Low-Cost, Net-Shape Ceramic Radial Turbine Program

DTIC Science & Technology

1985-05-01

PROGRAM ELEMENT. PROJECT. TASK Garrett Turbine Engine Company AE OKUI UBR 111 South 34th Street, P.O. Box 2517 Phoenix, Arizona 85010 %I. CONTROLLING...processing iterations. Program management and materials characterization were conducted at Garrett Turbine Engine Company (GTEC), test bar and rotor...automotive gas turbine engine rotor development efforts at ACC. xvii PREFACE This is the final technical report of the Low-Cost, Net- Shape Ceramic

One-step manufacturing of innovative flat-knitted 3D net-shape preforms for composite applications

NASA Astrophysics Data System (ADS)

Bollengier, Quentin; Wieczorek, Florian; Hellmann, Sven; Trümper, Wolfgang; Cherif, Chokri

2017-10-01

Mostly due to the cost-intensive manually performed processing operations, the production of complex-shaped fibre reinforced plastic composites (FRPC) is currently very expensive and therefore either restricted to sectors with high added value or for small batch applications (e.g. in the aerospace or automotive industry). Previous works suggest that the successful integration of conventional textile manufacturing processes in the FRPC-process chain is the key to a cost-efficient manufacturing of complex three-dimensional (3D) FRPC-components with stress-oriented fibre arrangement. Therefore, this work focuses on the development of the multilayer weft knitting technology for the one-step manufacturing of complex 3D net-shaped preforms for high performance FRPC applications. In order to highlight the advantages of net-shaped multilayer weft knitted fabrics for the production of complex FRPC parts, seamless preforms such as 3D skin-stringer structures and tubular fabrics with load oriented fibre arrangement are realised. In this paper, the development of the textile bindings and performed technical modifications on flat knitting machines are presented. The results show that the multilayer weft knitting technology meets perfectly the requirements for a fully automated and reproducible manufacturing of complex 3D textile preforms with stress-oriented fibre arrangement.

2D net shape weaving for cost effective manufacture of textile reinforced composites

NASA Astrophysics Data System (ADS)

Vo, D. M. P.; Kern, M.; Hoffmann, G.; Cherif, C.

2017-10-01

Despite significant weight and performance advantages over metal parts, the today’s demand for fibre-reinforced polymer composites (FRPC) has been limited mainly by their large manufacturing cost. The combination of dry textile preforms and low-cost consolidation processes such as resin transfer molding (RTM) has been appointed as a promising approach to low-cost FRPC manufacture. At the current state of the art, tooling and impregnation technology is well understood whereas preform fabrication technology has not been developed effectively. This paper presents an advanced 2D net shape weaving technology developed with the aim to establish a more cost effective system for the manufacture of dry textile preforms for FRPC. 2D net shape weaving is developed based on open reed weave (ORW) technology and enables the manufacture of 2D contoured woven fabrics with firm edge, so that oversize cutting and hand trimming after molding are no longer required. The introduction of 2D net shape woven fabrics helps to reduce material waste, cycle time and preform manufacturing cost significantly. Furthermore, higher grade of automation in preform fabrication can be achieved.

Metal Matrix Composite LOX Turbopump Housing Via Novel Tool-Less Net-Shape Pressure Infiltration Casting Technology

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Lee, Jonathan; Bhat, Biliyar; Wells, Doug; Gregg, Wayne; Marsh, Matthew; Genge, Gary; Forbes, John; Salvi, Alex; Cornie, James A.;

Progress in net shape fabrication of alpha SiC turbine components

NASA Technical Reports Server (NTRS)

Storm, R. S.; Naum, R. G.

1983-01-01

The development status of component technology in an automotive gas turbine Ceramic Applications in Turbine Engines program is discussed, with attention to such materials and processes having a low cost, net shape fabrication potential as sintered alpha-SiC that has been fashioned by means of injection molding, slip casting, and isostatic pressing. The gas turbine elements produced include a gasifier turbine rotor, a turbine wheel, a connecting duct, a combustor baffle, and a transition duct.

Advanced high-temperature alloys: Processing and properties; Proceedings of the Nicholas J. Grant Symposium, MIT, Cambridge, MA, June 16-18, 1985

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

Allen, S.M.; Pelloux, R.M.; Widmer, R.

1986-01-01

Historical and advanced methods of producing, forming and polishing alloys in billets and net shapes are explored. Attention is given to the deficiencies in arc furnace melts and to the benefits which are accruing from rapid solidification processing, powder metallurgy and superplastic forming. The techniques employed in these methods for processing materials to desired shapes, mainly for aircraft gas turbine engines, are described, along with the microstructures and mechanical properties which are obtained. The state of the art in casting and forming techniques which yield the most favorable properties in intermetallic compound-based alloys, superalloys, glasses and metacrystals are identified. Finally,more » research directions being pursued to obtain higher purity, enhanced temperature, longer lifetime, damage resistant alloys which can be formed to net shapes are discussed.« less

Development of ceramic matrix composites for application in the ceramic technology for Advanced Heat Engines Project: Phase 2a, Development of in-situ toughened silicon nitride. Final report

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

Pollinger, J.; Newson, D.; Yeh, H.

1992-06-01

The objective of this program was to develop a net shape forming process for an in-situ reinforced Si{sub 3}N{sub 4} (AS-700). AS-700 was initially developed using cold isostatic pressing (CIP) of alcohol milled powders. The CIP`ed AS-700 material exhibited a moderate strength (690 MPa) and high toughness (9 MPa{radical}m) at room temperature. In addition to net-shape process development, optimization of AS-700 properties was also investigated through the refinement of densification processes, and evaluation of the effect of Si{sub 3}N{sub 4} powder properties on resulting microstructure and mechanical properties. Slip casting was chosen as the net-shape forming process. A slip castingmore » process was successfully developed for forming green parts ranging from thin plates to thick cylinders, and to large complex shaped turbine rotors. The densification cycle was optimized to achieve full density parts without any cracks or warpage, and with comparable properties and microstructure to the CIP`ed baseline AS-700 material. The evaluation of six (6) alternate Si{sub 3}N{sub 4} powders indicated that Si{sub 3}N{sub 4} powders have a very strong influence on the development of resulting AS-700 in-situ microstructures and mechanical properties. The AS-700 slip casting process and optimized densification process were then combined and a number of test specimens were fabricated. The mechanical properties and microstructure of the optimized slip cast AS-700 Si{sub 3}N{sub 4} were then fully characterized. The key property values are: 695 MPa at room temperature, 446 MPa at 1370{degree}C flexural strengths and 8.25 MPa{radical}m toughness.« less

Progress on high-performance rapid prototype aluminum mirrors

NASA Astrophysics Data System (ADS)

Woodard, Kenneth S.; Myrick, Bruce H.

2017-05-01

Near net shape parts can be produced using some very old processes (investment casting) and the relatively new direct metal laser sintering (DMLS) process. These processes have significant advantages for complex blank lightweighting and costs but are not inherently suited for producing high performance mirrors. The DMLS process can provide extremely complex lightweight structures but the high residual stresses left in the material results in unstable mirror figure retention. Although not to the extreme intricacy of DMLS, investment casting can also provide complex lightweight structures at considerably lower costs than DMLS and even conventional wrought mirror blanks but the less than 100% density for casting (and also DMLS) limits finishing quality. This paper will cover the progress that has been made to make both the DMLS and investment casting processes into viable near net shape blank options for high performance aluminum mirrors. Finish and figure results will be presented to show performance commensurate with existing conventional processes.

Microgravity Manufacturing Via Fused Deposition

NASA Technical Reports Server (NTRS)

Cooper, K. G.; Griffin, M. R.

2003-01-01

Manufacturing polymer hardware during space flight is currently outside the state of the art. A process called fused deposition modeling (FDM) can make this approach a reality by producing net-shaped components of polymer materials directly from a CAE model. FDM is a rapid prototyping process developed by Stratasys, Inc.. which deposits a fine line of semi-molten polymer onto a substrate while moving via computer control to form the cross-sectional shape of the part it is building. The build platen is then lowered and the process is repeated, building a component directly layer by layer. This method enables direct net-shaped production of polymer components directly from a computer file. The layered manufacturing process allows for the manufacture of complex shapes and internal cavities otherwise impossible to machine. This task demonstrated the benefits of the FDM technique to quickly and inexpensively produce replacement components or repair broken hardware in a Space Shuttle or Space Station environment. The intent of the task was to develop and fabricate an FDM system that was lightweight, compact, and required minimum power consumption to fabricate ABS plastic hardware in microgravity. The final product of the shortened task turned out to be a ground-based breadboard device, demonstrating miniaturization capability of the system.

Pull-Up Nets

ERIC Educational Resources Information Center

Meenan, Liz

2008-01-01

When the author began teaching, she always hit a problem when it came to 3D shapes. She wanted the pupils to get a feel for them, and she would get them to make the shapes from their nets. The pupils would first try to visualize how the 2D nets could become 3D shapes and then they would physically fold the nets into the shapes for themselves.…

NASA Astrophysics Data System (ADS)

McHugh, K. M.; Key, J. F.

1994-06-01

Spray forming is a near- net- shape fabrication technology in which a spray of finely atomized liquid droplets is deposited onto a suitably shaped substrate or pattern to produce a coherent solid. The technology offers unique opportunities for simplifying materials processing, often while substantially improving product quality. Spray forming is applicable to a wide range of metals and nonmetals and offers property improvements resulting from rapid solidification (e.g., refined microstructures, extended solid solubilities, and reduced segregation). Economic benefits result from process simplification and the elimination of unit operations. Researchers at the Idaho National Engineering Laboratory (INEL) are developing spray forming technology for producing near- net- shape solids and coatings of a variety of metals, polymers, and composite materials using de Laval nozzles. This article briefly describes the atomization behavior of liquid metals in linear de Laval nozzles and illustrates the versatility of the process by summarizing results from two spray forming programs. In one program, low-carbon steel strip >0.75 mm thick was produced; in the other, polymer membranes ˜5 μm thick were spray formed.

Near-Net-Shape Production of Hollow Titanium Alloy Components via Electrochemical Reduction of Metal Oxide Precursors in Molten Salts

NASA Astrophysics Data System (ADS)

Hu, Di; Xiao, Wei; Chen, George Z.

2013-04-01

Metal oxide precursors (ca. 90 wt pct Ti, 6 wt pct Al, and 4 wt pct V) were prepared with a hollow structure in various shapes such as a sphere, miniature golf club head, and cup using a one-step solid slip-casting process. The precursors were then electro-deoxidized in molten calcium chloride [3.2 V, 1173 K (900 °C)] against a graphite anode. After 24 hours of electrolysis, the near-net-shape Ti-6Al-4V product maintained its original shape with controlled shrinkage. Oxygen contents in the Ti-6Al-4V components were typically below 2000 ppm. The maximum compressive stress and modulus of electrolytic products obtained in this work were approximately 243 MPa and 14 GPa, respectively, matching with the requirement for medical implants. Further research directions are discussed for mechanical improvement of the products via densification during or after electrolysis. This simple, fast, and energy-efficient near-net-shape manufacturing method could allow titanium alloy components with desired geometries to be prepared directly from a mixture of metal oxides, promising an innovative technology for the low-cost production of titanium alloy components.

Production of aluminum-lithium near net shape extruded cylinders

NASA Technical Reports Server (NTRS)

Hartley, Paula J.

1995-01-01

In the late 1980's, under funding from the Advanced Launch System Program, numerous near net shape technologies were investigated as a means for producing high quality, low cost Aluminum-Lithium (Al-Li) hardware. Once such option was to extrude near net shape barrel panels instead of producing panels by machining thick plate into a final tee-stiffened configuration (which produced up to 90% scrap). This method offers a reduction in the volume of scrap and consequently reduces the buy-to-fly cost. Investigation into this technology continued under Shuttle-C funding where four Al alloys 2219, 2195, 2096, and RX 818 were extruded. Presented herein are the results of that program. Each alloy was successfully extruded at Wyman Gordon, opened and flattened at Ticorm, and solution heat treated and stretched at Reynolds Metals Company. The first two processes were quite successful while the stretching process did offer some challenges. Due to the configuration of the panels and the stretch press set-up, it was difficult to induce a consistent percentage of cold work throughout the length and width of each panel. The effects of this variation will be assessed in the test program to be conducted at a future date.

Netcast™ Shape Casting Technology: A Technological Breakthrough that Enhances the Cost Effectiveness of Aluminum Forgings

NASA Astrophysics Data System (ADS)

Anderson, Mark; Bruski, Richard; Groszkiewicz, Daniel; Wagstaff, Bob

A new Direct Chill (DC) casting process is introduced to semi-continuous casting where near net shaped ingots are solidified. This process is currently being used at Alcan Engineered Cast Products (ECP) facility in Jonquiere, Canada, sectioned, then forged at Alcoa Automotive, Kentucky Casting Center (KCC). Finished forgings are machined and assembled into the Ford D/EW98 platform as suspension components. A brief description of the process and the implications on the forging process are presented.

Fast Response Shape Memory Effect Titanium Nickel (TiNi) Foam Torque Tubes

NASA Technical Reports Server (NTRS)

Jardine, Peter

2014-01-01

Shape Change Technologies has developed a process to manufacture net-shaped TiNi foam torque tubes that demonstrate the shape memory effect. The torque tubes dramatically reduce response time by a factor of 10. This Phase II project matured the actuator technology by rigorously characterizing the process to optimize the quality of the TiNi and developing a set of metrics to provide ISO 9002 quality assurance. A laboratory virtual instrument engineering workbench (LabVIEW'TM')-based, real-time control of the torsional actuators was developed. These actuators were developed with The Boeing Company for aerospace applications.

Neural-Net Processed Characteristic Patterns for Measurement of Structural Integrity of Pressure Cycled Components

NASA Technical Reports Server (NTRS)

Decker, A. J.

2001-01-01

A neural-net inspection process has been combined with a bootstrap training procedure and electronic holography to detect changes or damage in a pressure-cycled International Space Station cold plate to be used for cooling instrumentation. The cold plate was excited to vibrate in a normal mode at low amplitude, and the neural net was trained by example to flag small changes in the mode shape. The NDE (nondestructive-evaluation) technique is straightforward but in its infancy; its applications are ad-hoc and uncalibrated. Nevertheless previous research has shown that the neural net can detect displacement changes to better than 1/100 the maximum displacement amplitude. Development efforts that support the NDE technique are mentioned briefly, followed by descriptions of electronic holography and neural-net processing. The bootstrap training procedure and its application to detection of damage in a pressure-cycled cold plate are discussed. Suggestions for calibrating and quantifying the NDE procedure are presented.

Applications for Gradient Metal Alloys Fabricated Using Additive Manufacturing

NASA Technical Reports Server (NTRS)

Hofmann, Douglas C.; Borgonia, John Paul C.; Dillon, Robert P.; Suh, Eric J.; Mulder, jerry L.; Gardner, Paul B.

2013-01-01

Recently, additive manufacturing (AM) techniques have been developed that may shift the paradigm of traditional metal production by allowing complex net-shaped hardware to be built up layer-by-layer, rather than being machined from a billet. The AM process is ubiquitous with polymers due to their low melting temperatures, fast curing, and controllable viscosity, and 3D printers are widely available as commercial or consumer products. 3D printing with metals is inherently more complicated than with polymers due to their higher melting temperatures and reactivity with air, particularly when heated or molten. The process generally requires a high-power laser or other focused heat source, like an electron beam, for precise melting and deposition. Several promising metal AM techniques have been developed, including laser deposition (also called laser engineered net shaping or LENS® and laser deposition technology (LDT)), direct metal laser sintering (DMLS), and electron beam free-form (EBF). These machines typically use powders or wire feedstock that are melted and deposited using a laser or electron beam. Complex net-shape parts have been widely demonstrated using these (and other) AM techniques and the process appears to be a promising alternative to machining in some cases. Rather than simply competing with traditional machining for cost and time savings, the true advantage of AM involves the fabrication of hardware that cannot be produced using other techniques. This could include parts with "blind" features (like foams or trusses), parts that are difficult to machine conventionally, or parts made from materials that do not exist in bulk forms. In this work, the inventors identify that several AM techniques can be used to develop metal parts that change composition from one location in the part to another, allowing for complete control over the mechanical or physical properties. This changes the paradigm for conventional metal fabrication, which relies on an assortment of "post-processing" methods to locally alter properties (such as coating, heat treating, work hardening, shot peening, etching, anodizing, among others). Building the final part in an additive process allows for the development of an entirely new class of metals, so-called "functionally graded metals" or "gradient alloys." By carefully blending feedstock materials with different properties in an AM process, hardware can be developed with properties that cannot be obtained using other techniques but with the added benefit of the net-shaped fabrication that AM allows.

Investigation of the laser engineered net shaping process for nanostructured cermets

NASA Astrophysics Data System (ADS)

Xiong, Yuhong

Laser Engineered Net Shaping (LENSRTM) is a solid freeform fabrication (SFF) technology that combines high power laser deposition and powder metallurgy technologies. The LENSRTM technology has been used to fabricate a number of metallic alloys with improved physical and mechanical material properties. The successful application provides a motivation to also apply this method to fabricate non-metallic alloys, such as tungsten carbide-cobalt (WC-Co) cermets in a timely and easy way. However, reports on this topic are very limited. In this work, the LENSRTM technology was used to investigate its application to nanostructured WC-Co cermets, including processing conditions, microstructural evolution, thermal behavior, mechanical properties, and environmental and economic benefits. Details of the approaches are described as follows. A comprehensive analysis of the relationships between process parameters, microstructural evolution and mechanical properties was conducted through various analytical techniques. Effects of process parameters on sample profiles and microstructures were analyzed. Dissolution, shape change and coarsening of WC particles were investigated to study the mechanisms of microstructural evolution. The thermal features were correlated with the microstructure and mechanical properties. The special thermal behavior during this process and its relevant effects on the microstructure have been experimentally studied and numerically simulated. A high-speed digital camera was applied to study the temperature profile, temperature gradient and cooling rate in and near the molten pool. Numerical modeling was employed for 3D samples using finite element method with ADINA software for the first time. The validated modeling results were used to interpret microstructural evolution and thermal history. In order to fully evaluate the capability of the LENSRTM technology for the fabrication of cermets, material properties of WC-Co cermets produced by different powder metallurgy technologies were compared. In addition, another cermet system, nanostructured titanium/tungsten carbide-nickel ((Ti,W)C-Ni) powder, prepared using high-energy ball milling process, was also deposited by the LENSRTM technology. Because of the near net shape feature of the LENSRTM process, special emphasis was also placed on its potential environmental and economic benefits by applying life cycle assessment (LCA) and technical cost modeling (TCM). Comparisons were conducted between the conventional powder metallurgy processes and the LENSRTM process.

Material Gradients in Oxygen System Components Improve Safety

NASA Technical Reports Server (NTRS)

Forsyth, Bradley S.

2011-01-01

Oxygen system components fabricated by Laser Engineered Net Shaping (TradeMark) (LENS(TradeMark)) could result in improved safety and performance. LENS(TradeMark) is a near-net shape manufacturing process fusing powdered materials injected into a laser beam. Parts can be fabricated with a variety of elemental metals, alloys, and nonmetallic materials without the use of a mold. The LENS(TradeMark) process allows the injected materials to be varied throughout a single workpiece. Hence, surfaces exposed to oxygen could be constructed of an oxygen-compatible material while the remainder of the part could be one chosen for strength or reduced weight. Unlike conventional coating applications, a compositional gradient would exist between the two materials, so no abrupt material boundary exists. Without an interface between dissimilar materials, there is less tendency for chipping or cracking associated with thermal-expansion mismatches.

Non-Magnetic, Tough, Corrosion- and Wear-Resistant Knives From Bulk Metallic Glasses and Composites

NASA Technical Reports Server (NTRS)

Hoffman, Douglas C.; Potter, Benjamin

2013-01-01

Quality knives are typically fabricated from high-strength steel alloys. Depending on the application, there are different requirements for mechanical and physical properties that cause problems for steel alloys. For example, diver's knives are generally used in salt water, which causes rust in steel knives. Titanium diver's knives are a popular alternative due to their salt water corrosion resistance, but are too soft to maintain a sharp cutting edge. Steel knives are also magnetic, which is undesirable for military applications where the knives are used as a tactical tool for diffusing magnetic mines. Steel is also significantly denser than titanium (8 g/cu cm vs. 4.5 g/cu cm), which results in heavier knives for the same size. Steel is hard and wear-resistant, compared with titanium, and can keep a sharp edge during service. A major drawback of both steel and titanium knives is that they must be ground or machined into the final knife shape from a billet. Since most knives have a mirrored surface and a complex shape, manufacturing them is complex. It would be more desirable if the knife could be cast into a net or near-net shape in a single step. The solution to the deficiencies of titanium, steel, and ceramic knives is to fabricate them using bulk metallic glasses (or composites). These alloys can be cast into net or near-net shaped knives with a combination of properties that exceed both titanium and steel. A commercially viable BMG (bulk metallic glass) or composite knife is one that exhibits one or all of the following properties: It is based on titanium, has a self-sharpening edge, can retain an edge during service, is hard, is non-magnetic, is corrosion-resistant against a variety of corrosive environments, is tough (to allow for prying), can be cast into a net-shape with a mirror finish and a complex shape, has excellent wear resistance, and is low-density. These properties can be achieved in BMG and composites through alloy chemistry and processing. For each desired property for knife fabrication and performance, there is an alloy development strategy that optimizes behavior. Although BMG knives have been demonstrated as far back as 1995, they never found commercial success because they had to be ground (which presented problems because the alloys contained beryllium), they weren't low cost (because they weren't cast to a net-shape), they were brittle (because they were made with a low-quality commercial material), and they had extremely poor corrosion resistance (because corrosion was not well-understood in these materials). Ultimately, these shortcomings prevented the widespread commercialization. In the current work, the inventors have applied more than a decade of research on BMGs from Caltech and JPL to develop a better understanding of how to make BMG knives that exhibit an optimal combination of properties, processing and cost. Alloys have been developed based in titanium (and other metals), that exhibit high toughness, high hardness, excellent corrosion resistance, no ferromagnetism, edge-retaining selfsharpening, and the ability to be cast like a plastic using commercially available casting techniques (currently used by commercial companies such as Liquidmetal Technologies and Visser Precision Casting). The inventors argue that depending on the application (diving, military, tactical, utility, etc.) there is an optimal combination of design and alloy composition. Moreover, with new casting technologies not available at the inception of these materials, net-shaped knives can be cast into complex shapes that require no aftermarket forming, except for sharpening using water-cooled polishing wheel. These combinations of discoveries seek to make low-cost BMG knives commercially viable products that have no equal among metal or ceramic knives. Current work at JPL focuses on net-shape casting of these alloys and testing their mechanical properties versus commercially available knives to demonstrate their benefits.

Laser Metal Deposition as Repair Technology for a Gas Turbine Burner Made of Inconel 718

NASA Astrophysics Data System (ADS)

Petrat, Torsten; Graf, Benjamin; Gumenyuk, Andrey; Rethmeier, Michael

Maintenance, repair and overhaul of components are of increasing interest for parts of high complexity and expensive manufacturing costs. In this paper a production process for laser metal deposition is presented, and used to repair a gas turbine burner of Inconel 718. Different parameters for defined track geometries were determined to attain a near net shape deposition with consistent build-up rate for changing wall thicknesses over the manufacturing process. Spot diameter, powder feed rate, welding velocity and laser power were changed as main parameters for a different track size. An optimal overlap rate for a constant layer height was used to calculate the best track size for a fitting layer width similar to the part dimension. Deviations in width and height over the whole build-up process were detected and customized build-up strategies for the 3D sequences were designed. The results show the possibility of a near net shape repair by using different track geometries with laser metal deposition.

INEL Spray-forming Research

NASA Technical Reports Server (NTRS)

Mchugh, Kevin M.; Key, James F.

1993-01-01

Spray forming is a near-net-shape fabrication technology in which a spray of finely atomized liquid droplets is deposited onto a suitably shaped substrate or mold to produce a coherent solid. The technology offers unique opportunities for simplifying materials processing without sacrificing, and oftentimes substantially improving, product quality. Spray forming can be performed with a wide range of metals and nonmetals, and offers property improvements resulting from rapid solidification (e.g., refined microstructures, extended solid solubilities and reduced segregation). Economic benefits result from process simplification and the elimination of unit operations. Researchers at the Idaho National Engineering Laboratory (INEL) are developing spray-forming technology for producing near-net-shape solids and coatings of a variety of metals, polymers, and composite materials. Results from several spray forming programs are presented to illustrate the range of capabilities of the technique as well as the accompanying technical and economic benefits. Low-carbon steel strip greater than 0.75 mm thick and polymer membranes for gas/gas and liquid/liquid separations that were spray formed are discussed; recent advances in spray forming molds, dies, and other tooling using low-melting-point metals are described.

Powder-Coated Towpreg: Avenues to Near Net Shape Fabrication of High Performance Composites

NASA Technical Reports Server (NTRS)

Johnston, N. J.; Cano, R. J.; Marchello, J. M.; Sandusky, D. A.

1995-01-01

Near net shape parts were fabricated from powder-coated preforms. Key issues including powder loss during weaving and tow/tow friction during braiding were addressed, respectively, by fusing the powder to the fiber prior to weaving and applying a water-based gel to the towpreg prior to braiding. A 4:1 debulking of a complex 3-D woven powder-coated preform was achieved in a single step utilizing expansion rubber molding. Also, a process was developed for using powder-coated towpreg to fabricate consolidated ribbon having good dimensional integrity and low voids. Such ribbon will be required for in situ fabrication of structural components via heated head advanced tow placement. To implement process control and ensure high quality ribbon, the ribbonizer heat transfer and pulling force were modeled from fundamental principles. Most of the new ribbons were fabricated from dry polyarylene ether and polymide powders.

Formation of amorphous metal alloys by chemical vapor deposition

DOEpatents

Mullendore, Arthur W.

1990-01-01

Amorphous alloys are deposited by a process of thermal dissociation of mixtures or organometallic compounds and metalloid hydrides, e.g., transition metal carbonyl such as nickel carbonyl, and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit.

Hot working behavior of selective laser melted and laser metal deposited Inconel 718

NASA Astrophysics Data System (ADS)

Bambach, Markus; Sizova, Irina

2018-05-01

The production of Nickel-based high-temperature components is of great importance for the transport and energy sector. Forging of high-temperature alloys often requires expensive dies, multiple forming steps and leads to forged parts with tolerances that require machining to create the final shape and a large amount of scrap. Additive manufacturing offers the possibility to print the desired shapes directly as net-shape components, requiring only little additional effort in machining. Especially for high-temperature alloys carrying a large amount of energy per unit mass, additive manufacturing could be more energy-efficient than forging if the energy contained in the machining scrap exceeds the energy needed for powder production and laser processing. However, the microstructure and performance of 3d-printed parts will not reach the level of forged material unless further expensive processes such as hot-isostatic pressing are used. Using the design freedom and possibilities to locally engineer material, additive manufacturing could be combined with forging operations to novel process chains, offering the possibility to reduce the number of forging steps and to create near-net shape forgings with desired local properties. Some innovative process chains combining additive manufacturing and forging have been patented recently, but almost no scientific knowledge on the workability of 3D printed preforms exists. The present study investigates the flow stress and microstructure evolution during hot working of pre-forms produced by laser powder deposition and selective laser melting (Figure 1) and puts forward a model for the flow stress.

Lightweight Aluminum/Nano composites for Automotive Drive Train Applications

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

Chelluri, Bhanumathi; Knoth, Edward A.; Schumaker, Edward J.

2012-12-14

During Phase I, we successfully processed air atomized aluminum powders via Dynamic Magnetic Compaction (DMC) pressing and subsequent sintering to produce parts with properties similar to wrought aluminum. We have also showed for the first time that aluminum powders can be processed without lubes via press and sintering to 100 % density. This will preclude a delube cycle in sintering and promote environmentally friendly P/M processing. Processing aluminum powders via press and sintering with minimum shrinkage will enable net shape fabrication. Aluminum powders processed via a conventional powder metallurgy process produce too large a shrinkage. Because of this, sinter partsmore » have to be machined into specific net shape. This results in increased scrap and cost. Fully sintered aluminum alloy under this Phase I project has shown good particle-to-particle bonding and mechanical properties. We have also shown the feasibility of preparing nano composite powders and processing via pressing and sintering. This was accomplished by dispersing nano silicon carbide (SiC) powders into aluminum matrix comprising micron-sized powders (<100 microns) using a proprietary process. These composite powders of Al with nano SiC were processed using DMC press and sinter process to sinter density of 85-90%. The process optimization along with sintering needs to be carried out to produce full density composites.« less

Progress Toward an Integration of Process-Structure-Property-Performance Models for "Three-Dimensional (3-D) Printing" of Titanium Alloys

NASA Astrophysics Data System (ADS)

Collins, P. C.; Haden, C. V.; Ghamarian, I.; Hayes, B. J.; Ales, T.; Penso, G.; Dixit, V.; Harlow, G.

2014-07-01

Electron beam direct manufacturing, synonymously known as electron beam additive manufacturing, along with other additive "3-D printing" manufacturing processes, are receiving widespread attention as a means of producing net-shape (or near-net-shape) components, owing to potential manufacturing benefits. Yet, materials scientists know that differences in manufacturing processes often significantly influence the microstructure of even widely accepted materials and, thus, impact the properties and performance of a material in service. It is important to accelerate the understanding of the processing-structure-property relationship of materials being produced via these novel approaches in a framework that considers the performance in a statistically rigorous way. This article describes the development of a process model, the assessment of key microstructural features to be incorporated into a microstructure simulation model, a novel approach to extract a constitutive equation to predict tensile properties in Ti-6Al-4V (Ti-64), and a probabilistic approach to measure the fidelity of the property model against real data. This integrated approach will provide designers a tool to vary process parameters and understand the influence on performance, enabling design and optimization for these highly visible manufacturing approaches.

Method for Fabricating Composite Structures Using Pultrusion Processing

NASA Technical Reports Server (NTRS)

Farley, Gary L. (Inventor)

2000-01-01

A method for fabricating composite structures at a low-cost, moderate-to-high production rate. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform and debulking the partially debulked preform to form a netshape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length and electronbeam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates, resulting in lower cost and high structural performance.

Energetic additive manufacturing process with feed wire

DOEpatents

Harwell, Lane D.; Griffith, Michelle L.; Greene, Donald L.; Pressly, Gary A.

2000-11-07

A process for additive manufacture by energetic wire deposition is described. A source wire is fed into a energy beam generated melt-pool on a growth surface as the melt-pool moves over the growth surface. This process enables the rapid prototyping and manufacture of fully dense, near-net shape components, as well as cladding and welding processes. Alloys, graded materials, and other inhomogeneous materials can be grown using this process.

Formation of amorphous metal alloys by chemical vapor deposition

DOEpatents

Mullendore, A.W.

1988-03-18

Amorphous alloys are deposited by a process of thermal dissociation of mixtures of organometallic compounds and metalloid hydrides,e.g., transition metal carbonyl, such as nickel carbonyl and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit. 1 fig.

Mechanism of concave ``tafoni'' and convex ``domal shape'' formation on TRIASSIC red sandstone of some old buildings, Chester City, UK, Case study

NASA Astrophysics Data System (ADS)

Kamh, G. M. E.

2005-08-01

The weathering factors act on the recent and archaeological sites through different processes based on the dominant environmental conditions. The net result of weathering is deformation of the original form of construction rock. In the current case study, the main aim is to find out the mechanism of formation of two different weathering forms recorded on many old buildings taking Chester City as a case study. The construction rock in the case study is arenitic sandstone with carbonate content ranging from 0.0 to 15.6%. The sandstone blocks are cemented together by hydraulic lime mortar that can easily be altered chemically to salts by acid rain that dominates at the study area. In case of mortar with worse geotechnical limits than the sandstone blocks, the net result is convex “domal” shape blocks, but in case of mortar with better geotechnical limits than the construction sandstone, the net result of weathering is tafoni “concave” weathering form.

Collaboration for the Advancement of Indirect 3D Printing Technology

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

Cordero, Zachary; Elliott, Amy M.

Amorphous powders often possess high hardness values and other useful mechanical properties. However, densifying these powders into complex shapes while retaining their unique properties is a challenge with standard processing routes. Pressureless sintering, for example, can densify intricate green parts composed of rapidly-solidified powders. But this process typically involves long exposures to elevated temperatures, during which the non-equilibrium microstructure of the powder can evolve towards lower energy configurations with inferior properties. Pressure-assisted compaction techniques, by contrast, can consolidate green parts with simple shapes while preserving the microstructure and properties of the powder feedstock. But parts made with these processes generallymore » require additional post-processing, including machining, which introduces new challenges due to the high hardness of these materials. One processing route that can potentially avoid these issues is Indirect 3D Printing (I-3DP; aka Binder Jetting) followed by melt infiltration. In I-3DP, an organic binder is used to join powder feedstock, layer-by-layer, into a green part. In melt infiltration, this green preform is densified by placing it in contact with a molten alloy that wets the preform and wicks into the pores as a result of capillary forces. When these processes are paired together, they offer two key advantages for the densification of rapidly-solidified powders. The first advantage is that the timescale associated with melt infiltration is on the order of seconds for parts with cm-scale dimensions. So in many instances, infiltration requires only a brief thermal excursion that does not degrade the feedstock’s microstructure. The second advantage is that the combination of binder-jet 3D printing and melt infiltration gives fully-dense net shape objects, minimizing the need for subsequent post-processing. In this work, fully-dense, net shape objects have been fabricated from an amorphous powder using I-3DP and molten bronze infiltration while maintaining the amorphous microstructure. X-ray diffraction, scanning electron microscopy, and differential thermal analysis were used to characterize the structural evolution of the powder feedstock during an infiltration heating cycle. Microindentation and bend tests were performed on the infiltrated material to evaluate its mechanical properties. It was found that infiltration improved both the ductility and strength of the sintered preforms by eliminating the stress concentration at the interparticle necks. The infiltrated material had an 11 GPa Vickers hardness and moderate damage tolerance, making it well-suited for applications requiring hard, net shape parts.« less

Fabrication of High Temperature Cermet Materials for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Hickman, Robert; Panda, Binayak; Shah, Sandeep

2005-01-01

Processing techniques are being developed to fabricate refractory metal and ceramic cermet materials for Nuclear Thermal Propulsion (NTP). Significant advances have been made in the area of high-temperature cermet fuel processing since RoverNERVA. Cermet materials offer several advantages such as retention of fission products and fuels, thermal shock resistance, hydrogen compatibility, high conductivity, and high strength. Recent NASA h d e d research has demonstrated the net shape fabrication of W-Re-HfC and other refractory metal and ceramic components that are similar to UN/W-Re cermet fuels. This effort is focused on basic research and characterization to identify the most promising compositions and processing techniques. A particular emphasis is being placed on low cost processes to fabricate near net shape parts of practical size. Several processing methods including Vacuum Plasma Spray (VPS) and conventional PM processes are being evaluated to fabricate material property samples and components. Surrogate W-Re/ZrN cermet fuel materials are being used to develop processing techniques for both coated and uncoated ceramic particles. After process optimization, depleted uranium-based cermets will be fabricated and tested to evaluate mechanical, thermal, and hot H2 erosion properties. This paper provides details on the current results of the project.

Binder Jetting: A Novel NdFeB Bonded Magnet Fabrication Process

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

Paranthaman, M. Parans; Shafer, Christopher S.; Elliott, Amy M.

2016-04-05

Our goal of this research is to fabricate near-net-shape isotropic (Nd) 2Fe 14B-based (NdFeB) bonded magnets using a three dimensional printing process to compete with conventional injection molding techniques used for bonded magnets. Additive manufacturing minimizes the waste of critical materials and allows for the creation of complex shapes and sizes. The binder jetting process works similarly to an inkjet printer. A print-head passes over a bed of NdFeB powder and deposits a polymer binding agent to bind the layer of particles together. The bound powder is then coated with another layer of powder, building the desired shape in successivemore » layers of bonded powder. Upon completion, the green part and surrounding powders are placed in an oven at temperatures between 100°C and 150°C for 4–6 h to cure the binder. After curing, the excess powder can be brushed away to reveal the completed “green” part. Green magnet parts were then infiltrated with a clear urethane resin to achieve the measured density of the magnet of 3.47 g/cm 3 close to 46% relative to the NdFeB single crystal density of 7.6 g/cm 3. Magnetic measurements indicate that there is no degradation in the magnetic properties. In conclusion, this study provides a new pathway for preparing near-net-shape bonded magnets for various magnetic applications.« less

Process for making ceramic insulation

DOEpatents

Akash, Akash [Salt Lake City, UT; Balakrishnan, G Nair [Sandy, UT

2009-12-08

A method is provided for producing insulation materials and insulation for high temperature applications using novel castable and powder-based ceramics. The ceramic components produced using the proposed process offers (i) a fine porosity (from nano-to micro scale); (ii) a superior strength-to-weight ratio; and (iii) flexibility in designing multilayered features offering multifunctionality which will increase the service lifetime of insulation and refractory components used in the solid oxide fuel cell, direct carbon fuel cell, furnace, metal melting, glass, chemical, paper/pulp, automobile, industrial heating, coal, and power generation industries. Further, the ceramic components made using this method may have net-shape and/or net-size advantages with minimum post machining requirements.

A study of process parameters on workpiece anisotropy in the laser engineered net shaping (LENSTM) process

NASA Astrophysics Data System (ADS)

Chandra, Shubham; Rao, Balkrishna C.

2017-06-01

The process of laser engineered net shaping (LENSTM) is an additive manufacturing technique that employs the coaxial flow of metallic powders with a high-power laser to form a melt pool and the subsequent deposition of the specimen on a substrate. Although research done over the past decade on the LENSTM processing of alloys of steel, titanium, nickel and other metallic materials typically reports superior mechanical properties in as-deposited specimens, when compared to the bulk material, there is anisotropy in the mechanical properties of the melt deposit. The current study involves the development of a numerical model of the LENSTM process, using the principles of computational fluid dynamics (CFD), and the subsequent prediction of the volume fraction of equiaxed grains to predict process parameters required for the deposition of workpieces with isotropy in their properties. The numerical simulation is carried out on ANSYS-Fluent, whose data on thermal gradient are used to determine the volume fraction of the equiaxed grains present in the deposited specimen. This study has been validated against earlier efforts on the experimental studies of LENSTM for alloys of nickel. Besides being applicable to the wider family of metals and alloys, the results of this study will also facilitate effective process design to improve both product quality and productivity.

Productivity is a poor predictor of plant species richness

USDA-ARS?s Scientific Manuscript database

For 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating fine-scale species richness. The true relationship was thought to be hump-shaped, with richness peaking at intermediate levels of productivity, ...

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

Paranthaman, M. Parans; Sridharan, Niyanth; List, Fred A.

The technical objective of this technical collaboration phase I proposal is to fabricate near net-shaped permanent magnets using alloy powders utilizing direct metal deposition technologies at the ORNL MDF. Direct Manufacturing using the POM laser system was used to consolidate Nd 2Fe 14B (NdFeB) magnet powders into near net-shape parts efficiently and with virtually no wasted material as part of the feasibility study. We fabricated builds based on spherical NdFeB magnet particles. The results show that despite the ability to fabricate highly reactive materials in the laser deposition process, the magnetic coercivity and remanence of the NdFeB hard magnets ismore » significantly reduced. X-ray powder diffraction in conjunction with electron microscopy showed that the material experienced a primary Nd 2Fe 17B x solidification due to the undercooling effect (>60K). Consequently the presence of alpha iron phase resulted in deterioration of the build properties. Further optimization of the processing parameters is needed to maintain the Nd 2Fe 14B phase during fabrication.« less

Method for Fabricating Composite Structures Including Continuous Press Forming and Pultrusion Processing

NASA Technical Reports Server (NTRS)

Farley, Gary L. (Inventor)

1995-01-01

A method for fabricating composite structures at a low-cost, moderate-to-high production rate is disclosed. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply, and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform, and debulking the partially debulked preform to form a netshape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length, and electron-beam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates, resulting in lower cost and high structural performance.

CRADA/NFE-15-05761 Report: Additive Manufacturing of Isotropic NdFeB Bonded Permanent Magnets

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

Paranthaman, M. Parans

2016-07-18

The technical objective of this technical collaboration phase I proposal is to fabricate net shape isotropic NdFeB bonded magnets utilizing additive manufacturing technologies at the ORNL MDF. The goal is to form complex shapes of thermoplastic and/or thermoset bonded magnets without expensive tooling and with minimal wasted material. Two additive manufacturing methods; the binder jet process; and big area additive manufacturing (BAAM) were used. Binder jetting produced magnets with the measured density of the magnet of 3.47 g/cm 3, close to 46% relative to the NdFeB single crystal density of 7.6 g/cm 3 were demonstrated. Magnetic measurements indicate that theremore » is no degradation in the magnetic properties. In addition, BAAM was used to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm 3, and the room temperature magnetic properties are: Intrinsic coercivity Hci = 8.65 kOe, Remanence Br = 5.07 kG, and energy product (BH) max = 5.47 MGOe (43.50 kJ/m 3). This study provides a new pathway for preparing near-net shape bonded magnets for various magnetic applications.« less

Method for net-shaping using aerogels

DOEpatents

Brinker, C. Jeffrey; Ashey, Carol S.; Reed, Scott T.; Sriram, Chunangad S.; Harris, Thomas M.

2001-01-01

A method of net-shaping using aerogel materials is provided by first forming a sol, aging the sol to form a gel, with the gel having a fluid component and having been formed into a medium selected from the group consisting of a powder, bulk material, or granular aerobeads, derivatizing the surface of the gel to render the surface unreactive toward further condensation, removing a portion of the fluid component of the final shaped gel to form a partially dried medium, placing the medium into a cavity, wherein the volume of said medium is less that the volume of the cavity, and removing a portion of the fluid component of the medium. The removal, such as by heating at a temperature of approximately less than 50.degree. C., applying a vacuum, or both, causes the volume of the medium to increase and to form a solid aerogel. The material can be easily removed by exposing the material to a solvent, thereby reducing the volume of the material. In another embodiment, the gel is derivatized and then formed into a shaped medium, where subsequent drying reduces the volume of the shaped medium, forming a net-shaping material. Upon further drying, the material increases in volume to fill a cavity. The present invention is both a method of net-shaping and the material produced by the method.

Spray forming of NiTi and NiTiPd shape-memory alloys

NASA Astrophysics Data System (ADS)

Smith, Ronald; Mabe, James; Ruggeri, Robert; Noebe, Ronald

2008-03-01

In the work to be presented, vacuum plasma spray forming has been used as a process to deposit and consolidate prealloyed NiTi and NiTiPd powders into near net shape actuators. Testing showed that excellent shape memory behavior could be developed in the deposited materials and the investigation proved that VPS forming could be a means to directly form a wide range of shape memory alloy components. The results of DSC characterization and actual actuation test results will be presented demonstrating the behavior of a Nitinol 55 alloy and a higher transition temperature NiTiPd alloy in the form of torque tube actuators that could be used in aircraft and aerospace controls.

Spray Forming of NiTi and NiTiPd Shape-Memory Alloys

NASA Technical Reports Server (NTRS)

Mabe, James; Ruggeri, Robert; Noebe, Ronald

2008-01-01

In the work to be presented, vacuum plasma spray forming has been used as a process to deposit and consolidate prealloyed NiTi and NiTiPd powders into near net shape actuators. Testing showed that excellent shape memory behavior could be developed in the deposited materials and the investigation proved that VPS forming could be a means to directly form a wide range of shape memory alloy components. The results of DSC characterization and actual actuation test results will be presented demonstrating the behavior of a Nitinol 55 alloy and a higher transition temperature NiTiPd alloy in the form of torque tube actuators that could be used in aircraft and aerospace controls.

Advanced Materials and Fabrication Techniques for the Orion Attitude Control Motor

NASA Technical Reports Server (NTRS)

Gorti, Sridhar; Holmes, Richard; O'Dell, John; McKechnie, Timothy; Shchetkovskiy, Anatoliy

2013-01-01

Rhenium, with its high melting temperature, excellent elevated temperature properties, and lack of a ductile-to-brittle transition temperature (DBTT), is ideally suited for the hot gas components of the ACM (Attitude Control Motor), and other high-temperature applications. However, the high cost of rhenium makes fabricating these components using conventional fabrication techniques prohibitive. Therefore, near-net-shape forming techniques were investigated for producing cost-effective rhenium and rhenium alloy components for the ACM and other propulsion applications. During this investigation, electrochemical forming (EL-Form ) techniques were evaluated for producing the hot gas components. The investigation focused on demonstrating that EL-Form processing techniques could be used to produce the ACM flow distributor. Once the EL-Form processing techniques were established, a representative rhenium flow distributor was fabricated, and samples were harvested for material properties testing at both room and elevated temperatures. As a lower cost and lighter weight alternative to an all-rhenium component, rhenium- coated graphite and carbon-carbon were also evaluated. The rhenium-coated components were thermal-cycle tested to verify that they could withstand the expected thermal loads during service. High-temperature electroforming is based on electrochemical deposition of compact layers of metals onto a mandrel of the desired shape. Mandrels used for electro-deposition of near-net shaped parts are generally fabricated from high-density graphite. The graphite mandrel is easily machined and does not react with the molten electrolyte. For near-net shape components, the inner surface of the electroformed part replicates the polished graphite mandrel. During processing, the mandrel itself becomes the cathode, and scrap or refined refractory metal is the anode. Refractory metal atoms from the anode material are ionized in the molten electrolytic solution, and are deposited onto the cathodic mandrel by electrochemical reduction. Rotation of the mandrel ensures uniform distribution of refractory material. The EL-Form process allows for manufacturing in an inert atmosphere with deposition rates from 0.0004 to 0.002 in./h (10.2 to 50.8 m/h). Thicknesses typically range from microns to greater than 0.5 in. (13 mm). The refractory component produced is fabricated, dependably, to within one micron of the desired tolerances with no shrinkage or distortion as in other refractory metal manufacture techniques. The electroforming process has been used to produce solid, nonporous deposits of rhenium, iridium, niobium, tungsten, and their alloys.

Form finding in elastic gridshells.

PubMed

Baek, Changyeob; Sageman-Furnas, Andrew O; Jawed, Mohammad K; Reis, Pedro M

2018-01-02

Elastic gridshells comprise an initially planar network of elastic rods that are actuated into a shell-like structure by loading their extremities. The resulting actuated form derives from the elastic buckling of the rods subjected to inextensibility. We study elastic gridshells with a focus on the rational design of the final shapes. Our precision desktop experiments exhibit complex geometries, even from seemingly simple initial configurations and actuation processes. The numerical simulations capture this nonintuitive behavior with excellent quantitative agreement, allowing for an exploration of parameter space that reveals multistable states. We then turn to the theory of smooth Chebyshev nets to address the inverse design of hemispherical elastic gridshells. The results suggest that rod inextensibility, not elastic response, dictates the zeroth-order shape of an actuated elastic gridshell. As it turns out, this is the shape of a common household strainer. Therefore, the geometry of Chebyshev nets can be further used to understand elastic gridshells. In particular, we introduce a way to quantify the intrinsic shape of the empty, but enclosed regions, which we then use to rationalize the nonlocal deformation of elastic gridshells to point loading. This justifies the observed difficulty in form finding. Nevertheless, we close with an exploration of concatenating multiple elastic gridshell building blocks.

Form finding in elastic gridshells

NASA Astrophysics Data System (ADS)

Baek, Changyeob; Sageman-Furnas, Andrew O.; Jawed, Mohammad K.; Reis, Pedro M.

2018-01-01

Elastic gridshells comprise an initially planar network of elastic rods that are actuated into a shell-like structure by loading their extremities. The resulting actuated form derives from the elastic buckling of the rods subjected to inextensibility. We study elastic gridshells with a focus on the rational design of the final shapes. Our precision desktop experiments exhibit complex geometries, even from seemingly simple initial configurations and actuation processes. The numerical simulations capture this nonintuitive behavior with excellent quantitative agreement, allowing for an exploration of parameter space that reveals multistable states. We then turn to the theory of smooth Chebyshev nets to address the inverse design of hemispherical elastic gridshells. The results suggest that rod inextensibility, not elastic response, dictates the zeroth-order shape of an actuated elastic gridshell. As it turns out, this is the shape of a common household strainer. Therefore, the geometry of Chebyshev nets can be further used to understand elastic gridshells. In particular, we introduce a way to quantify the intrinsic shape of the empty, but enclosed regions, which we then use to rationalize the nonlocal deformation of elastic gridshells to point loading. This justifies the observed difficulty in form finding. Nevertheless, we close with an exploration of concatenating multiple elastic gridshell building blocks.

Neural-net Processed Electronic Holography for Rotating Machines

NASA Technical Reports Server (NTRS)

Decker, Arthur J.

2003-01-01

This report presents the results of an R&D effort to apply neural-net processed electronic holography to NDE of rotors. Electronic holography was used to generate characteristic patterns or mode shapes of vibrating rotors and rotor components. Artificial neural networks were trained to identify damage-induced changes in the characteristic patterns. The development and optimization of a neural-net training method were the most significant contributions of this work, and the training method and its optimization are discussed in detail. A second positive result was the assembly and testing of a fiber-optic holocamera. A major disappointment was the inadequacy of the high-speed-holography hardware selected for this effort, but the use of scaled holograms to match the low effective resolution of an image intensifier was one interesting attempt to compensate. This report also discusses in some detail the physics and environmental requirements for rotor electronic holography. The major conclusions were that neural-net and electronic-holography inspections of stationary components in the laboratory and the field are quite practical and worthy of continuing development, but that electronic holography of moving rotors is still an expensive high-risk endeavor.

An Investigation into the Comparative Costs of Additive Manufacture vs. Machine from Solid for Aero Engine Parts

DTIC Science & Technology

2006-05-01

welding power sources are not totally efficient at converting power drawn from the wall into heat energy used for the welding process . TIG sources are...Powder bed + Laser • Wire + Laser • Wire + Electron Beam • Wire + TIG Each system has its own unique attributes in terms of process variables...relative economics of producing a near net shape by Additive Manufacturing (AM) processes compared with traditional machine from solid processes (MFS

Demand and willingness-to-pay for bed nets in Tanzania: results from a choice experiment.

PubMed

Gingrich, Chris D; Ricotta, Emily; Kahwa, Amos; Kahabuka, Catherine; Koenker, Hannah

2017-07-14

Universal coverage campaigns for long-lasting insecticide-treated nets do not always reach the goal of one net for every two household members, and even when ownership of at least one net per household is high, many households may not own enough nets. The retail market provides these households options for replacing or increasing the number of nets they own with products that best fit their needs since a variety of net shapes, sizes, and colours are available. Hence, it is important to understand the factors affecting private net demand. This study explores private demand for nets in Tanzania using a discrete choice experiment. The experiment provides participants the option to buy nets with their own money, and thus should prove more accurate than a hypothetical survey of net preferences. Nearly 800 participants sampled in two regions showed an overall strong demand for nets, with 40% choosing to buy a net across all seven combinations of net prices and characteristics such as size, shape, and insecticide treatment. Only 8% of all participants chose not to buy a single net. A key factor influencing demand was whether a participant's household currently owned sufficient nets for all members, with rural participants showing lower net coverage and greater demand than urban participants. Both poor and less poor households showed strong evidence of making purchase decisions based on more than price alone. Mean willingness-to-pay values for a net started at US$1.10 and grew by US$0.50-1.40 for various attributes such as rectangular shape, large size, and insecticide treatment. The impact of price on demand was negative but small, with elasticity values between -0.25 and -0.45. The results suggest that private demand for nets in Tanzania could potentially supplement future coverage campaigns. Net manufacturers and retailers should advertise and promote consumers' preferred net attributes to improve sales and further expand net access and coverage. To overcome household liquidity concerns and best replicate the experiment results, policy makers should consider making credit available for interested buyers.

Productivity is a poor predictor of plant species richness

Treesearch

P.B. Adler; E.T. Borer; H. Hillebrand; Y. Hautier; A. Hector; S. Harpole; L.R. O’Halloran; J.B. Grace; M. Anderson; J.D. Bakker; L.A. Biederman; C.S. Brown; Y.M. Buckley; L.B. Calabrese; C.-J. Chu; E.E. Cleland; S.L. Collins; K.L. Cottingham; M.J. Crawley; E.I. Damschen; K.W. Davies; N.M. DeCrappeo; P.A. Fay; J. Firn; P. Frater; E.I. Gasarch; D.S. Gruner; N. Hagenah; J. Hille Ris Lambers

2011-01-01

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent...

Data indicating temperature response of Ti-6Al-4V thin-walled structure during its additive manufacture via Laser Engineered Net Shaping.

PubMed

Marshall, Garrett J; Thompson, Scott M; Shamsaei, Nima

2016-06-01

An OPTOMEC Laser Engineered Net Shaping (LENS(™)) 750 system was retrofitted with a melt pool pyrometer and in-chamber infrared (IR) camera for nondestructive thermal inspection of the blown-powder, direct laser deposition (DLD) process. Data indicative of temperature and heat transfer within the melt pool and heat affected zone atop a thin-walled structure of Ti-6Al-4V during its additive manufacture are provided. Melt pool temperature data were collected via the dual-wavelength pyrometer while the dynamic, bulk part temperature distribution was collected using the IR camera. Such data are provided in Comma Separated Values (CSV) file format, containing a 752×480 matrix and a 320×240 matrix of temperatures corresponding to individual pixels of the pyrometer and IR camera, respectively. The IR camera and pyrometer temperature data are provided in blackbody-calibrated, raw forms. Provided thermal data can aid in generating and refining process-property-performance relationships between laser manufacturing and its fabricated materials.

Data indicating temperature response of Ti–6Al–4V thin-walled structure during its additive manufacture via Laser Engineered Net Shaping

PubMed Central

Marshall, Garrett J.; Thompson, Scott M.; Shamsaei, Nima

2016-01-01

An OPTOMEC Laser Engineered Net Shaping (LENS™) 750 system was retrofitted with a melt pool pyrometer and in-chamber infrared (IR) camera for nondestructive thermal inspection of the blown-powder, direct laser deposition (DLD) process. Data indicative of temperature and heat transfer within the melt pool and heat affected zone atop a thin-walled structure of Ti–6Al–4V during its additive manufacture are provided. Melt pool temperature data were collected via the dual-wavelength pyrometer while the dynamic, bulk part temperature distribution was collected using the IR camera. Such data are provided in Comma Separated Values (CSV) file format, containing a 752×480 matrix and a 320×240 matrix of temperatures corresponding to individual pixels of the pyrometer and IR camera, respectively. The IR camera and pyrometer temperature data are provided in blackbody-calibrated, raw forms. Provided thermal data can aid in generating and refining process-property-performance relationships between laser manufacturing and its fabricated materials. PMID:27054180

Near-Net Shape Fabrication Using Low-Cost Titanium Alloy Powders

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

Dr. David M. Bowden; Dr. William H. Peter

2012-03-31

The use of titanium in commercial aircraft production has risen steadily over the last half century. The aerospace industry currently accounts for 58% of the domestic titanium market. The Kroll process, which has been used for over 50 years to produce titanium metal from its mineral form, consumes large quantities of energy. And, methods used to convert the titanium sponge output of the Kroll process into useful mill products also require significant energy resources. These traditional approaches result in product forms that are very expensive, have long lead times of up to a year or more, and require costly operationsmore » to fabricate finished parts. Given the increasing role of titanium in commercial aircraft, new titanium technologies are needed to create a more sustainable manufacturing strategy that consumes less energy, requires less material, and significantly reduces material and fabrication costs. A number of emerging processes are under development which could lead to a breakthrough in extraction technology. Several of these processes produce titanium alloy powder as a product. The availability of low-cost titanium powders may in turn enable a more efficient approach to the manufacture of titanium components using powder metallurgical processing. The objective of this project was to define energy-efficient strategies for manufacturing large-scale titanium structures using these low-cost powders as the starting material. Strategies include approaches to powder consolidation to achieve fully dense mill products, and joining technologies such as friction and laser welding to combine those mill products into near net shape (NNS) preforms for machining. The near net shape approach reduces material and machining requirements providing for improved affordability of titanium structures. Energy and cost modeling was used to define those approaches that offer the largest energy savings together with the economic benefits needed to drive implementation. Technical feasibility studies were performed to identify the most viable approaches to NNS preform fabrication using basic powder metallurgy mill product forms as the building blocks and advanced joining techniques including fusion and solid state joining to assemble these building blocks into efficient machining performs.« less

Effect of Al Addition on Microstructure of AZ91D

NASA Astrophysics Data System (ADS)

Joshi, Utsavi; Babu, Nadendla Hari

Casting is a net shape or near net shape forming process so work-hardening will not be applicable for improving properties of magnesium cast alloys. Grain refinement, solid-solution strengthening, precipitation hardening and specially designed heat treatment are the techniques used to enhance the properties of these alloys. This research focusses on grain refinement of magnesium alloy AZ91D, which is a widely used commercial cast alloy. Recently, Al-B based master alloys have shown potential in grain refining AZ91D. A comparative study of the grain refinement of AZ91D by addition of 0.02wt%B, 0.04wt%B, 0.1wt%B, 0.5wt%B and 1.0wt%B of A1-5B master alloy and equivalent amount of solute element aluminium is described in this paper. Hardness profile of AZ91D alloyed with boron and aluminium is compared.

Casting of weldable graphite/magnesium metal matrix composites with built-in metallic inserts

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.; Kashalikar, Uday; Majkowski, Patricia

1994-01-01

Technology innovations directed at the advanced development of a potentially low cost and weldable graphite/magnesium metal matrix composites (MMC) through near net shape pressure casting are described. These MMC components uniquely have built-in metallic inserts to provide an innovative approach for joining or connecting other MMC components through conventional joining techniques such as welding, brazing, mechanical fasteners, etc. Moreover, the metallic inserts trapped within the MMC components can be made to transfer the imposed load efficiently to the continuous graphite fiber reinforcement thus producing stronger, stiffer, and more reliable MMC components. The use of low pressure near net shape casting is economical compared to other MMC fabrication processes. These castable and potentially weldable MMC components can provide great payoffs in terms of high strength, high stiffness, low thermal expansion, lightweight, and easily joinable MMC components for several future NASA space structural, industrial, and commercial applications.

Scale-up of Carbon/Carbon Bipolar Plates

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

David P. Haack

2009-04-08

This project was focused upon developing a unique material technology for use in PEM fuel cell bipolar plates. The carbon/carbon composite material developed in this program is uniquely suited for use in fuel cell systems, as it is lightweight, highly conductive and corrosion resistant. The project further focused upon developing the manufacturing methodology to cost-effectively produce this material for use in commercial fuel cell systems. United Technology Fuel Cells Corp., a leading fuel cell developer was a subcontractor to the project was interested in the performance and low-cost potential of the material. The accomplishments of the program included the developmentmore » and testing of a low-cost, fully molded, net-shape carbon-carbon bipolar plate. The process to cost-effectively manufacture these carbon-carbon bipolar plates was focused on extensively in this program. Key areas for cost-reduction that received attention in this program was net-shape molding of the detailed flow structures according to end-user design. Correlations between feature detail and process parameters were formed so that mold tooling could be accurately designed to meet a variety of flow field dimensions. A cost model was developed that predicted the cost of manufacture for the product in near-term volumes and long-term volumes (10+ million units per year). Because the roduct uses lowcost raw materials in quantities that are less than competitive tech, it was found that the cost of the product in high volume can be less than with other plate echnologies, and can meet the DOE goal of $4/kW for transportation applications. The excellent performance of the all-carbon plate in net shape was verified in fuel cell testing. Performance equivalent to much higher cost, fully machined graphite plates was found.« less

Study of soft magnetic iron cobalt based alloys processed by powder injection molding

NASA Astrophysics Data System (ADS)

Silva, Aline; Lozano, Jaime A.; Machado, Ricardo; Escobar, Jairo A.; Wendhausen, Paulo A. P.

As a near net shape process, powder injection molding (PIM) opens new possibilities to process Fe-Co alloys for magnetic applications. Due to the fact that PIM does not involve plastic deformation of the material during processing, we envisioned the possibility of eliminating vanadium (V), which is generally added to Fe-Co alloys to improve the ductility in order to enable its further shaping by conventional processes such as forging and cold rolling. In our investigation we have found out two main futures related to the elimination of V, which lead to a cost-benefit gain in manufacturing small magnetic components where high-saturation induction is needed at low frequencies. Firstly, the elimination of V enables the achievement of much better magnetic properties when alloys are processed by PIM. Secondly, a lower sintering temperature can be used when the alloy is processed starting with elemental Fe and Co powders without the addition of V.

Near-Net Shape Powder Metallurgy Rhenium Thruster

NASA Technical Reports Server (NTRS)

Leonhardt, Todd; Hamister, Mark; Carlen, Jan C.; Biaglow, James; Reed, Brian

2001-01-01

This paper describes the development of a method to produce a near-net shape (NNS) powder metallurgy (PM) rhenium combustion chamber of the size 445 N (100 lbf) used in a high performance liquid apogee engine. These engines are used in low earth Orbit and geostationary orbit for satellite positioning systems. The developments in near-net shape powder metallurgy rhenium combustion chambers reported in this paper will reduce manufacturing cost of the rhenium chambers by 25 percent, and reduce the manufacturing time by 30 to 40 percent. The quantity of rhenium metal powder used to produce a rhenium chamber is reduced by approximately 70 percent and the subsequent reduction in machining schedule and costs is nearly 50 percent.

Networks of myelin covariance

PubMed Central

Slater, David; Ruef, Anne; Sanabria‐Diaz, Gretel; Preisig, Martin; Kherif, Ferath; Draganski, Bogdan; Lutti, Antoine

2017-01-01

Abstract Networks of anatomical covariance have been widely used to study connectivity patterns in both normal and pathological brains based on the concurrent changes of morphometric measures (i.e., cortical thickness) between brain structures across subjects (Evans, 2013). However, the existence of networks of microstructural changes within brain tissue has been largely unexplored so far. In this article, we studied in vivo the concurrent myelination processes among brain anatomical structures that gathered together emerge to form nonrandom networks. We name these “networks of myelin covariance” (Myelin‐Nets). The Myelin‐Nets were built from quantitative Magnetization Transfer data—an in‐vivo magnetic resonance imaging (MRI) marker of myelin content. The synchronicity of the variations in myelin content between anatomical regions was measured by computing the Pearson's correlation coefficient. We were especially interested in elucidating the effect of age on the topological organization of the Myelin‐Nets. We therefore selected two age groups: Young‐Age (20–31 years old) and Old‐Age (60–71 years old) and a pool of participants from 48 to 87 years old for a Myelin‐Nets aging trajectory study. We found that the topological organization of the Myelin‐Nets is strongly shaped by aging processes. The global myelin correlation strength, between homologous regions and locally in different brain lobes, showed a significant dependence on age. Interestingly, we also showed that the aging process modulates the resilience of the Myelin‐Nets to damage of principal network structures. In summary, this work sheds light on the organizational principles driving myelination and myelin degeneration in brain gray matter and how such patterns are modulated by aging. PMID:29271053

Metal Injection Moulding: A Near Net Shape Fabrication Method for the Manufacture of Turbine Engine Component

DTIC Science & Technology

2006-05-01

on the processing and characterization of Inconel 625 LPIM material are presented. In depth microstructural characterization was performed on the...annealing. 1 INTRODUCTION Nickel superalloys such as Inconel 625 were developed to withstand the intense conditions present in gas turbine engines...aeronautic parts. A low- pressure injection moulding process, LPIM, has been developed for the fabrication of parts made of Inconel 625 , which maximizes

Process Control and Development for Ultrasonic Additive Manufacturing with Embedded Fibers

NASA Astrophysics Data System (ADS)

Hehr, Adam J.

Ultrasonic additive manufacturing (UAM) is a recent additive manufacturing technology which combines ultrasonic metal welding, CNC machining, and mechanized foil layering to create large gapless near net-shape metallic parts. The process has been attracting much attention lately due to its low formation temperature, the capability to join dissimilar metals, and the ability to create complex design features not possible with traditional subtractive processes alone. These process attributes enable light-weighting of structures and components in an unprecedented way. However, UAM is currently limited to niche areas due to the lack of quality tracking and inadequate scientific understanding of the process. As a result, this thesis work is focused on improving both component quality tracking and process understanding through the use of average electrical power input to the welder. Additionally, the understanding and application space of embedding fibers into metals using UAM is investigated, with particular focus on NiTi shape memory alloy fibers.

Uniform-droplet spray forming

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

Blue, C.A.; Sikka, V.K.; Chun, Jung-Hoon

1997-04-01

The uniform-droplet process is a new method of liquid-metal atomization that results in single droplets that can be used to produce mono-size powders or sprayed-on to substrates to produce near-net shapes with tailored microstructure. The mono-sized powder-production capability of the uniform-droplet process also has the potential of permitting engineered powder blends to produce components of controlled porosity. Metal and alloy powders are commercially produced by at least three different methods: gas atomization, water atomization, and rotating disk. All three methods produce powders of a broad range in size with a very small yield of fine powders with single-sized droplets thatmore » can be used to produce mono-size powders or sprayed-on substrates to produce near-net shapes with tailored microstructures. The economical analysis has shown the process to have the potential of reducing capital cost by 50% and operating cost by 37.5% when applied to powder making. For the spray-forming process, a 25% savings is expected in both the capital and operating costs. The project is jointly carried out at Massachusetts Institute of Technology (MIT), Tuffs University, and Oak Ridge National Laboratory (ORNL). Preliminary interactions with both finished parts and powder producers have shown a strong interest in the uniform-droplet process. Systematic studies are being conducted to optimize the process parameters, understand the solidification of droplets and spray deposits, and develop a uniform-droplet-system (UDS) apparatus appropriate for processing engineering alloys.« less

Life cycle assessment and sustainable engineering in the context of near net shape grown components: striving towards a sustainable way of future production.

PubMed

Kämpfer, Christoph; Seiler, Thomas-Benjamin; Beger, Anna-Lena; Jacobs, Georg; Löwer, Manuel; Moser, Franziska; Reimer, Julia; Trautz, Martin; Usadel, Björn; Wormit, Alexandra; Hollert, Henner

2017-01-01

Technical product harvesting (TEPHA) is a newly developing interdisciplinary approach in which bio-based production is investigated from a technical and ecological perspective. Society's demand for ecologically produced and sustainably operable goods is a key driver for the substitution of conventional materials like metals or plastics through bio-based alternatives. Technical product harvesting of near net shape grown components describes the use of suitable biomass for the production of technical products through influencing the natural shape of plants during their growth period. The use of natural materials may show positive effects on the amount of non-renewable resource consumption. This also increases the product recyclability at the end of its life cycle. Furthermore, through the near net shape growth of biomass, production steps can be reduced. As a consequence such approaches may save energy and the needed resources like crude oil, coal or gas. The derived near net shape grown components are not only considered beneficial from an environmental point of view. They can also have mechanical advantages through an intrinsic topology optimization in contrast to common natural materials, which are influenced in their shape after harvesting. In order to prove these benefits a comprehensive, interdisciplinary scientific strategy is needed. Here, both mechanical investigations and life cycle assessment as a method of environmental evaluation are used.

Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

NASA Technical Reports Server (NTRS)

Kashalikar, Uday; Rozenoyer, Boris

2004-01-01

Isotropic composites of aluminum-alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less-expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 grams per cubic centimeter and specific strengths of about 200 MPa/(grams per cubic centimeter). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 F (260 C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbomachinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately, incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated. A composite part of this type can be fabricated in a pressure infiltration casting process. The process begins with the placement of a mold with alumina particulate preform of net or nearly net size and shape in a crucible in a vacuum furnace. A charge of the alloy is placed in the crucible with the preform. The interior of the furnace is evacuated, then the furnace heaters are turned on to heat the alloy above its liquidus temperature. Next, the interior of the furnace is filled with argon gas at a pressure about 900 psi (approximately equal to 6.2 MPa) to force the molten alloy to infiltrate the preform. Once infiltrated, the entire contents of the crucible can be allowed to cool in place, and the composite part recovered from the mold.

Development of a Scale to Explore Technology Literacy Skills of Turkish 8th Graders

ERIC Educational Resources Information Center

Misirli, Zeynel A.; Akbulut, Yavuz

2013-01-01

The use of emerging technologies shape learners' knowledge creation and transformation processes. In this regard, this study aimed to develop a scale to investigate 8 th graders' competencies regarding the educational technology standards based on ISTE-NETS. After a review of relevant literature, an item pool was prepared. The pool was improved…

Optics-Only Calibration of a Neural-Net Based Optical NDE Method for Structural Health Monitoring

NASA Technical Reports Server (NTRS)

Decker, Arthur J.

2004-01-01

A calibration process is presented that uses optical measurements alone to calibrate a neural-net based NDE method. The method itself detects small changes in the vibration mode shapes of structures. The optics-only calibration process confirms previous work that the sensitivity to vibration-amplitude changes can be as small as 10 nanometers. A more practical value in an NDE service laboratory is shown to be 50 nanometers. Both model-generated and experimental calibrations are demonstrated using two implementations of the calibration technique. The implementations are based on previously published demonstrations of the NDE method and an alternative calibration procedure that depends on comparing neural-net and point sensor measurements. The optics-only calibration method, unlike the alternative method, does not require modifications of the structure being tested or the creation of calibration objects. The calibration process can be used to test improvements in the NDE process and to develop a vibration-mode-independence of damagedetection sensitivity. The calibration effort was intended to support NASA s objective to promote safety in the operations of ground test facilities or aviation safety, in general, by allowing the detection of the gradual onset of structural changes and damage.

Additive manufacturing of near-net-shape bonded magnets: Prospects and challenges

DOE PAGES

Li, Ling; Post, Brian; Kunc, Vlastimil; ...

2017-01-03

Additive manufacturing (AM) or 3D printing is well known for producing arbitrary shaped parts without any tooling required, offering a promising alternative to the conventional injection molding method to fabricate near-net-shaped magnets. In order to determine their applicability in the fabrication of Nd-Fe-B bondedmagnets, we compare two 3D printing technologies, namely binder jetting and material extrusion. Some prospects and challenges of these state-of-the-art technologies for large-scale industrial applications will be discussed.

Near-Net Forging Technology Demonstration Program

NASA Technical Reports Server (NTRS)

Hall, I. Keith

1996-01-01

Significant advantages in specific mechanical properties, when compared to conventional aluminum (Al) alloys, make aluminum-lithium (Al-Li) alloys attractive candidate materials for use in cryogenic propellant tanks and dry bay structures. However, the cost of Al-Li alloys is typically five times that of 2219 aluminum. If conventional fabrication processes are employed to fabricate launch vehicle structure, the material costs will restrict their utilization. In order to fully exploit the potential cost and performance benefits of Al-Li alloys, it is necessary that near-net manufacturing methods be developed to off-set or reduce raw material costs. Near-net forging is an advanced manufacturing method that uses elevated temperature metal movement (forging) to fabricate a single piece, near-net shape, structure. This process is termed 'near-net' because only a minimal amount of post-forge machining is required. The near-net forging process was developed to reduce the material scrap rate (buy-to-fly ratio) and fabrication costs associated with conventional manufacturing methods. The goal for the near-net forging process, when mature, is to achieve an overall cost reduction of approximately 50 percent compared with conventional manufacturing options for producing structures fabricated from Al-Li alloys. This NASA Marshall Space Flight Center (MSFC) sponsored program has been a part of a unique government / industry partnership, coordinated to develop and demonstrate near-net forging technology. The objective of this program was to demonstrate scale-up of the near-net forging process. This objective was successfully achieved by fabricating four integrally stiffened, 170- inch diameter by 20-inch tall, Al-Li alloy 2195, Y-ring adapters. Initially, two 2195 Al-Li ingots were converted and back extruded to produce four cylindrical blockers. Conventional ring rolling of the blockers was performed to produce ring preforms, which were then contour ring rolled to produce 'contour preforms'. All of the contour preforms on this first-of-a-kind effort were imperfect, and the ingot used to fabricate two of the preforms was of an earlier vintage. As lessons were learned throughout the program, the tooling and procedures evolved, and hence the preform quality. Two of the best contour preforms were near- net forged to produce a process pathfinder Y-ring adapter and a 'mechanical properties pathfinder' Y-ring adapter. At this point, Lockheed Martin Astronautics elected to procure additional 2195 aluminum-lithium ingot of the latest vintage, produce two additional preforms, and substitute them for older vintage material non-perfectly filled preforms already produced on this contract. The existing preforms could have been used to fulfill the requirements of the contract.

Understanding the High Temperature Behavior of Niobium Aluminides; First Year Summary Report

DTIC Science & Technology

1990-11-08

characterization to follow. Near-net shape processing may be used to form test specimens. A transmission elec- tron microscopy effort will be used ...to identify deformation mechanisms. ,, 20 DISTRIBUTION/AVAII ABILITY OF ABSTRACT SK’NCI ASSIFIFD’UNL MITED • SAME AS R"T • DTC USEDS J...ingots have been processed for us (gratis) by Nippon Mining Corporation by vacuum induction melted from a stock of niobium oxide and elemental aluminum

Thermal analysis and evolution of shape loss phenomena during polymer burnout in powder metal processing

NASA Astrophysics Data System (ADS)

Enneti, Ravi Kumar

2005-07-01

Powder metallurgy technology involves manufacturing of net shape or near net shape components starting from metal powders. Polymers are used to provide lubrication during shaping and handling strength to the shaped component. After shaping, the polymers are removed from the shaped components by providing thermal energy to burnout the polymers. Polymer burnout is one of the most critical step in powder metal processing. Improper design of the polymer burnout cycle will result in formation of defects, shape loss, or carbon contamination of the components. The effect of metal particles on polymer burnout and shape loss were addressed in the present research. The study addressing the effect of metal powders on polymer burnout was based on the hypothesis that metal powders act to catalyze polymer burnout. Thermogravimetric analysis (TGA) on pure polymer, ethylene vinyl acetate (EVA), and on admixed powders of 316L stainless steel and 1 wt. % EVA were carried out to verify the hypothesis. The effect of metal powders additions was studied by monitoring the onset temperature for polymer degradation and the temperature at which maximum rate of weight loss occurred from the TGA data. The catalytic behavior of the powders was verified by varying the particle size and shape of the 316L stainless powder. The addition of metal particles lowered the polymer burnout temperatures. The onset temperature for burnout was found to be sensitive to the surface area of the metal particle as well as the polymer distribution. Powders with low surface area and uniform distribution of polymer showed a lower burnout temperature. The evolution of shape loss during polymer burnout was based on the hypothesis that shape loss occurs during the softening of the polymer and depends on the sequence of chemical bonding in the polymer during burnout. In situ observation of shape loss was carried out on thin beams compacted from admixed powders of 316L stainless steel and 1 wt. % ethylene vinyl acetate (EVA). The results showed that shape loss primarily occurs by viscous creep during the softening of the polymer. At the onset of burnout of EVA, a recovery in shape loss was observed. The recovery occurred primarily during the first stage burnout of EVA and was attributed to the formation of polyethylene co-polyacetylene which forms with a carbon double bond. The in situ strength was also found to increase during the formation of polyethylene co-polyacetylene. No recovery of shape loss was observed during burnout of polymers (polyethylene and polypropylene) which convert to yield hydrocarbons without forming carbon double bonds. (Abstract shortened by UMI.)

Carbon Fiber Reinforced Carbon Composite Valve for an Internal Combustion Engine

NASA Technical Reports Server (NTRS)

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor)

1999-01-01

A carbon fiber reinforced carbon composite valve for internal combustion engines and the like formed of continuous carbon fibers throughout the valve's stem and head is disclosed. The valve includes braided carbon fiber material over axially aligned unidirectional carbon fibers forming a valve stem; the braided and unidirectional carbon fibers being broomed out at one end of the valve stem forming the shape of the valve head; the valve-shaped structure being densified and rigidized with a matrix of carbon containing discontinuous carbon fibers: and the finished valve being treated to resist oxidation. Also disclosed is a carbon matrix plug containing continuous and discontinuous carbon fibers and forming a net-shape valve head acting as a mandrel over which the unidirectional and braided carbon fibers are formed according to textile processes. Also disclosed are various preform valves and processes for making finished and preform carbon fiber reinforced carbon composite valves.

The prediction of the building precision in the Laser Engineered Net Shaping process using advanced networks

NASA Astrophysics Data System (ADS)

Lu, Z. L.; Li, D. C.; Lu, B. H.; Zhang, A. F.; Zhu, G. X.; Pi, G.

2010-05-01

Laser Engineered Net Shaping (LENS) is an advanced manufacturing technology, but it is difficult to control the depositing height (DH) of the prototype because there are many technology parameters influencing the forming process. The effect of main parameters (laser power, scanning speed and powder feeding rate) on the DH of single track is firstly analyzed, and then it shows that there is the complex nonlinear intrinsic relationship between them. In order to predict the DH, the back propagation (BP) based network improved with Adaptive learning rate and Momentum coefficient (AM) algorithm, and the least square support vector machine (LS-SVM) network are both adopted. The mapping relationship between above parameters and the DH is constructed according to training samples collected by LENS experiments, and then their generalization ability, function-approximating ability and real-time are contrastively investigated. The results show that although the predicted result by the BP-AM approximates the experimental result, above performance index of the LS-SVM are better than those of the BP-AM. Finally, high-definition thin-walled parts of AISI316L are successfully fabricated. Hence, the LS-SVM network is more suitable for the prediction of the DH.

Development of a super-pressure balloon with a diamond-shaped net

NASA Astrophysics Data System (ADS)

Saito, Y.; Iijima, I.; Matsuzaka, Y.; Matsushima, K.; Tanaka, S.; Kajiwara, K.; Shimadu, S.

2014-10-01

The essential reason of the lobed-pumpkin shaped super-pressure balloon to withstand against the high pressure is that the local curvature of the balloon film is kept small. Recently, it has been found that the small local curvature can also be obtained if the balloon is covered by a diamond-shaped net with a vertically elongated shape. The development of the super-pressure balloon using this method was started from a 3-m balloon with a polyethylene film covered by a net using Kevlar ropes. The ground inflation test showed the expected high burst pressure. Then, a 6-m and a 12-m balloon using a polyethylene film and a net using the Vectran were developed and stable deployment was checked through the ground inflation tests. The flight test of a 3000 m3 balloon was performed in 2013 and shown to resist a pressure of at least 400 Pa. In the future, after testing a new design to relax a possible stress concentration around the polar area, test flights of scaled balloons will be performed gradually enlarging their size. The goal is to launch a 300,000 m3 super-pressure balloon.

Determining casting defects in near-net shape casting aluminum parts by computed tomography

NASA Astrophysics Data System (ADS)

Li, Jiehua; Oberdorfer, Bernd; Habe, Daniel; Schumacher, Peter

2018-03-01

Three types of near-net shape casting aluminum parts were investigated by computed tomography to determine casting defects and evaluate quality. The first, second, and third parts were produced by low-pressure die casting (Al-12Si-0.8Cu-0.5Fe-0.9Mg-0.7Ni-0.2Zn alloy), die casting (A356, Al-7Si-0.3Mg), and semi-solid casting (A356, Al-7Si-0.3Mg), respectively. Unlike die casting (second part), low-pressure die casting (first part) significantly reduced the formation of casting defects (i.e., porosity) due to its smooth filling and solidification under pressure. No significant casting defect was observed in the third part, and this absence of defects indicates that semi-solid casting could produce high-quality near-net shape casting aluminum parts. Moreover, casting defects were mostly distributed along the eutectic grain boundaries. This finding reveals that refinement of eutectic grains is necessary to optimize the distribution of casting defects and reduce their size. This investigation demonstrated that computed tomography is an efficient method to determine casting defects in near-net shape casting aluminum parts.

Networks of myelin covariance.

PubMed

Melie-Garcia, Lester; Slater, David; Ruef, Anne; Sanabria-Diaz, Gretel; Preisig, Martin; Kherif, Ferath; Draganski, Bogdan; Lutti, Antoine

2018-04-01

Networks of anatomical covariance have been widely used to study connectivity patterns in both normal and pathological brains based on the concurrent changes of morphometric measures (i.e., cortical thickness) between brain structures across subjects (Evans, ). However, the existence of networks of microstructural changes within brain tissue has been largely unexplored so far. In this article, we studied in vivo the concurrent myelination processes among brain anatomical structures that gathered together emerge to form nonrandom networks. We name these "networks of myelin covariance" (Myelin-Nets). The Myelin-Nets were built from quantitative Magnetization Transfer data-an in-vivo magnetic resonance imaging (MRI) marker of myelin content. The synchronicity of the variations in myelin content between anatomical regions was measured by computing the Pearson's correlation coefficient. We were especially interested in elucidating the effect of age on the topological organization of the Myelin-Nets. We therefore selected two age groups: Young-Age (20-31 years old) and Old-Age (60-71 years old) and a pool of participants from 48 to 87 years old for a Myelin-Nets aging trajectory study. We found that the topological organization of the Myelin-Nets is strongly shaped by aging processes. The global myelin correlation strength, between homologous regions and locally in different brain lobes, showed a significant dependence on age. Interestingly, we also showed that the aging process modulates the resilience of the Myelin-Nets to damage of principal network structures. In summary, this work sheds light on the organizational principles driving myelination and myelin degeneration in brain gray matter and how such patterns are modulated by aging. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Validated simulator for space debris removal with nets and other flexible tethers applications

NASA Astrophysics Data System (ADS)

Gołębiowski, Wojciech; Michalczyk, Rafał; Dyrek, Michał; Battista, Umberto; Wormnes, Kjetil

2016-12-01

In the context of active debris removal technologies and preparation activities for the e.Deorbit mission, a simulator for net-shaped elastic bodies dynamics and their interactions with rigid bodies, has been developed. Its main application is to aid net design and test scenarios for space debris deorbitation. The simulator can model all the phases of the debris capturing process: net launch, flight and wrapping around the target. It handles coupled simulation of rigid and flexible bodies dynamics. Flexible bodies were implemented using Cosserat rods model. It allows to simulate flexible threads or wires with elasticity and damping for stretching, bending and torsion. Threads may be combined into structures of any topology, so the software is able to simulate nets, pure tethers, tether bundles, cages, trusses, etc. Full contact dynamics was implemented. Programmatic interaction with simulation is possible - i.e. for control implementation. The underlying model has been experimentally validated and due to significant gravity influence, experiment had to be performed in microgravity conditions. Validation experiment for parabolic flight was a downscaled process of Envisat capturing. The prepacked net was launched towards the satellite model, it expanded, hit the model and wrapped around it. The whole process was recorded with 2 fast stereographic camera sets for full 3D trajectory reconstruction. The trajectories were used to compare net dynamics to respective simulations and then to validate the simulation tool. The experiments were performed on board of a Falcon-20 aircraft, operated by National Research Council in Ottawa, Canada. Validation results show that model reflects phenomenon physics accurately enough, so it may be used for scenario evaluation and mission design purposes. The functionalities of the simulator are described in detail in the paper, as well as its underlying model, sample cases and methodology behind validation. Results are presented and typical use cases are discussed showing that the software may be used to design throw nets for space debris capturing, but also to simulate deorbitation process, chaser control system or general interactions between rigid and elastic bodies - all in convenient and efficient way. The presented work was led by SKA Polska under the ESA contract, within the CleanSpace initiative.

Net Gains

ERIC Educational Resources Information Center

Fielker, David

2008-01-01

The Easter conference 2008 had several activities which for the author raised the same questions on cube nets in some work with eight-year-olds some time ago. In this article, the author muses on some problems from the Easter conference regarding nets of shapes. (Contains 1 note.)

Solidification in direct metal deposition by LENS processing

NASA Astrophysics Data System (ADS)

Hofmeister, William; Griffith, Michelle

2001-09-01

Thermal imaging and metallographic analysis were used to study Laser Engineered Net Shaping (LENS™) processing of 316 stainless steel and H13 tool steel. The cooling rates at the solid-liquid interface were measured over a range of conduction conditions. The length scale of the molten zone controls cooling rates during solidification in direct metal deposition. In LENS processing, the molten zone ranges from 0.5 mm in length to 1.5 mm, resulting in cooling rates at the solid-liquid interface ranging from 200 6,000 Ks-1.

Electrohydraulic Forming of Near-Net Shape Automotive Panels

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

Golovaschenko, Sergey F.

2013-09-26

The objective of this project was to develop the electrohydraulic forming (EHF) process as a near-net shape automotive panel manufacturing technology that simultaneously reduces the energy embedded in vehicles and the energy consumed while producing automotive structures. Pulsed pressure is created via a shockwave generated by the discharge of high voltage capacitors through a pair of electrodes in a liquid-filled chamber. The shockwave in the liquid initiated by the expansion of the plasma channel formed between two electrodes propagates towards the blank and causes the blank to be deformed into a one-sided die cavity. The numerical model of the EHFmore » process was validated experimentally and was successfully applied to the design of the electrode system and to a multi-electrode EHF chamber for full scale validation of the process. The numerical model was able to predict stresses in the dies during pulsed forming and was validated by the experimental study of the die insert failure mode for corner filling operations. The electrohydraulic forming process and its major subsystems, including durable electrodes, an EHF chamber, a water/air management system, a pulse generator and integrated process controls, were validated to be capable to operate in a fully automated, computer controlled mode for forming of a portion of a full-scale sheet metal component in laboratory conditions. Additionally, the novel processes of electrohydraulic trimming and electrohydraulic calibration were demonstrated at a reduced-scale component level. Furthermore, a hybrid process combining conventional stamping with EHF was demonstrated as a laboratory process for a full-scale automotive panel formed out of AHSS material. The economic feasibility of the developed EHF processes was defined by developing a cost model of the EHF process in comparison to the conventional stamping process.« less

Identification and characterization of neutrophil extracellular trap shapes in flow cytometry

NASA Astrophysics Data System (ADS)

Ginley, Brandon; Emmons, Tiffany; Sasankan, Prabhu; Urban, Constantin; Segal, Brahm H.; Sarder, Pinaki

2017-03-01

Neutrophil extracellular trap (NET) formation is an alternate immunologic weapon used mainly by neutrophils. Chromatin backbones fused with proteins derived from granules are shot like projectiles onto foreign invaders. It is thought that this mechanism is highly anti-microbial, aids in preventing bacterial dissemination, is used to break down structures several sizes larger than neutrophils themselves, and may have several more uses yet unknown. NETs have been implied to be involved in a wide array of systemic host immune defenses, including sepsis, autoimmune diseases, and cancer. Existing methods used to visually quantify NETotic versus non-NETotic shapes are extremely time-consuming and subject to user bias. These limitations are obstacles to developing NETs as prognostic biomarkers and therapeutic targets. We propose an automated pipeline for quantitatively detecting neutrophil and NET shapes captured using a flow cytometry-imaging system. Our method uses contrast limited adaptive histogram equalization to improve signal intensity in dimly illuminated NETs. From the contrast improved image, fixed value thresholding is applied to convert the image to binary. Feature extraction is performed on the resulting binary image, by calculating region properties of the resulting foreground structures. Classification of the resulting features is performed using Support Vector Machine. Our method classifies NETs from neutrophils without traps at 0.97/0.96 sensitivity/specificity on n = 387 images, and is 1500X faster than manual classification, per sample. Our method can be extended to rapidly analyze whole-slide immunofluorescence tissue images for NET classification, and has potential to streamline the quantification of NETs for patients with diseases associated with cancer and autoimmunity.

Effect of Tooling Material on the Internal Surface Quality of Ti6Al4V Parts Fabricated by Hot Isostatic Pressing

NASA Astrophysics Data System (ADS)

Cai, Chao; Song, Bo; Wei, Qingsong; Yan, Wu; Xue, Pengju; Shi, Yusheng

2017-01-01

For the net-shape hot isostatic pressing (HIP) process, control of the internal surface roughness of as-HIPped parts remains a challenge for practical engineering. To reveal the evolution mechanism of the internal surface of the parts during the HIP process, the effect of different tooling materials (H13, T8, Cr12 steel, and graphite) as internal cores on the interfacial diffusion and surface roughness was systematically studied.

Combustion Synthesis of Ca3(PO4)2 Net-Shape Surgical Implants

NASA Technical Reports Server (NTRS)

Ayers, Reed A.; Castillo, Martin; Gottoli, Guglielmo; Moore, John J.; Simske, Steven J.

2006-01-01

Self-propagating high-temperature combustion synthesis (SHS) is the basis of a method of making components of porous tricalcium phosphate [Ca3(PO4)2] and related compounds in net sizes and shapes for use as surgical implants that are compatible with bone. The SHS method offers advantages over prior methods of manufacturing Ca3(PO4)2-based surgical implants.

Rapid process for producing transparent, monolithic porous glass

DOEpatents

Coronado, Paul R [Livermore, CA

2006-02-14

A process for making transparent porous glass monoliths from gels. The glass is produced much faster and in much larger sizes than present technology for making porous glass. The process reduces the cost of making large porous glass monoliths because: 1) the process does not require solvent exchange nor additives to the gel to increase the drying rates, 2) only moderate temperatures and pressures are used so relatively inexpensive equipment is needed, an 3) net-shape glass monoliths are possible using this process. The process depends on the use of temperature to control the partial pressure of the gel solvent in a closed vessel, resulting in controlled shrinking during drying.

Constructivism, Optimality Theory and Language Acquisition. The Shapes We Make in Each Other's Heads.

ERIC Educational Resources Information Center

Whincop, Chris

1996-01-01

This paper identifies a feature of human brain neural nets that may be described as the principle of ease of processing (PEP), and that, it is argued, is the primary force guiding a learner towards a target grammar. It is suggested that the same principle lies at the heart of Optimality Theory, which characterizes the course of language…

Evaluating CMA equalization of SOQPSK-TG data for aeronautical telemetry

NASA Astrophysics Data System (ADS)

Cole-Rhodes, Arlene; KoneDossongui, Serge; Umuolo, Henry; Rice, Michael

2015-05-01

This paper presents the results of using a constant modulus algorithm (CMA) to recover shaped offset quadrature-phase shift keying (SOQPSK)-TG modulated data, which has been transmitted using the iNET data packet structure. This standard is defined and used for aeronautical telemetry. Based on the iNET-packet structure, the adaptive block processing CMA equalizer can be initialized using the minimum mean square error (MMSE) equalizer [3]. This CMA equalizer is being evaluated for use on iNET structured data, with initial tests being conducted on measured data which has been received in a controlled laboratory environment. Thus the CMA equalizer is applied at the receiver to data packets which have been experimentally generated in order to determine the feasibility of our equalization approach, and its performance is compared to that of the MMSE equalizer. Performance evaluation is based on computed bit error rate (BER) counts for these equalizers.

Cost-Benefit Analysis for the Advanced Near Net Shape Technology (ANNST) Method for Fabricating Stiffened Cylinders

NASA Technical Reports Server (NTRS)

Stoner, Mary Cecilia; Hehir, Austin R.; Ivanco, Marie L.; Domack, Marcia S.

2016-01-01

This cost-benefit analysis assesses the benefits of the Advanced Near Net Shape Technology (ANNST) manufacturing process for fabricating integrally stiffened cylinders. These preliminary, rough order-of-magnitude results report a 46 to 58 percent reduction in production costs and a 7-percent reduction in weight over the conventional metallic manufacturing technique used in this study for comparison. Production cost savings of 35 to 58 percent were reported over the composite manufacturing technique used in this study for comparison; however, the ANNST concept was heavier. In this study, the predicted return on investment of equipment required for the ANNST method was ten cryogenic tank barrels when compared with conventional metallic manufacturing. The ANNST method was compared with the conventional multi-piece metallic construction and composite processes for fabricating integrally stiffened cylinders. A case study compared these three alternatives for manufacturing a cylinder of specified geometry, with particular focus placed on production costs and process complexity, with cost analyses performed by the analogy and parametric methods. Furthermore, a scalability study was conducted for three tank diameters to assess the highest potential payoff of the ANNST process for manufacture of large-diameter cryogenic tanks. The analytical hierarchy process (AHP) was subsequently used with a group of selected subject matter experts to assess the value of the various benefits achieved by the ANNST method for potential stakeholders. The AHP study results revealed that decreased final cylinder mass and quality assurance were the most valued benefits of cylinder manufacturing methods, therefore emphasizing the relevance of the benefits achieved with the ANNST process for future projects.

Role of Erosion in Shaping Point Bars

NASA Astrophysics Data System (ADS)

Moody, J.; Meade, R.

2012-04-01

A powerful metaphor in fluvial geomorphology has been that depositional features such as point bars (and other floodplain features) constitute the river's historical memory in the form of uniformly thick sedimentary deposits waiting for the geomorphologist to dissect and interpret the past. For the past three decades, along the channel of Powder River (Montana USA) we have documented (with annual cross-sectional surveys and pit trenches) the evolution of the shape of three point bars that were created when an extreme flood in 1978 cut new channels across the necks of two former meander bends and radically shifted the location of a third bend. Subsequent erosion has substantially reshaped, at different time scales, the relic sediment deposits of varying age. At the weekly to monthly time scale (i.e., floods from snowmelt or floods from convective or cyclonic storms), the maximum scour depth was computed (by using a numerical model) at locations spaced 1 m apart across the entire point bar for a couple of the largest floods. The maximum predicted scour is about 0.22 m. At the annual time scale, repeated cross-section topographic surveys (25 during 32 years) indicate that net annual erosion at a single location can be as great as 0.5 m, and that the net erosion is greater than net deposition during 8, 16, and 32% of the years for the three point bars. On average, the median annual net erosion was 21, 36, and 51% of the net deposition. At the decadal time scale, an index of point bar preservation often referred to as completeness was defined for each cross section as the percentage of the initial deposit (older than 10 years) that was still remaining in 2011; computations indicate that 19, 41, and 36% of the initial deposits of sediment were eroded. Initial deposits were not uniform in thickness and often represented thicker pods of sediment connected by thin layers of sediment or even isolated pods at different elevations across the point bar in response to multiple floods during a water year. Erosion often was preferential and removed part or all of pods at lower elevations, and in time left what appears to be a random arrangement of sediment pods forming the point bar. Thus, we conclude that the erosional process is as important as the deposition process in shaping the final form of the point bar, and that point bars are not uniformly aggradational or transgressive deposits of sediment in which the age of the deposit increases monotonically downward at all locations across the point bar.

Fabrication of High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner for Advanced Rocket Engines

NASA Technical Reports Server (NTRS)

Bhat, Biliyar N.; Greene, Sandra E.; Singh, Jogender

2016-01-01

NARloy-Z alloy (Cu-3 percent, Ag-0.5 percent, Zr) is a state of the art alloy currently used for fabricating rocket engine combustion chamber liners. Research conducted at NASA-MSFC and Penn State – Applied Research Laboratory has shown that thermal conductivity of NARloy-Z can be increased significantly by adding diamonds to form a composite (NARloy-Z-D). NARloy-Z-D is also lighter than NARloy-Z. These attributes make this advanced composite material an ideal candidate for fabricating combustion chamber liner for an advanced rocket engine. Increased thermal conductivity will directly translate into increased turbopump power and increased chamber pressure for improved thrust and specific impulse. This paper describes the process development for fabricating a subscale high thermal conductivity NARloy-Z-D combustion chamber liner using Field Assisted Sintering Technology (FAST). The FAST process uses a mixture of NARloy-Z and diamond powders which is sintered under pressure at elevated temperatures. Several challenges were encountered, i.e., segregation of diamonds, machining the super hard NARloy-Z-D composite, net shape fabrication and nondestructive examination. The paper describes how these challenges were addressed. Diamonds coated with copper (CuD) appear to give the best results. A near net shape subscale combustion chamber liner is being fabricated by diffusion bonding cylindrical rings of NARloy-Z-CuD using the FAST process.

A novel one-pot process for near-net-shape fabrication of open-porous resorbable hydroxyapatite/protein composites and in vivo assessment.

PubMed

Mueller, Berit; Koch, Dietmar; Lutz, Rainer; Schlegel, Karl A; Treccani, Laura; Rezwan, Kurosch

2014-09-01

We present a mild one-pot freeze gelation process for fabricating near-net, complex-shaped hydroxyapatite scaffolds and to directly incorporate active proteins during scaffold processing. In particular, the direct protein incorporation enables a simultaneous adjustment and control of scaffold microstructure, porosity, resorbability and enhancement of initial mechanical and handling stability. Two proteins, serum albumin and lysozyme, are selected and their effect on scaffold stability and microstructure investigated by biaxial strength tests, electron microscopy, and mercury intrusion porosimetry. The resulting hydroxyapatite/protein composites feature adjustable porosities from 50% to 70% and a mechanical strength ranging from 2 to 6 MPa comparable to that of human spongiosa without any sintering step. Scaffold degradation behaviour and protein release are assessed by in vitro studies. A preliminary in vivo assessment of scaffold biocompatibility and resorption behaviour in adult domestic pigs is discussed. After implantation, composites were resorbed up to 50% after only 4 weeks and up to 65% after 8 weeks. In addition, 14% new bone formation after 4 weeks and 37% after 8 weeks were detected. All these investigations demonstrate the outstanding suitability of the one-pot-process to create, in a customisable and reliable way, biocompatible scaffolds with sufficient mechanical strength for handling and surgical insertion, and for potential use as biodegradable bone substitutes and versatile platform for local drug delivery. Copyright © 2014 Elsevier B.V. All rights reserved.

Powder Injection Molding (PIM) for Low Cost Manufacturing of Intricate Parts to Net-Shape

DTIC Science & Technology

2006-05-01

tungsten - or molybdenum-pseudoalloys, which can be net-shape manufactured only by PIM because of the tight dimension tolerances needed for the final...materials. Rhenium metal, for instance, which costs about US$ 800 /lb, offers the advantage of a high melting point. It can maintain reasonable...tubes, valves and thrusters of solid fluid propeller systems. Production of these components is however both expensive and difficult, as rhenium cannot

Additive Manufacturing of Shape Memory Alloys

NASA Astrophysics Data System (ADS)

Van Humbeeck, Jan

2018-04-01

Selective Laser Melting (SLM) is an additive manufacturing production process, also called 3D printing, in which functional, complex parts are produced by selectively melting patterns in consecutive layers of powder with a laser beam. The pattern the laser beam is following is controlled by software that calculates the pattern by slicing a 3D CAD model of the part to be constructed. Apart from SLM, also other additive manufacturing techniques such as EBM (Electron Beam Melting), FDM (Fused Deposition Modelling), WAAM (Wire Arc Additive Manufacturing), LENS (Laser Engineered Net Shaping such as Laser Cladding) and binder jetting allow to construct complete parts layer upon layer. But since more experience of AM of shape memory alloys is collected by SLM, this paper will overview the potentials, limits and problems of producing NiTi parts by SLM.

Processing study of injection molding of silicon nitride for engine applications

NASA Technical Reports Server (NTRS)

Rorabaugh, M. E.; Yeh, H. C.

1985-01-01

The high hardness of silicon nitride, which is currently under consideration as a structural material for such hot engine components as turbine blades, renders machining of the material prohibitively costly; the near net shape forming technique of injection molding is accordingly favored as a means for component fabrication. Attention is presently given to the relationships between injection molding processing parameters and the resulting microstructural and mechanical properties of the resulting engine parts. An experimental program has been conducted under NASA sponsorship which tests the quality of injection molded bars of silicon nitride at various stages of processing.

A Framework for Modeling and Simulation of the Artificial

DTIC Science & Technology

2012-01-01

y or n) >> y Name: petra Simple Aspects: face_shape/thin, nose/small, skintone/light, hair_color/black, hair_type/curly Integrated Aspects...Multiconference. Orlando, FL (2012) 23. Mittal, S., Risco- Martin , J.: Netcentric System of Systems Engineering with DEVS Unified Process. CRC Press (2012) 24...Mittal, S., Risco- Martin , J., Zeigler, B.: DEVS-based simulation web services for net-centric T&E. In: Proceedings of the 2007 summer computer

Effects of Temperature and Steam Environment on Fatigue Behavior of Three SIC/SIC Ceramic Matrix Composites

DTIC Science & Technology

2008-09-01

Infiltration (CVI), Chemical Vapor Deposition (CVD) and polymer impregnation/ pyrolysis (PIP) [5:20, 32]. The SiC fibers currently... composite was infiltrated with a mixture of polymer , filler particles and solvent. During pyrolysis under nitrogen at temperatures > 1000 °C, the...using polymer infiltration and pyrolysis (PIP) method. Polymer infiltration and pyrolysis processing method allows near-net-shape molding and

Net Shape Spin Formed Cryogenic Aluminum Lithium Cryogenic Tank Domes for Lower Cost Higher Performance Launch Vehicles

NASA Technical Reports Server (NTRS)

Curreri, Peter A.; Hoffman, Eric; Domack, Marcia; Brewster, Jeb; Russell, Carolyn

2013-01-01

With the goal of lower cost (simplified manufacturing and lower part count) and higher performance (higher strength to weight alloys) the NASA Technical Maturation Program in 2006 funded a proposal to investigate spin forming of space launch vehicle cryogenic tank domes. The project funding continued under the NASA Exploration Technology Development Program through completion in FY12. The first phase of the project involved spin forming of eight, 1 meter diameter "path finder" domes. Half of these were processed using a concave spin form process (MT Aerospace, Augsburg Germany) and the other half using a convex process (Spincraft, Boston MA). The convex process has been used to produce the Ares Common Bulkhead and the concave process has been used to produce dome caps for the Space Shuttle light weight external tank and domes for the NASDA H2. Aluminum Lithium material was chosen because of its higher strength to weight ratio than the Aluminum 2219 baseline. Aluminum lithium, in order to obtain the desired temper (T8), requires a cold stretch after the solution heat treatment and quench. This requirement favors the concave spin form process which was selected for scale up. This paper describes the results of processing four, 5.5 meter diameter (upper stage scale) net shaped spin formed Aluminum Lithium domes. In order to allow scalability beyond the limits of foundry and rolling mills (about 12 foot width) the circular blank contained one friction stir weld (heavy lifter scales require a flat blank containing two welds). Mechanical properties data (tensile, fracture toughness, stress corrosion, and simulated service testing) for the parent metal and weld will also be discussed.

Inspection of Space Station Cold Plate Using Visual and Automated Holographic Techniques

NASA Technical Reports Server (NTRS)

Decker, Arthur J.; Melis, Matthew E.; Weiland, Kenneth E.

1999-01-01

Real-time holography has been used to confirm the presence of non-uniformity in the construction of an International Space Station cold plate. Ultrasonic C-scans have previously shown suspected areas of cooling fin disbonds. But both neural-net processed and visual holography did not evidence any progressive permanent changes resulting from 3000 pressurization and relaxation cycles of a Dash 8 cold plate. Neural-net and visual inspections were performed of characteristic patterns generated from electronic time-average holograms of the vibrating cold plate. Normal modes of vibration were excited at very low amplitudes for this purpose, The neural nets were trained to flag very small changes in the mode shapes as encoded in the characteristic patterns. Both the whole cold plate and a zoomed region were inspected. The inspections were conducted before, after, and during pressurization and relaxation cycles of the cold plate. A water-filled cold plate was pressurized to 120 psig (827 kPa) and relaxed for each cycle. Each cycle required 5 seconds. Both the artificial neural networks and the inspectors were unable to detect changes in the mode shapes of the relaxed cold plate. The cold plate was also inspected visually using real-time holography and double-exposure holography. Regions of non-uniformity correlating with the C-scans were apparent, but the interference patterns did not change after 3000 pressurization and relaxation cycles. These tests constituted the first practical application of a neural-net inspection technique developed originally with support from the Director's Discretionary Fund at the Glenn Research Center at Lewis Field.

How small bugs tie down big rocks: Measuring and modeling the forces acting between nets spun by Caddisfly larvae (Hydropsychidae) and gravel particles at the onset of motion

NASA Astrophysics Data System (ADS)

Mclaughlin, M. K.; Tumolo, B.; Sklar, L. S.; Albertson, L.; Daniels, M.

2017-12-01

The influence of life on geomorphic processes is commonly inferred from correlations between the size and abundance of individual organisms and the change in process thresholds and rates from abiotic conditions. However, to understand and model the underlying mechanisms, it is helpful to make direct measurements of the forces acting between organisms and the earth materials they inhabit. For example, flume studies have found that the presence of net-spinning caddisfly larvae (Trichoptera: Hydropsychidae) can increase the shear stress required to initiate particle motion by more than a factor of two, with potentially significant implications for the timing and magnitude of bedload sediment transport in gravel-bedded rivers. To explore the underlying mechanics we conducted flume experiments at the Stroud Water Research center in Avonadale, Pennsylvania, using strain gages to measure the forces acting between caddisfly nets and sediment particles of various sizes, during the process of initial particle motion. We combine these measurements with high-speed video images to document for the first time, the three dimensional dynamics of net stretching, tearing, and detachment that govern the magnitude of the increase in critical shear stress. We are using these data and insights to substantially improve a previously published theoretical model for the mechanics of sediment stabilization by caddisfly larvae. In particular, we seek to constrain the range of particle sizes potentially stabilized by caddisfly larvae and explain mechanistically why the effect of caddisfly nets varies with particle size. These predictions have implications for understanding feedbacks between bed stabilization by caddisflies, insect density, inter-specific niche partitioning, and the movement of sediment that shapes gravel-bed channels.

Laser Hot Wire Process: A Novel Process for Near-Net Shape Fabrication for High-Throughput Applications

NASA Astrophysics Data System (ADS)

Kottman, Michael; Zhang, Shenjia; McGuffin-Cawley, James; Denney, Paul; Narayanan, Badri K.

2015-03-01

The laser hot wire process has gained considerable interest for additive manufacturing applications, leveraging its high deposition rate, low dilution, thermal stability, and general metallurgical control including the ability to introduce and preserve desired meta-stable phases. Recent advancements in closed-loop process control and laser technology have increased productivity, process stability, and control of deposit metallurgy. The laser hot wire process has shown success in several applications: repairing and rejuvenating casting dies, depositing a variety of alloys including abrasion wear-resistant overlays with solid and tubular wires, and producing low-dilution (<5%) nickel alloy overlays for corrosion applications. The feasibility of fabricating titanium buildups is being assessed for aerospace applications.

Precision cast vs. wrought superalloys

NASA Technical Reports Server (NTRS)

Tien, J. K.; Borofka, J. C.; Casey, M. E.

1986-01-01

While cast polycrystalline superalloys recommend themselves in virtue of better 'buy-to-fly' ratios and higher strengthening gamma-prime volume fractions than those of wrought superalloys, the expansion of their use into such critical superalloy applications as gas turbine hot section components has been slowed by insufficient casting process opportunities for microstructural control. Attention is presently drawn, however, to casting process developments facilitating the production of defect-tolerant superalloy castings having improved fracture reliability. Integrally bladed turbine wheel and thin-walled turbine exhaust case near-net-shape castings have been produced by these means.

Net Shape Technology in Aerospace Structures. Volume 1.

DTIC Science & Technology

1986-11-01

ofI nIo n- destructive evaluation methods, such a s ult rasonic inspection, in detecting otherwise hidden defects in parts made of the material. Pratt...SCHEDULE 4. PERFORMING ORGANIZATION REPORT NUMBER( S ) 5. MONITORING ORGANIZATION REPORT NUMBER( S ) n/a n/a 6a. NAME OF PERFORMING ORGANIZATION 6b...a n/a n/a 11 TITLE (Include Security Classification) Net Shape Technology in Aerospace Structures, Vol. I (U) 12. PERSONAL AUTHOR( S ) 13a. TYPE OF

Low Cost, Net Shape Fabrication of Rhenium and High Temperature Materials for Rocket Engine Components

DTIC Science & Technology

2001-03-01

tungsten thin wall nozzle liner removed from reusable mandrel. b) W and Re rocket, nozzle inserts (2 inserts per mandrel) for Air Force. Rhenium PPI...compares the fabrication time for the VPS nozzles with equivalent carbon / carbon composite (C/C) and forged tungsten materials. Table 5: Comparison of...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO1 1181 TITLE: Low Cost, Net Shape Fabrication of Rhenium and High

The pH dependency of N-converting enzymatic processes, pathways and microbes: effect on net N2 O production.

PubMed

Blum, Jan-Michael; Su, Qingxian; Ma, Yunjie; Valverde-Pérez, Borja; Domingo-Félez, Carlos; Jensen, Marlene Mark; Smets, Barth F

2018-05-01

Nitrous oxide (N 2 O) is emitted during microbiological nitrogen (N) conversion processes, when N 2 O production exceeds N 2 O consumption. The magnitude of N 2 O production vs. consumption varies with pH and controlling net N 2 O production might be feasible by choice of system pH. This article reviews how pH affects enzymes, pathways and microorganisms that are involved in N-conversions in water engineering applications. At a molecular level, pH affects activity of cofactors and structural elements of relevant enzymes by protonation or deprotonation of amino acid residues or solvent ligands, thus causing steric changes in catalytic sites or proton/electron transfer routes that alter the enzymes' overall activity. Augmenting molecular information with, e.g., nitritation or denitrification rates yields explanations of changes in net N 2 O production with pH. Ammonia oxidizing bacteria are of highest relevance for N 2 O production, while heterotrophic denitrifiers are relevant for N 2 O consumption at pH > 7.5. Net N 2 O production in N-cycling water engineering systems is predicted to display a 'bell-shaped' curve in the range of pH 6.0-9.0 with a maximum at pH 7.0-7.5. Net N 2 O production at acidic pH is dominated by N 2 O production, whereas N 2 O consumption can outweigh production at alkaline pH. Thus, pH 8.0 may be a favourable pH set-point for water treatment applications regarding net N 2 O production. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

Decision-making deficits in patients with chronic schizophrenia: Iowa Gambling Task and Prospect Valence Learning model.

PubMed

Kim, Myung-Sun; Kang, Bit-Na; Lim, Jae Young

2016-01-01

Decision-making is the process of forming preferences for possible options, selecting and executing actions, and evaluating the outcome. This study used the Iowa Gambling Task (IGT) and the Prospect Valence Learning (PVL) model to investigate deficits in risk-reward related decision-making in patients with chronic schizophrenia, and to identify decision-making processes that contribute to poor IGT performance in these patients. Thirty-nine patients with schizophrenia and 31 healthy controls participated. Decision-making was measured by total net score, block net scores, and the total number of cards selected from each deck of the IGT. PVL parameters were estimated with the Markov chain Monte Carlo sampling scheme in OpenBugs and BRugs, its interface to R, and the estimated parameters were analyzed with the Mann-Whitney U-test. The schizophrenia group received significantly lower total net scores compared to the control group. In terms of block net scores, an interaction effect of group × block was observed. The block net scores of the schizophrenia group did not differ across the five blocks, whereas those of the control group increased as the blocks progressed. The schizophrenia group obtained significantly lower block net scores in the fourth and fifth blocks of the IGT and selected cards from deck D (advantageous) less frequently than the control group. Additionally, the schizophrenia group had significantly lower values on the utility-shape, loss-aversion, recency, and consistency parameters of the PVL model. These results indicate that patients with schizophrenia experience deficits in decision-making, possibly due to failure in learning the expected value of each deck, and incorporating outcome experiences of previous trials into expectancies about options in the present trial.

Shape adjustment optimization and experiment of cable-membrane reflectors

NASA Astrophysics Data System (ADS)

Du, Jingli; Gu, Yongzhen; Bao, Hong; Wang, Congsi; Chen, Xiaofeng

2018-05-01

Cable-membrane structures are widely employed for large space reflectors due to their lightweight, compact and easy package. In these structures, membranes are attached to cable net, serving as reflectors themselves or as supporting structures for other reflective surface. The cable length and membrane shape have to be carefully designed and fabricated to guarantee the desired reflector surface shape. However, due to inevitable error in cable length and membrane shape during the manufacture and assembly of cable-membrane reflectors, some cables have to be designed to be capable of length adjustment. By carefully adjusting the length of these cables, the degeneration in reflector shape precision due to this inevitable error can be effectively reduced. In the paper a shape adjustment algorithm for cable-membrane reflectors is proposed. Meanwhile, model updating is employed during shape adjustment to decrease the discrepancy of the numerical model with respect to the actual reflector. This discrepancy has to be considered because during attaching membranes to cable net, the accuracy of the membrane shape is hard to guarantee. Numerical examples and experimental results demonstrate the proposed method.

Post-processing of 3D-printed parts using femtosecond and picosecond laser radiation

NASA Astrophysics Data System (ADS)

Mingareev, Ilya; Gehlich, Nils; Bonhoff, Tobias; Meiners, Wilhelm; Kelbassa, Ingomar; Biermann, Tim; Richardson, Martin C.

2014-03-01

Additive manufacturing, also known as 3D-printing, is a near-net shape manufacturing approach, delivering part geometry that can be considerably affected by various process conditions, heat-induced distortions, solidified melt droplets, partially fused powders, and surface modifications induced by the manufacturing tool motion and processing strategy. High-repetition rate femtosecond and picosecond laser radiation was utilized to improve surface quality of metal parts manufactured by laser additive techniques. Different laser scanning approaches were utilized to increase the ablation efficiency and to reduce the surface roughness while preserving the initial part geometry. We studied post-processing of 3D-shaped parts made of Nickel- and Titanium-base alloys by utilizing Selective Laser Melting (SLM) and Laser Metal Deposition (LMD) as additive manufacturing techniques. Process parameters such as the pulse energy, the number of layers and their spatial separation were varied. Surface processing in several layers was necessary to remove the excessive material, such as individual powder particles, and to reduce the average surface roughness from asdeposited 22-45 μm to a few microns. Due to the ultrafast laser-processing regime and the small heat-affected zone induced in materials, this novel integrated manufacturing approach can be used to post-process parts made of thermally and mechanically sensitive materials, and to attain complex designed shapes with micrometer precision.

Radiative and convective properties of 316L Stainless Steel fabricated using the Laser Engineered Net Shaping process

NASA Astrophysics Data System (ADS)

Knopp, Jonathan

Temperature evolution of metallic materials during the additive manufacturing process has direct influence in determining the materials microstructure and resultant characteristics. Through the power of Infrared (IR) thermography it is now possible to monitor thermal trends in a build structure, giving the power to adjust building parameters in real time. The IR camera views radiation in the IR wavelengths and determines temperature of an object by the amount of radiation emitted from the object in those wavelengths. Determining the amount of radiation emitted from the material, known as a materials emissivity, can be difficult in that emissivity is affected by both temperature and surface finish. It has been shown that the use of a micro-blackbody cavity can be used as an accurate reference temperature when the sample is held at thermal equilibrium. A micro-blackbody cavity was created in a sample of 316L Stainless Steel after being fabricated during using the Laser Engineered Net Shaping (LENS) process. Holding the sample at thermal equilibrium and using the micro-blackbody cavity as a reference and thermocouple as a second reference emissivity values were able to be obtained. IR thermography was also used to observe the manufacturing of these samples. When observing the IR thermography, patterns in the thermal history of the build were shown to be present as well as distinct cooling rates of the material. This information can be used to find true temperatures of 316L Stainless Steel during the LENS process for better control of desired material properties as well as future work in determining complete energy balance.

Quantitative CT analysis for the preoperative prediction of pathologic grade in pancreatic neuroendocrine tumors

NASA Astrophysics Data System (ADS)

Chakraborty, Jayasree; Pulvirenti, Alessandra; Yamashita, Rikiya; Midya, Abhishek; Gönen, Mithat; Klimstra, David S.; Reidy, Diane L.; Allen, Peter J.; Do, Richard K. G.; Simpson, Amber L.

2018-02-01

Pancreatic neuroendocrine tumors (PanNETs) account for approximately 5% of all pancreatic tumors, affecting one individual per million each year.1 PanNETs are difficult to treat due to biological variability from benign to highly malignant, indolent to very aggressive. The World Health Organization classifies PanNETs into three categories based on cell proliferative rate, usually detected using the Ki67 index and cell morphology: low-grade (G1), intermediate-grade (G2) and high-grade (G3) tumors. Knowledge of grade prior to treatment would select patients for optimal therapy: G1/G2 tumors respond well to somatostatin analogs and targeted or cytotoxic drugs whereas G3 tumors would be targeted with platinum or alkylating agents.2, 3 Grade assessment is based on the pathologic examination of the surgical specimen, biopsy or ne-needle aspiration; however, heterogeneity in the proliferative index can lead to sampling errors.4 Based on studies relating qualitatively assessed shape and enhancement characteristics on CT imaging to tumor grade in PanNET,5 we propose objective classification of PanNET grade with quantitative analysis of CT images. Fifty-five patients were included in our retrospective analysis. A pathologist graded the tumors. Texture and shape-based features were extracted from CT. Random forest and naive Bayes classifiers were compared for the classification of G1/G2 and G3 PanNETs. The best area under the receiver operating characteristic curve (AUC) of 0:74 and accuracy of 71:64% was achieved with texture features. The shape-based features achieved an AUC of 0:70 and accuracy of 78:73%.

Regional difference of the vertical structure of seasonal thermocline and its impact on sea surface temperature in the North Pacific

NASA Astrophysics Data System (ADS)

Yamaguchi, R.; Suga, T.

2016-12-01

Recent observational studies show that, during the warming season, a large amount of heat flux is penetrated through the base of thin mixed layer by vertical eddy diffusion, in addition to penetration of solar radiation [1]. In order to understand this heat penetration process due to vertical eddy diffusivity and its contribution to seasonal variation of sea surface temperature, we investigated the evolution of thermal stratification below the summertime thin mixed layer (i.e. evolution of seasonal thermocline) and its vertical structure in the North Pacific using high vertical resolution temperature profile observed by Argo floats. We quantified the vertical structure of seasonal thermocline as deviations from the linear structure where the vertical gradient of temperature is constant, that is, "shape anomaly". The shape anomaly is variable representing the extent of the bend of temperature profiles. We found that there are larger values of shape anomaly in the region where the seasonal sea surface temperature warming is relatively faster. To understand the regional difference of shape anomalies, we investigated the relationship between time changes in shape anomalies and net surface heat flux and surface kinetic energy flux. From May to July, the analysis indicated that, in a large part of North Pacific, there's a tendency for shape anomalies to develop strongly (weakly) under the conditions of large (small) downward net surface heat flux and small (large) downward surface kinetic energy flux. Since weak (strong) development of shape anomalies means efficient (inefficient) downward heat transport from the surface, these results suggest that the regional difference of the downward heat penetration below mixed layer is explained reasonably well by differences in surface heat forcing and surface wind forcing in a vertical one dimensional framework. [1] Hosoda et al. (2015), J. Oceanogr., 71, 541-556.

A novel restraint spraying-Conform process for manufacturing hypereutectic Al-Si alloy with enhanced properties

NASA Astrophysics Data System (ADS)

Chen, Y. G.; Yang, H.; Zhang, B. Q.; Liu, Y. L.; Yin, J. C.; Wei, W.; Zhong, Y.

2017-02-01

A novel restraint spraying-Conform (RS-C) process, which directly combines spraying with Conform to process metals in one step, has been proposed. Al-20Si alloy selected as experimental material was successfully fabricated by the RS-C process. The microstructures were dominated with fine and uniform primary silicon phases. The tensile strength and elongation to failure of the Al-20Si alloy were 204 MPa and 7.2% respectively after the RS-C process. The wear resistance of the processed Al-20Si alloy was increased significantly, about 1.7 times over the as-cast ingot. The experimental results indicate that RS-C is a promising near net shape forming technology.

Effects of process variables on the properties of YBa2Cu3O(7-x) ceramics formed by investment casting

NASA Technical Reports Server (NTRS)

Hooker, M. W.; Taylor, T. D.; Leigh, H. D.; Wise, S. A.; Buckley, J. D.; Vasquez, P.; Buck, G. M.; Hicks, L. P.

1993-01-01

An investment casting process has been developed to produce net-shape, superconducting ceramics. In this work, a factorial experiment was performed to determine the critical process parameters for producing cast YBa2Cu3O7 ceramics with optimum properties. An analysis of variance procedure indicated that the key variables in casting superconductive ceramics are the particle size distribution and sintering temperature. Additionally, the interactions between the sintering temperature and the other process parameters (e.g., particle size distribution and the use of silver dopants) were also found to influence the density, porosity, and critical current density of the fired ceramics.

Near net shape processing of continuous lengths of superconducting wire

DOEpatents

Danyluk, Steven; McNallan, Michael; Troendly, Robert; Poeppel, Roger; Goretta, Kenneth; Lanagan, Michael

1997-01-01

A system and method for mechanically forming a ceramic superconductor product. A system for making the ceramic superconductor includes a metallic channel portion having a cross section for receiving a ceramic superconductor powder, a roll to mechanically reduce the channel cross section and included superconductor powder and a cap portion welded to the channel portion using a localized high energy source. The assembled bar is then mechanically reduced to form a tape or wire end product.

Metal Matrix Composite LOX Turbopump Housing via Novel Tool-less Net-Shape Pressure Infiltration Casting Technology

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Lee, Jonathan; Bhat, Biliyar; Wells, Doug; Gregg, Wayne; Marsh, Matthew; Genge, Gary; Forbes, John; Salvi, Alex; Cornie, James A.

2003-01-01

Metal matrix composites for propulsion components offer high performance and affordability, resulting in low weight and cost. The following sections in this viewgraph presentation describe the pressure infiltration casting of a metal matrix composite LOX turbopump housing: 1) Baseline Pump Design and Stress Analysis; 2) Tool-less Advanced Pressure Infiltration Casting Process; 3) Preform Splicing and Joining for Large Components such as Pump Housing; 4) Fullscale Pump Housing Redesign.

Automated Fabrication Technologies for High Performance Polymer Composites

NASA Technical Reports Server (NTRS)

Shuart , M. J.; Johnston, N. J.; Dexter, H. B.; Marchello, J. M.; Grenoble, R. W.

1998-01-01

New fabrication technologies are being exploited for building high graphite-fiber-reinforced composite structure. Stitched fiber preforms and resin film infusion have been successfully demonstrated for large, composite wing structures. Other automatic processes being developed include automated placement of tacky, drapable epoxy towpreg, automated heated head placement of consolidated ribbon/tape, and vacuum-assisted resin transfer molding. These methods have the potential to yield low cost high performance structures by fabricating composite structures to net shape out-of-autoclave.

Neural-Net Processing of Characteristic Patterns From Electronic Holograms of Vibrating Blades

NASA Technical Reports Server (NTRS)

Decker, Arthur J.

1999-01-01

Finite-element-model-trained artificial neural networks can be used to process efficiently the characteristic patterns or mode shapes from electronic holograms of vibrating blades. The models used for routine design may not yet be sufficiently accurate for this application. This document discusses the creation of characteristic patterns; compares model generated and experimental characteristic patterns; and discusses the neural networks that transform the characteristic patterns into strain or damage information. The current potential to adapt electronic holography to spin rigs, wind tunnels and engines provides an incentive to have accurate finite element models lor training neural networks.

Mechanism study of biopolymer hair as a coupled thermo-water responsive smart material

NASA Astrophysics Data System (ADS)

Xiao, Xueliang; Zhou, Hongtao; Qian, Kun

2017-03-01

Animal hairs existing broadly in nature are found to be effectively responsive to stimuli of heat and water in sequence for shape deformation and recovery, namely, coupled shape memory function (CSMF). In the paper, the ability of thermo-water sensitive CSMF was first time investigated for animal hairs, the structural and molecular networks for net-points and switches were therefrom identified. Experimentally, animal hair manifested a high ability of shape fixation in thermal processing and good shape recovery by water stimulus. Characterizations of two stimuli (heating and hydration) were performed systematically on hair’s deformation, recovery, viscoelasticity and chemical components (crystalline phase, key bonds inamorphous area). The variations of related chemical components in molecular networks were also explored. A hybrid structural network model was thereafter proposed to interpret the thermo-water sensitive CSMF of hair. This study of two-sequential-stimuli CSMF is original and inspired to explore more complex functions of other smart natural materials and expected to make much smarter synthetic polymers.

Producing Zirconium Diboride Components with Complex, Near-Net Shape Geometries by Aqueous Room-Temperature Injection Molding

NASA Technical Reports Server (NTRS)

Wiesner, Valerie L.; Youngblood, Jeffrey; Trice, Rodney

2014-01-01

Room-temperature injection molding is proposed as a novel, low-cost and more energy efficient manufacturing process capable of forming complex-shaped zirconium diboride (ZrB2) parts. This innovative processing method utilized aqueous suspensions with high powder loading and a minimal amount (5 vol.) of water-soluble polyvinylpyrrolidone (PVP), which was used as a viscosity modifier. Rheological characterization was performed to evaluate the room-temperature flow properties of ZrB2-PVP suspensions. ZrB2 specimens were fabricated with high green body strength and were machinable prior to binder removal despite their low polymer content. After binder burnout and pressureless sintering, the bulk density and microstructure of specimens were characterized using Archimedes technique and scanning electron microscopy. X-Ray Diffraction was used to determine the phase compositions present in sintered specimens. Ultimate strength of sintered specimens will be determined using ASTM C1323-10 compressive C-ring test.

Plastic deformation history in infeed rotary swaging process

NASA Astrophysics Data System (ADS)

Liu, Yang; Herrmann, Marius; Schenck, Christian; Kuhfuss, Bernd

2017-10-01

In bulk forming processes, the net shape of a final product is achieved by plastic deformation as the material flows from the initial shape to the final shape of the workpiece. The material flow during the process is an important issue for its relationship with forging force, heat generation, microstructure transformation and energy consumption. Hence, the final properties of the product are directly influenced. Former researches showed that the material flow in the rotary swaging process is affected by different processing parameters like die angle, feeding velocity and friction condition. Thus, a profound knowledge of detailed material flow during the process is essential for a better understanding of the process. By using FEM, the material flow was investigated by the history of the plastic strain (PEEQ) development. In this study a 2D-axisymmetric model was built by using ABAQUS explicit. Both aluminum alloy (3.3206) and steel (1.0308) are studied with different feeding velocities and coefficients of friction. To achieve the development of PEEQ in different areas, the workpiece was divided into radial layers. The PEEQ history of each layer was tracked during the quasi-static forming process. Based on that, the plastic strain rate (PSR) was calculated and examined in a single stroke of the process. In that way, the material flow in different layers is presented and the material flow on the surface differs from that in the center, just the first 1/4 radial area from the surface is sensitive to different friction conditions.

What Shapes the Phylogenetic Structure of Anuran Communities in a Seasonal Environment? The Influence of Determinism at Regional Scale to Stochasticity or Antagonistic Forces at Local Scale

PubMed Central

Ferreira, Vanda Lúcia; Strüssmann, Christine; Tomas, Walfrido Moraes

2015-01-01

Ecological communities are structured by both deterministic and stochastic processes. We investigated phylogenetic patterns at regional and local scales to understand the influences of seasonal processes in shaping the structure of anuran communities in the southern Pantanal wetland, Brazil. We assessed the phylogenetic structure at different scales, using the Net Relatedness Index (NRI), the Nearest Taxon Index (NTI), and phylobetadiversity indexes, as well as a permutation test, to evaluate the effect of seasonality. The anuran community was represented by a non-random set of species with a high degree of phylogenetic relatedness at the regional scale. However, at the local scale the phylogenetic structure of the community was weakly related with the seasonality of the system, indicating that oriented stochastic processes (e.g. colonization, extinction and ecological drift) and/or antagonist forces drive the structure of such communities in the southern Pantanal. PMID:26102202

What Shapes the Phylogenetic Structure of Anuran Communities in a Seasonal Environment? The Influence of Determinism at Regional Scale to Stochasticity or Antagonistic Forces at Local Scale.

PubMed

Martins, Clarissa de Araújo; Roque, Fabio de Oliveira; Santos, Bráulio A; Ferreira, Vanda Lúcia; Strüssmann, Christine; Tomas, Walfrido Moraes

2015-01-01

Ecological communities are structured by both deterministic and stochastic processes. We investigated phylogenetic patterns at regional and local scales to understand the influences of seasonal processes in shaping the structure of anuran communities in the southern Pantanal wetland, Brazil. We assessed the phylogenetic structure at different scales, using the Net Relatedness Index (NRI), the Nearest Taxon Index (NTI), and phylobetadiversity indexes, as well as a permutation test, to evaluate the effect of seasonality. The anuran community was represented by a non-random set of species with a high degree of phylogenetic relatedness at the regional scale. However, at the local scale the phylogenetic structure of the community was weakly related with the seasonality of the system, indicating that oriented stochastic processes (e.g. colonization, extinction and ecological drift) and/or antagonist forces drive the structure of such communities in the southern Pantanal.

Phosphorus Segregation in Meta-Rapidly Solidified Carbon Steels

NASA Astrophysics Data System (ADS)

Li, Na; Qiao, Jun; Zhang, Junwei; Sha, Minghong; Li, Shengli

2017-09-01

Twin-roll strip casters for near-net-shape manufacture of steels have received increased attention in the steel industry. Although negative segregation of phosphorus occurred in twin-roll strip casting (TRSC) steels in our prior work, its mechanism is still unclear. In this work, V-shaped molds were designed and used to simulate a meta-rapid solidification process without roll separating force during twin roll casting of carbon steels. Experimental results show that no obvious phosphorus segregation exist in the V-shaped mold casting (VMC) steels. By comparing TRSC and the VMC, it is proposed that the negative phosphorus segregation during TRSC results from phosphorus redistribution driven by recirculating and vortex flow in the molten pool. Meanwhile, solute atoms near the advancing interface are overtaken and incorporated into the solid because of the high solidification speed. The high rolling force could promote the negative segregation of alloying elements in TRSC.

Modelling of current loads on aquaculture net cages

NASA Astrophysics Data System (ADS)

Kristiansen, Trygve; Faltinsen, Odd M.

2012-10-01

In this paper we propose and discuss a screen type of force model for the viscous hydrodynamic load on nets. The screen model assumes that the net is divided into a number of flat net panels, or screens. It may thus be applied to any kind of net geometry. In this paper we focus on circular net cages for fish farms. The net structure itself is modelled by an existing truss model. The net shape is solved for in a time-stepping procedure that involves solving a linear system of equations for the unknown tensions at each time step. We present comparisons to experiments with circular net cages in steady current, and discuss the sensitivity of the numerical results to a set of chosen parameters. Satisfactory agreement between experimental and numerical prediction of drag and lift as function of the solidity ratio of the net and the current velocity is documented.

Children's schemes for anticipating the validity of nets for solids

NASA Astrophysics Data System (ADS)

Wright, Vince; Smith, Ken

2017-09-01

There is growing acknowledgement of the importance of spatial abilities to student achievement across a broad range of domains and disciplines. Nets are one way to connect three-dimensional shapes and their two-dimensional representations and are a common focus of geometry curricula. Thirty-four students at year 6 (upper primary school) were interviewed on two occasions about their anticipation of whether or not given nets for the cube- and square-based pyramid would fold to form the target solid. Vergnaud's ( Journal of Mathematical Behavior, 17(2), 167-181, 1998, Human Development, 52, 83-94, 2009) four characteristics of schemes were used as a theoretical lens to analyse the data. Successful schemes depended on the interaction of operational invariants, such as strategic choice of the base, rules for action, particularly rotation of shapes, and anticipations of composites of polygons in the net forming arrangements of faces in the solid. Inferences were rare. These data suggest that students need teacher support to make inferences, in order to create transferable schemes.

Fatigue Behavior of Porous Ti-6Al-4V Made by Laser-Engineered Net Shaping.

PubMed

Razavi, Seyed Mohammad Javad; Bordonaro, Giancarlo G; Ferro, Paolo; Torgersen, Jan; Berto, Filippo

2018-02-12

The fatigue behavior and fracture mechanisms of additively manufactured Ti-6Al-4V specimens are investigated in this study. Three sets of testing samples were fabricated for the assessment of fatigue life. The first batch of samples was built by using Laser-Engineered Net Shaping (LENS) technology, a Direct Energy Deposition (DED) method. Internal voids and defects were induced in a second batch of samples by changing LENS machine processing parameters. Fatigue performance of these samples is compared to the wrought Ti-6Al-4V samples. The effects of machine-induced porosity are assessed on mechanical properties and results are presented in the form of SN curves for the three sets of samples. Fracture mechanisms are examined by using Scanning Electron Microscopy (SEM) to characterize the morphological characteristics of the failure surface. Different fracture surface morphologies are observed for porous and non-porous specimens due to the combination of head write speed and laser power. Formation of defects such as pores, unmelted regions, and gas entrapments affect the failure mechanisms in porous specimens. Non-porous specimens exhibit fatigue properties comparable with that of the wrought specimens, but porous specimens are found to show a tremendous reduced fatigue strength.

Synthesis and processing of composites by reactive metal penetration

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

Loehman, R.E.; Ewsuk, K.G.; Tomsia, A.P.

1997-04-01

Achieving better performance in commercial products and processes often is dependent on availability of new and improved materials. Ceramic-metal composites have advantages over more conventional materials because of their high stiffness-to-weight ratios, good fracture toughness, and because their electrical and thermal properties can be varied through control of their compositions and microstructures. However, ceramic composites will be more widely used only when their costs are competitive with other materials and when designers have more confidence in their reliability. Over the past four years reactive metal penetration has been shown to be a promising technique for making ceramic and metal-matrix compositesmore » to near-net-shape with control of both composition and microstructure. It appears that, with sufficient development, reactive metal penetration could be an economical process for manufacturing many of the advanced ceramic composites that are needed for light-weight structural and wear applications for transportation and energy conversion devices. Near-net-shape fabrication of parts is a significant advantage because costly and energy intensive grinding and machining operations are substantially reduced, and the waste generated from such finishing operations is minimized. The most promising compositions to date consist of Al and Al{sub 2}O{sub 3}; thus, these composites should be of particular interest to the aluminum industry. The goals of this ceramic-metal composite research and development program are: (1) to identify compositions favorable for making composites by reactive metal penetration; (2) to understand the mechanism(s) by which these composites are formed; (3) to control and optimize the process so that composites and composite coatings can be made economically; and (4) to apply R&D results to problems of interest to the aluminum industry.« less

Selecting mirror materials for high-performance optical systems

NASA Astrophysics Data System (ADS)

Parsonage, Thomas B.

1990-11-01

The properties of four candidate mirror materials--beryllium, silicon carbide, a silicon carbide/aluminum iretal-matrix carposite and aluminum--are corrpared. Because of its high specific stiffness and dirrensional stability under changing mschanical and thermal loads , beryllium is the best choice . Berjllium mirrors have been made irore cost-conpetitive by new processing technologies in which mirror blanks are isostatically pressed to near-net shape directly fran beiyllium pc1ers. Isostatic pressing also improves material properties and mskes it possible to develop mirror rraterials with superior properties.

Near net shape processing of continuous lengths of superconducting wire

DOEpatents

Danyluk, S.; McNallan, M.; Troendly, R.; Poeppel, R.; Goretta, K.; Lanagan, M.

1997-08-26

A system and method for mechanically forming a ceramic superconductor product are disclosed. A system for making the ceramic superconductor includes a metallic channel portion having a cross section for receiving a ceramic superconductor powder, a roll to mechanically reduce the channel cross section and included superconductor powder and a cap portion welded to the channel portion using a localized high energy source. The assembled bar is then mechanically reduced to form a tape or wire end product. 9 figs.

Process for preparing silicon carbide foam

DOEpatents

Whinnery, LeRoy Louis; Nichols, Monte Carl; Wheeler, David Roger; Loy, Douglas Anson

1997-01-01

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolized in an inert atmosphere to form a SiC foam.

Process for preparing silicon carbide foam

DOEpatents

Whinnery, L.L.; Nichols, M.C.; Wheeler, D.R.; Loy, D.A.

1997-09-16

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolyzed in an inert atmosphere to form a SiC foam. 9 figs.

Spray forming process for producing molds, dies and related tooling

DOEpatents

McHugh, Kevin M.; Key, James F.

1998-01-01

A method for spray forming manufacturing of near-net-shape molds, dies and related toolings, wherein liquid material such as molten metal, metallic alloys, or polymers are atomized into fine droplets by a high temperature, high velocity gas and deposited onto a pattern. Quenching of the atomized droplets provides a heat sink, thereby allowing undercooled and partially solidified droplets to be formed in-flight. Composites can be formed by combining the atomized droplets with solid particles such as whiskers or fibers.

Niobium-Matrix-Composite High-Temperature Turbine Blades

NASA Technical Reports Server (NTRS)

Kaplan, Richard B.; Tuffias, Robert H.; La Ferla, Raffaele; Heng, Sangvavann; Harding, John T.

1995-01-01

High-temperture composite-material turbine blades comprising mainly niobium matrices reinforced with refractory-material fibers being developed. Of refractory fibrous materials investigated, FP-AL(2)0(3), tungsten, and polymer-based SiC fibers most promising. Blade of this type hollow and formed in nearly net shape by wrapping mesh of reinforcing refractory fibers around molybdenum mandrel, then using thermal-gradient chemical-vapor infiltration (CVI) to fill interstices with niobium. CVI process controllable and repeatable, and kinetics of both deposition and infiltration well understood.

Spray forming process for producing molds, dies and related tooling

DOEpatents

McHugh, K.M.; Key, J.F.

1998-02-17

A method is disclosed for spray forming manufacturing of near-net-shape molds, dies and related toolings, wherein liquid material such as molten metal, metallic alloys, or polymers are atomized into fine droplets by a high temperature, high velocity gas and deposited onto a pattern. Quenching of the atomized droplets provides a heat sink, thereby allowing undercooled and partially solidified droplets to be formed in-flight. Composites can be formed by combining the atomized droplets with solid particles such as whiskers or fibers. 17 figs.

Numerical Simulation of Molten Flow in Directed Energy Deposition Using an Iterative Geometry Technique

NASA Astrophysics Data System (ADS)

Vincent, Timothy J.; Rumpfkeil, Markus P.; Chaudhary, Anil

2018-03-01

The complex, multi-faceted physics of laser-based additive metals processing tends to demand high-fidelity models and costly simulation tools to provide predictions accurate enough to aid in selecting process parameters. Of particular difficulty is the accurate determination of melt pool shape and size, which are useful for predicting lack-of-fusion, as this typically requires an adequate treatment of thermal and fluid flow. In this article we describe a novel numerical simulation tool which aims to achieve a balance between accuracy and cost. This is accomplished by making simplifying assumptions regarding the behavior of the gas-liquid interface for processes with a moderate energy density, such as Laser Engineered Net Shaping (LENS). The details of the implementation, which is based on the solver simpleFoam of the well-known software suite OpenFOAM, are given here and the tool is verified and validated for a LENS process involving Ti-6Al-4V. The results indicate that the new tool predicts width and height of a deposited track to engineering accuracy levels.

Numerical Simulation of Molten Flow in Directed Energy Deposition Using an Iterative Geometry Technique

NASA Astrophysics Data System (ADS)

Vincent, Timothy J.; Rumpfkeil, Markus P.; Chaudhary, Anil

2018-06-01

The complex, multi-faceted physics of laser-based additive metals processing tends to demand high-fidelity models and costly simulation tools to provide predictions accurate enough to aid in selecting process parameters. Of particular difficulty is the accurate determination of melt pool shape and size, which are useful for predicting lack-of-fusion, as this typically requires an adequate treatment of thermal and fluid flow. In this article we describe a novel numerical simulation tool which aims to achieve a balance between accuracy and cost. This is accomplished by making simplifying assumptions regarding the behavior of the gas-liquid interface for processes with a moderate energy density, such as Laser Engineered Net Shaping (LENS). The details of the implementation, which is based on the solver simpleFoam of the well-known software suite OpenFOAM, are given here and the tool is verified and validated for a LENS process involving Ti-6Al-4V. The results indicate that the new tool predicts width and height of a deposited track to engineering accuracy levels.

Future trends in metal forming—equipment, materials and processes in automotive applications

NASA Astrophysics Data System (ADS)

Hitz, D.; Duggirala, R.

1995-10-01

Global competition in the automotive market has made a significant impact in the materials, processes, tools, and equipment used to make components. Steels are being replaced by other materials, such as aluminum, composites, and plastics, that meet the demand for a higher performance per weight ratio. From a processing viewpoint, the customers demand production of parts to near-net shape with little or no machining. Competition in business depends on understanding the needs of the customer in the coming years in the area of metal forming. A workshop was conducted using a novel approach to address the above issue. This presentation describes the approach and the results of the study.

Additive manufacturing for steels: a review

NASA Astrophysics Data System (ADS)

Zadi-Maad, A.; Rohib, R.; Irawan, A.

2018-01-01

Additive manufacturing (AM) of steels involves the layer by layer consolidation of powder or wire feedstock using a heating beam to form near net shape products. For the past decades, the AM technique reaches the maturation of both research grade and commercial production due to significant research work from academic, government and industrial research organization worldwide. AM process has been implemented to replace the conventional process of steel fabrication due to its potentially lower cost and flexibility manufacturing. This paper provides a review of previous research related to the AM methods followed by current challenges issues. The relationship between microstructure, mechanical properties, and process parameters will be discussed. Future trends and recommendation for further works are also provided.

Exhaust-stack nozzle area and shape for individual cylinder exhaust-gas jet-propulsion system

NASA Technical Reports Server (NTRS)

Pinkel, Benjamin; Turner, Richard; Voss, Fred; Humble, Leroy V

1943-01-01

This report presents the results of an investigation conducted on the effect of exhaust-stack nozzle area, shape, and length on engine power, jet thrust, and gain in net thrust (engine propeller plus jet). Single-cylinder engine data were obtained using three straight stacks 25, 44, and 108 inches in length; an S-shaped stack, a 90 degree bend, a 180 degree bend, and a short straight stack having a closed branch faired into it. Each stack was fitted with nozzles varying in exit area from 0.91 square inch to the unrestricted area of the stack of 4.20 square inches. The engine was generally operated over a range of engine speeds from 1300 to 2100 r.p.m, inlet-manifold pressures from 22 to 30 inches of mercury absolute, and a fuel-air ratio of 0.08. The loss in engine power, the jet thrust, and the gain in net thrust are correlated in terms of several simple parameters. An example is given for determining the optimum nozzle area and the overall net thrust.

Producing High-Quality Titanium Alloy by a Cost-Effective Route Combining Fast Heating and Hot Processing

NASA Astrophysics Data System (ADS)

Yang, Fei; Raynova, Stella; Singh, Ajit; Zhao, Qinyang; Romero, Carlos; Bolzoni, Leandro

2018-02-01

Powder metallurgy is a very attractive method for producing titanium alloys, which can be near-net-shape formed and have freedom in composition selection. However, applications are still limited due to product affordability. In this paper, we will discuss a possible cost-effective route, combining fast heating and hot processing, to produce titanium alloys with similar or even better mechanical properties than that of ingot metallurgy titanium alloys. Two titanium alloys, Ti-5Al-5V-5Mo-3Cr (Ti-5553) and Ti-5Fe, were successfully produced from HDH titanium powder and other master alloy powders using the proposed processing route. The effect of the processing route on microstructural variation and mechanical properties have been discussed.

Fast-Response-Time Shape-Memory-Effect Foam Actuators

NASA Technical Reports Server (NTRS)

Jardine, Peter

2010-01-01

Bulk shape memory alloys, such as Nitinol or CuAlZn, display strong recovery forces undergoing a phase transformation after being strained in their martensitic state. These recovery forces are used for actuation. As the phase transformation is thermally driven, the response time of the actuation can be slow, as the heat must be passively inserted or removed from the alloy. Shape memory alloy TiNi torque tubes have been investigated for at least 20 years and have demonstrated high actuation forces [3,000 in.-lb (approximately equal to 340 N-m) torques] and are very lightweight. However, they are not easy to attach to existing structures. Adhesives will fail in shear at low-torque loads and the TiNi is not weldable, so that mechanical crimp fits have been generally used. These are not reliable, especially in vibratory environments. The TiNi is also slow to heat up, as it can only be heated indirectly using heater and cooling must be done passively. This has restricted their use to on-off actuators where cycle times of approximately one minute is acceptable. Self-propagating high-temperature synthesis (SHS) has been used in the past to make porous TiNi metal foams. Shape Change Technologies has been able to train SHS derived TiNi to exhibit the shape memory effect. As it is an open-celled material, fast response times were observed when the material was heated using hot and cold fluids. A methodology was developed to make the open-celled porous TiNi foams as a tube with integrated hexagonal ends, which then becomes a torsional actuator with fast response times. Under processing developed independently, researchers were able to verify torques of 84 in.-lb (approximately equal to 9.5 Nm) using an actuator weighing 1.3 oz (approximately equal to 37 g) with very fast (less than 1/16th of a second) initial response times when hot and cold fluids were used to facilitate heat transfer. Integrated structural connections were added as part of the net shape process, eliminating the need for welding, adhesives, or mechanical crimping. Inexpensive net-shape processing was used, which reduces the cost of the actuator by over a factor of 10 over nonporous TiNi made by hot drawing of tube or electrical discharge machining. By forming the alloy as an open-celled foam, the surface area for heat transfer is dramatically increased, allowing for much faster response times. The technology also allows for netshape fabrication of the actuator, which allows for structural connections to be integrated into the actuator material, making these actuators significantly less expensive. Commercial applications include actuators for concepts such as the variable area chevron and nozzle in jet aircraft. Lightweight tube or rod components can be supplied to interested parties.

Net shape fabrication of Alpha Silicon Carbide turbine components

NASA Technical Reports Server (NTRS)

Storm, R. S.

1982-01-01

Development of Alpha Silicon Carbide components by net shape fabrication techniques has continued in conjunction with several turbine engine programs. Progress in injection molding of simple parts has been extended to much larger components. Turbine rotors fabricated by a one piece molding have been successfully spin tested above design speeds. Static components weighing up to 4.5 kg and 33 cc in diameter have also been produced using this technique. Use of sintering fixtures significantly improves dimensional control. A new Si-SiC composite material has also been developed with average strengths up to 1000 MPa (150 ksi) at 1200 C.

"When I sleep under the net, nothing bothers me; I sleep well and I'm happy": Senegal's culture of net use and how inconveniences to net use do not translate to net abandonment.

PubMed

Berthe, Sara; Loll, Dana; Faye, Sylvain L; Wone, Issa; Koenker, Hannah; Arnold, Bethany; Weber, Rachel

2014-09-12

Despite recent advances in the fight against the disease, malaria remains a serious threat to the health and well-being of populations in endemic countries. The use of long-lasting insecticidal nets (LLIN) reduces contact between the vector and humans, thereby reducing transmission of the disease. LLINs have become an essential component of malaria control programmes worldwide. The Culture of Net Use study used qualitative and quantitative methods in a longitudinal and iterative design over two phases, in order to capture changes in net use over a year and a half period and covering both dry and rainy seasons. Data were collected from a total of 56 households in eight regions to understand variations due to geographical, cultural, and universal coverage differences. At the time of the data collection, the universal coverage campaign had been completed in six of the eight regions (Dakar and Thies excluded). Perceived barriers to use were primarily related to the characteristics of the net itself, include shape, insecticide, and a variety of minority responses, such as perceived lack of mosquito density and being unaccustomed to using nets. Insecticide-related complaints found that insecticide did not present a significant barrier to use, but was cited as a nuisance. Feelings of suffocation continued to be the most commonly cited nuisance. Respondents who favoured the use of insecticide on nets appeared to be more aware of the health and malaria prevention benefits of the insecticide than those who perceived it negatively. Despite prior evidence that barriers such as heat, shape, insecticide and perceived mosquito density contribute to non-use of LLINs in other countries, this study has shown that these factors are considered more as nuisances and that they do not consistently prevent the use of nets among respondents in Senegal. Of those who cited inconveniences with their nets, few were moved to stop using a net. Respondents from this study overcame these barriers and continue to value the importance of nets.

Microstructural and Mechanical Property Characterization of Shear Formed Aerospace Aluminum Alloys

NASA Technical Reports Server (NTRS)

Troeger, Lillianne P.; Domack, Marcia S.; Wagner, John A.

2000-01-01

Advanced manufacturing processes such as near-net-shape forming can reduce production costs and increase the reliability of launch vehicle and airframe structural components through the reduction of material scrap and part count and the minimization of joints. The current research is an investigation of the processing-microstructure-property relationships for shear formed cylinders of the Al-Cu-Li-Mg-Ag alloy 2195 for space applications and the Al-Cu-Mg-Ag alloy C415 for airframe applications. Cylinders which had undergone various amounts of shear-forming strain were studied to correlate the grain structure, texture, and mechanical properties developed during and after shear forming.

Microstructural and Mechanical Characterization of Shear Formed Aluminum Alloys for Airframe and Space Applications

NASA Technical Reports Server (NTRS)

Troeger, L. P.; Domack, M. S.; Wagner, J. A.

1998-01-01

Advanced manufacturing processes such as near-net-shape forming can reduce production costs and increase the reliability of launch vehicle and airframe structural components through the reduction of material scrap and part count and the minimization of joints. The current research is an investigation of the processing-microstructure-property relationship for shear formed cylinders of the Al-Cu-Li-Mg-Ag alloy 2195 for space applications and the Al-Cu-Mg-Ag alloy C415 for airframe applications. Cylinders which have undergone various amounts of shear-forming strain have been studied to assess the microstructure and mechanical properties developed during and after shear forming.

Activated carbon fiber composite material and method of making

DOEpatents

Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

2000-01-01

An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

Activated carbon fiber composite material and method of making

DOEpatents

Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

2001-01-01

An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner For Advanced Rocket Engines

NASA Technical Reports Server (NTRS)

Bhat, Biliyar N.; Ellis, David; Singh, Jogender

2014-01-01

Advanced high thermal conductivity materials research conducted at NASA Marshall Space Flight Center (MSFC) with state of the art combustion chamber liner material NARloy-Z showed that its thermal conductivity can be increased significantly by adding diamond particles and sintering it at high temperatures. For instance, NARloy-Z containing 40 vol. percent diamond particles, sintered at 975C to full density by using the Field assisted Sintering Technology (FAST) showed 69 percent higher thermal conductivity than baseline NARloy-Z. Furthermore, NARloy-Z-40vol. percent D is 30 percent lighter than NARloy-Z and hence the density normalized thermal conductivity is 140 percent better. These attributes will improve the performance and life of the advanced rocket engines significantly. By one estimate, increased thermal conductivity will directly translate into increased turbopump power up to 2X and increased chamber pressure for improved thrust and ISP, resulting in an expected 20 percent improvement in engine performance. Follow on research is now being conducted to demonstrate the benefits of this high thermal conductivity NARloy-Z-D composite for combustion chamber liner applications in advanced rocket engines. The work consists of a) Optimizing the chemistry and heat treatment for NARloy-Z-D composite, b) Developing design properties (thermal and mechanical) for the optimized NARloy-Z-D, c) Fabrication of net shape subscale combustion chamber liner, and d) Hot fire testing of the liner for performance. FAST is used for consolidating and sintering NARlo-Z-D. The subscale cylindrical liner with built in channels for coolant flow is also fabricated near net shape using the FAST process. The liner will be assembled into a test rig and hot fire tested in the MSFC test facility to determine performance. This paper describes the development of this novel high thermal conductivity NARloy-Z-D composite material, and the advanced net shape technology to fabricate the combustion chamber liner. Properties of optimized NARloy-Z-D composite material will also be presented.

Processing and mechanical characterization of alumina laminates

NASA Astrophysics Data System (ADS)

Montgomery, John K.

2002-08-01

Single-phase ceramics that combine property gradients or steps in monolithic bodies are sought as alternatives to ceramic composites made of dissimilar materials. This work describes novel processing methods to produce stepped-density (or laminated) alumina single-phase bodies that maintain their mechanical integrity. One arrangement consists of a stiff, dense bulk material with a thin, flaw tolerant, porous exterior layer. Another configuration consists of a lightweight, low-density bulk material with a thin, hard, wear resistant exterior layer. Alumina laminates with strong interfaces have been successfully produced in this work using two different direct-casting processes. Gelcasting is a useful near-net shape processing technique that has been combined with several techniques, such as reaction bonding of aluminum oxide and the use of starch as a fugative filler, to successfully produced stepped-density alumina laminates. The other direct casting process that has been developed in this work is thermoreversible gelcasting (TRG). This is a reversible gelation process that has been used to produce near-net shape dense ceramic bodies. Also, individual layers can be stacked together and heated to produce laminates. Bilayer laminate samples were produced with varied thickness of porous and dense layers. It was shown that due to the difference in modulus and hardness, transverse cracking is found upon Hertzian contact when the dense layer is on the exterior. In the opposite arrangement, compacted damage zones formed in the porous material and no damage occurred in the underlying dense layer. Flaw tolerant behavior of the porous exterior/dense underlayer was examined by measuring biaxial strength as a function of Vickers indentation load. It was found that the thinnest layer of porous material results in the greatest flaw tolerance. Also, higher strength was exhibited at large indentation loads when compared to dense monoliths. The calculated stresses on the surfaces and interface afforded an explanation of the behavior that failure initiates at the interface between the layers for the thinnest configuration, rather than the sample surface.

Ion-induced nucleation in solution: promotion of solute nucleation in charged levitated droplets.

PubMed

Draper, Neil D; Bakhoum, Samuel F; Haddrell, Allen E; Agnes, George R

2007-09-19

We have investigated the nucleation and growth of sodium chloride in both single quiescent charged droplets and charged droplet populations that were levitated in an electrodynamic levitation trap (EDLT). In both cases, the magnitude of a droplet's net excess charge (ions(DNEC)) influenced NaCl nucleation and growth, albeit in different capacities. We have termed the phenomenon ion-induced nucleation in solution. For single quiescent levitated droplets, an increase in ions(DNEC) resulted in a significant promotion of NaCl nucleation, as determined by the number of crystals observed. For levitated droplet populations, a change in NaCl crystal habit, from regular cubic shapes to dome-shaped dendrites, was observed once a surface charge density threshold of -9 x 10(-4) e.nm(-2) was surpassed. Although promotion of NaCl nucleation was observed for droplet population experiments, this can be attributed in part to the increased rate of solvent evaporation observed for levitated droplet populations having a high net charge. Promotion of nucleation was also observed for two organic acids, 2,4,6-trihydroxyacetophenone monohydrate (THAP) and alpha-cyano-4-hydroxycinnamic acid (CHCA). These results are of direct relevance to processes that occur in both soft-ionization techniques for mass spectrometry and to a variety of industrial processes. To this end, we have demonstrated the use of ion-induced nucleation in solution to form ammonium nitrate particles from levitated droplets to be used in in vitro toxicology studies of ambient particle types.

Neutrophil extracellular traps in immunity and disease.

PubMed

Papayannopoulos, Venizelos

2018-02-01

Neutrophils are innate immune phagocytes that have a central role in immune defence. Our understanding of the role of neutrophils in pathogen clearance, immune regulation and disease pathology has advanced dramatically in recent years. Web-like chromatin structures known as neutrophil extracellular traps (NETs) have been at the forefront of this renewed interest in neutrophil biology. The identification of molecules that modulate the release of NETs has helped to refine our view of the role of NETs in immune protection, inflammatory and autoimmune diseases and cancer. Here, I discuss the key findings and concepts that have thus far shaped the field of NET biology.

Productivity is a poor predictor of plant species richness

USGS Publications Warehouse

Adler, Peter B.; Seabloom, Eric W.; Borer, Elizabeth T.; Hillebrand, Helmut; Hautier, Yann; Hector, Andy; Harpole, W. Stanley; O'Halloran, Lydia R.; Grace, James B.; Anderson, T. Michael; Bakker, Jonathan D.; Biederman, Lori A.; Brown, Cynthia S.; Buckley, Yvonne M.; Calabrese, Laura B.; Chu, Cheng-Jin; Cleland, Elsa E.; Collins, Scott L.; Cottingham, Kathryn L.; Crawley, Michael J.; Damschen, Ellen Ingman; Davies, Kendi F.; DeCrappeo, Nicole M.; Fay, Philip A.; Firn, Jennifer; Frater, Paul; Gasarch, Eve I.; Gruner, Daneil S.; Hagenah, Nicole; Lambers, Janneke Hille Ris; Humphries, Hope; Jin, Virginia L.; Kay, Adam D.; Kirkman, Kevin P.; Klein, Julia A.; Knops, Johannes M.H.; La Pierre, Kimberly J.; Lambrinos, John G.; Li, Wei; MacDougall, Andrew S.; McCulley, Rebecca L.; Melbourne, Brett A.; Mitchell, Charles E.; Moore, Joslin L.; Morgan, John W.; Mortensen, Brent; Orrock, John L.; Prober, Suzanne M.; Pyke, David A.; Risch, Anita C.; Schuetz, Martin; Smith, Melinda D.; Stevens, Carly J.; Sullivan, Lauren L.; Wang, Gang; Wragg, Peter D.; Wright, Justin P.; Yang, Louie H.

2011-01-01

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters-2) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity an

Graphene nanoFlakes with large spin.

PubMed

Wang, Wei L; Meng, Sheng; Kaxiras, Efthimios

2008-01-01

We investigate, using benzenoid graph theory and first-principles calculations, the magnetic properties of arbitrarily shaped finite graphene fragments to which we refer as graphene nanoflakes (GNFs). We demonstrate that the spin of a GNF depends on its shape due to topological frustration of the pi-bonds. For example, a zigzag-edged triangular GNF has a nonzero net spin, resembling an artificial ferrimagnetic atom, with the spin value scaling with its linear size. In general, the principle of topological frustration can be used to introduce large net spin and interesting spin distributions in graphene. These results suggest an avenue to nanoscale spintronics through the sculpting of graphene fragments.

Microstructural investigation of D2 tool steel during rapid solidification

NASA Astrophysics Data System (ADS)

Delshad Khatibi, Pooya

Solidification is considered as a key processing step in developing the microstructure of most metallic materials. It is, therefore, important that the solidification process can be designed and controlled in such a way so as to obtain the desirable properties in the final product. Rapid solidification refers to the system's high undercooling and high cooling rate, which can yield a microstructure with unique chemical composition and mechanical properties. An area of interest in rapid solidification application is high-chromium, high-carbon tool steels which experience considerable segregation of alloying elements during their solidification in a casting process. In this dissertation, the effect of rapid solidification (undercooling and cooling rate) of D2 tool steel on the microstructure and carbide precipitation during annealing was explored. A methodology is described to estimate the eutectic and primary phase undercooling of solidifying droplets. The estimate of primary phase undercooling was confirmed using an online measurement device that measured the radiation energy of the droplets. The results showed that with increasing primary phase and eutectic undercooling and higher cooling rate, the amount of supersaturation of alloying element in metastable retained austenite phase also increases. In the case of powders, the optimum hardness after heat treatment is achieved at different temperatures for constant periods of time. Higher supersaturation of austenite results in obtaining secondary hardness at higher annealing temperature. D2 steel ingots generated using spray deposition have high eutectic undercooling and, as a result, high supersaturation of alloying elements. This can yield near net shape D2 tool steel components with good mechanical properties (specifically hardness). The data developed in this work would assist in better understanding and development of near net shape D2 steel spray deposit products with good mechanical properties.

Beryllium fabrication/cost assessment for ITER (International Thermonuclear Experimental Reactor)

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

Beeston, J.M.; Longhurst, G.R.; Parsonage, T.

1990-06-01

A fabrication and cost estimate of three possible beryllium shapes for the International Thermonuclear Experimental Reactor (ITER) blanket is presented. The fabrication method by hot pressing (HP), cold isostatic pressing plus sintering (CIP+S), cold isostatic pressing plus sintering plus hot isostatic pressing (CIP+S+HIP), and sphere production by atomization or rotary electrode will be discussed. Conventional hot pressing blocks of beryllium with subsequent machining to finished shapes can be more expensive than production of a net shape by cold isostatic pressing and sintering. The three beryllium shapes to be considered here and proposed for ITER are: (1) cubic blocks (3 tomore » 17 cm on an edge), (2) tubular cylinders (33 to 50 mm i.d. by 62 mm o.d. by 8 m long), and (3) spheres (1--5 mm dia.). A rough cost estimate of the basic shape is presented which would need to be refined if the surface finish and tolerances required are better than the sintering process produces. The final cost of the beryllium in the blanket will depend largely on the machining and recycling of beryllium required to produce the finished product. The powder preparation will be discussed before shape fabrication. 10 refs., 6 figs.« less

Near Net-Shape, Ultra High Melting, Erosion Resistant Carbide/Metal Composites with Tailored Fibrillar Microstructures via the Displacive Compensation of Porosity Process

DTIC Science & Technology

2006-11-26

vapor species, formed over tungsten trioxide powder, is 1.25xl0Ŗ atm at 1400°C and 1 atm total pressure (assuming an oxygen partial pressure greater...with CO(g). ■19- These hollow tungsten fibers were then carburized via reaction with CO(g) to generate the polycrystalline WC-based fibers shown in...of tungsten carbide via reaction with a hafnium-copper melt," Ada Mater., 57(13), 3924-3931 (2009).) The kinetic mechanism of incongruent reduction

Rapid solidification processing system for producing molds, dies and related tooling

DOEpatents

McHugh, Kevin M.

2004-06-08

A system for the spray forming manufacturing of near-net-shape molds, dies and related toolings, wherein liquid material such as molten metal, metallic alloys, or polymers are atomized into fine droplets by a high temperature, high velocity gas and deposited onto a pattern. Quenching of the in-flight atomized droplets provides a heat sink, thereby allowing undercooled and partially solidified droplets to be formed in-flight. Composites can be formed by combining the atomized droplets with solid particles such as powders, whiskers or fibers.

Development of a super-pressure balloon with a diamond-shaped net --- result of a ground inflation test of a 2,000 cubic-meter balloon ---

NASA Astrophysics Data System (ADS)

Saito, Yoshitaka; Nakashino, Kyoichi; Akita, Daisuke; Matsushima, Kiyoho; Shimadu, Shigeyuki; Goto, Ken; Hashimoto, Hiroyuki; Matsuo, Takuma

2016-07-01

A light super-pressure balloon has been developed using a method to cover a balloon with a diamond-shaped net of high-tensile fibers. The goal is to fly a payload of 900 kg to the altitude of 37 km with a 300,000 m^{3} balloon. Beginning from a demonstration test of the net-balloon with a 10 m^{3} balloon in 2010, we have been polished the net-balloon through ground inflation tests and flight tests, including a flight test of a 3,000 m ^{3} balloon in the tandem balloon configuration with a 15,000 m^{3} zero-pressure balloon in 2012, and a flight test of a 10 m^{3} balloon in the tandem balloon configuration with a 2 kg rubber balloon in 2013, as reported in the last COSPAR. In 2014, we developed a 5,000 m^{3} balloon and performed a ground inflation test to find that the balloon burst from a lip panel for termination with a differential pressure of 425 Pa. It was due to a stress concentration at the edge of a thick tape attached along the termination mechanism. In 2015, we modified the balloon by adding tapes on the lip panel to avoid the stress concentration, and also shorten the net length to leave some margin of the film and performed a ground inflation test again to find the balloon showed asymmetrical deployment and burst from the edge of the net with a differential pressure of 348 Pa. We consider it is due to the margin of the film along the circumferential direction, and proposed a gore shape which circumference length is kept as determined by the pumpkin shape of the balloon but setting meridian length longer than that. We developed a 10 m^{3} balloon with the gore design to find that the balloon deployed symmetrically and showed the burst pressure of 10,000 Pa. In 2016, we are going to develop a 2,000 m^{3} balloon with the gore design and perform its ground inflation test. In this paper, we are going to report its result with the sequence of the development.

Fatigue Behavior of Porous Ti-6Al-4V Made by Laser-Engineered Net Shaping

PubMed Central

Bordonaro, Giancarlo G.; Berto, Filippo

2018-01-01

The fatigue behavior and fracture mechanisms of additively manufactured Ti-6Al-4V specimens are investigated in this study. Three sets of testing samples were fabricated for the assessment of fatigue life. The first batch of samples was built by using Laser-Engineered Net Shaping (LENS) technology, a Direct Energy Deposition (DED) method. Internal voids and defects were induced in a second batch of samples by changing LENS machine processing parameters. Fatigue performance of these samples is compared to the wrought Ti-6Al-4V samples. The effects of machine-induced porosity are assessed on mechanical properties and results are presented in the form of SN curves for the three sets of samples. Fracture mechanisms are examined by using Scanning Electron Microscopy (SEM) to characterize the morphological characteristics of the failure surface. Different fracture surface morphologies are observed for porous and non-porous specimens due to the combination of head write speed and laser power. Formation of defects such as pores, unmelted regions, and gas entrapments affect the failure mechanisms in porous specimens. Non-porous specimens exhibit fatigue properties comparable with that of the wrought specimens, but porous specimens are found to show a tremendous reduced fatigue strength. PMID:29439510

Effect of Layer Thickness in Selective Laser Melting on Microstructure of Al/5 wt.%Fe2O3 Powder Consolidated Parts

PubMed Central

Hao, Liang

2014-01-01

In situ reaction was activated in the powder mixture of Al/5 wt.%Fe2O3 by using selective laser melting (SLM) to directly fabricate aluminium metal matrix composite parts. The microstructural characteristics of these in situ consolidated parts through SLM were investigated under the influence of thick powder bed, 75 μm layer thickness, and 50 μm layer thickness in various laser powers and scanning speeds. It was found that the layer thickness has a strong influence on microstructural outcome, mainly attributed to its impact on oxygen content of the matrix. Various microstructural features (such as granular, coralline-like, and particulate appearance) were observed depending on the layer thickness, laser power, and scanning speed. This was associated with various material combinations such as pure Al, Al-Fe intermetallics, and Al(-Fe) oxide phases formed after in situ reaction and laser rapid solidification. Uniformly distributed very fine particles could be consolidated in net-shape Al composite parts by using lower layer thickness, higher laser power, and lower scanning speed. The findings contribute to the new development of advanced net-shape manufacture of Al composites by combining SLM and in situ reaction process. PMID:24526879

Metal Matrix Composite LOX Turbopump Housing Via Novel Tool-Less Net-Shape Pressure Infiltration Casting Technology

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Lee, Jonathan; Bhat, Biliyar; Wells, Doug; Gregg, Wayne; Marsh, Matthew; Genge, Gary; Forbes, John; Salvi, Alex; Cornie, James A.;

Metal Matrix Composite LOX Turbopump Housing Via Novel Tool-Less Net-Shape Pressure Infiltration Casting Technology

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Lee, Jonathan; Bhat, Biliyar; Wells, Doug; Gregg, Wayne; Marsh, Matthew; Genge, Gary; Forbes, John; Salvi, Alex; Cornie, James A.;

Metal Matrix Composite LOX Turbopump Housing Via Novel Tool-less Net-Shape Pressure Infiltration Casting Technology

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Lee, Jonathan; Bhat, Biliyar; Wells, Doug; Gregg, Wayne; Marsh, Matthew; Genge, Gary; Forbes, John; Salvi, Alex; Cornie, James A.;

Laser engineered net shaping of quasi-continuous network microstructural TiB reinforced titanium matrix bulk composites: Microstructure and wear performance

NASA Astrophysics Data System (ADS)

Hu, Yingbin; Ning, Fuda; Wang, Hui; Cong, Weilong; Zhao, Bo

2018-02-01

Titanium (Ti) and its alloys have been successfully applied to the aeronautical and biomedical industries. However, their poor tribological properties restrict their fields of applications under severe wear conditions. Facing to these challenges, this study investigated TiB reinforced Ti matrix composites (TiB-TMCs), fabricated by in-situ laser engineered net shaping (LENS) process, through analyzing parts quality, microstructure formation mechanisms, microstructure characterizations, and workpiece wear performance. At high B content areas (original B particle locations), reaction between Ti and B particles took place, generating flower-like microstructure. At low B content areas, eutectic TiB nanofibers contacted with each other with the formation of crosslinking microstructure. The crosslinking microstructural TiB aggregated and connected at the boundaries of Ti grains, forming a three-dimensional quasi-continuous network microstructure. The results show that compared with commercially pure Ti bulk parts, the TiB-TMCs exhibited superior wear performance (i.e. indentation wear resistance and friction wear resistance) due to the present of TiB reinforcement and the innovative microstructures formed inside TiB-TMCs. In addition, the qualities of the fabricated parts were improved with fewer interior defects by optimizing laser power, thus rendering better wear performance.

Children's Schemes for Anticipating the Validity of Nets for Solids

ERIC Educational Resources Information Center

Wright, Vince; Smith, Ken

2017-01-01

There is growing acknowledgement of the importance of spatial abilities to student achievement across a broad range of domains and disciplines. Nets are one way to connect three-dimensional shapes and their two-dimensional representations and are a common focus of geometry curricula. Thirty-four students at year 6 (upper primary school) were…

Particle morphology influence on mechanical and biocompatibility properties of injection molded Ti alloy powder.

PubMed

Gülsoy, H Özkan; Gülsoy, Nagihan; Calışıcı, Rahmi

2014-01-01

Titanium and Titanium alloys exhibits properties that are excellent for various bio-applications. Metal injection molding is a processing route that offers reduction in costs, with the added advantage of near net-shape components. Different physical properties of Titanium alloy powders, shaped and processed via injection molding can achieve high complexity of part geometry with mechanical and bioactivity properties, similar or superior to wrought material. This study describes that the effect of particle morphology on the microstructural, mechanical and biocompatibility properties of injection molded Ti-6Al-4V (Ti64) alloy powder for biomaterials applications. Ti64 powders irregular and spherical in shape were injection molded with wax based binder. Binder debinding was performed in solvent and thermal method. After debinding the samples were sintered under high vacuum. Metallographic studies were determined to densification and the corresponding microstructural changes. Sintered samples were immersed in a simulated body fluid (SBF) with elemental concentrations that were comparable to those of human blood plasma for a total period of 15 days. Both materials were implanted in fibroblast culture for biocompatibility evaluations were carried out. The results show that spherical and irregular powder could be sintered to a maximum theoretical density. Maximum tensile strength was obtained for spherical shape powder sintered. The tensile strength of the irregular shape powder sintered at the same temperature was lower due to higher porosity. Finally, mechanical tests show that the irregular shape powder has lower mechanical properties than spherical shape powder. The sintered irregular Ti64 powder exhibited better biocompatibility than sintered spherical Ti64 powder. Results of study showed that sintered spherical and irregular Ti64 powders exhibited high mechanical properties and good biocompatibility properties.

The equivalency between logic Petri workflow nets and workflow nets.

PubMed

Wang, Jing; Yu, ShuXia; Du, YuYue

2015-01-01

Logic Petri nets (LPNs) can describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. Logic Petri workflow nets (LPWNs) are proposed based on LPNs in this paper. Process mining is regarded as an important bridge between modeling and analysis of data mining and business process. Workflow nets (WF-nets) are the extension to Petri nets (PNs), and have successfully been used to process mining. Some shortcomings cannot be avoided in process mining, such as duplicate tasks, invisible tasks, and the noise of logs. The online shop in electronic commerce in this paper is modeled to prove the equivalence between LPWNs and WF-nets, and advantages of LPWNs are presented.

The Equivalency between Logic Petri Workflow Nets and Workflow Nets

PubMed Central

Wang, Jing; Yu, ShuXia; Du, YuYue

2015-01-01

Logic Petri nets (LPNs) can describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. Logic Petri workflow nets (LPWNs) are proposed based on LPNs in this paper. Process mining is regarded as an important bridge between modeling and analysis of data mining and business process. Workflow nets (WF-nets) are the extension to Petri nets (PNs), and have successfully been used to process mining. Some shortcomings cannot be avoided in process mining, such as duplicate tasks, invisible tasks, and the noise of logs. The online shop in electronic commerce in this paper is modeled to prove the equivalence between LPWNs and WF-nets, and advantages of LPWNs are presented. PMID:25821845

Parametric Study of Reactive Melt Infiltration

NASA Technical Reports Server (NTRS)

Nelson, Emily S.; Colella, Phillip

2000-01-01

Reactive melt infiltration is viewed as a promising means of achieving near-net shape manufacturing with quick processing time and at low cost. Since the reactants and products are, in general, of varying density, overall conservation of mass dictates that there is a force related to chemical conversion which can directly influence infiltration behavior. In effect, the driving pressure forces may compete with the forces from chemical conversion, affecting the advancement of the front. We have developed a two-dimensional numerical code to examine these effects, using reaction-formed silicon carbide as a model system for this process. We have examined a range of initial porosities, pore radii, and reaction rates in order to investigate their effects on infiltration dynamics.

Evaluation of ceramics for stator application: Gas turbine engine report

NASA Technical Reports Server (NTRS)

Trela, W.; Havstad, P. H.

1978-01-01

Current ceramic materials, component fabrication processes, and reliability prediction capability for ceramic stators in an automotive gas turbine engine environment are assessed. Simulated engine duty cycle testing of stators conducted at temperatures up to 1093 C is discussed. Materials evaluated are SiC and Si3N4 fabricated from two near-net-shape processes: slip casting and injection molding. Stators for durability cycle evaluation and test specimens for material property characterization, and reliability prediction model prepared to predict stator performance in the simulated engine environment are considered. The status and description of the work performed for the reliability prediction modeling, stator fabrication, material property characterization, and ceramic stator evaluation efforts are reported.

Interdependence theory of tissue failure: bulk and boundary effects.

PubMed

Suma, Daniel; Acun, Aylin; Zorlutuna, Pinar; Vural, Dervis Can

2018-02-01

The mortality rate of many complex multicellular organisms increases with age, which suggests that net ageing damage is accumulative, despite remodelling processes. But how exactly do these little mishaps in the cellular level accumulate and spread to become a systemic catastrophe? To address this question we present experiments with synthetic tissues, an analytical model consistent with experiments, and a number of implications that follow the analytical model. Our theoretical framework describes how shape, curvature and density influences the propagation of failure in a tissue subjected to oxidative damage. We propose that ageing is an emergent property governed by interaction between cells, and that intercellular processes play a role that is at least as important as intracellular ones.

Additively Manufactured IN718 Components with Wirelessly Powered and Interrogated Embedded Sensing

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

Attridge, Paul; Bajekal, Sanjay; Klecka, Michael

A methodology is described for embedding commercial-off-the-shelf sensors together with wireless communication and power circuit elements using direct laser metal sintered additively manufactured components. Physics based models of the additive manufacturing processes and sensor/wireless level performance models guided the design and embedment processes. A combination of cold spray deposition and laser engineered net shaping was used to fashion the transmitter/receiving elements and embed the sensors, thereby providing environmental protection and component robustness/survivability for harsh conditions. By design, this complement of analog and digital sensors were wirelessly powered and interrogated using a health and utilization monitoring system; enabling real-time, in situmore » prognostics and diagnostics.« less

Interdependence theory of tissue failure: bulk and boundary effects

NASA Astrophysics Data System (ADS)

Suma, Daniel; Acun, Aylin; Zorlutuna, Pinar; Vural, Dervis Can

2018-02-01

The mortality rate of many complex multicellular organisms increases with age, which suggests that net ageing damage is accumulative, despite remodelling processes. But how exactly do these little mishaps in the cellular level accumulate and spread to become a systemic catastrophe? To address this question we present experiments with synthetic tissues, an analytical model consistent with experiments, and a number of implications that follow the analytical model. Our theoretical framework describes how shape, curvature and density influences the propagation of failure in a tissue subjected to oxidative damage. We propose that ageing is an emergent property governed by interaction between cells, and that intercellular processes play a role that is at least as important as intracellular ones.

Productivity, Social Networks and Net Communities in the Workplace

ERIC Educational Resources Information Center

Asunda, Paul

2010-01-01

The 21st century workplace is being shaped by ever-changing technological innovations, shifting demographic patterns, globalization and power shifts, in addition to different economic players such as policymakers, employers, education and training institutions that shape the quality of the future workforce. In today's work environment,…

Reactive processing and mechanical properties of polymer derived silicon nitride matrix composites and their use in coating and joining ceramics and ceramic matrix composites

NASA Astrophysics Data System (ADS)

Stackpoole, Margaret Mary

Use of preceramic polymers offers many advantages over conventional ceramic processing routes. Advantages include being able to plastically form the part, form a pyrolized ceramic material at lower temperatures and form high purity microstructures which are tailorable depending on property requirements. To date preceramic polymers are mostly utilized in the production of low dimensional products such as fibers since loss of volatiles during pyrolysis leads to porosity and large shrinkage (in excess of 30%). These problems have been partially solved by use of active fillers (e.g. Ti, Cr, B). The reactive filler converts to a ceramic material with a volume expansion and this increases the density and reduces shrinkage and porosity. The expansion of the reactive filler thus compensates for the polymer shrinkage if the appropriate volume fraction of filler is present in a reactive atmosphere (e.g. N2 or NH3). This approach has resulted in structural composites with limited success. The present research investigates the possibility of using filled preceramic polymers to form net shaped ceramic composite materials and to investigate the use of these unique composite materials to join and coat ceramics and ceramic composites. The initial research focused on phase and microstructural development of bulk composites from the filled polymer/ceramic systems. A processing technique was developed to insure consistency between different samples and the most promising filler/polymer choices for this application have been determined. The processing temperatures and atmospheres have also been optimized. The work covers processing and characterization of bulk composites, joints and coatings. With careful control of processing near net shape bulk composites were fabricated. Both ambient and high temperature strength and fracture toughness was obtained for these composite systems. The potential of using reactively filled preceramic polymers to process joints and coatings was also investigated. A critical thickness below which crack free joints/coatings could be processed was determined. Finally, mechanical properties of the joints and coatings at ambient and elevated temperatures (including oxidation studies) have been evaluated. The interfacial fracture behavior of the joints and coatings was also evaluated.

Animal Hairs as Water-stimulated Shape Memory Materials: Mechanism and Structural Networks in Molecular Assemblies

NASA Astrophysics Data System (ADS)

Xiao, Xueliang; Hu, Jinlian

2016-05-01

Animal hairs consisting of α-keratin biopolymers existing broadly in nature may be responsive to water for recovery to the innate shape from their fixed deformation, thus possess smart behavior, namely shape memory effect (SME). In this article, three typical animal hair fibers were first time investigated for their water-stimulated SME, and therefrom to identify the corresponding net-points and switches in their molecular and morphological structures. Experimentally, the SME manifested a good stability of high shape fixation ratio and reasonable recovery rate after many cycles of deformation programming under water stimulation. The effects of hydration on hair lateral size, recovery kinetics, dynamic mechanical behaviors and structural components (crystal, disulfide and hydrogen bonds) were then systematically studied. SME mechanisms were explored based on the variations of structural components in molecular assemblies of such smart fibers. A hybrid structural network model with single-switch and twin-net-points was thereafter proposed to interpret the water-stimulated shape memory mechanism of animal hairs. This original work is expected to provide inspiration for exploring other natural materials to reveal their smart functions and natural laws in animals including human as well as making more remarkable synthetic smart materials.

Animal Hairs as Water-stimulated Shape Memory Materials: Mechanism and Structural Networks in Molecular Assemblies

PubMed Central

Xiao, Xueliang; Hu, Jinlian

2016-01-01

Animal hairs consisting of α-keratin biopolymers existing broadly in nature may be responsive to water for recovery to the innate shape from their fixed deformation, thus possess smart behavior, namely shape memory effect (SME). In this article, three typical animal hair fibers were first time investigated for their water-stimulated SME, and therefrom to identify the corresponding net-points and switches in their molecular and morphological structures. Experimentally, the SME manifested a good stability of high shape fixation ratio and reasonable recovery rate after many cycles of deformation programming under water stimulation. The effects of hydration on hair lateral size, recovery kinetics, dynamic mechanical behaviors and structural components (crystal, disulfide and hydrogen bonds) were then systematically studied. SME mechanisms were explored based on the variations of structural components in molecular assemblies of such smart fibers. A hybrid structural network model with single-switch and twin-net-points was thereafter proposed to interpret the water-stimulated shape memory mechanism of animal hairs. This original work is expected to provide inspiration for exploring other natural materials to reveal their smart functions and natural laws in animals including human as well as making more remarkable synthetic smart materials. PMID:27230823

Triple-layer configuration for stable high-speed lubricated pipeline transport

NASA Astrophysics Data System (ADS)

Sarmadi, Parisa; Hormozi, Sarah; Frigaard, Ian A.

2017-04-01

Lubricated transport of heavy viscous oils is a popular technology in the pipelining industry, where pumping pressures can be reduced significantly by concentrating the strain rate in a lubricating layer. However, the interface between the lubricating layer and heavy oil is vulnerable to any perturbations in the system as well as transients due to start up, shut down, temperature change, etc. We present a method in which we purposefully position an unyielded skin of a viscoplastic fluid between the oil and the lubricating fluid. The objective is to reduce the frictional pressure gradient while avoiding interfacial instability. We study this methodology in both concentric and eccentric configurations and show its feasibility for a wide range of geometric and flow parameters found in oil pipelining. The eccentric configuration benefits the transport process via generating lift forces to balance the density differences among the layers. We use classical lubrication theory to estimate the leading order pressure distribution in the lubricating layer and calculate the net force on the skin. We explore the effects of skin shape, viscosity ratio, and geometry on the pressure drop, the flow rates of skin and lubricant fluids, and the net force on the skin. We show that the viscosity ratio and the radius of the core fluid are the main parameters that control the pressure drop and consumptions of outer fluids, respectively. The shape of the skin and the eccentricity mainly affect the lubrication pressure. These predictions are essential in designing a stable transport process. Finally, we estimate the yield stress required in order that the skin remain unyielded and ensure interfacial stability.

Bulk combinatorial synthesis and high throughput characterization for rapid assessment of magnetic materials: Application of laser engineered net shaping (LENS)

DOE PAGES

Geng, J.; Nlebedim, I. C.; Besser, M. F.; ...

2016-04-15

A bulk combinatorial approach for synthesizing alloy libraries using laser engineered net shaping (LENS; i.e., 3D printing) was utilized to rapidly assess material systems for magnetic applications. The LENS system feeds powders in different ratios into a melt pool created by a laser to synthesize samples with bulk (millimeters) dimensions. By analyzing these libraries with autosampler differential scanning calorimeter/thermal gravimetric analysis and vibrating sample magnetometry, we are able to rapidly characterize the thermodynamic and magnetic properties of the libraries. Furthermore, the Fe-Co binary alloy was used as a model system and the results were compared with data in the literature.

Advanced resin systems and 3D textile preforms for low cost composite structures

NASA Technical Reports Server (NTRS)

Shukla, J. G.; Bayha, T. D.

1993-01-01

Advanced resin systems and 3D textile preforms are being evaluated at Lockheed Aeronautical Systems Company (LASC) under NASA's Advanced Composites Technology (ACT) Program. This work is aimed towards the development of low-cost, damage-tolerant composite fuselage structures. Resin systems for resin transfer molding and powder epoxy towpreg materials are being evaluated for processability, performance and cost. Three developmental epoxy resin systems for resin transfer molding (RTM) and three resin systems for powder towpregging are being investigated. Various 3D textile preform architectures using advanced weaving and braiding processes are also being evaluated. Trials are being conducted with powdered towpreg, in 2D weaving and 3D braiding processes for their textile processability and their potential for fabrication in 'net shape' fuselage structures. The progress in advanced resin screening and textile preform development is reviewed here.

Manufacturing Processes for Long-Life Gas Turbines

NASA Astrophysics Data System (ADS)

Hoppin, G. S.; Danesi, W. P.

1986-07-01

Dual-alloy turbine wheels produced by solid-state diffusion bonding of vacuum investment cast blade rings of one superalloy to preconsolidated powder metal hubs of a second superalloy have the long cyclic lives characteristic of wrought or powder superalloys combined with the high creep strength and net-shape blades characteristic of cast superalloys. A wide variety of superalloys and turbine configurations are compatible with this technology. Improved temperature capability turbine blades and vanes of the MAR-M 247 alloy made by directional solidification casting processes are now in volume production for Garrett gas turbines. Single-crystal alloys derivative to MAR-M 247 further extend the temperature capability of turbine blades and have been successfully engine tested. These blades are produced by a relatively simple modification of the processes used to manufacture directionally solidified blades.

Dimensional control of die castings

NASA Astrophysics Data System (ADS)

Karve, Aniruddha Ajit

The demand for net shape die castings, which require little or no machining, is steadily increasing. Stringent customer requirements are forcing die casters to deliver high quality castings in increasingly short lead times. Dimensional conformance to customer specifications is an inherent part of die casting quality. The dimensional attributes of a die casting are essentially dependent upon many factors--the quality of the die and the degree of control over the process variables being the two major sources of dimensional error in die castings. This study focused on investigating the nature and the causes of dimensional error in die castings. The two major components of dimensional error i.e., dimensional variability and die allowance were studied. The major effort of this study was to qualitatively and quantitatively study the effects of casting geometry and process variables on die casting dimensional variability and die allowance. This was accomplished by detailed dimensional data collection at production die casting sites. Robust feature characterization schemes were developed to describe complex casting geometry in quantitative terms. Empirical modeling was utilized to quantify the effects of the casting variables on dimensional variability and die allowance for die casting features. A number of casting geometry and process variables were found to affect dimensional variability in die castings. The dimensional variability was evaluated by comparisons with current published dimensional tolerance standards. The casting geometry was found to play a significant role in influencing the die allowance of the features measured. The predictive models developed for dimensional variability and die allowance were evaluated to test their effectiveness. Finally, the relative impact of all the components of dimensional error in die castings was put into perspective, and general guidelines for effective dimensional control in the die casting plant were laid out. The results of this study will contribute to enhancement of dimensional quality and lead time compression in the die casting industry, thus making it competitive with other net shape manufacturing processes.

Fabrication of GRCop-84 Rocket Thrust Chambers

NASA Technical Reports Server (NTRS)

Loewenthal, William; Ellis, David

2006-01-01

GRCop-84, a copper alloy, Cu-8 at% Cr-4 at% Nb developed at NASA Glenn Research Center for regenerative1y cooled rocket engine liners has excellent combinations of elevated temperature strength, creep resistance, thermal conductivity and low cycle fatigue. GRCop-84 is produced from pre-alloyed atomized powder and has been fabricated into plate, sheet and tube forms as well as near net shapes. Fabrication processes to produce demonstration rocket combustion chambers will be presented and includes powder production, extruding, rolling, forming, friction stir welding, and metal spinning. GRCop-84 has excellent workability and can be readily fabricated into complex components using conventional powder and wrought metallurgy processes. Rolling was examined in detail for process sensitivity at various levels of total reduction, rolling speed and rolling temperature representing extremes of commercial processing conditions. Results indicate that process conditions can range over reasonable levels without any negative impact to properties.

Fabrication of GRCop-84 Rocket Thrust Chambers

NASA Technical Reports Server (NTRS)

Loewenthal, William S.; Ellis, David L.

2005-01-01

GRCop-84, a copper alloy, Cu-8 at% Cr-4 at% Nb developed at NASA Glenn Research Center for regeneratively cooled rocket engine liners has excellent combinations of elevated temperature strength, creep resistance, thermal conductivity and low cycle fatigue. GRCop-84 is produced from prealloyed atomized powder and has been fabricated into plate, sheet and tube forms as well as near net shapes. Fabrication processes to produce demonstration rocket combustion chambers will be presented and includes powder production, extruding, rolling, forming, friction stir welding, and metal spinning. GRCop-84 has excellent workability and can be readily fabricated into complex components using conventional powder and wrought metallurgy processes. Rolling was examined in detail for process sensitivity at various levels of total reduction, rolling speed and rolling temperature representing extremes of commercial processing conditions. Results indicate that process conditions can range over reasonable levels without any negative impact to properties.

Improved silicon nitride for advanced heat engines

NASA Technical Reports Server (NTRS)

Yeh, H. C.; Wimmer, J. M.

1986-01-01

Silicon nitride is a high temperature material currently under consideration for heat engine and other applications. The objective is to improve the net shape fabrication technology of Si3N4 by injection molding. This is to be accomplished by optimizing the process through a series of statistically designed matrix experiments. To provide input to the matrix experiments, a wide range of alternate materials and processing parameters was investigated throughout the whole program. The improvement in the processing is to be demonstrated by a 20 percent increase in strength and a 100 percent increase in the Weibull modulus over that of the baseline material. A full characterization of the baseline process was completed. Material properties were found to be highly dependent on each step of the process. Several important parameters identified thus far are the starting raw materials, sinter/hot isostatic pressing cycle, powder bed, mixing methods, and sintering aid levels.

Low cost fabrication development for oxide dispersion strengthened alloy vanes

NASA Technical Reports Server (NTRS)

Perkins, R. J.; Bailey, P. G.

1978-01-01

Viable processes were developed for secondary working of oxide dispersion strengthened (ODS) alloys to near-net shapes (NNS) for aircraft turbine vanes. These processes were shown capable of producing required microstructure and properties for vane applications. Material cost savings of 40 to 50% are projected for the NNS process over the current procedures which involve machining from rectangular bar. Additional machining cost savings are projected. Of three secondary working processes evaluated, directional forging and plate bending were determined to be viable NNS processes for ODS vanes. Directional forging was deemed most applicable to high pressure turbine (HPT) vanes with their large thickness variations while plate bending was determined to be most cost effective for low pressure turbine (LPT) vanes because of their limited thickness variations. Since the F101 LPT vane was selected for study in this program, development of plate bending was carried through to establishment of a preliminary process. Preparation of ODS alloy plate for bending was found to be a straight forward process using currently available bar stock, providing that the capability for reheating between roll passes is available. Advanced ODS-NiCrAl and ODS-FeCrAl alloys were utilized on this program. Workability of all alloys was adequate for directional forging and plate bending, but only the ODS-FeCrAl had adequate workability for shaped preform extrustion.

Development of Thixomolded{reg_sign} magnesium products

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

Ghosh, D.; Fan, R.; Kang, K.

1995-10-01

Thixomolding{reg_sign} is a racial new process which merges the technologies of die-casting and plastic injection molding for the net shape molding of magnesium based alloys. Properties of Thixomolded{reg_sign} magnesium alloys are discussed and compared with those of traditional die casting. Magnesium alloys are of great interest to automobile manufacturers because of the potential weight savings and corresponding energy savings due to increased fuel economy. For this reason, one of the first target markets for Thixomolded{reg_sign} products is the automotive industry. The use of Thixomolding{reg_sign} in the production of an automobile part is examined.

An analysis of polygenes affecting wing shape on chromosome 2 in Drosophila melanogaster.

PubMed Central

Weber, K; Eisman, R; Higgins, S; Morey, L; Patty, A; Tausek, M; Zeng, Z B

2001-01-01

Genetic effects on an index of wing shape on chromosome 2 of Drosophila melanogaster were mapped using isogenic recombinants with transposable element markers. At least 10 genes with small additive effects are dispersed evenly along the chromosome. Many interactions exist, with only small net effects in homozygous recombinants and little effect on phenotypic variance. Heterozygous chromosome segments show almost no dominance. Pleiotropic effects on leg shape are only minor. At first view, wing shape genes form a rather homogeneous class, but certain complexities remain unresolved. PMID:11729152

Cost-Benefit Analysis for the Advanced Near Net Shape Technology (ANNST) Method for Fabricating Stiffened Cylinders

NASA Technical Reports Server (NTRS)

Ivanco, Marie L.; Domack, Marcia S.; Stoner, Mary Cecilia; Hehir, Austin R.

2016-01-01

Low Technology Readiness Levels (TRLs) and high levels of uncertainty make it challenging to develop cost estimates of new technologies in the R&D phase. It is however essential for NASA to understand the costs and benefits associated with novel concepts, in order to prioritize research investments and evaluate the potential for technology transfer and commercialization. This paper proposes a framework to perform a cost-benefit analysis of a technology in the R&D phase. This framework was developed and used to assess the Advanced Near Net Shape Technology (ANNST) manufacturing process for fabricating integrally stiffened cylinders. The ANNST method was compared with the conventional multi-piece metallic construction and composite processes for fabricating integrally stiffened cylinders. Following the definition of a case study for a cryogenic tank cylinder of specified geometry, data was gathered through interviews with Subject Matter Experts (SMEs), with particular focus placed on production costs and process complexity. This data served as the basis to produce process flowcharts and timelines, mass estimates, and rough order-of-magnitude cost and schedule estimates. The scalability of the results was subsequently investigated to understand the variability of the results based on tank size. Lastly, once costs and benefits were identified, the Analytic Hierarchy Process (AHP) was used to assess the relative value of these achieved benefits for potential stakeholders. These preliminary, rough order-of-magnitude results predict a 46 to 58 percent reduction in production costs and a 7-percent reduction in weight over the conventional metallic manufacturing technique used in this study for comparison. Compared to the composite manufacturing technique, these results predict cost savings of 35 to 58 percent; however, the ANNST concept was heavier. In this study, the predicted return on investment of equipment required for the ANNST method was ten cryogenic tank barrels when compared with conventional metallic manufacturing. The AHP study results revealed that decreased final cylinder mass and improved quality assurance were the most valued benefits of cylinder manufacturing methods, therefore emphasizing the relevance of the benefits achieved with the ANNST process for future projects.

Effect of Surface Treatments on Electron Beam Freeform Fabricated Aluminum Structures

NASA Technical Reports Server (NTRS)

Taminger, Karen M. B.; Hafley, Robert A.; Fahringer, David T.; Martin, Richard E.

2004-01-01

Electron beam freeform fabrication (EBF3) parts exhibit a ridged surface finish typical of many layer-additive processes. This, post-processing is required to produce a net shape with a smooth surface finish. High speed milling wire electrical discharge machining (EDM), electron beam glazing, and glass bead blasting were performed on EBF3-build 2219 aluminum alloy parts to reduce or eliminate the ridged surface features. Surface roughness, surface residual stress state, and microstructural characteristics were examined for each of the different surface treatment to assess the quality and effect of the surface treatments on the underlying material. The analysis evaluated the effectivenes of the different surface finishing techniques for achieving a smooth surface finish on an electron beam freeform fabricated part.

Interdependence theory of tissue failure: bulk and boundary effects

PubMed Central

Suma, Daniel; Acun, Aylin; Zorlutuna, Pinar

2018-01-01

The mortality rate of many complex multicellular organisms increases with age, which suggests that net ageing damage is accumulative, despite remodelling processes. But how exactly do these little mishaps in the cellular level accumulate and spread to become a systemic catastrophe? To address this question we present experiments with synthetic tissues, an analytical model consistent with experiments, and a number of implications that follow the analytical model. Our theoretical framework describes how shape, curvature and density influences the propagation of failure in a tissue subjected to oxidative damage. We propose that ageing is an emergent property governed by interaction between cells, and that intercellular processes play a role that is at least as important as intracellular ones. PMID:29515857

Net Shaped Component Fabrication of Refractory Metal Alloys using Vacuum Plasma Spraying

NASA Technical Reports Server (NTRS)

Sen, S.; ODell, S.; Gorti, S.; Litchford, R.

2006-01-01

The vacuum plasma spraying (VPS) technique was employed to produce dense and net shaped components of a new tungsten-rhenium (W-Re) refractory metal alloy. The fine grain size obtained using this technique enhanced the mechanical properties of the alloy at elevated temperatures. The alloy development also included incorporation of thermodynamically stable dispersion phases to pin down grain boundaries at elevated temperatures and thereby circumventing the inherent problem of recrystallization of refractory alloys at elevated temperatures. Requirements for such alloys as related to high temperature space propulsion components will be discussed. Grain size distribution as a function of cooling rate and dispersion phase loading will be presented. Mechanical testing and grain growth results as a function of temperature will also be discussed.

Replication of microchannel structures in WC-Co feedstock using elastomeric replica moulds by hot embossing process.

PubMed

Sahli, M; Gelin, J-C; Barrière, T

2015-10-01

Hot embossing is a net shaping process that is able to produce the micro-components of polymers with intrinsic and complex shapes at lower cost compared with machining and injection moulding. However, the emboss of hard metals, such as WC-Co, is more challenging due to their high thermal conductivity and ease of agglomeration. Thus, a WC-Co alloy mixed with a wax-based binder feedstock was selected. The formed feedstock exhibited pseudo-plastic flow and was successfully embossed (green part). Here, we developed a novel process that is used to replicate polymer microfluidic chips while simultaneously reducing the channel surface roughness of the mould insert, yielding optical-grade (less than 100 nm surface roughness) channels and reservoirs. This paper concerns the replication of metallic microfluidic mould inserts in WC-Co and the parameters associated with feedstock formation via a hot embossing process. A suitable formulation for micro-powder hot embossing has been established and characterised by thermogravimetric analyses and measurements of mixing torques to verify and quantify the homogeneity of the proposed feedstocks. The relative density of the samples increased with processing temperature, and almost fully dense materials were obtained. In this work, the effects of the sintering temperature on the physical properties were systematically analysed. The evolution of the metal surface morphology during the hot embossing process was also investigated. The results indicate that the feedstock can be used to manufacture micro-fluidic die mould cavities with a low roughness, proper dimensions and good shape retention. The shrinkage of the sintered part was approximately 19-24% compared with that of the brown part. Copyright © 2015 Elsevier B.V. All rights reserved.

Modeling and experimental analysis of electrospinning bending region physics in determining fiber diameter for hydrophilic polymer solvent systems

NASA Astrophysics Data System (ADS)

Cai, Yunshen

Electrospinning produces submicron fibers from a wide range of polymer/solvent systems that enable a variety of different applications. In electrospinning process, a straight polymer/solvent charged jet is initially formed, followed by a circular moving jet in the shape of a cone, called the bending region. The process physics in the bending region are difficult to study since the jet diameter cannot be measured directly due to its rapid motion and small size ( microns and smaller), and due to complex coupling of multiple forces, mass transport, and changing jet geometry. Since the solutions studied are hydrophilic, they readily absorb ambient moisture. This thesis explores the role of the bending region in determining the resulting electrospun fiber diameter through a combined experimental and modeling analysis for a variety of hydrophilic polymer/solvent solutions. Electrospinning experiments were conducted over a broad range of operating conditions for 4 different polymer/solvent systems. Comparison of the final straight jet diameters to fiber diameters reveals that between 30% to 60% jet thinning occurs in the bending region. These experiments also reveal that relative humidity significantly affects the electrospinning process and final fiber diameter, even for non-aqueous solutions. A model is developed to obtain insight into the bending region process physics. Important ones include understanding the mass transport for non-aqueous hydrophilic jets (including solvent evaporation and water absorption on the jet surface, radial diffusion, and axial advection), and the coupling between the mass and force balances that determines the final fiber diameter. The absorption and evaporation physics is validated by evaporation experiments. The developed model predicts fiber diameter to within of 8%, even though the solution properties and operating conditions that determines net stretching forces and net evaporation rates vary over a large range. Model analysis reveals how the net evaporation rate affects the jet length and net stretching force, both of which ultimately determine the fiber diameter. It is also shown that the primary impact of RH on the process is through occupation of the surface states that limits solvent evaporation rate, rather than the amount of water absorbed. Correlation functions between process conditions, solution properties and the resulting fiber diameters are discussed.

Magnesium Powder Injection Molding (MIM) of Orthopedic Implants for Biomedical Applications

NASA Astrophysics Data System (ADS)

Wolff, M.; Schaper, J. G.; Suckert, M. R.; Dahms, M.; Ebel, T.; Willumeit-Römer, R.; Klassen, T.

2016-04-01

Metal injection molding (MIM) has a high potential for the economic near-net-shape mass production of small-sized and complex-shaped parts. The motivation for launching Mg into the MIM processing chain for manufacturing biodegradable medical implants is related to its compatibility with human bone and its degradation in a non-toxic matter. It has been recognized that the load-bearing capacity of MIM Mg parts is superior to that of biodegradable polymeric components. However, the choice of appropriate polymeric binder components and alloying elements enabling defect-free injection molding and sintering is a major challenge for the use of MIM Mg parts. This study considered the full processing chain for MIM of Mg-Ca alloys to achieve ultimate tensile strength of up to 141 MPa with tensile yield strength of 73 MPa, elongation at fracture Af of 7% and a Young's modulus of 38 GPa. To achieve these mechanical properties, a thermal debinding study was performed to determine optimal furnace and atmosphere conditions, sintering temperature, heating rates, sintering time and pressure.

Neural net classification of liver ultrasonogram for quantitative evaluation of diffuse liver disease

NASA Astrophysics Data System (ADS)

Lee, Dong Hyuk; Kim, JongHyo; Kim, Hee C.; Lee, Yong W.; Min, Byong Goo

1997-04-01

There have been a number of studies on the quantitative evaluation of diffuse liver disease by using texture analysis technique. However, the previous studies have been focused on the classification between only normal and abnormal pattern based on textural properties, resulting in lack of clinically useful information about the progressive status of liver disease. Considering our collaborative research experience with clinical experts, we judged that not only texture information but also several shape properties are necessary in order to successfully classify between various states of disease with liver ultrasonogram. Nine image parameters were selected experimentally. One of these was texture parameter and others were shape parameters measured as length, area and curvature. We have developed a neural-net algorithm that classifies liver ultrasonogram into 9 categories of liver disease: 3 main category and 3 sub-steps for each. Nine parameters were collected semi- automatically from the user by using graphical user interface tool, and then processed to give a grade for each parameter. Classifying algorithm consists of two steps. At the first step, each parameter was graded into pre-defined levels using neural network. in the next step, neural network classifier determined disease status using graded nine parameters. We implemented a PC based computer-assist diagnosis workstation and installed it in radiology department of Seoul National University Hospital. Using this workstation we collected 662 cases during 6 months. Some of these were used for training and others were used for evaluating accuracy of the developed algorithm. As a conclusion, a liver ultrasonogram classifying algorithm was developed using both texture and shape parameters and neural network classifier. Preliminary results indicate that the proposed algorithm is useful for evaluation of diffuse liver disease.

Do non-native plant species affect the shape of productivity-diversity relationships?

USGS Publications Warehouse

Drake, J.M.; Cleland, E.E.; Horner-Devine, M. C.; Fleishman, E.; Bowles, C.; Smith, M.D.; Carney, K.; Emery, S.; Gramling, J.; Vandermast, D.B.; Grace, J.B.

2008-01-01

The relationship between ecosystem processes and species richness is an active area of research and speculation. Both theoretical and experimental studies have been conducted in numerous ecosystems. One finding of these studies is that the shape of the relationship between productivity and species richness varies considerably among ecosystems and at different spatial scales, though little is known about the relative importance of physical and biological mechanisms causing this variation. Moreover, despite widespread concern about changes in species' global distributions, it remains unclear if and how such large-scale changes may affect this relationship. We present a new conceptual model of how invasive species might modulate relationships between primary production and species richness. We tested this model using long-term data on relationships between aboveground net primary production and species richness in six North American terrestrial ecosystems. We show that primary production and abundance of non-native species are both significant predictors of species richness, though we fail to detect effects of invasion extent on the shapes of the relationship between species richness and primary production.

Recycle of Immobilized Endocellulases in Different Conditions for Cellulose Hydrolysis

PubMed Central

Carvalho, A. F. A.; Shinya, T. Y.; Mazali, G. S.; Herculano, R. D.; Oliva-Neto, P.

2017-01-01

The immobilization of cellulases could be an economical alternative for cost reduction of enzyme application. The derivatives obtained in the immobilization derivatives were evaluated in recycles of paper filter hydrolysis. The immobilization process showed that the enzyme recycles were influenced by the shape (drop or sheet) and type of the mixture. The enzyme was recycled 28 times for sheets E′ and 13 times for drops B′. The derivative E′ showed the highest stability in the recycle obtaining 0.05 FPU/g, RA of 10%, and FPU Yield of 1.64 times, higher than FPU spent or Net FPU Yield of 5.3 times, saving more active enzymes. The derivative B showed stability in recycles reaching 0.15 FPU/g of derivative, yield of Recovered Activity (RA) of 25%, and FPU Yield of 1.57 times, higher than FPU spent on immobilization or Net PFU Yield of 2.81 times. The latex increased stability and resistance of the drops but did not improve the FPU/gram of derivative. PMID:28465836

Density of Spray-Formed Materials

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

Kevin M. McHugh; Volker Uhlenwinkel; Nils Ellendr

2008-06-01

Spray Forming is an advanced materials processing technology that transforms molten metal into a near-net-shape solid by depositing atomized droplets onto a substrate. Depending on the application, the spray-formed material may be used in the as-deposited condition or it may undergo post-deposition processing. Regardless, the density of the as-deposited material is an important issue. Porosity is detrimental because it can significantly reduce strength, toughness, hardness and other properties. While it is not feasible to achieve fully-dense material in the as-deposited state, density greater than 99% of theoretical density is possible if the atomization and impact conditions are optimized. Thermal conditionsmore » at the deposit surface and droplet impact angle are key processing parameters that influence the density of the material. This paper examines the factors that contribute to porosity formation during spray forming and illustrates that very high as-deposited density is achieved by optimizing processing parameters.« less

The role of rapid solidification processing in the fabrication of fiber reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Locci, Ivan E.; Noebe, Ronald D.

1989-01-01

Advanced composite processing techniques for fiber reinforced metal matrix composites require the flexibility to meet several widespread objectives. The development of uniquely desired matrix microstructures and uniformly arrayed fiber spacing with sufficient bonding between fiber and matrix to transmit load between them without degradation to the fiber or matrix are the minimum requirements necessary of any fabrication process. For most applications these criteria can be met by fabricating composite monotapes which are then consolidated into composite panels or more complicated components such as fiber reinforced turbine blades. Regardless of the end component, composite monotapes are the building blocks from which near net shape composite structures can be formed. The most common methods for forming composite monotapes are the powder cloth, foil/fiber, plasma spray, and arc spray processes. These practices, however, employ rapid solidification techniques in processing of the composite matrix phase. Consequently, rapid solidification processes play a vital and yet generally overlooked role in composite fabrication. The future potential of rapid solidification processing is discussed.

Rapid Processing of Net-Shape Thermoplastic Planar-Random Composite Preforms

NASA Astrophysics Data System (ADS)

Jespersen, S. T.; Baudry, F.; Schmäh, D.; Wakeman, M. D.; Michaud, V.; Blanchard, P.; Norris, R. E.; Månson, J.-A. E.

2009-02-01

A novel thermoplastic composite preforming and moulding process is investigated to target cost issues in textile composite processing associated with trim waste, and the limited mechanical properties of current bulk flow-moulding composites. The thermoplastic programmable powdered preforming process (TP-P4) uses commingled glass and polypropylene yarns, which are cut to length before air assisted deposition onto a vacuum screen, enabling local preform areal weight tailoring. The as-placed fibres are heat-set for improved handling before an optional preconsolidation stage. The preforms are then preheated and press formed to obtain the final part. The process stages are examined to optimize part quality and throughput versus processing parameters. A viable processing route is proposed with typical cycle times below 40 s (for a plate 0.5 × 0.5 m2, weighing 2 kg), enabling high production capacity from one line. The mechanical performance is shown to surpass that of 40 wt.% GMT and has properties equivalent to those of 40 wt.% GMTex at both 20°C and 80°C.

Electron Beam Freeform Fabrication: A Fabrication Process that Revolutionizes Aircraft Structural Designs and Spacecraft Supportability

NASA Technical Reports Server (NTRS)

Taminger, Karen M.

2008-01-01

The technological inception and challenges, as well as current applications of the electron beam freeform fabrication (EBF3) process are outlined. The process was motivated by the need for a new metals technology that would be cost-effective, enable the production of new alloys and that would could be used for efficient, lightweight structures. EBF3 is a rapid metal fabrication, layer-additive process that uses no molds or tools and which yields properties equivalent to wrought. The benefits of EBF3 include it near-net shape which minimizes scrap and reduces part count; efficiency in design which allows for lighter weight and enhanced performance; and, its "green" manufacturing process which yields minimal waste products. EBF3 also has a high tensile strength, while a structural test comparison found that EBF3 panels performed 5% lower than machined panels. Technical challenges in the EBF3 process include a need for process control monitoring and an improvement in localized heat response. Currently, the EBF3 process can be used to add details onto forgings and to construct and form complex shapes. However, it has potential uses in a variety of industries including aerospace, automotive, sporting goods and medical implant devices. The novel structural design capabilities of EBF3 have the ability to yield curved stiffeners which may be optimized for performance, low weight, low noise and damage tolerance applications. EBF3 has also demonstrated its usefulness in 0-gravity environments for supportability in space applications.

Measured Effects of Turbulence on the Loudness and Waveforms of Conventional and Shaped Minimized Sonic Booms

NASA Technical Reports Server (NTRS)

Plotkin, Kenneth J.; Maglieri, Domenic J.; Sullivan, Brenda M.

2005-01-01

Turbulence has two distinctive effects on sonic booms: there is distortion in the form of random perturbations that appear behind the shock waves, and shock rise times are increased randomly. A first scattering theory by S.C. Crow in the late 1960s quantified the random distortions, and Crow's theory was shown to agree with available flight test data. A variety of theories for the shock thickness have been presented, all supporting the role of turbulence in increasing rise time above that of a basic molecular-relaxation structure. The net effect of these phenomena on the loudness of shaped minimized booms is of significant interest. Initial analysis suggests that there would be no change to average loudness, but this had not been experimentally investigated. The January 2004 flight test of the Shaped Sonic Boom Demonstrator (SSBD), together with a reference unmodified F-5E, included a 12500- foot linear ground sensor array with 28 digitally recorded sensor sites. This data set provides an opportunity to re-test Crow's theory for the post-shock perturbations, and to examine the net effect of turbulence on the loudness of shaped sonic booms.

Method for making carbon super capacitor electrode materials

DOEpatents

Firsich, D.W.; Ingersoll, D.; Delnick, F.M.

1998-07-07

A method is described for making near-net-shape, monolithic carbon electrodes for energy storage devices. The method includes the controlled pyrolysis and activation of a pressed shape of methyl cellulose powder with pyrolysis being carried out in two stages; pre-oxidation, preferably in air at a temperature between 200--250 C, followed by carbonization under an inert atmosphere. An activation step to adjust the surface area of the carbon shape to a value desirable for the application being considered, including heating the carbon shape in an oxidizing atmosphere to a temperature of at least 300 C, follows carbonization. 1 fig.

Method for making carbon super capacitor electrode materials

DOEpatents

Firsich, David W.; Ingersoll, David; Delnick, Frank M.

1998-01-01

A method for making near-net-shape, monolithic carbon electrodes for energy storage devices. The method includes the controlled pyrolysis and activation of a pressed shape of methyl cellulose powder with pyrolysis being carried out in two stages; pre-oxidation, preferably in air at a temperature between 200.degree.-250.degree. C., followed by carbonization under an inert atmosphere. An activation step to adjust the surface area of the carbon shape to a value desirable for the application being considered, including heating the carbon shape in an oxidizing atmosphere to a temperature of at least 300.degree. C., follows carbonization.

NetCooperate: a network-based tool for inferring host-microbe and microbe-microbe cooperation.

PubMed

Levy, Roie; Carr, Rogan; Kreimer, Anat; Freilich, Shiri; Borenstein, Elhanan

2015-05-17

Host-microbe and microbe-microbe interactions are often governed by the complex exchange of metabolites. Such interactions play a key role in determining the way pathogenic and commensal species impact their host and in the assembly of complex microbial communities. Recently, several studies have demonstrated how such interactions are reflected in the organization of the metabolic networks of the interacting species, and introduced various graph theory-based methods to predict host-microbe and microbe-microbe interactions directly from network topology. Using these methods, such studies have revealed evolutionary and ecological processes that shape species interactions and community assembly, highlighting the potential of this reverse-ecology research paradigm. NetCooperate is a web-based tool and a software package for determining host-microbe and microbe-microbe cooperative potential. It specifically calculates two previously developed and validated metrics for species interaction: the Biosynthetic Support Score which quantifies the ability of a host species to supply the nutritional requirements of a parasitic or a commensal species, and the Metabolic Complementarity Index which quantifies the complementarity of a pair of microbial organisms' niches. NetCooperate takes as input a pair of metabolic networks, and returns the pairwise metrics as well as a list of potential syntrophic metabolic compounds. The Biosynthetic Support Score and Metabolic Complementarity Index provide insight into host-microbe and microbe-microbe metabolic interactions. NetCooperate determines these interaction indices from metabolic network topology, and can be used for small- or large-scale analyses. NetCooperate is provided as both a web-based tool and an open-source Python module; both are freely available online at http://elbo.gs.washington.edu/software_netcooperate.html.

A Petri Net-Based Software Process Model for Developing Process-Oriented Information Systems

NASA Astrophysics Data System (ADS)

Li, Yu; Oberweis, Andreas

Aiming at increasing flexibility, efficiency, effectiveness, and transparency of information processing and resource deployment in organizations to ensure customer satisfaction and high quality of products and services, process-oriented information systems (POIS) represent a promising realization form of computerized business information systems. Due to the complexity of POIS, explicit and specialized software process models are required to guide POIS development. In this chapter we characterize POIS with an architecture framework and present a Petri net-based software process model tailored for POIS development with consideration of organizational roles. As integrated parts of the software process model, we also introduce XML nets, a variant of high-level Petri nets as basic methodology for business processes modeling, and an XML net-based software toolset providing comprehensive functionalities for POIS development.

Improved Net-Level Filling And Finishing Of Large Castings

NASA Technical Reports Server (NTRS)

Johnson, Erik P.; Brown, Richard F.

1995-01-01

Improved method of vacuum casting of large, generally cylindrical objects to net sizes and shapes reduces amount of direct manual labor by workers in proximity to cast material. Original application for which method devised is fabrication of solid rocket-motor segments containing solid propellant, wherein need to minimize exposure of workers to propellant material being cast. Improved method adaptable to other applications involving large castings of toxic, flammable, or otherwise hazardous materials.

Ti Alloys Processed By Selective Laser Melting And By Laser Cladding: Microstructures And Mechanical Properties

NASA Astrophysics Data System (ADS)

Mertens, Anne; Contrepois, Quentin; Dormal, Thierry; Lemaire, Olivier; Lecomte-Beckers, Jacqueline

2012-07-01

In this study, samples of alloy Ti-6Al-4V have been processed by Selective Laser Melting (SLM) and by Laser Cladding (LC), two layer-by-layer near-net-shape processes allowing for economic production of complex parts. The resulting microstructures have been characterised in details, so as to allow for a better understanding of the solidification process and of the subsequent phase transformations taking place upon cooling for both techniques. On the one hand, a new “MesoClad” laser with a maximum power of 300 W has been used successfully to produce thin wall samples by LC. On the other hand, the influence of processing parameters on the mechanical properties was investigated by means of uniaxial tensile testing performed on samples produced by SLM with different orientations with respect to the direction of mechanical solicitation. A strong anisotropy in mechanical behaviour was thus interpreted in relations with the microstructures and processing conditions.

Experimental Modeling of the Formation of Saucer-Shaped sills

NASA Astrophysics Data System (ADS)

Galland, O.; Planke, S.; Malthe-Sorenssen, A.

2007-12-01

Many magma intrusions in sedimentary basins are sills, and especially saucer-shaped sills. These features are observed in many places (i.e. South Africa; the Norwegian and North Sea; Siberia; Argentina). Sand injectites exhibit similar geometries. The occurrence of such features in so various settings suggests that their emplacement results from fundamental processes in sedimentary basins. To understand such processes, we performed experimental modeling of saucer-shaped sill emplacement. The experiments consist of injecting a molten low viscosity vegetable oil (model magma) at a constant flow rate into a fine-grained Coulomb silica flour (model rock). When the oil starts intruding, the initially flat surface of the model inflates and forms a smooth dome. At the end of the experiment, the oil erupts at the edge of the dome. After the experiment, the oil cools and solidifies, the resulting solid intrusion is unburied and exposed, and its upper surface digitalized. For our purpose, we did our experiments without external deformation. We performed two series of experiments with varying depth of injection. The first series consisted of injection into a homogeneous medium. The resulting intrusions were cone-sheets and dykes. The second series consisted of heterogeneous models where the heterogeneity was a weak layer made of a flexible net. The resulting intrusions were made of (1) a horizontal basal sill emplaced along the weakness, and (2) inclined sheets nucleating at the edges of the basal sill and propagating upward and outward. The inclined sheets exhibited a convex shape, i.e. a decreasing slope outward. In addition, the deeper the sills emplaced, the larger they were. Our experimental results are consistent with saucer-shaped features in nature. We infer from our results that the transition between the basal sills and the inclined sheets results from a transition of emplacement processes. We suggest that the basal sill emplace by open (mode I) fracturing, whereas the inclined sheets result from shear (mode II) fracturing, i.e. along faults at the edge of the dome.

Periodic Cellular Structure Technology for Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Chen, Edward Y.

2015-01-01

Shape memory alloys are being considered for a wide variety of adaptive components for engine and airframe applications because they can undergo large amounts of strain and then revert to their original shape upon heating or unloading. Transition45 Technologies, Inc., has developed an innovative periodic cellular structure (PCS) technology for shape memory alloys that enables fabrication of complex bulk configurations, such as lattice block structures. These innovative structures are manufactured using an advanced reactive metal casting technology that offers a relatively low cost and established approach for constructing near-net shape aerospace components. Transition45 is continuing to characterize these structures to determine how best to design a PCS to better exploit the use of shape memory alloys in aerospace applications.

Ceramic Near-Net Shaped Processing Using Highly-Loaded Aqueous Suspensions

NASA Astrophysics Data System (ADS)

Rueschhoff, Lisa

Ceramic materials offer great advantages over their metal counterparts, due to their lower density, higher hardness and wear resistance, and higher melting temperatures. However, the use of ceramics in applications where their properties would offer tremendous advantages are often limited due to the difficulty of forming them into complex and near-net shaped parts. Methods that have been developed to injection-mold or cast ceramics into more complicated shapes often use significant volume fractions of a carrier (often greater than 35 vol.% polymer), elevated temperature processing, or less-than-environmentally friendly chemicals where a complex chemical synthesis reaction must be timed perfectly for the approach to work. Furthermore, the continuing maturation of additive manufacturing methods requires a new approach for flowing/placing ceramic powders into useful designs. This thesis addresses the limitations of the current ceramic forming approaches by developing highly-stabilized and therefore high solids loading ceramic suspensions, with the requisite rheology for a variety of complex and near-net shaped forming techniques. Silicon nitride was chosen as a material of focus due to its high fracture toughness compared to other ceramic materials. Designing ceramic suspensions that are flowable at room temperature greatly simplifies processing as neither heating nor cooling are required during forming. Highly-loaded suspensions (>40 vol.%) are desired because all formed ceramic bodies have to be sintered to remove pores. Finally, using aqueous-based suspensions reduces any detrimental effect on the environment and tooling. The preparation of highly-loaded suspensions requires the development of a suitable dispersant through which particle-particle interactions are controlled. However, silicon nitride is difficult to stabilize in water due to complex surface and solution chemistry. In this study, aqueous silicon nitride suspensions up to 45 vol.% solids loading were dispersed using commercially available comb-type copolymer. These copolymers are used as superplasticizers in the concrete industry and are referred to as water-reducing admixtures (WRAs). Four different WRA dispersants were examined and chemical analysis determined that each was made up of a sodium salt of polyacrylic acid (PAA-Na) backbone with neutral polyethylene oxide (PEO) side chains that afford steric stabilization. The general structures of the WRAs were compared to each other by measuring the relative areas of their prominent FTIR peaks and calculating a PAA-Na/PEO peak ratio. Suspensions were made with as-received silicon nitride powders with 5 wt.% aluminum oxide and 5 wt.% yttrium oxide added as sintering aids. Three of the four WRA dispersants studied were able to produce suspensions with 43 vol.% solids loading and 5 vol.% polymer dispersant, while exhibiting a yield-pseudoplastic behavior for shear rates up to 30 s-1. At higher solids loading (45 to 47 vol.%), a shift to shear thickening behavior was observed at a critical shear rate for these WRAs. Those WRAs with a lower PAA-Na/PEO peak ratio displayed better stabilization and diminished shear thickening behavior. The vol.% of the dispersant was optimized, producing yield-pseudoplastic suspensions containing 45 vol.% solids loading with yield stresses less than 75 Pa, no shear thickening behavior, and viscosities less than 75 Pa-s for shear rates in the range of 1 to 30 s-1. Using suspensions prepared with two of the WRAs investigated in this work, silicon nitride near-net shaped parts were formed via a novel injection molding process by loading each suspension in a syringe and injecting them at a controlled rate into a mold. Each suspensions had carefully tailored yield-pseudoplastic rheology such that they can be injection molded at room temperature and low pressures (< 150 kPa). Four suspensions were studied; two different commercially available concrete water-reducing admixtures (WRAs) were used as dispersants with and without a polymer binder (Polyvinylprolidone, PVP) added for rheological modification and improved green body strength. Test bars formed via this process were sintered to high densities (up to 97% TD) without the use of external pressure, and had complete conversion to the desirable beta-Si3N4 phase with high flexural strengths up to 700 MPa. The specimen sets with the smallest average pore size on the fracture surface (77 mum) had the highest average flexural strengths of 573 MPa. The hardness of all specimens was approximately 16 GPa. The water-based suspensions, ease and low cost of processing, and robust mechanical properties obtained demonstrate this as a viable process for the economical and environmentally friendly production of Si3N4 parts. Finally, additive manufacturing was also used as a method to overcome ceramic forming difficulties and to create near-net shaped dense components via room-temperature direct ink writing. In this processes, highly loaded aqueous alumina suspensions were extruded in a layer-by-layer fashion using a low-cost syringe style 3D printer. With alumina as a model material, the effect of solids loading on rheology, specimen uniformity, density, microstructure, and mechanical properties was studied. All suspensions contained a polymer binder ( 5 vol.%), dispersant, and 51 to 58 vol.% alumina powder. Rheological measurements indicated all suspensions to be yield-pseudoplastic, and both yield stress and viscosity were found to increase with increasing alumina solids loading. Shear rates ranging from 19.5 to 24.2 s-1, corresponding to viscosities of 9.8 to 17.2 Pa·s, for the 53 - 56 vol.% alumina suspensions were found to produce the best results for the 1.25 mm tip employed during writing. All parts were sintered to greater than 98% of true density, with grain sizes ranging from 3.2 to 3.7 mum. The average flexure strength, which ranged from 134 to 157 MPa, was not influenced by the alumina solids loading. In limited study, additive manufacturing of silicon nitride suspensions stabilized with a WRA has been established. These processing routes have been proven as low-cost and viable means for producing robust ceramic parts, both of which can be tailored to many systems to expand the use of ceramics materials. Further studies on utilizing the flow stress behavior during both injection molding and direct ink writing could be beneficial in creating ceramic materials with carefully tailored microstructure to increase mechanical performance.

Ohno continuous casting

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

Soda, H.; McLean, A.; Motoyasu, G.

1995-04-01

Production of net-shape products directly from the liquid is an attractive manufacturing route for alloys that are difficult to process or that cannot be rolled, drawn, or extruded. Developed at the Chiba Institute of Technology in Japan, the Ohno Continuous Casting (OCC) approach not only provides significant cost savings, but also has the potential to create new products. OCC process equipment includes a melting furnace, crucible, mold level-control block, cooling device, and pinch rolls. OCC is currently used to produce copper rods and wires for audio and video cables, and aluminum alloy welding rods for hard-surfacing applications. For example, Mitsuimore » Engineering and Ship Building Co. has used OCC to produce copper tubing products with internal fins and partitions for applications such as heat exchanger tubes and induction coils.« less

Production of al-si alloy feedstocks using the solvent hot mixing method

NASA Astrophysics Data System (ADS)

Ni, J. Q.; Han, K. Q.; Yu, M. H.

2018-05-01

Powder injection molding is a promising low-cost technique for net shape processing of metal and ceramic components. This study aimed to investigate a new method for preparing aluminium (Al) – silicon (Si) alloy feedstock using the solvent hot mixing process. For this purpose, micron-sized Al-Si (20 wt. %) alloy powder was mixed with a binder consisting of 55 wt. % carnauba wax, 45 wt. % high-density polyethylene, and 3 wt. % stearic acid in a hot xylene bath. The scanning electron microscopy technique, thermogravimetric analysis, density measurement and torque measurements were used to verify the homogeneity of the feedstock. Moreover, the feedstock was chosen to perform the molding, debinding cycle and sintering. An Al-Si (20 wt. %) alloy part was successfully produced using this new method.

Process qualification and testing of LENS deposited AY1E0125 D-bottle brackets.

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

Atwood, Clinton J.; Smugeresky, John E.; Jew, Michael

2006-11-01

The LENS Qualification team had the goal of performing a process qualification for the Laser Engineered Net Shaping{trademark}(LENS{reg_sign}) process. Process Qualification requires that a part be selected for process demonstration. The AY1E0125 D-Bottle Bracket from the W80-3 was selected for this work. The repeatability of the LENS process was baselined to determine process parameters. Six D-Bottle brackets were deposited using LENS, machined to final dimensions, and tested in comparison to conventionally processed brackets. The tests, taken from ES1E0003, included a mass analysis and structural dynamic testing including free-free and assembly-level modal tests, and Haversine shock tests. The LENS brackets performedmore » with very similar characteristics to the conventionally processed brackets. Based on the results of the testing, it was concluded that the performance of the brackets made them eligible for parallel path testing in subsystem level tests. The testing results and process rigor qualified the LENS process as detailed in EER200638525A.« less

BioNetSim: a Petri net-based modeling tool for simulations of biochemical processes.

PubMed

Gao, Junhui; Li, Li; Wu, Xiaolin; Wei, Dong-Qing

2012-03-01

BioNetSim, a Petri net-based software for modeling and simulating biochemistry processes, is developed, whose design and implement are presented in this paper, including logic construction, real-time access to KEGG (Kyoto Encyclopedia of Genes and Genomes), and BioModel database. Furthermore, glycolysis is simulated as an example of its application. BioNetSim is a helpful tool for researchers to download data, model biological network, and simulate complicated biochemistry processes. Gene regulatory networks, metabolic pathways, signaling pathways, and kinetics of cell interaction are all available in BioNetSim, which makes modeling more efficient and effective. Similar to other Petri net-based softwares, BioNetSim does well in graphic application and mathematic construction. Moreover, it shows several powerful predominances. (1) It creates models in database. (2) It realizes the real-time access to KEGG and BioModel and transfers data to Petri net. (3) It provides qualitative analysis, such as computation of constants. (4) It generates graphs for tracing the concentration of every molecule during the simulation processes.

Observing and modeling links between soil moisture, microbes and CH4 fluxes from forest soils

NASA Astrophysics Data System (ADS)

Christiansen, Jesper; Levy-Booth, David; Barker, Jason; Prescott, Cindy; Grayston, Sue

2017-04-01

Soil moisture is a key driver of methane (CH4) fluxes in forest soils, both of the net uptake of atmospheric CH4 and emission from the soil. Climate and land use change will alter spatial patterns of soil moisture as well as temporal variability impacting the net CH4 exchange. The impact on the resultant net CH4 exchange however is linked to the underlying spatial and temporal distribution of the soil microbial communities involved in CH4 cycling as well as the response of the soil microbial community to environmental changes. Significant progress has been made to target specific CH4 consuming and producing soil organisms, which is invaluable in order to understand the microbial regulation of the CH4 cycle in forest soils. However, it is not clear as to which extent soil moisture shapes the structure, function and abundance of CH4 specific microorganisms and how this is linked to observed net CH4 exchange under contrasting soil moisture regimes. Here we report on the results from a research project aiming to understand how the CH4 net exchange is shaped by the interactive effects soil moisture and the spatial distribution CH4 consuming (methanotrophs) and producing (methanogens). We studied the growing season variations of in situ CH4 fluxes, microbial gene abundances of methanotrophs and methanogens, soil hydrology, and nutrient availability in three typical forest types across a soil moisture gradient in a temperate rainforest on the Canadian Pacific coast. Furthermore, we conducted laboratory experiments to determine whether the net CH4 exchange from hydrologically contrasting forest soils responded differently to changes in soil moisture. Lastly, we modelled the microbial mediation of net CH4 exchange along the soil moisture gradient using structural equation modeling. Our study shows that it is possible to link spatial patterns of in situ net exchange of CH4 to microbial abundance of CH4 consuming and producing organisms. We also show that the microbial community responds different to environmental change dependent on the soil moisture regime. These results are important to include in future modeling efforts to predict changes in soil-atmosphere exchange of CH4 under global change.

Investigation of Friction Stir Welding and Laser Engineered Net Shaping of Metal Matrix Composite Materials

NASA Technical Reports Server (NTRS)

Diwan, Ravinder M.

2002-01-01

The improvement in weld quality by the friction stir welding (FSW) process invented by TWI of Cambridge, England, patented in 1991, has prompted investigation of this process for advanced structural materials including Al metal matrix composite (Al-MMC) materials. Such materials can have high specific stiffness and other potential beneficial properties for the extreme environments in space. Developments of discontinuous reinforced Al-MMCs have found potential space applications and the future for such applications is quite promising. The space industry has recognized advantages of the FSW process over conventional welding processes such as the absence of a melt zone, reduced distortion, elimination of the need for shielding gases, and ease of automation. The process has been well proven for aluminum alloys, and work is being carried out for ferrous materials, magnesium alloys and copper alloys. Development work in the FSW welding process for joining of Al-MMCs is relatively recent and some of this and related work can be found in referenced research publications. NASA engineers have undertaken to spear head this research development work for FSW process investigation of Al-MMCs. Some of the reported related work has pointed out the difficulty in fusion welding of particulate reinforced MMCs where liquid Al will react with SiC to precipitate aluminum carbide (Al4C3). Advantages of no such reaction and no need for joint preparation for the FSW process is anticipated in the welding of Al-MMCs. The FSW process has been best described as a combination of extrusion and forging of metals. This is carried out as the pin tool rotates and is slowly plunged into the bond line of the joint as the pin tool's shoulder is in intimate contact with the work piece. The material is friction-stirred into a quality weld. Al-MMCs, 4 in. x 12 in. plates of 0.25 in. (6.35mm) thickness, procured from MMCC, Inc. were butt welded using FSW process at Marshall Space Flight Center (MSFC) using prior set of operating conditions. Weld quality was evaluated using radiography and standard metallography techniques. Another aspect of the MMCs centered around the use of the laser engineered net shaping (LENS) processing of selected Narloy-Z composites. Such an approach has been earlier studied for fabrication of stainless steels. In the present study, attempts were made to fabricate straight cylindrical specimens using LENS process of Narloy-Z and Narloy-Z with 20 vol. % Al2O3 MMCs using the direct metal deposition Optomec LENS-750 system.

Variability of the contrail radiative forcing due to crystal shape

NASA Astrophysics Data System (ADS)

Markowicz, K. M.; Witek, M. L.

2011-12-01

The aim of this study is to examine the influence of particles' shape and particles' optical properties on the contrail radiative forcing. Contrail optical properties in the shortwave and longwave range are derived using a ray-tracing geometric method and the discrete dipole approximation method, respectively. Both methods present good correspondence of the single scattering albedo and the asymmetry parameter in a transition range (3-7μm). We compare optical properties defined following simple 10 crystals habits randomly oriented: hexagonal plates, hexagonal columns with different aspect ratio, and spherical. There are substantial differences in single scattering properties between ten crystal models investigated here (e.g. hexagonal columns and plates with different aspect ratios, spherical particles). The single scattering albedo and the asymmetry parameter both vary up to 0.1 between various crystal shapes. Radiative forcing calculations were performed using a model which includes an interface between the state-of-the-art radiative transfer model Fu-Liou and databases containing optical properties of the atmosphere and surface reflectance and emissivity. This interface allows to determine radiative fluxes in the atmosphere and to estimate the contrail radiative forcing for clear- and all-sky (including natural clouds) conditions for various crystal shapes. The Fu-Liou code is fast and therefore it is suitable for computing radiative forcing on a global scale. At the same time it has sufficiently good accuracy for such global applications. A noticeable weakness of the Fu-Liou code is that it does not take into account the 3D radiative effects, e.g. cloud shading and horizontal. Radiative transfer model calculations were performed at horizontal resolution of 5x5 degree and time resolution of 20 min during day and 3 h during night. In order to calculate a geographic distribution of the global and annual mean contrail radiative forcing, the contrail cover must be determined. Two cases are discussed here: a 1% homogeneous contrail cover and the contrail cover provided by Rädel and Shine (2008). In the second distribution case, a more realistic contrail cover is taken into account. This model combines the AERO2K flight inventory with meteorological data and normalizes it with respect to the contrail cover derived from satellite observations. Simulations performed by the Fu-Liou model show significant variability of the shortwave, longwave, and net radiative forcing with crystal shape. The nonspherical crystals have smaller net forcing in contrary to spherical particles. The differences in net radiative forcing between optical models reach up to 50%. The hexagonal column and hexagonal plate particles show the smallest net radiative forcing while the largest forcing is obtained for the spheres. The global and annual mean shortwave, longwave, and net contrail radiative forcing, average over all crystal models and assuming an optical depth of 0.3 at visible wavelengths, is -5.7, 16.8, and 11.1 mW/m2, respectively. A ratio of the radiative forcings' standard deviation to the mean value, derived using 10 different ice particle models, is about 0.2 for the shortwave, 0.14 for the longwave, and 0.23 for the net radiation.

Magnetic and microstructural investigation of high-coercivity net-shape Nd-Fe-B-type magnets produced from spark-plasma-sintered melt-spun ribbons blended with DyF3

NASA Astrophysics Data System (ADS)

Žagar, Kristina; Kocjan, Andraž; Kobe, Spomenka

2016-04-01

Nanostructured Nd-Fe-B-type materials produced by melt-spinning (MS) are used in a variety of applications in the electronics, automotive, and sensor industries. The very rapid MS process leads to flake-like powders with metastable, nanoscale, Nd2Fe14B grains. These powders are then formed into net-shaped, isotropic, polymer-bonded magnets, or they are hot formed into fully dense, metallic magnets that are isotropic and anisotropic. These fully dense magnets are usually produced with a conventional hot press without the inclusion of additives prior to the hot pressing. As a result, their properties, particularly the coercivity (Hci), are insufficient at automotive-relevant temperatures of 100-150 °C since the material Hci has a large temperature coefficient. In this study, we instead add a thin layer of DyF3 to the melt-spun ribbons prior to their hot consolidation in order to enhance the coercivity through a diffusion-based, partial substitution of the Nd by Dy. This is accomplished by applying extremely rapid, spark-plasma sintering to minimize any growth of the nanoscale Nd2Fe14B grains during consolidation. The result is a very high-coercivity magnet with drastically reduced amounts of heavy rare earths that is suitable for high-temperature applications. This work clearly demonstrates how rapidly formed, metastable states can provide us with properties that are unobtainable with conventional techniques.

High-strain slide-ring shape-memory polycaprolactone-based polyurethane.

PubMed

Wu, Ruiqing; Lai, Jingjuan; Pan, Yi; Zheng, Zhaohui; Ding, Xiaobin

2018-06-06

To enable shape-memory polymer networks to achieve recoverable high deformability with a simultaneous high shape-fixity ratio and shape-recovery ratio, novel semi-crystalline slide-ring shape-memory polycaprolactone-based polyurethane (SR-SMPCLU) with movable net-points constructed by a topologically interlocked slide-ring structure was designed and fabricated. The SR-SMPCLU not only exhibited good shape fixity, almost complete shape recovery, and a fast shape-recovery speed, it also showed an outstanding recoverable high-strain capacity with 95.83% Rr under a deformation strain of 1410% due to the pulley effect of the topological slide-ring structure. Furthermore, the SR-SMPCLU system maintained excellent shape-memory performance with increasing the training cycle numbers at 45% and even 280% deformation strain. The effects of the slide-ring cross-linker content, deformation strain, and successive shape-memory cycles on the shape-memory performance were investigated. A possible mechanism for the shape-memory effect of the SR-SMPCLU system is proposed.

Development and Demonstration of Adanced Tooling Alloys for Molds and Dies

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

Kevin M. McHugh; Enrique J. Lavernia

2006-01-01

This report summarizes research results in the project Development and Demonstration of Advanced Tooling Alloys for Molds and Dies. Molds, dies and related tooling are used to manufacture most of the plastic and metal products we use every day. Conventional fabrication of molds and dies involves a multiplicity of machining, benching and heat treatment unit operations. This approach is very expensive and time consuming. Rapid Solidifcation Process (RSP) Tooling is a spray-forming technology tailored for producing molds and dies. The appraoch combines rapid solidifcation processing and net-shape materials processing in a single step. An atomized spray of a tool-forming alloy,more » typically a tool steel, is deposited onto an easy-to-form tool pattern to replicate the pattern's shape and surface features. By so doing, the approach eliminates many machining operations in conventional mold making, significantly reducing cost, lead time and energy. Moreover, rapid solidification creates unique microstructural features by suppressing carbide precipitation and growth, and creating metastable phases. This can result in unique material properties following heat treatment. Spray-formed and aged tool steel dies have exhibited extended life compared to conventional dies in many forming operations such as forging, extrusion and die casting. RSP Tooling technolocy was commercialized with the formation of RSP Tooling, LLC in Solon, Oh.« less

Resin Film Infusion (RFI) Process Modeling for Large Transport Aircraft Wing Structures

NASA Technical Reports Server (NTRS)

Knott, Tamara W.; Loos, Alfred C.

2000-01-01

Resin film infusion (RFI) is a cost-effective method for fabricating stiffened aircraft wing structures. The RFI process lends itself to the use of near net shape textile preforms manufactured through a variety of automated textile processes such as knitting and braiding. Often, these advanced fiber architecture preforms have through-the-thickness stitching for improved damage tolerance and delamination resistance. The challenge presently facing RFI is to refine the process to ensure complete infiltration and cure of a geometrically complex shape preform with the high fiber volume fraction needed for structural applications. An accurate measurement of preform permeability is critical for successful modeling of the RFI resin infiltration process. Small changes in the permeability can result in very different infiltration behavior and times. Therefore, it is important to accurately measure the permeabilities of the textile preforms used in the RFI process. The objective of this investigation was to develop test methods that can be used to measure the compaction behavior and permeabilities of high fiber volume fraction, advanced fiber architecture textile preforms. These preforms are often highly compacted due to through-the-thickness stitching used to improve damage tolerance. Test fixtures were designed and fabricated and used to measure both transverse and in-plane permeabilities. The fixtures were used to measure the permeabilities of multiaxial warp knit and triaxial braided preforms at fiber volume fractions from 55% to 65%. In addition, the effects of stitching characteristics, thickness, and batch variability on permeability and compaction behavior were investigated.

Tensile Fracture Behavior and Failure Mechanism of Additively-Manufactured AISI 4140 Low Alloy Steel by Laser Engineered Net Shaping

PubMed Central

Kim, Hoyeol; Liu, Zhichao; Cong, Weilong; Zhang, Hong-Chao

2017-01-01

AISI 4140 powder was directly deposited on AISI 4140 wrought substrate using laser engineered net shaping (LENS) to investigate the compatibility of a LENS-deposited part with the substrate. Tensile testing at room temperature was performed to evaluate the interface bond performance and fracture behavior of the test specimens. All the samples failed within the as-deposited zone, indicating that the interfacial bond is stronger than the interlayer bond inside the deposit. The fracture surfaces were analyzed using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS). Results show that the tensile fracture failure of the as-deposited part is primarily affected by lack-of-fusion defects, carbide precipitation, and oxide particles inclusions, which causes premature failure of the deposit by deteriorating the mechanical properties and structural integrity. PMID:29120374

Tensile Fracture Behavior and Failure Mechanism of Additively-Manufactured AISI 4140 Low Alloy Steel by Laser Engineered Net Shaping.

PubMed

Kim, Hoyeol; Liu, Zhichao; Cong, Weilong; Zhang, Hong-Chao

2017-11-09

AISI 4140 powder was directly deposited on AISI 4140 wrought substrate using laser engineered net shaping (LENS) to investigate the compatibility of a LENS-deposited part with the substrate. Tensile testing at room temperature was performed to evaluate the interface bond performance and fracture behavior of the test specimens. All the samples failed within the as-deposited zone, indicating that the interfacial bond is stronger than the interlayer bond inside the deposit. The fracture surfaces were analyzed using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS). Results show that the tensile fracture failure of the as-deposited part is primarily affected by lack-of-fusion defects, carbide precipitation, and oxide particles inclusions, which causes premature failure of the deposit by deteriorating the mechanical properties and structural integrity.

Modeling and performance analysis of QoS data

NASA Astrophysics Data System (ADS)

Strzeciwilk, Dariusz; Zuberek, Włodzimierz M.

2016-09-01

The article presents the results of modeling and analysis of data transmission performance on systems that support quality of service. Models are designed and tested, taking into account multiservice network architecture, i.e. supporting the transmission of data related to different classes of traffic. Studied were mechanisms of traffic shaping systems, which are based on the Priority Queuing with an integrated source of data and the various sources of data that is generated. Discussed were the basic problems of the architecture supporting QoS and queuing systems. Designed and built were models based on Petri nets, supported by temporal logics. The use of simulation tools was to verify the mechanisms of shaping traffic with the applied queuing algorithms. It is shown that temporal models of Petri nets can be effectively used in the modeling and analysis of the performance of computer networks.

An Extended Petri-Net Based Approach for Supply Chain Process Enactment in Resource-Centric Web Service Environment

NASA Astrophysics Data System (ADS)

Wang, Xiaodong; Zhang, Xiaoyu; Cai, Hongming; Xu, Boyi

Enacting a supply-chain process involves variant partners and different IT systems. REST receives increasing attention for distributed systems with loosely coupled resources. Nevertheless, resource model incompatibilities and conflicts prevent effective process modeling and deployment in resource-centric Web service environment. In this paper, a Petri-net based framework for supply-chain process integration is proposed. A resource meta-model is constructed to represent the basic information of resources. Then based on resource meta-model, XML schemas and documents are derived, which represent resources and their states in Petri-net. Thereafter, XML-net, a high level Petri-net, is employed for modeling control and data flow of process. From process model in XML-net, RESTful services and choreography descriptions are deduced. Therefore, unified resource representation and RESTful services description are proposed for cross-system integration in a more effective way. A case study is given to illustrate the approach and the desirable features of the approach are discussed.

Metabolome-mediated biocryomorphic evolution promotes carbon fixation in Greenlandic cryoconite holes.

PubMed

Cook, Joseph M; Edwards, Arwyn; Bulling, Mark; Mur, Luis A J; Cook, Sophie; Gokul, Jarishma K; Cameron, Karen A; Sweet, Michael; Irvine-Fynn, Tristram D L

2016-12-01

Microbial photoautotrophs on glaciers engineer the formation of granular microbial-mineral aggregates termed cryoconite which accelerate ice melt, creating quasi-cylindrical pits called 'cryoconite holes'. These act as biogeochemical reactors on the ice surface and provide habitats for remarkably active and diverse microbiota. Evolution of cryoconite holes towards an equilibrium depth is well known, yet interactions between microbial activity and hole morphology are currently weakly addressed. Here, we experimentally perturbed the depths and diameters of cryoconite holes on the Greenland Ice Sheet. Cryoconite holes responded by sensitively adjusting their shapes in three dimensions ('biocryomorphic evolution') thus maintaining favourable conditions for net autotrophy at the hole floors. Non-targeted metabolomics reveals concomitant shifts in cyclic AMP and fucose metabolism consistent with phototaxis and extracellular polymer synthesis indicating metabolomic-level granular changes in response to perturbation. We present a conceptual model explaining this process and suggest that it results in remarkably robust net autotrophy on the Greenland Ice Sheet. We also describe observations of cryoconite migrating away from shade, implying a degree of self-regulation of carbon budgets over mesoscales. Since cryoconite is a microbe-mineral aggregate, it appears that microbial processes themselves form and maintain stable autotrophic habitats on the surface of the Greenland ice sheet. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Net motion of acoustically levitating nano-particles: A theoretical analysis

NASA Astrophysics Data System (ADS)

Lippera, Kevin; Dauchot, Olivier; Benzaquen, Michael; Gulliver-LadHyX Collaboration

2017-11-01

A particle 2D-trapped in the nodal planed of a standing acoustic wave is prone to acoustic-phoretic motion as soon as its shape breaks polar or chiral symmetry. such a setup constitues an ideal system to study boundaryless 2D collective behavior with purely hydrodynamic long range interactions. Recent studies have indeed shown that quasi-spherical particles may undergo net propulsion, a feature partially understood theoretically in the particular case of infinite viscous boundary layers. We here extend the theoretical results of to any boundary layer thickness, by that meeting typical experimental conditions. In addition, we propose an explanation for the net spinning of the trapped particles, as observed in experiments.

Electrohydrodynamic instabilities of viscous drops*

NASA Astrophysics Data System (ADS)

Vlahovska, Petia M.

2016-10-01

A classic result due to Taylor is that a weakly conducting drop bearing zero net charge placed in a uniform electric field adopts a prolate or oblate spheroidal shape, the flow and shape being axisymmetrically aligned with the applied field. Here I overview some intriguing symmetry-breaking instabilities occurring in strong applied dc fields: Quincke rotation resulting in drop steady tilt or tumbling, and pattern formation on the surface of a particle-coated drop.

Petri net based model of the body iron homeostasis.

PubMed

Formanowicz, Dorota; Sackmann, Andrea; Formanowicz, Piotr; Błazewicz, Jacek

2007-10-01

The body iron homeostasis is a not fully understood complex process. Despite the fact that some components of this process have been described in the literature, the complete model of the whole process has not been proposed. In this paper a Petri net based model of the body iron homeostasis is presented. Recently, Petri nets have been used for describing and analyzing various biological processes since they allow modeling the system under consideration very precisely. The main result presented in the paper is twofold, i.e., an informal description of the main part of the whole iron homeostasis process is described, and then it is also formulated in the formal language of Petri net theory. This model allows for a possible simulation of the process, since Petri net theory provides a lot of established analysis techniques.

Thermo-mechanical performance of precision C/SiC mounts

NASA Astrophysics Data System (ADS)

Goodman, William A.; Mueller, Claus E.; Jacoby, Marc T.; Wells, Jim D.

2001-12-01

For complex shaped, lightweight, high precision opto- mechanical structures that must operate in adverse environments and over wide ranges of temperature, we consider IABG's optical grade silicon carbide composite ceramic (C/SiC) as the material of choice. C/SiC employs conventional NC machining/milling equipment to rapidly fabricate near-net shape parts, providing substantial schedule, cost, and risk savings for high precision components. Unlike powder based SiC ceramics, C/SiC does not experience significant shrinkage during processing, nor does it suffer from incomplete densification. If required, e.g. for large-size components, a fully-monolithic ceramic joining technique can be applied. Generally, the thermal and mechanical properties of C/SiC are tunable in certain ranges by modifying certain process steps. This paper focuses on the thermo-mechanical performance of new, high precision mounts designed by Schafer Corporation and manufactured by IABG. The mounts were manufactured using standard optical grade C/SiC (formulation internally called A-3). The A-3 formulation has a near-perfect CTE match with silicon, making it the ideal material to athermally support Schafer produced Silicon Lightweight Mirrors (SLMs) that will operate in a cryogenic environment. Corresponding thermo- mechanical testing and analysis is presented in this manuscript.

Spray pattern analysis in TWAS using photogrammetry and digital image correlation

NASA Astrophysics Data System (ADS)

Tillmann, W.; Rademacher, H. G.; Hagen, L.; Abdulgader, M.; El Barad’ei, M.

2018-06-01

In terms of arc spraying processes, the spray plume characteristic is mainly affected by the flow characteristic of the atomization gas at the nozzle inlet and intersection point of the wire tips, which in turn affect the particle distribution at the moment of impact when molten spray particles splash onto the substrate. With respect to the route of manufacturing of near net-shaped coatings on complex geometries, the acquisition of the spray patterns is pressingly necessary to determine the produced coating thickness. Within the scope of this study, computer fluid dynamics (CFD) simulations were carried out to determine the distribution of spray particles for different spray parameter settings. The results were evaluated by three-dimensional spray spot analyses using an optical measurement based on photogrammetry and digital image correlation. The optical measurement represents a promising and much faster candidate to measure spray patterns compared to the tactile measurement system but with an equal accuracy. For given nozzle configurations and spray parameter settings, numerous spray patterns were examined to their shape factors, demonstrating the potential of an online analysis, which encompasses a “fast sample loop” and a data processing system to generate a three-dimensional surface of the spray spot profile.

Engineering fluid flow using sequenced microstructures

NASA Astrophysics Data System (ADS)

Amini, Hamed; Sollier, Elodie; Masaeli, Mahdokht; Xie, Yu; Ganapathysubramanian, Baskar; Stone, Howard A.; di Carlo, Dino

2013-05-01

Controlling the shape of fluid streams is important across scales: from industrial processing to control of biomolecular interactions. Previous approaches to control fluid streams have focused mainly on creating chaotic flows to enhance mixing. Here we develop an approach to apply order using sequences of fluid transformations rather than enhancing chaos. We investigate the inertial flow deformations around a library of single cylindrical pillars within a microfluidic channel and assemble these net fluid transformations to engineer fluid streams. As these transformations provide a deterministic mapping of fluid elements from upstream to downstream of a pillar, we can sequentially arrange pillars to apply the associated nested maps and, therefore, create complex fluid structures without additional numerical simulation. To show the range of capabilities, we present sequences that sculpt the cross-sectional shape of a stream into complex geometries, move and split a fluid stream, perform solution exchange and achieve particle separation. A general strategy to engineer fluid streams into a broad class of defined configurations in which the complexity of the nonlinear equations of fluid motion are abstracted from the user is a first step to programming streams of any desired shape, which would be useful for biological, chemical and materials automation.

Laser Additive Manufacturing of Magnetic Materials

NASA Astrophysics Data System (ADS)

Mikler, C. V.; Chaudhary, V.; Borkar, T.; Soni, V.; Jaeger, D.; Chen, X.; Contieri, R.; Ramanujan, R. V.; Banerjee, R.

2017-03-01

While laser additive manufacturing is becoming increasingly important in the context of next-generation manufacturing technologies, most current research efforts focus on optimizing process parameters for the processing of mature alloys for structural applications (primarily stainless steels, titanium base, and nickel base alloys) from pre-alloyed powder feedstocks to achieve properties superior to conventionally processed counterparts. However, laser additive manufacturing or processing can also be applied to functional materials. This article focuses on the use of directed energy deposition-based additive manufacturing technologies, such as the laser engineered net shaping (LENS™) process, to deposit magnetic alloys. Three case studies are presented: Fe-30 at.%Ni, permalloys of the type Ni-Fe-V and Ni-Fe-Mo, and Fe-Si-B-Cu-Nb (derived from Finemet) alloys. All these alloys have been processed from a blend of elemental powders used as the feedstock, and their resultant microstructures, phase formation, and magnetic properties are discussed in this paper. Although these alloys were produced from a blend of elemental powders, they exhibited relatively uniform microstructures and comparable magnetic properties to those of their conventionally processed counterparts.

Spray-formed tooling

NASA Astrophysics Data System (ADS)

McHugh, K. M.; Key, J. F.

The United States Council for Automotive Research (USCAR) has formed a partnership with the Idaho National Engineering Laboratory (INEL) to develop a process for the rapid production of low-cost tooling based on spray forming technology developed at the INEL. Phase 1 of the program will involve bench-scale system development, materials characterization, and process optimization. In Phase 2, prototype systems will be designed, constructed, evaluated, and optimized. Process control and other issues that influence commercialization will be addressed during this phase of the project. Technology transfer to USCAR, or a tooling vendor selected by USCAR, will be accomplished during Phase 3. The approach INEL is using to produce tooling, such as plastic injection molds and stamping dies, combines rapid solidification processing and net-shape materials processing into a single step. A bulk liquid metal is pressure-fed into a de Laval spray nozzle transporting a high velocity, high temperature inert gas. The gas jet disintegrates the metal into fine droplets and deposits them onto a tool pattern made from materials such as plastic, wax, clay, ceramics, and metals. The approach is compatible with solid freeform fabrication techniques such as stereolithography, selective laser sintering, and laminated object manufacturing. Heat is extracted rapidly, in-flight, by convection as the spray jet entrains cool inert gas to produce undercooled and semi-solid droplets. At the pattern, the droplets weld together while replicating the shape and surface features of the pattern. Tool formation is rapid; deposition rates in excess of 1 ton/h have been demonstrated for bench-scale nozzles.

A novel methodology for in-process monitoring of flow forming

NASA Astrophysics Data System (ADS)

Appleby, Andrew; Conway, Alastair; Ion, William

2017-10-01

Flow forming (FF) is an incremental cold working process with near-net-shape forming capability. Failures by fracture due to high deformation can be unexpected and sometimes catastrophic, causing tool damage. If process failures can be identified in real time, an automatic cut-out could prevent costly tool damage. Sound and vibration monitoring is well established and commercially viable in the machining sector to detect current and incipient process failures, but not for FF. A broad-frequency microphone was used to record the sound signature of the manufacturing cycle for a series of FF parts. Parts were flow formed using single and multiple passes, and flaws were introduced into some of the parts to simulate the presence of spontaneously initiated cracks. The results show that this methodology is capable of identifying both introduced defects and spontaneous failures during flow forming. Further investigation is needed to categorise and identify different modes of failure and identify further potential applications in rotary forming.

Propulsion Systems Panel

NASA Technical Reports Server (NTRS)

Bianca, Carmelo J.; Miner, Robert; Johnston, Lawrence M.; Bruce, R.; Dennies, Daniel P.; Dickenson, W.; Dreshfield, Robert; Karakulko, Walt; Mcgaw, Mike; Munafo, Paul M.

1993-01-01

Topics addressed are: (1) cryogenic tankage; (2) launch vehicle TPS/insulation; (3) durable passive thermal control devices and/or coatings; (4) development and characterization of processing methods to reduce anisotropy of material properties in Al-Li; (5) durable thermal protection system (TPS); (6) unpressurized Al-Li structures (interstages, thrust structures); (7) near net shape sections; (8) pressurized structures; (9) welding and joining; (10) micrometeoroid and debris hypervelocity shields; (11) state-of-the-art shell buckling structure optimizer program to serve as a rapid design tool; (12) test philosophy; (13) reduced load cycle time; (14) structural analysis methods; (15) optimization of structural criteria; and (16) develop an engineering approach to properly trade material and structural concepts selection, fabrication, facilities, and cost.

Long-term neighborhood poverty trajectories and obesity in a sample of california mothers.

PubMed

Sheehan, Connor M; Cantu, Phillip A; Powers, Daniel A; Margerison-Zilko, Claire E; Cubbin, Catherine

2017-07-01

Neighborhoods (and people) are not static, and are instead shaped by dynamic long-term processes of change (and mobility). Using the Geographic Research on Wellbeing survey, a population-based sample of 2339 Californian mothers, we characterize then investigate how long-term latent neighborhood poverty trajectories predict the likelihood of obesity, taking into account short-term individual residential mobility. We find that, net of individual and neighborhood-level controls, living in or moving to tracts that experienced long-term low poverty was associated with lower odds of being obese relative to living in tracts characterized by long-term high poverty. Copyright © 2017 Elsevier Ltd. All rights reserved.

Propulsion Systems Panel

NASA Astrophysics Data System (ADS)

Bianca, Carmelo J.; Miner, Robert; Johnston, Lawrence M.; Bruce, R.; Dennies, Daniel P.; Dickenson, W.; Dreshfield, Robert; Karakulko, Walt; McGaw, Mike; Munafo, Paul M.

1993-02-01

Topics addressed are: (1) cryogenic tankage; (2) launch vehicle TPS/insulation; (3) durable passive thermal control devices and/or coatings; (4) development and characterization of processing methods to reduce anisotropy of material properties in Al-Li; (5) durable thermal protection system (TPS); (6) unpressurized Al-Li structures (interstages, thrust structures); (7) near net shape sections; (8) pressurized structures; (9) welding and joining; (10) micrometeoroid and debris hypervelocity shields; (11) state-of-the-art shell buckling structure optimizer program to serve as a rapid design tool; (12) test philosophy; (13) reduced load cycle time; (14) structural analysis methods; (15) optimization of structural criteria; and (16) develop an engineering approach to properly trade material and structural concepts selection, fabrication, facilities, and cost.

The Effect of the Traverse Feed Rate on the Microstructure and Mechanical Properties of Laser Deposited Fe₃Al (Zr,B) Intermetallic Alloy.

PubMed

Łazińska, Magdalena; Durejko, Tomasz; Czujko, Tomasz; Bojar, Zbigniew

2018-05-14

The results of the fabrication of components made with Fe-30%Al-0.35%Zr-0.1%B alloy powder using the Laser Engineered Net Shaping (LENS TM ) system operated at different traverse feed rates are described in this paper. The temperature of the molten metal pool was recorded during this process. Depending on the assumed feed rate, the formation of Zr⁻based precipitates with various morphologies and distributions was observed in the structure of the investigated material. It was found that as the traverse speed increased, spheroidization, refinement, and a more homogeneous distribution of these precipitates occurred.

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

Li, Ling; Post, Brian; Kunc, Vlastimil

Additive manufacturing (AM) or 3D printing is well known for producing arbitrary shaped parts without any tooling required, offering a promising alternative to the conventional injection molding method to fabricate near-net-shaped magnets. In order to determine their applicability in the fabrication of Nd-Fe-B bondedmagnets, we compare two 3D printing technologies, namely binder jetting and material extrusion. Some prospects and challenges of these state-of-the-art technologies for large-scale industrial applications will be discussed.

Predicting catalyst-support interactions between metal nanoparticles and amorphous silica supports

NASA Astrophysics Data System (ADS)

Ewing, Christopher S.; Veser, Götz; McCarthy, Joseph J.; Lambrecht, Daniel S.; Johnson, J. Karl

2016-10-01

Metal-support interactions significantly affect the stability and activity of supported catalytic nanoparticles (NPs), yet there is no simple and reliable method for estimating NP-support interactions, especially for amorphous supports. We present an approach for rapid prediction of catalyst-support interactions between Pt NPs and amorphous silica supports for NPs of various sizes and shapes. We use density functional theory calculations of 13 atom Pt clusters on model amorphous silica supports to determine linear correlations relating catalyst properties to NP-support interactions. We show that these correlations can be combined with fast discrete element method simulations to predict adhesion energy and NP net charge for NPs of larger sizes and different shapes. Furthermore, we demonstrate that this approach can be successfully transferred to Pd, Au, Ni, and Fe NPs. This approach can be used to quickly screen stability and net charge transfer and leads to a better fundamental understanding of catalyst-support interactions.

Catalogue of X-Ray Texture Data for Al-Cu-Li Alloy 1460, 2090, 2096 and 2195 Near-Net-Shape Extrusions, Sheet and Plate

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Hafley, Robert A.; Alexa, Joel A.

1998-01-01

The effect of crystallographic texture on the mechanical properties of near-net-shape extrusions is of major interest ff these products are to find application in launch vehicle or aircraft structures. The objective of this research was to produce a catalogue containing quantitative texture information for extruded product, sheet and plate. The material characterized was extracted from wide, integrally stiffened panels fabricated from the Al-Cu-Li alloys 1460, 2090, 2096 and 2195. The textural characteristics of sheet and plate products of the same alloys were determined for comparison purposes. The approach involved using X-ray diffraction to generate pole figures in combination with orientation distribution function analysis. The data were compiled as a function of location in the extruded cross-sections and the variation in the major deformation- and recrystallization-related texture components was identified.

Net analyte signal standard addition method (NASSAM) as a novel spectrofluorimetric and spectrophotometric technique for simultaneous determination, application to assay of melatonin and pyridoxine

NASA Astrophysics Data System (ADS)

Asadpour-Zeynali, Karim; Bastami, Mohammad

2010-02-01

In this work a new modification of the standard addition method called "net analyte signal standard addition method (NASSAM)" is presented for the simultaneous spectrofluorimetric and spectrophotometric analysis. The proposed method combines the advantages of standard addition method with those of net analyte signal concept. The method can be applied for the determination of analyte in the presence of known interferents. The accuracy of the predictions against H-point standard addition method is not dependent on the shape of the analyte and interferent spectra. The method was successfully applied to simultaneous spectrofluorimetric and spectrophotometric determination of pyridoxine (PY) and melatonin (MT) in synthetic mixtures and in a pharmaceutical formulation.

Modeling of Ti-W Solidification Microstructures Under Additive Manufacturing Conditions

NASA Astrophysics Data System (ADS)

Rolchigo, Matthew R.; Mendoza, Michael Y.; Samimi, Peyman; Brice, David A.; Martin, Brian; Collins, Peter C.; LeSar, Richard

2017-07-01

Additive manufacturing (AM) processes have many benefits for the fabrication of alloy parts, including the potential for greater microstructural control and targeted properties than traditional metallurgy processes. To accelerate utilization of this process to produce such parts, an effective computational modeling approach to identify the relationships between material and process parameters, microstructure, and part properties is essential. Development of such a model requires accounting for the many factors in play during this process, including laser absorption, material addition and melting, fluid flow, various modes of heat transport, and solidification. In this paper, we start with a more modest goal, to create a multiscale model for a specific AM process, Laser Engineered Net Shaping (LENS™), which couples a continuum-level description of a simplified beam melting problem (coupling heat absorption, heat transport, and fluid flow) with a Lattice Boltzmann-cellular automata (LB-CA) microscale model of combined fluid flow, solute transport, and solidification. We apply this model to a binary Ti-5.5 wt pct W alloy and compare calculated quantities, such as dendrite arm spacing, with experimental results reported in a companion paper.

A peek into the history of sapphire crystal growth

NASA Astrophysics Data System (ADS)

Harris, Daniel C.

2003-09-01

After the chemical compositions of sapphire and ruby were unraveled in the middle of the 19th century, chemists set out to grow artificial crystals of these valuable gemstones. In 1885 a dealer in Geneva began to sell ruby that is now believed to have been created by flame fusion. Gemnologists rapidly concluded that the stones were artificial, but the Geneva ruby stimulated A. V. L. Verneuil in Paris to develop a flame fusion process to produce higher quality ruby and sapphire. By 1900 there was brisk demand for ruby manufactured by Verneuil's method, even though Verneuil did not publicly announce his work until 1902 and did not publish details until 1904. The Verneuil process was used with little alteration for the next 50 years. From 1932-1953, S. K. Popov in the Soviet Union established a capability for manufacturing high quality sapphire by the Verneuil process. In the U.S., under government contract, Linde Air Products Co. implemented the Verneuil process for ruby and sapphire when European sources were cut off during World War II. These materials were essential to the war effort for jewel bearings in precision instruments. In the 1960s and 1970s, the Czochralski process was implemented by Linde and its successor, Union Carbide, to make higher crystal quality material for ruby lasers. Stimulated by a government contract for structural fibers in 1966, H. LaBelle invented edge-defined film-fed growth (EFG). The Saphikon company, which is currently owned by Saint-Gobain, evolved from this effort. Independently and simultaneously, Stepanov developed edge-defined film-fed growth in the Soviet Union. In 1967 F. Schmid and D. Viechnicki at the Army Materials Research Lab grew sapphire by the heat exchanger method (HEM). Schmid went on to establish Crystal Systems, Inc. around this technology. Rotem Industries, founded in Israel in 1969, perfected the growth of sapphire hemispheres and near-net-shape domes by gradient solidification. In the U.S., growth of near-net-shape sapphire domes was demonstrated by both the EFG and HEM methods in the 1980s under government contract, but neither method entered commercial production. Today, domes in the U.S. are made by "scooping" sapphire boules with diamond-impregnated cutting tools. Commercial markets for sapphire, especially in the semiconductor industry, are healthy and growing at the dawn of the 21st century.

Research and Analysis of Image Processing Technologies Based on DotNet Framework

NASA Astrophysics Data System (ADS)

Ya-Lin, Song; Chen-Xi, Bai

Microsoft.Net is a kind of most popular program development tool. This paper gave a detailed analysis concluded about some image processing technologies of the advantages and disadvantages by .Net processed image while the same algorithm is used in Programming experiments. The result shows that the two best efficient methods are unsafe pointer and Direct 3D, and Direct 3D used to 3D simulation development, and the others are useful in some fields while these technologies are poor efficiency and not suited to real-time processing. The experiment results in paper will help some projects about image processing and simulation based DotNet and it has strong practicability.

Physico-chemical characterization of functionalized polypropylenic fibers for prosthetic applications

NASA Astrophysics Data System (ADS)

Nisticò, Roberto; Faga, Maria Giulia; Gautier, Giovanna; Magnacca, Giuliana; D'Angelo, Domenico; Ciancio, Emanuele; Piacenza, Giacomo; Lamberti, Roberta; Martorana, Selanna

2012-08-01

Polypropylene (PP) fibers can be manufactured to form nets which can find application as prosthesis in hernioplasty. One of the most important problem to deal with when nets are applied in vivo consists in the reproduction of bacteria within the net fibers intersections. This occurs right after the application of the prosthesis, and causes infections, thus it is fundamental to remove bacteria in the very early stage of the nets application. This paper deals with the physico-chemical characterization of such nets, pre-treated by atmospheric pressure plasma dielectric barrier discharge apparatus (APP-DBD) and functionalized with an antibiotic drug such as chitosan. The physico-chemical characterization of sterilized nets, before and after the functionalization with chitosan, was carried out by means of scanning electron microscopy (SEM) coupled with EDS spectroscopy, FTIR spectroscopy, drop shape analysis (DSA), X-ray diffraction and thermal analyses (TGA and DSC). The aim of the work is to individuate a good strategy to characterize this kind of materials, to understand the effects of polypropylene pre-treatment on functionalization efficiency, to follow the materials ageing in order to study the effects of the surface treatment for in vivo applications.

Variation of NEE and its affecting factors in a vineyard of arid region of northwest China

NASA Astrophysics Data System (ADS)

Guo, W. H.; Kang, S. Z.; Li, F. S.; Li, S. E.

2014-02-01

To understand the variation of net ecosystem CO2 exchange (NEE) in orchard ecosystem and it's affecting factors, carbon flux was measured using eddy covariance system in a wine vineyard in arid northwest China during 2008-2010. Results show that vineyard NEE was positive value at the early growth stage, higher negative value at the mid-growth stage, and lower negative value at the later growth stage. Diurnal variation of NEE was "W" shaped curve in sunny day, but "U" shaped curve in cloudy day. Irrigation and pruning did not affect diurnal variation shape of NEE, however, irrigation reduced the difference between maximal and minimal value of NEE and pruning reduced the carbon sink capacity. The main factors affecting hourly NEE were canopy conductance (gc) and net radiation (Rn). The hourly NEE increased with the increase of gc or Rn when gc was less than 0.02 m·s-1 or Rn was between 0 and 200 W·m-2. The main factors affecting both daily and seasonal NEE were gc, air temperature (Ta), atmospheric CO2 density, vapour pressure deficit (VPD) and soil moisture content.

Microstructure and Mechanical Properties of Vacuum Plasma Sprayed Cu-8Cr-4Nb

NASA Technical Reports Server (NTRS)

Holmes, Richard; Ellis, David; McKechnie, Timothy; Hickman, Robert

1997-01-01

This paper compares the tensile properties of Cu-8Cr-4Nb material produced by VPS to material previously produced by extrusion. The microstructure of the VPS material is also presented. The combustion chamber liner of rocket motors represents an extreme materials application. The liner hot wall is exposed to a 2760 C (5000 F) flame while the cold side is exposed to cryogenic hydrogen liquid. Materials for use in the combustion chamber liner require a combination of high temperature strength, creep resistance, and low cycle fatigue resistance along with high thermal conductivity. The hot side is also subject to localized cycles between reducing and oxidizing environments that degrade the liner by a process called blanching. A new Cu-8 at.% Cr-4 at% Nb (Cu-8Cr-4Nb) alloy has been developed at NASA Lewis Research Center as a replacement for the currently used alloy, NARloy-z (Cu-3 wt.% Ag-0.5 wt.% Zr). The alloy is strengthened by a fine dispersion of Cr2Nb particles. The alloy has better mechanical properties than NARloy-Z while retaining most of the thermal conductivity of pure copper. The alloy has been successfully consolidated by extrusion and hot isostatic pressing (HIPing). However, vacuum plasma spraying (VPS) offers several advantages over prior consolidation methods. VPS can produce a near net shape piece with the profile of the liner. In addition, oxidation resistant and thermal barrier coatings can be incorporated as an integral part of the liner hot wall during the VPS deposition. The low oxygen VPS Cu-8Cr-4Nb exhibits a higher strength than Cu-8Cr-4Nb produced by extrusion at elevated temperatures and a comparable strength at room temperature. Moduli and ductility were not significantly different. However, the ability to produce parts to near-net shape and maintain the good elevated temperature tensile properties of the extruded Cu-8Cr-4Nb makes VPS an attractive processing method for fabricating rocket engine combustion liners.

Graphite fiber textile preform/copper matrix composites

NASA Technical Reports Server (NTRS)

Gilatovs, G. J.; Lee, Bruce; Bass, Lowell

1995-01-01

Graphite fiber reinforced/copper matrix composites have sufficiently high thermal conduction to make them candidate materials for critical heat transmitting and rejection components. The term textile composites arises because the preform is braided from fiber tows, conferring three-dimensional reinforcement and near net shape. The principal issues investigated in the past two years have centered on developing methods to characterize the preform and fabricated composite and on braidability. It is necessary to have an analytic structural description for both processing and final property modeling. The structure of the true 3-D braids used is complex and has required considerable effort to model. A structural mapping has been developed as a foundation for analytic models for thermal conduction and mechanical properties. The conductivity has contributions both from the copper and the reinforcement. The latter is accomplished by graphitization of the fibers, the higher the amount of graphitization the greater the conduction. This is accompanied by an increase in the fiber modulus, which is desirable from a stiffness point of view but decreases the braidability; the highest conductivity fibers are simply too brittle to be braided. Considerable effort has been expended on determining the optimal braidability--conductivity region. While a number of preforms have been fabricated, one other complication intervenes; graphite and copper are immiscible, resulting in a poor mechanical bond and difficulties in infiltration by molten copper. The approach taken is to utilize a proprietary fiber coating process developed by TRA, of Salt Lake City, Utah, which forms an itermediary bond. A number of preforms have been fabricated from a variety of fiber types and two sets of these have been infiltrated with OFHC copper, one with the TRA coating and one without. Mechanical tests have been performed using a small-scale specimen method and show the coated specimens to have superior mechanical properties. Final batches of preforms, including a finned, near net shape tube, are being fabricated and will be infiltrated before summer.

Bed Net Durability Assessments: Exploring a Composite Measure of Net Damage

PubMed Central

Vanden Eng, Jodi L.; Chan, Adeline; Abílio, Ana Paula; Wolkon, Adam; Ponce de Leon, Gabriel; Gimnig, John; Morgan, Juliette

2015-01-01

Background The durability of Long Lasting Insecticidal Nets (LLINs) in field conditions is of great importance for malaria prevention and control efforts; however, the physical integrity of the net fabric is not well understood making it challenging to determine overall effectiveness of nets as they age. The 2011 World Health Organization Pesticide Evaluation Scheme (WHOPES) guidelines provide a simple, standardized method using a proportional hole index (PHI) for assessing net damage with the intent to provide national malaria control programs with guidelines to assess the useful life of LLINS and estimate the rate of replacement. Methods We evaluated the utility of the PHI measure using 409 LLINs collected over three years in Nampula Province, Mozambique following a mass distribution campaign in 2008. For each LLIN the diameter and distance from the bottom of the net were recorded for every hole. Holes were classified into four size categories and a PHI was calculated following WHOPES guidelines. We investigate how the size, shape, and location of holes influence the PHI. The areas of the WHOPES defined categories were compared to circular and elliptical areas based on approximate shape and actual measured axes of each hole and the PHI was compared to cumulative damaged surface area of the LLIN. Results The damaged area of small, medium, large, and extra-large holes was overestimated using the WHOPES categories compared to elliptical areas using the actual measured axes. Similar results were found when comparing to circular areas except for extra-large holes which were underestimated. (Wilcoxon signed rank test of differences p< 0.0001 for all sizes). Approximating holes as circular overestimated hole surface area by 1.5 to 2 times or more. There was a significant difference in the mean number of holes < 0.5 cm by brand and there were more holes of all sizes on the bottom of nets than the top. For a range of hypothetical PHI thresholds used to designate a “failed LLIN”, roughly 75 to 80% of failed LLINs were detected by considering large and extra-large holes alone, but sensitivity varied by brand. Conclusions Future studies may refine the PHI to better approximate overall damaged surface area. Furthermore, research is needed to identify whether or not appropriate PHI thresholds can be used to deem a net no longer protective. Once a cutoff is selected, simpler methods of determining the effective lifespan of LLINs can help guide replacement strategies for malaria control programs. PMID:26047494

Bed Net Durability Assessments: Exploring a Composite Measure of Net Damage.

PubMed

Vanden Eng, Jodi L; Chan, Adeline; Abílio, Ana Paula; Wolkon, Adam; Ponce de Leon, Gabriel; Gimnig, John; Morgan, Juliette

2015-01-01

The durability of Long Lasting Insecticidal Nets (LLINs) in field conditions is of great importance for malaria prevention and control efforts; however, the physical integrity of the net fabric is not well understood making it challenging to determine overall effectiveness of nets as they age. The 2011 World Health Organization Pesticide Evaluation Scheme (WHOPES) guidelines provide a simple, standardized method using a proportional hole index (PHI) for assessing net damage with the intent to provide national malaria control programs with guidelines to assess the useful life of LLINS and estimate the rate of replacement. We evaluated the utility of the PHI measure using 409 LLINs collected over three years in Nampula Province, Mozambique following a mass distribution campaign in 2008. For each LLIN the diameter and distance from the bottom of the net were recorded for every hole. Holes were classified into four size categories and a PHI was calculated following WHOPES guidelines. We investigate how the size, shape, and location of holes influence the PHI. The areas of the WHOPES defined categories were compared to circular and elliptical areas based on approximate shape and actual measured axes of each hole and the PHI was compared to cumulative damaged surface area of the LLIN. The damaged area of small, medium, large, and extra-large holes was overestimated using the WHOPES categories compared to elliptical areas using the actual measured axes. Similar results were found when comparing to circular areas except for extra-large holes which were underestimated. (Wilcoxon signed rank test of differences p< 0.0001 for all sizes). Approximating holes as circular overestimated hole surface area by 1.5 to 2 times or more. There was a significant difference in the mean number of holes < 0.5 cm by brand and there were more holes of all sizes on the bottom of nets than the top. For a range of hypothetical PHI thresholds used to designate a "failed LLIN", roughly 75 to 80% of failed LLINs were detected by considering large and extra-large holes alone, but sensitivity varied by brand. Future studies may refine the PHI to better approximate overall damaged surface area. Furthermore, research is needed to identify whether or not appropriate PHI thresholds can be used to deem a net no longer protective. Once a cutoff is selected, simpler methods of determining the effective lifespan of LLINs can help guide replacement strategies for malaria control programs.

Assessing bed net damage: comparisons of three measurement methods for estimating the size, shape, and distribution of holes on bed nets.

PubMed

Vanden Eng, Jodi L; Mathanga, Don P; Landman, Keren; Mwandama, Dyson; Minta, Anna A; Shah, Monica; Sutcliffe, James; Chisaka, Joseph; Lindblade, Kim A; Steinhardt, Laura

2017-10-10

Measuring the physical condition of long-lasting insecticidal nets (LLINs) under field conditions is of great importance for malaria control programmes to guide decisions on how frequently to replace LLINs. Current guidelines by the World Health Organization Pesticide Evaluation Scheme (WHOPES) propose a proportionate hole index (pHI) for assessing LLIN condition by counting the number of holes the size of a thumb, fist, head, and larger than a head. However, this method does not account for irregular hole shapes or exact hole sizes which could result in inaccurate decisions about when to replace LLINs. LLINs were collected during a 2013 health facility-based malaria case control study in Machinga District, Malawi. To evaluate the accuracy of the pHI, the physical condition of 277 LLINs was estimated by the WHOPES method and then compared with two more thorough measurement methods: image analysis of digital photographs of each LLIN side; and for 10 nets, ruler measurements of the length, width, and location of each hole. Total hole counts and areas per net were estimated by each method, and detailed results of hole shapes and composite pictures of hole locations were generated using image analysis. The WHOPES method and image analysis resulted in similar estimates of total hole counts, each with a median of 10 (inter-quartile range (IQR) 4-24 and 4-23, respectively; p = 0.004); however, estimated hole areas were significantly larger using the WHOPES method (median 162 cm 2 , IQR 28-793) than image analysis (median 13 cm 2 , IQR 3-101; p < 0.0001). The WHOPES method classified fewer LLINs in 'good condition' compared to image analysis (42% vs 74%). The ruler method detected significantly more holes than image analysis did (p = 0.002) in 10 LLINs; however, total hole area was not significantly different (p = 0.16). Most holes were not circular but roughly 2-5 times longer in one direction. The lower quarter of LLIN sides was found to have the most holes. The WHOPES method overestimated total hole area, likely because holes are elongated rather than circular, suggesting further adjustments to the pHI formula may be warranted when considering LLIN replacement strategies.

Modulation of Perineuronal Nets and Parvalbumin with Developmental Song Learning

PubMed Central

Balmer, Timothy S.; Carels, Vanessa M.; Frisch, Jillian L.; Nick, Teresa A.

2009-01-01

Neural circuits and behavior are shaped during developmental phases of maximal plasticity known as sensitive or critical periods. Neural correlates of sensory critical periods have been identified, but their roles remain unclear. Factors that define critical periods in sensorimotor circuits and behavior are not known. Birdsong learning in the zebra finch occurs during a sensitive period similar to that for human speech. We now show that perineuronal nets, which correlate with sensory critical periods, surround parvalbumin-positive neurons in brain areas that are dedicated to singing. The percentage of both total and parvalbumin-positive neurons with perineuronal nets increased with development. In HVC (this acronym is the proper name), a song area important for sensorimotor integration, the percentage of parvalbumin neurons with perineuronal nets correlated with song maturity. Shifting the vocal critical period with tutor song deprivation decreased the percentage of neurons that were parvalbumin positive and the relative staining intensity of both parvalbumin and a component of perineuronal nets. Developmental song learning shares key characteristics with sensory critical periods, suggesting shared underlying mechanisms. PMID:19828802

Automation of Presentation Record Production Based on Rich-Media Technology Using SNT Petri Nets Theory.

PubMed

Martiník, Ivo

2015-01-01

Rich-media describes a broad range of digital interactive media that is increasingly used in the Internet and also in the support of education. Last year, a special pilot audiovisual lecture room was built as a part of the MERLINGO (MEdia-rich Repository of LearnING Objects) project solution. It contains all the elements of the modern lecture room determined for the implementation of presentation recordings based on the rich-media technologies and their publication online or on-demand featuring the access of all its elements in the automated mode including automatic editing. Property-preserving Petri net process algebras (PPPA) were designed for the specification and verification of the Petri net processes. PPPA does not need to verify the composition of the Petri net processes because all their algebraic operators preserve the specified set of the properties. These original PPPA are significantly generalized for the newly introduced class of the SNT Petri process and agent nets in this paper. The PLACE-SUBST and ASYNC-PROC algebraic operators are defined for this class of Petri nets and their chosen properties are proved. The SNT Petri process and agent nets theory were significantly applied at the design, verification, and implementation of the programming system ensuring the pilot audiovisual lecture room functionality.

Automation of Presentation Record Production Based on Rich-Media Technology Using SNT Petri Nets Theory

PubMed Central

Martiník, Ivo

2015-01-01

Rich-media describes a broad range of digital interactive media that is increasingly used in the Internet and also in the support of education. Last year, a special pilot audiovisual lecture room was built as a part of the MERLINGO (MEdia-rich Repository of LearnING Objects) project solution. It contains all the elements of the modern lecture room determined for the implementation of presentation recordings based on the rich-media technologies and their publication online or on-demand featuring the access of all its elements in the automated mode including automatic editing. Property-preserving Petri net process algebras (PPPA) were designed for the specification and verification of the Petri net processes. PPPA does not need to verify the composition of the Petri net processes because all their algebraic operators preserve the specified set of the properties. These original PPPA are significantly generalized for the newly introduced class of the SNT Petri process and agent nets in this paper. The PLACE-SUBST and ASYNC-PROC algebraic operators are defined for this class of Petri nets and their chosen properties are proved. The SNT Petri process and agent nets theory were significantly applied at the design, verification, and implementation of the programming system ensuring the pilot audiovisual lecture room functionality. PMID:26258164

Processing and Properties of a Phenolic Composite System

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung; Bai, J. M.; Baughman, James M.

2006-01-01

Phenolic resin systems generate water as a reaction by-product via condensation reactions during curing at elevated temperatures. In the fabrication of fiber reinforced phenolic resin matrix composites, volatile management is crucial in producing void-free quality laminates. A commercial vacuum-bag moldable phenolic prepreg system was selected for this study. The traditional single-vacuum-bag (SVB) process was unable to manage the volatiles effectively, resulting in inferior voidy laminates. However, a double vacuum bag (DVB) process was shown to afford superior volatile management and consistently yielded void-free quality parts. The DVB process cure cycle (temperature /pressure profiles) for the selected composite system was designed, with the vacuum pressure application point carefully selected, to avoid excessive resin squeeze-outs and achieve the net shape and target resin content in the final consolidated laminate parts. Laminate consolidation quality was characterized by optical photomicrography for the cross sections and measurements of mechanical properties. A 40% increase in short beam shear strength, 30% greater flexural strength, 10% higher tensile and 18% higher compression strengths were obtained in composite laminates fabricated by the DVB process.

An assembly process model based on object-oriented hierarchical time Petri Nets

NASA Astrophysics Data System (ADS)

Wang, Jiapeng; Liu, Shaoli; Liu, Jianhua; Du, Zenghui

2017-04-01

In order to improve the versatility, accuracy and integrity of the assembly process model of complex products, an assembly process model based on object-oriented hierarchical time Petri Nets is presented. A complete assembly process information model including assembly resources, assembly inspection, time, structure and flexible parts is established, and this model describes the static and dynamic data involved in the assembly process. Through the analysis of three-dimensional assembly process information, the assembly information is hierarchically divided from the whole, the local to the details and the subnet model of different levels of object-oriented Petri Nets is established. The communication problem between Petri subnets is solved by using message database, and it reduces the complexity of system modeling effectively. Finally, the modeling process is presented, and a five layer Petri Nets model is established based on the hoisting process of the engine compartment of a wheeled armored vehicle.

Electroacoustics modeling of piezoelectric welders for ultrasonic additive manufacturing processes

NASA Astrophysics Data System (ADS)

Hehr, Adam; Dapino, Marcelo J.

2016-04-01

Ultrasonic additive manufacturing (UAM) is a recent 3D metal printing technology which utilizes ultrasonic vibrations from high power piezoelectric transducers to additively weld similar and dissimilar metal foils. CNC machining is used intermittent of welding to create internal channels, embed temperature sensitive components, sensors, and materials, and for net shaping parts. Structural dynamics of the welder and work piece influence the performance of the welder and part quality. To understand the impact of structural dynamics on UAM, a linear time-invariant model is used to relate system shear force and electric current inputs to the system outputs of welder velocity and voltage. Frequency response measurements are combined with in-situ operating measurements of the welder to identify model parameters and to verify model assumptions. The proposed LTI model can enhance process consistency, performance, and guide the development of improved quality monitoring and control strategies.

Simulation and experimental comparison of the thermo-mechanical history and 3D microstructure evolution of 304L stainless steel tubes manufactured using LENS

NASA Astrophysics Data System (ADS)

Johnson, Kyle L.; Rodgers, Theron M.; Underwood, Olivia D.; Madison, Jonathan D.; Ford, Kurtis R.; Whetten, Shaun R.; Dagel, Daryl J.; Bishop, Joseph E.

2018-05-01

Additive manufacturing enables the production of previously unachievable designs in conjunction with time and cost savings. However, spatially and temporally fluctuating thermal histories can lead to residual stress states and microstructural variations that challenge conventional assumptions used to predict part performance. Numerical simulations offer a viable way to explore the root causes of these characteristics, and can provide insight into methods of controlling them. Here, the thermal history of a 304L stainless steel cylinder produced using the Laser Engineered Net Shape process is simulated using finite element analysis (FEA). The resultant thermal history is coupled to both a solid mechanics FEA simulation to predict residual stress and a kinetic Monte Carlo model to predict the three-dimensional grain structure evolution. Experimental EBSD measurements of grain structure and in-process infrared thermal data are compared to the predictions.

Simulation and experimental comparison of the thermo-mechanical history and 3D microstructure evolution of 304L stainless steel tubes manufactured using LENS

NASA Astrophysics Data System (ADS)

Johnson, Kyle L.; Rodgers, Theron M.; Underwood, Olivia D.; Madison, Jonathan D.; Ford, Kurtis R.; Whetten, Shaun R.; Dagel, Daryl J.; Bishop, Joseph E.

2017-12-01

Additive manufacturing enables the production of previously unachievable designs in conjunction with time and cost savings. However, spatially and temporally fluctuating thermal histories can lead to residual stress states and microstructural variations that challenge conventional assumptions used to predict part performance. Numerical simulations offer a viable way to explore the root causes of these characteristics, and can provide insight into methods of controlling them. Here, the thermal history of a 304L stainless steel cylinder produced using the Laser Engineered Net Shape process is simulated using finite element analysis (FEA). The resultant thermal history is coupled to both a solid mechanics FEA simulation to predict residual stress and a kinetic Monte Carlo model to predict the three-dimensional grain structure evolution. Experimental EBSD measurements of grain structure and in-process infrared thermal data are compared to the predictions.

Metallic Fuel Casting Development and Parameter Optimization Simulations

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

R.S. Fielding; J. Crapps; C. Unal

One of the advantages of metallic fuel is the abilility to cast the fuel slugs to near net shape with little additional processing. However, the high aspect ratio of the fuel is not ideal for casting. EBR-II fuel was cast using counter gravity injection casting (CGIC) but, concerns have been raised concerning the feasibility of this process for americium bearing alloys. The Fuel Cycle Research and Development program has begun developing gravity casting techniques suitable for fuel production. Compared to CGIC gravity casting does not require a large heel that then is recycled, does not require application of a vacuummore » during melting, and is conducive to re-usable molds. Development has included fabrication of two separate benchscale, approximately 300 grams, systems. To shorten development time computer simulations have been used to ensure mold and crucible designs are feasible and to identify which fluid properties most affect casting behavior and therefore require more characterization.« less

Development Study of Cartridge/Crucible Tube Materials

NASA Technical Reports Server (NTRS)

McKechnie, Timothy N.; ODell, Scott J.

1998-01-01

The limitations of traditional alloys and the desire for improved performance for components is driving the increased utilization of refractory metals in tile space industry. From advanced propulsion systems to high temperature furnace components for microgravity processing, refractory metals are being used for their high melting temperatures and inherent chemical stability. Techniques have been developed to produce near net shape refractory metal components utilizing vacuum plasma spraying. Material utilization is very high, and laborious machining can be avoided. As-spray formed components have been tested and found to perform adequately. However, increased mechanical and thermal properties are needed. To improve these properties, post processing thermal treatments such as hydrogen sintering and vacuum annealing have been performed. Components formed from alloys of tungsten, rhenium, tantalum, niobium, and molybdenum are discussed and a metallurgical analyses detailing the results are presented. A qualitative comparison of mechanical properties is also included.

Effect of Surface Densification on the Microstructure and Mechanical Properties of Powder Metallurgical Gears by Using a Surface Rolling Process

PubMed Central

Peng, Jingguang; Zhao, Yan; Chen, Di; Li, Kiade; Lu, Wei; Yan, Biao

2016-01-01

Powder metallurgy (PM) components are widely used in the auto industry due to the advantage of net-shape forming, low cost, and high efficiency. Still, usage of PM components is limited in the auto industry when encountering rigorous situations, like heavy load, due to lower strength, hardness, wear resistance, and other properties compared to wrought components due to the existence of massive pores in the PM components. In this study, through combining the powder metallurgy process and rolling process, the pores in the PM components were decreased and a homogenous densified layer was formed on the surface, which resulted in the enhancement of the strength, hardness, wear resistance, and other properties, which can expand its range of application. In this paper, we study the impact of different rolling feeds on the performance of the components’ surfaces. We found that with the increase of the rolling feed, the depth of the densified layer increased. PMID:28773970

Process for preparing energetic materials

DOEpatents

Simpson, Randall L [Livermore, CA; Lee, Ronald S [Livermore, CA; Tillotson, Thomas M [Tracy, CA; Hrubesh, Lawrence W [Pleasanton, CA; Swansiger, Rosalind W [Livermore, CA; Fox, Glenn A [Livermore, CA

2011-12-13

Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

Effect of Surface Densification on the Microstructure and Mechanical Properties of Powder Metallurgical Gears by Using a Surface Rolling Process.

PubMed

Peng, Jingguang; Zhao, Yan; Chen, Di; Li, Kiade; Lu, Wei; Yan, Biao

2016-10-19

Powder metallurgy (PM) components are widely used in the auto industry due to the advantage of net-shape forming, low cost, and high efficiency. Still, usage of PM components is limited in the auto industry when encountering rigorous situations, like heavy load, due to lower strength, hardness, wear resistance, and other properties compared to wrought components due to the existence of massive pores in the PM components. In this study, through combining the powder metallurgy process and rolling process, the pores in the PM components were decreased and a homogenous densified layer was formed on the surface, which resulted in the enhancement of the strength, hardness, wear resistance, and other properties, which can expand its range of application. In this paper, we study the impact of different rolling feeds on the performance of the components' surfaces. We found that with the increase of the rolling feed, the depth of the densified layer increased.

Materials and processes for aircraft environmental controls in the 1990's

NASA Astrophysics Data System (ADS)

Delgrosso, E. J.; Zajac, T.; Tseka, J.

1980-10-01

Changes in materials and processes expected to be used in aircraft environmental control systems (ECS) in the 1990s are analyzed, and a forecast is presented. Results of the study show that the most advanced development would be in the use of a cast high strength alloy steel, i.e., a steel with below 8% alloy content, and a 225 KSI annealed tensile strength. To assure complete densification and enhancement of properties, the casting would be HIP, and modification of its surface chemistry could be achieved through ion implantation. As candidate methods for imparting surface protection, laser glazing and chemical vapor deposition are mentioned. The anticipated changes in the materials and techniques used for construction of ECS components are: the development of rapid solidification rate powders for the production of some alloy systems such as Al-Mg-Li, bearing alloy CRB-7, and titanium alloys, 'near-net-shape' processing, and the use of advanced fiber-reinforced plastics.

Inducing Stable α + β Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments.

PubMed

Barriobero-Vila, Pere; Gussone, Joachim; Haubrich, Jan; Sandlöbes, Stefanie; Da Silva, Julio Cesar; Cloetens, Peter; Schell, Norbert; Requena, Guillermo

2017-03-07

Selective laser melting is a promising powder-bed-based additive manufacturing technique for titanium alloys: near net-shaped metallic components can be produced with high resource-efficiency and cost savings [...].

The role of plasma/neutral source and loss processes in shaping the giant planet magnetospheres

NASA Astrophysics Data System (ADS)

Delamere, P. A.

2014-12-01

The giant planet magnetospheres are filled with neutral and ionized gases originating from satellites orbiting deep within the magnetosphere. The complex chemical and physical pathways for the flow of mass and energy in this partially ionized plasma environment is critical for understanding magnetospheric dynamics. The flow of mass at Jupiter and Saturn begins, primarily, with neutral gases emanating from Io (~1000 kg/s) and Enceladus (~200 kg/s). In addition to ionization losses, the neutral gases are absorbed by the planet, its rings, or escape at high speeds from the magnetosphere via charge exchange reactions. The net result is a centrifugally confined torus of plasma that is transported radially outward, distorting the magnetic field into a magnetodisc configuration. Ultimately the plasma is lost to the solar wind. A critical parameter for shaping the magnetodisc and determining its dynamics is the radial plasma mass transport rate (~500 kg/s and ~50 kg/s for Jupiter and Saturn respectively). Given the plasma transport rates, several simple properties of the giant magnetodiscs can be estimated including the physical scale of the magnetosphere, the magnetic flux transport, and the magnitude of azimuthal magnetic field bendback. We will discuss transport-related magnetic flux conservation and the mystery of plasma heating—two critical issues for shaping the giant planet magnetospheres.

An object-oriented description method of EPMM process

NASA Astrophysics Data System (ADS)

Jiang, Zuo; Yang, Fan

2017-06-01

In order to use the object-oriented mature tools and language in software process model, make the software process model more accord with the industrial standard, it’s necessary to study the object-oriented modelling of software process. Based on the formal process definition in EPMM, considering the characteristics that Petri net is mainly formal modelling tool and combining the Petri net modelling with the object-oriented modelling idea, this paper provides this implementation method to convert EPMM based on Petri net into object models based on object-oriented description.

Optical methods in modeling nicotine effect on the surface water of cell membranes

NASA Astrophysics Data System (ADS)

Alexandrova, Tatyana V.; Rogacheva, Svetlana M.; Kuznetsov, Pavel E.; Gubina, Tamara I.

2005-06-01

Fluorescence and spectrophotometric methods have been used for investigation of nicotine action on the state and mobility of the surface water. The surfaces of membranes and proteins were simulated with the help of liposomes and ultradispersive diamonds consequently. Nicotine was shown to reduce the stability of liposomes and to change the aggregative ability of ultradispersive diamonds. The wave-like curves for the nicotine concentration dependences of the pointed features were observed. Such shape of responses was suggested to be due to the changing in structure and dynamics of water hydrogen bonds net near the surface of the model systems induced by nicotine molecules. The surface water phase was supposed to be one of signal elements ofthe ligand receptor recognition process.

Reactive spark plasma synthesis of CaZrTi2O7 zirconolite ceramics for plutonium disposition

NASA Astrophysics Data System (ADS)

Sun, Shi-Kuan; Stennett, Martin C.; Corkhill, Claire L.; Hyatt, Neil C.

2018-03-01

Near single phase zirconolite ceramics, prototypically CaZrTi2O7, were fabricated by reactive spark plasma sintering (RSPS), from commercially available CaTiO3, ZrO2 and TiO2 reagents, after processing at 1200 °C for only 1 h. Ceramics were of theoretical density and formed with a controlled mean grain size of 1.9 ± 0.6 μm. The reducing conditions of RSPS afforded the presence of paramagnetic Ti3+, as demonstrated by EPR spectroscopy. Overall, this study demonstrates the potential for RSPS to be a disruptive technology for disposition of surplus separated plutonium stockpiles in ceramic wasteforms, given its inherent advantage of near net shape products and rapid throughput.

IPMC-driven thrust generation: a new conceptual design (Conference Presentation)

NASA Astrophysics Data System (ADS)

Olsen, Zakai; Kim, Kwang Jin

2017-04-01

Ionic Polymer-Metal Composites (IPMC) are highly functional actuators that find many uses in the field of soft robotics due to their low actuation voltage and ability to operate in aquatic environments. The actuation of an IPMC relies on the swelling of the negatively charged side when a potential is applied, due to the free-moving cations and water molecules migrating to that half. While this bending type actuation can be utilized to perform many tasks, it is ill suited for the primary propulsion mechanism in certain soft robotic applications. Here, a new conceptual design is presented which utilizes the bending of IPMC materials to achieve complex actuation motion in an attempt to generate a non-zero net thrust for propulsion of soft robots. The design capitalizes on advances in the manufacturing processes of electroactive polymer materials, which now allow for more complex shapes and thus new and unique modes of actuation. By utilizing the consistent bending deformation of IPMC actuators, in conjunction with carefully considered geometry, an IPMC driven body may serve as a primary mode of propulsion through a positive net thrust generation. This work consists of the initial feasibility study, concept testing, and optimization for such an actuator through computer modeling and simulation. COMSOL will be used for the finite element analysis to design the most efficient and optimized design for a positive net thrust generation. Such an IPMC design may find a great deal of applications, and the potential of future integration into other soft robotic systems is considered.

Saliency Detection and Deep Learning-Based Wildfire Identification in UAV Imagery.

PubMed

Zhao, Yi; Ma, Jiale; Li, Xiaohui; Zhang, Jie

2018-02-27

An unmanned aerial vehicle (UAV) equipped with global positioning systems (GPS) can provide direct georeferenced imagery, mapping an area with high resolution. So far, the major difficulty in wildfire image classification is the lack of unified identification marks, the fire features of color, shape, texture (smoke, flame, or both) and background can vary significantly from one scene to another. Deep learning (e.g., DCNN for Deep Convolutional Neural Network) is very effective in high-level feature learning, however, a substantial amount of training images dataset is obligatory in optimizing its weights value and coefficients. In this work, we proposed a new saliency detection algorithm for fast location and segmentation of core fire area in aerial images. As the proposed method can effectively avoid feature loss caused by direct resizing; it is used in data augmentation and formation of a standard fire image dataset 'UAV_Fire'. A 15-layered self-learning DCNN architecture named 'Fire_Net' is then presented as a self-learning fire feature exactor and classifier. We evaluated different architectures and several key parameters (drop out ratio, batch size, etc.) of the DCNN model regarding its validation accuracy. The proposed architecture outperformed previous methods by achieving an overall accuracy of 98%. Furthermore, 'Fire_Net' guarantied an average processing speed of 41.5 ms per image for real-time wildfire inspection. To demonstrate its practical utility, Fire_Net is tested on 40 sampled images in wildfire news reports and all of them have been accurately identified.

Energy Saving Melting and Revert Reduction Technology: Innovative Semi-Solid Metal (SSM) Processing

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

Diran Apelian

2012-08-15

Semi-solid metal (SSM) processing has emerged as an attractive method for near-net-shape manufacturing due to the distinct advantages it holds over conventional near-net-shape forming technologies. These advantages include lower cycle time, increased die life, reduced porosity, reduced solidification shrinkage, improved mechanical properties, etc. SSM processing techniques can not only produce the complex dimensional details (e.g. thin-walled sections) associated with conventional high-pressure die castings, but also can produce high integrity castings currently attainable only with squeeze and low-pressure permanent mold casting processes. There are two primary semi-solid processing routes, (a) thixocasting and (b) rheocasting. In the thixocasting route, one starts frommore » a non-dendritic solid precursor material that is specially prepared by a primary aluminum manufacturer, using continuous casting methods. Upon reheating this material into the mushy (a.k.a. "two-phase") zone, a thixotropic slurry is formed, which becomes the feed for the casting operation. In the rheocasting route (a.k.a. "slurry-on-demand" or "SoD"), one starts from the liquid state, and the thixotropic slurry is formed directly from the melt via careful thermal management of the system; the slurry is subsequently fed into the die cavity. Of these two routes, rheocasting is favored in that there is no premium added to the billet cost, and the scrap recycling issues are alleviated. The CRP (Trade Marked) is a process where the molten metal flows through a reactor prior to casting. The role of the reactor is to ensure that copious nucleation takes place and that the nuclei are well distributed throughout the system prior to entering the casting cavity. The CRP (Trade Marked) has been successfully applied in hyper-eutectic Al-Si alloys (i.e., 390 alloy) where two liquids of equal or different compositions and temperatures are mixed in the reactor and creating a SSM slurry. The process has been mostly used for hypo-eutectic Al-Si alloys (i.e., 356, 357, etc.) where a single melt passes through the reactor. In addition, the CRP (Trade Marked) was designed to be flexible for thixocasting or rheocasting applications as well as batch or continuous casting. Variable heat extraction rates can be obtained by controlling either the superheat of the melt, the temperature of the channel system, or the temperature of the reactor. This program had four main objectives all of which were focused on a mechanistic understanding of the process in order to be able to scale it up, to develop it into a robust process,and for SSM processing to be commercially used.« less

Willingness to pay for insecticide-treated nets in Berehet District, Amhara Region, Northern Ethiopia: implication of social marketing.

PubMed

Aleme, Adisu; Girma, Eshetu; Fentahun, Netsanet

2014-01-01

Understanding the feasibility of achieving widespread coverage with Insecticide-Treated Nets has to be preceded by learning how people value the Insecticide-Treated Nets and estimating the potential demand and willingness to pay so that sustainability of the intervention can be assured. The objective of this study was to determine willingness to pay for Insecticide-Treated Nets among households in Berehet District, Northern Ethiopia. A community-based cross-sectional study was conducted using both quantitative and qualitative methods in five randomly selected Kebeles from January-February 2012. Open ended contingent valuation technique with follow-up method was used. Qualitative data were collected through focus group discussions and observation methods. Binary logistic regression was used to determine the association between dependent and independent variables. The average number of individuals per Insecticide-Treated Nets was 3.83. Nearly 68.5% persons had willingness to buy Insecticide-Treated Nets if they have access to these Nets. The median maximum price a person is willingness to pay for blue rectangular Insecticide-Treated Net was 20 ETB. People had willingness to pay 30 ETB for blue and white conical insecticide-treated nets. Working on knowledge of malaria (OR=0.68, CI (0.47, 0.98; p<0.05), perceived benefit of Insecticide-Treated Nets (OR=0.28, CI (0.2-0.4; p<0.05), perceived susceptibility (OR=0.64(0.44-0.93; p<0.05) and perceived severity of malaria (OR=0.65(0.47-0.91, p<0.05) had significant association with a willingness to pay Insecticide-Treated Nets. Respondents who prefer Kebele/place/ to buy Insecticide-Treated Net for rectangular shape had a significant association with a willingness to pay for Insecticide-Treated Nets (OR=1.92, CI= 1.07-3.92). Promotions, products, price and place had significant association with willingness to pay for Insecticide-Treated Nets. Designing a social marketing strategy helps ensure sustainable supply of Insecticide-Treated Nets and proper use of Insecticide-Treated Nets.

Effects Of Thermal Exchange On Material Flow During Steel Thixoextrusion Process

NASA Astrophysics Data System (ADS)

Eric, Becker; Guochao, Gu; Laurent, Langlois; Raphaël, Pesci; Régis, Bigot

2011-01-01

Semisolid processing is an innovative technology for near net-shape production of components, where the metallic alloys are processed in the semisolid state. Taking advantage of the thixotropic behavior of alloys in the semisolid state, significant progress has been made in semisolid processing. However, the consequences of such behavior on the flow during thixoforming are still not completely understood. To explore and better understand the influence of the different parameters on material flow during thixoextrusion process, thixoextrusion experiments were performed using the low carbon steel C38. The billet was partially melted at high solid fraction. Effects of various process parameters including the initial billet temperature, the temperature of die, the punch speed during process and the presence of a Ceraspray layer at the interface of tool and billet were investigated through experiments and simulation. After analyzing the results thus obtained, it was identified that the aforementioned parameters mainly affect thermal exchanges between die and part. The Ceraspray layer not only plays a lubricant role, but also acts as a thermal barrier at the interface of tool and billet. Furthermore, the thermal effects can affect the material flow which is composed of various distinct zones.

Scheduling multirobot operations in manufacturing by truncated Petri nets

NASA Astrophysics Data System (ADS)

Chen, Qin; Luh, J. Y.

1995-08-01

Scheduling of operational sequences in manufacturing processes is one of the important problems in automation. Methods of applying Petri nets to model and analyze the problem with constraints on precedence relations, multiple resources allocation, etc. have been available in literature. Searching for an optimum schedule can be implemented by combining the branch-and-bound technique with the execution of the timed Petri net. The process usually produces a large Petri net which is practically not manageable. This disadvantage, however, can be handled by a truncation technique which divides the original large Petri net into several smaller size subnets. The complexity involved in the analysis of each subnet individually is greatly reduced. However, when the locally optimum schedules of the resulting subnets are combined together, it may not yield an overall optimum schedule for the original Petri net. To circumvent this problem, algorithms are developed based on the concepts of Petri net execution and modified branch-and-bound process. The developed technique is applied to a multi-robot task scheduling problem of the manufacturing work cell.

33 CFR 165.1301 - Puget Sound and Adjacent Waters in Northwestern Washington-Regulated Navigation Area.

Code of Federal Regulations, 2010 CFR

2010-07-01

... and shapes required by Part 81 of this title (72 COLREGS), display at the end of the net most distant... displayed from at least three feet above the surface of the water. (3) Vessels engaged in fishing, including...

Propagation characteristic of THz wave in camouflage net material

NASA Astrophysics Data System (ADS)

Dong, Hailong; Wang, Jiachun; Chen, Zongsheng; Lin, Zhidan; Zhao, Dapeng; Liu, Ruihuang

2017-10-01

Terahertz (THz) radar system, with excellent potentials such as high-resolution and strong penetration capability, is promising in the field of anti-camouflage. Camouflage net is processed by cutting the camouflage net material, which is fabricated on pre-processing substrate by depositing coatings with camouflage abilities in different bands, such as visible, infrared and radar. In this paper, we concentrate on the propagation characteristic of THz wave in camouflage net material. Firstly, function and structure of camouflage net were analyzed. Then the advantage and appliance of terahertz time-domain spectroscopy (THz-TDS) was introduced. And the relevant experiments were conducted by utilizing THz-TDS. The results obtained indicate that THz wave has better penetration capacity in camouflage net material, which demonstrates the feasibility of using THz radar to detect those targets covered with camouflage net.

Fabrication of near-net shape graphite/magnesium composites for large mirrors

NASA Astrophysics Data System (ADS)

Wendt, Robert; Misra, Mohan

1990-10-01

Successful development of space-based surveillance and laser systems will require large precision mirrors which are dimensionally stable under thermal, static, and dynamic (i.e., structural vibrations and retargeting) loading conditions. Among the advanced composites under consideration for large space mirrors, graphite fiber reinforced magnesium (Gr/Mg) is an ideal candidate material that can be tailored to obtain an optimum combination of properties, including a high modulus of elasticity, zero coefficient of thermal expansion, low density, and high thermal conductivity. In addition, an innovative technique, combining conventional filament winding and vacuum casting has been developed to produce near-net shape Gr/Mg composites. This approach can significantly reduce the cost of fabricating large mirrors by decreasing required machining. However, since Gr/Mg cannot be polished to a reflective surface, plating is required. This paper will review research at Martin Marietta Astronautics Group on Gr/Mg mirror blank fabrication and measured mechanical and thermal properties. Also, copper plating and polishing methods, and optical surface characteristics will be presented.

Disintegration of the net-shaped grain-boundary phase by multi-directional forging and its influence on the microstructure and properties of Cu-Ni-Si alloy

NASA Astrophysics Data System (ADS)

Zhang, Jinlong; Lu, Zhenlin; Zhao, Yuntao; Jia, Lei; Xie, Hui; Tao, Shiping

2017-09-01

Cu-Ni-Si alloys with 90% Cu content and Ni to Si ratios of 5:1 were fabricated by fusion casting, and severe plastic deformation of the Cu-Ni-Si alloy was carried out by multi-direction forging (MDF). The results showed that the as-cast and homogenized Cu-Ni-Si alloys consisted of three phases, namely the matrix phase α-Cu (Ni, Si), the reticular grain boundary phase Ni31Si12 and the precipitated phase Ni2Si. MDF significantly destroyed the net-shaped grain boundary phase, the Ni31Si12 phase and refined the grain size of the Cu matrix, and also resulted in the dissolving of Ni2Si precipitates into the Cu matrix. The effect of MDF on the conductivity of the solid solution Cu-Ni-Si alloy was very significant, with an average increase of 165.16%, and the hardness of the Cu-Ni-Si alloy also increased obviously.

The Lateral Occipital Complex shows no net response to object familiarity.

PubMed

Margalit, Eshed; Shah, Manan P; Tjan, Bosco S; Biederman, Irving; Keller, Brenton; Brenner, Rorry

2016-09-01

In 1995, Malach et al. discovered an area whose fMRI BOLD response was greater when viewing intact, familiar objects than when viewing their scrambled versions (resembling texture). Since then hundreds of studies have explored this late visual region termed the Lateral Occipital Complex (LOC), which is now known to be critical for shape perception (James, Culham, Humphrey, Milner, & Goodale, 2003). Malach et al. (1995) discounted a role of familiarity by showing that "abstract" Henry Moore sculptures, unfamiliar to the subjects, also activated this region. This characterization of LOC as a region that responds to shape independently of familiarity has been accepted but never tested with control of the same low-level features. We assessed LOC's response to objects that had identical parts in two different arrangements, one familiar and the other novel. Malach was correct: There is no net effect of familiarity in LOC. However, a multivoxel correlation analysis showed that LOC does distinguish familiar from novel objects.

Method of Manufacturing Carbon Fiber Reinforced Carbon Composite Valves

NASA Technical Reports Server (NTRS)

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor)

1998-01-01

A method for forming a carbon composite valve for internal combustion engines is discussed. The process includes the steps of braiding carbon fiber into a rope thereby forming a cylindrically shaped valve stem portion and continuing to braid said fiber while introducing into the braiding carbon fiber rope a carbon matrix plug having an outer surface in a net shape of a valve head thereby forming a valve head portion. The said carbon matrix plug acting as a mandrel over which said carbon fiber rope is braided, said carbon fiber rope and carbon matrix plug forming a valve head portion suitable for mating with a valve seat; cutting said braided carbon valve stem portion at one end to form a valve tip and cutting said braided carbon fiber after said valve head portion to form a valve face and thus provide a composite valve preform; and densifying said preform by embedding the braided carbon in a matrix of carbon to convert said valve stem portion to a valve stem and said valve head portion to a valve head thereby providing said composite valve.

Development of a 5,000 m(3) super-pressure balloon with a diamond-shaped net

NASA Astrophysics Data System (ADS)

Saito, Yoshitaka; Tanaka, Shigeki; Nakashino, Kyoichi; Matsushima, Kiyoho; Goto, Ken; Furuta, Ryosuke; Domoto, Kodai; Akita, Daisuke; Hashimoto, Hiroyuki

A light super-pressure balloon of which weight will be comparable to the weight of the zero-pressure balloon has been developed using a method to cover a balloon with a diamond-shaped net of high-tensile fibers. The goal is to fly a payload of 900 kg to the altitude of 37 km with a 300,000 m(3) balloon. A flight test of a 3,000 m(3) balloon in the tandem balloon configuration with a 15,000 m(3) zero-pressure balloon was performed in 2012. Although a small gas leak occurred in the super-pressure balloon at the differential pressure of 400 to 500 Pa, the differential pressure reached the highest value of 814 Pa and kept positive through the level flight lasting for 25 minutes due to its slow leakage. To avoid a possible stress concentration to films at the polar area, a new design setting the meridian length of the balloon gore film equal to the length of the net was adopted. A 3-m balloon with the design was developed and its capacity to resist pressure at room temperature and at -30 (°) C was checked through the ground inflation tests. In 2013, a balloon of the same model was launched in the tandem balloon configuration with 2 kg rubber balloons. It was confirmed that the balloon could withstand the maximum differential pressure of 6,280 Pa, could withstand the differential pressure of 5,600 Pa for 2 hours, and there was a small gas leak through a hole with an area of 0.4 mm(2) which was also found in the ground leakage test. These results indicated that the improvement was adequate and there was no problem for the super-pressure balloon to fly in the environment of the stratosphere except for the problem of the small gas leak. In 2014, a flight test of a 5,000 m(3) balloon will be performed. In this paper, after reviewing the method to cover a balloon with a diamond-shaped net, the current status of the development will be reported.

Two-stage coal liquefaction process

DOEpatents

Skinner, Ronald W.; Tao, John C.; Znaimer, Samuel

1985-01-01

An improved SRC-I two-stage coal liquefaction process which improves the product slate is provided. Substantially all of the net yield of 650.degree.-850.degree. F. heavy distillate from the LC-Finer is combined with the SRC process solvent, substantially all of the net 400.degree.-650.degree. F. middle distillate from the SRC section is combined with the hydrocracker solvent in the LC-Finer, and the initial boiling point of the SRC process solvent is increased sufficiently high to produce a net yield of 650.degree.-850.degree. F. heavy distillate of zero for the two-stage liquefaction process.

An analysis of the Petri net based model of the human body iron homeostasis process.

PubMed

Sackmann, Andrea; Formanowicz, Dorota; Formanowicz, Piotr; Koch, Ina; Blazewicz, Jacek

2007-02-01

In the paper a Petri net based model of the human body iron homeostasis is presented and analyzed. The body iron homeostasis is an important but not fully understood complex process. The modeling of the process presented in the paper is expressed in the language of Petri net theory. An application of this theory to the description of biological processes allows for very precise analysis of the resulting models. Here, such an analysis of the body iron homeostasis model from a mathematical point of view is given.

Multiparametric AFM reveals turgor-responsive net-like peptidoglycan architecture in live streptococci

NASA Astrophysics Data System (ADS)

Saar Dover, Ron; Bitler, Arkady; Shimoni, Eyal; Trieu-Cuot, Patrick; Shai, Yechiel

2015-05-01

Cell-wall peptidoglycan (PG) of Gram-positive bacteria is a strong and elastic multi-layer designed to resist turgor pressure and determine the cell shape and growth. Despite its crucial role, its architecture remains largely unknown. Here using high-resolution multiparametric atomic force microscopy (AFM), we studied how the structure and elasticity of PG change when subjected to increasing turgor pressure in live Group B Streptococcus. We show a new net-like arrangement of PG, which stretches and stiffens following osmotic challenge. The same structure also exists in isogenic mutants lacking surface appendages. Cell aging does not alter the elasticity of the cell wall, yet destroys the net architecture and exposes single segmented strands with the same circumferential orientation as predicted for intact glycans. Together, we show a new functional PG architecture in live Gram-positive bacteria.

Laser Engineered Net Shape (LENS) Technology for the Repair of Ni-Base Superalloy Turbine Components

NASA Astrophysics Data System (ADS)

Liu, Dejian; Lippold, John C.; Li, Jia; Rohklin, Stan R.; Vollbrecht, Justin; Grylls, Richard

2014-09-01

The capability of the laser engineered net shape (LENS) process was evaluated for the repair of casting defects and improperly machined holes in gas turbine engine components. Various repair geometries, including indentations, grooves, and through-holes, were used to simulate the actual repair of casting defects and holes in two materials: Alloy 718 and Waspaloy. The influence of LENS parameters, including laser energy density, laser scanning speed, and deposition pattern, on the repair of these defects and holes was studied. Laser surface remelting of the substrate prior to repair was used to remove machining defects and prevent heat-affected zone (HAZ) liquation cracking. Ultrasonic nondestructive evaluation techniques were used as a possible approach for detecting lack-of-fusion in repairs. Overall, Alloy 718 exhibited excellent repair weldability, with essentially no defects except for some minor porosity in repairs representative of deep through-holes and simulated large area casting defects. In contrast, cracking was initially observed during simulated repair of Waspaloy. Both solidification cracking and HAZ liquation cracking were observed in the repairs, especially under conditions of high heat input (high laser power and/or low scanning speed). For Waspaloy, the degree of cracking was significantly reduced and, in most cases, completely eliminated by the combination of low laser energy density and relatively high laser scanning speeds. It was found that through-hole repairs of Waspaloy made using a fine powder size exhibited excellent repair weldability and were crack-free relative to repairs using coarser powder. Simulated deep (7.4 mm) blind-hole repairs, representative of an actual Waspaloy combustor case, were successfully produced by the combination use of fine powder and relatively high laser scanning speeds.

Space Shuttle inflatable training articles

NASA Technical Reports Server (NTRS)

West, M. L.

1984-01-01

The design, development, construction, and testing of the Long Duration Exposure Facility inflatable and the space telescope training articles are discussed. While these articles are of similar nature, materials, and construction, they vary in size and present different problems with regards to size, shape, gross/net lift, and balance.

Automated inspection of bread and loaves

NASA Astrophysics Data System (ADS)

Batchelor, Bruce G.

1993-08-01

The prospects for building practical automated inspection machines, capable of detecting the following faults in ordinary, everyday loaves are reviewed: (1) foreign bodies, using X-rays, (2) texture changes, using glancing illumination, mathematical morphology and Neural Net learning techniques, and (3) shape deformations, using structured lighting and simple geometry.

Plasma Processing of Lunar Regolith Simulant for Diverse Applications

NASA Technical Reports Server (NTRS)

Schofield, Elizabeth C.; Sen, Subhayu; O'Dell, J. Scott

2008-01-01

Versatile manufacturing technologies for extracting resources from the moon are needed to support future space missions. Of particular interest is the production of gases and metals from lunar resources for life support, propulsion, and in-space fabrication. Deposits made from lunar regolith could yield highly emissive coatings and near-net shaped parts for replacement or repair of critical components. Equally important is development of high fidelity lunar simulants for ground based validation of potential lunar surface operations. Described herein is an innovative plasma processing technique for insitu production of gases, metals, coatings, and deposits from lunar regolith, and synthesis of high fidelity lunar simulant from NASA issued lunar simulant JSC-1. Initial plasma reduction trials of JSC-1 lunar simulant have indicated production of metallic iron and magnesium. Evolution of carbon monoxide has been detected subsequent to reduction of the simulant using the plasma process. Plasma processing of the simulant has also resulted in glassy phases resembling the volcanic glass and agglutinates found in lunar regolith. Complete and partial glassy phase deposits have been obtained by varying the plasma process variables. Experimental techniques, product characterization, and process gas analysis will be discussed.

Process Evaluation of AISI 4340 Steel Manufactured by Laser Powder Bed Fusion

NASA Astrophysics Data System (ADS)

Jelis, Elias; Hespos, Michael R.; Ravindra, Nuggehalli M.

2018-01-01

Laser powder bed fusion (L-PBF) involves the consolidation of metal powder, layer by layer, through laser melting and solidification. In this study, process parameters are optimized for AISI 4340 steel to produce dense and homogeneous structures. The optimized process parameters produce mechanical properties at the center of the build plate that are comparable to wrought in the vertical and horizontal orientations after heat treatment and machining. Four subsequent builds are filled with specimens to evaluate the mechanical behavior as a function of location and orientation. Variations in the mechanical properties are likely due to recoater blade interactions with the powder and uneven gas flow. The results obtained in this study are analyzed to assess the reliability and reproducibility of the process. A different build evaluates the performance of near-net-shaped tensile specimens angled 35°-90° from the build plate surface (horizontal). Ductility measurements and surface roughness vary significantly as a function of the build angle. In the stress-relieved and as-built conditions, the mechanical behavior of vertically oriented specimens exhibits somewhat lower and more variable ductility than horizontally oriented specimens. Therefore, several process variables affect the mechanical properties of parts produced by the L-PBF process.

Tailored Net-Shape Powder Composites by Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Khaleghi, Evan Aryan

This dissertation investigates the ability to produce net-shape and tailored composites in spark plasma sintering (SPS), with an analysis of how grain growth, densification, and mechanical properties are affected. Using alumina and four progressively anisotropic dies, we studied the impact of specimen shape on densification. We found specimen shape had an impact on overall densification, but no impact on localized properties. We expected areas of the specimen to densify differently, or have higher grain growth, based on current anisotropy in the specimen during sintering, and preliminary results indicated this, but further investigation showed this did not occur. Overall average grain size and porosity decreased as shape complexity increased. In Fe-V-C steel, we mechanical alloyed two rapidly solidified powders, and used spark sintering to retain the properties imparted during the rapid solidification. We noticed VC grains being produced during densification, which improved the final properties. We conducted spark plasma extrusion (SPE) of aluminum to understand the effect on microstructure. We found, through an analysis of the grain structure, that SPE did have a grain deformation potential, and grain size was severely decreased compared to conventional sintering. Dynamic recrystallization did not occur, due to the reduced temperatures we were able to extrude with SPS. Finally, we examined whether there were particular sintering conditions for SPS that reduced the complexity of the grain growth and porosity relationship to one similar to conventional sintering, of the form G = k G0 ε -1/. We found that although a reasonable case could be made for free sintering, as found in the literature, for hot-pressing and SPS the conditions required go against the common knowledge in grain growth and densification kinetics. We were able to fit our data very well to the model, but the correlated results do not make physical sense.

Modeling of the U1 snRNP assembly pathway in alternative splicing in human cells using Petri nets.

PubMed

Kielbassa, J; Bortfeldt, R; Schuster, S; Koch, I

2009-02-01

The investigation of spliceosomal processes is currently a topic of intense research in molecular biology. In the molecular mechanism of alternative splicing, a multi-protein-RNA complex - the spliceosome - plays a crucial role. To understand the biological processes of alternative splicing, it is essential to comprehend the biogenesis of the spliceosome. In this paper, we propose the first abstract model of the regulatory assembly pathway of the human spliceosomal subunit U1. Using Petri nets, we describe its highly ordered assembly that takes place in a stepwise manner. Petri net theory represents a mathematical formalism to model and analyze systems with concurrent processes at different abstraction levels with the possibility to combine them into a uniform description language. There exist many approaches to determine static and dynamic properties of Petri nets, which can be applied to analyze biochemical systems. In addition, Petri net tools usually provide intuitively understandable graphical network representations, which facilitate the dialog between experimentalists and theoreticians. Our Petri net model covers binding, transport, signaling, and covalent modification processes. Through the computation of structural and behavioral Petri net properties and their interpretation in biological terms, we validate our model and use it to get a better understanding of the complex processes of the assembly pathway. We can explain the basic network behavior, using minimal T-invariants which represent special pathways through the network. We find linear as well as cyclic pathways. We determine the P-invariants that represent conserved moieties in a network. The simulation of the net demonstrates the importance of the stability of complexes during the maturation pathway. We can show that complexes that dissociate too fast, hinder the formation of the complete U1 snRNP.

Long lasting insecticidal net use and its associated factors in Limmu Seka District, South West Ethiopia.

PubMed

Hambisa, Mitiku Teshome; Debela, Tessema; Dessie, Yadeta; Gobena, Tesfaye

2018-01-10

Many countries in sub-Saharan Africa, including Ethiopia, are focusing on the distribution of Long Lasting Insecticidal Nets (LLINs) to combat malaria. However, utilization of the LLIN is low when compared with LLIN possession because of various factors. This study was conducted to measure the actual LLIN usage and identify factors associated with its utilization in Limmu Seka District, South West Ethiopia. A community based cross-sectional survey was conducted among 830 households from December 25, 2011 to February 29, 2012. A total of 830 households were selected by stratified systematic sampling and surveyed. Ninety percent of those surveyed owned LLINs and 68.3% reported that someone had slept under the net on the night prior to the survey. The factors associated with LLIN usage were knowledge of the mode of malaria transmission (AOR; 0.086, 95% CI 0.03, 0.24), the preferred conical shapes of the LLIN (AOR; 1.6, 95% CI 1.31, 4.1), receiving information about their use from Health Extension Workers (HEWs) (AOR; 2.4, 95% CI 1.5, 3.9), hearing media campaigns (AOR; 3.2 95% CI 3.5, 9.2), education at a health facility (AOR; 2 95% CI 1.5, 3.9) or having a family size of three or less (AOR; 2.1, 95% CI 1.3, 3.5). Although ownership of Long Lasting Insecticidal Nets was high at 90%, the actual usage of LLIN was low, and not all family members were protected. Promoting the usage of LLINs utilization by those at most risk, especially the conical shaped ones, through intensified health education using HEWs and mass media campaigns at all health facilities, schools and communities will improve LLIN utilization.

A systematic petri net approach for multiple-scale modeling and simulation of biochemical processes.

PubMed

Chen, Ming; Hu, Minjie; Hofestädt, Ralf

2011-06-01

A method to exploit hybrid Petri nets for modeling and simulating biochemical processes in a systematic way was introduced. Both molecular biology and biochemical engineering aspects are manipulated. With discrete and continuous elements, the hybrid Petri nets can easily handle biochemical factors such as metabolites concentration and kinetic behaviors. It is possible to translate both molecular biological behavior and biochemical processes workflow into hybrid Petri nets in a natural manner. As an example, penicillin production bioprocess is modeled to illustrate the concepts of the methodology. Results of the dynamic of production parameters in the bioprocess were simulated and observed diagrammatically. Current problems and post-genomic perspectives were also discussed.

Substance P as a putative efferent transmitter mediates GABAergic inhibition in mouse taste buds.

PubMed

Huang, Anthony Y; Wu, Sandy Y

2018-04-01

Capsaicin-mediated modulation of taste nerve responses is thought to be produced indirectly by the actions of neuropeptides, for example, CGRP and substance P (SP), on taste cells implying they play a role in taste sensitivity. During the processing of gustatory information in taste buds, CGRP shapes peripheral taste signals via serotonergic signalling. The underlying assumption has been that SP exerts its effects on taste transmitter secretion in taste buds of mice. To test this assumption, we investigated the net effect of SP on taste-evoked ATP secretion from mouse taste buds, using functional calcium imaging with CHO cells expressing high-affinity transmitter receptors as cellular biosensors. Our results showed that SP elicited PLC activation-dependent intracellular Ca 2+ transients in taste cells via neurokinin 1 receptors, most likely on glutamate-aspartate transporter-expressing Type I cells. Furthermore, SP caused Type I cells to secrete GABA. Combined with the recent findings that GABA depresses taste-evoked ATP secretion, the current results indicate that SP elicited secretion of GABA, which provided negative feedback onto Type II (receptor) cells to reduce taste-evoked ATP secretion. These findings are consistent with a role for SP as an inhibitory transmitter that shapes the peripheral taste signals, via GABAergic signalling, during the processing of gustatory information in taste buds. Notably, the results suggest that SP is intimately associated with GABA in mammalian taste signal processing and demonstrate an unanticipated route for sensory information flow within the taste bud. © 2018 The British Pharmacological Society.

Dynamics of film. [two dimensional continua theory

NASA Technical Reports Server (NTRS)

Zak, M.

1979-01-01

The general theory of films as two-dimensional continua are elaborated upon. As physical realizations of such a model this paper examines: inextensible films, elastic films, and nets. The suggested dynamic equations have enabled us to find out the characteristic speeds of wave propagation of the invariants of external and internal geometry and formulate the criteria of instability of their shape. Also included herein is a detailed account of the equation describing the film motions beyond the limits of the shape stability accompanied by the formation of wrinkles. The theory is illustrated by examples.

Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers

USDA-ARS?s Scientific Manuscript database

The precipitation legacy effect, defined as the impact of historical precipitation (PPT) on extant ecosystem dynamics, has been recognized as an important driver in shaping the temporal variability of dryland aboveground net primary production (ANPP) and soil respiration. How the PPT legacy influenc...

Tuning the sapphire EFG process to the growth of Al2O3/YAG/ZrO2:Y eutectic

NASA Astrophysics Data System (ADS)

Carroz, L.; Duffar, T.

2018-05-01

In this work, a model is proposed, in order to analytically study the working point of the Edge defined Film-fed Growth (EFG) pulling of crystal plates. The model takes into account the heat equilibrium at the interface and the pressure equilibrium across the meniscus. It is validated on an industrial device dedicated to the pulling of sapphire ribbons. Then, the model is applied to pulling ceramic alloy plates, of the ternary eutectic Al2O3/YAG/ZrO2:Y. This allowed understanding the experimental difficulties of pulling this new material and suggested improvements of the control software. From these results, pulling net shaped ceramic alloy plates was successful in the same industrial equipment as used for sapphire.

Micro pumping with cardiomyocyte-polymer hybrid.

PubMed

Park, Jungyul; Kim, Il Chaek; Baek, Jeongeun; Cha, Misun; Kim, Jinseok; Park, Sukho; Lee, Junghoon; Kim, Byungkyu

2007-10-01

This paper presents a hybrid micropump actuated by the up-down motion of a dome shaped cell-polymer membrane composite. The contractile force induced from self-beating cardiomyocytes cultured on the membrane causes shrinkage and relaxation of a microchamber, leading to a flow in a microchannel. Flow direction is controlled by the geometry of diffuser/nozzle in the microchannel. The fabrication process is noninvasive to cells, thus, cardiomyocytes can robustly maintain their activity for a long time. The fluid motion in the microchannel was monitored by tracking 2 microm polystyrene beads. A net flow rate of 0.226 nl min(-1) was obtained in our microscale device. Our device demonstrates a unique performance of a cell-microdevice hybrid lab-on-a-chip that does not require any external power source, preventing electrical or heat shock to analytes.

Optimizing model: insemination, replacement, seasonal production, and cash flow.

PubMed

DeLorenzo, M A; Spreen, T H; Bryan, G R; Beede, D K; Van Arendonk, J A

1992-03-01

Dynamic programming to solve the Markov decision process problem of optimal insemination and replacement decisions was adapted to address large dairy herd management decision problems in the US. Expected net present values of cow states (151,200) were used to determine the optimal policy. States were specified by class of parity (n = 12), production level (n = 15), month of calving (n = 12), month of lactation (n = 16), and days open (n = 7). Methodology optimized decisions based on net present value of an individual cow and all replacements over a 20-yr decision horizon. Length of decision horizon was chosen to ensure that optimal policies were determined for an infinite planning horizon. Optimization took 286 s of central processing unit time. The final probability transition matrix was determined, in part, by the optimal policy. It was estimated iteratively to determine post-optimization steady state herd structure, milk production, replacement, feed inputs and costs, and resulting cash flow on a calendar month and annual basis if optimal policies were implemented. Implementation of the model included seasonal effects on lactation curve shapes, estrus detection rates, pregnancy rates, milk prices, replacement costs, cull prices, and genetic progress. Other inputs included calf values, values of dietary TDN and CP per kilogram, and discount rate. Stochastic elements included conception (and, thus, subsequent freshening), cow milk production level within herd, and survival. Validation of optimized solutions was by separate simulation model, which implemented policies on a simulated herd and also described herd dynamics during transition to optimized structure.

68Ga-DOTA-TOC uptake in neuroendocrine tumour and healthy tissue: differentiation of physiological uptake and pathological processes in PET/CT.

PubMed

Kroiss, A; Putzer, D; Decristoforo, C; Uprimny, C; Warwitz, B; Nilica, B; Gabriel, M; Kendler, D; Waitz, D; Widmann, G; Virgolini, I J

2013-04-01

We wanted to establish the range of (68)Ga-DOTA-TOC uptake in liver and bone metastases of patients with neuroendocrine tumours (NET) and to establish the range of its uptake in pancreatic NET. This would allow differentiation between physiological uptake and tumour-related somatostatin receptor expression in the pancreas (including the uncinate process), liver and bone. Finally, we wanted to test for differences in patients with NET, either treated or not treated with peptide receptor radionuclide therapy (PRRT). In 249 patients, 390 (68)Ga-DOTA-TOC PET/CT studies were performed. The clinical indications for PET/CT were gastroenteropancreatic NET (194 studies), nongastroenteropancreatic NET (origin in the lung and rectum; 46 studies), NET of unknown primary (111 studies), phaeochromocytoma/glomus tumours (18 studies), and radioiodine-negative metastatic thyroid carcinoma (21 studies). SUVmax (mean ± standard deviation) values of (68)Ga-DOTA-TOC were 29.8 ± 16.5 in 162 liver metastases, 19.8 ± 18.8 in 89 bone metastases and 34.6 ± 17.1 in 43 pancreatic NET (33.6 ± 14.3 in 30 tumours of the uncinate process and 36.3 ± 21.5 in 13 tumours of the pancreatic tail). A significant difference in SUVmax (p < 0.02) was found in liver metastases of NET patients treated with PRRT. There were significant differences in SUVmax between nonmalignant and malignant tissue for both bone and liver metastases and for pancreatic NET including the uncinate process (p < 0.0001). At a cut-off value of 17.1 the specificity and sensitivity of SUVmax for differentiating tumours in the uncinate process were 93.6 % and 90.0 %, respectively (p < 0.0001). (68)Ga-DOTA-TOC is an excellent tracer for the imaging of tumours expressing somatostatin receptors on the tumour cell surface, facilitating the detection of even small tumour lesions. The noninvasive PET/CT approach by measurement of regional SUVmax can offer important clinical information to distinguish between physiological and pathological somatostatin receptor expression, especially in the uncinate process. PRRT does not significantly influence SUVmax, except in liver metastases of patients with NET.

A versatile petri net based architecture for modeling and simulation of complex biological processes.

PubMed

Nagasaki, Masao; Doi, Atsushi; Matsuno, Hiroshi; Miyano, Satoru

2004-01-01

The research on modeling and simulation of complex biological systems is getting more important in Systems Biology. In this respect, we have developed Hybrid Function Petri net (HFPN) that was newly developed from existing Petri net because of their intuitive graphical representation and their capabilities for mathematical analyses. However, in the process of modeling metabolic, gene regulatory or signal transduction pathways with the architecture, we have realized three extensions of HFPN, (i) an entity should be extended to contain more than one value, (ii) an entity should be extended to handle other primitive types, e.g. boolean, string, (iii) an entity should be extended to handle more advanced type called object that consists of variables and methods, are necessary for modeling biological systems with Petri net based architecture. To deal with it, we define a new enhanced Petri net called hybrid functional Petri net with extension (HFPNe). To demonstrate the effectiveness of the enhancements, we model and simulate with HFPNe four biological processes that are diffcult to represent with the previous architecture HFPN.

Electron Beam Freeform Fabrication for Cost Effective Near-Net Shape Manufacturing

NASA Technical Reports Server (NTRS)

Taminger, Karen M.; Hafley, Robert A.

2006-01-01

Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF3), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. EBF3 deposits of 2219 aluminium and Ti-6Al-4V have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cm3/hr (150 in3/hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

Electron Beam Freeform Fabrication (EBF3) for Cost Effective Near-Net Shape Manufacturing

NASA Technical Reports Server (NTRS)

Taminger, Karen M.; Hafley, Robert A.

2006-01-01

Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF3), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. EBF3 deposits of 2219 aluminium and Ti-6Al-4V have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cubic centimeters per hour (150 in3/hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

Improved silicon nitride for advanced heat engines

NASA Technical Reports Server (NTRS)

Yeh, Hun C.; Fang, Ho T.

1987-01-01

The technology base required to fabricate silicon nitride components with the strength, reliability, and reproducibility necessary for actual heat engine applications is presented. Task 2 was set up to develop test bars with high Weibull slope and greater high temperature strength, and to conduct an initial net shape component fabrication evaluation. Screening experiments were performed in Task 7 on advanced materials and processing for input to Task 2. The technical efforts performed in the second year of a 5-yr program are covered. The first iteration of Task 2 was completed as planned. Two half-replicated, fractional factorial (2 sup 5), statistically designed matrix experiments were conducted. These experiments have identified Denka 9FW Si3N4 as an alternate raw material to GTE SN502 Si3N4 for subsequent process evaluation. A detailed statistical analysis was conducted to correlate processing conditions with as-processed test bar properties. One processing condition produced a material with a 97 ksi average room temperature MOR (100 percent of goal) with 13.2 Weibull slope (83 percent of goal); another condition produced 86 ksi (6 percent over baseline) room temperature strength with a Weibull slope of 20 (125 percent of goal).

Theoretical Estimation of Thermal Effects in Drilling of Woven Carbon Fiber Composite

PubMed Central

Díaz-Álvarez, José; Olmedo, Alvaro; Santiuste, Carlos; Miguélez, María Henar

2014-01-01

Carbon Fiber Reinforced Polymer (CFRPs) composites are extensively used in structural applications due to their attractive properties. Although the components are usually made near net shape, machining processes are needed to achieve dimensional tolerance and assembly requirements. Drilling is a common operation required for further mechanical joining of the components. CFRPs are vulnerable to processing induced damage; mainly delamination, fiber pull-out, and thermal degradation, drilling induced defects being one of the main causes of component rejection during manufacturing processes. Despite the importance of analyzing thermal phenomena involved in the machining of composites, only few authors have focused their attention on this problem, most of them using an experimental approach. The temperature at the workpiece could affect surface quality of the component and its measurement during processing is difficult. The estimation of the amount of heat generated during drilling is important; however, numerical modeling of drilling processes involves a high computational cost. This paper presents a combined approach to thermal analysis of composite drilling, using both an analytical estimation of heat generated during drilling and numerical modeling for heat propagation. Promising results for indirect detection of risk of thermal damage, through the measurement of thrust force and cutting torque, are obtained. PMID:28788685

Experimental observation of different soliton types in a net-normal group-dispersion fiber laser.

PubMed

Feng, Zhongyao; Rong, Qiangzhou; Qiao, Xueguang; Shao, Zhihua; Su, Dan

2014-09-20

Different soliton types are observed in a net-normal group-dispersion fiber laser based on nonlinear polarization rotation for passive mode locking. The proposed laser can deliver a dispersion-managed soliton, typical dissipation solitons, and a quasi-harmonic mode-locked pulse, a soliton bundle, and especially a dark pulse by only appropriately adjusting the linear cavity phase delay bias using one polarization controller at the fixed pump power. These nonlinear waves show different features, including the spectral shapes and time traces. The experimental observations show that the five soliton types could exist in the same laser cavity, which implies that integrable systems, dissipative systems, and dark pulse regimes can transfer and be switched in a passively mode-locked laser. Our studies not only verify the numeral simulation of the different soliton-types formation in a net-normal group-dispersion operation but also provide insight into Ginzburg-Landau equation systems.

`Googling' Terrorists: Are Northern Irish Terrorists Visible on Internet Search Engines?

NASA Astrophysics Data System (ADS)

Reilly, P.

In this chapter, the analysis suggests that Northern Irish terrorists are not visible on Web search engines when net users employ conventional Internet search techniques. Editors of mass media organisations traditionally have had the ability to decide whether a terrorist atrocity is `newsworthy,' controlling the `oxygen' supply that sustains all forms of terrorism. This process, also known as `gatekeeping,' is often influenced by the norms of social responsibility, or alternatively, with regard to the interests of the advertisers and corporate sponsors that sustain mass media organisations. The analysis presented in this chapter suggests that Internet search engines can also be characterised as `gatekeepers,' albeit without the ability to shape the content of Websites before it reaches net users. Instead, Internet search engines give priority retrieval to certain Websites within their directory, pointing net users towards these Websites rather than others on the Internet. Net users are more likely to click on links to the more `visible' Websites on Internet search engine directories, these sites invariably being the highest `ranked' in response to a particular search query. A number of factors including the design of the Website and the number of links to external sites determine the `visibility' of a Website on Internet search engines. The study suggests that Northern Irish terrorists and their sympathisers are unlikely to achieve a greater degree of `visibility' online than they enjoy in the conventional mass media through the perpetration of atrocities. Although these groups may have a greater degree of freedom on the Internet to publicise their ideologies, they are still likely to be speaking to the converted or members of the press. Although it is easier to locate Northern Irish terrorist organisations on Internet search engines by linking in via ideology, ideological description searches, such as `Irish Republican' and `Ulster Loyalist,' are more likely to generate links pointing towards the sites of research institutes and independent media organisations than sites sympathetic to Northern Irish terrorist organisations. The chapter argues that Northern Irish terrorists are only visible on search engines if net users select the correct search terms.

Effect of the Microstructure and Distribution of the Second Phase on the Stress Corrosion Cracking of Biomedical Mg-Zn-Zr-xSr Alloys

PubMed Central

Chen, Lianxi; Sheng, Yinying; Zhao, Xueyang; Liu, Hui; Li, Wei

2018-01-01

The stress corrosion cracking (SCC) properties of the bi-directional forged (BDF) Mg-4Zn-0.6Zr-xSr (ZK40-xSr, x = 0, 0.4, 0.8, 1.2, 1.6 wt %) alloys were studied by the slow strain rate tensile (SSRT) testing in modified simulated body fluid (m-SBF). The average grain size of the BDF alloys were approximately two orders of magnitude smaller than those of the as-cast alloys. However, grain refinement increased the hydrogen embrittlement effect, leading to a higher SCC susceptibility in the BDF ZK40-0/0.4Sr alloys. Apart from the grain refinements effect, the forging process also changed the distribution of second phase from the net-like shape along the grain boundary to a uniformly isolated island shape in the BDF alloys. The SCC susceptibility of the BDF ZK40-1.2/1.6Sr alloys were lower than those of the as-cast alloys. The change of distribution of the second phase suppressed the adverse effect of Sr on the SCC susceptibility in high Sr–containing magnesium alloys. The results indicated the stress corrosion behavior of magnesium alloys was related to the average grain size of matrix and the distribution and shape of the second phase. PMID:29614043

Improving Patient Safety in Public Hospitals: Developing Standard Measures to Track Medical Errors and Process Breakdowns.

PubMed

Ackerman, Sara L; Gourley, Gato; Le, Gem; Williams, Pamela; Yazdany, Jinoos; Sarkar, Urmimala

2018-03-14

The aim of the study was to develop standards for tracking patient safety gaps in ambulatory care in safety net health systems. Leaders from five California safety net health systems were invited to participate in a modified Delphi process sponsored by the Safety Promotion Action Research and Knowledge Network (SPARKNet) and the California Safety Net Institute in 2016. During each of the three Delphi rounds, the feasibility and validity of 13 proposed patient safety measures were discussed and prioritized. Surveys and transcripts from the meetings were analyzed to understand the decision-making process. The Delphi process included eight panelists. Consensus was reached to adopt 9 of 13 proposed measures. All 9 measures were unanimously considered valid, but concern was expressed about the feasibility of implementing several of the measures. Although safety net health systems face high barriers to standardized measurement, our study demonstrates that consensus can be reached on acceptable and feasible methods for tracking patient safety gaps in safety net health systems. If accompanied by the active participation key stakeholder groups, including patients, clinicians, staff, data system professionals, and health system leaders, the consensus measures reported here represent one step toward improving ambulatory patient safety in safety net health systems.

A mixture neural net for multispectral imaging spectrometer processing

NASA Technical Reports Server (NTRS)

Casasent, David; Slagle, Timothy

1990-01-01

Each spatial region viewed by an imaging spectrometer contains various elements in a mixture. The elements present and the amount of each are to be determined. A neural net solution is considered. Initial optical neural net hardware is described. The first simulations on the component requirements of a neural net are considered. The pseudoinverse solution is shown to not suffice, i.e. a neural net solution is required.

NASA Net Zero Energy Buildings Roadmap

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

Pless, S.; Scheib, J.; Torcellini, P.

In preparation for the time-phased net zero energy requirement for new federal buildings starting in 2020, set forth in Executive Order 13514, NASA requested that the National Renewable Energy Laboratory (NREL) to develop a roadmap for NASA's compliance. NASA detailed a Statement of Work that requested information on strategic, organizational, and tactical aspects of net zero energy buildings. In response, this document presents a high-level approach to net zero energy planning, design, construction, and operations, based on NREL's first-hand experience procuring net zero energy construction, and based on NREL and other industry research on net zero energy feasibility. The strategicmore » approach to net zero energy starts with an interpretation of the executive order language relating to net zero energy. Specifically, this roadmap defines a net zero energy acquisition process as one that sets an aggressive energy use intensity goal for the building in project planning, meets the reduced demand goal through energy efficiency strategies and technologies, then adds renewable energy in a prioritized manner, using building-associated, emission- free sources first, to offset the annual energy use required at the building; the net zero energy process extends through the life of the building, requiring a balance of energy use and production in each calendar year.« less

Entropy, pricing and macroeconomics of pumped-storage systems

NASA Astrophysics Data System (ADS)

Karakatsanis, Georgios; Mamassis, Nikos; Koutsoyiannis, Demetris; Efstratiadis, Andreas

2014-05-01

We propose a pricing scheme for the enhancement of macroeconomic performance of pumped-storage systems, based on the statistical properties of both geophysical and economic variables. The main argument consists in the need of a context of economic values concerning the hub energy resource; defined as the resource that comprises the reference energy currency for all involved renewable energy sources (RES) and discounts all related uncertainty. In the case of pumped-storage systems the hub resource is the reservoir's water, as a benchmark for all connected intermittent RES. The uncertainty of all involved natural and economic processes is statistically quantifiable by entropy. It is the relation between the entropies of all involved RES that shapes the macroeconomic state of the integrated pumped-storage system. Consequently, there must be consideration on the entropy of wind, solar and precipitation patterns, as well as on the entropy of economic processes -such as demand preferences on either current energy use or storage for future availability. For pumped-storage macroeconomics, a price on the reservoir's capacity scarcity should also be imposed in order to shape a pricing field with upper and lower limits for the long-term stability of the pricing range and positive net energy benefits, which is the primary issue of the generalized deployment of pumped-storage technology. Keywords: Entropy, uncertainty, pricing, hub energy resource, RES, energy storage, capacity scarcity, macroeconomics

IMPLEMENTATION OF A CAPE-OPEN COMPLIANT PROCESS SIMULATOR USING MICROSOFT'S VISUAL STUDIO.NET AND THE .NET FRAMEWORK

EPA Science Inventory

The United States Environmental Protection Agency is developing a Computer
Aided Process Engineering (CAPE) software tool for the metal finishing
industry that helps users design efficient metal finishing processes that
are less polluting to the environment. Metal finish...

Scalable Probabilistic Inference for Global Seismic Monitoring

NASA Astrophysics Data System (ADS)

Arora, N. S.; Dear, T.; Russell, S.

2011-12-01

We describe a probabilistic generative model for seismic events, their transmission through the earth, and their detection (or mis-detection) at seismic stations. We also describe an inference algorithm that constructs the most probable event bulletin explaining the observed set of detections. The model and inference are called NET-VISA (network processing vertically integrated seismic analysis) and is designed to replace the current automated network processing at the IDC, the SEL3 bulletin. Our results (attached table) demonstrate that NET-VISA significantly outperforms SEL3 by reducing the missed events from 30.3% down to 12.5%. The difference is even more dramatic for smaller magnitude events. NET-VISA has no difficulty in locating nuclear explosions as well. The attached figure demonstrates the location predicted by NET-VISA versus other bulletins for the second DPRK event. Further evaluation on dense regional networks demonstrates that NET-VISA finds many events missed in the LEB bulletin, which is produced by the human analysts. Large aftershock sequences, as produced by the 2004 December Sumatra earthquake and the 2011 March Tohoku earthquake, can pose a significant load for automated processing, often delaying the IDC bulletins by weeks or months. Indeed these sequences can overload the serial NET-VISA inference as well. We describe an enhancement to NET-VISA to make it multi-threaded, and hence take full advantage of the processing power of multi-core and -cpu machines. Our experiments show that the new inference algorithm is able to achieve 80% efficiency in parallel speedup.

The Seine Net--An Overlooked Environmental Testing Tool

ERIC Educational Resources Information Center

DuPont, Sidney I.

1977-01-01

Through seining individuals, families, camps, and schools can continuingly test the aquatic life just beyond the waterline. This article discusses the process of using a seine net and what can be found in the net. (NQ)

Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

NASA Technical Reports Server (NTRS)

Singh, M.; Levine, S. R.

1995-01-01

A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

Microstructure and tensile properties after thermohydrogen processing of Ti-6 Al-4V.

PubMed

Guitar, A; Vigna, G; Luppo, M I

2009-04-01

Thermohydrogen processing (THP), a technique in which hydrogen is used as a temporary alloying element, can refine the microstructure and improve the final mechanical properties of the Ti-6 Al-4V alloy. THP allows microstructural modification of titanium alloys near net shape such as biomaterial components obtained by powder metallurgy and castings, since it does not require mechanical working. Two THP, called THP-A and THP-B, have been evaluated in samples of Ti-6Al-4V with a coarse and lamellar microstructure typical of castings and powder metallurgy. The THP-A is based in the eutectoid decomposition of the beta(H) phase to alpha phase and hydride phase. The THP-B is based in the isothermal decomposition of alpha('') martensite phase, obtained by quenching of hydrogenated samples. The refinement of the microstructure due to THP has been evaluated by means of optical and electron microscopy. Tensile tests showed that while both processes were able to increase the strength of the alloy as compared with the starting material, the ductility in samples subjected to THP-B was severely reduced.

Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing.

PubMed

Ding, Donghong; Pan, Zengxi; van Duin, Stephen; Li, Huijun; Shen, Chen

2016-08-03

Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production.

Cell Structure Evolution of Aluminum Foams Under Reduced Pressure Foaming

NASA Astrophysics Data System (ADS)

Cao, Zhuokun; Yu, Yang; Li, Min; Luo, Hongjie

2016-09-01

Ti-H particles are used to increase the gas content in aluminum melts for reduced pressure foaming. This paper reports on the RPF process of AlCa alloy by adding TiH2, but in smaller amounts compared to traditional process. TiH2 is completely decomposed by stirring the melt, following which reduced pressure is applied. TiH2 is not added as the blowing agent; instead, it is added for increasing the H2 concentration in the liquid AlCa melt. It is shown that pressure change induces further release of hydrogen from Ti phase. It is also found that foam collapse is caused by the fast bubble coalescing during pressure reducing procedure, and the instability of liquid film is related to the significant increase in critical thickness of film rupture. A combination of lower amounts of TiH2, coupled with reduced pressure, is another way of increasing hydrogen content in the liquid aluminum. A key benefit of this process is that it provides time to transfer the molten metal to a mold and then apply the reduced pressure to produce net shape foam parts.

Microstructure and corrosion behavior of laser processed NiTi alloy.

PubMed

Marattukalam, Jithin J; Singh, Amit Kumar; Datta, Susmit; Das, Mitun; Balla, Vamsi Krishna; Bontha, Srikanth; Kalpathy, Sreeram K

2015-12-01

Laser Engineered Net Shaping (LENS™), a commercially available additive manufacturing technology, has been used to fabricate dense equiatomic NiTi alloy components. The primary aim of this work is to study the effect of laser power and scan speed on microstructure, phase constituents, hardness and corrosion behavior of laser processed NiTi alloy. The results showed retention of large amount of high-temperature austenite phase at room temperature due to high cooling rates associated with laser processing. The high amount of austenite in these samples increased the hardness. The grain size and corrosion resistance were found to increase with laser power. The surface energy of NiTi alloy, calculated using contact angles, decreased from 61 mN/m to 56 mN/m with increase in laser energy density from 20 J/mm(2) to 80 J/mm(2). The decrease in surface energy shifted the corrosion potentials to nobler direction and decreased the corrosion current. Under present experimental conditions the laser power found to have strong influence on microstructure, phase constituents and corrosion resistance of NiTi alloy. Copyright © 2015 Elsevier B.V. All rights reserved.

Evaluation of Braided Stiffener Concepts for Transport Aircraft Wing Structure Applications

NASA Technical Reports Server (NTRS)

Deaton, Jerry W.; Dexter, H. Benson (Editor); Markus, Alan; Rohwer, Kim

1995-01-01

Braided composite materials have potential for application in aircraft structures. Stiffeners, wing spars, floor beams, and fuselage frames are examples where braided composites could find application if cost effective processing and damage requirements are met. Braiding is an automated process for obtaining near-net shape preforms for fabrication of components for structural applications. Previous test results on braided composite materials obtained at NASA Langley indicate that damage tolerance requirements can be met for some applications. In addition, the braiding industry is taking steps to increase the material through-put to be more competitive with other preform fabrication processes. Data are presented on the compressive behavior of three braided stiffener preform fabric constructions as determined from individual stiffener crippling test and three stiffener wide panel tests. Stiffener and panel fabrication are described and compression data presented for specimens tested with and without impact damage. In addition, data are also presented on the compressive behavior of the stitched stiffener preform construction currently being used by McDonnell Douglas Aerospace in the NASA ACT wing development program.

Influence of Powder Metallurgical Processing Routes on Phase Formations in a Multicomponent NbSi-Alloy

NASA Astrophysics Data System (ADS)

Seemüller, C.; Hartwig, T.; Mulser, M.; Adkins, N.; Wickins, M.; Heilmaier, M.

2014-09-01

Refractory metal silicide composites on the basis of Nbss-Nb5Si3 have been investigated as potential alternatives for nickel-base superalloys for years because of their low densities and good high-temperature strengths. NbSi-based composites are typically produced by arc-melting or casting. Samples in this study, however, were produced by powder metallurgy because of the potential for near net-shape component fabrication with very homogeneous microstructures. Either gas atomized powder or high-energy mechanically alloyed elemental powders were compacted by powder injection molding or hot isostatic pressing. Heat treatments were applied for phase stability evaluation. Slight compositional changes (oxygen, nitrogen, or iron) introduced by the processing route, i.e., powder production and consolidation, can affect phase formations and phase transitions during the process. Special focus is put on the distinction between different silicides (Nb5Si3 and Nb3Si) and silicide modifications (α-, β-, and γ-Nb5Si3), respectively. These were evaluated by x-ray diffraction and energy-dispersive spectroscopy measurements with the additional inclusion of thermodynamic calculations using the calculated phase diagram method.

Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing

PubMed Central

Ding, Donghong; Pan, Zengxi; van Duin, Stephen; Li, Huijun; Shen, Chen

2016-01-01

Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production. PMID:28773774

Optimization of Training Sets for Neural-Net Processing of Characteristic Patterns from Vibrating Solids

NASA Technical Reports Server (NTRS)

Decker, Arthur J.

2001-01-01

Artificial neural networks have been used for a number of years to process holography-generated characteristic patterns of vibrating structures. This technology depends critically on the selection and the conditioning of the training sets. A scaling operation called folding is discussed for conditioning training sets optimally for training feed-forward neural networks to process characteristic fringe patterns. Folding allows feed-forward nets to be trained easily to detect damage-induced vibration-displacement-distribution changes as small as 10 nm. A specific application to aerospace of neural-net processing of characteristic patterns is presented to motivate the conditioning and optimization effort.

The implementation of microstructural and heat treatment models to development of forming technology of critical aluminum-alloy parts

NASA Astrophysics Data System (ADS)

Biba, Nikolay; Alimov, Artem; Shitikov, Andrey; Stebunov, Sergei

2018-05-01

The demand for high performance and energy efficient transportation systems have boosted interest in lightweight design solutions. To achieve maximum weight reductions, it is not enough just to replace steel parts by their aluminium analogues, but it is necessary to change the entire concept of vehicle design. In this case we must develop methods for manufacturing a variety of critical parts with unusual and difficult to produce shapes. The mechanical properties of the material in these parts must also be optimised and tightly controlled to provide the best distribution within the part volume. The only way to achieve these goals is to implement technology development methods based on simulation of the entire manufacturing chain from preparing a billet through the forming operations and heat treatment of the product. The paper presents an approach to such technology development. The simulation of the technological chain starts with extruding a round billet. Depending on the extrusion process parameters, the billet can have different levels of material workout and variation of grain size throughout the volume. After extrusion, the billet gets formed into the required shape in a forging process. The main requirements at this stage are to get the near net shape of the product without defects and to provide proper configuration of grain flow that strengthens the product in the most critical direction. Then the product undergoes solution treatment, quenching and ageing. The simulation of all these stages are performed by QForm FEM code that provides thermo-mechanical coupled deformation of the material during extrusion and forging. To provide microstructure and heat treatment simulation, special subroutines has been developed by the authors. The proposed approach is illustrated by an industrial case study.

Shaping the Latitudinal Diversity Gradient: New Perspectives from a Synthesis of Paleobiology and Biogeography.

PubMed

Jablonski, David; Huang, Shan; Roy, Kaustuv; Valentine, James W

2017-01-01

An impediment to understanding the origin and dynamics of the latitudinal diversity gradient (LDG)-the most pervasive large-scale biotic pattern on Earth-has been the tendency to focus narrowly on a single causal factor when a more synthetic, integrative approach is needed. Using marine bivalves as a model system and drawing on other systems where possible, we review paleobiologic and biogeographic support for two supposedly opposing views, that the LDG is shaped primarily by (a) local environmental factors that determine the number of species and higher taxa at a given latitude (in situ hypotheses) or (b) the entry of lineages arising elsewhere into a focal region (spatial dynamics hypotheses). Support for in situ hypotheses includes the fit of present-day diversity trends in many clades to such environmental factors as temperature and the correlation of extinction intensities in Pliocene bivalve faunas with net regional temperature changes. Support for spatial dynamics hypotheses includes the age-frequency distribution of bivalve genera across latitudes, which is consistent with an out-of-the-tropics dynamic, as are the higher species diversities in temperate southeastern Australia and southeastern Japan than in the tropical Caribbean. Thus, both in situ and spatial dynamics processes must shape the bivalve LDG and are likely to operate in other groups as well. The relative strengths of the two processes may differ among groups showing similar LDGs, but dissecting their effects will require improved methods of integrating fossil data with molecular phylogenies. We highlight several potential research directions and argue that many of the most dramatic biotic patterns, past and present, are likely to have been generated by diverse, mutually reinforcing drivers.

Time-Lapse Video Microscopy of Gliding Motility in Toxoplasma gondii Reveals a Novel, Biphasic Mechanism of Cell LocomotionV⃞

PubMed Central

Håkansson, Sebastian; Morisaki, Hiroshi; Heuser, John; Sibley, L. David

1999-01-01

Toxoplasma gondii is a member of the phylum Apicomplexa, a diverse group of intracellular parasites that share a unique form of gliding motility. Gliding is substrate dependent and occurs without apparent changes in cell shape and in the absence of traditional locomotory organelles. Here, we demonstrate that gliding is characterized by three distinct forms of motility: circular gliding, upright twirling, and helical rotation. Circular gliding commences while the crescent-shaped parasite lies on its right side, from where it moves in a counterclockwise manner at a rate of ∼1.5 μm/s. Twirling occurs when the parasite rights itself vertically, remaining attached to the substrate by its posterior end and spinning clockwise. Helical gliding is similar to twirling except that it occurs while the parasite is positioned horizontally, resulting in forward movement that follows the path of a corkscrew. The parasite begins lying on its left side (where the convex side is defined as dorsal) and initiates a clockwise revolution along the long axis of the crescent-shaped body. Time-lapse video analyses indicated that helical gliding is a biphasic process. During the first 180o of the turn, the parasite moves forward one body length at a rate of ∼1–3 μm/s. In the second phase, the parasite flips onto its left side, in the process undergoing little net forward motion. All three forms of motility were disrupted by inhibitors of actin filaments (cytochalasin D) and myosin ATPase (butanedione monoxime), indicating that they rely on an actinomyosin motor in the parasite. Gliding motility likely provides the force for active penetration of the host cell and may participate in dissemination within the host and thus is of both fundamental and practical interest. PMID:10564254

Ceramics in Restorative and Prosthetic DENTISTRY1

NASA Astrophysics Data System (ADS)

Kelly, J. Robert

1997-08-01

This review is intended to provide the ceramic engineer with information about the history and current use of ceramics in dentistry, contemporary research topics, and potential research agenda. Background material includes intra-oral design considerations, descriptions of ceramic dental components, and the origin, composition, and microstructure of current dental ceramics. Attention is paid to efforts involving net-shape processing, machining as a forming method, and the analysis of clinical failure. A rationale is presented for the further development of all-ceramic restorative systems. Current research topics receiving attention include microstructure/processing/property relationships, clinical failure mechanisms and in vitro testing, wear damage and wear testing, surface treatments, and microstructural modifications. The status of the field is critically reviewed with an eye toward future work. Significant improvements seem possible in the clinical use of ceramics based on engineering solutions derived from the study of clinically failed restorations, on the incorporation of higher levels of "biomimicry" in new systems, and on the synergistic developments in dental cements and adhesive dentin bonding.

Sol-Gel Manufactured Energetic Materials

DOEpatents

Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

2005-05-17

Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

Sol-gel manufactured energetic materials

DOEpatents

Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

2003-12-23

Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

Powder Injection Molding of Ceramic Engine Components for Transportation

NASA Astrophysics Data System (ADS)

Lenz, Juergen; Enneti, Ravi K.; Onbattuvelli, Valmikanathan; Kate, Kunal; Martin, Renee; Atre, Sundar

2012-03-01

Silicon nitride has been the favored material for manufacturing high-efficiency engine components for transportation due to its high temperature stability, good wear resistance, excellent corrosion resistance, thermal shock resistance, and low density. The use of silicon nitride in engine components greatly depends on the ability to fabricate near net-shape components economically. The absence of a material database for design and simulation has further restricted the engineering community in developing parts from silicon nitride. In this paper, the design and manufacturability of silicon nitride engine rotors for unmanned aerial vehicles by the injection molding process are discussed. The feedstock material property data obtained from experiments were used to simulate the flow of the material during injection molding. The areas susceptible to the formation of defects during the injection molding process of the engine component were identified from the simulations. A test sample was successfully injection molded using the feedstock and sintered to 99% density without formation of significant observable defects.

Double Vacuum Bag Process for Resin Matrix Composite Manufacturing

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung (Inventor); Jensen, Brian J. (Inventor)

2007-01-01

A double vacuum bag molding assembly with improved void management and laminate net shape control which provides a double vacuum enviromnent for use in fabricating composites from prepregs containing air and/or volatiles such as reactive resin matrix composites or composites from solvent containing prepregs with non-reactive resins matrices. By using two vacuum environments during the curing process, a vacuum can be drawn during a B-stage of a two-step cycle without placing the composite under significant relative pressure. During the final cure stage, a significant pressure can be applied by releasing the vacuum in one of the two environments. Inner and outer bags are useful for creating the two vacuum environments with a perforated tool intermediate the two. The composite is placed intermediate a tool plate and a caul plate in the first environment with the inner bag and tool plate defining the first environment. The second environment is characterized by the outer bag which is placed over the inner bag and the tool plate.

Quasi-Isentropic Compression of Wrought and Additively Manufactures 304L Stainless Steel

NASA Astrophysics Data System (ADS)

Specht, Paul; Brown, Justin; Wise, Jack; Furnish, Michael; Adams, David

2017-06-01

The thermodynamic and constitutive responses of both additively manufactured (AM) and traditional wrought processed 304L stainless steel (SS) were investigated through quasi-isentropic compression to peak stresses near 1Mbar using Sandia National Laboratories' Z machine. The AM 304L SS samples were made with a laser engineered net shaping (LENS™) technique. Compared to traditional wrought processed 304L SS, the AM samples were highly textured with larger grain sizes (i.e.near 1mm) and residual stresses (> 100 MPa). Interferometric measurements of interface velocities enabled inference of the quasi-isentropes for each fabrication type of 304L SS. Release from peak stress provided flow strength measurements of the wrought and AM 304L SS. Sandia National Laboratories is a multi-mission 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. Approved For Unclassified Unlimited Release SAND2017-2040A.

Mathematical Explorations: Maximizing Volume with Solids and Nets

ERIC Educational Resources Information Center

Miles, Victoria L.

2014-01-01

One of the most common household polyhedra is a cereal box. For over 100 years, American companies like Kellogg's™ have packaged cereal in containers shaped like rectangular prisms. Why is a rectangular prism the most commonly used solid for holding cereal? Would another design work equally or more efficient? This article describes an…

Poverty and Inequality. The Political Economy of Redistribution.

ERIC Educational Resources Information Center

Neill, Jon, Ed.

These six essays on the debate over the need for welfare reform offer a wide perspective on poverty and inequality. The "Introduction" (Jon Neill) is followed by "Welfare Report--1996 Style: Will We Sacrifice the 'Safety Net'?" (Robert Haveman), a critique of two proposals that shaped the current debate over welfare reform.…

A new approach to determining net impulse and identification of its characteristics in countermovement jumping: reliability and validity.

PubMed

Mizuguchi, Satoshi; Sands, William A; Wassinger, Craig A; Lamont, Hugh S; Stone, Michael H

2015-06-01

Examining a countermovement jump (CMJ) force-time curve related to net impulse might be useful in monitoring athletes' performance. This study aimed to investigate the reliability of alternative net impulse calculation and net impulse characteristics (height, width, rate of force development, shape factor, and proportion) and validate against the traditional calculation in the CMJ. Twelve participants performed the CMJ in two sessions (48 hours apart) for test-retest reliability. Twenty participants were involved for the validity assessment. Results indicated intra-class correlation coefficient (ICC) of ≥ 0.89 and coefficient of variation (CV) of ≤ 5.1% for all of the variables except for rate of force development (ICC = 0.78 and CV = 22.3%). The relationship between the criterion and alternative calculations was r = 1.00. While the difference between them was statistically significant (245.96 ± 63.83 vs. 247.14 ± 64.08 N s, p < 0.0001), the effect size was trivial and deemed practically minimal (d = 0.02). In conclusion, variability of rate of force development will pose a greater challenge in detecting performance changes. Also, the alternative calculation can be used practically in place of the traditional calculation to identify net impulse characteristics and monitor and study athletes' performance in greater depth.

Net ecosystem calcification and net primary production in two Hawaii back-reef systems

NASA Astrophysics Data System (ADS)

Kiili, S.; Colbert, S.; Hart, K.

2016-02-01

Back-reef systems have complex carbon cycling, driven by dominant benthic communities that change with environmental conditions and display characteristic patterns of net primary production (NP) and net ecosystem calcification (G). The G/NP ratio provides a fundamental community-level assessment to compare systems spatially and to evaluate temporal changes in carbon cycling. Carbon dynamics were examined at leeward Hōnaunau and windward Waíōpae, Hawaíi Island. Both locations discharge brackish groundwater, including geothermal water at Waíōpae. The change in total CO2 (TCO2) and total alkalinity (TA) between morning and afternoon was measured to calculate the G/NP ratio along a salinity gradient. At both sites, aragonite saturation (ΩAr) was lower than open ocean conditions, and increased with salinity. Between the morning and afternoon, ΩAr increased by at least 1 as photosynthesis consumed CO2. At Waíōpae, water was corrosive to aragonite due to the input of acidic groundwater, but not at Honaunau, demonstrating the importance of local watershed characteristics on ΩAr. Across the salinity gradient, TA and TCO2 decreased between morning and afternoon. At Hōnaunau, G/NP increased from 0.11 to 0.31 with salinity, consistent with an offshore increase in coral cover. But at Waíōpae, G/NP decreased from 0.49 to 0.0 with salinity, despite an increase in coral cover with salinity. Low G may be caused by benthic processes, including coral bleaching or high rates of carbonate dissolution in interstitial waters between tide pools. Broader environmental conditions than just salinity, including pH of fresh groundwater inputs, shape the carbon cycling in the back-reef system. Examining the G/NP ratio of a back-reef system allows for a simple method to establish community level activity, and possibly indicate changes in a dynamic system.

Detection and clustering of features in aerial images by neuron network-based algorithm

NASA Astrophysics Data System (ADS)

Vozenilek, Vit

2015-12-01

The paper presents the algorithm for detection and clustering of feature in aerial photographs based on artificial neural networks. The presented approach is not focused on the detection of specific topographic features, but on the combination of general features analysis and their use for clustering and backward projection of clusters to aerial image. The basis of the algorithm is a calculation of the total error of the network and a change of weights of the network to minimize the error. A classic bipolar sigmoid was used for the activation function of the neurons and the basic method of backpropagation was used for learning. To verify that a set of features is able to represent the image content from the user's perspective, the web application was compiled (ASP.NET on the Microsoft .NET platform). The main achievements include the knowledge that man-made objects in aerial images can be successfully identified by detection of shapes and anomalies. It was also found that the appropriate combination of comprehensive features that describe the colors and selected shapes of individual areas can be useful for image analysis.

Hierarchical structured tungsten oxide nanocrystals via hydrothermal route: microstructure, formation mechanism and humidity sensing

NASA Astrophysics Data System (ADS)

Pang, Hua-Feng; Li, Zhi-Jie; Xiang, Xia; Fu, Yong-Qing; Placido, Frank; Zu, Xiao-Tao

2013-09-01

Hierarchical structured tungsten oxide nanocrystals were synthesized via the hydrothermal route assisted by a capping agent of ammonium benzoate (AB). The products were characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that the crystal microstructures could be changed from flower-shape to star-shape by changing the mole ratio of ammonium benzoate to sodium tungstate (AB/ST). The crystal phases were changed from orthorhombic WO3ṡ0.33H2O to hexagonal WO3 with the increase in the concentration of AB. Based on the results from Fourier transform infrared spectroscopy and time-dependent growth analysis, a self-assembly growth mechanism has been proposed for the formation of flower, spherical, and star-netted microstructures at different mole ratios of the AB/ST. The star-netted WO3 nanocrystals were applied as a sensitive layer for humidity sensing performed using a Love-mode ZnO/36∘ Y-cut LiTaO3 surface acoustic wave device, and a stable and sensitive response to the change of relative humidity was obtained.

Video studies of passage by Anopheles gambiae mosquitoes through holes in a simulated bed net: effects of hole size, hole orientation and net environment.

PubMed

Sutcliffe, James; Colborn, Kathryn L

2015-05-13

Holes in netting provide potential routes for mosquitoes to enter ITNs. Despite this, there is little information on how mosquitoes respond to holes in bed nets and how their responses are affected by hole size, shape and orientation or by ambient conditions around the net. Female Anopheles gambiae (G3) were recorded in a simulated bed net consisting of two sizes of untreated netting-covered behavioural arenas placed above and beside (to simulate the bed net roof and sides respectively) the experimenter who was a source of host cues from 'inside' the net. A round hole of 9 mm or 13 mm diameter was cut into the centre of the netting of each arena. Videos of unfed female mosquitoes in arenas were analysed for time spent flying, walking and standing still and for exit through the hole. The effects of the experimenter on temperature and relative humidity around the simulated net were also measured. Mosquitoes were significantly more active in overhead arenas than in arenas to the side. Hole passage was significantly more likely in smaller arenas than larger ones and for larger holes than smaller ones. In arenas to the side, hole passage rate through small holes was about 50% less likely than what could be explained by area alone. Passage rate through holes in overhead arenas was consistent with hole area. Temperature in arenas did not strongly reflect the experimenter's presence in the simulated net. Relative humidity and absolute humidity in overhead arenas, but not in arenas to the side, were immediately affected by experimenter presence. Higher levels of activity in overhead arenas than in arenas to the side were likely due to the rising heat and humidity plume from the experimenter. Lower than expected passage rates through smaller vertically oriented holes may have been be due to an edge effect that does not apply to horizontally oriented holes. Results suggest that current methods of assessing the importance of physical damage to ITNs may not accurately reflect mosquito entry risk in all cases.

Influence of processing factors on the physical metallurgy of LENS deposited 316L stainless steel.

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

Yang, Nancy Y. C.; Yee, Joshua Keng; Zheng, Baolong

2015-12-01

Directed energy deposition (DED) is a type of additive manufacturing (AM) process; Laser Engineered Net Shaping (LENS) is a commercial DED process. We are developing LENS technology for printing 316L stainless steel components for structural applications. It is widely known that material properties of AM components are process dependent, attributed to different molten metal incorporation and thermal transport mechanisms. This investigation focuses on process-structure-property relationships for LENS deposits for enabling the process development and optimization to control material property. We observed interactions among powder melting, directional molten metal flow, and the molten metal solidification. The resultant LENS induced microstructure foundmore » to be dictated by the process-related characteristics, i.e., interpass boundaries from multi-layer deposition, molten metal flow lines, and solidification dendrite cells. Each characteristic bears the signature of the unique localized thermal history during deposition. Correlation observed between localized thermal transport, resultant microstructure, and its subsequent impact on the mechanical behavior of the current 316L is discussed. We also discuss how the structures of interpass boundaries are susceptible to localized recrystallization, grain growth and/or defect formation, and therefore, heterogeneous mechanical properties due to the adverse presence of unmelted powder inclusions.« less

Retrieving Vertical Air Motion and Raindrop Size Distributions from Vertically Pointing Doppler Radars

NASA Astrophysics Data System (ADS)

Williams, C. R.; Chandra, C. V.

2017-12-01

The vertical evolution of falling raindrops is a result of evaporation, breakup, and coalescence acting upon those raindrops. Computing these processes using vertically pointing radar observations is a two-step process. First, the raindrop size distribution (DSD) and vertical air motion need to be estimated throughout the rain shaft. Then, the changes in DSD properties need to be quantified as a function of height. The change in liquid water content is a measure of evaporation, and the change in raindrop number concentration and size are indicators of net breakup or coalescence in the vertical column. The DSD and air motion can be retrieved using observations from two vertically pointing radars operating side-by-side and at two different wavelengths. While both radars are observing the same raindrop distribution, they measure different reflectivity and radial velocities due to Rayleigh and Mie scattering properties. As long as raindrops with diameters greater than approximately 2 mm are in the radar pulse volumes, the Rayleigh and Mie scattering signatures are unique enough to estimate DSD parameters using radars operating at 3- and 35-GHz (Williams et al. 2016). Vertical decomposition diagrams (Williams 2016) are used to explore the processes acting on the raindrops. Specifically, changes in liquid water content with height quantify evaporation or accretion. When the raindrops are not evaporating, net raindrop breakup and coalescence are identified by changes in the total number of raindrops and changes in the DSD effective shape as the raindrops. This presentation will focus on describing the DSD and air motion retrieval method using vertical profiling radar observations from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) central facility in Northern Oklahoma.

Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

NASA Astrophysics Data System (ADS)

Li, Ling; Tirado, Angelica; Nlebedim, I. C.; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R. R.; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A.; Paranthaman, M. Parans

2016-10-01

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.

Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

PubMed Central

Li, Ling; Tirado, Angelica; Nlebedim, I. C.; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R. R.; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A.; Paranthaman, M. Parans

2016-01-01

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials. PMID:27796339

Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets.

PubMed

Li, Ling; Tirado, Angelica; Nlebedim, I C; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R R; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A; Paranthaman, M Parans

2016-10-31

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm 3 , and the room temperature magnetic properties are: intrinsic coercivity H ci  = 688.4 kA/m, remanence B r  = 0.51 T, and energy product (BH) max  = 43.49 kJ/m 3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.

Big area additive manufacturing of high performance bonded NdFeB magnets

DOE PAGES

Li, Ling; Tirado, Angelica; Nlebedim, I. C.; ...

2016-10-31

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic propertiesmore » are: intrinsic coercivity Hci = 688.4 kA/m, remanence B r = 0.51 T, and energy product (BH) max = 43.49 kJ/m 3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. As a result, the present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.« less

Big area additive manufacturing of high performance bonded NdFeB magnets

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

Li, Ling; Tirado, Angelica; Nlebedim, I. C.

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic propertiesmore » are: intrinsic coercivity Hci = 688.4 kA/m, remanence B r = 0.51 T, and energy product (BH) max = 43.49 kJ/m 3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. As a result, the present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.« less

Modeling biological gradient formation: combining partial differential equations and Petri nets.

PubMed

Bertens, Laura M F; Kleijn, Jetty; Hille, Sander C; Heiner, Monika; Koutny, Maciej; Verbeek, Fons J

2016-01-01

Both Petri nets and differential equations are important modeling tools for biological processes. In this paper we demonstrate how these two modeling techniques can be combined to describe biological gradient formation. Parameters derived from partial differential equation describing the process of gradient formation are incorporated in an abstract Petri net model. The quantitative aspects of the resulting model are validated through a case study of gradient formation in the fruit fly.

Identifying and Prioritizing Gaps in Neuroendocrine Tumor Research: A Modified Delphi Process With Patients and Health Care Providers to Set the Research Action Plan for the Newly Formed Commonwealth Neuroendocrine Tumor Collaboration

PubMed Central

Chan, David; Lawrence, Ben; Pavlakis, Nick; Kennecke, Hagen F.; Jackson, Christopher; Law, Calvin; Singh, Simron

2017-01-01

Purpose Neuroendocrine tumors (NETs) are a diverse group of malignancies that pose challenges common to all rare tumors. The Commonwealth Neuroendocrine Tumor Collaboration (CommNETS) was established in 2015 to enhance outcomes for patients with NETs in Canada, Australia, and New Zealand. A modified Delphi process was undertaken involving patients, clinicians, and researchers to identify gaps in NETs research to produce a comprehensive and defensible research action plan. Methods A three-round modified Delphi process was undertaken with larger representation than usual for medical consensus processes. Patient/advocate and health care provider/researcher expert panels undertook Round 1, which canvassed 17 research priorities and 42 potential topics; in Round 2, these priorities were ranked. Round 3 comprised a face-to-face meeting to generate final consensus rankings and formulate the research action plan. Results The Delphi groups consisted of 203 participants in Round 1 (64% health care providers/researchers, 36% patient/advocates; 52% Canadian, 32% Australian, and 17% New Zealander), of whom 132 participated in Round 2. The top eight priorities were biomarker development; peptide receptor radionuclide therapy optimization; trials of new agents in advanced NETs; functional imaging; sequencing therapies for metastatic NETs, including development of validated surrogate end points for studies; pathologic classification; early diagnosis; interventional therapeutics; and curative surgery. Two major areas were ranked significantly higher by patients/advocates: early diagnosis and curative surgery. Six CommNETS working parties were established. Conclusion This modified Delphi process resulted in a well-founded set of research priorities for the newly formed CommNETS collaboration by involving a large, diverse group of stakeholders. This approach to setting a research agenda for a new collaborative group should be adopted to ensure that research plans reflect unmet needs and priorities in the field. PMID:28831446

Identifying and Prioritizing Gaps in Neuroendocrine Tumor Research: A Modified Delphi Process With Patients and Health Care Providers to Set the Research Action Plan for the Newly Formed Commonwealth Neuroendocrine Tumor Collaboration.

PubMed

Segelov, Eva; Chan, David; Lawrence, Ben; Pavlakis, Nick; Kennecke, Hagen F; Jackson, Christopher; Law, Calvin; Singh, Simron

2017-08-01

Neuroendocrine tumors (NETs) are a diverse group of malignancies that pose challenges common to all rare tumors. The Commonwealth Neuroendocrine Tumor Collaboration (CommNETS) was established in 2015 to enhance outcomes for patients with NETs in Canada, Australia, and New Zealand. A modified Delphi process was undertaken involving patients, clinicians, and researchers to identify gaps in NETs research to produce a comprehensive and defensible research action plan. A three-round modified Delphi process was undertaken with larger representation than usual for medical consensus processes. Patient/advocate and health care provider/researcher expert panels undertook Round 1, which canvassed 17 research priorities and 42 potential topics; in Round 2, these priorities were ranked. Round 3 comprised a face-to-face meeting to generate final consensus rankings and formulate the research action plan. The Delphi groups consisted of 203 participants in Round 1 (64% health care providers/researchers, 36% patient/advocates; 52% Canadian, 32% Australian, and 17% New Zealander), of whom 132 participated in Round 2. The top eight priorities were biomarker development; peptide receptor radionuclide therapy optimization; trials of new agents in advanced NETs; functional imaging; sequencing therapies for metastatic NETs, including development of validated surrogate end points for studies; pathologic classification; early diagnosis; interventional therapeutics; and curative surgery. Two major areas were ranked significantly higher by patients/advocates: early diagnosis and curative surgery. Six CommNETS working parties were established. This modified Delphi process resulted in a well-founded set of research priorities for the newly formed CommNETS collaboration by involving a large, diverse group of stakeholders. This approach to setting a research agenda for a new collaborative group should be adopted to ensure that research plans reflect unmet needs and priorities in the field.

Near-Net-Shape Processing of Sintered Fibrous Ceramics Achieved

NASA Technical Reports Server (NTRS)

Angel, Paul W.

2000-01-01

A variety of sintered fibrous ceramic (SFC) materials have been developed over the last 50 years as thermal barrier materials for reentry applications. SFC materials typically exhibit very low thermal conductivities combined with low densities and good thermal stability up to 2500 F. These materials have flown successfully on the space shuttle orbiters since the 1960's. More recently, the McDonnell Douglas Corporation successfully used SFC tiles as a heat shield on the underside of its DC X test vehicle. For both of these applications, tiles are machined from blocks of a specific type of SFC called an alumina-enhanced thermal barrier (AETB). The sizes of these blocks have been limited by the manufacturing process. In addition, as much as 80 to 90 percent of the material can be lost during the machining of tiles with significant amounts of curvature. To address these problems, the NASA Glenn Research Center at Lewis Field entered a cooperative contract with the Boeing Company to develop a vacuum-assisted forming process that can produce large (approximately 4 square feet), severely contoured panels of AETB while saving costs in comparison to the conventional cast-and-machine billet process. For shuttle use, AETB is slurry cast, drained, and fired to form square billets conforming to the shape of the filtration box. The billets are then cut into tiles of the appropriate size for thermally protecting the space shuttle. Processing techniques have limited the maximum size of AETB billets to 21.5 square inches by 6.5-in. thick, but the space shuttles use discrete heat shield tiles no more than 8 to 12 square inches. However, in other applications, large, complex shapes are needed, and the tiling approach is undesirable. For such applications, vacuum-assisted forming can produce large parts with complex shapes while reducing machining waste and eliminating cemented joints between bonded billets. Because it allows contoured shapes to be formed, material utilization is inherently high. Initial estimates show that the amount of material lost during machining can be reduced by 50 percent or more. In addition, a fiber alignment favorable for minimum heat transfer is maintained for all panel shapes since the fibers are aligned parallel to the contoured surface of the forming tool or mold. The vacuum-assisted forming process can complete the entire forming operation in a matter of minutes and can produce multiple parts whose size is limited only by the size of the forming tool. To date, panels as large as 2 square feet have been demonstrated The vacuum-assisted forming process starts with the fabrication of a permeable forming tool, or mold, with the proper part contour. This reusable tool is mounted over an internal rib support structure, as depicted in the diagram, such that a vacuum can be pulled on the bottom portion of the tool. AETB slurry is then poured over and around the tool, liquid is drawn from the slurry, and the part forms over the tool surface. The part is then dried, fired, and finished machined. Future plans include an evaluation of the need for additional coatings and surface-toughness treatments to extend the durability and performance of this material.

Development of Web GIS for complex processing and visualization of climate geospatial datasets as an integral part of dedicated Virtual Research Environment

NASA Astrophysics Data System (ADS)

Gordov, Evgeny; Okladnikov, Igor; Titov, Alexander

2017-04-01

For comprehensive usage of large geospatial meteorological and climate datasets it is necessary to create a distributed software infrastructure based on the spatial data infrastructure (SDI) approach. Currently, it is generally accepted that the development of client applications as integrated elements of such infrastructure should be based on the usage of modern web and GIS technologies. The paper describes the Web GIS for complex processing and visualization of geospatial (mainly in NetCDF and PostGIS formats) datasets as an integral part of the dedicated Virtual Research Environment for comprehensive study of ongoing and possible future climate change, and analysis of their implications, providing full information and computing support for the study of economic, political and social consequences of global climate change at the global and regional levels. The Web GIS consists of two basic software parts: 1. Server-side part representing PHP applications of the SDI geoportal and realizing the functionality of interaction with computational core backend, WMS/WFS/WPS cartographical services, as well as implementing an open API for browser-based client software. Being the secondary one, this part provides a limited set of procedures accessible via standard HTTP interface. 2. Front-end part representing Web GIS client developed according to a "single page application" technology based on JavaScript libraries OpenLayers (http://openlayers.org/), ExtJS (https://www.sencha.com/products/extjs), GeoExt (http://geoext.org/). It implements application business logic and provides intuitive user interface similar to the interface of such popular desktop GIS applications, as uDIG, QuantumGIS etc. Boundless/OpenGeo architecture was used as a basis for Web-GIS client development. According to general INSPIRE requirements to data visualization Web GIS provides such standard functionality as data overview, image navigation, scrolling, scaling and graphical overlay, displaying map legends and corresponding metadata information. The specialized Web GIS client contains three basic tires: • Tier of NetCDF metadata in JSON format • Middleware tier of JavaScript objects implementing methods to work with: o NetCDF metadata o XML file of selected calculations configuration (XML task) o WMS/WFS/WPS cartographical services • Graphical user interface tier representing JavaScript objects realizing general application business logic Web-GIS developed provides computational processing services launching to support solving tasks in the area of environmental monitoring, as well as presenting calculation results in the form of WMS/WFS cartographical layers in raster (PNG, JPG, GeoTIFF), vector (KML, GML, Shape), and binary (NetCDF) formats. It has shown its effectiveness in the process of solving real climate change research problems and disseminating investigation results in cartographical formats. The work is supported by the Russian Science Foundation grant No 16-19-10257.

Optimal web investment in sub-optimal foraging conditions.

PubMed

Harmer, Aaron M T; Kokko, Hanna; Herberstein, Marie E; Madin, Joshua S

2012-01-01

Orb web spiders sit at the centre of their approximately circular webs when waiting for prey and so face many of the same challenges as central-place foragers. Prey value decreases with distance from the hub as a function of prey escape time. The further from the hub that prey are intercepted, the longer it takes a spider to reach them and the greater chance they have of escaping. Several species of orb web spiders build vertically elongated ladder-like orb webs against tree trunks, rather than circular orb webs in the open. As ladder web spiders invest disproportionately more web area further from the hub, it is expected they will experience reduced prey gain per unit area of web investment compared to spiders that build circular webs. We developed a model to investigate how building webs in the space-limited microhabitat on tree trunks influences the optimal size, shape and net prey gain of arboricolous ladder webs. The model suggests that as horizontal space becomes more limited, optimal web shape becomes more elongated, and optimal web area decreases. This change in web geometry results in decreased net prey gain compared to webs built without space constraints. However, when space is limited, spiders can achieve higher net prey gain compared to building typical circular webs in the same limited space. Our model shows how spiders optimise web investment in sub-optimal conditions and can be used to understand foraging investment trade-offs in other central-place foragers faced with constrained foraging arenas.

Optimal web investment in sub-optimal foraging conditions

NASA Astrophysics Data System (ADS)

Harmer, Aaron M. T.; Kokko, Hanna; Herberstein, Marie E.; Madin, Joshua S.

2012-01-01

Orb web spiders sit at the centre of their approximately circular webs when waiting for prey and so face many of the same challenges as central-place foragers. Prey value decreases with distance from the hub as a function of prey escape time. The further from the hub that prey are intercepted, the longer it takes a spider to reach them and the greater chance they have of escaping. Several species of orb web spiders build vertically elongated ladder-like orb webs against tree trunks, rather than circular orb webs in the open. As ladder web spiders invest disproportionately more web area further from the hub, it is expected they will experience reduced prey gain per unit area of web investment compared to spiders that build circular webs. We developed a model to investigate how building webs in the space-limited microhabitat on tree trunks influences the optimal size, shape and net prey gain of arboricolous ladder webs. The model suggests that as horizontal space becomes more limited, optimal web shape becomes more elongated, and optimal web area decreases. This change in web geometry results in decreased net prey gain compared to webs built without space constraints. However, when space is limited, spiders can achieve higher net prey gain compared to building typical circular webs in the same limited space. Our model shows how spiders optimise web investment in sub-optimal conditions and can be used to understand foraging investment trade-offs in other central-place foragers faced with constrained foraging arenas.

A Constrained Maximization Model for inspecting the impact of leaf shape on optimal leaf size and stoma resistance

NASA Astrophysics Data System (ADS)

Ding, J.; Johnson, E. A.; Martin, Y. E.

2017-12-01

Leaf is the basic production unit of plants. Water is the most critical resource of plants. Its availability controls primary productivity of plants by affecting leaf carbon budget. To avoid the damage of cavitation from lowering vein water potential t caused by evapotranspiration, the leaf must increase the stomatal resistance to reduce evapotranspiration rate. This comes at the cost of reduced carbon fixing rate as increasing stoma resistance meanwhile slows carbon intake rate. Studies suggest that stoma will operate at an optimal resistance to maximize the carbon gain with respect to water. Different plant species have different leaf shapes, a genetically determined trait. Further, on the same plant leaf size can vary many times in size that is related to soil moisture, an indicator of water availability. According to metabolic scaling theory, increasing leaf size will increase total xylem resistance of vein, which may also constrain leaf carbon budget. We present a Constrained Maximization Model of leaf (leaf CMM) that incorporates metabolic theory into the coupling of evapotranspiration and carbon fixation to examine how leaf size, stoma resistance and maximum net leaf primary productivity change with petiole xylem water potential. The model connects vein network structure to leaf shape and use the difference between petiole xylem water potential and the critical minor vein cavitation forming water potential as the budget. The CMM shows that both maximum net leaf primary production and optimal leaf size increase with petiole xylem water potential while optimal stoma resistance decreases. Narrow leaf has overall lower optimal leaf size and maximum net leaf carbon gain and higher optimal stoma resistance than those of broad leaf. This is because with small width to length ratio, total xylem resistance increases faster with leaf size. Total xylem resistance of narrow leaf increases faster with leaf size causing higher average and marginal cost of xylem water potential with respect to net leaf carbon gain. With same leaf area, total xylem resistance of narrow leaf is higher than broad leaf. Given same stoma resistance and petiole water potential, narrow leaf will lose more xylem water potential than broad leaf. Consequently, narrow leaf has smaller size and higher stoma resistance at optimum.

Influence of molecular shape, conformability, net surface charge, and tissue interaction on transscleral macromolecular diffusion.

PubMed

Srikantha, Nishanthan; Mourad, Fatma; Suhling, Klaus; Elsaid, Naba; Levitt, James; Chung, Pei Hua; Somavarapu, Satyanarayana; Jackson, Timothy L

2012-09-01

The purpose of this study was to investigate the influence of molecular shape, conformability, net surface charge and tissue interaction on transscleral diffusion. Unfixed, porcine sclera was clamped in an Ussing chamber. Fluorophore-labelled neutral albumin, neutral dextran, or neutral ficoll were placed in one hemi-chamber and the rate of transscleral diffusion was measured over 24 h using a spectrophotometer. Experiments were repeated using dextrans and ficoll with positive or negative net surface charges. Fluorescence recovery after photobleaching (FRAP) was undertaken to compare transscleral diffusion with diffusion through a solution. All molecules were 70 kDa. With FRAP, the diffusion coefficient (D) of neutral molecules was highest for albumin, followed by ficoll, then dextran (p < 0.0001). Positive dextrans diffused fastest, followed by negative, then neutral dextrans (p = 0.0004). Neutral ficoll diffused the fastest, followed by positive then negative ficoll (p = 0.5865). For the neutral molecules, transscleral D was highest for albumin, followed by dextran, then ficoll (p < 0.0001). D was highest for negative ficoll, followed by neutral, then positive ficoll (p < 0.0001). By contrast, D was highest for positive dextran, followed by neutral, then negative dextran (p = 0.0021). In conclusion, diffusion in free solution does not predict transscleral diffusion and the molecular-tissue interaction is important. Molecular size, shape, and charge may all markedly influence transscleral diffusion, as may conformability to a lesser degree, but their effects may be diametrically opposed in different molecules, and their influence on diffusion is more complex than previously thought. Each variable cannot be considered in isolation, and the interplay of all these variables needs to be tested, when selecting or designing drugs for transscleral delivery. Copyright © 2012 Elsevier Ltd. All rights reserved.

On the upper tail of Italian firms’ size distribution

NASA Astrophysics Data System (ADS)

Cirillo, Pasquale; Hüsler, Jürg

2009-04-01

In this paper we analyze the upper tail of the size distribution of Italian companies with limited liability belonging to the CEBI database. Size is defined in terms of net worth. In particular, we show that the largest firms follow a power law distribution, according to the well-known Pareto law, for which we give estimates of the shape parameter. Such a behavior seems to be quite persistent over time, view that for almost 20 years of observations, the shape parameter is always in the vicinity of 1.8. The power law hypothesis is also positively tested using graphical and analytical methods.

Fabrication of sinterable silicon nitride by injection molding

NASA Technical Reports Server (NTRS)

Quackenbush, C. L.; French, K.; Neil, J. T.

1982-01-01

Transformation of structural ceramics from the laboratory to production requires development of near net shape fabrication techniques which minimize finish grinding. One potential technique for producing large quantities of complex-shaped parts at a low cost, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material. Binder selection methodology, compounding of ceramic and binder components, injection molding techniques, and problems in binder removal are discussed. Strength, oxidation resistance, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material.

Gelcasting polymeric precursors for producing net-shaped graphites

DOEpatents

Klett, James W.; Janney, Mark A.

2002-01-01

The present invention discloses a method for molding complex and intricately shaped high density monolithic carbon, carbon-carbon, graphite, and thermoplastic composites using gelcasting technology. The method comprising a polymeric carbon precursor, a solvent, a dispersant, an anti-foaming agent, a monomer system, and an initiator system. The components are combined to form a suspension which is poured into a mold and heat-treated to form a thermoplastic part. The thermoplastic part can then be further densified and heat-treated to produce a high density carbon or graphite composite. The present invention also discloses the products derived from this method.

Resonance and streaming of armored microbubbles

NASA Astrophysics Data System (ADS)

Spelman, Tamsin; Bertin, Nicolas; Stephen, Olivier; Marmottant, Philippe; Lauga, Eric

2015-11-01

A new experimental technique involves building a hollow capsule which partially encompasses a microbubble, creating an ``armored microbubble'' with long lifespan. Under acoustic actuation, such bubble produces net streaming flows. In order to theoretically model the induced flow, we first extend classical models of free bubbles to describe the streaming flow around a spherical body for any known axisymmetric shape oscillation. A potential flow model is then employed to determine the resonance modes of the armored microbubble. We finally use a more detailed viscous model to calculate the surface shape oscillations at the experimental driving frequency, and from this we predict the generated streaming flows.

Attribution of Net Carbon Change by Disturbance Type across Forest Lands of the Continental United States

NASA Astrophysics Data System (ADS)

Hagen, S. C.; Harris, N.; Saatchi, S. S.; Domke, G. M.; Woodall, C. W.; Pearson, T.

2016-12-01

We generated spatially comprehensive maps of carbon stocks and net carbon changes from US forestlands between 2005 and 2010 and attributed the changes to natural and anthropogenic processes. The prototype system created to produce these maps is designed to assist with national GHG inventories and support decisions associated with land management. Here, we present the results and methodological framework of our analysis. In summary, combining estimates of net C losses and gains results in net carbon change of 269±49 Tg C yr-1 (sink) in the coterminous US forest land, with carbon loss from harvest acting as the predominent source process.

Toward 2D Seismic Wavefield Monitoring: Seismic Gradiometry for Long-Period Seismogram and Short-Period Seismogram Envelope applied to the Hi-net Array

NASA Astrophysics Data System (ADS)

Maeda, T.; Nishida, K.; Takagi, R.; Obara, K.

2015-12-01

The high-sensitive seismograph network Japan (Hi-net) operated by National Research Institute for Earth Science and Disaster Prevention (NIED) has about 800 stations with average separation of 20 km. We can observe long-period seismic wave propagation as a 2D wavefield with station separations shorter than wavelength. In contrast, short-period waves are quite incoherent at stations, however, their envelope shapes resemble at neighbor stations. Therefore, we may be able to extract seismic wave energy propagation by seismogram envelope analysis. We attempted to characterize seismic waveform at long-period and its envelope at short-period as 2D wavefield by applying seismic gradiometry. We applied the seismic gradiometry to a synthetic long-period (20-50s) dataset prepared by numerical simulation in realistic 3D medium at the Hi-net station layout. Wave amplitude and its spatial derivatives are estimated by using data at nearby stations. The slowness vector, the radiation pattern and the geometrical spreading are extracted from estimated velocity, displacement and its spatial derivatives. For short-periods at shorter than 1 s, seismogram envelope shows temporal and spatial broadening through scattering by medium heterogeneity. It is expected that envelope shape may be coherent among nearby stations. Based on this idea, we applied the same method to the time-integration of seismogram envelope to estimate its spatial derivatives. Together with seismogram envelope, we succeeded in estimating the slowness vector from the seismogram envelope as well as long-period waveforms by synthetic test, without using phase information. Our preliminarily results show that the seismic gradiometry suits the Hi-net to extract wave propagation characteristics both at long and short periods. This method is appealing that it can estimate waves at homogeneous grid to monitor seismic wave as a wavefield. It is promising to obtain phase velocity variation from direct waves, and to grasp wave packets originating from scattering from coda, by applying the seismic gradiometry to the Hi-net.

Role of spatial averaging in multicellular gradient sensing.

PubMed

Smith, Tyler; Fancher, Sean; Levchenko, Andre; Nemenman, Ilya; Mugler, Andrew

2016-05-20

Gradient sensing underlies important biological processes including morphogenesis, polarization, and cell migration. The precision of gradient sensing increases with the length of a detector (a cell or group of cells) in the gradient direction, since a longer detector spans a larger range of concentration values. Intuition from studies of concentration sensing suggests that precision should also increase with detector length in the direction transverse to the gradient, since then spatial averaging should reduce the noise. However, here we show that, unlike for concentration sensing, the precision of gradient sensing decreases with transverse length for the simplest gradient sensing model, local excitation-global inhibition. The reason is that gradient sensing ultimately relies on a subtraction of measured concentration values. While spatial averaging indeed reduces the noise in these measurements, which increases precision, it also reduces the covariance between the measurements, which results in the net decrease in precision. We demonstrate how a recently introduced gradient sensing mechanism, regional excitation-global inhibition (REGI), overcomes this effect and recovers the benefit of transverse averaging. Using a REGI-based model, we compute the optimal two- and three-dimensional detector shapes, and argue that they are consistent with the shapes of naturally occurring gradient-sensing cell populations.

Role of spatial averaging in multicellular gradient sensing

NASA Astrophysics Data System (ADS)

Smith, Tyler; Fancher, Sean; Levchenko, Andre; Nemenman, Ilya; Mugler, Andrew

2016-06-01

Gradient sensing underlies important biological processes including morphogenesis, polarization, and cell migration. The precision of gradient sensing increases with the length of a detector (a cell or group of cells) in the gradient direction, since a longer detector spans a larger range of concentration values. Intuition from studies of concentration sensing suggests that precision should also increase with detector length in the direction transverse to the gradient, since then spatial averaging should reduce the noise. However, here we show that, unlike for concentration sensing, the precision of gradient sensing decreases with transverse length for the simplest gradient sensing model, local excitation-global inhibition. The reason is that gradient sensing ultimately relies on a subtraction of measured concentration values. While spatial averaging indeed reduces the noise in these measurements, which increases precision, it also reduces the covariance between the measurements, which results in the net decrease in precision. We demonstrate how a recently introduced gradient sensing mechanism, regional excitation-global inhibition (REGI), overcomes this effect and recovers the benefit of transverse averaging. Using a REGI-based model, we compute the optimal two- and three-dimensional detector shapes, and argue that they are consistent with the shapes of naturally occurring gradient-sensing cell populations.

NetCDF-U - Uncertainty conventions for netCDF datasets

NASA Astrophysics Data System (ADS)

Bigagli, Lorenzo; Nativi, Stefano; Domenico, Ben

2013-04-01

To facilitate the automated processing of uncertain data (e.g. uncertainty propagation in modeling applications), we have proposed a set of conventions for expressing uncertainty information within the netCDF data model and format: the NetCDF Uncertainty Conventions (NetCDF-U). From a theoretical perspective, it can be said that no dataset is a perfect representation of the reality it purports to represent. Inevitably, errors arise from the observation process, including the sensor system and subsequent processing, differences in scales of phenomena and the spatial support of the observation mechanism, lack of knowledge about the detailed conversion between the measured quantity and the target variable. This means that, in principle, all data should be treated as uncertain. The most natural representation of an uncertain quantity is in terms of random variables, with a probabilistic approach. However, it must be acknowledged that almost all existing data resources are not treated in this way. Most datasets come simply as a series of values, often without any uncertainty information. If uncertainty information is present, then it is typically within the metadata, as a data quality element. This is typically a global (dataset wide) representation of uncertainty, often derived through some form of validation process. Typically, it is a statistical measure of spread, for example the standard deviation of the residuals. The introduction of a mechanism by which such descriptions of uncertainty can be integrated into existing geospatial applications is considered a practical step towards a more accurate modeling of our uncertain understanding of any natural process. Given the generality and flexibility of the netCDF data model, conventions on naming, syntax, and semantics have been adopted by several communities of practice, as a means of improving data interoperability. Some of the existing conventions include provisions on uncertain elements and concepts, but, to our knowledge, no general convention on the encoding of uncertainty has been proposed, to date. In particular, the netCDF Climate and Forecast Conventions (NetCDF-CF), a de-facto standard for a large amount of data in Fluid Earth Sciences, mention the issue and provide limited support for uncertainty representation. NetCDF-U is designed to be fully compatible with NetCDF-CF, where possible adopting the same mechanisms (e.g. using the same attributes name with compatible semantics). The rationale for this is that a probabilistic description of scientific quantities is a crosscutting aspect, which may be modularized (note that a netCDF dataset may be compliant with more than one convention). The scope of NetCDF-U is to extend and qualify the netCDF classic data model (also known as netCDF3), to capture the uncertainty related to geospatial information encoded in that format. In the future, a netCDF4 approach for uncertainty encoding will be investigated. The NetCDF-U Conventions have the following rationale: • Compatibility with netCDF-CF Conventions 1.5. • Human-readability of conforming datasets structure. • Minimal difference between certain/agnostic and uncertain representations of data (e.g. with respect to dataset structure). NetCDF-U is based on a generic mechanism for annotating netCDF data variables with probability theory semantics. The Uncertainty Markup Language (UncertML) 2.0 is used as a controlled conceptual model and vocabulary for NetCDF-U annotations. The proposed mechanism anticipates a generalized support for semantic annotations in netCDF. NetCDF-U defines syntactical conventions for encoding samples, summary statistics, and distributions, along with mechanisms for expressing dependency relationships among variables. The conventions were accepted as an Open Geospatial Consortium (OGC) Discussion Paper (OGC 11-163); related discussions are conducted on a public forum hosted by the OGC. NetCDF-U may have implications for future work directed at communicating geospatial data provenance and uncertainty in contexts other than netCDF. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement n° 248488.

WaveNet: A Web-Based Metocean Data Access, Processing, and Analysis Tool. Part 3 - CDIP Database

DTIC Science & Technology

2014-06-01

and Analysis Tool; Part 3 – CDIP Database by Zeki Demirbilek, Lihwa Lin, and Derek Wilson PURPOSE: This Coastal and Hydraulics Engineering...Technical Note (CHETN) describes coupling of the Coastal Data Information Program ( CDIP ) database to WaveNet, the first module of MetOcnDat (Meteorological...provides a step-by-step procedure to access, process, and analyze wave and wind data from the CDIP database. BACKGROUND: WaveNet addresses a basic

Software Tool Integrating Data Flow Diagrams and Petri Nets

NASA Technical Reports Server (NTRS)

Thronesbery, Carroll; Tavana, Madjid

2010-01-01

Data Flow Diagram - Petri Net (DFPN) is a software tool for analyzing other software to be developed. The full name of this program reflects its design, which combines the benefit of data-flow diagrams (which are typically favored by software analysts) with the power and precision of Petri-net models, without requiring specialized Petri-net training. (A Petri net is a particular type of directed graph, a description of which would exceed the scope of this article.) DFPN assists a software analyst in drawing and specifying a data-flow diagram, then translates the diagram into a Petri net, then enables graphical tracing of execution paths through the Petri net for verification, by the end user, of the properties of the software to be developed. In comparison with prior means of verifying the properties of software to be developed, DFPN makes verification by the end user more nearly certain, thereby making it easier to identify and correct misconceptions earlier in the development process, when correction is less expensive. After the verification by the end user, DFPN generates a printable system specification in the form of descriptions of processes and data.

NaNet-10: a 10GbE network interface card for the GPU-based low-level trigger of the NA62 RICH detector.

NASA Astrophysics Data System (ADS)

Ammendola, R.; Biagioni, A.; Fiorini, M.; Frezza, O.; Lonardo, A.; Lamanna, G.; Lo Cicero, F.; Martinelli, M.; Neri, I.; Paolucci, P. S.; Pastorelli, E.; Piandani, R.; Pontisso, L.; Rossetti, D.; Simula, F.; Sozzi, M.; Tosoratto, L.; Vicini, P.

2016-03-01

A GPU-based low level (L0) trigger is currently integrated in the experimental setup of the RICH detector of the NA62 experiment to assess the feasibility of building more refined physics-related trigger primitives and thus improve the trigger discriminating power. To ensure the real-time operation of the system, a dedicated data transport mechanism has been implemented: an FPGA-based Network Interface Card (NaNet-10) receives data from detectors and forwards them with low, predictable latency to the memory of the GPU performing the trigger algorithms. Results of the ring-shaped hit patterns reconstruction will be reported and discussed.

Ethnic diversity, traditional norms, and marriage behaviour in Indonesia.

PubMed

Buttenheim, Alison M; Nobles, Jenna

2009-11-01

What role do cultural norms play in shaping individual behaviour and how does this relationship change with rapid socio-economic development? While modernization and convergence theories predict a weakened relationship between culture and behaviour as individuals rely less on family and community members for economic opportunities, recent research suggests that such norms can persist and continue to influence behaviour. We explored this question for Indonesia, asking whether cultural norms for age at marriage and post-marriage residence-as embodied in local ethnicity-based laws and customs known as 'adat'-relate to actual marriage behaviour. We demonstrate that adat norms are strong predictors of marriage behaviour, both over time and net of large increases in educational attainment. Our results suggest more generally that traditional marriage norms can persist even when a society is in the process of rapid socio-economic development.

Computational Analysis of the Flow and Acoustic Effects of Jet-Pylon Interaction

NASA Technical Reports Server (NTRS)

Hunter, Craig A.; Thomas, Russell H.; Abdol-Hamid, K. S.; Pao, S. Paul; Elmiligui, Alaa A.; Massey, Steven J.

2005-01-01

Computational simulation and prediction tools were used to understand the jet-pylon interaction effect in a set of bypass-ratio five core/fan nozzles. Results suggest that the pylon acts as a large scale mixing vane that perturbs the jet flow and jump starts the jet mixing process. The enhanced mixing and associated secondary flows from the pylon result in a net increase of noise in the first 10 diameters of the jet s development, but there is a sustained reduction in noise from that point downstream. This is likely the reason the pylon nozzle is quieter overall than the baseline round nozzle in this case. The present work suggests that focused pylon design could lead to advanced pylon shapes and nozzle configurations that take advantage of propulsion-airframe integration to provide additional noise reduction capabilities.

Evaluation of mist-netting, nest-searching and other methods for monitoring demographic processes in landbird populations

Treesearch

Nadav Nur; Geoffrey R. Geupel

1993-01-01

Demographic processes (reproductive success, survival of young and adults, recruitment of young into the breeding population) are critical to monitoring and managing landbird populations. We discuss different techniques that have been used to monitor these demographic processes in landbird populations, focusing on constant-effort mist-netting (CEM). We assess whether...

The Role of Threat Assessment and Management in College Counseling: How's That Net Working?

ERIC Educational Resources Information Center

Pollard, Jeffrey W.; Flynn, Christopher; Eells, Gregory T.

2015-01-01

The authors respond to Goodwin's (2014) "Threat Assessment: Are We Using the Wrong Nets?" and use that article as a springboard to discuss various aspects of the threat assessment and management process. We find that Goodwin misses critical elements of the threat assessment and management process, conflates the process with two types of…

Blood circulation in the lower limbs

NASA Astrophysics Data System (ADS)

Pen'kovskiy, V. I.; Korsakova, N. K.

2018-03-01

Blood circulation process in inferior limbs is considered in the terms of the previously proposed mathematical model of sanguimotion in living organism tissues. The model includes the equations of homogeneous fluid flower in heterogeneous medium that consists of two or more interpenetrating continua. The continua (distributing net of arteries and collecting net of veins) interact through ramified capillary net. A volume of blood flowering from arterial net to venous one is proportional to pressure (head) difference in the nets. Some analytical solutions and numerical results are given.

Counter-Narratives That Challenge Neo-Liberal Discourses of Schooling "Disengagement": Youth Professionals Informing the Work of Teachers

ERIC Educational Resources Information Center

McGregor, Glenda

2017-01-01

Contemporary global economic contexts are shaped by a neo-liberal paradigm of hyper-individualism and meritocracy strongly influencing national policies in education and welfare. As social safety nets diminish, citizens are expected to be more personally accountable. This creates challenges for the poor and marginalised who are positionally…

The balance of planting and mortality in a street tree population

Treesearch

Lara A. Roman; John J. Battles; Joe R. McBride

2013-01-01

Street trees have aesthetic, environmental, human health, and economic benefits in urban ecosystems. Street tree populations are constructed by cycles of planting, growth, death, removal and replacement. The goals of this study were to understand how tree mortality and planting rates affect net population growth, evaluate the shape of the mortality curve, and assess...

Shaping Aid Policy for Increasing Revenue: Examining Admission Status, Unmet Need, and Demographic Characteristics as Persistence Predictors

ERIC Educational Resources Information Center

Sheren, Deborah L.

2018-01-01

Increasing costs and discount rates and decreasing persistence have led to deteriorating net tuition revenue at many colleges and universities. The lack of clarity about the relationship between student persistence and incoming student characteristics was interfering with the development of optimal tuition discounting policy and required research.…

Ontology based standardization of Petri net modeling for signaling pathways.

PubMed

Takai-Igarashi, Takako

2005-01-01

Taking account of the great availability of Petri nets in modeling and analyzing large complicated signaling networks, semantics of Petri nets is in need of systematization for the purpose of consistency and reusability of the models. This paper reports on standardization of units of Petri nets on the basis of an ontology that gives an intrinsic definition to the process of signaling in signaling pathways.

Ontology based standardization of petri net modeling for signaling pathways.

PubMed

Takai-Igarashi, Takako

2011-01-01

Taking account of the great availability of Petri nets in modeling and analyzing large complicated signaling networks, semantics of Petri nets is in need of systematization for the purpose of consistency and reusability of the models. This paper reports on standardization of units of Petri nets on the basis of an ontology that gives an intrinsic definition to the process of signaling in signaling pathways.

Modeling of Electrocardiograph Telediagnosing System Based on Petri Net

NASA Astrophysics Data System (ADS)

Hu, Wensong; Li, Ming; Li, Lan

This paper analyzed the characteristics of the electrocardiograph telediagnosing system. Firstly, we introduce the system and Petri nets. Secondly, we built a topological diagram of this system. Then we use Petri nets to show the physical process of this system. Finally, we verified the model of the electrocardiograph telediagnosing system. With the help of model based on Petri nets, we analyzed the system performance and feasibility.

Neutrophil Extracellular Traps: Formation and Involvement in Disease Progression.

PubMed

Kumar, Sanni; Gupta, Ena; Kaushik, Sanket; Jyoti, Anupam

2018-06-01

Neutrophils are the forerunner in innate immunity by defending the host organisms against infectious pathogens. During such process, neutrophils reach the site of inflammation/infection and eliminate the pathogens by phagocytosis as well as by forming the neutrophil extracellular traps (NETs). NETs trap and eradicate a number of microbes including bacteria, fungi, protozoa, viruses. NETs consist of DNA which is decorated with histones and granular proteins such as neutrophil elastase (NE), gelatinase, myeloperoxidase. NETosis (a process of NETs formation) is also involved in many inflammatory and autoimmune disorders with a major contribution to acute respiratory distress syndrome, sepsis, cystic fibrosis, periodontitis. Hyper NETosis or ineffective clearance of NETs would likely increase the risk of auto-antibody generation against NETs components and contribution in auto-inflammatory diseases. The purpose of this review is intended to highlight the molecular mechanisms of NETosis and its antimicrobial effect. Furthermore, a current status of NETosis in the pathogenesis of inflammatory and autoimmune disorders has been reviewed for better understanding.

Evaluation of Double-Vacuum-Bag Process For Composite Fabrication

NASA Technical Reports Server (NTRS)

Hou, T. H.; Jensen, B. J.

2004-01-01

A non-autoclave vacuum bag process using atmospheric pressure alone that eliminates the need for external pressure normally supplied by an autoclave or a press is an attractive method for composite fabrication. This type of process does not require large capital expenditures for tooling and processing equipment. In the molding cycle (temperature/pressure profile) for a given composite system, the vacuum application point has to be carefully selected to achieve the final consolidated laminate net shape and resin content without excessive resin squeeze-out. The traditional single-vacuum- bag (SVB) process is best suited for molding epoxy matrix based composites because of their superior flow and the absence of reaction by-products or other volatiles. Other classes of materials, such as polyimides and phenolics, generate water during cure. In addition, these materials are commonly synthesized as oligomers using solvents to facilitate processability. Volatiles (solvents and reaction byproducts) management therefore becomes a critical issue. SVB molding, without additional pressure, normally fails to yield void-free quality composites for these classes of resin systems. A double-vacuum- bag (DVB) process for volatile management was envisioned, designed and built at the NASA Langley Research Center. This experimental DVB process affords superior volatiles management compared to the traditional SVB process. Void-free composites are consistently fabricated as measured by C-scan and optical photomicroscopy for high performance polyimide and phenolic resins.

Modeling and Simulation of Metallurgical Process Based on Hybrid Petri Net

NASA Astrophysics Data System (ADS)

Ren, Yujuan; Bao, Hong

2016-11-01

In order to achieve the goals of energy saving and emission reduction of iron and steel enterprises, an increasing number of modeling and simulation technologies are used to research and analyse metallurgical production process. In this paper, the basic principle of Hybrid Petri net is used to model and analyse the Metallurgical Process. Firstly, the definition of Hybrid Petri Net System of Metallurgical Process (MPHPNS) and its modeling theory are proposed. Secondly, the model of MPHPNS based on material flow is constructed. The dynamic flow of materials and the real-time change of each technological state in metallurgical process are simulated vividly by using this model. The simulation process can implement interaction between the continuous event dynamic system and the discrete event dynamic system at the same level, and play a positive role in the production decision.

NCWin — A Component Object Model (COM) for processing and visualizing NetCDF data

USGS Publications Warehouse

Liu, Jinxun; Chen, J.M.; Price, D.T.; Liu, S.

2005-01-01

NetCDF (Network Common Data Form) is a data sharing protocol and library that is commonly used in large-scale atmospheric and environmental data archiving and modeling. The NetCDF tool described here, named NCWin and coded with Borland C + + Builder, was built as a standard executable as well as a COM (component object model) for the Microsoft Windows environment. COM is a powerful technology that enhances the reuse of applications (as components). Environmental model developers from different modeling environments, such as Python, JAVA, VISUAL FORTRAN, VISUAL BASIC, VISUAL C + +, and DELPHI, can reuse NCWin in their models to read, write and visualize NetCDF data. Some Windows applications, such as ArcGIS and Microsoft PowerPoint, can also call NCWin within the application. NCWin has three major components: 1) The data conversion part is designed to convert binary raw data to and from NetCDF data. It can process six data types (unsigned char, signed char, short, int, float, double) and three spatial data formats (BIP, BIL, BSQ); 2) The visualization part is designed for displaying grid map series (playing forward or backward) with simple map legend, and displaying temporal trend curves for data on individual map pixels; and 3) The modeling interface is designed for environmental model development by which a set of integrated NetCDF functions is provided for processing NetCDF data. To demonstrate that the NCWin can easily extend the functions of some current GIS software and the Office applications, examples of calling NCWin within ArcGIS and MS PowerPoint for showing NetCDF map animations are given.

A Design Verification of the Parallel Pipelined Image Processings

NASA Astrophysics Data System (ADS)

Wasaki, Katsumi; Harai, Toshiaki

2008-11-01

This paper presents a case study of the design and verification of a parallel and pipe-lined image processing unit based on an extended Petri net, which is called a Logical Colored Petri net (LCPN). This is suitable for Flexible-Manufacturing System (FMS) modeling and discussion of structural properties. LCPN is another family of colored place/transition-net(CPN) with the addition of the following features: integer value assignment of marks, representation of firing conditions as marks' value based formulae, and coupling of output procedures with transition firing. Therefore, to study the behavior of a system modeled with this net, we provide a means of searching the reachability tree for markings.

Improving timeliness and efficiency in the referral process for safety net providers: application of the Lean Six Sigma methodology.

PubMed

Deckard, Gloria J; Borkowski, Nancy; Diaz, Deisell; Sanchez, Carlos; Boisette, Serge A

2010-01-01

Designated primary care clinics largely serve low-income and uninsured patients who present a disproportionate number of chronic illnesses and face great difficulty in obtaining the medical care they need, particularly the access to specialty physicians. With limited capacity for providing specialty care, these primary care clinics generally refer patients to safety net hospitals' specialty ambulatory care clinics. A large public safety net health system successfully improved the effectiveness and efficiency of the specialty clinic referral process through application of Lean Six Sigma, an advanced process-improvement methodology and set of tools driven by statistics and engineering concepts.

Control of Wind Tunnel Operations Using Neural Net Interpretation of Flow Visualization Records

NASA Technical Reports Server (NTRS)

Buggele, Alvin E.; Decker, Arthur J.

1994-01-01

Neural net control of operations in a small subsonic/transonic/supersonic wind tunnel at Lewis Research Center is discussed. The tunnel and the layout for neural net control or control by other parallel processing techniques are described. The tunnel is an affordable, multiuser platform for testing instrumentation and components, as well as parallel processing and control strategies. Neural nets have already been tested on archival schlieren and holographic visualizations from this tunnel as well as recent supersonic and transonic shadowgraph. This paper discusses the performance of neural nets for interpreting shadowgraph images in connection with a recent exercise for tuning the tunnel in a subsonic/transonic cascade mode of operation. That mode was operated for performing wake surveys in connection with NASA's Advanced Subsonic Technology (AST) noise reduction program. The shadowgraph was presented to the neural nets as 60 by 60 pixel arrays. The outputs were tunnel parameters such as valve settings or tunnel state identifiers for selected tunnel operating points, conditions, or states. The neural nets were very sensitive, perhaps too sensitive, to shadowgraph pattern detail. However, the nets exhibited good immunity to variations in brightness, to noise, and to changes in contrast. The nets are fast enough so that ten or more can be combined per control operation to interpret flow visualization data, point sensor data, and model calculations. The pattern sensitivity of the nets will be utilized and tested to control wind tunnel operations at Mach 2.0 based on shock wave patterns.

Classification of pulmonary neuroendocrine tumors: new insights.

PubMed

Pelosi, Giuseppe; Sonzogni, Angelica; Harari, Sergio; Albini, Adriana; Bresaola, Enrica; Marchiò, Caterina; Massa, Federica; Righi, Luisella; Gatti, Gaia; Papanikolaou, Nikolaos; Vijayvergia, Namrata; Calabrese, Fiorella; Papotti, Mauro

2017-10-01

Neuroendocrine tumors of the lung (Lu-NETs) embrace a heterogeneous family of neoplasms classified into four histological variants, namely typical carcinoid (TC), atypical carcinoid (AC), large cell neuroendocrine carcinoma (LCNEC) and small cell lung carcinoma (SCLC). Defining criteria on resection specimens include mitotic count in 2 mm 2 and the presence or absence of necrosis, alongside a constellation of cytological and histological traits including cell size and shape, nuclear features and overall architecture. Clinically, TC are low-grade malignant tumors, AC intermediate-grade malignant tumors and SCLC/LCNEC high-grade malignant full-blown carcinomas with no significant differences in survival between them. Homologous tumors arise in the thymus that occasionally have some difficulties in differentiating from the lung counterparts when presented with large unresectable or metastatic lesions. Immunohistochemistry (IHC) helps refine NE diagnosis at various anatomical sites, particularly on small-sized tissue material, in which only TC and small cell carcinoma categories can be recognized easily on hematoxylin & eosin stain, while AC and LCNEC can only be suggested on such material. The Ki-67 labeling index effectively separates carcinoids from small cell carcinoma and may prove useful for the clinical management of a metastatic disease to help the therapeutic decision-making process. Although carcinoids and high-grade neuroendocrine carcinomas in the lung and elsewhere make up separate tumor categories on molecular grounds, emerging data supports the concept of secondary high-grade NETs arising in the preexisting carcinoids, whose clinical and biological relevance will have to be placed into the proper context for the optimal management of these patients. In this review, we will discuss the selected, recent literature with a focus on current issues regarding Lu-NET nosology, i.e., classification, derivation and tumor evolution.

Modelling of Biometric Identification System with Given Parameters Using Colored Petri Nets

NASA Astrophysics Data System (ADS)

Petrosyan, G.; Ter-Vardanyan, L.; Gaboutchian, A.

2017-05-01

Biometric identification systems use given parameters and function on the basis of Colored Petri Nets as a modelling language developed for systems in which communication, synchronization and distributed resources play an important role. Colored Petri Nets combine the strengths of Classical Petri Nets with the power of a high-level programming language. Coloured Petri Nets have both, formal intuitive and graphical presentations. Graphical CPN model consists of a set of interacting modules which include a network of places, transitions and arcs. Mathematical representation has a well-defined syntax and semantics, as well as defines system behavioural properties. One of the best known features used in biometric is the human finger print pattern. During the last decade other human features have become of interest, such as iris-based or face recognition. The objective of this paper is to introduce the fundamental concepts of Petri Nets in relation to tooth shape analysis. Biometric identification systems functioning has two phases: data enrollment phase and identification phase. During the data enrollment phase images of teeth are added to database. This record contains enrollment data as a noisy version of the biometrical data corresponding to the individual. During the identification phase an unknown individual is observed again and is compared to the enrollment data in the database and then system estimates the individual. The purpose of modeling biometric identification system by means of Petri Nets is to reveal the following aspects of the functioning model: the efficiency of the model, behavior of the model, mistakes and accidents in the model, feasibility of the model simplification or substitution of its separate components for more effective components without interfering system functioning. The results of biometric identification system modeling and evaluating are presented and discussed.

Modeling of wastewater treatment system of car parks from petroleum products

NASA Astrophysics Data System (ADS)

Savdur, S. N.; Stepanova, Yu V.; Kodolova, I. A.; Fesina, E. L.

2018-05-01

The paper discusses the technological complex of wastewater treatment of car parks from petroleum products. Based on the review of the main modeling methods of discrete-continuous chemical and engineering processes, it substantiates expediency of using the theory of Petri nets (PN) for modeling the process of wastewater treatment of car parks from petroleum products. It is proposed to use a modification of Petri nets which is focused on modeling and analysis of discrete-continuous chemical and engineering processes by prioritizing transitions, timing marks in positions and transitions. A model in the form of modified Petri nets (MPN) is designed. A software package to control the process for wastewater treatment is designed by means of SCADA TRACE MODE.

Measurement of stellar occultations

NASA Astrophysics Data System (ADS)

Eberle, Andreas

2008-09-01

Whenever an asteroid occults a star, we have the opportunity to study that asteroid in great detail. As frequently shown in the past, amateur astronomers1 have the necessary equipment to measure such events successfully2. Combined with the dense net of amateur observatories and online coordination tools3 for movable stations, they can create fine grids to detect even small bodies. The analysis of these events gives us the possibility to receive high precision astrometry data, to determine the asteroids size and shape (and therefore its albedo), and even to collect information on the star itself.4 While usually a set of several light curves is required to do so, a single recording5 of (10734) Wieck's occultation of HIP 22157 on 2008 Feb 08 was sufficient to retrieve the necessary data6. 1 Observation campaigns are organized by the International Occultation Timing Association (IOTA), http://www.iota-es.de/ 2 for results see e.g. euraster.net by E. Frappa, http://www.euraster.net/ 3 Occult Watcher by H. Pavlov, http://www.hristopavlov.net/OccultWatcher/OccultWatcher.html 4 see K. Miyashita's analysis of the observation of the occultation of TYC 1886-01206-1 by Kalliope and Linus, http://www005.upp.so-net.ne.jp/k miyash/occ02/kalliope/doublestar en.html 5 recording obtained by H. Michels, MPC Station Code 240 6 using Limovie by K. Miyashita

Climate response of the soil nitrogen cycle in three forest types of a headwater Mediterranean catchment

NASA Astrophysics Data System (ADS)

Lupon, Anna; Gerber, Stefan; Sabater, Francesc; Bernal, Susana

2015-05-01

Future changes in climate may affect soil nitrogen (N) transformations, and consequently, plant nutrition and N losses from terrestrial to stream ecosystems. We investigated the response of soil N cycling to changes in soil moisture, soil temperature, and precipitation across three Mediterranean forest types (evergreen oak, beech, and riparian) by fusing a simple process-based model (which included climate modifiers for key soil N processes) with measurements of soil organic N content, mineralization, nitrification, and concentration of ammonium and nitrate. The model describes sources (atmospheric deposition and net N mineralization) and sinks (plant uptake and hydrological losses) of inorganic N from and to the 0-10 cm soil pool as well as net nitrification. For the three forest types, the model successfully recreated the magnitude and temporal pattern of soil N processes and N concentrations (Nash-Sutcliffe coefficient = 0.49-0.96). Changes in soil water availability drove net N mineralization and net nitrification at the oak and beech forests, while temperature and precipitation were the strongest climatic factors for riparian soil N processes. In most cases, net N mineralization and net nitrification showed a different sensitivity to climatic drivers (temperature, soil moisture, and precipitation). Our model suggests that future climate change may have a minimal effect on the soil N cycle of these forests (<10% change in mean annual rates) because positive warming and negative drying effects on the soil N cycle may counterbalance each other.

Hardware implementation of fuzzy Petri net as a controller.

PubMed

Gniewek, Lesław; Kluska, Jacek

2004-06-01

The paper presents a new approach to fuzzy Petri net (FPN) and its hardware implementation. The authors' motivation is as follows. Complex industrial processes can be often decomposed into many parallelly working subprocesses, which can, in turn, be modeled using Petri nets. If all the process variables (or events) are assumed to be two-valued signals, then it is possible to obtain a hardware or software control device, which works according to the algorithm described by conventional Petri net. However, the values of real signals are contained in some bounded interval and can be interpreted as events which are not only true or false, but rather true in some degree from the interval [0, 1]. Such a natural interpretation from multivalued logic (fuzzy logic) point of view, concerns sensor outputs, control signals, time expiration, etc. It leads to the idea of FPN as a controller, which one can rather simply obtain, and which would be able to process both analog, and binary signals. In the paper both graphical, and algebraic representations of the proposed FPN are given. The conditions under which transitions can be fired are described. The algebraic description of the net and a theorem which enables computation of new marking in the net, based on current marking, are formulated. Hardware implementation of the FPN, which uses fuzzy JK flip-flops and fuzzy gates, are proposed. An example illustrating usefulness of the proposed FPN for control algorithm description and its synthesis as a controller device for the concrete production process are presented.

Process-Structure-Property Relationships for 316L Stainless Steel Fabricated by Additive Manufacturing and Its Implication for Component Engineering

NASA Astrophysics Data System (ADS)

Yang, Nancy; Yee, J.; Zheng, B.; Gaiser, K.; Reynolds, T.; Clemon, L.; Lu, W. Y.; Schoenung, J. M.; Lavernia, E. J.

2017-04-01

We investigate the process-structure-property relationships for 316L stainless steel prototyping utilizing 3-D laser engineered net shaping (LENS), a commercial direct energy deposition additive manufacturing process. The study concluded that the resultant physical metallurgy of 3-D LENS 316L prototypes is dictated by the interactive metallurgical reactions, during instantaneous powder feeding/melting, molten metal flow and liquid metal solidification. The study also showed 3-D LENS manufacturing is capable of building high strength and ductile 316L prototypes due to its fine cellular spacing from fast solidification cooling, and the well-fused epitaxial interfaces at metal flow trails and interpass boundaries. However, without further LENS process control and optimization, the deposits are vulnerable to localized hardness variation attributed to heterogeneous microstructure, i.e., the interpass heat-affected zone (HAZ) from repetitive thermal heating during successive layer depositions. Most significantly, the current deposits exhibit anisotropic tensile behavior, i.e., lower strain and/or premature interpass delamination parallel to build direction (axial). This anisotropic behavior is attributed to the presence of interpass HAZ, which coexists with flying feedstock inclusions and porosity from incomplete molten metal fusion. The current observations and findings contribute to the scientific basis for future process control and optimization necessary for material property control and defect mitigation.

Transient oscillation of shape and membrane conductivity changes by field pulse-induced electroporation in nano-sized phospholipid vesicles.

PubMed

Dimitrov, Vasil; Kakorin, Sergej; Neumann, Eberhard

2013-05-07

The results of electrooptical and conductometrical measurements on unilamellar lipid vesicles (of mean radius a = 90 nm), filled with 0.2 M NaCl solution, suspended in 0.33 M sucrose solution of 0.2 mM NaCl, and exposed to a stepwise decaying electric field (time constant τE = 154 μs) in the range 10 ≤ E0 (kV cm(-1)) ≤ 90, are analyzed in terms of cyclic changes in vesicle shape and vesicle membrane conductivity. The two peaks in the dichroitic turbidity relaxations reflect two cycles of rapid membrane electroporation and slower resealing of long-lived electropores. The field-induced changes reflect structural transitions between closed (C) and porated (P) membrane states, qualified by pores of type P1 and of type P2, respectively. The transient change in the membrane conductivity and the transient shape oscillation are based on changes in the pore density of the (larger) P2-pores along a hysteresis cycle. The P2-pore formation leads to transient net ion flows across the P2-pores and to transient changes in the membrane field. The kinetic data are numerically processed in terms of coupled structural relaxation modes. Using the torus-hole pore model, the mean inner pore radii are estimated to be r1 = 0.38 (±0.05) nm and r2 = 1.7 (±0.1) nm, respectively. The observation of a transient oscillation of membrane electroporation and of shape changes in a longer lasting external field pulse is suggestive of potential resonance enhancement, for instance, of electro-uptake by, and of electro-release of biogenic molecules from, biological cells in trains of long-lasting low-intensity voltage pulses.

Ohmsett test of NOFI Vee-Sweep and NOFI 600S oilboom. Final report

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

Goodwin, M.J.

1993-10-01

A NOFI Vee-Sweep and a NOFI 600S Oilboom, both manufactured by NOFI TROMSO A/S of Norway, were tested at the Ohmsett test tank in Leonardo, NJ. The V-Shaped Sweep is an oil boom designed for use with a skimmer at the apex of the V-Shaped configuration. Oil is funneled back to the skimmer by the converging sides of the V and concentrated for more efficient skimming. The 60 meter length of the sweep is doubled over to form the V and held in this shape by cross netting at the bottom of the skirt. The bottom netting is claimed tomore » help stabilize the oil in the sweep. The sweep was towed with a 700mm skirt depth and mouth opening of 16 meters. The mouth opening was reduced from the designed 19.8 meters to fit in the tow tank without causing excess blockage. The limiting towing speeds of the sweep were determined with and without oil present, in calm water and in small waves. The sweep's ability to conform to waves was also determined. Towing forces were measured. Limited data on oil loss rates were obtained. Testing confirmed the manufacturer's claim that the sweep can be towed at 1.0 and 1.4 knots with oil in calm water, based on the first loss of oil. The critical tow speed was found to be 3.4 to 3.6 knots in calm water. Oil booms, Tow tank testing.« less

Superplastic forming of ceramic insulation

NASA Technical Reports Server (NTRS)

Nieh, T. G.; Wittenauer, J. P.; Wadsworth, J.

1992-01-01

Superplasticity has been demonstrated in many fine-grained structural ceramics and ceramic composites, including yttria-stabilized tetragonal zirconia polycrystal (YTZP), alumina, and Al2O3-reinforced zirconia (Al2O3/YTZ) duplex composites and SiC-reinforced Si3N4. These superplastic ceramics obviously offer the potential benefit of forming net shape or near net shape parts. This could be particularly useful for forming complicated shapes that are difficult to achieve using conventional forming techniques, or require elaborate, subsequent machining. In the present study, we successfully demonstrated the following: (1) superplastic 3Y-TXP and 20 percent Al2O3/YTZ composite have for the first time been successfully deformed into hemispherical caps via a biaxial gas-pressure forming technique; (2) no experimental difficulty was encountered in applying the required gas pressures and temperatures to achieve the results, thus, it is certain that higher rates of deformation than those presented in this study will be possible by using the current test apparatus at higher temperatures and pressures; and (3) an analytical model incorporating material parameters, such as variations during forming in the strain rate sensitivity exponent and grain growth-induced strain hardening, is needed to model accurately and therefore precisely control the biaxial gas-pressure forming of superplastic ceramics. Based on the results of this study, we propose to fabricate zirconia insulation tubes by superplastic extrusion of zirconia polycrystal. This would not only reduce the cost, but also improve the reliability of the tube products.

High field terahertz pulse generation from plasma wakefield driven by tailored laser pulses

NASA Astrophysics Data System (ADS)

Chen, Zi-Yu

2013-06-01

A scheme to generate high field terahertz (THz) pulses by using tailored laser pulses interaction with a gas target is proposed. The laser wakefield based THz source is emitted from the asymmetric laser shape induced plasma transverse transient net currents. Particle-in-cell simulations show that THz emission with electric filed strength over 1 GV/cm can be obtained with incident laser at 1×1019 W/cm2 level, and the corresponding energy conversion efficiency is more than 10-4. The intensity scaling holds up to high field strengths. Such a source also has a broad tunability range in amplitude, frequency spectra, and temporal shape.

Can the collection of expired long-lasting insecticidal nets reduce their coverage and use? Sociocultural aspects related to LLIN life cycle management and use in four districts in Madagascar.

PubMed

Ramanantsoa, Ambinina; Wilson-Barthes, Marta; Rahenintsoa, Rindra; Hoibak, Sarah; Ranaivoharimina, Harilala; Rahelimalala, Martha Delphine; Rakotomanga, Avotiana; Finlay, Alyssa; Muela Ribera, Joan; Peeters Grietens, Koen

2017-10-10

There is growing awareness of the likely impact increased numbers of LLINs will have on the environment, if not disposed of or recycled appropriately. As part of a World Health Organization (WHO) and United Nations Environment Programme (UNEP) pilot study to assess environmentally-sound and cost-effective LLIN recycling strategies, the USAID-Deliver Project collected 22,559 used bed nets in Madagascar. A social science study was conducted to provide data on socio-cultural factors related to collection and replacement of LLINs, including impact on primary and other net uses. Ethnographic exploratory research was carried out following the pilot USAID-Deliver net collection and recycling campaign in Betioky, Tsihombe, Fenerive Est and Ambanja districts of Madagascar, triangulating participant observation, interviewing and group discussions. Sampling was theoretical and data analysis was a continuous and iterative process concurrent to data collection. Final analysis was conducted using NVivo10. The following themes emerged as contributing to the success of collecting expired LLINs in the community for recycling purposes: (i) net adequacy and preference: characteristic differences between collected and newly distributed nets lead to communities' reticence to relinquish old nets before confirming new nets were appropriate for intended use. Where newly distributed nets failed to meet local requirements, this was expected to increase alternative uses and decrease household turn over. (ii) Net collection strategies: the net collection campaign brought net use out of the private sphere and into the public arena. Net owners reported feeling ashamed when presenting damaged nets in public for collection, leading to reduced net relinquishment. (iii) Net lifecycle: communities perceived nets as being individually owned and economic value was attributed both to good-condition nets for sleeping and to worn nets for alternative/secondary purposes. Collecting nets at the stage of waste rather than at their prescribed end of life was locally acceptable. The collection of LLINs for recycling/disposal can lead to lower coverage under certain conditions. Collecting used LLINs may be appropriate under the following conditions: (i) nets are collected at the stage of waste; (ii) new nets are in line with community preferences; and (iii) collection strategies have been agreed upon within the community prior to replacement activities. Any collection/recycling of old LLINs should be based on in-depth understanding of the local context and include participatory processes to prevent reduced coverage.

Modeling of Biometric Identification System Using the Colored Petri Nets

NASA Astrophysics Data System (ADS)

Petrosyan, G. R.; Ter-Vardanyan, L. A.; Gaboutchian, A. V.

2015-05-01

In this paper we present a model of biometric identification system transformed into Petri Nets. Petri Nets, as a graphical and mathematical tool, provide a uniform environment for modelling, formal analysis, and design of discrete event systems. The main objective of this paper is to introduce the fundamental concepts of Petri Nets to the researchers and practitioners, both from identification systems, who are involved in the work in the areas of modelling and analysis of biometric identification types of systems, as well as those who may potentially be involved in these areas. In addition, the paper introduces high-level Petri Nets, as Colored Petri Nets (CPN). In this paper the model of Colored Petri Net describes the identification process much simpler.

Preventing Clogging In A Vacuum Plasma Spray Gun

NASA Technical Reports Server (NTRS)

Krotz, Phillip D.; Daniel, Ronald L., Jr.; Davis, William M.

1994-01-01

Modification of powder-injection ports enables lengthy, high-temperature deposition operations. Graphite inserts prevent clogging of ports through which copper powder injected into vacuum plasma spray (VPS) gun. Graphite liners eliminate need to spend production time refurbishing VPS gun, reducing cost of production and increasing productivity. Concept also applied to other material systems used for net-shape fabrication via VPS.

Guidelines for estimating volume, biomass, and smoke production for piled slash.

Treesearch

Colin C. Hardy

1998-01-01

Guidelines in the form of a six-step approach are provided for estimating volumes, oven-dry mass, consumption, and particulate matter emissions for piled logging debris. Seven stylized pile shapes and their associated geometric volume formulae are used to estimate gross pile volumes. The gross volumes are then reduced to net wood volume by applying an appropriate wood-...

Model-based occluded object recognition using Petri nets

NASA Astrophysics Data System (ADS)

Zhou, Chuan; Hura, Gurdeep S.

1998-09-01

This paper discusses the use of Petri nets to model the process of the object matching between an image and a model under different 2D geometric transformations. This transformation finds its applications in sensor-based robot control, flexible manufacturing system and industrial inspection, etc. A description approach for object structure is presented by its topological structure relation called Point-Line Relation Structure (PLRS). It has been shown how Petri nets can be used to model the matching process, and an optimal or near optimal matching can be obtained by tracking the reachability graph of the net. The experiment result shows that object can be successfully identified and located under 2D transformation such as translations, rotations, scale changes and distortions due to object occluded partially.

Deep learning application: rubbish classification with aid of an android device

NASA Astrophysics Data System (ADS)

Liu, Sijiang; Jiang, Bo; Zhan, Jie

2017-06-01

Deep learning is a very hot topic currently in pattern recognition and artificial intelligence researches. Aiming at the practical problem that people usually don't know correct classifications some rubbish should belong to, based on the powerful image classification ability of the deep learning method, we have designed a prototype system to help users to classify kinds of rubbish. Firstly the CaffeNet Model was adopted for our classification network training on the ImageNet dataset, and the trained network was deployed on a web server. Secondly an android app was developed for users to capture images of unclassified rubbish, upload images to the web server for analyzing backstage and retrieve the feedback, so that users can obtain the classification guide by an android device conveniently. Tests on our prototype system of rubbish classification show that: an image of one single type of rubbish with origin shape can be better used to judge its classification, while an image containing kinds of rubbish or rubbish with changed shape may fail to help users to decide rubbish's classification. However, the system still shows promising auxiliary function for rubbish classification if the network training strategy can be optimized further.

Getting drowned in a swirl: Deformable bead-spring model microswimmers in external flow fields

NASA Astrophysics Data System (ADS)

Küchler, Niklas; Löwen, Hartmut; Menzel, Andreas M.

2016-02-01

Deformability is a central feature of many types of microswimmers, e.g., for artificially generated self-propelled droplets. Here, we analyze deformable bead-spring microswimmers in an externally imposed solvent flow field as simple theoretical model systems. We focus on their behavior in a circular swirl flow in two spatial dimensions. Linear (straight) two-bead swimmers are found to circle around the swirl with a slight drift to the outside with increasing activity. In contrast to that, we observe for triangular three-bead or squarelike four-bead swimmers a tendency of being drawn into the swirl and finally getting drowned, although a radial inward component is absent in the flow field. During one cycle around the swirl, the self-propulsion direction of an active triangular or squarelike swimmer remains almost constant, while their orbits become deformed exhibiting an "egglike" shape. Over time, the swirl flow induces slight net rotations of these swimmer types, which leads to net rotations of the egg-shaped orbits. Interestingly, in certain cases, the orbital rotation changes sense when the swimmer approaches the flow singularity. Our predictions can be verified in real-space experiments on artificial microswimmers.

Cyber Situational Awareness through Operational Streaming Analysis

DTIC Science & Technology

2011-04-07

Our system makes use of two specific data sources from network traffic: raw packet data and NetFlow connection summary records (de- scribed below...implemented an operational prototype system using the following two data feeds. a) NetFlow Data: Our system processes the NetFlow records of all...Internet gateway traffic for a large enterprise network. It uses the standard Cisco NetFlow version 5 proto- col, which defines a flow as a

Channel size influence on the heat flux density at zero net mass flow in the non-linear transport regime between 1.2 and 2.1 K

NASA Technical Reports Server (NTRS)

Frederking, T. H. K.; Yuan, S. W. K.; Lee, J. M.; Sun, G. S.

1987-01-01

Porous media and narrow ducts of simple shape at zero net mass flow (ZNMF) are used to investigate the influence of pore size on the entropy/heat convection rate at ZNMF. The study is relevant to the development of specific types of phase separators. Previous work on heat transport by convection is extended to porous media without mass loss. The experimental results show the influence of pore size on heat flux for permeabilities between 10 to the -8th and 10 to the -6th sq cm. ZNMF plug data are found to be similar to results obtained for vapor liquid phase separation.

Deep feature classification of angiomyolipoma without visible fat and renal cell carcinoma in abdominal contrast-enhanced CT images with texture image patches and hand-crafted feature concatenation.

PubMed

Lee, Hansang; Hong, Helen; Kim, Junmo; Jung, Dae Chul

2018-04-01

To develop an automatic deep feature classification (DFC) method for distinguishing benign angiomyolipoma without visible fat (AMLwvf) from malignant clear cell renal cell carcinoma (ccRCC) from abdominal contrast-enhanced computer tomography (CE CT) images. A dataset including 80 abdominal CT images of 39 AMLwvf and 41 ccRCC patients was used. We proposed a DFC method for differentiating the small renal masses (SRM) into AMLwvf and ccRCC using the combination of hand-crafted and deep features, and machine learning classifiers. First, 71-dimensional hand-crafted features (HCF) of texture and shape were extracted from the SRM contours. Second, 1000-4000-dimensional deep features (DF) were extracted from the ImageNet pretrained deep learning model with the SRM image patches. In DF extraction, we proposed the texture image patches (TIP) to emphasize the texture information inside the mass in DFs and reduce the mass size variability. Finally, the two features were concatenated and the random forest (RF) classifier was trained on these concatenated features to classify the types of SRMs. The proposed method was tested on our dataset using leave-one-out cross-validation and evaluated using accuracy, sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), and area under receiver operating characteristics curve (AUC). In experiments, the combinations of four deep learning models, AlexNet, VGGNet, GoogleNet, and ResNet, and four input image patches, including original, masked, mass-size, and texture image patches, were compared and analyzed. In qualitative evaluation, we observed the change in feature distributions between the proposed and comparative methods using tSNE method. In quantitative evaluation, we evaluated and compared the classification results, and observed that (a) the proposed HCF + DF outperformed HCF-only and DF-only, (b) AlexNet showed generally the best performances among the CNN models, and (c) the proposed TIPs not only achieved the competitive performances among the input patches, but also steady performance regardless of CNN models. As a result, the proposed method achieved the accuracy of 76.6 ± 1.4% for the proposed HCF + DF with AlexNet and TIPs, which improved the accuracy by 6.6%p and 8.3%p compared to HCF-only and DF-only, respectively. The proposed shape features and TIPs improved the HCFs and DFs, respectively, and the feature concatenation further enhanced the quality of features for differentiating AMLwvf from ccRCC in abdominal CE CT images. © 2018 American Association of Physicists in Medicine.

Toroidal magnet system

DOEpatents

Ohkawa, Tihiro; Baker, Charles C.

1981-01-01

In a plasma device having a toroidal plasma containment vessel, a toroidal field-generating coil system includes fixed linking coils each formed of first and second sections with the first section passing through a central opening through the containment vessel and the second section completing the linking coil to link the containment vessel. A plurality of removable unlinked coils are each formed of first and second C-shaped sections joined to each other at their open ends with their bights spaced apart. The second C-shaped section of each movable coil is removably mounted adjacent the second section of a linking coil, with the containment vessel disposed between the open ends of the first and second C-shaped sections. Electric current is passed through the linking and removable coils in opposite sense in the respective adjacent second sections to produce a net toroidal field.

Hair bundles of cochlear outer hair cells are shaped to minimize their fluid-dynamic resistance.

PubMed

Ciganović, Nikola; Wolde-Kidan, Amanuel; Reichenbach, Tobias

2017-06-15

The mammalian sense of hearing relies on two types of sensory cells: inner hair cells transmit the auditory stimulus to the brain, while outer hair cells mechanically modulate the stimulus through active feedback. Stimulation of a hair cell is mediated by displacements of its mechanosensitive hair bundle which protrudes from the apical surface of the cell into a narrow fluid-filled space between reticular lamina and tectorial membrane. While hair bundles of inner hair cells are of linear shape, those of outer hair cells exhibit a distinctive V-shape. The biophysical rationale behind this morphology, however, remains unknown. Here we use analytical and computational methods to study the fluid flow across rows of differently shaped hair bundles. We find that rows of V-shaped hair bundles have a considerably reduced resistance to crossflow, and that the biologically observed shapes of hair bundles of outer hair cells are near-optimal in this regard. This observation accords with the function of outer hair cells and lends support to the recent hypothesis that inner hair cells are stimulated by a net flow, in addition to the well-established shear flow that arises from shearing between the reticular lamina and the tectorial membrane.

Raising the Degree of Service-Orientation of a SOA-based Software System: A Case Study

DTIC Science & Technology

2009-12-01

protocols, as well as executable processes that can be compiled into runtime scripts” [2] The Business Process Modeling Notation ( BPMN ) provides a...Notation ( BPMN ) 1.2. Jan. 2009. URL: http://www.omg.org/spec/ BPMN /1.2/ [25] .NET Framework Developer Center. .NET Remoting Overview. 2003. URL: http

The Microstructure Evolution of a Fe₃Al Alloy during the LENS Process.

PubMed

Karczewski, Krzysztof; Durejko, Tomasz; Czujko, Tomasz

2018-03-07

A Fe₃Al intermetallic alloy has been successfully prepared by the laser-engineered net shaping (LENS) process. The applied process parameters were selected to provide various cooling rates during the solidification of the laser-melted material. The macro- and microstructure and the micro- and macrotexture of Fe₃Al samples were investigated. The influence of the cooling rate on grain morphology and texture is discussed. For the applied cooling rate range of 0.64 × 10⁴ K/s-2.6 × 10⁴ K/s, the structure is characterized by the presence of columnar grains for which the growth is directed upwards from the substrate. The intensity of the microtexture varies with the height of the sample and the cooling rate. The intensity of the texture increases with the decrease in the cooling rate. The samples that were obtained with low and medium cooling rates are characterized by the well-developed <100> and <111> macrotextures. The Fe₃Al alloy that was produced with a high cooling rate did not show a specific texture, which is reflected in the fairly uniform distribution of the normalized density intensity. Only a very weak texture with a <100> type component was observed.

Twenty-First Century Energy Policy Making in New Hampshire: Lessons for Collaboration

NASA Astrophysics Data System (ADS)

Herndon, Henry Phillip

In this thesis I investigate the organizational field that is New Hampshire's energy policy-making community as it engages with the state regulatory institution, the Public Utilities Commission, to grapple the challenges of designing a 21st century electricity marketplace. The Public Utilities Commission structure and function are evolving. Historically, the Commission has used adjudicative proceedings to carry out a ratemaking function for monopoly utilities. The Commission's adjudicative process is evolving to become increasingly collaborative as it begins to carry out its new function of 21st century electricity market design. I analyze both the new structure (collaboration) and the new function (21 st century electricity market design) of the Commission through three in-depth case studies of dockets (policy-making processes): Energy Efficiency Resource Standard, Electric Grid Modernization, and Net Metering. My findings identify ways in which the Public Utilities Commission structure for making energy policy decisions is flexible and may be shaped by stakeholders engaging in policy processes. Stakeholders have the power to collectively design regulatory proceedings to incorporate greater opportunities for collaboration to better suit the challenges posed by a 21st century electricity sector. I provide recommendations on how that redesign should occur.

Five-Axis Ultrasonic Additive Manufacturing for Nuclear Component Manufacture

NASA Astrophysics Data System (ADS)

Hehr, Adam; Wenning, Justin; Terrani, Kurt; Babu, Sudarsanam Suresh; Norfolk, Mark

2017-03-01

Ultrasonic additive manufacturing (UAM) is a three-dimensional metal printing technology which uses high-frequency vibrations to scrub and weld together both similar and dissimilar metal foils. There is no melting in the process and no special atmosphere requirements are needed. Consequently, dissimilar metals can be joined with little to no intermetallic compound formation, and large components can be manufactured. These attributes have the potential to transform manufacturing of nuclear reactor core components such as control elements for the High Flux Isotope Reactor at Oak Ridge National Laboratory. These components are hybrid structures consisting of an outer cladding layer in contact with the coolant with neutron-absorbing materials inside, such as neutron poisons for reactor control purposes. UAM systems are built into a computer numerical control (CNC) framework to utilize intermittent subtractive processes. These subtractive processes are used to introduce internal features as the component is being built and for net shaping. The CNC framework is also used for controlling the motion of the welding operation. It is demonstrated here that curved components with embedded features can be produced using a five-axis code for the welder for the first time.

Five-axis ultrasonic additive manufacturing for nuclear component manufacture

DOE PAGES

Hehr, Adam; Wenning, Justin; Terrani, Kurt A.; ...

2016-01-01

Ultrasonic additive manufacturing (UAM) is a three-dimensional metal printing technology which uses high-frequency vibrations to scrub and weld together both similar and dissimilar metal foils. There is no melting in the process and no special atmosphere requirements are needed. Consequently, dissimilar metals can be joined with little to no intermetallic compound formation, and large components can be manufactured. These attributes have the potential to transform manufacturing of nuclear reactor core components such as control elements for the High Flux Isotope Reactor at Oak Ridge National Laboratory. These components are hybrid structures consisting of an outer cladding layer in contact withmore » the coolant with neutron-absorbing materials inside, such as neutron poisons for reactor control purposes. UAM systems are built into a computer numerical control (CNC) framework to utilize intermittent subtractive processes. These subtractive processes are used to introduce internal features as the component is being built and for net shaping. The CNC framework is also used for controlling the motion of the welding operation. Lastly, it is demonstrated here that curved components with embedded features can be produced using a five-axis code for the welder for the first time.« less

Effect Of Gravity On Porous Tricalcium Phosphate And Nonstoichiometric Titanium Carbide Produced Via Combustion Synthesis

NASA Technical Reports Server (NTRS)

Castillo, M.; Moore, J. J.; Schowengerdt, F. D.; Ayers, R. A.

2003-01-01

Novel processing techniques, such as self-propagating high temperature synthesis (SHS), have the capability to rapidly produce advanced porous materials that are difficult to fabricate by other methods. This processing technique is also capable of near net shape synthesis, while variable gravity allows the manipulation of the structure and composition of the material. The creation of porous tricalcium phosphate (TCP) is advantageous in the biomaterials field, since it is both a biocompatible material and an osteoconductive material. Porous tricalcium phosphate produced via SHS is an excellent candidate for bone scaffold material in the bone regeneration process. The porosity allows for great vascularization and ingrowth of tissue. Titanium Carbide is a nonstoichiometric biocompatible material that can be incorporated into a TiC-Ti composite system using combustion synthesis. The TiC-Ti composite exhibits a wide range of mechanical and chemical properties. Both of these material systems (TCP and TiC-Ti) can be used to advantage in designing novel bone replacement materials. Gravity plays an important role in both the pore structure and the chemical uniformity of these composite systems and offers considerable potential in advanced bone engineering.

A Winning Cast

NASA Technical Reports Server (NTRS)

2001-01-01

Howmet Research Corporation was the first to commercialize an innovative cast metal technology developed at Auburn University, Auburn, Alabama. With funding assistance from NASA's Marshall Space Flight Center, Auburn University's Solidification Design Center (a NASA Commercial Space Center), developed accurate nickel-based superalloy data for casting molten metals. Through a contract agreement, Howmet used the data to develop computer model predictions of molten metals and molding materials in cast metal manufacturing. Howmet Metal Mold (HMM), part of Howmet Corporation Specialty Products, of Whitehall, Michigan, utilizes metal molds to manufacture net shape castings in various alloys and amorphous metal (metallic glass). By implementing the thermophysical property data from by Auburn researchers, Howmet employs its newly developed computer model predictions to offer customers high-quality, low-cost, products with significantly improved mechanical properties. Components fabricated with this new process replace components originally made from forgings or billet. Compared with products manufactured through traditional casting methods, Howmet's computer-modeled castings come out on top.

Laser surface modification of 316 L stainless steel with bioactive hydroxyapatite.

PubMed

Balla, Vamsi Krishna; Das, Mitun; Bose, Sreyashree; Ram, G D Janaki; Manna, Indranil

2013-12-01

Laser-engineered net shaping (LENS™), a commercial additive manufacturing process, was used to modify the surfaces of 316 L stainless steel with bioactive hydroxyapatite (HAP). The modified surfaces were characterized in terms of their microstructure, hardness and apatite forming ability. The results showed that with increase in laser energy input from 32 J/mm(2) to 59 J/mm(2) the thickness of the modified surface increased from 222±12 μm to 355±6 μm, while the average surface hardness decreased marginally from 403±18 HV0.3 to 372±8 HV0.3. Microstructural studies showed that the modified surface consisted of austenite dendrites with HAP and some reaction products primarily occurring in the inter-dendritic regions. Finally, the surface-modified 316 L samples immersed in simulated body fluids showed significantly higher apatite precipitation compared to unmodified 316 L samples. © 2013.

Feasibility Assessment for Pressure Casting of Ceramic-Aluminum Composites for NASA's Propulsion Applications

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

2005-01-01

Feasibility assessment of pressure casting of ceramic-aluminum composites for NASA% propulsion applications is summarized. A combination of several demonstration projects to produce three unique components for liquid hydrogen-oxygen rocket engine% flanges, valves and turbo-pump housing are conducted. These components are made from boron carbide, silicon carbide and alumina powders fabricated into complex net shaped parts using dry green powder compaction, slip casting or a novel 3D ink-jet printing process, followed by sintering to produce performs that can be pressure cast by infiltration with molten aluminum. I n addition, joining techniques are also explored to insure that these components can be assembled into a structure without degrading their highly tailored properties. The feasibility assessment was made to determine if these new materials could provide a significant weight savings, thereby reducing vehicle launch costs, while being durable materials to increase safety and performance for propulsion system.

Application of superalloy powder metallurgy for aircraft engines

NASA Technical Reports Server (NTRS)

Dreshfield, R. L.; Miner, R. V., Jr.

1980-01-01

In the last decade, Government/Industry programs have advanced powder metallurgy-near-net-shape technology to permit the use of hot isostatic pressed (HIP) turbine disks in the commercial aircraft fleet. These disks offer a 30% savings of input weight and an 8% savings in cost compared in cast-and-wrought disks. Similar savings were demonstrated for other rotating engine components. A compressor rotor fabricated from hot-die-forged-HIP superalloy billets revealed input weight savings of 54% and cost savings of 35% compared to cast-and-wrought parts. Engine components can be produced from compositions such as Rene 95 and Astroloy by conventional casting and forging, by forging of HIP powder billets, or by direct consolidation of powder by HIP. However, each process produces differences in microstructure or introduces different defects in the parts. As a result, their mechanical properties are not necessarily identical. Acceptance methods should be developed which recognize and account for the differences.

Integration of Heat Treatment with Shot Peening of 17-4 Stainless Steel Fabricated by Direct Metal Laser Sintering

NASA Astrophysics Data System (ADS)

AlMangour, Bandar; Yang, Jenn-Ming

2017-11-01

Direct metal laser sintering (DMLS) is a promising powder-based additive manufacturing process for fabrication of near-net-shape parts. However, the typically poor fatigue performance of DMLS parts must be addressed for use in demanding industrial applications. Post-treatment can be applied to enhance the performance of such components. Earlier attempts at inducing grain refinement through severe plastic deformation of part surfaces using shot peening improved the physical and mechanical properties of metals without chemical alteration. However, heat treatment can modify the surface-hardening effects attained by shot peening. Hence, we examined the feasibility of applying shot peening combined with heat treatment to improve the performance of DMLS-fabricated 17-4 stainless steel parts through microstructural evolution studies and hardness measurements. Compared to a specimen treated only by shot peening, the sample exposed to additional heat treatment showed increased hardness due to aging of the dominant phase.

Plasma Chamber Design and Fabrication Activities

NASA Astrophysics Data System (ADS)

Parodi, B.; Bianchi, A.; Cucchiaro, A.; Coletti, A.; Frosi, P.; Mazzone, G.; Pizzuto, A.; Ramogida, G.; Coppi, B.

2006-10-01

A fabrication procedure for a typical Plasma Chamber (PC) sector has been developed to cover all the manufacturing phases, from the raw materials specification (including metallurgical processes) to the machining operations, acceptance procedures and vacuum tests. Basically, the sector is made of shaped elements (forged or rolled) welded together using special fixtures and then machined to achieve the final dimensional accuracy. An upgraded design of the plasma chamber's vertical support that can withstand the estimated electromagnetic loads (Eddy and Halo current plus horizontal net force resulting from the worst plasma disruption scenario VDE, Vertical Displacement Event) has been completed. The maintenance of the radial support can take place hands-on with a direct access from outside the cryostat. With the present design, vacuum tightness is achieved by welding conducted with automatic welding heads. On the outer surface of the PC a dedicated duct system, filled by helium gas, is included to cool down the PC to room temperature when needed.

Quantitative characterization of porosity in stainless steel LENS powders and deposits

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

Susan, D.F.; Puskar, J.D.; Brooks, J.A.

2006-07-15

Laser Engineered Net Shaping (LENS) utilizes a laser beam to melt fine powders to produce three-dimensional engineering structures line by line and layer by layer. When building these structures, defects including lack-of-fusion (LOF) at interlayer boundaries and intralayer porosity are sometimes observed. LOF defects can be minimized by adjusting processing parameters, but the sources of intralayer porosity are less apparent. In this paper, the amount and size distributions of 17-4PH and 304L powders and pores within the powder were characterized in parallel with the intralayer porosity in LENS deposits fabricated from the same materials. Intralayer porosity increased with increased powdermore » porosity; but was not well correlated with deposition parameters. The results demonstrate the importance of careful characterization and specification of starting powders on the quality of the final LENS deposits.« less

Dysprosium-free melt-spun permanent magnets.

PubMed

Brown, D N; Wu, Z; He, F; Miller, D J; Herchenroeder, J W

2014-02-12

Melt-spun NdFeB powders can be formed into a number of different types of permanent magnet for a variety of applications in electronics, automotive and clean technology industries. The melt-spinning process produces flake powder with a fine uniform array of nanoscale Nd2Fe14B grains. These powders can be net-shape formed into isotropic polymer-bonded magnets or hot formed into fully dense magnets. This paper discusses the influence of heavy rare earth elements and microstructure on the magnetic performance, thermal stability and material cost of NdFeB magnets. Evidence indicates that melt-spun nanocrystalline NdFeB magnets are less dependent on heavy rare earth elements for high-temperature performance than the alternative coarser-grained sintered NdFeB magnets. In particular, hot-pressed melt-spun magnets are an attractive low-cost solution for applications that require thermal stability up to 175-200 °C.

Information flow analysis and Petri-net-based modeling for welding flexible manufacturing cell

NASA Astrophysics Data System (ADS)

Qiu, T.; Chen, Shanben; Wang, Y. T.; Wu, Lin

2000-10-01

Due to the development of advanced manufacturing technology and the introduction of Smart-Manufacturing notion in the field of modern industrial production, welding flexible manufacturing system (WFMS) using robot technology has become the inevitable developing direction on welding automation. In WFMS process, the flexibility for different welding products and the realizing on corresponding welding parameters control are the guarantees for welding quality. Based on a new intelligent arc-welding flexible manufacturing cell (WFMC), the system structure and control policies are studied in this paper. Aiming at the different information flows among every subsystem and central monitoring computer in this WFMC, Petri net theory is introduced into the process of welding manufacturing. With its help, a discrete control model of WFMC has been constructed, in which the system status is regarded as place and the control process is regarded as transition. Moreover, grounded on automation Petri net principle, the judging and utilizing of information obtained from welding sensors are imported into net structure, which extends the traditional Petri net concepts. The control model and policies researched in this paper have established foundation for further intelligent real-time control on WFMC and WFMS.

Petri net model for analysis of concurrently processed complex algorithms

NASA Technical Reports Server (NTRS)

Stoughton, John W.; Mielke, Roland R.

1986-01-01

This paper presents a Petri-net model suitable for analyzing the concurrent processing of computationally complex algorithms. The decomposed operations are to be processed in a multiple processor, data driven architecture. Of particular interest is the application of the model to both the description of the data/control flow of a particular algorithm, and to the general specification of the data driven architecture. A candidate architecture is also presented.

Predicting soil formation on the basis of transport-limited chemical weathering

NASA Astrophysics Data System (ADS)

Yu, Fang; Hunt, Allen Gerhard

2018-01-01

Soil production is closely related to chemical weathering. It has been shown that, under the assumption that chemical weathering is limited by solute transport, the process of soil production is predictable. However, solute transport in soil cannot be described by Gaussian transport. In this paper, we propose an approach based on percolation theory describing non-Gaussian transport of solute to predict soil formation (the net production of soil) by considering both soil production from chemical weathering and removal of soil from erosion. Our prediction shows agreement with observed soil depths in the field. Theoretical soil formation rates are also compared with published rates predicted using soil age-profile thickness (SAST) method. Our formulation can be incorporated directly into landscape evolution models on a point-to-point basis as long as such models account for surface water routing associated with overland flow. Further, our treatment can be scaled-up to address complications associated with continental-scale applications, including those from climate change, such as changes in vegetation, or surface flow organization. The ability to predict soil formation rates has implications for understanding Earth's climate system on account of the relationship to chemical weathering of silicate minerals with the associated drawdown of atmospheric carbon, but it is also important in geomorphology for understanding landscape evolution, including for example, the shapes of hillslopes, and the net transport of sediments to sedimentary basins.

Application of modified Martinez-Silva algorithm in determination of net cover

NASA Astrophysics Data System (ADS)

Stefanowicz, Łukasz; Grobelna, Iwona

2016-12-01

In the article we present the idea of modifications of Martinez-Silva algorithm, which allows for determination of place invariants (p-invariants) of Petri net. Their generation time is important in the parallel decomposition of discrete systems described by Petri nets. Decomposition process is essential from the point of view of discrete system design, as it allows for separation of smaller sequential parts. The proposed modifications of Martinez-Silva method concern the net cover by p-invariants and are focused on two important issues: cyclic reduction of invariant matrix and cyclic checking of net cover.

How many holes is too many? A prototype tool for estimating mosquito entry risk into damaged bed nets.

PubMed

Sutcliffe, James; Ji, Xin; Yin, Shaoman

2017-08-01

Insecticide-treated bed nets (ITNs) have played an integral role in malaria reduction but how insecticide depletion and accumulating physical damage affect ITN performance is poorly understood. More accurate methods are needed to assess damage to bed nets so that they can be designed, deployed and replaced optimally. Video recordings of female Anopheles gambiae in near approach (1-½ cm) to occupied untreated rectangular bed nets in a laboratory study were used to quantify the amount of mosquito activity (appearances over time) around different parts of the net, the per-appearance probability of a mosquito coming close to holes of different sizes (hole encounter) and the per-encounter probability of mosquitoes passing through holes of different sizes (hole passage). Appearance frequency on different parts of the net reflected previously reported patterns: the area of the net under greatest mosquito pressure was the roof, followed by the bottom 30 cm of the sides, followed by the 30 cm area immediately above this, followed by the upper two-thirds of the sides. The ratio of activity in these areas was (respectively) 250:33:5:1. Per-appearance probability of hole encounter on all parts of the net was strongly predicted by a factor combining hole perimeter and area. Per-encounter probability of hole passage, in turn, was strongly predicted by hole width. For a given width, there was a 20% greater risk of passage through holes on the roof than holes on the sides. Appearance, encounter and passage predictors correspond to various mosquito behaviours that have previously been described and are combined into a prototype mosquito entry risk tool that predicts mosquito entry rates for nets with various amounts of damage. Scenarios that use the entry risk tool to test the recommendations of the WHOPES proportionate hole index (pHI) suggest that the pHI hole size categories and failure to account for hole location likely sometimes lead to incorrect conclusions about net serviceability that could be avoided by using an entry risk tool of the form presented here instead. Practical methods of collecting hole position, shape and size information for bed net assessments using the tool in the field are discussed and include using image analysis and on-line geometric analysis tools.

Climate change reduces the net sink of CH4 and N2O in a semiarid grassland.

PubMed

Dijkstra, Feike A; Morgan, Jack A; Follett, Ronald F; Lecain, Daniel R

2013-06-01

Atmospheric concentrations of methane (CH4 ) and nitrous oxide (N2 O) have increased over the last 150 years because of human activity. Soils are important sources and sinks of both potent greenhouse gases where their production and consumption are largely regulated by biological processes. Climate change could alter these processes thereby affecting both rate and direction of their exchange with the atmosphere. We examined how a rise in atmospheric CO2 and temperature affected CH4 and N2 O fluxes in a well-drained upland soil (volumetric water content ranging between 6% and 23%) in a semiarid grassland during five growing seasons. We hypothesized that responses of CH4 and N2 O fluxes to elevated CO2 and warming would be driven primarily by treatment effects on soil moisture. Previously we showed that elevated CO2 increased and warming decreased soil moisture in this grassland. We therefore expected that elevated CO2 and warming would have opposing effects on CH4 and N2 O fluxes. Methane was taken up throughout the growing season in all 5 years. A bell-shaped relationship was observed with soil moisture with highest CH4 uptake at intermediate soil moisture. Both N2 O emission and uptake occurred at our site with some years showing cumulative N2 O emission and other years showing cumulative N2 O uptake. Nitrous oxide exchange switched from net uptake to net emission with increasing soil moisture. In contrast to our hypothesis, both elevated CO2 and warming reduced the sink of CH4 and N2 O expressed in CO2 equivalents (across 5 years by 7% and 11% for elevated CO2 and warming respectively) suggesting that soil moisture changes were not solely responsible for this reduction. We conclude that in a future climate this semiarid grassland may become a smaller sink for atmospheric CH4 and N2 O expressed in CO2 -equivalents. © 2013 Blackwell Publishing Ltd.

Shuttle Net, Tuna Net

NASA Technical Reports Server (NTRS)

1983-01-01

Rockwell International, NASA's prime contractor for the Space Shuttle, asked West Coast Netting (WCN) to develop a safety net for personnel working on the Shuttle Orbiter. This could not be an ordinary net, it had to be relatively small, yet have extraordinary tensile strength. It also had to be fire resistant and resistant to ultraviolet (UV) light. After six months, WCN found the requisite fiber, a polyester-like material called NOMEX. The company was forced to invent a more sophisticated twisting process since conventional methods did not approach specified breaking strength. The resulting product, the Hyperester net, sinks faster and fishes deeper, making it attractive to fishing fleets. A patented treatment for UV protection and greater abrasion resistance make Hyperester nets last longer, and the no-shrink feature is an economic bonus.

Asteroids@Home

NASA Astrophysics Data System (ADS)

Durech, Josef; Hanus, J.; Vanco, R.

2012-10-01

We present a new project called Asteroids@home (http://asteroidsathome.net/boinc). It is a volunteer-computing project that uses an open-source BOINC (Berkeley Open Infrastructure for Network Computing) software to distribute tasks to volunteers, who provide their computing resources. The project was created at the Astronomical Institute, Charles University in Prague, in cooperation with the Czech National Team. The scientific aim of the project is to solve a time-consuming inverse problem of shape reconstruction of asteroids from sparse-in-time photometry. The time-demanding nature of the problem comes from the fact that with sparse-in-time photometry the rotation period of an asteroid is not apriori known and a huge parameter space must be densely scanned for the best solution. The nature of the problem makes it an ideal task to be solved by distributed computing - the period parameter space can be divided into small bins that can be scanned separately and then joined together to give the globally best solution. In the framework of the the project, we process asteroid photometric data from surveys together with asteroid lightcurves and we derive asteroid shapes and spin states. The algorithm is based on the lightcurve inversion method developed by Kaasalainen et al. (Icarus 153, 37, 2001). The enormous potential of distributed computing will enable us to effectively process also the data from future surveys (Large Synoptic Survey Telescope, Gaia mission, etc.). We also plan to process data of a synthetic asteroid population to reveal biases of the method. In our presentation, we will describe the project, show the first results (new models of asteroids), and discuss the possibilities of its further development. This work has been supported by the grant GACR P209/10/0537 of the Czech Science Foundation and by the Research Program MSM0021620860 of the Ministry of Education of the Czech Republic.

Modelling the Cast Component Weight in Hot Chamber Die Casting using Combined Taguchi and Buckingham's π Approach

NASA Astrophysics Data System (ADS)

Singh, Rupinder

2018-02-01

Hot chamber (HC) die casting process is one of the most widely used commercial processes for the casting of low temperature metals and alloys. This process gives near-net shape product with high dimensional accuracy. However in actual field environment the best settings of input parameters is often conflicting as the shape and size of the casting changes and one have to trade off among various output parameters like hardness, dimensional accuracy, casting defects, microstructure etc. So for online inspection of the cast components properties (without affecting the production line) the weight measurement has been established as one of the cost effective method (as the difference in weight of sound and unsound casting reflects the possible casting defects) in field environment. In the present work at first stage the effect of three input process parameters (namely: pressure at 2nd phase in HC die casting; metal pouring temperature and die opening time) has been studied for optimizing the cast component weight `W' as output parameter in form of macro model based upon Taguchi L9 OA. After this Buckingham's π approach has been applied on Taguchi based macro model for the development of micro model. This study highlights the Taguchi-Buckingham based combined approach as a case study (for conversion of macro model into micro model) by identification of optimum levels of input parameters (based on Taguchi approach) and development of mathematical model (based on Buckingham's π approach). Finally developed mathematical model can be used for predicting W in HC die casting process with more flexibility. The results of study highlights second degree polynomial equation for predicting cast component weight in HC die casting and suggest that pressure at 2nd stage is one of the most contributing factors for controlling the casting defect/weight of casting.

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

Galarraga, Haize; Warren, Robert J.; Lados, Diana A.

Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that is used to fabricate three-dimensional near-net-shaped parts directly from computer models. Ti-6Al-4V is the most widely used and studied alloy for this technology and is the focus of this work in its ELI (Extra Low Interstitial) variation. The mechanisms of microstructure formation, evolution, and its subsequent influence on mechanical properties of the alloy in as-fabricated condition have been documented by various researchers. In the present work, the thermal history resulting in the formation of the as-fabricated microstructure was analyzed and studied by a thermal simulation.more » Subsequently different heat treatments were performed based on three approaches in order to study the effects of heat treatments on the singular and exclusive microstructure formed during the EBM fabrication process. In the first approach, the effect of cooling rate after the solutionizing process was studied. In the second approach, the variation of α lath thickness during annealing treatment and correlation with mechanical properties was established. In the last approach, several solutionizing and aging experiments were conducted.« less

Optimization of Micro Metal Injection Molding By Using Grey Relational Grade

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

Ibrahim, M. H. I.; Precision Process Research Group, Dept. of Mechanical and Materials Engineering, Faculty of Engineering, Universiti Kebangsaan Malaysia; Muhamad, N.

2011-01-17

Micro metal injection molding ({mu}MIM) which is a variant of MIM process is a promising method towards near net-shape of metallic micro components of complex geometry. In this paper, {mu}MIM is applied to produce 316L stainless steel micro components. Due to highly stringent characteristic of {mu}MIM properties, the study has been emphasized on optimization of process parameter where Taguchi method associated with Grey Relational Analysis (GRA) will be implemented as it represents novel approach towards investigation of multiple performance characteristics. Basic idea of GRA is to find a grey relational grade (GRG) which can be used for the optimization conversionmore » from multi objectives case which are density and strength to a single objective case. After considering the form 'the larger the better', results show that the injection time(D) is the most significant followed by injection pressure(A), holding time(E), mold temperature(C) and injection temperature(B). Analysis of variance (ANOVA) is also employed to strengthen the significant of each parameter involved in this study.« less

Structure and performance of anisotropic nanocrystalline Nd-Fe-B magnets fabricated by high-velocity compaction followed by deformation

NASA Astrophysics Data System (ADS)

Zhao, L. Z.; Deng, X. X.; Yu, H. Y.; Guan, H. J.; Li, X. Q.; Xiao, Z. Y.; Liu, Z. W.; Greneche, J. M.

2017-12-01

High-velocity compaction (HVC) has been proposed as an effective approach for the fabrication of nanocrystalline Nd-Fe-B magnets. In this work, the effect of powder size on the density of HVCed magnets has been studied and the anisotropic nanocrystalline Nd-Fe-B magnets were prepared by HVC followed by hot deformation (HD). It is found that a proper particle size range is beneficial to high density. The investigations on the microstructure, magnetic domain structure, and hyperfine structure, indicate that the deformed grain structure and the magnetic domain structure with uniform paramagnetic grain boundary phase give good magnetic properties of HVC + HDed magnets. These magnets also have good mechanical and anti-corrosion properties. The results indicate that HVC is not only a near-net-shape, room temperature and binder-free process but is also able to maintain uniform nanostructure and to achieve good magnetic properties in both isotropic and anisotropic magnets. As a result, HVC can be employed as an ideal alternative process for bonding or hot pressing for the conventional MQI, MQII and MQIII magnets.

Finite element assisted prediction of ductile fracture in sheet bulging

NASA Astrophysics Data System (ADS)

Donald, Bryan J. Mac; Lorza, Ruben Lostado; Yoshihara, Shoichiro

2017-10-01

With growing demand for energy efficiency, there is much focus on reducing oil consumption rates and utilising alternative fuels. A contributor to the solution in this area is to produce lighter vehicles that are more fuel efficient and/or allow for the use of alternative fuel sources (e.g. electric powered automobiles). Near-net-shape manufacturing processes such as hydroforming have great potential to reduce structural weight while still maintaining structural strength and performance. Finite element analysis techniques have proved invaluable in optimizing such hydroforming processes, however, the majority of such studies have used simple predictors of failure which are usually yield criteria such as von Mises stress. There is clearly potential to obtain more optimal solutions using more advanced predictors of failure. This paper compared the Von Mises stress failure criteria and the Oyane's ductile fracture criteria in the sheet hydroforming of magnesium alloys. It was found that the results obtained from the models which used Oyane's ductile fracture criteria were more realistic than those obtained from those that used Von Mises stress as a failure criteria.

Laser rapid forming technology of high-performance dense metal components with complex structure

NASA Astrophysics Data System (ADS)

Huang, Weidong; Chen, Jing; Li, Yanming; Lin, Xin

2005-01-01

Laser rapid forming (LRF) is a new and advanced manufacturing technology that has been developed on the basis of combining high power laser cladding technology with rapid prototyping (RP) to realize net shape forming of high performance dense metal components without dies. Recently we have developed a set of LRF equipment. LRF experiments were carried out on the equipment to investigate the influences of processing parameters on forming characterizations systematically with the cladding powder materials as titanium alloys, superalloys, stainless steel, and copper alloys. The microstructure of laser formed components is made up of columnar grains or columnar dendrites which grow epitaxially from the substrate since the solid components were prepared layer by layer additionally. The result of mechanical testing proved that the mechanical properties of laser formed samples are similar to or even over that of forging and much better than that of casting. It is shown in this paper that LRF technology is providing a new solution for some difficult processing problems in the high tech field of aviation, spaceflight and automobile industries.

In Vivo Response of Laser Processed Porous Titanium Implants for Load-Bearing Implants.

PubMed

Bandyopadhyay, Amit; Shivaram, Anish; Tarafder, Solaiman; Sahasrabudhe, Himanshu; Banerjee, Dishary; Bose, Susmita

2017-01-01

Applications of porous metallic implants to enhance osseointegration of load-bearing implants are increasing. In this work, porous titanium implants, with 25 vol.% porosity, were manufactured using Laser Engineered Net Shaping (LENS™) to measure the influence of porosity towards bone tissue integration in vivo. Surfaces of the LENS™ processed porous Ti implants were further modified with TiO 2 nanotubes to improve cytocompatibility of these implants. We hypothesized that interconnected porosity created via additive manufacturing will enhance bone tissue integration in vivo. To test our hypothesis, in vivo experiments using a distal femur model of male Sprague-Dawley rats were performed for a period of 4 and 10 weeks. In vivo samples were characterized via micro-computed tomography (CT), histological imaging, scanning electron microscopy, and mechanical push-out tests. Our results indicate that porosity played an important role to establish early stage osseointegration forming strong interfacial bonding between the porous implants and the surrounding tissue, with or without surface modification, compared to dense Ti implants used as a control.

In vivo response of laser processed porous titanium implants for load-bearing implants

PubMed Central

Bandyopadhyay, Amit; Shivaram, Anish; Tarafder, Solaiman; Sahasrabudhe, Himanshu; Banerjee, Dishary; Bose, Susmita

2016-01-01

Applications of porous metallic implants to enhance osseointegration of load-bearing implants are increasing. In this work, porous titanium implants, with 25 volume% porosity, were manufactured using Laser Engineered Net Shaping (LENS™) to measure the influence of porosity towards bone tissue integration in vivo. Surfaces of the LENS™ processed porous Ti implants were further modified with TiO2 nanotubes to improve cytocompatibility of these implants. We hypothesized that interconnected porosity created via additive manufacturing will enhance bone tissue integration in vivo. To test our hypothesis, in vivo experiments using a distal femur model of male Sprague-Dawley rats were performed for a period of 4 and 10 weeks. In vivo samples were characterized via micro-computed tomography (CT), histological imaging, scanning electron microscopy, and mechanical push-out tests. Our results indicate that porosity played an important role to establish early stage osseointegration forming strong interfacial bonding between the porous implants and the surrounding tissue, with or without surface modification, compared to dense Ti implants used as a control. PMID:27307009

Electro-Optical Inspection For Tolerance Control As An Integral Part Of A Flexible Machining Cell

NASA Astrophysics Data System (ADS)

Renaud, Blaise

1986-11-01

Institut CERAC has been involved in optical metrology and 3-dimensional surface control for the last couple of years. Among the industrial applications considered is the on-line shape evaluation of machined parts within the manufacturing cell. The specific objective is to measure the machining errors and to compare them with the tolerances set by designers. An electro-optical sensing technique has been developed which relies on a projection Moire contouring optical method. A prototype inspection system has been designed, making use of video detection and computer image processing. Moire interferograms are interpreted, and the metrological information automatically retrieved. A structured database can be generated for subsequent data analysis and for real-time closed-loop corrective actions. A real-time kernel embedded into a synchronisation network (Petri-net) for the control of concurrent processes in the Electra-Optical Inspection (E0I) station was realised and implemented in a MODULA-2 program DIN01. The prototype system for on-line automatic tolerance control taking place within a flexible machining cell is described in this paper, together with the fast-prototype synchronisation program.

Accelerating Industrial Adoption of Metal Additive Manufacturing Technology

NASA Astrophysics Data System (ADS)

Vartanian, Kenneth; McDonald, Tom

2016-03-01

While metal additive manufacturing (AM) technology has clear benefits, there are still factors preventing its adoption by industry. These factors include the high cost of metal AM systems, the difficulty for machinists to learn and operate metal AM machines, the long approval process for part qualification/certification, and the need for better process controls; however, the high AM system cost is the main barrier deterring adoption. In this paper, we will discuss an America Makes-funded program to reduce AM system cost by combining metal AM technology with conventional computerized numerical controlled (CNC) machine tools. Information will be provided on how an Optomec-led team retrofitted a legacy CNC vertical mill with laser engineered net shaping (LENS®—LENS is a registered trademark of Sandia National Labs) AM technology, dramatically lowering deployment cost. The upgraded system, dubbed LENS Hybrid Vertical Mill, enables metal additive and subtractive operations to be performed on the same machine tool and even on the same part. Information on the LENS Hybrid system architecture, learnings from initial system deployment and continuing development work will also be provided to help guide further development activities within the materials community.

Net Operating Working Capital, Capital Budgeting, and Cash Budgets: A Teaching Example

ERIC Educational Resources Information Center

Tuner, James A.

2016-01-01

Many introductory finance texts present information on the capital budgeting process, including estimation of project cash flows. Typically, estimation of project cash flows begins with a calculation of net income. Getting from net income to cash flows requires accounting for non-cash items such as depreciation. Also important is the effect of…

Neutrophil extracellular traps: double-edged swords of innate immunity.

PubMed

Kaplan, Mariana J; Radic, Marko

2012-09-15

Spectacular images of neutrophils ejecting nuclear chromatin and bactericidal proteins, in response to microbes, were first reported in 2004. As externalized chromatin could entangle bacteria, these structures were named neutrophil extracellular traps (NETs). Subsequent studies identified microorganisms and sterile conditions that stimulate NETs, as well as additional cell types that release extracellular chromatin. The release of NETs is the most dramatic stage in a cell death process called NETosis. Experimental evidence suggests that NETs participate in pathogenesis of autoimmune and inflammatory disorders, with proposed involvement in glomerulonephritis, chronic lung disease, sepsis, and vascular disorders. Exaggerated NETosis or diminished NET clearance likely increases risk of autoreactivity to NET components. The biological significance of NETs is just beginning to be explored. A more complete integration of NETosis within immunology and pathophysiology will require better understanding of NET properties associated with specific disease states and microbial infections. This may lead to the identification of important therapeutic targets.

A Petri Net Approach Based Elementary Siphons Supervisor for Flexible Manufacturing Systems

NASA Astrophysics Data System (ADS)

Abdul-Hussin, Mowafak Hassan

2015-05-01

This paper presents an approach to constructing a class of an S3PR net for modeling, simulation and control of processes occurring in the flexible manufacturing system (FMS) used based elementary siphons of a Petri net. Siphons are very important to the analysis and control of deadlocks of FMS that is significant objectives of siphons. Petri net models in the efficiency structure analysis, and utilization of the FMSs when different policy can be implemented lead to the deadlock prevention. We are representing an effective deadlock-free policy of a special class of Petri nets called S3PR. Simulation of Petri net structural analysis and reachability graph analysis is used for analysis and control of Petri nets. Petri nets contain been successfully as one of the most powerful tools for modelling of FMS, where Using structural analysis, we show that liveness of such systems can be attributed to the absence of under marked siphons.

Tools for Atmospheric Radiative Transfer: Streamer and FluxNet. Revised

NASA Technical Reports Server (NTRS)

Key, Jeffrey R.; Schweiger, Axel J.

1998-01-01

Two tools for the solution of radiative transfer problems are presented. Streamer is a highly flexible medium spectral resolution radiative transfer model based on the plane-parallel theory of radiative transfer. Capable of computing either fluxes or radiances, it is suitable for studying radiative processes at the surface or within the atmosphere and for the development of remote-sensing algorithms. FluxNet is a fast neural network-based implementation of Streamer for computing surface fluxes. It allows for a sophisticated treatment of radiative processes in the analysis of large data sets and potential integration into geophysical models where computational efficiency is an issue. Documentation and tools for the development of alternative versions of Fluxnet are available. Collectively, Streamer and FluxNet solve a wide variety of problems related to radiative transfer: Streamer provides the detail and sophistication needed to perform basic research on most aspects of complex radiative processes while the efficiency and simplicity of FluxNet make it ideal for operational use.

Enhanced Impact Resistance of Three-Dimensional-Printed Parts with Structured Filaments.

PubMed

Peng, Fang; Zhao, Zhiyang; Xia, Xuhui; Cakmak, Miko; Vogt, Bryan D

2018-05-09

Net-shape manufacture of customizable objects through three-dimensional (3D) printing offers tremendous promise for personalization to improve the fit, performance, and comfort associated with devices and tools used in our daily lives. However, the application of 3D printing in structural objects has been limited by their poor mechanical performance that manifests from the layer-by-layer process by which the part is produced. Here, this interfacial weakness is overcome using a structured, core-shell polymer filament where a polycarbonate (PC) core solidifies quickly to define the shape, whereas an olefin ionomer shell contains functionality (crystallinity and ionic) that strengthen the interface between the printed layers. This structured filament leads to improved dimensional accuracy and impact resistance in comparison to the individual components. The impact resistance from structured filaments containing 45 vol % shell can exceed 800 J/m. The origins of this improved impact resistance are probed using X-ray microcomputed tomography. Energy is dissipated by delamination of the shell from PC near the crack tip, whereas PC remains intact to provide stability to the part after impact. This structured filament provides tremendous improvements in the critical properties for manufacture and represents a major leap forward in the impact properties obtainable for 3D-printed parts.

SpaceNet: Modeling and Simulating Space Logistics

NASA Technical Reports Server (NTRS)

Lee, Gene; Jordan, Elizabeth; Shishko, Robert; de Weck, Olivier; Armar, Nii; Siddiqi, Afreen

2008-01-01

This paper summarizes the current state of the art in interplanetary supply chain modeling and discusses SpaceNet as one particular method and tool to address space logistics modeling and simulation challenges. Fundamental upgrades to the interplanetary supply chain framework such as process groups, nested elements, and cargo sharing, enabled SpaceNet to model an integrated set of missions as a campaign. The capabilities and uses of SpaceNet are demonstrated by a step-by-step modeling and simulation of a lunar campaign.

Reactive Melt Infiltration Of Silicon Into Porous Carbon

NASA Technical Reports Server (NTRS)

Behrendt, Donald R.; Singh, Mrityunjay

1994-01-01

Report describes study of synthesis of silicon carbide and related ceramics by reactive melt infiltration of silicon and silicon/molybdenum alloys into porous carbon preforms. Reactive melt infiltration has potential for making components in nearly net shape, performed in less time and at lower temperature. Object of study to determine effect of initial pore volume fraction, pore size, and infiltration material on quality of resultant product.

Near Net Shape Rapid Manufacture & Repair by LENS(registered trademark)

DTIC Science & Technology

2006-05-01

J. Vlcek, “Property Investigation of Laser Cladded , Laser Sintered and Electron Beam Sintered Ti 6Al 4V”, AVT-139 Specialists Meeting on Cost...manufactured from advanced materials such as titanium alloys, superalloys or special steels are critical to the performance of the armed forces...10 years, CAD driven, additive manufacturing technologies have been developed. The leading technology for defence applications is Laser Engineered

Developmental switching in Physarum polycephalum: Petri net analysis of single cell trajectories of gene expression indicates responsiveness and genetic plasticity of the Waddington quasipotential landscape

NASA Astrophysics Data System (ADS)

Werthmann, Britta; Marwan, Wolfgang

2017-11-01

The developmental switch to sporulation in Physarum polycephalum is a phytochrome-mediated far-red light-induced cell fate decision that synchronously encompasses the entire multinucleate plasmodial cell and is associated with extensive reprogramming of the transcriptome. By repeatedly taking samples of single cells after delivery of a light stimulus pulse, we analysed differential gene expression in two mutant strains and in a heterokaryon of the two strains all of which display a different propensity for making the cell fate decision. Multidimensional scaling of the gene expression data revealed individually different single cell trajectories eventually leading to sporulation. Characterization of the trajectories as walks through states of gene expression discretized by hierarchical clustering allowed the reconstruction of Petri nets that model and predict the observed behavior. Structural analyses of the Petri nets indicated stimulus- and genotype-dependence of both, single cell trajectories and of the quasipotential landscape through which these trajectories are taken. The Petri net-based approach to the analysis and decomposition of complex cellular responses and of complex mutant phenotypes may provide a scaffold for the data-driven reconstruction of causal molecular mechanisms that shape the topology of the quasipotential landscape.

An advanced environment for hybrid modeling of biological systems based on modelica.

PubMed

Pross, Sabrina; Bachmann, Bernhard

2011-01-20

Biological systems are often very complex so that an appropriate formalism is needed for modeling their behavior. Hybrid Petri Nets, consisting of time-discrete Petri Net elements as well as continuous ones, have proven to be ideal for this task. Therefore, a new Petri Net library was implemented based on the object-oriented modeling language Modelica which allows the modeling of discrete, stochastic and continuous Petri Net elements by differential, algebraic and discrete equations. An appropriate Modelica-tool performs the hybrid simulation with discrete events and the solution of continuous differential equations. A special sub-library contains so-called wrappers for specific reactions to simplify the modeling process. The Modelica-models can be connected to Simulink-models for parameter optimization, sensitivity analysis and stochastic simulation in Matlab. The present paper illustrates the implementation of the Petri Net component models, their usage within the modeling process and the coupling between the Modelica-tool Dymola and Matlab/Simulink. The application is demonstrated by modeling the metabolism of Chinese Hamster Ovary Cells.

Strong seismic wave scattering beneath Kanto region derived from dense K-NET/KiK-net strong motion network and numerical simulation

NASA Astrophysics Data System (ADS)

Takemura, S.; Yoshimoto, K.

2013-12-01

Observed seismograms, which consist of the high-frequency body waves through the low-velocity (LV) region at depth of 20-40 km beneath northwestern Chiba in Kanto, show strong peak delay and spindle shape of S waves. By analyzing dense seismic records from K-NET/KiK-net, such spindle-shape S waves are clearly observed in the frequency range of 1-8 Hz. In order to investigate a specific heterogeneous structure to generate such observations, we conduct 3-D finite-difference method (FDM) simulation using realistic heterogeneous models and compare the simulation results with dense strong motion array observations. Our 3-D simulation model is covering the zone 150 km by 64 km in horizontal directions and 75 km in vertical direction, which has been discretized with uniform grid size 0.05 km. We assume a layered background velocity structure, which includes basin structure, crust, mantle and subducting oceanic plate, base on the model proposed by Koketsu et al. (2008). In order to introduce the effect of seismic wave scattering, we assume a stochastic random velocity fluctuation in each layer. Random velocity fluctuations are characterized by exponential-type auto-correlation function (ACF) with correlation distance a = 3 km and rms value of fluctuation e = 0.05 in the upper crust, a = 3 km and e = 0.07 in the lower crust, a = 10 km and e = 0.02 in the mantle. In the subducting oceanic plate, we assume an anisotropic random velocity fluctuation characterized by exponential-type ACF with aH = 10 km in horizontal direction, aZ = 0.5 km in vertical direction and e = 0.02 (e.g., Furumura and Kennett, 2005). In addition, we assume a LV zone at northeastern part of Chiba with depth of 20-40 km (e.g., Matsubara et al., 2004). In the LV zone, random velocity fluctuation characterized by Gaussian-type ACF with a = 1 km and e = 0.07 is superposed on exponential-type ACF with a = 3 km and e = 0.07, in order to modulate the S-wave propagation in the dominant frequency range of spindle-shape S waves. Such large-scale FDM simulations are conducted on the Earth Simulator at JAMSTEC. It is found that the FDM simulation of the model without strong velocity fluctuation cannot explain the characteristics of observed S waves. By introducing strong velocity fluctuation in the LV zone, strong peak delay and spindle-shape S waves observed at central and southern part of Chiba are simulated successfully. In addition, the strong amplitude decrease of S waves in the LV zone due to strong seismic scattering is good corresponding to results based on the tomographic study of Q in Kanto (e.g., Nakamura et al., 2006). Simulation results demonstrated that strong velocity fluctuation in the LV zone plays important role in the peak delay and waveform shape. The LV zone beneath northeastern Chiba is considered as a result of dehydration from oceanic crust of subducted Philippine Sea plate (e.g., Matsubara et al., 2005). Therefore strong small-scale velocity fluctuation in the LV zone may be related with dehydrated water.

Stroking the Net Whale: A Constructivist Grounded Theory of Self-Regulated Learning in Virtual Social Spaces

ERIC Educational Resources Information Center

Kasperiuniene, Judita; Zydziunaite, Vilma; Eriksson, Malin

2017-01-01

This qualitative study explored the self-regulated learning (SRL) of teachers and their students in virtual social spaces. The processes of SRL were analyzed from 24 semi-structured individual interviews with professors, instructors and their students from five Lithuanian universities. A core category stroking the net whale showed the process of…

WaveNet: A Web-Based Metocean Data Access, Processing and Analysis Tool. Part 4 - GLOS/GLCFS Database

DTIC Science & Technology

2014-06-01

and Coastal Data Information Program ( CDIP ). This User’s Guide includes step-by-step instructions for accessing the GLOS/GLCFS database via WaveNet...access, processing and analysis tool; part 3 – CDIP database. ERDC/CHL CHETN-xx-14. Vicksburg, MS: U.S. Army Engineer Research and Development Center

WaveNet: A Web-Based Metocean Data Access, Processing and Analysis Tool; Part 5 - WW3 Database

DTIC Science & Technology

2015-02-01

Program ( CDIP ); and Part 4 for the Great Lakes Observing System/Coastal Forecasting System (GLOS/GLCFS). Using step-by-step instructions, this Part 5...Demirbilek, Z., L. Lin, and D. Wilson. 2014a. WaveNet: A web-based metocean data access, processing, and analysis tool; part 3– CDIP database

Nicotine Levels and Presence of Selected Tobacco-Derived Toxins in Tobacco Flavoured Electronic Cigarette Refill Liquids

PubMed Central

Farsalinos, Konstantinos E.; Gillman, I. Gene; Melvin, Matt S.; Paolantonio, Amelia R.; Gardow, Wendy J.; Humphries, Kathy E.; Brown, Sherri E.; Poulas, Konstantinos; Voudris, Vassilis

2015-01-01

Background. Some electronic cigarette (EC) liquids of tobacco flavour contain extracts of cured tobacco leaves produced by a process of solvent extraction and steeping. These are commonly called Natural Extract of Tobacco (NET) liquids. The purpose of the study was to evaluate nicotine levels and the presence of tobacco-derived toxins in tobacco-flavoured conventional and NET liquids. Methods. Twenty-one samples (10 conventional and 11 NET liquids) were obtained from the US and Greek market. Nicotine levels were measured and compared with labelled values. The levels of tobacco-derived chemicals were compared with literature data on tobacco products. Results. Twelve samples had nicotine levels within 10% of the labelled value. Inconsistency ranged from −21% to 22.1%, with no difference observed between conventional and NET liquids. Tobacco-specific nitrosamines (TSNAs) were present in all samples at ng/mL levels. Nitrates were present almost exclusively in NET liquids. Acetaldehyde was present predominantly in conventional liquids while formaldehyde was detected in almost all EC liquids at trace levels. Phenols were present in trace amounts, mostly in NET liquids. Total TSNAs and nitrate, which are derived from the tobacco plant, were present at levels 200–300 times lower in 1 mL of NET liquids compared to 1 gram of tobacco products. Conclusions. NET liquids contained higher levels of phenols and nitrates, but lower levels of acetaldehyde compared to conventional EC liquids. The lower levels of tobacco-derived toxins found in NET liquids compared to tobacco products indicate that the extraction process used to make these products did not transfer a significant amount of toxins to the NET. Overall, all EC liquids contained far lower (by 2–3 orders of magnitude) levels of the tobacco-derived toxins compared to tobacco products. PMID:25811768

Nicotine levels and presence of selected tobacco-derived toxins in tobacco flavoured electronic cigarette refill liquids.

PubMed

Farsalinos, Konstantinos E; Gillman, I Gene; Melvin, Matt S; Paolantonio, Amelia R; Gardow, Wendy J; Humphries, Kathy E; Brown, Sherri E; Poulas, Konstantinos; Voudris, Vassilis

2015-03-24

Some electronic cigarette (EC) liquids of tobacco flavour contain extracts of cured tobacco leaves produced by a process of solvent extraction and steeping. These are commonly called Natural Extract of Tobacco (NET) liquids. The purpose of the study was to evaluate nicotine levels and the presence of tobacco-derived toxins in tobacco-flavoured conventional and NET liquids. Twenty-one samples (10 conventional and 11 NET liquids) were obtained from the US and Greek market. Nicotine levels were measured and compared with labelled values. The levels of tobacco-derived chemicals were compared with literature data on tobacco products. Twelve samples had nicotine levels within 10% of the labelled value. Inconsistency ranged from -21% to 22.1%, with no difference observed between conventional and NET liquids. Tobacco-specific nitrosamines (TSNAs) were present in all samples at ng/mL levels. Nitrates were present almost exclusively in NET liquids. Acetaldehyde was present predominantly in conventional liquids while formaldehyde was detected in almost all EC liquids at trace levels. Phenols were present in trace amounts, mostly in NET liquids. Total TSNAs and nitrate, which are derived from the tobacco plant, were present at levels 200-300 times lower in 1 mL of NET liquids compared to 1 gram of tobacco products. NET liquids contained higher levels of phenols and nitrates, but lower levels of acetaldehyde compared to conventional EC liquids. The lower levels of tobacco-derived toxins found in NET liquids compared to tobacco products indicate that the extraction process used to make these products did not transfer a significant amount of toxins to the NET. Overall, all EC liquids contained far lower (by 2-3 orders of magnitude) levels of the tobacco-derived toxins compared to tobacco products.

Linkages of plant stoichiometry to ecosystem production and carbon fluxes with increasing nitrogen inputs in an alpine steppe.

PubMed

Peng, Yunfeng; Li, Fei; Zhou, Guoying; Fang, Kai; Zhang, Dianye; Li, Changbin; Yang, Guibiao; Wang, Guanqin; Wang, Jun; Yang, Yuanhe

2017-12-01

Unprecedented levels of nitrogen (N) have entered terrestrial ecosystems over the past century, which substantially influences the carbon (C) exchange between the atmosphere and biosphere. Temperature and moisture are generally regarded as the major controllers over the N effects on ecosystem C uptake and release. N-phosphorous (P) stoichiometry regulates the growth and metabolisms of plants and soil organisms, thereby affecting many ecosystem C processes. However, it remains unclear how the N-induced shift in the plant N:P ratio affects ecosystem production and C fluxes and its relative importance. We conducted a field manipulative experiment with eight N addition levels in a Tibetan alpine steppe and assessed the influences of N on aboveground net primary production (ANPP), gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem exchange (NEE); we used linear mixed-effects models to further determine the relative contributions of various factors to the N-induced changes in these parameters. Our results showed that the ANPP, GEP, ER, and NEE all exhibited nonlinear responses to increasing N additions. Further analysis demonstrated that the plant N:P ratio played a dominate role in shaping these C exchange processes. There was a positive relationship between the N-induced changes in ANPP (ΔANPP) and the plant N:P ratio (ΔN:P), whereas the ΔGEP, ΔER, and ΔNEE exhibited quadratic correlations with the ΔN:P. In contrast, soil temperature and moisture were only secondary predictors for the changes in ecosystem production and C fluxes along the N addition gradient. These findings highlight the importance of plant N:P ratio in regulating ecosystem C exchange, which is crucial for improving our understanding of C cycles under the scenarios of global N enrichment. © 2017 John Wiley & Sons Ltd.

Frazzled/DCC facilitates cardiac cell outgrowth and attachment during Drosophila dorsal vessel formation.

PubMed

Macabenta, Frank D; Jensen, Amber G; Cheng, Yi-Shan; Kramer, Joseph J; Kramer, Sunita G

2013-08-15

Drosophila embryonic dorsal vessel (DV) morphogenesis is a highly stereotyped process that involves the migration and morphogenesis of 52 pairs of cardioblasts (CBs) in order to form a linear tube. This process requires spatiotemporally-regulated localization of signaling and adhesive proteins in order to coordinate the formation of a central lumen while maintaining simultaneous adhesion between CBs. Previous studies have shown that the Slit/Roundabout and Netrin/Unc5 repulsive signaling pathways facilitate site-specific loss of adhesion between contralateral CBs in order to form a luminal space. However, the concomitant mechanism by which attraction initiates CB outgrowth and discrete localization of adhesive proteins remains poorly understood. Here we provide genetic evidence that Netrin signals through DCC (Deleted in Colorectal Carcinoma)/UNC-40/Frazzled (Fra) to mediate CB outgrowth and attachment and that this function occurs prior to and independently of Netrin/UNC-5 signaling. fra mRNA is expressed in the CBs prior to and during DV morphogenesis. Loss-of-fra-function results in significant defects in cell shape and alignment between contralateral CB rows. In addition, CB outgrowth and attachment is impaired in both fra loss- and gain-of-function mutants. Deletion of both Netrin genes (NetA and NetB) results in CB attachment phenotypes similar to fra mutants. Similar defects are also seen when both fra and unc5 are deleted. Finally we show that Fra accumulates at dorsal and ventral leading edges of paired CBs, and this localization is dependent upon Netrin. We propose that while repulsive guidance mechanisms contribute to lumen formation by preventing luminal domains from coming together, site-specific Netrin/Frazzled signaling mediates CB attachment. Copyright © 2013 Elsevier Inc. All rights reserved.

Microstructure and Shape Memory Characteristics of Powder-Metallurgical-Processed Ti-Ni-Cu Alloys

NASA Astrophysics Data System (ADS)

Kim, Yeon-Wook; Chung, Young-Soo; Choi, Eunsoo; Nam, Tae-Hyun

2012-08-01

Even though Ti-Ni-Cu alloys have attracted a lot of attention because of their high performance in shape memory effect and decrease in thermal and stress hysteresis compared with Ti-Ni binary alloys, their poor workability restrains the practical applications of Ti-Ni-Cu shape memory alloys. Consolidation of Ti-Ni-Cu alloy powders is useful for the fabrication of bulk near-net-shape shape memory alloy. Ti50Ni30Cu20 shape memory alloy powders were prepared by gas atomization, and the sieved powders with the specific size range of 25 to 150 μm were chosen for this study. The evaluation of powder microstructures was based on a scanning electron microscope (SEM) examination of the surface and the polished and etched powder cross sections. The typical images showed cellular/dendrite morphology and high population of small shrinkage cavities at intercellular regions. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis showed that a B2-B19 one-step martensitic transformation occurred in the as-atomized powders. The martensitic transformation start temperature (Ms) of powders ranging between 25 and 50 μm was 304.5 K (31.5 °C). The Ms increased with increasing powder size. However, the difference of Ms in the as-atomized powders ranging between 25 and 150 μm was only 274 K (1 °C). A dense cylindrical specimen of 10 mm diameter and 15 mm length were fabricated by spark plasma sintering (SPS) at 1073 K (800 °C) and 10 MPa for 20 minutes. Then, this bulk specimen was heat treated for 60 minutes at 1123 K (850 °C) and quenched in ice water. The Ms of the SPS specimen was 310.5 K (37.5 °C) whereas the Ms of conventionally cast ingot is found to be as high as 352.7 K (79.7 °C). It is considered that the depression of the Ms in rapidly solidified powders is ascribed to the density of dislocations and the stored energy produced by rapid solidification.

Microstructural and micromechanical study of a Ti6Al4V component made by electron beam melting

NASA Astrophysics Data System (ADS)

Scherillo, F.; Franchitti, S.; Borrelli, R.; Pirozzi, C.; Squillace, A.; Langella, A.; Carrino, L.

2016-10-01

Additive Layer Manufacturing is one of the most promising and investigated manufacturing system due to its advantages to produces near net shape components, also with a very complex shape, in a single shot. Among the different techniques now available, the Electron Beam Melting (EBM) is of particular interest in the production of metal components. Particularly the application of this technique to titanium alloys allows to produces components with a very low buy to fly ratio. In the present paper the microstructure attained is accurately described and mini tensile tests performed allowed to understand the fracture behavior of specimen with the specific microstructure realized under static load.

A novel frequency tuned wireless actuator with snake-like motion

NASA Astrophysics Data System (ADS)

Zhang, Kewei; Zhu, Qianke; Chai, Yuesheng

2016-07-01

In this work, we propose a novel wireless actuator which is composed of magnetostrictive material/copper bi-layer film. The actuator can be controlled to move like a snake bi-directionally along a pipe by tuning the frequency of external magnetic field near its first order resonant frequency. The governing equation for the actuator is established and the vibration mode shape function is derived. Theoretical analysis shows that motion of the actuator is achieved by asymmetric vibration mode shape, specific vibration bending deformation, and effective net total impacting force. The simulation and experimental results well confirm the theoretical analysis. This work provides contribution to the development of wireless micro robots and autonomous magnetostrictive sensors.

Study of silicon carbide formation by liquid silicon infiltration of porous carbon structures

NASA Astrophysics Data System (ADS)

Margiotta, Jesse C.

Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making fully dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure followed by conversion of this carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low reactivity and porosity, and cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose:resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800°C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm-3 (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process were studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Such knowledge can be used to further refine the LSI technique. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial SiC materials are much lower due to phonon scattering by impurities (e.g., sintering aids located at the grain boundaries of these materials). The thermal conductivity of our SiC was determined using the laser flash method and it is 214 W/mK at 373 K and 64 W/mK at 1273 K. These values are very close to those of pure SiC and are much higher than those of SiC materials made by industrial processes. Thus, SiC made by our LSI process is an ideally suited material for use in high temperature heat exchanger applications. Electron probe microanalysis (EPMA) and Auger electron spectroscopy (AES) were used to study the chemical composition of LSI SiC materials. Optimized low voltage microanalysis conditions for EPMA of SiC were theoretically determined. EPMA and AES measurements indicate that the SiC phase in our materials is slightly carbon rich. Carbon contamination was identified as a possible source of error during EPMA of SiC, and this error was corrected by using high purity SiC standards. Cellulose and phenolic resin carbons lack the well-defined atomic structures associated with common carbon allotropes. Atomic-scale structure was studied using high resolution transmission electron microscopy (HRTEM), nitrogen gas adsorption and helium gas pycnometry. These studies revealed that cellulose carbon exhibits a very high degree of atomic disorder and angstrom-scale porosity. It has a density of only 93% of that of pure graphite, with primarily sp2 bonding character and a low concentration of graphene clusters. Phenolic resin carbon shows more structural order and substantially less angstrom-scale porosity. Its density is 98% of that of pure graphite, and Fourier transform analysis of its TEM micrographs has revealed high concentrations of sp3 diamond and sp 2 graphene nano-clusters. This is the first time that diamond nano-clusters have been observed in carbons produced from phenolic resin.

Factors shaping effective utilization of health information technology in urban safety-net clinics.

PubMed

George, Sheba; Garth, Belinda; Fish, Allison; Baker, Richard

2013-09-01

Urban safety-net clinics are considered prime targets for the adoption of health information technology innovations; however, little is known about their utilization in such safety-net settings. Current scholarship provides limited guidance on the implementation of health information technology into safety-net settings as it typically assumes that adopting institutions have sufficient basic resources. This study addresses this gap by exploring the unique challenges urban resource-poor safety-net clinics must consider when adopting and utilizing health information technology. In-depth interviews (N = 15) were used with key stakeholders (clinic chief executive officers, medical directors, nursing directors, chief financial officers, and information technology directors) from staff at four clinics to explore (a) nonhealth information technology-related clinic needs, (b) how health information technology may provide solutions, and (c) perceptions of and experiences with health information technology. Participants identified several challenges, some of which appear amenable to health information technology solutions. Also identified were requirements for effective utilization of health information technology including physical infrastructural improvements, funding for equipment/training, creation of user groups to share health information technology knowledge/experiences, and specially tailored electronic billing guidelines. We found that despite the potential benefit that can be derived from health information technologies, the unplanned and uninformed introduction of these tools into these settings might actually create more problems than are solved. From these data, we were able to identify a set of factors that should be considered when integrating health information technology into the existing workflows of low-resourced urban safety-net clinics in order to maximize their utilization and enhance the quality of health care in such settings.

Configuration of the magnetosome chain: a natural magnetic nanoarchitecture.

PubMed

Orue, I; Marcano, L; Bender, P; García-Prieto, A; Valencia, S; Mawass, M A; Gil-Cartón, D; Alba Venero, D; Honecker, D; García-Arribas, A; Fernández Barquín, L; Muela, A; Fdez-Gubieda, M L

2018-04-26

Magnetospirillum gryphiswaldense is a microorganism with the ability to biomineralize magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass. Rather than straight lines, magnetosome chains are slightly bent, as evidenced by electron cryotomography. Our experimental and theoretical results suggest that due to the competition between the magnetocrystalline and shape anisotropies, the effective magnetic moment of individual magnetosomes is tilted out of the [111] crystallographic easy axis of magnetite. This tilt does not affect the direction of the chain net magnetic moment, which remains along the [111] axis, but explains the arrangement of magnetosomes in helical-like shaped chains. Indeed, we demonstrate that the chain shape can be reproduced by considering an interplay between the magnetic dipolar interactions between magnetosomes, ruled by the orientation of the magnetosome magnetic moment, and a lipid/protein-based mechanism, modeled as an elastic recovery force exerted on the magnetosomes.

Magnetic Torque in Single Crystal Ni-Mn-Ga

NASA Astrophysics Data System (ADS)

Hobza, Anthony; Müllner, Peter

2017-06-01

Magnetic shape memory alloys deform in an external magnetic field in two distinct ways: by axial straining—known as magnetic-field-induced strain—and by bending when exposed to torque. Here, we examine the magnetic torque that a magnetic field exerts on a long Ni-Mn-Ga rod. A single crystal specimen of Ni-Mn-Ga was constrained with respect to bending and subjected to an external magnetic field. The torque required to rotate the specimen in the field was measured as a function of the orientation of the sample with the external magnetic field, strain, and the magnitude of the external magnetic field. The torque was analyzed based on the changes in the free energy with the angle between the field and the sample. The contributions of magnetocrystalline anisotropy and shape anisotropy to the Zeeman energy determine the net torque. The torque is large when magneotcrystalline and shape anisotropies act synergistically and small when these anisotropies act antagonistically.

Decadal-Scale Reduction in Forest Net Ecosystem Production Following Insect Defoliation Contrasts with Short-Term Impacts of Prescribed Fires

Treesearch

Kenneth L. Clark; Heidi J. Renninger; Nicholas Skowronski; Michael Gallagher; Karina V.R.  Schäfer

2018-01-01

Understanding processes underlying forest carbon dynamics is essential for accurately predicting the outcomes of non-stand-replacing disturbance in intermediate-age forests. We quantified net ecosystem production (NEP), aboveground net primary production (ANPP), and the dynamics of major carbon (C) pools before and during the decade following invasive insect...

Artificial neural network prediction of aircraft aeroelastic behavior

NASA Astrophysics Data System (ADS)

Pesonen, Urpo Juhani

An Artificial Neural Network that predicts aeroelastic behavior of aircraft is presented. The neural net was designed to predict the shape of a flexible wing in static flight conditions using results from a structural analysis and an aerodynamic analysis performed with traditional computational tools. To generate reliable training and testing data for the network, an aeroelastic analysis code using these tools as components was designed and validated. To demonstrate the advantages and reliability of Artificial Neural Networks, a network was also designed and trained to predict airfoil maximum lift at low Reynolds numbers where wind tunnel data was used for the training. Finally, a neural net was designed and trained to predict the static aeroelastic behavior of a wing without the need to iterate between the structural and aerodynamic solvers.

Decision net, directed graph, and neural net processing of imaging spectrometer data

NASA Technical Reports Server (NTRS)

Casasent, David; Liu, Shiaw-Dong; Yoneyama, Hideyuki; Barnard, Etienne

1989-01-01

A decision-net solution involving a novel hierarchical classifier and a set of multiple directed graphs, as well as a neural-net solution, are respectively presented for large-class problem and mixture problem treatments of imaging spectrometer data. The clustering method for hierarchical classifier design, when used with multiple directed graphs, yields an efficient decision net. New directed-graph rules for reducing local maxima as well as the number of perturbations required, and the new starting-node rules for extending the reachability and reducing the search time of the graphs, are noted to yield superior results, as indicated by an illustrative 500-class imaging spectrometer problem.

Time value of emission and technology discounting rate for off-grid electricity generation in India using intermediate pyrolysis

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

Patel, Amit, E-mail: amitrp@iitrpr.ac.in; Faculty of Technology and Engineering, The Maharaja Sayajirao University of Baroda, Vadodara 390001, Gujarat; Sarkar, Prabir

The environmental impact assessment of a process over its entire operational lifespan is an important issue. Estimation of life cycle emission helps in predicting the contribution of a given process to abate (or to pollute) the environmental emission scenario. Considering diminishing and time-dependent effect of emission, assessment of the overall effect of emissions is very complex. The paper presents a generalized methodology for arriving at a single emission discounting number for a process option, using the concept of time value of carbon emission flow. This number incorporates the effect of the emission resulting from the process over the entire operationalmore » lifespan. The advantage of this method is its quantitative aspect as well as its flexible nature. It can be applied to any process. The method is demonstrated with the help of an Intermediate Pyrolysis process when used to generate off-grid electricity and opting biochar route for disposing straw residue. The scenarios of very high net emission to very high net carbon sequestration is generated using process by careful selection of process parameters for different scenarios. For these different scenarios, the process discounting rate was determined and its outcome is discussed. The paper also proposes a process specific eco-label that mentions the discounting rates. - Highlight: • Methodology to obtain emission discounting rate for a process is proposed. • The method includes all components of life cycle emission converts into a time dependent discounting number. • A case study of Intermediate Pyrolysis is used to obtain such number for a range of processes. • The method is useful to determine if the effect from the operation of a process will lead to a net absorption of emission or net accumulation of emission in the environment.« less

Space webs based on rotating tethered formations

NASA Astrophysics Data System (ADS)

Palmerini, Giovanni B.; Sgubini, Silvano; Sabatini, Marco

2009-07-01

Several on-going studies indicate the interest for large, light orbiting structures, shaped as fish nets or webs: along the ropes of the web small spacecraft can move like spiders to position and re-locate, at will, pieces of hardware devoted to specific missions. The concept could be considered as an intermediate solution between the large monolithic structure, heavy and expensive to realize, but easy to control, and the formations of satellites, where all system members are completely free and should manoeuvre in order to acquire a desired configuration. Instead, the advantage of having a "hard-but-light" link among the different grids lays in the partition of the tasks among system components and in a possible overall reduction of the control system complexity and cost. Unfortunately, there is no stable configuration for an orbiting, two-dimensional web made by light, flexible tethers which cannot support compression forces. A possible solution is to make use of centrifugal forces to pull the net, with a reduced number of simple thrusters located at the tips of the tethers to initially acquire the required spin. In this paper a dynamic analysis of a simplified rotating web is performed, in order to evaluate the spinning velocity able to satisfy the requirement for the stability of the system. The model adopted overlaps simpler elements, each of them given by a tether (made up of a number of linear finite elements) connecting two extreme bodies accommodating the spinning thrusters. The combination of these "diameter-like" elements provides the web, shaped according to the specific requirements. The net is primarily considered as subjected to Keplerian attraction and J2 and drag perturbations only, but its behaviour under thermal inputs is also investigated.

Model for the architecture of caveolae based on a flexible, net-like assembly of Cavin1 and Caveolin discs

PubMed Central

Stoeber, Miriam; Schellenberger, Pascale; Siebert, C. Alistair; Leyrat, Cedric; Helenius, Ari

2016-01-01

Caveolae are invaginated plasma membrane domains involved in mechanosensing, signaling, endocytosis, and membrane homeostasis. Oligomers of membrane-embedded caveolins and peripherally attached cavins form the caveolar coat whose structure has remained elusive. Here, purified Cavin1 60S complexes were analyzed structurally in solution and after liposome reconstitution by electron cryotomography. Cavin1 adopted a flexible, net-like protein mesh able to form polyhedral lattices on phosphatidylserine-containing vesicles. Mutating the two coiled-coil domains in Cavin1 revealed that they mediate distinct assembly steps during 60S complex formation. The organization of the cavin coat corresponded to a polyhedral nano-net held together by coiled-coil segments. Positive residues around the C-terminal coiled-coil domain were required for membrane binding. Purified caveolin 8S oligomers assumed disc-shaped arrangements of sizes that are consistent with the discs occupying the faces in the caveolar polyhedra. Polygonal caveolar membrane profiles were revealed in tomograms of native caveolae inside cells. We propose a model with a regular dodecahedron as structural basis for the caveolae architecture. PMID:27834731

Optimal control, optimization and asymptotic analysis of Purcell's microswimmer model

NASA Astrophysics Data System (ADS)

Wiezel, Oren; Or, Yizhar

2016-11-01

Purcell's swimmer (1977) is a classic model of a three-link microswimmer that moves by performing periodic shape changes. Becker et al. (2003) showed that the swimmer's direction of net motion is reversed upon increasing the stroke amplitude of joint angles. Tam and Hosoi (2007) used numerical optimization in order to find optimal gaits for maximizing either net displacement or Lighthill's energetic efficiency. In our work, we analytically derive leading-order expressions as well as next-order corrections for both net displacement and energetic efficiency of Purcell's microswimmer. Using these expressions enables us to explicitly show the reversal in direction of motion, as well as obtaining an estimate for the optimal stroke amplitude. We also find the optimal swimmer's geometry for maximizing either displacement or energetic efficiency. Additionally, the gait optimization problem is revisited and analytically formulated as an optimal control system with only two state variables, which can be solved using Pontryagin's maximum principle. It can be shown that the optimal solution must follow a "singular arc". Numerical solution of the boundary value problem is obtained, which exactly reproduces Tam and Hosoi's optimal gait.

Fracture Strength of Single-Crystal Silicon Carbide Microspecimens at Room and Elevated Temperature

NASA Technical Reports Server (NTRS)

Nemeth, Noel N.; Sharpe, William N., Jr.; Beheim, Glenn M.; Evans, Laura J.; Jadaan, Osama M.

2007-01-01

Three shapes of tensile specimens were tested--curved with a very low stress concentration factor and straight with either a circular hole or an elliptical hole. The nominal thickness was 125 micron with a net section 100 micron wide; the overall length of these microspecimens was 3.1 mm. They were fabricated by an improved version of deep reactive ion etching, which produced specimens with smooth sidewalls and cross-sections having a slightly trapezoidal shape that was exaggerated inside the holes. The novel test setup used a vertical load train extending into a resistance furnace. The specimens had wedge-shaped ends which fit into ceramic grips. The fixed grip was mounted on a ceramic post, and the movable grip was connected to a load cell and actuator outside the furnace with a ceramic-encased nichrome wire. The same arrangement was used for tests at 24 and at 1000 C. The strengths of the curved specimens for two batches of material (made with slightly different processes) were 0.66+/-0.12 GPa and 0.45+/-0.20 GPa respectively at 24 C with identical values at 1000 C. The fracture strengths of the circular-hole and elliptical-hole specimens (computed from the stress concentration factors and measured loads at failure) were approximately 1.2 GPa with slight decreases at the higher temperature. Fractographic examinations showed failures initiating on the surface--primarily at corners. Weibull predictions of fracture strengths for the hole specimens based on the properties of the curved specimens were reasonably effective for the circular holes, but not for the elliptical holes.

Growing season net ecosystem CO2 exchange of two desert ecosystems with alkaline soils in Kazakhstan.

PubMed

Li, Longhui; Chen, Xi; van der Tol, Christiaan; Luo, Geping; Su, Zhongbo

2014-01-01

Central Asia is covered by vast desert ecosystems, and the majority of these ecosystems have alkaline soils. Their contribution to global net ecosystem CO2 exchange (NEE) is of significance simply because of their immense spatial extent. Some of the latest research reported considerable abiotic CO2 absorption by alkaline soil, but the rate of CO2 absorption has been questioned by peer communities. To investigate the issue of carbon cycle in Central Asian desert ecosystems with alkaline soils, we have measured the NEE using eddy covariance (EC) method at two alkaline sites during growing season in Kazakhstan. The diurnal course of mean monthly NEE followed a clear sinusoidal pattern during growing season at both sites. Both sites showed significant net carbon uptake during daytime on sunny days with high photosynthetically active radiation (PAR) but net carbon loss at nighttime and on cloudy and rainy days. NEE has strong dependency on PAR and the response of NEE to precipitation resulted in an initial and significant carbon release to the atmosphere, similar to other ecosystems. These findings indicate that biotic processes dominated the carbon processes, and the contribution of abiotic carbon process to net ecosystem CO2 exchange may be trivial in alkaline soil desert ecosystems over Central Asia.

Growing season net ecosystem CO2 exchange of two desert ecosystems with alkaline soils in Kazakhstan

PubMed Central

Li, Longhui; Chen, Xi; van der Tol, Christiaan; Luo, Geping; Su, Zhongbo

2014-01-01

Central Asia is covered by vast desert ecosystems, and the majority of these ecosystems have alkaline soils. Their contribution to global net ecosystem CO2 exchange (NEE) is of significance simply because of their immense spatial extent. Some of the latest research reported considerable abiotic CO2 absorption by alkaline soil, but the rate of CO2 absorption has been questioned by peer communities. To investigate the issue of carbon cycle in Central Asian desert ecosystems with alkaline soils, we have measured the NEE using eddy covariance (EC) method at two alkaline sites during growing season in Kazakhstan. The diurnal course of mean monthly NEE followed a clear sinusoidal pattern during growing season at both sites. Both sites showed significant net carbon uptake during daytime on sunny days with high photosynthetically active radiation (PAR) but net carbon loss at nighttime and on cloudy and rainy days. NEE has strong dependency on PAR and the response of NEE to precipitation resulted in an initial and significant carbon release to the atmosphere, similar to other ecosystems. These findings indicate that biotic processes dominated the carbon processes, and the contribution of abiotic carbon process to net ecosystem CO2 exchange may be trivial in alkaline soil desert ecosystems over Central Asia. PMID:24455157

A comparison of three macroinvertebrate sampling devices for use in conducting rapid-assessment procedures of Delmarva Peninsula wetlands

USGS Publications Warehouse

Lowe, Terrence (Peter); Tebbs, Kerry; Sparling, Donald W.

2016-01-01

Three types of macroinvertebrate collecting devices, Gerking box traps, D-shaped sweep nets, and activity traps, have commonly been used to sample macroinvertebrates when conducting rapid biological assessments of North American wetlands. We compared collections of macroinvertebrates identified to the family level made with these devices in 6 constructed and 2 natural wetlands on the Delmarva Peninsula of Maryland. We also assessed their potential efficacy in comparisons among wetlands using several proportional and richness attributes. Differences in median diversity among samples from the 3 devices were significant; the sweep-net samples had the greatest diversity and the activity-trap samples had the least diversity. Differences in median abundance were not significant between the Gerking box-trap samples and sweep-net samples, but median abundance among activity-trap samples was significantly lower than among samples of the other 2 devices. Within samples, the proportions of median diversity composed of major class and order groupings were similar among the 3 devices. However the proportions of median abundance composed of the major class and order groupings within activity-trap samples were not similar to those of the other 2 devices. There was a slight but significant increase in the total number of families captured when we combined activity-trap samples with Gerking box-trap samples or with sweep-net samples, and the per-sample median numbers of families of the combined activity-trap and sweep-net samples was significantly higher than that of the combined activity-trap and Gerking box-trap samples. We detected significant differences among wetlands for 4 macroinvertebrate attributes with the Gerking box-trap data, 6 attributes with sweep-net data, and 5 attributes with the activity-trap data. A small, but significant increase in the number of attributes showing differences among wetlands occurred when we combined activity-trap samples with those of the Gerking boxtrap or sweep net.