bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tests of Prestressed Expanded-Shale Concrete Beams Subjected to Short-Time and Sustained Loads
Authors: Davis RE , Troxell GE , McCall DO , McCann RA 
Published: September 2009

This paper gives the results of tests on 19 flexural members of prestressed concrete, of lengths ranging from 24 to 65 ft and including beams of doubletee section for floors and roofs, box beams for floor systems of bridges and buildings, and girders and purlins of I-section for roofs. Most of the members were composed of expanded-shale lightweight concrete, and the steel was pretensioned. Most of the tests were made under loading which would produce failure in bending; others in shear. All flexural members were loaded until first cracking was observed and then unloaded to observe recovery. Thereafter, one beam was loaded immediately until failure was produced and four beams were subjected continuously to their design loads for a period of 3 1/2 months. Observations were made on all flexural members to determine deflections and cracking, and on selected beams to determine longitudinal strains in flexure or strength in shear. Auxiliary tests were made to determine compressive strength and modulus of elasticity of concrete, creep of concrete under sustained compressive stress, and loss of tension in steel reinforcement due to creep.
It was found that live loads required to produce first cracking in flexure ranged from 1.5 to 2.2 times the design loads. Shearing loads required to produce failure in diagonal tension ranged from 1.0 to 1.7 times those computed for conventionally reinforced-concrete beams of similar section. Live-load deflections under short-time loading were generally considerably less than was expected. When the design loads were released, elastic recovery was practically complete. When loads somewhat in excess of those required to produce flexural cracking were released, residual deflections were insignificantly small. Deflections under sustained design loads were small, and elastic-plus-creep deflections were within customary limitations except for one roof beam of very long span. Loss of tension in reinforcement under sustained loading was substantially equal to that assumed in design and was not greater for the expanded-shale aggregate than for natural aggregate. Creep under sustained load was of the same order of magnitude as that commonly observed for concrete containing natural aggregate. In general, the tests confirm the assumptions commonly made in design of prestressed concrete beams.
A Physical Method for Determining The Composition of Hardened Concrete
Authors: Polivka M , Kelly JW , Best CH 
Published: September 2009

Determination of the proportions of materials in hardened concrete in structures becomes desirable when question arises as to the quality of the concrete actually placed. Existing methods of chemical analysis depend heavily on knowledge of the chemical composition of the aggregates, which is seldom available.
This paper describes a “point-count” method of determining the cement content of hardened portland-cement concrete by analysis of a cut section with a traveling microscope. The voids and aggregate content are estimated by direct observation; the cement content is then determined by difference, with correction for non-evaporable water in the cement paste. Sand-aggregate ratio is also computed.
Results of microscope analysis of various laboratory-mixed concretes are compared with original mix proportions. Comparisons are also made with results of chemical analysis according to ASTM Method C 85-54 and two other chemical methods developed during the investigation.
The precision of each method is estimated, and the advantages and limitations are discussed. It is concluded that the microscope analysis is at least as precise as the chemical methods, and that it requires less time and equipment. With further study and refinement, it offers promise of providing a reliable estimate of the cement content of hardened concrete within the precision of construction and sampling.
Effects of Various Cleaning Methods on Electronic Components in the Micromodule
Authors: Vossen J. L. 
Published: September 2009

This paper describes several interesting effects observed during evaluation of various procedures and solvents for cleaning electronic components used in micromodules. Cleaning is performed on partially fabricated components prior to the application of the encapsulant. All traces of flux and other contaminants must be removed from the components before encapsulation to ensure the high reliability required of each element and to provide a surface compatible with the final encapsulant.
Two cleaning methods were used in the tests. Each method was applied to 12 different components, including high-stability metal-film resistors, solid electrolytic tantalum capacitors, four types of ceramic capacitors, inductors having two different core materials, diodes similar to the 1N277 and 1N643, and transistors similar to the 2N404. Special emphasis was placed on the components which showed large changes in electrical chracteristics after cleaning. The method that removed the maximum amount of contaminants without damaging the components was selected. A complete analysis of the effect of the cleaning methods on each component is given, and the measures used to overcome damaging effects are outlined.
Noise-Tested Cathode Activation
Authors: Dlouhy F. , Schuetze H. J. 
Published: September 2009

The plate current of an electron tube producing a reasonable shot-noise level reflects the variation of the oxide cathode activity during the activation and aging process. When operating several lots of tubes at different cathode temperatures in the range from 1000 to 1500 K under stand-by conditions a set of emission curves is obtained showing maxima. A straight line is obtained by plotting the activating temperature versus time corresponding to the maxima. This is the base for developing activation schedules giving optimum activity of the cathode in the shortest time. The solution of the problem consists in an activation procedure with several temperature steps while simultaneously considering electron bombardment of the electrodes that affect the cathode activity. The net result is an approximate parallel shift of the straight line responsible for the so-called single-step activation. The position and the slope of this line in semilogarithmic representation are affected by core material and processing.
Tubes activated thermally often undergo an emission slump during aging when high voltages are applied, especially if passive core materials are used. This phenomenon, although influenced by several processing and operating parameters, has been used as a tool for studying the effect of cathode environment upon its activity. The experiments described in this paper were performed on a pentode equivalent to the type 6 BX 6.
An Experimental Study of the Strength and Ductility of Steel at Elevated Temperatures
Authors: Glen J. 
Published: September 2009

The object of the investigation was to explain the effect of various tempering treatments on the creep resistance of carbon and low-alloy steels and to elucidate the probable behavior of such steels during long-time service at high temperature. It was suspected that the problem was related to precipitation hardening since creep tests and tension tests carried out over a range of temperature showed that an increase or decrease in resistance to deformation could be brought about by different tempering treatments.
To follow up these preliminary tests true stress-strain tension tests were carried out on a series of low-carbon steels containing varied amounts of manganese and molybdenum. Similar steels killed with aluminum were also tested. In the absence of manganese and molybdenum a maximum in the stress for a given strain was obtained at about 200 C. When manganese was added a second maximum appeared at about 300 C, and with molybdenum at about 500 C. These maxima in stress are attributed to the precipitation of carbides during the process of straining, the type of carbide formed depending on the testing temperature and the alloying elements present. The influence of tempering is also indicated.
To each maximum in stress there corresponds a minimum in ductility. This suggests that the strain preceding rupture is also related to the precipitation of carbides, in this case at the grain boundaries.
From these tests it was possible to explain many of the effects of alloying elements on the creep resistance and ductility of steels under various conditions of testing. It was concluded that the factor which largely determined such effects was precipitation.
Mori me non vult. Seneca and Pseudo-Quintilian's IVth Major Declamation
Authors: Pasetti Lucia 
Published: September 2009

Riassunto
La IV Declamazione Maggiore pseudoquintilianea, un caso di mors voluntaria, è chiaramente influenzata da Seneca. Il rapporto intertestuale con Seneca filosofo può essere colto nei passaggi dell'argumentatio in cui il declamatore, che sostiene la necessità del suicidio, discute in generale il valore qualitativo del tempo, la vanità di una vita mal spesa, i vantaggi della mors opportuna. D'altra parte, il personaggio del figlio parricida presenta tratti tipicamente senecani: la percezione di una forza irrefrenabile che sorge dall'inconscio (nescioquid) e spinge il protagonista al delitto trova corrispondenze intertestuali nel Tieste e in altre tragedie di Seneca.
Copper Deposition Technology for Thru Silicon Via Formation Using Supercritical Carbon Dioxide Fluids Using a Flow Type Reaction System
Authors: Matsubara Masahiro , Kondoh Eiichi 
Published: September 2009

AbstractA supercritical fluid is a high-pressure medium that possesses both high diffusivity and solvent capabilities. Metal thin films can be deposited in supercritical fluids from an organometallic compound (precursor) through thermochemical reactions. In the present study, we used a technique, aimed at applying to the fabrication of through-silicon vias (TSVs), where copper thin films were deposited in silicon microholes 10 μm in diameter and 350 μm in depth. The temperature and pressure were varied from 180°C to 280°C and 1 MPa to 20 MPa, respectively. The maximum coating depth decreased with deposition temperature, whereas a peak maximum of the depth was observed at around 10 MPa. The temperature and pressure dependences on the coating depth were numerically studied. On the basis of the analysis, a deposition program was modified as to elongate the coating depth.
High-Speed and Low-Power Performance of n-type InSb/InP and InAs/InP Core/Shell Nanowire Field Effect Transistors for CMOS Logic Applications
Authors: Khayer Mohammad Abul , Lake Roger K 
Published: September 2009

AbstractThe performance metrics of highly scaled n-type InSb/InP and InAs/InP core/shell nanowire (NW) field-effect transistors (FETs) are theoretically investigated using an 8-band k•p model and a semiclassical ballistic transport model. We present the ON-current, the intrinsic cut-off frequency, the gate-delay time, the power-delay product, and the energy-delay product of NWFETs with two NW diameters of 10 nm and 12 nm, which operate in the quantum capacitance limit. We compare the results to the numbers predicted or projected for other materials and dimensionalities and find good agreement. Within a source Fermi energy range of 0.1 – 0.3 eV for all devices, the ON-current varies from 7 – 58 μA, the intrinsic cut-off frequency ranges from 8 – 15 THz, the power-delay product varies from 2×10-20 – 9.7×10-19 J, the gate-delay time varies from 2 – 19 fs, and the energy-delay product ranges from 7×10-35 – 1×10-32 Js. These NWFETs, thus, provide both ultra-low power switching and high-speed.
Hydrothermal Synthesis of Zinc Oxide Nanowires on Kevlar using ALD and Sputtered ZnO Seed Layers
Authors: Conley John , Mason Ashley Diane , Waggoner Todd Jason , Smith Sean Weston , Gibbons Brady , Price David , Allman Derryl 
Published: September 2009

AbstractLow temperature hydrothermal methods allow for growth of nanowires on novel substrates. We examine the impact of variations in chemical concentration, time, temperature, and seed layer on nanowire (NW) growth and crystallite formation. The majority of growth (NWs and crystallites) was found to occur within the first two hours. Lower Zn(NO3)2 concentrations produced a reduction in the undesired large crystallites, whereas hexamethylene tetramine (HMT) concentration did not largely impact crystallite density or nanowire morphology. Growth temperature appeared to impact NW diameter variation. Nanowires grow only on the ZnO seed layer and crystallites seem to attach preferentially to the bare Kevlar surface.
Thermocapillary Patterning of Nanoscale Polymer Films
Authors: Dietzel Mathias , Troian Sandra M 
Published: September 2009

AbstractWe investigate a method for non-contact patterning of molten polymer nanofilms based on thermocapillary modulation. Imposed thermal distributions along the surface of the film generate spatial gradients in surface tension. The resulting interfacial stresses are used to shape and mold nanofilms into 3D structures, which rapidly solidify when cooled to room temperature. Finite element simulations of the evolution of molten shapes illustrate how this technique can be used to fabricate features of different heights and separation distances in a single process step. These results provide useful guidelines for controlling proximity effects during evolution of adjacent structures.
Ion-beam Texturing at Nucleation – Manipulation of Crystallographic Orientation in Cubic Materials at the Nanometer Scale
Authors: Groves James , Hammond Robert , Marshall Ann , DePaula Raymond F , Stan Liliana , Clemens Bruce M 
Published: September 2009

AbstractThe use of an ion beam assist during the concurrent deposition of cubic materials can result in the growth of crystallographically oriented thin films. A model system, magnesium oxide (MgO), has been successfully used as a biaxially textured template film and develops texture in a different manner from that of other well-studied materials, like yttria-stablized zirconia. Here, we present data on the initial nucleation of biaxial texture in this model system using a novel in-situ quartz crystal microbalance (QCM) substrate combined with in-situ reflected high-energy electron diffraction (RHEED). Temporal correlation of mass uptake with the RHEED images of the growing surface can be used to elucidate the mechanism of texture development in these films. Experimental data shows that the initially polycrystalline MgO film develops biaxial crystallographic texture at a thickness of ˜2 nm, regardless of the ion-to-molecule ratio. RHEED images show the onset of texture occurs quickly and is somewhat analogous to a solid phase re-crystallization process with crystallite sizes of ˜3 to 4 nm. Imaging with transmission electron microscopy has corroborated these observations. Changes in the ion-to-molecule ratio can influence the crystallite size and affect the nucleation density of these films. Growth of these films on various substrates changes the sticking coefficient of the MgO and influences the nucleation density and film growth mode as well. This opens the possibility of using MgO and other materials to develop biaxially textured crystallites with a narrow, specified size distribution for nanoscale applications.
Quantitative Mechanical/Chemical Imaging of Bone from Dmp1 Null Mice
Authors: Yao Xiaomei , Bonewald Lynda F , Eick J David , Wang Yong 
Published: September 2009

AbstractDentin matrix protein 1 (DMP1) is an acidic noncollagenous protein which plays an important role in mineralized tissue formation. Dmp1 null adult mice are ricketic and osteomalacic and are a model for hypophosphatemic rickets [1]. Mutation in humans results is Autosomal Recessive Hypophosphatic Rickets [1]. The degree of bone mineralization significantly contributes to bone tissue mechanical properties, but precise relationships and interactions between chemical and mechanical variables are unknown. The objective of this study was to relate the differences in chemical properties in the Dmp1 wildtype (WT) and null (KO) mouse femoral cortical bone to their mechanical properties by using FTIR imaging and Scanning Acoustic Microscopy (SAM). Interactive mechanical (elastic modulus) and chemical images (i.e., mineral/matrix ratios) were generated from the same region of bone at a lateral resolution of ˜10 um. Mechanical analysis showed that elastic modulus, 75 percentile around 7.1 GPa, was ˜60% less in Dmp1 KO than that in WT, in which elastic modulus was 75 percentile around 15.2 GPa. The mineral-to-matrix ratios in Dmp1KO (4.96±1.63) were ˜2 times lower than that in Dmp1 WT (8.65±1.14). The mineral crystallinity and collagen crosslink ratios were not significantly different between KO and WT. Conclusions: The results relate the bone elastic modulus changes in Dmp1WT and KO mice with chemical changes within a specific bone site. These measurements provide a new tool for describing the variability of bone chemical and mechanical properties.
In vivo degradation behavior of PDC multiblock copolymers containing poly(para-dioxanone) hard segments and crystallizable poly(epsilon-caprolactone) switching segments
Authors: Hiebl Bernhard , Kratz Karl , Fuhrmann Rosemarie , Jung Friedrich , Lendlein Andres , Franke Ralf-Peter 
Published: September 2009

AbstractThe degradation behavior of biodegradable multiblock copolymers (PDC) containing poly(p-dioxanone) hard segments (PPDO) and crystallizable poly(epsilon-caprolactone) switching segments (PCL) synthesized via co-condensation of two oligomeric macrodiols with an aliphatic diisocyanate as junction unit was explored in in vivo and in vitro experiments. The in vitro experiments for enzymatic degradation resulted that the poly(epsilon-caprolactone) segments are degraded faster, than the poly(p-dioxanone) segments. During degradation the outer layer of the test specimen becomes porous. Finally non-soluble degradation products in form of particles were found at the surface. This observation is in good agreement with the in vivo studies, where the non-soluble degradation products in the periimplantary tissues showed a diameter of 1 – 3 micron.
Studies of the blue to red phase transition in polydiacetylene nanocomposites and blends
Authors: Patlolla Anitha , Wang Qi , Frenkel Anatoly , Zunino III James L , Skelton Donald R , Iqbal Zafar 
Published: September 2009

AbstractThe conjugated polymeric backbone of polydiacetylenes (PDAs), comprising of alternating ene-yne groups, undergo intriguing stress-, chemical- or temperature-induced chromatic phase transitions associated with the disruption of the backbone structure and shortening of the conjugation length. PDAs, such as polymerized 10, 12 pentacosadiynoic acids (PCDA), when incorporated with inorganic oxides form nanocomposites and uniform blends with polymers. Blends of poly-PCDA with polymers, such as polyvinyl alcohol, polyvinylidene fluoride and cellulose increase the blue to red transition temperature without affecting the irreversibility of the red phase. However, the addition of zinc oxide to pure poly-PCDA makes the red phase highly reversible and substantially increases the blue to red transition temperature. The addition of TiO2 to poly-PCDA on the other hand does not affect the irreversibility of the red phase and the chromatic transition temperature. In order to understand the atomic scale interactions associated with these changes in the chromatic transitions, we have investigated both the nanocomposites and polymer blends using Raman and Fourier-transform infrared spectroscopy, and extended X-ray absorption fine structure (EXAFS) measurements
Self-Assembled Ultra-thin Silica Layers for On-Chip Chromatography
Authors: Choi Sun , Park Inkyu , Pisano Albert P 
Published: September 2009

AbstractWe propose a novel method for self-assembled packing of silica microsphere in micro-channel which can be potentially used for on-chip chromatography. Chromatography has been one of the most widely used techniques for the analysis and separation of the mixtures of biochemical compounds in research laboratories and industrial factories. Numerous chromatography techniques such as High-Performance Liquid Chromatography (HPLC), Thin Layer Chromatography (TLC) use absorbents (ex: silica, alumina, cellulose) as stationary phase material [1]. Effective loading of absorbents in those techniques has been a huge challenge since it requires additional implementation of high-pressure pump system (for HPLC) or limits selective coating of absorbents on supporting plate (for TLC). In order for chromatography to be efficiently integrated with micro-fluidic Lab-on-a-chip devices, novel techniques for easy and simple packing of absorbents within micro channels should be developed.Solvent-evaporation based 2-D crystallization technique [2] can enable mono-dispersed micro-particles to be self-assembled by capillary attractive forces. We apply this technique to assemble dense packing of silica microsphere and form ultra thin layers (2˜3 layers) within open microchannel. Open micro-channel has been constructed by conventional photolithography of SU8 photoresist. A small droplet (Volume: 0.1μL) of silica suspension (Diameter: 3μm, Solvent: DI Water, Concentration: 1.25wt%) has been placed in the defined inlet of micro channel. Capillary force within the open SU8 microchannel induces the flow of silica suspension in the channel. The packing of microsphere starts from the outlet side of the channel, where the thickness of solvent drastically decreases due to sudden increase of cross-sectional area of channel, and this packing propagates to the inlet side of the channel until solvent evaporates completely. As a result, a dense packing of silica microspheres are successfully assembled and a thin layer of silica microspheres are formed within open micro-channel.We will present the characterization of silica packing with regard to various process parameters and also will include theoretical interpretation of this packing technique in more detail. We will also present our future approach to integrate our technique on-chip chromatography applications.