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1

Knoop Hardness - Apparent Yield Stress Relationship in Ceramics  

SciTech Connect

In Tabor's classical studies of the deformation of metals, the yield stress (Y) and hardness (H) were shown to be related according to H/Y {approx} 3 for complete or fully plastic deformation. Since then it has been anecdotally shown for ceramics that this ratio is <3. Interest exists to explore this further so Hertzian indentation was used to measure the apparent yield stress of numerous ceramics and metals and their results were compared with each material's load-dependent Knoop hardness. The evaluated ceramics included standard reference materials for hardness (silicon nitride and tungsten carbide), silicon carbide, alumina, and glass. Several steel compositions were also tested for comparison. Knoop hardness measurements at 19.6 N (i.e., toward 'complete or fully plastic deformation'), showed that 2 < H/Y < 3 for the metals and 0.8 < H/Y < 1.8 for the glasses and ceramics. Being that H/Y {ne} 3 for the ceramics indicates that Tabor's analysis is either not applicable to ceramics or that full plastic deformation is not achieved with a Knoop indentation or both.

Swab, Jeffrey J [ORNL; LaSalvia, Jerry [U.S. Army research Laboratory, Adelphi, MD; Wereszczak, Andrew A [ORNL; Strong, Kevin T [ORNL; Danna, Dominic [U.S. Army research Laboratory, Adelphi, MD; Ragan, Meredith E [ORNL; Ritt, Patrick J [ORNL

2012-01-01

2

Knoop hardness of dental resin cements: Effect of veneering material and light curing methods  

Microsoft Academic Search

This study evaluated the Knoop hardness of one resin cement (dual-cure mode or light-cure mode) when illuminated directly or through restorative materials—ceramic (HeraCeram) or composite (Artglass)—by two light curing units. Light curing was carried out using a conventional quartz tungsten halogen (QTH) light source (XL2500) for 40s, and a light emitting diodes (LED) light source (Ultrablue Is) for 40s. Bovine

Rubens Nisie Tango; Mário Alexandre Coelho Sinhoreti; Américo Bortolazzo Correr; Luis Felipe Jochims Schneider; Estevão Tomomitsu Kimpara; Lourenço Correr-Sobrinho

2007-01-01

3

Knoop microhardness mapping used to compare the efficacy of LED, QTH and PAC curing lights.  

PubMed

This study used a hardness mapping technique to compare the ability of seven curing lights to polymerize five composites. Six curing lights (Sapphire [plasma-arc: PAC], Bluephase16i [light emitting diode: LED], LEDemetron II [LED], SmartLite IQ [LED], Allegro [LED] and UltraLume-5 [Polywave LED]) were compared to an Optilux 501 (halogen: QTH) light. Five resin composites (Vit-1-escence, Tetric Evoceram, Filtek Z250, 4 Seasons and Solitaire 2) were polymerized at 4 mm and 8 mm from the end of the light guide. Four composites were light cured for the following times using these lights: Sapphire (5 seconds), Bluephase16i (5 seconds), LEDemetron II (5 seconds), SmartLite IQ (10 seconds), UltraLume-5 (10 seconds), Allegro (10 seconds) and Optilux 501 (20 seconds). Solitaire 2 required double these irradiation times. On each specimen, the Knoop microhardness (KHN) was measured at 49 locations across a 3 x 3 mm grid to determine the ability of each light to cure each brand of composite. The PAC light delivered the broadest spectrum of wavelengths, the greatest irradiance and hardness values that were 4.7 to 18.1 KHN(50gf) harder than the other lights. The ability of the lights to cure these five composites was ranked from highest to lowest: Sapphire, Optilux 501, Allegro, UltraLume-5, SmartLite IQ, LEDemetron II and Bluephase16i (ANOVA with REGWQ multiple comparison adjustment, p < 0.01). PMID:20166412

Price, Richard B T; Fahey, John; Felix, Christopher M

2010-01-01

4

Traceability in hardness measurements: from the definition to industry  

NASA Astrophysics Data System (ADS)

The measurement of hardness has been and continues to be of significant importance to many of the world's manufacturing industries. Conventional hardness testing is the most commonly used method for acceptance testing and production quality control of metals and metallic products. Instrumented indentation is one of the few techniques available for obtaining various property values for coatings and electronic products in the micrometre and nanometre dimensional scales. For these industries to be successful, it is critical that measurements made by suppliers and customers agree within some practical limits. To help assure this measurement agreement, a traceability chain for hardness measurement traceability from the hardness definition to industry has developed and evolved over the past 100 years, but its development has been complicated. A hardness measurement value not only requires traceability of force, length and time measurements but also requires traceability of the hardness values measured by the hardness machine. These multiple traceability paths are needed because a hardness measurement is affected by other influence parameters that are often difficult to identify, quantify and correct. This paper describes the current situation of hardness measurement traceability that exists for the conventional hardness methods (i.e. Rockwell, Brinell, Vickers and Knoop hardness) and for special-application hardness and indentation methods (i.e. elastomer, dynamic, portables and instrumented indentation).

Germak, Alessandro; Herrmann, Konrad; Low, Samuel

2010-04-01

5

The effect of sample size on Schmidt rebound hardness value of rocks  

Microsoft Academic Search

The Schmidt hammer has been commonly used device for hardness determination and for predicting the unconfined compressive strength and other mechanical properties of rocks, due to the fact that it is a quick, easy, inexpensive and non-destructive testing method. Testing is most commonly performed following the ISRM and ASTM standards. The effect of sample size for a consistent hardness value

S. Demirdag; H. Yavuz; R. Altindag

2009-01-01

6

Knoop microhardness and FT-Raman evaluation of composite resins: influence of opacity and photoactivation source.  

PubMed

The aim of this study was to evaluate the degree of conversion by Knoop microhardness (KHN) and FT-Raman spectroscopy (FTIR) of one nanofilled (Filtek Supreme-3M-ESPE [FS]) and one microhybrid composite (Charisma-Heraeus-Kulzer [CH]), each with different opacities, namely enamel, dentin, and translucent, which were photo-activated by a quartz-tungsten-halogen lamp (QTH) and a light-emitting diode (LED). Resin was bulk inserted into a disc-shaped mold that was 2.0 mm thick and 4 mm in diameter, obtaining 10 samples per group. KHN and FTIR values were analyzed by two-way ANOVA and Tukey's tests (? = 0.05). Nanofilled resin activated by a LED presented higher microhardness values than samples activated by a QTH for dentin opacity (p < 0.05). The microhybrid resin showed no differences in KHN or FTIR values with different activation sources or opacity. The nanofilled dentin and enamel resins showed lower FTIR values than the translucent resin. The KHN values of the translucent resins were not influenced by the light source. PMID:21670859

Albino, Luis Gustavo Barrotte; Rodrigues, José Augusto; Kawano, Yoshio; Cassoni, Alessandra

2011-01-01

7

Can cone beam CT predict the hardness of interradicular cortical bone?  

PubMed Central

Objectives Orthodontic mini implants can be inserted at the interradicular site. The bone quality at this site may affect the stability and anchorage of the implant. Bone density is clinically evaluated by Hounsfield units (HU) obtained from cone beam CT (CBCT). The objective of this study was to determine the correlations between HU, microhardness and cortical bone thickness of interradicular site at various segments (anterior/posterior) and aspects (buccal/lingual) of both jaws in a swine model. Materials and methods Eight mandible and maxilla swine bones were scanned by CBCT. The HU and thickness of the above-mentioned sites were determined. Then, a Knoop microhardness test was applied and the Knoop Hardness Number was obtained (KHN). Results The mandible parameters spread over a wider range than the maxilla. The buccal aspect of the maxilla had higher HU and KHN values than the mandible. The lingual aspect of the mandible had higher KHN values than the maxilla. Posterior segments had higher HU and KHN values. The thickness of the alveolar cortical bone was greater in the maxilla than in the mandible. Correlations were found between HU and KHN for 3 of the 4 sites (anterior or posterior, buccal or lingual) of the mandible only. No correlations were found for the maxilla. Upon pooling the HU and KHN data for the whole jaw, correlation was found for the maxilla as well. Conclusions Relying on HU values as a predictor of cortical bone hardness should be considered with caution.

2014-01-01

8

Applying Critical Thinking Skills to Character Education and Values Clarification with Students Who Are Deaf or Hard of Hearing  

ERIC Educational Resources Information Center

Students who are deaf or hard of hearing must learn to think critically. "Character education" (CE) refers to the effort to teach basic values and moral reasoning (Doyle & Ponder, 1977). "Values clarification" (VC) is the process of examining one's basic values and moral reasoning (Rokeach, 1973). Character education and values clarification as…

Easterbrooks, Susan R.; Scheetz, Nanci A.

2004-01-01

9

Singular Values of Products of Ginibre Random Matrices, Multiple Orthogonal Polynomials and Hard Edge Scaling Limits  

NASA Astrophysics Data System (ADS)

Akemann, Ipsen and Kieburg recently showed that the squared singular values of products of M rectangular random matrices with independent complex Gaussian entries are distributed according to a determinantal point process with a correlation kernel that can be expressed in terms of Meijer G-functions. We show that this point process can be interpreted as a multiple orthogonal polynomial ensemble. We give integral representations for the relevant multiple orthogonal polynomials and a new double contour integral for the correlation kernel, which allows us to find its scaling limits at the origin (hard edge). The limiting kernels generalize the classical Bessel kernels. For M = 2 they coincide with the scaling limits found by Bertola, Gekhtman, and Szmigielski in the Cauchy-Laguerre two-matrix model, which indicates that these kernels represent a new universality class in random matrix theory.

Kuijlaars, Arno B. J.; Zhang, Lun

2014-05-01

10

Hardness Test  

Microsoft Academic Search

\\u000a The hardness of materials is commonly characterized using indentation techniques. The hardness values depend on the tool employed\\u000a and the measured parameter, for wood, the anisotropy, heterogeneity and hygroscopicity also influence the measurements. In\\u000a this chapter, different methods used for hardness testing of wood are presented. Possible correlations between the different\\u000a hardness figures and other mechanical properties are indicated, in

Mariapaola Riggio; Maurizio Piazza

11

Chemical compositions and nutritional value of Asian hard clam (Meretrix lusoria) from the coast of Andaman Sea.  

PubMed

Chemical compositions and nutritive value of the edible portions including foot, mantle and viscera of Asian hard clam (Meretrix lusoria) harvested from the coast of Andaman Sea were determined. Proximate compositions varied with portions tested. Edible portions had moisture (76.23-84.22%) and protein (9.09-12.75%) as the major components. Carbohydrate (0.32-7.89%), fat (1.58-6.58%) and ash (1.23-2.58%) were also found at various levels, dependent upon portions. Myofibrillar proteins were observed as the major fraction in foot (40.54%) and mantle (31.65%), whilst non-protein nitrogen constituents were dominant in the viscera (36.85%). All portions contained a large amount of essential amino acids (167.66-187.63 mg/g sample), in which leucine (30.91-36.96 mg/g sample) and lysine (35.24-36.03 mg/g sample) were predominant. They were rich in polyunsaturated fatty acids (46.84-49.18% of total fatty acid) with high level of DHA (13.33-16.47 % of total fatty acids) and EPA (4.75-7.11% of total fatty acids). Cholesterol of 0.07-0.21% wet weight was detected. All portions were also rich in macro- (Na, K, Ca and Mg) and micro- (Fe, Zn, Cu and Cr) minerals. Therefore, Asian hard clam is an excellent source of several nutrients, which could be beneficial for the health of the consumers. PMID:23993597

Karnjanapratum, Supatra; Benjakul, Soottawat; Kishimura, Hideki; Tsai, Yung-Hsiang

2013-12-15

12

Hardness, polymerization depth, and internal adaptation of Class II silorane composite restorations as a function of polymerization protocol  

PubMed Central

Objectives: To evaluate the influence of various photoactivation techniques on the internal gap, Knoop-hardness, and polymerization depth of silorane- and methacrylate-based composites in Class II restorations. Methods: Preparations were made in third molars (n = 10), according to composites (Filtek P60: methacrylate; Filtek P90: silorane) and photoactivation techniques (OC: occlusal photoactivation (control); OBL: occlusal+buccal+lingual photoactivation; and BLO: buccal+lingual+occlusal photoactivation (transdental)). Composites were inserted in two increments, both individually photoactivated for 20s. After 24h, specimens were sectioned and the ratio of internal gaps to interface length (%) recorded. Hardness was tested across the transversal section of restorations (1–4 mm below the surface). Results: Silorane restorations showed significantly lower gaps compared with methacrylate, regardless of polymerization technique (P<.05). Supplementary energy dose in OBL and BLO protocols caused significant increase in gaps in silorane restorations (P<.05). For methacrylate restorations, OBL activation caused significantly higher gap formation (P<.05). Significantly lower hardness values were seen for silorane than for methacrylate composites (P<.05), regardless of depth and photoactivation. Significantly higher hardness values were seen in BLO activation for methacrylate restorations compared with control (P<.05); for silorane, no differences were observed. Significantly higher hardness values were observed at 1 and 3 mm compared to 2 and 4 mm for both composites. Conclusions: Internal gaps and hardness are affected by composite type and photoactivation. Despite the reduced values, hardness of silorane is not influenced by photoactivation or by depth. Internal gaps are dependent on the energy dose for both composites, with silorane showing lower internal gaps.

Bechtold, Janaina; dos Santos, Priscila Jaques; Anido-Anido, Andrea; Di Hipolito, Vinicius; Alonso, Roberta Caroline Bruschi; D'Alpino, Paulo Henrique Perlatti

2012-01-01

13

Vibration effect on hardness measurement  

Microsoft Academic Search

In this paper, the effect of ground vibration on hardness measurement, Rockwell scale C hardness, Vickers scale HV1 hardness and Leeb hardness is studied. The hardness machines were placed on the vibration table. The vibration signal is single frequency sinusoidal wave, which frequency and amplitude of vibration can be controlled. The hardness value at free from vibration state is used

Tassanai Sanponpute; Apichaya Meesaplak

2010-01-01

14

Hardness of Covalent Crystals  

Microsoft Academic Search

Based on the idea that the hardness of covalent crystal is intrinsic and equivalent to the sum of the resistance to the indenter of each bond per unit area, a semiempirical method for the evaluation of hardness of multicomponent crystals is presented. Applied to beta-BC2N crystal, the predicted value of hardness is in good agreement with the experimental value. It

Faming Gao; Julong He; Erdong Wu; Shimin Liu; Dongli Yu; Dongchun Li; Siyuan Zhang; Yongjun Tian

2003-01-01

15

Monte Carlo simulation of two-dimensional hard body systems with extreme values of the Poisson's ratio  

NASA Astrophysics Data System (ADS)

Monte Carlo computer simulations with variable shape of the periodic box were performed for a few two-dimensional, hard-body models showing elastically isotropic solid phases. Two examples of homo-molecular (i.e. consisting of identical molecules) systems of anisotropic molecules are discussed which form unusual solid phases, showing negative Poisson's ratio and know as auxetic ones, at densities and pressures higher than the elastically isotropic solid phases. Sharp extremes of the Poisson's ratio were observed for both systems at freezing of the orientational degrees of freedom of the molecules: a minimum was observed for the system for which the auxetic phase with frozen rotation is isotropic and a maximum was found for the other system. This indicates that isotropic auxetic phases can have auxetic precursors with much more negative Poisson's ratios than those characterizing the auxetic phases themselves. An example of a hetero-molecular (i.e. mixture consisting of different molecules), elastically isotropic system is also discussed - the polydisperse hard disc system. The simulations revealed a maximum of the Poisson's ratio in the close packing limit at any nonzero polydispersity. Although no manifestation of any auxetic behaviour has been found in this system, the obtained results indicate other unusual effect - a jump (discontinuity) of the Poisson's ratio at close packing when the polydispersity tends to zero. The results obtained in this work demonstrate that the Poisson's ratio can play the role of a sensitive indicator of (at least) some structural changes in solids.

Tretiakov, K. V.; Wojciechowski, K. W.

2005-03-01

16

Flexural strength and hardness of direct and indirect composites.  

PubMed

The objective of this study was to evaluate the flexural strength (sigma f) and hardness (H) of direct and indirect composites, testing the hypotheses that direct resin composites produce higher sigma f and H values than indirect composites and that these properties are positively related. Ten bar-shaped specimens (25 mm x 2 mm x 2 mm) were fabricated for each direct [D250 - Filtek Z250 (3M-Espe) and D350 - Filtek Z350 (3M-Espe)] and indirect [ISin - Sinfony (3M-Espe) and IVM - VitaVM LC (Vita Zahnfabrik)] materials, according to the manufacturer's instructions and ISO4049 specifications. The sigma f was tested in three-point bending using a universal testing machine (EMIC DL 2000) at a crosshead speed of 0.5 mm/min (ISO4049). Knoop hardness (H) was measured on the specimens' fragments resultant from the sigma f test and calculated as H = 14.2P/l(2), where P is the applied load (0.1 kg; dwell time = 15 s) and l is the longest diagonal of the diamond shaped indent (ASTM E384). The data were statistically analyzed using Anova and Tukey tests (alpha = 0.05). The mean sigma f and standard deviation values (MPa) and statistical grouping were: D250 - 135.4 +/- 17.6a; D350 - 123.7 +/- 11.1b; ISin - 98.4 +/- 6.4c; IVM - 73.1 +/- 4.9 d. The mean H and standard deviation values (kg/mm(2)) and statistical grouping were: D250 - 98.12 +/- 1.8a; D350 - 86.5 +/- 1.9b; ISin - 28.3 +/- 0.9 c; IVM - 30.8 +/- 1.0 c. The direct composite systems examined produce higher mean sigma f and H values than the indirect composites, and the mean values of these properties were positively correlated (r = 0.91), confirming the study hypotheses. PMID:19488465

Borba, Márcia; Della Bona, Alvaro; Cecchetti, Dileta

2009-01-01

17

Young's modulus and fracture during Knoop indentation of potassium, rubidium, cesium, and ammonium acid phthalate single crystals on the (010) plane  

NASA Astrophysics Data System (ADS)

The correlation of the anisotropy of the Young's modulus of organic single crystals of potassium, rubidium, cesium, and ammonium acid phthalates with strain and fracture patterns during Knoop indentation on the (010) cleavage plane in the [001] and [100] directions has been studied. The data on the maximum anisotropy of the strain and fracture patterns of the ammonium acid phthalate single crystal have been discussed in view of the published data on the structure, mechanical, elastic, and X-ray spectral properties of these crystals.

Sizova, N. L.; Moiseeva, N. A.

2012-12-01

18

Values.  

ERIC Educational Resources Information Center

GRADES OR AGES: Grades 1-12. SUBJECT MATTER: Values. ORGANIZATION AND PHYSICAL APPEARANCE: The guide is intended to define the development of the valuing process and contains ideas for classroom teachers. It is not a conventional curriculum guide but is recommended for use with the guide on drug education (SP 007 318). It contains the following…

Chapel Hill City Schools, NC.

19

Effect of thickness of indirect restoration and distance from the light-curing unit tip on the hardness of a dual-cured resin cement  

Microsoft Academic Search

This study evaluated the Knoop hardness and polymerization depth of a dual-cured resin cement, light-activated at different distances through different thicknesses of composite resin. One bovine incisor was embedded in resin and its buccal surface was flattened. Dentin was covered with PVC film where a mold (0.8-mm-thick and 5 mm diameter) was filled with cement and covered with another PVC

Andréia Bolzan de Paula; Rubens Nisie Tango; Mário Alexandre Coelho Sinhoreti; Marcelo Corrêa Alves; Regina M. Puppin-Rontani

2010-01-01

20

Evaluation of the diagnostic value of a computed radiography system by comparison of digital hard copy images with screen-film mammography: results of a prospective clinical trial.  

PubMed

The purpose of the study was to determine prospectively the diagnostic value of a computed radiography (CR) system by comparing mammographic hard copy images with screen-film mammography (SFM). A series of 100 patients, who came for diagnostic investigation, underwent two-view SFM (Lorad M-IV Platinum) and digital mammography with a CR system (AGFA CR system). The images were obtained by double exposure, i.e. same view without removing compression of the corresponding breast. The CR images were processed with dedicated processing for mammography. Six radiologists read sets of SFM and CR images. The primary efficacy parameter was the overall diagnostic value. The secondary efficacy parameters were lesion conspicuity and lesion details (for masses and micro-calcifications), tissue visibility at chest wall and at skin line, axillary details, overall density and sharpness impression and the overall noise impression. These parameters were scored by a 7-point scoring system. "CR non-inferior to SFM" was concluded if the lower confidence interval bound exceeded 80%. The confidence interval for the overall diagnostic value was between 96.4% and 100%. Pooled analysis of the ten features for image quality comparison demonstrated for all but one feature (lesion details of the calcifications) CR non-inferiority to SFM. PMID:16518656

Van Ongeval, C; Bosmans, H; Van Steen, A; Joossens, K; Celis, V; Van Goethem, M; Verslegers, I; Nijs, K; Rogge, F; Marchal, G

2006-06-01

21

Hybrid hard- and soft-modeling of spectrophotometric data for monitoring of ciprofloxacin and its main photodegradation products at different pH values  

NASA Astrophysics Data System (ADS)

A simple and fast on line spectrophotometric method combined with a hybrid hard-soft modeling multivariate curve resolution (HS-MCR) was proposed for the monitoring of photodegradation reaction of ciprofloxacin under UV radiation. The studied conditions attempt to emulate the effect of sunlight on these antibiotics that could be eventually present in the environment. The continuous flow system made it possible to study the ciprofloxacin degradation at different pH values almost at real time, avoiding errors that could arise from typical batch monitoring of the reaction. On the base of a concentration profiles obtained by previous pure soft-modeling approach, reaction pathways have been proposed for the parent compound and its photoproducts at different pH values. These kinetic models were used as a constraint in the HS-MCR analysis. The kinetic profiles and the corresponding pure response profile (UV-Vis spectra) of ciprofloxacin and its main degradation products were recovered after the application of HS-MCR analysis to the spectra recorded throughout the reaction. The observed behavior showed a good agreement with the photodegradation studies reported in the bibliography. Accordingly, the photodegradation reaction was studied by high performance liquid chromatography coupled with UV-Vis diode array detector (HPLC-DAD). The spectra recorded during the chromatographic analysis present a good correlation with the ones recovered by UV-Vis/HS-MCR method.

Razuc, Mariela; Garrido, Mariano; Caro, Yamile S.; Teglia, Carla M.; Goicoechea, Héctor C.; Fernández Band, Beatriz S.

2013-04-01

22

Hardness of Quasicrystals  

NASA Astrophysics Data System (ADS)

Vickers hardness measurements have been made at room temperature for four thermodynamically stable quasicrystals. The hardness value of Al-Li-Cu icosahedral quasicrystal is about 500 (kg/mm2) and those of Al-transition metal quasicrystals are commonly around 1000, which is extremely high for aluminum based alloys. Anisotropy in the hardness in Al-Co-Ni decagonal quasicrystal is rather small.

Takeuchi, Shin; Iwanaga, Hiroshi; Shibuya, Tadaharu

1991-03-01

23

National Transportation Safety Board Aircraft Accident Report: Ground Spoiler Activation in Flight/Hard Landing ValuJet Airlines Flight 558, Douglas D-9-32, N922VV, Nashville, Tennessee, January 7, 1996.  

National Technical Information Service (NTIS)

The report explains the ground spoiler activation in flight and subsequent hard landing of ValuJet Airlines flight 558, N922VV, a Douglas DC-9-32 at Nashville International Airport, Nashville, Tennessee. The safety issues discussed in the report include t...

1996-01-01

24

Effect of light energy density on conversion degree and hardness of dual-cured resin cement.  

PubMed

This study evaluated the effect of different light energy densities on conversion degree (CD) and Knoop hardness number (KHN) of RelyX ARC (RLX) resin cement. After manipulation according to the manufacturer's instructions, RLX was inserted into a rubber mold (0.8 mm x 5 mm) and covered with a Mylar strip. The tip of the light-curing unit (LCU) was positioned in contact with the Mylar surface. Quartz-tungsten-halogen (QTH) and light-emitting diode (LED) LCUs with light densities of 10, 20 and 30 J/cm2 were used to light-cure the specimens. After light curing, the specimens were stored dry in lightproof containers at 37 degrees C. After 24 hours, the CD was analyzed by FT-Raman and, after an additional 24-hours, samples were submitted to Knoop hardness testing. The data of the CD (%) and KHN were submitted to two-way ANOVA and the Tukey's test (alpha = 0.05). QTH and LED were effective light curing units. For QTH, there were no differences among the light energy densities for CD or KHN. For LED, there was a significant reduction in CD with the light energy density set at 10 J/cm2. KHN was not influenced by the light-curing unit and by its light energy density. PMID:20166419

Komori, Paula Carolina de Paiva; de Paula, Andréia Bolzan; Martin, Airton Abr?o; Tango, Rubens Nisie; Sinhoreti, Mario Alexandre Coelho; Correr-Sobrinho, Lourenço

2010-01-01

25

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

An iridium alloy, DOP-26, is used as cladding for {sup 238}PuO{sup 2} fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration`s Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.

Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E.

1992-05-15

26

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

An iridium alloy, DOP-26, is used as cladding for {sup 238}PuO{sup 2} fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.

Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E.

1992-05-15

27

Microindentation hardness evaluation of iridium alloy clad vent set cups  

SciTech Connect

An iridium alloy, DOP-26, is used as cladding for [sup 238]PuO[sub 2] fuel in radioisotope heat sources for space power systems. Presently, DOP-26 iridium alloy clad vent sets (CVS) are being manufactured at the Oak Ridge Y-12 Plant for potential use in the National Aeronautics and Space Administration's Cassini mission to Saturn. Wrought/ground/stress relieved blanks are warm formed into CVS cups. These cups are then annealed to recrystallize the material for subsequent fabrication/assembly operations as well as for final use. One of the cup manufacturing certification requirements is to test for Vickers microindentation hardness. New microindentation hardness specification limits, 210 to 310 HV, have been established for a test load of 1000 grams-force (gf). The original specification limits, 250 to 350 HV, were for 200 gf testing. The primary reason for switching to a higher test load was to reduce variability in the test data. The DOP-26 alloy exhibits microindentation hardness load dependence, therefore, new limits were needed for 1000 gf testing. The new limits were established by testing material from 15 CVS cups using 200 gf and 1000 gf loads and then statistically analyzing the data. Additional work using a Knoop indenter and a 10 gf load indicated that the DOP-26 alloy grain boundaries have higher hardnesses than the grain interiors.

Ulrich, G.B.; DeRoos, L.F.; Stinnette, S.E. (Oak Ridge Y-12 Plant, P.O. Box 2009, Oak Ridge, Tennessee 37831-8096 (United States))

1993-01-15

28

Value-relevant information on corporate intangibles – creation, use, and barriers in capital markets – “between a rock and a hard place”  

Microsoft Academic Search

The article reveals a need for greater understanding and use of corporate intellectual capital (IC) information within two connected capital market areas. Firstly with regard to the conceptualisation and valuation process these capital market agents (analysts and fund managers) conduct. Secondly, within the capital market agents' own value creation chain. The concept of the value creation chain is combined with

John Holland; Ulf Johanson

2003-01-01

29

Hardness of Electrodeposited Nano-Nickel Revisited  

NASA Astrophysics Data System (ADS)

In the past, hardness measurements on nanocrystalline metals were limited to Vickers microhardness and nano-indentation tests, mainly due to sample size/thickness limitations. On the other hand, most industries require hardness values on the Rockwell scale and make extensive use of hardness conversion relationships for various hardness scales. However, hardness conversions currently do not exist for nanocrystalline metals. With recent advances in electrodeposition technology, thicker specimens with a wide range of grain sizes can now be produced. In this study, the relationships between Vickers and Rockwell hardness scales have been developed for such materials. In addition, hardness indentations were used to gain further insight into the work hardening of nanocrystalline and polycrystalline nickel. Vickers microhardness and nano-indentation profiles below large Rockwell indentations showed that polycrystalline nickel exhibited considerable strain hardening, as expected. On the other hand, for nanocrystalline nickel the micro-Vickers and nano-indentations hardness profile showed low strain hardening capacity.

Tang, Bill Tsz Fai

30

Confined Hard Disk System Model  

NSDL National Science Digital Library

The Confined Hard Disk System is an idealized statistical mechanics model that simulates a two-dimensional system of hard disks confined to a box with a constant temperature thermal reservoir at one end and a movable piston at the other. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The model computes and plots the time evolution of the kinetic energy K per particle, the pressure P, and the volume V. The model also displays histograms and mean values of these quantities. The Confined Hard Disk System was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_hd_ConfinedHardDiskSystem.jar file will run the program if Java is installed.

Christian, Wolfgang

2010-12-27

31

COMPARATIVE MEASUREMENTS OF SLOVENIAN AND USA ROCKWELL C HARDNESS SCALES  

Microsoft Academic Search

A national scale is set up for each hardness scale representing the reference hardness values in each country. From metrological and international trade aspects agreement between the national scales is very important. Good agreement makes possible good industrial cooperation. Therefore comparison between national scales is necessary. Comparison between national hardness scales and hardness scales set up by the producers of

Robert Ellis

2004-01-01

32

Hard Rock Penetration Technology.  

National Technical Information Service (NTIS)

This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of five presentations: 'Hard Rock Penetration - Summary' by George P. Tennyson, Jr.; 'Overview - Hard Rock Penetration' by James C. Dunn; 'An Overvi...

2005-01-01

33

Wear of hard materials by hard particles  

SciTech Connect

Hard materials, such as WC-Co, boron carbide, titanium diboride and composite carbide made up of Mo2C and WC, have been tested in abrasion and erosion conditions. These hard materials showed negligible wear in abrasion against SiC particles and erosion using Al2O3 particles. The WC-Co materials have the highest wear rate of these hard materials and a very different material removal mechanism. Wear mechanisms for these materials were different for each material with the overall wear rate controlled by binder composition and content and material grain size.

Hawk, Jeffrey A.

2003-10-01

34

Handbook of hard coatings  

SciTech Connect

This book discusses the hard coatings classified as tribologically hard, which are wear resistant and low friction. Three sections discuss tribological properties and new developments. With the development of modern technology in the areas of optical, optoelectronic, and defense related applications, the traditional term hard coatings can be extended. Thus, a system which operates satisfactorily, in a given environment can be said to be hard with respect to that environment. Many hard coatings are ceramic compounds such as oxides, carbides, nitrides, ceramic alloys, cements, diamonds and cubic nitride.

Bunshah, R.; Weissmantel, C. [eds.

2000-07-01

35

Hard metal composition  

SciTech Connect

This patent describes a hard composition of matter having a Rockwell A hardness value of at least approximately 85, comprising the compressed and densified reaction product of: a minor amount of a boron carbide component selected from the group consisting of (a) boron carbide and (b) boron and carbon, the boron and carbon being present in amounts sufficient to form boron carbide in situ, wherein the boron carbide component consists essentially of B/sub 4/C; a major amount of a metal mixture consisting essentially of: (a) a first metal component selected from the group consisting of tungsten and molybdenum and mixtures thereof, and (b) a second metal component selected from the group consisting of nickel and iron and mixtures thereof; wherein the minor amount of the boron carbide component is between 3% and 6% by weight of the composition of matter when the first metal component is tungsten. The minor amount of the boron carbide component is between 6% and 10% by weight of the composition when the first metal component is molybdenum. The boron carbide component is between 3% and 10% when the first metal component is a mixture of tungsten and molybdenum, with the remainder of the composition being formed of the metal mixture, and wherein the first metal component is from 70% to less than about 90% by weight of the metal mixture when the first metal component is tungsten, and wherein the first metal component is from 72% to less than about 90% by weight of the metal mixture when the first metal component is molybdenum.

Sheinberg, H.

1986-12-02

36

DEFINITION OF NEW INDUSTRIAL HARDNESS TEST USING EQUIVALENT INDENTATION DEPTH  

Microsoft Academic Search

The Rockwell hardness test is commonly used and accepted by many industrial users, but the hardness value requires conversion between scales because the geometry of the indenters and the load ranges are different. On the other hand, hardness calculation using pyramidal indenters is quite simple and can be applied to any load range, though it is much more complicated to

Takashi Yamamoto; Kensuke Miyahara

37

Hard-square lattice gas  

Microsoft Academic Search

We have studied the hard-square lattice gas, using corner transfer matrices. In particular, we have obtained the first 24 terms of the high-density series for the order parameter?2-?1. From these we estimate the critical activity to be 3.7962±0.0001. This is in excellent agreement with the earlier work of Gaunt and Fisher. It conflicts with the value 4.0 given by Müller-Hartmann

R. J. Baxter; I. G. Enting; S. K. Tsang

1980-01-01

38

Dynamic indentation hardness of materials  

NASA Astrophysics Data System (ADS)

Indentation hardness is one of the simplest and most commonly used measures for quickly characterizing material response under static loads. Hardness may mean resistance to cutting to a machinist, resistance to wear to a tribologist, or a measure of flow stress to a design engineer. In this simple technique, a predetermined force is applied to an indenter for 5-30 seconds causing it to penetrate a specimen. By measuring the load and the indentation size, a hardness value is determined. However, the rate of deformation during indenter penetration is of the order of 10sp{-4}\\ ssp{-1}. In most practical applications, such as high speed machining or impact, material deforms at strain rates in excess of 10sp3{-}10sp5\\ ssp{-1}. At such high rates, it is well established that the plastic behavior of materials is considerably different from their static counterpart. For example, materials exhibit an increase in their yield stress, flow stress, fracture stress, and fracture toughness at high strain rates. Hence, the use of static hardness as an indicator of material response under dynamic loads may not be appropriate. Accordingly, a simple dynamic indentation hardness tester is developed for characterizing materials at strain rates similar to those encountered in realistic situations. The experimental technique uses elastic stress wave propagation phenomena in a slender rod. The technique is designed to deliver a single indentation load of 100-200 mus duration. Similar to static measurements, the dynamic hardness is determined from the measured load and indentation size. Hardness measurements on a range of metals have revealed that the dynamic hardness is consistently greater than the static hardness. The increase in hardness is strongly dependent on the crystal structure of the material. The observed trends in hardness are also found to be consistent with the yield and flow stresses of these materials under uniaxial compression. Therefore, it is suggested that the current technique can be used to assess the rate sensitive nature of engineering materials. To further characterize the plastic strains within the indentation volume, static microhardness measurements were also performed within this region. The contours of microhardness indicated that the plastic zone beneath the indenter is typically smaller under dynamic conditions compared to static loading for rate sensitive materials. To assess the influence of the elastic modulus, yield stress, and work hardening coefficient on the induced plastic volume, finite element simulations were performed using the explicit finite element code LS-DYNA3D. The parametric study revealed that the yield stress has the most significant influence on the size and shape of the plastic zone. The above microstructural and numerical results can be used as guidelines for proper selection and design of engineering materials in applications involving high strain rate loading. Moreover, the contours of microhardness variation can be used to verify the suitability of analytical models developed for characterizing the deformation behavior of engineering materials under complex three dimensional loads.

Koeppel, Brian James

39

The hard metal diseases  

SciTech Connect

Hard metal is a mixture of tungsten carbide and cobalt, to which small amounts of other metals may be added. It is widely used for industrial purposes whenever extreme hardness and high temperature resistance are needed, such as for cutting tools, oil well drilling bits, and jet engine exhaust ports. Cobalt is the component of hard metal that can be a health hazard. Respiratory diseases occur in workers exposed to cobalt--either in the production of hard metal, from machining hard metal parts, or from other sources. Adverse pulmonary reactions include asthma, hypersensitivity pneumonitis, and interstitial fibrosis. A peculiar, almost unique form of lung fibrosis, giant cell interstitial pneumonia, is closely linked with cobalt exposure.66 references.

Cugell, D.W. (Department of Medicine, Northwestern University Medical School, Chicago, IL (United States))

1992-06-01

40

Investigations on The Surface Properties of 4-Methoxy N-Methyl 4-Stilbazolium Tosylate Single Crystal  

NASA Astrophysics Data System (ADS)

The mechanical properties of crystals are evaluated by mechanical testing which reveals certain surface characteristics. The fastest and simplest type of mechanical testing is hardness measurement. The Vickers and Knoop microhardness studies have been carried out on 4-methoxy benzaldehyde N-methyl 4-stilbazolium tosylate crystals grown by slow evaporation technique over a load range of 10-100 g. The Vickers hardness number (Hv) and the Knoop microhardness number (Hk) were found to increase with the increase in load. The Meyer's index number 'n' was calculated from Hv. The Young's modulus was calculated using the Knoop hardness values. Hardness anisotropy has been observed in accordance with the orientation of the crystal. Laser damage threshold studies have been carried out for the crystal using a Q-switched Nd:YAG laser of ns pulses. The surface of the grown crystal was analyzed with etching. The results are discussed in detail.

Gill, Amirdha Sher; Kalainathan, S.

2011-07-01

41

Effects of preheating and precooling on the hardness and shrinkage of a composite resin cured with QTH and LED.  

PubMed

The aim of this study was to evaluate in vitro the hardness and shrinkage of a pre-cooled or preheated hybrid composite resin cured by a quartz-tungsten-halogen light (QTH) and light-emitting diode (LED) curing units. The temperature on the tip of the devices was also investigated. Specimens of Charisma resin composite were produced with a metal mold kept under 37°C. The syringes were submitted to 4°C, 23°C, and 60°C (n=20) before light-curing, which was carried out with the Optilux 501 VCL and Elipar FreeLight 2 units for 20 seconds. The specimens were kept under 37°C in a high humidity condition and darkness for 48 hours. The Knoop hardness test was carried out with a 50 gram-force (gf) load for 10 seconds, and the measurement of the shrinkage gap was carried out using an optical microscope. The data were subjected to analysis of variance and the Games-Howell test (?=0.05). The mean hardness of the groups were similar, irrespective of the temperatures (p>0.05). For 4°C and 60°C, the top surface light-cured by LED presented significantly reduced shrinkage when compared with the bottom and to both surfaces cured by QTH (p<0.05). It was concluded that the hardness was not affected by pre-cooling or preheating. However, polymerization shrinkage was slightly affected by different pre-polymerization temperatures. The QTH-curing generated greater shrinkage than LED-curing only when the composite was preheated. Different temperatures did not affect the composite hardness and shrinkage when cured by a LED curing unit. PMID:23088189

Osternack, F H; Caldas, D B M; Almeida, J B; Souza, E M; Mazur, R F

2013-01-01

42

Radiation from hard objects  

SciTech Connect

The inference of the diameter of hard objects is insensitive to radiation efficiency. Deductions of radiation efficiency from observations are very sensitive - possibly overly so. Inferences of the initial velocity and trajectory vary similarly, and hence are comparably sensitive.

Canavan, G.H.

1997-02-01

43

Indentation plastic displacement field: Part I. The case of soft films on hard substrates  

SciTech Connect

The plastic deformation behavior of Knoop indentations made in a soft, porous titanium/aluminum multilayered thin film on a hard silicon substrate is studied through use of the focused-ion-beam milling and imaging technique. Pileup is observed for indentations with depths larger than 30{percent} of the total film thickness. Analysis of the indentation cross sections shows that plastic deformation around the indentation is partly accommodated by the closing of the pores within the multilayers. This densification process reduces the amount of pileup formed below that predicted by finite element simulations. Experimental results show that the pileup is formed by an increase of the titanium layer thickness near the edges of the indentation. The thickness increase is largest near the film/substrate interface and decreases towards the surface of the multilayered film. The amount of normal compression near the center of the indenter is characterized, and it is demonstrated that the deformation becomes more nonuniform with increasing indentation depth. {copyright} {ital 1999 Materials Research Society.}

Tsui, T.Y. [Advanced Micro Devices, One AMD Place, Sunnyvale, California 94088 (United States); Vlassak, J.; Nix, W.D. [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)

1999-06-01

44

Novel hard compositions and methods of preparation  

DOEpatents

Novel very hard compositions of matter are prepared by using in all embodiments only a minor amount of a particular carbide (or materials which can form the carbide in situ when subjected to heat and pressure); and no strategic cobalt is needed. Under a particular range of conditions, densified compositions of matter of the invention are prepared having hardnesses on the Rockwell A test substantially equal to the hardness of pure tungsten carbide and to two of the hardest commercial cobalt-bonded tungsten carbides. Alternately, other compositions of the invention which have slightly lower hardnesses than those described above in one embodiment also possess the advantage of requiring no tungsten and in another embodiment possess the advantage of having a good fracture toughness value.

Sheinberg, H.

1981-02-03

45

Al-Mn coating electrodeposited from ionic liquid on NdFeB magnet with high hardness and corrosion resistance  

NASA Astrophysics Data System (ADS)

Al-Mn coatings were electrodeposited on sintered NdFeB permanent magnet in MnCl2-AlCl3-1-ethyl-3-methylim-idazolium chloride (MnCl2-AlCl3-EMIC) ionic liquid at room temperature. The coatings were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The adhesion strength of the coating on NdFeB substrate was evaluated by thermal shock and scratch test. The hardness and corrosion behavior of Al-Mn coating were measured by a Knoop microhardness tester, immersion test and neutral salt spray test respectively. The results showed that the amorphous structure of the deposits was obtained at the current density of 6 mA/cm2, while higher current densities resulted in a mixed structure of amorphous and crystalline. The Al-Mn coating showed excellent adhesion strength on NdFeB substrate with the thermal shock test over 30 cycles and Lc > 80 N. The hardness of Al-Mn coating was up to 5.4 GPa. The amorphous Al-Mn coating showed an anodic sacrificial protection with a low corrosion rate for NdFeB. Meanwhile, the magnetic properties measured by an AMT-4 magnetic measurement device showed that Al-Mn coating did not deteriorate the magnetic property of NdFeB.

Ding, Jingjing; Xu, Bajin; Ling, Guoping

2014-06-01

46

Hydrogen bonding and mechanical properties in segmented montmorillonite\\/polyurethane nanocomposites of different hard segment ratios  

Microsoft Academic Search

Hydrogen bonding in the hard segments of the synthesized montmorillonite\\/polyurethane nanocomposites of various hard segment ratios was found to decrease with the increasing amount of montmorillonite regardless of the hard segment ratios, but reached plateau values at 5wt% montmorillonite concentration. The maximal reductions of the hydrogen bonding in the polyurethane nanocomposites ranged from 20 to 37%, depending on the hard

Y. I Tien; K. H Wei

2001-01-01

47

What Would You Work Hard For?  

NSDL National Science Digital Library

This lesson plan helps young children begin to learn about the concept of value and why some items are considered more valuable than others. These concepts relate to a geographical understanding of natural resources and the reasons why people work very hard to extract resources, such as during the California gold rush. This lesson has students go through a simulation to learn about value, abundance, and scarcity and asks them to consider the things that they would be willing to work very hard for.

48

Abduction dealing with potential values  

Microsoft Academic Search

In this paper, we introduce the concept of “value” to the abduction procedure. In fact, “values” are dealt with outside of the abduction procedure. For usual abduction, we always consider values included in the knowledge (hard coded). However, for a certain procedure, such values are unnecessary and sometimes harmful. Outside of the main abduction procedure, the inference system can flexibly

Akinori Abe

2010-01-01

49

Laser quench hardening of steel: Effects of superimposed elastic pre-stress on the hardness and residual stress distribution  

NASA Astrophysics Data System (ADS)

Cold drawn AISI 4140 beams were LASER surface hardened with a 2 kW CO2 LASER. Specimens were treated in the free state and while restrained in a bending fixture inducing surface tensile stresses of 94 and 230 MPa. Knoop hardness indentation was used to evaluate the through thickness hardness distribution, and a layer removal methodology was used to evaluate the residual stress distribution. Results showed the maximum surface hardness attained was not affected by pre-stress during hardening, and ranged from 513 to 676 kg/mm2. The depth of effective hardening varied at different magnitudes of pre-stress, but did not vary proportionately to the pre-stress. The surface residual stress, coinciding with the maximum compressive residual stress, increased as pre-stress was increased, from 1040 MPa for the nominally treated specimens to 1270 MPa for specimens pre-stressed to 230 MPa. The maximum tensile residual stress observed in the specimens decreased from 1060 MPa in the nominally treated specimens to 760 MPa for specimens pre-stressed to 230 MPa. Similarly, thickness of the compressive residual stress region increased and the depth at which maximum tensile residual stress occurred increased as the pre-stress during treatment was increased Overall, application of tensile elastic pre-stress during LASER hardening is beneficial to the development of compressive residual stress in AISI 4140, with minimal impact to the hardness attained from the treatment. The newly developed approach for LASER hardening may support efforts to increase both the wear and fatigue resistance of parts made from hardenable steels.

Meserve, Justin

50

Absolute hardness: companion parameter to absolute electronegativity  

SciTech Connect

For neutral and charged species, atomic and molecular, a property called absolute hardness eta is defined. Let E(N) be a ground-state electronic energy as a function of the number of electrons N. As is well-known, the derivative of E(N) with respect to N, keeping nuclear charges Z fixed, is the chemical potential ..mu.. or the negative of the absolute electronegativity chi: ..mu.. = (deltaE/deltaN)/sub Z/ = /sup -/chi. The corresponding second derivative is hardness: 2eta = (delta..mu../deltaN)/sub Z/ = (deltachi/deltaN)/sub Z/ = (delta/sup 2/E/deltaN/sup 2/)/sub Z/. Operational definitions of chi and eta are provided by the finite difference formulas (the first due to Mulliken) chi = 1/2(I+A), eta = 1/2(I-A), where I and A are the ionization potential and electron affinity of the species in question. Softness is the opposite of hardness: a low value of eta means high softness. The principle of hard and soft acids and bases is derived theoretically by making use of the hypothesis that extra stability attends bonding of A to B when the ionization potentials of A and B in the molecule (after charge transfer) are the same. For bases B, hardness is identified as the hardness of the species B/sup +/. Tables of absolute hardness are given for a number of free atoms, Lewis acids, and Lewis bases, and the values are found to agree well with chemical facts. 1 figure, 3 tables.

Parr, R.G.; Pearson, R.G.

1983-12-28

51

THEORY OF FLUX CREEP IN HARD SUPERCONDUCTORS  

Microsoft Academic Search

Previous investigations of the critical state of the hard superconductor ; have defined it in terms of constants alpha and B\\/sub O\\/; alpha (T) = J\\/sub cr\\/; (B\\/sub cr\\/ + Bâ). If the current density J or the field B is increased ; beyond the critical values, a process called flux creep'' sets in, and flux ; leaks through the

P. Anderson

1962-01-01

52

Diffractive hard scattering  

SciTech Connect

I discuss events in high energy hadron collisions that contain a hard scattering, in the sense that very heavy quarks or high P/sub T/ jets are produced, yet are diffractive, in the sense that one of the incident hadrons is scattered with only a small energy loss. 8 refs.

Berger, E.L.; Collins, J.C.; Soper, D.E.; Sterman, G.

1986-03-01

53

Work Hard. Be Nice  

ERIC Educational Resources Information Center

In 1994, fresh from a two-year stint with Teach for America, Mike Feinberg and Dave Levin inaugurated the Knowledge Is Power Program (KIPP) in Houston with an enrollment of 49 5th graders. By this Fall, 75 KIPP schools will be up and running, setting children from poor and minority families on a path to college through a combination of hard work,…

Mathews, Jay

2009-01-01

54

Overview: Hard Rock Penetration  

Microsoft Academic Search

The Hard Rock Penetration program is developing technology to reduce the costs of drilling and completing geothermal wells. Current projects include: lost circulation control, rock penetration mechanics, instrumentation, and industry\\/DOE cost shared projects of the Geothermal Drilling organization. Last year, a number of accomplishments were achieved in each of these areas. A new flow meter being developed to accurately measure

Dunn

1992-01-01

55

Overview - Hard Rock Penetration  

Microsoft Academic Search

The Hard Rock Penetration program is developing technology to reduce the costs of drilling and completing geothermal wells. Current projects include: lost circulation control, rock penetration mechanics, instrumentation, and industry\\/DOE cost shared projects of the Geothermal Drilling Organization. Last year, a number of accomplishments were achieved in each of these areas. A new flow meter being developed to accurately measure

Dunn; James C

1992-01-01

56

CSI: Hard Drive  

ERIC Educational Resources Information Center

Acting on information from students who reported seeing a classmate looking at inappropriate material on a school computer, school officials used forensics software to plunge the depths of the PC's hard drive, searching for evidence of improper activity. Images were found in a deleted Internet Explorer cache as well as deleted file space.…

Sturgeon, Julie

2008-01-01

57

Budgeting in Hard Times.  

ERIC Educational Resources Information Center

Interviews with school board members and administrators produced a list of suggestions for balancing a budget in hard times. Among these are changing calendars and schedules to reduce heating and cooling costs; sharing personnel; rescheduling some extracurricular activities; and forming cooperative agreements with other districts. (MLF)

Parrino, Frank M.

2003-01-01

58

Running in Hard Times  

ERIC Educational Resources Information Center

Roberta Stevens and Kent Oliver are campaigning hard for the presidency of the American Library Association (ALA). Stevens is outreach projects and partnerships officer at the Library of Congress. Oliver is executive director of the Stark County District Library in Canton, Ohio. They have debated, discussed, and posted web sites, Facebook pages,…

Berry, John N., III

2009-01-01

59

Hard Sphere Gas Model  

NSDL National Science Digital Library

The Ejs Hard Sphere Gas model displays a three-dimensional (ideal) gas made out of hard disks. Particles are initialized with a random speed and in a random direction and move with constant velocity until a collision occurs. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Hard Sphere Gas model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_newton_HardShpereGas.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for statistical mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2008-07-06

60

Counting coins and value  

NSDL National Science Digital Library

Students will identify and add up coins. Please complete the games in order. You must finish each game before going on to the next one. Game #1: Counting Money - Values of coins Game #2:Counting Money (harder) Game #3: Let s Compare (hardest) Game #4: Money Hard Game #5: Cash Out--Very Difficult Math Game ...

Christian, Mrs.

2007-03-21

61

The Economic Impact of the Florida Cultured Hard Clam Industry  

Microsoft Academic Search

The objective of this study was to estimate the economic impact on the Florida economy generated by the cultured hard clam industry. Florida certified shellfish wholesalers that handle Florida cultured hard clams were interviewed by telephone survey to determine the number and value of clams that they process, the sources of their clams, prices received, and the marketing channels (wholesale,

Charles Adams; Alan Hodges; David Mulkey; Leslie Sturmer

2004-01-01

62

Novel hard compositions and methods of preparation  

DOEpatents

Novel very hard compositions of matter are prepared by using in all embodiments only a minor amount of a particular carbide (or materials which can form the carbide in situ when subjected to heat and pressure); and no strategic cobalt is needed. Under a particular range of conditions, densified compositions of matter of the invention are prepared having hardnesses on the Rockwell A test substantially equal to the hardness of pure tungsten carbide and to two of the hardest commercial cobalt-bonded tungsten carbides. Alternately, other compositions of the invention which have slightly lower hardnesses than those described above in one embodiment also possess the advantage of requiring no tungsten and in another embodiment possess the advantage of having a good fracture toughness value. Photomicrographs show that the shapes of the grains of the alloy mixture with which the minor amount of carbide (or carbide-formers) is mixed are radically altered from large, rounded to small, very angular by the addition of the carbide. Superiority of one of these hard compositions of matter over cobalt-bonded tungsten carbide for ultra-high pressure anvil applications was demonstrated. 3 figs.

Sheinberg, H.

1983-08-23

63

Novel hard compositions and methods of preparation  

DOEpatents

Novel very hard compositions of matter are prepared by using in all embodiments only a minor amount of a particular carbide (or materials which can form the carbide in situ when subjected to heat and pressure); and no strategic cobalt is needed. Under a particular range of conditions, densified compositions of matter of the invention are prepared having hardnesses on the Rockwell A test substantially equal to the hardness of pure tungsten carbide and to two of the hardest commercial cobalt-bonded tungsten carbides. Alternately, other compositions of the invention which have slightly lower hardnesses than those described above in one embodiment also possess the advantage of requiring no tungsten and in another embodiment possess the advantage of having a good fracture toughness value. Photomicrographs show that the shapes of the grains of the alloy mixture with which the minor amount of carbide (or carbide-formers) is mixed are radically altered from large, rounded to small, very angular by the addition of the carbide. Superiority of one of these hard compositions of matter over cobalt-bonded tungsten carbide for ultra-high pressure anvil applications was demonstrated.

Sheinberg, Haskell (Los Alamos, NM)

1983-08-23

64

Hard Metal Interstitial Lung Disease  

Microsoft Academic Search

Hard metal lung disease is an unusual disease which can occur in individuals exposed to hard metals. Clinically, the condition resembles hypersensitivity pneumonitis depending mainly on individual susceptibility, which eventually progresses to pulmonary fibrosis. We present two patients with pulmonary fibrosis, who were actually diagnosed after an exhaustive anamnesis and examination of the tissue by scanning microscope to discard hard

M. Ángeles Montero; Javier de Gracia; Ferràn Morell

2010-01-01

65

Effects of hard particles on friction coefficients and particle embedment in brake system during hard braking  

NASA Astrophysics Data System (ADS)

The effects of hard particles on the friction coefficients and particle embedment during hard braking were investigated. Silica sands grit of the size between 180 to 355 ?m were used during the experiments. The results were compared to the results obtained without the grit particles present in order to determine the change in friction coefficient, the fluctuation of frictional oscillation amplitude, and the percentage of particle embedment. Different sliding speeds were applied to investigate the relationship between particle embedment with friction coefficient and friction oscillation amplitude. Presence of hard particles of different grit size is found to significantly affect the friction coefficient and standard deviation of friction oscillation amplitude values. The friction coefficient and standard deviation values of friction oscillation amplitude increase with particle embedment due to the rapid changes of the effective contact area and the abrasion mode operating in the gap interface. Also, particle embedment tends to increase the disc surface roughness and influence the stopping time of the disc.

Abdul Hamid, M. K.; Stachowiak, G. W.; Syahrullail, S.

2012-06-01

66

Hard noncommutative loops resummation.  

PubMed

The noncommutative version of the Euclidean g2phi4 theory is considered. By using Wilsonian flow equations the ultraviolet renormalizability can be proved to all orders in perturbation theory. On the other hand, the infrared sector cannot be treated perturbatively and requires a resummation of the leading divergences in the two-point function. This is analogous to what is done in the hard thermal loops resummation of finite temperature field theory. Next-to-leading order corrections to the self-energy are computed, resulting in O(g3) contributions in the massless case, and O(g6logg2) in the massive one. PMID:11863880

Griguolo, Luca; Pietroni, Massimo

2002-02-18

67

Principal value resummation  

Microsoft Academic Search

We present a new resummation formula for the Drell-Yan cross section. The formal resummation of threshold corrections in Drell-Yan hard-scattering functions produces an exponent with singularities from the infrared pole of the QCD running coupling. Our reformulation treats such ``infrared renormalons'' by a principal value prescription, analogous to a modified Borel transform. The resulting expression includes all large threshold corrections

Harry Contopanagos; George Sterman

1994-01-01

68

Effect of Water Hardness on Bioremoval of Arsenic and Nickel  

NASA Astrophysics Data System (ADS)

Laboratory experiments explored the effect of water hardness on the ability of Lemna m to sorb Arsenic and Nickel from water. System variables included the presence of hardness (100 mg/L as CaCO3), Arsenic (1.0 mg/L), Nickel (1.0 mg/L), and the aquatic plant Lemna m. Values were chosen to represent approximate values from drainage water in a sulfide mine. A four factor, two level factorial experimental design was used to determine the effect of each variable and the interactions between the variables. Results suggest no significant interaction between water hardness and the bioremoval of As or Ni. This finding suggests a useful alternative to chemical precipitation based removals which commonly must reduce water hardness before removing other contaminants.

Sternberg, S. P.

2008-12-01

69

Place Value  

NSDL National Science Digital Library

Practice place value! Fight the pirates in Pirates Place Value Uncover the hidden picture in Place value hidden picture Take the quiz at place value quiz Keep practicing with Place value to 1000 Stretch your brain with Place value to 100,000 ...

Peake, Mrs.

2011-08-18

70

Transport coefficients of hard sphere fluids  

NASA Astrophysics Data System (ADS)

New calculations have been made of the self-diffusion coefficient D, the shear viscosity ?s , the bulk viscosity ?b and thermal conductivity ? of the hard sphere fluid, using molecular dynamics (MD) computer simulation. A newly developed hard sphere MD scheme was used to model the hard sphere fluid over a wide range up to the glass transition (~0.57 packing fraction). System sizes of up to 32 000 hard spheres were considered. This set of transport coefficient data was combined with others taken from the literature to test a number of previously proposed analytical formulae for these quantities together with some new ones given here. Only the self-diffusion coefficient showed any substantial n dependence for N > 500 at equilibrium fluid densities ( ? < 0.494). D increased with N , especially at intermediate densities in the range ? ~ 0.3-0.35. The expression for the packing fraction dependence of D proposed by Speedy, R. J., 1987, Molec. Phys. , 62 , 509 was shown to fit these data well for N ~ 500 particle systems. We found that the packing fraction ? dependence of the two viscosities and thermal conductivity, generically denoted by X , were represented well by the simple formula X/X0 = 1/[1 -( ? / gr;1)]m within the equilibrium fluid range 0 < ? <0.493. This formula has two disposable parameters, ?1 and m, and X0 is the value of the property X in the limit of zero density. This expression has the same form as the Krieger-Dougherty formula (Kreiger, I. M., 1972,Adv. Colloid. Interface Sci. , 3, 111) which is used widely in the colloid literature to represent the packing fraction dependence of the Newtonian shear viscosity of monodisperse colloidal near-hard spheres. Of course, in the present case, X0 was the dilute gas transport coefficient of the pure liquid rather than the solvent viscosity. It was not possible to fit the transport coefficient normalized by their Enskog values with such a simple expression because these ratios are typically of order unity until quite high packing fractions and then diverge rapidly at higher values over a relatively narrow density range. At the maximum equilibrium fluid packing fraction ? = 0.494 for both the hard sphere fluid and the corresponding colloidal case a very similar value was found for ?s/?0~ 30-40, suggesting that the 'crowding' effects and their consequences for the dynamics in this region of the phase diagram in the two types of liquid have much in common. For the hard sphere by MD, D0/D ~ 11 at the same packing fraction, possibly indicating the contribution from 'hydrodynamic enhancement' of this transport coefficient, which is largely absent for the shear viscosity. Interestingly the comparable ratio for hard sphere colloids is the same.

Sigurgeirsson, H.; Heyes, D. M.

71

Concept Mapping: Soft Science or Hard Art?  

NSDL National Science Digital Library

In this paper the scientific side of concept mapping is viewed as "soft science" and the artistic one as "hard art" to imply that the process has some qualities of both, but probably does not fall exclusively within either's domain. In the spirit of hard art, a "gallery" of final concept maps from twenty projects is presented, partly to illustrate more examples of the process when used in a variety of subject areas and for different purposes, and partly for their aesthetic value alone. In the spirit of soft science, two major issues are considered. First, the evidence for the validity and reliability of concept mapping is introduced, along with some suggestions for further research which might be undertaken to examine those characteristics. Second, the role of concept mapping is discussed, with special emphasis on its use in a pattern matching framework. This document is intended for use by novice evaluators and professional evaluators in workshops and conferences.

Trochim, William

72

Values and the Valuing Process.  

ERIC Educational Resources Information Center

This paper develops a basic conceptual framework of values and the valuing process. Section 1, Values and Value Claims, discusses the four different types of value claims (personal, market, real, and implicit) and their relationships. The second section considers the process of rational evaluation as a method of arriving at and supporting value

Scriven, Michael

73

Effects of differences in hardness measurement procedures on the traceability chain and calibration process  

NASA Astrophysics Data System (ADS)

Establishment of traceability in hardness measurement is still under discussion at the ISO TC 164 SC 3 subcommittee on hardness testing. Two paths for establishing traceability are proposed for the Rockwell hardness measurement in ISO 6508-1. One way is taking a route to SI units through direct calibration of machine components, and the other way is taking a route to a hardness measurement standard through indirect calibration of machine performance. In addition to this, the difference in hardness measurement procedures between Rockwell and Brinell/Vickers hardness causes further confusion in establishing a traceability chain and an uncertainty evaluation process. This confusion is partly caused by the characteristics of hardness value, i.e. a procedure-dependent property. In this paper, methods used for the establishment of traceability for Rockwell, Brinell and Vickers hardness measurements are discussed based on the concept defined in the VIM.

Tak, Nae Hyung; Moo Lee, Hae; Bahng, Gunwoong

2013-06-01

74

Elastic/plastic effects during very low-load hardness testing of copper  

SciTech Connect

A nanoindentation test system has been applied to obtaining continuous low-load/penetration depth results on a reference copper material. As usual, higher apparent hardness values occur at the lowest load values. An explanation is given in terms of the elastic load bearing capacity of the material. The analysis leads to a proposed hardness stress/strain description that appears to be satisfactory.

Armstrong, R.W. [Univ. of Maryland, College Park, MD (United States)] [Univ. of Maryland, College Park, MD (United States); Shin, H. [Univ. of Maryland, College Park, MD (United States)] [Univ. of Maryland, College Park, MD (United States); [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Ruff, A.W. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)] [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1995-03-01

75

STP Hard Disks MD Program  

NSDL National Science Digital Library

The STP Hard Disks MD program simulates the dynamics of a system of hard disks. The default parameters are N=64 particles in a box of length L = 18.0 and a temperature T=1.0. The particles are initially in a regular array. STP HardDisksMD is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double-clicking the stp_HardDisksMD.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2009-03-06

76

Water Hardness and Cardiovascular Disease.  

National Technical Information Service (NTIS)

A brief review of the present state of knowledge regarding the relationship of water hardness to cardiovascular disease. Also included are recommendations for future research and a statement on the appropriateness of modifying current water treatment prac...

1979-01-01

77

Ejs Hard Disk Gas Model  

NSDL National Science Digital Library

The Ejs Hard Disk Gas model displays a two-dimensional gas made out of hard disks. Particles are initialized with a speed v=1 in a random direction and move with constant velocity until a collision occurs. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Hard Disk Gas model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_newton_HardDiskGas.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for statistical mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2008-07-06

78

Elastic recovery at hardness indentations  

Microsoft Academic Search

The mechanics of hardness indentation are considered. On the basis of a cycle in which the loading is elastic-plastic and the unloading (and subsequent reloading) elastic, an expression is derived for the relative depth recovery of the impression as a function of hardness\\/modulus,H\\/E. Experimental observations on indented surfaces of selected materials, mostly ceramics, using a tilting procedure in the scanning

B. R. Lawn; V. R. Howes

1981-01-01

79

QPX Disease in Hard Clams  

NSDL National Science Digital Library

This New York SeaGrant PDF-brochure examines QPX (Quahog Parasite Unknown, a disease-causing parasite) as it relates to the hard clam fishery in New York. It discusses the origin of QPX, how it infects hard clams, where it has been found, signs of QPX disease, why people in New York should be concerned, and what is being done to control its spread.

Barnes, Debra; Allam, Bassem; Gall, Ken; Seagrant, New Y.

80

Microstructural design of hard coatings  

Microsoft Academic Search

Microstructural design has attracted increasing interest in modern development of hard coatings for wear-resistant applications. In plasma-assisted vapor deposited thin films, the material’s microstructure can be designed during growth or post-deposition annealing treatments. In this review, we demonstrate the correlation between microstructure and mechanical as well as tribological properties of hard ceramic coatings. This is done for single-phase coatings and

Paul H. Mayrhofer; Christian Mitterer; Lars Hultman; Helmut Clemens

2006-01-01

81

Place Value  

NSDL National Science Digital Library

These activites cover place value of ones, tens, hundreds and thousands. Please complete the games in order. You must finish each game before going on to the next one. Game #1: Dinosaur Numbers (place value) Game #2: Shark Numbers (place value) Game #3: Place Value Golf (harder) ...

Christian, Mrs.

2007-03-21

82

Capillary Adhesion Between Elastically Hard Rough Surfaces  

Microsoft Academic Search

The adhesion versus vapor pressure (p\\/p\\u000a s) trend between two elastically hard rough surfaces is modeled and compared with experimental results. The experimental samples\\u000a were hydrophilic surface-micromachined cantilevers, in which the nanometer-scale surface roughness is on the order of the\\u000a Kelvin radius. The experimental results indicated that adhesion increases exponentially from p\\/p\\u000a s=0.3 to 0.95, with values from 1 mJ\\/m2 to

M. P. de Boer

2007-01-01

83

The hard truth  

SciTech Connect

In the Bayesian methodology, the posterior probability combines uncertainty about prior knowledge, and available data about alternative models of reality. The posterior quantifies the degree of certainty one has in inferring the truth in terms of those models. We propose a method to determine the reliability of a specific feature of a Bayesian solution. Our approach is based on an analogy between the negative logarithm of the posterior and a physical potential. This analogy leads to the interpretation of gradient of this potential as a force that acts on the model. As model parameters are perturbed from their maximum a posteriori (MAP) values, the strength of the restoring force that drives them back to the MAP solution is directly related to the reliability of those parameter estimates. The correlations between the uncertainties of parameter estimates can be elucidated.

Hanson, K.M.; Cunningham, C.S.

1994-12-31

84

Evaluation of mechanical properties of some glycine complexes  

NASA Astrophysics Data System (ADS)

The variation of Vickers hardness with load for (101) glycine zinc chloride (GZC), (001) glycine lithium sulphate (GLS), (001) triglycine sulphate (TGS) and (010) glycine phosphite (GPI) crystals was studied. From the cracks initiated along the corners of the indentation impression, crack lengths were measured and the fracture toughness value and brittle index number were determined. The hardness related parameters viz. yield strength and Young's modulus were also estimated. The anisotropic nature of the crystals was studied using Knoop indentation technique.

Nagaraju, D.; Raja Shekar, P. V.; Chandra, Ch. Sateesh; Rao, K. Kishan; Krishna, N. Gopi

2014-04-01

85

STUDY OF THE BEST MEASUREMENT CAPABILITY IN ROCKWELL SCALE AT THE BRAZILIAN NMI INMETROS PRIMARY HARDNESS STANDARD MACHINE  

Microsoft Academic Search

This paper shows the actual status of an on- going metrological research that aims an upgrade of the current Rockwell C hardness scales best measurement capability (BMC), e.g. 0.3 HRC, referred to the Primary Hardness Standard Machine installed at the Brazilian NMI INMETRO. This value complies with the ISO hardness standards and the GUM uncertainty guide as well as the

Jorge Trota Filho; Sérgio Pinheiro de Oliveira; Islei Domingues da Silva; Renato Reis Machado; Cláudio Afonso Koch

86

Correlation of Yield Strength and Tensile Strength with Hardness for Steels  

NASA Astrophysics Data System (ADS)

Hardness values as well as yield and tensile strength values were compiled for over 150 nonaustenitic, hypoeutectoid steels having a wide range of compositions and a variety of microstructures. The microstructures include ferrite, pearlite, martensite, bainite, and complex multiphase structures. The yield strength of the steels ranged from approximately 300 MPa to over 1700 MPa. Tensile strength varied over the range of 450-2350 MPa. Regression analysis was used to determine the correlation of the yield strength and the tensile strength to the diamond pyramid hardness values for these steels. Both the yield strength and tensile strength of the steels exhibited a linear correlation with the hardness over the entire range of strength values. Empirical relationships are provided that enable the estimation of strength from a bulk hardness measurement. A weak effect of strain-hardening potential on the hardness-yield strength relationship was also observed.

Pavlina, E. J.; van Tyne, C. J.

2008-12-01

87

Hard-on-Hard Total Hip Impingement Causes Extreme Contact Stress Concentrations  

PubMed Central

Background Impingement events, in addition to their role immediately proximate to frank dislocation, hold the potential to damage new-generation hard-on-hard bearings as a result of the relatively unforgiving nature of the materials and designs. Because of the higher stiffness and tighter design tolerances of metal-on-metal and ceramic implants, surgical positioning plausibly has become even more important. Questions/purposes We asked (1) whether, and under what cup orientation conditions, hard-on-hard impingements might challenge implant material failure strength; and (2) whether particle generation propensity at impingement and egress sites would show similar dependence on cup orientation. Methods Realistic computational simulations were enabled by multistage finite element analyses, addressing both global construct motion and loading, and focal stress concentrations at neck impingement and rim egress sites. The global model, validated by a cadaveric simulation in a servohydraulic hip simulator, included both hardware components and advanced anisotropic capsule characterization. Parametric computational runs explored the effect of cup orientation for both ceramic-on-ceramic and metal-on-metal bearing couples for two distinct motion sequences associated with dislocation. Results Stress concentrations from impingement increased nearly linearly with increased cup tilt and with cup anteversion. In some situations, peak values of stress approached or exceeded 1 GPa, levels challenging the yield strength of cobalt-chromium implants, and potentially the fracture strength of ceramics. The tendency for impingement events to generate debris, indexed in terms of a new scraping severity metric, showed orientation dependences similar to that for bulk material failure. Conclusions Damage propensity arising from impingement events in hard total hip bearings is highly orientation-dependent.

Elkins, Jacob M.; O'Brien, Megan K.; Stroud, Nicholas J.; Pedersen, Douglas R.; Callaghan, John J.

2010-01-01

88

Hardness of ion implanted ceramics  

SciTech Connect

It has been established that the wear behavior of ceramic materials can be modified through ion implantation. Studies have been done to characterize the effect of implantation on the structure and composition of ceramic surfaces. To understand how these changes affect the wear properties of the ceramic, other mechanical properties must be measured. To accomplish this, a commercially available ultra low load hardness tester has been used to characterize Al/sub 2/O/sub 3/ with different implanted species and doses. The hardness of the base material is compared with the highly damaged crystalline state as well as the amorphous material.

Oliver, W.C.; McHargue, C.J.; Farlow, G.C.; White, C.W.

1985-01-01

89

Depletion effects in smectic phases of hard-rod-hard-sphere mixtures  

NASA Astrophysics Data System (ADS)

It is known that when hard spheres are added to a pure system of hard rods the stability of the smectic phase may be greatly enhanced, and that this effect can be rationalised in terms of depletion forces. In the present paper we first study the effect of orientational order on depletion forces in this particular binary system, comparing our results with those obtained adopting the usual approximation of considering the rods parallel and their orientations frozen. We consider mixtures with rods of different aspect ratios and spheres of different diameters, and we treat them within Onsager theory. Our results indicate that depletion effects, and consequently smectic stability, decrease significantly as a result of orientational disorder in the smectic phase when compared with corresponding data based on the frozen-orientation approximation. These results are discussed in terms of the ? parameter, which has been proposed as a convenient measure of depletion strength. We present closed expressions for ?, and show that it is intimately connected with the depletion potential. We then analyse the effect of particle geometry by comparing results pertaining to systems of parallel rods of different shapes (spherocylinders, cylinders and parallelepipeds). We finally provide results based on the Zwanzig approximation of a fundamental-measure density-functional theory applied to mixtures of parallelepipeds and cubes of different sizes. In this case, we show that the ? parameter exhibits a linear asymptotic behaviour in the limit of large values of the hard-rod aspect ratio, in conformity with Onsager theory, as well as in the limit of large values of the ratio of rod breadth to cube side length, d, in contrast to Onsager approximation, which predicts ? ˜ d3. Based on both this result and the Percus-Yevick approximation for the direct correlation function for a hard-sphere binary mixture in the same limit of infinite asymmetry, we speculate that, for spherocylinders and spheres, the ? parameter should be of order unity as d tends to infinity.

Mart?nez-Ratón, Y.; Cinacchi, G.; Velasco, E.; Mederos, L.

2006-10-01

90

TESTING HARDNESS OF METAL ITEMS WITH MET-UD COMBINED PORTABLE HARDNESS TESTER  

Microsoft Academic Search

A new approach to portable hardness testers has been developed and introduced. It makes it possible to inspect hardness by one and the same hardness tester applying both, the ultrasonic contact impedance method and rebound method. Hardness tester wide possibilities which allow to inspect hardness of metal and alloy products with all standardized scales (Rockwell, Brinell, Vickers and Shore) have

Edward Aslanyan; Alexander Doynikov; Victor Pivovarov

91

EQUATION OF STATE OF THE HARD-SPHERE CRYSTAL  

Microsoft Academic Search

A new approach to the averaged two-particle distribution function of a crystalline phase is presented. It includes an indirect check of the merit of the Gaussian approximation for the local density and a new way to inferring values of the thermodynamic variables from simulation data. The equa- tion of state and the compressibility of the hard-sphere FCC crystal is computed

C. Rascon; L. Mederos; G. Navascues

92

Equation of state of the hard-sphere crystal  

Microsoft Academic Search

An approach to the averaged two-particle distribution function of a crystalline phase is presented. It includes an indirect check of the merit of the Gaussian approximation for the local density and a way to infer values of the thermodynamic variables from simulation data. The equation of state and the compressibility of the hard-sphere fcc crystal is computed from the Tarazona

C. Rascón; L. Mederos; G. Navascués

1996-01-01

93

Solar cell nanotechnology for improved efficiency and radiation hardness  

Microsoft Academic Search

Space electronic equipment, and NASA future exploration missions in particular, require improvements in solar cell efficiency and radiation hardness. Novel nano-engineered materials and quantum-dot array based photovoltaic devices promise to deliver more efficient, lightweight solar cells and arrays which will be of high value to long term space missions. In this paper, we describe issues related to the development of

Alexander I. Fedoseyev; Marek Turowski; Qinghui Shao; Alexander A. Balandin

2006-01-01

94

Hard Disk Integrity Check by Hashing with Combinatorial Group Testing  

Microsoft Academic Search

In this paper, we describe the problem of verifying the integrity of a hard disk especially for forensics investigation after the computer of a suspect has been seized. Existing solutions do not provide a satisfactory solution to solve the problem. They either require a huge amount of storage to store the hash values of the sectors or may not be

Junbin Fang; Zoe L. Jiang; S. M. Yiu; Lucas C. K. Hui

2009-01-01

95

Metrics for Hard Goods Merchandising.  

ERIC Educational Resources Information Center

Designed to meet the job-related metric measurement needs of students interested in hard goods merchandising, this instructional package is one of five for the marketing and distribution cluster, part of a set of 55 packages for metric instruction in different occupations. The package is intended for students who already know the occupational…

Cooper, Gloria S., Ed.; Magisos, Joel H., Ed.

96

Is Carbon Hard or Soft?  

NSDL National Science Digital Library

The representation shows differences in the arrangement of carbon atoms that make up diamonds and graphite. Through text and pictures, the resource describes the difference in arrangement of two different carbon allotropes. The text relates the differences in arrangements to differences in the hardness (properties) of the materials.

97

Playing the Numbers: Hard Choices  

ERIC Educational Resources Information Center

Stateline.org recently called this recession the worst in 50 years for state budgets. As has been the case in past economic downturns, higher education looks to be particularly hard hit. Funds from the American Recovery and Relief Act may have postponed some of the difficulty for many colleges and universities, but the outlook for public higher…

Doyle, William R.

2009-01-01

98

Measuring the Hardness of Softballs  

Microsoft Academic Search

The following describes a method that may be used to measure the hardness and elasticity of balls with application to softballs. While standardized test methods currently exist to measure these properties, they do not represent the ball deformation rate and magnitude that occurs in play. The method described herein involves impacting a fixed solid cylinder (matched to the diameter of

Lloyd V. Smith

99

Ejs Hard Disk Collision Model  

NSDL National Science Digital Library

The Ejs Hard Disk Collision model displays a two-dimensional collision between two hard disks. The two disks have the same mass and only one mass is moving at the beginning of the simulation. The impact of the collision is offset by the impact parameter, b, which can be changed. The center-of-mass of the two masses is also shown. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Hard Disk Collision model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_newton_HardDiskCollision.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2008-07-06

100

A hard case for modeling  

Microsoft Academic Search

What happens to a human head when it is hit in an accident or by a weapon, or subjected to the violence of an emergency ejection from a combat plane? This question is something that interests QinetiQ, part of the former UK Defence Evaluation and Research Agency (DERA). Controlled experimentation on live subjects is hardly an option, but computer modeling

George Marsh

2002-01-01

101

Degree of conversion and hardness of an orthodontic resin cured with a light-emitting diode and a quartz-tungsten-halogen light.  

PubMed

The purpose of this study was to assess the influence of two light units, a quartz-tungsten-halogen (QTH) and a light-emitting diode (LED), on the hardness and degree of conversion of an orthodontic composite resin. Sixty specimen disks were prepared from Transbond XT composite resin (3M Unitek) and light cured for 10, 20, and 30 seconds with a QTH (Curing Light XL 3000, 3M Unitek) or a LED (Ortholux, 3M Unitek) light-curing unit for 5, 10, and 15 seconds. Composite resin polymerization was evaluated by Fourier-transform infrared (FTIR) spectrophotometry and Knoop hardness number (KHN). The results were statistically analysed using analysis of variance and Tukey's multiple comparisons test (alpha = 0.05). The highest KHN was obtained with the QTH at 30 (25.19 KHN) and 20 (24.01) seconds, which did not differ statistically, and in the LED 15 second (21.86) group. The QTH 10 second group (20.53) did not differ statistically from the QTH 20 second or the LED 5 (19.96) and 15, or 10 second (18.95) groups. According to FTIR, there was no statistical difference for the degree of conversion among the groups, QTH 10 (43.42 per cent), QTH 20 (46.12 per cent), QTH 30 (45.30 per cent), LED 10 (47.02 per cent), or LED 15 (47.24 per cent) seconds. The lowest degree of conversion was obtained for the LED 5 second group (38.97 per cent), which did not differ statistically from the QTH 10 second group. Light curing with the LED resulted in a reduction of 50 per cent in the time recommended for use of the QTH light with the composite resin, Transbond XT. PMID:19726490

Cerveira, Guilherme Pessôa; Berthold, Telmo Bandeira; Souto, André A; Spohr, Ana Maria; Marchioro, Ernani Menezes

2010-02-01

102

Exclusive, hard diffraction in QCD  

NASA Astrophysics Data System (ADS)

In the first chapter we give an introduction to hard diffractive scattering in QCD to introduce basic concepts and terminology, thus setting the stage for the following chapters. In the second chapter we make predictions for nondiagonal parton distributions in a proton in the LLA. We calculate the DGLAP-type evolution kernels in the LLA, solve the nondiagonal GLAP evolution equations with a modified version of the CTEQ-package and comment on the range of applicability of the LLA in the asymmetric regime. We show that the nondiagonal gluon distribution g(x1,x2,t,?2) can be well approximated at small x by the conventional gluon density xG(x,?2). In the third chapter, we discuss the algorithms used in the LO evolution program for nondiagonal parton distributions in the DGLAP region and discuss the stability of the code. Furthermore, we demonstrate that we can reproduce the case of the LO diagonal evolution within less than 0.5% of the original code as developed by the CTEQ-collaboration. In chapter 4, we show that factorization holds for the deeply virtual Compton scattering amplitude in QCD, up to power suppressed terms, to all orders in perturbation theory. Furthermore, we show that the virtuality of the produced photon does not influence the general theorem. In chapter 5, we demonstrate that perturbative QCD allows one to calculate the absolute cross section of diffractive exclusive production of photons at large Q2 at HERA, while the aligned jet model allows one to estimate the cross section for intermediate Q2~2GeV2. Furthermore, we find that the imaginary part of the amplitude for the production of real photons is larger than the imaginary part of the corresponding DIS amplitude, leading to predictions of a significant counting rate for the current generation of experiments at HERA. We also find a large azimuthal angle asymmetry in ep scattering for HERA kinematics which allows one to directly measure the real part of the DVCS amplitude and hence the nondiagonal parton distributions. In the last chapter, we propose a new methodology of gaining shape fits to nondiagonal parton distributions and, for the first time, to determine the ratio ? of the real to imaginary part of the DIS amplitude. We do this by using several recent fits to F2(x,Q2) to compute the asymmetry A for the combined DVCS and Bethe- Heitler cross section. The asymmetry A, isolates the interference term of DVCS and Bethe-Heitler in the total cross section, in other words, by isolating the real part of the DVCS amplitude through this asymmetry one has access to the nondiagonal parton distributions for the first time. Comparing the predictions for A against experiment would allow one to make a prediction of the shape, though not absolute value, of nondiagonal parton distributions. In the appendix, to illustrate an application of distributional methods as discussed in chapter 4, we will show, with the aid of simple examples, how to make simple estimates of the sizes of higher-order Feynman graphs. Our methods enable appropriate values of renormalization and factorization scales to be made. They allow the diagnosis of the source of unusually large corrections that are in need of resummation.

Freund, Andreas

103

Comparison of time-dependent changes in the surface hardness of different composite resins  

PubMed Central

Objective: The aim of this study was to evaluate the change in surface hardness of silorane-based composite resin (Filtek Silorane) in time and compare the results with the surface hardness of two methacrylate-based resins (Filtek Supreme and Majesty Posterior). Materials and Methods: From each composite material, 18 wheel-shaped samples (5-mm diameter and 2-mm depth) were prepared. Top and bottom surface hardness of these samples was measured using a Vicker's hardness tester. The samples were then stored at 37°C and 100% humidity. After 24 h and 7, 30 and 90 days, the top and bottom surface hardness of the samples was measured. In each measurement, the rate between the hardness of the top and bottom surfaces were recorded as the hardness rate. Statistical analysis was performed by one-way analysis of variance, multiple comparisons by Tukey's test and binary comparisons by t-test with a significance level of P = 0.05. Results: The highest hardness values were obtained from each two surfaces of Majesty Posterior and the lowest from Filtek Silorane. Both the top and bottom surface hardness of the methacrylate based composite resins was high and there was a statistically significant difference between the top and bottom hardness values of only the silorane-based composite, Filtek Silorane (P < 0.05). The lowest was obtained with Filtek Silorane. The hardness values of all test groups increased after 24 h (P < 0.05). Conclusion: Although silorane-based composite resin Filtek Silorane showed adequate hardness ratio, the use of incremental technic during application is more important than methacrylate based composites.

Ozcan, Suat; Yikilgan, Ihsan; Uctasli, Mine Betul; Bala, Oya; Kurklu, Zeliha Gonca Bek

2013-01-01

104

PLACE VALUE  

NSDL National Science Digital Library

DESK Standard: Identify the place and value of a given digit in a five-digit numeral, including decimals to the tenths. . DATES: You can begin this activity on October 2. You should complete it by October 6. OBJECTIVE: We have been studying place value skills this year, and now you have a chance to review what you have learned. You will visit a variety of fun Web sites ...

Hughes, Mr.

2006-03-09

105

Transpecific microsatellites for hard pines.  

PubMed

Microsatellites are difficult to recover from large plant genomes so cross-specific utilisation is an important source of markers. Fifty microsatellites were tested for cross-specific amplification and polymorphism to two New World hard pine species, slash pine ( Pinus elliottii var. elliottii) and Caribbean pine ( P. caribaea var. hondurensis). Twenty-nine (58%) markers amplified in both hard pine species, and 23 of these 29 were polymorphic. Soft pine (subgenus Strobus) microsatellite markers did amplify, but none were polymorphic. Pinus elliottii var. elliottii and P. caribaea var. hondurensis showed mutational changes in the flanking regions and the repeat motif that were informative for Pinus spp. phylogenetic relationships. Most allele length variation could be attributed to variability in repeat unit number. There was no evidence for ascertainment bias. PMID:12582642

Shepherd, M.; Cross, M.; Maguire, L.; Dieters, J.; Williams, G.; Henry, J.

2002-04-01

106

Ultrasonic material hardness depth measurement  

DOEpatents

The invention is an ultrasonic surface hardness depth measurement apparatus and method permitting rapid determination of hardness depth of shafts, rods, tubes and other cylindrical parts. The apparatus of the invention has a part handler, sensor, ultrasonic electronics component, computer, computer instruction sets, and may include a display screen. The part handler has a vessel filled with a couplant, and a part rotator for rotating a cylindrical metal part with respect to the sensor. The part handler further has a surface follower upon which the sensor is mounted, thereby maintaining a constant distance between the sensor and the exterior surface of the cylindrical metal part. The sensor is mounted so that a front surface of the sensor is within the vessel with couplant between the front surface of the sensor and the part. 12 figs.

Good, M.S.; Schuster, G.J.; Skorpik, J.R.

1997-07-08

107

Ultrasonic material hardness depth measurement  

DOEpatents

The invention is an ultrasonic surface hardness depth measurement apparatus and method permitting rapid determination of hardness depth of shafts, rods, tubes and other cylindrical parts. The apparatus of the invention has a part handler, sensor, ultrasonic electronics component, computer, computer instruction sets, and may include a display screen. The part handler has a vessel filled with a couplant, and a part rotator for rotating a cylindrical metal part with respect to the sensor. The part handler further has a surface follower upon which the sensor is mounted, thereby maintaining a constant distance between the sensor and the exterior surface of the cylindrical metal part. The sensor is mounted so that a front surface of the sensor is within the vessel with couplant between the front surface of the sensor and the part.

Good, Morris S. (Richland, WA); Schuster, George J. (Kennewick, WA); Skorpik, James R. (Kennewick, WA)

1997-01-01

108

Hard Disk PVT System Model  

NSDL National Science Digital Library

The Hard Disk PVT System simulates a two-dimensional system of particles confined between a thermal reservoir and a piston. This computer model is designed to study the equation of state for hard disks without other interactions. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. Users can set the initial particle energy, the initial particle separation, and the thermal reservoir temperature Tr. The thermal conductivity parameter ? determines the probability that a collision with the thermal wall will affect (thermalize) the colliding particle. If the conductivity is one, the particle velocity after a reservoir collision is set according to Maxwell-Boltzmann statistics. If the conductivity is zero, all reservoir collisions are elastic and the internal energy E of the system is conserved.   Particles in this model have unit mass and interact through contact forces. Collision times are computed analytically because particles and pistons move with constant velocity between collisions. The time evolution algorithm advances the particle and piston positions from collision to collision until the requested time step ?t is achieved. The time evolution is then paused, data is accumulated, and the screen is redrawn. The Hard Disk PVT model is a supplemental simulation for the article "Pressure Oscillations in Adiabatic Compression" by Roland Stout in The Physics Teacher 49(5), 280-281 (2011) and has been approved by the author and The Physics Teacher editor. The model was developed using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_hd_HardDiskPVTSystem.jar file will run the program if Java is installed.

Christian, Wolfgang

2011-03-12

109

Microwave assisted hard rock cutting  

DOEpatents

An apparatus for the sequential fracturing and cutting of subsurface volume of hard rock (102) in the strata (101) of a mining environment (100) by subjecting the volume of rock to a beam (25) of microwave energy to fracture the subsurface volume of rock by differential expansion; and , then bringing the cutting edge (52) of a piece of conventional mining machinery (50) into contact with the fractured rock (102).

Lindroth, David P. (Apple Valley, MN); Morrell, Roger J. (Bloomington, MN); Blair, James R. (Inver Grove Heights, MN)

1991-01-01

110

Charpy Impact Energy and Microindentation Hardness of 60-NITINOL  

NASA Technical Reports Server (NTRS)

60-NITINOL (60 wt.% Ni 40 wt.% Ti) is being studied as a material for advanced aerospace components. The Charpy impact energy and microindentation hardness has been studied for this material, fabricated by vacuum induction skull melting (casting) and by hot isostatic pressing. Test specimens were prepared in various hardened and annealed heat treatment conditions. The average impact energy ranged from 0.33 to 0.49J for the hardened specimens while the annealed specimens had impact energies ranging from 0.89 to 1.18J. The average hardness values of the hardened specimens ranged from 590 to 676 HV while that of the annealed specimens ranged from 298 to 366 HV, suggesting an inverse relationship between impact energy and hardness. These results are expected to provide guidance in the selection of heat treatment processes for the design of mechanical components.

Stanford, Malcolm K.

2012-01-01

111

UMass at TREC 2003: HARD and QA.  

National Technical Information Service (NTIS)

The Center for Intelligent Information Retrieval (CIIR) at UMass Amherst participated in two tracks for TREC 2003: High Accuracy Retrieval from Documents (HARD) and Question Answering (QA). In the HARD track, we developed document metadata to correspond t...

A. Corrada-Emmanuel C. Wade N. AbdulJaleel Q. Li X. Liu

2003-01-01

112

Parameterized Complexity of k-Anonymity: Hardness and Tractability  

NASA Astrophysics Data System (ADS)

The problem of publishing personal data without giving up privacy is becoming increasingly important. A precise formalization that has been recently proposed is the k-anonymity, where the rows of a table are partitioned in clusters of size at least k and all rows in a cluster become the same tuple after the suppression of some entries. The natural optimization problem, where the goal is to minimize the number of suppressed entries, is hard even when the stored values are over a binary alphabet or the table consists of a bounded number of columns. In this paper we study how the complexity of the problem is influenced by different parameters. First we show that the problem is W[1]-hard when parameterized by the value of the solution (and k). Then we exhibit a fixed-parameter algorithm when the problem is parameterized by the number of columns and the number of different values in any column.

Bonizzoni, Paola; Della Vedova, Gianluca; Dondi, Riccardo; Pirola, Yuri

113

Hardness of FeB4: density functional theory investigation.  

PubMed

A recent experimental study reported the successful synthesis of an orthorhombic FeB4 with a high hardness of 62(5) GPa [H. Gou et al., Phys. Rev. Lett. 111, 157002 (2013)], which has reignited extensive interests on whether transition-metal borides compounds will become superhard materials. However, it is contradicted with some theoretical studies suggesting transition-metal boron compounds are unlikely to become superhard materials. Here, we examined structural and electronic properties of FeB4 using density functional theory. The electronic calculations show the good metallicity and covalent Fe-B bonding. Meanwhile, we extensively investigated stress-strain relations of FeB4 under various tensile and shear loading directions. The calculated weakest tensile and shear stresses are 40 GPa and 25 GPa, respectively. Further simulations (e.g., electron localization function and bond length along the weakest loading direction) on FeB4 show the weak Fe-B bonding is responsible for this low hardness. Moreover, these results are consistent with the value of Vickers hardness (11.7-32.3 GPa) by employing different empirical hardness models and below the superhardness threshold of 40 GPa. Our current results suggest FeB4 is a hard material and unlikely to become superhard (>40 GPa). PMID:24811644

Zhang, Miao; Lu, Mingchun; Du, Yonghui; Gao, Lili; Lu, Cheng; Liu, Hanyu

2014-05-01

114

Hardness of FeB4: Density functional theory investigation  

NASA Astrophysics Data System (ADS)

A recent experimental study reported the successful synthesis of an orthorhombic FeB4 with a high hardness of 62(5) GPa [H. Gou et al., Phys. Rev. Lett. 111, 157002 (2013)], which has reignited extensive interests on whether transition-metal borides compounds will become superhard materials. However, it is contradicted with some theoretical studies suggesting transition-metal boron compounds are unlikely to become superhard materials. Here, we examined structural and electronic properties of FeB4 using density functional theory. The electronic calculations show the good metallicity and covalent Fe-B bonding. Meanwhile, we extensively investigated stress-strain relations of FeB4 under various tensile and shear loading directions. The calculated weakest tensile and shear stresses are 40 GPa and 25 GPa, respectively. Further simulations (e.g., electron localization function and bond length along the weakest loading direction) on FeB4 show the weak Fe-B bonding is responsible for this low hardness. Moreover, these results are consistent with the value of Vickers hardness (11.7-32.3 GPa) by employing different empirical hardness models and below the superhardness threshold of 40 GPa. Our current results suggest FeB4 is a hard material and unlikely to become superhard (>40 GPa).

Zhang, Miao; Lu, Mingchun; Du, Yonghui; Gao, Lili; Lu, Cheng; Liu, Hanyu

2014-05-01

115

Artificially soft and hard surfaces in electromagnetics  

Microsoft Academic Search

A transversely corrugated surface as used in corrugated horn antennas represents a soft boundary. A hard boundary is made by using longitudinal corrugations filled with dielectric material. The concept of soft and hard surfaces is treated in detail, considering different geometries. It is shown that both the hard and soft boundaries have the advantage of a polarization-independent reflection coefficient for

Per-Simon Kildal

1990-01-01

116

Model of hard spheroplatelets near a hard wall  

NASA Astrophysics Data System (ADS)

A system of hard spheroplatelets near an impenetrable wall is studied in the low-density Onsager approximation. Spheroplatelets have optimal shape between rods and plates, and the direct transition from the isotropic to biaxial nematic phase is present. A simple local approximation for the one-particle distribution function is used. Analytical results for the surface tension and the entropy contributions are derived. The density and the order-parameter profiles near the wall are calculated. The preferred orientation of the short molecule axes is perpendicular to the wall. Biaxiality close to the wall can appear only if the phase is biaxial in the bulk.

Kapanowski, A.; Abram, M.

2014-06-01

117

Redeeming Value.  

ERIC Educational Resources Information Center

Presents an essay on organizational transformation and the way successful marketing transformations redeem a sense of value. Focuses on challenges faced by not-for-profit institutions, current changes in the library profession, and implications of the American Library Association's Goal 2000. A sidebar summarizes an interview with the director of…

Whitwell, Stuart C. A.

1995-01-01

118

Place Value  

NSDL National Science Digital Library

The answers to these FAQ from the Teacher2Teacher service at The Math Forum @ Drexel contain many suggestions for providing students with practice on using place value skills. They include ideas contributed by T2T Associates and teacher participants. There are links to Ask Dr. Math resources, children's literature connections, and outside websites with related resources.

Math Forum, Teacher2Teacher FAQ; The Math Forum @ Drexel

2000-01-01

119

The maximum hardness principle implies the hard/soft acid/base rule  

NASA Astrophysics Data System (ADS)

A recent paper [P. W. Ayers, J. Chem. Phys122, 141102 (2005)] considered the hard/soft acid/base exchange reaction, showing that the products associated with the hard/soft acid/base rule (in which the hard acid and hard base are bound, as are the soft acid and soft base) have lower energy than the alternative (in which the hard acid and soft base would have been bound and similarly the soft acid and hard base). Here we show that the maximum hardness principle also predicts this result. Unlike the previous derivation, we do not need to make any assumptions about the relative strength of the acids and bases.

Chattaraj, Pratim K.; Ayers, Paul W.

2005-08-01

120

Hardness analysis of cubic metal mononitrides from first principles  

NASA Astrophysics Data System (ADS)

Density functional theory calculations are performed to evaluate the hardness of various cubic metal nitrides: rocksalt TiN, VN, ZrN, NbN, AlN, and SiN; zincblende AlN and BN; and diamond C for comparison. The isotropic elastic stiffness constants cij, bulk modulus K, shear modulus G, Young's modulus E, and isotropic Poisson's ratio ?¯ are calculated. From simulated uniaxial stress-strain curves, ideal strength values ?max in the [100], [110], and [111] directions are also evaluated for all systems. In particular, rocksalt AlN is found to possess both high elastic moduli and ideal strength. These quantities are then compared for correlations with existing experimental Vicker's hardness data. The bulk modulus is found to be a poor indicator of hardness, while E, G, 1/?¯, and ?max all exhibit stronger correlations. With a view to circumvent the need to run computationally expensive relaxation steps, different methodologies for approximating uniaxial stress-strain curves are introduced. Utilizing the anisotropic Poisson's ratio to approximate the relaxed transverse lattice parameters at a given axial strain is a good approximation to stress-strain curves, and the ideal strengths obtained in this way exhibit strong correlations to experimental Vicker's hardness values.

Fulcher, B. D.; Cui, X. Y.; Delley, B.; Stampfl, C.

2012-05-01

121

Expected Value  

NSDL National Science Digital Library

In this activity, students will use the random integer command on their graphing calculators to simulate rolling a die. They will then use operations on lists to analyze the probability of rolling the first 1 on the 1st roll, 2nd roll, and so on and finally find the expected value. Teacher notes explain in detail how to perform these actions on the graphing calculator.

2008-10-17

122

Local hardness equalization: Exploiting the ambiguity  

NASA Astrophysics Data System (ADS)

In the density-functional theory of chemical reactivity, the local hardness is known to be an ambiguous concept. The mathematical structure associated with this problematic situation is elaborated and three common definitions for the local hardness are critically examined: the frontier local hardness [S. K. Ghosh, Chem. Phys. Lett. 172, 77 (1990)], the total local hardness [S. K. Ghosh and M. Berkowitz, J. Chem. Phys. 83, 2976 (1985)], and the unconstrained local hardness [P. W. Ayers and R. G. Parr, J. Am. Chem. Soc. 122, 2010 (2000)]. The frontier local hardness has particularly nice properties: (a) it has smaller norm than most, if not all, other choices of the local hardness and (b) it is ``unbiased'' in an information-theoretic sense. For the ground electronic state of a molecular system, the frontier local hardness is equal to the global hardness. For an electronic system in its ground state, both the chemical potential and the frontier local hardness are equalized. The frontier local hardness equalization principle provides a computational approach for designing reagents with desirable chemical reactivity profiles.

Ayers, Paul W.; Parr, Robert G.

2008-05-01

123

Making Nozzles From Hard Materials  

NASA Technical Reports Server (NTRS)

Proposed method of electrical-discharge machining (EDM) cuts hard materials like silicon carbide into smoothly contoured parts. Concept developed for fabrication of interior and exterior surfaces and internal cooling channels of convergent/divergent nozzles. EDM wire at skew angle theta creates hyperboloidal cavity in tube. Wire offset from axis of tube and from axis of rotation by distance equal to throat radius. Maintaining same skew angle as that used to cut hyperboloidal inner surface but using larger offset, cooling channel cut in material near inner hyperboloidal surface.

Wells, Dennis L.

1989-01-01

124

Hard and Soft Safety Verifications  

NASA Technical Reports Server (NTRS)

The purpose of this paper is to examine the differences between and the effects of hard and soft safety verifications. Initially, the terminology should be defined and clarified. A hard safety verification is datum which demonstrates how a safety control is enacted. An example of this is relief valve testing. A soft safety verification is something which is usually described as nice to have but it is not necessary to prove safe operation. An example of a soft verification is the loss of the Solid Rocket Booster (SRB) casings from Shuttle flight, STS-4. When the main parachutes failed, the casings impacted the water and sank. In the nose cap of the SRBs, video cameras recorded the release of the parachutes to determine safe operation and to provide information for potential anomaly resolution. Generally, examination of the casings and nozzles contributed to understanding of the newly developed boosters and their operation. Safety verification of SRB operation was demonstrated by examination for erosion or wear of the casings and nozzle. Loss of the SRBs and associated data did not delay the launch of the next Shuttle flight.

Wetherholt, Jon; Anderson, Brenda

2012-01-01

125

Are Short GRBs Really Hard?  

SciTech Connect

Thanks to the rapid position notice and response by HETE-2 and Swift, the X-ray afterglow emissions have been found for four recent short gamma-ray bursts (GRBs; GRB 050509b, GRB 050709, GRB 050724, and GRB 050813). The positions of three out of four short GRBs are coincident with galaxies with no current or recent star formation. This discovery tightens the case for a different origin for short and long GRBs. On the other hand, from the prompt emission point of view, a short GRB shows a harder spectrum comparing to that of the long duration GRBs according to the BATSE observations. We investigate the prompt emission properties of four short GRBs observed by Swift/BAT. We found that the hardness of all four BAT short GRBs is in between the BATSE range for short and long GRBs. We will discuss the spectral properties of short GRBs including the short GRB sample of Konus-Wind and HETE-2 to understand the hard nature of the BATSE short GRBs.

Sakamoto, T.; Cummings, J. [NASA Goddard Space Flight Center (United States); Barbier, L.; Barthelmy, S.; Gehrels, N.; Parsons, A.; Tueller, J.; Cline, T. [NASA Goddard Space Flight Center (United States); Fenimore, E.; Palmer, D. [Los Alamos National Laboratory (United States); Hullinger, D. [NASA Goddard Space Flight Center (United States); University of Maryland (United States); Krimm, H.; Markwardt, C. [NASA Goddard Space Flight Center (United States); Sato, G. [Institute of Space and Astronautical Science (United States); Aptekar, R.; Golenetskii, S.; Mazets, E.; Pal'shin, V. [Ioffe Physico-Technical Institute (Russian Federation); Ricker, G. [Massachusetts Institute of Technology (United States); Lamb, D. [University of Chicago (United States)] (and others)

2006-05-19

126

Estimation of Young's modulus and of hardness by ultra-low load hardness tests with a Vickers indenter  

SciTech Connect

The evaluation of the elastic-plastic properties of a material by using an ultra-low load hardness test requires a geometrical calibration that must take into account the imperfect form of the diamond indenter. In the present work, the Vickers indenter offset of the microindentation equipment was estimated using differently heat-treated steel samples. To this end, the dimensions of the indentations have been evaluated by two different methods: optical measurement of the diagonals and direct measurement of the penetration depth during the test. The elastic-plastic properties are then calculated from the analysis of the penetration depth/indentation load curves. The Young's modulus values determined for the different high-speed steel samples were very similar and close to the literature value for steel if the appropriate corrections are performed. The hardness values decrease when the determination procedure includes the geometrical correction of the indenter offset, and still further when using the total correction obtained by means of optical measurements of the indenter diagonal. Variation of the hardness values with the applied load is much less when the corrections are carried out.

Trindade, A.C. (Instituto Politecnico de Viseu (Portugal). Escola Superior de Tecnologia); Cavaleiro, A.; Fernandes, J.V. (Univ. de Coimbra (Portugal). Dept. de Engenharia Mecanica)

1994-07-01

127

The dilepton-production cross section in principal value resummation  

Microsoft Academic Search

Using a recent calculation of the perturbative hard part for dilepton production that sums large threshold corrections to all orders in perturbative QCD, we compute the corresponding cross sections. The hard part has been evaluated using principal value resummation and contains all singular momentum-dependent corrections. We also include a resummation of large Sudakov terms, which are independent of parton momenta.

Lyndon Alvero; Harry Contopanagos

1995-01-01

128

The hard hexagon partition function for complex fugacity  

NASA Astrophysics Data System (ADS)

We study the analyticity of the partition function of the hard hexagon model in the complex fugacity plane by computing zeros and transfer matrix eigenvalues for large finite size systems. We find that the partition function per site computed by Baxter in the thermodynamic limit for positive real values of the fugacity is not sufficient to describe the analyticity in the full complex fugacity plane. We also obtain a new algebraic equation for the low density partition function per site.

Assis, M.; Jacobsen, J. L.; Jensen, I.; Maillard, J.-M.; McCoy, B. M.

2013-11-01

129

Hard Wear-Resistant Coatings: A Review  

Microsoft Academic Search

\\u000a Hard coatings have been used for many decades to provide wear resistance. In this paper, the industrial requirements and benefits\\u000a of such hard coatings are introduced. Common hard coatings (nitrides, carbides, multi-components, etc.) and some of the new\\u000a generation coatings (multiple layers, multi-layers, gradient and nano-scaled) are reviewed and compared. Furthermore, typical\\u000a industrial applications and performances as well as common

T. Hoornaert; Z. K. Hua; J. H. Zhang

130

Kinetics of hardness evolution during annealing of gamma-irradiated polycarbonate  

SciTech Connect

This study focuses on the evolution in microhardness values that accompany isothermal annealing in gamma-irradiated polycarbonate (PC). Hardness increases with increasing annealing time, temperature, and gamma radiation dose. A model composed of a mixture of first and zero order structure relaxation is proposed to interpret the hardness data. The rate constant data fit the Arrhenius equation, and the corresponding activation energy decreases with increasing dose. The extent of structural relaxation that controls the hardness in post-annealed PC increases with increasing annealing temperature and dose. The model demonstrates that hardness evolution in PC is an endothermic process. By contrast, when the model is applied to irradiated poly(methyl methacrylate) and hydroxyethyl methacrylate copolymer, hardness evolution is an exothermic process.

Yeh, S. H.; Chen, P. Y.; Lee, Sanboh [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Harmon, Julie [Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250 (United States)

2012-12-01

131

Origin and diversity of North American hard spring wheats.  

PubMed

Genetic diversity is an important safeguard against crop vulnerability to biotic and abiotic stresses. Coefficient-of-parentage (COP) values of 248 North American hard spring wheat (Triticum aestivum L. em. Thell) cultivars released from 1901 to 1991 were used to estimate the genetic similarity of cultivars. COP values were used: to (1) quantify germ plasm sources and their contributions to the North American hard spring wheat gene pool; (2) measure changes in genetic diversity through time; and (3) identify major groupings of related cultivars. Landraces and local cultivars that contributed to the formation of the gene pool were: spring wheat (64%), winter wheat (16%), T. turgidum var. durum L. (10%), and T. turgidum var. emmer L. (8%). 'Fife', 'Hard Red Calcutta', and 'Turkey Red' accounted for 18%, 13%, and 8%, respectively, of the hard spring wheat origins. 'Era' and 'Butte' in the US, and 'Neepawa' and 'HY 320' in Canada, were the most commonly used named parents of cultivars released from 1981 to 1991. Both Canada and US had the greatest level of similarity among new cultivar releases in the 1930s (Canada: r=0.39, US: r=0.34). Genetic similarity in the US declined to r=0.14 in the 1940s and remained relatively constant thereafter. Similarity among released Canadian cultivars remained relatively high until the 1970s when the introduction of new market classes resulted in a 50% reduction in genetic similarity to approximately the same level of similarity found in the US. Cluster analysis was used to group cultivars released after 1941 into 13 clusters of similar genotypes. The cultivar clusters may have value for the stratified sampling of spring wheat germ plasm or in identifying diverse germ plasm for intermating. PMID:24162353

Mercado, L A; Souza, E; Kephart, K D

1996-09-01

132

Measurements of the hard-x-ray reflectivity of iridium  

SciTech Connect

In connection with the design of a hard-x-ray telescope for the Constellation X-Ray Observatory we measured the reflectivity of an iridium-coated zerodur substrate as a function of angle at 55, 60, 70, and 80 keV at the National Synchrotron Light Source of Brookhaven National Laboratory. The optical constants were derived from the reflectivity data. The real component of the index of refraction is in excellent agreement with theoretical values at all four energies. However, the imaginary component, which is related to the mass attenuation coefficient, is 50% to 70% larger at 55, 60, and 70 keV than theoretical values.

Romaine, S.; Bruni, R.; Gorenstein, P.; Zhong, Z

2007-01-10

133

Measurements of the hard-x-ray reflectivity of iridium.  

PubMed

In connection with the design of a hard-x-ray telescope for the Constellation X-Ray Observatory we measured the reflectivity of an iridium-coated zerodur substrate as a function of angle at 55, 60, 70, and 80 keV at the National Synchrotron Light Source of Brookhaven National Laboratory. The optical constants were derived from the reflectivity data. The real component of the index of refraction is in excellent agreement with theoretical values at all four energies. However, the imaginary component, which is related to the mass attenuation coefficient, is 50% to 70% larger at 55, 60, and 70 keV than theoretical values. PMID:17268563

Romaine, S; Bruni, R; Gorenstein, P; Zhong, Z

2007-01-10

134

Hardness-based flow stress for numerical simulation of hard machining AISI H13 tool steel  

Microsoft Academic Search

The phenomenological models for material flow stress and fracture typically used in the finite element simulations of hard machining processes do not adequately represent the constitutive behavior of the workpiece that is usually heat treated to hardness levels ranging from 50 to 62HRC. Thus, new flow stress models which include also the hardness effect should be developed and used accordingly

D. Umbrello; S. Rizzuti; J. C. Outeiro; R. Shivpuri; R. M'Saoubi

2008-01-01

135

Structure, preparation and properties of refractory compounds and systems (hard materials and hard metals)  

NASA Technical Reports Server (NTRS)

The hardness optimization of cemented carbides is discussed. TaC-based cermets, cermets with low nonmetal/metal ratios, and composites with hard phases formed by the decomposition of Ta carbon-nitrides are described. The optimization of WC hard alloys with a FeCoNi binder, and phase relations in nitride and nitride/metal systems are reported.

Holleck, H.; Thuemmier, F.

1983-01-01

136

Hard projectile penetration and trajectory stability  

Microsoft Academic Search

We present a general framework to describe the dynamics of a hard projectile penetrating into a solid target. Rigid body dynamics, differential area force law and semi-empirical resistance function are used to formulate the motion of the hard projectile. The proposed model is capable of predicting the projectile trajectory under various oblique and yaw angles. Critical conditions for the occurrences

Q. M. Li; E. A. Flores-Johnson

2011-01-01

137

Hybrid Approach for Detection of Hard Exudates  

Microsoft Academic Search

Diabetic Retinopathy is a severe and widely spread eye disease which can lead to blindness. Hence, early detection of Diabetic Retinopathy is a must. Hard Exudates are the primary sign of Diabetic Retinopathy. Early treatment of Diabetic Retinopathy is possible if we detect Hard Exudates at the earliest stage. The main concentration of this paper is to discuss techniques for

2013-01-01

138

Retraction of Hard, Lozano, and Tversky (2006)  

ERIC Educational Resources Information Center

Reports a retraction of "Hierarchical encoding of behavior: Translating perception into action" by Bridgette Martin Hard, Sandra C. Lozano and Barbara Tversky (Journal of Experimental Psychology: General, 2006[Nov], Vol 135[4], 588-608). All authors retract this article. Co-author Tversky and co-author Hard believe that the research results cannot…

Hard, B. M.; Lozano, S. C.; Tversky, B.

2008-01-01

139

ROCK HARDNESS: FIELD ASSESSMENT AND GEOMORPHIC IMPORTANCE  

Microsoft Academic Search

The precise correlations between rock hardness, resistance to erosion, and landform development have hitherto been difficult to establish. Rock hardness has proved difficult to assess, particularly in the field, because suitable equipment has not been applied. The Schmidt Test Hammer is demonstrated to be an effective instrument for this purpose. The hammer gives an accurate and rapid measure of surface

Michael J. Day

1980-01-01

140

Hard ormosils prepared with ultrasonic irradiation  

Microsoft Academic Search

Organically modified silicates (ormosils) of high hardness were prepared by the reaction of TEOS (tetraethoxysilane) and PDMS (polydimethylsiloxane) aided by ultrasonic irradiation, which was chosen as the method for concentration of the solutions. The mechanisms leading to the hard ormosil formation were examined by liquid state 29Si NMR spectroscopy. PDMS chains were found to be broken into shorter chains and\\/or

Takashi Iwamoto; John D. Mackenzie

1995-01-01

141

Radiation Hard Silicon Nanowire Field Effect Transistors  

Microsoft Academic Search

Silicon nanowire-based transistors were fabricated and tested for their radiation hardness by exposure to Co60 X-ray radiation at doses ranging from 50-250 kRad. Minor degradation of the transistor characteristics was observed at 250 kRad. Our results show the inherent radiation hardness of nanowire devices.

L. Tsakalakos; P. Losee; J. Balch; A. L. Bogorad; W. J. Taft; J. J. Likar; R. Herschitz

2008-01-01

142

Thermodynamic properties of polydisperse hard spheres  

Microsoft Academic Search

The virial expansion of a polydisperse system of hard spheres has been studied. The virial coefficients are shown to be a function of the total number density and the first three moments of the diameter distribution. The small number of moment variables identified is used to construct a simple but physically reasonable model of a polydisperse hard sphere crystal. Analytical

Paul Bartlett

1999-01-01

143

Numerical prediction of microstructure and hardness in multicycle simulations  

NASA Astrophysics Data System (ADS)

Thermal-microstructural predictions are made and compared to physical simulations of heat-affected zones in multipass and weaved welds. The microstructural prediction algorithm includes reaustenitization kinetics, grain growth, austenite decomposition kinetics, hardness, and tempering. Microstructural simulation of weaved welds requires that the algorithm include transient reaustenitization, austenite decomposition for arbitrary thermal cycles including during reheating, and tempering. Material properties for each of these phenomena are taken from the best available literature. The numerical predictions are compared with the results of physical simulations made at the Metals Technology Laboratory, CANMET, on a Gleeble 1500 simulator. Thermal histories used in the physical simulations included single-pass welds, isothermal tempering, two-cycle, and three-cycle welds. The two-and three-cycle welds include temper-bead and weaved-weld simulations. A recurring theme in the analysis is the significant variation found in the material properties for the same grade of steel. This affected all the material properties used including those governing reaustenitization, austenite grain growth, austenite decomposition, and hardness. Hardness measurements taken from the literature show a variation of ±5 to 30 HV on the same sample. Alloy differences within the allowable range also led to hardness variations of ±30 HV for the heat-affected zone of multipass welds. The predicted hardnesses agree extremely well with those taken from the physical simulations. Some differences due to problems with the austenite decomposition properties were noted in that bainite formation was predicted to occur somewhat more rapidly than was found experimentally. Reaustenitization values predicted during the rapid excursions to intercritical temperatures were also in good qualitative agreement with those measured experimentally.

Oddy, A. S.; McDill, J. M. J.

1996-06-01

144

Phase diagram of hard tetrahedra.  

PubMed

Advancements in the synthesis of faceted nanoparticles and colloids have spurred interest in the phase behavior of polyhedral shapes. Regular tetrahedra have attracted particular attention because they prefer local symmetries that are incompatible with periodicity. Two dense phases of regular tetrahedra have been reported recently. The densest known tetrahedron packing is achieved in a crystal of triangular bipyramids (dimers) with a packing density of 4000/4671 ? 85.63%. In simulation a dodecagonal quasicrystal is observed; its approximant, with periodic tiling (3.4.3(2).4), can be compressed to a packing fraction of 85.03%. Here, we show that the quasicrystal approximant is more stable than the dimer crystal for packing densities below 84% using Monte Carlo computer simulations and free energy calculations. To carry out the free energy calculations, we use a variation of the Frenkel-Ladd method for anisotropic shapes and thermodynamic integration. The enhanced stability of the approximant can be attributed to a network substructure, which maximizes the free volume (and hence the wiggle room) available to the particles and facilitates correlated motion of particles, which further contributes to entropy and leads to diffusion for packing densities below 65%. The existence of a solid-solid transition between structurally distinct phases not related by symmetry breaking--the approximant and the dimer crystal--is unusual for hard particle systems. PMID:22112060

Haji-Akbari, Amir; Engel, Michael; Glotzer, Sharon C

2011-11-21

145

Radiation Hardness of Trigger Electronics  

NASA Astrophysics Data System (ADS)

As the maximum intensity of particle accelerators increases, probing the most basic questions of the Universe, detectors and electronics must be designed to insure reliability in high-radiation environments. As the Large Hadron Collider (LHC) beam intensity is increased, it is necessary to upgrade the electronics in the Compact Muon Solenoid (CMS). To select interesting events, CMS utilizes fast electronics, which are installed in the experimental cavern. However, much higher post-upgrade levels of radiation in the cavern set tight requirements on the radiation hardness of the new electronics. Damaging effects of high and low energy radiation leads to disruption of digital circuits and accumulated degradation of silicon components. Quantifying the radiation exposure is required for the design of a radiation-tolerant system, but current simulation studies suffer from large uncertainties. We compare simulation predictions with measured performance in two different experimental studies, which evaluate component performance for pre and post irradiation determining the survivability of electronics in the harsh CMS environment.

Zawisza, Irene; Safonov, Alexei; Gilmore, Jason; Khotilovich, Vadim

2011-10-01

146

Penetration resistance of titanium and ultra-hard steel at elevated velocities  

Microsoft Academic Search

Hypervelocity penetration data are reported for two high strength materials of potential importance for the next generation of armored vehicles—titanium and ultra-hard steel. For titanium, it is found that the mass efficiency has not achieved its hydrodynamic limit at 2.57 km\\/s. The observed Rt values can be explained with a penetration model that takes shear cracks into account. For ultra-hard

S. J. Bless; W. Gooch; S. Satapathy; J. Campos; M. Lee

1997-01-01

147

Estimating the unconfined compressive strength of intact rocks from Equotip hardness  

Microsoft Academic Search

In order to utilize the Equotip hardness tester, originally developed in the field of metallic engineering, as an indirect\\u000a method to predict the unconfined compressive strength (UCS) of rock, laboratory tests were undertaken to establish the UCS,\\u000a Equotip hardness (L-value) and porosity of nine rock types. Using existing data from Verwaal and Mulder (Int J Rock Mech Min Sci Geomech

Hisashi Aoki; Yukinori Matsukura

2008-01-01

148

Influence of design variables on radiation hardness of silicon MINP solar cells  

NASA Technical Reports Server (NTRS)

Metal-insulator-N/P silicon (MINP) solar cells were fabricated using different substrate resistivity values, different N-layer designs, and different I-layer designs. A shallow junction into an 0.3 ohm-cm substrate gave best efficiency whereas a deeper junction into a 1 to 4 ohm-cm substrate gave improved radiation hardness. I-layer design variation did little to influence radiation hardness.

Anderson, W. A.; Solaun, S.; Rao, B. B.; Banerjee, S.

1985-01-01

149

Principal-value resummation for dilepton production  

SciTech Connect

We present a new method of resummation of QCD threshold distributions to the hard scattering function of the dilepton production cross section in hadron-hadron collisions. Our formulation by-passes the infrared singularities of the QCD running coupling through a principal value prescription, and does not require an explicit infrared cut-off. The resulting large corrections exponentiate, and we discuss asymptotic properties of the exponent. We present a closed analytical formula for the resummed hard part in momentum space, and give predictions, at fixed-target energies, for the resulting cross section which is a bounded function of its kinematic variables in the entire partonic phase space.

Contopanagos, H. [Argonne National Lab., IL (United States); Alvero, L.; Sterman, G. [State Univ. of New York, Stony Brook, NY (United States). Inst. for Theoretical Physics

1994-10-01

150

Analysis of Hard Thin Film Coating  

NASA Technical Reports Server (NTRS)

Marshall Space Flight Center (MSFC) is interested in developing hard thin film coating for bearings. The wearing of the bearing is an important problem for space flight engine. Hard thin film coating can drastically improve the surface of the bearing and improve the wear-endurance of the bearing. However, many fundamental problems in surface physics, plasma deposition, etc, need further research. The approach is using Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD) to deposit hard thin film on stainless steel bearing. The thin films in consideration include SiC, SiN and other materials. An ECRCVD deposition system is being assembled at MSFC.

Shen, Dashen

1998-01-01

151

Analysis of Hard Thin Film Coating  

NASA Technical Reports Server (NTRS)

MSFC is interested in developing hard thin film coating for bearings. The wearing of the bearing is an important problem for space flight engine. Hard thin film coating can drastically improve the surface of the bearing and improve the wear-endurance of the bearing. However, many fundamental problems in surface physics, plasma deposition, etc, need further research. The approach is using electron cyclotron resonance chemical vapor deposition (ECRCVD) to deposit hard thin film an stainless steel bearing. The thin films in consideration include SiC, SiN and other materials. An ECRCVD deposition system is being assembled at MSFC.

Shen, Dashen

1998-01-01

152

Interacting Boson Problems Can Be QMA Hard  

NASA Astrophysics Data System (ADS)

Computing the ground-state energy of interacting electron problems has recently been shown to be hard for quantum Merlin Arthur (QMA), a quantum analogue of the complexity class NP. Fermionic problems are usually hard, a phenomenon widely attributed to the so-called sign problem. The corresponding bosonic problems are, according to conventional wisdom, tractable. Here, we demonstrate that the complexity of interacting boson problems is also QMA hard. Moreover, the bosonic version of N-representability problem is QMA complete. Consequently, these problems are unlikely to have efficient quantum algorithms.

Wei, Tzu-Chieh; Mosca, Michele; Nayak, Ashwin

2010-01-01

153

Automated radiation hard ASIC design tool  

NASA Technical Reports Server (NTRS)

A commercial based, foundry independent, compiler design tool (ChipCrafter) with custom radiation hardened library cells is described. A unique analysis approach allows low hardness risk for Application Specific IC's (ASIC's). Accomplishments, radiation test results, and applications are described.

White, Mike; Bartholet, Bill; Baze, Mark

1993-01-01

154

A theoretical overview on single hard diffraction  

SciTech Connect

The concept of the Pomeron structure function and its application in Single Hard Diffraction at hadron colliders and in diffractive Deep Inelastic Scattering is critically reviewed. Some alternative approaches are briefly surveyed with a focus on QCD inspired models.

Wuesthoff, M.

1996-12-31

155

Extended Hardness Limit in Bulk Nanoceramics.  

National Technical Information Service (NTIS)

Mechanical strengthening by grain refinement is a method whereby a material's strength and hardness can be increased by decreasing the average crystallite grain size. The empirical Hall-Petch relationship mathematically describes grain boundary strengthen...

B. N. Feigelson C. T. Ellis E. P. Gorzkowski J. A. Wollmershauser R. Goswami

2014-01-01

156

Cemented Alloy Carbides for Hard Rock Boring.  

National Technical Information Service (NTIS)

The report presents the results of work in progress to determine whether newly developed ordered alloy carbides can provide significant improvements in the performance of cutting tool materials used in the hard rock boring industry. The effort during the ...

J. A. S. Green J. D. Venables R. K. Viswanadham W. Precht

1976-01-01

157

Analytic studies of the hard dumbell fluid  

NASA Astrophysics Data System (ADS)

A closed form analytic theory for the structure of the hard dumbell fluid is introduced and evaluated. It is found to be comparable in accuracy to the reference interaction site approximation (RISA) of Chandler and Andersen.

Morriss, G. P.; Cummings, P. T.

158

Hard Rock Cutting with Abrasion Jet.  

National Technical Information Service (NTIS)

The usefulness of high-pressure waterjets in cutting hard materials such as concrete, rock, and minerals was significantly improved by entraining selective abrasives into the waterjet. In fact, good entrainment of abrasives into the waterjet was found to ...

G. G. Yie

1983-01-01

159

Intercomparison Study of Rockwell Hardness Test Blocks.  

National Technical Information Service (NTIS)

The National Institute of Standards and Technology undertook an intercomparison study of Rockwell hardness test blocks marketed in the United States. Test blocks from six different manufacturers were included in the study. Measurements were made generally...

T. R. Shives, J. H. Smith

1991-01-01

160

Capability in Rockwell C Scale Hardness.  

National Technical Information Service (NTIS)

A measurement system is capable if it produces measurements with uncertainties small enough for demonstration of compliance with product specifications. To establish the capability of a system for Rockwell C scale hardness, one must assess measurement unc...

W. S. Liggett, S. R. Low, D. J. Pitchure, J. Song

2000-01-01

161

Modeling of the flow stress for AISI H13 Tool Steel during Hard Machining Processes  

SciTech Connect

In general, the flow stress models used in computer simulation of machining processes are a function of effective strain, effective strain rate and temperature developed during the cutting process. However, these models do not adequately describe the material behavior in hard machining, where a range of material hardness between 45 and 60 HRC are used. Thus, depending on the specific material hardness different material models must be used in modeling the cutting process. This paper describes the development of a hardness-based flow stress and fracture models for the AISI H13 tool steel, which can be applied for range of material hardness mentioned above. These models were implemented in a non-isothermal viscoplastic numerical model to simulate the machining process for AISI H13 with various hardness values and applying different cutting regime parameters. Predicted results are validated by comparing them with experimental results found in the literature. They are found to predict reasonably well the cutting forces as well as the change in chip morphology from continuous to segmented chip as the material hardness change.

Umbrello, Domenico; Rizzuti, Stefania [Department of Mechanical Engineering, University of Calabria 87036 Rende (Italy); Outeiro, Jose C. [Portuguese Catholic University, 3080-024 Figueira da Foz (Portugal); Shivpuri, Rajiv [Industrial, Welding and Systems Engineering - Ohio State University 43210 Columbus (United States)

2007-04-07

162

Modeling of the flow stress for AISI H13 Tool Steel during Hard Machining Processes  

NASA Astrophysics Data System (ADS)

In general, the flow stress models used in computer simulation of machining processes are a function of effective strain, effective strain rate and temperature developed during the cutting process. However, these models do not adequately describe the material behavior in hard machining, where a range of material hardness between 45 and 60 HRC are used. Thus, depending on the specific material hardness different material models must be used in modeling the cutting process. This paper describes the development of a hardness-based flow stress and fracture models for the AISI H13 tool steel, which can be applied for range of material hardness mentioned above. These models were implemented in a non-isothermal viscoplastic numerical model to simulate the machining process for AISI H13 with various hardness values and applying different cutting regime parameters. Predicted results are validated by comparing them with experimental results found in the literature. They are found to predict reasonably well the cutting forces as well as the change in chip morphology from continuous to segmented chip as the material hardness change.

Umbrello, Domenico; Rizzuti, Stefania; Outeiro, José C.; Shivpuri, Rajiv

2007-04-01

163

Correlation between Fe–V–C alloys surface hardness and plasma temperature via LIBS technique  

NASA Astrophysics Data System (ADS)

Surface hardness is a very important characteristic of metals. Its monitoring plays a key role in industry. In the present paper, using laser induced breakdown spectroscopy (LIBS), Fe–V18%–C1% alloys with different heat treatments have been used for making the correlation between surface hardness and laser-induced plasma temperatures. All investigated samples were characterized by the same ferrite phase with different Vickers surface hardnesses. The differences in hardness values were attributed to the crystallite size changes. A linear relationship has been obtained between the Vickers surface hardness and the laser induced plasma temperature. For comparison the relation between surface hardness and the ratio of the vanadium ionic to atomic spectral lines intensities (VII/VI) provided good linear results too. However, adopting the proposed approach of using the plasma temperature, instead, is more reliable in view of the difficulties that could be encountered in choosing the proper ionic and atomic spectral lines. To validate this approach we have investigated the shock wave speed induced by laser interaction with the used samples. It was found that harder is the material faster is the shock wave. The determination of the surface hardness via measuring Te shows the feasibility of using LIBS as an easy and reliable method for in situ industrial application for production control.

Messaoud Aberkane, S.; Bendib, A.; Yahiaoui, K.; Boudjemai, S.; Abdelli-Messaci, S.; Kerdja, T.; Amara, S. E.; Harith, M. A.

2014-05-01

164

Hard Gamma Ray Emission from the Starburst Galaxy NGC 253  

NASA Technical Reports Server (NTRS)

We have completed the study to search for hard gamma ray emission from the starburst galaxy NGC 253. Since supernovae are thought to provide the hard gamma ray emission from the Milky Way, starburst galaxies, with their extraordinarily high supernova rates, are prime targets to search for hard gamma ray emission. We conducted a careful search for hard gamma ray emission from NGC 253 using the archival data from the EGRET experiment aboard the CGRO. Because this starburst galaxy happens to lie near the South Galactic Pole, the Galactic gamma ray background is minimal. We found no significant hard gamma ray signal toward NGC 253, although a marginal signal of about 1.5 sigma was found. Because of the low Galactic background, we obtained a very sensitive upper limit to the emission of greater than 100 MeV gamma-rays of 8 x 10(exp -8) photons/sq cm s. Since we expected to detect hard gamma ray emission, we investigated the theory of gamma ray production in a dense molecular medium. We used a leaky-box model to simulate diffusive transport in a starburst region. Since starburst galaxies have high infrared radiation fields, we included the effects of self-Compton scattering, which are usually ignored. By modelling the expected gamma-ray and synchrotron spectra from NGC 253, we find that roughly 5 - 15% of the energy from supernovae is transferred to cosmic rays in the starburst. This result is consistent with supernova acceleration models, and is somewhat larger than the value derived for the Galaxy (3 - 10%). Our calculations match the EGRET and radio data very well with a supernova rate of 0.08/ yr, a magnetic field B approx. greater than 5 x 10(exp -5) G, a density n approx. less than 100/sq cm, a photon density U(sub ph) approx. 200 eV/sq cm, and an escape time scale tau(sub 0) approx. less than 10 Myr. The models also suggest that NGC 253 should be detectable with only a factor of 2 - 3 improvement in sensitivity. Our results are consistent with the standard picture of gamma-ray acceleration by supernovae.

Jackson, James M.; Marscher, Alan M.

1996-01-01

165

Hard MeV-GeV spectra of blazars  

NASA Astrophysics Data System (ADS)

Aims: Very high energy (VHE) gamma-ray emission from a distant source (z ? 0.2) can be efficiently absorbed by means of the electron-positron pair creation process. Analyses of the unabsorbed spectra imply that the intrinsic TeV emission of some blazars is hard, with spectral indices of 0.5 < ? < 1. The absorption depends on the level of extragalactic background light (EBL) that is difficult to measure directly. This implies that it is difficult to estimate the slope of the intrinsic TeV emission. To test our blazar emission scenario that is capable of reproducing the hard spectra, we therefore used the observations made by the Fermi Gamma-ray Space Telescope in the unabsorbed MeV-GeV energy range. Methods: We assume that the X-ray and gamma-ray emission of TeV blazars is produced in a compact region of a jet uniformly filled by particles of relatively high energy (? ? 103, E = ?mec2). In other words, we assume a low energy cut-off in the particle energy distribution. The emission produced by the particles with this energy spectrum can explain hard intrinsic spectra in the energy range from MeV up to TeV. We demonstrate how to estimate the basic physical parameters of a source in this case and how to explain the observed spectra by a precise simulation of the particle energy evolution. Results: To test our estimation methods, we use the observations of two blazars with exceptionally hard spectral indices (? ? 0.5) in the MeV - GeV range and known redshifts: RGB J0710+591 and 1ES 0502+675. The estimated values of the Doppler factor and magnetic field are compared with our numerical simulations, which confirm that the particle energy distribution with a low energy cut-off can explain the observed hard spectra well. In addition, we demonstrate that the radiative cooling caused by the inverse-Compton emission in the Klein-Nishina regime may help us to explain the hard spectra.

Katarzy?ski, K.

2012-01-01

166

Communities on Deep-Sea Hard Bottoms  

Microsoft Academic Search

\\u000a Although most of the deep-sea floor is blanketed with a thick layer of soft sediment, surprising amounts of hard bottom are\\u000a available for community development, and specialized organisms and communities exploit these hard surfaces. The habitats include\\u000a rock outcroppings on continental slopes, seamounts and island slopes; ferromanganese nodules and crusts; volcanic basalts\\u000a and glasses associated with volcanoes and spreading centers;

Craig M. Young

167

Hard and flexible optical printed circuit board  

Microsoft Academic Search

We report on the design and fabrication of hard and flexible optical printed circuit boards (O-PCBs). The objective is to realize generic and application-specific O-PCBs, either in hard form or flexible form, that are compact, light-weight, low-energy, high-speed, intelligent, and environmentally friendly, for low-cost and high-volume universal applications. The O-PCBs consist of 2-dimensional planar arrays of micro\\/nano-scale optical wires, circuits

El-Hang Lee; Hyun Sik Lee; S. G. Lee; B. H. O; S. G. Park; K. H. Kim

2007-01-01

168

Laser Ablatin of Dental Hard Tissue  

SciTech Connect

This paper discusses ablation of dental hard tissue using pulsed lasers. It focuses particularly on the relevant tissue and laser parameters and some of the basic ablation processes that are likely to occur. The importance of interstitial water and its phase transitions is discussed in some detail along with the ablation processes that may or may not directly involve water. The interplay between tissue parameters and laser parameters in the outcome of the removal of dental hard tissue is discussed in detail.

Seka, W.; Rechmann, P.; Featherstone, J.D.B.; Fried, D.

2007-07-31

169

A Novel Approach to Hardness Testing  

NASA Technical Reports Server (NTRS)

This paper gives a description of the application of a simple rebound time measuring device and relates the determination of relative hardness of a variety of common engineering metals. A relation between rebound time and hardness will be sought. The effect of geometry and surface condition will also be discussed in order to acquaint the student with the problems associated with this type of method.

Spiegel, F. Xavier; West, Harvey A.

1996-01-01

170

Investigation Of Tool Wear In Hard Turning Using Taguchi Method  

NASA Astrophysics Data System (ADS)

Hard turning is a machining process defined of hardness higher than 45 HRC under appropriate cutting tools and cutting speed. The objective of this paper is to investigate the optimum process parameters for a particular work piece-tool material combination. . In this study, three levels of each parameters viz. Hardness (HRC), Speed(mm/min), Feed(mm/rev) and three different tool materials are evaluated for process quality characteristics such as tool wear. The three different tool materials used are High CBN, Low CBN, Mixed ceramic. AISI H 11 was taken as work piece material. The experiment is designed using Taguchi Method. The results obtained from the experiments are transformed into signal to noise (S/N) ratio and used to optimize the value of tool wear. The analysis of variance (ANOVA) is performed to indentify the statistical significance of parameters. The final results of experimental investigation are presented in this paper. The conclusions arrived at are critically discussed at the end.

Chaudhari, Y. D.

2013-03-01

171

Future Hard Disk Storage: Limits & Potential Solutions  

NASA Astrophysics Data System (ADS)

For several years the hard disk drive technology pace has raced along at 60-100products this year and laboratory demonstrations approaching what has been estimated as a physical thermal stability limit of around 40 Gbit/in2. For sometime now the data storage industry has recogniz d that doing business as usually will not be viable for long and so both incremental evolutionary and revolutionary technologies are being explored. While new recording head materials or thermal recording techniques may allow higher coercivity materials to be recorded upon, and while high sensitivity spin transport transducer technology may provide sufficient signals to extend beyond the 100 Gigabit/in2 regime, conventional isotropic longitudinal media will show large data retention problems at less than 1/2 of this value. We have recently developed a simple model which indicates that while thermal instability issues may appear at different areal densities, they are non-discriminatory as to the magnetic recording modality: longitudinal, perpendicular, magnetooptic, near field, etc. The model indicates that a strong orientation of the media tends to abate the onset of the thermal limit. Hence, for the past few years we have taken an approach of controlled growth of the microstructure of thin film media. This knowledge has lead us to believe that epitaxial growth of multiple thin film layers on single crystalline Si may provide a pathway to nearly perfect crystallites of various, highly oriented, thin film textures. Here we provide an overview of the recording system media challenges, which are useful for the development of a future media design philosophy and then discuss materials issues and processing techniques for multi-layered thin film material structures which may be used to achieve media structures which can easy exceed the limits predicted for isotropic media.

Lambeth, David N.

2000-03-01

172

Classical growth of hard-sphere colloidal crystals  

NASA Astrophysics Data System (ADS)

The classical theory of nucleation and growth of crystals is examined for concentrated suspensions of hard-sphere colloidal particles. The work of Russel is modified, extended, and evaluated, explicitly. Specifically, the Wilson-Frenkel growth law is modified to include the Gibbs-Thomson effect and is evaluated numerically. The results demonstrate that there is a critical nucleus radius below which crystal nuclei will not grow. A kinetic coefficient determines the maximum growth velocity possible. For large values of this coefficient, quenches to densities above the melting density show interface limited growth with the crystal radius increasing linearly with time. For quenches into the coexistence region the growth is diffusion limited, with the crystal radius increasing as the square root of elapsed time. Smaller values of the kinetic coefficient produce long lived transients which evidence quasi-power-law growth behavior with exponents between one half and unity. The smaller kinetic coefficients also lead to larger crystal compression. Crystal compression and nonclassical exponents have been observed in recent experiments. The theory is compared to data from small angle scattering studies of nucleation and growth in suspensions of hard colloidal spheres. The experimental nucleation rate is much larger than the theoretically predicted value as the freezing point is approached but shows better agreement near the melting point. The crystal growth with time is described reasonably well by the theory and suggests that the experiments are observing long lived transient rather than asymptotic growth behavior. (c) 1995 The American Physical Society

Ackerson, Bruce J.; Schätzel, Klaus

1995-12-01

173

RAD hard PROM design study  

NASA Technical Reports Server (NTRS)

The results of a preliminary study on the design of a radiation hardened fusible link programmable read-only memory (PROM) are presented. Various fuse technologies and the effects of radiation on MOS integrated circuits are surveyed. A set of design rules allowing the fabrication of a radiation hardened PROM using a Si-gate CMOS process is defined. A preliminary cell layout was completed and the programming concept defined. A block diagram is used to describe the circuit components required for a 4 K design. A design goal data sheet giving target values for the AC, DC, and radiation parameters of the circuit is presented.

1981-01-01

174

Controlling the jamming transition of sheared hard spheres  

NASA Astrophysics Data System (ADS)

Many applications require understanding how disordered materials flow under an external load such as a shear stress. Since external loads drive systems out of equilibrium, their behavior cannot be described solely in terms of equilibrium parameters like temperature and pressure. However, simulations and experiments show that sheared spherical particles possess an effective temperature that relates low-frequency fluctuations of various observable quantities to their associated response functions. Here, we show that the mobility of a mixture of sheared hard spheres is largely controlled by the dimensionless ratio of effective temperature to pressure, Teff/p3?, where ? is the sphere diameter. We define the effective temperature as the consistent value that relates the amplitudes of low-frequency shear stress and density fluctuations to their associated response functions. We find that the relaxation time ? characterizing the mobility depends on Teff/p3? according to two distinct mechanisms in two distinct regimes. In the solid response regime, the behavior at fixed packing fraction ? satisfies ??(-cp3?/Teff), where ? is the strain rate and c depends weakly on ?, suggesting that the effective temperature controls the average local yield strain. In the fluid response regime, ? depends on Teff/p3? as it depends on T/p3? in equilibrium. This regime comprises a large part of the hard-sphere jamming phase diagram including both near-equilibrium conditions where Teff is similar to the kinetic temperature Tkin and far-from-equilibrium conditions where TeffTkin. In particular, the dynamic jamming transition is largely controlled by the fluid-response mechanism; like equilibrium hard spheres, sheared hard spheres can flow only if low-frequency fluctuations are large enough compared to the pressure. By presenting our results in terms of the dimensionless jamming phase diagram, we show how these mechanisms likely apply to systems with soft repulsive interactions.

Haxton, Thomas

2012-02-01

175

Effect of impurities on the hardness of alkali halide single crystals  

NASA Astrophysics Data System (ADS)

Micro hardness number of KCl, KBr and KCl-Br grown by Czocharlski technique, in the presence of homovalent and aliovalent ions of different ionic radii were measured in the indentation load range from 5 to 80*10-3 N. The measured data showed that there is an indentation size effect and classical Meyer's law was used for the characterization of crystal hardness of these crystals. The Meyer's index was also found to be smaller than 2 indicating brittle material characteristic. The P.R.S. model was used for the determination of the load independent micro hardness value. Result can be explained on the basis of interaction between created dislocation and point defect. It was found that hardness of these crystals is depending on the type of impurity.

Verma, Ashok K.; Ojha, Chaturbhuj; Shrivastava, A. K.

2014-04-01

176

Automatic image processing algorithm to detect hard exudates based on mixture models.  

PubMed

Automatic detection of hard exudates from retinal images is clinically significant. Hard exudates are associated with diabetic retinopathy and have been found to be one of the most prevalent earliest clinical signs of retinopathy. In this study, an automatic method to detect hard exudates is proposed. The algorithm is based on mixture models to dynamically threshold the images in order to separate hard exudates from background. We prospectively assessed the algorithm performance using a database of 20 retinal images with variable color, brightness, and quality. The algorithm obtained a sensitivity of 90.23% and a predictive value of 82.5% using a lesion-based criterion. The image-based classification accuracy is also evaluated obtaining a sensitivity of 100% and a specificity of 90% PMID:17945839

Sánchez, Clara I; Mayo, Agustín; García, María; López, María I; Hornero, Roberto

2006-01-01

177

Communication: Radial distribution functions in a two-dimensional binary colloidal hard sphere system  

NASA Astrophysics Data System (ADS)

Two-dimensional hard disks are a fundamentally important many-body model system in classical statistical mechanics. Despite their significance, a comprehensive experimental data set for two-dimensional single component and binary hard disks is lacking. Here, we present a direct comparison between the full set of radial distribution functions and the contact values of a two-dimensional binary colloidal hard sphere model system and those calculated using fundamental measure theory. We find excellent quantitative agreement between our experimental data and theoretical predictions for both single component and binary hard disk systems. Our results provide a unique and fully quantitative mapping between experiments and theory, which is crucial in establishing the fundamental link between structure and dynamics in simple liquids and glass forming systems.

Thorneywork, Alice L.; Roth, Roland; Aarts, Dirk G. A. L.; Dullens, Roel P. A.

2014-04-01

178

Communication: Radial distribution functions in a two-dimensional binary colloidal hard sphere system.  

PubMed

Two-dimensional hard disks are a fundamentally important many-body model system in classical statistical mechanics. Despite their significance, a comprehensive experimental data set for two-dimensional single component and binary hard disks is lacking. Here, we present a direct comparison between the full set of radial distribution functions and the contact values of a two-dimensional binary colloidal hard sphere model system and those calculated using fundamental measure theory. We find excellent quantitative agreement between our experimental data and theoretical predictions for both single component and binary hard disk systems. Our results provide a unique and fully quantitative mapping between experiments and theory, which is crucial in establishing the fundamental link between structure and dynamics in simple liquids and glass forming systems. PMID:24784245

Thorneywork, Alice L; Roth, Roland; Aarts, Dirk G A L; Dullens, Roel P A

2014-04-28

179

Values in Education and Education in Values.  

ERIC Educational Resources Information Center

The major purpose of this book is to set out some of the key issues and debates relating to the importance of values in education and of education in values. After an introductory chapter about the concept of values and values education, part 1 provides a variety of perspectives on the values that underpin contemporary education. The introduction…

Halstead, J. Mark, Ed.; Taylor, Monica J., Ed.

180

Phase Transitions in a Mixture of Hard-Sphere Dipoles and Neutral Hard Spheres  

NASA Astrophysics Data System (ADS)

Using the reference hypernetted chain (RHNC) integral equation theory and a rigorous stability analysis method, we investigate the phase behavior of a mixture of hard-sphere dipoles and neutral hard spheres based on the correlations of the homogeneous isotropic phase. Lowering the temperature down to the points where the RHNC equations fail to have a solution, several fluctuations strongly increase. At low densities our results indicate the onset of chain formation, which is similar with the pure DHS system. At high densities, the results indicate the appearance of isotropic-to-ferroelectric transitions (small neutral hard spheres concentrations) and demixing transitions (large neutral hard spheres concentrations).

Li, Li; Li, Liang-Sheng; Chen, Xiao-Song

2009-09-01

181

Dielectric and hardness measurements of planetary analog rocks in support of in-situ subsurface sampling  

NASA Astrophysics Data System (ADS)

Accurate assessment of the subsurface mechanical characteristics and how they correlate with dielectric properties is crucial to optimize future drilling and sampling investigations on planetary bodies. For 12 different types of basaltic rocks with different hardnesses, we use capacitive cells to measure the real part of the dielectric constant over the frequency range 100-1000 MHz, and a Schmidt hammer hardness tester to measure the hardness using a scale of 10-100. Our measurements suggest that the real part of the dielectric constant and rock hardness are linearly correlated. Additionally, sample hardness was linearly correlated to density. For a density ranging from 0.82 to 3.05 g/cm3, the real part of the dielectric constant ?? and rebound hardness values R ranged from ??=1.8-7.6 and R=14.16-68 for the different basalt samples. Hence, high dielectric constants imply a high rock hardness value and vice versa. We concluded that for volcanic surfaces that are analogous to the Martian surface as well as other planetary surfaces, there is an inverse correlation between drilling penetration rate based on the rotary-percussive drill method and the dielectric constant. Dielectric inversion from planetary radar probing experiments proposed herein is a crucial method to locate regions with lowest hardness and hence highest drilling penetration rate in desiccated volcanic planetary subsurfaces. The use of these cross-correlation measurements can optimize future drilling experiments and ensure that they reach their targets of opportunities, minimize losses in drilling performance, or the unnecessary use of power that will be needed for the continuity of the investigation.

ElShafie, Ahmed; Heggy, Essam

2013-09-01

182

Abrasivity Assessment of Granitic Building Stones in Relation to Diamond Tool Wear Rate Using Mineralogy-Based Rock Hardness Indexes  

NASA Astrophysics Data System (ADS)

The objective of the present study was to determine the abrasive wear potential of granites in circular sawing using some mineralogy-based rock hardness indexes. A literature study indicated that little or no attention has been given to assessing this kind of relationship in the field of stone processing. To accomplish this objective, sawing experiments were performed on nine different granites used widely as building and decorative stone materials. The measured sawblade-specific wear rates were correlated with three different rock hardness indexes attained by combining the percentage content of hard mineral constituents with their known hardness values. Statistical analysis of the experimental data revealed that rock hardness indexes that are based on both Vickers hardness number and Rosiwal hardness could be accepted as reliable indicators of granite abrasivity. These two indexes were also found to correlate well with the average power drawn during the process. However, the rock abrasivity index based on Mohs relative scratch hardness did not show statistically significant correlations with sawblade wear rate and power drawn. Although quartz percentage content is regarded as an important abrasivity parameter by practitioners, the observations made here indicate that consideration of quartz percentage content alone is not sufficient to describe the abrasive potential of granites, and thus incorporation of other hard mineral constituents could be more suitable.

Y?lmaz, Nurdan Güne?

2011-11-01

183

Evaluation of surface roughness and hardness of different glass ionomer cements  

PubMed Central

Objectives: The aim of this study was to evaluate surface roughness and hardness of a nanofiller GIC, a resin-modified GIC, three conventional GICs, and a silver-reinforced GIC. Methods: For each material, 11 spcecimens were prepared and then stored in distilled water at 37 °C for 24 h. The surface roughness of 5 specimens was measured using a surface profilometer before polishing and after polishing with coarse, medium, fine, superfine aluminum oxide abrasive Sof-Lex discs respectively. The hardness of the upper surfaces of the remaining 6 specimens was measured with a Vickers microhardness measuring instrument. Results: All tested GICs showed lower surface roughness values after the polishing procedure. Surface finish of nanofiller GIC was smoother than the other tested GICs after polishing. This was followed by resin-modified GIC, Fuji II LC; then silver-reinforced GIC, Argion Molar, conventional GICs, Aqua Ionofil Plus, Fuji IX, and Ionofil Molar, respectively. The result of the hardness test indicated that the microhardness value of silver-reinforced GIC was greater than that of the other GICs. When the hardness values of all tested GICs were compared, the differences between materials (except Aqua Ionofil Plus with Ionofil Molar and Ketac N100 with Fuji II LC (P>.05)) were found statistically significant (P<.05). Conclusions: According to the results of this study, it can be concluded that the differences in the composition of GICs may affect their surface roughness and hardness.

Bala, Oya; Arisu, Hacer Deniz; Yikilgan, Ihsan; Arslan, Seda; Gullu, Abdulkadir

2012-01-01

184

Tribomechanical properties of ion-implantation-synthesized BN films and their dependence on Ti?6Al?4V substrate hardness  

Microsoft Academic Search

The tribomechanical properties (i.e. Knoop microhardness, friction coefficients and wear) of boron nitride films synthesized by ion implantation are studied. Boron was evaporated by electron beam heating and deposited as 1000 Å films onto polished Ti?6Al?4V cylindrical substrates (where the composition is in approximate weight per cent). The films were then bombarded with 50 keV N2+ ions to a dose

Tandjaoui Baazi; Emile J. Knystautas; Michel Fiset

1995-01-01

185

Development of hard white winter wheats for a hard red winter wheat region  

Microsoft Academic Search

Hard white winter wheat (HWWW) occupies a very limited area of the USA, but its purported advantages suggest that its production in the major hard red winter wheat (HRWW) region may be feasible. Objectives of our investigations were to develop experimental HWWW lines that combined desirable attributes-grain yield, functional grain quality, and resistance to preharvest sprouting-in single genotypes for comparison

M. P. Upadhyay; G. M. Paulsen; E. G. Heyne; R. G. Sears; R. C. Hoseney

1984-01-01

186

Flavor Characterization of Breads Made from Hard Red Winter Wheat and Hard White Winter Wheat  

Microsoft Academic Search

Cereal Chem. 69(5):556-559 Sensory flavor profiles for white pan bread and whole wheat bread impression than did HRW crust. HRW crumb was sweeter and more made from hard red winter (HRW) or hard white winter (HWW) wheat dairylike than HWW crumb. HWW crumb had a phenoliclike note not were developed by a professionally trained panel. The flavors of crust present

CHUN-YEN CHANG; EDGAR CHAMBERS

187

Depletion effects in smectic phases of hard rod--hard sphere mixtures  

Microsoft Academic Search

It is known that when hard spheres are added to a pure system of hard rods the stability of the smectic phase may be greatly enhanced, and that this effect can be rationalised in terms of depletion forces. In the present paper we first study the effect of orientational order on depletion forces in this particular binary system, comparing our

Yuri Martinez-Raton; Giorgio Cinacchi; Enrique Velasco; Luis Mederos

2007-01-01

188

Equation of State and Integral Equation Theory for Hard Sphere and Hard-Sphere Chain Fluids  

Microsoft Academic Search

The development of an accurate equation of state based on molecular thermodynamics for simple and complex fluids is important to chemical process design. In this dissertation we study the thermodynamic and intermolecular structural properties of hard sphere and hard-sphere chain fluids. These are theoretically challenging problems, the solution of which are useful for perturbation theory of more realistic potential models.

Jaeeon Chang

1994-01-01

189

Research in the Hard Sciences, and in Very Hard "Softer" Domains  

ERIC Educational Resources Information Center

The author of this commentary argues that physical scientists are attempting to advance knowledge in the so-called hard sciences, whereas education researchers are laboring to increase knowledge and understanding in an "extremely hard" but softer domain. Drawing on the work of Popper and Dewey, this commentary highlights the relative…

Phillips, D. C.

2014-01-01

190

Value of Travel Time.  

National Technical Information Service (NTIS)

The Record includes 6 papers covering important areas of travel time value analysis, such as travel time value theory, conceptual problems in travel time value, methods of deriving travel time values, review of empirical travel time value studies, applica...

R. Gronau

1976-01-01

191

Parameter and Return-value Analysis of Binary Executables  

Microsoft Academic Search

The recovery of parameter and return-value plays an important role in decompilation, reverse engineering, binary translation and software maintenance etc. Furthermore, related approaches are very useful to inter- procedural analyzing and slicing of binary executable. However, the operations on parameters and return- values always appear obscure after the optimizing phases of a compiler, which will make the recovery hard to

Jingbo Zhang; Rongcai Zhao; Jianmin Pang

2007-01-01

192

Scaled particle theory for hard sphere pairs. I. Mathematical structure.  

PubMed

We develop an extension of the original Reiss-Frisch-Lebowitz scaled particle theory that can serve as a predictive method for the hard sphere pair correlation function g(r). The reversible cavity creation work is analyzed both for a single spherical cavity of arbitrary size, as well as for a pair of identical such spherical cavities with variable center-to-center separation. These quantities lead directly to a prediction of g(r). Smooth connection conditions have been identified between the small-cavity situation where the work can be exactly and completely expressed in terms of g(r), and the large-cavity regime where macroscopic properties become relevant. Closure conditions emerge which produce a nonlinear integral equation that must be satisfied by the pair correlation function. This integral equation has a structure which straightforwardly generates a solution that is a power series in density. The results of this series replicate the exact second and third virial coefficients for the hard sphere system via the contact value of the pair correlation function. The predicted fourth virial coefficient is approximately 0.6% lower than the known exact value. Detailed numerical analysis of the nonlinear integral equation has been deferred to the subsequent paper. PMID:17144712

Stillinger, Frank H; Debenedetti, Pablo G; Chatterjee, Swaroop

2006-11-28

193

A replica approach to glassy hard spheres  

NASA Astrophysics Data System (ADS)

Hard spheres have been used to model many different systems in condensed matter. Amorphous packings have attracted a lot of interest as theoretical models for glasses. We will review here a theory of amorphous packings, and more generally glassy states, of hard spheres that is based on the replica method: this theory gives predictions on the structure and thermodynamics of these states. Replica theory relies on approximations and certain assumptions that will be elucidated in this paper. The aim of this paper is to identify a class of amorphous packings that might be described using equilibrium statistical mechanics, that is, in a static framework. These packings will be defined as the infinite pressure limit of glassy states of hard spheres.

Parisi, Giorgio; Zamponi, Francesco

2009-03-01

194

Potential Health Impacts of Hard Water  

PubMed Central

In the past five decades or so evidence has been accumulating about an environmental factor, which appears to be influencing mortality, in particular, cardiovascular mortality, and this is the hardness of the drinking water. In addition, several epidemiological investigations have demonstrated the relation between risk for cardiovascular disease, growth retardation, reproductive failure, and other health problems and hardness of drinking water or its content of magnesium and calcium. In addition, the acidity of the water influences the reabsorption of calcium and magnesium in the renal tubule. Not only, calcium and magnesium, but other constituents also affect different health aspects. Thus, the present review attempts to explore the health effects of hard water and its constituents.

Sengupta, Pallav

2013-01-01

195

Principal-value resummation for dilepton production  

Microsoft Academic Search

We present a new method of resummation of QCD threshold distributions to the hard scattering function of the dilepton production cross section in hadron-hadron collisions. Our formulation by-passes the infrared singularities of the QCD running coupling through a principal value prescription, and does not require an explicit infrared cut-off. The resulting large corrections exponentiate, and we discuss asymptotic properties of

HARRY CONTOPANAGOS; LYNDON ALVERO; GEORGE STERMAN

1994-01-01

196

Evaluation of the Shore A hardness of silicone for facial prosthesis as to the effect of storage period and chemical disinfection.  

PubMed

The failure of facial prostheses is caused by limitations in the properties of existing materials, especially flexibility and durability. Therefore, this study evaluated the Shore A hardness of silicone used for fabrication of facial prostheses, Silastic MDX4-4210, according to the influence of storage period, daily disinfection, and 2 types of pigmentation. Thirty specimens were fabricated and divided in 3 groups: colorless, pigmented with makeup, and pigmented with iron oxide. Analysis of results was assessed on a Shore A hardness meter immediately, 6 months, and 1 year after fabrication of specimens, following the guidelines of the American Society for Testing and Materials. The hardness values were statistically analyzed by the Tukey test. The silicone exhibited an increase in hardness with time. However, the hardness was stable from 6 months to 1 year. It was concluded that the silicone is within the values of Shore A hardness reported in the literature, regardless of the storage period, pigmentation, and chemical disinfection. PMID:20186092

Guiotti, Aimée Maria; Goiato, Marcelo Coelho; dos Santos, Daniela Micheline

2010-03-01

197

Hard Diffraction at D-Zero  

SciTech Connect

Preliminary results from the DO experiment on dijet production with forward rapidity gaps in {anti p}p collisions are presented at center-of-mass {radical}s = 1800 GeV and 630GeV. The number oi events with rapidity gaps at both center-of-mass energies is significantly greater than tne expectatmn from multiplicity fluctuations and is consistent with a hard single diffractive process. We also observe an excess of events which contain jets and two rapidity gaps, a topology which is consistent with hard double pomeron exchange.

Paul Rubinov

1999-01-21

198

Rad Hard Active Media For Calorimeters  

SciTech Connect

Zero-degree calorimeters have limited space and extreme levels of radiation. A simple, low cost, radiation hard design uses tungsten metal as the absorber and a suitable liquid as the Cerenkov radiator. In other applications a PPAC (Parallel Plate Avalanche Counter) operating with a suitable atmospheric-pressure gas is an attractive active material for a calorimeter. It can be made radiation hard and has sufficient gain in the gas that no electronic components are needed near the detector. It works well even with the highest concentration of shower particles. For this pressure range, R134A (used in auto air conditioners) has many desirable features.

Norbeck, E.; Olson, J. E.; Moeller, A.; Onel, Y. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA (United States)

2006-10-27

199

Rad Hard Active Media For Calorimeters  

NASA Astrophysics Data System (ADS)

Zero-degree calorimeters have limited space and extreme levels of radiation. A simple, low cost, radiation hard design uses tungsten metal as the absorber and a suitable liquid as the ?erenkov radiator. In other applications a PPAC (Parallel Plate Avalanche Counter) operating with a suitable atmospheric-pressure gas is an attractive active material for a calorimeter. It can be made radiation hard and has sufficient gain in the gas that no electronic components are needed near the detector. It works well even with the highest concentration of shower particles. For this pressure range, R134A (used in auto air conditioners) has many desirable features.

Norbeck, E.; Olson, J. E.; Moeller, A.; Onel, Y.

2006-10-01

200

Degenerate quasicrystal of hard triangular bipyramids.  

PubMed

We report a degenerate quasicrystal in Monte Carlo simulations of hard triangular bipyramids each composed of two regular tetrahedra sharing a single face. The dodecagonal quasicrystal is similar to that recently reported for hard tetrahedra [Haji-Akbari et al., Nature (London) 462, 773 (2009)] but degenerate in the pairing of tetrahedra, and self-assembles at packing fractions above 54%. This notion of degeneracy differs from the degeneracy of a quasiperiodic random tiling arising through phason flips. Free energy calculations show that a triclinic crystal is preferred at high packing fractions. PMID:22181897

Haji-Akbari, Amir; Engel, Michael; Glotzer, Sharon C

2011-11-18

201

Structural and relative stabilities, electronic properties, and hardness of iron tetraborides from first prinicples.  

PubMed

First-principles calculations were carried out to investigate the structure, phase stability, electronic property, and roles of metallicity in the hardness for recently synthesized FeB4 with various different structures. Our calculation indicates that the orthorhombic phase with Pnnm symmetry is the most energetically stable one. The other four new dynamically stable phases belong to space groups monoclinic C2/m, orthorhombic Pmmn, trigonal R3?m, and hexagonal P63/mmc. Their mechanical and thermodynamic stabilities are verified by calculating elastic constants, formation enthalpies, and phonon dispersions. We found that all phases are stabilized further under pressure. Above the pressure of about 50 GPa, the formation enthalpy of Pmmn is almost equal to that of P63/mmc phase. The analysis on density of states not only demonstrates that formation of strong covalent bonding in these compounds contributes greatly to their stabilities but also that they all exhibit metallic behavior which does not relate to the approach used. By considering metallic contributions, the estimated Vickers hardness values based on the semiempirical model show that the OsB4-structured FeB4, with a hardness of 48.1 GPa, well exceeding the limitation of superhardness (40 GPa), is more hard than the most stable phase. The others are predicted to be potential hard materials. Moreover, the atomic configuration and strong B-B covalent bonds are found to play important roles in the hardness of materials. PMID:24605919

Ding, Li-Ping; Kuang, Xiao-Yu; Shao, Peng; Huang, Xiao-Fen

2014-04-01

202

Phase behaviour of parallel hard rods in confinement: an Onsager theory study  

NASA Astrophysics Data System (ADS)

The effect of confinement on the positional ordering is examined in a system of parallel hard cylinders using the second virial theory of Onsager. Hard cylinders are arranged in a slit-like pore (two parallel planar hard walls) in such a way that the long axes of the particles are perpendicular to the surface of confining hard walls. We have incorporated the theories of the bulk and the confined systems into a single formalism, where a wij kernel function provides the link between the bulk and confined systems. It is shown that the presence of hard walls inhibits the second order nematic-smectic A phase transition irrespective of the value of the wall-to-wall separation. Instead, due to accommodation problems of the cylinders into the pore, an infinite number of first order layering phase transitions appears. Coexisting curves, corresponding to the equilibrium between two phases having n and n + 1 smectic-like periods, are bounded with lower critical points. The gap between the average densities of the coexisting phases shrinks with increasing pore width, while the properties of the critical points monotonically move towards those of the nematic-smectic A phase transition of the bulk system (d \\to \\infty ). The effect of only one hard wall is related to the bulk nematic-smectic A phase transition since a critical wetting transition of the wall induced layering takes place.

Malijevský, Alexandr; Varga, Szabolcs

2010-05-01

203

Physiological, perceptual, and technical responses to on-court tennis training on hard and clay courts.  

PubMed

The aim of this study was to investigate the effect of court surface (clay vs. hard court) on technical, physiological, and perceptual responses to on-court tennis training. Four high-performance junior male players performed 2 identical training sessions on hard and clay courts, respectively. Sessions included both physical conditioning and technical elements as led by the coach. Each session was filmed for later notational analysis of stroke count and error rates. Furthermore, players wore a global positioning satellite device to measure distance covered during each session, while heart rate, countermovement jump distance, and capillary blood measures of metabolites were measured before, during, and after each session. Additionally, a respective coach and athlete rating of perceived exertion (RPE) were measured after each session. Total duration and distance covered during each session were comparable (p > 0.05; d < 0.20). Although forehand and backhands stroke volume did not differ between sessions (p > 0.05; d < 0.30), large effects for increased unforced and forced errors were present on the hard court (p > 0.05; d > 0.90). Furthermore, large effects for increased heart rate, blood lactate, and RPE values were evident on clay compared with hard courts (p > 0.05; d > 0.90). Additionally, although player and coach RPE on hard courts were similar, there were large effects for coaches to underrate the RPE of players on clay courts (p > 0.05; d > 0.90). In conclusion, training on clay courts results in trends for increased heart rate, lactate, and RPE values, suggesting that sessions on clay courts tend towards higher physiological and perceptual loads than hard courts. Furthermore, coaches seem effective at rating player RPE on hard courts but may underrate the perceived exertion of sessions on clay courts. PMID:22890497

Reid, Machar M; Duffield, Rob; Minett, Geoffrey M; Sibte, Narelle; Murphy, Alistair P; Baker, John

2013-06-01

204

Columnar and smectic order in binary mixtures of aligned hard cylinders  

Microsoft Academic Search

We examine possible nematic to smectic and nematic to columnar phase transitions for binary mixtures of perfectly parallel aligned hard cylinders with equal diameters but different lengths by using the free-energy functional within the third virial coefficient approximation. The regions of stability are located and the phase diagram of the system is calculated for different values of the ratio of

Shi-Min Cui; Zheng Yu Chen

1994-01-01

205

Credit risk management in banks: Hard information, soft Information and manipulation  

Microsoft Academic Search

The role of information’s processing in bank intermediation is a crucial input. The bank has access to different types of information in order to manage risk through capital allocation for Value at Risk coverage. Hard information, contained in balance sheet data and produced with credit scoring, is quantitative and verifiable. Soft information, produced within a bank relationship, is qualitative and

Brigitte Godbillon-Camus; Christophe J. Godlewski

2005-01-01

206

Comparison of International Rockwell C and Vickers Hv 30 Hardness Scales During 1970 and 1971.  

National Technical Information Service (NTIS)

The results of comparisons, made over a period of two years, of the standarized Rockwell C scale and Vickers HV30 scale are presented in graphical form. The hardness values in Rockwell C scale and Vickers HV30 scale on the same test blocks are discussed i...

R. S. Marriner, J. G. Wood

1972-01-01

207

Note: Equation of state and the freezing point in the hard-sphere model  

NASA Astrophysics Data System (ADS)

The merits of different analytical equations of state for the hard-sphere system with respect to the recently computed high-accuracy value of the freezing-point packing fraction are assessed. It is found that the Carnahan-Starling-Kolafa and the branch-point approximant equations of state yield the best performance.

Robles, Miguel; López de Haro, Mariano; Santos, Andrés

2014-04-01

208

Note: Equation of state and the freezing point in the hard-sphere model.  

PubMed

The merits of different analytical equations of state for the hard-sphere system with respect to the recently computed high-accuracy value of the freezing-point packing fraction are assessed. It is found that the Carnahan-Starling-Kolafa and the branch-point approximant equations of state yield the best performance. PMID:24712819

Robles, Miguel; López de Haro, Mariano; Santos, Andrés

2014-04-01

209

Valuing Puget Sound's Valued Ecosystems Components.  

National Technical Information Service (NTIS)

Valued ecosystem components, or VECs, are key elements of the Puget Sound Nearshore Ecosystem Restoration Project (PSNERP) conceptual framework for nearshore restoration. This paper discusses the underlying human values that motivate the choice of VECs an...

A. W. Petersen T. M. Leschine

2007-01-01

210

Parameters controlling microstructure and hardness during friction-stir welding of precipitation-hardenable aluminum alloy 6063  

NASA Astrophysics Data System (ADS)

The aluminum (Al) alloys 6063-T5 and T4 were friction-stir welded at different tool rotation speeds ( R), and then distributions of the microstructure and hardness were examined in these welds. The maximum temperature of the welding thermal cycle rose with increasing R values. The recrystallized grain size of the weld increased exponentially with increasing maximum temperature. The relationship between the grain size and the maximum temperature satisfied the static grain-growth equation. In the as-welded condition, 6063-T5 Al was softened around the weld center, whereas 6063-T4 Al showed homogeneous hardness profiles. Different R values did not result in significant differences in the hardness profile in these welds, except for the width of the softened region in the weld of 6063-T5 Al. Postweld aging raised the hardness in most parts of the welds, but the increase in hardness was small in the stir zone produced at the lower R values. Transmission electron microscope (TEM) observations detected a similar distribution of the strengthening precipitates in the grain interiors and the presence of a precipitation-free zone (PFZ) adjacent to the grain boundaries in all the welds. Microstructural analyses suggested that the small increase in hardness in the stir zone produced at the lower R values was caused by an increase in the volume fraction of PFZs.

Sato, Yutaka S.; Urata, Mitsunori; Kokawa, Hiroyuki

2002-03-01

211

Improvement of Quench Factor Analysis in Phase and Hardness Prediction of a Quenched Steel  

NASA Astrophysics Data System (ADS)

The accurate prediction of alloys' properties introduced by heat treatment has been considered by many researchers. The advantages of such predictions are reduction of test trails and materials' consumption as well as time and energy saving. One of the most important methods to predict hardness in quenched steel parts is Quench Factor Analysis (QFA). Classical QFA is based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. In this study, a modified form of the QFA based on the work by Rometsch et al. is compared with the classical QFA, and they are applied to prediction of hardness of steels. For this purpose, samples of CK60 steel were utilized as raw material. They were austenitized at 1103 K (830 °C). After quenching in different environments, they were cut and their hardness was determined. In addition, the hardness values of the samples were fitted using the classical and modified equations for the quench factor analysis and the results were compared. Results showed a significant improvement in fitted values of the hardness and proved the higher efficiency of the new method.

Kianezhad, M.; Sajjadi, S. A.

2013-05-01

212

Mechanical modeling of wheat hardness and fragmentation  

Microsoft Academic Search

The mechanical origin of the wheat hardness used to classify wheat flours is an open issue. We propose a cohesive granular model of wheat endosperm involving a discrete phase composed of starch granules, a continuous phase representing the protein matrix, and pores. A lattice element method is employed to simulate the behavior of numerical samples with variable matrix volume fraction

Vincent Topin; Farhang Radjaï; Jean-Yves Delenne; Frédéric Mabille

2009-01-01

213

Reliability of Hard Plastic Clad Silica Fibers  

Microsoft Academic Search

New formulations of cladding materials have become available in recent times for Hard Plastic Clad Silica (HPCS) fibers, Initial data showed gains in some properties, particularly dynamic strength, especially for high numerical aperture (NA) fibers. A systematic study has been undertaken to determine the full strength and fatigue behavior of these HPCS fibers and to make comparisons to earlier HPCS

Bolesh J. Skutnik; Stefan Spaniol

214

A bibliography of micro-hardness testing  

NASA Astrophysics Data System (ADS)

Arranged chronologically by year of publicaton, this bibliography cites about 900 articles and books which appeared between 1937 and 1980. In addition to hardness measurement and test procedures, ductility, machineability, wear resistance, and tensile strength are considered. An author index is provided.

Leigh, I. C.

1981-09-01

215

Help, Libraries and the Hard of Hearing.  

National Technical Information Service (NTIS)

This transcript contains the text of three speeches on the problems of people with hearing impairments and the provision of library services to the hard of hearing. Howard Edward (Rocky) Stone, founder of Self-Help-For-Hearing-Impaired-People, Inc., descr...

1982-01-01

216

Periocular migration of hard contact lenses.  

PubMed Central

Six cases are presented in which hard contact lenses have migrated into the periocular soft tissues, four into the eyelid, one into the orbit and one which spontaneously reappeared on the cornea 12 years after the patient had last worn contact lenses. Some possible mechanisms of this phenomenon and a review of the literature are presented. Images

Roberts-Harry, T J; Davey, C C; Jagger, J D

1992-01-01

217

PROTEIN TEMPLATES IN HARD TISSUE ENGINEERING  

PubMed Central

Biomineralization processes such as formation of bones and teeth require controlled mineral deposition and self-assembly into hierarchical biocomposites with unique mechanical properties. Ideal biomaterials for regeneration and repair of hard tissues must be biocompatible, possess micro and macroporosity for vascular invasion, provide surface chemistry and texture that facilitate cell attachment, proliferation, differentiation of lineage specific progenitor cells, and induce deposition of calcium phosphate mineral. To expect in-vivo like cellular response several investigators have used extracellular matrix proteins as templates to recreate in-vivo microenvironment for regeneration of hard tissues. Recently, several novel methods of designing tissue repair and restoration materials using bioinspired strategies are currently being formulated. Nanoscale structured materials can be fabricated via the spontaneous organization of self-assembling proteins to construct hierarchically organized nanomaterials. The advantage of such a method is that polypeptides can be specifically designed as building blocks incorporated with molecular recognition features and spatially distributed bioactive ligands that would provide a physiological environment for cells in-vitro and in-vivo. This is a rapidly evolving area and provides a promising platform for future development of nanostructured templates for hard tissue engineering. In this review we try to highlight the importance of proteins as templates for regeneration and repair of hard tissues as well as the potential of peptide based nanomaterials for regenerative therapies.

George, Anne; Ravindran, Sriram

2010-01-01

218

Hard X ray Observations of Galactic Sources.  

National Technical Information Service (NTIS)

A number of galactic sources observed by the hard X-ray telescope Mifrasco during the course of two balloon flights from the Milo base in Trapani (Sicily) in July 1986 and 1987 are presented. Emission spectra was measured over the energy range 15 to 300 k...

A. Bazzano I. R. Carstairs M. J. Coe A. Court S. R. Davies

1989-01-01

219

MORPHOMETRICS OF HARD STRUCTURES IN CUTTLEFISH  

Microsoft Academic Search

Cuttlefishes exhibit several hard structures that have been charac- terised using morphometric analysis. Most of these data come from cuttlebones, al- though statoliths and beaks are also used. It appears that morphometric techniques are mainly used for taxonomic purposes. However, some analyses have emphasised functional morphology and macroevolution. Morphological features (including the inner shell) of cuttlefishes and their availability for

P. NEIGE

2006-01-01

220

Carbon implantation into hard chrome coatings  

Microsoft Academic Search

Carbon ions were implanted into hard chrome coatings at an energy of 30 keV for various doses up to 4 × 1017 C cm?2 to study possible new phase formation and its effect on the tribological properties. The retained doses and ion distributions were determined by ion beam analysis techniques and phase formation was monitored by grazing incidence X-ray diffraction.

Z. Rao; B. H. O'Connor; J. S. Williams; D. K. Sood

1996-01-01

221

Hard diffraction and deep inelastic scattering.  

National Technical Information Service (NTIS)

Since the advent of hard-collision physics, the study of diffractive processes - shadow physics - has been less prominent than before. However, there is now a renewed interest in the subject, especially in that aspect which synthesizes the short-distance,...

J. D. Bjorken

1994-01-01

222

Pathology of the Hard and Soft Palate.  

National Technical Information Service (NTIS)

Pathology of the palate can result from abnormalities of one or several of the tissue types making up the palate. This paper discusses a few of the more recently emphasized and pertinant conditions which may affect the hard and soft palate. It is not an a...

J. F. Nelson P. J. Tsaknis

1976-01-01

223

Cemented Alloy Carbides for Hard Rock Boring.  

National Technical Information Service (NTIS)

The objective of the project is to develop various cemented alloy carbides with improved properties for hard rock drilling. Initial work has concerned the (Ti, V)C carbide cemented in a Ni matrix and has focused on the fabrication, microstructure and test...

J. A. S. Green J. D. Venables W. Precht

1975-01-01

224

Phase behavior of parallel hard cylinders  

Microsoft Academic Search

We test the performance of a recently proposed fundamental measure density functional of aligned hard cylinders by calculating the phase diagram of a monodisperse fluid of these particles. We consider all possible liquid-crystalline symmetries, namely, nematic, smectic, and columnar, as well as the crystalline phase. For this purpose we introduce a Gaussian parametrization of the density profile and use it

José A. Capitán; Yuri Martínez-Ratón; José A. Cuesta

2008-01-01

225

Equation of state for parallel hard spherocylinders  

Microsoft Academic Search

A recent model for positional ordering in systems of monodisperse parallel hard spherocylinders is used to calculate the pressure over the entire range of densities and cylinder axial ratios. Reasonable quantitative agreement with Monte Carlo data is obtained for the full spectrum of nematic, smectic, columnar, and crystalline order. Analytical expressions are also given for the characteristic lengths of the

Reinhard Hentschke; Mark P. Taylor; Judith Herzfeld

1989-01-01

226

Cuttability assessment of hard coal seams  

Microsoft Academic Search

A number of field and laboratory tests have been carried out on more than 15 coal seams of compressive strengths ranging from 19 MPa to 44 MPa to evolve methods which would help in the selection of suitable coaling machines for hard coal seams. The effect of physico-mechanical properties on cuttability were studied in the laboratory for all these coal

R. Singh; J. K. Singh; T. N. Singh; B. B. Dhar

1995-01-01

227

Hard and flexible optical printed circuit board  

NASA Astrophysics Data System (ADS)

We report on the design and fabrication of hard and flexible optical printed circuit boards (O-PCBs). The objective is to realize generic and application-specific O-PCBs, either in hard form or flexible form, that are compact, light-weight, low-energy, high-speed, intelligent, and environmentally friendly, for low-cost and high-volume universal applications. The O-PCBs consist of 2-dimensional planar arrays of micro/nano-scale optical wires, circuits and devices that are interconnected and integrated to perform the functions of sensing, storing, transporting, processing, switching, routing and distributing optical signals on flat modular boards. For fabrication, the polymer and organic optical wires and waveguides are first fabricated on a board and are used to interconnect and integrate micro/nano-scale photonic devices. The micro/nano-optical functional devices include lasers, detectors, switches, sensors, directional couplers, multi-mode interference devices, ring-resonators, photonic crystal devices, plasmonic devices, and quantum devices. For flexible boards, the optical waveguide arrays are fabricated on flexible poly-ethylen terephthalate (PET) substrates by UV embossing. Electrical layer carrying VCSEL and PD array is laminated with the optical layer carrying waveguide arrays. Both hard and flexible electrical lines are replaced with high speed optical interconnection between chips over four waveguide channels up to 10Gbps on each. We discuss uses of hard or flexible O-PCBs for telecommunication systems, computer systems, transportation systems, space/avionic systems, and bio-sensor systems.

Lee, El-Hang; Lee, Hyun Sik; Lee, S. G.; O, B. H.; Park, S. G.; Kim, K. H.

2007-02-01

228

What Makes Science Hard? A Karplus Lecture.  

ERIC Educational Resources Information Center

Many students are deterred from science because of the way science courses are packaged. To find out what makes science hard for intelligent students, the author employed nonscience faculty and graduate students as surrogate students in science. Their responses to the sequence of the units, demonstrations, homework assignments, examinations, and…

Tobias, Sheila

1993-01-01

229

Thermal spray coatings replace hard chrome  

Microsoft Academic Search

Hard chrome plating provides good wear and erosion resistance, as well as good corrosion protection and fine surface finishes. Until a few years ago, it could also be applied at a reasonable cost. However, because of the many environmental and financial sanctions that have been imposed on the process over the past several years, cost has been on a consistent

M. Schroeder; R. Unger

1997-01-01

230

Most stable structure for hard spheres  

Microsoft Academic Search

The hard sphere model is known to show a liquid-solid phase transition, with the solid expected to be either face centered cubic or hexagonal close packed. The differences in free energy of the two structures are very small and various attempts have been made to determine which structure is the more stable. We contrast the different approaches and extend one.

Hans Koch; Charles Radin; Lorenzo Sadun

2005-01-01

231

Microfabricated electrostatic actuators for hard disk drives  

Microsoft Academic Search

A dual-stage servo system which utilizes a high-bandwidth secondary actuator has been proposed for magnetic hard disk drives. Microfabricated actuators are promising candidates for this secondary actuator, since they offer the benefits of extremely small size and weight and may be batch fabricated for reduced production cost. This paper presents the design of an electrostatic microactuator which produces sufficient output

David A. Horsley; Roberto Horowitz; Albert P. Pisano

1998-01-01

232

CRITICAL PERSISTENT CURRENTS IN HARD SUPERCONDUCTORS  

Microsoft Academic Search

Persistent currents induced in hard superconductors (HSC) were ; investigated by measuring the resulting magnetic effects. The tubular HSC ; examined were Nb powder, NbâSn, and 3Nb- Zr samples of uniform wall ; thickness and length large compared to the diameter. Experimental evidence is ; presented that in HSC the Lorentz force plays a crucial role in determining the ;

Y. B. Kim; C. F. Hempstead; A. R. Strnad

1962-01-01

233

‘SOFT’ VERSUS ‘HARD’ NEWS ON MICROBLOGGING NETWORKS  

Microsoft Academic Search

This article examines the variability of produsage (the hybridization of production and consumption) within popular social media by introducing semantic network analysis of information communication on Twitter. Utilizing user data (n[2,254,806]), the study examines the dynamics of produsage (a) as a function of user activity and (b) whether produsage levels vary based on either ‘soft’ or ‘hard’ news information. The

Tyler J. Horan

2012-01-01

234

Playing Fields and Hard Surface Areas.  

ERIC Educational Resources Information Center

Guidelines are presented regarding the planning, layout, construction, and maintenance of outdoor playing fields for physical education. Consideration is given to the dual use of playing fields by the school and the community, the planning of hard surface playing areas, and specifications and bills of quantities. Maintenance costs of grass playing…

Department of Education and Science, London (England).

235

A Method for Measuring the Hardness of the Surface Layer on Hot Forging Dies Using a Nanoindenter  

NASA Astrophysics Data System (ADS)

The properties and characteristics of the surface layer of forging dies are critical for understanding and controlling wear. However, the surface layer is very thin, and appropriate property measurements are difficult to obtain. The objective of the present study is to determine if nanoindenter testing provides a reliable method, which could be used to measure the surface hardness in forging die steels. To test the reliability of nanoindenter testing, nanoindenter values for two quenched and tempered steels (FX and H13) are compared to microhardness and macrohardness values. These steels were heat treated for various times to produce specimens with different values of hardness. The heat-treated specimens were tested using three different instruments—a Rockwell hardness tester for macrohardness, a Vickers hardness tester for microhardness, and a nanoindenter tester for fine scale evaluation of hardness. The results of this study indicate that nanoindenter values obtained using a Nanoindenter XP Machine with a Berkovich indenter reliably correlate with Rockwell C macrohardness values, and with Vickers HV microhardness values. Consequently, nanoindenter testing can provide reliable results for analyzing the surface layer of hot forging dies.

Mencin, P.; van Tyne, C. J.; Levy, B. S.

2009-11-01

236

A vocation of value.  

PubMed

What are the qualities needed to be a nurse? Hard working? Good sense of humour? A lovely smile? Oodles of common sense? These are the desirable attributes of nursing portrayed often by the popular press, even by nurses themselves. PMID:24779824

Leary, Alison

2014-04-30

237

Compressibility and hardness of Co-based bulk metallic glass: A combined experimental and density functional theory study  

NASA Astrophysics Data System (ADS)

An incompressible Co54Ta11B35 bulk metallic glass (BMG) was investigated using in situ high-pressure synchrotron diffraction and nanoindendation. The elastic constants were deduced from the experiments based on the isotropic model. The Vickers hardness was measured to be 17.1 GPa. The elastic moduli and hardness are the highest values known in BMGs. The theoretically calculated elastic properties by density-functional study were well consistent with experimental measurements. The analysis of charge density and bonding character indicates the covalent character of Co-B and B-B bonds, underlying the unusually high elastic modulus and hardness in this material.

Wang, Jianfeng; Li, Ran; Xiao, Ruijuan; Xu, Tao; Li, Yan; Liu, Zengqian; Huang, Lu; Hua, Nengbin; Li, Gong; Li, Yanchun; Zhang, Tao

2011-10-01

238

Evaluation of HardSys/HardDraw, an expert system for electromagnetic interactions modelling  

NASA Astrophysics Data System (ADS)

The Department of National Defense and the National Research Council have sponsored the development of HardSys/HardDraw, an expert system for the modelling of electromagnetic interactions in complex systems. This report gives a description of HardSys/HardDraw and reviews the main concepts used in its design. Various aspects of its implementation, user interaction and modelling concepts are evaluated. Some deficiencies are identified and enhancements are proposed to overcome them. Concepts of uncertainty are reviewed and an approach using confidence factors and fuzzy arithmetic is developed. A new method relating both the frequency and time domains is presented and is applied for the calculation of failure index and shielding effectiveness.

Dion, Marc

1993-05-01

239

The anode performance of the hard carbon for the lithium ion battery derived from the oxygen-containing aromatic precursors  

Microsoft Academic Search

The hard carbon is attractive for the Li ion secondary battery because of its higher capacity than the theoretical value of 372Ahkg?1 based on the composition of stage 1 Li-intercalated graphite, LiC6. However, the structure of hard carbon as an anode has not been optimized and the reaction mechanism also has not been clarified in detail. In the present study,

Hiroyuki Fujimoto; Katsuhisa Tokumitsu; Akihiro Mabuchi; Natarajan Chinnasamy; Takahiro Kasuh

2010-01-01

240

Evaporation and condensation on a plane condensed phase - Numerical analysis of the linearized Boltzmann equation for hard-sphere molecules  

Microsoft Academic Search

The behavior of a semi-infinite expanse of a gas bounded by its plane condensed phase, where evaporation or condensation is taking place, is considered on the basis of the linearized Boltzmann equation for hard-sphere molecules. The half-space boundary-value problem of the linearized Boltzmann equation for hard-sphere molecules is solved numerically by the finite difference method introduced in the temperature jump

Yoshio Sone; Taku Ohwada; Kazuo Aoki

1989-01-01

241

Depletion effects in smectic phases of hard-rod-hard-sphere mixtures  

Microsoft Academic Search

.  It is known that when hard spheres are added to a pure system of hard rods the stability of the smectic phase may be greatly\\u000a enhanced, and that this effect can be rationalised in terms of depletion forces. In the present paper we first study the effect\\u000a of orientational order on depletion forces in this particular binary system, comparing our

Y. Martinez-Ratón; Giorgio Cinacchi; Enrique Velasco; Luis Mederos

2006-01-01

242

Application of the hard and soft acids and bases concept to explain ligand coordination in double salt structures  

NASA Astrophysics Data System (ADS)

The coordination polyhedra in 43 double salt structures are examined. Each structure is formed by at least two kinds of polyhedra. The differences in the environment around the metal ions are explained using HSAB concept. The values of hardness for 25 cations are calculated according to Klopman. A factor ? = Hacid· Hbase, where H is the hardness value, is introduced. The value of this factor can be used as a criterion for the stability of the complexes. The possibilities which the ? factor gives in explaining ligand coordination in known structures as well as for predicting structures for double salts are illustrated.

Balarew, Christo; Duhlev, Rumen

1984-11-01

243

Solar cell nanotechnology for improved efficiency and radiation hardness  

NASA Astrophysics Data System (ADS)

Space electronic equipment, and NASA future exploration missions in particular, require improvements in solar cell efficiency and radiation hardness. Novel nano-engineered materials and quantum-dot array based photovoltaic devices promise to deliver more efficient, lightweight solar cells and arrays which will be of high value to long term space missions. In this paper, we describe issues related to the development of the quantum-dot based solar cells and comprehensive software tools for simulation of the nanostructure-based photovoltaic cells. Some experimental results used for the model validation are also reviewed. The novel modeling and simulation tools for the quantum-dot-based nanostructures help to better understand and predict behavior of the nano-devices and novel materials in space environment, assess technologies, devices, and materials for new electronic systems as well as to better evaluate the performance and radiation response of the devices at an early design stage. The overall objective is to investigate and design new photovoltaic structures based on quantum dots (QDs) with improved efficiency and radiation hardness. The inherently radiation tolerant quantum dots of variable sizes maximize absorption of different light wavelengths, i.e., create a "multicolor" cell, which improves photovoltaic efficiency and diminishes the radiation-induced degradation. The QD models described here are being integrated into the advanced photonic-electronic device simulator NanoTCAD, which can be useful for the optimization of QD superlattices as well as for the development and exploring of new solar cell designs.

Fedoseyev, Alexander I.; Turowski, Marek; Shao, Qinghui; Balandin, Alexander A.

2006-09-01

244

Nonequilibrium thermodynamics in sheared hard-sphere materials.  

PubMed

We combine the shear-transformation-zone (STZ) theory of amorphous plasticity with Edwards' statistical theory of granular materials to describe shear flow in a disordered system of thermalized hard spheres. The equations of motion for this system are developed within a statistical thermodynamic framework analogous to that which has been used in the analysis of molecular glasses. For hard spheres, the system volume V replaces the internal energy U as a function of entropy S in conventional statistical mechanics. In place of the effective temperature, the compactivity X=?V/?S characterizes the internal state of disorder. We derive the STZ equations of motion for a granular material accordingly, and predict the strain rate as a function of the ratio of the shear stress to the pressure for different values of a dimensionless, temperature-like variable near a jamming transition. We use a simplified version of our theory to interpret numerical simulations by Haxton, Schmiedeberg, and Liu, and in this way are able to obtain useful insights about internal rate factors and relations between jamming and glass transitions. PMID:23005087

Lieou, Charles K C; Langer, J S

2012-06-01

245

Hard-on-Hard Lubrication in the Artificial Hip under Dynamic Loading Conditions  

PubMed Central

The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal.

Sonntag, Robert; Reinders, Jorn; Rieger, Johannes S.; Heitzmann, Daniel W. W.; Kretzer, J. Philippe

2013-01-01

246

Hard-on-hard lubrication in the artificial hip under dynamic loading conditions.  

PubMed

The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal. PMID:23940772

Sonntag, Robert; Reinders, Jörn; Rieger, Johannes S; Heitzmann, Daniel W W; Kretzer, J Philippe

2013-01-01

247

Dimensional crossover of hard parallel cylinders confined on cylindrical surfaces.  

PubMed

We derive, from the dimensional-crossover criterion, a fundamental-measure density functional for parallel hard curved rectangles moving on a cylindrical surface. We derive it from the density functional of circular arcs of length ? with centers of mass located on an external circumference of radius R(0). The latter functional in turn is obtained from the corresponding two-dimensional functional for a fluid of hard disks of radius R on a flat surface with centers of mass confined onto a circumference of radius R(0). Thus the curved length of closest approach between the two centers of mass of hard disks on this circumference is ?=2R(0)sin(-1)(R/R(0)), the length of the circular arcs. From the density functional of circular arcs, and by applying a dimensional expansion procedure to the spatial dimension orthogonal to the plane of the circumference, we finally obtain the density functional of curved rectangles of edge lengths ? and L. Along with the derivation, we show that, when the centers of mass of the disks are confined to the exterior circumference of a circle of radius R(0),(i) for R(0)>R, the exact Percus one-dimensional (1D) density functional of circular arcs of length 2R(0)sin(-1)(R/R(0)) is obtained, and (ii) for R(0)R, the obtained functional is equivalent to that of parallel hard rectangles on a flat surface of the same lengths, except that now the density profile of curved rectangles is a periodic function of the azimuthal angle, ?(?,z)=?(?+2?,z). The phase behavior of a fluid of aligned curved rectangles is obtained by calculating the free-energy branches of smectic, columnar, and crystalline phases for different values of the ratio R(0)/R in the range 1

Martínez-Ratón, Yuri; Velasco, Enrique

2013-05-01

248

Dimensional crossover of hard parallel cylinders confined on cylindrical surfaces  

NASA Astrophysics Data System (ADS)

We derive, from the dimensional-crossover criterion, a fundamental-measure density functional for parallel hard curved rectangles moving on a cylindrical surface. We derive it from the density functional of circular arcs of length ? with centers of mass located on an external circumference of radius R0. The latter functional in turn is obtained from the corresponding two-dimensional functional for a fluid of hard disks of radius R on a flat surface with centers of mass confined onto a circumference of radius R0. Thus the curved length of closest approach between the two centers of mass of hard disks on this circumference is ?=2R0sin-1(R/R0), the length of the circular arcs. From the density functional of circular arcs, and by applying a dimensional expansion procedure to the spatial dimension orthogonal to the plane of the circumference, we finally obtain the density functional of curved rectangles of edge lengths ? and L. Along with the derivation, we show that, when the centers of mass of the disks are confined to the exterior circumference of a circle of radius R0, (i) for R0>R, the exact Percus one-dimensional (1D) density functional of circular arcs of length 2R0sin-1(R/R0) is obtained, and (ii) for R0R, the obtained functional is equivalent to that of parallel hard rectangles on a flat surface of the same lengths, except that now the density profile of curved rectangles is a periodic function of the azimuthal angle, ?(?,z)=?(?+2?,z). The phase behavior of a fluid of aligned curved rectangles is obtained by calculating the free-energy branches of smectic, columnar, and crystalline phases for different values of the ratio R0/R in the range 1

Martínez-Ratón, Yuri; Velasco, Enrique

2013-05-01

249

Hard and soft acids and bases: atoms and atomic ions.  

PubMed

The structural origin of hard-soft behavior in atomic acids and bases has been explored using a simple orbital model. The Pearson principle of hard and soft acids and bases has been taken to be the defining statement about hard-soft behavior and as a definition of chemical hardness. There are a number of conditions that are imposed on any candidate structure and associated property by the Pearson principle, which have been exploited. The Pearson principle itself has been used to generate a thermodynamically based scale of relative hardness and softness for acids and bases (operational chemical hardness), and a modified Slater model has been used to discern the electronic origin of hard-soft behavior. Whereas chemical hardness is a chemical property of an acid or base and the operational chemical hardness is an experimental measure of it, the absolute hardness is a physical property of an atom or molecule. A critical examination of chemical hardness, which has been based on a more rigorous application of the Pearson principle and the availability of quantitative measures of chemical hardness, suggests that the origin of hard-soft behavior for both acids and bases resides in the relaxation of the electrons not undergoing transfer during the acid-base interaction. Furthermore, the results suggest that the absolute hardness should not be taken as synonymous with chemical hardness but that the relationship is somewhat more complex. Finally, this work provides additional groundwork for a better understanding of chemical hardness that will inform the understanding of hardness in molecules. PMID:18510287

Reed, James L

2008-07-01

250

Process for casting hard-faced, lightweight camshafts and other cylindrical products  

DOEpatents

A process for casting a hard-faced cylindrical product such as an automobile camshaft includes the steps of: (a) preparing a composition formed from a molten base metal and an additive in particle form and having a hardness value greater than the hardness value of the base metal; (b) introducing the composition into a flask containing a meltable pattern of a cylindrical product such as an automobile camshaft to be manufactured and encased in sand to allow the composition to melt the pattern and assume the shape of the pattern within the sand; and (c) rotating the flask containing the pattern about the longitudinal axes of both the flask and the pattern as the molten base metal containing the additive in particle form is introduced into the flask to cause particles of the additive entrained in the molten base metal to migrate by centrifugal action to the radial extremities of the pattern and thereby provide a cylindrical product having a hardness value greater at it's radial extremities than at its center when the molten base metal solidifies.

Hansen, Jeffrey S. (Corvallis, OR); Turner, Paul C. (Albany, OR); Argetsinger, Edward R. (Albany, OR); Wilson, Rick D. (Corvallis, OR)

1996-01-01

251

Structure of Rigid Hard-Ring Fluids  

NASA Astrophysics Data System (ADS)

Structure of fluids of molecules consisting of rigid rings of hard spheres is studied in two, quasi two, and three dimensions, using Monte Carlo computer simulations in the canonical ensemble. For rings of various size and for a wide range of densities, results are reported for the pair distribution function of the ring centers and for the pair distribution of the ring orientations. For dense fluids in two dimensions, a shoulder, precursor of the freezing transition, is observed in the second peak of the pair distribution function of the ring centers, as previously seen in the simple hard-sphere fluid. In quasi two dimensions, where the centers of the rings are confined to a plane but the rings themselves can wobble out of plane, a liquid crystalline nematic phase is observed at sufficiently high densities. Results are also presented for three dimensions.

Nouri, Mariam; Robert, Marc

2011-03-01

252

Laser ablated hard coating for microtools  

DOEpatents

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

McLean, II, William (Oakland, CA); Balooch, Mehdi (Berkeley, CA); Siekhaus, Wigbert J. (Berkeley, CA)

1998-05-05

253

Laser ablated hard coating for microtools  

DOEpatents

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10--20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode. 12 figs.

McLean, W. II; Balooch, M.; Siekhaus, W.J.

1998-05-05

254

The gray-scale ink-jet printer: value in making hard copies of digital images.  

PubMed

Referring physicians often are supplied with copies of images to illustrate a report of the findings of a radiologic study or so that the radiologist can retain the original images. The increasing costs of production, film, and recovery of chemicals have enhanced the requirement for a clean, low-cost dry printing process. An ink-jet gray-scale paper printer (Unitone, Scitex Medical Systems, Bedford, MA) can print high-quality (300 dots per inch [dpi]) images with an effective 10-bit gray scale range by using the Hertz continuous ink-jet method [1-3], which does not require the use of a darkroom or hazardous chemicals. Several types of media (matte paper, glossy paper, transparency film) with a printing area of 26.9 x 43.7 cm (10.6 x 17.4 inches) may be used. The consumables are approximately 50-70% less expensive than the cost of silver halide film, providing a cost advantage over film for referral and archival copies. The results of an initial evaluation of the ink-jet printer at our institution are reported here. PMID:7998544

Combs, M J; Snell, J; Cail, W S; Maier, T; Buck, D A

1995-01-01

255

Stopping the Brain Drain of Skilled Veteran Teachers: Retaining and Valuing Their Hard-Won Experience  

ERIC Educational Resources Information Center

Veteran educators are being encouraged to take early retirement in order to create jobs for less-experienced, lower-paid novices. Veteran educators are not alone: early retirement promotions have become the norm for aging workers in America. Consequently, there is a brain-drain of skilled workers at the national, state, and local levels. The early…

Fibkins, William L.

2011-01-01

256

Conformal Solution Theory: Hard-Sphere Mixtures  

Microsoft Academic Search

Conformal solution theory is examined. It is suggested that most difficulties associated with previous applications of this theory arise from the use of concentration-independent reference fluids. For the particular case of a hard-sphere mixture, it is shown that if the reference fluid is chosen so as to make the first-order term in the theory vanish, good results are obtained.

Douglas Henderson; Peter J. Leonard

1971-01-01

257

The Boltzmann equation for very hard particles  

Microsoft Academic Search

The nonlinear Boltzmann equation is solved analytically for general initial distributions in a (spatially homogeneous) system of very hard particles (VHP) with two translational degrees of freedom and with a transition probability for binary collisions (vw -->v'w') proportional to delta(v2 + w2 - v'2 -w'2). The scattering cross-section corresponding to this model increases as the square root of the collision

E. M. Hendriks; M. H. Ernst

1983-01-01

258

Hard-sphere fluid in infinite dimensions  

NASA Technical Reports Server (NTRS)

The exact Mayer series is derived for the pressure, density, and equation of state of a hard-sphere fluid in the limit of infinite space dimensions D. The Mayer series can be analytically continued into the full (cut) activity plane, and there is no sign of a phase transition. The quantum-mechanical system is also treated. For D = infinity, the fluid behaves like an ideal Bose gas and undergoes a Bose-Einstein condensation.

Wyler, D.; Rivier, N.; Frisch, H. L.

1987-01-01

259

Threshold corrections to hard supersymmetric relations  

NASA Astrophysics Data System (ADS)

We compute the one-loop threshold corrections to hard supersymmetric relations involving gauge and gaugino couplings for the case of a Split-SUSY-like spectrum with moderate splitting. We show that these contributions are small, however in principle they will typically have to be taken into account if the heavy scalar sector is below 100 TeV and if one reaches, at future linear colliders, the precision that is necessary to perform this kind of measurements.

Giardino, Pier Paolo; Lodone, Paolo

2014-06-01

260

Hard spheres on the gyroid surface  

PubMed Central

We find that 48/64 hard spheres per unit cell on the gyroid minimal surface are entropically self-organized. Striking evidence is obtained in terms of the acceptance ratio of Monte Carlo moves and order parameters. The regular tessellations of the spheres can be viewed as hyperbolic tilings on the Poincaré disc with a negative Gaussian curvature, one of which is, equivalently, the arrangement of angels and devils in Escher's Circle Limit IV.

Dotera, Tomonari; Kimoto, Masakiyo; Matsuzawa, Junichi

2012-01-01

261

Radiation Hardness Assurance for Space Systems  

NASA Technical Reports Server (NTRS)

The space radiation environment can lead to extremely harsh operating conditions for on-board electronic box and systems. The characteristics of the radiation environment are highly dependent on the type of mission (date, duration and orbit). Radiation accelerates the aging of the electronic parts and material and can lead to a degradation of electrical performance; it can also create transient phenomena on parts. Such damage at the part level can induce damage or functional failure at electronic box, subsystem, and system levels. A rigorous methodology is needed to ensure that the radiation environment does not compromise the functionality and performance of the electronics during the system life. This methodology is called hardness assurance. It consists of those activities undertaken to ensure that the electronic piece parts placed in the space system perform to their design specifications after exposure to the space environment. It deals with system requirements, environmental definitions, part selection, part testing, shielding and radiation tolerant design. All these elements should play together in order to produce a system tolerant to.the radiation environment. An overview of the different steps of a space system hardness assurance program is given in section 2. In order to define the mission radiation specifications and compare these requirements to radiation test data, a detailed knowledge of the space environment and the corresponding electronic device failure mechanisms is required. The presentation by J. Mazur deals with the Earth space radiation environment as well as the internal environment of a spacecraft. The presentation by J. Schwank deals with ionization effects, and the presentation by T. Weatherford deals with Single particle Event Phenomena (SEP) in semiconductor devices and microcircuits. These three presentations provide more detailed background to complement the sections 3 and 4. Part selection and categorization are discussed in section 5. Section 6 presents the organization of the hardness assurance within a project. Section 7 discusses emerging radiation hardness assurance issues.

Poivey, Christian; Day, John H. (Technical Monitor)

2002-01-01

262

Nanotwinned diamond with unprecedented hardness and stability.  

PubMed

Although diamond is the hardest material for cutting tools, poor thermal stability has limited its applications, especially at high temperatures. Simultaneous improvement of the hardness and thermal stability of diamond has long been desirable. According to the Hall-Petch effect, the hardness of diamond can be enhanced by nanostructuring (by means of nanograined and nanotwinned microstructures), as shown in previous studies. However, for well-sintered nanograined diamonds, the grain sizes are technically limited to 10-30?nm (ref. 3), with degraded thermal stability compared with that of natural diamond. Recent success in synthesizing nanotwinned cubic boron nitride (nt-cBN) with a twin thickness down to ?3.8?nm makes it feasible to simultaneously achieve smaller nanosize, ultrahardness and superior thermal stability. At present, nanotwinned diamond (nt-diamond) has not been fabricated successfully through direct conversions of various carbon precursors (such as graphite, amorphous carbon, glassy carbon and C60). Here we report the direct synthesis of nt-diamond with an average twin thickness of ?5?nm, using a precursor of onion carbon nanoparticles at high pressure and high temperature, and the observation of a new monoclinic crystalline form of diamond coexisting with nt-diamond. The pure synthetic bulk nt-diamond material shows unprecedented hardness and thermal stability, with Vickers hardness up to ?200?GPa and an in-air oxidization temperature more than 200?°C higher than that of natural diamond. The creation of nanotwinned microstructures offers a general pathway for manufacturing new advanced carbon-based materials with exceptional thermal stability and mechanical properties. PMID:24919919

Huang, Quan; Yu, Dongli; Xu, Bo; Hu, Wentao; Ma, Yanming; Wang, Yanbin; Zhao, Zhisheng; Wen, Bin; He, Julong; Liu, Zhongyuan; Tian, Yongjun

2014-06-12

263

Hard Pion Electroproduction at Medium Energies  

SciTech Connect

Even at moderate energy machines, there is a regime where hard pion electroproduction proceeds by a perturbatively calculable process. The process, they claim, is not the leading twist fragmentation one but rather a higher twist process that produces kinematically isolated pions. Semiexclusive data may teach us more about parton distribution functions of the target and the pion distribution amplitude. In addition, there is a connection to generalized parton distribution calculations of exclusive processes in that the perturbative kernel is the same. The subject of this report is semiexclusive photoproduction of hard pions, and the semiexclusive deep inelastic scattering version of the same, e + p {yields} e + {pi} + X, which we can also write as p(e,e{prime}{prime})X. The authors are interested in pions with large transverse momentum (that is what ''hard'' means), and particularly in pions that are kinematically isolated, rather than pions that are part of a jet. And further, they shall hope to isolate processes that can be calculated perturbatively using Quantum Chromodynamics (QCD).

Andrei Afanasev; Carl E. Carlson

2002-09-01

264

Hard diffraction and deep inelastic scattering  

SciTech Connect

Since the advent of hard-collision physics, the study of diffractive processes - shadow physics - has been less prominent than before. However, there is now a renewed interest in the subject, especially in that aspect which synthesizes the short-distance, hard-collision phenomena with the classical physics of large rapidity-gaps. This is especially stimulated by the recent data on deep-inelastic scattering from HERA, as well as the theoretical work which relates to it. The word diffraction is sometimes used by high-energy physicists in a loose way. The author defines this term to mean: A diffractive process occurs if and only if there is a large rapidity gap in the produced-particle phase space which is not exponentially suppressed. Here a rapidity gap means essentially no hadrons produced into the rapidity gap (which operates in the {open_quotes}lego{close_quotes} phase-space of pseudo-rapidity and azimuthal angle). And non-exponential suppression implies that the cross-section for creating a gap with width {Delta}{eta} does not have a power-law decrease with increasing subenergy s=e{sup {Delta}{eta}}, but behaves at most like some power of pseudorapidity {Delta}{eta}{approx}log(s). The term hard diffraction shall simply refer to those diffractive process which have jets in the final-state phase-space.

Bjorken, J.D.

1994-04-01

265

Characterization of Radiation Hard Silicon Materials  

SciTech Connect

Segmented silicon detectors are widely used in modern high-energy physics (HEP) experiments due to their excellent spatial resolution and well-established manufacturing technology. However, in such experiments the detectors are exposed to high fluences of particle radiation, which causes irreversible crystallographic defects in the silicon material. Since 1990's, considerable amount of research has gone into improving the radiation hardness of silicon detectors. One very promising approach is to use magnetic Czochralski silicon (MCz-Si) that has been found to be more radiation hard against charged hadrons than traditional Float Zone silicon material (Fz-Si) used in the current HEP applications. Other approaches include operating the devices at cryogenic temperatures and designing special detector structures such as p-type detectors or semi-3D detectors. In order to demonstrate that the developed technologies are suitable for the HEP experiments, it is necessary to extensively characterize the potentially radiation hard detectors. We have an excellent instrument for this, the Cryogenic Transient Current Technique (C-TCT) measurement setup, which is an effective research tool for studying heavily irradiated silicon detectors. With the C-TCT setup it is possible to extract the full depletion voltage, effective trapping time, electric field distribution and the sign of the space charge in the silicon bulk in the temperature range of 45-300 K. This articles presents a description of this setup and measurement results from detectors processed of MCz-Si.

Luukka, P.; Li, Z.; J. Harkonen, E. Tuovinen, S. Czellar, V. Eremin, E. Tuominen, E. Verbitskaya

2009-02-24

266

Hard-tip, soft-spring lithography.  

PubMed

Nanofabrication strategies are becoming increasingly expensive and equipment-intensive, and consequently less accessible to researchers. As an alternative, scanning probe lithography has become a popular means of preparing nanoscale structures, in part owing to its relatively low cost and high resolution, and a registration accuracy that exceeds most existing technologies. However, increasing the throughput of cantilever-based scanning probe systems while maintaining their resolution and registration advantages has from the outset been a significant challenge. Even with impressive recent advances in cantilever array design, such arrays tend to be highly specialized for a given application, expensive, and often difficult to implement. It is therefore difficult to imagine commercially viable production methods based on scanning probe systems that rely on conventional cantilevers. Here we describe a low-cost and scalable cantilever-free tip-based nanopatterning method that uses an array of hard silicon tips mounted onto an elastomeric backing. This method-which we term hard-tip, soft-spring lithography-overcomes the throughput problems of cantilever-based scanning probe systems and the resolution limits imposed by the use of elastomeric stamps and tips: it is capable of delivering materials or energy to a surface to create arbitrary patterns of features with sub-50-nm resolution over centimetre-scale areas. We argue that hard-tip, soft-spring lithography is a versatile nanolithography strategy that should be widely adopted by academic and industrial researchers for rapid prototyping applications. PMID:21270890

Shim, Wooyoung; Braunschweig, Adam B; Liao, Xing; Chai, Jinan; Lim, Jong Kuk; Zheng, Gengfeng; Mirkin, Chad A

2011-01-27

267

Shock waves in dense hard disk fluids  

NASA Astrophysics Data System (ADS)

Media composed of colliding hard disks (2D) or hard spheres (3D) serve as good approximations for the collective hydrodynamic description of gases, liquids and granular media. In the present study, the compressible hydrodynamics and shock dynamics are studied for a two-dimensional hard-disk medium at both the continuum and discrete particle level descriptions. For the continuum description, closed form analytical expressions for the inviscid hydrodynamic description, shock Hugoniot, isentropic exponent and shock jump conditions were obtained using the Helfand equation of state. The closed-form analytical solutions permitted us to gain physical insight into the role of the material's density on its compressibility, i.e. how the medium compresses under mechanical loadings and sustains wave motion. Furthermore, the predictions were found in excellent agreement with calculations using the event driven molecular dynamics method involving 30,000 particles over the entire range of compressibility spanning the dilute ideal gas and liquid phases. In all cases, it was found that the energy imparted by the piston motion to the thermalized medium behind the propagating shock was quasi-independent of the medium's packing fraction, with a correction vanishing with increasing shock Mach numbers.

Sirmas, N.; Tudorache, M.; Barahona, J.; Radulescu, M. I.

2012-05-01

268

Condensation transition in polydisperse hard rods.  

PubMed

We study a mass transport model, where spherical particles diffusing on a ring can stochastically exchange volume v, with the constraint of a fixed total volume V= sum(i=1) (N)v(i), N being the total number of particles. The particles, referred to as p-spheres, have a linear size that behaves as v(i) (1/p) and our model thus represents a gas of polydisperse hard rods with variable diameters v(i) (1/p). We show that our model admits a factorized steady state distribution which provides the size distribution that minimizes the free energy of a polydisperse hard-rod system, under the constraints of fixed N and V. Complementary approaches (explicit construction of the steady state distribution on the one hand; density functional theory on the other hand) completely and consistently specify the behavior of the system. A real space condensation transition is shown to take place for p>1; beyond a critical density a macroscopic aggregate is formed and coexists with a critical fluid phase. Our work establishes the bridge between stochastic mass transport approaches and the optimal polydispersity of hard sphere fluids studied in previous articles. PMID:20078144

Evans, M R; Majumdar, S N; Pagonabarraga, I; Trizac, E

2010-01-01

269

Confined Hard Disk Two Piston System Model  

NSDL National Science Digital Library

The Confined Hard Disk Two Piston System simulates a constant-energy two-dimensional system of unit mass particles confined by two frictionless pistons of equal mass M. This computer model complements theoretical work describing the adiabatic expansion of an ideal gas using the quasi-static approximation. Users can set the number of particles N, their diameter and their initial particle kinetic energy. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The time evolution of temperature, pressure, and piston speed are shown in a second window.   Particles in this model have unit mass and interact through contact forces. Collision times are computed analytically because particles and pistons move with constant velocity between collisions. The time evolution algorithm advances the particle position from collision to collision until the requested time step is achieved. The time evolution is then paused, data is accumulated, and the screen is redrawn. The Confined Hard Disk Two Piston System was developed using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_hd_ConfinedHardDiskTwoPistonSystem.jar file will run the program if Java is installed.

Christian, Wolfgang

2011-03-09

270

Hard and soft spectral states of ULXs  

NASA Astrophysics Data System (ADS)

I discuss some differences between the observed spectral states of ultraluminous X-ray sources (ULXs) and the canonical scheme of spectral states defined in Galactic black holes. The standard interpretation of ULXs with a curved spectrum, or a moderately steep power-law with soft excess and high-energy downturn, is that they are an extension of the very high state, up to luminosities {? 1}-3 L_Edd. Two competing models are Comptonization in a warm corona, and slim disk; I suggest bulk motion Comptonization in the radiatively-driven outflow as another possibility. The interpretation of ULXs with a hard power-law spectrum is more problematic. Some of them remain in that state over a large range of luminosities; others switch directly to a curved state without going through a canonical high/soft state. I suggest that those ULXs are in a high/hard state not seen in Galactic black holes; that state may overlap with the low/hard state at lower accretion rates, and extend all the way to Eddington accretion rates. If some black holes can reach Eddington accretion rates without switching to a standard-disk-dominated state, it is also possible that they never quench their steady jets.

Soria, R.

2011-05-01

271

Demosaicing: heterogeneity-projection hard-decision adaptive interpolation using spectral-spatial correlation  

NASA Astrophysics Data System (ADS)

A novel heterogeneity-projection hard-decision adaptive interpolation (HPHD-AI) algorithm is proposed in this paper for color reproduction from Bayer mosaic images. The proposed algorithm aims to estimate the optimal interpolation direction and perform hard-decision interpolation, in which the decision is made before interpolation. To do so, a new heterogeneity-projection scheme based on spectral-spatial correlation is proposed to decide the best interpolation direction from the original mosaic image directly. Exploiting the proposed heterogeneity-projection scheme, a hard-decision rule can be designed easily to perform the interpolation. We have compared this technique with three recently proposed demosaicing techniques: Lu's, Gunturk's and Li's methods, by utilizing twenty-five natural images from Kodak PhotoCD. The experimental results show that HPHD-AI outperforms all of them in both PSNR values and S-CIELab ??*ab measures.

Tsai, Chi-Yi; Song, Kai-Tai

2006-02-01

272

Characterization of Indentation Impressions on Human Enamel for Hardness Measurement.  

National Technical Information Service (NTIS)

This paper presents results from investigating indentation impressions on human enamel under micro-hardness tests. The experiments of hardness testing were performed on a microhardness indentation machine under different loading conditions. Images of inde...

G. Zhang D. T. Le S. R. Tucker S. J. Ng

2006-01-01

273

Survival of Southern Hard Clams in Refrigerated Storage.  

National Technical Information Service (NTIS)

Hard clam (quahog) fishing along the southeastern coasts of the United States has been a traditional fishery, but recent levels of production suggest the present resource may be underutilized. Commercial hard clams harvested in Florida are primarily the n...

W. S. Otwell J. A. Koburger S. W. Andree

1986-01-01

274

The material co-construction of hard science fiction and physics  

NASA Astrophysics Data System (ADS)

This article explores the relationship between hard science fiction and physics and a gendered culture of science. Empirical studies indicate that science fiction references might spur some students' interest in physics and help develop this interest throughout school, into a university education and even further later inspire the practice of doing science. There are many kinds of fiction within the science fiction genre. In the presented empirical exploration physics students seem particularly fond of what is called `hard science fiction': a particular type of science fiction dealing with technological developments (Hartwell and Cramer in The hard SF renaissance, Orb/TOR, New York, 2002). Especially hard science fiction as a motivating fantasy may, however, also come with a gender bias. The locally materialized techno-fantasies spurring dreams of the terraforming of planets like Mars and travels in time and space may not be shared by all physics students. Especially female students express a need for other concerns in science. The entanglement of physics with hard science fiction may thus help develop some students' interest in learning school physics and help create an interest for studying physics at university level. But research indicates that especially female students are not captured by the hard techno-fantasies to the same extent as some of their male colleagues. Other visions (e.g. inspired by soft science fiction) are not materialized as a resource in the local educational culture. It calls for an argument of how teaching science is also teaching cultural values, ethics and concerns, which may be gendered. Teaching materials, like the use of hard science fiction in education, may not just be (yet another) gender bias in science education but also carrier of particular visions for scientific endeavours.

Hasse, Cathrine

2014-02-01

275

A study of the mechanism of hardness change of Al-Zn-Mg alloy during retrogression reaging treatments by small angle X-ray scattering (SAXS)  

SciTech Connect

In this work, the changes in hardness of Al-Zn-Mg alloy during retrogression and reaging (RRA) treatments were detected and the mechanism of the hardness change was studied by Small Angle X-ray Scattering (SAXS). It was discovered that the hardness changes during RRA treatments are as follows. (1) Hardness decreases at the beginning of retrogression, achieves a minimum value at 90 seconds, and then increases and achieves the second maximum value at 6 minutes, and finally decreases simply. (2) Hardness of the reaged sample is higher than that of the retrogressed sample. The following conclusions were drawn from the experimental results of SAXS. (1) The drop in hardness for short retrogression time is attributed to the decrease of volume fraction of the precipitates and the growth of the particles; the drop in hardness with increasing retrogression time after the second maximum of hardness achieved is attributed to coarsening of the particles. (2) The increase in hardness during reaging is due to the occurrence of new precipitates and the increase of volume fraction of the precipitates.

Meng, C.; Long, H.; Zheng, Y. [Jilin Univ., Changchun (China). Materials Science Inst.

1997-10-01

276

Hard X-ray Microscopic Images of the Human Hair  

NASA Astrophysics Data System (ADS)

The better visualization of the human organs or internal structure is challenging to the physicist and physicians. It can lead to more understanding of the morphology, pathophysiology and the diagnosis. Conventionally used methods to investigate cells or architectures, show limited value due to sample processing procedures and lower resolution. In this respect, Zernike type phase contrast hard x-ray microscopy using 6.95keV photon energy has advantages. We investigated hair fibers of the normal healthy persons. Coherence based phase contrast images revealed three distinct structures of hair, medulla, cortex, and cuticular layer. Some different detailed characters of each sample were noted. And further details would be shown and these results would be utilized as basic data of morphologic study of human hair.

Goo, Jawoong; Jeon, Soo Young; Oh, Tak Heon; Hong, Seung Phil; Yon, Hwa Shik; Lee, Won-Soo

2007-01-01

277

The effect of cold spray impact velocity on deposit hardness  

NASA Astrophysics Data System (ADS)

The deposition and consolidation of metal powders by means of cold spray is a method where powder particles are accelerated to high velocity through entrainment in a gas undergoing expansion in a de Laval nozzle and are subsequently impacted upon a surface. The impacted powder particles form a consolidated structure which can be several centimeters thick. The characteristics of this structure depend on the initial characteristics of the metal powder and upon impact velocity. Initially soft particles are strain hardened during impact, resulting in a structure that can have a hardness value greater than that which can be achieved by conventional cold working. A materials model is proposed for these phenomena, and model calculation is compared with experimental data from cold sprayed copper and aluminum.

Champagne, Victor K.; Helfritch, Dennis J.; Trexler, Matthew D.; Gabriel, Brian M.

2010-09-01

278

Osmium diboride, an ultra-incompressible, hard material.  

PubMed

The need for wear- and scratch-resistant materials drives the quest for new superhard materials. In this work, we apply two design parameters to identify ultra-incompressible, superhard materials-high valence electron density and high bond covalency. Our first example of such a material is OsB2. The bulk modulus of OsB2 was measured using in situ high-pressure X-ray diffraction and was determined to be in the range of 365-395 GPa. While this value is slightly less than that of the bulk modulus of diamond, due to the anisotropic crystal structure of OsB2, the axis compressibility in the orthorhombic c-direction is less than the axis compressibility found in diamond. OsB2 also scratches the surface of a sapphire window, indicating that the hardness of OsB2 exceeds 2000 kg/mm2. PMID:15898746

Cumberland, Robert W; Weinberger, Michelle B; Gilman, John J; Clark, Simon M; Tolbert, Sarah H; Kaner, Richard B

2005-05-25

279

Hard X-ray Microscopic Images of the Human Hair  

SciTech Connect

The better visualization of the human organs or internal structure is challenging to the physicist and physicians. It can lead to more understanding of the morphology, pathophysiology and the diagnosis. Conventionally used methods to investigate cells or architectures, show limited value due to sample processing procedures and lower resolution. In this respect, Zernike type phase contrast hard x-ray microscopy using 6.95keV photon energy has advantages. We investigated hair fibers of the normal healthy persons. Coherence based phase contrast images revealed three distinct structures of hair, medulla, cortex, and cuticular layer. Some different detailed characters of each sample were noted. And further details would be shown and these results would be utilized as basic data of morphologic study of human hair.

Goo, Jawoong; Jeon, Soo Young; Oh, Tak Heon; Hong, Seung Phil; Lee, Won-Soo [Department of Dermatology and Institute of Hair and Cosmetic Medicine, Yonsei University Wonju College of Medicine, Wonju (Korea, Republic of); Yon, Hwa Shik [Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang (Korea, Republic of)

2007-01-19

280

Influence of pore pressure on drilling response in hard shales  

SciTech Connect

Results are presented from laboratory drilling studies of two different hard shales similar to those found in some areas of the North Sea. Two laboratory drilling machines will milled-tooth bits were used. Pore pressure was measured in all the experiments, and in some it was reduced to several megapascals below bottomhole pressure (BHP). Pore-pressure reduction was achieved by allowing the pore fluid to drain out of the shale while external stresses were maintained constant. The influence of BHP was studied for values from 3 to 33 MPa (435 to 4,786 psi). The differential pressure, which equals BHP minus pore pressure, ranged from near balance to > 10 MPa (>1,450 psi). BHP was found to have a strong influence on drilling response, but differential pressure did not, contrary to conventional wisdom. The results are compared with other drilling experiments and single-cutting experiments in the literature.

Gray-Stephens, D.; Cook, J.M.; Sheppard, M.C.

1994-12-01

281

STRONGER KEY DERIVATION VIA SEQUENTIAL MEMORY-HARD FUNCTIONS  

Microsoft Academic Search

We introduce the concepts of memory-hard algorithms and se- quential memory-hard functions, and argue that in order for key derivation functions to be maximally secure against attacks using custom hardware, they should be constructed from sequential memory-hard functions. We present a family of key derivation functions which, under the random oracle model of cryptographic hash functions, are provably sequential memory-hard,

COLIN PERCIVAL

282

New York Sea Grant's Hard Clam Research Initiative  

NSDL National Science Digital Library

This New York Sea Grant website hosts the Hard Clam Research Initiative, a program launched in October 1999 to investigate the population dynamics of hard clams in Long Island's south shore estuary. The site features links to program information, the research projects involved, facts about hard clams and the hard clam industry, a list of publications, media links, and contact information. It also includes a "What's New" column that highlights current events associated with the project.

Focazio, Paul C.; Grant, New Y.

283

Fault-Tolerant, Radiation-Hard DSP  

NASA Technical Reports Server (NTRS)

Commercial digital signal processors (DSPs) for use in high-speed satellite computers are challenged by the damaging effects of space radiation, mainly single event upsets (SEUs) and single event functional interrupts (SEFIs). Innovations have been developed for mitigating the effects of SEUs and SEFIs, enabling the use of very-highspeed commercial DSPs with improved SEU tolerances. Time-triple modular redundancy (TTMR) is a method of applying traditional triple modular redundancy on a single processor, exploiting the VLIW (very long instruction word) class of parallel processors. TTMR improves SEU rates substantially. SEFIs are solved by a SEFI-hardened core circuit, external to the microprocessor. It monitors the health of the processor, and if a SEFI occurs, forces the processor to return to performance through a series of escalating events. TTMR and hardened-core solutions were developed for both DSPs and reconfigurable field-programmable gate arrays (FPGAs). This includes advancement of TTMR algorithms for DSPs and reconfigurable FPGAs, plus a rad-hard, hardened-core integrated circuit that services both the DSP and FPGA. Additionally, a combined DSP and FPGA board architecture was fully developed into a rad-hard engineering product. This technology enables use of commercial off-the-shelf (COTS) DSPs in computers for satellite and other space applications, allowing rapid deployment at a much lower cost. Traditional rad-hard space computers are very expensive and typically have long lead times. These computers are either based on traditional rad-hard processors, which have extremely low computational performance, or triple modular redundant (TMR) FPGA arrays, which suffer from power and complexity issues. Even more frustrating is that the TMR arrays of FPGAs require a fixed, external rad-hard voting element, thereby causing them to lose much of their reconfiguration capability and in some cases significant speed reduction. The benefits of COTS high-performance signal processing include significant increase in onboard science data processing, enabling orders of magnitude reduction in required communication bandwidth for science data return, orders of magnitude improvement in onboard mission planning and critical decision making, and the ability to rapidly respond to changing mission environments, thus enabling opportunistic science and orders of magnitude reduction in the cost of mission operations through reduction of required staff. Additional benefits of COTS-based, high-performance signal processing include the ability to leverage considerable commercial and academic investments in advanced computing tools, techniques, and infra structure, and the familiarity of the science and IT community with these computing environments.

Czajkowski, David

2011-01-01

284

Chronic toxicity of chloride to freshwater species: effects of hardness and implications for water quality guidelines.  

PubMed

Toxicity tests using nine freshwater species (Ceriodaphnia dubia, Daphnia magna, Oncorhynchus mykiss, Pimephales promelas, Lumbriculus variegatus, Tubifex tubifex, Chironomus dilutus, Hyallela azteca, and Brachionus calyciflorus) were conducted to evaluate their sensitivity to chloride. Acute-to-chronic ratios (ACRs) from these tests indicate the ACR of 7.59 employed by the United States Environmental Protection Agency (U.S. EPA) in deriving its water quality guideline for chloride may be conservative; a revised ACR of 3.50 is presented here. The endpoints used to calculate the ACR included 24-h to 96-h median lethal concentrations (LC50s) for acute tests, and 48-h to 54-d inhibition concentration (ICx) values for growth or reproduction for chronic exposures. Data from the present chronic toxicity tests, and other investigators, were used to propose a water quality guideline for long-term exposure to chloride using a species sensitivity distribution (SSD) approach. The 5th percentile from the SSD was calculated as 307?mg/L and proposed as the water quality guideline. Cladocerans were the most sensitive species in the dataset. Ceriodaphnia dubia was used to evaluate the relationship between water hardness and sensitivity to chloride. A strong relationship was observed and was used to establish a hardness-related equation to modify the proposed water quality guideline on the basis of water hardness, resulting in values ranging from 64?mg/L chloride at 10?mg/L hardness to 388?mg/L chloride at 160?mg/L hardness (as CaCO?). These data suggest that current water quality guidelines for chloride may be overly conservative in water with moderate-to-high hardness, and may not be sufficiently protective under soft-water conditions. PMID:20872898

Elphick, James R F; Bergh, Kelli D; Bailey, Howard C

2011-01-01

285

Runaway electron energy measurement using hard x-ray spectroscopy in "Damavand" tokamak.  

PubMed

Set of experiments has been developed to study existing runaway electrons in "Damavand" tokamak plasma upon characteristics of hard x-ray emissions produced by collision of the runaway electrons with the plasma particles and limiters. As a first step, spatial distribution of hard x-ray emissions on the equatorial plane of the torus was considered. Obtained spectra of hard x-ray emissions for different alignments of shielded detector indicate isotropic emissivity in the equatorial plane. This is in agreement with wide angle cone of bremsstrahlung radiations, deduced from the mean value of energy of the runaway electrons. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons. In the second stage in order to investigate time evolution of energy of the runaway electrons, similar technique were applied to obtain hard x-ray energy in every 3 ms intervals, from the beginning to the end of plasma. The mean energy of the runaway electrons increases during the ramp up phase and reaches its maximum between 3 and 9 ms after plasma formation. Also considering the time dependence of the counted photons in each energy range shows that energetic photons are emitted during the ramp up phase of the plasma current in Damavand tokamak. PMID:19191433

Rasouli, C; Iraji, D; Farahbod, A H; Akhtari, K; Rasouli, H; Modarresi, H; Lamehi, M

2009-01-01

286

Runaway electron energy measurement using hard x-ray spectroscopy in 'Damavand' tokamak  

SciTech Connect

Set of experiments has been developed to study existing runaway electrons in ''Damavand'' tokamak plasma upon characteristics of hard x-ray emissions produced by collision of the runaway electrons with the plasma particles and limiters. As a first step, spatial distribution of hard x-ray emissions on the equatorial plane of the torus was considered. Obtained spectra of hard x-ray emissions for different alignments of shielded detector indicate isotropic emissivity in the equatorial plane. This is in agreement with wide angle cone of bremsstrahlung radiations, deduced from the mean value of energy of the runaway electrons. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons. In the second stage in order to investigate time evolution of energy of the runaway electrons, similar technique were applied to obtain hard x-ray energy in every 3 ms intervals, from the beginning to the end of plasma. The mean energy of the runaway electrons increases during the ramp up phase and reaches its maximum between 3 and 9 ms after plasma formation. Also considering the time dependence of the counted photons in each energy range shows that energetic photons are emitted during the ramp up phase of the plasma current in Damavand tokamak.

Rasouli, C.; Farahbod, A. H.; Rasouli, H.; Lamehi, M. [School of Plasma Physics and Nuclear Fusion, Institute of Nuclear Science and Technology, AEOI, P.O. Box 14155-1339, Tehran (Iran, Islamic Republic of); Iraji, D. [Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CH-1015 (Switzerland); Akhtari, K. [Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Modarresi, H. [Department of Mechanical Engineering, Sharif University of Technology, P.O. Box 11365-9567, Tehran (Iran, Islamic Republic of)

2009-01-15

287

The ridge gap waveguide as a wideband rectangular hard waveguide  

Microsoft Academic Search

The present paper will give an overview of the research on hard surfaces and hard waveguides leading to the wideband ridge gap waveguide. The overview will be supported by both computed and measured results of the performance of hard waveguides and gap waveguides, clearly showing the wide bandwidth and low losses of the latter. This is a major improvement compared

Per-Simon Kildal; Malcolm Ng Mou Kehn

2010-01-01

288

21 CFR 133.148 - Hard grating cheeses.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Hard grating cheeses. 133.148 Section 133...Related Products § 133.148 Hard grating cheeses. (a) The cheeses for which...are prescribed by this section are hard grating cheeses for which specifically...

2009-04-01

289

21 CFR 133.148 - Hard grating cheeses.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Hard grating cheeses. 133.148 Section 133...Related Products § 133.148 Hard grating cheeses. (a) The cheeses for which...are prescribed by this section are hard grating cheeses for which specifically...

2010-04-01

290

Crystallization of hard-sphere colloids in microgravity  

Microsoft Academic Search

The structure of, and transitions between, liquids, crystals and glasses have commonly been studied with the hard-sphere model, in which the atoms are modelled as spheres that interact only through an infinite repulsion on contact. Suspensions of uniform colloidal polymer particles are good approximations to hard spheres, and so provide an experimental model system for investigating hard-sphere phases. They display

Jixiang Zhu; Min Li; R. Rogers; W. Meyer; R. H. Ottewill; W. B. Russel; P. M. Chaikin

1997-01-01

291

Hard-facing with electro-spark deposition. Final report  

Microsoft Academic Search

A common method to improve wear resistance of metals in rubbing contact is to increase their surface hardness. Electro-Spark Deposition is a process which uses capacitive discharge pulses of high current passing through a hard carbide electrode in contact with and scanning the metal surface to be hardened. The result is a thin, hard, adherent coating of carbide deposited with

Kees

1983-01-01

292

Characterization of tempered martensite embrittlement using hardness measurement  

Microsoft Academic Search

A series of experiments were carried out on three commercial steels to explore the possibility for characterizing tempered martensite embrittlement (TME) by Rockwell, macro- and micro-Vickers hardness tests. The results indicate distinct hardness peaks in two steels and an inflection in the other around the TME temperature. A new analytical approach for examining the slope of hardness-tempering temperature plots appear

A. Ghosh; A. Bhaduri; K. K. Ray

1994-01-01

293

Simulation of hardness distribution in quenched steel specimen  

Microsoft Academic Search

Hardness distribution in quenched steel specimen for two different steels with different hardenability has been investigated using 3D numerical simulation. Numerical simulation is consisted of computation of steel cooling curve and computation of hardness in specimen points. Numerical calculations of hardness distribution in steel specimen for two different steels and comparison of calculated results have been performed in order to

B. Smoljan; D. Rubeöa; S. Smokvina Hanz

294

Future for Hard Fibers and Competition from Synthetics.  

National Technical Information Service (NTIS)

The world's hard-fibers economy, already in a period of crisis, faces an uncertain future. Severe pressure from synthetic substitutes threatens the very future of the hard-fibers industry. The paper examines the structure of the hard-fibers economy, as we...

E. R. Grilli

1975-01-01

295

On the Performance of Thin Hard Coatings for Gearing Applications  

Microsoft Academic Search

Thin hard coatings are possible candidates for the enhancement of scuffing and micro-pitting performance of gears. They exhibit very high levels of surface hardness (typically 1000 HV) combined with a low traction coefficient (typically 0.2) against dry steel. The paper presents the results of an experimental program carried out in order to assess the scuffing performance of thin hard coatings

M. P. Alanou; R. W. Snidle; H. P. Evans; T. L. Krantz

2002-01-01

296

MicroHardness and Adhesion of Boron Carbon Nitride Coatings  

Microsoft Academic Search

Boron carbon nitride coatings have been synthesized by the pulsed laser deposition method. Vickers micro-hardness and adhesion of the coatings were studied. A new model was applied to determine the hardness of the coatings which were too thin to be directly measured by the Vickers micro-hardness test. An intermediate layer of silicon was used to enhance the adhesion of the

Hou Qingrun; J. Gao

1997-01-01

297

ESTABLISHMENT OF A HARDNESS METROLOGICAL SYSTEM IN BRAZIL  

Microsoft Academic Search

In the present work, part of a large project, developed in partnership among INMETRO, ITUC\\/PUC- Rio and INT since 1995, to establish a national hardness metrological system in Brazil to Brinell, Vickers and Rockwell hardness scales, is presented, e.g. the development of reference blocks, for different ranges of Rockwell B and C hardness scales. These results and the installation of

J. A. Cruz; R. R. Machado; S. P. Oliveira; A. R. Martins; A. C. Vidal; J. A. S. Pereira; I. Caminha; I. Abud; C. Barbosa

298

UNCERTAINTY EVALUATION OF THE REFERENCE HARDNESS STANDARD OF SLOVENIA  

Microsoft Academic Search

A commercial hardness testing machine has been provided to represent a reference hardness standard in Slovenia. Various hardness scales which are important for calibration purposes are realized on this machine. The evaluation of measurement uncertainty is one of the most important tasks for establishing this reference standard. Therefore the influence quantities contributing to the uncertainty are determined and the calibration

Konrad Herrmann

299

Study of hot hardness characteristics of tool steels  

NASA Technical Reports Server (NTRS)

Hardness measurements of tool steel materials in electric furnace at elevated temperatures and low oxygen environment are discussed. Development of equation to predict short term hardness as function of intial room temperature hardness of steel is reported. Types of steel involved in the process are identified.

Chevalier, J. L.; Dietrich, M. W.; Zaretsky, E. V.

1972-01-01

300

Tool crater wear depth modeling in CBN hard turning  

Microsoft Academic Search

Hard turning has been receiving increased attention because it offers many possible benefits over grinding in machining hardened steel. The wear of cubic boron nitride (CBN) tools, which are commonly used in hard turning, is an important issue that needs to be better understood. For hard turning to be a viable replacement technology, the high cost of CBN cutting tools

Yong Huang; Ty G. Dawson

2005-01-01

301

The Effect of Friabilin on Wheat Grain Hardness  

Microsoft Academic Search

A wheat marketing system established the primary classification of hexaploid wheat based on the endosperm texture, i.e. hardness or softness of the grain. Hardness affects a range of characters including the milling (tempering, milling yield, flour particle size, shape and density of flour particles), baking and end-use properties. Wheat grain hardness is largely controlled by genetic factors but it can

Daniela MIKULÍKOVÁ

2007-01-01

302

Development of method for evaluating cell hardness and correlation between bacterial spore hardness and durability  

PubMed Central

Background Despite the availability of conventional devices for making single-cell manipulations, determining the hardness of a single cell remains difficult. Here, we consider the cell to be a linear elastic body and apply Young’s modulus (modulus of elasticity), which is defined as the ratio of the repulsive force (stress) in response to the applied strain. In this new method, a scanning probe microscope (SPM) is operated with a cantilever in the “contact-and-push” mode, and the cantilever is applied to the cell surface over a set distance (applied strain). Results We determined the hardness of the following bacterial cells: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and five Bacillus spp. In log phase, these strains had a similar Young’s modulus, but Bacillus spp. spores were significantly harder than the corresponding vegetative cells. There was a positive, linear correlation between the hardness of bacterial spores and heat or ultraviolet (UV) resistance. Conclusions Using this technique, the hardness of a single vegetative bacterial cell or spore could be determined based on Young’s modulus. As an application of this technique, we demonstrated that the hardness of individual bacterial spores was directly proportional to heat and UV resistance, which are the conventional measures of physical durability. This technique allows the rapid and direct determination of spore durability and provides a valuable and innovative method for the evaluation of physical properties in the field of microbiology.

2012-01-01

303

High-order virial coefficients and equation of state for hard sphere and hard disk systems.  

PubMed

A very simple and accurate approach is proposed to predict the high-order virial coefficients of hard spheres and hard disks. In the approach, the nth virial coefficient B(n) is expressed as the sum of n(D-1) and a remainder, where D is the spatial dimension of the system. When n > or = 3, the remainders of the virials can be accurately expressed with Padé-type functions of n. The maximum deviations of predicted B(5)-B(10) for the two systems are only 0.0209%-0.0044% and 0.0390%-0.0525%, respectively, which are much better than the numerous existing approaches. The virial equation based on the predicted virials diverges when packing fraction eta = 1. With the predicted virials, the compressibility factors of hard sphere system can be predicted very accurately in the whole stable fluid region, and those in the metastable fluid region can also be well predicted up to eta = 0.545. The compressibility factors of hard disk fluid can be predicted very accurately up to eta = 0.63. The simulated B(7) and B(10) for hard spheres are found to be inconsistent with the other known virials and therefore they are modified as 53.2467 and 105.042, respectively. PMID:19830321

Hu, Jiawen; Yu, Yang-Xin

2009-11-01

304

Evaluation of degree of conversion and hardness of dental composites photo-activated with different light guide tips  

PubMed Central

Objective: The aim of this study was to evaluate the degree of conversion and hardness of different composite resins, photo-activated for 40 s with two different light guide tips, fiber optic and polymer. Methods: Five specimens were made for each group evaluated. The percentage of unreacted carbon double bonds (% C?C) was determined from the ratio of absorbance intensities of aliphatic C?C (peak at 1637 cm?1) against internal standard before and after curing of the specimen: aromatic C-C (peak at 1610 cm?1). The Vickers hardness measurements were performed in a universal testing machine. A 50 gf load was used and the indenter with a dwell time of 30 seconds. The degree of conversion and hardness mean values were analyzed separately by ANOVA and Tukey’s test, with a significance level set at 5%. Results: The mean values of degree of conversion for the polymer and fiber optic light guide tip were statistically different (P<.001). The hardness mean values were statistically different among the light guide tips (P<.001), but also there was difference between top and bottom surfaces (P<.001). Conclusions: The results showed that the resins photo-activated with the fiber optic light guide tip promoted higher values for degree of conversion and hardness.

Galvao, Marilia Regalado; Caldas, Sergei Godeiro Fernandes Rabelo; Bagnato, Vanderlei Salvador; de Souza Rastelli, Alessandra Nara; de Andrade, Marcelo Ferrarezi

2013-01-01

305

Values and Youth.  

ERIC Educational Resources Information Center

Every social studies teacher must consciously move to relate his course to the value dilemmas of youth and the value-laden issues of our time. A variety of writings by youth have been included to serve as source materials for classroom teachers and to provide significant insights into the values of youth. The section, Values in the Classroom:…

Barr, Robert D., Ed.

306

Values: A Symposium Report.  

ERIC Educational Resources Information Center

This publication brings together a set of four papers prepared for a symposium on values at the 1972 annual meeting of the American Educational Research Association. The first paper, by Fred N. Kerlinger, establishes a rationale for values research. The discussion focuses on the definition of values, relationship between values and attitudes,…

Ryan, T. A., Ed.

307

Teaching for Value.  

ERIC Educational Resources Information Center

The suggestion to equate values with purpose is considered. The advantage of value development over moral development is that values apply to a broader category of ideas while morality has a more confined and narrow application. All students and teachers should attempt to become both creators and appreciators of values. (JN)

Jarrett, James L.

1980-01-01

308

Values and Creativity.  

ERIC Educational Resources Information Center

The paper discusses creativity and the creative process, cites current methods used to improve creativity in the workplace, and explains the concept of values and value systems as they relate to creativity. Values and value systems are defined; and their source, their nature and functions, and their measurement are outlined. (JDD)

Fernald, Lloyd W., Jr.

1987-01-01

309

Land Values, 2012 Summary.  

National Technical Information Service (NTIS)

The United States farm real estate value, a measurement of the value of all land and buildings on farms, averaged $2,650 per acre for 2012, up 10.9 percent from revised 2011 values. Regional changes in the average value of farm real estate ranged from a 2...

2012-01-01

310

Influence of shade and irradiation time on the hardness of composite resins.  

PubMed

This study tested the following hypotheses: 1. increasing light irradiation time (IT) produces greater values of superficial hardness on different depths (0 and 3 mm); and 2. a dark shade composite (A3) needs longer IT than a light shade composite (A1) to produce similar hardness. Disk-shaped specimens (n=24 per shade) were fabricated using a 3-mm-thick increment of composite resin (Z100). Specimens were randomly assigned to 3 groups (n=8) according to the IT (400 mW/cm2) at the upper (U) surface: A1-10 and A3-10: 10 s; A1-20 and A3-20: 20 s; A1-40 and A3-40: 40 s. Specimens were stored in black lightproof containers at 37 masculineC for 24 h before indentation in a hardness tester. Three Vickers indentations were performed on the U and lower (L) surfaces of each specimen. The indent diagonals were measured and the hardness value calculated. The results were analyzed statistically by ANOVA and Tukey's test (alpha=0.05). Statistically significant differences were found between U and L surfaces of each composite shade-IT combination (p=0.0001) and among the ITs of same shade-surface combination (p=0.0001), except between groups A1-20U and A1-40U, confirming the study hypothesis 1 and partially rejecting the hypothesis 2. PMID:18176715

Della Bona, Alvaro; Rosa, Vinícius; Cecchetti, Dileta

2007-01-01

311

CO2 laser milling of hard tissue  

NASA Astrophysics Data System (ADS)

Drilling of bone and tooth tissue belongs to recurrent medical procedures (screw- and pin-bores, bores for implant inserting, trepanation etc.). Small round bores can be in general quickly produced with mechanical drills. Problems arise however by angled drilling, by the necessity to fulfill the drilling without damaging of sensitive soft tissue beneath the bone, or by the attempt to mill precisely noncircular small cavities. We present investigations on laser hard tissue "milling", which can be advantageous for solving these problems. The "milling" is done with a CO2 laser (10.6 ?m) with pulse duration of 50 - 100 ?s, combined with a PC-controlled galvanic beam scanner and with a fine water-spray, which helps to avoid thermal side-effects. The damaging of underlying soft tissue can be prevented through control of the optical or acoustical ablation signal. The ablation of hard tissue is accompanied with a strong glowing, which is absent during the laser beam action on soft tissue. The acoustic signals from the diverse tissue types exhibit distinct differences in the spectral composition. Also computer image analysis could be a useful tool to control the operation. Laser "milling" of noncircular cavities with 1 - 4 mm width and about 10 mm depth is particularly interesting for dental implantology. In ex-vivo investigations we found conditions for fast laser "milling" of the cavities without thermal damage and with minimal tapering. It included exploration of different filling patterns (concentric rings, crosshatch, parallel lines and their combinations), definition of maximal pulse duration, repetition rate and laser power, optimal position of the spray. The optimized results give evidences for the applicability of the CO2 laser for biologically tolerable "milling" of deep cavities in the hard tissue.

Werner, Martin; Ivanenko, Mikhail; Harbecke, Daniela; Klasing, Manfred; Steigerwald, Hendrik; Hering, Peter

2007-03-01

312

Non-leading logarithms in principal-value resummation  

Microsoft Academic Search

We apply the method of principal-value resummation of large momentum-dependent radiative corrections to the calculation of the Drell-Yan cross section. We sum all next-to-leading logarithms and provide numerical results for the resummed exponent and the corresponding hard scattering function.

Lyndon Alvero; Harry Contopanagos

1995-01-01

313

Non-leading logarithms in principle value resummation.  

SciTech Connect

We apply the method of principal-value resummation of large momentum-dependent radiative corrections to the calculation of the Drell-Yan cross section. We sum all next-to-leading logarithms and provide numerical results for the resummed exponent and the corresponding hard scattering function.

Alvero, L.; Contopanagos, H.; High Energy Physics; State Univ. of New York at Stony Brook

1995-02-20

314

Non-leading logarithms in principle value resummation  

Microsoft Academic Search

We apply the method of principal-value resummation of large momentum-dependent radiative corrections to the calculation of the Drell-Yan cross section. We sum all next-to-leading logarithms and provide numerical results for the resummed exponent and the corresponding hard scattering function.

L. Alvero; H. Contopanagos

1995-01-01

315

The hardness assurance wafer probe - HAWP  

NASA Astrophysics Data System (ADS)

Complete radiation sensitivity assessments of integrated circuits can now be performed at the wafer level using a new system, the Hardness Assurance Wafer Probe, HAWP. This system utilizes a pulsed Nd:YAG infrared laser impinging on the backside of the wafer to evaluate the transient behavior of the circuits. A low energy X ray source collimated to a single die site actually performs total dose irradiations. Finally, special electrical measurements are used to enable a prediction of the neutron sensitivity of bipolar devices. The HAWP System is described and correlations of wafer probe results to conventional radiation tests for a digital part type are provided.

King, E. E.; Tettemer, G. L.; Linderman, P. B.; Micheletti, P. E.

1983-12-01

316

Second virial coefficients of dipolar hard spheres  

NASA Astrophysics Data System (ADS)

An asymptotic formula is reported for the second virial coefficient B2 of a dipolar hard-sphere (DHS) fluid, in zero external field, for strongly coupled dipolar interactions. This simple formula, together with the one for the weak-coupling B2, provides an accurate prediction of the second virial coefficient for a wide range of dipole moments, including those that are experimentally accessible in magnetite ferrofluids. The weak-coupling B2 also yields an estimate of the magnetic moment minimally needed for isotropic gas-liquid phase-separation, if any, in the DHS fluid.

Philipse, Albert P.; Kuipers, Bonny W. M.

2010-08-01

317

Ultrafast switching of hard X-rays.  

PubMed

A new concept for shortening hard X-ray pulses emitted from a third-generation synchrotron source down to few picoseconds is presented. The device, called the PicoSwitch, exploits the dynamics of coherent acoustic phonons in a photo-excited thin film. A characterization of the structure demonstrates switching times of ??5?ps and a peak reflectivity of ?10(-3). The device is tested in a real synchrotron-based pump-probe experiment and reveals features of coherent phonon propagation in a second thin film sample, thus demonstrating the potential to significantly improve the temporal resolution at existing synchrotron facilities. PMID:24562559

Gaal, Peter; Schick, Daniel; Herzog, Marc; Bojahr, André; Shayduk, Roman; Goldshteyn, Jevgeni; Leitenberger, Wolfram; Vrejoiu, Ionela; Khakhulin, Dmitry; Wulff, Michael; Bargheer, Matias

2014-03-01

318

Survival of Hard-on-Hard Bearings in Total Hip Arthroplasty: A Systematic Review  

Microsoft Academic Search

Background  Improvements in prosthetic materials, designs, and implant fixation for THA have led to bearing surface wear being the limitation\\u000a of this technology. Hard-on-hard bearings promise decreased wear rates and increased survival. However, there may be different\\u000a survival rates based on bearing materials, manufacturing technologies, and femoral component designs. Additionally, survival\\u000a rate variability may be based on study design.\\u000a \\u000a \\u000a \\u000a \\u000a Questions\\/purposes  We determined

Michael G. Zywiel; Siraj A. Sayeed; Aaron J. Johnson; Thomas P. Schmalzried; Michael A. Mont

2011-01-01

319

Magnetic susceptibility and hardness of Au-xPt-yNb alloys for biomedical applications.  

PubMed

Metal devices in the human body induce serious metal artifacts in magnetic resonance imaging (MRI). Metals artifacts are mainly caused by a volume magnetic susceptibility (?v) mismatch between a metal device and human tissue. In this research, Au-xPt-yNb alloys were developed for fabricating MRI artifact-free biomedical metal devices. The magnetic properties, hardness and phase constitutions of these alloys were investigated. The Au-xPt-8Nb alloys showed satisfactory ?v values. Heat treatments did not clearly change the ?v values for Au-xPt-8Nb alloys. The Vickers hardness (HV) of these two alloys was much higher than that of high-Pt alloys; moreover, aging at 700°C increased the HV values of these two alloys. A dual phase structure consisting of face-centered cubic ?1 and ?2 phases was observed and aging at 700°C promoted phase separation. The Au-5Pt-8Nb and Au-10Pt-8Nb alloys showed satisfactory ?v values and high hardness and are thus suggested as candidates for MRI artifact-free alloys for biomedical applications. PMID:23747327

Uyama, Emi; Inui, Shihoko; Hamada, Kenichi; Honda, Eiichi; Asaoka, Kenzo

2013-09-01

320

Exploring Existence Value  

NASA Astrophysics Data System (ADS)

The notion that individuals value the preservation of water resources independent of their own use of these resources is discussed. Issues in defining this value, termed "existence value," are explored. Economic models are employed to assess the role of existence value in benefit-cost analysis. The motives underlying existence value are shown to matter to contingent valuation measurement of existence benefits. A stylized contingent valuation experiment is used to study nonusers' attitudes regarding projects to improve water quality in the Chesapeake Bay. Survey results indicate that altruism is one of the motives underlying existence value and that goods other than environmental and natural resources may provide existence benefits.

Madariaga, Bruce; McConnell, Kenneth E.

1987-05-01

321

Effects of explosions in hard rocks  

SciTech Connect

This work relates to explosions in hard rocks (ex: basalt, granite, limestone{hor_ellipsis}). Hard rock masses typically have a blocky structure created by the existence of geologic discontinuities such as bedding contacts, faults, and joints. At very high pressure-hundreds of kilobars and above-these discontinuities do not act separately, and the rock appears to be an equivalent continuous medium. At stress of a few tens of kilobars and below, the geologic discontinuities control the kinematics of the rock masses. Hence, the simulation of rock dynamics, anywhere but in the very-near source region, should account for those kinematics. In the very high pressure range continuum-based analysis is appropriate. In the discrete motion range one could consider: an equivalent continuum approach with anisotropy and plasticity. However, this is unlikely to provide the right kinematics; embedding discontinuities in continuum models, such as using joint elements and slip surfaces in finite elements. Typically, these are limited in terms of the separation of elements which may reconnect arbitrarily to new elements; complete discrete methods; ex: discrete elements, discontinuous displacement analysis (DDA). Discrete elements have progressed further than DDA We have chosen to develop and apply discrete elements models to explosion phenomenology in rocks.

Heuze, F.E.; Walton, O.R.; Maddix, D.M.; Shaffer, R.J.; Butkovich, T.R.

1993-05-01

322

Experimental investigation of hard pellicle purge processes  

NASA Astrophysics Data System (ADS)

Optical lithography with 157-nm light is expected to bridge the gap between 193-nm technology and next-generation lithography. One important practical difficulty facing the implementation of 157-nm technology is gas absorption of 157-nm light. The exposure process for 193-nm technology is carried out in air. However, oxygen and water vapor attenuate 157-nm radiation. Alternatively, the exposure can be carried out in a nitrogen-purged environment. The purification of the volume trapped between the reticle and the hard pellicle is challenging because of the delicate pellicle geometry. In this paper, experimental results are presented that support the design and development of pellicle purge processes for 157-nm optical lithography. Specifically, a hard pellicle was installed in the Pressure Bulge Tool (at the UW Computational Mechanics Center) and experimental measurements of the pressure-induced pellicle distortion were obtained. The pressure loads imposed on the pellicle are representative of those expected during in-tool purge processes. Separate testing quantified the pellicle fracture stress and the flow characteristics of the pellicle/reticle geometry for a particular vent configuration (i.e., frame vent hole size and number, and filter system). These flow characteristics are important, as they ultimately dictate the pressure difference imposed on the pellicle during any purging process. These various experimental measurements, when taken together, facilitate the assessment of the feasibility and requirements associated with alternative pellicle purging strategies for 157-nm lithography.

Abdo, Amr Y.; Nellis, Gregory F.; Diab, Aya K.; Cotte, Eric P.; Chalekian, Aaron J.; Engelstad, Roxann L.; Lovell, Edward G.; Peski, Chris V.

2003-12-01

323

LPE Garnet Films Without Hard Bubbles  

Microsoft Academic Search

In previous studies of hard bubbles, these anomalous domains were found to exist in all unimplanted single-layer LPE garnet films at room temperature. We have prepared five garnet film compositions in which it is not possible to generate hard bubbles at room temperature. These compositions are Y0.9Gd1.2Tm0.9Fe4.6Al0.1Ga0.3O12, Y0.9Gd1.5Yb0.6Fe4.5Al0.5O12, Y1.0Gd1.0Er1.0Fe4.5Al0.lGa0.4O12, Y1.5Eu0.75Gd0.75Fe4.4Al0.5Ga0.1O12 and Y2.0Tm1.0Fe4.1Ga0.9O12. All these films were prepared by standard LPE

A. B. Smith; M. Kestigian; W. R. Bekebrede

1974-01-01

324

Hard Real-Time: C++ Versus RTSJ  

NASA Technical Reports Server (NTRS)

In the domain of hard real-time systems, which language is better: C++ or the Real-Time Specification for Java (RTSJ)? Although ordinary Java provides a more productive programming environment than C++ due to its automatic memory management, that benefit does not apply to RTSJ when using NoHeapRealtimeThread and non-heap memory areas. As a result, RTSJ programmers must manage non-heap memory explicitly. While that's not a deterrent for veteran real-time programmers-where explicit memory management is common-the lack of certain language features in RTSJ (and Java) makes that manual memory management harder to accomplish safely than in C++. This paper illustrates the problem for practitioners in the context of moving data and managing memory in a real-time producer/consumer pattern. The relative ease of implementation and safety of the C++ programming model suggests that RTSJ has a struggle ahead in the domain of hard real-time applications, despite its other attractive features.

Dvorak, Daniel L.; Reinholtz, William K.

2004-01-01

325

Exotic hybrid mesons in hard electroproduction  

SciTech Connect

We estimate the sizeable cross section for deep exclusive electroproduction of an exotic J{sup PC}=1{sup -+} hybrid meson in the Bjorken regime. The production amplitude scales like the one for usual meson electroproduction, i.e., as 1/Q{sup 2}. This is due to the nonvanishing leading twist distribution amplitude for the hybrid meson, which may be normalized thanks to its relation to the energy-momentum tensor and to the QCD sum rules technique. The hard amplitude is considered up to next-to-leading order in {alpha}{sub S} and we explore the consequences of fixing the renormalization scale ambiguity through the Brodsky-Lepage-Mackenzie (BLM) procedure. We study the particular case where the hybrid meson decays through a {pi}{eta} meson pair. We discuss the {pi}{eta} generalized distribution amplitude and then calculate the production amplitude for this process. We propose a forward-backward asymmetry in the production of {pi} and {eta} mesons as a signal for the hybrid meson production. We briefly comment on hybrid electroproduction at very high energy, in the diffractive limit where a QCD Odderon exchange mechanism should dominate. The conclusion of our study is that hard electroproduction is a promising way to study exotic hybrid mesons, in particular, at JLAB, HERA (HERMES), or CERN (Compass)

Anikin, I.V. [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna (Russian Federation); LPT, Universite Paris-Sud, 91405-Orsay (France); Pire, B. [CPHT, Ecole Polytechnique, 91128 Palaiseau (France); Szymanowski, L. [Soltan Institute for Nuclear Studies, Warsaw (Poland); Phys. Theor. Fondam., Inst. de Physique, Univ. de Liege, B-4000 Liege (Belgium); Teryaev, O.V. [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna (Russian Federation); Wallon, S. [LPT, Universite Paris-Sud, 91405-Orsay (France)

2005-02-01

326

FlashStore: High Throughput Persistent Key-Value Store  

Microsoft Academic Search

We present FlashStore, a high throughput persistent key-value store, that uses flash memory as a non-volatile cache between RAM and hard disk. FlashStore is designed to store the working set of key-value pairs on flash and use one flash read per key lookup. As the working set changes over time, space is made for the current working set by destaging

Biplob Debnath; Sudipta Sengupta; Jin Li

2010-01-01

327

Consumer value orientation in Vietnam’ urban middle class  

Microsoft Academic Search

Asia’s modern middle class is strongly value oriented, balancing quality (product characteristics) against price. The economic\\u000a crisis may have forced consumers to watch their budgets more closely, but they have not shifted from their basic value orientation\\u000a to strong price orientation. Vietnam provides a good example of this. It was not hit as hard as many Asian countries, but\\u000a it

Mark Speece; ALUE ORIENT; TION IN

2002-01-01

328

Education, Values, and Valuing in Cosmopolitan Perspective  

ERIC Educational Resources Information Center

In this article we describe a cosmopolitan orientation toward the place of values in human life. We argue that a cosmopolitan outlook can assist people in engaging the challenges of being thrown together with others whose roots, traditions, and inheritances differ. We show that cosmopolitanism implies neither an elite nor an aloof posture toward…

Hansen, David T.; Burdick-Shepherd, Stephanie; Cammarano, Cristina; Obelleiro, Gonzalo

2009-01-01

329

ValuePro Stock Value Calculator  

NSDL National Science Digital Library

This online calculator tabulates the baseline valuation for any publicly traded stock. Enter the stock's ticker symbol, and the program will value the stock. Users may also change any of the input for a stock and revalue it. The site contains a brief helpful guide to using online valuation and a thoughtful review of the product from Business Week.

330

A multi-step system for screening and localization of hard exudates in retinal images  

NASA Astrophysics Data System (ADS)

The number of people being affected by Diabetes mellitus worldwide is increasing at an alarming rate. Monitoring of the diabetic condition and its effects on the human body are therefore of great importance. Of particular interest is diabetic retinopathy (DR) which is a result of prolonged, unchecked diabetes and affects the visual system. DR is a leading cause of blindness throughout the world. At any point of time 25 - 44% of people with diabetes are afflicted by DR. Automation of the screening and monitoring process for DR is therefore essential for efficient utilization of healthcare resources and optimizing treatment of the affected individuals. Such automation would use retinal images and detect the presence of specific artifacts such as hard exudates, hemorrhages and soft exudates (that may appear in the image) to gauge the severity of DR. In this paper, we focus on the detection of hard exudates. We propose a two step system that consists of a screening step that classifies retinal images as normal or abnormal based on the presence of hard exudates and a detection stage that localizes these artifacts in an abnormal retinal image. The proposed screening step automatically detects the presence of hard exudates with a high sensitivity and positive predictive value (PPV ). The detection/localization step uses a k-means based clustering approach to localize hard exudates in the retinal image. Suitable feature vectors are chosen based on their ability to isolate hard exudates while minimizing false detections. The algorithm was tested on a benchmark dataset (DIARETDB1) and was seen to provide a superior performance compared to existing methods. The two-step process described in this paper can be embedded in a tele-ophthalmology system to aid with speedy detection and diagnosis of the severity of DR.

Bopardikar, Ajit S.; Bhola, Vishal; Raghavendra, B. S.; Narayanan, Rangavittal

2012-02-01

331

Phase transition induced by a shock wave in hard-sphere and hard-disk systems.  

PubMed

Dynamic phase transition induced by a shock wave in hard-sphere and hard-disk systems is studied on the basis of the system of Euler equations with caloric and thermal equations of state. First, Rankine-Hugoniot conditions are analyzed. The quantitative classification of Hugoniot types in terms of the thermodynamic quantities of the unperturbed state (the state before a shock wave) and the shock strength is made. Especially Hugoniot in typical two possible cases (P-1 and P-2) of the phase transition is analyzed in detail. In the case P-1 the phase transition occurs between a metastable liquid state and a stable solid state, and in the case P-2 the phase transition occurs through coexistence states, when the shock strength changes. Second, the admissibility of the two cases is discussed from a viewpoint of the recent mathematical theory of shock waves, and a rule with the use of the maximum entropy production rate is proposed as the rule for selecting the most probable one among the possible cases, that is, the most suitable constitutive equation that predicts the most probable shock wave. According to the rule, the constitutive equation in the case P-2 is the most promising one in the dynamic phase transition. It is emphasized that hard-sphere and hard-disk systems are suitable reference systems for studying shock wave phenomena including the shock-induced phase transition in more realistic condensed matters. PMID:18698913

Zhao, Nanrong; Sugiyama, Masaru; Ruggeri, Tommaso

2008-08-01

332

BETWEEN A HARD ROCK AND POSTMODERNISM:Opening the Hard Rock Hotel and Casino  

Microsoft Academic Search

Various researchers have promoted the use of ethnographic accounts in subjective descriptions of postmodern spaces. The Hard Rock Hotel and Casino in Las Vegas represents such a space, embodying several key features of postmodern culture. These features include the commodification of image signs and popular culture, the commercial neutralization of signifying practices subversive to capitalism, ephemeral architecture informing ephemeral social

KURT BORCHARD

1998-01-01

333

Multidensity integral-equation theory for short diblock hard-sphere-sticky-hard-sphere chains.  

PubMed

The multidensity Ornstein-Zernike integral equation theory is applied to study a simple model of hard sphere/sticky hard sphere diblock chains. The multidensity integral equation formalism has been successfully used to model the equilibrium structure and thermodynamic properties of homonuclear chains and shorter dimer fluids; to our knowledge it has not been applied to model diblock chains. In this work, a diblock chain fluids is represented by an m-component equal molar mixture of hard spheres with species 1,2,...,mh and sticky hard spheres with species mh+1,mh+2,...,m. Each spherical particle has two attractive sites A and B except species 1 and m, which have only one site per particle. In the limit of complete association, this mixture yields a system of monodisperse diblock chains. A general solution of this model is obtained in the Percus-Yevick, Polymer Percus-Yevick and ideal chain approximations. Both structural and thermodynamic properties of this model are investigated. From this study, a microphase separation is predicted for relatively short diblock symmetric and asymmetric chains. This microphase separation is enhanced at lower temperature and higher density. When chain length increases, the phase transition changes from a microphase level to a macrophase level. The size of microdomain structure is found to be dependent on total chain length, relative ratio of block lengths, temperature, and density. PMID:20481746

Wu, Ning; Chiew, Y C

2010-04-01

334

Hard and Soft AcidBase Behavior in Aqueous Solution: Steric Effects Make Some Metal Ions Hard: A Quantitative Scale of Hardness-Softness for Acids and Bases  

Microsoft Academic Search

The idea of hard and Soft Acids and Bases (HSAB), developed by R. G. Pearson some 30 years ago, has been used as a unifying principle in several texts. In spite of this, HSAB has remained qualitative and largely intuitive. In this article, the behaviour of HSAB in aqueous solution is addressed. A quantitative scale of hardness-softness for acids and

Robert D. Hancock; Arthur E. Martell

1996-01-01

335

4-channel rad-hard delay generation ASIC with 1ns timing resolution for LHC  

SciTech Connect

An ASIC was developed to precisely delay digital signals within the range of 0--24ns in steps of 1ns. To obtain well defined delay values independent of variations in process, supply voltage and temperature, four independent delay channels are controlled by a common control voltage derived from a delay-locked loop (DLL), which is synchronized to an external 40 MHz clock signal. The delay values of the four signal channels and the clock channel can be individually programmed via an I{sup 2}C interface. Due to an automatic reset logic the chip does not need an external reset signal. A first version of the chip was developed in a non-rad-hard 0.8 {micro}m technology and the successful prototype was then transferred to a radiation hard process (DMILL). Measurement results for both chip variants will be presented.

Toifl, T.; Moreira, P.; Marchioro, A. [CERN, Geneva (Switzerland)] [CERN, Geneva (Switzerland); Vari, R. [INFN Roma, Rome (Italy)] [INFN Roma, Rome (Italy)

1999-06-01

336

Values: Lest We Forget.  

National Technical Information Service (NTIS)

This paper examines the Army's individual values of courage, commitment, competence and candor. Each value is examined and further defined through the use of historical vignettes, anecdotes, quotations and interviews. This discussion is followed by sectio...

G. T. Greco

1993-01-01

337

Crop Values. 2007 Summary.  

National Technical Information Service (NTIS)

The 2007 'Crop Values' includes average prices and values of production for major field crops and many specialty crops. All prices in this report are marketing year average (MYA) prices which do not include allowances or adjustments for commodities under ...

2008-01-01

338

Crop Values. 2009 Summary.  

National Technical Information Service (NTIS)

Crop Values includes average prices and values of production for major field crops and many specialty crops. All prices in this report are marketing year average (MYA) prices which do not include allowances or adjustments for commodities under government ...

2010-01-01

339

Crop Values. 2008 Summary.  

National Technical Information Service (NTIS)

Crop Values includes average prices and values of production for major field crops and many specialty crops. All prices in this report are marketing year average (MYA) prices which do not include allowances or adjustments for commodities under government ...

2009-01-01

340

Morality, Values, and Culture.  

ERIC Educational Resources Information Center

Considers the importance of ethical understanding, moral values, and cultural literacy in various aspects of life. Argues that community college leaders have a responsibility to enlighten students and the community with respect to morality, values, and culture. (DMM)

Martin, Warren Bryan

1985-01-01

341

Crop Values, 2011 Summary.  

National Technical Information Service (NTIS)

Crop Values includes average prices and values of production for major field crops and many specialty crops. All prices in this report are marketing year average (MYA) prices which do not include allowances or adjustments for commodities under government ...

2012-01-01

342

Crop Values. 2010 Summary.  

National Technical Information Service (NTIS)

Crop Values includes average prices and values of production for major field crops and many specialty crops. All prices in this report are marketing year average (MYA) prices which do not include allowances or adjustments for commodities under government ...

2011-01-01

343

Science, Values and Objectivity.  

ERIC Educational Resources Information Center

Attempts to ascertain whether the presence of biasing values in the practice of science is an inbuilt feature of an idealized institution, Science, and judges that those values inbuilt to Science are not a source of bias. (Author/MM)

Davson-Galle, Peter

2002-01-01

344

Tetraphosphonated thiophene ligand: mixing the soft and the hard.  

PubMed

The synthesis of ligand LTH8, based on a thiophene framework containing two bis(aminomethyldiphosphonate) functions in the ortho position to the central sulfur atom, is described, together with the characterization of the intermediate compounds. The physico-chemical properties of the ligand were first studied by means of potentiometry and UV-Vis absorption spectrophotometric titrations to determine its pK values. Six successive equilibrium constants were determined in aqueous solutions. The same means were then used to quantify the interactions of the ligand with Ni(ii), Cu(ii) and Zn(ii). Following the conventional Irving-Williams trend, LT was shown to have the highest affinity towards Cu(ii) (log K(CuLT) = 16.11(3)), while Zn(ii) and Ni(ii) showed similar values (log K(MLT) = 10.81(8) and 10.9(1), respectively), revealing a large selectivity of LT toward Cu(ii). Based on a combination of UV-Vis absorption spectroscopy and EPR measurements as a function of pH, along with DFT calculations, the coordination behavior of the hard phosphonate, medium amino and soft thiophene entities are questioned regarding their coordination to the Cu atom. PMID:24788186

Brandel, Jérémy; Lecointre, Alexandre; Kollek, Julien; Michel, Sylvia; Hubscher-Bruder, Véronique; Déchamps-Olivier, Isabelle; Platas-Iglesias, Carlos; Charbonnière, Loïc J

2014-05-28

345

Place Value Rocks!  

NSDL National Science Digital Library

Play these educational math games and test your knowledge of Place Value! Can you use Place Value Blocks to help you represent different digits? Test your ability to write out given numbers into sentences with Cookies! How sharp are your place value skills? Test your knowledge with Golfing with numbers!! Be the hero of the day as you practice place value skills in the Lifeguard game! Reveal the ...

Ms.roberts

2009-03-04

346

Education and Values.  

ERIC Educational Resources Information Center

The role of the university in moral and value issues are discussed in a 1987 inaugural address by the president of Indiana University. He suggests that a college education should include values through both intellectual inquiry and example. Liberty to speak and write is an essential value if faculty and students are to achieve their academic…

Ehrlich, Thomas

347

Measuring Teacher Value Systems.  

ERIC Educational Resources Information Center

The purpose of this study was to develop and assess the psychometric properties of a measure of teacher value systems. Three value systems were defined as values associated with (1) the pursuit of truth, (2) social and interpersonal relations, and (3) authority and its exercise. The scale was taken through three stages of development and field…

Ames, Russell; Lied, Terry

348

Open value creation  

Microsoft Academic Search

Open Value Creation extends Chesbrough's R&D concept of Open Innovation to all value creating processes within organizations. It encompasses all forms of organizational value creation that are enabled or enhanced by the inclusion of external knowledge. I am specifically interested in how organizations can benefit from end-consumer knowledge by opening information resources. Accordingly, the framing research question of the thesis

2010-01-01

349

The American Value System  

ERIC Educational Resources Information Center

The contradictory values in America (i.e., the "new morality" versus traditional morals) are examined along with the attendant ambiguity of the role in which the school is placed as transmitter of cultural values. The search for consensus in value contradictions is also discussed. (LBH)

Nussel, E. J.

1977-01-01

350

Emergy and Nonmarket Value  

EPA Science Inventory

The purpose of this study is to better understand the differences and similarities between emergy and nonmarket economic valuation, when both are applied to value the same policies or development alternatives. The emdollar value of a good or service often exceeds the market value...

351

Values in the Curriculum.  

ERIC Educational Resources Information Center

Teaching for values instead of knowledge would significantly change education. Could the psychosocial values of goodness, beauty, search for truth, social organization, and economics be rank ordered? Can and how should such life-survival values as health, sex, aggression and self-defense, language, and love be taught in school? (Author/SB)

Wees, W. R.

1980-01-01

352

Information Economics: Valuing Information.  

ERIC Educational Resources Information Center

Addresses the question of why previous articles and studies on the value of information have failed to provide meaningful techniques for measuring that value. The discussion covers four principle causes for confusion surrounding the valuation of information and draws conclusions about the value added model of information. (seven references) (CLB)

Brinberg, Herbert R.

1989-01-01

353

Summer Place Value  

NSDL National Science Digital Library

Play some fun games with your new place value skills Match the number words to the standard form to find the place value mystery picture. Can you solve the place value puzzler? Click on easy and follow the instructions. Check your score after the picture is shown. How many tries did it take you to be able to see the picture. If it ...

Korth, Mrs.

2009-07-27

354

Values in Further Education.  

ERIC Educational Resources Information Center

This book explores educational values in the British further education system. Following an introductory discussion of educational values by the editor, John Halliday, the book contains 21 short essays organized in the areas of cultural values, curriculum, and management and staff development. The following are included: "Democratic…

Halliday, John, Ed.

355

Spectroscopic identification of ten faint hard X-ray sources discovered by Chandra  

Microsoft Academic Search

We report optical spectroscopic identifications of 10 hard (2–10 keV) X-ray selected sources discovered by Chandra. The X-ray flux of the sources ranges between 1.5 and 25 ×10?14ergcm?2s?1, the lower value being 3 times fainter than in previous BeppoSAX and ASCA surveys. Their R band magnitudes are in the range 12.8–22. Six of the Chandra sources are broad line quasars

F. Fiore; F. La Franca; C. Vignali; A. Comastri; G. Matt; G. C. Perola; M. Cappi; M. Elvis; F. Nicastro

2000-01-01

356

Phase transitions in self-gravitating systems: Self-gravitating fermions and hard-sphere models  

Microsoft Academic Search

We discuss the nature of phase transitions in self-gravitating systems both in the microcanonical and in the canonical ensemble. We avoid the divergence of the gravitational potential at short distances by considering the case of self-gravitating fermions and hard-sphere models. Depending on the values of the parameters, three kinds of phase transitions (of zeroth, first, and second order) are evidenced.

Pierre-Henri Chavanis

2002-01-01

357

Role of Water Hardness in Rinsing Bacteria from the Skin of Processed Broiler Chickens  

Microsoft Academic Search

The effect of water hardness on the ability of water to rinse bacteria from broiler skin was examined. Very hard water (total hardness = 200 ppm) was prepared by dissolving calcium chloride and magnesium chloride in distilled (soft) water and moderately hard water (total hardness = 100 ppm) was prepared by diluting 1 part very hard with 1 part soft

Ronald Holser

2009-01-01

358

Dynamical localization in a chain of hard core bosons under periodic driving  

NASA Astrophysics Data System (ADS)

We study the dynamics of a one-dimensional lattice model of hard core bosons which is initially in a superfluid phase with a current being induced by applying a twist at the boundary. Subsequently, the twist is removed, and the system is subjected to periodic ?-function kicks in the staggered on-site potential. We present analytical expressions for the current and work done in the limit of an infinite number of kicks. Using these, we show that the current (work done) exhibits a number of dips (peaks) as a function of the driving frequency and eventually saturates to zero (a finite value) in the limit of large frequency. The vanishing of the current (and the saturation of the work done) can be attributed to a dynamic localization of the hard core bosons occurring as a consequence of the periodic driving. Remarkably, we show that for some specific values of the driving amplitude, the localization occurs for any value of the driving frequency. Moreover, starting from a half-filled lattice of hard core bosons with the particles localized in the central region, we show that the spreading of the particles occurs in a light-cone-like region with a group velocity that vanishes when the system is dynamically localized.

Nag, Tanay; Roy, Sthitadhi; Dutta, Amit; Sen, Diptiman

2014-04-01

359

Hard, heat-resistant nickel electrodeposits  

US Patent & Trademark Office Database

An article such as a screen printing cylinder prepared from a hard nickel electrodeposit is characterized by improved resistance to embrittlement when exposed to temperatures above about 200.degree. C. Electrodeposits affording improved resistance to embrittlement contain 0.007-1% sulfur and 0.02-5% manganese. The amount of manganese in the electrodeposits is correlated to the amount of sulfur present so that the manganese is present in an amount in excess of the stoichiometric amount required to form manganese sulfide. The electrodeposits which are also characterized by usefully low levels of internal stress are prepared using conventional nickel plating baths modified by the addition of sources of manganese ions and sulfur.

1978-08-22

360

Radiation hardness of the LHCb Outer Tracker  

NASA Astrophysics Data System (ADS)

This paper presents results on the radiation hardness of the LHCb Outer Tracker (OT) during LHC operation in 2010 and 2011. Modules of the OT have shown to suffer from ageing effects that lead to gain loss, after irradiation in the laboratory. Under irradiation at moderate intensities an insulating layer is formed on the anode wire of the OT straw cells. This ageing effect is caused by contamination of the counting gas due to outgassing of the glue used in the construction of the OT modules. Two methods to monitor gain stability in the OT are presented: module scans with radioactive sources and the study of hit efficiency as a function of amplifier threshold. No gain loss is observed after receiving 1.3 fb-1 of integrated luminosity corresponding to an integrated charge of 0.055 C/cm in the hottest spot of the detector.

van Eijk, D.; Bachmann, S.; Bauer, Th.; Färber, Ch.; Bien, A.; Coco, V.; Deckenhoff, M.; Dettori, F.; Ekelhof, R.; Gersabeck, E.; Karbach, T. M.; Koopman, R.; Kozlinskiy, A.; Langenbruch, Ch.; Linn, Ch.; Merk, M.; Meissner, M.; Morawski, P.; Pellegrino, A.; Serra, N.; Seyfert, P.; Spaan, B.; Swientek, S.; Storaci, B.; Szczekowski, M.; Tuning, N.; Uwer, U.; Visser, E.; Wiedner, D.; Witek, M.

2012-09-01

361

Radiation-hard optical link for SLHC  

NASA Astrophysics Data System (ADS)

We study the feasibility of fabricating an optical link for the SLHC ATLAS silicon tracker based on the current pixel optical link architecture. The electrical signals between the current pixel modules and the optical modules are transmitted via micro-twisted cables. The optical signals between the optical modules and the data acquisition system are transmitted via rad-hard SIMM fibres spliced to rad-tolerant GRIN fibres. The link has several nice features. We have measured the bandwidths of the micro twisted-pair cables to be bsim 1 Gb/s and the fusion spliced fibre ribbon to be bsim 2 Gb/s. We have irradiated PIN and VCSEL arrays with 24 GeV protons and find the arrays survive to the SLHC dosage. We have also demonstrated the feasibility of fabricating a novel opto-pack for housing VCSEL and PIN arrays with BeO as the substrate.

Gan, K. K.; Abi, B.; Fernando, W.; Kagan, H. P.; Kass, R. D.; Law, A.; Lebbai, M. R. M.; Rau, A.; Rizardinova, F.; Skubic, P. L.; Smith, D. S.

2008-05-01

362

Hard-core liquid-crystal fibers  

NASA Astrophysics Data System (ADS)

Self-organized liquid-crystal filamentary forms arise in many mixtures of the smectogen compounds at the transition from the isotropic melt. In some mixtures, a subsequent phase transition to the crystal or crystal smectic phase occurs at the core of the filaments. The resulting hard-core fibers act as anisotropic cylindrical lenses composed of the crystalline core surrounded by the nematic shell. In this work, the filaments, referred to as nematoids, have been obtained in several binary mixtures based on five mesogens: 4,4'-dipentylazoxybenzene, 4-dodecyloxy-4'- pentylbiphenyl, 4-hexyl-4'nonyloxybiphenyl, 4-acetyl-4'-dodecylbiphenyl and 4''-pentylcyclohexyl 4-(4'- pentylcyclohexyl) benzoate within a silicone oil as an inert liquid. To characterize the molecular arrangements within the nematoids, we present the microinterferometric measurements of the refractive index distribution within the fibers and its changes at the phase transitions.

Adamczyk, Antoni

2008-08-01

363

Nanomechanics of hard films on compliant substrates.  

SciTech Connect

Development of flexible thin film systems for biomedical, homeland security and environmental sensing applications has increased dramatically in recent years [1,2,3,4]. These systems typically combine traditional semiconductor technology with new flexible substrates, allowing for both the high electron mobility of semiconductors and the flexibility of polymers. The devices have the ability to be easily integrated into components and show promise for advanced design concepts, ranging from innovative microelectronics to MEMS and NEMS devices. These devices often contain layers of thin polymer, ceramic and metallic films where differing properties can lead to large residual stresses [5]. As long as the films remain substrate-bonded, they may deform far beyond their freestanding counterpart. Once debonded, substrate constraint disappears leading to film failure where compressive stresses can lead to wrinkling, delamination, and buckling [6,7,8] while tensile stresses can lead to film fracture and decohesion [9,10,11]. In all cases, performance depends on film adhesion. Experimentally it is difficult to measure adhesion. It is often studied using tape [12], pull off [13,14,15], and peel tests [16,17]. More recent techniques for measuring adhesion include scratch testing [18,19,20,21], four point bending [22,23,24], indentation [25,26,27], spontaneous blisters [28,29] and stressed overlayers [7,26,30,31,32,33]. Nevertheless, sample design and test techniques must be tailored for each system. There is a large body of elastic thin film fracture and elastic contact mechanics solutions for elastic films on rigid substrates in the published literature [5,7,34,35,36]. More recent work has extended these solutions to films on compliant substrates and show that increasing compliance markedly changes fracture energies compared with rigid elastic solution results [37,38]. However, the introduction of inelastic substrate response significantly complicates the problem [10,39,40]. As a result, our understanding of the critical relationship between adhesion, properties, and fracture for hard films on compliant substrates is limited. To address this issue, we integrated nanomechanical testing and mechanics-based modeling in a program to define the critical relationship between deformation and fracture of nanoscale films on compliant substrates. The approach involved designing model film systems and employing nano-scale experimental characterization techniques to isolate effects of compliance, viscoelasticity, and plasticity on deformation and fracture of thin hard films on substrates that spanned more than two orders of compliance magnitude exhibit different interface structures, have different adhesion strengths, and function differently under stress. The results of this work are described in six chapters. Chapter 1 provides the motivation for this work. Chapter 2 presents experimental results covering film system design, sample preparation, indentation response, and fracture including discussion on the effects of substrate compliance on fracture energies and buckle formation from existing models. Chapter 3 describes the use of analytical and finite element simulations to define the role of substrate compliance and film geometry on the indentation response of thin hard films on compliant substrates. Chapter 4 describes the development and application of cohesive zone model based finite element simulations to determine how substrate compliance affects debond growth. Chapter 5 describes the use of molecular dynamics simulations to define the effects of substrate compliance on interfacial fracture of thin hard tungsten films on silicon substrates. Chapter 6 describes the Workshops sponsored through this program to advance understanding of material and system behavior.

Reedy, Earl David, Jr. (Sandia National Laboratories, Albuquerque, NM); Emerson, John Allen (Sandia National Laboratories, Albuquerque, NM); Bahr, David F. (Washington State University, Pullman, WA); Moody, Neville Reid; Zhou, Xiao Wang; Hales, Lucas (University of Minnesota, Minneapolis, MN); Adams, David Price (Sandia National Laboratories, Albuquerque, NM); Yeager,John (Washington State University, Pullman, WA); Nyugen, Thao D. (Johns Hopkins University, Baltimore, MD); Corona, Edmundo (Sandia National Laboratories, Albuquerque, NM); Kennedy, Marian S. (Clemson University, Clemson, SC); Cordill, Megan J. (Erich Schmid Institute, Leoben, Austria)

2009-09-01

364

Hard scattering phenomena from RHIC to LHC  

SciTech Connect

In the Relativistic Heavy Ion Collider era the high-p{sub T} particle emerging from hard scattering became an important tool of exploration of excited nuclear medium formed in ultra-relativistic heavy ion collisions. Discovery of anomalous suppression of high-p{sub T} particle yield [1] together with an observation of disappearance of back-to-back hadron correlation in central Au+Au collisions in 2002 [2] were the key results interpreted as a manifestation of the deconfined QCD medium in heavy ion collisions. Analysis of the high-p{sub T} particle and jet production is already a standard experimental technique providing a test bench for pQCD description of the point-like constituent scattering in p+p collisions and sensitive probes of the excited nuclear medium in A+A collisions.

Rak, Jan [Jyvaeskylae University, FI-40014 Jyvaeskylae (Finland)

2011-05-23

365

Heterogeneous shear in hard sphere glasses.  

PubMed

There is growing evidence that the flow of driven amorphous solids is not homogeneous, even if the macroscopic stress is constant across the system. Via event-driven molecular dynamics simulations of a hard sphere glass, we provide the first direct evidence for a correlation between the fluctuations of the local volume fraction and the fluctuations of the local shear rate. Higher shear rates do preferentially occur at regions of lower density and vice versa. The temporal behavior of fluctuations is governed by a characteristic time scale, which, when measured in units of strain, is independent of shear rate in the investigated range. Interestingly, the correlation volume is also roughly constant for the same range of shear rates. A possible connection between these two observations is discussed. PMID:22463672

Mandal, Suvendu; Gross, Markus; Raabe, Dierk; Varnik, Fathollah

2012-03-01

366

Imaging the hard/soft tissue interface.  

PubMed

Interfaces between different tissues play an essential role in the biomechanics of native tissues and their recapitulation is now recognized as critical to function. As a consequence, imaging the hard/soft tissue interface has become increasingly important in the area of tissue engineering. Particularly as several biotechnology based products have made it onto the market or are close to human trials and an understanding of their function and development is essential. A range of imaging modalities have been developed that allow a wealth of information on the morphological and physical properties of samples to be obtained non-destructively in vivo or via destructive means. This review summarizes the use of a selection of imaging modalities on interfaces to date considering the strengths and weaknesses of each. We will also consider techniques which have not yet been utilized to their full potential or are likely to play a role in future work in the area. PMID:24129952

Bannerman, Alistair; Paxton, Jennifer Z; Grover, Liam M

2014-03-01

367

Radiation Hardness Assurance (RHA) for Space Systems  

NASA Technical Reports Server (NTRS)

This presentation discusses radiation hardness assurance (RHA) for space systems, providing both the programmatic aspects of RHA and the RHA procedure. RHA consists of all activities undertaken to ensure that the electronics and materials of a space system perform to their design specifications after exposure to the space radiation environment. RHA also pertains to environment definition, part selection, part testing, spacecraft layout, radiation tolerant design, and mission/system/subsystems requirements. RHA procedure consists of establishing mission requirements, defining and evaluating the radiation hazard, selecting and categorizing the appropriate parts, and evaluating circuit response to hazard. The RHA approach is based on risk management and is confined only to parts, it includes spacecraft layout, system/subsystem/circuit design, and system requirements and system operations. RHA should be taken into account in the early phases of a program including the proposal and feasibility analysis phases.

Poivey, Christian; Buchner, Stephen

2007-01-01

368

Crystallization in glassy suspensions of hard ellipsoids  

NASA Astrophysics Data System (ADS)

We have carried out computer simulations of overcompressed suspensions of hard monodisperse ellipsoids and observed their crystallization dynamics. The system was compressed very rapidly in order to reach the regime of slow, glass-like dynamics. We find that, although particle dynamics become sub-diffusive and the intermediate scattering function clearly develops a shoulder, crystallization proceeds via the usual scenario: nucleation and growth for small supersaturations, spinodal decomposition for large supersaturations. In particular, we compared the mobility of the particles in the regions where crystallization set in with the mobility in the rest of the system. We did not find any signature in the dynamics of the melt that pointed towards the imminent crystallization events.

Dorosz, Sven; Schilling, Tanja

2013-09-01

369

Hard turning micro-machine tool  

DOEpatents

A micro-scale apparatus for supporting a tool for hard turning comprises a base, a pivot coupled to the base, an actuator coupled to the base, and at least one member coupled to the actuator at one end and rotatably coupled to the pivot at another end. A tool mount is disposed on the at least one member. The at least one member defines a first lever arm between the pivot and the tool mount, and a second lever arm between the pivot and the actuator. The first lever arm has a length that is less than a length of the second lever arm. The actuator moves the tool mount along an arc.

DeVor, Richard E; Adair, Kurt; Kapoor, Shiv G

2013-10-22

370

Coendangered hard-ticks: threatened or threatening?  

PubMed Central

The overwhelming majority of animal conservation projects are focused on vertebrates, despite most of the species on Earth being invertebrates. Estimates state that about half of all named species of invertebrates are parasitic in at least one stage of their development. The dilemma of viewing parasites as biodiversity or pest has been discussed by several authors. However, ticks were omitted. The latest taxonomic synopses of non-fossil Ixodidae consider valid 700 species. Though, how many of them are still extant is almost impossible to tell, as many of them are known only from type specimens in museums and were never collected since their original description. Moreover, many hosts are endangered and as part of conservation efforts of threatened vertebrates, a common practice is the removal of, and treatment for external parasites, with devastating impact on tick populations. There are several known cases when the host became extinct with subsequent coextinction of their ectoparasites. For our synoptic approach we have used the IUCN status of the host in order to evaluate the status of specifically associated hard-ticks. As a result, we propose a number of 63 coendangered and one extinct hard-tick species. On the other side of the coin, the most important issue regarding tick-host associations is vectorial transmission of microbial pathogens (i.e. viruses, bacteria, protozoans). Tick-borne diseases of threatened vertebrates are sometimes fatal to their hosts. Mortality associated with pathogens acquired from ticks has been documented in several cases, mostly after translocations. Are ticks a real threat to their coendangered host and should they be eliminated? Up to date, there are no reliable proofs that ticks listed by us as coendangered are competent vectors for pathogens of endangered animals.

2011-01-01

371

Deglaciation mechanisms for a paleoproterozoic hard snowball  

NASA Astrophysics Data System (ADS)

Our earlier work on the Neoproterozoic hard snowball climate indicated that very high CO2 thresholds would be needed for deglaciation, owing to lapse rate feedbacks and snow cover effects that are not represented in standard energy balance models. We examine here a range of similar issues for the Paleoproterozoic, at which time the Sun was still fainter, but the geothermal heat flux was larger. The warmest position in a hard snowball climate occurs in the Summer subtropics, and we have found that many salient features of the climate there can be reproduced using a radiative-convective model, since the lateral heat fluxes are weak in this case. We show that the radiative-convective model reproduces the low tropopause height that leads to a weak greenhouse effect in full GCM simulations. We exploit this simplification to explore the role of surface boundary layer fluxes and atmospheric solar heating in determining the CO2 threshold for deglaciation. This technique is used to estimate deglaciation thresholds for the Paleoproterozoic. Cloud feedbacks remain a major source of uncertainty, but we remark that the shallow depth reached by convection makes extensive high cloud cover unlikely. We discuss also two aspects of ice dynamics that may be relevant to Paleoproterozoic climate and chemistry. The first is the "thin ice" solution proposed by McKay, shot down by Warren et al, but recently tentatively reinvigorated by Pollard and Kasting in the context of an energy balance model. We discuss the problem of whether such solutions are compatible with the lateral heat flux, vertical sensible heat transfer, and snow cover yielded by full GCM simulations, taking cognizance also of the higher geothermal heat flux estimated for the Paleoproterozoic. Finally, we provide some estimates of the mean age of "sea glacier" ice in Paleoproterozoic conditions, which is relevant to the prospects for a H2O2-based oxygenation theory proposed recently by Liang et al.

Pierrehumbert, R. T.; Mitchell, J.; Levine, X.

2006-05-01

372

Non-hard sphere thermodynamic perturbation theory.  

PubMed

A non-hard sphere (HS) perturbation scheme, recently advanced by the present author, is elaborated for several technical matters, which are key mathematical details for implementation of the non-HS perturbation scheme in a coupling parameter expansion (CPE) thermodynamic perturbation framework. NVT-Monte Carlo simulation is carried out for a generalized Lennard-Jones (LJ) 2n-n potential to obtain routine thermodynamic quantities such as excess internal energy, pressure, excess chemical potential, excess Helmholtz free energy, and excess constant volume heat capacity. Then, these new simulation data, and available simulation data in literatures about a hard core attractive Yukawa fluid and a Sutherland fluid, are used to test the non-HS CPE 3rd-order thermodynamic perturbation theory (TPT) and give a comparison between the non-HS CPE 3rd-order TPT and other theoretical approaches. It is indicated that the non-HS CPE 3rd-order TPT is superior to other traditional TPT such as van der Waals/HS (vdW/HS), perturbation theory 2 (PT2)/HS, and vdW/Yukawa (vdW/Y) theory or analytical equation of state such as mean spherical approximation (MSA)-equation of state and is at least comparable to several currently the most accurate Ornstein-Zernike integral equation theories. It is discovered that three technical issues, i.e., opening up new bridge function approximation for the reference potential, choosing proper reference potential, and/or using proper thermodynamic route for calculation of f(ex-ref), chiefly decide the quality of the non-HS CPE TPT. Considering that the non-HS perturbation scheme applies for a wide variety of model fluids, and its implementation in the CPE thermodynamic perturbation framework is amenable to high-order truncation, the non-HS CPE 3rd-order or higher order TPT will be more promising once the above-mentioned three technological advances are established. PMID:21861552

Zhou, Shiqi

2011-08-21

373

Theoretical hardness of the cubic BC 2N  

Microsoft Academic Search

Vickers hardness of the cubic BC2N has been investigated using the microscopic hardness model, in which the parameters have been obtained using first principles calculations. Ionicities of the chemical bonds in the cubic BC2N depend on their surrounding chemical environments, which are included in the hardness calculations of the cubic BC2N using the population ionicity scale. For the four selected

Xiaoju Guo; Zhongyuan Liu; Xiaoguang Luo; Dongli Yu; Julong He; Yongjun Tian; Jian Sun; Hui-Tian Wang

2007-01-01

374

Radiation hardness of VA1 with submicron process technology  

Microsoft Academic Search

We have studied the radiation hardness of the VA1, a Viking-architecture preamplifier VLSI chip. Large-scale integrated (LSI) samples are fabricated in 0.8 and 0.35 ?m process technologies to improve the radiation hardness of the LSI for the Belle silicon vertex detector upgrade. We have observed significant improvement of the radiation hardness with 0.8-?m technology compared to 1.2-?m technology. Little degradation

M. Yokoyama; H. Aihara; M. Hazumi; H. Ishino; J. Kaneko; Y. Li; D. Marlow; S. Mikkelsen; E. Nygard; H. Tajima; J. Talebi; G. Verner; H. Yamamoto

2001-01-01

375

On the development of nanostructured WC-Co hard alloys  

Microsoft Academic Search

A dimensional region of the existence of WC nanoparticles and nanostructured WC-Co hard alloys has been substantiated. It\\u000a has been shown that the existing technologies do not allow to obtain pore- free WC-Co hard alloys with carbide particles of\\u000a size 5–40 nm to be produced. A method of the formation of nanostructured hard alloys has been proposed.

A. F. Lisovskii

2010-01-01

376

Rate-hardness: a new performance metric for haptic interfaces  

Microsoft Academic Search

Rate-hardness is introduced as a quality metric for hard virtual surfaces, and linked to human perception of hardness via a psychophysical study. A 3 degree-of-freedom haptic interface is used to present pairs of virtual walls to users for side-by-side comparison, 19 subjects are tested in a series of three blocks of trials, where different virtual walls are presented in randomly

Dale A. Lawrence; Lucy Y. Pao; Anne M. Dougherty; Mark A. Salada; Yiannis Pavlou

2000-01-01

377

Rapid Spectral Changes of Cygnus X-1 in the Low/Hard State with Suzaku  

NASA Astrophysics Data System (ADS)

Rapid spectral changes in the hard X-ray on a timescale down to ~0.1 s are studied by applying a "shot analysis" technique to the Suzaku observations of the black hole binary Cygnus X-1, performed on 2008 April 18 during the low/hard state. We successfully obtained the shot profiles, covering 10-200 keV with the Suzaku HXD-PIN and HXD-GSO detector. It is notable that the 100-200 keV shot profile is acquired for the first time owing to the HXD-GSO detector. The intensity changes in a time-symmetric way, though the hardness changes in a time-asymmetric way. When the shot-phase-resolved spectra are quantified with the Compton model, the Compton y-parameter and the electron temperature are found to decrease gradually through the rising phase of the shot, while the optical depth appears to increase. All the parameters return to their time-averaged values immediately within 0.1 s past the shot peak. We have not only confirmed this feature previously found in energies below ~60 keV, but also found that the spectral change is more prominent in energies above ~100 keV, implying the existence of some instant mechanism for direct entropy production. We discuss possible interpretations of the rapid spectral changes in the hard X-ray band.

Yamada, S.; Negoro, H.; Torii, S.; Noda, H.; Mineshige, S.; Makishima, K.

2013-04-01

378

RAPID SPECTRAL CHANGES OF CYGNUS X-1 IN THE LOW/HARD STATE WITH SUZAKU  

SciTech Connect

Rapid spectral changes in the hard X-ray on a timescale down to {approx}0.1 s are studied by applying a ''shot analysis'' technique to the Suzaku observations of the black hole binary Cygnus X-1, performed on 2008 April 18 during the low/hard state. We successfully obtained the shot profiles, covering 10-200 keV with the Suzaku HXD-PIN and HXD-GSO detector. It is notable that the 100-200 keV shot profile is acquired for the first time owing to the HXD-GSO detector. The intensity changes in a time-symmetric way, though the hardness changes in a time-asymmetric way. When the shot-phase-resolved spectra are quantified with the Compton model, the Compton y-parameter and the electron temperature are found to decrease gradually through the rising phase of the shot, while the optical depth appears to increase. All the parameters return to their time-averaged values immediately within 0.1 s past the shot peak. We have not only confirmed this feature previously found in energies below {approx}60 keV, but also found that the spectral change is more prominent in energies above {approx}100 keV, implying the existence of some instant mechanism for direct entropy production. We discuss possible interpretations of the rapid spectral changes in the hard X-ray band.

Yamada, S.; Makishima, K. [Cosmic Radiation Laboratory, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198 (Japan); Negoro, H. [Department of Physics, College of Science and Technology, Nihon University, 1-8 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Torii, S.; Noda, H. [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Mineshige, S. [Department of Astronomy, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)

2013-04-20

379

The Influence of Wheel/Rail Contact Conditions on the Microstructure and Hardness of Railway Wheels  

PubMed Central

The susceptibility of railway wheels to wear and rolling contact fatigue damage is influenced by the properties of the wheel material. These are influenced by the steel composition, wheel manufacturing process, and thermal and mechanical loading during operation. The in-service properties therefore vary with depth below the surface and with position across the wheel tread. This paper discusses the stress history at the wheel/rail contact (derived from dynamic simulations) and observed variations in hardness and microstructure. It is shown that the hardness of an “in-service” wheel rim varies significantly, with three distinct effects. The underlying hardness trend with depth can be related to microstructural changes during manufacturing (proeutectoid ferrite fraction and pearlite lamellae spacing). The near-surface layer exhibits plastic flow and microstructural shear, especially in regions which experience high tangential forces when curving, with consequentially higher hardness values. Between 1?mm and 7?mm depth, the wheel/rail contacts cause stresses exceeding the material yield stress, leading to work hardening, without a macroscopic change in microstructure. These changes in material properties through the depth of the wheel rim would tend to increase the likelihood of crack initiation on wheels toward the end of their life. This correlates with observations from several train fleets.

Davis, Claire

2014-01-01

380

Numerical investigation of airflow inside a 1-in hard disk drive  

NASA Astrophysics Data System (ADS)

The increasing application of the hard disk drive in consumer electronic devices has pushed the usage of the small form factor hard drives. At the same time, the data storage industry continues to enhance the capacity and performance of computer hard disk drive. The concerns of track mis-registration caused by various runout still remain with the form factor change. The objective of the current study is to numerically investigate the airflow characteristic inside a 1 in hard disk drive. The simulation model is constructed based on the currently available 1-in micro-drive in the market, with 3600 rpm disk rotation speed, thus the flow Reynolds number based on the disk tip radius is around 4.8×10 3. Two models with different actuator arm positions (outside and middle-disk) were studied. The simulation results show that the standard k-epsilon model used allows us to extract similar information and understanding as that from more developed numerical model. Good agreement in normalized velocity magnitude and flow pattern is observed between the numerical and experimental results. At different actuator arm positions, streamlines and velocity vectors plots show the effect of the actuator arm position to the flow pattern, especially around the arm. This arm position also affects the radial and tangential shear stress values over the disk, which may help to estimate the wind loss and power consumption.

Suriadi, M. A.; Tan, C. S.; Zhang, Q. D.; Yip, T. H.; Sundaravadivelu, K.

2006-08-01

381

The influence of wheel/rail contact conditions on the microstructure and hardness of railway wheels.  

PubMed

The susceptibility of railway wheels to wear and rolling contact fatigue damage is influenced by the properties of the wheel material. These are influenced by the steel composition, wheel manufacturing process, and thermal and mechanical loading during operation. The in-service properties therefore vary with depth below the surface and with position across the wheel tread. This paper discusses the stress history at the wheel/rail contact (derived from dynamic simulations) and observed variations in hardness and microstructure. It is shown that the hardness of an "in-service" wheel rim varies significantly, with three distinct effects. The underlying hardness trend with depth can be related to microstructural changes during manufacturing (proeutectoid ferrite fraction and pearlite lamellae spacing). The near-surface layer exhibits plastic flow and microstructural shear, especially in regions which experience high tangential forces when curving, with consequentially higher hardness values. Between 1 mm and 7 mm depth, the wheel/rail contacts cause stresses exceeding the material yield stress, leading to work hardening, without a macroscopic change in microstructure. These changes in material properties through the depth of the wheel rim would tend to increase the likelihood of crack initiation on wheels toward the end of their life. This correlates with observations from several train fleets. PMID:24526883

Molyneux-Berry, Paul; Davis, Claire; Bevan, Adam

2014-01-01

382

The hard to soft spectral transition in LMXBs-affected by recondensation of gas into an inner disk  

NASA Astrophysics Data System (ADS)

Context: Soft and hard spectral states of X-ray transient sources reflect two modes of accretion, accretion via a geometrically thin, optically thick disk or an advection-dominated accretion flow (ADAF). Aims: The luminosity at transition between these two states seems to vary from source to source, or even for the same source during different outbursts, as observed for GX 339-4. We investigate how the existence of an inner weak disk in the hard state affects the transition luminosity. Methods: We evaluate the structure of the corona above an outer truncated disk and the resulting disk evaporation rate for different irradiation. Results: In some cases, recent observations of X-ray transients indicate the presence of an inner cool disk during the hard state. Such a disk can remain during quiescence after the last outburst as long as the luminosity does not drop to very low values (10-4-10-3 of the Eddington luminosity). Consequently, as part of the matter accretes via the inner disk, the hard irradiation is reduced. The hard irradiation is further reduced, occulted and partly reflected by the inner disk. This leads to a hard-soft transition at a lower luminosity. Conclusions: The spectral state transition is expected at lower luminosity if an inner disk exists below the ADAF. This seems to be supported by observations for GX 339-4.

Meyer-Hofmeister, E.; Liu, B. F.; Meyer, F.

2009-12-01

383

Hard and soft acids and bases: structure and process.  

PubMed

Under investigation is the structure and process that gives rise to hard-soft behavior in simple anionic atomic bases. That for simple atomic bases the chemical hardness is expected to be the only extrinsic component of acid-base strength, has been substantiated in the current study. A thermochemically based operational scale of chemical hardness was used to identify the structure within anionic atomic bases that is responsible for chemical hardness. The base's responding electrons have been identified as the structure, and the relaxation that occurs during charge transfer has been identified as the process giving rise to hard-soft behavior. This is in contrast the commonly accepted explanations that attribute hard-soft behavior to varying degrees of electrostatic and covalent contributions to the acid-base interaction. The ability of the atomic ion's responding electrons to cause hard-soft behavior has been assessed by examining the correlation of the estimated relaxation energies of the responding electrons with the operational chemical hardness. It has been demonstrated that the responding electrons are able to give rise to hard-soft behavior in simple anionic bases. PMID:22668421

Reed, James L

2012-07-01

384

Micromagnetic simulation of tunneling magnetoresistance junctions with parallel hard bias  

SciTech Connect

Tunneling magnetoresistance (TMR) films and devices were simulated to understand the response of the free layer with a parallel hard bias. In order to determine the effect of the granular hard bias material micromagnetic simulation was used to model both the hard bias and TMR material. Minimizing hysteresis and Barkhausen jumps in the response of the device involves an optimization of the spacing between the free layer and the hard bias coupled with the shape of the device edges. {copyright} 2001 American Institute of Physics.

Gibbons, M. R.; Sin, K.; Funada, S.; Mao, M.; Rao, D.; Chien, C.; Tong, H. C.

2001-06-01

385

Characterization of tempered martensite embrittlement using hardness measurement  

SciTech Connect

A series of experiments were carried out on three commercial steels to explore the possibility for characterizing tempered martensite embrittlement (TME) by Rockwell, macro- and micro-Vickers hardness tests. The results indicate distinct hardness peaks in two steels and an inflection in the other around the TME temperature. A new analytical approach for examining the slope of hardness-tempering temperature plots appear to reveal the TME phenomenon more sensitively. Dilatometric examinations substantiate that the temperature of hardness peak/inflection occurs beyond the second stage of tempering.

Ghosh, A.; Bhaduri, A.; Ray, K.K. (Indian Inst. of Tech., Kharagpur (India). Dept. of Metallurgical Engineering)

1994-12-01

386

Ultrasonically bonded value assembly  

NASA Technical Reports Server (NTRS)

A valve apparatus capable of maintaining a fluid-tight seal over a relatively long period of time by releasably bonding a valve member to its seat is described. The valve member is bonded or welded to the seat and then released by the application of the same energy to the bond joint. The valve member is held in place during the bonding by a clamping device. An appropriate force device can activate the opening and closing of the valve member. Various combinations of material for the valve member and valve seat can be utilized to provide an adequate sealing bond. Aluminum oxide, stainless steel, inconel, tungsten carbide as hard materials and copper, aluminum, titanium, silver, and gold as soft materials are suggested.

Salvinski, R. J. (inventor)

1975-01-01

387

Extreme-Value Copulas  

Microsoft Academic Search

\\u000a Being the limits of copulas of componentwise maxima in independent random samples, extreme-value copulas can be considered\\u000a to provide appropriate models for the dependence structure between rare events. Extreme-value copulas not only arise naturally\\u000a in the domain of extreme-value theory, they can also be a convenient choice to model general positive dependence structures.\\u000a The aim of this survey is to

Gordon Gudendorf; Johan Segers

2009-01-01

388

Place Value Frenzy  

NSDL National Science Digital Library

Today, we are going to practice place value. Please read all directions below. Play Find the Place Value 1 time. Leave, name to appear on title, Blank. Leave, minimum number, on 1 . Put the maximum number on 1000. Then, click on generate to start game. Play Place Value 2 times. When the webpage comes up click on countdown to play the game. Play Frog Palace 1 time. Please ...

Carter, Miss

2006-11-04

389

Structural precursor to freezing in the hard-disk and hard-sphere systems  

NASA Astrophysics Data System (ADS)

We show that the simplest model fluids in two and three dimensions, namely, the hard-disk and hard-sphere fluids, exhibit a structural precursor to the freezing transition, which manifests itself as a shoulder in the second peak of the radial distribution function. This feature is not present in the radial distribution function of the low-density fluid. Close examination of the two-dimensional fluid configurations in the vicinity of the freezing transition reveals that the shoulder corresponds to the formation of a distinct structural motif, identifiable as a four-particle hexagonally close-packed arrangement. As the dense fluid approaches the freezing transition, the ordered arrangements form large embryonic domains, commensurate with those seen in the crystal at the melting point. Contrary to the notion that the split second peak is a signature of the amorphous solid, our results support the idea that it is a precursor to the development of long-range order.

Truskett, Thomas M.; Torquato, Salvatore; Sastry, Srikanth; Debenedetti, Pablo G.; Stillinger, Frank H.

1998-09-01

390

Hardness test method, hardness tester, and computer-readable storage medium storing program  

US Patent & Trademark Office Database

A hardness test method includes a measurement step of forming an indent by indenting a surface of a sample with an indenter loaded with a predetermined load and detecting a displacement quantity of the indenter and a test force loaded on the indenter at a time of forming the indent to measure an indentation curve, a work load calculation step of calculating a work load by plastic deformation (Wp) from an area of an indentation curve obtained by the measurement step, and an estimation calculation step of calculating an estimation (HVe) of Vickers hardness by using the work load (Wp), calculated at the work load calculation step, and a previously determined coefficient K in conformity with HVe=(K/Wp).sup.2.

2014-02-18

391

Business Value Game  

NASA Astrophysics Data System (ADS)

Agile teams want to deliver maximum business value. That’s easy if the on-site Ccstomer assigns business value to each story. But how does the customer do that? How can you estimate business value? This workshop is run as a game, where teams have to make tough business decisions for their ”organizations”. Teams have to decide which orders to take and what to deliver first in order to earn more. The session gives the participants basic business value estimation techniques, but the main point is to make people live through the business situation and to help them feel the consequences of various choices.

Marchenko, Artem; Duarte, Vasco

392

Hard X-ray imaging of a solar gradual hard X-ray burst on April 1, 1981  

Microsoft Academic Search

An intense solar X-ray burst occurred on April 1, 1981. X-ray images of this gradual hard X-ray burst were observed with the hard X-ray telescope aboard the Hinotori satellite for the initial ten minutes of rise and maximum phases of the burst. The hard X-ray images (13–29 keV) look like a large loop without considerable time variation of an elongated

T. Takakura; K. Ohki; T. Sakurai; J. L. Wang; J. Y. Xuan; S. C. Li; R. Y. Zhao

1984-01-01

393

Relationships between hardness, Young's modulus and elastic recovery in hard nanocomposite coatings  

Microsoft Academic Search

The paper is devoted to an assessment of the mechanical behavior of hard and superhard nanocomposite coatings from loading\\/unloading curves measured by a computer-controlled Fischerscope H 100 microhardness tester and a maximum depth dmax of the diamond indenter impression into the coating at a given load L. It is shown that: (1) the area between the loading\\/unloading curve and the

J Musil; F Kunc; H Zeman; H Poláková

2002-01-01

394

Surface Effects on Young's Modulud and Hardness of Fused Silica by Nanoindentation Study  

SciTech Connect

The surface Young's modulus (E) and hardness (H) of fused silica samples have been studied by nanoindentation. Two factors strongly affect the results of E and H. One factor is the polishing quality of the fused silica surface. Poor polishing quality produces much smaller E and H than the literature values for bulk fused silica. The second factor is surface flatness. Even for a well-polished silica surface, an "arch bridge effect" may hinder the measurements of the true values of E and H. A correction procedure is proposed to eliminate this effect, and the corrected results show substantial improvements.

Zheng, L.; Schmid, A.W.; Lambropoulos, J.C.

2007-01-24

395

Toxicity of Copper to Cutthroat Trout ('Salmo clarki') under Different Conditions of Alkalinity, pH, and Hardness.  

National Technical Information Service (NTIS)

Median lethal concentration (96-h LC50) values for acute copper toxicity to 3-10 g cutthroat trout (Salmo clarki) have been determined for nine different combinations of alkalinity, hardness, and pH. Equilibrium calculations were performed on the copper L...

C. Chakoumakos R. C. Russo R. V. Thurston

1981-01-01

396

Phase Diagram of the Nematic-Smectic A Transition of the Binary Mixture of Parallel Hard Cylinders of Different Lengths  

Microsoft Academic Search

We study the nematic-smetic A phase transition of binary mixture of parallel hard cylinders of different lengths. We use the Helmholtz free energy truncated at the second virial term. Changing values of q (length of a longer cylinder), x (composition) and eta (packing fraction) of the cylinders, we obtained the transition points at which the nematic phase becomes unstable for

Tomonori Koda; Hatsuo Kimura

1994-01-01

397

Stability, convergence to self-similarity and elastic limit for the Boltzmann equation for inelastic hard spheres  

Microsoft Academic Search

We consider the spatially homogeneous Boltzmann equation for inelastic hard spheres, in the framework of so-called constant normal restitution coefficients? ? (0,1). In the physical regime of a small inelasticity (that is ? ? (??,1) for some constructive ?? > 0) we prove uniqueness of the self-similar profile for given values of the resti- tution coefficient? ? (??,1), the mass

S. Mischler; C. Mouhot

2007-01-01

398

The influence of pellet shape and film coating on the filling of pellets into hard shell capsules  

Microsoft Academic Search

Pellets of different shape, varying from spherical to cylindrical, were filled into hard shell capsules. When no film coat was applied, the pellets had not to be perfectly spherical in order to be filled reproducibly. An aspect ratio of 1.2 or less appeared to be the threshold value. However, pronounced surface roughness hindered the filling process, and hence it appears

Ranjana Chopra; Fridrun Podczeck; J. Michael Newton; Göran Alderborn

2002-01-01

399

The Effect of Stunning Methods and Season on Muscle Texture Hardness in Atlantic Salmon (Salmo salar L.).  

PubMed

Commercially collected records of Atlantic salmon (Salmo salar L.) muscle texture hardness were used to evaluate the effect of slaughter procedures and seasonality on texture quality. A database collected by Marine Harvest® contained flesh hardness records of Atlantic salmon slaughtered at processing plants in Norway from summer 2010 to summer 2011. The fish were slaughtered either by (1) percussion followed by automated bleeding ("Percussive") or (2) live chilling with exposure to carbon dioxide (CO2 ) followed by manual severing gill arches and bleeding ("CO2 ") or (3) live chilling with exposure to CO2 followed by percussive stunning and at the end automated bleeding ("CO2 ·percussive"). Hardness in salmon muscle cutlets was measured in Newtons (N) by Materials Testing Machine Zwick 500N. The hardness in salmon varied significantly over the study period (P < 0.05, mixed effect model) and showed the softest value of 21.2 (± 0.7) Newton (N) in summer 2011 and hardest 24.1 (± 0.2) N in autumn 2010. Slaughter procedures had a significant effect on salmon muscle hardness (P < 0.05, mixed effect model), where percussion followed by automated bleeding resulted in the hardest value (24.0 ± 0.4 N) as compared with CO2 stunning (21.8 ± 0.2 N) and combination of CO2 and percussive stunning (23.1 ± 0.15 N). CO2 is suspected as a causal factor in accelerated postmortem softening of the salmon muscle. PMID:24917421

Merkin, Grigory V; Stien, Lars Helge; Pittman, Karin; Nortvedt, Ragnar

2014-06-01

400

Cognitive and Social Values.  

ERIC Educational Resources Information Center

Criticizes Hugh Lacey's separation of cognitive values and social values in discussions of the nature of science. Claims that attempting to distinguish between cognitive and social ignores crucial complexities in the development and use of knowledge. Proposes that the proper distinction be between legitimate and illegitimate reasons in science as…

Machamer, Peter; Douglas, Heather

1999-01-01

401

Art's Educational Value  

ERIC Educational Resources Information Center

This paper explores critically the nature of art's value in education and argues in favor of both intrinsic and instrumental value. Form and expression, while being out of favor in some contemporary circles, are re-claimed as appropriate features of art. Concepts and forms in art as elsewhere serve to structure impressions and experience and…

Richmond, Stuart

2009-01-01

402

Weak Value Theory  

SciTech Connect

I show that the weak value theory is useful from the viewpoints of the experimentally verifiability, consistency, capacity for explanation as to many quantum paradoxes, and practical advantages. As an example, the initial state in the Hardy paradox can be experimentally verified using the weak value via the weak measurement.

Shikano, Yutaka [Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan) and Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

2011-03-28

403

Glycemic Index Values Database  

Cancer.gov

NCI has developed a listing of Glycemic Index (GI) values for individual foods. Food codes from the USDA Continuing Survey of Food Intakes of Individuals (CSFII) are used as a reference. This file provides GI values for those foods consumed by adults and queried on the DHQ or other FFQs used at NCI.

404

How I Taught Values  

ERIC Educational Resources Information Center

Values are principles or standards that people have decided are desirable to live by. The question of whether values can or should be taught to college students has been debated for decades, with the pros incorporating moral concepts into curricula and the antes scorning such efforts as not only inappropriate but also intellectually dull. In this…

Pratt, Annis

2005-01-01

405

Agricultural Land Values.  

National Technical Information Service (NTIS)

The January 1, 1999 U.S. farm real estate value, including land and buildings, averaged $992 per acre up 1.8 percent from 1998. The average U.S. farm real estate value rose $18 per acre from $974 in 1998 to $992 per acre, the smallest increase since 1992....

1999-01-01

406

Place Value Activities  

NSDL National Science Digital Library

This webpage contains instructions for several activities and games designed to develop students' understanding of place value while reinforcing addition and subtraction skills. Downloadable materials and suggestions for variations are included. A second page of additional activities is catalogued separately (More Place Value Activities).

Kawas, Terry

2003-01-01

407

Value Creation and Transfer  

Microsoft Academic Search

In this paper we address the issues of information as a means to value creation for a business enterprise or for an individual. To that end, we develop the concept of information and provide several definitive definitions that are of use for strategic and policy purposes. We then select a definition based upon the need to create and measure value

Terrence P. McGarty; NYNEX Corp; Sara J. McGarty

408

Value From Regulatory Fit  

Microsoft Academic Search

Where does value come from? I propose a new answer to this classic question. People experience regulatory fit when the manner of their engagement in an activity sustains their goal orientation or interests regarding that activity. When there is fit, people engage more strongly in what they are doing and “feel right” about it. Fit influences the strength of value

E. Tory Higgins

2005-01-01

409

The Struggles of Being Hard of Hearing.  

ERIC Educational Resources Information Center

Common experiences of Japanese children and adults with hearing loss are presented and strategies for enhancing socialization, self-concept, self-acceptance, public attitudes, education, employment, hearing aids, and society values and services are explored. (Author/VW)

Lutes, John W.

1987-01-01

410

Green's function analysis of an ideal hard surface rectangular waveguide  

Microsoft Academic Search

Green's function analysis of an ideal hard surface rectangular waveguide is proposed for characterization of the modal spectrum of the structure. A decomposition of the hard surface waveguide into perfect electric conductor and perfect magnetic conductor waveguides allows the representation of dyadic Green's function as a superposition of transverse magnetic (TM) and transverse electric (TE) waveguide modes, respectively. In addition,

Wei Huang; Alexander B. Yakovlev; Ahmed A. Kishk; Allen W. Glisson; Islam A. Eshrah

2005-01-01

411

Puroindolines: the molecular genetic basis of wheat grain hardness  

Microsoft Academic Search

The variation in grain hardness is the single most important trait that determines end-use quality of wheat. Grain texture classification is based primarily on either the resistance of kernels to crushing or the particle size distribution of ground grain or flour. Recently, the molecular genetic basis of grain hardness has become known, and it is the focus of this review.

Craig F. Morris

2002-01-01

412

Hard and soft acids and bases: small molecules.  

PubMed

The operational chemical hardness has been determined for the hydride, chloride, and fluoride derivatives of the anionic atomic bases of the second period. Of interest is the identification of the structure and associated processes that give rise to hard-soft behavior in small molecules. The Pearson Principle of Hard and Soft Acids and Bases has been taken to be the defining statement about hard-soft behavior and as a definition of chemical hardness. Similar to the case for atoms, the molecule's responding electrons have been identified as the structure giving rise to hard-soft behavior, and a relaxation described by a modified Slater model has been identified as the associated process. The responding electrons are the molecule's valence electrons that are not undergoing electron transfer in an acid-base interaction. However, it has been demonstrated that chemical hardness is a local property, and only those responding electrons that are associated with the base's binding atom directly impact chemical hardness. PMID:19588960

Reed, James L

2009-08-01

413

Hard-Facing with Electro-Spark Deposition. Final Report.  

National Technical Information Service (NTIS)

A common method to improve wear resistance of metals in rubbing contact is to increase their surface hardness. Electro-Spark Deposition is a process which uses capacitive discharge pulses of high current passing through a hard carbide electrode in contact...

K. P. Kees

1983-01-01

414

Educating Hard of Hearing Children. Special Education in Transition 2.  

ERIC Educational Resources Information Center

Viewpoints of an audiologist, speech-language pathologist, special educator, classroom teacher, and parent are presented in the book on the implications of P.L. 94-142, the Education for All Handicapped Children Act, for hard of hearing students. In the introduction, M. Ross considers the status of many hard of hearing students, noting the…

Ross, Mark, Ed.; Nober, Linda W., Ed.

415

On the hardness of approximating minimum vertex cover  

Microsoft Academic Search

We prove the Minimum Vertex Cover problem to be NP-hard to approx- imate to within a factor of 1.3606, extending on previous PCP and hardness of approximation technique. To that end, one needs to develop a new proof framework, and to borrow and extend ideas from several fields.

Irit Dinur; Samuel Safra

2004-01-01

416

Illustrated Manual of Hard Clam Reproduction and Development.  

National Technical Information Service (NTIS)

This manual is intended to be used as an aid for hatchery biologists and aquaculturists involved in hard clam larvae. It provides detailed illustrations and photographs of the difficult-to-observe early embryonic and larval stages of hard clams. Combining...

M. P. Russell C. J. Deming J. C. Gruber N. R. Dollahon R. Williams G. E. Flimlin J. Zodl

1998-01-01

417

Permanent hard water softening using carbon nanotube sheets  

Microsoft Academic Search

Permanent hard water softening using oxidized carbon nanotube (CNT) sheets was performed. CNT sheets were synthesized by chemical vapor deposition of cyclohexanol and ferrocene in nitrogen atmosphere at 750°C, and oxidized with concentrated nitric acid at room temperature and then employed as adsorbent for permanent hard water softening. Various isotherms and kinetic models were applied to fit the experimental data.

Maryam Ahmadzadeh Tofighy; Toraj Mohammadi

2011-01-01

418

Respiratory effects of hard-metal dust exposure  

SciTech Connect

Workers exposed to hard-metal dust are at risk of developing interstitial pulmonary fibrosis. Focusing on the lung parenchymal disorders that result, the author thoroughly reviews the background of the problem, animal studies and recent environmental data related to hard-metal disease, the clinical presentation, and finally its etiology.

Balmes, J.R.

1987-04-01

419

Cytotoxicity of hard and soft denture lining materials.  

PubMed

The cytotoxicity of nine soft and hard lining materials (Mollosil Plus, Ufi Gel SC, Visco-gel, Molloplast-B, GC Tissue Conditioner, Vertex Rapid Simplified, GC Reline Hard, Vertex Self-Curing, Ufi Gel hard C) was evaluated using human gingival fibroblasts (HGFs). Twelve disk samples per lining material were prepared and incubated for 24, 48, 72, and 96 h. Cytotoxicity of each lining material's extract on cultured HGFs was measured using XTT assay. Data were analyzed using one-way ANOVA, post hoc Dunnett's T3 and Bonferroni tests at a significance level of p<0.05. At all incubation periods, all the hard lining materials (Vertex-SC, GC Reline Hard, Vertex-RS, and Ufi Gel hard C) showed cell viability higher than 90%. Among the soft lining materials, although there were no significant differences in cell viability among the different incubation periods for each lining material (p>0.05), autopolymerized acrylic-based GC Tissue Conditioner showed significantly lower cell viability than the other soft lining materials at each incubation period. Among the hard lining materials, there were no significant differences both among the materials and across all incubation periods for each lining material (p>0.05). In conclusion, all soft and hard liners exhibited good biocompatibility regardless of incubation time, except for GC Tissue Conditioner. PMID:23207219

Atay, Ayse; Bozok Cetintas, Vildan; Cal, Ebru; Kosova, Buket; Kesercioglu, Atilla; Guneri, Pelin

2012-01-01

420

Deposition of hard surfacing layer by friction surfacing  

Microsoft Academic Search

Although several surfacing processes have been proposed and applied, none has been able to apply a 1 mm thick hard layer. This paper describes fundamental research to establish friction surfacing as a technique for applying a 1 mm thick hard layer.Experiments were run to clarify the effects of operating parameters on surface quality using a conventional friction welder fitted with

T. Shinoda; S. Okamoto; S. Takemoto; Y. Kato; T. Shimizu

1996-01-01

421

Hybrid technology hard coating – Electron beam surface hardening  

Microsoft Academic Search

Hard surface layers often cannot show advantages of their good hardness, strength and wear resistance over relatively soft materials so that an additional thermal treatment of the base materials before or after coating is necessary. Surface treatment technologies with high energy beams {electron beam (EB) or laser beam (LB)} offer a good and modern alternative to the mostly used bulk

R. Zenker; G. Sacher; A. Buchwalder; J. Liebich; A. Reiter; R. Häßler

2007-01-01

422

Classification of hard domains in garnet bubble films  

Microsoft Academic Search

The ``exercise'' experiment and the substantial difference in static characteristics show that those dumbbell domains, which can eventually contract to circular form and then collapse, should be classified as a kind of dumbbells rather than hard bubbles. Thus it is suggested that dumbbell domains can be divided into two kinds: ID and IID. Ordinary hard bubbles (OHB), ID and IID,

Xiang Fu Nie; Gui de Tang; Xiu de Niu; Bao Shan Han

1991-01-01

423

application of the Equotip hardness tester to weathering studies  

Microsoft Academic Search

Tafone-like depressions have developed on the Aoshima sandstone blocks used for a masonry bridge pier in the coastal spray zone. A thin layer of partial granular disintegration was found on the surface in depressions. To evaluate quantitatively the strength of the thin weathered layer, the hardness was measured at the surface of the sandstone blocks using both an Equotip hardness

Hisashi Aoki; Yukinori Matsukura

424

On the Hardness of 4Coloring a 3-Colorable Graph  

Microsoft Academic Search

We give a new proof showing that it is NP-hard to color a 3-colorable graph using just four colors. This result is already known (18), but our proof is novel as it does not rely on the PCP theorem, while the one in (18) does. This highlights a qualitative differ- ence between the known hardness result for coloring -colorable graphs

Venkatesan Guruswami; Sanjeev Khanna

2000-01-01

425

Grain Hardness: A Major Determinant of Wheat Quality  

Microsoft Academic Search

Wheat quality, a complex term, depends upon intentional use for unambiguous products. The foremost determinants of wheat quality are endosperm texture (grain hardness), protein content and gluten strength. Endosperm texture in wheat is the single most important and defining quality characteristic, as it facilitates wheat classification and affects milling, baking and end-use quality. Various techniques used for grain hardness measurement

I. Pasha; F. M. Anjum; C. F. Morris

2010-01-01

426

AMORPHOUS ALLOY SURFACE COATINGS FOR HARD CHROMIUM REPLACEMENT - PHASE I  

EPA Science Inventory

Hard chromium coatings (0.25 to10 mil thick) are used extensively for imparting wear and erosion resistance to components in both industrial and military applications. The most common means of depositing hard chromium has been through the use of chromic acid baths containing ...

427

Rhenium as a Hard Chrome Replacement for Gun Tubes  

Microsoft Academic Search

Hard chrome plating processes expose workers to toxic chromium compounds and are under a federal mandate for replacement with more environmentally friendly processes. In addition, hard chrome as a gun bore coating does not provide acceptable performance when used with modern ammunition. Replacement coating materials to date have been considered as too expensive, do not meet performance requirements, or have

W. Garrett; A. J. Sherman; J. Stiglich

2006-01-01

428

A generalized hard-sphere model for Monte Carlo simulation  

Microsoft Academic Search

A new molecular model, called the generalized hard-sphere, or GHS model, is introduced. This model contains, as a special case, the variable hard-sphere model of Bird (1981) and is capable of reproducing all of the analytic viscosity coefficients available in the literature that are derived for a variety of interaction potentials incorporating attraction and repulsion. In addition, a new procedure

H. A. Hassan; David B. Hash

1993-01-01

429

Hardness Analysis. Training Module 5.215.2.77.  

ERIC Educational Resources Information Center

This document is an instructional module package prepared in objective form for use by an instructor familiar with hardness analysis using the EDTA method and the calculation of hardness given metal ion concentrations and a factor table. Included are objectives, an instructor guide, student handouts, and transparency masters. A video tape is also…

Bonte, John L.; Davidson, Arnold C.

430

Proceedings of the Tungsten Workshop for Hard Target Weapons Program  

Microsoft Academic Search

The purpose of this meeting was to review and exchange information and provide technical input for improving technologies relevant to the Hard Target Weapons Program. This workshop was attended by representatives from 17 organizations, including 4 Department of Defense (DoD) agencies, 8 industrial companies, and 5 laboratories within DOE. Hard targets are defined as reinforced underground structures that house enemy

G. Mackiewicz-Ludtka; H. W. Hayden; R. M. Davis

1995-01-01

431

Functionally gradient hard carbon composites for improved adhesion and wear  

Microsoft Academic Search

A new approach is proposed for fabricating biomedical devices that last longer and are more biocompatible than those presently available. In this approach, a bulk material is chosen that has desirable mechanical properties (low modulus, high strength, high ductility and high fatigue strength). This material is coated with corrosion-resistant, wear-resistant, hard, and biocompatible hard carbon films. One of the many

Roger Jagdish Narayan

2002-01-01

432

VIBRATION EFFECT ON ROCKWELL SCALE C HARDNESS MEASUREMENT  

Microsoft Academic Search

Three ranges of Rockwell scale C reference hardness blocks: 20, 40, and 60 HRC were measured by deadweight-lever system hardness testing machine with two types of display: analog and digital. The testing machines were placed on the vibration table, whose frequency and amplitude of vibration can be controlled. Piezoelectric probe and vibration meter were used to confirm both amplitude and

Tassanai Sanponpute; Apichaya Meesaplak

433

PRACTICAL IMPLICATIONS TO THE IMPROVEMENT OF HARDNESS SCALES DEFINITIONS  

Microsoft Academic Search

Recently, in the framework of the Working Group on Hardness (WGH) of the Consultative Committee for Mass and Related Quantities (CCM) of the Comité International des Poids et Mesures (CIPM), the opportunity to improve the definitions of the hardness scales has been discussed. In this paper is investigated, from the theoretical point of view, the benefits in terms of decreasing

Giulio Barbato; Alessandro Germak

434

Crystallization time scales for polydisperse hard-sphere fluids  

NASA Astrophysics Data System (ADS)

We study the evolution of crystallization in dense mono- and polydisperse hard sphere fluids, initially quenched to an amorphous configuration. We use as signatures of crystallization both the decay of the reduced pressure Z and the increase in the local and global orientational order parameters Q¯6. For a given realization of the crystallization process these parameters show sudden changes, both large and small, separated by long periods of quiescence. However, averaging over a large number of realizations, a well-defined scenario for their evolution appears. We find an initial fast relaxation to a disordered state, followed by a period of slow variation, associated to the presence of nucleation events, followed by a fast change, composed of the growth of a few crystals with different orientations, and a final and slow coarsening in a domain-growth process. No clear scaling for this whole process was found. We also find that the transition to an stable glassy fluid is quite sharp as the polydispersity is increased, showing a probable first-order phase transition behavior. A well-defined boundary between crystallizing and permanently amorphous fluids should exist, at least for a region in packing fractions. We looked for segregation at large values of polydispersity, but no effects of this type were found.

Vargas, M. Cristina; Pérez-Ángel, Gabriel

2013-04-01

435

Influence of water hardness and sulfate on the acute toxicity of chloride to sensitive freshwater invertebrates.  

PubMed

Total dissolved solids (TDS) represent the sum of all common ions (e.g., Na, K, Ca, Mg, chloride, sulfate, and bicarbonate) in freshwater. Currently, no federal water quality criteria exist for the protection of aquatic life for TDS, but because the constituents that constitute TDS are variable, the development of aquatic life criteria for specific ions is more practical than development of aquatic life criteria for TDS. Chloride is one such ion for which aquatic life criteria exist; however, the current aquatic life criteria dataset for chloride is more than 20 years old. Therefore, additional toxicity tests were conducted in the current study to confirm the acute toxicity of chloride to several potentially sensitive invertebrates: water flea (Ceriodaphnia dubia), fingernail clams (Sphaerium simile and Musculium transversum), snail (Gyraulus parvus), and worm (Tubifex tubifex), and determine the extent to which hardness and sulfate modify chloride toxicity. The results indicated a significant ameliorating effect of water hardness (calcium and magnesium) on chloride toxicity for all species tested except the snail; for example, the 48-h chloride median lethal concentration (LC50) for C. dubia at 50?mg/L hardness (977?mg Cl(-) /L) was half that at 800?mg/L hardness (1,836?mg Cl(-) /L). Conversely, sulfate over the range of 25 to 600?mg/L exerted a negligible effect on chloride toxicity to C. dubia. Rank order of LC50 values for chloride at a given water hardness was in the order (lowest to highest): S. simile?

Soucek, David J; Linton, Tyler K; Tarr, Christopher D; Dickinson, Amy; Wickramanayake, Nilesh; Delos, Charles G; Cruz, Luis A

2011-04-01

436

Temperature rise during intraoral polymerization of self-cured hard denture base liners.  

PubMed

The aim of this in-vivo study was to evaluate the temperature rise during polymerization of five chairside self-cured hard denture base reliners. For the same patient, 30 identical baseplates, exposing a space on their tissue surface to accommodate the lining material, were made of a light-cured denture base material. A hole was drilled in the center of this area to enable the thermocouple wire of the temperature measuring device to have direct access to the palatal surface of the baseplate. Six baseplates were used for each of the five lining materials tested. Temperature recordings were made every 15 seconds. Data were analyzed using single factor analysis of variance (ANOVA) and the Scheffe's post-hoc analysis for multiple comparisons. The mean maximum temperature values ranged from 40.2 degrees C to 45.7 degrees C being statistically different among the materials (P<0.001). The maximum peak temperature was 53 degrees C and the lowest 39 degrees C. Also the difference between the time each material reached the peak of temperature was statistically significant (P<0.0001). A temperature range of 5.5 degrees C was demonstrated among materials, with the highest polymerization temperatures recorded for Flexacryl Hard and the lowest for Rebase and GC Reline hard. Ufi-gel hard showed the fastest polymerization cycle and was the first to reach the maximum temperature. The available chairside hard liners must be chosen with care considering the thermal effect on the oral mucosa and the discomfort of patient. PMID:20698423

Yannikakis, Stavros; Polychronakis, Nick; Zissis, Alcibiades

2010-06-01

437

A meta-analysis of host specificity in Neotropical hard ticks (Acari: Ixodidae).  

PubMed

Host specificity of Neotropical hard ticks (Acari: Ixodidae) was analyzed by using the number of hosts species for each tick species and the index of host specificity S(TD)*, which integrates phylogenetic and ecological information. The analyses were based on 4172 records of hard ticks collected from wild and domestic tetrapods. Most tick species included in this study were associated with three to 20 host species. No tick species has been associated either with a single species or with a single genus of host. It was found that the number of host species is sensitive to sampling effort, but not the S(TD)*. The most frequent values of S(TD)* were between 2.5 and 3.5, which shows that the host species more frequently used by Neotropical hard tick species belong to different families or different orders. Immature stages tend to use a broader taxonomic range of hosts than adults, and the interpretation of both measures of host specificity used in this study led to the conclusion that the impact of non-endemic hosts does not alter the patterns of host specificity in Neotropical hard ticks. The index S(TD)* showed that a high proportion of tick species has phylogenetically unrelated species as principal hosts. The conclusion reached in this work indicates that strict host specificity is not common among Neotropical hard ticks and suggests that the influence of tick ecology and evolution of habitat specificity, tick generation time, phenology, time spent off the host and the type of life-cycle could be more important than hosts species. PMID:22954015

Nava, S; Guglielmone, A A

2013-04-01

438

Hard X-ray photoemission spectroscopy  

NASA Astrophysics Data System (ADS)

Except in the very early stage of the development of X-ray photoemission spectroscopy (XPS) by Kai Siegbahn and his coworkers, the excitation sources for XPS studies have predominantly been the Al K? and Mg K? emission lines. The advent of synchrotron radiation sources opened up the possibility of tuning the excitation photon energy with much higher throughputs for photoemission spectroscopy, however the excitation energy range was limited to the vacuum ultra violet and soft X-ray regions. Over the past 5-6 years, bulk-sensitive hard X-ray photoemission spectroscopy using high-brilliance high-flux X-rays from third generation synchrotron radiation facilities has been developed. This article reviews the history of HXPES covering the period from Kai Siegbahn and his coworkers' pioneering works to the present, and describes the fundamental aspects, instrumentation, applications to solid state physics, applied physics, materials science, and industrial applications of HXPES. Finally, several challenging new developments which have been conducted at SPring-8 by collaborations among several groups are introduced.

Kobayashi, Keisuke

2009-03-01

439

Dynamics of hard sphere colloidal dispersions  

NASA Technical Reports Server (NTRS)

Our objective is to perform on homogeneous, fully equilibrated dispersions the full set of experiments characterizing the transition from fluid to solid and the properties of the crystalline and glassy solid. These include measurements quantifying the nucleation and growth of crystallites, the structure of the initial fluid and the fully crystalline solid, and Brownian motion of particles within the crystal, and the elasticity of the crystal and the glass. Experiments are being built and tested for ideal microgravity environment. Here we describe the ground based effort, which exploits a fluidized bed to create a homogeneous, steady dispersion for the studies. The differences between the microgravity environment and the fluidized bed is gauged by the Peclet number Pe, which measures the rate of convection/sedimentation relative to Brownian motion. We have designed our experiment to accomplish three types of measurements on hard sphere suspensions in a fluidized bed: the static scattering intensity as a function of angle to determine the structure factor, the temporal autocorrelation function at all scattering angles to probe the dynamics, and the amplitude of the response to an oscillatory forcing to deduce the low frequency viscoelasticity. Thus the scattering instrument and the colloidal dispersion were chosen such as that the important features of each physical property lie within the detectable range for each measurement.

Zhu, J. X.; Chaikin, Paul M.; Phan, S.-E.; Russel, W. B.

1994-01-01

440

Shear induced diffusion in hard sphere glasses  

NASA Astrophysics Data System (ADS)

The response of dense hard sphere suspensions is examined during the application of steady and non-linear oscillatory shear using Brownian Dynamics (BD) simulations and experimental Light Scattering echo coupled with rheology. At rest, volume fractions around the glass transition exhibit long or infinite relaxation times. However, non-linear shear induces out of cage motions of comparable time scale to the applied rates. We found two distinct regimes in terms of stresses and dynamic response under shear. One regime for lower rates or frequencies of oscillation, governed by Brownian activated diffusion, and a second for higher rates related to shear activated diffusion. A linear dependence with rate was found for the diffusivity in the high rate regime, mirroring the viscous loss due to shear activated particle rearrangements, while diffusivities in the Brownian activated regime showed a power law exponent of less than unity. The exponent was found to increase with volume fraction. For applied rates inducing diffusivities above the in-cage diffusivity at rest, we find a time window of super-diffusive behavior, between the short time (in-cage) and long time (out-of cage) diffusivities under shear, a signature of a dynamic breaking and reforming of the cage.

Koumakis, Nick; Petekidis, George; Brady, John

2012-02-01

441

Hard X-Ray Footprint Source Sized  

NASA Technical Reports Server (NTRS)

RHESSI has detected compact hard (25 - 100 keV) X-ray sources that are <4 arcseconds (FWHM) in extent for certain flares (Dennis and Pernak (2009). These sources are believed to be at magnetic loop footpoints that are known from observations at other wavelengths to be very small. Flare ribbons seen in the W with TRACE, for example, are approx. 1 arcsecond in width, and white light flares show structure at the approx. 1 arcsecond level. However, Kontar and Jeffrey (2010) have shown that the measured extent should be >6 arcseconds, even if the X-ray emitting thick-target source is point-like. This is because of the strong albedo contribution in the measured energy range for a source located at the expected altitude of 1 Mm near the top of the chromosphere. This discrepancy between observations and model predictions may indicate that the source altitude is significantly lower than assumed or that the RHESSI image reconstruction procedures are not sensitive to the more diffuse albedo patch in the presence of a strong compact source. Results will be presented exploring the latter possibility using the Pixon image reconstruction procedure and other methods based on visibilities.

Dennis, Brian R.; Kontar, E. P.

2010-01-01

442

The Hard X ray Telescope Mission  

NASA Technical Reports Server (NTRS)

The Hard X Ray Telescope (HXT) was selected for study as a possible new intermediate size mission for the early 21st century. Its principal attributes are: (1) multiwavelength observing with a system of focussing telescopes that collectively observe from the UV to over 1 MeV, (2) much higher sensitivity and much better angular resolution in the 10100 keV band, and (3) higher sensitivity for detecting gamma ray lines of known energy in the 100 keV to 1 MeV band. The institutions collaborating in the study are: Smithsonian Astrophysical Observatory, Marshall Space Flight Center, Naval Research Laboratory, Goddard Space Flight Center, Argonne National Laboratory, Danish Space Research Institute, Osservatorio Astronomica di Brera (Merate), and Centre d'Etudes Spatiale des Rayonnements (Toulouse). The instrumentation includes several grazing incidence double conical telescopes with multilayer coatings that focus up to 100 keV and a single Laue crystal telescope that functions to 1 MeV. The detectors are CCDs, and germanium, and/or CdZnTe position sensitive arrays.

Gorenstein, Paul

1997-01-01

443

The Boltzmann equation for very hard particles  

NASA Astrophysics Data System (ADS)

The nonlinear Boltzmann equation is solved analytically for general initial distributions in a (spatially homogeneous) system of very hard particles (VHP) with two translational degrees of freedom and with a transition probability for binary collisions ( vw ?v?w?) proportional to ?( v2 + w2 - v? 2 - w? 2). The scattering cross-section corresponding to this model increases as the square root of the collision energy (hence the name VHP-model). As the total energy of the system is finite, essentially no highly energetic particles are present to probe the unphysical high-energy behavior of the cross-section. The VHP-model is extended to a multicomponent mixture of particles, and solved by the same technique, viz. Laplace transformation. An analogous discrete variable model is solved by a generating function method. Finally the solutions of the nonlinear and linearized Boltzmann equation are compared. Their large-energy behavior at a fixed (large) time is different; their large-time behavior at a fixed energy is the same.

Hendriks, E. M.; Ernst, M. H.

1983-07-01

444

Computational Modeling Develops Ultra-Hard Steel  

NASA Technical Reports Server (NTRS)

Glenn Research Center's Mechanical Components Branch developed a spiral bevel or face gear test rig for testing thermal behavior, surface fatigue, strain, vibration, and noise; a full-scale, 500-horsepower helicopter main-rotor transmission testing stand; a gear rig that allows fundamental studies of the dynamic behavior of gear systems and gear noise; and a high-speed helical gear test for analyzing thermal behavior for rotorcraft. The test rig provides accelerated fatigue life testing for standard spur gears at speeds of up to 10,000 rotations per minute. The test rig enables engineers to investigate the effects of materials, heat treat, shot peen, lubricants, and other factors on the gear's performance. QuesTek Innovations LLC, based in Evanston, Illinois, recently developed a carburized, martensitic gear steel with an ultra-hard case using its computational design methodology, but needed to verify surface fatigue, lifecycle performance, and overall reliability. The Battelle Memorial Institute introduced the company to researchers at Glenn's Mechanical Components Branch and facilitated a partnership allowing researchers at the NASA Center to conduct spur gear fatigue testing for the company. Testing revealed that QuesTek's gear steel outperforms the current state-of-the-art alloys used for aviation gears in contact fatigue by almost 300 percent. With the confidence and credibility provided by the NASA testing, QuesTek is commercializing two new steel alloys. Uses for this new class of steel are limitless in areas that demand exceptional strength for high throughput applications.

2007-01-01

445

Phase behavior of parallel hard cylinders  

NASA Astrophysics Data System (ADS)

We test the performance of a recently proposed fundamental measure density functional of aligned hard cylinders by calculating the phase diagram of a monodisperse fluid of these particles. We consider all possible liquid-crystalline symmetries, namely, nematic, smectic, and columnar, as well as the crystalline phase. For this purpose we introduce a Gaussian parametrization of the density profile and use it to numerically minimize the functional. We also determine, from the analytic expression for the structure factor of the uniform fluid, the bifurcation points from the nematic to the smectic and columnar phases. The equation of state, as obtained from functional minimization, is compared to the available Monte Carlo simulation. The agreement is very good, nearly perfect in the description of the inhomogeneous phases. The columnar phase is found to be metastable with respect to the smectic or crystal phases, its free energy though being very close to that of the stable phases. This result justifies the observation of a window of stability of the columnar phase in some simulations, which disappears as the size of the system increases. The only important deviation between theory and simulations shows up in the location of the nematic-smectic transition. This is the common drawback of any fundamental measure functional of describing the uniform phase just with the accuracy of scaled particle theory.

Capitán, José A.; Martínez-Ratón, Yuri; Cuesta, José A.

2008-05-01

446

Revisiting the phase diagram of hard ellipsoids.  

PubMed

In this work, the well-known Frenkel-Mulder phase diagram of hard ellipsoids of revolution [D. Frenkel and B. M. Mulder, Mol. Phys. 55, 1171 (1985)] is revisited by means of replica exchange Monte Carlo simulations. The method provides good sampling of dense systems and so, solid phases can be accessed without the need of imposing a given structure. At high densities, we found plastic solids and fcc-like crystals for semi-spherical ellipsoids (prolates and oblates), and SM2 structures [P. Pfleiderer and T. Schilling, Phys. Rev. E 75, 020402 (2007)] for x : 1-prolates and 1 : x-oblates with x ? 3. The revised fluid-crystal and isotropic-nematic transitions reasonably agree with those presented in the Frenkel-Mulder diagram. An interesting result is that, for small system sizes (100 particles), we obtained 2:1- and 1.5:1-prolate equations of state without transitions, while some order is developed at large densities. Furthermore, the symmetric oblate cases are also reluctant to form ordered phases. PMID:22482570

Odriozola, Gerardo

2012-04-01

447

Aqueous highly acidic hard surface cleaning compositions  

US Patent & Trademark Office Database

Provided are highly aqueous liquid acidic hard surface cleaning compositions having a pH of about 3 or less which comprise: an acid constituent, preferably comprising a ternary acid system consisting formic acid, sulfamic acid and oxalic acid, optionally at least one or more further co-acids; at least one nonionic surfactant based on monobranched alkoxylated C10/C11-fatty alcohols; an organic solvent constituent which comprises at least one glycol ether solvent, preferably a glycol ether solvent which desirably mitigates or masks malodors of the acid constituent, especially when the acid constituent comprises formic acid; optionally a cosurfactant constituent, including one or more nonionic, cationic, amphoteric or zwitterionic surfactants but preferably one or more nonionic surfactants and excluding cationic, amphoteric or zwitterionic surfactants; optionally one or more further constituents selected coloring agents, fragrances and fragrance solubilizers, viscosity modifying agents including one or more thickeners, pH adjusting agents and pH buffers including organic and inorganic salts, optical brighteners, opacifying agents, hydrotropes, abrasives, and preservatives, as well as other optional constituents known to the art; and the balance, water, wherein water comprises at least 80% wt. of the composition.

2012-06-05

448

Surface Integrity of Hard Metal Parts Machined by WEDM  

NASA Astrophysics Data System (ADS)

Hard metal is characterised by having a extremely high hardness and high wear resistance, and those characteristics make difficult conventional machining. Electrical Discharge Machining (EDM) has become an attractive and feasible method for the manufacturing of precision hard metal tooling, and it is now an alternative to classical diamond grinding. This is due to the thermal nature of material removal mechanism in EDM, which is therefore independent on part hardness. This work pays attention to the analysis of surface integrity in wire EDM'ed hard metal parts. Damages on the machined surfaces have been characterised for different cutting regimes. Special attention has been paid to the heat affected zone, since it is in this zone where cracking mostly occurs. The study includes the analysis of the chemical composition of the affected layers. Additionally, the influence of successive trim cuts on surface roughness is addressed.

Plaza, S.; Izquierdo, B.; Sanchez, J. A.; Ortega, N.; Ramos, J. M.

2009-11-01

449

Narrow-line Seyfert 1 galaxies at hard X-rays  

NASA Astrophysics Data System (ADS)

Narrow-line Seyfert 1 (NLSy1) galaxies are a peculiar class of type 1 active galactic nuclei (broad-line Seyfert 1 galaxies, hereinafter BLSy1). The X-ray properties of individual objects belonging to this class are often extreme and associated with accretion at high Eddington ratios. Here, we present a study on a sample of 14 NLSy1 galaxies selected at hard X-rays (>20 keV) from the fourth INTEGRAL/IBIS catalogue. The 20-100 keV IBIS spectra show hard-X-ray photon indices flatly distributed (?20-100 keV ranging from ˜1.3 to ˜3.6) with an average value of = 2.3 ± 0.7, compatible with a sample of hard-X-ray BLSy1 average slopes. Instead, NLSy1 galaxies show steeper spectral indices with respect to BLSy1 galaxies when broad-band spectra are considered. Indeed, we combine XMM-Newton and Swift/XRT with INTEGRAL/IBIS data sets to obtain a wide energy spectral coverage (0.3-100 keV). A constraint on the high energy cut-off and on the reflection component is achieved only in one source, SWIFT J2127.4+5654 (Ecut-off˜ 50 keV, R= 1.0+0.5- 0.4). Hard-X-ray-selected NLSy1 galaxies do not display particularly strong soft excess emission, while absorption fully or partially covering the continuum is often measured as well as Fe line emission features. Variability is a common trait in this sample, both at X-rays and at hard X-rays. The fraction of NLSy1 galaxies in the hard-X-ray sky is likely to be ˜15 per cent, in agreement with estimates derived in optically selected NLSy1 samples. We confirm the association of NLSy1 galaxies with small black hole masses with a peak at 107 M? in the distribution; however, hard-X-ray NLSy1 galaxies seem to occupy the lower tail of the Eddington ratio distribution of classical NLSy1 galaxies. Based on observations obtained with the INTEGRAL/IBIS, XMM-Newton and Swift/XRT.

Panessa, F.; de Rosa, A.; Bassani, L.; Bazzano, A.; Bird, A.; Landi, R.; Malizia, A.; Miniutti, G.; Molina, M.; Ubertini, P.

2011-11-01

450

Does the temperature of beverages affect the surface roughness, hardness, and color stability of a composite resin?  

PubMed Central

Objective: To investigate the effect of beverages’ temperature on the surface roughness, hardness, and color stability of a composite resin. Materials and Methods: Fifty specimens of the Filtek Z250 composite (3M ESPE, Dental Products, St.Paul, MN, USA) were prepared and initial roughness, microhardness, and color were measured. Then the specimens were randomly divided into five groups of 10 specimens each: Coffee at 70°C, coffee at 37°C, cola at 10°C, cola at 37°C, and artificial saliva (control). After the samples were subjected to 15 min × 3 cycles per day of exposure to the solutions for 30 days, the final measurements were recorded. Results: After immersion in beverages, the artificial saliva group showed hardness values higher than those of the other groups (P < 0.001) and the microhardness values were significantly different from the initial values in all groups except for the control group. Both cola groups showed roughness values higher than the baseline values (P < 0.05), while the other groups showed values similar to the baseline measurements. When ?E measurements were examined, the 70°C coffee group showed the highest color change among all the groups (P < 0.05). Conclusion: High-temperature solutions caused alterations in certain properties of composites, such as increased color change, although they did not affect the hardness or roughness of the composite resin material tested.

Tuncer, Duygu; Karaman, Emel; Firat, Esra

2013-01-01

451

Elasticity, electronic properties and hardness of MoC investigated by first principles calculations  

NASA Astrophysics Data System (ADS)

The crystal structure, cohesive energy, formation enthalpy, mechanical anisotropy, electronic properties and hardness of ?-MoC, ?-MoC and ?-MoC are investigated by the first-principles calculations. The elastic constants and the bulk moduli, shear moduli, Young's moduli are calculated. The Young's modulus values of ?-MoC, ?-MoC and ?-MoC are 395.6 GPa, 551.2 GPa and 399.5 GPa, respectively. The surface constructions of Young's moduli identify the mechanical anisotropy of molybdenum carbide, and the results show that anisotropy of ?-MoC is stronger than others. The electronic structure indicates that the bonding behaviors of MoC are the combinations of covalent and metallic bonds. The hardness of ?-MoC is obviously higher than those of ?-MoC and ?-MoC.

Liu, YangZhen; Jiang, YeHua; Feng, Jing; Zhou, Rong

2013-06-01

452

Self-healing phenomenon and dynamic hardness of C60-based nanocomposite coatings.  

PubMed

The phenomenon of surface self-healing in C60-based polymer coatings deposited by ion-beam assisted physical vapor deposition was investigated. Nanoindentation of the coatings led to the formation of a protrusion rather than an indent. This protrusion was accompanied by an abnormal shape of the force-distance curve, where the unloading curve lies above the loading curve due to an additional force applied in pulling the indenter out of the media. The coatings exhibited a nanocomposite structure that was strongly affected by the ratio of C60 ion and C60 molecular beam intensities during deposition. The coatings also demonstrated the dynamic hardness effect, where the effective value of the hardness depends significantly on the indentation speed. PMID:24697539

Penkov, Oleksiy V; Pukha, Volodymyr E; Devizenko, Alexander Yu; Kim, Hae-Jin; Kim, Dae-Eun

2014-05-14

453

Working with Missing Values  

ERIC Educational Resources Information Center

Less than optimum strategies for missing values can produce biased estimates, distorted statistical power, and invalid conclusions. After reviewing traditional approaches (listwise, pairwise, and mean substitution), selected alternatives are covered including single imputation, multiple imputation, and full information maximum likelihood…

Acock, Alan C.

2005-01-01

454

Effect of cutting edge geometry and workpiece hardness on surface generation in the finish hard turning of AISI 52100 steel  

Microsoft Academic Search

An experimental investigation was conducted to determine the effects of tool cutting edge geometry and workpiece hardness on the surface roughness and cutting forces in the finish hard turning of AISI 52100 steel. Cubic boron nitride inserts with various representative cutting edge preparations and through-hardened AISI 52100 steel bars were used as the cutting tools and workpiece material, respectively. This

Jeffrey D Thiele; Shreyes N. Melkote

1999-01-01

455

Savings Bonds Value Calculator  

NSDL National Science Digital Library

From the Federal Reserve Bank of New York, this site computes the redemption value of users's US savings bonds. Easy-to-use pull-down menus allow visitors to enter information such as the date of issue and face value of their Series E bonds, Series EE bonds, and Series S bonds. After entering the information, the Calculator will then show a chart of issue dates and denominations and actual worth of the bonds, if cashed within a set period of time.

456

The value of information.  

PubMed

The value of information is only indirectly a function of its objective characteristics. Of greater importance is its potential to add value to what its users can do. The dramatic recent reductions in the costs of distributing information have made protection against unwanted information more valuable than finding wanted information. This makes active information management a much prized skill. Suggestions are offered for reducing the costs of information search and for framing the search question at the correct level of specificity. PMID:14977383

Chambers, David W

2003-01-01

457

Managing for multiple values  

Microsoft Academic Search

The public is expressing increasing interest in obtaining wildlife habitat, biodiversity, and other values from forests. However, landowners and land managers presently receive no compensation for providing these values. While the resulting dilemma is often characterized as a [open quotes]preservation versus timber-harvest[close quotes] tradeoff, several management options could contribute to both economic and other goals. Although many gradations exist, two

B. Lippke; C. D. Oliver

1993-01-01

458

The Expanding Place Value  

NSDL National Science Digital Library

This collection of three lesson plans is designed to provide students with practice understanding place value (0 to 999), using standard and word form to represent numbers, and using expanded form to represent place value. Each lesson plan provides activities that will help build student understanding of the concepts and practice to help reinforce the skill. Thirteen resource sheets are included and can be used with these lessons or as independent activities.

Thomson, Erin; Pugh, Dana

2005-01-01

459

Reliability and Validity of Quantifying Absolute Muscle Hardness Using Ultrasound Elastography  

PubMed Central

Muscle hardness is a mechanical property that represents transverse muscle stiffness. A quantitative method that uses ultrasound elastography for quantifying absolute human muscle hardness has been previously devised; however, its reliability and validity have not been completely verified. This study aimed to verify the reliability and validity of this quantitative method. The Young’s moduli of seven tissue-mimicking materials (in vitro; Young’s modulus range, 20–80 kPa; increments of 10 kPa) and the human medial gastrocnemius muscle (in vivo) were quantified using ultrasound elastography. On the basis of the strain/Young’s modulus ratio of two reference materials, one hard and one soft (Young’s moduli of 7 and 30 kPa, respectively), the Young’s moduli of the tissue-mimicking materials and medial gastrocnemius muscle were calculated. The intra- and inter-investigator reliability of the method was confirmed on the basis of acceptably low coefficient of variations (?6.9%) and substantially high intraclass correlation coefficients (?0.77) obtained from all measurements. The correlation coefficient between the Young’s moduli of the tissue-mimicking materials obtained using a mechanical method and ultrasound elastography was 0.996, which was equivalent to values previously obtained using magnetic resonance elastography. The Young’s moduli of the medial gastrocnemius muscle obtained using ultrasound elastography were within the range of values previously obtained using magnetic resonance elastography. The reliability and validity of the quantitative method for measuring absolute muscle hardness using ultrasound elastography were thus verified.

Chino, Kentaro; Akagi, Ryota; Dohi, Michiko; Fukashiro, Senshi; Takahashi, Hideyuki

2012-01-01

460

Operating illumination to differentiate dental hard tissues.  

PubMed

This in vitro study was designed to evaluate the ability of fluorescent tubes and dental lights to help operators distinguish tissues (fissures), differentiate between tissues (at the dentinoenamel junction or between carious and sound dentin), and distinguish form of a tooth preparation (Class II and Class V cavities). Operators with "normal" color vision ranked the lights in order of preference for each type of specimen. In general, for the fluorescent illuminants, operators preferred lights with high color temperature values and high color rendering index values. A small group of color-blind observers indicated a preference for an illuminant of low color temperature and low color rendering index value. For dental lights, operators preferred a higher color temperature for examining fissures, the dentinoenamel junction, and the cavity preparation. No particular illuminant was preferred for distinguishing between carious and sound dentin. Many observers had difficulty in choosing a preferred dental luminaire. PMID:2094878

Mann, D S; Makinson, O F; Pietrobon, R A

1990-09-01

461

High efficiency, radiation-hard solar cells  

SciTech Connect

The direct gap of the In{sub 1-x}Ga{sub x}N alloy system extends continuously from InN (0.7 eV, in the near IR) to GaN (3.4 eV, in the mid-ultraviolet). This opens the intriguing possibility of using this single ternary alloy system in single or multi-junction (MJ) solar cells of the type used for space-based surveillance satellites. To evaluate the suitability of In{sub 1-x}Ga{sub x}N as a material for space applications, high quality thin films were grown with molecular beam epitaxy and extensive damage testing with electron, proton, and alpha particle radiation was performed. Using the room temperature photoluminescence intensity as a indirect measure of minority carrier lifetime, it is shown that In{sub 1-x}Ga{sub x}N retains its optoelectronic properties at radiation damage doses at least 2 orders of magnitude higher than the damage thresholds of the materials (GaAs and GaInP) currently used in high efficiency MJ cells. This indicates that the In{sub 1-x}Ga{sub x}N is well-suited for the future development of ultra radiation-hard optoelectronics. Critical issues affecting development of solar cells using this material system were addressed. The presence of an electron-rich surface layer in InN and In{sub 1-x}Ga{sub x}N (0 < x < 0.63) was investigated; it was shown that this is a less significant effect at large x. Evidence of p-type activity below the surface in Mg-doped InN was obtained; this is a significant step toward achieving photovoltaic action and, ultimately, a solar cell using this material.

Ager III, J.W.; Walukiewicz, W.

2004-10-22

462

Radiation hardness of CMS pixel barrel modules  

NASA Astrophysics Data System (ADS)

Pixel detectors are used in the innermost part of the multi purpose experiments at the LHC and are therefore exposed to the highest fluences of ionising radiation, which in this part of the detectors consists mainly of charged pions. The radiation hardness of all detector components has been thoroughly tested up to the fluences expected at the LHC. In case of an LHC upgrade, the fluence will be much higher and it is not yet clear how long the present pixel modules will stay operative in such a harsh environment. The aim of this study was to establish such a limit as a benchmark for other possible detector concepts considered for the upgrade. As the sensors and the readout chip are the parts most sensitive to radiation damage, samples consisting of a small pixel sensor bump-bonded to a CMS-readout chip (PSI46V2.1) have been irradiated with positive 200 MeV pions at PSI up to 6×1014 neq/cm2 and with 21 GeV protons at CERN up to 5×1015 neq/cm2. After irradiation the response of the system to beta particles from a 90Sr source was measured to characterise the charge collection efficiency of the sensor. Radiation induced changes in the readout chip were also measured. The results show that the present pixel modules can be expected to be still operational after a fluence of 2.8×1015 neq/cm2. Samples irradiated up to 5×1015 neq/cm2 still see the beta particles. However, further tests are needed to confirm whether a stable operation with high particle detection efficiency is possible after such a high fluence.

Rohe, T.; Bean, A.; Erdmann, W.; Kästli, H.-C.; Khalatyan, S.; Meier, B.; Radicci, V.; Sibille, J.

2010-12-01

463

Converting hard copy documents for electronic dissemination  

SciTech Connect

Since the advent of computer systems, the goal of a paperless office, and even a paperless society, has been pursued. While the normal paper flow in an organization is far from totally automated, particularly for items requiring signatures or authorizations, electronic information dissemination is becoming an almost simple task. The reasons for providing on-line documents are many and include faster and easier access for everyone, elimination of printing costs, reduction of wasted shelf and desk space, and the security of having a centrally-located, always up-to-date document. New computer software even provides the user with the ability to annotate documents and to have bookmarks so that the old scribbled-in and dog-eared manual can be replaced without loosing this `customizability`. Moreover, new hypermedia capabilities mean that documents can be read in a non-linear fashion and can include color figures and photographs, audio, and even animation sequences, capabilities which exceed those of paper. The proliferation of network-based information servers, coupled with the growth of the Internet, has enticed academic, governmental, and even commercial organizations to provide increasing numbers of documents and data bases in electronic form via the network, not just to internal staff, but to the public as well. Much of this information, which includes everything from mundane company procedures to spiffy marketing brochures, was previously published only in hard copy. Converting existing documents to electronic form and producing only electronic versions of new documents poses some interesting challenges to the maintainer or author.

Hoffman, F.

1994-12-31

464

Reduced hardness as an indicator of susceptibility of timbers to attack by Euophryum confine Broun  

Microsoft Academic Search

The influence of early-wood hardness on the tunnelling activity of Euophryum confine Broun (Coleoptera: Curculionidae) is reported. The hardness of Pinus nigra (Arnold) sapwood blocks was measured using a micro-hardness testing device that simulated a mandible. Hardness was influenced by moisture content and wood decay. Hardness was found to be significantly lower at 25% equilibrium moisture content than at 15%

M. Green; H. D. Mansfield-Williams; A. J. Pitman

2004-01-01

465

Molecular dynamics calculations of the hard-sphere equation of state  

SciTech Connect

The equation of state of the hard-sphere fluid is studied by a Monte Carlo-molecular dynamics method for volumes ranging from 25 V/sub 0/ to 1.6V/sub 0/, where V/sub 0/ is the close-packed volume, and for systems sizes from 108 to 4000 particles. The N dependence of the equation of state is compared to the theoretical dependence given by Salsburg for the NPT ensemble, after correction for the ensemble difference, in order to obtain estimates for the thermodynamic limit. The observed values of the pressure are compared with both the (3/2) and the (2/3) Pade approximants to the virial series, using Kratky's value for the fifth virial coefficient B/sub 5/ and choosing B/sub 6/ and B/sub 7/ to obtain a least-squares fit. The resulting values of B/sub 6/ and B/sub 7/ lie within the uncertainties of the Ree-Hoover-Kratky Monte Carlo estimates for these virial coefficients. The values of B/sub 8/, B/sub 9/, and B/sub 10/ predicted by our optimal (3/2) approximant are also reported. Finally, the Monte Carlo-molecular dynamics equation of state is compared with a number of analytic number of analytic expressions for the hard-sphere equation of state.

Erpenbeck, J.J.; Wood, W.W.

1984-05-01

466

Local structure in hard-sphere chain-molecule fluids  

NASA Astrophysics Data System (ADS)

The conformation of a polymer chain in solvent is coupled to the local structure of the solvent environment. For hard-sphere systems, a monomeric solvent acts to compress a flexible hard-sphere-solute chain and, for a dense system, the local solvent structure is imprinted onto the chain. Here we use Monte Carlo simulation, including bond-rebridging moves, to study the size and conformation of a hard sphere chain in a hard-sphere solvent as a function of both solvent density and solvent diameter. We also study the structure of a hard-sphere-chain solute in a hard-sphere-chain solvent. In the case of a 5-mer chain in 5-mer solvent we show that the effects of solvent can be mapped to a set of two-body solvation potentials. Following our previous work on hard-sphere chains in monomeric solvent [1], we explore the application of these short chain potentials to the study of longer chain-molecule fluids. [4pt] [1] M.P. Taylor and S. Ichida, J. Polym. Sci. B: Polym. Phys. 45, 3319 (2007).

Wasti, Sambid; Taylor, Mark

2011-10-01

467

Local structure in hard-sphere chain-molecule fluids  

NASA Astrophysics Data System (ADS)

The conformation of a polymer chain in solvent is coupled to the local structure of the solvent environment. For hard-sphere systems, a monomeric solvent acts to compress a flexible hard-sphere-solute chain and, for a dense system, the local solvent structure is imprinted onto the chain. Here we use Monte Carlo simulation, including bond-rebridging moves, to study the size and conformation of a hard sphere chain in a hard-sphere solvent as a function of both solvent density and solvent diameter. We also study the structure of a hard-sphere-chain solute in a hard-sphere-chain solvent. In the case of a 5-mer chain in 5-mer solvent we show that the effects of solvent can be mapped to a set of two-body solvation potentials. Following our previous work on hard-sphere chains in monomeric solvent [1], we explore the application of these short chain potentials to the study of longer chain-molecule fluids. [4pt] [1] M.P. Taylor and S. Ichida, J. Polym. Sci. B: Polym. Phys. 45, 3319 (2007).

Wasti, Sambid; Taylor, Mark

2012-04-01

468

Nucleation-Mode Localization in Hard-Soft Nanocomposites  

NASA Astrophysics Data System (ADS)

Aligned hard-soft nanocomposites continue to be an active research area in permanent magnetism, challenged by demanding processing requirements but also encouraged by experimental proofs of principle. The approach was initially outlined by Kneller and Hawig (1991), who advocated hard-soft multilayers. Skomski and Coey (1993) considered three-dimensional nanostructures, such as soft spheres in a hard matrix, and predicted an upper energy-product limit of about 1000 kJ/m^3. It is well-established that the dimensions of the soft regions cannot be larger than twice the domain-wall width of the hard phase, but otherwise it was believed that geometry has a rather secondary effect. However, our recent research reveals substantial differences. Soft-in-hard geometries are better than hard-in-soft geometries and embedded soft spheres are better than multilayers. This is in close analogy to the dimensionality-dependent quantum-mechanical delocalization of electrons in an inhomogeneous potential and to the behavior of impurity states in the band gaps of solids. Transparent analytical nucleation-field solutions are found for some geometries and in the limit of very small soft inclusion as a function of the hard-phase coercivity and hysteresis-loop shape.

Skomski, Ralph; Balasubramanian, Balamurugan; Das, Bhaskar; Sellmyer, D. J.

2013-03-01

469

Chromium nitride-silver self-lubricating nanoporous hard coatings  

NASA Astrophysics Data System (ADS)

The focus of this thesis research is to explore a new approach to adaptive solid lubrication using nanoporous hard coatings. To investigate this approach, I deposited prototype coatings for study consisting of a hard chromium nitride (CrN) matrix co-deposited with a lubricious silver (Ag) phase by reactive magnetron co-sputtering. The idea is to exploit the relative immiscibility of the two phases to create nanocomposite structures with intrinsic lubricant transport properties enabled by the presence of the nanopores. Specifically, I develop the scientific understanding of the critical growth parameters that govern nanocomposite structural evolution which in turn control mechanical properties, solid lubricant diffusion, and tribological response. Mechanical properties were analyzed by both micro and nanoindentation measurements for the composites as a function of Ag aggregate morphology. For Ts ? 500°C, hardness as measured by nanoindentation into the surface is relatively uniform giving values of 14.6, 13.6, and 14.3 GPa for Ts = 300, 400, and 500°C respectively. For Ts > 500°C, the cross-sectional microhardness increases with T s from 16.5 to 19.7 to 24.3 GPa for Ts = 500, 600, and 700°C, respectively, which is attributed to a decrease in the effective Ag concentration associated with temperature activated segregation. The average hardness for pure CrN samples is 23.8 and 27.5 GPa as measured by surface nanoindentation and cross-sectional microindentation, respectively. Lubricant transport behavior was characterized by a series of vacuum annealing experiments. Vacuum annealing experiments at Ta = 425, 525, and 625°C show that Ag diffuses to the coating surface to form lubricious surface aggregates and that the rate for Ag lubricant transport increases with increasing DeltaT (Ta - Ts) for Ta > Ts, as determined by quantitative electron microscopy surface analyses. However, the Ag remains in the CrN matrix for Ta < Ts, which is attributed to the Ag aggregate size distribution within the coating which affects the chemical potential. Friction and wear behavior were measured in ambient air at test temperatures, Tt = 20°C to 700°C to study the self-lubricating properties and tribological mechanisms of the coatings as a function of structure and lubricant transport properties. Ball