Science.gov

Sample records for achieve high strength

  1. The Strengths of High-Achieving Black High School Students in a Racially Diverse Setting

    ERIC Educational Resources Information Center

    Marsh, Kris; Chaney, Cassandra; Jones, Derrick

    2012-01-01

    Robert Hill (1972) identified strengths of Black families: strong kinship bonds, strong work orientation, adaptability of family roles, high achievement orientation, and religious orientation. Some suggest these strengths sustain the physical, emotional, social, and spiritual needs of Blacks. This study used narratives and survey data from a…

  2. New Powder Metallurgical Approach to Achieve High Fatigue Strength in Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Cao, Fei; Ravi Chandran, K. S.; Kumar, Pankaj; Sun, Pei; Zak Fang, Z.; Koopman, Mark

    2016-05-01

    Recently, manufacturing of titanium by sintering and dehydrogenation of hydride powders has generated a great deal of interest. An overarching concern regarding powder metallurgy (PM) titanium is that critical mechanical properties, especially the high-cycle fatigue strength, are lower than those of wrought titanium alloys. It is demonstrated here that PM Ti-6Al-4V alloy with mechanical properties comparable (in fatigue strength) and exceeding (in tensile properties) those of wrought Ti-6Al-4V can be produced from titanium hydride powder, through the hydrogen sintering and phase transformation process. Tensile and fatigue behavior, as well as fatigue fracture mechanisms, have been investigated under three processing conditions. It is shown that a reduction in the size of extreme-sized pores by changing the hydride particle size distribution can lead to improved fatigue strength. Further densification by pneumatic isostatic forging leads to a fatigue strength of ~550 MPa, comparable to the best of PM Ti-6Al-4V alloys prepared by other methods and approaching the fatigue strengths of wrought Ti-6Al-4V alloys. The microstructural factors that limit fatigue strength in PM titanium have been investigated, and pathways to achieve greater fatigue strengths in PM Ti-6Al-4V alloys have been identified.

  3. Achieving high strength and high ductility in magnesium alloy using hard-plate rolling (HPR) process.

    PubMed

    Wang, Hui-Yuan; Yu, Zhao-Peng; Zhang, Lei; Liu, Chun-Guo; Zha, Min; Wang, Cheng; Jiang, Qi-Chuan

    2015-01-01

    Magnesium alloys are highly desirable for a wide range of lightweight structural components. However, rolling Mg alloys can be difficult due to their poor plasticity, and the strong texture yielded from rolling often results in poor plate forming ability, which limits their further engineering applications. Here we report a new hard-plate rolling (HPR) route which achieves a large reduction during a single rolling pass. The Mg-9Al-1Zn (AZ91) plates processed by HPR consist of coarse grains of 30-60 μm, exhibiting a typical basal texture, fine grains of 1-5 μm and ultrafine (sub) grains of 200-500 nm, both of the latter two having a weakened texture. More importantly, the HPR was efficient in gaining a simultaneous high strength and uniform ductility, i.e., ~371 MPa and ~23%, respectively. The superior properties should be mainly attributed to the cooperation effect of the multimodal grain structure and weakened texture, where the former facilitates a strong work hardening while the latter promotes the basal slip. The HPR methodology is facile and effective, and can avoid plate cracking that is prone to occur during conventional rolling processes. This strategy is applicable to hard-to-deform materials like Mg alloys, and thus has a promising prospect for industrial application. PMID:26603776

  4. Achieving high strength and high ductility in magnesium alloy using hard-plate rolling (HPR) process.

    PubMed

    Wang, Hui-Yuan; Yu, Zhao-Peng; Zhang, Lei; Liu, Chun-Guo; Zha, Min; Wang, Cheng; Jiang, Qi-Chuan

    2015-11-25

    Magnesium alloys are highly desirable for a wide range of lightweight structural components. However, rolling Mg alloys can be difficult due to their poor plasticity, and the strong texture yielded from rolling often results in poor plate forming ability, which limits their further engineering applications. Here we report a new hard-plate rolling (HPR) route which achieves a large reduction during a single rolling pass. The Mg-9Al-1Zn (AZ91) plates processed by HPR consist of coarse grains of 30-60 μm, exhibiting a typical basal texture, fine grains of 1-5 μm and ultrafine (sub) grains of 200-500 nm, both of the latter two having a weakened texture. More importantly, the HPR was efficient in gaining a simultaneous high strength and uniform ductility, i.e., ~371 MPa and ~23%, respectively. The superior properties should be mainly attributed to the cooperation effect of the multimodal grain structure and weakened texture, where the former facilitates a strong work hardening while the latter promotes the basal slip. The HPR methodology is facile and effective, and can avoid plate cracking that is prone to occur during conventional rolling processes. This strategy is applicable to hard-to-deform materials like Mg alloys, and thus has a promising prospect for industrial application.

  5. Achieving high strength and high ductility in magnesium alloy using hard-plate rolling (HPR) process

    PubMed Central

    Wang, Hui–Yuan; Yu, Zhao–Peng; Zhang, Lei; Liu, Chun–Guo; Zha, Min; Wang, Cheng; Jiang, Qi–Chuan

    2015-01-01

    Magnesium alloys are highly desirable for a wide range of lightweight structural components. However, rolling Mg alloys can be difficult due to their poor plasticity, and the strong texture yielded from rolling often results in poor plate forming ability, which limits their further engineering applications. Here we report a new hard-plate rolling (HPR) route which achieves a large reduction during a single rolling pass. The Mg-9Al-1Zn (AZ91) plates processed by HPR consist of coarse grains of 30–60 μm, exhibiting a typical basal texture, fine grains of 1–5 μm and ultrafine (sub) grains of 200–500 nm, both of the latter two having a weakened texture. More importantly, the HPR was efficient in gaining a simultaneous high strength and uniform ductility, i.e., ~371 MPa and ~23%, respectively. The superior properties should be mainly attributed to the cooperation effect of the multimodal grain structure and weakened texture, where the former facilitates a strong work hardening while the latter promotes the basal slip. The HPR methodology is facile and effective, and can avoid plate cracking that is prone to occur during conventional rolling processes. This strategy is applicable to hard-to-deform materials like Mg alloys, and thus has a promising prospect for industrial application. PMID:26603776

  6. A Positive Psychological Viewpoint for Success at School--10 Characteristic Strengths of the Finnish High-Achieving Students

    ERIC Educational Resources Information Center

    Salmela, Mari; Uusiautti, Satu

    2015-01-01

    People who exploit their strengths flourish; they are not only engaged with their goals, but also to their well-being and the content of life. In this study, interest focused on the high-achieving students in the Finnish general upper secondary education, in other words, on straight-A graduates' characteristic strengths. This was a narrative study…

  7. Achieving large linear elasticity and high strength in bulk nanocompsite via synergistic effect

    PubMed Central

    Hao, Shijie; Cui, Lishan; Guo, Fangmin; Liu, Yinong; Shi, Xiaobin; Jiang, Daqiang; Brown, Dennis E.; Ren, Yang

    2015-01-01

    Elastic strain in bulk metallic materials is usually limited to only a fraction of 1%. Developing bulk metallic materials showing large linear elasticity and high strength has proven to be difficult. Here, based on the synergistic effect between nanowires and orientated martensite NiTi shape memory alloy, we developed an in-situ Nb nanowires -orientated martensitic NiTi matrix composite showing an ultra-large linear elastic strain of 4% and an ultrahigh yield strength of 1.8 GPa. This material also has a high mechanical energy storage efficiency of 96% and a high energy storage density of 36 J/cm3 that is almost one order of larger than that of spring steel. It is demonstrated that the synergistic effect allows the exceptional mechanical properties of nanowires to be harvested at macro scale and the mechanical properties of matrix to be greatly improved, resulting in these superior properties. This study provides new avenues for developing advanced composites with superior properties by using effective synergistic effect between components. PMID:25749549

  8. Achieving large linear elasticity and high strength in bulk nanocompsite via synergistic effect

    SciTech Connect

    Hao, Shijie; Cui, Lishan; Guo, Fangmin; Liu, Yinong; Shi, Xiaobin; Jiang, Daqiang; Brown, Dennis E.; Ren, Yang

    2015-03-09

    Elastic strain in bulk metallic materials is usually limited to only a fraction of 1%. Developing bulk metallic materials showing large linear elasticity and high strength has proven to be difficult. Here, based on the synergistic effect between nanowires and orientated martensite NiTi shape memory alloy, we developed an in-situ Nb nanowires -orientated martensitic NiTi matrix composite showing an ultra-large linear elastic strain of 4% and an ultrahigh yield strength of 1.8 GPa. This material also has a high mechanical energy storage efficiency of 96% and a high energy storage density of 36 J/cm³ that is almost one order of larger than that of spring steel. It is demonstrated that the synergistic effect allows the exceptional mechanical properties of nanowires to be harvested at macro scale and the mechanical properties of matrix to be greatly improved, resulting in these superior properties. This study provides new avenues for developing advanced composites with superior properties by using effective synergistic effect between components.

  9. Achieving large linear elasticity and high strength in bulk nanocompsite via synergistic effect

    DOE PAGES

    Hao, Shijie; Cui, Lishan; Guo, Fangmin; Liu, Yinong; Shi, Xiaobin; Jiang, Daqiang; Brown, Dennis E.; Ren, Yang

    2015-03-09

    Elastic strain in bulk metallic materials is usually limited to only a fraction of 1%. Developing bulk metallic materials showing large linear elasticity and high strength has proven to be difficult. Here, based on the synergistic effect between nanowires and orientated martensite NiTi shape memory alloy, we developed an in-situ Nb nanowires -orientated martensitic NiTi matrix composite showing an ultra-large linear elastic strain of 4% and an ultrahigh yield strength of 1.8 GPa. This material also has a high mechanical energy storage efficiency of 96% and a high energy storage density of 36 J/cm³ that is almost one order ofmore » larger than that of spring steel. It is demonstrated that the synergistic effect allows the exceptional mechanical properties of nanowires to be harvested at macro scale and the mechanical properties of matrix to be greatly improved, resulting in these superior properties. This study provides new avenues for developing advanced composites with superior properties by using effective synergistic effect between components.« less

  10. Achieving High Strength Joint of Pure Copper Via Laser-Cold Metal Transfer Arc Hybrid Welding

    NASA Astrophysics Data System (ADS)

    Chen, Yulong; Chen, Cong; Gao, Ming; Zeng, Xiaoyan

    2016-06-01

    Fiber laser-cold metal transfer arc hybrid welding of pure copper was studied. Weld porosity was tested by X-ray nondestructive testing. Microstructure and fracture features were observed by scanning electron microscopy. Mechanical properties were evaluated by cross weld tensile test. Full penetrated and continuous welds were obtained by hybrid welding once the laser power reached 2 kW, while they could not be obtained by laser welding alone, even though the laser power reached 5 kW. The ultimate tensile strength (UTS), the yield strength (YS), and the elongation of the best hybrid weld material were up to 227, 201 MPa, and 21.5 pct, respectively. The joint efficiencies in UTS and YS of hybrid weld were up to 84 and 80 pct of the BM, respectively. The fracture location changes from the fusion zone to the heat-affected zone with the increase of laser power. Besides, the mechanisms of process stability and porosity suppression were clarified by laser-arc interaction and pool behavior. The strengthening mechanism was discussed by microstructure characteristics.

  11. High strength alloys

    DOEpatents

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  12. High strength alloys

    DOEpatents

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  13. High strength composites evaluation

    SciTech Connect

    Marten, S.M.

    1992-02-01

    A high-strength, thick-section, graphite/epoxy composite was identified. The purpose of this development effort was to evaluate candidate materials and provide LANL with engineering properties. Eight candidate materials (Samples 1000, 1100, 1200, 1300, 1400, 1500, 1600, and 1700) were chosen for evaluation. The Sample 1700 thermoplastic material was the strongest overall.

  14. High strength ferritic alloy

    DOEpatents

    Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.

    1977-01-01

    A high-strength ferritic alloy useful for fast reactor duct and cladding applications where an iron base contains from about 9% to about 13% by weight chromium, from about 4% to about 8% by weight molybdenum, from about 0.2% to about 0.8% by weight niobium, from about 0.1% to about 0.3% by weight vanadium, from about 0.2% to about 0.8% by weight silicon, from about 0.2% to about 0.8% by weight manganese, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight sulfur, a maximum of about 0.02% by weight phosphorous, and from about 0.04% to about 0.12% by weight carbon.

  15. Poor Results for High Achievers

    ERIC Educational Resources Information Center

    Bui, Sa; Imberman, Scott; Craig, Steven

    2012-01-01

    Three million students in the United States are classified as gifted, yet little is known about the effectiveness of traditional gifted and talented (G&T) programs. In theory, G&T programs might help high-achieving students because they group them with other high achievers and typically offer specially trained teachers and a more advanced…

  16. Development of high strength, high temperature ceramics

    NASA Technical Reports Server (NTRS)

    Hall, W. B.

    1982-01-01

    Improvement in the high-pressure turbopumps, both fuel and oxidizer, in the Space Shuttle main engine were considered. The operation of these pumps is limited by temperature restrictions of the metallic components used in these pumps. Ceramic materials that retain strength at high temperatures and appear to be promising candidates for use as turbine blades and impellers are discussed. These high strength materials are sensitive to many related processing parameters such as impurities, sintering aids, reaction aids, particle size, processing temperature, and post thermal treatment. The specific objectives of the study were to: (1) identify and define the processing parameters that affect the properties of Si3N4 ceramic materials, (2) design and assembly equipment required for processing high strength ceramics, (3) design and assemble test apparatus for evaluating the high temperature properties of Si3N4, and (4) conduct a research program of manufacturing and evaluating Si3N4 materials as applicable to rocket engine applications.

  17. High strength high modulus ceramic fiber

    NASA Technical Reports Server (NTRS)

    Fetterolf, R. N.

    1972-01-01

    Low cost method was developed for producing high strength, high modulus, continuous ceramic oxide fibers. Process transforms inexpensive metallic salts into syrup-like liquids that can be fiberized at room temperatures. Resulting salt fibers are then converted to oxides by calcination at relatively low temperatures.

  18. High strength, tough alloy steel

    DOEpatents

    Thomas, Gareth; Rao, Bangaru V. N.

    1979-01-01

    A high strength, tough alloy steel is formed by heating the steel to a temperature in the austenite range (1000.degree.-1100.degree. C.) to form a homogeneous austenite phase and then cooling the steel to form a microstructure of uniformly dispersed dislocated martensite separated by continuous thin boundary films of stabilized retained austenite. The steel includes 0.2-0.35 weight % carbon, at least 1% and preferably 3-4.5% chromium, and at least one other substitutional alloying element, preferably manganese or nickel. The austenite film is stable to subsequent heat treatment as by tempering (below 300.degree. C.) and reforms to a stable film after austenite grain refinement.

  19. High strength, high ductility low carbon steel

    DOEpatents

    Koo, Jayoung; Thomas, Gareth

    1978-01-01

    A high strength, high ductility low carbon steel consisting essentially of iron, 0.05-0.15 wt% carbon, and 1-3 wt% silicon. Minor amounts of other constituents may be present. The steel is characterized by a duplex ferrite-martensite microstructure in a fibrous morphology. The microstructure is developed by heat treatment consisting of initial austenitizing treatment followed by annealing in the (.alpha. + .gamma.) range with intermediate quenching.

  20. High strength and high toughness steel

    DOEpatents

    Parker, Earl R.; Zackay, Victor F.

    1979-01-01

    A structural steel which possess both high strength and high toughness and has particular application of cryogenic uses. The steel is produced by the utilization of thermally induced phase transformation following heating in a three-phase field in iron-rich alloys of the Fe-Ni-Ti system, with a preferred composition of 12% nickel, 0.5% titanium, the remainder being iron.

  1. Mathematics Achievement in High- and Low-Achieving Secondary Schools

    ERIC Educational Resources Information Center

    Mohammadpour, Ebrahim; Shekarchizadeh, Ahmadreza

    2015-01-01

    This paper identifies the amount of variance in mathematics achievement in high- and low-achieving schools that can be explained by school-level factors, while controlling for student-level factors. The data were obtained from 2679 Iranian eighth graders who participated in the 2007 Trends in International Mathematics and Science Study. Of the…

  2. High-Strength, Superelastic Compounds

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm; Noebe, Ronald; Dellacorte, Christopher; Bigelow, Glen; Thomas, Fransua

    2013-01-01

    In a previous disclosure, the use of 60- NiTiNOL, an ordered intermetallic compound composed of 60 weight percent nickel and 40 weight percent titanium, was investigated as a material for advanced aerospace bearings due to its unique combination of physical properties. Lessons learned during the development of applications for this material have led to the discovery that, with the addition of a ternary element, the resulting material can be thermally processed at a lower temperature to attain the same desirable hardness level as the original material. Processing at a lower temperature is beneficial, not only because it reduces processing costs from energy consumption, but because it also significantly reduces the possibility of quench cracking and thermal distortion, which have been problematic with the original material. A family of ternary substitutions has been identified, including Hf and Zr in various atomic percentages with varying concentrations of Ni and Ti. In the present innovation, a ternary intermetallic compound consisting of 57.6 weight percent Ni, 39.2 weight percent Ti, and 3.2 weight percent Hf (54Ni-45Ti-1Hf atomic percent) was prepared by casting. In this material, Hf substitutes for some of the Ti atoms in the material. In an alternate embodiment of the innovation, Zr, which is close in chemical behavior to Hf, is used as the substitutional element. With either substitution, the solvus temperature of the material is reduced, and lower temperatures can be used to obtain the necessary hardness values. The advantages of this innovation include the ability to solution-treat the material at a lower temperature and still achieve the required hardness for bearings (at least 50 Rockwell C) and superelastic behavior with recoverable strains greater than 2%. Most structural alloys will not return to their original shape after being deformed as little as 0.2% (a tenth of that possible with superelastic materials like 60 NiTiNOL). Because lower temperatures

  3. High-Hot-Strength Ceramic Fibers

    NASA Technical Reports Server (NTRS)

    Sayir, Ali; Matson, Lawrence E.

    1994-01-01

    Continuous fibers consisting of laminae of alumina and yttrium aluminum garnet offer exceptionally high strength, resistance to creep, and chemical stability at high temperatures. These fibers exceed tensile strength of sapphire fibers. Leading candidates for reinforcement of intermetallic-matrix composites in exhaust nozzles of developmental high-speed civil transport aircraft engines. Other applications are in aerospace, automotive, chemical-process, and power-generation industries.

  4. High-strength magnetic materials

    NASA Technical Reports Server (NTRS)

    Detert, K.

    1970-01-01

    Two new precipitation-hardened magnetic alloys are suitable for operation in 800 to 1600 deg F range. One is a martensitic alloy and the other a cobalt-based alloy. They possess improved creep resistance and have application in high temperature inductors and alternators.

  5. Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

    SciTech Connect

    Onishi, Yasuo; Baer, Ellen BK; Chun, Jaehun; Yokuda, Satoru T.; Schmidt, Andrew J.; Sande, Susan; Buchmiller, William C.

    2011-02-20

    K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., 185 C, 10 hours) have been observed to form agglomerates with a shear strength up to 170 kPa. These high values were estimated by measured unconfined compressive strength (UCS) obtained with a pocket penetrometer. Due to its ease of use, it is anticipated that a pocket penetrometer will be used to acquire additional shear strength data from archived K-Basin sludge samples stored at the PNNL Radiochemical Processing Laboratory (RPL) hot cells. It is uncertain whether the pocket penetrometer provides accurate shear strength measurements of the material. To assess the bounding material strength and potential for erosion, it

  6. High toughness-high strength iron alloy

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R. (Inventor)

    1980-01-01

    An iron alloy is provided which exhibits strength and toughness characteristics at cryogenic temperatures. The alloy consists essentially of about 10 to 16 percent by weight nickel, about 0.1 to 1.0 percent by weight aluminum, and 0 to about 3 percent by weight copper, with the balance being essentially iron. The iron alloy is produced by a process which includes cold rolling at room temperature and subsequent heat treatment.

  7. Development of High Specific Strength Envelope Materials

    NASA Astrophysics Data System (ADS)

    Komatsu, Keiji; Sano, Masa-Aki; Kakuta, Yoshiaki

    Progress in materials technology has produced a much more durable synthetic fabric envelope for the non-rigid airship. Flexible materials are required to form airship envelopes, ballonets, load curtains, gas bags and covering rigid structures. Polybenzoxazole fiber (Zylon) and polyalirate fiber (Vectran) show high specific tensile strength, so that we developed membrane using these high specific tensile strength fibers as a load carrier. The main material developed is a Zylon or Vectran load carrier sealed internally with a polyurethane bonded inner gas retention film (EVOH). The external surface provides weather protecting with, for instance, a titanium oxide integrated polyurethane or Tedlar film. The mechanical test results show that tensile strength 1,000 N/cm is attained with weight less than 230g/m2. In addition to the mechanical properties, temperature dependence of the joint strength and solar absorptivity and emissivity of the surface are measured. 

  8. Yield strength of molybdenum at high pressures.

    PubMed

    Jing, Qiumin; Bi, Yan; Wu, Qiang; Jing, Fuqian; Wang, Zhigang; Xu, Jian; Jiang, Sheng

    2007-07-01

    In the diamond anvil cell technology, the pressure gradient approach is one of the three major methods in determining the yield strength for various materials at high pressures. In the present work, by in situ measuring the thickness of the sample foil, we have improved the traditional technique in this method. Based on this modification, the yield strength of molybdenum at pressures has been measured. Our main experimental conclusions are as follows: (1) The measured yield strength data for three samples with different initial thickness (100, 250, and 500 microm) are in good agreement above a peak pressure of 10 GPa. (2) The measured yield strength can be fitted into a linear formula Y=0.48(+/-0.19)+0.14(+/-0.01)P (Y and P denote the yield strength and local pressure, respectively, both of them are in gigapascals) in the local pressure range of 8-21 GPa. This result is in good agreement with both Y=0.46+0.13P determined in the pressure range of 5-24 GPa measured by the radial x-ray diffraction technique and the previous shock wave data below 10 GPa. (3) The zero-pressure yield strength of Mo is 0.5 GPa when we extrapolate our experimental data into the ambient pressure. It is close to the tensile strength of 0.7 GPa determined by Bridgman [Phys. Rev. 48, 825 (1934)] previously. The modified method described in this article therefore provides the confidence in determination of the yield strength at high pressures. PMID:17672772

  9. Development of high strength high toughness third generation advanced high strength steels

    NASA Astrophysics Data System (ADS)

    Martis, Codrick John

    Third generation advanced high strength steels (AHSS's) are emerging as very important engineering materials for structural applications. These steels have high specific strength and thus will contribute significantly to weight reduction in automotive and other structural component. In this investigation two such low carbon low alloy steels (LCLA) with high silicon content (1.6-2wt %) has been developed. These two steel alloys were subjected to single step and two step austempering in the temperature range of 260-399°C to obtain desired microstructures and mechanical properties. Austempering heat treatment was carried out for 2 hours in a molten salt bath. The microstructures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and optical metallography. Quantitative analysis was carried out by image analysis technique. The effect of austempering temperature on the mechanical properties of these two alloys was examined. The influence of microstructures on the mechanical properties of alloys was also studied. Austempering heat treatment resulted in fine carbide free bainitic ferrite and high carbon austenite microstructure in the samples austempered above Ms temperature, whereas tempered martensite and austenite microstructure was obtained in samples austempered below Ms temperature. Yield strength, tensile strength and fracture toughness were found to increase as the austempering temperature decreases, whereas ductility increases as the austempering temperature increases. Tensile strength in the range of 1276MPa -1658 MPa and the fracture toughness in the range of 80-141MPa√m were obtained in these two steels. Volume fractions of different phases present and their lath sizes are related to the mechanical properties. Austempered samples consisting of mixed microstructure of bainitic ferrite and tempered martensite phases resulted in the exceptional combination of strength and toughness.

  10. Method for producing high dielectric strength microvalves

    DOEpatents

    Kirby, Brian J.; Reichmuth, David S.; Shepodd, Timothy J.

    2006-04-04

    A microvalve having a cast-in-place and lithographically shaped mobile, polymer monolith for fluid flow control in microfluidic devices and method of manufacture. The microvalve contains a porous fluorinated polymer monolithic element whose pores are filled with an electrically insulating, high dielectric strength fluid, typically a perfluorinated liquid. This combination provides a microvalve that combines high dielectric strength with extremely low electrical conductivity. These microvalves have been shown to have resistivities of at least 100 G.OMEGA. and are compatible with solvents such as water at a pH between 2.7 and 9.0, 1-1 propanol, acetonitrile, and acetone.

  11. Good character at school: positive classroom behavior mediates the link between character strengths and school achievement.

    PubMed

    Wagner, Lisa; Ruch, Willibald

    2015-01-01

    Character strengths have been found to be substantially related to children's and adolescents' well-being. Initial evidence suggests that they also matter for school success (e.g., Weber and Ruch, 2012). The present set of two studies aimed at replicating and extending these findings in two different age groups, primary school students (N = 179; mean age = 11.6 years) and secondary school students (N = 199; mean age = 14.4 years). The students completed the VIA-Youth (Values in Action Inventory of Strengths for Youth), a self-report measure of the 24 character strengths in the VIA classification. Their teachers rated the students' positive behavior in the classroom. Additionally, school achievement was assessed: For the primary school students (Study 1), teachers rated the students' overall school achievement and for the secondary school students (Study 2), we used their grades as a measure of school achievement. We found that several character strengths were associated with both positive classroom behavior and school achievement. Across both samples, school achievement was correlated with love of learning, perseverance, zest, gratitude, hope, and perspective. The strongest correlations with positive classroom behavior were found for perseverance, self-regulation, prudence, social intelligence, and hope. For both samples, there were indirect effects of some of the character strengths on school achievement through teacher-rated positive classroom behavior. The converging findings from the two samples support the notion that character strengths contribute to positive classroom behavior, which in turn enhances school achievement. Results are discussed in terms of their implications for future research and for school interventions based on character strengths. PMID:26029144

  12. Good character at school: positive classroom behavior mediates the link between character strengths and school achievement

    PubMed Central

    Wagner, Lisa; Ruch, Willibald

    2015-01-01

    Character strengths have been found to be substantially related to children’s and adolescents’ well-being. Initial evidence suggests that they also matter for school success (e.g., Weber and Ruch, 2012). The present set of two studies aimed at replicating and extending these findings in two different age groups, primary school students (N = 179; mean age = 11.6 years) and secondary school students (N = 199; mean age = 14.4 years). The students completed the VIA-Youth (Values in Action Inventory of Strengths for Youth), a self-report measure of the 24 character strengths in the VIA classification. Their teachers rated the students’ positive behavior in the classroom. Additionally, school achievement was assessed: For the primary school students (Study 1), teachers rated the students’ overall school achievement and for the secondary school students (Study 2), we used their grades as a measure of school achievement. We found that several character strengths were associated with both positive classroom behavior and school achievement. Across both samples, school achievement was correlated with love of learning, perseverance, zest, gratitude, hope, and perspective. The strongest correlations with positive classroom behavior were found for perseverance, self-regulation, prudence, social intelligence, and hope. For both samples, there were indirect effects of some of the character strengths on school achievement through teacher-rated positive classroom behavior. The converging findings from the two samples support the notion that character strengths contribute to positive classroom behavior, which in turn enhances school achievement. Results are discussed in terms of their implications for future research and for school interventions based on character strengths. PMID:26029144

  13. Self Regulated Learning of High Achievers

    ERIC Educational Resources Information Center

    Rathod, Ami

    2010-01-01

    The study was conducted on high achievers of Senior Secondary school. Main objectives were to identify the self regulated learners among the high achievers, to find out dominant components and characteristics operative in self regulated learners and to compare self regulated learning of learners with respect to their subject (science and non…

  14. Springback analysis of ultra high strength steel

    NASA Astrophysics Data System (ADS)

    Tenma, Kenji; Kina, Futoshi; Suzuki, Wataru

    2013-12-01

    It is an inevitable trend in the automotive industry to apply more and more high strength steels and even ultra-high strength steels. Even though these materials are more difficult to process the development time of forming tools must be reduced. In order to keep the development time under control, simulation tools are used to verify the forming process in advance. At Aoi Machine Industry a project has been executed to accurately simulate springback of ultra-high strength steels in order to reduce the tool tryout time. In the first phase of the project the simulation settings were optimized based on B-Pillar model A made of Dual Phase 980. In the second phase, it was verified with B-Pillar model B whether these simulation settings were usable as general setting. Results showed that with the right settings it is very well possible to accurately simulate springback of ultra-high strength steels. In the third phase the project the stamping of a B-Pillar of Dual Phase 1180 was studied.

  15. High strength composites evaluation. Final report

    SciTech Connect

    Marten, S.M.

    1992-02-01

    A high-strength, thick-section, graphite/epoxy composite was identified. The purpose of this development effort was to evaluate candidate materials and provide LANL with engineering properties. Eight candidate materials (Samples 1000, 1100, 1200, 1300, 1400, 1500, 1600, and 1700) were chosen for evaluation. The Sample 1700 thermoplastic material was the strongest overall.

  16. High-strength mineralized collagen artificial bone

    NASA Astrophysics Data System (ADS)

    Qiu, Zhi-Ye; Tao, Chun-Sheng; Cui, Helen; Wang, Chang-Ming; Cui, Fu-Zhai

    2014-03-01

    Mineralized collagen (MC) is a biomimetic material that mimics natural bone matrix in terms of both chemical composition and microstructure. The biomimetic MC possesses good biocompatibility and osteogenic activity, and is capable of guiding bone regeneration as being used for bone defect repair. However, mechanical strength of existing MC artificial bone is too low to provide effective support at human load-bearing sites, so it can only be used for the repair at non-load-bearing sites, such as bone defect filling, bone graft augmentation, and so on. In the present study, a high strength MC artificial bone material was developed by using collagen as the template for the biomimetic mineralization of the calcium phosphate, and then followed by a cold compression molding process with a certain pressure. The appearance and density of the dense MC were similar to those of natural cortical bone, and the phase composition was in conformity with that of animal's cortical bone demonstrated by XRD. Mechanical properties were tested and results showed that the compressive strength was comparable to human cortical bone, while the compressive modulus was as low as human cancellous bone. Such high strength was able to provide effective mechanical support for bone defect repair at human load-bearing sites, and the low compressive modulus can help avoid stress shielding in the application of bone regeneration. Both in vitro cell experiments and in vivo implantation assay demonstrated good biocompatibility of the material, and in vivo stability evaluation indicated that this high-strength MC artificial bone could provide long-term effective mechanical support at human load-bearing sites.

  17. Making High-Tensile-Strength Amalgam Components

    NASA Technical Reports Server (NTRS)

    Grugel, Richard

    2008-01-01

    Structural components made of amalgams can be made to have tensile strengths much greater than previously known to be possible. Amalgams, perhaps best known for their use in dental fillings, have several useful attributes, including room-temperature fabrication, corrosion resistance, dimensional stability, and high compressive strength. However, the range of applications of amalgams has been limited by their very small tensile strengths. Now, it has been discovered that the tensile strength of an amalgam depends critically on the sizes and shapes of the particles from which it is made and, consequently, the tensile strength can be greatly increased through suitable choice of the particles. Heretofore, the powder particles used to make amalgams have been, variously, in the form of micron-sized spheroids or flakes. The tensile reinforcement contributed by the spheroids and flakes is minimal because fracture paths simply go around these particles. However, if spheroids or flakes are replaced by strands having greater lengths, then tensile reinforcement can be increased significantly. The feasibility of this concept was shown in an experiment in which electrical copper wires, serving as demonstration substitutes for copper powder particles, were triturated with gallium by use of a mortar and pestle and the resulting amalgam was compressed into a mold. The tensile strength of the amalgam specimen was then measured and found to be greater than 10(exp 4) psi (greater than about 69 MPa). Much remains to be done to optimize the properties of amalgams for various applications through suitable choice of starting constituents and modification of the trituration and molding processes. The choice of wire size and composition are expected to be especially important. Perusal of phase diagrams of metal mixtures could give insight that would enable choices of solid and liquid metal constituents. Finally, whereas heretofore, only binary alloys have been considered for amalgams

  18. High-Strength Bolt Corrosion Fatigue Life Model and Application

    PubMed Central

    Hui-li, Wang; Si-feng, Qin

    2014-01-01

    The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture biggest crack depth reduces along with the material yield strength and the applied stress increases. The material yield strength was the major factor. And the high-strength bolt corrosion fatigue life reduced along with the increase of material strength, the applied stress or stress amplitude. The stress amplitude influenced the most, and the material yield strength influenced the least. Low bolt strength and a low stress amplitude level could extend high-strength bolt corrosion fatigue life. PMID:25152916

  19. High-strength bolt corrosion fatigue life model and application.

    PubMed

    Hui-li, Wang; Si-feng, Qin

    2014-01-01

    The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture biggest crack depth reduces along with the material yield strength and the applied stress increases. The material yield strength was the major factor. And the high-strength bolt corrosion fatigue life reduced along with the increase of material strength, the applied stress or stress amplitude. The stress amplitude influenced the most, and the material yield strength influenced the least. Low bolt strength and a low stress amplitude level could extend high-strength bolt corrosion fatigue life.

  20. The Bendability of Ultra High strength Steels

    NASA Astrophysics Data System (ADS)

    Hazra, S. K.; Efthymiadis, P.; Alamoudi, A.; Kumar, R. L. V.; Shollock, B.; Dashwood, R.

    2016-08-01

    Automotive manufacturers have been reducing the weight of their vehicles to meet increasingly stringent environmental legislation that reflects public demand. A strategy is to use higher strength materials for parts with reduced cross-sections. However, such materials are less formable than traditional grades. The frequent result is increased processing and piece costs. 3D roll forming is a novel and flexible process: it is estimated that a quarter of the structure of a vehicle can be made with a single set of tooling. Unlike stamping, this process requires material with low work hardening rates. In this paper, we present results of ultra high strength steels that have low elongation in a tension but display high formability in bending through the suppression of the necking response.

  1. PARADE Replication Manual: Projects Advancing Reading Achievement and Developing Ego-Strength.

    ERIC Educational Resources Information Center

    Colorado Springs Public Schools, CO.

    Provided is the replication manual for the PARADE (Projects Advancing Reading Achievement and Developing Ego-Strength) project, a program designed to identify and diagnose reading problems in elementary and secondary level students entering a new school, provide an intensive program of prescriptive training, and aid the child in development of…

  2. High-strength iron aluminide alloys

    SciTech Connect

    McKamey, C.G.; Maziasz, P.J.

    1996-06-01

    Past studies have shown that binary Fe{sub 3}Al possesses low creep-rupture strength compared to many other alloys, with creep-rupture lives of less than 5 h being reported for tests conducted at 593{degrees}C and 207 MPa. The combination of poor creep resistance and low room-temperature tensile ductility due to a susceptibility to environmentally-induced dynamic hydrogen embrittlement has limited use of these alloys for structural applications despite their excellent corrosion properties. With regard to the ductility problem, alloy development efforts have produced significant improvements, with ductilities of 10-20% and tensile yield strengths as high as 500 MPa being reported. Likewise, initial improvements in creep resistance have been realized through small additions of Mo, Nb, and Zr.

  3. Thermophilic anaerobic digestion of high strength wastewaters

    SciTech Connect

    Wiegant, W.M.; Claassen, J.A.; Lettinga, G.

    1985-09-01

    Investigations on the thermophilic anaerobic treatment of high-strength wastewaters (14-65 kg COD/mT) are presented. Vinasse, the wastewater of alcohol distilleries, was used as an example of such wastewaters. Semicontinuously fed digestion experiments at high retention times revealed that the effluent quality of digestion at 55C is comparable with that at 30C at similar loading rates. The amount of methane formed per kilogram of vinasse drops almost linearly with increasing vinasse concentrations. The treatment of vinasse was also investigated using upflow anaerobic sludge blanket (UASB) reactors.

  4. HIGH STRENGTH CONTROL RODS FOR NEUTRONIC REACTORS

    DOEpatents

    Lustman, B.; Losco, E.F.; Cohen, I.

    1961-07-11

    Nuclear reactor control rods comprised of highly compressed and sintered finely divided metal alloy panticles and fine metal oxide panticles substantially uniformly distributed theretbrough are described. The metal alloy consists essentially of silver, indium, cadmium, tin, and aluminum, the amount of each being present in centain percentages by weight. The oxide particles are metal oxides of the metal alloy composition, the amount of oxygen being present in certain percentages by weight and all the oxygen present being substantially in the form of metal oxide. This control rod is characterized by its high strength and resistance to creep at elevated temperatures.

  5. High Stakes Testing and Student Achievement.

    ERIC Educational Resources Information Center

    Ediger, Marlow

    The effects of high stakes testing may be critical in the lives of public school students and may have many consequences for schools and teachers. There are no easy answers in measuring student achievement and in holding teachers accountable for learner progress. High stakes testing also involves responsibilities on the part of the principal who…

  6. Student Perceptions of High-Achieving Classmates

    ERIC Educational Resources Information Center

    Händel, Marion; Vialle, Wilma; Ziegler, Albert

    2013-01-01

    The reported study investigated students' perceptions of their high-performing classmates in terms of intelligence, social skills, and conscientiousness in different school subjects. The school subjects for study were examined with regard to cognitive, physical, and gender-specific issues. The results show that high academic achievements in…

  7. High-strength iron aluminide alloys

    SciTech Connect

    McKamey, C.G.; Marrero-Santos, Y.; Maziasz, P.J.

    1995-06-01

    Past studies have shown that binary Fe{sub 3}Al possesses low creep-rupture strength compared to many other alloys, with creep-rupture lives of less than 5 h being reported for tests conducted at 593{degrees}C and 207 MPa. The combination of poor creep resistance and low room-temperature tensile density due to a susceptibility to environmentally-induced dynamic hydrogen embrittlement has limited use of these alloys for structural applications, despite their excellent corrosion properties. Improvements in room temperature tensile ductility have been realized mainly through alloying effects, changes in thermomechanical processing to control microstructure, and by control of the specimen`s surface condition. Ductilities of 10-20% and tensile yield strengths as high as 500 MPa have been reported. In terms of creep-rupture strength, small additions of Mo, Nb, and Zr have produced significant improvements, but at the expense of weldability and room-temperature tensile ductility. Recently an alloy containing these additions, designated FA-180, was shown to exhibit a creep-rupture life of over 2000 h after a heat treatment of 1 h at 1150{degrees}C. This study presents the results of creep-rupture tests at various test temperatures and stresses and discusses the results as part of our effort to understand the strengthening mechanisms involved with heat treatment at 1150{degrees}C.

  8. High Strength and Thermally Stable Nanostructured Magnesium Alloys and Nanocomposites

    NASA Astrophysics Data System (ADS)

    Chang, Yuan-Wei

    Magnesium and its alloys are currently in the spotlight of global research because of the need to limit energy consumption and reduce the environmental impact. In particular, their low densities compared to other structural metals make them a very attractive alternative in the automobile and aerospace industries. However, their low strength compared to other structural materials (e.g. Al and steels) has limited their widespread application. This dissertation presents the results of developing and investigation of a high strength nanostructured magnesium-aluminum alloy and composite. The nanostructured magnesium alloy is prepared by cryomilling and consolidated by spark-plasma-sintering. Focused ion beam is used to prepare micropillars with different diameters ranging from 1.5 to 8 mum and micro-compression test is conducted by nanoindenter in order to evaluate the mechanical properties. The yield strength obtained in the present study is around three times higher than conventional magnesium alloys (120 MPa vs. 370 MPa). The yield strength of the nanostructured magnesium alloy is further improved through hot extrusion, resulting in a yield strength of 550 MPa and an ultimate strength of 580 MPa. The nanostructured magnesium alloy exhibits a strong size-dependence, and a significant improvement in strength is observed when the pillar diameter is reduced to below 3.5 mum. The deformation mechanisms of the compressed pillars were characterized using transmission electron microscopy. The size-induced strengthening is attributed to a less number of dislocation sources along with a higher activity of non-basal deformation mechanisms. We have also developed a high strength and thermally stable nanostructured magnesium composite by adding diamantane. A yield strength of 500 MPa is achieved, moreover, excellent thermal stability is demonstrated in the magnesium alloy containing diamantanes. The strength and grain size are thermally stable after annealing at 400°C for 100

  9. Protective claddings for high strength chromium alloys

    NASA Technical Reports Server (NTRS)

    Collins, J. F.

    1971-01-01

    The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

  10. High Achievers: 23rd Annual Survey. Attitudes and Opinions from the Nation's High Achieving Teens.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Northbrook, IL.

    This report presents data from an annual survey of high school student leaders and high achievers. It is noted that of the nearly 700,000 high achievers featured in this edition, 5,000 students were sent the survey and 2,092 questionnaires were completed. Subjects were high school juniors and seniors selected for recognition by their principals or…

  11. The Progress Achieved By Judokas After Strength Training With A Judo-Specific Machine

    PubMed Central

    Blais, Laurent; Trilles, Francis

    2006-01-01

    For judo players, as in many sports activities, strength development has become an important element of performance. However, this should not be done separately from the development of technique. Specific strength training is thus used for the controlled strengthening of specific muscles or muscle groups, corresponding to the movement in a competitive situation. In line with this, the use of a judo specific apparatus is proposed. The aim of this study is to analyze the progress of a group of judokas after a training program with the apparatus. The results have shown that, using the apparatus, the heaviest weight achieved using the throwing technique is greater. In addition, the judokas' technique improves as a consequence of this training program. This judo specific apparatus could therefore be used to complement traditional judo training. Key Points Judo, strength training, machine, technical progress. PMID:24357985

  12. Achieving High Performance Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Yang, Yang

    2015-03-01

    Recently, metal halide perovskite based solar cell with the characteristics of rather low raw materials cost, great potential for simple process and scalable production, and extreme high power conversion efficiency (PCE), have been highlighted as one of the most competitive technologies for next generation thin film photovoltaic (PV). In UCLA, we have realized an efficient pathway to achieve high performance pervoskite solar cells, where the findings are beneficial to this unique materials/devices system. Our recent progress lies in perovskite film formation, defect passivation, transport materials design, interface engineering with respect to high performance solar cell, as well as the exploration of its applications beyond photovoltaics. These achievements include: 1) development of vapor assisted solution process (VASP) and moisture assisted solution process, which produces perovskite film with improved conformity, high crystallinity, reduced recombination rate, and the resulting high performance; 2) examination of the defects property of perovskite materials, and demonstration of a self-induced passivation approach to reduce carrier recombination; 3) interface engineering based on design of the carrier transport materials and the electrodes, in combination with high quality perovskite film, which delivers 15 ~ 20% PCEs; 4) a novel integration of bulk heterojunction to perovskite solar cell to achieve better light harvest; 5) fabrication of inverted solar cell device with high efficiency and flexibility and 6) exploration the application of perovskite materials to photodetector. Further development in film, device architecture, and interfaces will lead to continuous improved perovskite solar cells and other organic-inorganic hybrid optoelectronics.

  13. Reliability achievement in high technology space systems

    NASA Technical Reports Server (NTRS)

    Lindstrom, D. L.

    1981-01-01

    The production of failure-free hardware is discussed. The elements required to achieve such hardware are: technical expertise to design, analyze, and fully understand the design; use of high reliability parts and materials control in the manufacturing process; and testing to understand the system and weed out defects. The durability of the Hughes family of satellites is highlighted.

  14. ULTRA-HIGH STRENGTH IN NANOCRYSTALLINE MATERIALS UNDER SHOCK LOADING

    SciTech Connect

    Bringa, E M; Caro, A; Wang, Y M; Victoria, M; McNaney, J; Remington, B A; Smith, R; Torralva, B; Van Swygenhoven, H

    2005-04-11

    Molecular dynamics simulations of nanocrystalline (nc) copper under shock loading show an unexpected ultra-high strength behind the shock front. The strength at high pressure can be up to twice the value at low pressure, for all grain sizes studied here (5-50 nm grains, with up to {approx}4 10{sup 8} atoms). Partial and perfect dislocations, twinning, and debris from dislocation interactions are found behind the shock front. Results are interpreted in terms of the pressure dependence of both deformation mechanisms active at these grain sizes, namely dislocation plasticity and grain boundary sliding. These simulations, together with new shock experiments on nc nickel, raise the possibility of achieving ultra-hard materials during and after shock loading.

  15. High strength ferritic alloy-D53

    DOEpatents

    Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.

    1977-01-01

    A high strength ferritic alloy is described having from about 0.2% to about 0.8% by weight nickel, from about 2.5% to about 3.6% by weight chromium, from about 2.5% to about 3.5% by weight molybdenum, from about 0.1% to about 0.5% by weight vanadium, from about 0.1% to about 0.5% by weight silicon, from about 0.1% to about 0.6% by weight manganese, from about 0.12% to about 0.20% by weight carbon, from about 0.02% to about 0.1% by weight boron, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight phosphorous, a maximum of about 0.02% by weight sulfur, and the balance iron.

  16. High strength air-dried aerogels

    SciTech Connect

    Coronado, Paul R.; Satcher, Jr., Joe H.

    2012-11-06

    A method for the preparation of high strength air-dried organic aerogels. The method involves the sol-gel polymerization of organic gel precursors, such as resorcinol with formaldehyde (RF) in aqueous solvents with R/C ratios greater than about 1000 and R/F ratios less than about 1:2.1. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be air dried at ambient temperatures and pressures. The method significantly reduces the time and/or energy required to produce a dried aerogel compared to conventional methods using either supercritical solvent extraction. The air dried gel exhibits typically less than 5% shrinkage.

  17. Early predictors of high school mathematics achievement.

    PubMed

    Siegler, Robert S; Duncan, Greg J; Davis-Kean, Pamela E; Duckworth, Kathryn; Claessens, Amy; Engel, Mimi; Susperreguy, Maria Ines; Chen, Meichu

    2012-07-01

    Identifying the types of mathematics content knowledge that are most predictive of students' long-term learning is essential for improving both theories of mathematical development and mathematics education. To identify these types of knowledge, we examined long-term predictors of high school students' knowledge of algebra and overall mathematics achievement. Analyses of large, nationally representative, longitudinal data sets from the United States and the United Kingdom revealed that elementary school students' knowledge of fractions and of division uniquely predicts those students' knowledge of algebra and overall mathematics achievement in high school, 5 or 6 years later, even after statistically controlling for other types of mathematical knowledge, general intellectual ability, working memory, and family income and education. Implications of these findings for understanding and improving mathematics learning are discussed.

  18. Electrostatic precipitator having high strength discharge electrode

    SciTech Connect

    Bakke, E.; Willett, H.P.

    1983-06-21

    There is disclosed an electrostatic precipitator with a discharge electrode having dimensional and configuration characteristics which provide high field strength and high current density particularly in a wet electrostatic precipitator. The round cylindrical collector tube of length (L) and with an inner diameter (D) has a coaxially positioned discharge electrode having an electrode supporting mast of a diameter from 0.25 to 40 D with an electrically conducting closed screw fli secured to the mast. The screw flight has an overall diameter (D) of from 0.33 to 0.67 D with a pitch of from d-d/2 to d-d and an overall length of from one screw revolution to l-(D-d), preferably one-half L or less and most preferably one to two revolutions. The short screw flight is economical and readily adjusted. The screw flight has a thickness of from about 0.05 to 15 inch and has a symmetrically curved outer edge. Collector tube is flared at its lower end to direct water away from the electrode mast as the water is discharged from the tube. The discharge electrode is supported from above and centered by means of adjustable tie rods at its lower end.

  19. Strength analysis of laser welded lap joint for ultra high strength steel

    NASA Astrophysics Data System (ADS)

    Jeong, Young Cheol; Kim, Cheol Hee; Cho, Young Tae; Jung, Yoon Gyo

    2013-12-01

    Several industries including the automotive industry have recently applied the process of welding high strength steel. High strength steel is steel that is harder than normal high strength steel, making it much stronger and stiffer. HSS can be formed in pieces that can be up to 10 to 15 percent thinner than normal steel without sacrificing strength, which enables weight reduction and improved fuel economy. Furthermore, HSS can be formed into complex shapes that can be welded into structural areas. This study is based on previous experiments and is aimed at establishing the stress distribution for laser welded high strength steel. Research on the stress distribution for laser welded high strength steel is conducted by using Solid Works, a program that analyzes the stress of a virtual model. In conclusion, we found that the stress distribution is changed depending on the shape of welded lap joint. In addition, the Influence of the stress distribution on welded high strength steel can be used to standard for high energy welding of high strength steel, and we can also predict the region in welded high strength steel that may cracked.

  20. Attitudes and Opinions from the Nation's High Achieving Teens. 18th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Educational Communications, Inc., Lake Forest, IL.

    This document contains factsheets and news releases which cite findings from a national survey of 1,985 high achieving high school students. Factsheets describe the Who's Who Among American High School Students recognition and service program for high school students and explain the Who's Who survey. A summary report of this eighteenth annual…

  1. 21st Annual Survey of High Achievers: Attitudes and Opinions from the Nation's High Achieving Teens.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This survey was conducted by Who's Who Among American High School Students during the spring of 1990, to determine the attitudes of student leaders in U.S. high schools. A survey of high achievers sent to 5,000 students was completed and returned by approximately 2,000 students. All students were members of the junior or senior class during the…

  2. 22nd Annual Survey of High Achievers: Attitudes and Opinions from the Nation's High Achieving Teens.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Northbrook, IL.

    This study surveyed high school students (N=1,879) who were student leaders or high achievers in the spring of 1991 for the purpose of determining their attitudes. Students were members of the junior or senior high school class during the 1990-91 academic year and were selected for recognition by their principals or guidance counselors, other…

  3. High Breakdown Strength, Multilayer Ceramics for Compact Pulsed Power Applications

    SciTech Connect

    Gilmore, B.; Huebner, W.; Krogh, M.L.; Lundstrom, J.M.; Pate, R.C.; Rinehart, L.F.; Schultz, B.C.; Zhang, S.C.

    1999-07-20

    Advanced ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (>10 6 J/m 3 ) and physical size reduction. Initial materials based on slip cast TiO2 exhibited a high bulk breakdown strength (BDS >300 kV/cm) and high permittivity with low dispersion (e�100). However, strong area and thickness dependencies were noted. To increase the BDS, multilayer dielectric compositions are being developed based on glass/TiO2 composites. The addition of glass increases the density (�99.8% theoretical), forms a continuous grain boundary phase, and also allows the use of high temperature processes to change the physical shape of the dielectric. The permittivity can also be manipulated since the volume fraction and connectivity of the glassy phase can be readily shifted. Results from this study on bulk breakdown of TiO2 multilayer structures with an area of 2cm 2 and 0.1cm thickness have measured 650 kV/cm. Furthermore, a strong dependence of breakdown strength and permittivity has been observed and correlated with microstructure and the glass composition. This paper presents the interactive effects of manipulation of these variables.

  4. Structural application of high strength, high temperature ceramics

    NASA Technical Reports Server (NTRS)

    Hall, W. B.

    1982-01-01

    The operation of rocket engine turbine pumps is limited by the temperature restrictions of metallic components used in the systems. Mechanical strength and stability of these metallic components decrease drastically at elevated temperatures. Ceramic materials that retain high strength at high temperatures appear to be a feasible alternate material for use in the hot end of the turbopumps. This project identified and defined the processing parameters that affected the properties of Si3N4, one of candidate ceramic materials. Apparatus was assembled and put into operation to hot press Si3N4 powders into bulk material for in house evaluation. A work statement was completed to seek outside contract services to design, manufacture, and evaluate Si3N4 components in the service environments that exists in SSME turbopumps.

  5. Gaseous hydrogen embrittlement of high strength steels

    NASA Technical Reports Server (NTRS)

    Gangloff, R. P.; Wei, R. P.

    1977-01-01

    The effects of temperature, hydrogen pressure, stress intensity, and yield strength on the kinetics of gaseous hydrogen assisted crack propagation in 18Ni maraging steels were investigated experimentally. It was found that crack growth rate as a function of stress intensity was characterized by an apparent threshold for crack growth, a stage where the growth rate increased sharply, and a stage where the growth rate was unchanged over a significant range of stress intensity. Cracking proceeded on load application with little or no detectable incubation period. Gaseous hydrogen embrittlement susceptibility increased with increasing yield strength.

  6. Attitudes and Opinions from the Nation's High Achieving Teens: 26th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    A national survey of 3,351 high achieving high school students (junior and senior level) was conducted. All students had A or B averages. Topics covered include lifestyles, political beliefs, violence and entertainment, education, cheating, school violence, sexual violence and date rape, peer pressure, popularity, suicide, drugs and alcohol,…

  7. Attitudes and Opinions from the Nation's High Achieving Teens. 24th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This survey represents information compiled by the largest national survey of adolescent leaders and high achievers. Of the 5,000 students selected demographically from "Who's Who Among American High School Students," 1,957 responded. All students surveyed had "A" or "B" averages, and 98% planned on attending college. Questions were asked about…

  8. Silicon nitride having a high tensile strength

    DOEpatents

    Pujari, Vimal K.; Tracey, Dennis M.; Foley, Michael R.; Paille, Norman I.; Pelletier, Paul J.; Sales, Lenny C.; Willkens, Craig A.; Yeckley, Russell L.

    1996-01-01

    A silicon nitride ceramic comprising: a) inclusions no greater than 25 microns in length, b) agglomerates no greater than 20 microns in diameter, and c) a surface finish of less than about 8 microinches, said ceramic having a four-point flexural strength of at least about 900 MPa.

  9. Silicon nitride having a high tensile strength

    DOEpatents

    Pujari, V.K.; Tracey, D.M.; Foley, M.R.; Paille, N.I.; Pelletier, P.J.; Sales, L.C.; Willkens, C.A.; Yeckley, R.L.

    1996-11-05

    A silicon nitride ceramic is disclosed comprising: (a) inclusions no greater than 25 microns in length, (b) agglomerates no greater than 20 microns in diameter, and (c) a surface finish of less than about 8 microinches, said ceramic having a four-point flexural strength of at least about 900 MPa. 4 figs.

  10. Manipulating the interfacial structure of nanomaterials to achieve a unique combination of strength and ductility

    PubMed Central

    Khalajhedayati, Amirhossein; Pan, Zhiliang; Rupert, Timothy J.

    2016-01-01

    The control of interfaces in engineered nanostructured materials has met limited success compared with that which has evolved in natural materials, where hierarchical structures with distinct interfacial states are often found. Such interface control could mitigate common limitations of engineering nanomaterials. For example, nanostructured metals exhibit extremely high strength, but this benefit comes at the expense of other important properties like ductility. Here, we report a technique for combining nanostructuring with recent advances capable of tuning interface structure, a complementary materials design strategy that allows for unprecedented property combinations. Copper-based alloys with both grain sizes in the nanometre range and distinct grain boundary structural features are created, using segregating dopants and a processing route that favours the formation of amorphous intergranular films. The mechanical behaviour of these alloys shows that the trade-off between strength and ductility typically observed for metallic materials is successfully avoided here. PMID:26887444

  11. Manipulating the interfacial structure of nanomaterials to achieve a unique combination of strength and ductility.

    PubMed

    Khalajhedayati, Amirhossein; Pan, Zhiliang; Rupert, Timothy J

    2016-01-01

    The control of interfaces in engineered nanostructured materials has met limited success compared with that which has evolved in natural materials, where hierarchical structures with distinct interfacial states are often found. Such interface control could mitigate common limitations of engineering nanomaterials. For example, nanostructured metals exhibit extremely high strength, but this benefit comes at the expense of other important properties like ductility. Here, we report a technique for combining nanostructuring with recent advances capable of tuning interface structure, a complementary materials design strategy that allows for unprecedented property combinations. Copper-based alloys with both grain sizes in the nanometre range and distinct grain boundary structural features are created, using segregating dopants and a processing route that favours the formation of amorphous intergranular films. The mechanical behaviour of these alloys shows that the trade-off between strength and ductility typically observed for metallic materials is successfully avoided here. PMID:26887444

  12. High Strength, Large Core Pure Silica Fibers For Laser Surgery

    NASA Astrophysics Data System (ADS)

    Skutnik, B. J.; Hodge, M. H.; Clarkin, J. P.

    1988-06-01

    Recently many researchers, doctors and instrument companies have begun developing fiber optic laser power delivery systems to accomplish less traumatic surgery or localized irradiation treatment(1). With high power levels, particularly in short bursts, large core fibers are needed to keep the power densities from approaching the damage threshold of silica. Among the many advantages of using optical fibers in laser surgery are the following: microsurgery can be employed, trauma is reduced, access to interior through catheter introduction into vascular, gastrointestinal or respiratory tracts, accurate application of laser power through a flexible lightweight medium to provide localized irradiation as well as surgical removal, and the devices are sterilizable and of moderate cost permitting one-time use (disposable) probes. To achieve these wonderful gains in surgical procedures, the optical fibers must satisfy many optical and mechanical requirements. In use the optical fibers are often required to bend around curves or obstructions to reach the desired application area. Large tensile stresses can occur on the outer radius of the bent fiber, especially with large core fibers, thus high strength fibers are needed. Furthermore, since body fluids are primarily water, stress corrosion and fatigue(2-6) will occur. Therefore, the fibers should have excellent fatigue resistance as well as high strength. This paper further describes these requirements and presents details about an optical fiber which meets these requirements and provides additional very useful properties. These fibers with pure silica cores are called Hard Clad Silica, HCS*, fibers because of their hard bonded cladding over silica structure.

  13. Highly controllable and green reduction of graphene oxide to flexible graphene film with high strength

    SciTech Connect

    Wan, Wubo; Zhao, Zongbin; Hu, Han; Gogotsi, Yury; Qiu, Jieshan

    2013-11-15

    Graphical abstract: Highly controllable and green reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant. Self-assembly of the as-made CCG sheets results in a flexible CCG film, of which the tensile strength strongly depends on the deoxygenation degree of graphene sheets. - Highlights: • Graphene was synthesized by an effective and environmentally friendly approach. • We introduced a facile X-ray diffraction analysis method to investigate the reduction process from graphene oxide to graphene. • Flexible graphene films were prepared by self-assembly of the graphene sheets. • The strength of the graphene films depends on the reduction degree of graphene. - Abstract: Graphene film with high strength was fabricated by the assembly of graphene sheets derived from graphene oxide (GO) in an effective and environmentally friendly approach. Highly controllable reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant, in which the reduction process was monitored by XRD analysis and UV–vis absorption spectra. Self-assembly of the as-made CCG sheets results in a flexible CCG film. This method may open an avenue to the easy and scalable preparation of graphene film with high strength which has promising potentials in many fields where strong, flexible and electrically conductive films are highly demanded.

  14. Mechanical behavior of high strength ceramic fibers at high temperatures

    NASA Technical Reports Server (NTRS)

    Tressler, R. E.; Pysher, D. J.

    1991-01-01

    The mechanical behavior of commercially available and developmental ceramic fibers, both oxide and nonoxide, has been experimentally studied at expected use temperatures. In addition, these properties have been compared to results from the literature. Tensile strengths were measured for three SiC-based and three oxide ceramic fibers for temperatures from 25 C to 1400 C. The SiC-based fibers were stronger but less stiff than the oxide fibers at room temperature and retained more of both strength and stiffness to high temperatures. Extensive creep and creep-rupture experiments have been performed on those fibers from this group which had the best strengths above 1200 C in both single filament tests and tests of fiber bundles. The creep rates for the oxides are on the order of two orders of magnitude faster than the polymer derived nonoxide fibers. The most creep resistant filaments available are single crystal c-axis sapphire filaments. Large diameter CVD fabricated SiC fibers are the most creep and rupture resistant nonoxide polycrystalline fibers tested to date.

  15. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Hovanski, Yuri; Grant, Glenn J.; Santella, M. L.

    2009-11-13

    Friction stir spot welding techniques were developed to successfully join several advanced high strength steels. Two distinct tool materials were evaluated to determine the effect of tool materials on the process parameters and joint properties. Welds were characterized primarily via lap shear, microhardness, and optical microscopy. Friction stir spot welds were compared to the resistance spot welds in similar strength alloys by using the AWS standard for resistance spot welding high strength steels. As further comparison, a primitive cost comparison between the two joining processes was developed, which included an evaluation of the future cost prospects of friction stir spot welding in advanced high strength steels.

  16. High Involvement Mothers of High Achieving Children: Potential Theoretical Explanations

    ERIC Educational Resources Information Center

    Hunsaker, Scott L.

    2013-01-01

    In American society, parents who have high aspirations for the achievements of their children are often viewed by others in a negative light. Various pejoratives such as "pushy parent," "helicopter parent," "stage mother," and "soccer mom" are used in the common vernacular to describe these parents. Multiple…

  17. High Ability Readers and the Achievement Gap

    ERIC Educational Resources Information Center

    Hunsaker, Scott L.; Parke, Cynthia J.; Bramble, Joan G.

    2004-01-01

    To close the achievement gap, the "No Child Left Behind" law calls for all students to make appropriate yearly progress. This presumably means that progress is being made by capable readers at the same time progress is being made by struggling readers. However, there appear to be unintended effects of "No Child Left Behind" that may impede the…

  18. Increasing Lean Mass and Strength: A Comparison of High Frequency Strength Training to Lower Frequency Strength Training

    PubMed Central

    THOMAS, MICHAEL H.; BURNS, STEVE P.

    2016-01-01

    The purpose of this study was to determine the effect strength training frequency has on improvements in lean mass and strength. Participants were 7 women and 12 men, age (χ̄= 34.64 years ± 6.91 years), with strength training experience, training age (χ̄= 51.16 months ± 39.02 months). Participants were assigned to one of two groups to equal baseline group demographics. High frequency training group (HFT) trained each muscle group as the agonist, 3 times per week, exercising with 3 sets per muscle group per session (3 total body workouts). Low frequency training group (LFT) trained each muscle group as the agonist one time per week, completing all 9 sets during that one workout. LFT consisted of a routine split over three days: 1) pectoralis, deltoids, and triceps; 2) upper back and biceps; 3) quadriceps, hamstrings, calves, and abdominals. Following eight weeks of training, HFT increased lean mass by 1.06 kg ± 1.78 kg, (1.9%), and LFT increased lean mass by .99 kg ± 1.31 kg, (2.0%). HFT strength improvements on the chest press was 9.07 kg ± 6.33 kg, (11%), and hack squat 20.16 kg ± 11.59 kg, (21%). LFT strength improvements on chest press was 5.80kg ± 4.26 kg, (7.0%), and hack squat 21.83 kg ± 11.17 kg, (24 %). No mean differences between groups were significant. These results suggest that HFT and LFT of equal set totals result in similar improvements in lean mass and strength, following 8 weeks of strength training. PMID:27182422

  19. High Strength Stainless Steel Properties that Affect Resistance Welding

    SciTech Connect

    Kanne, W.R.

    2001-08-01

    This report discusses results of a study on selected high strength stainless steel alloy properties that affect resistance welding. The austenitic alloys A-286, JBK-75 (Modified A-286), 21-6-9, 22-13-5, 316 and 304L were investigated and compared. The former two are age hardenable, and the latter four obtain their strength through work hardening. Properties investigated include corrosion and its relationship to chemical cleaning, the effects of heat treatment on strength and surface condition, and the effect of mechanical properties on strength and weldability.

  20. High-strength silicon carbides by hot isostatic pressing

    NASA Technical Reports Server (NTRS)

    Dutta, Sunil

    1989-01-01

    Silicon carbide has strong potential for heat engine hardware and other high-temperature applications because of its low density, good strength, high oxidation resistance, and good high-temperature creep resistance. Hot isostatic pressing (HIP) was used for producing alpha and beta silicon carbide (SiC) bodies with near-theoretical density, ultrafine grain size, and high strength at processing temperatures of 1900 to 2000 C. The HIPed materials exhibited ultrafine grain size. Furthermore, no phase transformation from beta to alpha was observed in HIPed beta-SiC. Both materials exhibited very high average flexural strength. It was also shown that alpha-SiC bodies without any sintering aids, when HIPed to high final density, can exhibit very high strength. Fracture toughness K (sub C) values were determined to be 3.6 to 4.0 MPa m (sup 1/2) for HIPed alpha-SiC and 3.7 to 4.1 MPa m (sup 1/2) for HIPed beta-SiC. In the HIPed specimens strength-controlling flaws were typically surface related. In spite of improvements in material properties such as strength and fracture toughness by elimination of the larger strength-limiting flaws and by grain size refinement, HIPing has no effect on the Weibull modulus.

  1. High-strength silicon carbides by hot isostatic pressing

    NASA Technical Reports Server (NTRS)

    Dutta, Sunil

    1988-01-01

    Silicon carbide has strong potential for heat engine hardware and other high-temperature applications because of its low density, good strength, high oxidation resistance, and good high-temperature creep resistance. Hot isostatic pressing (HIP) was used for producing alpha and beta silicon carbide (SiC) bodies with near-theoretical density, ultrafine grain size, and high strength at processing temperatures of 1900 to 2000 C. The HIPed materials exhibited ultrafine grain size. Furthermore, no phase transformation from beta to alpha was observed in HIPed beta-SiC. Both materials exhibited very high average flexural strength. It was also shown that alpha-SiC bodies without any sintering aids, when HIPed to high final density, can exhibit very high strength. Fracture toughness K (sub C) values were determined to be 3.6 to 4.0 MPa m (sup 1/2) for HIPed alpha-SiC and 3.7 to 4.1 MPa m (sup 1/2) for HIPed beta-SiC. In the HIPed specimens strength-controlling flaws were typically surface related. In spite of improvements in material properties such as strength and fracture toughness by elimination of the larger strength-limiting flaws and by grain size refinement, HIPing has no effect on the Weibull modulus.

  2. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Santella, M. L.; Hovanski, Yuri; Grant, Glenn J.; Carpenter, Joseph A.; Warren, C. D.; Smith, Mark T.

    2008-12-28

    Experiments are continuing to evaluate the feasibility of friction stir spot welding advanced high-strength steels including, DP780, martensitic hot-stamp boron steel, and TRIP steels. Spot weld lap-shear strengths can exceed those required by industry standards such as AWS D8.1.

  3. The High School Strength and Conditioning Professional: A Job Description.

    ERIC Educational Resources Information Center

    Best, Randy

    2001-01-01

    Presents a job description for the high school strength and conditioning professional, who is in a unique position to integrate athletics and academics, highlighting: minimum qualifications; school-related benefits derived from employing a strength and conditioning professional; whom the professional reports to and works with; job…

  4. High-Achieving Students in the Era of NCLB

    ERIC Educational Resources Information Center

    Loveless, Tom; Parkas, Steve; Duffett, Ann

    2008-01-01

    This report contains two separate studies examining the status of high-achieving students in the No Child Left Behind (NCLB) era. Part I, An Analysis of NAEP Data, authored by Brookings Institution scholar Tom Loveless, examines achievement trends for high-achieving students (defined, like low-achieving students, by their performance on the…

  5. Investigation of the plastic fracture of high strength steels

    NASA Technical Reports Server (NTRS)

    Cox, T. B.; Low, J. R., Jr.

    1972-01-01

    This investigation deals in detail with the three recognized stages of plastic fracture in high strength steels, namely, void initiation, void growth, and void coalescence. The particular steels under investigation include plates from both commercial purity and high purity heats of AISI 4340 and 18 Ni, 200 grade maraging steels. A scanning electron microscope equipped with an X-ray energy dispersive analyzer, together with observations made using light microscopy, revealed methods of improving the resistance of high strength steels to plastic fracture.

  6. High strength forgeable tantalum base alloy

    NASA Technical Reports Server (NTRS)

    Buckman, R. W., Jr.

    1975-01-01

    Increasing tungsten content of tantalum base alloy to 12-15% level will improve high temperature creep properties of existing tantalum base alloys while retaining their excellent fabrication and welding characteristics.

  7. Formability Characterization of a New Generation High Strength Steels

    SciTech Connect

    Sriram Sadagopan; Dennis Urban; Chris Wong; Mai Huang; Benda Yan

    2003-05-16

    Advanced high strength steels (AHSS) are being progressively explored by the automotive industry all around the world for cost-effective solutions to accomplish vehicle lightweighting, improve fuel economy, and consequently reduce greenhouse emissions. Because of their inherent high strength, attractive crash energy management properties, and good formability, the effective use of AHSS such as Duel Phase and TRIP (Transformation Induced Plasticity) steels, will significantly contribute to vehicle lightweighting and fuel economy. To further the application of these steels in automotive body and structural parts, a good knowledge and experience base must be developed regarding the press formability of these materials. This project provides data on relevant intrinsic mechanical behavior, splitting limits, and springback behavior of several lots of mild steel, conventional high strength steel (HSS), advanced high strength steel (AHSS) and ultra-high strength steel (UHSS), supplied by the member companies of the Automotive Applications Committee (AAC) of the American Iron and Steel Institute (AISI). Two lots of TRIP600, which were supplied by ThyssenKrupp Stahl, were also included in the study. Since sheet metal forming encompasses a very diverse range of forming processes and deformation modes, a number of simulative tests were used to characterize the forming behavior of these steel grades. In general, it was found that formability, as determined by the different tests, decreased with increased tensile strength. Consistant with previous findings, the formability of TRIP600 was found to be exceptionally good for its tensile strength.

  8. The Effect of Achievement Test Selection on Identification of Learning Disabilities within a Patterns of Strengths and Weaknesses Framework

    PubMed Central

    Miciak, Jeremy; Taylor, Pat; Denton, Carolyn A.; Fletcher, Jack M.

    2014-01-01

    Purpose Few empirical investigations have evaluated learning disabilities (LD) identification methods based on a pattern of cognitive strengths and weaknesses (PSW). This study investigated the reliability of LD classification decisions of the concordance/discordance method (C/DM) across different psychoeducational assessment batteries. Methods C/DM criteria were applied to assessment data from 177 second grade students based on two psychoeducational assessment batteries. The achievement tests were different, but were highly correlated and measured the same latent construct. Resulting LD identifications were then evaluated for agreement across batteries on LD status and the academic domain of eligibility. Results The two batteries identified a similar number of participants as having LD (80 and 74). However, indices of agreement for classification decisions were low (kappa = .29), especially for percent positive agreement (62%). The two batteries demonstrated agreement on the academic domain of eligibility for only 25 participants. Conclusions Cognitive discrepancy frameworks for LD identification are inherently unstable because of imperfect reliability and validity at the observed level. Methods premised on identifying a PSW profile may never achieve high reliability because of these underlying psychometric factors. An alternative is to directly assess academic skills to identify students in need of intervention. PMID:25243467

  9. Improving Student Achievement: A Study of High-Poverty Schools with Higher Student Achievement Outcomes

    ERIC Educational Resources Information Center

    Butz, Stephen D.

    2012-01-01

    This research examined the education system at high-poverty schools that had significantly higher student achievement levels as compared to similar schools with lower student achievement levels. A multischool qualitative case study was conducted of the educational systems where there was a significant difference in the scores achieved on the…

  10. High School Employment and Youths' Academic Achievement

    ERIC Educational Resources Information Center

    Rothstein, Donna S.

    2007-01-01

    This paper asks whether employment during high school impacts youths' grade point average. Unlike much of the prior literature, it allows for the endogeneity of the hours and dropout decisions, uses ASVAB test scores, and tests whether youth employment is dynamic. The results indicate that high school employment and its lag have small, negative…

  11. Achieving high energy absorption capacity in cellular bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Chen, S. H.; Chan, K. C.; Wu, F. F.; Xia, L.

    2015-05-01

    Cellular bulk metallic glasses (BMGs) have exhibited excellent energy-absorption performance by inheriting superior strength from the parent BMGs. However, how to achieve high energy absorption capacity in cellular BMGs is vital but mysterious. In this work, using step-by-step observations of the deformation evolution of a series of cellular BMGs, the underlying mechanisms for the remarkable energy absorption capacity have been investigated by studying two influencing key factors: the peak stress and the decay of the peak stress during the plastic-flow plateau stages. An analytical model of the peak stress has been proposed, and the predicted results agree well with the experimental data. The decay of the peak stress has been attributed to the geometry change of the macroscopic cells, the formation of shear bands in the middle of the struts, and the “work-softening” nature of BMGs. The influencing factors such as the effect of the strut thickness and the number of unit cells have also been investigated and discussed. Strategies for achieving higher energy absorption capacity in cellular BMGs have been proposed.

  12. Achieving high energy absorption capacity in cellular bulk metallic glasses

    PubMed Central

    Chen, S. H.; Chan, K. C.; Wu, F. F.; Xia, L.

    2015-01-01

    Cellular bulk metallic glasses (BMGs) have exhibited excellent energy-absorption performance by inheriting superior strength from the parent BMGs. However, how to achieve high energy absorption capacity in cellular BMGs is vital but mysterious. In this work, using step-by-step observations of the deformation evolution of a series of cellular BMGs, the underlying mechanisms for the remarkable energy absorption capacity have been investigated by studying two influencing key factors: the peak stress and the decay of the peak stress during the plastic-flow plateau stages. An analytical model of the peak stress has been proposed, and the predicted results agree well with the experimental data. The decay of the peak stress has been attributed to the geometry change of the macroscopic cells, the formation of shear bands in the middle of the struts, and the “work-softening” nature of BMGs. The influencing factors such as the effect of the strut thickness and the number of unit cells have also been investigated and discussed. Strategies for achieving higher energy absorption capacity in cellular BMGs have been proposed. PMID:25973781

  13. Survey of Processing Methods for High Strength High Conductivity Wires for High Field Magnet Applications

    SciTech Connect

    Han, K.; Embury, J.D.

    1998-10-01

    This paper will deal with the basic concepts of attaining combination of high strength and high conductivity in pure materials, in-situ composites and macrocomposites. It will survey current attainments, and outline where some future developments may lie in developing wire products that are close to the theoretical strength of future magnet applications.

  14. High-strength braze joints between copper and steel

    NASA Technical Reports Server (NTRS)

    Kuhn, R. F.

    1967-01-01

    High-strength braze joints between copper and steel are produced by plating the faying surface of the copper with a layer of gold. This reduces porosity in the braze area and strengthens the resultant joint.

  15. Investigation of the plastic fracture of high strength steels

    NASA Technical Reports Server (NTRS)

    Cox, T. B.; Low, J. R., Jr.

    1972-01-01

    An investigation of the plastic fracture process to improve tensile strength in high strength steels is presented. Two generic types of steels are considered: a quenched and tempered grade and a maraging grade, in order to compare two different matrix microstructures. Each type of steel was studied in commercial grade purity and in special melted high purity form, low in residual and impurity elements. The specific alloys dealt with include AISI 4340 and 18 Ni, 200 grade maraging steel, both heat treated to the same yield strength level of approximately 200 ksi.

  16. Stress corrosion of high strength aluminum alloys.

    NASA Technical Reports Server (NTRS)

    Cocks, F. H.; Brummer, S. B.

    1972-01-01

    An investigation has been carried out to examine the relationship of the observed chemical and mechanical properties of Al-Cu and Al-Zn-Mg alloys to the stress corrosion mechanisms which dominate in each case. Two high purity alloys and analogous commercial alloys were selected. Fundamental differences between the behavior of Al-Cu and of Al-Zn-Mg alloys were observed. These differences in the corrosion behavior of the two types of alloys are augmented by substantial differences in their mechanical behavior. The relative cleavage energy of the grain boundaries is of particular importance.

  17. Physical processes at high field strengths

    SciTech Connect

    Rhodes, C.K.

    1986-01-01

    Measurements of the radiation produced by the high field interaction with the rare gases have revealed the presence of both copious harmonic production and fluorescence. The highest harmonic observed was the seventeenth (14.6 rm) in Ne, the shortest wavelength ever produced by that means. Strong fluorescence was seen in Ar, Kr, and Xe with the shortest wavelengths observed being below 10 nm. Furthermore, radiation from inner-shell excited configurations in Xe, specifically the 4d/sup 9/5s5p ..-->.. 4d/sup 10/5s manifold at approx. 17.7 nm, was detected. The behaviors of the rare gases with respect to multiquantum ionization, harmonic production, and fluorescence were found to be correlated so that the materials fell into two groups, He and Ne in one and Ar, Kr, and Xe in the other. These experimental findings, in alliance with other studies on inner-shell decay processes, give evidence for a role of atomic correlations in a direct nonlinear process of inner-shell excitation. It is expected that an understanding of these high-field processes will enable the generation of stimulated emission in the x-ray range. 59 refs., 6 figs., 5 tabs.

  18. Achieving strategic surety for high consequence software

    SciTech Connect

    Pollock, G.M.

    1996-09-01

    A strategic surety roadmap for high consequence software systems under the High Integrity Software (HIS) Program at Sandia National Laboratories guides research in identifying methodologies to improve software surety. Selected research tracks within this roadmap are identified and described detailing current technology and outlining advancements to be pursued over the coming decade to reach HIS goals. The tracks discussed herein focus on Correctness by Design, and System Immunology{trademark}. Specific projects are discussed with greater detail given on projects involving Correct Specification via Visualization, Synthesis, & Analysis; Visualization of Abstract Objects; and Correct Implementation of Components.

  19. Investigation of ultra violet (UV) resistance for high strength fibers

    NASA Astrophysics Data System (ADS)

    Said, M. A.; Dingwall, Brenda; Gupta, A.; Seyam, A. M.; Mock, G.; Theyson, T.

    Ultra long duration balloons (ULDB), currently under development by the National Aeronautics and Space Administration (NASA), requires the use of high strength fibers in the selected super-pressure pumpkin design. The pumpkin shape balloon concept allows clear separation of the load transferring functions of the major structural elements of the pneumatic envelope, the tendons and the film. Essentially, the film provides the gas barrier and transfers only local pressure load to the tendons. The tendons, in the mean time, provide the global pressure containing strength. In that manner, the strength requirement for the film only depends on local parameters. The tendon is made of p-phenylene-2,6-benzobisoxazole (PBO) fibers, which is selected due to its high strength to weight ratio when compared to other high performance, commercially available, fibers. High strength fibers, however, are known to degrade upon exposure to light, particularly at short wavelengths. This paper reports the results of an investigation of the resistance of four commercial high strength fibers to ultra violet (UV) exposure. The results indicate that exposing high strength fibers in continuous yarn form to UV led to serious loss in strength of the fibers except for Spectra® fibers. The adverse changes in mechanical behavior occurred over short duration of exposure compared to the 100 day duration targeted for these missions. UV blocking finishes to improve the UV resistance of these fibers are being investigated. The application of these specially formulated coatings is expected to lead to significant improvement of the UV resistance of these high performance fibers. In this publication, we report on the mechanical behavior of the fibers pre- and post-exposure to UV, but without application of the blocking finishes.

  20. Early Predictors of High School Mathematics Achievement

    ERIC Educational Resources Information Center

    Siegler, Robert S.; Duncan, Greg J.; Davis-Kean, Pamela E.; Duckworth, Kathryn; Claessens, Amy; Engel, Mimi; Susperreguy, Maria Ines; Meichu, Chen

    2012-01-01

    Identifying the types of mathematics content knowledge that are most predictive of students' long-term learning is essential for improving both theories of mathematical development and mathematics education. To identify these types of knowledge, we examined long-term predictors of high school students' knowledge of algebra and overall mathematics…

  1. Norview High School: Leadership Fosters Achievment

    ERIC Educational Resources Information Center

    Principal Leadership, 2013

    2013-01-01

    Often little unsaid things demonstrate what is truly important in a school. When teachers have common planning time and all of the department chairs share a single space as they do at Norview High School in Norfolk, VA, the unmistakable message is that instructional collaboration and leadership are expected and valued. Norview, an urban,…

  2. Achieving High-Temperature Ferromagnetic Topological Insulator

    NASA Astrophysics Data System (ADS)

    Katmis, Ferhat

    Topological insulators (TIs) are insulating materials that display conducting surface states protected by time-reversal symmetry, wherein electron spins are locked to their momentum. This unique property opens new opportunities for creating next-generation electronic and spintronic devices, including TI-based quantum computation. Introducing ferromagnetic order into a TI system without compromising its distinctive quantum coherent features could lead to a realization of several predicted novel physical phenomena. In particular, achieving robust long-range magnetic order at the TI surface at specific locations without introducing spin scattering centers could open up new possibilities for devices. Here, we demonstrate topologically enhanced interface magnetism by coupling a ferromagnetic insulator (FMI) to a TI (Bi2Se3); this interfacial ferromagnetism persists up to room temperature, even though the FMI (EuS) is known to order ferromagnetically only at low temperatures (<17 K). The induced magnetism at the interface resulting from the large spin-orbit interaction and spin-momentum locking feature of the TI surface is found to greatly enhance the magnetic ordering (Curie) temperature of the TI/FMI bilayer system. Due to the short range nature of the ferromagnetic exchange interaction, the time-reversal symmetry is broken only near the surface of a TI, while leaving its bulk states unaffected. The topological magneto-electric response originating in such an engineered TI could allow for an efficient manipulation of the magnetization dynamics by an electric field, providing an energy efficient topological control mechanism for future spin-based technologies. Work supported by MIT MRSEC through the MRSEC Program of NSF under award number DMR-0819762, NSF Grant DMR-1207469, the ONR Grant N00014-13-1-0301, and the STC Center for Integrated Quantum Materials under NSF grant DMR-1231319.

  3. Exceptional high fatigue strength in Cu-15at.%Al alloy with moderate grain size

    PubMed Central

    Liu, Rui; Tian, Yanzhong; Zhang, Zhenjun; An, Xianghai; Zhang, Peng; Zhang, Zhefeng

    2016-01-01

    It is commonly proposed that the fatigue strength can be enhanced by increasing the tensile strength, but this conclusion needs to be reconsidered according to our study. Here a recrystallized α-Cu-15at.%Al alloy with moderate grain size of 0.62 μm was fabricated by cold rolling and annealing, and this alloy achieved exceptional high fatigue strength of 280 MPa at 107 cycles. This value is much higher than the fatigue strength of 200 MPa for the nano-crystalline counterpart (0.04 μm in grain size) despite its higher tensile strength. The remarkable improvement of fatigue strength should be mainly attributed to the microstructure optimization, which helps achieve the reduction of initial damage and the dispersion of accumulated damage. A new strategy of “damage reduction” was then proposed for fatigue strength improvement, to supplement the former strengthening principle. The methods and strategies summarized in this work offer a general pathway for further improvement of fatigue strength, in order to ensure the long-term safety of structural materials. PMID:27264347

  4. Exceptional high fatigue strength in Cu-15at.%Al alloy with moderate grain size

    NASA Astrophysics Data System (ADS)

    Liu, Rui; Tian, Yanzhong; Zhang, Zhenjun; An, Xianghai; Zhang, Peng; Zhang, Zhefeng

    2016-06-01

    It is commonly proposed that the fatigue strength can be enhanced by increasing the tensile strength, but this conclusion needs to be reconsidered according to our study. Here a recrystallized α-Cu-15at.%Al alloy with moderate grain size of 0.62 μm was fabricated by cold rolling and annealing, and this alloy achieved exceptional high fatigue strength of 280 MPa at 107 cycles. This value is much higher than the fatigue strength of 200 MPa for the nano-crystalline counterpart (0.04 μm in grain size) despite its higher tensile strength. The remarkable improvement of fatigue strength should be mainly attributed to the microstructure optimization, which helps achieve the reduction of initial damage and the dispersion of accumulated damage. A new strategy of “damage reduction” was then proposed for fatigue strength improvement, to supplement the former strengthening principle. The methods and strategies summarized in this work offer a general pathway for further improvement of fatigue strength, in order to ensure the long-term safety of structural materials.

  5. Exceptional high fatigue strength in Cu-15at.%Al alloy with moderate grain size.

    PubMed

    Liu, Rui; Tian, Yanzhong; Zhang, Zhenjun; An, Xianghai; Zhang, Peng; Zhang, Zhefeng

    2016-01-01

    It is commonly proposed that the fatigue strength can be enhanced by increasing the tensile strength, but this conclusion needs to be reconsidered according to our study. Here a recrystallized α-Cu-15at.%Al alloy with moderate grain size of 0.62 μm was fabricated by cold rolling and annealing, and this alloy achieved exceptional high fatigue strength of 280 MPa at 10(7) cycles. This value is much higher than the fatigue strength of 200 MPa for the nano-crystalline counterpart (0.04 μm in grain size) despite its higher tensile strength. The remarkable improvement of fatigue strength should be mainly attributed to the microstructure optimization, which helps achieve the reduction of initial damage and the dispersion of accumulated damage. A new strategy of "damage reduction" was then proposed for fatigue strength improvement, to supplement the former strengthening principle. The methods and strategies summarized in this work offer a general pathway for further improvement of fatigue strength, in order to ensure the long-term safety of structural materials. PMID:27264347

  6. High strength alumina produced by direct coagulation casting

    SciTech Connect

    Baader, F.H.; Will, J.; Tieche, D.

    1995-09-01

    Direct Coagulation Casting is a new colloidal forming technique. Double layer stabilized, concentrated alumina suspensions are solidified by shifting the suspensions pH from 4 towards the isoelectric point at 9 using the in situ enzyme-catalyzed decomposition of urea. This reaction minimizes the repulsive forces between the suspended particles. The remaining, attractive Van der Waals forces form a stiff particle network. Suspensions with low viscosities (0.3 Pa*s, 59 vol%) were prepared at pH 4. Deagglomeration of the suspensions by ball milling reduced the agglomerate size below 5 pm. The coagulation kinetics could be influenced either by the urease concentration or by the suspension temperature. Process variables were established, providing long idle times, which allowed additional filtration and degassing steps. Coagulation was followed by drying and sintering, whereby densities of more than 3.97 g/cm{sup 3}, a 4-point bending strength of 685 MPa (HIPed) and a high reliablility (m = 40) for high purity alumina were achieved. DCC has the potential to improve the reliability of alumina components of complex shape, as well as to avoid expensive molding.

  7. The Mediating Effects of Child Strengths and Hopes on Academic Achievement for Palestinian Children Exposed to Armed Conflict

    ERIC Educational Resources Information Center

    Khamis, Vivian

    2013-01-01

    This study investigated predictors of academic achievement among Palestinian children, including child and parent characteristics, exposure to armed conflict, child strengths, and children's hope. Participants were 1,697 children of both genders. The mean age of participants was 12 years, 10 months. Results of the final hierarchical multiple…

  8. Self-Concept and Achievement Motivation of High School Students

    ERIC Educational Resources Information Center

    Lawrence, A. S. Arul; Vimala, A.

    2013-01-01

    The present study "Self-concept and Achievement Motivation of High School Students" was investigated to find the relationship between Self-concept and Achievement Motivation of High School Students. Data for the study were collected using Self-concept Questionnaire developed by Raj Kumar Saraswath (1984) and Achievement Motive Test (ACMT)…

  9. High strength nickel-chromium-iron austenitic alloy

    DOEpatents

    Gibson, Robert C.; Korenko, Michael K.

    1980-01-01

    A solid solution strengthened Ni-Cr-Fe alloy capable of retaining its strength at high temperatures and consisting essentially of 42 to 48% nickel, 11 to 13% chromium, 2.6 to 3.4% niobium, 0.2 to 1.2% silicon, 0.5 to 1.5% vanadium, 2.6 to 3.4% molybdenum, 0.1 to 0.3% aluminum, 0.1 to 0.3% titanium, 0.02 to 0.05% carbon, 0.002 to 0.015% boron, up to 0.06 zirconium, and the balance iron. After solution annealing at 1038.degree. C. for one hour, the alloy, when heated to a temperature of 650.degree. C., has a 2% yield strength of 307 MPa, an ultimate tensile strength of 513 MPa and a rupture strength of as high as 400 MPa after 100 hours.

  10. Corrosion fatigue of high strength fastener materials in seawater

    NASA Technical Reports Server (NTRS)

    Tipton, D. G.

    1983-01-01

    Environmental effects which significantly reduce the fatigue life of metals are discussed. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure.

  11. Corrosion fatigue of high strength fastener materials in seawater

    NASA Astrophysics Data System (ADS)

    Tipton, D. G.

    1983-12-01

    Environmental effects which significantly reduce the fatigue life of metals are discussed. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure.

  12. Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices

    SciTech Connect

    Geoffrey Krafft

    2005-09-15

    Since the earliest papers on undulaters were published, it has been known how to calculate the spontaneous emission spectrum from ''short'' undulaters when the magnetic field strength parameter is small compared to unity, or in ''single'' frequency sinusoidal undulaters where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulater. Fewer general results have been obtained in the case where the insertion device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the insertion device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field insertion devices. It is used to calculate the emission from some insertion device designs of recent interest.

  13. High Strength Development at Incompatible Semicrystalline Polymer-Polymer Interfaces

    NASA Astrophysics Data System (ADS)

    Hong, C. H.; Wool, Richard

    2007-03-01

    For incompatible A/B interfaces, the strength G1c is related to the equilibrium width w (normalized to the tube diameter) of the interface by G1c/G* = (w-1), where G* is the virgin strength [R.P. Wool, C.R, Chimie, 9 (2006) 25]. However, the interface strength is quite weak due to very limited interdiffusion. The mechanism of high strength development of a series of thermoplastic polyurethane elastomers (TPU) bonding with ethylene vinyl alcohol copolymers (EVOH) was investigated. During cool down of the A/B interface in the co-extruded melt, there exits a unique process window---the α-β window-which promotes considerable strength development. We used the differences in melting points and the volume contraction during asymmetric crystallization to generate influxes (σ nano-nails/unit area), where an influx occurs by the fluid being pulled into the crystallizing side. TPU samples with higher degree of crystallization typically exhibited higher peel strengths, due to the formation of both inter- and intra- spherulitic influxes of nano-dimension across the interface. The peel energy now behaves as G1c˜ σL^2, where L is the length of the influx and L>>w. Annealing between the α and βt relaxation temperatures of the EVOH generated additional influxes which provided significant connectivity and peel strength.

  14. A universal fracture criterion for high-strength materials

    PubMed Central

    Qu, Rui Tao; Zhang, Zhe Feng

    2013-01-01

    Recently developed advanced high-strength materials like metallic glasses, nanocrystalline metallic materials, and advanced ceramics usually fracture in a catastrophic brittle manner, which makes it quite essential to find a reasonable fracture criterion to predict their brittle failure behaviors. Based on the analysis of substantial experimental observations of fracture behaviors of metallic glasses and other high-strength materials, here we developed a new fracture criterion and proved it effective in predicting the critical fracture conditions under complex stress states. The new criterion is not only a unified one which unifies the three classical failure criteria, i.e., the maximum normal stress criterion, the Tresca criterion and the Mohr-Coulomb criterion, but also a universal criterion which has the ability to describe the fracture mechanisms of a variety of different high-strength materials under various external loading conditions.

  15. Scientific Temper among Academically High and Low Achieving Adolescent Girls

    ERIC Educational Resources Information Center

    Kour, Sunmeet

    2015-01-01

    The present study was undertaken to compare the scientific temper of high and low achieving adolescent girl students. Random sampling technique was used to draw the sample from various high schools of District Srinagar. The sample for the present study consisted of 120 school going adolescent girls (60 high and 60 low achievers). Data was…

  16. Uncertainties in obtaining high reliability from stress-strength models

    NASA Technical Reports Server (NTRS)

    Neal, Donald M.; Matthews, William T.; Vangel, Mark G.

    1992-01-01

    There has been a recent interest in determining high statistical reliability in risk assessment of aircraft components. The potential consequences are identified of incorrectly assuming a particular statistical distribution for stress or strength data used in obtaining the high reliability values. The computation of the reliability is defined as the probability of the strength being greater than the stress over the range of stress values. This method is often referred to as the stress-strength model. A sensitivity analysis was performed involving a comparison of reliability results in order to evaluate the effects of assuming specific statistical distributions. Both known population distributions, and those that differed slightly from the known, were considered. Results showed substantial differences in reliability estimates even for almost nondetectable differences in the assumed distributions. These differences represent a potential problem in using the stress-strength model for high reliability computations, since in practice it is impossible to ever know the exact (population) distribution. An alternative reliability computation procedure is examined involving determination of a lower bound on the reliability values using extreme value distributions. This procedure reduces the possibility of obtaining nonconservative reliability estimates. Results indicated the method can provide conservative bounds when computing high reliability. An alternative reliability computation procedure is examined involving determination of a lower bound on the reliability values using extreme value distributions. This procedure reduces the possibility of obtaining nonconservative reliability estimates. Results indicated the method can provide conservative bounds when computing high reliability.

  17. Effects of Rock High Pressure Strength on Penetration

    NASA Astrophysics Data System (ADS)

    Huang, Hongfa

    2011-06-01

    Perforating of oil/gas well creates communication tunnel between reservoir and wellbore. Shaped charges are widely used as perforators in oilfield industry. The liners of the charges are mostly made of powder metal to prevent solid slug clogging the entrance hole of well casing or locking the hole in perforating gun. High speed jet from the shaped charge pierces through perforating gun, well fluid, well casing, and then penetrates into reservoir formation. Prediction of jet penetration in reservoir rock is critical in modeling of well production. An analytical penetration model developed for solid rod by Tate and Alekseevskii is applied. However, strength of formation rock at high pressure needs to be measured. Lateral stress gauge measurements in plate impact tests are conducted. Piezoelectric pressure gauges are imbedded in samples to measure the longitudinal and transverse stress. The two stresses provide Hugoniot and material compressive strength. Indiana limestone, a typical rock in perforation testing, is selected as target sample material in the plate impact tests. Since target strength effect on penetration is more significant in late stage of penetration when the strength of material becomes significant compared to the impact pressure, all the impact tests are focused on lower impact pressure up to 9 GPa. The measurements show that the strength increases with impact pressure. The results are applied in the penetration calculations. The final penetration matches testing data very well.

  18. The Tensile Behavior of High-Strength Carbon Fibers.

    PubMed

    Langston, Tye

    2016-08-01

    Carbon fibers exhibit exceptional properties such as high stiffness and specific strength, making them excellent reinforcements for composite materials. However, it is difficult to directly measure their tensile properties and estimates are often obtained by tensioning fiber bundles or composites. While these macro scale tests are informative for composite design, their results differ from that of direct testing of individual fibers. Furthermore, carbon filament strength also depends on other variables, including the test length, actual fiber diameter, and material flaw distribution. Single fiber tensile testing was performed on high-strength carbon fibers to determine the load and strain at failure. Scanning electron microscopy was also conducted to evaluate the fiber surface morphology and precisely measure each fiber's diameter. Fiber strength was found to depend on the test gage length and in an effort to better understand the overall expected performance of these fibers at various lengths, statistical weak link scaling was performed. In addition, the true Young's modulus was also determined by taking the system compliance into account. It was found that all properties (tensile strength, strain to failure, and Young's modulus) matched very well with the manufacturers' reported values at 20 mm gage lengths, but deviated significantly at other lengths.

  19. The Tensile Behavior of High-Strength Carbon Fibers.

    PubMed

    Langston, Tye

    2016-08-01

    Carbon fibers exhibit exceptional properties such as high stiffness and specific strength, making them excellent reinforcements for composite materials. However, it is difficult to directly measure their tensile properties and estimates are often obtained by tensioning fiber bundles or composites. While these macro scale tests are informative for composite design, their results differ from that of direct testing of individual fibers. Furthermore, carbon filament strength also depends on other variables, including the test length, actual fiber diameter, and material flaw distribution. Single fiber tensile testing was performed on high-strength carbon fibers to determine the load and strain at failure. Scanning electron microscopy was also conducted to evaluate the fiber surface morphology and precisely measure each fiber's diameter. Fiber strength was found to depend on the test gage length and in an effort to better understand the overall expected performance of these fibers at various lengths, statistical weak link scaling was performed. In addition, the true Young's modulus was also determined by taking the system compliance into account. It was found that all properties (tensile strength, strain to failure, and Young's modulus) matched very well with the manufacturers' reported values at 20 mm gage lengths, but deviated significantly at other lengths. PMID:27278219

  20. Material Strength at High Pressure LDRD Strategic Initiative Final Report

    SciTech Connect

    Lassila, D H; Bonner, B P; Bulatov, V V; Cazamias, J U; Chandler, E A; Farber, D L; Moriarty, J A; Zaug, J M

    2004-03-02

    Various aspects of the Laboratory's national security mission are now highly dependent on accurate computer code simulations of plastic flow (i.e., non-reversible deformation) of materials under conditions of high hydrostatic pressure. Strength models are typically dependent on pressure, temperature, and strain rate. Current strength models can not be extrapolated to high pressure because they are not based on the underlying mechanisms of plastic deformation. The critical need for predictive models of material strength, which describe flow stress in computer code simulations, has motivated LLNL's multiscale modeling efforts. Over the past three years, the ''Material Strength at High Pressure'' LDRD Strategic Initiative has established a framework for the development of predictive strength models for deformation of metals under conditions of high hydrostatic pressure. Deformation experiments have been developed to measure the effect of high pressure on the yield strength and work hardening behavior of high purity Mo and Ta single crystals. The over arching goal of the SI is to experimentally validate multiscale-modeling capabilities for deformation of metals under conditions of high pressure. The work performed and accomplished is a necessary next step in the development of predictive strength models. Our initial experimental results show that the influence of pressure is to dramatically increase the work hardening rate of Ta. Bridgman also observed this in experiments performed in the 1950's. Currently there is very little modern data on this phenomena, or theoretical understanding. The work started by this SI is a first step in a comprehensive understanding of plasticity under conditions of high pressure and we expect eventually to be able to incorporate the proper physics into dislocation dynamics (DD) simulations to capture the increase in work hardening that we observe experimentally. In the following sections we briefly describe the work that was performed in

  1. Strength Development of High-Strength Ductile Concrete Incorporating Metakaolin and PVA Fibers

    PubMed Central

    Nuruddin, Muhammad Fadhil; Shafiq, Nasir

    2014-01-01

    The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers. PMID:24707202

  2. Strength development of high-strength ductile concrete incorporating Metakaolin and PVA fibers.

    PubMed

    Nuruddin, Muhammad Fadhil; Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

    2014-01-01

    The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers.

  3. Strength development of high-strength ductile concrete incorporating Metakaolin and PVA fibers.

    PubMed

    Nuruddin, Muhammad Fadhil; Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

    2014-01-01

    The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers. PMID:24707202

  4. A low-cost hierarchical nanostructured beta-titanium alloy with high strength

    NASA Astrophysics Data System (ADS)

    Devaraj, Arun; Joshi, Vineet V.; Srivastava, Ankit; Manandhar, Sandeep; Moxson, Vladimir; Duz, Volodymyr A.; Lavender, Curt

    2016-04-01

    Lightweighting of automobiles by use of novel low-cost, high strength-to-weight ratio structural materials can reduce the consumption of fossil fuels and in turn CO2 emission. Working towards this goal we achieved high strength in a low cost β-titanium alloy, Ti-1Al-8V-5Fe (Ti185), by hierarchical nanostructure consisting of homogenous distribution of micron-scale and nanoscale α-phase precipitates within the β-phase matrix. The sequence of phase transformation leading to this hierarchical nanostructure is explored using electron microscopy and atom probe tomography. Our results suggest that the high number density of nanoscale α-phase precipitates in the β-phase matrix is due to ω assisted nucleation of α resulting in high tensile strength, greater than any current commercial titanium alloy. Thus hierarchical nanostructured Ti185 serves as an excellent candidate for replacing costlier titanium alloys and other structural alloys for cost-effective lightweighting applications.

  5. Smart and Bored: Are We Failing Our High Achievers?

    ERIC Educational Resources Information Center

    Cleaver, Samantha

    2008-01-01

    Some high achievers are not as easy to engage. Sometimes motivating high achievers is "a matter of being more sensitive to what they are interested in," says Don Ambrose, a professor of education at Rider University in New Jersey. But too often classrooms are not set up for that kind of sensitivity. Research shows that schools are consistently…

  6. Perspectives of High-Achieving Women on Teaching

    ERIC Educational Resources Information Center

    Snodgrass, Helen

    2010-01-01

    High-achieving women are significantly less likely to enter the teaching profession than they were just 40 years ago. Why? While the social and economic reasons for this decline have been well documented in the literature, what is lacking is a discussion with high-achieving women, as they make their first career decisions, about their perceptions…

  7. High-strength porous carbon and its multifunctional applications

    DOEpatents

    Wojtowicz, Marek A; Rubenstein, Eric P; Serio, Michael A; Cosgrove, Joseph E

    2013-12-31

    High-strength porous carbon and a method of its manufacture are described for multifunctional applications, such as ballistic protection, structural components, ultracapacitor electrodes, gas storage, and radiation shielding. The carbon is produced from a polymer precursor via carbonization, and optionally by surface activation and post-treatment.

  8. Fabrication Routes for High Strength High Conductivity Wires

    SciTech Connect

    Han, K.; Embury, J.D.; Sims, J.R.; Pantsyrnyi, V.I.; Shikov, A.; Bochvar, A.A.

    1998-10-01

    The development of suitable wires for magnet windings requires both the attainment of suitable combinations of properties (electrical conductivity and strength), the development of a production route capable of fabricating suitable quantity of wire of required dimension (5.2x7.6mm{sup 2} cross-section and 120 m in length) and a product with acceptable fabricability, joinability and service life. In this survey, the authors consider methods of producing suitable wire products by the codeformation of in-situ composites. This will include details of the quality control of the processing of Cu-Ag and Cu-Nb and the assessment of their detailed mechanical properties.

  9. High strength graphite and method for preparing same

    DOEpatents

    Overholser, Lyle G.; Masters, David R.; Napier, John M.

    1976-01-01

    High strength graphite is manufactured from a mixture of a particulate filler prepared by treating a particulate carbon precursor at a temperature in the range of about 400.degree. to 1000.degree. C., an organic carbonizable binder, and green carbonizable fibers in a concentration of not more than 2 weight per cent of the filler. The use of the relatively small quantity of green fibers provides a substantial increase in the flexural strength of the graphite with only a relatively negligible increase in the modulus of elasticity.

  10. A novel technique of unilateral percutaneous kyphoplasty achieves effective biomechanical strength and reduces radiation exposure

    PubMed Central

    Zhuang, Yan; Yang, Lei; Li, Haijun; Ren, Yajun; Cao, Xiaojian

    2016-01-01

    Purpose: To develop a novel technique of percutaneous kyphoplasty (PKP) with effective biomechanical strength and lower radiation exposure. Methods: Thirty fresh lumbar vertebrae isolated from six hogs were decalcified and compressed to induce osteoporotic vertebral compression fractures. Kyphoplasty was performed using three different techniques (ten for each group): conventional unilateral approach (group A), conventional bilateral approach (group B) and novel unilateral approach (group C). Biomechanical indexes including Yield load and stiffness were tested before and after kyphoplasty. The anterior height of each vertebral body (AHVB) was measured before compression, after compression and after kyphoplasty. Frequency of C-arm use and volume of bone cement were also recorded in the process. Results: Compared with group A, our novel technique in group C can significantly improve the recovery of AHVB after compression fractures. However, there was no statistical difference between group B and group C. Values of Yield load in both group B and group C were statistically higher than that in group A, however, no significant difference was found between group B and C. Statistical results of stiffness were similar to Yield load. Regarding volume of bone cement and radiation exposure, the novel technique in group C needed more bone cement and fluoroscopy use than in group A but less than in group B. Conclusions: This novel device makes unilateral kyphoplasty feasible, safe and effective. In the premise of guaranteed biomechanical strength, the new technique significantly reduces risk of radiation exposure in kyphoplasty. PMID:27158403

  11. Microcracking and engineering properties of high-strength concrete

    NASA Astrophysics Data System (ADS)

    Carrasquillo, R. L.

    1980-03-01

    The differences in mechanical properties between high strength and normal strength concretes are established and those differences are explained in terms of differences in observed internal microcracking in concrete at different stages of loading. Concretes made using gravel and crushed limestone coarse aggregates at each of three different strength levels ranging from 4,000 psi to 11,000 psi were studied. The results of the microcracking study and the study of the mechanical properties are presented. A criterion for definition of failure in uniaxial compression for the concretes tested is presented. Failure is considered to occur at the discontinuity point defined as that point when a self propagating microcracking mechanism is developed eventually causing disruptive failure with time. The predicted stress and strain ratios at discontinuity based on the microcracking study are compared to those at which sudden changes occur in the Poisson's ratio and volume change curves.

  12. Gradient twinned 304 stainless steels for high strength and high ductility

    DOE PAGES

    Chen, Aiying; Liu, Jiabin; Wang, Hongtao; Lu, Jian; Wang, Y. Morris

    2016-04-23

    Gradient materials often have attractive mechanical properties that outperform uniform microstructure counterparts. It remains a difficult task to investigate and compare the performance of various gradient microstructures due to the difficulty of fabrication, the wide range of length scales involved, and their respective volume percentage variations. We have investigated four types of gradient microstructures in 304 stainless steels that utilize submicrotwins, nanotwins, nanocrystalline-, ultrafine- and coarse-grains as building blocks. Tensile tests reveal that the gradient microstructure consisting of submicrotwins and nanotwins has a persistent and stable work hardening rate and yields an impressive combination of high strength and high ductility,more » leading to a toughness that is nearly 50% higher than that of the coarse-grained counterpart. Ex- and in-situ transmission electron microscopy indicates that nanoscale and submicroscale twins help to suppress and limit martensitic phase transformation via the confinement of martensite within the twin lamellar. Twinning and detwinning remain active during tensile deformation and contribute to the work hardening behavior. We discuss the advantageous properties of using submicrotwins as the main load carrier and nanotwins as the strengthening layers over those coarse and nanocrystalline grains. Furthermore, our work uncovers a new gradient design strategy to help metals and alloys achieve high strength and high ductility.« less

  13. Development of third generation advanced high strength steels

    NASA Astrophysics Data System (ADS)

    McGrath, Meghan Colleen

    Lightweight duplex steels with combinations of either bainite, acicular ferrite, and austenite or martensite and austenite were investigated as third generation advanced high strength steels targeted for automotive applications. Large additions of manganese (> 13 wt%) and carbon (<0.2wt%) were employed to stabilize the austenite phase. Silicon additions between 1 and 2 wt% were added to suppress cementite formation. Strength and ductility were increased while density was decreased with aluminum additions between 2.4 and 5.5 wt% to the steel. This research addressed the dependence of alloying on microstructures and mechanical behavior for high manganese and aluminum duplex steels that were cast and subsequently hot rolled. Duplex steels with different volume fractions of primary delta-ferrite were used to study the crystallography of austenite fanned during the peritectic reaction. Solute profiles across the peritectic interface showed aluminum segregated near the interface which promoted bainitic ferrite formation. Thermal treatments were used to manipulate the concentration and type of oxides and the ferrite plate density was found to correlate with inclusions of low misfit in steels with austenite grain size of 16.5 microm. A steel with bainite and acicular ferrite produced an ultimate tensile strength of 970 MPa and elongation of 40%. The mechanical prope1iies depended on the strengths and size of the microstructural constituents. Work hardening behavior was examined in a steel exhibiting multiple martensitic transformation induced plasticity (gamma-austenite→epsilon-smartensite→alpha-martensite). A strain hardening exponent as high as 1.4 was observed with ultimate tensile strength and elongation as high as 1,165 MPa and 34%.

  14. NEW HIGH STRENGTH AND FASTER DRILLING TSP DIAMOND CUTTERS

    SciTech Connect

    Robert Radtke

    2006-01-31

    The manufacture of thermally stable diamond (TSP) cutters for drill bits used in petroleum drilling requires the brazing of two dissimilar materials--TSP diamond and tungsten carbide. The ENDURUS{trademark} thermally stable diamond cutter developed by Technology International, Inc. exhibits (1) high attachment (shear) strength, exceeding 345 MPa (50,000 psi), (2) TSP diamond impact strength increased by 36%, (3) prevents TSP fracture when drilling hard rock, and (4) maintains a sharp edge when drilling hard and abrasive rock. A novel microwave brazing (MWB) method for joining dissimilar materials has been developed. A conventional braze filler metal is combined with microwave heating which minimizes thermal residual stress between materials with dissimilar coefficients of thermal expansion. The process results in preferential heating of the lower thermal expansion diamond material, thus providing the ability to match the thermal expansion of the dissimilar material pair. Methods for brazing with both conventional and exothermic braze filler metals have been developed. Finite element modeling (FEM) assisted in the fabrication of TSP cutters controllable thermal residual stress and high shear attachment strength. Further, a unique cutter design for absorbing shock, the densification of otherwise porous TSP diamond for increased mechanical strength, and diamond ion implantation for increased diamond fracture resistance resulted in successful drill bit tests.

  15. Hydrogen Embrittlement of Automotive Advanced High-Strength Steels

    NASA Astrophysics Data System (ADS)

    Lovicu, Gianfranco; Bottazzi, Mauro; D'Aiuto, Fabio; De Sanctis, Massimo; Dimatteo, Antonella; Santus, Ciro; Valentini, Renzo

    2012-11-01

    Advanced high-strength steels (AHSS) have a better combination between strength and ductility than conventional HSS, and higher crash resistances are obtained in concomitance with weight reduction of car structural components. These steels have been developed in the last few decades, and their use is rapidly increasing. Notwithstanding, some of their important features have to be still understood and studied in order to completely characterize their service behavior. In particular, the high mechanical resistance of AHSS makes hydrogen-related problems a great concern for this steel grade. This article investigates the hydrogen embrittlement (HE) of four AHSS steels. The behavior of one transformation induced plasticity (TRIP), two martensitic with different strength levels, and one hot-stamping steels has been studied using slow strain rate tensile (SSRT) tests on electrochemically hydrogenated notched samples. The embrittlement susceptibility of these AHSS steels has been correlated mainly to their strength level and to their microstructural features. Finally, the hydrogen critical concentrations for HE, established by SSRT tests, have been compared to hydrogen contents absorbed during the painting process of a body in white (BIW) structure, experimentally determined during a real cycle in an industrial plant.

  16. Measurement of Strength at High Pressures Using Oblique Shock Waves

    NASA Astrophysics Data System (ADS)

    Stolyar, Victoria; Ravichandran, Guruswami; Alexander, Scott

    2013-06-01

    At high pressures and high strain rates, the measurement of strength is important to many implications including planetary impact and inertial confinement fusion. Understanding how strength depends on pressure allows for the characterization of materials and validation of constitutive models. Slotted barrel guns have traditionally been used in experiments, such as the pressure-shear plate impact technique, to generate longitudinal and shear waves through an oblique impact. A new methodology for measuring material strength using normal impact (1-2 km/s) is described. In this configuration, a composite target is designed with an angled material of interest embedded into a driver material. This driver material is used to generate an oblique shock wave that is followed by a shear wave, due to the angled nature of the target material. Using shock polar analysis, the rear surface of the target is designed to be parallel to the transmitted shock wave in order to mitigate wave interactions at the rear surface. A window is used on the rear surface of the target to measure the in-situ particle velocities at the target-window interface. Using three VISAR measurements, the tangential and longitudinal particle velocities at the rear surface of the target are found from which the shear stress (strength) is inferred as a function of pressure. Results are presented for 6061-T6 Aluminum as well as Tantalum. Hydrocode simulations are used to predict the experimental results as well as characterize the wave interactions in the oblique wedge experiments.

  17. Mechanical Properties of Heat Affected Zone of High Strength Steels

    NASA Astrophysics Data System (ADS)

    Sefcikova, K.; Brtnik, T.; Dolejs, J.; Keltamaki, K.; Topilla, R.

    2015-11-01

    High Strength Steels became more popular as a construction material during last decade because of their increased availability and affordability. On the other hand, even though general use of Advanced High Strength Steels (AHSS) is expanding, the wide utilization is limited because of insufficient information about their behaviour in structures. The most widely used technique for joining steels is fusion welding. The welding process has an influence not only on the welded connection but on the area near this connection, the so-called heat affected zone, as well. For that reason it is very important to be able to determine the properties in the heat affected zone (HAZ). This area of investigation is being continuously developed in dependence on significant progress in material production, especially regarding new types of steels available. There are currently several types of AHSS on the world market. Two most widely used processes for AHSS production are Thermo-Mechanically Controlled Processing (TMCP) and Quenching in connection with Tempering. In the presented study, TMCP and QC steels grade S960 were investigated. The study is focused on the changes of strength, ductility, hardness and impact strength in heat affected zone based on the used amount of heat input.

  18. Test-Taking Strategies of High and Low Mathematics Achievers

    ERIC Educational Resources Information Center

    Hong, Eunsook; Sas, Maggie; Sas, John C.

    2006-01-01

    The authors explored test-preparation and test-taking strategies that high school students used in algebra tests. From a pool of high school students (N = 156), 61 students participated in interviews, and of those interviewed, 26 represented those who were high achieving as well as highly interested in mathematics (n = 15) vs. those who were low…

  19. Oxidation resistant high creep strength austenitic stainless steel

    DOEpatents

    Brady, Michael P.; Pint, Bruce A.; Liu, Chain-Tsuan; Maziasz, Philip J.; Yamamoto, Yukinori; Lu, Zhao P.

    2010-06-29

    An austenitic stainless steel displaying high temperature oxidation and creep resistance has a composition that includes in weight percent 15 to 21 Ni, 10 to 15 Cr, 2 to 3.5 Al, 0.1 to 1 Nb, and 0.05 to 0.15 C, and that is free of or has very low levels of N, Ti and V. The alloy forms an external continuous alumina protective scale to provide a high oxidation resistance at temperatures of 700 to 800.degree. C. and forms NbC nanocarbides and a stable essentially single phase fcc austenitic matrix microstructure to give high strength and high creep resistance at these temperatures.

  20. Effectiveness of High Schools in Australia: Holding Power and Achievement.

    ERIC Educational Resources Information Center

    Ainley, John; Sheret, Michael

    High schools in Australia are increasingly expected to be effective in holding students at school to year 12 as well as in promoting achievement. Analysis of quantitative data gathered as part of a longitudinal study of 22 New South Wales (Australia) schools shows that schools differ in their holding power as well as in the achievement levels of…

  1. Tracking and Detracking: High Achievers in Massachusetts Middle Schools

    ERIC Educational Resources Information Center

    Loveless, Tom

    2009-01-01

    This study examines tracking--the practice of grouping students into separate classes or courses based on their prior academic achievement--at the middle-school level, and the percentage of high-achieving students in tracked and untracked schools. It focuses on Massachusetts, a leader in "reforming" tracking, and the changes that have…

  2. Some Correlates of High School Foreign Language Achievement.

    ERIC Educational Resources Information Center

    Beanblossom, Gary F.

    This paper investigates the influences of traditional kinds of verbal and quantitative achievement and aptitude variables on high school foreign language achievement, as measured by Modern Language Association and University of Washington tests of language skills administered to entering college students. The report focuses on: (1) the sample and…

  3. Biculturalism and Academic Achievement of African American High School Students

    ERIC Educational Resources Information Center

    Rust, Jonathan P.; Jackson, Margo A.; Ponterotto, Joseph G.; Blumberg, Fran C.

    2011-01-01

    Biculturalism was examined as a factor that may positively affect the academic achievement of African American high school students, beyond cultural identity and self-esteem. Hierarchical regression analyses determined that cultural identity and academic self-esteem were important factors for academic achievement, but not biculturalism.…

  4. Mobility and Student Achievement in High Poverty Schools

    ERIC Educational Resources Information Center

    Dalton, Janet Denise

    2013-01-01

    Student mobility is an issue for high poverty schools in the shadow of increased rigor and accountability for student performance. Whereas mobility is not a sole cause for poor achievement, it is a contributing factor for students in poverty who are already considered to be at risk of low achievement. Student mobility creates a hardship for…

  5. Properties of Galvanized and Galvannealed Advanced High Strength Hot Rolled Steels

    SciTech Connect

    V.Y. Guertsman; E. Essadiqi; S. Dionne; O. Dremmailova; R. Bouchard; B. Voyzelle; J. McDermid; R. Fourmentin

    2008-04-01

    The objectives of the project were (i) to develop the coating process information to achieve good quality coatings on 3 advanced high strength hot rolled steels while retaining target mechanical properties, (ii) to obtain precise knowledge of the behavior of these steels in the various forming operations and (iii) to establish accurate user property data in the coated conditions. Three steel substrates (HSLA, DP, TRIP) with compositions providing yield strengths in the range of 400-620 MPa were selected. Only HSLA steel was found to be suitable for galnaizing and galvannealing in the hot rolled condition.

  6. Low-noise, high-strength, spiral-bevel gears for helicopter transmissions

    NASA Astrophysics Data System (ADS)

    Lewicki, David G.; Handschuh, Robert F.; Henry, Zachary S.; Litvin, Faydor L.

    1994-05-01

    Advanced-design spiral-bevel gears were tested in an OH-58D helicopter transmission using the NASA 500-hp Helicopter Transmission Test Stand. Three different gear designs tested included: the current design of the OH-58D transmission; a higher-strength design the same as the current but with a full fillet radius to reduce gear tooth bending stress (and thus, weight); and a lower-noise design the same as the high-strength but with modified tooth geometry to reduce transmission error and noise. Noise, vibration, and tooth strain tests were performed and significant gear stress and noise reductions were achieved.

  7. Attitudes and Opinions from the Nation's High Achieving Teens: 29th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This report presents the 1998 statistical findings of the annual survey to determine the attitudes of national high school student leaders. Questionnaires were completed by 3,123 high school juniors and seniors, all of whom were selected for recognition in "Who's Who among American High School Students." In addition to demographic information, the…

  8. Grain refinement of high strength steels to improve cryogenic toughness

    NASA Technical Reports Server (NTRS)

    Rush, H. F.

    1985-01-01

    Grain-refining techniques using multistep heat treatments to reduce the grain size of five commercial high-strength steels were investigated. The goal of this investigation was to improve the low-temperature toughness as measured by Charpy V-notch impact test without a significant loss in tensile strength. The grain size of four of five alloys investigated was successfully reduced up to 1/10 of original size or smaller with increases in Charpy impact energy of 50 to 180 percent at -320 F. Tensile properties were reduced from 0 to 25 percent for the various alloys tested. An unexpected but highly beneficial side effect from grain refining was improved machinability.

  9. High ionic strength electrokinetics of melamine-formaldehyde latex.

    PubMed

    Kosmulski, Marek; Dahlsten, Per; Próchniak, Piotr; Rosenholm, Jarl B

    2006-09-15

    The electrokinetic potential of melamine-formaldehyde latex at high ionic strengths was measured by means of two different instruments. The present study confirms that the zeta potentials in 1 M 1-1 electrolyte solutions can be as high as +/-20 mV. The IEP of latex at low ionic strengths was at pH 11. The increase in the electrolyte concentration induced a shift in the IEP to low pH for all studied salts, and this indicates specific adsorption of the anions. The magnitude of the shift depends chiefly on the nature of the anion and increases in the series Cl < NO(3) = Br < I, and the nature of the cation (Li, Na, K, Cs) plays a rather insignificant role.

  10. NDE detectability of fatigue type cracks in high strength alloys

    NASA Technical Reports Server (NTRS)

    Christner, B. K.; Rummel, W. D.

    1983-01-01

    Specimens suitable for investigating the reliability of production nondestructive evaluation (NDE) to detect tightly closed fatigue cracks in high strength alloys representative of those materials used in spacecraft engine/booster construction were produced. Inconel 718 was selected as representative of nickel base alloys and Haynes 188 was selected as representative of cobalt base alloys used in this application. Cleaning procedures were developed to insure the reusability of the test specimens and a flaw detection reliability assessment of the fluorescent penetrant inspection method was performed using the test specimens produced to characterize their use for future reliability assessments and to provide additional NDE flaw detection reliability data for high strength alloys. The statistical analysis of the fluorescent penetrant inspection data was performed to determine the detection reliabilities for each inspection at a 90% probability/95% confidence level.

  11. Effect of size, shape, and end condition of test specimen on compressive strength of high-strength concrete

    NASA Astrophysics Data System (ADS)

    Ipatti, A.

    Compressive testing of high-strength concrete is a critical issue on which no consensus has yet been reached. Among the many factors that are under discussion are the size, shape, and end condition of test specimens for high-strength concrete. The experimental program described herein was designed primarily to investigate the effects and the possible interactions of the above-mentioned factors on compressive strength of high-strength concrete. Three levels of specimen sizes, three methods of specimen capping (mould surface, sulphur capping, grinding), and four grades of concrete strengths were selected. A 3 x 3 x 4 factorial experimental design was adopted with two replicates (each an average of three specimens), giving a total of 72 test values (216 specimens). The strictest possible precautions were taken to ensure that all other factors which would conceivably effect the compressive strength were held constant. The statistical methods utilized included analyses of variance, linear regressions, and pairwise comparisons of factor main effects.

  12. The "Renaissance Child": High Achievement and Gender in Late Modernity

    ERIC Educational Resources Information Center

    Skelton, Christine; Francis, Becky

    2012-01-01

    This paper draws on the concept of the "Renaissance Child" to illustrate the ways in which gender influences the opportunities and possibilities of high-achieving pupils. Using data from a study of 12-13-year high-achieving boys and girls based in schools in England, the paper considers the ways in which a group of popular boys was able to show an…

  13. Magnetic and Magnetostrictive Characterization and Modeling of High Strength Steel

    NASA Astrophysics Data System (ADS)

    Burgy, Christopher Donald

    High strength steels exhibit small amounts of magnetostriction, which is a useful property for non-destructive testing amongst other things. This property cannot currently be fully utilized due to a lack of adequate measurements and models. This thesis reports measurements of these material parameters, and derives a model using these parameters to predict magnetization changes due to the application of compressive stresses and magnetic fields. The resulting Preisach model, coupled with COMSOL MultiphysicsRTM finite element modeling, accurately predicts the magnetization change seen in a separate high strength steel sample previously measured by the National Institute of Standards and Technology. Three sets of measurements on low-carbon, low-alloy high strength steel are introduced in this research. The first experiment measured magnetostriction in steel rods under uniaxial compressive stresses and magnetic fields. The second experiment consisted of magnetostriction and magnetization measurements of the same steel rods under the influence of bi-axially applied magnetic fields. The final experiment quantified the small effect that temperature has on magnetization of steels. The experiments demonstrated that the widely used approximation of stress as an "effective field" is inadequate, and that temperatures between -50 and 100 °C cause minimal changes in magnetization. Preisach model parameters for the prediction of the magnetomechanical effect were derived from the experiments. The resulting model accurately predicts experimentally derived major and minor loops for a high strength steel sample, including the bulging and coincident points attributed to compressive stresses. A framework is presented which couples the uniaxial magnetomechanical model with a finite element package, and was used successfully to predict experimentally measured magnetization changes on a complex sample. These results show that a 1-D magnetomechanical model can be applied to predict 3-D

  14. Damage tolerance of a helicopter rotor high-strength steel

    NASA Astrophysics Data System (ADS)

    Henaff, Gilbert; Petit, Jean; Ranganathan, Narayamaswami

    1992-07-01

    The fatique crack growth behavior of a high strength steel is investigated in air and in vacuum under loading representative of helicopter spectra. The near threshold regime is considered with a high baseline level (R = 0.7). Although strong interaction effects are brought out, non concomitant closure is detected due to the high mean level of the different loading blocks. A model of the observed retardation phenomenon, which incorporates crack growth laws previously developed to describe the influence of environment, is proposed. The results are in good agreement with experimental data.

  15. Attitudes and Opinions from the Nation's High Achieving Teens: 27th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This report details the 27th annual study to examine the attitudes of student leaders in U.S. high schools. Participating in the survey were 3,370 adolescents, primarily 16- and 17-year-olds, who had been featured in the 1996 edition of "Who's Who Among American High School Students." The report presents demographic information on the survey…

  16. Attitudes and Opinions from the Nation's High Achieving Teens: 28th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This report details the 28th annual study to examine the attitudes of student leaders in U.S. high schools. Participating in the survey were 3,210 adolescents, primarily 16- and 17-year-olds, who had been featured in the 1997 edition of "Who's Who Among American High School Students." The report presents demographic information on the survey…

  17. Development of ductile high-strength chromium alloys, phase 2

    NASA Technical Reports Server (NTRS)

    Filippi, A. M.

    1973-01-01

    Strength and ductility were evaluated for chromium alloys dispersion hardened with the putative TaC, TaB, CbC, and CbB compounds. TaC and TaB proved to be the most potent strengtheners, but when combined, their effect far outweighed that produced individually. Tests at 1422 K (2100 F) on an alloy containing these two compounds at the combined level of 0.5 m/o revealed a 495 MN/sq m (70 ksi) tensile strength for wrought material, and a 100 hour rupture strength of 208 MN/sq m (30 ksi) when solution annealed and aged to maximize creep resistance. These levels of high temperature strength greatly exceed that reported for any other chromium-base alloy. The ductile-to-brittle transition temperature (DBTT) of the two phase strengthened alloy occurred at approximately 588 K (600 F) when heat treated to optimize creep strength and was not improved by fabrication to produce a wrought and recovered microstructure. The lowest DBTT measured on any of the alloys investigated was 422 K (300 F). Strengthening phases actually formed in Cr-Ta-B and Cr-Cb-B compositions are probable M2CrB2 (M=Ta or Cb) compounds of tetragonal crystal structure. The likely habit relationship between these compounds and chromium is postulated. Cube habit coherency was identified for TaC precipitation in chromium by electron microscopy. In another study, the maximum solubility of carbon in chromium was indicated to lie between 3/4 and 1 a/o and that of boron to be 1/2 a/o.

  18. A Novel Method for Electroplating Ultra-High-Strength Glassy Metals

    NASA Technical Reports Server (NTRS)

    Ramsey, Brian; Engelhaupt, Darell; Six, N. Frank (Technical Monitor)

    2002-01-01

    A novel method for electroplating ultra-high-strength glassy metals, nickel-phosphorous and nickel-cobalt-phosphorous, has been developed at NASA Marshall Space Flight Center, cooperatively with the University of Alabama in Huntsville. Traditionally, thin coatings of these metals are achieved via electroless deposition. Benefits of the new electrolytic process include thick, low-stress deposits, free standing shapes, lower plating temperature, low maintenance, and safer operation with substantially lower cost.

  19. High Strength Discontinuously Reinforced Aluminum For Rocket Applications

    NASA Technical Reports Server (NTRS)

    Pandey, A. B.; Shah, S. R.; Shadoan, M.

    2003-01-01

    This study presents results on the development of a new aluminum alloy with very high strength and ductility. Five compositions of Al-Mg-Sc-Gd-Zr alloy were selected for this purpose. These alloys were also reinforced with 15 volume percent silicon-carbide and boron-carbide particles to produce Discontinuously Reinforced Aluminum (DRA) materials. Matrix alloys and DRA were processed using a powder metallurgy process. The helium gas atomization produced very fine powder with cellular-dentritic microstructure. The microstructure of matrix alloys showed fine Al3Sc based precipitate which provides significant strengthening in these alloys. DRA showed uniform distribution of reinforcement in aluminum matrix. DRA materials were tested at -320 F, 75 F in air and 7S F in gaseous hydrogen environments and matrix alloys were tested at 75 F in air. DRA showed high strengths in the range of 89-111 ksi (614-697 MPa) depending on alloy compositions and test environments. Matrix alloys had a good combination of strength, 84-89 ksi (579-621 MPa) and ductility, 4.5-6.5%. The properties of these materials can further be improved by proper control of processing parameters.

  20. Development of high-strength and high-conductivity conductor materials for pulsed high-field magnets at Dresden

    NASA Astrophysics Data System (ADS)

    Grünberger, W.; Heilmaier, M.; Schultz, L.

    2001-01-01

    The work at the IFW Dresden is focused on the development of microcomposite Cu-Ag alloys and steel-copper macrocomposites with high-nitrogen steel and pearlitic steel jackets, respectively. In Cu-Ag alloys the investigation of continuously cast rods with different starting diameters suggests that the cooling rate during solidification determining the dendrite arm spacing has a minor influence on the development of the strength compared to the cooling velocity after solidification which determines the extent of the Ag-supersaturation in the Cu solid solution. Maximum strength at minimum drawing strain demands (i) a sufficient volume fraction of eutectic in order to suppress discontinuous precipitation (absence of grain boundaries) and (ii) a sufficiently rapid cooling after solidification in order to prevent pre-precipitation. With a continuously cast starting rod of 12 mm diameter a maximum tensile strength of 1.3 GPa was obtained after a drawing strain of only η=4.3. Steel-copper macrocomposites were fabricated by the ‘rod-in-tube’ technology. The experiments with austenitic high-nitrogen steels were performed with two alloys. With the commercial alloy Nicrofer 3033 a strength level of 1.2 GPa has been achieved with a 52 vol% Cu composite at a drawing strain of η=2.3. A composite with pearlitic C60-steel (0.6 wt% C) and 56 vol% Cu showed a tensile strength of 1.53 GPa after a final patenting at a diameter of 14.7 mm and a drawing strain of η=4.

  1. Attitudes and Opinions from the Nation's High Achieving Teens. 25th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This survey was conducted during the spring of 1994 for the purpose of determining the attitudes of student leaders in the nation's high schools. Eight thousand surveys were sent out to students, of which 3177 were returned. All students surveyed were members of the junior or senior class during the 1993-94 academic year. They were selected for…

  2. New high-strength neodymium phosphate laser glass

    SciTech Connect

    Galagan, B I; Glushchenko, I N; Denker, B I; Kalachev, Yu L; Mikhailov, Viktor A; Sverchkov, S E; Shcherbakov, Ivan A; Kuleshov, N V

    2009-12-31

    A high-strength neodymium laser glass (SNLG) based on an alumoborophosphate composition is developed and synthesised; its physicochemical, spectral, luminescent, and lasing characteristics are studied. It is found that the chemical stability and thermal resistance of the new glass are considerably higher than the corresponding characteristics of known neodymium-doped phosphate laser glasses. Investigations of lasing upon longitudinal diode pumping showed that, due to the higher thermal resistance, the new glass allows one to obtain output powers twice as high as those of industrial GLS22 glass. (active media)

  3. Nitrate removal from high strength nitrate-bearing wastes in granular sludge sequencing batch reactors.

    PubMed

    Krishna Mohan, Tulasi Venkata; Renu, Kadali; Nancharaiah, Yarlagadda Venkata; Satya Sai, Pedapati Murali; Venugopalan, Vayalam Purath

    2016-02-01

    A 6-L sequencing batch reactor (SBR) was operated for development of granular sludge capable of denitrification of high strength nitrates. Complete and stable denitrification of up to 5420 mg L(-1) nitrate-N (2710 mg L(-1) nitrate-N in reactor) was achieved by feeding simulated nitrate waste at a C/N ratio of 3. Compact and dense denitrifying granular sludge with relatively stable microbial community was developed during reactor operation. Accumulation of large amounts of nitrite due to incomplete denitrification occurred when the SBR was fed with 5420 mg L(-1) NO3-N at a C/N ratio of 2. Complete denitrification could not be achieved at this C/N ratio, even after one week of reactor operation as the nitrite levels continued to accumulate. In order to improve denitrification performance, the reactor was fed with nitrate concentrations of 1354 mg L(-1), while keeping C/N ratio at 2. Subsequently, nitrate concentration in the feed was increased in a step-wise manner to establish complete denitrification of 5420 mg L(-1) NO3-N at a C/N ratio of 2. The results show that substrate concentration plays an important role in denitrification of high strength nitrate by influencing nitrite accumulation. Complete denitrification of high strength nitrates can be achieved at lower substrate concentrations, by an appropriate acclimatization strategy.

  4. Student Achievement for Whom? High-Performing and Still "Playing the Game," the Meaning of School Achievement among High Achieving African American Students

    ERIC Educational Resources Information Center

    Wiggan, Greg

    2014-01-01

    The preponderance of the research on African American students has generally focused on issues of school failure and underperformance. While the literature on high achieving Black students is sparse, very little is known about these students' school experiences and the meanings that they assign to achievement. Using student-based inquiry…

  5. High School Employment and Academic Achievement: A Note for Educators

    ERIC Educational Resources Information Center

    Keister, Mary; Hall, Joshua

    2010-01-01

    Educators are often in a position to affect student decisions to work during the school term. This study reviews and summarizes the literature on the effect that employment during high school has on academic achievement. The available evidence suggests that part-time jobs for high school students are beneficial as long as the number of hours…

  6. Exploring High-Achieving Students' Images of Mathematicians

    ERIC Educational Resources Information Center

    Aguilar, Mario Sánchez; Rosas, Alejandro; Zavaleta, Juan Gabriel Molina; Romo-Vázquez, Avenilde

    2016-01-01

    The aim of this study is to describe the images that a group of high-achieving Mexican students hold of mathematicians. For this investigation, we used a research method based on the Draw-A-Scientist Test (DAST) with a sample of 63 Mexican high school students. The group of students' pictorial and written descriptions of mathematicians assisted us…

  7. Brain Hemisphericity and Mathematics Achievement of High School Students

    ERIC Educational Resources Information Center

    Fernandez, Sanny F.

    2011-01-01

    This study aimed to find out the brain hemisphericity and mathematics achievement of high school students. The respondents of the study were the 168 first year high school students of Colegio de San Jose, during school year 2010-2011 who were chosen through stratified random sampling. The descriptive and interview methods of research were used in…

  8. High-strength silk protein scaffolds for bone repair

    PubMed Central

    Mandal, Biman B.; Grinberg, Ariela; Seok Gil, Eun; Panilaitis, Bruce; Kaplan, David L.

    2012-01-01

    Biomaterials for bone tissue regeneration represent a major focus of orthopedic research. However, only a handful of polymeric biomaterials are utilized today because of their failure to address critical issues like compressive strength for load-bearing bone grafts. In this study development of a high compressive strength (~13 MPa hydrated state) polymeric bone composite materials is reported, based on silk protein-protein interfacial bonding. Micron-sized silk fibers (10–600 µm) obtained utilizing alkali hydrolysis were used as reinforcement in a compact fiber composite with tunable compressive strength, surface roughness, and porosity based on the fiber length included. A combination of surface roughness, porosity, and scaffold stiffness favored human bone marrow-derived mesenchymal stem cell differentiation toward bone-like tissue in vitro based on biochemical and gene expression for bone markers. Further, minimal in vivo immunomodulatory responses suggested compatibility of the fabricated silk-fiber-reinforced composite matrices for bone engineering applications. PMID:22552231

  9. Scratch-resistant, highly conductive, and high-strength carbon nanotube-based composite yarns.

    PubMed

    Liu, Kai; Sun, Yinghui; Lin, Xiaoyang; Zhou, Ruifeng; Wang, Jiaping; Fan, Shoushan; Jiang, Kaili

    2010-10-26

    High-strength and conductive carbon nanotube (CNT) yarns are very attractive in many potential applications. However, there is a difficulty when simultaneously enhancing the strength and conductivity of CNT yarns. Adding some polymers into CNT yarns to enhance their strength will decrease their conductivity, while treating them in acid or coating them with metal nanoparticles to enhance their conductivity will reduce their strength. To overcome this difficulty, here we report a method to make high-strength and highly conductive CNT-based composite yarns by using a continuous superaligned CNT (SACNT) yarn as a conductive framework and then inserting polyvinyl alcohol (PVA) into the intertube spaces of the framework through PVA/dimethyl sulphoxide solution to enhance the strength of yarns. The as-produced CNT/PVA composite yarns possess very high tensile strengths up to 2.0 GPa and Young's moduli more than 120 GPa, much higher than those of the CNT/PVA yarns reported. The electric conductivity of as-produced composite yarns is as high as 9.2 × 10(4) S/m, comparable to HNO(3)-treated or Au nanoparticle-coated CNT yarns. These composite yarns are flexible, lightweight, scratch-resistant, very stable in the lab environment, and resistant to extremely humid ambient and as a result can be woven into high-strength and heatable fabrics, showing potential applications in flexible heaters, bullet-proof vests, radiation protection suits, and spacesuits.

  10. High-strength and thermally stable bulk nanolayered composites due to twin-induced interfaces.

    PubMed

    Zheng, Shijian; Beyerlein, Irene J; Carpenter, John S; Kang, Keonwook; Wang, Jian; Han, Weizhong; Mara, Nathan A

    2013-01-01

    Bulk nanostructured metals can attribute both exceptional strength and poor thermal stability to high interfacial content, making it a challenge to utilize them in high-temperature environments. Here we report that a bulk two-phase bimetal nanocomposite synthesised via severe plastic deformation uniquely possesses simultaneous high-strength and high thermal stability. For a bimetal spacing of 10 nm, this composite achieves an order of magnitude increase in hardness of 4.13 GPa over its constituents and maintains it (4.07 GPa), even after annealing at 500 °C for 1 h. It owes this extraordinary property to an atomically well-ordered bimaterial interface that results from twin-induced crystal reorientation, persists after extreme strains and prevails over the entire bulk. This discovery proves that interfaces can be designed within bulk nanostructured composites to radically outperform previously prepared bulk nanocrystalline materials, with respect to both mechanical and thermal stability. PMID:23591863

  11. Microstructure and mechanical properties of high strength Al—Mg—Si—Cu profiles for safety parts

    NASA Astrophysics Data System (ADS)

    Österreicher, J. A.; Schiffl, A.; Falkinger, G.; Bourret, G. R.

    2016-03-01

    Aluminium extrudate used for safety parts in cars need to exhibit high yield strength and ductility, a combination that is not easily achieved. In this work, the mechanical properties and microstructure of profiles with a yield strength greater than 280MPa achieved by two different artificial ageing treatments were studied. Profiles from one of the heat treatments performed well in quasi-static compression testing while those from the other heat treatment clearly failed. The batch of profiles that failed showed higher uniform elongation in tensile testing but a lower reduction in area. However, the difference in bending angles in the three-point-bending test were not as pronounced. Microscopic investigation of polished sections and fracture surfaces revealed that failure is dominated by the fracture of intermetallic phases resulting in voids. The growth and coalescence of these voids is facilitated by another population of smaller voids within the matrix, presumably nucleating at secondary phases.

  12. TOUGHREACT Testing in High Ionic Strength Brine Sandstone Systems

    SciTech Connect

    Xu, Tianfu

    2008-09-01

    Deep saline formations and oil and gas reservoirs often contain concentrated brine solutions of ionic strength greater than 1 (I > 1 M). Geochemical modeling, involving high ionic strength brines, is a challenge. In the original TOUGHREACT code (Xu et al., 2004; Xu et al., 2006), activity coefficients of charged aqueous species are computed using an extended Debye-Huckel (DH) equation and parameters derived by Helgeson et al. (1981). The DH model can deal with ionic strengths from dilute to moderately saline water (up to 6 molal for an NaCl-dominant solution). The equations implemented for the DH model are presented in Appendix A. During the course of the Yucca Mountain project, a Pitzer ion-interaction model was implemented into TOUGHREACT. This allows the application of this simulator to problems involving much more concentrated aqueous solutions, such as those involving geochemical processes in and around high-level nuclear waste repositories where fluid evaporation and/or boiling is expected to occur (Zhang et al., 2007). The Pitzer ion-interaction model, which we refer to as the Pitzer virial approach, and associated ion-interaction parameters have been applied successfully to study non-ideal concentrated aqueous solutions. The formulation of the Pitzer model is presented in Appendix B; detailed information can be founded in Zhang et al. (2007). For CO{sub 2} geological sequestration, the Pitzer ion-interaction model for highly concentrated brines was incorporated into TOUGHREACT/ECO2N, then was tested and compared with a previously implemented extended Debye-Hueckel (DH) ion activity model. The comparison was made through a batch geochemical system using a Gulf Coast sandstone saline formation.

  13. An Analysis of High School Mathematics Achievement and English Language Arts Achievement as Predictors of Science Achievement

    ERIC Educational Resources Information Center

    Edwards, Anthony C.

    2012-01-01

    Science assessments require students to read and comprehend questions and to solve mathematical problems. The purpose of this study is to determine whether the following variables can be used to predict science achievement: English language arts achievement, mathematics achievement, socioeconomic status (SES), limited English proficiency (LEP)…

  14. Method for providing a low density high strength polyurethane foam

    SciTech Connect

    Whinnery, Jr., Leroy L.; Goods, Steven H.; Skala, Dawn M.; Henderson, Craig C.; Keifer, Patrick N.

    2013-06-18

    Disclosed is a method for making a polyurethane closed-cell foam material exhibiting a bulk density below 4 lbs/ft.sup.3 and high strength. The present embodiment uses the reaction product of a modified MDI and a sucrose/glycerine based polyether polyol resin wherein a small measured quantity of the polyol resin is "pre-reacted" with a larger quantity of the isocyanate in a defined ratio such that when the necessary remaining quantity of the polyol resin is added to the "pre-reacted" resin together with a tertiary amine catalyst and water as a blowing agent, the polymerization proceeds slowly enough to provide a stable foam body.

  15. Metastable high-entropy dual-phase alloys overcome the strength-ductility trade-off

    NASA Astrophysics Data System (ADS)

    Li, Zhiming; Pradeep, Konda Gokuldoss; Deng, Yun; Raabe, Dierk; Tasan, Cemal Cem

    2016-06-01

    Metals have been mankind’s most essential materials for thousands of years; however, their use is affected by ecological and economical concerns. Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off. Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases. High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization. Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection, the concept is overturned. We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase). This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels and massive solid-solution strengthening of high-entropy alloys. In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength. Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility. This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials. This metastability-engineering strategy should

  16. Metastable high-entropy dual-phase alloys overcome the strength-ductility trade-off.

    PubMed

    Li, Zhiming; Pradeep, Konda Gokuldoss; Deng, Yun; Raabe, Dierk; Tasan, Cemal Cem

    2016-06-01

    Metals have been mankind's most essential materials for thousands of years; however, their use is affected by ecological and economical concerns. Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off. Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases. High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization. Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection, the concept is overturned. We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase). This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels and massive solid-solution strengthening of high-entropy alloys. In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength. Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility. This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials. This metastability-engineering strategy should

  17. Magnetic Implosion for Novel Strength Measurements at High Strain Rates

    SciTech Connect

    Lee, H.; Preston, D.L.; Bartsch, R.R.; Bowers, R.L.; Holtkamp, D.; Wright, B.L.

    1998-10-19

    Recently Lee and Preston have proposed to use magnetic implosions as a new method for measuring material strength in a regime of large strains and high strain rates inaccessible to previously established techniques. By its shockless nature, this method avoids the intrinsic difficulties associated with an earlier approach using high explosives. The authors illustrate how the stress-strain relation for an imploding liner can be obtained by measuring the velocity and temperature history of its inner surface. They discuss the physical requirements that lead us to a composite liner design applicable to different test materials, and also compare the code-simulated prediction with the measured data for the high strain-rate experiments conducted recently at LANL. Finally, they present a novel diagnostic scheme that will enable us to remove the background in the pyrometric measurement through data reduction.

  18. Cardiac work remains high after strength exercise in elderly.

    PubMed

    Queiroz, A C C; Kanegusuku, H; Chehuen, M R; Costa, L A R; Wallerstein, L F; Dias da Silva, V J; Mello, M T; Ugrinowitsch, C; Forjaz, C L M

    2013-05-01

    Moderate- to high-intensity strength training is recommended for healthy adults. In young subjects, a single session of strength training decreases blood pressure, while heart rate and cardiac work remain elevated afterwards. However, these effects have not been clearly demonstrated in elderly subjects. To investigate this issue, 16 elderly subjects each underwent a Control and an Exercise (3 sets, 8 RM, 9 exercises) session conducted in random order. Haemodynamic variables and heart rate variability were measured before and after the interventions. Systolic blood pressure did not change after the exercise session but did increase after the control session (+8.1±1.6 mm Hg, P≤0.05). Diastolic blood pressure, as well as systemic vascular resistance increased similarly after both sessions. Cardiac output and stroke volume decreased, while heart rate, rate-pressure product and the low- to high-frequency ratio of heart rate variability increased only after the exercise session ( - 0.5±0.1 L/min, - 9.3±2.0 ml,+3.8±1.6 bpm, +579.3±164.1 mmHg.bpm and +0.71±0.34, P≤0.05). Ambulatory blood pressure was similar after both sessions, while heart rate and rate pressure product remained higher after the exercise session for up to 4.5 h. After a single session of strength training, cardiac sympathetic modulation and heart rate remain elevated in elderly subjects, keeping cardiac work elevated for a long period of time.

  19. Fatigue behavior of high-strength concrete under marine conditions

    SciTech Connect

    Mor, A.

    1987-01-01

    In this study, 24 high-strength reinforced concrete beams were tested in fatigue under simulated marine conditions. Low-cycle, high-magnitude loading was imposed on beams, some of which were exposed to air, and others which were submerged in water. The beams were cycled at 1 Hz, to 80% of their yield capacity in negative and positive flexure. Four concrete mixes were compared. Half of the specimens were made with lightweight aggregate (LWA), and half were made with river gravel (NWA). Half of each group contained silica-fume as partial replacement of cement (13%). By manipulating the water/cement ratio, the 28-day compressive strength of all concretes was 9500 {plus minus} 300 psi. The previously reported phenomenon of water pumping through the cracks was observed, but did not appear to be directly related to the subsequent failure. When silica fume is added to the concrete mix, the adhesion is greatly improved. LWA concrete utilizes this additional adhesion effectively. NWA concrete with silica-fume, on the other hand, is not able to utilize the increased adhesion due to microcracking. Main findings of both the fatigue and pull-out bond tests are listed.

  20. Behind the High Achievement of East Asian Students.

    ERIC Educational Resources Information Center

    Leung, Frederick K. S.

    2002-01-01

    Studied reasons for the high achievement students from Hong Kong, Japan, South Korea, and Singapore on the Third International Mathematics and Science Study (TIMSS). Questionnaire data provided by students participating show that the superior results of these students may have come at the expense of other aspects of student development. Results…

  1. Progress Lags in High School, Especially for Advanced Achievers

    ERIC Educational Resources Information Center

    Education Digest: Essential Readings Condensed for Quick Review, 2012

    2012-01-01

    This report by the Center on Education Policy (CEP), an independent nonprofit organization, examines trends in the achievement of high school students on the state reading/English language arts (ELA) and mathematics tests used for accountability under the No Child Left Behind Act (NCLB). This study confirms that there is reason for concern about…

  2. Learning Environment, Motivation, and Achievement in High School Science.

    ERIC Educational Resources Information Center

    Nolen, Susan Bobbitt

    2003-01-01

    Examines the relationship between high school students' perceptions of their science learning environments and their motivation, learning strategies, and achievement. Discusses the focus of shared perceptions and instruction and indicates that shared perceptions focused on understanding and independent thinking positively predicted students'…

  3. High Achieving Girls in Mathematics: What's Wrong with Working Hard?

    ERIC Educational Resources Information Center

    Howe, Ann C.; Berenson, Sarah B.

    2003-01-01

    The participation of women in graduate studies and mathematics-related careers remains a social and economic problem in the United States. Part of a larger study to understand this lack of participation, here we present preliminary findings of girls who are high achievers in middle grades mathematics. This interpretive study documents girls'…

  4. Relationship between High School Leadership Team Practices and Student Achievement

    ERIC Educational Resources Information Center

    McInnis, Timothy M.

    2009-01-01

    This study investigated if a relationship existed between student achievement in 10th grade Missouri Assessment Program mathematics and 11th grade communication arts scores in 2007 and high school leadership team perceptions of the extent to which they demonstrated leadership practices. The secondary purpose was to compare perceptional…

  5. Improving Student Achievement in Today's High Schools: What Works.

    ERIC Educational Resources Information Center

    Shields, Marie S.

    This paper is based on a study of two high schools in Maine that achieved outstanding and consistent gains in English, math, and science over a 5-year period. Three strands of inquiry were used for the study: surveys, interviews, and observations. A multiple-perspective approach was used to integrate the information so as to evaluate the…

  6. Mercer Middle School Case Study: High Science and Math Achievement

    ERIC Educational Resources Information Center

    Washington State Board of Education, 2010

    2010-01-01

    To spotlight effective practices, the Washington State Board of Education (SBE) is highlighting schools that are closing achievement gaps and performing at high levels. In 2009, the SBE partnered with the Office of Superintendent of Public Instruction (OSPI) to create the Washington Accountability Index. The Index is a new way to measure schools'…

  7. Supplementary Education: The Hidden Curriculum of High Academic Achievement

    ERIC Educational Resources Information Center

    Gordon, Edmund W., Ed.; Bridglall, Beatrice L., Ed.; Meroe, Aundra Saa, Ed.

    2004-01-01

    In this book, the editors argue that while access to schools that enable and expect academic achievement is a necessary ingredient for the education of students, schools alone may not be sufficient to ensure universally high levels of academic development. Supplemental educational experiences may also be needed. The idea of supplementary education…

  8. Analysis of Three High-Achieving Young Adolescent Girls

    ERIC Educational Resources Information Center

    Lim, Jae Hoon; Chae, Jeong-Lim; Schinck-Mikel, Amelie G.; Watson, Jimmy

    2013-01-01

    This paper presents an in-depth cross-case analysis of three high-achieving young adolescent girls who had contrasting mathematics learning experiences during the first year of middle school. In particular, this study examines the foundation for their motivation, as well as the dominant mode of learning and academic engagement in relation to three…

  9. Test Score Decline Among High Achievers: Policy Implications.

    ERIC Educational Resources Information Center

    Goldman, Jerrold; Hsia, Jayjia

    Since 1967, the mean Scholastic Aptitude Test (SAT) score has declined. Likewise, the numbers of candidates receiving high SAT scores have been decreasing steadily. The same downward trend in student achievement can be seen among student groups from grade 4 through post graduate studies. In recent years, policy has been directed towards making…

  10. Student Achievement through the Development of Complete High School Culture

    ERIC Educational Resources Information Center

    Lamphere, Michael Frederick, Jr.

    2012-01-01

    This dissertation undertook an investigation of school culture and achievement in the high school setting. The national data set ELS:2002 was used as the pool of variables because it allows for a complete picture of school culture comprising students, parents, administrators, and teachers. The data were selected based on current literature and…

  11. The High Trust Classroom: Raising Achievement from the Inside Out

    ERIC Educational Resources Information Center

    Moore, Lonnie

    2009-01-01

    This book provides a roadmap to developing a high-trust classroom, a classroom: (1) With increased student achievement; (2) With few discipline problems; (3) Where students are intrinsically motivated; and (4) Where the teacher can confidently use creative lesson planning. The author presents a simple step by step approach to earning the trust of…

  12. Self-Esteem and Academic Achievement of High School Students

    ERIC Educational Resources Information Center

    Moradi Sheykhjan, Tohid; Jabari, Kamran; Rajeswari, K.

    2014-01-01

    The primary purpose of this study was to determine the influence of self-esteem on academic achievement among high school students in Miandoab City of Iran. The methodology of the research is descriptive and correlation that descriptive and inferential statistics were used to analyze the data. Statistical Society includes male and female high…

  13. The development of high strength corrosion resistant precipitation hardening cast steels

    NASA Astrophysics Data System (ADS)

    Abrahams, Rachel A.

    Precipitation Hardened Cast Stainless Steels (PHCSS) are a corrosion resistant class of materials which derive their properties from secondary aging after a normalizing heat treatment step. While PHCSS materials are available in austenitic and semi-austenitic forms, the martensitic PHCSS are most widely used due to a combination of high strength, good toughness, and corrosion resistance. If higher strength levels can be achieved in these alloys, these materials can be used as a lower-cost alternative to titanium for high specific strength applications where corrosion resistance is a factor. Although wrought precipitation hardened materials have been in use and specified for more than half a century, the specification and use of PHCSS has only been recent. The effects of composition and processing on performance have received little attention in the cast steel literature. The work presented in these investigations is concerned with the experimental study and modeling of microstructural development in cast martensitic precipitation hardened steels at high strength levels. Particular attention is focused on improving the performance of the high strength CB7Cu alloy by control of detrimental secondary phases, notably delta ferrite and retained austenite, which is detrimental to strength, but potentially beneficial in terms of fracture and impact toughness. The relationship between age processing and mechanical properties is also investigated, and a new age hardening model based on simultaneous precipitation hardening and tempering has been modified for use with these steels. Because the CB7Cu system has limited strength even with improved processing, a higher strength prototype Fe-Ni-Cr-Mo-Ti system has been designed and adapted for use in casting. This prototype is expected to develop high strengths matching or exceed that of cast Ti-6Al-4V alloys. Traditional multicomponent constitution phase diagrams widely used for phase estimation in conventional stainless steels

  14. Microstructural effects on the springback of advanced high-strength steel

    NASA Astrophysics Data System (ADS)

    Gan, Wei; Babu, S. S.; Kapustka, Nick; Wagoner, Robert H.

    2006-11-01

    The application of advanced high-strength steels (AHSS) has been growing rapidly in the automotive industry. Because of their high-strength, thinner sheet metals can be used for body components to achieve both weight savings and increased safety. However, this will lead to greater springback deviation from design after the forming operation. Fundamental understanding and prediction of springback are required for springback compensation and tooling design. While various types of continuum mechanics based models have been proposed to simulate the mechanical behavior of advanced high-strength steels, few of them consider microstructural effects such as material heterogeneity. In this study, through sheet thickness strength variation has been observed in DP 780 and TRIP 780 steels. Finite-element simulation indicates that the through thickness effect (TTE) can have a significant impact on the springback behavior of these sheet metals. This is verified through our experimental work using draw-bend testing. The results suggest that microstructural effects should be considered to accurately simulate springback of AHSS. Based on these results, implications of different microstructural designs will be discussed.

  15. Experimental investigation of bond strength under high loading rates

    NASA Astrophysics Data System (ADS)

    Michal, Mathias; Keuser, Manfred; Solomos, George; Peroni, Marco; Larcher, Martin; Esteban, Beatriz

    2015-09-01

    The structural behaviour of reinforced concrete is governed significantly by the transmission of forces between steel and concrete. The bond is of special importance for the overlapping joint and anchoring of the reinforcement, where rigid bond is required. It also plays an important role in the rotational capacity of plastic hinges, where a ductile bond behaviour is preferable. Similar to the mechanical properties of concrete and steel also the characteristics of their interaction changes with the velocity of the applied loading. For smooth steel bars with its main bond mechanisms of adhesion and friction, nearly no influence of loading rate is reported in literature. In contrast, a high rate dependence can be found for the nowadays mainly used deformed bars. For mechanical interlock, where ribs of the reinforcing steel are bracing concrete material surrounding the bar, one reason can be assumed to be in direct connection with the increase of concrete compressive strength. For splitting failure of bond, characterized by the concrete tensile strength, an even higher dynamic increase is observed. For the design of Structures exposed to blast or impact loading the knowledge of a rate dependent bond stress-slip relationship is required to consider safety and economical aspects at the same time. The bond behaviour of reinforced concrete has been investigated with different experimental methods at the University of the Bundeswehr Munich (UniBw) and the Joint Research Centre (JRC) in Ispra. Both static and dynamic tests have been carried out, where innovative experimental apparatuses have been used. The bond stress-slip relationship and maximum pull-out-forces for varying diameter of the bar, concrete compressive strength and loading rates have been obtained. It is expected that these experimental results will contribute to a better understanding of the rate dependent bond behaviour and will serve for calibration of numerical models.

  16. Prediction of Microstructure in High-Strength Ductile Forging Parts

    SciTech Connect

    Urban, M.; Back, A.; Hirt, G.; Keul, C.; Bleck, W.

    2010-06-15

    Governmental, environmental and economic demands call for lighter, stiffer and at the same time cheaper products in the vehicle industry. Especially safety relevant parts have to be stiff and at the same time ductile. The strategy of this project was to improve the mechanical properties of forging steel alloys by employing a high-strength and ductile bainitic microstructure in the parts while maintaining cost effective process chains to reach these goals for high stressed forged parts. Therefore, a new steel alloy combined with an optimized process chain has been developed. To optimize the process chain with a minimum of expensive experiments, a numerical approach was developed to predict the microstructure of the steel alloy after the process chain based on FEM simulations of the forging and cooling combined with deformation-time-temperature-transformation-diagrams.

  17. Mechanical Properties of High Strength Al-Mg Alloy Sheet

    NASA Astrophysics Data System (ADS)

    Choi, Bong-Jae; Hong, Kyung-Eui; Kim, Young-Jig

    The aim of this research is to develop the high strength Al alloy sheet for the automotive body. For the fabrication Al-Mg alloy sheet, the composition of alloying elements was designed by the properties database and CALPHAD (Calculation Phase Diagram) approach which can predict the phases during solidification using thermodynamic database. Al-Mg alloys were designed using CALPHAD approach according to the high content of Mg with minor alloying elements. After phase predictions by CALPHAD, designed Al-Mg alloys were manufactured. Addition of Mg in Al melts were protected by dry air/Sulphur hexafluoride (SF6) mixture gas which can control the severe Mg ignition and oxidation. After rolling procedure of manufactured Al-Mg alloys, mechanical properties were examined with the variation of the heat treatment conditions.

  18. Guidelines for Stretch Flanging Advanced High Strength Steels

    NASA Astrophysics Data System (ADS)

    Sriram, S.; Chintamani, J.

    2005-08-01

    Advanced High Strength Steels (AHSS) are currently being considered for use in closure and structural panels in the automotive industry because of their high potential for affordable weight reduction and improved performance. AHSS such as dual phase steels are currently being used in some vehicle platforms. From a manufacturing perspective, stretch flanging during stamping is an important deformation mode requiring careful consideration of geometry and the die process. This paper presents some geometric and process guidelines for stretch flanging AHSS. Hole expansion experiments were conducted to determine the failure limit for a sheared edge condition. Effects of punching clearance, prestrain and prior strain path on hole expansion were explored in these experiments. In addition, dynamic explicit FE calculations using LS-DYNA were also conducted for a typical stretch flange by varying some key geometric parameters. The experimental and FEA results were then analyzed to yield process and geometric guidelines to enable successful stretch flanging of AHSS.

  19. High strain rate characterization of low-density low-strength materials

    NASA Astrophysics Data System (ADS)

    Sawas, O.; Brar, N. S.; Brockman, R. A.

    1998-07-01

    The Conventional Split Hopkinson Bar (CSHB) is a reliable experimental technique for measuring high strain rate properties of high-strength materials. Attempts to use the CSHB for similar measurements in more compliant materials, such as plastics and foams, are limited by the maximum achievable strain and high noise-to-signal ratios. This work introduces an all-polymeric split Hopkinson bar (APSHB) experiment, which overcomes these limitations. The proposed method uses polymeric pressure bars to achieve a closer impedance match between the pressure bars and the specimen materials, thus providing both low noise-to-signal ratio data and a longer input pulse for higher maximum strain. Data reduction procedures for APSHB that account for the viscoelastic behavior of the pressure bars are presented. Comparing the high strain rate response of 1100 Al obtained from CSHB and APSHB validates these procedures. Stress-strain data at strain rates of 500-2000/s for polycarbonate, polyurethane foam, and styrofoam are presented.

  20. High strain rate characterization of low-density low-strength materials

    NASA Astrophysics Data System (ADS)

    Sawas, Omar

    The Split Hopkinson Bar (SHB) is a reliable experimental technique for measuring high strain rate properties of high-strength, ductile materials. Attempts to apply the SHB in measurement on more compliant materials, such as polymers and foams, are limited by the maximum achievable strain and high noise-to-signal ratios. This work introduces an all-polymeric split Hopkinson bar (APSHB) experiment, which overcomes these limitations. The proposed method uses polymeric pressure bars to achieve a closer impedance match between the pressure bars and the specimen material, thus providing both low signal-to-noise ratio data and a longer input pulse for higher maximum strain. The APSHB requires very careful data reduction procedures because of the viscoelastic behavior of the incident and transmitter pressure bars. The APSHB produces high-quality stress-strain data for a variety of compliant materials, including polycarbonate, elastomer, polyurethane, and styrofoam.

  1. Analysis of particle size and interface effects on the strength and ductility of advanced high strength steels

    NASA Astrophysics Data System (ADS)

    Ettehad, Mahmood

    This thesis is devoted to the numerical investigation of mechanical behavior of Dual phase (DP) steels. Such grade of advanced high strength steels (AHSS) is favorable to the automotive industry due the unique properties such as high strength and ductility with low finished cost. Many experimental and numerical studies have been done to achieve the optimized behavior of DP steels by controlling their microstructure. Experiments are costly and time consuming so in recent years numerical tools are utilized to help the metallurgist before doing experiments. Most of the numerical studies are based on classical (local) constitutive models where no material length scale parameters are incorporated in the model. Although these models are proved to be very effective in modeling the material behavior in the large scales but they fail to address some critical phenomena which are important for our goals. First, they fail to address the size effect phenomena which materials show at microstructural scale. This means that materials show stronger behavior at small scales compared to large scales. Another issue with classical models is the mesh size dependency in modeling the softening behavior of materials. This means that in the finite element context (FEM) the results will be mesh size dependent and no converged solution exist upon mesh refinement. Thereby by applying the classical (local) models one my loose the accuracy on measuring the strength and ductility of DP steels. Among the non-classical (nonlocal) models, gradient-enhanced plasticity models which consider the effect of neighboring point on the behavior of one specific point are proved to be numerically effective and versatile tools to accomplish the two concerns mentioned above. So in this thesis a gradient-enhanced plasticity model which incorporates both the energetic and dissipative material length scales is derived based on the laws of thermodynamics. This model also has a consistent yield-like function for the

  2. Nitriding of high speed steel by bipolar PBII for improvement in adhesion strength of DLC films

    NASA Astrophysics Data System (ADS)

    Choi, Junho; Soejima, Koji; Kato, Takahisa; Kawaguchi, Masahiro; Lee, Wonsik

    2012-02-01

    In the present study, bipolar plasma based ion implantation and deposition (bipolar PBII) was used for plasma nitriding of high speed steel (SKH2), and the effects of the treatment parameters (positive pulse voltage, negative pulse voltage, treatment pressure, treatment time, and precursor gases) on the nitriding process were investigated. The hardness, roughness, and depth of nitride layer were also measured. The adhesion strength of diamond-like carbon (DLC) films coated on the nitride substrate was evaluated by carrying out Rockwell indentation and microscratch tests. Nitriding by bipolar PBII was achieved in the combining of two effects: nitrogen ion implantation by applying a high negative pulse voltage and thermal diffusion of nitrogen atoms under the application of a high positive pulse voltage. However, a very high voltage negative pulse caused surface roughening of the nitride layer. Application of a high positive pulse voltage during nitriding was found to be effective in promoting the thermal diffusion of the implanted nitrogen atoms. Effective nitriding could be achieved under the following conditions: high positive pulse voltage, low negative pulse voltage, high nitrogen gas pressure, and addition of hydrogen to the precursor gas. The adhesion strength of the DLC films on the SKH2 substrate was well improved after nitriding.

  3. Learning environment, motivation, and achievement in high school science

    NASA Astrophysics Data System (ADS)

    Bobbitt Nolen, Susan

    2003-04-01

    In a study of the relationship between high school students' perceptions of their science learning environments and their motivation, learning strategies, and achievement, 377 students in 22 introductory science classrooms completed surveys in the fall and spring of their ninth-grade year. Hierarchical linear regression was used to model the effects of variables at both the classroom and individual level simultaneously. High intraclass agreement (indicated by high parameter reliability) on all classroom environment measures indicated that students shared perceptions of the classroom learning environment. Controlling for other factors, shared perceptions that only the most able could succeed in science classrooms and that instruction was fast-paced and focused on correct answers negatively predicted science achievement, as measured on a districtwide curriculum-linked test. Shared perceptions that classrooms focused on understanding and independent thinking positively predicted students' self-reported satisfaction with learning. Implications of these results for both teaching and research into classroom environments are discussed.

  4. Accelerated Creep Testing of High Strength Aramid Webbing

    NASA Technical Reports Server (NTRS)

    Jones, Thomas C.; Doggett, William R.; Stnfield, Clarence E.; Valverde, Omar

    2012-01-01

    A series of preliminary accelerated creep tests were performed on four variants of 12K and 24K lbf rated Vectran webbing to help develop an accelerated creep test methodology and analysis capability for high strength aramid webbings. The variants included pristine, aged, folded and stitched samples. This class of webbings is used in the restraint layer of habitable, inflatable space structures, for which the lifetime properties are currently not well characterized. The Stepped Isothermal Method was used to accelerate the creep life of the webbings and a novel stereo photogrammetry system was used to measure the full-field strains. A custom MATLAB code is described, and used to reduce the strain data to produce master creep curves for the test samples. Initial results show good correlation between replicates; however, it is clear that a larger number of samples are needed to build confidence in the consistency of the results. It is noted that local fiber breaks affect the creep response in a similar manner to increasing the load, thus raising the creep rate and reducing the time to creep failure. The stitched webbings produced the highest variance between replicates, due to the combination of higher local stresses and thread-on-fiber damage. Large variability in the strength of the webbings is also shown to have an impact on the range of predicted creep life.

  5. High-Strength Low-Alloy (HSLA) Mg-Zn-Ca Alloys with Excellent Biodegradation Performance

    NASA Astrophysics Data System (ADS)

    Hofstetter, J.; Becker, M.; Martinelli, E.; Weinberg, A. M.; Mingler, B.; Kilian, H.; Pogatscher, S.; Uggowitzer, P. J.; Löffler, J. F.

    2014-04-01

    This article deals with the development of fine-grained high-strength low-alloy (HSLA) magnesium alloys intended for use as biodegradable implant material. The alloys contain solely low amounts of Zn and Ca as alloying elements. We illustrate the development path starting from the high-Zn-containing ZX50 (MgZn5Ca0.25) alloy with conventional purity, to an ultrahigh-purity ZX50 modification, and further to the ultrahigh-purity Zn-lean alloy ZX10 (MgZn1Ca0.3). It is shown that alloys with high Zn-content are prone to biocorrosion in various environments, most probably because of the presence of the intermetallic phase Mg6Zn3Ca2. A reduction of the Zn content results in (Mg,Zn)2Ca phase formation. This phase is less noble than the Mg-matrix and therefore, in contrast to Mg6Zn3Ca2, does not act as cathodic site. A fine-grained microstructure is achieved by the controlled formation of fine and homogeneously distributed (Mg,Zn)2Ca precipitates, which influence dynamic recrystallization and grain growth during hot forming. Such design scheme is comparable to that of HSLA steels, where low amounts of alloying elements are intended to produce a very fine dispersion of particles to increase the material's strength by refining the grain size. Consequently our new, ultrapure ZX10 alloy exhibits high strength (yield strength R p = 240 MPa, ultimate tensile strength R m = 255 MPa) and simultaneously high ductility (elongation to fracture A = 27%), as well as low mechanical anisotropy. Because of the anodic nature of the (Mg,Zn)2Ca particles used in the HSLA concept, the in vivo degradation in a rat femur implantation study is very slow and homogeneous without clinically observable hydrogen evolution, making the ZX10 alloy a promising material for biodegradable implants.

  6. Optimization Correction Strength Using Contra Bending Technique without Anterior Release Procedure to Achieve Maximum Correction on Severe Adult Idiopathic Scoliosis

    PubMed Central

    Rahyussalim, Ahmad Jabir; Saleh, Ifran; Purnaning, Dyah; Kurniawati, Tri

    2016-01-01

    Adult scoliosis is defined as a spinal deformity in a skeletally mature patient with a Cobb angle of more than 10 degrees in the coronal plain. Posterior-only approach with rod and screw corrective manipulation to add strength of contra bending manipulation has correction achievement similar to that obtained by conventional combined anterior release and posterior approach. It also avoids the complications related to the thoracic approach. We reported a case of 25-year-old male adult idiopathic scoliosis with double curve. It consists of main thoracic curve of 150 degrees and lumbar curve of 89 degrees. His curve underwent direct contra bending posterior approach using rod and screw corrective manipulation technique to achieve optimal correction. After surgery the main thoracic Cobb angle becomes 83 degrees and lumbar Cobb angle becomes 40 degrees, with 5 days length of stay and less than 800 mL blood loss during surgery. There is no complaint at two months after surgery; he has already come back to normal activity with good functional activity. PMID:27064801

  7. Parent Involvement Practices of High-Achieving Elementary Science Students

    NASA Astrophysics Data System (ADS)

    Waller, Samara Susan

    This study addressed a prevalence of low achievement in science courses in an urban school district in Georgia. National leaders and educators have identified the improvement of science proficiency as critical to the future of American industry. The purpose of this study was to examine parent involvement in this school district and its contribution to the academic achievement of successful science students. Social capital theory guided this study by suggesting that students achieve best when investments are made into their academic and social development. A collective case study qualitative research design was used to interview 9 parent participants at 2 elementary schools whose children scored in the exceeds category on the Science CRCT. The research questions focused on what these parents did at home to support their children's academic achievement. Data were collected using a semi-structured interview protocol and analyzed through the categorical aggregation of transcribed interviews. Key findings revealed that the parents invested time and resources in 3 practices: communicating high expectations, supporting and developing key skills, and communicating with teachers. These findings contribute to social change at both the local and community level by creating a starting point for teachers, principals, and district leaders to reexamine the value of parent input in the educational process, and by providing data to support the revision of current parent involvement policies. Possibilities for further study building upon the findings of this study may focus on student perceptions of their parents' parenting as it relates to their science achievement.

  8. High-strength carbon nanotube fibre-like ribbon with high ductility and high electrical conductivity.

    PubMed

    Wang, J N; Luo, X G; Wu, T; Chen, Y

    2014-01-01

    Macroscopic fibres made up of carbon nanotubes exhibit properties far below theoretical predictions and even much lower than those for conventional carbon fibres. Here we report improvements of mechanical and electrical properties by more than one order of magnitude by pressurized rolling. Our carbon nanotubes self-assemble to a hollow macroscopic cylinder in a tube reactor operated at high temperature and then condense in water or ethanol to form a fibre, which is continually spooled in an open-air environment. This initial fibre is densified by rolling under pressure, leading to a combination of high tensile strength (3.76-5.53 GPa), high tensile ductility (8-13%) and high electrical conductivity ((1.82-2.24) × 10(4) S cm(-1)). Our study therefore demonstrates strategies for future performance maximization and the very considerable potential of carbon nanotube assemblies for high-end uses.

  9. Time-Dependent Behavior of High-Strength Kevlar and Vectran Webbing

    NASA Technical Reports Server (NTRS)

    Jones, Thomas C.; Doggett, William R.

    2014-01-01

    High-strength Kevlar and Vectran webbings are currently being used by both NASA and industry as the primary load-bearing structure in inflatable space habitation modules. The time-dependent behavior of high-strength webbing architectures is a vital area of research that is providing critical material data to guide a more robust design process for this class of structures. This paper details the results of a series of time-dependent tests on 1-inch wide webbing including an initial set of comparative tests between specimens that underwent realtime and accelerated creep at 65 and 70% of their ultimate tensile strength. Variability in the ultimate tensile strength of the webbings is investigated and compared with variability in the creep life response. Additional testing studied the effects of load and displacement rate, specimen length and the time-dependent effects of preconditioning the webbings. The creep test facilities, instrumentation and test procedures are also detailed. The accelerated creep tests display consistently longer times to failure than their real-time counterparts; however, several factors were identified that may contribute to the observed disparity. Test setup and instrumentation, grip type, loading scheme, thermal environment and accelerated test postprocessing along with material variability are among these factors. Their effects are discussed and future work is detailed for the exploration and elimination of some of these factors in order to achieve a higher fidelity comparison.

  10. Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS)

    SciTech Connect

    Santella, M. L.; Hovanski, Yuri; Pan, Tsung-Yu

    2012-04-16

    Friction stir spot welding (FSSW) is applied to join advanced high strength steels (AHSS): galvannealed dual phase 780 MPa steel (DP780GA), transformation induced plasticity 780 MPa steel (TRIP780), and hot-stamped boron steel (HSBS). A low-cost Si3N4 ceramic tool was developed and used for making welds in this study instead of polycrystalline cubic boron nitride (PCBN) material used in earlier studies. FSSW has the advantages of solid-state, low-temperature process, and the ability of joining dissimilar grade of steels and thicknesses. Two different tool shoulder geometries, concave with smooth surface and convex with spiral pattern, were used in the study. Welds were made by a 2-step displacement control process with weld time of 4, 6, and 10 seconds. Static tensile lap-shear strength achieved 16.4 kN for DP780GA-HSBS and 13.2kN for TRIP780-HSBS, above the spot weld strength requirements by AWS. Nugget pull-out was the failure mode of the joint. The joining mechanism was illustrated from the cross-section micrographs. Microhardness measurement showed hardening in the upper sheet steel (DP780GA or TRIP780) in the weld, but softening of HSBS in the heat-affect zone (HAZ). The study demonstrated the feasibility of making high-strength AHSS spot welds with low-cost tools.

  11. Study on technology of high-frequency pulsed magnetic field strength measurement.

    PubMed

    Chen, Yi-Mei; Liu, Zhi-Peng; Yin, Tao

    2012-01-01

    High-frequency transient weak magnetic field is always involved in researches about biomedical engineering field while common magnetic-field sensors cannot work properly at frequencies as high as MHz. To measure the value of MHz-level weak pulsed magnetic-field strength accurately, this paper designs a measurement and calibration method for pulsed magnetic-field. In this paper, a device made of Nonferromagnetic material was independently designed and applied to pulsed magnetic field measurement. It held an accurately relative position between the magnetic field generating coil and the detecting coil. By applying a sinusoidal pulse to the generator, collecting the induced electromotive force of the detector, the final magnetic field strength was worked out through algorithms written in Matlab according to Faraday's Law. Experiments were carried out for measurement and calibration. Experiments showed that, under good stability and consistency, accurate measurement of magnetic-field strength of a sinepulse magnetic-field can be achieved, with frequency at 0.5, 1, 1.5 MHz and strength level at micro-Tesla. Calibration results carried out a measuring relative error about 2.5%.

  12. Method of making high strength, tough alloy steel

    DOEpatents

    Thomas, Gareth; Rao, Bangaru V. N.

    1979-01-01

    A high strength, tough alloy steel, particularly suitable for the mining industry, is formed by heating the steel to a temperature in the austenite range (1000.degree.-1100.degree. C.) to form a homogeneous austenite phase and then cooling the steel to form a microstructure of uniformly dispersed dislocated martensite separated by continuous thin boundary films of stabilized retained austenite. The steel includes 0.2-0.35 weight % carbon, at least 1% and preferably 3-4.5% chromium, and at least one other subsitutional alloying element, preferably manganese or nickel. The austenite film is stable to subsequent heat treatment as by tempering (below 300.degree. C.) and reforms to a stable film after austenite grain refinement.

  13. Strength and flexibility of bulk high-{Tc} superconductors

    SciTech Connect

    Goretta, K.C.; Jiang, M.; Kupperman, D.S.; Lanagan, M.T.; Singh, J.P.; Vasanthamohan, N.; Hinks, D.G.; Mitchell, J.F.; Richardson, J.W. Jr.

    1996-08-01

    Strength, fracture toughness, and elastic modulus data have been gathered for bulk high-temperature superconductors, commercial 99.9% Ag, and a 1.2 at.% Mg/Ag alloy. These data have been used to calculate fracture strains for bulk conductors. The calculations indicate that the superconducting cores of clad tapes should begin to fracture at strains below 0.2%. In addition, residual strains in Ag-clad (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} tapes have been measured by neutron diffraction. An explanation is offered for why many tapes appear to be able to tolerate large strains before exhibiting a reduction in current transport.

  14. Thermal Transport in High-Strength Polymethacrylimide (PMI) Foam Insulations

    NASA Astrophysics Data System (ADS)

    Qiu, L.; Zheng, X. H.; Zhu, J.; Tang, D. W.; Yang, S. Y.; Hu, A. J.; Wang, L. L.; Li, S. S.

    2015-11-01

    Thermal transport in high-strength polymethacrylimide (PMI) foam insulations is described, with special emphasis on the density and temperature effects on the thermal transport performance. Measurements of the effective thermal conductivity are performed by a freestanding sensor-based 3ω method. A linear relationship between the density and the effective thermal conductivity is observed. Based on the analysis of the foam insulation morphological structures and the corresponding geometrical cell model, the quantitative contribution of the solid conductivity and the gas conductivity as well as the radiative conductivity to the total effective thermal conductivity as a function of the density and temperature is calculated. The agreement between the curves of the results from the developed model and experimental data indicate the model can be used for PMI foam insulating performance optimization.

  15. The Will to Achieve: A Phenomenological Study of the Experiences of African American High Achieving Students and Their Parents

    ERIC Educational Resources Information Center

    Spencer, Natalie Faye

    2012-01-01

    The purpose of this research study was to understand the experiences of high achieving African American students and their parents. The experiences of high achieving African American students and their parents have been missing from literature on the academic achievement of African American students. Much of the literature that has been published…

  16. Advanced Gear Alloys for Ultra High Strength Applications

    NASA Technical Reports Server (NTRS)

    Shen, Tony; Krantz, Timothy; Sebastian, Jason

    2011-01-01

    Single tooth bending fatigue (STBF) test data of UHS Ferrium C61 and C64 alloys are presented in comparison with historical test data of conventional gear steels (9310 and Pyrowear 53) with comparable statistical analysis methods. Pitting and scoring tests of C61 and C64 are works in progress. Boeing statistical analysis of STBF test data for the four gear steels (C61, C64, 9310 and Pyrowear 53) indicates that the UHS grades exhibit increases in fatigue strength in the low cycle fatigue (LCF) regime. In the high cycle fatigue (HCF) regime, the UHS steels exhibit better mean fatigue strength endurance limit behavior (particularly as compared to Pyrowear 53). However, due to considerable scatter in the UHS test data, the anticipated overall benefits of the UHS grades in bending fatigue have not been fully demonstrated. Based on all the test data and on Boeing s analysis, C61 has been selected by Boeing as the gear steel for the final ERDS demonstrator test gearboxes. In terms of potential follow-up work, detailed physics-based, micromechanical analysis and modeling of the fatigue data would allow for a better understanding of the causes of the experimental scatter, and of the transition from high-stress LCF (surface-dominated) to low-stress HCF (subsurface-dominated) fatigue failure. Additional STBF test data and failure analysis work, particularly in the HCF regime and around the endurance limit stress, could allow for better statistical confidence and could reduce the observed effects of experimental test scatter. Finally, the need for further optimization of the residual compressive stress profiles of the UHS steels (resulting from carburization and peening) is noted, particularly for the case of the higher hardness C64 material.

  17. High-strength, thermally-stable nanostructured materials

    NASA Astrophysics Data System (ADS)

    Shankar, Ravi

    The properties of two technologically important precipitation-treatable alloys - Al 6061 and Inconel 718, that are deformed to large plastic strains at room temperature by machining, are presented. The strong effect of prior density of precipitates on the consequent microstructure refinement during chip formation was determined by deforming Al 6061 of different tempers to varying levels of strain, by varying the tool rake angle. Chips cut from peak-aged 6061, consisting of a fine dispersion of precipitates, produced the finest microstructure and are composed of sub-100 nm grains. On the other hand, coarser precipitate distributions in over-aged 6061 and an absence of precipitates in solution-treated 6061 resulted in much coarser microstructures. Thermal stability of such nanostructured chips with different levels of strain and precipitate distributions is analyzed by studying evolution of Vickers micro-hardness and microstructure after different heat treatments. Chips produced from the peak-aged temper and over-aged temper soften following heat treatment while those from the solution-treated state first, gain strength before softening. The results are rationalized based on prior studies of the characteristics and kinetics of precipitation and coarsening in Al-Mg-Si systems. It is then demonstrated that precipitate-stabilized nanostructured materials synthesized from a prototypical alloy system - Inconel 718, are extremely stable even after prolonged heat treatment for 240 hours at temperatures as high as one-half of the melting point. This extraordinary thermal stability is traced to the retention of a fine dispersion of precipitates in a nanostructured matrix even after extended heat treatment. It is anticipated that general design principles garnered from understanding of the causal phenomena determining strengthening and thermal stability, can lead to the development of alloy systems for the manufacture of high-strength, thermally-stable nanostructured materials.

  18. Corrosion and embrittlement of high-strength steel bridge wires

    NASA Astrophysics Data System (ADS)

    Vermaas, Garry Wayne

    Suspension bridge cable inspections have revealed severely corroded and broken wires in some main cables. Accelerated cyclic corrosion studies were conducted to assess the relative effect of corrosion on high-strength steel bridge wire. Galvanized and ungalvanized wire samples were corroded under various levels of sustained loads in a cabinet that cyclically applied an acidic salt spray, dry conditions, and 100% relative humidity at elevated temperature. Mass loss, hydrogen concentration, ultimate load, and elongation at failure were measured for corroded and uncorroded samples. Elongation measurements indicated a significant embrittlement of the wires that could not be explained only by the presence of absorbed hydrogen (hydrogen embrittlement). The main cause of reduction of wire elongation was found to be the surface irregularities induced by the corrosion process. The corrosion process in a high-strength steel wire was modeled and analyzed using finite element methods. Forty-one separate FEM tests were run and this data was compared to the experimental data. In addition, for the purpose of comparison, a previously developed hydrogen embrittlement model was analyzed and its validity was discussed in detail. SEM photographs of the fracture surfaces were taken and possible causes and mechanisms of fracture were suggested by observations of the fracture morphology. It was shown through this experimental and numerical research work that the geometry of the wire, determined by the amount of corrosion, pitting, and surface irregularities, controls the ultimate elongation of the wire sample, as also confirmed by the SEM analysis of the fracture surfaces. It was also shown that, using a generally accepted hydrogen embrittlement model, there is no evidence that hydrogen embrittlement is occurring, or at least that hydrogen evolution is not the controlling factor in the loss of wire's ductility.

  19. Fracture strength of glass chips for high-pressure microfluidics

    NASA Astrophysics Data System (ADS)

    Andersson, Martin; Hjort, Klas; Klintberg, Lena

    2016-09-01

    High-pressure microfluidics exposes new areas in chemistry. In this paper, the reliability of transparent borosilicate glass chips is investigated. Two designs of circular cavities are used for fracture strength tests, either 1.6 mm wide with rounded corners to the fluid inlets, or 2.0 mm wide with sharp inlet corners. Two kinds of tests are done, either short-term, e.g. pressurization to fracture at room temperature, or long-term, with fracture at constant pressurization for up to one week, in the temperature region 11-125 °C. The speed of crack fronts is measured using a high-speed camera. Results show fracture stresses in the range of 129 and 254 MPa for short-term measurements. Long-term measurements conclude the presences of a temperature and stress dependent delayed fracture. For a reliability of one week at 11-38 °C, a pressure limit is found at the lower end of the short-term measurements, or 15% lower than the average. At 80 °C, this pressure limit is 45% lower. Crack speeds are measured to be 10-5 m s-1 during short-term fracture. These measurements are comparable with estimations based on slow crack growth and show that the growth affects the reliability of glass chips. This effect is strongly affected by high temperatures, thus lowers the operating window of high-pressure glass microfluidic devices.

  20. Fracture strength of glass chips for high-pressure microfluidics

    NASA Astrophysics Data System (ADS)

    Andersson, Martin; Hjort, Klas; Klintberg, Lena

    2016-09-01

    High-pressure microfluidics exposes new areas in chemistry. In this paper, the reliability of transparent borosilicate glass chips is investigated. Two designs of circular cavities are used for fracture strength tests, either 1.6 mm wide with rounded corners to the fluid inlets, or 2.0 mm wide with sharp inlet corners. Two kinds of tests are done, either short-term, e.g. pressurization to fracture at room temperature, or long-term, with fracture at constant pressurization for up to one week, in the temperature region 11–125 °C. The speed of crack fronts is measured using a high-speed camera. Results show fracture stresses in the range of 129 and 254 MPa for short-term measurements. Long-term measurements conclude the presences of a temperature and stress dependent delayed fracture. For a reliability of one week at 11–38 °C, a pressure limit is found at the lower end of the short-term measurements, or 15% lower than the average. At 80 °C, this pressure limit is 45% lower. Crack speeds are measured to be 10‑5 m s‑1 during short-term fracture. These measurements are comparable with estimations based on slow crack growth and show that the growth affects the reliability of glass chips. This effect is strongly affected by high temperatures, thus lowers the operating window of high-pressure glass microfluidic devices.

  1. Achieving High Performance on the i860 Microprocessor

    NASA Technical Reports Server (NTRS)

    Lee, King; Kutler, Paul (Technical Monitor)

    1998-01-01

    The i860 is a high performance microprocessor used in the Intel Touchstone project. This paper proposes a paradigm for programming the i860 that is modelled on the vector instructions of the Cray computers. Fortran callable assembler subroutines were written that mimic the concurrent vector instructions of the Cray. Cache takes the place of vector registers. Using this paradigm we have achieved twice the performance of compiled code on a traditional solve.

  2. Anomalous softening of yield strength in tantalum at high pressures

    SciTech Connect

    Jing, Qiumin Wu, Qiang; Xu, Ji-an; Bi, Yan; Liu, Lei; Liu, Shenggang; Zhang, Yi; Geng, Huayun

    2015-02-07

    The pressure dependence of the yield strength of tantalum was investigated experimentally up to 101 GPa at room temperature using a diamond anvil cell. A yield strength softening is observed between 52 and 84 GPa, whereas a normal trend is observed below 52 GPa and above 84 GPa. The onset pressure of the softening is in agreement with previous results obtained by the pressure gradient method and shock wave experiments. This unusual strength softening in tantalum is not related with structural transformation, preferred orientation, or material damage. Our measurements indicate that microscopic deviatoric strain is the major reason for the observed strength softening in tantalum.

  3. A low-cost hierarchical nanostructured beta-titanium alloy with high strength

    DOE PAGES

    Devaraj, Arun; Joshi, Vineet V.; Srivastava, Ankit; Manandhar, Sandeep; Moxson, Vladimir; Duz, Volodymyr A.; Lavender, Curt

    2016-04-01

    Lightweighting of automobiles by use of novel low-cost, high strength-to-weight ratio structural materials can reduce the consumption of fossil fuels and in turn CO2 emission. Working towards this goal we achieved high strength in a low cost β-titanium alloy, Ti-1Al-8V-5Fe (Ti185), by hierarchical nanostructure consisting of homogenous distribution of micron-scale and nanoscale α-phase precipitates within the β-phase matrix. The sequence of phase transformation leading to this hierarchical nanostructure is explored using electron microscopy and atom probe tomography. Our results suggest that the high number density of nanoscale α-phase precipitates in the β-phase matrix is due to ω assisted nucleation ofmore » α resulting in high tensile strength, greater than any current commercial titanium alloy. Furthermore hierarchical nanostructured Ti185 serves as an excellent candidate for replacing costlier titanium alloys and other structural alloys for cost-effective lightweighting applications.« less

  4. A low-cost hierarchical nanostructured beta-titanium alloy with high strength.

    PubMed

    Devaraj, Arun; Joshi, Vineet V; Srivastava, Ankit; Manandhar, Sandeep; Moxson, Vladimir; Duz, Volodymyr A; Lavender, Curt

    2016-01-01

    Lightweighting of automobiles by use of novel low-cost, high strength-to-weight ratio structural materials can reduce the consumption of fossil fuels and in turn CO2 emission. Working towards this goal we achieved high strength in a low cost β-titanium alloy, Ti-1Al-8V-5Fe (Ti185), by hierarchical nanostructure consisting of homogenous distribution of micron-scale and nanoscale α-phase precipitates within the β-phase matrix. The sequence of phase transformation leading to this hierarchical nanostructure is explored using electron microscopy and atom probe tomography. Our results suggest that the high number density of nanoscale α-phase precipitates in the β-phase matrix is due to ω assisted nucleation of α resulting in high tensile strength, greater than any current commercial titanium alloy. Thus hierarchical nanostructured Ti185 serves as an excellent candidate for replacing costlier titanium alloys and other structural alloys for cost-effective lightweighting applications. PMID:27034109

  5. A low-cost hierarchical nanostructured beta-titanium alloy with high strength

    PubMed Central

    Devaraj, Arun; Joshi, Vineet V.; Srivastava, Ankit; Manandhar, Sandeep; Moxson, Vladimir; Duz, Volodymyr A.; Lavender, Curt

    2016-01-01

    Lightweighting of automobiles by use of novel low-cost, high strength-to-weight ratio structural materials can reduce the consumption of fossil fuels and in turn CO2 emission. Working towards this goal we achieved high strength in a low cost β-titanium alloy, Ti–1Al–8V–5Fe (Ti185), by hierarchical nanostructure consisting of homogenous distribution of micron-scale and nanoscale α-phase precipitates within the β-phase matrix. The sequence of phase transformation leading to this hierarchical nanostructure is explored using electron microscopy and atom probe tomography. Our results suggest that the high number density of nanoscale α-phase precipitates in the β-phase matrix is due to ω assisted nucleation of α resulting in high tensile strength, greater than any current commercial titanium alloy. Thus hierarchical nanostructured Ti185 serves as an excellent candidate for replacing costlier titanium alloys and other structural alloys for cost-effective lightweighting applications. PMID:27034109

  6. Extracting strength from high pressure ramp-release experiments

    SciTech Connect

    Brown, J. L.; Alexander, C. S.; Asay, J. R.; Vogler, T. J.; Ding, J. L.

    2013-12-14

    Unloading from a plastically deformed state has long been recognized as a sensitive measure of a material's deviatoric response. In the case of a ramp compression and unload, time resolved particle velocity measurements of a sample/window interface may be used to gain insight into the sample material's strength. Unfortunately, measurements of this type are often highly perturbed by wave interactions associated with impedance mismatches. Additionally, wave attenuation, the finite pressure range over which the material elastically unloads, and rate effects further complicate the analysis. Here, we present a methodology that overcomes these shortcomings to accurately calculate a mean shear stress near peak compression for experiments of this type. A new interpretation of the self-consistent strength analysis is presented and then validated through the analysis of synthetic data sets on tantalum to 250 GPa. The synthetic analyses suggest that the calculated shear stresses are within 3% of the simulated values obtained using both rate-dependent and rate-independent constitutive models. Window effects are addressed by a new technique referred to as the transfer function approach, where numerical simulations are used to define a mapping to transform the experimental measurements to in situ velocities. The transfer function represents a robust methodology to account for complex wave interactions and a dramatic improvement over the incremental impedance matching methods traditionally used. The technique is validated using experiments performed on both lithium fluoride and tantalum ramp compressed to peak stresses of 10 and 15 GPa, respectively. In each case, various windows of different shock impedance are used to ensure consistency within the transfer function analysis. The data are found to be independent of the window used and in good agreement with previous results.

  7. A promising structure for fabricating high strength and high electrical conductivity copper alloys

    PubMed Central

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-01-01

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application. PMID:26856764

  8. A promising structure for fabricating high strength and high electrical conductivity copper alloys.

    PubMed

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-02-09

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application.

  9. A promising structure for fabricating high strength and high electrical conductivity copper alloys.

    PubMed

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-01-01

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application. PMID:26856764

  10. A high-specific-strength and corrosion-resistant magnesium alloy.

    PubMed

    Xu, Wanqiang; Birbilis, Nick; Sha, Gang; Wang, Yu; Daniels, John E; Xiao, Yang; Ferry, Michael

    2015-12-01

    Ultra-lightweight alloys with high strength, ductility and corrosion resistance are desirable for applications in the automotive, aerospace, defence, biomedical, sporting and electronic goods sectors. Ductility and corrosion resistance are generally inversely correlated with strength, making it difficult to optimize all three simultaneously. Here we design an ultralow density (1.4 g cm(-3)) Mg-Li-based alloy that is strong, ductile, and more corrosion resistant than Mg-based alloys reported so far. The alloy is Li-rich and a solute nanostructure within a body-centred cubic matrix is achieved by a series of extrusion, heat-treatment and rolling processes. Corrosion resistance from the environment is believed to occur by a uniform lithium carbonate film in which surface coverage is much greater than in traditional hexagonal close-packed Mg-based alloys, explaining the superior corrosion resistance of the alloy. PMID:26480229

  11. Experiences of High-Achieving High School Students Who Have Taken Multiple Concurrent Advanced Placement Courses

    ERIC Educational Resources Information Center

    Milburn, Kristine M.

    2011-01-01

    Problem: An increasing number of high-achieving American high school students are enrolling in multiple Advanced Placement (AP) courses. As a result, high schools face a growing need to understand the impact of taking multiple AP courses concurrently on the social-emotional lives of high-achieving students. Procedures: This phenomenological…

  12. Phthalonitrile-Based Carbon Foam with High Specific Mechanical Strength and Superior Electromagnetic Interference Shielding Performance.

    PubMed

    Zhang, Liying; Liu, Ming; Roy, Sunanda; Chu, Eng Kee; See, Kye Yak; Hu, Xiao

    2016-03-23

    Electromagnetic interference (EMI) performance materials are urgently needed to relieve the increasing stress over electromagnetic pollution problems arising from the growing demand for electronic and electrical devices. In this work, a novel ultralight (0.15 g/cm(3)) carbon foam was prepared by direct carbonization of phthalonitrile (PN)-based polymer foam aiming to simultaneously achieve high EMI shielding effectiveness (SE) and deliver effective weight reduction without detrimental reduction of the mechanical properties. The carbon foam prepared by this method had specific compressive strength of ∼6.0 MPa·cm(3)/g. High EMI SE of ∼51.2 dB was achieved, contributed by its intrinsic nitrogen-containing structure (3.3 wt% of nitrogen atoms). The primary EMI shielding mechanism of such carbon foam was determined to be absorption. Moreover, the carbon foams showed excellent specific EMI SE of 341.1 dB·cm(3)/g, which was at least 2 times higher than most of the reported material. The remarkable EMI shielding performance combined with high specific compressive strength indicated that the carbon foam could be considered as a low-density and high-performance EMI shielding material for use in areas where mechanical integrity is desired.

  13. High strength glass-ceramic to metal seals

    SciTech Connect

    Haws, L D; Kramer, D P; Moddeman, W E; Wooten, G W

    1986-12-01

    In many applications, ceramics are joined to other materials, especially metals. In such cases, interfacial strength is as important as the strength of each constituent material. Examples are presented for tailoring materials and processes to optimize the glass-ceramic-to-metal seal. Means for detecting defects, nondestructively, are also identified.

  14. Telescoping Solar Array Concept for Achieving High Packaging Efficiency

    NASA Technical Reports Server (NTRS)

    Mikulas, Martin; Pappa, Richard; Warren, Jay; Rose, Geoff

    2015-01-01

    Lightweight, high-efficiency solar arrays are required for future deep space missions using high-power Solar Electric Propulsion (SEP). Structural performance metrics for state-of-the art 30-50 kW flexible blanket arrays recently demonstrated in ground tests are approximately 40 kW/cu m packaging efficiency, 150 W/kg specific power, 0.1 Hz deployed stiffness, and 0.2 g deployed strength. Much larger arrays with up to a megawatt or more of power and improved packaging and specific power are of interest to mission planners for minimizing launch and life cycle costs of Mars exploration. A new concept referred to as the Compact Telescoping Array (CTA) with 60 kW/cu m packaging efficiency at 1 MW of power is described herein. Performance metrics as a function of array size and corresponding power level are derived analytically and validated by finite element analysis. Feasible CTA packaging and deployment approaches are also described. The CTA was developed, in part, to serve as a NASA reference solar array concept against which other proposed designs of 50-1000 kW arrays for future high-power SEP missions could be compared.

  15. Generating high temperature tolerant transgenic plants: Achievements and challenges.

    PubMed

    Grover, Anil; Mittal, Dheeraj; Negi, Manisha; Lavania, Dhruv

    2013-05-01

    Production of plants tolerant to high temperature stress is of immense significance in the light of global warming and climate change. Plant cells respond to high temperature stress by re-programming their genetic machinery for survival and reproduction. High temperature tolerance in transgenic plants has largely been achieved either by over-expressing heat shock protein genes or by altering levels of heat shock factors that regulate expression of heat shock and non-heat shock genes. Apart from heat shock factors, over-expression of other trans-acting factors like DREB2A, bZIP28 and WRKY proteins has proven useful in imparting high temperature tolerance. Besides these, elevating the genetic levels of proteins involved in osmotic adjustment, reactive oxygen species removal, saturation of membrane-associated lipids, photosynthetic reactions, production of polyamines and protein biosynthesis process have yielded positive results in equipping transgenic plants with high temperature tolerance. Cyclic nucleotide gated calcium channel proteins that regulate calcium influxes across the cell membrane have recently been shown to be the key players in induction of high temperature tolerance. The involvement of calmodulins and kinases in activation of heat shock factors has been implicated as an important event in governing high temperature tolerance. Unfilled gaps limiting the production of high temperature tolerant transgenic plants for field level cultivation are discussed.

  16. Tailoring the dipole properties in dielectric polymers to realize high energy density with high breakdown strength and low dielectric loss

    SciTech Connect

    Thakur, Yash; Lin, Minren; Wu, Shan; Zhang, Q. M. E-mail: qxz1@psu.edu; Cheng, Zhaoxi; Jeong, D.-Y. E-mail: qxz1@psu.edu

    2015-03-21

    High energy density polymer materials are desirable for a broad range of modern power electronic systems. Here, we report the development of a new class of polymer dielectrics based on polyurea and polythiourea, which possess high thermal stability. By increasing the dipole density, the dielectric constant of meta-phenylene polyurea and methylene polythiourea can be increased to 5.7, compared with aromatic polyurea and aromatic polythiourea, which have a dielectric constant in the range of 4.1–4.3. The random dipoles with high dipolar moment and amorphous structure of these polyurea and polythiourea based polymers provide strong scattering to the charge carriers, resulting in low losses even at high electric fields. Consequently, this new class of polymers exhibit a linear dielectric response to the highest field measured (>700 MV/m) with a high breakdown strength, achieving high energy density (>13 J/cm{sup 3}) with high efficiency (>90%)

  17. High-strength and high-ductility nanostructured and amorphous metallic materials.

    PubMed

    Kou, Hongning; Lu, Jian; Li, Ying

    2014-08-20

    The development of materials with dual properties of high strength and high ductility has been a constant challenge since the foundation of the materials science discipline. The rapid progress of nanotechnology in recent decades has further brought this challenge to a new era. This Research News highlights a few newly developed strategies to optimize advanced nanomaterials and metallic glasses with exceptional dual mechanical properties of high strength and high ductility. A general concept of strain non-localization is presented to describe the role of multiscale (i.e., macroscale, microscale, nanoscale, and atomic scale) heterogeneities in the ductility enhancement of materials reputed to be intrinsically brittle, such as nanostructured metallic materials and bulk metallic glasses. These nanomaterials clearly form a new group of materials that display an extraordinary relationship between yield strength and the uniform elongation with the same chemical composition. Several other examples of nanomaterials such as those reinforced by nanoprecipitates will also be described.

  18. High-strength alloy with resistance to hydrogen-environment embrittlement

    NASA Technical Reports Server (NTRS)

    Mcnamara, T. G.

    1975-01-01

    Alloy is precipitation-hardened, high-strength, and low-thermal-expansion materials. It is iron-based and contains nickel and chromium at lower levels than high-strength alloys. It is readily welded and brazed and has good oxidation resistance. Tests indicated there was no reduction of notched or smooth strength.

  19. Orbital Winch for High-Strength, Space-Survivable Tethers

    NASA Technical Reports Server (NTRS)

    Hoyt, Robert; Barnes, Ian; Slostad, Jeffrey; Frank, Scott

    2010-01-01

    An Orbital Winch mechanism enables high-load, multi-line tethers to be deployed and retracted without rotating the spool on which the tether is wound. To minimize damage to the tether and the wound package during retraction or deployment under load, it can incorporate a Tension Management Module that reduces the infeed tension by a factor of 15 through the use of a powered capstan with guide rollers. This design eliminates the need for rotating high-voltage electrical connections in tether systems that use propellantless electro-dynamic propulsion. It can also eliminate the need for rotating optical connections in applications where the tether contains optical fibers. This winch design was developed to deploy a 15-km-long, 15-kg high-strength Hoytether structure incorporating conductive wires as part of the MXER-1 demonstration mission concept. Two slewing rings that orbit around the tether spool, combined with translation of one of the slewing rings back and forth along the spool axis to traverse the wind point, enables the winch to wind the tether. Variations of the traverse motion of the slewing ring can accomplish level winds and conical pirn winds. By removing the non-traversing slewing ring, and adding an actuated guide arm, the winch can manage rapid, low-drag deployment of a tether off the end of a pirn-wound spool, followed by controlled retraction and rewinding, in a manner very similar to a spin-casting reel. The winch requires at least two motor driver controller units to coordinate the action of two stepper motors to accomplish tether deployment or retraction.

  20. High-strength transparent spinel with fine, unimodal grain size

    NASA Astrophysics Data System (ADS)

    Sweeney, S. M.; Brun, M. K.; Yosenick, T. J.; Kebbede, A.; Manoharan, M.

    2009-05-01

    Spinel (MgAl2O4) is a good candidate material for transparent armor and IR window applications. Traditionally, transparent spinel has suffered from poor strength and difficult polishing owing to its large, bimodal grain structure. Starting from a spinel nanopowder, spinel ceramics with a grain size of less than 2 microns have been made with better than 80% in-line transmittance at 632 nm wavelength for 3/8" thick samples. A ring-on-ring test has been used to measure biaxial flexural strength on samples machined to 0.8 mm thickness. The average strength was found to exceed 480 MPa.

  1. A lightweight, high strength dexterous manipulator for commercial applications

    NASA Technical Reports Server (NTRS)

    Marzwell, Neville I.; Schena, Bruce M.; Cohan, Steve M.

    1991-01-01

    The concept, design, and features are described of a lightweight, high strength, modular robot manipulator being developed for space and commercial applications. The manipulator has seven fully active degrees of freedom and is fully operational in 1 G. Each of the seven joints incorporates a unique drivetrain design which provides zero backlash operation, is insensitive to wear, and is single fault tolerant to motor or servo amplifier failure. Feedback sensors provide position, velocity, torque, and motor winding temperature information at each joint. This sensing system is also designed to be single fault tolerant. The manipulator consists of five modules (not including gripper). These modules join via simple quick-disconnect couplings and self-mating connectors which allow rapid assembly and/or disassembly for reconfiguration, transport, or servicing. The manipulator is a completely enclosed assembly, with no exposed components or wires. Although the initial prototype will not be space qualified, the design is well suited to meeting space requirements. The control system provides dexterous motion by controlling the endpoint location and arm pose simultaneously. Potential applications are discussed.

  2. Thermal Desorption Analysis of Hydrogen in High Strength Martensitic Steels

    NASA Astrophysics Data System (ADS)

    Enomoto, M.; Hirakami, D.; Tarui, T.

    2012-02-01

    Thermal desorption analyses (TDA) were conducted in high strength martensitic steels containing carbon from 0.33 to 1.0 mass pct, which were charged with hydrogen at 1223 K (950 °C) under hydrogen of one atmospheric pressure and quenched to room temperature. In 0.33C steel, which had the highest M s temperature, only one desorption peak was observed around 373 K (100 °C), whereas two peaks, one at a similar temperature and the other around and above 573 K (300 °C), were observed in the other steels, the height of the second peak increasing with carbon content. In 0.82C steel, both peaks disappeared during exposure at room temperature in 1 week, whereas the peak heights decreased gradually over 2 weeks in specimens electrolytically charged with hydrogen and aged for varying times at room temperature. From computer simulation, by means of the McNabb-Foster theory coupled with theories of carbon segregation, these peaks are likely to be due to trapping of hydrogen in the strain fields and cores of dislocations, and presumably to a lesser extent in prior austenite grain boundaries. The results also indicate that carbon atoms prevent and even expel hydrogen from trapping sites during quenching and aging in these steels.

  3. Anomolous Fatigue Crack Growth Phenomena in High-Strength Steel

    NASA Technical Reports Server (NTRS)

    Forth, Scott C.; James, Mark A.; Johnston, William M., Jr.; Newman, James C., Jr.

    2004-01-01

    The growth of a fatigue crack through a material is the result of a complex interaction between the applied loading, component geometry, three-dimensional constraint, load history, environment, material microstructure and several other factors. Previous studies have developed experimental and computational methods to relate the fatigue crack growth rate to many of the above conditions, with the intent of discovering some fundamental material response, i.e. crack growth rate as a function of something. Currently, the technical community uses the stress intensity factor solution as a simplistic means to relate fatigue crack growth rate to loading, geometry and all other variables. The stress intensity factor solution is a very simple linear-elastic representation of the continuum mechanics portion of crack growth. In this paper, the authors present fatigue crack growth rate data for two different high strength steel alloys generated using standard methods. The steels exhibit behaviour that appears unexplainable, compared to an aluminium alloy presented as a baseline for comparison, using the stress intensity factor solution.

  4. Titanium cholla : lightweight, high-strength structures for aerospace applications.

    SciTech Connect

    Atwood, Clinton J.; Voth, Thomas Eugene; Taggart, David G.; Gill, David Dennis; Robbins, Joshua H.; Dewhurst, Peter

    2007-10-01

    Aerospace designers seek lightweight, high-strength structures to lower launch weight while creating structures that are capable of withstanding launch loadings. Most 'light-weighting' is done through an expensive, time-consuming, iterative method requiring experience and a repeated design/test/redesign sequence until an adequate solution is obtained. Little successful work has been done in the application of generalized 3D optimization due to the difficulty of analytical solutions, the large computational requirements of computerized solutions, and the inability to manufacture many optimized structures with conventional machining processes. The Titanium Cholla LDRD team set out to create generalized 3D optimization routines, a set of analytically optimized 3D structures for testing the solutions, and a method of manufacturing these complex optimized structures. The team developed two new computer optimization solutions: Advanced Topological Optimization (ATO) and FlexFEM, an optimization package utilizing the eXtended Finite Element Method (XFEM) software for stress analysis. The team also developed several new analytically defined classes of optimized structures. Finally, the team developed a 3D capability for the Laser Engineered Net Shaping{trademark} (LENS{reg_sign}) additive manufacturing process including process planning for 3D optimized structures. This report gives individual examples as well as one generalized example showing the optimized solutions and an optimized metal part.

  5. High strength bioactive glass-ceramic scaffolds for bone regeneration.

    PubMed

    Vitale-Brovarone, Chiara; Baino, Francesco; Verné, Enrica

    2009-02-01

    This research work is focused on the preparation of macroporous glass-ceramic scaffolds with high mechanical strength, equivalent with cancellous bone. The scaffolds were prepared using an open-cells polyurethane sponge as a template and glass powders belonging to the system SiO(2)-P(2)O(5)-CaO-MgO-Na(2)O-K(2)O. The glass, named as CEL2, was synthesized by a conventional melting-quenching route, ground and sieved to obtain powders of specific size. A slurry of CEL2 powders, polyvinyl alcohol (PVA) as a binder and water was prepared in order to coat, by a process of impregnation, the polymeric template. A thermal treatment was then used to remove the sponge and to sinter the glass powders, in order to obtain a replica of the template structure. The scaffolds were characterized by means of X-ray diffraction analysis, morphological observations, density measurements, volumetric shrinkage, image analysis, capillarity tests, mechanical tests and in vitro bioactivity evaluation.

  6. Cleavage fracture in high strength low alloy weld metal

    SciTech Connect

    Bose, W.W.; Bowen, P.; Strangwood, M.

    1996-12-31

    The present investigation gives an evaluation of the effect of microstructure on the cleavage fracture process of High Strength Low Alloy (HSLA) multipass weld metals. With additions of alloying elements, such as Ti, Ni, Mo and Cr, the microstructure of C-Mn weld metal changes from the classical composition, i.e., allotriomorphic ferrite with acicular ferrite and Widmanstaetten ferrite, to bainite and low carbon martensite. Although the physical metallurgy of some HSLA weld metals has been studied before, more work is necessary to correlate the effect of the microstructure on the fracture behavior of such weld metals. In this work detailed microstructural analysis was carried out using optical and electron (SEM and TEM) microscopy. Single edge notched (SEN) bend testpieces were used to assess the cleavage fracture stress, {sigma}{sub F}. Inclusions beneath the notch surface were identified as the crack initiators of unstable cleavage fracture. From the size of such inclusions and the value of tensile stress predicted at the initiation site, the effective surface energy for cleavage was calculated using a modified Griffth energy balance for a penny shape crack. The results suggest that even though inclusions initiate cleavage fracture, the local microstructure may play an important role in the fracture process of these weld metals. The implications of these observations for a quantitative theory of the cleavage fracture of ferritic steels is discussed.

  7. Unlocking Emergent Talent: Supporting High Achievement of Low-Income, High Ability Students

    ERIC Educational Resources Information Center

    Olszewski-Kubilius, Paula; Clarenbach, Jane

    2012-01-01

    This report takes a comprehensive look at achievement for low-income promising learners--past, present, and future. At its core, it challenges the nation to move beyond its near-singular focus of achieving minimum performance for all students, to identifying and developing the talent of all students who are capable of high achievement, including…

  8. Polyimide films from vapor deposition: toward high strength, NIF capsules

    SciTech Connect

    Cook, R C; Hsieh, E J; Letts, S A; Roberts, C C; Saculla, M

    1998-10-16

    The focus of recent efforts at LLNL has been to demonstrate that vapor deposition processing is a suitable technique to form polyimide fnms with sufficient strength for current national ignition facility target specifications. Production of polyimide films with controlled stoichiometry was acccomplished by: 1) depositing a novel co-functional monomer and 2) matching the vapor pressure of each monomer in PMDA/ODA co-depositions. The sublimation and deposition rate for the monomers was determined over a range of temperatures. Polyimide films with thicknesses up to 30 p.m were fabricated. Composition, structure and strength were assessed using FTIR, SEM and biaxial burst testing. The best films had a tensile strength of approximately 100 MPa. A qualitative relationship between the stoichiometry and tensile strength of the film was demonstrated. Thin films ({approximately}3.5 {micro}m) were typically smooth with an rms of 1.5 nm.

  9. High field strength (4.7T) magnetic resonance imaging of hydrocephalus in an African Grey parrot (Psittacus erithacus).

    PubMed

    Fleming, Gregory J; Lester, Nola V; Stevenson, Rhoda; Silver, Xeve S

    2003-01-01

    Hydrocephalus was diagnosed in a juvenile African Grey parrot by high-field strength (4.7-Tesla) magnetic resonance imaging (MRI). Excellent anatomic detail was achieved, and there was severe dilation of all ventricles. Relative obstruction was localized to the level of or beyond the outflow of the fourth ventricle. There have been several reports of hydrocephalus diagnosed postmortem in psittacines (i.e., hook-billed parrots), however, this is the first report of an antemortem diagnosis in a psittacine using high-field strength MRI.

  10. Monitoring deep twist drilling for a rapid manufacturing of light high-strength parts

    NASA Astrophysics Data System (ADS)

    López de Lacalle, L. N.; Fernández, A.; Olvera, D.; Lamikiz, A.; Olvera, D.; Rodríguez, C.; Elias, A.

    2011-10-01

    In this work the manufacturing of high strength and/or high functional components is presented, using a new technique based on considerably long twist drills, called Deep Twist Drilling (DTD). This technology opens a rapid and economical method to manufacture parts for structural applications. Components made with this technique can reach high mass reduction and better stress distribution in comparison with welding or bolted parts with the same weight. However the application of DTD must be optimized to improve the reliability of the process and to make it economically feasible. In order to reach it, previous optimization by process monitoring was performed in AISI 1045, stainless steels, Ti6Al4V and nodular cat iron GGG70(AISI A536, SAE-ASTM 100-70-03). These materials are commonly used for structural applications in several sectors. Monitoring opened the way to improve cutting conditions and allow the application of the DTD technique focusing on a new design concept. In the same way monitoring makes drilling process reliable enough to be systematically used in industrial applications by a controlled increase of the performance demanded from the tool. In this manner, not only the objective to produce high-strength and light pieces is achieved, but also a high repetitive process is reached. In this research work a case of study is presented. A monolithic satellite-type component, its mass were reduced from 25 to 4.5 kg. The structural behavior of the component was studied under FEM analysis and the results showed high strength to compression and shear forces. During the machining of this element there was a serious risk of drill breakage due to the depth of the holes and crossing points between them; however, the previous process optimization eliminated this drawback. As a matter of fact, this paper brings out a good example where manufacturing technology allows a better performance of mechanical components within the philosophy of "new processes drive to new

  11. Achieving High Resolution Timer Events in Virtualized Environment

    PubMed Central

    Adamczyk, Blazej; Chydzinski, Andrzej

    2015-01-01

    Virtual Machine Monitors (VMM) have become popular in different application areas. Some applications may require to generate the timer events with high resolution and precision. This however may be challenging due to the complexity of VMMs. In this paper we focus on the timer functionality provided by five different VMMs—Xen, KVM, Qemu, VirtualBox and VMWare. Firstly, we evaluate resolutions and precisions of their timer events. Apparently, provided resolutions and precisions are far too low for some applications (e.g. networking applications with the quality of service). Then, using Xen virtualization we demonstrate the improved timer design that greatly enhances both the resolution and precision of achieved timer events. PMID:26177366

  12. Achieving High Resolution Timer Events in Virtualized Environment.

    PubMed

    Adamczyk, Blazej; Chydzinski, Andrzej

    2015-01-01

    Virtual Machine Monitors (VMM) have become popular in different application areas. Some applications may require to generate the timer events with high resolution and precision. This however may be challenging due to the complexity of VMMs. In this paper we focus on the timer functionality provided by five different VMMs-Xen, KVM, Qemu, VirtualBox and VMWare. Firstly, we evaluate resolutions and precisions of their timer events. Apparently, provided resolutions and precisions are far too low for some applications (e.g. networking applications with the quality of service). Then, using Xen virtualization we demonstrate the improved timer design that greatly enhances both the resolution and precision of achieved timer events. PMID:26177366

  13. Design considerations for achieving high vacuum integrity in fusion devices

    SciTech Connect

    Fuller, G.M.; Haines, J.R.

    1983-01-01

    Achieving high vacuum integrity in fusion devices requires close attention to both the overall system configuration and the design details of joints and seals. This paper describes the factors in selecting the system configuration, from a vacuum standpoint, for the Princeton Plasma Physics Laboratory (PPPL) DCT-8 Tokamak device. The DCT-8 (driven current tokamak) is the eighth design in a series of tokamak concepts defined to cover the magnetic confinement and development gap between the Tokamak Fusion Test Reactor (TFTR) and the Engineering Test Reactor (ETR). Leak detection concept development is considered a vital activity, as well as the definition of a configuration that minimizes the consequences of leaks. A major part of the vacuum boundaries of the magnet system and the plasma system is common. For the major penetrations, primary and secondary seals are provided with vacuum control over the region between seals. The intent is to instrument these cavities and provide automated recordings of these measurements for leak maintenance.

  14. Achieving ultra-high temperatures with a resistive emitter array

    NASA Astrophysics Data System (ADS)

    Danielson, Tom; Franks, Greg; Holmes, Nicholas; LaVeigne, Joe; Matis, Greg; McHugh, Steve; Norton, Dennis; Vengel, Tony; Lannon, John; Goodwin, Scott

    2016-05-01

    The rapid development of very-large format infrared detector arrays has challenged the IR scene projector community to also develop larger-format infrared emitter arrays to support the testing of systems incorporating these detectors. In addition to larger formats, many scene projector users require much higher simulated temperatures than can be generated with current technology in order to fully evaluate the performance of their systems and associated processing algorithms. Under the Ultra High Temperature (UHT) development program, Santa Barbara Infrared Inc. (SBIR) is developing a new infrared scene projector architecture capable of producing both very large format (>1024 x 1024) resistive emitter arrays and improved emitter pixel technology capable of simulating very high apparent temperatures. During earlier phases of the program, SBIR demonstrated materials with MWIR apparent temperatures in excess of 1400 K. New emitter materials have subsequently been selected to produce pixels that achieve even higher apparent temperatures. Test results from pixels fabricated using the new material set will be presented and discussed. A 'scalable' Read In Integrated Circuit (RIIC) is also being developed under the same UHT program to drive the high temperature pixels. This RIIC will utilize through-silicon via (TSV) and Quilt Packaging (QP) technologies to allow seamless tiling of multiple chips to fabricate very large arrays, and thus overcome the yield limitations inherent in large-scale integrated circuits. Results of design verification testing of the completed RIIC will be presented and discussed.

  15. TRP 9904 - Constitutive Behavior of High Strength Multiphase Sheel Steel Under High Strain Rate Deformation

    SciTech Connect

    David Matlock; John Speer

    2005-03-31

    The focus of the research project was to systematically assess the strain rate dependence of strengthening mechanisms in new advanced high strength sheet steels. Data were obtained on specially designed and produced Duel Phase and TRIP steels and compared to the properties of automotive steels currently in use.

  16. Large-deformation and high-strength amorphous porous carbon nanospheres

    NASA Astrophysics Data System (ADS)

    Yang, Weizhu; Mao, Shimin; Yang, Jia; Shang, Tao; Song, Hongguang; Mabon, James; Swiech, Wacek; Vance, John R.; Yue, Zhufeng; Dillon, Shen J.; Xu, Hangxun; Xu, Baoxing

    2016-04-01

    Carbon is one of the most important materials extensively used in industry and our daily life. Crystalline carbon materials such as carbon nanotubes and graphene possess ultrahigh strength and toughness. In contrast, amorphous carbon is known to be very brittle and can sustain little compressive deformation. Inspired by biological shells and honeycomb-like cellular structures in nature, we introduce a class of hybrid structural designs and demonstrate that amorphous porous carbon nanospheres with a thin outer shell can simultaneously achieve high strength and sustain large deformation. The amorphous carbon nanospheres were synthesized via a low-cost, scalable and structure-controllable ultrasonic spray pyrolysis approach using energetic carbon precursors. In situ compression experiments on individual nanospheres show that the amorphous carbon nanospheres with an optimized structure can sustain beyond 50% compressive strain. Both experiments and finite element analyses reveal that the buckling deformation of the outer spherical shell dominates the improvement of strength while the collapse of inner nanoscale pores driven by twisting, rotation, buckling and bending of pore walls contributes to the large deformation.

  17. Large-deformation and high-strength amorphous porous carbon nanospheres.

    PubMed

    Yang, Weizhu; Mao, Shimin; Yang, Jia; Shang, Tao; Song, Hongguang; Mabon, James; Swiech, Wacek; Vance, John R; Yue, Zhufeng; Dillon, Shen J; Xu, Hangxun; Xu, Baoxing

    2016-01-01

    Carbon is one of the most important materials extensively used in industry and our daily life. Crystalline carbon materials such as carbon nanotubes and graphene possess ultrahigh strength and toughness. In contrast, amorphous carbon is known to be very brittle and can sustain little compressive deformation. Inspired by biological shells and honeycomb-like cellular structures in nature, we introduce a class of hybrid structural designs and demonstrate that amorphous porous carbon nanospheres with a thin outer shell can simultaneously achieve high strength and sustain large deformation. The amorphous carbon nanospheres were synthesized via a low-cost, scalable and structure-controllable ultrasonic spray pyrolysis approach using energetic carbon precursors. In situ compression experiments on individual nanospheres show that the amorphous carbon nanospheres with an optimized structure can sustain beyond 50% compressive strain. Both experiments and finite element analyses reveal that the buckling deformation of the outer spherical shell dominates the improvement of strength while the collapse of inner nanoscale pores driven by twisting, rotation, buckling and bending of pore walls contributes to the large deformation.

  18. Effects of Oil Palm Shell Coarse Aggregate Species on High Strength Lightweight Concrete

    PubMed Central

    Yew, Ming Kun; Bin Mahmud, Hilmi; Ang, Bee Chin; Yew, Ming Chian

    2014-01-01

    The objective of this study was to investigate the effects of different species of oil palm shell (OPS) coarse aggregates on the properties of high strength lightweight concrete (HSLWC). Original and crushed OPS coarse aggregates of different species and age categories were investigated in this study. The research focused on two OPS species (dura and tenera), in which the coarse aggregates were taken from oil palm trees of the following age categories (3–5, 6–9, and 10–15 years old). The results showed that the workability and dry density of the oil palm shell concrete (OPSC) increase with an increase in age category of OPS species. The compressive strength of specimen CD3 increases significantly compared to specimen CT3 by 21.8%. The maximum achievable 28-day and 90-day compressive strength is 54 and 56 MPa, respectively, which is within the range for 10–15-year-old crushed dura OPS. The water absorption was determined to be within the range for good concrete for the different species of OPSC. In addition, the ultrasonic pulse velocity (UPV) results showed that the OPS HSLWC attain good condition at the age of 3 days. PMID:24982946

  19. Large-deformation and high-strength amorphous porous carbon nanospheres.

    PubMed

    Yang, Weizhu; Mao, Shimin; Yang, Jia; Shang, Tao; Song, Hongguang; Mabon, James; Swiech, Wacek; Vance, John R; Yue, Zhufeng; Dillon, Shen J; Xu, Hangxun; Xu, Baoxing

    2016-01-01

    Carbon is one of the most important materials extensively used in industry and our daily life. Crystalline carbon materials such as carbon nanotubes and graphene possess ultrahigh strength and toughness. In contrast, amorphous carbon is known to be very brittle and can sustain little compressive deformation. Inspired by biological shells and honeycomb-like cellular structures in nature, we introduce a class of hybrid structural designs and demonstrate that amorphous porous carbon nanospheres with a thin outer shell can simultaneously achieve high strength and sustain large deformation. The amorphous carbon nanospheres were synthesized via a low-cost, scalable and structure-controllable ultrasonic spray pyrolysis approach using energetic carbon precursors. In situ compression experiments on individual nanospheres show that the amorphous carbon nanospheres with an optimized structure can sustain beyond 50% compressive strain. Both experiments and finite element analyses reveal that the buckling deformation of the outer spherical shell dominates the improvement of strength while the collapse of inner nanoscale pores driven by twisting, rotation, buckling and bending of pore walls contributes to the large deformation. PMID:27072412

  20. Large-deformation and high-strength amorphous porous carbon nanospheres

    PubMed Central

    Yang, Weizhu; Mao, Shimin; Yang, Jia; Shang, Tao; Song, Hongguang; Mabon, James; Swiech, Wacek; Vance, John R.; Yue, Zhufeng; Dillon, Shen J.; Xu, Hangxun; Xu, Baoxing

    2016-01-01

    Carbon is one of the most important materials extensively used in industry and our daily life. Crystalline carbon materials such as carbon nanotubes and graphene possess ultrahigh strength and toughness. In contrast, amorphous carbon is known to be very brittle and can sustain little compressive deformation. Inspired by biological shells and honeycomb-like cellular structures in nature, we introduce a class of hybrid structural designs and demonstrate that amorphous porous carbon nanospheres with a thin outer shell can simultaneously achieve high strength and sustain large deformation. The amorphous carbon nanospheres were synthesized via a low-cost, scalable and structure-controllable ultrasonic spray pyrolysis approach using energetic carbon precursors. In situ compression experiments on individual nanospheres show that the amorphous carbon nanospheres with an optimized structure can sustain beyond 50% compressive strain. Both experiments and finite element analyses reveal that the buckling deformation of the outer spherical shell dominates the improvement of strength while the collapse of inner nanoscale pores driven by twisting, rotation, buckling and bending of pore walls contributes to the large deformation. PMID:27072412

  1. Effects of oil palm shell coarse aggregate species on high strength lightweight concrete.

    PubMed

    Yew, Ming Kun; Bin Mahmud, Hilmi; Ang, Bee Chin; Yew, Ming Chian

    2014-01-01

    The objective of this study was to investigate the effects of different species of oil palm shell (OPS) coarse aggregates on the properties of high strength lightweight concrete (HSLWC). Original and crushed OPS coarse aggregates of different species and age categories were investigated in this study. The research focused on two OPS species (dura and tenera), in which the coarse aggregates were taken from oil palm trees of the following age categories (3-5, 6-9, and 10-15 years old). The results showed that the workability and dry density of the oil palm shell concrete (OPSC) increase with an increase in age category of OPS species. The compressive strength of specimen CD3 increases significantly compared to specimen CT3 by 21.8%. The maximum achievable 28-day and 90-day compressive strength is 54 and 56 MPa, respectively, which is within the range for 10-15-year-old crushed dura OPS. The water absorption was determined to be within the range for good concrete for the different species of OPSC. In addition, the ultrasonic pulse velocity (UPV) results showed that the OPS HSLWC attain good condition at the age of 3 days. PMID:24982946

  2. High-strength high-conductivity Cu-Nb microcomposite sheet fabricated via multiple roll bonding

    NASA Astrophysics Data System (ADS)

    Jha, S. C.; Delagi, R. G.; Forster, J. A.; Krotz, P. D.

    1993-01-01

    Copper-niobium microcomposites are a new class of high-strength high-conductivity materials that have attractive properties for room- and elevated-temperature applications. Since Nb has little solid solubility in Cu, addition of Nb to Cu does not affect its conductivity. Copper-niobium microcomposites are melted and cast so that the microstructure of cast Cu-Nb ingots consists of 1-to 10 μm Nb dendrites uniformly distributed within the copper matrix. Extensive wire drawing with a true processing strain ( η > 12) of Cu-Nb alloy leads to refinement and elongation of Nb dendrites into 1-to 10 nm-thick filaments. The presence of such fine Nb filaments causes a significant increase in the strength of Cu-Nb wires. The tensile strength of heavily drawn Cu-Nb wires was determined to be significantly higher than the values predicted by the rule of mixtures. This article reports the fabrication of high-strength Cu-Nb micro-composite sheet by multiple roll bonding. It is difficult and impractical to attain high processing strains ( η > 3) by simple cold rolling. In most practical cold-rolling operation, the thickness reduction does not exceed 90 pct ( η ≅ 2). Therefore, innovative processing is required to generate high strength in Cu-Nb microcomposite sheet. Multiple roll bonding of Cu-Nb has been utilized to store high processing strain ( η > 10) in the material and refine the Nb particle size within the copper matrix. This article describes the microstructure, mechanical properties, and thermal stability of roll-bonded Cu-Nb microcomposite sheet.

  3. Growing the Seeds of Strength in High Risk Urban Neighborhoods.

    ERIC Educational Resources Information Center

    Saegert, Susan

    The lives of poor minority city residents demonstrate the diversity, multiple potentials, and vulnerability to external structures. In spite of the stereotypes of failure and the very real problems of the urban poor, there are many strengths among the so-called urban underclass and there are aspects of life that are successful and productive. In…

  4. High-pressure reactions and shear strength of serpentinized dunite.

    PubMed

    Sclar, C B; Carrison, L C; Rooney, T P; Riecker, R E

    1966-09-01

    The recently reported Pronounced decrease in shear strength of serpentine-bearing rocks at 30 to 40 kilobars in the temperature range 300 degrees to 520 degrees C may be attributed to the transformation of serpentine to a Pressure-dependent, 10-angstrom,2: 1 layer silicate plus brucite and periclase. This reaction increases density by about 8.5 percent. PMID:17754251

  5. How to achieve high-level expression of microbial enzymes

    PubMed Central

    Liu, Long; Yang, Haiquan; Shin, Hyun-dong; Chen, Rachel R.; Li, Jianghua; Du, Guocheng; Chen, Jian

    2013-01-01

    Microbial enzymes have been used in a large number of fields, such as chemical, agricultural and biopharmaceutical industries. The enzyme production rate and yield are the main factors to consider when choosing the appropriate expression system for the production of recombinant proteins. Recombinant enzymes have been expressed in bacteria (e.g., Escherichia coli, Bacillus and lactic acid bacteria), filamentous fungi (e.g., Aspergillus) and yeasts (e.g., Pichia pastoris). The favorable and very advantageous characteristics of these species have resulted in an increasing number of biotechnological applications. Bacterial hosts (e.g., E. coli) can be used to quickly and easily overexpress recombinant enzymes; however, bacterial systems cannot express very large proteins and proteins that require post-translational modifications. The main bacterial expression hosts, with the exception of lactic acid bacteria and filamentous fungi, can produce several toxins which are not compatible with the expression of recombinant enzymes in food and drugs. However, due to the multiplicity of the physiological impacts arising from high-level expression of genes encoding the enzymes and expression hosts, the goal of overproduction can hardly be achieved, and therefore, the yield of recombinant enzymes is limited. In this review, the recent strategies used for the high-level expression of microbial enzymes in the hosts mentioned above are summarized and the prospects are also discussed. We hope this review will contribute to the development of the enzyme-related research field. PMID:23686280

  6. Weld Metallurgy and Mechanical Properties of High Manganese Ultra-high Strength Steel Dissimilar Welds

    NASA Astrophysics Data System (ADS)

    Dahmen, Martin; Lindner, Stefan; Monfort, Damien; Petring, Dirk

    The increasing demand for ultra-high strength steels in vehicle manufacturing leads to the application of new alloys. This poses a challenge on joining especially by fusion welding. A stainless high manganese steel sheet with excellent strength and deformation properties stands in the centre of the development. Similar and dissimilar welds with a metastable austenitic steel and a hot formed martensitic stainless steel were performed. An investigation of the mixing effects on the local microstructure and the hardness delivers the metallurgical features of the welds. Despite of carbon contents above 0.4 wt.% none of the welds have shown cracks. Mechanical properties drawn from tensile tests deliver high breaking forces enabling a high stiffness of the joints. The results show the potential for the application of laser beam welding for joining in assembly of structural parts.

  7. High strength-high conductivity Cu--Fe composites produced by powder compaction/mechanical reduction

    DOEpatents

    Verhoeven, John D.; Spitzig, William A.; Gibson, Edwin D.; Anderson, Iver E.

    1991-08-27

    A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an "in-situ" Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite.

  8. High strength-high conductivity Cu-Fe composites produced by powder compaction/mechanical reduction

    DOEpatents

    Verhoeven, J.D.; Spitzig, W.A.; Gibson, E.D.; Anderson, I.E.

    1991-08-27

    A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an ''in-situ'' Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite. 5 figures.

  9. Comparison of the Level of Using Metacognitive Strategies during Study between High Achieving and Low Achieving Prospective Teachers

    ERIC Educational Resources Information Center

    Doganay, Ahmet; Demir, Ozden

    2011-01-01

    The main purpose of this study is to compare the level of using metacognitive strategies during study between high achieving and low achieving prospective classroom teachers. This study was designed as a mixed method study. Metacognitive Learning Strategies Scale developed by Namlu (2004) was used to measure the use of metacognitive strategies…

  10. Effects of Partner's Ability on the Achievement and Conceptual Organization of High-Achieving Fifth-Grade Students.

    ERIC Educational Resources Information Center

    Carter, Glenda; Jones, M. Gail; Rua, Melissa

    2003-01-01

    Investigates high-achieving fifth-grade students' achievement gains and conceptual reorganization on convection. Features an instructional sequence of three dyadic inquiry investigations related to convection currents as well as pre- and post-assessment consisting of a multiple-choice test, a card sorting task, construction of a concept map, and…

  11. Gender Differences in Attitudes toward Mathematics between Low-Achieving and High-Achieving Fifth Grade Elementary Students.

    ERIC Educational Resources Information Center

    Rathbone, A. Sue

    Possible gender differences in attitudes toward mathematics were studied between low-achieving and high-achieving fifth-grade students in selected elementary schools within a large, metropolitan area. The attitudes of pre-adolescent children at an intermediate grade level were assessed to determine the effects of rapidly emerging gender-related…

  12. High breakdown-strength composites from liquid silicone rubbers

    NASA Astrophysics Data System (ADS)

    Vudayagiri, Sindhu; Zakaria, Shamsul; Yu, Liyun; Sager Hassouneh, Suzan; Benslimane, Mohamed; Ladegaard Skov, Anne

    2014-10-01

    In this paper we investigate the performance of liquid silicone rubbers (LSRs) as dielectric elastomer transducers. Commonly used silicones in this application include room-temperature vulcanisable (RTV) silicone elastomers and composites thereof. Pure LSRs and their composites with commercially available fillers (an anatase TiO2, a core-shell TiO2-SiO2 and a CaCu3Ti4O12 filler) are evaluated with respect to dielectric permittivity, elasticity (Young’s modulus) and electrical breakdown strength. Film formation properties are also evaluated. The best-performing formulations are those with anatase TiO2 nanoparticles, where the highest relative dielectric permittivity of 5.6 is obtained, and with STX801, a core-shell morphology TiO2-SiO2 filler from Evonik, where the highest breakdown strength of 173 V μm-1 is obtained.

  13. High strength and high ductility behavior of 6061-T6 alloy after laser shock processing

    NASA Astrophysics Data System (ADS)

    Gencalp Irizalp, Simge; Saklakoglu, Nursen

    2016-02-01

    The plastic deformation behavior of 6061-T6 alloy which was subjected to severe plastic deformation (SPD) at high strain rates during laser shock processing (LSP) was researched. In LSP-treated materials, the near surface microstructural change was examined by TEM and fracture surfaces after tensile testing were examined by SEM. An increase in strength of metallic materials brings about the decrease in ductility. In this study, the results showed that LSP-treated 6061-T6 alloy exhibited both high strength and high ductility. TEM observation showed that stacking fault (SF) ribbon enlarged, deformation twins formed and twin boundary increased in LSP-treated 6061-T6 alloy. This observation was an indication of stacking fault energy (SFE) decrease. Work hardening capability was recovered after LSP impacts.

  14. The issues and tentative solutions for contrast-enhanced magnetic resonance imaging at ultra-high field strength.

    PubMed

    Fries, Peter; Morelli, John N; Lux, Francois; Tillement, Olivier; Schneider, Günther; Buecker, Arno

    2014-01-01

    Magnetic resonance imaging (MRI) performed at ultra-high field strengths beyond 3 Tesla (T) has become increasingly prevalent in research and preclinical applications. As such, the inevitable clinical implementation of such systems lies on the horizon. The major benefit of ultra-high field MRI is the markedly increased signal-to-noise ratios achievable, enabling acquisition of MR images with simultaneously greater spatial and temporal resolution. However, at field strengths higher than 3 T, the efficacy of Gd(III)-based contrast agents is diminished due to decreased r1 relaxivity, somewhat limiting imaging of the vasculature and contrast-enhanced imaging of tumors. There have been extensive efforts to design new contrast agents with high r1 relaxivities based on macromolecular compounds or nanoparticles; however, the efficacy of these agents at ultra-high field strengths has not yet been proven. The aim of this review article is to provide an overview of the basic principles of MR contrast enhancement processes and to highlight the main factors influencing relaxivity. In addition, challenges and opportunities for contrast-enhanced MRI at ultra-high field strengths will be explored. Various approaches for the development of effective contrast agent molecules that are suitable for a broad spectrum of applied field strengths will be discussed in the context of the current literature.

  15. Achieving High Throughput for Data Transfer over ATM Networks

    NASA Technical Reports Server (NTRS)

    Johnson, Marjory J.; Townsend, Jeffrey N.

    1996-01-01

    File-transfer rates for ftp are often reported to be relatively slow, compared to the raw bandwidth available in emerging gigabit networks. While a major bottleneck is disk I/O, protocol issues impact performance as well. Ftp was developed and optimized for use over the TCP/IP protocol stack of the Internet. However, TCP has been shown to run inefficiently over ATM. In an effort to maximize network throughput, data-transfer protocols can be developed to run over UDP or directly over IP, rather than over TCP. If error-free transmission is required, techniques for achieving reliable transmission can be included as part of the transfer protocol. However, selected image-processing applications can tolerate a low level of errors in images that are transmitted over a network. In this paper we report on experimental work to develop a high-throughput protocol for unreliable data transfer over ATM networks. We attempt to maximize throughput by keeping the communications pipe full, but still keep packet loss under five percent. We use the Bay Area Gigabit Network Testbed as our experimental platform.

  16. Student Perception of Academic Achievement Factors at High School

    ERIC Educational Resources Information Center

    Bahar, Mustafa

    2016-01-01

    Measuring the quality of the "product" is elemental in education, and most studies depend on observational data about student achievement factors, focusing overwhelmingly on quantitative data namely achievement scores, school data like attendance, facilities, expenditure class size, etc. But there is little evidence of learner…

  17. Learning Styles and High School Students' Chemistry Achievement

    ERIC Educational Resources Information Center

    Uzuntiryaki, Esen

    2007-01-01

    The aim of the present study was to investigate the effects of students' learning styles on their chemistry achievement, and whether matching between teaching and learning styles also affects students' chemistry achievement. Two hundred and sixty-five tenth-grade students enrolled in a chemistry course and seven chemistry teachers participated in…

  18. Does Recreational Computer Use Affect High School Achievement?

    ERIC Educational Resources Information Center

    Bowers, Alex J.; Berland, Matthew

    2013-01-01

    Historically, the relationship between student academic achievement and use of computers for fun and video gaming has been described from a multitude of perspectives, from positive, to negative, to neutral. However, recent research has indicated that computer use and video gaming may be positively associated with achievement, yet these studies…

  19. High-Achieving High School Students and Not so High-Achieving College Students: A Look at Lack of Self-Control, Academic Ability, and Performance in College

    ERIC Educational Resources Information Center

    Honken, Nora B.; Ralston, Patricia A. S.

    2013-01-01

    This study investigated the relationship among lack of self-control, academic ability, and academic performance for a cohort of freshman engineering students who were, with a few exceptions, extremely high achievers in high school. Structural equation modeling analysis led to the conclusion that lack of self-control in high school, as measured by…

  20. Achievement of Hispanic Students in American High Schools: Background Characteristics and Achievement. Contractor Report.

    ERIC Educational Resources Information Center

    Nielsen, Francois; Fernandez, Roberto M.

    Presenting data and analyses from the first wave of the study "High School and Beyond" (HS&B), a longitudinal study of United States high school sophomores and seniors, the report focuses on the composition of the Hispanic tenth and twelfth grade student population with respect to various characteristics; i.e., language use and proficiency, length…

  1. Understanding Depth Variation of Deep Seismicity from in situ Measurements of Mineral Strengths at High Pressures

    SciTech Connect

    Chen, J.

    2010-01-01

    Strengths of major minerals of Earth's mantle have been measured using in situ synchrotron X-ray diffraction at high pressures. Analysis of the diffraction peak widths is used to derive the yield strengths. Systematic analysis of the experimental result for olivine, wadsleyite, ringwoodite and perovskite indicates that minerals in the upper mantle, the transition zone and the lower mantle have very distinct strength character. Increasing temperature weakens the upper mantle mineral, olivine, significantly. At high temperature and high pressure, the transition zone minerals, wadsleyite and ringwoodite, have higher strengths than the upper mantle mineral. Among all the minerals studied, the lower mantle mineral, perovskite, has the highest strength. While both the upper mantle and the transition zone minerals show a notable strength drop, the strength of the lower mantle mineral shows just an increase of relaxation rate (no strength drop) when the temperature is increased stepwise by 200 K. The strength characteristics of these major mantle minerals at high pressures and temperatures indicate that yield strength may play a crucial role in defining the profile of deep earthquake occurrence with depth.

  2. Influence of Manufacturing Processes and Microstructures on the Performance and Manufacturability of Advanced High Strength Steels

    SciTech Connect

    Choi, Kyoo Sil; Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

    2009-10-01

    Advanced high strength steels (AHSS) are performance-based steel grades and their global material properties can be achieved with various steel chemistries and manufacturing processes, leading to various microstructures. In this paper, we investigate the influence of supplier variation and resulting microstructure difference on the overall mechanical properties as well as local formability behaviors of advanced high strength steels (AHSS). For this purpose, we first examined the basic material properties and the transformation kinetics of TRansformation Induced Plasticity (TRIP) 800 steels from three different suppliers under different testing temperatures. The experimental results show that there is a significant supplier (i.e., manufacturing process) dependency of the TRIP 800 steel mechanical and microstructure properties. Next, we examined the local formability of two commercial Dual Phase (DP) 980 steels during stamping process. The two commercial DP 980 steels also exhibit noticeably different formability during stamping process in the sense that one of them shows severe tendency for shear fracture. Microstructure-based finite element analyses are carried out next to simulate the localized deformation process with the two DP 980 microstructures, and the results suggest that the possible reason for the difference in formability lies in the morphology of the hard martensite phase in the DP microstructure.

  3. Ultra-High Strength and Ductile Lamellar-Structured Powder Metallurgy Binary Ti-Ta Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Xu, Shenghang; Wang, Xin; Li, Kaiyang; Liu, Bin; Wu, Hong; Tang, Huiping

    2016-03-01

    Ultra-high strength and ductile powder metallurgy (PM) binary Ti-20at.%Ta alloy has been fabricated via sintering from elemental Ti and Ta powders and subsequent hot swaging and annealing. The microstructural evolution and mechanical properties in each stage were evaluated. Results show that inhomogeneous microstructures with Ti-rich and Ta-rich areas formed in the as-sintered Ti-Ta alloys due to limited diffusion of Ta. In addition, Kirkendall porosity was observed as a result of the insufficient diffusion of Ta. Annealing at 1000°C for up to 24 h failed to eliminate the pores. Hot swaging eliminated the residual sintering porosity and created a lamellar microstructure, consisting of aligned Ta-enriched and Ti-enriched phases. The hot-swaged and annealed PM Ti-20Ta alloy achieved an ultimate tensile strength of 1600 MPa and tensile elongation of more than 25%, due to its unique lamellar microstructure including the high toughness of Ta-enriched phases, the formation of α phase in the β matrix and the refined lamellae.

  4. Commercialization of NASA's High Strength Cast Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2003-01-01

    In this paper, the commercialization of a new high strength cast aluminum alloy, invented by NASA-Marshall Space Flight Center, for high temperature applications will be presented. Originally developed to meet U.S. automotive legislation requiring low- exhaust emission, the novel NASA aluminum alloy offers dramatic improvement in tensile and fatigue strengths at elevated temperatures (450 F-750 F), which can lead to reducing part weight and cost as well as improving performance for automotive engine applications. It is an ideal low cost material for cast components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. NASA alloy also offers greater wear resistance, dimensional stability, and lower thermal expansion compared to conventional aluminum alloys, and the new alloy can be produced economically from sand, permanent mold and investment casting. Since 2001, this technology was licensed to several companies for automotive and marine internal combustion engines applications.

  5. Advanced nickel base alloys for high strength, corrosion applications

    DOEpatents

    Flinn, John E.

    1998-01-01

    Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0-20Fe, 10-30Cr, 2-12Mo, 6 max. Nb, 0.05-3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01-0.08C, less than 0.2N, 0.1 max. 0, bal. Ni.

  6. Advanced nickel base alloys for high strength, corrosion applications

    DOEpatents

    Flinn, J.E.

    1998-11-03

    Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0--20Fe, 10--30Cr, 2--12Mo, 6 max. Nb, 0.05--3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01--0.08C, less than 0.2N, 0.1 max. 0, bal. Ni. 3 figs.

  7. Local heat treatment of high strength steels with zoom-optics and 10kW-diode laser

    NASA Astrophysics Data System (ADS)

    Baumann, Markus; Krause, Volker; Bergweiler, Georg; Flaischerowitz, Martin; Banik, Janko

    2012-03-01

    High strength steels enable new solutions for weight optimized car bodies without sacrificing crash safety. However, cold forming of these steels is limited due to the need of high press capacity, increased tool wear, and limitations in possible geometries. One can compensate for these drawbacks by local heat treatment of the blanks. In high-deformation areas the strength of the material is reduced and the plasticity is increased by diode laser irradiation. Local heat treatment with diode laser radiation could also yield key benefits for the applicability of press hardened parts. High strength is not desired all over the part. Joint areas or deformation zones for requested crash properties require locally reduced strength. In the research project "LOKWAB" funded by the German Federal Ministry of Education and Research (BMBF), heat treatment of high strength steels was investigated in cooperation with Audi, BMW, Daimler, ThyssenKrupp, Fraunhofer- ILT, -IWU and others. A diode laser with an output power of 10 kW was set up to achieve acceptable process speed. Furthermore a homogenizing zoom-optics was developed, providing a rectangular focus with homogeneous power density. The spot size in x- and y-direction can be changed independently during operation. With pyrometer controlled laser power the surface temperature is kept constant, thus the laser treated zone can be flexibly adapted to the needs. Deep-drawing experiments show significant improvement in formability. With this technique, parts can be manufactured, which can conventionally only be made of steel with lower strength. Locally reduced strength of press hardened serial parts was demonstrated.

  8. Preferences of High Achieving High School Students in Their Career Development

    ERIC Educational Resources Information Center

    Kim, Mihyeon

    2010-01-01

    The intent of this study was to identify the needs and preference of high-achieving high school students. In terms of career related programs in high school, students listed AP courses and mentoring as their preferred career-related programs. Also, students stated that career guidance by counselors, workshops or sessions, and tech prep were the…

  9. Threatened and Placed at Risk: High Achieving African American Males in Urban High Schools

    ERIC Educational Resources Information Center

    McGee, Ebony O.

    2013-01-01

    This study investigated the risk and protective factors of 11 high-achieving African American males attending 4 urban charter high schools in a Midwestern city to determine what factors account for their resilience and success in mathematics courses, and in high school more generally. This research was guided by a Phenomenological Variant of…

  10. Development of high toughness, high strength aluminide-bonded carbide ceramics

    SciTech Connect

    Becher, P.F.; Plucknett, K.P.; Tiegs, T.N.

    1997-04-01

    Cemented carbides are widely used in applications where resistance to abrasion and wear are important, particularly in combination with high strength and stiffness. In the present case, ductile aluminides have been used as a binder phase to fabricate dense carbide cermets by either sintering of mixed powders or a melt-infiltration sintering process. The choice of an aluminide binder was based on the exceptional high temperature strength and chemical stability exhibited by these alloys. For example, TiC-based composites with a Ni{sub 3}Al binder phase exhibit improved oxidation resistance, Young`s moduli > 375 GPa, high fracture strengths (> 1 GPa) that are retained to {ge} 900{degrees}C, and fracture toughness values of 10 to 15 MPa{radical}m, identical to that measured in commercial cobalt-bonded WC with the same test method. The thermal diffusivity values at 200{degrees}C for these composites are {approximately} 0.070 to 0.075 cm{sup 2}/s while the thermal expansion coefficients rise with Ni3Al content from {approximately} 8 to {approximately}11 x 10{sup {minus}6}/{degrees}C over the range of 8 to 40 vol. % Ni{sub 3}Al. The oxidation and acidic corrosion resistances are quite promising as well. Finally, these materials also exhibit good electrical conductivity allowing them to be sectioned and shaped by electrical discharge machining (EDM) processes.

  11. Candidate materials for high-strength fastener applications in both the aerospace and automotive industries

    NASA Astrophysics Data System (ADS)

    Ferrero, J. G.

    2005-12-01

    There are many commercially available titanium alloys that have exhibited the capability of achieving high strength. Many of these alloys have not been seriously considered for fastener applications due to their cost or availability as coil or bar product. However, because new designs, increased material requirements, and larger aircraft are being built, the need to reduce weight and improve performance continues to be a major issue. The possibility of reducing weight by replacing currently used steel or Ni-based fasteners in various sizes is a great incentive. Over the past few years, many of these titanium alloys have been processed to bar and coil products to evaluate their capabilities as potential fastener materials. This article will review and summarize the mechanical properties, tensile, shear, notch tensile, and available fatigue, as well as the microstructure of these candidate alloys.

  12. ETV Program Report: Big Fish Septage and High Strength Waste Water Treatment System

    EPA Science Inventory

    Verification testing of the Big Fish Environmental Septage and High Strength Wastewater Processing System for treatment of high-strength wastewater was conducted at the Big Fish facility in Charlevoix, Michigan. Testing was conducted over a 13-month period to address different c...

  13. The Effect of Music Participation on Mathematical Achievement and Overall Academic Achievement of High School Students

    ERIC Educational Resources Information Center

    Cox, H. A.; Stephens, L. J.

    2006-01-01

    A study was conducted on high school students, comparing those with some music credits to those with none. No statistically significant difference was found in their mean math grade point averages (GPA) or their mean cumulative GPAs. Students were then separated into two groups based on the number of music credits. Students who had earned at least…

  14. Study to determine and analyze the strength of high modulus glass in epoxy-matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.

    1974-01-01

    Glass composition research was conducted to produce a high modulus, high strength beryllium-free glass fiber. This program was built on the previous research for developing high modulus, high strength glass fibers which had a 5 weight percent beryllia content. The fibers resulting from the composition program were then used to produce fiber reinforced-epoxy resin composites which were compared with composites reinforced by commercial high modulus glass fibers, Thornel S graphite fiber, and hybrids where the external quarters were reinforced with Thornel S graphite fiber and the interior half with glass fiber as well as the reverse hybrid. The composites were given tensile strength, compressive strength, short-beam shear strength, creep and fatigue tests. Comments are included on the significance of the test data.

  15. Anisotropy of high temperature strength in precipitation-hardened nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Nakagawa, Y. G.; Terashima, H.; Yoshizawa, H.; Ohta, Y.; Murakami, K.

    1986-01-01

    The anisotropy of high temperature strength of nickel-base superalloy, Alloy 454, in service for advanced jet engine turbine blades and vanes, was investigated. Crystallographic orientation dependence of tensile yield strength, creep and creep rupture strength was found to be marked at about 760C. In comparison with other single crystal data, a larger allowance in high strength off-axial orientation from the 001 axis, and relatively poor strength at near the -111 axis were noted. From transmission electron microscopy the anisotropic characteristics of this alloy were explained in terms of available slip systems and stacking geometries of gamma-prime precipitate cuboids which are well hardened by a large tantalum content. 100 cube slip was considered to be primarily responsible for the poor strength of the -111 axis orientation replacing the conventional 111 plane slip systems.

  16. Alumina fiber strength improvement

    NASA Technical Reports Server (NTRS)

    Pepper, R. T.; Nelson, D. C.

    1982-01-01

    The effective fiber strength of alumina fibers in an aluminum composite was increased to 173,000 psi. A high temperature heat treatment, combined with a glassy carbon surface coating, was used to prevent degradation and improve fiber tensile strength. Attempts to achieve chemical strengthening of the alumina fiber by chromium oxide and boron oxide coatings proved unsuccessful. A major problem encountered on the program was the low and inconsistent strength of the Dupont Fiber FP used for the investigation.

  17. Low-noise, high-strength, spiral-bevel gears for helicopter transmissions

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.; Handschuh, Robert F.; Henry, Zachary S.; Litvin, Faydor L.

    1993-01-01

    Improvements in spiral-bevel gear design were investigated to support the Army/NASA Advanced Rotorcraft Transmission program. Program objectives were to reduce weight by 25 percent, reduce noise by 10 dB, and increase life to 5000 hr mean-time-between-removal. To help meet these goals, advanced-design spiral-bevel gears were tested in an OH-58D helicopter transmission using the NASA 500-hp Helicopter Transmission Test Stand. Three different gear designs tested included: (1) the current design of the OH-58D transmission except gear material X-53 instead of AISI 9310; (2) a higher-strength design the same as the current but with a full fillet radius to reduce gear tooth bending stress (and thus, weight); and (3) a lower-noise design the same as the high-strength but with modified tooth geometry to reduce transmission error and noise. Noise, vibration, and tooth strain tests were performed and significant gear stress and noise reductions were achieved.

  18. Low-noise, high-strength, spiral-bevel gears for helicopter transmissions

    SciTech Connect

    Lewicki, D.G.; Handschuh, R.F.; Henry, Z.S.; Litvin, F.L.

    1993-06-01

    Improvements in spiral-bevel gear design were investigated to support the Army/NASA Advanced Rotorcraft Transmission program. Program objectives were to reduce weight by 25 percent, reduce noise by 10 dB, and increase life to 5000 hr mean-time-between-removal. To help meet these goals, advanced-design spiral-bevel gears were tested in an OH-58D helicopter transmission using the NASA 500-hp Helicopter Transmission Test Stand. Three different gear designs tested included: (1) the current design of the OH-58D transmission except gear material X-53 instead of AISI 9310; (2) a higher-strength design the same as the current but with a full fillet radius to reduce gear tooth bending stress (and thus, weight); and (3) a lower-noise design the same as the high-strength but with modified tooth geometry to reduce transmission error and noise. Noise, vibration, and tooth strain tests were performed and significant gear stress and noise reductions were achieved.

  19. "Brains before "Beauty"?" High Achieving Girls, School and Gender Identities

    ERIC Educational Resources Information Center

    Skelton, Christine; Francis, Becky; Read, Barbara

    2010-01-01

    In recent years educational policy on gender and achievement has concentrated on boys' underachievement, frequently comparing it with the academic success of girls. This has encouraged a perception of girls as the "winners" of the educational stakes and assumes that they no longer experience the kinds of gender inequalities identified in earlier…

  20. High-Achieving Middle Schools for Latino Students in Poverty

    ERIC Educational Resources Information Center

    Jesse, Dan; Davis, Alan; Pokorny, Nancy

    2004-01-01

    This study was conducted to examine the characteristics of middle schools in which Latino students from low-income families made substantial achievement gains. Nine schools in Texas were selected where Latino students had shown strong gains in the Texas Assessment of Academic Skills. Data from onsite interviews, focus groups, and documents were…

  1. Dominant Achievement Goals across Tracks in High School

    ERIC Educational Resources Information Center

    Scheltinga, Peter A. M.; Kuyper, Hans; Timmermans, Anneke C.; van der Werf, Greetje P. C.

    2016-01-01

    The dominant achievement goals (DAGs) of 7,008 students in the third grade of Dutch secondary education (US grade 9) were investigated, based on Elliot & McGregors' 2 × 2 framework (2001), in relation to track-level and motivational variables. We found the mastery-approach goal and the performance-approach goal, generally considered adaptive,…

  2. Success Despite Socioeconomics: A Case Study of a High-Achieving, High-Poverty School

    ERIC Educational Resources Information Center

    Tilley, Thomas Brent; Smith, Samuel J.; Claxton, Russell L.

    2012-01-01

    This case study of a high-achieving, high-poverty school describes the school's leadership, culture, and programs that contributed to its success. Data were collected from two surveys (the School Culture Survey and the Vanderbilt Assessment of Leadership in Education), observations at the school site, and interviews with school personnel. The…

  3. Parenting Style, Perfectionism, and Creativity in High-Ability and High-Achieving Young Adults

    ERIC Educational Resources Information Center

    Miller, Angie L.; Lambert, Amber D.; Speirs Neumeister, Kristie L.

    2012-01-01

    The current study explores the potential relationships among perceived parenting style, perfectionism, and creativity in a high-ability and high-achieving young adult population. Using data from 323 honors college students at a Midwestern university, bivariate correlations suggested positive relationships between (a) permissive parenting style and…

  4. Extraordinary high ductility/strength of the interface designed bulk W-ZrC alloy plate at relatively low temperature

    PubMed Central

    Xie, Z. M.; Liu, R.; Miao, S.; Yang, X. D.; Zhang, T.; Wang, X. P.; Fang, Q. F.; Liu, C. S.; Luo, G. N.; Lian, Y. Y.; Liu, X.

    2015-01-01

    The refractory tungsten alloys with high ductility/strength/plasticity are highly desirable for a wide range of critical applications. Here we report an interface design strategy that achieves 8.5 mm thick W-0.5 wt. %ZrC alloy plates with a flexural strength of 2.5 GPa and a strain of 3% at room temperature (RT) and ductile-to-brittle transition temperature of about 100 °C. The tensile strength is about 991 MPa at RT and 582 MPa at 500 °C, as well as total elongation is about 1.1% at RT and as large as 41% at 500 °C, respectively. In addition, the W-ZrC alloy plate can sustain 3.3 MJ/m2 thermal load without any cracks. This processing route offers the special coherent interfaces of grain/phase boundaries (GB/PBs) and the diminishing O impurity at GBs, which significantly strengthens GB/PBs and thereby enhances the ductility/strength/plasticity of W alloy. The design thought can be used in the future to prepare new alloys with higher ductility/strength. PMID:26531172

  5. Extraordinary high ductility/strength of the interface designed bulk W-ZrC alloy plate at relatively low temperature

    NASA Astrophysics Data System (ADS)

    Xie, Z. M.; Liu, R.; Miao, S.; Yang, X. D.; Zhang, T.; Wang, X. P.; Fang, Q. F.; Liu, C. S.; Luo, G. N.; Lian, Y. Y.; Liu, X.

    2015-11-01

    The refractory tungsten alloys with high ductility/strength/plasticity are highly desirable for a wide range of critical applications. Here we report an interface design strategy that achieves 8.5 mm thick W-0.5 wt. %ZrC alloy plates with a flexural strength of 2.5 GPa and a strain of 3% at room temperature (RT) and ductile-to-brittle transition temperature of about 100 °C. The tensile strength is about 991 MPa at RT and 582 MPa at 500 °C, as well as total elongation is about 1.1% at RT and as large as 41% at 500 °C, respectively. In addition, the W-ZrC alloy plate can sustain 3.3 MJ/m2 thermal load without any cracks. This processing route offers the special coherent interfaces of grain/phase boundaries (GB/PBs) and the diminishing O impurity at GBs, which significantly strengthens GB/PBs and thereby enhances the ductility/strength/plasticity of W alloy. The design thought can be used in the future to prepare new alloys with higher ductility/strength.

  6. Laser-Assisted Sheet Metal Working of High Strength Steels in Serial Production

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus

    Within the sheet metal working industry the demand for thinner sheet materials with very high strength is growing due to the increasing need to save energy and a responsible use of natural resources. The high strength and the low ductility restricts using state of art technology to sheer, bend, emboss or deep draw parts with the needed complexity and quality. The Fraunhofer IPT developed a combination of laser-assisted preheating and conventional punching to a new hybrid technology which allows to shear, bend, emboss and draw high strength materials with a high quality and complexity in a serial production.

  7. Precision continuous high-strength Azimuth track for large telescopes

    NASA Astrophysics Data System (ADS)

    Antebi, Joseph; Kan, Frank W.

    2003-01-01

    A novel track joint was developed for the azimuth track of the 50-m diameter Large Millimeter Telescope (LMT) now under construction in Mexico at an elevation of 4,600 m. The track, which is 430 mm wide by 230 mm deep, must be flat to within +/- 0.3 mm, and the material hardness at least 290 Brinell. This design uses a partial penetration narrow gap groove weld on the top surface of the track and a splice plate welded to the underside of the track. Pre-camber of the joint compensates for weld shrinkage which is small because of the use of the narrow gap groove weld. The residual deviations from flatness are reduced to the required tolerance by adjusting anchor bolts using an optimization procedure. The feasibility of the design with respect to fabrication, strength, fatigue, and alignment was demonstrated by detailed finite element analyses, trial welding and alignment of full scale joints, and testing of the mechanical properties of the joint and adjacent metal.

  8. Fabrication of carbon nanotube high-frequency nanoelectronic biosensor for sensing in high ionic strength solutions.

    PubMed

    Kulkarni, Girish S; Zhong, Zhaohui

    2013-01-01

    The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) make them good candidates for high sensitivity biosensors. When a charged molecule binds to such a sensor surface, it alters the carrier density in the sensor, resulting in changes in its DC conductance. However, in an ionic solution a charged surface also attracts counter-ions from the solution, forming an electrical double layer (EDL). This EDL effectively screens off the charge, and in physiologically relevant conditions ~100 millimolar (mM), the characteristic charge screening length (Debye length) is less than a nanometer (nm). Thus, in high ionic strength solutions, charge based (DC) detection is fundamentally impeded. We overcome charge screening effects by detecting molecular dipoles rather than charges at high frequency, by operating carbon nanotube field effect transistors as high frequency mixers. At high frequencies, the AC drive force can no longer overcome the solution drag and the ions in solution do not have sufficient time to form the EDL. Further, frequency mixing technique allows us to operate at frequencies high enough to overcome ionic screening, and yet detect the sensing signals at lower frequencies. Also, the high transconductance of SWNT transistors provides an internal gain for the sensing signal, which obviates the need for external signal amplifier. Here, we describe the protocol to (a) fabricate SWNT transistors, (b) functionalize biomolecules to the nanotube, (c) design and stamp a poly-dimethylsiloxane (PDMS) micro-fluidic chamber onto the device, and (d) carry out high frequency sensing in different ionic strength solutions. PMID:23912795

  9. Fabrication of carbon nanotube high-frequency nanoelectronic biosensor for sensing in high ionic strength solutions.

    PubMed

    Kulkarni, Girish S; Zhong, Zhaohui

    2013-01-01

    The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) make them good candidates for high sensitivity biosensors. When a charged molecule binds to such a sensor surface, it alters the carrier density in the sensor, resulting in changes in its DC conductance. However, in an ionic solution a charged surface also attracts counter-ions from the solution, forming an electrical double layer (EDL). This EDL effectively screens off the charge, and in physiologically relevant conditions ~100 millimolar (mM), the characteristic charge screening length (Debye length) is less than a nanometer (nm). Thus, in high ionic strength solutions, charge based (DC) detection is fundamentally impeded. We overcome charge screening effects by detecting molecular dipoles rather than charges at high frequency, by operating carbon nanotube field effect transistors as high frequency mixers. At high frequencies, the AC drive force can no longer overcome the solution drag and the ions in solution do not have sufficient time to form the EDL. Further, frequency mixing technique allows us to operate at frequencies high enough to overcome ionic screening, and yet detect the sensing signals at lower frequencies. Also, the high transconductance of SWNT transistors provides an internal gain for the sensing signal, which obviates the need for external signal amplifier. Here, we describe the protocol to (a) fabricate SWNT transistors, (b) functionalize biomolecules to the nanotube, (c) design and stamp a poly-dimethylsiloxane (PDMS) micro-fluidic chamber onto the device, and (d) carry out high frequency sensing in different ionic strength solutions.

  10. Fabrication of Carbon Nanotube High-Frequency Nanoelectronic Biosensor for Sensing in High Ionic Strength Solutions

    PubMed Central

    Kulkarni, Girish S.; Zhong, Zhaohui

    2013-01-01

    The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) 1-4 make them good candidates for high sensitivity biosensors. When a charged molecule binds to such a sensor surface, it alters the carrier density5 in the sensor, resulting in changes in its DC conductance. However, in an ionic solution a charged surface also attracts counter-ions from the solution, forming an electrical double layer (EDL). This EDL effectively screens off the charge, and in physiologically relevant conditions ~100 millimolar (mM), the characteristic charge screening length (Debye length) is less than a nanometer (nm). Thus, in high ionic strength solutions, charge based (DC) detection is fundamentally impeded6-8. We overcome charge screening effects by detecting molecular dipoles rather than charges at high frequency, by operating carbon nanotube field effect transistors as high frequency mixers9-11. At high frequencies, the AC drive force can no longer overcome the solution drag and the ions in solution do not have sufficient time to form the EDL. Further, frequency mixing technique allows us to operate at frequencies high enough to overcome ionic screening, and yet detect the sensing signals at lower frequencies11-12. Also, the high transconductance of SWNT transistors provides an internal gain for the sensing signal, which obviates the need for external signal amplifier. Here, we describe the protocol to (a) fabricate SWNT transistors, (b) functionalize biomolecules to the nanotube13, (c) design and stamp a poly-dimethylsiloxane (PDMS) micro-fluidic chamber14 onto the device, and (d) carry out high frequency sensing in different ionic strength solutions11. PMID:23912795

  11. Bond and fatigue characteristics of high-strength cement-based composites

    SciTech Connect

    Chimamphant, S.D.

    1989-01-01

    The results of a series of tests on a variety of high strength cementitious composites yield a model from which an empirical equation of general normalized pull-out stress vs. pull-out displacement relationship is developed. A new variable named the Brittleness Index and is defined and used in the proposed equation. Additionally, the concept of maximum strain is used to predict the fatigue life of high strength concrete. Three sizes of deformed bars and two types of steel fiber with four different volume fractions were used to observe bond-slip and pull-out characteristics of high strength concrete. The results indicate that the maximum slippage of deformed bars is only about 10% of that observed in normal concrete. Consequently, the required development length may have to be longer for high strength concrete members as compared to normal concrete. For the fatigue characteristics study, standard 3 x 6 in. cylinders were tested at the rates of 6 and 12 Hz. in a closed-loop load-controlled system. The results show that as the compressive strength of the composites increases from 4000 to 11000 psi., the fatigue strength increases by 17 percents. The rate of loading does not significantly affect the S-N relationship, fatigue strength and fatigue limit of the high strength cement-based composites. The S-N curves of high strength concrete shows a faster decay rate than those of normal concrete. The maximum strain at any cycle under cyclic loading is always less than the maximum strain at failure under monotonic loading. Also observed is that the maximum strain-cycle relationship is linear. These results indicate that the design code for flexure of normal concrete cannot be applied to high strength concrete.

  12. Changes in peak torque arm-shoulder strength of high school baseball pitchers during the season.

    PubMed

    Whitley, J D; Terrio, T

    1998-06-01

    Pre- and postseason measurements of peak torque arm strength were made at 180 deg./sec. and 300 deg./sec. on both throwing and nonthrowing arms of five male high school varsity baseball pitchers. The major findings were significant losses in adduction strength in both throwing and nonthrowing shoulders at 180 deg./ sec. and internal rotation strength for both sides at both speeds. The primary implication from these preliminary findings is that significant losses of arm-shoulder strength may be associated with injuries to the pitching arm.

  13. Elimination of strength degrading effects caused by surface microdefect: A prevention achieved by silicon nanotexturing to avoid catastrophic brittle fracture

    PubMed Central

    Kashyap, Kunal; Kumar, Amarendra; Huang, Chuan-Torng; Lin, Yu-Yun; Hou, Max T.; Andrew Yeh, J.

    2015-01-01

    The unavoidable occurrence of microdefects in silicon wafers increase the probability of catastrophic fracture of silicon-based devices, thus highlighting the need for a strengthening mechanism to minimize fractures resulting from defects. In this study, a novel mechanism for manufacturing silicon wafers was engineered based on nanoscale reinforcement through surface nanotexturing. Because of nanotexturing, different defect depths synthetically emulated as V-notches, demonstrated a bending strength enhancement by factors of 2.5, 3.2, and 6 for 2-, 7-, and 14-μm-deep V-notches, respectively. A very large increase in the number of fragments observed during silicon fracturing was also indicative of the strengthening effect. Nanotextures surrounding the V-notch reduced the stress concentration factor at the notch tip and saturated as the nanotexture depth approached 1.5 times the V-notch depth. The stress reduction at the V-notch tip measured by micro-Raman spectroscopy revealed that nanotextures reduced the effective depth of the defect. Therefore, the nanotextured samples were able to sustain a larger fracture force. The enhancement in Weibull modulus, along with an increase in bending strength in the nanotextured samples compared to polished single-crystal silicon samples, demonstrated the reliability of the strengthening method. These results suggest that this method may be suitable for industrial implementation. PMID:26040924

  14. Surrogate Modeling of High-Fidelity Fracture Simulations for Real-Time Residual Strength Predictions

    NASA Technical Reports Server (NTRS)

    Spear, Ashley D.; Priest, Amanda R.; Veilleux, Michael G.; Ingraffea, Anthony R.; Hochhalter, Jacob D.

    2011-01-01

    A surrogate model methodology is described for predicting in real time the residual strength of flight structures with discrete-source damage. Starting with design of experiment, an artificial neural network is developed that takes as input discrete-source damage parameters and outputs a prediction of the structural residual strength. Target residual strength values used to train the artificial neural network are derived from 3D finite element-based fracture simulations. A residual strength test of a metallic, integrally-stiffened panel is simulated to show that crack growth and residual strength are determined more accurately in discrete-source damage cases by using an elastic-plastic fracture framework rather than a linear-elastic fracture mechanics-based method. Improving accuracy of the residual strength training data would, in turn, improve accuracy of the surrogate model. When combined, the surrogate model methodology and high-fidelity fracture simulation framework provide useful tools for adaptive flight technology.

  15. Conducting High Cycle Fatigue Strength Step Tests on Gamma TiAl

    NASA Technical Reports Server (NTRS)

    Lerch, Brad; Draper, Sue; Pereira, J. Mike

    2002-01-01

    High cycle fatigue strength testing of gamma TiAl by the step test method is investigated. A design of experiments was implemented to determine if the coaxing effect occurred during testing. Since coaxing was not observed, step testing was deemed a suitable method to define the fatigue strength at 106 cycles.

  16. Production of small diameter high-temperature-strength refractory metal wires

    NASA Technical Reports Server (NTRS)

    Petrasek, D. W.; Signorelli, R. A.; King, G. W.

    1973-01-01

    Special thermomechanical techniques (schedules) have been developed to produce small diameter wire from three refractory metal alloys: colombian base alloy, tantalum base alloy, and tungsten base alloy. High strengths of these wires indicate their potential for contributing increased strength to metallic composites.

  17. Strength of Tantalum at High Pressures through Richtmyer-Meshkov Laser Compression Experiments and Simulations

    NASA Astrophysics Data System (ADS)

    John, Kristen Kathleen

    agreement between the data from the simulations and the experiments. The peak growth factors from the simulations and the experiments are within 10% agreement. For the multimode simulations, the goal is to assist in the design of the laser driven experiments using the Omega laser. A series of three-mode and four-mode patterns are simulated at various energies and the resulting growth of the RM instability is computed. Based on the results of the simulations, a configuration is selected for the multimode experiments. These simulations also serve as validation for the constitutive model and the material parameters for tantalum that are used in the simulations. By designing samples with initial perturbations in the form of single-mode and multimode ripples and subjecting these samples to high pressures, the Richtmyer-Meshkov instability is investigated in both laser compression experiments and simulations. By correlating the growth of these ripples to measures of strength, a better understanding of the strength of tantalum at high pressures is achieved.

  18. Enhanced long-term strength and durability of shotcrete with high-strength C{sub 12}A{sub 7} mineral-based accelerator

    SciTech Connect

    Won, Jong-Pil Hwang, Un-Jong; Lee, Su-Jin

    2015-10-15

    This study evaluated the performance of shotcrete using high strength C{sub 12}A{sub 7} mineral-based accelerator that has been developed to improve the durability and long-term strength. Rebound, compressive strength and flexural strength were tested in the field. Test result showed that existing C{sub 12}A{sub 7} mineral-based accelerator exhibits better early strength than the high-strength C{sub 12}A{sub 7} mineral-based accelerator until the early age, but high-strength C{sub 12}A{sub 7} mineral-based accelerator shows about 29% higher at the long-term age of 28 days. Microstructural analysis such as scanning electron microscope (SEM), X-ray diffraction (XRD) and nitrogen adsorption method was evaluated to analyze long-term strength development mechanism of high strength C{sub 12}A{sub 7} mineral-based accelerator. As analysis result, it had more dense structure due to the reaction product by adding material that used to enhanced strength. It had better resistance performance in chloride ion penetration, freezing–thawing and carbonation than shotcrete that used existing C{sub 12}A{sub 7} mineral-based accelerator.

  19. Double Sided Irradiation for Laser-assisted Shearing of Ultra High Strength Steels with Process Integrated Hardening

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus; Weinbach, Matthias

    Most small or medium sized parts produced in mass production are made by shearing and forming of sheet metal. This technology is cost effective, but the achievable quality and geometrical complexity are limited when working high and highest strength steel. Based on the requirements for widening the process limits of conventional sheet metal working the Fraunhofer IPT has developed the laser-assisted sheet metal working technology. With this enhancement it is possible to produce parts made of high and highest strength steel with outstanding quality, high complexity and low tool wear. Additionally laser hardening has been implemented to adjust the mechanical properties of metal parts within the process. Currently the process is limited to lower sheet thicknesses (<2 mm) to maintain short cycle times. To enable this process for larger geometries and higher sheet thicknesses the Fraunhofer IPT developed a system for double sided laser-assisted sheet metal working within progressive dies.

  20. Cup-Drawing Behavior of High-Strength Steel Sheets Containing Different Volume Fractions of Martensite

    NASA Astrophysics Data System (ADS)

    Choi, Shi-Hoon; Kim, Dae-Wan; Yang, Hoe-Seok; Han, Seong-Ho; Yoon, Jeong Whan

    2010-06-01

    Planar anisotropy and cup-drawing behavior were investigated for high-strength steel sheets containing different volume fractions of martensite. Macrotexture analysis using XRD was conducted to capture the effect of crystallographic orientation on the planar anisotropy of high-strength steel sheets. A phenomenological yield function, Yld96, which accounts for the anisotropy of yield stress and r-values, was implemented into ABAQUS using the user subroutine UMAT. Cup drawing of high-strength steel sheets was simulated using the FEM code. The profiles of earing and thickness strain were compared with the experimentally measured results.

  1. Achieving highly dispersed nanofibres at high loading in carbon nanofibre-metal composites

    NASA Astrophysics Data System (ADS)

    Kang, Jianli; Nash, Philip; Li, Jiajun; Shi, Chunsheng; Zhao, Naiqin

    2009-06-01

    In order to tap into the advantages of the properties of carbon nanotubes (CNTs) or carbon nanofibres (CNFs) in composites, the high dispersion of CNTs (or CNFs) and strong interfacial bonding are the key issues which are still challenging. In the current work, a novel approach, consisting of in situ synthesis of CNFs within the Cu powders and mixing Cu ions with the in situ CNF(Ni/Y)-Cu composite powders in a solvent, was developed to highly disperse CNFs in a Cu matrix. The composite, produced by vacuum hot pressing, shows extremely high strength, 3.6 times more than that of the matrix material alone. It is worth mentioning that this method can disperse CNFs at high loading in a metal matrix, inferring good potential for applications, such as electronic packaging materials.

  2. Membrane bioreactor application within the treatment of high-strength textile effluent.

    PubMed

    De Jager, D; Sheldon, M S; Edwards, W

    2012-01-01

    A pilot-scale dual-stage membrane bioreactor (dsMBR) incorporating two ultra-filtration (UF) side-stream membrane modules was designed, constructed, operated and evaluated on-site for treating high-strength textile effluent. The effluent stream was characterised by a COD range of between 45 to 2,820 mg/L and an average BOD of 192.5 mg/L. The dsMBR achieved an average COD reduction of 75% with a maximum of 97% over the 9 month test period. The COD concentration obtained after dsMBR treatment averaged at 190 mg/L, which was well within the discharge standard. The average reduction in turbidity and TSS were 94% and 19.6%, respectively, during the UF-MBR stage of the system. Subsequent treatment of the UF-permeate with nanofiltration (NF) and reverse osmosis (RO) removed both the residual colour and remaining salt. A consistent reduction in the color of the incoming effluent was evident. The ADMI was reduced from an average of 659 to ∼20, a lower ADMI and colour compared to the potable water. An average conductivity rejection of 91% was achieved with conductivity being reduced from an average of 7,700 to 693 μS/cm and the TDS reduced from an average of 5,700 to 473 mg/L, which facilitated an average TDS rejection of 92%.

  3. Evaluation of high strength, high conductivity CuNiBe alloys for fusion energy applications

    SciTech Connect

    Zinkle, Steven J

    2014-06-01

    The unirradiated tensile properties for several different heats and thermomechanical treatment conditions of precipitation strengthened Hycon 3HPTM CuNiBe (Cu-2%Ni-0.35%Be in wt.%) have been measured over the temperature range of 20-500 C for longitudinal and long transverse orientations. The room temperature electrical conductivity has also been measured for several heats, and the precipitate microstructure was characterized using transmission electron microscopy. The CuNiBe alloys exhibit very good combination of strength and conductivity at room temperature, with yield strengths of 630-725 MPa and electrical conductivities of 65-72% International Annealed Copper Standard (IACS). The strength remained relatively high at all test temperatures, with yield strengths of 420-520 MPa at 500 C. However, low levels of ductility (<5% uniform elongation) were observed at test temperatures above 200-250 C, due to flow localization near grain boundaries (exacerbated by having only 10-20 grains across the gage thickness of the miniaturized sheet tensile specimens). Scanning electron microscopy observation of the fracture surfaces found a transition from ductile transgranular to ductile intergranular fracture with increasing test temperature. Fission neutron irradiation to a dose of ~0.7 displacements per atom (dpa) at temperatures between 100 and 240 C produced a slight increase in strength and a significant decrease in ductility. The measured tensile elongation increased with increasing irradiation temperature, with a uniform elongation of ~3.3% observed at 240 C. The electrical conductivity decreased slightly following irradiation, due to the presence of defect clusters and Ni, Zn, Co transmutation products. Considering also previously published fracture toughness data, this indicates that CuNiBe alloys have irradiated tensile and electrical properties comparable or superior to CuCrZr and oxide dispersion strengthened copper at temperatures <250 C, and may be an attractive

  4. Unravel the key genes potentially related to high strength of cotton fiber by comparative phenotypic and genomic analyses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The demand of high strength of cotton fibers has been increased dramatically with the advent of modern high speed spinning technology for producing yarn. Bundle fiber strength is affected by fiber-to-fiber interactions in addition to the individual fiber strength. The bundle fiber strength is not al...

  5. Relationship between High School Mathematical Achievement and Quantitative GPA

    ERIC Educational Resources Information Center

    Brown, Jennifer L.; Halpin, Glennelle; Halpin, Gerald

    2015-01-01

    The demand for STEM graduates has increased, but the number of incoming freshmen who declare a STEM major has remained stagnant. High school courses, such as calculus, can open or close the gate for students interested in careers in STEM. The purpose of this study was to determine if high school mathematics preparation was a significant…

  6. Relationships among Stress, Coping, and Mental Health in High-Achieving High School Students

    ERIC Educational Resources Information Center

    Suldo, Shannon M.; Shaunessy, Elizabeth; Hardesty, Robin

    2008-01-01

    This study investigates the relationships among stress, coping, and mental health in 139 students participating in an International Baccalaureate (IB) high school diploma program. Mental health was assessed using both positive indicators (life satisfaction, academic achievement, academic self-efficacy) and negative indicators (psychopathology) of…

  7. The Information Search Process of High-, Middle-, and Low-Achieving High School Seniors.

    ERIC Educational Resources Information Center

    Kuhlthau, Carol C.

    1989-01-01

    Presents a model of the information search process as a complex series of stages involving thoughts and feelings as well as actions. A study that sought to verify the model using high school seniors from three different achievement levels is described, and the implications for library instruction are discussed. (five references) (CLB)

  8. Examining Organizational Practices That Predict Persistence among High-Achieving Black Males in High School

    ERIC Educational Resources Information Center

    Anderson, Kenneth Alonzo

    2016-01-01

    Background/Context: This article summarizes an increasing trend of antideficit Black male research in mathematics and highlights opportunities to add to the research. A review of the literature shows that antideficit researchers often examine relationships between individual traits and persistence of high-achieving Black males in mathematics.…

  9. The strain-rate sensitivity of high-strength high-toughness steels.

    SciTech Connect

    Dilmore, M.F.; Crenshaw, Thomas B.; Boyce, Brad Lee

    2006-01-01

    The present study examines the strain-rate sensitivity of four high strength, high-toughness alloys at strain rates ranging from 0.0002 s-1 to 200 s-1: Aermet 100, a modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A refined dynamic servohydraulic method was used to perform tensile tests over this entire range. Each of these alloys exhibit only modest strain-rate sensitivity. Specifically, the strain-rate sensitivity exponent m, is found to be in the range of 0.004-0.007 depending on the alloy. This corresponds to a {approx}10% increase in the yield strength over the 7-orders of magnitude change in strain-rate. Interestingly, while three of the alloys showed a concominant {approx}3-10% drop in their ductility with increasing strain-rate, the ES1-c alloy actually exhibited a 25% increase in ductility with increasing strain-rate. Fractography suggests the possibility that at higher strain-rates ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.

  10. On the achievement of strength at high temperature in binary alloys

    SciTech Connect

    Louat, N.P.; Imam, M.A. )

    1989-05-01

    The authors address the fining that the strengthening encountered in polycrystals, the Hall-Petch effect, can also be expected in materials which are not necessarily polycrystalline but, insofar as the effect is concerned, are similar to them. Specifically considered were two-phase alloys in which the matrix forms the minor constituent and in which the other, major phase, is particulate. Such alloys are to be considered as equivalent to polycrystals if the matrix is so thin that, at the stress involved, it cannot, independent of the particles, deform plastically. This restriction is also available in circumstances where the particles are replaced by rods or plates, effectively infinite in length.

  11. The plane strain shear fracture of the advanced high strength steels

    SciTech Connect

    Sun, Li

    2013-12-16

    The “shear fracture” which occurs at the high-curvature die radii in the sheet metal forming has been reported to remarkably limit the application of the advanced high strength steels (AHSS) in the automobile industry. However, this unusual fracture behavior generally cannot be predicted by the traditional forming limit diagram (FLD). In this research, a new experimental system was developed in order to simulate the shear fracture, especially at the plane strain state which is the most common state in the auto-industry and difficult to achieve in the lab due to sample size. Furthermore, the system has the capability to operate in a strain rate range from quasi-static state to the industrial forming state. One kinds of AHSS, Quenching-Partitioning (QP) steels have been performed in this test and the results show that the limiting fracture strain is related to the bending ratio and strain rate. The experimental data support that deformation-induced heating is an important cause of “shear fracture” phenomena for AHSS: a deformation-induced quasi-heating caused by smaller bending ratio and high strain rate produce a smaller limiting plane strain and lead a “shear fracture” in the component.

  12. Palm tree mulch as substrate for primary treatment wetlands processing high strength urban wastewater.

    PubMed

    Herrera-Melián, J A; González-Bordón, A; Martín-González, M A; García-Jiménez, P; Carrasco, M; Araña, J

    2014-06-15

    The life span of subsurface flow treatment wetlands is determined by the clogging of the substrate. Thus, the influent should undergo primary treatment to reduce loadings of suspended solids and dissolved organic matter. An-organic based substrate should be less prone to clogging because of its remarkably higher porosity and plasticity. Mulch obtained from branches of the Canarian palm tree (Phoenix canariensis) has been tested as substrate for mixed flow, intermittently fed treatment wetland mesocosms processing high strength urban wastewater. The effect of the presence of plants (Phragmites and Cyperus), influent pressure and hydraulic loading rate was studied. The best removals (SS: 89%, COD: 77%, turbidity: 82%) have been obtained with planted reactors treating highly concentrated influents at the lower hydraulic loading rates tested. The palm tree mulch units achieved similar removals of SS, COD and turbidity to one having gravel as substrate and planted with common reed. Mulch obtained from stems of giant reed (Arundo donax) provided similar removals of SS and turbidity but that of COD was lower. The combination of organic-based TWs with gravel-based ones provided high removals (SS: 95%, COD: 78%, turbidity: 95%) while the risk of clogging was strongly reduced. PMID:24681361

  13. Japanese High School Entrance Examinations and Scholastic Achievement.

    ERIC Educational Resources Information Center

    Togashi, Yutaka

    1985-01-01

    The Japanese high school entrance examinations were examined in detail for social studies, mathematics, and science test items. Most items measured knowledge and comprehension rather than synthesis, analysis, or scientific thinking. Implications for middle school instruction were discussed. (GDC)

  14. Practically Perfect in Every Way: Can Reframing Perfectionism for High-Achieving Undergraduates Impact Academic Resilience?

    ERIC Educational Resources Information Center

    Dickinson, Mary J.; Dickinson, David A. G.

    2015-01-01

    This study focuses on a pan-disciplinary scheme that targeted high-achieving undergraduate students. Earlier research from the scheme argued that high achievers have discernibly different learning and personal development support needs. One of the most frequent self-reported challenges within this high-achieving group is perfectionism. This…

  15. Application technologies for effective utilization of advanced high strength steel sheets

    NASA Astrophysics Data System (ADS)

    Suehiro, Masayoshi

    2013-12-01

    Recently, application of high strength steel sheets for automobiles has increased in order to meet a demand of light weighting of automobiles to reduce a carbon footprint while satisfying collision safety. The formability of steel sheets generally decreases with the increase in strength. Fracture and wrinkles tend to occur easily during forming. The springback phenomenon is also one of the issues which we should cope with, because it makes it difficult to obtain the desired shape after forming. Advanced high strength steel sheets with high formability have been developed in order to overcome these issues, and at the same time application technologies have been developed for their effective utilization. These sheets are normally used for cold forming. As a different type of forming, hot forming technique has been developed in order to produce parts with ultra high strength. In this report, technologies developed at NSSMC in this field will be introduced.

  16. Treatment of semivolatile compounds in high strength wastes using an anaerobic expanded-bed GAC reactor

    EPA Science Inventory

    The potential of the anaerobic, expanded bed granular activated carbon (GAC) reactor in treating a high strength waste containing RCRA semivolatile organic compounds (VOCs) was studied. Six semivolatiles, orthochlorophenol, nitrobenzene, naphthalene, para-nitrophenol, lindane, a...

  17. TREATMENT OF VOCS IN HIGH STRENGTH WASTES USING AN ANAEROBIC EXPANDED-BED GAS REACTOR

    EPA Science Inventory

    The potential of the expanded-bed granular activated carbon (GAC) anaerobic reactor in treating a high strength waste containing RCRA volatile organic compounds (VOCs) was studied. A total of six VOCs, methylene chloride, chlorobenzene, carbon tetrachloride, chloroform, toluene ...

  18. Application technologies for effective utilization of advanced high strength steel sheets

    SciTech Connect

    Suehiro, Masayoshi

    2013-12-16

    Recently, application of high strength steel sheets for automobiles has increased in order to meet a demand of light weighting of automobiles to reduce a carbon footprint while satisfying collision safety. The formability of steel sheets generally decreases with the increase in strength. Fracture and wrinkles tend to occur easily during forming. The springback phenomenon is also one of the issues which we should cope with, because it makes it difficult to obtain the desired shape after forming. Advanced high strength steel sheets with high formability have been developed in order to overcome these issues, and at the same time application technologies have been developed for their effective utilization. These sheets are normally used for cold forming. As a different type of forming, hot forming technique has been developed in order to produce parts with ultra high strength. In this report, technologies developed at NSSMC in this field will be introduced.

  19. Comparison of high and moderate intensity of strength training on mood and anxiety in older adults.

    PubMed

    Tsutsumi, T; Don, B M; Zaichkowsky, L D; Takenaka, K; Oka, K; Ohno, T

    1998-12-01

    This study was designed to examine the psychological benefits of anaerobic exercise for older adults. Specifically, strength training was employed to examine the effects on mood and anxiety in a group of healthy but sedentary older women. 36 women (mean age = 68.5 yr.) were randomly assigned to groups given high intensity or moderate intensity strength training or to a control group. Strength training was conducted three days a week for 12 weeks. After the training period, both high and moderate strength-training programs produced marked improvements in muscle strength and body composition compared to the control subjects. The average improvements in the high and moderate intensity strength-training groups for muscle strength were 40.5 and 35.5%, respectively, and for percent body fat 1.52 and 2.50%, respectively. As for psychological changes, both training groups significantly improved positive mood (vigor), and the moderate intensity group significantly reduced trait anxiety compared to means of the control group. Also, both training groups showed some decrease in tension and state anxiety after the training period. These findings provide evidence for the effectiveness of anaerobic training to enhance perception of psychological well-being in older women. A moderate intensity rather than high intensity of training regimen may be more beneficial for sedentary older women to improve psychological health.

  20. Development of a Low Loss, High Dielectric Strength Microwave Substrate

    SciTech Connect

    Sanders, D; Sampayan, S; Caporaso, G; Rhodes, M; Watson, J; Slenes, K; Jacquina, J; De La Fuenta, R; Thurmond, L

    2006-06-05

    This work describes a comparison of two candidate materials for pulse forming line fabrication with respect to bulk dielectric breakdown, frequency response of relative permittivity and dielectric loss. One material is a commercially available microwave substrate material that can be procured in sheet form without a high voltage specification while the other is a newly developed material that also comes in sheet form that can also be cast between the electrodes.

  1. Cold-rolled, high-strength sheet steels for auto applications

    NASA Astrophysics Data System (ADS)

    Bleck, Wolfgang

    1996-07-01

    Several groups of cold-rolled, high-strength sheet steels have been developed to optimize the required strength and formability levels for automotive applications. Multiphase steels offer new opportunities where high-strength levels are demanded. The future in steel development will be determined by the physical modeling of properties and by adapting new process routes such as thin slab casting and in-line rolling. In this article, developments in traditional strengthening concepts (e.g., microalloying and substitutional hardening with phosphorus) and more recently developed concepts (e.g., bake hardening and strengthening of interstitial-free steels) are reviewed.

  2. Nanostructured Cu-Cr alloy with high strength and electrical conductivity

    SciTech Connect

    Islamgaliev, R. K. Nesterov, K. M.; Bourgon, J.; Champion, Y.; Valiev, R. Z.

    2014-05-21

    The influence of nanostructuring by high pressure torsion (HPT) on strength and electrical conductivity in the Cu-Cr alloy has been investigated. Microstructure of HPT samples was studied by transmission electron microscopy with special attention on precipitation of small chromium particles after various treatments. Effect of dynamic precipitation leading to enhancement of strength and electrical conductivity was observed. It is shown that nanostructuring leads to combination of high ultimate tensile strength of 790–840 MPa, enhanced electrical conductivity of 81%–85% IACS and thermal stability up to 500 °C. The contributions of grain refinement and precipitation to enhanced properties of nanostructured alloy are discussed.

  3. High Strength and Wear Resistant Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.; Chen, Po Shou

    2003-01-01

    Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent thermal growth stability, surface hardness and wear resistant properties.

  4. Achieving high-value cardiac imaging: challenges and opportunities.

    PubMed

    Wiener, David H

    2014-01-01

    Cardiac imaging is under intense scrutiny as a contributor to health care costs, with multiple initiatives under way to reduce and eliminate inappropriate testing. Appropriate use criteria are valuable guides to selecting imaging studies but until recently have focused on the test rather than the patient. Patient-centered means are needed to define the true value of imaging for patients in specific clinical situations. This article provides a definition of high-value cardiac imaging. A paradigm to judge the efficacy of echocardiography in the absence of randomized controlled trials is presented. Candidate clinical scenarios are proposed in which echocardiography constitutes high-value imaging, as well as stratagems to increase the likelihood that high-value cardiac imaging takes place in those circumstances.

  5. Achieving high CRI from warm to super white

    NASA Astrophysics Data System (ADS)

    Bailey, Edward; Tormey, Ellen S.

    2007-09-01

    Light sources which produce a high color rendering index (CRI) have many applications in the lighting industry today. High color rendering accents the rich color which abounds in nature, interior design, theatrical costumes and props, clothing and fabric, jewelry, and machine vision applications. Multi-wavelength LED sources can pump phosphors at multiple stokes shift emission regimes and when combined with selected direct emission sources can allow for greater flexibility in the production of warm-white and cool white light of specialty interest. Unique solutions to R8 and R14 CRI >95 at 2850K, 4750K, 5250K, and 6750K presented.

  6. Community Schools Seek to Improve High School Achievement, College Readiness

    ERIC Educational Resources Information Center

    Gilroy, Marilyn

    2011-01-01

    The Coalition for Community Schools, an alliance of more than 150 national, state, and local organizations, is bringing public schools in partnership with community resources to improve student success. While that might seem like an abstract idea, it has very concrete goals, such as boosting high school graduation rates and college readiness.…

  7. High-Achieving Schools Put Equity Front and Center

    ERIC Educational Resources Information Center

    Gleason, Sonia Caus; Gerzon, Nancy

    2014-01-01

    How does professional learning look and feel in high-poverty schools where every student makes at least one year's worth of progress every year? How do schools and leaders put all the varied components of professional learning together so that they support all students learning every day? What professional learning grounds and sustains…

  8. Organizational Citizenship of Faculty and Achievement of High School Students

    ERIC Educational Resources Information Center

    DiPaola, Michael F.; Hoy, Wayne K.

    2005-01-01

    All successful organizations, including successful high schools, have employees who go beyond their formal job responsibilities and freely give of their time and energy to succeed. Organ was the first to use the phrase "organizational citizenship behavior" (OCB) to denote organizationally beneficial behavior of workers that was not prescribed but…

  9. Academic Dishonesty among Gifted and High-Achieving Students

    ERIC Educational Resources Information Center

    Geddes, Kimberly A.

    2011-01-01

    Gifted high school students are essentially absent in the research concerning academic integrity; however, over the past few years, educators of gifted students have noticed an increase in the occurrences of academic dishonesty among students in gifted classrooms (Abilock, 2009). This research may be analyzed to provide some insight into the…

  10. Vocational Interests of Intellectually Gifted and Highly Achieving Young Adults

    ERIC Educational Resources Information Center

    Vock, Miriam; Koller, Olaf; Nagy, Gabriel

    2013-01-01

    Background: Vocational interests play a central role in the vocational decision-making process and are decisive for the later job satisfaction and vocational success. Based on Ackerman's (1996) notion of "trait complexes," specific interest profiles of gifted high-school graduates can be expected. Aims: Vocational interests of gifted and highly…

  11. Common Core and America's High-Achieving Students

    ERIC Educational Resources Information Center

    Plucker, Jonathan A.

    2015-01-01

    While the merit and politics of the Common Core State Standards (CCSS) have been much debated and discussed, one topic has been virtually ignored: What do the standards portend for America's high-ability students? This brief addresses that question and provides guidance for CCSS-implementing districts and schools as they seek to help these…

  12. The Relationship between Highly Qualified Teachers and Student Academic Achievement

    ERIC Educational Resources Information Center

    Macken, Sherry Lou

    2013-01-01

    This study examined the relationship between the percentage of highly qualified teachers and standardized measures of student proficiency in the core academic subjects of mathematics, reading, science, social studies, and writing. Signed into law in January of 2002 by President George W. Bush, the No Child Left Behind (NCLB) Act requires teachers…

  13. More High-Achieving Students Are Choosing Community Colleges First

    ERIC Educational Resources Information Center

    Pluviose, David

    2008-01-01

    Certainly, "Tonight Show" host Jay Leno has nurtured the perception that community colleges are a punishment for underperforming high school students by joking that community colleges aren't "real colleges." This article shows that this perception belies the reality that contemporary community colleges serve students seeking trade skills but also…

  14. Park View High School: A World of Achievement

    ERIC Educational Resources Information Center

    Principal Leadership, 2010

    2010-01-01

    Entering the lobby of Park View High School in Sterling, VA, is like entering another world. The diversity in the student body is reflected in flags from 63 of the 80 countries that are represented in the student population, and in a special project for Hispanic Heritage Month, which covers the walls of an entire hallway. The school walls,…

  15. Testing Theories of Learning: Effects on High School Achievement.

    ERIC Educational Resources Information Center

    Keith, Timothy Z.; Cool, Valerie A.

    Theories of school learning consistently point to variables such as ability, time (e.g., homework), quality of instruction, motivation, and academic coursework as important influences on learning. In this study, path analysis was used to test the direct and indirect effects of these variables on high school learning, with learning measured by both…

  16. Gender, Student Motivation and Academic Achievement in a Midsized Wisconsin High School

    ERIC Educational Resources Information Center

    Lutzke, Steven Ronald

    2013-01-01

    This mixed-methods study investigated relationships among gender, academic motivation and achievement in a mid-sized Wisconsin high school. A questionnaire was developed that focused on perceived ability, achievement motives and achievement goals. Interviews with teachers focused on relationships among academic motivation and gender achievement.…

  17. Surrogate Modeling of High-Fidelity Fracture Simulations for Real-Time Residual Strength Predictions

    NASA Technical Reports Server (NTRS)

    Spear, Ashley D.; Priest, Amanda R.; Veilleux, Michael G.; Ingraffea, Anthony R.; Hochhalter, Jacob D.

    2011-01-01

    A surrogate model methodology is described for predicting, during flight, the residual strength of aircraft structures that sustain discrete-source damage. Starting with design of experiment, an artificial neural network is developed that takes as input discrete-source damage parameters and outputs a prediction of the structural residual strength. Target residual strength values used to train the artificial neural network are derived from 3D finite element-based fracture simulations. Two ductile fracture simulations are presented to show that crack growth and residual strength are determined more accurately in discrete-source damage cases by using an elastic-plastic fracture framework rather than a linear-elastic fracture mechanics-based method. Improving accuracy of the residual strength training data does, in turn, improve accuracy of the surrogate model. When combined, the surrogate model methodology and high fidelity fracture simulation framework provide useful tools for adaptive flight technology.

  18. Impact of learning orientation on African American children's attitudes toward high-achieving peers.

    PubMed

    Marryshow, Derrick; Hurley, Eric A; Allen, Brenda A; Tyler, Kenneth M; Boykin, A Wade

    2005-01-01

    This study examined Ogbu's widely accepted thesis that African American students reject high academic achievement because they perceive its limited utility in a world where their upward mobility is constrained by racial discrimination. Boykin's psychosocial integrity model contends that Black students value high achievement but that discrepancies between their formative cultural experiences and those imposed in school lead them to reject the modes of achievement available in classrooms. Ninety Black children completed a measure of attitudes toward students who achieve via mainstream or African American cultural values. Participants rejected the mainstream achievers and embraced the African American cultural achievers. Moreover, they expected their teachers to embrace the mainstream achievers and reject those who achieved through high-verve behavior. Results suggest that Boykin's thesis is a needed refinement to Ogbu's ideas. They indicate that Black children may reject not high achievement but some of the mainstream cultural values and behaviors on which success in mainstream classrooms is made contingent.

  19. Principals’ Perception of Influence on Factors Affecting Student Achievement in Low- and High-Achieving Urban High Schools

    ERIC Educational Resources Information Center

    Bloom, Collette M.; Owens, Emiel W.

    2013-01-01

    The purpose of the study was to compare and contrast influences principals have on staffing, curriculum issues, and discipline policies in high- and low-performing urban high schools. The data for the present study were drawn from the first year follow up of the Educational Longitudinal Survey of 2002-2004 (ELS: 02), administered by the National…

  20. Achievement of a 920-MHz High Resolution NMR

    NASA Astrophysics Data System (ADS)

    Hashi, Kenjiro; Shimizu, Tadashi; Goto, Atsushi; Kiyoshi, Tsukasa; Matsumoto, Shinji; Wada, Hitoshi; Fujito, Teruaki; Hasegawa, Ken-ichi; Yoshikawa, Masatoshi; Miki, Takashi; Ito, Satoshi; Hamada, Mamoru; Hayashi, Seiji

    2002-06-01

    We have developed a 920-MHz NMR system and performed the proton NMR measurement of H 2O and ethylbenzene using the superconducting magnet operating at 21.6 T (920 MHz for proton), which is the highest field produced by a superconducting NMR magnet in the persistent mode. From the NMR measurements, it is verified that both homogeneity and stability of the magnet have a specification sufficient for a high resolution NMR.

  1. Efforts toward achieving an unmanned, high-altitude LTA platform

    SciTech Connect

    Onda, Masahiko; Ford, M.L.

    1996-10-01

    The modern demands for an unmanned aerospace platform, capable of long-duration stationkeeping at high-altitudes, are well-known. Satellites, balloons, and aircraft have traditionally served in the role of platform, facilitating tasks ranging from telecommunications to deep-space astronomy. However, limitations on the performance and flexibility of these systems, as well as the intrinsically high-cost of satellite construction, operation, and repair, warrants development of a supplemental technology for the platform. Much has been written in the literature on the possible advantages of a lighter-than-air (LTA) platform, if such an LTA could be constructed. Potential applications include remote sensing, environmental monitoring, mobile communications, space and polar observations, cargo delivery, military reconnaissance, and others. At present, conventional LTA`s are not capable of serving in the manner specified. Within this context, a research program known as HALROP (High Altitude Long Range Observational Platform) is currently underway. The goal is to create a stratospheric platform, possibly in the form of a next generation LTA vehicle. The authors present a qualitative review of their efforts, focusing on milestones in the HALROP Program. 12 refs., 6 figs., 2 tabs.

  2. Achieving High Reliability Operations Through Multi-Program Integration

    SciTech Connect

    Holly M. Ashley; Ronald K. Farris; Robert E. Richards

    2009-04-01

    Over the last 20 years the Idaho National Laboratory (INL) has adopted a number of operations and safety-related programs which has each periodically taken its turn in the limelight. As new programs have come along there has been natural competition for resources, focus and commitment. In the last few years, the INL has made real progress in integrating all these programs and are starting to realize important synergies. Contributing to this integration are both collaborative individuals and an emerging shared vision and goal of the INL fully maturing in its high reliability operations. This goal is so powerful because the concept of high reliability operations (and the resulting organizations) is a masterful amalgam and orchestrator of the best of all the participating programs (i.e. conduct of operations, behavior based safety, human performance, voluntary protection, quality assurance, and integrated safety management). This paper is a brief recounting of the lessons learned, thus far, at the INL in bringing previously competing programs into harmony under the goal (umbrella) of seeking to perform regularly as a high reliability organization. In addition to a brief diagram-illustrated historical review, the authors will share the INL’s primary successes (things already effectively stopped or started) and the gaps yet to be bridged.

  3. Anaerobic treatment of a simulated high-strength industrial wastewater containing chlorophenols

    SciTech Connect

    Flora, J.R.V.; Suidan, M.T.; Wuellner, A.M.; Boyer, T.K.

    1994-01-01

    An anaerobic fluidized-bed granular activated carbon (GAC) reactor employing carbon replacement was evaluated for the treatment of a simulated high strength industrial wastewater containing inhibitory concentrations of chlorophenols. The reactor was fed 2000-5900 mg/l acetic acid, 1000-3000 mg/l phenol, 1200 mg/l ortho-chlorophenol (2-CP), 600 mg/l 2,4-dichlorophenol (2,4-DCP), and 150 mg/l 2,4,6-trichlorophenol (2,4,6-TCP). The effects of varying the carbon replacement rate, the bulk operating pH, and the organic loading on reactor performance were investigated. The system was highly effective for treating the wastewater and an overall chemical oxygen demand (COD) removal greater than 98% was achieved. Carbon replacement resulting in a GAC solids mean retention time (SMRT) of 100 days was necessary to control the build-up of an inhibitory degradation by-product, para-chlorophenol (4-CP).

  4. NIR-Triggered Rapid Shape Memory PAM-GO-Gelatin Hydrogels with High Mechanical Strength.

    PubMed

    Huang, Jiahe; Zhao, Lei; Wang, Tao; Sun, Weixiang; Tong, Zhen

    2016-05-18

    Shape memory hydrogels containing over 76 wt % of water were synthesized in a one-pot method, and interpenetrating double network was formed by physically cross-linked gelatin network and chemically cross-linked polyacrylamide (PAM) network with graphene oxide (GO). The temporary shape was quickly fixed by cooling in ice water for 30 s after deformation at 80 °C for 10 s. Shape recovery started in 10 s under near-infrared (NIR) irradiation and almost completed within 60 s depending on the curling angle. A small amount of GO in the hydrogels (≤1.5 mg/mL) played a key role in NIR energy absorption and transformation into thermal energy. The hydrogel without GO showed no response to the NIR irradiation and cannot recover to its permanent shape by NIR irradiation. Temperature sweep was conducted in the cycle of 20 °C → 80 °C → 20 °C, and the structure change in the hydrogels with temperature was investigated according to the storage modulus G' and tangent of the loss angle tan δ as a function of the hydrogel composition. The shape-memory capability was confirmed as the contribution from the triple-helix cross-linking network of gelatin. High mechanical toughness (strength > 400 kPa and broken strain > 500%) was achieved by the double-network with the sacrificial gelatin network and GO bridging to dissipate deformation energy. The optimized composition of the hydrogel was found to be a key point to realize stable temporary shape and rapid recovery to the permanent shape controlled by NIR irradiation with reasonable strength. The facile preparation and noncontact gentle stimulus of the present hydrogel hold great potential to be used in soft actuator materials. PMID:27116394

  5. Grain-refining heat treatments to improve cryogenic toughness of high-strength steels

    NASA Technical Reports Server (NTRS)

    Rush, H. F.

    1984-01-01

    The development of two high Reynolds number wind tunnels at NASA Langley Research Center which operate at cryogenic temperatures with high dynamic pressures has imposed severe requirements on materials for model construction. Existing commercial high strength steels lack sufficient toughness to permit their safe use at temperatures approaching that of liquid nitrogen (-320 F). Therefore, a program to improve the cryogenic toughness of commercial high strength steels was conducted. Significant improvement in the cryogenic toughness of commercial high strength martensitic and maraging steels was demonstrated through the use of grain refining heat treatments. Charpy impact strength at -320 F was increased by 50 to 180 percent for the various alloys without significant loss in tensile strength. The grain sizes of the 9 percent Ni-Co alloys and 200 grade maraging steels were reduced to 1/10 of the original size or smaller, with the added benefit of improved machinability. This grain refining technique should permit these alloys with ultimate strengths of 220 to 270 ksi to receive consideration for cryogenic service.

  6. Advancing Minority High Achievement: National Trends and Promising Programs and Practices. A Report Prepared for the National Task Force on Minority High Achievement, the College Board.

    ERIC Educational Resources Information Center

    Borman, Geoffrey D.; Stringfield, Sam; Rachuba, Laura

    This report documents recent national progress in advancing the achievements of elementary-aged minority children, the potential for replicable whole-school reform designs to contribute to this advancement, and the individual, classroom, and school characteristics that distinguish those minority students who attain high levels of achievement. The…

  7. Development of high-strength, high-corrosion resistant austenitic stainless steel for sour gas service

    SciTech Connect

    Nakayama, T.; Fujiwara, K.; Torii, Y.; Inoue, T.

    1988-01-01

    An austenitic stainless steel for sour gas service has been developed. The new steel has been shown to offer high strength, i.e., 0.2% PS exceeding 42kgf/mm/sup 2/ (414MPa) under solution-annealed conditions, along with excellent resistance to sulphide stress corrosion cracking, pitting corrosion, and crevice corrosion, in comparison with conventional martensitic stainless steel such as CA-6NM, duplex stainless steel such as ASTM A790 UNS S31803, and austenitic stainless steels such as Type 316. Its higher resistance to corrosion cracking, etc., then Type 316 was thought to be attributable to the higher contents of Cr, Mo, and N, which help to form more stable passive film in a shorter time.

  8. The Relationship between Parental Involvement and Student Achievement in a Rural Florida High School

    ERIC Educational Resources Information Center

    Jackson, Willie A.

    2011-01-01

    Parental involvement is viewed as critical to the development of effective schools and student achievement. The relationship between parental involvement and achievement test scores at a rural high school in Florida was not known. This high school has not met the state standards as determined by the Florida Comprehensive Achievement Test (FCAT)…

  9. High Achievement in Mathematics Education in India: A Report from Mumbai

    ERIC Educational Resources Information Center

    Raman, Manya

    2010-01-01

    This paper reports a study aimed at characterizing the conditions that lead to high achievement in mathematics in India. The study involved eight schools in the greater Mumbai region. The main result of the study is that the notion of high achievement itself is problematic, as reflected in the reports about mathematics achievement within and…

  10. Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors.

    PubMed

    Samant, Saumil P; Grabowski, Christopher A; Kisslinger, Kim; Yager, Kevin G; Yuan, Guangcui; Satija, Sushil K; Durstock, Michael F; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-01

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ∼50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the "barrier effect", where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials. PMID:26942835

  11. Directed self-assembly of block copolymers for high breakdown strength polymer film capacitors

    DOE PAGES

    Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim; Yager, Kevin G.; Yuan, Guangcui; Satija, Sushil K.; Durstock, Michael F.; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-04

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayeredmore » films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ~50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. Lastly, this approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.« less

  12. Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors.

    PubMed

    Samant, Saumil P; Grabowski, Christopher A; Kisslinger, Kim; Yager, Kevin G; Yuan, Guangcui; Satija, Sushil K; Durstock, Michael F; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-01

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ∼50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the "barrier effect", where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.

  13. Garnet Yield Strength at High Pressures and Implications for Upper Mantle and Transition Zone Rheology

    SciTech Connect

    Kavner,A.

    2008-01-01

    Garnet helps control the mechanical behavior of the Earth's crust, mantle, and transition zone. Here, measurements are presented suggesting that garnet, long considered to be a high-viscosity phase, is actually weaker than the other dominant components in the transition zone. The mechanical behavior of garnet at high pressures was examined using radial diffraction techniques in the diamond anvil cell. The yield strength of grossular garnet was inferred from synchrotron X-ray measurements of differential lattice strains. The differential stress was found to increase from 1.3 ({+-}0.6) GPa at a hydrostatic pressure 5.8 ({+-}1.1) GPa to 4.1 ({+-}0.4) GPa at 15.7 ({+-}1.0) GPa, where it was level to 19 GPa. The strength results are consistent with inferred strength values for majorite garnet from measurements in the diamond cell normal geometry, bolstering the idea that garnet-structured materials may all have similar strengths. In this low-temperature, high differential stress regime, garnet is shown to be significantly weaker than anhydrous ringwoodite and to have a strength similar to hydrous ringwoodite. This result suggests that the presence of water in the transition zone may not be required to explain a weak rheology, and therefore models of transition zone behavior built assuming that garnet is the high-strength phase may need to be revised.

  14. Predicting delay in reading achievement in a highly transparent language.

    PubMed

    Holopainen, L; Ahonen, T; Lyytinen, H

    2001-01-01

    A random sample of 91 preschool children was assessed prior to receiving formal reading instruction. Verbal and nonverbal measures were used as predictors for the time of instruction required to accurately decode pseudowords in the highly orthographically regular Finnish language. After 2 years, participants were divided into four groups depending on the duration of instruction they had required to reach 90 % accuracy in their reading of pseudowords. Participants were classified as precocious decoders (PD), who could read at school entry; early decoders (ED), who learned to read within the first 4 months of Grade 1; ordinary decoders (OD), who learned to read within 9 months; and late decoders (LD), who failed to reach the criterion after 18 months of reading instruction at Grade 2. Phonological awareness played a significant role only in differentiating PD from ED and OD. However, phonological awareness failed to predict the delayed learning process of LD. LD differed from all other groups in visual analogical reasoning in an analysis not containing phonological awareness measures. Letter knowledge and visual analogical reasoning explained above 90% of the PD-LD difference. Preschool composite (objects, colors, and digits) naming speed measures best predicted reading fluency at the end of Grade 2. The supportive role of orthographic knowledge in phonological awareness, the role of visual analogical reasoning, and the inability of phonological measures to discriminate late decoders are discussed.

  15. Study of X80 grade high strength line pipe for sour service

    SciTech Connect

    Kushida, T.; Okaguchi, S.; Hamada, M.; Yamamoto, A.; Ohnishi, K.; Fujino, J.

    1997-08-01

    X80 grade high strength large diameter line pipe (UOE Pipe) for sour service have been studied. Increasing Mn content to provide strength of X80 increases HIC susceptibility due to center segregation of Mn in continuously cast slabs. The Mn content should be controlled less than 1.4% to maintain HIC resistance in the NACE TM0177 solution. The required strength can be obtained by addition of 0.5% Cr and accelerated controlled cooling after rolling. It has been clarified that Cr is very useful in providing high strength X70 without accelerating the center segregation of Mn. SSC resistance can be improved by controlling maximum hardness of weld metal lower than 230 Hv. Sour service X80 UOE pipes of two sizes were manufactured on large scales based on these experimental results. These pipes showed good low temperature toughness and HIC resistance in the NACE TM0177 solution.

  16. Process study of polycyanate resin for wet-filament wound high-strength composites

    SciTech Connect

    Frame, B.J.

    1997-12-31

    Polycyanate (or cyanate ester) resins offer advantages as composite matrices because of their high thermal stability, low outgassing, low water absorption and radiation resistance. This report describes the results of a processing study to develop high-strength hoop-wound composite by the wet-filament winding method using Toray T1000G carbon fiber and YLA RS-14 polycyanate resin as the constituent materials. T1000G/RS-14 composite cylinders were wet-wound and cured using different process schedules and then evaluated for hoop tensile strength and modulus, transverse flexural strength and short beam shear strength. The results of material characterization tests performed on the T1000G carbon fiber and RS-14 resin constituents used in this study are also presented.

  17. The resistance of selected high strength alloys to embrittlement by a hydrogen environment

    NASA Technical Reports Server (NTRS)

    Benson, R. B., Jr.

    1974-01-01

    Selected high strength iron base and cobalt base alloys with yield strengths in the range from 1233 to 2129 MN per sq m (179 to 309 KSI) were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced epsilon prime-hcp martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level to a maximum of 2129 MN per sq m (309 KSI). High-strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.

  18. Achieving High-Frequency Optical Control of Synaptic Transmission

    PubMed Central

    Jackman, Skyler L.; Beneduce, Brandon M.; Drew, Iain R.

    2014-01-01

    The optogenetic tool channelrhodopsin-2 (ChR2) is widely used to excite neurons to study neural circuits. Previous optogenetic studies of synapses suggest that light-evoked synaptic responses often exhibit artificial synaptic depression, which has been attributed to either the inability of ChR2 to reliably fire presynaptic axons or to ChR2 elevating the probability of release by depolarizing presynaptic boutons. Here, we compare light-evoked and electrically evoked synaptic responses for high-frequency stimulation at three synapses in the mouse brain. At synapses from Purkinje cells to deep cerebellar nuclei neurons (PC→DCN), light- and electrically evoked synaptic currents were remarkably similar for ChR2 expressed transgenically or with adeno-associated virus (AAV) expression vectors. For hippocampal CA3→CA1 synapses, AAV expression vectors of serotype 1, 5, and 8 led to light-evoked synaptic currents that depressed much more than electrically evoked currents, even though ChR2 could fire axons reliably at up to 50 Hz. The disparity between optical and electrical stimulation was eliminated when ChR2 was expressed transgenically or with AAV9. For cerebellar granule cell to stellate cell (grc→SC) synapses, AAV1 also led to artificial synaptic depression and AAV9 provided superior performance. Artificial synaptic depression also occurred when stimulating over presynaptic boutons, rather than axons, at CA3→CA1 synapses, but not at PC→DCN synapses. These findings indicate that ChR2 expression methods and light stimulation techniques influence synaptic responses in a neuron-specific manner. They also identify pitfalls associated with using ChR2 to study synapses and suggest an approach that allows optogenetics to be applied in a manner that helps to avoid potential complications. PMID:24872574

  19. Role of interfaces i nthe design of ultra-high strength, radiation damage tolerant nanocomposites

    SciTech Connect

    Misra, Amit; Wang, Yongqiang; Nastasi, Michael A; Baldwin, Jon K; Wei, Qiangmin; Li, Nan; Mara, Nathan; Zhang, Xinghang; Fu, Engang; Anderoglu, Osman; Li, Hongqi; Bhattacharyya, Dhriti

    2010-12-09

    The combination of high strength and high radiation damage tolerance in nanolaminate composites can be achieved when the individual layers in these composites are only a few nanometers thick and contain special interfaces that act both as obstacles to slip, as well as sinks for radiation-induced defects. The morphological and phase stabilities and strength and ductility of these nano-composites under ion irradiation are explored as a function of layer thickness, temperature and interface structure. Magnetron sputtered metallic multilayers such as Cu-Nb and V-Ag with a range of individual layer thickness from approximately 2 nm to 50 nm and the corresponding 1000 nm thick single layer films were implanted with helium ions at room temperature. Cross-sectional Transmission Electron Microscopy (TEM) was used to measure the distribution of helium bubbles and correlated with the helium concentration profile measured vis ion beam analysis techniques to obtain the helium concentration at which bubbles are detected in TEM. It was found that in multilayers the minimum helium concentration to form bubbles (approximately I nm in size) that are easily resolved in through-focus TEM imaging was several atomic %, orders of magnitude higher than that in single layer metal films. This observation is consistent with an increased solubility of helium at interfaces that is predicted by atomistic modeling of the atomic structures of fcc-bcc interfaces. At helium concentrations as high as 7 at.%, a uniform distribution of I nm diameter bubbles results in negligible irradiation hardening and loss of deformability in multi layers with layer thicknesses of a few nanometers. The control of atomic structures of interfaces to produce high helium solubility at interfaces is crucial in the design of nano-composite materials that are radiation damage tolerant. Reduced radiation damage also leads to a reduction in the irradiation hardening, particularly at layer thickness of approximately 5 run

  20. Aromatic Polythiourea Dielectrics with High Energy Density, High Breakdown Strength, and Low Dielectric Loss

    NASA Astrophysics Data System (ADS)

    Wu, Shan; Burlingame, Quinn; Lin, Minren; Zhang, Qiming

    2013-03-01

    There is an increasing demand on dielectric materials with high electric energy density and low loss for a broad range of applications in modern electronics and electrical power systems such as hybrid electric vehicles (HEV), medical defibrillators, filters, and switched-mode power supplies. One major challenge in developing dielectric polymers is how to achieve high energy density Ue while maintaining low dielectric loss, even at very high-applied electric fields. Here we show that amorphous polar-polymers with very low impurity concentration can be promising for realizing such a dielectric polymer. Polar-polymer with high dipole moment and weak dipole coupling can provide relatively high dielectric constant for high Ue, eliminate polarization and conduction losses due to weak dipolar coupling and strong polar-scattering to charge carriers. Indeed, an aromatic polythiourea thin film can maintain low loss to high fields (>1 GV/m) with a high Ue (~ 24 J/cm3) , which is very attractive for energy storage capacitors.

  1. Evaluation of the stress corrosion cracking resistance of several high strength low alloy steels

    NASA Technical Reports Server (NTRS)

    Humphries, T. S.; Nelson, E. E.

    1980-01-01

    The stress corrosion cracking resistance was studied for high strength alloy steels 4130, 4340, for H-11 at selected strength levels, and for D6AC and HY140 at a single strength. Round tensile and C-ring type specimens were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, salt spray, the atmosphere at Marshall Space Flight Center, and the seacoast at Kennedy Space Center. Under the test conditions, 4130 and 4340 steels heat treated to a tensile strength of 1240 MPa (180 ksi), H-11 and D6AC heat treated to a tensile strength of 1450 MPa (210 ksi), and HY140 (1020 MPa, 148 ksi) are resistant to stress corrosion cracking because failures were not encountered at stress levels up to 75 percent of their yield strengths. A maximum exposure period of one month for alternate immersion in salt water or salt spray and three months for seacoast is indicated for alloy steel to avoid false indications of stress corrosion cracking because of failure resulting from severe pitting.

  2. Comparative analysis of the processing accuracy of high strength metal sheets by AWJ, laser and plasma

    NASA Astrophysics Data System (ADS)

    Radu, M. C.; Schnakovszky, C.; Herghelegiu, E.; Tampu, N. C.; Zichil, V.

    2016-08-01

    Experimental tests were carried out on two high-strength steel materials (Ramor 400 and Ramor 550). Quantification of the dimensional accuracy was achieved by measuring the deviations from some geometric parameters of part (two lengths and two radii). It was found that in case of Ramor 400 steel, at the jet inlet, the deviations from the part radii are quite small for all the three analysed processes. Instead for the linear dimensions, the deviations are small only in case of laser cutting. At the jet outlet, the deviations raised in small amount compared to those obtained at the jet inlet for both materials as well as for all the three processes. Related to Ramor 550 steel, at the jet inlet the deviations from the part radii are very small in case of AWJ and laser cutting but larger in case of plasma cutting. At the jet outlet, the deviations from the part radii are very small for all processes; in case of linear dimensions, there was obtained very small deviations only in the case of laser processing, the other two processes leading to very large deviations.

  3. Hollow fiber vs. flat sheet MBR for the treatment of high strength stabilized landfill leachate.

    PubMed

    Hashisho, J; El-Fadel, M; Al-Hindi, M; Salam, D; Alameddine, I

    2016-09-01

    The Membrane Bioreactor (MBR) technology is increasingly becoming a prominent process in the treatment of high-strength wastewater such as leachate resulting from the decomposition of waste in landfills. This study presents a performance comparative assessment of flat sheet and hollow fiber membranes in bioreactors for the treatment of relatively stable landfill leachate with the objective of defining guidelines for pilot/full scale plants. For this purpose, a laboratory scale MBR system was constructed and operated to treat a leachate with Chemical Oxygen Demand (COD) (3900-7800mg/L), Biochemical Oxygen Demand (BOD5) (∼440-1537mg/L), Total Phosphorus (TP) (∼10-59mg/L), Phosphate (PO4(3)(-)) (5-58mg/L), Total Nitrogen (TN) (1500-5200mg/L), and ammonium (NH4(+)) (1770-4410mg/L). Both membranes achieved comparable BOD (92.2% vs. 93.2%) and TP (79.4% vs. 78.5%) removals. Higher PO4(3)(-) removal efficiency or percentage (87.3% vs. 81.3%) and slightly higher, but not statistically significant, COD removal efficiency were obtained with the hollow fiber membrane (71.4% vs. 68.5%). On the other hand, the flat sheet membrane achieved significantly higher TN and NH4(+) removal efficiencies (61.2% vs. 49.4% and 63.4% vs. 47.8%, respectively), which may be attributed to the less frequent addition of NaOCl compared to the hollow fiber system.

  4. Bond strength to high-crystalline content zirconia after different surface treatments.

    PubMed

    de Souza, Grace M Dias; Silva, Nelson R F A; Paulillo, Luis A M S; De Goes, Mario F; Rekow, E Dianne; Thompson, Van P

    2010-05-01

    The aim of this study was to evaluate the effect of primers, luting systems and aging on bond strength to zirconium oxide substrates. Eighteen zirconia discs (19.5 x 4 mm) were polished and treated (n = 3) either with a MDP primer (Md) or with a MDP and VBATDT primer (MV). In the control group (n = 3) no surface chemical treatment was performed. Zirconia specimens were cemented to prepolymerized composite discs utilizing resin cements - RelyX Unicem or Panavia 21 (RU and Pa, respectively). After 24 h, samples were sectioned for microtensile testing and returned to water at 37 degrees C for two different periods before being tested: 72 h or 60 days + thermocycling (5-55 degrees C/5000 cycles). Bond strength testing was performed at 1 mm/min. Values in MPa were analyzed through ANOVA and Tukey's Studentized Range (HSD) (p > 0.05). The application of MV primer resulted in the highest bond strength (22.77 MPa), statistically superior to Md primer (12.78 MPa), and control groups presented the lowest values (9.17 MPa). When luting systems were compared, RU promoted the highest bond strength (16.07 MPa) in comparison with Pa (13.75 MPa). The average bond strength decrease after aging (9.35 MPa) when compared with initial values (20.46 MPa). The results presented by this in vitro study suggest that a chemical surface treatment based on the MDP and VBATDT combination may improve bond strength between zirconia and luting system, without any previous mechanical treatment, depending on the luting system used. This chemical treatment may result in a reliable alternative to achieve adequate and durable bond strength.

  5. Laser beam welding of new ultra-high strength and supra-ductile steels

    NASA Astrophysics Data System (ADS)

    Dahmen, Martin

    2015-03-01

    Ultra-high strength and supra-ductile are entering fields of new applications. Those materials are excellent candidates for modern light-weight construction and functional integration. As ultra-high strength steels the stainless martensitic grade 1.4034 and the bainitic steel UNS 53835 are investigated. For the supra-ductile steels stand two high austenitic steels with 18 and 28 % manganese. As there are no processing windows an approach from the metallurgical base on is required. Adjusting the weld microstructure the Q+P and the QT steels require weld heat treatment. The HSD steel is weldable without. Due to their applications the ultra-high strength steels are welded in as-rolled and strengthened condition. Also the reaction of the weld on hot stamping is reflected for the martensitic grades. The supra-ductile steels are welded as solution annealed and work hardened by 50%. The results show the general suitability for laser beam welding.

  6. EXPERIMENTAL TESTS OF VANADIUM STRENGTH MODELS AT HIGH PRESSURES AND STRAIN RATES

    SciTech Connect

    Park, H; Barton, N R; Becker, R C; Bernier, J V; Cavallo, R M; Lorenz, K T; Pollaine, S M; Remington, B A; Rudd, R E

    2010-03-02

    Experimental results showing significant reductions from classical in the Rayleigh-Taylor (RT) instability growth rate due to high pressure material strength or effective lattice viscosity in metal foils are presented. On the Omega Laser in the Laboratory for Laser Energetics, University of Rochester, target samples of polycrystalline vanadium are compressed and accelerated quasi-isentropically at {approx}1 Mbar pressures, while maintaining the samples in the solid-state. Comparison of the results with constitutive models for solid state strength under these conditions show that the measured RT growth is substantially lower than predictions using existing models that work well at low pressures and long time scales. High pressure, high strain rate data can be explained by the enhanced strength due to a phonon drag mechanism, creating a high effective lattice viscosity.

  7. High-strength bioresorbable Fe–Ag nanocomposite scaffolds: Processing and properties

    SciTech Connect

    Sharipova, Aliya; Psakhie, Sergey G.; Swain, Sanjaya K.; Gutmanas, Elazar Y. Gotman, Irena

    2015-10-27

    High strength ductile iron-silver nanocomposite scaffolds were fabricated employing high energy attrition milling of micron-submicron powders, followed by cold sintering/high pressure consolidation. Particulate leaching method with soluble Na{sub 2}SO{sub 4} and K{sub 2}CO{sub 3} salts as porogens was used to create scaffolds with 50, 55, 60 and 73% volume fraction of pores. Part of specimens was annealed at 600, 800 and 900°C. Specimens were characterized employing X-ray diffraction, scanning electron microscopy (SEM) with electron probe microanalysis (EDS) and high resolution SEM. Mechanical properties were measured in compression and permeability was measured in permeameter based on Darcy’s law. Scaffolds with 50% and 55% porosity exhibited high compressive strength (18–22 MPa), compressive strength of 8–12 MPa was observed for scaffolds with 73% porosity. Treatments at 800 and 900°C result in increase of strength and ductility with some coarsening of microstructure. Best combination of compressive strength (15 MPa) and permeability (0.6{sup −6} cm{sup 2}) is close to the range of trabecular bone.

  8. High Salt Diets, Bone Strength and Mineral Content of Mature Femur After Skeletal Unloading

    NASA Technical Reports Server (NTRS)

    Liang, Michael T. C.

    1998-01-01

    It is known that high salt diets increase urinary calcium (Ca) loss, but it is not known whether this effect weakens bone during space flight. The Bone Hormone Lab has studied the effect of high salt diets on Ca balance and whole body Ca in a space flight model (2,8). Neither the strength nor mineral content of the femurs from these studies has been evaluated. The purpose of this study was to determine the effect of high salt diets (HiNa) and skeletal unloading on femoral bone strength and bone mineral content (BMC) in mature rats.

  9. STRENGTH PROPERTIES OF POLED PZT SUBJECTED TO BIAXIAL FLEXURAL LOADING IN HIGH ELECTRIC FIELD

    SciTech Connect

    Wang, Hong; Lin, Hua-Tay; Wereszczak, Andrew A

    2010-01-01

    Failure of poled PZT has been experimentally studied using ball-on-ring (BoR) biaxial flexure strength tests with an electric field concurrently applied. The as-received and aged PZTs were tested in high electric fields of -3 to 4 times the coercive field. Both the sign and the magnitude of electric field had a significant effect on the strength of poled PZT. A surface flaw type with a depth of around 18 m was identified as the strength limiter and responsible for the failure of the tested PZT. With a value of 0.76 MPa m1/2 in the open circle condition, the fracture toughness of the poled PZT was affected by an applied electric field just as the strength was affected. These results and observations have the potential to serve probabilistic reliability analysis and design optimization of multilayer PZT piezo actuators.

  10. High efficient preparation of carbon nanotube-grafted carbon fibers with the improved tensile strength

    NASA Astrophysics Data System (ADS)

    Fan, Wenxin; Wang, Yanxiang; Wang, Chengguo; Chen, Jiqiang; Wang, Qifen; Yuan, Yan; Niu, Fangxu

    2016-02-01

    An innovative technique has been developed to obtain the uniform catalyst coating on continuously moving carbon fibers. Carbon nanotube (CNT)-grafted carbon fibers with significantly improved tensile strength have been succeeded to produce by using chemical vapor deposition (CVD) when compared to the tensile strength of untreated carbon fibers. The critical requirements for preparation of CNT-grafted carbon fibers with high tensile strength have been found, mainly including (i) the obtainment of uniform coating of catalyst particles with small particle size, (ii) the low catalyst-induced and mechano-chemical degradation of carbon fibers, and (iii) the high catalyst activity which could facilitate the healing and strengthening of carbon fibers during the growth of CNTs. The optimum growth temperature was found to be about 500 °C, and the optimum catalyst is Ni due to its highest activity, there is a pronounced increase of 10% in tensile strength of carbon fibers after CNT growth at 500 °C by using Ni catalyst. Based on the observation from HRTEM images, a healing and crosslink model of neighboring carbon crystals by CNTs has been formulated to reveal the main reason that causes an increase in tensile strength of carbon fibers after the growth of CNTs. Such results have provided the theoretical and experimental foundation for the large-scale preparation of CNT-grafted carbon fibers with the improved tensile strength, significantly promoting the development of CNT-grafted carbon fiber reinforced polymer composites.

  11. High-capacity, high-strength trailer designs for the GA-4/GA-9 Casks

    SciTech Connect

    Kissinger, J.A.; Rickard, N.D.; Taylor, C.; Zimmer, A.

    1991-01-01

    General Atomics (GA) is developing final designs for two dedicated legal-weight trailers to transport the GA-4 and GA-9 Spent-Fuel Casks. The basic designs for these high-capacity, high-strength trailers are essentially identical except for small modifications to account for the differences in cask geometry. We are designing both trailers to carry a 55,000 lb (24,900 kg) payload and to withstand a 2.5 g vertical design load. The GA-4 and GA-9 trailers are designed for significantly higher loads than are typical commercial semitrailers, which are designed to loads in the range of 1.7 to 2.0 g. To meet the federal gross vehicle weight limit for legal-weight trucks, GA has set a target design weight for the trailers of 9000 lb (4080 kg). This weight includes the personnel barrier, cask tiedowns, and impact limiter removal and storage system. Based on the preliminary trailer designs, the final design weight is expected to be very close to this target weight. 3 refs., 3 figs.

  12. Strength-Based Factors for Successful Adaptation to an Early College High School Environment

    ERIC Educational Resources Information Center

    Abernethy, Catherine

    2010-01-01

    In an early college high school setting, students are subject to varying academic, social and contextual demands of a higher educational environment. In a strength-based study of 136 diverse early college high school students, this research explored the relationship of internal and external developmental assets to adaptive functioning of…

  13. Strength-toughness requirements for thick-walled high pressure vessels

    NASA Astrophysics Data System (ADS)

    Kapp, Joseph A.

    1992-05-01

    The strength and toughness requirements of materials used in high pressure vessels has been the subject of some discussion in the meetings of the Materials Task Group of the Special Working Group - High Pressure Vessels. A fracture mechanics analysis has been performed to theoretically establish the required toughness for a high pressure vessel. The analysis is based on the validity requirement for plane-strain fracture of fracture toughness test specimens. This means that at fracture, the crack length, uncracked ligament, and vessel length must each be greater than fifty times the crack tip plastic zone since for brittle fracture to occur. For high pressure piping applications, the limiting physical dimension is the uncracked ligament, since it can be assumed that the other dimensions are always greater than fifty times the crack tip plastic zone. To perform the fracture mechanics analysis, several parameters must be known, including vessel dimensions, material strength, degree of autofrettage, and design pressure. Remarkably, the results of the analysis show that the effects of radius ratio, pressure, and degree of autofrettage can be ignored when establishing strength and toughness requirements for design code purposes. The only parameters that enter into the calculation are yield strength, toughness and vessel thickness. The final results can easily be represented as a graph of yield strength against toughness on which several curves, one for each vessel thickness, are plotted.

  14. The Chinese High School Student's Stress in the School and Academic Achievement

    ERIC Educational Resources Information Center

    Liu, Yangyang; Lu, Zuhong

    2011-01-01

    In a sample of 466 Chinese high school students, we examined the relationships between Chinese high school students' stress in the school and their academic achievements. Regression mixture modelling identified two different classes of the effects of Chinese high school students' stress on their academic achievements. One class contained 87% of…

  15. The Effects of Magnet Schools on Neighborhood High Schools: An Examination of Achievement among Entering Freshmen

    ERIC Educational Resources Information Center

    Neild, Ruth Curran

    2004-01-01

    Magnet schools have been criticized for intensifying the concentration of disadvantaged, low-achieving students at neighborhood high schools. This article investigates the impact of academically selective magnet high schools on the average achievement of ninth graders enrolling in neighborhood high schools in a large urban school district. The…

  16. Beyond Academic Reputation: Factors that Influence the College of First Choice for High Achieving Students

    ERIC Educational Resources Information Center

    Schoenherr, Holly J.

    2009-01-01

    Studies that have investigated college choice factors for high-achieving students repeatedly cite academic reputation as one of the top indicators of choice but have not indicated why some high-achieving students choose to attend universities with a less prestigious reputation than the more highly prestigious options available to them. The purpose…

  17. Preferred Homework Style and Homework Environment in High- versus Low-Achieving Chinese Students.

    ERIC Educational Resources Information Center

    Hong, Eunsook; Lee, Kit-hung

    This study compared preferred homework styles of Chinese students who were characterized by: (1) high versus low self-perceived homework achievement and attitude; (2) high versus low teacher-rated homework completion and quality; (3) high versus low academic achievement in mathematics. Gender differences in homework styles were also examined.…

  18. A COMPREHENSIVE STUDY OF THE MOTIVATIONAL FACTORS UNDERLYING ACHIEVEMENT OF ELEVENTH-GRADE HIGH SCHOOL STUDENTS.

    ERIC Educational Resources Information Center

    FARQUHAR, WILLIAM W.

    ACHIEVEMENT MOTIVATION WAS STUDIED BETWEEN OVER- AND UNDER-ACHIEVING STUDENTS IN THE ELEVENTH-GRADE TO DEVELOP AN OBJECTIVE MEASURE OF MOTIVATION FOR USE IN PREDICTING ACADEMIC SUCCESS OR FAILURE. APPROXIMATELY 800 STUDENTS IN PUBLIC HIGH SCHOOLS WERE SELECTED FOR VALIDATION AND CROSS-VALIDATION SAMPLES. THEY WERE DIVIDED BY SEX AND ACHIEVEMENT.…

  19. Does High School Facility Quality Affect Student Achievement? A Two-Level Hierarchical Linear Model

    ERIC Educational Resources Information Center

    Bowers, Alex J.; Urick, Angela

    2011-01-01

    The purpose of this study is to isolate the independent effects of high school facility quality on student achievement using a large, nationally representative U.S. database of student achievement and school facility quality. Prior research on linking school facility quality to student achievement has been mixed. Studies that relate overall…

  20. Fabrication and processing of high-strength densely packed carbon nanotube yarns without solution processes.

    PubMed

    Liu, Kai; Zhu, Feng; Liu, Liang; Sun, Yinghui; Fan, Shoushan; Jiang, Kaili

    2012-06-01

    Defects of carbon nanotubes, weak tube-tube interactions, and weak carbon nanotube joints are bottlenecks for obtaining high-strength carbon nanotube yarns. Some solution processes are usually required to overcome these drawbacks. Here we fabricate ultra-long and densely packed pure carbon nanotube yarns by a two-rotator twisting setup with the aid of some tensioning rods. The densely packed structure enhances the tube-tube interactions, thus making high tensile strengths of carbon nanotube yarns up to 1.6 GPa. We further use a sweeping laser to thermally treat as-produced yarns for recovering defects of carbon nanotubes and possibly welding carbon nanotube joints, which improves their Young's modulus by up to ∼70%. The spinning and laser sweeping processes are solution-free and capable of being assembled together to produce high-strength yarns continuously as desired. PMID:22538869

  1. Fabrication and processing of high-strength densely packed carbon nanotube yarns without solution processes

    NASA Astrophysics Data System (ADS)

    Liu, Kai; Zhu, Feng; Liu, Liang; Sun, Yinghui; Fan, Shoushan; Jiang, Kaili

    2012-05-01

    Defects of carbon nanotubes, weak tube-tube interactions, and weak carbon nanotube joints are bottlenecks for obtaining high-strength carbon nanotube yarns. Some solution processes are usually required to overcome these drawbacks. Here we fabricate ultra-long and densely packed pure carbon nanotube yarns by a two-rotator twisting setup with the aid of some tensioning rods. The densely packed structure enhances the tube-tube interactions, thus making high tensile strengths of carbon nanotube yarns up to 1.6 GPa. We further use a sweeping laser to thermally treat as-produced yarns for recovering defects of carbon nanotubes and possibly welding carbon nanotube joints, which improves their Young's modulus by up to ~70%. The spinning and laser sweeping processes are solution-free and capable of being assembled together to produce high-strength yarns continuously as desired.

  2. Improvement of formability of high strength steel sheets in shrink flanging

    NASA Astrophysics Data System (ADS)

    Hamedon, Z.; Abe, Y.; Mori, K.

    2016-02-01

    In the shrinkage flanging, the wrinkling tends to occur due to compressive stress. The wrinkling will cause a difficulty in assembling parts, and severe wrinkling may leads to rupture of parts. The shrinkage flange of the ultra-high strength steel sheets not only defects the product by the occurrence of the wrinkling but also causes seizure and wear of the dies and shortens the life of dies. In the present study, a shape of a punch having gradual contact was optimized in order to prevent the wrinkling in shrinkage flanging of ultra-high strength steel sheets. The sheet was gradually bent from the corner of the sheet to reduce the compressive stress. The wrinkling in the shrink flanging of the ultra-high strength steel sheets was prevented by the punch having gradual contact. It was found that the punch having gradual contact is effective in preventing the occurrence of wrinkling in the shrinkage flanging.

  3. Bulk metallic glass composite with good tensile ductility, high strength and large elastic strain limit

    PubMed Central

    Wu, Fu-Fa; Chan, K. C.; Jiang, Song-Shan; Chen, Shun-Hua; Wang, Gang

    2014-01-01

    Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility. However, bulk metallic glass composites reinforced by in-situ dendrites possess significantly improved toughness but at the expense of high strength and large elastic strain limit. Here, we report a bulk metallic glass composite with strong strain-hardening capability and large elastic strain limit. It was found that, by plastic predeformation, the bulk metallic glass composite can exhibit both a large elastic strain limit and high strength under tension. These unique elastic mechanical properties are attributed to the reversible B2↔B19′ phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. These findings are significant for the design and application of bulk metallic glass composites with excellent mechanical properties. PMID:24931632

  4. The Effects of Web-Based/Non-Web-Based Problem-Solving Instruction and High/Low Achievement on Students' Problem-Solving Ability and Biology Achievement

    ERIC Educational Resources Information Center

    Yu, Wen-Feng; She, Hsiao-Ching; Lee, Yu-Mei

    2010-01-01

    This study investigates the effects of two factors: the mode of problem-solving instruction (i.e. Web-based versus non-Web-based) and the level of academic achievement (i.e. high achievers versus low achievers) on students' problem-solving ability and biology achievement. A quasi-experimental design was used, in which the experimental group…

  5. FE Simulation Models for Hot Stamping an Automobile Component with Tailor-Welded High-Strength Steels

    NASA Astrophysics Data System (ADS)

    Tang, Bingtao; Wang, Qiaoling; Wei, Zhaohui; Meng, Xianju; Yuan, Zhengjun

    2016-05-01

    Ultra-high-strength in sheet metal parts can be achieved with hot stamping process. To improve the crash performance and save vehicle weight, it is necessary to produce components with tailored properties. The use of tailor-welded high-strength steel is a relatively new hot stamping process for saving weight and obtaining desired local stiffness and crash performance. The simulation of hot stamping boron steel, especially tailor-welded blanks (TWBs) stamping, is more complex and challenging. Information about thermal/mechanical properties of tools and sheet materials, heat transfer, and friction between the deforming material and the tools is required in detail. In this study, the boron-manganese steel B1500HS and high-strength low-alloy steel B340LA are tailor welded and hot stamped. In order to precisely simulate the hot stamping process, modeling and simulation of hot stamping tailor-welded high-strength steels, including phase transformation modeling, thermal modeling, and thermal-mechanical modeling, is investigated. Meanwhile, the welding zone of tailor-welded blanks should be sufficiently accurate to describe thermal, mechanical, and metallurgical parameters. FE simulation model using TWBs with the thickness combination of 1.6 mm boron steel and 1.2 mm low-alloy steel is established. In order to evaluate the mechanical properties of the hot stamped automotive component (mini b-pillar), hardness and microstructure at each region are investigated. The comparisons between simulated results and experimental observations show the reliability of thermo-mechanical and metallurgical modeling strategies of TWBs hot stamping process.

  6. Life cycle CO{sub 2} evaluation on reinforced concrete structures with high-strength concrete

    SciTech Connect

    Tae, Sungho; Baek, Cheonghoon Shin, Sungwoo

    2011-04-15

    The purpose of this study is to evaluate the environment performance of high-strength concrete used in super tall buildings as material of environmental load reduction. To this end, this study proposed a plan for the evaluation of energy consumption and CO{sub 2} emission throughout the life cycle of the building, and calculated the energy consumption and CO{sub 2} emission throughout the life cycle of tall apartment building that was actually constructed using this plan. Then, we evaluated the energy consumption and CO{sub 2} emission reduction performance for the life cycle of the building by the decrease of concrete and reinforced rebar quantities and the increase of building lifespan obtained through conversion of existing building's concrete compressive strength to 40 MPa high-strength concrete. As a result, the life cycle energy consumption in case 3, a high-strength concrete building, decreased 15.53% and 2.95% respectively compared with cases 1 and 2. The evaluation of the general strength concrete buildings and the life cycle CO{sub 2} emission also decreased 16.70% and 3.37% respectively, compared with cases 1 and 2.

  7. Coseismic landslides reveal near-surface rock strength in a high-relief tectonically active setting

    USGS Publications Warehouse

    Gallen, Sean F; Clark, Marin K; Godt, Jonathan W.

    2014-01-01

    We present quantitative estimates of near-surface rock strength relevant to landscape evolution and landslide hazard assessment for 15 geologic map units of the Longmen Shan, China. Strength estimates are derived from a novel method that inverts earthquake peak ground acceleration models and coseismic landslide inventories to obtain material proper- ties and landslide thickness. Aggregate rock strength is determined by prescribing a friction angle of 30° and solving for effective cohesion. Effective cohesion ranges are from 70 kPa to 107 kPa for 15 geologic map units, and are approximately an order of magnitude less than typical laboratory measurements, probably because laboratory tests on hand-sized specimens do not incorporate the effects of heterogeneity and fracturing that likely control near-surface strength at the hillslope scale. We find that strength among the geologic map units studied varies by less than a factor of two. However, increased weakening of units with proximity to the range front, where precipitation and active fault density are the greatest, suggests that cli- matic and tectonic factors overwhelm lithologic differences in rock strength in this high-relief tectonically active setting.

  8. High strength, low carbon, dual phase steel rods and wires and process for making same

    DOEpatents

    Thomas, Gareth; Nakagawa, Alvin H.

    1986-01-01

    A high strength, high ductility, low carbon, dual phase steel wire, bar or rod and process for making the same is provided. The steel wire, bar or rod is produced by cold drawing to the desired diameter in a single multipass operation a low carbon steel composition characterized by a duplex microstructure consisting essentially of a strong second phase dispersed in a soft ferrite matrix with a microstructure and morphology having sufficient cold formability to allow reductions in cross-sectional area of up to about 99.9%. Tensile strengths of at least 120 ksi to over 400 ksi may be obtained.

  9. ZERODUR glass ceramics: strength data for the design of structures with high mechanical stresses

    NASA Astrophysics Data System (ADS)

    Hartmann, Peter; Nattermann, Kurt; Döhring, Thorsten; Kuhr, Markus; Thomas, Peter; Kling, Guenther; Gath, Peter; Lucarelli, Stefano

    2008-07-01

    With an increasing number of applications mirrors and support structures made of the zero expansion glass ceramic material ZERODUR® has to endure high mechanical loads, e.g. rocket launches or controlled deformations for optical image correction. Like for other glassy materials, the strength of glass ceramics is dominated by its surface condition. Test specimens have been ground with fine grain tools (e.g. D64 diamond grains) and / or subsequently etched. The strength data basis for the design of highly stressed structures has been extended and new information has been derived for the extrapolation to low failure probabilities.

  10. Metastable β-type Ti-30Nb-1Mo-4Sn Alloy with Ultralow Young's Modulus and High Strength

    NASA Astrophysics Data System (ADS)

    Hu, Liang; Guo, Shun; Meng, Qingkun; Zhao, Xinqing

    2014-02-01

    The effect of thermo-mechanical treatment on the mechanical properties of a novel metastable β-type Ti-30Nb-1Mo-4Sn (wt pct) alloy has been investigated. The solution-treated alloy consists of β and α″ phases and exhibits a two-stage yielding with a low yield stress (around 100 MPa). After cold rolling at a reduction of 87.5 pct and subsequent annealing treat at 623 K (350 °C) for 30 minutes, a fine microstructure with nano-sized α precipitates distributed in small β grains as well as high density of dislocations was obtained to achieve a yield strength of 954 MPa and an ultimate tensile strength of 999 MPa. With low stability of β phase and small volume fraction of α precipitates, the annealed specimen exhibits a low Young's modulus of 45 GPa. Such an excellent combination of the low elastic modulus and high strength in mechanical properties indicates a great potential candidate for biomedical applications.

  11. Effect of preseason concurrent muscular strength and high-intensity interval training in professional soccer players.

    PubMed

    Wong, Pui-lam; Chaouachi, Anis; Chamari, Karim; Dellal, Alexandre; Wisloff, Ulrik

    2010-03-01

    This study examined the effect of concurrent muscular strength and high-intensity running interval training on professional soccer players' explosive performances and aerobic endurance. Thirty-nine players participated in the study, where both the experimental group (EG, n = 20) and control group (CG, n = 19) participated in 8 weeks of regular soccer training, with the EG receiving additional muscular strength and high-intensity interval training twice per week throughout. Muscular strength training consisted of 4 sets of 6RM (repetition maximum) of high-pull, jump squat, bench press, back half squat, and chin-up exercises. The high-intensity interval training consisted of 16 intervals each of 15-second sprints at 120% of individual maximal aerobic speed interspersed with 15 seconds of rest. EG significantly increased (p < or = 0.05) 1RM back half squat and bench press but showed no changes in body mass. Within-subject improvement was significantly higher (p < or = 0.01) in the EG compared with the CG for vertical jump height, 10-m and 30-m sprint times, distances covered in the Yo-Yo Intermittent Recovery Test and maximal aerobic speed test, and maximal aerobic speed. High-intensity interval running can be concurrently performed with high load muscular strength training to enhance soccer players' explosive performances and aerobic endurance.

  12. Neck strength: a protective factor reducing risk for concussion in high school sports.

    PubMed

    Collins, Christy L; Fletcher, Erica N; Fields, Sarah K; Kluchurosky, Lisa; Rohrkemper, Mary Kay; Comstock, R Dawn; Cantu, Robert C

    2014-10-01

    As the number of high school students participating in athletics continues to increase, so will the number of sports-related concussions unless effective concussion prevention programs are developed. We sought to develop and validate a cost-effective tool to measure neck strength in a high school setting, conduct a feasibility study to determine if the developed tool could be reliably applied by certified athletic trainers (ATs) in a high school setting, and conduct a pilot study to determine if anthropometric measurements captured by ATs can predict concussion risk. In the study's first phase, 16 adult subjects underwent repeated neck strength testing by a group of five ATs to validate the developed hand-held tension scale, a cost effective alternative to a hand-held dynamometer. In the second phase, during the 2010 and 2011 academic years, ATs from 51 high schools in 25 states captured pre-season anthropometric measurements for 6,704 high school athletes in boys' and girls' soccer, basketball, and lacrosse, as well as reported concussion incidence and athletic exposure data. We found high correlations between neck strength measurements taken with the developed tool and a hand-held dynamometer and the measurements taken by five ATs. Smaller mean neck circumference, smaller mean neck to head circumference ratio, and weaker mean overall neck strength were significantly associated with concussion. Overall neck strength (p < 0.001), gender (p < 0.001), and sport (p = 0.007) were significant predictors of concussions in unadjusted models. After adjusting for gender and sport, overall neck strength remained a significant predictor of concussion (p = 0.004). For every one pound increase in neck strength, odds of concussion decreased by 5 % (OR = 0.95, 95 % CI 0.92-0.98). We conclude that identifying differences in overall neck strength may be useful in developing a screening tool to determine which high school athletes are at higher risk of concussion. Once identified

  13. Neck strength: a protective factor reducing risk for concussion in high school sports.

    PubMed

    Collins, Christy L; Fletcher, Erica N; Fields, Sarah K; Kluchurosky, Lisa; Rohrkemper, Mary Kay; Comstock, R Dawn; Cantu, Robert C

    2014-10-01

    As the number of high school students participating in athletics continues to increase, so will the number of sports-related concussions unless effective concussion prevention programs are developed. We sought to develop and validate a cost-effective tool to measure neck strength in a high school setting, conduct a feasibility study to determine if the developed tool could be reliably applied by certified athletic trainers (ATs) in a high school setting, and conduct a pilot study to determine if anthropometric measurements captured by ATs can predict concussion risk. In the study's first phase, 16 adult subjects underwent repeated neck strength testing by a group of five ATs to validate the developed hand-held tension scale, a cost effective alternative to a hand-held dynamometer. In the second phase, during the 2010 and 2011 academic years, ATs from 51 high schools in 25 states captured pre-season anthropometric measurements for 6,704 high school athletes in boys' and girls' soccer, basketball, and lacrosse, as well as reported concussion incidence and athletic exposure data. We found high correlations between neck strength measurements taken with the developed tool and a hand-held dynamometer and the measurements taken by five ATs. Smaller mean neck circumference, smaller mean neck to head circumference ratio, and weaker mean overall neck strength were significantly associated with concussion. Overall neck strength (p < 0.001), gender (p < 0.001), and sport (p = 0.007) were significant predictors of concussions in unadjusted models. After adjusting for gender and sport, overall neck strength remained a significant predictor of concussion (p = 0.004). For every one pound increase in neck strength, odds of concussion decreased by 5 % (OR = 0.95, 95 % CI 0.92-0.98). We conclude that identifying differences in overall neck strength may be useful in developing a screening tool to determine which high school athletes are at higher risk of concussion. Once identified

  14. Status of High-Strength Nanotube Composites at Johnson Space Center

    NASA Technical Reports Server (NTRS)

    Files, Bradley S.; Mayeaux, Brian; Proft, William; Nikolaev, Pavel; Nicholson, Leonard S. (Technical Monitor)

    2000-01-01

    Single-wall carbon nanotubes offer extraordinary mechanical properties that could start a revolution in materials science. The combination of very high strength and modulus with high strain to failure makes nanotubes an ideal fiber for strengthening in composites. Because of the scale of these fibers, new challenges exist for processing of composite materials and materials characterization. Our project includes aspects of nanotube materials from production and characterization to purification and incorporation into composites for mechanical testing. Early results show that some new techniques will be necessary for the strength of single wall nanotubes to be fully utilized. Current research at JSC focuses on structural polymeric materials to attempt to lower the weight of spacecraft necessary for interplanetary missions. Studies show good nanotube dispersion and wetting by the epoxy materials. Results of tensile strength tests will also be reported. This presentation will focus on current research into polymer nanotube composites and the next steps toward this revolution in aerospace materials.

  15. An Analysis of Java Programming Behaviors, Affect, Perceptions, and Syntax Errors among Low-Achieving, Average, and High-Achieving Novice Programmers

    ERIC Educational Resources Information Center

    Rodrigo, Ma. Mercedes T.; Andallaza, Thor Collin S.; Castro, Francisco Enrique Vicente G.; Armenta, Marc Lester V.; Dy, Thomas T.; Jadud, Matthew C.

    2013-01-01

    In this article we quantitatively and qualitatively analyze a sample of novice programmer compilation log data, exploring whether (or how) low-achieving, average, and high-achieving students vary in their grasp of these introductory concepts. High-achieving students self-reported having the easiest time learning the introductory programming…

  16. CSCS certification and school enrollment impacts upon high school strength facilities, equipment, and safety.

    PubMed

    Judge, Lawrence W; Petersen, Jeffrey C; Bellar, David M; Craig, Bruce W; Gilreath, Erin L

    2013-09-01

    The rapid growth and expanding use of high school strength and conditioning facilities (SCFs) creates a need to research and better understand these vital facilities. This study was designed to examine SCFs at the high school level including facility size, equipment, leadership/staffing, and safety. A 70-item online survey instrument, developed with expert input from certified strength professionals, was used to collect data regarding the SCFs in high schools throughout a midwestern state, and was distributed via email to a total of 390 high school athletic directors. Survey respondents (n = 108) all reported the presence of SCFs with 95.4% indicating a dedicated SCF space. A strong positive correlation (r = 0.610, p ≤ 0.001) was determined between the variables of SCF size in square feet and school size measured by total enrollment. Analysis of variance and χ² analyses revealed significant differences in equipment, facility size, and safety factors based on the categorical variables of school size and the presence of certified strength and conditioning specialist (CSCS) leadership. It appears the CSCS's application of their scientific knowledge goes beyond training athletes for the goal of improving athletic performance to actually influence the SCF itself. Athletic administrators at the high school level need to recognize the impact CSCS program leadership can have on the overall quality of the strength and conditioning program and facility.

  17. A Study on Forming Characteristics of Roll Forming Process with High Strength Steel

    NASA Astrophysics Data System (ADS)

    Joo, ByeongDon; Lee, HyunJong; Kim, DongKyu; Moon, YoungHoon

    2011-08-01

    Roll forming is a kind of sheet metal forming process used to manufacture long sheet metal products with constant cross section. Recently, roll forming technology draws attentions of automotive industries due to its various advantages, such as high production speed, reduced tooling cost and improved quality. In automotive industries, roll formed automotive parts used as structural components in vehicle body frame or sub frame and high strength steel becomes more common to improve safety and fuel efficiency. However, when roll forming process is performed with high strength steel, rolling forming defects, such as spring back, buckling and scratch should be considered more carefully. In this study, efforts to avoid roll forming defects and to optimize forming parameters were performed. FE analysis was performed with high strength steels using commercially available simulation software, COPRA-RF™ and SHAPE-RF™. Forming characteristics were analyzed and roll flower model and proper roll-pass sequences were suggested by analyzing longitudinal strain and deformation behavior. This study provided considerable experience about roll forming process design that using high strength steel.

  18. Effects of high pressure strength of rock material on penetration by shaped charge jet

    NASA Astrophysics Data System (ADS)

    Huang, Hongfa

    2012-03-01

    Perforating of oil/gas well creates communication tunnel between reservoir and wellbore. Shaped charges are widely used as perforators in oilfield industry. The liners of the charges are mostly made of powder metal to prevent solid slug clogging the entrance hole of well casing or locking the hole in perforating gun. High speed jet from the shaped charge pierces through perforating gun, well fluid, well casing, and then penetrates into reservoir formation. Prediction of jet penetration in reservoir rock is critical in modeling of well production. An analytical penetration model developed for solid rod by Tate and Alekseevskii is applied in this work. For better results, strength of formation rock at high pressure needs to be measured. Lateral stress gauge measurements in plate impact tests are conducted. Piezoelectric pressure gauges are imbedded in samples to measure the longitudinal and transverse stress simultaneously. The two stresses provide Hugoniot and material compressive strength. Indiana limestone, a typical rock in perforation testing, is selected as target sample material in the plate impact tests. Since target strength effect on penetration is more important in late stage of penetration when the strength of material becomes significant compared to the impact pressure, all the impact tests are focused on lower impact pressure up to 9 GPa. The measurements show that the strength increases with impact pressure. The results are applied in the penetration calculations. The final penetration matches testing data very well.

  19. Performance optimization and computational design of ultra-high strength gear steels

    NASA Astrophysics Data System (ADS)

    Tiemens, Benjamin Lee

    Rising power density requirements in transmission gear applications are swiftly outpacing gear redesign alone and will ultimately depend on better materials. Ni-Co secondary hardening steels show great promise for these applications due to their optimized combination of strength and toughness. The commercially available secondary hardening alloys GearMet RTM C61 and C67 have already demonstrated promising contact fatigue resistance, however bending fatigue is anticipated to be the primary failure mode limiting high power density gear applications. Single tooth bending fatigue testing was therefore completed on C61 and C67 spur gears to both assess the optimized performance of these alloys as well as identify defect populations currently limiting further advances. The resultant best-practice C61 spur gears in a shot peened and isotropic superfinished condition outperformed the top-ranking premium gear steel, demonstrating an approximate 15% improvement in bending fatigue endurance limit. Fatigue failures limiting further bending fatigue performance were identified to primarily initiate at three defect classes: shot peening-induced surface damage, subsurface inter-granular cleavage facets and Al2O3 and La2O2S inclusions. C67 spur gears did not show increased performance despite elevated surface hardness levels due to the inability of current shot peening practices to achieve maximum compressive stress in ultra-high hardness materials. In an effort to reduce the material cost of these alloys through minimization/elimination of cobalt alloying additions, BCC Cu precipitation was incorporated to offset ensuing losses in temper resistance by providing additional heterogeneous nucleation sites for the M2C strengthening dispersion. Fifty-pound experimental heats were made of four designed compositions. Peak hardness levels achieved during tempering fell on average 200 VHN short of the 900 VHN designed surface hardness. 3-dimensional local electrode atom probe (LEAP

  20. International Note: Between-Domain Relations of Chinese High School Students' Academic Achievements

    ERIC Educational Resources Information Center

    Yangyang, Liu

    2012-01-01

    The present study examined the between-domain relations of Chinese high school students' academic achievements. In a sample of 1870 Chinese 10th grade students, the results indicated that Chinese high school students' academic achievements were correlated across nine subjects. In line with the previous Western findings, the findings suggested that…

  1. The Effect of the Time Management Art on Academic Achievement among High School Students in Jordan

    ERIC Educational Resources Information Center

    Al-Zoubi, Maysoon

    2016-01-01

    This study aimed at recognizing the effect of the Time Management Art on academic achievement among high school students in the Hashemite Kingdom of Jordan. The researcher employed the descriptive-analytic research to achieve the purpose of the study where he chose a sample of (2000) high school female and male students as respondents to the…

  2. High-Achieving and Average Students' Reading Growth: Contrasting School and Summer Trajectories

    ERIC Educational Resources Information Center

    Rambo-Hernandez, Karen E.; McCoach, D. Betsy

    2015-01-01

    Much is unknown about how initially high-achieving students grow academically, especially given the measurement issues inherent in assessing growth for the highest performing students. This study compared initially high-achieving and average students' growth in reading (in a cohort of third-grade students from 2,000 schools) over 3 years.…

  3. A Longitudinal Investigation of Project-Based Instruction and Student Achievement in High School Social Studies

    ERIC Educational Resources Information Center

    Summers, Emily J.; Dickinson, Gail

    2012-01-01

    This longitudinal study focused on how project-based instruction (PBI) influenced secondary social studies students' academic achievement and promoted College and Career Readiness (CCR). We explored and compared student achievement in a PBI high school versus a traditional instruction high school within the same rural school district. While…

  4. The Meaning High-Achieving African-American Males in an Urban High School Ascribe to Mathematics

    ERIC Educational Resources Information Center

    Thompson, LaTasha; Davis, Julius

    2013-01-01

    Many researchers, educators, administrators, policymakers and members of the general public doubt the prevalence of high-achieving African-American males in urban high schools capable of excelling in mathematics. As part of a larger study, the current study explored the educational experiences of four high-achieving African-American males…

  5. High dose weekly oral prednisone improves strength in boys with Duchenne muscular dystrophy.

    PubMed

    Connolly, Anne M; Schierbecker, Jeanine; Renna, Renee; Florence, Julaine

    2002-12-01

    Daily prednisone improves strength in boys with Duchenne muscular dystrophy, but side effects are almost universal. We used a different dosing regimen of prednisone to determine if benefit to boys with Duchenne muscular dystrophy might be maintained with fewer side effects. Twice weekly oral prednisone was given each Friday and Saturday (5mg/kg/dose). This total dose is twice as high as the daily low dosage prednisone regimen (0.75 mg/kg/day). Twenty boys (8.0+/-1.2 years) were treated. Historical control groups included 18 untreated boys (6.1+/-1.6 years) and four boys (7.3+/-0.6 years) treated with daily prednisone. Strength (using a hand-held manometer and grip meter) and timed functional testing were measured. There was an improvement in upper extremity strength for 95% of boys (n=20) at 6 months using quantitative strength testing. Improvement in lower extremity strength occurred in all boys with antigravity quadriceps strength (17/17). The improvement (P=0.001 for proximal upper extremities; P=0.002 for grip; and P<0.0001 for proximal lower extremities) was significant compared to untreated boys. Sixteen boys were treated continuously for more than 12 months (22+/-1.5 months). Of these, 15 remained significantly stronger than prior to treatment and 8/16 showed additional gains in strength after six months of treatment. Six boys were on the weekly prednisolone 2 years or longer without interruption. All six had upper and lower extremity strength at follow-up that was as good or better than at baseline. Functional testing improved in boys less than 8 years without contractures. Three boys without antigravity quadriceps strength at the start of treatment lost the ability to walk unassisted within 6 months. Eight other boys lost the ability to ambulate unassisted between 12 and 24 months of treatment. In each, progressive contractures developed. Linear growth was maintained in all boys on weekly treatment. Obesity rates did not differ from untreated boys. Twice

  6. Span-to-depth ratio effect on shear strength of steel fiber-reinforced high-strength concrete deep beams using ANN model

    NASA Astrophysics Data System (ADS)

    Naik, Uday; Kute, Sunil

    2013-12-01

    The paper predicts the shear strength of high-strength steel fiber-reinforced concrete deep beams. It studies the effect of clear span-to-overall depth ratio on shear capacity of steel fiber high-strength deep beams using artificial neural network (ANN8). The three-layered model has eight input nodes which represent width, effective depth, volume fraction, fiber aspect ratio and shear span-to-depth ratio, longitudinal steel, compressive strength of concrete, and clear span-to-overall depth ratio. The model predicts the shear strength of high-strength steel fiber deep beams to be reasonably good when compared with the results of proposed equations by researchers as well as the results obtained by neural network (ANN7) which is developed for seven inputs excluding span-to-depth ratio. The developed neural network ANN8 proves the versatility of artificial neural networks to establish the relations between various parameters affecting complex behavior of steel fiber-reinforced concrete deep beams and costly experimental processes.

  7. Formability Analysis of Diode-Laser-Welded Tailored Blanks of Advanced High-Strength Steel Sheets

    NASA Astrophysics Data System (ADS)

    Panda, S. K.; Baltazar Hernandez, V. H.; Kuntz, M. L.; Zhou, Y.

    2009-08-01

    Currently, advances due to tailored blanking can be enhanced by the development of new grades of advanced high-strength steels (HSSs), for the further weight reduction and structural improvement of automotive components. In the present work, diode laser welds of three different grades of advanced high-strength dual-phase (DP) steel sheets (with tensile strengths of 980, 800, and 450 MPa) to high-strength low-alloy (HSLA) material were fabricated by applying the proper welding parameters. Formability in terms of Hecker’s limiting dome height (LDH), the strain distribution on the hemispherical dome surface, the weld line movement during deformation, and the load-bearing capacity during the stretch forming of these different laser-welded blanks were compared. Finite element (FE) analysis of the LDH tests of both the parent metals and laser-welded blanks was done using the commercially available software package LS-DYNA (Livermore Software Technology Corporation, Livermore, CA); the results compared well with the experimental data. It was also found that the LDH was not affected by the soft zone or weld zone properties; it decreased, however, with an increase in a nondimensional parameter, the “strength ratio” (SR). The weld line movement during stretch forming is an indication of nonuniform deformation resulting in a decrease in the LDH. In all the dissimilar weldments, fracture took place on the HSLA side, but the fracture location shifted to near the weld line (at the pole) in tailor-welded blanks (TWBs) of a higher strength ratio.

  8. Design of Hierarchically Cut Hinges for Highly Stretchable and Reconfigurable Metamaterials with Enhanced Strength.

    PubMed

    Tang, Yichao; Lin, Gaojian; Han, Lin; Qiu, Songgang; Yang, Shu; Yin, Jie

    2015-11-25

    Applying hierarchical cuts to thin sheets of elastomer generates super-stretchable and reconfigurable metamaterials, exhibiting highly nonlinear stress-strain behaviors and tunable phononic bandgaps. The cut concept fails on brittle thin sheets due to severe stress concentration in the rotating hinges. By engineering the local hinge shapes and global hierarchical structure, cut-based reconfigurable metamaterials with largely enhanced strength are realized.

  9. Hydration and muscular performance: does fluid balance affect strength, power and high-intensity endurance?

    PubMed

    Judelson, Daniel A; Maresh, Carl M; Anderson, Jeffrey M; Armstrong, Lawrence E; Casa, Douglas J; Kraemer, William J; Volek, Jeff S

    2007-01-01

    Significant scientific evidence documents the deleterious effects of hypohydration (reduced total body water) on endurance exercise performance; however, the influence of hypohydration on muscular strength, power and high-intensity endurance (maximal activities lasting >30 seconds but <2 minutes) is poorly understood due to the inconsistent results produced by previous investigations. Several subtle methodological choices that exacerbate or attenuate the apparent effects of hypohydration explain much of this variability. After accounting for these factors, hypohydration appears to consistently attenuate strength (by approximately 2%), power (by approximately 3%) and high-intensity endurance (by approximately 10%), suggesting alterations in total body water affect some aspect of force generation. Unfortunately, the relationships between performance decrement and crucial variables such as mode, degree and rate of water loss remain unclear due to a lack of suitably uninfluenced data. The physiological demands of strength, power and high-intensity endurance couple with a lack of scientific support to argue against previous hypotheses that suggest alterations in cardiovascular, metabolic and/or buffering function represent the performance-reducing mechanism of hypohydration. On the other hand, hypohydration might directly affect some component of the neuromuscular system, but this possibility awaits thorough evaluation. A critical review of the available literature suggests hypohydration limits strength, power and high-intensity endurance and, therefore, is an important factor to consider when attempting to maximise muscular performance in athletic, military and industrial settings.

  10. Preparation of high-strength nanometer scale twinned coating and foil

    DOEpatents

    Zhang, Xinghang; Misra, Amit; Nastasi, Michael A.; Hoagland, Richard G.

    2006-07-18

    Very high strength single phase stainless steel coating has been prepared by magnetron sputtering onto a substrate. The coating has a unique microstructure of nanometer spaced twins that are parallel to each other and to the substrate surface. For cases where the coating and substrate do not bind strongly, the coating can be peeled off to provide foil.

  11. High strength, light weight Ti-Y composites and method of making same

    DOEpatents

    Verhoeven, J.D.; Ellis, T.W.; Russell, A.M.; Jones, L.L.

    1993-04-06

    A high strength, light weight in-situ'' Ti-Y composite is produced by deformation processing a cast body having Ti and Y phase components distributed therein. The composite comprises elongated, ribbon-shaped Ti and Y phase components aligned along an axis of the deformed body.

  12. High strength, light weight Ti-Y composites and method of making same

    DOEpatents

    Verhoeven, John D.; Ellis, Timothy W.; Russell, Alan M.; Jones, Lawrence L.

    1993-04-06

    A high strength, light weight "in-situ" Ti-Y composite is produced by deformation processing a cast body having Ti and Y phase components distributed therein. The composite comprises elongated, ribbon-shaped Ti and Y phase components aligned along an axis of the deformed body.

  13. An investigation of the plastic fracture of high strength steels. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Cox, T. B.; Low, J. R., Jr.

    1973-01-01

    Three generally recognized stages of plastic fracture in high strength steels are considered in detail. These stages consist of void initiation, void growth, and void coalescence. A brief review of the existing literature on plastic fracture is included along with an outline of the experimental approach used in the investigation.

  14. Relationship of Muscular Strength on Work Performance in High School Students with Mental Retardation

    ERIC Educational Resources Information Center

    Smail, Karen M.; Horvat, Michael

    2006-01-01

    The relationship of muscular strength on work performance measures in high school students with mild mental retardation was investigated. Ten students from a self contained Special Education class were matched according to age, gender, height, and weight then randomly assigned to either the treatment group or control group. The treatment group…

  15. Kic size effect study on two high-strength steels using notched bend specimens

    NASA Technical Reports Server (NTRS)

    Stonesifer, F. R.

    1974-01-01

    Five methods are used to calculate plane strain fracture toughness (K sub Q) values for bend-specimens of various sizes from two high-strength steels. None of the methods appeared to satisfactorily predict valid stress intensity factor (K sub IC) values from specimens of sizes well below that required by E399 standard tests.

  16. Marketing research for EE G Mound Applied Technologies' heat treatment process of high strength materials

    SciTech Connect

    Shackson, R.H.

    1991-10-09

    This report summarizes research conducted by ITI to evaluate the commercialization potential of EG G Mound Applied Technologies' heat treatment process of high strength materials. The remainder of the report describes the nature of demand for maraging steel, extent of demand, competitors, environmental trends, technology life cycle, industry structure, and conclusion. (JL)

  17. Extrusion Die Design and Process Simulation of High Strength Aluminium Alloy

    NASA Astrophysics Data System (ADS)

    Sheu, Jinn-Jong; Chen, Yan-Hong; Su, Guan-Cheng

    2011-01-01

    Aluminium alloy 7075 is an excellent metal with the features of high strength and light weight. The solid extruded parts of AL 7075 are commonly used in the structure members of airplanes and bicycles. The seamless tubes of AL 7075 are also used, while tubes with welding line (seamed) are mainly made by the other types of aluminium alloy. This research is focused on the extrusion die design and process simulation of the rectangular seamed AL 7075 tubes. A new die design concept is proposed to increase the welding pressure in the chamber to solve the problem of poor welding ability of AL 7075. The key points of welding ability improvement are the higher welding pressure, the crucial billet temperature, and the extrusion speed. The designed extrusion die should have some features to control the material flow and achieve the higher welding pressure. In this paper, not only use the traditional die bearing and the welding chamber, but also add a conical guiding chamber (specified with chamber height and width) to improve the material flow control. Finite element method is used to simulate the extrusion process and evaluate the effect of die design parameters for a seamed rectangular 7075 tube extrusion. The die stress should be considered carefully because of increasing the welding pressure also increases the die stress. Taguchi method is used to obtain the optimum combination of die design parameters to get higher welding pressure and keep the die stress at a reasonable low level. The method proposed in this paper is able to increase the welding pressure with the cost of reasonable die stress.

  18. Neptunium(V) Adsorption to Bacteria at Low and High Ionic Strength

    NASA Astrophysics Data System (ADS)

    Ams, D.; Swanson, J. S.; Reed, D. T.

    2010-12-01

    Np(V) is expected to be the predominant oxidation state of neptunium in aerobic natural waters. Np(V), as the NpO2+ aquo and associated complexed species, is readily soluble, interacts weakly with geologic media, and has a high redox stability under a relatively wide range of subsurface conditions. These chemical properties, along with a long half-life make it a primary element of concern regarding long-term nuclear waste storage and subsurface containment. The fate and transport of neptunium in the environment may be influenced by adsorption onto bacterial surfaces. The adsorption of neptunium to bacterial surfaces ties the mobility of the contaminant to the mobility of the bacterium. In this study, the adsorption of the neptunyl (NpO2+) ion was evaluated at low ionic strength on a common soil bacterium and at high ionic strength on a halophilic bacterium isolated from a briny groundwater near the Waste Isolation Pilot Plant (WIPP) in southeast New Mexico. Adsorption experiments were performed in batch reactors as a function of pH, ionic strength, and bacteria/Np mass ratio. Np(V) adsorption was modeled using a surface complexation approach with the mathematical program FITEQL to determine functional group specific binding constants. The data from acid and base titrations of the bacteria used were also modeled to estimate the concentrations and deprotonation constants of discrete bacterial surface functional groups. Bacterial functional group characteristics and Np(V) adsorption behavior between the soil bacterium and the halophilic bacterium were compared. These results highlight key similarities and differences in actinide adsorption behavior in environments of significantly different ionic strength. The observed adsorption behavior may be linked to similarities and differences in the characteristics of the moieties between the cell walls of common gram-negative soil and halophilic bacteria. Moreover, differences in adsorption behavior may also reflect ionic

  19. Neptunium(V) adsorption to bacteria at low and high ionic strength

    SciTech Connect

    Ams, David A; Swanson, Juliet S; Reed, Donald T; Fein, Jeremy B

    2010-12-08

    Np(V) is expected to be the predominant oxidation state of neptunium in aerobic natural waters. Np(V), as the NpO{sub 2}{sup +} aquo and associated complexed species, is readily soluble, weakly interacting with geologic media, and has a high redox stability under a relatively wide range of subsurface conditions. These chemical properties, along with a long half-life make it a primary element of concern regarding long-term nuclear waste storage and subsurface contaminant. The fate and transport of neptunium in the environment may be influenced by adsorption onto bacterial surfaces. The adsorption of neptunium to bacterial surfaces ties the mobility of the contaminant to the mobility of the bacterium. In this study, the adsorption of the neptunyl (NpO{sub 2}{sup +}) ion was evaluated at low ionic strength on a common soil bacterium and at high ionic strength on a halophilic bacterium isolated from a briny groundwater near the Waste Isolation Pilot Plant (WIPP) in southeast New Mexico. Adsorption experiments were performed in batch reactors as a function of pH, ionic strength, and bacterialNp mass ratio. Np(V) adsorption was modeled using a surface complexation approach with the mathematical program FITEQL to determine functional group specific binding constants. The data from acid and base titrations of the bacteria were also modeled to estimate the concentrations and deprotonation constants of discrete bacterial surface functional groups. Bacterial functional group characteristics and Np(V) adsorption behavior between the soil bacterium and the halophilic bacterium were compared. These results highlight the key similarities and differences in actinide adsorption behavior in environments of significantly different ionic strength. Similarities in adsorption behavior may be linked to similarities in the characteristics of the moieties between all bacterial cell walls. Differences in adsorption behavior may reflect differences in ionic strength effects, rather than

  20. Blood flow-restricted strength training displays high functional and biological efficacy in women: a within-subject comparison with high-load strength training.

    PubMed

    Ellefsen, Stian; Hammarström, Daniel; Strand, Tor A; Zacharoff, Erika; Whist, Jon E; Rauk, Irene; Nygaard, Håvard; Vegge, Geir; Hanestadhaugen, Marita; Wernbom, Mathias; Cumming, Kristoffer T; Rønning, Roar; Raastad, Truls; Rønnestad, Bent R

    2015-10-01

    Limited data exist on the efficacy of low-load blood flow-restricted strength training (BFR), as compared directly to heavy-load strength training (HST). Here, we show that 12 wk of twice-a-week unilateral BFR [30% of one repetition maximum (1RM) to exhaustion] and HST (6-10RM) of knee extensors provide similar increases in 1RM knee extension and cross-sectional area of distal parts of musculus quadriceps femoris in nine untrained women (age 22 ± 1 yr). The two protocols resulted in similar acute increases in serum levels of human growth hormone. On the cellular level, 12 wk of BFR and HST resulted in similar shifts in muscle fiber composition in musculus vastus lateralis, evident as increased MyHC2A proportions and decreased MyHC2X proportions. They also resulted in similar changes of the expression of 29 genes involved in skeletal muscle function, measured both in a rested state following 12 wk of training and subsequent to singular training sessions. Training had no effect on myonuclei proportions. Of particular interest, 1) gross adaptations to BFR and HST were greater in individuals with higher proportions of type 2 fibers, 2) both BFR and HST resulted in approximately four-fold increases in the expression of the novel exercise-responsive gene Syndecan-4, and 3) BFR provided lesser hypertrophy than HST in the proximal half of musculus quadriceps femoris and also in CSApeak, potentially being a consequence of pressure from the tourniquet utilized to achieve blood flow restriction. In conclusion, BFR and HST of knee extensors resulted in similar adaptations in functional, physiological, and cell biological parameters in untrained women.

  1. Blood flow-restricted strength training displays high functional and biological efficacy in women: a within-subject comparison with high-load strength training

    PubMed Central

    Hammarström, Daniel; Strand, Tor A.; Zacharoff, Erika; Whist, Jon E.; Rauk, Irene; Nygaard, Håvard; Vegge, Geir; Hanestadhaugen, Marita; Wernbom, Mathias; Cumming, Kristoffer T.; Rønning, Roar; Raastad, Truls; Rønnestad, Bent R.

    2015-01-01

    Limited data exist on the efficacy of low-load blood flow-restricted strength training (BFR), as compared directly to heavy-load strength training (HST). Here, we show that 12 wk of twice-a-week unilateral BFR [30% of one repetition maximum (1RM) to exhaustion] and HST (6-10RM) of knee extensors provide similar increases in 1RM knee extension and cross-sectional area of distal parts of musculus quadriceps femoris in nine untrained women (age 22 ± 1 yr). The two protocols resulted in similar acute increases in serum levels of human growth hormone. On the cellular level, 12 wk of BFR and HST resulted in similar shifts in muscle fiber composition in musculus vastus lateralis, evident as increased MyHC2A proportions and decreased MyHC2X proportions. They also resulted in similar changes of the expression of 29 genes involved in skeletal muscle function, measured both in a rested state following 12 wk of training and subsequent to singular training sessions. Training had no effect on myonuclei proportions. Of particular interest, 1) gross adaptations to BFR and HST were greater in individuals with higher proportions of type 2 fibers, 2) both BFR and HST resulted in approximately four-fold increases in the expression of the novel exercise-responsive gene Syndecan-4, and 3) BFR provided lesser hypertrophy than HST in the proximal half of musculus quadriceps femoris and also in CSApeak, potentially being a consequence of pressure from the tourniquet utilized to achieve blood flow restriction. In conclusion, BFR and HST of knee extensors resulted in similar adaptations in functional, physiological, and cell biological parameters in untrained women. PMID:26202071

  2. Effects of atamp-charging coke making on strength and high temperature thermal properties of coke.

    PubMed

    Zhang, Yaru; Bai, Jinfeng; Xu, Jun; Zhong, Xiangyun; Zhao, Zhenning; Liu, Hongchun

    2013-12-01

    The stamp-charging coke making process has some advantages of improving the operation environment, decreasing fugitive emission, higher gas collection efficiency as well as less environmental pollution. This article describes the different structure strength and high temperature thermal properties of 4 different types of coke manufactured using a conventional coking process and the stamp-charging coke making process. The 4 kinds of cokes were prepared from the mixture of five feed coals blended by the petrography blending method. The results showed that the structure strength indices of coke prepared using the stamp-charging coke method increase sharply. In contrast with conventional coking process, the stamp-charging process improved the coke strength after reaction but had little impact on the coke reactivity index.

  3. Carbon nanotube yarns with high tensile strength made by a twisting and shrinking method.

    PubMed

    Liu, Kai; Sun, Yinghui; Zhou, Ruifeng; Zhu, Hanyu; Wang, Jiaping; Liu, Liang; Fan, Shoushan; Jiang, Kaili

    2010-01-29

    We report a simple and continuous spinning method that combines twisting and shrinking processes to produce carbon nanotube yarns. In this method, a yarn freshly spun from a super-aligned carbon nanotube array is first twisted and then passes through a volatile solvent for shrinking. The as-produced yarn consists of densely packed carbon nanotubes, and thus has a tensile strength up to about 1 GPa. The tensile strength depends on the diameter and the twisting angle of the yarn. Different kinds of solvents, such as water, ethanol, and acetone, are used to shrink the twisted yarns, and acetone shows the best shrinking effect. The origin of the solvent shrinking effect is investigated. Our method is favorable for continuous mass production of high strength carbon nanotube yarns with a wide range of diameters, especially ultra-thin yarns. PMID:20009208

  4. High Tensile Strength Amalgams for In-Space Fabrication and Repair

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.

    2006-01-01

    Amalgams are well known for their use in dental practice as a tooth filling material. They have a number of useful attributes that include room temperature fabrication, corrosion resistance, dimensional stability, and very good compressive strength. These properties well serve dental needs but, unfortunately, amalgams have extremely poor tensile strength, a feature that severely limits other potential applications. Improved material properties (strength and temperature) of amalgams may have application to the freeform fabrication of repairs or parts that might be necessary during an extended space mission. Advantages would include, but are not limited to: the ability to produce complex parts, a minimum number of processing steps, minimum crew interaction, high yield - minimum wasted material, reduced gravity compatibility, minimum final finishing, safety, and minimum power consumption. The work presented here shows how the properties of amalgams can be improved by changing particle geometries in conjunction with novel engineering metals.

  5. High Tensile Strength Amalgams for In-Space Repair and Fabrication

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.

    2005-01-01

    Amalgams are defined as an alloy of mercury with one or more other metals. These, along with those based on gallium (also liquid at near room temperature), are widely used in dental practice as a tooth filling material. Amalgams have a number of useful attributes that indude room temperature compounding. corrosion resistance, dimensional stability, and good compressive strength. These properties well serve dental needs but, unfortunately, amalgams have extremely poor tensile strength, a feature that severely limits their applications. The work presented here demonstrates how, by modifying particle geometry, the tensile strength of amalgams can be increased and thus extending the range of potential applications. This is relevant to, for example, the freeform fabrication of replacement parts that might be necessary during an extended space mission. Advantages, i.e. Figures-of-Merit. include the ability to produce complex parts, minimum crew interaction, high yield - minimum wasted material, reduced gravity compatibility, minimum final finishing, safety, and minimum power consumption.

  6. Structural optimization of 3D-printed synthetic spider webs for high strength

    NASA Astrophysics Data System (ADS)

    Qin, Zhao; Compton, Brett G.; Lewis, Jennifer A.; Buehler, Markus J.

    2015-05-01

    Spiders spin intricate webs that serve as sophisticated prey-trapping architectures that simultaneously exhibit high strength, elasticity and graceful failure. To determine how web mechanics are controlled by their topological design and material distribution, here we create spider-web mimics composed of elastomeric filaments. Specifically, computational modelling and microscale 3D printing are combined to investigate the mechanical response of elastomeric webs under multiple loading conditions. We find the existence of an asymptotic prey size that leads to a saturated web strength. We identify pathways to design elastomeric material structures with maximum strength, low density and adaptability. We show that the loading type dictates the optimal material distribution, that is, a homogeneous distribution is better for localized loading, while stronger radial threads with weaker spiral threads is better for distributed loading. Our observations reveal that the material distribution within spider webs is dictated by the loading condition, shedding light on their observed architectural variations.

  7. Structural optimization of 3D-printed synthetic spider webs for high strength.

    PubMed

    Qin, Zhao; Compton, Brett G; Lewis, Jennifer A; Buehler, Markus J

    2015-01-01

    Spiders spin intricate webs that serve as sophisticated prey-trapping architectures that simultaneously exhibit high strength, elasticity and graceful failure. To determine how web mechanics are controlled by their topological design and material distribution, here we create spider-web mimics composed of elastomeric filaments. Specifically, computational modelling and microscale 3D printing are combined to investigate the mechanical response of elastomeric webs under multiple loading conditions. We find the existence of an asymptotic prey size that leads to a saturated web strength. We identify pathways to design elastomeric material structures with maximum strength, low density and adaptability. We show that the loading type dictates the optimal material distribution, that is, a homogeneous distribution is better for localized loading, while stronger radial threads with weaker spiral threads is better for distributed loading. Our observations reveal that the material distribution within spider webs is dictated by the loading condition, shedding light on their observed architectural variations. PMID:25975372

  8. Nonlinear finite element analysis of high-strength concrete columns and experimental verification

    NASA Astrophysics Data System (ADS)

    Lu, Xilin; Chen, Shaolin

    2008-03-01

    This paper describes a nonlinear finite element (FE) analysis of high strength concrete (HSC) columns, and verifies the results through laboratory experiments. First, a cyclically lateral loading test on nine cantilever column specimens of HSC is described and a numerical simulation is presented to verify the adopted FE models. Next, based on the FE model for specimen No.6, numerical simulations for 70 cases, in which different concrete strengths, stirrup ratios and axial load ratios are considered, are presented to explore the effect of these parameters on the behavior of the HSC columns, and to check the rationality of requirements for these columns specified in the China Code for Seismic Design of Buildings ( GB 50011-2001). In addition, three cases with different stirrup strengths are analyzed to investigate their effect on the behavior of HSC columns. Finally, based on the numerical results some conclusions are presented.

  9. Structural optimization of 3D-printed synthetic spider webs for high strength

    PubMed Central

    Qin, Zhao; Compton, Brett G.; Lewis, Jennifer A.; Buehler, Markus J.

    2015-01-01

    Spiders spin intricate webs that serve as sophisticated prey-trapping architectures that simultaneously exhibit high strength, elasticity and graceful failure. To determine how web mechanics are controlled by their topological design and material distribution, here we create spider-web mimics composed of elastomeric filaments. Specifically, computational modelling and microscale 3D printing are combined to investigate the mechanical response of elastomeric webs under multiple loading conditions. We find the existence of an asymptotic prey size that leads to a saturated web strength. We identify pathways to design elastomeric material structures with maximum strength, low density and adaptability. We show that the loading type dictates the optimal material distribution, that is, a homogeneous distribution is better for localized loading, while stronger radial threads with weaker spiral threads is better for distributed loading. Our observations reveal that the material distribution within spider webs is dictated by the loading condition, shedding light on their observed architectural variations. PMID:25975372

  10. Sliding wear, toughness and microstructural relationships in high strength Fe/Cr/C experimental steels

    SciTech Connect

    Salesky, W.J.

    1980-06-01

    Hardness has been believed to be the major parameter influencing wear resistance of materials. Recently, it was suggested that combinations of high strength and toughness may lead to optimum wear resistance. It is known that the martensite transformation can be exploited to provide a variety of strength-toughness combinations. Small additions of Mn or Ni to the Fe/4Cr/.3C martensitic alloys have been shown to increase toughness while maintaining strength via increasing the volume fraction of retained austenite. An investigation of the relationships between microstructure, toughness, and sliding wear resistance for these experimental alloys is reported. Comparative studies were performed on several industrial alloys to provide a practical basis for comparison of these medium carbon experimental steels.

  11. High-Strength Composite Fabric Tested at Structural Benchmark Test Facility

    NASA Technical Reports Server (NTRS)

    Krause, David L.

    2002-01-01

    Large sheets of ultrahigh strength fabric were put to the test at NASA Glenn Research Center's Structural Benchmark Test Facility. The material was stretched like a snare drum head until the last ounce of strength was reached, when it burst with a cacophonous release of tension. Along the way, the 3-ft square samples were also pulled, warped, tweaked, pinched, and yanked to predict the material's physical reactions to the many loads that it will experience during its proposed use. The material tested was a unique multi-ply composite fabric, reinforced with fibers that had a tensile strength eight times that of common carbon steel. The fiber plies were oriented at 0 and 90 to provide great membrane stiffness, as well as oriented at 45 to provide an unusually high resistance to shear distortion. The fabric's heritage is in astronaut space suits and other NASA programs.

  12. Metallurgical and mechanical properties of laser welded high strength low alloy steel.

    PubMed

    Oyyaravelu, Ramachandran; Kuppan, Palaniyandi; Arivazhagan, Natarajan

    2016-05-01

    The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure. PMID:27222751

  13. A study on high strength concrete prepared with large volumes of low calcium fly ash

    SciTech Connect

    Poon, C.S.; Lam, L.; Wong, Y.L.

    2000-03-01

    This paper presents the results of a laboratory study on high strength concrete prepared with large volumes of low calcium fly ash. The parameters studied included compressive strength, heat of hydration, chloride diffusivity, degree of hydration, and pore structures of fly ash/cement concrete and corresponding pastes. The experimental results showed that concrete with a 28-day compressive strength of 80 MPA could be obtained with a water-to-binder (w/b) ratio of 0.24, with a fly ash content of 45%. Such concrete has lower heat of hydration and chloride diffusivity than the equivalent plain cement concrete or concrete prepared with lower fly ash contents. The test results showed that at lower w/b ratios, the contribution to strength by the fly ash was higher than in the mixes prepared with higher w/b ratios. The study also quantified the reaction rates of cement and fly ash in the cementitious materials. The results demonstrated the dual effects of fly ash in concrete: (1) act as a micro-aggregate and (2) being a pozzolana. It was also noted that the strength contribution of fly ash in concrete was better than in the equivalent cement/fly ash pastes suggesting the fly ash had improved the interfacial bond between the past and the aggregates in the concrete. Such an improvement was also reflected in the results of the mercury intrusion porosimetry (MIP) test.

  14. Metallurgical and mechanical properties of laser welded high strength low alloy steel

    PubMed Central

    Oyyaravelu, Ramachandran; Kuppan, Palaniyandi; Arivazhagan, Natarajan

    2016-01-01

    The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure. PMID:27222751

  15. Metallurgical and mechanical properties of laser welded high strength low alloy steel.

    PubMed

    Oyyaravelu, Ramachandran; Kuppan, Palaniyandi; Arivazhagan, Natarajan

    2016-05-01

    The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure.

  16. Springback analysis for the stamping of an automotive part with high strength steel sheet

    NASA Astrophysics Data System (ADS)

    Hung, Tzu-Hao; Tsai, Heng-Kuang; Chang, Chih-Kai; Hsu, Yu-Hung; Chen, Fuh-Kuo; Chung, Kuo-Hsin

    2013-05-01

    The study of springback analysis of 440MPa high strength steel is investigated in this paper. Because of the springback phenomenon is related to the material properties and the deformation mechanism during the forming process, the material properties of 440MPa high strength steel are studied at first. The material properties of 440MPa high strength steel are obtained by conducting cyclic uniaxial tension-compression tests with different strain ranges. In order to apply the material properties obtained from the experiments to the finite element analysis, the material constants required in the Yoshida-Uemori model (Y-U model) with the Bauschinger effect considered are established. For realizing the springback characteristics of 440MPa high strength steel, the U-hat draw-bending and V-shape bending are examined by the finite element analysis. From the simulation results, it finds that the side wall curl phenomenon occurs in the U-hat drawbending and the springback phenomenon appears in the V-shape bending. Moreover, it also shows that the side wall curl phenomenon and springback phenomenon are more obvious in the finite element simulations with the Bauschinger effect considered. Finally, the validation of springback prediction is performed by stamping an engine hood reinforcement with 440MPa high strength steel sheet. From the stamping results, it shows that the simulation results of springback prediction are in a well agreement to the production part data. It also finds that the springback predictions are more accurate by the finite element simulations with the use of the Y-U model. It is also found that for a stamping part which is subjected to a reversed tension-compression deformation in the forming process, the occurrence of the Bauschinger effect is obvious. It is also concluded that the accuracy of springback prediction can be much improved by the use of material model with the Bauschinger effect considered.

  17. High-strength stainless steels for corrosion mitigation in prestressed concrete: Development and evaluation

    NASA Astrophysics Data System (ADS)

    Moser, Robert D.

    Corrosion of prestressing reinforcement in concrete structures exposed to marine environments and/or deicing chemicals is a problem of critical concern. While many corrosion mitigation technologies are available for reinforced concrete (RC), those available for use in prestressed concrete (PSC) are limited and in many cases cannot provide the 100+ year service life needed in new construction, particularly when exposed to severe marine environments. The use of stainless steel alloys in RC structures has shown great success in mitigating corrosion in even the most severe of exposures. However, the use of high-strength stainless steels (HSSSs) for corrosion mitigation in PSC structures has received limited attention. To address these deficiencies in knowledge, an experimental study was conducted to investigate the feasibility of using HSSSs for corrosion mitigation in PSC. The study examined mechanical behavior, corrosion resistance, and techniques for the production of HSSS prestressing strands. Stainless steel grades 304, 316, 2101, 2205, 2304, and 17-7 were produced as cold drawn wires with diameters of approximately 4 mm (0.16 in). A 1080 prestressing steel was also included to serve as a control. Tensile strengths of 1250 to 1550 MPa (181 to 225 ksi) were achieved in the cold-drawn candidate HSSSs. Non-ductile failure modes with no post-yield strain hardening were observed in all candidate HSSSs. 1000 hr stress relaxation of all candidate HSSSs was predicted to be between 6 and 8 % based on the results of 200 hr tests conducted at 70 % of the ultimate tensile strength. Residual stresses due to the cold drawing had a significant influence on stress vs. strain behavior and stress relaxation. Electrochemical corrosion testing found that in solutions simulating alkaline concrete, all candidate HSSSs showed exceptional corrosion resistance at chloride (Cl-) concentrations from zero to 0.25 M. However, when exposed to solutions simulating carbonated concrete, corrosion

  18. Notch fatigue behavior: Metallic glass versus ultra-high strength steel

    PubMed Central

    Wang, X. D.; Qu, R. T.; Wu, S. J.; Duan, Q. Q.; Liu, Z. Q.; Zhu, Z. W.; Zhang, H. F.; Zhang, Z. F.

    2016-01-01

    Studying the effect of notch on the fatigue behavior of structural materials is of significance for the reliability and safety designing of engineering structural components. In this work, we conducted notch fatigue experiments of two high-strength materials, i.e. a Ti32.8Zr30.2Ni5.3Cu9Be22.7 metallic glass (MG) and a 00Ni18Co15Mo8Ti ultra-high strength steel (CM400 UHSS), and compared their notch fatigue behavior. Experimental results showed that although both the strength and plasticity of the MG were much lower than those of the UHSS, the fatigue endurance limit of the notched MG approached to that of the notched UHSS, and the fatigue ratio of the notched MG was even higher. This interesting finding can be attributed to the unique shear banding mechanism of MG. It was found that during fatigue process abundant shear bands formed ahead of the notch root and in the vicinity of the crack in the notched MG, while limited plastic deformation was observed in the notched UHSS. The present results may improve the understanding on the fatigue mechanisms of high-strength materials and offer new strategies for structural design and engineering application of MG components with geometrical discontinuities. PMID:27752136

  19. Nano DCPA-whisker composites with high strength and Ca and PO(4) release.

    PubMed

    Xu, H H K; Sun, L; Weir, M D; Antonucci, J M; Takagi, S; Chow, L C; Peltz, M

    2006-08-01

    The main challenges facing composite restorations are secondary caries and bulk fracture. The objective of this study was to develop nano DCPA (dicalcium phosphate anhydrous)-whisker composites with high strength and Ca and PO(4) ion release to combat caries. Flexural strength for the nano DCPA-whisker composites at a nano DCPA:whisker mass ratio of 1:2 ranged from (148 +/- 9) MPa to (167 +/- 23) MPa, significantly higher than the (103 +/- 32) MPa of an inlay/onlay commercial control composite without Ca-PO(4) release. The nano DCPA-whisker composite released PO(4) to a concentration of (1.95 +/- 0.13) mmol/L and Ca of (0.68 +/- 0.05) mmol/L. Compared with previous conventional Ca- and PO(4)-releasing composites, the nano DCPA-whisker composites had strengths two-fold higher, and released comparable or higher levels of Ca and PO(4). In conclusion, combining nano-DCPA with whiskers yielded novel composites that released high levels of Ca and PO(4) requisite for remineralization. These high-strength composites may provide a unique combination of stress-bearing and caries-inhibiting capabilities.

  20. Nano DCPA-Whisker Composites with High Strength and Ca and PO4 Release

    PubMed Central

    Xu, H.H.K.; Sun, L.; Weir, M.D.; Antonucci, J.M.; Takagi, S.; Chow, L.C.; Peltz, M.

    2008-01-01

    The main challenges facing composite restorations are secondary caries and bulk fracture. The objective of this study was to develop nano DCPA (dicalcium phosphate anhydrous)-whisker composites with high strength and Ca and PO4 ion release to combat caries. Flexural strength for the nano DCPA-whisker composites at a nano DCPA:whisker mass ratio of 1:2 ranged from (148 ± 9) MPa to (167 ± 23) MPa, significantly higher than the (103 ± 32) MPa of an inlay/onlay commercial control composite without Ca-PO4 release. The nano DCPA-whisker composite released PO4 to a concentration of (1.95 ± 0.13) mmol/L and Ca of (0.68 ± 0.05) mmol/L. Compared with previous conventional Ca- and PO4-releasing composites, the nano DCPA-whisker composites had strengths two-fold higher, and released comparable or higher levels of Ca and PO4. In conclusion, combining nano-DCPA with whiskers yielded novel composites that released high levels of Ca and PO4 requisite for remineralization. These high-strength composites may provide a unique combination of stress-bearing and caries-inhibiting capabilities. PMID:16861289

  1. High-velocity frictional strength across the Tohoku-Oki megathrust determined from surface drilling torque

    NASA Astrophysics Data System (ADS)

    Ujiie, Kohtaro; Inoue, Tomoya; Ishiwata, Junya

    2016-03-01

    High-velocity frictional strength is one of the primary factors controlling earthquake faulting. The Japan Trench Fast Drilling Project drilled through the shallow plate boundary fault, where displacement was ~50 m during the 2011 Tohoku-Oki earthquake. To determine downhole frictional strength, we analyzed the surface drilling torque data acquired at rotation rates equivalent to seismic slip rates (0.8-1.3 m/s). The results show a clear contrast in high-velocity frictional strength across the plate boundary fault: the apparent friction coefficient of frontal prism sediments (hemipelagic mudstones) in the hanging wall is 0.1-0.3, while that of the underthrust sediments (mudstone, laminar pelagic claystone, and chert) in the footwall increases to 0.2-0.4. The apparent friction coefficient of the smectite-rich pelagic clay in the plate boundary fault is 0.08-0.19, which is consistent with that determined from high-velocity (1.1-1.3 m/s) friction experiments. This suggests that surface drilling torque is useful in obtaining downhole frictional strength.

  2. High Temperature Strength of YSZ Joints Brazed with Palladium Silver Copper Oxide Filler Metals

    SciTech Connect

    Darsell, Jens T.; Weil, K. Scott

    2010-06-09

    The Ag-CuOx system is being investigated as potential filler metals for use in air brazing high-temperature electrochemical devices such as solid oxide fuel cells and gas concentrators. The current study examines the effects of palladium addition on the high temperature joint strength of specimens prepared from yttria stabilized zirconia (YSZ) bars brazed with the binary Ag-CuOx, and 15Pd-Ag-CuO. It was found that while the binary Ag-CuOx system exhibits stronger room temperature strength than the 15Pd system the strength is reduced to values equivalent of the 15Pd system at 800°C. The 15Pd system exhibits a lower ambient temperature strength that is retained at 800°C. In both systems the failure mechanism at high temperature appears to be peeling of the noble metal component from the oxide phases and tearing through the noble metal phase whereas sufficient adhesion is retained at lower temperatures to cause fracture of the YSZ substrate.

  3. A Study of Organizational Justice, Organizational Citizenship Behavior, and Student Achievement in High Schools

    ERIC Educational Resources Information Center

    Burns, W. R. Travis; DiPaola, Michael F.

    2013-01-01

    Emerging research suggests that teachers' perceptions of fairness with respect to interactions with school administrators, decision-making processes, and decision outcomes can contribute greatly to understanding effective schools. This study of Virginia public high schools used correlational analysis to measure the strength of the…

  4. Energetic-particle synthesis of high-strength Al(O) alloys

    SciTech Connect

    Follstaedt, D.M.; Knapp, J.A.; Barbour, J.C.; Myers, S.M.; Dugger, M.T.

    1995-09-28

    High-strength Al(O) alloys, initially discovered by ion implantation, have now been produced with electron-cyclotron resonance plasma deposition and pulsed-laser deposition. The mechanical properties of these deposited alloy layers were examined with nanoindentation, and finite element modeling of the indented layer on Si substrates was used to determine yield stresses for the alloys of {approximately} 1--5 GPa. The key to these high strengths is the high density of nanometer-size {gamma}-Al{sub 2}O{sub 3} precipitates formed when high concentrations (5--30 at.%) of oxygen are introduced into aluminum as individual atoms or molecules. The strongest alloys have precipitates as small as 1 nm, implying that such small precipitates block dislocation motion. Based upon previous studies with oxygen-implanted aluminum, improved tribological properties are expected for layers made by the two new deposition methods.

  5. Biodegradability oriented treatability studies on high strength segregated wastewater of a woolen textile dyeing plant.

    PubMed

    Baban, Ahmet; Yediler, Ayfer; Ciliz, NilgunKiran; Kettrup, Antonius

    2004-11-01

    Textile dyeing and finishing industry involves considerable amount of water usage as well as polluted and highly colored wastewater discharges. Biological treatability by means of mineralization, nitrification and denitrification of high strength woolen textile dye bathes, first- and second-rinses is presented. COD fractionation study was carried out and kinetic parameters were determined. Biodegradability of organic compounds in highly loaded composite wastewater after segregation and the effluent of applied biological treatment of high strength composite wastewater were measured by determining oxygen consumption rates. The results were used in terms of assessing an alternative method for inert COD fractionation. The study implied that about 80% soluble COD, 50% color and 75% toxicity reduction were possible by single sludge biological processes. Sixteen per cent of total COD was found to be initially inert. Inert fraction was increased to 22% by production of soluble and particulate microbial products through biological treatment. PMID:15488936

  6. Temperature Dependence of Sound Velocity in High-Strength Fiber-Reinforced Plastics

    NASA Astrophysics Data System (ADS)

    Nomura, Ryuji; Yoneyama, Keiichi; Ogasawara, Futoshi; Ueno, Masashi; Okuda, Yuichi; Yamanaka, Atsuhiko

    2003-08-01

    Longitudinal sound velocity in unidirectional hybrid composites or high-strength fiber-reinforced plastics (FRPs) was measured along the fiber axis over a wide temperature range (from 77 K to 420 K). We investigated two kinds of high-strength crystalline polymer fibers, polyethylene (Dyneema) and polybenzobisoxazole (Zylon), which are known to have negative thermal expansion coefficients and high thermal conductivities along the fiber axis. Both FRPs had very high sound velocities of about 9000 m/s at low temperatures and their temperature dependences were very strong. Sound velocity monotonically decreased with increasing temperature. The temperature dependence of sound velocity was much stronger in Dyneema-FRP than in Zylon-FRP.

  7. Stress corrosion cracking of several high strength ferrous and nickel alloys

    NASA Technical Reports Server (NTRS)

    Nelson, E. E.

    1971-01-01

    The stress corrosion cracking resistance of several high strength ferrous and nickel base alloys has been determined in a sodium chloride solution. Results indicate that under these test conditions Multiphase MP35N, Unitemp L605, Inconel 718, Carpenter 20Cb and 20Cb-3 are highly resistant to stress corrosion cracking. AISI 410 and 431 stainless steels, 18 Ni maraging steel (250 grade) and AISI 4130 steel are susceptible to stress corrosion cracking under some conditions.

  8. Improving UV Resistance of High Strength Fibers Used In Large Scientific Balloons

    NASA Technical Reports Server (NTRS)

    Said, M.; Gupta, A.; Seyam, A.; Mock, G.; Theyson, T.

    2004-01-01

    For the last three decades, NASA has been involved in the development of giant balloons that are capable of lifting heavy payloads of equipment (such as large telescopes and scientific instruments) to the upper atmosphere. While the use of such balloons has led to scientific discoveries, the demand for competitive science payloads and observational programs continues to rise. The NASA Balloon Program Office has entered a new phase of research to develop an Ultra Long Duration Balloon (ULDB) that will lift payloads of up to 3,600 kg to altitudes of up to 40 km. The flight duration is targeted to ranges between 30 to 100 days. Attaining these target durations requires the development of a super-pressure balloon design. The use of textile structures have already been established in these missions in the form of high strength tendons essential for the super pressure pumpkin design. Unfortunately, high strength fibers lose significant strength upon exposure to Ultra Violet (UV) radiation. Such UV degradation poses a serious challenge for the development of the ULDB. To improve the mission performance of the ULDB, new methods for protecting the tendons from the environmental effects need to be developed. NASA and NC State University College of Textiles are undertaking a research program to address these issues. Four tracks have been identified to prepare finishes that are believed to enhance the resistance of high strength fibers to UV. These tracks are: (a) self-polymerizing, (b) diffusion application, (c) polymer-filled with 30-40% UV absorber, and (d) combination of dyeing plus surface application. Four high performance fibers have been selected for this research investigation. These are Vectran (trademark), Spectra (trademark), Kevlar (trademark) and, PBO (Zylon (trademark)). This work will address the current progress of evaluating the performance of the UV finishes. This will be accomplished by comparing the tensile properties (strength, breaking elongation

  9. Lipid target achievement among patients with very high and high cardiovascular risk in a lipid clinic.

    PubMed

    Barkas, Fotios; Liberopoulos, Evangelos N; Kostapanos, Michael S; Liamis, George; Tziallas, Dimitrios; Elisaf, Moses

    2015-04-01

    This was a retrospective study that assessed achievement of lipid-lowering treatment targets in the setting of a University Hospital Lipid Clinic. Low-density lipoprotein cholesterol (LDL-C) goal attainment according to National Cholesterol Education Program-Adult Treatment Panel III (NCEP ATP III) and European Society of Cardiology/European Atherosclerosis Society (ESC/EAS) guidelines was recorded in 1000 consecutive adult patients followed for ≥3 years (mean 8 years). The LDL-C targets according to the NCEP ATP III were attained by 66% and 86% of patients with "very high" (n = 477) and "high" (n = 408) cardiovascular risk, respectively. Fewer patients were within LDL-C goals according to the ESC/EAS guidelines: 25% and 42%. Overall, 92% of the patients were on statins: 67% were on statin monotherapy, while 33% were on combinations with ezetimibe (25%), ω-3 fatty acids (5%), fibrates (4%), or colesevelam (2%). Even in a specialist lipid clinic, a large proportion of patients are not at goal according to the recent ESC/EAS guidelines. PMID:24830420

  10. Hydration and strength development of binder based on high-calcium oil shale fly ash

    SciTech Connect

    Freidin, C.

    1998-06-01

    The properties of high-calcium oil shale fly ash and low-calcium coal fly ash, which are produced in Israeli power stations, were investigated. High-calcium oil shale fly ash was found to contain a great amount of CaO{sub free} and SO{sub 3} in the form of lime and anhydrite. Mixtures of high-calcium oil shale fly ash and low-calcium coal fly ash, termed fly ash binder, were shown to cure and have improved strength. The influence of the composition and curing conditions on the compressive strength of fly ash binders was examined. The microstructure and the composition of fly ash binder after curing and long-term exposure in moist air, water and open air conditions were studied. It was determined that ettringite is the main variable in the strength and durability of cured systems. The positive effect of calcium silicate hydrates, CSH, which are formed by interaction of high-calcium oil shale fly ash and low-calcium coal fly ash components, on the carbonation and dehydration resistance of fly ash binder in open air is pronounced. It was concluded that high-calcium oil shale fly ash with high CaO{sub free} and SO{sub 3} content can be used as a binder for building products.

  11. [Anaerobic membrane bioreactors for treating agricultural and food processing wastewater at high strength].

    PubMed

    Wei, Yuan-Song; Yu, Da-Wei; Cao, Lei

    2014-04-01

    As the second largest amounts of COD discharged in 41 kinds of industrial wastewater, it is of great urgency for the agricultural and food processing industry to control water pollution and reduce pollutants. Generally the agricultural and food processing industrial wastewater with high strength COD of 8 000-30 000 mg x L(-1), is mainly treated with anaerobic and aerobic processes in series, but which exists some issues of long process, difficult maintenance and high operational costs. Through coupling anaerobic digestion and membrane separation together, anaerobic membrane bioreactor (AnMBR) has typical advantages of high COD removal efficiency (92%-99%), high COD organic loading rate [2.3-19.8 kg x (m3 x d)(-1)], little sludge discharged (SRT > 40 d) and low cost (HRT of 8-12 h). According to COD composition of high strength industrial wastewater, rate-limiting step of methanation could be either hydrolysis and acidification or methanogenesis. Compared with aerobic membrane bioreactor (MBR), membrane fouling of AnMBR is more complicated in characterization and more difficult in control. Measures for membrane fouling control of AnMBR are almost the same as those of MBR, including cross flow, air sparging and membrane relaxation. For meeting discharging standard of food processing wastewater with high strength, AnMBR is a promising technology with very short process, by enhancing COD removal efficiency, controlling membrane fouling and improving energy recovery.

  12. High Strength and Compatible Aluminum Alloy for Hydrogen-Peroxide Fuel Tanks

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2004-01-01

    This paper describes the development of a new high strength and Hydrogen Peroxide (HP) propellant compatible aluminum alloy for NASA Hyper-X vehicle's fuel tanks and structures. The tensile strength of the new alloy is more than 3 times stronger than the conventional 5254 alloy while it still maintains HP compatibility similar to 5254 (Class 1 category). The alloy development strategy consists of selecting certain rare earth and transition metals, with unique electrochemical properties, that will not act as catalysts to decompose liquid HP at the atomic level. Such elements will added to the aluminum alloy and the mixture will be cast and rolled into thin sheet metals. Test coupons are machined from sheet metals for HP long-term exposure testing and mechanical properties testing. In addition, the ability to weld the new alloy using Friction Stir Welding has also been explored. Currently, aluminum alloy 5254 is the state-of-the-art material for HP storage, but its yield strength is very low (420 ksi) and may not be suitable for the development of light-weight fuel tanks for Hyper-X vehicles. The new high strength and HP compatible alloy could represent an enabling material technology for NASA's Hyper-X vehicles, where flight weight reduction is a critical requirement. These X-planes are currently under studied as air-breathing hypersonic research vehicles featuring a lifting body configuration with a Rocket Based Combined Cycle (RBCC) engine system.

  13. Improved Tensile Adhesion Specimens for High Strength Epoxy Systems in Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Haddock, M. Reed; McLennan, Michael L.

    2000-01-01

    An improved tensile adhesion button has been designed and tested that results in higher measured tensile adhesion strength while providing increased capability for testing high strength epoxy adhesive systems. The best attributes of two well-established tensile button designs were combined and refined into an optimized tensile button. The most significant design change to the tensile button was to improve alignment of the bonded tensile button specimens during tensile testing by changing the interface between the tensile button and the tensile test machine. The established or old button design uses a test fixture that pulls from a grooved annulus or anvil head while the new button design pulls from a threaded hole in the centerline of the button. Finite element (FE) analysis showed that asymmetric loading of the established anvil head tensile button significantly increases the stress concentration in the adhesive, causing failure at lower tensile test loads. The new tensile button was designed to eliminate asymmetric loading and eliminate misalignment sensitivity. Enhanced alignment resulted in improved tensile adhesion strength measurement up to 13.8 MPa (2000psi) over the established button design. Another design change increased the capability of the button by increasing the threaded hole diameter allowing it to test high strength epoxy systems up to 85 MPa(less than 12,000 psi). The improved tensile button can be used in button- to-button or button-to-panel configurations.

  14. GMA-laser Hybrid Welding of High-strength Fine-grain Structural Steel with an Inductive Preheating

    NASA Astrophysics Data System (ADS)

    Lahdo, Rabi; Seffer, Oliver; Springer, André; Kaierle, Stefan; Overmeyer, Ludger

    The industrial useof GMA-laser hybrid welding has increased in the last 10 years, due to the brilliant quality of the laser beam radiation, and higher laser output powers. GMA-laser hybrid welding processes operate in a common molten pool. The combination of the laser beam and the arc results in improved welding speed, penetration depth, heat affected zone and gap bridgeability. Single-layer, GMA-laser hybrid welding processes have been developed for high-strength fine-grain structural steels with a grade of S690QL and a thickness of 15 mm and 20 mm. In addition, the welding process is assisted by an integrated, inductive preheating process to improve the mechanical properties of the welding seam. By using the determined parameters regarding the energy per unit length, and the preheating temperature, welding seams with high quality can be achieved.

  15. The micro-mechanics of strength, durability and damage tolerance in composites: new insights from high resolution computed tomography

    NASA Astrophysics Data System (ADS)

    Spearing, S. Mark; Sinclair, Ian

    2016-07-01

    Recent work, led by the authors, on impact damage resistance, particle toughening and tensile fibre failure is reviewed in order to illustrate the use of high-resolution X-ray tomography to observe and quantify damage mechanisms in carbon fibre composite laminates. Using synchrotron and micro-focus X-ray sources resolutions of less than 1 μm have been routinely achieved. This enables individual broken fibres and the micromechanisms of particle toughening to be observed and quantified. The data for fibre failure, cluster formation and overall tensile strength are compared with model predictions. This allows strategies for future model development to be identified. The overall implications for using such high-resolution 3-D measurements to inform a “data-rich mechanics” approach to materials evaluation and modeling is discussed.

  16. Decreased latent inhibition is associated with increased creative achievement in high-functioning individuals.

    PubMed

    Carson, Shelley H; Peterson, Jordan B; Higgins, Daniel M

    2003-09-01

    Reductions in latent inhibition (LI), the capacity to screen from conscious awareness stimuli previously experienced as irrelevant, have been generally associated with the tendency towards psychosis. However, "failure" to screen out previously irrelevant stimuli might also hypothetically contribute to original thinking, particularly in combination with high IQ. Meta-analysis of two studies, conducted on youthful high-IQ samples. demonstrated that high lifetime creative achievers had significantly lower LI scores than low creative achievers (r(effect size) = .31, p = .0003, one-tailed). Eminent creative achievers (participants under 21 years who reported unusually high scores in a single domain of creative achievement) were 7 times more likely to have low rather than high LI scores, chi2 (1, N = 25) = 10.69, phi = .47. p = .003.

  17. Understanding and Reversing Underachievement, Low Achievement, and Achievement Gaps among High-Ability African American Males in Urban School Contexts

    ERIC Educational Resources Information Center

    Ford, Donna Y.; Moore, James L., III

    2013-01-01

    This article focuses on the achievement gap, with attention devoted to underachievement and low achievement among African American males in urban school contexts. More specifically, the article explains problems and issues facing or confronting these Black male students in urban education settings. A central part of this discussion is grounded in…

  18. Hugoniot-measurements of room- and high-temperature metals for study of EOS and strength

    NASA Astrophysics Data System (ADS)

    Mashimo, Tsutomu; Gomoto, Yuya; Takashima, Hideyuki; Murai, Mitsuru; Yoshiasa, Akira

    2011-06-01

    Pressure calibration in static high-pressure experiments has been undertaken on the basis of the EOS derived from the Hugoniot compression curves of metals (Au, Pt, Cu, W, etc.), MgO, etc. To obtain the strict EOS at room- and high-temperatures, we need to precisely measure the Hugoniot data, and access the strength and Grüneisen parameter under shock compression. If the Hugoniot data of elevated temperature samples are measured, the high-temperature EOS can be accurately derived, and the Grüneisen parameter can be directly discussed. The strength might decrease at high temperature. The Hugoniot-measurement experiments have been performed on single crystal Au, oxygen-free Cu, forged Ta and W by a streak photographic system equipped with a powder gun and two-stage light gas gun in the pressure range up to >200 GPa. In addition, the Hugoniot-measurement experiment of the elevated temperature samples was started using high-frequency heating on W, Au, etc. Some of the results will be presented, and the EOS and strength are discussed.

  19. Instructional, Transformational, and Managerial Leadership and Student Achievement: High School Principals Make a Difference

    ERIC Educational Resources Information Center

    Valentine, Jerry W.; Prater, Mike

    2011-01-01

    This statewide study examined the relationships between principal managerial, instructional, and transformational leadership and student achievement in public high schools. Differences in student achievement were found when schools were grouped according to principal leadership factors. Principal leadership behaviors promoting instructional and…

  20. Low and High Mathematics Achievement in Japanese, Chinese, and American Elementary-School Children.

    ERIC Educational Resources Information Center

    Uttal, David H.; And Others

    1988-01-01

    First and fifth grade students who scored high or low on a mathematics test were tested for intellectual ability and reading achievement. Students and their mothers were interviewed. Results indicated that factors associated with levels of achievement in mathematics operate in a similar fashion across three cultures that differ greatly in their…

  1. Accelerated Mathematics and High-Ability Students' Math Achievement in Grades Three and Four

    ERIC Educational Resources Information Center

    Stanley, Ashley M.

    2011-01-01

    The purpose of this study was to explore the relationship between the use of a computer-managed integrated learning system entitled Accelerated Math (AM) as a supplement to traditional mathematics instruction on achievement as measured by TerraNova achievement tests of third and fourth grade high-ability students. Gender, socioeconomic status, and…

  2. A Quantitative Comparison of Pennsylvania High School Student Achievement by Middle States Association's Accreditation Status

    ERIC Educational Resources Information Center

    Johnson, Christopher A.

    2012-01-01

    As public school accountability for student achievement has continued to increase, prior to and as a result of the No Child Left Behind Act of 2001, schools have sought ways of bringing new instructional services to their students to raise their levels of achievement. Some Pennsylvania public high schools have attempted to improve student…

  3. Achievement Motivation in High School: Contrasting Theoretical Models in the Classroom.

    ERIC Educational Resources Information Center

    Garcia-Celay, I. Montero; Tapia, J. Alonso

    1992-01-01

    Three models of achievement motivation in the classroom are contrasted. Results with 155 high school students suggest that the model of C. S. Dweck and E. S. Elliott offers a better explanation of the relationships among achievement motivation, attributions, emotional reactions, expectancies, and performance than do the other models. (SLD)

  4. The Effects of Cooperative Learning on Student Achievement and Motivation in a High School Geometry Class.

    ERIC Educational Resources Information Center

    Nichols, Joe D.; Hall, Neff

    In this study, the effects of a form of cooperative group instruction (Student Teams Achievement Divisions) on student motivation and achievement in a high school geometry class were examined. Ninety (mostly 10th-grade) students were randomly assigned to either a control group receiving traditional instruction or one of two treatment groups…

  5. Early Reading Skills and Academic Achievement Trajectories of Students Facing Poverty, Homelessness, and High Residential Mobility

    ERIC Educational Resources Information Center

    Herbers, Janette E.; Cutuli, J. J.; Supkoff, Laura M.; Heistad, David; Chan, Chi-Keung; Hinz, Elizabeth; Masten, Ann S.

    2012-01-01

    This investigation tested the importance of early academic achievement for later achievement trajectories among 18,011 students grouped by level of socioeconomic risk. Students considered to be at highest risk were those who experienced homelessness or high residential mobility (HHM). HHM students were compared with students eligible for free…

  6. Intergenerational Closure and Academic Achievement in High School: A New Evaluation of Coleman's Conjecture

    ERIC Educational Resources Information Center

    Morgan, Stephen L.; Todd, Jennifer J.

    2009-01-01

    This article reexamines the conjecture of James S. Coleman that intergenerational social closure promotes student achievement in high schools, analyzing the best national data on academic achievement and social networks: the 2002 and 2004 waves of the Education Longitudinal Study. The results show that within the Catholic school sector, schools…

  7. Unforgiving Confucian Culture: A Breeding Ground for High Academic Achievement, Test Anxiety and Self-Doubt?

    ERIC Educational Resources Information Center

    Stankov, Lazar

    2010-01-01

    This paper reviews findings from several studies that contribute to our understanding of cross-cultural differences in academic achievement, anxiety and self-doubt. The focus is on comparisons between Confucian Asian and European regions. Recent studies indicate that high academic achievement of students from Confucian Asian countries is…

  8. Gender and High School Chemistry: Student Perceptions on Achievement in a Selective Setting

    ERIC Educational Resources Information Center

    Cousins, Andrew; Mills, Martin

    2015-01-01

    This paper reports on research undertaken in a middle-class Australian school. The focus of the research was on the relationship between gender and students' engagement with high school chemistry. Achievement data from many OECD [Organisation for Economic Co-operation and Development] countries suggest that middle-class girls are achieving equally…

  9. Parental Involvement, Homework, and TV Time: Direct and Indirect Effects on High School Achievement.

    ERIC Educational Resources Information Center

    Keith, Timothy Z.; And Others

    1986-01-01

    A set of High School and Beyond data was used to study the effect of three variables on academic achievement. Homework had a positive effect, TV a negative, and parental involvement no direct effect on seniors' achievement scores, but influenced the amount of time students spent on homework. (Author/JAZ)

  10. Effects of high NH(+) 4 on K(+) uptake, culm mechanical strength and grain filling in wheat.

    PubMed

    Kong, Lingan; Sun, Mingze; Wang, Fahong; Liu, Jia; Feng, Bo; Si, Jisheng; Zhang, Bin; Li, Shengdong; Li, Huawei

    2014-01-01

    It is well established that a high external NH(+) 4 concentration depresses many processes in plant development, but the underlying mechanisms are still not well understood. To determine whether the negative effects of high levels of NH(+) 4 are related to competitive cation uptake, wheat was grown in a field with moderate (18 g N m(-2)) and high (30 g N m(-2)) supplies of NH(+) 4 in the presence or absence of additional K(+) (6 g K2O m(-2)) to examine culm mechanical strength, the main components of the vascular bundle, nitrogen (N) remobilization and the grain-filling rate. The results indicated that an excessive supply of NH(+) 4 significantly decreased culm mechanical strength, the cellulose and lignin contents of vascular bundles, the N remobilization efficiency (NRE) and the grain-filling rate compared with a moderate level of NH(+) 4. The additional provision of K(+) considerably alleviated these negative effects of high NH(+) 4, resulting in a 19.41-26.95% increase in culm mechanical strength during grain filling and a 34.59% increase in the NRE. An assay using the scanning ion-selective electrode technique (SIET) showed that the net rate of transmembrane K(+) influx decreased by 84.62%, and measurements using flame photometry demonstrated that the K(+) content decreased by 36.13% in wheat plants subjected to high NH(+) 4. This study indicates that the effects of high NH(+) 4 on culm mechanical strength, cellulose and lignin contents, the NRE and the grain-filling rate are probably associated with inhibition of K(+) uptake in wheat. PMID:25566278

  11. Effects of high NH+4 on K+ uptake, culm mechanical strength and grain filling in wheat

    PubMed Central

    Kong, Lingan; Sun, Mingze; Wang, Fahong; Liu, Jia; Feng, Bo; Si, Jisheng; Zhang, Bin; Li, Shengdong; Li, Huawei

    2014-01-01

    It is well established that a high external NH+4 concentration depresses many processes in plant development, but the underlying mechanisms are still not well understood. To determine whether the negative effects of high levels of NH+4 are related to competitive cation uptake, wheat was grown in a field with moderate (18 g N m−2) and high (30 g N m−2) supplies of NH+4 in the presence or absence of additional K+ (6 g K2O m−2) to examine culm mechanical strength, the main components of the vascular bundle, nitrogen (N) remobilization and the grain-filling rate. The results indicated that an excessive supply of NH+4 significantly decreased culm mechanical strength, the cellulose and lignin contents of vascular bundles, the N remobilization efficiency (NRE) and the grain-filling rate compared with a moderate level of NH+4. The additional provision of K+ considerably alleviated these negative effects of high NH+4, resulting in a 19.41–26.95% increase in culm mechanical strength during grain filling and a 34.59% increase in the NRE. An assay using the scanning ion-selective electrode technique (SIET) showed that the net rate of transmembrane K+ influx decreased by 84.62%, and measurements using flame photometry demonstrated that the K+ content decreased by 36.13% in wheat plants subjected to high NH+4. This study indicates that the effects of high NH+4 on culm mechanical strength, cellulose and lignin contents, the NRE and the grain-filling rate are probably associated with inhibition of K+ uptake in wheat. PMID:25566278

  12. Process for making a high toughness-high strength iron alloy

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R. (Inventor)

    1979-01-01

    A steel alloy is produced by a process which includes using cold rolling at room temperature and subsequent heat treatment at temperatures ranging from 500 C to 650 C. The resulting alloys exhibits excellent strength and toughness characteristics at cryogenic temperatures. This alloy consists essentially of about 10 to 16 percent by weight nickel, to about 1.0 percent by weight aluminum, and 0 to about 3 percent by weight of at least one of the following additional elements: copper, lanthanum, niobium, tantalum, titanium, vanadium, yttrium, zirconium and the rare earth metals, with the balance being essentially iron. The improved alloy possesses a fracture toughness ranging from 200 to 230 ksi sq in. and yield strengths up to 230 ksi.

  13. Can Community and School-Based Supports Improve the Achievement of First-Generation Immigrant Children Attending High-Poverty Schools?

    PubMed

    Dearing, Eric; Walsh, Mary E; Sibley, Erin; Lee-St John, Terry; Foley, Claire; Raczek, Anastacia E

    2016-05-01

    Using a quasi-experimental design, the effects of a student support intervention were estimated for the math and reading achievement of first-generation immigrant children (n = 667, M = 11.05 years of age) attending high-poverty, urban elementary schools. The intervention was designed to help schools identify developmental strengths and barriers to learning and, in turn, connect children to community and school supports aligned with their strengths and needs. By exploiting within-school changes in the implementation of the intervention, the present study revealed statistically and practically significant treatment effects indicating improvements in math and reading achievement at the end of elementary school. In addition, the intervention appears to considerably narrow achievement gaps between English language learners and immigrant children proficient in English.

  14. Temperature and strain rate effects in high strength high conductivity copper alloys tested in air

    SciTech Connect

    Edwards, D.J.

    1998-03-01

    The tensile properties of the three candidate alloys GlidCop{trademark} Al25, CuCrZr, and CuNiBe are known to be sensitive to the testing conditions such as strain rate and test temperature. This study was conducted on GlidCop Al25 (2 conditions) and Hycon 3HP (3 conditions) to ascertain the effect of test temperature and strain rate when tested in open air. The results show that the yield strength and elongation of the GlidCop Al25 alloys exhibit a strain rate dependence that increases with temperature. Both the GlidCop and the Hycon 3 HP exhibited an increase in strength as the strain rate increased, but the GlidCop alloys proved to be the most strain rate sensitive. The GlidCop failed in a ductile manner irrespective of the test conditions, however, their strength and uniform elongation decreased with increasing test temperature and the uniform elongation also decreased dramatically at the lower strain rates. The Hycon 3 HP alloys proved to be extremely sensitive to test temperature, rapidly losing their strength and ductility when the temperature increased above 250 C. As the test temperature increased and the strain rate decreased the fracture mode shifted from a ductile transgranular failure to a ductile intergranular failure with very localized ductility. This latter observation is based on the presence of dimples on the grain facets, indicating that some ductile deformation occurred near the grain boundaries. The material failed without any reduction in area at 450 C and 3.9 {times} 10{sup {minus}4} s{sup {minus}1}, and in several cases failed prematurely.

  15. Impacts of comprehensive reading instruction on diverse outcomes of low- and high-achieving readers.

    PubMed

    Guthrie, John T; McRae, Angela; Coddington, Cassandra S; Lutz Klauda, Susan; Wigfield, Allan; Barbosa, Pedro

    2009-01-01

    Low-achieving readers in Grade 5 often lack comprehension strategies, domain knowledge, word recognition skills, fluency, and motivation to read. Students with such multiple reading needs seem likely to benefit from instruction that supports each of these reading processes. The authors tested this expectation experimentally by comparing the effects of Concept-Oriented Reading Instruction (CORI) with traditional instruction (TI) on several outcomes in a 12-week intervention for low achievers and high achievers. Low achievers in the CORI group were afforded explicit instruction, leveled texts, and motivation support. Compared with TI students, CORI students scored higher on posttest measures of word recognition speed, reading comprehension on the Gates-MacGinitie Reading Test, and ecological knowledge. CORI was equally effective for lower achievers and higher achievers. Explicitly supporting multiple aspects of reading simultaneously appeared to benefit diverse learners on a range of reading outcomes.

  16. Sleep monitoring of a six-day microcycle in strength and high-intensity training.

    PubMed

    Kölling, Sarah; Wiewelhove, Thimo; Raeder, Christian; Endler, Stefan; Ferrauti, Alexander; Meyer, Tim; Kellmann, Michael

    2016-08-01

    This study examined the effect of microcycles in eccentric strength and high-intensity interval training (HIT) on sleep parameters and subjective ratings. Forty-two well-trained athletes (mean age 23.2 ± 2.4 years) were either assigned to the strength (n = 21; mean age 23.6 ± 2.1 years) or HIT (n = 21; mean age 22.8 ± 2.6 years) protocol. Sleep monitoring was conducted with multi-sensor actigraphy (SenseWear Armband™, Bodymedia, Pittsburg, PA, USA) and sleep log for 14 days. After a five-day baseline phase, participants completed either eccentric accented strength or high-intensity interval training for six days, with two training sessions per day. This training phase was divided into two halves (part 1 and 2) for statistical analyses. A three-day post phase concluded the monitoring. The Recovery-Stress Questionnaire for Athletes was applied at baseline, end of part 2, and at the last post-day. Mood ratings were decreased during training, but returned to baseline values afterwards in both groups. Sleep parameters in the strength group remained constant over the entire process. The HIT group showed trends of unfavourable sleep during the training phase (e.g., objective sleep efficiency at part 2: mean = 83.6 ± 7.8%, F3,60 = 2.57, P = 0.06, [Formula: see text] = 0.114) and subjective improvements during the post phase for awakenings (F3,60 = 2.96, P = 0.04, [Formula: see text] = 0.129) and restfulness of sleep (F3,60 = 9.21, P < 0.001, [Formula: see text] = 0.315). Thus, the HIT protocol seems to increase higher recovery demands than strength training, and sufficient sleep time should be emphasised and monitored.

  17. Dentin bond strength after ablation using a CO2 laser operating at high pulse repetition rates

    NASA Astrophysics Data System (ADS)

    Hedayatollahnajafi, Saba; Staninec, Michal; Watanabe, Larry; Lee, Chulsung; Fried, Daniel

    2009-02-01

    Pulsed CO2 lasers show great promise for the rapid and efficient ablation of dental hard tissues. Our objective was to demonstrate that CO2 lasers operated at high repetition rates can be used for the rapid removal of dentin without excessive thermal damage and without compromising adhesion to restorative materials. Human dentin samples (3x3mm2) were rapidly ablated with a pulsed CO2 laser operating at a wavelength of 9.3-µm, pulse repetition rate of 300-Hz and an irradiation intensity of 18-J/cm2. The bond strength to composite was determined by the modified single plane shear test. There were 8 test groups each containing 10 blocks: negative control (non-irradiated non-etched), positive control (non-irradiated acid-etched), and six laser treated groups (three etched and three non-etched sets). The first and second etched and non-etched sets were ablated at a speed of 25 mm/sec and 50 mm/sec with water, respectively. The third set was also ablated at 50 mm/sec without application of water during laser irradiation. Minimal thermal damage was observed on the dentin surfaces for which water cooling was applied. Bond strengths exceeded 20 MPa for laser treated surfaces that were acid-etched after ablation (25-mm/sec: 29.9-MPa, 50-mm/sec: 21.3-MPa). The water-cooled etched laser groups all produced significantly stronger bonds than the negative control (p<0.001) and a lower bond strength than the positive control (p<0.05). These measurements demonstrate that dentin surfaces can be rapidly ablated by a CO2 lasers with minimal peripheral thermal damage. Additional studies are needed to determine if a lower bond strength than the acid-etched control samples is clinically significant where durability of these bonded restoration supersedes high bond strength.

  18. High-velocity frictional strength across the Tohoku-Oki megathrust determined from surface drilling torque

    NASA Astrophysics Data System (ADS)

    Ujiie, K.; Inoue, T.; Ishiwata, J.

    2015-12-01

    Frictional strength at seismic slip rates is a key to evaluate fault weakening and rupture propagation during earthquakes. The Japan Trench First Drilling Project (JFAST) drilled through the shallow plate-boundary thrust, where huge displacements of ~50 m occurred during the 2011 Tohoku-Oki earthquake. To determine the downhole frictional strength at drilled site (Site C0019), we analyzed surface drilling data. The equivalent slip rate estimated from the rotation rate and inner and outer radiuses of the drill bit ranges from 0.8 to 1.3 m/s. The measured torque includes the frictional torque between the drilling string and borehole wall, the viscous torque between the drilling string and seawater/drilling fluid, and the drilling torque between the drill bit and sediments. We subtracted the former two from the measured torque using the torque data during bottom-up rotating operations at several depths. Then, the shear stress was calculated from the drilling torque taking the configuration of the drill bit into consideration. The normal stress was estimated from the weight on bit data and the projected area of the drill bit. Assuming negligible cohesion, the frictional strength was obtained by dividing shear stress by normal stress. The results show a clear contrast in high-velocity frictional strength across the plate-boundary thrust: the friction coefficient of frontal prism sediments (hemipelagic mudstones) in hanging wall is 0.1-0.2, while that in subducting sediments (hemipelagic to pelagic mudstones and chert) in footwall increases to 0.2-0.4. The friction coefficient of smectite-rich pelagic clay in the plate-boundary thrust is ~0.1, which is consistent with that obtained from high-velocity (1.3 m/s) friction experiments and temperature measurements. We conclude that surface drilling torque provides useful data to obtain a continuous downhole frictional strength.

  19. Perspectives and limitations of parallel MR imaging at high field strengths.

    PubMed

    Heidemann, Robin M; Seiberlich, Nicole; Griswold, Mark A; Wohlfarth, Katrin; Krueger, Gunnar; Jakob, Peter M

    2006-05-01

    In medical magnetic resonance imaging (MRI) imaging, it is standard practice to use MR scanners with a field strength of 1.5 Tesla. Recently, an ongoing trend towards higher field strengths can be observed, with a new potential clinical standard of 3.0 Tesla. High-field MR imaging, with its intrinsic higher signal-to-noise ratio (SNR), can enable new applications for MRI in medical diagnosis, or can serve to improve existing methods. The use of high field MRI is not without its limitations, however. Besides SNR, other unwanted effects increase with a higher field strength. Without correction, these high field problems can cause a serious loss in image quality. An elegant way to address these problems is the use of parallel imaging. In many clinical applications, parallel MRI (pMRI) is part of the standard protocol, as pMRI can enhance virtually every MRI application without necessarily affecting the contrast behavior of the underlying imaging sequence. In addition to the speed advantages offered by pMRI, the capability of parallel imaging to reduce significant high field-specific problems, thereby improving image quality, will be of major importance.

  20. Analysis of local warm forming of high strength steel using near infrared ray energy

    NASA Astrophysics Data System (ADS)

    Yang, W. H.; Lee, K.; Lee, E. H.; Yang, D. Y.

    2013-12-01

    The automotive industry has been pressed to satisfy more rigorous fuel efficiency requirements to promote energy conservation, safety features and cost containment. To satisfy this need, high strength steel has been developed and used for many different vehicle parts. The use of high strength steels, however, requires careful analysis and creativity in order to accommodate its relatively high springback behavior. An innovative method, called local warm forming with near infrared ray, has been developed to help promote the use of high strength steels in sheet metal forming. For this method, local regions of the work piece are heated using infrared ray energy, thereby promoting the reduction of springback behavior. In this research, a V-bend test is conducted with DP980. After springback, the bend angles for specimens without local heating are compared to those with local heating. Numerical analysis has been performed using the commercial program, DEFORM-2D. This analysis is carried out with the purpose of understanding how changes to the local stress distribution will affect the springback during the unloading process. The results between experimental and computational approaches are evaluated to assure the accuracy of the simulation. Subsequent numerical simulation studies are performed to explore best practices with respect to thermal boundary conditions, timing, and applicability to the production environment.