An MDOE Investigation of Chevrons for Supersonic Jet Noise Reduction

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Bridges, James

2010-01-01

The impact of chevron design on the noise radiated from heated, overexpanded, supersonic jets is presented. The experiments used faceted bi-conic convergent-divergent nozzles with design Mach numbers equal to 1.51 and 1.65. The purpose of the facets was to simulate divergent seals on a military style nozzle. The nozzle throat diameter was equal to 4.5 inches. Modern Design of Experiment (MDOE) techniques were used to investigate the impact of chevron penetration, length, and width on the resulting acoustic radiation. All chevron configurations used 12 chevrons to match the number of facets in the nozzle. Most chevron designs resulted in increased broadband shock noise relative to the baseline nozzle. In the peak jet noise direction, the optimum chevron design reduced peak sound pressure levels by 4 dB relative to the baseline nozzle. The penetration was the parameter having the greatest impact on radiated noise at all observation angles. While increasing chevron penetration decreased acoustic radiation in the peak jet noise direction, broadband shock noise was adversely impacted. Decreasing chevron length increased noise at most observation angles. The impact of chevron width on radiated noise depended on frequency and observation angle.

Chevron Behavior and Isostable Enthalpic Barriers in Protein Folding: Successes and Limitations of Simple Gō-like Modeling

PubMed Central

Kaya, Hüseyin; Liu, Zhirong; Chan, Hue Sun

2005-01-01

It has been demonstrated that a “near-Levinthal” cooperative mechanism, whereby the common Gō interaction scheme is augmented by an extra favorability for the native state as a whole, can lead to apparent two-state folding/unfolding kinetics over a broad range of native stabilities in lattice models of proteins. Here such a mechanism is shown to be generalizable to a simplified continuum (off-lattice) Langevin dynamics model with a Cα protein chain representation, with the resulting chevron plots exhibiting an extended quasilinear regime reminiscent of that of apparent two-state real proteins. Similarly high degrees of cooperativity are possible in Gō-like continuum models with rudimentary pairwise desolvation barriers as well. In these models, cooperativity increases with increasing desolvation barrier height, suggesting strongly that two-state-like folding/unfolding kinetics would be achievable when the pairwise desolvation barrier becomes sufficiently high. Besides cooperativity, another generic folding property of interest that has emerged from published experiments on several apparent two-state proteins is that their folding relaxation under constant native stability (isostability) conditions is essentially Arrhenius, entailing high intrinsic enthalpic folding barriers of ∼17–30 kcal/mol. Based on a new analysis of published data on barnase, here we propose that a similar property should also apply to a certain class of non-two-state proteins that fold with chevron rollovers. However, several continuum Gō-like constructs considered here fail to predict any significant intrinsic enthalpic folding barrier under isostability conditions; thus the physical origin of such barriers in real proteins remains to be elucidated. PMID:15863486

Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles

NASA Technical Reports Server (NTRS)

Brown, Clifford A.; Bridges, James

2006-01-01

The link between azimuthal modes in jet turbulence and in the acoustic sound field has been examined in cold, round jets. Chevron nozzles, however, impart an azimuthal structure on the jet with a shape dependent on the number, length and penetration angle of the chevrons. Two particular chevron nozzles, with 3 and 4 primary chevrons respectively, and a round baseline nozzle are compared at both cold and hot jet conditions to determine how chevrons impact the modal structure of the flow and how that change relates to the sound field. The results show that, although the chevrons have a large impact on the azimuthal shape of the mean axial velocity, the impact of chevrons on the azimuthal structure of the fluctuating axial velocity is small at the cold jet condition and smaller still at the hot jet condition. This is supported by results in the azimuthal structure of the sound field, which also shows little difference in between the two chevron nozzles and the baseline nozzle in the distribution of energy across the azimuthal modes measured.

The use of nested chevron rails in a distributed energy store railgun

NASA Astrophysics Data System (ADS)

Marshall, R. A.

1984-03-01

It is pointed out that the large amounts of energy required by electromagnetic launchers will necessitate that energy stores be distributed along their length. The nested chevron rail construction will make it possible for a railgun launcher to be produced in which most of the switching requirements for the launcher/energy store system will be met automatically. Each nested chevron-shaped conductor will be electrically insulated from its neighbors, and each opposing chevron pair (one on each rail) will be connected to the terminals of one energy store (Marshall, 1982). It is explained that as the projectile moves down the railgun the chevrons and associated energy stores at first are unaffected by the approach. At this time the inductors can be charged, and any other preliminary operation can be performed. When the armature comes into contact with the Nth chevron, charge begins to flow from the Nth energy storage system; it flows through one chevron, into the armature, out of the armature into the other chevron, and from that chevron back to the energy storage system.

78 FR 69659 - Chevron U.S.A. Inc. v. Kinder Morgan Louisiana Pipeline LLC; Notice of Complaint

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-20

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. RP14-161-000] Chevron U.S.A... Commission (Commission), 18 CFR 385.206, Chevron U.S.A. Inc. (Chevron or Complainant), filed a complaint..., Commission policy, and contractual obligations. [[Page 69660

Fluidic Chevrons for Jet Noise Reduction

NASA Technical Reports Server (NTRS)

Kinzie, Kevin; Henderson, Brenda; Whitmire, Julia

2004-01-01

Chevron mixing devices are used to reduce noise from commercial separate-flow turbofan engines. Mechanical chevron serrations at the nozzle trailing edge generate axial vorticity that enhances jet plume mixing and consequently reduces far-field noise. Fluidic chevrons generated with air injected near the nozzle trailing edge create a vorticity field similar to that of the mechanical chevrons and allow more flexibility in controlling acoustic and thrust performance than a passive mechanical design. In addition, the design of such a system has the future potential for actively controlling jet noise by pulsing or otherwise optimally distributing the injected air. Scale model jet noise experiments have been performed in the NASA Langley Low Speed Aeroacoustic Wind Tunnel to investigate the fluidic chevron concept. Acoustic data from different fluidic chevron designs are shown. Varying degrees of noise reduction are achieved depending on the injection pattern and injection flow conditions. CFD results were used to select design concepts that displayed axial vorticity growth similar to that associated with mechanical chevrons and qualitatively describe the air injection flow and the impact on acoustic performance.

Testing of SMA-enabled Active Chevron Prototypes under Representative Flow Conditions

NASA Technical Reports Server (NTRS)

Turner, Travis L.; Cabell,Randolph H.; Cano, Roberto J.; Silcox, Richard J.

2008-01-01

Control of jet noise continues to be an important research topic. Exhaust-nozzle chevrons have been shown to reduce jet noise, but parametric effects are not well understood. Additionally, thrust loss due to chevrons at cruise suggests significant benefit from active chevrons. The focus of this study is development of an active chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and secondarily for technology development to leverage for full scale systems. The active chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy (SMA) actuators, termed a SMA hybrid composite (SMAHC). SMA actuators are embedded on one side of the neutral axis of the structure such that thermal excitation, via joule heating, generates a moment and deflects the structure. The performance of two active chevron concepts is demonstrated in the presence of representative flow conditions. One of the concepts is shown to possess significant advantages for the proposed application and is selected for further development. Fabrication and design changes are described and shown to produce a chevron prototype that meets the performance objectives.

Numerical Investigation on Aerodynamic and Combustion Performance of Chevron Mixer Inside an Afterburner.

PubMed

Yong, Shan; JingZhou, Zhang; Yameng, Wang

2014-11-01

To improve the performance of the afterburner for the turbofan engine, an innovative type of mixer, namely, the chevron mixer, was considered to enhance the mixture between the core flow and the bypass flow. Computational fluid dynamics (CFD) simulations investigated the aerodynamic performances and combustion characteristics of the chevron mixer inside a typical afterburner. Three types of mixer, namely, CC (chevrons tilted into core flow), CB (chevrons tilted into bypass flow), and CA (chevrons tilted into core flow and bypass flow alternately), respectively, were studied on the aerodynamic performances of mixing process. The chevrons arrangement has significant effect on the mixing characteristics and the CA mode seems to be advantageous for the generation of the stronger streamwise vortices with lower aerodynamic loss. Further investigations on combustion characteristics for CA mode were performed. Calculation results reveal that the local temperature distribution at the leading edge section of flame holder is improved under the action of streamwise vortices shedding from chevron mixers. Consequently, the combustion efficiency increased by 3.5% compared with confluent mixer under the same fuel supply scheme.

Flight Test Results for Uniquely Tailored Propulsion-Airframe Aeroacoustic Chevrons: Community Noise

NASA Technical Reports Server (NTRS)

Nesbitt, Eric; Mengle, Vinod; Czech, Michael; Callendar, Bryan; Thomas, Russ

2006-01-01

The flow/acoustic environment around the jet exhaust of an engine when installed on an airplane, say, under the wing, is highly asymmetric due to the pylon, the wing and the high-lift devices. Recent scale model tests have shown that such Propulsion Airframe Aeroacoustic (PAA) interactions and the jet mixing noise can be reduced more than with conventional azimuthally uniform chevrons by uniquely tailoring the chevrons to produce enhanced mixing near the pylon. This paper describes the community noise results from a flight test on a large twin-engine airplane using this concept of azimuthally varying chevrons for engines installed under the wing. Results for two different nozzle configurations are described: azimuthally varying "PAA T-fan" chevrons on the fan nozzle with a baseline no-chevron core nozzle and a second with PAA T-fan chevrons with conventional azimuthally uniform chevrons on the core nozzle. We analyze these test results in comparison to the baseline no-chevron nozzle on both spectral and integrated power level bases. The study focuses on the peak jet noise reduction and the effects at high frequencies for typical take-off power settings. The noise reduction and the absolute noise levels are then compared to model scale results. The flight test results verify that the PAA T-fan nozzles in combination with standard core chevron nozzles can, indeed, give a reasonable amount of noise reduction at low frequencies without high-frequency lift during take-off conditions and hardly any impact on the cruise thrust coefficient.

33 CFR 147.825 - Chevron Genesis Spar safety zone.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Chevron Genesis Spar safety zone... (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.825 Chevron Genesis Spar safety zone. (a) Description. The Chevron Genesis Spar, Green Canyon 205A (GC205A), is located at position 27°46′46.365″ N, 90...

33 CFR 147.825 - Chevron Genesis Spar safety zone.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Chevron Genesis Spar safety zone... (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.825 Chevron Genesis Spar safety zone. (a) Description. The Chevron Genesis Spar, Green Canyon 205A (GC205A), is located at position 27°46′46.365″ N, 90...

33 CFR 147.825 - Chevron Genesis Spar safety zone.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Chevron Genesis Spar safety zone... (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.825 Chevron Genesis Spar safety zone. (a) Description. The Chevron Genesis Spar, Green Canyon 205A (GC205A), is located at position 27°46′46.365″ N, 90...

33 CFR 147.825 - Chevron Genesis Spar safety zone.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Chevron Genesis Spar safety zone... (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.825 Chevron Genesis Spar safety zone. (a) Description. The Chevron Genesis Spar, Green Canyon 205A (GC205A), is located at position 27°46′46.365″ N, 90...

Chevron formation of the zebrafish muscle segments

PubMed Central

Rost, Fabian; Eugster, Christina; Schröter, Christian; Oates, Andrew C.; Brusch, Lutz

2014-01-01

The muscle segments of fish have a folded shape, termed a chevron, which is thought to be optimal for the undulating body movements of swimming. However, the mechanism shaping the chevron during embryogenesis is not understood. Here, we used time-lapse microscopy of developing zebrafish embryos spanning the entire somitogenesis period to quantify the dynamics of chevron shape development. By comparing such time courses with the start of movements in wildtype zebrafish and analysing immobile mutants, we show that the previously implicated body movements do not play a role in chevron formation. Further, the monotonic increase of chevron angle along the anteroposterior axis revealed by our data constrains or rules out possible contributions by previously proposed mechanisms. In particular, we found that muscle pioneers are not required for chevron formation. We put forward a tension-and-resistance mechanism involving interactions between intra-segmental tension and segment boundaries. To evaluate this mechanism, we derived and analysed a mechanical model of a chain of contractile and resisting elements. The predictions of this model were verified by comparison with experimental data. Altogether, our results support the notion that a simple physical mechanism suffices to self-organize the observed spatiotemporal pattern in chevron formation. PMID:25267843

Assessment of chevron dikes for the enhancement of physical-aquatic habitat within the Middle Mississippi River, USA

NASA Astrophysics Data System (ADS)

Remo, Jonathan W. F.; Khanal, Anish; Pinter, Nicholas

2013-09-01

Blunt-nosed chevron dikes, a new invention now being widely constructed on the Middle Mississippi River (MMR), have been justified as a tool for enhancing physical-aquatic habitat. Chevron dikes were initially designed to concentrate flow, induce channel scour, and thus facilitate river navigation. More recently, these structures have been justified, in part, for promoting habitat heterogeneity. The ability of chevrons to create and diversify physical-aquatic habitat, however, has not been empirically evaluated. To assess the ability of chevrons to create and diversify physical-aquatic habitat, we compiled hydrologic and geospatial data for three channel reference conditions along a 2.0 km (∼140 ha) reach of the MMR where three chevrons were constructed in late 2007. We used the hydrologic and hydraulic data to construct detailed 2-D hydrodynamic models for three reference condition: historic (circa 1890), pre-chevron, and post-chevron channel conditions. These models documented changes in depths and flow dynamics for a wide range of in-channel discharges. Depth-velocity habitat classes were used to assess change in physical-aquatic habitat patches and spatial statistical tools in order to evaluate the reach-scale habitat patch diversity. Comparisons of pre- and post-chevron conditions revealed increases in deep to very deep (>3.0 m) areas of slow moving (<0.6 m/s) water downstream of these structures under emergent flow conditions (⩽1.5 × mean annual flow [MAF]). Chevron construction added up to 7.6 ha of potential over-wintering habitat (deep [>3.0 m], low velocity [<0.6 m/s]). Chevron construction also created some (0.8-3.8 ha) shallow-water habitat (0-1.5 m depth with a 0-0.6 m/s velocity) for flows ⩽2.0 × MAF and contributed to an 8-35% increase in physical-aquatic-habitat diversity compared to pre-chevron channel conditions. However, modeling of the historic reference condition (less engineered channel, circa 1890) revealed that the historical physical-aquatic-habitat mosaic consisted of a wider and shallower channel with: 45-390% more shallow-water habitat (2.4-11.0 ha) and 22-83% more physical-aquatic-habitat diversity, but little over-wintering habitat (<0.4 ha). Thus, while chevron construction increased over-wintering habitat, shallow-water habitat, and physical-aquatic-habitat diversity relative to the pre-chevron channel condition, these types of physical-aquatic habitat are different from what was historically found along this reach. Constructing chevrons dikes, or other dike-like structures in the river channel, can change the physical-aquatic habitat patch mosaic and likely contribute to small increases in physical-aquatic-habitat heterogeneity. However, differences in the types, quantity, and diversity of physical-aquatic-habitat patches created by chevron dikes in comparison to the physical-aquatic-habitat patch mosaic of historic channel underscore the need for additional research to determine which physical-aquatic-habitat patches are critical for the recovery of endangered or threatened aquatic organisms.

High-Temperature Smart Structures for Engine Noise Reduction and Performance Enhancement

NASA Technical Reports Server (NTRS)

Quackenbush, Todd R.; McKillip, Robert M., Jr.

2011-01-01

One of key NASA goals is to develop and integrate noise reduction technology to enable unrestricted air transportation service to all communities. One of the technical priorities of this activity has been to account for and reduce noise via propulsion/airframe interactions, identifying advanced concepts to be integrated with the airframe to mitigate these noise-producing mechanisms. An adaptive geometry chevron using embedded smart structures technology offers the possibility of maximizing engine performance while retaining and possibly enhancing the favorable noise characteristics of current designs. New high-temperature shape memory alloy (HTSMA) materials technology enables the devices to operate in both low-temperature (fan) and high-temperature (core) exhaust flows. Chevron-equipped engines have demonstrated reduced noise in testing and operational use. It is desirable to have the noise benefits of chevrons in takeoff/landing conditions, but have them deployed into a minimum drag position for cruise flight. The central feature of the innovation was building on rapidly maturing HTSMA technology to implement a next-generation aircraft noise mitigation system centered on adaptive chevron flow control surfaces. In general, SMA-actuated devices have the potential to enhance the demonstrated noise reduction effectiveness of chevron systems while eliminating the associated performance penalty. The use of structurally integrated smart devices will minimize the mechanical and subsystem complexity of this implementation. The central innovations of the effort entail the modification of prior chevron designs to include a small cut that relaxes structural stiffness without compromising the desired flow characteristics over the surface; the reorientation of SMA actuation devices to apply forces to deflect the chevron tip, exploiting this relaxed stiffness; and the use of high-temperature SMA (HTSMA) materials to enable operation in the demanding core chevron environment. The overall conclusion of these design studies was that the cut chevron concept is a critical enabling step in bringing the variable geometry core chevron within reach. The presence of the cut may be aerodynamically undesirable in some respects, but it is present only when the chevron is not immersed in the core jet exhaust. When deployed, the gap closes as the chevron tip enters the high-speed, high-temperature core stream. Aeroacoustic testing and flow visualization support the contention that this cut is inconsequential to chevron performance.

Effect of chevron nozzle penetration on aero-acoustic characteristics of jet at M = 0.8

NASA Astrophysics Data System (ADS)

Nikam, S. R.; Sharma, S. D.

2017-12-01

Aero-acoustic characteristics of a high-speed jet with chevron nozzles are experimentally investigated at a Mach number of 0.8. The main focus is to examine the effects of the extent of chevron penetration and its position in the mixing layer. Chevron nozzles with three different levels of penetration employed at three different longitudinal locations from the nozzle lip are tested, and the results are compared with those of a plain baseline nozzle. The chevrons are found to produce a lobed shear layer through the notched region, thereby increasing the surface area of the jet, particularly in the close vicinity of the nozzle, which increases the mixing and reduces the potential core length. This effect becomes more prominent with increasing penetration closer to the nozzle lip in the thinner mixing layer. Near field and far field noise measurements show distinctly different acoustic features due to chevrons. The chevrons are found to effectively shift the dominant noise source upstream closer to the nozzle. Present investigation proposes a simpler method for locating the dominant noise source from the peak of the centerline velocity decay rate. The overall noise levels registered along the jet edge immediately downstream of the chevrons are higher, but further downstream they are reduced in comparison with the plain baseline nozzle. Also, the chevrons beam the noise towards higher polar angles at higher frequencies. At shallow polar angles with respect to the jet axis in the far field, chevrons suppress the noise at low frequencies with increasing penetration, but for higher polar angles, while they continue to suppress the low frequency noise, at higher frequencies the trend is found to reverse. The noise measured in the near field close to the jet edge is composed of two components: acoustic and hydrodynamic. Of these two components, the chevrons are found to reduce the hydrodynamic component in comparison with the acoustic one.

75 FR 79367 - Combined Notice of Filings #1

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-20

..., December 28, 2010. Docket Numbers: ER10-2785-004. Applicants: Chevron Coalinga Energy Company. Description: Chevron Coalinga Energy Company submits tariff filing per 35: Chevron Coalinga Energy Company Tariff to be...

Equivalent correction in scarf and chevron osteotomy in moderate and severe hallux valgus: a randomized controlled trial.

PubMed

Deenik, Axel; van Mameren, Henk; de Visser, Enrico; de Waal Malefijt, Maarten; Draijer, Frits; de Bie, Rob

2008-12-01

Chevron osteotomy is a widely accepted osteotomy for correction of hallux valgus.(18) Algorithms were developed to overcome the limitations of distal osteotomies. Scarf osteotomy has become popular as a versatile procedure that should be able to correct most cases of acquired hallux valgus. The purpose of this study was to evaluate whether patients with moderate or severe hallux valgus have better correction with a scarf osteotomy as compared to chevron osteotomy. After informed consent, 136 feet in 115 patients were randomized to 66 scarf and 70 chevron osteotomies. Deformities of patients were classified as mild, moderate and severe according to IMA, and both groups were compared with independent t-tests. The results were measured using radiographic HVA, IMA and DMAA measurements. There were no statistical differences in HVA, IMA and DMAA between scarf and chevron osteotomy in mild to moderate hallux valgus. In severe hallux valgus, chevron osteotomy corrected HVA better than scarf osteotomy, although this group consisted of twelve patients only. Five patients in the chevron group and seven in the scarf group developed recurrent subluxation of the metatarsophalangeal joint. In patients with moderate and severe hallux valgus, the results of chevron osteotomy were at least as effective as a scarf osteotomy. Recurrent subluxation of the first metatatarsophalangeal joint was the main cause for insufficient correction. We favor the chevron osteotomy because it is less invasive, without sacrificing correction of HVA and IMA.

Chevron formation of the zebrafish muscle segments.

PubMed

Rost, Fabian; Eugster, Christina; Schröter, Christian; Oates, Andrew C; Brusch, Lutz

2014-11-01

The muscle segments of fish have a folded shape, termed a chevron, which is thought to be optimal for the undulating body movements of swimming. However, the mechanism shaping the chevron during embryogenesis is not understood. Here, we used time-lapse microscopy of developing zebrafish embryos spanning the entire somitogenesis period to quantify the dynamics of chevron shape development. By comparing such time courses with the start of movements in wildtype zebrafish and analysing immobile mutants, we show that the previously implicated body movements do not play a role in chevron formation. Further, the monotonic increase of chevron angle along the anteroposterior axis revealed by our data constrains or rules out possible contributions by previously proposed mechanisms. In particular, we found that muscle pioneers are not required for chevron formation. We put forward a tension-and-resistance mechanism involving interactions between intra-segmental tension and segment boundaries. To evaluate this mechanism, we derived and analysed a mechanical model of a chain of contractile and resisting elements. The predictions of this model were verified by comparison with experimental data. Altogether, our results support the notion that a simple physical mechanism suffices to self-organize the observed spatiotemporal pattern in chevron formation. © 2014. Published by The Company of Biologists Ltd.

A review of chevron-notched fracture specimens

NASA Technical Reports Server (NTRS)

Newman, J. C., Jr.

1984-01-01

The historical development of chevron notched fracture specimens is reviewed. Stress intensity factors and load line displacement solutions proposed for some of these specimens are compared. The original bend bar configurations up to the present day short rod and bar specimens are reviewed. The results of an analytical round robin that was conducted on chevron-notched specimens are presented. In the round robin, stress-intensity factors for either the chevron notched round rod or square bar specimens were calculated. The consensus stress intensity factor (compliance) solution for these specimens is assessed. The stress intensity factor solutions proposed for three and four point bend chevron notched specimens are reviewed.

Publications - GMC 287 | Alaska Division of Geological & Geophysical

Science.gov Websites

of cuttings from the following wells: Chevron USA Inc. Jeanette Island #1, Chevron USA Inc. Karluk #1 , rock-eval, vitrinite reflectance, and gas chromatography of cuttings from the following wells: Chevron

Crash Modification Factors for Chevrons in Iowa

DOT National Transportation Integrated Search

2018-02-02

Although chevron alignment signs have been utilized for some time along horizontal curves, their effectiveness is not well documented. The Crash Modification Factors Clearinghouse includes crash modification factors (CMFs) for chevrons from 0.41 to 1...

Aeroacoustic Improvements to Fluidic Chevron Nozzles

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Kinzie, Kevin; Whitmire, Julia; Abeysinghe, Amal

2006-01-01

Fluidic chevrons use injected air near the trailing edge of a nozzle to emulate mixing and jet noise reduction characteristics of mechanical chevrons. While previous investigations of "first generation" fluidic chevron nozzles showed only marginal improvements in effective perceived noise levels when compared to nozzles without injection, significant improvements in noise reduction characteristics were achieved through redesigned "second generation" nozzles on a bypass ratio 5 model system. The second-generation core nozzles had improved injection passage contours, external nozzle contour lines, and nozzle trailing edges. The new fluidic chevrons resulted in reduced overall sound pressure levels over that of the baseline nozzle for all observation angles. Injection ports with steep injection angles produced lower overall sound pressure levels than those produced by shallow injection angles. The reductions in overall sound pressure levels were the result of noise reductions at low frequencies. In contrast to the first-generation nozzles, only marginal increases in high frequency noise over that of the baseline nozzle were observed for the second-generation nozzles. The effective perceived noise levels of the new fluidic chevrons are shown to approach those of the core mechanical chevrons.

CFD Analyses and Jet-Noise Predictions of Chevron Nozzles with Vortex Stabilization

NASA Technical Reports Server (NTRS)

Dippold, Vance

2008-01-01

The wind computational fluid dynamics code was used to perform a series of analyses on a single-flow plug nozzle with chevrons. Air was injected from tubes tangent to the nozzle outer surface at three different points along the chevron at the nozzle exit: near the chevron notch, at the chevron mid-point, and near the chevron tip. Three injection pressures were used for each injection tube location--10, 30, and 50 psig-giving injection mass flow rates of 0.1, 0.2, and 0.3 percent of the nozzle mass flow. The results showed subtle changes in the jet plume s turbulence and vorticity structure in the region immediately downstream of the nozzle exit. Distinctive patterns in the plume structure emerged from each injection location, and these became more pronounced as the injection pressure was increased. However, no significant changes in centerline velocity decay or turbulent kinetic energy were observed in the jet plume as a result of flow injection. Furthermore, computational acoustics calculations performed with the JeNo code showed no real reduction in jet noise relative to the baseline chevron nozzle.

Assessment of chevron dikes for the enhancement of physical-aquatic habitat within the Middle Mississippi River, USA

NASA Astrophysics Data System (ADS)

Remo, J. W.; Pinter, N.

2012-12-01

Along the Middle Mississippi River (MMR), rehabilitation of aquatic habitat is being undertaken using river-training structures such as the blunt-nose chevron dike. Chevron dikes were initially designed to concentrate flow and thus facilitate river navigation, but this new river-training structure is now justified, in part, as a tool for creating aquatic habitat and promoting habitat heterogeneity. The ability of chevrons to create and diversify physical-aquatic habitat has not been verified. In this study, we used 2-D hydrodynamic modeling and reach-scale habitat metrics to assess changes in physical habitat and habitat heterogeneity for pre-chevron and post-chevron along a 2- km reach of the Mississippi River at St. Louis, MO. A historic reference condition (circa 1890) was also modeled to compare physical habitat in a less engineered river channel versus the new physical-habitat patches created by chevron-dike enhancement. This modeling approach quantified changes in habitat availability and diversity among selected reference conditions for a wide range of in-channel flows. Depth-velocity habitat classes were used for assessment of change in physical-habitat patches, and spatial statistical tools were employed to evaluate the reach-scale habitat patch diversity. Modeling of post-chevron channel conditions revealed increases in deep to very deep (>3.0 m) areas of slow moving (<0.6 m/s) water downstream of these structures under emergent flow conditions (≤ 1.5 x mean annual flow[MAF]) relative to pre-construction conditions. Chevron construction increased potential over-wintering habitat (deep [>3.0 m], low velocity [<0.6 m/s]) by up to 7.6 ha. The addition of the chevrons to the river channel also created some (0.8-3.8 ha) shallow-water habitat (0-1.5 m depth with a 0-0.6 m/s velocity) for flows ≤2.0 x MAF and contributed to an 8-35% increase in physical-habitat diversity compared to pre-chevron channel conditions. Comparison of the historic reference condition (less engineered channel, circa 1890) with the post-chevron channel condition, however, revealed historical conditions consisted of a physical-habitat mosaic comprised of a wider and shallower historic river channel with: very little over-wintering habitat (<0.4 ha), 45-390% more shallow-water habitat (2.4 - 11.0 ha), and 22-83% more physical-habitat diversity. Thus, while chevrons construction within the study reaches increased over-wintering habitat, shallow-water habitat, and physical-habitat diversity relative to the pre-chevron channel condition, the type of physical habitat(s) are different from what was historically found along this reach. Constructing chevrons dikes, or other dike-like structures in the river channel, can change the physical-habitat patch mosaic and likely contribute to small increases in physical-habitat heterogeneity. However, differences in the types, quantity, and diversity of physical-habitat patches created by chevron dikes in comparison to the physical-habitat patch mosaic of historic channel underscore the need for additional research to determine which physical-habitat patches are critical for the recovery of endangered or threatened aquatic organisms.

The relationship between perceived length and egocentric location in Muller-Lyer figures with one versus two chevrons

NASA Technical Reports Server (NTRS)

Welch, Robert B.; Post, Robert B.; Lum, Wayland; Prinzmetal, William

2004-01-01

We examined the apparent dissociation of perceived length and perceived position with respect to the Muller-Lyer (M-L) illusion. With the traditional (two-chevron) figure, participants made accurate open-loop pointing responses at the endpoints of the shaft, despite the presence of a strong length illusion. This apparently non-Euclidean outcome replicated that of Mack, Heuer, Villardi, and Chambers (1985) and Gillam and Chambers (1985) and contradicts any theory of the M-L illusion in which mislocalization of shaft endpoints plays a role. However, when one of the chevrons was removed, a constant pointing error occurred in the predicted direction, as well as a strong length illusion. Thus, with one-chevron stimuli, perceived length and location were no longer completely dissociated. We speculated that the presence of two opposing chevrons suppresses the mislocalizing effects of a single chevron, especially for figures with relatively short shafts.

High Bypass Ratio Jet Noise Reduction and Installation Effects Including Shielding Effectiveness

NASA Technical Reports Server (NTRS)

Thomas, Russell H.; Czech, Michael J.; Doty, Michael J.

2013-01-01

An experimental investigation was performed to study the propulsion airframe aeroacoustic installation effects of a separate flow jet nozzle with a Hybrid Wing Body aircraft configuration where the engine is installed above the wing. Prior understanding of the jet noise shielding effectiveness was extended to a bypass ratio ten application as a function of nozzle configuration, chevron type, axial spacing, and installation effects from additional airframe components. Chevron types included fan chevrons that are uniform circumferentially around the fan nozzle and T-fan type chevrons that are asymmetrical circumferentially. In isolated testing without a pylon, uniform chevrons compared to T-fan chevrons showed slightly more low frequency reduction offset by more high frequency increase. Phased array localization shows that at this bypass ratio chevrons still move peak jet noise source locations upstream but not to nearly the extent, as a function of frequency, as for lower bypass ratio jets. For baseline nozzles without chevrons, the basic pylon effect has been greatly reduced compared to that seen for lower bypass ratio jets. Compared to Tfan chevrons without a pylon, the combination with a standard pylon results in more high frequency noise increase and an overall higher noise level. Shielded by an airframe surface 2.17 fan diameters from nozzle to airframe trailing edge, the T-fan chevron nozzle can produce reductions in jet noise of as much as 8 dB at high frequencies and upstream angles. Noise reduction from shielding decreases with decreasing frequency and with increasing angle from the jet inlet. Beyond an angle of 130 degrees there is almost no noise reduction from shielding. Increasing chevron immersion more than what is already an aggressive design is not advantageous for noise reduction. The addition of airframe control surfaces, including vertical stabilizers and elevon deflection, showed only a small overall impact. Based on the test results, the best overall nozzle configuration design was selected for application to the N2A Hybrid Wing Body concept that will be the subject of the NASA Langley 14 by 22 Foot Subsonic Tunnel high fidelity aeroacoustic characterization experiment. The best overall nozzle selected includes T-fan type chevrons, uniform chevrons on the core nozzle, and no additional pylon of the type that created a strong acoustic effect at lower bypass ratios. The T-fan chevrons are oriented azimuthally away from the ground observer locations. This best overall nozzle compared to the baseline nozzle was assessed, at equal thrust, to produce sufficient installed noise reduction of the jet noise component to enable the N2A HWB to meet NASA s noise goal of 42 dB cumulative below Stage 4.

78 FR 63560 - Notice of Receipt of an Application by Magellan Pipeline Company, L.P., for Issuance of a...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-24

... facilities permitted under a 1995 Presidential Permit issued to Chevron Pipeline Company (``Chevron... Paso, Texas to the U.S. boundary with Mexico. Through corporate transactions, Chevron assigned the...

Comparison of the Modified McBride Procedure and the Distal Chevron Osteotomy for Mild to Moderate Hallux Valgus.

PubMed

Choi, Gi Won; Kim, Hak Jun; Kim, Taik Seon; Chun, Sung Kwang; Kim, Tae Wan; Lee, Yong In; Kim, Kyoung Ho

2016-01-01

Distal metatarsal osteotomy and the modified McBride procedure have each been used for the treatment of mild to moderate hallux valgus. However, few studies have compared the results of these 2 procedures for mild to moderate hallux valgus. The purpose of the present study was to compare the results of distal chevron osteotomy and the modified McBride procedure for treatment of mild to moderate hallux valgus according to the severity of the deformity. We analyzed the data from 45 patients (49.5%; 48 feet [49.0%]), who had undergone an isolated modified McBride procedure (McBride group), and 46 patients (50.5%; 50 feet [51.0%]), who had a distal chevron osteotomy (chevron group). We subdivided each group into those with mild and moderate deformity and compared the clinical and radiologic outcomes between the groups in relation to the severity of the deformity. The improvements in the American Orthopaedic Foot and Ankle Society scale score and the visual analog scale for pain were significantly better for the chevron group for both mild and moderate deformity. The chevron group experienced significantly greater correction in the hallux valgus angle and intermetatarsal angle for both mild and moderate deformity. The chevron group experienced a significantly greater decrease in the grade of sesamoid displacement for patients with moderate deformity. The McBride group had a greater risk of recurrence than did the chevron group for moderate deformity (odds ratio 14.00, 95% confidence interval 3.91 to 50.06, p < .001). The results of the present study have demonstrated the superiority of the distal chevron osteotomy over the modified McBride procedure for mild to moderate deformity. For patients with moderate deformity, the McBride group had a greater risk of hallux valgus recurrence than did the distal chevron group. Therefore, we recommend distal chevron osteotomy rather than a modified McBride procedure for the treatment of mild and moderate hallux valgus. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Computational Analysis of a Chevron Nozzle Uniquely Tailored for Propulsion Airframe Aeroacoustics

NASA Technical Reports Server (NTRS)

Massey, Steven J.; Elmiligui, Alaa A.; Hunter, Craig A.; Thomas, Russell H.; Pao, S. Paul; Mengle, Vinod G.

2006-01-01

A computational flow field and predicted jet noise source analysis is presented for asymmetrical fan chevrons on a modern separate flow nozzle at take off conditions. The propulsion airframe aeroacoustic asymmetric fan nozzle is designed with an azimuthally varying chevron pattern with longer chevrons close to the pylon. A baseline round nozzle without chevrons and a reference nozzle with azimuthally uniform chevrons are also studied. The intent of the asymmetric fan chevron nozzle was to improve the noise reduction potential by creating a favorable propulsion airframe aeroacoustic interaction effect between the pylon and chevron nozzle. This favorable interaction and improved noise reduction was observed in model scale tests and flight test data and has been reported in other studies. The goal of this study was to identify the fundamental flow and noise source mechanisms. The flow simulation uses the asymptotically steady, compressible Reynolds averaged Navier-Stokes equations on a structured grid. Flow computations are performed using the parallel, multi-block, structured grid code PAB3D. Local noise sources were mapped and integrated computationally using the Jet3D code based upon the Lighthill Acoustic Analogy with anisotropic Reynolds stress modeling. In this study, trends of noise reduction were correctly predicted. Jet3D was also utilized to produce noise source maps that were then correlated to local flow features. The flow studies show that asymmetry of the longer fan chevrons near the pylon work to reduce the strength of the secondary flow induced by the pylon itself, such that the asymmetric merging of the fan and core shear layers is significantly delayed. The effect is to reduce the peak turbulence kinetic energy and shift it downstream, reducing overall noise production. This combined flow and noise prediction approach has yielded considerable understanding of the physics of a fan chevron nozzle designed to include propulsion airframe aeroacoustic interaction effects.

Computational Analysis of a Pylon-Chevron Core Nozzle Interaction

NASA Technical Reports Server (NTRS)

Thomas, Russell H.; Kinzie, Kevin W.; Pao, S. Paul

2001-01-01

In typical engine installations, the pylon of an engine creates a flow disturbance that interacts with the engine exhaust flow. This interaction of the pylon with the exhaust flow from a dual stream nozzle was studied computationally. The dual stream nozzle simulates an engine with a bypass ratio of five. A total of five configurations were simulated all at the take-off operating point. All computations were performed using the structured PAB3D code which solves the steady, compressible, Reynolds-averaged Navier-Stokes equations. These configurations included a core nozzle with eight chevron noise reduction devices built into the nozzle trailing edge. Baseline cases had no chevron devices and were run with a pylon and without a pylon. Cases with the chevron were also studied with and without the pylon. Another case was run with the chevron rotated relative to the pylon. The fan nozzle did not have chevron devices attached. Solutions showed that the effect of the pylon is to distort the round Jet plume and to destroy the symmetrical lobed pattern created by the core chevrons. Several overall flow field quantities were calculated that might be used in extensions of this work to find flow field parameters that correlate with changes in noise.

Cathodoluminescence studies of chevron features in semi-polar (11 2 ¯ 2 ) InGaN/GaN multiple quantum well structures

NASA Astrophysics Data System (ADS)

Brasser, C.; Bruckbauer, J.; Gong, Y.; Jiu, L.; Bai, J.; Warzecha, M.; Edwards, P. R.; Wang, T.; Martin, R. W.

2018-05-01

Epitaxial overgrowth of semi-polar III-nitride layers and devices often leads to arrowhead-shaped surface features, referred to as chevrons. We report on a study into the optical, structural, and electrical properties of these features occurring in two very different semi-polar structures, a blue-emitting multiple quantum well structure, and an amber-emitting light-emitting diode. Cathodoluminescence (CL) hyperspectral imaging has highlighted shifts in their emission energy, occurring in the region of the chevron. These variations are due to different semi-polar planes introduced in the chevron arms resulting in a lack of uniformity in the InN incorporation across samples, and the disruption of the structure which could cause a narrowing of the quantum wells (QWs) in this region. Atomic force microscopy has revealed that chevrons can penetrate over 150 nm into the sample and quench light emission from the active layers. The dominance of non-radiative recombination in the chevron region was exposed by simultaneous measurement of CL and the electron beam-induced current. Overall, these results provide an overview of the nature and impact of chevrons on the luminescence of semi-polar devices.

Compliance measurements of chevron notched four point bend specimen

NASA Technical Reports Server (NTRS)

Calomino, Anthony; Bubsey, Raymond; Ghosn, Louis J.

1994-01-01

The experimental stress intensity factors for various chevron notched four point bend specimens are presented. The experimental compliance is verified using the analytical solution for a straight through crack four point bend specimen and the boundary integral equation method for one chevron geometry. Excellent agreement is obtained between the experimental and analytical results. In this report, stress intensity factors, loading displacements and crack mouth opening displacements are reported for different crack lengths and different chevron geometries, under four point bend loading condition.

Reducing Propulsion Airframe Aeroacoustic Interactions with Uniquely Tailored Chevrons. 1.; Isolated Nozzles

NASA Technical Reports Server (NTRS)

Mengle, Vinod G.; Elkroby, Ronen; Brunsniak, Leon; Thomas, Russ H.

2006-01-01

The flow/acoustic environment surrounding an engine nozzle installed on an airplane, say, under the wing, is asymmetric due to the pylon, the wing and the interaction of the exhaust jet with flaps on the wing. However, the conventional chevrons, which are azimuthally uniform serrations on the nozzle lip, do not exploit the asymmetry due to these propulsion airframe aeroacoustic interactions to reduce jet noise. In this pioneering study we use this non-axisymmetry to our advantage and examine if the total jet-related noise radiated to the ground can be reduced by using different types of azimuthally varying chevrons (AVC) which vary the mixing around the nozzle periphery. Several scale models of the isolated nozzle, representative of high bypass ratio engine nozzles, were made with a pylon and azimuthally varying chevrons on both fan and core nozzles to enhance mixing at the top (near the pylon) with less mixing at the bottom (away from the pylon) or vice versa. Various combinations of fan and core AVC nozzles were systematically tested at typical take-off conditions inside a free jet wind-tunnel and, here, in Part 1 we analyze the acoustics results for the isolated nozzle with a pylon, with installation effects reported in Parts 2 and 3. Several interesting results are discovered: amongst the fan AVCs the top-enhanced mixing T-fan chevron nozzle is quieter in combination with any core AVC nozzle when compared to conventional chevrons; however, the bottom-mixing B-fan chevrons, as well as the core AVC nozzles, by themselves, are noisier. Further, the low-frequency source strengths in the jet plume, obtained via phased microphone arrays, also corroborate the far field sound, and for the T-fan chevrons such sources move further downstream than those for baseline or conventional chevron nozzles.

Numerical Prediction of Chevron Nozzle Noise Reduction using Wind-MGBK Methodology

NASA Technical Reports Server (NTRS)

Engblom, W.A.; Bridges, J.; Khavarant, A.

2005-01-01

Numerical predictions for single-stream chevron nozzle flow performance and farfield noise production are presented. Reynolds Averaged Navier Stokes (RANS) solutions, produced via the WIND flow solver, are provided as input to the MGBK code for prediction of farfield noise distributions. This methodology is applied to a set of sensitivity cases involving varying degrees of chevron inward bend angle relative to the core flow, for both cold and hot exhaust conditions. The sensitivity study results illustrate the effect of increased chevron bend angle and exhaust temperature on enhancement of fine-scale mixing, initiation of core breakdown, nozzle performance, and noise reduction. Direct comparisons with experimental data, including stagnation pressure and temperature rake data, PIV turbulent kinetic energy fields, and 90 degree observer farfield microphone data are provided. Although some deficiencies in the numerical predictions are evident, the correct farfield noise spectra trends are captured by the WIND-MGBK method, including the noise reduction benefit of chevrons. Implications of these results to future chevron design efforts are addressed.

Scarf versus chevron osteotomy in hallux valgus: a randomized controlled trial in 96 patients.

PubMed

Deenik, A R; Pilot, P; Brandt, S E; van Mameren, H; Geesink, R G T; Draijer, W F

2007-05-01

The degree of correction of hallux valgus deformity using a distal chevron osteotomy is reported as limited. The scarf osteotomy is reported to correct large intermetatarsal angles (IMA). The purpose of this study was to evaluate if one technique gave greater correction of the IMA and hallux valgus angle (HVA) than the other. After informed consent, 96 feet in 83 patients were randomized into two treatment groups (49 scarf and 47 chevron osteotomies). The results were evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) Hallux Valgus Scale and radiographic HVA and IMA measurements. At 27 (range 23-31) months followup both groups improved. The AOFAS score in the chevron group improved from 48 to 89 points and in the scarf group from 47 to 91 points. In the chevron group the HVA corrected from 30 to 17 degrees, and in the scarf group the HVA corrected from 29 to 18 degrees. In both groups, the IMA was corrected from 13 to 10 degrees. The differences were not statistically significant. Three patients in the chevron group developed a partial metatarsal head necrosis. In the scarf group, four patients developed grade 1 complex regional pain syndrome compared to one patient in the chevron group. No differences of statistical significance could be measured between the two groups with respect to the AOFAS score, HVA, and IMA. Although both groups showed good to excellent results, we favor the chevron osteotomy because the procedure is technically less demanding.

Hazardous Waste Cleanup: Chevron Incorporated-NWPMG00037 Bacon Site in Glenham, New York

EPA Pesticide Factsheets

Chevron, Inc., former Texaco Research Center, also known as Texaco or Chevron Texaco, operated a Research Center in Glenham, New York from 1931 until its closure in 2003. The Main Facility includes all of the developed areas located north of Fishkill Creek

Evaluation of chevron patterns for use on traffic control devices in street and highway work zones.

DOT National Transportation Integrated Search

1980-01-01

The chevron pattern consists of alternate orange and white stripes that form an arrow pointing in the direction in which traffic is being diverted. The objectives of this research were (1) to select the most effective design for the chevron pattern, ...

Impact of Fluidic Chevrons on Supersonic Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Norum, Thomas

2007-01-01

The impact of fluidic chevrons on broadband shock noise and mixing noise for single stream and coannular jets was investigated. Air was injected into the core flow of a bypass ratio 5 nozzle system using a core fluidic chevron nozzle. For the single stream experiments, the fan stream was operated at the wind tunnel conditions and the core stream was operated at supersonic speeds. For the dual stream experiments, the fan stream was operated at supersonic speeds and the core stream was varied between subsonic and supersonic conditions. For the single stream jet at nozzle pressure ratio (NPR) below 2.0, increasing the injection pressure of the fluidic chevron increased high frequency noise at observation angles upstream of the nozzle exit and decreased mixing noise near the peak jet noise angle. When the NPR increased to a point where broadband shock noise dominated the acoustic spectra at upstream observation angles, the fluidic chevrons significantly decreased this noise. For dual stream jets, the fluidic chevrons reduced broadband shock noise levels when the fan NPR was below 2.3, but had little or no impact on shock noise with further increases in fan pressure. For all fan stream conditions investigated, the fluidic chevron became more effective at reducing mixing noise near the peak jet noise angle as the core pressure increased.

Modeling the influence of Chevron alignment sign on young male driver performance: A driving simulator study.

PubMed

Wu, Yiping; Zhao, Xiaohua; Chen, Chen; He, Jiayuan; Rong, Jian; Ma, Jianming

2016-10-01

In China, the Chevron alignment sign on highways is a vertical rectangle with a white arrow and border on a blue background, which differs from its counterpart in other countries. Moreover, little research has been devoted to the effectiveness of China's Chevron signs; there is still no practical method to quantitatively describe the impact of Chevron signs on driver performance in roadway curves. In this paper, a driving simulator experiment collected data on the driving performance of 30 young male drivers as they navigated on 29 different horizontal curves under different conditions (presence of Chevron signs, curve radius and curve direction). To address the heterogeneity issue in the data, three models were estimated and tested: a pooled data linear regression model, a fixed effects model, and a random effects model. According to the Hausman Test and Akaike Information Criterion (AIC), the random effects model offers the best fit. The current study explores the relationship between driver performance (i.e., vehicle speed and lane position) and horizontal curves with respect to the horizontal curvature, presence of Chevron signs, and curve direction. This study lays a foundation for developing procedures and guidelines that would allow more uniform and efficient deployment of Chevron signs on China's highways. Copyright © 2016 Elsevier Ltd. All rights reserved.

Androgynous rex - the utility of chevrons for determining the sex of crocodilians and non-avian dinosaurs.

PubMed

Erickson, Gregory M; Kristopher Lappin, A; Larson, Peter

2005-01-01

The sex of non-avian dinosaurs has been inferred on numerous occasions using a variety of anatomical criteria, but the efficacy of none has been proven. Nearly 50 years ago Romer suggested that the cranial-most or first chevron in the tails of some reptiles, including crocodilians, is sexually dimorphic. Recent work on this subject purportedly substantiated that the female first chevron articulates in a more caudal position than in males. Furthermore, it was concluded that this element is shorter in females. These phenotypic attributes theoretically provide a broader cloacal passageway for eggs by ovipositing females and a greater attachment area for male "penile retractor muscles". Because theropod dinosaurs such as Tyrannosaurus rex presumably show similar variation in chevron anatomy, the same criteria has been advocated for sexing dinosaurs. We tested the neontological model for the chevron sexual dimorphism hypothesis using a skeletonized growth series of American alligators (Alligator mississippiensis) of known sex. No statistical support for the hypothesis was found. Furthermore, analysis of a diversity of crocodilian taxa from museum collections revealed similar findings suggesting the alligator results are not taxon specific. Study of well-preserved tyrannosaurid dinosaurs in museum collections showed nearly invariant chevron positioning like that seen in crocodilians. This suggests the usefulness of chevron anatomy for sexing dinosaurs is tenuous.

Characterization and 3-D modeling of Ni60Ti SMA for actuation of a variable geometry jet engine chevron

NASA Astrophysics Data System (ADS)

Hartl, Darren J.; Lagoudas, Dimitris C.

2007-04-01

This work describes the thermomechanical characterization and FEA modeling of commercial jet engine chevrons incorporating active Shape Memory Alloy (SMA) beam components. The reduction of community noise at airports generated during aircraft take-off has become a major research goal. Serrated aerodynamic devices along the trailing edge of a jet engine primary and secondary exhaust nozzle, known as chevrons, have been shown to greatly reduce jet noise by encouraging advantageous mixing of the streams. To achieve the noise reduction, the secondary exhaust nozzle chevrons are typically immersed into the fan flow which results in drag, or thrust losses during cruise. SMA materials have been applied to this problem of jet engine noise. Active chevrons, utilizing SMA components, have been developed and tested to create maximum deflection during takeoff and landing while minimizing deflection into the flow during the remainder of flight, increasing efficiency. Boeing has flight tested one Variable Geometry Chevron (VGC) system which includes active SMA beams encased in a composite structure with a complex 3-D configuration. The SMA beams, when activated, induce the necessary bending forces on the chevron structure to deflect it into the fan flow and reduce noise. The SMA composition chosen for the fabrication of these beams is a Ni60Ti40 (wt%) alloy. In order to calibrate the material parameters of the constitutive SMA model, various thermomechanical experiments are performed on trained (stabilized) standard SMA tensile specimens. Primary among these tests are thermal cycles at various constant stress levels. Material properties for the shape memory alloy components are derived from this tensile experimentation. Using this data, a 3-D FEA implementation of a phenomenological SMA model is calibrated and used to analyze the response of the chevron. The primary focus of this work is the full 3-D modeling of the active chevron system behavior by considering the SMA beams as fastened to the elastic chevron structure. Experimental and numerical results are compared. Discussion is focused on actuation properties such as tip deflection and chevron bending profile. The model proves to be an accurate tool for predicting the mechanical response of such a system subject to defined thermal inputs.

76 FR 63294 - Chevron Products Company v. SFPP, L.P. ; Notice of Complaint

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-12

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. OR12-1-000; Docket No. IS11-585-000] Chevron Products Company v. SFPP, L.P. ; Notice of Complaint Take notice that on October 5.... 13(1), Chevron Products Company (Complainants) filed a complaint against SFPP, L.P. (Respondent...

Designing a chevron unit for a microelectronic position-sensitive detector with two microchannel plates

NASA Astrophysics Data System (ADS)

Kosulya, A. V.; Verbitskii, V. G.

2017-09-01

The dependence of the transverse section of an electron beam on the distance between plates and on the accelerating potential difference is determined for a chevron unit of a microelectronic position-sensitive detector (MPSD) with two microchannel plates. The geometry of the MPSD chevron unit is designed and optimized.

Chevron nails: a normal variant in the pediatric population.

PubMed

Delano, Sofia; Belazarian, Leah

2014-01-01

A 7-month-old girl was evaluated for V-shaped ridging of the fingernails consistent with chevron nails. Chevron nails are a normal variant in the pediatric population that is frequently outgrown. This case nicely demonstrates this normal finding that has so rarely been reported in the literature. © 2013 Wiley Periodicals, Inc.

Hazardous Waste Cleanup: Chevron Products Company - Division of Chevron USA Incorporated in Perth Amboy, New Jersey

EPA Pesticide Factsheets

The Chevron Refinery is an active, 339-acre facility located in a heavily industrial area on the east side the city of Perth Amboy, Middlesex County, New Jersey. The facility was built by the Barber Asphalt Company in 1920, who operated it as an asphalt

Extended plantar limb (modified) chevron osteotomy versus scarf osteotomy for hallux valgus correction: A randomised controlled trial.

PubMed

Mahadevan, Devendra; Lines, Stephen; Hepple, Stephen; Winson, Ian; Harries, William

2016-06-01

The purpose of this RCT was to compare the extended plantar limb (modified) chevron osteotomy with the scarf osteotomy in correcting hallux valgus deformity and improving functional scores and patient satisfaction. Patients were randomly assigned and kept blind to surgical allocation. Cases requiring additional procedures including the Akin osteotomy were excluded. Outcomes were measured at 1 year following surgery. 84 patients (109 feet) were analysed (60 modified chevron; 49 Scarf). The mean age was 50.7 years (75F: 9M). Post-operative intermetatarsal angle (IMA) was significantly lower in the modified chevron group (5.8° versus 6.9°, p=0.045). Hallux valgus angle and distal metatarsal articular angle were similar. The magnitude of IMA correction with the modified chevron was also significantly greater (9.1° versus 7.1°, p=0.007). Both osteotomies produced comparable MOxFQ scores and satisfaction ratings. The modified chevron was superior to the scarf osteotomy in correcting IMA in hallux valgus deformity. Copyright © 2015 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.

Clinical results of the re-fixation of a Chevron olecranon osteotomy using an intramedullary cancellous screw and suture tension band.

PubMed

Wagener, Marc L; Dezillie, Marleen; Hoendervangers, Yvette; Eygendaal, Denise

2015-04-01

Exposure of the distal humerus in case of an articular fracture is often performed through a Chevron osteotomy of the olecranon. Several options have been described for re-fixation of the Chevron osteotomy. Pull-out of the hard-wear is often seen as complication. In this study, an evaluation of the re-fixation of the Chevron osteotomy through a cancellous screw and suture tension band was performed. The data of 19 patients in whom a Chevron osteotomy was re-fixated with a cancellous screw in combination with a suture tension band were used. Evaluation was performed by assessment of the post-operative X-rays and documentation of complications. In all 19 cases, evaluation of the post-operative X-rays showed complete consolidation without dislocation or other complications. Re-fixation of a Chevron osteotomy of the olecranon with a large cancellous screw with a suture tension band provides adequate stability to result in proper healing of the osteotomy in primary cases when early post-operative mobilisation is allowed. Complications as pull-out of the hard-wear were not reported.

Electro-optic response in thin smectic C* film with chevron structures

NASA Astrophysics Data System (ADS)

Kudreyko, Aleksey A.; Migranov, Nail G.; Migranova, Dana N.

2016-12-01

The effects in electrostatic models of chevron surface-stabilized ferroelectric liquid crystals are investigated through numerical modeling. To study smectic C* director distribution within the cell, we consider two nonlinear approaches: the chevron interface does not interplay with the electric field; the electric field interplays with the chevron interface. The obtained results of the director field distribution are compared with the earlier linearized studies. We find that whether or not the electric field interplays with the chevron interface, the electro-optic response requires a generalized approach for its description. The threshold electric field, which is necessary for switching between two stable director states in the chevron cell is evaluated. This study suggests that, in many cases of practical interest, electro-optic response to the electric field and the threshold electric field can be precisely estimated. We argue that, beside being numerically efficient, our approach provides a convenient and a novel standpoint for looking at the electro-optic response problem. Project supported by the Russian Foundation for Basic Research (RFBR) (Grant Nos. 16-32-00043 and 14-02-97026).

Trailing edge cooling using angled impingement on surface enhanced with cast chevron arrangements

DOEpatents

Lee, Ching-Pang; Heneveld, Benjamin E.; Brown, Glenn E.; Klinger, Jill

2015-05-26

A gas turbine engine component, including: a pressure side (12) having an interior surface (34); a suction side (14) having an interior surface (36); a trailing edge portion (30); and a plurality of suction side and pressure side impingement orifices (24) disposed in the trailing edge portion (30). Each suction side impingement orifice is configured to direct an impingement jet (48) at an acute angle (52) onto a target area (60) that encompasses a tip (140) of a chevron (122) within a chevron arrangement (120) formed in the suction side interior surface. Each pressure side impingement orifice is configured to direct an impingement jet at an acute angle onto an elongated target area that encompasses a tip of a chevron within a chevron arrangement formed in the pressure side interior surface.

Electrothermal Microactuators With Peg Drive Improve Performance for Brain Implant Applications

PubMed Central

Anand, Sindhu; Sutanto, Jemmy; Baker, Michael S.; Okandan, Murat; Muthuswamy, Jit

2013-01-01

This paper presents a new actuation scheme for in-plane bidirectional translation of polysilicon microelectrodes. The new Chevron-peg actuation scheme uses microelectromechanical systems (MEMS) based electrothermal microactuators to move microelectrodes for brain implant applications. The design changes were motivated by specific needs identified by the in vivo testing of an earlier generation of MEMS microelectrodes that were actuated by the Chevron-latch type of mechanism. The microelectrodes actuated by the Chevron-peg mechanism discussed here show improved performance in the following key areas: higher force generation capability (111 μN per heat strip compared to 50 μN), reduced power consumption (91 mW compared to 360 mW), and reliable performance with consistent forward and backward movements of microelectrodes. Failure analysis of the Chevron-latch and the Chevron-peg type of actuation schemes showed that the latter is more robust to wear over four million cycles of operation. The parameters for the activation waveforms for Chevron-peg actuators were optimized using statistical analysis. Waveforms with a 1-ms time period and a 1-Hz frequency of operation showed minimal error between the expected and the actual movement of the microelectrodes. The new generation of Chevron-peg actuators and microelectrodes are therefore expected to enhance the longevity and performance of implanted microelectrodes in the brain.  [2011-0341] PMID:24431926

76 FR 35880 - Chevron Products Company v. SFPP, L.P.; Notice of Complaint

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-20

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. OR11-16-000] Chevron Products Company v. SFPP, L.P.; Notice of Complaint Take notice that on June 13, 2011, pursuant to 13(1) of... Proceedings, 18 CFR 343.1(a), Chevron Products Company (Complaint) filed a formal complaint challenging the...

76 FR 35881 - Chevron Products Company v. SFPP, L.P.; Notice of Complaint

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-20

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. OR11-15-000] Chevron Products Company v. SFPP, L.P.; Notice of Complaint Take notice that on June 13, 2011, pursuant to 13(1) of... Proceedings, 18 CFR 343.1(a), Chevron Products Company (Complainant) filed a formal complaint against SFPP, L...

78 FR 42061 - Notice of Complaint; Chevron Products Company v. Enterprise TE Products Pipeline Company, LLC

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-15

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. OR13-26-000] Notice of Complaint; Chevron Products Company v. Enterprise TE Products Pipeline Company, LLC Take notice that on July... Procedural Rules Applicable to Oil Pipeline Proceedings, 18 CFR 343.1(a) and 343.2(c), Chevron Products...

The energy spectrum of a microchannel multiplier with two microchannel plates in the chevron assembly

NASA Astrophysics Data System (ADS)

Kosulya, A. V.; Verbitskii, V. G.

2017-11-01

A mathematical model of the response of a microchannel multiplier based on two microchannel plates in the chevron assembly has been considered. Analytical expressions relating the parameters of input and output signals have been obtained. The geometry of the chevron unit has been determined, and it has been optimized.

75 FR 51479 - Notice of Availability of the Final Environmental Impact Statement for the Chevron Energy...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-20

... (EIS) for the Chevron Energy Solutions/Solar Millennium (CESSM), LLC's Blythe Solar Power Plant (BSPP... project and amend the CDCA Plan to prohibit solar energy projects on the project site. The BLM will take..., LVRWB09B2600] Notice of Availability of the Final Environmental Impact Statement for the Chevron Energy...

Impact of New Chevron Configurations on Mixing Enhancement in Subsonic Jets

NASA Astrophysics Data System (ADS)

Mullick, Sunayan

A major contributor to the overall noise of an aircraft is jet noise - the noise generated by the gases exiting the exhaust nozzle of a jet engine. One approach to mitigate jet noise is through the implementation of chevron nozzles. In the present context, first, a baseline axisymmetric separate-flow nozzle, termed the 3BB model, with an external plug having a bypass ratio of 5 is analyzed. The specifications of this nozzle are taken from an acoustic study carried out at the NASA John H. Glenn Research Center. Then, various chevron configurations are added to the core and fan nozzles to produce three chevron nozzles. Of these, two are presented as modified versions of the conventional chevron nozzle and form the essence of this work. The third chevron nozzle represents the conventional chevron nozzle in use today. For all the nozzles considered in this study, the flow conditions used represent the takeoff environment of a contemporary subsonic aircraft. The fan nozzle total pressure is set to 1.8 atm while the core nozzle total pressure is 1.65 atm. The total temperature inside the fan nozzle is set to 333.3 K while the core nozzle has a total temperature of 833.3 K. The freestream conditions are given as: static pressure = 0.98 atm, total pressure = 1.04 atm, total temperature = 298.8 K and Mach number = 0.28. For the three chevron nozzles, the core and fan nozzles have 12 chevrons each. Each chevron extends over a sector of 30 degrees of the circumference. To carry out the study presented herein, first, computer-aided design (CAD) models of the four nozzles are created. These models are then used to carry out computational fluid dynamics (CFD) simulations with the conditions stated above. The CFD simulations are performed on STAR-CCM+. The results of the simulations carried out for the baseline nozzle are compared with existing experimental and numerical data to validate the use of STAR-CCM+ as a tool for studying jet flows. Once this step is complete, numerical simulations are carried out for the three chevron nozzles. The results from these are compared with those obtained for the baseline nozzle. The turbulent kinetic energy (TKE) and the mean axial velocity are the two main parameters that represent mixing enhancement and are focused on in this work. Since the TKE levels for a given nozzle are directly linked to the jet noise generated, the TKE is an important indication of the jet noise produced by a given nozzle. Other jet mixing parameters such as the centerline total temperature decay and the centerline velocity of the jet flow exiting each nozzle are also analyzed. A 2-D axisymmetric grid is produced for the 3BB nozzle while a 3-D mesh is generated for each of the chevron nozzles. To reduce the computation cost, only a 30° sector of the chevron nozzles is modeled. Since the Shear Stress Transport (SST) k-o turbulence model has been widely used in several aerospace applications, it is chosen for all simulations here as well. The numerical analysis shows that STAR-CCM+ can successfully be used for the study of jet flows. Although some shortcomings do exist, the simulations provide a reasonable understanding of jet flows. Of the three chevron nozzles studied, the simulations demonstrate that in comparison to the baseline nozzle, all three chevron nozzles register peak values of the turbulent kinetic energy that are lower than that observed for the 3BB nozzle. The regions of highest turbulence also appear further upstream for the chevron nozzles. Compared to the conventional chevron nozzle, the two parametric designs presented in this work show a potential reduction in the peak values of the turbulent kinetic energy in their respective flows. A slight reduction in the mean axial velocities is also observed for these nozzles. Further, a close inspection of the turbulent flowfield of one of the parametric designs shows that the highest intensity turbulence in the flow is first observed at the most upstream location for this nozzle. The high levels of TKE are also confined to a smaller region in this case. Based on these results, the two parametric chevron nozzle designs demonstrate a potential to produce lower jet noise than what is observed in case of a conventional chevron nozzle. Finally, a study of the turbulent flowfields of all the nozzles shows that the mixing between the fan and freestream shear layers still dominates the mixing in the jet flow. However, the chevrons are able to add streamwise vortices to the flow that enhance mixing between the core and fan shear layers to some extent. This promotes better mixing and as a result, the turbulence in the jet plume is reduced.

Plantar-to-dorsal compared to dorsal-to-plantar screw fixation for proximal chevron osteotomy: a biomechanical analysis.

PubMed

Sharma, Krishn M; Parks, Brent G; Nguyen, Augustine; Schon, Lew C

2005-10-01

A change in screw orientation in fixing the chevron proximal first metatarsal osteotomy was noted anecdotally to improve fixation strength. The authors hypothesized that plantar-to-dorsal screw orientation would be more stable than the conventional dorsal-to-plantar screw orientation for fixation of the chevron osteotomy. The purpose of this study was to determine if the load-to-failure and stiffness of the chevron type proximal first metatarsal osteotomy stabilized using plantar-to-dorsal screw fixation were greater than with the more conventional dorsal-to-plantar screw fixation method. One foot from each of eight matched cadaver pairs was randomly assigned to one of two groups: 1) fixation with a dorsal-to-plantar lag screw or 2) fixation with a plantar-to-dorsal lag screw. A proximal chevron osteotomy was then created using standard technique and the metatarsal was fixed according to previously established method. The bone was potted in polyester resin, and the construct was fitted into a materials testing system machine in which load was applied to the plantar aspect of the metatarsal until failure. The two groups were compared using a two-tailed Student t test. The average load-to-failure and stiffness of the chevron osteotomy fixed with the plantar-to-dorsal lag screw were significantly greater (p < 0.05) than the group fixed with more conventional dorsal-to-plantar lag screws. Plantar-to-dorsal screw orientation was more stable than the conventional dorsal-to-plantar screw orientation for fixation of the proximal chevron osteotomy. Plantar-to-dorsal screw orientation should be considered when using the chevron proximal first metatarsal osteotomy.

Comparison of Chevron and Distal Oblique Osteotomy for Bunion Correction.

PubMed

Scharer, Brandon M; DeVries, J George

2016-01-01

The chevron osteotomy is a standard procedure by which bunions are corrected. One of us routinely performs a distal oblique osteotomy, which, to the best of our knowledge, has not been described for the correction of bunion deformities. The purpose of the present study was to compare the short- and medium-term results of the distal oblique and chevron osteotomies for bunion correction. We performed a retrospective clinical and radiographic comparison of patients who had undergone a distal oblique or chevron osteotomy for the correction of bunion deformity. In addition, a prospective patient satisfaction survey was undertaken. A total of 55 patients were included in the present study and were treated from January 2012 to November 2014. Of the 55 patients, 27 (49.2%) were in the chevron group and 28 (50.8%) in the distal oblique group. Radiographically, no statistically significant difference was found between the 2 groups with respect to postoperative first intermetatarsal angle (p < .0001) and hallux valgus angle (p < .0001), but a greater change was found in the intermetatarsal angle in the distal oblique group (p = .467). Prospective patient satisfaction scores were available for 33 patients (60%), 16 (29%) in the chevron group and 17 (31%) in the distal oblique group. When converting the satisfaction score to a numerical score, the chevron group scored 3.3 ± 1.1 and the distal oblique group scored 3.2 ± 0.8 (p = .812). We found that the distal oblique osteotomy used in the present study is simple and reliable and showed radiographic correction and patient satisfaction equivalent to those in the chevron osteotomy. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

The risk of avascular necrosis following chevron osteotomy: a prospective study using bone scintigraphy.

PubMed

Shariff, Raheel; Attar, Fahad; Osarumwene, Donald; Siddique, Rehan; Attar, Gulam Dastagir

2009-04-01

Controversy exists with regard to the effects of chevron osteotomy on blood supply and subsequent development of avascular necrosis (AVN) of the first metatarsal head. The aim of this study was to assess the incidence of avascular necrosis in our centre following chevron osteotomy for hallux valgus, using bone scintigraphy. Thirty nine patients who had a chevron osteotomy for treatment of hallux valgus were prospectively studied. Mean follow-up was 14 months. Bone scintigraphy was used to assess metatarsal head perfusion at an average 8.5 weeks post operatively. Three patients (7.7%) showed abnormal bone scan around the metatarsal head. Further evaluation of these patients did not show any sign of AVN. We conclude there appears to be a risk of circulatory disturbance to the metatarsal head following chevron osteotomy of the first metarsal (7.7% in this study); however this does not translate into clinically significant AVN.

Bulk properties of solution-synthesized chevron-like graphene nanoribbons.

PubMed

Vo, Timothy H; Shekhirev, Mikhail; Lipatov, Alexey; Korlacki, Rafal A; Sinitskii, Alexander

2014-01-01

Graphene nanoribbons (GNRs) have received a great deal of attention due to their promise for electronic and optoelectronic applications. Several recent studies have focused on the synthesis of GNRs by the bottom-up approaches that could yield very narrow GNRs with atomically precise edges. One type of GNRs that has received a considerable attention is the chevron-like GNR with a very distinct periodic structure. Surface-assisted and solution-based synthetic approaches for the chevron-like GNRs have been developed, but their electronic properties have not been reported yet. In this work, we synthesized chevron-like GNRs in bulk by a solution-based method, characterized them by a number of spectroscopic techniques and measured their bulk conductivity. We demonstrate that solution-synthesized chevron-like GNRs are electrically conductive in bulk, which makes them a potentially promising material for applications in organic electronics and photovoltaics.

Active Noise Control of Radiated Noise from Jets Originating NASA

NASA Technical Reports Server (NTRS)

Doty, Michael J.; Fuller, Christopher R.; Schiller, Noah H.; Turner, Travis L.

2013-01-01

The reduction of jet noise using a closed-loop active noise control system with highbandwidth active chevrons was investigated. The high frequency energy introduced by piezoelectrically-driven chevrons was demonstrated to achieve a broadband reduction of jet noise, presumably due to the suppression of large-scale turbulence. For a nozzle with one active chevron, benefits of up to 0.8 dB overall sound pressure level (OASPL) were observed compared to a static chevron nozzle near the maximum noise emission angle, and benefits of up to 1.9 dB OASPL were observed compared to a baseline nozzle with no chevrons. The closed-loop actuation system was able to effectively reduce noise at select frequencies by 1-3 dB. However, integrated OASPL did not indicate further reduction beyond the open-loop benefits, most likely due to the preliminary controller design, which was focused on narrowband performance.

75 FR 18497 - Chevron Keystone Gas Storage, LLC; Notice of Notification of Change in Market Power Analysis and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-12

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. PR10-13-000; PR03-17-000] Chevron Keystone Gas Storage, LLC; Notice of Notification of Change in Market Power Analysis and Request for Renewed Approval of Market-Based Rates April 5, 2010. Take notice that on March 31, 2010, Chevron...

The Chevron ENCORE Midcareer Program and the Mid-life Career Change to Teaching Science and Mathematics Study.

ERIC Educational Resources Information Center

Madfes, Tania J.

In 1986, responding to the nation's teacher shortage, especially in the fields of mathematics and science, Chevron USA funded the ENCORE Program to facilitate the entrance of nontraditional recruits into the profession with alternative credentialing. Chevron also funded this study of mid-life career change to teaching in order to enable…

MASH full-scale crash testing of 4-ft mounting height, 24"\\0xD730" Chevron sign installed on 5.5H:1V slope ditch.

DOT National Transportation Integrated Search

2013-03-01

Current TxDOT practice allows installation of all existing chevron sizes on 7-ft mounting height, but restricts the use of 4-ft mounting height for the three smallest existing chevron signsthat is, 12 inches 18 inches, 18 inches 24 inches, a...

Experimental investigation of heat transfer and effectiveness in corrugated plate heat exchangers having different chevron angles

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; İpek, Osman

2017-02-01

In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.

Compliance calibration of the short rod chevron-notch specimen for fracture toughness testing of brittle materials

NASA Technical Reports Server (NTRS)

Bubsey, R. T.; Pierce, W. S.; Shannon, J. L., Jr.; Munz, D.

1982-01-01

The short rod chevron-notch specimen has the advantages of (1) crack development at the chevron tip during the early stage of test loading, and (2) convenient calculation of plane-strain fracture toughness from the maximum test load and from a calibration factor which depends only on the specimen geometry and manner of loading. For generalized application, calibration of the specimen over a range of specimen proportions and chevron-notch configurations is necessary. Such was the objective of this investigation, wherein calibration of the short rod specimen was made by means of experimental compliance measurements converted into dimensionless stress intensity factor coefficients.

Relation between textured surface and diffuse reflectance of Cu films

NASA Astrophysics Data System (ADS)

Shukla, Gaurav; Angappane, S.

2018-04-01

Cu nanostructures namely chevron, slanted and vertical posts deposited on Si substrate by glancing angle deposition (GLAD) technique using DC magnetron sputtering are studied to understand the optical reflectance properties of various textures. The X-ray diffraction analysis confirmed the crystalline nature of the different structures of deposited Cu films. The FESEM images confirmed the formation of chevron, slanted and vertical posts. From the optical reflectance spectra, we found that the reflectance is more for chevron than vertical and slanted posts which have almost the same reflectance over the entire wavelength. The films with chevron texture would find various applications, like, light detector, light trapping, sensors etc.

Design, fabrication, and testing of a SMA hybrid composite jet engine chevron

NASA Technical Reports Server (NTRS)

Turner, Travis L.; Cabell, Randolph H.; Cano, Roberto J.; Fleming, Gary A.

2006-01-01

Control of jet noise continues to be an important research topic. Exhaust nozzle chevrons have been shown to reduce jet noise, but parametric effects are not well understood. Additionally, thrust loss due to chevrons at cruise suggests significant benefit from deployable chevrons. The focus of this study is development of an active chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and technology development to leverage for full scale systems. The active chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy (SMA) actuators, termed a SMA hybrid composite (SMAHC). The actuators are embedded on one side of the middle surface such that thermal excitation generates a moment and deflects the structure. A brief description of the chevron design is given followed by details of the fabrication approach. Results from bench top tests are presented and correlated with numerical predictions from a model for such structures that was recently implemented in MSC.Nastran and ABAQUS. Excellent performance and agreement with predictions is demonstrated. Results from tests in a representative flow environment are also presented. Excellent performance is again achieved for both open- and closed-loop tests, the latter demonstrating control to a specified immersion into the flow. The actuation authority and immersion performance is shown to be relatively insensitive to nozzle pressure ratio (NPR). Very repeatable immersion control with modest power requirements is demonstrated.

Active Chevrons for Jet Noise Reduction

NASA Technical Reports Server (NTRS)

Depuru-Mohan, N. K.; Doty, M. J.

2017-01-01

Jet noise is often a dominant component of aircraft noise, particularly at takeoff. To meet the stringent noise regulations, the aircraft industry is in a pressing need of advanced noise reduction concepts. In the present study, the potential of piezoelectrically-activated chevrons for jet noise reduction was experimentally investigated. The perturbations near the nozzle exit caused by piezoelectrically-activated chevrons could be used to modify the growth rate of the mixing layer and thereby potentially reduce jet noise. These perturbations are believed to increase the production of small-scale disturbances at the expense of large-scale turbulent structures. These large-scale turbulent structures are responsible for the dominant portion of the jet mixing noise, particularly low-frequency noise. Therefore, by exciting the static chevron geometry through piezoelectric actuators, an additional acoustic benefit could possibly be achieved. To aid in the initial implementation of this concept, several flat-faced faceted nozzles (four, six, and eight facets) were investigated. Among the faceted nozzles, it was found that the eight-faceted nozzle behaves very similarly to the round nozzle. Furthermore, among the faceted nozzles with static chevrons, the four-faceted nozzle with static chevrons was found to be most effective in terms of jet noise reduction. The piezoelectrically-activated chevrons reduced jet noise up to 2 dB compared to the same nozzle geometry without excitation. This benefit was observed over a wide range of excitation frequencies by applying very low voltages to the piezoelectric actuators.

Scarf versus chevron osteotomy for the correction of 1-2 intermetatarsal angle in hallux valgus: a systematic review and meta-analysis.

PubMed

Smith, Simon E; Landorf, Karl B; Butterworth, Paul A; Menz, Hylton B

2012-01-01

The chevron and scarf osteotomies are commonly used for the surgical management of hallux valgus (HV). However, there is debate as to whether one osteotomy provides more 1-2 intermetatarsal (1-2 IMA) correction than the other. The objective of this systematic review and meta-analysis was to compare the effectiveness of 3 types of first metatarsal osteotomy for reducing the 1-2 IMA in HV correction: the chevron osteotomy, the long plantar arm (modified) chevron osteotomy, and the scarf osteotomy. A systematic search for eligible studies was performed of the following databases: Medline, Embase (Ovid), CINAHL (EBSCO Host), and The Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Clinical Trials. Only English-language studies previous to May 2010 were included in the review. Additional hand and electronic content searches of relevant foot and orthopaedic journals were performed. Criteria for inclusion in this analysis included systematic reviews of randomized controlled trials, prospective and retrospective cohort studies, and case-control studies, as well as case-series studies involving the chevron, scarf, or long plantar arm chevron osteotomy of >20 participants with a minimum of 80% follow-up. Quality of evidence of the included studies was assessed with the Grading of Recommendations Assessment, Development and Evaluation system. All pooled analyses were based on a fixed effects model. There was a total of 1351 participants who underwent either a chevron (n = 1028), scarf (n = 300), or long plantar arm chevron osteotomy (n = 23). Only one study for the long plantar arm chevron group fitted the eligibility criteria for this review; however, it was not amenable to meta-analysis. The chevron osteotomy was associated with a mean reduction of 1-2 IMA from preoperative to postoperative of 5.33° (95% confidence interval, 5.12 to 5.54, p < .001), and the scarf osteotomy was associated with a mean reduction of 6.21° (95% confidence interval, 5.70 to 6.72, p < .001). There was a statistically significant 0.88° increase in the correction of the 1-2 IMA in favor of the scarf osteotomy compared with the chevron osteotomy. The studies included in this review were of very low- to low-quality evidence. Our findings indicate that the scarf osteotomy provides greater correction of the 1-2 IMA when used for HV correction. However, only a weak recommendation in favor of the scarf osteotomy can be made based on the low quality of evidence of the studies included in this analysis. Copyright © 2012 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

The chevron osteotomy and avascular necrosis.

PubMed

Rothwell, Matthew; Pickard, James

2013-03-01

Avascular necrosis (AVN) of the first metatarsal head following the chevron procedure for hallux valgus correction, has been reported widely in the literature; however, in practice it is rarely encountered and may be an over reported myth associated with the chevron technique. Although an infrequent complication, the consequences for those who develop post-operative AVN can be severe. This paper presents an overview of the pathogenesis and classification of AVN. It reviews the vascular anatomy of the first metatarsal with reference to the surgical technique of chevron osteotomy with lateral release. Imaging techniques are described and the management of AVN and revision surgery are also discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.

Chevron cutting: Experiment with new runway mixtures

NASA Technical Reports Server (NTRS)

Tyran, K. (Compiler)

1978-01-01

Chevron cutting is shown to occur in different forms depending on the type of tire and the rubber on the running surface. Hardest wear is shown by the main tires of the B-747. Four defects occurred, in the form of two rip separation and two breakouts of the running surface. Tires capped by Thompson are more affected than any of the other rubber-capping fabrics. For Thompson tires, Chevron Cutting is greatly reduced with a fiberglass-rubber mixture. For Goodyear tires, it is eliminated with spiral wrap rubbercapping; resistance to damages through cuts seems to be more positive for Goodyear tires. For Mader tires, the extent of Chevron Cutting is generally smaller than for Thompson cappings.

Intelligent Engine Systems: Acoustics

NASA Technical Reports Server (NTRS)

Wojno, John; Martens, Steve; Simpson, Benjamin

2008-01-01

An extensive study of new fan exhaust nozzle technologies was performed. Three new uniform chevron nozzles were designed, based on extensive CFD analysis. Two new azimuthally varying variants were defined. All five were tested, along with two existing nozzles, on a representative model-scale, medium BPR exhaust nozzle. Substantial acoustic benefits were obtained from the uniform chevron nozzle designs, the best benefit being provided by an existing design. However, one of the azimuthally varying nozzle designs exhibited even better performance than any of the uniform chevron nozzles. In addition to the fan chevron nozzles, a new technology was demonstrated, using devices that enhance mixing when applied to an exhaust nozzle. The acoustic benefits from these devices applied to medium BPR nozzles were similar, and in some cases superior to, those obtained from conventional uniform chevron nozzles. However, none of the low noise technologies provided equivalent acoustic benefits on a model-scale high BPR exhaust nozzle, similar to current large commercial applications. New technologies must be identified to improve the acoustics of state-of-the-art high BPR jet engines.

Chevron closing base wedge bunionectomy.

PubMed

Bruyn, J M

1993-01-01

The Chevron-base wedge Association for Osteosynthesis fixated bunionectomy provides a stable, aggressive correction of the severe hallux abducto valgus deformity. It is intended for the bunion requiring a double osteotomy in order to adequately reduce both intermetatarsal and proximal articular facet angle with minimal shortening and elevation. This article presents the rationale for the procedure, technique, and a 4-year follow-up of six patients with eight Chevron-base wedge bunionectomies.

Instability waves and low-frequency noise radiation in the subsonic chevron jet

NASA Astrophysics Data System (ADS)

Ran, Lingke; Ye, Chuangchao; Wan, Zhenhua; Yang, Haihua; Sun, Dejun

2017-11-01

Spatial instability waves associated with low-frequency noise radiation at shallow polar angles in the chevron jet are investigated and are compared to the round counterpart. The Reynolds-averaged Navier-Stokes equations are solved to obtain the mean flow fields, which serve as the baseflow for linear stability analysis. The chevron jet has more complicated instability waves than the round jet, where three types of instability modes are identified in the vicinity of the nozzle, corresponding to radial shear, azimuthal shear, and their integrated effect of the baseflow, respectively. The most unstable frequency of all chevron modes and round modes in both jets decrease as the axial location moves downstream. Besides, the azimuthal shear effect related modes are more unstable than radial shear effect related modes at low frequencies. Compared to a round jet, a chevron jet reduces the growth rate of the most unstable modes at downstream locations. Moreover, linearized Euler equations are employed to obtain the beam pattern of pressure generated by spatially evolving instability waves at a dominant low frequency St=0.3 , and the acoustic efficiencies of these linear wavepackets are evaluated for both jets. It is found that the acoustic efficiency of linear wavepacket is able to be reduced greatly in the chevron jet, compared to the round jet.

Instability waves and low-frequency noise radiation in the subsonic chevron jet

NASA Astrophysics Data System (ADS)

Ran, Lingke; Ye, Chuangchao; Wan, Zhenhua; Yang, Haihua; Sun, Dejun

2018-06-01

Spatial instability waves associated with low-frequency noise radiation at shallow polar angles in the chevron jet are investigated and are compared to the round counterpart. The Reynolds-averaged Navier-Stokes equations are solved to obtain the mean flow fields, which serve as the baseflow for linear stability analysis. The chevron jet has more complicated instability waves than the round jet, where three types of instability modes are identified in the vicinity of the nozzle, corresponding to radial shear, azimuthal shear, and their integrated effect of the baseflow, respectively. The most unstable frequency of all chevron modes and round modes in both jets decrease as the axial location moves downstream. Besides, the azimuthal shear effect related modes are more unstable than radial shear effect related modes at low frequencies. Compared to a round jet, a chevron jet reduces the growth rate of the most unstable modes at downstream locations. Moreover, linearized Euler equations are employed to obtain the beam pattern of pressure generated by spatially evolving instability waves at a dominant low frequency St=0.3, and the acoustic efficiencies of these linear wavepackets are evaluated for both jets. It is found that the acoustic efficiency of linear wavepacket is able to be reduced greatly in the chevron jet, compared to the round jet.

Design, Fabrication, and Testing of SMA Enabled Adaptive Chevrons for Jet Noise Reduction

NASA Technical Reports Server (NTRS)

Turner, Travis L.; Buehrle, Ralph D.; Cano, Roberto J.; Fleming, Gary A.

2004-01-01

This study presents the status and results from an effort to design, fabricate, and test an adaptive jet engine chevron concept based upon embedding shape memory alloy (SMA) actuators in a composite laminate, termed a SMA hybrid composite (SMAHC). The approach for fabricating the adaptive SMAHC chevrons involves embedding prestrained Nitinol actuators on one side of the mid-plane of the composite laminate such that thermal excitation generates a thermal moment and deflects the structure. A glass-epoxy pre-preg/Nitinol ribbon material system and a vacuum hot press consolidation approach are employed. A versatile test system for control and measurement of the chevron deflection performance is described. Projection moire interferometry (PMI) is used for global deformation measurement and infrared (IR) thermography is used for 2-D temperature measurement and feedback control. A recently commercialized constitutive model for SMA and SMAHC materials is used in the finite element code ABAQUS to perform nonlinear static analysis of the chevron prototypes. Excellent agreement is achieved between the predicted and measured chevron deflection performance, thereby validating the design tool. Although the performance results presented in this paper fall short of the requirement, the concept is proven and an approach for achieving the performance objectives is evident.

Multi-phase inversion tectonics related to the Hendijan-Nowrooz-Khafji Fault activity, Zagros Mountains, SW Iran

NASA Astrophysics Data System (ADS)

Kazem Shiroodi, Sadjad; Ghafoori, Mohammad; Faghih, Ali; Ghanadian, Mostafa; Lashkaripour, Gholamreza; Hafezi Moghadas, Naser

2015-11-01

Distinctive characteristics of inverted structures make them important criteria for the identification of certain structural styles of folded belts. The interpretation of 3D seismic reflection and well data sheds new light on the structural evolution and age of inverted structures associated to the Hendijan-Nowrooz-Khafji Fault within the Persian Gulf Basin and northeastern margin of Afro-Arabian plate. Analysis of thickness variations of growth strata using "T-Z plot" (thickness versus throw plot) method revealed the kinematics of the fault. Obtained results show that the fault has experienced a multi-phase evolutionary history over six different extension and compression deformation events (i.e. positive and negative inversion) between 252.2 and 11.62 Ma. This cyclic activity of the growth fault was resulted from alteration of sedimentary processes during continuous fault slip. The structural development of the study area both during positive and negative inversion geometry styles was ultimately controlled by the relative motion between the Afro-Arabian and Central-Iranian plates.

Clinical outcome after Chevron-Akin double osteotomy versus isolated Chevron procedure: a prospective matched group analysis.

PubMed

Lechler, Philipp; Feldmann, Christine; Köck, Franz Xaver; Schaumburger, Jens; Grifka, Joachim; Handel, Martin

2012-01-01

Hallux valgus is a frequent condition of the forefoot, resulting in cosmetic deformity and pain. Chevron osteotomy (CO) is widely employed for the treatment of hallux valgus. Chevron-Akin double osteotomy (CAO) was previously described and superiority over an isolated Chevron procedure was assumed. The objective of this study was to compare the short-to-middle term outcomes of CO and CAO. This study included 72 patients with established diagnosis of mild-to-moderate hallux valgus, treated by either isolated CO or CAO. The CO group included 46 patients (mean 51.5 years) with a mean hallux valgus angle of 27°, while the CAO group included 26 subjects (mean 53.1 years) and a mean hallux valgus angle of 32° preoperatively. All patients were reviewed by physical examination, and standardized questionnaire, and pre- and postoperative standing X-rays were performed. Matched group analysis was carried out to analyze statistical differences of both techniques. The patients were assessed and group matched at a mean of 1.37 years for the CO group and 1.04 years for the CAO group, postoperatively. Mean improvement of HVA (hallux valgus angle) was 10.6° in the CO group and the CAO group improved by 17.5°. DMAA (distal metatarsal articular angle) improved in the CO group by 5.4° and in the CAO by 13.7°. Mean AOFAS score improved by 27.9 (CO) and 21.5 (CAO). Patient satisfaction was high in both groups, with a tendency towards higher values within the CAO group. These findings indicate that Chevron-Akin double osteotomy is a save and practicable procedure for the treatment of mild-to-moderate hallux valgus. Superiority of combined Chevron-Akin procedure over an isolated Chevron osteotomy might be limited to distinct clinical settings, but should not be generally assumed.

Reducing Propulsion Airframe Aeroacoustic Interactions With Uniquely Tailored Chevrons: 3. Jet-Flap Interaction

NASA Technical Reports Server (NTRS)

Thomas, Russ H.; Mengle, Vinod G.; Brunsniak, Leon; Elkoby, Ronen

2006-01-01

Propulsion airframe aeroacoustic (PAA) interactions, resulting from the integration of engine and airframe, lead to azimuthal asymmetries in the flow/acoustic field, e.g., due to the interaction between the exhaust jet flow and the pylon, the wing and its high-lift devices, such as, flaps and flaperons. In the first two parts of this series we have presented experimental results which show that isolated and installed nozzles with azimuthally varying chevrons (AVCs) can reduce noise more than conventional chevrons when integrated with a pylon and a wing with flaps at take-off conditions. In this paper, we present model-scale experimental results for the reduction of jet-flap interaction noise source due to these AVCs and document the PAA installation effects (difference in noise between installed and isolated nozzle configurations) at both approach and take-off conditions. It is found that the installation effects of both types of chevron nozzles, AVCs and conventional, are reversed at approach and take-off, in that there is more installed noise reduction at approach and less at take-off compared to that of the isolated nozzles. Moreover, certain AVCs give larger total installed noise benefits at both conditions compared to conventional chevrons. Phased microphone array results show that at approach conditions (large flap deflection, low jet speed and low ambient Mach number), chevrons gain more noise benefit from reducing jetflap interaction noise than they do from quieting the jet plume noise source which is already weak at these low jet speeds. In contrast, at take-off (small flap deflection, high jet speed and high ambient Mach number) chevrons reduce the dominant jet plume noise better than the reduction they create in jet-flap interaction noise source. In addition, fan AVCs with enhanced mixing near the pylon are found to reduce jet-flap interaction noise better than conventional chevrons at take-off.

Specimen size and geometry effects on fracture toughness of Al2O3 measured with short rod and short bar chevron-notch specimens

NASA Technical Reports Server (NTRS)

Shannon, J. L., Jr.; Munz, D. G.

1983-01-01

Plane strain fracture toughness measurements were made on Al2O3 using short rod and short bar chevron notch specimens previously calibrated by the authors for their dimensionless stress intensity factor coefficients. The measured toughness varied systematically with variations in specimen size, proportions, and chevron notch angle apparently due to their influence on the amount of crack extension to maximum load (the measurement point). The toughness variations are explained in terms of a suspected rising R curve for the material tested, along with a discussion of an unavoidable imprecision in the calculation of K sub Ic for materials with rising R curves when tested with chevron notch specimens.

Reducing Propulsion Airframe Aeroacoustic Interactions with Uniquely Tailored Chevrons. 2; Installed Nozzles

NASA Technical Reports Server (NTRS)

Mengle, Vinod G.; Elkoby, Ronen; Brusniak, Leon; Thomas, Russ H.

2006-01-01

Propulsion airframe aeroacoustic (PAA) interactions arise due to the manner in which an engine is installed on the airframe and lead to an asymmetry in the flow/acoustic environment, for example, for under-the-wing installations due to the pylon, the wing and the high-lift devices. In this work we study how we can affect these PAA interactions to reduce the overall jet-related installed noise by tailoring the chevron shapes on fan and core nozzles in a unique fashion to take advantage of this asymmetry. In part 1 of this trio of papers we introduced the concept of azimuthally varying chevrons (AVC) and showed how some types of AVCs can be more beneficial than the conventional chevrons when tested on "isolated" scaled nozzles inclusive of the pylon effect. In this paper, we continue to study the effect of installing these AVC nozzles under a typical scaled modern wing with high-lift devices placed in a free jet. The noise benefits of these installed nozzles, as well as their installation effects are systematically studied for several fan/core AVC combinations at typical take-off conditions with high bypass ratio. We show, for example, that the top-enhanced mixing T-fan AVC nozzle (with enhanced mixing near the pylon and less mixing away from it) when combined with conventional chevrons on the core nozzle is quieter than conventional chevrons on both nozzles, and hardly produces any high-frequency lift, just as in the isolated case; however, its installed nozzle benefit is less than its isolated nozzle benefit. This suppression of take-off noise benefit under installed conditions, compared to its isolated nozzle benefit, is seen for all other chevron nozzles. We show how these relative noise benefits are related to the relative installation effects of AVCs and baseline nozzles.

Structural evolution of trimesic acid (TMA)/Zn2 + ion network on Au(111) to final structure of (10√3 × 10√3)

NASA Astrophysics Data System (ADS)

Kim, Jandee; Lee, Jaesung; Rhee, Choong Kyun

2016-02-01

Presented is a scanning tunneling microscopy (STM) study of structural evolution of TMA/Zn2 + ion network on Au(111) to the final structure of (10√3 × 10√3) during solution phase post-modification of pristine trimesic acid (TMA) network of a (5√3 × 5√3) structure with Zn2 + ions. Coordination of Zn2 + ions into adsorbed TMA molecules transforms crown-like TMA hexamers in pristine TMA network to chevron pairs in TMA/Zn2 + ion network. Two ordered transient structures of TMA/Zn2 + ion network were observed. One is a (5√7 × 5√7) structure consisting of Zn2 + ion-containing chevron pairs and Zn2 + ion-free TMA dimers. The other is a (5√39 × 5√21) structure made of chevron pairs and chevron-pair-missing sites. An STM image showing domains of different stages of crystallization of chevron pairs demonstrates that the TMA/Zn2 + network before reaching to the final one is quite dynamic. The observed structural evolution of the TMA/Zn2 + ion network is discussed in terms of modification of configurations of adsorbed TMA as accommodating Zn2 + ions and re-ordering of Zn2 + ion-containing chevron pairs.

Performance optimization of plate heat exchangers with chevron plates

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

Muley, A.; Manglik, R.M.

1999-07-01

The enhanced heat transfer performance of a chevron plate heat exchanger (PHE) is evaluated employing (1) energy-conservation based performance evaluation criteria (PECs), and (2) the second-law based minimization of entropy generation principle. Single-phase laminar and turbulent flow convection for three different chevron-plate arrangements are considered. The influence of plate surface corrugation characteristics and their stack arrangements on the heat exchanger's thermal-hydraulic performance is delineated. Based on the different figures of merit, the results show that the extent of heat transfer enhancement increases with flow Re and chevron angle {beta} in laminar flow, but it diminishes with increasing Re in turbulentmore » flows. With up to 2.9 times higher Q, 48% lower A, and entropy generation number N{sub s,a} {lt} 1, relative to an equivalent flat-plate pack, chevron plates are found to be especially suitable in the low to medium flow rates range (20 {le} Re {le} 2,000). Also, there appears to be no significant advantage of using a mixed-plate over a symmetric-plate arrangement.« less

Feedback Control of a Morphing Chevron for Takeoff and Cruise Noise Reduction

NASA Technical Reports Server (NTRS)

Cabell, Randolph H.; Schiller, Noah H.; Mabe, James H.; Ruggeri, Robert T.; Butler, G. W.

2004-01-01

Noise from commercial high-bypass ratio turbofan engines is generated by turbulent mixing of the hot jet exhaust, fan stream, and ambient air. Serrated aerodynamic devices, known as chevrons, along the trailing edges of a jet engine primary and secondary exhaust nozzle have been shown to reduce jet noise at takeoff and shock-cell noise at cruise conditions. Their optimum shape is a finely tuned compromise between noise-benefit and thrust-loss. The design of a full scale Variable Geometry Chevron (VGC) fan-nozzle incorporating Shape Memory Alloy (SMA) actuators is described in a companion paper. This paper describes the development and testing of a proportional-integral control system that regulates the heating of the SMA actuators to control the VGC s tip immersion. The VGC and control system were tested under representative flow conditions in Boeing s Nozzle Test Facility (NTF). Results from the NTF test which demonstrate controllable immersion of the VGC are described. The paper also describes the correlation between strains and temperatures on the chevron with a photogrammetric measurement of the chevron's tip immersion.

Fractured toughness of Si3N4 measured with short bar chevron-notched specimens

NASA Technical Reports Server (NTRS)

Salem, J. A.; Shannon, J. L., Jr.

1985-01-01

The short bar chevron-notched specimen is used to measure the plane strain fracture toughness of hot pressed Si3N4. Specimen proportions and chevron-notch angle are varied, thereby varying the amount of crack extension to maximum load (upon which K sub IC is based). The measured toughness (4.68 + or - 0.19 MNm to the 3/2 power) is independent of these variations, inferring that the material has a flat crack growth resistance curve.

Digital Coordinates and Age for 3,869 Foraminifer Samples Collected by Chevron Petroleum Geologists in Washington and Oregon

USGS Publications Warehouse

West, William B.; Brabb, Earl E.; Malmborg, William T.; Parker, John M.

2009-01-01

The general location and age of more than 33,500 mostly foraminifer samples from Chevron Petroleum Company surface localities in California were provided by Brabb and Parker (2003, 2005). Malmborg and others (2008) provided digital latitude, longitude, and age for more than 13,000 of these samples. We provide here for the first time the digital latitude, longitude, and age for nearly 4,000 Chevron surface and auger samples in Washington and Oregon.

Fracture toughness of Si3N4 measured with short bar chevron-notched specimens

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Shannon, John L., Jr.

1987-01-01

The short bar chevron-notched specimen is used to measure the plane strain fracture toughness of hot pressed Si3N4. Specimen proportions and chevron-notch angle are varied, thereby varying the amount of crack extension to maximum load (upon which K sub IC is based). The measured toughness (4.68 + or 0.19 MNm to the 3/2 power) is independent of these variations, inferring that the material has a flat crack growth resistance curve.

Proximal opening wedge osteotomy with wedge-plate fixation compared with proximal chevron osteotomy for the treatment of hallux valgus: a prospective, randomized study.

PubMed

Glazebrook, Mark; Copithorne, Peter; Boyd, Gordon; Daniels, Timothy; Lalonde, Karl-André; Francis, Patricia; Hickey, Michael

2014-10-01

Hallux valgus with an increased intermetatarsal angle is usually treated with a proximal metatarsal osteotomy. The proximal chevron osteotomy is commonly used but is technically difficult. This study compares the proximal opening wedge osteotomy of the first metatarsal with the proximal chevron osteotomy for the treatment of hallux valgus with an increased intermetatarsal angle. This prospective, randomized multicenter (three-center) study was based on the clinical outcome scores of the Short Form-36, the American Orthopaedic Foot & Ankle Society forefoot questionnaire, and the visual analog scale for pain, activity, and patient satisfaction. Subjects were assessed prior to surgery and at three, six, and twelve months postoperatively. Surgeon preference was evaluated based on questionnaires and the operative times required for each procedure. No significant differences were found for any of the patients' clinical outcome measurements between the two procedures. The proximal opening wedge osteotomy was found to lengthen, and the proximal chevron osteotomy was found to shorten, the first metatarsal. The intermetatarsal angles improved (decreased) significantly, from 14.8° ± 3.2° to 9.1° ± 2.9 (mean and standard deviation) after a proximal opening wedge osteotomy and from 14.6° ± 3.9° to 11.3° ± 4.0° after a proximal chevron osteotomy (p < 0.05 for both). Operative time required for performing a proximal opening wedge osteotomy is similar to that required for performing a proximal chevron osteotomy (mean and standard deviation, 67.1 ± 16.5 minutes compared with 69.9 ± 18.6 minutes; p = 0.510). Opening wedge and proximal chevron osteotomies have comparable radiographic outcomes and comparable clinical outcomes for pain, satisfaction, and function. The proximal opening wedge osteotomy lengthens, and the proximal chevron osteotomy shortens, the first metatarsal. The proximal opening wedge osteotomy was subjectively less technically demanding and was preferred by the orthopaedic surgeons in this study. Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence. Copyright © 2014 by The Journal of Bone and Joint Surgery, Incorporated.

Miranda - Chevron Grooves

NASA Image and Video Library

1996-01-29

This image of Miranda, obtained by NASA Voyager 2 on approach in 1986, shows an unusual chevron figure and regions of distinctly differing terrain on the Uranian moon. http://photojournal.jpl.nasa.gov/catalog/PIA00038

78 FR 78811 - Sunshine Act Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-27

..., fire at the Chevron refinery that endangered 19 workers and sent more than 15,000 residents to the...-resistant metal alloys. The first interim report also found a failure by Chevron to identify and evaluate...

Compliance and stress intensity coefficients for short bar specimens with chevron notches

NASA Technical Reports Server (NTRS)

Munz, D.; Bubsey, R. T.; Srawley, J. E.

1980-01-01

For the determination of fracture toughness especially with brittle materials, a short bar specimen with rectangular cross section and chevron notch can be used. As the crack propagates from the tip of the triangular notch, the load increases to a maximum then decreases. To obtain the relation between the fracture toughness and maximum load, calculations of Srawley and Gross for specimens with a straight-through crack were applied to the specimens with chevron notches. For the specimens with a straight-through crack, an analytical expression was obtained. This expression was used for the calculation of the fracture toughness versus maximum load relation under the assumption that the change of the compliance with crack length for the specimen with a chevron notch is the same as for a specimen with a straight-through crack.

PIV Measurements of Chevrons on F400 Tactical Aircraft Nozzle Model

NASA Technical Reports Server (NTRS)

Bridges, James; Wernet, Mark; Frate, Franco

2010-01-01

Previous talks at this meeting have covered our collaborative work on high-energy jets such as present in tactical aircraft (those with supersonic plumes). The emphasis of this work is improving our understanding of flow physics and our prediction tools. In this presentation we will discuss recent flow diagnostics acquired using Particle Image Velocimetry (PIV) made on an underexpanded shocked jet plume from a tactical aircraft nozzle. In this presentation we show cross-sectional and streamwise cuts of both mean and turbulent velocities of an F404 engine nozzle with various chevron designs applied. The impact of chevron penetration, length, and width are documented. The impact of the parameters is generally nonlinear in measures considered here, a surprising result given the relatively smooth behavior of the noise to variations in these chevron parameters.

Passive chevron replicator

NASA Technical Reports Server (NTRS)

Oeffinger, Thomas R. (Inventor); Tocci, Leonard R. (Inventor)

1977-01-01

There is described a passive replicator device to be used in magnetic bubble domain systems. The replicator is passive, i.e., does not require an active element such as a current source or the like, and both propagates and replicates bubble domains. In a preferred embodiment, the replicator uses chevron type elements arranged in an appropriate pattern so as to interact with a pair of propagation paths wherein bubble domains are propagated. A bubble in one propagation path is routinely transferred therealong and, concurrently, replicated by the instant device into another propagation path. A plurality of elements arranged in juxtaposition to the chevrons assists in controlling the propagation of the bubbles through the respective propagation paths and, at the appropriate time, provides a cutting action wherein a bubble which is elongated between the chevrons of the two propagation paths is split into two separate bubbles.

Comparison of the proximal chevron and Ludloff osteotomies for the correction of hallux valgus.

PubMed

Choi, Woo Jin; Yoon, Han Kook; Yoon, Hang Seob; Kim, Bom Soo; Lee, Jin Woo

2009-12-01

Although several studies have described good results of proximal chevron and Ludloff osteotomies, there have been no studies comparing the results of these two techniques at a single institution. We consecutively evaluated 46 patients who underwent proximal chevron osteotomies and 52 patients who underwent Ludloff osteotomies. Patients were evaluated by preoperative and postoperative weight bearing radiographs and the American Orthopaedic Foot and Ankle Society (AOFAS) hallux MP score. Both groups had similarly high AOFAS scores and good correction by radiographic parameters. No statistically significant differences were found with respect to correction of hallux valgus angle (HVA) and intermetatarsal angle (IMA) between the two groups. Significant shortening of the first metatarsal was found after Ludloff osteotomy (p < 0.05). At 6 weeks after surgery, the pain subscore was significantly lower in the proximal chevron group than in the Ludloff group (p < 0.05). The proximal chevron and Ludloff osteotomies yielded equivalent clinical and radiological results. The Ludloff osteotomy with lag screw fixation is more stable and does not require postoperative hardware removal, although it is technically demanding and has a tendency toward greater shortening of the first metatarsal.

Stress Intensity Factors of Semi-Circular Bend Specimens with Straight-Through and Chevron Notches

NASA Astrophysics Data System (ADS)

Ayatollahi, M. R.; Mahdavi, E.; Alborzi, M. J.; Obara, Y.

2016-04-01

Semi-circular bend specimen is one of the useful test specimens for determining fracture toughness of rock and geo-materials. Generally, in rock test specimens, initial cracks are produced in two shapes: straight-edge cracks and chevron notches. In this study, the minimum dimensionless stress intensity factors of semi-circular bend specimen (SCB) with straight-through and chevron notches are calculated. First, using finite element analysis, a suitable relation for the dimensionless stress intensity factor of SCB with straight-through crack is presented based on the normalized crack length and half-distance between supports. For evaluating the validity and accuracy of this relation, the obtained results are then compared with numerical and experimental results reported in the literature. Subsequently, by performing some experiments and also finite element analysis of the SCB specimen with chevron notch, the minimum dimensionless stress intensity factor of this specimen is obtained. Using the new equation for the dimensionless stress intensity factor of SCB with straight-through crack and an analytical method, i.e., Bluhm's slice synthesis method, the minimum (critical) dimensionless stress intensity factor of chevron notched semi-circular bend specimens is calculated. Good agreement is observed between the results of two mentioned methods.

Particle Data Group - Downloads

Science.gov Websites

Particle Data Group HOME: pdgLive Summary Tables Reviews, Tables, Plots Particle Listings Errata ; inverted mass hierarchy Page 10 of Leptons Summary Table, Neutrino Mixing: Leptons Summary Tables (page 10 . Pages 3 and 63 of Mesons Summary Tables: Bottom Mesons Summary Tables (page 3) Mesons Summary Tables

[Distal osteotomy for the treatment of hallux valgus (Chevron osteotomy)].

PubMed

Stukenborg-Colsman, C; Claaßen, L; Ettinger, S; Yao, D; Lerch, M; Plaaß, C

2017-05-01

Distal osteotomies, like the Chevron osteotomy, is indicated for mild to moderate hallux valgus deformities. Splayfoot, painful pseudoexostosis, and transfer metatasalgia are observed in the clinical examination. Radiographic examination should be done with weight bearing in two planes. Preoperatively the intermetatarsal (IM), hallux valgus, and distal metatarsal articular (DMAA) angles should be measured. The operative technique is based on soft tissue and bony correction. Modifications of the osteotomy allow a shortening, lengthening, or neutral correction of the first metatarsal. With a modified Chevron osteotomy, an increased DMAA can be also corrected.

Effect of First Tarsometatarsal Joint Derotational Arthrodesis on First Ray Dynamic Stability Compared to Distal Chevron Osteotomy.

PubMed

Klemola, Tero; Leppilahti, Juhana; Laine, Vesa; Pentikäinen, Ilkka; Ojala, Risto; Ohtonen, Pasi; Savola, Olli

2017-08-01

Hallux valgus alters gait, compromising first ray stability and function of the windlass mechanism at the late stance. Hallux valgus correction should restore the stability of the first metatarsal. Comparative studies reporting the impact of different hallux valgus correction methods on gait are rare. We report the results of a case-control study between distal chevron osteotomy and first tarsometatarsal joint derotational arthrodesis (FTJDA). Two previously studied hallux valgus cohorts were matched: distal chevron osteotomy and FTJDA. Seventy-seven feet that underwent distal chevron osteotomy (chevron group) and 76 feet that underwent FTJDA (FTJDA group) were available for follow-up, with a mean of 7.9 years (range, 5.8-9.4 years) and 5.1 years (range, 3.0-8.3 years), respectively. Matching criteria were the hallux valgus angle (HVA) and a follow-up time difference of a maximum 24 months. Two matches were made: according to the preoperative HVA and the HVA at late follow-up. Matching provided 30 and 31 pairs, respectively. Relative impulses (%) of the first toe (T1) and metatarsal heads 1 to 5 (MTH1-5), weightbearing radiographs, and American Orthopaedic Foot & Ankle Society (AOFAS) (hallux metatarsophalangeal-interphalangeal [MTP-IP]) scores were studied. The relative impulse of MTH1 was higher in the FTJDA group, whereas a central dynamic loading pattern was seen in the chevron group. This result remained when relative impulses were analyzed according to the postoperative HVA. The mean difference in the HVA at follow-up was 6.2 degrees (95% confidence interval, 3.0-9.5; P = .001) in favor of the FTJDA group. The dynamic loading capacity of MTH1 was higher in the FTJDA group in comparison to the chevron group. The follow-up HVA remained better in the FTJDA group. Level III, case-control study.

A mathematical model of the chevron-like wave pattern on a weld piece

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

Dowden, J.; Kapadia, P.

1996-12-31

In welding processes in general the surface of a metallic weld displays a chevron-like pattern. Such a pattern is also clearly seen to be present if welding is carried out using a laser beam. In the welding process a laser beam is directed normally on the metal undergoing translation and usually penetrates it to form a keyhole. The keyhole is surrounded by a molten region, the weld pool. Even if a CO{sub 2} laser is used, there are numerous fluctuations and instabilities that occur, so that the keyhole imposes forcing frequencies on the molten weld pool, additional to vibrations attendantmore » on the process of translation. The weld pool in turn responds by supporting a spectrum of waves of different frequencies involving the natural frequency of the weld pool as well as various forcing frequencies. These waves are surface tension-type capillary waves and previous publications have attempted to model their behavior mathematically, although not all aspects of the problem have always been included. The wave pattern that is manifested in the chevron-like pattern seen on the weld piece is, however, not necessarily identical to the wave pattern present in the weld pool. This is because the chevron-like wave pattern forms as a result of several complicating effects that arise as the weld specimen cools on its surface immediately after the weld has been formed. This process involves the waves on the surface of the weld pool freezing to form the chevron-like wave pattern. A feature that is often ignored is the fact that the waves on the weld pool can only be regarded as irrotational if the translation speed is sufficiently low. This paper describes mathematically the formation of the chevron-like wave pattern based on suitable simplifying assumptions to model the process. The mathematical description of the way in which this chevron-like pattern forms is a step toward a more comprehensive understanding of this process.« less

Analysis of a Chevron Beam Thermal Actuator

NASA Astrophysics Data System (ADS)

Joshi, Amey Sanjay; Mohammed, Hussain; Kulkarni, S. M., Dr.

2018-02-01

Thermal MEMS (Micro-Electro-Mechanical Systems) actuators and sensors have a wide range of applications. The chevron type thermal actuators comparatively show superior performance over other existing electrostatic and thermal actuators. This paper describes the design and analysis of chevron type thermal actuator. Here standard design of Chevron type thermal actuator is considered which comprises of proof mass at center and array of six beams of a uniform cross section of 3 3 microns and an initial angle of 5°. The thermal actuator was designed and analyzed using analytical and finite element method and the results were compared. The model was also analyzed for initial angles of 2.5° and 7.5°, and the results were compared with FEA model. The cross section of the beam was varied and the finite element analysis of all three models was compared to suggest the best suitable thermal actuator structure.

Real time analysis of self-assembled InAs/GaAs quantum dot growth by probing reflection high-energy electron diffraction chevron image

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

Kudo, Takuya; Inoue, Tomoya; Kita, Takashi

2008-10-01

Self-assembling process of InAs/GaAs quantum dots has been investigated by analyzing reflection high-energy electron diffraction chevron images reflecting the crystal facet structure surrounding the island. The chevron image shows dramatic changes during the island formation. From the temporal evolution of the chevron tail structure, the self-assembling process has been found to consist of four steps. The initial islands do not show distinct facet structures. Then, the island surface is covered by high-index facets, and this is followed by the formation of stable low-index facets. Finally, the flow of In atoms from the islands occurs, which contributes to flatten the wettingmore » layer. Furthermore, we have investigated the island shape evolution during the GaAs capping layer growth by using the same real-time analysis technique.« less

Performance of Chevron-notch short bar specimen in determining the fracture toughness of silicon nitride and aluminum oxide

NASA Technical Reports Server (NTRS)

Munz, D.; Bubsey, R. T.; Shannon, J. L., Jr.

1980-01-01

Ease of preparation and testing are advantages unique to the chevron-notch specimen used for the determination of the plane strain fracture toughness of extremely brittle materials. During testing, a crack develops at the notch tip and extends stably as the load is increased. For a given specimen and notch configuration, maximum load always occurs at the same relative crack length independent of the material. Fracture toughness is determined from the maximum load with no need for crack length measurement. Chevron notch acuity is relatively unimportant since a crack is produced during specimen loading. In this paper, the authors use their previously determined stress intensity factor relationship for the chevron-notch short bar specimen to examine the performance of that specimen in determining the plane strain fracture toughness of silicon nitride and aluminum oxide.

Subcaptial oblique fifth metatarsal osteotomy versus distal chevron osteotomy for correction of bunionette deformity: a cadaveric study.

PubMed

Cooper, Minton Truitt; Coughlin, Michael J

2012-10-01

The aim of this study was to compare a distal subcapital oblique fifth metatarsal with a distal chevron osteotomy for correction of bunionette deformity. Twenty cadaveric feet were randomly assigned to undergo either a subcapital oblique or chevron osteotomy of the distal fifth metatarsal. Radiographic measurements, including 4-5 intermetatarsal angle (IMA), fifth metatarsophalangeal angle (5-MPA) and foot width, were compared between the 2 groups. Foot width and 5-MPA was significantly decreased in both groups with no difference between the groups. The 4-5 IMA was not significantly altered in either group. Decrease in foot width and 5-MPA was similarly achieved with either distal chevron or subcapital oblique osteotomy of the fifth metatarsal in normal cadaveric specimens. No significant difference was found between the 2 techniques in any of the radiographic parameters measured.

Quantitative Analysis of the Lamellarity of Giant Liposomes Prepared by the Inverted Emulsion Method

PubMed Central

Chiba, Masataka; Miyazaki, Makito; Ishiwata, Shin’ichi

2014-01-01

The inverted emulsion method is used to prepare giant liposomes by pushing water-in-oil droplets through the oil/water interface into an aqueous medium. Due to the high encapsulation efficiency of proteins under physiological conditions and the simplicity of the protocol, it has been widely used to prepare various cell models. However, the lamellarity of liposomes prepared by this method has not been evaluated quantitatively. Here, we prepared liposomes that were partially stained with a fluorescent dye, and analyzed their fluorescence intensity under an epifluorescence microscope. The fluorescence intensities of the membranes of individual liposomes were plotted against their diameter. The plots showed discrete distributions, which were classified into several groups. The group with the lowest fluorescence intensity was determined to be unilamellar by monitoring the exchangeability of the inner and the outer solutions of the liposomes in the presence of the pore-forming toxin α-hemolysin. Increasing the lipid concentration dissolved in oil increased the number of liposomes ∼100 times. However, almost all the liposomes were unilamellar even at saturating lipid concentrations. We also investigated the effects of lipid composition and liposome content, such as highly concentrated actin filaments and Xenopus egg extracts, on the lamellarity of the liposomes. Remarkably, over 90% of the liposomes were unilamellar under all conditions examined. We conclude that the inverted emulsion method can be used to efficiently prepare giant unilamellar liposomes and is useful for designing cell models. PMID:25028876

Biomechanical analysis of two fixation methods for proximal chevron osteotomy of the first metatarsal.

PubMed

Schuh, Reinhard; Hofstaetter, Jochen Gerhard; Benca, Emir; Willegger, Madeleine; von Skrbensky, Gobert; Zandieh, Shahin; Wanivenhaus, Axel; Holinka, Johannes; Windhager, Reinhard

2014-05-01

The proximal chevron osteotomy provides high correctional power. However, relatively high rates of dorsiflexion malunion of up to 17 % are reported for this procedure. This leads to insufficient weight bearing of the first ray and therefore to metatarsalgia. Recent biomechanical and clinical studies pointed out the importance of rigid fixation of proximal metatarsal osteotomies. Therefore, the aim of the present study was to compare biomechanical properties of fixation of proximal chevron osteotomies with variable locking plate and cancellous screw respectively. Ten matched pairs of human fresh frozen cadaveric first metatarsals underwent proximal chevron osteotomy with either variable locking plate or cancellous screw fixation after obtaining bone mineral density. Biomechanical testing included repetitive plantar to dorsal loading from 0 to 31 N with the 858 Mini Bionix(®) (MTS(®) Systems Corporation, Eden Prairie, MN, USA). Dorsal angulation of the distal fragment was recorded. The variable locking plate construct reveals statistically superior results in terms of bending stiffness and dorsal angulation compared to the cancellous screw construct. There was a statistically significant correlation between bone mineral density and maximum tolerated load until construct failure occurred for the screw construct (r = 0.640, p = 0.406). The results of the present study indicate that variable locking plate fixation shows superior biomechanical results to cancellous screw fixation for proximal chevron osteotomy. Additionally, screw construct failure was related to levels of low bone mineral density. Based on the results of the present study we recommend variable locking plate fixation for proximal chevron osteotomy, especially in osteoporotic bone.

A comparison of proximal and distal Chevron osteotomy, both with lateral soft-tissue release, for moderate to severe hallux valgus in patients undergoing simultaneous bilateral correction: a prospective randomised controlled trial.

PubMed

Lee, K B; Cho, N Y; Park, H W; Seon, J K; Lee, S H

2015-02-01

Moderate to severe hallux valgus is conventionally treated by proximal metatarsal osteotomy. Several recent studies have shown that the indications for distal metatarsal osteotomy with a distal soft-tissue procedure could be extended to include moderate to severe hallux valgus. The purpose of this prospective randomised controlled trial was to compare the outcome of proximal and distal Chevron osteotomy in patients undergoing simultaneous bilateral correction of moderate to severe hallux valgus. The original study cohort consisted of 50 female patients (100 feet). Of these, four (8 feet) were excluded for lack of adequate follow-up, leaving 46 female patients (92 feet) in the study. The mean age of the patients was 53.8 years (30.1 to 62.1) and the mean duration of follow-up 40.2 months (24.1 to 80.5). After randomisation, patients underwent a proximal Chevron osteotomy on one foot and a distal Chevron osteotomy on the other. At follow-up, the American Orthopedic Foot and Ankle Society (AOFAS) hallux metatarsophalangeal interphalangeal (MTP-IP) score, patient satisfaction, post-operative complications, hallux valgus angle, first-second intermetatarsal angle, and tibial sesamoid position were similar in each group. Both procedures gave similar good clinical and radiological outcomes. This study suggests that distal Chevron osteotomy with a distal soft-tissue procedure is as effective and reliable a means of correcting moderate to severe hallux valgus as proximal Chevron osteotomy with a distal soft-tissue procedure. ©2015 The British Editorial Society of Bone & Joint Surgery.

Chevron Mining, Inc. McKinley Mine, Gallup, NM: NN0029386

EPA Pesticide Factsheets

NPDES Permit #NN0029386 for the Chevron Mining, Inc. McKinley Mine to tributaries to the Puerco River located on Tribal, private, and public lands within the Navajo Nation and near the Arizona border in New Mexico.

Publications - GMC 148 | Alaska Division of Geological & Geophysical

Science.gov Websites

feet) from the Chevron USA Eagle Creek #1 well Authors: Weber, F.F. Publication Date: 1989 Publisher ., 1989, Visual kerogen and TAI data of select cuttings (1530 - 12000 feet) from the Chevron USA Eagle

Publications - GMC 75 | Alaska Division of Geological & Geophysical Surveys

Science.gov Websites

DGGS GMC 75 Publication Details Title: Vitrinite reflectance data for the Chevron U.S.A. Inc. Eagle Chevron U.S.A. Inc. Eagle Creek #1 well: Alaska Division of Geological & Geophysical Surveys Geologic

Safety performance evaluation of converging chevron pavement markings : final report.

DOT National Transportation Integrated Search

2014-12-01

The objectives of this study were (1) to perform a detailed safety analysis of converging chevron : pavement markings, quantifying the potential safety benefits and developing an understanding of the : incident types addressed by the treatment, and (...

Evaluation of the effectiveness of converging chevron pavement markings.

DOT National Transportation Integrated Search

2011-10-01

Converging chevron pavement markings have recently seen rising interest in the United States as a : means to reduce speeds at high-speed locations in a desire to improve safety performance. This report : presents an investigation into the effectivene...

Evaluating the effectiveness of converging chevron pavement markings.

DOT National Transportation Integrated Search

2010-10-01

Converging chevron pavement markings have recently seen rising interest in the United States as a : means to reduce speeds at high-speed locations in a desire to improve safety performance. This report : presents an investigation into the effectivene...

33 CFR 165.1197 - Security Zones; San Francisco Bay, San Pablo Bay, Carquinez Strait, Suisun Bay, California.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., Carquinez Strait, Suisun Bay, California. (a) Locations. The following areas are security zones: (1) Chevron... sea floor within approximately 100 yards of the Chevron Long Wharf, Richmond, CA, and encompasses all...

33 CFR 165.1197 - Security Zones; San Francisco Bay, San Pablo Bay, Carquinez Strait, Suisun Bay, California.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., Carquinez Strait, Suisun Bay, California. (a) Locations. The following areas are security zones: (1) Chevron... sea floor within approximately 100 yards of the Chevron Long Wharf, Richmond, CA, and encompasses all...

33 CFR 165.1197 - Security Zones; San Francisco Bay, San Pablo Bay, Carquinez Strait, Suisun Bay, California.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., Carquinez Strait, Suisun Bay, California. (a) Locations. The following areas are security zones: (1) Chevron... sea floor within approximately 100 yards of the Chevron Long Wharf, Richmond, CA, and encompasses all...

33 CFR 165.1197 - Security Zones; San Francisco Bay, San Pablo Bay, Carquinez Strait, Suisun Bay, California.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., Carquinez Strait, Suisun Bay, California. (a) Locations. The following areas are security zones: (1) Chevron... sea floor within approximately 100 yards of the Chevron Long Wharf, Richmond, CA, and encompasses all...

33 CFR 165.1197 - Security Zones; San Francisco Bay, San Pablo Bay, Carquinez Strait, Suisun Bay, California.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., Carquinez Strait, Suisun Bay, California. (a) Locations. The following areas are security zones: (1) Chevron... sea floor within approximately 100 yards of the Chevron Long Wharf, Richmond, CA, and encompasses all...

76 FR 19343 - Combined Notice of Filings No. 1

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-07

... Transmission Company submits tariff filing per 154.203: Compliance NCA Chevron to be effective 2/1/2011. Filed...: Chevron U.S.A. Inc. FA0910 to be effective 4/1/ 2011. Filed Date: 03/28/2011. Accession Number: 20110328...

Wet active chevron nozzle for controllable jet noise reduction

NASA Technical Reports Server (NTRS)

Thomas, Russell H. (Inventor); Kinzie, Kevin W. (Inventor)

2011-01-01

Disposed at or toward the trailing edge of one or more nozzles associated with a jet engine are injection ports which can selectively be made to discharge a water stream into a nozzle flow stream for the purpose of increasing turbulence in somewhat of a similar fashion as mechanically disposed chevrons have done in the known art. Unlike mechanically disposed chevrons of the known art, the fluid flow may be secured thereby increasing the engine efficiency. Various flow patterns, water pressures, orifice designs or other factors can be made operative to provide desired performance characteristics.

Short-Term Radiographic Outcome After Distal Chevron Osteotomy for Hallux Valgus Using Intramedullary Plates With an Amended Algorithm for the Surgical Management of Hallux Valgus.

PubMed

Matsumoto, Takumi; Gross, Christopher E; Parekh, Selene G

2018-03-01

Distal Chevron osteotomy is a well-established surgical procedure for mild to moderate hallux valgus deformity. Many methods have been described for fixation of osteotomy site; secure fixation, enabling large displacement of the metatarsal head, is one of the essentials of this procedure. The purpose of the present study was to evaluate the short-term radiographic outcome of a distal Chevron osteotomy using an intramedullary plate for the correction of hallux valgus deformity. The present study evaluated 37 patients (40 feet) who underwent distal Chevron osteotomy using an intramedullary plate by periodic radiographs obtained preoperatively and at 4 weeks, 8 weeks, 3 months, and 6 months postoperatively. Correction of the hallux valgus angle averaged 17.8°, intermetatarsal angle 7.4°, distal metatarsal articular angle 2.7°, and sesamoid position 1.4 stages at 3 months postoperatively. The average lateral shift of the capital fragment was 6.5 mm. All patients achieved bone union, and there were no cases of dislocation, displacement, or avascular necrosis of the metatarsal head fragment. In conclusion, a distal Chevron osteotomy using an intramedullary plate was a favorable method for the correction of mild to moderate hallux valgus deformity. Level IV: Case series.

Heat transfer and pressure drop characteristics of a plate heat exchanger using water based Al2O3 nanofluid for 30° and 60° chevron angles

NASA Astrophysics Data System (ADS)

Elias, M. M.; Saidur, R.; Ben-Mansour, R.; Hepbasli, A.; Rahim, N. A.; Jesbains, K.

2018-04-01

Nanofluid is a new class of engineering fluid that has good heat transfer characteristics which is essential to increase the heat transfer performance in various engineering applications such as heat exchangers and cooling of electronics. In this study, experiments were conducted to compare the heat transfer performance and pressure drop characteristics in a plate heat exchanger (PHE) for 30° and 60° chevron angles using water based Al2O3 nanofluid at the concentrations from 0 to 0.5 vol.% for different Reynolds numbers. The thermo-physical properties has been determined and presented in this paper. At 0.5 vol% concentration, the maximum heat transfer coefficient, the overall heat transfer coefficient and the heat transfer rate for 60° chevron angle have attained a higher percentage of 15.14%, 7.8% and 15.4%, respectively in comparison with the base fluid. Consequently, when the volume concentration or Reynolds number increases, the heat transfer coefficient and the overall heat transfer coefficient as well as the heat transfer rate of the PHE (Plate Heat Exchangers) increases respectively. Similarly, the pressure drop increases with the volume concentration. 60° chevron angle showed better performance in comparison with 30° chevron angle.

A comparison of Chevron and Lindgren-Turan osteotomy techniques in hallux valgus surgery: a prospective randomized controlled study.

PubMed

Uygur, Esat; Özkan, Namık Kemal; Akan, Kaya; Çift, Hakan

2016-01-01

The aim of this prospective randomized controlled single-blind study was to compare the results of Chevron and Lindgren-Turan osteotomy techniques for treatment of moderate hallux valgus. A total of 66 female patients (34 in Chevron group, 32 Lindgren-Turan group) were recruited in this study and followed up for an average of 26.08 months. Operative procedures were performed by 2 surgeons, and patients were evaluated by an another researcher who was blinded to the surgical technique. The groups were compared for their radiological and clinical results. Both techniques was clinically and radiologically effective (p<0.01). However, no significant differences were found between the 2 groups regarding American Orthopaedic Foot and Ankle Society's clinical rating system, Painful Foot Evaluation scale of Maryland University scores, or radiologic evaluation (p>0.05). Compared to the Chevron group, the Lindgren-Turan group was found to have shorter surgical duration (p<0.05) and significantly more shortening at the first metatarsal (p<0.05). In moderate hallux valgus deformity, both the Chevron and Lindgren-Turan osteotomy techniques are clinically and radiologically safe, effective, and reliable alternatives. No superiority was detected in either technique. Although shortening at the first metatarsal in the Lindgren-Turan group was radiologically significant, the results were clinically tolerable.

Fracture toughness of brittle materials determined with chevron notch specimens

NASA Technical Reports Server (NTRS)

Shannon, J. L., Jr.; Bursey, R. T.; Munz, D.; Pierce, W. S.

1980-01-01

The use of chevron-notch specimens for determining the plane strain fracture toughness (K sub Ic) of brittle materials is discussed. Three chevron-notch specimens were investigated: short bar, short rod, and four-point-bend. The dimensionless stress intensity coefficient used in computing K sub Ic is derived for the short bar specimen from the superposition of ligament-dependent and ligament-independent solutions for the straight through crack, and also from experimental compliance calibrations. Coefficients for the four-point-bend specimen were developed by the same superposition procedure, and with additional refinement using the slice model of Bluhm. Short rod specimen stress intensity coefficients were determined only by experimental compliance calibration. Performance of the three chevron-notch specimens and their stress intensity factor relations were evaluated by tests on hot-pressed silicon nitride and sintered aluminum oxide. Results obtained with the short bar and the four-point-bend specimens on silicon nitride are in good agreement and relatively free of specimen geometry and size effects within the range investigated. Results on aluminum oxide were affected by specimen size and chevron-notch geometry, believed due to a rising crack growth resistance curve for the material. Only the results for the short bar specimen are presented in detail.

Dropping the Other U: An Alternative Approach to U-Shaped Developmental Functions

ERIC Educational Resources Information Center

Brainerd, C. J.

2004-01-01

The aim of this article is to introduce readers to an alternative way of applying U-shaped functions to understand development, especially cognitive development. In classical developmental applications, age is the abscissa; that is, in the fundamental equation B = f(A), some behavioral variable (B) plots as a U-shaped or inverted U-shaped function…

Musical Preferences as a Function of Stimulus Complexity of Piano Jazz

ERIC Educational Resources Information Center

Gordon, Josh; Gridley, Mark C.

2013-01-01

Seven excerpts of modern jazz piano improvisations were selected to represent a range of perceived complexities. Audio recordings of the excerpts were played for 27 listeners who were asked to indicate their level of enjoyment on 7-point scales. Indications of enjoyment followed an inverted-U when plotted against perceived complexity of the music.…

Smectic C chevrons in nanocylinders

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

Lefort, R., E-mail: ronan.lefort@univ-rennes1.fr; Morineau, D.; Jean, F.

2014-11-17

The structure of an achiral smectic-C liquid crystal confined in nanocylinders with a planar surface anchoring is studied by small angle neutron scattering. We observe an invariant alignment of the nematic director with the pore axis, that promotes an original chevron structure with revolution symmetry.

Relative strength of tailor's bunion osteotomies and fixation techniques.

PubMed

Haddon, Todd B; LaPointe, Stephan J

2013-01-01

A paucity of data is available on the mechanical strength of fifth metatarsal osteotomies. The present study was designed to provide that information. Five osteotomies were mechanically tested to failure using a materials testing machine and compared with an intact fifth metatarsal using a hollow saw bone model with a sample size of 10 for each construct. The osteotomies tested were the distal reverse chevron fixated with a Kirschner wire, the long plantar reverse chevron osteotomy fixated with 2 screws, a mid-diaphyseal sagittal plane osteotomy fixated with 2 screws, the mid-diaphyseal sagittal plane osteotomy fixated with 2 screws, and an additional cerclage wire and a transverse closing wedge osteotomy fixated with a box wire technique. Analysis of variance was performed, resulting in a statistically significant difference among the data at p <.0001. The Tukey-Kramer honestly significant difference with least significant differences was performed post hoc to separate out the pairs at a minimum α of 0.05. The chevron was statistically the strongest construct at 130 N, followed by the long plantar osteotomy at 78 N. The chevron compared well with the control at 114 N, and they both fractured at the proximal model to fixture interface. The other osteotomies were statistically and significantly weaker than both the chevron and the long plantar constructs, with no statistically significant difference among them at 36, 39, and 48 N. In conclusion, the chevron osteotomy was superior in strength to the sagittal and transverse plane osteotomies and similar in strength and failure to the intact model. Copyright © 2013 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Native Contact Density and Nonnative Hydrophobic Effects in the Folding of Bacterial Immunity Proteins

PubMed Central

Chen, Tao; Chan, Hue Sun

2015-01-01

The bacterial colicin-immunity proteins Im7 and Im9 fold by different mechanisms. Experimentally, at pH 7.0 and 10°C, Im7 folds in a three-state manner via an intermediate but Im9 folding is two-state-like. Accordingly, Im7 exhibits a chevron rollover, whereas the chevron arm for Im9 folding is linear. Here we address the biophysical basis of their different behaviors by using native-centric models with and without additional transferrable, sequence-dependent energies. The Im7 chevron rollover is not captured by either a pure native-centric model or a model augmented by nonnative hydrophobic interactions with a uniform strength irrespective of residue type. By contrast, a more realistic nonnative interaction scheme that accounts for the difference in hydrophobicity among residues leads simultaneously to a chevron rollover for Im7 and an essentially linear folding chevron arm for Im9. Hydrophobic residues identified by published experiments to be involved in nonnative interactions during Im7 folding are found to participate in the strongest nonnative contacts in this model. Thus our observations support the experimental perspective that the Im7 folding intermediate is largely underpinned by nonnative interactions involving large hydrophobics. Our simulation suggests further that nonnative effects in Im7 are facilitated by a lower local native contact density relative to that of Im9. In a one-dimensional diffusion picture of Im7 folding with a coordinate- and stability-dependent diffusion coefficient, a significant chevron rollover is consistent with a diffusion coefficient that depends strongly on native stability at the conformational position of the folding intermediate. PMID:26016652

The Role of Crack Formation in Chevron-Notched Four-Point Bend Specimens

NASA Technical Reports Server (NTRS)

Calomino, Anthony M.; Ghosn, Louis J.

1994-01-01

The failure sequence following crack formation in a chevron-notched four-point bend 1 specimen is examined in a parametric study using the Bluhm slice synthesis model. Premature failure resulting from crack formation forces which exceed those required to propagate a crack beyond alpha (min) is examined together with the critical crack length and critical crack front length. An energy based approach is used to establish factors which forecast the tendency of such premature failure due to crack formation for any selected chevron-notched geometry. A comparative study reveals that, for constant values of alpha (1) and alpha (0), the dimensionless beam compliance and stress intensity factor are essentially independent of specimen width and thickness. The chevron tip position, alpha (0) has its primary effect on the force required to initiate a sharp crack. Small values for alpha (0) maximize the stable region length, however, the premature failure tendency is also high for smaller alpha (0) values. Improvements in premature failure resistance can be realized for larger values of alpha (0) with only a minor reduction in the stable region length. The stable region length is also maximized for larger chevron based positions, alpha (1) but the chance for premature failure is also raised. Smaller base positions improve the premature failure resistance with only minor decreases in the stable region length. Chevron geometries having a good balance of premature failure resistance, stable region length, and crack front length are 0.20 less than or equal to alpha (0) is less than or equal to 0.30 and 0.70 is less than or equal to alpha (1) is less than or equal to 0.80.

A chevron beam-splitter interferometer

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.

1979-01-01

Fully tilt compensated double-pass chevron beam splitter, that removes channelling effects and permits optical phase tuning, is wavelength independent and allows small errors in alignment that are not tolerated in Michelson, Machzender, or Sagnac interferometers. Device is very useful in experiments where background vibration affects conventional interferometers.

33 CFR 147.825 - Chevron Genesis Spar safety zone.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) Description. The Chevron Genesis Spar, Green Canyon 205A (GC205A), is located at position 27°46′46.365″ N, 90... is a safety zone. (b) Regulation. No vessel may enter or remain in this safety zone except the...

Evaluation of an Innovative Fixation System for Chevron Bunionectomy.

PubMed

Bennett, Gordon L; Sabetta, James A

2016-02-01

Distal chevron metatarsal osteotomy bunionectomy is a commonly performed procedure for the treatment of mild to moderate hallux valgus deformity. There are several different methods to stabilize this osteotomy. We evaluated a new intramedullary plate system. We prospectively evaluated 57 consecutive patients who underwent distal chevron metatarsal osteotomy bunionectomy utilizing the intramedullary plate system. All operative procedures were performed by the senior author. Patients were evaluated preoperatively, postoperatively, and at a final follow-up utilizing the American Orthopaedic Foot & Ankle Society (AOFAS) forefoot scoring system. Sixty-three surgically corrected feet went on to heal the osteotomy site. There were no hardware failures. We had one patient that expressed mild discomfort over the plate. All patients significantly improved their AOFAS scores compared with preoperative values. We concluded that the distal chevron metatarsal osteotomy bunionectomy resulted in excellent function and pain relief. The new plate system was a reliable and stable implant with a low profile, good strength, and ease of use. Level IV, retrospective case series. © The Author(s) 2015.

Magnetic, electronic and optical properties of different graphene, BN and BC2N nanoribbons

NASA Astrophysics Data System (ADS)

Guerra, T.; Leite, L.; Azevedo, S.; de Lima Bernardo, B.

2017-04-01

Graphene nanoribbons are predicted to be essential components in future nanoelectronics. The size, edge type, form, arrangement of atoms and width of nanoribbons drastically change their properties. However, magnetic, electronic and optical properties of armchair, chevron and sawtooth of graphene, BN and BC2N nanoribbons are not fully understood so far. Here, we make use of first-principles calculations based on the density functional theory (DFT) to investigate the structural, magnetic, electronic and optical properties of nanoribbons of graphene, boron nitride and BC2N with armchair edge, chevron-type and sawtooth forms. The lowest formation energies were found for the armchair and chevron nanoribbons of graphene and boron nitride. We have shown that the imbalance of carbon atoms between different sublattices generates a net magnetic moment. Chevron-type nanoribbons of BC2N and graphene showed a band gap comparable with silicon, and a high light absorption in the visible spectrum when compared to the other configurations.

Chevron starts U.S. gulf`s first Lower Cretaceous flow

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

Petzet, G.A.

1998-06-15

Chevron plans to start production from its Mobile 991 No. 1 well this month. The trend`s first producer is the Viosca Knoll 68 No. 2 well, which went on line April 26 at the anticipated rate of about 15 MMcfd of gas. Chevron has also tested its Viosca Knoll 114 discovery well, drilled in August 1997. Five gas discoveries since 1994 in a trend that extends now Mobile Block 991 to Viosca Knoll Block 252 have recoverable reserve potential of over 600 bcf (gross trend) of natural gas. The paper describes the carbonate trend and exploring the Lower Cretaceous Jamesmore » deposit.« less

Chevron: Refinery Identifies $4.4 Million in Annual Savings by Using Process Simulation Models to Perform Energy-Efficiency Assessment

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

Not Available

2004-05-01

In an energy-efficiency study at its refinery near Salt Lake City, Utah, Chevron focused on light hydrocarbons processing. The company found it could recover hydrocarbons from its fuel gas system and sell them. By using process simulation models of special distillation columns and associated reboilers and condensers, Chevron could predict the performance of potential equipment configuration changes and process modifications. More than 25,000 MMBtu in natural gas could be saved annually if a debutanizer upgrade project and a new saturated gas plant project were completed. Together, these projects would save $4.4 million annually.

Hazardous Waste Cleanup: Chevron Chemical Company in South Plainfield, New Jersey

EPA Pesticide Factsheets

The Chevron Chemical Co. occupies approximately 19 acres in an industrial area of South Plainfield, New Jersey. The facility is bordered on the east by Conrail Property (railroad) and the Hummel Chemical Co.; on the south by a tributary of Bound Brook and

Advanced stimulation technology deployment program, Chevron USA Production Company, Wolfcamp A2 Sand, Pakenham Field, Val Verde Basin. Topical report, July 1995-March 1996

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

Wright, C.A.; Weijers, L.; Minner, W.A.

1996-07-01

This report describes the results from Chevron`s Pakenham Field effort at fracture stimulation engineering which incorporated, to the greatest extent possible, the results of actual measured field data. Measurement of the sand-shale closure stress contrast around the Wolfcamp A2 sand and the relatively high net fracturing pressures (compared to the closure stress contrast) that were observed during real-data (net pressure) fracture treatment analysis revealed that fractures obtained in most of the treatments were much shorter and less confined than originally expected: the fracture half-length was about 200 to 300 ft (instead of about 600 ft), which is consistent with estimatesmore » from post-fracture pressure build-up tests. Based on these measurements, Chevron`s fracturing practices in the Pakenham Field could be carefully reviewed to enhance fracture economics. Supported by the real-data fracture treatment analysis, several changes in completion, fracture treatment design and data-collection procedures were made, such as: (1) using cheaper 20/40 Ottawa sand instead of pre-cured 20/40 resin coated sand; (2) reducing the pad fluid size, as fluid leakoff from the fracture into the formation was relatively low; and, (3) utilizing stepdown tests and proppant slugs to minimize near-wellbore screen-out potential (in the Wolfcamp D sand).« less

Rectus abdominis atrophy after ventral abdominal incisions: midline versus chevron.

PubMed

Vigneswaran, Y; Poli, E; Talamonti, M S; Haggerty, S P; Linn, J G; Ujiki, M B

2017-08-01

Although many outcomes have been compared between a midline and chevron incision, this is the first study to examine rectus abdominis atrophy after these two types of incisions. Patients undergoing open pancreaticobiliary surgery between 2007 and 2011 at our single institution were included in this study. Rectus abdominis muscle thickness was measured on both preoperative and follow-up computed tomography (CT) scans to calculate percent atrophy of the muscle after surgery. At average follow-up of 24.5 and 19.0 months, respectively, rectus abdominis atrophy was 18.9% greater in the chevron (n = 30) than in the midline (n = 180) group (21.8 vs. 2.9%, p < 0.0001). Half the patients with a chevron incision had >20% atrophy at follow-up compared with 10% with a midline incision [odds ratio (OR) 9.0, p < 0.0001]. No significant difference was observed in incisional hernia rates or wound infections between groups. In this study, chevron incisions resulted in seven times more atrophy of the rectus abdominis compared with midline incisions. The long-term effects of transecting the rectus abdominis and disrupting its innervation creates challenging abdominal wall pathology. Atrophy of the abdominal wall can not be readily fixed with an operation, and this significant side effect of a transverse incision should be factored into the surgeon's decision-making process when choosing a transverse over a midline incision.

Distal chevron osteotomy with distal soft tissue procedure for moderate to severe hallux valgus deformity.

PubMed

Bai, Long Bin; Lee, Keun Bae; Seo, Chang Young; Song, Eun Kyoo; Yoon, Taek Rim

2010-08-01

Distal chevron osteotomy has been widely employed to treat mild to moderate hallux valgus deformity. The purpose of the present study was to evaluate the outcomes of distal chevron osteotomy with a distal soft tissue procedure for the correction of moderate to severe hallux valgus. We reviewed 76 patients (86 feet) that underwent distal chevron osteotomy with a distal soft tissue procedure for symptomatic moderate to severe hallux valgus deformity. At a mean followup of 31 months, all patients were evaluated using subjective, objective and radiographic measurements. Ninety-four percent of the patients were very satisfied or satisfied. Average AOFAS score improved from 54.7 points preoperatively to 92.9 at final followup. Average hallux valgus angle changed from 36.2 degrees preoperatively to 12.4 degrees at final followup, and average first-second intermetatarsal angle changed from 17.1 to 7.3 degrees. Average tibial sesamoid position changed from 2.4 preoperatively to 1.2 at final followup. Dorsal angulation of the head was observed in two feet, and plantaflexion of the head in four feet. There were no cases of avascular necrosis of the metatarsal head. Our results indicate that distal chevron osteotomy with a distal soft tissue procedure provides an effective and reliable means of correcting moderate to severe hallux valgus deformity, and that it does so with high levels of patient satisfaction and low incidence of complications.

Ninety-Degree Chevron Osteotomy for Correction of Hallux Valgus Deformity: Clinical Data and Finite Element Analysis

PubMed Central

Matzaroglou, Charalambos; Bougas, Panagiotis; Panagiotopoulos, Elias; Saridis, Alkis; Karanikolas, Menelaos; Kouzoudis, Dimitris

2010-01-01

Hallux valgus is a very common foot disorder, with its prevalence estimated at 33% in adult shoe-wearing populations. Conservative management is the initial treatment of choice for this condition, but surgery is sometimes needed. The 600 angle Chevron osteotomy is an accepted method for correction of mild to moderate hallux valgus in adults less than 60 years old. A modified 900 angle Chevron osteotomy has also been described; this modified technique can confer some advantages compared to the 600 angle method, and reported results are good. In the current work we present clinical data from a cohort of fifty-one female patients who had surgery for sixty-two hallux valgus deformities. In addition, in order to get a better physical insight and study the mechanical stresses along the two osteotomies, Finite Element Analysis (FEA) was also conducted. FEA indicated enhanced mechanical bonding with the modified 900 Chevron osteotomy, because the compressive stresses that keep the two bone parts together are stronger, and the shearing stresses that tend to slide the two bone parts apart are weaker, compared to the typical 600 technique. Follow-up data on our patient cohort show good or excellent long-term clinical results with the modified 900 angle technique. These results are consistent with the FEA-based hypothesis that a 900 Chevron osteotomy confers certain mechanical advantages compared to the typical 600 procedure. PMID:20648223

Jet Noise Modeling for Supersonic Business Jet Application

NASA Technical Reports Server (NTRS)

Stone, James R.; Krejsa, Eugene A.; Clark, Bruce J.

2004-01-01

This document describes the development of an improved predictive model for coannular jet noise, including noise suppression modifications applicable to small supersonic-cruise aircraft such as the Supersonic Business Jet (SBJ), for NASA Langley Research Center (LaRC). For such aircraft a wide range of propulsion and integration options are under consideration. Thus there is a need for very versatile design tools, including a noise prediction model. The approach used is similar to that used with great success by the Modern Technologies Corporation (MTC) in developing a noise prediction model for two-dimensional mixer ejector (2DME) nozzles under the High Speed Research Program and in developing a more recent model for coannular nozzles over a wide range of conditions. If highly suppressed configurations are ultimately required, the 2DME model is expected to provide reasonable prediction for these smaller scales, although this has not been demonstrated. It is considered likely that more modest suppression approaches, such as dual stream nozzles featuring chevron or chute suppressors, perhaps in conjunction with inverted velocity profiles (IVP), will be sufficient for the SBJ.

Analysis of some compliance calibration data for chevron-notch bar and rod specimens

NASA Technical Reports Server (NTRS)

Orange, Thomas W.; Bubsey, Raymond T.; Pierce, William S.; Shannon, John L., Jr.

1991-01-01

A set of equations describing certain fracture mechanics parameters for chevron-notch bar and rod specimens are presented. They are developed by fitting earlier compliance calibration data. The difficulty in determining the minimum stress intensity coefficient and the critical crack length is discussed.

Networking among Chevron Libraries.

ERIC Educational Resources Information Center

Linden, Margaret J.

1989-01-01

Describes the process by which librarians at the Chevron and Gulf Oil Corporations managed the merger of corporation libraries and developed a framework for a company-wide library network. The discussion covers corporate policies for information exchange, shared resources, and cost control, and examines factors that led to the success of the…

Oil Exploration Mapping

NASA Technical Reports Server (NTRS)

1994-01-01

After concluding an oil exploration agreement with the Republic of Yemen, Chevron International needed detailed geologic and topographic maps of the area. Chevron's remote sensing team used imagery from Landsat and SPOT, combining images into composite views. The project was successfully concluded and resulted in greatly improved base maps and unique topographic maps.

Hazardous Waste Cleanup: Chevron Phillips Chemical Puerto Rico Core in Guayama, Puerto Rico

EPA Pesticide Factsheets

Chevron Phillips Chemical Puerto Rico Core (CPCPRC) plant is located on Road 710, km 1.3, approximately 2.5 miles southwest of Guayama, Puerto Rico, and northeast of Las Mareas Harbor. CPCPRC has operated at the Guayama site since 1966. The Guamani River

Development of plane strain fracture toughness test for ceramics using Chevron notched specimens

NASA Technical Reports Server (NTRS)

Bubsey, R. T.; Shannon, J. L., Jr.; Munz, D.

1983-01-01

Chevron-notched four-point-bend and short-bar specimens have been used to determine the fracture toughness of sintered aluminum oxide and hot-pressed silicon nitride ceramics. The fracture toughness for Si3N4 is found to be essentially independent of the specimen size and chevron notch configuration, with values ranging from 4.6 to 4.9 MNm exp -3/2. In contrast, significant specimen size and notch geometry effects have been observed for Al2O3, with the fracture toughness ranging from 3.1 to 4.7 MNm exp -3/2. These effects are attributed to a rising crack growth resistance curve for the Al2O3 tested.

Single absorbable polydioxanone pin fixation for distal chevron bunion osteotomies.

PubMed

Deorio, J K; Ware, A W

2001-10-01

The distal chevron osteotomy is a well-established technique for correction of symptomatic mild to moderate metatarsus primus varus with hallux valgus deformity. Fixation of the osteotomy ranges from none to bone pegs, Kirschner wires, screws, or absorbable pins. We evaluated one surgeon's (J.K.D.) results of distal chevron osteotomy fixation with a single, nonpredrilled, 1.3-mm poly-p-dioxanone pin and analyzed any differences in patients with unilateral or bilateral symptomatic metatarsus primus varus with hallux valgus deformities. All osteotomies healed without evidence of infection, osteolysis, nonunion, or necrosis. Equal correction was achieved in unilateral and bilateral procedures. The technique is quick and easy, and adequate fixation is achieved.

Creative Collaboration between Chevron and CSUB: Research Experience Vitalizing Science -- University Program

ERIC Educational Resources Information Center

Wang, Jianjun

2013-01-01

Since 2007, Chevron has funded the Research Experience Vitalizing Science -- University Program (REVS-UP), which lasts four weeks each summer to develop Science, Technology, Engineering, and Mathematics (STEM) projects at CSUB [California State University, Bakersfield]. Over the past six years, a total of 26 STEM professors have led the…

75 FR 49515 - Notice of Availability of the Final Environmental Impact Statement for the Chevron Energy...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-13

... megawatt (MW) solar photovoltaic project which would connect to an existing Southern California Edison 33... Solutions Lucerne Valley Solar Project, California and the Proposed Amendment to the California Desert... Chevron Energy Solutions Lucerne Valley Solar Project and by this notice is announcing its availability...

Publications - GMC 160 | Alaska Division of Geological & Geophysical

Science.gov Websites

Publications Geologic Materials Center General Information Inventory Monthly Report Hours and Location Policy DGGS GMC 160 Publication Details Title: A geochemical summary report of cuttings from the Chevron USA Schiefelbein, C.F., 1990, A geochemical summary report of cuttings from the Chevron USA Inc. Koniag #1 well

Evaluation of channelizing devices for work zones : type II barricades and chevron panels.

DOT National Transportation Integrated Search

1982-01-01

The objectives of this research were (1) to evaluate the 4-in. (10.2-cm) and 6-in. (15.2-cm) wide alternating diagonal stripes on barricade rails less than 3 ft. (0.92-m) long, and (2) to select the most effective chevron panel. A secondary objective...

Modified Chevron osteotomy for hallux valgus deformity in female athletes. A 2-year follow-up study.

PubMed

Giotis, Dimitrios; Paschos, Nikolaos K; Zampeli, Franceska; Giannoulis, Dionisios; Gantsos, Apostolos; Mantellos, George

2016-09-01

Hallux valgus is an increasingly common deformity in young female athletes that constricts their daily athletic activities and influences foot cosmesis. The aim of this study was to evaluate the outcome of modified Chevron osteotomy for hallux valgus deformity in this specific population. Forty-two cases of modified Chevron osteotomies were carried out in 33 patients with mild to moderate hallux valgus deformity. Each participant was evaluated for AOFAS score, pain, range of motion, cosmetic and radiological outcome. Mean AOFAS score improved to 96.3 (p<0.001) while the mean range of motion of the metatarsophalangeal joint was maintained (p=0.138). The cosmetic result was excellent/good in 40 cases (95%). Mean metatarsophalangeal and intermetatarsal angles were decreased from 29.8° and 14.2° preoperatively to 12.2° and 8.1° postoperatively (p<0.001 and p<0.036), respectively. Modified Chevron osteotomy could offer substantial correction of hallux valgus deformity in young female athletes, with excellent clinical outcome. Copyright © 2015 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.

Boeing's variable geometry chevron: morphing aerospace structures for jet noise reduction

NASA Astrophysics Data System (ADS)

Calkins, Frederick T.; Mabe, James H.; Butler, George W.

2006-03-01

Boeing is applying cutting edge smart material actuators to the next generation morphing technologies for aircraft. This effort has led to the Variable Geometry Chevrons (VGC), which utilize compact, light weight, and robust shape memory alloy (SMA) actuators. These actuators morph the shape of chevrons on the trailing edge of a jet engine in order to optimize acoustic and performance objectives at multiple flight conditions. We have demonstrated a technical readiness level of 7 by successfully flight testing the VGCs on a Boeing 777-300ER with GE-115B engines. In this paper we describe the VGC design, development and performance during flight test. Autonomous operation of the VGCs, which did not require a control system or aircraft power, was demonstrated. A parametric study was conducted showing the influence of VGC configurations on shockcell generated cabin noise reduction during cruise. The VGC system provided a robust test vehicle to explore chevron configurations for community and shockcell noise reduction. Most importantly, the VGC concept demonstrated an exciting capability to optimize jet nozzle performance at multiple flight conditions.

Comparison of distal chevron osteotomy with and without lateral soft tissue release for the treatment of hallux valgus.

PubMed

Lee, Ho-Jin; Chung, Jin-Wha; Chu, In-Tak; Kim, Yoon-Chung

2010-04-01

A lateral soft tissue release is often performed with distal chevron osteotomy for the correction of hallux valgus deformities. However, many complications of lateral soft tissue release have been reported. To define the necessity of lateral soft tissue release, the authors compared the clinical and radiographic results of distal chevron osteotomy with and without it. 86 consecutive patients (152 feet) were enrolled in this prospective study. In Group A, 45 patients (74 feet) underwent a chevron osteotomy with lateral soft tissue release. In Group B, 41 patients (78 feet) underwent a chevron osteotomy without it. Mean followup was 1.7 years and 2.1 years, respectively. The hallux valgus angle (HVA) and intermetatarsal angle (IMA), and AOFAS score were measured preoperatively, and 1-year followup postoperatively and complications were evaluated. The change in HVA, IMA and AOFAS score were insignificant (p > 0.05) between Group A and Group B, however, the range of motion of the first metatarsophalangeal joint was significantly less in Group A (p < 0.05). Complications of digital neuritis and cosmetically dissatisfied scarring of the dorsal web space were seen only in Group A. No cases had avascular necrosis of the metatarsal head, malunion or nonunion. Lateral soft tissue release may not be needed for mild or moderate hallux valgus deformities which may prevent decreased range of motion of the first metatarsophalangeal joint, neuritis of dorsal or plantar lateral digital nerve and cosmetic dissatisfaction of a dorsal scar.

Ninety-degree chevron osteotomy for correction of hallux valgus deformity: clinical data and finite element analysis.

PubMed

Matzaroglou, Charalambos; Bougas, Panagiotis; Panagiotopoulos, Elias; Saridis, Alkis; Karanikolas, Menelaos; Kouzoudis, Dimitris

2010-04-22

Hallux valgus is a very common foot disorder, with its prevalence estimated at 33% in adult shoe-wearing populations. Conservative management is the initial treatment of choice for this condition, but surgery is sometimes needed. The 60(0) angle Chevron osteotomy is an accepted method for correction of mild to moderate hallux valgus in adults less than 60 years old. A modified 90(0) angle Chevron osteotomy has also been described; this modified technique can confer some advantages compared to the 60(0) angle method, and reported results are good. In the current work we present clinical data from a cohort of fifty-one female patients who had surgery for sixty-two hallux valgus deformities. In addition, in order to get a better physical insight and study the mechanical stresses along the two osteotomies, Finite Element Analysis (FEA) was also conducted. FEA indicated enhanced mechanical bonding with the modified 90(0) Chevron osteotomy, because the compressive stresses that keep the two bone parts together are stronger, and the shearing stresses that tend to slide the two bone parts apart are weaker, compared to the typical 60(0) technique. Follow-up data on our patient cohort show good or excellent long-term clinical results with the modified 90(0) angle technique. These results are consistent with the FEA-based hypothesis that a 90(0) Chevron osteotomy confers certain mechanical advantages compared to the typical 60(0) procedure.

Comparative study of scarf and extended chevron osteotomies for correction of hallux valgus.

PubMed

Vopat, Bryan G; Lareau, Craig R; Johnson, Julie; Reinert, Steven E; DiGiovanni, Christopher W

2013-12-01

Scarf and chevron osteotomies are two described treatments for the correction of hallux valgus deformity, but they have traditionally been employed for different levels of severity. We hypothesized that there would be no statistically significant difference between the results of these two treatments. This study is a retrospective review of 70 consecutive patients treated operatively for moderate and severe hallux valgus malalignment. The two groups based on their operative treatment: scarf osteotomy (Group A) and extended chevron osteotomy (Group B). Preoperative and postoperative hallux valgus angle (HVA), intermetatarsal angle and distal metatarsal articular angle (DMAA) were measured at final follow-up. Charts were also assessed to determine the postoperative rate of satisfaction, stiffness, and pain. There were no statistically significant differences between Groups A and B with regard to the HVA preoperatively and postoperatively. The DMAA was statistically significantly higher for Group B both preoperatively (p=0.0403) and postoperatively (p<0.0001). The differences in HVA correction and IMA correction were not statistically significant. There were no statistically significant differences with regard to post-operative stiffness, pain, and satisfaction. The scarf and extended chevron osteotomies are capable of adequately reducing the HVA and IMA in patients with moderate to severe hallux valgus. These two techniques yielded similar patient outcomes in terms of stiffness, pain and satisfaction. Based on these results, we recommend both the scarf and extended chevron osteotomy as acceptable forms of correction for moderate to severe hallux valgus.

TSSGNEO suggestions for refinement of safety criteria for dam at the Sayano-Shushenskaya HPP

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

Savich, A. I.; Gaziev, E. G.

2013-09-15

Analysis of radial-displacements of the dam, measured by direct and inverted plumb lines, indicates that curves of the variation in radial displacements of the dam at different elevations make it possible to plot diagrams of increases in the radial displacement over the entire height of the dam, i.e., inclines of the axis of the dam to the vertical.

Blood supply to the first metatarsal head and vessels at risk with a chevron osteotomy.

PubMed

Malal, J J George; Shaw-Dunn, J; Kumar, C Senthil

2007-09-01

Chevron osteotomy, a commonly performed procedure for the treatment of hallux valgus, results in osteonecrosis of the first metatarsal head in 0% to 20% of cases. The aim of this study was to map out the arrangement of the vascular supply to the first metatarsal head and its relationship to the limbs of the chevron osteotomy. Ten cadaveric lower limbs were injected with an India ink-latex mixture, and the feet were dissected to assess the blood supply to the first metatarsal head. The dissection was carried out by tracing the branches of the dorsalis pedis and posterior tibial vessels. A distal chevron osteotomy was mapped, with the limbs of the osteotomy set at an angle of 60 degrees from the geometric center of the first metatarsal head. The relationship of the limbs of the osteotomy to the blood vessels was recorded. The first metatarsal head was found to be supplied by branches from the first dorsal metatarsal, first plantar metatarsal, and medial plantar arteries. The first dorsal metatarsal artery was the dominant vessel among the three arteries in eight specimens. All of the vessels formed a plexus at the plantar-lateral aspect of the metatarsal neck, just proximal to the capsular attachment, with a varying number of branches from the plexus then entering the metatarsal head. The plantar limb of the proposed chevron cuts exited through this plexus of vessels in all specimens. Contrary to the widely held view, only minor vascular branches could be found entering the dorsal aspect of the neck. The identification of the plantar-lateral corner of the metatarsal neck as the major site of vascular ingress into the first metatarsal head suggests that constructing the chevron osteotomy with a long plantar limb exiting well proximal to the capsular attachment may decrease the postoperative prevalence of osteonecrosis of the first metatarsal head.

Flight Test Results for Uniquely Tailored Propulsion-Airframe Aeroacoustic Chevrons: Shockcell Noise

NASA Technical Reports Server (NTRS)

Mengle, Vinod G.; Ganz, Ulrich W.; Nesbitt, Eric; Bultemeier, Eric J.; Thomas, Russell H.; Nesbitt, Eric

2006-01-01

Azimuthally varying chevrons (AVC) which have been uniquely tailored to account for the asymmetric propulsion-airframe aeroacoustic interactions have recently shown significant reductions in jet-related community noise at low-speed take-off conditions in scale model tests of coaxial nozzles with high bypass ratio. There were indications that such AVCs may also provide shockcell noise reductions at high cruise speeds. This paper describes the flight test results when one such AVC concept, namely, the T-fan chevrons with enhanced mixing near the pylon, was tested at full-scale on a modern large twin-jet aircraft (777-300ER) with focus on shockcell noise at mid-cruise conditions. Shockcell noise is part of the interior cabin noise at cruise conditions and its reduction is useful from the viewpoint of passenger comfort. Noise reduction at the source, in the exhaust jet, especially, at low frequencies, is beneficial from the perspective of reduced fuselage sidewall acoustic lining. Results are shown in terms of unsteady pressure spectra both on the exterior surface of the fuselage at several axial stations and also microphone arrays placed inside the fuselage aft of the engine. The benefits of T-fan chevrons, with and without conventional chevrons on the core nozzle, are shown for several engine operating conditions at cruise involving supersonic fan stream and subsonic or supersonic core stream. The T-fan AVC alone provides up to 5 dB low-frequency noise reduction on the fuselage exterior skin and up to 2 dB reduction inside the cabin. Addition of core chevrons appears to increase the higher frequency noise. This flight test result with the previous model test observation that the T-fan AVCs have hardly any cruise thrust coefficient loss (< 0.05%) make them viable candidates for reducing interior cabin noise in high bypass ratio engines.

Motor System Upgrades Smooth the Way to Savings of $700,000 at Chevron Refinery

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

None

1999-01-01

By upgrading its motor systems at its Richmond, California refinery, Chevron was able to realize cost savings of more than $700,000 per year, in addition to reduced energy consumption of approximately 1 million kilowatts per month and improved equipment reliability and process control. This fact sheet tells how they did it.

LEAK AND GAS PERMEABILITY TESTING DURING SOIL-GAS SAMPLING AT HAL'S CHEVRON LUST SITE IN GREEN RIVER, UTAH

EPA Science Inventory

The results of gas permeability and leak testing during active soil-gas sampling at Hal’s Chevron LUST Site in Green River, Utah are presented. This study was conducted to support development of a passive soil-gas sampling method. Gas mixtures containing helium and methane were...

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Science.gov Websites

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75 FR 6057 - Notice of Availability of the Draft Environmental Impact Statement for the Proposed Chevron...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-05

... right-of-way (ROW) authorization to construct and operate a 45-megawatt solar photovoltaic project and... Energy Solutions Lucerne Valley Solar Project, San Bernardino County, CA, and the Draft California Desert... Statement (EIS) for the proposed Chevron Energy Solutions Lucerne Valley Solar Project and by this notice is...

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Science.gov Websites

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Adaptation of the chevron-notch beam fracture toughness method to specimens harvested from diesel particulate filters

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

Wereszczak, Andrew; Jadaan, Osama; Modugno, Max

In this paper, the apparent fracture toughness of a porous cordierite ceramic was estimated using a large specimen whose geometry was inspired by the ASTM-C1421-standardized chevron-notch beam. In this paper, using the same combination of experiment and analysis used to develop the standardized chevron-notch test for small, monolithic ceramic bend bars, an apparent fracture toughness of 0.6 and 0.9 MPa√m were estimated for an unaged and aged cordierite diesel particulate filter structure, respectively. Finally, the effectiveness and simplicity of this adapted specimen geometry and test method lends itself to the evaluation of (macroscopic) apparent fracture toughness of an entire porous-ceramic,more » diesel particulate filter structure.« less

Adaptation of the chevron-notch beam fracture toughness method to specimens harvested from diesel particulate filters

DOE PAGES

Wereszczak, Andrew; Jadaan, Osama; Modugno, Max; ...

2017-01-18

In this paper, the apparent fracture toughness of a porous cordierite ceramic was estimated using a large specimen whose geometry was inspired by the ASTM-C1421-standardized chevron-notch beam. In this paper, using the same combination of experiment and analysis used to develop the standardized chevron-notch test for small, monolithic ceramic bend bars, an apparent fracture toughness of 0.6 and 0.9 MPa√m were estimated for an unaged and aged cordierite diesel particulate filter structure, respectively. Finally, the effectiveness and simplicity of this adapted specimen geometry and test method lends itself to the evaluation of (macroscopic) apparent fracture toughness of an entire porous-ceramic,more » diesel particulate filter structure.« less

Biomechanical Comparison of Fixation With a Single Screw Versus Two Kirschner Wires in Distal Chevron Osteotomies of the First Metatarsal: A Cadaver Study.

PubMed

Trost, Matthias; Bredow, Jan; Boese, Christoph Kolja; Loweg, Lennard; Schulte, Tobias Ludger; Scaal, Martin; Eysel, Peer; Oppermann, Johannes

Distal chevron osteotomy is a common procedure for surgical correction of hallux valgus. Osteosynthesis with 1 screw or 2 Kirschner wires has been commonly used. We compared the stability of the 2 techniques in distal chevron osteotomy. Sixteen first metatarsals from fresh-frozen human cadaver feet (9 different cadaveric specimens) were used. A standardized distal chevron osteotomy was performed. One first metatarsal from each pair was assigned to group 1 (3.5-mm cortical screw; n = 8) and one to group 2 (two 1.6-mm Kirschner wires; n = 8). Using a materials testing machine, the head of the first metatarsals was loaded in 2 different configurations (cantilever and physiologic) in succession. In the cantilever configuration, the relative stiffness of the osteosynthesis compared with intact bone was 59% ± 27% in group 1 and 68% ± 18% in group 2 (p = .50). In the physiologic configuration, it was 38% ± 25% in group 1 and 35% ± 7% in group 2 (p = .75). The failure strength in the cantilever configuration was 187 ± 105 N in group 1 and 259 ± 71 N in group 2 (p = .21). No statistically significant differences were found in stability between the 2 techniques. The use of 1 screw or 2 Kirschner wires had no significant differences in their biomechanical loading capacity for osteosynthesis in distal chevron osteotomies for treatment of hallux valgus. Copyright © 2017 The American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Outcomes of proximal chevron osteotomy for moderate versus severe hallux valgus deformities.

PubMed

Moon, Jae-Young; Lee, Keun-Bae; Seon, Jong Keun; Moon, Eun-Sun; Jung, Sung-Taek

2012-08-01

Proximal chevron osteotomy with a distal soft tissue procedure has been widely used to treat moderate to severe hallux valgus deformities. However, there have been no studies comparing the results of proximal chevron osteotomy between patients with moderate and severe hallux valgus. We compared the results of this procedure among these groups. A retrospective review of 95 patients (108 feet) that underwent proximal chevron osteotomy and distal soft tissue procedure for moderate and severe hallux valgus was conducted. The 108 feet were divided into two groups: moderate hallux valgus (Group A) and severe hallux valgus (Group B). Group A was composed of 57 feet (52 patients) and Group B of 51 feet (43 patients). Average followup was 45 months. Mean American Orthopedic Foot and Ankle Society hallux metatarsophalangeal-interphalangeal scores were 54.1 points in Group A and 53.0 points in Group B preoperatively, and these improved to 90.8 and 92.6, respectively, at the last followup. Mean hallux valgus angles in Groups A and B reduced from 32.3 and 40.8 degrees, preoperatively to 10.7 and 13.2 degrees, postoperatively. Similarly, mean first intermetatarsal angles in Groups A and B reduced from 15.0 and 19.2 degrees, preoperatively to 9.0 and 9.2 degrees, postoperatively. The clinical and radiographic outcomes of proximal chevron osteotomy with a distal soft tissue procedure were found to be comparable for moderate and severe hallux valgus. Accordingly, our results suggest that this procedure provides an effective and reliable means of correcting hallux valgus regardless of severity of deformity.

Correlation of Postoperative Position of the Sesamoids After Chevron Osteotomy With Outcome.

PubMed

Shi, Glenn G; Henning, Peter; Marks, Richard M

2016-03-01

Postoperative incomplete reduction of the sesamoids has been identified as a potential risk factor for hallux valgus recurrence after proximal osteotomy. However, it is not known whether the postoperative sesamoid position is a risk factor in hallux valgus correction via distal chevron osteotomy with or without dorsal webspace release (DWSR). In this retrospective study, 169 patients who underwent distal chevron osteotomy with or without DWSR were reviewed. Preoperative and postoperative (6 weeks, 6 months, 12 months) weightbearing radiographs were evaluated. Functional hallux valgus angle (HVA), intermetatarsal angle (IMA), and the position of the tibial sesamoid were graded using the center of head method. Seventy-six radiographs were available for review at the 12-month follow-up. Of these, 41 patients underwent DWSR procedure and 35 did not. In both groups, correction of all 3 parameters (HVA, IMA, tibial sesamoid position) were significant at the 12-month follow-up. Comparison of the postoperative results of the 2 groups showed no statistically significant differences. Four feet demonstrated displaced sesamoid position at the 12-month follow-up, with radiographic evidence of recurrence in just one. No significant relationship was found between postoperative sesamoid position and hallux valgus recurrence that occurred in 4 feet. Combining DWSR with a distal chevron osteotomy did not delay healing or increase risk of avascular necrosis, but it did not significantly improve angular measurements or sesamoid position. The concept that postoperative sesamoid position can be used to predict hallux valgus recurrence was not supported by our results when looking at distal chevron correction. Level III, retrospective comparative study. © The Author(s) 2015.

Treatment of Crowe Type-IV Hip Dysplasia Using Cementless Total Hip Arthroplasty and Double Chevron Subtrochanteric Shortening Osteotomy: A 5- to 10-Year Follow-Up Study.

PubMed

Li, Xigong; Lu, Yang; Sun, Junying; Lin, Xiangjin; Tang, Tiansi

2017-02-01

The purpose of this study was to evaluate the functional and radiographic results of patients with Crowe type-IV hip dysplasia treated by cementless total hip arthroplasty and double chevron subtrochanteric osteotomy. From January 2000 to February 2006, cementless total hip arthroplasty with a double chevron subtrochanteric shortening osteotomy was performed on 18 patients (22 hips) with Crowe type-IV dysplasia. The acetabular cup was placed in the position of the anatomic hip center, and subtrochanteric femoral shortening osteotomy was performed with the use of a double chevron design. The clinical and radiographic outcomes were reviewed with a mean follow-up of 6.5 years (5-10 years). The mean amount of femoral subtrochanteric shortening was 38 mm (25-60 mm). All osteotomy sites were healed by 3-6 months without complications. The mean Harris Hip Score improved significantly from 47 points (35-65 points) preoperatively to 88 points (75-97 points) at the final follow-up. The Trendelenburg sign was corrected from a positive preoperative status to a negative postoperative status in 12 of 22 hips. No acetabular and femoral components have loosened or required revision during the period of follow-up. Cementless total hip arthroplasty using double chevron subtrochanteric osteotomy allowed for restoration of anatomic hip center with safely functional limb lengthening, achieved correction of preoperative limp, and good functional and radiographic outcomes for 22 Crowe type-IV dislocation hips at the time of the 5- to 10-year follow-up. Copyright © 2016 Elsevier Inc. All rights reserved.

Analytical and computational studies on the vacuum performance of a chevron ejector

NASA Astrophysics Data System (ADS)

Kong, F. S.; Jin, Y. Z.; Kim, H. D.

2016-11-01

The effects of chevrons on the performance of a supersonic vacuum ejector-diffuser system are investigated numerically and evaluated theoretically in this work. A three-dimensional geometrical domain is numerically solved using a fully implicit finite volume scheme based on the unsteady Reynolds stress model. A one-dimensional mathematical model provides a useful tool to reveal the steady flow physics inside the vacuum ejector-diffuser system. The effects of the chevron nozzle on the generation of recirculation regions and Reynolds stress behaviors are studied and compared with those of a conventional convergent nozzle. The present performance parameters obtained from the simulated results and the mathematical results are validated with existing experimental data and show good agreement. Primary results show that the duration of the transient period and the secondary chamber pressure at a dynamic equilibrium state depend strongly on the primary jet conditions, such as inlet pressure and primary nozzle shape. Complicated oscillatory flow, generated by the unsteady movement of recirculation, finally settles into a dynamic equilibrium state. As a vortex generator, the chevron demonstrated its strong entrainment capacity to accelerate the starting transient flows to a certain extent and reduce the dynamic equilibrium pressure of the secondary chamber significantly.

Chevron folding patterns and heteroclinic orbits

NASA Astrophysics Data System (ADS)

Budd, Christopher J.; Chakhchoukh, Amine N.; Dodwell, Timothy J.; Kuske, Rachel

2016-09-01

We present a model of multilayer folding in which layers with bending stiffness EI are separated by a very stiff elastic medium of elasticity k2 and subject to a horizontal load P. By using a dynamical system analysis of the resulting fourth order equation, we show that as the end shortening per unit length E is increased, then if k2 is large there is a smooth transition from small amplitude sinusoidal solutions at moderate values of P to larger amplitude chevron folds, with straight limbs separated by regions of high curvature when P is large. The chevron solutions take the form of near heteroclinic connections in the phase-plane. By means of this analysis, values for P and the slope of the limbs are calculated in terms of E and k2.

Miranda - 'Chevron' Grooves

NASA Technical Reports Server (NTRS)

1986-01-01

This image of Miranda, obtained by Voyager 2 on approach, shows an unusual 'chevron' figure and regions of distinctly differing terrain on the Uranian moon. Voyager was 42,000 kilometers (26,000 miles) away when its narrow-angle camera acquired this clear-filter view. Grooved areas baring light and dark bands, distinct from other areas of mottled terrain, are visible at this resolution of about 600 meters (2,000 feet). The bright V-shaped feature in the grooved areas is the 'chevron' observed in earlier, lower-resolution images. Cutting across the bands are sinuous scarps, probably faults. Superimposed on both types of terrain are many bowl-shaped impact craters less than 5 km (3 mi) wide. The entire picture spans an area about 220 km (140 mi) across. The Voyager project is managed for NASA by the Jet Propulsion Laboratory.

Mean Flow and Noise Prediction for a Separate Flow Jet With Chevron Mixers

NASA Technical Reports Server (NTRS)

Koch, L. Danielle; Bridges, James; Khavaran, Abbas

2004-01-01

Experimental and numerical results are presented here for a separate flow nozzle employing chevrons arranged in an alternating pattern on the core nozzle. Comparisons of these results demonstrate that the combination of the WIND/MGBK suite of codes can predict the noise reduction trends measured between separate flow jets with and without chevrons on the core nozzle. Mean flow predictions were validated against Particle Image Velocimetry (PIV), pressure, and temperature data, and noise predictions were validated against acoustic measurements recorded in the NASA Glenn Aeroacoustic Propulsion Lab. Comparisons are also made to results from the CRAFT code. The work presented here is part of an on-going assessment of the WIND/MGBK suite for use in designing the next generation of quiet nozzles for turbofan engines.

The Bare Area of the Proximal Ulna: An Anatomic Study With Relevance to Chevron Osteotomy.

PubMed

Ao, Rongguang; Zhang, Xu; Li, Dejian; Chen, Fancheng; Zhou, Jianhua; Yu, Baoqing

2017-06-01

A chevron osteotomy of the ulna is widely used to obtain intra-articular access to the elbow in the treatment of type C distal humerus fractures. The trochlear notch of the proximal ulna is divided into 2 articular parts by the "bare area." Ideally, the olecranon osteotomy should be centered on the bare area to minimize damage to the joint cartilage. The goals of this study were to describe the anatomy of the bare area and design an ideal chevron-shaped osteotomy. We dissected 38 cadaver elbows and measured the width of the bare area, the distance between the tip of the triceps insertion and the area on the olecranon cortex corresponding to the bare area. We then designed a chevron osteotomy to stay within the bare area and measured the distance from the tip of the triceps insertion to the osteotomy apex as well as the angle of the osteotomy plane and the angle of the chevron cuts. The bare area existed in all 38 cadavers. The mean longitudinal and transverse widths were 4.0 mm (range, 1.0-8.6 mm) and 19.0 mm (range, 16.9-23.8 mm), respectively. The mean distance between the tip of the triceps insertion and the area on the olecranon cortex corresponding to the bare area was 19.0 mm (range, 16.0-23.0 mm). The mean transverse and longitudinal widths of the cortical notch were 3.0 mm (range, 1.6-4.5 mm) and 8.0 mm (range, 6.5-14.8 mm), respectively. The mean distance between the tip of the triceps insertion and the osteotomy apex was 22.0 mm (range, 18.0-24.0 mm) and the mean angle between the osteotomy surface and the vertical plane corresponding to the tangent plane was 20° (range, 10° to 25°). The mean angle of the V shape was 140° (range, 130° to 150°). Using the narrowest edge lacking cartilage (lateral or medial side) as a point of reference to locate the bare area, the designed chevron osteotomy entered the joint in the bare area in most specimens and decreased associated damage to the joint cartilage. This study describes the anatomy of the bare area and the design of the ideal chevron-shaped osteotomy to treat type C distal humerus fractures. Copyright © 2017 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Crack resistance determination of material by wedge splitting a chevron-notched specimen

NASA Astrophysics Data System (ADS)

Deryugin, Ye. Ye.

2017-12-01

An original method is proposed for the crack resistance determination of a material by wedge splitting of a chevron-notched specimen. It was developed at the Institute of Strength Physics and Materials Science SB RAS in the laboratory of Physical Mesomechanics and Nondestructive Methods of Control. An example of the crack resistance test of technical titanium VT1-0 is considered.

Chevron osteotomy with lateral release and adductor tenotomy for hallux valgus.

PubMed

Potenza, Vito; Caterini, Roberto; Farsetti, Pasquale; Forconi, Fabrizio; Savarese, Eugenio; Nicoletti, Simone; Ippolito, Ernesto

2009-06-01

Distal chevron osteotomy is a procedure widely performed for the surgical treatment of painful hallux valgus. The risks and benefits of a lateral capsular release and adductor tenotomy combined with chevron osteotomy are still debated. The aim of our study was to report the clinical and radiographic outcomes of this combined procedure in mild and moderate incongruent bunion deformities, with a hallux valgus angle (HVA) up to 40 degrees and an intermetatarsal angle (IMA) up to 20 degrees. Forty-two patients (52 feet) who consecutively underwent chevron osteotomy combined with lateral release and adductor tenotomy were reviewed 24-36 months after surgery. The mean age of the patients was 53.5 (range, 43 to 64) years. All the deformities were mild to moderate, with a mean preoperative value of 28 degrees in the HVA (range, 16 degrees to 40 degrees) and of 13 degrees in the IMA (range, 9 degrees to 20 degrees). At followup, the AOFAS hallux score improved from an average of 46 to an average of 88. The HVA and IMA had an average postoperative decrease respectively of 12 degrees and 6 degrees; lateral sesamoid displacement decreased by a mean of 15%. In no case did we observe infection or nonunion of the osteotomy. In one case, painless avascular necrosis of the first metatarsal head developed. Our short-term results show that distal chevron osteotomy combined with lateral release and adductor tenotomy is a feasible surgical option to address mild to moderate hallux valgus deformity, even with an IM angle between 15 and 20 degrees. Clinical and radiographic outcomes are generally good and patient satisfaction is generally high.

Long-term Follow-up of a Randomized Controlled Trial Comparing Scarf to Chevron Osteotomy in Hallux Valgus Correction.

PubMed

Jeuken, Ralph M; Schotanus, Martijn G M; Kort, Nanne P; Deenik, Axel; Jong, Bob; Hendrickx, Roel P M

2016-07-01

Hallux valgus is one of the most common foot deformities. This long-term follow-up study compared the results of 2 widely used operative treatments for hallux valgus: the scarf and chevron osteotomy. Conventional weight bearing anteroposterior (AP) radiographs of the foot were made for evaluating the intermetatarsal angle and hallux valgus angle. For clinical evaluation, the American Orthopaedic Foot & Ankle Society (AOFAS) rating system for the hallux metatarsophalangeal-interphalangeal scale was used together with physical examination of the foot. These data were compared with the results from the original study. The Short Form 36 questionnaire, the Manchester-Oxford Foot Questionnaire (MOXFQ), and a general questionnaire including a visual analog scale (VAS) pain score were used for subjective evaluation. The primary outcome measures were the radiologic recurrence of hallux valgus and reoperation rate of the same toe. Secondary outcome measures were the results from the radiographs and subjective and clinical evaluation. The response rate was 76% at the follow-up of 14 years; in the chevron group, 37 feet were included compared with 36 feet in the scarf group. Twenty-eight feet in the chevron group and 27 in the scarf group developed recurrence of hallux valgus (P = .483). One patient in the scarf group had a reoperation of the same toe compared with none in the chevron group (P = .314). Current VAS pain scores and results from the SF-36, MOXFQ, and AOFAS did not significantly differ between groups. Both techniques showed similar results after 2 years of follow-up. At 14 years of follow-up, neither technique was superior in preventing recurrence. Level II, randomized controlled trial. © The Author(s) 2016.

Role of intraoperative varus stress test for lateral soft tissue release during chevron bunion procedure.

PubMed

Kim, Hyong-Nyun; Suh, Dong-Hyun; Hwang, Pil-Sung; Yu, Sun-O; Park, Yong-Wook

2011-04-01

The purpose of this study was to evaluate the clinical results of distal chevron osteotomy performed in conjunction with selective lateral soft tissue release. The criterion for doing a lateral soft tissue release was assessed by determining the ease and completeness of passive hallux valgus correction at the time of surgery. Between August 2005 and November 2007, 48 feet in 43 patients classified as having mild to moderate hallux valgus were retrospectively studied. Distal chevron osteotomy without lateral soft tissue release was performed in 26 cases (Group 1) when passive correction of the hallux valgus deformity was possible. Distal chevron osteotomy with lateral soft tissue release was performed in 22 cases (Group 2) when passive correction was not possible. Average followup was 23 (range, 12 to 28) months. Clinical results were assessed using radiographic parameters [hallux valgus angle (HVA), first and second intermetatarsal angle (1,2 IMA)], AOFAS scale and patient's subjective satisfaction. For Group 1: the average correction of HVA was 12.8 degrees, the average correction of IMA was 4.7 degrees, and the AOFAS score improved an average of 29.2 points at the last followup. Thirteen patients were very satisfied and ten patients were satisfied with the results. No patient was dissatisfied. For Group 2: the average correction of HVA was 19.1 degrees, the average correction of IMA was 7 degrees and AOFAS score improved at an average of 31.8 points at the last followup. Twelve patients were very satisfied, seven patients were satisfied and one patient, who had stiffness of the first metatarsophalangeal joint, was dissatisfied with the result. Distal chevron osteotomy with selective lateral soft tissue release based on the ability to passively correct the hallux valgus deformity lead to safe and stable correction.

Holocene Indian Ocean Cosmic Impacts: The Megatsunami Chevron Evidence From Madagascar

NASA Astrophysics Data System (ADS)

Masse, W.; Bryant, E.; Gusiakov, V.; Abbott, D.; Rambolamana, G.; Raza, H.; Courty, M.; Breger, D.; Gerard-Little, P.; Burckle, L.

2006-12-01

The 2.6 million year Quaternary period terrestrial physical record lacks definitive crater evidence for major regional catastrophic impacts by asteroids and comets other than the 10.5-km diameter Botsumtwi structure in Ghana and the 14.0-km diameter Zhamanshin structure in Kazakhstan [1] dating between about 900 and 1100 kya. Current cosmic impact rate models suggest that an average of between 3-6 globally catastrophic impacts should have occurred on the Earth during the Quaternary, along with several additional significant regional impacts in addition to Zhamanshin and Botsumtwi. These models and data indicate that the great majority of the "missing" major impact locations would likely have occurred in poorly studied oceanic settings. Only recently have Late Quaternary and Holocene period coastal paleo-megatsunami chevron deposits been defined in the Caribbean and along the western coasts of Australia, along with the suggestion that some may have been created by oceanic cosmic impacts in distinction to those caused by landslips, eruptions, and seismic events. We investigate the possibility that many or most megatsunami chevrons occurring along the southern coast of Madagascar were caused by two or more major Holocene Indian Ocean cosmic impacts. This hypothesis is based on an initial study of the worldwide archaeological and anthropological record, and the preliminary study of satellite images of the chevrons, selected Indian Ocean deep-sea cores, sea-floor bathymetry, and physical examination of the Madagascar deposits themselves. Candidate Indian Ocean impact structures are identified and correlated with the southern Madagascar megatsunami chevron deposits. [1] Masse, W.B. 2007 The Archaeology and Anthropology of Quaternary Period Cosmic Impact. In Bobrowsky, P.T. & Rickman, H. (eds.)Comets/Asteroid Impacts and Human Society. Springer, Berlin (in press).

Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

NASA Technical Reports Server (NTRS)

Simon-Miller, Amy A.; Choi, David; Rogers, John H.; Gierasch, Peter J.; Allison, Michael D.; Adamoli, Gianluigi; Mettig, Hans-Joerg

2012-01-01

A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 S planetographic latitude shows variations in velocity with longitude and time. The presence of the large anticyclonic South Equatorial Disturbance (SED) has a profound effect on the chevron velocity, causing slower velocities to its east and accelerations over distance from the disturbance. The chevrons move with velocities near the maximum wind jet velocity of approx 140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 N latitude. Their repetitive nature is consistent with a gravity-inertia wave (n = 75 to 100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, for the first time, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a 6.7 +/- 0.7-day period. This oscillating motion has a wavelength of approx 20 and a speed of 101 +/- 3 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it. All dates show chevron latitude variability, but it is unclear if this larger wave is present during other epochs, as there are no other suitable time series movies that fully delineate it. In the presence of mUltiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S is likely due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

Studies of the acoustic transmission characteristics of coaxial nozzles with inverted velocity profiles, volume 1. [jet engine noise radiation through coannular exhaust nozzles

NASA Technical Reports Server (NTRS)

Dean, P. D.; Salikuddin, M.; Ahuja, K. K.; Plumblee, H. E.; Mungur, P.

1979-01-01

The efficiency of internal noise radiation through coannular exhaust nozzle with an inverted velocity profile was studied. A preliminary investigation was first undertaken to: (1) define the test parameters which influence the internal noise radiation; (2) develop a test methodology which could realistically be used to examine the effects of the test parameters; (3) and to validate this methodology. The result was the choice of an acoustic impulse as the internal noise source in the in the jet nozzles. Noise transmission characteristics of a nozzle system were then investigated. In particular, the effects of fan nozzle convergence angle, core extention length to annulus height ratio, and flow Mach number and temperatures were studied. The results are presented as normalized directivity plots.

Effects of subcritical crack growth on fracture toughness of ceramics assessed in chevron-notched three-point bend tests

NASA Technical Reports Server (NTRS)

Chao, L. Y.; Singh, D.; Shetty, D. K.

1988-01-01

A numerical computational study was carried out to assess the effects of subcritical crack growth on crack stability in the chevron-notched three-point bend specimens. A power-law relationship between the subcritical crack velocity and the applied stress intensity were used along with compliance and stress-intensity relationships for the chevron-notched bend specimen to calculate the load response under fixed deflection rate and a machine compliance. The results indicate that the maximum load during the test occurs at the same crack length for all the deflection rates; the maximum load, however, is dependent on the deflection rate for rates below the critical rate. The resulting dependence of the apparent fracture toughness on the deflection rate is compared to experimental results on soda-lime glass and polycrystalline alumina.

Resistive anode image converter

NASA Technical Reports Server (NTRS)

Lampton, M. L.; Paresce, F. (Inventor)

1976-01-01

The invention of an apparatus for imaging soft X-ray and ultraviolet electromagnetic radiation and charged particles was described. The apparatus includes a pair of microchannel electron multiplier plates connected in a cascaded chevron configuration which intercepts an incident beam of radiation or charged particles. Incident photons or charged particles strike the front surface of the chevron configuration causing emission of electrons. The electrons are accelerated by a voltage gradient and strike the inner side walls of the individual channels, causing emission of secondary electrons. Accelerated and multiplied secondary electrons impinge upon a resistive anode after they transverse the chevron configuration. A pulse position circuit converts the magnitude or transit time of the currents flowing from the point of impact of the electrons on the resistive anode to four contact electrodes mounted on their periphery of the resistive anode into the spatial coordinates of electron impact.

Seismic data compression speeds exploration projects

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

Galibert, P.Y.

As part of an ongoing commitment to ensure industry-wide distribution of its revolutionary seismic data compression technology, Chevron Petroleum Technology Co. (CPTC) has entered into licensing agreements with Compagnie Generale de Geophysique (CGG) and other seismic contractors for use of its software in oil and gas exploration programs. CPTC expects use of the technology to be far-reaching to all of its industry partners involved in seismic data collection, processing, analysis and storage. Here, CGG--one of the world`s leading seismic acquisition and processing companies--talks about its success in applying the new methodology to replace full on-board seismic processing. Chevron`s technology ismore » already being applied on large off-shore 3-D seismic surveys. Worldwide, CGG has acquired more than 80,000 km of seismic data using the data compression technology.« less

Experimental study of turbulent flow heat transfer and pressure drop in a plate heat exchanger with chevron plates

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

Muley, A.; Manglik, R.M.

1997-07-01

Experimental data for isothermal pressure drop and heat transfer in single-phase water flows in a plate heat exchanger (PHE) with chevron plates are presented. A single-pass, U-type, counterflow PHE, with three different chevron plate arrangements is employed: two symmetric plate arrangements with {beta} = 30/30{degree} and 60/60{degree}, and a mixed-plate arrangement with {beta} = 30/60{degree}. With water flow rates in the turbulent flow regime (600 < Re < 10{sup 4} and 2 < Pr < 6), effects of the chevron corrugation inclination angle {beta} on Nu and f characteristics of the PHE are investigated. As {beta} increases and compared tomore » a flat-plate pack, up to 2 to 5 times higher Nu are obtained; the concomitant f, however, are 13 to 44 times higher. Based on the experimental data for Re {le} 1,000, predictive correlations of the form Nu = C{sub 1}{beta} Re{sup p1({beta})} Pr{sup 1/3} ({mu}/{mu}{sub w}){sup 0.14} and f = C{sub 2}{beta} Re{sup p2({beta})} are devised. Also, at constant pumping power and depending upon {beta}, the heat transfer is found to be enhanced over 1.8 times that in equivalent flat-plate channels.« less

Two genetic loci control syllable sequences of ultrasonic courtship vocalizations in inbred mice

PubMed Central

2011-01-01

Background The ultrasonic vocalizations (USV) of courting male mice are known to possess a phonetic structure with a complex combination of several syllables. The genetic mechanisms underlying the syllable sequence organization were investigated. Results This study compared syllable sequence organization in two inbred strains of mice, 129S4/SvJae (129) and C57BL6J (B6), and demonstrated that they possessed two mutually exclusive phenotypes. The 129S4/SvJae (129) strain frequently exhibited a "chevron-wave" USV pattern, which was characterized by the repetition of chevron-type syllables. The C57BL/6J strain produced a "staccato" USV pattern, which was characterized by the repetition of short-type syllables. An F1 strain obtained by crossing the 129S4/SvJae and C57BL/6J strains produced only the staccato phenotype. The chevron-wave and staccato phenotypes reappeared in the F2 generations, following the Mendelian law of independent assortment. Conclusions These results suggest that two genetic loci control the organization of syllable sequences. These loci were occupied by the staccato and chevron-wave alleles in the B6 and 129 mouse strains, respectively. Recombination of these alleles might lead to the diversity of USV patterns produced by mice. PMID:22018021

Experimental and Numerical Study on the Cracked Chevron Notched Semi-Circular Bend Method for Characterizing the Mode I Fracture Toughness of Rocks

NASA Astrophysics Data System (ADS)

Wei, Ming-Dong; Dai, Feng; Xu, Nu-Wen; Liu, Jian-Feng; Xu, Yuan

2016-05-01

The cracked chevron notched semi-circular bending (CCNSCB) method for measuring the mode I fracture toughness of rocks combines the merits (e.g., avoidance of tedious pre-cracking of notch tips, ease of sample preparation and loading accommodation) of both methods suggested by the International Society for Rock Mechanics, which are the cracked chevron notched Brazilian disc (CCNBD) method and the notched semi-circular bend (NSCB) method. However, the limited availability of the critical dimensionless stress intensity factor (SIF) values severely hinders the widespread usage of the CCNSCB method. In this study, the critical SIFs are determined for a wide range of CCNSCB specimen geometries via three-dimensional finite element analysis. A relatively large support span in the three point bending configuration was considered because the fracture of the CCNSCB specimen in that situation is finely restricted in the notch ligament, which has been commonly assumed for mode I fracture toughness measurements using chevron notched rock specimens. Both CCNSCB and NSCB tests were conducted to measure the fracture toughness of two different rock types; for each rock type, the two methods produce similar toughness values. Given the reported experimental results, the CCNSCB method can be reliable for characterizing the mode I fracture toughness of rocks.

A comparison of proximal and distal chevron osteotomy for the correction of moderate hallux valgus deformity.

PubMed

Park, C-H; Jang, J-H; Lee, S-H; Lee, W-C

2013-05-01

The purpose of this study was to compare the results of proximal and distal chevron osteotomy in patients with moderate hallux valgus. We retrospectively reviewed 34 proximal chevron osteotomies without lateral release (PCO group) and 33 distal chevron osteotomies (DCO group) performed sequentially by a single surgeon. There were no differences between the groups with regard to age, length of follow-up, demographic or radiological parameters. The clinical results were assessed using the American Orthopaedic Foot and Ankle Society (AOFAS) scoring system and the radiological results were compared between the groups. At a mean follow-up of 14.6 months (14 to 32) there were no significant differences in the mean AOFAS scores between the DCO and PCO groups (93.9 (82 to 100) and 91.8 (77 to 100), respectively; p = 0.176). The mean hallux valgus angle, intermetatarsal angle and sesamoid position were the same in both groups. The metatarsal declination angle decreased significantly in the PCO group (p = 0.005) and the mean shortening of the first metatarsal was significantly greater in the DCO group (p < 0.001). We conclude that the clinical and radiological outcome after a DCO is comparable with that after a PCO; longer follow-up would be needed to assess the risk of avascular necrosis.

Advanced Subsonic Technology (AST) Separate-Flow High-Bypass Ratio Nozzle Noise Reduction Program Test Report

NASA Technical Reports Server (NTRS)

Low, John K. C.; Schweiger, Paul S.; Premo, John W.; Barber, Thomas J.; Saiyed, Naseem (Technical Monitor)

2000-01-01

NASA s model-scale nozzle noise tests show that it is possible to achieve a 3 EPNdB jet noise reduction with inwardfacing chevrons and flipper-tabs installed on the primary nozzle and fan nozzle chevrons. These chevrons and tabs are simple devices and are easy to be incorporated into existing short duct separate-flow nonmixed nozzle exhaust systems. However, these devices are expected to cause some small amount of thrust loss relative to the axisymmetric baseline nozzle system. Thus, it is important to have these devices further tested in a calibrated nozzle performance test facility to quantify the thrust performances of these devices. The choice of chevrons or tabs for jet noise suppression would most likely be based on the results of thrust loss performance tests to be conducted by Aero System Engineering (ASE) Inc. It is anticipated that the most promising concepts identified from this program will be validated in full scale engine tests at both Pratt & Whitney and Allied-Signal, under funding from NASA s Engine Validation of Noise Reduction Concepts (EVNRC) programs. This will bring the technology readiness level to the point where the jet noise suppression concepts could be incorporated with high confidence into either new or existing turbofan engines having short-duct, separate-flow nacelles.

No midterm benefit from low intensity pulsed ultrasound after chevron osteotomy for hallux valgus.

PubMed

Zacherl, Max; Gruber, Gerald; Radl, Roman; Rehak, Peter H; Windhager, Reinhard

2009-08-01

Chevron osteotomy is a widely accepted method for correction of symptomatic hallux valgus deformity. Full weight bearing in regular shoes is not recommended before 6 weeks after surgery. Low intensity pulsed ultrasound is known to stimulate bone formation leading to more stable callus and faster bony fusion. We performed a randomized, placebo-controlled, double-blinded study on 44 participants (52 feet) who underwent chevron osteotomy to evaluate the influence of daily transcutaneous low intensity pulsed ultrasound (LIPUS) treatment at the site of osteotomy. Follow-up at 6 weeks and 1 year included plain dorsoplantar radiographs, hallux-metatarsophalangeal-interphalangeal scale and a questionnaire on patient satisfaction. There was no statistical difference in any pre- or postoperative clinical features, patient satisfaction or radiographic measurements (hallux valgus angle, intermetatarsal angle, sesamoid index and metatarsal index) except for the first distal metatarsal articular angle (DMAA). The DMAA showed statistically significant (p = 0.046) relapse in the placebo group upon comparison of intraoperative radiographs after correction and fixation (5.2 degrees) and at the 6-week follow-up (10.6 degrees). Despite potential impact of LIPUS on bone formation, we found no evidence of an influence on outcome 6 weeks and 1 year after chevron osteotomy for correction of hallux valgus deformity.

Influence of transition metal electronegativity on the oxygen storage capacity of perovskite oxides.

PubMed

Liu, Lu; Taylor, Daniel D; Rodriguez, Efrain E; Zachariah, Michael R

2016-08-16

The selection of highly efficient oxygen carriers (OCs) is a key step necessary for the practical development of chemical looping combustion (CLC). In this study, a series of ABO3 perovskites, where A = La, Ba, Sr, Ca and B = Cr, Mn, Fe, Co, Ni, Cu, are synthesized and tested in a fixed bed reactor for reactivity and stability as OCs with CH4 as the fuel. We find that the electronegativity of the transition metal on the B-site (λB), is a convenient descriptor for oxygen storage capacity (OSC) of our perovskite samples. By plotting OSC for total methane oxidation against λB, we observe an inverted volcano plot relationship. These results could provide useful guidelines for perovskite OC design and their other energy related applications.

Electronic characterization of silicon intercalated chevron graphene nanoribbons on Au(111).

PubMed

Deniz, O; Sánchez-Sánchez, C; Jaafar, R; Kharche, N; Liang, L; Meunier, V; Feng, X; Müllen, K; Fasel, R; Ruffieux, P

2018-02-08

Electronic and thermal properties of chevron-type graphene nanoribbons can be widely tuned, making them interesting candidates for electronic and thermoelectric applications. Here, we use post-growth silicon intercalation to unambiguously access nanoribbons' energy position of their electronic frontier states. These are otherwise obscured by substrate effects when investigated directly on the growth substrate. In agreement with first-principles calculations we find a band gap of 2.4 eV.

Thermal-hydraulic behavior of a mixed chevron single-pass plate-and-frame heat exchanger

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

Manglik, R.M.; Muley, A.

1995-12-31

Effective heat exchange is very critical for improving the process efficiency and operating economy of chemical and process plants. Here, experimental friction factor and heat transfer data for single-phase water flows in a plate-and-frame heat exchanger are presented. A mixed chevron plate arrangement with {beta} = 30{degree}/60{degree} in a single-pass U-type, counterflow configuration is employed. The friction factor and heat transfer data are for isothermal flow and cooling conditions, respectively, and the flow rates correspond to transition and turbulent flow regimes (300 < Re < 6,000 and 2.4 < Pr < 4.5). Based on these data, Nusselt number and frictionmore » factor correlations for fully developed turbulent flows (Re {ge} 1,000) are presented. The results highlight the effects of {beta} on the thermal-hydraulic performance, transition to turbulent flows, and the relative impact of using symmetric or mixed chevron plate arrangements.« less

Investigations on the performance of chevron type plate heat exchangers

NASA Astrophysics Data System (ADS)

Dutta, Oruganti Yaga; Nageswara Rao, B.

2018-01-01

This paper presents empirical relations for the chevron type plate heat exchangers (PHEs) and demonstrated their validity through comparison of test data of PHEs. In order to examine the performance of PHEs, the pressure drop(Δ P), the overall heat transfer coefficient ( U m ) and the effectiveness ( ɛ) are estimated by considering the properties of plate material and working fluid, number of plates ( N t ) and chevron angle( β). It is a known fact that, large surface area of the plate provides more rate of heat transfer ( \\dot{Q} ) thereby more effectiveness ( ɛ). However, there is a possibility to achieve the required performance by increasing the number of plates without altering the plate dimensions, which avoids the new design of the system. Application of the Taguchi's design of experiments is examined with less number of experiments and demonstrated by setting the levels for the parameters and compared the test data with the estimated output responses.

Articles which include chevron film cooling holes, and related processes

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

Bunker, Ronald Scott; Lacy, Benjamin Paul

An article is described, including an inner surface which can be exposed to a first fluid; an inlet; and an outer surface spaced from the inner surface, which can be exposed to a hotter second fluid. The article further includes at least one row or other pattern of passage holes. Each passage hole includes an inlet bore extending through the substrate from the inlet at the inner surface to a passage hole-exit proximate to the outer surface, with the inlet bore terminating in a chevron outlet adjacent the hole-exit. The chevron outlet includes a pair of wing troughs having amore » common surface region between them. The common surface region includes a valley which is adjacent the hole-exit; and a plateau adjacent the valley. The article can be an airfoil. Related methods for preparing the passage holes are also described.« less

Characterizing Natural Gas Hydrates in the Deep Water Gulf of Mexico: Applications for Safe Exploration and Production Activities

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

Bent, Jimmy

2014-05-31

In 2000 Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deep water portion of the Gulf of Mexico (GOM). Chevron is an active explorer and operator in the Gulf of Mexico and is aware that natural gas hydrates need to be understood to operate safely in deep water. In August 2000 Chevron worked closely with the National Energy Technology Laboratory (NETL) of the United States Department of Energy (DOE) and held a workshop in Houston, Texas to define issues concerning the characterization of natural gas hydrate deposits. Specifically, the workshop was meantmore » to clearly show where research, the development of new technologies, and new information sources would be of benefit to the DOE and to the oil and gas industry in defining issues and solving gas hydrate problems in deep water.« less

Towards the development of multifunctional molecular indicators combining soil biogeochemical and microbiological variables to predict the ecological integrity of silvicultural practices.

PubMed

Peck, Vincent; Quiza, Liliana; Buffet, Jean-Philippe; Khdhiri, Mondher; Durand, Audrey-Anne; Paquette, Alain; Thiffault, Nelson; Messier, Christian; Beaulieu, Nadyre; Guertin, Claude; Constant, Philippe

2016-05-01

The impact of mechanical site preparation (MSP) on soil biogeochemical structure in young larch plantations was investigated. Soil samples were collected in replicated plots comprising simple trenching, double trenching, mounding and inverting site preparation. Unlogged natural mixed forest areas were used as a reference. Analysis of soil nutrients, abundance of bacteria and gas exchanges unveiled no significant difference among the plots. However, inverting site preparation resulted in higher variations of gas exchanges when compared with trenching, mounding and unlogged natural forest. A combination of the biological and physicochemical variables was used to define a multifunctional classification of the soil samples into four distinct groups categorized as a function of their deviation from baseline ecological conditions. According to this classification model, simple trenching was the approach that represented the lowest ecological risk potential at the microsite level. No relationship was observed between MSP method and soil bacterial community structure as assessed by high-throughput sequencing of bacterial 16S rRNA gene; however, indicator genotypes were identified for each multifunctional soil class. This is the first identification of multifunctional molecular indicators for baseline and disturbed ecological conditions in soil, demonstrating the potential of applied microbial ecology to guide silvicultural practices and ecological risk assessment. © 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Electronic characterization of silicon intercalated chevron graphene nanoribbons on Au(111)

DOE PAGES

Deniz, O.; Sánchez-Sánchez, C.; Jaafar, R.; ...

2018-01-08

Electronic and thermal properties of chevron-type graphene nanoribbons can be widely tuned, making them interesting candidates for electronic and thermoelectric applications. In this paper, we use post-growth silicon intercalation to unambiguously access nanoribbons’ energy position of their electronic frontier states. These are otherwise obscured by substrate effects when investigated directly on the growth substrate. Finally, in agreement with first-principles calculations we find a band gap of 2.4 eV.

Chevron-type medial malleolar osteotomy: a functional, radiographic and quantitative T2-mapping MRI analysis.

PubMed

Lamb, Joshua; Murawski, Christopher D; Deyer, Timothy W; Kennedy, John G

2013-06-01

The purpose of this study was to retrospectively evaluate a large series of patients for functional, radiographic and MRI outcomes after a Chevron-type medial malleolar osteotomy. Sixty-two patients underwent a Chevron-type medial malleolar osteotomy with a median follow-up of 34.5 months. Standard digital radiographs were used to determine bony union and the angle of the osteotomy relative to the longitudinal axis of the tibia. Morphologic and quantitative T2-mapping MRI was also analysed in 32 patients. Fifty-eight patients (94 %) reported being asymptomatic at the site of the medial malleolar osteotomy. The median time to healing on standard radiograph was 6 weeks (range, 4-6 weeks) with an angle of 31.7° ± 6.9°. Quantitative T2-mapping MRI analysis demonstrated that the deep half of interface repair tissue had relaxation times that were not significantly different from normal tibial cartilage. In contrast, interface repair tissue in the superficial half demonstrated significant prolongation from normal relaxation time values, indicating a more fibrocartilaginous repair. Four patients (6 %) reported pain post-operatively. A Chevron-type medial malleolar osteotomy demonstrates satisfactory healing and fixation, with fibrocartilaginous tissue evident superficially at the osteotomy interface. Further investigation is warranted in the form of longitudinal study to assess the long-term outcomes of medial malleolar osteotomy.

Comparison of Clinical Outcomes of Scarf and Chevron Osteotomies and the McBride Procedure in the Treatment of Hallux Valgus Deformity

PubMed Central

Fakoor, Mohammad; Sarafan, Naser; Mohammadhoseini, Payam; Khorami, Mohsen; Arti, Hamidreza; Mosavi, SeyedShahnam; Aghaeeaghdam, Amir

2014-01-01

Background: Hallux valgus deformity is a common chronic problem with a reported prevalence of 28.4% and its chief complaint is pain. Thus far, different surgical procedures with their proposed indications have been introduced. This study compared three current procedures, namely the chevron and scarf osteotomies and the McBride procedure. Methods: This retrospective cohort was conducted at the Ahvaz University of Medical Sciences on 44 patients with moderate hallux valgus deformity from 2010 and 2013. All of the patients underwent one of the three procedures (chevron, scarf or McBride). Preoperative and follow up radiographies were evaluated in terms of hallux valgus and intermetatarsal angle correction. The Foot and Ankle Disability Index was filled out to assess the functional outcome and the Visual Analogue Scale was used to evaluate pain. Also, satisfaction, aesthetics and the rate of recurrence was evaluated. Results: Hallux valgus angle and intermetatarsal angle correction were significantly higher in scarf, but not in chevron and McBride. However, from amongst the three procedures, there was no significant difference in terms of the Foot and Ankle Disability Index score, aesthetics, satisfaction level, pain score and recurrence rate. Conclusions: Considering that scarf osteotomy had better results in this study, we think that scarf osteotomy can be considered as a first choice for the treatment of moderate hallux valgus deformity. PMID:25207310

Hallux valgus correction using transarticular lateral release with distal chevron osteotomy.

PubMed

Choi, Young Rak; Lee, Ho Seong; Jeong, Jae Jung; Kim, Sang Woo; Jeon, In-Ho; Lee, Dong Ho; Lee, Woo Chun

2012-10-01

Transarticular lateral release through a medial incision can avoid a dorsal incision. This study investigated outcomes following hallux valgus correction using transarticular lateral release, distal chevron metatarsal osteotomy and Akin phalangeal osteotomy through one medial incision. Between June 2004 and May 2009, a single surgeon performed a transarticular lateral release, distal chevron metatarsal osteotomy and Akin phalangeal osteotomy through one medial incision for hallux valgus on a total of 103 feet of 68 patients. The average patient age at the time of surgery was 51 years, and the average followup was 27 months. The average preoperative and final followup results were: 1) hallux valgus angle improvement from 29 degrees to 5 degrees, 2) intermetatarsal angle from 13 degrees to 5 degrees and 3) medial sesamoid bone position from 3 to 1 (p < 0.05 for each variable). The average AOFAS scores were improved from 49 to 92, and the VAS pain scores were improved from 7 to 1 (p < 0.05 for both variables). No patient had a serious complication such as infection, avascular necrosis, nonunion, transfer-metatarsalgia, or first metatarsophalangeal joint arthritis. Hallux valgus correction using transarticular lateral release, distal chevron metatarsal osteotomy and Akin phalangeal osteotomy through one medial incision was found to be effective and safe. The advantages include that the procedure is simple, early ambulation is possible, and there is no dorsal scarring.

Methods for the accurate estimation of confidence intervals on protein folding ϕ-values

PubMed Central

Ruczinski, Ingo; Sosnick, Tobin R.; Plaxco, Kevin W.

2006-01-01

ϕ-Values provide an important benchmark for the comparison of experimental protein folding studies to computer simulations and theories of the folding process. Despite the growing importance of ϕ measurements, however, formulas to quantify the precision with which ϕ is measured have seen little significant discussion. Moreover, a commonly employed method for the determination of standard errors on ϕ estimates assumes that estimates of the changes in free energy of the transition and folded states are independent. Here we demonstrate that this assumption is usually incorrect and that this typically leads to the underestimation of ϕ precision. We derive an analytical expression for the precision of ϕ estimates (assuming linear chevron behavior) that explicitly takes this dependence into account. We also describe an alternative method that implicitly corrects for the effect. By simulating experimental chevron data, we show that both methods accurately estimate ϕ confidence intervals. We also explore the effects of the commonly employed techniques of calculating ϕ from kinetics estimated at non-zero denaturant concentrations and via the assumption of parallel chevron arms. We find that these approaches can produce significantly different estimates for ϕ (again, even for truly linear chevron behavior), indicating that they are not equivalent, interchangeable measures of transition state structure. Lastly, we describe a Web-based implementation of the above algorithms for general use by the protein folding community. PMID:17008714

Comparison of Clinical Outcomes of Scarf and Chevron Osteotomies and the McBride Procedure in the Treatment of Hallux Valgus Deformity.

PubMed

Fakoor, Mohammad; Sarafan, Naser; Mohammadhoseini, Payam; Khorami, Mohsen; Arti, Hamidreza; Mosavi, SeyedShahnam; Aghaeeaghdam, Amir

2014-03-01

Hallux valgus deformity is a common chronic problem with a reported prevalence of 28.4% and its chief complaint is pain. Thus far, different surgical procedures with their proposed indications have been introduced. This study compared three current procedures, namely the chevron and scarf osteotomies and the McBride procedure. This retrospective cohort was conducted at the Ahvaz University of Medical Sciences on 44 patients with moderate hallux valgus deformity from 2010 and 2013. All of the patients underwent one of the three procedures (chevron, scarf or McBride). Preoperative and follow up radiographies were evaluated in terms of hallux valgus and intermetatarsal angle correction. The Foot and Ankle Disability Index was filled out to assess the functional outcome and the Visual Analogue Scale was used to evaluate pain. Also, satisfaction, aesthetics and the rate of recurrence was evaluated. Hallux valgus angle and intermetatarsal angle correction were significantly higher in scarf, but not in chevron and McBride. However, from amongst the three procedures, there was no significant difference in terms of the Foot and Ankle Disability Index score, aesthetics, satisfaction level, pain score and recurrence rate. Considering that scarf osteotomy had better results in this study, we think that scarf osteotomy can be considered as a first choice for the treatment of moderate hallux valgus deformity.

Flaperon Modification Effect on Jet-Flap Interaction Noise Reduction for Chevron Nozzles

NASA Technical Reports Server (NTRS)

Thomas, Russell H.; Mengle, Vinod G.; Stoker, Robert W.; Brusniak, Leon; Elkoby, Ronen

2007-01-01

Jet-flap interaction (JFI) noise can become an important component of far field noise when a flap is immersed in the engine propulsive stream or is in its entrained region, as in approach conditions for under-the-wing engine configurations. We experimentally study the effect of modifying the flaperon, which is a high speed aileron between the inboard and outboard flaps, at both approach and take-off conditions using scaled models in a free jet. The flaperon modifications were of two types: sawtooth trailing edge and mini vortex generators (vg s). Parametric variations of these two concepts were tested with a round coaxial nozzle and an advanced chevron nozzle, with azimuthally varying fan chevrons, using both far field microphone arrays and phased microphone arrays for source diagnostics purposes. In general, the phased array results corroborated the far field results in the upstream quadrant pointing to JFI near the flaperon trailing edge as the origin of the far field noise changes. Specific sawtooth trailing edges in conjunction with the round nozzle gave marginal reduction in JFI noise at approach, and parallel co-rotating mini-vg s were somewhat more beneficial over a wider range of angles, but both concepts were noisier at take-off conditions. These two concepts had generally an adverse JFI effect when used in conjunction with the advanced chevron nozzle at both approach and take-off conditions.

Design and fabrication of a MEMS chevron-type thermal actuator

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

Baracu, Angela, E-mail: angela.baracu@imt.ro; Voicu, Rodica; Müller, Raluca

This paper presents the design and fabrication of a MEMS chevron-type thermal actuator. The device was designed for fabrication in the standard MEMS technology, where the topography of the upper layers depends on the patterns of structural and sacrificial layers underneath. The proposed actuator presents some advantages over usual thermal vertical chevron actuators by means of low operating voltages, high output force and linear movement without deformation of the shaft. The device simulations were done using COVENTOR software. The movement obtained by simulation was 12 μm, for a voltage of 0.2 V and the current intensity of 257 mA. Themore » design optimizes the in-plane displacement by fixed anchors and beam inclination angle. Heating is provided by Joule dissipation. The material used for manufacture of chevron-based actuator was aluminum due to its thermal and mechanical properties. The release of the movable part was performed using isotropic dry etching by Reactive Ion Etching (RIE). A first inspection was achieved using Scanning Electron Microscope (SEM). In order to obtain the in-plane displacement we carried out electrical measurements. The thermal actuator can be used for a variety of optical and microassembling applications. This kind of thermal actuator could be integrated easily with other micro devices since its fabrication is compatible with the general semiconductor processes.« less

Outcomes in chevron osteotomy for Hallux Valgus in a large cohort.

PubMed

van Groningen, Bart; van der Steen, M C Marieke; Reijman, Max; Bos, Janneke; Hendriks, Johannes G E

2016-12-01

Clinical and radiological related outcomes have been reported for Chevron osteotomy as correction for mild to moderate hallux valgus, but only for relatively small patient series. Moreover, evaluation of the patient's point of view has mostly been conducted by means of more physician-based outcome measures. The goal of this study was to evaluate the effect of the Chevron osteotomy for hallux valgus on patients' daily lives using the Foot and Ankle Outcome Score (FAOS) as a validated and a hallux valgus specific patient reported outcome measure (PROM). Secondary outcome measures were radiological correction, complication rate, and re-operations. All 438 Chevron procedures (336 patients), at two surgical hospital sites in the period between January 2010 and October 2014, were retrospectively evaluated with a follow-up of at least 6 months. Patients were invited to fill in a cross-sectional online FAOS. For the FAOS, a total response of 60% was achieved. The FAOS ranged between 71 and 88 with a follow-up of on average 36 months. Patients with an undercorrection of their hallux valgus (11.6% of the procedures) scored significantly lower on three subscales of the FAOS (range between 61 and 77 versus 72-84). Patients who had a reoperation (12.6% of the procedures) also scored significantly lower on four subscales: 58-100 versus 73-89. Postoperative radiological measurements improved significantly with a mean difference of 6.1 (5.9; 6.4) degrees for the intermetatarsal angle and 13.7 (13.0; 14.5) degrees for the hallux valgus angle. In this large study cohort, Chevron osteotomy for hallux valgus offers good PROM scores on FAOS. These scores were significantly lower in patients with radiological undercorrection or with a reoperation. Results of the FAOS appear to modulate with physician based outcomes and therapeutic incidents. Improvement of outcome may therefore well be possible by increased attention on these surgical details. Copyright © 2016 Elsevier Ltd. All rights reserved.

PIV Measurements of Chevrons on F400-Series Tactical Aircraft Nozzle Model

NASA Technical Reports Server (NTRS)

Bridges, James; Wernet, Mark P.; Frate, Franco C.

2011-01-01

Reducing noise of tactical jet aircraft has taken on fresh urgency as core engine technologies allow higher specific-thrust engines and as society become more concerned for the health of its military workforce. Noise reduction on this application has lagged the commercial field as incentives for quieting military aircraft have not been as strong as in their civilian counterparts. And noise reduction strategies employed on civilian engines may not be directly applicable due to the differences in exhaust system architecture and mission. For instance, the noise reduction technology of chevrons, examined in this study, will need to be modified to take into account the special features of tactical aircraft nozzles. In practice, these nozzles have divergent slats that are tied to throttle position, and at take off the jet flow is highly overexpanded as the nozzle is optimized for cruise altitude rather than sea level. In simple oil flow visualization experiments conducted at the onset of the current test program flow barely stays attached at end of nozzle at takeoff conditions. This adds a new twist to the design of chevrons. Upon reaching the nozzle exit the flow shrinks inward radially, meaning that for a chevron to penetrate the flow it must extend much farther away from the baseline nozzle streamline. Another wrinkle is that with a variable divergence angle on the nozzle, the effective penetration will differ with throttle position and altitude. The final note of realism introduced in these experiments was to simulate the manner in which bypass flow is bled into the nozzle wall in real engines to cool the nozzle, which might cause very fat boundary layer at exit. These factors, along with several other issues specific to the application of chevrons to convergent-divergent nozzles have been explored with particle image velocimetry measurements and are presented in this paper.

Numerical and experimental evaluations of the flow past nested chevrons

NASA Technical Reports Server (NTRS)

Foss, J. F.; Foss, J. K.; Spalart, P. R.

1989-01-01

An effort is made to contribute to the development of CFD by relating the successful use of vortex dynamics in the computation of the pressure drop past a planar array of chevron-shaped obstructions. An ensemble of results was used to compute the loss coefficient k, stimulating an experimental program for the assessment of the measured loss coefficient for the same geometry. The most provocative result of this study has been the representation of kinetic energy production in terms of vorticity source terms.

Chevron facility focused on commercial orifice-meter research

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

Jones, E.H.; Ferguson, K.R.

1987-07-27

Research to determine the accuracy of commercial orifice meters for custody-transfer measurement has indicated that high-volume gas meters can be flow-proven while in such service. The research further yielded more accurate orifice-meter discharge coefficient equations (at Reynolds numbers greater than 4,000,000) than current equations of the International Standards Organization (ISO) and the American Petroleum Institute (API). These are partial findings of a major study conducted by Chevron Oil Field Research Co. at its Venice, La., calibration facility.

Modeling and Bayesian Parameter Estimation for Shape Memory Alloy Bending Actuators

DTIC Science & Technology

2012-02-01

prosthetic hand,” Technology and Health Care 10, 91–106 (2002). 4. Hartl , D., Lagoudas, D., Calkins, F., and Mabe , J., “Use of a ni60ti shape memory...alloy for active jet engine chevron application: I. thermomechanical characterization,” Smart Materials and Structures 19, 1–14 (2010). 5. Hartl , D...Lagoudas, D., Calkins, F., and Mabe , J., “Use of a ni60ti shape memory alloy for active jet engine chevron application: II. experimentally validated

Closed form expressions for crack mouth displacements and stress intensity factors for chevron notched short bar and short rod specimens based on experimental compliance measurements

NASA Technical Reports Server (NTRS)

Bubsey, R. T.; Orange, T. W.; Pierce, W. S.; Shannon, J. L., Jr.

1992-01-01

A set of equations are presented describing certain fracture mechanics parameters for chevron notch bar and rod specimens. They are developed by fitting compliance calibration data reported earlier. The equations present the various parameters in their most useful forms. The data encompass the entire range of the specimen geometries most commonly used. Their use will facilitate the testing and analysis of brittle metals, ceramics, and glasses.

Noise of Embedded High Aspect Ratio Nozzles

NASA Technical Reports Server (NTRS)

Bridges, James E.

2011-01-01

A family of high aspect ratio nozzles were designed to provide a parametric database of canonical embedded propulsion concepts. Nozzle throat geometries with aspect ratios of 2:1, 4:1, and 8:1 were chosen, all with convergent nozzle areas. The transition from the typical round duct to the rectangular nozzle was designed very carefully to produce a flow at the nozzle exit that was uniform and free from swirl. Once the basic rectangular nozzles were designed, external features common to embedded propulsion systems were added: extended lower lip (a.k.a. bevel, aft deck), differing sidewalls, and chevrons. For the latter detailed Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) simulations were made to predict the thrust performance and to optimize parameters such as bevel length, and chevron penetration and azimuthal curvature. Seventeen of these nozzles were fabricated at a scale providing a 2.13 inch diameter equivalent area throat." ! The seventeen nozzles were tested for far-field noise and a few data were presented here on the effect of aspect ratio, bevel length, and chevron count and penetration. The sound field of the 2:1 aspect ratio rectangular jet was very nearly axisymmetric, but the 4:1 and 8:1 were not, the noise on their minor axes being louder than the major axes. Adding bevel length increased the noise of these nozzles, especially on their minor axes, both toward the long and short sides of the beveled nozzle. Chevrons were only added to the 2:1 rectangular jet. Adding 4 chevrons per wide side produced some decrease at aft angles, but increased the high frequency noise at right angles to the jet flow. This trend increased with increasing chevron penetration. Doubling the number of chevrons while maintaining their penetration decreased these effects. Empirical models of the parametric effect of these nozzles were constructed and quantify the trends stated above." Because it is the objective of the Supersonics Project that future design work be done more by physics-based computations and less by experiments, several codes under development were evaluated against these test cases. Preliminary results show that the RANS-based code JeNo predicts the spectral directivity of the low aspect ratio jets well, but has no capability to predict the non-axisymmetry. An effort to address this limitations, used in the RANS-based code of Leib and Goldstein, overpredicted the impact of aspect ratio. The broadband shock noise code RISN, also limited to axisymmetric assumptions, did a good job of predicting the spectral directivity of underexpanded 2:1 cold jet case but was not as successful on high aspect ratio jets, particularly when they are hot. All results are preliminary because the underlying CFD has not been validated yet. An effort using a Large Eddy Simulation code by Stanford University predicted noise that agreed with experiments to within a few dB.

Biomechanical evaluation of three different fixation methods of the Chevron osteotomy of the olecranon: an analysis with Roentgen Stereophotogrammatic Analysis.

PubMed

Wagener, Marc L; Driesprong, Marco; Heesterbeek, Petra J C; Verdonschot, Nico; Eygendaal, Denise

2013-08-01

In this study three different methods for fixating the Chevron osteotomy of the olecranon are evaluated. Transcortical fixed Kirschner wires with a tension band, a large cancellous screw with a tension band, and a large cancellous screw alone are compared using Roentgen Stereophotogrammatic Analysis (RSA). The different fixation methods were tested in 17 cadaver specimens by applying increasing repetitive force to the triceps tendon. Forces applied were 200N, 350N, and 500N. Translation and rotation of the osteotomy were recorded using Roentgen Stereophotogrammatic Analysis. Both the fixations with a cancellous screw with tension band and with bi-cortical placed Kirschner wires with a tension band provide enough stability to withstand the forces of normal daily use. Since fixation with a cancellous screw with tension band is a fast and easy method and is related to minimal soft tissue damage this method can preferably be used for fixation of a Chevron osteotomy of the olecranon. © 2013.

Solution-Synthesized Chevron Graphene Nanoribbons Exfoliated onto H:Si(100).

PubMed

Radocea, Adrian; Sun, Tao; Vo, Timothy H; Sinitskii, Alexander; Aluru, Narayana R; Lyding, Joseph W

2017-01-11

There has been tremendous progress in designing and synthesizing graphene nanoribbons (GNRs). The ability to control the width, edge structure, and dopant level with atomic precision has created a large class of accessible electronic landscapes for use in logic applications. One of the major limitations preventing the realization of GNR devices is the difficulty of transferring GNRs onto nonmetallic substrates. In this work, we developed a new approach for clean deposition of solution-synthesized atomically precise chevron GNRs onto H:Si(100) under ultrahigh vacuum. A clean transfer allowed ultrahigh-vacuum scanning tunneling microscopy (STM) to provide high-resolution imaging and spectroscopy and reveal details of the electronic structure of chevron nanoribbons that have not been previously reported. We also demonstrate STM nanomanipulation of GNRs, characterization of multilayer GNR cross-junctions, and STM nanolithography for local depassivation of H:Si(100), which allowed us to probe GNR-Si interactions and revealed a semiconducting-to-metallic transition. The results of STM measurements were shown to be in good agreement with first-principles computational modeling.

Computational and Experimental Flow Field Analyses of Separate Flow Chevron Nozzles and Pylon Interaction

NASA Technical Reports Server (NTRS)

Massey, Steven J.; Thomas, Russell H.; AbdolHamid, Khaled S.; Elmiligui, Alaa A.

2003-01-01

A computational and experimental flow field analyses of separate flow chevron nozzles is presented. The goal of this study is to identify important flow physics and modeling issues required to provide highly accurate flow field data which will later serve as input to the Jet3D acoustic prediction code. Four configurations are considered: a baseline round nozzle with and without a pylon, and a chevron core nozzle with and without a pylon. The flow is simulated by solving the asymptotically steady, compressible, Reynolds-averaged Navier-Stokes equations using an implicit, up-wind, flux-difference splitting finite volume scheme and standard two-equation kappa-epsilon turbulence model with a linear stress representation and the addition of a eddy viscosity dependence on total temperature gradient normalized by local turbulence length scale. The current CFD results are seen to be in excellent agreement with Jet Noise Lab data and show great improvement over previous computations which did not compensate for enhanced mixing due to high temperature gradients.

Effect of nano/micro B4C and SiC particles on fracture properties of aluminum 7075 particulate composites under chevron-notch plane strain fracture toughness test

NASA Astrophysics Data System (ADS)

Morovvati, M. R.; Lalehpour, A.; Esmaeilzare, A.

2016-12-01

Reinforcing aluminum with SiC and B4C nano/micro particles can lead to a more efficient material in terms of strength and light weight. The influence of adding these particles to an aluminum 7075 matrix is investigated using chevron-notch fracture toughness test method. The reinforcing factors are type, size (micro/nano), and weight percent of the particles. The fracture parameters are maximum load, notch opening displacement, the work up to fracture and chevron notch plane strain fracture toughness. The findings demonstrate that addition of micro and nano size particles improves the fracture properties; however, increasing the weight percent of the particles leads to increase of fracture properties up to a certain level and after that due to agglomeration of the particles, the improvement does not happen for both particle types and size categories. Agglomeration of particles at higher amounts of reinforcing particles results in improper distribution of particles and reduction in mechanical properties.

The Chevron Foil Thrust Bearing: Improved Performance Through Passive Thermal Management and Effective Lubricant Mixing

NASA Technical Reports Server (NTRS)

Bruckner, Robert

2013-01-01

An improved foil thrust bearing is described that eliminates or reduces the need for forced cooling of the bearing foils while at the same time improves the load capacity of the bearing, enhances damping, provides overload tolerance, and eliminates the high speed load capacity drop-off that plagues the current state of the art. The performance improvement demonstrated by the chevron foil thrust bearing stems from a novel trailing edge shape that splays the hot lubricant in the thin film radially, thus preventing hot lubricant carry-over into the ensuing bearing sector. Additionally, the chevron shaped trailing edge induces vortical mixing of the hot lubricant with the gas that is naturally resident within the inter-pad region of a foil thrust bearing. The elimination of hot gas carry-over in combination with the enhanced mixing has enabled a completely passive thermally managed foil bearing design. Laboratory testing at NASA has confirmed the original analysis and reduced this concept to practice.

Inertial focusing and passive micro-mixing techniques for rare cells capturing microfluidic platform

NASA Astrophysics Data System (ADS)

Phadke, Manisha; Shaner, Sebastian; Shah, Shreyas; Rodriguez, Ygnacio; Wibowo, Denni; Whulanza, Yudan; Teriete, Peter; Allen, Jeff; Kassegne, Sam

2018-02-01

Isolation and capture of rare cells continues to be a daunting task that is still looking for an innovative and efficient method. While a variety of approaches have been suggested over the past several years, immunocapturing in a microfluidic platform carries a substantial promise as shown by recent published works. In this paper, we introduced a combination of inertial focusing and passive micro-mixing through 3D chevron-type features in a microchannel to induce chaotic mixing within antibody-coated microchannels and, ultimately, promote rare cell capture. The device introduced in this work contains curved microchannels that consist of a series of staggered chevron grooves. The curved channels enable inertial focusing while the chevron grooves allow for chaotic mixing. The microfluidics platform microfabricated through soft lithography has a polydimethylsiloxane (PDMS) foundation and was thinly coated with an alginate hydrogel derivatized with streptavidin. We submitted that our qualitative and quantitative results demonstrated the potentials in advancements in rare cell isolation through this integration of two techniques.

Stabilization of chevron bunionectomy with a capsuloperiosteal flap.

PubMed

Guclu, Berk; Kaya, Alper; Akan, Burak; Koken, Murat; Kemal Us, Ali

2011-04-01

Distal chevron osteotomy (DCO) for mild to moderate hallux valgus deformity is inherently more stable than the other forms of distal metatarsal osteotomy, but complications such as loss of correction, infection, joint stiffness, delayed union, malunion and nonunion can occur. In this study, we evaluated the use of a capsuloperiosteal flap for stabilization of DCO in the treatment of hallux valgus. A retrospective study was conducted on 59 patients (88 feet) that underwent distal Chevron osteotomy stabilized only with a capsuloperiosteal flap for mild and moderate hallux valgus deformity with a mean followup of 11.3 years. Clinical evaluation was calculated using the hallux score of the American Orthopaedic Foot and Ankle Society (AOFAS). The score improved from a preoperative mean of 52 to a mean of 91.5 points at last followup. Average hallux valgus angle changed from 30.3 degrees preoperatively to 14.2 degrees postoperatively at the last followup. Intermetatarsal angle 1-2 changed from 13.6 degrees preoperatively to 10.2 degrees postoperatively. The correction proved to be consistent with only an average of 3.4-degree correction loss and 4.9-degree loss in the range of motion. Eighty-six feet (97.7%) were pain free. Discomfort with shoewear was absent in 84 feet (95.5%) postoperatively and 24 of 25 (96%) patients were satisfied cosmetically. Capsuloperiosteal flap stabilization of distal chevron osteotomy for mild-moderate hallux valgus yielded excellent clinical results at long-term followup.

Experimental study of turbulent flow heat transfer and pressure drop in plate heat exchanger with chevron plates

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

Muley, A.; Manglik, R.M.

1999-02-01

Experimental heat transfer and isothermal pressure drop data for single-phase water flows in a plate heat exchanger (PHE) with chevron plates are presented. In a single-pass U-type counterflow PHE, three different chevron plate arrangements are considered: two symmetric plate arrangements with {beta} = 30 deg/30 deg and 60 deg/60 deg, and one mixed-plate arrangement with {beta} = 30 deg/60 deg. For water (2 < Pr < 6) flow rates in the 600 < Re < 10{sup 4} regime, data for Nu and f are presented. The results show significant effects of both the chevron angle {beta} and surface area enlargementmore » factor {phi}. As {beta} increases, and compared to a flat-plate pack, up to two to five times higher Nu are obtained; the concomitant f, however, are 13 to 44 times higher. Increasing {phi} also has a similar, though smaller effect. Based on experimental data for Re {ge} 1000 and 30 deg {le} {beta} {le} 60 deg, predictive correlations of the form Nu = C{sub 1}({beta}) D{sub 1}({phi}) Re{sup p1({beta})} Pr{sup 1/3} ({mu}/{mu}{sub w}){sup 0.14} and f = C{sub 2}({beta}) D{sub 2}({phi}) Re{sup p2({beta})} are devised. Finally, at constant pumping power, and depending upon Re, {beta}, and {phi}, the heat transfer is found to be enhanced by up to 2.8 times that in an equivalent flat-plate channel.« less

Effects of the lapidus arthrodesis and chevron bunionectomy on plantar forefoot pressures.

PubMed

King, Christy M; Hamilton, Graham A; Ford, Lawrence A

2014-01-01

Hallux valgus with or without first ray insufficiency has been strongly implicated as a contributing factor in lesser metatarsal overload. The principle goals of a bunionectomy are to relieve the pain, correct the deformity, and restore first metatarsophalangeal joint congruity. Until now, little evidence has been available to assess the effects of bunionectomy procedures on forefoot pressure. The primary aim of the present prospective study was to evaluate the preoperative and postoperative plantar pressures after 2 specific bunionectomies: the chevron bunionectomy and Lapidus arthrodesis. A total of 68 subjects, 34 in each group, were included for radiographic and pedographic evaluation. Both procedures demonstrated radiographic improvements in the mean intermetatarsal and hallux abductus angles. The mean hallux plantar pressure decreased significantly in both procedure groups (p < .001). However, Lapidus group exhibited an increase in the mean fifth metatarsal head plantar pressure (p = .008) and pressure under the fifth metatarsal as a percentage of the total forefoot pressure (p = .01). Furthermore, the pressure under the second metatarsal as a percentage of the total forefoot pressure decreased significantly (p = .01). This study suggests that the Lapidus arthrodesis and chevron bunionectomy both provide correction for hallux valgus deformity, but when comparing forefoot load sharing pressures, the Lapidus arthrodesis appeared to have greater influence on the load sharing distribution of forefoot pressure than did the bunionectomy employing the chevron osteotomy. Copyright © 2014 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Ultrasonically assisted anchoring of biodegradable implants for chevron osteotomies - clinical evaluation of a novel fixation method.

PubMed

Olms, Kai; Randt, Thorsten; Reimers, Nils; Zander, Nils; Schulz, Arndt P

2014-01-01

Reconstructive osteotomies for the treatment of Hallux valgus are among the most prevalent procedures in foot and ankle surgery. The combination of biodegradable materials with an innovative method for fixation by application of ultrasonic energy facilitates a new bonding method for fractures or osteotomies. As clinical experience is still limited, the aim of this study was to assess the safety and performance of the SonicPin system for fixation of Austin/Chevron osteotomies. Chevron osteotomy was performed on 30 patients for the treatment of Hallux valgus. The used SonicPins were made from polylactide and are selectively melted into the cancellous bone structure during insertion by ultrasonic energy. Patients were followed for one year, which included X-ray and MRI examinations as well as evaluation of life quality by EQ-5D (EuroQol). The MRI after three months showed adequate bone healing in all cases and no signs of foreign body reactions, which was again confirmed by MRI 12 months postoperatively. The bony healing after 12 months was uneventful without any signs of foreign body reactions. In summary, based on the low complication rate and the significant improvement in health related quality of life (EQ-5D) reported in this study, fixation of an Austin/Chevron osteotomy with a SonicPin for treatment of Hallux valgus can be considered to be safe and efficient over the short term. Therapeutic Level III.

Preoperative radiological factors correlated to long-term recurrence of hallux valgus following distal chevron osteotomy.

PubMed

Pentikainen, Ilkka; Ojala, Risto; Ohtonen, Pasi; Piippo, Jouni; Leppilahti, Juhana

2014-12-01

The purpose of this article was to analyze the long-term radiologic results after distal chevron osteotomy for hallux valgus treatment and to determine the preoperative radiographic factors correlating with radiological recurrence of the deformity. The study included 100 consecutive patients who received distal chevron osteotomy for hallux valgus. The osteotomy included fixation with an absorbable pin in 50 cases, and no fixation in the other 50. For 6 weeks postoperatively, half of each group used a soft cast and half had a traditional elastic bandage. Weight-bearing radiographs were evaluated at 6 weeks, 6 months, 1 year, and a mean of 7.9 (range, 5.8-9.4) years postoperatively. At the final follow-up, radiological recurrence of hallux valgus deformity (HVA > 15 degrees) was observed in 56 feet (73%). Eleven feet (14%) had mild recurrence (HVA < 20 degrees), 44 (57%) moderate (20 degrees ≥ HVA < 40 degrees), and 1 (1%) severe (HVA ≥ 40 degrees). All recurrences were painless, and thus no revision surgery was required. Long-term hallux valgus recurrence was significantly affected by preoperative congruence, DMAA, sesamoid position, HVA, and I/II IMA. Radiological recurrence of hallux valgus deformity of 15 degrees or more was very common at long-term follow-up after distal chevron osteotomy. Preoperative congruence, DMAA, sesamoid position (LaPorta), HVA, and I/II IMA significantly affected recurrence. Level III, comparative case series. © The Author(s) 2014.

Ultrasonically Assisted Anchoring of Biodegradable Implants for Chevron Osteotomies – Clinical Evaluation of a Novel Fixation Method

PubMed Central

Olms, Kai; Randt, Thorsten; Reimers, Nils; Zander, Nils; Schulz, Arndt P.

2014-01-01

Reconstructive osteotomies for the treatment of Hallux valgus are among the most prevalent procedures in foot and ankle surgery. The combination of biodegradable materials with an innovative method for fixation by application of ultrasonic energy facilitates a new bonding method for fractures or osteotomies. As clinical experience is still limited, the aim of this study was to assess the safety and performance of the SonicPin system for fixation of Austin/Chevron osteotomies. Chevron osteotomy was performed on 30 patients for the treatment of Hallux valgus. The used SonicPins were made from polylactide and are selectively melted into the cancellous bone structure during insertion by ultrasonic energy. Patients were followed for one year, which included X-ray and MRI examinations as well as evaluation of life quality by EQ-5D (EuroQol). The MRI after three months showed adequate bone healing in all cases and no signs of foreign body reactions, which was again confirmed by MRI 12 months postoperatively. The bony healing after 12 months was uneventful without any signs of foreign body reactions. In summary, based on the low complication rate and the significant improvement in health related quality of life (EQ-5D) reported in this study, fixation of an Austin/Chevron osteotomy with a SonicPin for treatment of Hallux valgus can be considered to be safe and efficient over the short term. Level of Clinical Evidence: Therapeutic Level III. PMID:24851140

Proactive investigation of hydrocarbons released into a linked groundwater-surfacewater hydrologic system: Chevron Estero Marine Terminal

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

Tormey, D.; Waldron, J.; Culbertson, D.

When regulatory concern is high, it is critical to address potential ecological impacts early, and hence [open quotes]close the door[close quotes] on further unnecessary studies, as illustrated by the Chevron Estero Marine Terminal case study. Cutter stock (diesel-like hydrocarbons) leaked from a facility sump, reached the water table, and migrated laterally an unknown distance. Media reports led to heightened public and regulatory concern, and the information gap led to worst-case assumptions about the extent and impact of the release to the biota of a nearby creek (Toro Creek). Chevron undertook a rapid assessment with two goals: define the extent ofmore » cutter stock in soil and groundwater, and close the door on expensive biological studies of Toro Creek. The assessment consisted of installing a large number of small-diameter soil borings and temporary well points, monitor wells, and analyzing soil, groundwater, and hydraulic gradient. The information gap was very rapidly filled with the following comprehensive picture: (1) the cutter stock had mixed with heavy crude oil, was highly adsorptive to soil and practically insoluble in water; (2) the cutter stock had not reached Toro Creek; (3) Toro Creek is always a losing stream, hydraulically connected to groundwater beneath the Chevron facility; (4) the groundwater basin is isolated by bedrock boundaries. Early attention to Toro Creek and the Pacific Ocean, and open communication with concerned agencies effectively limited the investigation to soil and water.« less

Proactive investigation of hydrocarbons released into a linked groundwater-surfacewater hydrologic system: Chevron Estero Marine Terminal

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

Tormey, D.; Waldron, J.; Culbertson, D.

When regulatory concern is high, it is critical to address potential ecological impacts early, and hence {open_quotes}close the door{close_quotes} on further unnecessary studies, as illustrated by the Chevron Estero Marine Terminal case study. Cutter stock (diesel-like hydrocarbons) leaked from a facility sump, reached the water table, and migrated laterally an unknown distance. Media reports led to heightened public and regulatory concern, and the information gap led to worst-case assumptions about the extent and impact of the release to the biota of a nearby creek (Toro Creek). Chevron undertook a rapid assessment with two goals: define the extent of cutter stockmore » in soil and groundwater, and close the door on expensive biological studies of Toro Creek. The assessment consisted of installing a large number of small-diameter soil borings and temporary well points, monitor wells, and analyzing soil, groundwater, and hydraulic gradient. The information gap was very rapidly filled with the following comprehensive picture: (1) the cutter stock had mixed with heavy crude oil, was highly adsorptive to soil and practically insoluble in water; (2) the cutter stock had not reached Toro Creek; (3) Toro Creek is always a losing stream, hydraulically connected to groundwater beneath the Chevron facility; (4) the groundwater basin is isolated by bedrock boundaries. Early attention to Toro Creek and the Pacific Ocean, and open communication with concerned agencies effectively limited the investigation to soil and water.« less

Oregon transect: Comparison of leaf-level reflectance with canopy-level and modelled reflectance

NASA Technical Reports Server (NTRS)

Johnson, Lee F.; Baret, Frederic; Peterson, David L.

1992-01-01

The Oregon Transect Ecosystem Research (OTTER) project involves the collection of a variety of remotely-sensed and in situ measurements for characterization of forest biophysical and biochemical parameters. The project includes nine study plots located along an environmental gradient in west-central Oregon, extending from the Pacific coast inland approximately 300km. These plots represent a broad range in ecosystem structure and function. Within the OTTER project, the sensitivity of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) signal to absorption by foliar biochemicals is being examined. AVIRIS data were acquired over all plots in conjunction with the four OTTER Multi-sensor Aircraft Campaigns spanning the growing season. Foilage samples were gathered during each campaign for biochemical determination (at Ames Research Center), to estimate stand-level constituency at each plot. Directional-hemispheric leaf reflectance throughout the 400-2400nm region was measured in the laboratory as an aid to interpreting concurrent AVIRIS data. Obtaining leaf spectra in this manner reduces or eliminates the confounding influences of atmosphere, canopy architecture, and reflectance by woody components, understory, and exposed soils which are present in airborne observations. These laboratory spectra were compared to simulated spectra derived by inverting the PROSPECT leaf-level canopy reflectance derived from AVIRIS data by use of the LOWTRAN-7 atmospheric radiative-transfer model.

Predicting repeat protein folding kinetics from an experimentally determined folding energy landscape

PubMed Central

Street, Timothy O; Barrick, Doug

2009-01-01

The Notch ankyrin domain is a repeat protein whose folding has been characterized through equilibrium and kinetic measurements. In previous work, equilibrium folding free energies of truncated constructs were used to generate an experimentally determined folding energy landscape (Mello and Barrick, Proc Natl Acad Sci USA 2004;101:14102–14107). Here, this folding energy landscape is used to parameterize a kinetic model in which local transition probabilities between partly folded states are based on energy values from the landscape. The landscape-based model correctly predicts highly diverse experimentally determined folding kinetics of the Notch ankyrin domain and sequence variants. These predictions include monophasic folding and biphasic unfolding, curvature in the unfolding limb of the chevron plot, population of a transient unfolding intermediate, relative folding rates of 19 variants spanning three orders of magnitude, and a change in the folding pathway that results from C-terminal stabilization. These findings indicate that the folding pathway(s) of the Notch ankyrin domain are thermodynamically selected: the primary determinants of kinetic behavior can be simply deduced from the local stability of individual repeats. PMID:19177351

Data-driven Techniques to Estimate Parameters in the Homogenized Energy Model for Shape Memory Alloys

DTIC Science & Technology

2011-11-01

sensor. volume 79781K. Proceedings of the SPIE 7978, 2011. [9] D.J. Hartl , D.C. Lagoudas, F.T. Calkins, and J.H. Mabe . Use of a ni60ti shape memory...alloy for active jet engine chevron application: I. thermomechanical characterization. Smart Materials and Structures, 19:1–14, 2010. [10] D.J. Hartl ...D.C. Lagoudas, F.T. Calkins, and J.H. Mabe . Use of a ni60ti shape memory alloy for active jet engine chevron application: II. experimentally validated

Investigation of Acoustic Emission during Fracture Toughness Testing of Chevron-Notched Specimens.

DTIC Science & Technology

1984-03-01

chevron-notched specimlens was employed to investigate crack growth in four steels )rel)ared by electroslag-remelt casting. 15-5PH, AISI 4140 , D6AC, and...this investigation: 15-SPH, AISI 4140 , D6AC and AISI 440C. The composition of each steel is given in Table 1. Castings were prepared by electro- slag...well defined, it appears that the AISI 4140 (Figure 2b) and the D6AC (Figure 2c) failed primarily by cleavage also. The fracture illustrated in Figure

Recurrence plots revisited

NASA Astrophysics Data System (ADS)

Casdagli, M. C.

1997-09-01

We show that recurrence plots (RPs) give detailed characterizations of time series generated by dynamical systems driven by slowly varying external forces. For deterministic systems we show that RPs of the time series can be used to reconstruct the RP of the driving force if it varies sufficiently slowly. If the driving force is one-dimensional, its functional form can then be inferred up to an invertible coordinate transformation. The same results hold for stochastic systems if the RP of the time series is suitably averaged and transformed. These results are used to investigate the nonlinear prediction of time series generated by dynamical systems driven by slowly varying external forces. We also consider the problem of detecting a small change in the driving force, and propose a surrogate data technique for assessing statistical significance. Numerically simulated time series and a time series of respiration rates recorded from a subject with sleep apnea are used as illustrative examples.

Source Identification and Location Techniques

NASA Technical Reports Server (NTRS)

Weir, Donald; Bridges, James; Agboola, Femi; Dougherty, Robert

2001-01-01

Mr. Weir presented source location results obtained from an engine test as part of the Engine Validation of Noise Reduction Concepts program. Two types of microphone arrays were used in this program to determine the jet noise source distribution for the exhaust from a 4.3 bypass ratio turbofan engine. One was a linear array of 16 microphones located on a 25 ft. sideline and the other was a 103 microphone 3-D "cage" array in the near field of the jet. Data were obtained from a baseline nozzle and from numerous nozzle configuration using chevrons and/or tabs to reduce the jet noise. Mr. Weir presented data from two configurations: the baseline nozzle and a nozzle configuration with chevrons on both the core and bypass nozzles. This chevron configuration had achieved a jet noise reduction of 4 EPNdB in small scale tests conducted at the Glenn Research Center. IR imaging showed that the chevrons produced significant improvements in mixing and greatly reduced the length of the jet potential core. Comparison of source location data from the 1-D phased array showed a shift of the noise sources towards the nozzle and clear reductions of the sources due to the noise reduction devices. Data from the 3-D array showed a single source at a frequency of 125 Hz. located several diameters downstream from the nozzle exit. At 250 and 400 Hz., multiple sources, periodically spaced, appeared to exist downstream of the nozzle. The trend of source location moving toward the nozzle exit with increasing frequency was also observed. The 3-D array data also showed a reduction in source strength with the addition of chevrons. The overall trend of source location with frequency was compared for the two arrays and with classical experience. Similar trends were observed. Although overall trends with frequency and addition of suppression devices were consistent between the data from the 1-D and the 3-D arrays, a comparison of the details of the inferred source locations did show differences. A flight test is planned to determine if the hardware tested statically will achieve similar reductions in flight.

Rate of Malunion Following Bi-plane Chevron Medial Malleolar Osteotomy.

PubMed

Bull, Patrick E; Berlet, Gregory C; Canini, Cameron; Hyer, Christopher F

2016-06-01

Access to the medial half of the talus can be challenging even with an osteotomy. Although several techniques are presented in the literature, critical evaluation of fixation, union, and alignment is lacking. The chevron medial malleolar osteotomy provides advantages of perpendicular instrumentation access and wide exposure to the medial talus. Postoperative displacement resulting in malunion, and possibly provoking ankle osteoarthritis, is a known complication. The present study describes our experience with the osteotomy. A consecutive series cohort of 50 bi-plane chevron osteotomies performed from 2004 to 2013 were evaluated. Forty-six were secured using 2 lag screws, and 4 were secured using 2 lag screws and a medial buttress plate. Radiographic studies performed at 2, 6, and 12 weeks and at final follow-up were analyzed for postoperative displacement, malunion, non-union, and hardware-related complications. At initial postoperative follow-up, 47 of 50 had adequate radiographs for review, and 18 of 47 (38.3%) showed some displacement when compared to the initial osteotomy fixation position. By final follow-up, 15 of 50 (30.0%) had measurable incongruence. Hardware removal was performed in 13 (26.0%) cases at an average of 2.4 years postoperation. Bi-plane medial malleolar chevron osteotomy fixed with 2 lag screws showed a 30.0% malunion rate with an average of 2 mm of incongruence on final follow-up radiographs, which is higher than what has been reported in the literature. In our practice, we now use a buttress plate and more recently have eliminated postoperative osteotomy displacement. Level IV, retrospective case series. © The Author(s) 2016.

Refinery spreadsheet highlights microcomputer process applications

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

Tucker, M.A.

1984-01-23

Microcomputer applications in the process areas at Chevron U.S.A. refineries and at the Chevron Research Co. illustrate how the microcomputer has changed the way we do our jobs. This article will describe major uses of the microcomputer as a personal work tool in Chevron process areas. It will also describe how and why many of Chevron's microcomputer applications were developed and their characteristics. One of our earliest microcomputer applications, developed in late 1981, was an electronic spreadsheet program using a small desktop microcomputer. It was designed to help a refinery planner prepare monthly plans for a small portion of onemore » of our major refineries. This particular microcomputer had a tiny 4-in. screen, and the reports were several strips of print-out from the microcomputer's 3-in.-wide internal printer taped together. In spite of these archaic computing conditions, it was a successful application. It automated what had been very tedious and time-consuming calculations with a pencil, a calculator, and a great deal of erasing. It eliminated filling out large ''horseblanket'' reports. The electronic spreadsheet was also flexible; the planner could easily change the worksheet to match new operating constraints, new process conditions, and new feeds and products. Fortunately, within just a few months, this application graduated to a similar electronic spreadsheet program on a new, more powerful microcomputer. It had a bigger display screen and a letter-size printer. The same application is still in use today, although it has been greatly enhanced and altered to match extensive plant modifications. And there are plans to expand it again onto yet another, more powerful microcomputer.« less

Structural, electronic and magnetic properties of chevron-type graphene, BN and BC{sub 2}N nanoribbons

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

Guerra, T.; Azevedo, S.; Kaschny, J.R.

2017-04-15

Graphene nanoribbons are predicted to be essential components in future nanoelectronics. The size, edge type, arrangement of atoms and width of nanoribbons drastically change their properties. Boronnitrogencarbon nanoribbons properties are not fully understood so far. In the present contribution it was investigated the structural, electronic and magnetic properties of chevron-type carbon, boron nitride and BC{sub 2}N nanoribbons, using first-principles calculations. The results indicate that the structural stability is closely related to the discrepancies in the bond lengths, which can induce structural deformations and stress. Such nanoribbons present a wide range of electronic behaviors, depending on their composition and particularities ofmore » the atomic arrangement. A net magnetic moment is found for structures that present carbon atoms at the nanoribbon borders. Nevertheless, the calculated magnetic moment depends on the peculiarities of the symmetric arrangement of atoms and imbalance of carbon atoms between different sublattices. It was found that all structures which have a significant energy gap do not present magnetic moment, and vice-versa. Such result indicates the strong correlation between the electronic and magnetic properties of the chevron-type nanoribbons. - Highlights: • Small discrepancies between distinct bond lengths can influence the formation energy of the BC{sub 2}N nanoribbons. • The electronic behavior of the BC{sub 2}N chevron-type nanoribbons depends on the atomic arrangement and structural symmetries. • There is a strong correlation between the electronic and magnetic properties for the BC{sub 2}N structures.« less

Discovery Of A Rossby Wave In Jupiter's South Equatorial Region

NASA Technical Reports Server (NTRS)

Simon-Miller, Amy A.; Choi, D. S.; Rogers, J. H.; Gierasch, P. J.

2012-01-01

A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 deg S planetographic latitude shows variations in velocity with longitude and time. The chevrons move with velocities near the maximum wind jet velocity of approx.140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 deg N latitude. Their repetitive nature is consistent with an inertia-gravity wave (n = 75-100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a approx.7-day period. This oscillating motion has a wavelength of approx.20 deg and a speed of approx.100 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it, though they are not perfectly in phase. The transient anticyclonic South Equatorial Disturbance (SED) may be a similar wave feature, but moves at slower velocity. All data show chevron latitude variability, but it is unclear if this Rossby wave is present during other epochs, without time series movies that fully delineate it. In the presence of multiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S may be due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

Three-dimensional finite-element analysis of chevron-notched fracture specimens

NASA Technical Reports Server (NTRS)

Raju, I. S.; Newman, J. C., Jr.

1984-01-01

Stress-intensity factors and load-line displacements were calculated for chevron-notched bar and rod fracture specimens using a three-dimensional finite-element analysis. Both specimens were subjected to simulated wedge loading (either uniform applied displacement or uniform applied load). The chevron-notch sides and crack front were assumed to be straight. Crack-length-to-specimen width ratios (a/w) ranged from 0.4 to 0.7. The width-to-thickness ratio (w/B) was 1.45 or 2. The bar specimens had a height-to-width ratio of 0.435 or 0.5. Finite-element models were composed of singularity elements around the crack front and 8-noded isoparametric elements elsewhere. The models had about 11,000 degrees of freedom. Stress-intensity factors were calculated by using a nodal-force method for distribution along the crack front and by using a compliance method for average values. The stress intensity factors and load-line displacements are presented and compared with experimental solutions from the literature. The stress intensity factors and load-line displacements were about 2.5 and 5 percent lower than the reported experimental values, respectively.

Structural, electronic and magnetic properties of chevron-type graphene, BN and BC2N nanoribbons

NASA Astrophysics Data System (ADS)

Guerra, T.; Azevedo, S.; Kaschny, J. R.

2017-04-01

Graphene nanoribbons are predicted to be essential components in future nanoelectronics. The size, edge type, arrangement of atoms and width of nanoribbons drastically change their properties. Boronnitrogencarbon nanoribbons properties are not fully understood so far. In the present contribution it was investigated the structural, electronic and magnetic properties of chevron-type carbon, boron nitride and BC2N nanoribbons, using first-principles calculations. The results indicate that the structural stability is closely related to the discrepancies in the bond lengths, which can induce structural deformations and stress. Such nanoribbons present a wide range of electronic behaviors, depending on their composition and particularities of the atomic arrangement. A net magnetic moment is found for structures that present carbon atoms at the nanoribbon borders. Nevertheless, the calculated magnetic moment depends on the peculiarities of the symmetric arrangement of atoms and imbalance of carbon atoms between different sublattices. It was found that all structures which have a significant energy gap do not present magnetic moment, and vice-versa. Such result indicates the strong correlation between the electronic and magnetic properties of the chevron-type nanoribbons.

A Prospective Study of Distal Metatarsal Chevron Osteotomies with K-Wire Fixations to Treat Hallux Valgus Deformities.

PubMed

Baig, M N; Baig, Usman; Tariq, Ali; Din, Robert

2017-09-20

Introduction Hallux valgus is one of the most common forefoot deformities worldwide. Females are affected more often than males. The three most common clinical symptoms are the painful bunion, transfer metatarsalgia, and hammer or claw toes. Methods This case series consisted of 20 patients who had chevron osteotomy from January 2015 to January 2016. The clinical assessment was measured by The American Orthopedic Foot and Ankle Score (AOFAS), and radiologic assessment was determined by preoperative and postoperative hallux valgus angle (HVA) and intermetatarsal angle (IMA). Results The patients' mean age was 56 years. Out of 20 patients, 19 were female, and one was male. The mean AOFAS improved from 51 preoperatively to 82 postoperatively. The HVA improved from 26° preoperatively to 14°. There were five complications including four Kirschner (K)-wire complications. Conclusion Distal chevron osteotomy is a reliable and time-tested procedure. The K-wire fixation has a relatively high complication rate. We planned to use other methods of fixation and then compared them with K-wires fixation results for future studies.

Chevron versus Mitchell osteotomy in hallux valgus surgery: a comparative study.

PubMed

Lambers Heerspink, F O; Verburg, H; Reininga, I H F; van Raaij, T M

2015-01-01

Good clinical results have been reported for chevron and Mitchell osteotomies in mild hallux valgus (HV). The primary aim of the present study was to compare first metatarsal shortening after chevron and Mitchell osteotomies in HV. The secondary outcome measures were the degree of valgus correction, metatarsalgia, and patient satisfaction. A total of 84 patients were included in the present study and were treated from 2005 to 2007; 42 patients were in each group. The outcome measurements-first metatarsal length, HV angle, 1-2 intermetatarsal angle, satisfaction, and metatarsalgia-were taken preoperatively and at follow-up. The Mitchell osteotomy resulted in a significantly larger decrease in the first metatarsal length. No significant difference in transfer metatarsalgia was found. Approximately 30% of patients were mildly or not satisfied after HV surgery. Mitchell osteotomy leads to a larger decrease in the first metatarsal length. Patients with metatarsalgia performed poorly, and no significant differences in metatarsalgia were found. Preventing postoperative metatarsalgia is important for a successful outcome after HV surgery. Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

A Prospective Study of Distal Metatarsal Chevron Osteotomies with K-Wire Fixations to Treat Hallux Valgus Deformities

PubMed Central

Baig, Usman; Tariq, Ali; Din, Robert

2017-01-01

Introduction Hallux valgus is one of the most common forefoot deformities worldwide. Females are affected more often than males. The three most common clinical symptoms are the painful bunion, transfer metatarsalgia, and hammer or claw toes. Methods This case series consisted of 20 patients who had chevron osteotomy from January 2015 to January 2016. The clinical assessment was measured by The American Orthopedic Foot and Ankle Score (AOFAS), and radiologic assessment was determined by preoperative and postoperative hallux valgus angle (HVA) and intermetatarsal angle (IMA). Results The patients’ mean age was 56 years. Out of 20 patients, 19 were female, and one was male. The mean AOFAS improved from 51 preoperatively to 82 postoperatively. The HVA improved from 26° preoperatively to 14°. There were five complications including four Kirschner (K)-wire complications. Conclusion Distal chevron osteotomy is a reliable and time-tested procedure. The K-wire fixation has a relatively high complication rate. We planned to use other methods of fixation and then compared them with K-wires fixation results for future studies. PMID:29167752

An Analysis of Model Scale Data Transformation to Full Scale Flight Using Chevron Nozzles

NASA Technical Reports Server (NTRS)

Brown, Clifford; Bridges, James

2003-01-01

Ground-based model scale aeroacoustic data is frequently used to predict the results of flight tests while saving time and money. The value of a model scale test is therefore dependent on how well the data can be transformed to the full scale conditions. In the spring of 2000, a model scale test was conducted to prove the value of chevron nozzles as a noise reduction device for turbojet applications. The chevron nozzle reduced noise by 2 EPNdB at an engine pressure ratio of 2.3 compared to that of the standard conic nozzle. This result led to a full scale flyover test in the spring of 2001 to verify these results. The flyover test confirmed the 2 EPNdB reduction predicted by the model scale test one year earlier. However, further analysis of the data revealed that the spectra and directivity, both on an OASPL and PNL basis, do not agree in either shape or absolute level. This paper explores these differences in an effort to improve the data transformation from model scale to full scale.

Optimizing Micromixer Surfaces To Deter Biofouling.

PubMed

Waters, James T; Liu, Ya; Li, Like; Balazs, Anna C

2018-03-07

Using computational modeling, we show that the dynamic interplay between a flowing fluid and the appropriately designed surface relief pattern can inhibit the fouling of the substrate. We specifically focus on surfaces that are decorated with three-dimensional (3D) chevron or sawtooth "micromixer" patterns and model the fouling agents (e.g., cells) as spherical microcapsules. The interaction between the imposed shear flow and the chevrons on the surface generates 3D vortices in the system. We pinpoint a range of shear rates where the forces from these vortices can rupture the bonds between the two mobile microcapsules near the surface. Notably, the patterned surface offers fewer points of attachment than a flat substrate, and the shear flows readily transport the separated capsules away from the layer. We contrast the performance of surfaces that encompass rectangular posts, chevrons, and asymmetric sawtooth patterns and thereby identify the geometric factors that cause the sawtooth structure to be most effective at disrupting the bonding between the capsules. By breaking up nascent clusters of contaminant cells, these 3D relief patterns can play a vital role in disrupting the biofouling of surfaces immersed in flowing fluids.

Chevron's October 21, 2003 Petition for the Administrator to Object to Chevron's Richmond Refinery Title V Permit

EPA Pesticide Factsheets

This document may be of assistance in applying the Title V air operating permit regulations. This document is part of the Title V Petition Database available at www2.epa.gov/title-v-operating-permits/title-v-petition-database. Some documents in the database are a scanned or retyped version of a paper photocopy of the original. Although we have taken considerable effort to quality assure the documents, some may contain typographical errors. Contact the office that issued the document if you need a copy of the original.

Iterative direct inversion: An exact complementary solution for inverting fault-slip data to obtain palaeostresses

NASA Astrophysics Data System (ADS)

Mostafa, Mostafa E.

2005-10-01

The present study shows that reconstructing the reduced stress tensor (RST) from the measurable fault-slip data (FSD) and the immeasurable shear stress magnitudes (SSM) is a typical iteration problem. The result of direct inversion of FSD presented by Angelier [1990. Geophysical Journal International 103, 363-376] is considered as a starting point (zero step iteration) where all SSM are assigned constant value ( λ=√{3}/2). By iteration, the SSM and RST update each other until they converge to fixed values. Angelier [1990. Geophysical Journal International 103, 363-376] designed the function upsilon ( υ) and the two estimators: relative upsilon (RUP) and (ANG) to express the divergence between the measured and calculated shear stresses. Plotting individual faults' RUP at successive iteration steps shows that they tend to zero (simulated data) or to fixed values (real data) at a rate depending on the orientation and homogeneity of the data. FSD of related origin tend to aggregate in clusters. Plots of the estimators ANG versus RUP show that by iteration, labeled data points are disposed in clusters about a straight line. These two new plots form the basis of a technique for separating FSD into homogeneous clusters.

Biomechanical Comparison Study of Three Fixation Methods for Proximal Chevron Osteotomy of the First Metatarsal in Hallux Valgus.

PubMed

Kim, Jin Su; Cho, Hun Ki; Young, Ki Won; Kim, Ji Soo; Lee, Kyung Tai

2017-12-01

Fixation of proximal chevron metatarsal osteotomy has been accomplished using K-wires traditionally and with a locking plate recently. However, both methods have many disadvantages. Hence, we developed an intramedullary fixation technique using headless cannulated screws and conducted a biomechanical study to evaluate the superiority of the technique to K-wire and locking plate fixations. Proximal chevron metatarsal osteotomy was performed on 30 synthetic metatarsal models using three fixation techniques. Specimens in group I were fixated with K-wires (1.6 mm × 2) and in group II with headless cannulated screws (3.0 mm × 2) distally through the intramedullary canal. Specimens in group III were fixated with a locking X-shaped plate (1.3-mm thick) and screws (2.5 mm × 4). Eight metatarsal specimens were selected from each group for walking fatigue test. Bending stiffness and dorsal angulation were measured by 1,000 repetitions of a cantilever bending protocol in a plantar to dorsal direction. The remaining two samples from each group were subjected to 5 mm per minute axial loading to assess the maximal loading tolerance. All samples in group I failed walking fatigue test while group II and group III tolerated the walking fatigue test. Group II showed greater resistance to bending force and smaller dorsal angulation than group III ( p = 0.001). On the axial loading test, group I and group II demonstrated superior maximum tolerance to group III (54.8 N vs. 47.2 N vs. 28.3 N). Authors have demonstrated proximal chevron metatarsal osteotomy with intramedullary screw fixation provides superior biomechanical stability to locking plate and K-wire fixations. The new technique using intramedullary screw fixation can offer robust fixation and may lead to better outcomes in surgical treatment of hallux valgus.

Fracture resistance measurement of advanced ceramics at elevated-temperatures using Chevron-notched specimens and other novel techniques

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

Jenkins, M.G.

1995-12-31

The quasi-static fracture behavior of advanced ceramics was assessed in the temperature range of 20{degrees} to 1400{degrees}C. Chevron-notched, three-point flexure specimens and a laser-based CMOD measurement systems were used in testing. Types of materials characterized included monolithic ceramics (SiC, Si{sub 3}N{sub 4}, MgAl{sub 2}O{sub 4}), self-reinforced monoliths (acicular-grained Si{sub 3}N{sub 4}, acicular grained mullite), and ceramic matrix composites (SiC whisker/Al{sub 2}O{sub 3} matrix, TiB{sub 2} particulate/SiC matrix, SiC fibre/CVI SiC matrix, Al{sub 2}O{sub 3} fibre/CVI SiC matrix). Fracture resistance behaviour of the materials was quantified as three distinct regimes of the fracture histories. At crack initiation, the apparent fracture toughnessmore » was evaluated as the critical stress intensity factor, K{sub IC}. During stable crack propagation, the crack growth resistance was characterized by the instantaneous strain energy release rate, G{sub R} using a compliance method assuming linear-elastic unloading to calculate the effective crack lengths. At final fracture, the complete fracture process was quantified using the work-of-fracture, WOF, which can be equated to the fracture surface energy for linearelastic materials. Results indicate that the chevron-notched, three-point flexure specimen facilitates the study of fracture behavior in a wide range of brittle and quasi-brittle materials at elevated temperatures. The unique features of the chevron geometry, which are automatic, in-situ crack initiation and inherent stable crack growth, are crucial to the successful evaluation of the fracture tests.« less

Enhanced heat transfer characteristics of viscous liquid flows in a chevron plate heat exchanger

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

Muley, A.; Manglik, R.M.; Metwally, H.M.

1999-11-01

Thermal processing and manufacturing in the chemical, foods, pharmaceutical, hygiene products, and biochemical industries invariably involve heating and cooling of highly viscous fluid media. These fluids tend to flow in the low Reynolds number regime, inherently have relatively low heat transfer coefficients, and are often temperature sensitive and prone to thermal degradation in the presence of large temperature differences. In recent times, plate heat exchangers (PHEs) have found increasing usage in such applications, primarily due to their features that promote enhanced heat transfer, and provide for the flexibility in altering their unit thermal size with ease, close approach temperature operation,more » and mitigation of thermal degradation of the process fluid. Here, steady-state heat transfer and pressure drop data for single-phase viscous fluid flows (2 {le} Re {le} 400) in a single-pass U-type counterflow plate heat exchanger (PHE) with chevron plates are presented. With vegetable oil as test fluid (130 {lt} Pr {lt} 290), three different plate arrangements are employed: two symmetric ({beta} = 30 deg/30 deg and 60 deg/60 deg) and one mixed ({beta} = 30 deg/60 deg). The effects of chevron angle {beta}, corrugation aspect ratio {gamma}, and flow conditions (Re, Pr, {mu}/{mu}{sub w}) on Nu and f characteristics of the PHE are delineated. The results show a rather complex influence of plate surface corrugations on the enhanced thermal-hydraulic behavior. Relative to the performance of equivalent flat-plate packs, chevron plates sustain up to 2.9 times higher heat transfer rates on a fixed geometry and constant pumping power basis, and require up to 48% less surface area for the fixed heat load and pressure drop constraint.« less

Ultra-Low-Energy Sub-Threshold Circuits: Program Overview

DTIC Science & Technology

2007-04-10

with global > 0.1 corner, but so does VUL, VIH 0 .0 5 -_ "or ni n a Global Variatlion 0.0a 0•,lN& 0.24.. 7 Mir" Output Swing Metrics " Need a... VIH . lines plot the VTCs when random local VT mismatch is ap- In Figure 1(b), a NAND gate has sufficient output swing plied to the inverter. One case...the VTC is input-dependent, all inputs are varied simultaneously to >P 1 0 SNM side of largest obtain the worst case ViH and VIL. > 0 ins0nbedsquare

Probing optical excitations in chevron-like armchair graphene nanoribbons.

PubMed

Denk, Richard; Lodi-Rizzini, Alberto; Wang, Shudong; Hohage, Michael; Zeppenfeld, Peter; Cai, Jinming; Fasel, Roman; Ruffieux, Pascal; Berger, Reinhard Franz Josef; Chen, Zongping; Narita, Akimitsu; Feng, Xinliang; Müllen, Klaus; Biagi, Roberto; De Renzi, Valentina; Prezzi, Deborah; Ruini, Alice; Ferretti, Andrea

2017-11-30

The bottom-up fabrication of graphene nanoribbons (GNRs) has opened new opportunities to specifically tune their electronic and optical properties by precisely controlling their atomic structure. Here, we address excitation in GNRs with periodic structural wiggles, the so-called chevron GNRs. Based on reflectance difference and high-resolution electron energy loss spectroscopies together with ab initio simulations, we demonstrate that their excited-state properties are of excitonic nature. The spectral fingerprints corresponding to different reaction stages in their bottom-up fabrication are also unequivocally identified, allowing us to follow the exciton build-up from the starting monomer precursor to the final GNR structure.

Three-dimensional analysis of chevron-notched specimens by boundary integral method

NASA Technical Reports Server (NTRS)

Mendelson, A.; Ghosn, L.

1983-01-01

The chevron-notched short bar and short rod specimens was analyzed by the boundary integral equations method. This method makes use of boundary surface elements in obtaining the solution. The boundary integral models were composed of linear triangular and rectangular surface segments. Results were obtained for two specimens with width to thickness ratios of 1.45 and 2.00 and for different crack length to width ratios ranging from 0.4 to 0.7. Crack opening displacement and stress intensity factors determined from displacement calculations along the crack front and compliance calculations were compared with experimental values and with finite element analysis.

Epitaxial growth of aligned atomically precise chevron graphene nanoribbons on Cu(111).

PubMed

Teeter, Jacob D; Costa, Paulo S; Mehdi Pour, Mohammad; Miller, Daniel P; Zurek, Eva; Enders, Axel; Sinitskii, Alexander

2017-07-25

Atomically precise chevron graphene nanoribbons (GNRs) have been synthesized on Cu(111) substrates by the surface-assisted coupling of 6,11-dibromo-1,2,3,4-tetraphenyltriphenylene (C 42 Br 2 H 26 ) and thermal cyclodehydrogenation of the resulting polymer. The GNRs form on Cu(111) epitaxially along the 〈112〉 crystallographic directions, which was found to be in agreement with the computational results, and at lower temperatures than on Au(111). This work demonstrates that the substrate plays an important role in the on-surface synthesis of GNRs and can result in new assembly modes of GNR structures.

Chevron osteotomy for the treatment of hallux valgus.

PubMed

Horne, G; Tanzer, T; Ford, M

1984-03-01

Seventy-six chevron osteotomies with follow-up periods ranging from six months to eight years were reviewed. The majority of patients had pain over the bunion prior to operation, and 27 also presented with second metatarsalgia. After surgery there was a marked decrease of pain in the first metatarsophalangeal joint, and in 18 feet the second metatarsalgia was either eliminated or markedly decreased. Most patients were pleased with the appearance of the feet after surgery, but almost one-third of the women complained of difficulty in wearing high heels. The surgical technique is straightforward, but careful attention to detail is necessary to obtain a consistent and satisfactory result.

Cementless total hip arthroplasty with a double chevron subtrochanteric shortening osteotomy in patients with Crowe type-IV hip dysplasia.

PubMed

Li, Xigong; Sun, Junying; Lin, Xiangjin; Xu, Sanzhong; Tang, Tiansi

2013-06-01

The authors describe a modified double chevron subtrochanteric shortening osteotomy combined with cementless total hip arthroplasty for Crowe type-IV hip dysplasia. Shortening the femur allows to relax the shortened musculature. This operation was performed in 18 patients (22 hips) between January 2000 and February 2006. The mean follow-up period was 5.6 years (range: 3 to 8 years). The mean amount of femoral subtrochanteric shortening was 38 mm (range: 25 to 60 mm). The mean Harris hip score improved from 47 (range: 35 to 65) preoperatively to 88 points (range: 75 to 97) at final follow-up. The Trendelenburg sign was corrected from positive to negative in 12 of 22 hips. No acetabular or femoral components loosened or required revision during the follow-up period. All osteotomy sites healed in 3 to 6 months without complications. Cementless total hip arthroplasty using the modified double chevron subtrochanteric osteotomy provided good short- to midterm results in all 22 Crowe type-IV hip dislocations. Moreover, it restored the anatomic hip center and the limb length, which contributed to correction of the preoperative limp.

Comparison of outcomes between proximal and distal chevron osteotomy, both with supplementary lateral soft-tissue release, for severe hallux valgus deformity: A prospective randomised controlled trial.

PubMed

Park, H-W; Lee, K-B; Chung, J-Y; Kim, M-S

2013-04-01

Severe hallux valgus deformity is conventionally treated with proximal metatarsal osteotomy. Distal metatarsal osteotomy with an associated soft-tissue procedure can also be used in moderate to severe deformity. We compared the clinical and radiological outcomes of proximal and distal chevron osteotomy in severe hallux valgus deformity with a soft-tissue release in both. A total of 110 consecutive female patients (110 feet) were included in a prospective randomised controlled study. A total of 56 patients underwent a proximal procedure and 54 a distal operation. The mean follow-up was 39 months (24 to 54) in the proximal group and 38 months (24 to 52) in the distal group. At follow-up the hallux valgus angle, intermetatarsal angle, distal metatarsal articular angle, tibial sesamoid position, American Orthopaedic Foot and Ankle Society (AOFAS) hallux metatarsophalangeal-interphalangeal score, patient satisfaction level, and complications were similar in each group. Both methods showed significant post-operative improvement and high levels of patient satisfaction. Our results suggest that the distal chevron osteotomy with an associated distal soft-tissue procedure provides a satisfactory method for correcting severe hallux valgus deformity.

Simulation of Strain Induced Pseudomagnetic Fields in Graphene Suspended on MEMS Chevron Actuators

NASA Astrophysics Data System (ADS)

Vutukuru, Mounika; Christopher, Jason; Bishop, David; Swan, Anna

Graphene has been shown to withstand remarkable levels of mechanical strain an order of magnitude larger than bulk crystalline materials. This exceptional stretchability of graphene allows for the direct tuning of fundamental material properties, as well as for the investigation of novel physics such as generation of strain induced pseudomagnetic fields. However, current methods for strain such as polymer elongation or pressurized wells do not integrate well into devices. We propose microelectromechanical (MEMS) Chevron actuators as a reliable platform for applying strain to graphene. In addition to their advantageous controllable output force, low input power and ease of integration into existing technologies, MEMS allow for different strain orientations to optimize pseudomagnetic field generation in graphene. Here, we model nonuniform strain in suspended graphene on Chevron actuators using COMSOL Multiphysics. By simulating the deformation of the graphene geometry under the device actuation, we explore the pseudomagnetic field map induced by numerically calculating the components of the strain tensor. Our models provide the theoretical framework with which experimental analysis is compared, and optimize our MEMS designs for further exploration of novel physics in graphene. The authors would like to thank NSF DMR 1411008 for their support on this project.

Approximate correlations for chevron-type plate heat exchangers

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

Wanniarachchi, A.S.; Ratnam, U.; Tilton, B.E.

1995-12-31

There exists very little useful data representing the performance of industrial plate heat exchangers (PHEs) in the open literature. As a result, it has been difficult to arrive at any generalized correlations. While every PHE manufacturer is believed to have a comprehensive set of performance curves for their own designs, there exists the need to generate an approximate set of generalized correlations for the heat-transfer community. Such correlations can be used for preliminary designs and analytical studies. This paper attempts to develop such a set of generalized correlations to quantify the heat-transfer and pressure-drop performance of chevron-type PHEs. For thismore » purpose, the experimental data reported by Heavner et al. were used for the turbulent region. For the laminar region, a semi-theoretical approach was used to express, for example, the friction factor as a function of the Reynolds number and the chevron angle. Asymptotic curves were used for the transitional region. Physical explanations are provided for the trends shown by the generalized correlations. The correlations are compared against the open-literature data, where appropriate. These correlations are expected to be improved in the future when more data become available.« less

Indirect Field Measurement of Wine-Grape Vineyard Canopy Leaf Area Index

NASA Technical Reports Server (NTRS)

Johnson, Lee F.; Pierce, Lars L.; Skiles, J. W. (Technical Monitor)

2002-01-01

Leaf area index (LAI) indirect measurements were made at 12 study plots in California's Napa Valley commercial wine-grape vineyards with a LI-COR LI-2000 Plant Canopy Analyzer (PCA). The plots encompassed different trellis systems, biological varieties, and planting densities. LAI ranged from 0.5 - 2.25 sq m leaf area/ sq m ground area according to direct (defoliation) measurements. Indirect LAI reported by the PCA was significantly related to direct LAI (r(exp 2) = 0.78, p less than 001). However, the PCA tended to underestimate direct LAI by about a factor of two. Narrowing the instrument's conical field of view from 148 deg to 56 deg served to increase readings by approximately 30%. The PCA offers a convenient way to discern relative differences in vineyard canopy density. Calibration by direct measurement (defoliation) is recommended in cases where absolute LAI is desired. Calibration equations provided herein may be inverted to retrieve actual vineyard LAI from PCA readings.

Robust and novel two degree of freedom fractional controller based on two-loop topology for inverted pendulum.

PubMed

Dwivedi, Prakash; Pandey, Sandeep; Junghare, A S

2018-04-01

A rotary single inverted pendulum (RSIP) typically represents a space booster rocket, Segway and similar systems with unstable equilibrium. This paper proposes a novel two degree of freedom (2-DOF) fractional control strategy based on 2-loop topology for RSIP system which can be extended to control the systems with unstable equilibrium. It comprises feedback and feed-forward paths. Primary controller relates the perturbation attenuation while the secondary controller is accountable for set point tracking. To tune the parameters of proposed fractional controller a simple graphical tuning method based on frequency response is used. The study will serve the outstanding experimental results for both, stabilization and trajectory tracking tasks. The study will also serve to present a comparison of the performance of the proposed controller with the 1-DOF FOPID controller and sliding mode controller (SMC) for the RSIP system. Further to confirm the usability of the proposed controller and to avoid the random perturbations sensitivity, robustness, and stability analysis through fractional root-locus and Bode-plot is investigated. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Interpreting Observations of Large-Scale Traveling Ionospheric Disturbances by Ionospheric Sounders

NASA Astrophysics Data System (ADS)

Pederick, L. H.; Cervera, M. A.; Harris, T. J.

2017-12-01

From July to October 2015, the Australian Defence Science and Technology Group conducted an experiment during which a vertical incidence sounder (VIS) was set up at Alice Springs Airport. During September 2015 this VIS observed the passage of many large-scale traveling ionospheric disturbances (TIDs). By plotting the measured virtual heights across multiple frequencies as a function of time, the passage of the TID can be clearly displayed. Using this plotting method, we show that all the TIDs observed during the campaign by the VIS at Alice Springs show an apparent downward phase progression of the crests and troughs. The passage of the TID can be more clearly interpreted by plotting the true height of iso-ionic contours across multiple plasma frequencies; the true heights can be obtained by inverting each ionogram to obtain an electron density profile. These plots can be used to measure the vertical phase speed of a TID and also reveal a time lag between events seen in true height compared to virtual height. To the best of our knowledge, this style of analysis has not previously been applied to other swept-frequency sounder observations. We develop a simple model to investigate the effect of the passage of a large-scale TID on a VIS. The model confirms that for a TID with a downward vertical phase progression, the crests and troughs will appear earlier in virtual height than in true height and will have a smaller apparent speed in true height than in virtual height.

Trapping self-propelled micromotors with microfabricated chevron and heart-shaped chips† †Electronic supplementary information (ESI) available: Supporting videos (S1; S2 and S3). See DOI: 10.1039/c3lc51419f Click here for additional data file. Click here for additional data file. Click here for additional data file. Click here for additional data file.

PubMed Central

Restrepo-Pérez, Laura; Soler, Lluís; Martínez-Cisneros, Cynthia S.; Schmidt, Oliver G.

2014-01-01

We demonstrate that catalytic micromotors can be trapped in microfluidic chips containing chevron and heart-shaped structures. Despite the challenge presented by the reduced size of the traps, microfluidic chips with different trapping geometries can be fabricated via replica moulding. We prove that these microfluidic chips can capture micromotors without the need for any external mechanism to control their motion. PMID:24643940

Single-grain growth in Si film by chevron-shaped cw laser beam scanning

NASA Astrophysics Data System (ADS)

Yeh, Wenchang; Yamazaki, Satoki; Ishimoto, Akihisa; Morito, Shigekazu

2016-02-01

A single grain with a length of 450 µm and a width of 5-6 µm was grown in a 60 nm Si film on SiO2 by scanning a chevron-shaped cw laser beam, which was formed by passing a linear laser beam through a novel one-sided Dove prism. The crystal did not have any dominant orientations in both the growth and normal directions. The orientation rotated about the transverse direction at a rate of 0.47-0.51°/µm in the forward direction, which suggests that the lattice constant at the film surface was 0.049-0.053% larger than that at the film bottom.

Chevron v Echazabal: Protection, Opportunity, and Paternalism

PubMed Central

Daniels, Norman

2003-01-01

The Supreme Court, in Chevron v Echazabal, ruled that risks to a disabled worker, if established by an individualized medical assessment, can disqualify the worker from protections offered by the Americans with Disabilities Act (ADA). This decision rejected the antipaternalist position of ADA advocates that workers with disabilities should be able to determine, through their own consent, the risks they will take. Such strong antipaternalism may not be compatible with the underlying justification for the protection of workers against health hazards. Stringent regulation of workplace hazards involves restricting the scope of consent to risk. Resolution of this conflict will depend on more careful examination of the degree to which individualized medical assessments avoid stereotyping and bias. PMID:12660194

The influence of geometry on jet plume development

NASA Astrophysics Data System (ADS)

Xia, H.; Tucker, P. G.; Eastwood, S.; Mahak, M.

2012-07-01

Our recent efforts of using large-eddy simulation (LES) type methods to study complex and realistic geometry single stream and co-flow nozzle jets and acoustics are summarized in this paper. For the LES, since the solver being used tends towards having dissipative qualities, the subgrid scale (SGS) model is omitted, giving a numerical type LES (NLES). To overcome near wall streak resolution problems a near wall RANS (Reynolds averaged Navier-Stokes) model is smoothly blended in the LES making a hybrid RANS-NLES approach. Several complex nozzle geometries including the serrated (chevron) nozzle, realistic co-axial nozzles with eccentricity, pylon and wing-flap are discussed. The hybrid RANS-NLES simulations show encouraging predictions for the chevron jets. The chevrons are known to increase the high frequency noise at high polar angles, but decrease the low frequency noise at lower angles. The deflection effect of the potential core has an important mechanism of noise reduction. As for co-axial nozzles, the eccentricity, the pylon and the deployed wing-flap are shown to influence the flow development, especially the former to the length of potential core and the latter two having a significant impact on peak turbulence levels and spreading rates. The studies suggest that complex and real geometry effects are influential and should be taken into count when moving towards real engine simulations.

Chevron beam dump for ITER edge Thomson scattering system.

PubMed

Yatsuka, E; Hatae, T; Vayakis, G; Bassan, M; Itami, K

2013-10-01

This paper contains the design of the beam dump for the ITER edge Thomson scattering system and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due to nuclear heating, radiation from the plasma, and numerous incident laser pulses throughout the entire ITER project with a reasonable margin for the peak factor of the beam profile. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Moreover, detailed issues for more accurate assessments of the beam dump's lifetime are clarified. Variation of the bi-directional reflection distribution function (BRDF) due to erosion by or contamination of neutral particles derived from the plasma is one of the most critical issues that needs to be resolved. In this paper, the BRDF was assumed, and the total amount of stray light and the absorbed laser energy profile on the beam dump were evaluated.

Commercialization of the Chevron FCC vanadium trap

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

Kennedy, J.V.; Kuehler, C.W.; Krishna, A.S.

1995-09-01

Vanadium, present to varying degrees in FCC feed, deposits on the catalyst virtually quantitatively in the cracking process. In resid operations, vanadium levels on catalyst can reach 10,000 ppm at typical catalyst make-up rates. Once on the catalyst, vanadium destroys the zeolite and restricts access to active sites. This reduces catalyst activity. A vanadium trap is a material that when introduced into the catalyst inventory selectively reacts with migrating vanadium, thus protecting the zeolite and other active components of the catalyst. The trap may be incorporated into the catalyst, or introduced as a separate particle. Only a limited amount ofmore » trap can be incorporated into the catalyst without limiting the amount of zeolite that can be included. Gulf began development of a vanadium trap during the early 1980`s. The work produced a variety of promising materials whose use as vanadium traps was subsequently patented. The work ultimately led to a formulation with a phase very active for trapping vanadium while still quite sulfur tolerant. Based on these results, an extensive pilot plant evaluation was undertaken by Chevron after the Chevron-Gulf merger to better simulate commercial operation. The paper describes pilot plant tests as well as 3 commercial tests of this vanadium trap.« less

Early results using a biodegradable magnesium screw for modified chevron osteotomies.

PubMed

Plaass, Christian; Ettinger, Sarah; Sonnow, Lena; Koenneker, Soeren; Noll, Yvonne; Weizbauer, Andreas; Reifenrath, Janin; Claassen, Leif; Daniilidis, Kiriakos; Stukenborg-Colsman, Christina; Windhagen, Henning

2016-12-01

This is the first larger study analyzing the use of magnesium-based screws for fixation of modified Chevron osteotomies in hallux valgus surgery. Forty-four patients (45 feet) were included in this prospective study. A modified Chevron osteotomy was performed on every patient and a magnesium screw used for fixation. The mean clinical follow up was 21.4 weeks. The mean age of the patients was 45.5 years. Forty patients could be provided with the implant, in four patients the surgeon decided to change to a standard metallic implant. The AOFAS, FAAM and pain NRS-scale improved markedly. The hallux valgus angle, intermetatarsal angle and sesamoid position improved significantly. Seven patients showed dorsal subluxation, rotation or medial shifting of the metatarsal heads within the first 3 months. One of these patients was revised, in all others the findings were considered clinically not significant or the patients refused revision. This study shows the feasibility of using magnesium screws in hallux valgus-surgery. Surgeons starting with the use of these implants should be aware of the proper handling of these implants and should know about corrosion effects during healing and its radiographic appearance. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2207-2214, 2016. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

The Influence of Specimen Type on Tensile Fracture Toughness of Rock Materials

NASA Astrophysics Data System (ADS)

Aliha, Mohammad Reza Mohammad; Mahdavi, Eqlima; Ayatollahi, Majid Reza

2017-03-01

Up to now, several methods have been proposed to determine the mode I fracture toughness of rocks. In this research, different cylindrical and disc shape samples, namely: chevron bend (CB), short rod (SR), cracked chevron notched Brazilian disc (CCNBD), and semi-circular bend (SCB) specimens were considered for investigating mode I fracture behavior of a marble rock. It is shown experimentally that the fracture toughness values of the tested rock material obtained from different test specimens are not consistent. Indeed, depending on the geometry and loading type of the specimen, noticeable discrepancies can be observed for the fracture toughness of a same rock material. The difference between the experimental mode I fracture resistance results is related to the magnitude and sign of T-stress that is dependent on the geometry and loading configuration of the specimen. For the chevron-notched samples, the critical value of T-stress corresponding to the critical crack length was determined using the finite element method. The CCNBD and SR specimens had the most negative and positive T-stress values, respectively. The dependency of mode I fracture resistance to the T-stress was shown using the extended maximum tangential strain (EMTSN) criterion and the obtained experimental rock fracture toughness data were predicted successfully with this criterion.

Impact of chevron spacing and asymmetric distribution on supersonic jet acoustics and flow

NASA Astrophysics Data System (ADS)

Heeb, N.; Gutmark, E.; Kailasanath, K.

2016-05-01

An experimental investigation into the effect of chevron spacing and distribution on supersonic jets was performed. Cross-stream and streamwise particle imaging velocimetry measurements were used to relate flow field modification to sound field changes measured by far-field microphones in the overexpanded, ideally expanded, and underexpanded regimes. Drastic modification of the jet cross-section was achieved by the investigated configurations, with both elliptic and triangular shapes attained downstream. Consequently, screech was nearly eliminated with reductions in the range of 10-25 dB depending on the operating condition. Analysis of the streamwise velocity indicated that both the mean shock spacing and strength were reduced resulting in an increase in the broadband shock associated noise spectral peak frequency and a reduction in the amplitude, respectively. Maximum broadband shock associated noise amplitude reductions were in the 5-7 dB range. Chevron proximity was found to be the primary driver of peak vorticity production, though persistence followed the opposite trend. The integrated streamwise vorticity modulus was found to be correlated with peak large scale turbulent mixing noise reduction, though optimal overall sound pressure level reductions did not necessarily follow due to the shock/fine scale mixing noise sources. Optimal large scale mixing noise reductions were in the 5-6 dB range.

Chevron osteotomy in patients with scheduled osteotomy of the medial malleolus.

PubMed

Gül, Murat; Yavuz, Umut; Çetinkaya, Engin; Aykut, Ümit Selçuk; Özkul, Barış; Kabukçuoğlu, Yavuz Selim

2015-01-01

The aim of the present study was to evaluate intermediate-term outcomes of Chevron osteotomy for treatment of osteochondral lesions of the talus with mosaicplasty and to assess its effect on surgery and whether it reduces complications that might occur intraoperatively. The present study included a total of 42 patients (31 men, 11 women) who underwent Chevron osteotomy of the medial malleolus and who had been followed for more than 2 years. Mean age of the patients was 34 years (range: 18-54 years). Preoperatively, size of the lesions was measured in millimeters in the coronal and sagittal planes using magnetic resonance imaging (MRI). The angle between the osteotomy with the long axis of the tibia was measured on the coronal plane, the angle between the arms and the angle for the screws to be directed to the osteotomy line were measured on the sagittal plane on the postoperative images. Nonunion, malunion, and complications from the screws were evaluated from X-ray images taken at the final follow-up. Mean duration for follow-up was 31.4 years (range: 24-46). On the X-ray images taken at the final follow-up, no distraction, migration of the distal part, or rotation was observed. Only 1 patient experienced radiological non-union. Mean duration to union was 5.8 weeks (range: 4-14 weeks). Screws of 8 patients were removed at an average of 7.4 months (range: 5-11 months). The angle between the osteotomy line and long axis of the tibia was 29.0°±6.5°, the angel between the osteotomy arms on the sagittal plane was 74.7°±8.3°, and the direction angle of the screws on the coronal plane was 85.7°±5.9°. Chevron osteotomy is an assistive surgical method used for treatment of osteochondral lesions located in the medial talar joint surface (TOL) which provides fast anatomical healing because it allows efficient fixation due to its geometry.

Screw Versus Plate Fixation for Chevron Osteotomy: A Retrospective Study.

PubMed

Andrews, Boyd J; Fallat, Lawrence M; Kish, John P

2016-01-01

The chevron osteotomy is a popular procedure used for the correction of moderate hallux abducto valgus deformity. Fixation is typically accomplished with Kirschner wires or bone screws; however, in cystic or osteoporotic bone, these could be inadequate, resulting in displacement of the capital fragment. We propose using a locking plate and interfragmental screw for fixation of the chevron osteotomy that could reduce the healing time and decrease the incidence of displacement. We performed a retrospective cohort study for chevron osteotomies on 75 feet (73 patients). The control groups underwent fixation with 1 screw in 30 feet (40%) and 2 screws in 30 feet (40%). A total of 15 feet (20%) were included in the locking plate and interfragmental screw group. The patients were followed up until bone healing was achieved at a median of 7 (range 6 to 14) weeks. Our hypothesis was that those treated with the locking plate and interfragmental screw would have a faster healing time and fewer incidents of capital fragment displacement compared with the 1- or 2-screw groups. The corresponding mean intervals to healing for the 1-screw group was 7.71 ± 1.28 (range 6 to 10) weeks, for the 2-screw group was 7.27 ± 1.57 (range 6 to 14) weeks, and for the locking plate and interfragmental screw group was 7.01 ± 1.00 (range 6 to 9) weeks. One case of capital fragment displacement occurred in the single screw group and one in the 2-screw group. No displacement occurred in the locking plate and interfragmental screw group. Neither finding was statistically significant. However, we believe the locking plate and interfragmental screw could be a viable option in patients with osteoporotic and cystic bone changes for correction of hallux abducto valgus. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Minimally Invasive and Open Distal Chevron Osteotomy for Mild to Moderate Hallux Valgus.

PubMed

Brogan, Kit; Lindisfarne, Edward; Akehurst, Harold; Farook, Usama; Shrier, Will; Palmer, Simon

2016-11-01

Minimally invasive surgical (MIS) techniques are increasingly being used in foot and ankle surgery but it is important that they are adopted only once they have been shown to be equivalent or superior to open techniques. We believe that the main advantages of MIS are found in the early postoperative period, but in order to adopt it as a technique longer-term studies are required. The aim of this study was to compare the 2-year outcomes of a third-generation MIS distal chevron osteotomy with a comparable traditional open distal chevron osteotomy for mild-moderate hallux valgus. Our null hypothesis was that the 2 techniques would yield equivalent clinical and radiographic results at 2 years. This was a retrospective cohort study. Eighty-one consecutive feet (49 MIS and 32 open distal chevron osteotomies) were followed up for a minimum 24 months (range 24-58). All patients were clinically assessed using the Manchester-Oxford Foot Questionnaire. Radiographic measures included hallux valgus angle, the intermetatarsal angle, hallux interphalangeal angle, metatarsal phalangeal joint angle, distal metatarsal articular angle, tibial sesamoid position, shape of the first metatarsal head, and plantar offset. Statistical analysis was done using Student t test or Wilcoxon rank-sum test for continuous data and Pearson chi-square test for categorical data. Clinical and radiologic postoperative scores in all domains were substantially improved in both groups (P < .001), but there was no statistically significant difference in improvement of any domain between open and MIS groups (P > .05). There were no significant differences in complications between the 2 groups ( > .5). The midterm results of this third-generation technique show that it was a safe procedure with good clinical outcomes and comparable to traditional open techniques for symptomatic mild-moderate hallux valgus. Level III, retrospective comparative study. © The Author(s) 2016.

[Clinical effect modified Chevron osteotomy combined with lateral tissue loosening in treating mild-moderate hallux valgus through internal signal approach].

PubMed

Chen, Xue-Qiang; Wu, Qun-Feng; Dong, Wei-Qin; Yu, Li-Xin; Li, Xiong-Feng

2018-03-25

To explore clinical effect of modified Chevron osteotomy combined with lateral tissue loosening for the treatment of mild-moderate hallux valgus through internal signal approach. From July 2015 to June 2016, 26 patients with mild-moderate hallux valgus treated with modified Chevron osteotomy combined with lateral tissue loosening through internal signal approach, including 2 males and 24 females aged from 45 to 65 years old with an average of(54.6±4.8) years old;the courses of diseases ranged from 1 to 5 months with an average of (7.5±3.3) months. Hallux valgus angle(HVA), inter metatarsal angle(IMA) were measured at 12 months after operation, and AOFAS score was applied to evaluate clinical effect before and after operation. All incisions were healed at stage I. No incision occurred infection, metatarsal necrosis and recurrence of hallux valgus deformity. Two patients occurred skin numbness caused by musculocutaneous nerve injury. Twenty-six patients were followed up from 6 to 12 months with an average of(9.12±2.06) months. HVA, IMA were(30.01±3.71)°, (14.00±1.50)° before operation and(9.41±4.16)°, (7.00±0.60)° after operation, which had significant difference. There was statistical significance in AOFAS score before operation 54.77±9.59 and after operation 92.73±5.47, and 19 cases obtained excellent results and 7 moderate. Modified Chevron osteotomy combined with full thread headless pressure screw fixation and lateral tissue loosening for the treatment of mild-moderate hallux valgus has advantages of excellent exposure, simple operation, stable fixation, rapid recovery. Akin osteotomy with internal capsulorrhaphy were used with lateral loosening and could recover soft tissue balance between lateral and internal, and could receive satisfied clinical effects. Copyright© 2018 by the China Journal of Orthopaedics and Traumatology Press.

Biomechanical Comparison Study of Three Fixation Methods for Proximal Chevron Osteotomy of the First Metatarsal in Hallux Valgus

PubMed Central

Kim, Jin Su; Young, Ki Won; Kim, Ji Soo; Lee, Kyung Tai

2017-01-01

Background Fixation of proximal chevron metatarsal osteotomy has been accomplished using K-wires traditionally and with a locking plate recently. However, both methods have many disadvantages. Hence, we developed an intramedullary fixation technique using headless cannulated screws and conducted a biomechanical study to evaluate the superiority of the technique to K-wire and locking plate fixations. Methods Proximal chevron metatarsal osteotomy was performed on 30 synthetic metatarsal models using three fixation techniques. Specimens in group I were fixated with K-wires (1.6 mm × 2) and in group II with headless cannulated screws (3.0 mm × 2) distally through the intramedullary canal. Specimens in group III were fixated with a locking X-shaped plate (1.3-mm thick) and screws (2.5 mm × 4). Eight metatarsal specimens were selected from each group for walking fatigue test. Bending stiffness and dorsal angulation were measured by 1,000 repetitions of a cantilever bending protocol in a plantar to dorsal direction. The remaining two samples from each group were subjected to 5 mm per minute axial loading to assess the maximal loading tolerance. Results All samples in group I failed walking fatigue test while group II and group III tolerated the walking fatigue test. Group II showed greater resistance to bending force and smaller dorsal angulation than group III (p = 0.001). On the axial loading test, group I and group II demonstrated superior maximum tolerance to group III (54.8 N vs. 47.2 N vs. 28.3 N). Conclusions Authors have demonstrated proximal chevron metatarsal osteotomy with intramedullary screw fixation provides superior biomechanical stability to locking plate and K-wire fixations. The new technique using intramedullary screw fixation can offer robust fixation and may lead to better outcomes in surgical treatment of hallux valgus. PMID:29201305

A novel procedure for introducing large sheet-type surgical material with a self-expanding origami structure using a slim trocar (chevron pleats procedure).

PubMed

Nakase, Yuen; Nakamura, Kei; Sougawa, Akira; Nagata, Tomoyuki; Mochizuki, Satoshi; Kitai, Shouzo; Inaba, Seishirou

2017-09-01

Large sheet-type surgical materials (e.g., absorbable hemostat, adhesion barrier membranes, and flat surgical mesh) are difficult to introduce into a corporeal cavity using a 5-mm trocar; however, laparoscopic surgeries that use mainly 5-mm trocars are increasing. Furthermore, it is necessary not only to introduce but also to secure the applied surgical material and expand it from the original surgical site. To address these challenges, we developed a novel procedure for introducing such surgical materials into a corporeal cavity using a 5-mm trocar and a self-expanding origami structure, called the "chevron pleats procedure (CPP)". We used CPP in 114 cases of laparoscopic surgery for gastrointestinal diseases. The chevron folding pattern is an excellent origami structure and compactly folds a large sheet of material for use with a slim trocar. Surgical materials were folded using a chevron pleats pattern and inserted into a novel, slim, long syringe-type device, which was made from a specially ordered precision polypropylene tube, for introduction into a corporeal cavity. When the surgical material was used, the end of the device was placed above the surgical site and the inner rod was pushed. The surgical material was securely injected and expanded over the surgical site. Surgical materials were introduced smoothly and securely using a 5-mm trocar to a site of intraoperative bleeding, the incisional surface of the liver, and defects of the abdominal wall or peritoneum. Efficient hemostasis was attained, the introduction and expansion of surgical mesh was made simpler, and the covering of defects of the peritoneum with adhesion barrier membranes, which is typically difficult during laparoscopic surgery, was easily performed. CPP is a basic utility procedure for introducing several sheet-type surgical materials into a corporeal cavity with a 5-mm trocar and might help ensure efficient and safe laparoscopic surgery.

Distal chevron osteotomy with lateral soft tissue release for moderate to severe hallux valgus decided using intraoperative varus stress radiographs.

PubMed

Kim, Hyong-Nyun; Park, Yoo-Jung; Kim, Gab-Lae; Park, Yong-Wook

2013-01-01

The purpose of the present study was to investigate the outcomes of distal chevron osteotomy with lateral soft tissue release for moderate to severe hallux valgus. The patients were selected using criteria that included the degree of lateral soft tissue contracture and metatarsocuneiform joint flexibility. The contracture and flexibility were determined from intraoperative varus stress radiographs. From April 2007 to May 2009, 56 feet in 51 consecutive patients with moderate to severe hallux valgus had undergone distal chevron osteotomy with lateral soft tissue release. This was done when the lateral soft tissue contracture was not so severe that passive correction of the hallux valgus deformity was not possible and when the metatarsocuneiform joint was flexible enough to permit additional correction of the first intermetatarsal angle after lateral soft tissue release. The mean patient age was 45.2 (range 23 to 54) years, and the duration of follow-up was 27.5 (range 24 to 46) months. The mean hallux abductus angle decreased from 33.5° ± 3.1° to 11.6° ± 3.3°, and the first intermetatarsal angle decreased from 16.4° ± 2.7° to 9.7° ± 2.1°. The mean American Orthopaedic Foot and Ankle Society hallux-interphalangeal scores increased from 66.6° ± 10.7° to 92.6° ± 9.4° points, and 46 of the 51 patients (90%) were either very satisfied or satisfied with the outcome. No recurrence of deformity or osteonecrosis of the metatarsal head occurred. When lateral soft tissue contracture is not severe and when the metatarsocuneiform joint is flexible enough, distal chevron osteotomy with lateral soft tissue release can be a useful and effective choice for moderate to severe hallux valgus deformity. Copyright © 2013 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Effect of viscosity on photoinduced electron transfer reaction: An observation of the Marcus inverted region in homogeneous solvents

NASA Astrophysics Data System (ADS)

Saini, Rajesh Kumar; Kuchlyan, Jagannath; Sarkar, Nilmoni

2016-09-01

The viscosity effect of homogeneous solvents on the dynamics of photoinduced electron transfer (PET) reaction among the coumarins and N,N-dimethylaniline (DMA) is investigated using steady-state and time-resolved fluorescence spectroscopy. A bell shape Marcus inversion in the ET rates has been detected in the plot of ET rate constant (kq) with free energy change (ΔG0) in viscous solvents decanol and EG, but it is not observed in DMSO like low viscous solvent. We have also reported that there is no complex formation between the coumarin dye and DMA molecule by using fluorescence correlation spectroscopy.

Full-scale flight tests of aircraft morphing structures using SMA actuators

NASA Astrophysics Data System (ADS)

Mabe, James H.; Calkins, Frederick T.; Ruggeri, Robert T.

2007-04-01

In August of 2005 The Boeing Company conducted a full-scale flight test utilizing Shape Memory Alloy (SMA) actuators to morph an engine's fan exhaust to correlate exhaust geometry with jet noise reduction. The test was conducted on a 777-300ER with GE-115B engines. The presence of chevrons, serrated aerodynamic surfaces mounted at the trailing edge of the thrust reverser, have been shown to greatly reduce jet noise by encouraging advantageous mixing of the free, and fan streams. The morphing, or Variable Geometry Chevrons (VGC), utilized compact, light weight, and robust SMA actuators to morph the chevron shape to optimize the noise reduction or meet acoustic test objectives. The VGC system was designed for two modes of operation. The entirely autonomous operation utilized changes in the ambient temperature from take-off to cruise to activate the chevron shape change. It required no internal heaters, wiring, control system, or sensing. By design this provided one tip immersion at the warmer take-off temperatures to reduce community noise and another during the cooler cruise state for more efficient engine operation, i.e. reduced specific fuel consumption. For the flight tests a powered mode was added where internal heaters were used to individually control the VGC temperatures. This enabled us to vary the immersions and test a variety of chevron configurations. The flight test demonstrated the value of SMA actuators to solve a real world aerospace problem, validated that the technology could be safely integrated into the airplane's structure and flight system, and represented a large step forward in the realization of SMA actuators for production applications. In this paper the authors describe the development of the actuator system, the steps required to integrate the morphing structure into the thrust reverser, and the analysis and testing that was required to gain approval for flight. Issues related to material strength, thermal environment, vibration, electrical power, controls, data acquisition, and engine operability are discussed. Furthermore the authors layout a road map for the next stage of development of SMA aerospace actuators. A detailed look at the requirements and specifications that may define a production SMA actuator and the technology development required to meet them are presented. A path for meeting production requirements and achieving the next level of technology readiness for both autonomous and controlled SMA actuators is proposed. This path relies strongly on cross functional and organizational teaming including industry, academia, and government.

Non-exhibition of Bragg phenomenon by chevronic sculptured thin films

NASA Astrophysics Data System (ADS)

Vepachedu, Vikas; McAtee, Patrick D.; Lakhtakia, Akhlesh

2017-08-01

The unit cell of a chevronic sculptured thin film (ChevSTF) comprises two identical columnar thin films (CTFs) except that the nanocolumns of the first are oriented at an angle Χ and nanocolumns of the second are oriented at an angle π - χ with respect to the interface of the two CTFs. A ChevSTF containing 10 unit cells was fabricated and its planewave reflectance and transmittance spectrums of this ChevSTF were measured. Despite its structural periodicity, the ChevSTF did not exhibit the Bragg phenomenon. Theoretical calculations with the CTFs modeled as biaxial dielectric materials indicated that the Bragg phenomenon would not be manifested for normal and near-normal incidence, but vestigial manifestation was possible for sufficiently oblique incidence.

The effect of Fusarium culmorum infection and deoxynivalenol (DON) application on proteome response in barley cultivars Chevron and Pedant.

PubMed

Kosová, Klára; Chrpová, Jana; Šantrůček, Jiří; Hynek, Radovan; Štěrbová, Lenka; Vítámvás, Pavel; Bradová, Jana; Prášil, Ilja Tom

2017-10-03

Fusarium head blight (FHB) disease adversely affects grain quality and final yield in small-grain cereals including barley. In the present study, the effect of an artificial infection with Fusarium culmorum and an application of deoxynivalenol (DON) on barley spikes of cultivars Chevron and Pedant during flowering was investigated at grain mid-dough stage (BBCH 73) 10days after pathogen inoculation (10 dai). Proteomic analysis using a two-dimensional differential gel electrophoresis (2D-DIGE) technique coupled with LC-MS/MS investigated 98 protein spots revealing quantitative or qualitative differences between the experimental variants. Protein functional annotation of 93 identified protein spots revealed that most affected functional groups represent storage proteins (globulins, hordeins), followed by proteins involved in carbohydrate metabolism (α-amylase inhibitor, β-amylase, glycolytic enzymes), amino acid metabolism (aminotransferases), defence response (chitinase, xylanase inhibitor, serpins, SGT1, universal stress protein USP), protein folding (chaperones, chaperonins), redox metabolism (ascorbate-glutathione cycle), and proteasome-dependent protein degradation. The obtained results indicate adverse effects of infection on plant proteome as well as an active plant response to pathogen as shown by enhanced levels of several inhibitors of pathogen-produced degradation enzymes (α-amylase inhibitor, xylanase inhibitor, serpins), chaperones, and other stress-related proteins (SGT1, USP). Genotypic differences were found in hordein abundance between Chevron and Pedant. Copyright © 2017 Elsevier B.V. All rights reserved.

Chevron beam dump for ITER edge Thomson scattering system

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

Yatsuka, E.; Hatae, T.; Bassan, M.

This paper contains the design of the beam dump for the ITER edge Thomson scattering system and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due tomore » nuclear heating, radiation from the plasma, and numerous incident laser pulses throughout the entire ITER project with a reasonable margin for the peak factor of the beam profile. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Moreover, detailed issues for more accurate assessments of the beam dump's lifetime are clarified. Variation of the bi-directional reflection distribution function (BRDF) due to erosion by or contamination of neutral particles derived from the plasma is one of the most critical issues that needs to be resolved. In this paper, the BRDF was assumed, and the total amount of stray light and the absorbed laser energy profile on the beam dump were evaluated.« less

Toxicity of Chevron Escravos crude oil and chemical dispersant on guinea pig testicular function.

PubMed

Afonne, Onyenmechi Johnson; Onyiaorah, Igwebuike Victor; Orisakwe, Orish Ebere

2013-01-01

Chemical contaminants have been found to affect reproductive functions in mammals. This study investigated the effect of Chevron Escravos crude oil and Emulsol L.W. dispersant on the testicular functions of guinea pig. Eight groups of seven sexually mature male guinea pigs each were given 1250, 2500, or 5000 mg/kg of crude oil and dispersant for 7 days. The fluid and food intake and body weight of the animals were measured daily throughout the study. After the exposure period, sperm quality analysis was carried out, and fructose and lactate dehydrogenase were analyzed in tissue homogenate, while testosterone and estradiol were assayed in blood. The right testis was also processed for histological analysis. The epididymal sperm number and fructose level of treated animals showed a significant dose-dependent decrease (p<0.05) compared with controls. Also, sperm motility and morphology were altered in the treated groups, while testosterone and estradiol levels were increased significantly (p<0.05) in the treated groups. Histological examination showed signs of toxicity in the treated animals. From the findings, it was evident that Chevron Escravos crude oil and Emulsol L.W. oil dispersant are able to cause acute testicular toxicity in guinea pigs. The possible mechanism of toxicity is suggested to be by stimulation of hormone production from the adrenal cortex, causing a negative feedback on gonadotropin-releasing hormone in the pituitary gland to suppress spermatogenesis.

AST Critical Propulsion and Noise Reduction Technologies for Future Commercial Subsonic Engines: Separate-Flow Exhaust System Noise Reduction Concept Evaluation

NASA Technical Reports Server (NTRS)

Janardan, B. A.; Hoff, G. E.; Barter, J. W.; Martens, S.; Gliebe, P. R.; Mengle, V.; Dalton, W. N.; Saiyed, Naseem (Technical Monitor)

2000-01-01

This report describes the work performed by General Electric Aircraft Engines (GEAE) and Allison Engine Company (AEC) on NASA Contract NAS3-27720 AoI 14.3. The objective of this contract was to generate quality jet noise acoustic data for separate-flow nozzle models and to design and verify new jet-noise-reduction concepts over a range of simulated engine cycles and flight conditions. Five baseline axisymmetric separate-flow nozzle models having bypass ratios of five and eight with internal and external plugs and 11 different mixing-enhancer model nozzles (including chevrons, vortex-generator doublets, and a tongue mixer) were designed and tested in model scale. Using available core and fan nozzle hardware in various combinations, 28 GEAE/AEC separate-flow nozzle/mixing-enhancer configurations were acoustically evaluated in the NASA Glenn Research Center Aeroacoustic and Propulsion Laboratory. This report describes model nozzle features, facility and data acquisition/reduction procedures, the test matrix, and measured acoustic data analyses. A number of tested core and fan mixing enhancer devices and combinations of devices gave significant jet noise reduction relative to separate-flow baseline nozzles. Inward-flip and alternating-flip core chevrons combined with a straight-chevron fan nozzle exceeded the NASA stretch goal of 3 EPNdB jet noise reduction at typical sideline certification conditions.

A trade-off solution between model resolution and covariance in surface-wave inversion

USGS Publications Warehouse

Xia, J.; Xu, Y.; Miller, R.D.; Zeng, C.

2010-01-01

Regularization is necessary for inversion of ill-posed geophysical problems. Appraisal of inverse models is essential for meaningful interpretation of these models. Because uncertainties are associated with regularization parameters, extra conditions are usually required to determine proper parameters for assessing inverse models. Commonly used techniques for assessment of a geophysical inverse model derived (generally iteratively) from a linear system are based on calculating the model resolution and the model covariance matrices. Because the model resolution and the model covariance matrices of the regularized solutions are controlled by the regularization parameter, direct assessment of inverse models using only the covariance matrix may provide incorrect results. To assess an inverted model, we use the concept of a trade-off between model resolution and covariance to find a proper regularization parameter with singular values calculated in the last iteration. We plot the singular values from large to small to form a singular value plot. A proper regularization parameter is normally the first singular value that approaches zero in the plot. With this regularization parameter, we obtain a trade-off solution between model resolution and model covariance in the vicinity of a regularized solution. The unit covariance matrix can then be used to calculate error bars of the inverse model at a resolution level determined by the regularization parameter. We demonstrate this approach with both synthetic and real surface-wave data. ?? 2010 Birkh??user / Springer Basel AG.

Workers’ Liberty, Workers’ Welfare: The Supreme Court Speaks on the Rights of Disabled Employees

PubMed Central

Bayer, Ronald

2003-01-01

On June 10, 2002, a unanimous US Supreme Court rejected the claim by Mario Echazabal that he had been denied his rights under the Americans with Disabilities Act when Chevron USA had refused to employ him because he had hepatitis C. Chevron believed that Echazabal’s exposure to hepatotoxic chemicals in its refinery would pose a grave risk to his health. This case poses critical questions about the ethics of public health: When, if ever, is paternalism justified? Must choice always trump other values? What ought to be the balance between welfare and liberty? Strikingly, the groups that came to Echazabal’s defense adopted an antipaternalistic posture fundamentally at odds with the ethical foundations of occupational health and safety policy. PMID:12660193

Russia joins Kazakh/Omani pipeline venture group

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

Not Available

1992-08-03

Russia has agreed to become a founding partner in a joint venture pipeline project formed by Kazakhstan and Oman. The agreement, signed in Bermuda July 24, is related to Chevron Corp.'s further development of supergiant Tengiz and Korolev fields along the Caspian Sea coast in Kazakhstan. Azerbaijan last month signed an agreement to become a founding member of the group, accepting terms agreed to by original joint venturers Kazakhstan and Oman. Azerbaijan's new government still must formally ratify its agreement. In addition, Chevron in June signed a memorandum of understanding to join the group at a future date. This papermore » reports that each of the founding members holds an equal interest in Caspian Pipeline Consortium Ltd., which will operate as a limited liability company incorporated in Bermuda.« less

[Modified Chevron osteotomy combined distal soft tissue reconstruction to treat high-grade bunionette deformity].

PubMed

Feng, S M; Wang, A G; Ding, P; Zhang, Z Y; Zhou, M M; Li, C K; Sun, Q Q

2016-07-26

To explore the surgical method of using the modified chevron osteotomy combined distal soft tissue reconstruction to treat high-grade bunionette deformity. From June 2013 to June 2015, the modified chevron osteotomy combined distal soft tissue reconstruction was used for surgical treatment of high-grade bunionette deformity in the Department of Hand and Foot Microsurgery in Xuzhou Central Hospital.Twenty-six patients with 28 feet high-grade bunionette deformity were hospitalized for treatment, with 3 male (3 feet) and 23 female (25 feet) cases, aged 22-73 (mean 47.1) years old.The average fourth-fifth intermetatarsal angle, lateral deviation of the fifth metatarsal angle and metatarsophalangeal-fifth angle were measured on the pre-and post- operative anterior to posterior weight-beating X rays of treated feet.The American Orthopaedic Foot and Ankle Society (AOFAS) Lesser Toe Metatarsophalangeal-Interphalangeal Scale was used to evaluate the post-operative outcomes. All of 26 patients were followed, with a mean 15.7 months (range 8-25 months). Primarily healing of the wound was achieved in all cases.No postoperative infection and nonunion on the osteotomy site was found during the follow-up time.The fracture healing time was 6-15 (mean 12.2) weeks.All the patients had satisfactory appearance and sensory function without callosum and metastatic metatarsalgia at the final follow-up.The post-operative fourth-fifth intermetatarsal angle, lateral deviation of the fifth metatarsal angle and metatarsophalangeal-fifth angle were significantly lesser than the pre-operative at the 6th week after operation, respectively [(5.5±1.7)°, (2.1±0.8)°, (5.7±2.6)°vs (16.4±4.2)°, (6.0±2.2)°, (10.5±7.4)°; all P<0.01]. The post-operative AOFAS score was significantly greater than the pre-operative [(87.1±6.7) vs (62.3±9.8) points, P<0.001]. The modified chevron osteotomy combined distal soft tissue reconstruction is a safe and easy treatment option for the high-grade bunionette deformity and provides patient satisfaction results.

Proximal Intermetatarsal Divergence in Distal Chevron Osteotomy for Hallux Valgus: An Overlooked Finding.

PubMed

Akpinar, Evren; Buyuk, Abdul Fettah; Cetinkaya, Engin; Gursu, Sarper; Ucpunar, Hanifi; Albayrak, Akif

2016-01-01

The goal of distal chevron osteotomy for hallux valgus is to restore proper first-toe joint alignment by performing lateral translation of the distal first metatarsal fragment (the metatarsal head). We hypothesized that in some patients this procedure might also result in involuntary medial translation of the proximal first metatarsal fragment, which we called proximal intermetatarsal divergence. The aim of the present study was to compare the pre- and postoperative radiographs of patients with hallux valgus to determine whether we could identify proximal intermetatarsal divergence. We retrospectively compared the pre- and postoperative radiographs of 29 feet in 28 patients treated with distal chevron osteotomy. Two different methods were used to measure the intermetatarsal angles: the anatomic intermetatarsal angle (aIMA) and the mechanical intermetatarsal angle (mIMA). The maximum intermetatarsal distance (MID) was also measured. We defined proximal intermetatarsal divergence as a postoperative increase in the aIMA or MID, coupled with a decrease in the mIMA. For data analysis, we divided the patients into low-angle (mild deformity) and high-angle (severe deformity) groups, according to their preoperative mIMA. The mean ± standard deviation patient age was 41 ± 14 years. In the low-angle group, the mean mIMA decreased (from 10.91° to 7.00°), the mean aIMA increased (from 11.80° to 13.55°), and the mean MID increased (from 17.97 mm to 20.60 mm; p = .001, for all). In the high-angle group, the mean mIMA decreased (from 14.30° to 6.90°; p = .001), the mean aIMA decreased (from 14.77° to 13.54°; p = .06), and the mean MID decreased (from 20.74 mm to 20.37 mm; p = .64). The results of our study suggest that proximal intermetatarsal divergence might occur after distal chevron osteotomy for hallux valgus, primarily in patients with a low preoperative mIMA. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Madison Avenue vs. the Environmentalists

ERIC Educational Resources Information Center

Sandman, Peter M.

1973-01-01

The Chevron F-310 advertising program is studied as an example of large companies' use of environmental and conservation themes for attracting customers. The effects of such advertising on the society are discussed. (JP)

75 FR 49486 - Environmental Impacts Statements; Notice Of Availability

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-13

..., CA, Chevron Energy Solutions Lucerne Valley Solar Project, Proposing To Develop a 45-megawatt (MW) Solar Photovotaic (PV) Plant and Associated Facilities on 516 Acres of Federal Land Managed, California...

78 FR 20089 - Sunshine Act Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-03

... recommendations to the Board Members based on the CSB's investigation into a hydrocarbon release and fire that... determined that nineteen Chevron employees were engulfed in a vapor cloud formed by the hydrocarbon release...

Publications - GMC 131 | Alaska Division of Geological & Geophysical

Science.gov Websites

and core from the Chevron USA Inc. Eagle Creek #1 well Authors: Unknown Publication Date: 1989 Inc. Eagle Creek #1 well: Alaska Division of Geological & Geophysical Surveys Geologic Materials

75 FR 7479 - Environmental Impact Statements; Notice of Availability

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-19

... EIS, BLM, CA Chevron Energy Solutions Lucerne Valley Solar Project, Proposing To Develop a 45-megawatt (MW) Solar Photovoltaic (PV) Plant and Associated Facilities on 516 Acres of Federal Land Managed...

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

Wood, A.

Cyclohexane buyers, hit by a string of US plant closures, are breathing a sigh of relief at signs of an upswing in capacity. Phillips Petroleum has assured the future of a cyclohexane plant at its Guayama, PR site, while Kerr-McGee Chemical has confirmed it will acquire a mothballed 30-million gal/year unit from Unocal and restart it. Phillips deal is connected to an agreement to license Chevron Chemical's Aromax catalytic reforming technology for its Guayama refinery. The technology, which will cut the company's aromatics production costs, secures the future of Phillips petrochemical operations at the site, including the downstream 90-million gal/yearmore » cyclohexane plant. The Chevron process is said to boost yields of benzene, toluene, and xylene above those of conventional reforming processes. It relies on a zeolite catalyst to convert light paraffins into aromatics; conventional reforming converts higher-valued aromatic naphthas.« less

Negative Differential Resistance and Steep Switching in Chevron Graphene Nanoribbon Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Smith, Samuel; Llinas, Juan-Pablo; Bokor, Jeffrey; Salahuddin, Sayeef

2018-01-01

Ballistic quantum transport calculations based on the non-equilbrium Green's function formalism show that field-effect transistor devices made from chevron-type graphene nanoribbons (CGNRs) could exhibit negative differential resistance with peak-to-valley ratios in excess of 4800 at room temperature as well as steep-slope switching with 6 mV/decade subtheshold swing over five orders of magnitude and ON-currents of 88$\\mu$A/$\\mu$m. This is enabled by the superlattice-like structure of these ribbons that have large periodic unit cells with regions of different effective bandgap, resulting in minibands and gaps in the density of states above the conduction band edge. The CGNR ribbon used in our proposed device has been previously fabricated with bottom-up chemical synthesis techniques and could be incorporated into an experimentally-realizable structure.

A modified Austin/chevron osteotomy for treatment of hallux valgus and hallux rigidus.

PubMed

Vasso, Michele; Del Regno, Chiara; D'Amelio, Antonio; Schiavone Panni, Alfredo

2016-03-01

The purpose of this brief paper is to present the preliminary results of a modified Austin/chevron osteotomy for treatment of hallux valgus and hallux rigidus. In this procedure, the dorsal arm of the osteotomy is performed orthogonal to the horizontal plane of the first metatarsal, the main advantage being that this allows much easier and more accurate multiplanar correction of first metatarsal deformities. From 2010 to 2013, 184 consecutive patients with symptomatic hallux valgus and 48 patients with hallux rigidus without severe metatarsophalangeal joint degeneration underwent such modified chevron osteotomy. Mean patient age was 54.9 (range 21-70) years, and mean follow-up duration was 41.7 (range 24-56) months. Ninety-three percent of patients were satisfied with the surgery. Mean American Orthopaedic Foot and Ankle Society (AOFAS) score improved from 56.6 preoperatively to 90.6 at last follow-up, and mean visual analog scale (VAS) pain score decreased from 5.7 preoperatively to 1.6 at final follow-up (p < 0.05). In patients treated for hallux valgus, mean hallux valgus angle decreased from 34.1° preoperatively to 6.2° at final follow-up, and mean intermetatarsal angle decreased from 18.5° preoperatively to 4.1° at final follow-up (p < 0.05). One patient developed postoperative transfer metatarsalgia, treated successfully with second-time percutaneous osteotomy of the minor metatarsals, whilst one patient had wound infection that resolved with systemic antibiotics. Level IV.

Change in First Metatarsal Length After Proximal and Distal Chevron Osteotomies for Hallux Valgus Deformity.

PubMed

Lee, Jun Young; Lee, Yeon Soo; Song, Kyoung Chul; Choi, Kwi Youn

2015-01-01

The present study assessed the changes in the length of the first metatarsal bone after performing proximal chevron metatarsal osteotomy (PCMO) or distal Chevron metatarsal osteotomy (DCMO) for patients with hallux valgus deformity. A total of 60 patients with moderate-to-severe hallux valgus deformity from July 2009 to July 2011 were randomly divided into the PCMO and DCMO groups, with 30 patients in each group. The distal soft tissue procedure was performed in the same method for both groups. Measurements were performed preoperatively, postoperatively, and at the last follow-up visit at 6.1 ± 0.8 months. The postoperative length change with respect to the preoperative length was 0.7 ± 2.5 mm and -0.7 ± 5.1 mm for the PCMO and DCMO groups, respectively, with a slight lengthening of the first metatarsal bone in the PCMO group and a shortening in the DCMO group (p < .01). The follow-up length change with respect to the preoperative length was -2.1 ± 3.0 mm and -4.4 ± 2.2 mm for the PCMO and DCMO groups, respectively, demonstrating a clear shortening of the first metatarsal length at the last follow-up point in the DCMO group (p < .01).When DCMO and the distal soft tissue procedure were performed, significant shortening was found at 6 months of follow-up. Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Axial loading screw fixation for chevron type osteotomies of the distal first metatarsal: a retrospective outcomes analysis.

PubMed

Murphy, Ryan M; Fallat, Lawrence M; Kish, John P

2014-01-01

The distal chevron osteotomy is a widely accepted technique for the treatment of hallux abductovalgus deformity. Although the osteotomy is considered to be stable, displacements of the capital fragment has been described. We propose a new method for fixation of the osteotomy involving the axial loading screw (ALS) used in addition to single screw fixation. We believe this method will provide a more mechanically stable construct. We reviewed the charts of 46 patients in whom 52 feet underwent a distal chevron osteotomy that was fixated with either 1 screw or 2 screws that included the ALS. We hypothesized that the ALS group would have fewer displacements and would heal more quickly than the single screw fixation group. We found that the group with ALS fixation had healed at a mean of 6.5 weeks and that the group with single screw fixation had healed at 9.53 weeks (p = .001). Also, 8 cases occurred of displacement of the capital fragment in the single screw, control group compared with 2 cases of displacement in the ALS group. However, this finding was not statistically significant. The addition of the ALS to single screw fixation allowed the patients to heal approximately 3 weeks earlier than single screw fixation alone. The ALS is a fixation option for the surgeon to consider when osseous correction of hallux abducto valgus is performed. Copyright © 2014 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Mariano Lake Mine: Technical Reports

EPA Pesticide Factsheets

This Final Removal Site Evaluation describes the objectives, work performed, and results of a Removal Site Evaluation (RSE) at the Mariano Lake Mine, which was performed by ARCADIS U.S., Inc. on behalf of Chevron Environmental Management Company.

California Coast

Atmospheric Science Data Center

2014-05-15

... shades of red. The distinctive chevron shape of the Mojave Desert is bordered by the San Andreas Fault on the south and the Garlock Fault ... March 14, 2000 - Southern California with the Mojave Desert and surrounding area. project:  MISR ...

76 FR 41302 - Request for Certification of Compliance-Rural Industrialization Loan and Grant Program

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-13

... venture involving a Chevron gas station, Burger King Restaurant, McAlister's Deli and a convenience store... (gasoline stations with convenience stores) and 722211 (limited-service restaurants). DATES: All interested...

75 FR 34448 - Proposed CERCLA Administrative Cost Recovery Settlement; Great Lakes Container Corporation...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-17

... Cyanamid Company); Hubbard Hall, Inc.; Invesys, Inc. on behalf of Elmwood Sensors, Inc.; Chevron..., subsidiaries and divisions; BP Products North America, Inc.; Eastern Color & Chemical Company. Dated: June 3...

Publications - GMC 214 | Alaska Division of Geological & Geophysical

Science.gov Websites

Chevron USA Inc. OCS Y-0996-1 (Diamond #1) well Authors: Unknown Publication Date: 1993 Publisher: Alaska see our publication sales page for more information. Bibliographic Reference Unknown, 1993, Vitrinite

Rippled Surfaces on a Slope in Coloe Fossae

NASA Image and Video Library

2014-01-09

This observation from NASA Mars Reconnaissance Orbiter shows a set of landforms that appears to form a nested chevron pattern on a slope in Coloe Fossae. Interestingly, nearby surfaces on the same slope are all parallel.

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

Kuehler, C.W.

This paper reports on the need for specialty fluid catalytic cracking (FCC) additives which is likely to increase, given the refining environment and the arrival of reformulated gasoline prompted by the most recent national environmental laws. C.W. Kuehler of Chevron Research and Technology Co., U.S.A. covered the participants in the field and the state of FCC additive technology this past June at Akzo Chemie's catalysts symposium in Scheveningen, The Netherlands. Other authors of the paper presented were A.S. Krishna, C.R. Hsieh, A.R.English, and T.A. Pecoraro, all with Chevron. The FCC process has undergone numerous changes in its 50-year history, Kuehlermore » pointed out. It shows the impressive continual growth of the process. One important aspect of additives is their ability to alter and control the nature of the FCC catalyst, thereby controlling the reactions carried out in the reactor and regenerator.« less

Fracture toughness of brittle materials determined with chevron notch specimens

NASA Technical Reports Server (NTRS)

Shannon, J. L., Jr.; Bubsey, R. T.; Pierce, W. S.; Munz, D.

1981-01-01

Short bar, short rod, and four-point-bend chevron-notch specimens were used to determine the plane strain fracture toughness of hot-pressed silicon nitride and sintered aluminum oxide brittle ceramics. The unique advantages of this specimen type are: (1) the production of a sharp natural crack during the early stage of test loading, so that no precracking is required, and (2) the load passes through a maximum at a constant, material-independent crack length-to-width ratio for a specific geometry, so that no post-test crack measurement is required. The plane strain fracture toughness is proportional to the maximum test load and functions of the specimen geometry and elastic compliance. Although results obtained for silicon nitride are in good mutual agreement and relatively free of geometry and size effects, aluminum oxide results were affected in both these respects by the rising crack growth resistance curve of the material.

Impact of Air Injection on Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Norum, Tom

2007-01-01

The objective of this viewgraph presentation is to review the program to determine impact of core fluidic chevrons on noise produced by dual stream jets (i.e., broadband shock noise - supersonic, and mixing noise - subsonic and supersonic). The presentation reviews the sources of jet noise. It shows designs of Generation II Fluidic Chevrons. The injection impacts shock structure and stream disturbances through enhanced mixing. This may impact constructive interference between acoustic sources. The high fan pressures may inhibit mixing produced by core injectors. A fan stream injection may be required for better noise reduction. In future the modification of Gen II nozzles to allow for some azimuthal control: will allow for higher mass flow rates and will allow for shallower injection angles A Flow field study is scheduled for spring, 2008 The conclusions are that injection can reduce well-defined shock noise and injection reduces mixing noise near peak jet noise angle

Plate fixation for proximal chevron osteotomy has greater risk for hallux valgus recurrence than Kirschner wire fixation.

PubMed

Park, Chul-Hyun; Ahn, Ji-Yong; Kim, Yu-Mi; Lee, Woo-Chun

2013-06-01

The purpose of this study was to compare the results of hallux valgus surgery between feet fixed with Kirschner wires and those fixed with a plate and screws. Between December 2008 and November 2009, 53 patients (62 feet) were treated with proximal chevron osteotomy and distal soft tissue procedure for symptomatic moderate to severe hallux valgus deformity. Thirty-four patients (41 feet) were stabilised with Kirschner wires (K-wire group) and 19 patients (21 feet) were stabilised with a locking plate (plate group). Clinical results were assessed using American Orthopaedic Foot and Ankle Society (AOFAS) score. Radiographic parameters were compared between these groups. Recurrence rate at the last follow-up was compared between the K-wire and plate groups. Mean AOFAS score was lower in the plate group, however, the difference between the groups was not statistically significant in AOFAS score at the last follow-up. Hallux valgus angle and intermetatarsal angle were significantly larger in the plate group at the last follow-up. Mean 1-2 metatarsal (MT) distance on immediately postoperative radiographs was significant larger in the plate group. Four (9.8 %) of the 41 feet in the K-wire group and 7 (33.3 %) of the 21 feet in the plate group showed hallux valgus recurrence at the last follow-up. The plate group had a significantly higher risk of recurrence than the K-wire group. Fixation of proximal chevron osteotomy using a plate and screws has a greater risk of hallux valgus recurrence than fixation using Kirschner wires.

Energy insurance for Anchorage, Alaska - Beluga river gas field, Cook Inlet

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

Stone, N.D.; Lindblom, R.G.

1987-05-01

The Beluga River gas field is the primary energy source for Anchorage, Alaska. The field is located 40 mi west of Anchorage astride the northwest shoreline of the Cook Inlet. Gas was discovered in December 1962 by Chevron's Beluga River unit (BRU) 1 well in section 35, T13N, R10W, S.B. and M. There are 16 producing wells in the field capable of a total gas potential of 140,000 MCFD. The current production averages 75,000 MCFD and the field has produced 220 BCF gas. Chevron, Shell, and ARCO have equal interests in the field. The Beluga River unit was formed inmore » 1962 with Chevron as operator. The produced gas is sold to the Chugach Electric Company and the Enstar Gas Company, both Anchorage-based utilities. The gas accumulation is trapped by a doubly plunging, slightly asymmetric anticlinal fold trending northeast-southwest. Gas is found from 3000 to 6000 ft vertical depth in sands within the lower Sterling (Pliocene) and Beluga River (upper Miocene) Formations. Reservoir sands range in thickness from 5 to 85 ft with average porosities of 24 to 30%. The Sterling sands were deposited in broad sand channels in a fluvial-deltaic setting, whereas Beluga sands were deposited in a high-energy fluvial environment in shifting stream courses. The use of the wireline repeat formation tester has aided in correlation, evaluation, and management of the multiple sand reservoirs. New gas sand reservoirs and partly depleted reservoirs are recognized, enabling completion from reservoirs of similar pressures and reducing risks associated with cross flow between reservoirs.« less

Controlled Hydrogen Fleet and Infrastructure Demonstration and Validation Project Final Technical Report

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

Verma, Puneet; Casey, Dan

This report summarizes the work conducted under U.S. Department of Energy (US DOE) contract DE-FC36-04GO14286 by Chevron Technology Ventures (CTV, a division of Chevron U.S.A., Inc.), Hyundai Motor Company (HMC), and UTC Power (UTCP, a United Technologies company) to validate hydrogen (H2) infrastructure technology and fuel cell hybrid vehicles. Chevron established hydrogen filling stations at fleet operator sites using multiple technologies for on-site hydrogen generation, storage, and dispensing. CTV constructed five demonstration stations to support a vehicle fleet of 33 fuel cell passenger vehicles, eight internal combustion engine (ICE) vehicles, three fuel cell transit busses, and eight internal combustion enginemore » shuttle busses. Stations were operated between 2005 and 2010. HMC introduced 33 fuel cell hybrid electric vehicles (FCHEV) in the course of the project. Generation I included 17 vehicles that used UTCP fuel cell power plants and operated at 350 bar. Generation II included 16 vehicles that had upgraded UTC fuel cell power plants and demonstrated options such as the use of super-capacitors and operation at 700 bar. All 33 vehicles used the Hyundai Tucson sports utility vehicle (SUV) platform. Fleet operators demonstrated commercial operation of the vehicles in three climate zones (hot, moderate, and cold) and for various driving patterns. Fleet operators were Southern California Edison (SCE), AC Transit (of Oakland, California), Hyundai America Technical Center Inc. (HATCI), and the U.S. Army Tank Automotive Research, Development and Engineering Center (TARDEC, in a site agreement with Selfridge Army National Guard Base in Selfridge, Michigan).« less

Anchor enhanced capsulorraphy in bunionectomies using an L-shaped capsulotomy.

PubMed

Gould, John S; Ali, Sheriff; Fowler, Rachel; Fleisig, Glenn S

2003-01-01

The objective of this study was to investigate potential benefit of a suture anchor-enhanced capsulorraphy in the early maintenance of correction in bunionectomies. We compared, retrospectively, in successive series, the loss of correction of the Hallux Valgus (HV) and intermetatarsal (IM) angle, in those repaired with an L-shaped capsulorraphy enhanced with anchors to those without. Intraoperative and second week postoperative simulated weightbearing anterior posterior (AP) X-rays were used to evaluate results. By using only intraoperative and early postoperative X-rays, we should have effectively eliminated extraneous factors that might have influenced our results. A Total of 106 cases were investigated, 65 of which were repaired using anchors, the remaining 41 without. In the anchor group, 38 underwent a proximal metatarsal concentric shelf osteotomy (CSO)/modified McBride procedure, while the remaining 27 had a distal Chevron correction. In the without-anchor group, 21 had a CSO/modified McBride procedure while 20 underwent the Chevron procedure. In the without-anchor group, the average HV and IM loss of correction was 4.60 degrees (range, -2 to 21 degrees) and 0.6 degrees (range, -1 to 9 degrees) respectively. In the anchor group, the corresponding loss was 2.8 degrees (range, -3 to 17 degrees) and 0.6 degrees (range, -2 to 14 degrees) respectively. These results, when statistically analyzed, demonstrated that while the IM angle change was not statistically significant, the HV angle change was statistically significant, implying that the anchor plays a significant role in maintaining the surgical correction in both the distal Chevron and CSO/ modified McBride bunionectomies.

Supersymmetric quantum mechanics method for the Fokker-Planck equation with applications to protein folding dynamics

NASA Astrophysics Data System (ADS)

Polotto, Franciele; Drigo Filho, Elso; Chahine, Jorge; Oliveira, Ronaldo Junio de

2018-03-01

This work developed analytical methods to explore the kinetics of the time-dependent probability distributions over thermodynamic free energy profiles of protein folding and compared the results with simulation. The Fokker-Planck equation is mapped onto a Schrödinger-type equation due to the well-known solutions of the latter. Through a semi-analytical description, the supersymmetric quantum mechanics formalism is invoked and the time-dependent probability distributions are obtained with numerical calculations by using the variational method. A coarse-grained structure-based model of the two-state protein Tm CSP was simulated at a Cα level of resolution and the thermodynamics and kinetics were fully characterized. Analytical solutions from non-equilibrium conditions were obtained with the simulated double-well free energy potential and kinetic folding times were calculated. It was found that analytical folding time as a function of temperature agrees, quantitatively, with simulations and experiments from the literature of Tm CSP having the well-known 'U' shape of the Chevron Plots. The simple analytical model developed in this study has a potential to be used by theoreticians and experimentalists willing to explore, quantitatively, rates and the kinetic behavior of their system by informing the thermally activated barrier. The theory developed describes a stochastic process and, therefore, can be applied to a variety of biological as well as condensed-phase two-state systems.

Protein Folding Mechanism of the Dimeric AmphiphysinII/Bin1 N-BAR Domain

PubMed Central

Gruber, Tobias; Balbach, Jochen

2015-01-01

The human AmphyphisinII/Bin1 N-BAR domain belongs to the BAR domain superfamily, whose members sense and generate membrane curvatures. The N-BAR domain is a 57 kDa homodimeric protein comprising a six helix bundle. Here we report the protein folding mechanism of this protein as a representative of this protein superfamily. The concentration dependent thermodynamic stability was studied by urea equilibrium transition curves followed by fluorescence and far-UV CD spectroscopy. Kinetic unfolding and refolding experiments, including rapid double and triple mixing techniques, allowed to unravel the complex folding behavior of N-BAR. The equilibrium unfolding transition curve can be described by a two-state process, while the folding kinetics show four refolding phases, an additional burst reaction and two unfolding phases. All fast refolding phases show a rollover in the chevron plot but only one of these phases depends on the protein concentration reporting the dimerization step. Secondary structure formation occurs during the three fast refolding phases. The slowest phase can be assigned to a proline isomerization. All kinetic experiments were also followed by fluorescence anisotropy detection to verify the assignment of the dimerization step to the respective folding phase. Based on these experiments we propose for N-BAR two parallel folding pathways towards the homodimeric native state depending on the proline conformation in the unfolded state. PMID:26368922

Unfolding Kinetics of β-Lactoglobulin Induced by Surfactant and Denaturant: A Stopped-Flow/Fluorescence Study

PubMed Central

Viseu, Maria Isabel; Melo, Eduardo P.; Carvalho, Teresa Isabel; Correia, Raquel F.; Costa, Sílvia M. B.

2007-01-01

The β→α transition of β-lactoglobulin, a globular protein abundant in the milk of several mammals, is investigated in this work. This transition, induced by the cationic surfactant dodecyltrimethylammonium chloride (DTAC), is accompanied by partial unfolding of the protein. In this work, unfolding of bovine β-lactoglobulin in DTAC is compared with its unfolding induced by the chemical denaturant guanidine hydrochloride (GnHCl). The final protein states attained in the two media have quite different secondary structure: in DTAC the α-helical content increases, leading to the so-called α-state; in GnHCl the amount of ordered secondary-structure decreases, resulting in a random coil-rich final state (denatured, or D, state). To obtain information on both mechanistic routes, in DTAC and GnHCl, and to characterize intermediates, the kinetics of unfolding were investigated in the two media. Equilibrium and kinetic data show the partial accumulation of an on-pathway intermediate in each unfolding route: in DTAC, an intermediate (I1) with mostly native secondary structure but loose tertiary structure appears between the native (β) and α-states; in GnHCl, another intermediate (I2) appears between states β and D. Kinetic rate constants follow a linear Chevron-plot representation in GnHCl, but show a more complex mechanism in DTAC, which acts like a stronger binding species. PMID:17693475

Evaluation of strains in bituminous surfaces : stiffness-fatigue investigation.

DOT National Transportation Integrated Search

1973-01-01

The study was designed to determine if strains in Virginia's thin asphaltic pavements were high enough to cause early fatigue failure. Strains were computed with the Chevron multilayer computer program, and also measured on selected highways using el...

77 FR 43614 - Notice of Lodging of Consent Decree Pursuant to the Clean Air Act

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-25

... (``LDAR'') for hazardous air pollutants, 40 CFR Part 63, Subparts A, H and CC, at an asphalt petroleum... penalty. In addition, although the plant has not refined asphalt since 2008, Chevron agrees to implement...

FACILITY 858, PORTION OF NORTHEAST SIDE (APRON AVENUE SIDE), SHOWING ...

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

FACILITY 858, PORTION OF NORTHEAST SIDE (APRON AVENUE SIDE), SHOWING CHEVRON DESIGN OVER FORMER PASSAGEWAY, OBLIQUE VIEW FACING WEST. - Schofield Barracks Military Reservation, Quadrangle K Barracks Type, Between Wilson Street & Capron Avenue near Williston Avenue, Wahiawa, Honolulu County, HI

FACILITY 859, DETAIL OF SOUTHWEST SIDE (WILSON STREET SIDE), SHOWING ...

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

FACILITY 859, DETAIL OF SOUTHWEST SIDE (WILSON STREET SIDE), SHOWING CHEVRON DESIGN OVER FORMER PASSAGEWAY, VIEW FACING NORTHEAST. - Schofield Barracks Military Reservation, Quadrangle K Barracks Type, Between Wilson Street & Capron Avenue near Williston Avenue, Wahiawa, Honolulu County, HI

Publications - GMC 129 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 129 Publication Details Title: Visual kerogen and TAI data of select cuttings and core from , Visual kerogen and TAI data of select cuttings and core from the Chevron USA Inc. Akulik #1 well: Alaska

Mariano Lake Mine

EPA Pesticide Factsheets

Mariano Lake Mine is located in the Mariano Lake Chapter of the Navajo Nation, approximately 25 miles east of Gallup, N.M in McKinley County. EPA is working with Navajo Nation Environmental Protection Agency (NNEPA) to oversee cleanup work by Chevron U.S.A

76 FR 45617 - Notice of Lodging of the Consent Decree Under the Resource Conservation and Recovery Act

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-29

... underground storage tank (UST) facilities; failure to perform annual tests of automatic line leak detectors... detectors for piping on the UST systems. CHEVRON also agrees under the Consent Decree to install dispenser...

75 FR 53284 - Chevron Keystone Gas Storage, LLC; Bridgeline Holdings, L.P.; New York State Electric & Gas...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-31

... Holdings, L.P.; New York State Electric & Gas Corporation; Notice of Baseline Filings August 24, 2010. Take... above submitted their baseline filing of its Statement of Operating Conditions for services provided...

Stabilometer "S" value study on asphalt concrete samples.

DOT National Transportation Integrated Search

1985-07-01

During the late fall of 1969 a study was made to determine the precision when testing asphalt concrete specimens for the Hveem stabilometer ("S") value (AASHTO T 246). Fifty samples, using Chevron 85-100 asphalt cement and aggregate from Walling Sand...

Computer programs for eddy-current defect studies

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

Pate, J. R.; Dodd, C. V.

Several computer programs to aid in the design of eddy-current tests and probes have been written. The programs, written in Fortran, deal in various ways with the response to defects exhibited by four types of probes: the pancake probe, the reflection probe, the circumferential boreside probe, and the circumferential encircling probe. Programs are included which calculate the impedance or voltage change in a coil due to a defect, which calculate and plot the defect sensitivity factor of a coil, and which invert calculated or experimental readings to obtain the size of a defect. The theory upon which the programs aremore » based is the Burrows point defect theory, and thus the calculations of the programs will be more accurate for small defects. 6 refs., 21 figs.« less

WITHDRAWN: Interventions for treating hallux valgus (abductovalgus) and bunions.

PubMed

Ferrari, Jill; Higgins, Julian Pt; Prior, Trevor D

2009-04-15

Hallux valgus is classified as an abnormal deviation of the great toe (hallux) towards the midline of the foot. To identify and evaluate the evidence from randomised trials of interventions used to correct hallux valgus. We searched the Cochrane Bone, Joint and Muscle Trauama Group trials register (2003/1), the Cochrane Central Register of Controlled Trials (The Cochrane Library issue 1, 2003), MEDLINE (January 1966 to March 2003) and EMBASE (1980 to January 2003). No language restrictions were applied. Hand searching of specific foot journals was also undertaken.Date of the most recent search: 31st March 2003. Randomised or quasi-randomised trials of both conservative and surgical treatments of hallux valgus. Excluded were studies comparing areas of surgery not specific to the control of the deformity such as use of anaesthetics or tourniquet placement. Methodological quality of trials which met the inclusion criteria was independently assessed by two reviewers. Data extraction was undertaken by two reviewers. The trials were grouped according to the interventions being compared, but the dissimilarity in the comparisons prevented pooling of results. The methodological quality of the 21 included trials was generally poor and trial sizes were small.Three trials involving 332 participants evaluated conservative treatments versus no treatment. There was no evidence of a difference in outcomes between treatment and no treatment.One good quality trial involving 140 participants compared surgery to conservative treatment. Evidence was shown of an improvement in all outcomes in patients receiving chevron osteotomy compared with those receiving orthoses. The same trial also compared surgery to no treatment in 140 participants. Evidence was shown of an improvement in all outcomes in patients receiving chevron osteotomy compared with those receiving no treatment.Two trials involving 133 people with hallux valgus compared Keller's arthroplasty with other surgical techniques. In general, there was no advantage or disadvantage using Keller's over the other techniques. When the distal osteotomy was compared to Keller's arthroplasty, the osteotomy showed evidence of improving the intermetatarsal angle and preserving joint range of motion. The arthroplasty was found to have less of an impact on walking ability compared to the arthrodesis.Six trials involving 309 participants compared chevron (and chevron-type) osteotomy with other techniques. The chevron osteotomy offered no advantages in these trials. For some outcomes, other techniques gave better results. Two of these trials (94 participants) compared a type of proximal osteotomy to a proximal chevron osteotomy and found no evidence of a difference in outcomes between techniques.Three trials involving 157 participants compared outcomes between original operations and surgeon's adaptations. There was no advantage found for any of the adaptations.Three trials involving 71 people with hallux valgus compared new methods of fixation to traditional methods. There was no evidence that the new methods of fixation were detrimental to the outcome of the patients.Four trials involving 162 participants evaluated methods of post-operative rehabilitation. The use of continuous passive motion appeared to give an improved range of motion and earlier recovery following surgery. Early weightbearing or the use of a crepe bandage were not found to be detrimental to final outcome. Only a few studies had considered conservative treatments. The evidence from these suggested that orthoses and night splints did not appear to be any more beneficial in improving outcomes than no treatment. Surgery (chevron osteotomy) was shown to be beneficial compared to orthoses or no treatment, but when compared to other osteotomies, no technique was shown to be superior to any other. Only one trial had compared an osteotomy to an arthroplasty. There was limited evidence to suggest that the osteotomy gave the better outcomes. It was notable that the numbers of participants in some trials remaining dissatisfied at follow-up were consistently high (25 to 33%), even when the hallux valgus angle and pain had improved. A few of the more recent trials used assessment scores that combine several aspects of the patients outcomes. These scoring systems are useful to the clinician when comparing techniques but are of dubious relevance to the patient if they do not address their main concern and such scoring systems are frequently unvalidated. Only one study simply asked the patient if they were better than before the treatment. Final outcomes were most frequently measured at one year, with a few trials maintaining follow-up for 3 years. Such time-scales are minimal given that the patients will be on their feet for at least another 20-30 years after treatment. Future research should include patient-focused outcomes, standardised assessment criteria and longer surveillance periods, more usefully in the region of 5-10 years.

Interventions for treating hallux valgus (abductovalgus) and bunions.

PubMed

Ferrari, J; Higgins, J P T; Prior, T D

2004-01-01

Hallux valgus is classified as an abnormal deviation of the great toe (hallux) towards the midline of the foot. To identify and evaluate the evidence from randomised trials of interventions used to correct hallux valgus. We searched the Cochrane Musculoskeletal Injuries Group trials register (2003/1), the Cochrane Central Register of Controlled Trials (The Cochrane Library issue 1, 2003), MEDLINE (January 1966 to March 2003) and EMBASE (1980 to January 2003). No language restrictions were applied. Hand searching of specific foot journals was also undertaken. Date of the most recent search: 31st March 2003. Randomised or quasi-randomised trials of both conservative and surgical treatments of hallux valgus. Excluded were studies comparing areas of surgery not specific to the control of the deformity such as use of anaesthetics or tourniquet placement. Methodological quality of trials which met the inclusion criteria was independently assessed by two reviewers. Data extraction was undertaken by two reviewers. The trials were grouped according to the interventions being compared, but the dissimilarity in the comparisons prevented pooling of results. The methodological quality of the 21 included trials was generally poor and trial sizes were small. Three trials involving 332 participants evaluated conservative treatments versus no treatment. There was no evidence of a difference in outcomes between treatment and no treatment. One good quality trial involving 140 participants compared surgery to conservative treatment. Evidence was shown of an improvement in all outcomes in patients receiving chevron osteotomy compared with those receiving orthoses. The same trial also compared surgery to no treatment in 140 participants. Evidence was shown of an improvement in all outcomes in patients receiving chevron osteotomy compared with those receiving no treatment. Two trials involving 133 people with hallux valgus compared Keller's arthroplasty with other surgical techniques. In general, there was no advantage or disadvantage using Keller's over the other techniques. When the distal osteotomy was compared to Keller's arthroplasty, the osteotomy showed evidence of improving the intermetatarsal angle and preserving joint range of motion. The arthroplasty was found to have less of an impact on walking ability compared to the arthrodesis. Six trials involving 309 participants compared chevron (and chevron-type) osteotomy with other techniques. The chevron osteotomy offered no advantages in these trials. For some outcomes, other techniques gave better results. Two of these trials (94 participants) compared a type of proximal osteotomy to a proximal chevron osteotomy and found no evidence of a difference in outcomes between techniques. Three trials involving 157 participants compared outcomes between original operations and surgeon's adaptations. There was no advantage found for any of the adaptations. Three trials involving 71 people with hallux valgus compared new methods of fixation to traditional methods. There was no evidence that the new methods of fixation were detrimental to the outcome of the patients. Four trials involving 162 participants evaluated methods of post-operative rehabilitation. The use of continuous passive motion appeared to give an improved range of motion and earlier recovery following surgery. Early weightbearing or the use of a crepe bandage were not found to be detrimental to final outcome. Only a few studies had considered conservative treatments. The evidence from these suggested that orthoses and night splints did not appear to be any more beneficial in improving outcomes than no treatment. Surgery (chevron osteotomy) was shown to be beneficial compared to orthoses or no treatment, but when compared to other osteotomies, no technique was shown to be superior to any other. Only one trial had compared an osteotomy to an arthroplasty. There was limited evidence to suggest that the osteotomy gat the osteotomy gave the better outcomes. It was notable that the numbers of participants in some trials remaining dissatisfied at follow-up were consistently high (25 to 33%), even when the hallux valgus angle and pain had improved. A few of the more recent trials used assessment scores that combine several aspects of the patients outcomes. These scoring systems are useful to the clinician when comparing techniques but are of dubious relevance to the patient if they do not address their main concern and such scoring systems are frequently unvalidated. Only one study simply asked the patient if they were better than before the treatment. Final outcomes were most frequently measured at one year, with a few trials maintaining follow-up for 3 years. Such time-scales are minimal given that the patients will be on their feet for at least another 20-30 years after treatment. Future research should include patient-focused outcomes, standardised assessment criteria and longer surveillance periods, more usefully in the region of 5-10 years.

At what age do biomedical scientists do their best work?

PubMed

Falagas, Matthew E; Ierodiakonou, Vrettos; Alexiou, Vangelis G

2008-12-01

Several human characteristics that influence scientific research performance, including set goals, mental and physical abilities, education, and experience, may vary considerably during the life cycle of scientists. We sought to answer the question of whether high-quality research productivity is associated with investigator's age. We randomly selected 300 highly cited scientists (50 from each of 6 different biomedical fields, specifically immunology, microbiology, neuroscience, psychology-psychiatry, clinical medicine, and biology-biochemistry). Then, we identified the top 5 highly cited articles (within 10 yr after publication adjusted for the expansion of the literature) as first author of each of them. Subsequently, we plotted the distribution of the 1500 analyzed articles of the 300 studied scientists in the eight 5-year intervals of investigator's age during the year of article publication (21-25 to 55-60 yr of age), adjusted for person-years of contribution of each scientist in the various age groups. Highly cited research productivity plotted a curve that peaked at the age group of 31-35 yr of age and then gradually decreased with advancing age. However, a considerable proportion of this highly cited research was produced by older scientists (in almost 20% of the analyzed articles, researchers were older than 50 yr). The results were similar in another analysis of the single most cited article of each studied scientist. In conclusion, high-quality scientific productivity in the biomedical fields as a function of investigator's age plots an inverted U-shaped curve, in which significant decreases take place from around 40 yr of age and beyond.

77 FR 71668 - Andean Trade Preference Act (ATPA), as Amended: Notice Regarding the 2012 Annual Review

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-03

... remain under review through July 31, 2013, which is the period that the ATPA is in effect: Ecuador--Human Rights Watch Ecuador--U.S./Labor Education in the Americas Project Ecuador--Chevron Texaco. Douglas Bell...

Membrane protection for steel stringer tops : Yaquina Bay Bridge, Newport, Oregon : construction report.

DOT National Transportation Integrated Search

1980-10-01

The experimental feature of this project was to evaluate the application and performance of Chevron Industrial Membrane applied to the tops of steel deck stringers and other similar members as corrosion protection in conjunction with the deck replace...

40 CFR 62.3852 - Identification of sources.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Emissions from Existing Phosphate Fertilizer Plants § 62.3852 Identification of sources. (a) The plan applies to existing facilities at the following phosphate fertilizer plants: (1) Agrico Chemical Company, Fort Madison, Iowa. (2) Chevron Chemical Company, Fort Madison, Iowa. (3) Occidental Chemical Company...

40 CFR 62.3852 - Identification of sources.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Emissions from Existing Phosphate Fertilizer Plants § 62.3852 Identification of sources. (a) The plan applies to existing facilities at the following phosphate fertilizer plants: (1) Agrico Chemical Company, Fort Madison, Iowa. (2) Chevron Chemical Company, Fort Madison, Iowa. (3) Occidental Chemical Company...

40 CFR 62.3852 - Identification of sources.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Emissions from Existing Phosphate Fertilizer Plants § 62.3852 Identification of sources. (a) The plan applies to existing facilities at the following phosphate fertilizer plants: (1) Agrico Chemical Company, Fort Madison, Iowa. (2) Chevron Chemical Company, Fort Madison, Iowa. (3) Occidental Chemical Company...

The build-up of the cD halo of M 87: evidence for accretion in the last Gyr

NASA Astrophysics Data System (ADS)

Longobardi, A.; Arnaboldi, M.; Gerhard, O.; Mihos, J. C.

2015-07-01

Aims: We present kinematic and photometric evidence for an accretion event in the halo of the cD galaxy M 87 in the last Gyr. Methods: Using velocities for ~300 planetary nebulas (PNs) in the M 87 halo, we identify a chevron-like substructure in the PN phase-space. We implement a probabilistic Gaussian mixture model to identify PNs that belong to the chevron. From analysis of deep V-band images of M 87, we find that the region with the highest density of chevron PNs is a crown-shaped substructure in the light. Results: We assign a total of NPN,sub = 54 to the substructure, which extends over ~50 kpc along the major axis where we also observe radial variations of the ellipticity profile and a colour gradient. The substructure has highest surface brightness in a 20 kpc × 60 kpc region around 70 kpc in radius. In this region, the substructure causes an increase in surface brightness by ≳60%. The accretion event is consistent with a progenitor galaxy with a V-band luminosity of L = 2.8±1.0×109 L⊙ ,V, a colour of (B - V) = 0.76±0.05, and a stellar mass of M = 6.4±2.3×109 M⊙. Conclusions: The accretion of this progenitor galaxy has caused an important modification of the outer halo of M 87 in the last Gyr. This result provides strong evidence that the galaxy's cD halo is growing through the accretion of smaller galaxies as predicted by hierarchical galaxy evolution models. Based on observations made with the VLT at Paranal Observatory under programme 088.B-0288(A) and 093.B-066(A), and with the Subaru Telescope under programme S10A-039.

Impact of Fluidic Chevrons on Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Kinzie, Kevin W.; Whitmire, Julia; Abeysinghe, Amal

2005-01-01

The impact of alternating fluidic core chevrons on the production of jet noise is investigated. Core nozzles for a representative 1/9th scale, bypass ratio 5 model system were manufactured with slots cut near the trailing edges to allow for air injection into the core and fan streams. The injectors followed an alternating pattern around the nozzle perimeter so that the injection alternated between injection into the core stream and injection into the fan stream. For the takeoff condition and a forward flight Mach number of 0.10, the overall sound pressure levels at the peak jet noise angle decrease with increasing injection pressure. Sound pressure levels increase for observation angles less than 110o at higher injection pressures due to increases in high frequency noise. Greater increases in high frequency noise are observed when the number of injectors increases from 8 to 12. When the forward flight Mach number is increased to 0.28, jet noise reduction (relative to the baseline) is observed at aft angles for increasing injection pressure while significant increases in jet noise are observed at forward observation angles due to substantial acoustic radiation at high frequencies. A comparison between inflow and alternating injectors shows that, for equal mass injection rates, the inflow nozzle produces greater low frequency noise reduction (relative to the baseline) than the alternating injectors at 90o and aft observation angles and a forward flight Mach number of 0.28. Preliminary computational fluid dynamic simulations indicate that the spatial decay rate of the hot potential core flow is less for the inflow nozzle than for the alternating nozzles which indicates that gentle mixing may be preferred over sever mixing when fluidic chevrons are used for jet noise reduction.

Investigation of the Influence of Shapes-Texture on Surface Deformation of UHMWPE as a Bearing Material in Static Normal Load and Rolling Contact

NASA Astrophysics Data System (ADS)

Lestari, W. D.; Ismail, R.; Jamari, J.; Bayuseno, A. P.

2017-05-01

Surface texture is a common method for improving wear properties of a tribo-pair of soft and hard bearing material. The reduction of wear rates on the contacting surface material is becoming important issues. In the present study, analysis of the contact pressure on the flat surface of UHMWPE (Ultra High Molecular Weight Polyethylene) under the static- and rolling motion with the surface of steel ball used the 3D finite element method (FEM) (the ABAQUS software version 6.12). Five shaped-texture models (square, circle, ellipse, triangle, and chevron) were presented on the flat surface for analysis. The normal load of 17, 30 and 50 N was deliberately set-up for static and rolling contact analysis. The contact pressure was determined to predict the wear behavior of the shaped-texture on the flat surface of UHMWPE. The results have shown that the static normal load yielded the lowest von-Mises stress distribution on the shaped-texture of the ellipse for all values applied a load, while the square shape experienced the highest stress distribution. Under rolling contact, however, the increasing load yielded the increasing von Mises stress distribution for the texture with a triangle shape. Moreover, the texture shapes for circle, ellipse, and chevron respectively, may undergo the lowest stress distribution for all load. The wear calculation provided that the circle and square shape may undergo the highest wear rates. Obviously, the surface texture of circle, ellipse, and chevron may experience the lowest wear rates and is potential for use in the surface engineering of bearing materials.

Clinical and Radiological Outcomes Comparing Percutaneous Chevron-Akin Osteotomies vs Open Scarf-Akin Osteotomies for Hallux Valgus.

PubMed

Lai, Mun Chun; Rikhraj, Inderjeet Singh; Woo, Yew Lok; Yeo, William; Ng, Yung Chuan Sean; Koo, Kevin

2018-03-01

Minimally invasive surgeries have gained popularity due to less soft tissue trauma and better wound healing. To date, limited studies have compared the outcomes of percutaneous and open osteotomies. This study aims to investigate the clinical and radiological outcomes of percutaneous chevron-Akin osteotomies vs open scarf-Akin osteotomies at 24-month follow-up. We reviewed a prospectively collected database in a tertiary hospital hallux valgus registry. Twenty-nine feet that underwent a percutaneous technique were matched to 58 feet that underwent open scarf and Akin osteotomies. Clinical outcome measures assessed included visual analog scale (VAS) scores, American Orthopaedic Foot & Ankle Society Hallux Metatarsophalangeal-Interphalangeal score (AOFAS Hallux MTP-IP), and Short Form 36 (SF-36) Health Survey. Radiological outcomes included hallux valgus angle (HVA) and intermetatarsal angle (IMA). All patients were prospectively followed up at 6 and 24 months. Both groups showed comparable clinical and radiological outcomes at the 24-month follow-up. However, the percutaneous group demonstrated less pain in the perioperative period ( P < .001). There were significant differences in the change in HVA between the groups but comparable radiological outcomes in IMA at the 24-month follow-up. The percutaneous group demonstrated shorter length of operation ( P < .001). There were no complications in the percutaneous group but 3 wound complications in the open group. We conclude that clinical and radiological outcomes of third-generation percutaneous chevron-Akin osteotomies were comparable with open scarf and Akin osteotomies at 24 months but with significantly less perioperative pain, shorter length of operation, and less risk of wound complications. Level III, retrospective comparative series.

Treatment of moderate hallux valgus by percutaneous, extra-articular reverse-L Chevron (PERC) osteotomy.

PubMed

Lucas y Hernandez, J; Golanó, P; Roshan-Zamir, S; Darcel, V; Chauveaux, D; Laffenêtre, O

2016-03-01

The aim of this study was to report a single surgeon series of consecutive patients with moderate hallux valgus managed with a percutaneous extra-articular reverse-L chevron (PERC) osteotomy. A total of 38 patients underwent 45 procedures. There were 35 women and three men. The mean age of the patients was 48 years (17 to 69). An additional percutaneous Akin osteotomy was performed in 37 feet and percutaneous lateral capsular release was performed in 22 feet. Clinical and radiological assessments included the type of forefoot, range of movement, the American Orthopedic Foot and Ankle (AOFAS) score, a subjective rating and radiological parameters. The mean follow-up was 59.1 months (45.9 to 75.2). No patients were lost to follow-up. The mean AOFAS score increased from 62.5 (30 to 80) pre-operatively to 97.1 (75 to 100) post-operatively. A total of 37 patients (97%) were satisfied. At the last follow up there was a statistically significant decrease in the hallux valgus angle, the intermetatarsal angle and the proximal articular set angle. The range of movement of the first metatarsophalangeal joint improved significantly.. There was more improvement in the range of movement in patients who had fixation of the osteotomy of the proximal phalanx. Preliminary results of this percutaneous approach are promising. This technique is reliable and reproducible. Its main asset is that it maintains an excellent range of movement. The PERC osteotomy procedure is an effective approach for surgical management of moderate hallux valgus which combines the benefits of percutaneous surgery with the versatility of the chevron osteotomy whilst maintaining excellent first MTPJ range of motion. ©2016 The British Editorial Society of Bone & Joint Surgery.

Point-Connecting Measurements of the Hallux Valgus Deformity: A New Measurement and Its Clinical Application

PubMed Central

Seo, Jeong-Ho; Boedijono, Dimas

2016-01-01

Purpose The aim of this study was to investigate new point-connecting measurements for the hallux valgus angle (HVA) and the first intermetatarsal angle (IMA), which can reflect the degree of subluxation of the first metatarsophalangeal joint (MTPJ). Also, this study attempted to compare the validity of midline measurements and the new point-connecting measurements for the determination of HVA and IMA values. Materials and Methods Sixty feet of hallux valgus patients who underwent surgery between 2007 and 2011 were classified in terms of the severity of HVA, congruency of the first MTPJ, and type of chevron metatarsal osteotomy. On weight-bearing dorsal-plantar radiographs, HVA and IMA values were measured and compared preoperatively and postoperatively using both the conventional and new methods. Results Compared with midline measurements, point-connecting measurements showed higher inter- and intra-observer reliability for preoperative HVA/IMA and similar or higher inter- and intra-observer reliability for postoperative HVA/IMA. Patients who underwent distal chevron metatarsal osteotomy (DCMO) had higher intraclass correlation coefficient for inter- and intra-observer reliability for pre- and post-operative HVA and IMA measured by the point-connecting method compared with the midline method. All differences in the preoperative HVAs and IMAs determined by both the midline method and point-connecting methods were significant between the deviated group and subluxated groups (p=0.001). Conclusion The point-connecting method for measuring HVA and IMA in the subluxated first MTPJ may better reflect the severity of a HV deformity with higher reliability than the midline method, and is more useful in patients with DCMO than in patients with proximal chevron metatarsal osteotomy. PMID:26996576

Comparative performance study of smart structure for thermal microactuators

NASA Astrophysics Data System (ADS)

Yahya, Zulkarnain; Johar, Muhammad Akmal

2017-04-01

Thermal microactuator is one of earliest types of microactuators. Typical thermal actuators are in the form of Bimorph and Chevron structures. A bimorph thermal actuator has a complex movement direction, in arc motion and thus it is not feasible in the most MEMS designs. While Chevron actuator has a tendency to produce an off-plane movement which lead to low precision in lateral movement. A new thermal actuator design in the form of serpentine structures shows promising feature to have better performances in terms of more predictive lateral movement with smaller off-plane displacement. In MEMS chip design, areas play a critical role as it will impact with the cost of the final product. In this study, four different structures of thermal actuator were simulated using ANSYS v15. Three different set of area sizes which are 240 µm x 1000 µm, 240 µm x 1500 µm and 240 µm x 2000 µm have been analyzed. All four structures were named as Serpentine01, Serpentine02, Bimorph and Chevron. The data with regards to temperature produced by the structure and z-axis directional deformation were collected and analyzed. This paper reported the investigation result of comparison between these three types of thermal actuator structures design with a given area. From all of the result obtained, it is shown that the area 240 µm x 1500 µm showed a well balance performance in term of huge deformations and low power consumption. The Serpentine01 structure produced 16.7 µm deformation at 4mA of current. The results shows the potential of Serpentine01 structure as a new candidate for thermal microactuator for MEMS applications.

Active Flow Effectors for Noise and Separation Control

NASA Technical Reports Server (NTRS)

Turner, Travis L.

2011-01-01

New flow effector technology for separation control and enhanced mixing is based upon shape memory alloy hybrid composite (SMAHC) technology. The technology allows for variable shape control of aircraft structures through actively deformable surfaces. The flow effectors are made by embedding shape memory alloy actuator material in a composite structure. When thermally actuated, the flow effector def1ects into or out of the flow in a prescribed manner to enhance mixing or induce separation for a variety of applications, including aeroacoustic noise reduction, drag reduction, and f1ight control. The active flow effectors were developed for noise reduction as an alternative to fixed-configuration effectors, such as static chevrons, that cannot be optimized for airframe installation effects or variable operating conditions and cannot be retracted for off-design or fail-safe conditions. Benefits include: Increased vehicle control, overall efficiency, and reduced noise throughout all f1ight regimes, Reduced flow noise, Reduced drag, Simplicity of design and fabrication, Simplicity of control through direct current stimulation, autonomous re sponse to environmental heating, fast re sponse, and a high degree of geometric stability. The concept involves embedding prestrained SMA actuators on one side of the chevron neutral axis in order to generate a thermal moment and def1ect the structure out of plane when heated. The force developed in the host structure during def1ection and the aerodynamic load is used for returning the structure to the retracted position. The chevron design is highly scalable and versatile, and easily affords active and/or autonomous (environmental) control. The technology offers wide-ranging market applications, including aerospace, automotive, and any application that requires flow separation or noise control.

A partnership in upstream HSE technology transfer

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

Olszewski, R.E. Wahjosoedibjo, A.S.; Hunley, M.; Peargin, J.C.

1996-11-01

The oil and gas industry was for nearly two decades the dominant force in the Indonesian economy and the single largest contributor to the nation`s development. Because of the success of Indonesia`s long-term development and diversification program, this once-dominant sector today occupies a more equal but still vital position in a better-balanced economy. The Indonesian government understands the danger to the environment posed by rapid industrial expansion and has enacted laws and regulations to ensure the sustainable development of its resources while protecting its rain forest environment. In 1992, the government oil company approached Chevron and Texaco for assistance inmore » training its Health, Safety, and Environment (HSE) professionals. The upstream environment, health and safety training program was developed to transfer HSE knowledge and technology to PERTAMINA, PT Caltex Pacific Indonesia, a C&T affiliate, and indirectly, to the entire Indonesian oil and gas industry and government ministries. The four companies have demonstrated the effectiveness of a partnership approach in developing and carrying out HSE training. During 1994 and 1995, four groups, each consisting of about twenty representatives from PERTAMINA, the Directorate of Oil and Gas (MIGAS), the Indonesian Environmental Impact Management Agency (BAPEDAL), CPI, and Chevron and Texaco worldwide subsidiaries, traveled to the United States for an intensive four-month program of study in HSE best practices and technology conducted by Chevron and Texaco experts. This paper describes the development and realization of The PERTAMINA/CPI Health, Safety and Environment Training Program, outlines subjects covered and explains the methodology used to ensure the effective transfer of HSE knowledge and technology. The paper also offers an evaluation of the sessions and presents the plans developed by participant-teams for follow up on their return to Indonesia.« less

Location and age of foraminifer samples collected by Chevron Petroleum geologists in California

USGS Publications Warehouse

Brabb, Earl E.; Parker, John M.

2003-01-01

Most of the geologic maps published for parts of central California in the past century have been made without the benefit of ages from microfossils. The ages of Jurassic, Cretaceous and Tertiary rocks in the mostly poorly exposed and structurally complex sedimentary rocks represented in the Coast Ranges are critical in determining stratigraphic succession or lack of it, and in determining whether the juxtaposition of similar appearing but different age formations means that a fault is present. Since the 1940's, at least, oil company geologists have used microfossils to assist them in geologic mapping and in determining the environments of deposition of the sedimentary rocks containing them. This information had been so confidential that even the names of species were coded by some paleontologists to prevent disclosure. In the past 20 years, however, the attitude of petroleum companies about this information has changed, and many of the formerly confidential materials and reports are now available. We report here on an estimated 50,000 Chevron foraminifer samples from surface localities in more than 600 U.S. Geological Survey 7.5' quadrangles in California. Ages are provided for more than 27,000 of these samples which have been donated by Chevron, along with locality maps, paleontology reports, and other data, to the California Academy of Sciences. To our knowledge, this collection is the largest ever released to the public by a petroleum company for the West Coast. The information from the slides can be used to update geologic maps prepared without the benefit of microfossils, to study foraminifers of Jurassic, Cretaceous and Tertiary age collected from a variety of geologic environments, to analyze the depth and temperature of ocean water covering parts of California during these periods, and for solving nomenclature and other scientific problems.

Fast Eigensolver for Computing 3D Earth's Normal Modes

NASA Astrophysics Data System (ADS)

Shi, J.; De Hoop, M. V.; Li, R.; Xi, Y.; Saad, Y.

2017-12-01

We present a novel parallel computational approach to compute Earth's normal modes. We discretize Earth via an unstructured tetrahedral mesh and apply the continuous Galerkin finite element method to the elasto-gravitational system. To resolve the eigenvalue pollution issue, following the analysis separating the seismic point spectrum, we utilize explicitly a representation of the displacement for describing the oscillations of the non-seismic modes in the fluid outer core. Effectively, we separate out the essential spectrum which is naturally related to the Brunt-Väisälä frequency. We introduce two Lanczos approaches with polynomial and rational filtering for solving this generalized eigenvalue problem in prescribed intervals. The polynomial filtering technique only accesses the matrix pair through matrix-vector products and is an ideal candidate for solving three-dimensional large-scale eigenvalue problems. The matrix-free scheme allows us to deal with fluid separation and self-gravitation in an efficient way, while the standard shift-and-invert method typically needs an explicit shifted matrix and its factorization. The rational filtering method converges much faster than the standard shift-and-invert procedure when computing all the eigenvalues inside an interval. Both two Lanczos approaches solve for the internal eigenvalues extremely accurately, comparing with the standard eigensolver. In our computational experiments, we compare our results with the radial earth model benchmark, and visualize the normal modes using vector plots to illustrate the properties of the displacements in different modes.

Magic with Magic Squares.

ERIC Educational Resources Information Center

Wills, Herbert III

1989-01-01

Describes ways to make magic squares of 4 by 4 matrices. Presents two handouts: (1) Sets of 4 Numbers from 1 to 16 Whose Sum is 34; and (2) The Durer Square. Shows patterns which appeared in the magic squares, such as squares, chevrons, rhomboids, and trapezoids. (YP)

From the Research Laboratory to the Operating Company: How Information Travels.

ERIC Educational Resources Information Center

Coppin, Ann S.; Palmer, Linda L.

1980-01-01

Reviews transmission processes of Chevron Oil Field Research Company (COFRC) research results from laboratories to end-user operating companies worldwide. Information dissemination methods described included informal communication, intercompany meetings, visits by COFRC personnel to operating company offices, distribution of written reports,…

Laser beam generating apparatus

DOEpatents

Warner, Bruce E.; Duncan, David B.

1993-01-01

Laser beam generating apparatus including a septum segment disposed longitudinally within the tubular structure of the apparatus. The septum provides for radiatively dissipating heat buildup within the tubular structure and for generating relatively uniform laser beam pulses so as to minimize or eliminate radial pulse delays (the chevron effect).

Laser beam generating apparatus

DOEpatents

Warner, Bruce E.; Duncan, David B.

1994-01-01

Laser beam generating apparatus including a septum segment disposed longitudinally within the tubular structure of the apparatus. The septum provides for radiatively dissipating heat buildup within the tubular structure and for generating relatively uniform laser beam pulses so as to minimize or eliminate radial pulse delays (the chevron effect).

Sulfur-doped Graphene Nanoribbons with a Sequence of Distinct Band Gaps

NASA Astrophysics Data System (ADS)

Du, Shi-Xuan; Zhang, Yan-Fang; Zhang, Yi; Berger, Reinhard; Feng, Xinliang; Mullen, Klaus; Lin, Xiao; Zhang, Yu-Yang; Pantelides, Sokrates T.; Gao, Hong-Jun

Unlike free-standing graphene, graphene nanoribbons (GNRs) can possess semiconducting band gap. However, achieving such control has been a major challenge in the fabrication of GNRs. Chevron-type GNRs were recently achieved by surface-assisted polymerization of pristine or N-substituted oligophenylene monomers. By mixing two different monomers, GNR heterojunctions can in principle be fabricated. Here we report fabrication and characterization of chevron-type GNRs by using sulfur-substituted oligophenylene monomers to achieve GNRs and related heterostructures for the first time. Importantly, our first-principles calculations show that the band gaps of GNRs can be tailored by different S configurations in cyclodehydrogenated isomers through debromination and intramolecular cyclodehydrogenation. This feature should open up new avenues to create multiple GNR heterojunctions by engineering the sulfur configurations. These predictions have been confirmed by Scanning Tunneling Microscopy (STM) and Scanning Tunneling Spectroscopy (STS). The unusual sequence of intraribbon heterojunctions may be useful for nanoscale optoelectronic applications based on quantum dots

The von Mises stress distribution on the surface of UHMWPE with texture-shaped variation in the presence of normal load and dry sliding contact

NASA Astrophysics Data System (ADS)

Lestari, W. D.; Jamari, J.; Bayuseno, A. P.

2017-04-01

The texture shapes play a key role in the tribological performance of the surface material. This paper presents a study on the use of the 3D finite element method for surface stress analysis on the different texture shape under load and dry sliding contact. The five texture-shaped model was investigated in this work, namely square, circle, ellipse, triangle, and chevron. The result shown that the square shape has the highest value of von Mises resultant stress under static load. In contrast, the dry sliding contact on the triangle shape provided the highest von Mises stress distribution. The lowest value of von Mises stress can be found in the texture pattern of circle, square, and chevron under influence of load for 17 N, 30 N, and 50 N, respectively. Those texture patterns applied to surface of Ultra High Molecular Weight Polyethylene (UHMWPE) may have a strong effect on the reduction of wear rate and enhance tribological performance.

Magnetoresistance and noise properties of chevron stretcher detectors for field access bubble domain devices

NASA Technical Reports Server (NTRS)

George, P. K.; Oeffinger, T. R.; Chen, T. T.

1976-01-01

Experiments were devised to study the angular variation of the resistance and noise properties of one- and two-level chevron stretcher magnetoresistive detectors for use in field access bubble memory devices. All measurements, made with an electronic system, were performed on glass or garnet samples upon which 1 micron of SiO2 was sputter-deposited, followed by 4000 A of Permalloy for the 28-micron-period devices and 0.8 microns of SiO2, followed by 3000 A of Permalloy for the 20-micron-period devices. The geometrical and drive-state dependence of the zero-state noise were studied, as was its frequency dependence. It is found that both types of detectors operate primarily in the amplitude-shift mode for drive fields of interest and that the presence of a bubble in a detector causes a magnetoresistance change equal to that produced by increasing the in-plane drive field about 8 Oe in the absence of a bubble.

Density Fluctuation in Asymmetric Nozzle Plumes and Correlation with Far Field Noise

NASA Technical Reports Server (NTRS)

Panda, J.; Zaman, K. B. M. Q.

2001-01-01

A comparative experimental study of air density fluctuations in the unheated plumes of a circular, 4-tabbed-circular, chevron-circular and 10-lobed rectangular nozzles was performed at a fixed Mach number of 0.95 using a recently developed Rayleigh scattering based technique. Subsequently, the flow density fluctuations are cross-correlated with the far field sound pressure fluctuations to determine sources for acoustics emission. The nearly identical noise spectra from the baseline circular and the chevron nozzles are found to be in agreement with the similarity in spreading, turbulence fluctuations, and flow-sound correlations measured in the plumes. The lobed nozzle produced the least low frequency noise, in agreement with the weakest overall density fluctuations and flow-sound correlation. The tabbed nozzle took an intermediate position in the hierarchy of noise generation, intensity of turbulent fluctuation and flow-sound correlation. Some of the features in the 4-tabbed nozzle are found to be explainable in terms of splitting of the jet in a central large core and 4 side jetlets.

Design and Simulation of an Electrothermal Actuator Based Rotational Drive

NASA Astrophysics Data System (ADS)

Beeson, Sterling; Dallas, Tim

2008-10-01

As a participant in the Micro and Nano Device Engineering (MANDE) Research Experience for Undergraduates program at Texas Tech University, I learned how MEMS devices operate and the limits of their operation. Using specialized AutoCAD-based design software and the ANSYS simulation program, I learned the MEMS fabrication process used at Sandia National Labs, the design limitations of this process, the abilities and drawbacks of micro devices, and finally, I redesigned a MEMS device called the Chevron Torsional Ratcheting Actuator (CTRA). Motion is achieved through electrothermal actuation. The chevron (bent-beam) actuators cause a ratcheting motion on top of a hub-less gear so that as voltage is applied the CTRA spins. The voltage applied needs to be pulsed and the frequency of the pulses determine the angular frequency of the device. The main objective was to design electromechanical structures capable of transforming the electrical signals into mechanical motion without overheating. The design was optimized using finite element analysis in ANSYS allowing multi-physics simulations of our model system.

Fabrication of single crystalline stripe in Si and Ge film on rolled flexible glass substrate by UV cw micro-chevron laser beam

NASA Astrophysics Data System (ADS)

Yeh, Wenchang

2017-08-01

Micro chevron laser beam annealing (μCLBA) of Si film and Ge film were introduced. Single crystal stripe with a dimension of several tens to hundreds μm in length and 3-8μm in width was formed in Si film or Ge film by scanning μCLBA over the film. Main boundaries in the c-Si stripe were Σ3 CSL twin boundary. Scanning speed of micro linear laser beam annealing (μLLBA) was varied from 0.05 m/s to 8m/s to investigate its influence to crystallinity. Even at 8m/s lateral growth taken place, however, crystal quality was better for slower lateral growth. Crystallization area per energy (APE) of μLLBA was evaluated and compared with other methods. It was found APE of μLLBA was larger than other method, especially for a display with low fill factor of TFT, APE can be several orders of magnitude larger.

Book review: A new view on the species abundance distribution

USGS Publications Warehouse

DeAngelis, Donald L.

2018-01-01

The sampled relative abundances of species of a taxonomic group, whether birds, trees, or moths, in a natural community at a particular place vary in a way that suggests a consistent underlying pattern, referred to as the species abundance distribution (SAD). Preston [1] conjectured that the numbers of species, plotted as a histogram of logarithmic abundance classes called octaves, seemed to fit a lognormal distribution; that is, the histograms look like normal distributions, although truncated on the left-hand, or low-species-abundance, end. Although other specific curves for the SAD have been proposed in the literature, Preston’s lognormal distribution is widely cited in textbooks and has stimulated attempts at explanation. An important aspect of Preston’s lognormal distribution is the ‘veil line’, a vertical line drawn exactly at the point of the left-hand truncation in the distribution, to the left of which would be species missing from the sample. Dewdney rejects the lognormal conjecture. Instead, starting with the long-recognized fact that the number of species sampled from a community, when plotted as histograms against population abundance, resembles an inverted J, he presents a mathematical description of an alternative that he calls the ‘J distribution’, a hyperbolic density function truncated at both ends. When multiplied by species richness, R, it becomes the SAD of the sample.

A Program of Leadership Development.

ERIC Educational Resources Information Center

Charitat, Mac

1988-01-01

The Chevron/Mayoral Fellowship program in New Orleans is described. The program provides private funding to support 30 selected high school students each summer in internships in city government agencies. Evaluation after three years has been positive and demonstrate the potential of a governmental/public/private educational program. (DB)

Laser beam generating apparatus

DOEpatents

Warner, B.E.; Duncan, D.B.

1993-12-28

Laser beam generating apparatus including a septum segment disposed longitudinally within the tubular structure of the apparatus. The septum provides for radiatively dissipating heat buildup within the tubular structure and for generating relatively uniform laser beam pulses so as to minimize or eliminate radial pulse delays (the chevron effect). 11 figures.

Propulsion Airframe Aeroacoustic Integration Effects for a Hybrid Wing Body Aircraft Configuration

NASA Technical Reports Server (NTRS)

Czech, Michael J.; Thomas, Russell H.; Elkoby, Ronen

2010-01-01

An extensive experimental investigation was performed to study the propulsion airframe aeroacoustic effects of a high bypass ratio engine for a hybrid wing body aircraft configuration where the engine is installed above the wing. The objective was to provide an understanding of the jet noise shielding effectiveness as a function of engine gas condition and location as well as nozzle configuration. A 4.7% scale nozzle of a bypass ratio seven engine was run at characteristic cycle points under static and forward flight conditions. The effect of the pylon and its orientation on jet noise was also studied as a function of bypass ratio and cycle condition. The addition of a pylon yielded significant spectral changes lowering jet noise by up to 4dB at high polar angles and increasing it by 2 to 3dB at forward angles. In order to assess jet noise shielding, a planform representation of the airframe model, also at 4.7% scale was traversed relative to the jet nozzle from downstream to several diameters upstream of the wing trailing edge. Installations at two fan diameters upstream of the wing trailing edge provided only limited shielding in the forward arc at high frequencies for both the axisymmetric and a conventional round nozzle with pylon. This was consistent with phased array measurements suggesting that the high frequency sources are predominantly located near the nozzle exit and, consequently, are amenable to shielding. The mid to low frequencies sources were observed further downstream and shielding was insignificant. Chevrons were designed and used to impact the distribution of sources with the more aggressive design showing a significant upstream migration of the sources in the mid frequency range. Furthermore, the chevrons reduced the low frequency source levels and the typical high frequency increase due to the application of chevron nozzles was successfully shielded. The pylon was further modified with a technology that injects air through the shelf of the pylon which was effective in reducing low frequency noise and moving jet noise sources closer to the nozzle exit. In general, shielding effectiveness varied as a function of cycle condition with the cutback condition producing higher shielding compared to sideline power. The configuration with a more strongly immersed chevron and a pylon oriented opposite to the microphones produced the largest reduction in jet noise. In addition to the jet noise source, the shielding of a broadband point noise source was documented with up to 20 dB of noise reduction at directivity angles directly under the shielding surface.

Propulsion Airframe Aeroacoustic Integration Effects for a Hybrid Wing Body Aircraft Configuration

NASA Technical Reports Server (NTRS)

Czech, Michael J.; Thomas, Russell H; Elkoby, Ronen

2012-01-01

An extensive experimental investigation was performed to study the propulsion airframe aeroacoustic effects of a high bypass ratio engine for a hybrid wing body aircraft configuration where the engine is installed above the wing. The objective was to provide an understanding of the jet noise shielding effectiveness as a function of engine gas condition and location as well as nozzle configuration. A 4.7% scale nozzle of a bypass ratio seven engine was run at characteristic cycle points under static and forward flight conditions. The effect of the pylon and its orientation on jet noise was also studied as a function of bypass ratio and cycle condition. The addition of a pylon yielded significant spectral changes lowering jet noise by up to 4 dB at high polar angles and increasing it by 2 to 3 dB at forward angles. In order to assess jet noise shielding, a planform representation of the airframe model, also at 4.7% scale was traversed such that the jet nozzle was positioned from downstream of to several diameters upstream of the airframe model trailing edge. Installations at two fan diameters upstream of the wing trailing edge provided only limited shielding in the forward arc at high frequencies for both the axisymmetric and a conventional round nozzle with pylon. This was consistent with phased array measurements suggesting that the high frequency sources are predominantly located near the nozzle exit and, consequently, are amenable to shielding. The mid to low frequency sources were observed further downstream and shielding was insignificant. Chevrons were designed and used to impact the distribution of sources with the more aggressive design showing a significant upstream migration of the sources in the mid frequency range. Furthermore, the chevrons reduced the low frequency source levels and the typical high frequency increase due to the application of chevron nozzles was successfully shielded. The pylon was further modified with a technology that injects air through the shelf of the pylon which was effective in reducing low frequency noise and moving jet noise sources closer to the nozzle exit. In general, shielding effectiveness varied as a function of cycle condition with the cutback condition producing higher shielding compared to sideline power. The configuration with a more strongly immersed chevron and a pylon oriented opposite to the microphones produced the largest reduction in jet noise. In addition to the jet noise source, the shielding of a broadband point noise source was documented with up to 20 dB of noise reduction at directivity angles directly under the shielding surface.

Single molecule imaging of RNA polymerase II using atomic force microscopy

NASA Astrophysics Data System (ADS)

Rhodin, Thor; Fu, Jianhua; Umemura, Kazuo; Gad, Mohammed; Jarvis, Suzi; Ishikawa, Mitsuru

2003-03-01

An atomic force microscopy (AFM) study of the shape, orientation and surface topology of RNA polymerase II supported on silanized freshly cleaved mica was made. The overall aim is to define the molecular topology of RNA polymerase II in appropriate fluids to help clarify the relationship of conformational features to biofunctionality. A Nanoscope III atomic force microscope was used in the tapping mode with oxide-sharpened (8-10 nm) Si 3N 4 probes in aqueous zinc chloride buffer. The main structural features observed by AFM were compared to those derived from electron-density plots based on X-ray crystallographic studies. The conformational features included a bilobal silhouette with an inverted umbrella-shaped crater connected to a reaction site. These studies provide a starting point for constructing a 3D-AFM profiling analysis of proteins such as RNA polymerase complexes.

Laser beam generating apparatus

DOEpatents

Warner, B.E.; Duncan, D.B.

1994-02-15

Laser beam generating apparatus including a septum segment disposed longitudinally within the tubular structure of the apparatus is described. The septum provides for radiatively dissipating heat buildup within the tubular structure and for generating relatively uniform laser beam pulses so as to minimize or eliminate radial pulse delays (the chevron effect). 7 figures.

Lost Hills Field Trial - incorporating new technology for resevoir management

NASA Technical Reports Server (NTRS)

Fielding, E. J.; Brink, J. L.; Patzek, T. W.; Silin, D. B.

2002-01-01

This paper will discuss how Chevron U.S.A. Production Company is implementing a field trial that will use Supervisory Control and Data Acquisition (SCADA)on injection wells, in conjunction with satellite images to measure ground elevation changes, to perform real-time resevoir management in the Lost Hills Field.

Energy landscape of knotted protein folding

PubMed Central

Sułkowska, Joanna I.; Noel, Jeffrey K.; Onuchic, Jose N.

2012-01-01

Recent experiments have conclusively shown that proteins are able to fold from an unknotted, denatured polypeptide to the knotted, native state without the aid of chaperones. These experiments are consistent with a growing body of theoretical work showing that a funneled, minimally frustrated energy landscape is sufficient to fold small proteins with complex topologies. Here, we present a theoretical investigation of the folding of a knotted protein, 2ouf, engineered in the laboratory by a domain fusion that mimics an evolutionary pathway for knotted proteins. Unlike a previously studied knotted protein of similar length, we see reversible folding/knotting and a surprising lack of deep topological traps with a coarse-grained structure-based model. Our main interest is to investigate how evolution might further select the geometry and stiffness of the threading region of the newly fused protein. We compare the folding of the wild-type protein to several mutants. Similarly to the wild-type protein, all mutants show robust and reversible folding, and knotting coincides with the transition state ensemble. As observed experimentally, our simulations show that the knotted protein folds about ten times slower than an unknotted construct with an identical contact map. Simulated folding kinetics reflect the experimentally observed rollover in the folding limbs of chevron plots. Successful folding of the knotted protein is restricted to a narrow range of temperature as compared to the unknotted protein and fits of the kinetic folding data below folding temperature suggest slow, nondiffusive dynamics for the knotted protein. PMID:22891304

Posterior all-pedicle screw instrumentation combined with multiple chevron and concave rib osteotomies in the treatment of adolescent congenital kyphoscoliosis.

PubMed

Ayvaz, Mehmet; Olgun, Z Deniz; Demirkiran, H Gokhan; Alanay, Ahmet; Yazici, Muharrem

2014-01-01

Congenital kyphoscoliosis is a disorder that often requires surgical treatment. Although many methods of surgical treatment exist, posterior-only vertebral column resection with instrumentation and fusion seem to have become the gold standard for very severe and very rigid curves. Multiple chevron and concave rib osteotomies have been previously reported to be effective in the treatment of neglected severe idiopathic curves. We hypothesized that this method may also be used successfully in the treatment of congenital kyphoscoliosis. To evaluate the effectiveness and safety of multiple chevron osteotomies combined with concave rib osteotomy and posterior pedicle screw instrumentation. Retrospective chart review in the spine service of a large university hospital. Adolescent patients undergoing a specific surgical treatment for the indication of rigid congenital kyphoscoliotic deformity. Radiographic images were used for the measurement of deformity correction. The Turkish version of the Scoliosis Research Society 22 (SRS-22) Patient Questionnaire has been used as a clinical outcome measure in the patient population. A retrospective chart review was performed. Patients admitted to Hacettepe Hospital Spine Center during the period of 2005 to 2009 were included. Criteria for inclusion were as follows: adolescent age group (10-16 years); congenital kyphoscoliosis; formation and/or segmentation defect of at least two vertebral motion segments; surgical treatment of deformity by posterior all-pedicle screw instrumentation, multiple chevron osteotomies, and multiple concave rib osteotomies; follow-up of at least 24 months; and a complete set of preoperative, postoperative, and follow-up standing posteroanterior and lateral full spinal radiographs. The patients' hospital records and X-rays were reviewed. Duration of surgery, intraoperative blood loss, postoperative transfusion requirements, postoperative stay in postanesthesia care unit (PACU), time of hospitalization, and complications were recorded. Deformity in both coronal and sagittal planes was analyzed for correction and maintenance of the correction in preoperative, postoperative, and follow-up radiographs. Patients' health-related quality of life was assessed using the SRS-22 questionnaire at the final follow-up. Eighteen patients met the inclusion criteria. Their average age was 13.6 years (range, 11-16 years). Chevron osteotomies were performed at apical segments (three to seven levels) and concave rib osteotomies at Cobb-to-Cobb (five to eight levels). No patient had preoperative cord compression because of the sharply angulated deformity or neurologic deficit. The average preoperative scoliosis was 66.0° (range, 31°-116°), 52.4° (range, 22°-85°) on flexibility X-rays, and became 24.9° (range, 12°-52°) postoperatively. The average preoperative global kyphosis (T2-T12) of 75.9° (range, 50°-106°) became 49.5° (range, 18°-66°). The average preoperative local kyphosis of 71.9° (range, 35°-114°) became 31.4° (range, -44° to 64°). The average intraoperative bleeding was 989 cc, surgical time was 292 minutes, and intraoperative transfusion was 2.3 units. The maximum PACU stay was overnight. There were no neurologic complications except one pneumothorax and one pneumonia. The average follow-up was 34.3 months. At follow-up, average scoliosis was 27.5° (range, 10°-50°), global kyphosis was 50.3° (range, 28°-73°), and local kyphosis was 36.9°(range, -36° to 58°). Performed on the last follow-up, the average scores for the five domains of SRS-22 were 4.3, 4.4, 4.2, 4.1, and 4.8 for function, pain, self-image, mental health, satisfaction, and total, respectively. Multiple chevron and concave rib osteotomies with posterior instrumentation provide an acceptable rate of deformity correction and maintenance of correction at 2 years with acceptable intraoperative bleeding, surgical time, postoperative morbidity, and rate of complications. It can be considered as an alternative in the treatment of rigid congenital curves involving more than three levels or multiple curves separated by at least two segments that would otherwise require multiple vertebral resections. Copyright © 2014 Elsevier Inc. All rights reserved.

Addressable inverter matrix for process and device characterization

NASA Technical Reports Server (NTRS)

Buehler, M. G.; Sayah, H. R.

1985-01-01

The addressable inverter matrix consists of 222 inverters each accessible with the aid of a shift register. The structure has proven useful in characterizing the variability of inverter transfer curves and in diagnosing processing faults. For good 3-micron CMOS bulk inverters investigated, the percent standard deviation of the inverter threshold voltage was less than one percent and the inverter gain (the slope of the inverter transfer curve at the inverter threshold vltage) was less than 3 percent. The average noise margin for the inverters was near 2 volts for a power supply voltage of 5 volts. The specific faults studied included undersize pull-down transistor widths and various open contacts in the matrix.

Addressable inverter matrix for process and device characterization

NASA Technical Reports Server (NTRS)

Buehler, M. G.; Sayah, H. R.

1985-01-01

The addressable inverter matrix consists of 222 inverters each accessible with the aid of a shift register. The structure has proven useful in characterizing the variability of inverter transfer curves and in diagnosing processing faults. For good 3-micron CMOS bulk inverters investigated in this study, the percent standard deviation of the inverter threshold voltage was less than one percent and the inverter gain (the slope of the inverter transfer curve at the inverter threshold voltage) was less than 3 percent. The average noise margin for the inverters was near 2 volts for a power supply voltage of 5 volts. The specific faults studied included undersize pull-down transistor widths and various open contacts in the matrix.

Field test of polymer modified asphalt concrete : Murphy Road to Lava Butte Section, The Dalles - California Highway, Deschutes County, Oregon : construction report.

DOT National Transportation Integrated Search

1990-12-01

This report covers the construction of open-graded asphalt concrete test sections using one conventional and three different polymerized binders. The binders were: 1) Chevron's conventional AC-20 as a control, 2) Elf Aquitane's Styrelf with SB polyme...

A passive chevron replicator

NASA Technical Reports Server (NTRS)

Oeffinger, T. R.; Tocci, L. R.

1977-01-01

Instrument design provides replicate function between device storage area and guardrail detector in order that nondestructive read-out of memory can be achieved. Use of guardrail detectors in magnetic domain (bubble) circuits is proposed method of increasing detector signal output by increasing detector size without dedicating an excessive amount of device chip area to detector portion.

Morphology and molecular taxonomy of Evlachovaea-like fungi, and the status of this unusual conidial genus

USDA-ARS?s Scientific Manuscript database

The entomopathogenic anamorphic genus Evlachovaea was described to differ from other fungi in forming its conidia obliquely to the axis of the conidiogenous cell and with successive conidia having alternate orientations with a zipper- or chevron-like arrangement resulting in flat, ribbon-like chains...

75 FR 62852 - Notice of Availability of the Record of Decision for the Chevron Energy Solutions Lucerne Valley...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-13

...-way (ROW) authorization to construct and operate a 45-megawatt (MW) solar photovoltaic project which... Solar Project, California and the Approved Plan Amendment to the California Desert Conservation Area...) Lucerne Valley Solar Project located in San Bernardino County, California. The Secretary of the Interior...

Energy Industry

DTIC Science & Technology

2007-01-01

Coal Power Plant , Dickerson, MD Consol Corporation, Morgantown and Wanna, WV Chevron Corporation, San Ramon, CA Valero Refinery , Benicia, CA Pacific...important petrochemical industry Cons: Reliance on imports from volatile regions Greenhouse gas emissions Policy Recommendations: Limit number...nuclear power, and reduce hazardous emissions through the development of cleaner burning technologies and use of alternative fuels. Specifically, the

Publications - GMC 123 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 123 Publication Details Title: Total organic carbon and rock-eval pyrolysis data of select organic carbon and rock-eval pyrolysis data of select cuttings from the Chevron USA Akulik #1 well: Alaska Pyrolysis; Rock-Eval Pyrolysis Top of Page Department of Natural Resources, Division of Geological &

Defense Industry Consolidation and Weapon Systems Cost Growth

DTIC Science & Technology

2008-06-01

consolidation in the industry. Year Buyer Target Price ($Billions) 1988 Kohlberg Kravis RJR Nabisco 25.1 1984 Chevron Gulf Oil 13.3 1988 Philip Morris Kraft...Steel Marathon Oil 6.6 1988 Campeau Federated Stores 6.5 1986 Kohlberg Kravis Beatrice 6.2 Table 7. Ten Largest Acquisitions 1981 – 1989 (Aftrer54

Proximal metatarsal osteotomies: a comparative geometric analysis conducted on sawbone models.

PubMed

Nyska, Meir; Trnka, Hans-Jörg; Parks, Brent G; Myerson, Mark S

2002-10-01

We evaluated the change in position of the first metatarsal head using a three-dimensional digitizer on sawbone models. Crescentic, closing wedge, oblique shaft (Ludloff 8 degrees and 16 degrees), reverse oblique shaft (Mau 8 degrees and 16 degrees), rotational "Z" (Scarf), and proximal chevron osteotomies were performed and secured using 3-mm screws. The 16 degrees Ludloff provided the most lateral shift (9.5 mm) and angular correction (14.5 degrees) but also produced the most elevation (1.4 mm) and shortening (2.9 mm). The 8 degrees Ludloff provided lateral and angular corrections similar to those of the crescentic and closing wedge osteotomies with less elevation and shortening. Because the displacement osteotomies (Scarf, proximal chevron) provided less angular correction, the same lateral displacement, and less shortening than the basilar angular osteotomies, based upon this model they can be more reliably used for a patient with a mild to moderate deformity, a short first metatarsal, or an intermediate deformity with a large distal metatarsal articular angle. These results can serve as recommendations for selecting the optimal osteotomy with which to correct a deformation.

On the feasibility of the Chevron Notch Beam method to measure fracture toughness of fine-grained zirconia ceramics.

PubMed

Kailer, Andreas; Stephan, Marc

2016-10-01

The fracture toughness determination of fine-grained zirconia ceramics using the chevron notched beam method (CNB) was investigated to assess the feasibility of this method for quality assurance and material characterization. CNB tests were performed using four different yttria-stabilized zirconia ceramics under various testing modes and conditions, including displacement-controlled and load-rate-controlled four point bending to assess the influence of slow crack growth and identify most suitable test parameters. For comparison, tests using single-edge V-notch beams (SEVNB) were conducted. It was observed that the CNB method yields well-reproducible results. However, slow crack growth effects significantly affect the measured KIC values, especially when slow loading rates are used. To minimize the effect of slow crack growth, the application of high loading rates is recommended. Despite a certain effort needed for setting up a sample preparation routine, the CNB method is considered to be very useful for measuring and controlling the fracture toughness of zirconia ceramics. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Folding and faulting of an elastic continuum

NASA Astrophysics Data System (ADS)

Bigoni, Davide; Gourgiotis, Panos A.

2016-03-01

Folding is a process in which bending is localized at sharp edges separated by almost undeformed elements. This process is rarely encountered in Nature, although some exceptions can be found in unusual layered rock formations (called `chevrons') and seashell patterns (for instance Lopha cristagalli). In mechanics, the bending of a three-dimensional elastic solid is common (for example, in bulk wave propagation), but folding is usually not achieved. In this article, the route leading to folding is shown for an elastic solid obeying the couple-stress theory with an extreme anisotropy. This result is obtained with a perturbation technique, which involves the derivation of new two-dimensional Green's functions for applied concentrated force and moment. While the former perturbation reveals folding, the latter shows that a material in an extreme anisotropic state is also prone to a faulting instability, in which a displacement step of finite size emerges. Another failure mechanism, namely the formation of dilation/compaction bands, is also highlighted. Finally, a geophysical application to the mechanics of chevron formation shows how the proposed approach may explain the formation of natural structures.

Characterization of a highly efficient chevron-shaped anti-contamination device

NASA Astrophysics Data System (ADS)

Fiore, M.; Vermeersch, O.; Forte, M.; Casalis, G.; François, C.

2016-04-01

This paper is devoted to the characterization of an optimized chevron-shaped anti-contamination device (ACD). This device can prevent efficiently the propagation of turbulence from the fuselage along the attachment line (hypothetical streamline that spreads the flow going to suction side and the one going to pressure side) of swept wings and enables the development of a new laminar boundary layer downstream. More specifically, the aim is to prevent boundary-layer transition along the attachment line by a contamination process. This process is characterized by the typical Reynolds number overline{R} and the associated Poll's criterion. Thus, ACD efficiency will be expressed in terms of overline{R} values. Some experiments performed on a new numerically optimized ACD have shown its ability to prevent leading-edge contamination up to overline{R} values close to the natural transition process of the laminar boundary layer along the attachment line. The corresponding stability analysis of the laminar boundary layer is made using the Görtler-Hämmerlin stability approach. The study is completed with the different transition processes that can occur downstream the attachment line, around the airfoil, especially with crossflow analysis.

Phased Array Noise Source Localization Measurements of an F404 Nozzle Plume at Both Full and Model Scale

NASA Technical Reports Server (NTRS)

Podboy, Gary G.; Bridges, James E.; Henderson, Brenda S.

2010-01-01

A 48-microphone planar phased array system was used to acquire jet noise source localization data on both a full-scale F404-GE-F400 engine and on a 1/4th scale model of a F400 series nozzle. The full-scale engine test data show the location of the dominant noise sources in the jet plume as a function of frequency for the engine in both baseline (no chevron) and chevron configurations. Data are presented for the engine operating both with and without afterburners. Based on lessons learned during this test, a set of recommendations are provided regarding how the phased array measurement system could be modified in order to obtain more useful acoustic source localization data on high-performance military engines in the future. The data obtained on the 1/4th scale F400 series nozzle provide useful insights regarding the full-scale engine jet noise source mechanisms, and document some of the differences associated with testing at model-scale versus fullscale.

Drug and alcohol abuse: The pattern and magnitude of the problem

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

Ajayi, P.A.

In the last 12 months, many more cases of alcohol and drug (substance) abuse in the workplace were seen in the Escravos operations of Chevron Nigeria Limited than in previous years. This called the attention to the rising prevalence of drug and alcohol abuse in contradistinction to reports from similar organizations in other parts of the world. Chevron Nigeria has a written Drug and Alcohol Policy which has been dormant for some time because of the apparent rarity of the problem of substance abuse in the workplace. This Policy is being reviewed to broaden its scope and make it moremore » effective. A total of 30 employees were tested for drugs and alcohol .6 exceeded the legal limits of Blood Alcohol Concentration (BAC) and 5 tested positive for drugs. Tests were mainly post-accident, reasonable cause and random. The common substances abused were alcohol, cannabis, cocaine and morphine in that order. The findings are compared with those of similar organizations in UK and USA. Efforts to control substance abuse in the workplace are being put into place.« less

Development of a Jet Noise Prediction Method for Installed Jet Configurations

NASA Technical Reports Server (NTRS)

Hunter, Craig A.; Thomas, Russell H.

2003-01-01

This paper describes development of the Jet3D noise prediction method and its application to heated jets with complex three-dimensional flow fields and installation effects. Noise predictions were made for four separate flow bypass ratio five nozzle configurations tested in the NASA Langley Jet Noise Laboratory. These configurations consist of a round core and fan nozzle with and without pylon, and an eight chevron core nozzle and round fan nozzle with and without pylon. Predicted SPL data were in good agreement with experimental noise measurements up to 121 inlet angle, beyond which Jet3D under predicted low frequency levels. This is due to inherent limitations in the formulation of Lighthill's Acoustic Analogy used in Jet3D, and will be corrected in ongoing development. Jet3D did an excellent job predicting full scale EPNL for nonchevron configurations, and captured the effect of the pylon, correctly predicting a reduction in EPNL. EPNL predictions for chevron configurations were not in good agreement with measured data, likely due to the lower mixing and longer potential cores in the CFD simulations of these cases.

Testing of molded high temperature plastic actuator road seals for use in advanced aircraft hydraulic systems

NASA Technical Reports Server (NTRS)

Waterman, A. W.; Huxford, R. L.; Nelson, W. G.

1976-01-01

Molded high temperature plastic first and second stage rod seal elements were evaluated in seal assemblies to determine performance characteristics. These characteristics were compared with the performance of machined seal elements. The 6.35 cm second stage Chevron seal assembly was tested using molded Chevrons fabricated from five molding materials. Impulse screening tests conducted over a range of 311 K to 478 K revealed thermal setting deficiencies in the aromatic polyimide molding materials. Seal elements fabricated from aromatic copolyester materials structurally failed during impulse cycle calibration. Endurance testing of 3.85 million cycles at 450 K using MIL-H-83283 fluid showed poorer seal performance with the unfilled aromatic polyimide material than had been attained with seals machined from Vespel SP-21 material. The 6.35 cm first stage step-cut compression loaded seal ring fabricated from copolyester injection molding material failed structurally during impulse cycle calibration. Molding of complex shape rod seals was shown to be a potentially controllable technique, but additional molding material property testing is recommended.

Comparison of microtweezers based on three lateral thermal actuator configurations

NASA Astrophysics Data System (ADS)

Luo, J. K.; Flewitt, A. J.; Spearing, S. M.; Fleck, N. A.; Milne, W. I.

2005-06-01

Thermal actuator-based microtweezers with three different driving configurations have been designed, fabricated and characterized. Finite element analysis has been used to model the device performance. It was found that one configuration of microtweezer, based on two lateral bimorph thermal actuators, has a small displacement (tip opening of the tweezers) and a very limited operating power range. An alternative configuration consisting of two horizontal hot bars with separated beams as the arms can deliver a larger displacement with a much-extended operating power range. This structure can withstand a higher temperature due to the wider beams used, and has flexible arms for increased displacement. Microtweezers driven by a number of chevron structures in parallel have similar maximum displacements but at a cost of higher power consumption. The measured temperature of the devices confirms that the device with the chevron structure can deliver the largest displacement for a given working temperature, while the bimorph thermal actuator design has the highest operating temperature at the same power due to its thin hot arm, and is prone to structural failure.

Effects of annealing on arrays of Ge nanocolumns formed by glancing angle deposition

NASA Astrophysics Data System (ADS)

Khare, C.; Gerlach, J. W.; Höche, T.; Fuhrmann, B.; Leipner, H. S.; Rauschenbach, B.

2012-10-01

Post-deposition thermal annealing of glancing angle deposited Ge nanocolumn arrays was carried out in a continuous Ar-flow at temperatures ranging from TA = 300 to 800 °C for different annealing durations. Morphological alterations and the recrystallization process induced by the thermal annealing treatment were investigated for the Ge nanocolumns deposited on planar and pre-patterned Si substrates. From X-ray diffraction (XRD) measurements, the films annealed at TA ≥ 500 °C were found to be polycrystalline. On planar Si substrates, at TA = 600 °C nanocolumns exhibited strong coarsening and merging, while a complete disintegration of the nanocolumns was detected at TA = 700 °C. The morphology of nanostructures deposited on pre-patterned substrates differs substantially, where the merging or column-disintegration effect was absent at elevated annealing temperatures. The two-arm-chevron nanostructures grown on pre-patterned substrates retained their complex shape and morphology, after extended annealing intervals. Investigations by transmission electron microscopy revealed nanocrystalline domains of the order of 5-30 nm (in diameter) present within the chevron structures after the annealing treatment.

Chevrons, filaments, spinning clusters and phase coexistence: emergent dynamics of 2- and 3-d particle suspensions driven by multiaxial magnetic fields

DOE PAGES

Solis, Kyle J.; Martin, James E.

2017-07-06

In recent years a rich variety of emergent phenomena have been observed when suspensions of magnetic particles are subjected to alternating magnetic fields. These particle assemblies often exhibit vigorous dynamics due to the injection of energy from the field. These include surface and interface phenomena, such as highly organized, segmented “snakes” that can be induced to swim by structural symmetry breaking, and “asters” and “anti-asters,” particle assemblies that can be manipulated to capture and transport cargo. In bulk suspensions of magnetic platelets subjected to multiaxial alternating fields, advection lattices and even vortex lattices have been created, and a variety ofmore » biomimetic dynamics – serpents, bees and amoebas – have been discovered in magnetic fluids suspended in an immiscible liquid. In this paper several new driven phases are presented, including flying chevrons, dense spinning clusters, filaments, and examples of phase coexistence in driven phases. These observations broaden the growing field of driven magnetic suspensions and present new challenges to those interested in simulating the dynamics of these complex systems.« less

Origin and tectonic significance of a Mesozoic multi-layer over-thrust system within the Yangtze Block (South China)

NASA Astrophysics Data System (ADS)

Yan, Dan-Ping; Zhou, Mei-Fu; Song, Hong-Lin; Wang, Xin-Wen; Malpas, John

2003-01-01

In the Yangtze Block (South China), a well-developed Mesozoic thrust system extends through the Xuefeng and Wuling mountains in the southeast to the Sichuan basin in the northwest. The system comprises both thin- and thick-skinned thrust units separated by a boundary detachment fault, the Dayin fault. To the northwest, the thin-skinned belt is characterized by either chevron anticlines and box synclines to the northwest or chevron synclines to the southeast. The former structural style displays narrow exposures for the cores of anticlines and wider exposures for the cores of synclines. Thrust detachments occur along Silurian (Fs) and Lower Cambrian (Fc) strata and are dominantly associated with the anticlines. To the southeast, this style of deformation passes gradually into one characterized by chevron synclines with associated principal detachment faults along Silurian (Fs), Cambrian (Fc) and Lower Sinian (Fz) strata. There are, however, numerous secondary back thrusts. Therefore, the thin-skinned belt is like the Valley and Ridge Province of the North American Applachian Mountains. The thick-skinned belt structurally overlies the thin-skinned belt and is characterized by a number of klippen including the Xuefeng and Wuling nappes. It is thus comparable to the Blue Ridge Province of Appalachia. The structural pattern of this thrust system in South China can be explained by a model involving detachment faulting along various stratigraphic layers at different stages of its evolution. The system was developed through a northwest stepwise progression of deformation with the earliest delamination along Lower Sinian strata (Fz). Analyses of balanced geological cross-sections yield about 18.1-21% (total 88 km) shortening for the thin-skinned unit and at least this amount of shortening for the thick-skinned unit. The compressional deformation from southeast to northwest during Late Jurassic to Cretaceous time occurred after the westward progressive collision of the Yangtze Block with the North China Block and suggests that the orogenic event was intracontinental in nature.

Preliminary Results and Learning Curve of the Minimally Invasive Chevron Akin Operation for Hallux Valgus.

PubMed

Jowett, Charlie R J; Bedi, Harvinder S

Minimally invasive surgery is increasing in popularity. It is relevant in hallux valgus surgery owing to the potential for reduced disruption of the soft tissues and improved wound healing. We present our results and assess the learning curve of the minimally invasive Chevron Akin operation for hallux valgus. A total of 120 consecutive feet underwent minimally invasive Chevron Akin for symptomatic hallux valgus, of which 14 were excluded. They were followed up for a mean of 25 (range 18 to 38) months. The patients were clinically assessed using the American Orthopaedic Foot and Ankle Society score. Complications and patient satisfaction were recorded. The radiographs were analyzed and measurements recorded for hallux valgus and intermetatarsal angle correction. The mean age of the patients undergoing surgery was 55 (range 25 to 81) years. Of the 78 patients, 76 (97.4%) were female and 2 (2.6%) were male; 28 (35.9%) cases were bilateral. The mean American Orthopaedic Foot and Ankle Society score improved from 56 (range 23 to 76) preoperatively to 87 (range 50 to 100) postoperatively (p < .001). The mean hallux valgus and intermetatarsal angles preoperatively were 29.7° (range 12° to 46°) and 14.0° (range 8° to 20°). The corresponding postoperative angles were 10.3° (range 0° to 25°) and 7.6° (range 3° to 15°; p < .001). The patients were satisfied with the results of surgery in 87% of cases (92 of 106). The incidence of reoperation was 14% (15 of 106). These are the only reported results for this technique. They display a steep associated learning curve. However, the results are promising, and the learning curve is comparable to that for open hallux valgus surgery. Copyright © 2017 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Is Double Metatarsal Osteotomy Superior to Proximal Chevron Osteotomy in Treatment of Hallux Valgus With Increased Distal Metatarsal Articular Angle?

PubMed

Park, Chul Hyun; Lee, Woo-Chun

We compared the results of proximal chevron osteotomy and double metatarsal osteotomy for hallux valgus with an increased distal metatarsal articular angle (DMAA). From October 2008 to December 2012, first metatarsal osteotomies were performed in 64 patients (69 feet) with symptomatic hallux valgus associated with an increased DMAA. Proximal chevron with Akin osteotomy and lateral soft tissue release was performed in 46 feet (PCO group); double metatarsal osteotomy and Akin osteotomy without lateral soft tissue release was performed in 23 feet (DMO group). Clinical assessments were performed using the American Orthopaedic Foot and Ankle Society (AOFAS) scale and visual analog scale (VAS). The hallux valgus angles, intermetatarsal angles, sesamoid positions, metatarsus adductus angles, and DMAAs were compared at different postoperative times. Postoperative shortening of first the metatarsal and complications were compared. The mean AOFAS scale and VAS scores showed significant improvement in both groups after surgery; however, no significant difference was observed between the 2 groups. The immediate postoperative hallux valgus angle and sesamoid position were significantly larger in DMO group; however, no intergroup difference was observed at the last follow-up visit, with the hallux valgus angle gradually increasing in the PCO group. The postoperative DMAA was significantly smaller in the DMO group. The mean shortening of the first metatarsal after surgery was significantly larger in the DMO group than in the PCO group. Transfer metatarsalgia developed in 1 foot (2.2%) in the PCO group and 2 feet (8.7%) in the DMO group. Partial avascular necrosis of the metatarsal head with advanced arthritis of the first metatarsophalangeal joint developed in 1 foot (4.3%) in the DMO group. In conclusion, no differences in the clinical and radiographic results were observed between the 2 groups for hallux valgus deformity with an increased DMAA. Copyright © 2017 The American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

[Modified chevron osteotomy with lateral release and screw fixation for treatment of severe hallux deformity].

PubMed

Hofstaetter, S G; Schuh, R; Trieb, K; Trnka, H J

2012-12-01

This prospective study examined the clinical and radiological results of the Chevron osteotomy with screw fixation and distal soft tissue release up to an intermetatarsal angle of 19°. Furthermore, the results are presented for patients over the age of 70 years, and whether or not there is a higher complication rate. 86 feet of patients between 23 and 81 years were included in the study. Apart from the overall group, a group with an intermetatarsal angle of 16° to 19° and a group of patients over 70 years old were eavaluated. They were evaluated preoperatively and at follow-up after an average of 3.3 years according to the American Orthopaedic Foot and Ankle Society score. The AOFAS score showed a significant improvement from 55 points preoperatively to 90 points at follow-up. The preoperative hallux valgus angle decreased significantly from 32° to 5° and the preoperative intermetatarsal angle decreased from 14° to 6°. Patient satisfaction in the overall group was rated in 92 % as excellent or good. Also, the patient group with 16° to 19° angles and the patients over 70 years showed a significant improvement of clinical and radiological parameters. The complication rate was very low in all groups. The results show that the Chevron osteotomy is a very good surgical technique with few complications for the correction of splay foot with hallux valgus deformity. We showed that by using the modified technique with a long plantar arm, an excessive soft tissue release and screw fixation, the indication can be extended up to an intermetatarsal angle of 19° when using screw fixation. Furthermore the patients over 70 years of age showed a significant improvement of clinical and radiological parameters without serious complications such as avascular necrosis or dislocation of the metatarsal head. Georg Thieme Verlag KG Stuttgart · New York.

Fischer-Tropsch fuel for use by the U.S. military as battlefield-use fuel of the future

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

Delanie Lamprecht

2007-06-15

The United States Department of Defense (DoD) has been interested in low-sulfur, environmentally cleaner Fischer-Tropsch (FT) fuels since 2001 because they want to be less dependent upon foreign crude oil and ensure the security of the supply. A three-phase Joint Battlefield-Use Fuel of the Future (BUFF) program was initiated to evaluate, demonstrate, certify, and implement turbine fuels produced from alternative energy resources for use in all of its gas turbine and diesel engine applications. Sasol Synfuels International (Pty) Ltd. and Sasol Chevron Holdings Ltd., among others, were invited to participate in the program with the objective to supply the DoDmore » with a FT BUFF that conforms to Jet Propulsion 8 (JP-8) and JP-5 fuel volatility and low-temperature fluidity requirements. Although the DoD is more interested in coal-to-liquid (CTL) technology, the product from a gas-to-liquid (GTL) Products Work-Up Demonstration Unit in Sasolburg, South Africa, was used to evaluate (on a bench scale) the possibility of producing a BUFF fraction from the Sasol Slurry Phase Distillate (Sasol SPD) low-temperature FT (LTFT) process and Chevron Isocracking technology. It was concluded from the study that the production of a synthetic FT BUFF is feasible using the Sasol SPD LTFT technology together with the current Chevron isocracking technology. The product yield for a BUFF conforming to JP-8 requirements is 30 vol % of the fractionator feed, whereas the product yield for a BUFF conforming to the JP-5 volatility requirement is slightly less than 22 vol % of the fractionator feed. Also concluded from the study was that the end point of the Sasol SPD LTFT BUFF will be restricted by the freezing point requirement of the DoD and not the maximum viscosity requirement. One would therefore need to optimize the hydrocracking process conditions to increase the Sasol SPD LTFT BUFF product yield. 16 refs., 8 figs., 6 tabs.« less

Impressions from Cassini

NASA Technical Reports Server (NTRS)

2005-01-01

Saturn's turbulent atmosphere is reminiscent of a Van Gogh painting in this view from Cassini. However, unlike the famous impressionist painter, Cassini records the world precisely as it appears to the spacecraft's cameras.

The feathery band that cuts across from the upper left corner to the right side of this scene has a chevron, or arrow, shape near the right. The center of the chevron is located at the latitude (about 28 degrees South) of an eastward-flowing zonal jet in the atmosphere. Counter-flowing eastward and westward jets are the dominant dynamic features seen in the giant planet atmospheres. A chevron-shaped feature with the tip pointed east means that this is a local maximum in the eastward wind and a region of horizontal wind shear, where clouds to the north and south of the jet are being swept back by the slower currents on the sides of the jet.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 6, 2005, at a distance of approximately 2.5 million kilometers (1.5 million miles) from Saturn using a filter sensitive to wavelengths of infrared light centered at 727 nanometers. The image scale is 14 kilometers (9 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Overload protection system for power inverter

NASA Technical Reports Server (NTRS)

Nagano, S. (Inventor)

1977-01-01

An overload protection system for a power inverter utilized a first circuit for monitoring current to the load from the power inverter to detect an overload and a control circuit to shut off the power inverter, when an overload condition was detected. At the same time, a monitoring current inverter was turned on to deliver current to the load at a very low power level. A second circuit monitored current to the load, from the monitoring current inverter, to hold the power inverter off through the control circuit, until the overload condition was cleared so that the control circuit may be deactivated in order for the power inverter to be restored after the monitoring current inverter is turned off completely.

The fault-tree compiler

NASA Technical Reports Server (NTRS)

Martensen, Anna L.; Butler, Ricky W.

1987-01-01

The Fault Tree Compiler Program is a new reliability tool used to predict the top event probability for a fault tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N gates. The high level input language is easy to understand and use when describing the system tree. In addition, the use of the hierarchical fault tree capability can simplify the tree description and decrease program execution time. The current solution technique provides an answer precise (within the limits of double precision floating point arithmetic) to the five digits in the answer. The user may vary one failure rate or failure probability over a range of values and plot the results for sensitivity analyses. The solution technique is implemented in FORTRAN; the remaining program code is implemented in Pascal. The program is written to run on a Digital Corporation VAX with the VMS operation system.

The Fault Tree Compiler (FTC): Program and mathematics

NASA Technical Reports Server (NTRS)

Butler, Ricky W.; Martensen, Anna L.

1989-01-01

The Fault Tree Compiler Program is a new reliability tool used to predict the top-event probability for a fault tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, AND m OF n gates. The high-level input language is easy to understand and use when describing the system tree. In addition, the use of the hierarchical fault tree capability can simplify the tree description and decrease program execution time. The current solution technique provides an answer precisely (within the limits of double precision floating point arithmetic) within a user specified number of digits accuracy. The user may vary one failure rate or failure probability over a range of values and plot the results for sensitivity analyses. The solution technique is implemented in FORTRAN; the remaining program code is implemented in Pascal. The program is written to run on a Digital Equipment Corporation (DEC) VAX computer with the VMS operation system.

[Application of three-dimensional printing technology to design individual angle section on Chevron of hallux valgus osteotomy].

PubMed

Zhang, Yu-Hang; Bi, Da-Wei; Chen, Yi-Min; Zu, Gang; Ma, Hai-Tao

2018-03-25

To explore clinical application of three-dimensional printing technology to design individual angle section on Chevron of hallux valgus osteotomy. From May 2013 to May 2016, 47 patients(66 feet) with mild to moderate hallux valgus treated by Chevron osteotomy according to different preoperative design were divided into computer osteotomy group(group A) and traditional osteotomy group(group B). In group A, there were 25 patients (33 feet), including 4 males(5 feet) and 21 females(28 feet) with an average age of (47.88±6.08) years old, average weight IMA was (13.58±1.15) degree, AOFAS score was 59.00±5.86, and treated individual 3D printing technology to design operation scheme. While in group B, there were 22 patients (33 feet), including 3 males (3 feet) and 19 females (28 feet) with an average age of (48.16±6.16) years old, average weight IMA was(13.51±1.14) degree, AOFAS score was 60.67±5.85, and treated with osteotomy according to surgical experience. Operation time, blood loss, hospital stays, VAS score at 1 week after operation, wound healing and improvement of postoperative weight-bearing intermetatarsal angle(IMA) were compared between two groups, AOFAS score system was used to evaluate ankle function after surgery. There was no significant difference in following-up between group A 12.41±2.32 and group B 11.73±2.76. There was 1 patient in group B were excluded. Others perform good wounds healing on the first stage after operation. There were no significant differences in operation time, blood loss, hospital stays and VAS score at 1 week after operation( P <0.05); IMA in group A was (5.21±0.88)°, (6.42±0.85)° in group B, and had significant differences between two groups ( t =5.68, P <0.05). There was obvious meaning in AOFAS score between group A 88.15±5.19 and group B 82.90±5.01( t =4.14, P <0.05). Fourteen feet in group A obtained excellent results and 19 feet good, while 5 feet in group B obtained excellent results and 27 feet good. Compared with traditional osteotomy group, three-dimensional printing technology to design individual angle section on Chevron of hallux valgus osteotomy could better correct IMA, improve postoperative foot function, and it is a kind of individualized and digital method to design operation. Copyright© 2018 by the China Journal of Orthopaedics and Traumatology Press.

Gas tube-switched high voltage DC power converter

DOEpatents

She, Xu; Bray, James William; Sommerer, Timothy John; Chokhawala, Rahul

2018-05-15

A direct current (DC)-DC converter includes a transformer and a gas tube-switched inverter circuit. The transformer includes a primary winding and a secondary winding. The gas tube-switched inverter circuit includes first and second inverter load terminals and first and second inverter input terminals. The first and second inverter load terminals are coupled to the primary winding. The first and second inverter input terminals are couplable to a DC node. The gas tube-switched inverter circuit further includes a plurality of gas tube switches respectively coupled between the first and second inverter load terminals and the first and second inverter input terminals. The plurality of gas tube switches is configured to operate to generate an alternating current (AC) voltage at the primary winding.

Confirmatory Survey Report for Area B1S/B2S at the Chevron Mining Washington Remediation Project, Washington, PA

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

W. C. Adams

2007-11-20

During the period of October 2 and 3, 2007, the Oak Ridge Institute for Science and Education (ORISE) performed confirmatory radiological survey activities which included gamma surface scans within Area B1S/B2S and the collection of soil samples from these areas.

Flow Solution for Advanced Separate Flow Nozzles Response A: Structured Grid Navier-Stokes Approach

NASA Technical Reports Server (NTRS)

Kenzakowski, D. C.; Shipman, J.; Dash, S. M.; Saiyed, Naseem (Technical Monitor)

2001-01-01

NASA Glenn Research Center funded a computational study to investigate the effect of chevrons and tabs on the exhaust plume from separate flow nozzles. Numerical studies were conducted at typical takeoff power with 0.28 M flight speed. Report provides numerical data and insights into the mechanisms responsible for increased mixing.

75 FR 62510 - Chevron U.S.A. Inc.; Application for Blanket Authorization To Export Liquefied Natural Gas

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-12

... Authorization To Export Liquefied Natural Gas AGENCY: Office of Fossil Energy, DOE. ACTION: Notice of application. SUMMARY: The Office of Fossil Energy (FE) of the Department of Energy (DOE) gives notice of... Security and Supply, Office of Fossil Energy, Forrestal Building, Room 3E-042, 1000 Independence Avenue, SW...

77 FR 66597 - Chevron U.S.A. Inc.; Application for Blanket Authorization To Export Previously Imported...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-06

... Authorization To Export Previously Imported Liquefied Natural Gas on a Short-Term Basis AGENCY: Office of Fossil Energy, DOE. ACTION: Notice of application. SUMMARY: The Office of Fossil Energy (FE) of the Department.... Department of Energy (FE-34), Office of Oil and Gas Global Security and Supply, Office of Fossil Energy...

CWC Industry Outreach III: Chemical Weapons Convention Ratification, Implementation, Compliance and Verification (CWC Video). Volume 2. Annexes.

DTIC Science & Technology

1995-08-01

7515 (818) 791-8805 (FAX) (415) 742-7540 (FAX) CHEVRON CORPORATION HUISH DETERGENTS, INC. CHARLOTTE R. FARBER DON GOLLADAY 225 BUSH STREET P.O. BOX 25057...USA) TEXAS INSTRUMENTS KENT BOSSART ZAK KARAMALLY 1701 PENNSYLVANIA AVE., NW #500 TEXAS INSTRUMENTS WASHINGTON, DC 20006 ZAK KARAMALLY 202-861-0668 P

Reduced-Order Structure-Preserving Model for Parallel-Connected Three-Phase Grid-Tied Inverters

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

Johnson, Brian B; Purba, Victor; Jafarpour, Saber

Next-generation power networks will contain large numbers of grid-connected inverters satisfying a significant fraction of system load. Since each inverter model has a relatively large number of dynamic states, it is impractical to analyze complex system models where the full dynamics of each inverter are retained. To address this challenge, we derive a reduced-order structure-preserving model for parallel-connected grid-tied three-phase inverters. Here, each inverter in the system is assumed to have a full-bridge topology, LCL filter at the point of common coupling, and the control architecture for each inverter includes a current controller, a power controller, and a phase-locked loopmore » for grid synchronization. We outline a structure-preserving reduced-order inverter model with lumped parameters for the setting where the parallel inverters are each designed such that the filter components and controller gains scale linearly with the power rating. By structure preserving, we mean that the reduced-order three-phase inverter model is also composed of an LCL filter, a power controller, current controller, and PLL. We show that the system of parallel inverters can be modeled exactly as one aggregated inverter unit and this equivalent model has the same number of dynamical states as any individual inverter in the system. Numerical simulations validate the reduced-order model.« less

Operating temperatures of open-rack installed photovoltaic inverters

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

Zhang, Z.; Wang, L.; Kurtz, S.

This paper presents a model for evaluating the heat-sink and component temperatures of open-rack installed photovoltaic inverters. These temperatures can be used for predicting inverter reliability. Inverter heat-sink temperatures were measured for inverters connected to three grid-connected PV (photovoltaic) test systems in Golden, Colorado, US. A model is proposed for calculating the inverter heat-sink temperature based on the ambient temperature, the ratio of the consumed power to the rated power of the inverter, and the measured wind speed. To verify and study this model, more than one year of inverter DC/AC power, irradiance, wind speed, and heat sink temperature risemore » data were collected and analyzed. The model is shown to be accurate in predicting average inverter temperatures, but will require further refinement for prediction of transient temperatures.« less

Comparative analysis of the folding dynamics and kinetics of an engineered knotted protein and its variants derived from HP0242 of Helicobacter pylori

NASA Astrophysics Data System (ADS)

Wang, Liang-Wei; Liu, Yu-Nan; Lyu, Ping-Chiang; Jackson, Sophie E.; Hsu, Shang-Te Danny

2015-09-01

Understanding the mechanism by which a polypeptide chain thread itself spontaneously to attain a knotted conformation has been a major challenge in the field of protein folding. HP0242 is a homodimeric protein from Helicobacter pylori with intertwined helices to form a unique pseudo-knotted folding topology. A tandem HP0242 repeat has been constructed to become the first engineered trefoil-knotted protein. Its small size renders it a model system for computational analyses to examine its folding and knotting pathways. Here we report a multi-parametric study on the folding stability and kinetics of a library of HP0242 variants, including the trefoil-knotted tandem HP0242 repeat, using far-UV circular dichroism and fluorescence spectroscopy. Equilibrium chemical denaturation of HP0242 variants shows the presence of highly populated dimeric and structurally heterogeneous folding intermediates. Such equilibrium folding intermediates retain significant amount of helical structures except those at the N- and C-terminal regions in the native structure. Stopped-flow fluorescence measurements of HP0242 variants show that spontaneous refolding into knotted structures can be achieved within seconds, which is several orders of magnitude faster than previously observed for other knotted proteins. Nevertheless, the complex chevron plots indicate that HP0242 variants are prone to misfold into kinetic traps, leading to severely rolled-over refolding arms. The experimental observations are in general agreement with the previously reported molecular dynamics simulations. Based on our results, kinetic folding pathways are proposed to qualitatively describe the complex folding processes of HP0242 variants.

NREL Evaluates Advanced Solar Inverter Performance for Hawaiian Electric

Science.gov Websites

Companies | Energy Systems Integration Facility | NREL NREL Evaluates Advanced Solar Inverter Performance for Hawaiian Electric Companies NREL Evaluates Advanced Solar Inverter Performance for Hawaiian performance and impacts of today's advanced solar inverters, as well as proprietary feedback to the inverter

Inverter design for high frequency power distribution

NASA Technical Reports Server (NTRS)

King, R. J.

1985-01-01

A class of simple resonantly commutated inverters are investigated for use in a high power (100 KW - 1000 KW) high frequency (10 KHz - 20 KHz) AC power distribution system. The Mapham inverter is found to provide a unique combination of large thyristor turn-off angle and good utilization factor, much better than an alternate 'current-fed' inverter. The effects of loading the Mapham inverter entirely with rectifier loads are investigated by simulation and with an experimental 3 KW 20 KHz inverter. This inverter is found to be well suited to a power system with heavy rectifier loading.

Status and Needs of Power Electronics for Photovoltaic Inverters

NASA Astrophysics Data System (ADS)

Qin, Y. C.; Mohan, N.; West, R.; Bonn, R.

2002-06-01

Photovoltaics is the utility connected distributed energy resource (DER) that is in widespread use today. It has one element, the inverter, which is common with all DER sources except rotating generators. The inverter is required to transfer dc energy to ac energy. With all the DER technologies, (solar, wind, fuel cells, and microturbines) the inverter is still an immature product that will result in reliability problems in fielded systems. Today, the PV inverter is a costly and complex component of PV systems that produce ac power. Inverter MTFF (mean time to first failure) is currently unacceptable. Low inverter reliability contributes to unreliable fielded systems and a loss of confidence in renewable technology. The low volume of PV inverters produced restricts the manufacturing to small suppliers without sophisticated research and reliability programs or manufacturing methods. Thus, the present approach to PV inverter supply has low probability of meeting DOE reliability goals.

Reduced-Order Structure-Preserving Model for Parallel-Connected Three-Phase Grid-Tied Inverters: Preprint

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

Johnson, Brian B; Purba, Victor; Jafarpour, Saber

Given that next-generation infrastructures will contain large numbers of grid-connected inverters and these interfaces will be satisfying a growing fraction of system load, it is imperative to analyze the impacts of power electronics on such systems. However, since each inverter model has a relatively large number of dynamic states, it would be impractical to execute complex system models where the full dynamics of each inverter are retained. To address this challenge, we derive a reduced-order structure-preserving model for parallel-connected grid-tied three-phase inverters. Here, each inverter in the system is assumed to have a full-bridge topology, LCL filter at the pointmore » of common coupling, and the control architecture for each inverter includes a current controller, a power controller, and a phase-locked loop for grid synchronization. We outline a structure-preserving reduced-order inverter model for the setting where the parallel inverters are each designed such that the filter components and controller gains scale linearly with the power rating. By structure preserving, we mean that the reduced-order three-phase inverter model is also composed of an LCL filter, a power controller, current controller, and PLL. That is, we show that the system of parallel inverters can be modeled exactly as one aggregated inverter unit and this equivalent model has the same number of dynamical states as an individual inverter in the paralleled system. Numerical simulations validate the reduced-order models.« less

Comparative study of SiC- and Si-based photovoltaic inverters

NASA Astrophysics Data System (ADS)

Ando, Yuji; Oku, Takeo; Yasuda, Masashi; Shirahata, Yasuhiro; Ushijima, Kazufumi; Murozono, Mikio

2017-01-01

This article reports comparative study of 150-300 W class photovoltaic inverters (Si inverter, SiC inverter 1, and SiC inverter 2). In these sub-kW class inverters, the ON-resistance was considered to have little influence on the efficiency. The developed SiC inverters, however, have exhibited an approximately 3% higher direct current (DC)-alternating current (AC) conversion efficiency as compared to the Si inverter. Power loss analysis indicated a reduction in the switching and reverse recovery losses of SiC metal-oxide-semiconductor field-effect transistors used for the DC-AC converter is responsible for this improvement. In the SiC inverter 2, an increase of the switching frequency up to 100 kHz achieved a state-of-the-art combination of the weight (1.25 kg) and the volume (1260 cm3) as a 150-250 W class inverter. Even though the increased switching frequency should cause the increase of the switching losses, the SiC inverter 2 exhibited an efficiency comparable to the SiC inverter 1 with a switching frequency of 20 kHz. The power loss analysis also indicated a decreased loss of the DC-DC converter built with SiC Schottky barrier diodes led to the high efficiency for its increased switching frequency. These results clearly indicated feasibility of SiC devices even for sub-kW photovoltaic inverters, which will be available for the applications where compactness and efficiency are of tremendous importance.

Monitoring of Cyclic Steam Stimulation by Inversion of Surface Tilt Measurements

NASA Astrophysics Data System (ADS)

Maharramov, M.; Zoback, M. D.

2014-12-01

Temperature and pressure changes associated with the cyclic steam simulation (CSS) used in heavy oil production from sands are accompanied by significant deformation. Inversion of geomechanical data may provide a potentially powerful reservoir monitoring tool where geomechanical effects are significant. Induced pore pressure changes can be inverted from measurable surface deformations by solving an inverse problem of poroelasticity. In this work, we apply this approach to estimating pore pressure changes from surface tilt measurements at a heavy oil reservoir undergoing cyclic steam simulation. Steam was injected from November 2007 through January 2008. Surface tilt measurements were collected from 25 surface tilt stations during this period. The injection ran in two overlapping phases: Phase 1 ran from the beginning of the injection though mid-December, and Phase 2 overlapped with Phase 1 and ran through the beginning of January. During Phase 1 steam was injected in the western part of the reservoir, followed by injection in the eastern part in Phase 2. The pore pressure evolution was inverted from daily tilt measurements using regularized constrained least squares fitting, the results are shown on the plot. Estimated induced pore pressure change (color scale), observed daily incremental tilts (green arrows) and modeled daily incremental tilts (red arrows) are shown in three panels corresponding to two and five weeks of injection, and the end of injection period. DGPS measurements available for a single location were used as an additional inversion constraint. The results indicate that the pore pressure increase in the reservoir follows the same pattern as the steam injection, from west to east. This qualitative behaviour is independent of the amount of regularization, indirectly validating our inversion approach. Patches of lower pressure appear to be stable with regard to regularization and may provide valuable insight into the efficiency of steam injection. Inversion of pore pressure (and surface deformation) from tilts in this case is non-unique, and the DGPS measurement provided an important additional constraint. The method can be applied to inverting pore pressure changes from InSAR observations, and the latter can be expected to reduce limitations due to noise in tilt measurements.

Fault-tolerant three-level inverter

DOEpatents

Edwards, John; Xu, Longya; Bhargava, Brij B.

2006-12-05

A method for driving a neutral point clamped three-level inverter is provided. In one exemplary embodiment, DC current is received at a neutral point-clamped three-level inverter. The inverter has a plurality of nodes including first, second and third output nodes. The inverter also has a plurality of switches. Faults are checked for in the inverter and predetermined switches are automatically activated responsive to a detected fault such that three-phase electrical power is provided at the output nodes.

21 CFR 184.1859 - Invert sugar.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Invert sugar. 184.1859 Section 184.1859 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD....1859 Invert sugar. (a) Invert sugar (CAS Reg. No. 8013-17-0) is an aqueous solution of inverted or...

Accelerated Schools Centers: How To Address Challenges to Institutionalization and Growth.

ERIC Educational Resources Information Center

Meza, James, Jr.

The Accelerated Schools Project (ASP) at the University of New Orleans (UNO) was established in spring 1990, funded by a 3-year grant from Chevron. Beginning with 1 pilot school in 1991, the UNO Accelerated Schools Center has expanded to 36 schools representing 19 school districts in Louisiana and 3 schools from the Memphis City Schools district.…

Norwegian Cyber Defense

DTIC Science & Technology

2013-12-01

21   a.   Siberian Pipeline Explosion (1982) ............................21   b.   Chevron Emergency Alert...the fifth domain: Are the mouse and keyboard the new weapons of conflict?,” The Economist, July 1, 2010, http://www.economist.com/node/16478792. 15...a. Siberian Pipeline Explosion (1982) In 1982, intruders planted a Trojan horse in the SCADA system that controls the Siberian Pipeline. This is the

American Avocet (Recurvirostra americana)

USGS Publications Warehouse

Ackerman, Joshua T.; Hartman, C. Alex; Herzog, Mark P.; Takekawa, John Y.; Robinson, Julie A.; Oring, Lewis W.; Skorupa, Joseph P.; Boettcher, Ruth; Poole, A.

2013-01-01

This large, striking shorebird with long bluish-gray legs, a long recurved bill, and a black-and-white chevron pattern on its back and wings is one of four Avocet species in the world, the only one with distinct breeding and non-breeding plumages -- its grayish-white head and neck feathers become cinnamon in early spring as birds begin to form pairs and migrate to breeding areas.

Incidence of Negative Appendectomy: Experience From a Company Hospital in Nigeria

PubMed Central

Osime, OC; Ajayi, PA

2005-01-01

Objective: The aim of this study was to determine the rate of negative appendectomy in a company hospital in Nigeria. Background: Appendicitis is one of the most common abdominal conditions requiring surgical intervention. Appendectomy, like most surgical procedures, has its complications and therefore should only be undertaken when indicated. Case series have reported the incidence of negative appendectomy in Western nations. The purpose of this retrospective study is to evaluate the incidence of negative appendectomy in a Nigerian hospital, where all the operations were carried out by consultant surgeons. Methods: All case files of patients who received an appendectomy at Chevron Hospital in Warri, Nigeria between January, 1999 and December, 2003 were reviewed. Demographic data, symptoms and signs on presentation, intra-operative findings and histological reports on the excised vermiform appendixes were extracted from the case files and analyzed. Results: The incidence of negative appendectomy in this study was 16.1%; all nine patients that had negative appendectomy were female. Conclusion: The incidence of negative appendectomy observed at Chevron Hospital in Warri, Nigeria is lower than that reported by most studies; one factor may be that all the patients in the present study were evaluated and operated on by consultant surgeons. PMID:20847869

Ballistic thermoelectric properties of nitrogenated holey graphene nanostructures

NASA Astrophysics Data System (ADS)

Cao, Wei; Xiao, Huaping; Ouyang, Tao; Zhong, Jianxin

2017-11-01

In this study, we theoretically investigate the ballistic thermoelectric performance of a new two-dimensional material, nitrogenated holey graphene (NHG), using nonequilibrium Green's function method. The calculations show that compared to graphene, such novel single atomic layer structure exhibits better thermoelectric performance. At room temperature, the stable hole (electron) thermoelectric figure of merit ( Z T ) could approach 0.75 (0.2) and 0.6 (0.2) for zigzag-edged (Z-NHGNRs) and armchair-edged NHGNRs (A-NHGNRs), respectively. To achieve better thermoelectric performance, the effect of geometric engineering (chevron-type nanoribbons and rhomboid quantum dot) on the electronic and phononic transport properties of Z-NHGNRs is further discussed. The results indicate that structure modulation is indeed a viable approach to enhance the thermoelectric properties (the figure of merit could exceed 1.5 and 1.3 for the chevron-type and rhomboid quantum dot system, respectively). On analyzing the transport properties, such improvement on the figure of merit is mainly attributed to the increased Seebeck coefficient and reduced thermal conductance (including both electronic and phononic contributions). Our findings presented in this paper qualify NHG as a promising thermoelectric material and provide theoretical guidance for fabricating the outstanding thermoelectric devices.

Prediction of Central Burst Defects in Copper Wire Drawing Process

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

Vega, G.; NEXANS France, NMC Nexans Metallurgy Centre, Boulevard du Marais, BP39, F-62301 Lens; Haddi, A.

2011-01-17

In this study, the prediction of chevron cracks (central bursts) in copper wire drawing process is investigated using experimental and numerical approaches. The conditions of the chevron cracks creation along the wire axis depend on (i) the die angle, the friction coefficient between the die and the wire, (ii) the reduction in crosssectional area of the wire, (iii) the material properties and (iv) the drawing velocity or strain rate. Under various drawing conditions, a numerical simulation for the prediction of central burst defects is presented using an axisymmetric finite element model. This model is based on the application of themore » Cockcroft and Latham fracture criterion. This criterion was used as the damage value to estimate if and where defects will occur during the copper wire drawing. The critical damage value of the material is obtained from a uniaxial tensile test. The results show that the die angle and the reduction ratio have a significant effect on the stress distribution and the maximum damage value. The central bursts are expected to occur when the die angle and reduction ratio reach a critical value. Numerical predictions are compared with experimental observations.« less

[The minimally invasive Chevron and Akin osteotomy (MICA)].

PubMed

Altenberger, Sebastian; Kriegelstein, Stefanie; Gottschalk, Oliver; Dreyer, Florian; Mehlhorn, Alexander; Röser, Anke; Walther, Markus

2018-04-18

Percutaneous correction of a hallux valgus deformity with or without transfer metatarsalgia. Hallux valgus deformity up to 20° intermetatarsal angle, without instability of the first tarsometatarsal joint. Symptomatic arthritis of the first metatarsophalangeal joint, as well as instability of the first tarsometatarsal joint. Percutaneous performed osteotomy of the distal metatarsal 1 in combination with a medial closing wedge osteotomy of the proximal phalanx of the first toe. The use of a postoperative shoe with a rigid sole allows adapted weight bearing in the first 6 weeks. Active and passive mobilization can start immediately after surgery. The method is very effective to treat even severe deformities with or without metatarsalgia. The amount of correction is similar to open procedures. We recommend cadaver training to become familiar with this technique. Thus, complications such as nerve, vessel or tendon injuries can be avoided. The intraoperative radiation exposure remains significantly elevated even for experienced surgeons. In addition to the aesthetic benefits, there is less soft tissue traumatization compared to conventional open procedures. There is no need of bloodlessness. The minimally invasive Chevron and Akin osteotomy is a safe and powerful technique for the treatment of hallux valgus deformity.

Elevated-temperature fracture resistances of monolithic and composite ceramics using chevron-notched bend tests

NASA Technical Reports Server (NTRS)

Ghosh, Asish; Jenkins, Michael G.; Ferber, Mattison K.; Peussa, Jouko; Salem, Jonathan A.

1992-01-01

The quasi-static fracture behaviors of monolithic ceramics (SiC, Si3N4, MgAl2O4), self-reinforced monoliths (acicular grained Si3N4, acicular grained mullite), and ceramic matrix composites (SiC whisker/Al2O3 matrix, TiB2 particulate/SiC matrix, SiC fiber/CVI SiC matrix, Al2O3 fiber/CVI SiC matrix) were measured over the temperature range of 20 to 1400 C. The chevron notched, bend bar test geometry was essential for characterizing the elevated temperature fracture resistances of this wide range of quasi-brittle materials during stable crack growth. Fractography revealed the differences in the fracture behavior of the different materials at the various temperatures. The fracture resistances of the self-reinforced monoliths were comparable to those of the composites and the fracture mechanisms were found to be similar at room temperature. However at elevated temperatures the differences of the fracture behavior became apparent where the superior fracture resistance of the self-reinforced monoliths were attributed to the minor amounts of glassy, intergranular phases which were often more abundant in the composites and affected the fracture behavior when softened by elevated temperatures.

Petroleum developments in North Africa in 1979

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

Nicod, M.A.

In the 6 countries covered by this report, the extent of valid petroleum rights, seismic work, and drilling was nearly the same as in 1978. The success rate of wildcat drilling decreased slightly, to 28% (33% in 1978), with 26 oil or gas discoveries. In southwestern Tunisia, the Amoco Sabrina Nord 1 tested 930 bbl of 39/sup 0/ APl oil from Cambrian-Ordovician sandstones - the first oil to come from lower Paleozoic rocks in Tunisia. First commercial oil from Cambrian-Ordovician rocks in western Libya was discovered by Agip A1-NC40 which flowed 1,400 b/d. Highlight of the year in North Africamore » was in the interior basin of Sudan where the Chevron Abu Gabra 1 tested 900 BOPD of 40/sup 0/ APl oil from Cretaceous rocks; 2 other wells, spudded in late 1979 in the same area, have tested 3,200 and 7,300 b/d, respectively, in early 1980. Discovery well of the interior basin was Chevron Unity 1 which tested small amounts of oil in 1978. Oil production in North Africa in 1979 averaged 3,939,500 b/d compared with 3,802,800 b/d in 1978, an increase of 3.6%.« less

Electronic structure changes during the on-surface synthesis of nitrogen-doped chevron-shaped graphene nanoribbons

NASA Astrophysics Data System (ADS)

Maaß, Friedrich; Utecht, Manuel; Stremlau, Stephan; Gille, Marie; Schwarz, Jutta; Hecht, Stefan; Klamroth, Tillmann; Tegeder, Petra

2017-07-01

Utilizing suitable precursor molecules, a thermally activated and surface-assisted synthesis results in the formation of defect-free graphene nanoribbons (GNRs), which exhibit electronic properties that are not present in extended graphene. Most importantly, they have a band gap in the order of a few electron volts, depending on the nanoribbon width. In this study, we investigate the electronic structure changes during the formation of GNRs, nitrogen-doped (singly and doubly N-doped) as well as non-N-doped chevron-shaped CGNRs on Au(111). Thus we determine the optical gaps of the precursor molecules, the intermediate nonaromatic polymers, and finally the aromatic GNRs, using high-resolution electron energy loss spectroscopy and density functional theory calculations. As expected, we find no influence of N-doping on the size of the optical gaps. The gap of the precursor molecules is around 4.5 eV. Polymerization leads to a reduction of the gap to a value of 3.2 eV due to elongation and thus enhanced delocalization. The CGNRs exhibit a band gap of 2.8 eV, thus the gap is further reduced in the nanoribbons, since they exhibit an extended delocalized π -electron system.

Permian paleoclimate data from fluid inclusions in halite

USGS Publications Warehouse

Benison, K.C.; Goldstein, R.H.

1999-01-01

This study has yielded surface water paleotemperatures from primary fluid inclusions in mid Permian Nippewalla Group halite from western Kansas. A 'cooling nucleation' method is used to generate vapor bubbles in originally all-liquid primary inclusions. Then, surface water paleotemperatures are obtained by measuring temperatures of homogenization to liquid. Homogenization temperatures ranged from 21??C to 50??C and are consistent along individual fluid inclusion assemblages, indicating that the fluid inclusions have not been altered by thermal reequilibration. Homogenization temperatures show a range of up to 26??C from base to top of individual cloudy chevron growth bands. Petrographic and fluid inclusion evidence indicate that no significant pressure correction is needed for the homogenization temperature data. We interpret these homogenization temperatures to represent shallow surface water paleotemperatures. The range in temperatures from base to top of single chevron bands may reflect daily temperatures variations. These Permian surface water temperatures fall within the same range as some modern evaporative surface waters, suggesting that this Permian environment may have been relatively similar to its modern counterparts. Shallow surface water temperatures in evaporative settings correspond closely to local air temperatures. Therefore, the Permian surface water temperatures determined in this study may be considered proxies for local Permian air temperatures.

Fracture mechanics analysis of the dentine-luting cement interface.

PubMed

Ryan, A K; Mitchell, C A; Orr, J F

2002-01-01

The objectives of this study were to determine the fracture toughness of adhesive interfaces between dentine and clinically relevant, thin layers of dental luting cements. Cements tested included a conventional glass-ionomer, F (Fuji 1), a resin-modified glass-ionomer, FP (Fuji Plus) and a compomer cement, D (DyractCem). Ten miniature short-bar chevron notch specimens were manufactured for each cement, each comprising a 40 microm thick chevron of lute, between two 1.5 mm thick blocks of bovine dentine, encased in resin composite. The interfacial K(IC) results (MN/m3/2) were median (range): F; 0.152 (0.14-0.16), FP; 0.306 (0.27-0.37), D; 0.351 (0.31-0.37). Non-parametric statistical analysis showed that the fracture toughness of F was significantly lower (p <0.05) than those of FP or D, and all were significantly lower than values for monolithic cement specimens. Scanning electron microscopy of the specimens suggested crack propagation along the interface. However, energy dispersive X-ray analysis indicated that failure was cohesive within the cement. It is concluded that the fracture toughness of luting cement was lowered by cement-dentine interactions.

Estimation of Rainfall Rates from Passive Microwave Remote Sensing.

NASA Astrophysics Data System (ADS)

Sharma, Awdhesh Kumar

Rainfall rates have been estimated using the passive microwave and visible/infrared remote sensing techniques. Data of September 14, 1978 from the Scanning Multichannel Microwave Radiometer (SMMR) on board SEA SAT-A and the Visible and Infrared Spin Scan Radiometer (VISSR) on board GOES-W (Geostationary Operational Environmental Satellite - West) was obtained and analyzed for rainfall rate retrieval. Microwave brightness temperatures (MBT) are simulated, using the microwave radiative transfer model (MRTM) and atmospheric scattering models. These MBT were computed as a function of rates of rainfall from precipitating clouds which are in a combined phase of ice and water. Microwave extinction due to ice and liquid water are calculated using Mie-theory and Gamma drop size distributions. Microwave absorption due to oxygen and water vapor are based on the schemes given by Rosenkranz, and Barret and Chung. The scattering phase matrix involved in the MRTM is found using Eddington's two stream approximation. The surface effects due to winds and foam are included through the ocean surface emissivity model. Rainfall rates are then inverted from MBT using the optimization technique "Leaps and Bounds" and multiple linear regression leading to a relationship between the rainfall rates and MBT. This relationship has been used to infer the oceanic rainfall rates from SMMR data. The VISSR data has been inverted for the rainfall rates using Griffith's scheme. This scheme provides an independent means of estimating rainfall rates for cross checking SMMR estimates. The inferred rainfall rates from both techniques have been plotted on a world map for comparison. A reasonably good correlation has been obtained between the two estimates.

Photovoltaic system with improved DC connections and method of making same

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

Cioffi, Philip Michael; Todorovic, Maja Harfman; Herzog, Michael Scott

A micro-inverter assembly includes a housing having an opening formed in a bottom surface thereof, and a direct current (DC)-to-alternating current (AC) micro-inverter disposed within the housing at a position adjacent to the opening. The micro-inverter assembly further includes a micro-inverter DC connector electrically coupled to the DC-to-AC micro-inverter and positioned within the opening of the housing, the micro-inverter DC connector having a plurality of exposed electrical contacts.

Frequency domain model for analysis of paralleled, series-output-connected Mapham inverters

NASA Technical Reports Server (NTRS)

Brush, Andrew S.; Sundberg, Richard C.; Button, Robert M.

1989-01-01

The Mapham resonant inverter is characterized as a two-port network driven by a selected periodic voltage. The two-port model is then used to model a pair of Mapham inverters connected in series and employing phasor voltage regulation. It is shown that the model is useful for predicting power output in paralleled inverter units, and for predicting harmonic current output of inverter pairs, using standard power flow techniques. Some sample results are compared to data obtained from testing hardware inverters.

Frequency domain model for analysis of paralleled, series-output-connected Mapham inverters

NASA Technical Reports Server (NTRS)

Brush, Andrew S.; Sundberg, Richard C.; Button, Robert M.

1989-01-01

The Mapham resonant inverter is characterized as a two-port network driven by a selected periodic voltage. The two-port model is then used to model a pair of Mapham inverters connected in series and employing phasor voltage regulation. It is shown that the model is useful for predicting power output in paralleled inverter units, and for predicting harmonic current output of inverter pairs, using standard power flow techniques. Some examples are compared to data obtained from testing hardware inverters.

Status and Needs of Power Electronics for Photovoltaic Inverters: Summary Document

NASA Astrophysics Data System (ADS)

West, R.; Mauch, K.; Qin, Y. C.; Mohan, N.; Bonn, R.

2002-05-01

Photovoltaic inverters are the most mature of any DER inverter, and their mean time to first failure (MTFF) is about five years. This is an unacceptable MTFF and will inhibit the rapid expansion of PV. With all DER technologies, (solar, wind, fuel cells, and microturbines) the inverter is still an immature product that will result in reliability problems in fielded systems. The increasing need for all of these technologies to have a reliable inverter provides a unique opportunity to address these needs with focused R&D development projects. The requirements for these inverters are so similar that modular designs with universal features are obviously the best solution for a 'next generation' inverter. A 'next generation' inverter will have improved performance, higher reliability, and improved profitability. Sandia National Laboratories has estimated that the development of a 'next generation' inverter could require approximately 20 man-years of work over an 18- to 24-month time frame, and that a government-industry partnership will greatly improve the chances of success.

Single phase inverter for a three phase power generation and distribution system

NASA Technical Reports Server (NTRS)

Lindena, S. J.

1976-01-01

A breadboard design of a single-phase inverter with sinusoidal output voltage for a three-phase power generation and distribution system was developed. The three-phase system consists of three single-phase inverters, whose output voltages are connected in a delta configuration. Upon failure of one inverter the two remaining inverters will continue to deliver three-phase power. Parallel redundancy as offered by two three-phase inverters is substituted by one three-phase inverter assembly with high savings in volume, weight, components count and complexity, and a considerable increase in reliability. The following requirements must be met: (1) Each single-phase, current-fed inverter must be capable of being synchronized to a three-phase reference system such that its output voltage remains phaselocked to its respective reference voltage. (2) Each single-phase, current-fed inverter must be capable of accepting leading and lagging power factors over a range from -0.7 through 1 to +0.7.

An SCR inverter with an integral battery charger for electric vehicles

NASA Technical Reports Server (NTRS)

Thimmeach, D.

1983-01-01

The feasibility of incorporating an onboard battery charger into the inverter previously developed under a NASA contract is successfully demonstrated. The rated output power of the resulting isolated battery charger is 3.6 kW at 220 Vac with an 86 percent efficiency and a 95 percent power factor. Also achieved are improved inverter efficiency (from 90 to 93 percent at 15 kW motor shaft power), inverter peak power capability (from 26 to 34 kW), and reduced weight and volume of the combined inverter/charger package (47 kg, 49 x 44 x 24 cm). Some major conclusions are that using the inverter commutation circuitry to perform the battery charging function is advantageous, and that the input-commutated thyristor inverter has the potential to be an excellent inverter and battery charger for use in electric vehicle applications.

Microgrid and Inverter Control and Simulator Software

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

2012-09-13

A collection of software that can simulate the operation of an inverter on a microgrid or control a real inverter. In addition, it can simulate the control of multiple nodes on a microgrid." Application: Simulation of inverters and microgrids; control of inverters on microgrids." The MMI submodule is designed to control custom inverter hardware, and to simulate that hardware. The INVERTER submodule is only the simulator code, and is of an earlier generation than the simulator in MMI. The MICROGRID submodule is an agent-based simulator of multiple nodes on a microgrid which presents a web interface. The WIND submodule producesmore » movies of wind data with a web interface.« less

Design and Implementation of nine level multilevel Inverter

NASA Astrophysics Data System (ADS)

Dhineshkumar, K.; Subramani, C.

2018-04-01

In this paper the solar based boost converter integrated Nine level multilevel inverter presented. It uses 7 switches to produce nine level output stepped waveform. The aim of the work to produce 9 level wave form using solar and boost converter. The conventional inverter has multiple sources and has 16 switches are required and also more number of voltage sources required. The proposed inverter required single solar panel and reduced number of switches and integrated boost converter which increase the input voltage of the inverter. The proposed inverter simulated and compared with R load using Mat lab and prototype model experimentally verified. The proposed inverter can be used in n number of solar applications.

System and method for regulating resonant inverters

DOEpatents

Stevanovic, Ljubisa Dragoljub [Clifton Park, NY; Zane, Regan Andrew [Superior, CO

2007-08-28

A technique is provided for direct digital phase control of resonant inverters based on sensing of one or more parameters of the resonant inverter. The resonant inverter control system includes a switching circuit for applying power signals to the resonant inverter and a sensor for sensing one or more parameters of the resonant inverter. The one or more parameters are representative of a phase angle. The resonant inverter control system also includes a comparator for comparing the one or more parameters to a reference value and a digital controller for determining timing of the one or more parameters and for regulating operation of the switching circuit based upon the timing of the one or more parameters.

Stability Assessment of a System Comprising a Single Machine and Inverter with Scalable Ratings

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

Johnson, Brian B; Lin, Yashen; Gevorgian, Vahan

Synchronous machines have traditionally acted as the foundation of large-scale electrical infrastructures and their physical properties have formed the cornerstone of system operations. However, with the increased integration of distributed renewable resources and energy-storage technologies, there is a need to systematically acknowledge the dynamics of power-electronics inverters - the primary energy-conversion interface in such systems - in all aspects of modeling, analysis, and control of the bulk power network. In this paper, we assess the properties of coupled machine-inverter systems by studying an elementary system comprised of a synchronous generator, three-phase inverter, and a load. The inverter model is formulatedmore » such that its power rating can be scaled continuously across power levels while preserving its closed-loop response. Accordingly, the properties of the machine-inverter system can be assessed for varying ratios of machine-to-inverter power ratings. After linearizing the model and assessing its eigenvalues, we show that system stability is highly dependent on the inverter current controller and machine exciter, thus uncovering a key concern with mixed machine-inverter systems and motivating the need for next-generation grid-stabilizing inverter controls.« less

Hemispheric specialization and the perception of emotion: evidence from right-handers and from inverted and non-inverted left-handers.

PubMed

Reuter-Lorenz, P A; Givis, R P; Moscovitch, M

1983-01-01

Right-handers and inverted and non-inverted left-handers viewed emotional expressions in one hemifield and, simultaneously, a neutral expression of the same poser in the other hemifield. Subjects were required to identify the side containing the affective face. Happy faces with open (i.e. salient) and closed mouth smiles and sad faces were used as stimuli. For right-handers and inverters reaction time was faster to right hemifield presentations for happy faces and to left hemifield presentations for sad faces. Non-inverters showed the reverse pattern. The saliency of the happy expressions had no effect on the magnitude and direction of asymmetry for any group. The data support the hypothesis of differential hemispheric specialization for positive and negative emotion and demonstrate opposite patterns of asymmetry in affect perception for inverted and non-inverted left-handers.

Voltage balanced multilevel voltage source converter system

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

1997-01-01

A voltage balanced multilevel converter for high power AC applications such as adjustable speed motor drives and back-to-back DC intertie of adjacent power systems. This converter provides a multilevel rectifier, a multilevel inverter, and a DC link between the rectifier and the inverter allowing voltage balancing between each of the voltage levels within the multilevel converter. The rectifier is equipped with at least one phase leg and a source input node for each of the phases. The rectifier is further equipped with a plurality of rectifier DC output nodes. The inverter is equipped with at least one phase leg and a load output node for each of the phases. The inverter is further equipped with a plurality of inverter DC input nodes. The DC link is equipped with a plurality of rectifier charging means and a plurality of inverter discharging means. The plurality of rectifier charging means are connected in series with one of the rectifier charging means disposed between and connected in an operable relationship with each adjacent pair of rectifier DC output nodes. The plurality of inverter discharging means are connected in series with one of the inverter discharging means disposed between and connected in an operable relationship with each adjacent pair of inverter DC input nodes. Each of said rectifier DC output nodes are individually electrically connected to the respective inverter DC input nodes. By this means, each of the rectifier DC output nodes and each of the inverter DC input nodes are voltage balanced by the respective charging and discharging of the rectifier charging means and the inverter discharging means.

Voltage balanced multilevel voltage source converter system

DOEpatents

Peng, F.Z.; Lai, J.S.

1997-07-01

Disclosed is a voltage balanced multilevel converter for high power AC applications such as adjustable speed motor drives and back-to-back DC intertie of adjacent power systems. This converter provides a multilevel rectifier, a multilevel inverter, and a DC link between the rectifier and the inverter allowing voltage balancing between each of the voltage levels within the multilevel converter. The rectifier is equipped with at least one phase leg and a source input node for each of the phases. The rectifier is further equipped with a plurality of rectifier DC output nodes. The inverter is equipped with at least one phase leg and a load output node for each of the phases. The inverter is further equipped with a plurality of inverter DC input nodes. The DC link is equipped with a plurality of rectifier charging means and a plurality of inverter discharging means. The plurality of rectifier charging means are connected in series with one of the rectifier charging means disposed between and connected in an operable relationship with each adjacent pair of rectifier DC output nodes. The plurality of inverter discharging means are connected in series with one of the inverter discharging means disposed between and connected in an operable relationship with each adjacent pair of inverter DC input nodes. Each of said rectifier DC output nodes are individually electrically connected to the respective inverter DC input nodes. By this means, each of the rectifier DC output nodes and each of the inverter DC input nodes are voltage balanced by the respective charging and discharging of the rectifier charging means and the inverter discharging means. 15 figs.

Radiometric Dating of Folds: A new approach to determine the timing of deformation at shallow-crustal conditions, with examples from the Mexican Fold-Thrust Belt

NASA Astrophysics Data System (ADS)

Fitz Diaz, E.; van der Pluijm, B. A.

2012-12-01

We are developing a robust method to obtain absolute ages of folds that were formed at shallow crustal conditions. The method takes advantage of illite neocrystallization in folded, clay-bearing layers and the ability to obtain accurate retention and total gas ages from small size fractions using encapsulated Ar analysis, analogous to prior work on fault gouge dating. We illustrate our approach in folded Cretaceous shale-bentonitic layers that are interbedded with carbonates of the Zimapán and the Tampico-Misantla cretaceous basins in central-eastern Mexico. Basinal carbonates were buried by syntectonic turbidites and inverted during the formation of the Mexican Fold-Thrust in the Late Cretaceous. Results were obtained from four chevron folds that are representative of different stages of deformation, burial/temperature conditions and location within this thin-skinned orogenic wedge: two from the Zimapán Basin (Folds 1 and 2) in the west and two from the Tampico-Misantla Basin (Folds 3 and 4) in the east. Mineralogic compositions and variations in illite-polytypes, crystallite-size (CS) and Ar/Ar ages were obtained from size fractions in limbs and hinges of folded layers. Ar retention ages produce a folding age of ~81 Ma for Fold 1 and ~69 Ma for Fold 2, which are fully consistent with stratigraphic limits from syn-orogenic turbidities and observed overprinting events in the Mexican Fold-Thrust Belt. The total gas age of Fold 3, on the easternmost margin of the Tampico-Misantla Basin is similar to that of Fold 2, indicating that the second event is regional in scale. In addition to presenting a new, reliable method to constrain the timing of local deformation, we interpret folding and associated clay neo-mineralization in terms of the regional burial history, and localization and propagation of deformation within a heterogeneous orogenic wedge involving progressive deformation of two basins separated by a platform block.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

1997-01-01

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

2002-01-01

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

2001-04-03

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with separate DC sources

DOEpatents

Peng, F.Z.; Lai, J.S.

1997-06-24

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations. 15 figs.

Impacts of Inverter-Based Advanced Grid Support Functions on Islanding Detection

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

Nelson, Austin; Hoke, Anderson; Miller, Brian

A long-standing requirement for inverters paired with distributed energy resources is that they are required to disconnect from the electrical power system (EPS) when an electrical island is formed. In recent years, advanced grid support controls have been developed for inverters to provide voltage and frequency support by integrating functions such as voltage and frequency ride-through, volt-VAr control, and frequency-Watt control. With these new capabilities integrated into the inverter, additional examination is needed to determine how voltage and frequency support will impact pre-existing inverter functions like island detection. This paper inspects how advanced inverter functions will impact its ability tomore » detect the formation of an electrical island. Results are presented for the unintentional islanding laboratory tests of three common residential-scale photovoltaic inverters performing various combinations of grid support functions. For the inverters tested, grid support functions prolonged island disconnection times slightly; however, it was found that in all scenarios the inverters disconnected well within two seconds, the limit imposed by IEEE Std 1547-2003.« less

Effect of Mixing Enhancement Devices on Turbulence in Separate Flow Nozzles

NASA Technical Reports Server (NTRS)

Bridges, James

2001-01-01

This paper presents the effects of several mixing enhancement devices on turbulence in jet nozzles. The topics include: 1) The Advanced Subsonic Technology (AST) Program; 2) Test Programs SFNT97 and SFNT2K; 3) Facility; 4) Mixing Enhancement Nozzles; 5) IR reductions; 6) Schlieren of Chevrons; and 7) Aeroacoustics of Enhanced Mixing-Paradigm. This paper is presented in viewgraph form.

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

Deniz, O.; Sánchez-Sánchez, C.; Jaafar, R.

Electronic and thermal properties of chevron-type graphene nanoribbons can be widely tuned, making them interesting candidates for electronic and thermoelectric applications. In this paper, we use post-growth silicon intercalation to unambiguously access nanoribbons’ energy position of their electronic frontier states. These are otherwise obscured by substrate effects when investigated directly on the growth substrate. Finally, in agreement with first-principles calculations we find a band gap of 2.4 eV.

R-Curve Behavior for Silicon Carbide Whisker Reinforced Aluminum Oxide Composites

DTIC Science & Technology

1990-01-01

Ltd, Tokyo, Japan. Aremco Accu-Cut 5255, AREMCO PRODUCTS, Inc., Ossining , N.Y., U.S.A. e°120 Series Accu-Cut Diamond Saw Blade, AREMCO PRODUCTS, Inc... Ossining , N.Y., U.S.A. 93 P/2 P/2 40 mm 60 mm E 20 mm P/2 P/2 FIGURE 12: Schematic Diagram of the Chevron Notched Specimen. 94 III.D.2.d

Thermal Actuation Based 3-DoF Non-Resonant Microgyroscope Using MetalMUMPs

PubMed Central

Shakoor, Rana Iqtidar; Bazaz, Shafaat Ahmed; Kraft, Michael; Lai, Yongjun; Masood ul Hassan, Muhammad

2009-01-01

High force, large displacement and low voltage consumption are a primary concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of high force generation combined with the large displacements at a low operating voltage in comparison with traditional electrostatic actuators. A Nickel based 3-DoF micromachined gyroscope comprising 2-DoF drive mode and 1-DoF sense mode oscillator utilizing the chevron-shaped thermal actuators is presented here. Analytical derivations and finite element simulations are carried out to predict the performance of the proposed device using the thermo-physical properties of electroplated nickel. The device sensitivity is improved by utilizing the dynamical amplification of the oscillation in 2-DoF drive mode using an active-passive mass configuration. A comprehensive theoretical description, dynamics and mechanical design considerations of the proposed gyroscopes model are discussed in detail. Parametric optimization of gyroscope, its prototype modeling and fabrication using MetalMUMPs has also been investigated. Dynamic transient simulation results predicted that the sense mass of the proposed device achieved a drive displacement of 4.1μm when a sinusoidal voltage of 0.5V is applied at 1.77 kHz exhibiting a mechanical sensitivity of 1.7μm /°/s in vacuum. The wide bandwidth frequency response of the 2-DoF drive mode oscillator consists of two resonant peaks and a flat region of 2.11 kHz between the peaks defining the operational frequency region. The sense mode resonant frequency can lie anywhere within this region and therefore the amplitude of the response is insensitive to structural parameter variations, enhancing device robustness against such variations. The proposed device has a size of 2.2 × 2.6 mm2, almost one third in comparison with existing M-DoF vibratory gyroscope with an estimated power consumption of 0.26 Watts. These predicted results illustrate that the chevron-shaped thermal actuator has a large voltage-stroke ratio shifting the paradigm in MEMS gyroscope design from the traditional interdigitated comb drive electrostatic actuator. These actuators have low damping compared to electrostatic comb drive actuators which may result in high quality factor microgyroscopes operating at atmospheric pressure. PMID:22574020

Integral inverter/battery charger for use in electric vehicles

NASA Technical Reports Server (NTRS)

Thimmesch, D.

1983-01-01

The design and test results of a thyristor based inverter/charger are discussed. A battery charger is included integral to the inverter by using a subset of the inverter power circuit components. The resulting charger provides electrical isolation between the vehicle propulsion battery and ac line and is capable of charging a 25 kWh propulsion battery in 8 hours from a 220 volt ac line. The integral charger employs the inverter commutation components at a resonant ac/dc isolated converter rated at 3.6 kW. Charger efficiency and power factor at an output power of 3.6 kW are 86% and 95% respectively. The inverter, when operated with a matching polyphase ac induction motor and nominal 132 volt propulsion battery, can provide a peak shaft power of 34 kW (45 ph) during motoring operation and 45 kW (60 hp) during regeneration. Thyristors are employed for the inverter power switching devices and are arranged in an input-commutated topology. This configuration requires only two thyristors to commutate the six main inverter thyristors. Inverter efficiency during motoring operation at motor shaft speeds above 450 rad/sec (4300 rpm) is 92-94% for output power levels above 11 KW (15 hp). The combined ac inverter/charger package weighs 47 kg (103 lbs).

An Optimal Current Controller Design for a Grid Connected Inverter to Improve Power Quality and Test Commercial PV Inverters.

PubMed

Algaddafi, Ali; Altuwayjiri, Saud A; Ahmed, Oday A; Daho, Ibrahim

2017-01-01

Grid connected inverters play a crucial role in generating energy to be fed to the grid. A filter is commonly used to suppress the switching frequency harmonics produced by the inverter, this being passive, and either an L- or LCL-filter. The latter is smaller in size compared to the L-filter. But choosing the optimal values of the LCL-filter is challenging due to resonance, which can affect stability. This paper presents a simple inverter controller design with an L-filter. The control topology is simple and applied easily using traditional control theory. Fast Fourier Transform analysis is used to compare different grid connected inverter control topologies. The modelled grid connected inverter with the proposed controller complies with the IEEE-1547 standard, and total harmonic distortion of the output current of the modelled inverter has been just 0.25% with an improved output waveform. Experimental work on a commercial PV inverter is then presented, including the effect of strong and weak grid connection. Inverter effects on the resistive load connected at the point of common coupling are presented. Results show that the voltage and current of resistive load, when the grid is interrupted, are increased, which may cause failure or damage for connecting appliances.

An Optimal Current Controller Design for a Grid Connected Inverter to Improve Power Quality and Test Commercial PV Inverters

PubMed Central

Altuwayjiri, Saud A.; Ahmed, Oday A.; Daho, Ibrahim

2017-01-01

Grid connected inverters play a crucial role in generating energy to be fed to the grid. A filter is commonly used to suppress the switching frequency harmonics produced by the inverter, this being passive, and either an L- or LCL-filter. The latter is smaller in size compared to the L-filter. But choosing the optimal values of the LCL-filter is challenging due to resonance, which can affect stability. This paper presents a simple inverter controller design with an L-filter. The control topology is simple and applied easily using traditional control theory. Fast Fourier Transform analysis is used to compare different grid connected inverter control topologies. The modelled grid connected inverter with the proposed controller complies with the IEEE-1547 standard, and total harmonic distortion of the output current of the modelled inverter has been just 0.25% with an improved output waveform. Experimental work on a commercial PV inverter is then presented, including the effect of strong and weak grid connection. Inverter effects on the resistive load connected at the point of common coupling are presented. Results show that the voltage and current of resistive load, when the grid is interrupted, are increased, which may cause failure or damage for connecting appliances. PMID:28540362

New type of transformerless high efficiency inverter

NASA Astrophysics Data System (ADS)

Naaijer, G. J.

Inverter architectures are presented which allow economical ac/dc switching for solar cell array and battery power use in domestic and industrial applications. The efficiencies of currently available inverters are examined and compared with a new 2.2 kW transformerless stepped wave inverter. The inverter has low no-load losses, amounting to 200 Wh/24 hr, and features voltage steps occurring 15-30 times/sine wave period. An example is provided for an array/battery/inverter assembly with the inverter control electronics activating or disconnecting the battery subassemblies based on the total number of activated subassemblies in relation to a reference sinewave, and the need to average the battery subassembly discharge rates. A total harmonic distortion of 6 percent was observed, and the system is noted to be usable as a battery charger.

Inverter for Interchangeable Use as Current Source Inverter and Voltage Source Inverter for Interconnecting to Grid

NASA Astrophysics Data System (ADS)

Teruya, Daisuke; Masukawa, Shigeo; Iida, Shoji

We propose a novel inverter that can be operated either as a Current Source Inverter (CSI) or as a Voltage Source Inverter (VSI) by changing only the control signals. It is proper to apply it to the interconnecting system with renewal energy, such as photovoltaic cells or wind generation systems, to a grid. This inverter is usually operated as the CSI connected to the grid. Even if the energy source has a lower voltage than the grid, the energy can be supplied to the grid through the proposed inverter. The power factor can be briefly maintained at almost unity. When power supply from the grid is interrupted, the proposed circuit should be operated as the VSI in the stand-alone operation mode. In this way, the circuit can maintain a constant output voltage to the loads. In this paper, the proposed circuit configuration and the control schemes for both the CSI and the VSI are described. Further, the circuit characteristics for both are discussed experimentally.

Integration of supercapacitive storage in renewable energy system to compare the response of two level and five level inverter with RL type load

NASA Astrophysics Data System (ADS)

Jana, Suman; Biswas, Pabitra Kumar; Das, Upama

2018-04-01

The analytical and simulation-based study in this presented paper shows a comparative report between two level inverter and five-level inverter with the integration of Supercapacitive storage in Renewable Energy system. Sometime dependent numerical models are used to measure the voltage and current response of two level and five level inverter in MATLAB Simulink based environment. In this study supercapacitive sources, which are fed by solar cells are used as input sources to experiment the response of multilevel inverter with integration of su-percapacitor as a storage device of Renewable Energy System. The RL load is used to compute the time response in MATLABSimulink based environment. With the simulation results a comparative study has been made of two different level types of inverters. Two basic types of inverter are discussed in the study with reference to their electrical behavior. It is also simulated that multilevel inverter can convert stored energy within supercapacitor which is extracted from Renewable Energy System.

Chapter 11.2: Inverters, Power Optimizers, and Microinverters

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

Deline, Christopher A

Inverters span a wide range of sizes, topologies, and connection voltages: from utility-scale megawatt inverters to string inverters. Switch-mode power conversion relies on high frequency chopping of DC signal to periodically charge and discharge energy storage elements, such as inductors and capacitors. Additional circuit components are required to address practical issues in inverters such as voltage ripple and harmonic distortion. Inverters are beginning to incorporate components with a bandgap above should be 3 eV, such as SiC and GaN. Photovoltaic (PV) modules respond dynamically to changing temperature and irradiation conditions. Thus, maximum DC power extraction requires periodic adjustment of themore » PV voltage and current operating point. An inverter's total efficiency is measured by the product of its conversion efficiency and the maximum-power-point tracking (MPPT) efficiency. This chapter lists the primary functions of inverters that include auxiliary capabilities, such as monitoring of DC and AC performance, and other error reporting.« less

A new type of single-phase five-level inverter

NASA Astrophysics Data System (ADS)

Xu, Zhi; Li, Shengnan; Qin, Risheng; Zhao, Yanhang

2017-11-01

At present, Neutral Point Clamped (NPC) multilevel inverter is widely applied in new energy field. However, it has some disadvantages including low utilization rate of direct current (DC) voltage source and the unbalance of neutral potential. Therefore, a new single-phase five level inverter is proposed in this paper. It has two stage structure, the former stage is equivalent to three level DC/DC converter, and the back stage uses H bridge to realize inverter. Compared with the original central clamp type inverter, the new five level inverter can improve the utilization of DC voltage, and realize the neutral point potential balance with hysteresis comparator.

A study on the impact of high penetration distributed generation inverters on grid operation and stability

NASA Astrophysics Data System (ADS)

Gu, Fei; Brouwer, Jack; Samuelsen, Scott

2013-09-01

Recent advances in inverter technology have enabled ancillary services such as volt/VAR regulation, SCADA communications, and active power filtering. Smart inverters can not only provide real power, but can be controlled to use excess capacity to provide reactive power compensation, power flow control, and active power filtering without supplementary inverter hardware. A transient level inverter model based on the Solectria 7700 inverter is developed and used to assess these control strategies using field data from an existing branch circuit containing two Amonix 68kW CPV-7700 systems installed at the University of California, Irvine.

Nonlinear analysis of a family of LC tuned inverters. [dc to square wave circuits for power conditioning

NASA Technical Reports Server (NTRS)

Lee, F. C. Y.; Wilson, T. G.

1974-01-01

A family of four dc-to-square-wave LC tuned inverters are analyzed using singular point. Limit cycles and waveshape characteristics are given for three modes of oscillation: quasi-harmonic, relaxation, and discontinuous. An inverter in which the avalanche breakdown of the transistor emitter-to-base junction occurs is discussed and the starting characteristics of this family of inverters are presented. The LC tuned inverters are shown to belong to a family of inverters with a common equivalent circuit consisting of only three 'series' elements: a five-segment piecewise-linear current-controlled resistor, linear inductor, and linear capacitor.

DC-DC Type High-Frequency Link DC for Improved Power Quality of Cascaded Multilevel Inverter

NASA Astrophysics Data System (ADS)

Sadikin, Muhammad; Senjyu, Tomonobu; Yona, Atsushi

2013-06-01

Multilevel inverters are emerging as a new breed of power converter options for power system applications. Recent advances in power switching devices enabled the suitability of multilevel inverters for high voltage and high power applications because they are connecting several devices in series without the need of component matching. Usually, a transformerless battery energy storage system, based on a cascaded multilevel inverter, is used as a measure for voltage and frequency deviations. System can be reduced in size, weight, and cost of energy storage system. High-frequency link circuit topology is advantageous in realizing compact and light-weight power converters for uninterruptible power supply systems, new energy systems using photovoltaic-cells, fuel-cells and so on. This paper presents a DC-DC type high-frequency link DC (HFLDC) cascaded multilevel inverter. Each converter cell is implemented a control strategy for two H-bridge inverters that are controlled with the same multicarrier pulse width modulation (PWM) technique. The proposed cascaded multilevel inverter generates lower voltage total harmonic distortion (THD) in comparison with conventional cascaded multilevel inverter. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of the proposed cascaded multilevel inverter.

A Single-Phase Embedded Z-Source DC-AC Inverter

PubMed Central

Kim, Se-Jin; Lim, Young-Cheol

2014-01-01

In the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DC-AC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with a common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, an equivalent level of AC output voltages can be obtained. Moreover, by controlling the output capacitor voltages asymmetrically, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments were performed with a DC source voltage of 38 V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that efficiencies of up to 95% and 97% can be achieved with the proposed inverter using symmetric and asymmetric control, respectively. PMID:25133241

A single-phase embedded Z-source DC-AC inverter.

PubMed

Kim, Se-Jin; Lim, Young-Cheol

2014-01-01

In the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DC-AC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with a common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, an equivalent level of AC output voltages can be obtained. Moreover, by controlling the output capacitor voltages asymmetrically, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments were performed with a DC source voltage of 38 V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that efficiencies of up to 95% and 97% can be achieved with the proposed inverter using symmetric and asymmetric control, respectively.

Universality of bridge functions and its relation to variational perturbation theory and additivity of equations of state

NASA Astrophysics Data System (ADS)

Rosenfeld, Yaakov

1984-05-01

Featuring the modified hypernetted-chain (MHNC) scheme as a variational fitting procedure, we demonstrate that the accuracy of the variational perturbation theory (VPT) and of the method based on additivity of equations of state is determined by the excess entropy dependence of the bridge-function parameters [i.e., η(s) when the Percus-Yevick hard-sphere bridge functions are employed]. It is found that η(s) is nearly universal for all soft (i.e., "physical") potentials while it is distinctly different for the hard spheres, providing a graphical display of the "jump" in pair-potential space (with respect to accuracy of VPT) from "hard" to "soft" behavior. The universality of η(s) provides a local criterion for the MHNC scheme that should be useful for inverting structure-factor data in order to obtain the potential. An alternative local MHNC criterion due to Lado is rederived and extended, and it is also analyzed in light of the plot of η(s).

Marcus Bell-Shaped Electron Transfer Kinetics Observed in an Arrhenius Plot.

PubMed

Waskasi, Morteza M; Kodis, Gerdenis; Moore, Ana L; Moore, Thomas A; Gust, Devens; Matyushov, Dmitry V

2016-07-27

The Marcus theory of electron transfer predicts a bell-shaped dependence of the reaction rate on the reaction free energy. The top of the "inverted parabola" corresponds to zero activation barrier when the electron-transfer reorganization energy and the reaction free energy add up to zero. Although this point has traditionally been reached by altering the chemical structures of donors and acceptors, the theory suggests that it can also be reached by varying other parameters of the system including temperature. We find here dramatic evidence of this phenomenon from experiments on a fullerene-porphyrin dyad. Following photoinduced electron transfer, the rate of charge recombination shows a bell-shaped dependence on the inverse temperature, first increasing with cooling and then decreasing at still lower temperatures. This non-Arrhenius rate law is a result of a strong, approximately hyperbolic temperature variation of the reorganization energy and the reaction free energy. Our results provide potentially the cleanest confirmation of the Marcus energy gap law so far since no modification of the chemical structure is involved.

Quantum Transport near the Charge Neutrality Point in Inverted Type-II InAs/GaSb Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Pan, W.; Klem, J. F.; Kim, J. K.; Thalakulam, M.; Cich, M. J.; Lyo, S. K.

2013-03-01

We present here our recent quantum transport results around the charge neutrality point (CNP) in a type-II InAs/GaSb field-effect transistor. At zero magnetic field, a conductance minimum close to 4e2 / h develops at the CNP and it follows semi-logarithmic temperature dependence. In quantized magnetic (B) fields and at low temperatures, well developed integer quantum Hall states are observed in the electron as well as hole regimes. Electron transport shows noisy behavior around the CNP at extremely high B fields. When the diagonal conductivity σxx is plotted against the Hall conductivity σxy, a conductivity circle law is discovered, suggesting a chaotic quantum transport behavior. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

A compact holographic optical tweezers instrument

NASA Astrophysics Data System (ADS)

Gibson, G. M.; Bowman, R. W.; Linnenberger, A.; Dienerowitz, M.; Phillips, D. B.; Carberry, D. M.; Miles, M. J.; Padgett, M. J.

2012-11-01

Holographic optical tweezers have found many applications including the construction of complex micron-scale 3D structures and the control of tools and probes for position, force, and viscosity measurement. We have developed a compact, stable, holographic optical tweezers instrument which can be easily transported and is compatible with a wide range of microscopy techniques, making it a valuable tool for collaborative research. The instrument measures approximately 30×30×35 cm and is designed around a custom inverted microscope, incorporating a fibre laser operating at 1070 nm. We designed the control software to be easily accessible for the non-specialist, and have further improved its ease of use with a multi-touch iPad interface. A high-speed camera allows multiple trapped objects to be tracked simultaneously. We demonstrate that the compact instrument is stable to 0.5 nm for a 10 s measurement time by plotting the Allan variance of the measured position of a trapped 2 μm silica bead. We also present a range of objects that have been successfully manipulated.

Demodulation RFI statistics for a 3-stage op amp LED circuit

NASA Astrophysics Data System (ADS)

Whalen, James J.

An experiment has been performed to demonstrate the feasibility of combining several methods of electromagnetic-compatibility analysis. The part of the experiment that demonstrates how RF signals cause interference in an audio-frequency (AF) circuit and how the interference can be suppressed is described. The circuit includes three operational amplifiers (op amps) and a light-emitting diode (LED). A 50 percent amplitude-modulated (AM) radio-frequency-interference (RFI) signal is used, varied over the range from 0.1 to 400 MHz. The AM frequency is 1 kHz. The RFI is injected into the inverting input of the first op amp, and the 1-kHz demodulation response of the amplifier is amplified by the second and third op amps and lights the LED to provide a visual display of the existence of RFI. An RFI suppression capacitor was added to reduce the RFI. The demodulation RFI results are presented as scatter plots for 35 741 op amps. Mean values and standard deviations are also shown.

A Comparison of Landsat TM and ASTER for Equivalent Water Thickness Derivation in a Ponderosa Pine Ecosystem

NASA Astrophysics Data System (ADS)

Toomey, M.; Vierling, L.

2004-12-01

Landsat TM and ASTER satellite data can be used to make physically-based estimates of equivalent water thickness (EWT) in a Pinus ponderosa ecosystem. EWT is a measure of ecosystem water status and is an important parameter for studying ecosystem dynamics, fire potential, and biological responses to climate change. Near infrared (NIR) and shortwave infrared (SWIR) reflectances were simulated using the LIBERTY and GeoSAIL leaf and canopy reflectance models; the results were used to calculate a NIR/SWIR ratio and a normalized NIR/SWIR index. Index-EWT relationships were modeled and inverted for EWT derivation. Landsat and ASTER were used to make reasonably accurate estimates of EWT (± 17.3% and 19.4% mean error, respectively); TM band 5 and ASTER band 4 produced the best results. Exclusion of plots with dense understory vegetation reduced point scatter substantially, especially with Landsat (r2 = 0.847, ±13%), indicating that this method can provide robust EWT quantification in homogeneous conifer ecosystems.

Construction and evaluation of photovoltaic power generation and power storage system using SiC field-effect transistor inverter

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

Oku, Takeo, E-mail: oku@mat.usp.ac.jp; Matsumoto, Taisuke; Ohishi, Yuya

A power storage system using spherical silicon (Si) solar cells, maximum power point tracking charge controller, lithium-ion battery and a direct current-alternating current (DC-AC) inverter was constructed. Performance evaluation of the DC-AC inverter was carried out, and the DC-AC conversion efficiencies of the SiC field-effect transistor (FET) inverter was improved compared with those of the ordinary Si-FET based inverter.

Telomerase reverse transcriptase (TERT) promoter mutation analysis of benign, malignant and reactive urothelial lesions reveals a subpopulation of inverted papilloma with immortalizing genetic change.

PubMed

Cheng, Liang; Davidson, Darrell D; Wang, Mingsheng; Lopez-Beltran, Antonio; Montironi, Rodolfo; Wang, Lisha; Tan, Puay-Hoon; MacLennan, Gregory T; Williamson, Sean R; Zhang, Shaobo

2016-07-01

To understand more clearly the genetic ontogeny of inverted papilloma of urinary bladder, we analysed telomerase reverse transcriptase (TERT) promoter mutation status in a group of 26 inverted papillomas in comparison with the mutation status of urothelial carcinoma with inverted growth (26 cases), conventional urothelial carcinoma (36 Ta non-invasive urothelial carcinoma, 35 T2 invasive urothelial carcinoma) and cystitis glandularis (25 cases). TERT promoter mutations in inverted papilloma, urothelial carcinoma with inverted growth, urothelial carcinoma and cystitis glandularis were found in 15% (four of 26), 58% (15 of 26), 63% (45 of 71) and 0% (none of 25), respectively. C228T mutations were the predominant mutations (97%) found in bladder tumours, while C250T aberrations occurred in approximately 3% of bladder tumours. In the inverted papilloma group, TERT mutation occurred predominantly in female patients (P = 0.006). Among urothelial carcinomas, TERT promoter mutation status did not correlate with gender, histological grade or pathological stage. TERT promoter mutations were found in 15% of inverted papillomas. Our data suggest that there is a subpopulation of inverted papilloma that shares a carcinogenetic pathway with urothelial carcinoma with inverted growth and conventional urothelial carcinomas. Caution is warranted in exploring TERT promoter mutation status as a screening or adjunct diagnostic test for bladder cancer. © 2015 John Wiley & Sons Ltd.

Etiological role of human papillomavirus infection for inverted papilloma of the bladder.

PubMed

Shigehara, Kazuyoshi; Sasagawa, Toshiyuki; Doorbar, John; Kawaguchi, Shohei; Kobori, Yoshitomo; Nakashima, Takao; Shimamura, Masayoshi; Maeda, Yuji; Miyagi, Tohru; Kitagawa, Yasuhide; Kadono, Yoshifumi; Konaka, Hiroyuki; Mizokami, Atsushi; Koh, Eitetsu; Namiki, Mikio

2011-02-01

The status of human papillomavirus (HPV) infection in urothelial inverted papilloma was examined in the present study. Formalin-fixed and paraffin-embedded tissues from eight cases of inverted papilloma of the bladder were studied. The presence of HPV-DNA was examined by modified GP5/6+PCR using archival tissue sections by microdissection. HPV genotype was determined with a Hybri-Max HPV genotyping kit. Immunohistochemical analysis for p16-INK4a, mcm7, HPV-E4, and L1, and in situ hybridization for the HPV genome were performed. HPV was detected in seven of eight cases (87.5%) of inverted papilloma. Three cases were diagnosed as inverted papilloma with atypia, while the remaining five were typical cases. HPV-18 was detected in two cases, including one inverted papilloma with atypia, and HPV-16 was detected in four cases, including one inverted papilloma with atypia. Multiple HPV type infection was detected in one typical case and one atypical case. High-risk HPV was present in all HPV-positive cases. Cellular proteins, p16-INK4a and mcm7, which are surrogate markers for HPV-E7 expression, were detected in all HPV-positive cases, and their levels were higher in inverted papilloma with atypia than in typical cases. In contrast, HPV-E4 and L1, which are markers for HPV propagation, were observed in some parts of the typical inverted papilloma tissue. High-risk HPV infection may be one of the causes of urothelial inverted papilloma, and inverted papilloma with atypia may have malignant potential. 2010 Wiley-Liss, Inc.

Improved Performance via the Inverted Classroom

ERIC Educational Resources Information Center

Weinstein, Randy D.

2015-01-01

This study examined student performance in an inverted thermodynamics course (lectures provided by video outside of class) compared to a traditional lecture class. Students in the inverted class performed better on their exams. Students in the bottom third of the inverted course showed the greatest improvement. These bottom third students had a C…

Inverting the Linear Algebra Classroom

ERIC Educational Resources Information Center

Talbert, Robert

2014-01-01

The inverted classroom is a course design model in which students' initial contact with new information takes place outside of class meetings, and students spend class time on high-level sense-making activities. The inverted classroom model is so called because it inverts or "flips" the usual classroom design where typically class…

Efficient/reliable dc-to-dc inverter circuit

NASA Technical Reports Server (NTRS)

Pasciutti, E. R.

1970-01-01

Feedback loop, which contains an inductor in series with a saturable reactor, is added to a standard inverter circuit to permit the inverter power transistors to be switched in a controlled and efficient manner. This inverter is applicable where the power source has either high or low impedance properties.

Milliwatt dc/dc Inverter

NASA Technical Reports Server (NTRS)

Mclyman, C. W.

1983-01-01

Compact dc/dc inverter uses single integrated-circuit package containing six inverter gates that generate and amplify 100-kHz square-wave switching signal. Square-wave switching inverts 10-volt local power to isolated voltage at another desired level. Relatively high operating frequency reduces size of filter capacitors required, resulting in small package unit.

75 FR 36119 - In the Matter of Certain Cold Cathode Fluorescent Lamp (“CCFL”) Inverter Circuits and Products...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-24

... Cathode Fluorescent Lamp (``CCFL'') Inverter Circuits and Products Containing the Same; Notice of... States after importation of certain cold cathode fluorescent lamp inverter circuits and products..., and the sale within the United States after importation of CCFL inverter circuits and products...

Experimental Evaluation of PV Inverter Anti-Islanding with Grid Support Functions in Multi-Inverter Island Scenarios

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

Hoke, Anderson; Nelson, Austin; Miller, Brian

As PV and other DER systems are connected to the grid at increased penetration levels, island detection may become more challenging for two reasons: 1.) In islands containing many DERs, active inverter-based anti-islanding methods may have more difficulty detecting islands because each individual inverter's efforts to detect the island may be interfered with by the other inverters in the island. 2.) The increasing numbers of DERs are leading to new requirements that DERs ride through grid disturbances and even actively try to regulate grid voltage and frequency back towards nominal operating conditions. These new grid support requirements may directly ormore » indirectly interfere with anti-islanding controls. This report describes a series of tests designed to examine the impacts of both grid support functions and multi-inverter islands on anti-islanding effectiveness. Crucially, the multi-inverter anti-islanding tests described in this report examine scenarios with multiple inverters connected to multiple different points on the grid. While this so-called 'solar subdivision' scenario has been examined to some extent through simulation, this is the first known work to test it using hardware inverters. This was accomplished through the use of power hardware-in-the-loop (PHIL) simulation, which allows the hardware inverters to be connected to a real-time transient simulation of an electric power system that can be easily reconfigured to test various distribution circuit scenarios. The anti-islanding test design was a modified version of the unintentional islanding test in IEEE Standard 1547.1, which creates a balanced, resonant island with the intent of creating a highly challenging condition for island detection. Three common, commercially available single-phase PV inverters from three different manufacturers were tested. The first part of this work examined each inverter individually using a series of pure hardware resistive-inductive-capacitive (RLC) resonant load based anti-islanding tests to determine the worst-case configuration of grid support functions for each inverter. A grid support function is a function an inverter performs to help stabilize the grid or drive the grid back towards its nominal operating point. The four grid support functions examined here were voltage ride-through, frequency ride-through, Volt-VAr control, and frequency-Watt control. The worst-case grid support configuration was defined as the configuration that led to the maximum island duration (or run-on time, ROT) out of 50 tests of each inverter. For each of the three inverters, it was observed that maximum ROT increased when voltage and frequency ride-through were activated. No conclusive evidence was found that Volt-VAr control or frequency-Watt control increased maximum ROT. Over all single-inverter test cases, the maximum ROT was 711 ms, well below the two-second limit currently imposed by IEEE Standard 1547-2003. A subsequent series of 244 experiments tested all three inverters simultaneously in the same island. These tests again used a procedure based on the IEEE 1547.1 unintentional islanding test to create a difficult-to-detect island condition. For these tests, which used the two worst-case grid support function configurations from the single-inverter tests, the inverters were connected to a variety of island circuit topologies designed to represent the variety of multiple-inverter islands that may occur on real distribution circuits. The interconnecting circuits and the resonant island load itself were represented in the real-time PHIL model. PHIL techniques similar to those employed here have been previously used and validated for anti-islanding tests, and the PHIL resonant load model used in this test was successfully validated by comparing single-inverter PHIL tests to conventional tests using an RLC load bank.« less

A new approach to large area microchannel plate manufacture

NASA Technical Reports Server (NTRS)

1986-01-01

Methods of manufacture of twisted single elements as the base for producing microchannel plates (MCP) are discussed. Initial evaluations validated the off-axis channel concept and no technological roadblocks were identified which would prevent fabrication of high gain, high spatial resolution, large format MCP's using this technique. The first MP's have operated at stable gains of 3 million with pulse height resolution superior to results obtained by standard chevron MCP's.

Stimulated Electron Desorption Studies from Microwave Vacuum Electronics / High Power Microwave Materials

DTIC Science & Technology

2010-02-11

purchase a new gun. Mr. Mike Ackeret ( Transfer Engineering Inc.) Transfer Engineering’s expertise in specialty UHV work and machining propelled...modifications they helped design for the test stand. With UNLV guidance, Transfer Engineering designed and built the original UNLV SEE Test Stand...Staib electron gun, an isolated beam drift tube, a hexanode delay line with a chevron microchannel plate (MCP) stack, an isolated grid, an isolated