Three-dimensional numerical simulation of water droplet emerging from a gas diffusion layer surface in micro-channels

NASA Astrophysics Data System (ADS)

Ding, Y.; Bi, H. T.; Wilkinson, D. P.

The dynamic formation of water droplets emerging from a gas diffusion layer (GDL) surface in micro-channels was simulated using the volume of fluid (VOF) method. The influence of GDL surface microstructure was investigated by changing the pore diameter and the number of pore openings on the GDL surface. Simulation results show that the microstructure of the GDL surface has a significant impact on the two-phase flow patterns in gas flow channels. For a non-uniform GDL surface, three stages were identified, namely emergence and merging on the GDL surface, accumulation on the channel sidewalls and detachment from the top wall. It was also found that if the pore size is small enough, the flow pattern in the channel does not change with further reduction in the pore diameter. However, the two-phase flow patterns change significantly with the wettability of the GDL surface and sidewalls, but remain the same when the liquid flow rate is reduced by two orders of magnitude from the reference case.

Fragment size distribution in viscous bag breakup of a drop

NASA Astrophysics Data System (ADS)

Kulkarni, Varun; Bulusu, Kartik V.; Plesniak, Michael W.; Sojka, Paul E.

2015-11-01

In this study we examine the drop size distribution resulting from the fragmentation of a single drop in the presence of a continuous air jet. Specifically, we study the effect of Weber number, We, and Ohnesorge number, Oh on the disintegration process. The regime of breakup considered is observed between 12 <= We <= 16 for Oh <= 0.1. Experiments are conducted using phase Doppler anemometry. Both the number and volume fragment size probability distributions are plotted. The volume probability distribution revealed a bi-modal behavior with two distinct peaks: one corresponding to the rim fragments and the other to the bag fragments. This behavior was suppressed in the number probability distribution. Additionally, we employ an in-house particle detection code to isolate the rim fragment size distribution from the total probability distributions. Our experiments showed that the bag fragments are smaller in diameter and larger in number, while the rim fragments are larger in diameter and smaller in number. Furthermore, with increasing We for a given Ohwe observe a large number of small-diameter drops and small number of large-diameter drops. On the other hand, with increasing Oh for a fixed We the opposite is seen.

Method for applying pyrolytic carbon coatings to small particles

DOEpatents

Beatty, Ronald L.; Kiplinger, Dale V.; Chilcoat, Bill R.

1977-01-01

A method for coating small diameter, low density particles with pyrolytic carbon is provided by fluidizing a bed of particles wherein at least 50 per cent of the particles have a density and diameter of at least two times the remainder of the particles and thereafter recovering the small diameter and coated particles.

Effect of Stepwise Pressure Change on Porosity Evolution during Directional Solidification in Small Cylindrical Channels

NASA Technical Reports Server (NTRS)

Grugel, R.N.; Lee, C.P.; Cox, M.C.; Blandford, B.T.; Anilkumar, A.V.

2008-01-01

Controlled directional solidification experiments were performed in capillary channels, using nitrogen-saturated succinonitrile, to examine the effect of an in-situ stepwise processing pressure increase on an isolated pore evolution. Two experiments were performed using different processing pressure input profiles. The results indicate that a processing pressure increase has a transient effect on pore growth geometry characterized by an initial phase of decreasing pore diameter, followed by a recovery phase of increasing pore diameter. The experimental results also show that processing pressure can be used as a control parameter to either increase or terminate porosity formation. A theoretical model is introduced which indicates that the pore formation process is limited by the diffusion of solute-gas through the melt, and that the observed response toa pressure increase is attributed to the re-equilibration of solute concentration in the melt associated with the increased melt pressure.

Fabrication of aluminum-carbon composites

NASA Technical Reports Server (NTRS)

Novak, R. C.

1973-01-01

A screening, optimization, and evaluation program is reported of unidirectional carbon-aluminum composites. During the screening phase both large diameter monofilament and small diameter multifilament reinforcements were utilized to determine optimum precursor tape making and consolidation techniques. Difficulty was encountered in impregnating and consolidating the multifiber reinforcements. Large diameter monofilament reinforcement was found easier to fabricate into composites and was selected to carry into the optimization phase in which the hot pressing parameters were refined and the size of the fabricated panels was scaled up. After process optimization the mechanical properties of the carbon-aluminum composites were characterized in tension, stress-rupture and creep, mechanical fatigue, thermal fatigue, thermal aging, thermal expansion, and impact.

Agreement between experimental and theoretical effects of nitrogen gas flowrate on liquid jet atomization

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1987-01-01

Two-phase flows were investigated by using high velocity nitrogen gas streams to atomize small-diameter liquid jets. Tests were conducted primarily in the acceleration-wave regime for liquid jet atomization, where it was found that the loss of droplets due to vaporization had a marked effect on drop size measurements. In addition, four identically designed two-fluid atomizers were fabricated and tested for similarity of spray profiles. A scattered-light scanner was used to measure a characteristic drop diameter, which was correlated with nitrogen gas flowrate. The exponent of 1.33 for nitrogen gas flowrate is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime. This is higher than the value of 1.2 which was previously obtained at a sampling distance of 4.4 cm downstream of the atomizer. The difference is attributed to the fact that drop-size measurements obtained at a 2.2 cm sampling distance are less effected by vaporization and dispersion of small droplets and therefore should give better agreement with atomization theory. Profiles of characteristic drop diameters were also obtained by making at least five line-of-sight measurements across the spray at several horizontal positions above and below the center line of the spray.

Agreement between experimental and theoretical effects of nitrogen gas flowrate on liquid jet atomization

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1987-01-01

Two-phase flows were investigated by using high velocity nitrogen gas streams to atomize small-diameter liquid jets. Tests were conducted primarily in the acceleration-wave regime for liquid jet atomization, where it was found that the loss of droplets due to vaporization had a marked effect on drop-size measurements. In addition, four identically designed two-fluid atomizers were fabricated and tested for similarity of spray profiles. A scattered-light scanner was used to measure a characteristic drop diameter, which was correlated with nitrogen gas flowrate. The exponent of 1.33 for nitrogen gas flowrate is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime. This is higher than the value of 1.2 which was previously obtained at a smapling distance of 4.4 cm downstream of the atomizer. The difference is attributed to the fact that drop-size measurements obtained at a 2.2 cm sampling distance are less affected by vaporization and dispersion of small droplets and therefore should give better agreement with atomization theory. Profiles of characteristic drop diameters were also obtained by making at least five line-of-sight measurements across the spray at several horizontal positions above and below the center line of the spray.

Effect of Two-Step Metal Organic Chemical Vapor Deposition Growth on Quality, Diameter and Density of InAs Nanowires on Si (111) Substrate

NASA Astrophysics Data System (ADS)

Yu, Hung Wei; Anandan, Deepak; Hsu, Ching Yi; Hung, Yu Chih; Su, Chun Jung; Wu, Chien Ting; Kakkerla, Ramesh Kumar; Ha, Minh Thien Huu; Huynh, Sa Hoang; Tu, Yung Yi; Chang, Edward Yi

2018-02-01

High-density (˜ 80/um2) vertical InAs nanowires (NWs) with small diameters (˜ 28 nm) were grown on bare Si (111) substrates by means of two-step metal organic chemical vapor deposition. There are two critical factors in the growth process: (1) a critical nucleation temperature for a specific In molar fraction (approximately 1.69 × 10-5 atm) is the key factor to reduce the size of the nuclei and hence the diameter of the InAs NWs, and (2) a critical V/III ratio during the 2nd step growth will greatly increase the density of the InAs NWs (from 45 μm-2 to 80 μm-2) and at the same time keep the diameter small. The high-resolution transmission electron microscopy and selected area diffraction patterns of InAs NWs grown on Si exhibit a Wurtzite structure and no stacking faults. The observed longitudinal optic peaks in the Raman spectra were explained in terms of the small surface charge region width due to the small NW diameter and the increase of the free electron concentration, which was consistent with the TCAD program simulation of small diameter (< 40 nm) InAs NWs.

Geometric Limitations Of Ultrasonic Measurements

NASA Astrophysics Data System (ADS)

von Nicolai, C.; Schilling, F.

2006-12-01

Laboratory experiments are a key for interpreting seismic field observations. Due to their potential in many experimental set-ups, the determination of elastic properties of minerals and rocks by ultrasonic measurements is common in Geosciences. The quality and thus use of ultrasonic data, however, strongly depends on the sample geometry and wavelength of the sound wave. Two factors, the diameter-to-wavelength- ratio and the diameter-to-length-ratio, are believed to be the essential parameters to affect ultrasonic signal quality. In this study, we determined under well defined conditions the restricting dimensional parameters to test the validity of published assumptions. By the use of commercial ultrasonic transducers a number of experiments were conducted on aluminium, alumina, and acrylic glass rods of varying diameter (30-10 mm) and constant length. At each diameter compressional wave travel times were measured by pulse- transmission method. From the observed travel times ultrasonic wave velocities were calculated. One additional experiment was performed with a series of square-shaped aluminium blocks in order to investigate the effect of the geometry of the samples cross-sectional area. The experimental results show that the simple diameter-to-wavelength ratios are not valid even under idealized experimental conditions and more complex relation has to be talen into account. As diameter decreases the P-waves direct phase is increasingly interfered and weakened by sidewall reflections. At very small diameters compressional waves are replaced by bar waves and P-wave signals become non resolvable. Considering the suppression of both effects, a critical D/ë-ratio was determined and compared to experimental set-ups from various publications. These tests indicate that some published and cited data derived from small diameter set-ups are out off the range of physical possibility.

Examination of a Wear-Reducing Muzzle Device

DTIC Science & Technology

2013-08-01

resistant material attached to the muzzle end of the gun tube. The bore diameter of the device is slightly less than the bore diameter of the gun. The...3  Figure 3. Weapon and universal bearing slide used for firings ...small caliber round of ammunition. ..........21  v List of Tables Table 1. Firing test matrix for phase 1

Determination of relative phase permeabilities in stochastic model of pore channel distribution by diameter

NASA Astrophysics Data System (ADS)

Zemenkova, M. Y.; Shabarov, A.; Shatalov, A.; Puldas, L.

2018-05-01

The problem of the pore space description and the calculation of relative phase permeabilities (RPP) for two-phase filtration is considered. A technique for constructing a pore-network structure for constant and variable channel diameters is proposed. A description of the design model of RPP based on the capillary pressure curves is presented taking into account the variability of diameters along the length of pore channels. By the example of the calculation analysis for the core samples of the Urnenskoye and Verkhnechonskoye deposits, the possibilities of calculating RPP are shown when using the stochastic distribution of pores by diameters and medium-flow diameters.

Pretransitional phenomena and pinning in liquid-crystalline blue phases

NASA Astrophysics Data System (ADS)

Demikhov, E.; Stegemeyer, H.; Tsukruk, V.

1992-10-01

Blue phases (BP's) in liquid-crystalline systems of high chirality exhibiting a short cholesteric temperature interval are investigated. In a BP I supercooled with respect to the cholesteric phase, the orientation of the cubic lattice with the (1,1,0) wave vector perpendicular to the substrate is spontaneously turned to a [200] orientation within small areas of several tenths of micrometers in diameter. A pinning of BP I lattice temperature waves is observed on the [200] orientational inhomogeneities. The pinning effect explains the observed saturation of the BP I lattice constant on decreasing temperature and its dependence on the cooling rate observed in supercooled region. A different type of cubic blue phase, BP S (``S'' represents supercooled), is observed transforming reversibly from the supercooled BP I but metastable with respect to the cholesteric phase. The BP S has two scales of order: a long-range orientational blue-phase-like order and a short-range positional smecticlike order.

Two-phase flow characteristics of liquid nitrogen in vertically upward 0.5 and 1.0 mm micro-tubes: Visualization studies

NASA Astrophysics Data System (ADS)

Zhang, P.; Fu, X.

2009-10-01

Application of liquid nitrogen to cooling is widely employed in many fields, such as cooling of the high temperature superconducting devices, cryosurgery and so on, in which liquid nitrogen is generally forced to flow inside very small passages to maintain good thermal performance and stability. In order to have a full understanding of the flow and heat transfer characteristics of liquid nitrogen in micro-tube, high-speed digital photography was employed to acquire the typical two-phase flow patterns of liquid nitrogen in vertically upward micro-tubes of 0.531 and 1.042 mm inner diameters. It was found from the experimental results that the flow patterns were mainly bubbly flow, slug flow, churn flow and annular flow. And the confined bubble flow, mist flow, bubble condensation and flow oscillation were also observed. These flow patterns were characterized in different types of flow regime maps. The surface tension force and the size of the diameter were revealed to be the major factors affecting the flow pattern transitions. It was found that the transition boundaries of the slug/churn flow and churn/annular flow of the present experiment shifted to lower superficial vapor velocity; while the transition boundary of the bubbly/slug flow shifted to higher superficial vapor velocity compared to the results of the room-temperature fluids in the tubes with the similar hydraulic diameters. The corresponding transition boundaries moved to lower superficial velocity when reducing the inner diameter of the micro-tubes. Time-averaged void fraction and heat transfer characteristics for individual flow patterns were presented and special attention was paid to the effect of the diameter on the variation of void fraction.

Studies on aqueous two phase polymer systems useful for partitioning of biological materials

NASA Technical Reports Server (NTRS)

Brooks, D. E.; Bamberger, S.

1982-01-01

The two phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) (PEG) are mixed above a critical concentration of a few percent provide a useful medium for the separation of biological cell subpopulations via partition between the top, PEG-rich phase and the liquid-liquid phase boundary. Interfacial tensions of such systems have been measured by the rotating drop technique and found to range between 0.1-100 micro-N/m. The tension was found to depend on the length of the tie line describing the system on a phase diagram, via a power law relationship which differed depending on the concentration of Na phosphate buffer present. The electrokinetic properties of drops of one phase suspended in the other were studied for a variety of systems. It was found that the droplet electrophoretic mobility increased monotonically with phosphate concentration and drop diameter but exhibited the opposite sign from that anticipated from phosphate partition measurements. It was possible to take advantage of these electrokinetic properties and dramatically enhance the speed of phase separation through application of relatively small electric fields.

CFD Simulation of flow pattern in a bubble column reactor for forming aerobic granules and its development.

PubMed

Fan, Wenwen; Yuan, LinJiang; Li, Yonglin

2018-06-22

The flow pattern is considered to play an important role in the formation of aerobic granular sludge in a bubble column reactor; therefore, it is necessary to understand the behavior of the flow in the reactor. A three-dimensional computational fluid dynamics (CFD) simulation for bubble column reactor was established to visualize the flow patterns of two-phase air-liquid flow and three-phase air-liquid-sludge flow under different ratios of height to diameter (H/D ratio) and superficial gas upflow velocities (SGVs). Moreover, a simulation of the three-phase flow pattern at the same SGV and different characteristics of the sludge was performed in this study. The results show that not only SGV but also properties of sludge involve the transformation of flow behaviors and relative velocity between liquid and sludge. For the original activated sludge floc to cultivate aerobic granules, the flow pattern has nothing to do with sludge, but is influenced by SGV, and the vortices is occurred and the relative velocity is increased with an increase in SGV; the two-phase flow can simplify the three-phase flow that predicts the flow pattern development in bubble column reactor (BCR) for aerobic granulation. For the aerobic granules, the liquid flow behavior developed from the symmetrical circular flow to numbers and small-size vortices with an increase in the sludge diameter, the relative velocity is amount up to u r  = 5.0, it is 29.4 times of original floc sludge.

Method of filling a microchannel separation column

DOEpatents

Arnold, Don W.

2002-01-01

A method for packing a stationary phase into a small diameter fluid passageway or flow channel. Capillary action is employed to distribute a stationary phase uniformly along both the length and diameter of the flow channel. The method disclosed here: 1) eliminates the need for high pressure pumps and fittings and the safety hazards associated therewith; 2) allows the use of readily available commercial microparticles, either coated or uncoated, as the stationary phase; 3) provides for different types of particles, different particle sizes, and different particle size distributions to be packed in sequence, or simultaneously; 4) eliminates the need for plugging the flow channel prior to adding the stationary phase to retain the packing particles; and 5) many capillaries can be filled simultaneously.

Coordinate measuring machine test standard apparatus and method

DOEpatents

Bieg, L.F.

1994-08-30

A coordinate measuring machine test standard apparatus and method are disclosed which includes a rotary spindle having an upper phase plate and an axis of rotation, a kinematic ball mount attached to the phase plate concentric with the axis of rotation of the phase plate, a groove mounted at the circumference of the phase plate, and an arm assembly which rests in the groove. The arm assembly has a small sphere at one end and a large sphere at the other end. The small sphere may be a coordinate measuring machine probe tip and may have variable diameters. The large sphere is secured in the kinematic ball mount and the arm is held in the groove. The kinematic ball mount includes at least three mounting spheres and the groove is an angular locating groove including at least two locking spheres. The arm may have a hollow inner core and an outer layer. The rotary spindle may be a ratio reducer. The device is used to evaluate the measuring performance of a coordinate measuring machine for periodic recertification, including 2 and 3 dimensional accuracy, squareness, straightness, and angular accuracy. 5 figs.

Coordinate measuring machine test standard apparatus and method

DOEpatents

Bieg, Lothar F.

1994-08-30

A coordinate measuring machine test standard apparatus and method which iudes a rotary spindle having an upper phase plate and an axis of rotation, a kinematic ball mount attached to the phase plate concentric with the axis of rotation of the phase plate, a groove mounted at the circumference of the phase plate, and an arm assembly which rests in the groove. The arm assembly has a small sphere at one end and a large sphere at the other end. The small sphere may be a coordinate measuring machine probe tip and may have variable diameters. The large sphere is secured in the kinematic ball mount and the arm is held in the groove. The kinematic ball mount includes at least three mounting spheres and the groove is an angular locating groove including at least two locking spheres. The arm may have a hollow inner core and an outer layer. The rotary spindle may be a ratio reducer. The device is used to evaluate the measuring performance of a coordinate measuring machine for periodic recertification, including 2 and 3 dimensional accuracy, squareness, straightness, and angular accuracy.

Low-thrust chemical propulsion system propellant expulsion and thermal conditioning study

NASA Technical Reports Server (NTRS)

Merino, F.; Wakabayashi, I.; Pleasant, R. L.; Hill, M.

1982-01-01

Thermal conditioning systems for satisfying engine net positive suction pressure (NPSP) requirements, and propellant expulsion systems for achieving propellant dump during a return-to-launch site (RTLS) abort were studied for LH2/LO2 and LCH4/LO2 upper stage propellant combinations. A state-of-the-art thermal conditioning system employing helium injection beneath the liquid surface shows the lowest weight penalty for LO2 and LCH4. A technology system incorporating a thermal subcooler (heat exchanger) for engine NPSP results in the lowest weight penalty for the LH2 tank. A preliminary design of two state-of-the-art and two new technology systems indicates a weight penalty difference too small to warrant development of a LH2 thermal subcooler. Analysis results showed that the LH2/LO2 propellant expulsion system is optimized for maximum dump line diameters, whereas the LCH4/LO2 system is optimized for minimum dump line diameter (LCH4) and maximum dump line diameter (LO2). The primary uncertainty is the accurate determination of two-phase flow rates through the dump system; experimentation is not recommended because this uncertainty is not considered significant.

Bulk nucleation and growth of inorganic nanowires and nanotubes

NASA Astrophysics Data System (ADS)

Sharma, Shashank

The nanometer scale materials such as nanowires and nanotubes will be of particular interest as building blocks for designing novel sensors, catalysts, electronic, optical, and optoelectronic devices. However, in order to realize these applications, bulk amounts of nanowires and nanotubes need to be synthesized with precise control over the nanostructure characteristics. In addition, the structure-property relationships for one-dimensional structures are expected to be different than their bulk when their diameters are less than a characteristic Bohr exciton radius. This fundamental curiosity also necessitates bulk synthesis of nanostructures. The current bulk nanowire synthesis methods utilize either nanometer scale porous molds or nanometer scale transition metal clusters to template one-dimensional growth. All these techniques have inherent limitations in terms of control over the nanowire diameter distribution, composition, the growth direction, and the ability to generate abrupt interfaces within individual nanowires. In this dissertation, a new concept for bulk nucleation and growth of one-dimensional nanostructures is proposed and demonstrated for a variety of inorganic material systems. In this technique, multiple nanowires nucleate and grow from pools of low-melting metal melts when exposed to an activated gas phase containing the necessary precursors. This concept, hereby termed Low Melting Metals and Activated Gas phase (LMAG) mediated method, is specifically demonstrated for the synthesis of, (a) silicon nanowires grown using molten gallium and silane precursors; (b) silicon compound nanowires using solution of molten gallium and appropriate gas phase precursors, and (c) metal-oxide nanostructures grown using direct reaction of the respective metal melts and oxygen precursors. Nanowires resulted from the same molten gallium pool at high densities (>1011/cm2) and with narrow diameter distribution. The silicon nanowires synthesized using the LMAG technique were single crystalline, defect free, and contained a non uniform, extremely thin oxide sheath (<1.5 nm). The nanowire diameter could be varied from 3 to 100 nm, with lengths up to hundreds of microns. Unique tubular and paintbrush-like morphologies were obtained in gallium oxide (Ga2O3) nanostructures. Small gallium droplets (<100 nm size) allowed Ga2O3 nanowire growth parallel to the substrate, followed by 2-dimensional nanoweb formation. These experiments using small gallium droplets resulted in the growth of crystalline Ga2O3 nanotubes with outer diameters as small as 5 nm and inner diameters as small as 2.5 nm.

Acoustic measurements of the 1999 basaltic eruption of Shishaldin volcano, Alaska 2. Precursor to the Subplinian phase

USGS Publications Warehouse

Vergniolle, S.; Caplan-Auerbach, J.

2004-01-01

The 1999 eruption of Shishaldin volcano (Alaska, USA) displayed both Strombolian and Subplinian basaltic activity. The Subplinian phase was preceded by a signal of low amplitude and constant frequency (??? 2 Hz) lasting 13 h. This "humming signal" is interpreted as the coalescence of the very shallow part of a foam building up in the conduit, which produces large gas bubbles before bursting. The acoustic waveform of the hum event is modelled by a Helmholtz resonator: gas is trapped into a rigid cavity and can only escape through a tiny upper hole producing sound waves. At Shishaldin, the radius of the hole (??? 5 m) is close to that of the conduit (??? 6 m), the cavity has a length of ??? 60 m, and gas presents only a small overpressure between (??? 1.2 ?? 10-3 and 4.5 ?? 10-3 MPa). Such an overpressure is obtained by the partial coalescence of a foam formed by bubbles with a diameter from ??? 2.3 mm at the beginning of the episode towards ??? 0.64 mm very close to the end of the phase. The intermittency between hum events is explained by the ripening of the foam induced by the H2O diffusion through the liquid films. The two extreme values, from 600 to 10 s, correspond to a bubble diameter from 2.2 to 0.3 mm at the beginning and end of the pre-Subplinian phase, respectively. The extremely good agreement between two independent estimates of bubble diameters in the shallow foam reinforces the validity of such an interpretation. The total gas volume lost at the surface during the humming events is at most 5.9 ?? 106 m3. At the very end of the pre-Subplinian phase, there is a single large bubble with an overpressure of ???0.42 MPa. The large overpressure suggests that it comes from significant depth, unlike other bubbles in the pre-Subplinian phase. This deep bubble may be responsible for the entire foam collapse, resulting in the Subplinian phase. ?? 2004 Elsevier B.V. All rights reserved.

Biomechanical evaluation of one-piece and two-piece small-diameter dental implants: In-vitro experimental and three-dimensional finite element analyses.

PubMed

Wu, Aaron Yu-Jen; Hsu, Jui-Ting; Chee, Winston; Lin, Yun-Te; Fuh, Lih-Jyh; Huang, Heng-Li

2016-09-01

Small-diameter dental implants are associated with a higher risk of implant failure. This study used both three-dimensional finite-element (FE) simulations and in-vitro experimental tests to analyze the stresses and strains in both the implant and the surrounding bone when using one-piece (NobelDirect) and two-piece (NobelReplace) small-diameter implants, with the aim of understanding the underlying biomechanical mechanisms. Six experimental artificial jawbone models and two FE models were prepared for one-piece and two-piece 3.5-mm diameter implants. Rosette strain gauges were used for in-vitro tests, with peak values of the principal bone strain recorded with a data acquisition system. Implant stability as quantified by Periotest values (PTV) were also recorded for both types of implants. Experimental data were analyzed statistically using Wilcoxon's rank-sum test. In FE simulations, the peak value and distribution of von-Mises stresses in the implant and bone were selected for evaluation. In in-vitro tests, the peak bone strain was 42% lower for two-piece implants than for one-piece implants. The PTV was slightly lower for one-piece implants (PTV = -6) than for two-piece implants (PTV = -5). In FE simulations, the stresses in the bone and implant were about 23% higher and 12% lower, respectively, for one-piece implants than those for two-piece implants. Due to the higher peri-implant bone stresses and strains, one-piece implants (NobelDirect) might be not suitable for use as small-diameter implants. Copyright © 2016. Published by Elsevier B.V.

Development of a 5.5 m diameter vertical axis wind turbine, phase 3

NASA Astrophysics Data System (ADS)

Dekitsch, A.; Etzler, C. C.; Fritzsche, A.; Lorch, G.; Mueller, W.; Rogalla, K.; Schmelzle, J.; Schuhwerk, W.; Vollan, A.; Welte, D.

1982-06-01

In continuation of development of a 5.5 m diameter vertical axis windmill that consists in conception, building, and wind tunnel testing, a Darrieus rotor windpowered generator feeding an isolated network under different wind velocity conditions and with optimal energy conversion efficiency was designed built, and field tested. The three-bladed Darrieus rotor tested in the wind tunnel was equiped with two variable pitch Savonius rotors 2 m in diameter. By means of separate measures of the aerodynamic factors and the energy consumption, effect of revisions and optimizations on different elements was assessed. Pitch adjustement of the Savonius blades, lubrication of speed reducer, rotor speed at cut-in of generator field excitation, time constant of field excitation, stability conditions, switch points of ohmic resistors which combined with a small electric battery simulated a larger isolated network connected with a large storage battery, were investigated. Fundamentals for the economic series production of windpowered generators with Darrieus rotors for the control and the electric conversion system are presented.

A Local Condensation Analysis Representing Two-phase Annular Flow in Condenser/radiator Capillary Tubes

NASA Technical Reports Server (NTRS)

Karimi, Amir

1991-01-01

NASA's effort for the thermal environmental control of the Space Station Freedom is directed towards the design, analysis, and development of an Active Thermal Control System (ATCS). A two phase, flow through condenser/radiator concept was baselined, as a part of the ATCS, for the radiation of space station thermal load into space. The proposed condenser rejects heat through direct condensation of ATCS working fluid (ammonia) in the small diameter radiator tubes. Analysis of the condensation process and design of condenser tubes are based on the available two phase flow models for the prediction of flow regimes, heat transfer, and pressure drops. The prediction formulas use the existing empirical relationships of friction factor at gas-liquid interface. An attempt is made to study the stability of interfacial waves in two phase annular flow. The formulation is presented of a stability problem in cylindrical coordinates. The contribution of fluid viscosity, surface tension, and transverse radius of curvature to the interfacial surface is included. A solution is obtained for Kelvin-Helmholtz instability problem which can be used to determine the critical and most dangerous wavelengths for interfacial waves.

Effect of hole geometry and Electric-Discharge Machining (EDM) on airflow rates through small diameter holes in turbine blade material

NASA Technical Reports Server (NTRS)

Hippensteele, S. A.; Cochran, R. P.

1980-01-01

The effects of two design parameters, electrode diameter and hole angle, and two machine parameters, electrode current and current-on time, on air flow rates through small-diameter (0.257 to 0.462 mm) electric-discharge-machined holes were measured. The holes were machined individually in rows of 14 each through 1.6 mm thick IN-100 strips. The data showed linear increase in air flow rate with increases in electrode cross sectional area and current-on time and little change with changes in hole angle and electrode current. The average flow-rate deviation (from the mean flow rate for a given row) decreased linearly with electrode diameter and increased with hole angle. Burn time and finished hole diameter were also measured.

Bimodal electric tissue ablation (BETA) - in-vivo evaluation of the effect of applying direct current before and during radiofrequency ablation of porcine liver.

PubMed

Cockburn, J F; Maddern, G J; Wemyss-Holden, S A

2007-03-01

To examine the effect of applying increasing amounts of direct current (DC) before and during alternating current radiofrequency ablation of porcine liver. Using a Radiotherapeutics RF3000 generator, a 9 V AC/DC transformer and a 16 G plain aluminium tube as an electrode, a control group of 24 porcine hepatic radiofrequency ablation zones was compared with 24 zones created using a bimodal electric tissue ablation (BETA) technique in three pigs. All ablations were terminated when tissue impedance rose to greater than 999 Omega or radiofrequency energy input fell below 5 W on three successive measurements taken at 1 min intervals. BETA ablations were performed in two phases: an initial phase of variable duration DC followed by a second phase during which standard radiofrequency ablation was applied simultaneously with DC. During this second phase, radiofrequency power input was regulated by the feedback circuitry of the RF3000 generator according to changes in tissue impedance. The diameters (mm) of each ablation zone were measured by two observers in two planes perpendicular to the plane of needle insertion. The mean short axis diameter of each ablation zone was subjected to statistical analysis. With increased duration of prior application of DC, there was a progressive increase in the diameter of the ablation zone (p<0.001). This effect increased sharply up to 300 s of pre-treatment after which a further increase in diameter occurred, but at a much lesser rate. A maximum ablation zone diameter of 32 mm was produced (control diameters 10-13 mm). Applying a 9 V DC to porcine liver in vivo, and continuing this DC application during subsequent radiofrequency ablation, results in larger ablation zone diameters compared with radiofrequency ablation alone.

Numerical simulation of two-phase slug flow with liquid carryover in different diameter ratio T-junction

NASA Astrophysics Data System (ADS)

Pao, W.; Hon, L.; Saieed, A.; Ban, S.

2017-10-01

A smaller diameter conduit pointing at 12 o’clock position is typically hot-tapped to a horizontal laying production header in offshore platform to tap produced gas for downstream process train. This geometric feature is commonly known as T-junction. The nature of multiphase fluid splitting at the T-junction is a major operational challenge due to unpredictable production environment. Often, excessive liquid carryover occurs in the T-junction, leading to complete platform trip and halt production. This is because the downstream process train is not designed to handle excessive liquid. The objective of this research is to quantify the effect of different diameter ratio on phase separation efficiency in T-junction. The liquid carryover is modelled as two-phase air-water flow using Eulerian Mixture Model coupled with Volume of Fluid Method to mimic the slug flow in the main pipe. The focus in this paper is 0.0254 m (1 inch) diameter horizontal main arm and vertical branch arm with diameter ratio of 1.0, 0.5 and 0.3. The present research narrowed the investigation to only slug flow regime using Baker’s map as reference. The investigation found that, contrary to common believe, smaller diameter ratio T-junction perform worse than larger diameter ratio T-junction.

Studies of Two-Phase Gas-Liquid Flow in Microgravity. Ph.D. Thesis, Dec. 1994

NASA Technical Reports Server (NTRS)

Bousman, William Scott

1995-01-01

Two-phase gas-liquid flows are expected to occur in many future space operations. Due to a lack of buoyancy in the microgravity environment, two-phase flows are known to behave differently than those in earth gravity. Despite these concerns, little research has been conducted on microgravity two-phase flow and the current understanding is poor. This dissertation describes an experimental and modeling study of the characteristics of two-phase flows in microgravity. An experiment was operated onboard NASA aircraft capable of producing short periods of microgravity. In addition to high speed photographs of the flows, electronic measurements of void fraction, liquid film thickness, bubble and wave velocity, pressure drop and wall shear stress were made for a wide range of liquid and gas flow rates. The effects of liquid viscosity, surface tension and tube diameter on the behavior of these flows were also assessed. From the data collected, maps showing the occurrence of various flow patterns as a function of gas and liquid flow rates were constructed. Earth gravity two-phase flow models were compared to the results of the microgravity experiments and in some cases modified. Models were developed to predict the transitions on the flow pattern maps. Three flow patterns, bubble, slug and annular flow, were observed in microgravity. These patterns were found to occur in distinct regions of the gas-liquid flow rate parameter space. The effect of liquid viscosity, surface tension and tube diameter on the location of the boundaries of these regions was small. Void fraction and Weber number transition criteria both produced reasonable transition models. Void fraction and bubble velocity for bubble and slug flows were found to be well described by the Drift-Flux model used to describe such flows in earth gravity. Pressure drop modeling by the homogeneous flow model was inconclusive for bubble and slug flows. Annular flows were found to be complex systems of ring-like waves and a substrate film. Pressure drop was best fitted with the Lockhart- Martinelli model. Force balances suggest that droplet entrainment may be a large component of the total pressure drop.

Phase matched parametric amplification via four-wave mixing in optical microfibers.

PubMed

Abdul Khudus, Muhammad I M; De Lucia, Francesco; Corbari, Costantino; Lee, Timothy; Horak, Peter; Sazio, Pier; Brambilla, Gilberto

2016-02-15

Four-wave mixing (FWM) based parametric amplification in optical microfibers (OMFs) is demonstrated over a wavelength range of over 1000 nm by exploiting their tailorable dispersion characteristics to achieve phase matching. Simulations indicate that for any set of wavelengths satisfying the FWM energy conservation condition there are two diameters at which phase matching in the fundamental mode can occur. Experiments with a high-power pulsed source working in conjunction with a periodically poled silica fiber (PPSF), producing both fundamental and second harmonic signals, are undertaken to investigate the possibility of FWM parametric amplification in OMFs. Large increases of idler output power at the third harmonic wavelength were recorded for diameters close to the two phase matching diameters. A total amplification of more than 25 dB from the initial signal was observed in a 6 mm long optical microfiber, after accounting for the thermal drift of the PPSF and other losses in the system.

Fabrication of Ni-silicide/Si heterostructured nanowire arrays by glancing angle deposition and solid state reaction.

PubMed

Hsu, Hsun-Feng; Huang, Wan-Ru; Chen, Ting-Hsuan; Wu, Hwang-Yuan; Chen, Chun-An

2013-05-10

This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni3Si2 phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi2 with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation.

Fabrication of Ni-silicide/Si heterostructured nanowire arrays by glancing angle deposition and solid state reaction

PubMed Central

2013-01-01

This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni3Si2 phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi2 with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation. PMID:23663726

Measurement of average density and relative volumes in a dispersed two-phase fluid

DOEpatents

Sreepada, Sastry R.; Rippel, Robert R.

1992-01-01

An apparatus and a method are disclosed for measuring the average density and relative volumes in an essentially transparent, dispersed two-phase fluid. A laser beam with a diameter no greater than 1% of the diameter of the bubbles, droplets, or particles of the dispersed phase is directed onto a diffraction grating. A single-order component of the diffracted beam is directed through the two-phase fluid and its refraction is measured. Preferably, the refracted beam exiting the fluid is incident upon a optical filter with linearly varing optical density and the intensity of the filtered beam is measured. The invention can be combined with other laser-based measurement systems, e.g., laser doppler anemometry.

PHOS Experiment: Thermal Response of a Large Diameter Pulsating Heat Pipe on Board REXUS-18 Rocket

NASA Astrophysics Data System (ADS)

Creatini, F.; Guidi, G. M.; Belfi, F.; Cicero, G.; Fioriti, D.; Di Prizio, D.; Piacquadio, S.; Becatti, G.; Orlandini, G.; Frigerio, A.; Fontanesi, S.; Nannipieri, P.; Rognini, M.; Morganti, N.; Filippeschi, S.; Di Marco, P.; Fanucci, L.; Baronti, F.; Mameli, M.; Marengo, M.; Manzoni, M.

2015-09-01

In the present work, the results of two Closed Loop Pulsating Heat Pipes (CLPHPs) tested on board REXUS-1 8 sounding rocket in order to get experimental data over a relatively broad reduced gravity period (about 90 s) are thoroughly discussed. The CLPHPs are partially filled with refrigerant FC-72 and have, respectively, an inner tube diameter larger (3 .0 mm) and slightly smaller (1 .6 mm) than a critical diameter defined on Earth gravity conditions. On ground, the small diameter CLPHP works as a real Pulsating Heat Pipe (PHP): the typical capillary slug flow pattern forms inside the device and the heat exchange is triggered by self-sustained thermally driven oscillations of the working fluid. Conversely, the large diameter CLPHP behaves like a two-phase thermosyphon in vertical position while does not operate in horizontal position as the working fluid stratifies within the tube and surface tension is not able to balance buoyancy. Then, the idea to test the CLPHPs under reduced gravity conditions: as soon as gravity reduces, buoyancy becomes less intense and the typical capillary slug flow pattern can also forms within a tube with a larger diameter. Moreover, this allows to increase the heat transfer rate and, consequently, to decrease the overall thermal resistance. Even though it was not possible to experience the expected reduced gravity conditions due to a failure of the yo-yo de-spin system, the thermal response to the peculiar acceleration field (hyper-gravity) experienced on board are thoroughly described.

Pulsating Heat pipe Only for Space (PHOS): results of the REXUS 18 sounding rocket campaign

NASA Astrophysics Data System (ADS)

Creatini, F.; Guidi, G. M.; Belfi, F.; Cicero, G.; Fioriti, D.; Di Prizio, D.; Piacquadio, S.; Becatti, G.; Orlandini, G.; Frigerio, A.; Fontanesi, S.; Nannipieri, P.; Rognini, M.; Morganti, N.; Filippeschi, S.; Di Marco, P.; Fanucci, L.; Baronti, F.; Mameli, M.; Manzoni, M.; Marengo, M.

2015-11-01

Two Closed Loop Pulsating Heat Pipes (CLPHPs) are tested on board REXUS 18 sounding rocket in order to obtain data over a relatively long microgravity period (approximately 90 s). The CLPHPs are partially filled with FC-72 and have, respectively, an inner tube diameter larger (3 mm) and slightly smaller (1.6 mm) than the critical diameter evaluated in static Earth gravity conditions. On ground, the small diameter CLPHP effectively works as a Pulsating Heat Pipe (PHP): the characteristic slug and plug flow pattern forms inside the tube and the heat exchange is triggered by thermally driven self-sustained oscillations of the working fluid. On the other hand, the large diameter CLPHP works as a two- phase thermosyphon in vertical position and doesn't work in horizontal position: in this particular condition, the working fluid stratifies within the device as the surface tension force is no longer able to balance buoyancy. Then, the idea to test the CLPHPs in reduced gravity conditions: as the gravity reduces the buoyancy forces becomes less intense and it is possible to recreate the typical PHP flow pattern also for larger inner tube diameters. This allows to increase the heat transfer rate and, consequently, to decrease the overall thermal resistance. Even though it was not possible to experience low gravity conditions due to a failure in the yoyo de-spin system, the thermal response to the peculiar acceleration field (hyper-gravity) experienced on board are thoroughly described.

Condensation heat transfer and flow friction in silicon microchannels

NASA Astrophysics Data System (ADS)

Wu, Huiying; Wu, Xinyu; Qu, Jian; Yu, Mengmeng

2008-11-01

An experimental investigation was performed on heat transfer and flow friction characteristics during steam condensation flow in silicon microchannels. Three sets of trapezoidal silicon microchannels, with hydraulic diameters of 77.5 µm, 93.0 µm and 128.5 µm respectively, were tested under different flow and cooling conditions. It was found that both the condensation heat transfer Nusselt number (Nu) and the condensation two-phase frictional multiplier (phi2Lo) were dependent on the steam Reynolds number (Rev), condensation number (Co) and dimensionless hydraulic diameter (Dh/L). With the increase in the steam Reynolds number, condensation number and dimensionless hydraulic diameter, the condensation Nusselt number increased. However, different variations were observed for the condensation two-phase frictional multiplier. With the increase in the steam Reynolds number and dimensionless hydraulic diameter, the condensation two-phase frictional multiplier decreased, while with the increase in the condensation number, the condensation two-phase frictional multiplier increased. Based on the experimental results, dimensionless correlations for condensation heat transfer and flow friction in silicon microchannels were proposed for the first time. These correlations can be used to determine the condensation heat transfer coefficient and pressure drop in silicon microchannels if the steam mass flow rate, cooling rate and geometric parameters are fixed. It was also found that the condensation heat transfer and flow friction have relations to the injection flow (a transition flow pattern from the annular flow to the slug/bubbly flow), and with injection flow moving toward the outlet, both the condensation heat transfer coefficient and the condensation two-phase frictional multiplier increased.

The AKARI IRC asteroid flux catalogue: updated diameters and albedos

NASA Astrophysics Data System (ADS)

Alí-Lagoa, V.; Müller, T. G.; Usui, F.; Hasegawa, S.

2018-05-01

The AKARI IRC all-sky survey provided more than twenty thousand thermal infrared observations of over five thousand asteroids. Diameters and albedos were obtained by fitting an empirically calibrated version of the standard thermal model to these data. After the publication of the flux catalogue in October 2016, our aim here is to present the AKARI IRC all-sky survey data and discuss valuable scientific applications in the field of small body physical properties studies. As an example, we update the catalogue of asteroid diameters and albedos based on AKARI using the near-Earth asteroid thermal model (NEATM). We fit the NEATM to derive asteroid diameters and, whenever possible, infrared beaming parameters. We fit groups of observations taken for the same object at different epochs of the survey separately, so we compute more than one diameter for approximately half of the catalogue. We obtained a total of 8097 diameters and albedos for 5170 asteroids, and we fitted the beaming parameter for almost two thousand of them. When it was not possible to fit the beaming parameter, we used a straight line fit to our sample's beaming parameter-versus-phase angle plot to set the default value for each fit individually instead of using a single average value. Our diameters agree with stellar-occultation-based diameters well within the accuracy expected for the model. They also match the previous AKARI-based catalogue at phase angles lower than 50°, but we find a systematic deviation at higher phase angles, at which near-Earth and Mars-crossing asteroids were observed. The AKARI IRC All-sky survey is an essential source of information about asteroids, especially the large ones, since, it provides observations at different observation geometries, rotational coverages and aspect angles. For example, by comparing in more detail a few asteroids for which dimensions were derived from occultations, we discuss how the multiple observations per object may already provide three-dimensional information about elongated objects even based on an idealised model like the NEATM. Finally, we enumerate additional expected applications for more complex models, especially in combination with other catalogues. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A85

Coronary vasodilation by the use of sublingual nitroglycerin using 64-slice dual-source coronary computed tomography angiography.

PubMed

Okada, Munemasa; Nakashima, Yoshiteru; Nomura, Takafumi; Miura, Toshiro; Nao, Tomoko; Yoshimura, Masayuki; Sano, Yuichi; Matsunaga, Naofumi

2015-03-01

Sublingual nitroglycerin capsules or spray is routinely used to treat anginal attacks and to maximally dilate the epicardial coronary arteries during coronary angiography. These dilated coronary vessels have an advantage, but increased heart rates were disadvantageous for coronary computed tomography angiography (CTA). The influence of applying nitroglycerin was analyzed regarding the coronary diameter, coronary luminal attenuation, evaluable number of coronary segments, heart rate (HR), HR variability, the optimal reconstruction phase, and image scoring of CTA in the same patients using a 64-slice dual-source CT. Fifty-two patients with atypical chest pain underwent coronary CTA before and after the administration of sublingual nitroglycerin without heart rate control. The coronary diameter and luminal attenuation were measured on short-axial images in each coronary segment. The coronary vasodilation ratios (VRs) were calculated from the coronary diameters at the same location before and after the use of nitroglycerin. The local institutional review board approved this study and written informed consent was obtained from all the patients. No significant differences were noted in the HR variability or optimal reconstruction phase, despite an increase in HR after the use of nitroglycerin. Nitroglycerin significantly enlarged the coronary artery diameter, and VRs of each coronary segment ranged from 7.54% to 22.26%. As compared with baseline coronary diameter, VRs of minor segments (16.91%) were significantly larger than those of major segments (11.35%), and the magnitude of VR correlated with the baseline coronary diameter (r=-0.48, p<0.001). Coronary luminal attenuation significantly increased due to additional administration of contrast material after the use of nitroglycerin (p<0.01), but no significant difference was noted in the image quality after the use of nitroglycerin. Sublingual nitroglycerin significantly enlarged the coronary diameters, especially in peripheral small coronary arteries, and increased the evaluable number of coronary segments on coronary CTA. Copyright © 2014 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

Comparison of two methods of digital imaging technology for small diameter K-file length determination.

PubMed

Maryam, Ehsani; Farida, Abesi; Farhad, Akbarzade; Soraya, Khafri

2013-11-01

Obtaining the proper working length in endodontic treatment is essential. The aim of this study was to compare the working length (WL) assessment of small diameter K-files using the two different digital imaging methods. The samples for this in-vitro experimental study consisted of 40 extracted single-rooted premolars. After access cavity preparation, the ISO files no. 6, 8, and 10 stainless steel K-files were inserted in the canals in the three different lengths to evaluate the results in a blinded manner: At the level of apical foramen(actual)1 mm short of apical foramen2 mm short of apical foramen A digital caliper was used to measure the length of the files which was considered as the Gold Standard. Five observers (two oral and maxillofacial radiologists and three endodontists) observed the digital radiographs which were obtained using PSP and CCD digital imaging sensors. The collected data were analyzed by SPSS 17 and Repeated Measures Paired T-test. In WL assessment of small diameter K-files, a significant statistical relationship was seen among the observers of two digital imaging techniques (P<0.001). However, no significant difference was observed between the two digital techniques in WL assessment of small diameter K-files (P<0.05). PSP and CCD digital imaging techniques were similar in WL assessment of canals using no. 6, 8, and 10 K-files.

Compact and highly stable quantum dots through optimized aqueous phase transfer

NASA Astrophysics Data System (ADS)

Tamang, Sudarsan; Beaune, Grégory; Poillot, Cathy; De Waard, Michel; Texier-Nogues, Isabelle; Reiss, Peter

2011-03-01

A large number of different approaches for the aqueous phase transfer of quantum dots have been proposed. Surface ligand exchange with small hydrophilic thiols, such as L-cysteine, yields the lowest particle hydrodynamic diameter. However, cysteine is prone to dimer formation, which limits colloidal stability. We demonstrate that precise pH control during aqueous phase transfer dramatically increases the colloidal stability of InP/ZnS quantum dots. Various bifunctional thiols have been applied. The formation of disulfides, strongly diminishing the fluorescence QY has been prevented through addition of appropriate reducing agents. Bright InP/ZnS quantum dots with a hydrodynamic diameter <10 nm and long-term stability have been obtained. Finally we present in vitro studies of the quantum dots functionalized with the cell-penetrating peptide maurocalcine.

Bubble Formation from Wall Orifice in Liquid Cross-Flow Under Low Gravity

NASA Technical Reports Server (NTRS)

Nahra, Henry K.; Kamotani, Y.

2000-01-01

Two-phase flows present a wide variety of applications for spacecraft thermal control systems design. Bubble formation and detachment is an integral part of the two phase flow science. The objective of the present work is to experimentally investigate the effects of liquid cross-flow velocity, gas flow rate, and orifice diameter on bubble formation in a wall-bubble injection configuration. Data were taken mainly under reduced gravity conditions but some data were taken in normal gravity for comparison. The reduced gravity experiment was conducted aboard the NASA DC-9 Reduced Gravity Aircraft. The results show that the process of bubble formation and detachment depends on gravity, the orifice diameter, the gas flow rate, and the liquid cross-flow velocity. The data are analyzed based on a force balance, and two different detachment mechanisms are identified. When the gas momentum is large, the bubble detaches from the injection orifice as the gas momentum overcomes the attaching effects of liquid drag and inertia. The surface tension force is much reduced because a large part of the bubble pinning edge at the orifice is lost as the bubble axis is tilted by the liquid flow. When the gas momentum is small, the force balance in the liquid flow direction is important, and the bubble detaches when the bubble axis inclination exceeds a certain angle.

Thermocouple design for measuring temperatures of small insects

Treesearch

A.A. Hanson; R.C. Venette

2013-01-01

Contact thermocouples often are used to measure surface body temperature changes of insects during cold exposure. However, small temperature changes of minute insects can be difficult to detect, particularly during the measurement of supercooling points. We developed two thermocouple designs, which use 0.51 mm diameter or 0.127 mm diameter copper-constantan wires, to...

Numerical simulation of flow and melting characteristics of seawater-ice crystals two-phase flow in inlet straight pipe of shell and tube heat exchanger of polar ship

NASA Astrophysics Data System (ADS)

Xu, Li; Huang, Chang-Xu; Huang, Zhen-Fei; Sun, Qiang; Li, Jie

2018-05-01

The ice crystal particles are easy to enter into the seawater cooling system of polar ship together with seawater when it sails in the Arctic. They are easy to accumulate in the pipeline, causing serious blockage of the cooling pipe. In this study, the flow and melting characteristics of ice particles-seawater two-phase flow in inlet straight pipe of shell-and-tube heat exchanger were numerically simulated by using Eulerian-Eulerian two-fluid model coupled with the interphase heat and mass transfer model. The influences of inlet ice packing factor, ice crystal particle diameter, and inlet velocity on the distribution and melting characteristics of ice crystals were investigated. The degree of asymmetry of the distribution of ice crystals in the cross section decreases gradually when the IPF changes from 5 to 15%. The volume fractions of ice crystals near the top of the outlet cross section are 19.59, 19.51, and 22.24% respectively for ice packing factor of 5, 10 and 15%. When the particle diameter is 0.5 mm, the ice crystals are gradually stratified during the flow process. With particle diameters of 1.0 and 2.0 mm, the region with the highest volume fraction of ice crystals is a small circle and the contours in the cloud map are compact. The greater the inlet flow velocity, the less stratified the ice crystals and the more obvious the turbulence on the outlet cross section. The average volume fraction of ice crystals along the flow direction is firstly rapidly reduced and then stabilized after 300 mm.

Selected test-well data from the MX-missile siting study, Tooele, Juab, Millard, Beaver, and Iron counties, Utah

USGS Publications Warehouse

Mason, James L.; Atwood, John W.; Buettner, Priscilla S.

1985-01-01

This report contains well data collected from 1979 to 1983 in a part of the Great Basin in western Utah (fig. 1). The area is characterized by a series of generally north-trending mountain ranges separated by alluviumfilled basins that are partially filled with sedimentary deposits eroded from the adjacent mountains and lacustrine sediments deposited by Lake Bonneville. Most of the intermountain basins are elongated in the northward direction, but some are almost equidimensional.This report was prepared as part of the Great Basin Regional AquiferSystem Analysis (RASA) program. The report is intended to make well data from the MX-missile siting study readily available to water-resource managers and the general public. It includes well data obtained in areas for which little or no such data have been published previously. Well-drilling and well-completion data were compiled by Ertec, Inc. (formerly Fugro National, Inc.) under contract with the U. S. Air Force. Those data along with aquifer test data, geophysical logs, and drillers1 or geologists1 logs were obtained from Ertec, Inc. under an agreement with the U.S. Air Force. The authors thank the officials of both Ertec, Inc. and the U.S. Air Force for their helpful cooperation. The U.S. Geological Survey obtained accurate locations of the test wells (pi. 1) and accurate water-level measurements in those wells (table 1). Chemical analyses of water samples collected from several of the test wells drilled in the Sevier Desert have been published in a report by Enright and Holmes (1982, table 5).Test drilling for the MX-missile siting study consisted of two parts, the verification phase and the water-resources phase. The verification jhase was designed to obtain information necessary for the design and construction of the MX-basing system. Numerous small diameter wells were bored with depths ranging from 92 to 205 feet. Two-inch diameter JVC casing with the bottom 20 feet perforated was installed in each borehole. The water-resources phase was designed to determine ground-water availibility and to estimate the effects of ground-water withdrawals required for the construction of the MX-basing system. Six large-diameter production test wells were drilled along with associated small-diameter observation wells. Depths ranged from 310 to 1,399 feet. Lithologic logs for selected production test wells or associated observation wells are listed in table 2. Geophysical logs and aquifer test data are available in the files of the U. S. Geological Survey, as indicated in table 1.

Flowfield predictions for multiple body launch vehicles

NASA Technical Reports Server (NTRS)

Deese, Jerry E.; Pavish, D. L.; Johnson, Jerry G.; Agarwal, Ramesh K.; Soni, Bharat K.

1992-01-01

A method is developed for simulating inviscid and viscous flow around multicomponent launch vehicles. Grids are generated by the GENIE general-purpose grid-generation code, and the flow solver is a finite-volume Runge-Kutta time-stepping method. Turbulence effects are simulated using Baldwin and Lomax (1978) turbulence model. Calculations are presented for three multibody launch vehicle configurations: one with two small-diameter solid motors, one with nine small-diameter solid motors, and one with three large-diameter solid motors.

A microwave interferometer for small and tenuous plasma density measurements.

PubMed

Tudisco, O; Lucca Fabris, A; Falcetta, C; Accatino, L; De Angelis, R; Manente, M; Ferri, F; Florean, M; Neri, C; Mazzotta, C; Pavarin, D; Pollastrone, F; Rocchi, G; Selmo, A; Tasinato, L; Trezzolani, F; Tuccillo, A A

2013-03-01

The non-intrusive density measurement of the thin plasma produced by a mini-helicon space thruster (HPH.com project) is a challenge, due to the broad density range (between 10(16) m(-3) and 10(19) m(-3)) and the small size of the plasma source (2 cm of diameter). A microwave interferometer has been developed for this purpose. Due to the small size of plasma, the probing beam wavelength must be small (λ = 4 mm), thus a very high sensitivity interferometer is required in order to observe the lower density values. A low noise digital phase detector with a phase noise of 0.02° has been used, corresponding to a density of 0.5 × 10(16) m(-3).

Pulsed Laser Ablation-Induced Green Synthesis of TiO2 Nanoparticles and Application of Novel Small Angle X-Ray Scattering Technique for Nanoparticle Size and Size Distribution Analysis.

PubMed

Singh, Amandeep; Vihinen, Jorma; Frankberg, Erkka; Hyvärinen, Leo; Honkanen, Mari; Levänen, Erkki

2016-12-01

This paper aims to introduce small angle X-ray scattering (SAXS) as a promising technique for measuring size and size distribution of TiO 2 nanoparticles. In this manuscript, pulsed laser ablation in liquids (PLAL) has been demonstrated as a quick and simple technique for synthesizing TiO 2 nanoparticles directly into deionized water as a suspension from titanium targets. Spherical TiO 2 nanoparticles with diameters in the range 4-35 nm were observed with transmission electron microscopy (TEM). X-ray diffraction (XRD) showed highly crystalline nanoparticles that comprised of two main photoactive phases of TiO 2 : anatase and rutile. However, presence of minor amounts of brookite was also reported. The traditional methods for nanoparticle size and size distribution analysis such as electron microscopy-based methods are time-consuming. In this study, we have proposed and validated SAXS as a promising method for characterization of laser-ablated TiO 2 nanoparticles for their size and size distribution by comparing SAXS- and TEM-measured nanoparticle size and size distribution. SAXS- and TEM-measured size distributions closely followed each other for each sample, and size distributions in both showed maxima at the same nanoparticle size. The SAXS-measured nanoparticle diameters were slightly larger than the respective diameters measured by TEM. This was because SAXS measures an agglomerate consisting of several particles as one big particle which slightly increased the mean diameter. TEM- and SAXS-measured mean diameters when plotted together showed similar trend in the variation in the size as the laser power was changed which along with extremely similar size distributions for TEM and SAXS validated the application of SAXS for size distribution measurement of the synthesized TiO 2 nanoparticles.

Gas-driven pump for ground-water samples

USGS Publications Warehouse

Signor, Donald C.

1978-01-01

Observation wells installed for artificial-recharge research and other wells used in different ground-water programs are frequently cased with small-diameter steel pipe. To obtain samples from these small-diameter wells in order to monitor water quality, and to calibrate solute-transport models, a small-diameter pump with unique operating characteristics is required that causes a minimum alternation of samples during field sampling. A small-diameter gas-driven pump was designed and built to obtain water samples from wells of two-inch diameter or larger. The pump is a double-piston type with the following characteristics: (1) The water sample is isolated from the operating gas, (2) no source of electricity is ncessary, (3) operation is continuous, (4) use of compressed gas is efficient, and (5) operation is reliable over extended periods of time. Principles of operation, actual operation techniques, gas-use analyses and operating experience are described. Complete working drawings and a component list are included. Recent modifications and pump construction for high-pressure applications also are described. (Woodard-USGS)

Alumina nanowire growth by water decomposition and the peritectic reaction of decagonal Al{sub 65}Cu{sub 15}Co{sub 20} quasicrystals

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

Téllez-Vázquez, J.O., E-mail: oswald.tellez@gmail.com; Patiño-Carachure, C., E-mail: cpatino@pampano.unacar.mx; Rosas, G., E-mail: grtrejo@yahoo07.com.mx

2016-02-15

In this paper, the results of the Al{sub 2}O{sub 3} nanowires' growth through a chemical reaction between Al and water vapor at 1050 °C are presented. Our approach is based on two primary considerations. First, at room temperature, the Al{sub 65}Cu{sub 15}Co{sub 20} alloy is affected by the following mechanism: 2Al (s) + 3H{sub 2}O (g) → Al{sub 2}O{sub 3} (s) + H{sub 2} (g). In this reaction, the released hydrogen induces cleavage fracture of the material to form small particles. Second, the Al{sub 65}Cu{sub 15}Co{sub 20} quasicrystalline phase is transformed on heating to liquid + Al (Cu, Co) cubicmore » phase through a peritectic reaction at 1050 °C. The Al-rich liquid then reacts with water vapor, forming Al{sub 2}O{sub 3} nanowires. X-ray diffraction (XRD) analysis shows that the formed nanowires have a hexagonal structure, and infrared analysis further confirms the presence of α-Al{sub 2}O{sub 3} phase in the final products. Transmission electron microscopy observations show that nanoparticles are present at the end of nanowires, suggesting the VLS growth mechanism. Elemental analysis by energy dispersive spectroscopy (EDS) indicates that the particles at the tip of the nanowires are mainly formed by Co and Cu alloying elements and small amounts of Al. Electron microscopy observations showed nanowires with diameters ranging from 20 to 70 nm; the average diameter was 37 nm and the nanowire lengths were up to several micrometers. - Highlights: • Hexagonal alumina nanowires are grown at 1050 °C through the VLS process. • Alumina nanowires are obtained by the decomposition of decagonal quasicrystalline phase. • The decagonal phase decomposition follows a peritectic reaction at 1030 °C. • Nanoparticles are obtained by hydrogen embrittlement mechanism. • The nanoparticles catalyze the water decomposition to form wires.« less

Wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes with surface and nonlocal effects

NASA Astrophysics Data System (ADS)

Zhen, Ya-Xin

2017-02-01

In this paper, the transverse wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes is investigated based on nonlocal elasticity theory with consideration of surface effect. The governing equation is formulated utilizing nonlocal Euler-Bernoulli beam theory and Kelvin-Voigt model. Explicit wave dispersion relation is developed and wave phase velocities and frequencies are obtained. The effect of the fluid flow velocity, structural damping, surface effect, small scale effects and tube diameter on the wave propagation properties are discussed with different wave numbers. The wave frequency increases with the increase of fluid flow velocity, but decreases with the increases of tube diameter and wave number. The effect of surface elasticity and residual surface tension is more significant for small wave number and tube diameter. For larger values of wave number and nonlocal parameters, the real part of frequency ratio raises.

Usefulness of ultrasound examination in the evaluation of a neonate's body fluid status.

PubMed

Kieliszczyk, Joanna; Baranowski, Wojciech; Kosiak, Wojciech

2016-06-01

Appropriate hydration is a very important prognostic factor for the patient's health. Ultrasonographic assessment of hydration status is rarely used in pediatric medicine and it is not used at all in neonates due to the fact that no reference values have been established for this age group. The aim of the paper was to establish reference values for neonates. The study included 50 neonates from two hospitals in the Lower Silesia region of Poland; 25 of them were healthy patients (full-term newborns with no perinatal complications) and 25 were sick patients (newborns with heart defects such as ostium secundum atrial septal defect, ventricular septal defect, permanent foramen ovale and patent ductus arteriosus as well as newborns with neonatal jaundice or pneumonia that occurred during the first days of life). The ultrasound scans were conducted during the first days of the children's life. For every child inferior vena cava diameter was measured in the substernal area, longitudinal plane, M-mode in two respiratory phases: inhalation and exhalation. In addition, abdominal aorta diameter was determined (substernal area, transverse plane). The study demonstrated a statistically significant difference in the calculated inferior vena cava collapsibility index between both groups. Two other indices included the ratio of the inferior vena cava diameter during the expiratory phase to the diameter of the aorta and the ratio of the inferior vena cava diameter during the inspiratory phase to the diameter of the aorta; a statistically significant difference between both groups was found only for the measurements in the inspiratory phase. Based on the study results normal ranges for hydration indices in neonates were established. The need for the measurement of the abovementioned parameters in the inspiratory phase was determined. In addition, the usefulness of the ultrasound examination for the evaluation of body fluid status in this pediatric age group, particularly in preterm newborns, was noted due to its painless and non-invasive nature as well as easy access to equipment at neonatology wards.

OPTICAL FIBRES AND FIBREOPTIC SENSORS: Spun microstructured optical fibresfor Faraday effect current sensors

NASA Astrophysics Data System (ADS)

Chamorovsky, Yury K.; Starostin, Nikolay I.; Morshnev, Sergey K.; Gubin, Vladimir P.; Ryabko, Maksim V.; Sazonov, Aleksandr I.; Vorob'ev, Igor'L.

2009-11-01

We report a simple design of spun holey fibres and the first experimental study of the magneto-optical response of spun microstructured fibres with high built-in birefringence. Such fibres enable the Faraday-effect-induced phase shift to effectively accumulate in a magnetic field even at very small coiling diameters. For example, the magneto-optical sensitivity of a 5-mm-diameter fibre coil consisting of 100 turns is ~70% that of an ideal fibre, in good agreement with theoretical predictions.

Measurements of characteristic parameters of extremely small cogged wheels with low module by means of low-coherence interferometry

NASA Astrophysics Data System (ADS)

Pakula, Anna; Tomczewski, Slawomir; Skalski, Andrzej; Biało, Dionizy; Salbut, Leszek

2010-05-01

This paper presents novel application of Low Coherence Interferometry (LCI) in measurements of characteristic parameters as circular pitch, foot diameter, heads diameter, in extremely small cogged wheels (cogged wheel diameter lower than θ=3 mm and module m = 0.15) produced from metal and ceramics. The most interesting issue concerning small diameter cogged wheels occurs during their production. The characteristic parameters of the wheel depend strongly on the manufacturing process and while inspecting small diameter wheels the shrinkage during the cast varies with the slight change of fabrication process. In the paper the LCI interferometric Twyman - Green setup with pigtailed high power light emitting diode, for cogged wheels measurement, is described. Due to its relatively big field of view the whole wheel can be examined in one measurement, without the necessity of numerical stitching. For purposes of small cogged wheel's characteristic parameters measurement the special binarization algorithm was developed and successfully applied. At the end the results of measurement of heads and foot diameters of two cogged wheels obtained by proposed LCI setup are presented and compared with the results obtained by the commercial optical profiler. The results of examination of injection moulds used for fabrication of measured cogged wheels are also presented. Additionally, the value of cogged wheels shrinkage is calculated as a conclusion for obtained results. Proposed method is suitable for complex measurements of small diameter cogged wheels with low module especially when there are no measurements standards for such objects.

Gas phase fractionation method using porous ceramic membrane

DOEpatents

Peterson, Reid A.; Hill, Jr., Charles G.; Anderson, Marc A.

1996-01-01

Flaw-free porous ceramic membranes fabricated from metal sols and coated onto a porous support are advantageously used in gas phase fractionation methods. Mean pore diameters of less than 40 .ANG., preferably 5-20 .ANG. and most preferably about 15 .ANG., are permeable at lower pressures than existing membranes. Condensation of gases in small pores and non-Knudsen membrane transport mechanisms are employed to facilitate and increase membrane permeability and permselectivity.

High-frequency ultrasound Doppler system for biomedical applications with a 30-MHz linear array.

PubMed

Xu, Xiaochen; Sun, Lei; Cannata, Jonathan M; Yen, Jesse T; Shung, K Kirk

2008-04-01

In this paper, we report the development of the first high-frequency (HF) pulsed-wave Doppler system using a 30-MHz linear array transducer to assess the cardiovascular functions in small animals. This array-based pulsed-wave Doppler system included a 16-channel HF analog beamformer, a HF pulsed-wave Doppler module, timing circuits, HF bipolar pulsers and analog front ends. The beamformed echoes acquired by the 16-channel analog beamformer were fed directly to the HF pulsed-wave Doppler module. Then the in-phase and quadrature-phase (IQ) audio Doppler signals were digitized by either a sound card or a Gage digitizer and stored in a personal computer. The Doppler spectrogram was displayed on a personal computer in real time. The two-way beamwidths were determined to be 160 microm to 320 microm when the array was electronically focused at different focal points at depths from 5 to 10 mm. A micro-flow phantom, consisting of a polyimide tube with an inner diameter of 127 microm and the wire phantom were used to evaluate and calibrate the system. The results show that the system is capable of detecting motion velocity of the wire phantom as low as 0.1 mm/s, and detecting blood-mimicking flow velocity in the 127-microm tube lower than 7 mm/s. The system was subsequently used to measure the blood flow in vivo in two mouse abdominal superficial vessels, with diameters of approximately 200 microm, and a mouse aorta close to the heart. These results demonstrated that this system may become an indispensable part of the current HF array-based imaging systems for small animal studies.

Improved utilization of small-diameter ponderosa pine in glulam timber

Treesearch

Roland Hernandez; David W. Green; David E. Kretschmann; Steven P. Verrill

2005-01-01

This study involved the evaluation of ponderosa pine glulam made from lumber that was sawn from a small-diameter timber resource. Two different glulam beam depths were evaluated: 8 and 13 laminations. A comprehensive glulam test program was conducted to evaluate edgewise and flat-wise bending, shear, and tensile strength. Beam deflection was measured and a variety of...

Numerical study of the influence of geometrical characteristics of a vertical helical coil on a bubbly flow

NASA Astrophysics Data System (ADS)

Saffari, H.; Moosavi, R.

2014-11-01

In this article, turbulent single-phase and two-phase (air-water) bubbly fluid flows in a vertical helical coil are analyzed by using computational fluid dynamics (CFD). The effects of the pipe diameter, coil diameter, coil pitch, Reynolds number, and void fraction on the pressure loss, friction coefficient, and flow characteristics are investigated. The Eulerian-Eulerian model is used in this work to simulate the two-phase fluid flow. Three-dimensional governing equations of continuity, momentum, and energy are solved by using the finite volume method. The k- ɛ turbulence model is used to calculate turbulence fluctuations. The SIMPLE algorithm is employed to solve the velocity and pressure fields. Due to the effect of a secondary force in helical pipes, the friction coefficient is found to be higher in helical pipes than in straight pipes. The friction coefficient increases with an increase in the curvature, pipe diameter, and coil pitch and decreases with an increase in the coil diameter and void fraction. The close correlation between the numerical results obtained in this study and the numerical and empirical results of other researchers confirm the accuracy of the applied method. For void fractions up to 0.1, the numerical results indicate that the friction coefficient increases with increasing the pipe diameter and keeping the coil pitch and diameter constant and decreases with increasing the coil diameter. Finally, with an increase in the Reynolds number, the friction coefficient decreases, while the void fraction increases.

Mitigation of cross-beam energy transfer: Implication of two-state focal zooming on OMEGA

NASA Astrophysics Data System (ADS)

Froula, D. H.; Kessler, T. J.; Igumenshchev, I. V.; Betti, R.; Goncharov, V. N.; Huang, H.; Hu, S. X.; Hill, E.; Kelly, J. H.; Meyerhofer, D. D.; Shvydky, A.; Zuegel, J. D.

2013-08-01

Cross-beam energy transfer (CBET) during OMEGA low-adiabat cryogenic experiments reduces the hydrodynamic efficiency by ˜35%, which lowers the calculated one-dimensional (1-D) yield by a factor of 7. CBET can be mitigated by reducing the diameter of the laser beams relative to the target diameter. Reducing the diameter of the laser beams by 30%, after a sufficient conduction zone has been generated (two-state zooming), is predicted to maintain low-mode uniformity while recovering 90% of the kinetic energy lost to CBET. A radially varying phase plate is proposed to implement two-state zooming on OMEGA. A beam propagating through the central half-diameter of the phase plate will produce a large spot, while a beam propagating through the outer annular region of the phase plate will produce a narrower spot. To generate the required two-state near-field laser-beam profile, a picket driver with smoothing by spectral dispersion (SSD) would pass through an apodizer, forming a beam of half the standard diameter. A second main-pulse driver would co-propagate without SSD through its own apodizer, forming a full-diameter annular beam. Hydrodynamic simulations, using the designed laser spots produced by the proposed zooming scheme on OMEGA, show that implementing zooming will increase the implosion velocity by 25% resulting in a 4.5× increase in the 1-D neutron yield. Demonstrating zooming on OMEGA would validate a viable direct-drive CBET mitigation scheme and help establish a pathway to hydrodynamically equivalent direct-drive-ignition implosions by increasing the ablation pressure (1.6×), which will allow for more stable implosions at ignition-relevant velocities.

Bubble behavior characteristics based on virtual binocular stereo vision

NASA Astrophysics Data System (ADS)

Xue, Ting; Xu, Ling-shuang; Zhang, Shang-zhen

2018-01-01

The three-dimensional (3D) behavior characteristics of bubble rising in gas-liquid two-phase flow are of great importance to study bubbly flow mechanism and guide engineering practice. Based on the dual-perspective imaging of virtual binocular stereo vision, the 3D behavior characteristics of bubbles in gas-liquid two-phase flow are studied in detail, which effectively increases the projection information of bubbles to acquire more accurate behavior features. In this paper, the variations of bubble equivalent diameter, volume, velocity and trajectory in the rising process are estimated, and the factors affecting bubble behavior characteristics are analyzed. It is shown that the method is real-time and valid, the equivalent diameter of the rising bubble in the stagnant water is periodically changed, and the crests and troughs in the equivalent diameter curve appear alternately. The bubble behavior characteristics as well as the spiral amplitude are affected by the orifice diameter and the gas volume flow.

Distant Secondary Craters and Age Constraints on Young Martian Terrains

NASA Technical Reports Server (NTRS)

McEwen, A.; Preblich, B.; Turtle, E.; Studer, D.; Artemieva, N.; Golombek, M.; Hurst, M.; Kirk, R.; Burr, D.

2005-01-01

Are small (less than approx. 1 km diameter) craters on Mars and the Moon dominated by primary impacts, by secondary impacts of much larger primary craters, or are both primaries and secondaries significant? This question is critical to age constraints for young terrains and for older terrains covering small areas, where only small craters are superimposed on the unit. If the martian rayed crater Zunil is representative of large impact events on Mars, then the density of secondaries should exceed the density of primaries at diameters a factor of 1000 smaller than that of the largest contributing primary crater. On the basis of morphology and depth/diameter measurements, most small craters on Mars could be secondaries. Two additional observations (discussed below) suggest that the production functions of Hartmann and Neukum predict too many primary craters smaller than a few hundred meters in diameter. Fewer small, high-velocity impacts may explain why there appears to be little impact regolith over Amazonian terrains. Martian terrains dated by small craters could be older than reported in recent publications.

LSST (Hoop/Column) Maypole Antenna Development Program, phase 1, part 1

NASA Technical Reports Server (NTRS)

Sullivan, M. R.

1982-01-01

The first of a two-phase program was performed to develop the technology necessary to evaluate, design, manufacture, package, transport and deploy the hoop/column deployable antenna reflector by means of a ground based program. The hoop/column concept consists of a cable stiffened large diameter hoop and central column structure that supports and contours a radio frequency reflective mesh surface. Mission scenarios for communications, radiometer and radio astronomy, were studied. The data to establish technology drivers that resulted in a specification of a point design was provided. The point design is a multiple beam quadaperture offset antenna system wich provides four separate offset areas of illumination on a 100 meter diameter symmetrical parent reflector. The periphery of the reflector is a hoop having 48 segments that articulate into a small stowed volume around a center extendable column. The hoop and column are structurally connected by graphite and quartz cables. The prominence of cables in the design resulted in the development of advanced cable technology. Design verification models were built of the hoop, column, and surface stowage subassemblies. Model designs were generated for a half scale sector of the surface and a 1/6 scale of the complete deployable reflector.

Effect of graphite particle size and content on the formation mechanism of detonation polycrystalline diamond

NASA Astrophysics Data System (ADS)

Tong, Y.; Cao, Y.; Liu, R.; Shang, S. Y.; Huang, F. L.

2018-03-01

The formation mechanism of detonation polycrystalline diamond (DPD) generated from the detonation of a mixed RDX/graphite explosive is investigated. It is found experimentally that the DPD conversion rate decreases with both the content and the particle size of the graphite. Moreover, the particle sizes of the generated DPD powder are analyzed, which shows that, with the decrease in the graphite particle size, the mean number diameter of DPD decreases, but the mean volume diameter increases. In addition, with the help of scanning electron microscopy, it is observed that the in situ phase change occurs in the graphite particles, by which the small particles combine to form numerous large DPD particles. Based on both the experimental data and the classical ZND detonation model, we divide such a DPD synthesis process into two stages: In the first stage, the in situ phase change from graphite to diamond is dominant, supplemented by some coalescence growth at high pressure and temperature, which is affected mainly by the detonation performance of the mixed explosive under consideration. In the second stage, the graphitization of DPD caused by the residual heat is dominant, which is affected mainly by the unloading rate of the particle temperature.

Dynamics of an experimental two bladed horizontal axis wind turbine with blade cyclic pitch variation

NASA Technical Reports Server (NTRS)

Hotenemser, K. H.; Swift, A. H. P.

1981-01-01

The turbine under study incorporates the combination of two features: the application of blade cyclic pitch variation; and the use of yaw angle control for rotor speed and torque regulation. Due to its emasculation by passive cyclic pitch variation the rotor can be rapidly yawed without encountering gyroscopic and aerodynamic hub moments and without noticeable out of plane excursions. The two bladed upwind rotor is vane stabilized and of very simple and rugged design. The principle was first checked out with a small scale wind tunnel model and then tested in the atmosphere with a 7.6 meter diameter experimental fully instrumented wind turbine driving a 3 phase alternator. The test results are summarized with respect to structural dynamics and yaw dynamics.

Slug-flow dynamics with phase change heat transfer in compact heat exchangers with oblique wavy walls

NASA Astrophysics Data System (ADS)

Morimoto, Kenichi; Kinoshita, Hidenori; Matsushita, Ryo; Suzuki, Yuji

2017-11-01

With abundance of low-temperature geothermal energy source, small-scale binary-cycle power generation system has gained renewed attention. Although heat exchangers play a dominant role in thermal efficiency and the system size, the optimum design strategy has not been established due to complex flow phenomena and the lack of versatile heat transfer models. In the present study, the concept of oblique wavy walls, with which high j/f factor is achieved by strong secondary flows in single-phase system, is extended to two-phase exchangers. The present analyses are based on evaporation model coupled to a VOF technique, and a train of isolated bubbles is generated under the controlled inlet quality. R245fa is adopted as a low boiling-point working media, and two types of channels are considered with a hydraulic diameter of 4 mm: (i) a straight circular pipe and (ii) a duct with oblique wavy walls. The focus is on slug-flow dynamics with evaporation under small capillary but moderate Weber numbers, where the inertial effect as well as the surface tension is of significance. A possible direction of the change in thermo-physical properties is explored by assuming varied thermal conductivity. Effects of the vortical motions on evaporative heat transfer are highlighted. This work has been supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan.

Exergy optimization in a steady moving bed heat exchanger.

PubMed

Soria-Verdugo, A; Almendros-Ibáñez, J A; Ruiz-Rivas, U; Santana, D

2009-04-01

This work provides an energy and exergy optimization analysis of a moving bed heat exchanger (MBHE). The exchanger is studied as a cross-flow heat exchanger where one of the phases is a moving granular medium. The optimal MBHE dimensions and the optimal particle diameter are obtained for a range of incoming fluid flow rates. The analyses are carried out over operation data of the exchanger obtained in two ways: a numerical simulation of the steady-state problem and an analytical solution of the simplified equations, neglecting the conduction terms. The numerical simulation considers, for the solid, the convection heat transfer to the fluid and the diffusion term in both directions, and for the fluid only the convection heat transfer to the solid. The results are compared with a well-known analytical solution (neglecting conduction effects) for the temperature distribution in the exchanger. Next, the analytical solution is used to derive an expression for the exergy destruction. The optimal length of the MBHE depends mainly on the flow rate and does not depend on particle diameter unless they become very small (thus increasing sharply the pressure drop). The exergy optimal length is always smaller than the thermal one, although the difference is itself small.

Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

DOE PAGES

Scott, Jamieson; Tong, Katie; William, Hamilton; ...

2014-10-31

The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate tomore » a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.« less

Small angle neutron scattering (SANS) studies on the structural evolution of pyromellitamide self-assembled gels.

PubMed

Jamieson, Scott A; Tong, Katie W K; Hamilton, William A; He, Lilin; James, Michael; Thordarson, Pall

2014-11-25

The kinetics of aggregation of two pyromellitamide gelators, tetrabutyl- (C4) and tetrahexyl-pyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to 6 days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 h) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4, indicating one-dimensional stacking and aggregation corresponding to a multifiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggest that the C6 also forms one-dimensional stacks but that these aggregate to a thicker multifiber braided cluster that has a diameter of about 62 Å. Over a longer period of time, the radius, persistence length, and contour length all continue to increase in 6 days after cooling. These data suggest that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g., tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.

Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

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

Scott, Jamieson; Tong, Katie; William, Hamilton

The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate tomore » a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.« less

PHYSICAL PROPERTIES OF LARGE AND SMALL GRANULES IN SOLAR QUIET REGIONS

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

Yu Daren; Xie Zongxia; Hu Qinghua

The normal mode observations of seven quiet regions obtained by the Hinode spacecraft are analyzed to study the physical properties of granules. An artificial intelligence technique is introduced to automatically find the spatial distribution of granules in feature spaces. In this work, we investigate the dependence of granular continuum intensity, mean Doppler velocity, and magnetic fields on granular diameter. We recognized 71,538 granules by an automatic segmentation technique and then extracted five properties: diameter, continuum intensity, Doppler velocity, and longitudinal and transverse magnetic flux density to describe the granules. To automatically explore the intrinsic structures of the granules in themore » five-dimensional parameter space, the X-means clustering algorithm and one-rule classifier are introduced to define the rules for classifying the granules. It is found that diameter is a dominating parameter in classifying the granules and two families of granules are derived: small granules with diameters smaller than 1.''44, and large granules with diameters larger than 1.''44. Based on statistical analysis of the detected granules, the following results are derived: (1) the averages of diameter, continuum intensity, and Doppler velocity in the upward direction of large granules are larger than those of small granules; (2) the averages of absolute longitudinal, transverse, and unsigned flux density of large granules are smaller than those of small granules; (3) for small granules, the average of continuum intensity increases with their diameters, while the averages of Doppler velocity, transverse, absolute longitudinal, and unsigned magnetic flux density decrease with their diameters. However, the mean properties of large granules are stable; (4) the intensity distributions of all granules and small granules do not satisfy Gaussian distribution, while that of large granules almost agrees with normal distribution with a peak at 1.04 I{sub 0}.« less

Endothelial Dysfunction and Blood Viscosity Inpatients with Unstable Angina in Different Periods of a Solar Activity

NASA Astrophysics Data System (ADS)

Parshina, S. S.; Tokaeva, L. K.; Dolgova, E. M.; Afanas'yeva, T. N.; Strelnikova, O. A.

The origin of hemorheologic and endothelial defects in patients with unstable angina (comparing with healthy persons) is determined by a solar activity period: the blood viscosity increases in a period of high solar activity in the vessels of small, medium and macro diameters, a local decompensate dysfunction of small vessels endothelium had been fixed (microcirculation area). In the period of a low solar activity there is an increase of a blood viscosity in vessels of all diameters, generalized subcompensated endothelial dysfunction is developed (on the background of the III phase blood clotting activating). In the period of a high solar activity a higher blood viscosity had been fixed, comparing with the period of a low solar activity.

Multi-phase-fluid discrimination with local fibre-optical probes: I. Liquid/liquid flows

NASA Astrophysics Data System (ADS)

Fordham, E. J.; Holmes, A.; Ramos, R. T.; Simonian, S.; Huang, S.-M.; Lenn, C. P.

1999-12-01

We demonstrate the use of a novel design of fibre-optical sensor (or `local probe') for immiscible-fluid discrimination in multi-phase flows. These probes are made from standard silica fibres with plane oblique facets polished at the fibre tip, with various surface treatments, including a crucial one for wettability control. Total internal reflection is used to distinguish drops, bubbles or other regions of fluid in multi-phase flows, on the basis of refractive-index contrast. Such probes have quasi-binary outputs; we demonstrate in this paper their use in distinguishing water from oil (kerosene) in oil/water two-phase flows and compare the results with those obtained from a simple cleaved fibre relying on the (small) difference in Fresnel reflectivity for discrimination. Quantitative accuracy is demonstrated by comparison of profiles, across a pipe diameter, of local, time-averaged volume fractions (`hold-ups'), with pipe-averaged hold-ups determined from a carefully calibrated gradio-manometer in a fully developed region of the flow. Companion papers deal with the sensors used and results achieved in gas/liquid flows and three-phase flows.

Phase behavior and formation of o/w nano-emulsion in vegetable oil/ mixture of polyglycerol polyricinoleate and polyglycerin fatty acid ester/water systems.

PubMed

Wakisaka, Satoshi; Nakanishi, Masami; Gohtani, Shoichi

2014-01-01

It is reported that mixing polyglycerol polyricinoleate (PGPR) and polyglycerol laurilester has a great emulsifying capacity, and consequently fine oil-in-water (o/w) emulsions can be formed. However, the role of PGPR is not clear. The objective of this research is to investigate the phase behavior of vegetable oil/mixture of PGPR and polyglycerol fatty acid ester/water systems, and to clarify the role of PGPR in making a fine emulsion. Phase diagrams were constructed to elucidate the optimal process for preparing fine emulsions. In all the systems examined in this study, the phases, including the liquid crystal phase (L(c)) and sponge phase (L(3)), spread widely in the phase diagrams. We examined droplet size of the emulsions prepared from each phase and found that o/w nano-emulsions with droplet sizes as small as 50 nm were formed by emulsifying either from a single L(3) phase or a two-phase region, L(c) + L(3). These results indicate that a sponge phase L(3) or liquid crystal phase L(c) or both is necessary to form an o/w nano-emulsion whose average droplet diameter is less than 50 nm for PGPR and polyglycerin fatty acid ester mixtures used as surfactant.

Dependence of CO2 Reactivity of Carbon Anodes on Pore Structure

NASA Astrophysics Data System (ADS)

Chen, Tong; Xue, Jilai; Lang, Guanghui; Liu, Rui; Gao, Shoulei; Wang, Zengjie

2017-09-01

The correlation between the CO2 reactivity and pore structure of carbon anodes was experimentally investigated. The pore structures of the anodes before and after CO2 oxidation were characterized using image analysis. The porosity, mean pore diameter, and the number of micro-cracks decreased with increasing anode forming pressure, while they increased with over-compaction. With prolonged CO2 oxidation time, the porosity, pore density, mean pore diameter, pore aspect ratio, and the number of micro-cracks increased due to the merging of small pores, increased pore connectivity, and generation of new pores. The activation energy decreased with increasing porosity of the anodes' pitch phase due to easier CO2 penetration and reaction within the anodes. The results confirm that the fine pitch-coke phase of anodes is preferentially consumed, a cause of carbon dusting. Optimization of the pore structures to balance the pitch, coke, and butt phases may potentially further reduce carbon dusting.

Evaluation of small-diameter timber for value-added manufacturing : a stress wave approach

Treesearch

Xiping Wang; Robert J. Ross; John Punches; R. James Barbour; John W. Forsman; John R. Erickson

2003-01-01

The objective of this research was to investigate the use of a stress wave technology to evaluate the structural quality of small-diameter timber before harvest. One hundred and ninety-two Douglas-fir and ponderosa pine trees were sampled from four stands in southwestern Oregon and subjected to stress wave tests in the field. Twelve of the trees, six Douglas-fir and...

Advanced one-dimensional optical strain measurement system, phase 4

NASA Technical Reports Server (NTRS)

Lant, Christian T.

1992-01-01

An improved version of the speckle-shift strain measurement system was developed. The system uses a two-dimensional sensor array to maintain speckle correlation in the presence of large off-axis rigid body motions. A digital signal processor (DSP) is used to calculate strains at a rate near the RS-170 camera frame rate. Strain measurements were demonstrated on small diameter wires and fibers used in composite materials research. Accurate values of Young's modulus were measured on tungsten wires, and silicon carbide and sapphire fibers. This optical technique has measured surface strains at specimen temperatures above 750 C and has shown the potential for measurements at much higher temperatures.

Measurement of Two-Phase Flow Characteristics Under Microgravity Conditions

NASA Technical Reports Server (NTRS)

Keshock, E. G.; Lin, C. S.; Edwards, L. G.; Knapp, J.; Harrison, M. E.; Xhang, X.

1999-01-01

This paper describes the technical approach and initial results of a test program for studying two-phase annular flow under the simulated microgravity conditions of KC-135 aircraft flights. A helical coil flow channel orientation was utilized in order to circumvent the restrictions normally associated with drop tower or aircraft flight tests with respect to two-phase flow, namely spatial restrictions preventing channel lengths of sufficient size to accurately measure pressure drops. Additionally, the helical coil geometry is of interest in itself, considering that operating in a microgravity environment vastly simplifies the two-phase flows occurring in coiled flow channels under 1-g conditions for virtually any orientation. Pressure drop measurements were made across four stainless steel coil test sections, having a range of inside tube diameters (0.95 to 1.9 cm), coil diameters (25 - 50 cm), and length-to-diameter ratios (380 - 720). High-speed video photographic flow observations were made in the transparent straight sections immediately preceding and following the coil test sections. A transparent coil of tygon tubing of 1.9 cm inside diameter was also used to obtain flow visualization information within the coil itself. Initial test data has been obtained from one set of KC-135 flight tests, along with benchmark ground tests. Preliminary results appear to indicate that accurate pressure drop data is obtainable using a helical coil geometry that may be related to straight channel flow behavior. Also, video photographic results appear to indicate that the observed slug-annular flow regime transitions agree quite reasonably with the Dukler microgravity map.

Drug nanocarriers for cancer chemotherapy based on microemulsions: The case of Vemurafenib analog PLX4720.

PubMed

Theochari, Ioanna; Goulielmaki, Maria; Danino, Dganit; Papadimitriou, Vassiliki; Pintzas, Alexandros; Xenakis, Aristotelis

2017-06-01

Oil-in-water (O/W) microemulsions based on Tween 80 as the emulsifier and triacetin as the dispersed oil phase were formulated to be used as delivery vehicles of Vemurafenib analog PLX4720. PLX4720 is a lipophilic antitumor drug against various cancer types correlated with the BRAF V600E mutation. The limits of the single-phase region corresponding to O/W microemulsions as described by ternary phase diagrams were examined. Droplet size measurements determined by dynamic light scattering (DLS) showed mean droplet diameters equal to 10±0.1nm both in the presence and in absence of the drug. Cryogenic-transmission electron microscopy (Cryo-TEM) images of the microemulsions showed the existence of small structures with uniform size distribution having also average diameters of approximately 10nm. Electron paramagnetic resonance (EPR) spectroscopy applying the spin probing technique confirmed PLX4720 location in the oil cores excluding its participation in the surfactants monolayer. Furthermore, cell viability assays on colon cancer cell lines Colo-205 and HT29 showed that microemulsions did not exhibit any cytotoxicity when added in ratios between 0.005% v/v and 0.2% v/v. When the cells were treated with encapsulated PLX4720 at two different concentrations (0.063 and 0.12μΜ) the same response as when dissolved in classic DMSO was observed. Copyright © 2017 Elsevier B.V. All rights reserved.

Experimental Investigations of Two-Phase Cooling in Microgap Channel

DTIC Science & Technology

2011-04-25

several classification of micro to macro channel. In general, a microchannel is a channel for which the heat transfer characteristics deviate from...examined the heat transfer and fluid flow characteristics of two-phase flow in microchannels with hydraulic diameters of 150 - 450 micrometers for...inherent with two-phase microchannel heat sinks. Bar- Cohen and Rahim [5] performed a detailed analysis of microchannel /microgap heat transfer data

Two phase flow bifurcation due to turbulence: transition from slugs to bubbles

NASA Astrophysics Data System (ADS)

Górski, Grzegorz; Litak, Grzegorz; Mosdorf, Romuald; Rysak, Andrzej

2015-09-01

The bifurcation of slugs to bubbles within two-phase flow patterns in a minichannel is analyzed. The two-phase flow (water-air) occurring in a circular horizontal minichannel with a diameter of 1 mm is examined. The sequences of light transmission time series recorded by laser-phototransistor sensor is analyzed using recurrence plots and recurrence quantification analysis. Recurrence parameters allow the two-phase flow patterns to be found. On changing the water flow rate we identified partitioning of slugs or aggregation of bubbles.

Meso and Micro Scale Propulsion Concepts for Small Spacecraft

DTIC Science & Technology

2005-06-14

the inner diameter of the fuel jet tube was 500 gm, while the inner diameter of the air jet tube was 760 pim. Figure 2. Meso-scale whirl combustion of...decomposition. This mechanism was developed by comparison of model predictions with experimental data obtained from shock tube and static reactor...relative to the true gas phase temperature. Air on for exhaust tube cooling•" 2500 0L- CH3 NO 2 off 񓟰 Air off 򒶜 CH3NO 2 on H2 off T Ŕ 1000 S500 Air

Selective area growth of InAs nanowires from SiO2/Si(1 1 1) templates direct-written by focused helium ion beam technology

NASA Astrophysics Data System (ADS)

Yang, Che-Wei; Chen, Wei-Chieh; Chou, Chieh; Lin, Hao-Hsiung

2018-02-01

We report on the selective area growth of InAs nanowires on patterned SiO2/Si (1 1 1) nano-holes, prepared by focused helium ion beam technology. We used a single spot mode, in which the focused helium ion beam was fixed on a single point with a He+-ion dosage, ranging from 1.5 pC to 8 pC, to drill the nano-holes. The smallest hole diameter achieved is ∼8 nm. We found that low He+-ion dosage is able to facilitate the nucleation of (1 1 1)B InAs on the highly mismatched Si, leading to the vertical growth of InAs nanowires (NWs). High He-ion dosage, on the contrary, severely damaged Si surface, resulting in tilted and stripe-like NWs. In addition to titled NW grown from (1 1 1)A InAs domain, a new titled growth direction due to defect induced twinning was observed. Cross-sectional TEM images of vertical NWs show mixed wurtizite (WZ) and zincblende (ZB) phases, while WZ phase dominants. The stacking faults resulting from the phase change is proportional to NW diameter, suggesting that the critical diameter of phase turning is larger than 110 nm, the maximum diameter of our NWs. Period of misfit dislocation at the InAs/Si interface of vertical NW is also found larger than the theoretical value when the diameter of heterointerface is smaller than 50 nm, indicating that the small contact area is able to accommodate the large lattice and thermal mismatch between InAs and Si.

Mechanical behavior of shock-wave consolidated nano and micron-sized aluminum/silicon carbide and aluminum/aluminum oxide two-phase systems characterized by light and electron metallography

NASA Astrophysics Data System (ADS)

Alba-Baena, Noe Gaudencio

This dissertation reports the results of the exploratory study of two-phase systems consisting of 150 microm diameter aluminum powder mechanically mixed with 30 nm and 30 microm diameter SiC and Al2O3 powders (in volume fractions of 2, 4, and 21 percent). Powders were mechanically mixed and green compacted to ˜80% theorical density in a series of cylindrical fixtures (steel tubes). The compacted arrangements were explosively consolidated using ammonium nitrate-fuel oil (ANFO) to form stacks of two-phase systems. As result, successfully consolidated cylindrical monoliths of 50 mm (height) x 32 mm (in diameter) were obtained. By taking advantage of the use of SWC (shock wave consolidation) and WEDM (wire-electric discharge machining), the heterogeneous systems were machined in a highly efficiency rate. The sample cuts used for characterization and mechanical properties testing, require the use of less that 10cc of each monolith, in consequence there was preserved an average of 60% of the obtained system monoliths. Consolidated test cylinders of the pure Al and two-phase composites were characterized by optical metallography and TEM. The light micrographs for the five explosively consolidated regimes: aluminum powder, nano and micron-sized Al/Al2O3 systems, and the nano and micron-sized Al/SiC systems exhibit similar ductility in the aluminum grains. Low volume fraction systems exhibit small agglomerations at the grain boundaries for the Al/Al2O3 system and the Al/SiC system reveal a well distributed phase at the grain boundaries. Large and partially bonded agglomerations were observable in the nano-sized high volume fraction (21%) systems, while the micron-sized Al/ceramic systems exhibit homogeneous distribution along the aluminum phase grains. TEM images showed the shock-induced dislocation cell structure, which has partially recrystallized to form a nano grain structure in the consolidated aluminum powder. Furthermore, the SiC nano-agglomerates appeared to have been shock consolidated into a contiguous phase regime bonded to aluminum grains in the nano-sized Al/SiC systems. Mechanical properties were measured from the pure Al powder reference monoliths showing that the starting Al powder had a Vickers hardness of ˜24HV 25; in contrast to pure Al explosively consolidated reference cylinders that had a residual hardness of ˜43HV25. Average Rockwell hardnesses were also compared with room temperature stress-strain data measured for tensile specimens cut from the test cylinders. The results were compared with rule-of-mixtures formalisms applied to these novel two-phase systems. Correspondingly the Rockwell hardness for 21% SiC and Al2O3 mixtures in Al increased by ˜60%, from the Al reference (single-phase) monolith; while the elongation declined by ˜60%. The prominent Al intergranular-like fracture within the 21% (volume) SiC or Al2O3 phase regime was observed by SEM. At 21% (volume) SiC a distinct 2-phase Al/SiC regime was formed with fracture occurring prominently in the SiC consolidated phase. The fracture surface features are somewhat characteristic of the signature variation in the stress-strain diagrams. The aluminum ductile-dimple fracture characteristics, the failure around the SiC particles and particle agglomerates producing the discontinuous yield-like phenomenon and the poor mechanical behavior of the nano-sized Al/SiC systems are characteristic of the significantly different fracture features.

Condensation of Forced Convection Two-Phase Flow in a Miniature Tube

NASA Technical Reports Server (NTRS)

Begg, E.; Faghri, A.; Krustalev, D.

1999-01-01

A physical/mathematical model of annular film condensation at the inlet of a miniature tube has been developed. In the model, the liquid flow is coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and leads to the conclusion that there is complete condensation at a certain distance from the condenser inlet. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads and that this is a special case of a more general condensation regime with two-phase bubbly flow downstream of the initial annular film condensation region. Observations from the flow visualization experiment confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in a small diameter (3.25 mm) circular tube condenser.

Closed Loop Two-Phase Thermosyphon of Small Dimensions: a Review of the Experimental Results

NASA Astrophysics Data System (ADS)

Franco, Alessandro; Filippeschi, Sauro

2012-06-01

A bibliographical review on the heat and mass transfer in gravity assisted Closed Loop Two Phase Thermosyphons (CLTPT) with channels having a hydraulic diameter of the order of some millimetres and input power below 1 kW is proposed. The available experimental works in the literature are critically analysed in order to highlight the main results and the correlation between mass flow rate and heat input in natural circulation loops. A comparison of different experimental apparatuses and results is made. It is observed that the results are very different among them and in many cases the experimental data disagree with the conventional theory developed for an imposed flow rate. The paper analyses the main differences among the experimental devices and try to understand these disagreements. From the present analysis it is evident that further systematic studies are required to generate a meaningful body of knowledge of the heat and mass transport mechanism in these devices for practical applications in cooling devices or energy systems.

Synthesis, surface chemistry and pseudocapacitance mechanisms of VN nanocrystals derived by a simple two-step halide approach

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

Choi, Daiwon; Jampani, Prashanth H.; Jayakody, J. R. P.

Chloroamide precursors generated via a simple two-step ammonolysis reaction of transition metal chloride in the liquid phase at room temperature were heat treated in ammonia at moderate temperature to yield nano-sized VN crystallites. Grain growth inhibited by lowering the synthesis temperature (≈400°C) yielded agglomerated powders of spherical crystallites of cubic phase of VN with particle sizes as small as 6nm in diameter. X-ray diffraction, FTIR, mass spectroscopy (MS), and nuclear magnetic resonance (NMR) spectroscopy assessed the ammonolysis and nitridation reaction of the VCl 4-NH 3 system. X-ray Rietveld refinement, the BET technique and high-resolution transmission microscopy (HRTEM), energy dispersive x-raymore » (EDX) and thermogravimetric analysis (TGA) helped assess the crystallographic and microstructural nature of the VN nanocrystals. The surface chemistry and redox reaction leading to the gravimetric pseudo-capacitance value of (≈855 F/g) measured for the VN nanocrystals was determined and validated using FTIR, XPS and cyclic voltammetry analyses.« less

Synthesis of mono-dispersed nanofluids using solution plasma

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

Heo, Yong Kang, E-mail: yk@rd.numse.nagoya-u.ac.jp; Bratescu, Maria Antoaneta, E-mail: maria@rd.numse.nagoya-u.ac.jp; Knowledge Hub Aichi, Yakusa-cho, Nagakute-ku, Toyota

2014-07-14

Small-sized and well-dispersed gold nanoparticles (NPs) for nanofluidics have been synthesized by electrical discharge in liquid environment using termed solution plasma processing (SPP). Electrons and the hydrogen radicals are reducing the gold ions to the neutral form in plasma gas phase and liquid phase, respectively. The gold NPs have the smallest diameter of 4.9 nm when the solution temperature was kept at 20 °C. Nucleation and growth theory describe the evolution of the NP diameter right after the reduction reaction in function of the system temperature, NP surface energy, dispersion energy barrier, and nucleation rate. Negative charges on the NPs surface duringmore » and after SPP generate repulsive forces among the NPs avoiding their agglomeration in solution. Increasing the average energy in the SPP determines a decrease of the zeta potential and an increase of the NPs diameter. An important enhancement of the thermal conductivity of 9.4% was measured for the synthesized nanofluids containing NPs with the smallest size.« less

Engineer Examines Cluster of Ion Engines in the Electric Propulsion Laboratory

NASA Image and Video Library

1963-01-21

New staff member Paul Margosian inspects a cluster of ion engines in the Electric Propulsion Laboratory’s 25-foot diameter vacuum tank at the National Aeronautics and Space Administration (NASA) Lewis Research Center. Lewis researchers had been studying different methods of electric rocket propulsion since the mid-1950s. Harold Kaufman created the first successful engine, the electron bombardment ion engine, in the early 1960s. These engines used electric power to create and accelerate small particles of propellant material to high exhaust velocities. Electric engines have a very small thrust, and but can operate for long periods of time. The ion engines are often clustered together to provide higher levels of thrust. The Electric Propulsion Laboratory contained two large vacuum tanks capable of simulating the space environment. The tanks were designed especially for testing ion and plasma thrusters and spacecraft. The larger 25-foot diameter tank was intended for testing electric thrusters with condensable propellants. The tank’s test compartment, seen here, was 10 feet in diameter. Margosian joined Lewis in late 1962 during a major NASA hiring phase. The Agency reorganized in 1961 and began expanding its ranks through a massive recruiting effort. Lewis personnel increased from approximately 2,700 in 1961 to over 4,800 in 1966. Margosian, who worked with Bill Kerslake in the Electromagnetic Propulsion Division’s Propulsion Systems Section, wrote eight technical reports on mercury and electron bombardment thrusters, thermoelectrostatic generators, and a high voltage insulator.

Manufacturing and characterization of Ni-free N-containing ODS austenitic alloy

NASA Astrophysics Data System (ADS)

Mori, A.; Mamiya, H.; Ohnuma, M.; Ilavsky, J.; Ohishi, K.; Woźniak, Jarosław; Olszyna, A.; Watanabe, N.; Suzuki, J.; Kitazawa, H.; Lewandowska, M.

2018-04-01

Ni-free N-containing oxide dispersion strengthened (ODS) austenitic alloys were manufactured by mechanical alloying (MA) followed by spark plasma sintering (SPS). The phase evolutions during milling under a nitrogen atmosphere and after sintering were studied by X-ray diffraction (XRD). Transmission electron microcopy (TEM) and alloy contrast variation analysis (ACV), including small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS), revealed the existence of nanoparticles with a diameter of 3-51 nm for the samples sintered at 950 °C. Sintering at 1000 °C for 5 and 15 min caused slight growth and a significant coarsening of the nanoparticles, up to 70 nm and 128 nm, respectively. The ACV analysis indicated the existence of two populations of Y2O3, ε-martensite and MnO. The dispersive X-ray spectrometry (EDS) confirmed two kinds of nanoparticles, Y2O3 and MnO. The material was characterized by superior micro-hardness, of above 500 HV0.1.

Manufacturing and characterization of Ni-free N-containing ODS austenitic alloys

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

Kowalska-Mori, A.; Mamiya, H.; Ohnuma, M.

Ni-free N-containing oxide dispersion strengthened (ODS) austenitic alloys were manufactured by mechanical alloying (MA) followed by spark plasma sintering (SPS). The phase evolutions during milling under a nitrogen atmosphere and after sintering were studied by X-ray diffraction (XRD). Transmission electron microcopy (TEM) and contrast variation analysis (ACV), including small-angle neutron scattering (SANS) and ultra-small X-ray scattering (USAXS), revealed the existence of nanoparticles with a diameter of 3-51 nm for the samples sintered at 950 ºC. Sintering at 1000 ºC for 5 and 15 min caused slight growth and a significant coarsening of the nanoparticles, up to 70 nm and 128more » nm, respectively. The ACV analysis indicated the existence of two populations of Y2O3, ε-martensite and MnO. The dispersive X-ray spectrometry (EDS) confirmed two kinds of nanoparticles, Y2O3 and MnO. The material was characterized by superior micro-hardness, of above 500 HV0.1.« less

Manufacturing and characterization of Ni-free N-containing ODS austenitic alloys

DOE PAGES

Kowalska-Mori, A.; Mamiya, H.; Ohnuma, M.; ...

2018-01-17

Ni-free N-containing oxide dispersion strengthened (ODS) austenitic alloys were manufactured by mechanical alloying (MA) followed by spark plasma sintering (SPS). The phase evolutions during milling under a nitrogen atmosphere and after sintering were studied by X-ray diffraction (XRD). Transmission electron microcopy (TEM) and contrast variation analysis (ACV), including small-angle neutron scattering (SANS) and ultra-small X-ray scattering (USAXS), revealed the existence of nanoparticles with a diameter of 3-51 nm for the samples sintered at 950 ºC. Sintering at 1000 ºC for 5 and 15 min caused slight growth and a significant coarsening of the nanoparticles, up to 70 nm and 128more » nm, respectively. The ACV analysis indicated the existence of two populations of Y2O3, ε-martensite and MnO. The dispersive X-ray spectrometry (EDS) confirmed two kinds of nanoparticles, Y2O3 and MnO. The material was characterized by superior micro-hardness, of above 500 HV0.1.« less

R1234yf vs. R134a Flow Boiling Heat Transfer Inside a 3.4 mm ID Microfin Tube

NASA Astrophysics Data System (ADS)

Diani, A.; Mancin, S.; Rossetto, L.

2014-11-01

The refrigerant charge minimization as well as the use of eco-friendly fluids can be considered two of the most important targets for these applications to cope with the new environmental challenges. This paper compares the R1234yf and R134a flow boiling heat transfer and pressure drop measurements inside a small microfin tube with internal diameter at the fin tip of 3.4 mm. This study is carried out in an experimental facility built at the Dipartimento di Ingegneria Industriale of the University of Padova especially designed to study both single and two phase heat transfer processes. The microfin tube is brazed inside a copper plate and electrically heated from the bottom. Several T -type thermocouples are inserted in the wall to measure the temperature distribution during the phase change process. In particular, the experimental measurements were carried out at constant saturation temperature of 30 °C, by varying the refrigerant mass velocity between 190 kg m-2 s-1 and 940 kg m-2 s-1, the vapour quality from 0.2 to 0.99, at different imposed heat fluxes. The two refrigerants are compared considering the values of the two-phase heat transfer coefficient and pressure drop.

Liquid-crystal panel with microdots on an electrode used to modulate optical phase profiles.

PubMed

Kishima, Koichiro; Yoshida, Naoko; Osato, Kiyoshi; Nakagawa, Nobuyoshi

2006-05-20

The optical characteristics of a liquid-crystal (LC) panel with microdots on an electrode are investigated. Although 3 mum is larger than 1 molecule of LC material, microdots with a 3 microm diameter are sufficiently small to produce a smooth index profile. We use an electrode patterned in a new way to modulate the index profile of the LC panel, which allows us to modulate the optical phase of the passing light.

Validation of geometric measurements of the left atrium and pulmonary veins for analysis of reverse structural remodeling following ablation therapy

NASA Astrophysics Data System (ADS)

Rettmann, M. E.; Holmes, D. R., III; Gunawan, M. S.; Ge, X.; Karwoski, R. A.; Breen, J. F.; Packer, D. L.; Robb, R. A.

2012-03-01

Geometric analysis of the left atrium and pulmonary veins is important for studying reverse structural remodeling following cardiac ablation therapy. It has been shown that the left atrium decreases in volume and the pulmonary vein ostia decrease in diameter following ablation therapy. Most analysis techniques, however, require laborious manual tracing of image cross-sections. Pulmonary vein diameters are typically measured at the junction between the left atrium and pulmonary veins, called the pulmonary vein ostia, with manually drawn lines on volume renderings or on image cross-sections. In this work, we describe a technique for making semi-automatic measurements of the left atrium and pulmonary vein ostial diameters from high resolution CT scans and multi-phase datasets. The left atrium and pulmonary veins are segmented from a CT volume using a 3D volume approach and cut planes are interactively positioned to separate the pulmonary veins from the body of the left atrium. The cut plane is also used to compute the pulmonary vein ostial diameter. Validation experiments are presented which demonstrate the ability to repeatedly measure left atrial volume and pulmonary vein diameters from high resolution CT scans, as well as the feasibility of this approach for analyzing dynamic, multi-phase datasets. In the high resolution CT scans the left atrial volume measurements show high repeatability with approximately 4% intra-rater repeatability and 8% inter-rater repeatability. Intra- and inter-rater repeatability for pulmonary vein diameter measurements range from approximately 2 to 4 mm. For the multi-phase CT datasets, differences in left atrial volumes between a standard slice-by-slice approach and the proposed 3D volume approach are small, with percent differences on the order of 3% to 6%.

Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities

NASA Astrophysics Data System (ADS)

Mustonen, K.; Laiho, P.; Kaskela, A.; Zhu, Z.; Reynaud, O.; Houbenov, N.; Tian, Y.; Susi, T.; Jiang, H.; Nasibulin, A. G.; Kauppinen, E. I.

2015-07-01

We present a floating catalyst synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3-4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67% to 80%. Limiting the nanotube gas phase number concentration to ˜105 cm-3 prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80% of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ω/□ at 90% transparency for 550 nm light.

Three-dimensional mid-air acoustic manipulation by ultrasonic phased arrays.

PubMed

Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

2014-01-01

The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method.

Three-Dimensional Mid-Air Acoustic Manipulation by Ultrasonic Phased Arrays

PubMed Central

Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

2014-01-01

The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method. PMID:24849371

System 6 used to make kitchen cabinet C2F blanks from small-diameter, low-grade red oak

Treesearch

Hugh W. Reynolds; Philip A. Araman; Charles J. Gatchell; Bruce G. Hansen

1983-01-01

Hardwood dimension manufacturers can make profitable use of plentiful small-diameter, low-grade timber when System 6 technology is used. We describe a System 6 plant designed to make clear-two-face (C2F) blanks for the kitchen cabinet industry. Data for plant operation are taken from a study in which red oak bolts (from a reforestation clearcut) were used to make 33-,...

Novel method to assess gastric emptying in humans: the Pellet Gastric Emptying Test

NASA Technical Reports Server (NTRS)

Choe, S. Y.; Neudeck, B. L.; Welage, L. S.; Amidon, G. E.; Barnett, J. L.; Amidon, G. L.

2001-01-01

To further validate the Pellet Gastric Emptying Test (PGET) as a marker of gastric emptying, a randomized, four-way crossover study was conducted with 12 healthy subjects. The study consisted of oral co-administration of enteric coated caffeine (CAFF) and acetaminophen (APAP) pellets in four treatment phases: Same Size (100 kcal), Fasted, Small Liquid Meal (100 kcal), and Standard Meal (847 kcal). The time of first appearance of measurable drug marker in plasma, t(initial), was taken as the emptying time for the markers. Co-administration of same size enteric coated pellets of CAFF and APAP (0.7 mm in diameter) revealed no statistically significant differences in t(initial) values indicating that emptying was dependent only on size and not on chemical make-up of the pellets. Co-administration of different size pellets indicated that the smaller 0.7-mm diameter (CAFF) pellets were emptied and absorbed significantly earlier than the larger 3.6-mm diameter (APAP) pellets with both the Small Liquid Meal (by 35 min) and the Standard Meal (by 33 min) (P<0.05). The differences in emptying of the pellets were not significant in the Fasted Phase. The results suggest that the pellet gastric emptying test could prove useful in monitoring changes in transit times in the fasted and fed states and their impact on drug absorption.

The quantitative properties of three soft X-ray flare kernels observed with the AS&E X-ray telescope on Skylab

NASA Technical Reports Server (NTRS)

Kahler, S. W.; Petrasso, R. D.; Kane, S. R.

1976-01-01

The physical parameters for the kernels of three solar X-ray flare events have been deduced using photographic data from the S-054 X-ray telescope on Skylab as the primary data source and 1-8 and 8-20 A fluxes from Solrad 9 as the secondary data source. The kernels had diameters of about 5-7 seconds of arc and in two cases electron densities at least as high as 0.3 trillion per cu cm. The lifetimes of the kernels were 5-10 min. The presence of thermal conduction during the decay phases is used to argue: (1) that kernels are entire, not small portions of, coronal loop structures, and (2) that flare heating must continue during the decay phase. We suggest a simple geometric model to explain the role of kernels in flares in which kernels are identified with emerging flux regions.

Brown rot in inner heartwood: why large logs support characteristics saproxylic beetle assemblages of conservation concern

Treesearch

Marie Yee; Simon J. Grove; Alastair M.M. Richardson; Caroline L. Mohammed

2006-01-01

It is not clear why large diameter logs generally host saproxylic beetle assemblages that are different from those of small diameter logs. In a study in Tasmanian wet eucalypt forest, two size-classes of Eucalyptus obliqua logs (>100cm and 30-60cm diameter) were destructively sampled to assess their beetle fauna and the associations of this fauna...

Modeling process of embolization arteriovenous malformation on the basis of two-phase filtration model

NASA Astrophysics Data System (ADS)

Cherevko, A. A.; Gologush, T. S.; Ostapenko, V. V.; Petrenko, I. A.; Chupakhin, A. P.

2016-06-01

Arteriovenous malformation is a chaotic disordered interlacement of very small diameter vessels, performing reset of blood from the artery into the vein. In this regard it can be adequately modeled using porous medium. In this model process of embolization described as penetration of non-adhesive substance ONYX into the porous medium, filled with blood, both of these fluids are not mixed with each other. In one-dimensional approximation such processes are well described by Buckley-Leverett equation. In this paper Buckley-Leverett equation is solved numerically by using a new modification of Cabaret scheme. The results of numerical modeling process of embolization of AVM are shown.

Rotary drum separator system

NASA Technical Reports Server (NTRS)

Barone, Michael R. (Inventor); Murdoch, Karen (Inventor); Scull, Timothy D. (Inventor); Fort, James H. (Inventor)

2009-01-01

A rotary phase separator system generally includes a step-shaped rotary drum separator (RDS) and a motor assembly. The aspect ratio of the stepped drum minimizes power for both the accumulating and pumping functions. The accumulator section of the RDS has a relatively small diameter to minimize power losses within an axial length to define significant volume for accumulation. The pumping section of the RDS has a larger diameter to increase pumping head but has a shorter axial length to minimize power losses. The motor assembly drives the RDS at a low speed for separating and accumulating and a higher speed for pumping.

Hybrid Propulsion Technology Program

NASA Technical Reports Server (NTRS)

Jensen, G. E.; Holzman, A. L.

1990-01-01

Future launch systems of the United States will require improvements in booster safety, reliability, and cost. In order to increase payload capabilities, performance improvements are also desirable. The hybrid rocket motor (HRM) offers the potential for improvements in all of these areas. The designs are presented for two sizes of hybrid boosters, a large 4.57 m (180 in.) diameter booster duplicating the Advanced Solid Rocket Motor (ASRM) vacuum thrust-time profile and smaller 2.44 m (96 in.), one-quater thrust level booster. The large booster would be used in tandem, while eight small boosters would be used to achieve the same total thrust. These preliminary designs were generated as part of the NASA Hybrid Propulsion Technology Program. This program is the first phase of an eventual three-phaes program culminating in the demonstration of a large subscale engine. The initial trade and sizing studies resulted in preferred motor diameters, operating pressures, nozzle geometry, and fuel grain systems for both the large and small boosters. The data were then used for specific performance predictions in terms of payload and the definition and selection of the requirements for the major components: the oxidizer feed system, nozzle, and thrust vector system. All of the parametric studies were performed using realistic fuel regression models based upon specific experimental data.

Ultrahigh-density sub-10 nm nanowire array formation via surface-controlled phase separation.

PubMed

Tian, Yuan; Mukherjee, Pinaki; Jayaraman, Tanjore V; Xu, Zhanping; Yu, Yongsheng; Tan, Li; Sellmyer, David J; Shield, Jeffrey E

2014-08-13

We present simple, self-assembled, and robust fabrication of ultrahigh density cobalt nanowire arrays. The binary Co-Al and Co-Si systems phase-separate during physical vapor deposition, resulting in Co nanowire arrays with average diameter as small as 4.9 nm and nanowire density on the order of 10(16)/m(2). The nanowire diameters were controlled by moderating the surface diffusivity, which affected the lateral diffusion lengths. High resolution transmission electron microscopy reveals that the Co nanowires formed in the face-centered cubic structure. Elemental mapping showed that in both systems the nanowires consisted of Co with undetectable Al or Si and that the matrix consisted of Al with no distinguishable Co in the Co-Al system and a mixture of Si and Co in the Co-Si system. Magnetic measurements clearly indicate anisotropic behavior consistent with shape anisotropy. The dynamics of nanowire growth, simulated using an Ising model, is consistent with the experimental phase and geometry of the nanowires.

Numerical investigation for one bad-behaved flow in a Pelton turbine

NASA Astrophysics Data System (ADS)

Wei, X. Z.; Yang, K.; Wang, H. J.; Gong, R. Z.; Li, D. Y.

2015-01-01

The gas-liquid two-phase flow in pelton turbines is very complicated, there are many kinds of bad-behaved flow in pelton turbines. In this paper, CFD numerical simulation for the pelton turbine was conducted using VOF two-phase model. One kind of bad-behaved flow caused by the two jets was captured, and the bad-behaved flow was analysed by torque on buckets. It can be concluded that the angle between the two jets and the value of ratio of runner diameter and jet diameter are important parameters for the bad-behaved flow. Furthermore, the reason why the efficiency of some multi-jet type turbines is very low can be well explained by the analysis of bad-behaved flow. Finally, some suggestions for improvement were also provided in present paper.

The effect of neutrally buoyant finite-size particles on channel flows in the laminar-turbulent transition regime

NASA Astrophysics Data System (ADS)

Loisel, Vincent; Abbas, Micheline; Masbernat, Olivier; Climent, Eric

2013-12-01

The presence of finite-size particles in a channel flow close to the laminar-turbulent transition is simulated with the Force Coupling Method which allows two-way coupling with the flow dynamics. Spherical particles with channel height-to-particle diameter ratio of 16 are initially randomly seeded in a fluctuating flow above the critical Reynolds number corresponding to single phase flow relaminarization. When steady-state is reached, the particle volume fraction is homogeneously distributed in the channel cross-section (ϕ ≅ 5%) except in the near-wall region where it is larger due to inertia-driven migration. Turbulence statistics (intensity of velocity fluctuations, small-scale vortical structures, wall shear stress) calculated in the fully coupled two-phase flow simulations are compared to single-phase flow data in the transition regime. It is observed that particles increase the transverse r.m.s. flow velocity fluctuations and they break down the flow coherent structures into smaller, more numerous and sustained eddies, preventing the flow to relaminarize at the single-phase critical Reynolds number. When the Reynolds number is further decreased and the suspension flow becomes laminar, the wall friction coefficient recovers the evolution of the laminar single-phase law provided that the suspension viscosity is used in the Reynolds number definition. The residual velocity fluctuations in the suspension correspond to a regime of particulate shear-induced agitation.

Experimental constraints on the outgassing dynamics of basaltic magmas

NASA Astrophysics Data System (ADS)

Pioli, L.; Bonadonna, C.; Azzopardi, B. J.; Phillips, J. C.; Ripepe, M.

2012-03-01

The dynamics of separated two-phase flow of basaltic magmas in cylindrical conduits has been explored combining large-scale experiments and theoretical studies. Experiments consisted of the continuous injection of air into water or glucose syrup in a 0.24 m diameter, 6.5 m long bubble column. The model calculates vesicularity and pressure gradient for a range of gas superficial velocities (volume flow rates/pipe area, 10-2-102 m/s), conduit diameters (100-2 m), and magma viscosities (3-300 Pa s). The model is calibrated with the experimental results to extrapolate key flow parameters such as Co (distribution parameter) and Froude number, which control the maximum vesicularity of the magma in the column, and the gas rise speed of gas slugs. It predicts that magma vesicularity increases with increasing gas volume flow rate and decreases with increasing conduit diameter, until a threshold value (45 vol.%), which characterizes churn and annular flow regimes. Transition to annular flow regimes is expected to occur at minimum gas volume flow rates of 103-104 m3/s. The vertical pressure gradient decreases with increasing gas flow rates and is controlled by magma vesicularity (in bubbly flows) or the length and spacing of gas slugs. This study also shows that until conditions for separated flow are met, increases in magma viscosity favor stability of slug flow over bubbly flow but suggests coexistence between gas slugs and small bubbles, which contribute to a small fraction of the total gas outflux. Gas flow promotes effective convection of the liquid, favoring magma homogeneity and stable conditions.

Attached cavitation at a small diameter ultrasonic horn tip

NASA Astrophysics Data System (ADS)

Žnidarčič, Anton; Mettin, Robert; Cairós, Carlos; Dular, Matevž

2014-02-01

Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids, for instance, for cell disruption or sonochemical reactions. They are operated typically in the frequency range up to about 50 kHz and have tip diameters from some mm to several cm. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e., below the acoustic driving frequency. Here, we present a systematic study of the cavitation dynamics in water at a 20 kHz horn tip of 3 mm diameter. The system was investigated by high-speed imaging with simultaneous recording of the acoustic emissions. Measurements were performed under variation of acoustic power, air saturation, viscosity, surface tension, and temperature of the liquid. Our findings show that the liquid properties play no significant role in the dynamics of the attached cavitation at the small ultrasonic horn. Also the variation of the experimental geometry, within a certain range, did not change the dynamics. We believe that the main two reasons for the peculiar dynamics of cavitation on a small ultrasonic horn are the higher energy density on a small tip and the inability of the big tip to "wash" away the gaseous bubbles. Calculation of the somewhat adapted Strouhal number revealed that, similar to the hydrodynamic cavitation, values which are relatively low characterize slow cavitation structure dynamics. In cases where the cavitation follows the driving frequency this value lies much higher - probably at Str > 20. In the spirit to distinguish the observed phenomenon with other cavitation dynamics at ultrasonic transducer surfaces, we suggest to term the observed phenomenon of attached cavities partly covering the full horn tip as "acoustic supercavitation." This reflects the conjecture that not the sound field in terms of acoustic (negative) pressure in the liquid is responsible for nucleation, but the motion of the transducer surface.

Measured Performance of a Varied Airflow Small-Diameter Duct System

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

Poerschke, Andrew

2017-03-01

This study tests the performance of a variable airflow small-diameter duct heating, ventilation, and air conditioning (HVAC) system in a new construction unoccupied low-load test house in Pittsburgh, Pennsylvania. The duct system was installed entirely in conditioned space and was operated from the winter through summer seasons. Measurements were collected on the in-room temperatures and energy consumed by the air handler and heat pump unit. Operation modes with three different volumes of airflow were compared to determine the ideal airflow scenario that maximizes room-to-room thermal uniformity while minimizing fan energy consumption. Black felt infrared imagery was used as a measuremore » of diffuser throw and in-room air mixing. Measured results indicate the small-diameter, high velocity airflow system can provide comfort under some conditions. Solar heat gains resulted in southern rooms drifting beyond acceptable temperature limits. Insufficient airflow to some bedrooms also resulted in periods of potential discomfort. Homebuilders or HVAC contractors can use these results to assess whether this space conditioning strategy is an attractive alternative to a traditional duct system. The team performed a cost analysis of two duct system configurations: (1) a conventional diameter and velocity duct system, and (2) the small-diameter duct system. This work applies to both new and retrofit homes that have achieved a low heating and cooling density either by energy conservation or by operation in a mild climate with few heating or cooling degree days. Guidance is provided on cost trade-offs between the conventional duct system and the small-diameter duct system.« less

Measured Performance of a Varied Airflow Small-Diameter Duct System

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

Poerschke, Andrew

This study tests the performance of a variable airflow small-diameter duct heating, ventilation, and air conditioning (HVAC) system in a new construction unoccupied low-load test house in Pittsburgh, Pennsylvania. The duct system was installed entirely in conditioned space and was operated from the winter through summer seasons. Measurements were collected on the in-room temperatures and energy consumed by the air handler and heat pump unit. Operation modes with three different volumes of airflow were compared to determine the ideal airflow scenario that maximizes room-to-room thermal uniformity while minimizing fan energy consumption. Black felt infrared imagery was used as a measuremore » of diffuser throw and in-room air mixing. Measured results indicate the small-diameter, high velocity airflow system can provide comfort under some conditions. Solar heat gains resulted in southern rooms drifting beyond acceptable temperature limits. Insufficient airflow to some bedrooms also resulted in periods of potential discomfort. Homebuilders or HVAC contractors can use these results to assess whether this space conditioning strategy is an attractive alternative to a traditional duct system. The team performed a cost analysis of two duct system configurations: (1) a conventional diameter and velocity duct system, and (2) the small-diameter duct system. This work applies to both new and retrofit homes that have achieved a low heating and cooling density either by energy conservation or by operation in a mild climate with few heating or cooling degree days. Guidance is provided on cost trade-offs between the conventional duct system and the small-diameter duct system.« less

Building America Case Study: High-Velocity Small-Diameter Duct System, Pittsburgh, Pennsylvania

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

A. Poerschke

This study tests the performance of a variable airflow small-diameter duct heating, ventilation, and air conditioning (HVAC) system in a new construction unoccupied low-load test house in Pittsburgh, Pennsylvania. The duct system was installed entirely in conditioned space and was operated from the winter through summer seasons. Measurements were collected on the in-room temperatures and energy consumed by the air handler and heat pump unit. Operation modes with three different volumes of airflow were compared to determine the ideal airflow scenario that maximizes room-to-room thermal uniformity while minimizing fan energy consumption. Black felt infrared imagery was used as a measuremore » of diffuser throw and in-room air mixing. Measured results indicate the small-diameter, high velocity airflow system can provide comfort under some conditions. Solar heat gains resulted in southern rooms drifting beyond acceptable temperature limits. Insufficient airflow to some bedrooms also resulted in periods of potential discomfort. Homebuilders or HVAC contractors can use these results to assess whether this space conditioning strategy is an attractive alternative to a traditional duct system. The team performed a cost analysis of two duct system configurations: (1) a conventional diameter and velocity duct system, and (2) the small-diameter duct system. This work applies to both new and retrofit homes that have achieved a low heating and cooling density either by energy conservation or by operation in a mild climate with few heating or cooling degree days. Guidance is provided on cost trade-offs between the conventional duct system and the small-diameter duct system.« less

Variable wide range of lens power and its improvement in a liquid-crystal lens using highly resistive films divided into two regions with different diameters

NASA Astrophysics Data System (ADS)

Kawamura, Marenori; Sato, Susumu

2018-05-01

The variable range of lens power of a liquid-crystal (LC) lens driven by two voltages is discussed on the basis of calculated and experimental results. The LC lens has two electrodes, which are a circularly hole-patterned electrode and a circular electrode, in addition to a common electrode, and highly resistive transparent films. The variable range of lens power increases with increasing driving voltage applied across the circularly hole-patterned electrode and the common electrode, and with decreasing diameter of highly resistive films. However, the optical-phase retardation profile tends to deviate from a parabolic curve in these cases. As a method to improve the trade-off properties, the highly resistive film is divided into two regions with different diameters, where the sheet resistance of an outer film is larger than that of an inner one. The improved LC lens has a lens power that varies in a wide range, and it exhibits a good parabolic phase retardation profile.

Stripping the Sheath From Stranded Cables

NASA Technical Reports Server (NTRS)

Prisk, A. L.; Rotta, J. W.

1985-01-01

Device similar to tubing cutter removes tough plastic cover. Insulation stripper is 3 in. (7.6 cm) long and 1.5 (3.8 cm) in diameter. Two rollers are small-diameter bearings. Cutter blade journaled for rotation between pair of similar bearings. Bearings either pin or ball types of suitable dimensions.

Origin and the mechanical properties of asbestos

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

O'Hanley, D.S.

1986-01-01

Dual networks and chemographic analysis are used to investigate the stability of lizardite and chrysotile in the simplest multisystem that describes serpentinization. Phase diagrams for Mg serpentinites described by MgO-SiO/sub 2/-H/sub 2/O are constructed for systems of five, six and seven phases using dual networks. The seven-phase system brucite, forsterite, lizardite, chrysotile, antigorite, enstatite, and talc describes the serpentinization of Mg peridotites. The chrysotile asbestos deposits of southeastern Quebec occur in serpentinized peridotites of Ordovician ophiolites. The asbestos is localized in veins within blocks of partly serpentinized peridotite bounded by zones containing schistose serpentinite and granitic masses. A simple, rapidmore » microscopic test was designed to obtain semi-quantitative measurements of the bending strength of acicular or fibrous crystals. The instrument was tested on samples of asbestiform tremolite from Baltimore, Maryland, and non-asbestiform tremolite from the Warren Head mine in New Hampshire. The samples ranged in size from 0.3 to 0.8 mm in length and 0.9 to 15 ..mu..m in diameter. The asbestiform tremolite was stronger than the non-asbestiform tremolite at every diameter, with an order of magnitude higher strength at small diameters. This indicates that asbestiform tremolite behaves as a whisker, whereas non-asbestiform tremolite does not.« less

Formation and characterization of simulated small droplet icing clouds

NASA Technical Reports Server (NTRS)

Ingebo, R. D.

1986-01-01

Two pneumatic two-fluid atomizers operating at high liquid and gas pressures produced water sprays that simulated small droplet clouds for use in studying icing effects on aircraft performance. To measure median volume diameter, MVD or D sub v.5, of small droplet water sprays, a scattered-light scanning instrument was developed. Drop size data agreed fairly well with calculated values at water and nitrogen pressures of 60 and 20 psig, respectively, and at water and nitrogen pressures of 250 and 100 psig, respectively, but not very well at intermediate values of water and nitrogen pressure. MVD data were correlated with D sub 0, W sub N, and W sub w, i.e., orifice diameter, nitrogen, and water flowrate, respectively, to give the expression for MVD in microns.

Annular ring zoom system using two positive axicons

NASA Astrophysics Data System (ADS)

Dickey, Fred M.; Conner, Jacob D.

2011-10-01

The production of an annular ring of light with a variable diameter has applications in laser material processing and machining, particle manipulation, and corneal surgery. This can readily be accomplished using a positive and negative axicon pair. However, negative axicons are very expensive and difficult to obtain with small diameters. In this paper, we present a design of an annular ring zoom system using two positive axicons. One axicon is placed a distance before a primary lens that is greater than some prescribed minimum, and the second axicon is placed after the primary lens. The position of the second axicon determines the ring diameter. The ring diameter can be zoomed from some maximum design size to a zero diameter ring (spot). Experimental results from a developmental system will be presented.

76 FR 36092 - Small Diameter Graphite Electrodes From the People's Republic of China: Extension of Time Limit...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-21

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... antidumping duty order on small diameter graphite electrodes from the People's Republic of China (``PRC'') for... preliminary results of this review were published on March 7, 2011. See Small Diameter Graphite Electrodes...

77 FR 6060 - Small Diameter Graphite Electrodes from the People's Republic of China: Extension of Time Limit...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-07

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... Department) initiated an administrative review of the antidumping duty order on small diameter graphite... preliminary results of this review by 95 days until February 3, 2012. See Small Diameter Graphite Electrodes...

Teardrop chunker performance.

Treesearch

Joseph B. Sturos

1989-01-01

Describes a new machine designed to reduce small-diameter logs into small chunks or blocks. The chunks can be used to manufacture flakeboard and composite wood products as well as for energy wood. Presents data on the physical character of chunkwood produced; production rates; and torque, power, and energy requirements for two species and two nominal chunk lengths....

Design for a Simple and Inexpensive Cylinder-within-a-Cylinder Gradient Maker for the Undergraduate Biochemistry Laboratory

ERIC Educational Resources Information Center

Sims, Paul A.; O'Mealey, Gary B.; Khan, Nabeel A.; Larabee, Chelsea M.

2011-01-01

A design for a simple and inexpensive gradient maker is described. The gradient maker is assembled by (i) cutting the tops off two plastic bottles of differing diameters to produce two cylinders with intact bottoms; (ii) drilling a small hole toward the bottom of the smaller diameter cylinder and plugging the hole with a size 00 cork stopper; and…

Shapes and dynamics of miscible liquid/liquid interfaces in horizontal capillary tubes.

PubMed

Stevar, M S P; Vorobev, A

2012-10-01

We report optical observations of the dissolution behaviour of glycerol/water, soybean oil/hexane, and isobutyric acid (IBA)/water binary mixtures within horizontal capillary tubes. Tubes with diameters as small as 0.2mm were initially filled with one component of the binary mixture (solute) and then immersed into a solvent-filled thermostatic bath. Both ends of the tubes were open, and no pressure difference was applied between the ends. In the case of glycerol/water and soybean oil/hexane mixtures, we managed to isolate the dissolution (the interfacial mass transfer) from the hydrodynamic motion. Two phase boundaries moving from the ends into the middle section of the tube with the speeds v∼D(1/3)t(-2/3)d(2) (D,t and d are the coefficient of diffusion, time and the diameter of the tube, respectively) were observed. The boundaries slowly smeared but their smearing occurred considerably slower than their motion. The motion of the phase boundaries cannot be explained by the dependency of the diffusion coefficient on concentration, and should be explained by the effect of barodiffusion. The shapes of the solute/solvent boundaries are defined by the balance between gravity and surface tension effects. The contact line moved together with the bulk interface: no visible solute remained on the walls after the interface passage. Changes in temperature and in the ratio between gravity and capillary forces altered the apparent contact angles. The IBA/water system had different behaviour. Below the critical (consolute) point, no dissolution was observed: IBA and water behaved like two immiscible liquids, with the IBA phase being displaced from the tube by capillary pressure (the spontaneous imbibition process). Above the critical point, two IBA/water interfaces could be identified, however the interfaces did not penetrate much into the tube. Copyright © 2012 Elsevier Inc. All rights reserved.

Magnetic hysteresis in small-grained CoxPd1-x nanowire arrays

NASA Astrophysics Data System (ADS)

Viqueira, M. S.; Pozo-López, G.; Urreta, S. E.; Condó, A. M.; Cornejo, D. R.; Fabietti, L. M.

2015-11-01

Co-Pd nanowires with small grain size are fabricated by AC electrodeposition into hexagonally ordered alumina pores, 20-35 nm in diameter and about 1 μm long. The effects of the alloy composition, the nanowire diameter and the grain size on the hysteresis properties are considered. X-ray diffraction indicates that the nanowires are single phase, a fcc Co-Pd solid solution; electron microscopy results show that they are polycrystalline, with randomly oriented grains (7-12 nm), smaller than the wire diameter. Nanowire arrays are ferromagnetic, with an easy magnetization axis parallel to the nanowire long axis. Both, the coercive field and the loop squareness monotonously increase with the Co content and with the grain size, but no clear correlation with the wire diameter is found. The Co and Co-rich nanowire arrays exhibit coercive fields and reduced remanence values quite insensitive to temperature in the range 4 K-300 K; on the contrary, in Pd-rich nanowires both magnitudes are smaller and they largely increase during cooling below 100 K. These behaviors are systematized by considering the strong dependences displayed by the magneto-crystalline anisotropy and the saturation magnetostriction on composition and temperature. At low temperatures the effective anisotropy value and the domain-wall width to grain size ratio drastically change, promoting less cooperative and harder nucleation modes.

Numerical and analytical simulation of the production process of ZrO2 hollow particles

NASA Astrophysics Data System (ADS)

Safaei, Hadi; Emami, Mohsen Davazdah

2017-12-01

In this paper, the production process of hollow particles from the agglomerated particles is addressed analytically and numerically. The important parameters affecting this process, in particular, the initial porosity level of particles and the plasma gun types are investigated. The analytical model adopts a combination of quasi-steady thermal equilibrium and mechanical balance. In the analytical model, the possibility of a solid core existing in agglomerated particles is examined. In this model, a range of particle diameters (50μm ≤ D_{p0} ≤ 160 μ m) and various initial porosities ( 0.2 ≤ p ≤ 0.7) are considered. The numerical model employs the VOF technique for two-phase compressible flows. The production process of hollow particles from the agglomerated particles is simulated, considering an initial diameter of D_{p0} = 60 μm and initial porosity of p = 0.3, p = 0.5, and p = 0.7. Simulation results of the analytical model indicate that the solid core diameter is independent of the initial porosity, whereas the thickness of the particle shell strongly depends on the initial porosity. In both models, a hollow particle may hardly develop at small initial porosity values ( p < 0.3), while the particle disintegrates at high initial porosity values ( p > 0.6.

A New 4D Imaging Method for Three-Phase Analogue Experiments in Volcanology (and Other Three-Phase Systems)

NASA Astrophysics Data System (ADS)

Oppenheimer, J.; Patel, K. B.; Lev, E.; Hillman, E. M. C.

2017-12-01

Bubbles and crystals suspended in magmas interact with each other on a small scale, which affects large-scale volcanic processes. Studying these interactions on relevant scales of time and space is a long-standing challenge. Therefore, the fundamental explanations for the behavior of bubble- and crystal-rich magmas are still largely speculative. Recent application of X-ray tomography to experiments with synthetic magmas has already improved our understanding of small-scale 4D (3D + time) phenomena. However, this technique has low imaging rates < 20 volumes per second (vps) and does not work well with analogues, making experiments costly and slow. We demonstrate a novel methodology for imaging bubble-particle interactions in analogue suspensions by utilizing Swept Confocally Aligned Planar Excitation (SCAPE) microscopy. This method based on laser-fluorescence has been used to image live biological processes at high speed and in 3D. It allows imaging rates of up to several hundred vps and image volumes up to 1 x 1 x 0.5 mm3, with a trade-off between speed and spatial resolution. We ran two sets of experiments with silicone oil and soda-lime glass beads of <50 µm diameter, contained within a vertical glass casing 50 x 5 x 4 mm3. We used two different bubble generation methods. In the first set of experiments, small air bubbles (< 1 mm) were introduced through a hole at the bottom of the sample and allowed to rise through a suspension with low-viscosity oil. We successfully imaged bubble rise and particle movements around the bubble. In the second set, bubbles were generated by mixing acetone into the suspension and decreasing the surface pressure to cause a phase change to gaseous acetone. This bubble generation method compared favorably with previous gum rosin-acetone experiments: they provided similar degassing behaviors, along with more control on suspension viscosity and optimal optical properties for laser transmission. Large volumes of suspended bubbles, however, interfered with the laser path. In this set, we were able to track bubble nucleation sites and nucleation rates in 4D. This promising technique allows the study of small-scale interactions in two- and three-phase systems, at high imaging rates and at low cost.

Innovative grinding wheel design for cost-effective machining of advanced ceramics

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

Licht, R.H.; Kuo, P.; Liu, S.

2000-05-01

This Final Report covers the Phase II Innovative Grinding Wheel (IGW) program in which Norton Company successfully developed a novel grinding wheel for cost-effective cylindrical grinding of advanced ceramics. In 1995, Norton Company successfully completed the 16-month Phase I technical effort to define requirements, design, develop, and evaluate a next-generation grinding wheel for cost-effective cylindrical grinding of advanced ceramics using small prototype wheels. The Phase II program was initiated to scale-up the new superabrasive wheel specification to larger diameters, 305-mm to 406-mm, required for most production grinding of cylindrical ceramic parts, and to perform in-house and independent validation grinding tests.

A Tissue-Mimicking Ultrasound Test Object Using Droplet Vaporization to Create Point Targets

PubMed Central

Carneal, Catherine M.; Kripfgans, Oliver D.; Krücker, Jochen; Carson, Paul L.; Fowlkes, J. Brian

2012-01-01

Ultrasound test objects containing reference point targets could be useful for evaluating ultrasound systems and phase aberration correction methods. Polyacrylamide gels containing albumin-stabilized droplets (3.6 µm mean diameter) of dodecafluoropentane (DDFP) are being developed for this purpose. Perturbation by ultrasound causes spontaneous vaporization of the superheated droplets to form gas bubbles, a process termed acoustic droplet vaporization (ADV). The resulting bubbles (20 to 160 µm diameter) are small compared with acoustic wavelengths in diagnostic ultrasound and are theoretically suitable for use as point targets (phase errors <20° for typical f-numbers). Bubbles distributed throughout the material are convenient for determining the point spread function in an imaging plane or volume. Cooling the gel causes condensation of the DDFP droplets, which may be useful for storage. Studying ADV in such viscoelastic media could provide insight into potential bioeffects from rapid bubble formation. PMID:21937339

A refined 'standard' thermal model for asteroids based on observations of 1 Ceres and 2 Pallas

NASA Technical Reports Server (NTRS)

Lebofsky, Larry A.; Sykes, Mark V.; Tedesco, Edward F.; Veeder, Glenn J.; Matson, Dennis L.

1986-01-01

An analysis of ground-based thermal IR observations of 1 Ceres and 2 Pallas in light of their recently determined occultation diameters and small amplitude light curves has yielded a new value for the IR beaming parameter employed in the standard asteroid thermal emission model which is significantly lower than the previous one. When applied to the reduction of thermal IR observations of other asteroids, this new value is expected to yield model diameters closer to actual values. The present formulation incorporates the IAU magnitude convention for asteroids that employs zero-phase magnitudes, including the opposition effect.

Segmentation of hepatic artery in multi-phase liver CT using directional dilation and connectivity analysis

NASA Astrophysics Data System (ADS)

Wang, Lei; Schnurr, Alena-Kathrin; Zidowitz, Stephan; Georgii, Joachim; Zhao, Yue; Razavi, Mohammad; Schwier, Michael; Hahn, Horst K.; Hansen, Christian

2016-03-01

Segmentation of hepatic arteries in multi-phase computed tomography (CT) images is indispensable in liver surgery planning. During image acquisition, the hepatic artery is enhanced by the injection of contrast agent. The enhanced signals are often not stably acquired due to non-optimal contrast timing. Other vascular structure, such as hepatic vein or portal vein, can be enhanced as well in the arterial phase, which can adversely affect the segmentation results. Furthermore, the arteries might suffer from partial volume effects due to their small diameter. To overcome these difficulties, we propose a framework for robust hepatic artery segmentation requiring a minimal amount of user interaction. First, an efficient multi-scale Hessian-based vesselness filter is applied on the artery phase CT image, aiming to enhance vessel structures with specified diameter range. Second, the vesselness response is processed using a Bayesian classifier to identify the most probable vessel structures. Considering the vesselness filter normally performs not ideally on the vessel bifurcations or the segments corrupted by noise, two vessel-reconnection techniques are proposed. The first technique uses a directional morphological operator to dilate vessel segments along their centerline directions, attempting to fill the gap between broken vascular segments. The second technique analyzes the connectivity of vessel segments and reconnects disconnected segments and branches. Finally, a 3D vessel tree is reconstructed. The algorithm has been evaluated using 18 CT images of the liver. To quantitatively measure the similarities between segmented and reference vessel trees, the skeleton coverage and mean symmetric distance are calculated to quantify the agreement between reference and segmented vessel skeletons, resulting in an average of 0:55+/-0:27 and 12:7+/-7:9 mm (mean standard deviation), respectively.

Understanding the breathing phenomena in nano-ZIF-7 upon gas adsorption

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

Cuadrado-Collados, Carlos; Fernández-Català, Javier; Fauth, François

For this research, synchrotron X-ray diffraction and inelastic neutron scattering measurements have been applied to evaluate the breathing phenomena in small nanocrystals of ZIF-7 upon gas adsorption. The experimental results show that an extended solvent exchange process with methanol is crucial to get a solvent-free narrow pore structure. Under these conditions, nano-ZIF-7 is indeed able to adsorb N 2 with a total BET surface area of around 380 m 2 g -1, in close agreement with theoretical predictions. The breathing phenomenon upon nitrogen adsorption is accompanied by a phase-to-phase transition, from a narrow-pore (phase II) to a large-pore (phase I)more » structure and a suppression of the cooperative deformation of the framework involving mainly the flapping motion of the benzimidazolate (bIm) ligand with the 4- and 6-membered rings. Whereas nitrogen requires temperature and pressure conditions close to condensation (close to 1 bar and 77 K) to induce the breathing in ZIF-7, CO 2 can do it under milder conditions (at room temperature and low relative pressures). These results reflect that the nature of the adsorptive probe and the gas–framework interactions, rather than the molecular diameter and/or shape, play a crucial role in defining the pressure and temperature conditions required to induce the breathing. Lastly, the presence of two different cavities in ZIF-7 as suggested by theoretical predictions, one with a window diameter of below 0.4 nm (cavity A) and the other with a pore size of around 0.6 nm (cavity B), has been confirmed experimentally using immersion calorimetry.« less

Understanding the breathing phenomena in nano-ZIF-7 upon gas adsorption

DOE PAGES

Cuadrado-Collados, Carlos; Fernández-Català, Javier; Fauth, François; ...

2017-09-11

For this research, synchrotron X-ray diffraction and inelastic neutron scattering measurements have been applied to evaluate the breathing phenomena in small nanocrystals of ZIF-7 upon gas adsorption. The experimental results show that an extended solvent exchange process with methanol is crucial to get a solvent-free narrow pore structure. Under these conditions, nano-ZIF-7 is indeed able to adsorb N 2 with a total BET surface area of around 380 m 2 g -1, in close agreement with theoretical predictions. The breathing phenomenon upon nitrogen adsorption is accompanied by a phase-to-phase transition, from a narrow-pore (phase II) to a large-pore (phase I)more » structure and a suppression of the cooperative deformation of the framework involving mainly the flapping motion of the benzimidazolate (bIm) ligand with the 4- and 6-membered rings. Whereas nitrogen requires temperature and pressure conditions close to condensation (close to 1 bar and 77 K) to induce the breathing in ZIF-7, CO 2 can do it under milder conditions (at room temperature and low relative pressures). These results reflect that the nature of the adsorptive probe and the gas–framework interactions, rather than the molecular diameter and/or shape, play a crucial role in defining the pressure and temperature conditions required to induce the breathing. Lastly, the presence of two different cavities in ZIF-7 as suggested by theoretical predictions, one with a window diameter of below 0.4 nm (cavity A) and the other with a pore size of around 0.6 nm (cavity B), has been confirmed experimentally using immersion calorimetry.« less

Structural characterization and gas reactions of small metal particles by high resolution in-situ TEM (Transmission Electron Microscopy) and TED (Transmission Electron Diffraction)

NASA Technical Reports Server (NTRS)

Heinemann, K.

1987-01-01

The detection and size analysis of small metal particles supported on amorphous substrates becomes increasingly difficult when the particle size approaches that of the phase contrast background structures of the support. An approach of digital image analysis, involving Fourier transformation of the original image, filtering, and image reconstruction was studied with respect to the likelihood of unambiguously detecting particles of less than 1 nm diameter on amorphous substrates from a single electron micrograph.

Mesoscopic effect of spectral modulation for the light transmitted by a SNOM tip

NASA Astrophysics Data System (ADS)

Rähn, M.; Pärs, M.; Palm, V.; Jaaniso, R.; Hizhnyakov, V.

2010-06-01

The effect of a tapered metal-coated optical fiber terminated by a sub-wavelength aperture (SWA) on the spectrum of the transmitted light is investigated experimentally. Under certain conditions a remarkable spectral modulation of the transmitted light can be observed. This effect is of a mesoscopic origin, occurring only for a certain interval of SWA diameters. One can conclude that a noticeable modulation appears when the number of the transmitted fiber modes is small but exceeds unity, thus indicating the presence of a phase shift between different modes. To discern between two possible sources of such phase shift, the fiber length dependence of the output spectrum has been studied. According to the results obtained for the used sample of 200 nm SNOM tip, the observed phase shift is mostly caused rather by the inherent modal dispersion of the multimode fiber than by the mode-dependent light slowdown in the tapered region close to SWA due to the coupling to surface plasmons of the metal coating. The SWA acts here mainly as an effective mode filter.

Oxidation of High-temperature Alloy Wires in Dry Oxygen and Water Vapor

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Lorincz, Jonathan A.; DeMange, Jeffrey J.

2004-01-01

Small diameter wires (150 to 250 microns) of the high temperature alloys Haynes 188, Haynes 230, Haynes 230, Haynes 214, Kanthal Al and PM2000 were oxidized at 1204 C in dry oxygen or 50% H2O /50% O2 for 70 Hours. The oxidation kinetics were monitored using a thermogravimetric technique. Oxide phase composition and morphology of the oxidized wires were determined by X-ray diffraction,field emission scanning electron microscopy, and energy dispersive spectroscopy. The alumina-forming alloys, Kanthal Al and PM2000, out-performed the chromia-forming alloys under this conditions. PM2000 was recommended as the most promising candidate for advanced hybrid seal applications for space reentry control surface seals or hypersonic propulsion system seals. This study also demonstrated that thermogravimetric analysis of small diameter wires is a powerful technique for the study of oxide volatility, oxide adherence, and breakaway oxidation.

Interfacial Thickness Guidelines for SiC(Fiber)/SiC(Matrix) Composites

NASA Technical Reports Server (NTRS)

Hurst, Janet B.

1998-01-01

Researchers at the NASA Lewis Research Center have developed a guideline for the interface thickness necessary for SiC(Fiber)/SiC(Matrix) composites to demonstrate good composite properties. These composite materials have potential commercial applications for high-temperature structural components such as engine hot sections. Several samples of each were composed from three different small-diameter (less than 20 mm), polymer-derived SiC fibers that were woven into two-dimensional cloths and laid up as preforms. The preforms were treated with a chemical-vapor-infiltrated boron nitride layer as an interfacial coating on the fiber surfaces to provide the necessary debonding characteristics for successful composite behavior. Then, the preforms were filled with additional SiC as a matrix phase.

Preparation and features of polycaprolactone vascular grafts with the incorporated vascular endothelial growth factor

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

Sevostyanova, V. V., E-mail: sevostyanova.victoria@gmail.com; Khodyrevskaya, Y. I.; Glushkova, T. V.

The development of tissue-engineered small-diameter vascular grafts is an urgent issue in cardiovascular surgery. In this study, we assessed how the incorporation of the vascular endothelial growth factor (VEGF) affects morphological and mechanical properties of polycaprolactone (PCL) vascular grafts along with its release kinetics. Vascular grafts were prepared using two-phase electrospinning. In pursuing our aims, we performed scanning electron microscopy, mechanical testing, and enzyme-linked immunosorbent assay. Our results demonstrated the preservation of a highly porous structure and improvement of PCL/VEGF scaffold mechanical properties as compared to PCL grafts. A prolonged VEGF release testifies the use of this construct as amore » scaffold for tissue-engineered vascular grafts.« less

Pulsed plasma chemical synthesis of carbon-containing titanium and silicon oxide based nanocomposite

NASA Astrophysics Data System (ADS)

Kholodnaya, Galina; Sazonov, Roman; Ponomarev, Denis; Zhirkov, Igor

2018-03-01

The paper presents the results of the experimental investigation of the physical and chemical properties of the TixSiyCzOw composite nanopowders, which were first obtained using a pulsed plasma chemical method. The pulsed plasma chemical synthesis was achieved using a technological electron accelerator (TEA-500). The parameters of the electron beam are as follows: 400-450 keV electron energy, 60 ns half-amplitude pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. The main physical and chemical properties of the obtained composites were studied (morphology, chemical, elemental and phase composition). The morphology of the TixSiyCzOw composites is multiform. There are large round particles, with an average size of above 150 nm. Besides, there are small particles (an average size is in the range of 15-40 nm). The morphology of small particles is in the form of crystallites. In the TixSiyCzOw synthesised composite, the peak with a maximum of 946 cm-1 was registered. The presence of IR radiation in this region of the spectrum is typical for the deformation of atomic oscillations in the Si‒О‒Ti bond, which indicates the formation of the solid solution. The composites consist of two crystal phases - anatase and rutile. The prevailing phase of the crystal structure is rutile.

Localized compliance of small airways in excised rat lungs using microfocal X-ray computed tomography.

PubMed

Sera, Toshihiro; Fujioka, Hideki; Yokota, Hideo; Makinouchi, Akitake; Himeno, Ryutaro; Schroter, Robert C; Tanishita, Kazuo

2004-05-01

Airway compliance is a key factor in understanding lung mechanics and is used as a clinical diagnostic index. Understanding such mechanics in small airways physiologically and clinically is critical. We have determined the "morphometric change" and "localized compliance" of small airways under "near"-physiological conditions; namely, the airways were embedded in parenchyma without dehydration and fixation. Previously, we developed a two-step method to visualize small airways in detail by staining the lung tissue with a radiopaque solution and then visualizing the tissue with a cone-beam microfocal X-ray computed tomography system (Sera et al. J Biomech 36: 1587-1594, 2003). In this study, we used this technique to analyze changes in diameter and length of the same small airways ( approximately 150 microm ID) and then evaluated the localized compliance as a function of airway generation (Z). For smaller (<300-microm-diameter) airways, diameter was 36% larger at end-tidal inspiration and 89% larger at total lung capacity; length was 18% larger at end-tidal inspiration and 43% larger at total lung capacity than at functional residual capacity. Diameter, especially at smaller airways, did not behave linearly with V(1/3) (where V is volume). With increasing lung pressure, diameter changed dramatically at a particular pressure and length changed approximately linearly during inflation and deflation. Percentage of airway volume for smaller airways did not behave linearly with that of lung volume. Smaller airways were generally more compliant than larger airways with increasing Z and exhibited hysteresis in their diameter behavior. Airways at higher Z deformed at a lower pressure than those at lower Z. These results indicated that smaller airways did not behave homogeneously.

Expander for Thin-Wall Tubing

NASA Technical Reports Server (NTRS)

Pessin, R.

1983-01-01

Tool locally expands small-diameter tubes. Tube expander locally expands and deforms tube: Compressive lateral stress induced in elastomeric sleeve by squeezing axially between two metal tool parts. Adaptable to situations in which tube must have small bulge for mechanical support or flow control.

Comparative Cooling Season Performance of Air Distribution Systems in Multistory Townhomes

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

A. Poerschke; Beach, R.; Beggs, T.

2016-08-26

IBACOS investigated the performance of a small-diameter high velocity heat pump system compared to a conventional system in a new construction triplex townhouse. A ductless heat pump system also was installed for comparison, but the homebuyer backed out because of aesthetic concerns about that system. In total, two buildings, having identical solar orientation and comprised of six townhomes, were monitored for comfort and energy performance. Results show that the small-diameter system provides more uniform temperatures from floor to floor in the three-story townhome. No clear energy consumption benefit was observed from either system. The builder is continuing to explore themore » small-diameter system as its new standard system to provide better comfort and indoor air quality. The homebuilder also explored the possibility of shifting its townhome product to meet the U.S. Department of Energy Challenge Home National Program Requirements.« less

Evaluation of the approach based on the concept of hyperbolicity breaking for prediction of flooding velocity of both room temperature and cryogenic fluids

NASA Astrophysics Data System (ADS)

Zhou, Rui; Yu, Liu; Xie, Huangjun; Qiu, Limin; Zhi, Xiaoqin; Zhang, Xiaobin

2018-07-01

The theoretical approach for the prediction of flooding velocity based on the concept of hyperbolicity breaking was evaluated in the counter-current two-phase flow. Detailed mathematical derivations of neutral stability condition together with the correlation of the void fraction are presented. The flooding velocity is obtained by assuming that the wavelength at flooding is proportional to the wavelength of the fastest-growing wave at Helmholtz instability. Some available experimental data for different fluid pair flow in inclined tubes is adopted for comparison with the theoretical calculations, which includes the data of water/air, aqueous oleic acid natrium solution/air, Aq. butanol 2%/air and kerosene/air in the published papers, as well as the liquid nitrogen/vapor nitrogen by the present authors. The comparison of flooding velocity proves that the approach can predict the flooding velocity with accepted accuracy for the water/air and liquid nitrogen/vapor nitrogen flow if the tube diameter is greater than 9 mm. While the diameter is smaller than 9 mm, regardless of the inclinations and the fluid pairs, the error becomes larger relative to the cases of diameter larger than 9 mm. The calculations for small diameter cases also fail to predict the critical liquid velocity at which the flooding velocity of gas reaches the maximum value, as revealed by the experiments. The reasons for the increased errors were qualitatively explained.

Particle shape-controlled sorting and transport behaviour of mixed siliciclastic/bioclastic sediments in a mesotidal lagoon, South Africa

NASA Astrophysics Data System (ADS)

Flemming, Burghard W.

2017-08-01

This study investigates the effect of particle shape on the transport and deposition of mixed siliciclastic-bioclastic sediments in the lower mesotidal Langebaan Lagoon along the South Atlantic coast of South Africa. As the two sediment components have undergone mutual sorting for the last 7 ka, they can be expected to have reached a highest possible degree of hydraulic equivalence. A comparison of sieve and settling tube data shows that, with progressive coarsening of the size fractions, the mean diameters of individual sediment components increasingly depart from the spherical quartz standard, the experimental data demonstrating the hydraulic incompatibility of the sieve data. Overall, the spatial distribution patterns of textural parameters (mean settling diameter, sorting and skewness) of the siliciclastic and bioclastic sediment components are very similar. Bivariate plots between them reveal linear trends when averaged over small intervals. A systematic deviation is observed in sorting, the trend ranging from uniformity at poorer sorting levels to a progressively increasing lag of the bioclastic component relative to the siliciclastic one as overall sorting improves. The deviation amounts to 0.8 relative sorting units at the optimal sorting level. The small textural differences between the two components are considered to reflect the influence of particle shape, which prevents the bioclastic fraction from achieving complete textural equivalence with the siliciclastic one. This is also reflected in the inferred transport behaviour of the two shape components, the bioclastic fraction moving closer to the bed than the siliciclastic one because of the higher drag experienced by low shape factor particles. As a consequence, the bed-phase development of bioclastic sediments departs significantly from that of siliciclastic sediments. Systematic flume experiments, however, are currently still lacking.

The CETAC ADX-500 Autodiluter System: A Study of Dilution Performance with the ELAN 6000 ICP-MS and ELAN Software

USGS Publications Warehouse

May, T.W.; Wiedmeyer, Ray H.

1998-01-01

The CETAC ADX-500 autodiluter system was tested with ELAN?? v 2.1 software and the ELAN 6000 ICP-MS instrument to determine on-line automated dilution performance during analysis of standard solutions containing nine analytes representative of the mass spectral range (mass 9 to mass 238). Two or more dilution schemes were tested for each of 5 test tube designs. Dilution performance was determined by comparison of analyte concentration means of diluted and non-diluted standards. Accurate dilutions resulted with one syringe pump addition of diluent in small diameter round-bottomed (13 mm OD) or conical-tipped (18 mm OD) tubes and one or more syringe pump additions in large diameter (28 mm OD) conical-tipped tubes. Inadequate dilution mixing which produced high analyte concentration means was observed for all dilutions conducted in flat-bottomed tubes, and for dilutions requiring multiple syringe additions of diluent in small diameter round-bottomed and conical tipped tubes. Effective mixing of diluted solutions was found to depend largely upon tube diameter and liquid depth: smaller tube diameters and greater liquid depth resulted in ineffective mixing, whereas greater tube diameter and shallower liquid depth facilitated effective mixing. Two design changes for the autodiluter were suggested that would allow effective mixing to occur using any dilution scheme and tube design.

Topographical distribution and morphology of NADPH-diaphorase-stained neurons in the human claustrum

PubMed Central

Hinova-Palova, Dimka V.; Edelstein, Lawrence; Landzhov, Boycho; Minkov, Minko; Malinova, Lina; Hristov, Stanislav; Denaro, Frank J.; Alexandrov, Alexandar; Kiriakova, Teodora; Brainova, Ilina; Paloff, Adrian; Ovtscharoff, Wladimir

2014-01-01

We studied the topographical distribution and morphological characteristics of NADPH-diaphorase-positive neurons and fibers in the human claustrum. These neurons were seen to be heterogeneously distributed throughout the claustrum. Taking into account the size and shape of stained perikarya as well as dendritic and axonal characteristics, Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHd)-positive neurons were categorized by diameter into three types: large, medium and small. Large neurons ranged from 25 to 35 μm in diameter and typically displayed elliptical or multipolar cell bodies. Medium neurons ranged from 20 to 25 μm in diameter and displayed multipolar, bipolar and irregular cell bodies. Small neurons ranged from 14 to 20 μm in diameter and most often displayed oval or elliptical cell bodies. Based on dendritic characteristics, these neurons were divided into spiny and aspiny subtypes. Our findings reveal two populations of NADPHd-positive neurons in the human claustrum—one comprised of large and medium cells consistent with a projection neuron phenotype, the other represented by small cells resembling the interneuron phenotype as defined by previous Golgi impregnation studies. PMID:24904317

Mouse blood vessel imaging by in-line x-ray phase-contrast imaging

NASA Astrophysics Data System (ADS)

Zhang, Xi; Liu, Xiao-Song; Yang, Xin-Rong; Chen, Shao-Liang; Zhu, Pei-Ping; Yuan, Qing-Xi

2008-10-01

It is virtually impossible to observe blood vessels by conventional x-ray imaging techniques without using contrast agents. In addition, such x-ray systems are typically incapable of detecting vessels with diameters less than 200 µm. Here we show that vessels as small as 30 µm could be detected using in-line phase-contrast x-ray imaging without the use of contrast agents. Image quality was greatly improved by replacing resident blood with physiological saline. Furthermore, an entire branch of the portal vein from the main axial portal vein to the eighth generation of branching could be captured in a single phase-contrast image. Prior to our work, detection of 30 µm diameter blood vessels could only be achieved using x-ray interferometry, which requires sophisticated x-ray optics. Our results thus demonstrate that in-line phase-contrast x-ray imaging, using physiological saline as a contrast agent, provides an alternative to the interferometric method that can be much more easily implemented and also offers the advantage of a larger field of view. A possible application of this methodology is in animal tumor models, where it can be used to observe tumor angiogenesis and the treatment effects of antineoplastic agents.

High pressure fiber optic sensor system

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

Guida, Renato; Xia, Hua; Lee, Boon K

2013-11-26

The present application provides a fiber optic sensor system. The fiber optic sensor system may include a small diameter bellows, a large diameter bellows, and a fiber optic pressure sensor attached to the small diameter bellows. Contraction of the large diameter bellows under an applied pressure may cause the small diameter bellows to expand such that the fiber optic pressure sensor may measure the applied pressure.

Two phase microstructure for Ag-Ni nanowires

NASA Astrophysics Data System (ADS)

Srivastava, Chandan; Rai, Rajesh Kumar

2013-03-01

In the present study, electrodeposition technique was used to produce Ag-Ni nanowires. Ag-Ni system shows extremely high bulk immiscibility. Nanowire morphology was achieved by employing an anodic alumina membrane having pores of ˜200 nm diameter. Microstructure of as-deposited wire was composed of nano-sized solid solution structured Ag-Ni nanoparticles embedded in a matrix of pure Ag phase. It is proposed that the two phase microstructure resulted from an initial formation of solid solution structured nanoparticles in the alumina template pore followed by nucleation of pure Ag phase over the particles which eventually grew to form the matrix phase.

Evaluation of stability and size distribution of sunflower oil-coated micro bubbles for localized drug delivery.

PubMed

Filho, Walter Duarte de Araujo; Schneider, Fábio Kurt; Morales, Rigoberto E M

2012-09-20

Micro bubbles were initially introduced as contrast agents for ultrasound examinations as they are able to modify the signal-to-noise ratio in imaging, thus improving the assessment of clinical information on human tissue. Recent developments have demonstrated the feasibility of using these bubbles as drug carriers in localized delivery. In micro fluidics devices for generation of micro bubbles, the bubbles are formed at interface of liquid gas through a strangulation process. A device that uses these features can produce micro bubbles with small size dispersion in a single step. A T-junction micro fluidic device constructed using 3D prototyping was made for the production of mono dispersed micro bubbles. These micro bubbles use sunflower oil as a lipid layer. Stability studies for micro bubbles with diameters different generated from a liquid phase of the same viscosity were conducted to evaluate whether micro bubbles can be used as drug carriers. The biocompatibility of coating layer, the ability to withstand environmental pressure variations combined with echogenicity, are key factors that they can safely play the role of drug transporters. The normal distribution curve with small dispersion of the diameter of bubbles validates the process of generating micro bubbles with low value of variation coefficient, i.e., 0.381 at 1.90%. The results also showed the feasibility of using sunflower oil as the lipid matrix with stable population of bubbles over 217 minutes for micro bubbles with an average diameter of 313.04 μm and 121 minutes for micro bubbles with an average diameter of 73.74 μm, considering bubbles with air as gaseous phase. The results indicate that the micro fluidic device designed can be used for producing micro bubbles with low variation coefficient using sunflower oil as a coating of micro bubbles. These carriers were stable for periods of time that are long enough for clinical applications even when regular air is used as the gas phase. Improved stability can be achieved when biocompatible gas with lower permeability is used.

Breakdown of Shape Memory Effect in Bent Cu-Al-Ni Nanopillars: When Twin Boundaries Become Stacking Faults.

PubMed

Liu, Lifeng; Ding, Xiangdong; Sun, Jun; Li, Suzhi; Salje, Ekhard K H

2016-01-13

Bent Cu-Al-Ni nanopillars (diameters 90-750 nm) show a shape memory effect, SME, for diameters D > 300 nm. The SME and the associated twinning are located in a small deformed section of the nanopillar. Thick nanopillars (D > 300 nm) transform to austenite under heating, including the deformed region. Thin nanopillars (D < 130 nm) do not twin but generate highly disordered sequences of stacking faults in the deformed region. No SME occurs and heating converts only the undeformed regions into austenite. The defect-rich, deformed region remains in the martensite phase even after prolonged heating in the stability field of austenite. A complex mixture of twins and stacking faults was found for diameters 130 nm < D < 300 nm. The size effect of the SME in Cu-Al-Ni nanopillars consists of an approximately linear reduction of the SME between 300 and 130 nm when the SME completely vanishes for smaller diameters.

Dominant height-based height-diameter equations for trees in southern Indiana

Treesearch

John A., Jr. Kershaw; Robert C. Morrissey; Douglass F. Jacobs; John R. Seifert; James B. McCarter

2008-01-01

Height-diameter equations are developed based on dominant tree data collected in 1986 in 8- to 17-year-old clearcuts and the phase 2 Forest Inventory and Analysis plots on the Hoosier National Forest in south central Indiana. Two equation forms are explored: the basic, three-parameter Chapman-Richards function, and a modification of the three-parameter equation...

Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments.

PubMed

Zhang, Yan; Inouye, Hideyo; Yang, Lin; Himmel, Michael E; Tucker, Melvin; Makowski, Lee

Cellulose is an attractive candidate as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose at two distinct length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. These results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.

Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments

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

Zhang, Yan; Inouye, Hideyo; Yang, Lin

2015-02-28

Cellulose can work as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose at two distinctmore » length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. Our results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.« less

Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments

DOE PAGES

Zhang, Yan; Inouye, Hideyo; Yang, Lin; ...

2015-02-28

Cellulose is an attractive candidate as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose atmore » two distinct length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. Lastly, these results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.« less

Experimental strategies for imaging bioparticles with femtosecond hard X-ray pulses

DOE PAGES

Daurer, Benedikt J.; Okamoto, Kenta; Bielecki, Johan; ...

2017-04-07

This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. AerosolizedOmono River virusparticles of ~40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles. The results point to amore » wider than expected size distribution (from ~35 to ~300 nm in diameter). This is likely to be owing to nonvolatile contaminants from larger droplets during aerosolization and droplet evaporation. The results suggest that the concentration of nonvolatile contaminants and the ratio between the volumes of the initial droplet and the sample particles is critical in such studies. The maximum beam intensity in the focus was found to be 1.9 × 10 12photons per µm 2per pulse. The full-width of the focus at half-maximum was estimated to be 500 nm (assuming 20% beamline transmission), and this width is larger than expected. Under these conditions, the diffraction signal from a sample-sized particle remained above the average background to a resolution of 4.25 nm. Finally, the results suggest that reducing the size of the initial droplets during aerosolization is necessary to bring small particles into the scope of detailed structural studies with X-ray lasers.« less

Measurements and predictions of a liquid spray from an air-assist nozzle

NASA Technical Reports Server (NTRS)

Bulzan, Daniel L.; Levy, Yeshayahou; Aggarwal, Suresh K.; Chitre, Susheel

1991-01-01

Droplet size and gas velocity were measured in a water spray using a two-component Phase/Doppler Particle Analyzer. A complete set of measurements was obtained at axial locations from 5 to 50 cm downstream of the nozzle. The nozzle used was a simple axisymmetric air-assist nozzle. The sprays produced, using the atomizer, were extremely fine. Sauter mean diameters were less than 20 microns at all locations. Measurements were obtained for droplets ranging from 1 to 50 microns. The gas phase was seeded with micron sized droplets, and droplets having diameters of 1.4 microns and less were used to represent gas-phase properties. Measurements were compared with predictions from a multi-phase computer model. Initial conditions for the model were taken from measurements at 5 cm downstream. Predictions for both the gas phase and the droplets showed relatively good agreement with the measurements.

Binary nanoparticle superlattices of soft-particle systems

DOE PAGES

Travesset, Alex

2015-08-04

The solid-phase diagram of binary systems consisting of particles of diameter σ A=σ and σ B=γσ (γ≤1) interacting with an inverse p = 12 power law is investigated as a paradigm of a soft potential. In addition to the diameter ratio γ that characterizes hard-sphere models, the phase diagram is a function of an additional parameter that controls the relative interaction strength between the different particle types. Phase diagrams are determined from extremes of thermodynamic functions by considering 15 candidate lattices. In general, it is shown that the phase diagram of a soft repulsive potential leads to the morphological diversitymore » observed in experiments with binary nanoparticles, thus providing a general framework to understand their phase diagrams. In addition, particular emphasis is shown to the two most successful crystallization strategies so far: evaporation of solvent from nanoparticles with grafted hydrocarbon ligands and DNA programmable self-assembly.« less

Micro-structured heat exchanger for cryogenic mixed refrigerant cycles

NASA Astrophysics Data System (ADS)

Gomse, D.; Reiner, A.; Rabsch, G.; Gietzelt, T.; Brandner, J. J.; Grohmann, S.

2017-12-01

Mixed refrigerant cycles (MRCs) offer a cost- and energy-efficient cooling method for the temperature range between 80 and 200 K. The performance of MRCs is strongly influenced by entropy production in the main heat exchanger. High efficiencies thus require small temperature gradients among the fluid streams, as well as limited pressure drop and axial conduction. As temperature gradients scale with heat flux, large heat transfer areas are necessary. This is best achieved with micro-structured heat exchangers, where high volumetric heat transfer areas can be realized. The reliable design of MRC heat exchangers is challenging, since two-phase heat transfer and pressure drop in both fluid streams have to be considered simultaneously. Furthermore, only few data on the convective boiling and condensation kinetics of zeotropic mixtures is available in literature. This paper presents a micro-structured heat exchanger designed with a newly developed numerical model, followed by experimental results on the single-phase pressure drop and their implications on the hydraulic diameter.

Application of cross recurrence plot for identification of temperature fluctuations synchronization in parallel minichannels

NASA Astrophysics Data System (ADS)

Grzybowski, H.; Mosdorf, R.

2016-09-01

The temperature fluctuations occurring in flow boiling in parallel minichannels with diameter of 1 mm have been experimentally investigated and analysed. The wall temperature was recorded at each minichannel outlet by thermocouple with 0.08 mm diameter probe. The time series where recorded during dynamic two-phase flow instabilities which are accompanied by chaotic temperature fluctuations. Time series were denoised using wavelet decomposition and were analysed using cross recurrence plots (CRP) which enables the study of two time series synchronization.

Effect of operating frequency and phase angle on performance of Alpha Stirling cryocooler driven by a novel compact mechanism

NASA Astrophysics Data System (ADS)

Sant, K. D.; Bapat, S. L.

2015-12-01

Amongst the mechanical cryocoolers in use, Stirling cycle cryocoolers exhibit the desirable features such as high efficiency, low specific power consumption, small size and mass and large mean time before failure. Stirling cycle cryocooler of Alpha configuration exhibits better theoretical performance as compared to Gamma. However, the theory could not be put into practice due to unavailability of compatible drive mechanism for Alpha cryocooler providing large stroke to diameter ratio. The concept of novel compact drive mechanism can be made functional to operate miniature Alpha Stirling cryocoolers. It allows the use of multicylinder system while converting rotary motion to reciprocating. This permits the drive mechanism to be employed for driving different configurations of Stirling cryocooler simultaneously. This drive is capable of providing large stroke to diameter ratio compared to other drive mechanisms generally in use for the purpose. A stroke to diameter ratio of three is chosen in the present work and the drive dimensions are calculated for four piston-cylinder arrangements with 90° phase difference between adjacent arrangements providing two Alpha Stirling cryocoolers working simultaneously. It has to be noted that the coolers operate at half the frequency of the motor used. As the two coolers operate at phase difference of 180°, during compression stroke of one unit, the suction stroke occurs for the other unit. Due to power output of second unit, the combined peak torque requirement falls by 26.81% below the peak torque needed when one unit is operated separately. This allows for use of a comparatively lower torque motor. The practicability of the drive ensuring smooth operation of the system is decided based on comparison between torque availability from the motor and torque requirement of the complete unit. The second order method of cyclic (or thermodynamic) analysis provides a simple computational procedure useful for the design of Stirling cryocooler and is adopted for the present theoretical investigations. An appropriate choice of the equations to compute different losses, from available co-relations, is made in accordance with the conditions existing in the present system. The effects of operating frequency and phase angle between compressor and expander pistons are presented in this paper. The cryocooler performance enhances with increase in operating frequency. However, cryocooler operation at 24 Hz (motor operation at 48 Hz) is considered for theoretical performance prediction. The maximum net refrigeration effect as well as COP is available at phase angle of 81° However, it is essential to fix the phase angle at 90° for both the cryocoolers for the positive functioning of drive mechanism.

Undercooling Behavior and Intermetallic Compound Coalescence in Microscale Sn-3.0Ag-0.5Cu Solder Balls and Sn-3.0Ag-0.5Cu/Cu Joints

NASA Astrophysics Data System (ADS)

Zhou, M. B.; Ma, X.; Zhang, X. P.

2012-11-01

The microstructure of microscale solder interconnects and soldering defects have long been known to have a significant influence on the reliability of electronic packaging, and both are directly related to the solidification behavior of the undercooled solder. In this study, the undercooling behavior and solidification microstructural evolution of Sn-3.0Ag-0.5Cu solder balls with different diameters (0.76 mm, 0.50 mm, and 0.30 mm) and the joints formed by soldering these balls on Cu open pads of two diameters (0.48 mm and 0.32 mm) on a printed circuit board (PCB) substrate were characterized by differential scanning calorimetry (DSC) incorporated into the reflow process. Results show that the decrease in diameter of the solder balls leads to an obvious increase in the undercooling of the balls, while the undercooling of the solder joints shows a dependence on both the diameter of the solder balls and the diameter ratio of solder ball to Cu pad (i.e., D s/ D p), and the diameter of the solder balls has a stronger influence on the undercooling of the joints than the dimension of the Cu pad. Coarse primary intermetallic compound (IMC) solidification phases were formed in the smaller solder balls and joints. The bulk Ag3Sn IMC is the primary solidification phase in the as-reflowed solder balls. Due to the interfacial reaction and dissolution of Cu atoms into the solder matrix, the primary Ag3Sn phase can be suppressed and the bulk Cu6Sn5 IMC is the only primary solidification phase in the as-reflowed solder joints.

Bayesian hierarchical models for smoothing in two-phase studies, with application to small area estimation.

PubMed

Ross, Michelle; Wakefield, Jon

2015-10-01

Two-phase study designs are appealing since they allow for the oversampling of rare sub-populations which improves efficiency. In this paper we describe a Bayesian hierarchical model for the analysis of two-phase data. Such a model is particularly appealing in a spatial setting in which random effects are introduced to model between-area variability. In such a situation, one may be interested in estimating regression coefficients or, in the context of small area estimation, in reconstructing the population totals by strata. The efficiency gains of the two-phase sampling scheme are compared to standard approaches using 2011 birth data from the research triangle area of North Carolina. We show that the proposed method can overcome small sample difficulties and improve on existing techniques. We conclude that the two-phase design is an attractive approach for small area estimation.

Pore-scale modeling of saturated permeabilities in random sphere packings.

PubMed

Pan, C; Hilpert, M; Miller, C T

2001-12-01

We use two pore-scale approaches, lattice-Boltzmann (LB) and pore-network modeling, to simulate single-phase flow in simulated sphere packings that vary in porosity and sphere-size distribution. For both modeling approaches, we determine the size of the representative elementary volume with respect to the permeability. Permeabilities obtained by LB modeling agree well with Rumpf and Gupte's experiments in sphere packings for small Reynolds numbers. The LB simulations agree well with the empirical Ergun equation for intermediate but not for small Reynolds numbers. We suggest a modified form of Ergun's equation to describe both low and intermediate Reynolds number flows. The pore-network simulations agree well with predictions from the effective-medium approximation but underestimate the permeability due to the simplified representation of the porous media. Based on LB simulations in packings with log-normal sphere-size distributions, we suggest a permeability relation with respect to the porosity, as well as the mean and standard deviation of the sphere diameter.

Diffuse interface simulation of bubble rising process: a comparison of adaptive mesh refinement and arbitrary lagrange-euler methods

NASA Astrophysics Data System (ADS)

Wang, Ye; Cai, Jiejin; Li, Qiong; Yin, Huaqiang; Yang, Xingtuan

2018-06-01

Gas-liquid two phase flow exists in several industrial processes and light-water reactors (LWRs). A diffuse interface based finite element method with two different mesh generation methods namely, the Adaptive Mesh Refinement (AMR) and the Arbitrary Lagrange Euler (ALE) methods is used to model the shape and velocity changes in a rising bubble. Moreover, the calculating speed and mesh generation strategies of AMR and ALE are contrasted. The simulation results agree with the Bhagat's experiments, indicating that both mesh generation methods can simulate the characteristics of bubble accurately. We concluded that: the small bubble rises as elliptical with oscillation, whereas a larger bubble (11 mm > d > 7 mm) rises with a morphology between the elliptical and cap type with a larger oscillation. When the bubble is large (d > 11 mm), it rises up as a cap type, and the amplitude becomes smaller. Moreover, it takes longer to achieve the stable shape from the ellipsoid to the spherical cap type with the increase of the bubble diameter. The results also show that for smaller diameter case, the ALE method uses fewer grids and has a faster calculation speed, but the AMR method can solve the case of a large geometry deformation efficiently.

Comparison between wire mesh sensor and gamma densitometry void measurements in two-phase flows

NASA Astrophysics Data System (ADS)

Sharaf, S.; Da Silva, M.; Hampel, U.; Zippe, C.; Beyer, M.; Azzopardi, B.

2011-10-01

Wire mesh sensors (WMS) are fast imaging instruments that are used for gas-liquid and liquid-liquid two-phase flow measurements and experimental investigations. Experimental tests were conducted at Helmholtz-Zentrum Dresden-Rossendorf to test both the capacitance and conductance WMS against a gamma densitometer (GD). A small gas-liquid test facility was utilized. This consisted of a vertical round pipe approximately 1 m in length, and 50 mm internal diameter. A 16 × 16 WMS was used with high spatial and temporal resolutions. Air-deionized water was the two-phase mixture. The gas superficial velocity was varied between 0.05 m s-1 and 1.4 m s-1 at two liquid velocities of 0.2 and 0.7 m s-1. The GD consisted of a collimated source and a collimated detector. The GD was placed on a moving platform close to the plane of wires of the sensor, in order to align it accurately using a counter mechanism, with each of the wires of the WMS, and the platform could scan the full section of the pipe. The WMS was operated as a conductivity WMS for a half-plane with eight wires and as a capacitance WMS for the other half. For the cross-sectional void (time and space averaged), along each wire, there was good agreement between WMS and the GD chordal void fraction near the centre of the pipe.

Gas density effect on dropsize of simulated fuel sprays

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1989-01-01

Two-phase flow in pneumatic two-fluid fuel nozzles was investigated experimentally to determine the effect of atomizing-gas density and gas mass-flux on liquid-jet breakup in sonic-velocity gas-flow. Dropsize data were obtained for the following atomizing-gases: nitrogen; argon; carbon dioxide; and helium. They were selected to cover a gas molecular-weight range of 4 to 44. Atomizing-gas mass-flux ranged from 6 to 50 g/sq cm-sec and four differently sized two-fluid fuel nozzles were used having orifice diameters that varied from 0.32 to 0.56 cm. The ratio of liquid-jet diameter to SMD, D sub o/D sub 32, was correlated with aerodynamic and liquid-surface forces based on the product of the Weber and Reynolds number, We*Re, and gas-to-liquid density ratio, rho sub g/rho sub l. To correlate spray dropsize with breakup forces produced by using different atomizing-gases, a new molecular-scale dimensionless group was derived. The derived dimensionless group was used to obtain an expression for the ratio of liquid-jet diameter to SMD, D sub o/D sub 32. The mathematical expression of this phenomenon incorporates the product of the Weber and Reynolds number, liquid viscosity, surface tension, acoustic gas velocity, the RMS velocity of gas molecules, the acceleration of gas molecules due to gravity, and gas viscosity. The mathematical expression encompassing these parameters agrees well with the atomization theory for liquid-jet breakup in high velocity gas flow. Also, it was found that at the same gas mass-flux, helium was considerably more effective than nitrogen in producing small droplet sprays with SMD's in the order of 5 micrometers.

Size-dependent interaction of silica nanoparticles with lysozyme and bovine serum albumin proteins

NASA Astrophysics Data System (ADS)

Yadav, Indresh; Aswal, Vinod K.; Kohlbrecher, Joachim

2016-05-01

The interaction of three different sized (diameter 10, 18, and 28 nm) anionic silica nanoparticles with two model proteins—cationic lysozyme [molecular weight (MW) 14.7 kDa)] and anionic bovine serum albumin (BSA) (MW 66.4 kDa) has been studied by UV-vis spectroscopy, dynamic light scattering (DLS), and small-angle neutron scattering (SANS). The adsorption behavior of proteins on the nanoparticles, measured by UV-vis spectroscopy, is found to be very different for lysozyme and BSA. Lysozyme adsorbs strongly on the nanoparticles and shows exponential behavior as a function of lysozyme concentration irrespective of the nanoparticle size. The total amount of adsorbed lysozyme, as governed by the surface-to-volume ratio, increases on lowering the size of the nanoparticles for a fixed volume fraction of the nanoparticles. On the other hand, BSA does not show any adsorption for all the different sizes of the nanoparticles. Despite having different interactions, both proteins induce similar phase behavior where the nanoparticle-protein system transforms from one phase (clear) to two phase (turbid) as a function of protein concentration. The phase behavior is modified towards the lower concentrations for both proteins with increasing the nanoparticle size. DLS suggests that the phase behavior arises as a result of the nanoparticles' aggregation on the addition of proteins. The size-dependent modifications in the interaction potential, responsible for the phase behavior, have been determined by SANS data as modeled using the two-Yukawa potential accounting for the repulsive and attractive interactions in the systems. The protein-induced interaction between the nanoparticles is found to be short-range attraction for lysozyme and long-range attraction for BSA. The magnitude of attractive interaction irrespective of protein type is enhanced with increase in the size of the nanoparticles. The total (attractive+repulsive) potential leading to two-phase formation is found to be more attractive for larger sized nanoparticles. The nanoparticle aggregates are characterized by mass fractal.

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

This study tests the performance of a variable airflow small-diameter duct heating, ventilation, and air conditioning (HVAC) system in a new construction unoccupied low-load test house in Pittsburgh, Pennsylvania. The duct system was installed entirely in conditioned space and was operated from the winter through summer seasons. Measurements were collected on the in-room temperatures and energy consumed by the air handler and heat pump unit. Operation modes with three different volumes of airflow were compared to determine the ideal airflow scenario that maximizes room-to-room thermal uniformity while minimizing fan energy consumption. Black felt infrared imagery was used as a measuremore » of diffuser throw and in-room air mixing. Measured results indicate the small-diameter, high velocity airflow system can provide comfort under some conditions. Solar heat gains resulted in southern rooms drifting beyond acceptable temperature limits. Insufficient airflow to some bedrooms also resulted in periods of potential discomfort. Homebuilders or HVAC contractors can use these results to assess whether this space conditioning strategy is an attractive alternative to a traditional duct system. The team performed a cost analysis of two duct system configurations: (1) a conventional diameter and velocity duct system, and (2) the small-diameter duct system. This work applies to both new and retrofit homes that have achieved a low heating and cooling density either by energy conservation or by operation in a mild climate with few heating or cooling degree days. Guidance is provided on cost trade-offs between the conventional duct system and the small-diameter duct system.« less

Determination of Hydrodynamic Parameters on Two--Phase Flow Gas - Liquid in Pipes with Different Inclination Angles Using Image Processing Algorithm

NASA Astrophysics Data System (ADS)

Montoya, Gustavo; Valecillos, María; Romero, Carlos; Gonzáles, Dosinda

2009-11-01

In the present research a digital image processing-based automated algorithm was developed in order to determine the phase's height, hold up, and statistical distribution of the drop size in a two-phase system water-air using pipes with 0 , 10 , and 90 of inclination. Digital images were acquired with a high speed camera (up to 4500fps), using an equipment that consist of a system with three acrylic pipes with diameters of 1.905, 3.175, and 4.445 cm. Each pipe is arranged in two sections of 8 m of length. Various flow patterns were visualized for different superficial velocities of water and air. Finally, using the image processing program designed in Matlab/Simulink^, the captured images were processed to establish the parameters previously mentioned. The image processing algorithm is based in the frequency domain analysis of the source pictures, which allows to find the phase as the edge between the water and air, through a Sobel filter that extracts the high frequency components of the image. The drop size was found using the calculation of the Feret diameter. Three flow patterns were observed: Annular, ST, and ST&MI.

Evidence of a complex shallow reservoir network from micro-textural observations of the scoria products of the 1085 AD Sunset Crater eruption

NASA Astrophysics Data System (ADS)

Alfano, F.; Pioli, L.; Clarke, A. B.; Ort, M. H.; Roggensack, K.; Self, S.

2014-12-01

Sunset Crater volcano is the youngest scoria cone of the San Francisco Volcanic Field (SFVF). The >300-m-high Sunset Crater, located ~25 km northeast of Flagstaff, erupted about 1085 AD and is a remarkable example of a highly explosive basaltic eruption. The explosive activity produced a tephra sequence of at least eight main fall units associated with major explosive phases. The total cumulative volume is ~0.3 km3 DRE. The volume of individual fall units varies between 0.02 and 0.08 km3 DRE, and an associated column height was up to 20 km high. The products have uniform chemical composition (~47 wt.% SiO2), with phenocrysts of plagioclase, olivine and pyroxene that represent about the 6 vol% of the samples. Despite the uniform chemical and crystal-phase characteristics of the products, the textures are very heterogeneous. Two textural endmembers, intimately intermingled at the mm-scale within a single clast, were identified: one endmember (sideromelane) is characterized by higher vesicularity (~66%), with large regular sub-spherical vesicles (modal diameter 0.6 mm), a glass-rich groundmass (> 95 vol%) and evidence of post-fragmentation vesicle expansion; the second endmember texture (tachylite) is characterized by lower vesicularity (~32%), with small highly irregular vesicles (modal diameter 0.3 mm) that result in a higher vesicle number density than the sideromelane, and a groundmass rich in microcrysts (> 95 vol%), mainly Fe-oxides. Textural characteristics suggest interaction between magmas stored at different depths. The tachylitic texture is present in different proportions in the products of the different eruptive phases, while some small-scale variability seems to suggest variation in the crystallization conditions. However, given the uniform phenocryst composition, these small-scale variations are probably due to differences in the residence time rather than to different storage depths. As a result, our observations suggest the temporary storage of portions of the erupted magma in a complex fracture network or conduit system located at very shallow levels (and possibly within the cone) where the magma could degas and crystallize, producing the observed tachylitic texture. These processes also caused an increase in magma viscosity, likely enhancing eruption explosivity.

Colloidal properties of sodium caseinate-stabilized nanoemulsions prepared by a combination of a high-energy homogenization and evaporative ripening methods.

PubMed

Montes de Oca-Ávalos, J M; Candal, R J; Herrera, M L

2017-10-01

Nanoemulsions stabilized by sodium caseinate (NaCas) were prepared using a combination of a high-energy homogenization and evaporative ripening methods. The effects of protein concentration and sucrose addition on physical properties were analyzed by dynamic light scattering (DLS), Turbiscan analysis, confocal laser scanning microscopy (CLSM) and small angle X-ray scattering (SAXS). Droplets sizes were smaller (~100nm in diameter) than the ones obtained by other methods (200 to 2000nm in diameter). The stability behavior was also different. These emulsions were not destabilized by creaming. As droplets were so small, gravitational forces were negligible. On the contrary, when they showed destabilization the main mechanism was flocculation. Stability of nanoemulsions increased with increasing protein concentrations. Nanoemulsions with 3 or 4wt% NaCas were slightly turbid systems that remained stable for at least two months. According to SAXS and Turbiscan results, aggregates remained in the nano range showing small tendency to aggregation. In those systems, interactive forces were weak due to the small diameter of flocs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Lateral mode coupling to reduce the electrical impedance of small elements required for high power ultrasound therapy phased arrays.

PubMed

Hynynen, Kullervo; Yin, Jianhua

2009-03-01

A method that uses lateral coupling to reduce the electrical impedance of small transducer elements in generating ultrasound waves was tested. Cylindrical, radially polled transducer elements were driven at their length resonance frequency. Computer simulation and experimental studies showed that the electrical impedance of the transducer element could be controlled by the cylinder wall thickness, while the operation frequency was determined by the cylinder length. Acoustic intensity (averaged over the cylinder diameter) over 10 W / cm(2) (a therapeutically relevant intensity) was measured from these elements.

Metallurgical Investigation of Hot Ductility Loss in Ti-6211 Alloy.

DTIC Science & Technology

1986-01-15

Yttrium, Effect of Fractography Phase Transformations Massive Transformations Martensite Widmanstatten a + 0 19. ductility specimens supplied by TNRDC...atom diameters deep . Also, with the recent development of improved gun and detector designs, spot sizes as small as 0.2 um dia. can be employed. Attempts...of deep holes Scattered about the fracture surface, particularly along prior 71 a-grain boundaries and in transgranular locations on ductile rupture

Irradiation-induced microchemical changes in highly irradiated 316 stainless steel

NASA Astrophysics Data System (ADS)

Fujii, K.; Fukuya, K.

2016-02-01

Cold-worked 316 stainless steel specimens irradiated to 74 dpa in a pressurized water reactor (PWR) were analyzed by atom probe tomography (APT) to extend knowledge of solute clusters and segregation at higher doses. The analyses confirmed that those clusters mainly enriched in Ni-Si or Ni-Si-Mn were formed at high number density. The clusters were divided into three types based on their size and Mn content; small Ni-Si clusters (3-4 nm in diameter), and large Ni-Si and Ni-Si-Mn clusters (8-10 nm in diameter). The total cluster number density was 7.7 × 1023 m-3. The fraction of large clusters was almost 1/10 of the total density. The average composition (in at%) for small clusters was: Fe, 54; Cr, 12; Mn, 1; Ni, 22; Si, 11; Mo, 1, and for large clusters it was: Fe, 44; Cr, 9; Mn, 2; Ni, 29; Si, 14; Mo,1. It was likely that some of the Ni-Si clusters correspond to γ‧ phase precipitates while the Ni-Si-Mn clusters were precursors of G phase precipitates. The APT analyses at grain boundaries confirmed enrichment of Ni, Si, P and Cu and depletion of Fe, Cr, Mo and Mn. The segregation behavior was consistent with previous knowledge of radiation induced segregation.

Inspection of aircraft fastener holes using a conically shaped multi-element phased array probe

NASA Astrophysics Data System (ADS)

Selman, J. J.; Miller, J. T.; Moles, M. D. C.; Dupuis, O.; Herzog, P. G.

2002-05-01

A novel inspection technique is described using phased ultrasonic arrays to detect faying surface cracks in the first layer around the base of a fastener hole with fasteners installed. A unique phased array probe incorporates a matrix of ultrasonic elements arranged in a conical configuration encircling the fastener head. This arrangement permits deflection of the ultrasonic beam in three dimensions, and adapts to different hole diameters and skin thickness. Full circumferential scans are performed using a pre-programmed sequence of phased array focal laws. The inspection method uses pulse-echo at a variety of angles incident on the crack to thoroughly cover the fastener hole and surrounding area, and is designed to detect cracks as small as 0.030″ in length.

SPH Calculations of Comet Shoemaker-Levy-9/Jupiter Impact

NASA Astrophysics Data System (ADS)

Wingate, C. A.; Hoffman, N. M.; Stellingwerf, R. F.

1994-05-01

The impact of Comet Shoemaker-Levy 9 has been simulated in 2D axisymmetric geometry and full 3D using the Los Alamos Smooth Particle Hydrodynamics code (SPHINX). The objective of this study is to calculate energy deposition profiles and fireball evolution histories for a range of comet parameters. We hope to use these results to infer comet properties from observations. The modeling proceeds in two phases. In Phase I, the collision of the incoming fragment, or bolide, is calculated, and its kinetic energy profile is differentiated to give an energy deposition profile. The deposition profile is used as input to Phase II (see companion paper by Stellingwerf et al.) in which the fireball evolution is calculated. Two different bolide densities were simulated, 0.2 g/cm(3) and 0.92 g/cm(3) . The incoming bolide velocity was 60 km/sec and the impact angle was taken to be 45 degrees. Since the calculation is 2D, this means simply that the bolide's depth in the atmosphere is equal to its distance traveled times the cosine of 45 degrees. The baseline calculation assumed a spherical bolide with a diameter of 1 km. Various physical models were used for the bolide including perfect gas equations of state (eos), more realistic eos's and strength of materials. The model for the Jupiter atmosphere was a fit to the Orton atmosphere. The eos for the atmosphere for most of the calculations was taken to be a perfect gas with a gamma of 1.2. A sesame tabular eos was also used. Rather than modeling the entire atmosphere, small sections were modeled using blocks of particles with blocks being shuffled in and out as the calculation progressed. Calculations were done with different size sections to test the sensitivity of the results to this procedure. The results indicate energy deposition for the 0.2 density, 1 km diameter case occurring between 50-200 km. The penetration is seen to increase somewhat as the bolide resolution is improved.

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

Pavlou, A. T.; Betzler, B. R.; Burke, T. P.

Uncertainties in the composition and fabrication of fuel compacts for the Fort St. Vrain (FSV) high temperature gas reactor have been studied by performing eigenvalue sensitivity studies that represent the key uncertainties for the FSV neutronic analysis. The uncertainties for the TRISO fuel kernels were addressed by developing a suite of models for an 'average' FSV fuel compact that models the fuel as (1) a mixture of two different TRISO fuel particles representing fissile and fertile kernels, (2) a mixture of four different TRISO fuel particles representing small and large fissile kernels and small and large fertile kernels and (3)more » a stochastic mixture of the four types of fuel particles where every kernel has its diameter sampled from a continuous probability density function. All of the discrete diameter and continuous diameter fuel models were constrained to have the same fuel loadings and packing fractions. For the non-stochastic discrete diameter cases, the MCNP compact model arranged the TRISO fuel particles on a hexagonal honeycomb lattice. This lattice-based fuel compact was compared to a stochastic compact where the locations (and kernel diameters for the continuous diameter cases) of the fuel particles were randomly sampled. Partial core configurations were modeled by stacking compacts into fuel columns containing graphite. The differences in eigenvalues between the lattice-based and stochastic models were small but the runtime of the lattice-based fuel model was roughly 20 times shorter than with the stochastic-based fuel model. (authors)« less

Mechanics of evolving thin film structures

NASA Astrophysics Data System (ADS)

Liang, Jim

In the Stranski-Krastanov system, the lattice mismatch between the film and the substrate causes the film to break into islands. During annealing, both the surface energy and the elastic energy drive the islands to coarsen. Motivated by several related studies, we suggest that stable islands should form when a stiff ceiling is placed at a small gap above the film. We show that the role of elasticity is reversed: with the ceiling, the total elastic energy stored in the system increases as the islands coarsen laterally. Consequently, the islands select an equilibrium size to minimize the combined elastic energy and surface energy. In lithographically-induced self-assembly, when a two-phase fluid confined between parallel substrates is subjected to an electric field, one phase can self-assemble into a triangular lattice of islands in another phase. We describe a theory of the stability of the island lattice. The islands select the equilibrium diameter to minimize the combined interface energy and electrostatic energy. Furthermore, we study compressed SiGe thin film islands fabricated on a glass layer, which itself lies on a silicon wafer. Upon annealing, the glass flows, and the islands relax. A small island relaxes by in-plane expansion. A large island, however, wrinkles at the center before the in-plane relaxation arrives. The wrinkles may cause significant tensile stress in the island, leading to fracture. We model the island by the von Karman plate theory and the glass layer by the Reynolds lubrication theory. Numerical simulations evolve the in-plane expansion and the wrinkles simultaneously. We determine the critical island size, below which in-plane expansion prevails over wrinkling. Finally, in devices that integrate dissimilar materials in small dimensions, crack extension in one material often accompanies inelastic deformation in another. We analyze a channel crack advancing in an elastic film under tension, while an underlayer creeps. We use a two-dimensional shear lag model to approximate the three-dimensional fracture process. Based on the computational results, we propose new experiments to measure fracture toughness and creep laws in small structures. Similarly, we study delayed crack initiation, steady crack growth, and transient crack growth when the underlayer is viscoelastic.

A High-Resolution Endoscope of Small Diameter Using Electromagnetically Vibration of Single Fiber

NASA Astrophysics Data System (ADS)

Matsunaga, Tadao; Hino, Ryunosuke; Makishi, Wataru; Esashi, Masayoshi; Haga, Yoichi

For high resolution visual inspection in the narrow space of the human body, small diameter endoscope has been developed which utilize electromagnetically vibration of single fiber. Thin endoscopes are effective for inspection in the narrow space of the human body, for example, in the blood vessel, lactiferous duct for detection infiltration of breast cancer, and periodontal gap between gingiva and tooth. This endoscope consists of single optical fiber and photofabricated driving coils. A collimator lens and a cylindrical permanent magnet are fixed on the optical fiber, and the tilted driving coils have been patterned on a 1.08 mm outer diameter thin tube. The fiber is positioned at the center of the tube which is patterned the coils. When an electrical alternating current at the resonance frequency is supplied to the coils, the permanent magnet which is fixed to the fiber is vibrated electromagnetically and scanned one or two dimensionally. This paper reports small diameter endoscope by using electromagnetically vibration of single fiber. Optical coherence tomography imaging has also been carried out with the fabricated endoscope and cross-section image of sub-surface skin of thumb was observed.

Laser two focus techniques

NASA Astrophysics Data System (ADS)

Schodl, R.

The development of the laser two focus velocimetry are reviewed. The fundamentals of this nonintrusive fluid flow velocity measurement technique are described. Emphasis is placed upon the advances of this technique. Results of measurements in a very small flow channel and in a small turbocharger compressor rotor are presented. The influence of beam diameter - beam separation ratio on the measuring accuracy and on the measuring time is treated. A multicolor two dimensional system with selectable beam separation is presented. The laser Doppler and the laser two focus techniques are compared.

Effect of membrane microheterogeneity and domain size on fluorescence resonance energy transfer.

PubMed

Towles, Kevin B; Brown, Angela C; Wrenn, Steven P; Dan, Nily

2007-07-15

Studies of multicomponent membranes suggest lateral inhomogeneity in the form of membrane domains, but the size of small (nanoscale) domains in situ cannot be determined with current techniques. In this article, we present a model that enables extraction of membrane domain size from time-resolved fluorescence resonance energy transfer (FRET) data. We expand upon a classic approach to the infinite phase separation limit and formulate a model that accounts for the presence of disklike domains of finite dimensions within a two-dimensional infinite planar bilayer. The model was tested against off-lattice Monte Carlo calculations of a model membrane in the liquid-disordered (l(d)) and liquid-ordered (l(o)) coexistence regime. Simulated domain size was varied from 5 to 50 nm, and two fluorophores, preferentially partitioning into opposite phases, were randomly mixed to obtain the simulated time-resolved FRET data. The Monte Carlo data show clear differences in the efficiency of energy transfer as a function of domain size. The model fit of the data yielded good agreement for the domain size, especially in cases where the domain diameter is <20 nm. Thus, data analysis using the proposed model enables measurement of nanoscale membrane domains using time-resolved FRET.

Phase equilibrium in argon films stabilized by homogeneous surfaces and thermodynamics of two-stage melting transition.

PubMed

Ustinov, E A

2014-02-21

Freezing of gases adsorbed on open surfaces (e.g., graphite) and in narrow pores is a widespread phenomenon which is a subject of a large number of publications. Modeling of the gas/liquid-solid transition is usually accomplished with a molecular simulation technique. However, quantitative analysis of the gas/liquid-solid coexistence and thermodynamic properties of the solid layer still encounters serious difficulties. This is mainly due to the effect of simulation box size on the lattice constant. Since the lattice constant is a function of loading and temperature, once the ordering transition has occurred, the simulation box size must be corrected in the course of simulation according to the Gibbs-Duhem equation. A significant problem is also associated with accurate prediction of the two-dimensional liquid-solid coexistence because of a small difference in densities of coexisting phases. The aim of this study is thermodynamic analysis of the two-dimensional phase coexistence in systems involving crystal-like free of defects layers in narrow slit pores. A special attention was paid to the determination of triple point temperatures. It is shown that intrinsic properties of argon monolayer adsorbed on the graphite surface are similar to those of isolated monolayer accommodated in the slit pore having width of two argon collision diameters. Analysis of the latter system is shown to be clearer and less time-consuming than the former one, which has allowed for explanation of the experimentally observed two-stage melting transition of argon monolayer on graphite without invoking the periodic surface potential modulation and orientational transition.

Phase equilibrium in argon films stabilized by homogeneous surfaces and thermodynamics of two-stage melting transition

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

Ustinov, E. A., E-mail: eustinov@mail.wplus.net

Freezing of gases adsorbed on open surfaces (e.g., graphite) and in narrow pores is a widespread phenomenon which is a subject of a large number of publications. Modeling of the gas/liquid–solid transition is usually accomplished with a molecular simulation technique. However, quantitative analysis of the gas/liquid–solid coexistence and thermodynamic properties of the solid layer still encounters serious difficulties. This is mainly due to the effect of simulation box size on the lattice constant. Since the lattice constant is a function of loading and temperature, once the ordering transition has occurred, the simulation box size must be corrected in the coursemore » of simulation according to the Gibbs–Duhem equation. A significant problem is also associated with accurate prediction of the two-dimensional liquid–solid coexistence because of a small difference in densities of coexisting phases. The aim of this study is thermodynamic analysis of the two-dimensional phase coexistence in systems involving crystal-like free of defects layers in narrow slit pores. A special attention was paid to the determination of triple point temperatures. It is shown that intrinsic properties of argon monolayer adsorbed on the graphite surface are similar to those of isolated monolayer accommodated in the slit pore having width of two argon collision diameters. Analysis of the latter system is shown to be clearer and less time-consuming than the former one, which has allowed for explanation of the experimentally observed two-stage melting transition of argon monolayer on graphite without invoking the periodic surface potential modulation and orientational transition.« less

Examination of a modified cell cycle synchronization method and bovine nuclear transfer using synchronized early G1 phase fibroblast cells.

PubMed

Urakawa, Manami; Ideta, Atsushi; Sawada, Tokihiko; Aoyagi, Yoshito

2004-08-01

Somatic cell nuclear transfer has a low success rate, due to a high incidence of fetal loss and increased perinatal morbidity/mortality. One factor that may affect the successful development of nuclear transfer embryos is the cell cycle stage of the donor cell. In order to establish a cell cycle synchronization method that can consistently produce cloned embryos and offspring, we examined the effects of different combinations of three cell treatments on the recovery rate of mitotic phase cells using bovine fetal fibroblasts. In the first experiment, we examined the recovery rate of mitotic phase cells by a combination of treatment with a metaphase arrestant (1 microM 2-methoxyestradiol), shaking the plate and selecting cells with a diameter of 20 microns. As a result, 99% of mitotic phase cells were recovered by repeating the combined treatment of metaphase arrestant and shaking, and collection of cells with a specific diameter. In the second experiment, nuclear transfer was carried out using early G1 phase cells by choosing pairs of bridged cells derived from mitotic phase cells recovered by the combined treatment of 1 microM 2-methoxyestradiol and shaking, and collection of cells with a diameter of 20 microns. The reconstructed embryos were transferred to recipient heifers to determine post-implantation development. Development of embryos reconstructed from early G1 phase cells from the >/=6 cells stage on Day 3 to the morula-blastocyst stage on Day 6 was 100%. Ten blastocysts constructed from two cell lines were transferred into 10 recipient heifers. Nine of the 10 recipients delivered single live calves. In conclusion, mitotic phase bovine fibroblast cells were easily recovered by the combined treatments of 1 microM 2-methoxyestradiol, shaking, and selecting cells of the appropriate diameter. Furthermore, nuclear transfer using cells in the early G1 phase as donor cells gave a high rate of offspring production.

Bubble Generation in a Flowing Liquid Medium and Resulting Two-Phase Flow in Microgravity

NASA Technical Reports Server (NTRS)

Pais, S. C.; Kamotani, Y.; Bhunia, A.; Ostrach, S.

1999-01-01

The present investigation reports a study of bubble generation under reduced gravity conditions, using both a co-flow and a cross-flow configuration. This study may be used in the conceptual design of a space-based thermal management system. Ensuing two-phase flow void fraction can be accurately monitored using a single nozzle gas injection system within a continuous liquid flow conduit, as utilized in the present investigation. Accurate monitoring of void fraction leads to precise control of heat and mass transfer coefficients related to a thermal management system; hence providing an efficient and highly effective means of removing heat aboard spacecraft or space stations. Our experiments are performed in parabolic flight aboard the modified DC-9 Reduced Gravity Research Aircraft at NASA Lewis Research Center, using an air-water system. For the purpose of bubble dispersion in a flowing liquid, we use both a co-flow and a cross-flow configuration. In the co-flow geometry, air is introduced through a nozzle in the same direction with the liquid flow. On the other hand, in the cross-flow configuration, air is injected perpendicular to the direction of water flow, via a nozzle protruding inside the two-phase flow conduit. Three different flow conduit (pipe) diameters are used, namely, 1.27 cm, 1.9 cm and 2.54 cm. Two different ratios of nozzle to pipe diameter (D(sub N))sup * are considered, namely (D(sub N))sup * = 0.1 and 0.2, while superficial liquid velocities are varied from 8 to 70 cm/s depending on flow conduit diameter. It is experimentally observed that by holding all other flow conditions and geometry constant, generated bubbles decrease in size with increase in superficial liquid velocity. Detached bubble diameter is shown to increase with air injection nozzle diameter. Likewise, generated bubbles grow in size with increasing pipe diameter. Along the same lines, it is shown that bubble frequency of formation increases and hence the time to detachment of a forming bubble decreases, as the superficial liquid velocity is in-creased. Furthermore, it is shown that the void fraction of the resulting two-phase flow increases with volumetric gas flow rate Q(sub d), pipe diameter and gas injection nozzle diameter, while they decrease with surrounding liquid flow. The important role played by flowing liquid in detaching bubbles in a reduced gravity environment is thus emphasized. We observe that the void fraction can be accurately controlled by using single nozzle gas injection, rather than by employing multiple port injection, since the later system gives rise to unpredictable coalescence of adjacent bubbles. It is of interest to note that empirical bubble size and corresponding void fraction are somewhat smaller for the co-flow geometry than the cross-flow configuration at similar flow conditions with similar pipe and nozzle diameters. In order to supplement the empirical data, a theoretical model is employed to study single bubble generation in the dynamic (Q(sub d) = 1 - 1000 cu cm/s) and bubbly flow regime within the framework of the co-flow configuration. This theoretical model is based on an overall force balance acting on the bubble during the two stages of generation, namely the expansion and the detachment stage. Two sets of forces, one aiding and the other inhibiting bubble detachment are identified. Under conditions of reduced gravity, gas momentum flux enhances, while the surface tension force at the air injection nozzle tip inhibits bubble detachment. In parallel, liquid drag and inertia can act as both attaching and detaching forces, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with our experimental results. However, at higher superficial liquid velocities, as the bubble loses its spherical form, empirical bubble size no longer matches the theoretical predictions. In summary, we have developed a combined experimental and theoretical work, which describes the complex process of bubble generation and resulting two-phase flow in a microgravity environment. Results of the present study can be used in a wide range of space-based applications, such as thermal energy and power generation, propulsion, cryogenic storage and long duration life support systems, necessary for programs such as NASA's Human Exploration for the Development of Space (HEDS).

A high-speed photographic system for flow visualization in a steam turbine

NASA Technical Reports Server (NTRS)

Barna, G. J.

1973-01-01

A photographic system was designed to visualize the moisture flow in a steam turbine. Good performance of the system was verified using dry turbine mockups in which an aerosol spray simulated, in a rough way, the moisture flow in the turbine. Borescopes and fiber-optic light tubes were selected as the general instrumentation approach. High speed motion-picture photographs of the liquid flow over the stator blade surfaces were taken using stroboscopic lighting. Good visualization of the liquid flow was obtained. Still photographs of drops in flight were made using short duration flash sources. Drops with diameters as small as 30 micrometers (0.0012 in.) could be resolved. In addition, motion pictures of a spray of water simulating the spray off the rotor blades and shrouds were taken at normal framing rates. Specially constructed light tubes containing small tungsten-halogen lamps were used. Sixteen millimeter photography was used in all cases. Two potential problems resulting from the two-phase turbine flow (attenuation and scattering of light by the fog present and liquid accumulation on the borescope mirrors) were taken into account in the photographic system design but not evaluated experimentally.

Selective control of small versus large diameter axons using infrared laser light (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lothet, Emilie H.; Shaw, Kendrick M.; Horn, Charles C.; Lu, Hui; Wang, Yves T.; Jansen, E. Duco; Chiel, Hillel J.; Jenkins, Michael W.

2016-03-01

Sensory information is conveyed to the central nervous system via small diameter unmyelinated fibers. In general, smaller diameter axons have slower conduction velocities. Selective control of such fibers could create new clinical treatments for chronic pain, nausea in response to chemo-therapeutic agents, or hypertension. Electrical stimulation can control axonal activity, but induced axonal current is proportional to cross-sectional area, so that large diameter fibers are affected first. Physiologically, however, synaptic inputs generally affect small diameter fibers before large diameter fibers (the size principle). A more physiological modality that first affected small diameter fibers could have fewer side effects (e.g., not recruiting motor axons). A novel mathematical analysis of the cable equation demonstrates that the minimum length along the axon for inducing block scales with the square root of axon diameter. This implies that the minimum length along an axon for inhibition will scale as the square root of axon diameter, so that lower radiant exposures of infrared light will selectively affect small diameter, slower conducting fibers before those of large diameter. This prediction was tested in identified neurons from the marine mollusk Aplysia californica. Radiant exposure to block a neuron with a slower conduction velocity (B43) was consistently lower than that needed to block a faster conduction velocity neuron (B3). Furthermore, in the vagus nerve of the musk shrew, lower radiant exposure blocked slow conducting fibers before blocking faster conducting fibers. Infrared light can selectively control smaller diameter fibers, suggesting many novel clinical treatments.

Devices to protect seedlings from deer browsing

Treesearch

David A. Marquis

1977-01-01

Studies on the Allegheny Plateau of Pennsylvania have shown that several types of wire or plastic tubes can be erected around tree seedlings to protect them from deer browsing. The two most promising devices are a 4- to 6-inch diameter plastic tube with small mesh and a 12-inch diameter tube constructed of chicken wire. Both types need to be at least 5 feet tall to...

Wood density and anatomical properties in suppressed-growth trees : comparison of two methods

Treesearch

David W. Vahey; J. Y. Zhu; C. Tim Scott

2007-01-01

Interest in the commercial value of small-diameter timber has led to testing core samples with SilviScan to characterize density and transverse fiber dimensions. Data showed that latewood density and tracheid diameter in suppressed-growth material can vary spatially on a scale comparable to the 50-_m resolution of the instrument used in our testing. An optical imaging...

Crystal-phase intergradation in InAs nanostructures grown by van der Waals heteroepitaxy on graphene

NASA Astrophysics Data System (ADS)

Choi, Ji Eun; Yoo, Jinkyoung; Lee, Donghwa; Hong, Young Joon; Fukui, Takashi

2018-04-01

This study demonstrates the crystal-phase intergradation of InAs nanostructures grown on graphene via van der Waals epitaxy. InAs nanostructures with diverse diameters are yielded on graphene. High-resolution transmission electron microscopy (HR-TEM) reveals two crystallographic features of (i) wurtzite (WZ)-to-zinc blende (ZB) intergradation along the growth direction of InAs nanostructures and (ii) an increased mean fraction of ZB according to diameter increment. Based on the HR-TEM observations, a crystal-phase intergradation diagram is depicted. We discuss how the formation of a WZ-rich phase during the initial growth stage is an effective way of releasing heterointerfacial stress endowed by the lattice mismatch of InAs/graphene for energy minimization in terms of less in-plane lattice mismatching between WZ-InAs and graphene. The WZ-to-ZB evolution is responsible for the attenuation of the bottom-to-top surface charge interaction as growth proceeds.

Apparatus for measuring surface particulate contamination

DOEpatents

Woodmansee, Donald E.

2002-01-01

An apparatus for measuring surface particulate contamination includes a tool for collecting a contamination sample from a target surface, a mask having an opening of known area formed therein for defining the target surface, and a flexible connector connecting the tool to the mask. The tool includes a body portion having a large diameter section defining a surface and a small diameter section extending from the large diameter section. A particulate collector is removably mounted on the surface of the large diameter section for collecting the contaminants. The tool further includes a spindle extending from the small diameter section and a spool slidingly mounted on the spindle. A spring is disposed between the small diameter section and the spool for biasing the spool away from the small diameter section. An indicator is provided on the spindle so as to be revealed when the spool is pressed downward to compress the spring.

Room temperature synthesis and optical properties of small diameter (5 nm) ZnO nanorod arrays.

PubMed

Cho, Seungho; Jang, Ji-Wook; Lee, Jae Sung; Lee, Kun-Hong

2010-10-01

We report a simple wet-chemical synthesis of ∼5 nm diameter ZnO nanorod arrays at room temperature (20 °C) and normal atmospheric pressure (1 atm) and their optical properties. They were single crystalline in nature, and grew in the [001] direction. These small diameter ZnO nanorod arrays can also be synthesized at 0 °C. Control experiments were also conducted. On the basis of the results, we propose a mechanism for the spontaneous growth of the small diameter ZnO structures. The optical properties of the 5 nm diameter ZnO nanorod arrays synthesized using this method were probed by UV-Visible diffuse reflectance spectroscopy. A clear blue-shift, relative to the absorption band from 50 nm diameter ZnO nanorod arrays, was attributed to the quantum confinement effects caused by the small nanocrystal size in the 5 nm diameter ZnO nanorods.

Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting

PubMed Central

Lu, Xing; Zhao, Guoqun; Zhou, Jixue; Zhang, Cunsheng; Yu, Junquan

2018-01-01

In this paper, a new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt %) alloy ingot with a diameter of 130 mm and a length of 4800 mm was fabricated by semicontinuous casting. The microstructure and mechanical properties at different areas of the ingot were investigated. The microstructure and mechanical properties of the alloy under different one-step and two-step homogenization conditions were studied. For the as-cast alloy, the average grain size and the second phase size decrease from the center to the surface of the ingot, while the area fraction of the second phase increases gradually. At one-half of the radius of the ingot, the alloy presents the optimum comprehensive mechanical properties along the axial direction, which is attributed to the combined effect of relatively small grain size, low second-phase fraction, and uniform microstructure. For the as-homogenized alloy, the optimum two-step homogenization process parameters were determined as 340 °C × 10 h + 520 °C × 16 h. After the optimum homogenization, the proper size and morphology of CaMgSn phase are conducive to improve the microstructure uniformity and the mechanical properties of the alloy. Besides, the yield strength of the alloy is reduced by 20.7% and the elongation is increased by 56.3%, which is more favorable for the subsequent hot deformation processing. PMID:29710818

Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting.

PubMed

Lu, Xing; Zhao, Guoqun; Zhou, Jixue; Zhang, Cunsheng; Yu, Junquan

2018-04-29

In this paper, a new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt %) alloy ingot with a diameter of 130 mm and a length of 4800 mm was fabricated by semicontinuous casting. The microstructure and mechanical properties at different areas of the ingot were investigated. The microstructure and mechanical properties of the alloy under different one-step and two-step homogenization conditions were studied. For the as-cast alloy, the average grain size and the second phase size decrease from the center to the surface of the ingot, while the area fraction of the second phase increases gradually. At one-half of the radius of the ingot, the alloy presents the optimum comprehensive mechanical properties along the axial direction, which is attributed to the combined effect of relatively small grain size, low second-phase fraction, and uniform microstructure. For the as-homogenized alloy, the optimum two-step homogenization process parameters were determined as 340 °C × 10 h + 520 °C × 16 h. After the optimum homogenization, the proper size and morphology of CaMgSn phase are conducive to improve the microstructure uniformity and the mechanical properties of the alloy. Besides, the yield strength of the alloy is reduced by 20.7% and the elongation is increased by 56.3%, which is more favorable for the subsequent hot deformation processing.

Flow of High Internal Phase Ratio Emulsions through Pipes

NASA Astrophysics Data System (ADS)

Kostak, K.; Özsaygı, R.; Gündüz, I.; Yorgancıoǧlu, E.; Tekden, E.; Güzel, O.; Sadıklar, D.; Peker, S.; Helvacı, Ş. Ş.

2015-04-01

The flow behavior of W/O type of HIPRE stabilized by hydrogen bonds with a sugar (sorbitol) in the aqueous phase, was studied. Two groups of experiments were done in this work: The effect of wall shear stresses were investigated in flow through pipes of different diameters. For this end, HIPREs prestirred at constant rate for the same duration were used to obtain similar drop size distributions. Existence and extent of elongational viscosity were used as a probe to elucidate the effect of drop size distribution on the flow behavior: HIPREs prestirred for the same duration at different rates were subjected to flow through converging pipes. The experimental flow curves for flow through small cylindrical pipes indicated four different stages: 1) initial increase in the flow rate at low pressure difference, 2) subsequent decrease in the flow rate due to capillary flow, 3) pressure increase after reaching the minimum flow rate and 4) slip flow after a critical pressure difference. HIPREs with sufficient external liquid phase in the plateau borders can elongate during passage through converging pipes. In the absence of liquid stored in the plateau borders, the drops rupture during extension and slip flow takes place without elongation.

Engineering Photon-Photon Interactions within Rubidium-Filled Waveguides

NASA Astrophysics Data System (ADS)

Perrella, C.; Light, P. S.; Vahid, S. Afshar; Benabid, F.; Luiten, A. N.

2018-04-01

Strong photon-photon interactions are a required ingredient for deterministic two-photon optical quantum logic gates. Multiphoton transitions in dense atomic vapors have been shown to be a promising avenue for producing such interactions. The strength of a multiphoton interaction can be enhanced by conducting the interaction in highly confined geometries such as small-cross-section optical waveguides. We demonstrate, both experimentally and theoretically, that the strength of such interactions scale only with the optical mode diameter, d , not d2 as might be initially expected. This weakening of the interaction arises from atomic motion inside the waveguides. We create an interaction between two optical signals, at 780 and 776 nm, using the 5 S1 /2→5 D5 /2 two-photon transition in rubidium vapor within a range of hollow-core fibers with different core sizes. The interaction strength is characterized by observing the absorption and phase shift induced on the 780-nm beam, which is in close agreement with theoretical modeling that accounts for the atomic motion inside the fibers. These observations demonstrate that transit-time effects upon multiphoton transitions are of key importance when engineering photon-photon interactions within small-cross-section waveguides that might otherwise be thought to lead to enhanced optical nonlinearity through increased intensities.

Synthesis of monodisperse silica microspheres and modification with diazoresin for mixed-mode ultra high performance liquid chromatography separations.

PubMed

Cong, Hailin; Yu, Bing; Tian, Chao; Zhang, Shuai; Yuan, Hua

2017-11-01

Monodisperse silica particles with average diameters of 1.9-2.9 μm were synthesized by a modified Stöber method, in which tetraethyl orthosilicate was continuously supplied to the reaction mixture containing KCl electrolyte, water, ethanol, and ammonia. The obtained silica particles were modified by self-assembly with positively charged photosensitive diazoresin on the surface. After treatment with ultraviolet light, the ionic bonding between silica and diazoresin was converted into covalent bonding through a unique photochemistry reaction of diazoresin. Depending on the chemical structure of diazoresin and mobile phase composition, the diazoresin-modified silica stationary phase showed different separation mechanisms, including reversed phase and hydrophilic interactions. Therefore, a variety of baseline separation of benzene analogues and organic acids was achieved by using the diazoresin-modified silica particles as packing materials in ultra high performance liquid chromatography. According to the π-π interactional difference between carbon rings of fullerenes and benzene rings of diazoresin, C 60 and C 70 were also well separated by ultra-high performance liquid chromatography. Because it has a small size, the ∼2.5 μm monodisperse diazoresin-modified silica stationary phase shows ultra-high efficiency compared with the commercial C 18 -silica high-performance liquid chromatography stationary phase with average diameters of ∼5 μm. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exchange coupling and microwave absorption in core/shell-structured hard/soft ferrite-based CoFe2O4/NiFe2O4 nanocapsules

NASA Astrophysics Data System (ADS)

Feng, Chao; Liu, Xianguo; Or, Siu Wing; Ho, S. L.

2017-05-01

Core/shell-structured, hard/soft spinel-ferrite-based CoFe2O4/NiFe2O4 (CFO/NFO) nanocapsules with an average diameter of 17 nm are synthesized by a facile two-step hydrothermal process using CFO cores of ˜15 nm diameter as the hard magnetic phase and NFO shells of ˜1 nm thickness as the soft magnetic phase. The single-phase-like hysteresis loop with a high remnant-to-saturation magnetization ratio of 0.7, together with a small grain size of ˜16 nm, confirms the existence of exchange-coupling interaction between the CFO cores and the NFO shells. The effect of hard/soft exchange coupling on the microwave absorption properties is studied. Comparing to CFO and NFO nanoparticles, the finite-size NFO shells and the core/shell structure enable a significant reduction in electric resistivity and an enhancement in dipole and interfacial polarizations in the CFO/NFO nanocapsules, resulting in an obvious increase in dielectric permittivity and loss in the whole S-Ku bands of microwaves of 2-18 GHz, respectively. The exchange-coupling interaction empowers a more favorable response of magnetic moment to microwaves, leading to enhanced exchange resonances in magnetic permeability and loss above 10 GHz. As a result, strong absorption, as characterized by a large reflection loss (RL) of -20.1 dB at 9.7 GHz for an absorber thickness of 4.5 mm as well as a broad effective absorption bandwidth (for RL<-10 dB) of 8.4 GHz (7.8-16.2 GHz) at an absorber thickness range of 3.0-4.5 mm, is obtained.

78 FR 56864 - Small Diameter Graphite Electrodes From the People's Republic of China: Affirmative Final...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-16

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... (Department) determines that imports from the People's Republic of China (PRC) of graphite electrodes... Act of 1930, as amended (the Act).\\1\\ \\1\\ See Antidumping Duty Order: Small Diameter Graphite...

A New Pulse Shape to Obtain Selective Small Fiber Activation by Anodal Blocking

DTIC Science & Technology

2001-10-25

anodal blocking a tripolar cuff electrode is most commonly used. When external stimulation is applied, the fiber membrane is depolarized close to...would be safer if somehow the charge per phase could be reduced. Charge reduction might be possible with the following idea: In a tripolar cuff...inhomogeneous and anisotropic volume conductor model [3]. A symmetrical tripolar cuff electrode with an inner diameter of 2 mm was placed around a

Biomaterials patterned with discontinuous microwalls for vascular smooth muscle cell culture: biodegradable small diameter vascular grafts and stable cell culture substrates.

PubMed

Heath, Daniel E; Kang, Gavin C W; Cao, Ye; Poon, Yin Fun; Chan, Vincent; Chan-Park, Mary B

2016-10-01

The medial layer of small diameter blood vessels contains circumferentially aligned vascular smooth muscle cells (vSMC) that possess contractile phenotype. In tissue-engineered constructs, these cellular characteristics are usually achieved by seeding planar scaffolds with vSMC, rolling the cell-laden scaffold into a tubular structure, and maturing the construct in a pulsatile bioreactor, a lengthy process that can take up to two months. During the maturation phase, the cells circumferentially orient, their contractile protein expression increases, and they obtain a contractile phenotype. Generating cell culture platforms that enable the rapid production of directionally oriented vSMC with increased contractile protein expression would be a major step forward for blood vessel tissue engineering and would greatly facilitate the in vitro study of vSMC biology. Previously, we developed a micropatterned cell culture surface that promotes orientation and contractile protein expression of vSMC. Herein, we explore two potential applications of this technology. First, we fabricate tubular and biodegradable scaffolds that possess the micropatterning on their exterior surface. When vSMC are seeded on these scaffolds, they initially proliferate in order to fill the microchannels and as confluence is reached the cells align in the direction of the micropatterning resulting in a biodegradable scaffold that is inhabited by circumferentially aligned vSMC within a week. Second, we illustrate that we can generate biostable cell culture surfaces that allow the in vitro study of the cells in a more contractile state. Specifically, we explore contractile protein expression of cells cultured on the micropatterned surfaces with the addition of soluble transforming growth factor beta one (TGFβ1).

Small Scale Turbopump Manufacturing Technology and Material Processes

NASA Technical Reports Server (NTRS)

Alvarez, Erika; Morgan, Kristin; Wells, Doug; Zimmerman, Frank

2011-01-01

As part of an internal research and development project, NASA Marshall Space Flight Center (MSFC) has been developing a high specific impulse 9,000-lbf LOX/LH2 pump-fed engine testbed with the capability to throttle 10:1. A Fuel Turbopump (FTP) with the ability to operate across a speed range of 30,000-rpm to 100,000-rpm was developed and analyzed. This small size and flight-like Fuel Turbopump has completed the design and analysis phase and is currently in the manufacturing phase. This paper highlights the manufacturing and processes efforts to fabricate an approximately 20-lb turbopump with small flow passages, intricately bladed components and approximately 3-in diameter impellers. As a result of the small scale and tight tolerances of the hardware on this turbopump, several unique manufacturing and material challenges were encountered. Some of the technologies highlighted in this paper include the use of powder metallurgy technology to manufacture small impellers, electron beam welding of a turbine blisk shroud, and casting challenges. The use of risk reduction efforts such as non-destructive testing (NDT) and evaluation (NDE), fractography, material testing, and component spin testing are also discussed in this paper.

Synthesis and spectroscopic study of CdS nanoparticles using hydrothermal method

NASA Astrophysics Data System (ADS)

AL-Mamoori, Mohammed H. K.; Mahdi, Dunia K.; Al-Shrefi, Saif M.

2018-05-01

In this work, cadmium sulfide nanoparticles (powder) with diameter 50.8 nm was prepared using hydrothermal method. The structural and optical properties of CdS nanoparticles was studied by X-ray diffraction, FESEM, EDS, FTIR, UV-Diffuse Reflectance spectroscopy and Photoluminance spectrum. X-ray diffraction reveal the formation the purity of prepared phase of CdS particles with hexagonal wurtzite structure with particle size 31.8nm by using sheerer equation. The energy dispersion scattering (EDS) examination explains that the sample is composed of a large amount of Cd and S which are exactly CdS nanoparticles and there is a very small trace of (Zn) and (O) element observed because of there is a small pollutions in the measurement place of samples. FESEM shows the spherical shape of nanoparticles with around 50.8 nm diameter. The optical absorption spectral study identified the red shift of the sample in comparison to bulk ZnO in three dimensions. Photoluminance spectrum (PL) at room temperature showed that there are two luminescence peaks at 433.14 nm and 518.21nm. Samples demonstrate a sharp emission band at around 433.18 nm, which is attributed to the typical exciton luminescence. The broad band at 518.21nm which were attributed to the trapped luminescence. The green emission band at 518.21 nm was associated with the emission due to electronic transition from the conduction band to an accepter level due to interstitial sulphur ion.

Polymeric Nanofibers in Tissue Engineering

PubMed Central

Dahlin, Rebecca L.; Kasper, F. Kurtis

2011-01-01

Polymeric nanofibers can be produced using methods such as electrospinning, phase separation, and self-assembly, and the fiber composition, diameter, alignment, degradation, and mechanical properties can be tailored to the intended application. Nanofibers possess unique advantages for tissue engineering. The small diameter closely matches that of extracellular matrix fibers, and the relatively large surface area is beneficial for cell attachment and bioactive factor loading. This review will update the reader on the aspects of nanofiber fabrication and characterization important to tissue engineering, including control of porous structure, cell infiltration, and fiber degradation. Bioactive factor loading will be discussed with specific relevance to tissue engineering. Finally, applications of polymeric nanofibers in the fields of bone, cartilage, ligament and tendon, cardiovascular, and neural tissue engineering will be reviewed. PMID:21699434

Characterization and morphology of prepared titanium dioxide nanofibers by electrospinning.

PubMed

Park, Ju-Young; Lee, In-Hwa

2010-05-01

Dispersed titanium dioxide in polymer nanofibers were prepared by sol-gel processing and electrospinning techniques using titanium isopropoxide (TiP)/polyvinylpyrrolidone (PVP) solution. The prepared titanium dioxide nanofibers were characterized by FE-SEM, TEM, XRD, and FT-IR. Pure titanium dioxide nanofibers were obtained from calcination of inorganic-organic composite fiber. The diameter of titanium oxide nanofibers were in the range of 70 nm to 150 nm. Prepared titanium dioxide nanofibers show rough surface and rather small diameter compare with TiP/PVP composite nanofibers. After calcined at 500 degrees C, TiO2 nanofibers convert into anatase and rutile mixed phased from amorphous structure. Calcination of these composite fibers above 600 degrees C resulted in pure rutile TiO2 nanofibers.

Estimating air-drying times of small-diameter ponderosa pine and Douglas-fir logs

Treesearch

William T. Simpson; Xiping Wang

2004-01-01

One potential use for small-diameter ponderosa pine and Douglas-fir timber is in log form. Many potential uses of logs require some degree of drying. Even though these small diameters may be considered small in the forestry context, their size when compared to typical lumber thickness dimensions is large. These logs, however, may require uneconomically long kiln-drying...

Experimental strategies for imaging bioparticles with femtosecond hard X-ray pulses

PubMed Central

Okamoto, Kenta; Bielecki, Johan; Maia, Filipe R. N. C.; Mühlig, Kerstin; Seibert, M. Marvin; Hantke, Max F.; Benner, W. Henry; Svenda, Martin; Ekeberg, Tomas; Loh, N. Duane; Pietrini, Alberto; Zani, Alessandro; Rath, Asawari D.; Westphal, Daniel; Kirian, Richard A.; Awel, Salah; Wiedorn, Max O.; van der Schot, Gijs; Carlsson, Gunilla H.; Hasse, Dirk; Sellberg, Jonas A.; Barty, Anton; Andreasson, Jakob; Boutet, Sébastien; Williams, Garth; Koglin, Jason; Hajdu, Janos; Larsson, Daniel S. D.

2017-01-01

This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. Aerosolized Omono River virus particles of ∼40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles. The results point to a wider than expected size distribution (from ∼35 to ∼300 nm in diameter). This is likely to be owing to nonvolatile contaminants from larger droplets during aerosolization and droplet evaporation. The results suggest that the concentration of nonvolatile contaminants and the ratio between the volumes of the initial droplet and the sample particles is critical in such studies. The maximum beam intensity in the focus was found to be 1.9 × 1012 photons per µm2 per pulse. The full-width of the focus at half-maximum was estimated to be 500 nm (assuming 20% beamline transmission), and this width is larger than expected. Under these conditions, the diffraction signal from a sample-sized particle remained above the average background to a resolution of 4.25 nm. The results suggest that reducing the size of the initial droplets during aerosolization is necessary to bring small particles into the scope of detailed structural studies with X-ray lasers. PMID:28512572

Spatial smoothing coherence factor for ultrasound computed tomography

NASA Astrophysics Data System (ADS)

Lou, Cuijuan; Xu, Mengling; Ding, Mingyue; Yuchi, Ming

2016-04-01

In recent years, many research studies have been carried out on ultrasound computed tomography (USCT) for its application prospect in early diagnosis of breast cancer. This paper applies four kinds of coherence-factor-like beamforming methods to improve the image quality of synthetic aperture focusing method for USCT, including the coherence-factor (CF), the phase coherence factor (PCF), the sign coherence factor (SCF) and the spatial smoothing coherence factor (SSCF) (proposed in our previous work). The performance of these methods was tested with simulated raw data which were generated by the ultrasound simulation software PZFlex 2014. The simulated phantom was set to be water of 4cm diameter with three nylon objects of different diameters inside. The ring-type transducer had 72 elements with a center frequency of 1MHz. The results show that all the methods can reveal the biggest nylon circle with the radius of 2.5mm. SSCF gets the highest SNR among the proposed methods and provides a more homogenous background. None of these methods can reveal the two smaller nylon circles with the radius of 0.75mm and 0.25mm. This may be due to the small number of elements.

Correlations for Vapor Nucleating Critical Embryo Parameters

NASA Astrophysics Data System (ADS)

Magnusson, Lars-Erik; Koropchak, John A.; Anisimov, Michael P.; Poznjakovskiy, Valeriy M.; de la Mora, Juan Fernandez

2003-12-01

Condensation nucleation light scattering detection in principle works by converting the effluent of the chromatographic separation into an aerosol and then selectively evaporating the mobile phase, leaving less volatile analytes and nonvolatile impurities as dry aerosol particles. The dry particles produced are then exposed to an environment that is saturated with the vapors of an organic solvent (commonly n-butanol). The blend of aerosol particles and organic vapor is then cooled so that conditions of vapor supersaturation are achieved. In principle, the vapor then condenses onto the dry particles, growing each particle (ideally) from as small as a few nanometers in diameter into a droplet with a diameter up to about 10 μm. The grown droplets are then passed through a beam of light, and the light scattered by the droplets is detected and used as the detector response. This growth and detection step is generally carried out using commercial continuous-flow condensation nucleus counters. In the present research, the possibility of using other fluids than the commonly used n-butanol is investigated. The Kelvin equation and the Nucleation theorem [Anisimov et al. (1978)] are used to evaluate a range of fluids for efficacy of growing small particles by condensation nucleation. Using the available experimental data on vapor nucleation, the correlations of Kelvin diameters (the critical embryo sizes) and the bulk surface tension with dielectric constants of working liquids are found. A simple method for choosing the most efficient fluid, within a class of fluids, for growth of small particles is suggested.

Extrusion of small-diameter, thin-wall tungsten tubing

NASA Technical Reports Server (NTRS)

Blankenship, C. P.; Gyorgak, C. A.

1967-01-01

Small-diameter, thin-wall seamless tubing of tungsten has been fabricated in lengths of up to 10 feet by hot extrusion over a floating mandrel. Extrusion of 0.50-inch-diameter tubing over 0.4-inch-diameter mandrels was accomplished at temperatures ranging from 3000 degrees to 4000 degrees F.

Effect of the Polymeric Stabilizer in the Aqueous Phase Fischer-Tropsch Synthesis Catalyzed by Colloidal Cobalt Nanocatalysts

PubMed Central

Delgado, Jorge A.; Claver, Carmen; Castillón, Sergio; Curulla-Ferré, Daniel; Godard, Cyril

2017-01-01

A series of small and well defined cobalt nanoparticles were synthesized by the chemical reduction of cobalt salts in water using NaBH4 as a reducing agent and using various polymeric stabilizers. The obtained nanocatalysts of similar mean diameters (ca. 2.6 nm) were fully characterized and tested in the aqueous phase Fischer-Tropsch Synthesis (AFTS). Interestingly, the nature and structure of the stabilizers used during the synthesis of the CoNPs affected the reduction degree of cobalt and the B-doping of these NPs and consequently, influenced the performance of these nanocatalysts in AFTS. PMID:28336892

77 FR 59374 - Certain Small Diameter Carbon and Alloy Seamless Standard, Line and Pressure Pipe (Under 41/2

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-27

... DEPARTMENT OF COMMERCE International Trade Administration [A-588-851] Certain Small Diameter Carbon and Alloy Seamless Standard, Line and Pressure Pipe (Under 4\\1/2\\ Inches) From Japan: Rescission... antidumping order on certain small diameter carbon and alloy seamless standard, line and pressure pipe (under...

Forest Products Laboratory research program on small-diameter material.

Treesearch

2000-01-01

Forests in the United States contain a significant amount of small-diameter and underutilized material. These overstocked stands not only increase the risk of insect, disease, fire, and drought damage, but also are costly to remove. Finding economical and marketable uses for small-diameter and underutilized material would alleviate these problems while improving...

75 FR 64250 - Small Diameter Graphite Electrodes From the People's Republic of China: Extension of Time Limit...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-19

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite Electrodes From the People's Republic of China: Extension of Time Limit for the Preliminary Results of the... review of the antidumping duty order on small diameter graphite electrodes from the People's Republic of...

Developing high coercivity in large diameter cobalt nanowire arrays

NASA Astrophysics Data System (ADS)

Montazer, A. H.; Ramazani, A.; Almasi Kashi, M.; Zavašnik, J.

2016-11-01

Regardless of the synthetic method, developing high magnetic coercivity in ferromagnetic nanowires (NWs) with large diameters has been a challenge over the past two decades. Here, we report on the synthesis of highly coercive cobalt NW arrays with diameters of 65 and 80 nm, which are embedded in porous anodic alumina templates with high-aspect-ratio pores. Using a modified electrochemical deposition method enabled us to reach room temperature coercivity and remanent ratio up to 3000 Oe and 0.70, respectively, for highly crystalline as-synthesized hcp cobalt NW arrays with a length of 8 μm. The first-order reversal curve (FORC) analysis showed the presence of both soft and hard magnetic phases along the length of the resulting NWs. To develop higher coercive fields, the length of the NWs was then gradually reduced in order from bottom to top, thereby reaching NW sections governed by the hard phase. Consequently, this resulted in record high coercivities of 4200 and 3850 Oe at NW diameters of 65 and 80 nm, respectively. In this case, the FORC diagrams confirmed a significant reduction in interactions between the magnetic phases of the remaining sections of NWs. At this stage, x-ray diffraction (XRD) and dark-field transmission electron microscopy analyses indicated the formation of highly crystalline bamboo-like sections along the [0 0 2] direction during a progressive pulse-controlled electrochemical growth of NW arrays under optimized parameters. Our results both provide new insights into the growth process, crystalline characteristics and magnetic phases along the length of large diameter NW arrays and, furthermore, develop the performance of pure 3d transition magnetic NWs.

Energy Efficient Engine exhaust mixer model technology report addendum; phase 3 test program

NASA Technical Reports Server (NTRS)

Larkin, M. J.; Blatt, J. R.

1984-01-01

The Phase 3 exhaust mixer test program was conducted to explore the trends established during previous Phases 1 and 2. Combinations of mixer design parameters were tested. Phase 3 testing showed that the best performance achievable within tailpipe length and diameter constraints is 2.55 percent better than an optimized separate flow base line. A reduced penetration design achieved about the same overall performance level at a substantially lower level of excess pressure loss but with a small reduction in mixing. To improve reliability of the data, the hot and cold flow thrust coefficient analysis used in Phases 1 and 2 was augmented by calculating percent mixing from traverse data. Relative change in percent mixing between configurations was determined from thrust and flow coefficient increments. The calculation procedure developed was found to be a useful tool in assessing mixer performance. Detailed flow field data were obtained to facilitate calibration of computer codes.

Lumber volume and value recovery from small-diameter black cherry, sugar maple, and red oak logs

Treesearch

Jan Wiedenbeck; Matthew Scholl; Paul Blankenhorn; Chuck Ray

2017-01-01

While only a very small percentage of hardwood logs sawn by conventional sawmills in the U.S. have small-end diameters less than 10 in, portable and scragg mills often saw smaller logs. With the closure of regionally important oriented strand board and pulpwood operations, small-diameter logs are considered to have no value in some markets. This study was...

Process property studies of melt blown thermoplastic polyurethane polymers

NASA Astrophysics Data System (ADS)

Lee, Youn Eung

The primary goal of this research was to determine optimum processing conditions to produce commercially acceptable melt blown (MB) thermoplastic polyurethane (TPU) webs. The 6-inch MB line and the 20-inch wide Accurate Products MB pilot line at the Textiles and Nonwovens Development Center (TANDEC), The University of Tennessee, Knoxville, were utilized for this study. The MB TPU trials were performed in four different phases: Phase 1 focused on the envelope of the MB operating conditions for different TPU polymers; Phase 2 focused on the production of commercially acceptable MB TPU webs; Phase 3 focused on the optimization of the processing conditions of MB TPU webs, and the determination of the significant relationships between processing parameters and web properties utilizing statistical analyses; Based on the first three phases, a more extensive study of fiber and web formation in the MB TPU process was made and a multi liner regression model for the MB TPU process versus properties was also developed in Phase 4. In conclusion, the basic MB process was fundamentally valid for the MB TPU process; however, the MB process was more complicated for TPU than PP, because web structures and properties of MB TPUs are very sensitive to MB process conditions: Furthermore, different TPU grades responded very differently to MB processing and exhibited different web structure and properties. In Phase 3 and Phase 4, small fiber diameters of less than 5mum were produced from TPU237, TPU245 and TPU280 pellets, and the mechanical strengths of MB TPU webs including the tensile strength, tear strength, abrasion resistance and tensile elongation were notably good. In addition, the statistical model showed useful interaction regarding trends for processing parameters versus properties of MB TPU webs. Die and air temperature showed multicollinearity problems and fiber diameter was notably affected by air flow rate, throughput and die/air temperature. It was also shown that most of the MB TPU web properties including mechanical strength, air permeability and fiber diameters were affected by air velocity and die temperature.

Phase behavior of colloidal dimers and hydrodynamic instabilities in binary mixtures

NASA Astrophysics Data System (ADS)

Milinkovic, K.

2013-05-01

We use computer simulations to study colloidal suspensions comprised of either bidisperse spherical particles or monodisperse dimer particles. The two main simulation techniques employed are a hybrid between molecular dynamics and stochastic rotation dynamics (MD-SRD), and a Monte Carlo (MC) algorithm. MD-SRD allows us to take Brownian motion and hydrodynamic interactions into account, while we use MC simulations to study equilibrium phase behavior. The first part of this thesis is dedicated to studying the Rayleigh-Taylor-like hydrodynamic instabilities which form in binary colloidal mixtures. Configurations with initially inhomogeneous distributions of colloidal species let to sediment in confinement will undergo the instability, and here we have studied the formation, evolution and the structural organization of the colloids within the instability as a function of the properties of the binary mixture. We found that the distribution of the colloids within the instability does not depend significantly on the composition of the mixtures, but does depend greatly on the relative magnitudes of the particle Peclet numbers. To follow the time evolution of the instability formation we calculated the spatial colloid velocity correlation functions, observing alternating regions in which the particle sedimentation velocities are correlated and anticorrelated. These observations are consistent with the network-like structures which are characteristic for Rayleigh-Taylor instabilities. We also calculated the growth rates of the unstable modes both from our simulation data and theoretically, finding good agreement between the obtained results. The second part of this thesis focuses on the phase behavior of monodisperse dimer systems. We first studied the phase behavior of hard snowman-shaped particles which consist of tangential hard spheres with different diameters. We used Monte Carlo simulations and free energy calculations to obtain the phase diagram as a function of the sphere diameter ratio, predicting stable isotropic fluid, plastic crystal and aperiodic crystalline phases. The crystalline phases found to be stable for a given diameter ratio at high densities correspond to the close packed structures of equimolar binary hard-sphere mixtures with the same diameter ratio. However, we also predict several crystal-crystal phase transitions, such that the best packed structures are stable at higher densities, while those with a higher degree of degeneracy are stable at lower densities. To explore the effects of degeneracy entropy on the phase behavior of dimer particles, we calculated the phase diagram of hard asymmetric dumbbells. These particles consist of two spheres with fixed diameters and varying center-to-center separation. We predicted stable isotropic fluid, plastic crystal, and periodic NaCl-based and both periodic and aperiodic CrB-based crystalline phases, and found that reducing the sphere separation results in the aperiodic crystalline phases of snowman-shaped particles becoming destabilized. Finally, we have also studied the phase behavior of dumbbell particles interacting with hard-core repulsive Yukawa potentials. We found that dumbbells with sufficiently long-ranged interactions crystallize spontaneously into plastic crystals in which the particle centers of mass are located on average on a BCC crystal lattice. The auto- and spatial orientational correlation functions reveal no significant hindrance of the particle rotations even for the shortest ranged interactions studied.

Thermodynamically stable vesicle formation from glycolipid biosurfactant sponge phase.

PubMed

Imura, Tomohiro; Yanagishita, Hiroshi; Ohira, Junko; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

2005-06-25

Thermodynamically stable vesicle (L(alpha1)) formation from glycolipid biosurfactant sponge phase (L(3)) and its mechanism were investigated using a "natural" biocompatible mannosyl-erythritol lipid-A (MEL-A)/L-alpha-dilauroylphosphatidylcholine (DLPC) mixture by varying the composition. The trapping efficiency for calcein and turbidity measurements clearly indicated the existence of three regions: while the trapping efficiencies of the mixed MEL-A/DLPC assemblies at the compositions with X(DLPC)< or =0.1 or X(DLPC)> or =0.8 were almost zero, the mixed assemblies at the compositions with 0.1 or =0.8 were multilamellar vesicles (L(alpha)) with diameter from 2 to 10 microm. Meanwhile, dynamic light scattering (DLS) measurement revealed that the average size of the vesicles at the composition of X(DLPC)=0.3 was 633.2 nm, which is remarkably small compared to other compositions. Moreover, the mixed vesicle solution at the composition of X(DLPC)=0.3 was slightly bluish and turbid and kept its dispersion stability at 25 degrees C for more than 3 months, indicating the formation of a thermodynamically stable vesicle (L(alpha1)). These results exhibited the formation of a thermodynamically stable vesicle (L(alpha1)) with a high dispersibility from the MEL-A/DLPC mixture. The asymmetric distribution of MEL-A and DLPC in the two vesicle monolayers caused by the difference in geometrical structures is very likely to have changed their self-assembled structure from a sponge phase (L(3)) to a thermodynamically stable vesicle (L(alpha1)).

Liquid-liquid equilibrium in the- n-heptane- n-perfluorohexane system

NASA Astrophysics Data System (ADS)

Khairulin, R. A.; Stankus, S. V.; Gruzdev, V. A.; Bityutskii, V. A.

2009-01-01

The shape of the liquid-liquid coexistence curve in the C7H16-C6F14 system in the molar concentration-temperature coordinates close to the critical solution point was studied by narrow-beam gamma-raying of two-phase samples. The molar volumes of the coexisting liquid phases and critical point coordinates (critical temperature T c = 316.266 ± 0.03 K and critical concentration x c = 39.0 ± 0.4 mol % C6F14) were determined. The critical index β of the coexistence curve was found to be 0.322 ± 0.005. The diameter of the coexistence curve did not obey the classic “rectilinear diameter rule.”

Leakage effect analysis on the performance of a cylindrical adjustable inertance tube

NASA Astrophysics Data System (ADS)

Zhou, Wenjie; Pfotenhauer, John M.; Zhi, Xiaoqin

2018-04-01

The inertance tube plays a significant role in improving the performance of the Stirling type pulse tube cryocooler by providing the desired phase angle between the mass flow and pressure wave. The phase angle is highly depended on the inertance tube geometry, such as diameter and length. A cylindrical threaded root device with variable thread depth on the outer screw and inner screw creates an adjustable inertance tube whose diameter and length can be adjusted in the real time. However, due to its geometry imperfectness, the performance of this threaded inertance tube is reduced by the leaks through the roots between the two screws. Its phase angle shift ability is decreased by 30% with the leakage clearance thickness of 15.5 μm according to both the theoretical prediction and the experimental verification.

Production and cost of harvesting, processing, and transporting small-diameter (< 5 inches) trees for energy

Treesearch

Fei Pan; Han-Sup Han; Leonard R. Johnson; William J. Elliot

2008-01-01

Dense, small-diameter stands generally require thinning from below to improve fire-tolerance. The resulting forest biomass can be used for energy production. The cost of harvesting, processing, and transporting small-diameter trees often exceeds revenues due to high costs associated with harvesting and transportation and low market values for forest biomass....

Options for small-diameter hardwood utilization: past and present

Treesearch

Matthew S. Bumgardner; Bruce G. Hansen; Albert T. Schuler; Philip A. Araman

2000-01-01

Effective and maximum value use of small-diameter hardwood timber has long been of interest to forest managers and researchers. In addition to being a significant component of the standing forest base, small-diameter hardwoods often are available after thinning or other tending operations. Although the use of this material is important to achieving healthy and...

Evaluation of roll-off trailers in small-diameter applications

Treesearch

Bob Rummer; John Klepac

2003-01-01

Concern about wildfire in overstocked forests of the western U.S. has led to increased emphasis on extraction of small-diameter material. Removing this material improves forest health, reduces fuel loading, and may generate value that can be used to offset the costs of operation. However, the cost of small-diameter operations (both in-woods and secondary processing)...

Small-diameter success stories II

Treesearch

Jean Livingston

2006-01-01

Many of our national forests are in critical need of restoration. These forests are dense, with an abundance of small-diameter, tightly spaced trees and underbrush that can contribute to the rapid growth of fire. If economic and value-added uses for this small-diameter and unmerchantable material can be found, forest restoration costs could be offset and catastrophic...

Options for Small-Diameter Hardwood Utilization: Past and Present

Treesearch

Matthew S. Bumgardner; Bruce G. Hansen; Albert T. Schuler; Philip A. Araman; Philip A. Araman

2001-01-01

Effective and maximum value use of small-diameter hardwood timber has long been of interest to forest managers and researchers. In addition to being a significant component of the standing forest base, small-diameter hardwoods often are available after thinning or other tending operations. Although the use of this material is important to achieving healthy and...

Multiple Small Diameter Drillings Increase Femoral Neck Stability Compared with Single Large Diameter Femoral Head Core Decompression Technique for Avascular Necrosis of the Femoral Head.

PubMed

Brown, Philip J; Mannava, Sandeep; Seyler, Thorsten M; Plate, Johannes F; Van Sikes, Charles; Stitzel, Joel D; Lang, Jason E

2016-10-26

Femoral head core decompression is an efficacious joint-preserving procedure for treatment of early stage avascular necrosis. However, postoperative fractures have been described which may be related to the decompression technique used. Femoral head decompressions were performed on 12 matched human cadaveric femora comparing large 8mm single bore versus multiple 3mm small drilling techniques. Ultimate failure strength of the femora was tested using a servo-hydraulic material testing system. Ultimate load to failure was compared between the different decompression techniques using two paired ANCOVA linear regression models. Prior to biomechanical testing and after the intervention, volumetric bone mineral density was determined using quantitative computed tomography to account for variation between cadaveric samples and to assess the amount of bone disruption by the core decompression. Core decompression, using the small diameter bore and multiple drilling technique, withstood significantly greater load prior to failure compared with the single large bore technique after adjustment for bone mineral density (p< 0.05). The 8mm single bore technique removed a significantly larger volume of bone compared to the 3mm multiple drilling technique (p< 0.001). However, total fracture energy was similar between the two core decompression techniques. When considering core decompression for the treatment of early stage avascular necrosis, the multiple small bore technique removed less bone volume, thereby potentially leading to higher load to failure.

Applications of the Analytical Electron Microscope to Materials Science

NASA Technical Reports Server (NTRS)

Goldstein, J. I.

1992-01-01

In the last 20 years, the analytical electron microscope (AEM) as allowed investigators to obtain chemical and structural information from less than 50 nanometer diameter regions in thin samples of materials and to explore problems where reactions occur at boundaries and interfaces or within small particles or phases in bulk samples. Examples of the application of the AEM to materials science problems are presented in this paper and demonstrate the usefulness and the future potential of this instrument.

Phase rainbow refractometry for accurate droplet variation characterization.

PubMed

Wu, Yingchun; Promvongsa, Jantarat; Saengkaew, Sawitree; Wu, Xuecheng; Chen, Jia; Gréhan, Gérard

2016-10-15

We developed a one-dimensional phase rainbow refractometer for the accurate trans-dimensional measurements of droplet size on the micrometer scale as well as the tiny droplet diameter variations at the nanoscale. The dependence of the phase shift of the rainbow ripple structures on the droplet variations is revealed. The phase-shifting rainbow image is recorded by a telecentric one-dimensional rainbow imaging system. Experiments on the evaporating monodispersed droplet stream show that the phase rainbow refractometer can measure the tiny droplet diameter changes down to tens of nanometers. This one-dimensional phase rainbow refractometer is capable of measuring the droplet refractive index and diameter, as well as variations.

Method and device for tensile testing of cable bundles

DOEpatents

Robertson, Lawrence M; Ardelean, Emil V; Goodding, James C; Babuska, Vit

2012-10-16

A standard tensile test device is improved to accurately measure the mechanical properties of stranded cables, ropes, and other composite structures wherein a witness is attached to the top and bottom mounting blocks holding the cable under test. The witness is comprised of two parts: a top and a bottom rod of similar diameter with the bottom rod having a smaller diameter stem on its upper end and the top rod having a hollow opening in its lower end into which the stem fits forming a witness joint. A small gap is present between the top rod and the larger diameter portion of the bottom rod. A standard extensometer is attached to the top and bottom rods of the witness spanning this small witness gap. When a force is applied to separate the mounting blocks, the gap in the witness expands the same length that the entire test specimen is stretched.

Multi-scale imaging and elastic simulation of carbonates

NASA Astrophysics Data System (ADS)

Faisal, Titly Farhana; Awedalkarim, Ahmed; Jouini, Mohamed Soufiane; Jouiad, Mustapha; Chevalier, Sylvie; Sassi, Mohamed

2016-05-01

Digital Rock Physics (DRP) is an emerging technology that can be used to generate high quality, fast and cost effective special core analysis (SCAL) properties compared to conventional experimental techniques and modeling techniques. The primary workflow of DRP conssits of three elements: 1) image the rock sample using high resolution 3D scanning techniques (e.g. micro CT, FIB/SEM), 2) process and digitize the images by segmenting the pore and matrix phases 3) simulate the desired physical properties of the rocks such as elastic moduli and velocities of wave propagation. A Finite Element Method based algorithm, that discretizes the basic Hooke's Law equation of linear elasticity and solves it numerically using a fast conjugate gradient solver, developed by Garboczi and Day [1] is used for mechanical and elastic property simulations. This elastic algorithm works directly on the digital images by treating each pixel as an element. The images are assumed to have periodic constant-strain boundary condition. The bulk and shear moduli of the different phases are required inputs. For standard 1.5" diameter cores however the Micro-CT scanning reoslution (around 40 μm) does not reveal smaller micro- and nano- pores beyond the resolution. This results in an unresolved "microporous" phase, the moduli of which is uncertain. Knackstedt et al. [2] assigned effective elastic moduli to the microporous phase based on self-consistent theory (which gives good estimation of velocities for well cemented granular media). Jouini et al. [3] segmented the core plug CT scan image into three phases and assumed that micro porous phase is represented by a sub-extracted micro plug (which too was scanned using Micro-CT). Currently the elastic numerical simulations based on CT-images alone largely overpredict the bulk, shear and Young's modulus when compared to laboratory acoustic tests of the same rocks. For greater accuracy of numerical simulation prediction, better estimates of moduli inputs for this current unresolved phase is important. In this work we take a multi-scale imaging approach by first extracting a smaller 0.5" core and scanning at approx 13 µm, then further extracting a 5mm diameter core scanned at 5 μm. From this last scale, region of interests (containing unresolved areas) are identified for scanning at higher resolutions using Focalised Ion Beam (FIB/SEM) scanning technique reaching 50 nm resolution. Numerical simulation is run on such a small unresolved section to obtain a better estimate of the effective moduli which is then used as input for simulations performed using CT-images. Results are compared with expeirmental acoustic test moduli obtained also at two scales: 1.5" and 0.5" diameter cores.

Research on the cavitation characteristic of Kaplan turbine under sediment flow condition

NASA Astrophysics Data System (ADS)

Weili, L.; Jinling, L.; Xingqi, L.; Yuan, L.

2010-08-01

The sediment concentration in many rivers in our world is very high, and the Kaplan turbine running in these rivers are usually seriously abraded. Since the existence of sand, the probability of cavitation is greatly enhanced. Under the joint action and mutual promotion of cavitation and sand erosion, serious abrasion could be made, the hydraulic performance of the Kaplan turbine may be descended, and the safety and stability of turbine are greatly threatened. Therefore, it is very important and significant to investigate the cavitation characteristic of Kaplan turbine under sediment flow condition. In this paper, numerical simulation of cavitation characteristic in pure water and solid-liquid two-phase flow in Kaplan turbine was performed. The solid-liquid two-fluid model were adopted in the numerical simulation, and the pressure, velocity and particle concentration distributive regularity on turbine blade surface under different diameter and concentration was revealed. Particle trajectory model was used to investigate the region and degree of runner blade abrasion in different conditions. The results showed that serious sand abrasion could be found near the blade head and outlet in large flow rate working condition. Relatively slight abrasion may be found near blade flange in small flow rate working condition. The more the sediment concentration and the large the sand diameter, the serious the runner is abraded, and the greater the efficiency is decreased. further analysis of the combined effects of wear and abrasion was performed. The result shows that the cavitation in silt flow is more serious than in pure water. The runner cavitation performance become worse under high sand concentration and large particle diameter, and the efficiency decrease greatly with the increase of sediment concentration.

Critical Coupling Between Optical Fibers and WGM Resonators

NASA Technical Reports Server (NTRS)

Matsko, Andrey; Maleki, Lute; Itchenko, Vladimir; Savchenkov, Anatoliy

2009-01-01

Two recipes for ensuring critical coupling between a single-mode optical fiber and a whispering-gallery-mode (WGM) optical resonator have been devised. The recipes provide for phase matching and aperture matching, both of which are necessary for efficient coupling. There is also a provision for suppressing intermodal coupling, which is detrimental because it drains energy from desired modes into undesired ones. According to one recipe, the tip of the single-mode optical fiber is either tapered in diameter or tapered in effective diameter by virtue of being cleaved at an oblique angle. The effective index of refraction and the phase velocity at a given position along the taper depend on the diameter (or effective diameter) and the index of refraction of the bulk fiber material. As the diameter (or effective diameter) decreases with decreasing distance from the tip, the effective index of refraction also decreases. Critical coupling and phase matching can be achieved by placing the optical fiber and the resonator in contact at the proper point along the taper. This recipe is subject to the limitation that the attainable effective index of refraction lies between the indices of refraction of the bulk fiber material and the atmosphere or vacuum to which the resonator and fiber are exposed. The other recipe involves a refinement of the previously developed technique of prism coupling, in which the light beam from the optical fiber is collimated and focused onto one surface of a prism that has an index of refraction greater than that of the resonator. Another surface of the prism is placed in contact with the resonator. The various components are arranged so that the collimated beam is focused at the prism/resonator contact spot. The recipe includes the following additional provisions:

Evaluation of a Two-Phase Experimental Study of a Small Group ("MultiLit") Reading Intervention for Older Low-Progress Readers

ERIC Educational Resources Information Center

Buckingham, Jennifer; Beaman-Wheldall, Robyn; Wheldall, Kevin

2014-01-01

The study reported here examined the efficacy of a small group (Tier 2 in a three-tier Response to Intervention model) literacy intervention for older low-progress readers (in Years 3-6). This article focuses on the second phase of a two-phase, crossover randomized control trial involving 26 students. In Phase 1, the experimental group (E1)…

Status of use of lunar irradiance for on-orbit calibration

USGS Publications Warehouse

Stone, T.C.; Kieffer, H.H.; Anderson, J.M.; ,

2002-01-01

Routine observations of the Moon have been acquired by the Robotic Lunar Observatory (ROLO) for over four years. The ROLO instruments measure lunar radiance in 23 VNIR (Moon diameter ???500 pixels) and 9 SWIR (???250 pixels) passbands every month when the Moon is at phase angle less than 90 degrees. These are converted to exoatmospheric values at standard distances using an atmospheric extinction model based on observations of standard stars and a NIST-traceable absolute calibration source. Reduction of the stellar images also provides an independent pathway for absolute calibration. Comparison of stellar-based and lamp-based absolute calibrations of the lunar images currently shows unacceptably large differences. An analytic model of lunar irradiance as a function of phase angle and viewing geometry is derived from the calibrated lunar images. Residuals from models which fit hundreds of observations at each wavelength average less than 2%. Comparison with SeaWiFS observations over three years reveals a small quasi-periodic change in SeaWiFS responsivity that correlates with distance from the Sun for the first two years, then departs from this correlation.

CFD Modelling of Particle Mixtures in a 2D CFB

NASA Astrophysics Data System (ADS)

Seppälä, M.; Kallio, S.

The capability of Fluent 6.2.16 to simulate particle mixtures in a laboratory scale 2D circulating fluidized bed (CFB) unit has been tested. In the simulations, the solids were described as one or two particle phases. The loading ratio of small to large particles, particle diameters and the gas inflow velocity were varied. The 40 cm wide and 3 m high 2D CFB was modeled using a grid with 31080 cells. The outflow of particles at the top of the CFB was monitored and emanated particles were fed back to the riser through a return duct. The paper presents the segregation patterns of the particle phases obtained from the simulations. When the fraction of large particles was 50% or larger, large particles segregated, as expected, to the wall regions and to the bottom part of the riser. However, when the fraction of large particles was 10%, an excess of large particles was found in the upper half of the riser. The explanation for this unexpected phenomenon was found in the distribution of the large particles between the slow clusters and the faster moving lean suspension.

A flexible, bolaamphiphilic template for mesoporous silicas.

PubMed

Yuen, Alexander K L; Heinroth, Falk; Ward, Antony J; Masters, Anthony F; Maschmeyer, Thomas

2013-08-28

A novel symmetrical bolaamphiphile, containing two N-methylimidazolium head-groups bridged by a 32-methylene linker, was synthesized and characterized. A variety of mesoporous silicas was prepared using the bolaamphiphile as a "soft template". The effects of absolute surfactant concentration and synthesis conditions upon the morphologies of these silicas were investigated. For a given surfactant concentration, particle morphology; pore size; and pore ordering were modified through control of the template to silica-precursor ratio and synthesis conditions. Observed morphologies included: lenticular core-shell nanoparticles and decorticated globules, truncated hexagonal plates, and sheets. In all cases the mesopores are aligned along the shortest axis of the nanomaterial. Decorticated materials displayed surface areas of up to 1200 m(2) g(-1) and pore diameters (D(BJH)) of 24-28 Å. Small-angle X-ray diffraction and transmission electron microscopy measurements revealed that the majority of the materials has elliptical pores arranged in rectangular lattices (c2mm). Adoption of this symmetry group is a result of the template aggregate deformation from a regular hexagonal phase of cylindrical rods to a ribbon phase under the synthetic conditions.

3D visualization of two-phase flow in the micro-tube by a simple but effective method

NASA Astrophysics Data System (ADS)

Fu, X.; Zhang, P.; Hu, H.; Huang, C. J.; Huang, Y.; Wang, R. Z.

2009-08-01

The present study provides a simple but effective method for 3D visualization of the two-phase flow in the micro-tube. An isosceles right-angle prism combined with a mirror located 45° bevel to the prism is employed to synchronously obtain the front and side views of the flow patterns with a single camera, where the locations of the prism and the micro-tube for clear imaging should satisfy a fixed relationship which is specified in the present study. The optical design is proven successfully by the tough visualization work at the cryogenic temperature range. The image deformation due to the refraction and geometrical configuration of the test section is quantitatively investigated. It is calculated that the image is enlarged by about 20% in inner diameter compared to the real object, which is validated by the experimental results. Meanwhile, the image deformation by adding a rectangular optical correction box outside the circular tube is comparatively investigated. It is calculated that the image is reduced by about 20% in inner diameter with a rectangular optical correction box compared to the real object. The 3D re-construction process based on the two views is conducted through three steps, which shows that the 3D visualization method can easily be applied for two-phase flow research in micro-scale channels and improves the measurement accuracy of some important parameters of the two-phase flow such as void fraction, spatial distribution of bubbles, etc.

Building America Case Study: Standard- Versus High-Velocity Air Distribution in High-Performance Townhomes, Denver, Colorado

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

IBACOS investigated the performance of a small-diameter high velocity heat pump system compared to a conventional system in a new construction triplex townhouse. A ductless heat pump system also was installed for comparison, but the homebuyer backed out because of aesthetic concerns about that system. In total, two buildings, having identical solar orientation and comprised of six townhomes, were monitored for comfort and energy performance. Results show that the small-diameter system provides more uniform temperatures from floor to floor in the three-story townhome. No clear energy consumption benefit was observed from either system. The builder is continuing to explore themore » small-diameter system as its new standard system to provide better comfort and indoor air quality. The homebuilder also explored the possibility of shifting its townhome product to meet the U.S. Department of Energy Challenge Home National Program Requirements. Ultimately, the builder decided that adoption of these practices would be too disruptive midstream in the construction cycle. However, the townhomes met the ENERGY STAR Version 3.0 program requirements.« less

Comparative Cooling Season Performance of Air Distribution Systems in Multistory Townhomes

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

Poerschke, Andrew; Beach, Rob; Beggs, Timothy

2016-08-01

IBACOS investigated the performance of a small-diameter high velocity heat pump system compared to a conventional system in a new construction triplex townhouse. A ductless heat pump system also was installed for comparison, but the homebuyer backed out because of aesthetic concerns about that system. In total, two buildings, having identical solar orientation and comprised of six townhomes, were monitored for comfort and energy performance. Results show that the small-diameter system provides more uniform temperatures from floor to floor in the three-story townhome. No clear energy consumption benefit was observed from either system. The builder is continuing to explore themore » small-diameter system as its new standard system to provide better comfort and indoor air quality. The homebuilder also explored the possibility of shifting its townhome product to meet the U.S. Department of Energy Challenge Home National Program Requirements. Ultimately, the builder decided that adoption of these practices would be too disruptive midstream in the construction cycle. However, the townhomes met the ENERGY STAR Version 3.0 program requirements.« less

Shiitake mushroom production on small diameter oak logs in Ohio

Treesearch

S.M. Bratkovich

1991-01-01

Yields of different strains of shiitake mushrooms (Lentinus edodes) were evaluated when produced on small diameter oak logs in Ohio. Logs averaging between 3-4 inches in diameter were inoculated with four spawn strains in 1985.

Experiment data for determination of uncertainty of two-phase mass flow rate in a Semiscale Mod-3 system spool piece at Karlsruhe Kernforschungzentrum. [PWR

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

Stephens, A.G.

1979-06-01

Steady state, steam-water testing of a Semiscale Mod-3 system instrumented spool piece was accomplished in the Gesellschaft fur Kernforschung (GfK) facility at Karlsruhe Kernforschungzentrum, West Germany. The testing was undertaken to determine the accuracy of spool piece, two-phase mass flow rate, inferential measurements by comparison with upstream single-phase reference measurements. Other two-phase measurements were also made to aid in understanding the flow conditions and to implement data reduction. A total of 132 single- and two-phase test points were acquired, covering pressures from 0.4 to 7.5 MPa, flow rates from 0.5 to 4.9 kg/s, and two-phase mixture qualities from 1.0 tomore » 83% in the 66.7 mm inside diameter spool piece. The report includes a detailed description of the hardware and software and a tabulation of the data.« less

Investigation of two-phase heat transfer coefficients of argon-freon cryogenic mixed refrigerants

NASA Astrophysics Data System (ADS)

Baek, Seungwhan; Lee, Cheonkyu; Jeong, Sangkwon

2014-11-01

Mixed refrigerant Joule Thomson refrigerators are widely used in various kinds of cryogenic systems these days. Although heat transfer coefficient estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in the heat exchanger design of mixed refrigerant Joule Thomson refrigerators, it has been rarely discussed so far. In this paper, condensation and evaporation heat transfer coefficients of argon-freon mixed refrigerant are measured in a microchannel heat exchanger. A Printed Circuit Heat Exchanger (PCHE) with 340 μm hydraulic diameter has been developed as a compact microchannel heat exchanger and utilized in the experiment. Several two-phase heat transfer coefficient correlations are examined to discuss the experimental measurement results. The result of this paper shows that cryogenic two-phase mixed refrigerant heat transfer coefficients can be estimated by conventional two-phase heat transfer coefficient correlations.

Economic feasibility of products from inland West small-diameter timber

Treesearch

Spelter Henry; Rong Wang; Peter Ince

1996-01-01

A large part of the forests located in the Rocky Mountain region of the U.S. West (inland West) is characterized by densely packed, small-diameter stands. The purpose of this study was to examine the economic feasibility of using small-diameter material from this resource to manufacture various wood products: oriented strandboard (OSB), stud lumber, random-length...

78 FR 62597 - 36(b)(1) Arms Sales Notification

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-22

... Block II missiles, 1000 GBU-39/B Small Diameter Bomb (SDB) with BRU-61 carriage systems, 40 CATM-84H... missiles, 1000 GBU-39/B Small Diameter Bombs (SDB), 40 CATM-84H Captive Air Training Missiles (CATM), 20... Small Diameter Bomb (SDB) I weapon is a 250-lb class, all-up round (AUR) that provides greater than 50nm...

78 FR 62594 - 36(b)(1) Arms Sales Notification

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-22

... Consideration for Purchase: 5000 GBU-39/B Small Diameter Bombs (SDB) with BRU-61 carriage systems, 8 SDB Guided... Emirates has requested a possible sale of 5000 GBU-39/B Small Diameter Bombs (SDB) with BRU-61 carriage... environmental conditions. 5. The GBU-39/B Small Diameter Bomb (SDB) I weapon is a 250-lb class, all-up round...

Suitability of live and fire-killed small-diameter ponderosa and lodgepole pine trees for manufacturing a new structural wood composite

Treesearch

J.M. Linton; H.M. Barnes; R.D. Seale; P.D. Jones; E. Lowell; S.S. Hummel

2010-01-01

Finding alternative uses for raw material from small-diameter trees is a critical problem throughout the United States. In western states, a lack of markets for small-diameter ponderosa pine (Pinus ponderosa) and lodgepole pine (Pinus contorta ) can contribute to problems associated with overstocking. To test the feasibility of...

Gas dispersion and immobile gas volume in solid and porous particle biofilter materials at low air flow velocities.

PubMed

Sharma, Prabhakar; Poulsen, Tjalfe G

2010-07-01

Gas-phase dispersion in granular biofilter materials with a wide range of particle sizes was investigated using atmospheric air and nitrogen as tracer gases. Two types of materials were used: (1) light extended clay aggregates (LECA), consisting of highly porous particles, and (2) gravel, consisting of solid particles. LECA is a commercial material that is used for insulation, as a soil conditioner, and as a carrier material in biofilters for air cleaning. These two materials were selected to have approximately the same particle shape. Column gas transport experiments were conducted for both materials using different mean particle diameters, different particle size ranges, and different gas flow velocities. Measured breakthrough curves were modeled using the advection-dispersion equation modified for mass transfer between mobile and immobile gas phases. The results showed that gas dispersivity increased with increasing mean particle diameter for LECA but was independent of mean particle diameter for gravel. Gas dispersivity also increased with increasing particle size range for both media. Dispersivities in LECA were generally higher than for gravel. The mobile gas content in both materials increased with increasing gas flow velocity but it did not show any strong dependency on mean particle diameter or particle size range. The relative fraction of mobile gas compared with total porosity was highest for gravel and lowest for LECA likely because of its high internal porosity.

[Characterization of microstructure of ibuprofen-hydroxypropyl-beta-cyclodextrin and ibuprofen-beta-cyclodextrin by atomic force microscope].

PubMed

Wang, Li-juan; Zhu, Zhao-jing; Che, Ke-ke; Ju, Feng-ge

2008-09-01

The microstructures of ibuprofen-hydroxypropyl-bets-cyclodextrin (IBU-HP-beta-CyD) and ibuprofen-beta-cyclodextrin (IBU-beta-CyD) were observed by atomic force microscope (AFM). The high resolving capability of AFM has the tungsten filament probe with the spring constant of 0.06 N x m(-1). Samples were observed in a small scale scanning area of 10.5 nm x 10.5 nm and 800 x 800 pixels. The original scanning images were gained by tapping mode at room temperature. Their three-dimensional reconstruction of microstructure was performed by G3DR software. The outer diameters of HP-beta-CyD and beta-CyD are 1.53 nm. The benzene diameter of IBU is 0.62 nm, fitting to the inner diameters of HP-beta-CyD and beta-CyD. The benzene and hydrophobic chain of IBU enter into the hole of cyclodextrin at 1:1 ratio. The results were evidenced by IR, X-ray diffraction and the phase solubility.

Structure and mechanical properties of as-received and heat-treated stainless steel orthodontic wires.

PubMed

Khier, S E; Brantley, W A; Fournelle, R A

1988-03-01

A combination of x-ray diffraction analysis with mechanical testing in tension and bending has been used to investigate the metallurgical structures and mechanical properties for as-received and heat-treated stainless steel orthodontic wires. Two different proprietary wire types were selected, having a wide range in cross-sectional dimensions: 0.016-, 0.030-, and 0.050- or 0.051-inch diameters, and 0.017 X 0.025-inch rectangular specimens. Heat treatments were performed for 10 minutes in air at temperatures of 700 degrees, 900 degrees, and 1100 degrees F. The x-ray diffraction patterns showed that the as-received 0.016-inch diameter and 0.017 X 0.025-inch wires of both proprietary types consisted of a two-phase structure containing a martensitic phase along with the austenitic phase. This duplex structure was converted entirely to austenite with heat treatment for one wire type, but persisted after heat treatment for the other wire type. The largest diameter, 0.050- or 0.051-inch, wires of both types were single-phase austenitic structure for both the as-received and heat-treated conditions. Evidence of substantial preferred crystallographic orientation or texturing in these orthodontic wires was also found by x-ray diffraction. As in our previous studies, the modulus of elasticity in bending was significantly less than the value obtained in tension for only the smaller cross-sectional wires. The 0.05 radian flexural yield strength correlated more closely with the 0.2% offset yield strength in tension than with the yield strength for 0.05% and 0.1% permanent offsets.

Propulsion simulator for magnetically-suspended wind tunnel models

NASA Technical Reports Server (NTRS)

Joshi, P. B.; Malonson, M. R.; Sacco, G. P.; Goldey, C. L.; Garbutt, Keith; Goodyer, M.

1992-01-01

In order to demonstrate the measurement of aerodynamic forces/moments, including the effects of exhaust jets in Magnetic Suspension and Balance System (MSBS) wind tunnels, two propulsion simulator models were developed at Physical Sciences Inc. (PSI). Both the small-scale model (1 in. diameter X 8 in. long) and the large-scale model (2.5 in. diameter X 15 in. long) employed compressed, liquefied carbon dioxide as a propellant. The small-scale simulator, made from a highly magnetizable iron alloy, was demonstrated in the 7 in. MSBS wind tunnel at the University of Southampton. It developed a maximum thrust of approximate 1.3 lbf with a 0.098 in. diameter nozzle and 0.7 lbf with a 0.295 in. diameter nozzle. The Southampton MSBS was able to control the simulator at angles-of attack up to 20 deg. The large-scale simulator was demonstrated to operate in both a steady-state and a pulse mode via a miniaturized solinoid valve. It developed a stable and repeatable thrust of 2.75 lbf over a period of 4s and a nozzle pressure ratio (NPR) of 5.

The effects of nanostructures on the mechanical and tribological properties of TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Yoon, Yeoungchin; Park, Jeongwon

2018-04-01

TiO2 nanotubes were prepared by anodization on Ti substrates with a diameter variation of 30-100 nm, and the structure of the nanotubes were studied using x-ray diffraction and Raman spectroscopy, which confirmed the structure changes from the anatase phase to the rutile phase of TiO2 at a diameter below 50 nm. The tribological behaviors of TiO2 nanotubes were investigated with different diameters. The effectiveness of the rutile phase and the diameter size enhanced the frictional performance of TiO2 nanotubes.

The effects of nanostructures on the mechanical and tribological properties of TiO2 nanotubes.

PubMed

Yoon, Yeoungchin; Park, Jeongwon

2018-04-20

TiO 2 nanotubes were prepared by anodization on Ti substrates with a diameter variation of 30-100 nm, and the structure of the nanotubes were studied using x-ray diffraction and Raman spectroscopy, which confirmed the structure changes from the anatase phase to the rutile phase of TiO 2 at a diameter below 50 nm. The tribological behaviors of TiO 2 nanotubes were investigated with different diameters. The effectiveness of the rutile phase and the diameter size enhanced the frictional performance of TiO 2 nanotubes.

Simulation and experiment for the inspection of stainless steel bolts in servicing using an ultrasonic phased array

NASA Astrophysics Data System (ADS)

Chen, Jinzhong; He, Renyang; Kang, Xiaowei; Yang, Xuyun

2015-10-01

The non-destructive testing of small-sized (M12-M20) stainless steel bolts in servicing is always a technical problem. This article focuses on the simulation and experimental research of stainless steel bolts with an artificial defect reflector using ultrasonic phased array inspection. Based on the observation of the sound field distribution of stainless steel bolts in ultrasonic phased array as well as simulation modelling and analysis of the phased array probes' detection effects with various defect sizes, different artificial defect reflectors of M16 stainless steel bolts are machined in reference to the simulation results. Next, those bolts are tested using a 10-wafer phased array probe with 5 MHz. The test results finally prove that ultrasonic phased array can detect 1-mm cracks in diameter with different depths of M16 stainless steel bolts and a metal loss of Φ1 mm of through-hole bolts, which provides technical support for future non-destructive testing of stainless steel bolts in servicing.

Transfer-matrix study of a hard-square lattice gas with two kinds of particles and density anomaly

NASA Astrophysics Data System (ADS)

Oliveira, Tiago J.; Stilck, Jürgen F.

2015-09-01

Using transfer matrix and finite-size scaling methods, we study the thermodynamic behavior of a lattice gas with two kinds of particles on the square lattice. Only excluded volume interactions are considered, so that the model is athermal. Large particles exclude the site they occupy and its four first neighbors, while small particles exclude only their site. Two thermodynamic phases are found: a disordered phase where large particles occupy both sublattices with the same probability and an ordered phase where one of the two sublattices is preferentially occupied by them. The transition between these phases is continuous at small concentrations of the small particles and discontinuous at larger concentrations, both transitions are separated by a tricritical point. Estimates of the central charge suggest that the critical line is in the Ising universality class, while the tricritical point has tricritical Ising (Blume-Emery-Griffiths) exponents. The isobaric curves of the total density as functions of the fugacity of small or large particles display a minimum in the disordered phase.

Application of small-diameter FBG sensors for detection of damages in composites

NASA Astrophysics Data System (ADS)

Okabe, Yoji; Mizutani, Tadahito; Yashiro, Shigeki; Takeda, Nobuo

2001-08-01

Small-diameter fiber Bragg grating (FBG) sensors have been developed by Hitachi Cable Ltd. and the authors. Since the outside diameter of polyimide coating is 52 micrometers , embedding of the sensors into carbon fiber reinforced plastic (CFRP) composites prepregs of 125 micrometers in thickness does not deteriorate the mechanical properties of the composite laminates. In this research, the small-diameter FBG sensor was applied for the detection of transverse cracks in CFRP composites. The FBG sensor was embedded in 0 degree(s) ply of a CFRP cross-ply laminate.

Two-phase damping and interface surface area in tubes with vertical internal flow

NASA Astrophysics Data System (ADS)

Béguin, C.; Anscutter, F.; Ross, A.; Pettigrew, M. J.; Mureithi, N. W.

2009-01-01

Two-phase flow is common in the nuclear industry. It is a potential source of vibration in piping systems. In this paper, two-phase damping in the bubbly flow regime is related to the interface surface area and, therefore, to flow configuration. Experiments were performed with a vertical tube clamped at both ends. First, gas bubbles of controlled geometry were simulated with glass spheres let to settle in stagnant water. Second, air was injected in stagnant alcohol to generate a uniform and measurable bubble flow. In both cases, the two-phase damping ratio is correlated to the number of bubbles (or spheres). Two-phase damping is directly related to the interface surface area, based on a spherical bubble model. Further experiments were carried out on tubes with internal two-phase air-water flows. A strong dependence of two-phase damping on flow parameters in the bubbly flow regime is observed. A series of photographs attests to the fact that two-phase damping in bubbly flow increases for a larger number of bubbles, and for smaller bubbles. It is highest immediately prior to the transition from bubbly flow to slug or churn flow regimes. Beyond the transition, damping decreases. It is also shown that two-phase damping increases with the tube diameter.

Analyzing the feasibility of utilizing small diameter hardwood timber for solid wood products and residues

Treesearch

Brian Perkins; Bob Smith; Philip Araman

2008-01-01

The eastern hardwood forest contains small diameter timber that is often of lower quality and lower value than larger sawtimber. This small diameter hardwood timber has traditionally been utilized for pulpwood, but it can also be used for lumber and residue production. In order to increase the utilization of this resource by sawmills, a number of analyses need to be...

Erratum: Erratum to: "Numerical simulation of the two-phase flow produced by spraying a liquid by a nozzle"

NASA Astrophysics Data System (ADS)

Simakov, N. N.

2018-04-01

Page 1010, left column, line 4 from bottom should read "radius R APP" instead of "diameter D APP" Page 1010, right column, before the formula (19) should read " R APP" instead of " D APP" Page 1010, in the caption to Fig. 5 should read "radius R APP" instead of "diameter D APP" Page 1011, in the caption to Fig. 6 should read "radius R APP" instead of "diameter D APP" Page 1011, left column, second paragraph after Fig. 6, line 4 from top should read "radius R APP" instead of "diameter D APP" Page 1011, the same paragraph, lines 1, 2 from bottom, in the expression for Qm and after it should read "radius R APP" instead of "diameter D APP" Page 1011, left column, paragraph 3 after Fig. 6, last two lines should read " R APP =" instead of " D APP =" Page 1011, Fig. 7, the notation on the abscissa axis should read " R APP" instead of " D APP" Page 1011, in the caption to Fig. 7 should read "radius R APP" instead of "diameter D APP" Page 1011, in caption to Fig. 8 should read "for both radii R APP" instead of "for both diameters D APP" Page 1012, in caption to Fig. 9 should read "for both radii R APP" instead of "for both diameters D APP"

Electron microscopic quantification of collagen fibril diameters in the rabbit medial collateral ligament: a baseline for comparison.

PubMed

Frank, C; Bray, D; Rademaker, A; Chrusch, C; Sabiston, P; Bodie, D; Rangayyan, R

1989-01-01

To establish a normal baseline for comparison, thirty-one thousand collagen fibril diameters were measured in calibrated transmission electron (TEM) photomicrographs of normal rabbit medial collateral ligaments (MCL's). A new automated method of quantitation was used to compare statistically fibril minimum diameter distributions in one midsubstance location in both MCL's from six animals at 3 months of age (immature) and three animals at 10 months of age (mature). Pooled results demonstrate that rabbit MCL's have statistically different (p less than 0.001) mean minimum diameters at these two ages. Interanimal differences in mean fibril minimum diameters were also significant (p less than 0.001) and varied by 20% to 25% in both mature and immature animals. Finally, there were significant differences (p less than 0.001) in mean diameters and distributions from side-to-side in all animals. These mean left-to-right differences were less than 10% in all mature animals but as much as 62% in some immature animals. Statistical analysis of these data demonstrate that animal-to-animal comparisons using these protocols require a large number of animals with appropriate numbers of fibrils being measured to detect small intergroup differences. With experiments which compare left to right ligaments, far fewer animals are required to detect similarly small differences. These results demonstrate the necessity for rigorous control of sampling, an extensive normal baseline and statistically confirmed experimental designs in any TEM comparisons of collagen fibril diameters.

A Study on Phase Changes of Heterogeneous Composite Materials

NASA Astrophysics Data System (ADS)

Hirasawa, Yoshio; Saito, Akio; Takegoshi, Eisyun

In this study, a phase change process in heterogeneous composite materials which consist of water and coiled copper wires as conductive solid is investigated by four kinds of typical calculation models : 1) model-1 in which the effective thermal conductivity of the composite material is used, 2) model-2 in which a fin metal acts for many conductive solids, 3) model-3 in which the effective thermal conductivities between nodes are estimated and three-dimensional calculation is performed, 4) model-4 proposed by authors in the previous paper in which effective thermal conductivity is not needed. Consequently, model-1 showed the phase change rate considerably lower than the experimental results. Model-2 gave the larger amount of the phase change rate. Model-3 agreed well with the experiment in the case of small coil diameter and relatively large Vd. Model-4 showed a very well agreement with the experiment in the range of this study.

Biomechanics and load resistance of small-diameter and mini dental implants: a review of literature.

PubMed

Hasan, Istabrak; Bourauel, Christoph; Mundt, Torsten; Stark, Helmut; Heinemann, Friedhelm

2014-02-01

In recent years, the application of small-diameter and mini dental implants to support removable and fixed prosthesis has dramatically increased. However, the success of these implants under functional biting forces and the reaction of the bone around them need to be analyzed. This review was aimed to present studies that deal with the fatigue life of small-diameter and mini dental implants under normal biting force, and their survival rate. The numerical and experimental studies concluded that an increase in the risk of bone damage or implant failure may be assumed in critical clinical situations and implants with <3 mm diameter have a risk of fracture in clinical practice. The survival rate of the small-diameter and mini dental implants over 5 years was 98.3-99.4%.

Growth of copper-zinc and copper-magnesium particles by gas-evaporation technique

NASA Astrophysics Data System (ADS)

Ohno, T.

1984-12-01

Fine particles of Cu-Zn and Cu-Mg systems of diameter less than 500 nm were prepared by evaporating the constituent metals simultaneously from two evaporation sources in an atmosphere of argon of 10 to 30 Torr. The composition, crystal structure and habit of the alloy particles were investigated by electron microscopy. The composition of the alloy particles varied depending on the growth zone of metal smoke and almost all phases known in Cu-Zn or Cu-Mg system were found at the same time. The particles with single phase showed generally well-defined crystal habits characteristic of their crystal structures. For the particles with two phases, a fixed lattice relation between the two phases was generally recognized. The formation process of the alloy particles is discussed through these observations.

Changes in wood density, wood anatomy and hydraulic properties of the xylem along the root-to-shoot flow path in tropical rainforest trees.

PubMed

Schuldt, Bernhard; Leuschner, Christoph; Brock, Nicolai; Horna, Viviana

2013-02-01

It is generally assumed that the largest vessels are occurring in the roots and that vessel diameters and the related hydraulic conductance in the xylem are decreasing acropetally from roots to leaves. With this study in five tree species of a perhumid tropical rainforest in Sulawesi (Indonesia), we searched for patterns in hydraulic architecture and axial conductivity along the flow path from small-diameter roots through strong roots and the trunk to distal sun-canopy twigs. Wood density differed by not more than 10% across the different flow path positions in a species, and branch and stem wood density were closely related in three of the five species. Other than wood density, the wood anatomical and xylem hydraulic traits varied in dependence on the position along the flow path, but were unrelated to wood density within a tree. In contrast to reports from conifers and certain dicotyledonous species, we found a hump-shaped variation in vessel diameter and sapwood area--specific conductivity along the flow path in all five species with a maximum in the trunk and strong roots and minima in both small roots and twigs; the vessel size depended on the diameter of the organ. This pattern might be an adaptation to the perhumid climate with a low risk of hydraulic failure. Despite a similar mean vessel diameter in small roots and twigs, the two distal organs, hydraulically weighted mean vessel diameters were on average 30% larger in small roots, resulting in ∼ 85% higher empirical and theoretical specific conductivities. Relative vessel lumen area in percent of sapwood area decreased linearly by 70% from roots to twigs, reflecting the increase in sclerenchymatic tissue and tracheids in acropetal direction in the xylem. Vessel size was more closely related to the organ diameter than to the distance along the root-to-shoot flow path. We conclude that (i) the five co-occurring tree species show convergent patterns in their hydraulic architecture despite different growth strategies, and (ii) the paradigm assuming continuous acropetal vessel tapering and decrease in specific conductance from fine roots towards distal twigs needs reconsideration.

Jeffamine derivatized TentaGel beads and poly(dimethylsiloxane) microbead cassettes for ultrahigh-throughput in situ releasable solution-phase cell-based screening of one-bead-one-compound combinatorial small molecule libraries.

PubMed

Townsend, Jared B; Shaheen, Farzana; Liu, Ruiwu; Lam, Kit S

2010-09-13

A method to efficiently immobilize and partition large quantities of microbeads in an array format in microfabricated poly(dimethylsiloxane) (PDMS) cassette for ultrahigh-throughput in situ releasable solution-phase cell-based screening of one-bead-one-compound (OBOC) combinatorial libraries is described. Commercially available Jeffamine triamine T-403 (∼440 Da) was derivatized such that two of its amino groups were protected by Fmoc and the remaining amino group capped with succinic anhydride to generate a carboxyl group. This resulting trifunctional hydrophilic polymer was then sequentially coupled two times to the outer layer of topologically segregated bilayer TentaGel (TG) beads with solid phase peptide synthesis chemistry resulting in beads with increased loading capacity, hydrophilicity, and porosity at the outer layer. We have found that such bead configuration can facilitate ultrahigh-throughput in situ releasable solution-phase screening of OBOC libraries. An encoded releasable OBOC small molecule library was constructed on Jeffamine derivatized TG beads with library compounds tethered to the outer layer via a disulfide linker and coding tags in the interior of the beads. Compound-beads could be efficiently loaded (5-10 min) into a 5 cm diameter Petri dish containing a 10,000-well PDMS microbead cassette, such that over 90% of the microwells were each filled with only one compound-bead. Jurkat T-lymphoid cancer cells suspended in Matrigel were then layered over the microbead cassette to immobilize the compound-beads. After 24 h of incubation at 37 °C, dithiothreitol was added to trigger the release of library compounds. Forty-eight hours later, MTT reporter assay was used to identify regions of reduced cell viability surrounding each positive bead. From a total of about 20,000 beads screened, 3 positive beads were detected and physically isolated for decoding. A strong consensus motif was identified for these three positive compounds. These compounds were resynthesized and found to be cytotoxic (IC(50) 50-150 μM) against two T-lymphoma cell lines and less so against the MDA-MB 231 breast cancer cell line. This novel ultrahigh-throughput OBOC releasable method can potentially be adapted to many existing 96- or 384-well solution-phase cell-based or biochemical assays.

Jeffamine Derivatized TentaGel Beads and PDMS Microbead Cassettes for Ultra-high Throughput in situ Releasable Solution-Phase Cell-based Screening of OBOC Combinatorial Small Molecule Libraries

PubMed Central

Townsend, Jared B.; Shaheen, Farzana; Liu, Ruiwu; Lam, Kit S.

2011-01-01

A method to efficiently immobilize and partition large quantities of microbeads in an array format in microfabricated polydimethylsiloxane (PDMS) cassette for high-throughput in situ releasable solution-phase cell-based screening of one-bead-one-compound (OBOC) combinatorial libraries is described. Commercially available Jeffamine triamine T-403 (∼440 Da) was derivatized such that two of its amino groups were protected by Fmoc and the remaining amino group capped with succinic anhydride to generate a carboxyl group. This resulting tri-functional hydrophilic polymer was then sequentially coupled two times to the outer layer of topologically segregated bilayer TentaGel (TG) beads with solid phase peptide synthesis chemistry, resulting in beads with increased loading capacity, hydrophilicity and porosity at the outer layer. We have found that such bead configuration can facilitate ultra high-throughput in situ releasable solution-phase screening of OBOC libraries. An encoded releasable OBOC small molecule library was constructed on Jeffamine derivatized TG beads with library compounds tethered to the outer layer via a disulfide linker and coding tags in the interior of the beads. Compound-beads could be efficiently loaded (5-10 minutes) into a 5 cm diameter Petri dish containing a 10,000-well PDMS microbead cassette, such that over 90% of the microwells were each filled with only one compound-bead. Jurkat T-lymphoid cancer cells suspended in Matrigel® were then layered over the microbead cassette to immobilize the compound-beads. After 24 hours of incubation at 37°C, dithiothreitol was added to trigger the release of library compounds. Forty-eight hours later, MTT reporter assay was used to identify regions of reduced cell viability surrounding each positive bead. From a total of about 20,000 beads screened, 3 positive beads were detected and physically isolated for decoding. A strong consensus motif was identified for these three positive compounds. These compounds were re-synthesized and found to be cytotoxic (IC50 50-150 μM) against two T-lymphoma cell lines and less so against the MDA-MB 231 breast cancer cell line. This novel ultra high-throughput OBOC releasable method can potentially be adapted to many existing 96- or 384-well solution-phase cell-based or biochemical assays. PMID:20593859

FAST TRACK COMMUNICATION Far-field x-ray phase contrast imaging has no detailed information on the object

NASA Astrophysics Data System (ADS)

Kohn, V. G.; Argunova, T. S.; Je, J. H.

2010-11-01

We show that x-ray phase contrast images of some objects with a small cross-section diameter d satisfy a condition for a far-field approximation d Lt r1 where r1 = (λz)1/2, λ is the x-ray wavelength, z is the distance from the object to the detector. In this case the size of the image does not match the size of the object contrary to the edge detection technique. Moreover, the structure of the central fringes of the image is universal, i.e. it is independent of the object cross-section structure. Therefore, these images have no detailed information on the object.

Implications of delayed initiation of radiotherapy: accelerated repopulation after induction chemotherapy for stage III non-small cell lung cancer.

PubMed

Chen, Chien P; Weinberg, Vivian K; Jahan, Thierry M; Jablons, David M; Yom, Sue S

2011-11-01

For patients with stage III non-small cell lung cancer treated with induction chemotherapy (ICT), delayed initiation of subsequent radiotherapy (RT) may allow for repopulation in the interval between treatment modalities and during the early phase of RT. We quantified the impact of postinduction RT timing by evaluating the pace of tumor regrowth. Institutionally approved retrospective review identified 21 analyzable patients with stage III non-small cell lung cancer who had platinum-based ICT followed by RT+/- chemotherapy from 2002 to 2009. Radiographic response was determined by RECIST criteria and the volume of the single largest tumor mass on the pre-ICT, post-ICT, and RT-planning computed tomography scans. After ICT, the median percent volume change from pre-ICT baseline was -41% (range -86 to +86%). By the RT-planning computed tomography scan, the median percent volume change from the post-ICT timepoint was +40% (range -11 to +311%) and the median volume change was +20 ml (range -4 to 102 ml); these changes were significant (p = 0.0002). Similar results were seen for tumor diameter. A correlation was observed between the amount of delay and degree of regrowth for percent volume (p = 0.0006) and percent diameter change (p = 0.003). A delay greater than 21 days produced greater increases in percent volume change (p = 0.002) and percent diameter (p = 0.055) than lesser delays. After ICT, tumor regrowth can occur within a few weeks. Radiation treatment planning should begin as soon as possible after the administration of ICT to maximize the benefits of cytoreduction.

A Heat Transfer Investigation of Liquid and Two-Phase Methane

NASA Technical Reports Server (NTRS)

VanNoord, Jonathan

2010-01-01

A heat transfer investigation was conducted for liquid and two-phase methane. The tests were conducted at the NASA Glenn Research Center Heated Tube Facility (HTF) using resistively heated tube sections to simulate conditions encountered in regeneratively cooled rocket engines. This testing is part of NASA s Propulsion and Cryogenics Advanced Development (PCAD) project. Nontoxic propellants, such as liquid oxygen/liquid methane (LO2/LCH4), offer potential benefits in both performance and safety over equivalently sized hypergolic propulsion systems in spacecraft applications. Regeneratively cooled thrust chambers are one solution for high performance, robust LO2/LCH4 engines, but cooling data on methane is limited. Several test runs were conducted using three different diameter Inconel 600 tubes, with nominal inner diameters of 0.0225-, 0.054-, and 0.075-in. The mass flow rate was varied from 0.005 to 0.07 lbm/sec. As the current focus of the PCAD project is on pressure fed engines for LO2/LCH4, the average test section outlet pressures were targeted to be 200 psia or 500 psia. The heat flux was incrementally increased for each test condition while the test section wall temperatures were monitored. A maximum average heat flux of 6.2 Btu/in.2 sec was achieved and, at times, the temperatures of the test sections reached in excess of 1800 R. The primary objective of the tests was to produce heat transfer correlations for methane in the liquid and two-phase regime. For two-phase flow testing, the critical heat flux values were determined where the fluid transitions from nucleate boiling to film boiling. A secondary goal of the testing was to measure system pressure drops in the two-phase regime.

Composition Based Strategies for Controlling Radii in Lipid Nanotubes

PubMed Central

Kurczy, Michael E.; Mellander, Lisa J.; Najafinobar, Neda; Cans, Ann-Sofie

2014-01-01

Nature routinely carries out small-scale chemistry within lipid bound cells and organelles. Liposome–lipid nanotube networks are being developed by many researchers in attempt to imitate these membrane enclosed environments, with the goal to perform small-scale chemical studies. These systems are well characterized in terms of the diameter of the giant unilamellar vesicles they are constructed from and the length of the nanotubes connecting them. Here we evaluate two methods based on intrinsic curvature for adjusting the diameter of the nanotube, an aspect of the network that has not previously been controllable. This was done by altering the lipid composition of the network membrane with two different approaches. In the first, the composition of the membrane was altered via lipid incubation of exogenous lipids; either with the addition of the low intrinsic curvature lipid soy phosphatidylcholine (soy-PC) or the high intrinsic curvature lipid soy phosphatidylethanolamine (soy-PE). In the second approach, exogenous lipids were added to the total lipid composition during liposome formation. Here we show that for both lipid augmentation methods, we observed a decrease in nanotube diameter following soy-PE additions but no significant change in size following the addition of soy-PC. Our results demonstrate that the effect of soy-PE on nanotube diameter is independent of the method of addition and suggests that high curvature soy-PE molecules facilitate tube membrane curvature. PMID:24392077

Analysis of Nd3+:glass, solar-pumped, high-powr laser systems

NASA Technical Reports Server (NTRS)

Zapata, L. E.; Williams, M. D.

1989-01-01

The operating characteristics of Nd(3+):glass lasers energized by a solar concentrator were analyzed for the hosts YAG, silicate glass, and phosphate glass. The modeling is based on the slab zigzag laser geometry and assumes that chemical hardening methods for glass are successful in increasing glass hardness by a factor of 4. On this basis, it was found that a realistic 1-MW solar-pumped laser might be constructed from phosphate glass 4 sq m in area and 2 mm thick. If YAG were the host medium, a 1-MW solar-pumped laser need only be 0.5 sq m in area and 0.5 cm thick, which is already possible. In addition, Nd(3+) doped glass fibers were found to be excellent solar-pumped laser candidates. The small diameter of fibers eliminates thermal stress problems, and if their diameter is kept small (10 microns), they propagate a Gaussian single mode which can be expanded and transmitted long distances in space. Fiber lasers could then be used for communications in space or could be bundled and the individual beams summed or phase-matched for high-power operation.

Small Craters Engulfed by Smooth Plains

NASA Image and Video Library

2000-08-05

This double ring basin top center of image was photographed during NASA Mariner 10 second encounter and shows two craters about 30 km in diameter which have been engulfed by smooth plains on the floor of the inner ring.

Revised albedos of Trojan asteroids (911) Agamemnon and (4709) Ennomos

NASA Astrophysics Data System (ADS)

Shevchenko, V. G.; Slyusarev, I. G.; Belskaya, I. N.

2014-01-01

CCD-photometry was performed for two Jupiter Trojan asteroids (911) Agamemnon and (4709) Ennomos for which the diameters were obtained from occultation events. New data on rotation periods, lightcurve amplitudes, color indices, magnitude-phase slopes, and absolute magnitudes were obtained for these asteroids. We have used the diameters from occultations (166 and 99 km) and new data on absolute magnitudes at the instant occultation (7.95 and 8.85 mag) to revise their albedos to 0.042 (911 Agamemnon) and 0.052 (4709 Ennomos).

Processing Science of Advanced Ceramics. Materials Research Society Symposium Proceedings. Volume 155

DTIC Science & Technology

1990-09-01

can see that as the particle diameter ratio decreased more from unity, the freezing curve in the D - x phase diagram begins to show a maximum with...predicted for the rod area fraction of 0.26. Free energy curves for the two phases are shown as a function of rod concentration. The random phise has lower...fabrication techniques leing used range from consolidation of subinicron-sized powders to vapor phase deposition. ’hc papers included in this

Smaller Footprint Drilling System for Deep and Hard Rock Environments; Feasibility of Ultra-High-Speed Diamond Drilling

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

Arnis Judzis; Homer Robertson; Alan Black

2006-06-22

The two phase program addresses long-term developments in deep well and hard rock drilling. TerraTek believes that significant improvements in drilling deep hard rock will be obtained by applying ultra-high rotational speeds (greater than 10,000 rpm). The work includes a feasibility of concept research effort aimed at development that will ultimately result in the ability to reliably drill ''faster and deeper'' possibly with smaller, more mobile rigs. The principle focus is on demonstration testing of diamond bits rotating at speeds in excess of 10,000 rpm to achieve high rate of penetration (ROP) rock cutting with substantially lower inputs of energymore » and loads. The significance of the ''ultra-high rotary speed drilling system'' is the ability to drill into rock at very low weights on bit and possibly lower energy levels. The drilling and coring industry today does not practice this technology. The highest rotary speed systems in oil field and mining drilling and coring today run less than 10,000 rpm-usually well below 5,000 rpm. This document details the progress at the end of Phase 1 on the program entitled ''Smaller Footprint Drilling System for Deep and Hard Rock Environments: Feasibility of Ultra-High-Speed Diamond Drilling'' for the period starting 1 March 2006 and concluding 30 June 2006. (Note: Results from 1 September 2005 through 28 February 2006 were included in the previous report (see Judzis, Black, and Robertson)). Summarizing the accomplished during Phase 1: {lg_bullet} TerraTek reviewed applicable literature and documentation and convened a project kickoff meeting with Industry Advisors in attendance (see Black and Judzis). {lg_bullet} TerraTek designed and planned Phase I bench scale experiments (See Black and Judzis). Some difficulties continued in obtaining ultra-high speed motors. Improvements were made to the loading mechanism and the rotational speed monitoring instrumentation. New drill bit designs were developed to provided a more consistent product with consistent performance. A test matrix for the final core bit testing program was completed. {lg_bullet} TerraTek concluded Task 3 ''Small-scale cutting performance tests.'' {sm_bullet} Significant testing was performed on nine different rocks. {sm_bullet} Five rocks were used for the final testing. The final tests were based on statistical design of experiments. {sm_bullet} Two full-faced bits, a small diameter and a large diameter, were run in Berea sandstone. {lg_bullet} Analysis of data was completed and indicates that there is decreased specific energy as the rotational speed increases (Task 4). Data analysis from early trials was used to direct the efforts of the final testing for Phase I (Task 5). {lg_bullet} Technology transfer (Task 6) was accomplished with technical presentations to the industry (see Judzis, Boucher, McCammon, and Black).« less

Entropy and the driving force for the filling of carbon nanotubes with water.

PubMed

Pascal, Tod A; Goddard, William A; Jung, Yousung

2011-07-19

The spontaneous filling of hydrophobic carbon nanotubes (CNTs) by water observed both experimentally and from simulations is counterintuitive because confinement is generally expected to decrease both entropy and bonding, and remains largely unexplained. Here we report the entropy, enthalpy, and free energy extracted from molecular dynamics simulations of water confined in CNTs from 0.8 to 2.7-nm diameters. We find for all sizes that water inside the CNTs is more stable than in the bulk, but the nature of the favorable confinement of water changes dramatically with CNT diameter. Thus we find (i) an entropy (both rotational and translational) stabilized, vapor-like phase of water for small CNTs (0.8-1.0 nm), (ii) an enthalpy stabilized, ice-like phase for medium-sized CNTs (1.1-1.2 nm), and (iii) a bulk-like liquid phase for tubes larger than 1.4 nm, stabilized by the increased translational entropy as the waters sample a larger configurational space. Simulations with structureless coarse-grained water models further reveal that the observed free energies and sequence of transitions arise from the tetrahedral structure of liquid water. These results offer a broad theoretical basis for understanding water transport through CNTs and other nanostructures important in nanofluidics, nanofiltrations, and desalination.

Entropy and the driving force for the filling of carbon nanotubes with water

PubMed Central

Pascal, Tod A.; Goddard, William A.; Jung, Yousung

2011-01-01

The spontaneous filling of hydrophobic carbon nanotubes (CNTs) by water observed both experimentally and from simulations is counterintuitive because confinement is generally expected to decrease both entropy and bonding, and remains largely unexplained. Here we report the entropy, enthalpy, and free energy extracted from molecular dynamics simulations of water confined in CNTs from 0.8 to 2.7-nm diameters. We find for all sizes that water inside the CNTs is more stable than in the bulk, but the nature of the favorable confinement of water changes dramatically with CNT diameter. Thus we find (i) an entropy (both rotational and translational) stabilized, vapor-like phase of water for small CNTs (0.8–1.0 nm), (ii) an enthalpy stabilized, ice-like phase for medium-sized CNTs (1.1–1.2 nm), and (iii) a bulk-like liquid phase for tubes larger than 1.4 nm, stabilized by the increased translational entropy as the waters sample a larger configurational space. Simulations with structureless coarse-grained water models further reveal that the observed free energies and sequence of transitions arise from the tetrahedral structure of liquid water. These results offer a broad theoretical basis for understanding water transport through CNTs and other nanostructures important in nanofluidics, nanofiltrations, and desalination. PMID:21709268

Diameter Control and Photoluminescence of ZnO Nanorods from Trialkylamines

DOE PAGES

Andelman, Tamar; Gong, Yinyan; Neumark, Gertrude; ...

2007-01-01

A novel solution method to control the diameter of ZnO nanorods is reported. Small diameter (2-3 nm) nanorods were synthesized from trihexylamine, and large diameter (50–80 nm) nanorods were synthesized by increasing the alkyl chain length to tridodecylamine. The defect (green) emission of the photoluminescence (PL) spectra of the nanorods varies with diameter, and can thus be controlled by the diameter control. The small ZnO nanorods have strong green emission, while the large diameter nanorods exhibit a remarkably suppressed green band. We show that this observation supports surface oxygen vacancies as the defect that gives rise to the green emission.

Comparison of detectability in step-and-shoot mode and continuous mode digital tomosynthesis systems

NASA Astrophysics Data System (ADS)

Lee, Changwoo; Han, Minah; Baek, Jongduk

2017-03-01

Digital tomosynthesis system has been widely used in chest, dental, and breast imaging. Since the digital tomosynthesis system provides volumetric images from multiple projection data, structural noise inherent in X-ray radiograph can be reduced, and thus signal detection performance is improved. Currently, tomosynthesis system uses two data acquisition modes: step-and-shoot mode and continuous mode. Several studies have been conducted to compare the system performance of two acquisition modes with respect to spatial resolution and contrast. In this work, we focus on signal detectability in step-and-shoot mode and continuous mode. For evaluation, uniform background is considered, and eight spherical objects with diameters of 0.5, 0.8, 1, 2, 3, 5, 8, 10 mm are used as signals. Projection data with and without spherical objects are acquired in step-and-shoot mode and continuous mode, respectively, and quantum noise are added. Then, noisy projection data are reconstructed by FDK algorithm. To compare the detection performance of two acquisition modes, we calculate task signal-to-noise ratio (SNR) of channelized Hotelling observer with Laguerre-Gauss channels for each spherical object. While the task-SNR values of two acquisition modes are similar for spherical objects larger than 1 mm diameter, step-and-shoot mode yields higher detectability for small signal sizes. The main reason of this behavior is that small signal is more affected by X-ray tube motion blur than large signal. Our results indicate that it is beneficial to use step-and-shoot data acquisition mode to improve the detectability of small signals (i.e., less than 1 mm diameter) in digital tomosynthesis systems.

Small tractors for harvesting fuelwood in low-volume small-diameter hardwood stands

Treesearch

Neil K. Huyler; Chris B. LeDoux

1989-01-01

Much of the nonindustrial, private forest land in the Northeast is characterized by small diameter trees with low volume. Conventional harvesting systems used in logging these stands generally results in submarginal economic returns. Often, small-scale harvesting systems have economic advantages in these areas. Time and motion studies were conducted for several small...

Diagnostic criteria for hepatocellular carcinoma ⩽3 cm with hepatocyte-specific contrast-enhanced magnetic resonance imaging.

PubMed

Choi, Sang Hyun; Byun, Jae Ho; Lim, Young-Suk; Yu, Eunsil; Lee, So Jung; Kim, So Yeon; Won, Hyung Jin; Shin, Yong Moon; Kim, Pyo Nyun

2016-05-01

Current diagnostic imaging criteria for hepatocellular carcinoma (HCC) are dedicated to imaging with nonspecific extracellular contrast agents. This study aimed to evaluate diagnostic criteria for HCC ⩽3 cm on magnetic resonance imaging (MRI) with a hepatocyte-specific contrast agent through an inception cohort study. Of 291 patients with chronic liver disease and new nodules of 1-3 cm in diameter at surveillance ultrasonography, 295 solid nodules (194 HCCs, 98 benign nodules, and three other malignancies) in 198 patients with a confirmed final diagnosis or ⩾24 months follow-up were evaluated on gadoxetic acid-enhanced MRI. Through univariate and multivariate logistic regression analyses, various diagnostic criteria were developed by combining significant MRI findings for diagnosing HCC. The diagnostic performance of each criterion was compared with that of the European Association for the Study of the Liver (EASL) criteria. Four MRI findings (arterial-phase hyperintensity, transitional-phase hypointensity, hepatobiliary-phase hypointensity, and rim enhancement) were independently significant for diagnosis of HCC ⩽3 cm. For whole nodules, EASL criteria showed the best performance for diagnosing HCC (sensitivity, 83.5%; specificity, 81.2%). For nodules ⩽2 cm in diameter, a new criterion (arterial-phase hyperintensity and hepatobiliary-phase hypointensity) showed a significantly higher sensitivity than that of the EASL criteria (83.0% vs. 74.5%, p=0.008), without a significantly different specificity (76.7% vs. 81.1%, p=0.125). EASL criteria exhibit the best diagnostic performance for HCC ⩽3 cm on hepatocyte-specific contrast-enhanced MRI. A newly identified criterion (arterial-phase hyperintensity and hepatobiliary-phase hypointensity) may increase the diagnostic sensitivity of small (⩽2 cm) HCC. Copyright © 2016 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Multiple scattering by infinitely long cylindrical glass inclusions in a saturated Biot porous medium of glass beads.

PubMed

Trabelsi, W; Franklin, H; Tinel, A

2016-05-01

The resonance spectrum of sets of two to five infinitely long parallel cylindrical glass inclusions in a fluid saturated porous matrix of unconsolidated glass beads is investigated. The ratio of bead diameters to inclusion diameters is 1/5. The far field form functions and the related phase derivatives are calculated by using an exact multiple scattering formalism and by assuming that the porous medium obeys Biot's model. In order to validate this hypothesis, comparisons between theory and experiments are done in the special case of a fast incident wave on a set of two and three inclusions.

A compact 3 T all HTS cryogen-free MRI system

NASA Astrophysics Data System (ADS)

Parkinson, B. J.; Bouloukakis, K.; Slade, R. A.

2017-12-01

We have designed and built a passively shielded, cryogen-free 3 T 160 mm bore bismuth strontium calcium copper oxide HTS magnet with shielded gradient coils suitable for use in small animal imaging applications. The magnet is cooled to approximately 16 K using a two-stage cryocooler and is operated at 200 A. The magnet has been passively shimmed so as to achieve ±10 parts per million (ppm) homogeneity over a 60 mm diameter imaging volume. We have demonstrated that B 0 temporal stability is fit-for-purpose despite the magnet operating in the driven mode. The system has produced good quality spin-echo and gradient echo images. This compact HTS-MRI system is emerging as a true alternative to conventional low temperature superconductor based cryogen-free MRI systems, with much more efficient cryogenics since it operates entirely from a single phase alternating current electrical supply.

Numerical modeling process of embolization arteriovenous malformation

NASA Astrophysics Data System (ADS)

Cherevko, A. A.; Gologush, T. S.; Petrenko, I. A.; Ostapenko, V. V.

2017-10-01

Cerebral arteriovenous malformation is a difficult, dangerous, and most frequently encountered vascular failure of development. It consists of vessels of very small diameter, which perform a discharge of blood from the artery to the vein. In this regard it can be adequately modeled using porous medium. Endovascular embolization of arteriovenous malformation is effective treatment of such pathologies. However, the danger of intraoperative rupture during embolization still exists. The purpose is to model this process and build an optimization algorithm for arteriovenous malformation embolization. To study the different embolization variants, the initial-boundary value problems, describing the process of embolization, were solved numerically by using a new modification of CABARET scheme. The essential moments of embolization process were modeled in our numerical experiments. This approach well reproduces the essential features of discontinuous two-phase flows, arising in the embolization problems. It can be used for further study on the process of embolization.

Predicted accommodative response from image quality in young eyes fitted with different dual-focus designs.

PubMed

Faria-Ribeiro, Miguel; Amorim-de-Sousa, Ana; González-Méijome, José M

2018-05-01

To investigate the separated and combined influences of inner zone (IZ) diameter and effective add power of dual-focus contact lenses (CL) in the image quality at distance and near viewing, in a functional accommodating model eye. Computational wave-optics methods were used to define zonal bifocal pupil functions, representing the optic zones of nine dual-focus centre-distance CLs. The dual-focus pupil functions were defined having IZ diameters of 2.10 mm, 3.36 mm and 4.00 mm, with add powers of 1.5 D, 2.0 D and 2.5 D (dioptres), for each design, that resulted in a ratio of 64%/36% between the distance and treatment zone areas, bounded by a 6 mm entrance pupil. A through-focus routine was implemented in MATLAB to simulate the changes in image quality, calculated from the Visual Strehl ratio, as the eye with the dual-focus accommodates, from 0 to -3.00 D target vergences. Accommodative responses were defined as the changes in the defocus coefficient, combined with a change in fourth and sixth order spherical aberration, which produced a peak in image quality at each target vergence. Distance viewing image quality was marginally affected by IZ diameter but not by add power. Near image quality obtained when focussing the image formed by the near optics was only higher by a small amount compared to the other two IZ diameters. The mean ± standard deviation values obtained with the three adds were 0.28 ± 0.02, 0.23 ± 0.02 and 0.22 ± 0.02, for the small, medium and larger IZ diameters, respectively. On the other hand, near image quality predicted by focussing the image formed by the distance optics was considerably lower relatively to the other two IZ diameters. The mean ± standard deviation values obtained with the three adds were 0.15 ± 0.01, 0.38 ± 0.00 and 0.54 ± 0.01, for the small, medium and larger IZ diameters, respectively. During near viewing through dual-focus CLs, image quality depends on the diameter of the most inner zone of the CL, while add power only affects the range of clear focus when focussing the image formed by the CL near optics. When only image quality gain is taken into consideration, medium and large IZ diameters designs are most likely to promote normal accommodative responses driven by the CL distance optics, while a smaller IZ diameter design is most likely to promote a reduced accommodative response driven by the dual-focus CL near optics. © 2018 The Authors Ophthalmic & Physiological Optics © 2018 The College of Optometrists.

Nanoparticle growth by particle-phase chemistry

NASA Astrophysics Data System (ADS)

Apsokardu, Michael J.; Johnston, Murray V.

2018-02-01

The ability of particle-phase chemistry to alter the molecular composition and enhance the growth rate of nanoparticles in the 2-100 nm diameter range is investigated through the use of a kinetic growth model. The molecular components included are sulfuric acid, ammonia, water, a non-volatile organic compound, and a semi-volatile organic compound. Molecular composition and growth rate are compared for particles that grow by partitioning alone vs. those that grow by a combination of partitioning and an accretion reaction in the particle phase between two organic molecules. Particle-phase chemistry causes a change in molecular composition that is particle diameter dependent, and when the reaction involves semi-volatile molecules, the particles grow faster than by partitioning alone. These effects are most pronounced for particles larger than about 20 nm in diameter. The modeling results provide a fundamental basis for understanding recent experimental measurements of the molecular composition of secondary organic aerosol showing that accretion reaction product formation increases linearly with increasing aerosol volume-to-surface-area. They also allow initial estimates of the reaction rate constants for these systems. For secondary aerosol produced by either OH oxidation of the cyclic dimethylsiloxane (D5) or ozonolysis of β-pinene, oligomerization rate constants on the order of 10-3 to 10-1 M-1 s-1 are needed to explain the experimental results. These values are consistent with previously measured rate constants for reactions of hydroperoxides and/or peroxyacids in the condensed phase.

Isotachophoresis system having larger-diameter channels flowing into channels with reduced diameter and with selectable counter-flow

DOEpatents

Mariella, Jr., Raymond P.

2018-03-06

An isotachophoresis system for separating a sample containing particles into discrete packets including a flow channel, the flow channel having a large diameter section and a small diameter section; a negative electrode operably connected to the flow channel; a positive electrode operably connected to the flow channel; a leading carrier fluid in the flow channel; a trailing carrier fluid in the flow channel; and a control for separating the particles in the sample into discrete packets using the leading carrier fluid, the trailing carrier fluid, the large diameter section, and the small diameter section.

Development and Short-Range Testing of a 100 kW Side-Illuminated Millimeter-Wave Thermal Rocket

NASA Technical Reports Server (NTRS)

Bruccoleri, Alexander; Eilers, James A.; Lambot, Thomas; Parkin, Kevin

2015-01-01

The objective of the phase described here of the Millimeter-Wave Thermal Launch System (MTLS) Project was to launch a small thermal rocket into the air using millimeter waves. The preliminary results of the first MTLS flight vehicle launches are presented in this work. The design and construction of a small thermal rocket with a planar ceramic heat exchanger mounted along the axis of the rocket is described. The heat exchanger was illuminated from the side by a millimeter-wave beam and fed propellant from above via a small tank containing high pressure argon or nitrogen. Short-range tests where the rocket was launched, tracked, and heated with the beam are described. The rockets were approximately 1.5 meters in length and 65 millimeters in diameter, with a liftoff mass of 1.8 kilograms. The rocket airframes were coated in aluminum and had a parachute recovery system activated via a timer and Pyrodex. At the rocket heat exchanger, the beam distance was 40 meters with a peak power intensity of 77 watts per square centimeter. and a total power of 32 kilowatts in a 30 centimeter diameter circle. An altitude of approximately 10 meters was achieved. Recommendations for improvements are discussed.

A case of child death caused by intestinal volvulus following magnetic toy ingestion.

PubMed

Olczak, Mieszko; Skrzypek, Ewa

2015-05-01

An 8-year boy was admitted to the ER of one of Warsaw's pediatric hospitals with a history of having bloody vomiting the day before. During admission the boy collapsed and lost consciousness. CPR was unsuccessful. On medico-legal autopsy, two foreign objects (small magnetic spheres--0.5 cm in diameter) were found in two different places in the small and large intestines and were notably attracted magnetically one to another. A loop of approximately 1-m length with features of small intestinal hemorrhagic necrosis and small intestinal mechanical obstruction was found. The cause of death was intestinal volvulus and small intestinal mechanical obstruction caused by ingestion of foreign objects (two neodymium magnets). Most likely these small magnetic spheres were part of a popular toy, the safety of which, lately, has been widely discussed. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Differential expression of CART in ewes with differing ovulation rates.

PubMed

Juengel, Jennifer L; French, Michelle C; Quirke, Laurel D; Kauff, Alexia; Smith, George W; Johnstone, Peter D

2017-04-01

We hypothesised that cocaine- and amphetamine-regulated transcript ( CARTPT ) would be differentially expressed in ewes with differing ovulation rates. Expression of mRNA for CARTPT , as well as LHCGR , FSHR , CYP19A1 and CYP17A1 was determined in antral follicles ≥1 mm in diameter collected during the follicular phase in ewes heterozygous for the Booroola and Inverdale genes (I+B+; average ovulation rate 4) and ++ contemporaries (++; average ovulation rate 1.8). In ++ ewes ( n  = 6), CARTPT was expressed in small follicles (1 to <3 mm diameter), where 18.8 ± 2.5% follicles expressed CARTPT CART peptide was also detected in follicular fluid of some follicles of ++ ewes. In I+B+ ewes, 5/6 ewes did not have any follicles that expressed CARTPT , and no CART peptide was detected in any follicle examined. Expression pattern of CYP19A1 differed between I+B+ and ++ ewes with an increased percentage of small and medium follicles (3 to <4.5 mm diameter) but decreased percentage of large follicles (≥4.5 mm diameter) expressing CYP19A1 in the I+B+ ewes. Many of the large follicles from the I+B+ ewes appeared non-functional and expression of LHCGR , FSHR , CYP17A1 and CYP19A1 was less than that observed in ++ ewes. Expression of FSHR and CYP17A1 was not different between groups in small and medium follicles, but LHCGR expression was approximately double in I+B+ ewes compared to that in ++ ewes. Thus, ewes with high ovulation rates had a distinct pattern of expression of CARTPT mRNA and protein compared to ewes with normal ovulation rates, providing evidence for CART being important in the regulation of ovulation rate. © 2017 Society for Reproduction and Fertility.

SU-E-J-229: Magnetic Resonance Imaging of Small Fiducial Markers for Proton Beam Therapy

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

Hu, Y; James, J; Panda, A

2015-06-15

Purpose: For proton beam therapy, small fiducial markers are preferred for patient alignment due to less interference with the proton beam. Visualizing small fiducial markers can be challenging in MRI. This study intends to investigate MRI imaging protocols for better visualization of small fiducial markers. Methods: Two carbon and two coil-shaped gold markers were placed into a gel phantom. Both carbon markers had a diameter of 1mm and a length of 3mm. Both gold markers had a length of 5mm. One gold marker had a diameter of 0.5mm and the other had a diameter of 0.75mm. T1 VIBE, T2 SPACE,more » TrueFISP and susceptibility weighted (SW) images were acquired. To improve marker contrast, high spatial resolution was used to reduce partial volume effect. Slice thickness was 1.5mm for all four sequences and in-plane resolution was 0.6mm for TrueFISP, 0.7mm for T1 VIBE, and 0.8mm for T2 SPACE and SW. For comparison purpose, a 3D T1 VIBE image set at 3mm slice thickness and 1.2mm in-plane resolution was also acquired. Results: All markers were visible in all high-resolution image sets. In each image set, marker-induced signal void was the smallest (in diameter) for carbon markers, followed by the 0.5mm gold marker and the largest for the 0.75mm gold marker. The SW images had the largest marker-induced signal void. However, those might be confused by susceptibility-gradient-induced signal voids. T1 VIBE had good visualization of markers with nicely defined edges. T2 SPACE had reasonable visualization of markers but edges were slightly blurred. TrueFISP had good visualization of markers only if they were not masked by banding artifacts. As a comparison, all markers were hardly visible in the standard resolution T1 VIBE images. Conclusion: 3D high-resolution T1 VIBE and SW have great potential in providing good visualization of small fiducial markers for proton beam therapy.« less

Water dynamics in large and small reverse micelles: From two ensembles to collective behavior

PubMed Central

Moilanen, David E.; Fenn, Emily E.; Wong, Daryl; Fayer, Michael D.

2009-01-01

The dynamics of water in Aerosol-OT reverse micelles are investigated with ultrafast infrared spectroscopy of the hydroxyl stretch. In large reverse micelles, the dynamics of water are separable into two ensembles: slow interfacial water and bulklike core water. As the reverse micelle size decreases, the slowing effect of the interface and the collective nature of water reorientation begin to slow the dynamics of the core water molecules. In the smallest reverse micelles, these effects dominate and all water molecules have the same long time reorientational dynamics. To understand and characterize the transition in the water dynamics from two ensembles to collective reorientation, polarization and frequency selective infrared pump-probe experiments are conducted on the complete range of reverse micelle sizes from a diameter of 1.6–20 nm. The crossover between two ensemble and collective reorientation occurs near a reverse micelle diameter of 4 nm. Below this size, the small number of confined water molecules and structural changes in the reverse micelle interface leads to homogeneous long time reorientation. PMID:19586114

Small bowel dilation in children with short bowel syndrome is associated with mucosal damage, bowel-derived bloodstream infections, and hepatic injury.

PubMed

Hukkinen, Maria; Mutanen, Annika; Pakarinen, Mikko P

2017-09-01

Liver disease occurs frequently in short bowel syndrome. Whether small bowel dilation in short bowel syndrome could influence the risk of liver injury through increased bacterial translocation remains unknown. Our aim was to analyze associations between small bowel dilation, mucosal damage, bloodstream infections, and liver injury in short bowel syndrome patients. Among short bowel syndrome children (n = 50), maximal small bowel diameter was measured in contrast series and expressed as the ratio to the height of the fifth lumbar vertebra (small bowel diameter ratio), and correlated retrospectively to fecal calprotectin and plasma citrulline-respective markers of mucosal inflammation and mass-bloodstream infections, liver biochemistry, and liver histology. Patients with pathologic small bowel diameter ratio >2.17 had increased fecal calprotectin and decreased citrulline (P < .04 each). Of 33 bloodstream infections observed during treatment with parenteral nutrition, 16 were caused by intestinal bacteria, cultured 15 times more frequently when small bowel diameter ratio was >2.17 (P < .001). Intestinal bloodstream infections were predicted by small bowel diameter ratio (odds ratio 1.88, P = .017), and their frequency decreased after operative tapering procedures (P = .041). Plasma bilirubin concentration, gamma-glutamyl transferase activity, and histologic grade of cholestasis correlated with small bowel diameter ratio (0.356-0.534, P < .014 each), and were greater in the presence of intestinal bloodstream infections (P < .001 for all). Bloodstream infections associated with portal inflammation, cholestasis, and fibrosis grades (P < .031 for each). In linear regression, histologic cholestasis was predicted by intestinal bloodstream infections, small bowel diameter ratio, and parenteral nutrition (β = 0.36-1.29; P < .014 each), while portal inflammation by intestinal bloodstream infections only (β = 0.62; P = .033). In children with short bowel syndrome, small bowel dilation correlates with mucosal damage, bloodstream infections of intestinal origin, and cholestatic liver injury. In addition to parenteral nutrition, small bowel dilation and intestinal bloodstream infections contribute to development of short bowel syndrome-associated liver disease. Copyright © 2017 Elsevier Inc. All rights reserved.

Establishing a Mouse Model of a Pure Small Fiber Neuropathy with the Ultrapotent Agonist of Transient Receptor Potential Vanilloid Type 1.

PubMed

Lee, Yi-Chen; Lu, Shui-Chin; Hsieh, Yu-Lin

2018-02-13

Patients with diabetes mellitus (DM) or those experiencing the neurotoxic effects of chemotherapeutic agents may develop sensation disorders due to degeneration and injury of small-diameter sensory neurons, referred to as small fiber neuropathy. Present animal models of small fiber neuropathy affect both large- and small-diameter sensory fibers and thus create a neuropathology too complex to properly assess the effects of injured small-diameter sensory fibers. Therefore, it is necessary to develop an experimental model of pure small fiber neuropathy to adequately examine these issues. This protocol describes an experimental model of small fiber neuropathy specifically affecting small-diameter sensory nerves with resiniferatoxin (RTX), an ultrapotent agonist of transient receptor potential vanilloid type 1 (TRPV1), through a single dose of intraperitoneal injection, referred to as RTX neuropathy. This RTX neuropathy showed pathological manifestations and behavioral abnormalities that mimic the clinical characteristics of patients with small fiber neuropathy, including intraepidermal nerve fiber (IENF) degeneration, specifically injury in small-diameter neurons, and induction of thermal hypoalgesia and mechanical allodynia. This protocol tested three doses of RTX (200, 50, and 10 µg/kg, respectively) and concluded that a critical dose of RTX (50 µg/kg) is required for the development of typical small fiber neuropathy manifestations, and prepared a modified immunostaining procedure to investigate IENF degeneration and neuronal soma injury. The modified procedure is fast, systematic, and economic. Behavioral evaluation of neuropathic pain is critical to reveal the function of small-diameter sensory nerves. The evaluation of mechanical thresholds in experimental rodents is particularly challenging and this protocol describes a customized metal mesh that is suitable for this type of assessment in rodents. In summary, RTX neuropathy is a new and easily established experimental model to evaluate the molecular significance and intervention underlying neuropathic pain for the development of therapeutic agents.

Surface modification of silk fibroin fabric using layer-by-layer polyelectrolyte deposition and heparin immobilization for small-diameter vascular prostheses.

PubMed

Elahi, M Fazley; Guan, Guoping; Wang, Lu; Zhao, Xinzhe; Wang, Fujun; King, Martin W

2015-03-03

There is an urgent need to develop a biologically active implantable small-diameter vascular prosthesis with long-term patency. Silk-fibroin-based small-diameter vascular prosthesis is a promising candidate having higher patency rate; however, the surface modification is indeed required to improve its further hemocompatibility. In this study, silk fibroin fabric was modified by a two-stage process. First, the surface of silk fibroin fabric was coated using a layer-by-layer polyelectrolyte deposition technique by stepwise dipping the silk fibroin fabric into a solution of cationic poly(allylamine hydrochloride) (PAH) and anionic poly(acrylic acid) (PAA) solution. The dipping procedure was repeated to obtain the PAH/PAA multilayers deposited on the silk fibroin fabrics. Second, the polyelectrolyte-deposited silk fibroin fabrics were treated in EDC/NHS-activated low-molecular-weight heparin (LMWH) solution at 4 °C for 24 h, resulting in immobilization of LMWH on the silk fibroin fabrics surface. Scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray data revealed the accomplishment of LMWH immobilization on the polyelectrolyte-deposited silk fibroin fabric surface. The higher the number of PAH/PAA coating layers on the silk fibroin fabric, the more surface hydrophilicity could be obtained, resulting in a higher fetal bovine serum protein and platelets adhesion resistance properties when tested in vitro. In addition, compared with untreated sample, the surface-modified silk fibroin fabrics showed negligible loss of bursting strength and thus reveal the acceptability of polyelectrolytes deposition and heparin immobilization approach for silk-fibroin-based small-diameter vascular prostheses modification.

Factors influencing interlocking screw failure in unreamed small diameter nails--a biomechanical study using a distal tibia fracture model.

PubMed

Weninger, Patrick; Schueller, Michael; Jamek, Michael; Stanzl-Tschegg, Stefanie; Redl, Heinz; Tschegg, Elmar K

2009-05-01

Unreamed tibia nails with small diameters are increasingly used for fracture fixation. However, little is known about the fatigue strength of proximal and distal interlocking screws in those nails. To date, no data are available reporting on mechanical differences of solid compared to cannulated tibial nails. The aim of this study was to assess the fatigue strength of proximal and distal interlocking screws of solid and cannulated small diameter tibia nails. We created a distal tibia fracture model (AO/OTA 43 A3) using 16 Sawbones. After fracture stabilization with one of four different nail types (Expert Tibial Nail, VersaNail, T2 Tibial Nailing System, Connex), mechanical testing was performed in three loading series (40,000 cycles each) with incremental loads. Timing and type of interlocking screw failure were assessed. Interlocking screw failure was observed significantly earlier (after a mean interval of 57,042 cycles) in cannulated tibial nails (VersaNail, T2) compared to solid nails (after a mean interval of 88,415 cycles; P < 0.001). Proximal interlocking screw failure was recorded if oblique screws were used proximally (VersaNail, T2, Connex). No distal interlocking screw failure was recorded in the Connex nail. Two- and three-part fractures of proximal or distal interlocking screws were observed in all specimen. Proximal and distal interlocking screw failure has to be considered in small diameter nails in case of delayed fracture healing. To support our results, further experimental studies and clinical series are necessary.

Ecology and life history of an amoebomastigote, Paratetramitus jugosus, from a microbial mat: new evidence for multiple fission

NASA Technical Reports Server (NTRS)

Enzien, M.; McKhann, H. I.; Margulis, L.

1989-01-01

Five microbial habitats (gypsum crust, gypsum photosynthetic community, Microcoleus mat, Thiocapsa scum, and black mud) were sampled for the presence of the euryhaline, rapidly growing amoebomastigote, Paratetramitus jugosus. Field investigations of microbial mats from Baja California Norte, Mexico, and Salina Bido near Matanzas, Cuba, reveal that P. jugosus is most frequently found in the Thiocapsa layer of microbial mats. Various stages of the life history were studied using phase-contrast, differential-interference, and transmission electron microscopy. Mastigote stages were induced and studied by electron microscopy; mastigotes that actively feed on bacteria bear two or more undulipodia. A three-dimensional drawing of the kinetid ("basal apparatus") based on electron micrographs is presented. Although promitoses were occasionally observed, it is unlikely that they can account for the rapid growth of P. jugosus populations on culture media. Dense, refractile, spherical, and irregular-shaped bodies were seen at all times in all cultures along with small mononucleate (approximately 2-7 micrometers diameter) amoebae. Cytochemical studies employing two different fluorescent stains for DNA (DAPI, mithramycin) verified the presence of DNA in these small bodies. Chromatin-like material seen in electron micrographs within the cytoplasm and blebbing off nuclei were interpreted to the chromatin bodies. Our interpretation, consistent with the data but not proven, is that propagation by multiple fission of released chromatin bodies that become small amoebae may occur in Paratetramitus jugosus. These observations are consistent with descriptions of amoeba propagules in the early literature (Hogue, 1914).

Gallium ion-assisted room temperature synthesis of small-diameter ZnO nanorods.

PubMed

Cho, Seungho; Kim, Semi; Lee, Kun-Hong

2011-09-15

We report a method for synthesizing small-diameter ZnO nanorods at room temperature (20 °C), under normal atmospheric pressure (1 atm), and using a relatively short reaction time (1 h) by adding gallium salts to the reaction solution. The ZnO nanorods were, on average, 92 nm in length and 9 nm in diameter and were single crystalline in nature. Quantitative analyses revealed that gallium atoms were not incorporated into the synthesized nanocrystals. On the basis of the experimental results, we propose a mechanism for the formation of small-diameter ZnO nanorods in the presence of gallium ions. The optical properties were probed by UV-Vis diffuse reflectance spectroscopy. The absorption band of the small-diameter ZnO nanorods was blue-shifted relative to the absorption band of the ~230 nm diameter ZnO nanorods (control samples). Control experiments demonstrated that the absence of metal ion-containing precipitants (except ZnO) at room temperature is essential, and that the ZnO nanorod diameter distributions were narrow for the stirred reaction solution and broad when prepared without stirring. Copyright © 2011 Elsevier Inc. All rights reserved.

Pore-Fractal Structure in Porous Carbons Made from Corn and Wheat

NASA Astrophysics Data System (ADS)

Kapoor, Y. M.; Schmidt, P. W.; Rice, Randall D.; Shulse, Laural; Voss, D. J.; Venkatraman, A.; Fan, L. T.; Walawender, W. P.; Rieker, T. P.

1998-03-01

Small-angle X-ray scattering has been used in a study of the pore structure of some porous and activated carbons on length scales between about 5 and 10^4 ÅThe carbons were obtained by pyrolysis and activation of wheat and American corn (maize). The scattering data showed that in each carbon there are at least two of the following four types of pores: (1) pores with diameters of at least 10^4 Åpores with smooth or fractal surfaces and diameters of at least 5 x 10^3 Åpore-fractals with diameters of no more than about 10^3 Åand (4) pores with diameters no larger than 100 ÅThe relation between the pore structure and the procedure used to obtain the carbon and will be discussed.

Intercomparison of fog water samplers

NASA Astrophysics Data System (ADS)

Schell, Dieter; Georgii, Hans-Walter; Maser, Rolf; Jaeschke, Wolfgang; Arends, Beate G.; Kos, Gerard P. A.; Winkler, Peter; Schneider, Thomas; Berner, Axel; Kruisz, Christian

1992-11-01

During the Po Valley Fog Experiment 1989, two fogwater collectors were operated simultaneously at the ground and the results were compared to each other. The chemical analyses of the samples as well as the collection efficiencies showed remarkable differences between both collectors. Some differences in the solute concentrations in the samples of both collectors could be expected due to small differences in the 50-percent cut-off diameters. The large differences in the collection efficiencies however cannot be explained by these small variations of d sub 50, because normally only a small fraction of the water mass is concentrated in the size range of 5-7-micron droplets. It is shown that it is not sufficient to characterize a fogwater collector only by its cut-off diameter. The results of several wind tunnel calibration tests show that the collection efficiencies of the fogwater collectors are a function of windspeed and shape of the droplet spectra.

Venus small volcano classification and description

NASA Technical Reports Server (NTRS)

Aubele, J. C.

1993-01-01

The high resolution and global coverage of the Magellan radar image data set allows detailed study of the smallest volcanoes on the planet. A modified classification scheme for volcanoes less than 20 km in diameter is shown and described. It is based on observations of all members of the 556 significant clusters or fields of small volcanoes located and described by this author during data collection for the Magellan Volcanic and Magmatic Feature Catalog. This global study of approximately 10 exp 4 volcanoes provides new information for refining small volcano classification based on individual characteristics. Total number of these volcanoes was estimated to be 10 exp 5 to 10 exp 6 planetwide based on pre-Magellan analysis of Venera 15/16, and during preparation of the global catalog, small volcanoes were identified individually or in clusters in every C1-MIDR mosaic of the Magellan data set. Basal diameter (based on 1000 measured edifices) generally ranges from 2 to 12 km with a mode of 34 km, and follows an exponential distribution similar to the size frequency distribution of seamounts as measured from GLORIA sonar images. This is a typical distribution for most size-limited natural phenomena unlike impact craters which follow a power law distribution and continue to infinitely increase in number with decreasing size. Using an exponential distribution calculated from measured small volcanoes selected globally at random, we can calculate total number possible given a minimum size. The paucity of edifice diameters less than 2 km may be due to inability to identify very small volcanic edifices in this data set; however, summit pits are recognizable at smaller diameters, and 2 km may represent a significant minimum diameter related to style of volcanic eruption. Guest, et al, discussed four general types of small volcanic edifices on Venus: (1) small lava shields; (2) small volcanic cones; (3) small volcanic domes; and (4) scalloped margin domes ('ticks'). Steep-sided domes or 'pancake domes', larger than 20 km in diameter, were included with the small volcanic domes. For the purposes of this study, only volcanic edifices less than 20 km in diameter are discussed. This forms a convenient cutoff since most of the steep-sided domes ('pancake domes') and scalloped margin domes ('ticks') are 20 to 100 km in diameter, are much less numerous globally than are the smaller diameter volcanic edifices (2 to 3 orders of magnitude lower in total global number), and do not commonly occur in large clusters or fields of large numbers of edifices.

Characterization of multilayer coated replicated Wolter optics for imaging x-ray emission from pulsed power

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

Ames, Andrew; Ampleford, David; Bourdon, Chris

Here, we have developed a process for indirectly coating small diameter electroformed nickel replicated optics with multilayers to increase their response at high energy (i.e. >10 keV). The ability to fabricate small diameter multilayer-coated full-shell Wolter X-ray optics with narrow bandpass opens the door to several applications within astronomy and also provides a path for cross-fertilization to other fields. We report on the characterization and evaluation of the first two prototype X-ray Wolter optics to be delivered to the Z Pulsed Power Facility at Sandia National Laboratories. The intent is to develop and field several optics as part of anmore » imaging system with targeted spectral ranges.« less

Characterization of multilayer coated replicated Wolter optics for imaging x-ray emission from pulsed power

DOE PAGES

Ames, Andrew; Ampleford, David; Bourdon, Chris; ...

2017-08-29

Here, we have developed a process for indirectly coating small diameter electroformed nickel replicated optics with multilayers to increase their response at high energy (i.e. >10 keV). The ability to fabricate small diameter multilayer-coated full-shell Wolter X-ray optics with narrow bandpass opens the door to several applications within astronomy and also provides a path for cross-fertilization to other fields. We report on the characterization and evaluation of the first two prototype X-ray Wolter optics to be delivered to the Z Pulsed Power Facility at Sandia National Laboratories. The intent is to develop and field several optics as part of anmore » imaging system with targeted spectral ranges.« less

Characterization of multilayer coated replicated Wolter optics for imaging x-ray emission from pulsed power

NASA Astrophysics Data System (ADS)

Ames, A.; Ampleford, D.; Bourdon, C.; Bruni, R.; Kilaru, K.; Kozioziemski, B.; Pivovaroff, M.; Ramsey, B.; Romaine, S.; Vogel, J.; Walton, C.; Wu, M.

2017-08-01

We have developed a process for indirectly coating arbitrarily small diameter electroformed nickel replicated optics with multilayers to increase their response at high energy (i.e. >10 keV). The ability to fabricate small diameter multilayer coated full shell Wolter X-ray optics with narrow bandpass opens the door to several applications within astronomy and also provides a path for cross-fertilization to other fields. We report on the characterization and evaluation of the first two prototype X-ray Wolter optics to be delivered to the Z Pulsed Power Facility at Sandia National Laboratories. The intent is to develop and field several optics as part of an imaging system with targeted spectral ranges.

Small asteroids temporarily captured in the Earth-Moon system

NASA Astrophysics Data System (ADS)

Jedicke, Robert; Bolin, Bryce; Bottke, William F.; Chyba, Monique; Fedorets, Grigori; Granvik, Mikael; Patterson, Geoff

2016-01-01

We present an update on our work on understanding the population of natural objects that are temporarily captured in the Earth-Moon system like the 2-3 meter diameter, 2006 RH120, that was discovered by the Catalina Sky Survey. We use the term `minimoon' to refer to objects that are gravitationally bound to the Earth-Moon system, make at least one revolution around the barycenter in a co-rotating frame relative to the Earth-Sun axis, and are within 3 Earth Hill-sphere radii. There are one or two 1 to 2 meter diameter minimoons in the steady state population at any time, and about a dozen larger than 50 cm diameter. `Drifters' are also bound to the Earth-Moon system but make less than one revolution about the barycenter. The combined population of minimoons and drifters provide a new opportunity for scientific exploration of small asteroids and testing concepts for in-situ resource utilization. These objects provide interesting challenges for rendezvous missions because of their limited lifetime and complicated trajectories. Furthermore, they are difficult to detect because they are small, available for a limited time period, and move quickly across the sky.

Small asteroids temporarily captured in the Earth-Moon system

NASA Astrophysics Data System (ADS)

Jedicke, Robert; Bolin, Bryce; Bottke, William F.; Chyba, Monique; Fedorets, Grigori; Granvik, Mikael; Patterson, Geoff

2015-08-01

We will present an update on our work on understanding the population of natural objects that are temporarily captured in the Earth-Moon system, such as the 2-3 meter diameter 2006 RH120 that was discovered by the Catalina Sky Survey. We use the term 'minimoon' to refer to objects that are gravitationally bound to the Earth-Moon system, make at least one revolution around the barycenter in a co-rotating frame relative to the Earth-Sun axis, and are within 3 Earth Hill-sphere radii. There are one or two 1 to 2 meter diameter minimoons in the steady state population at any time, and about a dozen larger than 50 cm diameter. `Drifters' are also bound to the Earth-Moon system but make less than one revolution about the barycenter. The combined population of minimoons and drifters provide a new opportunity for scientific exploration of small asteroids and testing concepts for in-situ resource utilization. These objects provide interesting challenges for rendezvous missions because of their limited lifetime and complicated trajectories. Furthermore, they are difficult to detect because they are small, available for a limited time period, and move quickly across the sky.

Development of a sapphire fiber thermometer using two wavelength bands

NASA Astrophysics Data System (ADS)

Ye, Linhua; Shen, Yonghang

1996-09-01

This paper reports the development of a sapphire ((alpha) - Al2O3) single crystal optical fiber thermometer using two wavelength bands. A thin film of precious metal or ceramic deposited onto one end of the sapphire fiber forms a mini-radiation cavity. The other end of the sapphire fiber is coupled to a low-loss silica fiber. Radiation from the small cavity is transmitted along the silica fiber into a photodetection system which consists of a lens, beam splitter, two interference filters (820 nm and 940 nm center wavelength, 30 nm bandwidth) and two silicon photocells. The temperature measurement is based on the detection of radiation from the small cavity. The sapphire fiber (0.25 - 1.0 mm diameter, 100 - 450 mm length) was grown by the laser heated pedestal growth (LHPG) methods. Transmission loss in the sapphire fiber was experimentally measured. Theoretical analysis shows the apparent emittance of the small cavity with a length to diameter (L/D) ratio greater than eight is a constant value near to one, so the small cavity can be considered as a small black-body cavity. Using the developed sapphire fiber temperature sensor, we have built a sapphire fiber thermometer based on a 8098 single-chip microcomputer system. It was calibrated at some known stable temperature point and uses the fundamental radiation law to extrapolate to other temperatures. By taking the ratio of the optical power at two wavelengths, errors due to changes in the system, such as emissivity and transmission losses, can be canceled out. The thermometer has an operating temperature range of 800 to 1900 degrees Celsius, and an accuracy of 0.2% at 1000 degrees Celsius. There are a number of applications of the thermometer both in science and industry.

Olive Oil Tracer Particle Size Analysis for Optical Flow Investigations in a Gas Medium

NASA Astrophysics Data System (ADS)

Harris, Shaun; Smith, Barton

2014-11-01

Seed tracer particles must be large enough to scatter sufficient light while being sufficiently small to follow the flow. These requirements motivate a desire for control over the particle size. For gas measurements, it is common to use atomized oil droplets as tracer particles. A Laskin nozzle is a device for generating oil droplets in air by directing high-pressure air through small holes under an oil surface. The droplet diameter frequency distribution can be varied by altering the hole diameter, the number of holes, or the inlet pressure. We will present a systematic study of the effect of these three parameters on the resultant particle distribution as it leaves the Laskin nozzle. The study was repeated for cases where the particles moved through a typical jet facility before their size was measured. While the jet facility resulted in an elimination of larger particles, the average particle diameter could be varied by a factor of two at both the seeder exit and downstream of the jet facility.

Hyaluronic acid enhancement of expanded polytetrafluoroethylene for small diameter vascular grafts

NASA Astrophysics Data System (ADS)

Lewis, Nicole R.

Cardiovascular disease is the leading cause of mortality and morbidity in the United States and other developed countries. In the United States alone, 8 million people are diagnosed with peripheral arterial disease per year and over 250,000 patients have coronary bypass surgery each year. Autologous blood vessels are the standard graft used in small diameter (<6mm) arterial bypass procedures. Synthetic small diameter grafts have had limited success. While polyethylene (Dacron) and expanded polytetrafluoroethylene (ePTFE) are the most commonly used small diameter synthetic vascular graft materials, there are significant limitations that make these materials unfavorable for use in the low blood flow conditions of the small diameter arteries. Specifically, Dacron and ePTFE grafts display failure due to early thrombosis or late intimal hyperplasia. With the shortage of tissue donors and the limited supply of autologous blood vessels available, there is a need for a small diameter synthetic vascular graft alternative. The aim of this research is to create and characterize ePTFE grafts prepared with hyaluronic acid (HA), evaluate thrombogenic potential of ePTFE-HA grafts, and evaluate graft mechanical properties and coating durability. The results in this work indicate the successful production of ePTFE-HA materials using a solvent infiltration technique. Surface interactions with blood show increased platelet adhesion on HA-modified surfaces, though evidence may suggest less platelet activation and erythrocyte lysis. Significant changes in mechanical properties of HA-modified ePTFE materials were observed. Further investigation into solvent selection, uniformity of HA, endothelialization, and dynamic flow testing would be beneficial in the evaluation of these materials for use in small diameter vascular graft bypass procedures.

76 FR 67411 - Small Diameter Graphite Electrodes From the People's Republic of China: Extension of Time Limit...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-01

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... diameter graphite electrodes from the People's Republic of China (PRC) for the period February 1, 2010... Graphite, Co. The preliminary results of the review are currently due no later than October 31, 2011...

Embolization Materials Made of Gelatin: Comparison Between Gelpart and Gelatin Microspheres

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

Ohta, Shinichi, E-mail: junryuhei@belle.shiga-med.ac.jp; Nitta, Norihisa; Sonoda, Akinaga

2010-02-15

Purpose:The object of this study was to assess the level of embolization in the embolized artery and the degradation period of these two embolic agents in the renal arteries using rabbit models.Materials and Methods: The renal artery was embolized using 5 mg of gelatin microspheres (GMSs; diameter, 35-100 {mu}m; group 1) or 1 mg of Gelpart (diameter, 1 mm; group 2). For each group, angiographies were performed on two kidneys immediately after the embolic procedure and on days 3, 7, and 14 after embolization. This was followed by histopathological examinations of the kidneys.Results:Follow-up angiograms on each day revealed the persistencemore » of poorly enhanced wedge-shaped areas in the parenchymal phase in all cases. In group 1, four of six cases showed poorly enhanced small areas in the follow-up angiograms. In group 2, all cases showed poorly enhanced large areas. In the histopathological specimens, it was observed that immediately after embolization, the particles reached the interlobular arteries in group 1 and the interlobar arteries in group 2. In all cases in group 1, the particles were histologically identified even on day 14. In one case in group 2 on day 14, the particles were not identified.Conclusion:In conclusion, although GMSs and Gelpart were similar in the point of gelatin particles, the level of embolization and the degradation period were different between GMSs and Gelpart.« less

Increasing number of small hole diameter microfracture compared with traditional microfracture in same size cartilage defects and effect of HA based aselluler scaffold. An animal study

PubMed Central

Uzer, Gökçer; Elmadağ, Nuh Mehmet; Yıldız, Fatih; Güzel, Yunus; Tok, Olgu Enis

2017-01-01

Purpose: The purpose of this study is small hole microfracure method comparing with traditional microfracture method and investigation of effect of HA based acellular matrix scaffold on microfracture area. Materials-Methods: 21 Twenty-one New Zealand white rabbits were used for the in vitro portion of this study, bilateral knee joint from the same rabbit were same technic. An articular cartilage defect was established in the femoral trochlear groove about 5 mm. Control group was established alone microfracture (MF). 6 groups were formed in this study and each group has 3 rabbits and their six knees. In 3 groups were applied different number of small diameter hole microfracture (4,5,6 small holes microfracture respectively)and the other 3 groups were applied different number of small diameter hole microfracture (4,5,6 small holes micro fracture respectively added HA based acellular matrix scaffold in the same size ostechondral lesion. The regenerated tissues were harvested for gross morphology, histology at 12 weeks postoperatively. Results: Cartilage were regenerated, maintaining a constant thickness of cartilage. MF group has worse Wakitani scores than 6 small diameter holes mıcrofracture groups(group 6 and group 7) in either parameter of the score. (p=0,043, p=0,016) Matrix addition did not contribute to healing. (p=1,000) Conclusions: Increasing number of the small diameter holes microfracture (minimum %15 of defect size) improves cartilage repair compared with traditional MF in the same size ostechondral lesion. Also small diameter holes microfracture combined with HA-based AM implantation didn’t result in improved quality of the regenerated cartilage tissue.

The Importance of Large-Diameter Trees to Forest Structural Heterogeneity

PubMed Central

Lutz, James A.; Larson, Andrew J.; Freund, James A.; Swanson, Mark E.; Bible, Kenneth J.

2013-01-01

Large-diameter trees dominate the structure, dynamics and function of many temperate and tropical forests. However, their attendant contributions to forest heterogeneity are rarely addressed. We established the Wind River Forest Dynamics Plot, a 25.6 ha permanent plot within which we tagged and mapped all 30,973 woody stems ≥1 cm dbh, all 1,966 snags ≥10 cm dbh, and all shrub patches ≥2 m2. Basal area of the 26 woody species was 62.18 m2/ha, of which 61.60 m2/ha was trees and 0.58 m2/ha was tall shrubs. Large-diameter trees (≥100 cm dbh) comprised 1.5% of stems, 31.8% of basal area, and 17.6% of the heterogeneity of basal area, with basal area dominated by Tsuga heterophylla and Pseudotsuga menziesii. Small-diameter subpopulations of Pseudotsuga menziesii, Tsuga heterophylla and Thuja plicata, as well as all tree species combined, exhibited significant aggregation relative to the null model of complete spatial randomness (CSR) up to 9 m (P≤0.001). Patterns of large-diameter trees were either not different from CSR (Tsuga heterophylla), or exhibited slight aggregation (Pseudotsuga menziesii and Thuja plicata). Significant spatial repulsion between large-diameter and small-diameter Tsuga heterophylla suggests that large-diameter Tsuga heterophylla function as organizers of tree demography over decadal timescales through competitive interactions. Comparison among two forest dynamics plots suggests that forest structural diversity responds to intermediate-scale environmental heterogeneity and disturbances, similar to hypotheses about patterns of species richness, and richness- ecosystem function. Large mapped plots with detailed within-plot environmental spatial covariates will be required to test these hypotheses. PMID:24376579

The importance of large-diameter trees to forest structural heterogeneity.

PubMed

Lutz, James A; Larson, Andrew J; Freund, James A; Swanson, Mark E; Bible, Kenneth J

2013-01-01

Large-diameter trees dominate the structure, dynamics and function of many temperate and tropical forests. However, their attendant contributions to forest heterogeneity are rarely addressed. We established the Wind River Forest Dynamics Plot, a 25.6 ha permanent plot within which we tagged and mapped all 30,973 woody stems ≥ 1 cm dbh, all 1,966 snags ≥ 10 cm dbh, and all shrub patches ≥ 2 m(2). Basal area of the 26 woody species was 62.18 m(2)/ha, of which 61.60 m(2)/ha was trees and 0.58 m(2)/ha was tall shrubs. Large-diameter trees (≥ 100 cm dbh) comprised 1.5% of stems, 31.8% of basal area, and 17.6% of the heterogeneity of basal area, with basal area dominated by Tsuga heterophylla and Pseudotsuga menziesii. Small-diameter subpopulations of Pseudotsuga menziesii, Tsuga heterophylla and Thuja plicata, as well as all tree species combined, exhibited significant aggregation relative to the null model of complete spatial randomness (CSR) up to 9 m (P ≤ 0.001). Patterns of large-diameter trees were either not different from CSR (Tsuga heterophylla), or exhibited slight aggregation (Pseudotsuga menziesii and Thuja plicata). Significant spatial repulsion between large-diameter and small-diameter Tsuga heterophylla suggests that large-diameter Tsuga heterophylla function as organizers of tree demography over decadal timescales through competitive interactions. Comparison among two forest dynamics plots suggests that forest structural diversity responds to intermediate-scale environmental heterogeneity and disturbances, similar to hypotheses about patterns of species richness, and richness- ecosystem function. Large mapped plots with detailed within-plot environmental spatial covariates will be required to test these hypotheses.

a Study of a High Frequency Miniature Reservoir-Less Pulse Tube

NASA Astrophysics Data System (ADS)

Garaway, I.; Grossman, G.

2008-03-01

A miniature high frequency reservoir-less pulse tube cryocooler has been designed and tested in our laboratory. The cryocooler having a regenerator length of 12.0 mm and an overall volume of 2.3cc (excluding the compressor) reached a low temperature of 146K and provided 100mW of cooling at 160K. This experimental study shows that it is possible to miniaturize a pulse tube cryocooler to very short regenerator lengths by implementing a few basic principles: Most importantly, high operating frequencies at small tidal displacements, a regenerator matrix with small hydraulic diameters, and increased helium fill pressures. This study also shows that as the operating frequency of a miniature cryocooler increases, the reservoir becomes less necessary as a phase shifting device. At higher frequencies and appropriate inertance tube geometries, the impedance and capacitance of the inertance tube itself takes over the phase shifting task. An outline of the design and modeling principles is presented along with some details of the experimental apparatus and testing procedures.

DYLOS DC110

EPA Science Inventory

The Dylos DC1100 air quality monitor measures particulate matter (PM) to provide a continuous assessment of indoor air quality. The unit counts particles in two size ranges: large and small. According to the manufacturer, large particles have diameters between 2.5 and 10 micromet...

A small-diameter NMR logging tool for groundwater investigations

USGS Publications Warehouse

Walsh, David; Turner, Peter; Grunewald, Elliot; Zhang, Hong; Butler, James J.; Reboulet, Ed; Knobbe, Steve; Christy, Tom; Lane, John W.; Johnson, Carole D.; Munday, Tim; Fitzpatrick, Andrew

2013-01-01

A small-diameter nuclear magnetic resonance (NMR) logging tool has been developed and field tested at various sites in the United States and Australia. A novel design approach has produced relatively inexpensive, small-diameter probes that can be run in open or PVC-cased boreholes as small as 2 inches in diameter. The complete system, including surface electronics and various downhole probes, has been successfully tested in small-diameter monitoring wells in a range of hydrogeological settings. A variant of the probe that can be deployed by a direct-push machine has also been developed and tested in the field. The new NMR logging tool provides reliable, direct, and high-resolution information that is of importance for groundwater studies. Specifically, the technology provides direct measurement of total water content (total porosity in the saturated zone or moisture content in the unsaturated zone), and estimates of relative pore-size distribution (bound vs. mobile water content) and hydraulic conductivity. The NMR measurements show good agreement with ancillary data from lithologic logs, geophysical logs, and hydrogeologic measurements, and provide valuable information for groundwater investigations.

Oil-Water Interface Templating of Mesoporous Macroscale Structures

PubMed

Schacht; Huo; Voigt-Martin; Stucky; Schuth

1996-08-09

Ordered mesostructured porous silicas that are also macroscopically structured were created by control of the interface on two different length scales simultaneously. Micellar arrays controlled the nanometer-scale assembly, and at the static boundary between an aqueous phase and an organic phase, control was achieved on the micrometer to centimeter scale. Acid-prepared mesostructures of silica were made with the p6, Pm3n, and the P63/mmc structures in the form of porous fibers 50 to 1000 micrometers in length, hollow spheres with diameters of 1 to 100 micrometers, and thin sheets up to 10 centimeters in diameter and about 10 to 500 micrometers in thickness. These results might have implications for technical applications, such as slow drug-release systems or membranes, and in biomineralization, where many processes are also interface-controlled.

Demonstrate Scale-up Procedure for Glass Composite Material (GCM) for Incorporation of Iodine Loaded AgZ.

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

Nenoff, Tina M.; Garino, Terry J.; Croes, Kenneth James

2015-07-01

Two large size Glass Composite Material (GCM) waste forms containing AgI-MOR were fabricated. One contained methyl iodide-loaded AgI-MOR that was received from Idaho National Laboratory (INL, Test 5, Beds 1 – 3) and the other contained iodine vapor loaded AgIMOR that was received from Oak Ridge National Laboratory (ORNL, SHB 2/9/15 ). The composition for each GCM was 20 wt% AgI-MOR and 80 wt% Ferro EG2922 low sintering temperature glass along with enough added silver flake to prevent any I2 loss during the firing process. The silver flake amounts were 1.2 wt% for the GCM with the INL AgI-MOR andmore » 3 wt% for the GCM contained the ORNL AgI-MOR. The GCMs, nominally 100 g, were first uniaxially pressed to 6.35 cm (2.5 inch) diameter disks then cold isostatically pressed, before firing in air to 550°C for 1hr. They were cooled slowly (1°C/min) from the firing temperature to avoid any cracking due to temperature gradients. The final GCMs were ~5 cm in diameter (~2 inches) and non-porous with densities of ~4.2 g/cm³. X-ray diffraction indicated that they consisted of the amorphous glass phase with small amounts of mordenite and AgI. Furthermore, the presence of the AgI was confirmed by X-ray fluorescence. Methodology for the scaled up production of GCMs to 6 inch diameter or larger is also presented.« less

Normal stresses in shear thickening granular suspensions.

PubMed

Pan, Zhongcheng; de Cagny, Henri; Habibi, Mehdi; Bonn, Daniel

2017-05-24

When subjected to shear, granular suspensions exhibit normal stresses perpendicular to the shear plane but the magnitude and sign of the different components of the normal stresses are still under debate. By performing both oscillatory and rotational rheology measurements on shear thickening granular suspensions and systematically varying the particle diameters and the gap sizes between two parallel-plates, we show that a transition from a positive to a negative normal stress can be observed. We find that frictional interactions which determine the shear thickening behavior of suspensions contribute to the positive normal stresses. Increasing the particle diameters or decreasing the gap sizes leads to a growing importance of hydrodynamic interactions, which results in negative normal stresses. We determine a relaxation time for the system, set by both the pore and the gap sizes, that governs the fluid flow through the inter-particle space. Finally, using a two-fluid model we determine the relative contributions from the particle phase and the liquid phase.

Ultra-minimally invasive local immune cell therapy and regenerative therapy by multi-piercing surgery for abdominal solid tumor: therapeutic simulation by natural orifice translumenal endoscopic surgery-assisted needlescopic surgery using 3-mm diameter robots.

PubMed

Ohdaira, Takeshi; Tsutsumi, Norifumi; Xu, Hao; Mori, Megumu; Uemura, Munenori; Ieiri, Satoshi; Hashizume, Makoto

2011-07-01

We have invented multi-piercing surgery (MPS) which could potentially solve the triangular formation loss and device clashing which occur in single-port surgery (SPS), as well as restricted visual field, organ damage by needle-type instruments, and impaired removal of a resected organ from the body which occur in needlescopic surgery (NS). MPS is natural orifice translumenal endoscopic surgery (NOTES)-assisted NS. We used 3-mm diameter robots as needle-type instruments for MPS to examine the possibility of local immune cell therapy and regenerative therapy using stem cells for pancreatic cancer. In MPS using two robots, the therapeutic cell suspension was injected into a target region of pancreas in two pigs. Both retention of a capsule of liquid cell suspension and invasive level were evaluated. Triangular formation could be ensured. The use of small-diameter robots allowed (1) the surgical separation of the pancreas and the retroperitoneum, and (2) the formation of the capsule containing the immune cell and stem cell suspension. The endoscope for NOTES provided a clear visual field and also assisted the removal of a resected organ from the body. The visual field of the endoscope could be oriented well by using an electromagnetic navigation system. MPS using small-diameter robots could potentially solve the issues inherent in SPS and NS and could allow minimally invasive local immune cell and stem cell therapy.

Synthoil hydrodynamics. Combined third and fourth quarterly report, December 1, 1975--May 31, 1976

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

Brenner, H.; Prieve, D.C.; Fitch, B.

1977-08-01

This report deals with two-phase flow (gas and liquid) in a packed bed in the synthoil process reactor and preheater; in particular, nonuniform radial distribution of the liquid phase is studied. In addition, temperature profiles and possible instability of control due to the exothermic reactions are studied with respect to the synthoil reactor. This factor may limit the reactor diameter to about six inches. (LTN)

SMALL DIAMETER CEMENT LINING FROM STAIRWAY. United States Pipe ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

SMALL DIAMETER CEMENT LINING FROM STAIRWAY. - United States Pipe & Foundry Company Plant, Coating, Painting, Lining & Packaging Building, 2023 St. Louis Avenue at I-20/59, Bessemer, Jefferson County, AL

Proper Orthogonal Decomposition on Experimental Multi-phase Flow in a Pipe

NASA Astrophysics Data System (ADS)

Viggiano, Bianca; Tutkun, Murat; Cal, Raúl Bayoán

2016-11-01

Multi-phase flow in a 10 cm diameter pipe is analyzed using proper orthogonal decomposition. The data were obtained using X-ray computed tomography in the Well Flow Loop at the Institute for Energy Technology in Kjeller, Norway. The system consists of two sources and two detectors; one camera records the vertical beams and one camera records the horizontal beams. The X-ray system allows measurement of phase holdup, cross-sectional phase distributions and gas-liquid interface characteristics within the pipe. The mathematical framework in the context of multi-phase flows is developed. Phase fractions of a two-phase (gas-liquid) flow are analyzed and a reduced order description of the flow is generated. Experimental data deepens the complexity of the analysis with limited known quantities for reconstruction. Comparison between the reconstructed fields and the full data set allows observation of the important features. The mathematical description obtained from the decomposition will deepen the understanding of multi-phase flow characteristics and is applicable to fluidized beds, hydroelectric power and nuclear processes to name a few.

New Capabilities in the Analysis of Sub-micrometer Regions in Geological Materials with the Field Emission Electron Microprobe

NASA Astrophysics Data System (ADS)

Armstrong, J. T.; McSwiggen, P.; Nielsen, C.

2013-12-01

Quantitative electron microprobe analysis has revolutionized two-dimensional elemental analysis of Earth materials at the micrometer-scale. Newly available commercial field emission (FE-) source instruments represent significant technological advances in quantitative measurement with high spatial resolution at sub-micrometer scale - helping to bridge the gap between conventional microprobe and AEM analyses. Their performance specifications suggest the ability to extend routine quantitative analyses from ~3-5 micrometer diameter areas down to 1-2 micrometer diameter at beam energies of 15 keV; and, with care, down to 200-500 nm diameter at reduced beam energies. . In order to determine whether the level of performance suggested by the specifications is realistic, we spent a week doing analyses at the newly installed JEOL JXA-8530F field emission microprobe at Arizona State University, using a series of samples that are currently being studied in various projects at CIW. These samples included: 1) high-pressure experiment run product containing intergrowths of sub-micrometer grains of metal, sulfide, Fe-Mg-perovskite, and ferropericlase; 2) a thin section of the Ivankinsky basalt, part of the Siberian flood basalt sequence containing complex sub-micrometer intergrowths of magnetite, titanomagnetite, ilmenite, titanite and rutile; 3) a polished section of the Giroux pallasite, being studied for element partitioning, that we used as an analogue to test the capabilities for zonation and diffusion determination; and 4) a polished section of the Semarkona ordinary chondrite containing chondules comprised of highly zoned and rimmed olivines and pyroxenes in a complex mesostasis of sub-micrometer pyroxenes and glass. The results of these analyses that we will present confirmed our optimism regarding the new analytical capabilities of a field emission microprobe. We were able, at reduced voltages, to accurately analyze the major and minor element composition of intergrowth and rimming phases as small as 200 nm without artifact contribution from the surrounding phases. We were able to determine the compositional gradients at kamacite-taenite boundaries in the pallasite specimen with a resolution of ~180 nm, enabling much higher precision and accuracy determination of the meteorite's cooling rate than previously possible with microprobe measurements. We were able to determine the composition and zonation of phases in the experimental run product, none of which were large enough to be analyzable in a conventional electron microprobe.

Simulations of two sedimenting-interacting spheres with different sizes and initial configurations using immersed boundary method

NASA Astrophysics Data System (ADS)

Liao, Chuan-Chieh; Hsiao, Wen-Wei; Lin, Ting-Yu; Lin, Chao-An

2015-06-01

Numerical investigations are carried out for the drafting, kissing and tumbling (DKT) phenomenon of two freely falling spheres within a long container by using an immersed-boundary method. The method is first validated with flows induced by a sphere settling under gravity in a small container for which experimental data are available. The hydrodynamic interactions of two spheres are then studied with different sizes and initial configurations. When a regular sphere is placed below the larger one, the duration of kissing decreases in pace with the increase in diameter ratio. On the other hand, the time duration of the kissing stage increases in tandem with the increase in diameter ratio as the large sphere is placed below the regular one, and there is no DKT interactions beyond threshold diameter ratio. Also, the gap between homogeneous spheres remains constant at the terminal velocity, whereas the gaps between the inhomogeneous spheres increase due to the differential terminal velocity.

Performance Comparisons and Down Selection of Small Motors for Two-Blade Heliogyro Solar Sail 6U CubeSat

NASA Technical Reports Server (NTRS)

Wiwattananon, Peerawan; Bryant, Robert G.

2015-01-01

This report compiles a review of 130 commercial small scale motors (piezoelectric and electric motors) and almost 20 researched-type small scale piezoelectricmotors for potential use in a 2 blades Heliogyro Solar Sail 6U CubeSat. In this application, a motor and gearhead (drive system) will deploy a roll of solar sailthin film (2 um thick)accommodated in a 2U CubeSat (100 x 200 x 100 mm) housing. The application requirements are: space rated, output torque at fulldeployment of 0.8 Nm, reel speed of 3 rpm, drive system weight limited to 150 grams, diameter limited to 50 mm, and the length not to exceed 40 mm. The 50mm diameter limit was imposed as motors with larger diameters would likely weigh too much and use more space on the satellite wall. This would limit theamount of the payload. The motors performance are compared between small scale, volume within 3x102 cm3 (3x105 mm3), commercial electric DC motors,commercial piezoelectric motors, and researched-type (non-commercial) piezoelectric motors extracted from scientific and product literature. The comparisonssuggest that piezoelectric motors without a gearhead exhibit larger output torque with respect to their volume and weight and require less input power toproduce high torque. A commercially available electric motor plus a gearhead was chosen through a proposed selection process to meet the applications designrequirements.

[Value of asymmetry criterion in MRI for the diagnosis of small pelvic lymphadenopathies (inferior or equal to 1 cm)].

PubMed

Roy, C; Le Bras, Y; Mangold, L; Tuchmann, C; Vasilescu, C; Saussine, C; Jacqmin, D

1996-12-01

The purpose of this study was to determine if lymph node asymmetry in small (< 1.0 cm) pelvic nodes was a significant prognostic feature in determining metastatic disease. 216 patients who presented pelvic carcinoma underwent MR imaging. They were correlated to pathological findings obtained by surgery. We considered on the axial plan the maximum diameter (MAD) of both round or oval-shaped suspicious masses. Two different cut-off values were determined: node diameter superior to 1.0 cm (criterion 1) and node diameter superior to 0.5 cm with asymmetry relative to the opposite side for nodes ranging from 0.5 cm to 1.0 cm (criterion 2). With criterion 1 MR Imaging had an accuracy of 88%, a sensitivity of 65%, a specificity of 96%, a PPV of 88% and a NPV of 88% in detection of pelvic node metastasis. By considering criterion 2, MR Imaging had an accuracy of 85%, a sensitivity of 75%, a specificity of 89%, a PPV of 71% and a NPV of 91%. Normal small asymmetric lymph nodes were present in 5.6% of cases. Asymmetry of normal or inflammatory pelvic nodes is not uncommon. It cannot be relied on to diagnose metastatic involvement in cases of small suspicious lymph nodes, especially because of its low specificity and positive predictive value.

Theoretical Basis for Estimated Test Times and Conditions for Drop Tower and Space-Based Droplet Burning Experiments With Methanol and N-Heptane

NASA Technical Reports Server (NTRS)

Marchese, Anthony J.; Dryer, Fredrick L.; Choi, Mun Y.

1994-01-01

In order to develop an extensive envelope of test conditions for NASA's space-based Droplet Combustion Experiment (DCE) as well those droplet experiments which can be performed using a drop tower, the transient vaporization and combustion of methanol and n-heptane droplets were simulated using a recently developed fully time-dependent, spherically symmetric droplet combustion model. The transient vaporization of methanol and n-heptane was modeled to characterize the instantaneous gas phase composition surrounding the droplet prior to the introduction of an ignition source. The results for methanol/air showed that the entire gas phase surrounding a 2 mm methanol droplet deployed in zero-g .quickly falls outside the lean flammability limit. The gas phase surrounding an identically-sized n-heptane droplet, on the other hand, remains flammable. The combustion of methanol was then modeled considering a detailed gas phase chemical kinetic mechanism (168 steps, 26 species) and the effect of the dissolution of flame-generated water into the liquid droplet. These results were used to determine the critical ignition diameter required to achieve quasi-steady droplet combustion in a given oxidizing environment. For droplet diameters greater than the critical ignition diameter, the model predicted a finite diameter at which the flame would extinguish. These extinction diameters were found to vary significantly with initial droplet diameter. This phenomenon appears to be unique to the transient heat transfer, mass transfer and chemical kinetics of the system and thus has not been reported elsewhere to date. The extinction diameter was also shown to vary significantly with the liquid phase Lewis number since the amount of water present in the droplet at extinction is largely governed by the rate at which water is transported into the droplet via mass diffusion. Finally, the numerical results for n-heptane combustion were obtained using both 2 step and 96 step semi-emperical chemical kinetic mechanisms. Neither mechanism exhibited the variation of extinction diameter with initial diameter.

New Method of Producing Titanium Carbide, Monoxide, and Dioxide Grains in Laboratory

NASA Astrophysics Data System (ADS)

Kumamoto, Akihito; Kurumada, Mami; Kimura, Yuki; Kaito, Chihiro

By making a carbon rod covered with Ti on the surface without exposure to air, TiC grains less than 10nm in diameter were predominantly produced. The introduction of a small amount of oxygen in Ar gas (partial pressure 1/1000), allowed the continuous formation of TiO2 and TiO-TiC. The infrared spectra of TiO2, TiO, and TiC were measured. An absorption feature attributed to TiO phase in oxidized TiC grains showed a characteristic peak at 14.7 μm.

New Method of Producing Titanium Carbide, Monoxide, and Dioxide Grains in Laboratory

NASA Astrophysics Data System (ADS)

Kumamoto, Akihito; Kurumada, Mami; Kimura, Yuki; Kaito, Chihiro

By making a carbon rod covered with Ti on the surface without exposure to air, TiC grains less than 10 nm in diameter were predominantly produced. The introduction of a small amount of oxygen in Ar gas (partial pressure 1/1000), allowed the continuous formation of TiO2 and TiO-TiC. The infrared spectra of TiO2, TiO, and TiC were measured. An absorption feature attributed to TiO phase in oxidized TiC grains showed a characteristic peak at 14.7 μm.

Puget Sound Dredged Disposal Analysis (PSDDA). Unconfined, Open-Water Disposal Sites for Dredged Material. Phase 1 (Central Puget Sound). National Environmental Policy Act (NEPA)/State Environmental Policy Act (SEPA)

DTIC Science & Technology

1988-06-01

confined to a relatively small area. In 400 feet of water the descending cloud is approximately 250 feet in diameter (B. Trawle, personal communica- tion...when it hits the bottom, occuring 30 seconds after disposal is initiated. The collapsing cloud then spreads out in all directions. Ten minutes later...Compliance inspection6. Environ- mental monitorig an permin dp&nce insp ecti, arso part -disposal site management, are described in the MPR and the Management

Investigations on the droplet distributions in the atomization of kerosene jets in supersonic crossflows

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

Wu, Liyin; Wang, Zhen-guo, E-mail: wangzhenguo-wzg@163.com; Li, Qinglian

2015-09-07

Phase Doppler anemometry was applied to investigate the atomization processes of a kerosene jet injected into Ma = 1.86 crossflow. Physical behaviors, such as breakup and coalescence, are reproduced through the analysis of the spatial distribution of kerosene droplets' size. It is concluded that Sauter mean diameter distribution shape transforms into “I” type from “C” type as the atomization development. Simultaneously, the breakup of large droplets and the coalescence of small droplets can be observed throughout the whole atomization process.

Spin-echo small-angle neutron scattering (SESANS) measurements of needle-like crystallites of gelator compounds

NASA Astrophysics Data System (ADS)

Coumou, Pieter-Jan C. J. J.; Brizard, Aurelie M. A.; van Esch, Jan H.; de Schepper, Ignatz M.; Bouwman, Wim G.

2010-11-01

From dibenzoyl cystine, a low molecular weight gelator, we have prepared needle shaped crystals at relatively high concentrations. For the first time SESANS measurements are performed on objects with this geometry. From the measurements the average diameter can be seen directly. From a more careful analysis the width distribution is determined. The gel phase itself prepared at lower concentrations did not show any signal, in contrast to what one observes with conventional SANS. This shows the complementarity of SESANS and SANS.

Doppler imaging using spectrally-encoded endoscopy

PubMed Central

Yelin, Dvir; Bouma, B. E.; Rosowsky, J. J.; Tearney, G. J.

2009-01-01

The capability to image tissue motion such as blood flow through an endoscope could have many applications in medicine. Spectrally encoded endoscopy (SEE) is a recently introduced technique that utilizes a single optical fiber and miniature diffractive optics to obtain endoscopic images through small diameter probes. Using spectral-domain interferometry, SEE is furthermore capable of three-dimensional volume imaging at video rates. Here we show that by measuring relative spectral phases, this technology can additionally measure Doppler shifts. Doppler SEE is demonstrated in flowing Intralipid phantoms and vibrating middle ear ossicles. PMID:18795020

Adherence of oral streptococci to nanostructured titanium surfaces.

PubMed

Narendrakumar, Krunal; Kulkarni, Mukta; Addison, Owen; Mazare, Anca; Junkar, Ita; Schmuki, Patrik; Sammons, Rachel; Iglič, Aleš

2015-12-01

Peri-implantitis and peri-mucositis pose a severe threat to the success of dental implants. Current research focuses on the development of surfaces that inhibit biofilm formation while not inferring with tissue integration. This study compared the adherence of two oral bacterial species, Streptococcus sanguinis and Streptococcus mutans to nanostructured titanium surfaces. The samples included TiO2 nanotubes formed by anodization of titanium foil of 100, 50 and 15nm diameter (NT15, NT50, NT100), a nanoporous (15nm pore diameter) surface and compact TiO2 control. Adherent surviving bacteria were enumerated after 1h in an artificial saliva medium containing bovine mucin. Lowest numbers of adherent bacteria of both species were recovered from the original titanium foil and nanoporous surface and highest numbers from the Ti100 nanotubes. Numbers of attached S. sanguinis increased in the order (NT15

A Comparison of Four-Image Reconstruction Algorithms for 3-D PET Imaging of MDAPET Camera Using Phantom Data

NASA Astrophysics Data System (ADS)

Baghaei, H.; Wong, Wai-Hoi; Uribe, J.; Li, Hongdi; Wang, Yu; Liu, Yaqiang; Xing, Tao; Ramirez, R.; Xie, Shuping; Kim, Soonseok

2004-10-01

We compared two fully three-dimensional (3-D) image reconstruction algorithms and two 3-D rebinning algorithms followed by reconstruction with a two-dimensional (2-D) filtered-backprojection algorithm for 3-D positron emission tomography (PET) imaging. The two 3-D image reconstruction algorithms were ordered-subsets expectation-maximization (3D-OSEM) and 3-D reprojection (3DRP) algorithms. The two rebinning algorithms were Fourier rebinning (FORE) and single slice rebinning (SSRB). The 3-D projection data used for this work were acquired with a high-resolution PET scanner (MDAPET) with an intrinsic transaxial resolution of 2.8 mm. The scanner has 14 detector rings covering an axial field-of-view of 38.5 mm. We scanned three phantoms: 1) a uniform cylindrical phantom with inner diameter of 21.5 cm; 2) a uniform 11.5-cm cylindrical phantom with four embedded small hot lesions with diameters of 3, 4, 5, and 6 mm; and 3) the 3-D Hoffman brain phantom with three embedded small hot lesion phantoms with diameters of 3, 5, and 8.6 mm in a warm background. Lesions were placed at different radial and axial distances. We evaluated the different reconstruction methods for MDAPET camera by comparing the noise level of images, contrast recovery, and hot lesion detection, and visually compared images. We found that overall the 3D-OSEM algorithm, especially when images post filtered with the Metz filter, produced the best results in terms of contrast-noise tradeoff, and detection of hot spots, and reproduction of brain phantom structures. Even though the MDAPET camera has a relatively small maximum axial acceptance (/spl plusmn/5 deg), images produced with the 3DRP algorithm had slightly better contrast recovery and reproduced the structures of the brain phantom slightly better than the faster 2-D rebinning methods.

Small GSH-Capped CuInS2 Quantum Dots: MPA-Assisted Aqueous Phase Transfer and Bioimaging Applications.

PubMed

Zhao, Chuanzhen; Bai, Zelong; Liu, Xiangyou; Zhang, Yijia; Zou, Bingsuo; Zhong, Haizheng

2015-08-19

An efficient ligand exchange strategy for aqueous phase transfer of hydrophobic CuInS2/ZnS quantum dots was developed by employing glutathione (GSH) and mercaptopropionic acid (MPA) as the ligands. The whole process takes less than 20 min and can be scaled up to gram amount. The material characterizations show that the final aqueous soluble samples are solely capped with GSH on the surface. Importantly, these GSH-capped CuInS2/ZnS quantum dots have small size (hydrodynamic diameter <10 nm), moderate fluorescent properties (up to 34%) as well as high stability in aqueous solutions (stable for more than three months in 4 °C without any significant fluorescence quenching). Moreover, this ligand exchange strategy is also versatile for the aqueous phase transfer of other hydrophobic quantum dots, for instance, CuInSe2 and CdSe/ZnS quantum dots. We further demonstrated that GSH-capped quantum dots could be suitable fluorescence markers to penetrate cell membrane and image the cells. In addition, the GSH-capped CuInS2 quantum dots also have potential use in other fields such as photocatalysis and quantum dots sensitized solar cells.

Pupil dilation dynamics with an intracameral fixed combination of mydriatics and anesthetic during cataract surgery.

PubMed

Chiambaretta, Frederic; Pleyer, Uwe; Behndig, Anders; Pisella, Pierre-Jean; Mertens, Erik; Limao, Antonio; Fasce, Francesco; Fernandez, Joaquin; Benmoussa, Salah-Eddine; Labetoulle, Marc; Cochener, Beatrice

2018-03-01

To compare the pupil dynamics of an intracameral combination of 2 mydriatics and 1 anesthetic (Mydrane) to a standard topical regimen for cataract surgery. Sixty-two centers in Europe and 6 centers in Algeria. Prospective case series. Pupil size measurements were performed in 2 randomized studies (phase 2 and phase 3) under masked conditions (recorded videography, masked reading center). The outcomes in the phase 2 study supported evaluation of the timeframe to obtain pupil dilation and the phase 3 study provided results on mydriasis stability. Phase 2 and phase 3 comprised 139 patients and 591 patients, respectively. After intracameral combination administration, 95% of the pupil dilation was achieved within a mean of 28.6 seconds ± 4.6 (SD). At the beginning of capsulorhexis creation, the mean pupil diameter was larger than 7.0 mm in both groups. The intraoperative pupil diameter remained stable in the intracameral combination group and decreased in the topical group. The mean change in pupil size just before capsulorhexis to the end of surgery (just before cefuroxime injection) was -0.22 ± 0.72 mm and -1.67 ± 0.98 mm, respectively. No clinically significant change in pupil diameter (change <1.0 mm) occurred in the majority of the intracameral combination group (89.3%) compared with the topical group (26.8%). Intracameral combination of 2 mydriatics and 1 anesthetic is an alternative to topical mydriatics for cataract surgery. The prompt onset of pupil dilation and the stable mydriasis induced by this drug combination improved the intraoperative conditions during crucial steps, such as intraocular lens implantation. Copyright © 2018. Published by Elsevier Inc.

[Indication for limited surgery on small lung cancer tumors measuring 1cm or less in diameter on preoperative computed tomography and long-term results].

PubMed

Togashi, K; Koike, T; Emura, I; Usuda, H

2008-07-01

Non-invasive lung cancers showed a good prognosis after limited surgery. But it is still uncertain about invasive lung cancers. We investigated the indications for limited surgery for small lung cancer tumors measuring 1 cm or less in diameter on preoperative computed tomography (CT). This study retrospectively analyzed of 1,245 patients who underwent complete resection of lung cancer between 1989 and 2004 in our hospital. Sixty-two patients (5%) had tumors measuring 1 cm or less in diameter. The probability of survival was calculated using the Kaplan-Meier method. All diseases were detected by medical checkup, 52 % of the patients were not definitively diagnosed with lung cancer before surgery. Adenocarcinoma was histologically diagnosed in 49 patients (79%). Other histologic types included squamous cell carcinoma (8), large cell carcinoma (1), small cell carcinoma (1), carcinoid (2), and adenosquamous cell carcinoma (1). Fifty-seven patients (92%) showed pathologic stage IA. The other stages were IB (2), IIA (1), and IIIB (2). There were 14 bronchioloalveolar carcinomas (25% of IA diseases). The 5-year survival rates of IA patients were 90%. The 5-year survival rate of patients with tumors measuring 1cm or less diameter was 91% after lobectomy or pneumonectomy, and 90% after wedge resection or segmentectomy. There were 3 deaths from cancer recurrence, while there were no deaths in 14 patients with bronchioloalveolar carcinoma After limited surgery, non-invasive cancer showed good long-term results, while invasive cancer showed a recurrence rate of 2.3% to 79% even though the tumor measured 1 cm or less in diameter on preoperative CT.

[Comparison of the anterior corneal asphericity after small incision lenticule extraction and femtosecond laser in situ keratomileusis].

PubMed

Su, X L; Wang, Y; Wu, W J; Wu, Z Q; Wu, Y N; Yu, C J

2016-09-11

To evaluate and compare the anterior corneal asphericity after small incision lenticule extraction(SMILE)and femtosecond laser in situ keratomileusis(FS-LASIK). In this case-control study, 45 subjects who underwent SMILE operation comprised the study group, and 33 subjects with FS-LASIK operation comprised the control group. The asphericity coefficient Q-value of the right eyes in both groups was measured at diameters of 6, 7, 8 and 9 mm, respectively, before surgery and at 1 day, 1 week, 1 month and 6 months following surgery. The correlation between the variation of Q-value and the central cutting depth was analyzed. The Q-value of anterior corneal surface was 0.85 ± 0.31, 0.80±0.28, 0.69±0.25 and 0.51±0.23 after SMILE, and 1.13±0.56, 1.01±0.47, 0.80±0.39 and 0.51±0.31 after FS-LASIK at 1 week. In both groups, the Q-value was significantly different before and after surgery(P< 0.05); there were interaction effects between the operation method and time; the difference between the two groups at 6-mm and 7-mm diameters was statistically significant(P<0.05). The variation of the Q-value before and after operation(ΔQ)showed significant difference(P6mm=0.004, P7mm=0.014)between the two groups at 6-mm and 7-mm diameters. The cap diameter of the SMILE group was smaller than that of the FS-LASIK group, but the cutting depth was larger. There was no correlation between ΔQ and the cap/disc diameter. It showed a linear relationship(P<0.05)between ΔQ and the central cutting depth at all examined diameters in the two groups, and the relation degree in the FS-LASIK group was superior to the SMILE group. Both SMILE and FS-LASIK operations can change the negative Q-value of the anterior corneal surface to the positive. The impact of SMILE on the asphericity is smaller than that of FS-LASIK. (Chin J Ophthalmol, 2016, 52: 681-685).

Soil compaction after yarding of small-diameter Douglas-fir with a small tractor in southwest Oregon.

Treesearch

Michael P. Amaranthus; David E. Steinfeld

1997-01-01

This study evaluated the effect on soil bulk density of yarding small-diameter Douglas-fir (Pseudosuga menziesii var. glauca (Beissn.) Franco) with a small tractor. Levels of compaction were measured before yarding and after one trip, three trips, and six trips by the tractor. Bulk densities in the surface (10 cm) and...

SMALL DIAMETER PRECEMENT LINING FROM CATWALK ABOVE. United States ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

SMALL DIAMETER PRE-CEMENT LINING FROM CATWALK ABOVE. - United States Pipe & Foundry Company Plant, Coating, Painting, Lining & Packaging Building, 2023 St. Louis Avenue at I-20/59, Bessemer, Jefferson County, AL

An experimental investigation of the effect of walls on gas-liquid flows through fixed particle beds.

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

Cooper, Marcia A.; Cote, Raymond O.; Torczynski, John Robert

The effect of particle diameter on downward co-current gas-liquid flow through a fixed bed of particles confined within a cylindrical column is investigated. Several hydrodynamic regimes that depend strongly on the properties of the gas stream, the liquid stream, and the packed particle bed are known to exist within these systems. This experimental study focuses on characterizing the effect of wall confinement on these hydrodynamic regimes as the diameter d of the spherical particles becomes comparable to the column diameter D (or D/d becomes order-unity). The packed bed consists of polished, solid, spherical, monodisperse particles (beads) with mean diameter inmore » the range of 0.64-2.54 cm. These diameters yield D/d values between 15 and 3.75, so this range overlaps and extends the previously investigated range for two-phase flow, Measurements of the pressure drop across the bed and across the pulses are obtained for varying gas and liquid flow rates.« less

Pressure Dependence of the Liquid-Liquid Phase Transition of Nanopore Water Doped Slightly with Hydroxylamine, and a Phase Behavior Predicted for Pure Water

NASA Astrophysics Data System (ADS)

Nagoe, Atsushi; Iwaki, Shinji; Oguni, Masaharu; Tôzaki, Ken-ichi

2014-09-01

Phase transition behaviors of confined pure water and confined water doped with a small amount of hydroxylamine (HA) with a mole fraction of xHA = 0.03 were examined by high-pressure differential thermal analyses at 0.1, 50, 100, and 150 MPa; the average diameters of silica pores used were 2.0 and 2.5 nm. A liquid-liquid phase transition (LLPT) of the confined HA-doped water was clearly observed and its pressurization effect could be evaluated, unlike in the experiments on undoped water. It was found that pressurization causes the transition temperature (Ttrs) to linearly decrease, indicating that the low-temperature phase has a lower density than the high-temperature one. Transition enthalpy (ΔtrsH) decreased steeply with increasing pressure. Considering the linear decrease in Ttrs with increasing pressure, the steep decrease in ΔtrsH indicates that the LLPT effect of the HA-doped water attenuates with pressure. We present a new scenario of the phase behavior concerning the LLPT of pure water based on the analogy from the behavior of slightly HA-doped water, where a liquid-liquid critical point (LLCP) and a coexistence line are located in a negative-pressure regime but not in a positive-pressure one. It is reasonably understood that doping a small amount of HA into water results in negative chemical pressurization and causes the LLPT to occur even at ambient pressure.

James Webb Space Telescope segment phasing using differential optical transfer functions

PubMed Central

Codona, Johanan L.; Doble, Nathan

2015-01-01

Differential optical transfer function (dOTF) is an image-based, noniterative wavefront sensing method that uses two star images with a single small change in the pupil. We describe two possible methods for introducing the required pupil modification to the James Webb Space Telescope, one using a small (<λ/4) displacement of a single segment's actuator and another that uses small misalignments of the NIRCam's filter wheel. While both methods should work with NIRCam, the actuator method will allow both MIRI and NIRISS to be used for segment phasing, which is a new functionality. Since the actuator method requires only small displacements, it should provide a fast and safe phasing alternative that reduces the mission risk and can be performed frequently for alignment monitoring and maintenance. Since a single actuator modification can be seen by all three cameras, it should be possible to calibrate the non-common-path aberrations between them. Large segment discontinuities can be measured using dOTFs in two filter bands. Using two images of a star field, aberrations along multiple lines of sight through the telescope can be measured simultaneously. Also, since dOTF gives the pupil field amplitude as well as the phase, it could provide a first approximation or constraint to the planned iterative phase retrieval algorithms. PMID:27042684

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

Pallesen, T.R.; Braestrup, M.W.; Jorgensen, O.

Development of Danish North Sea hydrocarbon resources includes the 17-km Rolf pipeline installed in 1985. This one consists of an insulated 8-in. two-phase flow product line with a 3-in. piggyback gas lift line. A practical solution to design of this insulated pipeline, including the small diameter, piggyback injection line was corrosion coating of fusion bonded epoxy (FBE) and polyethylene (PE) sleeve pipe. The insulation design prevents hydrate formation under the most conservative flow regime during gas lift production. Also, the required minimum flow rate during the initial natural lift period is well below the value anticipiated at the initiation ofmore » gas lift. The weight coating design ensures stability on the seabed during the summer months only; thus trenching was required during the same installation season. Installation of insulated flowlines serving marginal fields is a significant feature of North Sea hydrocarbon development projects. The Skjold field is connected to Gorm by a 6-in., two-phase-flow line. The 11-km line was installed in 1982 as the first insulated pipeline in the North Sea. The Rolf field, located 17 km west of Gorm, went on stream Jan. 2. The development includes an unmanned wellhead platform and an insulated, two-phase-flow pipeline to the Gorm E riser platform. After separation on the Gorm C process platform, the oil and condensate are transported to shore through the 20-in. oil pipeline, and the natural gas is piped to Tyra for transmission through the 30-in. gas pipeline. Oil production at Rolf is assisted by the injection of lift gas, transported from Gorm through a 3-in. pipeline, installed piggyback on the insulated 8-in. product line. The seabed is smooth and sandy, the water depth varying between 33.7 m (110.5 ft) at Rolf and 39.1 m (128 ft) at Gorm.« less

Management of non-traumatic avascular necrosis of the femoral head-a comparative analysis of the outcome of multiple small diameter drilling and core decompression with fibular grafting.

PubMed

Mohanty, S P; Singh, K A; Kundangar, R; Shankar, V

2017-04-01

The purpose of this study was to compare the clinical and radiological outcomes of multiple small diameter drilling and core decompression with fibular strut grafting in the management of non-traumatic avascular necrosis (AVN) of the femoral head. Outcomes of patients with AVN treated by multiple small diameter drilling (group 1) were compared retrospectively with patients treated by core decompression and fibular grafting (group 2). Harris hip score (HHS) was used to assess the clinical status pre- and postoperatively. Modified Ficat and Arlet classification was used to assess the radiological stage pre- and postoperatively. Forty-six patients (68 hips) were included in this study. Group 1 consisted of 33 hips, and group 2 consisted of 35 hips. In stages I and IIB, there was no statistically significant difference in the final HHS between the two groups. However, in stages IIA and III, hips in group 2 had a better final HHS (P < 0.05). In terms of radiographic progression, there was no statistical difference between hips in stages I, IIA and stage IIB. However, in stage III, hips belonging to group 2 had better results (P < 0.05). Kaplan-Meier survivorship analysis showed better outcome in group 2 in stage III (P < 0.05). Hips with AVN in the precollapse stage can be salvaged by core decompression with or without fibular grafting. Multiple small diameter drilling is relatively simple and carries less morbidity and hence preferred in stages I and II. However, in stage III disease, core decompression with fibular strut grafting gives better results.

Comparison of Two-Phase Pipe Flow in OpenFOAM with a Mechanistic Model

NASA Astrophysics Data System (ADS)

Shuard, Adrian M.; Mahmud, Hisham B.; King, Andrew J.

2016-03-01

Two-phase pipe flow is a common occurrence in many industrial applications such as power generation and oil and gas transportation. Accurate prediction of liquid holdup and pressure drop is of vast importance to ensure effective design and operation of fluid transport systems. In this paper, a Computational Fluid Dynamics (CFD) study of a two-phase flow of air and water is performed using OpenFOAM. The two-phase solver, interFoam is used to identify flow patterns and generate values of liquid holdup and pressure drop, which are compared to results obtained from a two-phase mechanistic model developed by Petalas and Aziz (2002). A total of 60 simulations have been performed at three separate pipe inclinations of 0°, +10° and -10° respectively. A three dimensional, 0.052m diameter pipe of 4m length is used with the Shear Stress Transport (SST) k - ɷ turbulence model to solve the turbulent mixtures of air and water. Results show that the flow pattern behaviour and numerical values of liquid holdup and pressure drop compare reasonably well to the mechanistic model.

AUTOSAW simulations of lumber recovery for small-diameter Douglas-fir and ponderosa pine from southwestern Oregon.

Treesearch

R. James Barbour; Dean L. Parry; John Punches; John Forsman; Robert Ross

2003-01-01

Small-diameter (5- to 10-inch diameter at breast height) Douglas-fi r (Pseudotsuga menziesii (Mirb.) Franco) and ponderosa pine (Pinus ponderosa Dougl. ex Laws) trees were assessed for product potential by diagramming the location, size, and type of knots visible on the wood surface (inside bark) and using the AUTOSAW sawing simulator to evaluate...

Analysis of replication factories in human cells by super-resolution light microscopy

PubMed Central

2009-01-01

Background DNA replication in human cells is performed in discrete sub-nuclear locations known as replication foci or factories. These factories form in the nucleus during S phase and are sites of DNA synthesis and high local concentrations of enzymes required for chromatin replication. Why these structures are required, and how they are organised internally has yet to be identified. It has been difficult to analyse the structure of these factories as they are small in size and thus below the resolution limit of the standard confocal microscope. We have used stimulated emission depletion (STED) microscopy, which improves on the resolving power of the confocal microscope, to probe the structure of these factories at sub-diffraction limit resolution. Results Using immunofluorescent imaging of PCNA (proliferating cell nuclear antigen) and RPA (replication protein A) we show that factories are smaller in size (approximately 150 nm diameter), and greater in number (up to 1400 in an early S- phase nucleus), than is determined by confocal imaging. The replication inhibitor hydroxyurea caused an approximately 40% reduction in number and a 30% increase in diameter of replication factories, changes that were not clearly identified by standard confocal imaging. Conclusions These measurements for replication factory size now approach the dimensions suggested by electron microscopy. This agreement between these two methods, that use very different sample preparation and imaging conditions, suggests that we have arrived at a true measurement for the size of these structures. The number of individual factories present in a single nucleus that we measure using this system is greater than has been previously reported. This analysis therefore suggests that each replication factory contains fewer active replication forks than previously envisaged. PMID:20015367

Ecological Importance of Small-Diameter Trees to the Structure, Diversity and Biomass of a Tropical Evergreen Forest at Rabi, Gabon.

PubMed

Memiaghe, Hervé R; Lutz, James A; Korte, Lisa; Alonso, Alfonso; Kenfack, David

2016-01-01

Tropical forests have long been recognized for their biodiversity and ecosystem services. Despite their importance, tropical forests, and particularly those of central Africa, remain understudied. Until recently, most forest inventories in Central Africa have focused on trees ≥10 cm in diameter, even though several studies have shown that small-diameter tree population may be important to demographic rates and nutrient cycling. To determine the ecological importance of small-diameter trees in central African forests, we used data from a 25-ha permanent plot that we established in the rainforest of Gabon to study the diversity and dynamics of these forests. Within the plot, we censused 175,830 trees ≥1 cm dbh from 54 families, 192 genera, and 345 species. Average tree density was 7,026 trees/ha, basal area 31.64 m2/ha, and above-ground biomass 369.40 Mg/ha. Fabaceae, Ebenaceae and Euphorbiaceae were the most important families by basal area, density and above-ground biomass. Small-diameter trees (1 cm ≥ dbh <10 cm) comprised 93.7% of the total tree population, 16.5% of basal area, and 4.8% of the above-ground biomass. They also had diversity 18% higher at family level, 34% higher at genus level, and 42% higher at species level than trees ≥10 cm dbh. Although the relative contribution of small-diameter trees to biomass was comparable to other forests globally, their contribution to forest density, and diversity was disproportionately higher. The high levels of diversity within small-diameter classes may give these forests high levels of structural resilience to anthropogenic/natural disturbance and a changing climate.

Ecological Importance of Small-Diameter Trees to the Structure, Diversity and Biomass of a Tropical Evergreen Forest at Rabi, Gabon

PubMed Central

Memiaghe, Hervé R.; Lutz, James A.; Korte, Lisa; Alonso, Alfonso; Kenfack, David

2016-01-01

Tropical forests have long been recognized for their biodiversity and ecosystem services. Despite their importance, tropical forests, and particularly those of central Africa, remain understudied. Until recently, most forest inventories in Central Africa have focused on trees ≥10 cm in diameter, even though several studies have shown that small-diameter tree population may be important to demographic rates and nutrient cycling. To determine the ecological importance of small-diameter trees in central African forests, we used data from a 25-ha permanent plot that we established in the rainforest of Gabon to study the diversity and dynamics of these forests. Within the plot, we censused 175,830 trees ≥1 cm dbh from 54 families, 192 genera, and 345 species. Average tree density was 7,026 trees/ha, basal area 31.64 m2/ha, and above-ground biomass 369.40 Mg/ha. Fabaceae, Ebenaceae and Euphorbiaceae were the most important families by basal area, density and above-ground biomass. Small-diameter trees (1 cm ≥ dbh <10 cm) comprised 93.7% of the total tree population, 16.5% of basal area, and 4.8% of the above-ground biomass. They also had diversity 18% higher at family level, 34% higher at genus level, and 42% higher at species level than trees ≥10 cm dbh. Although the relative contribution of small-diameter trees to biomass was comparable to other forests globally, their contribution to forest density, and diversity was disproportionately higher. The high levels of diversity within small-diameter classes may give these forests high levels of structural resilience to anthropogenic/natural disturbance and a changing climate. PMID:27186658

A Linear Ion Trap with an Expanded Inscribed Diameter to Improve Optical Access for Fluorescence Spectroscopy

NASA Astrophysics Data System (ADS)

Rajagopal, Vaishnavi; Stokes, Chris; Ferzoco, Alessandra

2018-02-01

We report a custom-geometry linear ion trap designed for fluorescence spectroscopy of gas-phase ions at ambient to cryogenic temperatures. Laser-induced fluorescence from trapped ions is collected from between the trapping rods, orthogonal to the excitation laser that runs along the axis of the linear ion trap. To increase optical access to the ion cloud, the diameter of the round trapping rods is 80% of the inscribed diameter, rather than the roughly 110% used to approximate purely quadrupolar electric fields. To encompass as much of the ion cloud as possible, the first collection optic has a 25.4 mm diameter and a numerical aperture of 0.6. The choice of geometry and collection optics yields 107 detected photons/s from trapped rhodamine 6G ions. The trap is coupled to a closed-cycle helium refrigerator, which in combination with two 50 Ohm heaters enables temperature control to below 25 K on the rod electrodes. The purpose of the instrument is to broaden the applicability of fluorescence spectroscopy of gas-phase ions to cases where photon emission is a minority relaxation pathway. Such studies are important to understand how the microenvironment of a chromophore influences excited state charge transfer processes.

Detailed analysis of particle launch velocities, size distributions and gas densities during normal explosions at Stromboli

NASA Astrophysics Data System (ADS)

Harris, Andrew J. L.; Ripepe, Maurizio; Hughes, Elizabeth A.

2012-06-01

Using high frame rate (33 Hz) thermal video data we describe and parameterize the emission and ascent dynamics of a mixed plume of gas and particles emitted during a normal explosion at Stromboli (Aeolian Islands, Italy). Analysis of 34 events showed that 31 of them were characterized by a first phase characterized by an initial diffuse spray of relatively small (lapilli-sized) particles moving at high velocities (up to 213 m s- 1; average 66-82 m s- 1). This was followed, typically within 0.1 s, by a burst comprising a mixture of ash and lapilli, but dominated by larger bomb-sized particles, moving at lower exit velocities of up to 129 m s- 1, but typically 46 m s- 1. We interpret these results as revealing initial emission of a previously unrecorded high velocity gas-jet phase, to which the lapilli are coupled. This is followed by emission of slower moving larger particles that are decoupled from the faster moving gas-phase. Diameters for particles carried by the gas phase are typically around 4 cm, but can be up to 9 cm, with the diameter of the particles carried by the gas jet (D) decreasing with increased density and velocity of the erupted gas cloud (ρgas and Ugas). Data for 101 particles identified as moving with the gas jet during 32 eruptions allow us to define a new relation, whereby Ugas = Uparticle + a [ρgas√{D}]b. Here, Uparticle is the velocity of bombs whose motion is decoupled from that of the gas cloud, and a and b are two empirically-derived coefficients. This replaces the old relation, whereby Ugas = Uparticle + k √{D}; a relation that requires a constant gas density for each eruption. This is an assumption that we show to be invalid, with gas density potentially varying between 0.04 kg m- 3 and 9 kg m- 3 for the 32 cases considered, so that k varies between 54 m1/2 s- 1 and 828 m1/2 s- 1, compared with the traditionally used constant of 150 m1/2 s- 1.

Evaluation of latent variances in Monte Carlo dose calculations with Varian TrueBeam photon phase-spaces used as a particle source

NASA Astrophysics Data System (ADS)

Alhakeem, Eyad; Zavgorodni, Sergei

2018-01-01

The purpose of this study was to evaluate the latent variance (LV) of Varian TrueBeam photon phase-space files (PSF) for open 10  ×  10 cm2 and small stereotactic fields and estimate the number of phase spaces required to be summed up in order to maintain sub-percent LV in Monte Carlo (MC) dose calculations. BEAMnrc/DOSXYZnrc software was used to transport particles from Varian phase-space files (PSFA) through the secondary collimators. Transported particles were scored into another phase-space located under the jaws (PSFB), or transported further through the cone collimators and scored straight below, forming PSFC. Phase-space files (PSFB) were scored for 6 MV-FFF, 6 MV, 10 MV-FFF, 10 MV and 15 MV beams with 10  ×  10 cm2 field size, and PSFC were scored for 6 MV beam under circular cones of 0.13, 0.25, 0.35, and 1 cm diameter. Both PSFB and PSFC were transported into a water phantom with particle recycling number ranging from 10 to 1000. For 10  ×  10 cm2 fields 0.5  ×  0.5  ×  0.5 cm3 voxels were used to score the dose, whereas the dose was scored in 0.1  ×  0.1  ×  0.5 cm3 voxels for beams collimated with small cones. In addition, for small 0.25 cm diameter cone-collimated 6 MV beam, phantom voxel size varied as 0.02  ×  0.02  ×  0.5 cm3, 0.05  ×  0.05  ×  0.5 cm3 and 0.1  ×  0.1  ×  0.5 cm3. Dose variances were scored in all cases and LV evaluated as per Sempau et al. For the 10  ×  10 cm2 fields calculated LVs were greatest at the phantom surface and decreased with depth until they reached a plateau at 5 cm depth. LVs were found to be 0.54%, 0.96%, 0.35%, 0.69% and 0.57% for the 6 MV-FFF, 6 MV, 10 MV-FFF, 10 MV and 15 MV energies, respectively at the depth of 10 cm. For the 6 MV phase-space collimated with cones of 0.13, 0.25, 0.35, 1.0 cm diameter, the LVs calculated at 1.5 cm depth were 75.6%, 25.4%, 17.6% and 8.0% respectively. Calculated LV for the 0.25 cm cone-collimated 6 MV beam were 61.2%, 40.7%, 22.5% in 0.02  ×  0.02  ×  0.5 cm3, 0.05  ×  0.05  ×  0.5 cm3 and 0.1  ×  0.1  ×  0.5 cm3 voxels respectively. In order to achieve sub-percent LV in open 10  ×  10 cm2 field MC simulations a single PSF can be used, whereas for small SRS fields (0.13-1.0 cm) more PSFs (66-8 PSFs) would have to be summed.

Particle-Laden Liquid Jet Impingement on a Moving Substrate

NASA Astrophysics Data System (ADS)

Rahmani, Hatef; Green, Sheldon

2017-11-01

The impingement of high-speed jets on a moving substrate is salient to a number of industrial processes such as surface coating in the railroad industry. The particular jet fluids studied were dilute suspensions of neutrally buoyant particles in water-glycerin solutions. At these low particle concentrations, the suspensions have Newtonian fluid viscosity. A variety of jet and surface velocities, solution properties, nozzle diameters, mean particle sizes, and volume fractions were studied. It was observed that for jets with very small particles, addition of solids to the jet enhances deposition and postpones splash relative to a particle-free water-glycerin solution with the same viscosity. In contrast, jets with larger particles in suspension were more prone to splash than single phase jets of the same viscosity. It is speculated that the particle diameter, relative to the lamella thickness, is the key parameter to determine whether splash is suppressed or enhanced. An existing splash model for single phase liquid jets was found to be in good agreement with the experimental results, provided that the single fitting parameter in that model is a function of the particle size, volume fraction, and surface roughness.

A new device for slow progressive narrowing of vessels.

PubMed

Lange, P E; Sievers, H H; Nürnberg, J H; Engler, K; Pilarczyk, J; Onnasch, D G; Bernhard, A; Heintzen, P H

1985-01-01

The purpose of this work was to develop a device which allows slow progressive banding of a great artery in infants within 4 to 5 weeks. Employed was the hygroscopic casein ameroid. When brought in contact with fluids, an ameroid cylinder expands characteristically. An early phase of fast expansion proceeds gradually to a phase of slow growth. Size, shape, and encasement of ameroid as well as temperature and type of surrounding fluid modify but do not alter the typical pattern of expansion. The developed constrictor (weight: 5.8 kg, length: 18 mm, diameter: 12 mm) includes a stainless steel socket containing an ameroid cylinder (length: 8.5 mm, diameter: 8 mm). The expanding ameroid pushes a piston with a concave extension (makrolon) a maximum of 2 mm against the artery, which is fixed to the metal housing by a teflon band (width: 4 mm, thickness: 0.5 mm). The band runs in 2 fitting grooves on the metal housing to which it is fixed by a metal ring with a precisely manufactured internal thread allowing exact tightening and loosening of the band around the artery. Utilization of inert materials like teflon, makrolon, and stainless steel warrants experimental and possibly clinical application of the developed small constrictor.

Electronically steerable ultrasound-driven long narrow air stream

NASA Astrophysics Data System (ADS)

Hasegawa, Keisuke; Qiu, Liwei; Noda, Akihito; Inoue, Seki; Shinoda, Hiroyuki

2017-08-01

Acoustic streaming, which is the unidirectional movement of a medium driven by its internal intense acoustic vibrations, has been known for more than a century. Despite the long history of research, there have been no scientific reports on the creation of long stretching steerable airflows in an open space, generated by ultrasound. Here, we demonstrated the creation of a narrow, straight flow in air to a distance of 400 mm from an ultrasound phased array emitting a Bessel beam. We also demonstrated that the direction of the flow could be controlled by appropriately tuning the wavefronts of the emission from the phased array. Unlike conventional airflows such as those generated by jets or fans, which decelerate and spread out as they travel farther, the flow that we created proceeded while being accelerated by the kinetic energy supplied from the ultrasound beam and keeping the diameter as small as the wavelength. A flow of 3 m/s with a 10 mm diameter extended for several hundreds of millimeters in a room that was large enough to be regarded as an open-boundary environment. These properties of the generated flow will enable fine and rapid control of three-dimensional airflow distributions.

Heat transfer and hydrodynamic investigations of a baffled slurry bubble column

NASA Astrophysics Data System (ADS)

Saxena, S. C.; Chen, Z. D.

1992-09-01

Heat transfer and hydrodynamic investigations have been conducted in a 0.108 m internal diameter bubble column at ambient conditions. The column is equipped with seven 19mm diameter tubes arranged in an equilateral triangular pitch of 36.5 mm. A Monsanto synthetic heat transfer fluid, Therminol-66 having a viscosity of 39.8 cP at 303 K, is used as a liquid medium. Magnetite powders, average diameters 27.7 and 36.6 µm, in five concentrations up to 50 weight percent in the slurry, are used. As a gas phase, industrial grade nitrogen of purity 99.6 percent is employed. Gas holdup in different operating modes and regimes have been measured for the two- and three-phase systems over a superficial gas velocity range up to 0.20 m/s in the semi-batch mode. Heat transfer coefficients are measured at different tube locations in the bundle at different radial and vertical locations over a range of operating conditions. All these data are compared with the existing literature correlations and models. New correlations are proposed.

Aqueous Nucleation and Growth of Titanium Oxides Using Time-Resolved Synchrotron X- ray Diffraction

NASA Astrophysics Data System (ADS)

Hummer, D. R.; Heaney, P. J.; Post, J. E.

2006-05-01

The inorganic precipitation of oxide minerals in soil environments has profound effects on a variety of geochemical processes. These include the removal of metals from the aqueous phase, the production of coatings that reduce the reactive surface area of pre-existing mineral grains, and the generation of feedstocks for microbial metabolic reactions. Recent observations of transient, metastable phases during the growth of oxide crystallites has raised questions about their role in crystallization mechanisms, and created a need for more detailed structural measurements. To better understand the process of nucleation and growth, we investigated the crystallization of Ti oxides from aqueous 0.5 M TiCl4 solutions using synchrotron X-ray diffraction at temperatures of 100 and 150 °C. Solutions were heated in a 1.0 mm internal diameter quartz glass capillary sealed with epoxy. Powder diffraction patterns of the growing crystallites were collected using image plate technology with a time step of ~ 4 minutes, providing high resolution in situ measurements of structural changes during the crystallization process. The data indicate a co-precipitation of the two crystalline phases anatase and rutile within the first 30 minutes of heating, followed by a gradual phase transition from anatase to rutile during particle coarsening throughout the 10 hour duration of an experiment. The co-existence of anatase and rutile at the onset of crystallization lends additional support to the assertion of nearly identical free energies for anatase and rutile at the nanoscale, believed to be due to the prominence of surface energy effects (Ranade et al., 2001). Whole pattern analyses using the Rietveld refinement method also documented previously unobserved changes in lattice parameters of both phases during growth, on the order of 0.2-0.3 % expansion for each axis. The trends in lattice parameters are observed to be temperature dependent, generally having lower values at higher crystallization temperature. In addition to increased surface energy, these small but measurable structural changes may be partially responsible for the observed reversals in thermodynamic stability between crystalline Ti oxide phases at very small particle sizes.

PCL-PGLA composite tubular scaffold preparation and biocompatibility investigation.

PubMed

Mo, X; Weber, H-J; Ramakrishna, S

2006-08-01

The objective of this paper was to fabricate a biodegradable tubular scaffold for small diameter (d<6 mm) blood vessel tissue engineering. The tube scaffold needed a porous wall for cell attachment, proliferation and tissue regeneration with its degradation. A novel method given in this paper was to coat a porous layer of poly (epsilon-caprolactone) (PCL) on the outside of a poly (glycolic-co-lactic acid) (PGLA with GA:LA=90:10) fiber braided tube to give a PCL-PGLA composite. The PGLA tube was fabricated using a braiding machine by inserting a Teflon tube with the desired diameter in center of the 20 spindles, which are the carriers of PGLA fibers. Changing the diameter of the Teflon tube can vary the inner diameter of a braided PGLA tube. Thermally induced phase separation method was used for PCL solution coating on the surface of the PGLA braided tube. Controlling the polymer concentration, non-solvent addition and quenching temperature generated the pore structures, with pore sizes ranging from 10-30 microm. The fibroblast cells were seeded on the tubular scaffold and cultured in vitro for the biocompatibility investigation. Histology results showed that the fibroblast cells proliferated on the interconnected pore of the PCL porous layer in 1 week.

Comparison of preoperative nepafenac (0.1%) and flurbiprofen (0.03%) eye drops in maintaining mydriasis during small incision cataract surgery in patients with senile cataract: A randomized, double-blind study.

PubMed

Sarkar, Saumya; Mondal, Kanchan Kumar; Roy, Sukalyan Saha; Gayen, Sharmistha; Ghosh, Abhishek; De, Radha Raman

2015-01-01

This study compared the effectiveness of prophylactic administration of topical flurbiprofen 0.03% and nepafenac 0.1% in maintaining mydriasis during small incision cataract surgery (SICS). This study was a prospective, randomized, double-blind comparative study in adult cataract patients given topical flurbiprofen or nepafenac prior to SICS and capsular bag intraocular lens (IOL) implantation at a tertiary care hospital. Horizontal and vertical diameters of pupil were measured at the beginning and end of surgery, and the mean values were compared across the two groups. Unpaired t-test and Fisher's exact test were used to analyse the results. A total of 70 eyes of cataract surgery patients, 33 males and 37 females, with a mean age of 58.5 ± 11.24 years, were included in the study. The mean horizontal and vertical diameters of the two groups were similar at the start of surgery. Significant differences were seen after IOL implantation, with the nepafenac group having the larger mean diameters in both horizontal (P = 0.03) and vertical (P = 0.04) pupillary measurements. Topical nepafenac has been shown to be a more effective inhibitor of meiosis during SICS and provides a more stable mydriatic effect compared to topical flurbiprofen.

Gas holdup and flow regime transition in spider-sparger bubble column: effect of liquid phase properties

NASA Astrophysics Data System (ADS)

Besagni, G.; Inzoli, F.; De Guido, G.; Pellegrini, L. A.

2017-01-01

This paper discusses the effects of the liquid velocity and the liquid phase properties on the gas holdup and the flow regime transition in a large-diameter and large-scale counter-current two-phase bubble column. In particular, we compared and analysed the experimental data obtained in our previous experimental studies. The bubble column is 5.3 m in height, has an inner diameter of 0.24 m, it was operated with gas superficial velocities in the range of 0.004-0.20 m/s and, in the counter-current mode, the liquid was recirculated up to a superficial velocity of -0.09 m/s. Air was used as the dispersed phase and various fluids (tap water, aqueous solutions of sodium chloride, ethanol and monoethylene glycol) were employed as liquid phases. The experimental dataset consist in gas holdup measurements and was used to investigate the global fluid dynamics and the flow regime transition between the homogeneous flow regime and the transition flow regime. We found that the liquid velocity and the liquid phase properties significantly affect the gas holdup and the flow regime transition. In this respect, a possible relationship (based on the lift force) between the flow regime transition and the gas holdup was proposed.

Evidence of low-density and high-density liquid phases and isochore end point for water confined to carbon nanotube

PubMed Central

Nomura, Kentaro; Kaneko, Toshihiro; Bai, Jaeil; Francisco, Joseph S.; Yasuoka, Kenji; Zeng, Xiao Cheng

2017-01-01

Possible transition between two phases of supercooled liquid water, namely the low- and high-density liquid water, has been only predicted to occur below 230 K from molecular dynamics (MD) simulation. However, such a phase transition cannot be detected in the laboratory because of the so-called “no-man’s land” under deeply supercooled condition, where only crystalline ices have been observed. Here, we show MD simulation evidence that, inside an isolated carbon nanotube (CNT) with a diameter of 1.25 nm, both low- and high-density liquid water states can be detected near ambient temperature and above ambient pressure. In the temperature–pressure phase diagram, the low- and high-density liquid water phases are separated by the hexagonal ice nanotube (hINT) phase, and the melting line terminates at the isochore end point near 292 K because of the retracting melting line from 292 to 278 K. Beyond the isochore end point (292 K), low- and high-density liquid becomes indistinguishable. When the pressure is increased from 10 to 600 MPa along the 280-K isotherm, we observe that water inside the 1.25-nm-diameter CNT can undergo low-density liquid to hINT to high-density liquid reentrant first-order transitions. PMID:28373562

Study of two-phase flows in reduced gravity

NASA Astrophysics Data System (ADS)

Roy, Tirthankar

Study of gas-liquid two-phase flows under reduced gravity conditions is extremely important. One of the major applications of gas-liquid two-phase flows under reduced gravity conditions is in the design of active thermal control systems for future space applications. Previous space crafts were characterized by low heat generation within the spacecraft which needed to be redistributed within the craft or rejected to space. This task could easily have been accomplished by pumped single-phase loops or passive systems such as heat pipes and so on. However with increase in heat generation within the space craft as predicted for future missions, pumped boiling two-phase flows are being considered. This is because of higher heat transfer co-efficients associated with boiling heat transfer among other advantages. Two-phase flows under reduced gravity conditions also find important applications in space propulsion as in space nuclear power reactors as well as in many other life support systems of space crafts. Two-fluid model along with Interfacial Area Transport Equation (IATE) is a useful tool available to predict the behavior of gas-liquid two-phase flows under reduced gravity conditions. It should be noted that considerable differences exist between two-phase flows under reduced and normal gravity conditions especially for low inertia flows. This is because due to suppression of the gravity field the gas-liquid two-phase flows take a considerable time to develop under reduced gravity conditions as compared to normal gravity conditions. Hence other common methods of analysis applicable for fully developed gas-liquid two-phase flows under normal gravity conditions, like flow regimes and flow regime transition criteria, will not be applicable to gas-liquid two-phase flows under reduced gravity conditions. However the two-fluid model and the IATE need to be evaluated first against detailed experimental data obtained under reduced gravity conditions. Although lot of studies have been done in the past to understand the global structure of gas-liquid two-phase flows under reduced gravity conditions, using experimental setups aboard drop towers or aircrafts flying parabolic flights, detailed data on local structure of such two-phase flows are extremely rare. Hence experiments were carried out in a 304 mm inner diameter (ID) test facility on earth. Keeping in mind the detailed experimental data base that needs to be generated to evaluate two-fluid model along with IATE, ground based simulations provide the only economic path. Here the reduced gravity condition is simulated using two-liquids of similar densities (water and Therminol 59 RTM in the present case). Only adiabatic two-phase flows were concentrated on at this initial stage. Such a large diameter test section was chosen to study the development of drops to their full extent (it is to be noted that under reduced gravity conditions the stable bubble size in gas-liquid two-phase flows is much larger than that at normal gravity conditions). Twelve flow conditions were chosen around predicted bubbly flow to cap-bubbly flow transition region. Detailed local data was obtained at ten radial locations for each of three axial locations using state-of-the art multi-sensor conductivity probes. The results are presented and discussed. Also one-group as well as two-group, steady state, one-dimensional IATE was evaluated against data obtained here and by other researchers, and the results presented and discussed.

Controllable synthesis of mesoporous carbon nanospheres and Fe-N/carbon nanospheres as efficient oxygen reduction electrocatalysts

NASA Astrophysics Data System (ADS)

Wei, Jing; Liang, Yan; Zhang, Xinyi; Simon, George P.; Zhao, Dongyuan; Zhang, Jin; Jiang, Sanping; Wang, Huanting

2015-03-01

The synthesis of mesoporous carbon nanospheres (MCNs), especially with diameters below 200 nm remains a great challenge due to weak interactions between the carbon precursors and soft templates, as well as the uncontrollable cross-linking rate of carbon precursors. Herein, we demonstrate a simple acid-assisted, hydrothermal synthesis approach to synthesizing such uniform MCNs with well controlled diameters ranging from 20 to 150 nm under highly acidic conditions (2 M HCl). Both the carbon precursor and the template are partly protonated under such conditions and show additional Coulombic interactions with chloride ions (acts as mediators). This kind of enhanced interaction is similar to that of the ``I+X-S+'' mechanism in the synthesis of mesoporous metal oxide, which can effectively retard the cross-linking rate of resol molecules and avoid macroscopic phase separation during the hydrothermal synthesis. Due to their uniform spherical morphology, small diameter, and high surface areas, MCNs can be modified with Fe and N species via impregnation of cheap precursors (ferric nitrate and dicyandiamide), which are further converted into nonprecious electrocatalysts for oxygen reduction reactions. The resulting Fe-N/MCNs exhibit high catalytic activities, long-term stability and improved methanol tolerance under alkaline conditions, which can be potentially used in direct methanol fuel cells and metal-air batteries.The synthesis of mesoporous carbon nanospheres (MCNs), especially with diameters below 200 nm remains a great challenge due to weak interactions between the carbon precursors and soft templates, as well as the uncontrollable cross-linking rate of carbon precursors. Herein, we demonstrate a simple acid-assisted, hydrothermal synthesis approach to synthesizing such uniform MCNs with well controlled diameters ranging from 20 to 150 nm under highly acidic conditions (2 M HCl). Both the carbon precursor and the template are partly protonated under such conditions and show additional Coulombic interactions with chloride ions (acts as mediators). This kind of enhanced interaction is similar to that of the ``I+X-S+'' mechanism in the synthesis of mesoporous metal oxide, which can effectively retard the cross-linking rate of resol molecules and avoid macroscopic phase separation during the hydrothermal synthesis. Due to their uniform spherical morphology, small diameter, and high surface areas, MCNs can be modified with Fe and N species via impregnation of cheap precursors (ferric nitrate and dicyandiamide), which are further converted into nonprecious electrocatalysts for oxygen reduction reactions. The resulting Fe-N/MCNs exhibit high catalytic activities, long-term stability and improved methanol tolerance under alkaline conditions, which can be potentially used in direct methanol fuel cells and metal-air batteries. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00331h

Harbour porpoise distribution can vary at small spatiotemporal scales in energetic habitats

NASA Astrophysics Data System (ADS)

Benjamins, Steven; van Geel, Nienke; Hastie, Gordon; Elliott, Jim; Wilson, Ben

2017-07-01

Marine habitat heterogeneity underpins species distribution and can be generated through interactions between physical and biological drivers at multiple spatiotemporal scales. Passive acoustic monitoring (PAM) is used worldwide to study potential impacts of marine industrial activities on cetaceans, but understanding of animals' site use at small spatiotemporal scales (<1 km, <1 day) remains limited. Small-scale variability in vocalising harbour porpoise (Phocoena phocoena) distribution within two Scottish marine renewable energy development (MRED) sites was investigated by deploying dense arrays of C-POD passive acoustic detectors at a wave energy test site (the European Marine Energy Centre [Billia Croo, Orkney]) and by a minor tidal-stream site (Scarba [Inner Hebrides]). Respective arrays consisted of 7 and 11 moorings containing two C-PODs each and were deployed for up to 55 days. Minimum inter-mooring distances varied between 300-600 m. All C-POD data were analysed at a temporal resolution of whole minutes, with each minute classified as 1 or 0 on the basis of presence/absence of porpoise click trains (Porpoise-Positive Minutes/PPMs). Porpoise detection rates were analysed using Generalised Additive Models (GAMs) with Generalised Estimation Equations (GEEs). Although there were many porpoise detections (wave test site: N=3,432; tidal-stream site: N=17,366), daily detection rates varied significantly within both arrays. Within the wave site array (<1 km diameter), average daily detection rates varied from 4.3 to 14.8 PPMs/day. Within the tidal-stream array (<2 km diameter), average daily detection rates varied from 10.3 to 49.7 PPMs/day. GAM-GEE model results for individual moorings within both arrays indicated linkages between porpoise presence and small-scale heterogeneity among different environmental covariates (e.g., tidal phase, time of day). Porpoise detection rates varied considerably but with coherent patterns between moorings only several hundred metres apart and within hours. These patterns presumably have ecological relevance. These results indicate that, in energetically active and heterogeneous areas, porpoises can display significant spatiotemporal variability in site use at scales of hundreds of metres and hours. Such variability will not be identified when using solitary moored PAM detectors (a common practice for site-based cetacean monitoring), but may be highly relevant for site-based impact assessments of MRED and other coastal developments. PAM arrays encompassing several detectors spread across a site therefore appear to be a more appropriate tool to study site-specific cetacean use of spatiotemporally heterogeneous habitat and assess the potential impacts of coastal and nearshore developments at small scales.

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

Masiero, Joseph R.; Mainzer, A. K.; Bauer, J. M.

We present preliminary diameters and albedos for 13511 Main Belt asteroids (MBAs) that were observed during the 3-Band Cryo phase of the Wide-field Infrared Survey Explorer (WISE; after the outer cryogen tank was exhausted) and as part of the NEOWISE Post-Cryo Survey (after the inner cryogen tank was exhausted). With a reduced or complete loss of sensitivity in the two long wavelength channels of WISE, the uncertainty in our fitted diameters and albedos is increased to {approx}20% for diameter and {approx}40% for albedo. Diameter fits using only the 3.4 and 4.6 {mu}m channels are shown to be dependent on themore » literature optical H absolute magnitudes. These data allow us to increase the number of size estimates for large MBAs which have been identified as members of dynamical families. We present thermal fits for 14 asteroids previously identified as the parents of a dynamical family that were not observed during the fully cryogenic mission.« less

Dynamics of a two-phase flow through a minichannel: Transition from churn to slug flow

NASA Astrophysics Data System (ADS)

Górski, Grzegorz; Litak, Grzegorz; Mosdorf, Romuald; Rysak, Andrzej

2016-04-01

The churn-to-slug flow bifurcations of two-phase (air-water) flow patterns in a 2mm diameter minichannel were investigated. With increasing a water flow rate, we observed the transition of slugs to bubbles of different sizes. The process was recorded by a digital camera. The sequences of light transmission time series were recorded by a laser-phototransistor sensor, and then analyzed using the recurrence plots and recurrence quantification analysis (RQA). Due to volume dependence of bubbles velocities, we observed the formation of periodic modulations in the laser signal.

Ground Based Studies of Gas-Liquid Flows in Microgravity Using Learjet Trajectories

NASA Technical Reports Server (NTRS)

Bousman, W. S.; Dukler, A. E.

1994-01-01

A 1.27 cm diameter two phase gas-liquid flow experiment has been developed with the NASA Lewis Research Center to study two-phase flows in microgravity. The experiment allows for the measurement of void fraction, pressure drop, film thickness and bubble and wave velocities as well as for high speed photography. Three liquids were used to study the effects of liquid viscosity and surface tension, and flow pattern maps are presented for each. The experimental results are used to develop mechanistically based models to predict void fraction, bubble velocity, pressure drop and flow pattern transitions in microgravity.

Preparation of porous hollow silica spheres via a layer-by-layer process and the chromatographic performance

NASA Astrophysics Data System (ADS)

Wei, Xiaobing; Gong, Cairong; Chen, Xujuan; Fan, Guoliang; Xu, Xinhua

2017-03-01

Hollow silica spheres possessing excellent mechanical properties were successfully prepared through a layer-by-layer process using uniform polystyrene (PS) latex fabricated by dispersion polymerization as template. The formation of hollow SiO2 micro-spheres, structures and properties were observed in detail by zeta potential, SEM, TEM, FTIR, TGA and nitrogen sorption porosimetry. The results indicated that the hollow spheres were uniform with particle diameter of 1.6 μm and shell thickness of 150 nm. The surface area was 511 m2/g and the pore diameter was 8.36 nm. A new stationary phase for HPLC was obtained by using C18-derivatized hollow SiO2 micro-spheres as packing materials and the chromatographic properties were evaluated for the separation of some regular small molecules. The packed column showed low column pressure, high values of efficiency (up to about 43 000 plates/m) and appropriate asymmetry factors.

Transmission electron microscopy characterization of macromolecular domain cavities and microstructure of single-crystal calcite tooth plates of the sea urchin Lytechinus variegatus.

PubMed

Robach, J S; Stock, S R; Veis, A

2005-07-01

The calcite plates and prisms in Lytechinus variegatus teeth form a complex biocomposite and employ a myriad of strengthening and toughening strategies. These crystal elements have macromolecule-containing internal cavities that may act to prevent cleavage. Transmission electron microscopy employing a small objective aperture was used to quantify several characteristics of these cavities. Cavity diameters ranged from 10 to 225 nm, the mean cavity diameter was between 50 and 60 nm, and cavities comprised approximately 20% of the volume of the crystal. Some cavities exhibited faceting and trace analysis identified these planes as being predominately of {1014} type. Through focus series of micrographs show the cavities were homogeneously distributed throughout the foil. The electron beam decomposed a substance within cavities and this suggests that these cavities are filled with a hydrated organic phase.

Growth of modern branched columnar stromatolites in Lake Joyce, Antarctica.

PubMed

Mackey, T J; Sumner, D Y; Hawes, I; Jungblut, A D; Andersen, D T

2015-07-01

Modern decimeter-scale columnar stromatolites from Lake Joyce, Antarctica, show a change in branching pattern during a period of lake level rise. Branching patterns correspond to a change in cyanobacterial community composition as preserved in authigenic calcite crystals. The transition in stromatolite morphology is preserved by mineralized layers that contain microfossils and cylindrical molds of cyanobacterial filaments. The molds are composed of two populations with different diameters. Large diameter molds (>2.8 μm) are abundant in calcite forming the oldest stromatolite layers, but are absent from younger layers. In contrast, <2.3 μm diameter molds are common in all stromatolites layers. Loss of large diameter molds corresponds to the transition from smooth-sided stromatolitic columns to branched and irregular columns. Mold diameters are similar to trichome diameters of the four most abundant living cyanobacteria morphotypes in Lake Joyce: Phormidium autumnale morphotypes have trichome diameters >3.5 μm, whereas Leptolyngbya antarctica, L. fragilis, and Pseudanabaena frigida morphotypes have diameters <2.3 μm. P. autumnale morphotypes were only common in mats at <12 m depth. Mats containing abundant P. autumnale morphotypes were smooth, whereas mats with few P. autumnale morphotypes contained small peaks and protruding bundles of filaments, suggesting that the absence of P. autumnale morphotypes allowed small-scale topography to develop on mats. Comparisons of living filaments and mold diameters suggest that P. autumnale morphotypes were present early in stromatolite growth, but disappeared from the community through time. We hypothesize that the mat-smoothing behavior of P. autumnale morphotypes inhibited nucleation of stromatolite branches. When P. autumnale morphotypes were excluded from the community, potentially reflecting a rise in lake level, short-wavelength roughness provided nuclei for stromatolite branches. This growth history provides a conceptual model for initiation of branched stromatolite growth resulting from a change in microbial community composition. © 2015 John Wiley & Sons Ltd.

Thermal-capillary analysis of small-scale floating zones Steady-state calculations

NASA Technical Reports Server (NTRS)

Duranceau, J. L.; Brown, R. A.

1986-01-01

Galerkin finite element analysis of a thermal-capillary model of the floating zone crystal growth process is used to predict the dependence of molten zone shape on operating conditions for the growth of small silicon boules. The model accounts for conduction-dominated heat transport in the melt, feed rod and growing crystal and for radiation between these phases, the ambient and a heater. Surface tension acting on the shape of the melt/gas meniscus counteracts gravity to set the shape of the molten zone. The maximum diameter of the growing crystal is set by the dewetting of the melt from the feed rod when the crystal radius is large. Calculations with small Bond number show the increased zone lengths possible for growth in a microgravity environment. The sensitivity of the method to the shape and intensity of the applied heating distribution is demonstrated. The calculations are compared with experimental observations.

Finite element analysis and performance study of switched reluctance generator

NASA Astrophysics Data System (ADS)

Zhang, Qianhan; Guo, Yingjun; Xu, Qi; Yu, Xiaoying; Guo, Yajie

2017-03-01

Analyses a three-phase 12/8 switched reluctance generator (SRG) which is based on its structure and performance principle. The initial size data were calculated by MathCAD, and the simulation model was set up in the ANSOFT software environment with the maximum efficiency and the maximum output power as the main reference parameters. The outer diameter of the stator and the inner diameter of the rotor were parameterized. The static magnetic field distribution, magnetic flux, magnetic energy, torque, inductance characteristics, back electromotive force and phase current waveform of SRG is obtained by analyzing the static magnetic field and the steady state motion of two-dimensional transient magnetic field in ANSOFT environment. Finally, the experimental data of the prototype are compared with the simulation results, which provide a reliable basis for the design and research of SRG wind turbine system.

Method and apparatus for water jet drilling of rock

DOEpatents

Summers, David A.; Mazurkiewicz, Marian; Bushnell, Dwight J.; Blaine, James

1978-01-01

Rock drilling method and apparatus utilizing high pressure water jets for drilling holes of relatively small diameter at speeds significantly greater than that attainable with existing drilling tools. Greatly increased drilling rates are attained due to jet nozzle geometry and speed of rotation. The jet nozzle design has two orifices, one pointing axially ahead in the direction of travel and the second inclined at an angle of approximately 30.degree. from the axis. The two orifices have diameters in the ratio of approximately 1:2. Liquid jet velocities in excess of 1,000 ft/sec are used, and the nozzle is rotated at speeds up to 1,000 rpm and higher.

Photometric Study Of 28978 Ixion At Small Phase Angle

NASA Astrophysics Data System (ADS)

Rousselot, Philippe; Petit, J.

2010-10-01

Discovered in 2001, the Kuiper Belt Object 28978 Ixion belongs to the dynamical class of Plutinos. Because of its brightness (R magnitude about 19.5) it has been extensively studied, its diameter and albedo being estimated by Spitzer to be about 570 km and 15% (Stansberry et al., 2008). Absorption feature of cristalline water ice has been detected (Merlin et al., 2010) and negative linear polarisation has been measured (Boehnhardt et al., 2004). So far no lightcurve nor phase curve at very small phase angle has been published, the only information being that the lightcurve amplitude was inferior to 0.15 magnitude (Ortiz et al., 2003). We present new photometric observations obtained with the 3.5-m telescope NTT at the European Southern Observatory with broad band filters (B, V, R and I). These observations permit to derive a rotation period of 15.9+/-0.5 hr (if a single-peaked lightcurve is assumed) with a peak to peak amplitude of 0.06+/-0.03 magnitude. The phase curve does not reveal any bright opposition surge even for very small phase angle (α=0.02 deg). When our data are combined with the one of Boehnhardt et al. (up to α=1.34 deg) a linear fit provides a slope of 0.201+/-0.014 mag/deg. References : Boehnhardt H., Bagnulo S., Muinonen K. et al., 2004, A&A 415, L21-L25 Merlin F., Barucci M.A., de Bergh C. et al., 2010, Icarus 208, 945-954 Ortiz J.L., Gutiérrez P.J., Casanova V., Sota A., 2003, A&A 407, 1149-1155 Stansberry J., Grundy W., Brown M. et al., 2008, The Solar System Beyond Neptune, Univ. of Arizona Press, pp161-179

Combustion of solid carbon rods in zero and normal gravity. Ph.D. Thesis - Toledo Univ., Ohio

NASA Technical Reports Server (NTRS)

Spuckler, C. M.

1981-01-01

In order to investigate the mechanism of carbon combustion and to assess the importance of gravitational induced convection on the process, zero and normal gravity experiments were conducted in which spectroscopic carbon rods were resistance ignitied and burned in dry oxygen environments. In the zero-gravity drop tower tests, a blue flame surrounded the rod, showing that a gas phase reaction in which carbon monoxide was oxidized to carbon dioxide was taking place. The ratio of flame diameter to rod diameter was obtained as a function of time. It was found that this ratio was inversely proportional to both the oxygen pressure and the rod diameter. In the normal gravity tests, direct mass spectrometric sampling was used to measure gas phase concentrations. The gas sampling probe was positioned near the circumference of a horizontally mounted 0.615 cm diameter carbon rod, either at the top or at angles of 45 deg to 90 deg from the top, and yielded concentration profiles of CO2, CO, and O2 as a function of distance from the surface. The mechanism controlling the combustion process was found to change from chemical process control at the 90 deg and 45 deg probe positions to mass transfer control at the 0 deg probe position at the top of the rod. Under the experimental conditions used, carbon combustion was characterized by two surface reactions, 2C + O2 yields 2CO and CO2 + C yields 2CO, and a gas phase reaction, 2CO + O2 yields 2CO2.

Low-Power Testing of Losses in Millimeter-Wave Transmission Lines for High-Power Applications

PubMed Central

Han, S. T.; Comfoltey, E. N.; Shapiro, M. A.; Sirigiri, J. R.; Tax, D. S.; Temkin, R. J.; Woskov, P. P.; Rasmussen, D. A.

2008-01-01

We report the measurement of small losses in transmission line (TL) components intended for high-power millimeter-wave applications. Measurements were made using two different low-power techniques: a coherent technique using a vector network analyzer (VNA) and an incoherent technique using a radiometer. The measured loss in a 140 GHz 12.7 mm diameter TL system, consisting of 1.7 m of circular corrugated waveguide and three miter bends, is dominated by the miter bend loss. The measured loss was 0.3±0.1 dB per miter bend using a VNA; and 0.22±0.1 dB per miter bend using a radiometer. Good agreement between the two measurement techniques implies that both are useful for measuring small losses. To verify the methodology, the VNA technique was employed to measure the extremely small transmission loss in a 170 GHz ITER prototype TL system consisting of three lengths of 1 m, 63.5 mm diameter, circular corrugated waveguide and two miter bends. The measured loss of 0.05±0.02 dB per miter bend may be compared with the theoretical loss of 0.027 dB per miter bend. These results suggest that low-power testing of TL losses, utilizing a small, simple TL system and a VNA, is a reliable method for evaluating performance of low-loss millimeter-wave TL components intended for use in high-power applications. PMID:19081774

Generation of net sediment transport by velocity skewness in oscillatory sheet flow

NASA Astrophysics Data System (ADS)

Chen, Xin; Li, Yong; Chen, Genfa; Wang, Fujun; Tang, Xuelin

2018-01-01

This study utilizes a qualitative approach and a two-phase numerical model to investigate net sediment transport caused by velocity skewness beneath oscillatory sheet flow and current. The qualitative approach is derived based on the pseudo-laminar approximation of boundary layer velocity and exponential approximation of concentration. The two-phase model can obtain well the instantaneous erosion depth, sediment flux, boundary layer thickness, and sediment transport rate. It can especially illustrate the difference between positive and negative flow stages caused by velocity skewness, which is considerably important in determining the net boundary layer flow and sediment transport direction. The two-phase model also explains the effect of sediment diameter and phase-lag to sediment transport by comparing the instantaneous-type formulas to better illustrate velocity skewness effect. In previous studies about sheet flow transport in pure velocity-skewed flows, net sediment transport is only attributed to the phase-lag effect. In the present study with the qualitative approach and two-phase model, phase-lag effect is shown important but not sufficient for the net sediment transport beneath pure velocity-skewed flow and current, while the asymmetric wave boundary layer development between positive and negative flow stages also contributes to the sediment transport.

Carbon nanotube (CNT) and nanofibrillated cellulose (NFC) reinforcement effect on thermoplastic polyurethane (TPU) scaffolds fabricated via phase separation using dimethyl sulfoxide (DMSO) as solvent.

PubMed

Mi, Hao-Yang; Jing, Xin; Salick, Max R; Cordie, Travis M; Turng, Lih-Sheng

2016-09-01

Although phase separation is a simple method of preparing tissue engineering scaffolds, it suffers from organic solvent residual in the scaffold. Searching for nontoxic solvents and developing effective solvent removal methods are current challenges in scaffold fabrication. In this study, thermoplastic polyurethane (TPU) scaffolds containing carbon nanotubes (CNTs) or nanofibrillated cellulose fibers (NFCs) were prepared using low toxicity dimethyl sulfoxide (DMSO) as a solvent. The effects of two solvent removal approaches on the final scaffold morphology were studied. The freeze drying method caused large pores, with small pores on the pore walls, which created connections between the pores. Meanwhile, the leaching and freeze drying method led to interconnected fine pores with smaller pore diameters. The nucleation effect of CNTs and the phase separation behavior of NFCs in the TPU solution resulted in significant differences in the microstructures of the resulting scaffolds. The mechanical performance of the nanocomposite scaffolds with different morphologies was investigated. Generally, the scaffolds with a fine pore structure showed higher compressive properties, and both the CNTs and NFCs improved the compressive properties of the scaffolds, with greater enhancement found in TPU/NFC nanocomposite scaffolds. In addition, all scaffolds showed good sustainability under cyclical load bearing, and the biocompatibility of the scaffolds was verified via 3T3 fibroblast cell culture. Copyright © 2016 Elsevier Ltd. All rights reserved.

Carcinoid tumor of the small intestine: MDCT findings with pathologic correlation.

PubMed

Coulier, B; Pringot, J; Gielen, I; Maldague, P; Broze, B; Ramboux, A; Clausse, M

2007-01-01

MDCT currently frequently represents the first choice modality for imaging in acute or subacute abdominal conditions implicating the small bowel. As a consequence, the MDCT features of intestinal carcinoid tumors and of their peculiar metastatic spread have to be known by abdominal radiologists. These features are described and illustrated in the retrospective review of seven proven cases of small intestine carcinoids diagnosed and treated in our institution. The findings are described and correlated with gross anatomy specimens. The primary tumour clearly appeared as a contrast-enhancing intraluminal lesion in all cases except in one case in which the primary lesion remained unlocalized and in another in which the primary tumour finally appeared infracted at gross anatomy. The maximal tumoral enhancement was obtained in 3 patients imaged during the acute arterial phase. The diameter of the primary tumour ranged from 1 to 3 cm and all masses were ileal comprising one lesion in the proximal ileum, two in the medium ileum and three in the distal ileum. 6/7 patients had multiple prominent mesenteric nodal metastases, all also appearing as hypervascularised enhancing masses. In 4/7 patients the nodal metastases represented the major finding being much prominent and larger than the primary tumour. Signs of retractile mesenteritis with soft tissue stranding, retraction and stellate pattern of the mesentery were found around the mesenteric metastases in 5/7 patients and direct incarceration of vessels were found in 3 cases. The analysis of the arterial phase of MDCT study appears primordial to detect the sometimes very small but intensively enhancing primary tumor and to delineate encasement or direct obstruction of mesenteric vessels frequently caused by enhancing nodal metastases which volume often exceeds that of the primary tumor. Secondary retractile mesenteritis, deformation or ischemia of bowel loops, and hypervascular hepatic metastases are typical associated findings.

Short pulse duration shock initiation experiments plus ignition and growth modeling on Composition B

NASA Astrophysics Data System (ADS)

May, Chadd M.; Tarver, Craig M.

2014-05-01

Composition B (63% RDX, 36% TNT, 1% wax) is still a widely used energetic material whose shock initiation characteristics are necessary to understand. It is now possible to shock initiate Composition B and other secondary explosives at diameters well below their characteristic failure diameters for unconfined self-sustaining detonation. This is done using very high velocity, very thin, small diameter flyer plates accelerated by electric or laser power sources. Recently experimental detonation versus failure to detonate threshold flyer velocity curves for Composition B using several KaptonTM flyer thicknesses and diameters were measured. Flyer plates with diameters of 2 mm successfully detonated Composition B, which has a nominal failure diameter of 4.3 mm. The shock pressures required for these initiations are greater than the Chapman-Jouguet (C-J) pressure in self-sustaining Composition B detonation waves. The initiation process is two-dimensional, because both rear and side rarefactions can affect the shocked Composition B reaction rates. The Ignition and Growth reactive flow model for Composition B is extended to yield accurate simulations of this new threshold velocity data for various flyer thicknesses.

Experimental study on interfacial area transport in downward two-phase flow

NASA Astrophysics Data System (ADS)

Wang, Guanyi

In view of the importance of two group interfacial area transport equations and lack of corresponding accurate downward flow database that can reveal two group interfacial area transport, a systematic database for adiabatic, air-water, vertically downward two-phase flow in a round pipe with inner diameter of 25.4 mm was collected to gain an insight of interfacial structure and provide benchmarking data for two-group interfacial area transport models. A four-sensor conductivity probe was used to measure the local two phase flow parameters and data was collected with data sampling frequency much higher than conventional data sampling frequency to ensure the accuracy. Axial development of local flow parameter profiles including void fraction, interfacial area concentration, and Sauter mean diameter were presented. Drastic inter-group transfer of void fraction and interfacial area was observed at bubbly to slug transition flow. And the wall peaked interfacial area concentration profiles were observed in churn-turbulent flow. The importance of local data about these phenomenon on flow structure prediction and interfacial area transport equation benchmark was analyzed. Bedsides, in order to investigate the effect of inlet conditions, all experiments were repeated after installing the flow straightening facility, and the results were briefly analyzed. In order to check the accuracy of current data, the experiment results were cross-checked with rotameter measurement as well as drift-flux model prediction, the averaged error is less than 15%. Current models for two-group interfacial area transport equation were evaluated using these data. The results show that two-group interfacial area transport equations with current models can predict most flow conditions with error less than 20%, except some bubbly to slug transition flow conditions and some churn-turbulent flow conditions. The disagreement between models and experiments could result from underestimate of inter-group void transfer.

Effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks

NASA Astrophysics Data System (ADS)

Sun, Xiaojuan; Perc, Matjaž; Kurths, Jürgen

2017-05-01

In this paper, we study effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks. Our focus is on the impact of two parameters, namely the time delay τ and the probability of partial time delay pdelay, whereby the latter determines the probability with which a connection between two neurons is delayed. Our research reveals that partial time delays significantly affect phase synchronization in this system. In particular, partial time delays can either enhance or decrease phase synchronization and induce synchronization transitions with changes in the mean firing rate of neurons, as well as induce switching between synchronized neurons with period-1 firing to synchronized neurons with period-2 firing. Moreover, in comparison to a neuronal network where all connections are delayed, we show that small partial time delay probabilities have especially different influences on phase synchronization of neuronal networks.

Effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks.

PubMed

Sun, Xiaojuan; Perc, Matjaž; Kurths, Jürgen

2017-05-01

In this paper, we study effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks. Our focus is on the impact of two parameters, namely the time delay τ and the probability of partial time delay p delay , whereby the latter determines the probability with which a connection between two neurons is delayed. Our research reveals that partial time delays significantly affect phase synchronization in this system. In particular, partial time delays can either enhance or decrease phase synchronization and induce synchronization transitions with changes in the mean firing rate of neurons, as well as induce switching between synchronized neurons with period-1 firing to synchronized neurons with period-2 firing. Moreover, in comparison to a neuronal network where all connections are delayed, we show that small partial time delay probabilities have especially different influences on phase synchronization of neuronal networks.

The effect of nozzle diameter, injection pressure and ambient temperature on spray characteristics in diesel engine

NASA Astrophysics Data System (ADS)

Rhaodah Andsaler, Adiba; Khalid, Amir; Sharifhatul Adila Abdullah, Nor; Sapit, Azwan; Jaat, Norrizam

2017-04-01

Mixture formation of the ignition process is a key element in the diesel combustion as it influences the combustion process and exhaust emission. Aim of this study is to elucidate the effects of nozzle diameter, injection pressure and ambient temperature to the formation of spray. This study investigated diesel formation spray using Computational Fluid Dynamics. Multiphase volume of fluid (VOF) behaviour in the chamber are determined by means of transient simulation, Eulerian of two phases is used for implementation of mixing fuel and air. The detail behaviour of spray droplet diameter, spray penetration and spray breakup length was visualised using the ANSYS 16.1. This simulation was done in different nozzle diameter 0.12 mm and 0.2 mm performed at the ambient temperature 500 K and 700 K with different injection pressure 40 MPa, 70 MPa and 140 MPa. Results show that high pressure influence droplet diameter become smaller and the penetration length longer with the high injection pressure apply. Smaller nozzle diameter gives a shorter length of the breakup. It is necessary for nozzle diameter and ambient temperature condition to improve the formation of spray. High injection pressure is most effective in improvement of formation spray under higher ambient temperature and smaller nozzle diameter.

Flow and clog in a silo with oscillating exit

NASA Astrophysics Data System (ADS)

To, Kiwing; Tai, Hsiang-Ting

2017-09-01

When grains flow out of a silo, flow rate W increases with exit size D . If D is too small, an arch may form and the flow may be blocked at the exit. To recover from clogging, the arch has to be destroyed. Here we construct a two-dimensional silo with movable exit and study the effects of exit oscillation (with amplitude A and frequency f ) on flow rate, clogging, and unclogging of grains through the exit. We find that, if exit oscillates, W remains finite even when D (measured in unit of grain diameter) is only slightly larger than one. Surprisingly, while W increases with oscillation strength Γ ≡4 π2A f2 as expected at small D , W decreases with Γ when D ≥5 due to induced random motion of the grains at the exit. When D is small and oscillation speed v ≡2 π A f is slow, temporary clogging events cause the grains to flow intermittently. In this regime, W depends only on v —a feature consistent to a simple arch breaking mechanism, and the phase boundary of intermittent flow in the D -v plane is consistent to either a power law: D ∝v-7 or an exponential form: D ∝e-D /0.55 . Furthermore, the flow time statistic is Poissonian whereas the recovery time statistic follows a power-law distribution.

Interior of Vacuum Tank at the Electric Propulsion Laboratory

NASA Image and Video Library

1961-08-21

Interior of the 20-foot diameter vacuum tank at the NASA Lewis Research Center’s Electric Propulsion Laboratory. Lewis researchers had been studying different electric rocket propulsion methods since the mid-1950s. Harold Kaufman created the first successful ion engine, the electron bombardment ion engine, in the early 1960s. These engines used electric power to create and accelerate small particles of propellant material to high exhaust velocities. Electric engines have a very small thrust, but can operate for long periods of time. The ion engines are often clustered together to provide higher levels of thrust. The Electric Propulsion Laboratory, which began operation in 1961, contained two large vacuum tanks capable of simulating a space environment. The tanks were designed especially for testing ion and plasma thrusters and spacecraft. The larger 25-foot diameter tank included a 10-foot diameter test compartment to test electric thrusters with condensable propellants. The portals along the chamber floor lead to the massive exhauster equipment that pumped out the air to simulate the low pressures found in space.

Factors affecting the transformation of a pyritic tailing: scaled-up column tests.

PubMed

García, C; Ballester, A; González, F; Blázquez, M L

2005-02-14

Two different methods for predicting the quality of the water draining from a pyritic tailing are compared; for this, a static test (ABA test) and a kinetic test in large columns were chosen. The different results obtained in the two experimental set-ups show the necessity of being careful in selecting both the adequate predictive method and the conclusions and extrapolations derived from them. The tailing chosen for the weathering tests (previously tested in shake flasks and in small weathering columns) was a pyritic residue produced in a flotation plant of complex polymetallic sulphides (Huelva, Spain). The ABA test was a modification of the conventional ABA test reported in bibliography. The modification consisted in the soft conditions employed in the digestion phase. For column tests, two identical methacrylate columns (150 cm high and 15 cm diameter) were used to study the chemical and microbiological processes controlling the leaching of pyrite. The results obtained in the two tests were very different. The static test predicted a strong potential acidity for the tailing. On the contrary, pH value in the effluents draining from the columns reached values of only 5 units, being the concentration of metals (<600 mg/L) and sulphate ions (<17,000 mg/L) very small and far from the values of a typical acid mine drainage. In consequence, the static test may oversize the potential acidity of the tailing; whereas large columns may be saturated in water, displacing the oxygen and inhibiting the microbial activity necessary to catalyse mineral oxidation.

Optical phased array configuration for an extremely large telescope.

PubMed

Meinel, Aden Baker; Meinel, Marjorie Pettit

2004-01-20

Extremely large telescopes are currently under consideration by several groups in several countries. Extrapolation of current technology up to 30 m indicates a cost of over dollars 1 billion. Innovative concepts are being explored to find significant cost reductions. We explore the concept of an Optical Phased Array (OPA) telescope. Each element of the OPA is a separate Cassegrain telescope. Collimated beams from the array are sent via an associated set of delay lines to a central beam combiner. This array of small telescope elements offers the possibility of starting with a low-cost array of a few rings of elements, adding structure and additional Cass elements until the desired diameter telescope is attained. We address the salient features of such an extremely large telescope and cost elements relative to more conventional options.

Observations of electron phase-space holes driven during magnetic reconnection in a laboratory plasma

NASA Astrophysics Data System (ADS)

Fox, W.; Porkolab, M.; Egedal, J.; Katz, N.; Le, A.

2012-03-01

This work presents detailed experimental observations of electron phase-space holes driven during magnetic reconnection events on the Versatile Toroidal Facility. The holes are observed to travel on the order of or faster than the electron thermal speed, and are of large size scale, with diameter of order 60 Debye lengths. In addition, they have 3D spheroidal structure with approximately unity aspect ratio. We estimate the direct anomalous resistivity due to ion interaction with the holes and find it to be too small to affect the reconnection rate; however, the holes may play a role in reining in a tail of accelerated electrons and they indicate the presence of other processes in the reconnection layer, such as electron energization and electron beam formation.

Characterization of wood strands from young, small-diameter Douglas-fir and western hemlock trees

Treesearch

Vikram Yadama; Eini C. Lowell; Christopher E. Langum

2012-01-01

Tensile properties of strands processed from small-diameter Douglas-fir and western hemlock trees grown on the Washington coast were analyzed and effects of location within the tree on properties was examined. Reduction factors for strand properties relative to small, clear solid wood specimen properties were determined by correlating strand properties to previously...

Monodisperse hydrogel microspheres by forced droplet formation in aqueous two-phase systems.

PubMed

Ziemecka, Iwona; van Steijn, Volkert; Koper, Ger J M; Rosso, Michel; Brizard, Aurelie M; van Esch, Jan H; Kreutzer, Michiel T

2011-02-21

This paper presents a method to form micron-sized droplets in an aqueous two-phase system (ATPS) and to subsequently polymerize the droplets to produce hydrogel beads. Owing to the low interfacial tension in ATPS, droplets do not easily form spontaneously. We enforce the formation of drops by perturbing an otherwise stable jet that forms at the junction where the two aqueous streams meet. This is done by actuating a piezo-electric bending disc integrated in our device. The influence of forcing amplitude and frequency on jet breakup is described and related to the size of monodisperse droplets with a diameter in the range between 30 and 60 μm. Rapid on-chip polymerization of derivatized dextran inside the droplets created monodisperse hydrogel particles. This work shows how droplet-based microfluidics can be used in all-aqueous, surfactant-free, organic-solvent-free biocompatible two-phase environment.

Comparison of UNL laser imaging and sizing system and a phase/Doppler system for analyzing sprays from a NASA nozzle

NASA Technical Reports Server (NTRS)

Alexander, Dennis R.

1988-01-01

Aerosol spray characterization was done using a P/DPA and a laser imaging/video processing system on a NASA MOD-1 air-assist nozzle being evaluated for use in aircraft icing research. Benchmark tests were performed on monodispersed particles and on the NASA MOD-1 nozzle under identical laboratory operating conditions. The laser imaging/video processing system and the P/DPA showed agreement on calibration tests in monodispersed aerosol sprays of + or - 2.6 microns with a standard deviation of + or - 2.6 microns. Tests were performed on the NASA MOD-1 nozzle on the centerline and radially at one-half inch increments to the outer edge of the spray plume at a distance two feet (0.61 m) downstream from the exit of the nozzle. Comparative results at two operating conditions of the nozzle are presented for the two instruments. For the first case, the deviation in arithmetic mean diameters determined by the two instruments was in a range of 0.1 to 2.8 microns, and the deviation in Sauter mean diameters varied from 0 to 2.2 microns. Operating conditions in the second case were more severe which resulted in the arithmetic mean diameter deviating from 1.4 to 7.1 microns and the deviation in the Sauter mean diameters ranging from 0.4 to 6.7 microns.

Simulations of Collisional Disruption at the Catastrophic Impact Energy Threshold: Effect of the Target's Internal Structure and Diameter

NASA Astrophysics Data System (ADS)

Michel, P.; Benz, W.; Richardson, D. C.

2005-08-01

Recent simulations of asteroid break-ups, including both the fragmentation of the parent body and the gravitational interactions of the fragments, have allowed to reproduced successfully the main properties of asteroid families formed in different regimes of impact energy. Here, using the same kind of simulations, we concentrate on a single regime of impact energy, the so-called catastrophic threshold usually designated by Qcrit, which results in the escape of half of the target's mass. Considering a wide range of diameter values and two kinds of internal structures of the parent body, monolithic and pre-shattered, we analyse their potential influences on the value of Qcrit and on the collisional outcome limited here to the fragment size and ejection speed distributions, which are the main outcome properties used by collisional models to study the evolutions of the different populations of small bodies. For all the considered diameters and the two internal structures of the parent body, we confirm that the process of gravitational reaccumulation is at the origin of the largest remnant's mass. We then find that, for a given diameter of the parent body, the impact energy corresponding to the catastrophic disruption threshold is highly dependent on the internal structure of the parent body. In particular, a pre-shattered parent body containing only damaged zones but no macroscopic voids is easier to disrupt than a monolithic parent body. Other kinds of internal properties that can also characterize small bodies in real populations will be investigated in a future work.

Characteristics of small young lunar impact craters focusing on current production and degradation on the Moon

NASA Astrophysics Data System (ADS)

Kereszturi, Akos; Steinmann, Vilmos

2017-11-01

Analysing the size-frequency distribution of very small lunar craters (sized below 100 m including ones below 10 m) using LROC images, spatial density and related age estimations were calculated for mare and terra terrains. Altogether 1.55 km2 area was surveyed composed of 0.1-0.2 km2 units, counting 2784 craters. The maximal areal density was present at the 4-8 m diameter range at every analysed terrain suggesting the bombardment is areally relatively homogeneous. Analysing the similarities and differences between various areas, the mare terrains look about two times older than the terra terrains using <100 m diameter craters. The calculated ages ranged between 13 and 20 Ma for mare, 4-6 Ma for terra terrains. Substantial fluctuation (min: 936 craters/km2, max: 2495 craters/km2) was observed without obvious source of nearby secondaries or fresh ejecta blanket produced fresh crater. Randomness analysis and visual inspection also suggested no secondary craters or ejecta blanket from fresh impact could contribute substantially in the observed heterogeneity of the areal distribution of small craters - thus distant secondaries or even other, poorly known resurfacing processes should be considered in the future. The difference between the terra/mare ages might come only partly from the easier identification of small craters on smooth mare terrains, as the differences were observed for larger (30-60 m diameter) craters too. Difference in the target hardness could more contribute in this effect. It was possible to separate two groups of small craters based on their appearance: a rimmed thus less eroded, and a rimless thus more eroded one. As the separate usage of different morphology groups of craters for age estimation at the same area is not justifiable, this was used only for comparison. The SFD curves of these two groups showed characteristic differences: the steepness of the fresh craters' SFD curves are similar to each other and were larger than the isochrones. The eroded craters' SFD curves also resemble to each other, which are less steep than the isochrones. These observations confirm the expectation that as the time passes by, rims are erased and depressions became shallower, presenting such observations for the first time in this small crater size range.

Investigation of transient chill down phenomena in tubes using liquid nitrogen

NASA Astrophysics Data System (ADS)

Shukla, A. K.; Sridharan, Arunkumar; Atrey, M. D.

2017-12-01

Chill down of cryogenic transfer lines is a crucial part of cryogenic propulsion as chill down ensures transfer of single phase fluid to the storage tanks of cryogenic engines. It also ensures single phase liquid flow at the start of the engine. Chill down time depends on several parameters such as length of the pipe, pipe diameter, orientation, mass flux etc. To understand the effect of these parameters, experiments are carried out in a set up designed and fabricated at Indian Institute of Technology Bombay using tubes of two different diameters. Experiments are conducted at different inlet pressures and mass flow rate values to understand their effect. Two different pipe sizes are taken to study the effect of variation in diameter on chill down time and quantity of cryogen required. Different orientations are taken to understand their effect on the chill down time, heat transfer coefficient and critical heat flux for the same inlet pressure and mass flux. Pipe inner wall temperature, heat transfer coefficient for different boiling regimes and critical heat flux are calculated based on measured outer surface temperature history for each case. A one dimensional energy conservation equation is solved for transient chill down process considering constant mass flux and inlet pressure to predict the chill down time. Temperature variation during chill down obtained from the numerical simulations are compared with the measured temperature history.

Diagnostic capability of gadoxetate disodium-enhanced liver MRI for diagnosis of hepatocellular carcinoma: comparison with multi-detector CT.

PubMed

Toyota, Naoyuki; Nakamura, Yuko; Hieda, Masashi; Akiyama, Naoko; Terada, Hiroaki; Matsuura, Noriaki; Nishiki, Masayo; Kono, Hirotaka; Kohno, Hiroshi; Irei, Toshimitsu; Yoshikawa, Yukinobu; Kuraoka, Kazuya; Taniyama, Kiyomi; Awai, Kazuo

2013-09-01

The purpose of this study was to evaluate the diagnostic capability of gadoxetate disodium (Gd-EOB)-MRI for the detection of hepatocellular carcinoma (HCC) compared with multidetector CT (MDCT). Fifty patients with 57 surgically proven HCCs who underwent Gd-EOB-MRI and MDCT from March 2008 to June 2011 were evaluated. Two observers evaluated MR and CT on a lesion-by-lesion basis. We analyzed sensitivity by grading on a 5-point scale, the degree of arterial enhancement and the differences in histological grades in the diffusion-weighted images (DWI). The results showed that the sensitivity of Gd-EOB-MRI was higher than that of MDCT especially for HCCs that were 1 cm in diameter or smaller. The hepatobiliary phase was useful for the detecting of small HCC. We had few cases in which it was difficult to judge HCC in the arterial enhancement between MRI and MDCT. In the diffusion-weighted image, well differentiated HCC tended to show a low signal intensity, and poorly differentiated HCC tended to show a high signal intensity. In moderately differentiated HCC's, the mean diameter of the high signal intensity group was larger than that of the low signal intensity group (24.5 mm vs. 15.8 mm). In conclusion, Gd-EOB-MRI tended to show higher sensitivity compared to MDCT in the detection of HCC.

Seismic Shaking Removal of Craters 0.2-0.5 km in Diameter on Asteroid 433 Eros

NASA Technical Reports Server (NTRS)

Thomas, P. C.; Robinson, M. S.

2005-01-01

Impact cratering acts in a variety of ways to create a surprising range of scenery on small satellites and asteroids. The visible crater population is a self-modifying characteristic of these airless objects, and determining the various ways younger craters can add or subtract from the population is an important aspect of small body "geology." Asteroid 433 Eros, the most closely studied of any small body, has two aspects of its crater population that have attracted attention: a fall-off of crater densities below approx.100 m diameter relative to an expected equilibrium population [1] and regions of substantially lower large crater densities [2, 3, 4]. In this work we examine the global variation of the density of craters on Eros larger than 0.177 km, a size range above that involved in small crater depletion hypotheses [1, 5]. We counted all craters on Eros to a size range somewhat below 0.177 km diameter (and different from data used in [3]). The primary metric for this study is the number of craters between 0.177 and 1.0 km within a set radius of each grid point on the 2deg x 2deg shape model of Eros. This number can be expressed as an R-value [6], provided that it is remembered that the large bin size makes individual R values slightly different from those obtained in the usual root-2 bins.

SPECIATION OF GAS-PHASE AND FINE PARTICLE EMISSIONS FROM BURNING OF FOLIAR FUELS

EPA Science Inventory

Particle size distributions (10-1000 nm aerodynamic diameter), physical and chemical properties of fine particle matter (PM2.5) with aerodynamic diameter <2.5 micrometers, and gas-phase emissions from controlled open burning of assorted taxa were measured. Chemical speciation of ...

Sound controlled rotation of a cluster of small particles on an ultrasonically vibrating metal strip

NASA Astrophysics Data System (ADS)

Zhang, Xueyi; Zheng, Yun; Hu, Junhui

2008-01-01

We show that a vibrating metal strip, mechanically driven by an ultrasonic transducer, can rotate a cluster of small particles around a fixed point, and the diameter of the cluster of small particles can reach a stable value (steady diameter) for a given driving condition. The rotation is very stable when the vibration of the metal strip is appropriate. The revolution speed, its direction, and steady diameter of the particle cluster can be controlled by the operating frequency of the ultrasonic transducer. For shrimp eggs, a revolution speed up to 360rpm can be obtained.

Additional nuclear criticality safety calculations for small-diameter containers

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

Hone, M.J.

This report documents additional criticality safety analysis calculations for small diameter containers, which were originally documented in Reference 1. The results in Reference 1 indicated that some of the small diameter containers did not meet the criteria established for criticality safety at the Portsmouth facility (K{sub eff} +2{sigma}<.95) when modeled under various contingency assumptions of reflection and moderation. The calculations performed in this report reexamine those cases which did not meet the criticality safety criteria. In some cases, unnecessary conservatism is removed, and in other cases mass or assay limits are established for use with the respective containers.

Role of aerosols in enhancing SVOC flux between air and indoor surfaces and its influence on exposure

NASA Astrophysics Data System (ADS)

Liu, Cong; Morrison, Glenn C.; Zhang, Yinping

2012-08-01

Indoor surfaces play an important role in the transport of, and exposure to, semi-volatile organic compounds (SVOCs) in buildings. In this study, we develop a model that accounts for SVOC transport mediated by particles and find that, due to large gas-particle partition coefficients along with large differences in Brownian and gas diffusivities, SVOC transport across concentration boundary layers is significantly enhanced in the presence of particles. Two important dimensionless parameters, Bim,g and Bim,g/Bim,p, were identified: Bim,g is the ratio of 1) the characteristic time for the SVOC to transport across the concentration boundary layer to 2) the characteristic time for boundary layer to either be "swept" of SVOCs by particles or "saturated" by release of SVOCs from particles. This parameter can be regarded as a dimensionless mass transfer coefficient. Bim,g/Bim,p characterizes the SVOC mass associated with particles, relative to SVOCs in the gas-phase. Analysis on monodisperse particles shows that flux can be enhanced by as much as a factor of 5 over transport in the absence of particles, for a large particle/gas partition coefficient (log Kpart = 13), small particles (dp ˜ 0.1 μm) and a small free stream velocity (U∞ = 0.01 m s-1). As particle diameter decreases, flux enhancement tends to increase. However, as particles become very small (e.g., dp < 0.05 μm), flux enhancement for SVOCs with log Kpart = 13 decreases slightly. Particles larger than 2 μm do not significantly influence the flux. An exponential correlation is found to fit the results for polydisperse particles associated with typical indoor environments, cooking and smoking. Two illustrative examples are used to show that, 1) the timescale for di(2-ethylhexyl) phthalate (DEHP) to approach equilibrium between the gas and a surface is shortened from 3.0 years to 0.45 years; and 2) in the presence of particles, the gas-phase DEHP concentration and emission rate are predicted to be as much as 4 times higher by our model than that by prior model estimates. Particle mediated gas-phase transport of SVOCs can result an increase in occupant exposure by a factor of 4-10.

A Mechanistic Study of Nucleate Boiling Heat Transfer Under Microgravity Conditions

NASA Technical Reports Server (NTRS)

Dhir, V. K.; Hasan, M. M.

2000-01-01

Experimental studies of growth and detachment processes of a single bubble and multiple bubbles formed on a heated surface have been conducted in the parabola flights of KC-135 aircraft. Distilled water and PF5060 were used as the test liquids. A micro-fabricated test surface was designed and built. Artificial cavities of diameters 10 microns, 7 microns and 4 microns were made on a thin polished Silicon wafer that was electrically heated by a number of small heating elements on the back side in order to control the surface superheat. Bubble growth period, bubble size and shape from nucleation to departure were measured under subcooled and saturation conditions. Significantly larger bubble departure diameters and bubble growth periods than those at earth normal gravity were observed. Bubble departure diameters as large as 20 mm for water and 6 mm for PF5060 were observed as opposed to about 3 mm for water and less than 1 mm for PF5060 at earth normal gravity respectively. It is found that the bubble departure diameter can be approximately related to the gravity level through the relation D(sub d) proportional 1/g(exp 1/2). For water,the effect of wall superheat and liquid subcooling on bubble departure diameter is found to be small.The growth periods are found to be very sensitive to liquid subcooling at a given wall superheat. However,the preliminary results of single bubble dynamics using PF5060 showed that the departure diameter increases when wall superheat is elevated at the same gravity and subcooling. Growth period of single bubbles in water has been found to vary as t(sub g) proportional g(exp -.93). For water, when the magnitude of horizontal gravitational components was comparable to that of gravity normal to the surface, single bubbles slid along the heater surface and departed with smaller diameter at the same gravity level in the direction normal to the surface. For PF5060, even a very small horizontal gravitational component caused the sliding of bubble along the surface. The numerical simulation has been carried out by solving under the condition of axisymmetry, the mass, momentum, and energy equations for the vapor and the liquid phases. In the model the contribution of micro-layer has been included and instantaneous shape of the evolving vapor-liquid interface is determined from the analysis. Consistent with the experimental results, it is found that effect of reduced gravity is to stretch the growth period and bubble diameter It is found that effect of reduced gravity is to stretch the growth period and bubble diameter at departure. The numerical simulations are in good agreement with the experimental data for both the departure diameters and the growth periods. In the study on dynamics of multiple bubbles, horizontal merger of 2,3 4,and 5 bubbles was observed. It is found that after merger of 2 and 3 bubbles the equivalent diameter of the detached bubble is smaller than that of a single bubble departing at the same gravity level. During and after bubble merger, liquid still fills the space between the vapor stems so as to form mushroom type bubbles. The experimental and numerical studies conducted so far have brought us a step closer to prediction of nucleate boiling heat fluxes under low gravity conditions. Preparations for a space flight are continuing.

Boring apparatus capable of boring straight holes

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

Peterson, C.R.

The invention relates to a rock boring assembly for producing a straight hole for use in a drill string above a pilot boring bit of predetermined diameter smaller than the desired final hole size. The boring assembly comprises a small conical boring bit and a larger conical boring, the conical boring bits mounted on lower and upper ends of an enlongated spacer, respectively, and the major effective cutting diameters of each of the conical boring bits being at least 10% greater than the minor effective cutting diameter of the respective bit. The spacer has a cross-section resistant bending and spacesmore » the conical boring bits apart a distance at least 5 times the major cutting diameter of the small conical boring bit, thereby spacing the pivot points provided by the two conical boring bits to limit bodily angular deflection of the assembly and providing a substantial moment arm to resist lateral forces applied to the assembly by the pilot bit and drill string. The spacing between the conical bits is less than about 20 times the major cutting diameter of the lower conical boring bit to enable the spacer to act as a bend-resistant beam to resist angular deflection of the axis of either of the conical boring bits relative to the other when it receives uneven lateral force due to non-uniformity of cutting conditions about the circumference of the bit. Advantageously the boring bits also are self-advancing and feature skewed rollers. 7 claims.« less

Unexpectedly acidic nanoparticles formed in dimethylamine-ammonia-sulfuric-acid nucleation experiments at CLOUD

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

Lawler, Michael J.; Winkler, Paul M.; Kim, Jaeseok

New particle formation driven by acid–base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethylaminium ratios were higher than the gas-phase ammonia-to-DMA ratios, suggesting preferential uptake of ammonia over DMA for the collected 10–30 nm VMD particles. This behavior is not consistent with present nanoparticle physicochemical models,more » which predict a higher dimethylaminium fraction when NH 3 and DMA are present at similar gas-phase concentrations. Despite the presence in the gas phase of at least 100 times higher base concentrations than sulfuric acid, the recently formed particles always had measured base : acid ratios lower than 1 : 1. The lowest base fractions were found in particles below 15 nm VMD, with a strong size-dependent composition gradient. The reasons for the very acidic composition remain uncertain, but a plausible explanation is that the particles did not reach thermodynamic equilibrium with respect to the bases due to rapid heterogeneous conversion of SO 2 to sulfate. Furthermore, these results indicate that sulfuric acid does not require stabilization by ammonium or dimethylaminium as acid–base pairs in particles as small as 10 nm.« less

Unexpectedly acidic nanoparticles formed in dimethylamine-ammonia-sulfuric-acid nucleation experiments at CLOUD

DOE PAGES

Lawler, Michael J.; Winkler, Paul M.; Kim, Jaeseok; ...

2016-11-03

New particle formation driven by acid–base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethylaminium ratios were higher than the gas-phase ammonia-to-DMA ratios, suggesting preferential uptake of ammonia over DMA for the collected 10–30 nm VMD particles. This behavior is not consistent with present nanoparticle physicochemical models,more » which predict a higher dimethylaminium fraction when NH 3 and DMA are present at similar gas-phase concentrations. Despite the presence in the gas phase of at least 100 times higher base concentrations than sulfuric acid, the recently formed particles always had measured base : acid ratios lower than 1 : 1. The lowest base fractions were found in particles below 15 nm VMD, with a strong size-dependent composition gradient. The reasons for the very acidic composition remain uncertain, but a plausible explanation is that the particles did not reach thermodynamic equilibrium with respect to the bases due to rapid heterogeneous conversion of SO 2 to sulfate. Furthermore, these results indicate that sulfuric acid does not require stabilization by ammonium or dimethylaminium as acid–base pairs in particles as small as 10 nm.« less

Heat transfer to small horizontal cylinders immersed in a fluidized bed

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

Friedman, J.; Koundakjian, P.; Naylor, D.

2006-10-15

Heat transfer to horizontal cylinders immersed in fluidized beds has been extensively studied, but mainly in the context of heat transfer to boiler tubes in coal-fired beds. As a result, most correlations in the literature have been derived for cylinders of 25-50 mm diameter in vigorously fluidizing beds. In recent years, fluidized bed heat treating furnaces fired by natural gas have become increasingly popular, particularly in the steel wire manufacturing industry. These fluidized beds typically operate at relatively low fluidizing rates and with small diameter wires (1-6 mm). Nusselt number correlations developed based on boiler tube studies do not extrapolatemore » down to these small size ranges and low fluidizing rates. In order to obtain reliable Nusselt number data for these size ranges, an experimental investigation has been undertaken using two heat treating fluidized beds; one a pilot-scale industrial unit and the other a lab-scale (300 mm diameter) unit. Heat transfer measurements were obtained using resistively heated cylindrical samples ranging from 1.3 to 9.5 mm in diameter at fluidizing rates ranging from approximately 0.5 x G{sub mf} (packed bed condition) to over 10 x G{sub mf} using aluminum oxide sand particles ranging from d{sub p}=145-330 {mu}m (50-90 grit). It has been found that for all cylinder sizes tested, the Nusselt number reaches a maximum near 2 x G{sub mf}, then remains relatively steady ({+-}5-10%) to the maximum fluidizing rate tested, typically 8-12xG{sub mf}. A correlation for maximum Nusselt number is developed.« less

PHYSICAL CHARACTERIZATION OF ∼2 m DIAMETER NEAR-EARTH ASTEROID 2015 TC25: A POSSIBLE BOULDER FROM E-TYPE ASTEROID (44) NYSA

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

Reddy, Vishnu; Sanchez, Juan A.; Bottke, William F.

Small near-Earth asteroids (NEAs) (<20 m) are interesting, because they are progenitors for meteorites in our terrestrial collection. The physical characteristics of these small NEAs are crucial to our understanding of the effectiveness of our atmosphere in filtering low-strength impactors. In the past, the characterization of small NEAs has been a challenge, because of the difficulty in detecting them prior to close Earth flyby. In this study, we physically characterized the 2 m diameter NEA 2015 TC25 using ground-based optical, near-infrared and radar assets during a close flyby of the Earth (distance 128,000 km) in 2015 October 12. Our observationsmore » suggest that its surface composition is similar to aubrites, a rare class of high-albedo differentiated meteorites. Aubrites make up only 0.14% of all known meteorites in our terrestrial meteorite collection. 2015 TC25 is also a very fast rotator with a period of 133 ± 6 s. We combined the spectral and dynamical properties of 2015 TC25 and found the best candidate source body in the inner main belt to be the 70 km diameter E-type asteroid (44) Nysa. We attribute the difference in spectral slope between the two objects to the lack of regolith on the surface of 2015 TC25. Using the albedo of E-type asteroids (50%–60%) we refine the diameter of 2015 TC25 to 2 m, making it one of the smallest NEAs ever to be characterized.« less

Mechanical properties of PP/PA blends in addition with PP-g-MAH with different PP molecular weight and MAH content

NASA Astrophysics Data System (ADS)

Tokumitsu, Katuhisa; Nakajima, Yuki; Aoki, Kenji

2016-03-01

The mechanical properties and morphological changes of PP/PA6/PP-g-MAH blends were investigated. In particular, various kinds of PP-g-MAH, which have a series of different Mw of PP and MAH content, were investigated. From the tensile test results of PP/PA6 blends, although the elongation at break and yield stress can be improved by adding PP-g-MAH, modulus slightly decreased. In particular, elongation at break of PP/PA in addition with PP-g-MAH increased twentyfold from 27.0% (without PP-g-MAH) to 570%. On the basis of Charpy impact test results, the impact strength can also be improved by adding PP-g-MAH. From SEM observation, it was found that the diameter of the dispersed PA6 phase in PP matrix was getting much smaller with PP-g-MAH content. From the TEM observation, the boundary of the PA phase in PP/PA blends without PP-g-MAH compatibilizer can be observed clearly, but it becomes hard to see the boundary part of the PA phase in PP/PA blend with compatibilizer. Furthermore, when comparing the inside of the PA phase, small amount of PP phase can be observed in the PA phase of PP/PA blend with compatibilizer. Here, we defined a parameter, Comprehensive Mechanical Property Factor (CMPF), which can be calculated by multiple each mechanical property (elongation at break, yield stress, modulus and impact strength) against each maximum value, and it was found that CMPF has a good correlation with the diameter of PA6 phase. In conclusion, an optimum mechanical property of PP/PA6 can be obtained by using PP-g-MAH with Mw around 35,000 ˜ 50,000 g mol-1 and MAH content around 2.0 ˜ 3.5 %.

Tailoring of Microstructure and Properties of Titanium Parts with Local Rapid Heat Treatment

DTIC Science & Technology

2010-07-19

an approximate approach. Specifically, the temperature at the surface was measured using a two-color pyrometer (IMPAC IGA100) having a 0.2 μs...with pyrometer are shown in Fig. 34. It is necessary to underline, that due to very small diameter of spot measured by pyrometer every temperature...special surface vibro- acoustic treatment (of shot peening type) [19]. So, application of LRHT, from one hand – forming small-grained beta-transformed

Combustion of a Polymer (PMMA) Sphere in Microgravity

NASA Technical Reports Server (NTRS)

Yang, Jiann C.; Hamins, Anthony; Donnelly, Michelle K.

1999-01-01

A series of low gravity, aircraft-based, experiments was conducted to investigate the combustion of supported thermoplastic polymer spheres under varying ambient conditions. The three types of thermoplastic investigated were polymethylmethacrylate (PMMA), polypropylene (PP). and polystyrene (PS). Spheres with diameters ranging from 2 mm to 6.35 mm were tested. The total initial pressure varied from 0.05 MPa to 0. 15 MPa whereas the ambient oxygen concentration varied from 19 % to 30 % (by volume). The ignition system consisted of a pair of retractable energized coils. Two CCD cameras recorded the burning histories of the spheres. The video sequences revealed a number of dynamic events including bubbling and sputtering, as well as soot shell formation and break-up during combustion of the spheres at reduced gravity. The ejection of combusting material from the burning spheres represents a fire hazard that must be considered at reduced gravity. The ejection process was found to be sensitive to polymer type. All average burning rates were measured to increase with initial sphere diameter and oxygen concentration, whereas the initial pressure had little effect. The three thermoplastic types exhibited different burning characteristics. For the same initial conditions, the burning rate of PP was slower than PMMA, whereas the burning rate of PS was comparable to PMMA. The transient diameter of the burning thermoplastic exhibited two distinct periods: an initial period (enduring approximately half of the total burn duration) when the diameter remained approximately constant, and a final period when the square of the diameter linearly decreased with time. A simple homogeneous two-phase model was developed to understand the changing diameter of the burning sphere. Its value is based on a competition between diameter reduction due to mass loss from burning and sputtering, and diameter expansion due to the processes of swelling (density decrease with heating) and bubble growth. The model relies on empirical parameters for input, such as the burning rate and the duration of the initial and final burning periods.

Clinical evaluation of whole-body oncologic PET with time-of-flight and point-spread function for the hybrid PET/MR system.

PubMed

Shang, Kun; Cui, Bixiao; Ma, Jie; Shuai, Dongmei; Liang, Zhigang; Jansen, Floris; Zhou, Yun; Lu, Jie; Zhao, Guoguang

2017-08-01

Hybrid positron emission tomography/magnetic resonance (PET/MR) imaging is a new multimodality imaging technology that can provide structural and functional information simultaneously. The aim of this study was to investigate the effects of the time-of-flight (TOF) and point-spread function (PSF) on small lesions observed in PET/MR images from clinical patient image sets. This study evaluated 54 small lesions in 14 patients who had undergone 18 F-fluorodeoxyglucose (FDG) PET/MR. Lesions up to 30mm in diameter were included. The PET data were reconstructed with a baseline ordered-subsets expectation-maximization (OSEM) algorithm, OSEM+PSF, OSEM+TOF and OSEM+TOF+PSF. PET image quality and small lesions were visually evaluated and scored by a 3-point scale. A quantitative analysis was then performed using the mean and maximum standardized uptake value (SUV) of the small lesions (SUV mean and SUV max ). The lesions were divided into two groups according to the long-axis diameter and the location respectively and evaluated with each reconstruction algorithm. We also evaluated the background signal by analyzing the SUV liver . OSEM+TOF+PSF provided the highest value and OSEM+TOF or PSF showed a higher value than OSEM for the visual assessment and quantitative analysis. The combination of TOF and PSF increased the SUV mean by 26.6% and the SUV max by 30.0%. The SUV liver was not influenced by PSF or TOF. For the OSEM+TOF+PSF model, the change in SUV mean and SUV max for lesions <10mm in diameter was 31.9% and 35.8%, and 24.5% and 27.6% for lesions 10-30mm in diameter, respectively. The abdominal lesions obtained the higher SUV than those of chest on the images with TOF and/or PSF. Application of TOF and PSF significantly increased the SUV of small lesions in hybrid PET/MR images, potentially improving small lesion detectability. Copyright © 2017 Elsevier B.V. All rights reserved.

Experimental and numerical simulation of three-dimensional gravity currents on smooth and rough bottom

NASA Astrophysics Data System (ADS)

La Rocca, Michele; Adduce, Claudia; Sciortino, Giampiero; Pinzon, Allen Bateman

2008-10-01

The dynamics of a three-dimensional gravity current is investigated by both laboratory experiments and numerical simulations. The experiments take place in a rectangular tank, which is divided into two square reservoirs with a wall containing a sliding gate of width b. The two reservoirs are filled to the same height H, one with salt water and the other with fresh water. The gravity current starts its evolution as soon as the sliding gate is manually opened. Experiments are conducted with either smooth or rough surface on the bottom of the tank. The bottom roughness is created by gluing sediment material of different diameters to the surface. Five diameter values for the surface roughness and two salinity conditions for the fluid are investigated. The mathematical model is based on shallow-water theory together with the single-layer approximation, so that the model is strictly hyperbolic and can be put into conservative form. Consequently, a finite-volume-based numerical algorithm can be applied. The Godunov formulation is used together with Roe's approximate Riemann solver. Comparisons between the numerical and experimental results show satisfactory agreement. The behavior of the gravity current is quite unusual and cannot be interpreted using the usual model framework adopted for two-dimensional and axisymmetric gravity currents. Two main phases are apparent in the gravity current evolution; during the first phase the front velocity increases, and during the second phase the front velocity decreases and the dimensionless results, relative to the different densities, collapse onto the same curve. A systematic discrepancy is seen between the numerical and experimental results, mainly during the first phase of the gravity current evolution. This discrepancy is attributed to the limits of the mathematical formulation, in particular, the neglect of entrainment in the mathematical model. An interesting result arises from the influence of the bottom surface roughness; it both reduces the front velocity during the second phase of motion and attenuates the differences between the experimental and numerical front velocities during the first phase of motion.

Evaluation of moisture reduction in small diameter trees after crushing

Treesearch

Donald L. Sirois; Cynthia L. Rawlins; Bryce J. Stokes

1991-01-01

Past studies have suggested that processing small diameter whole trees like those foumd on rights-of-way (ROWs) would help reduce transportion costs and increase energy value by lowering stem moisture content. Small stems were crushed by a roller crusher/splitter test bench machine and allowed dry under field conditions in Alabama. Tests were conducted in winter and...

Users guide for STHARVEST: software to estimate the cost of harvesting small timber.

Treesearch

Roger D. Fight; Xiaoshan Zhang; Bruce R. Hartsough

2003-01-01

The STHARVEST computer application is Windows-based, public-domain software used to estimate costs for harvesting small-diameter stands or the small-diameter component of a mixed-sized stand. The equipment production rates were developed from existing studies. Equipment operating cost rates were based on November 1998 prices for new equipment and wage rates for the...

CFD Analysis of nanofluid forced convection heat transport in laminar flow through a compact pipe

NASA Astrophysics Data System (ADS)

Yu, Kitae; Park, Cheol; Kim, Sedon; Song, Heegun; Jeong, Hyomin

2017-08-01

In the present paper, developing laminar forced convection flows were numerically investigated by using water-Al2O3 nano-fluid through a circular compact pipe which has 4.5mm diameter. Each model has a steady state and uniform heat flux (UHF) at the wall. The whole numerical experiments were processed under the Re = 1050 and the nano-fluid models were made by the Alumina volume fraction. A single-phase fluid models were defined through nano-fluid physical and thermal properties calculations, Two-phase model(mixture granular model) were processed in 100nm diameter. The results show that Nusselt number and heat transfer rate are improved as the Al2O3 volume fraction increased. All of the numerical flow simulations are processed by the FLUENT. The results show the increment of thermal transfer from the volume fraction concentration.

Effective separation technique for small diameter whiskers.

NASA Technical Reports Server (NTRS)

Westfall, L. J.

1972-01-01

Description of a technique for separating small-diameter whiskers from the as-grown matt by gently agitating the whisker matts in a solution of deionized or distilled water for six to eight hours. High-strength Al2O3 whiskers were effectively separated by this technique, comprising an average 48% of the original weight of the whisker matt. According to estimation, more than 90% of separated whiskers had diameters between 0.7 and 2.0 microns.

Wood and bark specific gravity of small-diameter, pine-site hardwood in the south

Treesearch

F.G. Manwiller

1979-01-01

Ten small-diameter trees from each of the 22 species (220 trees) were sampled from throughout the southern United States. Mean SG was determined for stem wood and bark and the whole stem, for branch wood and bark and whole branches (to a minimum diameter of 0.05 in.), and for tree wood and bark and the whole tree. Significant differences were determined a) among the...

Ga-doped indium oxide nanowire phase change random access memory cells

NASA Astrophysics Data System (ADS)

Jin, Bo; Lim, Taekyung; Ju, Sanghyun; Latypov, Marat I.; Kim, Hyoung Seop; Meyyappan, M.; Lee, Jeong-Soo

2014-02-01

Phase change random access memory (PCRAM) devices are usually constructed using tellurium based compounds, but efforts to seek other materials providing desirable memory characteristics have continued. We have fabricated PCRAM devices using Ga-doped In2O3 nanowires with three different Ga compositions (Ga/(In+Ga) atomic ratio: 2.1%, 11.5% and 13.0%), and investigated their phase switching properties. The nanowires (˜40 nm in diameter) can be repeatedly switched between crystalline and amorphous phases, and Ga concentration-dependent memory switching behavior in the nanowires was observed with ultra-fast set/reset rates of 80 ns/20 ns, which are faster than for other competitive phase change materials. The observations of fast set/reset rates and two distinct states with a difference in resistance of two to three orders of magnitude appear promising for nonvolatile information storage. Moreover, we found that increasing the Ga concentration can reduce the power consumption and resistance drift; however, too high a level of Ga doping may cause difficulty in achieving the phase transition.

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

Khlystova, Anna; Toriumi, Shin, E-mail: hlystova@iszf.irk.ru, E-mail: shin.toriumi@nao.ac.jp

We study the plasma flows in the solar photosphere during the emergence of two small active regions, NOAA 9021 and 10768. Using Solar and Heliospheric Observatory /Michelson Doppler Imager data, we find that the strong plasma upflows appear at the initial stage of active region formation, with maximum upflow velocities of −1650 and −1320 m s{sup −1}. The structures with enhanced upflows have size ∼8 Mm in diameter, and they exist for 1–2 hr. The parameters of the enhanced upflows are consistent with those of the large active region NOAA 10488, which may suggest the possibility that the elementary emergingmore » magnetic loops that appear at the earliest phase of active region formation have similar properties, irrespective of scales of active regions. Comparison between the observations and a numerical simulation of magnetic flux emergence shows a striking consistency. We find that the driving force of the plasma upflow is at first the gas pressure gradient and later the magnetic pressure gradient.« less

Synthesis of platinum nanowire networks using a soft template.

PubMed

Song, Yujiang; Garcia, Robert M; Dorin, Rachel M; Wang, Haorong; Qiu, Yan; Coker, Eric N; Steen, William A; Miller, James E; Shelnutt, John A

2007-12-01

Platinum nanowire networks have been synthesized by chemical reduction of a platinum complex using sodium borohydride in the presence of a soft template formed by cetyltrimethylammonium bromide in a two-phase water-chloroform system. The interconnected polycrystalline nanowires possess the highest surface area (53 +/- 1 m2/g) and electroactive surface area (32.4 +/- 3.6 m2/g) reported for unsupported platinum nanomaterials; the high surface area results from the small average diameter of the nanowires (2.2 nm) and the 2-10 nm pores determined by nitrogen adsorption measurements. Synthetic control over the network was achieved simply by varying the stirring rate and reagent concentrations, in some cases leading to other types of nanostructures including wormlike platinum nanoparticles. Similarly, substitution of a palladium complex for platinum gives palladium nanowire networks. A mechanism of formation of the metal nanowire networks is proposed based on confined metal growth within a soft template consisting of a network of swollen inverse wormlike micelles.

Exploring Transitions in Notions of Identity as Perceived by Beginning Post-Compulsory Teachers

ERIC Educational Resources Information Center

Wright, Victoria; Loughlin, Theresa; Hall, Val

2018-01-01

This paper reports on Phase Two of a small-scale qualitative research project. Phase One (2015-2016) focused on pre-service student teachers' perceptions of observation and feedback in relation to their developing identity as teachers. In Phase Two, two previous participants reflected on the research findings as qualified and beginning teachers.…

Interaction of nanosecond ultraviolet laser pulses with reactive dusty plasma

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

Wetering, F. M. J. H. van de; Oosterbeek, W.; Beckers, J.

2016-05-23

Even though UV laser pulses that irradiate a gas discharge are small compared to the plasma volume (≲3%) and plasma-on time (≲6 × 10{sup −6}%), they are found to dramatically change the discharge characteristics on a global scale. The reactive argon–acetylene plasma allows the growth of nanoparticles with diameters up to 1 μm, which are formed inside the discharge volume due to spontaneous polymerization reactions. It is found that the laser pulses predominantly accelerate and enhance the coagulation phase and are able to suppress the formation of a dust void.

Application of the Baxter model for hard-spheres with surface adhesion to SANS data for the U(VI) - HNO{sub 3}, TBP-n-dodecane system.

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

Chiarizia, R.; Nash, K. L.; Jensen, M. P.

2003-11-11

Small-angle neutron scattering (SANS) data for the tri-n-butyl phosphate (TBP)-n-dodecane, HNO{sub 3}-UO{sub 2}(NO{sub 3}){sub 2} solvent extraction system have been interpreted using the Baxter model for hard spheres with surface adhesion. The increase in the scattering intensity in the low Q range observed when increasing amounts of HNO{sub 3} or UO{sub 2}(NO{sub 3}){sub 2} are transferred into the organic phase has been interpreted as arising from interactions between solute particles. The SANS data have been reproduced using a 12--16 {angstrom} diameter of the hard sphere, d{sub hs}, and a 5.6k{sub B}T-7.1k{sub B}T stickiness parameter, {tau}{sup -1}. When in contact withmore » an aqueous phase, TBP in n-dodecane forms small reverse micelles containing three TBP molecules. Upon extraction of water, HNO{sub 3}, and UO{sub 2}(NO{sub 3}){sub 2}, the swollen micelles interact through attractive forces between their polar cores with a potential energy of about 2k{sub B}T and an effective Hamaker constant of about 4k{sub B}T. The intermicellar attraction, under suitable conditions, leads to third-phase formation. Upon phase splitting, most of the solutes in the original organic phase (water, TBP, HNO{sub 3}, and UO{sub 2}(NO{sub 3}){sub 2}) separate in a continuous phase containing interspersed layers of n-dodecane.« less

Small-Diameter Awls Improve Articular Cartilage Repair After Microfracture Treatment in a Translational Animal Model.

PubMed

Orth, Patrick; Duffner, Julia; Zurakowski, David; Cucchiarini, Magali; Madry, Henning

2016-01-01

Microfracture is the most commonly applied arthroscopic marrow stimulation procedure. Articular cartilage repair is improved when the subchondral bone is perforated by small-diameter microfracture awls compared with larger awls. Controlled laboratory study. Standardized rectangular (4 × 8 mm) full-thickness chondral defects (N = 24) were created in the medial femoral condyle of 16 adult sheep and debrided down to the subchondral bone plate. Three treatment groups (n = 8 defects each) were tested: 6 microfracture perforations using small-diameter awls (1.0 mm; group 1), large-diameter awls (1.2 mm; group 2), or without perforations (debridement control; group 3). Osteochondral repair was assessed at 6 months in vivo using established macroscopic, histological, immunohistochemical, biochemical, and micro-computed tomography analyses. Compared with control defects, histological cartilage repair was always improved after both microfracture techniques (P < .023). Application of 1.0-mm microfracture awls led to a significantly improved histological overall repair tissue quality (7.02 ± 0.70 vs 9.03 ± 0.69; P = .008) and surface grading (1.05 ± 0.28 vs 2.10 ± 0.19; P = .001) compared with larger awls. The small-diameter awl decreased relative bone volume of the subarticular spongiosa (bone volume/tissue volume ratio: 23.81% ± 3.37% vs 30.58% ± 2.46%; P = .011). Subchondral bone cysts and intralesional osteophytes were frequently observed after either microfracture treatment. Macroscopic grading, DNA, proteoglycan, and type I and type II collagen contents as well as degenerative changes within the adjacent cartilage remained unaffected by the awl diameter. Small-diameter microfracture awls improve articular cartilage repair in the translational sheep model more effectively than do larger awls. These data support the use of small microfracture instruments for the surgical treatment of cartilage defects and warrant prolonged clinical investigations. © 2015 The Author(s).

Emergence of synchronization induced by the interplay between two prisoner's dilemma games with volunteering in small-world networks

NASA Astrophysics Data System (ADS)

Chen, Yong; Qin, Shao-Meng; Yu, Lianchun; Zhang, Shengli

2008-03-01

We studied synchronization between prisoner’s dilemma games with voluntary participation in two Newman-Watts small-world networks. It was found that there are three kinds of synchronization: partial phase synchronization, total phase synchronization, and complete synchronization, for varied coupling factors. Besides, two games can reach complete synchronization for the large enough coupling factor. We also discussed the effect of the coupling factor on the amplitude of oscillation of cooperator density.

Role of small-norm components in extended random-phase approximation

NASA Astrophysics Data System (ADS)

Tohyama, Mitsuru

2017-09-01

The role of the small-norm amplitudes in extended random-phase approximation (RPA) theories such as the particle-particle and hole-hole components of one-body amplitudes and the two-body amplitudes other than two-particle/two-hole components are investigated for the one-dimensional Hubbard model using an extended RPA derived from the time-dependent density matrix theory. It is found that these amplitudes cannot be neglected in strongly interacting regions where the effects of ground-state correlations are significant.

Acoustic response of compliable microvessels containing ultrasound contrast agents

NASA Astrophysics Data System (ADS)

Qin, Shengping; Ferrara, Katherine W.

2006-10-01

The existing models of the dynamics of ultrasound contrast agents (UCAs) have largely been focused on an UCA surrounded by an infinite liquid. Preliminary investigations of a microbubble's oscillation in a rigid tube have been performed using linear perturbation, under the assumption that the tube diameter is significantly larger than the UCA diameter. In the potential application of drug and gene delivery, it may be desirable to fragment the agent shell within small blood vessels and in some cases to rupture the vessel wall, releasing drugs and genes at the site. The effect of a compliant small blood vessel on the UCA's oscillation and the microvessel's acoustic response are unknown. The aim of this work is to propose a lumped-parameter model to study the interaction of a microbubble oscillation and compliable microvessels. Numerical results demonstrate that in the presence of UCAs, the transmural pressure through the blood vessel substantially increases and thus the vascular permeability is predicted to be enhanced. For a microbubble within an 8 to 40 µm vessel with a peak negative pressure of 0.1 MPa and a centre frequency of 1 MHz, small changes in the microbubble oscillation frequency and maximum diameter are observed. When the ultrasound pressure increases, strong nonlinear oscillation occurs, with an increased circumferential stress on the vessel. For a compliable vessel with a diameter equal to or greater than 8 µm, 0.2 MPa PNP at 1 MHz is predicted to be sufficient for microbubble fragmentation regardless of the vessel diameter; however, for a rigid vessel 0.5 MPa PNP at 1 MHz may not be sufficient to fragment the bubbles. For a centre frequency of 1 MHz, a peak negative pressure of 0.5 MPa is predicted to be sufficient to exceed the stress threshold for vascular rupture in a small (diameter less than 15 µm) compliant vessel. As the vessel or surrounding tissue becomes more rigid, the UCA oscillation and vessel dilation decrease; however the circumferential stress is predicted to increase. Decreasing the vessel size or the centre frequency increases the circumferential stress. For the two frequencies considered in this work, the circumferential stress does not scale as the inverse of the square root of the acoustic frequency va as in the mechanical index, but rather has a stronger frequency dependence, 1/va.

Cutting Diameter Influences Early Survival and Growth of Several Populus Clones

Treesearch

Donald Dickmann; Howard Phipps; Daniel Netzer

1980-01-01

The effects of cutting diameter on early survival and growth of several Populus clones were studied in field tests in Wisconsin and Michigan. Generally, large diameter cuttings survived and grew better than small diameter cuttings. Response differences among clones were evident.

Two-phase flow pressure drop and heat transfer during condensation in microchannels with uniform and converging cross-sections

NASA Astrophysics Data System (ADS)

Kuo, Ching Yi; Pan, Chin

2010-09-01

This study experimentally investigates steam condensation in rectangular microchannels with uniform and converging cross-sections and a mean hydraulic diameter of 135 µm. The steam flow in the microchannels was cooled by water cross-flowing along its bottom surface, which is different from other methods reported in the literature. The flow patterns, two-phase flow pressure drop and condensation heat transfer coefficient are determined. The microchannels with the uniform cross-section design have a higher heat transfer coefficient than those with the converging cross-section under condensation in the mist/annular flow regimes, although the latter work best for draining two-phase fluids composed of uncondensed steam and liquid water, which is consistent with the result of our previous study. From the experimental results, dimensionless correlations of condensation heat transfer for the mist and annular flow regions and a two-phase frictional multiplier are developed for the microchannels with both types of cross-section designs. The experimental data agree well with the obtained correlations, with the maximum mean absolute errors of 6.4% for the two-phase frictional multiplier and 6.0% for the condensation heat transfer.

Comparison of carbon footprints of steel versus concrete pipelines for water transmission.

PubMed

Chilana, Lalit; Bhatt, Arpita H; Najafi, Mohammad; Sattler, Melanie

2016-05-01

The global demand for water transmission and service pipelines is expected to more than double between 2012 and 2022. This study compared the carbon footprint of the two most common materials used for large-diameter water transmission pipelines, steel pipe (SP) and prestressed concrete cylinder pipe (PCCP). A planned water transmission pipeline in Texas was used as a case study. Four life-cycle phases for each material were considered: material production and pipeline fabrication, pipe transportation to the job site, pipe installation in the trench, and operation of the pipeline. In each phase, the energy consumed and the CO2-equivalent emissions were quantified. It was found that pipe manufacturing consumed a large amount of energy, and thus contributed more than 90% of life cycle carbon emissions for both kinds of pipe. Steel pipe had 64% larger CO2-eq emissions from manufacturing compared to PCCP. For the transportation phase, PCCP consumed more fuel due to its heavy weight, and therefore had larger CO2-eq emissions. Fuel consumption by construction equipment for installation of pipe was found to be similar for steel pipe and PCCP. Overall, steel had a 32% larger footprint due to greater energy used during manufacturing. This study compared the carbon footprint of two large-diameter water transmission pipeline materials, steel and prestressed concrete cylinder, considering four life-cycle phases for each. The study provides information that project managers can incorporate into their decision-making process concerning pipeline materials. It also provides information concerning the most important phases of the pipeline life cycle to target for emission reductions.

Effect of liquid droplets on turbulence in a round gaseous jet

NASA Technical Reports Server (NTRS)

Mostafa, A. A.; Elghobashi, S. E.

1986-01-01

The main objective of this investigation is to develop a two-equation turbulence model for dilute vaporizing sprays or in general for dispersed two-phase flows including the effects of phase changes. The model that accounts for the interaction between the two phases is based on rigorously derived equations for turbulence kinetic energy (K) and its dissipation rate epsilon of the carrier phase using the momentum equation of that phase. Closure is achieved by modeling the turbulent correlations, up to third order, in the equations of the mean motion, concentration of the vapor in the carrier phase, and the kinetic energy of turbulence and its dissipation rate for the carrier phase. The governing equations are presented in both the exact and the modeled formes. The governing equations are solved numerically using a finite-difference procedure to test the presented model for the flow of a turbulent axisymmetric gaseous jet laden with either evaporating liquid droplets or solid particles. The predictions include the distribution of the mean velocity, volume fractions of the different phases, concentration of the evaporated material in the carrier phase, turbulence intensity and shear stress of the carrier phase, droplet diameter distribution, and the jet spreading rate. The predictions are in good agreement with the experimental data.

Large-scale laboratory testing of bedload-monitoring technologies: overview of the StreamLab06 Experiments

USGS Publications Warehouse

Marr, Jeffrey D.G.; Gray, John R.; Davis, Broderick E.; Ellis, Chris; Johnson, Sara; Gray, John R.; Laronne, Jonathan B.; Marr, Jeffrey D.G.

2010-01-01

A 3-month-long, large-scale flume experiment involving research and testing of selected conventional and surrogate bedload-monitoring technologies was conducted in the Main Channel at the St. Anthony Falls Laboratory under the auspices of the National Center for Earth-surface Dynamics. These experiments, dubbed StreamLab06, involved 25 researchers and volunteers from academia, government, and the private sector. The research channel was equipped with a sediment-recirculation system and a sediment-flux monitoring system that allowed continuous measurement of sediment flux in the flume and provided a data set by which samplers were evaluated. Selected bedload-measurement technologies were tested under a range of flow and sediment-transport conditions. The experiment was conducted in two phases. The bed material in phase I was well-sorted siliceous sand (0.6-1.8 mm median diameter). A gravel mixture (1-32 mm median diameter) composed the bed material in phase II. Four conventional bedload samplers – a standard Helley-Smith, Elwha, BLH-84, and Toutle River II (TR-2) sampler – were manually deployed as part of both experiment phases. Bedload traps were deployed in study Phase II. Two surrogate bedload samplers – stationarymounted down-looking 600 kHz and 1200 kHz acoustic Doppler current profilers – were deployed in experiment phase II. This paper presents an overview of the experiment including the specific data-collection technologies used and the ambient hydraulic, sediment-transport and environmental conditions measured as part of the experiment. All data collected as part of the StreamLab06 experiments are, or will be available to the research community.

Population and size distribution of solute-rich mesospecies within mesostructured aqueous amino acid solutions.

PubMed

Jawor-Baczynska, Anna; Moore, Barry D; Lee, Han Seung; McCormick, Alon V; Sefcik, Jan

2013-01-01

Aqueous solutions of highly soluble substances such as small amino acids are usually assumed to be essentially homogenous systems with some degree of short range local structuring due to specific interactions on the sub-nanometre scale (e.g. molecular clusters, hydration shells), usually not exceeding several solute molecules. However, recent theoretical and experimental studies have indicated the presence of much larger supramolecular assemblies or mesospecies in solutions of small organic and inorganic molecules as well as proteins. We investigated both supersaturated and undersaturated aqueous solutions of two simple amino acids (glycine and DL-alanine) using Dynamic Light Scattering (DLS), Brownian Microscopy/Nanoparticles Tracking Analysis (NTA) and Cryogenic Transmission Electron Microscopy (Cryo-TEM). Colloidal scale mesospecies (nanodroplets) were previously reported in supersaturated solutions of these amino acids and were implicated as intermediate species on non-classical crystallization pathways. Surprisingly, we have found that the mesospecies are also present in significant numbers in undersaturated solutions even when the solute concentration is well below the solid-liquid equilibrium concentration (saturation limit). Thus, mesopecies can be observed with mean diameters ranging from 100 to 300 nm and a size distribution that broadens towards larger size with increasing solute concentration. We note that the mesospecies are not a separate phase and the system is better described as a thermodynamically stable mesostructured liquid containing solute-rich domains dispersed within bulk solute solution. At a given temperature, solute molecules in such a mesostructured liquid phase are subject to equilibrium distribution between solute-rich mesospecies and the surrounding bulk solution.

Experimental Investigation of a Helicopter Rotor Hub Flow

NASA Astrophysics Data System (ADS)

Reich, David

The rotor hub system is by far the largest contributor to helicopter parasite drag and a barrier to increasing helicopter forward-flight speed and range. Additionally, the hub sheds undesirable vibration- and instability-inducing unsteady flow over the empennage. The challenges associated with rotor hub flows are discussed, including bluff body drag, interactional aerodynamics, and the effect of the turbulent hub wake on the helicopter empennage. This study was conducted in three phases to quantify model-scale rotor hub flows in water tunnels at The Pennsylvania State University Applied research lab. The first phase investigated scaling and component interaction effects on a 1:17 scale rotor hub model in the 12-inch diameter water tunnel. Effects of Reynolds number, advance ratio, and hub geometry configuration on the drag and wake shed from the rotor hub were quantified using load cell measurements and particle-image velocimetry (PIV). The second phase focused on flow visualization and measurement on a rotor hub and rotor hub/pylon geometry in the 12-inch diameter water tunnel. Stereo PIV was conducted in a cross plane downstream of the hub and flow visualization was conducted using oil paint and fluorescent dye. The third phase concentrated on high accuracy load measurement and prediction up to full-scale Reynolds number on a 1:4.25 scale model in the 48-inch diameter water tunnel. Measurements include 6 degree of freedom loads on the hub and two-component laser-Doppler velocimetry in the wake. Finally, results and conclusions are discussed, followed by recommendations for future investigations.

Phytoscreening with SPME: Variability Analysis.

PubMed

Limmer, Matt A; Burken, Joel G

2015-01-01

Phytoscreening has been demonstrated at a variety of sites over the past 15 years as a low-impact, sustainable tool in delineation of shallow groundwater contaminated with chlorinated solvents. Collection of tree cores is rapid and straightforward, but low concentrations in tree tissues requires sensitive analytics. Solid-phase microextraction (SPME) is amenable to the complex matrix while allowing for solvent-less extraction. Accurate quantification requires the absence of competitive sorption, examined here both in laboratory experiments and through comprehensive examination of field data. Analysis of approximately 2,000 trees at numerous field sites also allowed testing of the tree genus and diameter effects on measured tree contaminant concentrations. Collectively, while these variables were found to significantly affect site-adjusted perchloroethylene (PCE) concentrations, the explanatory power of these effects was small (adjusted R(2) = 0.031). 90th quantile chemical concentrations in trees were significantly reduced by increasing Henry's constant and increasing hydrophobicity. Analysis of replicate tree core data showed no correlation between replicate relative standard deviation (RSD) and wood type or tree diameter, with an overall median RSD of 30%. Collectively, these findings indicate SPME is an appropriate technique for sampling and analyzing chlorinated solvents in wood and that phytoscreening is robust against changes in tree type and diameter.

High Sensitivity Refractometer Based on Reflective Smf-Small Diameter No Core Fiber Structure.

PubMed

Zhou, Guorui; Wu, Qiang; Kumar, Rahul; Ng, Wai Pang; Liu, Hao; Niu, Longfei; Lalam, Nageswara; Yuan, Xiaodong; Semenova, Yuliya; Farrell, Gerald; Yuan, Jinhui; Yu, Chongxiu; Zeng, Jie; Tian, Gui Yun; Fu, Yong Qing

2017-06-16

A high sensitivity refractive index sensor based on a single mode-small diameter no core fiber structure is proposed. In this structure, a small diameter no core fiber (SDNCF) used as a sensor probe, was fusion spliced to the end face of a traditional single mode fiber (SMF) and the end face of the SDNCF was coated with a thin film of gold to provide reflective light. The influence of SDNCF diameter and length on the refractive index sensitivity of the sensor has been investigated by both simulations and experiments, where results show that the diameter of SDNCF has significant influence. However, SDNCF length has limited influence on the sensitivity. Experimental results show that a sensitivity of 327 nm/RIU (refractive index unit) has been achieved for refractive indices ranging from 1.33 to 1.38, which agrees well with the simulated results with a sensitivity of 349.5 nm/RIU at refractive indices ranging from 1.33 to 1.38.

Studies of Two-Phase Flow Dynamics and Heat Transfer at Reduced Gravity Conditions

NASA Technical Reports Server (NTRS)

Witte, Larry C.; Bousman, W. Scott; Fore, Larry B.

1996-01-01

The ability to predict gas-liquid flow patterns is crucial to the design and operation of two-phase flow systems in the microgravity environment. Flow pattern maps have been developed in this study which show the occurrence of flow patterns as a function of gas and liquid superficial velocities as well as tube diameter, liquid viscosity and surface tension. The results have demonstrated that the location of the bubble-slug transition is affected by the tube diameter for air-water systems and by surface tension, suggesting that turbulence-induced bubble fluctuations and coalescence mechanisms play a role in this transition. The location of the slug-annular transition on the flow pattern maps is largely unaffected by tube diameter, liquid viscosity or surface tension in the ranges tested. Void fraction-based transition criteria were developed which separate the flow patterns on the flow pattern maps with reasonable accuracy. Weber number transition criteria also show promise but further work is needed to improve these models. For annular gas-liquid flows of air-water and air- 50 percent glycerine under reduced gravity conditions, the pressure gradient agrees fairly well with a version of the Lockhart-Martinelli correlation but the measured film thickness deviates from published correlations at lower Reynolds numbers. Nusselt numbers, based on a film thickness obtained from standard normal-gravity correlations, follow the relation, Nu = A Re(sup n) Pr(exp l/3), but more experimental data in a reduced gravity environment are needed to increase the confidence in the estimated constants, A and n. In the slug flow regime, experimental pressure gradient does not correlate well with either the Lockhart-Martinelli or a homogeneous formulation, but does correlate nicely with a formulation based on a two-phase Reynolds number. Comparison with ground-based correlations implies that the heat transfer coefficients are lower at reduced gravity than at normal gravity under the same flow conditions. Nusselt numbers can be correlated in a fashion similar to Chu and Jones.

Production of small diameter high-temperature-strength refractory metal wires

NASA Technical Reports Server (NTRS)

Petrasek, D. W.; Signorelli, R. A.; King, G. W.

1973-01-01

Special thermomechanical techniques (schedules) have been developed to produce small diameter wire from three refractory metal alloys: colombian base alloy, tantalum base alloy, and tungsten base alloy. High strengths of these wires indicate their potential for contributing increased strength to metallic composites.

Microscopic origin of black hole reentrant phase transitions

NASA Astrophysics Data System (ADS)

Zangeneh, M. Kord; Dehyadegari, A.; Sheykhi, A.; Mann, R. B.

2018-04-01

Understanding the microscopic behavior of the black hole ingredients has been one of the important challenges in black hole physics during the past decades. In order to shed some light on the microscopic structure of black holes, in this paper, we explore a recently observed phenomenon for black holes namely reentrant phase transition, by employing the Ruppeiner geometry. Interestingly enough, we observe two properties for the phase behavior of small black holes that leads to reentrant phase transition. They are correlated and they are of the interaction type. For the range of pressure in which the system underlies reentrant phase transition, it transits from the large black holes phase to the small one which possesses higher correlation than the other ranges of pressures. On the other hand, the type of interaction between small black holes near the large/small transition line differs for usual and reentrant phase transitions. Indeed, for the usual case, the dominant interaction is repulsive whereas for the reentrant case we encounter an attractive interaction. We show that in the reentrant phase transition case, the small black holes behave like a bosonic gas whereas in the usual phase transition case, they behave like a quantum anyon gas.

Miniature sheathed thermocouples for turbine blade temperature measurement

NASA Technical Reports Server (NTRS)

Holanda, R.; Glawe, G. E.; Krause, L. N.

1974-01-01

An investigation was made of sheathed thermocouples for turbine blade temperature measurements. Tests were performed on the Chromel-Alumel sheathed thermocouples with both two-wire and single-wire configurations. Sheath diameters ranged from 0.25 to 0.76 mm, and temperatures ranged from 1080 to 1250 K. Both steady-state and thermal cycling tests were performed for times up to 450 hr. Special-order and commercial-grade thermocouples were tested. The tests showed that special-order single-wire sheathed thermocouples can be obtained that are reliable and accurate with diameters as small as 0.25 mm. However, all samples of 0.25-mm-diameter sheathed commercial-grade two-wire and single-wire thermocouples that were tested showed unacceptable drift rates for long-duration engine testing programs. The drift rates were about 1 percent in 10 hr. A thermocouple drift test is recommended in addition to the normal acceptance tests in order to select reliable miniature sheathed thermocouples for turbine blade applications.

Fast synthesis and consolidation of porous FeAl by pressureless Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Dudina, D. V.; Brester, A. E.; Anisimov, A. G.; Bokhonov, B. B.; Legan, M. A.; Novoselov, A. N.; Skovorodin, I. N.; Uvarov, N. F.

2017-07-01

We report one-step fast synthesis and consolidation of iron aluminide FeAl of high open porosity by pressureless reactive Spark Plasma Sintering (SPS). The starting material of the Fe-40at.%Al composition was a mixture of an iron powder with an average particle diameter of 4 μm and an aluminum powder with an average particle diameter of 6 μm. The rationale behind the choice of the SPS as a processing technique and fine and comparable sizes of the two reactants for the synthesis of high-open porosity FeAl was realization of fast full chemical conversion of Fe and Al into single-phase FeAl reducing the time available for the compact shrinkage. According to the XRD phase analysis, single-phase FeAl compacts formed after SPS at 800 and 900°C. These compacts had open porosities of 41 and 46%, respectively. The transverse rupture strength of the compacts sintered at 700-900°C was found to change little with the sintering temperature in the selected range.

Lesion size affects diagnostic performance of IOTA logistic regression models, IOTA simple rules and risk of malignancy index in discriminating between benign and malignant adnexal masses.

PubMed

Di Legge, A; Testa, A C; Ameye, L; Van Calster, B; Lissoni, A A; Leone, F P G; Savelli, L; Franchi, D; Czekierdowski, A; Trio, D; Van Holsbeke, C; Ferrazzi, E; Scambia, G; Timmerman, D; Valentin, L

2012-09-01

To estimate the ability to discriminate between benign and malignant adnexal masses of different size using: subjective assessment, two International Ovarian Tumor Analysis (IOTA) logistic regression models (LR1 and LR2), the IOTA simple rules and the risk of malignancy index (RMI). We used a multicenter IOTA database of 2445 patients with at least one adnexal mass, i.e. the database previously used to prospectively validate the diagnostic performance of LR1 and LR2. The masses were categorized into three subgroups according to their largest diameter: small tumors (diameter < 4 cm; n = 396), medium-sized tumors (diameter, 4-9.9 cm; n = 1457) and large tumors (diameter ≥ 10 cm, n = 592). Subjective assessment, LR1 and LR2, IOTA simple rules and the RMI were applied to each of the three groups. Sensitivity, specificity, positive and negative likelihood ratio (LR+, LR-), diagnostic odds ratio (DOR) and area under the receiver-operating characteristics curve (AUC) were used to describe diagnostic performance. A moving window technique was applied to estimate the effect of tumor size as a continuous variable on the AUC. The reference standard was the histological diagnosis of the surgically removed adnexal mass. The frequency of invasive malignancy was 10% in small tumors, 19% in medium-sized tumors and 40% in large tumors; 11% of the large tumors were borderline tumors vs 3% and 4%, respectively, of the small and medium-sized tumors. The type of benign histology also differed among the three subgroups. For all methods, sensitivity with regard to malignancy was lowest in small tumors (56-84% vs 67-93% in medium-sized tumors and 74-95% in large tumors) while specificity was lowest in large tumors (60-87%vs 83-95% in medium-sized tumors and 83-96% in small tumors ). The DOR and the AUC value were highest in medium-sized tumors and the AUC was largest in tumors with a largest diameter of 7-11 cm. Tumor size affects the performance of subjective assessment, LR1 and LR2, the IOTA simple rules and the RMI in discriminating correctly between benign and malignant adnexal masses. The likely explanation, at least in part, is the difference in histology among tumors of different size. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.

Toward Small-Diameter Carbon Nanotubes Synthesized from Captured Carbon Dioxide: Critical Role of Catalyst Coarsening.

PubMed

Douglas, Anna; Carter, Rachel; Li, Mengya; Pint, Cary L

2018-06-06

Small-diameter carbon nanotubes (CNTs) often require increased sophistication and control in synthesis processes, but exhibit improved physical properties and greater economic value over their larger-diameter counterparts. Here, we study mechanisms controlling the electrochemical synthesis of CNTs from the capture and conversion of ambient CO 2 in molten salts and leverage this understanding to achieve the smallest-diameter CNTs ever reported in the literature from sustainable electrochemical synthesis routes, including some few-walled CNTs. Here, Fe catalyst layers are deposited at different thicknesses onto stainless steel to produce cathodes, and atomic layer deposition of Al 2 O 3 is performed on Ni to produce a corrosion-resistant anode. Our findings indicate a correlation between the CNT diameter and Fe metal layer thickness following electrochemical catalyst reduction at the cathode-molten salt interface. Further, catalyst coarsening during long duration synthesis experiments leads to a 2× increase in average diameters from 3 to 60 min durations, with CNTs produced after 3 min exhibiting a tight diameter distribution centered near ∼10 nm. Energy consumption analysis for the conversion of CO 2 into CNTs demonstrates energy input costs much lower than the value of CNTs-a concept that strictly requires and motivates small-diameter CNTs-and is more favorable compared to other costly CO 2 conversion techniques that produce lower-value materials and products.

Hierarchically self-assembled hexagonal honeycomb and kagome superlattices of binary 1D colloids.

PubMed

Lim, Sung-Hwan; Lee, Taehoon; Oh, Younghoon; Narayanan, Theyencheri; Sung, Bong June; Choi, Sung-Min

2017-08-25

Synthesis of binary nanoparticle superlattices has attracted attention for a broad spectrum of potential applications. However, this has remained challenging for one-dimensional nanoparticle systems. In this study, we investigate the packing behavior of one-dimensional nanoparticles of different diameters into a hexagonally packed cylindrical micellar system and demonstrate that binary one-dimensional nanoparticle superlattices of two different symmetries can be obtained by tuning particle diameter and mixing ratios. The hexagonal arrays of one-dimensional nanoparticles are embedded in the honeycomb lattices (for AB 2 type) or kagome lattices (for AB 3 type) of micellar cylinders. The maximization of free volume entropy is considered as the main driving force for the formation of superlattices, which is well supported by our theoretical free energy calculations. Our approach provides a route for fabricating binary one-dimensional nanoparticle superlattices and may be applicable for inorganic one-dimensional nanoparticle systems.Binary mixtures of 1D particles are rarely observed to cooperatively self-assemble into binary superlattices, as the particle types separate into phases. Here, the authors design a system that avoids phase separation, obtaining binary superlattices with different symmetries by simply tuning the particle diameter and mixture composition.

Blood circulation in the ascidian tunicate Corella inflata (Corellidae)

PubMed Central

2016-01-01

The body of the ascidian tunicate Corella inflata is relatively transparent. Thus, the circulatory system can be visualized by injecting high molecular weight fluorescein labeled dextran into the heart or the large vessels at the ends of the heart without surgery to remove the body wall. In addition, after staining with neutral red, the movement of blood cells can be easily followed to further characterize the circulatory system. The heart is two gently curved concentric tubes extending across the width of the animal. The inner myocardial tube has a partial constriction approximately in the middle. As in other tunicates, the heart is peristaltic and periodically reverses direction. During the branchial phase blood leaves the anterior end of the heart by two asymmetric vessels that connect to the two sides of the branchial basket. Blood then flows in both transverse directions through a complex system of ducts in the basket into large ventral and dorsal vessels which carry blood back to the visceral organs in the posterior of the animal. During the visceral phase blood leaves the posterior end of the heart in two vessels that repeatedly bifurcate and fan into the stomach and gonads. Blood velocity, determined by following individual cells in video frames, is high and pulsatory near the heart. A double peak in velocity at the maximum may be due to the constriction in the middle of the heart tube. Blood velocity progressively decreases with distance from the heart. In peripheral regions with vessels of small diameter blood cells frequently collide with vessel walls and cell motion is erratic. The estimated volume of blood flow during each directional phase is greater than the total volume of the animal. Circulating blood cells are confined to vessels or ducts in the visible parts of the animal and retention of high molecular weight dextran in the vessels is comparable to that seen in vertebrates. These are characteristics of a closed circulatory system. PMID:27994977

COMPUTATIONAL MODELING OF CIRCULATING FLUIDIZED BED REACTORS

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

Ibrahim, Essam A

2013-01-09

Details of numerical simulations of two-phase gas-solid turbulent flow in the riser section of Circulating Fluidized Bed Reactor (CFBR) using Computational Fluid Dynamics (CFD) technique are reported. Two CFBR riser configurations are considered and modeled. Each of these two riser models consist of inlet, exit, connecting elbows and a main pipe. Both riser configurations are cylindrical and have the same diameter but differ in their inlet lengths and main pipe height to enable investigation of riser geometrical scaling effects. In addition, two types of solid particles are exploited in the solid phase of the two-phase gas-solid riser flow simulations tomore » study the influence of solid loading ratio on flow patterns. The gaseous phase in the two-phase flow is represented by standard atmospheric air. The CFD-based FLUENT software is employed to obtain steady state and transient solutions for flow modulations in the riser. The physical dimensions, types and numbers of computation meshes, and solution methodology utilized in the present work are stated. Flow parameters, such as static and dynamic pressure, species velocity, and volume fractions are monitored and analyzed. The differences in the computational results between the two models, under steady and transient conditions, are compared, contrasted, and discussed.« less

Precision wire feeder for small diameter wire

DOEpatents

Brandon, Eldon D.; Hooper, Frederick M.; Reichenbach, Marvin L.

1992-01-01

A device for feeding small diameter wire having a diameter less than 0.04 mm (16 mil) to a welding station includes a driving wheel for controllably applying a non-deforming driving force to the wire to move the free end of the wire towards the welding station; and a tension device such as a torque motor for constantly applying a reverse force to the wire in opposition to the driving force to keep the wire taut.

Precision wire feeder for small diameter wire

DOEpatents

Brandon, E.D.; Hooper, F.M.; Reichenbach, M.L.

1992-08-11

A device for feeding small diameter wire having a diameter less than 0.04 mm (16 mil) to a welding station includes a driving wheel for controllably applying a non-deforming driving force to the wire to move the free end of the wire towards the welding station; and a tension device such as a torque motor for constantly applying a reverse force to the wire in opposition to the driving force to keep the wire taut. 1 figure.

Optimization of post-column reactor radius in capillary high performance liquid chromatography Effect of chromatographic column diameter and particle diameter

PubMed Central

Xu, Hongjuan; Weber, Stephen G.

2006-01-01

A post-column reactor consisting of a simple open tube (Capillary Taylor Reactor) affects the performance of a capillary LC in two ways: stealing pressure from the column and adding band spreading. The former is a problem for very small radius reactors, while the latter shows itself for large reactor diameters. We derived an equation that defines the observed number of theoretical plates (Nobs) taking into account the two effects stated above. Making some assumptions and asserting certain conditions led to a final equation with a limited number of variables, namely chromatographic column radius, reactor radius and chromatographic particle diameter. The assumptions and conditions are that the van Deemter equation applies, the mass transfer limitation is for intraparticle diffusion in spherical particles, the velocity is at the optimum, the analyte’s retention factor, k′, is zero, the post-column reactor is only long enough to allow complete mixing of reagents and analytes and the maximum operating pressure of the pumping system is used. Optimal ranges of the reactor radius (ar) are obtained by comparing the number of observed theoretical plates (and theoretical plates per time) with and without a reactor. Results show that the acceptable reactor radii depend on column diameter, particle diameter, and maximum available pressure. Optimal ranges of ar become narrower as column diameter increases, particle diameter decreases or the maximum pressure is decreased. When the available pressure is 4000 psi, a Capillary Taylor Reactor with 12 μm radius is suitable for all columns smaller than 150 μm (radius) packed with 2–5 μm particles. For 1 μm packing particles, only columns smaller than 42.5 μm (radius) can be used and the reactor radius needs to be 5 μm. PMID:16494886

Long-term results of small-diameter proximal splenorenal venous shunt: A retrospective study

PubMed Central

Chen, Hao; Yang, Wei-Ping; Yan, Ji-Qi; Li, Qin-Yu; Ma, Di; Li, Hong-Wei

2011-01-01

AIM: To investigate recurrent variceal hemorrhage and long-term survival rates of patients treated with partial proximal splenorenal venous shunt. METHODS: Patients with variceal hemorrhage who were treated with small-diameter proximal splenorenal venous shunt in Ruijin Hospital between 1996 and 2009 were included in this study. Shunt diameter was determined before operation using Duplex Doppler ultrasonography. Peri-operative and long-term results in term of rehemorrhage, encephalopathy and mortality were followed up. RESULTS: Ninety-eight patients with Child A and B variceal hemorrhage received small-diameter proximal splenorenal venous shunt with a diameter of 7-10 mm. After operation, the patients’ mean free portal pressure (P < 0.01) and the flow rate of main portal vein (P < 0.01) decreased significantly compared with that before operation. The rates of rebleeding and mortality were 6.12% (6 cases) and 2.04% (2 cases), respectively. Ninety-one patients were followed up for 7 mo-14 years (median, 48.57 mo). Long-term rates of rehemorrhage and encephalopathy were 4.40% (4 cases) and 3.30% (3 cases), respectively. Thirteen patients (14.29%) died mainly due to progressive hepatic dysfunction. Five- and ten-year survival rates were 82.12% and 71.24%, respectively. CONCLUSION: Small-diameter proximal splenorenal venous shunt affords protection against variceal rehemorrhage with a low occurrence of encephalopathy in patients with normal liver function. PMID:21876638

Phase transitions in four-dimensional binary hard hypersphere mixtures

NASA Astrophysics Data System (ADS)

Bishop, Marvin; Whitlock, Paula A.

2013-02-01

Previous Monte Carlo investigations of binary hard hyperspheres in four-dimensional mixtures are extended to higher densities where the systems may solidify. The ratios of the diameters of the hyperspheres examined were 0.4, 0.5, and 0.6. Only the 0.4 system shows a clear two phase, solid-liquid transition and the larger component solidifies into a D4 crystal state. Its pair correlation function agrees with that of a one component fluid at an appropriately scaled density. The 0.5 systems exhibit states that are a mix of D4 and A4 regions. The 0.6 systems behave similarly to a jammed state rather than solidifying into a crystal. No demixing into two distinct fluid phases was observed for any of the simulations.

Analysis of Fractional Flow for Transient Two-Phase Flow in Fractal Porous Medium

NASA Astrophysics Data System (ADS)

Lu, Ting; Duan, Yonggang; Fang, Quantang; Dai, Xiaolu; Wu, Jinsui

2016-03-01

Prediction of fractional flow in fractal porous medium is important for reservoir engineering and chemical engineering as well as hydrology. A physical conceptual fractional flow model of transient two-phase flow is developed in fractal porous medium based on the fractal characteristics of pore-size distribution and on the approximation that porous medium consist of a bundle of tortuous capillaries. The analytical expression for fractional flow for wetting phase is presented, and the proposed expression is the function of structural parameters (such as tortuosity fractal dimension, pore fractal dimension, maximum and minimum diameters of capillaries) and fluid properties (such as contact angle, viscosity and interfacial tension) in fractal porous medium. The sensitive parameters that influence fractional flow and its derivative are formulated, and their impacts on fractional flow are discussed.

Analysis of nanoscale two-phase flow of argon using molecular dynamics

NASA Astrophysics Data System (ADS)

Verma, Abhishek Kumar; Kumar, Rakesh

2014-12-01

Two phase flows through micro and nanochannels have attracted a lot of attention because of their immense applicability to many advanced fields such as MEMS/NEMS, electronic cooling, bioengineering etc. In this work, a molecular dynamics simulation method is employed to study the condensation process of superheated argon vapor force driven flow through a nanochannel combining fluid flow and heat transfer. A simple and effective particle insertion method is proposed to model phase change of argon based on non-periodic boundary conditions in the simulation domain. Starting from a crystalline solid wall of channel, the condensation process evolves from a transient unsteady state where we study the influence of different wall temperatures and fluid wall interactions on interfacial and heat transport properties of two phase flows. Subsequently, we analyzed transient temperature, density and velocity fields across the channel and their dependency on varying wall temperature and fluid wall interaction, after a dynamic equilibrium is achieved in phase transition. Quasi-steady nonequilibrium temperature profile, heat flux and interfacial thermal resistance were analyzed. The results demonstrate that the molecular dynamics method, with the proposed particle insertion method, effectively solves unsteady nonequilibrium two phase flows at nanoscale resolutions whose interphase between liquid and vapor phase is typically of the order of a few molecular diameters.

A two-dimensional modeling of the warm-up phase of a high-pressure mercury discharge lamp

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

Araoud, Z.; Ben Ahmed, R.; Ben Hamida, M. B.

2010-06-15

The main objective of this work is to provide a better understanding of the warm-up phase of high-intensity discharge lamps. As an example of application, we chose the high-pressure mercury lamp. Based on two-dimensional fluid model parameters, such as the electric current, the length and the diameter of the burner are modified and the effect of the convective transport is studied. This allows us to obtain a thorough understanding of the physics of these lamps in their transitory phase. The simulation of the warm-up phase is a must for the proper predictions of the lamp behavior and can be conductedmore » by solving the energy balance, momentum, and Laplace's equations for the plasma, using the frame of the local thermodynamic equilibrium coupled with the energy balance of the wall.« less

Crash testing of Louisiana's 3 1/2" diameter multi-directional, single steel post, small sign support : final report.

DOT National Transportation Integrated Search

1993-03-01

The Louisiana Department of Transportation and Development (LDOTD) contracted with the Texas Transportation Institute (TTI) to evaluate the impact characteristics of Louisiana's multi-directional, 8.9 cm (3-1/2 in) diameter steel post, small sigh sup...

Gas-liquid-liquid three-phase flow pattern and pressure drop in a microfluidic chip: similarities with gas-liquid/liquid-liquid flows.

PubMed

Yue, Jun; Rebrov, Evgeny V; Schouten, Jaap C

2014-05-07

We report a three-phase slug flow and a parallel-slug flow as two major flow patterns found under the nitrogen-decane-water flow through a glass microfluidic chip which features a long microchannel with a hydraulic diameter of 98 μm connected to a cross-flow mixer. The three-phase slug flow pattern is characterized by a flow of decane droplets containing single elongated nitrogen bubbles, which are separated by water slugs. This flow pattern was observed at a superficial velocity of decane (in the range of about 0.6 to 10 mm s(-1)) typically lower than that of water for a given superficial gas velocity in the range of 30 to 91 mm s(-1). The parallel-slug flow pattern is characterized by a continuous water flow in one part of the channel cross section and a parallel flow of decane with dispersed nitrogen bubbles in the adjacent part of the channel cross section, which was observed at a superficial velocity of decane (in the range of about 2.5 to 40 mm s(-1)) typically higher than that of water for each given superficial gas velocity. The three-phase slug flow can be seen as a superimposition of both decane-water and nitrogen-decane slug flows observed in the chip when the flow of the third phase (viz. nitrogen or water, respectively) was set at zero. The parallel-slug flow can be seen as a superimposition of the decane-water parallel flow and the nitrogen-decane slug flow observed in the chip under the corresponding two-phase flow conditions. In case of small capillary numbers (Ca ≪ 0.1) and Weber numbers (We ≪ 1), the developed two-phase pressure drop model under a slug flow has been extended to obtain a three-phase slug flow model in which the 'nitrogen-in-decane' droplet is assumed as a pseudo-homogeneous droplet with an effective viscosity. The parallel flow and slug flow pressure drop models have been combined to obtain a parallel-slug flow model. The obtained models describe the experimental pressure drop with standard deviations of 8% and 12% for the three-phase slug flow and parallel-slug flow, respectively. An example is given to illustrate the model uses in designing bifurcated microchannels that split the three-phase slug flow for high-throughput processing.

Small-Body Extensions for the Satellite Orbit Analysis Program (SOAP)

NASA Technical Reports Server (NTRS)

Carnright, Robert; Stodden, David; Coggi, John

2008-01-01

An extension to the SOAP software allows users to work with tri-axial ellipsoid-based representations of planetary bodies, primarily for working with small, natural satellites, asteroids, and comets. SOAP is a widely used tool for the visualization and analysis of space missions. The small body extension provides the same visualization and analysis constructs for use with small bodies. These constructs allow the user to characterize satellite path and instrument cover information for small bodies in both 3D display and numerical output formats. Tri-axial ellipsoids are geometric shapes the diameters of which are different in each of three principal x, y, and z dimensions. This construct provides a better approximation than using spheres or oblate spheroids (ellipsoids comprising two common equatorial diameters as a distinct polar diameter). However, the tri-axial ellipsoid is considerably more difficult to work with from a modeling perspective. In addition, the SOAP small-body extensions allow the user to actually employ a plate model for highly irregular surfaces. Both tri-axial ellipsoids and plate models can be assigned to coordinate frames, thus allowing for the modeling of arbitrary changes to body orientation. A variety of features have been extended to support tri-axial ellipsoids, including the computation and display of the spacecraft sub-orbital point, ground trace, instrument footprints, and swathes. Displays of 3D instrument volumes can be shown interacting with the ellipsoids. Longitude/latitude grids, contour plots, and texture maps can be displayed on the ellipsoids using a variety of projections. The distance along an arbitrary line of sight can be computed between the spacecraft and the ellipsoid, and the coordinates of that intersection can be plotted as a function of time. The small-body extension supports the same visual and analytical constructs that are supported for spheres and oblate spheroids in SOAP making the implementation of the more complex algorithms largely transparent to the user.

A study of the diffusional behavior of a two-phase metal matrix composite exposed to a high temperature environment

NASA Technical Reports Server (NTRS)

Tenney, D. R.

1974-01-01

The progress of diffusion-controlled filament-matrix interaction in a metal matrix composite where the filaments and matrix comprise a two-phase binary alloy system was studied by mathematically modeling compositional changes resulting from prolonged elevated temperature exposure. The analysis treats a finite, diffusion-controlled, two-phase moving-interface problem by means of a variable-grid finite-difference technique. The Ni-W system was selected as an example system. Modeling was carried out for the 1000 to 1200 C temperature range for unidirectional composites containing from 6 to 40 volume percent tungsten filaments in a Ni matrix. The results are displayed to show both the change in filament diameter and matrix composition as a function of exposure time. Compositional profiles produced between first and second nearest neighbor filaments were calculated by superposition of finite-difference solutions of the diffusion equations.

Numerical simulation of two-phase filtration in the near well bore zone

NASA Astrophysics Data System (ADS)

Maksat, Kalimoldayev; Kalipa, Kuspanova; Kulyash, Baisalbayeva; Orken, Mamyrbayev; Assel, Abdildayeva

2018-04-01

On the basis of the fundamental laws of energy conservation, nonstationary processes of filtration of two-phase liquids in multilayered reservoirs in the near well bore zone are considered. Number of reservoirs, fluid pressure in the given reservoirs, reservoir permeability, oil viscosity, etc. are taken into account upon that. Plane-parallel flow and axisymmetric cases have been studied. In the numerical solution, non-structured meshes are used. Closer to the well, the meshes thicken. The integration step over time is defined by the generalized Courant inequality. As a result, there are no large oscillations in the numerical solutions obtained. Oil production rates, Poisson's ratios, D-diameters of the well, filter height, filter permeability, and cumulative thickness of the filter cake and the area have been taken as the main inputs in numerical simulation of non-stationary processes of two-phase filtration.

Automated measurement and classification of pulmonary blood-flow velocity patterns using phase-contrast MRI and correlation analysis.

PubMed

van Amerom, Joshua F P; Kellenberger, Christian J; Yoo, Shi-Joon; Macgowan, Christopher K

2009-01-01

An automated method was evaluated to detect blood flow in small pulmonary arteries and classify each as artery or vein, based on a temporal correlation analysis of their blood-flow velocity patterns. The method was evaluated using velocity-sensitive phase-contrast magnetic resonance data collected in vitro with a pulsatile flow phantom and in vivo in 11 human volunteers. The accuracy of the method was validated in vitro, which showed relative velocity errors of 12% at low spatial resolution (four voxels per diameter), but was reduced to 5% at increased spatial resolution (16 voxels per diameter). The performance of the method was evaluated in vivo according to its reproducibility and agreement with manual velocity measurements by an experienced radiologist. In all volunteers, the correlation analysis was able to detect and segment peripheral pulmonary vessels and distinguish arterial from venous velocity patterns. The intrasubject variability of repeated measurements was approximately 10% of peak velocity, or 2.8 cm/s root-mean-variance, demonstrating the high reproducibility of the method. Excellent agreement was obtained between the correlation analysis and radiologist measurements of pulmonary velocities, with a correlation of R2=0.98 (P<.001) and a slope of 0.99+/-0.01.

Design and development of aqueous nanoformulations for mosquito control.

PubMed

Montefuscoli, Antonela Rita; Werdin González, Jorge Omar; Palma, Santiago Daniel; Ferrero, Adriana Alicia; Fernández Band, Beatriz

2014-02-01

Microemulsions (ME) are thermodynamically stable isotropic mixtures of oil, water, and surfactant; they would also be attractive as potential insecticidal products due to the high bioviability of the active ingredient, attributable to the small sizes of the oil drops. A laboratory study was conducted in order to compare the biological effect of oil in water (o/w) geranium essential oil (EO) and geraniol MEs and emulsions, against Culex pipiens pipiens mosquito larvae. The systems were based on three nonionic surfactants (Cremophor EL, Brij 35, Tween 80). The MEs showed dispersed phase diameters in the range of 8 to 14 nm and had low PDI values (<0.2). The MEs were analyzed by TEM, indicating that they had nearly spherical morphology. The microemulsified systems based on geranium EO and those of geraniol produced a notable increase of the larvicidal activity when compared with the respectably emulsions, concluding that the biological effect is related with the diameter of the dispersed phase. The smallest drops achieved the highest larvicidal activity, being the aqueous nanoformulations based on geraniol most effective than those of geranium EO. However, geranium microemulsions are preferred due to their residual toxicological profiles. The results indicate that these novel systems could be used in integrated pest management program for the C. pipiens pipiens.

MICROBIAL SOLUTION: APPLICATION OF MICROORGANISMS FOR BIOFUEL PRODUCTION AND CO2 MITIGATION

EPA Science Inventory

A 100 L photobioreactor for biodiesel generation from microalga Chlorella vulgaris was constructed from two parallel clear PVC 10 feet tubes (6’ diameter) with a small slope (10%). The gas mixture (5% CO2 and air) flowed up the top of the PVC tubes from the bottom as...

An experimental investigation of two large annular diffusers with swirling and distorted inflow

NASA Technical Reports Server (NTRS)

Eckert, W. T.; Johnston, J. P.; Simons, T. D.; Mort, K. W.; Page, V. R.

1980-01-01

Two annular diffusers downstream of a nacelle-mounted fan were tested for aerodynamic performance, measured in terms of two static pressure recovery parameters (one near the diffuser exit plane and one about three diameters downstream in the settling duct) in the presence of several inflow conditions. The two diffusers each had an inlet diameter of 1.84 m, an area ratio of 2.3, and an equivalent cone angle of 11.5, but were distinguished by centerbodies of different lengths. The dependence of diffuser performance on various combinations of swirling, radially distorted, and/or azimuthally distorted inflow was examined. Swirling flow and distortions in the axial velocity profile in the annulus upstream of the diffuser inlet were caused by the intrinsic flow patterns downstream of a fan in a duct and by artificial intensification of the distortions. Azimuthal distortions or defects were generated by the addition of four artificial devices (screens and fences). Pressure recovery data indicated beneficial effects of both radial distortion (for a limited range of distortion levels) and inflow swirl. Small amounts of azimuthal distortion created by the artificial devices produced only small effects on diffuser performance. A large artificial distortion device was required to produce enough azimuthal flow distortion to significantly degrade the diffuser static pressure recovery.

Orbiting Rainbows Simulation

NASA Image and Video Library

2015-04-22

This simulated image shows how a cloud of glitter in geostationary orbit would be illuminated and controlled by two laser beams. As the cloud orbits Earth, grains scatter the sun's light at different angles like many tiny prisms, similar to how rainbows are produced from light being dispersed by water droplets. That is why the project concept is called "Orbiting Rainbows." The cloud functions like a reflective surface, allowing the exoplanet (displayed in the bottom right) to be imaged. The orbit path is shown in the top right. On the bottom left, Earth's image is seen behind the cloud. To image an exoplanet, the cloud would need to have a diameter of nearly 98 feet (30 meters). This simulation confines the cloud to a 3.3 x 3.3 x 3.3 foot volume (1 x 1 x 1 meter volume) to simplify the computations. The elements of the orbiting telescope are not to scale. Orbiting Rainbows is currently in Phase II development through the NASA Innovative Advanced Concepts (NIAC) Program. It was one of five technology proposals chosen for continued study in 2014. In the current phase, Orbiting Rainbows researchers are conducting small-scale ground experiments to demonstrate how granular materials can be manipulated using lasers and simulations of how the imaging system would behave in orbit. http://photojournal.jpl.nasa.gov/catalog/PIA19318

Evaluating effective pair and multisite interactions for Ni-Mo system

NASA Astrophysics Data System (ADS)

Banerjee, Rumu H.; Arya, A.; Banerjee, S.

2018-04-01

Cluster expansion (CE) method was used to calculate the energies of various Ni-Mo phases. The clusters comprising of few nearest neighbours can describe any phase of Ni-Mo system by suitable choice of effective pair and multisite interaction parameters (ECI). The ECIs were evaluated in present study by fitting the ground state energies obtained by first principle calculations. The ECIs evaluated for Ni-Mo system were mostly pair clusters followed by triplets and quadruplet clusters with cluster diameters in the range 2.54 - 10.20 Å. The ECI values diminished for multi-body (triplets and quadruplets) clusters as compared to 2-point or pair clusters indicating a good convergence of CE model. With these ECIs the predicted energies of all the Ni-Mo structures across the Mo concentration range 0-100 at% were obtained. The quantitative error in the energies calculated by CE approach and first principle is very small (< 0.026 meV/atom). The appreciable values of 2-point ECIs upto 4th nearest neighbour reveal that two body interactions are dominant in the case of Ni-Mo system. These ECIs are compared with the reported values of compositional dependent effective pair interactions evaluated by first principle as well as by Monte Carlo method.

Magnetization pinning in modulated nanowires: from topological protection to the "corkscrew" mechanism.

PubMed

Fernandez-Roldan, Jose Angel; Perez Del Real, Rafael; Bran, Cristina; Vazquez, Manuel; Chubykalo-Fesenko, Oksana

2018-03-29

Diameter-modulated nanowires offer an important paradigm to design the magnetization response of 3D magnetic nanostructures by engineering the domain wall pinning. With the aim to understand its nature and to control the process, we analyze the magnetization response in FeCo periodically modulated polycrystalline nanowires varying the minor segment diameter. Our modelling indicates a very complex behavior with a strong dependence on the disorder distribution and an important role of topologically non-trivial magnetization structures. We demonstrate that modulated nanowires with a small diameter difference are characterized by an increased coercive field in comparison to the straight ones, which is explained by a formation of topologically protected walls formed by two 3D skyrmions with opposite chiralities. For a large diameter difference we report the occurrence of a novel pinning type called here the "corkscrew": the magnetization of the large diameter segment forms a skyrmion tube with a core position in a helical modulation along the nanowire. This structure is pinned at the constriction and in order to penetrate the narrow segments the vortex/skyrmion core size should be reduced.

Light propagation in Swiss-cheese models of random close-packed Szekeres structures: Effects of anisotropy and comparisons with perturbative results

NASA Astrophysics Data System (ADS)

Koksbang, S. M.

2017-03-01

Light propagation in two Swiss-cheese models based on anisotropic Szekeres structures is studied and compared with light propagation in Swiss-cheese models based on the Szekeres models' underlying Lemaitre-Tolman-Bondi models. The study shows that the anisotropy of the Szekeres models has only a small effect on quantities such as redshift-distance relations, projected shear and expansion rate along individual light rays. The average angular diameter distance to the last scattering surface is computed for each model. Contrary to earlier studies, the results obtained here are (mostly) in agreement with perturbative results. In particular, a small negative shift, δ DA≔D/A-DA ,b g DA ,b g , in the angular diameter distance is obtained upon line-of-sight averaging in three of the four models. The results are, however, not statistically significant. In the fourth model, there is a small positive shift which has an especially small statistical significance. The line-of-sight averaged inverse magnification at z =1100 is consistent with 1 to a high level of confidence for all models, indicating that the area of the surface corresponding to z =1100 is close to that of the background.

Thermocouple design for measuring temperatures of small insects.

PubMed

Hanson, A A; Venette, R C

2013-01-01

Contact thermocouples often are used to measure surface body temperature changes of insects during cold exposure. However, small temperature changes of minute insects can be difficult to detect, particularly during the measurement of supercooling points. We developed two thermocouple designs, which use 0.51 mm diameter or 0.127 mm diameter copper-constantan wires, to improve our ability to resolve insect exotherms. We tested the designs with adults from three parasitoid species: Tetrastichus planipennisi, Spathius agrili, and S. floridanus. These species are <3 mm long and <0.1 mg. Mean exotherms were greater for fine-gauge thermocouples than thick-gauge thermocouples for the smallest species tested, T. planipennisi. This difference was not apparent for larger species S. agrili and S. floridanus. Thermocouple design did not affect the mean supercooling point for any of the species. The cradle thermocouple design developed with the fine gauge wire was reusable and allowed for easy insect recovery after cold exposure.

Mechanical Properties of Hydrogel Beads

NASA Astrophysics Data System (ADS)

Criddle, Keely; Benns, Thomas; Shorts, Dan; Feitosa, Klebert

2015-03-01

Fragile solids made of dense disordered packing of bubbles, droplets and grains are able to withstand small stresses by virtue of system-wide force chains that lock the system into a jammed state. The nature of the jamming transition in such soft materials has been the subject of intense research, but despite much effort, a deep understanding remains elusive. In this experiment we study the mechanical properties of hydrogel beads to exploit them as force transducers in densely packed systems. The experiment consists of applying uniaxial planar compressions on the beads, and correlating the force to the bead's strain and contact area. The results show that while the strain scales linearly with the diameter of the contact area, the force and strain are found to obey a power law relation with two distinct exponents at small and large strains. This result leads to a power law dependence of the force on the contact area diameter of the compressed bead.

System Performance Simulations of the RatCAP Awake Rat Brain Scanner

NASA Astrophysics Data System (ADS)

Shokouhi, S.; Vaska, P.; Schlyer, D. J.; Stoll, S. P.; Villanueva, A.; Kriplani, A.; Woody, C. L.

2005-10-01

The capability to create high quality images from data acquired by the Rat Conscious Animal PET tomograph (RatCAP) has been evaluated using modified versions of the PET Monte Carlo code Simulation System for Emission Tomography (SimSET). The proposed tomograph consists of lutetium oxyorthosilicate (LSO) crystals arranged in 12 4 /spl times/ 8 blocks. The effects of the RatCAPs small ring diameter (/spl sim/40 mm) and its block detector geometry on image quality for small animal studies have been investigated. Since the field of view will be almost as large as the ring diameter, radial elongation artifacts due to parallax error are expected to degrade the spatial resolution and thus the image quality at the edge of the field of view. In addition to Monte Carlo simulations, some preliminary results of experimentally acquired images in both two-dimensional (2-D) and 3-D modes are presented.

New anastomosis technique for (laparoscopic) instrumental small-diameter anastomosis.

PubMed

Schöb, O; Schmid, R; Schlumpf, R; Klotz, H P; Spiess, M; Largiadèr, F

1995-04-01

This study presents a new technique for visceral anastomosis. The principle consists of connecting the two parts to be anastomosed around a reabsorbable stent which is transluminally introduced into small-diameter viscus, where it is fixed. Advancing a larger tube along the axis of the machine, the larger, perforated viscus is inverted and pulled over the stent, and finally a rubber band pops off the machine endoluminally in order to fix the intestinal walls in seroserosal contact onto the stent. To evaluate this "micro" anastomosis, a biliary bypass (choledochojejunostomy and roux-en-y-loop) was performed in ten pigs. Nine of ten animals showed biliary bypass with good runoff in contrast radiography and completely reabsorbed stent after a 3-month follow-up. Weight gain, bilirubin, and alkaline phosphatase were normal. This technology demonstrates a safe and quick way to perform instrumental "micro" anastomosis without remnant foreign material.

Therapeutic Challenge in a Severely Atrophic Mandible

PubMed Central

Janev, Edvard; Janeva, Nadica; Peeva–Petreska, Marija; Mitic, Kristina

2018-01-01

BACKGROUND: After tooth loss, however, severely atrophic residual alveolar ridges are fairly common, especially in patients who have been edentulous for a long period. Anterior area of the mandible is areas where clinicians have greater anatomical limitations. Reduced alveolar bone height very often represents a contraindication to implant therapy, unless a procedure such as a ridge augmentation is performed. CASE REPORT: This study aims to present two separate cases in highly selected edentulous anterior mandibular sites, where one stage, mini implants were used to support total prostheses. Small diameter implants have been used for retention of complete removable mandibular overdentures. This is an excellent option for those who suffer from the inconvenience and embarrassment of loose lower dentures and are tired of having to use sticky pastes and creams to make their dentures stay in place. CONCLUSION: Small diameter implants, when used multiples may offer adequate support for a removable prosthesis and overcome this problem. PMID:29610621

Contrasting styles of welding observed in the proximal Askja 1875 eruption deposits II: Local welding

NASA Astrophysics Data System (ADS)

Carey, R. J.; Houghton, B. F.; Thordarson, T.

2008-03-01

As an alternative to classical welding models of fall deposits due to the progressive accumulation of hot tephra which then weld, we describe here welded deposits on the northern 1875 caldera rim of Askja volcano that have welded due to the influence of hot, discrete spatter bombs impacting into and supplying heat to a halo of surrounding tephra. This style of welding we term 'local welding' in contrast to 'regional welding' which is described elsewhere [Carey, R.J., Houghton, B.F., Thordarson, T., 2008. Contrasting styles of welding observed in the proximal Askja 1875 eruption deposits I: Regional welding. J. Volcanol. Geotherm. Res. 171, 1-19. doi:10.1016/j.jvolgeores.2007.11.020]. Locally welded deposits are associated with the rhyolitic Plinian phase of the 1875 eruption of Askja volcano. Two distinct welding units (W1 and W2) are interbedded with Plinian fall on the northern caldera rim, and grade outwards to weakly dispersed non-welded fall. Spatter bombs are found in both welding units but vary in their characteristic sizes and internal features. In the W1 unit simple bombs with homogeneous internal characteristics up to ˜ 60 cm in diameter are found. In the W2 unit, large discrete spatter bombs with complex internal features range up to 9 m in diameter. We describe here two case studies showing the effects of a) single small spatter bombs; b) multiple small spatter bombs and c) large discrete spatter bombs varying in size. Vertical and lateral profiles through welding zones reveal that the primary controls on local welding are the availability of supplied or added heat and the loading capacity of the spatter bomb. Local welding grades are much higher than that of regional welding, as the combined effects of heat, compaction and insulation can provide suitable conditions which lead to dense welding and, proximal to the spatter bomb, rheomorphic flowage. If heating and loading exceed the critical requirement for welding, porosity loss via matrix welding and vesicle collapse occurs to a point where further strain must be accommodated as shearing and ductile flowage. The spatter bombs are found only within the weakly dispersed welding units and are the final erupted products of each fountaining phase. Their low viscosities are evident by their deformation on impact and fluidal forms, and hold some important clues to eruption dynamics in the shallow conduit and vent regions.

Phase-Angle Dependence of Determinations of Diameter, Albedo, and Taxonomy: A Case Study of NEO 3691 Bede

NASA Technical Reports Server (NTRS)

Wooden, Diane H.; Lederer, Susan M.; Jehin, Emmanuel; Howell, Ellen S.; Fernandez, Yan; Harker, David E.; Ryan, Erin; Lovell, Amy; Woodward, Charles E.; Benner, Lance A.

2015-01-01

Parameters important for NEO risk assessment and mitigation include Near-Earth Object diameter and taxonomic classification, which translates to surface composition. Diameters of NEOs are derived from the thermal fluxes measured by WISE, NEOWISE, Spitzer Warm Mission and ground-based telescopes including the IRTF and UKIRT. Diameter and its coupled parameters Albedo and IR beaming parameter (a proxy for thermal inertia and/or surface roughness) are dependent upon the phase angle, which is the Sun-target-observer angle. Orbit geometries of NEOs, however, typically provide for observations at phase angles greater than 20 degrees. At higher phase angles, the observed thermal emission is sampling both the day and night sides of the NEO. We compare thermal models for NEOs that exclude (NEATM) and include (NESTM) night-side emission. We present a case study of NEO 3691 Bede, which is a higher albedo object, X (Ec) or Cgh taxonomy, to highlight the range of H magnitudes for this object (depending on the albedo and phase function slope parameter G), and to examine at different phase angles the taxonomy and thermal model fits for this NEO. Observations of 3691 Bede include our observations with IRTF+SpeX and with the 10 micrometer UKIRT+Michelle instrument, as well as WISE and Spitzer Warm mission data. By examining 3691 Bede as a case study, we highlight the interplay between the derivation of basic physical parameters and observing geometry, and we discuss the uncertainties in H magnitude, taxonomy assignment amongst the X-class (P, M, E), and diameter determinations. Systematic dependencies in the derivation of basic characterization parameters of H-magnitude, diameter, albedo and taxonomy with observing geometry are important to understand. These basic characterization parameters affect the statistical assessments of the NEO population, which in turn, affects the assignment of statistically-assessed basic parameters to discovered but yet-to-be-fully-characterized NEOs.

Formation of self-ordered porous anodized alumina template for growing tungsten trioxide nanowires

NASA Astrophysics Data System (ADS)

Hussain, Tajamal; Shah, Asma Tufail; Shehzad, Khurram; Mujahid, Adnan; Farooqi, Zahoor Hussain; Raza, Muhammad Hamid; Ahmed, Mirza Nadeem; Nisa, Zaib Un

2015-12-01

Uniform porous anodized aluminum oxide (AAO) membrane has been synthesized by two-step anodization for fabricating tungsten trioxide (WO3) nanowires. Under assayed conditions, uniform porous structure of alumina (Al2O3) membrane with long range ordered hexagonal arrangements of nanopores was achieved. The self-assembled template possesses pores of internal diameter of 50 nm and interpore distance ( d int) of 80 nm with a thickness of about 80 µm, i.e., used for fabrication of nanostructures. WO3 nanowires have been fabricated by simple electroless deposition method inside Al2O3 nanopores. SEM images show tungsten trioxide nanowire with internal diameter of about 50 nm, similar to porous diameter of AAO template. XRD results showed that nanowires exist in cubic crystalline state with minor proportion of monoclinic phase.

Advanced propulsion concepts study: Comparative study of solar electric propulsion and laser electric propulsion

NASA Technical Reports Server (NTRS)

Forward, R. L.

1975-01-01

Solar electric propulsion (SEP) and laser electric propulsion (LEP) was compared. The LEP system configuration consists of an 80 kW visible laser source on earth, transmitting via an 8 m diameter adaptively controlled phased array through the atmosphere to a 4 m diameter synchronous relay mirror that tracks the LEP spacecraft. The only significant change in the SEP spacecraft for an LEP mission is the replacement of the two 3.7 m by 33.5 m solar cell arrays with a single 8 m diameter laser photovoltaic array. The solar cell array weight is decreased from 320 kg to 120 kg for an increase in payload of 200 kg and a decrease in specific mass of the power system from 20.5 kg/kW to 7.8 kg/kW.

High impact strength polymers having novel nano-structures produced via reactive extrusion

NASA Astrophysics Data System (ADS)

Tortorella, Nathan Fraser

A major focus of scientists and engineers over the last century has been to increase the impact strength and therefore reduce the brittleness of materials. By altering and adding energy absorption mechanisms, brittle failure can be averted. Isotactic polypropylene (PP) is the focus of this dissertation because it is an extremely low cost, high volume, versatile plastic but behaves in a brittle manner at or below room temperature or in a notched state. Early work on impact modification of polypropylene focused on blending energy-absorbing low density elastomers and rubbers. These binary blends all had a common problem---an increase in impact strength was paralleled by a significant decrease in both elastic modulus and yield stress. Reactive extrusion processing has allowed the in-situ compatibilization of isotactic polypropylene and metallocene-catalyzed ethylene-octene copolymers (EOCs). This process involves combining both the comonomer and vector fluid approaches to grafting polyolefins. Styrene monomer and a multifunctional acrylate monomer undergo peroxide-induced copolymerization and grafting in the presence of both PP and EOC. This results in a phase separated alloy with an impact strength over 13 times that of pure polypropylene and double that of the physical blend. There is also a significant improvement in stress-strain performance when comparing the alloys to physical blend counterparts. Many researchers have categorized the necessary components to toughening polypropylene as pertaining to the amorphous phase. The alloys described in this dissertation meet the criteria put forth by these researchers, namely low density, crystallinity, and modulus of the elastomer phase, sub-micron particle diameter, close inter-particle distance, and a high degree of entanglements of both the PP matrix phase and EOC minor phase. But many people neglect to study the crystalline state of impact modified PP in conjunction with the amorphous phase. This work shows that the typical 10-100 mum diameter spherulitic structures found in pure PP are not present in the alloys. In fact, the spherulites are less than a micron in diameter, are uniformly distributed throughout the sample, and crystallize at much higher temperatures. SEM images, when coupled with DSC and XRD, reveal the presence of a high number of small lamellar crystals composed of a unique highly dense cross-hatched structure. Thus, impact strength and stiffness can be simultaneously improved by controlling the size and cross-hatch density of the lamellar crystals and applying phase transformation toughening concepts.

Processing of alnico permanent magnets by advanced directional solidification methods

DOE PAGES

Zou, Min; Johnson, Francis; Zhang, Wanming; ...

2016-07-05

Advanced directional solidification methods have been used to produce large (>15 cm length) castings of Alnico permanent magnets with highly oriented columnar microstructures. In combination with subsequent thermomagnetic and draw thermal treatment, this method was used to enable the high coercivity, high-Titanium Alnico composition of 39% Co, 29.5% Fe, 14% Ni, 7.5% Ti, 7% Al, 3% Cu (wt%) to have an intrinsic coercivity (H ci) of 2.0 kOe, a remanence (B r) of 10.2 kG, and an energy product (BH) max of 10.9 MGOe. These properties compare favorably to typical properties for the commercial Alnico 9. Directional solidification of highermore » Ti compositions yielded anisotropic columnar grained microstructures if high heat extraction rates through the mold surface of at least 200 kW/m 2 were attained. This was achieved through the use of a thin walled (5 mm thick) high thermal conductivity SiC shell mold extracted from a molten Sn bath at a withdrawal rate of at least 200 mm/h. However, higher Ti compositions did not result in further increases in magnet performance. Images of the microstructures collected by scanning electron microscopy (SEM) reveal a majority α phase with inclusions of secondary αγ phase. Transmission electron microscopy (TEM) reveals that the α phase has a spinodally decomposed microstructure of FeCo-rich needles in a NiAl-rich matrix. In the 7.5% Ti composition the diameter distribution of the FeCo needles was bimodal with the majority having diameters of approximately 50 nm with a small fraction having diameters of approximately 10 nm. The needles formed a mosaic pattern and were elongated along one <001> crystal direction (parallel to the field used during magnetic annealing). Cu precipitates were observed between the needles. Regions of abnormal spinodal morphology appeared to correlate with secondary phase precipitates. The presence of these abnormalities did not prevent the material from displaying superior magnetic properties in the 7.5% Ti composition. As a result, higher Ti compositions did not display the preferred spinodal microstructure, explaining their inferior magnetic properties.« less