and provides a high-speed reciprocating motion required for the displacement of the cutting tool for generating a nonaxisymmetric surface at a selected location on the workpiece.

An atlas of monthly mean distributions of SSMI surface wind speed, AVHRR/2 sea surface temperature, AMI surface wind velocity, TOPEX/POSEIDON sea surface height, and ECMWF surface wind velocity during 1993

NASA Technical Reports Server (NTRS)

Halpern, D.; Fu, L.; Knauss, W.; Pihos, G.; Brown, O.; Freilich, M.; Wentz, F.

1995-01-01

The following monthly mean global distributions for 1993 are presented with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States (U.S.) Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) satellite; 10-m height wind speed and direction estimated from the Active Microwave Instrument (AMI) on the European Space Agency (ESA) European Remote Sensing (ERS-1) satellite; sea surface height estimated from the joint U.S.-France Topography Experiment (TOPEX)/POSEIDON spacecraft; and 10-m height wind speed and direction produced by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of annual mean, monthly mean, and sampling distributions are displayed.

The Kirchhoff Formula for a Supersonically Moving Surface

NASA Technical Reports Server (NTRS)

Farassat, F.; Myers, M. K.

1996-01-01

The Kirchhoff formula for radiation from stationary surfaces first appeared in 1882, and it has since found many applications in wave propagation theory. In 1930, Morgans extended the formula to apply to surfaces moving at speeds below the wave propagation speed; we refer to Morgans formula as the subsonic formulation. A modern derivation of Morgans result was published by Farassat and Myers in 1988, and it has now been used extensively in acoustics, particularly for high speed helicopter rotor noise prediction. Under some common conditions in this application, however, the appropriate Kirchhoff surface must be chosen such that portions of it travel at supersonic speed. The available Kirchhoff formula for moving surfaces is not suitable for this situation. In the current paper we derive the Kirchhoff formula applicable to a supersonically moving surface using some results from generalized function theory. The new formula requires knowledge of the same surface data as in the subsonic case. Complications that arise from apparent singularities in the new formulation are discussed briefly in the paper.

Pixel-wise deblurring imaging system based on active vision for structural health monitoring at a speed of 100 km/h

NASA Astrophysics Data System (ADS)

Hayakawa, Tomohiko; Moko, Yushi; Morishita, Kenta; Ishikawa, Masatoshi

2018-04-01

In this paper, we propose a pixel-wise deblurring imaging (PDI) system based on active vision for compensation of the blur caused by high-speed one-dimensional motion between a camera and a target. The optical axis is controlled by back-and-forth motion of a galvanometer mirror to compensate the motion. High-spatial-resolution image captured by our system in high-speed motion is useful for efficient and precise visual inspection, such as visually judging abnormal parts of a tunnel surface to prevent accidents; hence, we applied the PDI system for structural health monitoring. By mounting the system onto a vehicle in a tunnel, we confirmed significant improvement in image quality for submillimeter black-and-white stripes and real tunnel-surface cracks at a speed of 100 km/h.

Corrosion Inhibition of High Speed Steel by Biopolymer HPMC Derivatives

PubMed Central

Shi, Shih-Chen; Su, Chieh-Chang

2016-01-01

The corrosion inhibition characteristics of the derivatives of biopolymer hydroxypropyl methylcellulose (HPMC), hydroxypropyl methylcellulose phthalate (HPMCP), and hydroxypropyl methylcellulose acetate succinate (HPMCAS) film are investigated. Based on electrochemical impedance spectroscopic measurements and potentiodynamic polarization, the corrosion inhibition performance of high speed steel coated with HPMC derivatives is evaluated. The Nyquist plot and Tafel polarization demonstrate promising anti-corrosion performance of HPMC and HPMCP. With increasing film thickness, both materials reveal improvement in corrosion inhibition. Moreover, because of a hydrophobic surface and lower moisture content, HPMCP shows better anti-corrosion performance than HPMCAS. The study is of certain importance for designing green corrosion inhibitors of high speed steel surfaces by the use of biopolymer derivatives. PMID:28773733

High-speed high-efficiency 500-W cw CO2 laser hermetization of metal frames of microelectronics devices

NASA Astrophysics Data System (ADS)

Levin, Andrey V.

1996-04-01

High-speed, efficient method of laser surface treatment has been developed using (500 W) cw CO2 laser. The principal advantages of CO2 laser surface treatment in comparison with solid state lasers are the basis of the method. It has been affirmed that high efficiency of welding was a consequence of the fundamental properties of metal-IR-radiation (10,6 mkm) interaction. CO2 laser hermetization of metal frames of microelectronic devices is described as an example of the proposed method application.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajauria, Sukumar, E-mail: sukumar.rajauria@hgst.com; Canchi, Sripathi V., E-mail: sripathi.canchi@hgst.com; Schreck, Erhard

The kinetic friction and wear at high sliding speeds is investigated using the head-disk interface of hard disk drives, wherein the head and the disk are less than 10 nm apart and move at sliding speeds of 5–10 m/s relative to each other. While the spacing between the sliding surfaces is of the same order of magnitude as various AFM based fundamental studies on friction, the sliding speed is nearly six orders of magnitude larger, allowing a unique set-up for a systematic study of nanoscale wear at high sliding speeds. In a hard disk drive, the physical contact between the head andmore » the disk leads to friction, wear, and degradation of the head overcoat material (typically diamond like carbon). In this work, strain gauge based friction measurements are performed; the friction coefficient as well as the adhering shear strength at the head-disk interface is extracted; and an experimental set-up for studying friction between high speed sliding surfaces is exemplified.« less

Investigation of multi-scale flash-weakening of rock surfaces during high speed slip

NASA Astrophysics Data System (ADS)

Barbery, M. R.; Saber, O.; Chester, F. M.; Chester, J. S.

2017-12-01

A significant reduction in the coefficient of friction of rock can occur if sliding velocity approaches seismic rates as a consequence of weakening of microscopic sliding contacts by flash heating. Using a high-acceleration and -speed biaxial apparatus equipped with a high-speed Infra-Red (IR) camera to capture thermographs of the sliding surface, we have documented the heterogeneous distribution of temperature on flash-heated decimetric surfaces characterized by linear arrays of high-temperature, mm-size spots, and streaks. Numerical models that are informed by the character of flash heated surfaces and that consider the coupling of changes in temperature and changes in the friction of contacts, supports the hypothesis that independent mechanisms of flash weakening operate at different contact scales. Here, we report on new experiments that provide additional constraints on the life-times and rest-times of populations of millimeter-scale contacts. Rock friction experiments conducted on Westerly granite samples in a double-direct shear configuration achieve velocity steps from 1 mm/s to 900 mm/s at 100g accelerations over 2 mm of displacement with normal stresses of 22-36 MPa and 30 mm of displacement during sustained high-speed sliding. Sliding surfaces are machined to roughness similar to natural fault surfaces and that allow us to control the characteristics of millimeter-scale contact populations. Thermographs of the sliding surface show temperatures up to 200 C on millimeter-scale contacts, in agreement with 1-D heat conduction model estimates of 180 C. Preliminary comparison of thermal modeling results and experiment observations demonstrate that we can distinguish the different life-times and rest-times of contacts in thermographs and the corresponding frictional weakening behaviors. Continued work on machined surfaces that lead to different contact population characteristics will be used to test the multi-scale and multi-mechanism hypothesis for flash weakening during seismic slip on rough fault surfaces.

Using high-speed texture measurements to improve the uniformity of hot-mix asphalt.

DOT National Transportation Integrated Search

2003-01-01

This study introduces Virginia's efforts to apply high-speed texture measurement as a tool to improve the uniformity of hot-mix asphalt (HMA) pavements. Three approaches for detecting and quantifying HMA segregation through measuring pavement surface...

High-speed micro-scale laser shock peening using a fiber laser (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhang, Chenfei; Deng, Leimin; Sun, Shiding; Lu, Yongfeng

2017-03-01

Laser shock peening using low-energy nanosecond (ns) fiber lasers was investigated in this study to realize high-speed micro-scale laser shock peening on selected positions without causing surface damage. Due to the employment of a fiber laser with high-frequency and prominent environmental adaptability, the laser peening system is able to work with a much higher speed compared to traditional peening systems using Nd:YAG lasers and is promising for in-situ applications in harsh environments. Detailed surface morphology investigations both on sacrificial coatings and Al alloy surfaces after the fiber laser peening revealed the effects of focal position, pulse duration, peak power density, and impact times. Micro-dent arrays were also obtained with different spot-to-spot distances. Obvious micro-hardness improvement was observed inside the laser-peening-induced microdents after the fiber laser shock peening.

Three-dimensional stress intensity factor analysis of a surface crack in a high-speed bearing

NASA Technical Reports Server (NTRS)

Ballarini, Roberto; Hsu, Yingchun

1990-01-01

The boundary element method is applied to calculate the stress intensity factors of a surface crack in the rotating inner raceway of a high-speed roller bearing. The three-dimensional model consists of an axially stressed surface cracked plate subjected to a moving Hertzian contact loading. A multidomain formulation and singular crack-tip elements were employed to calculate the stress intensity factors accurately and efficiently for a wide range of configuration parameters. The results can provide the basis for crack growth calculations and fatigue life predictions of high-performance rolling element bearings that are used in aircraft engines.

Supercavitating flow around high-speed underwater projectile near free surface induced by air entrainment

NASA Astrophysics Data System (ADS)

Xu, Chang; Huang, Jian; Wang, Yiwei; Wu, Xiaocui; Huang, Chenguang; Wu, Xianqian

2018-03-01

Cavitating flow near free surface is a complicated issue and may provide new inspiration on high-speed surface cruising. This study observes stable supercavitating flow as a new phenomenon in a launch experiment of axisymmetric projectile when the upper side of the projectile coincides with the free surface. A numerical approach is established using large eddy-simulation and volume-of-fluid methods, and good agreements are achieved between numerical and experimental results. Supercavity formation mechanism is revealed by analyzing the experiment photographs and the iso-surface of 90% water volume fraction in numerical results. The entrainment of a large amount of air into the cavity can cause the pressure inside the cavity to similarly increase with the pressure outside the cavity, which makes the actual cavitation number close to zero and is similar to supercavitation. Cases with various headforms of the projectile and cavitation numbers on the cavitating flow, as well as the drag reduction effects are further examined. Results indicate that the present strategy near the free surface could possibly be a new effective approach for high-speed cruising after vigorous design optimization in the future.

High-speed Imaging of Global Surface Temperature Distributions on Hypersonic Ballistic-Range Projectiles

NASA Technical Reports Server (NTRS)

Wilder, Michael C.; Reda, Daniel C.

2004-01-01

The NASA-Ames ballistic range provides a unique capability for aerothermodynamic testing of configurations in hypersonic, real-gas, free-flight environments. The facility can closely simulate conditions at any point along practically any trajectory of interest experienced by a spacecraft entering an atmosphere. Sub-scale models of blunt atmospheric entry vehicles are accelerated by a two-stage light-gas gun to speeds as high as 20 times the speed of sound to fly ballistic trajectories through an 24 m long vacuum-rated test section. The test-section pressure (effective altitude), the launch velocity of the model (flight Mach number), and the test-section working gas (planetary atmosphere) are independently variable. The model travels at hypersonic speeds through a quiescent test gas, creating a strong bow-shock wave and real-gas effects that closely match conditions achieved during actual atmospheric entry. The challenge with ballistic range experiments is to obtain quantitative surface measurements from a model traveling at hypersonic speeds. The models are relatively small (less than 3.8 cm in diameter), which limits the spatial resolution possible with surface mounted sensors. Furthermore, since the model is in flight, surface-mounted sensors require some form of on-board telemetry, which must survive the massive acceleration loads experienced during launch (up to 500,000 gravities). Finally, the model and any on-board instrumentation will be destroyed at the terminal wall of the range. For these reasons, optical measurement techniques are the most practical means of acquiring data. High-speed thermal imaging has been employed in the Ames ballistic range to measure global surface temperature distributions and to visualize the onset of transition to turbulent-flow on the forward regions of hypersonic blunt bodies. Both visible wavelength and infrared high-speed cameras are in use. The visible wavelength cameras are intensified CCD imagers capable of integration times as short as 2 ns. The infrared camera uses an Indium Antimonide (InSb) sensor in the 3 to 5 micron band and is capable of integration times as short as 500 ns. The projectiles are imaged nearly head-on using expendable mirrors offset slightly from the flight path. The proposed paper will discuss the application of high-speed digital imaging systems in the NASA-Ames hypersonic ballistic range, and the challenges encountered when applying these systems. Example images of the thermal radiation from the blunt nose of projectiles flying at nearly 14 times the speed of sound will be given.

Design of noise barrier inspection system for high-speed railway

NASA Astrophysics Data System (ADS)

Liu, Bingqian; Shao, Shuangyun; Feng, Qibo; Ma, Le; Cholryong, Kim

2016-10-01

The damage of noise barriers will highly reduce the transportation safety of the high-speed railway. In this paper, an online inspection system of noise barrier based on laser vision for the safety of high-speed railway is proposed. The inspection system, mainly consisted of a fast camera and a line laser, installed in the first carriage of the high-speed CIT(Composited Inspection Train).A Laser line was projected on the surface of the noise barriers and the images of the light line were received by the camera while the train is running at high speed. The distance between the inspection system and the noise barrier can be obtained based on laser triangulation principle. The results of field tests show that the proposed system can meet the need of high speed and high accuracy to get the contour distortion of the noise barriers.

Aerodynamic design on high-speed trains

NASA Astrophysics Data System (ADS)

Ding, San-San; Li, Qiang; Tian, Ai-Qin; Du, Jian; Liu, Jia-Li

2016-04-01

Compared with the traditional train, the operational speed of the high-speed train has largely improved, and the dynamic environment of the train has changed from one of mechanical domination to one of aerodynamic domination. The aerodynamic problem has become the key technological challenge of high-speed trains and significantly affects the economy, environment, safety, and comfort. In this paper, the relationships among the aerodynamic design principle, aerodynamic performance indexes, and design variables are first studied, and the research methods of train aerodynamics are proposed, including numerical simulation, a reduced-scale test, and a full-scale test. Technological schemes of train aerodynamics involve the optimization design of the streamlined head and the smooth design of the body surface. Optimization design of the streamlined head includes conception design, project design, numerical simulation, and a reduced-scale test. Smooth design of the body surface is mainly used for the key parts, such as electric-current collecting system, wheel truck compartment, and windshield. The aerodynamic design method established in this paper has been successfully applied to various high-speed trains (CRH380A, CRH380AM, CRH6, CRH2G, and the Standard electric multiple unit (EMU)) that have met expected design objectives. The research results can provide an effective guideline for the aerodynamic design of high-speed trains.

On blockage effects for a marine hydrokinetic turbine in free surface proximity

NASA Astrophysics Data System (ADS)

Banerjee, A.; Kolekar, N.

2016-12-01

Experimental investigation was carried out with a three-bladed, constant chord marine hydrokinetic turbine to understand the influence of free surface proximity on blockage effects and near wake flow field. The turbine was placed at various depths of immersion as rotational speeds and flow speeds were varied; thrust and torque data was acquired through a submerged thrust torque sensor positioned in-line with the turbine axis. Blockage effects were quantified in terms of changes in power coefficient and were found to be dependent on flow velocity, rotational speed and blade-tip clearence (from free-surface). Flow acceleration near turbine rotation plane was attributed to blockage offered by the rotor, wake, and free surface deformation; the resulting performance improvements were calculated based on the measured thrust values. In addition, stereoscopic particle imaging velocimetry was carried out in the near-wake region using time-averaged and phase-averaged techniques to understand the mechanism responsible for variation of torque (and power coefficient) with rotational speed and free-surface proximity. Flow vizualisation revealed slower wake propagation for higher rotational velocities and increased assymetry in the wake with increasing free surface proximity. Improved performance at high rotational speed was attributed to enhanced wake blockage; performance enhancements with free-surface proximity was attributed to additional blockage effects caused by free surface deformation.

Ejection mechanics and trajectory of the ascospores of Gibberella zeae (anamorph Fuarium graminearum).

PubMed

Trail, Frances; Gaffoor, Iffa; Vogel, Steven

2005-06-01

Since wind speed drops to zero at a surface, forced ejection should facilitate spore dispersal. But for tiny spores, with low mass relative to surface area, high ejection speed yields only a short range trajectory, so pernicious is their drag. Thus, achieving high speeds requires prodigious accelerations. In the ascomycete Gibberella zeae, we determined the launch speed and kinetic energy of ascospores shot from perithecia, and the source and magnitude of the pressure driving the launch. We asked whether the pressure inside the ascus suffices to account for launch speed and energy. Launch speed was 34.5 ms-1, requiring a pressure of 1.54 MPa and an acceleration of 870,000 g--the highest acceleration reported in a biological system. This analysis allows us to discount the major sugar component of the epiplasmic fluid, mannitol, as having a key role in driving discharge, and supports the role of potassium ion flux in the mechanism.

Influence of track surface on the equine superficial digital flexor tendon loading in two horses at high speed trot.

PubMed

Crevier-Denoix, N; Pourcelot, P; Ravary, B; Robin, D; Falala, S; Uzel, S; Grison, A C; Valette, J P; Denoix, J M; Chateau, H

2009-03-01

Although track surfaces are a risk factor of tendon injuries, their effects on tendon loading at high speed are unknown. Using a noninvasive ultrasonic technique, it is now possible to evaluate the forces in the superficial digital flexor tendon (SDFT) in exercise conditions. To compare the effects of an all-weather waxed track (W) vs. a crushed sand track (S), on the SDFT loading in the trotter horse at high speed. Two trotter horses were equipped with the ultrasonic device (1 MHz ultrasonic probe, fixed on the palmar metacarpal area of the right forelimb). For each trial, data acquisition was made at 400 Hz and 10 consecutive strides were analysed. In each session, the 2 track surfaces were tested in a straight line. The speed was imposed at 10 m/s and recorded. The right forelimb was also equipped with a dynamometric horseshoe and skin markers. The horse was filmed with a high-speed camera (600 Hz); all recordings were synchronised. Statistical differences were tested using the GLM procedure (SAS; P < 0.05). Maximal tendon force was significantly lower on W compared with S. In addition to maximal force peaks around mid-stance, earlier peaks were observed, more pronounced on S than on W, at about 13% (horse 2) and 30% (both horses) of the stance phase. Comparison with kinematic data revealed that these early peaks were accompanied by plateaux in the fetlock angle-time chart. For high tendon forces, the tendon maximal loading rate was significantly lower on W than on S. CONCLUSIONS AND POTENTIAL CLINICAL RELEVANCE: The all-weather waxed track appears to induce a lesser and more gradual SDFT loading than crushed sand. The SDFT loading pattern at high speed trot suggests proximal interphalangeal joint movements during limb loading.

Airfoil shape for flight at subsonic speeds. [design analysis and aerodynamic characteristics of the GAW-1 airfoil

NASA Technical Reports Server (NTRS)

Whitcomb, R. T. (Inventor)

1976-01-01

An airfoil is examined that has an upper surface shaped to control flow accelerations and pressure distribution over the upper surface and to prevent separation of the boundary layer due to shock wave formulation at high subsonic speeds well above the critical Mach number. A highly cambered trailing edge section improves overall airfoil lifting efficiency. Diagrams illustrating supersonic flow and shock waves over the airfoil are shown.

The Effect of Saline Coolant on Temperature Levels during Decortication with a Midas Rex: An in Vitro Model Using Sheep Cervical Vertebrae.

PubMed

Livingston, Asher; Wang, Tian; Christou, Chris; Pelletier, Matthew H; Walsh, William R

2015-01-01

Decortication of bone with a high-speed burr in the absence of coolant may lead to local thermal necrosis and decreased healing ability, which may negatively impact clinical outcome. Little data are available on the impact of applying a coolant during the burring process. This study aims to establish an in vitro model to quantitatively assess peak temperatures during endplate preparation with a high-speed burr. Six sheep cervical vertebrae were dissected and mounted. Both end plates were used to give a total of 12 sites. Two thermocouples were inserted into each vertebra, 2 mm below the end plate surface and a thermal camera set up to measure surface temperature. A 3 mm high-pneumatic speed burr (Midas Rex, Medtronic, Fort Worth, TX, USA) was used to decorticate the bone in a side to side sweeping pattern, using a matchstick burr (M-8/9MH30) with light pressure. This procedure was repeated while dripping saline onto the burr and bone. Data were compared between groups using a Student's t-test. Application of coolant at the bone-burr interface during decortication resulted in a significant decrease in final temperature. Without coolant, maximum temperatures 2 mm from the surface were not sufficient to cause thermal osteonecrosis, although peak surface temperatures would cause local damage. The use of a high-speed burr provides a quick and an effective method of vertebral end plate preparation. Thermal damage to the bone can be minimized through the use of light pressure and saline coolant. This has implications for any bone preparation performed with a high-speed burr.

Evaluating the use of high speed laser line sensors for improved rideability measurement.

DOT National Transportation Integrated Search

2016-09-01

This research project compared rideability readings and repeatability for both point laser and line laser systems on the high-speed profiler. Both systems were Dynatest 5051 Mark III Road Surface Profilers, one equipped with single point lasers and t...

High-speed AFM and the reduction of tip-sample forces

NASA Astrophysics Data System (ADS)

Miles, Mervyn; Sharma, Ravi; Picco, Loren

High-speed DC-mode AFM has been shown to be routinely capable of imaging at video rate, and, if required, at over 1000 frames per second. At sufficiently high tip-sample velocities in ambient conditions, the tip lifts off the sample surface in a superlubricity process which reduces the level of shear forces imposed on the sample by the tip and therefore reduces the potential damage and distortion of the sample being imaged. High-frequency mechanical oscillations, both lateral and vertical, have been reported to reduced the tip-sample frictional forces. We have investigated the effect of combining linear high-speed scanning with these small amplitude high-frequency oscillations with the aim of reducing further the force interaction in high-speed imaging. Examples of this new version of high-speed AFM imaging will be presented for biological samples.

Error trends in SASS winds as functions of atmospheric stability and sea surface temperature

NASA Technical Reports Server (NTRS)

Liu, W. T.

1983-01-01

Wind speed measurements obtained with the scatterometer instrument aboard the Seasat satellite are compared equivalent neutral wind measurements obtained from ship reports in the western N. Atlantic and eastern N. Pacific where the concentration of ship reports are high and the ranges of atmospheric stability and sea surface temperature are large. It is found that at low wind speeds the difference between satellite measurements and surface reports depends on sea surface temperature. At wind speeds higher than 8 m/s the dependence was greatly reduced. The removal of systematic errors due to fluctuations in atmospheric stability reduced the r.m.s. difference from 1.7 m/s to 0.8 m/s. It is suggested that further clarification of the effects of fluctuations in atmospheric stability on Seasat wind speed measurements should increase their reliability in the future.

Method and Apparatus for the Portable Identification of Material Thickness and Defects Using Spatially Controlled Heat Application

NASA Technical Reports Server (NTRS)

Cramer, K. Elliott (Inventor); Winfree, William P. (Inventor)

1999-01-01

A method and a portable apparatus for the nondestructive identification of defects in structures. The apparatus comprises a heat source and a thermal imager that move at a constant speed past a test surface of a structure. The thermal imager is off set at a predetermined distance from the heat source. The heat source induces a constant surface temperature. The imager follows the heat source and produces a video image of the thermal characteristics of the test surface. Material defects produce deviations from the constant surface temperature that move at the inverse of the constant speed. Thermal noise produces deviations that move at random speed. Computer averaging of the digitized thermal image data with respect to the constant speed minimizes noise and improves the signal of valid defects. The motion of thermographic equipment coupled with the high signal to noise ratio render it suitable for portable, on site analysis.

Dynamic fracture of the surface of an aluminum alloy under conditions of high-speed erosion

NASA Astrophysics Data System (ADS)

Petrov, Yu. V.; Atroshenko, S. A.; Kazarinov, N. A.; Evstifeev, A. D.; Solov'ev, V. Yu.

2017-04-01

The kinetics of fracture and deformation of the standard aluminum alloy AD1 and a similar alloy subjected to severe plastic deformation by high-pressure torsion under conditions of high-speed erosion has been investigated. It has been shown that, with an increase in the loading rate, the fraction of the brittle component on the fracture surface of the standard material, as well as the thickness of the damaged layer, increases more significantly than that for the material after the severe plastic deformation by high-pressure torsion. A relationship of the surface roughness of the material after the erosion with the loading rate and the thickness of the erosion-damaged layer has been established.

Surface Roughness Optimization Using Taguchi Method of High Speed End Milling For Hardened Steel D2

NASA Astrophysics Data System (ADS)

Hazza Faizi Al-Hazza, Muataz; Ibrahim, Nur Asmawiyah bt; Adesta, Erry T. Y.; Khan, Ahsan Ali; Abdullah Sidek, Atiah Bt.

2017-03-01

The main challenge for any manufacturer is to achieve higher quality of their final products with maintains minimum machining time. In this research final surface roughness analysed and optimized with maximum 0.3 mm flank wear length. The experiment was investigated the effect of cutting speed, feed rate and depth of cut on the final surface roughness using D2 as a work piece hardened to 52-56 HRC, and coated carbide as cutting tool with higher cutting speed 120-240 mm/min. The experiment has been conducted using L9 design of Taguchi collection. The results have been analysed using JMP software.

High speed fabrication of absorbance-enhanced micro-nanostructures on nickel surface using hundred-nanosecond pulsed laser

NASA Astrophysics Data System (ADS)

Fu, Jinxiang; Zhang, Jingyuan; Liang, Hao; Wang, Yibo; Zhang, Zhiyan; Liu, Yannan; Lin, Xuechun

2017-01-01

We report the generation of micro-nanostructures on nickel surface using a pulsed laser with pulse duration of 100/200 ns. The blacken nickel, which is covered with dense broccoli-like clusters having strong light trapping capacity covering broad spectrum (200-2000 nm), can be produced at a high laser scanning speed up to 100 mm/s. The absorbance of the blacken nickel can be over 98% in the UV, more than 97% in the visible, and over 90% in the near IR. In addition, by treating the nickel surface with two crossing scans of the laser, highly organized and shape-controllable periodic arrays of hump-craters can be fabricated.

High-speed sorting of grains by color and surface texture

USDA-ARS?s Scientific Manuscript database

A high-speed, low-cost, image-based sorting device was developed to detect and separate grains with different colors/textures. The device directly combines a complementary metal–oxide–semiconductor (CMOS) color image sensor with a field-programmable gate array (FPGA) that was programmed to execute ...

Development of Fractal Dimension and Characteristic Roughness Models for Turned Surface of Carbon Steels

NASA Astrophysics Data System (ADS)

Zuo, Xue; Zhu, Hua; Zhou, Yuankai; Ding, Cong; Sun, Guodong

2016-08-01

Relationships between material hardness, turning parameters (spindle speed and feed rate) and surface parameters (surface roughness Ra, fractal dimension D and characteristic roughness τ∗) are studied and modeled using response surface methodology (RSM). The experiments are carried out on a CNC lathe for six carbon steel material AISI 1010, AISI 1020, AISI 1030, AISI 1045, AISI 1050 and AISI 1060. The profile of turned surface and the surface roughness value are measured by a JB-5C profilometer. Based on the profile data, D and τ∗ are computed through the root-mean-square method. The analysis of variance (ANOVA) reveals that spindle speed is the most significant factors affecting Ra, while material hardness is the most dominant parameter affecting τ∗. Material hardness and spindle speed have the same influence on D. Feed rate has less effect on three surface parameters than spindle speed and material hardness. The second-order models of RSM are established for estimating Ra, D and τ∗. The validity of the developed models is approximately 80%. The response surfaces show that a surface with small Ra and large D and τ∗ can be obtained by selecting a high speed and a large hardness material. According to the established models, Ra, D and τ∗ of six carbon steels surfaces can be predicted under cutting conditions studied in this paper. The results have an instructive meaning to estimate the surface quality before turning.

Effects on Vibration and Surface Roughness in High Speed Micro End-Milling of Inconel 718 with Minimum Quantity Lubrication

NASA Astrophysics Data System (ADS)

Rahman, Mohamed Abd; Yeakub Ali, Mohammad; Saddam Khairuddin, Amir

2017-03-01

This paper presents the study on vibration and surface roughness of Inconel 718 workpiece produced by micro end-milling using Mikrotools Integrated Multi-Process machine tool DT-110 with control parameters; spindle speed (15000 rpm and 30000 rpm), feed rate (2 mm/min and 4 mm/min) and depth of cut (0.10 mm and 0.15mm). The vibration was measured using DYTRAN accelerometer instrument and the average surface roughness Ra was measured using Wyko NT1100. The analysis of variance (ANOVA) by using Design Expert software revealed that feed rate and depth of cut are the most significant factors on vibration meanwhile for average surface roughness, Ra, spindle speed is the most significant factor.

Note: Four-port microfluidic flow-cell with instant sample switching

NASA Astrophysics Data System (ADS)

MacGriff, Christopher A.; Wang, Shaopeng; Tao, Nongjian

2013-10-01

A simple device for high-speed microfluidic delivery of liquid samples to a surface plasmon resonance sensor surface is presented. The delivery platform is comprised of a four-port microfluidic cell, two ports serve as inlets for buffer and sample solutions, respectively, and a high-speed selector valve to control the alternate opening and closing of the two outlet ports. The time scale of buffer/sample switching (or sample injection rise and fall time) is on the order of milliseconds, thereby minimizing the opportunity for sample plug dispersion. The high rates of mass transport to and from the central microfluidic sensing region allow for SPR-based kinetic analysis of binding events with dissociation rate constants (kd) up to 130 s-1. The required sample volume is only 1 μL, allowing for minimal sample consumption during high-speed kinetic binding measurement.

Hurricane Imaging Radiometer (HIRAD) Wind Speed Retrievals and Assessment Using Dropsondes

NASA Technical Reports Server (NTRS)

Cecil, Daniel J.; Biswas, Sayak K.

2018-01-01

The Hurricane Imaging Radiometer (HIRAD) is an experimental C-band passive microwave radiometer designed to map the horizontal structure of surface wind speed fields in hurricanes. New data processing and customized retrieval approaches were developed after the 2015 Tropical Cyclone Intensity (TCI) experiment, which featured flights over Hurricanes Patricia, Joaquin, Marty, and the remnants of Tropical Storm Erika. These new approaches produced maps of surface wind speed that looked more realistic than those from previous campaigns. Dropsondes from the High Definition Sounding System (HDSS) that was flown with HIRAD on a WB-57 high altitude aircraft in TCI were used to assess the quality of the HIRAD wind speed retrievals. The root mean square difference between HIRAD-retrieved surface wind speeds and dropsonde-estimated surface wind speeds was 6.0 meters per second. The largest differences between HIRAD and dropsonde winds were from data points where storm motion during dropsonde descent compromised the validity of the comparisons. Accounting for this and for uncertainty in the dropsonde measurements themselves, we estimate the root mean square error for the HIRAD retrievals as around 4.7 meters per second. Prior to the 2015 TCI experiment, HIRAD had previously flown on the WB-57 for missions across Hurricanes Gonzalo (2014), Earl (2010), and Karl (2010). Configuration of the instrument was not identical to the 2015 flights, but the methods devised after the 2015 flights may be applied to that previous data in an attempt to improve retrievals from those cases.

Subsidence Evaluation of High-Speed Railway in Shenyang Based on Time-Series Insar

NASA Astrophysics Data System (ADS)

Zhang, Yun; Wei, Lianhuan; Li, Jiayu; Liu, Shanjun; Mao, Yachun; Wu, Lixin

2018-04-01

More and more high-speed railway are under construction in China. The slow settlement along high-speed railway tracks and newly-built stations would lead to inhomogeneous deformation of local area, and the accumulation may be a threat to the safe operation of high-speed rail system. In this paper, surface deformation of the newly-built high-speed railway station as well as the railway lines in Shenyang region will be retrieved by time series InSAR analysis using multi-orbit COSMO-SkyMed images. This paper focuses on the non-uniform subsidence caused by the changing of local environment along the railway. The accuracy of the settlement results can be verified by cross validation of the results obtained from two different orbits during the same period.

Performance Enhancement of a High Speed Jet Impingement System for Nonvolatile Residue Removal

NASA Technical Reports Server (NTRS)

Klausner, James F.; Mei, Renwei; Near, Steve; Stith, Rex

1996-01-01

A high speed jet impingement cleaning facility has been developed to study the effectiveness of the nonvolatile residue removal. The facility includes a high pressure air compressor which charges the k-bottles to supply high pressure air, an air heating section to vary the temperature of the high pressure air, an air-water mixing chamber to meter the water flow and generate small size droplets, and a converging- diverging nozzle to deliver the supersonic air-droplet mixture flow to the cleaning surface. To reliably quantify the cleanliness of the surface, a simple procedure for measurement and calibration is developed to relate the amount of the residue on the surface to the relative change in the reflectivity between a clean surface and the greased surface. This calibration procedure is economical, simple, reliable, and robust. a theoretical framework is developed to provide qualitative guidance for the design of the test and interpretation of the experimental results. The result documented in this report support the theoretical considerations.

Silicon Ingot Casting: Heat Exchanger Method. Multi-wire Slicing: Fixed Abrasine Slicing Technique, Phase 3

NASA Technical Reports Server (NTRS)

Schmid, F.; Khattak, C. P.

1979-01-01

Ingot casting was scaled up to 16 cm by 16 cm square cross section size and ingots weighing up to 8.1 kg were cast. The high degree of crystallinity was maintained in the large ingot. For large sizes, the nonuniformity of heat treatment causes chipping of the surface of the ingot. Progress was made in the development of a uniform graded structure in the silica crucibles. The high speed slicer blade-head weight was reduced to 37 pounds, allowing surface speeds of up to 500 feet per minute. Slicing of 10 cm diameter workpieces at these speeds increased the through-put of the machine to 0.145 mm/min.

Role of the Coronal Alfvén Speed in Modulating the Solar-wind Helium Abundance

NASA Astrophysics Data System (ADS)

Wang, Y.-M.

2016-12-01

The helium abundance He/H in the solar wind is relatively constant at ˜0.04 in high-speed streams, but varies in phase with the sunspot number in slow wind, from ˜0.01 at solar minimum to ˜0.04 at maximum. Suggested mechanisms for helium fractionation have included frictional coupling to protons and resonant interactions with high-frequency Alfvénic fluctuations. We compare He/H measurements during 1995-2015 with coronal parameters derived from source-surface extrapolations of photospheric field maps. We find that the near-Earth helium abundance is an increasing function of the magnetic field strength and Alfvén speed v A in the outer corona, while being only weakly correlated with the proton flux density. Throughout the solar cycle, fast wind is associated with short-term increases in v A near the source surface; resonance with Alfvén waves, with v A and the relative speed of α-particles and protons decreasing with increasing heliocentric distance, may then lead to enhanced He/H at 1 au. The modulation of helium in slow wind reflects the tendency for the associated coronal Alfvén speeds to rise steeply from sunspot minimum, when this wind is concentrated around the source-surface neutral line, to sunspot maximum, when the source-surface field attains its peak strengths. The helium abundance near the source surface may represent a balance between collisional decoupling from protons and Alfvén wave acceleration.

Voltage assisted asymmetric nanoscale wear on ultra-smooth diamond like carbon thin films at high sliding speeds

PubMed Central

Rajauria, Sukumar; Schreck, Erhard; Marchon, Bruno

2016-01-01

The understanding of tribo- and electro-chemical phenomenons on the molecular level at a sliding interface is a field of growing interest. Fundamental chemical and physical insights of sliding surfaces are crucial for understanding wear at an interface, particularly for nano or micro scale devices operating at high sliding speeds. A complete investigation of the electrochemical effects on high sliding speed interfaces requires a precise monitoring of both the associated wear and surface chemical reactions at the interface. Here, we demonstrate that head-disk interface inside a commercial magnetic storage hard disk drive provides a unique system for such studies. The results obtained shows that the voltage assisted electrochemical wear lead to asymmetric wear on either side of sliding interface. PMID:27150446

Voltage assisted asymmetric nanoscale wear on ultra-smooth diamond like carbon thin films at high sliding speeds

NASA Astrophysics Data System (ADS)

Rajauria, Sukumar; Schreck, Erhard; Marchon, Bruno

2016-05-01

The understanding of tribo- and electro-chemical phenomenons on the molecular level at a sliding interface is a field of growing interest. Fundamental chemical and physical insights of sliding surfaces are crucial for understanding wear at an interface, particularly for nano or micro scale devices operating at high sliding speeds. A complete investigation of the electrochemical effects on high sliding speed interfaces requires a precise monitoring of both the associated wear and surface chemical reactions at the interface. Here, we demonstrate that head-disk interface inside a commercial magnetic storage hard disk drive provides a unique system for such studies. The results obtained shows that the voltage assisted electrochemical wear lead to asymmetric wear on either side of sliding interface.

Influence of shock waves from plasma actuators on transonic and supersonic airflow

NASA Astrophysics Data System (ADS)

Mursenkova, I. V.; Znamenskaya, I. A.; Lutsky, A. E.

2018-03-01

This paper presents experimental and numerical investigations of high-current sliding surface discharges of nanosecond duration and their effect on high-speed flow as plasma actuators in a shock tube. This study deals with the effectiveness of a sliding surface discharge at low and medium air pressure. Results cover the electrical characteristics of the discharge and optical visualization of the discharge and high-speed post-discharge flow. A sliding surface discharge is first studied in quiescent air conditions and then in high-speed flow, being initiated in the boundary layer at a transverse flow velocity of 50-950 m s-1 behind a flat shock wave in air of density 0.04-0.45 kg m-3. The discharge is powered by a pulse voltage of 25-30 kV and the electric current is ~0.5 kA. Shadow imaging and particle image velocimetry (PIV) are used to measure the flow field parameters after the pulse surface discharge. Shadow imaging reveals shock waves originating from the channels of the discharge configurations. PIV is used to measure the velocity field resulting from the discharge in quiescent air and to determine the homogeneity of energy release along the sliding discharge channel. Semicylindrical shock waves from the channels of the sliding discharge have an initial velocity of more than 600 m s-1. The shock-wave configuration floats in the flow along the streamlined surface. Numerical simulation based on the equations of hydrodynamics matched with the experiment showed that 25%-50% of the discharge energy is instantly transformed into heat energy in a high-speed airflow, leading to the formation of shock waves. This energy is comparable to the flow enthalpy and can result in significant modification of the boundary layer and the entire flow.

The Effect of Surface Irregularities on Wing Drag. 3; Roughness

NASA Technical Reports Server (NTRS)

Hood, Manley J.

1938-01-01

Tests have been made in the N.A.C.A. 8-foot high-speed wind tunnel of the drag caused by roughness on the surface of an airfoil of N.A.C.A. 23012 section and 5-foot chord. The tests were made at speeds from 80 t o 500 miles per hour at lift coefficients from 0 to 0.30. For conditions corresponding to high-speed flight, the increase in the drag was 30 percent of the profile drag of the smooth airfoil for the roughness produced by spray painting and 63 percent for the roughness produced. by 0.0037-inch carborundum grains. About one-half the drag increase was caused by the roughness on the forward one-fourth of the airfoil. Sandpapering the painted surface with No. 400 sandpaper made it sufficiently smooth that the drag was no greater than when the surface was polished. In the lower part of the range investigated the drag due to roughness increased rapidly with Reynolds Number.

Distal hindlimb kinematics of galloping Thoroughbred racehorses on dirt and synthetic racetrack surfaces.

PubMed

Symons, J E; Garcia, T C; Stover, S M

2014-03-01

The effect of racetrack surface (dirt or synthetic) on distal hindlimb kinematics of racehorses running at competition speeds is not known. To compare distal hindlimb and hoof kinematics during stance of breezing (unrestrained gallop) racehorses between dirt and synthetic surfaces. Two-dimensional kinematic video analysis of 5 Thoroughbred racehorses galloping at high speeds (12-17 m/s) on a dirt racetrack and a synthetic racetrack. The positions of kinematic markers applied to the left hindlimb were recorded at 500 Hz. Position, velocity and acceleration of joint angles and hoof translation during stance were calculated in the sagittal plane. Peak translational and angular kinematic values were compared between the dirt and synthetic race surfaces using mixed model analyses of covariance. Maximum and heel-strike metatarsophalangeal (fetlock) angles were greater (P<0.05) on the dirt surface than on the synthetic surface. Maximum fetlock angle occurred earlier during stance on the dirt surface (P<0.05). Greater horizontal displacement of the heel during slide occurred on the dirt surface (P<0.05). During high-speed gallop, hindlimb fetlock hyperextension and horizontal hoof slide are greater on a dirt surface than on a synthetic surface. Synthetic race surfaces may mitigate risk of injury to hindlimb fetlock structures by reducing fetlock hyperextension and associated strains in fetlock support structures. Differences in hoof slide may contribute to different distal hindlimb kinematics between surfaces. © 2013 EVJ Ltd.

Near-surface compressional and shear wave speeds constrained by body-wave polarization analysis

NASA Astrophysics Data System (ADS)

Park, Sunyoung; Ishii, Miaki

2018-06-01

A new technique to constrain near-surface seismic structure that relates body-wave polarization direction to the wave speed immediately beneath a seismic station is presented. The P-wave polarization direction is only sensitive to shear wave speed but not to compressional wave speed, while the S-wave polarization direction is sensitive to both wave speeds. The technique is applied to data from the High-Sensitivity Seismograph Network in Japan, and the results show that the wave speed estimates obtained from polarization analysis are compatible with those from borehole measurements. The lateral variations in wave speeds correlate with geological and physical features such as topography and volcanoes. The technique requires minimal computation resources, and can be used on any number of three-component teleseismic recordings, opening opportunities for non-invasive and inexpensive study of the shallowest (˜100 m) crustal structures.

Surface and Bulk Carbide Transformations in High-Speed Steel

PubMed Central

Godec, M.; Večko Pirtovšek, T.; Šetina Batič, B.; McGuiness, P.; Burja, J.; Podgornik, B.

2015-01-01

We have studied the transformation of carbides in AISI M42 high-speed steels in the temperature window used for forging. The annealing was found to result in the partial transformation of the large, metastable M2C carbides into small, more stable grains of M6C, with an associated change in the crystal orientation. In addition, MC carbides form during the transformation of M2C to M6C. From the high-speed-steel production point of view, it is beneficial to have large, metastable carbides in the cast structure, which later during annealing, before the forging, transform into a structure of polycrystalline carbides. Such carbides can be easily decomposed into several small carbides, which are then randomly distributed in the microstructure. The results also show an interesting difference in the carbide-transformation reactions on the surface versus the bulk of the alloy, which has implications for in-situ studies of bulk phenomena that are based on surface observations. PMID:26537780

Chip morphology as a performance predictor during high speed end milling of soda lime glass

NASA Astrophysics Data System (ADS)

Bagum, M. N.; Konneh, M.; Abdullah, K. A.; Ali, M. Y.

2018-01-01

Soda lime glass has application in DNA arrays and lab on chip manufacturing. Although investigation revealed that machining of such brittle material is possible using ductile mode under controlled cutting parameters and tool geometry, it remains a challenging task. Furthermore, ability of ductile machining is usually assed through machined surface texture examination. Soda lime glass is a strain rate and temperature sensitive material. Hence, influence on attainment of ductile surface due to adiabatic heat generated during high speed end milling using uncoated tungsten carbide tool is investigated in this research. Experimental runs were designed using central composite design (CCD), taking spindle speed, feed rate and depth of cut as input variable and tool-chip contact point temperature (Ttc) and the surface roughness (Rt) as responses. Along with machined surface texture, Rt and chip morphology was examined to assess machinability of soda lime glass. The relation between Ttc and chip morphology was examined. Investigation showed that around glass transition temperature (Tg) ductile chip produced and subsequently clean and ductile final machined surface produced.

Systems Engineering Methodology for Fuel Efficiency and its Application to the TARDEC Fuel Efficient Demonstrator (FED) Program

DTIC Science & Technology

2010-08-19

highlight the benefits of regenerative braking . Parameters within the drive cycle may include vehicle speed, elevation/grade changes, road surface...assist to downsize the engine due to infinite maximum speed requirements • Drive cycle less suited to regenerative braking improvement compared to...will be cycle dependent. A high speed drive cycle may for example drive a focus on aerodynamic improvements, while high frequency of braking will

A generalized model for the air-sea transfer of dimethyl sulfide at high wind speeds

NASA Astrophysics Data System (ADS)

Vlahos, Penny; Monahan, Edward C.

2009-11-01

The air-sea exchange of dimethyl sulfide (DMS) is an important component of ocean biogeochemistry and global climate models. Both laboratory experiments and field measurements of DMS transfer rates have shown that the air-sea flux of DMS is analogous to that of other significant greenhouse gases such as CO2 at low wind speeds (<10 m/s) but that these DMS transfer rates may diverge from other gases as wind speeds increase. Herein we provide a mechanism that predicts the attenuation of DMS transfer rates at high wind speeds. The model is based on the amphiphilic nature of DMS that leads to transfer delay at the water-bubble interface and becomes significant at wind speeds above >10 m/s. The result is an attenuation of the dimensionless Henry's Law constant (H) where (Heff = H/(1 + (Cmix/Cw) ΦB) by a solubility enhancement Cmix/Cw, and the fraction of bubble surface area per m2 surface ocean.

Dental handpiece contamination: a proteomics and surface analysis approach.

PubMed

Smith, Andrew; Smith, Gordon; Lappin, David F; Baxter, Helen C; Jones, Anita; Baxter, Robert L

2014-01-01

Dental handpieces (DHPs) become biofouled internally with patient derived material that is difficult to access for removal and inactivation. This study undertook a quantitative and qualitative investigation of protein contamination of internal components from three different types of DHP: the turbine, slow speed contra-angle and surgical. Eluates from the high speed turbine, low speed spray channels and surgical gear were assayed for protein using an orthophthaldehyde assay. Eluates concentrated by Amicon ultrafiltration were also analysed by SDS-PAGE, mass spectroscopy, Western blotting and ELISA. The surfaces of handpiece components were also investigated by SEM, EFSCAN and EDAX microscopy. Surgical gears contained highest levels of protein (403 μg), followed by low speed spray channels (17.7 μg) and the high speed turbine (<5 μg). Mass spectroscopy of surgical gears demonstrated mostly serum derived proteins. Decontamination of the DHPs using an automated washer disinfector and handpiece irrigator showed a significant reduction in residual protein levels.

Visualization of the separation and subsequent transition near the leading edge of airfoils

NASA Technical Reports Server (NTRS)

Arena, A. V.; Mueller, T. J.

1978-01-01

A visual study was performed using the low speed smoke wind tunnels with the objective of obtaining a better understanding of the structure of leading edge separation bubbles on airfoils. The location of separation, transition and reattachment for a cylindrical nose constant-thickness airfoil model were obtained from smoke photographs and surface oil flow techniques. These data, together with static pressure distributions along the leading edge and upper surface of the model, produced the influence of Reynolds number, angle of attack, and trailing edge flap angle on the size and characteristics of the bubble. Additional visual insight into the unsteady nature of the separation bubble was provided by high speed 16 mm movies. The 8 mm color movies taken of the surface oil flow supported the findings of the high speed movies and clearly showed the formation of a scalloped spanwise separation line at the higher Reynolds number.

Supersonic Quadrupole Noise Theory for High-Speed Helicopter Rotors

NASA Technical Reports Server (NTRS)

Farassat, F.; Brentner, Kenneth S.

1997-01-01

High-speed helicopter rotor impulsive noise prediction is an important problem of aeroacoustics. The deterministic quadrupoles have been shown to contribute significantly to high-speed impulsive (HSI) noise of rotors, particularly when the phenomenon of delocalization occurs. At high rotor-tip speeds, some of the quadrupole sources lie outside the sonic circle and move at supersonic speed. Brentner has given a formulation suitable for efficient prediction of quadrupole noise inside the sonic circle. In this paper, we give a simple formulation based on the acoustic analogy that is valid for both subsonic and supersonic quadrupole noise prediction. Like the formulation of Brentner, the model is exact for an observer in the far field and in the rotor plane and is approximate elsewhere. We give the full analytic derivation of this formulation in the paper. We present the method of implementation on a computer for supersonic quadrupoles using marching cubes for constructing the influence surface (Sigma surface) of an observer space- time variable (x; t). We then present several examples of noise prediction for both subsonic and supersonic quadrupoles. It is shown that in the case of transonic flow over rotor blades, the inclusion of the supersonic quadrupoles improves the prediction of the acoustic pressure signature. We show the equivalence of the new formulation to that of Brentner for subsonic quadrupoles. It is shown that the regions of high quadrupole source strength are primarily produced by the shock surface and the flow over the leading edge of the rotor. The primary role of the supersonic quadrupoles is to increase the width of a strong acoustic signal.

Investigation at High Subsonic Speeds of the Static Longitudinal and Lateral Stability Characteristics of Two Canard Airplane Configurations

NASA Technical Reports Server (NTRS)

Sleeman, William C., Jr.

1957-01-01

The present investigation was conducted in the Langley high-speed 7-by 10-foot tunnel to determine the static longitudinal and lateral stability characteristics at high subsonic speeds of two canard airplane configurations previously tested at supersonic speeds. The Mach number range of this investigation extended from 0.60 to 0.94 and a maximum angle-of-attack range of -2dewg to 24deg was obtained at the lowest test Mach number. Two wing plan forms of equal area were studied in the present tests; one was a 60deg delta wing and the other was a trapezoid wing having an aspect ratio of 3, taper ratio of 0.143, and an unswept 80-percent-chord line. The canard control had a trapezoidal plan form and its area was approximately 11.5 percent of the wing area. The model also had a low-aspect-ratio highly swept vertical tail and twin ventral fins. The longitudinal control characteristics of the models were consistent with past experience at low speed on canard configurations in that stalling of the canard surface occurred at moderate and high control deflections for moderate values of angle of attack. This stalling could impose appreciable limitations on the maximum trim-lift coefficient attainable. The control effectiveness and maximum value of trim-lift was significantly increased by addition of a body flap having a conical shape and located slightly behind the canard surface on the bottom of the body. Addition of the canard surface at 0deg deflection had relatively little effect on overall directional stability of the delta-wing configuration; however, deflection of the canard surface from 0deg to 10deg had a large favorable effect on directional stability at high angles of attack for both the trapezoid- and delta-wing configurations.

Three-dimensional optical reconstruction of vocal fold kinematics using high-speed video with a laser projection system

PubMed Central

Luegmair, Georg; Mehta, Daryush D.; Kobler, James B.; Döllinger, Michael

2015-01-01

Vocal fold kinematics and its interaction with aerodynamic characteristics play a primary role in acoustic sound production of the human voice. Investigating the temporal details of these kinematics using high-speed videoendoscopic imaging techniques has proven challenging in part due to the limitations of quantifying complex vocal fold vibratory behavior using only two spatial dimensions. Thus, we propose an optical method of reconstructing the superior vocal fold surface in three spatial dimensions using a high-speed video camera and laser projection system. Using stereo-triangulation principles, we extend the camera-laser projector method and present an efficient image processing workflow to generate the three-dimensional vocal fold surfaces during phonation captured at 4000 frames per second. Initial results are provided for airflow-driven vibration of an ex vivo vocal fold model in which at least 75% of visible laser points contributed to the reconstructed surface. The method captures the vertical motion of the vocal folds at a high accuracy to allow for the computation of three-dimensional mucosal wave features such as vibratory amplitude, velocity, and asymmetry. PMID:26087485

Control of surface defects on plasma-MIG hybrid welds in cryogenic aluminum alloys

NASA Astrophysics Data System (ADS)

Lee, Hee-Keun; Chun, Kwang-San; Park, Sang-Hyeon; Kang, Chung-Yun

2015-07-01

Lately, high production rate welding processes for Al alloys, which are used as LNG FPSO cargo containment system material, have been developed to overcome the limit of installation and high rework rates. In particular, plasma-metal inert gas (MIG) hybrid (PMH) welding can be used to obtain a higher deposition rate and lower porosity, while facilitating a cleaning effect by preheating and post heating the wire and the base metal. However, an asymmetric undercut and a black-colored deposit are created on the surface of PMH weld in Al alloys. For controlling the surface defect formation, the wire feeding speed and nozzle diameter in the PMH weld was investigated through arc phenomena with high-speed imaging and metallurgical analysis.

Investigating the effect of the high power and high speed CO2 laser surface melting on the residual stresses and corrosion resistance of 316L stainless steel

NASA Astrophysics Data System (ADS)

Obeidi, Muhannad A.; McCarthy, Eanna; Brabazon, Dermot

2018-05-01

This study is investigating the effect of the laser surface melting of 316L stainless steel cylindrical samples on the surface residual stresses and the corrosion resistance. A high speed CO2 laser beam with power range of 300-500 W was used in pulse mode to initiate the surface melting in an argon and argon-nitrogen atmosphere. The produced samples were cross sectioned and the elastic modulus and nano-hardness test were carried out showing no alteration between the modified and the bulk material. A noticeable degradation in the corrosion resistance was found due to the formation of the chromium carbide and chromium nitride which act as electrolytic cells in addition to the disruption of the free chromium content at the melted zone.

SEAL FOR HIGH SPEED CENTRIFUGE

DOEpatents

Skarstrom, C.W.

1957-12-17

A seal is described for a high speed centrifuge wherein the centrifugal force of rotation acts on the gasket to form a tight seal. The cylindrical rotating bowl of the centrifuge contains a closure member resting on a shoulder in the bowl wall having a lower surface containing bands of gasket material, parallel and adjacent to the cylinder wall. As the centrifuge speed increases, centrifugal force acts on the bands of gasket material forcing them in to a sealing contact against the cylinder wall. This arrangememt forms a simple and effective seal for high speed centrifuges, replacing more costly methods such as welding a closure in place.

Homogenization of Tianjin monthly near-surface wind speed using RHtestsV4 for 1951-2014

NASA Astrophysics Data System (ADS)

Si, Peng; Luo, Chuanjun; Liang, Dongpo

2018-05-01

Historical Chinese surface meteorological records provided by the special fund for basic meteorological data from the National Meteorological Information Center (NMIC) were processed to produce accurate wind speed data. Monthly 2-min near-surface wind speeds from 13 observation stations in Tianjin covering 1951-2014 were homogenized using RHtestV4 combined with their metadata. Results indicate that 10 stations had significant breakpoints—77% of the Tianjin stations—suggesting that inhomogeneity was common in the Tianjin wind speed series. Instrument change accounted for most changes, based on the metadata, including changes in type and height, especially for the instrument type. Average positive quantile matching (QM) adjustments were more than negative adjustments at 10 stations; positive biases with a probability density of 0.2 or more were mainly concentrates in the range 0.2 m s-1 to 1.2 m s-1, while the corresponding negative biases were mainly in the range -0.1 to -1.2 m s-1. Here, changes in variances and trends in the monthly mean surface wind speed series at 10 stations before and after adjustment were compared. Climate characteristics of wind speed in Tianjin were more reasonably reflected by the adjusted data; inhomogeneity in wind speed series was largely corrected. Moreover, error analysis reveals that there was a high consistency between the two datasets here and that from the NMIC, with the latter as the reference. The adjusted monthly near-surface wind speed series shows a certain reliability for the period 1951-2014 in Tianjin.

Surface ozone concentrations in Europe: Links with the regional-scale atmospheric circulation

NASA Astrophysics Data System (ADS)

Davies, T. D.; Kelly, P. M.; Low, P. S.; Pierce, C. E.

1992-06-01

Daily surface ozone observations from 1978 (1976 for some analyses) to 1988 for Bottesford (United Kingdom), Cabauw, Kloosterburen (The Netherlands), Hohenpeissenberg, Neuglobsow, Hamburg, and Arkona (Germany) are used to analyze links between surface ozone variations and the atmospheric circulation. A daily Europe-wide synoptic classification highlights marked differences between surface ozone/meteorology relationships in summer and winter. These relationships are characterized by correlations between daily surface ozone concentrations at each station and a local subregional surface pressure gradient (a wind speed index). Although there are geographical variations, which are explicable in terms of regional climatology, there are distinct annual cycles. In summer, the surface ozone/wind speed relationship exhibits the expected negative sign; however, in winter, the relationship is, in the main, strongly positive, especially at those stations which are more influenced by the vigorous westerlies. Spring and autumn exhibit negative, positive, or transitional (between summer and winter) behavior, depending on geographical position. It is suggested that these relationships reflect the importance of vertical exchange from the free troposphere to the surface in the nonsummer months. Composite surface pressure patterns and surface pressure anomaly (from the long-term mean) patterns associated with high surface ozone concentrations on daily and seasonal time scales are consistent with the surface ozone/wind speed relationships. Moreover, they demonstrate that high surface ozone concentrations, in a climatological time frame, can be associated with mean surface pressure patterns which have a synoptic reality and are robust. Such an approach may be useful in interpreting past variations in surface ozone and may help to isolate the effect of human activity. It is also possible that assessments can be made of the effect of projected future changes in the atmospheric circulation. This potential is illustrated by the fact that up to 65% of the interannual variance in 6-month mean surface ozone concentrations can be explained by the subregional wind speed index.

An atlas of monthly mean distributions of GEOSAT sea surface height, SSMI surface wind speed, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1988

NASA Technical Reports Server (NTRS)

Halpern, D.; Zlotnicki, V.; Newman, J.; Brown, O.; Wentz, F.

1991-01-01

Monthly mean global distributions for 1988 are presented with a common color scale and geographical map. Distributions are included for sea surface height variation estimated from GEOSAT; surface wind speed estimated from the Special Sensor Microwave Imager on the Defense Meteorological Satellite Program spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer on NOAA spacecrafts; and the Cartesian components of the 10m height wind vector computed by the European Center for Medium Range Weather Forecasting. Charts of monthly mean value, sampling distribution, and standard deviation value are displayed. Annual mean distributions are displayed.

Engineered Surface Properties of Porous Tungsten from Cryogenic Machining

NASA Astrophysics Data System (ADS)

Schoop, Julius Malte

Porous tungsten is used to manufacture dispenser cathodes due to it refractory properties. Surface porosity is critical to functional performance of dispenser cathodes because it allows for an impregnated ceramic compound to migrate to the emitting surface, lowering its work function. Likewise, surface roughness is important because it is necessary to ensure uniform wetting of the molten impregnate during high temperature service. Current industry practice to achieve surface roughness and surface porosity requirements involves the use of a plastic infiltrant during machining. After machining, the infiltrant is baked and the cathode pellet is impregnated. In this context, cryogenic machining is investigated as a substitutionary process for the current plastic infiltration process. Along with significant reductions in cycle time and resource use, surface quality of cryogenically machined un-infiltrated (as-sintered) porous tungsten has been shown to significantly outperform dry machining. The present study is focused on examining the relationship between machining parameters and cooling condition on the as-machined surface integrity of porous tungsten. The effects of cryogenic pre-cooling, rake angle, cutting speed, depth of cut and feed are all taken into consideration with respect to machining-induced surface morphology. Cermet and Polycrystalline diamond (PCD) cutting tools are used to develop high performance cryogenic machining of porous tungsten. Dry and pre-heated machining were investigated as a means to allow for ductile mode machining, yet severe tool-wear and undesirable smearing limited the feasibility of these approaches. By using modified PCD cutting tools, high speed machining of porous tungsten at cutting speeds up to 400 m/min is achieved for the first time. Beyond a critical speed, brittle fracture and built-up edge are eliminated as the result of a brittle to ductile transition. A model of critical chip thickness ( hc ) effects based on cutting force, temperature and surface roughness data is developed and used to study the deformation mechanisms of porous tungsten under different machining conditions. It is found that when hmax = hc, ductile mode machining of otherwise highly brittle porous tungsten is possible. The value of hc is approximately the same as the average ligament size of the 80% density porous tungsten workpiece.

Parameter optimization and evaluation of mechanical and thermal properties of nanographene reinforced Al 6060 surface composite using FSP

NASA Astrophysics Data System (ADS)

Kalyanamanohar, V.; Appalachari, D. Gireesh Chandra

2018-04-01

Friction stir processing (FSP) is emerging as a promising technique for making surface composites. FSP can improve surface properties such as hardness, strength, ductility, corrosion resistance, fatigue life and formability without affecting the bulk properties of the material. The literatures reported that FSP can produces very fine equiaxed and homogeneous grain structure for different Al alloys. Al 6060 is heat treatable alloy which has high thermal and electrical properties than remaining Al alloys. Al 6060 is being used where high rate of heat exchange is needed i.e. engine cylinders, heat exchangers etc. As derived from the carbon materials, like graphene and CNTs dissipates heat rapidly that improves the life of the engine cylinders and heat exchangers. In this work, nanographene is reinforced in the Al 6060 using friction stir processing at different rotational speeds, traverse speeds, and at constant load and tool tilt angle. After processed, the effect of process parameters on microstructure of the surface composite was investigated. The SEM studies shows that the FSP produces very fine and homogenous grain structure and it is observed that smaller grain size structure is obtained at lower traverse speed and higher rotational speeds. Significant improvement in ultimate tensile strength(22.9%) and hardness (22.44%) when compared friction stir processed plate at 1400 rotational speed and 20mm/min traverse speed with base Al 6060 plate. Coefficient of thermal expansion test of nanographene reinforced Al 6060 shows 7.33% decrease in its coefficient of thermal expansion as graphene has tendency to reduce the anisotropic nature.

A compressible multiphase framework for simulating supersonic atomization

NASA Astrophysics Data System (ADS)

Regele, Jonathan D.; Garrick, Daniel P.; Hosseinzadeh-Nik, Zahra; Aslani, Mohamad; Owkes, Mark

2016-11-01

The study of atomization in supersonic combustors is critical in designing efficient and high performance scramjets. Numerical methods incorporating surface tension effects have largely focused on the incompressible regime as most atomization applications occur at low Mach numbers. Simulating surface tension effects in high speed compressible flow requires robust numerical methods that can handle discontinuities caused by both material interfaces and shocks. A shock capturing/diffused interface method is developed to simulate high-speed compressible gas-liquid flows with surface tension effects using the five-equation model. This includes developments that account for the interfacial pressure jump that occurs in the presence of surface tension. A simple and efficient method for computing local interface curvature is developed and an acoustic non-dimensional scaling for the surface tension force is proposed. The method successfully captures a variety of droplet breakup modes over a range of Weber numbers and demonstrates the impact of surface tension in countering droplet deformation in both subsonic and supersonic cross flows.

Extension of Kirchhoff's formula to radiation from moving surfaces

NASA Technical Reports Server (NTRS)

Farassat, F.; Myers, M. K.

1988-01-01

Kirchhoff's formula for radiation from a closed surface has been used recently for prediction of the noise of high speed rotors and propellers. Because the closed surface on which the boundary data are prescribed in these cases is in motion, an extension of Kirchhoff's formula to this condition is required. In this paper such a formula, obtained originally by Morgans for the interior problem, is derived for regions exterior to surfaces moving at speeds below the wave propagation speed by making use of some results of generalized function theory. It is shown that the usual Kirchhoff formula is a special case of the main result of the paper. The general result applies to a deformable surface. However, the special form it assumes for a rigid surface in motion is also noted. In addition, Morgans' result is further extended by showing that edge line integrals appear in the formula when applied to a surface that is piecewise smooth. Some possible areas of application of the formula to problems of current interest in aeroacoustics are discussed.

Extension of Kirchhoff's formula to radiation from moving surfaces

NASA Technical Reports Server (NTRS)

Farassat, F.; Myers, M. K.

1987-01-01

Kirchhoff's formula for radiation from a closed surface has been used recently for prediction of the noise of high speed rotors and propellers. Because the closed surface on which the boundary data are prescribed in these cases is in motion, an extension of Kirchhoff's formula to this condition is required. In this paper such a formula, obtained originally by Morgans for the interior problem, is derived for regions exterior to surfaces moving at speeds below the wave propagation speed by making use of some results of generalized function theory. It is shown that the usual Kirchhoff formula is a special case of the main result of the paper. The general result applies to a deformable surface. However, the special form it assumes for a rigid surface in motion is also noted. In addition, Morgans' result is further extended by showing that edge line integrals appear in the formula when applied to a surface that is piecewise smooth. Some possible areas of application of the formula to problems of current interest in aeroacoustics are discussed.

Note: development of high speed confocal 3D profilometer.

PubMed

Ang, Kar Tien; Fang, Zhong Ping; Tay, Arthur

2014-11-01

A high-speed confocal 3D profilometer based on the chromatic confocal technology and spinning Nipkow disk technique has been developed and tested. It can measure a whole surface topography by taking only one image that requires less than 0.3 s. Surface height information is retrieved based on the ratios of red, green, and blue color information. A new vector projection technique has developed to enhance the vertical resolution of the measurement. The measurement accuracy of the prototype system has been verified via different test samples.

ROLE OF THE CORONAL ALFVÉN SPEED IN MODULATING THE SOLAR-WIND HELIUM ABUNDANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Y.-M., E-mail: yi.wang@nrl.navy.mil

The helium abundance He/H in the solar wind is relatively constant at ∼0.04 in high-speed streams, but varies in phase with the sunspot number in slow wind, from ∼0.01 at solar minimum to ∼0.04 at maximum. Suggested mechanisms for helium fractionation have included frictional coupling to protons and resonant interactions with high-frequency Alfvénic fluctuations. We compare He/H measurements during 1995–2015 with coronal parameters derived from source-surface extrapolations of photospheric field maps. We find that the near-Earth helium abundance is an increasing function of the magnetic field strength and Alfvén speed v {sub A} in the outer corona, while being onlymore » weakly correlated with the proton flux density. Throughout the solar cycle, fast wind is associated with short-term increases in v {sub A} near the source surface; resonance with Alfvén waves, with v {sub A} and the relative speed of α -particles and protons decreasing with increasing heliocentric distance, may then lead to enhanced He/H at 1 au. The modulation of helium in slow wind reflects the tendency for the associated coronal Alfvén speeds to rise steeply from sunspot minimum, when this wind is concentrated around the source-surface neutral line, to sunspot maximum, when the source-surface field attains its peak strengths. The helium abundance near the source surface may represent a balance between collisional decoupling from protons and Alfvén wave acceleration.« less

Single-mode temperature and polarisation-stable high-speed 850nm vertical cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Nazaruk, D. E.; Blokhin, S. A.; Maleev, N. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Vasil'ev, A. P.; Gladyshev, A. G.; Pavlov, M. M.; Blokhin, A. A.; Kulagina, M. M.; Vashanova, K. A.; Zadiranov, Yu M.; Fefelov, A. G.; Ustinov, V. M.

2014-12-01

A new intracavity-contacted design to realize temperature and polarization-stable high-speed single-mode 850 nm vertical cavity surface emitting lasers (VCSELs) grown by molecular-beam epitaxy is proposed. Temperature dependences of static and dynamic characteristics of the 4.5 pm oxide aperture InGaAlAs VCSEL were investigated in detail. Due to optimal gain-cavity detuning and enhanced carrier localization in the active region the threshold current remains below 0.75 mA for the temperature range within 20-90°C, while the output power exceeds 1 mW up to 90°C. Single-mode operation with side-mode suppression ratio higher than 30 dB and orthogonal polarization suppression ratio more than 18 dB was obtained in the whole current and temperature operation range. Device demonstrates serial resistance less than 250 Ohm, which is rather low for any type of single-mode short- wavelength VCSELs. VCSEL demonstrates temperature robust high-speed operation with modulation bandwidth higher than 13 GHz in the entire temperature range of 20-90°C. Despite high resonance frequency the high-speed performance of developed VCSELs was limited by the cut-off frequency of the parasitic low pass filter created by device resistances and capacitances. The proposed design is promising for single-mode high-speed VCSEL applications in a wide spectral range.

Evaluation of reanalysis near-surface winds over northern Africa in Boreal summer

NASA Astrophysics Data System (ADS)

Engelstaedter, Sebastian; Washington, Richard

2014-05-01

The emission of dust from desert surfaces depends on the combined effects of surface properties such as surface roughness, soil moisture, soil texture and particle size (erodibility) and wind speed (erosivity). In order for dust cycle models to realistically simulate dust emissions for the right reasons, it is essential that erosivity and erodibility controlling factors are represented correctly. There has been a focus on improving dust emission schemes or input fields of soil distribution and texture even though it has been shown that the use of wind fields from different reanalysis datasets to drive the same model can result in significant differences in the dust emissions. Here we evaluate the representation of near-surface wind speed from three different reanalysis datasets (ERA-Interim, CFSR and MERRA) over the North African domain. Reanalysis 10m wind speeds are compared with observations from SYNOP and METAR reports available from the UK Meteorological Office Integrated Data Archive System (MIDAS) Land and Marine Surface Stations Dataset. We compare 6-hourly observations of 10m wind speed between 1 January 1989 and 31 December 2009 from more the 500 surface stations with the corresponding reanalysis values. A station data based mean wind speed climatology for North Africa is presented. Overall, the representation of 10m winds is relatively poor in all three reanalysis datasets with stations in the northern parts of the Sahara still being better simulated (correlation coefficients ~ 0.5) than stations in the Sahel (correlation coefficients < 0.3) which points at the reanalyses not being able to realistically capture the Sahel dynamics systems. All three reanalyses have a systematic bias towards overestimating wind speed below 3-4 m/s and underestimating wind speed above 4 m/s. This bias becomes larger with increasing wind speed but is independent of the time of day. For instance, 14 m/s observed wind speeds are underestimated on average by 6 m/s in the ERA-Interim reanalysis. Given the cubic relationship between wind speed and dust emission this large underestimation is expected to significantly impact the simulation of dust emissions. A negative relationship between observed and ERA-Interim wind speed is found for winds above 14 m/s indicating that high wind speed generating processes are not well (if at all) represented in the model.

Vibration compensation for high speed scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Croft, D.; Devasia, S.

1999-12-01

Low scanning speed is a fundamental limitation of scanning tunneling microscopes (STMs), making real time imaging of surface processes and nanofabrication impractical. The effective scanning bandwidth is currently limited by the smallest resonant vibrational frequency of the piezobased positioning system (i.e., scanner) used in the STM. Due to this limitation, the acquired images are distorted during high speed operations. In practice, the achievable scan rates are much less than 1/10th of the resonant vibrational frequency of the STM scanner. To alleviate the scanning speed limitation, this article describes an inversion-based approach that compensates for the structural vibrations in the scanner and thus, allows STM imaging at high scanning speeds (relative to the smallest resonant vibrational frequency). Experimental results are presented to show the increase in scanning speeds achievable by applying the vibration compensation methods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Ming-Hung; School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan; Haung, Chiung-Fang

In this study, neodymium-doped yttrium orthovanadate (Nd:YVO{sub 4}) as a laser source with different scanning speeds was used on biomedical Ti surface. The microstructural and biological properties of laser-modified samples were investigated by means of optical microscope, electron microscope, X-ray diffraction, surface roughness instrument, contact angle and cell cytotoxicity assay. After laser modification, the rough volcano-like recast layer with micro-/nanoporous structure and wave-like recast layer with nanoporous structure were generated on the surfaces of laser-modified samples, respectively. It was also found out that, an α → (α + rutile-TiO{sub 2}) phase transition occurred on the recast layers of laser-modified samples.more » The Ti surface becomes hydrophilic at a high speed laser scanning. Moreover, the cell cytotoxicity assay demonstrated that laser-modified samples did not influence the cell adhesion and proliferation behaviors of osteoblast (MG-63) cell. The laser with 50 mm/s scanning speed induced formation of rough volcano-like recast layer accompanied with micro-/nanoporous structure, which can promote cell adhesion and proliferation of MG-63 cell on Ti surface. The results indicated that the laser treatment was a potential technology to enhance the biocompatibility for titanium. - Highlights: • Laser induced the formation of recast layer with micro-/nanoporous structure on Ti. • An α → (α + rutile-TiO{sub 2}) phase transition was observed within the recast layer. • The Ti surface becomes hydrophilic at a high speed laser scanning. • Laser-modified samples exhibit good biocompatibility to osteoblast (MG-63) cell.« less

Research of Adhesion Bonds Between Gas-Thermal Coating and Pre-Modified Base

NASA Astrophysics Data System (ADS)

Kovalevskaya, Z.; Zaitsev, K.; Klimenov, V.

2016-08-01

Nature of adhesive bonds between gas-thermal nickel alloy coating and carbon steel base was examined using laser profilometry, optical metallography, transmission and scanning electron microscopy. The steel surface was plastically pre-deformed by an ultrasonic tool. Proved that ultrasound pre-treatment modifies the steel surface. Increase of dislocation density and formation of sub micro-structure are base elements of surface modification. While using high-speed gas-flame, plasma and detonation modes of coatings, surface activation occurs and durable adhesion is formed. Ultrasonic pre-treatment of base material is effective when sprayed particles and base material interact through physical-chemical bond formation. Before applying high-speed gas flame and plasma sprayed coatings, authors recommend ultrasonic pretreatment, which creates periodic wavy topography with a stroke of 250 microns on the steel surface. Before applying detonation sprayed coatings, authors recommend ultrasound pretreatment that create modified surface with a uniform micro-topography.

A feasibility study regarding the addition of a fifth control to a rotorcraft in-flight simulator

NASA Technical Reports Server (NTRS)

Turner, Simon; Andrisani, Dominick, II

1992-01-01

The addition of a large movable horizontal tail surface to the control system of a rotorcraft in-flight simulator being developed from a Sikorsky UH-60A Black Hawk Helicopter is evaluated. The capabilities of the control surface as a trim control and as an active control are explored. The helicopter dynamics are modeled using the Generic Helicopter simulation program developed by Sikorsky Aircraft. The effect of the horizontal tail on the helicopter trim envelope is examined by plotting trim maps of the aircraft attitude and controls as a function of the flight speed and horizontal tail incidence. The control power of the tail surface relative to that of the other controls is examined by comparing control derivatives extracted from the simulation program over the flight speed envelope. The horizontal tail's contribution as an active control is evaluated using an explicit model following control synthesis involving a linear model of the helicopter in steady, level flight at a flight speed of eighty knots. The horizontal tail is found to provide additional control flexibility in the longitudinal axis. As a trim control, it provides effective control of the trim pitch attitude at mid to high forward speeds. As an active control, the horizontal tail provides useful pitching moment generating capabilities at mid to high forward speeds.

Estimation of the remote-sensing reflectance from above-surface measurements.

PubMed

Mobley, C D

1999-12-20

The remote-sensing reflectance R(rs) is not directly measurable, and various methodologies have been employed in its estimation. I review the radiative transfer foundations of several commonly used methods for estimating R(rs), and errors associated with estimating R(rs) by removal of surface-reflected sky radiance are evaluated using the Hydrolight radiative transfer numerical model. The dependence of the sea surface reflectance factor rho, which is not an inherent optical property of the surface, on sky conditions, wind speed, solar zenith angle, and viewing geometry is examined. If rho is not estimated accurately, significant errors can occur in the estimated R(rs) for near-zenith Sun positions and for high wind speeds, both of which can give considerable Sun glitter effects. The numerical simulations suggest that a viewing direction of 40 deg from the nadir and 135 deg from the Sun is a reasonable compromise among conflicting requirements. For this viewing direction, a value of rho approximately 0.028 is acceptable only for wind speeds less than 5 m s(-1). For higher wind speeds, curves are presented for the determination of rho as a function of solar zenith angle and wind speed. If the sky is overcast, a value of rho approximately 0.028 is used at all wind speeds.

The fall of a viscous thread onto a moving surface: a ‘fluid-mechanical sewing machine’

NASA Astrophysics Data System (ADS)

Chiu-Webster, S.; Lister, J. R.

2006-12-01

A viscous thread falling onto a steadily moving horizontal belt shows a surprisingly complex range of behaviour in experiments. Low belt speeds produce coiling, as might be expected from the behaviour of a thread falling onto a stationary surface. High belt speeds produce a steady thread, whose shape is predicted well by theory developed to describe a stretching viscous catenary with surface tension and inertia. Intermediate belt speeds show several novel modes of oscillation, which lay down a wide variety of patterns on the belt. The patterns include meanders, side kicks, slanted loops, braiding, figures-of-eight, Ws, and also period-doubled versions of figures-of-eight, meanders and coiling. The experimental boundary between steady and unsteady behaviour occurs at a slightly lower belt speed than the loss of the steady solution for a stretching catenary.

Study of surface integrity AISI 4140 as result of hard, dry and high speed machining using CBN

NASA Astrophysics Data System (ADS)

Ginting, B.; Sembiring, R. W.; Manurung, N.

2017-09-01

The concept of hard, dry and high speed machining can be combined, to produce high productivity, with lower production costs in manufacturing industry. Hard lathe process can be a solution to reduce production time. In lathe hard alloy steels reported problems relating to the integrity of such surface roughness, residual stress, the white layer and the surface integrity. AISI 4140 material is used for high reliable hydraulic system components. This material includes in cold work tool steel. Consideration election is because this material is able to be hardened up to 55 HRC. In this research, the experimental design using CCD model fit with three factors, each factor is composed of two levels, and six central point, experiments were conducted with 1 replications. The experimental design research using CCD model fit.

Surface inspection system for carriage parts

NASA Astrophysics Data System (ADS)

Denkena, Berend; Acker, Wolfram

2006-04-01

Quality standards are very high in carriage manufacturing, due to the fact, that the visual quality impression is highly relevant for the purchase decision for the customer. In carriage parts even very small dents can be visible on the varnished and polished surface by observing reflections. The industrial demands are to detect these form errors on the unvarnished part. In order to meet the requirements, a stripe projection system for automatic recognition of waviness and form errors is introduced1. It bases on a modified stripe projection method using a high resolution line scan camera. Particular emphasis is put on achieving a short measuring time and a high resolution in depth, aiming at a reliable automatic recognition of dents and waviness of 10 μm on large curved surfaces of approximately 1 m width. The resulting point cloud needs to be filtered in order to detect dents. Therefore a spatial filtering technique is used. This works well on smoothly curved surfaces, if frequency parameters are well defined. On more complex parts like mudguards the method is restricted by the fact that frequencies near the define dent frequencies occur within the surface as well. To allow analysis of complex parts, the system is currently extended by including 3D CAD models into the process of inspection. For smoothly curved surfaces, the measuring speed of the prototype is mainly limited by the amount of light produced by the stripe projector. For complex surfaces the measuring speed is limited by the time consuming matching process. Currently, the development focuses on the improvement of the measuring speed.

Dynamics of collision of a vortex ring and a planar surface

NASA Astrophysics Data System (ADS)

McErlean, Michael; Krane, Michael; Fontaine, Arnold

2009-11-01

The dynamics of the impact between a vortex ring and a planar surface orientated perpendicular to the direction of travel are presented. High Reynolds number vortex rings are injected into a quiescent tank of water using a piston-cylinder generator before colliding with a target at a long distance. Both the pressure at the stagnation point on the surface and the force imparted to the target by the ring impact are measured directly. The changes in both are related to the ring motion and deformation captured by high speed digital video, and DPIV measurements. These relations are used to develop a scaling law relation between impact force and vortex ring circulation, speed, and size.

How merging droplets jump off a superhydrophobic surface: Measurements and model

NASA Astrophysics Data System (ADS)

Mouterde, Timothée; Nguyen, Thanh-Vinh; Takahashi, Hidetoshi; Clanet, Christophe; Shimoyama, Isao; Quéré, David

2017-11-01

We investigate how drops merging on a nonwettable surface jump off this surface, for both symmetric and asymmetric coalescences. For this purpose, we design and build a microelectromechanical system sensor able to quantify forces down to the micro-Newton scale at a high acquisition rate (200 kHz). Using this device, we perform direct force measurements of self-propelled droplets coupled to high-speed imaging. Experimental data show that the total momentum of the drop after coalescence mainly depends on the size of the smaller drop. Exploiting this finding, we quantitatively predict the takeoff speed of jumping drop pairs and show how to correct the usual argument based on energy conservation.

Movement of fine particles on an air bubble surface studied using high-speed video microscopy.

PubMed

Nguyen, Anh V; Evans, Geoffrey M

2004-05-01

A CCD high-speed video microscopy system operating at 1000 frames per second was used to obtain direct quantitative measurements of the trajectories of fine glass spheres on the surface of air bubbles. The glass spheres were rendered hydrophobic by a methylation process. Rupture of the intervening water film between a hydrophobic particle and an air bubble with the consequent formation of a three-phase contact was observed. The bubble-particle sliding attachment interaction is not satisfactorily described by the available theories. Surface forces had little effect on the particle sliding with a water film, which ruptured probably due to the submicrometer-sized gas bubbles existing at the hydrophobic particle-water interface.

A fluid-mechanical sewing machine

NASA Astrophysics Data System (ADS)

Lister, John; Chiu-Webster, Sunny

2004-11-01

It is a breakfast-table experience that when a viscous fluid thread falls a sufficient height onto a stationary horizontal surface the thread is undergoes a coiling instability. We describe experimental observations of a viscous thread falling onto a steadily moving horizontal belt. Low (or zero) belt speeds produce coiling as expected. High belt speeds produce a steady thread, whose shape is well-predicted by theory for a stretching catenary with surface tension and inertia. Intermediate belt speeds show various modes of oscillation, which produce a variety of `stitching' patterns on the belt. The onset of oscillations is predicted theoretically.

A novel method of freeform surface grinding with a soft wheel based on industrial robots

NASA Astrophysics Data System (ADS)

Sha, Sheng-chun; Guo, Xiao-ling

2011-08-01

In order to meet the growing demand for high-quality images, optical elements of freeform surface are more and more applied to imaging system. However the fabrication of freeform surface optical elements is much more difficult than that of traditional spherical ones. Recent research on freeform surface manufacture often deals with precision machine tools which have limitations on dimensions and are always expensive. Little has been researched on industrial robots. In this paper, a new method of freeform surface grinding based on industrial robots was found. This method could be applied to both whole surface grinding as well as partial surface grinding. The diameter of lenses to be ground would not be restricted to the machine tool's size. In this method a high-speed-rotating soft wheel was used. The relation between removing amount and grinding time which could be called removing function was established and measured. The machining precision was achieved by means of controlling the grinding time instead of the machine tool or industrial robot itself. There are two main factors affecting the removing function: i).rotating speed of the soft wheel; ii).pressure between the wheel and the work piece. In this paper, two groups of experiments have been conducted. One is the removing function tested at constant rotating speed while under different pressure. The other is that tested under a certain pressure with variable speed. Tables and curves which can show the effect of speed and pressure on the removing efficiency have been obtained. Cause for inaccuracy between experiment data and calculated result according to the theory and the non-linearity in the curves was analyzed. Through these analyses the removing function could be concluded under certain condition including rotating speed and pressure. Finally several experiments were performed to verify the appropriateness of the removing function. It could also be concluded that this method was more efficient in comparison with traditional grinding technology particularly in the aspect of partial surface grinding. This paper also brought up a new idea that this method could be combined with other freeform surface grinding technics to realize a more flexible, efficient, reliable and economical type of optical fabrication. It would become a potential technic especially for partial optical surface grinding and repair.

Reducing the content of alloying elements in high-speed steel during heating in salt baths

NASA Astrophysics Data System (ADS)

Kandalovskii, I. P.; Kirillov, F. F.; Dobler, V. I.

1985-07-01

A decrease in molebdenum content occurs in the surface layers during the quench heating of a tool formed from high-speed tungsten-molybdenum steel in a barium chloride salt bath after the required heating time, while a decrease in the tungsten content takes place with more prolonged hold times.

Intense sub-kilometer-scale boundary layer rolls observed in hurricane fran

PubMed

Wurman; Winslow

1998-04-24

High-resolution observations obtained with the Doppler On Wheels (DOW) mobile weather radar near the point of landfall of hurricane Fran (1996) revealed the existence of intense, sub-kilometer-scale, boundary layer rolls that strongly modulated the near-surface wind speed. It is proposed that these structures are one cause of geographically varying surface damage patterns that have been observed after some landfalling hurricanes and that they cause much of the observed gustiness, bringing high-velocity air from aloft to the lowest observable levels. High-resolution DOW radar observations are contrasted with lower-resolution observations obtained with an operational weather radar, which underestimated peak low-level wind speeds.

High-speed 850 nm VCSELs with 28 GHz modulation bandwidth for short reach communication

NASA Astrophysics Data System (ADS)

Westbergh, Petter; Safaisini, Rashid; Haglund, Erik; Gustavsson, Johan S.; Larsson, Anders; Joel, Andrew

2013-03-01

We present results from our new generation of high performance 850 nm oxide confined vertical cavity surface-emitting lasers (VCSELs). With devices optimized for high-speed operation under direct modulation, we achieve record high 3dB modulation bandwidths of 28 GHz for ~4 μm oxide aperture diameter VCSELs, and 27 GHz for devices with a ~7 μm oxide aperture diameter. Combined with a high-speed photoreceiver, the ~7 μm VCSEL enables error-free transmission at data rates up to 47 Gbit/s at room temperature, and up to 40 Gbit/s at 85°C.

Intermittent impact dynamics of a cantilever scanning a surface at high speed

NASA Astrophysics Data System (ADS)

Dey, S.; Kartik, V.

2018-03-01

In contact-mode scanning probe microscopy (SPM), the cantilever's dynamics are conventionally investigated by assuming the tip to be always in contact with the sample's surface. At high scanning speeds, however, the cantilever's inertia becomes dominant and the tip can therefore completely detach from the surface and start impacting upon it. Experiments at the macro-scale cannot emulate the complex micro-scale dynamics, as the system exhibits negligible effects due to meniscus forces and the surrounding medium's squeeze film damping; however, they can provide qualitative insight into the cantilever's dynamics at high frequencies, corresponding to those likely to be excited during video-rate SPM imaging. This paper investigates such intermittent impact dynamics for an upscaled cantilever, analytically, numerically, and experimentally. In contact-mode scanning, a critical scan speed exists beyond which the cantilever's tip loses contact with the sample's surface; a closed-form expression for this contact loss frequency is derived. At high scan speeds, impacts cause the cantilever to switch between different contact regimes: in-, off-, and grazing-contact; within each regime, the system's modal configuration is different. Experimentally-obtained Poincare maps indicate quasi-periodic behaviour at frequencies for which the response is repetitive, as is also predicted by the model. Intermittent impacts excite the sub- and super-harmonics of the excitation frequency, which are related to the natural frequencies of different system configurations based on the "effective" tip-end boundary conditions. The cantilever's response exhibits several phenomena, such as modal transition, beating, grazing, and possible chaotic behaviour, depending upon the relation between the excitation harmonics and the natural frequencies.

Sea spray contributions to the air-sea fluxes at moderate and hurricane wind speeds

NASA Astrophysics Data System (ADS)

Mueller, J. A.; Veron, F.

2009-12-01

At sufficiently high wind speed conditions, the surface of the ocean separates to form a substantial number of sea spray drops, which can account for a significant fraction of the total air-sea surface area and thus make important contributions to the aggregate air-sea momentum, heat and mass fluxes. Although consensus around the qualitative impacts of these drops has been building in recent years, the quantification of their impacts has remained elusive. Ultimately, the spray-mediated fluxes depend on three controlling factors: the number and size of drops formed at the surface, the duration of suspension within the atmospheric marine boundary layer, and the rate of momentum, heat and mass transfer between the drops and the atmosphere. While the latter factor can be estimated from an established, physically-based theory, the estimates for the former two are not well established. Using a recent, physically-based model of the sea spray source function along with the results from Lagrangian stochastic simulations of individual drops, we estimate the aggregate spray-mediated fluxes, finding reasonable agreement with existing models and estimates within the empirical range of wind speed conditions. At high wind speed conditions that are outside the empirical range, however, we find somewhat lower spray-mediated fluxes than previously reported in the literature, raising new questions about the relative air-sea fluxes at high wind speeds as well as the development and sustainment of hurricanes.

An atomic-scale and high efficiency finishing method of zirconia ceramics by using magnetorheological finishing

NASA Astrophysics Data System (ADS)

Luo, Hu; Guo, Meijian; Yin, Shaohui; Chen, Fengjun; Huang, Shuai; Lu, Ange; Guo, Yuanfan

2018-06-01

Zirconia ceramics is a valuable crucial material for fabricating functional components applied in aerospace, biology, precision machinery, military industry and other fields. However, the properties of its high brittleness and high hardness could seriously reduce its finishing efficiency and surface quality by conventional processing technology. In this work, we present a high efficiency and high-quality finishing process by using magnetorheological finishing (MRF), which employs the permanent magnetic yoke with straight air gap as excitation unit. The sub-nanoscale surface roughness and damage free surface can be obtained after magnetorheological finishing. The XRD results and SEM morphologies confirmed that the mechanical shear removal with ductile modes are the dominant material removal mechanism for the magnetorheological finishing of zirconia ceramic. With the developed experimental apparatus, the effects of workpiece speed, trough speed and work gap on material removal rate and surface roughness were systematically investigated. Zirconia ceramics finished to ultra-smooth surface with surface roughness less than Ra 1 nm was repeatedly achieved during the parametric experiments. Additionally, the highest material removal rate exceeded 1 mg/min when using diamond as an abrasive particle. Magnetorheological finishing promises to be an adaptable and efficient method for zirconia ceramics finishing.

Functional form for plasma velocity in a rapidly rotating tokamak discharge

DOE PAGES

Burrell, Keith H.; Chrystal, C. olin

2014-07-25

A recently developed technique using charge exchange spectroscopy determines the ion poloidal rotation in tokamak plasmas from the poloidal variation in the toroidal angular rotation speed. The basis for this technique is the functional form for the plasma velocity calculated from the equilibrium equations. The initial development of this technique utilized the functional form determined for conditions where the ion toroidal rotation speed is much smaller than the ion thermal speed. There are cases, however, where the toroidal rotation can be comparable to the ion thermal speed, especially for high atomic number impurities. Furthermore, the present paper extends the previousmore » analysis to this high rotation speed case and demonstrates how to extract the poloidal rotation speed from measurements of the toroidal angular rotation speed at two points on a flux surface.« less

Pressure Distribution Over Airfoils at High Speeds

NASA Technical Reports Server (NTRS)

Briggs, L J; Dryden, H L

1927-01-01

This report deals with the pressure distribution over airfoils at high speeds, and describes an extension of an investigation of the aerodynamic characteristics of certain airfoils which was presented in NACA Technical Report no. 207. The results presented in report no. 207 have been confirmed and extended to higher speeds through a more extensive and systematic series of tests. Observations were also made of the air flow near the surface of the airfoils, and the large changes in lift coefficients were shown to be associated with a sudden breaking away of the flow from the upper surface. The tests were made on models of 1-inch chord and comparison with the earlier measurements on models of 3-inch chord shows that the sudden change in the lift coefficient is due to compressibility and not to a change in the Reynolds number. The Reynolds number still has a large effect, however, on the drag coefficient. The pressure distribution observations furnish the propeller designer with data on the load distribution at high speeds, and also give a better picture of the air-flow changes.

Optical dynamic deformation measurements at translucent materials.

PubMed

Philipp, Katrin; Koukourakis, Nektarios; Kuschmierz, Robert; Leithold, Christoph; Fischer, Andreas; Czarske, Jürgen

2015-02-15

Due to their high stiffness-to-weight ratio, glass fiber-reinforced polymers are an attractive material for rotors, e.g., in the aerospace industry. A fundamental understanding of the material behavior requires non-contact, in-situ dynamic deformation measurements. The high surface speeds and particularly the translucence of the material limit the usability of conventional optical measurement techniques. We demonstrate that the laser Doppler distance sensor provides a powerful and reliable tool for monitoring radial expansion at fast rotating translucent materials. We find that backscattering in material volume does not lead to secondary signals as surface scattering results in degradation of the measurement volume inside the translucent medium. This ensures that the acquired signal contains information of the rotor surface only, as long as the sample surface is rough enough. Dynamic deformation measurements of fast-rotating fiber-reinforced polymer composite rotors with surface speeds of more than 300 m/s underline the potential of the laser Doppler sensor.

Periodic structures on germanium induced by high repetition rate femtosecond laser

NASA Astrophysics Data System (ADS)

Lin, Xiaoming; Li, Xiaohong; Zhang, Yanbin; Xie, Changxin; Liu, Kaijun; Zhou, Qiang

2018-05-01

Laser-induced periodic surface structures (LIPSS) are studied on germanium surface in air by the femtosecond pulsed laser with repetition frequency of 76 MHz and wavelength λ of 800 nm. Three types of LIPSS were found and they are low-spatial-frequency LIPSS (LSFL), high-spatial-frequency LIPSS (HSFL), and LSFL superimposed with HSFL. The period ΛLSFL of LSFL shrinks quickly from approximately 650 nm to 400 nm (∼λ/2) when lowering the scanning speed. Comparatively, the period ΛHSFL of HSFL keeps almost constant between 90 and 100 nm (∼λ/8) when the scanning speed and the laser pulse energy vary. LSFL and HSFL coexist when the laser pulse energy is around 3.3 nJ/pulse and the scanning speed ranges between 3 and 8 mm/s. The surface plasmon polariton waves make a contribution to the formation of LIPSS and the fourth harmonic generation (FHG) might be involved in the formation of HSFL.

MEASUREMENT OF WIND SPEED FROM COOLING LAKE THERMAL IMAGERY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrett, A; Robert Kurzeja, R; Eliel Villa-Aleman, E

2009-01-20

The Savannah River National Laboratory (SRNL) collected thermal imagery and ground truth data at two commercial power plant cooling lakes to investigate the applicability of laboratory empirical correlations between surface heat flux and wind speed, and statistics derived from thermal imagery. SRNL demonstrated in a previous paper [1] that a linear relationship exists between the standard deviation of image temperature and surface heat flux. In this paper, SRNL will show that the skewness of the temperature distribution derived from cooling lake thermal images correlates with instantaneous wind speed measured at the same location. SRNL collected thermal imagery, surface meteorology andmore » water temperatures from helicopters and boats at the Comanche Peak and H. B. Robinson nuclear power plant cooling lakes. SRNL found that decreasing skewness correlated with increasing wind speed, as was the case for the laboratory experiments. Simple linear and orthogonal regression models both explained about 50% of the variance in the skewness - wind speed plots. A nonlinear (logistic) regression model produced a better fit to the data, apparently because the thermal convection and resulting skewness are related to wind speed in a highly nonlinear way in nearly calm and in windy conditions.« less

Large-scale Advanced Prop-fan (LAP) high speed wind tunnel test report

NASA Technical Reports Server (NTRS)

Campbell, William A.; Wainauski, Harold S.; Arseneaux, Peter J.

1988-01-01

High Speed Wind Tunnel testing of the SR-7L Large Scale Advanced Prop-Fan (LAP) is reported. The LAP is a 2.74 meter (9.0 ft) diameter, 8-bladed tractor type rated for 4475 KW (6000 SHP) at 1698 rpm. It was designated and built by Hamilton Standard under contract to the NASA Lewis Research Center. The LAP employs thin swept blades to provide efficient propulsion at flight speeds up to Mach .85. Testing was conducted in the ONERA S1-MA Atmospheric Wind Tunnel in Modane, France. The test objectives were to confirm that the LAP is free from high speed classical flutter, determine the structural and aerodynamic response to angular inflow, measure blade surface pressures (static and dynamic) and evaluate the aerodynamic performance at various blade angles, rotational speeds and Mach numbers. The measured structural and aerodynamic performance of the LAP correlated well with analytical predictions thereby providing confidence in the computer prediction codes used for the design. There were no signs of classical flutter throughout all phases of the test up to and including the 0.84 maximum Mach number achieved. Steady and unsteady blade surface pressures were successfully measured for a wide range of Mach numbers, inflow angles, rotational speeds and blade angles. No barriers were discovered that would prevent proceeding with the PTA (Prop-Fan Test Assessment) Flight Test Program scheduled for early 1987.

Real-time color measurement using active illuminant

NASA Astrophysics Data System (ADS)

Tominaga, Shoji; Horiuchi, Takahiko; Yoshimura, Akihiko

2010-01-01

This paper proposes a method for real-time color measurement using active illuminant. A synchronous measurement system is constructed by combining a high-speed active spectral light source and a high-speed monochrome camera. The light source is a programmable spectral source which is capable of emitting arbitrary spectrum in high speed. This system is the essential advantage of capturing spectral images without using filters in high frame rates. The new method of real-time colorimetry is different from the traditional method based on the colorimeter or the spectrometers. We project the color-matching functions onto an object surface as spectral illuminants. Then we can obtain the CIE-XYZ tristimulus values directly from the camera outputs at every point on the surface. We describe the principle of our colorimetric technique based on projection of the color-matching functions and the procedure for realizing a real-time measurement system of a moving object. In an experiment, we examine the performance of real-time color measurement for a static object and a moving object.

Process optimization of an auger pyrolyzer with heat carrier using response surface methodology.

PubMed

Brown, J N; Brown, R C

2012-01-01

A 1 kg/h auger reactor utilizing mechanical mixing of steel shot heat carrier was used to pyrolyze red oak wood biomass. Response surface methodology was employed using a circumscribed central composite design of experiments to optimize the system. Factors investigated were: heat carrier inlet temperature and mass flow rate, rotational speed of screws in the reactor, and volumetric flow rate of sweep gas. Conditions for maximum bio-oil and minimum char yields were high flow rate of sweep gas (3.5 standard L/min), high heat carrier temperature (∼600 °C), high auger speeds (63 RPM) and high heat carrier mass flow rates (18 kg/h). Regression models for bio-oil and char yields are described including identification of a novel interaction effect between heat carrier mass flow rate and auger speed. Results suggest that auger reactors, which are rarely described in literature, are well suited for bio-oil production. The reactor achieved liquid yields greater than 73 wt.%. Copyright © 2011 Elsevier Ltd. All rights reserved.

In vivo cross-sectional imaging of the phonating larynx using long-range Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Coughlan, Carolyn A.; Chou, Li-Dek; Jing, Joseph C.; Chen, Jason J.; Rangarajan, Swathi; Chang, Theodore H.; Sharma, Giriraj K.; Cho, Kyoungrai; Lee, Donghoon; Goddard, Julie A.; Chen, Zhongping; Wong, Brian J. F.

2016-03-01

Diagnosis and treatment of vocal fold lesions has been a long-evolving science for the otolaryngologist. Contemporary practice requires biopsy of a glottal lesion in the operating room under general anesthesia for diagnosis. Current in-office technology is limited to visualizing the surface of the vocal folds with fiber-optic or rigid endoscopy and using stroboscopic or high-speed video to infer information about submucosal processes. Previous efforts using optical coherence tomography (OCT) have been limited by small working distances and imaging ranges. Here we report the first full field, high-speed, and long-range OCT images of awake patients’ vocal folds as well as cross-sectional video and Doppler analysis of their vocal fold motions during phonation. These vertical-cavity surface-emitting laser source (VCSEL) OCT images offer depth resolved, high-resolution, high-speed, and panoramic images of both the true and false vocal folds. This technology has the potential to revolutionize in-office imaging of the larynx.

Correlation of cycles in Lava Lake motion and degassing at Erebus Volcano, Antarctica

NASA Astrophysics Data System (ADS)

Peters, Nial; Oppenheimer, Clive; Killingsworth, Drea Rae; Frechette, Jed; Kyle, Philip

2014-08-01

Several studies at Erebus volcano have recorded pulsatory behavior in many of the observable properties of its active lava lake. A strong correlation between the variations in surface speed of the lake and the composition of gas emitted has previously been noted. While previous studies have shown that the SO2 flux and the surface elevation exhibit pulsatory behavior with a similar period to that of the surface speed and gas composition, suggesting they are linked, a lack of overlap between the different measurements has prevented direct comparisons from being made. Using high time-resolution measurements of surface elevation, surface speed, gas composition, and SO2 flux, we demonstrate for the first time an unambiguous link between the cyclic behavior in each of these properties. We also show that the variation in gas composition may be explained by a subtle change in oxygen fugacity. The cycles are found to be in-phase with each other, with a small but consistent lag of 1-3 min between the peaks in surface elevation and surface speed. Explosive events are found to have no observable effect on the pulsatory behavior beyond the ˜5 min period required for lake refill. The close correspondences between the varying lake surface motion, gas flux and composition, and modeled oxygen fugacity suggest strong links between magma degassing, redox change, and the fluid dynamics of the shallow magmatic system.

Performance of Ti-multilayer coated tool during machining of MDN431 alloyed steel

NASA Astrophysics Data System (ADS)

Badiger, Pradeep V.; Desai, Vijay; Ramesh, M. R.

2018-04-01

Turbine forgings and other components are required to be high resistance to corrosion and oxidation because which they are highly alloyed with Ni and Cr. Midhani manufactures one of such material MDN431. It's a hard-to-machine steel with high hardness and strength. PVD coated insert provide an answer to problem with its state of art technique on the WC tool. Machinability studies is carried out on MDN431 steel using uncoated and Ti-multilayer coated WC tool insert using Taguchi optimisation technique. During the present investigation, speed (398-625rpm), feed (0.093-0.175mm/rev), and depth of cut (0.2-0.4mm) varied according to Taguchi L9 orthogonal array, subsequently cutting forces and surface roughness (Ra) were measured. Optimizations of the obtained results are done using Taguchi technique for cutting forces and surface roughness. Using Taguchi technique linear fit model regression analysis carried out for the combination of each input variable. Experimented results are compared and found the developed model is adequate which supported by proof trials. Speed, feed and depth of cut are linearly dependent on the cutting force and surface roughness for uncoated insert whereas Speed and depth of cut feed is inversely dependent in coated insert for both cutting force and surface roughness. Machined surface for coated and uncoated inserts during machining of MDN431 is studied using optical profilometer.

Experimental investigation on the effects of cooling system on surface quality in high speed milling of an aluminium alloy

NASA Astrophysics Data System (ADS)

Chirita, B.; Tampu, N. C.; Brabie, G.; Radu, M. C.

2016-08-01

Surface quality is often an important feature of industrial products, not only from the impact it has on the aesthetic aspect but also for the functional role of the parts. High quality surface increases corrosion resistance, assures a longer life cycle for the product and lowers the wear. For a machined part, surface quality is influenced by a series of factors such as the material of the part, the process type, tool geometry, cutting parameters or the cooling system. The choice of the cooling system is especially important, taking into account that the proper conditions will not only assure a superior surface quality, but will also lower the costs and reduce the environmental impact and health risks. The present study aims to investigate the performance of the cooling system and the effect of the cutting parameters on the characteristics of the surfaces resulted from high speed face milling of some parts made of Al 7050-T7451 aluminium alloy. Dry cutting conditions and minimum quantity lubrication (MQL) where used. The results were analysed using analysis of variance (ANOVA).

Surface evolution of perfluoropolyether film at high speed quasi-contact conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yung-Kan, E-mail: fftransform@gmail.com, E-mail: ykchen@berkeley.edu; Bogy, David B.; Peng, Jih-Ping

2016-05-30

Nanoscale analysis characterized by microscopy with atomic resolution demand that the targeted surface remains nearly static. Therefore, the interaction between two fast moving surfaces requires a unique methodology to capture its dynamics when contacts are of nominal area on the order of 100 μm{sup 2} but only a few angstroms in depth. We present a contact study of the head-disk interface in hard disk drives, which consists of a disk surface coated with a molecularly thin perfluoropolyether lubricant and a slider surface moving slightly separated from it with a relative velocity of 20 m/s and with 10 nm spacing. By investigating the slidermore » dynamics and lubricant topography in-situ, we disclose that high-speed contact initiates when the slider shears the top surface of the lubricant. Such contact can pile up molecules a few angstroms high as “moguls” or annihilate existing ones through a 5–10 Å interference. The transitional spacing regime of mogul evolution is defined as “quasi-contact,” and it is the initial contact in the fast sliding interface.« less

Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction.

PubMed

Yonehara, Yoshinari; Goto, Yusuke; Yoda, Ken; Watanuki, Yutaka; Young, Lindsay C; Weimerskirch, Henri; Bost, Charles-André; Sato, Katsufumi

2016-08-09

Ocean surface winds are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface winds measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of wind that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface winds. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground speed fluctuated presumably due to tail winds and head winds. Taking advantage of the ground speed difference in relation to flight direction, we reliably estimated wind speed and direction experienced by the birds. These bird-based wind velocities were significantly correlated with wind velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution wind observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface winds, potentially complementing conventional wind measurements by covering spatial and temporal measurement gaps.

Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction

PubMed Central

Yonehara, Yoshinari; Goto, Yusuke; Yoda, Ken; Watanuki, Yutaka; Young, Lindsay C.; Weimerskirch, Henri; Bost, Charles-André; Sato, Katsufumi

2016-01-01

Ocean surface winds are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface winds measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of wind that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface winds. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground speed fluctuated presumably due to tail winds and head winds. Taking advantage of the ground speed difference in relation to flight direction, we reliably estimated wind speed and direction experienced by the birds. These bird-based wind velocities were significantly correlated with wind velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution wind observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface winds, potentially complementing conventional wind measurements by covering spatial and temporal measurement gaps. PMID:27457932

Hypersonic code efficiency and validation studies

NASA Technical Reports Server (NTRS)

Bennett, Bradford C.

1992-01-01

Renewed interest in hypersonic and supersonic flows spurred the development of the Compressible Navier-Stokes (CNS) code. Originally developed for external flows, CNS was modified to enable it to also be applied to internal high speed flows. In the initial phase of this study CNS was applied to both internal flow applications and fellow researchers were taught to run CNS. The second phase of this research was the development of surface grids over various aircraft configurations for the High Speed Research Program (HSRP). The complex nature of these configurations required the development of improved surface grid generation techniques. A significant portion of the grid generation effort was devoted to testing and recommending modifications to early versions of the S3D surface grid generation code.

The Interaction of High-Speed Turbulence with Flames: Turbulent Flame Speed

DTIC Science & Technology

2010-08-05

AND ADDRESS(ES) 10. SPONSOR / MONITOR’S ACRONYM(S) 9 . SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 11. SPONSOR / MONITOR’S REPORT NUMBER(S...UL 38 A.Y. Poludnenko (202) 767-6582 05 -08-2010 Memorandum Report Turbulent premixed combustion Turbulence Flamelet Turbulent flame speed Office of...3.4. Stretch factor and the balance between ST and AT ...................................................................... 9 4. Flame surface

Study on the high-frequency laser measurement of slot surface difference

NASA Astrophysics Data System (ADS)

Bing, Jia; Lv, Qiongying; Cao, Guohua

2017-10-01

In view of the measurement of the slot surface difference in the large-scale mechanical assembly process, Based on high frequency laser scanning technology and laser detection imaging principle, This paragraph designs a double galvanometer pulse laser scanning system. Laser probe scanning system architecture consists of three parts: laser ranging part, mechanical scanning part, data acquisition and processing part. The part of laser range uses high-frequency laser range finder to measure the distance information of the target shape and get a lot of point cloud data. Mechanical scanning part includes high-speed rotary table, high-speed transit and related structure design, in order to realize the whole system should be carried out in accordance with the design of scanning path on the target three-dimensional laser scanning. Data processing part mainly by FPGA hardware with LAbVIEW software to design a core, to process the point cloud data collected by the laser range finder at the high-speed and fitting calculation of point cloud data, to establish a three-dimensional model of the target, so laser scanning imaging is realized.

High-speed manufacturing of highly regular femtosecond laser-induced periodic surface structures: physical origin of regularity.

PubMed

Gnilitskyi, Iaroslav; Derrien, Thibault J-Y; Levy, Yoann; Bulgakova, Nadezhda M; Mocek, Tomáš; Orazi, Leonardo

2017-08-16

Highly regular laser-induced periodic surface structures (HR-LIPSS) have been fabricated on surfaces of Mo, steel alloy and Ti at a record processing speed on large areas and with a record regularity in the obtained sub-wavelength structures. The physical mechanisms governing LIPSS regularity are identified and linked with the decay length (i.e. the mean free path) of the excited surface electromagnetic waves (SEWs). The dispersion of the LIPSS orientation angle well correlates with the SEWs decay length: the shorter this length, the more regular are the LIPSS. A material dependent criterion for obtaining HR-LIPSS is proposed for a large variety of metallic materials. It has been found that decreasing the spot size close to the SEW decay length is a key for covering several cm 2 of material surface by HR-LIPSS in a few seconds. Theoretical predictions suggest that reducing the laser wavelength can provide the possibility of HR-LIPSS production on principally any metal. This new achievement in the unprecedented level of control over the laser-induced periodic structure formation makes this laser-writing technology to be flexible, robust and, hence, highly competitive for advanced industrial applications based on surface nanostructuring.

Quantitative assessment of the enamel machinability in tooth preparation with dental diamond burs.

PubMed

Song, Xiao-Fei; Jin, Chen-Xin; Yin, Ling

2015-01-01

Enamel cutting using dental handpieces is a critical process in tooth preparation for dental restorations and treatment but the machinability of enamel is poorly understood. This paper reports on the first quantitative assessment of the enamel machinability using computer-assisted numerical control, high-speed data acquisition, and force sensing systems. The enamel machinability in terms of cutting forces, force ratio, cutting torque, cutting speed and specific cutting energy were characterized in relation to enamel surface orientation, specific material removal rate and diamond bur grit size. The results show that enamel surface orientation, specific material removal rate and diamond bur grit size critically affected the enamel cutting capability. Cutting buccal/lingual surfaces resulted in significantly higher tangential and normal forces, torques and specific energy (p<0.05) but lower cutting speeds than occlusal surfaces (p<0.05). Increasing material removal rate for high cutting efficiencies using coarse burs yielded remarkable rises in cutting forces and torque (p<0.05) but significant reductions in cutting speed and specific cutting energy (p<0.05). In particular, great variations in cutting forces, torques and specific energy were observed at the specific material removal rate of 3mm(3)/min/mm using coarse burs, indicating the cutting limit. This work provides fundamental data and the scientific understanding of the enamel machinability for clinical dental practice. Copyright © 2014 Elsevier Ltd. All rights reserved.

Performance and Near-Wake Flow field of A Marine Hydrokinetic Turbine Operating in Free surface Proximity

NASA Astrophysics Data System (ADS)

Banerjee, Arindam; Kolekar, Nitin

2015-11-01

The current experimental investigation aims at understanding the effect of free surface proximity and associated blockage on near-wake flow-field and performance of a three bladed horizontal axis marine hydrokinetic turbine. Experiments were conducted on a 0.14m radius, three bladed constant chord turbine in a 0.61m ×0.61m test section water channel. The turbine was subjected to various rotational speeds, flow speeds and depths of immersion. Experimental data was acquired through a submerged in-line thrust-torque sensor that was corrected to an unblocked dataset with a blockage correction using measured thrust data. A detailed comparison is presented between blocked and unblocked datasets to identify influence of Reynolds number and free surface proximity on blockage effects. The percent change in Cp was found to be dependent on flow velocity, rotational speed and free surface to blade tip clearance. Further, flow visualization using a stereoscopic particle image velocimetry was carried out in the near-wake region of turbine to understand the mechanism responsible for variation of Cp with rotational speed and free surface proximity. Results revealed presence of slower wake at higher rotational velocities and increased asymmetry in the wake at high free surface proximity.

Research on the impact of surface properties of particle on damping effect in gear transmission under high speed and heavy load

NASA Astrophysics Data System (ADS)

Xiao, Wangqiang; Chen, Zhiwei; Pan, Tianlong; Li, Jiani

2018-01-01

The vibration and noise from gear transmission have great damage on the mechanical equipment and operators. Through inelastic collisions and friction between particles, the energy can be dissipated in gear transmission. A dynamic model of particle dampers in gear transmission was put forward in this paper. The performance of particle dampers in centrifugal fields under different rotational speeds and load was investigated. The surface properties such as the impact of coefficient of restitution and friction coefficient of the particle on the damping effect were analyzed and the total energy loss was obtained by discrete element method (DEM). The vibration from time-varying mesh stiffness was effectively reduced by particle dampers and the optimum coefficient of restitution was discovered under different rotational speeds and load. Then, a test bench for gear transmission was constructed, and the vibration of driven gear and driving gear were measured through a three-directional wireless acceleration sensor. The research results agree well with the simulation results. While at relatively high speed, smaller coefficient of restitution achieves better damping effect. As to friction coefficient, at relatively high speed, the energy dissipation climbs up and then declines with the increase of the friction coefficient. The results can provide guidelines for the application of particle damper in gear transmission.

Fracture Forces of Dentin after Surface Treatment with High Speed Drill Compared to Er:YAG and Er,Cr:YSGG Laser Irradiation

PubMed Central

Franzen, Rene; Kianimanesh, Nasrin; Marx, Rudolf; Ahmed, Asma; Gutknecht, Norbert

2016-01-01

Dental tooth restorative procedures may weaken the structural integrity of the tooth, with the possibility of leading to fracture. In this study we present findings of coronal dentin strength after different techniques of surface modification. The fracture strength of dentin beams after superficial material removal with a fine diamond bur high speed drill hand piece, Er:YAG (2.94 μm, 8 J/cm2), and Er,Cr:YSGG (2.78 μm, 7.8 J/cm2) laser irradiation slightly above the ablation threshold was measured by a four-point bending apparatus. Untreated dentin beams served as a control. A total of 58 dentin beams were manufactured from sterilized human extracted molars using the coronal part of the available dentin. Mean values of fracture strength were calculated as 82.0 ± 27.3 MPa for the control group (n = 10), 104.5 ± 26.3 MPa for high speed drill treatment (n = 10), 96.1 ± 28.1 MPa for Er,Cr:YSGG laser irradiation (n = 20), and 89.1 ± 36.3 MPa for Er:YAG laser irradiation (n = 18). Independent Student's t-tests showed no significant difference between each two groups (p > 0.05). Within the parameter settings and the limits of the experimental setup used in this study, both lasers systems as well as the high speed drill do not significantly weaken coronal dentin after surface treatment. PMID:26962473

Full-field transient vibrometry of the human tympanic membrane by local phase correlation and high-speed holography

NASA Astrophysics Data System (ADS)

Dobrev, Ivo; Furlong, Cosme; Cheng, Jeffrey T.; Rosowski, John J.

2014-09-01

Understanding the human hearing process would be helped by quantification of the transient mechanical response of the human ear, including the human tympanic membrane (TM or eardrum). We propose a new hybrid high-speed holographic system (HHS) for acquisition and quantification of the full-field nanometer transient (i.e., >10 kHz) displacement of the human TM. We have optimized and implemented a 2+1 frame local correlation (LC) based phase sampling method in combination with a high-speed (i.e., >40 K fps) camera acquisition system. To our knowledge, there is currently no existing system that provides such capabilities for the study of the human TM. The LC sampling method has a displacement difference of <11 nm relative to measurements obtained by a four-phase step algorithm. Comparisons between our high-speed acquisition system and a laser Doppler vibrometer indicate differences of <10 μs. The high temporal (i.e., >40 kHz) and spatial (i.e., >100 k data points) resolution of our HHS enables parallel measurements of all points on the surface of the TM, which allows quantification of spatially dependent motion parameters, such as modal frequencies and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM.

Study on Stability of High Speed Traction Drive CVT for Aircraft Generator

NASA Astrophysics Data System (ADS)

Goi, Tatsuhiko; Tanaka, Hirohisa; Nakashima, Kenichi; Watanabe, Koji

A half-toroidal traction drive CVT has a feature of small spin at traction pitch in whole speed ratio range of 1:4, which suits to transmit high rotational speed with minimum temperature increase of traction surface. Research activity on traction drive CVT has commenced in 1996 for applying it to an aircraft 24,000rpm constant-speed generator instead of a hydro-static transmission. This paper shows fundamental design of 90kW traction drive integrated drive generator, ``T-IDG", and stability analysis on a sensor-less electro-hydraulic speed control servo-mechanism by bond graphs. The performance test of T-IDG mounted on a test bench and an actual jet engine proved that the control system using sensor-less servomechanism can keep the generator speed within MIL-STD-704E allowable limit against steep changes of speed and load.

Wind tunnel results for a high-speed, natural laminar-flow airfoil designed for general aviation aircraft

NASA Technical Reports Server (NTRS)

Sewall, William G.; Mcghee, Robert J.; Viken, Jeffery K.; Waggoner, Edgar G.; Walker, Betty S.; Millard, Betty F.

1985-01-01

Two dimensional wind tunnel tests were conducted on a high speed natural laminar flow airfoil in both the Langley 6 x 28 inch Transonic Tunnel and the Langley Low Turbulence Pressure Tunnel. The test conditions consisted of Mach numbers ranging from 0.10 to 0.77 and Reynolds numbers ranging from 3 x 1 million to 11 x 1 million. The airfoil was designed for a lift coefficient of 0.20 at a Mach number of 0.70 and Reynolds number of 11 x 1 million. At these conditions, laminar flow would extend back to 50 percent chord of the upper surface and 70 percent chord of the lower surface. Low speed results were also obtained with a 0.20 chord trailing edge split flap deflected 60 deg.

Assessing simulated summer 10-m wind speed over China: influencing processes and sensitivities to land surface schemes

NASA Astrophysics Data System (ADS)

Zeng, Xin-Min; Wang, Ming; Wang, Ning; Yi, Xiang; Chen, Chaohui; Zhou, Zugang; Wang, Guiling; Zheng, Yiqun

2018-06-01

We assessed the sensitivity of 10-m wind speed to land surface schemes (LSSs) and the processes affecting wind speed in China during the summer of 2003 using the ARWv3 mesoscale model. The derived hydrodynamic equation, which directly reflects the effects of the processes that drive changes in the full wind speed, shows that the convection term CON (the advection effect) plays the smallest role; thus, the summer 10-m wind speed is largely dominated by the pressure gradient (PRE) and the diffusion (DFN) terms, and the equation shows that both terms are highly sensitive to the choice of LSS within the studied subareas (i.e., Northwest China, East China, and the Tibetan Plateau). For example, Northwest China had the largest DFN, with a PRE four times that of CON and the highest sensitivity of PRE to the choice of LSS, as indicated by a difference index value of 63%. Moreover, we suggest that two types of mechanisms, direct and indirect effects, affect the 10-m wind speed. Through their simulated surface fluxes (mainly the sensible heat flux), the different LSSs directly provide different amounts of heat to the surface air at local scales, which influences atmospheric stratification and the characteristics of downward momentum transport. Meanwhile, through the indirect effect, the LSS-induced changes in surface fluxes can significantly modify the distributions of the temperature and pressure fields in the lower atmosphere over larger scales. These changes alter the thermal and geostrophic winds, respectively, as well as the 10-m wind speed. Due to the differences in land properties and climates, the indirect effect (e.g., PRE) can be greater than the direct effect (e.g., DFN).

A rotational ablation tool for calcified atherosclerotic plaque removal.

PubMed

Kim, Min-Hyeng; Kim, Hyung-Jung; Kim, Nicholas N; Yoon, Hae-Sung; Ahn, Sung-Hoon

2011-12-01

Atherosclerosis is a major cardiovascular disease involving accumulations of lipids, white blood cells, and other materials on the inside of artery walls. Since the calcification found in the advanced stage of atherosclerosis dramatically enhances the mechanical properties of the plaque, restoring the original lumen of the artery remains a challenge. High-speed rotational atherectomy, when performed with an ablating grinder to remove the plaque, produces much better results in the treatment of calcified plaque compared to other methods. However, the high-speed rotation of the Rotablator commercial rotational atherectomy device produces microcavitation, which should be avoided because of the serious complications it can cause. This research involves the development of a high-speed rotational ablation tool that does not generate microcavitation. It relies on surface modification to achieve the required surface roughness. The surface roughness of the tool for differential cutting was designed based on lubrication theory, and the surface of the tool was modified using Nd:YAG laser beam engraving. Electron microscope images and profiles indicated that the engraved surface of the tool had approximately 1 μm of root mean square surface roughness. The ablation experiment was performed on hydroxyapatite/polylactide composite with an elastic modulus similar to that of calcified plaque. In addition, differential cutting was verified on silicone rubber with an elastic modulus similar to that of a normal artery. The tool performance and reliability were evaluated by measuring the ablation force exerted, the size of the debris generated during ablation, and through visual inspection of the silicone rubber surface.

Measuring wintertime surface fluxes at the Tiksi observatory in northern Sakha (Yakutia)

NASA Astrophysics Data System (ADS)

Laurila, Thomas; Aurela, Mika; Hatakka, Juha; Tuovinen, Juha-Pekka; Asmi, Eija; Kondratyev, Vladimir; Ivakhov, Victor; Reshetnikov, Alexander; Makshtas, Alexander; Uttal, Taneil

2013-04-01

Tiksi hydrometeorological observatory has been equipped by new instrumentation for meteorology, turbulence, trace gas and aerosols studies as a joint effort by National Oceanic and Atmospheric Administration (NOAA), Roshydromet (Yakutian Hydrometeorological Service, Arctic and Antarctic Research Institute and Voeikov Main Geophysical Observatory units) and the Finnish Meteorological Institute (FMI). The site is close to the coast of the Laptev Sea on deep permafrost soil with low tundra vegetation and patches of arctic semidesert. Near-by terrain is gently sloping to the south. Further away they are hills in the NE- and W-directions. Turbulence (3-d wind components and sonic temperature) was measured at 10 Hz by USA-1Scientific sonic by Metek, Gmbh. Concentrations of CO2 and H2O were measured by LiCor LI7000 analyzer and CH4 concentrations by Los Gatos RMT200 analyzer. Measurement height was 2.5m. Active layer freeze up took place in extended October period. Methane and carbon dioxide emissions were observed up to early December. Emissions to the atmosphere were enhanced by turbulence created by high wind speeds. Midwinter conditions existed from the end of October to the beginning of April based on rather constant negative net radiation between 20-30 Wm-2 that cools the surface and forms highly stable stratification. Weather conditions are characterized by either low or high wind speed modes. Roughly half of the time wind speed was low, below 2 ms-1. Then, katabatic winds were common and air temperature was between -40..-30°C. High wind speeds, up to 24 ms-1, were observed during synoptic disturbances which lasted typically a few days. In this presentation we will show climatology of surface layer characteristics in late autumn and winter. We will show frequency of well-developed turbulence vs. katabatic low wind speed conditions and related atmospheric stability. The effect of wind speed on methane and carbon dioxide emissions during the freezing period will be shown.

Wind tunnel investigations of forebody strakes for yaw control on F/A-18 model at subsonic and transonic speeds

NASA Technical Reports Server (NTRS)

Erickson, Gary E.; Murri, Daniel G.

1993-01-01

Wind tunnel investigations have been conducted of forebody strakes for yaw control on 0.06-scale models of the F/A-18 aircraft at free-stream Mach numbers of 0.20 to 0.90. The testing was conducted in the 7- by 10-Foot Transonic Tunnel at the David Taylor Research Center and the Langley 7- by 10-Foot High-Speed Tunnel. The principal objectives of the testing were to determine the effects of the Mach number and the strake plan form on the strake yaw control effectiveness and the corresponding strake vortex induced flow field. The wind tunnel model configurations simulated an actuated conformal strake deployed for maximum yaw control at high angles of attack. The test data included six-component forces and moments on the complete model, surface static pressure distributions on the forebody and wing leading-edge extensions, and on-surface and off-surface flow visualizations. The results from these studies show that the strake produces large yaw control increments at high angles of attack that exceed the effect of conventional rudders at low angles of attack. The strake yaw control increments diminish with increasing Mach number but continue to exceed the effect of rudder deflection at angles of attack greater than 30 degrees. The character of the strake vortex induced flow field is similar at subsonic and transonic speeds. Cropping the strake planform to account for geometric and structural constraints on the F-18 aircraft has a small effect on the yaw control increments at subsonic speeds and no effect at transonic speeds.

Touch and Go Surface Sampler (TGSS)

NASA Technical Reports Server (NTRS)

Gorevan, S. P.; Rafeek, S.

2001-01-01

The Touch and Go Surface Sampler (TGSS) is a new class of planetary and small body sample acquisition tool that can be used for the surface exploration of Europa, Titan and comets. TGSS in its basic configuration consists of a high speed sampling head attached to the end of a flexible shaft. The sampling head consists of counter rotating cutters that rotates at speeds of 3000 to 15000 RPM. The attractive feature of this if touch and go type sampler is that there are no requirements for a lander type spacecraft. Additional information is contained in the original extended abstract.

High Speed Aerodynamic Characteristics of the GAF0PH Aerofoil

DTIC Science & Technology

1980-09-01

upper surface of the aerofoil for angles of incidence greater than 210. POSTAL ADDRESS: Chief Superintendent, Aeronautical Research Laboratories, Box...kCLAERO-.NOTE3 98 -AR-002-223 -LEVEL m DEPARTMENT OF DEFENCE 00 DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION AERONAUTICAL RESEARCH LABORATORIES...MELBOURNE, VICTORIA AERODYNAMICS NOTE 398 ’,\\ HIGH SPEED AERODYNAMIC CHARACTERISTICS OF THE GAFPH AEROFOIL by ~B D :, . , .IR-© Approved for Public Release

Manual and automatic control of surface effect ships. [operator steering servomechanisms analysis

NASA Technical Reports Server (NTRS)

Clement, W. F.; Shanahan, J. J.; Allen, R. W.

1975-01-01

A recent investigation of crew performance in the motion environment of a large generic high speed surface effect ship by means of a motion base simulation addressed some of the helmsman's control task with an external forward visual field of the seascape and navigation and steering displays in the pilot house. In addition to the primary steering control task, a subcritical speed tracking task provided a secondary surrogate for trimming the water speed of the craft. The results of helsmen's steering describing function measurements are presented, and some suggestions for their interpretation are offered. The likely steering loop closures comprise heading and lateral displacement for the course keeping task investigated. Also discussed is the manner in which these loop closures were implemented for automatic steering of the surface effect ship. Regardless of the influence of workload, steering technique, water speed and sea state, the helmsmen apparently adopted a disturbance regulation bandwidth of about 0.2 rad/sec for lateral displacement.

High-speed holographic system for full-field transient vibrometry of the human tympanic membrane

NASA Astrophysics Data System (ADS)

Dobrev, I.; Harrington, E. J.; Cheng, T.; Furlong, C.; Rosowski, J. J.

2014-07-01

Understanding of the human hearing process requires the quantification of the transient response of the human ear and the human tympanic membrane (TM or eardrum) in particular. Current state-of-the-art medical methods to quantify the transient acousto-mechanical response of the TM provide only averaged acoustic or local information at a few points. This may be insufficient to fully describe the complex patterns unfolding across the full surface of the TM. Existing engineering systems for full-field nanometer measurements of transient events, typically based on holographic methods, constrain the maximum sampling speed and/or require complex experimental setups. We have developed and implemented of a new high-speed (i.e., > 40 Kfps) holographic system (HHS) with a hybrid spatio-temporal local correlation phase sampling method that allows quantification of the full-field nanometer transient (i.e., > 10 kHz) displacement of the human TM. The HHS temporal accuracy and resolution is validated versus a LDV on both artificial membranes and human TMs. The high temporal (i.e., < 24 μs) and spatial (i.e., >100k data points) resolution of our HHS enables simultaneous measurement of the time waveform of the full surface of the TM. These capabilities allow for quantification of spatially-dependent motion parameters such as energy propagation delays surface wave speeds, which can be used to infer local material properties across the surface of the TM. The HHS could provide a new tool for the investigation of the auditory system with applications in medical research, in-vivo clinical diagnosis as well as hearing aids design.

Modeling wind adjustment factor and midflame wind speed for Rothermel's surface fire spread model

Treesearch

Patricia L. Andrews

2012-01-01

Rothermel's surface fire spread model was developed to use a value for the wind speed that affects surface fire, called midflame wind speed. Models have been developed to adjust 20-ft wind speed to midflame wind speed for sheltered and unsheltered surface fuel. In this report, Wind Adjustment Factor (WAF) model equations are given, and the BehavePlus fire modeling...

21st Century HVAC System for Future Naval Surface Combatants - Concept Development Report

DTIC Science & Technology

2007-09-01

application of permanent magnet motors to ventilation fans3. The study emphasized reducing the motor size, incorporating variable speed operation to reduce...Incorporation of permanent magnet motors and variable speed is also feasible. Permanent magnet motor technology is ideally suited for variable...family incorporates high speed permanent magnet motors and further fan blade design improvements. The fan diameters will be reduced, substantially, at the

High wind speeds prevent formation of a distinct bacterioneuston community in the sea-surface microlayer

PubMed Central

Stolle, Christian; Giebel, Helge-Ansgar; Brinkhoff, Thorsten; Ribas-Ribas, Mariana; Hodapp, Dorothee; Wurl, Oliver

2017-01-01

Abstract The sea-surface microlayer (SML) at the boundary between atmosphere and hydrosphere represents a demanding habitat for bacteria. Wind speed is a crucial but poorly studied factor for its physical integrity. Increasing atmospheric burden of CO2, as suggested for future climate scenarios, may particularly act on this habitat at the air–sea interface. We investigated the effect of increasing wind speeds and different pCO2 levels on SML microbial communities in a wind-wave tunnel, which offered the advantage of low spatial and temporal variability. We found that enrichment of bacteria in the SML occurred solely at a U10 wind speed of ≤5.6 m s−1 in the tunnel and ≤4.1 m s−1 in the Baltic Sea. High pCO2 levels further intensified the bacterial enrichment in the SML during low wind speed. In addition, low wind speed and pCO2 induced the formation of a distinctive bacterial community as revealed by 16S rRNA gene fingerprints and influenced the presence or absence of individual taxonomic units within the SML. We conclude that physical stability of the SML below a system-specific wind speed threshold induces specific bacterial communities in the SML entailing strong implications for ecosystem functioning by wind-driven impacts on habitat properties, gas exchange and matter cycling processes. PMID:28369320

High wind speeds prevent formation of a distinct bacterioneuston community in the sea-surface microlayer.

PubMed

Rahlff, Janina; Stolle, Christian; Giebel, Helge-Ansgar; Brinkhoff, Thorsten; Ribas-Ribas, Mariana; Hodapp, Dorothee; Wurl, Oliver

2017-05-01

The sea-surface microlayer (SML) at the boundary between atmosphere and hydrosphere represents a demanding habitat for bacteria. Wind speed is a crucial but poorly studied factor for its physical integrity. Increasing atmospheric burden of CO2, as suggested for future climate scenarios, may particularly act on this habitat at the air-sea interface. We investigated the effect of increasing wind speeds and different pCO2 levels on SML microbial communities in a wind-wave tunnel, which offered the advantage of low spatial and temporal variability. We found that enrichment of bacteria in the SML occurred solely at a U10 wind speed of ≤5.6 m s-1 in the tunnel and ≤4.1 m s-1 in the Baltic Sea. High pCO2 levels further intensified the bacterial enrichment in the SML during low wind speed. In addition, low wind speed and pCO2 induced the formation of a distinctive bacterial community as revealed by 16S rRNA gene fingerprints and influenced the presence or absence of individual taxonomic units within the SML. We conclude that physical stability of the SML below a system-specific wind speed threshold induces specific bacterial communities in the SML entailing strong implications for ecosystem functioning by wind-driven impacts on habitat properties, gas exchange and matter cycling processes. © FEMS 2017.

Diffusion of Drag-Reducing Polymers within a High-Reynolds-Number, Rough-Wall Turbulent Boundary Layer

NASA Astrophysics Data System (ADS)

Elbing, Brian; Perlin, Marc; Dowling, David; Solomon, Michael; Ceccio, Steven

2008-11-01

Two experiments were conducted to investigate polymer drag reduction (PDR) within high Reynolds number (to 200 million based on downstream distance), rough-wall turbulent boundary layers. The first experiment was conducted at the U.S. Navy's Large Cavitation Channel on a 12.9 m long flat-plate at speeds to 20 m/s with the surface hydraulically smooth and fully rough. Local skin-friction measurements on the smooth and rough surfaces had maximum PDR levels of 65 and 75 percent, respectively. However, PDR decreased with increasing downstream distance and flow speed more rapidly on the rough surface, and at the top speed no measureable level of PDR was observed. The roughness-induced increased diffusion was quantified with near-wall concentration measurements and the second experiment, which measured concentration profiles on a 0.94 m long flat-plate with three surface conditions: smooth, 240-grit, and 60-grit sandpaper. The increased diffusion does not fully explain the smooth-rough PDR differences observed in the first experiment. Rheological analysis of drawn samples from the first experiment indicates that polymer degradation (chain scission) could be responsible for the remaining loss of rough-wall PDR. These results have implications for the cost effectiveness of PDR for surface ships.

A self-assembled microbonded germanium/silicon heterojunction photodiode for 25 Gb/s high-speed optical interconnects

PubMed Central

Tseng, Chih-Kuo; Chen, Wei-Ting; Chen, Ku-Hung; Liu, Han-Din; Kang, Yimin; Na, Neil; Lee, Ming-Chang M.

2013-01-01

A novel technique using surface tension to locally bond germanium (Ge) on silicon (Si) is presented for fabricating high performance Ge/Si photodiodes. Surface tension is a cohesive force among liquid molecules that tends to bring contiguous objects in contact to maintain a minimum surface energy. We take advantage of this phenomenon to fabricate a heterojunction optoelectronic device where the lattice constants of joined semiconductors are different. A high-speed Ge/Si heterojunction waveguide photodiode is presented by microbonding a beam-shaped Ge, first grown by rapid-melt-growth (RMG) method, on top of a Si waveguide via surface tension. Excellent device performances such as an operating bandwidth of 17 GHz and a responsivity of 0.66 and 0.70 A/W at the reverse bias of −4 and −6 V, respectively, are demonstrated. This technique can be simply implemented via modern complementary metal-oxide-semiconductor (CMOS) fabrication technologies for integrating Ge on Si devices. PMID:24232956

High speed, self-acting, face-contact shaft seal has low leakage and very low wear

NASA Technical Reports Server (NTRS)

Zuk, J.; Ludwig, L. P.; Johnson, R. L.

1972-01-01

Design adds gas thrust bearing to face of conventional face seal. Bearing lifts seal's carbon face out of contact after startup and establishes thin gas film between sealing surfaces. Operating pressure and speed capabilities are greater than those of conventional face seals.

Filamentary superhydrophobic Teflon surfaces: Moderate apparent contact angle but superior air-retaining properties.

PubMed

Di Mundo, Rosa; Bottiglione, Francesco; Palumbo, Fabio; Notarnicola, Michele; Carbone, Giuseppe

2016-11-15

Micro-scale textured Teflon surfaces, resulting from plasma etching modification, show extremely high water contact angle values and fairly good resistance to water penetration when hit by water drops at medium-high speed. This behavior is more pronounced when these surfaces present denser and smaller micrometric reliefs. Tailoring the top of these reliefs with a structure which further stabilizes the air may further increase resistance to wetting (water penetration) under static and dynamic conditions. Conditions of the oxygen fed plasma were tuned in order to explore the possibility of obtaining differently topped structures on the surface of the polymer. Scanning Electron Microscopy (SEM) was used to explore topography and X-ray Photoelectron Spectroscopy (XPS) to assess chemical similarity of the modified surfaces. Beside the usual advancing and receding water contact angle (WCA) measurements, surfaces were subjected to high speed impacting drops and immersion in water. At milder, i.e. shorter time and lower input power, plasma conditions formation of peculiar filaments is observed on the top of the sculpted reliefs. Filamentary topped surfaces result in a lower WCA than the spherical ones, appearing in this sense less superhydrophobic. However, these surfaces give rise to the formation of a more pronounced air layer when placed underwater. Further, when hit by water drops falling at medium/high speed, they show a higher resistance to water penetration and a sensitively lower surface-liquid contact time. The contact time is as low as previously observed only on heated solids. This behavior may be ascribed to the cavities formed beneath the filaments which, similarly with the salvinia leaf structures, require a surplus of pressure to be filled by water. Also, it suggests a different concept of superhydrophobicity, which cannot be expected on the basis of the conventional water contact angle characterization. Copyright © 2016 Elsevier Inc. All rights reserved.

High-speed and on-chip graphene blackbody emitters for optical communications by remote heat transfer.

PubMed

Miyoshi, Yusuke; Fukazawa, Yusuke; Amasaka, Yuya; Reckmann, Robin; Yokoi, Tomoya; Ishida, Kazuki; Kawahara, Kenji; Ago, Hiroki; Maki, Hideyuki

2018-03-29

High-speed light emitters integrated on silicon chips can enable novel architectures for silicon-based optoelectronics, such as on-chip optical interconnects, and silicon photonics. However, conventional light sources based on compound semiconductors face major challenges for their integration with a silicon-based platform because of their difficulty of direct growth on a silicon substrate. Here we report ultra-high-speed (100-ps response time), highly integrated graphene-based on-silicon-chip blackbody emitters in the near-infrared region including telecommunication wavelength. Their emission responses are strongly affected by the graphene contact with the substrate depending on the number of graphene layers. The ultra-high-speed emission can be understood by remote quantum thermal transport via surface polar phonons of the substrates. We demonstrated real-time optical communications, integrated two-dimensional array emitters, capped emitters operable in air, and the direct coupling of optical fibers to the emitters. These emitters can open new routes to on-Si-chip, small footprint, and high-speed emitters for highly integrated optoelectronics and silicon photonics.

Morphological differences in coronary arteries following rotational atherectomy versus balloon angioplasty: ultrasound and angioscopic observations

NASA Astrophysics Data System (ADS)

Bass, Theodore A.; Gilmore, Paul S.; White, Christopher J.; Chami, Youssef G.; Kircher, Barbara J.; Conetta, Donald A.

1993-09-01

Percutaneous transluminal coronary rotational atherectomy (PTCRA) is an exciting new device to recannulate obstructed coronary arteries. This device works as a high speed `drill,' selectively cutting hard atherosclerotic plaque while preferentially sparing the softer, less diseased vascular luminal surface. At speeds as high as 200,000 rpm the plaque is pulverized into small particles easily handled by the circulatory system with no untoward clinical sequela. Balloon angioplasty does not remove atherosclerotic plaque. It dilates the vessel by mechanically stretching, compressing and splitting the plaque and vessel lining. We compare morphological and surface luminal characteristics of vessels post PTCRA to vessels post PTCA.

High-speed detection of DNA translocation in nanopipettes.

PubMed

Fraccari, Raquel L; Ciccarella, Pietro; Bahrami, Azadeh; Carminati, Marco; Ferrari, Giorgio; Albrecht, Tim

2016-04-14

We present a high-speed electrical detection scheme based on a custom-designed CMOS amplifier which allows the analysis of DNA translocation in glass nanopipettes on a microsecond timescale. Translocation of different DNA lengths in KCl electrolyte provides a scaling factor of the DNA translocation time equal to p = 1.22, which is different from values observed previously with nanopipettes in LiCl electrolyte or with nanopores. Based on a theoretical model involving electrophoresis, hydrodynamics and surface friction, we show that the experimentally observed range of p-values may be the result of, or at least be affected by DNA adsorption and friction between the DNA and the substrate surface.

Wear evaluation of flank in burins of high speed steel modified with titanium ions

NASA Astrophysics Data System (ADS)

E Caballero, J.; V-Niño, E. D.

2017-12-01

This report shows the results obtained researching the flank wearing resistance performed by the high-speed steel (HSS) burins without any surface treatment (reference substrate) and others with surface treatment based on Titanium ions. The flank wearing was carried out by means of an industrial process by chip removal with repetitive tests of dry finished turning of AISI/SAE 1045 steel bars. The useful service life of the burins was evaluated according to ISO 3685:1993, and it was found that the burins treated with Titanium ions showed an increase in the flank wearing resistance with respect to the ones used as reference.

Research methods of plasma stream interaction with heat-resistant materials

NASA Astrophysics Data System (ADS)

Tyuftyaev, A. S.; Gadzhiev, M. Kh; Sargsyan, M. A.; Chinnov, V. F.; Demirov, N. A.; Kavyrshin, D. I.; Ageev, A. G.; Khromov, M. A.

2016-11-01

An experimental automated system was designed and constructed for studying the parameters and characteristics of non-stationary interacting system high-enthalpy-plasma stream-investigated sample: enthalpy of plasma in the incident stream; speed and temperature of plasma stream; temperature of electrons and heavy particles, ionic composition and their spatial distribution; heat flux incident on the sample (kW/cm2); surface temperature of the sample; ablation of the sample material, and others. Measurements of achievable plasma heat flux levels are carried out by calorimetry of plasma streams incident on the surface of multisection copper calorimeter. Determination of acceleration characteristics for profiled plasma torch nozzle, as well as the gas flow rate is produced by measuring the total pressure using the Pitot tube. Video visualization of interacting system is carried out using synchronized high-speed cameras. Micropyrometry of the selected zone on the sample surface is carried out by high-speed, three-wavelength pyrometer. To measure the rate of mass loss of the sample, in addition to the weighing method of evaluation the methods of laser knife and two-position stereoscopy are used. Plasma and sample emission characteristics are performed with two separate spectrometers.

The effects of interplanetary dust impacts on the accumulation of volatiles in the lunar permanently shadowed regions

NASA Astrophysics Data System (ADS)

Horanyi, Mihaly; Szalay, Jamey

2017-10-01

The lunar regolith has been formed, and remains continually reworked, by the intermitten impacts of comets, asteroids, meteoroids, and the continual bombardment by interplanetary dust particles (IDP). Thick atmospheres protect Venus, Earth, and Mars, ablating the incoming IDPs into “shooting stars” that rarely reach the surface. However, the surfaces of airless bodies near 1 AU are directly exposed to the high-speed (>> 1 km/s) IDP impacts. The Moon is expected to be bombarded by 5x103 kg/day of IDPs arriving with a characteristic speed of ~ 20 km/s. The IDP sources impacting the Moon at high latitudes remain largely uncharacterized due to the lack of optical and radar observations in the polar regions on Earth. These high latitude sources have very large impact speeds in the range of 30 < v < 50 km/ hence they are expected to have a significant effect on the lunar surface, including the removal and burial of volatile deposits in the lunar polar regions.Water is thought to be continually delivered to the Moon through geological timescales by water-bearing comets and asteroids, and produced continuously in situ by the impacts of solar wind protons of oxygen rich minerals exposed on the surface. IDPs are an unlikely source of water due to their long UV exposure in the inner solar system, but their high-speed impacts can mobilize secondary ejecta dust particles, atoms and molecules, some with high-enough speed to escape the Moon. Other surface processes that can lead to mobilization, transport and loss of water molecules and other volatiles include solar heating, photochemical processes, and solar wind sputtering. Since none of these are at work in permanently shadowed regions (PSR), dust impacts remain the dominant process to dictate the evolution of volatiles in PSRs. The competing effects of dust impacts are: a) ejecta production leading to loss out of a PSR; b) gardening and overturning the regolith; and c) the possible accumulation of impact ejecta, leading to the burial of the volatiles. This talk will summarize the expected effects of dust impacts on volatile accumulation in the lunar PSRs based on theoretical models, recent laboratory results, and observations by the LADEE spacecraft.

High-Speed Lateral Flow Strategy for a Fast Biosensing with an Improved Selectivity and Binding Affinity.

PubMed

Cho, Dong Guk; Yoo, Haneul; Lee, Haein; Choi, Yeol Kyo; Lee, Minju; Ahn, Dong June; Hong, Seunghun

2018-05-10

We report a high-speed lateral flow strategy for a fast biosensing with an improved selectivity and binding affinity even under harsh conditions. In this strategy, biosensors were fixed at a location away from the center of a round shape disk, and the disk was rotated to create the lateral flow of a target solution on the biosensors during the sensing measurements. Experimental results using the strategy showed high reaction speeds, high binding affinity, and low nonspecific adsorptions of target molecules to biosensors. Furthermore, binding affinity between target molecules and sensing molecules was enhanced even in harsh conditions such as low pH and low ionic strength conditions. These results show that the strategy can improve the performance of conventional biosensors by generating high-speed lateral flows on a biosensor surface. Therefore, our strategy can be utilized as a simple but powerful tool for versatile bio and medical applications.

Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

NASA Astrophysics Data System (ADS)

Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

2013-05-01

Shipboard measurements of eddy covariance DMS air/sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air/sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near surface water side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air/sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

NASA Astrophysics Data System (ADS)

Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

2013-11-01

Shipboard measurements of eddy covariance dimethylsulfide (DMS) air-sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air-sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near-surface water-side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air-sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

Linking molecular level chemistry to macroscopic combustion behavior for nano-energetic materials with halogen containing oxides.

PubMed

Farley, Cory W; Pantoya, Michelle L; Losada, Martin; Chaudhuri, Santanu

2013-08-21

Coupling molecular scale reaction kinetics with macroscopic combustion behavior is critical to understanding the influences of intermediate chemistry on energy propagation, yet bridging this multi-scale gap is challenging. This study integrates ab initio quantum chemical calculations and condensed phase density functional theory to elucidate factors contributing to experimentally measured high flame speeds (i.e., >900 m∕s) associated with halogen based energetic composites, such as aluminum (Al) and iodine pentoxide (I2O5). Experiments show a direct correlation between apparent activation energy and flame speed suggesting that flame speed is directly influenced by chemical kinetics. Toward this end, the first principle simulations resolve key exothermic surface and intermediate chemistries contributing toward the kinetics that promote high flame speeds. Linking molecular level exothermicity to macroscopic experimental investigations provides insight into the unique role of the alumina oxide shell passivating aluminum particles. In the case of Al reacting with I2O5, the alumina shell promotes exothermic surface chemistries that reduce activation energy and increase flame speed. This finding is in contrast to Al reaction with metal oxides that show the alumina shell does not participate exothermically in the reaction.

Development of a laser-based sensor to measure true road surface deflection.

DOT National Transportation Integrated Search

2017-04-01

The high-speed measurement of accurate pavement surface deflections under a moving wheel at a networklevel : still remains a challenge in pavement engineering. This goal cannot be accomplished with stationary deflectionmeasuring : devices. Engineers ...

High speed, self-acting shaft seal. [for use in turbine engines

NASA Technical Reports Server (NTRS)

Ludwig, L. P.; Hady, W. F. (Inventor)

1975-01-01

A high-speed, self-acting circumferential type shaft seal for use in turbine engines is disclosed. One or more conventional circumferential ring seals having a central aperture are mounted in a housing. In three of the four embodiments of the invention, a helical groove and one or more dam seals are cut in the inner cylindrical surface of the one or more ring seals. In a fourth embodiment, two or more lift pads are disposed in surface contact with the inner cylindrical surface of the seal rings. To the outside of the lift pads, two dam seals are cut in the inner cylindrical surface of two of the ring seals. In each of the embodiments, a net outward radial force was produced during rotation of the turbine causing the ring seals to lift out of contact with the turbine shaft to minimize wear of the ring seals.

Scalable Emergency Response System for Oceangoing Assets. Final Summary Report

DTIC Science & Technology

2009-01-20

Developed for platform defense of submarines and surface ships at sea and in port, the iRobot High Speed UUV enables rapid transit with respect to a ... high level decontamination, resulting in a return to port Decision Making Option C is to sealift via decontamination vessel contingent, and perform a ...the world aboard a prepared LCAC.48 A high - speed , over- 47 One Marine’s View. Retrieved from http://www.onemarinesview.com/one_marines_view/2006/09

HIGH SPEED CAMERA

DOEpatents

Rogers, B.T. Jr.; Davis, W.C.

1957-12-17

This patent relates to high speed cameras having resolution times of less than one-tenth microseconds suitable for filming distinct sequences of a very fast event such as an explosion. This camera consists of a rotating mirror with reflecting surfaces on both sides, a narrow mirror acting as a slit in a focal plane shutter, various other mirror and lens systems as well as an innage recording surface. The combination of the rotating mirrors and the slit mirror causes discrete, narrow, separate pictures to fall upon the film plane, thereby forming a moving image increment of the photographed event. Placing a reflecting surface on each side of the rotating mirror cancels the image velocity that one side of the rotating mirror would impart, so as a camera having this short a resolution time is thereby possible.

SU-D-213AB-06: Surface Texture and Insertion Speed Effect on Needle Friction.

PubMed

Abdullah, A; Golecki, C; Barnett, A; Moore, J

2012-06-01

High frictional forces between the needle surface and tissue cause tissue deflection which hinders accurate needle placement for procedures such as brachytherapy and needle biopsy. Accurate needle placement isimportant to maximize procedure efficacy. This work investigates how needle surface roughness and insertion speed affect the frictional forcebetween a needle and tissue. A friction experiment was conducted to measure the force of friction between bovine liver and three 11 gauge needles having Ra surface roughness of 3.43, 1.33, and 0.2 μm. Each of the three needles were mounted on a linear slide and were advanced and retracted through bovine liver at speeds of 50, 100, 150, and 200 mm/s for a total of 12 trials. In each trial the needle was advanced and retracted in 10 cycles producing a steady state insertion force and a steady state retraction force for each cycle. A force sensor connecting the needle to the linear slide recorded the resistance force of the needle sliding through the liver. The liver was mounted in a box with a pneumatic cylinder which compressed the liver sample by 11.65 kPa. The roughest needle (Ra = 3.43 μm) on average produced 68, 73, 74, and 73% lower friction force than the smoothest needle (Ra = 0.2 μm) for the speeds of 50, 100, 150, and 200mm/s, respectively. The second roughest needle (Ra = 1.33 μm) on average produced 25, 45, 60 and 64% lower friction force than the smoothest needle (Ra = 0.2 μm) for the speeds of 50, 100, 150, and 200 mm/s, respectively. Rougher needle surface texture and higher insertion speed reduced frictional forces between the tissue and the needle. Future studies will examine how frictional forces can be modeled and predicted given surface texture and insertion speed. © 2012 American Association of Physicists in Medicine.

High-Speed Transport of Fluid Drops and Solid Particles via Surface Acoustic Waves

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph; Bao, Xiaoqi; Sherrit, Stewart; Badescu, Mircea; Lih, Shyh-shiuh

2012-01-01

A compact sampling tool mechanism that can operate at various temperatures, and transport and sieve particle sizes of powdered cuttings and soil grains with no moving parts, has been created using traveling surface acoustic waves (SAWs) that are emitted by an inter-digital transducer (IDT). The generated waves are driven at about 10 MHz, and it causes powder to move towards the IDT at high speed with different speeds for different sizes of particles, which enables these particles to be sieved. This design is based on the use of SAWs and their propelling effect on powder particles and fluids along the path of the waves. Generally, SAWs are elastic waves propagating in a shallow layer of about one wavelength beneath the surface of a solid substrate. To generate SAWs, a piezoelectric plate is used that is made of LiNbO3 crystal cut along the x-axis with rotation of 127.8 along the y-axis. On this plate are printed pairs of fingerlike electrodes in the form of a grating that are activated by subjecting the gap between the electrodes to electric field. This configuration of a surface wave transmitter is called IDT. The IDT that was used consists of 20 pairs of fingers with 0.4-mm spacing, a total length of 12.5 mm. The surface wave is produced by the nature of piezoelectric material to contract or expand when subjected to an electric field. Driving the IDT to generate wave at high amplitudes provides an actuation mechanism where the surface particles move elliptically, pulling powder particles on the surface toward the wavesource and pushing liquids in the opposite direction. This behavior allows the innovation to separate large particles and fluids that are mixed. Fluids are removed at speed (7.5 to 15 cm/s), enabling this innovation of acting as a bladeless wiper for raindrops. For the windshield design, the electrodes could be made transparent so that they do not disturb the driver or pilot. Multiple IDTs can be synchronized to transport water or powder over larger distances. To demonstrate the transporting action, a video camera was used to record the movement. The speed of particles was measured from the video images.

CYGNSS Surface Wind Observations and Surface Flux Estimates within Low-Latitude Extratropical Cyclones

NASA Astrophysics Data System (ADS)

Crespo, J.; Posselt, D. J.

2017-12-01

The Cyclone Global Navigation Satellite System (CYGNSS), launched in December 2016, aims to improve estimates of surface wind speeds over the tropical oceans. While CYGNSS's core mission is to provide better estimates of surface winds within the core of tropical cyclones, previous research has shown that the constellation, with its orbital inclination of 35°, also has the ability to observe numerous extratropical cyclones that form in the lower latitudes. Along with its high spatial and temporal resolution, CYGNSS can provide new insights into how extratropical cyclones develop and evolve, especially in the presence of thick clouds and precipitation. We will demonstrate this by presenting case studies of multiple extratropical cyclones observed by CYGNSS early on in its mission in both Northern and Southern Hemispheres. By using the improved estimates of surface wind speeds from CYGNSS, we can obtain better estimates of surface latent and sensible heat fluxes within and around extratropical cyclones. Surface heat fluxes, driven by surface winds and strong vertical gradients of water vapor and temperature, play a key role in marine cyclogenesis as they increase instability within the boundary layer and may contribute to extreme marine cyclogenesis. In the past, it has been difficult to estimate surface heat fluxes from space borne instruments, as these fluxes cannot be observed directly from space, and deficiencies in spatial coverage and attenuation from clouds and precipitation lead to inaccurate estimates of surface flux components, such as surface wind speeds. While CYGNSS only contributes estimates of surface wind speeds, we can combine this data with other reanalysis and satellite data to provide improved estimates of surface sensible and latent heat fluxes within and around extratropical cyclones and throughout the entire CYGNSS mission.

A reference Pelton turbine - High speed visualization in the rotating frame

NASA Astrophysics Data System (ADS)

Solemslie, Bjørn W.; Dahlhaug, Ole G.

2016-11-01

To enable a detailed study the flow mechanisms effecting the flow within the reference Pelton runner designed at the Waterpower Laboratory (NTNLT) a flow visualization system has been developed. The system enables high speed filming of the hydraulic surface of a single bucket in the rotating frame of reference. It is built with an angular borescopes adapter entering the turbine along the rotational axis and a borescope embedded within a bucket. A stationary high speed camera located outside the turbine housing has been connected to the optical arrangement by a non-contact coupling. The view point of the system includes the whole hydraulic surface of one half of a bucket. The system has been designed to minimize the amount of vibrations and to ensure that the vibrations felt by the borescope are the same as those affecting the camera. The preliminary results captured with the system are promising and enable a detailed study of the flow within the turbine.

Influence of particle size on Cutting Forces and Surface Roughness in Machining of B4Cp - 6061 Aluminium Matrix Composites

NASA Astrophysics Data System (ADS)

Hiremath, Vijaykumar; Badiger, Pradeep; Auradi, V.; Dundur, S. T.; Kori, S. A.

2016-02-01

Amongst advanced materials, metal matrix composites (MMC) are gaining importance as materials for structural applications in particular, particulate reinforced aluminium MMCs have received considerable attention due to their superior properties such as high strength to weight ratio, excellent low-temperature performance, high wear resistance, high thermal conductivity. The present study aims at studying and comparing the machinability aspects of B4Cp reinforced 6061Al alloy metal matrix composites reinforced with 37μm and 88μm particulates produced by stir casting method. The micro structural characterization of the prepared composites is done using Scanning Electron Microscopy equipped with EDX analysis (Hitachi Su-1500 model) to identify morphology and distribution of B4C particles in the 6061Al matrix. The specimens are turned on a conventional lathe machine using a Polly crystalline Diamond (PCD) tool to study the effect of particle size on the cutting forces and the surface roughness under varying machinability parameters viz., Cutting speed (29-45 m/min.), Feed rate (0.11-0.33 mm/rev.) and depth of cut (0.5-1mm). Results of micro structural characterization revealed fairly uniform distribution of B4C particles (in both cases i.e., 37μm and 88μm) in 6061Al matrix. The surface roughness of the composite is influenced by cutting speed. The feed rate and depth of cut have a negative influence on surface roughness. The cutting forces decreased with increase in cutting speed whereas cutting forces increased with increase in feed and depth of cut. Higher cutting forces are noticed while machining Al6061 base alloy compared to reinforced composites. Surface finish is high during turning of the 6061Al base alloy and surface roughness is high with 88μm size particle reinforced composites. As the particle size increases Surface roughness also increases.

Invited Article: Quantitative imaging of explosions with high-speed cameras

DOE PAGES

McNesby, Kevin L.; Homan, Barrie E.; Benjamin, Richard A.; ...

2016-05-31

Here, the techniques presented in this paper allow for mapping of temperature, pressure, chemical species, and energy deposition during and following detonations of explosives, using high speed cameras as the main diagnostic tool. Additionally, this work provides measurement in the explosive near to far-field (0-500 charge diameters) of surface temperatures, peak air-shock pressures, some chemical species signatures, shock energy deposition, and air shock formation.

Shock wave driven microparticles for pharmaceutical applications

NASA Astrophysics Data System (ADS)

Menezes, V.; Takayama, K.; Gojani, A.; Hosseini, S. H. R.

2008-10-01

Ablation created by a Q-switched Nd:Yttrium Aluminum Garnet (Nd:YAG) laser beam focusing on a thin aluminum foil surface spontaneously generates a shock wave that propagates through the foil and deforms it at a high speed. This high-speed foil deformation can project dry micro- particles deposited on the anterior surface of the foil at high speeds such that the particles have sufficient momentum to penetrate soft targets. We used this method of particle acceleration to develop a drug delivery device to deliver DNA/drug coated microparticles into soft human-body targets for pharmaceutical applications. The device physics has been studied by observing the process of particle acceleration using a high-speed video camera in a shadowgraph system. Though the initial rate of foil deformation is over 5 km/s, the observed particle velocities are in the range of 900-400 m/s over a distance of 1.5-10 mm from the launch pad. The device has been tested by delivering microparticles into liver tissues of experimental rats and artificial soft human-body targets, modeled using gelatin. The penetration depths observed in the experimental targets are quite encouraging to develop a future clinical therapeutic device for treatments such as gene therapy, treatment of cancer and tumor cells, epidermal and mucosal immunizations etc.

MEMS high-speed angular-position sensing system with rf wireless transmission

NASA Astrophysics Data System (ADS)

Sun, Winston; Li, Wen J.

2001-08-01

A novel surface-micromachined non-contact high-speed angular-position sensor with total surface area under 4mm2 was developed using the Multi-User MEMS Processes (MUMPs) and integrated with a commercial RF transmitter at 433MHz carrier frequency for wireless signal detection. Currently, a 2.3 MHz internal clock of our data acquisition system and a sensor design with a 13mg seismic mass is sufficient to provide visual observation of a clear sinusoidal response wirelessly generated by the piezoresistive angular-position sensing system within speed range of 180 rpm to around 1000 rpm. Experimental results showed that the oscillation frequency and amplitude are related to the input angular frequency of the rotation disk and the tilt angle of the rotation axis, respectively. These important results could provide groundwork for MEMS researchers to estimate how gravity influences structural properties of MEMS devices under different circumstances.

Modelling storm development and the impact when introducing waves, sea spray and heat fluxes

NASA Astrophysics Data System (ADS)

Wu, Lichuan; Rutgersson, Anna; Sahlée, Erik

2015-04-01

In high wind speed conditions, sea spray generated due to intensity breaking waves have big influence on the wind stress and heat fluxes. Measurements show that drag coefficient will decrease in high wind speed. Sea spray generation function (SSGF), an important term of wind stress parameterization in high wind speed, usually treated as a function of wind speed/friction velocity. In this study, we introduce a wave state depended SSGG and wave age depended Charnock number into a high wind speed wind stress parameterization (Kudryavtsev et al., 2011; 2012). The proposed wind stress parameterization and sea spray heat fluxes parameterization from Andreas et al., (2014) were applied to an atmosphere-wave coupled model to test on four storm cases. Compared with measurements from the FINO1 platform in the North Sea, the new wind stress parameterization can reduce the forecast errors of wind in high wind speed range, but not in low wind speed. Only sea spray impacted on wind stress, it will intensify the storms (minimum sea level pressure and maximum wind speed) and lower the air temperature (increase the errors). Only the sea spray impacted on the heat fluxes, it can improve the model performance on storm tracks and the air temperature, but not change much in the storm intensity. If both of sea spray impacted on the wind stress and heat fluxes are taken into account, it has the best performance in all the experiment for minimum sea level pressure and maximum wind speed and air temperature. Andreas, E. L., Mahrt, L., and Vickers, D. (2014). An improved bulk air-sea surface flux algorithm, including spray-mediated transfer. Quarterly Journal of the Royal Meteorological Society. Kudryavtsev, V. and Makin, V. (2011). Impact of ocean spray on the dynamics of the marine atmospheric boundary layer. Boundary-layer meteorology, 140(3):383-410. Kudryavtsev, V., Makin, V., and S, Z. (2012). On the sea-surface drag and heat/mass transfer at strong winds. Technical report, Royal Netherlands Meteorological Institute.

Effect of Cutting Parameters on Thrust Force and Surface Roughness in Drilling of Al-2219/B4C/Gr Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Ravindranath, V. M.; Basavarajappa, G. S. Shiva Shankar S.; Suresh, R.

2016-09-01

In aluminium matrix composites, reinforcement of hard ceramic particle present inside the matrix which causes tool wear, high cutting forces and poor surface finish during machining. This paper focuses on effect of cutting parameters on thrust force, surface roughness and burr height during drilling of MMCs. In the present work, discuss the influence of spindle speed and feed rate on drilling the pure base alloy (Al-2219), mono composite (Al- 2219+8% B4C) and hybrid composite (Al-2219+8%B4C+3%Gr). The composites were fabricated using liquid metallurgy route. The drilling experiments were conducted by CNC machine with TiN coated HSS tool, M42 (Cobalt grade) and carbide tools at various spindle speeds and feed rates. The thrust force, surface roughness and burr height of the drilled hole were investigated in mono composite and hybrid composite containing graphite particles, the experimental results show that the feed rate has more influence on thrust force and surface roughness. Lesser thrust force and discontinuous chips were produced during machining of hybrid composites when compared with mono and base alloy during drilling process. It is due to solid lubricant property of graphite which reduces the lesser thrust force, burr height and lower surface roughness. When machining with Carbide tool at low feed and high speeds good surface finish was obtained compared to other two types of cutting tool materials.

Changes in body surface temperature during speed endurance work-out in highly-trained male sprinters

NASA Astrophysics Data System (ADS)

Korman, Paweł; Straburzyńska-Lupa, Anna; Kusy, Krzysztof; Kantanista, Adam; Zieliński, Jacek

2016-09-01

The mechanism of thermoregulatory adaptation to exercise cannot yet be fully explained, however, infrared thermography (IRT) seems to have potential for monitoring physiological changes during exercise and training. It is a non-contact and easy to use technology to measure heat radiation from the body surface. The objective of the study was to examine the temperature changes over time on lower limbs in sprinters during speed endurance training session. Eight sprinters, specialized in distances 100 m and 200 m, aged 21-29 years, members of the Polish national team, were evaluated during an outdoor speed endurance work-out. Their track session comprised of warm-up, specific drills for sprinting technique, and speed endurance exercise. The surface temperature of lower limbs was measured and thermal images were taken using infrared camera after each part of the session. The speed endurance training session brought about specific time course of body surface (legs) temperature. The warm-up induced a significant decline in surface temperature by ∼2.5 °C, measured both on the front and back of lower limbs (p < 0.001), followed by a temperature stabilization until the end of the session. No significant asymmetry between the front and back sides of legs was observed. Body surface temperature may help identify an individual optimal time to terminate warm up and start the main part of the training session. It may also be useful for the assessment of muscle activity symmetry in cyclical activities, such as sprint running. This is of particular relevance when a training session is performed outdoors in changeable weather conditions.

In-flight flow visualization with pressure measurements at low speeds on the NASA F-18 high alpha research vehicle

NASA Technical Reports Server (NTRS)

Delfrate, John H.; Fisher, David F.; Zuniga, Fanny A.

1990-01-01

In-flight results from surface and off-surface flow visualizations and from extensive pressure distributions document the vortical flow on the leading edge extensions (LEX) and forebody of the NASA F-18 high alpha research vehicle for low speeds and angles of attack up to 50 degs. Surface flow visualization data, obtained using the emitted fluid technique, were used to define separation lines and laminar separation bubbles. Off-surface flow visualization data, obtained by smoke injection, were used to document both the path of the vortex cores and the location of vortex core breakdown. The location of vortex core breakdown correlated well with the loss of suction pressure on the LEX and with the flow visualization results from ground facilities. Surface flow separation lines on the LEX and forebody corresponded well with the end of pressure recovery under the vortical flows. Correlation of the pressures with wind tunnel results show fair to good correlation.

Dust emissions created by low-level rotary-winged aircraft flight over desert surfaces

NASA Astrophysics Data System (ADS)

Gillies, J. A.; Etyemezian, V.; Kuhns, H.; McAlpine, J. D.; King, J.; Uppapalli, S.; Nikolich, G.; Engelbrecht, J.

2010-03-01

There is a dearth of information on dust emissions from sources that are unique to U.S. Department of Defense testing and training activities. Dust emissions of PM 10 and PM 2.5 from low-level rotary-winged aircraft travelling (rotor-blade ≈7 m above ground level) over two types of desert surfaces (i.e., relatively undisturbed desert pavement and disturbed desert soil surface) were characterized at the Yuma Proving Ground (Yuma, AZ) in May 2007. Fugitive emissions are created by the shear stress of the outflow of high speed air created by the rotor-blade. The strength of the emissions was observed to scale primarily as a function of forward travel speed of the aircraft. Speed affects dust emissions in two ways: 1) as speed increases, peak shear stress at the soil surface was observed to decline proportionally, and 2) as the helicopter's forward speed increases its residence time over any location on the surface diminishes, so the time the downward rotor-generated flow is acting upon that surface must also decrease. The state of the surface over which the travel occurs also affects the scale of the emissions. The disturbed desert test surface produced approximately an order of magnitude greater emission than the undisturbed surface. Based on the measured emission rates for the test aircraft and the established scaling relationships, a rotary-winged aircraft similar to the test aircraft traveling 30 km h -1 over the disturbed surface would need to travel 4 km to produce emissions equivalent to one kilometer of travel by a light wheeled military vehicle also traveling at 30 km h -1 on an unpaved road. As rotary-winged aircraft activity is substantially less than that of off-road vehicle military testing and training activities it is likely that this source is small compared to emissions created by ground-based vehicle movements.

Preparation and characterization of a thermoresponsive gigaporous medium for high-speed protein chromatography.

PubMed

Qu, Jian-Bo; Chen, Yan-Li; Huan, Guan-Sheng; Zhou, Wei-Qing; Liu, Jian-Guo; Zhu, Hu; Zhang, Xiao-Yun

2015-01-01

A high-speed thermoresponsive medium was developed by grafting poly(N-isopropylacrylamide-co-butyl methacrylate) (P(NIPAM-co-BMA)) brushes onto gigaporous polystyrene (PS) microspheres via surface-initiated atom transfer radical polymerization (ATRP) technique, which has strong mechanical strength, good chemical stability and high mass transfer rate for biomacromolecules. The gigaporous structure, surface chemical composition, static protein adsorption, and thermoresponsive chromatographic properties of prepared medium (PS-P(NIPAM-co-BMA)) were characterized in detail. Results showed that the PS microspheres were successfully grafted with P(NIPAM-co-BMA) brushes and that the gigaporous structure was robustly maintained. After grafting, the nonspecific adsorption of proteins on PS microspheres was greatly reduced. A column packed with PS-P(NIPAM-co-BMA) exhibited low backpressure and significant thermo-responsibility. By simply changing the column temperature, it was able to separate three model proteins at the mobile phase velocity up to 2167 cm h(-1). In conclusion, the thermoresponsive polymer brushes grafted gigaporous PS microspheres prepared by ATRP are very promising in 'green' high-speed preparative protein chromatography. Copyright © 2014 Elsevier B.V. All rights reserved.

Enamel and Dentin Surface Finishing Influence on the Roughness and Microshear Bond Strength of a Lithium Silicate Glass-Ceramic for Laminate Veneers

PubMed Central

Gonzaga, Carla Castiglia; Bravo, Ruth Peggy; Pavelski, Thiago Vinícius; Garcia, Paula Pontes; Correr, Gisele Maria; Leonardi, Denise Piotto; da Cunha, Leonardo Fernandes; Furuse, Adilson Yoshio

2015-01-01

Objectives. This study evaluated the influence of cavity surface finishing with diamond burs of different grit mounted on high-speed turbine and ultrasound on the roughness and microshear bond strength (MBS) of a lithium silicate glass-ceramic to enamel and dentin. Methods. Enamel and dentin specimens were divided into seven groups, according to the type of surface finishing: 1200-grit sandpaper (control), two different brands of medium-grit and fine-grit diamond burs in a high-speed turbine; medium-grit and fine-grit CVD (chemical vapor deposition) tips in an ultrasonic device. Roughness parameters (n = 5) and MSBS to a glass-ceramic (n = 10) were determined. Data were analyzed using ANOVA and Tukey's test (α = 5%). Results. Control group showed lower mean roughness readings and groups that used medium-grit diamond burs showed the highest mean roughness values. Regarding MSBS, there was no statistical difference when comparing the groups gritted with the same brand of medium- and fine-grit burs and tips. Conclusions. Cavity surface finishing influenced the roughness parameters and MSBS of a glass-ceramic to enamel and dentin. Medium-grit diamond burs in high-speed turbine showed the highest mean roughness values. Fine-grit CVD tips in ultrasound presented the highest MSBS values for both enamel and dentin. PMID:27347507

Enamel and Dentin Surface Finishing Influence on the Roughness and Microshear Bond Strength of a Lithium Silicate Glass-Ceramic for Laminate Veneers.

PubMed

Gonzaga, Carla Castiglia; Bravo, Ruth Peggy; Pavelski, Thiago Vinícius; Garcia, Paula Pontes; Correr, Gisele Maria; Leonardi, Denise Piotto; da Cunha, Leonardo Fernandes; Furuse, Adilson Yoshio

2015-01-01

Objectives. This study evaluated the influence of cavity surface finishing with diamond burs of different grit mounted on high-speed turbine and ultrasound on the roughness and microshear bond strength (MBS) of a lithium silicate glass-ceramic to enamel and dentin. Methods. Enamel and dentin specimens were divided into seven groups, according to the type of surface finishing: 1200-grit sandpaper (control), two different brands of medium-grit and fine-grit diamond burs in a high-speed turbine; medium-grit and fine-grit CVD (chemical vapor deposition) tips in an ultrasonic device. Roughness parameters (n = 5) and MSBS to a glass-ceramic (n = 10) were determined. Data were analyzed using ANOVA and Tukey's test (α = 5%). Results. Control group showed lower mean roughness readings and groups that used medium-grit diamond burs showed the highest mean roughness values. Regarding MSBS, there was no statistical difference when comparing the groups gritted with the same brand of medium- and fine-grit burs and tips. Conclusions. Cavity surface finishing influenced the roughness parameters and MSBS of a glass-ceramic to enamel and dentin. Medium-grit diamond burs in high-speed turbine showed the highest mean roughness values. Fine-grit CVD tips in ultrasound presented the highest MSBS values for both enamel and dentin.

High and low torque handpieces: cutting dynamics, enamel cracking and tooth temperature.

PubMed

Watson, T F; Flanagan, D; Stone, D G

2000-06-24

The aim of these experiments was to compare the cutting dynamics of high-speed high-torque (speed-increasing) and high-speed low-torque (air-turbine) handpieces and evaluate the effect of handpiece torque and bur type on sub-surface enamel cracking. Temperature changes were also recorded in teeth during cavity preparation with high and low torque handpieces with diamond and tungsten carbide (TC) burs. The null hypothesis of this study was that high torque handpieces cause more damage to tooth structure during cutting and lead to a rise in temperature within the pulp-chamber. Images of the dynamic interactions between burs and enamel were recorded at video rate using a confocal microscope. Central incisors were mounted on a specially made servomotor driven stage for cutting with a type 57 TC bur. The two handpiece types were used with simultaneous recording of cutting load and rate. Sub-surface enamel cracking caused by the use of diamond and TC burs with high and low torque was also examined. Lower third molars were sectioned horizontally to remove the cusp tips and then the two remaining crowns cemented together with cyanoacrylate adhesive, by their flat surfaces. Axial surfaces of the crowns were then prepared with the burs and handpieces. The teeth were then separated and the original sectioned surface examined for any cracks using a confocal microscope. Heat generation was measured using thermocouples placed into the pulp chambers of extracted premolars, with diamond and TC burs/high-low torque handpiece variables, when cutting occlusal and cervical cavities. When lightly loaded the two handpiece types performed similarly. However, marked differences in cutting mechanisms were noted when increased forces were applied to the handpieces with, generally, an increase in cutting rate. The air turbine could not cope with steady heavy loads, tending to stall. 'Rippling' was seen in the interface as this stall developed, coinciding with the bur 'clearing' itself. No differences were noted between different handpieces and burs, in terms of sub-surface enamel cracking. Similarly, no differences were recorded for temperature rise during cavity preparation. Differences in cutting mechanisms were seen between handpieces with high and low torque, especially when the loads and cutting rates were increased. The speed increasing handpiece was better able to cope with increased loading. Nevertheless, there was no evidence of increased tooth cracking or heating with this type handpiece, indicating that these do not have any deleterious effects on the tooth.

Application of Reflected Global Navigation Satellite System (GNSS-R) Signals in the Estimation of Sea Roughness Effects in Microwave Radiometry

NASA Technical Reports Server (NTRS)

Voo, Justin K.; Garrison, James L.; Yueh, Simon H.; Grant, Michael S.; Fore, Alexander G.; Haase, Jennifer S.; Clauss, Bryan

2010-01-01

In February-March 2009 NASA JPL conducted an airborne field campaign using the Passive Active L-band System (PALS) and the Ku-band Polarimetric Scatterometer (PolSCAT) collecting measurements of brightness temperature and near surface wind speeds. Flights were conducted over a region of expected high-speed winds in the Atlantic Ocean, for the purposes of algorithm development for salinity retrievals. Wind speeds encountered were in the range of 5 to 25 m/s during the two weeks deployment. The NASA-Langley GPS delay-mapping receiver (DMR) was also flown to collect GPS signals reflected from the ocean surface and generate post-correlation power vs. delay measurements. This data was used to estimate ocean surface roughness and a strong correlation with brightness temperature was found. Initial results suggest that reflected GPS signals, using small low-power instruments, will provide an additional source of data for correcting brightness temperature measurements for the purpose of sea surface salinity retrievals.

A Method for Calculating Transient Surface Temperatures and Surface Heating Rates for High-Speed Aircraft

NASA Technical Reports Server (NTRS)

Quinn, Robert D.; Gong, Leslie

2000-01-01

This report describes a method that can calculate transient aerodynamic heating and transient surface temperatures at supersonic and hypersonic speeds. This method can rapidly calculate temperature and heating rate time-histories for complete flight trajectories. Semi-empirical theories are used to calculate laminar and turbulent heat transfer coefficients and a procedure for estimating boundary-layer transition is included. Results from this method are compared with flight data from the X-15 research vehicle, YF-12 airplane, and the Space Shuttle Orbiter. These comparisons show that the calculated values are in good agreement with the measured flight data.

Contraction of an air disk caught between two different liquids

NASA Astrophysics Data System (ADS)

Thoraval, M.-J.; Thoroddsen, S. T.

2013-12-01

When a drop impacts a pool of liquid it entraps a thin disk of air under its center. This disk contracts rapidly into a bubble to minimize surface energy. Herein we use ultra-high-speed imaging to measure the contraction speed of this disk when the drop and pool are of different liquids. For miscible liquids the contraction rate is governed by the weaker of the two surface tensions. Some undulations are observed on the edge of the disk for a water drop impacting a pool of water, but not on a pool of lower surface tension. Similar results are observed for a pair of immiscible liquids.

Tribology

NASA Technical Reports Server (NTRS)

2004-01-01

Tribology-the study of friction, lubrication, and wear of surfaces in relative motion-is the subject of many tests and evaluation being conducted at Marshall Space Flight Center. Marshall's need to develop state-of-the-art tribological materials and components for NASA's on-going space program is spurring these technological advances. High speed, high performance machinery is plagued by periodic mainteneance and replacement of worn parts. Tribology investigations are important to manufacturers who provide aerospace components, air conditioning, and refrigeration parts, and devices used in power plants with high-speed turbines.

Dynamic, Hot Surface Ignition of Aircraft Fuels and Hydraulic Fluids

DTIC Science & Technology

1980-10-01

fuels on a heated stainless steel surface. Higher local surface air speeds necessitated higher surface temperatures for ignition of an applied fluid._-7...Aircraft Fuels ( stainless steel surface) 8. Air Speed and Surface Material Effects on Hot Surface 21 Ignition Temperature of Aircraft Fuels (Titanium...Material Effects on Hot Surface 26 Ignition Temperature of Aircraft Hydraulic Fluids ( Stainless steel surface) 11. Air Speed and Surface Material

Climate projection of synoptic patterns forming extremely high wind speed over the Barents Sea

NASA Astrophysics Data System (ADS)

Surkova, Galina; Krylov, Aleksey

2017-04-01

Frequency of extreme weather events is not very high, but their consequences for the human well-being may be hazardous. These seldom events are not always well simulated by climate models directly. Sometimes it is more effective to analyze numerical projection of large-scale synoptic event generating extreme weather. For example, in mid-latitude surface wind speed depends mainly on the sea level pressure (SLP) field - its configuration and horizontal pressure gradient. This idea was implemented for analysis of extreme wind speed events over the Barents Sea. The calendar of high surface wind speed V (10 m above the surface) was prepared for events with V exceeding 99th percentile value in the central part of the Barents Sea. Analysis of probability distribution function of V was carried out on the base of ERA-Interim reanalysis data (6-hours, 0.75x0.75 degrees of latitude and longitude) for the period 1981-2010. Storm wind events number was found to be 240 days. Sea level pressure field over the sea and surrounding area was selected for each storm wind event. For the climate of the future (scenario RCP8.5), projections of SLP from CMIP5 numerical experiments were used. More than 20 climate models results of projected SLP (2006-2100) over the Barents Sea were correlated with modern storm wind SLP fields. Our calculations showed the positive tendency of annual frequency of storm SLP patterns over the Barents Sea by the end of 21st century.

Fabrication of an infrared Shack-Hartmann sensor by combining high-speed single-point diamond milling and precision compression molding processes.

PubMed

Zhang, Lin; Zhou, Wenchen; Naples, Neil J; Yi, Allen Y

2018-05-01

A novel fabrication method by combining high-speed single-point diamond milling and precision compression molding processes for fabrication of discontinuous freeform microlens arrays was proposed. Compared with slow tool servo diamond broaching, high-speed single-point diamond milling was selected for its flexibility in the fabrication of true 3D optical surfaces with discontinuous features. The advantage of single-point diamond milling is that the surface features can be constructed sequentially by spacing the axes of a virtual spindle at arbitrary positions based on the combination of rotational and translational motions of both the high-speed spindle and linear slides. By employing this method, each micro-lenslet was regarded as a microstructure cell by passing the axis of the virtual spindle through the vertex of each cell. An optimization arithmetic based on minimum-area fabrication was introduced to the machining process to further increase the machining efficiency. After the mold insert was machined, it was employed to replicate the microlens array onto chalcogenide glass. In the ensuing optical measurement, the self-built Shack-Hartmann wavefront sensor was proven to be accurate in detecting an infrared wavefront by both experiments and numerical simulation. The combined results showed that precision compression molding of chalcogenide glasses could be an economic and precision optical fabrication technology for high-volume production of infrared optics.

Full-field transient vibrometry of the human tympanic membrane by local phase correlation and high-speed holography

PubMed Central

Dobrev, Ivo; Furlong, Cosme; Cheng, Jeffrey T.; Rosowski, John J.

2014-01-01

Abstract. Understanding the human hearing process would be helped by quantification of the transient mechanical response of the human ear, including the human tympanic membrane (TM or eardrum). We propose a new hybrid high-speed holographic system (HHS) for acquisition and quantification of the full-field nanometer transient (i.e., >10  kHz) displacement of the human TM. We have optimized and implemented a 2+1 frame local correlation (LC) based phase sampling method in combination with a high-speed (i.e., >40  K fps) camera acquisition system. To our knowledge, there is currently no existing system that provides such capabilities for the study of the human TM. The LC sampling method has a displacement difference of <11  nm relative to measurements obtained by a four-phase step algorithm. Comparisons between our high-speed acquisition system and a laser Doppler vibrometer indicate differences of <10  μs. The high temporal (i.e., >40  kHz) and spatial (i.e., >100  k data points) resolution of our HHS enables parallel measurements of all points on the surface of the TM, which allows quantification of spatially dependent motion parameters, such as modal frequencies and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM. PMID:25191832

Numerical simulation of humping phenomenon in high speed gas metal arc welding

NASA Astrophysics Data System (ADS)

Chen, Ji; Wu, Chuan-Song

2011-06-01

It is of great significance to obtain a thorough understanding of the physical mechanisms responsible for humping bead phenomenon in high speed gas metal arc welding (GMAW) in order to raise welding efficiency. Experiments were conducted to observe the weld pool behaviors in high speed GMAW, and it was found that both the severely deformed weld pool surface and strong backward flowing play a dominant role in humping bead formation. In this study, a mathematical model is developed to quantitatively analyze the forming mechanism of humping beads for high speed GMAW through considering both the momentum and heat content distribution of the backward flowing molten metal inside the weld pool. The transient development of temperature profiles in the weld pool with severe deformation demonstrates the humping bead forming process under some welding conditions. The predicted and measured humping bead dimensions are in agreement.

High-speed atomic force microscopy combined with inverted optical microscopy for studying cellular events

PubMed Central

Suzuki, Yuki; Sakai, Nobuaki; Yoshida, Aiko; Uekusa, Yoshitsugu; Yagi, Akira; Imaoka, Yuka; Ito, Shuichi; Karaki, Koichi; Takeyasu, Kunio

2013-01-01

A hybrid atomic force microscopy (AFM)-optical fluorescence microscopy is a powerful tool for investigating cellular morphologies and events. However, the slow data acquisition rates of the conventional AFM unit of the hybrid system limit the visualization of structural changes during cellular events. Therefore, high-speed AFM units equipped with an optical/fluorescence detection device have been a long-standing wish. Here we describe the implementation of high-speed AFM coupled with an optical fluorescence microscope. This was accomplished by developing a tip-scanning system, instead of a sample-scanning system, which operates on an inverted optical microscope. This novel device enabled the acquisition of high-speed AFM images of morphological changes in individual cells. Using this instrument, we conducted structural studies of living HeLa and 3T3 fibroblast cell surfaces. The improved time resolution allowed us to image dynamic cellular events. PMID:23823461

High-speed atomic force microscopy combined with inverted optical microscopy for studying cellular events.

PubMed

Suzuki, Yuki; Sakai, Nobuaki; Yoshida, Aiko; Uekusa, Yoshitsugu; Yagi, Akira; Imaoka, Yuka; Ito, Shuichi; Karaki, Koichi; Takeyasu, Kunio

2013-01-01

A hybrid atomic force microscopy (AFM)-optical fluorescence microscopy is a powerful tool for investigating cellular morphologies and events. However, the slow data acquisition rates of the conventional AFM unit of the hybrid system limit the visualization of structural changes during cellular events. Therefore, high-speed AFM units equipped with an optical/fluorescence detection device have been a long-standing wish. Here we describe the implementation of high-speed AFM coupled with an optical fluorescence microscope. This was accomplished by developing a tip-scanning system, instead of a sample-scanning system, which operates on an inverted optical microscope. This novel device enabled the acquisition of high-speed AFM images of morphological changes in individual cells. Using this instrument, we conducted structural studies of living HeLa and 3T3 fibroblast cell surfaces. The improved time resolution allowed us to image dynamic cellular events.

Explosive-driven, high speed, arcless switch

DOEpatents

Skogmo, P.J.; Tucker, T.J.

1986-05-02

An explosive-actuated, fast-acting arcless switch contains a highly conductive foil to carry high currents positioned adjacent a dielectric surface within a casing. At one side of the foil opposite the dielectric surface is an explosive which, when detonated, drives the conductive foil against the dielectric surface. A pattern of grooves in the dielectric surface ruptures the foil to establish a rupture path having a pattern corresponding to the pattern of the grooves. The impedance of the ruptured foil is greater than that of the original foil to divert high current to a load. Planar and cylindrical embodiments of the switch are disclosed.

Explosive-driven, high speed, arcless switch

DOEpatents

Skogmo, Phillip J.; Tucker, Tillman J.

1987-01-01

An explosive-actuated, fast-acting arcless switch contains a highly conductive foil to carry high currents positioned adjacent a dielectric surface within a casing. At one side of the foil opposite the dielectric surface is an explosive which, when detonated, drives the conductive foil against the dielectric surface. A pattern of grooves in the dielectric surface ruptures the foil to establish a rupture path having a pattern corresponding to the pattern of the grooves. The impedance of the ruptured foil is greater than that of the original foil to divert high current to a load. Planar and cylindrical embodiments of the switch are disclosed.

Design of quantum dot-conjugated lipids for long-term, high-speed tracking experiments on cell surfaces.

PubMed

Murcia, Michael J; Minner, Daniel E; Mustata, Gina-Mirela; Ritchie, Kenneth; Naumann, Christoph A

2008-11-12

The current study reports the facile design of quantum dot (QD)-conjugated lipids and their application to high-speed tracking experiments on cell surfaces. CdSe/ZnS core/shell QDs with two types of hydrophilic coatings, 2-(2-aminoethoxy)ethanol (AEE) and a 60:40 molar mixture of 1,2-dipalmitoyl- sn-glycero-3-phosphocholine and 1,2-dipalmitoyl- sn-glycero-3-phosphoethanolamine- N-[methoxy(polyethylene glycol-2000], are conjugated to sulfhydryl lipids via maleimide reactive groups on the QD surface. Prior to lipid conjugation, the colloidal stability of both types of coated QDs in aqueous solution is confirmed using fluorescence correlation spectroscopy. A sensitive assay based on single lipid tracking experiments on a planar solid-supported phospholipid bilayer is presented that establishes conditions of monovalent conjugation of QDs to lipids. The QD-lipids are then employed as single-molecule tracking probes in plasma membranes of several cell types. Initial tracking experiments at a frame rate of 30 frames/s corroborate that QD-lipids diffuse like dye-labeled lipids in the plasma membrane of COS-7, HEK-293, 3T3, and NRK cells, thus confirming monovalent labeling. Finally, QD-lipids are applied for the first time to high-speed single-molecule imaging by tracking their lateral mobility in the plasma membrane of NRK fibroblasts with up to 1000 frames/s. Our high-speed tracking data, which are in excellent agreement with previous tracking experiments that used larger (40 nm) Au labels, not only push the time resolution in long-time, continuous fluorescence-based single-molecule tracking but also show that highly photostable, photoluminescent nanoprobes of 10 nm size can be employed (AEE-coated QDs). These probes are also attractive because, unlike Au nanoparticles, they facilitate complex multicolor experiments.

Wave-Induced Momentum Flux over Wind-driven Surface Waves

NASA Astrophysics Data System (ADS)

Yousefi, Kianoosh; Veron, Fabrice; Buckley, Marc; Husain, Nyla; Hara, Tetsu

2017-11-01

In recent years, the exchange of momentum between the atmosphere and the ocean has been the subject of several investigations. Although the role of surface waves on the air-sea momentum flux is now well established, detailed quantitative measurements of wave-induced momentum fluxes are lacking. In the current study, using a combined Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF) system, we obtained laboratory measurements of the airflow velocity above surface waves for wind speeds ranging from 0.86 to 16.63 m s-1. The mean, turbulent, and wave-coherent velocity fields are then extracted from instantaneous measurements. Wave-induced stress can, therefore, be estimated. In strongly forced cases in high wind speeds, the wave-induced stress near the surface is a significant fraction of the total stress. At lower wind speeds and larger wave ages, the wave-induced stress is positive very close to the surface, below the critical height and decreases to a negative value further above the critical height. This indicates a shift in the direction of the wave-coherent momentum flux across the critical layer. NSF OCE1458977, NSF OCE1634051.

Visualization of hump formation in high-speed gas metal arc welding

NASA Astrophysics Data System (ADS)

Wu, C. S.; Zhong, L. M.; Gao, J. Q.

2009-11-01

The hump bead is a typical weld defect observed in high-speed welding. Its occurrence limits the improvement of welding productivity. Visualization of hump formation during high-speed gas metal arc welding (GMAW) is helpful in the better understanding of the humping phenomena so that effective measures can be taken to suppress or decrease the tendency of hump formation and achieve higher productivity welding. In this study, an experimental system was developed to implement vision-based observation of the weld pool behavior during high-speed GMAW. Considering the weld pool characteristics in high-speed welding, a narrow band-pass and neutral density filter was equipped for the CCD camera, the suitable exposure time was selected and side view orientation of the CCD camera was employed. The events that took place at the rear portion of the weld pools were imaged during the welding processes with and without hump bead formation, respectively. It was found that the variation of the weld pool surface height and the solid-liquid interface at the pool trailing with time shows some useful information to judge whether the humping phenomenon occurs or not.

Magnetically-focusing biochip structures for high-speed active biosensing with improved selectivity.

PubMed

Yoo, Haneul; Lee, Dong Jun; Kim, Daesan; Park, Juhun; Chen, Xing; Hong, Seunghun

2018-06-29

We report a magnetically-focusing biochip structure enabling a single layered magnetic trap-and-release cycle for biosensors with an improved detection speed and selectivity. Here, magnetic beads functionalized with specific receptor molecules were utilized to trap target molecules in a solution and transport actively to and away from the sensor surfaces to enhance the detection speed and reduce the non-specific bindings, respectively. Using our method, we demonstrated the high speed detection of IL-13 antigens with the improved detection speed by more than an order of magnitude. Furthermore, the release step in our method was found to reduce the non-specific bindings and improve the selectivity and sensitivity of biosensors. This method is a simple but powerful strategy and should open up various applications such as ultra-fast biosensors for point-of-care services.

Magnetically-focusing biochip structures for high-speed active biosensing with improved selectivity

NASA Astrophysics Data System (ADS)

Yoo, Haneul; Lee, Dong Jun; Kim, Daesan; Park, Juhun; Chen, Xing; Hong, Seunghun

2018-06-01

We report a magnetically-focusing biochip structure enabling a single layered magnetic trap-and-release cycle for biosensors with an improved detection speed and selectivity. Here, magnetic beads functionalized with specific receptor molecules were utilized to trap target molecules in a solution and transport actively to and away from the sensor surfaces to enhance the detection speed and reduce the non-specific bindings, respectively. Using our method, we demonstrated the high speed detection of IL-13 antigens with the improved detection speed by more than an order of magnitude. Furthermore, the release step in our method was found to reduce the non-specific bindings and improve the selectivity and sensitivity of biosensors. This method is a simple but powerful strategy and should open up various applications such as ultra-fast biosensors for point-of-care services.

Aerodynamic heating and surface temperatures on vehicles for computer-aided design studies

NASA Technical Reports Server (NTRS)

Dejarnette, F. R.; Kania, L. A.; Chitty, A.

1983-01-01

A computer subprogram has been developed to calculate aerodynamic and radiative heating rates and to determine surface temperatures by integrating the heating rates along the trajectory of a vehicle. Convective heating rates are calculated by applying the axisymmetric analogue to inviscid surface streamlines and using relatively simple techniques to calculate laminar, transitional, or turbulent heating rates. Options are provided for the selection of gas model, transition criterion, turbulent heating method, Reynolds Analogy factor, and entropy-layer swallowing effects. Heating rates are compared to experimental data, and the time history of surface temperatures are given for a high-speed trajectory. The computer subprogram is developed for preliminary design and mission analysis where parametric studies are needed at all speeds.

Impact of Increased Football Field Width on Player High-Speed Collision Rate.

PubMed

Joseph, Jacob R; Khalsa, Siri S; Smith, Brandon W; Park, Paul

2017-07-01

High-acceleration head impact is a known risk for mild traumatic brain injury (mTBI) based on studies using helmet accelerometry. In football, offensive and defensive players are at higher risk of mTBI due to increased speed of play. Other collision sport studies suggest that increased playing surface size may contribute to reductions in high-speed collisions. We hypothesized that wider football fields lead to a decreased rate of high-speed collisions. Computer football game simulation was developed using MATLAB. Four wide receivers were matched against 7 defensive players. Each offensive player was randomized to one of 5 typical routes on each play. The ball was thrown 3 seconds into play; ball flight time was 2 seconds. Defensive players were delayed 0.5 second before reacting to ball release. A high-speed collision was defined as the receiver converging with a defensive player within 0.5 second of catching the ball. The simulation counted high-speed collisions for 1 team/season (65 plays/game for 16 games/season = 1040 plays/season) averaged during 10 seasons, and was validated against existing data using standard field width (53.3 yards). Field width was increased in 1-yard intervals up to 58.3 yards. Using standard field width, 188 ± 4 high-speed collisions were seen per team per season (18% of plays). When field width increased by 3 yards, high-speed collision rate decreased to 135 ± 3 per team per season (28% decrease; P < 0.0001). Even small increases in football field width can lead to substantial decline in high-speed collisions, with potential for reducing instances of mTBI in football players. Copyright © 2017 Elsevier Inc. All rights reserved.

Modeling corneal surfaces with rational functions for high-speed videokeratoscopy data compression.

PubMed

Schneider, Martin; Iskander, D Robert; Collins, Michael J

2009-02-01

High-speed videokeratoscopy is an emerging technique that enables study of the corneal surface and tear-film dynamics. Unlike its static predecessor, this new technique results in a very large amount of digital data for which storage needs become significant. We aimed to design a compression technique that would use mathematical functions to parsimoniously fit corneal surface data with a minimum number of coefficients. Since the Zernike polynomial functions that have been traditionally used for modeling corneal surfaces may not necessarily correctly represent given corneal surface data in terms of its optical performance, we introduced the concept of Zernike polynomial-based rational functions. Modeling optimality criteria were employed in terms of both the rms surface error as well as the point spread function cross-correlation. The parameters of approximations were estimated using a nonlinear least-squares procedure based on the Levenberg-Marquardt algorithm. A large number of retrospective videokeratoscopic measurements were used to evaluate the performance of the proposed rational-function-based modeling approach. The results indicate that the rational functions almost always outperform the traditional Zernike polynomial approximations with the same number of coefficients.

About a flame propagation by a premixed gas mixture at high turbulence

NASA Astrophysics Data System (ADS)

Gaponov, Sergey A.

2018-03-01

In the paper the new model of the turbulent flame propagation in a premixed gas is offered. In its basis the diffusion equation of combustion products with a source, which is proportional to the contact surface of combustion products with a fresh mixture and an expansion coefficient is put. It is shown that the dependence of the generation rate of combustion products on their mass concentration satisfies conditions of the KPP (Kolmogorov, Petrovsky, Piskounov). In this case, the flame propagation speed depends on the flame surface in a unit volume near the leading front. But at turbulent motion the isolated fragments of combustion products surrounded with fresh mix can be formed on the forward front. It is assumed that the isolated fragments are the sphere shape at the weak turbulence, and with increase in intensity of turbulent pulsations the flame surface of each center is proportional to the pulsations velocity and inversely proportional to the flame speed relatively combustion products, i.e. it is inversely proportional to the product of normal flame speed and expansion coefficient. As a result the formula for the propagation speed calculation of the turbulent flame is proposed which includes not only traditional values of a pulsations velocity and normal flame speed, but also values of an expansion coefficient. On its basis it is explained why the turbulent flame speed exceeds the pulsations velocity by many times at moderate turbulence. It is shown that at the power dependence the turbulent flame speed on the pulsation velocity exponent can vary from 0.5 to unit. The received dependence can be improved if to replace the flat laminar flame with average on the surface of the curved flame, i.e. to take into account the Markstein theory.

Tribological properties of multifunctional coatings with Shape Memory Effect in abrasive wear

NASA Astrophysics Data System (ADS)

Blednova, Zh. M.; Dmitrenko, D. V.; Balaev, E. U. O.

2018-01-01

The article gives research results of the abrasive wear process on samples made of Steel 1045, U10 and with applied composite surface layer "Nickel-Multicomponent material with Shape Memory Effect (SME) based on TiNi". For the tests we have chosen TiNiZr, which is in the martensite state and TiNiHfCu, which is in the austenitic state at the test temperature. The formation of the surface layer was carried out by high-speed oxygen-fuel deposition in a protective atmosphere of argon. In the wear test, Al2O3 corundum powder was used as an abrasive. It is shown that the wear rate of samples with a composite surface layer of multicomponent materials with SME is significantly reduced in comparison with the base, which is explained by reversible phase transformations of the surface layer with SME. After carrying out the additional surface plastic deformation (SPD), the resistance of the laminated composition to abrasion wear has greatly enhanced, due to the reinforcing effect of the SPD. It is recommended for products working in conditions of abrasive wear and high temperatures to use the complex formation technology of the surface composition "steel-nickel-material with high-temperature SME", including preparation of the substrate surface and the deposited material, high-speed spraying in the protective atmosphere of argon, followed by SPD.

Ejection and Lofting of Dust from Hypervelocity Impacts on the Moon

NASA Astrophysics Data System (ADS)

Hermalyn, B.; Schultz, P. H.

2011-12-01

Hypervelocity impact events mobilize and redistribute fine-grained regolith dust across the surfaces of planetary bodies. The ejecta mass-velocity distribution controls the location and emplacement of these materials. The current flux of material falling on the moon is dominated by small bolides and should cause frequent impacts that eject dust at high speeds. For example, approximately 25 LCROSS-sized (~20-30m diameter) craters are statistically expected to be formed naturally on the moon during any given earth year. When scaled to lunar conditions, the high-speed component of ejecta from hypervelocity impacts can be lofted for significant periods of time (as evidenced by the LCROSS mission results, c.f., Schultz, et al., 2010, Colaprete, et al., 2010). Even at laboratory scales, ejecta can approach orbital velocities; the higher impact speeds and larger projectiles bombarding the lunar surface may permit a significant portion of material to be launched closer to escape velocity. When these ejecta return to the surface (or encounter local topography), they impact at hundreds of meters per second or faster, thereby "scouring" the surface with low mass oblique impacts. While these high-speed ejecta represent only a small fraction of the total ejected mass, the lofting and subsequent ballistic return of this dust has the highest mobilization potential and will be directly applicable to the upcoming LADEE mission. A suite of hypervelocity impact experiments into granular materials was performed at the NASA Ames Vertical Gun Range (AVGR). This study incorporates both canonical sand targets and air-fall pumice dust to simulate the mechanical properties of lunar regolith. The implementation of a Particle Tracking Velocimetry (PTV) technique permits non-intrusive measurement of the ejecta velocity distribution within the ejecta curtain by following the path of individual ejecta particles. The PTV system developed at the AVGR uses a series of high-speed cameras (ranging from 11,000 to 500,000 frames per second) to allow measurement of particle velocity over the large dynamic range required for early-time, high-speed components of ejecta. Preliminary results for impacts into sand (Hermalyn and Schultz, 2010, 2011) reveal that early in the cratering process, ejection velocities are higher than assumed by dimensional scaling laws (Housen, et al., 1983). Moreover, the ejection angles of this early-time component are initially low (~30°) and gradually increase to reach nominal ejection angles (~45° for impacts into sand). In this study, we assess the expected ejecta velocities on the moon from the current impact flux and the possible effects of the secondary impacts of ejecta dust particles. By convolving these ejecta measurements with the lunar impact flux rate, an estimate can be derived for the amount and ballistic flight time of dust lofted above the surface of the moon over a given year.

Atmospheric Dispersion Modeling of 137Cs generated from Nuclear Spent Fuel under Hypothetic Accidental Condition in the BNPP Area

NASA Astrophysics Data System (ADS)

Lee, Jongkuk; Lee, Kwan-Hee; Yook, Daesik; Kim, Sung Il; Lee, Byung Soo

2016-04-01

This study presents the results of atmosphere dispersion modeling using CALPUFF code that are based on computational simulation to evaluate the environmental characteristics of the Barakah nuclear power plant (BNPP) in west area of UAE. According to meteorological data analysis (2012~2013), the winds from the north(7.68%) and west(9.05%) including NNW(41.63%), NW(28.55%), and WNW(6.31%) winds accounted for more than 90% of the wind directions. East(0.2%) and south(0.6%) direction wind, including ESE(0.31%), SE(0.38%), and SSE(0.38%) were rarely distributed during the simulation period. Seasonal effects were not showed. However, a discrepancy in the tendency between daytime and night-time was observed. Approximately 87% of the wind speed was distributed below 5.4m/s (17%, 47% and 23% between the speeds of 0.5-1.8m/s 1.8-3.3m/s and 3.3-5.4m/s, respectively) during the annual period. Seasonal wind speed distribution results presented very similar pattern of annual distribution. Wind speed distribution of day and night, on the other hand, had a discrepancy with annual modeling results than seasonal distribution in some sections. The results for high wind speed (more than 10.8m/s) showed that this wind blew from the west. This high wind speed is known locally as the 'Shamal', which occurs rarely, lasting one or two days with the strongest winds experienced in association with gust fronts and thunderstorms. Six variations of cesium-137 (137Cs) dispersion test were simulated under hypothetic severe accidental condition. The 137Cs dispersion was strongly influenced by the direction and speed of the main wind. From the test cases, east-south area of the BNPP site was mainly influenced by 137Cs dispersion. A virtual receptor was set and calculated for observation of the 137Cs movement and accumulation. Surface roughness tests were performed for the analysis of topographic conditions. According to the surface condition, there are various surface roughness length. Four types of surface conditions were selected, including city area, hedge area, cut grass, and desert area. Four cases of simulations were performed under the same conditions except for surface the roughness factor. The results indicated that relatively high concentrations were found at the high surface roughness near the origin of the source point. The city area contained approximately four times 137Cs concentration than that of desert area. The atmospheric dispersion of 137Cs was affected by the surface condition in the proximal area. Moreover, movement of the radioactive material had a tendency to be dispersed in a relatively wide range in the desert areas compared to in the higher surface roughness areas. The results of these study offer useful information for developing environmental radiation monitoring systems (ERMSs) and evacuation plan under unexpected emergency condition for the BNPP and can be used to assess the environmental effects of new nuclear power plant. This work was supported by the Nuclear Safety Research Program through the Korea Nuclear Safety Foundation(KORSAFe), granted financial resource from the Nuclear Safety and Security Commission(NSSC), Republic of Korea (No. 1503003).

Influence of Surface Tension and Surface Shear on Final Coat Thickness in Jet-Stripped Continuous Coating of Sheet Materials.

DTIC Science & Technology

1983-11-01

galvanising industry, this pressure distribution is created by blowing a thin high-speed air jet onto the coated steel sheet, just after it emerges from the...if that free surface possesses curvature and non-zero surface tension, the internal pressure will differ from that in the jet. In the galvanising

Contact geometry and mechanics predict friction forces during tactile surface exploration.

PubMed

Janko, Marco; Wiertlewski, Michael; Visell, Yon

2018-03-20

When we touch an object, complex frictional forces are produced, aiding us in perceiving surface features that help to identify the object at hand, and also facilitating grasping and manipulation. However, even during controlled tactile exploration, sliding friction forces fluctuate greatly, and it is unclear how they relate to the surface topography or mechanics of contact with the finger. We investigated the sliding contact between the finger and different relief surfaces, using high-speed video and force measurements. Informed by these experiments, we developed a friction force model that accounts for surface shape and contact mechanical effects, and is able to predict sliding friction forces for different surfaces and exploration speeds. We also observed that local regions of disconnection between the finger and surface develop near high relief features, due to the stiffness of the finger tissues. Every tested surface had regions that were never contacted by the finger; we refer to these as "tactile blind spots". The results elucidate friction force production during tactile exploration, may aid efforts to connect sensory and motor function of the hand to properties of touched objects, and provide crucial knowledge to inform the rendering of realistic experiences of touch contact in virtual reality.

Comparison of surface wind stress measurements - Airborne radar scatterometer versus sonic anemometer

NASA Technical Reports Server (NTRS)

Brucks, J. T.; Leming, T. D.; Jones, W. L.

1980-01-01

Sea surface wind stress measurements recorded by a sonic anemometer are correlated with airborne scatterometer measurements of ocean roughness (cross section of radar backscatter) to establish the accuracy of remotely sensed data and assist in the definition of geophysical algorithms for the scatterometer sensor aboard Seasat A. Results of this investigation are as follows: Comparison of scatterometer and sonic anemometer wind stress measurements are good for the majority of cases; however, a tendency exists for scatterometer wind stress to be somewhat high for higher wind conditions experienced in this experiment (6-9 m/s). The scatterometer wind speed algorithm tends to overcompute the higher wind speeds by approximately 0.5 m/s. This is a direct result of the scatterometer overestimate of wind stress from which wind speeds are derived. Algorithmic derivations of wind speed and direction are, in most comparisons, within accuracies defined by Seasat A scatterometer sensor specifications.

The dynamic response of Kennicott Glacier, Alaska, USA, to the Hidden Creek Lake outburst flood

USGS Publications Warehouse

Anderson, R. Scott; Walder, J.S.; Anderson, S.P.; Trabant, D.C.; Fountain, A.G.

2005-01-01

Glacier sliding is commonly linked with elevated water pressure at the glacier bed. Ice surface motion during a 3 week period encompassing an outburst of ice-dammed Hidden Creek Lake (HCL) at Kennicott Glacier, Alaska, USA, showed enhanced sliding during the flood. Two stakes, 1.2 km from HCL, revealed increased speed in two episodes, both associated with uplift of the ice surface relative to the trajectory of bed-parallel motion. Uplift of the surface began 12 days before the flood, initially stabilizing at a value of 0.25 m. Two days after lake drainage began, further uplift (reaching 0.4 m) occurred while surface speed peaked at 1.2 m d-1. Maximum surface uplift coincided with peak discharge from HCL, high water level in a down-glacier ice-marginal basin, and low solute concentrations in the Kennicott River. Each of these records is consistent with high subglacial water pressure. We interpret the ice surface motion as arising from sliding up backs of bumps on the bed, which enlarges cavities and produces bed separation. The outburst increased water pressure over a broad region, promoting sliding, inhibiting cavity closure, and blocking drainage of solute-rich water from the distributed system. Pressure drop upon termination of the outburst drained water from and depressurized the distributed system, reducing sliding speeds. Expanded cavities then collapsed with a 1 day time-scale set by the local ice thickness.

Prediction of the wear and evolution of cutting tools in a carbide / titanium-aluminum-vanadium machining tribosystem by volumetric tool wear characterization and modeling

NASA Astrophysics Data System (ADS)

Kuttolamadom, Mathew Abraham

The objective of this research work is to create a comprehensive microstructural wear mechanism-based predictive model of tool wear in the tungsten carbide / Ti-6Al-4V machining tribosystem, and to develop a new topology characterization method for worn cutting tools in order to validate the model predictions. This is accomplished by blending first principle wear mechanism models using a weighting scheme derived from scanning electron microscopy (SEM) imaging and energy dispersive x-ray spectroscopy (EDS) analysis of tools worn under different operational conditions. In addition, the topology of worn tools is characterized through scanning by white light interferometry (WLI), and then application of an algorithm to stitch and solidify data sets to calculate the volume of the tool worn away. The methodology was to first combine and weight dominant microstructural wear mechanism models, to be able to effectively predict the tool volume worn away. Then, by developing a new metrology method for accurately quantifying the bulk-3D wear, the model-predicted wear was validated against worn tool volumes obtained from corresponding machining experiments. On analyzing worn crater faces using SEM/EDS, adhesion was found dominant at lower surface speeds, while dissolution wear dominated with increasing speeds -- this is in conformance with the lower relative surface speed requirement for micro welds to form and rupture, essentially defining the mechanical load limit of the tool material. It also conforms to the known dominance of high temperature-controlled wear mechanisms with increasing surface speed, which is known to exponentially increase temperatures especially when machining Ti-6Al-4V due to its low thermal conductivity. Thus, straight tungsten carbide wear when machining Ti-6Al-4V is mechanically-driven at low surface speeds and thermally-driven at high surface speeds. Further, at high surface speeds, craters were formed due to carbon diffusing to the tool surface and being carried away by the rubbing action of the chips -- this left behind a smooth crater surface predominantly of tungsten and cobalt as observed from EDS analysis. Also, at high surface speeds, carbon from the tool was found diffused into the adhered titanium layer to form a titanium carbide (TiC) boundary layer -- this was observed as instances of TiC build-up on the tool edge from EDS analysis. A complex wear mechanism interaction was thus observed, i.e., titanium adhered on top of an earlier worn out crater trough, additional carbon diffused into this adhered titanium layer to create a more stable boundary layer (which could limit diffusion-rates on saturation), and then all were further worn away by dissolution wear as temperatures increased. At low and medium feeds, notch discoloration was observed -- this was detected to be carbon from EDS analysis, suggesting that it was deposited from the edges of the passing chips. Mapping the dominant wear mechanisms showed the increasing dominance of dissolution wear relative to adhesion, with increasing grain size -- this is because a 13% larger sub-micron grain results in a larger surface area of cobalt exposed to chemical action. On the macro-scale, wear quantification through topology characterization elevated wear from a 1D to 3D concept. From investigation, a second order dependence of volumetric tool wear (VTW) and VTW rate with the material removal rate (MRR) emerged, suggesting that MRR is a more consistent wear-controlling factor instead of the traditionally used cutting speed. A predictive model for VTW was developed which showed its exponential dependence with workpiece stock volume removed. Also, both VTW and VTW rate were found to be dependent on the accumulated cumulative wear on the tool. Further, a ratio metric of stock material removed to tool volume lost is now possible as a tool efficiency quantifier and energy-based productivity parameter, which was found to inversely depend on MRR - this led to a more comprehensive tool wear definition based on cutting tool efficiency. (Abstract shortened by UMI.)

Dynamic strength properties of the surface of an ultra-fine-grained aluminum alloy under conditions of high-speed erosion

NASA Astrophysics Data System (ADS)

Kazarinov, N. A.; Evstifeev, A. D.; Petrov, Yu. V.; Lashkov, V. A.

2016-05-01

The influence of severe plastic deformation on the material surface is investigated under highspeed erosion conditions. The AD1 aluminum alloy was tested with the structure changed by severe plastic torsional deformation.

Ultra-high surface speed for metal removal, artillery shell

NASA Astrophysics Data System (ADS)

Pugh, R. F.; Walsh, M. R.; Pohl, R. F.

1981-07-01

Four types of steel (AISI 1340, 4140, 4340, and HF-1) which are commonly used in large caliber projectile manufacture were machined with five types of tools at different hardness ranges representing the as-forged and the heat-treated condition. Results show that machining speeds can be increased significantly over current practice using the present available tooling.

Molecular-Based Optical Measurement Techniques for Transition and Turbulence in High-Speed Flow

NASA Technical Reports Server (NTRS)

Bathel, Brett F.; Danehy, Paul M.; Cutler, Andrew D.

2013-01-01

High-speed laminar-to-turbulent transition and turbulence affect the control of flight vehicles, the heat transfer rate to a flight vehicle's surface, the material selected to protect such vehicles from high heating loads, the ultimate weight of a flight vehicle due to the presence of thermal protection systems, the efficiency of fuel-air mixing processes in high-speed combustion applications, etc. Gaining a fundamental understanding of the physical mechanisms involved in the transition process will lead to the development of predictive capabilities that can identify transition location and its impact on parameters like surface heating. Currently, there is no general theory that can completely describe the transition-to-turbulence process. However, transition research has led to the identification of the predominant pathways by which this process occurs. For a truly physics-based model of transition to be developed, the individual stages in the paths leading to the onset of fully turbulent flow must be well understood. This requires that each pathway be computationally modeled and experimentally characterized and validated. This may also lead to the discovery of new physical pathways. This document is intended to describe molecular based measurement techniques that have been developed, addressing the needs of the high-speed transition-to-turbulence and high-speed turbulence research fields. In particular, we focus on techniques that have either been used to study high speed transition and turbulence or techniques that show promise for studying these flows. This review is not exhaustive. In addition to the probe-based techniques described in the previous paragraph, several other classes of measurement techniques that are, or could be, used to study high speed transition and turbulence are excluded from this manuscript. For example, surface measurement techniques such as pressure and temperature paint, phosphor thermography, skin friction measurements and photogrammetry (for model attitude and deformation measurement) are excluded to limit the scope of this report. Other physical probes such as heat flux gauges, total temperature probes are also excluded. We further exclude measurement techniques that require particle seeding though particle based methods may still be useful in many high speed flow applications. This manuscript details some of the more widely used molecular-based measurement techniques for studying transition and turbulence: laser-induced fluorescence (LIF), Rayleigh and Raman Scattering and coherent anti-Stokes Raman scattering (CARS). These techniques are emphasized, in part, because of the prior experience of the authors. Additional molecular based techniques are described, albeit in less detail. Where possible, an effort is made to compare the relative advantages and disadvantages of the various measurement techniques, although these comparisons can be subjective views of the authors. Finally, the manuscript concludes by evaluating the different measurement techniques in view of the precision requirements described in this chapter. Additional requirements and considerations are discussed to assist with choosing an optical measurement technique for a given application.

The Influence of Spatial Resolutions on the Retrieval Accuracy of Sea Surface Wind Speed with Cross-polarized C-band SAR images

NASA Astrophysics Data System (ADS)

Zhang, K.; Han, B.; Mansaray, L. R.; Xu, X.; Guo, Q.; Jingfeng, H.

2017-12-01

Synthetic aperture radar (SAR) instruments on board satellites are valuable for high-resolution wind field mapping, especially for coastal studies. Since the launch of Sentinel-1A on April 3, 2014, followed by Sentinel-1B on April 25, 2016, large amount of C-band SAR data have been added to a growing accumulation of SAR datasets (ERS-1/2, RADARSAT-1/2, ENVISAT). These new developments are of great significance for a wide range of applications in coastal sea areas, especially for high spatial resolution wind resource assessment, in which the accuracy of retrieved wind fields is extremely crucial. Recently, it is reported that wind speeds can also be retrieved from C-band cross-polarized SAR images, which is an important complement to wind speed retrieval from co-polarization. However, there is no consensus on the optimal resolution for wind speed retrieval from cross-polarized SAR images. This paper presents a comparison strategy for investigating the influence of spatial resolutions on sea surface wind speed retrieval accuracy with cross-polarized SAR images. Firstly, for wind speeds retrieved from VV-polarized images, the optimal geophysical C-band model (CMOD) function was selected among four CMOD functions. Secondly, the most suitable C-band cross-polarized ocean (C-2PO) model was selected between two C-2POs for the VH-polarized image dataset. Then, the VH-wind speeds retrieved by the selected C-2PO were compared with the VV-polarized sea surface wind speeds retrieved using the optimal CMOD, which served as reference, at different spatial resolutions. Results show that the VH-polarized wind speed retrieval accuracy increases rapidly with the decrease in spatial resolutions from 100 m to 1000 m, with a drop in RMSE of 42%. However, the improvement in wind speed retrieval accuracy levels off with spatial resolutions decreasing from 1000 m to 5000 m. This demonstrates that the pixel spacing of 1 km may be the compromising choice for the tradeoff between the spatial resolution and wind speed retrieval accuracy with cross-polarized images obtained from RADASAT-2 fine quad polarization mode. Figs. 1 illustrate the variation of the following statistical parameters: Bias, Corr, R2, RMSE and STD as a function of spatial resolution.

Effect of parameters on picosecond laser ablation of Cr12MoV cold work mold steel

NASA Astrophysics Data System (ADS)

Wu, Baoye; Liu, Peng; Zhang, Fei; Duan, Jun; Wang, Xizhao; Zeng, Xiaoyan

2018-01-01

Cr12MoV cold work mold steel, which is a difficult-to-machining material, is widely used in the mold and dye industry. A picosecond pulse Nd:YVO4 laser at 1064 nm was used to conduct the study. Effects of operation parameters (i.e., laser fluence, scanning speed, hatched space and number of scans) were studied on ablation depth and quality of Cr12MoV at the repetition rate of 20 MHz. The experimental results reveal that all the four parameters affect the ablation depth significantly. While the surface roughness depends mainly on laser fluence or scanning speed and secondarily on hatched space or number of scans. For laser fluence and scanning speed, three distinct surface morphologies were observed experiencing transition from flat (Ra < 1.40 μm) to bumpy (Ra = 1.40 - 2.40 μm) eventually to rough (Ra > 2.40 μm). However, for hatched space and number of scan, there is a small bumpy and rough zone or even no rough zone. Mechanisms including heat accumulation, plasma shielding and combustion reaction effects are proposed based on the ablation depth and processing morphology. By appropriate management of the laser fluence and scanning speed, high ablation depth with low surface roughness can be obtained at small hatched space and high number of scans.

In-Roll Stress Analysis Considering Air-Entrainment at the Roll-Inlet with the Effect of Grooves on Nip Roll Surface

NASA Astrophysics Data System (ADS)

Sasaki, Masashi; Tanimoto, Koshi; Kohno, Kazukiyo; Takahashi, Sadamu; Kometani, Hideo; Hashimoto, Hiromu

High-speed winding of paper web sometimes leads the winding system into unstable states, interlayer slippage of wound roll, paper breakage and so on, due to the excessive air-entrainment at the roll-inlet of nip contact region. These phenomena are more frequently observed on coated paper or plastic film comparing with newspaper, because the former allows little permeation of air and their surface roughness is small. Therefore, it is of vital importance to clarify the in-roll stress of wound roll considering the effect of air-entrainment. Generally, it is known that the amount of air-entrainment is affected by grooving shape of nip roll surface. In this paper, we focused on the grooving shape and investigated the relationship with the air-entrainment into two rolls being pressed each other and the grooving shape in order to achieve stable winding at high speed. We conducted experiments using small sized test machine. Entrained air-film thickness was evaluated applying the solution of the elasto-hydrodynamic lubrication for foil bearing with the consideration of nip profile at the grooved area. Air film thickness was measured to ensure the applicability of the above theory. Consequently, we found that the air film thickness can be estimated considering the effect of grooves on the nip roll surface, and that the validity of the above estimations was ensured from experimental investigations. Furthermore, it became to be able to propose the optimal shape of grooves on nip roll surface to maintain the stable winding at high speed and at large-diameter in reel.

Characterization of perovskite layer on various nanostructured silicon wafer

NASA Astrophysics Data System (ADS)

Rostan, Nur Fairuz Mohd; Sepeai, Suhaila; Ramli, Noor Fadhilah; Azhari, Ayu Wazira; Ludin, Norasikin Ahmad; Teridi, Mohd Asri Mat; Ibrahim, Mohd Adib; Zaidi, Saleem H.

2017-05-01

Crystalline silicon (c-Si) solar cell dominates 90% of photovoltaic (PV) market. The c-Si is the most mature of all PV technologies and expected to remain leading the PV technology by 2050. The attractive characters of Si solar cell are stability, long lasting and higher lifetime. Presently, the efficiency of c-Si solar cell is still stuck at 25% for one and half decades. Tandem approach is one of the attempts to improve the Si solar cell efficiency with higher bandgap layer is stacked on top of Si bottom cell. Perovskite offers a big potential to be inserted into a tandem solar cell. Perovskite with bandgap of 1.6 to 1.9 eV will be able to absorb high energy photons, meanwhile c-Si with bandgap of 1.124 eV will absorb low energy photons. The high carrier mobility, high carrier lifetime, highly compatible with both solution and evaporation techniques makes perovskite an eligible candidate for perovskite-Si tandem configuration. The solution of methyl ammonium lead iodide (MAPbI3) was prepared by single step precursor process. The perovskite layer was deposited on different c-Si surface structure, namely planar, textured and Si nanowires (SiNWs) by using spin-coating technique at different rotation speeds. The nanostructure of Si surface was textured using alkaline based wet chemical etching process and SiNW was grown using metal assisted etching technique. The detailed surface morphology and absorbance of perovskite were studied in this paper. The results show that the thicknesses of MAPbI3 were reduced with the increasing of rotation speed. In addition, the perovskite layer deposited on the nanostructured Si wafer became rougher as the etching time and rotation speed increased. The average surface roughness increased from ˜24 nm to ˜38 nm for etching time range between 5-60 min at constant low rotation speed (2000 rpm) for SiNWs Si wafer.

Resistive method for measuring the disintegration speed of Prince Rupert's drops

NASA Astrophysics Data System (ADS)

Bochkov, Mark; Gusenkova, Daria; Glushkov, Evgenii; Zotova, Julia; Zhabin, S. N.

2016-09-01

We have successfully applied the resistance grid technique to measure the disintegration speed in a special type of glass objects, widely known as Prince Rupert's drops. We use a fast digital oscilloscope and a simple electrical circuit, glued to the surface of the drops, to detect the voltage changes, corresponding to the breaks in the specific parts of the drops. The results obtained using this method are in good qualitative and quantitative agreement with theoretical predictions and previously published data. Moreover, the proposed experimental setup does not include any expensive equipment (such as a high-speed camera) and can therefore be widely used in high schools and universities.

Improvement of adhesion properties of low density polyethylene (LDPE) substrate using atmospheric plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanchez-Nacher, L.; Garcia-Sanoguera, D.; Fenollar, O.

2010-06-02

In this work we have used atmospheric plasma technology on polyethylene surface with different treatment conditions. These modify surface pre-treatments on polyethylene, thus having a positive effect on overall surface activity of polymer surface and, consequently, adhesion properties can be remarkably improved. We have evaluated the influence of the nozzle/substrate distance and atmospheric plasma speed on wettability changes and adhesion properties. Wettability changes have been studied by contact angle measurements and subsequent surface energy calculation. Mechanical characterization of adhesion joints has been carried out in two different ways: peel and shear tensile test. The overall results show a remarkable increasemore » in mechanical properties of adhesion joints for low nozzle/substrate distances and low speed. So plasma atmospheric technology is highly useful to increase adhesion properties of polypropylene.« less

Machining approach of freeform optics on infrared materials via ultra-precision turning.

PubMed

Li, Zexiao; Fang, Fengzhou; Chen, Jinjin; Zhang, Xiaodong

2017-02-06

Optical freeform surfaces are of great advantage in excellent optical performance and integrated alignment features. It has wide applications in illumination, imaging and non-imaging, etc. Machining freeform surfaces on infrared (IR) materials with ultra-precision finish is difficult due to its brittle nature. Fast tool servo (FTS) assisted diamond turning is a powerful technique for the realization of freeform optics on brittle materials due to its features of high spindle speed and high cutting speed. However it has difficulties with large slope angles and large rise-and-falls in the sagittal direction. In order to overcome this defect, the balance of the machining quality on the freeform surface and the brittle nature in IR materials should be realized. This paper presents the design of a near-rotational freeform surface (NRFS) with a low non-rotational degree (NRD) to constraint the variation of traditional freeform optics to solve this issue. In NRFS, the separation of the surface results in a rotational part and a residual part denoted as a non-rotational surface (NRS). Machining NRFS on germanium is operated by FTS diamond turning. Characteristics of the surface indicate that the optical finish of the freeform surface has been achieved. The modulation transfer function (MTF) of the freeform optics shows a good agreement to the design expectation. Images of the final optical system confirm that the fabricating strategy is of high efficiency and high quality. Challenges and prospects are discussed to provide guidance of future work.

Tribology of thin wetting films between bubble and moving solid surface.

PubMed

Karakashev, Stoyan I; Stöckelhuber, Klaus W; Tsekov, Roumen; Phan, Chi M; Heinrich, Gert

2014-08-01

This work shows a successful example of coupling of theory and experiment to study the tribology of bubble rubbing on solid surface. Such kind of investigation is reported for the first time in the literature. A theory about wetting film intercalated between bubble and moving solid surface was developed, thus deriving the non-linear evolution differential equation which accounted for the friction slip coefficient at the solid surface. The stationary 3D film thickness profile, which appears to be a solution of the differential equation, for each particular speed of motion of the solid surface was derived by means of special procedure and unique interferometric experimental setup. This allowed us to determine the 3D map of the lift pressure within the wetting film, the friction force per unit area and the friction coefficient of rubbing at different speeds of motion of the solid surface. Thus, we observed interesting tribological details about the rubbing of the bubble on the solid surface like for example: 1. A regime of mixed friction between dry and lubricated friction exists in the range of 6-170 μm/s, beyond which the rubbing between the bubble and solid becomes completely lubricated and passes through the maximum; 2. The friction coefficient of rubbing has high values at very small speeds of solid's motion and reduces substantially with the increase of the speed of the solid motion until reaching small values, which change insignificantly with the further increase of the speed of the solid. Despite the numerous studies on the motion of bubble/droplet in close proximity to solid wall in the literature, the present investigation appears to be a step ahead in this area as far as we were able to derive 3D maps of the bubble close to the solid surface, which makes the investigation more profound. © 2013.

Fabrication of wear-resistant silicon microprobe tips for high-speed surface roughness scanning devices

NASA Astrophysics Data System (ADS)

Wasisto, Hutomo Suryo; Yu, Feng; Doering, Lutz; Völlmeke, Stefan; Brand, Uwe; Bakin, Andrey; Waag, Andreas; Peiner, Erwin

2015-05-01

Silicon microprobe tips are fabricated and integrated with piezoresistive cantilever sensors for high-speed surface roughness scanning systems. The fabrication steps of the high-aspect-ratio silicon microprobe tips were started with photolithography and wet etching of potassium hydroxide (KOH) resulting in crystal-dependent micropyramids. Subsequently, thin conformal wear-resistant layer coating of aluminum oxide (Al2O3) was demonstrated on the backside of the piezoresistive cantilever free end using atomic layer deposition (ALD) method in a binary reaction sequence with a low thermal process and precursors of trimethyl aluminum and water. The deposited Al2O3 layer had a thickness of 14 nm. The captured atomic force microscopy (AFM) image exhibits a root mean square deviation of 0.65 nm confirming the deposited Al2O3 surface quality. Furthermore, vacuum-evaporated 30-nm/200-nm-thick Au/Cr layers were patterned by lift-off and served as an etch mask for Al2O3 wet etching and in ICP cryogenic dry etching. By using SF6/O2 plasma during inductively coupled plasma (ICP) cryogenic dry etching, micropillar tips were obtained. From the preliminary friction and wear data, the developed silicon cantilever sensor has been successfully used in 100 fast measurements of 5- mm-long standard artifact surface with a speed of 15 mm/s and forces of 60-100 μN. Moreover, the results yielded by the fabricated silicon cantilever sensor are in very good agreement with those of calibrated profilometer. These tactile sensors are targeted for use in high-aspect-ratio microform metrology.

Characterization of dynamic droplet impaction and deposit formation on leaf surfaces

USDA-ARS?s Scientific Manuscript database

Elucidation of droplet dynamic impaction and deposition formation on leaf surfaces would assist to optimize application strategies, improve biological control efficiency, and minimize pesticide waste. A custom-designed system consisting of two high-speed digital cameras and a uniform-size droplet ge...

Thermal behavior in single track during selective laser melting of AlSi10Mg powder

NASA Astrophysics Data System (ADS)

Wei, Pei; Wei, Zhengying; Chen, Zhen; He, Yuyang; Du, Jun

2017-09-01

A three-dimensional model was developed to simulate the radiation heat transfer in the AlSi10Mg packed bed. The volume of fluid method (VOF) was used to capture the free surface during selective laser melting (SLM). A randomly packed powder bed was obtained using discrete element method (DEM) in Particle Flow Code (PFC). The proposed model has demonstrated a high potential to simulate the selective laser melting process (SLM) with high accuracy. In this paper, the effect of the laser scanning speed and laser power on the thermodynamic behavior of the molten pool was investigated numerically. The results show that the temperature gradient and the resultant surface tension gradient between the center and the edge of the molten pool increase with decreasing the scanning speed or increasing the laser power, thereby intensifying the Marangoni flow and attendant turbulence within the molten pool. However, at a relatively high scanning speed, a significant instability may be generated in the molten pool. The perturbation and instability in the molten pool during SLM may result in an irregular shaped track.

Investigation on the Effect of a Pre-Center Drill Hole and Tool Material on Thrust Force, Surface Roughness, and Cylindricity in the Drilling of Al7075.

PubMed

Ghasemi, Amir Hossein; Khorasani, Amir Mahyar; Gibson, Ian

2018-01-16

Drilling is one of the most useful metal cutting processes and is used in various applications, such as aerospace, electronics, and automotive. In traditional drilling methods, the thrust force, torque, tolerance, and tribology (surface roughness) are related to the cutting condition and tool geometry. In this paper, the effects of a pre-center drill hole, tool material, and drilling strategy (including continuous and non-continuous feed) on thrust force, surface roughness, and dimensional accuracy (cylindricity) have been investigated. The results show that using pre-center drill holes leads to a reduction of the engagement force and an improvement in the surface quality and cylindricity. Non-continuous drilling reduces the average thrust force and cylindricity value, and High Speed Steels HSS-Mo (high steel speed + 5-8% Mo) reduces the maximum quantity of cutting forces. Moreover, cylindricity is directly related to cutting temperature and is improved by using a non-continuous drilling strategy.

Investigation on the Effect of a Pre-Center Drill Hole and Tool Material on Thrust Force, Surface Roughness, and Cylindricity in the Drilling of Al7075

PubMed Central

Ghasemi, Amir Hossein; Khorasani, Amir Mahyar

2018-01-01

Drilling is one of the most useful metal cutting processes and is used in various applications, such as aerospace, electronics, and automotive. In traditional drilling methods, the thrust force, torque, tolerance, and tribology (surface roughness) are related to the cutting condition and tool geometry. In this paper, the effects of a pre-center drill hole, tool material, and drilling strategy (including continuous and non-continuous feed) on thrust force, surface roughness, and dimensional accuracy (cylindricity) have been investigated. The results show that using pre-center drill holes leads to a reduction of the engagement force and an improvement in the surface quality and cylindricity. Non-continuous drilling reduces the average thrust force and cylindricity value, and High Speed Steels HSS-Mo (high steel speed + 5–8% Mo) reduces the maximum quantity of cutting forces. Moreover, cylindricity is directly related to cutting temperature and is improved by using a non-continuous drilling strategy. PMID:29337858

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

NASA Technical Reports Server (NTRS)

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high speed flow fields.

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

NASA Technical Reports Server (NTRS)

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high-speed flowfields.

Explosive-driven, high speed, arcless switch

DOEpatents

Skogmo, P.J.; Tucker, T.J.

1987-07-14

An explosive-actuated, fast-acting arcless switch contains a highly conductive foil to carry high currents positioned adjacent a dielectric surface within a casing. At one side of the foil opposite the dielectric surface is an explosive which, when detonated, drives the conductive foil against the dielectric surface. A pattern of grooves in the dielectric surface ruptures the foil to establish a rupture path having a pattern corresponding to the pattern of the grooves. The impedance of the ruptured foil is greater than that of the original foil to divert high current to a load. Planar and cylindrical embodiments of the switch are disclosed. 7 figs.

A low-cost, high-efficiency and high-flexibility surface modification technology for a black bisphenol A polycarbonate board

NASA Astrophysics Data System (ADS)

Wang, Suhuan; Liu, Jianguo; Lv, Ming; Zeng, Xiaoyan

2014-09-01

In this paper, a low-cost, high-efficiency and high-flexibility surface modification technology for polymer materials was achieved at high laser scanning speeds (600-1000 mm s-1) and using an all-solid state, Q-switched, high-average power, and nanosecond pulse ultraviolet (355 nm wavelength) laser. During the surface modification of a very important engineering plastic, i.e., black bisphenol A polycarbonate (BAPC) board, it was found that different laser parameters (e.g., laser fluence and pulse frequency) were able to result in different surface microstructures (e.g., many tiny protuberances or a porous microstructure with periodical V-type grooves). After the modification, although the total relative content of the oxygen-containing groups (e.g., Csbnd O and COO-) on the BAPC surface increased, however, the special microstructures played a deciding role in the surface properties (e.g., contact angle and surface energy) of the BAPC. The change trend of the water contact angle on the BAPC surface was with an obvious increase, that of the diiodomethane contact angle was with a most decrease, and that of the ethylene glycol contact angle was between the above two. It showed that the wetting properties of the three liquids on the modified BAPC surface were different. Basing on the measurements of the contact angles of the three liquids, and according to the Young equation and the Lifshitz van der Waals and Lewis acid-base theory, the BAPC surface energy after the modification was calculated. The results were that, in a broad range of laser fluences, pulse frequencies and scanning speeds, the surface energy had a significant increase (e.g., from the original of about 44 mJ m-2 to the maximum of about 70 mJ m-2), and the higher the laser pulse frequency, the more significant the increase. This would be very advantageous to fabricate the high-quality micro-devices and micro-systems on the modified surface.

Inferring the high-pressure strength of copper by measurement of longitudinal sound speed in a symmetric impact and release experiment

NASA Astrophysics Data System (ADS)

Rothman, Stephen; Edwards, Rhys; Vogler, Tracy J.; Furnish, M. D.

2012-03-01

Velocity-time histories of free- or windowed-surfaces have been used to calculate wave speeds and hence deduce the shear moduli for materials at high pressure. This is important to high velocity impact phenomena, e.g. shaped-charge jets, long rod penetrators, and other projectile/armour interactions. Historically the shock overtake method has required several experiments with different depths of material to account for the effect of the surface on the arrival time of the release. A characteristics method, previously used for analysis of isentropic compression experiments, has been modified to account for the effect of the surface interactions, thus only one depth of material is required. This analysis has been applied to symmetric copper impacts performed at Sandia National Laboratory's Star Facility. A shear modulus of 200GPa, at a pressure of ~180GPa, has been estimated. These results are in broad agreement with previous work by Hayes et al.

Inferring the High-Pressure Strength of Copper by Measurement of Longitudinal Sound Speed in a Symmetric Impact and Release Experiment

NASA Astrophysics Data System (ADS)

Rothman, Stephen; Edwards, Rhys; Vogler, Tracy; Furnish, Mike

2011-06-01

Velocity-time histories of free- or windowed-surfaces have been used to calculate wave speeds and hence deduce the shear modulus for materials at high pressure. This is important to high velocity impact phenomena, e.g. shaped-charge jets, long rod penetrators, and other projectile/armour interactions. Historically the shock overtake method has required several experiments with different depths of material to account for the effect of the surface on the arrival time of the release. A characteristics method, previously used for analysis of isentropic compression experiments, has been modified to account for the effect of the surface interactions, thus only one depth of material is required. This analysis has been applied to symmetric copper impacts performed at Sandia National Laboratory's Star Facility. A shear modulus of 200Gpa, at a pressure of ~180GPa, has been estimated. These results are in broad agreement with previous work by Hayes et al.

High-frequency pressure variations in the vicinity of a surface CO2 flux chamber

Treesearch

Eugene S. Takle; James R. Brandle; R. A. Schmidt; Rick Garcia; Irina V. Litvina; William J. Massman; Xinhua Zhou; Geoffrey Doyle; Charles W. Rice

2003-01-01

We report measurements of 2Hz pressure fluctuations at and below the soil surface in the vicinity of a surface-based CO2 flux chamber. These measurements were part of a field experiment to examine the possible role of pressure pumping due to atmospheric pressure fluctuations on measurements of surface fluxes of CO2. Under the moderate wind speeds, warm temperatures,...

Technology of high-speed combined machining with brush electrode

NASA Astrophysics Data System (ADS)

Kirillov, O. N.; Smolentsev, V. P.; Yukhnevich, S. S.

2018-03-01

The new method was proposed for high-precision dimensional machining with a brush electrode when the true position of bundles of metal wire is adjusted by means of creating controlled centrifugal forces appeared due to the increased frequency of rotation of a tool. There are the ultimate values of circumferential velocity at which the bundles are pressed against a machined area of a workpiece in a stable manner despite the profile of the machined surface and variable stock of the workpiece. The special aspects of design of processing procedures for finishing standard parts, including components of products with low rigidity, are disclosed. The methodology of calculation and selection of processing modes which allow one to produce high-precision details and to provide corresponding surface roughness required to perform finishing operations (including the preparation of a surface for metal deposition) is presented. The production experience concerned with the use of high-speed combined machining with an unshaped tool electrode in knowledge-intensive branches of the machine-building industry for different types of production is analyzed. It is shown that the implementation of high-speed dimensional machining with an unshaped brush electrode allows one to expand the field of use of the considered process due to the application of a multipurpose tool in the form of a metal brush, as well as to obtain stable results of finishing and to provide the opportunities for long-term operation of the equipment without its changeover and readjustment.

Comparison of high-speed rail and maglev systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Najafi, F.T.; Nassar, F.E.

1996-07-01

European and Japanese high-speed rail (HSR) and magnetically levitated (maglev) systems were each developed to respond to specific transportation needs within local economic, social, and political constraints. Not only is maglev technology substantially different from that of HSR, but also HSR and maglev systems differ in trainset design, track characteristics, cost structure, and cost sensitivity to design changes. This paper attempts to go beyond the traditional technology comparison table and focuses on the characteristics and conditions for which existing European and Japanese systems were developed. The technologies considered are the French train a grand vitesse (TGV), the Swedish X2000, themore » German Intercity Express (ICE) and Transrapid, and the Japanese Shinkansen, MLU, and high-speed surface train (HSST).« less

Study of plastic strain localization mechanisms caused by nonequilibrium transitions in mesodefect ensembles under high-speed loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sokovikov, Mikhail, E-mail: sokovikov@icmm.ru; Chudinov, Vasiliy; Bilalov, Dmitry

2015-10-27

The behavior of specimens dynamically loaded during split Hopkinson (Kolsky) bar tests in a regime close to simple shear conditions was studied. The lateral surface of the specimens was investigated in-situ using a high-speed infrared camera CEDIP Silver 450M. The temperature field distribution obtained at different time allowed one to trace the evolution of plastic strain localization. The process of target perforation involving plug formation and ejection was examined using a high-speed infrared camera and a VISAR velocity measurement system. The microstructure of tested specimens was analyzed using an optical interferometer-profiler and a scanning electron microscope. The development of plasticmore » shear instability regions has been simulated numerically.« less

Bag-breakup control of surface drag in hurricanes

NASA Astrophysics Data System (ADS)

Troitskaya, Yuliya; Zilitinkevich, Sergej; Kandaurov, Alexander; Ermakova, Olga; Kozlov, Dmitry; Sergeev, Daniil

2016-04-01

Air-sea interaction at extreme winds is of special interest now in connection with the problem of the sea surface drag reduction at the wind speed exceeding 30-35 m/s. This phenomenon predicted by Emanuel (1995) and confirmed by a number of field (e.g., Powell, et al, 2003) and laboratory (Donelan et al, 2004) experiments still waits its physical explanation. Several papers attributed the drag reduction to spume droplets - spray turning off the crests of breaking waves (e.g., Kudryavtsev, Makin, 2011, Bao, et al, 2011). The fluxes associated with the spray are determined by the rate of droplet production at the surface quantified by the sea spray generation function (SSGF), defined as the number of spray particles of radius r produced from the unit area of water surface in unit time. However, the mechanism of spume droplets' formation is unknown and empirical estimates of SSGF varied over six orders of magnitude; therefore, the production rate of large sea spray droplets is not adequately described and there are significant uncertainties in estimations of exchange processes in hurricanes. Herewith, it is unknown what is air-sea interface and how water is fragmented to spray at hurricane wind. Using high-speed video, we observed mechanisms of production of spume droplets at strong winds by high-speed video filming, investigated statistics and compared their efficiency. Experiments showed, that the generation of the spume droplets near the wave crest is caused by the following events: bursting of submerged bubbles, generation and breakup of "projections" and "bag breakup". Statistical analysis of results of these experiments showed that the main mechanism of spray-generation is attributed to "bag-breakup mechanism", namely, inflating and consequent blowing of short-lived, sail-like pieces of the water-surface film. Using high-speed video, we show that at hurricane winds the main mechanism of spray production is attributed to "bag-breakup", namely, inflating and consequent breaking of short-lived, sail-like pieces of the water-surface film - "bags". On the base of general principles of statistical physics (model of a canonical ensemble) we developed statistics of the "bag-breakup" events: their number and statistical distribution of geometrical parameters depending on wind speed. Basing on the developed statistics, we estimated the surface stress caused by bags as the average sum of stresses caused by individual bags depending on their eometrical parameters. The resulting stress is subjected to counteracting impacts of the increasing wind speed: the increasing number of bags, and their decreasing sizes and life times and the balance yields a peaking dependence of the bag resistance on the wind speed: the share of bag-stress peaks at U10  35 m/s and then reduces. Peaking of surface stress associated with the "bag-breakup" explains seemingly paradoxical non-monotonous wind-dependence of surface drag coefficient peaking at winds about 35 m/s. This work was supported by the Russian Foundation of Basic Research (14-05-91767, 13-05-12093, 16-05-00839, 14-05-91767, 16-55-52025, 15-35-20953) and experiment and equipment was supported by Russian Science Foundation (Agreements 14-17-00667 and 15-17-20009 respectively), Yu.Troitskaya, A.Kandaurov and D.Sergeev were partially supported by FP7 Collaborative Project No. 612610.

High-intensity focused ultrasound ablation around the tubing

PubMed Central

Siu, Jun Yang; Liu, Chenhui

2017-01-01

High-intensity focused ultrasound (HIFU) has been emerging as an effective and noninvasive modality in cancer treatment with very promising clinical results. However, a small vessel in the focal region could be ruptured, which is an important concern for the safety of HIFU ablation. In this study, lesion formation in the polyacrylamide gel phantom embedded with different tubing (inner diameters of 0.76 mm and 3 mm) at varied flow speeds (17–339 cm/s) by HIFU ablation was photographically recorded. Produced lesions have decreased length (~30%) but slightly increased width (~6%) in comparison to that without the embedded tubing. Meanwhile, bubble activities during the exposures were measured by passive cavitation detection (PCD) at the varied pulse repetition frequency (PRF, 10–30 Hz) and duty cycle (DC, 10%-20%) of the HIFU bursts. High DC and low flow speed were found to produce stronger bubble cavitation whereas no significant influence of the PRF. In addition, high-speed photography illustrated that the rupture of tubing was produced consistently after the first HIFU burst within 20 ms and then multiple bubbles would penetrate into the intraluminal space of tubing through the rupture site by the acoustic radiation force. Alignment of HIFU focus to the anterior surface, middle, and posterior surface of tubing led to different characteristics of vessel rupture and bubble introduction. In summary, HIFU-induced vessel rupture is possible as shown in this phantom study; produced lesion sizes and shapes are dependent on the focus alignment to the tubing, flow speed, and tubing properties; and bubble cavitation and the formation liquid jet may be one of the major mechanisms of tubing rupture as shown in the high-speed photography. PMID:29161293

High-intensity focused ultrasound ablation around the tubing.

PubMed

Siu, Jun Yang; Liu, Chenhui; Zhou, Yufeng

2017-01-01

High-intensity focused ultrasound (HIFU) has been emerging as an effective and noninvasive modality in cancer treatment with very promising clinical results. However, a small vessel in the focal region could be ruptured, which is an important concern for the safety of HIFU ablation. In this study, lesion formation in the polyacrylamide gel phantom embedded with different tubing (inner diameters of 0.76 mm and 3 mm) at varied flow speeds (17-339 cm/s) by HIFU ablation was photographically recorded. Produced lesions have decreased length (~30%) but slightly increased width (~6%) in comparison to that without the embedded tubing. Meanwhile, bubble activities during the exposures were measured by passive cavitation detection (PCD) at the varied pulse repetition frequency (PRF, 10-30 Hz) and duty cycle (DC, 10%-20%) of the HIFU bursts. High DC and low flow speed were found to produce stronger bubble cavitation whereas no significant influence of the PRF. In addition, high-speed photography illustrated that the rupture of tubing was produced consistently after the first HIFU burst within 20 ms and then multiple bubbles would penetrate into the intraluminal space of tubing through the rupture site by the acoustic radiation force. Alignment of HIFU focus to the anterior surface, middle, and posterior surface of tubing led to different characteristics of vessel rupture and bubble introduction. In summary, HIFU-induced vessel rupture is possible as shown in this phantom study; produced lesion sizes and shapes are dependent on the focus alignment to the tubing, flow speed, and tubing properties; and bubble cavitation and the formation liquid jet may be one of the major mechanisms of tubing rupture as shown in the high-speed photography.

Evaluation of the WRF-Urban Modeling System Coupled to Noah and Noah-MP Land Surface Models Over a Semiarid Urban Environment

NASA Astrophysics Data System (ADS)

Salamanca, Francisco; Zhang, Yizhou; Barlage, Michael; Chen, Fei; Mahalov, Alex; Miao, Shiguang

2018-03-01

We have augmented the existing capabilities of the integrated Weather Research and Forecasting (WRF)-urban modeling system by coupling three urban canopy models (UCMs) available in the WRF model with the new community Noah with multiparameterization options (Noah-MP) land surface model (LSM). The WRF-urban modeling system's performance has been evaluated by conducting six numerical experiments at high spatial resolution (1 km horizontal grid spacing) during a 15 day clear-sky summertime period for a semiarid urban environment. To assess the relative importance of representing urban surfaces, three different urban parameterizations are used with the Noah and Noah-MP LSMs, respectively, over the two major cities of Arizona: Phoenix and Tucson metropolitan areas. Our results demonstrate that Noah-MP reproduces somewhat better than Noah the daily evolution of surface skin temperature and near-surface air temperature (especially nighttime temperature) and wind speed. Concerning the urban areas, bulk urban parameterization overestimates nighttime 2 m air temperature compared to the single-layer and multilayer UCMs that reproduce more accurately the daily evolution of near-surface air temperature. Regarding near-surface wind speed, only the multilayer UCM was able to reproduce realistically the daily evolution of wind speed, although maximum winds were slightly overestimated, while both the single-layer and bulk urban parameterizations overestimated wind speed considerably. Based on these results, this paper demonstrates that the new community Noah-MP LSM coupled to an UCM is a promising physics-based predictive modeling tool for urban applications.

Study of surface topography, roughness, and microleakage after dental preparation with different instrumentation.

PubMed

Solá-Ruiz, Ma Fernanda; Faus-Matoses, Ignacio; Del Rio Highsmith, Jamie; Fons-Font, Antonio

2014-01-01

The purpose of this study was to compare the differences in surface characteristics and roughness of teeth finished for porcelain veneer laminates using different instrumentation and to assess their influence on microleakage. Fifty-six extracted human maxillary central incisors were divided randomly into two groups: Group HsR teeth were finished with a high-speed handpiece with diamond burs; group SO teeth were finished with a sonic oscillating diamond instrument. Porcelain veneers were bonded to 24 teeth in each group. Microleakage was measured in the cervical area. Four remaining teeth in each group were examined using confocal laser-scanning microscopy and scanning electron microscopy. Oscillating instruments produced a rougher dentinal surface (Ra values; P = .029) than those finished with high-speed rotary technology. There is less microleakage when bonded restoration edges are situated over dentin that has been finished with sonic oscillating instrumentation (P = .006).

Coaxial atomization of a round liquid jet in a high speed gas stream: A phenomenological study

NASA Astrophysics Data System (ADS)

Mayer, W. O. H.

1994-05-01

Coaxial injectors have proven to be advantageous for the injection, atomization and mixing of propellants in cryogenic H2/O2 rocket engines. Thereby, a round liquid oxygen jet is atomized by a fast, coaxial gaseous hydrogen jet. This article summarizes phenomenological studies of coaxial spray generation under a broad variation of influencing parameters including injector design, inflow, and fluid conditions. The experimental investigations, performed using spark light photography and high speed cinematography in a shadow graph setup as main diagnostic means, illuminate the most important processes leading to atomization. These are identified as turbulence in the liquid jet, surface instability, surface wave growth and droplet detachment. Numerical simulations including free surface flow phenomena are a further diagnostic tool to elucidate some atomization particulars. The results of the study are of general importance in the field of liquid atomization.

Imaging laser radar for high-speed monitoring of the environment

NASA Astrophysics Data System (ADS)

Froehlich, Christoph; Mettenleiter, M.; Haertl, F.

1998-01-01

In order to establish mobile robot operations and to realize survey and inspection tasks, robust and precise measurements of the geometry of the 3D environment is the basis sensor technology. For visual inspection, surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent range and reflectance images. The laser radar developed at Zoller + Froehlich (ZF) is an optical-wavelength system measuring the range between sensor and target surface as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to other range sensing devices, the ZF system is designed for high-speed and high- performance operation in real indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a single-point laser measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports details of the laser radar which is designed to cover requirements with medium range applications. It outlines the performance requirements and introduces the two-frequency phase-shift measurement principle. The hardware design of the single-point laser measurement system, including the main modulates, such as the laser head, the high frequency unit and the signal processing unit are discussed in detail. The paper focuses on performance data of the laser radar, including noise, drift over time, precision, and accuracy with measurements. It discusses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of tunnels, buildings, monuments and industrial environments are presented. The paper concludes by summarizing results and gives a short outlook to future work.

850-nm Zn-diffusion vertical-cavity surface-emitting lasers with with oxide-relief structure for high-speed and energy-efficient optical interconnects from very-short to medium (2km) reaches

NASA Astrophysics Data System (ADS)

Shi, Jin-Wei; Wei, Chia-Chien; Chen, Jason (Jyehong); Yang, Ying-Jay

2015-03-01

High-speed and "green" ~850 nm vertical-cavity surface-emitting lasers (VCSELs) have lately attracted lots of attention due to their suitability for applications in optical interconnects (OIs). To further enhance the speed and its maximum allowable linking distance of VCSELs are two major trends to meet the requirement of OI in next generation data centers. Recently, by use of the advanced 850 nm VCSEL technique, data rate as high as 64 Gbit/sec over 57m and 20 Gbit/sec over 2km MMF transmission have been demonstrated, respectively. Here, we will review our recent work about 850 nm Zn-diffusion VCSELs with oxide-relief apertures to further enhance the above-mentioned performances. By using Zn-diffusion, we can not only reduce the device resistance but also manipulate the number of optical modes to benefit transmission. Combing such device, which has excellent single-mode (SMSR >30 dB) and high-power (~7mW) performance, with advanced modulation format (OFDM), record-high bit-rate-distance-product through MMF (2.3 km×28 Gbit/sec) has been demonstrated. Furthermore, by selective etching away the oxide aperture inside Zn-diffusion VCSEL, significant enhancement of device speed, D-factor, and reliability can be observed. With such unique VCSEL structure, >40 Gbit/sec energy-efficient transmission over 100m MMF under extremely low-driving current density (<10kA/cm2) has been successfully demonstrated.

A high velocity impact experiment of micro-scale ice particles using laser-driven system

NASA Astrophysics Data System (ADS)

Yu, Hyeonju; Kim, Jungwook; Yoh, Jack J.

2014-11-01

A jet engine for high speed air breathing propulsion is subject to continuous wear as a result of impacts of micro-scale ice particles during a flight in the atmosphere. The inlet duct and compressor blades are exposed to on-coming frozen moisture particles that may result in the surface damage and significantly shorten the designed lifetime of the aircraft. Under such prolonged high-speed impact loading, the performance parameters such as flight instability and power loss of a jet engine can be significantly degraded. In this work, a laser-driven system was designed to accelerate micro-scale ice particles to the velocity up to Mach 2 using a Q-switched Nd:YAG laser beam at 100-600 mJ with 1064 nm wavelength and 9 ns pulse duration. The high speed images (Phantom v711) and double exposure shadowgraphs were used to calculate the average velocity of ice particles and their deceleration. Velocity Interferometer System for Any Reflector measurements were also utilized for the analysis of free surface velocity of a metal foil in order to understand the interfacial dynamics between the impacting particles and accepting metal target. The velocity of our ice particles is sufficiently fast for studying the effect of moisture particle collision on an air-breathing duct of high speed aircraft, and thus the results can provide insight into how minute space debris or micrometeorites cause damage to the orbiting spacecraft at large.

Study on Finite Element Method of Stress Field in Aluminum Alloy High-Speed Milling Process

NASA Astrophysics Data System (ADS)

Zhang, Wei; Li, Shunming; Wu, Qijun; An, Zenghui

2017-11-01

Three-dimensional numerical simulation model has been built by means of Advantage FEM. Perform simulation the stress fields of 7050-T7451 aluminum alloy in high speed milling process at the speed range of 628 m/min∼5946 m/min. The dynamic change and speed’s influence of stress fields and residual stress in machined layer is systematically analyzed. Some conclusions were drawn. With the cutting process development, the stress field converts to the stress state that crushing stress occupies a leading position. The magnitudes of crushing stress in all directions reduce with milling processes as the effect of Thermal-Mechanical-Coupled weakens; With the cutting speed increasing the magnitudes of crushing stress in all directions fluctuate near -950Mpa first, and then increase at the speed of 3000m/min; The residual pulling stress beneath the surface 0.03mm has been found and the magnitude increases with the cutting speed. A good agreement was obtained between predictions and experiments.

Evaluation of Microstructure, Mechanical Properties and Corrosion Resistance of Friction Stir-Welded Aluminum and Magnesium Dissimilar Alloys

NASA Astrophysics Data System (ADS)

Verma, Jagesvar; Taiwade, Ravindra V.; Sapate, Sanjay G.; Patil, Awanikumar P.; Dhoble, Ashwinkumar S.

2017-10-01

Microstructure, mechanical properties and corrosion resistance of dissimilar friction stir-welded aluminum and magnesium alloys were investigated by applying three different rotational speeds at two different travel speeds. Sound joints were obtained in all the conditions. The microstructure was examined by an optical and scanning electron microscope, whereas localized chemical information was studied by energy-dispersive spectroscopy. Stir zone microstructure showed mixed bands of Al and Mg with coarse and fine equiaxed grains. Grain size of stir zone reduced compared to base metals, indicated by dynamic recrystallization. More Al patches were observed in the stir zone as rotational speed increased. X-ray diffraction showed the presence of intermetallics in the stir zone. Higher tensile strength and hardness were obtained at a high rotational speed corresponding to low travel speed. Tensile fractured surface indicated brittle nature of joints. Dissimilar friction stir weld joints showed different behaviors in different corrosive environments, and better corrosion resistance was observed at a high rotational speed corresponding to low travel speed (FW3) in a sulfuric and chloride environments. Increasing travel speed did not significantly affect on microstructure, mechanical properties and corrosion resistance as much as the rotational speed.

Mapping near-surface air temperature, pressure, relative humidity and wind speed over Mainland China with high spatiotemporal resolution

NASA Astrophysics Data System (ADS)

Li, Tao; Zheng, Xiaogu; Dai, Yongjiu; Yang, Chi; Chen, Zhuoqi; Zhang, Shupeng; Wu, Guocan; Wang, Zhonglei; Huang, Chengcheng; Shen, Yan; Liao, Rongwei

2014-09-01

As part of a joint effort to construct an atmospheric forcing dataset for mainland China with high spatiotemporal resolution, a new approach is proposed to construct gridded near-surface temperature, relative humidity, wind speed and surface pressure with a resolution of 1 km×1 km. The approach comprises two steps: (1) fit a partial thin-plate smoothing spline with orography and reanalysis data as explanatory variables to ground-based observations for estimating a trend surface; (2) apply a simple kriging procedure to the residual for trend surface correction. The proposed approach is applied to observations collected at approximately 700 stations over mainland China. The generated forcing fields are compared with the corresponding components of the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis dataset and the Princeton meteorological forcing dataset. The comparison shows that, both within the station network and within the resolutions of the two gridded datasets, the interpolation errors of the proposed approach are markedly smaller than the two gridded datasets.

Optical clock distribution in supercomputers using polyimide-based waveguides

NASA Astrophysics Data System (ADS)

Bihari, Bipin; Gan, Jianhua; Wu, Linghui; Liu, Yujie; Tang, Suning; Chen, Ray T.

1999-04-01

Guided-wave optics is a promising way to deliver high-speed clock-signal in supercomputer with minimized clock-skew. Si- CMOS compatible polymer-based waveguides for optoelectronic interconnects and packaging have been fabricated and characterized. A 1-to-48 fanout optoelectronic interconnection layer (OIL) structure based on Ultradel 9120/9020 for the high-speed massive clock signal distribution for a Cray T-90 supercomputer board has been constructed. The OIL employs multimode polymeric channel waveguides in conjunction with surface-normal waveguide output coupler and 1-to-2 splitters. Surface-normal couplers can couple the optical clock signals into and out from the H-tree polyimide waveguides surface-normally, which facilitates the integration of photodetectors to convert optical-signal to electrical-signal. A 45-degree surface- normal couplers has been integrated at each output end. The measured output coupling efficiency is nearly 100 percent. The output profile from 45-degree surface-normal coupler were calculated using Fresnel approximation. the theoretical result is in good agreement with experimental result. A total insertion loss of 7.98 dB at 850 nm was measured experimentally.

Study on the Correlation Between Dynamical Behavior and Friction/Wear Mechanism Under the Effect of Grooves

NASA Astrophysics Data System (ADS)

Zhu, Z. Y.; Mo, J. L.; Wang, D. W.; Zhao, J.; Zhu, M. H.; Zhou, Z. R.

2018-04-01

In this work, the interfacial friction and wear and vibration characteristics are studied by sliding a chromium bearing steel ball (AISI 52100) over both multi-grooved and single-grooved forged steel disks (20CrMnMo) at low and high rotating speeds in order to reveal the effect mechanism of groove-textured surface on tribological behaviors. The results show that the grooves modify the contact state of the ball and the disk at the contact interface. This consequently causes variations in the normal displacement, normal force, and friction force signals. The changes in these three signals become more pronounced with increasing groove width at a low speed. The collision behavior between the ball and the groove increase the amplitude of vibration acceleration at a high speed. The test results suggest that grooves with appropriate widths could trap wear debris on the ball surface while avoiding a strong collision between the disk and the ball, resulting in an improvement in the wear states.

High-speed noncontact acoustic inspection method for civil engineering structure using multitone burst wave

NASA Astrophysics Data System (ADS)

Sugimoto, Tsuneyoshi; Sugimoto, Kazuko; Kosuge, Nobuaki; Utagawa, Noriyuki; Katakura, Kageyoshi

2017-07-01

The noncontact acoustic inspection method focuses on the resonance phenomenon, and the target surface is measured by being vibrated with an airborne sound. It is possible to detect internal defects near the surface layer of a concrete structure from a long distance. However, it requires a fairly long measurement time to achieve the signal-to-noise (S/N) ratio just to find some resonance frequencies. In our method using the conventional waveform “single-tone burst wave”, only one frequency was used for one-sound-wave emission to achieve a high S/N ratio using a laser Doppler vibrometer (LDV) at a safe low power (e.g., He-Ne 1 mW). On the other hand, in terms of the difference in propagation velocity between laser light and sound waves, the waveform that can be used for high-speed measurement was devised using plural frequencies for one-sound-wave emission (“multitone burst wave”). The measurement time at 35 measurement points has been dramatically decreased from 210 to 28 s when using this waveform. Accordingly, 7.5-fold high-speed measurement became possible. By some demonstration experiments, we confirmed the effectiveness of our measurement technique.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sibley, L.B.; Mace, A.E.; Grieser, D.R.

Various ceramic and cermet materials were evaluated for unlubricated wear resistance at high sliding speed (100 to 200 fps) and low unit load (5to 50 psi) in 1000 to 1800 deg F air. A statistical correlation was obtained between the measured wear rates under these conditions and the coefficient of friction, the thermal-stress resistance, and the thermal dlffusivity of the mated materials on which wear predominated. A mechanism of wear was evolved based on the above correlation and on the experimental study of friction and wear surface- temperature fluctuations using special transducers and color-motion-picture photography. During high-speed sliding, wear appearsmore » to be induced by the inability of ceramic and cermet materials to resist thermal stresses produced by temperature gradients within each rubbing surface between small asperities or hot spots. in frictional contact and the body of the respective materials. In this situation the wear rate is influenced both by the configuration of the rubbing pants and by the thermalstress-resistance properties of the materials. Promising materials for high-temperature high-speed sliding bearings and seals include Al/ sub 2/O/sub 3/-Cr-Mo cermets, SiC ceramics, and TiC-Ni-Mo cermets. (auth)« less

Pose measurement method and experiments for high-speed rolling targets in a wind tunnel.

PubMed

Jia, Zhenyuan; Ma, Xin; Liu, Wei; Lu, Wenbo; Li, Xiao; Chen, Ling; Wang, Zhengqu; Cui, Xiaochun

2014-12-12

High-precision wind tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-speed pose vision measurement method is proposed for high-speed and rolling targets in a supersonic wind tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-speed image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-speed targets in the laboratory and in a supersonic wind tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°.

Pose Measurement Method and Experiments for High-Speed Rolling Targets in a Wind Tunnel

PubMed Central

Jia, Zhenyuan; Ma, Xin; Liu, Wei; Lu, Wenbo; Li, Xiao; Chen, Ling; Wang, Zhengqu; Cui, Xiaochun

2014-01-01

High-precision wind tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-speed pose vision measurement method is proposed for high-speed and rolling targets in a supersonic wind tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-speed image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-speed targets in the laboratory and in a supersonic wind tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°. PMID:25615732

77 FR 5990 - Special Conditions: Learjet Inc., Model LJ-200-1A10 Airplane, Pilot-Compartment View Through...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-07

... airflow to maintain a clear-vision area. The heavy rain and high speed conditions specified in the current... to maintain a sufficiently clear area of the windshield in low-speed flight or during surface... airflow disturbance or separation on the windshield could cause failure to maintain a clear-vision area on...

High-fidelity large area nano-patterning of silicon with femtosecond light sheet

NASA Astrophysics Data System (ADS)

Sidhu, Mehra S.; Munjal, Pooja; Singh, Kamal P.

2018-01-01

We employ a femtosecond light sheet generated by a cylindrical lens to rapidly produce high-fidelity nano-structures over large area on silicon surface. The Fourier analysis of electron microscopy images of the laser-induced surface structures reveals sharp peaks indicating good homogeneity. We observed an emergence of second-order spatial periodicity on increasing the scan speed. Our reliable approach may rapidly nano-pattern curved solid surfaces and tiny objects for diverse potential applications in optical devices, structural coloring, plasmonic substrates and in high-harmonic generation.

Design and analysis of axial aspirated compressor stages

NASA Astrophysics Data System (ADS)

Merchant, Ali A.

The pressure ratio of axial compressor stages can be significantly increased by controlling the development of blade and endwall boundary layers in regions of adverse pressure gradient by means of boundary layer suction. This concept is validated and demonstrated through the design and analysis of two unique aspirated compressor stages: a low-speed stage with a design pressure ratio of 1.6 at a tip speed of 750 ft/s, and a high-speed stage with a design pressure ratio of 3.5 at a tip speed of 1500 ft/s. The aspirated compressor stages were designed using a new procedure which is a synthesis of low speed and high speed blade design techniques combined with a flexible inverse design method which enabled precise independent control over the shape of the blade suction and pressure surfaces. Integration of the boundary layer suction calculation into the overall design process is an essential ingredient of the new procedure. The blade design system consists of two axisymmetric through-flow codes coupled with a quasi three-dimensional viscous cascade plane code with inverse design capability. Validation of the completed designs were carried out with three-dimensional Euler and Navier-Stokes calculations. A single spanwise slot on the blade suction surface is used to bleed the boundary layer. The suction mass flow requirement for the low-speed and high-speed stages are 1% and 4% of the inlet mass flow, respectively. Additional suction between 1-2% is also required on the compressor endwalls near shock impingement locations. The rotor is modeled with a tip shroud to eliminate tip clearance effects and to discharge the suction flow radially from the flowpath. Three-dimensional viscous evaluation of the designs showed good agreement with the quasi three-dimensional design intent, except in the endwall regions. The suction requirements predicted by the quasi three-dimensional calculation were confirmed by the three-dimensional viscous calculations. The three-dimensional viscous analysis predicted a peak pressure ratio of 1.59 at an isentropic efficiency of 89% for the low-speed stage, and a peak pressure ratio of 3.68 at an isentropic efficiency of 94% for the high-speed rotor. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

High-speed noncontacting instrumentation for jet engine testing

NASA Astrophysics Data System (ADS)

Scotto, M. J.; Eismeier, M. E.

1980-03-01

This paper discusses high-speed, noncontacting instrumentation systems for measuring the operating characteristics of jet engines. The discussion includes optical pyrometers for measuring blade surface temperatures, capacitance clearanceometers for measuring blade tip clearance and vibration, and optoelectronic systems for measuring blade flex and torsion. In addition, engine characteristics that mandate the use of such unique instrumentation are pointed out as well as the shortcomings of conventional noncontacting devices. Experimental data taken during engine testing are presented and recommendations for future development discussed.

Low-speed aerodynamic characteristics of a 13.1-percent-thick, high-lift airfoil

NASA Technical Reports Server (NTRS)

Sivier, K. R.; Ormsbee, A. I.; Awker, R. W.

1974-01-01

Experimental study of the low-speed, sectional characteristics of a high-lift airfoil, and comparison of these characteristics with the predictions of the theoretical methods used in the airfoil's design. The 13.1% thick UI-1720 airfoil was found to achieve the predicted maximum lift coefficient of nearly 2.0. No upper-surface flow separation was found below the stall angle of attack of 16 deg; it appeared that stall was due to an abrupt leading-edge flow separation.

Aircraft High-Lift Aerodynamic Analysis Using a Surface-Vorticity Solver

NASA Technical Reports Server (NTRS)

Olson, Erik D.; Albertson, Cindy W.

2016-01-01

This study extends an existing semi-empirical approach to high-lift analysis by examining its effectiveness for use with a three-dimensional aerodynamic analysis method. The aircraft high-lift geometry is modeled in Vehicle Sketch Pad (OpenVSP) using a newly-developed set of techniques for building a three-dimensional model of the high-lift geometry, and for controlling flap deflections using scripted parameter linking. Analysis of the low-speed aerodynamics is performed in FlightStream, a novel surface-vorticity solver that is expected to be substantially more robust and stable compared to pressure-based potential-flow solvers and less sensitive to surface perturbations. The calculated lift curve and drag polar are modified by an empirical lift-effectiveness factor that takes into account the effects of viscosity that are not captured in the potential-flow solution. Analysis results are validated against wind-tunnel data for The Energy-Efficient Transport AR12 low-speed wind-tunnel model, a 12-foot, full-span aircraft configuration with a supercritical wing, full-span slats, and part-span double-slotted flaps.

Preparative isolation and purification of hainanmurpanin, meranzin, and phebalosin from leaves of Murraya exotica L. using supercritical fluid extraction combined with consecutive high-speed countercurrent chromatography.

PubMed

Yan, Rongwei; Shen, Jie; Liu, Xiaojing; Zou, Yong; Xu, Xinjun

2018-05-01

The objective of this study was to develop a consecutive preparation method for the isolation and purification of hainanmurpanin, meranzin, and phebalosin from leaves of Murraya exotica L. The process involved supercritical fluid extraction with CO 2 , solvent extraction, and two-step high-speed countercurrent chromatography. Pressure, temperature, and the volume of entrainer were optimized as 27 MPa, 52°C, and 60 mL by response surface methodology in supercritical fluid extraction with CO 2 , and the yield of the crude extracts was 7.91 g from 100 g of leaves. Subsequently, 80% methanol/water was used to extract and condense the three compounds from the crude extracts, and 4.23 g of methanol/water extracts was obtained. Then, a two-step high-speed countercurrent chromatography procedure was developed for the isolation of the three target compounds from methanol/water extracts, including conventional high-speed countercurrent chromatography for further enrichment and consecutive high-speed countercurrent chromatography for purification. The yield of concentrates from high-speed countercurrent chromatography was 2.50 g from 4.23 g of methanol/water extracts. Finally, the consecutive high-speed countercurrent chromatography produced 103.2 mg of hainanmurpanin, 244.7 mg of meranzin, and 255.4 mg of phebalosin with purities up to 97.66, 99.36, and 98.64%, respectively, from 900 mg of high-speed countercurrent chromatography concentrates in one run of three consecutive sample loadings without exchanging a solvent system. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

STABILITY OF AQUEOUS FILMS BETWEEN BUBBLES

PubMed Central

Ohnishi, Satomi; Vogler, Erwin A.; Horn, Roger G.

2010-01-01

Film thinning experiments have been conducted with aqueous films between two air phases in a thin film pressure balance. The films are free of added surfactant but simple NaCl electrolyte is added in some experiments. Initially the experiments begin with a comparatively large volume of water in a cylindrical capillary tube a few mm in diameter, and by withdrawing water from the center of the tube the two bounding menisci are drawn together at a prescribed rate. This models two air bubbles approaching at a controlled speed. In pure water the results show three regimes of behavior depending on the approach speed: at slow speed (<1 µm/s) it is possible to form a flat film of pure water, ~100 nm thick, that is stabilised indefinitely by disjoining pressure due to repulsive double-layer interactions between naturally-charged air/water interfaces. The data are consistent with a surface potential of −57 mV on the bubble surfaces. At intermediate approach speed (~1 – 150 µm/s) the films are transiently stable due to hydrodynamic drainage effects, and bubble coalescence is delayed by ~10 – 100 s. At approach speeds greater than ~150 µm/s the hydrodynamic resistance appears to become negligible, and the bubbles coalesce without any measurable delay. Explanations for these observations are presented that take into account DLVO and Marangoni effects entering through disjoining pressure, surface mobility and hydrodynamic flow regimes in thin film drainage. In particular, it is argued that the dramatic reduction in hydrodynamic resistance is a transition from viscosity-controlled drainage to inertia-controlled drainage associated with a change from immobile to mobile air/water interfaces on increasing the speed of approach of two bubbles. A simple model is developed that accounts for the boundaries between different film stability or coalescence regimes. Predictions of the model are consistent with the data, and the effects of adding electrolyte can be explained. In particular, addition of electrolyte at high concentration inhibits the near-instantaneous coalescence phenomenon, thereby contributing to increased foam film stability at high approach speeds, as reported in previous literature. This work highlights the significance of bubble approach speed as well as electrolyte concentration in affecting bubble coalescence. PMID:20146434

Surface acoustic wave solid-state rotational micromotor

NASA Astrophysics Data System (ADS)

Shilton, Richie J.; Langelier, Sean M.; Friend, James R.; Yeo, Leslie Y.

2012-01-01

Surface acoustic waves (SAWs) are used to drive a 1 mm diameter rotor at speeds exceeding 9000 rpm and torque of nearly 5 nNm. Unlike recent high-speed SAW rotary motors, however, the present design does not require a fluid coupling layer but interestingly exploits adhesive stiction as an internal preload, a force usually undesirable at these scales; with additional preloads, smaller rotors can be propelled to 15 000 rpm. This solid-state motor has no moving parts except for the rotor and is sufficiently simple to allow integration into miniaturized drive systems for potential use in microfluidic diagnostics, optical switching and microrobotics.

Investigation of structural and magnetic properties of rapidly-solidified iron-silicon alloys at ambient and elevated temperatures

DOE PAGES

Jayaraman, T. V.; Meka, V. M.; Jiang, X.; ...

2018-01-09

Here we investigated the ambient temperature structural properties (thickness, width, microstructure, and lattice parameter), and the ambient and high temperature (up to 900 K) direct current (DC) magnetic properties—saturation magnetization (M S) and intrinsic coercivity (H CI)—of rapidly-solidified (melt-spun) Fe-x wt.% Si (x = 3, 5, & 8) alloys. The wheel surface speeds selected for the study were 30 m/s and 40 m/s. The ribbons produced at the lower wheel surface speed (30 m/s) were continuous having relatively uniform edges compared to the ribbons produced at the higher wheel surface speed. The thickness and the width of the melt-spun ribbonsmore » ranged between ~15 and 60 μm and 500–800 μm, respectively. The x-ray diffraction spectra of the melt-spun ribbons indicated the presence of disordered α-phase, irrespective of the composition, and the wheel surface speed. The lattice parameter decreased gradually as a function of increasing silicon content from ~0.2862 nm (Fe-3 wt.% Si) to ~0.2847 nm (Fe-8 wt.% Si). The wheel surface speed showed an insignificant effect on M S while increased silicon content resulted in a decreasing trend in M S. Elevated temperature evaluation of the magnetization (M-T curves at ~7.96 kA/m) in the case of Fe-3 & 5 wt.% Si alloy ribbons was distinctly different from that of the Fe-8 wt.% Si alloy ribbons. The curves of the as-prepared Fe-3 wt.% Si and Fe-5 wt.% Si alloy ribbons were irreversible while that of Fe-8 wt.% Si was reversible. The M S for any of the combinations of wheel surface speed and composition decreased monotonically with the increase in temperature (from 300 to 900 K). While H CI increased with the increase in temperature for all the wheel surface speed and composition combination, its nature of increase is distinct for Fe-8 wt.% Si alloy ribbons compared to Fe-3 & 5 wt.% Si alloys ribbons. Finally, it appears that rapidly-solidified Fe-3 wt.% Si and Fe-5 wt.% Si alloys ribbons are primarily comprised of the α phase (disordered phase) while the Fe-8 wt.% Si alloy ribbons are comprised primarily of disordered phase along with minor constituents of an ordered phase.« less

Investigation of structural and magnetic properties of rapidly-solidified iron-silicon alloys at ambient and elevated temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jayaraman, T. V.; Meka, V. M.; Jiang, X.

Here we investigated the ambient temperature structural properties (thickness, width, microstructure, and lattice parameter), and the ambient and high temperature (up to 900 K) direct current (DC) magnetic properties—saturation magnetization (M S) and intrinsic coercivity (H CI)—of rapidly-solidified (melt-spun) Fe-x wt.% Si (x = 3, 5, & 8) alloys. The wheel surface speeds selected for the study were 30 m/s and 40 m/s. The ribbons produced at the lower wheel surface speed (30 m/s) were continuous having relatively uniform edges compared to the ribbons produced at the higher wheel surface speed. The thickness and the width of the melt-spun ribbonsmore » ranged between ~15 and 60 μm and 500–800 μm, respectively. The x-ray diffraction spectra of the melt-spun ribbons indicated the presence of disordered α-phase, irrespective of the composition, and the wheel surface speed. The lattice parameter decreased gradually as a function of increasing silicon content from ~0.2862 nm (Fe-3 wt.% Si) to ~0.2847 nm (Fe-8 wt.% Si). The wheel surface speed showed an insignificant effect on M S while increased silicon content resulted in a decreasing trend in M S. Elevated temperature evaluation of the magnetization (M-T curves at ~7.96 kA/m) in the case of Fe-3 & 5 wt.% Si alloy ribbons was distinctly different from that of the Fe-8 wt.% Si alloy ribbons. The curves of the as-prepared Fe-3 wt.% Si and Fe-5 wt.% Si alloy ribbons were irreversible while that of Fe-8 wt.% Si was reversible. The M S for any of the combinations of wheel surface speed and composition decreased monotonically with the increase in temperature (from 300 to 900 K). While H CI increased with the increase in temperature for all the wheel surface speed and composition combination, its nature of increase is distinct for Fe-8 wt.% Si alloy ribbons compared to Fe-3 & 5 wt.% Si alloys ribbons. Finally, it appears that rapidly-solidified Fe-3 wt.% Si and Fe-5 wt.% Si alloys ribbons are primarily comprised of the α phase (disordered phase) while the Fe-8 wt.% Si alloy ribbons are comprised primarily of disordered phase along with minor constituents of an ordered phase.« less

Analysis by oxygen atom number density measurement of high-speed hydrophilic treatment of polyimide using atmospheric pressure microwave plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ono, S.

2015-03-30

This paper describes the fundamental experimental data of the plasma surface modification of the polyimide using atmospheric pressure microwave plasma source. The experimental results were discussed from the point of view of the radical’s behavior, which significantly affects the modification mechanism. The purpose of the study is to examine how the value of the oxygen atom density will affect the hydrophilic treatment in the upstream region of the plasma where gas temperature is very high. The surface modification experiments were performed by setting the polyimide film sample in the downstream region of the plasma. The degree of the modification wasmore » measured by a water contact angle measurement. The water contact angle decreased less than 30 degrees within 1 second treatment time in the upstream region. Very high speed modification was observed. The reason of this high speed modification seems that the high density radical which contributes the surface modification exist in the upstream region of the plasma. This tendency is supposed to the measured relatively high electron density (~10{sup 15}cm{sup −3}) at the center of the plasma. We used the electric heating catalytic probe method for oxygen radical measurement. An absolute value of oxygen radical density was determined by catalytic probe measurement and the results show that ~10{sup 15}cm{sup −3} of the oxygen radical density in the upstream region and decreases toward downstream region. The experimental results of the relation of the oxygen radical density and hydrophilic modification of polyimide was discussed.« less

Revised ocean backscatter models at C and Ku band under high-wind conditions

NASA Astrophysics Data System (ADS)

Donnelly, William J.; Carswell, James R.; McIntosh, Robert E.; Chang, Paul S.; Wilkerson, John; Marks, Frank; Black, Peter G.

1999-05-01

A series of airborne scatterometer experiments designed to collect C and Ku band ocean backscatter data in regions of high ocean surface winds has recently been completed. More than 100 hours of data were collected using the University of Massachusetts C and Ku band scatterometers, CSCAT and KUSCAT. These instruments measure the full azimuthal normalized radar cross section (NRCS) of a common surface area of the ocean simultaneously at four incidence angles. Our results demonstrate limitations of the current empirical models, C band geophysical model function 4 (CMOD4), SeaSat scatterometer 2 (SASS 2), and NASA scatterometer 1 (NSCAT) 1, that relate ocean backscatter to the near-surface wind at high wind speeds. The discussion focuses on winds in excess of 15 m s-1 in clear atmospheric conditions. The scatterometer data are collocated with measurements from ocean data buoys and Global Positioning System dropsondes, and a Fourier analysis is performed as a function of wind regime. A three-term Fourier series is fit to the backscatter data, and a revised set of coefficients is tabulated. These revised models, CMOD4HW and KUSCAT 1, are the basis for a discussion of the NRCS at high wind speeds. Our scatterometer data show a clear overprediction of the derived NRCS response to high winds based on the CMOD4, SASS 2, and NSCAT 1 models. Furthermore, saturation of the NRCS response begins to occur above 15 m s-1. Sensitivity of the upwind and crosswind response is discussed with implications toward high wind speed retrieval.

Aeolian sediment transport on a beach: Surface moisture, wind fetch, and mean transport

NASA Astrophysics Data System (ADS)

Bauer, B. O.; Davidson-Arnott, R. G. D.; Hesp, P. A.; Namikas, S. L.; Ollerhead, J.; Walker, I. J.

2009-04-01

Temporal and spatial changes in wind speed, wind direction, and moisture content are ubiquitous across sandy coastal beaches. Often these factors interact in unknown ways to create complexity that confounds our ability to model sediment transport at any point across the beach as well as our capacity to predict sediment delivery into the adjacent foredunes. This study was designed to measure wind flow and sediment transport over a beach and foredune at Greenwich Dunes, Prince Edward Island National Park, with the express purpose of addressing these complex interactions. Detailed measurements are reported for one stormy day, October 11, 2004, during which meteorological conditions were highly variable. Wind speed ranged from 4 ms - 1 to over 20 ms - 1 , wind direction was highly oblique varying between 60° and 85° from shore perpendicular, and moisture content of the sand surface ranged from a minimum of about 3% (by mass) to complete saturation depending on precipitation, tidal excursion, and storm surge that progressively inundated the beach. The data indicate that short-term variations (i.e., minutes to hours) in sediment transport across this beach arise predominantly because of short-term changes in wind speed, as is expected, but also because of variations in wind direction, precipitation intensity, and tide level. Even slight increases in wind speed are capable of driving more intense saltation events, but this relationship is mediated by other factors on this characteristically narrow beach. As the angle of wind approach becomes more oblique, the fetch distance increases and allows greater opportunity for the saltation system to evolve toward an equilibrium transport state before reaching the foredunes. Whether the theoretically-predicted maximum rate of transport is ever achieved depends on the character of the sand surface (e.g., grain size, slope, roughness, vegetation, moisture content) and on various attributes of the wind field (e.g., average wind speed, unsteadiness, approach angle, flow compression, boundary layer development). Moisture content is widely acknowledged as an important factor in controlling release of sediment from the beach surface. All other things being equal, the rate of sediment transport over a wet surface is lesser than over a dry surface. On this beach, the moisture effect has two important influences: (a) in a temporal sense, the rate of sediment transport typically decreases in association with rainfall and increases when surface drying takes place; and (b) in a spatio-temporal sense, shoreline excursions associated with nearshore processes (such as wave run-up, storm surge, and tidal excursions) have the effect of constraining the fetch geometry of the beach—i.e., narrowing the width of the beach. Because saturated sand surfaces, such as found in the swash zone, will only reluctantly yield sediments to aeolian entrainment, the available beach surface across which aeolian transport can occur becomes narrower as the sea progressively inundates the beach. Under these constrained conditions, the transport system begins to shut down unless wind angle becomes highly oblique (thereby increasing fetch distance). In this study, maximum sediment transport was usually measured on the mid-beach rather than the upper beach (i.e., closer to the foredunes). This unusual finding is likely because of internal boundary layer development across the beach, which yields a decrease in near-surface wind speed (and hence, transport capacity) in the landward direction. Although widely recognized in the fluid mechanics literature, this decrease in near-surface shear stress as a by-product of a developing boundary layer in the downwind direction has not been adequately investigated in the context of coastal aeolian geomorphology.

Machinability of IPS Empress 2 framework ceramic.

PubMed

Schmidt, C; Weigl, P

2000-01-01

Using ceramic materials for an automatic production of ceramic dentures by CAD/CAM is a challenge, because many technological, medical, and optical demands must be considered. The IPS Empress 2 framework ceramic meets most of them. This study shows the possibilities for machining this ceramic with economical parameters. The long life-time requirement for ceramic dentures requires a ductile machined surface to avoid the well-known subsurface damages of brittle materials caused by machining. Slow and rapid damage propagation begins at break outs and cracks, and limits life-time significantly. Therefore, ductile machined surfaces are an important demand for machine dental ceramics. The machining tests were performed with various parameters such as tool grain size and feed speed. Denture ceramics were machined by jig grinding on a 5-axis CNC milling machine (Maho HGF 500) with a high-speed spindle up to 120,000 rpm. The results of the wear test indicate low tool wear. With one tool, you can machine eight occlusal surfaces including roughing and finishing. One occlusal surface takes about 60 min machining time. Recommended parameters for roughing are middle diamond grain size (D107), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 1000 mm/min, depth of cut a(e) = 0.06 mm, width of contact a(p) = 0.8 mm, and for finishing ultra fine diamond grain size (D46), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 100 mm/min, depth of cut a(e) = 0.02 mm, width of contact a(p) = 0.8 mm. The results of the machining tests give a reference for using IPS Empress(R) 2 framework ceramic in CAD/CAM systems. Copyright 2000 John Wiley & Sons, Inc.

A Novel Approach to Constrain Near-Surface Seismic Wave Speed Based on Polarization Analysis

NASA Astrophysics Data System (ADS)

Park, S.; Ishii, M.

2016-12-01

Understanding the seismic responses of cities around the world is essential for the risk assessment of earthquake hazards. One of the important parameters is the elastic structure of the sites, in particular, near-surface seismic wave speed, that influences the level of ground shaking. Many methods have been developed to constrain the elastic structure of the populated sites or urban basins, and here, we introduce a new technique based on analyzing the polarization content or the three-dimensional particle motion of seismic phases arriving at the sites. Polarization analysis of three-component seismic data was widely used up to about two decades ago, to detect signals and identify different types of seismic arrivals. Today, we have good understanding of the expected polarization direction and ray parameter for seismic wave arrivals that are calculated based on a reference seismic model. The polarization of a given phase is also strongly sensitive to the elastic wave speed immediately beneath the station. This allows us to compare the observed and predicted polarization directions of incoming body waves and infer the near-surface wave speed. This approach is applied to High-Sensitivity Seismograph Network in Japan, where we benchmark the results against the well-log data that are available at most stations. There is a good agreement between our estimates of seismic wave speeds and those from well logs, confirming the efficacy of the new method. In most urban environments, where well logging is not a practical option for measuring the seismic wave speeds, this method can provide a reliable, non-invasive, and computationally inexpensive estimate of near-surface elastic properties.

Shear bond strength of a new self-adhering flowable composite resin for lithium disilicate-reinforced CAD/CAM ceramic material

PubMed Central

Sancakli, Hande Sar; Sancakli, Erkan; Eren, Meltem Mert; Ozel, Sevda; Yucel, Taner; Yildiz, Esra

2014-01-01

PURPOSE The purpose of this study was to evaluate and compare the effects of different surface pretreatment techniques on the surface roughness and shear bond strength of a new self-adhering flowable composite resin for use with lithium disilicate-reinforced CAD/CAM ceramic material. MATERIALS AND METHODS A total of one hundred thirty lithium disilicate CAD/CAM ceramic plates with dimensions of 6 mm × 4 mm and 3 mm thick were prepared. Specimens were then assigned into five groups (n=26) as follows: untreated control, coating with 30 µm silica oxide particles (Cojet™ Sand), 9.6% hydrofluoric acid etching, Er:YAG laser irradiation, and grinding with a high-speed fine diamond bur. A self-adhering flowable composite resin (Vertise Flow) was applied onto the pre-treated ceramic plates using the Ultradent shear bond Teflon mold system. Surface roughness was measured by atomic force microscopy. Shear bond strength test were performed using a universal testing machine at a crosshead speed of 1 mm/min. Surface roughness data were analyzed by one-way ANOVA and the Tukey HSD tests. Shear bond strength test values were analyzed by Kruskal-Wallis and Mann-Whitney U tests at α=.05. RESULTS Hydrofluoric acid etching and grinding with high-speed fine diamond bur produced significantly higher surface roughness than the other pretreatment groups (P<.05). Hydrofluoric acid etching and silica coating yielded the highest shear bond strength values (P<.001). CONCLUSION Self-adhering flowable composite resin used as repair composite resin exhibited very low bond strength irrespective of the surface pretreatments used. PMID:25551002

Dynamics of skirting droplets

NASA Astrophysics Data System (ADS)

Akers, Caleb; Hale, Jacob

2014-11-01

It has been observed that non-coalescence between a droplet and pool of like fluid can be prolonged or inhibited by sustained relative motion between the two fluids. In this study, we quantitatively describe the motion of freely moving droplets that skirt across the surface of a still pool of like fluid. Droplets of different sizes and small Weber number were directed horizontally onto the pool surface. After stabilization of the droplet shape after impact, the droplets smoothly moved across the surface, slowing until coalescence. Using high-speed imaging, we recorded the droplet's trajectory from a top-down view as well as side views both slightly above and below the fluid surface. The droplets' speed is observed to decrease exponentially, with the smaller droplets slowing down at a greater rate. Droplets infused with neutral density micro beads showed that the droplet rolls along the surface of the pool. A qualitative model of this motion is presented.

Enhanced optical absorbance and fabrication of periodic arrays on nickel surface using nanosecond laser

NASA Astrophysics Data System (ADS)

Fu, Jinxiang; Liang, Hao; Zhang, Jingyuan; Wang, Yibo; Liu, Yannan; Zhang, Zhiyan; Lin, Xuechun

2017-04-01

A hundred-nanosecond pulsed laser was employed to structure the nickel surface. The effects of laser spatial filling interval and laser scanning speed on the optical absorbance capacity and morphologies on the nickel surface were experimentally investigated. The black nickel surface covered with dense micro/nanostructured broccoli-like clusters with strong light trapping capacity ranging from the UV to the near IR was produced at a high laser scanning speed up to v=100 mm/s. The absorbance of the black nickel is as high as 98% in the UV range of 200-400 nm, more than 97% in the visible spectrum, ranging from 400 to 800 nm, and over 90% in the IR between 800 and 2000 nm. In addition, when the nickel surface was irradiated in two-dimensional crossing scans by laser with different processing parameters, self-organized and shape-controllable structures of three-dimensional (3D) periodic arrays can be fabricated. Compared with ultrafast laser systems previously used for such processing, the nanosecond fiber laser used in this work is more cost-effective, compact and allows higher processing rates. This nickel surface structured technique may be applicable in optoelectronics, batteries industry, solar/wave absorbers, and wettability materials.

Investigation of surface wave amplitudes in 3-D velocity and 3-D Q models

NASA Astrophysics Data System (ADS)

Ruan, Y.; Zhou, Y.

2010-12-01

It has been long recognized that seismic amplitudes depend on both wave speed structures and anelasticity (Q) structures. However, the effects of lateral heterogeneities in wave speed and Q structures on seismic amplitudes has not been well understood. We investigate the effects of 3-D wave speed and 3-D anelasticity (Q) structures on surface-wave amplitudes based upon wave propagation simulations of twelve globally-distributed earthquakes and 801 stations in Earth models with and without lateral heterogeneities in wave speed and anelasticity using a Spectral Element Method (SEM). Our tomographic-like 3-D Q models are converted from a velocity model S20RTS using a set of reasonable mineralogical parameters, assuming lateral perturbations in both velocity and Q are due to temperature perturbations. Surface-wave amplitude variations of SEM seismograms are measured in the period range of 50--200 s using boxcar taper, cosine taper and Slepian multi-tapers. We calculate ray-theoretical predictions of surface-wave amplitude perturbations due to elastic focusing, attenuation, and anelastic focusing which respectively depend upon the second spatial derivative (''roughness'') of perturbations in phase velocity, 1/Q, and the roughness of perturbations in 1/Q. Both numerical experiments and theoretical calculations show that (1) for short-period (~ 50 s) surface waves, the effects of amplitude attenuation due to 3-D Q structures are comparable with elastic focusing effects due to 3-D wave speed structures; and (2) for long-period (> 100 s) surface waves, the effects of attenuation become much weaker than elastic focusing; and (3) elastic focusing effects are correlated with anelastic focusing at all periods due to the correlation between velocity and Q models; and (4) amplitude perturbations are depend on measurement techniques and therefore cannot be directly compared with ray-theoretical predictions because ray theory does not account for the effects of measurement techniques. We calculate 3-D finite-frequency sensitivity of surface-wave amplitude to perturbations in wave speed and anelasticity (Q) which fully account for the effects of elastic focusing, attenuation, anelastic focusing as well as measurement techniques. We show that amplitude perturbations calculated using wave speed and Q sensitivity kernels agree reasonably well with SEM measurements and therefore the sensitivity kernels can be used in a joint inversion of seismic phase delays and amplitudes to simultaneously image high resolution 3-D wave speed and 3-D Q structures in the upper mantle.

SANDKLENE 950

EPA Pesticide Factsheets

Technical product bulletin: this surface washing agent used in oil spill cleanups on sand is most effective in enclosed systems using centrifuges, shearing devices, or similar high speed equipment to process material.

Estimating Tropical Cyclone Surface Wind Field Parameters with the CYGNSS Constellation

NASA Astrophysics Data System (ADS)

Morris, M.; Ruf, C. S.

2016-12-01

A variety of parameters can be used to describe the wind field of a tropical cyclone (TC). Of particular interest to the TC forecasting and research community are the maximum sustained wind speed (VMAX), radius of maximum wind (RMW), 34-, 50-, and 64-kt wind radii, and integrated kinetic energy (IKE). The RMW is the distance separating the storm center and the VMAX position. IKE integrates the square of surface wind speed over the entire storm. These wind field parameters can be estimated from observations made by the Cyclone Global Navigation Satellite System (CYGNSS) constellation. The CYGNSS constellation consists of eight small satellites in a 35-degree inclination circular orbit. These satellites will be operating in standard science mode by the 2017 Atlantic TC season. CYGNSS will provide estimates of ocean surface wind speed under all precipitating conditions with high temporal and spatial sampling in the tropics. TC wind field data products can be derived from the level-2 CYGNSS wind speed product. CYGNSS-based TC wind field science data products are developed and tested in this paper. Performance of these products is validated using a mission simulator prelaunch.

Hardness and microstructure analysis of damaged gear caused by adhesive wear

NASA Astrophysics Data System (ADS)

Mahendra, Rizky Budi; Nugroho, Sri; Ismail, Rifky

2018-03-01

This study was a result from research on repairing project of damaged elevator gear box. The objective of this research is to analyze the failure part on elevator gearbox at flourmill factory. The equipment was damaged after one year installed and running on factory. Severe wear was occurred on high speed helical gear. These helical gear was one of main part of elevator gearbox in flour mill manufacture. Visually, plastic deformation didn't occurred and not visible on the failure helical gear shaft. Some test would be performed to check the chemical composition, microstructure and hardness of failure helical gear. The material of failure helical gear shaft was a medium carbon steel alloy. The microstructure was showed a martensitic phase formed on the surface to the center area of gear shaft. Otherwise, the depth of hardness layer slight formed on surface and lack depth of hardness layer was a main trigger of severe wear. It was not enough to resist wear due to friction caused by rolling and sliding on surface between high speed gear and low speed gear. Enhancement of hardness layer on surface and depth of hardness layer will make the component has more long life time. Furthermore, to perform next research is needed to analyze the reliability of enhanced hardness on layer and depth of hardness layer on helical gear shaft.

The hydrodynamics of bubble rise and impact with solid surfaces.

PubMed

Manica, Rogerio; Klaseboer, Evert; Chan, Derek Y C

2016-09-01

A bubble smaller than 1mm in radius rises along a straight path in water and attains a constant speed due to the balance between buoyancy and drag force. Depending on the purity of the system, within the two extreme limits of tangentially immobile or mobile boundary conditions at the air-water interface considerably different terminal speeds are possible. When such a bubble impacts on a horizontal solid surface and bounces, interesting physics can be observed. We study this physical phenomenon in terms of forces, which can be of colloidal, inertial, elastic, surface tension and viscous origins. Recent advances in high-speed photography allow for the observation of phenomena on the millisecond scale. Simultaneous use of such cameras to visualize both rise/deformation and the dynamics of the thin film drainage through interferometry are now possible. These experiments confirm that the drainage process obeys lubrication theory for the spectrum of micrometre to millimetre-sized bubbles that are covered in this review. We aim to bridge the colloidal perspective at low Reynolds numbers where surface forces are important to high Reynolds number fluid dynamics where the effect of the surrounding flow becomes important. A model that combines a force balance with lubrication theory allows for the quantitative comparison with experimental data under different conditions without any fitting parameter. Copyright © 2016 Elsevier B.V. All rights reserved.

3D finite element modeling of sliding wear

NASA Astrophysics Data System (ADS)

Buentello Hernandez, Rodolfo G.

Wear is defined as "the removal of material volume through some mechanical process between two surfaces". There are many mechanical situations that can induce wear and each can involve many wear mechanisms. This research focuses on the mechanical wear due to dry sliding between two surfaces. Currently there is a need to identify and compare materials that would endure sliding wear under severe conditions such as high velocities. The high costs associated with the field experimentation of systems subject to high-speed sliding, has prevented the collection of the necessary data required to fully characterize this phenomena. Simulating wear through Finite Elements (FE) would enable its prediction under different scenarios and would reduce experimentation costs. In the aerospace, automotive and weapon industries such a model can aid in material selection, design and/or testing of systems subjected to wear in bearings, gears, brakes, gun barrels, slippers, locomotive wheels, or even rocket test tracks. The 3D wear model presented in this dissertation allows one to reasonably predict high-speed sliding mechanical wear between two materials. The model predictions are reasonable, when compared against those measured on a sled slipper traveling over the Holloman High Speed Tests Track. This slipper traveled a distance of 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s.

Mechanisms of high-regularity periodic structuring of silicon surface by sub-MHz repetition rate ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Gnilitskyi, Iaroslav; Gruzdev, Vitaly; Bulgakova, Nadezhda M.; Mocek, Tomáš; Orazi, Leonardo

2016-10-01

Silicon is one of the most abundant materials which is used in many areas of modern research and technology. A variety of those applications require surface nanopatterning with minimum structure defects. However, the high-quality nanostructuring of large areas of silicon surface at industrially acceptable speed is still a challenge. Here, we report a rapid formation of highly regular laser-induced periodic surface structures (HR-LIPSS) in the regime of strong ablation by infrared femtosecond laser pulses at sub-MHz repetition rate. Parameters of the laser-surface interactions and obtained experimental results suggest an important role of electrostatically assisted bond softening in initiating the HR-LIPSS formation.

Preliminary results and assessment of the MAR outputs over High Mountain Asia

NASA Astrophysics Data System (ADS)

Linares, M.; Tedesco, M.; Margulis, S. A.; Cortés, G.; Fettweis, X.

2017-12-01

Lack of ground measurements has made the use of regional climate models (RCMs) over the High Mountain Asia (HMA) pivotal for understanding the impact of climate change on the hydrological cycle and on the cryosphere. Here, we show an analysis of the assessment of the outputs of Modèle Atmosphérique Régionale (MAR) model RCM over the HMA region as part of the NASA-funded project `Understanding and forecasting changes in High Mountain Asia snow hydrology via a novel Bayesian reanalysis and modeling approach'. The first step was to evaluate the impact of the different forcings on MAR outputs. To this aim, we performed simulations for the 2007 - 2008 and 2014 - 2015 years forcing MAR at its boundaries either with reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) or from the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). The comparison between the outputs obtained with the two forcings indicates that the impact on MAR simulations depends on specific parameters. For example, in case of surface pressure the maximum percentage error is 0.09 % while the 2-m air temperature has a maximum percentage error of 103.7%. Next, we compared the MAR outputs with reanalysis data fields over the region of interest. In particular, we evaluated the following parameters: surface pressure, snow depth, total cloud cover, two meter temperature, horizontal wind speed, vertical wind speed, wind speed, surface new solar radiation, skin temperature, surface sensible heat flux, and surface latent heat flux. Lastly, we report results concerning the assessment of MAR surface albedo and surface temperature over the region through MODIS remote sensing products. Next steps are to determine whether RCMs and reanalysis datasets are effective at capturing snow and snowmelt runoff processes in the HMA region through a comparison with in situ datasets. This will help determine what refinements are necessary to improve RCM outputs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salvador Palau, A.; Eder, S. D., E-mail: sabrina.eder@uib.no; Kaltenbacher, T.

Time-of-flight (TOF) is a standard experimental technique for determining, among others, the speed ratio S (velocity spread) of a molecular beam. The speed ratio is a measure for the monochromaticity of the beam and an accurate determination of S is crucial for various applications, for example, for characterising chromatic aberrations in focussing experiments related to helium microscopy or for precise measurements of surface phonons and surface structures in molecular beam scattering experiments. For both of these applications, it is desirable to have as high a speed ratio as possible. Molecular beam TOF measurements are typically performed by chopping the beammore » using a rotating chopper with one or more slit openings. The TOF spectra are evaluated using a standard deconvolution method. However, for higher speed ratios, this method is very sensitive to errors related to the determination of the slit width and the beam diameter. The exact sensitivity depends on the beam diameter, the number of slits, the chopper radius, and the chopper rotation frequency. We present a modified method suitable for the evaluation of TOF measurements of high speed ratio beams. The modified method is based on a systematic variation of the chopper convolution parameters so that a set of independent measurements that can be fitted with an appropriate function are obtained. We show that with this modified method, it is possible to reduce the error by typically one order of magnitude compared to the standard method.« less

Impact dynamics of liquid marbles

NASA Astrophysics Data System (ADS)

Marston, Jeremy; Supakar, Tinku

2016-11-01

The impact of particle coated droplets (a.k.a. liquid marbles or armored droplets) onto solid substrates is assessed experimentally with high-speed video. The impact is characterized by the maximum spread diameter, which conforms to scaling laws in terms of the impact Weber number, meaning that the marbles behave similar to water droplets during this stage. However, the motion of the particles across the surface allows us to observe both clustering and divergence of the particle shell and, in particular, we observe the formation of arrested shapes (i.e. jammed interfaces) after impact onto hydrophobic surfaces, from an initially spherical shape. In this case, we postulate that the speed of retraction and rate of change of surface coverage is a key ingredient leading to arrested shapes.

High Resolution CH4 Emissions and Dissolved CH4 Measurements Elucidate Surface Gas Exchange Processes in Toolik Lake, Arctic Alaska

NASA Astrophysics Data System (ADS)

Del Sontro, T.; Sollberger, S.; Kling, G. W.; Shaver, G. R.; Eugster, W.

2013-12-01

Approximately 14% of the Alaskan North Slope is covered in lakes of various sizes and depths. Diffusive carbon emissions (CH4 and CO2) from these lakes offset the tundra sink by ~20 %, but the offset would substantially increase if ebullitive CH4 emissions were also considered. Ultimately, arctic lake CH4 emissions are not insignificant in the global CH4 budget and their contribution is bound to increase due to impacts from climate change. Here we present high resolution CH4 emission data as measured via eddy covariance and a Los Gatos gas analyzer during the ice free period from Toolik Lake, a deep (20 m) Arctic lake located on the Alaskan North Slope, over the last few summers. Emissions are relatively low (< 25 mg CH4 m-2 d-1) with little variation over the summer. Diurnal variations regularly occur, however, with up to 3 times higher fluxes at night. Gas exchange is a relatively difficult process to estimate, but is normally done so as the product of the CH4 gradient across the air-water interface and the gas transfer velocity, k. Typically, k is determined based on the turbulence on the water side of the interface, which is most commonly approximated by wind speed; however, it has become increasingly apparent that this assumption does not remain valid across all water bodies. Dissolved CH4 profiles in Toolik revealed a subsurface peak in CH4 at the thermocline of up to 3 times as much CH4 as in the surface water. We hypothesize that convective mixing at night due to cooling surface waters brings the subsurface CH4 to the surface and causes the higher night fluxes. In addition to high resolution flux emission estimates, we also acquired high resolution data for dissolved CH4 in surface waters of Toolik Lake during the last two summers using a CH4 equilibrator system connected to a Los Gatos gas analyzer. Thus, having both the flux and the CH4 gradient across the air-water interface measured directly, we can calculate k and investigate the processes influencing CH4 gas exchange in this lake. Preliminary results indicate that there are two regimes in wind speed that impact k - one at low wind speeds up to ~5 m s-1 and another at higher wind speeds (max ~10 m s-1). The differential wind speeds during night and day may compound the effect of convective mixing and cause the diurnal variation in observed fluxes.

Additional Effects of Silver Nanoparticles on Bactericidal Efficiency Depend on Calcination Temperature and Dip-Coating Speed▿

PubMed Central

Le, Nhung Thi Tuyet; Nagata, Hirofumi; Aihara, Mutsumi; Takahashi, Akira; Okamoto, Toshihiro; Shimohata, Takaaki; Mawatari, Kazuaki; Kinouchi, Yhosuke; Akutagawa, Masatake; Haraguchi, Masanobu

2011-01-01

There is an increasing interest in the application of photocatalytic properties for disinfection of surfaces, air, and water. Titanium dioxide is widely used as a photocatalyst, and the addition of silver reportedly enhances its bactericidal action. However, the synergy of silver nanoparticles and TiO2 is not well understood. The photocatalytic elimination of Bacillus atrophaeus was examined under different calcination temperatures, dip-coating speeds, and ratios of TiO2, SiO2, and Ag to identify optimal production conditions for the production of TiO2- and/or TiO2/Ag-coated glass for surface disinfection. Photocatalytic disinfection of pure TiO2 or TiO2 plus Ag nanoparticles was dependent primarily on the calcination temperature. The antibacterial activity of TiO2 films was optimal with a high dip-coating speed and high calcination temperature (600°C). Maximal bacterial inactivation using TiO2/Ag-coated glass was also observed following high-speed dip coating but with a low calcination temperature (250°C). Scanning electron microscopy (SEM) showed that the Ag nanoparticles combined together at a high calcination temperature, leading to decreased antibacterial activity of TiO2/Ag films due to a smaller surface area of Ag nanoparticles. The presence of Ag enhanced the photocatalytic inactivation rate of TiO2, producing a more pronounced effect with increasing levels of catalyst loading. PMID:21724887

The estimation of dynamic contact angle of ultra-hydrophobic surfaces using inclined surface and impinging droplet methods

NASA Astrophysics Data System (ADS)

Jasikova, Darina; Kotek, Michal

2014-03-01

The development of industrial technology also brings with optimized surface quality, particularly where there is contact with food. Application ultra-hydrophobic surface significantly reduces the growth of bacteria and facilitates cleaning processes. Testing and evaluation of surface quality are used two methods: impinging droplet and inclined surface method optimized with high speed shadowgraphy, which give information about dynamic contact angle. This article presents the results of research into new methods of measuring ultra-hydrophobic patented technology.

Summary and recent results from the NASA advanced High Speed Propeller Research Program

NASA Technical Reports Server (NTRS)

Mitchell, G. A.; Mikkelson, D. C.

1982-01-01

Advanced high-speed propellers offer large performance improvements for aircraft that cruise in the Mach 0.7 to 0.8 speed regime. The current status of the NASA research program on high-speed propeller aerodynamics, acoustics, and aeroelastics is described. Recent wind tunnel results for five 8- to 10-blade advanced models are compared with analytical predictions. Test results show that blade sweep was important in achieving net efficiencies near 80 percent at Mach 0.8 and reducing near-field cruise noise by dB. Lifting line and lifting surface aerodynamic analysis codes are under development and some initial lifting line results are compared with propeller force and probe data. Some initial laser velocimeter measurements of the flow field velocities of an 8-bladed 45 deg swept propeller are shown. Experimental aeroelastic results indicate that cascade effects and blade sweep strongly affect propeller aeroelastic characteristics. Comparisons of propeller near-field noise data with linear acoustic theory indicate that the theory adequate predicts near-field noise for subsonic tip speeds but overpredicts the noise for supersonic tip speeds. Potential large gains in propeller efficiency of 7 to 11 percent at Mach 0.8 may be possible with advanced counter-rotation propellers.

Hybrid Eulerian and Lagrangian Simulation of Steep and Breaking Waves and Surface Fluxes in High Winds

DTIC Science & Technology

2011-09-30

simulation provides boundary condition to the SPH simulation in a sub- domain. For the test with surface wave propagation, the free surface and the...This project aims at developing an advanced simulation tool for multi-fluids free - surface flows that can be used to study the fundamental physics...of horizontal velocity(normalized by wave phase speed c) obtained from SPH simulation and the corresponding free surface obtained from LSM

Sensitivity of Global Sea-Air CO2 Flux to Gas Transfer Algorithms, Climatological Wind Speeds, and Variability of Sea Surface Temperature and Salinity

NASA Technical Reports Server (NTRS)

McClain, Charles R.; Signorini, Sergio

2002-01-01

Sensitivity analyses of sea-air CO2 flux to gas transfer algorithms, climatological wind speeds, sea surface temperatures (SST) and salinity (SSS) were conducted for the global oceans and selected regional domains. Large uncertainties in the global sea-air flux estimates are identified due to different gas transfer algorithms, global climatological wind speeds, and seasonal SST and SSS data. The global sea-air flux ranges from -0.57 to -2.27 Gt/yr, depending on the combination of gas transfer algorithms and global climatological wind speeds used. Different combinations of SST and SSS global fields resulted in changes as large as 35% on the oceans global sea-air flux. An error as small as plus or minus 0.2 in SSS translates into a plus or minus 43% deviation on the mean global CO2 flux. This result emphasizes the need for highly accurate satellite SSS observations for the development of remote sensing sea-air flux algorithms.

The Aeroacoustics and Aerodynamics of High-Speed Coanda Devices, Part 1: Conventional Arrangement of Exit Nozzle and Surface

NASA Astrophysics Data System (ADS)

Carpenter, P. W.; Green, P. N.

1997-12-01

The literature on high-speed Coanda flows and its applications is reviewed. The lack of basic information for design engineers is noted. The present paper is based on an investigation of the aeroacoustics and aerodynamics of the high-speed Coanda flow that is formed when a supersonic jet issues from a radial nozzle and adheres to a tulip-shaped body of revolution. Schlieren and other flow visualization techniques together with theoretical methods are used to reveal the various features of this complex flow field. The acoustic characteristics were obtained from measurements with an array of microphones in an anechoic chamber. The emphasis is placed on those features of the aerodynamics and aeroacoustics which may be of general interest.

Experimental and numerical study of plastic shear instability under high-speed loading conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sokovikov, Mikhail, E-mail: sokovikov@icmm.ru, E-mail: naimark@icmm.ru; Chudinov, Vasiliy, E-mail: sokovikov@icmm.ru, E-mail: naimark@icmm.ru; Bilalov, Dmitry, E-mail: sokovikov@icmm.ru, E-mail: naimark@icmm.ru

2014-11-14

The behavior of specimens dynamically loaded during the split Hopkinson (Kolsky) bar tests in a regime close to simple shear conditions was studied. The lateral surface of the specimens was investigated in a real-time mode with the aid of a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time made it possible to trace the evolution of plastic strain localization. The process of target perforation involving plug formation and ejection was examined using a high-speed infra-red camera and a VISAR velocity measurement system. The microstructure of tested specimens was analyzed using an optical interferometer-profilometer andmore » a scanning electron microscope. The development of plastic shear instability regions has been simulated numerically.« less

An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1990

NASA Technical Reports Server (NTRS)

Halpern, D.; Knauss, W.; Brown, O.; Wentz, F.

1993-01-01

The following monthly mean global distributions for 1990 are proposed with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States (US) Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the advanced very high resolution radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) spacecraft; Cartesian components of free drifting buoys which are tracked by the ARGOS navigation system on NOAA satellites; and Cartesian components on the 10-m height wind vector computed by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of monthly mean value, sampling distribution, and standard deviation values are displayed. Annual mean distributions are displayed.

An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1991

NASA Technical Reports Server (NTRS)

Halpern, D.; Knauss, W.; Brown, O.; Wentz, F.

1993-01-01

The following monthly mean global distributions for 1991 are presented with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the advanced very high resolution radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) spacecraft; Cartesian components of free-drifting buoys which are tracked by the ARGOS navigation system on NOAA satellites; and Cartesian components of the 10-m height wind vector computed by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of monthly mean value, sampling distribution, and standard deviation value are displayed. Annual mean distributions are displayed.

Rough-Water Tests of Models of the Vosper and Plum Planing Boats

NASA Technical Reports Server (NTRS)

Chambliss, Derrill B.; Blanchard, Ulysse J.

1950-01-01

Models of two types of high-speed surface craft were tested in Langley tank no. 1 to obtain rough-water data for an evaluation by the David Taylor .Model Basin of the relative merits of the designs. Time-history records were obtained of trim, rise, and normal acceleration at two points in the hulls for various speeds and two sizes of waves.

The optimization study on the tool wear of carbide cutting tool during milling Carbon Fibre Reinforced (CFRP) using Response Surface Methodology (RSM)

NASA Astrophysics Data System (ADS)

Nor Khairusshima, M. K.; Hafiz Zakwan, B. Muhammad; Suhaily, M.; Sharifah, I. S. S.; Shaffiar, N. M.; Rashid, M. A. N.

2018-01-01

Carbon Fibre Reinforced Plastic (CFRP) composite has become one of famous materials in industry, such as automotive, aeronautics, aerospace and aircraft. CFRP is attractive due to its properties, which promising better strength and high specification of mechanical properties other than its high resistance to corrosion. Other than being abrasive material due to the carbon nature, CFRP is an anisotropic material, which the knowledge of machining metal and steel cannot be applied during machining CFRP. The improper technique and parameters used to machine CFRP may result in high tool wear. This paper is to study the tool wear of 8 mm diameter carbide cutting tool during milling CFRP. To predict the suitable cutting parameters within range of 3500-6220 (rev/min), 200-245 (mm/min), and 0.4-1.8 (mm) for cutting speed, speed, feed rate and depth of cut respectively, which produce optimized result (less tool wear), Response Surface Methodology (RSM) has been used. Based on the developed mathematical model, feed rate was identified as the primary significant item that influenced tool wear. The optimized cutting parameters are cutting speed, feed and depth of cut of 3500 rev/min, 200 mm/min and 0.5 mm, respectively, with tool wear of 0.0267 mm. It is also can be observed that as the cutting speed and feed rate increased the tool wear is increasing.

P- and S-Wave Speeds of the Very Upper Crust Estimated by a New Technique Based Upon Body-Wave Polarization

NASA Astrophysics Data System (ADS)

Park, S.; Ishii, M.

2017-12-01

Various seismic imaging methods have been developed, such as traveltime, waveform, and noise tomography, improving our knowledge of the subsurface structure and evolution. Near-surface structure, in particular, is crucial in understanding earthquake and volcano hazards. Seismic speed is directly related to the level of ground shaking, and monitoring its temporal change is valuable in volcanic hazard assessment. Here, we introduce a novel technique to constrain seismic wave speed of the very upper crust based upon the polarization measurements of teleseismic body-wave arrivals. The technique relates the orientation of recorded body waves to the wave speed immediately beneath a seismic instrument. We develop a counter-intuitive relationship that the P-wave polarization direction is only sensitive to subsurface shear wave speed but not to compressional wave speed, while the S-wave polarization direction is sensitive to both wave speeds. This approach is applied to the High-Sensitivity Seismograph Network in Japan, where the results are benchmarked against the borehole well data available at most stations. There is a good agreement between polarization-based estimates and the well measurements at as shallow as 100 m, confirming the efficacy of the new method in resolving the shallow structure. The lateral variation of wave speeds shows that sedimentary basins and mountainous regions are characterized by low and high wave speeds, respectively. It also correlates with volcano locations and geological units of different ages. Moreover, the analysis is expanded into 3D by examining the frequency dependence, where some preliminary results using broadband data are presented. These 2D and 3D wave speed estimates can be used to identify zones of high seismic risk by comparison with population distribution. This technique requires minimal computation resources and can be applied to any single three-component seismograph. It opens a new path to a reliable, non-invasive, and inexpensive earthquake hazard assessment in any environment where a drilling or a field experiment using vibro-trucks or explosives is not a practical option for measuring the near-surface seismic wave speeds. It can also provide means of monitoring changes that occur within the very upper crust such as from volcanic or hydrological phenomena.

Thermal structures and materials for high-speed flight; Collection of Papers of the 1st Thermal Structures Conference, University of Virginia, Charlottesville, Nov. 13-15, 1990

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornton, E.A.

1992-01-01

The present conference discusses aerobrake-maneuver vehicle aerothermodynamics, aerothermal issues in the structural design of high speed vehicles, laser surface-alloying of superlight metals with ceramic surfaces, high-temperature Al alloys for supersonic and hypersonic vehicles, advanced metallics for high temperature airframes, novel materials for engine applications, and the development status of computational methods for high temperature structural design. Also discussed are a transient thermal-structural analysis using adaptive unstructured remeshing and mesh movement, the FEM thermoviscoplastic analysis of aerospace structures, hot-structures testing techniques, a thermal-structural analysis of a carbon-carbon/refractory metal heat pipe-cooled leading edge, dynamic effects in thermoviscoplastic structures, microlevel thermal effects inmore » metal-matrix composites (MMCs), thermomechanical effects in the plasma spray manufacture of MMC monotapes, and intelligent HIP processing. Most of the presentations at this conference were abstracted previously (see A91-16027 to A91-16047).« less

Hierarchically porous carbon with high-speed ion transport channels for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Lu, Haoyuan; Li, Qingwei; Guo, Jianhui; Song, Aixin; Gong, Chunhong; Zhang, Jiwei; Zhang, Jingwei

2018-01-01

Hierarchically porous carbons (HPC) are considered as promising electrode materials for supercapacitors, due to their outstanding charge/discharge cycling stabilities and high power densities. However, HPC possess a relatively low ion diffusion rate inside the materials, which challenges their application for high performance supercapacitor. Thus tunnel-shaped carbon pores with a size of tens of nanometers were constructed by inducing the self-assembly of lithocholic acid with ammonium chloride, thereby providing high-speed channels for internal ion diffusion. The as-formed one-dimensional pores are beneficial to the activation process by KOH, providing a large specific surface area, and then facilitate rapid transport of electrolyte ions from macropores to the microporous surfaces. Therefore, the HPC achieve an outstanding gravimetric capacitance of 284 F g-1 at a current density of 0.1 A g-1 and a remarkable capacity retention of 64.8% when the current density increases by 1000 times to 100 A g-1.

Effect of process parameters on formability of laser melting deposited 12CrNi2 alloy steel

NASA Astrophysics Data System (ADS)

Peng, Qian; Dong, Shiyun; Kang, Xueliang; Yan, Shixing; Men, Ping

2018-03-01

As a new rapid prototyping technology, the laser melting deposition technology not only has the advantages of fast forming, high efficiency, but also free control in the design and production chain. Therefore, it has drawn extensive attention from community.With the continuous improvement of steel performance requirements, high performance low-carbon alloy steel is gradually integrated into high-tech fields such as aerospace, high-speed train and armored equipment.However, it is necessary to further explore and optimize the difficult process of laser melting deposited alloy steel parts to achieve the performance and shape control.This article took the orthogonal experiment on alloy steel powder by laser melting deposition ,and revealed the influence rule of the laser power, scanning speed, powder gas flow on the quality of the sample than the dilution rate, surface morphology and microstructure analysis were carried out.Finally, under the optimum technological parameters, the Excellent surface quality of the alloy steel forming part with high density, no pore and cracks was obtained.

Progress and issues for high-speed vertical cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Lear, Kevin L.; Al-Omari, Ahmad N.

2007-02-01

Extrinsic electrical, thermal, and optical issues rather than intrinsic factors currently constrain the maximum bandwidth of directly modulated vertical cavity surface emitting lasers (VCSELs). Intrinsic limits based on resonance frequency, damping, and K-factor analysis are summarized. Previous reports are used to compare parasitic circuit values and electrical 3dB bandwidths and thermal resistances. A correlation between multimode operation and junction heating with bandwidth saturation is presented. The extrinsic factors motivate modified bottom-emitting structures with no electrical pads, small mesas, copper plated heatsinks, and uniform current injection. Selected results on high speed quantum well and quantum dot VCSELs at 850 nm, 980 nm, and 1070 nm are reviewed including small-signal 3dB frequencies up to 21.5 GHz and bit rates up to 30 Gb/s.

Role of cavitation in high-speed droplet impact problems

NASA Astrophysics Data System (ADS)

Kondo, Tomoki; Ando, Keita

2014-11-01

High-speed droplet impact is found in physical cleaning using liquid jets, but its mechanisms for particle removal from target surfaces are yet unclear. In this study, we explore the possibility of having cavitation inside the droplet. The pressure evolution within a droplet colliding with a flat surface of deformable materials is determined by multicomponent Euler equations. Dynamics of cavitation bubbles heterogeneously nucleated from preexisting nuclei are determined from Rayleigh-Plesset calculations according to the pressure evolution within the droplet in one-way-coupling manner. The simulation shows that cavitation indeed occurs due to tension that arises from the water hammer shock reflection at the droplet interface. The role of cavitation including pressure emission from its collapse is to be discussed based on the one-way-coupling computations.

Development of a miniaturized optical viscosity sensor with an optical surface tracking system

NASA Astrophysics Data System (ADS)

Abe, H.; Nagamachi, R.; Taguchi, Y.; Nagasaka, Y.

2010-02-01

A new viscosity sensor enabling non-contact measurement at high speed, with less sample volume and high stability is required in a broad field. For example, in the industrial field, process control by real time monitoring of viscosity can enhance the quality of coating films and the process yield such as conductive films and optical films. Therefore, we have developed a new miniaturized optical viscosity sensor, namely MOVS (Miniaturized Optical Viscosity Sensor), based on a laser-induced capillary wave (LiCW) method which can meet the requirements above. In the MOVS, viscosity is estimated by observing the damping oscillation of LiCW, which is generated by an interference of two excitation laser beams on a liquid surface. By irradiating a probing laser on LiCW, a first order diffracted beam containing information of sample viscosity, is generated. The intensity of the reflected beam is utilized to control the distance between liquid-level and the sensor. The newly integrated optical surface tracking system makes possible the stable viscosity measurement in the presence of disturbance such as evaporation and external vibration. MOVS consists of five U-grooves fabricated by MEMS (Micro Electro Mechanical Systems) process to possess the optical fibers (photonic crystal fibers and fusion-spliced lensed fibers). In this study, by integrating the optical surface tracking system on the chip, nanosecond order damping oscillation of LiCW is successfully observed in the presence of external forced vibration, high speed evaporation (speed of 1 micrometer per second) and drying process of a liquid film (thickness of hundreds micrometer order).

A New Fiber Preform with Nanocarbon Binder for Manufacturing Carbon Fiber Reinforced Composite by Liquid Molding Process.

PubMed

Seong, Dong Gi; Ha, Jong Rok; Lee, Jea Uk; Lee, Wonoh; Kim, Byung Sun

2015-11-01

Carbon fiber reinforced composite has been a good candidate of lightweight structural component in the automotive industry. As fast production speed is essential to apply the composite materials for the mass production area such as automotive components, the high speed liquid composite molding processes have been developed. Fast resin injection through the fiber preform by high pressure is required to improve the production speed, but it often results in undesirable deformations of the fiber preform which causes defectives in size and properties of the final composite products. In order to prevent the undesirable deformation and improve the stability of preform shape, polymer type binder materials are used. More stable fiber preform can be obtained by increasing the amount of binder material, but it disturbs the resin impregnation through the fiber preform. In this study, carbon nanomaterials such as graphene oxide were embedded on the surface of carbon fiber by electrophoretic deposition method in order to improve the shape stability of fiber preform and interfacial bonding between polymer and the reinforcing fiber. Effects of the modified reinforcing fiber were investigated in two respects. One is to increase the binding energy between fiber tows, and the other is to increase the interfacial bonding between polymer matrix and fiber surface. The effects were analyzed by measuring the binding force of fiber preform and interlaminar shear strength of the composite. This study also investigated the high speed liquid molding process of the composite materials composed of polymer matrix and the carbon fiber preforms embedded by carbon nanomaterials. Process parameter such as permeability of fiber preform was measured to investigate the effect of nanoscale surface modification on the macroscale processing condition for composite manufacturing.

Laboratory and on-road evaluations of cabin air filters using number and surface area concentration monitors.

PubMed

Qi, Chaolong; Stanley, Nick; Pui, David Y H; Kuehn, Thomas H

2008-06-01

An automotive cabin air filter's effectiveness for removing airborne particles was determined both in a laboratory wind tunnel and in vehicle on-road tests. The most penetrating particle size for the test filter was approximately 350 nm, where the filtration efficiency was 22.9 and 17.4% at medium and high fan speeds, respectively. The filtration efficiency increased for smaller particles and was 43.9% for 100 nm and 72.0% for 20 nm particles at a medium fan speed. We determined the reduction in passenger exposure to particles while driving in freeway traffic caused by a vehicle ventilation system with a cabin air filter installed. Both particle number and surface area concentration measurements were made inside the cabin and in the surrounding air. At medium fan speed, the number and surface area concentration-based exposure reductions were 65.6 +/- 6.0% and 60.6 +/- 9.4%, respectively. To distinguish the exposure reduction contribution from the filter alone and the remainder of the ventilation system, we also performed tests with and without the filter in place using the surface area monitors. The ventilation system operating in the recirculation mode with the cabin air filter installed provided the maximum protection, reducing the cabin particle concentration exponentially over time and usually taking only 3 min to reach 10 microm2/cm3 (a typical office air condition) under medium fan speed.

A high-precision instrument for analyzing nonlinear dynamic behavior of bearing cage.

PubMed

Yang, Z; Chen, H; Yu, T; Li, B

2016-08-01

The high-precision ball bearing is fundamental to the performance of complex mechanical systems. As the speed increases, the cage behavior becomes a key factor in influencing the bearing performance, especially life and reliability. This paper develops a high-precision instrument for analyzing nonlinear dynamic behavior of the bearing cage. The trajectory of the rotational center and non-repetitive run-out (NRRO) of the cage are used to evaluate the instability of cage motion. This instrument applied an aerostatic spindle to support and spin test the bearing to decrease the influence of system error. Then, a high-speed camera is used to capture images when the bearing works at high speeds. A 3D trajectory tracking software tema Motion is used to track the spot which marked the cage surface. Finally, by developing the matlab program, a Lissajous' figure was used to evaluate the nonlinear dynamic behavior of the cage with different speeds. The trajectory of rotational center and NRRO of the cage with various speeds are analyzed. The results can be used to predict the initial failure and optimize cage structural parameters. In addition, the repeatability precision of instrument is also validated. In the future, the motorized spindle will be applied to increase testing speed and image processing algorithms will be developed to analyze the trajectory of the cage.

A high-precision instrument for analyzing nonlinear dynamic behavior of bearing cage

NASA Astrophysics Data System (ADS)

Yang, Z.; Chen, H.; Yu, T.; Li, B.

2016-08-01

The high-precision ball bearing is fundamental to the performance of complex mechanical systems. As the speed increases, the cage behavior becomes a key factor in influencing the bearing performance, especially life and reliability. This paper develops a high-precision instrument for analyzing nonlinear dynamic behavior of the bearing cage. The trajectory of the rotational center and non-repetitive run-out (NRRO) of the cage are used to evaluate the instability of cage motion. This instrument applied an aerostatic spindle to support and spin test the bearing to decrease the influence of system error. Then, a high-speed camera is used to capture images when the bearing works at high speeds. A 3D trajectory tracking software tema Motion is used to track the spot which marked the cage surface. Finally, by developing the matlab program, a Lissajous' figure was used to evaluate the nonlinear dynamic behavior of the cage with different speeds. The trajectory of rotational center and NRRO of the cage with various speeds are analyzed. The results can be used to predict the initial failure and optimize cage structural parameters. In addition, the repeatability precision of instrument is also validated. In the future, the motorized spindle will be applied to increase testing speed and image processing algorithms will be developed to analyze the trajectory of the cage.

A high-precision instrument for analyzing nonlinear dynamic behavior of bearing cage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Z., E-mail: zhaohui@nwpu.edu.cn; Yu, T.; Chen, H.

2016-08-15

The high-precision ball bearing is fundamental to the performance of complex mechanical systems. As the speed increases, the cage behavior becomes a key factor in influencing the bearing performance, especially life and reliability. This paper develops a high-precision instrument for analyzing nonlinear dynamic behavior of the bearing cage. The trajectory of the rotational center and non-repetitive run-out (NRRO) of the cage are used to evaluate the instability of cage motion. This instrument applied an aerostatic spindle to support and spin test the bearing to decrease the influence of system error. Then, a high-speed camera is used to capture images whenmore » the bearing works at high speeds. A 3D trajectory tracking software TEMA Motion is used to track the spot which marked the cage surface. Finally, by developing the MATLAB program, a Lissajous’ figure was used to evaluate the nonlinear dynamic behavior of the cage with different speeds. The trajectory of rotational center and NRRO of the cage with various speeds are analyzed. The results can be used to predict the initial failure and optimize cage structural parameters. In addition, the repeatability precision of instrument is also validated. In the future, the motorized spindle will be applied to increase testing speed and image processing algorithms will be developed to analyze the trajectory of the cage.« less

High speed CMOS acquisition system based on FPGA embedded image processing for electro-optical measurements

NASA Astrophysics Data System (ADS)

Rosu-Hamzescu, Mihnea; Polonschii, Cristina; Oprea, Sergiu; Popescu, Dragos; David, Sorin; Bratu, Dumitru; Gheorghiu, Eugen

2018-06-01

Electro-optical measurements, i.e., optical waveguides and plasmonic based electrochemical impedance spectroscopy (P-EIS), are based on the sensitive dependence of refractive index of electro-optical sensors on surface charge density, modulated by an AC electrical field applied to the sensor surface. Recently, P-EIS has emerged as a new analytical tool that can resolve local impedance with high, optical spatial resolution, without using microelectrodes. This study describes a high speed image acquisition and processing system for electro-optical measurements, based on a high speed complementary metal-oxide semiconductor (CMOS) sensor and a field-programmable gate array (FPGA) board. The FPGA is used to configure CMOS parameters, as well as to receive and locally process the acquired images by performing Fourier analysis for each pixel, deriving the real and imaginary parts of the Fourier coefficients for the AC field frequencies. An AC field generator, for single or multi-sine signals, is synchronized with the high speed acquisition system for phase measurements. The system was successfully used for real-time angle-resolved electro-plasmonic measurements from 30 Hz up to 10 kHz, providing results consistent to ones obtained by a conventional electrical impedance approach. The system was able to detect amplitude variations with a relative variation of ±1%, even for rather low sampling rates per period (i.e., 8 samples per period). The PC (personal computer) acquisition and control software allows synchronized acquisition for multiple FPGA boards, making it also suitable for simultaneous angle-resolved P-EIS imaging.

High-speed wavelength switching of tunable MEMS vertical cavity surface emitting laser by ringing suppression

NASA Astrophysics Data System (ADS)

Inoue, Shunya; Nishimura, Shun; Nakahama, Masanori; Matsutani, Akihiro; Sakaguchi, Takahiro; Koyama, Fumio

2018-04-01

For use in wavelength division multiplexing (WDM) with high-speed wavelength routing functions, the fast wavelength switching of tunable lasers is a key function. A tunable MEMS vertical cavity surface emitting laser (VCSEL) is a good candidate as a light source for this purpose. The cantilever in MEMS VCSELs has a high mechanical resonance frequency thanks to its small size, but the switching time is limited by the ringing of the cantilever structure. In this paper, we analyzed the mechanical behavior of a cantilever MEMS mirror and demonstrated ringing-free operation with an engineered voltage signal. The applied voltage waveform was optimized in a two-step format and we experimentally obtained ringing free wavelength switching. We measured the transient response of the wavelength by inserting a tunable filter, exhibiting the settling time of less than 2.5 µs, which corresponds to a half period of the cantilever resonance frequency.

All-organic superhydrophobic coatings with mechanochemical robustness and liquid impalement resistance

NASA Astrophysics Data System (ADS)

Peng, Chaoyi; Chen, Zhuyang; Tiwari, Manish K.

2018-03-01

Superhydrophobicity is a remarkable evolutionary adaption manifested by several natural surfaces. Artificial superhydrophobic coatings with good mechanical robustness, substrate adhesion and chemical robustness have been achieved separately. However, a simultaneous demonstration of these features along with resistance to liquid impalement via high-speed drop/jet impact is challenging. Here, we describe all-organic, flexible superhydrophobic nanocomposite coatings that demonstrate strong mechanical robustness under cyclic tape peels and Taber abrasion, sustain exposure to highly corrosive media, namely aqua regia and sodium hydroxide solutions, and can be applied to surfaces through scalable techniques such as spraying and brushing. In addition, the mechanical flexibility of our coatings enables impalement resistance to high-speed drops and turbulent jets at least up to 35 m s-1 and a Weber number of 43,000. With multifaceted robustness and scalability, these coatings should find potential usage in harsh chemical engineering as well as infrastructure, transport vehicles and communication equipment.

Study of advanced composite structural design concepts for an arrow wing supersonic cruise configuration

NASA Technical Reports Server (NTRS)

Turner, M. J.; Grande, D. L.

1978-01-01

Based on estimated graphite and boron fiber properties, allowable stresses and strains were established for advanced composite materials. Stiffened panel and conventional sandwich panel concepts were designed and analyzed, using graphite/polyimide and boron/polyimide materials. The conventional sandwich panel was elected as the structural concept for the modified wing structure. Upper and lower surface panels of the arrow wing structure were then redesigned, using high strength graphite/polyimide sandwich panels, retaining the titanium spars and ribs from the prior study. The ATLAS integrated analysis and design system was used for stress analysis and automated resizing of surface panels. Flutter analysis of the hybrid structure showed a significant decrease in flutter speed relative to the titanium wing design. The flutter speed was increased to that of the titanium design by selective increase in laminate thickness and by using graphite fibers with properties intermediate between high strength and high modulus values.

Dynamics of near-surface electric discharges and mechanisms of their interaction with the airflow

NASA Astrophysics Data System (ADS)

Leonov, Sergey B.; Adamovich, Igor V.; Soloviev, Victor R.

2016-12-01

The main focus of the review is on dynamics and kinetics of near-surface discharge plasmas, such as surface dielectric barrier discharges sustained by AC and repetitively pulsed waveforms, pulsed DC discharges, and quasi-DC discharges, generated in quiescent air and in the airflow. A number of technical issues related to plasma flow control applications are discussed in detail, including discharge development via surface ionization waves, charge transport and accumulation on dielectric surface, discharge contraction, different types of flow perturbations generated by surface discharges, and effect of high-speed flow on discharge dynamics. In the first part of the manuscript, plasma morphology and results of electrical and optical emission spectroscopy measurements are discussed. Particular attention is paid to dynamics of surface charge accumulation and dissipation, both in diffuse discharges and during development of ionization instabilities resulting in discharge contraction. Contraction leads to significant increase of both the surface area of charge accumulation and the energy coupled to the plasma. The use of alternating polarity pulse waveforms accelerates contraction of surface dielectric barrier discharges and formation of filamentary plasmas. The second part discusses the interaction of discharge plasmas with quiescent air and the external airflow. Four major types of flow perturbations have been identified: (1) low-speed near-surface jets generated by electrohydrodynamic interaction (ion wind); (2) spanwise and streamwise vortices formed by both electrohydrodynamic and thermal effects; (3) weak shock waves produced by rapid heating in pulsed discharges on sub-microsecond time scale; and (4) near-surface localized stochastic perturbations, on sub-millisecond time, detected only recently. The mechanism of plasma-flow interaction remains not fully understood, especially in filamentary surface dielectric barrier discharges. Localized quasi-DC surface discharges sustained in a high-speed flow are discussed in the third part of the review. Although dynamics of this type of the discharge is highly transient, due to its strong interaction with the flow, the resultant flow structure is stationary, including the oblique shock and the flow separation region downstream of the discharge. The oblique shock is attached to a time-averaged, wedge-shaped, near-wall plasma layer, with the shock angle controlled by the discharge power, which makes possible changing the flow structure and parameters in a controlled way. Finally, unresolved and open-ended issues are discussed in the summary.

Laboratory Study of Topographic Effects on the Near-surface Tornado Flow Field

NASA Astrophysics Data System (ADS)

Razavi, Alireza; Sarkar, Partha P.

2018-03-01

To study topographic effects on the near-surface tornado flow field, the Iowa State University tornado simulator was used to simulate a translating tornado passing over three different two-dimensional topographies: a ridge, an escarpment and a valley. The effect of the translation speed on maximum horizontal wind speeds is observed for translation speeds of 0.15 and 0.50 m s^{-1} , with the lower value resulting in a larger maximum horizontal wind speed. The tornado translation over the three topographies with respect to flat terrain is assessed for changes in: (a) the maximum horizontal wind speeds in terms of the flow-amplification factor; (b) the maximum aerodynamic drag in terms of the tornado speed-up ratio; (c) the maximum duration of exposure at any location to high wind speeds of a specific range in terms of the exposure amplification factor. Results show that both the maximum wind amplification factor of 14%, as well as the maximum speed-up ratio of 14%, occur on the ridge. For all topographies, the increase in aerodynamic drag is observed to be maximized for low-rise buildings, which illustrates the importance of the vertical profiles of the horizontal wind speed near the ground. The maximum exposure amplification factors, estimated for the range of wind speeds corresponding to the EF2 (50-60 m s^{-1} ) and EF3 (61-75 m s^{-1}) scales, are 86 and 110% for the ridge, 4 and 60% for the escarpment and - 6 and 47% for the valley, respectively.

Evaluation of the surface roughness effect on suspended particle deposition near unpaved roads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Dongzi; Gillies, J. A.; Etyemezian, V.

2015-11-11

The downwind transport and deposition of suspended dust raised by a vehicle driving on unpaved roads was studied for four differently vegetated surfaces in the USA states of Kansas and Washington, and one barren surface in Nevada. A 10 m high tower adjacent to the source (z10 m downwind) and an array of multi-channel optical particle counters at three positions downwind of the source measured the flux of particles and the particle size distribution in the advecting dust plumes in the horizontal and vertical directions. Aerodynamic parameters such as friction velocity (u*) and surface roughness length (z0) were calculated frommore » wind speed measurements made on the tower. Particle number concentration, PM10 mass exhibited an exponential decay along the direction of transport. Coarse particles accounted for z95% of the PM10 mass, at least to a downwind distance of 200 m from the source. PM10 removed by deposition was found to increase with increasing particle size and increasing surface roughness under similar moderate wind speed conditions. The surface of dense, long grass (1.2 m high and complete surface cover) had the greatest reduction of PM10 among the five surfaces tested due to deposition induced by turbulence effects created by the rougher surface and by enhanced particle impaction/ interception effects to the grass blades.« less

Numerical Study of High-Speed Droplet Impact on Surfaces and its Physical Cleaning Effects

NASA Astrophysics Data System (ADS)

Kondo, Tomoki; Ando, Keita

2015-11-01

Spurred by the demand for cleaning techniques of low environmental impact, one favors physical cleaning that does not rely on any chemicals. One of the promising candidates is based on water jets that often involve fission into droplet fragments and collide with target surfaces to which contaminant particles (often micron-sized or even smaller) stick. Hydrodynamic force (e.g., shearing and lifting) arising from the droplet impact will play a role to remove the particles, but its detailed mechanism is still unknown. To explore the role of high-speed droplet impact in physical cleaning, we solve compressible Navier-Stokes equations with a finite volume method that is designed to capture both shocks and material interfaces in accurate and robust manners. Water hammer and shear flow accompanied by high-speed droplet impact at a rigid wall is simulated to evaluate lifting force and rotating torque, which are relevant to the application of particle removal. For the simulation, we use the numerical code recently developed by Computational Flow Group lead by Tim Colonius at Caltech. The first author thanks Jomela Meng for her help in handling the code during his stay at Caltech.

Effect of Tail Dihedral on Lateral Control Effectiveness at High Subsonic Speeds of Differentially Deflected Horizontal-Tail Surfaces on a Configuration having a Thin Highly Tapered Wing

NASA Technical Reports Server (NTRS)

Fournier, Paul G.

1959-01-01

Tests have been conducted in the Langley high-speed 7- by 10-foot tunnel to determine the effect of tail dihedral on lateral control effectiveness of a complete-model configuration having differentially deflected horizontal-tail surfaces. Limited tests were made to determine the lateral characteristics as well as the longitudinal characteristics in sideslip. The wing had an aspect ratio of 3, a taper ratio of 0.14, 28.80 deg sweep of the quarter-chord line with zero sweep at the 80-percent-chord line, and NACA 65A004 airfoil sections. The test Mach number range extended from 0.60 to 0.92. There are only small variations in the roll effectiveness parameter C(sub iota delta) with negative tail dihedral angle. The tail size used on the test model, however, is perhaps inadequate for providing the roll rates specified by current military requirements at subsonic speeds. The lateral aerodynamic characteristics were essentially constant throughout the range of sideslip angle from 12 deg to -12 deg. A general increase in yawing moment was noted with increased negative dihedral throughout the Mach number range.

High-speed measurements of steel-plate deformations during laser surface processing.

PubMed

Jezersek, Matija; Gruden, Valter; Mozina, Janez

2004-10-04

In this paper we present a novel approach to monitoring the deformations of a steel plate's surface during various types of laser processing, e.g., engraving, marking, cutting, bending, and welding. The measuring system is based on a laser triangulation principle, where the laser projector generates multiple lines simultaneously. This enables us to measure the shape of the surface with a high sampling rate (80 Hz with our camera) and high accuracy (+/-7 microm). The measurements of steel-plate deformations for plates of different thickness and with different illumination patterns are presented graphically and in an animation.

A Moving Tale

ERIC Educational Resources Information Center

Science Teacher, 2005

2005-01-01

Massachusetts Institute of Technology (MIT) mathematicians have discovered how certain insects can climb what to them are steep, slippery slopes in the water's surface without moving their limbs, and do it at high speed. Welcome to the world of the tiny creatures that live on the surface of ponds, lakes, and other standing bodies of water. For the…

Ultra-high speed permanent magnet axial gap alternator with multiple stators

DOEpatents

Hawsey, Robert A.; Bailey, J. Milton

1991-01-01

An ultra-high speed, axial gap alternator that can provide an output to a plurality of loads, the alternator providing magnetic isolation such that operating conditions in one load will not affect operating conditions of another load. This improved alternator uses a rotor member disposed between a pair of stator members, with magnets disposed in each of the rotor member surfaces facing the stator members. The magnets in one surface of the rotor member, which alternate in polarity, are isolated from the magnets in the other surface of the rotor member by a disk of magnetic material disposed between the two sets of magents. In the preferred embodiment, this disk of magnetic material is laminated between two layers of non-magnetic material that support the magnets, and the magnetic material has a peripheral rim that extends to both surfaces of the rotor member to enhance the structural integrity. The stator members are substantially conventional in construction in that equally-spaced and radially-oriented slots are provided, and winding members are laid in these slots. A unit with multiple rotor members and stator members is also described.

The Effects of Some Surface Irregularities on Wing Drag

NASA Technical Reports Server (NTRS)

Drag, Manley

1939-01-01

The N.A.C.A. has conducted tests to provide more complete data than were previously available for estimating the effects of common surface irregularities on wing drag. The irregularities investigated included: brazier-head and countersunk rivets, spot welds, several types of sheet-metal joints, and surface roughness. Tests were also conducted to determine the over-all effect of manufacturing irregularities incidental to riveted aluminum alloy and to spot-welded stainless-steel construction. The tests were made in the 8-foot high speed wind tunnel at Reynolds Numbers up to 18,000,000. The results show that any of the surface irregularities investigated may increase wing drag enough to have important adverse effects on high-speed performance and economy. A method of estimating increases in wing drag caused by brazier-head rivets and lapped joints under conditions outside the range of the tests is suggested. Estimated drag increases due to rivets and lapped joints under conditions outside the range of the tests is suggested. Estimated drag increases due to rivets and lapped joints on a wing of 20-foot chord flying at 250 miles per hour are shown.

High-speed AFM for scanning the architecture of living cells

NASA Astrophysics Data System (ADS)

Li, Jing; Deng, Zhifeng; Chen, Daixie; Ao, Zhuo; Sun, Quanmei; Feng, Jiantao; Yin, Bohua; Han, Li; Han, Dong

2013-08-01

We address the modelling of tip-cell membrane interactions under high speed atomic force microscopy. Using a home-made device with a scanning area of 100 × 100 μm2, in situ imaging of living cells is successfully performed under loading rates from 1 to 50 Hz, intending to enable detailed descriptions of physiological processes in living samples.We address the modelling of tip-cell membrane interactions under high speed atomic force microscopy. Using a home-made device with a scanning area of 100 × 100 μm2, in situ imaging of living cells is successfully performed under loading rates from 1 to 50 Hz, intending to enable detailed descriptions of physiological processes in living samples. Electronic supplementary information (ESI) available: Movie of the real-time change of inner surface within fresh blood vessel. The movie was captured at a speed of 30 Hz in the range of 80 μm × 80 μm. See DOI: 10.1039/c3nr01464a

Cryogenic, high speed, turbopump bearing cooling requirements

NASA Technical Reports Server (NTRS)

Dolan, Fred J.; Gibson, Howard G.; Cannon, James L.; Cody, Joe C.

1988-01-01

Although the Space Shuttle Main Engine (SSME) has repeatedly demonstrated the capability to perform during launch, the High Pressure Oxidizer Turbopump (HPOTP) main shaft bearings have not met their 7.5 hour life requirement. A tester is being employed to provide the capability of subjecting full scale bearings and seals to speeds, loads, propellants, temperatures, and pressures which simulate engine operating conditions. The tester design permits much more elaborate instrumentation and diagnostics than could be accommodated in an SSME turbopump. Tests were made to demonstrate the facilities; and the devices' capabilities, to verify the instruments in its operating environment and to establish a performance baseline for the flight type SSME HPOTP Turbine Bearing design. Bearing performance data from tests are being utilized to generate: (1) a high speed, cryogenic turbopump bearing computer mechanical model, and (2) a much improved, very detailed thermal model to better understand bearing internal operating conditions. Parametric tests were also made to determine the effects of speed, axial loads, coolant flow rate, and surface finish degradation on bearing performance.

Microplastic sampling with the AVANI trawl compared to two neuston trawls in the Bay of Bengal and South Pacific.

PubMed

Eriksen, Marcus; Liboiron, Max; Kiessling, Tim; Charron, Louis; Alling, Abigail; Lebreton, Laurent; Richards, Heather; Roth, Barent; Ory, Nicolas C; Hidalgo-Ruz, Valeria; Meerhoff, Erika; Box, Carolynn; Cummins, Anna; Thiel, Martin

2018-01-01

Many typical neuston trawls can only be used during relatively calm sea states and slow tow speeds. During two expeditions to the Bay of Bengal and the eastern South Pacific we investigated whether the new, high-speed AVANI trawl (All-purpose Velocity Accelerated Net Instrument) collects similar amounts and types of microplastics as two established scientific trawl designs, the manta trawl and the DiSalvo neuston net. Using a 335 μm net, the AVANI trawl can collect microplastics from the sea surface at speeds up to 8 knots as it "skis" across the surface, whereas the manta and DiSalvo neuston trawls must be towed slowly in a less turbulent sea state and often represent shorter tow lengths. Generally, the AVANI trawl collected a greater numerical abundance and weight of plastic particles in most size classes and debris types than the manta trawl and DiSalvo neuston net, likely because these trawls only skim the surface layer while the AVANI trawl, moving vertically in a random fashion, collects a "deeper" sample, capturing the few plastics that float slightly lower in the water column. However, the samples did not differ enough that results were significantly affected, suggesting that studies done with these different trawls are comparable. The advantage of the AVANI trawl over traditional research trawls is that it allows for collection on vessels underway at high speeds and during long transits, allowing for a nearly continuous sampling effort over long distances. As local surface currents make sea surface abundance widely heterogeneous, widely spaced short-tow trawls, such as the manta and DiSalvo trawls, can catch or miss hotspots or meso-scale variability of microplastic accumulations, whereas the AVANI trawl, if utilized for back-to-back tows of intermediate distances (5-10 km), can bridge variable wind conditions and debris concentrations potentially reducing variance and provide a greater resolution of spatial distribution. Copyright © 2017 Elsevier Ltd. All rights reserved.

A study examining the effects of water-miscible cutting fluids for end milling process of carbon fiber reinforced plastic

NASA Astrophysics Data System (ADS)

Anan, Ruito; Matsuoka, Hironori; Ono, Hajime; Ryu, Takahiro; Nakae, Takashi; Shuto, Schuichi; Watanabe, Suguru; Sato, Yuta

2017-04-01

This study examined the improvements to the tool life and finished surface roughness by using water-miscible cutting fluids in carbon fiber reinforced plastics end milling. In cutting tests, it was found that the use of emulsion type, soluble type, and solution type cutting fluids improved tool life compared with the case of dry cutting. Specifically, significant differences in tool life were observed at a high cutting speed of 171 m/min. In addition, the finished surface exhibited a low level of roughness when the solution type cutting fluid was used, regardless of the cutting speed.

A vectorization of the Hess McDonnell Douglas potential flow program NUED for the STAR-100 computer

NASA Technical Reports Server (NTRS)

Boney, L. R.; Smith, R. E., Jr.

1979-01-01

The computer program NUED for analyzing potential flow about arbitrary three dimensional lifting bodies using the panel method was modified to use vector operations and run on the STAR-100 computer. A high speed of computation and ability to approximate the body surface with a large number of panels are characteristics of NUEDV. The new program shows that vector operations can be readily implemented in programs of this type to increase the computational speed on the STAR-100 computer. The virtual memory architecture of the STAR-100 facilitates the use of large numbers of panels to approximate the body surface.

Sea surface mean square slope from Ku-band backscatter data

NASA Technical Reports Server (NTRS)

Jackson, F. C.; Walton, W. T.; Hines, D. E.; Walter, B. A.; Peng, C. Y.

1992-01-01

A surface mean-square-slope parameter analysis is conducted for 14-GHz airborne radar altimeter near-nadir, quasi-specular backscatter data, which in raw form obtained by least-squares fitting of an optical scattering model to the return waveform show an approximately linear dependence over the 7-15 m/sec wind speed range. Slope data are used to draw inferences on the structure of the high-wavenumber portion of the spectrum. A directionally-integrated model height spectrum that encompasses wind speed-dependent k exp -5/2 and classical Phillips k exp -3 power laws subranges in the range of gravity waves is supported by the data.

Mechanism and experimental research on ultra-precision grinding of ferrite

NASA Astrophysics Data System (ADS)

Ban, Xinxing; Zhao, Huiying; Dong, Longchao; Zhu, Xueliang; Zhang, Chupeng; Gu, Yawen

2017-02-01

Ultra-precision grinding of ferrite is conducted to investigate the removal mechanism. Effect of the accuracy of machine tool key components on grinding surface quality is analyzed. The surface generation model of ferrite ultra-precision grinding machining is established. In order to reveal the surface formation mechanism of ferrite in the process of ultraprecision grinding, furthermore, the scientific and accurate of the calculation model are taken into account to verify the grinding surface roughness, which is proposed. Orthogonal experiment is designed using the high precision aerostatic turntable and aerostatic spindle for ferrite which is a typical hard brittle materials. Based on the experimental results, the influence factors and laws of ultra-precision grinding surface of ferrite are discussed through the analysis of the surface roughness. The results show that the quality of ferrite grinding surface is the optimal parameters, when the wheel speed of 20000r/mm, feed rate of 10mm/min, grinding depth of 0.005mm, and turntable rotary speed of 5r/min, the surface roughness Ra can up to 75nm.

Sensitivity of Offshore Surface Fluxes and Sea Breezes to the Spatial Distribution of Sea-Surface Temperature

NASA Astrophysics Data System (ADS)

Lombardo, Kelly; Sinsky, Eric; Edson, James; Whitney, Michael M.; Jia, Yan

2018-03-01

A series of numerical sensitivity experiments is performed to quantify the impact of sea-surface temperature (SST) distribution on offshore surface fluxes and simulated sea-breeze dynamics. The SST simulations of two mid-latitude sea-breeze events over coastal New England are performed using a spatially-uniform SST, as well as spatially-varying SST datasets of 32- and 1-km horizontal resolutions. Offshore surface heat and buoyancy fluxes vary in response to the SST distribution. Local sea-breeze circulations are relatively insensitive, with minimal differences in vertical structure and propagation speed among the experiments. The largest thermal perturbations are confined to the lowest 10% of the sea-breeze column due to the relatively high stability of the mid-Atlantic marine atmospheric boundary layer (ABL) suppressing vertical mixing, resulting in the depth of the marine layer remaining unchanged. Minimal impacts on the column-averaged virtual potential temperature and sea-breeze depth translates to small changes in sea-breeze propagation speed. This indicates that the use of datasets with a fine-scale SST may not produce more accurate sea-breeze simulations in highly stable marine ABL regimes, though may prove more beneficial in less stable sub-tropical environments.

X-4 with Pilot Joe Walker, Preflight Briefing

NASA Technical Reports Server (NTRS)

1952-01-01

In this 1952 photograph NACA test pilot Joe Walker (on left) is seen discussing tests points to be flown on the X-4 aircraft with NACA research engineer Donald Bellman. The X-4 Bantam, a single-place, low swept-wing, semi-tailless aircraft, was designed and built by Northrop Aircraft, Inc. It had no horizontal tail surfaces and its mission was to obtain in-flight data on the stability and control of semi-tailless aircraft at high subsonic speeds. The Northrop X-4, Bantam, was a single-place, swept-wing, semi-tailless airplane designed and built to investigate that configuration at transonic speeds (defined as speeds just below and just above the speed of sound, but in this case, the testing was done primarily at just below the speed of sound). The hope of some aerodynamicists was that eliminating the horizontal tail would also do away with stability problems at transonic speeds resulting from the interaction of supersonic shock waves from the wings and the horizontal stabilizers. Northrop Aircraft, Inc. built two X-4 aircraft, the first of which proved to be mechanically unsound. However, ship number 2, with a thicker trailing edge on the wings and elevon, was very reliable. Ship 1 was then grounded and used as parts for ship 2. While being tested from 1950 to 1953 at the NACA High-Speed Flight Research Station (predecessor of today's NASA Dryden Flight Research Center, Edwards, California), the X-4's semi-tailless configuration exhibited inherent longitudinal stability problems (porpoising) as it approached the speed of sound. The X-4 was a small twinjet-engine airplane that had no horizontal tail surfaces, depending instead on combined elevator and aileron control surfaces (called elevons) for control in pitch and roll attitudes. Data gathered from the aircraft's blunt elevon research were helpful in the design of the Bell X-2, which had ailerons with blunted trailing edges. The NACA X-4 program also provided substantial data on the interactions of combined pitching, rolling, and yawing motions. This interaction was soon to become critical to upcoming high-performance military fighters. The X-4, ship 2, flew 82 research flights from 1950 to 1953. With a minimal lift-to-drag ratio of less than 3, the X-4 performance was similar to the soon-to-be-developed X-15. With this similarity in mind, NACA conducted approach and landing studies of X-15-generation aircraft using the X-4. The X-4, retired in 1954, ended its days as a pilot trainer.

Comparative study on stained InGaAs quantum wells for high-speed optical-interconnect VCSELs

NASA Astrophysics Data System (ADS)

Li, Hui; Jia, Xiaowei

2018-05-01

The gain-carrier characteristics of InGaAs quantum well for 980 nm high-speed, energy-efficient vertical-cavity surface-emitting lasers are investigated. We specially studied the potentially InGaAs quantum well designs can be used for the active region of energy-efficient, temperature-stable 980-nm VCSEL, which introduced a quantum well gain peak wavelength-to-cavity resonance wavelength offset to improve the dynamic performance at high operation temperature. Several candidate quantum wells are being compared in theory and measurement. We found that ∼5 nm InGaAs QW with ∼6 nm barrier thickness is suitable for the active region of high-speed optical interconnect 980 nm VCSELs, and no significant improvement in the 20% range of In content of InGaAs QWs. The results are useful for next generation green photonic device design.

Non-Contact Measurement Using A Laser Scanning Probe

NASA Astrophysics Data System (ADS)

Modjarrad, Amir

1989-03-01

Traditional high accuracy touch-trigger probing can now be complemented by high speed, non-contact, profile scanning to give another "dimension" to the three-dimensional Co-ordinate Measuring Machines (CMMs). Some of the features of a specially developed laser scanning probe together with the trade-offs involved in the design of inspection systems that use triangulation are examined. Applications of such a laser probe on CMMs are numerous since high speed scanning allows inspection of many different components and surfaces. For example, car body panels, tyre moulds, aircraft wing skins, turbine blades, wax and clay models, plastics, etc. Other applications include in-process surveillance in manufacturing and food processing, robotics vision and many others. Some of these applications are discussed and practical examples, case studies and experimental results are given with particular reference to use on CMMs. In conclusion, future developments and market trends in high speed non-contact measurement are discussed.

How well can we measure the vertical wind speed? Implications for fluxes of energy and mass

Treesearch

John Kochendorfer; Tilden P. Meyers; John Frank; William J. Massman; Mark W. Heuer

2012-01-01

Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10­50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a nonorthogonal transducer...

Analysis of multi lobe journal bearings with surface roughness using finite difference method

NASA Astrophysics Data System (ADS)

PhaniRaja Kumar, K.; Bhaskar, SUdaya; Manzoor Hussain, M.

2018-04-01

Multi lobe journal bearings are used for high operating speeds and high loads in machines. In this paper symmetrical multi lobe journal bearings are analyzed to find out the effect of surface roughnessduring non linear loading. Using the fourth order RungeKutta method, time transient analysis was performed to calculate and plot the journal centre trajectories. Flow factor method is used to evaluate the roughness and the finite difference method (FDM) is used to predict the pressure distribution over the bearing surface. The Transient analysis is done on the multi lobe journal bearings for threedifferent surface roughness orientations. Longitudinal surface roughness is more effective when compared with isotopic and traverse surface roughness.

Research on the Effect of Welding Speed on the Quality of Welding Seam Based on the Local Dry Underwater Welding

NASA Astrophysics Data System (ADS)

Liu, Lei; Chen, Wu; Wang, Huagang; Ba, Jinyu; Li, Bing

2017-12-01

The repair of nuclear spent fuel pool has a high requirement for the quality of welding, the welding speed directly affects the quality of the weld when local dry automatic underwater welding is used to repair the damaged surface. Under the condition of the same condition, the local dry automatic underwater welding test was carried out under the condition of the same welding condition. Taking the 20cm as the experimental condition, after massive experiments show that when the welding speed is approximately 48cm/min the weld quality is high, meeting the design requirements, based on the double layer shrinkage nozzle chamber of local dry underwater automatic welding.

The structure of the inner heliosphere from Pioneer Venus and IMP observations

NASA Technical Reports Server (NTRS)

Gazis, P. R.; Barnes, A.; Mihalov, J. D.; Lazarus, A. J.

1992-01-01

The IMP 8 and Pioneer Venus Orbiter (PVO) spacecraft explore the region of heliographic latitudes between 8 deg N and 8 deg S. Solar wind observations from these spacecraft are used to construct synoptic maps of solar wind parameters in this region. These maps provide an explicit picture of the structure of high speed streams near 1 AU and how that structure varies with time. From 1982 until early 1985, solar wind parameters varied little with latitude. During the last solar minimum, the solar wind developed strong latitudinal structure; high speed streams were excluded from the vicinity of the solar equator. Synoptic maps of solar wind speed are compared with maps of the coronal source surface magnetic field. This comparison reveals the expected correlation between solar wind speed near 1 AU, the strength of the coronal magnetic field, and distance from the coronal neutral line.

Evaluation of NOAA's High Resolution Rapid Refresh (HRRR), 12 km North America Model (NAM12) and 4km North America Model (NAM 4) hub-height wind speed forecasts

NASA Astrophysics Data System (ADS)

Pendergrass, W.; Vogel, C. A.

2013-12-01

As an outcome of discussions between Duke Energy Generation and NOAA/ARL following the 2009 AMS Summer Community Meeting, in Norman Oklahoma, ARL and Duke Energy Generation (Duke) signed a Cooperative Research and Development Agreement (CRADA) which allows NOAA to conduct atmospheric boundary layer (ABL) research using Duke renewable energy sites as research testbeds. One aspect of this research has been the evaluation of forecast hub-height winds from three NOAA atmospheric models. Forecasts of 10m (surface) and 80m (hub-height) wind speeds from (1) NOAA/GSD's High Resolution Rapid Refresh (HRRR) model, (2) NOAA/NCEP's 12 km North America Model (NAM12) and (3) NOAA/NCEP's 4k high resolution North America Model (NAM4) were evaluated against 18 months of surface-layer wind observations collected at the joint NOAA/Duke Energy research station located at Duke Energy's West Texas Ocotillo wind farm over the period April 2011 through October 2012. HRRR, NAM12 and NAM4 10m wind speed forecasts were compared with 10m level wind speed observations measured on the NOAA/ATDD flux-tower. Hub-height (80m) HRRR , NAM12 and NAM4 forecast wind speeds were evaluated against the 80m operational PMM27-28 meteorological tower supporting the Ocotillo wind farm. For each HRRR update, eight forecast hours (hour 01, 02, 03, 05, 07, 10, 12, 15) plus the initialization hour (hour 00), evaluated. For the NAM12 and NAM4 models forecast hours 00-24 from the 06z initialization were evaluated. Performance measures or skill score based on absolute error 50% cumulative probability were calculated for each forecast hour. HRRR forecast hour 01 provided the best skill score with an absolute wind speed error within 0.8 m/s of observed 10m wind speed and 1.25 m/s for hub-height wind speed at the designated 50% cumulative probability. For both NAM4 and NAM12 models, skill scores were diurnal with comparable best scores observed during the day of 0.7 m/s of observed 10m wind speed and 1.1 m/s for hub-height wind speed at the designated 50% cumulative probability level.

High-Speed Semiconductor Vertical-Cavity Surface-Emitting Lasers for Optical Data-Transmission Systems (Review)

NASA Astrophysics Data System (ADS)

Blokhin, S. A.; Maleev, N. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Sakharov, A. V.; Ustinov, V. M.

2018-01-01

The main problems of providing a high-speed operation semiconductor lasers with a vertical microcavity (so-called "vertical-cavity surface-emitting lasers") under amplitude modulation and ways to solve them have been considered. The influence of the internal properties of the radiating active region and the electrical parasitic elements of the equivalent circuit of lasers are discussed. An overview of approaches that lead to an increase of the cutoff parasitic frequency, an increase of the differential gain of the active region, the possibility of the management of mode emission composition and the lifetime of photons in the optical microcavities, and reduction of the influence of thermal effects have been presented. The achieved level of modulation bandwidth of ˜30 GHz is close to the maximum achievable for the classical scheme of the direct-current modulation, which makes it necessary to use a multilevel modulation format to further increase the information capacity of optical channels constructed on the basis of vertical-cavity surface-emitting lasers.

A new aerodynamic integral equation based on an acoustic formula in the time domain

NASA Technical Reports Server (NTRS)

Farassat, F.

1984-01-01

An aerodynamic integral equation for bodies moving at transonic and supersonic speeds is presented. Based on a time-dependent acoustic formula for calculating the noise emanating from the outer portion of a propeller blade travelling at high speed (the Ffowcs Williams-Hawking formulation), the loading terms and a conventional thickness source terms are retained. Two surface and three line integrals are employed to solve an equation for the loading noise. The near-field term is regularized using the collapsing sphere approach to obtain semiconvergence on the blade surface. A singular integral equation is thereby derived for the unknown surface pressure, and is amenable to numerical solutions using Galerkin or collocation methods. The technique is useful for studying the nonuniform inflow to the propeller.

Time-optimized laser micro machining by using a new high dynamic and high precision galvo scanner

NASA Astrophysics Data System (ADS)

Jaeggi, Beat; Neuenschwander, Beat; Zimmermann, Markus; Zecherle, Markus; Boeckler, Ernst W.

2016-03-01

High accuracy, quality and throughput are key factors in laser micro machining. To obtain these goals the ablation process, the machining strategy and the scanning device have to be optimized. The precision is influenced by the accuracy of the galvo scanner and can further be enhanced by synchronizing the movement of the mirrors with the laser pulse train. To maintain a high machining quality i.e. minimum surface roughness, the pulse-to-pulse distance has also to be optimized. Highest ablation efficiency is obtained by choosing the proper laser peak fluence together with highest specific removal rate. The throughput can now be enhanced by simultaneously increasing the average power, the repetition rate as well as the scanning speed to preserve the fluence and the pulse-to-pulse distance. Therefore a high scanning speed is of essential importance. To guarantee the required excellent accuracy even at high scanning speeds a new interferometry based encoder technology was used, that provides a high quality signal for closed-loop control of the galvo scanner position. Low inertia encoder design enables a very dynamic scanner system, which can be driven to very high line speeds by a specially adapted control solution. We will present results with marking speeds up to 25 m/s using a f = 100 mm objective obtained with a new scanning system and scanner tuning maintaining a precision of about 5 μm. Further it will be shown that, especially for short line lengths, the machining time can be minimized by choosing the proper speed which has not to be the maximum one.

Characterizing Secondary Debris Impact Ejecta

NASA Technical Reports Server (NTRS)

Schonberg, W. P.

1999-01-01

All spacecraft in low-Earth orbit are subject to high-speed impacts by meteoroids and orbital debris particles. These impacts can damage flight-critical systems which can in turn lead to catastrophic failure of the spacecraft. Therefore, the design of a spacecraft for an Earth-orbiting mission must take into account the possibility of such impacts and their effects on the spacecraft structure and on all of its exposed subsystem components. In addition to threatening the operation of the spacecraft itself, on-orbit impacts also generate a significant amount of ricochet particles. These high-speed particles can destroy critical external spacecraft subsystem and also increase the contamination of the orbital environment. This report presents a summary of the work performed towards the development of an empirical model that characterizes the secondary ejecta created by a high-speed impacta on a typical aerospace structural surface.

Serial number coding and decoding by laser interference direct patterning on the original product surface for anti-counterfeiting.

PubMed

Park, In-Yong; Ahn, Sanghoon; Kim, Youngduk; Bae, Han-Sung; Kang, Hee-Shin; Yoo, Jason; Noh, Jiwhan

2017-06-26

Here, we investigate a method to distinguish the counterfeits by patterning multiple reflective type grating directly on the surface of the original product and analyze the serial number from its rotation angles of diffracted fringes. The micro-sized gratings were fabricated on the surface of the material at high speeds by illuminating the interference fringe generated by passing a high-energy pulse laser through the Fresnel biprism. In addition, analysis of the grating's diffraction fringes was performed using a continuous wave laser.

Wear Resistance of Steels with Surface Nanocrystalline Structure Generated by Mechanical-Pulse Treatment.

PubMed

Nykyforchyn, Hryhoriy; Kyryliv, Volodymyr; Maksymiv, Olha

2017-12-01

The influence of the surface mechanical-pulse treatment based on high-speed friction with a rapid cooling by the technological environment on the wear resistance of medium- and high-carbon steels was considered. The treatment due to a severe plastic deformation enabled obtaining the nanocrystalline structure with a grain size of 14-40 nm. A high positive effect of this treatment was obtained not only because of metal nanocrystallization but also thanks to other factors, namely, structural-phase transformations, carbon saturation of the surface due to decomposition of the coolant and the friction coefficient decrease. Higher carbon content leads to better strengthening of the surface, and its microhardness can reach 12 GPa.

Chemical etching mechanism and properties of microstructures in sapphire modified by femtosecond laser

NASA Astrophysics Data System (ADS)

Liu, Manyu; Hu, Youwang; Sun, Xiaoyan; Wang, Cong; Zhou, Jianying; Dong, Xinran; Yin, Kai; Chu, Dongkai; Duan, Ji'an

2017-01-01

Sapphire, with extremely high hardness, high-temperature stability and wear resistance, often corroded in molten KOH at 300 °C after processing. The fabrication of microstructures on sapphire substrate performed by femtosecond laser irradiation combined with KOH solution chemical etching at room temperature is presented. It is found that this method reduces the harsh requirements of sapphire corrosion. After femtosecond irradiation, the sapphire has a high corrosion speed at room temperature. Through the analysis of Raman spectrum and XRD spectrum, a novel insight of femtosecond laser interaction with sapphire (α-Al2O3) is proposed. Results indicated that grooves on sapphire surface were formed by the lasers ablation removal, and the groove surface was modified in a certain depth. The modified area of the groove surface was changed from α-Al2O3 to γ-Al2O3. In addition, the impacts of three experimental parameters, laser power, scanning velocities and etching time, on the width and depth of microstructures are investigated, respectively. The modified area dimension is about 2 μm within limits power and speed. This work could fabricate high-quality arbitrary microstructures and enhance the performance of sapphire processing.

Novel Aerodynamic Design for Formula SAE Vehicles

NASA Astrophysics Data System (ADS)

Sentongo, Samuel; Carter, Austin; Cecil, Christopher; Feier, Ioan

2017-11-01

This paper identifies and evaluates the design characteristics of a novel airfoil that harnesses the Magnus Effect, applying a moving-surface boundary-layer control (MSBC) method to a Formula SAE Vehicle. The MSBC minimizes adverse pressure gradient and delays boundary layer separation through the use of a conveyor belt that interacts with the airfoil boundary layer. The MSBC allows dynamic control of the aerodynamic coefficients by variation of the belt speed, minimizing drag in high speed straights and maximizing downforce during vehicle cornering. A conveyer belt wing measuring approximately 0.9 x 0.9m in planform was designed and built to test the mechanical setup for such a MSBC wing. This study follows the relationship between inputted power and outputted surface velocity, with the goal being to maximize speed output vs. power input. The greatest hindrance to maximizing speed output is friction among belts, rollers, and stationary members. The maximum belt speed achieved during testing was 5.9 m/s with a power input of 48.8 W, which corresponds to 45.8 N of downforce based on 2D CFD results. Ongoing progress on this project is presented. United States Air Force Academy.

Aquatic burst locomotion by hydroplaning and paddling in common eiders (Somateria mollissima).

PubMed

Gough, William T; Farina, Stacy C; Fish, Frank E

2015-06-01

Common eiders (Somateria mollissima) are heavy sea-ducks that spend a large portion of their time swimming at the water surface. Surface swimming generates a bow and hull wave that can constructively interfere and produce wave drag. The speed at which the wavelengths of these waves equal the waterline length of the swimming animal is the hull speed. To increase surface swimming speed beyond the hull speed, an animal must overtake the bow wave. This study found two distinct behaviors that eider ducks used to exceed the hull speed: (1) 'steaming', which involved rapid oaring with the wings to propel the duck along the surface of the water, and (2) 'paddle-assisted flying', during which the ducks lifted their bodies out of the water and used their feet to paddle against the surface while flapping their wings in the air. An average hull speed (0.732±0.046 m s(-1)) was calculated for S. mollissima by measuring maximum waterline length from museum specimens. On average, steaming ducks swam 5.5 times faster and paddle-assisted flying ducks moved 6.8 times faster than the hull speed. During steaming, ducks exceeded the hull speed by increasing their body angle and generating dynamic lift to overcome wave drag and hydroplane along the water surface. During paddle-assisted flying, ducks kept their bodies out of the water, thereby avoiding the limitations of wave drag altogether. Both behaviors provided alternatives to flight for these ducks by allowing them to exceed the hull speed while staying at or near the water surface. © 2015. Published by The Company of Biologists Ltd.

Probing and Manipulating the Interfacial Defects of InGaAs Dual-Layer Metal Oxides at the Atomic Scale.

PubMed

Wu, Xing; Luo, Chen; Hao, Peng; Sun, Tao; Wang, Runsheng; Wang, Chaolun; Hu, Zhigao; Li, Yawei; Zhang, Jian; Bersuker, Gennadi; Sun, Litao; Pey, Kinleong

2018-01-01

The interface between III-V and metal-oxide-semiconductor materials plays a central role in the operation of high-speed electronic devices, such as transistors and light-emitting diodes. The high-speed property gives the light-emitting diodes a high response speed and low dark current, and they are widely used in communications, infrared remote sensing, optical detection, and other fields. The rational design of high-performance devices requires a detailed understanding of the electronic structure at this interface; however, this understanding remains a challenge, given the complex nature of surface interactions and the dynamic relationship between the morphology evolution and electronic structures. Herein, in situ transmission electron microscopy is used to probe and manipulate the structural and electrical properties of ZrO 2 films on Al 2 O 3 and InGaAs substrate at the atomic scale. Interfacial defects resulting from the spillover of the oxygen-atom conduction-band wavefunctions are resolved. This study unearths the fundamental defect-driven interfacial electric structure of III-V semiconductor materials and paves the way to future high-speed and high-reliability devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Protection from high-velocity impact particles for quartz glass by coatings on the basis of Al-Si-N

NASA Astrophysics Data System (ADS)

Bozhko, I. A.; Rybalko, E. V.; Fedorischeva, M. V.; Solntsev, V. L.; Cherniavsky, A. G.; Kaleri, A. Yu.; Psakhie, S. G.; Sergeev, V. P.

2016-11-01

The paper presents the results of the research of the phase composition and the mechanical properties of the coatings on the basis of Al-Si-N system produced by pulsed magnetron sputtering on the KV glass substrates. By the X-ray diffraction method, it has been discovered that the coatings contain AlN phase (hcp) with different thickness. The deposition of Al-Si-N coating system allows both increasing the microhardness of the surface layer of the quartz glass up to 29 GPa, and maintaining high elastic properties (We > 0.70). The laboratory tests have been carried out involving the impact of high-speed flows of iron particles on the Al-Si-N protective coating with different thicknesses produced by pulsed magnetron sputtering. The increase of Al-Si-N coating thickness from 1µm to 10µm decreases 4-fold the surface density of the craters on the samples caused by a high-speed flow of iron particles.

Measurement of instantaneous rotational speed using double-sine-varying-density fringe pattern

NASA Astrophysics Data System (ADS)

Zhong, Jianfeng; Zhong, Shuncong; Zhang, Qiukun; Peng, Zhike

2018-03-01

Fast and accurate rotational speed measurement is required both for condition monitoring and faults diagnose of rotating machineries. A vision- and fringe pattern-based rotational speed measurement system was proposed to measure the instantaneous rotational speed (IRS) with high accuracy and reliability. A special double-sine-varying-density fringe pattern (DSVD-FP) was designed and pasted around the shaft surface completely and worked as primary angular sensor. The rotational angle could be correctly obtained from the left and right fringe period densities (FPDs) of the DSVD-FP image sequence recorded by a high-speed camera. The instantaneous angular speed (IAS) between two adjacent frames could be calculated from the real-time rotational angle curves, thus, the IRS also could be obtained accurately and efficiently. Both the measurement principle and system design of the novel method have been presented. The influence factors on the sensing characteristics and measurement accuracy of the novel system, including the spectral centrobaric correction method (SCCM) on the FPD calculation, the noise sources introduce by the image sensor, the exposure time and the vibration of the shaft, were investigated through simulations and experiments. The sampling rate of the high speed camera could be up to 5000 Hz, thus, the measurement becomes very fast and the change in rotational speed was sensed within 0.2 ms. The experimental results for different IRS measurements and characterization of the response property of a servo motor demonstrated the high accuracy and fast measurement of the proposed technique, making it attractive for condition monitoring and faults diagnosis of rotating machineries.

Removing function model and experiments on ultrasonic polishing molding die

NASA Astrophysics Data System (ADS)

Huang, Qitai; Ni, Ying; Yu, Jingchi

2010-10-01

Low temperature glass molding technology is the main method on volume-producing high precision middle and small diameter optical cells in the future. While the accuracy of the molding die will effect the cell precision, so the high precision molding die development is one of the most important part of the low temperature glass molding technology. The molding die is manufactured from high rigid and crisp metal alloy, with the ultrasonic vibration character of high vibration frequency and concentrative energy distribution; abrasive particles will impact the rigid metal alloy surface with very high speed that will remove the material from the work piece. Ultrasonic can make the rigid metal alloy molding die controllable polishing and reduce the roughness and surface error. Different from other ultrasonic fabrication method, untouched ultrasonic polishing is applied on polish the molding die, that means the tool does not touch the work piece in the process of polishing. The abrasive particles vibrate around the balance position with high speed and frequency under the drive of ultrasonic vibration in the liquid medium and impact the workspace surface, the energy of abrasive particles come from ultrasonic vibration, while not from the direct hammer blow of the tool. So a nummular vibrator simple harmonic vibrates on an infinity plane surface is considered as a model of ultrasonic polishing working condition. According to Huygens theory the sound field distribution on a plane surface is analyzed and calculated, the tool removing function is also deduced from this distribution. Then the simple point ultrasonic polishing experiment is proceeded to certificate the theory validity.

Laser Measurement Of Convective-Heat-Transfer Coefficient

NASA Technical Reports Server (NTRS)

Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.

1994-01-01

Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.

Optimization of wheel-rail interface friction using top-of-rail friction modifiers: State of the art

NASA Astrophysics Data System (ADS)

Khan, M. Roshan; Dasaka, Satyanarayana Murty

2018-05-01

High Speed Railways and Dedicated Freight Corridors are the need of the day for fast and efficient transportation of the ever growing population and freight across long distances of travel. With the increase in speeds and axle loads carried by these trains, wearing out of rails and train wheel sections are a common issue, which is due to the increase in friction at the wheel-rail interfaces. For the cases where the wheel-rail interface friction is less than optimum, as in case of high speed trains with very low axle loads, wheel-slips are imminent and loss of traction occurs when the trains accelerate rapidly or brake all of a sudden. These vast variety of traction problems around the wheel-rail interface friction need to be mitigated carefully, so that the contact interface friction neither ascents too high to cause material wear and need for added locomotive power, nor be on the lower side to cause wheel-slips and loss of traction at high speeds. Top-of-rail friction modifiers are engineered surface coatings applied on top of rails, to maintain an optimum frictional contact between the train wheels and the rails. Extensive research works in the area of wheel-rail tribology have revealed that the optimum frictional coefficients at wheel-rail interfaces lie at a value of around 0.35. Application of top-of-rail (TOR) friction modifiers on rail surfaces add an extra layer of material coating on top of the rails, with a surface frictional coefficient of the desired range. This study reviews the common types of rail friction modifiers, the methods for their application, issues related with the application of friction modifiers, and a guideline on selection of the right class of coating material based on site specific requirements of the railway networks.

Reconfiguration control system for an aircraft wing

NASA Technical Reports Server (NTRS)

Wakayama, Sean R. (Inventor)

2008-01-01

Independently deflectable control surfaces are located on the trailing edge of the wing of a blended wing-body aircraft. The reconfiguration control system of the present invention controls the deflection of each control surface to optimize the spanwise lift distribution across the wing for each of several flight conditions, e.g., cruise, pitch maneuver, and high lift at low speed. The control surfaces are deflected and reconfigured to their predetermined optimal positions when the aircraft is in each of the aforementioned flight conditions. With respect to cruise, the reconfiguration control system will maximize the lift to drag ratio and keep the aircraft trimmed at a stable angle of attack. In a pitch maneuver, the control surfaces are deflected to pitch the aircraft and increase lift. Moreover, this increased lift has its spanwise center of pressure shifted inboard relative to its location for cruise. This inboard shifting reduces the increased bending moment about the aircraft's x-axis occasioned by the increased pitch force acting normal to the wing. To optimize high lift at low speed, during take-off and landing for example, the control surfaces are reconfigured to increase the local maximum coefficient of lift at stall-critical spanwise locations while providing pitch trim with control surfaces that are not stall critical.

Statistical downscaling of IPCC sea surface wind and wind energy predictions for U.S. east coastal ocean, Gulf of Mexico and Caribbean Sea

NASA Astrophysics Data System (ADS)

Yao, Zhigang; Xue, Zuo; He, Ruoying; Bao, Xianwen; Song, Jun

2016-08-01

A multivariate statistical downscaling method is developed to produce regional, high-resolution, coastal surface wind fields based on the IPCC global model predictions for the U.S. east coastal ocean, the Gulf of Mexico (GOM), and the Caribbean Sea. The statistical relationship is built upon linear regressions between the empirical orthogonal function (EOF) spaces of a cross- calibrated, multi-platform, multi-instrument ocean surface wind velocity dataset (predictand) and the global NCEP wind reanalysis (predictor) over a 10 year period from 2000 to 2009. The statistical relationship is validated before applications and its effectiveness is confirmed by the good agreement between downscaled wind fields based on the NCEP reanalysis and in-situ surface wind measured at 16 National Data Buoy Center (NDBC) buoys in the U.S. east coastal ocean and the GOM during 1992-1999. The predictand-predictor relationship is applied to IPCC GFDL model output (2.0°×2.5°) of downscaled coastal wind at 0.25°×0.25° resolution. The temporal and spatial variability of future predicted wind speeds and wind energy potential over the study region are further quantified. It is shown that wind speed and power would significantly be reduced in the high CO2 climate scenario offshore of the mid-Atlantic and northeast U.S., with the speed falling to one quarter of its original value.

Three-dimensional digital holographic aperture synthesis for rapid and highly-accurate large-volume metrology

NASA Astrophysics Data System (ADS)

Crouch, Stephen; Kaylor, Brant M.; Barber, Zeb W.; Reibel, Randy R.

2015-09-01

Currently large volume, high accuracy three-dimensional (3D) metrology is dominated by laser trackers, which typically utilize a laser scanner and cooperative reflector to estimate points on a given surface. The dependency upon the placement of cooperative targets dramatically inhibits the speed at which metrology can be conducted. To increase speed, laser scanners or structured illumination systems can be used directly on the surface of interest. Both approaches are restricted in their axial and lateral resolution at longer stand-off distances due to the diffraction limit of the optics used. Holographic aperture ladar (HAL) and synthetic aperture ladar (SAL) can enhance the lateral resolution of an imaging system by synthesizing much larger apertures by digitally combining measurements from multiple smaller apertures. Both of these approaches only produce two-dimensional imagery and are therefore not suitable for large volume 3D metrology. We combined the SAL and HAL approaches to create a swept frequency digital holographic 3D imaging system that provides rapid measurement speed for surface coverage with unprecedented axial and lateral resolution at longer standoff ranges. The technique yields a "data cube" of Fourier domain data, which can be processed with a 3D Fourier transform to reveal a 3D estimate of the surface. In this paper, we provide the theoretical background for the technique and show experimental results based on an ultra-wideband frequency modulated continuous wave (FMCW) chirped heterodyne ranging system showing ~100 micron lateral and axial precisions at >2 m standoff distances.

Broadband ground-motion simulation using a hybrid approach

USGS Publications Warehouse

Graves, R.W.; Pitarka, A.

2010-01-01

This paper describes refinements to the hybrid broadband ground-motion simulation methodology of Graves and Pitarka (2004), which combines a deterministic approach at low frequencies (f 1 Hz). In our approach, fault rupture is represented kinematically and incorporates spatial heterogeneity in slip, rupture speed, and rise time. The prescribed slip distribution is constrained to follow an inverse wavenumber-squared fall-off and the average rupture speed is set at 80% of the local shear-wave velocity, which is then adjusted such that the rupture propagates faster in regions of high slip and slower in regions of low slip. We use a Kostrov-like slip-rate function having a rise time proportional to the square root of slip, with the average rise time across the entire fault constrained empirically. Recent observations from large surface rupturing earthquakes indicate a reduction of rupture propagation speed and lengthening of rise time in the near surface, which we model by applying a 70% reduction of the rupture speed and increasing the rise time by a factor of 2 in a zone extending from the surface to a depth of 5 km. We demonstrate the fidelity of the technique by modeling the strong-motion recordings from the Imperial Valley, Loma Prieta, Landers, and Northridge earthquakes.

The Hurricane Imaging Radiometer: Present and Future

NASA Technical Reports Server (NTRS)

Miller, Timothy L.; James, M. W.; Roberts, J. B.; Biswas, S. K.; Cecil, D.; Jones, W. L.; Johnson, J.; Farrar, S.; Sahawneh, S.; Ruf, C. S.;

Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations

NASA Technical Reports Server (NTRS)

Yueh, Simon H.; Chaubell, Mario J.

2012-01-01

Several L-band microwave radiometer and radar missions have been, or will be, operating in space for land and ocean observations. These include the NASA Aquarius mission and the Soil Moisture Active Passive (SMAP) mission, both of which use combined passive/ active L-band instruments. Aquarius s passive/active L-band microwave sensor has been designed to map the salinity field at the surface of the ocean from space. SMAP s primary objectives are for soil moisture and freeze/thaw detection, but it will operate continuously over the ocean, and hence will have significant potential for ocean surface research. In this innovation, an algorithm has been developed to retrieve simultaneously ocean surface salinity and wind from combined passive/active L-band microwave observations of sea surfaces. The algorithm takes advantage of the differing response of brightness temperatures and radar backscatter to salinity, wind speed, and direction, thus minimizing the least squares error (LSE) measure, which signifies the difference between measurements and model functions of brightness temperatures and radar backscatter. The algorithm uses the conjugate gradient method to search for the local minima of the LSE. Three LSE measures with different measurement combinations have been tested. The first LSE measure uses passive microwave data only with retrieval errors reaching 1 to 2 psu (practical salinity units) for salinity, and 1 to 2 m/s for wind speed. The second LSE measure uses both passive and active microwave data for vertical and horizontal polarizations. The addition of active microwave data significantly improves the retrieval accuracy by about a factor of five. To mitigate the impact of Faraday rotation on satellite observations, the third LSE measure uses measurement combinations invariant under the Faraday rotation. For Aquarius, the expected RMS SSS (sea surface salinity) error will be less than about 0.2 psu for low winds, and increases to 0.3 psu at 25 m/s wind speed for warm waters (25 C). To achieve the required 0.2 psu accuracy, the impact of sea surface roughness (e.g. wind-generated ripples) on the observed brightness temperature has to be corrected to better than one tenth of a degree Kelvin. With this algorithm, the accuracy of retrieved wind speed will be high, varying from a few tenths to 0.6 m/s. The expected direction accuracy is also excellent (less than 10 ) for mid to high winds, but degrades for lower speeds (less than 7 m/s).

Control of interior surface materials for speech privacy in high-speed train cabins.

PubMed

Jang, H S; Lim, H; Jeon, J Y

2017-05-01

The effect of interior materials with various absorption coefficients on speech privacy was investigated in a 1:10 scale model of one high-speed train cabin geometry. The speech transmission index (STI) and privacy distance (r P ) were measured in the train cabin to quantify speech privacy. Measurement cases were selected for the ceiling, sidewall, and front and back walls and were classified as high-, medium- and low-absorption coefficient cases. Interior materials with high absorption coefficients yielded a low r P , and the ceiling had the largest impact on both the STI and r P among the interior elements. Combinations of the three cases were measured, and the maximum reduction in r P by the absorptive surfaces was 2.4 m, which exceeds the space between two rows of chairs in the high-speed train. Additionally, the contribution of the interior elements to speech privacy was analyzed using recorded impulse responses and a multiple regression model for r P using the equivalent absorption area. The analysis confirmed that the ceiling was the most important interior element for improving speech privacy. These results can be used to find the relative decrease in r P in the acoustic design of interior materials to improve speech privacy in train cabins. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

High-speed digital holography for neutral gas and electron density imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Granstedt, E. M., E-mail: egranstedt@gmail.com; Thomas, C. E.; Kaita, R.

2016-05-15

An instrument was developed using digital holographic reconstruction of the wavefront from a CO{sub 2} laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1–25 μs pulses from a continuous-wave CO{sub 2} laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfullymore » reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.« less

Machinability of Al 6061 Deposited with Cold Spray Additive Manufacturing

NASA Astrophysics Data System (ADS)

Aldwell, Barry; Kelly, Elaine; Wall, Ronan; Amaldi, Andrea; O'Donnell, Garret E.; Lupoi, Rocco

2017-10-01

Additive manufacturing techniques such as cold spray are translating from research laboratories into more mainstream high-end production systems. Similar to many additive processes, finishing still depends on removal processes. This research presents the results from investigations into aspects of the machinability of aluminum 6061 tubes manufactured with cold spray. Through the analysis of cutting forces and observations on chip formation and surface morphology, the effect of cutting speed, feed rate, and heat treatment was quantified, for both cold-sprayed and bulk aluminum 6061. High-speed video of chip formation shows changes in chip form for varying material and heat treatment, which is supported by the force data and quantitative imaging of the machined surface. The results shown in this paper demonstrate that parameters involved in cold spray directly impact on machinability and therefore have implications for machining parameters and strategy.

In-process, non-destructive, dynamic testing of high-speed polymer composite rotors

NASA Astrophysics Data System (ADS)

Kuschmierz, Robert; Filippatos, Angelos; Günther, Philipp; Langkamp, Albert; Hufenbach, Werner; Czarske, Jürgen; Fischer, Andreas

2015-03-01

Polymer composite rotors are lightweight and offer great perspectives in high-speed applications such as turbo machinery. Currently, novel rotor structures and materials are investigated for the purpose of increasing machine efficiency and lifetime, as well as allowing for higher dynamic loads. However, due to the complexity of the composite materials an in-process measurement system is required. This allows for monitoring the evolution of damages under dynamic loads, for testing and predicting the structural integrity of composite rotors in process. In rotor design, it can be used for calibrating and improving models, simulating the dynamic behaviour of polymer composite rotors. The measurement system is to work non-invasive, offer micron uncertainty, as well as a high measurement rate of several tens of kHz. Furthermore, it must be applicable at high surface speeds and under technical vacuum. In order to fulfil these demands a novel laser distance measurement system was developed. It provides the angle resolved measurement of the biaxial deformation of a fibre-reinforced polymer composite rotor with micron uncertainty at surface speeds of more than 300 m/s. Furthermore, a simulation procedure combining a finite element model and a damage mechanics model is applied. A comparison of the measured data and the numerically calculated data is performed to validate the simulation towards rotor expansion. This validating procedure can be used for a model calibration in the future. The simulation procedure could be used to investigate different damage-test cases of the rotor, in order to define its structural behaviour without further experiments.

The Structure of a Hypersonic Air Flow near a Plane Surface at Various Intensities of Magnetogasdynamic Interaction

NASA Astrophysics Data System (ADS)

Fomichev, V. P.; Yadrenkin, M. A.

2017-12-01

This Letter presents a systematization of the effects observed in experiments on the magnetogasdynamic interaction near the surface of a plate in a high-speed gas flow. Ranges of the hydromagnetic-interaction parameter determining various levels of influence on the shock-wave structure of the flow are established.

Determination of the Static Friction Coefficient from Circular Motion

ERIC Educational Resources Information Center

Molina-Bolívar, J. A.; Cabrerizo-Vílchez, M. A.

2014-01-01

This paper describes a physics laboratory exercise for determining the coefficient of static friction between two surfaces. The circular motion of a coin placed on the surface of a rotating turntable has been studied. For this purpose, the motion is recorded with a high-speed digital video camera recording at 240 frames s[superscript-1], and the…

Acoustic characteristics of a large-scale wind tunnel model of an upper-surface blown flap transport having two engines

NASA Technical Reports Server (NTRS)

Falarski, M. D.; Aoyagi, K.; Koenig, D. G.

1973-01-01

The upper-surface blown (USB) flap as a powered-lift concept has evolved because of the potential acoustic shielding provided when turbofan engines are installed on a wing upper surface. The results from a wind tunnel investigation of a large-scale USB model powered by two JT15D-1 turbofan engines are-presented. The effects of coanda flap extent and deflection, forward speed, and exhaust nozzle configuration were investigated. To determine the wing shielding the acoustics of a single engine nacelle removed from the model were also measured. Effective shielding occurred in the aft underwing quadrant. In the forward quadrant the shielding of the high frequency noise was counteracted by an increase in the lower frequency wing-exhaust interaction noise. The fuselage provided shielding of the opposite engine noise such that the difference between single and double engine operation was 1.5 PNdB under the wing. The effects of coanda flap deflection and extent, angle of attack, and forward speed were small. Forward speed reduced the perceived noise level (PNL) by reducing the wing-exhaust interaction noise.

Scaling of Polymer Degradation Rate within a High-Reynolds-Number Turbulent Boundary Layer

NASA Astrophysics Data System (ADS)

Elbing, Brian; Solomon, Michael; Perlin, Marc; Dowling, David; Ceccio, Steven

2009-11-01

An experiment conducted at the U.S. Navy's Large Cavitation Channel on a 12.9 m long flat-plate test model produced the first quantitative measurements of polymer molecular weight within a turbulent boundary layer. Testing was conducted at speeds to 20 m/s and downstream distance based Reynolds numbers to 220 million. These results showed that the rate of polymer degradation by scission of the polymer chains increases with increased speed, downstream distance and surface roughness. With the surface fully rough at 20 m/s there was no measureable level of drag reduction at the first measurement location (0.56 m downstream of injection). These results are scaled with the assumption that the rate of degradation is dependent on the polymer residence time in the flow and the local shear rate. A successful collapse of the data within the measurement uncertainty was achieved over a range of flow speed (6.6 to 20 m/s), surface roughness (smooth and fully rough) and downstream distance from injection (0.56 to 9.28 m).

Schlieren visualization of flow-field modification over an airfoil by near-surface gas-density perturbations generated by a nanosecond-pulse-driven plasma actuator

NASA Astrophysics Data System (ADS)

Komuro, Atsushi; Takashima, Keisuke; Konno, Kaiki; Tanaka, Naoki; Nonomura, Taku; Kaneko, Toshiro; Ando, Akira; Asai, Keisuke

2017-06-01

Gas-density perturbations near an airfoil surface generated by a nanosecond dielectric-barrier-discharge plasma actuator (ns-DBDPA) are visualized using a high-speed Schlieren imaging method. Wind-tunnel experiments are conducted for a wind speed of 20 m s-1 with an NACA0015 airfoil whose chord length is 100 mm. The results show that the ns-DBDPA first generates a pressure wave and then stochastic perturbations of the gas density near the leading edge of the airfoil. Two structures with different characteristics are observed in the stochastic perturbations. One structure propagates along the boundary between the shear layer and the main flow at a speed close to that of the main flow. The other propagates more slowly on the surface of the airfoil and causes mixing between the main and shear flows. It is observed that these two heated structures interact with each other, resulting in a recovery in the negative pressure coefficient at the leading edge of the airfoil.

High-speed observation of ZnO microspherical crystals produced by laser ablation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Nakamura, Daisuke; Tasaki, Ryohei; Fujiwara, Yuki; Nagasaki, Fumiaki; Higashihata, Mitsuhiro; Ikenoue, Hiroshi; Okada, Tatsuo

2017-03-01

ZnO nano/microstructures have attracted much attention as building blocks for optoelectronic devices because of their high crystalline quality and unique structures. We have succeeded in synthesizing ZnO microspherical crystals by a simple atmospheric laser ablation method, and demonstrated ultraviolet whispering-gallery-mode lasing from the spheres. In the microsphere synthesis process, molten droplets formed into spherical shapes by surface tension, and crystalized during ejection from the ablation spot. In this study, we observed the generation of ZnO microspheres by high-speed camera. Now we are trying to control and manipulate the microspheres using a vortex beam.

Future ultra-speed tube-flight

NASA Astrophysics Data System (ADS)

Salter, Robert M.

1994-05-01

Future long-link, ultra-speed, surface transport systems will require electromagnetically (EM) driven and restrained vehicles operating under reduced-atmosphere in very straight tubes. Such tube-flight trains will be safe, energy conservative, pollution-free, and in a protected environment. Hypersonic (and even hyperballistic) speeds are theoretically achievable. Ultimate system choices will represent tradeoffs between amoritized capital costs (ACC) and operating costs. For example, long coasting links might employ aerodynamic lift coupled with EM restraint and drag make-up. Optimized, combined EM lift, and thrust vectors could reduce energy costs but at increased ACC. (Repulsive levitation can produce lift-over-drag l/d ratios a decade greater than aerodynamic), Alternatively, vehicle-emanated, induced-mirror fields in a conducting (aluminum sheet) road bed could reduce ACC but at substantial energy costs. Ultra-speed tube flight will demand fast-acting, high-precision sensors and computerized magnetic shimming. This same control system can maintain a magnetic 'guide way' invariant in inertial space with inertial detectors imbedded in tube structures to sense and correct for earth tremors. Ultra-speed tube flight can complete with aircraft for transit time and can provide even greater passenger convenience by single-model connections with local subways and feeder lines. Although cargo transport generally will not need to be performed at ultra speeds, such speeds may well be desirable for high throughput to optimize channel costs. Thus, a large and expensive pipeline might be replaced with small EM-driven pallets at high speeds.

Future ultra-speed tube-flight

NASA Technical Reports Server (NTRS)

Salter, Robert M.

1994-01-01

Future long-link, ultra-speed, surface transport systems will require electromagnetically (EM) driven and restrained vehicles operating under reduced-atmosphere in very straight tubes. Such tube-flight trains will be safe, energy conservative, pollution-free, and in a protected environment. Hypersonic (and even hyperballistic) speeds are theoretically achievable. Ultimate system choices will represent tradeoffs between amoritized capital costs (ACC) and operating costs. For example, long coasting links might employ aerodynamic lift coupled with EM restraint and drag make-up. Optimized, combined EM lift, and thrust vectors could reduce energy costs but at increased ACC. (Repulsive levitation can produce lift-over-drag l/d ratios a decade greater than aerodynamic), Alternatively, vehicle-emanated, induced-mirror fields in a conducting (aluminum sheet) road bed could reduce ACC but at substantial energy costs. Ultra-speed tube flight will demand fast-acting, high-precision sensors and computerized magnetic shimming. This same control system can maintain a magnetic 'guide way' invariant in inertial space with inertial detectors imbedded in tube structures to sense and correct for earth tremors. Ultra-speed tube flight can complete with aircraft for transit time and can provide even greater passenger convenience by single-model connections with local subways and feeder lines. Although cargo transport generally will not need to be performed at ultra speeds, such speeds may well be desirable for high throughput to optimize channel costs. Thus, a large and expensive pipeline might be replaced with small EM-driven pallets at high speeds.

Water surface locomotion in tropical canopy ants.

PubMed

Yanoviak, S P; Frederick, D N

2014-06-15

Upon falling onto the water surface, most terrestrial arthropods helplessly struggle and are quickly eaten by aquatic predators. Exceptions to this outcome mostly occur among riparian taxa that escape by walking or swimming at the water surface. Here we document sustained, directional, neustonic locomotion (i.e. surface swimming) in tropical arboreal ants. We dropped 35 species of ants into natural and artificial aquatic settings in Peru and Panama to assess their swimming ability. Ten species showed directed surface swimming at speeds >3 body lengths s(-1), with some swimming at absolute speeds >10 cm s(-1). Ten other species exhibited partial swimming ability characterized by relatively slow but directed movement. The remaining species showed no locomotory control at the surface. The phylogenetic distribution of swimming among ant genera indicates parallel evolution and a trend toward negative association with directed aerial descent behavior. Experiments with workers of Odontomachus bauri showed that they escape from the water by directing their swimming toward dark emergent objects (i.e. skototaxis). Analyses of high-speed video images indicate that Pachycondyla spp. and O. bauri use a modified alternating tripod gait when swimming; they generate thrust at the water surface via synchronized treading and rowing motions of the contralateral fore and mid legs, respectively, while the hind legs provide roll stability. These results expand the list of facultatively neustonic terrestrial taxa to include various species of tropical arboreal ants. © 2014. Published by The Company of Biologists Ltd.

The air bubble entrapped under a drop impacting on a solid surface

NASA Astrophysics Data System (ADS)

Thoroddsen, S. T.; Etoh, T. G.; Takehara, K.; Ootsuka, N.; Hatsuki, Y.

2005-12-01

We present experimental observations of the disk of air caught under a drop impacting onto a solid surface. By imaging the impact through an acrylic plate with an ultra-high-speed video camera, we can follow the evolution of the air disk as it contracts into a bubble under the centre of the drop. The initial size and contraction speed of the disk were measured for a range of impact Weber and Reynolds numbers. The size of the initial disk is related to the bottom curvature of the drop at the initial contact, as measured in free-fall. The initial contact often leaves behind a ring of micro-bubbles, marking its location. The air disk contracts at a speed comparable to the corresponding air disks caught under a drop impacting onto a liquid surface. This speed also seems independent of the wettability of the liquid, which only affects the azimuthal shape of the contact line. For some impact conditions, the dynamics of the contraction leaves a small droplet at the centre of the bubble. This arises from a capillary wave propagating from the edges of the contracting disk towards the centre. As the wave converges its amplitude grows until it touches the solid substrate, thereby pinching off the micro-droplet at the plate, in the centre of the bubble. The effect of increasing liquid viscosity is to slow down the contraction speed and to produce a more irregular contact line leaving more micro-bubbles along the initial ring.

Probing the nanoscale with high-speed interferometry of an impacting drop

NASA Astrophysics Data System (ADS)

Thoroddsen, S. T.; Li, E. Q.; Vakarelski, I. U.; Langley, K.

2017-02-01

The simple phenomenon of a water drop falling onto a glass plate may seem like a trivial fluid mechanics problem. However, detailed imaging has shown that this process is highly complex and a small air-bubble is always entrapped under the drop when it makes contact with the solid. This bubble can interfere with the uniformity of spray coatings and degrade inkjet fabrication of displays etc. We will describe how we use high-speed interferometry at 5 million frames per second to understand the details of this process. As the impacting drop approaches the solid, the dynamics are characterized by a balance between the lubrication pressure in the thin air layer and the inertia of the bot-tom of the drop. This deforms the drop, forming a dimple at its bottom and making the drop touch the surface along a ring, thereby entrapping the air-layer, which is typically 1-3 μm thick. This air-layer can be highly compressed and the deceleration of the bottom of the drop can be as large as 300,000 g. We describe how the thickness evolution of the lubricating air-layer is extracted from following the interference fringes between frames. Two-color interferometry is also used to extract absolute layer thicknesses. Finally, we identify the effects of nanometric surface roughness on the first contact of the drop with the substrate. Here we need to resolve the 100 nm thickness changes occurring during 200 ns intervals, requiring these state of the art high-speed cameras. Surprisingly, we see a ring of micro-bubbles marking the first contact of the drop with the glass, only for microscope slides, which have a typical roughness of 20 nm, while such rings are absent for drop impacts onto molecularly smooth mica surfaces.

Experimental Measurement of Frozen and Partially Melted Water Droplet Impact Dynamics

NASA Technical Reports Server (NTRS)

Palacios, Jose; Yan, Sihong; Tan, Jason; Kreeger, Richard E.

2014-01-01

High-speed video of single frozen water droplets impacting a surface was acquired. The droplets diameter ranged from 0.4 mm to 0.9 mm and impacted at velocities ranging from 140 m/sec to 309 m/sec. The techniques used to freeze the droplets and launch the particles against the surfaces is described in this paper. High-speed video was used to quantify the ice accretion area to the surface for varying impact angles (30 deg, 45 deg, 60 deg), impacting velocities, and break-up angles. An oxygen /acetylene cross-flow flame used to ensure partial melting of the traveling frozen droplets is also discussed. A linear relationship between impact angle and ice accretion is identified for fully frozen particles. The slope of the relationship is affected by impact speed. Perpendicular impacts, i.e. 30 deg, exhibited small differences in ice accretion for varying velocities, while an increase of 60% in velocity from 161 m/sec to 259 m/sec, provided an increase on ice accretion area of 96% at an impact angle of 60 deg. The increase accretion area highlights the importance of impact angle and velocity on the ice accretion process of ice crystals. It was experimentally observed that partial melting was not required for ice accretion at the tested velocities when high impact angles were used (45 and 60 deg). Partially melted droplets doubled the ice accretion areas on the impacting surface when 0.0023 Joules were applied to the particle. The partially melted state of the droplets and a method to quantify the percentage increase in ice accretion area is also described in the paper.

Formation Mechanism of Finished Surface in Ultrahigh-Speed Grinding with cubic Boron Nitride (cBN) Wheels

NASA Astrophysics Data System (ADS)

Ichida, Yoshio; Sato, Ryunosuke; Morimoto, Yoshitaka; Ohsawa, Yoshiteru; Fredj, Nabil Ben

In this paper, we describe the formation mechanism of a finished surface in ultrahigh-speed grinding under a peripheral wheel speed higher than 200m/s. Grinding experiments using a grinding machine tool equipped with an active magnetic bearing spindle have been conducted over a range of grinding speeds from 60 to 300m/s. Moreover, grinding tests for producing some individual grooves using a grinding tool with multiple cBN grit have been carried out to clarify the effects of grinding speed on the side swelling formed along both sides of the grinding grooves. From the results of these experiments, we have confirmed that the roughness of the ground surface decreases with an increase in grinding speed, and this decrease is mainly due to the reduction of the swelling ratio with increasing grinding speed.

Will surface winds weaken in response to global warming?

NASA Astrophysics Data System (ADS)

Ma, Jian; Foltz, Gregory R.; Soden, Brian J.; Huang, Gang; He, Jie; Dong, Changming

2016-12-01

The surface Walker and tropical tropospheric circulations have been inferred to slow down from historical observations and model projections, yet analysis of large-scale surface wind predictions is lacking. Satellite measurements of surface wind speed indicate strengthening trends averaged over the global and tropical oceans that are supported by precipitation and evaporation changes. Here we use corrected anemometer-based observations to show that the surface wind speed has not decreased in the averaged tropical oceans, despite its reduction in the region of the Walker circulation. Historical simulations and future projections for climate change also suggest a near-zero wind speed trend averaged in space, regardless of the Walker cell change. In the tropics, the sea surface temperature pattern effect acts against the large-scale circulation slow-down. For higher latitudes, the surface winds shift poleward along with the eddy-driven mid-latitude westerlies, resulting in a very small contribution to the global change in surface wind speed. Despite its importance for surface wind speed change, the influence of the SST pattern change on global-mean rainfall is insignificant since it cannot substantially alter the global energy balance. As a result, the precipitation response to global warming remains ‘muted’ relative to atmospheric moisture increase. Our results therefore show consistency between projections and observations of surface winds and precipitation.

Effect of engraving speeds of CO₂ laser irradiation on In-Ceram Alumina roughness: a pilot study.

PubMed

Ersu, Bahadır; Ersoy, Orkun; Yuzugullu, Bulem; Canay, Senay

2015-05-01

The aim of the study was to determine the effect of CO₂ laser on surface roughness of In-Ceram-Alumina-ceramic. Four aluminum-oxide ceramic disc specimens were prepared of In-Ceram Alumina. Discs received CO₂ laser irradiation with different engraving speeds (100, 400, 600 and 800 mm/min) as a surface treatment. The roughness of the surfaces was measured on digital elevation models reconstructed from stereoscopic images acquired by scanning-electron-microscope. Surface roughness data were analyzed with One-Way-Analysis-of-Variance at a significance level of p<0.05. There was no significant difference between the roughness values (p=0.82). Due to higher laser durations, partial melting signs were observed on the surfaces. Tearing, smearing and swelling occurred on melted surfaces. Swelling accompanying melting increased the surface roughness, while laser power was fixed and different laser engraving speeds were applied. Although different laser irradiation speeds did not affect the roughness of ceramic surfaces, swelling was observed which led to changes on surfaces.

New insights into modeling an organic mass fraction of sea spray aerosol

NASA Astrophysics Data System (ADS)

Meskhidze, N.; Gantt, B.

2010-12-01

As the study of climate change progresses, a need to separate the effects of natural and anthropogenic processes becomes essential in order to correctly forecast the future climate. Due to their massive source regions underlying an atmosphere with low aerosol concentration, marine aerosols derived from sea spray and ocean emitted biogenic volatile organic compounds (BVOCs) are extremely important for the Earth’s radiative budget, regional air quality and biogeochemical cycling of elements. Measurements of freshly-emitted sea spray have revealed that bubble bursting processes, largely responsible for the production of sea salt aerosol, also control sea-to-air transfer of marine organic matter. It has been established that the organic mass fraction of sea spray can be a function of sea-water composition (e.g., concentrations of Chlorophyll-a, [Chl-a], dissolved organic carbon, [DOC], particulate organic carbon, [POC], types of organic carbon, and the amount of surfactants). Current paramaterizations of marine primary organic aerosol emissions use remotely sensed [Chl-a] data as a proxy for oceanic biological activity. However, it has also been shown that the path length, size, and lifetime of bubbles in seawater as well as spatial coverage of seawater surface by streaks or slicks (visible film of a roughly 50 μm thick layer, highly enriched in organics) can have dramatic effect on organic mass fraction of sea spray (OCss). Dynamics of bubble entrainment and the level of microlayer enrichment by organics relative to the underlying bulk water can be controlled by surface wind speed. For bubble entrainment, high winds can increase rising bubble path length and therefore the amount of organics scavenged by the bubble. However, when the surface wind speeds exceed 8 m s-1 breaking of ocean waves can entirely destroy surface organic films and diminish the amount of organics leaving the sea. Despite the probable impact of wind speed, existing parameterizations do not consider the wind speed dependence of OCss. In this study we use remotely sensed data for ocean slick coverage and surface wind speed in conjunction with an upwind averaged concentrations of [Chl-a], [DOC] and [POC] to derive marine primary organic aerosol emission function. Derived empirical relationships between the aerosol and ocean/meteorological data are then compared to observed OCss at Mace Head and Point Reyes National Seashore. MATLAB curve fitting tool revealed that multi-variable regression analysis (with both wind speed and [Chl-a]) yields a significant improvement between model predicted and observed submicron fraction of OCss. The coefficient of determination increased from R2=0.1 for previous parameterizations to R2=0.6. Based on the results of this study we propose that in addition to sea-water composition, future parameterizations of marine primary organic aerosol emissions should include sea spray organic mass fraction dependence on surface wind speed.

Dynamic Impacts of Water Droplets onto Icephobic Soft Surfaces at High Weber Numbers

NASA Astrophysics Data System (ADS)

Ma, Liqun; Liu, Yang; Hu, Hui; Wang, Wei; Kota, Arun

2017-11-01

An experimental investigation was performed to examine the effects of the stiffness of icephobic soft PDMS materials on the impact dynamics of water drops at high weber numbers pertinent to aircraft icing phenomena. The experimental study was performed in the Icing Research Tunnel available at Iowa State University (ISU-IRT). During the experiments, both the shear modulus of the soft PDMS surface and the Weber numbers of the impinging water droplets are controlled for the comparative study. While the shear modulus of the soft PDMS surface was changed by tuning the recipes to make the PDMS materials, the Weber number of the impinging water droplets was altered by adjusting the airflow speed in the wind tunnel. A suite of advanced flow diagnostic techniques, which include high-speed photographic imaging, digital image projection (DIP), and infrared (IR) imaging thermometry, were used to quantify the transient behavior of water droplet impingement, unsteady heat transfer and dynamic ice accreting process over the icephobic soft airfoil surfaces. The findings derived from the icing physics studies can be used to improve current icing accretion models for more accurate prediction of ice formation and accretion on aircraft wings and to develop effective anti-/deicing strategies for safer and more efficient operation of aircraft in cold weather.

Continuous cryopump with a device for regenerating the cryosurface

DOEpatents

Foster, C.A.

1988-02-16

A high throughput continuous cryopump is provided. The cryopump incorporates an improved method for regenerating the cryopumping surface while the pump is in continuous operation. The regeneration of the cryopumping surface does not thermally cycle the pump, and to this end a small chamber connected to a secondary pumping source serves to contain and exhaust frost removed from the cryopumping surface during such regeneration. The frost is exhausted at a rate substantially independent of the speed of the cryopump which enhances the capability of the pump to achieve a high compression ratio and allow the pump to operate continuously while the cryopumping surface is being regenerated. 8 figs.

Developing an Empirical Model for Jet-Surface Interaction Noise

NASA Technical Reports Server (NTRS)

Brown, Clifford A.

2014-01-01

The process of developing an empirical model for jet-surface interaction noise is described and the resulting model evaluated. Jet-surface interaction noise is generated when the high-speed engine exhaust from modern tightly integrated or conventional high-bypass ratio engine aircraft strikes or flows over the airframe surfaces. An empirical model based on an existing experimental database is developed for use in preliminary design system level studies where computation speed and range of configurations is valued over absolute accuracy to select the most promising (or eliminate the worst) possible designs. The model developed assumes that the jet-surface interaction noise spectra can be separated from the jet mixing noise and described as a parabolic function with three coefficients: peak amplitude, spectral width, and peak frequency. These coefficients are fit to functions of surface length and distance from the jet lipline to form a characteristic spectra which is then adjusted for changes in jet velocity and/or observer angle using scaling laws from published theoretical and experimental work. The resulting model is then evaluated for its ability to reproduce the characteristic spectra and then for reproducing spectra measured at other jet velocities and observer angles; successes and limitations are discussed considering the complexity of the jet-surface interaction noise versus the desire for a model that is simple to implement and quick to execute.

Developing an Empirical Model for Jet-Surface Interaction Noise

NASA Technical Reports Server (NTRS)

Brown, Clif

2014-01-01

The process of developing an empirical model for jet-surface interaction noise is described and the resulting model evaluated. Jet-surface interaction noise is generated when the high-speed engine exhaust from modern tightly integrated or conventional high-bypass ratio engine aircraft strikes or flows over the airframe surfaces. An empirical model based on an existing experimental database is developed for use in preliminary design system level studies where computation speed and range of configurations is valued over absolute accuracy to select the most promising (or eliminate the worst) possible designs. The model developed assumes that the jet-surface interaction noise spectra can be separated from the jet mixing noise and described as a parabolic function with three coefficients: peak amplitude, spectral width, and peak frequency. These coefficients are t to functions of surface length and distance from the jet lipline to form a characteristic spectra which is then adjusted for changes in jet velocity and/or observer angle using scaling laws from published theoretical and experimental work. The resulting model is then evaluated for its ability to reproduce the characteristic spectra and then for reproducing spectra measured at other jet velocities and observer angles; successes and limitations are discussed considering the complexity of the jet-surface interaction noise versus the desire for a model that is simple to implement and quick to execute.

Separation of three phenolic high-molecular-weight compounds from the crude extract of Terminalia Chebula Retz. by ultrasound-assisted extraction and high-speed counter-current chromatography.

PubMed

Zou, Deng-lang; Chen, Tao; Li, Hong-mei; Chen, Chen; Zhao, Jing-yang; Li, Yu-lin

2016-04-01

This study presents an efficient strategy for separation of three phenolic compounds with high molecular weight from the crude extract of Terminalia chebula Retz. by ultrasound-assisted extraction and high-speed counter-current chromatography. The ultrasound-assisted extraction conditions were optimized by response surface methodology and the results showed the target compounds could be well enriched under the optimized extraction conditions. Then the crude extract was directly separated by high-speed counter-current chromatography without any pretreatment using n-hexane/ethyl acetate/methanol/water (1:7:0.5:3, v/v/v/v) as the solvent system. In 180 min, 13 mg of A, 18 mg of B, and 9 mg of C were obtained from 200 mg of crude sample. Their structures were identified as Chebulagic acid (A, 954 Da), Chebulinic acid (B, 956 Da), and Ellagic acid (C) by (1) H NMR spectroscopy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface Roughness Investigation of Ultrafine-Grained Aluminum Alloy Subjected to High-Speed Erosion

NASA Astrophysics Data System (ADS)

Kazarinov, N. A.; Evstifeev, A. D.; Petrov, Y. V.; Atroshenko, S. A.; Lashkov, V. A.; Valiev, R. Z.; Bondarenko, A. S.

2016-09-01

This study is the first attempt to investigate the influence of severe plastic deformation (SPD) treatment on material surface behavior under intensive erosive conditions. Samples of aluminum alloy 1235 (99.3 Al) before and after high-pressure torsion (HPT) were subjected to intensive erosion by corundum particles accelerated via air flow in a small-scale wind tunnel. Velocity of particles varied from 40 to 200 m/s, while particle average diameter was around 100 μm. Surface roughness measurements provided possibility to compare surface properties of both materials after erosion tests. Moreover, SPD processing appeared to increase noticeably the threshold velocity of the surface damaging process. Additionally, structural analysis of the fracture surfaces of the tested samples was carried out.

CNSFV code development, virtual zone Navier-Stokes computations of oscillating control surfaces and computational support of the laminar flow supersonic wind tunnel

NASA Technical Reports Server (NTRS)

Klopfer, Goetz H.

1993-01-01

The work performed during the past year on this cooperative agreement covered two major areas and two lesser ones. The two major items included further development and validation of the Compressible Navier-Stokes Finite Volume (CNSFV) code and providing computational support for the Laminar Flow Supersonic Wind Tunnel (LFSWT). The two lesser items involve a Navier-Stokes simulation of an oscillating control surface at transonic speeds and improving the basic algorithm used in the CNSFV code for faster convergence rates and more robustness. The work done in all four areas is in support of the High Speed Research Program at NASA Ames Research Center.

The Effect of Surface Irregularities on Wing Drag. II - Lap Joints. 2; Lap Joints

NASA Technical Reports Server (NTRS)

Hood, Manley J.

1938-01-01

Tests have been made in the NACA 8-foot high-speed wind tunnel of the drag caused by four types of lap joint. The tests were made on an airfoil of NACA 23012 section and 5-foot chord and covered in a range of speeds from 80 to 500 miles per hour and lift coefficients from 0 to 0.30. The increases in profile drag caused by representative arrangements of laps varied from 4 to 9%. When there were protruding rivet heads on the surface, the addition of laps increased the drag only slightly. Laps on the forward part of a wing increased the drag considerably more than those farther back.

Instantaneous phase-shifting Fizeau interferometry with high-speed pixelated phase-mask camera

NASA Astrophysics Data System (ADS)

Yatagai, Toyohiko; Jackin, Boaz Jessie; Ono, Akira; Kiyohara, Kosuke; Noguchi, Masato; Yoshii, Minoru; Kiyohara, Motosuke; Niwa, Hayato; Ikuo, Kazuyuki; Onuma, Takashi

2015-08-01

A Fizeou interferometer with instantaneous phase-shifting ability using a Wollaston prism is designed. to measure dynamic phase change of objects, a high-speed video camera of 10-5s of shutter speed is used with a pixelated phase-mask of 1024 × 1024 elements. The light source used is a laser of wavelength 532 nm which is split into orthogonal polarization states by passing through a Wollaston prism. By adjusting the tilt of the reference surface it is possible to make the reference and object beam with orthogonal polarizations states to coincide and interfere. Then the pixelated phase-mask camera calculate the phase changes and hence the optical path length difference. Vibration of speakers and turbulence of air flow were successfully measured in 7,000 frames/sec.

Foil bearings for axial and radial support of high speed rotors: Design, development, and determination of operating characteristics

NASA Technical Reports Server (NTRS)

Licht, L.

1978-01-01

Flexible surface thrust and journal foil bearings were fabricated, and their performance was demonstrated, both individually and jointly as a unified rotor support system. Experimental results are documented with graphs and oscilloscopic data of trajectories, waveforms, and scans of amplitude response. At speeds of 40,000 to 45,000 rpm and a mean clearance of the order of 15 to 20 micrometers (600 to 800 micrometers, the resilient, air lubricated, spiral groove thrust bearings support a load of 127 N (29 lb; 13 kgf), equivalent to 3.0 N/sq cm (4.5 lb/sq in 0.31 kgf sq cm). Journal bearings with polygonal sections provided stable and highly damped supports at speeds up to 50,000 rpm.

The effect of three surface conditions, speed and running experience on vertical acceleration of the tibia during running.

PubMed

Boey, Hannelore; Aeles, Jeroen; Schütte, Kurt; Vanwanseele, Benedicte

2017-06-01

Research has focused on parameters that are associated with injury risk, e.g. vertical acceleration. These parameters can be influenced by running on different surfaces or at different running speeds, but the relationship between them is not completely clear. Understanding the relationship may result in training guidelines to reduce the injury risk. In this study, thirty-five participants with three different levels of running experience were recruited. Participants ran on three different surfaces (concrete, synthetic running track, and woodchip trail) at two different running speeds: a self-selected comfortable speed and a fixed speed of 3.06 m/s. Vertical acceleration of the lower leg was measured with an accelerometer. The vertical acceleration was significantly lower during running on the woodchip trail in comparison with the synthetic running track and the concrete, and significantly lower during running at lower speed in comparison with during running at higher speed on all surfaces. No significant differences in vertical acceleration were found between the three groups of runners at fixed speed. Higher self-selected speed due to higher performance level also did not result in higher vertical acceleration. These results may show that running on a woodchip trail and slowing down could reduce the injury risk at the tibia.

Measurement of Wall Shear Stress in High Speed Air Flow Using Shear-Sensitive Liquid Crystal Coating.

PubMed

Zhao, Jisong

2018-05-17

Wall shear stress is an important quantity in fluid mechanics, but its measurement is a challenging task. An approach to measure wall shear stress vector distribution using shear-sensitive liquid crystal coating (SSLCC) is described. The wall shear stress distribution on the test surface beneath high speed jet flow is measured while using the proposed technique. The flow structures inside the jet flow are captured and the results agree well with the streakline pattern that was visualized using the oil-flow technique. In addition, the shock diamonds inside the supersonic jet flow are visualized clearly using SSLCC and the results are compared with the velocity contour that was measured using the particle image velocimetry (PIV) technique. The work of this paper demonstrates the application of SSLCC in the measurement/visualization of wall shear stress in high speed flow.

A Study Of High Speed Friction Behavior Under Elastic Loading Conditions

NASA Astrophysics Data System (ADS)

Crawford, P. J.; Hammerberg, J. E.

2005-03-01

The role of interfacial dynamics under high strain-rate conditions is an important constitutive relationship in modern modeling and simulation studies of dynamic events (<100 μs in length). The frictional behavior occurring at the interface between two metal surfaces under high elastic loading and sliding speed conditions is studied using the Rotating Barrel Gas Gun (RBGG) facility. The RBGG utilizes a low-pressure gas gun to propel a rotating annular projectile towards an annular target rod. Upon striking the target, the projectile imparts both an axial and a torsional impulse into the target. Resulting elastic waves are measured using strain gauges attached to the target rod. The kinetic coefficient of friction is obtained through an analysis of the resulting strain wave data. Experiments performed using Cu/Cu, Cu/Stainless steel and Cu/Al interfaces provide some insight into the kinetic coefficient of friction behavior at varying sliding speeds and impact loads.

TECHNICAL NOTE: High-speed grinding using thin abrasive disks for microcomponents

NASA Astrophysics Data System (ADS)

Yeo, S. H.; Balon, S. A. P.

2002-01-01

This paper introduces the development of a high-speed grinding device for cylindrical grinding of microcomponents made of hard and brittle materials. The study made use of an ultraprecision diamond turning machine tool as a basic platform. The novelty of the device is based on the high-speed air bearing spindle with a thin grinding wheel, similar to the dicing technology for silicon wafer fabrication. The spindle attachment is inclined at an angle to the main spindle which holds the precision fixture mechanism via the vacuum chuck. Experiments have been conducted to verify the design and implementation of the grinding methodology. A feature size as small as 31 μm in diameter and average surface roughness of 98 nm were obtained in the experimental work. It is found that the work done is capable of manufacturing miniature components, such as microcylindrical stepped shafts.

Measurement of Wall Shear Stress in High Speed Air Flow Using Shear-Sensitive Liquid Crystal Coating

PubMed Central

Zhao, Jisong

2018-01-01

Wall shear stress is an important quantity in fluid mechanics, but its measurement is a challenging task. An approach to measure wall shear stress vector distribution using shear-sensitive liquid crystal coating (SSLCC) is described. The wall shear stress distribution on the test surface beneath high speed jet flow is measured while using the proposed technique. The flow structures inside the jet flow are captured and the results agree well with the streakline pattern that was visualized using the oil-flow technique. In addition, the shock diamonds inside the supersonic jet flow are visualized clearly using SSLCC and the results are compared with the velocity contour that was measured using the particle image velocimetry (PIV) technique. The work of this paper demonstrates the application of SSLCC in the measurement/visualization of wall shear stress in high speed flow. PMID:29772822

Thermo-Mechanical Characterization of Silicon Carbide-Silicon Carbide Composites at Elevated Temperatures Using a Unique Combustion Facility

DTIC Science & Technology

2009-09-10

Calibration Tool(s) Surface Temperature ~1250oC Furnace, R-type TC & IR Gas Temperature < 1800oC R-type TC Gas Velocity ~ Mach 0.5 XS -4 High Speed...Camera Equivalence Ratio ~ 0.9 HVOFTM Flow Controller Gas Composition H 2 O, O 2 ,CO 2 , CO, NOx Testo XL 350 Gas Analyzer Mechanical Loading Fatigue...unavailability, however, gas velocity was measured using the X-StreamTM XS -4 High Speed Camera. The range of our interest was the velocity in the upstream of a

Application of TURBO-AE to Flutter Prediction: Aeroelastic Code Development

NASA Technical Reports Server (NTRS)

Hoyniak, Daniel; Simons, Todd A.; Stefko, George (Technical Monitor)

2001-01-01

The TURBO-AE program has been evaluated by comparing the obtained results to cascade rig data and to prediction made from various in-house programs. A high-speed fan cascade, a turbine cascade, a turbine cascade and a fan geometry that shower flutter in torsion mode were analyzed. The steady predictions for the high-speed fan cascade showed the TURBO-AE predictions to match in-house codes. However, the predictions did not match the measured blade surface data. Other researchers also reported similar disagreement with these data set. Unsteady runs for the fan configuration were not successful using TURBO-AE .

Pressure measurements on a thick cambered and twisted 58 deg delta wing at high subsonic speeds

NASA Technical Reports Server (NTRS)

Chu, Julio; Lamar, John E.

1987-01-01

A pressure experiment at high subsonic speeds was conducted by a cambered and twisted thick delta wing at the design condition (Mach number 0.80), as well as at nearby Mach numbers (0.75 and 0.83) and over an angle-of-attack range. Effects of twin vertical tails on the wing pressure measurements were also assessed. Comparisons of detailed theoretical and experimental surface pressures and sectional characteristics for the wing alone are presented. The theoretical codes employed are FLO-57, FLO-28, PAN AIR, and the Vortex Lattice Method-Suction Analogy.

Estimation of wind stress using dual-frequency TOPEX data

NASA Astrophysics Data System (ADS)

Elfouhaily, Tanos; Vandemark, Douglas; Gourrion, Jéro‸me; Chapron, Bertrand

1998-10-01

The TOPEX/POSEIDON satellite carries the first dual-frequency radar altimeter. Monofrequency (Ku-band) algorithms are presently used to retrieve surface wind speed from the altimeter's radar cross-section measurement (σ0Ku). These algorithms work reasonably well, but it is also known that altimeter wind estimates can be contaminated by residual effects, such as sea state, embedded in the σ0Ku measurement. Investigating the potential benefit of using two frequencies for wind retrieval, it is shown that a simple evaluation of TOPEX data yields previously unavailable information, particularly for high and low wind speeds. As the wind speed increases, the dual-frequency data provides a measurement more directly linked to the short-scale surface roughness, which in turn is associated with the local surface wind stress. Using a global TOPEX σ0° data set and TOPEX's significant wave height (Hs) estimate as a surrogate for the sea state's degree of development, it is also shown that differences between the two TOPEX σ0 measurements strongly evidence nonlocal sea state signature. A composite scattering theory is used to show how the dual-frequency data can provide an improved friction velocity model, especially for winds above 7 m/s. A wind speed conversion is included using a sea state dependent drag coefficient fed with TOPEX Hs data. Two colocated TOPEX-buoy data sets (from the National Data Buoy Center (NDBC) and the Structure des Echanges Mer-Atmosphre, Proprietes des Heterogeneites Oceaniques: Recherche Expérimentale (SEMAPHORE) campaign) are employed to test the new wind speed algorithm. A measurable improvement in wind speed estimation is obtained when compared to the monofrequency Witter and Chelton [1991] model.

Tribology of Si/SiO2 in humid air: transition from severe chemical wear to wearless behavior at nanoscale.

PubMed

Chen, Lei; He, Hongtu; Wang, Xiaodong; Kim, Seong H; Qian, Linmao

2015-01-13

Wear at sliding interfaces of silicon is a main cause for material loss in nanomanufacturing and device failure in microelectromechanical system (MEMS) applications. However, a comprehensive understanding of the nanoscale wear mechanisms of silicon in ambient conditions is still lacking. Here, we report the chemical wear of single crystalline silicon, a material used for micro/nanoscale devices, in humid air under the contact pressure lower than the material hardness. A transmission electron microscopy (TEM) analysis of the wear track confirmed that the wear of silicon in humid conditions originates from surface reactions without significant subsurface damages such as plastic deformation or fracture. When rubbed with a SiO2 ball, the single crystalline silicon surface exhibited transitions from severe wear in intermediate humidity to nearly wearless states at two opposite extremes: (a) low humidity and high sliding speed conditions and (b) high humidity and low speed conditions. These transitions suggested that at the sliding interfaces of Si/SiO2 at least two different tribochemical reactions play important roles. One would be the formation of a strong "hydrogen bonding bridge" between hydroxyl groups of two sliding interfaces and the other the removal of hydroxyl groups from the SiO2 surface. The experimental data indicated that the dominance of each reaction varies with the ambient humidity and sliding speed.

Why does radar reflectivity tend to increase downward toward the ocean surface, but decrease downward toward the land surface?

NASA Astrophysics Data System (ADS)

Liu, Chuntao; Zipser, Edward J.

2013-01-01

Both ground and space borne radars have shown that radar reflectivity profiles below the freezing level have different slopes over land and ocean in general. This is critical in correctly estimating the surface precipitation rate in the usual situation in which the radar reflectivity cannot be measured as close to the surface as one would like. Using 14 years of Tropical Rainfall Measuring Mission precipitation radar observations, the variations of slopes of the radar reflectivity in the low troposphere are examined over the stratiform and convective precipitation regions. Radar reflectivity below the freezing level usually decreases toward the surface over land, but increases toward the surface over the ocean. Increasing reflectivity toward the surface is hypothesized to occur mainly when raindrops grow while falling through low clouds, which is favored by high humidity at low levels, and by updraft speeds lower than the fall speed of raindrops, both more likely over oceans. Other things being equal, proxy evidence is presented that the more intense the convection, the more likely reflectivity is to decrease toward the surface, and that this is at least as important as low-level relative humidity. Over monsoon regions with more moderate convection but higher humidity, such as southeast China and the Amazon, there are more profiles with reflectivity increasing toward the surface than over other continental regions such as Africa. Radar reflectivity tends to increase toward the surface in shallow warm rain systems in trade cumulus regions, but tends to decrease toward the surface when high reflectivity values are present at or above the freezing level.

Water Surface Impact and Ricochet of Deformable Elastomeric Spheres

NASA Astrophysics Data System (ADS)

Hurd, Randy C.

Soft and deformable silicone rubber spheres ricochet from a water surface when rigid spheres and disks (or skipping stones) cannot. This dissertation investigates why these objects are able to skip so successfully. High speed cameras allow us to see that these unique spheres deform significantly as they impact the water surface, flattening into pancake-like shapes with greater area. Though the water entry behavior of deformable spheres deviates from that of rigid spheres, our research shows that if this deformation is accounted for, their behavior can be predicted from previously established methods. Soft spheres skip more easily because they deform significantly when impacting the water surface. We present a diagram which enables the prediction of a ricochet from sphere impact conditions such as speed and angle. Experiments and mathematical representations of the sphere skipping both show that these deformable spheres skip more readily because deformation momentarily increases sphere area and produces an attack angle with the water which is favorable to skipping. Predictions from our mathematical representation of sphere skipping agree strongly with observations from experiments. Even when a sphere was allowed to skip multiple times in the laboratory, the mathematical predictions show good agreement with measured impact conditions through subsequent skipping events. While studying multiple impact events in an outdoor setting, we discovered a previously unidentified means of skipping, which is unique to deformable spheres. This new skipping occurs when a relatively soft sphere first hits the water at a high speed and low impact angle and the sphere begins to rotate very quickly. This quick rotation causes the sphere to stretch into a shape similar to an American football and maintain this shape while it spins. The sphere is observed to move nearly parallel with the water surface with the tips of this "football" dipping into the water as it rotates and the sides passing just over the surface. This sequence of rapid impact events give the impression that the sphere is walking across the water surface.

A systematic experimental investigation of significant parameters affecting model tire hydroplaning

NASA Technical Reports Server (NTRS)

Wray, G. A.; Ehrlich, I. R.

1973-01-01

The results of a comprehensive parametric study of model and small pneumatic tires operating on a wet surface are presented. Hydroplaning inception (spin down) and rolling restoration (spin up) are discussed. Conclusions indicate that hydroplaning inception occurs at a speed significantly higher than the rolling restoration speed. Hydroplaning speed increases considerably with tread depth, surface roughness and tire inflation pressure of footprint pressure, and only moderately with increased load. Water film thickness affects spin down speed only slightly. Spin down speed varies inversely as approximately the one-sixth power of film thickness. Empirical equations relating tire inflation pressure, normal load, tire diameter and water film thickness have been generated for various tire tread and surface configurations.

Safety and EEG data quality of concurrent high-density EEG and high-speed fMRI at 3 Tesla.

PubMed

Foged, Mette Thrane; Lindberg, Ulrich; Vakamudi, Kishore; Larsson, Henrik B W; Pinborg, Lars H; Kjær, Troels W; Fabricius, Martin; Svarer, Claus; Ozenne, Brice; Thomsen, Carsten; Beniczky, Sándor; Paulson, Olaf B; Posse, Stefan

2017-01-01

Concurrent EEG and fMRI is increasingly used to characterize the spatial-temporal dynamics of brain activity. However, most studies to date have been limited to conventional echo-planar imaging (EPI). There is considerable interest in integrating recently developed high-speed fMRI methods with high-density EEG to increase temporal resolution and sensitivity for task-based and resting state fMRI, and for detecting interictal spikes in epilepsy. In the present study using concurrent high-density EEG and recently developed high-speed fMRI methods, we investigate safety of radiofrequency (RF) related heating, the effect of EEG on cortical signal-to-noise ratio (SNR) in fMRI, and assess EEG data quality. The study compared EPI, multi-echo EPI, multi-band EPI and multi-slab echo-volumar imaging pulse sequences, using clinical 3 Tesla MR scanners from two different vendors that were equipped with 64- and 256-channel MR-compatible EEG systems, respectively, and receive only array head coils. Data were collected in 11 healthy controls (3 males, age range 18-70 years) and 13 patients with epilepsy (8 males, age range 21-67 years). Three of the healthy controls were scanned with the 256-channel EEG system, the other subjects were scanned with the 64-channel EEG system. Scalp surface temperature, SNR in occipital cortex and head movement were measured with and without the EEG cap. The degree of artifacts and the ability to identify background activity was assessed by visual analysis by a trained expert in the 64 channel EEG data (7 healthy controls, 13 patients). RF induced heating at the surface of the EEG electrodes during a 30-minute scan period with stable temperature prior to scanning did not exceed 1.0° C with either EEG system and any of the pulse sequences used in this study. There was no significant decrease in cortical SNR due to the presence of the EEG cap (p > 0.05). No significant differences in the visually analyzed EEG data quality were found between EEG recorded during high-speed fMRI and during conventional EPI (p = 0.78). Residual ballistocardiographic artifacts resulted in 58% of EEG data being rated as poor quality. This study demonstrates that high-density EEG can be safely implemented in conjunction with high-speed fMRI and that high-speed fMRI does not adversely affect EEG data quality. However, the deterioration of the EEG quality due to residual ballistocardiographic artifacts remains a significant constraint for routine clinical applications of concurrent EEG-fMRI.

Residual vibration control based on a global search method in a high-speed white light scanning interferometer.

PubMed

Song, Zhenyuan; Guo, Tong; Fu, Xing; Hu, Xiaotang

2018-05-01

To achieve high-speed measurements using white light scanning interferometers, the scanning devices used need to have high feedback gain in closed-loop operations. However, flexure hinges induce a residual vibration that can cause a misidentification of the fringe order. The reduction of this residual vibration is crucial because the highly nonlinear distortions in interferograms lead to clearly incorrect measured profiles. Input shaping can be used to control the amplitude of the residual vibration. The conventional method uses continuous wavelet transform (CWT) to estimate parameters of the scanning device. Our proposed method extracts equivalent modal parameters using a global search algorithm. Due to its simplicity, ease of implementation, and response speed, this global search method outperforms CWT. The delay time is shortened by searching, because fewer modes are needed for the shaper. The effectiveness of the method has been confirmed by the agreement between simulated shaped responses and experimental displacement information from the capacitive sensor inside the scanning device, and the intensity profiles of the interferometer have been greatly improved. An experiment measuring the surface of a silicon wafer is also presented. The method is shown to be effective at improving the intensity profiles and recovering accurate surface topography. Finally, frequency localizations are found to be almost stable with different proportional gains, but their energy distributions change.

CFD validation experiments at McDonnell Aircraft Company

NASA Technical Reports Server (NTRS)

Verhoff, August

1987-01-01

Information is given in viewgraph form on computational fluid dynamics (CFD) validation experiments at McDonnell Aircraft Company. Topics covered include a high speed research model, a supersonic persistence fighter model, a generic fighter wing model, surface grids, force and moment predictions, surface pressure predictions, forebody models with 65 degree clipped delta wings, and the low aspect ratio wing/body experiment.

[Application Progress of Three-dimensional Laser Scanning Technology in Medical Surface Mapping].

PubMed

Zhang, Yonghong; Hou, He; Han, Yuchuan; Wang, Ning; Zhang, Ying; Zhu, Xianfeng; Wang, Mingshi

2016-04-01

The booming three-dimensional laser scanning technology can efficiently and effectively get spatial three-dimensional coordinates of the detected object surface and reconstruct the image at high speed,high precision and large capacity of information.Non-radiation,non-contact and the ability of visualization make it increasingly popular in three-dimensional surface medical mapping.This paper reviews the applications and developments of three-dimensional laser scanning technology in medical field,especially in stomatology,plastic surgery and orthopedics.Furthermore,the paper also discusses the application prospects in the future as well as the biomedical engineering problems it would encounter with.

High-speed non-contact measuring apparatus for gauging the thickness of moving sheet material

DOEpatents

Grann, Eric B.; Holcomb, David E.

2000-01-01

An optical measurement apparatus is provided for measuring the thickness of a moving sheet material (18). The apparatus has a pair of optical measurement systems (21, 31) attached to opposing surfaces (14, 16) of a rigid support structure (10). A pair of high-power laser diodes (20,30) and a pair of photodetector arrays (22,32) are attached to the opposing surfaces. Light emitted from the laser diodes is reflected off of the sheet material surfaces (17, 19) and received by the respective photodetector arrays. An associated method for implementing the apparatus is also provided.

Closed-loop ARS mode for scanning ion conductance microscopy with improved speed and stability for live cell imaging applications.

PubMed

Jung, Goo-Eun; Noh, Hanaul; Shin, Yong Kyun; Kahng, Se-Jong; Baik, Ku Youn; Kim, Hong-Bae; Cho, Nam-Joon; Cho, Sang-Joon

2015-07-07

Scanning ion conductance microscopy (SICM) is an increasingly useful nanotechnology tool for non-contact, high resolution imaging of live biological specimens such as cellular membranes. In particular, approach-retract-scanning (ARS) mode enables fast probing of delicate biological structures by rapid and repeated approach/retraction of a nano-pipette tip. For optimal performance, accurate control of the tip position is a critical issue. Herein, we present a novel closed-loop control strategy for the ARS mode that achieves higher operating speeds with increased stability. The algorithm differs from that of most conventional (i.e., constant velocity) approach schemes as it includes a deceleration phase near the sample surface, which is intended to minimize the possibility of contact with the surface. Analysis of the ion current and tip position demonstrates that the new mode is able to operate at approach speeds of up to 250 μm s(-1). As a result of the improved stability, SICM imaging with the new approach scheme enables significantly improved, high resolution imaging of subtle features of fixed and live cells (e.g., filamentous structures & membrane edges). Taken together, the results suggest that optimization of the tip approach speed can substantially improve SICM imaging performance, further enabling SICM to become widely adopted as a general and versatile research tool for biological studies at the nanoscale level.

Surface tension dominates insect flight on fluid interfaces.

PubMed

Mukundarajan, Haripriya; Bardon, Thibaut C; Kim, Dong Hyun; Prakash, Manu

2016-03-01

Flight on the 2D air-water interface, with body weight supported by surface tension, is a unique locomotion strategy well adapted for the environmental niche on the surface of water. Although previously described in aquatic insects like stoneflies, the biomechanics of interfacial flight has never been analysed. Here, we report interfacial flight as an adapted behaviour in waterlily beetles (Galerucella nymphaeae) which are also dexterous airborne fliers. We present the first quantitative biomechanical model of interfacial flight in insects, uncovering an intricate interplay of capillary, aerodynamic and neuromuscular forces. We show that waterlily beetles use their tarsal claws to attach themselves to the interface, via a fluid contact line pinned at the claw. We investigate the kinematics of interfacial flight trajectories using high-speed imaging and construct a mathematical model describing the flight dynamics. Our results show that non-linear surface tension forces make interfacial flight energetically expensive compared with airborne flight at the relatively high speeds characteristic of waterlily beetles, and cause chaotic dynamics to arise naturally in these regimes. We identify the crucial roles of capillary-gravity wave drag and oscillatory surface tension forces which dominate interfacial flight, showing that the air-water interface presents a radically modified force landscape for flapping wing flight compared with air. © 2016. Published by The Company of Biologists Ltd.

A new reactive atom plasma technology (RAPT) for precision machining: the etching of ULE optical surfaces

NASA Astrophysics Data System (ADS)

Fanara, Carlo; Shore, Paul; Nicholls, John R.; Lyford, Nicholas; Sommer, Phil; Fiske, Peter

2006-06-01

The next generation of 30-100 metre diameter extremely large telescopes (ELTs) requires large numbers of hexagonal primary mirror segments. As part of the Basic Technology programme run jointly by UCL and Cranfield University, a reactive atomic plasma technology (RAP(tm)) emerged from the US Lawrence Livermore National Laboratory (LLNL), is employed for the finishing of these surfaces. Results are presented on this novel etching technology. The Inductively Coupled Plasma (ICP) operated at atmospheric pressure using argon, activates the chemical species injected through its centre and promotes the fluorine-based chemical reactions at the surface. Process assessment trials on Ultra Low Expansion (ULE(tm)) plates, previously ground at high material removal rates, have been conducted. The quality of the surfaces produced on these samples using the RAP process are discussed. Substantial volumetric material removal rates of up to 0.446(21) mm 3/s at the highest process speed (1,200 mm/min) were found to be possible without pre-heating the substrate. The influences of power transfer, process speed and gas concentration on the removal rates have been determined. The suitability of the RAP process for revealing and removing sub-surface damage induced by high removal rate grinding is discussed. The results on SiC samples are reported elsewhere in this conference.

Surface tension dominates insect flight on fluid interfaces

PubMed Central

Mukundarajan, Haripriya; Bardon, Thibaut C.; Kim, Dong Hyun; Prakash, Manu

2016-01-01

ABSTRACT Flight on the 2D air–water interface, with body weight supported by surface tension, is a unique locomotion strategy well adapted for the environmental niche on the surface of water. Although previously described in aquatic insects like stoneflies, the biomechanics of interfacial flight has never been analysed. Here, we report interfacial flight as an adapted behaviour in waterlily beetles (Galerucella nymphaeae) which are also dexterous airborne fliers. We present the first quantitative biomechanical model of interfacial flight in insects, uncovering an intricate interplay of capillary, aerodynamic and neuromuscular forces. We show that waterlily beetles use their tarsal claws to attach themselves to the interface, via a fluid contact line pinned at the claw. We investigate the kinematics of interfacial flight trajectories using high-speed imaging and construct a mathematical model describing the flight dynamics. Our results show that non-linear surface tension forces make interfacial flight energetically expensive compared with airborne flight at the relatively high speeds characteristic of waterlily beetles, and cause chaotic dynamics to arise naturally in these regimes. We identify the crucial roles of capillary–gravity wave drag and oscillatory surface tension forces which dominate interfacial flight, showing that the air–water interface presents a radically modified force landscape for flapping wing flight compared with air. PMID:26936640

The Kaye effect revisited: High speed imaging of leaping shampoo

NASA Astrophysics Data System (ADS)

Versluis, Michel; Blom, Cock; van der Meer, Devaraj; van der Weele, Ko; Lohse, Detlef

2003-11-01

When a visco-elastic fluid such as shampoo or shower gel is poured onto a flat surface the fluid piles up forming a heap on which rather irregular combinations of fluid buckling, coiling and folding are observed. Under specific conditions a string of fluid leaps from the heap and forms a steady jet fed by the incoming stream. Momentum transfer of the incoming jet, combined with the shear-thinning properties of the fluid, lead to a spoon-like dimple in the highly viscous fluid pool in which the jet recoils. The jet can be stable for several seconds. This effect is known as the Kaye effect. In order to reveal its mechanism we analyzed leaping shampoo through high-speed imaging. We studied the jet formation, jet stability and jet disruption mechanisms. We measured the velocity of both the incoming and recoiled jet, which was found to be thicker and slower. By inclining the surface on which the fluid was poured we observed jets leaping at upto five times.

Fiber optic interferometry for industrial process monitoring and control applications

NASA Astrophysics Data System (ADS)

Marcus, Michael A.

2002-02-01

Over the past few years we have been developing applications for a high-resolution (sub-micron accuracy) fiber optic coupled dual Michelson interferometer-based instrument. It is being utilized in a variety of applications including monitoring liquid layer thickness uniformity on coating hoppers, film base thickness uniformity measurement, digital camera focus assessment, optical cell path length assessment and imager and wafer surface profile mapping. The instrument includes both coherent and non-coherent light sources, custom application dependent optical probes and sample interfaces, a Michelson interferometer, custom electronics, a Pentium-based PC with data acquisition cards and LabWindows CVI or LabView based application specific software. This paper describes the development evolution of this instrument platform and applications highlighting robust instrument design, hardware, software, and user interfaces development. The talk concludes with a discussion of a new high-speed instrument configuration, which can be utilized for high speed surface profiling and as an on-line web thickness gauge.

Experiences with the hydraulic design of the high specific speed Francis turbine

NASA Astrophysics Data System (ADS)

Obrovsky, J.; Zouhar, J.

2014-03-01

The high specific speed Francis turbine is still suitable alternative for refurbishment of older hydro power plants with lower heads and worse cavitation conditions. In the paper the design process of such kind of turbine together with the results comparison of homological model tests performed in hydraulic laboratory of ČKD Blansko Engineering is introduced. The turbine runner was designed using the optimization algorithm and considering the high specific speed hydraulic profile. It means that hydraulic profiles of the spiral case, the distributor and the draft tube were used from a Kaplan turbine. The optimization was done as the automatic cycle and was based on a simplex optimization method as well as on a genetic algorithm. The number of blades is shown as the parameter which changes the resulting specific speed of the turbine between ns=425 to 455 together with the cavitation characteristics. Minimizing of cavitation on the blade surface as well as on the inlet edge of the runner blade was taken into account during the design process. The results of CFD analyses as well as the model tests are mentioned in the paper.

PSP Measurement of Stator Vane Surface Pressures in a High Speed Fan

NASA Technical Reports Server (NTRS)

Lepicovsky, Jan

1998-01-01

This paper presents measurements of static pressures on the stator vane suction side of a high-speed single stage fan using the technique of pressure sensitive paint (PSP). The paper illustrates development in application of the relatively new experimental technique to the complex environment of internal flows in turbomachines. First, there is a short explanation of the physics of the PSP technique and a discussion of calibration methods for pressure sensitive paint in the turbomachinery environment. A description of the image conversion process follows. The recorded image of the stator vane pressure field is skewed due to the limited optical access and must be converted to the meridional plane projection for comparison with analytical predictions. The experimental results for seven operating conditions along an off-design rotational speed line are shown in a concise form, including performance map points, mindspan static tap pressure distributions, and vane suction side pressure fields. Then, a comparison between static tap and pressure sensitive paint data is discussed. Finally, the paper lists shortcomings of the pressure sensitive paint technology and lessons learned in this high-speed fan application.

Examples of the Influence of Turbine Wakes on Downwind Power Output, Surface Wind Speed, Turbulence and Flow Convergence in Large Wind Farms

NASA Astrophysics Data System (ADS)

Takle, E. S.; Rajewski, D. A.; Lundquist, J. K.; Doorenbos, R. K.

2014-12-01

We have analyzed turbine power and concurrent wind speed, direction and turbulence data from surface 10-m flux towers in a large wind farm for experiments during four summer periods as part of the Crop Wind Energy Experiment (CWEX). We use these data to analyze surface differences for a near-wake (within 2.5 D of the turbine line), far wake (17 D downwind of the turbine line), and double wake (impacted by two lines of turbines about 34 D downwind of the first turbine line) locations. Composites are categorized by10 degree directional intervals and three ambient stability categories as defined by Rajewski et al. (2013): neutral (|z/L|<0.05), stable (z/L>0.05) and unstable (z/L<-0.05), where z is the height of the measurement and L is the Monin-Obhukov length. The dominant influence of the turbines is under stably stratified conditions (i. e., mostly at night). A 25% to 40% increase in mean wind speed occurs when turbine wakes are moving over the downwind station at a distance of 2.8 D and 5.4 D (D = fan diameter). For the double wake condition (flux station leeward of two lines of turbines) we find a daytime (unstable conditions) speed reduction of 20% for southerly wind, but for nighttime (stable conditions) the surface speeds are enhancedby 40-60% for SSW-SW winds. The speedup is reduced as wind directions shift to the west. We interpret these speed variations as due to the rotation of the wake and interaction (or not) with higher speed air above the rotor layer in highly sheared nocturnal low-level jet conditions. From a cluster of flux stations and three profiling lidars deployed within and around a cluster of turbines in 2013 (CWEX-13) we found evidence of mesoscale influences. In particular, surface convergence (wind direction deflection of 10-20 degrees) was observed during periods of low nighttime winds (hub-height winds of 4-6 m/s) with power reduction of 50-75%. This is consistent with a similar range of deflection observed from a line of turbines in CWEX-11, In the mid to late afternoon hours when hub-height wind speeds are between 5-10 m/s convergence periods have been observed, with power enhancements of 20-40% at several locations around the farm.

Entropy generation analysis for film boiling: A simple model of quenching

NASA Astrophysics Data System (ADS)

Lotfi, Ali; Lakzian, Esmail

2016-04-01

In this paper, quenching in high-temperature materials processing is modeled as a superheated isothermal flat plate. In these phenomena, a liquid flows over the highly superheated surfaces for cooling. So the surface and the liquid are separated by the vapor layer that is formed because of the liquid which is in contact with the superheated surface. This is named forced film boiling. As an objective, the distribution of the entropy generation in the laminar forced film boiling is obtained by similarity solution for the first time in the quenching processes. The PDE governing differential equations of the laminar film boiling including continuity, momentum, and energy are reduced to ODE ones, and a dimensionless equation for entropy generation inside the liquid boundary and vapor layer is obtained. Then the ODEs are solved by applying the 4th-order Runge-Kutta method with a shooting procedure. Moreover, the Bejan number is used as a design criterion parameter for a qualitative study about the rate of cooling and the effects of plate speed are studied in the quenching processes. It is observed that for high speed of the plate the rate of cooling (heat transfer) is more.

Rapid, sensitive and direct analysis of exopolysaccharides from biofilm on aluminum surfaces exposed to sea water using MALDI-TOF MS.

PubMed

Hasan, Nazim; Gopal, Judy; Wu, Hui-Fen

2011-11-01

Biofilm studies have extensive significance since their results can provide insights into the behavior of bacteria on material surfaces when exposed to natural water. This is the first attempt of using matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) for detecting the polysaccharides formed in a complex biofilm consisting of a mixed consortium of marine microbes. MALDI-MS has been applied to directly analyze exopolysaccharides (EPS) in the biofilm formed on aluminum surfaces exposed to seawater. The optimal conditions for MALDI-MS applied to EPS analysis of biofilm have been described. In addition, microbiologically influenced corrosion of aluminum exposed to sea water by a marine fungus was also observed and the fungus identity established using MALDI-MS analysis of EPS. Rapid, sensitive and direct MALDI-MS analysis on biofilm would dramatically speed up and provide new insights into biofilm studies due to its excellent advantages such as simplicity, high sensitivity, high selectivity and high speed. This study introduces a novel, fast, sensitive and selective platform for biofilm study from natural water without the need of tedious culturing steps or complicated sample pretreatment procedures. Copyright © 2011 John Wiley & Sons, Ltd.

Skin friction and heat transfer correlations for high-speed low-density flow past a flat plate

NASA Technical Reports Server (NTRS)

Woronowicz, Michael S.; Baganoff, Donald

1991-01-01

The independent and dependent variables associated with drag and heat transfer to a flat plate at zero incidence in high-speed, rarefied flow are analyzed anew to reflect the importance of kinetic effects occurring near the plate surface on energy and momentum transfer, rather than following arguments normally used to describe continuum, higher density flowfields. A new parameter, the wall Knudsen number Knx,w, based on an estimate of the mean free path length of molecules having just interacted with the surface of the plate, is introduced and used to correlate published drag and heat transfer data. The new parameter is shown to provide better correlation than either the viscous interaction parameter X or the widely-used slip parameter Voo for drag and heat transfer data over a wide range of Mach numbers, Reynolds numbers, and plate-to-freestream stagnation temperature ratios.

Effect of surface tension on the dynamical behavior of bubble in rotating fluids under low gravity environment

NASA Technical Reports Server (NTRS)

Hung, R. J.; Tsao, Y. D.; Leslie, Fred W.; Hong, B. B.

1988-01-01

Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) linear functions of increasing and decreasing gravity enviroment in high and low rotating cylidner speeds, (3) step functions of spin-up and spin-down in a low gravity environment, and (4) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds. The initial condition of bubble profiles was adopted from the steady-state formulations in which the computer algorithms have been developed by Hung and Leslie (1988), and Hung et al. (1988).

Dynamical behavior of surface tension on rotating fluids in low and microgravity environments

NASA Technical Reports Server (NTRS)

Hung, R. J.; Tsao, Y. D.; Hong, B. B.; Leslie, F. W.

1989-01-01

Consideration is given to the time-dependent evolutions of the free surface profile (bubble shapes) of a cylindrical container, partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry in low and microgravity environments. The dynamics of the bubble shapes are calculated for four cases: linear time-dependent functions of spin-up and spin-down in low and microgravity, linear time-dependent functions of increasing and decreasing gravity at high and low rotating cylinder speeds, time-dependent step functions of spin-up and spin-down in low gravity, and sinusoidal function oscillation of the gravity environment in high and low rotating cylinder speeds. It is shown that the computer algorithms developed by Hung et al. (1988) may be used to simulate the profile of time-dependent bubble shapes under variations of centrifugal, capillary, and gravity forces.

Simulation of Mechanical Behavior of Agglutinates

NASA Technical Reports Server (NTRS)

Nakagawa, Masami; Moon, Tae-Hyun

2005-01-01

Due to lack of "real" lunar soil or even lunar simulant, it is difficult to characterize the interaction between lunar soil (or simulant) with different surfaces that are involved in excavation and processing machinery. One unique feature possessed by lunar soil is the agglutinates produced by repeated high-speed micrometeoroid impacts and subsequent pulverization[l and 2]. The large particles are impacted by micrometeoroids [Fig.l] and pulverized to produce finer particles. This process continues until there are no more "large" particles left on the surface of the moon. Due to high impact speed, the impact melting process fuses fines to make agglutinates such as shown in Fig. 2. We will present a series of simulation results and movies will be shown to indicate brittle behavior of each individual agglutinate and also similar compressibility charts shown by Carrier et al. [3]. Fig. 3 shows our preliminary result of the simulated oedometer tests.

A novel serrated columnar phased array ultrasonic transducer

NASA Astrophysics Data System (ADS)

Zou, Cheng; Sun, Zhenguo; Cai, Dong; Song, Hongwei; Chen, Qiang

2016-02-01

Traditionally, wedges are required to generate transverse waves in a solid specimen and mechanical rotation device is needed for interrogation of a specimen with a hollow bore, such as high speed railway locomotive axles, turbine rotors, etc. In order to eliminate the mechanical rotation process, a novel array pattern of phased array ultrasonic transducers named as serrated columnar phased array ultrasonic transducer (SCPAUT) is designed. The elementary transducers are planar rectangular, located on the outside surface of a cylinder. This layout is aimed to generate electrically rotating transverse waveforms so as to inspect the longitudinal cracks on the outside surface of a specimen which has a hollow bore at the center, such as the high speed railway locomotive axles. The general geometry of the SCPAUT and the inspection system are illustrated. A FEM model and mockup experiment has been carried out. The experiment results are in good agreement with the FEM simulation results.

Structure of propagating arc in a magneto-hydrodynamic rail plasma actuator

NASA Astrophysics Data System (ADS)

Gray, Miles D.; Choi, Young-Joon; Sirohi, Jayant; Raja, Laxminarayan L.

2016-01-01

The spatio-temporal evolution of a magnetically driven arc in a rail plasma flow actuator has been characterized with high-speed imaging, electrical measurements, and spectroscopy. The arc draws a peak current of ~1 kA. High-speed framing cameras were used to observe the complex arc propagation phenomenon. In particular, the anode and cathode roots were observed to have different modes of transit, which resulted in distinct types of electrode degradation on the anode and cathode surfaces. Observations of the arc electrical properties and induced magnetic fields are used to explain the transit mechanism of the arc. Emission spectroscopy revealed the arc temperature and species composition as a function of transit distance of the arc. The results obtained offer significant insights into the electromagnetic properties of the arc-rail system as well as arc-surface interaction phenomena in a propagating arc.

Laser Surface Treatment of Sintered Alumina

NASA Astrophysics Data System (ADS)

Hagemann, R.; Noelke, C.; Kaierle, S.; Wesling, V.

Sintered alumina ceramics are used as refractory materials for industrial aluminum furnaces. In this environment the ceramic surface is in permanent contact with molten aluminum resulting in deposition of oxidic material on its surface. Consequently, a lower volume capacity as well as thermal efficiency of the furnaces follows. To reduce oxidic adherence of the ceramic material, two laser-based surface treatment processes were investigated: a powder- based single-step laser cladding and a laser surface remelting. Main objective is to achieve an improved surface quality of the ceramic material considering the industrial requirements as a high process speed.

Eastern North American finite-frequency, compressional and shear tomographic models

NASA Astrophysics Data System (ADS)

Savage, B.; Shen, Y.

2017-12-01

The Eastern North American margin and continental interior is imaged using a finite-frequency, tomographic method. Each of the P and S teleseismic body wave date sets consists of over 80,000 usable measurements recorded on the Transportable Array (TA). Sensitivity kernels are computed from a 1D model with grid spacing of 50 x 50 x 25 km. Measurements are performed automatically at three individual frequency bands, allowing a more effective use of the available broadband data. Imaged shear and compressional wave speeds show similar long-wavelength features of reduced wave speeds along the continent-ocean margin and increased wave speeds within the stable interior. Wave speeds throughout the model are highly variable at the scale of 100 to 200 km. Large wave speed reductions are present near New England, the Mid-Atlantic states, and the Gulf Coast states; these variations are present in previous models. Interestingly, the strongly reduced wave speeds near South Carolina are absent at depths greater than of 150 km within this model and recent teleseismic body-wave models. This result is contrary to a variety of surface wave models which contain an intense, reduced wave speed anomaly extending past 250 km depth and interpreted as a mantle upwelling associated with edge driven convection. An anomaly along the West Virginia-Virginia border, associated with volcanism and mantle upwelling, is also present, tightly constrained, and extends to 200 km depth. Moreover, the interior of the continent contains significant, regional wave speed variations. Variation of this style is present in other surface and body wave models and is not consistent with a massive, homogeneous continent with no internal variations. These internal continental variations suggest a compositional influence as temperature, melt and water are thought to have minimal effect. Unlike surface wave models that include a distinct continental base around 175 km, teleseismic body wave models, including this one, do not show this base. However, this model does include the deep, positive wave speed anomaly within the mantle transition zone interpreted as a slab fragment, agreeing with previous models.

Feasibility Study on CNC Multioperation Grinding of Jet Engine Components Using Force Sensing Adaptive Control.

DTIC Science & Technology

1982-09-30

OF TI4IS PIAGE(,,aW Date Eateed) cont. block 20: .... differential wheelwear and thereby prevent form errors. Wheel sharpness can also be monitored to...80 5. NOMENCLATURE V = Work surface speed (m/s) w Nw = Work speed (RPM) Vs = Wheel surface speed (m/sec) Ns = Wheel ...speed (RPM) Vt = Traverse speed (m/sec) 0 = Work diameter (mm)W D = Wheel diameter (mm) z= Dress lead (um/rev) c = 2*diamond depth-of-dress (um) d

Towards a parameterization of convective wind gusts in Sahel

NASA Astrophysics Data System (ADS)

Largeron, Yann; Guichard, Françoise; Bouniol, Dominique; Couvreux, Fleur; Birch, Cathryn; Beucher, Florent

2014-05-01

West Africa is responsible for between 25 and 50 % of the global emissions of mineral dust (cf [Engelstaedter et al., 2006]) and these dust emissions have a huge impact on climate (cf [Carslaw et al., 2010]) and soil erosion. Numerous studies have focused on the quantification of the dust emission fluxes from knowledges of the soil surface characteristics, leading to the formulation of a threshold wind friction velocity (cf [Marticorena and Bergametti, 1995]) above which the dust can be uplifted. That flux varies with the cube of the surface wind speed above the threshold and is therefore particularly sensitive to the way the wind speed is modeled (cf [Menut, 2008]). Moreover, in the Sahelian belt, about half of the dust uplift happens during isolated events which generate violent cold pool outflows from moist deep convection, and associated high surface wind speeds. Therefore, the representation of convectively generated winds appears critical (cf [Marsham et al., 2011], [Knippertz and Todd, 2012]). The present study is motivated by these issues, and is carried out within the CAVIARS French Research National Agency (ANR) project. First, we examine the ERA interim reanalysis of the ECMWF, frequently used as an input wind field for off-line dust emission models (cf [Pierre et al., 2012]). The comparison with high-frequency local measurements shows that, not unexpectedly, the increase of the surface wind speed from deep convection is not represented in large-scale reanalysis. Therefore, following [Redelsperger et al., 2000], we propose a statistical approach to introduce a formulation of the surface wind gusts during deep convection, based on the analysis of convection-permitting high resolution simulations made with the UKMO atmospheric model (CASCADE project), the AROME operational model from Meteo-France, and the MesoNH Large Eddy Simulations model. High-frequency observations are also used to complement the analysis. However, unlike [Redelsperger et al., 2000] who focused on the wet tropical Pacific region, and linked wind gusts to convective precipitation rates alone, here, we also analyse the subgrid wind distribution during convective events, and quantify the statistical moments (variance, skewness and kurtosis) in terms of mean wind speed and convective indexes such as DCAPE. Next step of the work will be to formulate a parameterization of the cold pool convective gust from those probability density functions and analytical formulaes obtained from basic energy budget models. References : [Carslaw et al., 2010] A review of natural aerosol interactions and feedbacks within the earth system. Atmospheric Chemistry and Physics, 10(4):1701{1737. [Engelstaedter et al., 2006] North african dust emissions and transport. Earth-Science Reviews, 79(1):73{100. [Knippertz and Todd, 2012] Mineral dust aerosols over the sahara: Meteorological controls on emission and transport and implications for modeling. Reviews of Geophysics, 50(1). [Marsham et al., 2011] The importance of the representation of deep convection for modeled dust-generating winds over west africa during summer.Geophysical Research Letters, 38(16). [Marticorena and Bergametti, 1995] Modeling the atmospheric dust cycle: 1. design of a soil-derived dust emission scheme. Journal of Geophysical Research, 100(D8):16415{16. [Menut, 2008] Sensitivity of hourly saharan dust emissions to ncep and ecmwf modeled wind speed. Journal of Geophysical Research: Atmospheres (1984{2012), 113(D16). [Pierre et al., 2012] Impact of vegetation and soil moisture seasonal dynamics on dust emissions over the sahel. Journal of Geophysical Research: Atmospheres (1984{2012), 117(D6). [Redelsperger et al., 2000] A parameterization of mesoscale enhancement of surface fluxes for large-scale models. Journal of climate, 13(2):402{421.

High-Sensitive Two-Layer Photoresistors Based on p-Cd x Hg1- x Te with a Converted Near-Surface Layer

NASA Astrophysics Data System (ADS)

Ismailov, N. D.; Talipov, N. Kh.; Voitsekhovskii, A. V.

2018-04-01

The results of an experimental study of photoelectric characteristics of two-layer photoresistors based on p-Cd x Hg1- x Te (x = 0.24-0.28) with a thin near-surface layer of n-type obtained by treatment in atmospheric gas plasma are presented. It is shown that the presence of a potential barrier between the p- and n-regions causes high photosensitivity and speed of operation of such photoresistors at T = 77 K

High-Sensitive Two-Layer Photoresistors Based on p-Cd x Hg1-x Te with a Converted Near-Surface Layer

NASA Astrophysics Data System (ADS)

Ismailov, N. D.; Talipov, N. Kh.; Voitsekhovskii, A. V.

2018-04-01

The results of an experimental study of photoelectric characteristics of two-layer photoresistors based on p-Cd x Hg1-x Te (x = 0.24-0.28) with a thin near-surface layer of n-type obtained by treatment in atmospheric gas plasma are presented. It is shown that the presence of a potential barrier between the p- and n-regions causes high photosensitivity and speed of operation of such photoresistors at T = 77 K

Near-surface Salinity and Temperature Structure Observed with Dual-Sensor Drifters in the Subtropical South Pacific

NASA Astrophysics Data System (ADS)

Dong, Shenfu; Goni, Gustavo; Volkov, Denis; Lumpkin, Rick; Foltz, Gregory

2017-04-01

Three surface drifters equipped with temperature and salinity sensors at 0.2 m and 5 m depths were deployed in April/May 2015 in the subtropical South Pacific Ocean with the objective of measuring near-surface salinity differences seen by satellite and in situ sensors and examining the causes of the differences. Measurements from these drifters indicate that, on average, water at a depth of 0.2 m is about 0.013 psu fresher than at 5 m and about 0.024°C warmer. Events with large temperature and salinity differences between the two depths often occur when surface winds are weak. In addition to the expected surface freshening and cooling during rainfall events, surface salinification occurs under weak wind conditions when there is strong surface warming that enhances evaporation and upper ocean stratification. Further examination of the drifter measurements demonstrate that (i) the amount of surface freshening and vertical salinity gradient heavily depend on wind speed during rain events, (ii) salinity differences between 0.2 m and 5 m are positively correlated with the corresponding temperature differences, and (iii) temperature exhibits a diurnal cycle at both depths, whereas the diurnal cycle of salinity is observed only at 0.2 m when the wind speed is less than 4 m/s. Its phase is consistent with diurnal changes in surface temperature-induced evaporation. Below a wind speed of 6 m/s, the amplitudes of the diurnal cycles of temperature at both depths decrease with increasing wind speed. Wind speed also affects the phasing of the diurnal cycle of T5m with the time of maximum T5m increasing gradually with decreasing wind speed. Wind speed does not affect the phasing of the diurnal cycle of T0.2m. At 0.2 m and 5 m, the diurnal cycle of temperature also depends on surface solar radiation, with the amplitude and time of diurnal maximum increasing as solar radiation increases.

Unstructured Grid Euler Method Assessment for Longitudinal and Lateral/Directional Aerodynamic Performance Analysis of the HSR Technology Concept Airplane at Supersonic Cruise Speed

NASA Technical Reports Server (NTRS)

Ghaffari, Farhad

1999-01-01

Unstructured grid Euler computations, performed at supersonic cruise speed, are presented for a High Speed Civil Transport (HSCT) configuration, designated as the Technology Concept Airplane (TCA) within the High Speed Research (HSR) Program. The numerical results are obtained for the complete TCA cruise configuration which includes the wing, fuselage, empennage, diverters, and flow through nacelles at M (sub infinity) = 2.4 for a range of angles-of-attack and sideslip. Although all the present computations are performed for the complete TCA configuration, appropriate assumptions derived from the fundamental supersonic aerodynamic principles have been made to extract aerodynamic predictions to complement the experimental data obtained from a 1.675%-scaled truncated (aft fuselage/empennage components removed) TCA model. The validity of the computational results, derived from the latter assumptions, are thoroughly addressed and discussed in detail. The computed surface and off-surface flow characteristics are analyzed and the pressure coefficient contours on the wing lower surface are shown to correlate reasonably well with the available pressure sensitive paint results, particularly, for the complex flow structures around the nacelles. The predicted longitudinal and lateral/directional performance characteristics for the truncated TCA configuration are shown to correlate very well with the corresponding wind-tunnel data across the examined range of angles-of-attack and sideslip. The complementary computational results for the longitudinal and lateral/directional performance characteristics for the complete TCA configuration are also presented along with the aerodynamic effects due to empennage components. Results are also presented to assess the computational method performance, solution sensitivity to grid refinement, and solution convergence characteristics.

Cross-infection risks associated with current procedures for using high-speed dental handpieces.

PubMed Central

Lewis, D L; Boe, R K

1992-01-01

When a dye solution used to simulate patient material was either injected into high-speed dental handpiece (drill) waterlines or applied to the equipment externally, internal air turbine chambers became contaminated. These chambers served as a reservoir of the material, which was slowly dislodged by air expelled during subsequent handpiece operation and which was diluted by water spray used for cooling the drilling surface. Considering the fact that patient materials could reside in internal parts of the equipment that are not usually disinfected and that the material may be subsequently sprayed into cuts and abrasions in the oral cavity, the common approach to reprocessing handpieces (external wiping in combination with flushing) may pose unacceptably high risks to those individuals treated soon after infected patients. Therefore, unless reliable data on cross-infection frequencies are obtained and prove it unnecessary, heat-treating high-speed handpieces between each patient should be considered an essential component of standard procedures whenever universal precautions are practiced in dentistry. PMID:1537909

Analysis of small scale turbulent structures and the effect of spatial scales on gas transfer

NASA Astrophysics Data System (ADS)

Schnieders, Jana; Garbe, Christoph

2014-05-01

The exchange of gases through the air-sea interface strongly depends on environmental conditions such as wind stress and waves which in turn generate near surface turbulence. Near surface turbulence is a main driver of surface divergence which has been shown to cause highly variable transfer rates on relatively small spatial scales. Due to the cool skin of the ocean, heat can be used as a tracer to detect areas of surface convergence and thus gather information about size and intensity of a turbulent process. We use infrared imagery to visualize near surface aqueous turbulence and determine the impact of turbulent scales on exchange rates. Through the high temporal and spatial resolution of these types of measurements spatial scales as well as surface dynamics can be captured. The surface heat pattern is formed by distinct structures on two scales - small-scale short lived structures termed fish scales and larger scale cold streaks that are consistent with the footprints of Langmuir Circulations. There are two key characteristics of the observed surface heat patterns: 1. The surface heat patterns show characteristic features of scales. 2. The structure of these patterns change with increasing wind stress and surface conditions. In [2] turbulent cell sizes have been shown to systematically decrease with increasing wind speed until a saturation at u* = 0.7 cm/s is reached. Results suggest a saturation in the tangential stress. Similar behaviour has been observed by [1] for gas transfer measurements at higher wind speeds. In this contribution a new model to estimate the heat flux is applied which is based on the measured turbulent cell size und surface velocities. This approach allows the direct comparison of the net effect on heat flux of eddies of different sizes and a comparison to gas transfer measurements. Linking transport models with thermographic measurements, transfer velocities can be computed. In this contribution, we will quantify the effect of small scale processes on interfacial transport and relate it to gas transfer. References [1] T. G. Bell, W. De Bruyn, S. D. Miller, B. Ward, K. Christensen, and E. S. Saltzman. Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed. Atmos. Chem. Phys. , 13:11073-11087, 2013. [2] J Schnieders, C. S. Garbe, W.L. Peirson, and C. J. Zappa. Analyzing the footprints of near surface aqueous turbulence - an image processing based approach. Journal of Geophysical Research-Oceans, 2013.

Taphonomic evidence for high-speed adapted fins in thunniform ichthyosaurs.

PubMed

Lingham-Soliar, Theagarten; Plodowski, Gerhard

2007-01-01

Ichthyosaurs have been compared with the fast-swimming thunniform groups of marine vertebrates, tuna, lamnid sharks, and dolphins, based on similarity of shape of the body and locomotory organs. In addition to shape, high-tensile stiffness of the control surfaces has been shown to be essential in maximizing hydrodynamic efficiency in extant thunniform swimmers. To date, there has been no evidence of a stiffening support system for the dorsal fin and dorsal lobe of the caudal fin in ichthyosaurs, the sole stiffening structure of the ventral lobe being an extension of the vertebral column along its leading edge. Stenopterygius SMF 457 is arguably the best soft-tissue preserved ichthyosaur specimen known. Here, we examine soft-tissue preservation in this specimen in the control surfaces and provide the first evidence of a complex architecture of stiff fibers in the dorsal and caudal fins. We find by comparisons and by analogy that these fibers provided a remarkable mechanism for high tensile stiffness and efficiency of the locomotory organs virtually identical to that of the great white shark, Carcharodon carcharias. It is the first mechanostructural study of the control surfaces of a Jurassic ichthyosaur that adds essential evidence in support of the view that these forms were high-speed thunniform swimmers.

Taphonomic evidence for high-speed adapted fins in thunniform ichthyosaurs

NASA Astrophysics Data System (ADS)

Lingham-Soliar, Theagarten; Plodowski, Gerhard

2007-01-01

Ichthyosaurs have been compared with the fast-swimming thunniform groups of marine vertebrates, tuna, lamnid sharks, and dolphins, based on similarity of shape of the body and locomotory organs. In addition to shape, high-tensile stiffness of the control surfaces has been shown to be essential in maximizing hydrodynamic efficiency in extant thunniform swimmers. To date, there has been no evidence of a stiffening support system for the dorsal fin and dorsal lobe of the caudal fin in ichthyosaurs, the sole stiffening structure of the ventral lobe being an extension of the vertebral column along its leading edge. Stenopterygius SMF 457 is arguably the best soft-tissue preserved ichthyosaur specimen known. Here, we examine soft-tissue preservation in this specimen in the control surfaces and provide the first evidence of a complex architecture of stiff fibers in the dorsal and caudal fins. We find by comparisons and by analogy that these fibers provided a remarkable mechanism for high tensile stiffness and efficiency of the locomotory organs virtually identical to that of the great white shark, Carcharodon carcharias. It is the first mechanostructural study of the control surfaces of a Jurassic ichthyosaur that adds essential evidence in support of the view that these forms were high-speed thunniform swimmers.

Slamming pressures on the bottom of a free-falling vertical wedge

NASA Astrophysics Data System (ADS)

Ikeda, C. M.; Judge, C. Q.

2013-11-01

High-speed planing boats are subjected to repeat impacts due to slamming, which can cause structural damage and injury to passengers. A first step in understanding and predicting the physics of a craft re-entering the water after becoming partially airborne is an experimental vertical drop test of a prismastic wedge (deadrise angle, β =20° beam, B = 300 mm; and length, L = 600 mm). The acrylic wedge was mounted to a rig allowing it to free-fall into a deep-water tank (5.2m × 5.2m × 4.2m deep) from heights 0 <= H <= 635 mm, measured from the keel to the free surface. The wedge was instrumented to record vertical position, acceleration, and pressure on the bottom surface. A pressure mapping system, capable of measuring several points over the area of the thin (0.1 mm) film sensor at sampling rates up to 20 kHz, is used and compared to surface-mounted pressure transducers (sampled at 10 kHz). A high speed camera (1000 fps, resolution of 1920 × 1200 pixels) is mounted above the wedge model to record the wetted surface as the wedge descended below the free surface. The pressure measurements taken with both conventional surface pressure transducers and the pressure mapping system agree within 10% of the peak pressure values (0.7 bar, typical). Supported by the Office of Naval Research.

Use of a new high-speed digital data acquisition system in airborne ice-sounding

USGS Publications Warehouse

Wright, David L.; Bradley, Jerry A.; Hodge, Steven M.

1989-01-01

A high-speed digital data acquisition and signal averaging system for borehole, surface, and airborne radio-frequency geophysical measurements was designed and built by the US Geological Survey. The system permits signal averaging at rates high enough to achieve significant signal-to-noise enhancement in profiling, even in airborne applications. The first field use of the system took place in Greenland in 1987 for recording data on a 150 by 150-km grid centered on the summit of the Greenland ice sheet. About 6000-line km were flown and recorded using the new system. The data can be used to aid in siting a proposed scientific corehole through the ice sheet.

Exponential increase in the on-off ratio of conductance in organic memory devices by controlling the surface morphology of the devices

NASA Astrophysics Data System (ADS)

Vyas, Giriraj; Dagar, Parveen; Sahu, Satyajit

2018-05-01

We have shown an exponential increase in the ratio of conductance in the on and off states of switching devices by controlling the surface morphology of the thin films for the device by depositing at different rotational speeds. The pinholes which are preferred topography on the surface at higher rotational speed give rise to higher on-off ratio of current from the devices fabricated at the speed. The lower rotational speed contributes to higher thickness of the film and hence no switching. For thicker films, the domain is formed due to phase segregation between the two components in the film, which also indicates that the film is far from thermal equilibrium. At higher speed, there is very little scope of segregation when the film is drying up. Hence, there are only few pinholes on the surface of the film which are shallow. So, the filamentary mechanism of switching in memory devices can be firmly established by varying the speed of thin film deposition which leads to phase segregation of the materials. Thus, the formation of filament can be regulated by controlling the thickness and the surface morphology.

Background Oriented Schlieren Implementation in a Jet-Surface Interaction Test

NASA Technical Reports Server (NTRS)

Clem, Michelle M.; Brown, Clifford A.; Fagan, Amy

2013-01-01

Many current and future aircraft designs rely on the wing or other aircraft surfaces to shield the engine noise from observers on the ground. However the available data regarding how a planar surface interacts with a jet to shield and/or enhance the jet noise are currently limited. Therefore, the Jet-Surface Interaction Tests supported by NASA's Fundamental Aeronautics Program's Fixed Wing Project were undertaken to supply experimental data covering a wide range of surface geometries and positions interacting with high-speed jet flows in order to support the development of noise prediction methods. Phase 1 of the Test was conducted in the Aero-Acoustic Propulsion Laboratory at NASA Glenn Research Center and consisted of validating noise prediction schemes for a round nozzle interacting with a planar surface. Phased array data and far-field acoustic data were collected for both the shielded and reflected sides of the surface. Phase 1 results showed that the broadband shock noise was greatly reduced by the surface when the jet was operated at the over-expanded condition, however, it was unclear whether this reduction was due a change in the shock cell structure by the surface. In the present study, Background Oriented Schlieren is implemented in Phase 2 of the Jet-Surface Interaction Tests to investigate whether the planar surface interacts with the high-speed jet ow to change the shock cell structure. Background Oriented Schlieren data are acquired for under-expanded, ideally-expanded, and over-expanded ow regimes for multiple axial and radial positions of the surface at three different plate lengths. These data are analyzed with far-field noise measurements to relate the shock cell structure to the broadband shock noise produced by a jet near a surface.

Drag reduction using metallic engineered surfaces with highly ordered hierarchical topographies: nanostructures on micro-riblets

NASA Astrophysics Data System (ADS)

Kim, Taekyung; Shin, Ryung; Jung, Myungki; Lee, Jinhyung; Park, Changsu; Kang, Shinill

2016-03-01

Durable drag-reduction surfaces have recently received much attention, due to energy-saving and power-consumption issues associated with harsh environment applications, such as those experienced by piping infrastructure, ships, aviation, underwater vehicles, and high-speed ground vehicles. In this study, a durable, metallic surface with highly ordered hierarchical structures was used to enhance drag-reduction properties, by combining two passive drag-reduction strategies: an air-layer effect induced by nanostructures and secondary vortex generation by micro-riblet structures. The nanostructures and micro-riblet structures were designed to increase slip length. The top-down fabrication method used to form the metallic hierarchical structures combined laser interference lithography, photolithography, thermal reflow, nanoimprinting, and pulse-reverse-current electrochemical deposition. The surfaces were formed from nickel, which has high hardness and corrosion resistance, making it suitable for use in harsh environments. The drag-reduction properties of various metal surfaces were investigated based on the surface structure: a bare surface, a nanostructured surface, a micro-riblet surface, and a hierarchically structured surface of nanostructures on micro-riblets.

Dynamic Torsional and Cyclic Fracture Behavior of ProFile Rotary Instruments at Continuous or Reciprocating Rotation as Visualized with High-speed Digital Video Imaging.

PubMed

Tokita, Daisuke; Ebihara, Arata; Miyara, Kana; Okiji, Takashi

2017-08-01

This study examined the dynamic fracture behavior of nickel-titanium rotary instruments in torsional or cyclic loading at continuous or reciprocating rotation by means of high-speed digital video imaging. The ProFile instruments (size 30, 0.06 taper; Dentsply Maillefer, Ballaigues, Switzerland) were categorized into 4 groups (n = 7 in each group) as follows: torsional/continuous (TC), torsional/reciprocating (TR), cyclic/continuous (CC), and cyclic/reciprocating (CR). Torsional loading was performed by rotating the instruments by holding the tip with a vise. For cyclic loading, a custom-made device with a 38° curvature was used. Dynamic fracture behavior was observed with a high-speed camera. The time to fracture was recorded, and the fractured surface was examined with scanning electron microscopy. The TC group initially exhibited necking of the file followed by the development of an initial crack line. The TR group demonstrated opening and closing of a crack according to its rotation in the cutting and noncutting directions, respectively. The CC group separated without any detectable signs of deformation. In the CR group, initial crack formation was recognized in 5 of 7 samples. The reciprocating rotation exhibited a longer time to fracture in both torsional and cyclic fatigue testing (P < .05). The scanning electron microscopic images showed a severely deformed surface in the TR group. The dynamic fracture behavior of NiTi rotary instruments, as visualized with high-speed digital video imaging, varied between the different modes of rotation and different fatigue testing. Reciprocating rotation induced a slower crack propagation and conferred higher fatigue resistance than continuous rotation in both torsional and cyclic loads. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

The effectiveness of detection of splashed particles using a system of three integrated high-speed cameras

NASA Astrophysics Data System (ADS)

Ryżak, Magdalena; Beczek, Michał; Mazur, Rafał; Sochan, Agata; Bieganowski, Andrzej

2017-04-01

The phenomenon of splash, which is one of the factors causing erosion of the soil surface, is the subject of research of various scientific teams. One of efficient methods of observation and analysis of this phenomenon are high-speed cameras to measure particles at 2000 frames per second or higher. Analysis of the phenomenon of splash with the use of high-speed cameras and specialized software can reveal, among other things, the number of broken particles, their speeds, trajectories, and the distances over which they were transferred. The paper presents an attempt at evaluation of the efficiency of detection of splashed particles with the use of a set of 3 cameras (Vision Research MIRO 310) and software Dantec Dynamics Studio, using a 3D module (Volumetric PTV). In order to assess the effectiveness of estimating the number of particles, the experiment was performed on glass beads with a diameter of 0.5 mm (corresponding to the sand fraction). Water droplets with a diameter of 4.2 mm fell on a sample from a height of 1.5 m. Two types of splashed particles were observed: particle having a low range (up to 18 mm) splashed at larger angles and particles of a high range (up to 118 mm) splashed at smaller angles. The detection efficiency the number of splashed particles estimated by the software was 45 - 65% for particles with a large range. The effectiveness of the detection of particles by the software has been calculated on the basis of comparison with the number of beads that fell on the adhesive surface around the sample. This work was partly financed from the National Science Centre, Poland; project no. 2014/14/E/ST10/00851.

Scanned-wavelength diode laser sensors for harsh environments

NASA Astrophysics Data System (ADS)

Jeffries, Jay B.; Sanders, Scott T.; Zhou, Xin; Ma, Lin; Mattison, Daniel W.; Hanson, Ronald K.

2002-09-01

Diode laser absorption offers the possibility of high-speed, robust, and rugged sensors for a wide variety of practical applications. Pressure broadening complicates absorption measurements of gas temperature and species concentrations in high-pressure, high-temperature practical environments. More agile wavelength scanning can enable measurements of temperature and species concentrations in flames and engines as demonstrated by example measurements using wavelength scanning of a single DFB in laboratory flames or a vertical cavity surface emitting laser (VCSEL) in a pulse detonation engine environment. Although the blending of multiple transitions by pressure broadening complicates the atmospheric pressure spectrum of C2H4 fuel, a scanned wavelength strategy enables quantitative measurement of fuel/oxidizer stoichiometry. Wavelength-agile scanning techniques enable high-speed measurements in these harsh environments.

Impacts of Future Climate Change on Ukraine Transportation System

NASA Astrophysics Data System (ADS)

Khomenko, Inna

2016-04-01

Transportation not only affects climate, but are strongly influenced with the climate conditions, and key hubs of the transportation sector are cities. Transportation decision makers have an opportunity now to prepare for projected climate changes owing to development of emission scenarios. In the study impact of climate change on operation of road transport along highways are analyzed on the basis of RCP 4.5 and RCP 8.5 scenarios. Data contains series of daily mean and maximum temperature, daily liquid (or mixed) and solid precipitation, daily mean relative humidity and daily mean and maximum wind speed, obtained for the period of 2011 to 2050 for 8 cities (Dnipropetrovsk, Khmelnytskyi, Kirovohrad, Kharkiv, Odesa, Ternopil, Vinnytsia and Voznesensk) situated down the highways. The highways of 'Odesa-Voznesensk-Dnipropetrovsk-Kharkiv' and 'Dnipropetrovsk-Kirovohrad-Vinnytsia-Khmelnytskyi-Ternopil' are considered. The first highway goes across the Black Sea Lowland, the Dnieper Upland and Dnieper Lowland, the other passes through the Dnieper and Volhynia-Podillia Uplands. The both highways are situated in steppe and forest-steppe native zones. For both scenarios, significant climate warming is registered; it is revealed in significant increase of average monthly and yearly temperature by 2-3°C in all cities in questions, and also, in considerable increment of frequency of days with maximum temperature higher than +30 and 35°C, except Kharkiv, where decrease number of days with such temperatures is observed. On the contrary, number of days with daily mean temperature being equal to or below 0°C decreases in the south of steppe, is constant in the north of steppe and increases in the forest-steppe native zone. Extreme negative temperatures don't occur in the steppe zone, but takes place in the forest-steppe zone. Results obtained shows that road surface must hold in extreme maximum temperature, and in the forest-steppe zone hazards of extreme negative temperatures must be considered. Frequency of winter events that make road surface worse such as glaze-clear ice, frozen snow that had initially melted on a warm road surface, ice and snow slippery coats etc., are high enough, especially in the forest-steppe zone. In the Black Sea Lowland among winter events the frozen snow that had initially melted on a warm road surface is most commonly observed, that is connected with high occurrence of the thaws. Because of increase in frequency of shower precipitation in all cities wet road surface is observed most frequently, especially in May and June; it must be taken into account for construction of roads, too. Monthly mean wind speed shows that in Odesa and Kharkiv significant increase in average monthly and yearly wind speeds are observed, by 0,5-1 m/s in comparison with the period of 1961 to 1990. On the contrary, in Dnipropetrovsk, wind speed decreases by 0,7 m/s. Frequency distribution of maximum wind speed shows that high wind speeds are more frequent in the winter months.

City transport of the future - the high speed pedestrian conveyor. Part 1: ergonomic considerations of accelerators, decelerators and transfer sections.

PubMed

Browning, A C

1974-12-01

In this article, an uncommon form of passenger transport is considered, the moving pavement or pedestrian conveyor running at speeds of up to 16 km/h. There are very little relevant ergonomic data for such devices and some specific laboratory experiments have been carried out using 1000 subjects to represent the general public. It is concluded that whilst high speed pedestrian conveyors are quite feasible, stations along them are likely to be large. The most attractive type is a set of parallel surfaces moving at different speeds and with handholds provided in the form of poles. This type could be extremely convenient for certain locations but will probably have to be restricted in its use to fairly fit adults carrying little luggage, and would find applications in situations where a large number of people need to travel in the same direction. Part 2, Ergonomic considerations of complete conveyor systems, will follow.

Large Amplitude IMF Fluctuations in Corotating Interaction Regions: Ulysses at Midlatitudes

NASA Technical Reports Server (NTRS)

Tsurutani, Bruce T.; Ho, Christian M.; Arballo, John K.; Goldstein, Bruce E.; Balogh, Andre

1995-01-01

Corotating Interaction Regions (CIRs), formed by high-speed corotating streams interacting with slow speed streams, have been examined from -20 deg to -36 deg heliolatitudes. The high-speed streams emanate from a polar coronal hole that Ulysses eventually becomes fully embedded in as it travels towards the south pole. We find that the trailing portion of the CIR, from the interface surface (IF) to the reverse shock (RS), contains both large amplitude transverse fluctuations and magnitude fluctuations. Similar fluctuations have been previously noted to exist within CIRs detected in the ecliptic plane, but their existence has not been explained. The normalized magnetic field component variances within this portion of the CIR and in the trailing high-speed stream are approximately the same, indicating that the fluctuations in the CIR are compressed Alfven waves. Mirror mode structures with lower intensities are also observed in the trailing portion of the CIR, presumably generated from a local instability driven by free energy associated with compression of the high-speed solar wind plasma. The mixture of these two modes (compressed Alfven waves and mirror modes) plus other modes generated by three wave processes (wave-shock interactions) lead to a lower Alfvenicity within the trailing portion of the CfR than in the high-speed stream proper. The results presented in this paper suggest a mechanism for generation of large amplitude B(sub z) fluctuations within CIRS. Such phenomena have been noted to be responsible for the generation of moderate geomagnetic storms during the declining phase of the solar cycle.

High-speed micro-droplet impact on a super-heated surface

NASA Astrophysics Data System (ADS)

Fujita, Yuta; Tran, Tuan; Tagawa, Yoshiyuki; Xie, Yanbo; Sun, Chao; Lohse, Detlef

2017-11-01

In this study, we experimentally show that the condition for micro-droplets to splash depends on the temperature of the surface on which the droplets impact. We vary droplet diameter (30 120 μm) and surface temperature (20 500°C). For an impacting droplet, splashing becomes possible for high surface temperature T > 160°C and Weber number We > 100. In contrast, at low surface temperature T < 140°C, no splash was observed up to the maximum Weber number in our experiments, i.e. We 7,000. Our results show that the criteria for splashing of micro-droplets may be different from those of milli-sized droplets, in particular when the impacted surface is heated. This work was supported by JSPS KAKENHI Grant Number 16K14166.

Continuous cryopump with a device for regenerating the cryosurface

DOEpatents

Foster, Christopher A.

1988-01-01

A high throughput continuous cryopump is provided. The cryopump (10) incorporates an improved method for regenerating the cryopumping surface (22) while the pump is in continuous operation. The regeneration of the cryopumping surface (22) does not thermally cycle the pump, and to this end a small chamber (91) connected to a secondary pumping source (60) serves to contain and exhaust frost removed from the cryopumping surface (22) during such regeneration. The frost is exhausted at a rate substantially independent of the speed of the cryopump which enhances the capability of the pump to achieve a high compression ratio and allow the pump to operate continuously while the cryopumping surface is being regenerated.

Comparison of two ways of altering carpal tunnel pressure with ultrasound surface wave elastography.

PubMed

Cheng, Yu-Shiuan; Zhou, Boran; Kubo, Kazutoshi; An, Kai-Nan; Moran, Steven L; Amadio, Peter C; Zhang, Xiaoming; Zhao, Chunfeng

2018-06-06

Higher carpal tunnel pressure is related to the development of carpal tunnel syndrome. Currently, the measurement of carpal tunnel pressure is invasive and therefore, a noninvasive technique is needed. We previously demonstrated that speed of wave propagation through a tendon in the carpal tunnel measured by ultrasound elastography could be used as an indicator of carpal tunnel pressure in a cadaveric model, in which a balloon had to be inserted into the carpal tunnel to adjust the carpal tunnel pressure. However, the method for adjusting the carpal tunnel pressure in the cadaveric model is not applicable for the in vivo model. The objective of this study was to utilize a different technique to adjust carpal tunnel pressure via pressing the palm and to validate it with ultrasound surface wave elastography in a human cadaveric model. The outcome was also compared with a previous balloon insertion technique. Results showed that wave speed of intra-carpal tunnel tendon and the ratio of wave speed of intra-and outer-carpal tunnel tendons increased linearly with carpal tunnel pressure. Moreover, wave speed of intra carpal tunnel tendon via both ways of altering carpal tunnel pressure showed similar results with high correlation. Therefore, it was concluded that the technique of pressing the palm can be used to adjust carpal tunnel pressure, and pressure changes can be detected via ultrasound surface wave elastography in an ex vivo model. Future studies will utilize this technique in vivo to validate the usefulness of ultrasound surface wave elastography for measuring carpal tunnel pressure. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of Riblets on Skin Friction in High-Speed Turbulent Boundary Layers

NASA Technical Reports Server (NTRS)

Duan, Lian; Choudhari, Meelan M.

2012-01-01

Direct numerical simulations of spatially developing turbulent boundary layers over riblets are conducted to examine the effects of riblets on skin friction at supersonic speeds. Zero-pressure gradient boundary layers with an adiabatic wall, a Mach number of M1 = 2.5, and a Reynolds number based on momentum thickness of Re = 1720 are considered. Simulations are conducted for boundary-layer flows over a clean surface and symmetric V- groove riblets with nominal spacings of 20 and 40 wall units. The DNS results confirm the few existing experimental observations and show that a drag reduction of approximately 7% is achieved for riblets with proper spacing. The influence of riblets on turbulence statistics is analyzed in detail with an emphasis on identifying the differences, if any, between the drag reduction mechanisms for incompressible and high-speed boundary layers.

High-throughput controllable generation of droplet arrays with low consumption

NASA Astrophysics Data System (ADS)

Lin, Yinyin; Wu, Zhongsheng; Gao, Yibo; Wu, Jinbo; Wen, Weijia

2018-06-01

We describe a controllable sliding method for fabricating millions of isolated femto- to nanoliter-sized droplets with defined volume, geometry and position and a speed of up to 375 kHz. In this work, without using a superhydrophobic or superoleophobic surface, arrays of droplets are instantly formed on the patterned substrate by sliding a strip of liquid, including water, low-surface-tension organic solvents and solution, along the substrate. To precisely control the volume of the droplets, we systemically investigate the effects of the size of the wettable pattern, the viscosity of the liquid and sliding speed, which were found to vary independently to tune the height and volume of the droplets. Through this method, we successfully fabricated an oriented single metal-organic framework crystal array with control over their XY positioning on the surface, as characterized by microscopy and X-ray diffraction (XRD) techniques.

Morphology of supercooled droplets freezing on solid surfaces

NASA Astrophysics Data System (ADS)

La, Shiren; Huang, Zhiting; Liu, Cong; Zhang, Xingyi

2018-05-01

Supercooled droplets freezing on solid surfaces are ubiquitous in nature. This letter investigates the influences of droplet viscosity on freezing velocity and frosting formation. Several experiments were conducted for three kinds of sessile droplets (water, silicone oil and oil) on two types of substrates (copper and iron) with different surface roughness at various temperatures. The results show that the water droplets exhibit obvious phase transition lines and their freezing speeds increase when the temperature of substrates decreases. It is found that the freezing speed is independent of the thermal conductivities of the substrates. Notably, the water droplets develop prominent bulges after freezing and subsequently nucleate to frost. In contrast, the high viscosity oil and silicone oil do not manifest an obvious phase transition line. Besides, no bulges are observed in these two kinds of droplets, suggesting that these frosting forms are of different mechanisms compared with water droplets.

Freezing Behavior of a Supercooled Water Droplet Impacting on Surface Using Dual-Luminescent Imaging Technique

NASA Astrophysics Data System (ADS)

Tanaka, Mio; Morita, Katsuaki; Yamamoto, Makoto; Sakaue, Hirotaka

2015-11-01

A collision of a supercooled-water droplet on an object creates ice accretion on its surface. These icing problems can be seen in any cold environments and may lead to severe damages on aircrafts, ships, power cables, trees, road signs, and architectures. To solve these problems, various studies on ice-prevention and ice-prediction techniques have been conducted. It is very important to know the detail freezing mechanism of supercooled water droplets to propose or improve those techniques. The icing mechanism of a single supercooled-water droplet impacting on object surface would give us great insights for constructing those techniques. In the present study, we use a dual-luminescent imaging technique to measure the time-resolved temperatures of a supercooled water droplet impacting with different speed. The technique we applied consists of high-speed color camera and two luminescent probes. We will report the current status of this experiment in the presentation.

Long-Wavelength Beam Steerer Based on a Micro-Electromechanical Mirror

PubMed Central

Kos, Anthony B; Gerecht, Eyal

2013-01-01

Commercially available mirrors for scanning long-wavelength beams are too large for high-speed imaging. There is a need for a smaller, more agile pointing apparatus to provide images in seconds, not minutes or hours. A fast long-wavelength beam steerer uses a commercial micro-electro-mechanical system (MEMS) mirror controlled by a high-performance digital signal processor (DSP). The DSP allows high-speed raster scanning of the incident radiation, which is focused to a small waist onto the 9mm2, gold-coated, MEMS mirror surface, while simultaneously acquiring an undistorted, high spatial-resolution image of an object. The beam steerer hardware, software and performance are described. The system can also serve as a miniaturized, high-performance long-wavelength beam chopper for lock-in detection. PMID:26401426

Effect of wing-tip dihedral on the longitudinal and lateral aerodynamic characteristics of a supersonic cruise configuration at subsonic speeds

NASA Technical Reports Server (NTRS)

Washburn, K. E.; Gloss, B. B.

1976-01-01

Force and moment data studies were conducted to determine the effect of wing-tip dihedral on the longitudinal and lateral aerodynamic characteristics of a supersonic cruise fighter configuration. Oil flow studies were also performed to investigate the model surface flow. Three models were tested: a flat (0 deg dihedral) wing tip, a dihedral, and an anhedral wing tip. The tests were conducted at the NASA Langley high-speed 7- by 10-foot wind tunnel.

Investigation of advanced thrust vectoring exhaust systems for high speed propulsive lift

NASA Technical Reports Server (NTRS)

Hutchison, R. A.; Petit, J. E.; Capone, F. J.; Whittaker, R. W.

1980-01-01

The paper presents the results of a wind tunnel investigation conducted at the NASA-Langley research center to determine thrust vectoring/induced lift characteristics of advanced exhaust nozzle concepts installed on a supersonic tactical airplane model. Specific test objectives include: (1) basic aerodynamics of a wing body configuration, (2) investigation of induced lift effects, (3) evaluation of static and forward speed performance, and (4) the effectiveness of a canard surface to trim thrust vectoring/induced lift forces and moments.

Surface waves on the tailward flanks of the Earth's magnetopause

NASA Technical Reports Server (NTRS)

Seon, J.; Frank, L. A.; Lazarus, A. J.; Lepping, R. P.

1995-01-01

Forty-three examples of ISEE 1 tailward flank side magnetopause crossings are examined and directly compared with upstream solar wind parameters. The crossings are classified into two groups. In the first group, a few sudden magnetopause crossings are observed, whereas repeated magnetopause crossings and oscillatory motions, often with boundary layer signatures, are observed in the second group. These distinctive characteristics of the two groups are interpreted in terms of the surface waves due to the Kelvin-Helmholtz instability. It is found that low solar wind speed tends to favor characteristics of the first group, whereas high solar wind speed yields those of the second group. However, no evident correlations between the groups and the interplanetary magnetic field directions are found.

Industrial applications of high-average power high-peak power nanosecond pulse duration Nd:YAG lasers

NASA Astrophysics Data System (ADS)

Harrison, Paul M.; Ellwi, Samir

2009-02-01

Within the vast range of laser materials processing applications, every type of successful commercial laser has been driven by a major industrial process. For high average power, high peak power, nanosecond pulse duration Nd:YAG DPSS lasers, the enabling process is high speed surface engineering. This includes applications such as thin film patterning and selective coating removal in markets such as the flat panel displays (FPD), solar and automotive industries. Applications such as these tend to require working spots that have uniform intensity distribution using specific shapes and dimensions, so a range of innovative beam delivery systems have been developed that convert the gaussian beam shape produced by the laser into a range of rectangular and/or shaped spots, as required by demands of each project. In this paper the authors will discuss the key parameters of this type of laser and examine why they are important for high speed surface engineering projects, and how they affect the underlying laser-material interaction and the removal mechanism. Several case studies will be considered in the FPD and solar markets, exploring the close link between the application, the key laser characteristics and the beam delivery system that link these together.

Use of the Azimuth Wavelength Cut-Off to Retrieve the Sea Surface Wind Speed from Sentinel 1 and COSMO-SkyMed SAR Data

NASA Astrophysics Data System (ADS)

Grieco, G.; Nirchio, F.; Montuori, A.; Migliaccio, M.; Lin, W.; Portabella, M.

2016-08-01

The dependency of the azimuth wavelength cut-off on the wind speed has been studied through a dataset of Sentinel-1 multi look SAR images co-located with wind speed measurements, significant wave height and mean wave direction from ECMWF operational output.A Geophysical Model Function (GMF) has been fitted and a retrieval exercise has been done comparing the results to a set of independent wind speed scatterometer measurements of the Chinese mission HY-2A. The preliminary results show that the dependency of the azimuth cut-off on the wind speed is linear only for fully developed sea states and that the agreement between the retrieved values and the measurements is good especially for high wind speed.A similar approach has been used to assess the dependency of the azimuth cut-off also for X-band COSMO-SkyMed data. The dataset is still incomplete but the preliminary results show a similar trend.

Highly Transparent Water-Repelling Surfaces based on Biomimetic Hierarchical Structure

NASA Astrophysics Data System (ADS)

Wooh, Sanghyuk; Koh, Jai; Yoon, Hyunsik; Char, Kookheon

2013-03-01

Nature is a great source of inspiration for creating unique structures with special functions. The representative examples of water-repelling surfaces in nature, such as lotus leaves, rose petals, and insect wings, consist of an array of bumps (or long hairs) and nanoscale surface features with different dimension scales. Herein, we introduced a method of realizing multi-dimensional hierarchical structures and water-repellancy of the surfaces with different drop impact scenarios. The multi-dimensional hierarchical structures were fabricated by soft imprinting method with TiO2 nanoparticle pastes. In order to achieve the enhanced hydrophobicity, fluorinated moieties were attached to the etched surfaces to lower the surface energy. As a result, super-hydrophobic surfaces with high transparency were realized (over 176° water contact angle), and for further investigation, these hierarchical surfaces with different drop impact scenarios were characterized by varying the impact speed, drop size, and the geometry of the surfaces.

Overview of High Speed Close-Up Imaging in an Icing Environment

NASA Technical Reports Server (NTRS)

Miller, Dean R.; Lynch, Christopher J.; Tate, Peter A.

2004-01-01

The Icing Branch and Imaging Technology Center at NASA Glenn Research Center have recently been involved in several projects where high speed close-up imaging was used to investigate water droplet impact/splash, and also ice particle impact/bounce in an icing wind tunnel. The combination of close-up and high speed imaging capabilities were required because the particles being studied were relatively small (d < 1 mm in diameter), and the impact process occurred in a very short time period (t(sub impact) << 1 sec). High speed close-up imaging was utilized to study the dynamics of droplet impact and splash in simulated Supercooled Large Droplet (SLD) icing conditions. The objective of this test was to evaluate the capability of a ultra high speed camera system to acquire quantitative information about the impact process (e.g., droplet size, velocity). Imaging data were obtained in an icing wind tunnel for spray cloud MVD > 50 m. High speed close-up imaging was also utilized to characterize the impact of ice particles on an airfoil with a thermally protected leading edge. The objective of this investigation was to determine whether ice particles tend to "stick" or "bounce" after impact. Imaging data were obtained for cases where the airfoil surface was heated and unheated. Based on the results from this test, follow on tests were conducted to investigate ice particle impact on the sensing elements of water content measurement devices. This paper will describe the use of the imaging systems to support these experimental investigations, present some representative results, and summarize what was learned about the use of these systems in an icing environment.

Jumping without slipping: leafhoppers (Hemiptera: Cicadellidae) possess special tarsal structures for jumping from smooth surfaces.

PubMed

Clemente, Christofer J; Goetzke, Hanns Hagen; Bullock, James M R; Sutton, Gregory P; Burrows, Malcolm; Federle, Walter

2017-05-01

Many hemipteran bugs can jump explosively from plant substrates, which can be very smooth. We therefore analysed the jumping performance of froghoppers ( Philaenus spumarius, Aphrophoridae) and leafhoppers ( Aphrodes bicinctus/makarovi, Cicadellidae) taking off from smooth (glass) and rough (sandpaper, 30 µm asperity size) surfaces. On glass, the propulsive hind legs of Philaenus froghoppers slipped, resulting in uncontrolled jumps with a fast forward spin, a steeper angle and only a quarter of the velocity compared with jumps from rough surfaces. By contrast, Aphrodes leafhoppers took off without their propulsive hind legs slipping, and reached low take-off angles and high velocities on both substrates. This difference in jumping ability from smooth surfaces can be explained not only by the lower acceleration of the long-legged leafhoppers, but also by the presence of 2-9 soft pad-like structures (platellae) on their hind tarsi, which are absent in froghoppers. High-speed videos of jumping showed that platellae contact the surface briefly (approx. 3 ms) during the acceleration phase. Friction force measurements on individual hind tarsi on glass revealed that at low sliding speeds, both pushing and pulling forces were small, and insufficient to explain the recorded jumps. Only when the tarsi were pushed with higher velocities did the contact area of the platellae increase markedly, and high friction forces were produced, consistent with the observed jumps. Our findings show that leafhoppers have special adhesive footpads for jumping from smooth surfaces, which achieve firm grip and rapid control of attachment/detachment by combining anisotropic friction with velocity dependence. © 2017 The Authors.

Atmospheric structure favoring high sea surface temperatures in the western equatorial Pacific

NASA Astrophysics Data System (ADS)

Wirasatriya, Anindya; Kawamura, Hiroshi; Shimada, Teruhisa; Hosoda, Kohtaro

2016-10-01

We investigated the atmospheric processes over high sea surface temperature called Hot Event (HE) in the western equatorial Pacific from climatological analysis and a case study of the HE which began on 28 May 2003 (hereafter, HE030528). Climatological analysis shows that during the development stage of HE, solar radiation inside the HE area is higher than its climatology and wind speed is lower than the decay stage. During the decay stage, strong westerly wind often occurs inside HE area. The case study of HE030528 shows that the suppressed convection above high SST area resulted from the deep convection from the northern and southern areas outside HE. The suppressed convection created a band-shaped structure of low cloud cover along HE area increasing solar radiation during the development stage. Thus, the theory of "remote convection" was supported for the HE030528 formation mechanisms. The large sea level pressure gradient magnitude between the southern side of the terrain gap and the northern coast of the Solomon Islands, through which strong wind blew, indicated the role of land topography for the increase of wind speed during the decay of HE030528. Moreover, surface wind had an important role to influence the variability of solar radiation during the occurrence of HE030528 by controlling the water vapor supply in the upper troposphere through surface evaporation and surface convergence variation. Thus, surface wind was the key factor for HE030528 occurrence. The representativeness of HE030528 and the possible relation between HE and Madden-Julian Oscillation are also discussed.

Jumping without slipping: leafhoppers (Hemiptera: Cicadellidae) possess special tarsal structures for jumping from smooth surfaces

PubMed Central

Bullock, James M. R.

2017-01-01

Many hemipteran bugs can jump explosively from plant substrates, which can be very smooth. We therefore analysed the jumping performance of froghoppers (Philaenus spumarius, Aphrophoridae) and leafhoppers (Aphrodes bicinctus/makarovi, Cicadellidae) taking off from smooth (glass) and rough (sandpaper, 30 µm asperity size) surfaces. On glass, the propulsive hind legs of Philaenus froghoppers slipped, resulting in uncontrolled jumps with a fast forward spin, a steeper angle and only a quarter of the velocity compared with jumps from rough surfaces. By contrast, Aphrodes leafhoppers took off without their propulsive hind legs slipping, and reached low take-off angles and high velocities on both substrates. This difference in jumping ability from smooth surfaces can be explained not only by the lower acceleration of the long-legged leafhoppers, but also by the presence of 2–9 soft pad-like structures (platellae) on their hind tarsi, which are absent in froghoppers. High-speed videos of jumping showed that platellae contact the surface briefly (approx. 3 ms) during the acceleration phase. Friction force measurements on individual hind tarsi on glass revealed that at low sliding speeds, both pushing and pulling forces were small, and insufficient to explain the recorded jumps. Only when the tarsi were pushed with higher velocities did the contact area of the platellae increase markedly, and high friction forces were produced, consistent with the observed jumps. Our findings show that leafhoppers have special adhesive footpads for jumping from smooth surfaces, which achieve firm grip and rapid control of attachment/detachment by combining anisotropic friction with velocity dependence. PMID:28468924