KoreaScience (Korea)

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The high temperature abrasive wear resistant of the composites with different Al{sub 2}O{sub 3} volume fractions, particle coating and size were investigated and the failure action of composites under different conditions at high temperature was analyzed. The results showed that the high temperature abrasive wear resistant of composite with Ni coating and wide size and 39% volume fraction of particle is the best among all composites examined. (orig.)

Energy Technology Data Exchange (ETDEWEB)

A brief description is given of some commercially-available wear-resistant products suitable for use in mine environments. The materials are cast basalt, cast or sintered alumina, and a heat-treated martensitic iron, and they can be used as linings for pipes, bunkers and chutes.

Energy Technology Data Exchange (ETDEWEB)

The wear behaviour of 722M24 (En40B) steel plasma nitrided at high temperatures for long durations was investigated. Under dry sliding and abrasive-containing lubricated conditions, the wear characteristics of the steel were studied as a function of load, time and white layer thickness. The white layer and the wear debris were characterized by X-ray diffraction. The topography of the wear surface was examined in a scanning electron microscope. The plasma nitriding process was carried out using a 20 kW plasma processing unit in cracked ammonia atmosphere. Treatment times of up to 100 h were employed with temperatures of 550, 570 and 590 C. Wear tests were performed with plasma nitrided AMS 6472 as the counterface material. The tests under abrasive-containing lubricated conditions were carried out with 10% carborundum powder 10 [mu]m in size ...

Energy Technology Data Exchange (ETDEWEB)

A composite material consisting of WC-Co particles in a steel matrix was fabricated by sintering mixtures of WC-Co particles and a steel powder and infiltrating the sintered pieces with a copper alloy. Its wear resistance and mechanical properties were studied as a function of the content in WC-Co particles and other characteristics of the composite material microstructure. Infiltration provided a simple means to obtain a strong cohesion between WC-Co particles and the steel matrix. An effective matrix protection against wear is obtained with relatively low additions of particles especially with a silica abrasive which is soft with respect to cemented carbide. The experimental results show that this material has good mechanical properties and wear resistance. Depending upon abrasion resistance, wear losses are reduced up to 10 times by a 30 vol% addition of ...

Energy Technology Data Exchange (ETDEWEB)

Contamination of the lube-oil with hard abrasive particles leads to a three-body abrasive wear mechanism that highly accelerates piston ring/cylinder liner wear in coal-fueled diesel engines. One approach to reducing that wear is to modify the size and orientation of surface asperities on the cylinder to enhance the formation of a hydrodynamic film, and to provide avenues of escape for particles that would otherwise be trapped in the wear zone. Another approach is to introduce additives into the contaminated lube-oil that further enhance hydrodynamic film formation, form chemical films on the wearing surfaces, or form films on the contaminant particles. This work focuses on defining the effects of cylinder liner surface finish, various configurations of slots in the cylinder liner surface, and various additives in the contaminated lube-oil ...

Energy Technology Data Exchange (ETDEWEB)

Contamination of the lube-oil with hard abrasive particles leads to a three-body abrasive wear mechanism that highly accelerates piston ring/cylinder liner wear in coal-fueled diesel engines. One approach to reducing that wear is to modify the size and orientation of surface asperities on the cylinder to enhance the formation of a hydrodynamic film, and to provide avenues of escape for particles that would otherwise be trapped in the wear zone. Another approach is to introduce additives into the contaminated lube-oil that further enhance hydrodynamic film formation, form chemical films on the wearing surfaces, or form films on the contaminant particles. This work focuses on defining the effects of cylinder liner surface finish, various configurations of slots in the cylinder liner surface, and various additives in the contaminated lube-oil ...

Energy Technology Data Exchange (ETDEWEB)

Prior to 1986, the abrasive coking coal processed in the coal preparation plant at the Fording River operation at Elkford, British Columbia, was destroying the mild steel straight pipe and elbows at such a rate that they were having to be replaced annually and every 6-8 months respectively. To solve the problem, Fording River began to replace existing pipe and elbows with fused-cast, basalt-lined abrasion-resistant pipe, elbows and fittings manufactured by Abresist Corp. of Urbana, Indiana. The Abresist straight pipe has lasted 7 seven years and the Abresist elbows 5 years and both are still in use. 2 photos.

International Nuclear Information System (INIS)

For several decades, ceramic matrix composite have been attracted attention in advanced structural and tribological applications. Advanced structural ceramics are presently used in diverse tribological applications such as tips for ballpoint pens, precision instrument bearings and cutting tools inserts. Design and selection of ceramics for these applications require reliable data on the effects of temperature, load and environment on the tribological behavior of these ceramics. In the present work, #alpha#-sialon matrix composites reinforced with different amounts of #beta#-sialon fibers were produced with the aim of improving their toughness to increase the industrial applications. The wear properties of #alpha#-sialon matrix composites were evaluated by carried out wear tests using a pin-on-disk tribometer under dry conditions. The #alpha#-sialon matrix composites were manufactured by slip casting and sintered by uniaxial hot pressing. ...

Energy Technology Data Exchange (ETDEWEB)

A combination of erosion and corrosion at the Victoria Junction coal preparation plant in Sydney, Nova Scotia was causing serious problems. Schedule 80 mild steel pipes were starting to fail as well as some quarter-inch steel plates in the lauders and chutes. Some corrosion tests were carried out and the high chloride level in the process water was felt to be the single most important contribution to the corrosion problem. Cast basalt was selected as a solution to the pipe wear problem. Three different types of abrasion/corrosion-resistant tiling - basalt tiles, kalceram tiles and ceramic tiles were well suited to the chloride conditions at this plant.

British Library Electronic Table of Contents (United Kingdom)

A type of Si3N4-based nanocomposites ceramic cutting tool material was prepared by the addition of nano-scale Si3N4W whisker and nano-scale TiN particle. Cutting performance of the Si3N4/Si3N4W/TiN nanocomposite ceramic tool in machining of cast iron was investigated in comparison with a commercial sialon ceramic tool, and the tool wear mechanism was studied. The two types of cutting tools have similar cutting performance at relatively low cutting parameters, while Si3N4/Si3N4W/TiN nanocomposite tool exhibits a better wear resistance than sialon tool at the relatively high cutting parameters. The wear of sialon ceramic cutting tool is dominated by the plastic deformation, abrasive action, microcracking, pullout of grains and chemical action at the higher cutting parameters. The higher mech...

Energy Technology Data Exchange (ETDEWEB)

This paper summarizes the results of a long-term research project by SKBV which aimed to find ways of increasing spiral chute capacity while minimizing particle degradation, and also to extend the life of chute linings. Spiral chutes have been redesigned in such a way that chute speeds are considerably slower. The most wear-resistant and economic material for the inlet area was found to be slabs of tempered alloy cast steel, and for normal chute sections, cast basalt plates. Vertical rom bunkers can now be lined with thin cladding sections of GRC. Staple pit spiral chutes have been considerably improved in respect to wear and abrasion by the use of toughened steel as the chute lining material. Several of the innovations developed during the course of the research project are in use in West German mines and some have also been introduced abroad. (In German)

Energy Technology Data Exchange (ETDEWEB)

PVD-coatings based on TiB{sub 2} are expected to show high wear resistance and low tendency of adhesion on metal forming tools. Coating adhesion and morphology can be modified over a wide range by varying the content of nitrogen (N{sub 2}) and the deposition parameters power and bias voltage. All coatings were deposited using commercial unbalanced magnetron equipment, the deposition was homogeneous in a volume of 400 x 400 x 400 mm{sup 3}. Hipped and hot pressed TiB{sub 2}-targets were used, nitrogen (N{sub 2}) was added as gas, Ti and Al by a solid Ti-Al-target. The tribological behaviour was tested by a pin-on-disc wear test. The coatings investigated were TiB{sub 2}, TiAlB(N), TiAl(N) and TiB{sub 2}/TiAl(N). As counterpart in the pin-on-disc wear test, 6 mm diameter spheres of steel (100Cr6), aluminium, brass and bronze were used. The experiments showed a non-uniform wear behaviour. For the ...

Energy Technology Data Exchange (ETDEWEB)

The dispersion of more than 20 vol pct submicrometer ceramic particles within a metallic matrix and the deposition of such a cermet to form a thick and tough coating presents problems. Most of the coating techniques have failed in attempting to homogeneously disperse very fine and hard particles in large amounts while avoiding their decomposition or reaction with the metal matrix during the deposition process. A simple and efficient method has been developed for producing ceramic-containing composite coatings. It consists in synthesizing cermet-based materials and in depositing them by a rapid solidification process, such as thermal spraying. Boride- and carbide-based materials have been successfully obtained by plasma spraying reactive powders comprising the basic reagents. These materials, with a microstructure of submicrometer ceramic particles dispersed in a metallic matrix, exhibit good wear-resistant properties (abrasion and sliding ...

Energy Technology Data Exchange (ETDEWEB)

Particulate Reinforced Titanium matrix composites (PRTi) exhibit some improved specific mechanical properties in comparison with those of unreinforced titanium alloys as a result of the combination of the high strength and stiffness of ceramic particles with the toughness and damage tolerance provided by the metal matrix. The poor tribological properties of the titanium exclude titanium alloys from applications where wear resistance is required (brakes, rotating parts, sliding parts). The addition of ceramic particles improves the tribological properties of metals sensitive to adhesive and /or abrasive wear significantly. In this work, the wear resistance and the friction coefficient of Ti6Al-6V-2Sn reinforced with TiC particles and Ti6Al-4V reinforced with SiC particles (prototype material) are compared with the unreinforced alloys. Pin on disc and pin on ring tests were carried out against standard ...

Energy Technology Data Exchange (ETDEWEB)

The durability of ball bearings, 32-mm- and 45-mm-bore, with a retainer or glass cloth-polytetrafluoroethylene (PTFE) laminate was tested under a high radial load at a speed of 20,000 rpm in LOX or LN2. The retainers were characterized as good self-lubricators because the abrasive glass-cloth fiber tips exposed on the retainer were chemicaly etched away with hydrofluoric acid (HF). During testing, the bearing-cartridge-acceleration was monitored to detect bearing damage. Testing in LOX for about 2.2 hr showed that excellent lubricating conditions were obtained for all bearings. Testing in LN2 for about 5.1 hr detected that the fatigue life of the bearing was about the same as the calculated B10 fatigue life. The HF chemical treatment resulted in a reacted fluoride-oxide material which remained in the etched part of the glass fiber. Several chemical products, particularly MgO, CaO, and CaCO3, enhanced adhesion of PTFE transfer film to the counterface, resulting in ...

British Library Electronic Table of Contents (United Kingdom)

To improve the friction and wear behavior of carbon fabric reinforced polymer composites (CFRP), nano-SiO2 was deposited on the fabric surface. The friction and wear behavior of the resulting composites were investigated on a model ring-on-block test rig. Experimental results revealed that fiber surface treatment contributed to largely improve the tribological properties of the CFRP composites. Scanning electron microscope (SEM) investigation showed that the worn surface of the surface modified CFRP composite was smoother under given load and sliding rate. Field emission scanning electron microscopy (FESEM), FTIR and X-ray photoelectron spectroscopy (XPS) studies of the carbon fiber surface showed that nanostructured Sio2 thin film can be obtained by SiO2 sols deposition, which improved th...

Energy Technology Data Exchange (ETDEWEB)

The present paper deals with the fouling process of calcium sulfate dehydrate on heat-transfer surfaces. The crystallization of calcium sulfate showed typical asymptotic fouling curves, the asymptotic value of which was greatly influenced by the surface temperature and fluid velocity. The fouling mechanism was discussed with a generalized fouling model and proved to be surface process controlled, where the activation energy was 6.2 {times} 10{sup 4} J/mol. The availability of mechanical cleaning against the formed scale was quantitatively evaluated by applying the particle abrasion method. The removal test verified that the removing rate per unit particle concentration decreased in an inverse proportion to the overall particle load, to the power of 0.8, and that it was affected by the fluid velocity. The observed final residual fouling resistance decreased asymptotically with an increase in particle concentration. The suitable concentration of ...

British Library Electronic Table of Contents (United Kingdom)

Polyacrylonitrile (PAN)-based carbon fabric (CF) was modified with strong HNO3 oxidation and then introduced into polyimide (PI) composites. The friction and wear properties of the carbon fabric reinforced polyimide composites (CFRP), sliding against GCr15 stainless steel rings, were investigated on an M-2000 model ring-on-block test rig under dry sliding. Experimental results revealed that the carbon fiber surface treatment largely reduced the friction and wear of the CFRP. Compared with the untreated ones, the surface-modified CF can enhance the tribological properties of CFRP efficiently due to the improved adhesion between the CF and the PI matrix. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) study of the carbon fiber surface showed that the fiber surfa...

Energy Technology Data Exchange (ETDEWEB)

Lining of fused cast basalt tiles is recommended for various pieces of equipment constituting a coal preparation plant.

Energy Technology Data Exchange (ETDEWEB)

The surface of low alloy steel (En40B) has been engineered in the plasma of a glow discharge via plasma nitriding and ion plating of titanium nitride (TiN) coatings on the nitrided substrates with the purpose of enhancing the surface properties and fatigue strength. The nitriding response of the steel has been accessed by the evaluation of phase composition, layer thickness, hardness profile, residual stresses and nitrogen and carbon distributions. The wear and fatigue characteristics of the plasma-nitrided steel have been investigated and simple models have been developed to describe the influence of such properties as depth and strength of the nitrided case on the fatigue limit and load-bearing capacity of the nitrided steel. In order to further improve the tribological properties and load-bearing capacity of the low alloy steel, a duplex plasma surface-engineering technique has been developed. This is achieved by plasma nitriding the steel ...

Energy Technology Data Exchange (ETDEWEB)

Ferrography is a technique for isolating wear particle debris from lubricating and hydraulic oils, the presence of which carry with them a history of the wear processes in the machine. Thus, the technique has fundamental applications in machine condition monitoring and failure prevention. The wear particles are significant in the metal types that are present in the particle distribution as an indication of the wearing machine components and in the particle size distribution and morphology which indicates the severity of wear in the system. In this paper, the fundamental principles which describe the working of the ferrograph, concentrating on the working of the on-line ferrograph are discussed. The significance of equilibrium particle concentration in the oil system and its measurement using the ferrograph are also discussed.

Science.gov (United States)

... Title : Wear Rate and Friction Coefficient in Liquid Nitrogen and Hydrogen of Steel Sliding on Polymer Laminates (Various Fabrics and Polymers. ...

International Nuclear Information System (INIS)

This paper presents the first results on formation and study of structure and properties of micro- and nanocomposite combined coatings. By means of modeling the deposition processes (deposition conditions, current density-discharge, plasma composition and density, voltage) we formed the three-layer nanocomposite coatings of Ti-Al-N/Ti-N/Al_2O_3. The coating composition, structure and properties were studied using physical and nuclear-physical methods. The Rutherford proton and helium ion backscattering, scanning electron microscopy with microanalysis, grazing incidence X-ray diffraction, as well as nanohardness tests (hardness) were used. Measurements of wear resistance and corrosion resistance in NaCl, HCl and H_2SO_4 solutions were also performed. For testing mechanical properties such characteristics of layered structures as hardness H, elastic modulus E: H"3/E"2 etc. were measured. It is demonstrated that the formed three-layer ...

Energy Technology Data Exchange (ETDEWEB)

Molecular imaging represents a modern research area that allows the in vivo study of molecular biological process kinetics using appropriate probes and visualization methods. This methodology may be defined- apart from the contrast media injection - as non-abrasive. In order to reach an in vivo molecular process imaging as accurate as possible the effects of the used probes on the biological should not be too large. The contrast media as important part of the molecular imaging can significantly contribute to the understanding of molecular processes and to the development of tailored diagnostics and therapy. Since more than 15 years PTB is developing optic imaging systems that may be used for fluorescence based visualization of tissue phantoms, small animal models and the localization of tumors and their predecessors, and for the early recognition of inflammatory processes in clinical trials. Cellular changes occur during many diseases, thus the ...

KoreaScience (Korea)

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Energy Technology Data Exchange (ETDEWEB)

Fretting wear test in room temperature water was performed to evaluate the wear coefficient of CANDU (CANadian Deuterium Uranium) steam generator (SG) tube material (Alloy 800) against 410 type martensitic stainless steels. The main focus is to compare the wear behaviors between Alloy 800 and Inconel 690. Test conditions are 10{approx}30N of normal load, 200{approx}450mm of sliding amplitude and 30Hz of frequency. The result indicated that the wear rate of Alloy 800 was higher than those of Inconel 690 at various test condition such as normal loads, sliding amplitudes etc. From the results of SEM observation, there was little evidence of plastic deformation layer that were dominantly formed on the worn surfaces of Inconel 690. Also, wear particles in Alloy 800 were released from contacting asperities deformed by severe plastic flow during fretting wear. Main ...

International Nuclear Information System (INIS)

A super-hydrophobic coating was prepared by combining a rigid base film with crater-like hemispherical holes and acicular nanoparticles. The acicular boehmite powder provides a high contact angle on the film surface. The rigid base film with crater-like hemispherical holes inhibits the rapid decrease of contact angle by surface rubbing. The combination of different roughness is an effective method for improving the abrasion resistance of super-hydrophobic films.

Energy Technology Data Exchange (ETDEWEB)

To make the surface composites with hard ceramics particles is an effective means for satisfying the request for the wear-resistance of the casting products. Covering casting is a general method for forming the composites by adding the adhesive into ceramics particles. However, due to the using of adhesive, pore and intermediate are easy to generate, and it is one of the reasons making the wear-resistance unstable. In the present study, it is attempted to form the wear-resistant composite layer by dispersing cast tungsten carbide (CTC) particles on the surface of wear-resistant 7 mass% Mn steel without using adhesives. Subsequently, the experiments on the wear-resistance of the obtained surface composites under several wear conditions are carried out. It is revealed by the results thereof that 7 mass% Mn steel surface composites with CTC particles have the ...

Energy Technology Data Exchange (ETDEWEB)

Engineering materials for use in low heat rejection engines are required to function under stringent tribological conditions. Severe wear damage and high friction between the components of the tribosystem limit the number of potential materials suitable for such application conditions. The superalloys X-750 and 188 are composed of alloying elements that not only promote a high mechanical and chemical stability but may also result in a reduced wear rate and friction coefficient at elevated temperatures. As a part of the DOE-ECUT Tribology program at Argonne, the present study was undertaken to evaluate the tribological characteristics of these alloys that will also be utilized as the substrates for ion beam deposited lubricous coatings. A wear test rig that crudely simulated the sliding conditions between a piston ring and a cylinder liner in an operating engine was utilized for friction and wear ...

International Nuclear Information System (INIS)

A series of ball-on-disc wear and friction measurements were made for surfaces which have a chemical vapour deposition carbon silicon alloy layer on a carbon substrate (fine grain POCO graphite). Nitrogen ion irradiation was used to improve the wear resistance of the carbon alloy surface. For comparison, measurements were also taken for alumina against alumina. It was found that the lowest friction coefficient and lowest wear occurred for ion irradiated coated samples containing 4% Si in the alloy and that the performance was superior to that of alumina. ((orig.)).

KoreaScience (Korea)

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Energy Technology Data Exchange (ETDEWEB)

Very good friction and wear measurements are reported for MRCC (metal reinforced carbon composites), made from low-wear non-graphitic carbon matrix with metal-fiber reinforcement. Counterfaces include austenitic and martensitic stainless steels, Si nitride, and alumina. Effects of high load, high temperature, and gaseous environments are reported: removal of humidity, atm. oxygen have little effect on friction, wear for MRCC sliding against ceramic or stainless steel. Wear of Al oxide riders on MRCC is very low, not affected by contact load. 260 C temperatures do not degrade performance of 440-C riders on MRCC disks or raise friction. In small or large sizes, MRCC is made in a single-pass process for about the same volume cost as cast iron. It can survive heating in nitrogen above 1600 C without loss of integrity or major change of dimensions.

International Nuclear Information System (INIS)

Four very common long term mineralogical changes in salt formations are discussed in the view of the safety considerations for underground repositories. Two of these processes, the 'Hartsalz' and 'Carnallite' dissolution were studied in two scale in situ experiments. The results are presented and compared with the results of the geochemical modelling with the computer code EQ3/6. Furthermore the reactions leading to the formation of the gypsum cap rock on the top of the Zechstein salt formations and to the polyhalitization of anhydrite are discussed. Geological field observations and mineral assemblages agree well with the results of the geochemical modelling employing the Pitzer formalism along with the Harvie, Moller and Weare database. We conclude that once the mechanisms of the chemical reactions are well understood it becomes possible to evaluate realistically whether such processes, when encountered in the repository, ...

Energy Technology Data Exchange (ETDEWEB)

Youngkwang Unit 3,4 and Ulchin Unit 3 and 4 have had problem of the KSNP Steam Generator due to a severe fretting wear on the tube. In particular, the wears were localized and concentrated in the upper part of U-bend of the Central Cavity region. At the upper tube bundle Central Cavity, the fluid flow velocities and void fraction are very high, because the steam is made by high heat transfer at secondary region. Also, this region is affected easily by fretting wear due to it's unsupported span is longer than another regions. The fretting wear is assumed to be result of Flow-Induced Vibration (F. I. V), which can occur by many mechanisms. EFDP was added to UCN 5,6 for prevent fretting wear by the SEC LCC and DSHIC, a company of design and manufacture of the steam generator, respectively. In order to evaluate the efficacy of EFDP, ANSYS and ATHOS-3 Code were used. From ...

International Nuclear Information System (INIS)

Current light water reactor (LWR) steam generators have been affected by a variety of corrosion and mechanical damage degradation mechanisms. Included are wear caused by tube vibration, intergranular corrosion, pitting, and thinning or wastage of the steam generator tubing and accelerated corrosion of carbon steel supports (denting). The Electric Power Research Institute (EPRI) and the Steam Generator Owners Groups (I, II) have sponsored laboratory and field studies to provide ameliorative actions for the majority of the damage forms experienced to date. Some of the current corrosion mechanisms are aggravated or caused by unique materials choices or materials interactions. New materials have been proposed and at least partially qualified for use in replacement model steam generators, including an advanced LWR design. In so far as possible, the materials choices for the advanced LWR steam generator avoid the corrosion pitfalls seemingly inherent ...

International Nuclear Information System (INIS)

The tool materials durability problem, in particular shock and wear resistance, has allowed to formulate a set of requirements and also to stablish the dependence between physical properties and wear. However, for understanding the nature of the process, for example determining the tribological property of the cutting tool, it is necessary to consider the atom interactions in a crystal. A theoretical study of the physical properties of cutting tool materials (W-Ti-C) with varying concentration of titanium is presented. Total and partial local electronic density for each atom in such hard solutions were calculated. (nevyjel)

Energy Technology Data Exchange (ETDEWEB)

Extensive experimental investigation has been carried out on used flight bearings of the high pressure oxidizer turbopumps (HPOTP) of the space shuttle main engine (SSME) in order to determine the dominant wear modes, their extent, and causes. The paper presents the methodology, various surface analysis techniques used, results, and discussion. The mode largely responsible for premature bearing wear has been identified as adhesive/shear peeling of the upper layers of bearing balls and rings. This mode relies upon the mechanisms of scale formation, breakdown, and removal, all of which are greatly enhanced by the heavy oxidation environment of the HPOTP. Major causes of the high wear rates appear to be lubrication and cooling, both inadequate for the imposed conditions of operation. Numerous illustrations and evidence are provided. 22 refs.

International Science & Technology Center (ISTC)

Corrosion- and Wear Resistant Silicon Containing Chromium-Manganese and Nickel-Chromium-Manganese Nonmagnetic Steels with Increased Strength and Toughness for Reliable Work at Normal and Cryogenic Temperatures

UK PubMed Central (United Kingdom)

The incidence of candidiasis in two groups of voluntary participants wearing tight and loose fitted dresses was investigated by both microscopic and cultural techniques for a period of two months....Full Text Available

Science.gov (United States)

This study investigated the effect of board type (unmodified vs. MAPE modified) on the surface quality and thickness swelling-water absorption properties of recycled high density polyethylene (HDPE) based wood plastic composites. Additionally, two commercially available coatings (cellulosic coating and polyurethane lacquer coating) were also applied to composite surfaces and their adhesion strength, abrasion and scratch resistance, and gloss values were determined. This study showed that modification of the composites with MAPE coupling agent increased the surface smoothness and reduced the water absorption and thickness swelling of the panels. Abrasion resistance of the composites was also improved through MAPE modification. Regardless of board type, higher scratch resistance and gloss values were observed for polyurethane lacquer coated samples compared to those of cellulosic varnish coated ones. Improvement of adhesion strength was also seen ...

Energy Technology Data Exchange (ETDEWEB)

Energy Related Inventions Program Number 613 was a two year program to commercialize a unique new wear material, Metal Reinforced Carbon Composite, MRCC. The program was designed to manufacture sample components of MRCC for evaluation by potential users and manufacturers. As a result of the program Burton Technologies Inc. and Rotary Power International are forming a joint company to manufacture, market and license MRCC materials to a wide range of industries.

International Nuclear Information System (INIS)

The structure and properties of composite powder coatings on the base of titanium carbide are studied. It is shown the electron-beam welding deposition of powders on the base of nickel and titanium carbide allows to produce of high-quality wear-resistant coatings which superior in density and hardness compared with sputtered ones. Changes of hardening phase volume percentage as well as composition of metal matrix make possible to control coatings hardness

Energy Technology Data Exchange (ETDEWEB)

This study presents the results of an 18-year long investigation of pipe deterioration in cyclone slag slurry transport. The goal was to study pipe behaviour in this extremely abrasive service and select an optimum piping material. Comparisons are given for high quality alloy cast steel pipes and pipes lined with cast basalt rings marketed under the name Abresist. Based on the results, thoughts are offered on the broader meanings of certain findings.

Energy Technology Data Exchange (ETDEWEB)

The study presented in this thesis is a contribution about the analysis of failures modes of electrolytic capacitors and thyristors. The studied components are main elements of the protection system of the superconductive magnets of the LHC. The study of the ageing of the electrolytic capacitors has shown that their reliability is strongly related to their technological characteristic. Evolution of their principal indicator of ageing (ESR) can be modeled according to different laws chosen according to their running mode. It appears that the prediction of failure of these components other than that due to wear can be only statistical taking into account the many causes of failure involving various modes of failure. In order to be able to evaluate influence of the ageing of the electrolytic capacitors on a system, simple models taking into account this parameters as well as the effective temperature of the component are ...

Energy Technology Data Exchange (ETDEWEB)

High-strength, fully hardening steels are used in general for applications involving severe wear and frequently also additional cyclic stress. For the latter condition, the available information and experimental data for component dimensioning are insufficient. Work reported in the dissertation therefore was intended to establish experimental information showing the performance of the bainitic roller bearing steel 100Cr6 and deducing rules of applicability to components, of the fatigue strength data obtained with the specimens. Various models for calculating the fatigue strength are presented together with their application to the steel 100Cr6. The results show that the weakest link model is a good concept for fatigue strength calculation, taking into account multiaxial loading. (orig/CB) [Deutsch] Hochfeste durchhaertende Staehle unterliegen in der Regel hohen Verschleissbeanspruchungen und werden darueber hinaus oftmals ...

Energy Technology Data Exchange (ETDEWEB)

This paper describes the experimental results of long-life solid lubricated ball bearings tested under high-vacuum of 10 exp -4 Pa, high-temperature of 300 C, and high-speed (9000 rpm) conditions. For full ball-type bearings, the thin soft metals, either Ag or Pb, which were coated on the races and balls, appeared to have good torque properties. However, the durability of such bearings was less than 300 hours. The transfer films from the lamellar solid MoS2 and metal composite retainers improved the torque and wear properties. For ceramic, i.e., silicon nitride, balls used with steel rings, wear occurred on the inner rings. All ceramic bearings with composite retainers showed improved torque and wear properties. 18 refs.

International Nuclear Information System (INIS)

The purpose of the present study is to develop a new method for chemical state analysis by means of EPMA(Electron probe microanalyser). The measured X-ray intensity of Si-K#beta# characteristic X-ray spectra were read-out by a 16 bit microcomputer with a RS-232C interface. And using the curve fitting method the quantitative analysis of chemical compositions in a ternary compound that constituted of the same element has been established. The present method was applied to analyse of the friction and wear properties of Si-base ceramics sliding materials. It was found that the wear debris contains both the compositions of the sliding materials and SiO_2, and the SiO_2 contents in wear debris was changed with relative humidity. The results clearly showed that the proposed method is very useful for determing the compositions in the ternary compound. (author).

Energy Technology Data Exchange (ETDEWEB)

In the present paper the tribological behavior of the coatings are discussed. Duplex coatings were applied on cold working steel 100Cr6. Samples were plasma nitrided at different thickness of plasma surface layers. TiN was deposited with a classic BALZERS PVD equipment and subsequent ion implantation. Ion implantation was provided with N{sup 5+} ions. The other samples were produced with IBAD technology in DANFYSIK chamber. Wear resistance and exchanges of friction coefficient were measured with on-line test using special designed tribology equipment. Following the tests, the wear zone morphology and characteristics of surface layer structure as well as important properties were investigated by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Scratch adhesion testing was performed using commercially available equipment. Energy dispersive X-ray analysis (EDAX) of the wear-scars on pins provided ...

Energy Technology Data Exchange (ETDEWEB)

In the second part of this paper the author concludes his examination of the application of thermoplastic materials and also considers alumina ceramics, cast basalt and glass, rubbers, resins and wear-resistant steels

Energy Technology Data Exchange (ETDEWEB)

A duplex surface treatment technique based on calorizing and plasma nitriding was developed to improve the wear and oxidation resistance of H13 steel at high temperatures. The effects of the relative thickness of the calorized layer to the depth of plasma nitriding on the wear and oxidation properties at temperatures up to 900 C were investigated in this work. High-temperature wear tests were performed at 500 C with dry conditions in open air using a ball-on-disk type tribotest machine. Isothermal oxidation tests were performed at 900 C for up to 100 h under controlled atmosphere. The results indicated that the specimens with a calorized layer as an intermediate phase between the surface duplex layer and the base metal showed higher wear and oxidation resistance than the specimens with a nitrided layer alone. During exposure to elevated temperatures, the aluminum in the calorized layer diffused to the ...

UK PubMed Central (United Kingdom)

Dogs are domestic reservoir hosts of Trypanosoma cruzi, the etiological agent of Chagas disease. We evaluated the effect of deltamethrin-treated dog collars (DTDCs) over time...Full Text Available

International Nuclear Information System (INIS)

The possibility of surface modification of high-speed steel cutting tool by means of vacuum-plasma treatment including ion nitriding in gas plasma followed by the deposition of wear resistant (Ti, Al)N coatings in metal-gas plasma of a vacuum arc discharge is studied. The regularities of nitrided layer formation and the structure of these layers under various operation conditions of cutting tool are investigated. Optimum conditions of vacuum-plasma treatment providing the best wear resistance of cutting are determined

International Nuclear Information System (INIS)

17-4PH stainless steel was modified by direct current (DC) plasma nitriding and titanium nitride film duplex treatment in this study. The microstructure, wear resistance and corrosion resistance were characterized by X-ray diffraction (XRD), pin-on-disk tribological test and polarization experiment. The results revealed that the DC plasma nitriding pretreatment was in favor of improving properties of titanium nitride film. The corrosion resistance and wear resistance of duplex treatment specimen was more superior to that of only coated titanium nitride film.

Energy Technology Data Exchange (ETDEWEB)

The refractory nature and high ductility of body centered cubic (bcc) phase tantalum makes it a suitable material for corrosion- and wear-resistant coatings on surfaces that are subjected to high stresses and harsh chemical and erosive environments. Sputter deposition can produce thick tantalum films but is prone to forming the brittle tetragonal beta phase of this material. Efforts aimed at forming thick bcc phase tantalum coatings in both flat plate and cylindrical geometries by high-rate triode sputtering methods are discussed. In addition to substrate temperature, the bcc-to-beta phase ratio in sputtered tantalum coatings is shown to be sensitive to other substrate surface effects.

Energy Technology Data Exchange (ETDEWEB)

This invention relates with a pot-type catalyst carrier which excels as a catalyst carrier when such heavy oils as ordinary pressure distillation residue, oil sand oil, and shale oil are decomposed or treated by hydrogenation. The conventional pot-type carrier is produced by dropping a small drop of a slurry (containing a catalyst component) onto a particle bed and drying it. But the demerit is a large particle size and less catalyst activity or strength. In this invention, a mixture of such carrier components as allophane, red mud, bauxite and latellite, etc.. 60 - 80 weight parts. and a binder 20 - 40 weight parts is added with water to form a slurry of 10 - 30 weight% solid concentration. Slurry is wet-crushed to make the average particle size 0.6 - 2.0 micron, then spray-dried and burned to obtain a pot-type catalyst carrier with average particle size 30 - 200 micron and abrasion index below 10. This catalyst showed high yield of kerosene and light oil in the ...

Energy Technology Data Exchange (ETDEWEB)

Aluminum matrix composite Al356/SiCp(Vol. 15%)(Al MMC) material has been cut under various cutting conditions using Abrasive WaterJet (AWJ) machining process. The experimental cutting was carried out using three different material thicknesses of 10, 20, 30mm with a 0.33mm diameter orifice. The pump pressure, traverse rate, StandOff Distance(SOD) were taken as process parameters. After cutting the quality of the specimen in terms of kerf width, kerf taper, and surface finish were measured to characterize machinability of the material. As a result of the study, the maximum traverse rate for 30mm thick Al MMC under the pump pressure of 350 MPa reached up to 70 mm/min and the surface roughness of the material showed surface finish Ra in the range of 2.3{approx}23.4{mu}m.

Energy Technology Data Exchange (ETDEWEB)

In this study samples of AISI 4140 steel were pretreated by plasma nitriding and coated with two different physical vapour deposited coatings (TiN and TiAlN). A hardened AISI 4140 sample and a coated sample were also included in the investigation. To examine the influence of the nitrided zone on the performance of the coating-substrate composite, two different nitriding conditions - a conventional 25% N{sub 2} and an N{sub 2}-poor gas mixture - were used. The specimens were investigated with respect to their microhardness, surface roughness, scratch adhesion and dry sliding wear resistance. Wear tests in which the duplex-treated pins were mated to hardened ball bearing steel discs were performed in a pin-on-disc machine under dry sliding conditions. Metallography, scanning electron microscopy and profilometry were used to analyse the worn surfaces in order to determine the dominant friction and wear characteristics of the ...

Energy Technology Data Exchange (ETDEWEB)

The friction and wear properties of glass fiber reinforced composites of nylons (nylon 6, nylon 66 and nylon 46) with different crystallinities due to their molecular structures were investigated by sliding them with alumina ceramics and using a pin-on-disk friction machine. The friction coefficients of the glass fiber reinforced nylons in oil were lower and more stable than those in air from the initial stage of friction. The transfer of nylon matrix to adhere onto the alumina surface in air was so much greater than in oil that the alumina surface could not be recognized. Consequently, a different between the friction and wear properties in air and in oil was resulted. Reinforcement of nylons with glass fiber remarkably improved their friction properties in oil by its lubricating action, while the wears were rather high contrary to what was expected. This tendency was conspicuous for nylon 46 with high crystallinity. ...

Energy Technology Data Exchange (ETDEWEB)

After pioneering work in the 1980s, plasma-based ion implantation (PBII) and plasma-based ion implantation and deposition (PBIID) can now be considered mature technologies for surface modification and thin film deposition. This review starts by looking at the historical development and recalling the basic ideas of PBII. Advantages and disadvantages are compared to conventional ion beam implantation and physical vapor deposition for PBII and PBIID, respectively, followed by a summary of the physics of sheath dynamics, plasma and pulse specifications, plasma diagnostics, and process modeling. The review moves on to technology considerations for plasma sources and process reactors. PBII surface modification and PBIID coatings are applied in a wide range of situations. They include the by-now traditional tribological applications of reducing wear and corrosion through the formation of hard, tough, smooth, low-friction and chemically inert phases ...

International Nuclear Information System (INIS)

Thermo-reactive diffusion chromizing followed by pulsed plasma nitriding were carried out on AISI 52100 and 8620 bearing steels. The chromized samples were pulse-plasma nitrided for 5 h at 500 deg. C in various N_2-H_2 gas mixtures. The coated steels were characterized using scanning electron microscopy, X-ray diffraction and microhardness testing. The unlubricated wear behaviors of only chromized and duplex treated steels were investigated in ball-on-disc system tests at room temperature. X-ray diffraction patterns of the duplex treated samples containing H_2 indicated the formation of dominant CrN and Cr_2N nitrides as well as the formation of Cr_3C_2 and Cr_7C_3 carbides. Gas mixtures in the plasma nitriding, which was performed after chromizing, have a significant influence on the wear rate of the duplex treated steels. The wear and friction tests showed that the lowest friction coefficient and wear ...

British Library Electronic Table of Contents (United Kingdom)

One of the main causes of hip prostheses failure is the premature wear of its components. Wear of metal-on-metal joints is a concern due to the toxicity and biological reaction of wear debris and metallic corrosion. The main aim of the present study was to investigate the tribological and corrosion behavior of surface engineering CoCrMo alloy. Different surface conditions were obtained on surgical grade wrought CoCrMo alloy: plasma nitrided (520^oC by 7h at gas mixture of 10% N2+90% H2), PVD coated (monolayer CrN and multilayer (TiN/CrN)x3) and modified using duplex surface engineering technology (a combination of the two previous approaches: plasma nitriding followed by plasma assisted PVD). Surfaces were characterized using scanning electron microscopy, nanoindentation, AFM and scratch t...

International Nuclear Information System (INIS)

Nitrogen ion implantation improves the wear resistance of Ti-6Al-4V alloys by forming a hard TiN superficial passivation layer. However, the thickness of the layer formed by traditional ion implantation is typically 100-200 nm and may not be adequate for many industrial applications. We propose to use radio-frequency (RF) plasma nitriding and nitrogen plasma immersion ion implantation (PIII) to increase the layer thickness. By using a newly designed inductively coupled RF plasma source and applying a series of negative high voltage pulses to the Ti-6Al-4V samples. RF plasma nitriding and nitrogen PIII can be achieved. Our process yields a substantially thicker modified layer exhibiting more superior wear resistance characteristics, as demonstrated by data from micro-hardness testing, pin-on-disc wear testing, scanning electron microscopy (SEM), as well as Auger electron spectroscopy (AES). The performance of our newly ...

Energy Technology Data Exchange (ETDEWEB)

45{number_sign} steel, which has good mechanical strength and is relatively cheap, is a common constituent in industrial components, such as precision gears, piston columns of oil pumps, and so on. However, since the working environment of these industrial parts is sometimes quite harsh and unforgiving, they are vulnerable to wear and corrosion. Replacing 45{number_sign} steel with stainless or alloy steel increases the cost significant, and a better alternative is to improve its surface properties and lifetime using plasma immersion ion implantation (PIII). The authors have devised a variety of treatment processes using PIII, including radio-frequency (RF) plasma nitriding, RF plasma nitriding and nitrogen PIII, Ti deposition in conjunction with nitrogen PIII (IBED), as well as Cr deposition followed by nitrogen PIII (IBED). To assess the efficacy of the processes, the microhardness and mass loss due to wear were measured for both the ...

Energy Technology Data Exchange (ETDEWEB)

Recent work has been carried out on development of isotope wear analysis and optical and eddy current technologies to provide bearing wear measurements and real time monitoring of shaft speed, shaft axial displacement and shaft orbit of the Orbit Transfer Vehicle hydrostatic bearing tester. Results show shaft axial displacement can be optically measured (at the same time as shaft orbital motion and speed) to within 0.3 mils by two fiberoptic deflectometers. Evaluation of eddy current probes showed that, in addition to measuring shaft orbital motion, they can be used to measure shaft speed without having to machine grooves on the shaft surface as is the usual practice for turbomachinery. The interim results of this condition monitoring effort are presented.

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Interest in the tribological properties of plasma nitriding has increased substantially over the past years because plasma nitriding provides a high nitride depth and improved hard facing. The present study examines the tribological properties of AISI H11 plasma nitrided, hot-worked steel. Different nitriding temperatures and durations were considered. Characterization of the composite structures was investigated with wear tests, x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and microhardness tests. The depth profile of the nitrided zone was measured using the nuclear reaction analysis (NRA) technique. Plasma nitriding affected the microhardness, wear properties, and morphology considerably. Increase in process temperature increased the nitride zone depth.

Energy Technology Data Exchange (ETDEWEB)

The refractory nature and high ductility of body centered cubic (bcc) phase tantalum makes it a suitable material for corrosion- and wear-resistant coatings on surfaces which are subjected to high stresses and harsh chemical and erosive environments. Sputter deposition can produce thick tantalum films but is prone to forming the brittle tetragonal beta phase of this material. Efforts aimed at forming thick bcc phase tantalum coatings in both flat plate and cylindrical geometries by high-rate triode sputtering methods are discussed. In addition to substrate temperature, the bcc-to-beta phase ratio in sputtered tantalum coatings is shown to be sensitive to other substrate surface effects.

British Library Electronic Table of Contents (United Kingdom)

Superalloys, such as Inconels and Incoloys, are extensively used where high strength is a requirement. However, where these materials are required to slide against one another, particularly with poor or no lubrication, high friction levels and seizure are commonly seen to occur, which can cause component failure. In this work seizure characteristics of three superalloys (Inconel 718 and Incoloys 945 and 945X) were investigated, uncoated, coated with Armoloy (a hard, thin, dense chrome coating with a micro-nodular surface texture) and plasma nitrided in dry sliding conditions. A rig purpose built for initiating seizure was used. It involves sliding a ball against a disc at constant speed while the load is increased. Tests are designed to last less than one rotation so that the wear scar can...

British Library Electronic Table of Contents (United Kingdom)

Statement of problem The use of titanium has increased for metal ceramic restorations, as well as for use in titanium implants, with developments in CAD/CAM technology. Some surface treatments of titanium have been introduced to enhance the titanium bond strength to low-fusing porcelains; however, a more reliable, easily used dental laboratory method has not been established. Purpose The purpose of this study was to compare the effect of laser etching as a titanium surface treatment with 3 other surface treatments (machining, airborne-particle abrasion, and acid etching), evaluating their ability to enhance the bond strength between a titanium substrate and porcelain. Material and methods A total of 64 specimen rods of commercially pure titanium (ASTM grade 2, 20 mm in length and 5.7 mm in...

Energy Technology Data Exchange (ETDEWEB)

This paper considers the physical and mechanical properties of rocks (volumetric density, angle of repose, lump size, abrasive strength, etc.), and their influence on choice of belt conveyors for overburden haulage. Technological parameters (length and output of benches, coefficient of utilization and reliability of equipment, investment cost, etc.) are also considered. Data are given on the capacity and length of conveyors widely used in coal surface mining (width up to 3,000 mm, speed up to 6 m/s and capacity 24,000-35,000 t/h at lengths of 1,400-3,000 m). (12 refs.) (In Serbo-Croat)

International Nuclear Information System (INIS)

There are a total of nine operational nuclear plants in Spain totalling 7.350 MWe. These units produced 54.265 x 106 KWh in 1990, 36% of the total generation in Spain. Seven of these plants are of the PWR type. The first plant in operation was Jose Cabrera (ZORITA) in 1968, one loop Westinghouse plant with a model 24 Steam Generator. Due to the design margin and careful operation of the Steam Generator of this plant its performance have been very good, with only 5% tubes plugged after 23 years of operation. This is one of the few units in the world that remains in phosphate chemistry. During the period 1981-1985 a total of four units, two in Almaraz and two in Asco entered in operation. These three loop s Westinghouse units use model D-3 preheater Steam Generators. The poor design and manufacture of the Steam Generators of these units have caused a large number of problems: mechanical (Preheater and AVB's vibration), denting, and primary and ...

Energy Technology Data Exchange (ETDEWEB)

In support of the efforts to apply ceramics in advanced heat engines, a study was made of the sliding performance of ceramics at the ring/cylinder interface of low heat rejection engines. The objective was to understand the basic mechanisms controlling the wear of candidate ceramics and thereby identify means for applying these ceramics effectively. Attempts to operate three different zirconias, silicon carbide, silicon nitride, and several plasma-sprayed ceramic coatings without lubrication were unsuccessful because of high friction and high wear rates. Experiments using a polyalphaolefin lubricant at temperatures to 260 C identified several combinations having wear rates in the general range likely to be acceptable for engines. Plasma-sprayed coatings of chromium oxide and hypersonic powder flame sprayed coatings of cobalt-bonded tungsten carbide performed particularly well as ring coatings. Similar performance was ...

Energy Technology Data Exchange (ETDEWEB)

A hydrocarbon composition having a major portion of a hydrocarbon preferably a lubricating oil such as mineral oil and at least a friction-reducing amount usually 0.01 to 10 weight percent of an amine or amine derivative of a hydrocarbon-soluble polymerized fatty acid e.g. a dimeramine derived from a dicarboxylic acid containing at least 12 carbon atoms such as 9(10)-carboxy stearic acid has improved antifriction and flue economy properties.

Energy Technology Data Exchange (ETDEWEB)

In order to investigate the role of amorphous SiO{sub 2} particles in corrosion and wear resistance of Ni-based metal matrix composite alloying layer, the amorphous nano-SiO{sub 2} particles reinforced Ni-based composite alloying layer has been prepared by double glow plasma alloying on AISI 316L stainless steel surface, where Ni/amorphous nano-SiO{sub 2} was firstly predeposited by brush plating. The composition and microstructure of the nano-SiO{sub 2} particles reinforced Ni-based composite alloying layer were analyzed by using SEM, TEM and XRD. The results indicated that the composite alloying layer consisted of {gamma}-phase and amorphous nano-SiO{sub 2} particles, and under alloying temperature (1000 deg. C) condition, the nano-SiO{sub 2} particles were uniformly distributed in the alloying layer and still kept the amorphous structure. The corrosion resistance of composite alloying layer was investigated by an electrochemical method in 3.5%NaCl solution. ...

Science.gov (United States)

This study evaluated the heat strain induced by six configurations of a new modular body armor (MBA) design. Tests were conducted in two environments differing only by wind speed. The environments were 40 deg C (104 deg F), 20% rh, wind speeds 1.0 msec-1 ...

Energy Technology Data Exchange (ETDEWEB)

Processing certain raw materials containing natural radioactive isotopes (e.g. U-238, Th-232 or K- 40) into products such as glas, abrasives, grinding materials or electrodes used for gasshielded tungsten-arc welding also leads to certain concentrations of industrial waste containing natural radioactive materials. Such industrial waste does not necessarily contain natural radioactive substances in concentrations exceeding the highest possible levels but nevertheless in significantly measurable quantities. This, however, frequently leads to confusion bordering on irritation by entities processing such substances as well as the general public, since they tend to believe natural radioactive substances in unobjectable concentration to cause similar or identical - health - consequences as man made radioactive substances in detrimental concentration. Radioactive materials may be incorporated intentionally or unintentionally into the product as main or additional ...

Energy Technology Data Exchange (ETDEWEB)

The instrument ball bearings are the key components of movable components for various kinds of measuring and control instruments; they often operate in the environmental condition of high-speed and light preload. In general, the non metal, disposable oilimpregnated retainer material has been used for these kinds of high precision miniature bearing. The engineering practice shows that the common failure mode of them is the wear which appears under the condition of insufficient lubrication condition. As the results, the vibration and noise will be enlarged, so does the frictional torque, which makes the ball bearings to lose its original working accuracy. It is the lifetime test of bearings that can enable the designers and manufacturers to chose the material of the bearing properly, optimize the product structure, mend the manufacturing technique process, and to enhance the technical level of the bearing products significantly. In this paper, the ...

Energy Technology Data Exchange (ETDEWEB)

This paper describes high speed rolling and gauge control in cold tandem mill for ultra-thin gauge strip at the Chiba Works of Kawasaki Steel Corporation. To improve the plate-out property of rolling oil, cationic polymeric coagulant was prepared. Rolling oil with cohesion independent of inorganic inclusions or phosphatide was developed, to improve the lubrication for cold rolling, remarkably. In addition, a low-cost Ti-enhanced work roll having high wear resistance and excellent grindability was developed. Rolling can be conducted at the optimal rolling roughness and operation can be performed at the highest rolling speed independent of the rolling treatment amount. Rolling speed at 2800 m/min was confirmed by developing the rolling oil with excellent lubrication and the work roll having high wear resistance. For the improvement of strip thickness accuracy at the steady state rolling, use of the backup roll as roller bearing was more effective ...

Energy Technology Data Exchange (ETDEWEB)

A radio frequency sputtering apparatus with a pair of targets has been developed for depositing a film of uniform thickness onto a complex-geometric specimen such as the retainer of a ball bearing. The deposition characteristics of the apparatus were compared with those of the conventional sputtering apparatus. Lubrication properties of MoS/sub 2/ films made by these devices were also compared under a variety of conditions. Finally, friction and wear of MoS/sub 2/ films applied to angular-contact type ball bearings of 20 mm bore were studied in air, nitrogen and vacuo. The two-target sputtering has an advantage mentioned above. However, the films deposited by the method exhibited a rather short wear life because of the temperature rise of the substrate during ion bombardment and during the sputtering process. This temperature dependence was observed in films on those substrates that had been heated with a built-in heater during sputtering. The ...

Energy Technology Data Exchange (ETDEWEB)

The usually low wear resistance of titanium materials can be increased by the thermochemical surface treatment nitriding. In result of comparative investigations of gas and plasma nitriding it will be shown that it is possible to obtain a specific variation of the properties in the highly stressed case by means of these both technologies on example of the ({alpha}+{beta}) alloy Ti-6Al-4V. Gas and plasma nitriding was carried out in the temperature range from 650 to 800 C over 4 to 48 h in different gas atmospheres, i.e. 100% NH{sub 3} (gas), 100% N{sub 2} (gas and plasma), 20% H{sub 2} + 80% N{sub 2} and 20% Ar + 20% H{sub 2} (plasma). The temperature range was fixed in the middle of ({alpha}+{beta}) region, because the core properties are influenced negative in the field of {beta}-transustemperature. The relations between the applied nitriding technologies, the layer structure (chemical, phases, geometrical) and selected layer properties (microroughness, ...

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study is to develop the radioisotope tracer technology, which can be used in solving industrial and environmental problems and to build a strong tracer group to support the local industries. In relation to the tracer technology in 1999, experiments to estimate the efficiencies of a sludge digester of a waste water treatment plant and a submerged biological reactor of a dye industry were conducted. As a result, the tracer technology for optimization of facilities related to wastewater treatment has been developed and is believed to contribute to improve their operation efficiency. The quantification of the experimental result was attempted to improve the confidence of tracer technology by ECRIN program which basically uses the MCNP simulation principle. Using thin layer activation technique, wear of tappet shim was estimated. Thin layer surface of a tappet shim was irradiated by proton beam and the correlation between the measured activity loss ...

International Nuclear Information System (INIS)

Advanced structural ceramics are presently used in several tribological applications, such as precision instrument bearings, automotive engine parts and cutting tools inserts. Design and selection of advanced ceramics for these applications require reliable data on the effects of temperature, load and environment on the tribological behaviour of these materials. In the present work, the friction and wear behaviour of colloidally processed and pressureless sintered sialon ceramics with phase (#alpha#) have been studied, aiming at increasing #alpha#-sialon in industrial applications as cutting tools. The friction and wear behaviour of sialon ceramics against steel DIN-Ck45K were investigated using a pin-on-disk tribometer under dry sliding conditions at room temperature, in order to eliminate the contribution of lubricant. The experiments were performed with a constant sliding velocity of 0.5 m/s and a contact stress of 2.85 MPa for 2000 m of ...

Energy Technology Data Exchange (ETDEWEB)

Twenty years after its building, the tertiary sector of La Defense district near Paris has been rehabilitated. The main reason is not only the age and wear of materials but the heating costs, the fire protection regulations, the search for a better air quality and air renewing with less dusts, smells and noise and a controlled moisture. This paper describes first the original installation of the Monge CB 6 office building and then the renovated installation: the central hot and cold air-treatment plant, the variable flow ventilation system, the air extraction and supply system threw the roofs and the pressure and thermal regulation of the installation. (J.S.)

Energy Technology Data Exchange (ETDEWEB)

Silicon nitride hybrid ball bearings used in high temperature applications undergo mechanical and environmental degradation. To study the surface chemistry of silicon nitride, a CAChe{trademark} Worksystem* has been used to generate the clusters and corresponding transmission vibrational spectra of silicon nitride. In the present study, the effect of surface conditions on the surface chemistry and wear degradation of silicon nitride was evaluated. Infrared reflection spectroscopy (IRRS) used to determine molecular orientations shows a difference in reflectance spectra for fractured and as-received.

International Nuclear Information System (INIS)

A carbon nanotube (CNT) tip, which assembled on the sharp end of a Si tip by dielectrophoresis, was structurally modified using focused ion beam (FIB). We described the imaging characterization of the FIB-modified CNT tip in noncontact AFM mode in terms of wear, deep trench accessibility, and imaging resolution. Compared to a conventional Si tip, the FIB-modified CNT tip was superior, especially for prolonged scanning over 10 h. We conclude that modified CNT tips have the potential to obtain high-quality images of nanoscale structures.

International Nuclear Information System (INIS)

In the present work, using a pad-on-disc-type wear tester, the tribological properties of the pad next to the disk made of cast iron were investigated with changing the substance of the components. As well, micro-structural characterisation of braking pads was performed using scanning electron microscopy and also temperature outcome of the pads was examined at the temperatures of 50-400 "oC in the pressure of 1050 and 3000 kPa. Finally, the effect of environment to the pads was studied in water, salty water, oil and braking liquid media.

Energy Technology Data Exchange (ETDEWEB)

On March 28, 1979, the Pennsylvania Three Mile Island nuclear power plant Unit 2 (TMI-2) suffered a partial fuel-melt accident. During this accident, over 20,000 lb of molten fuel flowed through holes melted through the baffle plates and through the lower-core support assembly (LCSA). The molten fuel subsequently resolidified in the bottom of the reactor vessel. The lower-core support assembly of the TMI-2 reactor was not structurally damaged during the accident. In order to permit defueling of that region of the core, the LCSA was cut to permit access. A five-axis teleoperator was developed to deliver plasma arc cutting, rotary grinding and abrasive waterjet cutting of end effectors to the LCSA. Complex geometry sectioning was completed in a mock-up facility at chemistry and pressure conditions simulating those of the vessel, prior to actual in-vessel operations. In-vessel activities began in early May 1988 and were completed on April 11, 1989. This paper presents ...

British Library Electronic Table of Contents (United Kingdom)

Zirconium and particularly Zr-2.5wt%Nb (Zr2.5Nb) alloy are useful for engineering bearing applications because they can be oxidized in air to form a hard surface ceramic. Oxidized zirconium (OxZr) due to its abrasion resistant ceramic surface and biocompatible substrate alloy has been used as a bearing surface in total joint arthroplasty for several years. OxZr is characterized by hard zirconium oxide (oxide) formed on Zr2.5Nb using one step thermal oxidation carried out in air. Because the oxide is only at the surface, the bulk material behaves like a metal, with high toughness. The oxide, furthermore, exhibits high adhesion to the substrate because of an oxygen-rich diffusion hardened zone (DHZ) interposing between the oxide and the substrate. In this study, we demonstrate a two step pro...

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Leakfree compression of gaseous liquids prevents impurities resulting from entry of lubricants and abrasive particles and is therefore an important requirement on modern compressors. Another requirement voiced increasingly often is the reduction or even prevention of problematic off-gases and contaminated residues of libricating oils. Further, compressors should have high corrosion resistance, low noise, a long service life and high reliability. Membrane compressors are largely able to meet these requirements. The article describes the technical concept and applications of membrane compressors. (orig.) [Deutsch] Umweltschutz und steigende Forderungen der Industrie an die Reinheit technischer Gase verlangen Kompressoren, die weitgehend leckagefrei verdichten und keine Verunreinigungen des Gases durch Schmierstoffe und Abrieb hervorrufen. Immer haeufiger wird in diesem Zusammenhang die Reduzierung oder sogar die Vermeidung von schwer zu entsorgenden Abgasen und ...

Energy Technology Data Exchange (ETDEWEB)

Deformation of the ground can be considered as a sum of volume deformation and shear deformation. At circumferential ground of pile axis, simple shear type of shear deformation becomes main factor of settlement. As shear forces with reverse direction are overlapped at parallel face for pile around face of the ground between the piles, the shear deformation is relaxed. At deeper place from top of the pile, volume deformation becomes larger and component of shear deformation approaches to a pure shear type. In case of the land surface loading type consolidation settlement calculation, a method adopting one dimensional consolidation calculating method using only vertical component within stress obtained by elasticity theory even when investigating multi dimensionally is used widely. In Japanese design standards, the method calculating the consolidation settlement by presuming imaginary loading face for land surface is widely adopted. In case of abrasion pile, the ...

Energy Technology Data Exchange (ETDEWEB)

Out of the R and D of mesoscopic metal group composite materials, the paper described the fiscal 1997 results. In the in-situ method as a composite material making method, elucidated to some degree were chemical composition of Fe-C-Cr-V-Nb-Mo-W-Ni base multi-dimensional alloys, and wear resistance and oxidation resistance of MC type carbide dispersion multi-phase texture crystallizing as primary crystal and eutectic. In the composite material making with ceramic fiber and alloy by the pressure infiltration method, the paper clarified the texture formation mechanism in solidification/heat treatment by a combination of Al alloys and alumina long fiber, and the relation between fiber configuration and wear resistance. By MA and MG methods as the powder metallurgy composite material making method, a composed body of {alpha}-stainless steel of Fe-12%Cr composition and M23C6 of 40-90vol% are designed for alloy composition, and powder of amorphous or ...

International Nuclear Information System (INIS)

Plasma immersion ion implantation (PIII) is an effective materials modification and synthesis technique but has seldom been applied to ceramic materials due to the high electrical resistance that reduces the ion bombardment energy and sometimes causes serious electrical arcing in the instrument. Even in cases where PIII is applicable, the surface properties of the implanted insulating materials can be seriously affected due to the low ion energy and materials damage from electrical arcing. In order to enhance the surface and mechanical properties such as wear resistance of ceramic materials used in many industrial applications, surface modification is needed. In this work, we conduct carbon implantation into sintered #alpha#-SiC (silicon carbides that are widely used in vacuum ceramic bearings) using mesh-assisted plasma immersion ion implantation to enhance the surface properties. The use of a conducting grid is necessitated by the high electrical resistance that ...

Wastenet

heterogeneity bias Static models: Other models:

Energy Technology Data Exchange (ETDEWEB)

Thin films of new metastable materials from the system Ti-B-C-N were deposited on metallic substrates by d.c. magnetron sputtering in different Ar+N{sub 2} atmospheres. The multiphase compound targets used were based on various compositions on the TiC-TiB{sub 2} and TiB{sub 2}-C tie lines of the Ti-B-C phase diagram. The structure and chemical composition of the films were characterized by electron microprobe analysis, depth profiling Auger electron spectroscopy, X-ray diffraction and transmission electron microscopy. The hardness, critical load of failure and the tribological behavior of the coatings were investigated. Superhard single-phase crystalline metastable Ti-B-C-N layers with hardness values exceeding 5000 HV{sub 0.05} and extremely low sliding wear against 100Cr6 and Al{sub 2}O{sub 3} counterparts could be produced by reactive sputtering of various TiC-TiB{sub 2} targets in Ar+N{sub 2} atmospheres with low nitrogen flows. In the case of carbon-rich ...

Energy Technology Data Exchange (ETDEWEB)

A set of materials property data for potential wear resistant materials was collected. These materials are designated for use as the ''core'' materials in the Fibrous Monolith structure. The material properties of hardness, toughness, thermal conductivity and cost were selected as determining factors for material choice. Data for these four properties were normalized, and weighting factors were assigned for each property to establish priority and evaluate the effects of priority fluctuation. Materials were then given a score based on the normalized parameters and weighting values. Using the initial estimates for parameter priority, the highest ranking material was tungsten carbide, with diamond as the second ranked material. Several materials were included in the trade study, and five were selected as promising ''core'' materials to include in this effort. These materials are tungsten carbide, ...

Energy Technology Data Exchange (ETDEWEB)

During the first phase of this project, significant progress was made in several of the connected issues that make up the objectives of this grant. The central thrust or theme of this work under the DOE/ERIP grant is to carry out prototype testing of the concept of tribopolymerization as a novel mechanism of boundary lubrication--under more severe, high-load, high-speed conditions that are most likely to exist in field applications. The authors see this as an important step in attracting industries to license and market the results of this new technology. In addition, they have began to explore other potential, energy-saving applications of the concept of tribopolymerization. These exploratory studies are quite promising; they are likely to open new doors in industrial applications. To carry out the experimental part of this program, a new device has been built. Highlights of these and other developments are given.

International Nuclear Information System (INIS)

The Steam Generator (SG) tubing degradation caused by corrosion and other age-related mechanisms continues to be a significant safety and cost concern for many Nuclear Power Plants (NPP). The understanding of the steam generator ageing mechanisms is the key to effective management of steam generator ageing and consists of the knowledge of steam generator materials and these one properties, stressors and operating conditions, like degradation sites and wear mechanisms. The principal types of corrosion are presented which can occur in CANDU steam generator. There are also presented the operation conditions, the specifications referring to the water chemistry and the construction materials of Steam Generator, the factors that have a great influence on the corrosion behaviour during the whole exploitation period of this equipment. (R.P.)

Energy Technology Data Exchange (ETDEWEB)

Stainless steels can be nitrided at temperatures {<=}400 C to increase their hardness and wear resistance without a decreasing of their excellent corrosion resistance. Structure and properties of the surface layers produced by plasma nitriding and plasma immersion ion implantation in this temperature range were tested. There are negligible differences in the structure of the produced surface layers in spite of different interaction principles of the used technologies. However there are clear differences between the case of different steels. The case of ferritic chromium steels mainly consists of {epsilon}-nitride. Whereas the cases of austenitic and ferritic austenitic steels are characterized by expanded austenite. The corrosion resistance of the steels is reduced by nitriding only, if evident CrN-formation occurs. (orig.) 11 refs.

International Nuclear Information System (INIS)

Until a decade ago, only the differential bobbin type eddy current probe was considered necessary for reliable heat exchanger tube inspection. The introduction of different tube materials, manufacturing processes and a variety of service induced failures has greatly increased the demands of eddy current testing. Optimized probe designs enhanced by improved instrumentation can help satisfy some of these demands. Some of the more difficult inspection problems are detection of circumferential cracks, fretting wear under non-ferromagnetic support plates and shallow internal defects. Reliable detection and sizing of such defects is often made more difficult by the fact they frequently occur in defect prone regions such as under tubesheets or support plates and in transition regions of finned tubes. Probe designs effective in overcoming these difficulties exist. This paper describes a number of such probes and their performance.

British Library Electronic Table of Contents (United Kingdom)

Mobile offshore drilling rigs are used to drill, complete and workover wellbores in marine environments. The fleet that exists today consists of a wide variety of vessels built to various specifications over the past three decades, and because they operate in harsh, corrosive environments, they wear out structurally and require periodic maintenance. Rig designs have evolved with changes in operating requirements and new technology and rigs are frequently modified and upgraded, depending upon market conditions, operator preferences and other factors. The construction and replacement costs of offshore rigs are often used for management planning, financial valuation and insurance analysis, and because of the wide variety of designs, specifications and upgrades, cost estimates vary widely. In ...

International Nuclear Information System (INIS)

A ternary nickel-base alloy Ni-W-B has been developed for surface corrosion and wear resistance to replace chromium plating, which uses environmentally hazardous solutions. The deposition conditions used an alkaline bath and insoluble anodes. The as-deposited alloy typically contains 40 wt% W and 1 wt% B and has an amorphous or partially amorphous structure. These deposits compare favorably with hexavalent chromium deposits in throwing power, color uniformity, and reflectivity. The corrosion resistance of Ni-W-B alloy was compared with hexavalent chromium and electroless nickel deposits in a variety of acids, including hydrochloric, sulfuric, fluoroboric, and phosphoric. In all cases, best results were obtained with the Ni-W-B deposits.

British Library Electronic Table of Contents (United Kingdom)

The carbon fibers (CF) were pre-treated in two different ways: no pre-treatment, and activation in HNO3 plus application of toluene-2,4-diisocyanate (TDI). Carbon fibers have been introduced into polyurethane (PU) composite coatings. The tribological behaviors of the polyurethane composite coating filled with CF or TDI-modified CF (TDI-CF) were studied using a ring-on-block wear tester under dry sliding, and the worn surfaces of the filled PU coatings and transfer films formed on the surface of the counterpart ring sliding against the PU coating were investigated by SEM and optical microscope (OM), respectively. Owing to the effective improvement of the interfacial adhesion between the CF and polyurethane matrix, compared with the cases of untreated CF, the employment of low content TDI-CF...

Energy Technology Data Exchange (ETDEWEB)

Nanocrystalline and nanostructured materials offer unique microstructure-dependent properties that are superior to coarse-grained materials. These materials have been shown to have very high hardness, strength, and wear resistance. However, most current methods of producing nanostructured materials in weapons-relevant materials create powdered metal that must be consolidated into bulk form to be useful. Conventional consolidation methods are not appropriate due to the need to maintain the nanocrystalline structure. This research investigated new ways of creating nanocrystalline material, new methods of consolidating nanocrystalline material, and an analysis of these different methods of creation and consolidation to evaluate their applicability to mesoscale weapons applications where part features are often under 100 {micro}m wide and the material's microstructure must be very small to give homogeneous properties across the feature.

British Library Electronic Table of Contents (United Kingdom)

In the present work, the plasma nitriding behavior of a nickel based dental alloy was investigated. Plasma nitriding experiments carried out under constant gas mixture (15% H2?85% N2) for different process parameters including time (4, 6, 10, and 20?h) and temperature (400, 450, 500, and 550??C). Depending on nitriding parameters, it was found that triple or double layers formed on the surface of the samples. Increasing of treatment time and temperature has resulted in a double layer. ?N1 layer was in formed all nitrided samples. However, ?N2 layer is formed only at low temperatures and in short times. Layer growth of nickel based alloys increases until a critical time or a critical temperature reached. Above these critical values, it is observed that the layer thickness decreases. It was ...

International Nuclear Information System (INIS)

Composite nitrides (such as BN, TiN) are widely used in various industrial applications because of their extreme wear and corrosion resistance, thermal and electrical properties. in order to obtain composite materials with these optimal properties, it is important to elucidate whether any chemical reactions occur at nitride/metal interfaces, e.g., those involving BN-Ti/TiN. Materials of interest include the deposition by PVD of Ti and TiN on BN substrates. Some of these systems were then subjected to varying degrees of physical and thermal alteration. Detailed X-ray photoelectron spectroscopy (XPS) has therefore been rendered of these interfaces using cross-sectional display and sputter etching. Resulting structural and morphological features have been investigated with transmission electron microscopy (TEM) and X-ray diffraction (XRD). Diffusion of the nitridation, oxynitride formation and interfacial growth are of general interest.

British Library Electronic Table of Contents (United Kingdom)

The combined processes of plasma nitriding and cathodic arc deposition of (Ti,Cr,Nb)CN coatings were applied to HSS substrates. The nitrided layers, obtained in a mixture of H2 (70%) and N2 (30%) at two different temperatures (480^oC and 510^oC), were examined for the microhardness depth profiles. Characterization of the duplex coatings was performed by investigating elemental and phase composition, texture, hardness, friction and wear. XRD and XPS analyses revealed the formation of a mixture of a carbonitride fcc solid solution, in a dominant proportion, and metallic chromium. The film hardness was measured to be ~34GPa. The duplex (Ti,Cr,Nb)CN coatings exhibited superior tribological behavior as compared to both nitrided layers and non-duplex coatings.

Energy Technology Data Exchange (ETDEWEB)

The recent rapid progress in surface treatment techniques dictates that the titanium alloys should have an improved resistance to frictional wear without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface layers of specified microstructure and phase composition. The present paper describes a modification of the plasma discharge nitriding treatment of titanium alloys, i.e. the glow discharge-assisted oxycarbonitriding, which by introducing oxygen, nitrogen and carbon into the surface zone of the layer [a Ti(NCO) type layer] improves its useful properties, primarily the resistance to frictional wear and the resistance to corrosion [T. Wierzchon, J. Sobiecki, Vacuum, 44 (1993) 975; T. Wierzchon et al., in: G. Hecht, F. Richter, J. Hahn (Eds.), Thin Films, DGM Informationgesellschaft, Germany, 1994, p. 195] [1:2]. This is because titanium shows a good affinity to oxygen, carbon and nitrogen, ...

International Nuclear Information System (INIS)

The physical, chemical and mechanical properties of magnesium alloys make them attractive materials for automotive and aerospace applications. However, these materials are susceptible to corrosion and wear. This work discusses the potential of using sol-gel based coatings consisting of ZrO_2 and 15 wt.% of CeO_2. The CeO_2 component provides enhanced corrosion protection, while ZrO_2 impart corrosion as well as wear resistance. Coating deposition was performed by the dip coating technique on two magnesium alloy substrates with different surface finishes: AZ91D (as-casted, sand-blasted, and machined) and AZ31 (rolled and machined). All as-deposited coatings (xerogel coatings) were then subjected to 10 h annealing: a temperature of 180 C was applied to the AZ91D alloy and 140 C to the AZ31 alloy. Morphological and structural properties of the annealed coatings were investigated by scanning electron microscopy, atomic force microscopy and ...

International Nuclear Information System (INIS)

When materials such as metal are into the secondary side of steam generator, they, so called foreign objects, may have influences on the integrity of the steam generator tubes. They cause the tube wear due to the relative motion between the tubes and foreign objects and the tube impact due to flow. The best way to avoid the effects is to remove all the foreign objects. However, it is not easy to remove the foreign materials thoroughly due to their condition such as the location. If the locations of the foreign materials are in the middle of tube bundle and the tube arrangement of the steam generator is the triangle type, the equipment such as FOSAR(Foreign Object Search and Retrieval) can not reach their locations. If the foreign materials stick together with the tubes or tube sheet, they can not be removed. In the case of operating the steam generator with the foreign materials, the licensee must prove that the materials do not affect the tube integrity and do not ...

Science.gov (United States)

The first part of the conference dealt with environmental effects of using coal. Papers dealt with the use of fly ash in agriculture and its effect on plant growth; the effect of airborne emissions on fish and wildlife resources, on watersheds, and on airsheds; the effects of surface mining on the ecology; blast effects; and health hazards associated with coal. The session on policy studies addressed the issue of cost of synthetic fuels and discussed the state and federal pollution regulations on burning coal and waste disposal. The session on combustion presented papers on atmospheric and pressurized fluidized-bed combustion for industrial and utility boilers. It also included papers on MHD power plants, coal-oil and coal-water mixtures, emission characterization and control, and catalytic combustors. The design of gasification plants, reaction kinetics, specific heats of coals and chars, simultaneous production of liquid and gaseous fuels, and economics of fuel substitution with coal ...

Energy Technology Data Exchange (ETDEWEB)

The characteristics of fractures in unit 2 of the Tshirege Member of the Bandelier Tuff were documented in Pit 39, a newly excavated 13.7 m deep disposal pit at Material Disposal Area G on Mesita del Buey. The average spacing between fractures is about 1.0 to 1.3 m, the average fracture aperture is about 3 to 5 mm, and the average fracture dip is about 76o to 77o. Fracture spacing and dip in Pit 39 are generally consistent with that reported from other fracture studies on the Pajarito Plateau, although the fracture apertures in Pit 39 are less than reported elsewhere. Measured fracture orientations are strongly affected by biases imparted by the orientations of the pit walls, which, combined with a small data set, make identification of potential preferred orientations dlfflcult. The most prominent fracture orientations observed in Pit 39, about E-W and N20E, are often not well represented elsewhere on the Pajarito Plateau. Fracture fills contain smectite to about 3 m depth, and ...

UK PubMed Central (United Kingdom)

SIMV (simulation and modeling of ventilation) is a quantitative system for the mathematical modeling and simulation of pulmonary...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Science.gov (United States)

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Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

ScienceCinema

...english ...

Science.gov (United States)

... Multivibrators were used in the first model, which is called the "MV Model." Mwe second model, "1ST Model," has a saw-toothed voltage. ...

Energy Technology Data Exchange (ETDEWEB)

The program goals for the first quarter were to located and contact potential manufacturers of these components, evaluate their level of interest, and begin discussions of the type and design of the prototypes to be fabricated for their evaluation. Thoughtful discussion at this stage would result in fabricating prototypes which answer the greatest number of questions possible for a given manufacturer at the lowest cost to this program. In the present economy many manufacturing firms have almost no funds for testing and evaluating new materials. This places a greater burden on the data obtained from outside laboratories. In many cases this data will be used to make that first evaluation on MRCC`s (metal reinforced carbon composites) suitability for a given application and give firms the confidence to commit to a evaluation program. In Exhibit 1, which is attached to this report the authors have the first set of data from outside laboratories. This has been incorporated into a paper ...

Energy Technology Data Exchange (ETDEWEB)

The authors investigated the development of tribochemical reaction layers and surface-level structural changes in a fuel-lubricated roller bearing steel 100Cr6 in the limiting friction range, using two different variants of surface treatment and heat treatment. Tribological experiments were carried out in a laboratory test stand with reversing sliding wear under varying loads and with a varying number of friction cycles. [German] Ziel der vorliegenden Arbeit war es, die Entstehung von tribochemischen Reaktionsschichten und oberflaechennahen Gefuegeaenderungen am Waelzlagerstahl 100Cr6 bei Kraftstoffschmierung im Grenzreibungsbereich fuer je zwei Oberflaechenbearbeitungen und Waermebehandlungen zu untersuchen. Dazu wurden tribologische Kurzversuche in einem Laborpruefstand mit reversierender Gleitbeanspruchung unter Variation der Last und der Anzahl der Reibzyklen durchgefuehrt. (orig.)

Energy Technology Data Exchange (ETDEWEB)

The present work describes the surface improvement and biocompatibility of TiAl{sub 24}Nb{sub 10} intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400 W to 650 W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium ...

Energy Technology Data Exchange (ETDEWEB)

Wildland fire suppression personnel employed by the CDF do not currently have the equipment to protect themselves from the short-term acute affects of smoke from wildland fires. In addition, no regulations exist that specify appropriate respiratory protection and the current air-purifying respirator technology and carbon monoxide monitoring has not been adapted to fit wildland fire suppression requirements. This three-year limited study evaluated the ability of wildland fire fighters to perform their normal job function while wearing full-face air-purifying respirators. In the first two years of this study we designed, developed and field tested a prototype ``smart`` air-purifying respirator which incorporated a real-time carbon monoxide monitor into a commercial full-face respirator.` Data on carbon monoxide exposure while fighting wildland fires was collected. During the third year of this study we evaluated eight different commercially available full-face ...

International Nuclear Information System (INIS)

We report the radiation exposure dose received by the anesthesiologist and nurse in the orthopaedic operating room, when a fluoroscopic image intensifier is in use. This study was done in 12 femoral neck fracture operations performed from January to May 1995. Radiation was monitored with the MYDOSE MINIX PDM 107 made by Aloka Co. which were attached in front and behind the nurse's lead apron, in front of the lead apron of the anesthesiologist. The average imaging time was 9.78 min. The average radiation dose in front of the anesthesiologist is lead apron was 2.08#mu#SV, and in front and behind the nurse's lead apron were 5.67#mu#SV, 0.08#mu#SV respectively. This study and review of the literature indicate that the operating room anesthesiologist and nurse receive a lower exposure than the orthopaedist. We can disregard the problem of radiation exposure to the anesthesiologist and nurse during an orthopaedic operation when they wear lead aprons and stand far from ...

International Nuclear Information System (INIS)

Aluminium nitride (AlN) is a very interesting ceramic because of its combination of properties such as high thermal stability, high hardness and an unusual combination of high thermal and low electrical conductivity. But it is very difficulty to obtain an AlN layer on the aluminium substrates by thermochemical nitriding process. Since a thin film of aluminium oxide existing on the surface of every aluminium substrate prevents the nitrogen atoms from diffusing into the aluminium lattice. However, it is possible to sputter the oxide film away from the aluminium surface in a glow discharge with the use of plasma nitriding technique and to allow the formation of AlN layer on the aluminium bulk. In the present work specimen of aluminium Al 99.5 has been plasma nitrided in a modified plasma nitriding unit, in which a diffusion pump was used to obtain an especially low partial pressure of oxygen in the vauum chamber. The sputter-cleaning prior to the nitriding was conducted with the variation ...

International Nuclear Information System (INIS)

Within the framework of a study on the chemical wear behaviour of sialon ceramics a range of compositions were prepared in which the alumina content was varied from 6 to 77 weight percent. The materials were hot-pressed from alumina and silicon nitride powders to a density of at least 97%. The structure and compositions of the phases occurring in these samples i.e. the O' phase, #beta#'-sialon solid solution and especially the X-phase were thoroughly characterized with respect to structure and composition using electron microprobe and transmission electron microscopy techniques. These results will be discussed in the light of earlier phase diagram studies. Some basic properties such as E-modulus and toughness were measured and related to microstructural features. E-modulus as well as toughness are at a minimum for materials with a high content of the X-phase. Oxidation of the materials was studied at 1300 deg C and 1450 deg C using weight gain measurements and ...

Energy Technology Data Exchange (ETDEWEB)

The fuel-injection system of the Niigata 6L 16X-AG dual-fuel engine is structured to steadily supply injected fuel during diesel-engine operation, and to distribute oil at a low rate to all the cylinders during gas-engine operation. The dual-fuel engine is started by the diesel engine operation and is changed over to gas-engine operation when the load increases. This change over is done automatically with a link mechanism. Regarding the gas-supply system, the changing pressure of supply gas is controlled by a pressure control valve which is stable and most adequate for the engine. The dual-fuel engine has the following features: (1) a high compression ratio is adopted, which reduces fuel consumption and thermal efficiently; (2) if the supply of gas decreases or stops, while continuing loaded operations, it can immediately shift to diesel engine operation automatically and continue the operation; (3) ignition is done by the injection of pilot oil, thus eliminating ignition failures; and ...

Science.gov (United States)

Potential exposure of workers to phosphide was examined during an in-depth industrial hygiene survey at the Bunge Corporation, in Kansas City, Kansas, where the gas was used as a grain fumigant. During the study, 14 men were employed at the facility. Tablets of aluminum phosphide were added to the grain mass for fumigation. General dilution ventilation resulted from outside air entering the work areas through ventilation louvers; there was also a local-exhaust ventilation system. Air samples revealed that, when the fumigant dispensers were being filled, workers in the area had significant exposure. At the time of the survey the relative humidity in the facility was high, permitting the reaction to phosphide to occur more readily. The levels of phosphide and respirable dust were reasonably low in the elevators, suggesting that the ventilation system was adequate. The author recommends that workers filling the dispenser with the aluminum phosphide be required to wear ...

Energy Technology Data Exchange (ETDEWEB)

Microelectronic failure analysis (FA) has been an integral part of the development of state-of-the-art integrated circuits. FA of MicroElectroMechanical Systems (MEMS) is moving from its infancy stage to assume an important role in the successful design, fabrication, performance and reliability analysis for this new technology. In previous work, the authors focused on the application of several techniques developed for integrated circuit analysis to an earlier version of a surface micromachined microengine fabricated at Sandia. Recently, they have identified important new failure modes in binary counters that incorporate a newer design of the microengine, using a subset of integrated circuit failure analysis techniques including optical microscopy, focused ion beam (FIB) techniques, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The primary failure mode they have identified is directly related to visible wear on bearing surfaces. In this ...

International Nuclear Information System (INIS)

Activation has been used for many kinds of useful applications, such as use of the radioisotopes for diagnosis and treatment of cancer, and wear (or corrosion) investigation for using thin layer activation (TLA) technique, etc. But activation also has severe problems for the post-processing of the samples; such as time-loss, inconvenience of sample handling, personal radiation safety, etc. For in-vitro experiments, we observed death of tumor cells by proton irradiation. The use of large activated container material can cause erroneous results in this case. To solve these problems, we studied why the samples were activated and how the level of the activation could be reduced. In proton beam irradiation experiments, the target materials could be defined as the container and sample itself. We could easily reduce activation of container material comparing to activation of sample itself. Therefore, we tried to find less activated container material by irradiating proton ...

Energy Technology Data Exchange (ETDEWEB)

Several components of high-temperature reactor units have roller bearings in order to carry out their motions without much friction. The use of such bearings poses friction and wear problems which cannot be mastered by commercial roller bearing technology. Possible improvements of coating, cage design and bearing materials as well as of their parameters were registered and studied. The service life of dry lubricated bearings was considerably improved. With a radial or axial load on the bearing of {>=} 10% of the static load, {approx_equal} 20x10{sup 6} rolling motions/actuations can be performed. The connections between surface compression and wear were determined, and optimum conditions for the transfer of lubricants from the cage onto the bearing race were worked out. Coating of corrosion-resistant roller bearing steels with the HRB-M{sub 0}S{sub 2} running-in coating could be proved. New cage designs and materials were tested with ...

Science.gov (United States)

... 4 Joint Committee on Atomic Energy as a Model . . . . . ... Joint Committee on Atomic Energy as a Model ...

Wastenet

Institutional and organizational models ... Review individual centre institutional and organizational models in the light of the tasks to be performed by

Energy Technology Data Exchange (ETDEWEB)

The role of natural enemies in the regulation of populations is one of the major questions facing population ecologists. Simplification have led to two theoretical ways of incorporating the role of natural enemies in single ecological models: diffusion models and patch-type models. The predictions of the models are different because of the way variability is incorporated. Three equations are presented for diffusion models and one for patch models. Since the two types of models apply at different combinations of spatial and temporal scales, the right model(s) to choose for a particular study requires careful assessment. A continuing dialogue between experimentalists and theoreticians will lead to a better understanding of natural systems such as those that occur in biological control.

Science.gov (United States)

terms of 11) numerical models, 2D SPH simulations, and analytic models. The 1D model was useful for determining the evolution over very long timescales. ...

UK PubMed Central (United Kingdom)

Models can be useful at many different levels when considering complex issues such as biological control of mosquitoes. At an early stage, exploratory models are valuable in exploring the characteristics...Full Text Available

Science.gov (United States)

Engine model: An engine and governor model adapted from a heavy lift helicopter simulation provides a restistic time delay between aerodynamic rotor ...

CERN Document Server

The Inner Model Hypothesis (IMH) and the Strong Inner Model Hypothesis (SIMH) were introduced by the first author in ``Internal consistency and the inner model hypothesis'', Bulletin of Symbolic Logic, December 2006. In this article we establish some upper and lower bounds for their consistency strength.

Science.gov (United States)

This 1978 annual report contains the results of ''Seismic testing of Wolsung-1 steam generator model'' which was initiated in 1977 as a part of a study on nuclear components testing. Model 78, improved version of Model 77 which did not take into account f...

KoreaScience (Korea)

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Science.gov (United States)

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CERN Document Server

Multiphase reacting flows

Energy Technology Data Exchange (ETDEWEB)

No abstract available.

Norwegian Open Research Archives (NORA)

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KoreaScience (Korea)

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Norwegian Open Research Archives (NORA)

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Czech Academy of Sciences Repository

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Energy Technology Data Exchange (ETDEWEB)

In recent years the modelling of interannual climate variability has been studied, the atmospheric energy and water cycles, and climate simulations with the ECHAM3 model. In addition, the climate simulations of several models have been compared with special emphasis in the area of northern Europe

Norwegian Open Research Archives (NORA)

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KoreaScience (Korea)

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Science.gov (United States)

processes, we construct a stochastic dynamic model for air- craft counts in ... Also , queueing models for the arrival of aircraft at ... A queueing model has also been used to study ...... Assignment and Aircraft-Sequencing Algorithms in Terminal ...

KoreaScience (Korea)

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Energy Technology Data Exchange (ETDEWEB)

This paper presents research work concerning the mathematical modelling of air pollution in the Athens basin. A mathematical model based on aerodynamics and conservation equations together with turbulence modelling in body-fitted coordinates is used to provide the necessary input information to a similar but more detailed (i.e. small scale) model around Athens. Both models consist of solving the full Navier-Stokes equations and take into account the precise topography of the region. Different roughness heights are used for sea, coastal regions and land. The smaller scale model makes use of a two-equation turbulence model ({kappa}-{epsilon}) and the large scale model assumes a constant turbulence viscosity. The pollutant sources used in these models are based on actual emissions in the Athens area and ...

CERN Document Server

This paper presents a model of the dynamics of the wage income distribution.

Science.gov (United States)

... 1]. Results and Discussion A cross section of liquid feed direct borohydride fuel cell model was created and studied. The ...

Science.gov (United States)

... Lincoln Laboratory Distribution Models for Optical Scintillation Due to Atmospheric Turbulence RR Parenti RJ Susiela Group 107 ...

Energy Technology Data Exchange (ETDEWEB)

Non-linear autoregressive Markov regime-switching models are intuitive. Time-series approaches for the modelling of electricity spot prices are frequently proposed. In this paper, such models are compared with an ordinary linear autoregressive model with regard to their forecast performances. The study is carried out using German daily spot-prices from the European Energy Exchange in Leipzig. Four non-linear models are used for the forecast study. The results of the study suggest that Markov regime-switching models provide better forecasts than linear models. (author)

Science.gov (United States)

... 3 Joint Committee on Atomic Energy as a Model . . . . . ... Joint Committee on Atomic Energy as a Model Page 8. CRS-4 ...

CERN Document Server

The concept of frailty offers a convenient way to introduce unobserved heterogeneity and associations into models for survival data. In its simplest form, frailty is an unobserved random proportionality factor that modifies the hazard function of an individual or a group of related individuals. "Frailty Models in Survival Analysis" presents a comprehensive overview of the fundamental approaches in the area of frailty models. The book extensively explores how univariate frailty models can represent unobserved heterogeneity. It also emphasizes correlated frailty models as extensions of

CERN Document Server

This paper proposes the use of particle swarm optimization method (PSO) for finite element (FE) model updating. The PSO method is compared to the existing methods that use simulated annealing (SA) or genetic algorithms (GA) for FE model for model updating. The proposed method is tested on an unsymmetrical H-shaped structure. It is observed that the proposed method gives updated natural frequencies the most accurate and followed by those given by an updated model that was obtained using the GA and a full FE model. It is also observed that the proposed method gives updated mode shapes that are best correlated to the measured ones, followed by those given by an updated model that was obtained using the SA and a full FE model. Furthermore, it is observed that the PSO achieves this accuracy at a computational speed that is faster than that by the ...

Energy Technology Data Exchange (ETDEWEB)

A detailed component-based simulation model of a geothermal heat pump system has been calibrated to monitored data taken from a family housing unit located at Fort Polk, Louisiana. The simulation model represents the housing unit, geothermal heat pump, ground heat exchanger, thermostat, blower, and ground-loop pump. Each of these component models was tuned to better match the measured data from the site. These tuned models were then interconnected to form the system model. The system model was then exercised in order to demonstrate its capabilities.

British Library Electronic Table of Contents (United Kingdom)

This paper introduces a new way of estimating parameters in a Brownian motion regime switching asset model to incorporate volatility clustering. The regime switching model is then applied to pricing of up-and-in barrier call options. We take the probability of crossing the barrier between simulation points into account, and we increase accuracy in simulations by importance sampling. The regime switching model is compared to the Normal Inverse Gaussian model and the traditional Black-Scholes model, and option prices from the regime switching model are compared to the closed form expression of up-and-in barrier calls in a Black-Scholes market.

International Nuclear Information System (INIS)

An integrated approach to the modelling of hydrogen assisted failure in 316L steel is presented. The approach includes experimental, fractographic, numerical and theoretical analysis of the phenomenon. The physical adequacy of the mechanical models of hydrogen embrittlement (notch extension model and notch cracking model) is discussed by comparing the virtual damage depth (theoretical) predicted by the models with the embrittled zone (microphysical) measured in the fractographic analysis by scanning electron microscopy. In addition, a numerical modelling of hydrogen diffusion is performed, concluding that bulk diffusion is not important in hydrogen embrittlement of 316L steel, so that hydrogen transport accelerated by the microdamage itself should be taken into account. (orig.)

Energy Technology Data Exchange (ETDEWEB)

Damage survey of protective coats of modern gas turbine blade shows that most damages are not due to classic wear mechanisms such as oxydation or high-temperature corrosion but caused by foreign bodies, poor coating during manufacturing, or operation-caused cracks. Mere visual inspection of cracks is often not sufficient to tell whether cracks are superficial or whether they have already progressed into the base material. Non-destructive methods such as ultrasonic inspection or eddy-current testing are helpful tools but there is not yet a fully matured testing concept at hand. Metallographical tests can give important information about crack mechanisms and thermal, chemical and mechanical stresses.(orig.) [German] Die Schadenerfahrung mit Schutzschichten moderner Gasturbinenschaufeln zeigt, dass die meisten Schaeden nicht auf die klassischen Verbrauchsmechanismen wie Oxydation und Hochtemperaturkorrosion zurueckzufuehren sind, sondern durch Fremdkoerper, ...

Energy Technology Data Exchange (ETDEWEB)

This fourteenth quarterly technical progress report of the MHD Integrated Topping Cycle Project presents the accomplishments during the period November 1, 1990 to January 31, 1991. Testing of the High Pressure Cooling Subsystem electrical isolator was completed. The PEEK material successfully passed the high temperature, high pressure duration tests (50 hours). The Combustion Subsystem drawings were CADAM released. The procurement process is in progress. An equipment specification and RFP were prepared for the new Low Pressure Cooling System (LPCS) and released for quotation. Work has been conducted on confirmation tests leading to final gas-side designs and studies to assist in channel fabrication.The final cathode gas-side design and the proposed gas-side designs of the anode and sidewall are presented. Anode confirmation tests and related analyses of anode wear mechanisms used in the selection of the proposed anode design are presented. Sidewall confirmation ...

Science.gov (United States)

Several randomized placebo-controlled trials have consistently shown antidyskinetic effects of amantadine in levodopa treated patients with advanced Parkinson's disease (PD). However, all of these were of short duration and there have been claims that the effect of amantadine on levodopa induced dyskinesias (LID's) wear off after about 9 months of treatment. This randomized placebo-controlled parallel-group study was performed to assess the long-term antidyskinetic effect of amantadine in 32 PD patients, who after having been on stable amantadine therapy for LID over at least one year- were switched in a double blind manner to amantadine or placebo and followed for 3 weeks. Dyskinesia duration and intensity were assessed by UPDRS IV items 32 and 33 as well as by patient's diaries. The primary outcome was the score change of UPDRS IV items 32 + 33 between baseline and 3 weeks after treatment as well as the between treatment group comparison of the score change of ...

Energy Technology Data Exchange (ETDEWEB)

The steam generator (SG) is one of the most critical components of the heat transfer system in nuclear generation stations. Testing the structural integrity of SG tubing and SG internals is a key element of the fitness-for-service assessments to assure the safe and continuous operation of nuclear power plants. Recent eddy current (ET) inspections of two nuclear power plants revealed degradation of some of the tube support plate (TSP) structures, which was also confirmed by visual inspection. The phenomena was described as metal loss, caused by flow-accelerated corrosion of the carbon steel trefoil support plate and varying from minor to complete loss of the ligaments. This loss of TSP ligaments results in lack of support for the adjacent tubes making them more susceptible to fretting-wear damage and fatigue cracking. A signal analysis method, based on the responses at low frequency of two types of eddy current probes, has been developed to assess the degree of ...

Energy Technology Data Exchange (ETDEWEB)

The constitutive model used to describe the deformation of crushed salt is presented in this report. Two mechanisms -- dislocation creep and grain boundary diffusional pressure solution -- are combined to form the basis for the constitutive model governing the deformation of crushed salt. The constitutive model is generalized to represent three-dimensional states of stress. Upon complete consolidation, the crushed-salt model reproduces the Multimechanism Deformation (M-D) model typically used for the Waste Isolation Pilot Plant (WIPP) host geological formation salt. New shear consolidation tests are combined with an existing database that includes hydrostatic consolidation and shear consolidation tests conducted on WIPP and southeastern New Mexico salt. Nonlinear least-squares model fitting to the database produced two sets of material parameter values for the ...

Science.gov (United States)

The objective of this Task Group is the coordination of research studies on biokinetic models and the evaluation of the implications of new biokinetic models on dose assessment and safety standards. For this the new ICRP models, which will be used for a revision of ICRP Publications 30, 54, 68 and 78, are implemented into six different computer codes in five European countries and quality assured by intercomparison procedures. The work has started with the implementation of the new ICRP Alimentary Tract Model. New systemic models and the new NCRP wound model will follow. The work also includes the evaluation of experimental results in terms of formulation by the new model structures and a quality assurance of model formulation. PMID:17556343

Energy Technology Data Exchange (ETDEWEB)

The heat capacity and heat of fusion were measured for a number of minerals using differential scanning calorimetry (DSC). The DSC measurements showed that the heat of fusion for the minerals is very low compared to the heat of fusion for pure crystalline phases reported elsewhere. A model for the melting behaviour of mineral materials in terms of melting interval, heat capacities and heat of fusion has been developed. The only model input is the chemical composition of the mineral material. The model was developed to be implemented in a detailed model of a cupola furnace, thus the focus for the development was not only precision but also to obtain a model that was continuous and differentiable. The model is based on several different submodels that each covers a part of the heating and melting of rocks. Each submodel is based on large amounts of empirical data. ...

International Nuclear Information System (INIS)

The high-power model of Disk-and Washer (DAW) cavity for electron acceleration is under fabrication. Basic Dimensions of the cavity were determined from aluminum model measurement and electromagnetic field calculation. We have fabricated model made of OFC (Oxygen Free Copper) five times in total. Some details are optimized and corrected, and then the final brazing are proceeding. These model results and present status are described. (author)

Energy Technology Data Exchange (ETDEWEB)

This report to the Nuclear Regulatory Commission (NRC) describes the development and application of a methodology to systematically and quantitatively assess predictive uncertainty in groundwater flow and transport modeling that considers the combined impact of hydrogeologic uncertainties associated with the conceptual-mathematical basis of a model, model parameters, and the scenario to which the model is applied. The methodology is based on a n extension of a Maximum Likelihood implementation of Bayesian Model Averaging. Model uncertainty is represented by postulating a discrete set of alternative conceptual models for a site with associated prior model probabilities that reflect a belief about the relative plausibility of each model based on its apparent consistency with available knowledge and ...

Science.gov (United States)

This paper presents a case study in the design and implementation of a numerical weather prediction model on a supercomputer (CRAY-1). Following a historical introduction to the evolution of the model, the governing equations of the model are presented and the numerical solution of these forecast equations is described. A brief tutorial on the architecture of the CRAY-1 is presented with a discussion of how it affects the choice of algorithms and code design of the model. A summary of the advantages gained by use of the vector aspects of the CRAY-1 is included.

UK PubMed Central (United Kingdom)

The brain maintains internal models of its environment to interpret sensory inputs and prepare actions. While behavioral studies demonstrated that these internal models are optimally adapted...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

We obtain a symmetry algebra for any unitary minimal model by using the representation of conformal field theories. This symmetry algebra can be interpreted as a quantum group. The generalization to non-unitary minimal models is direct. (orig.).

UK PubMed Central (United Kingdom)

BackgroundLiquid chromatography-mass spectrometry (LC-MS) is one of the major techniques for the quantification of metabolites in complex biological samples. Peak modeling is one...Full Text Available

Science.gov (United States)

In this paper two different models of brain regulation of exercise performance are critically compared: the central governor model proposed by Noakes and colleagues, and an alternative psycholobiological model based on motivational intensity theory. PMID:18618133

International Nuclear Information System (INIS)

We show the existence of a rather general class of closed cosmological models of Bianchi type IX that do not exhibit recollapse but expand for all times. This is despite the fact that these models satisfy the strong energy condition by a wide margin.

UK PubMed Central (United Kingdom)

We present the formulation and testing of a mathematical model for the kinetics of homotypic cellular aggregation. The model considers cellular aggregation under no-flow conditions as a two-step process....Full Text Available

Energy Technology Data Exchange (ETDEWEB)

Volume VII of the documentation for the Phase I Data Analysis Task performed in support of the current Regional Flow Model, Transport Model, and Risk Assessment for the Nevada Test Site Underground Test Area Subproject contains the tritium transport model documentation. Because of the size and complexity of the model area, a considerable quantity of data was collected and analyzed in support of the modeling efforts. The data analysis task was consequently broken into eight subtasks, and descriptions of each subtask's activities are contained in one of the eight volumes that comprise the Phase I Data Analysis Documentation.

Energy Technology Data Exchange (ETDEWEB)

;Contents: Comparison of Simulation Modules of TRANSYT and INTEGRATION Models; Evaluation of SCATSIM-RTA Adaptive Traffic Network Simulation Model; Comparison NETSIM, NETFLO I, and NETFLO II Traffic Simulation Models for Fixed-Time Signal Control; Traffic Flow Simulation Through Parallel Processing; Cluster Analysis as Tool in Traffic Engineering; Traffic Platoon Dispersion Modeling on Arterial Streets; Hybrid Model for Estimating Permitted Left-Turn Saturations Flow Rate; and Passing Sight Distance and Overtaking Dilemma on Two-Lane Roads.

Energy Technology Data Exchange (ETDEWEB)

We discuss the asymptotic dynamical evolution of spatially homogeneous brane-world cosmological models close to the initial singularity. We find that generically the cosmological singularity is isotropic in Bianchi type IX brane-world models and consequently these models do not exhibit Mixmaster or chaotic-like behaviour close to the initial singularity. We argue that this is typical of more general cosmological models in the brane-world scenario. In particular, we show that an isotropic singularity is a past-attractor in all orthogonal Bianchi models and is a local past-attractor in a class of inhomogeneous brane-world models. (letter to the editor)

International Nuclear Information System (INIS)

In this paper extended models for estimating price developments on electricity markets are presented. The models consider deviations from the normality hypothesis of the prices. Based on an ARMA model combination with GARCH, Gaussian-mixture and switching-regime approaches are comparatively discussed. The comparison is based on historic electricity prices of the spot and two reserve markets in Germany. It is shown that the proposed extended models lead to significantly improved representations of the considered stochastic price processes. It is inferred that these models may be preferred for estimating price developments on electricity markets. (author)

Science.gov (United States)

Models are proposed which explain the mechanism of action on a molecular level for the initiation of cancer by electrons or alpha particles. (ACR)

International Nuclear Information System (INIS)

A review is made of some recent developments in the application of the Bohr Hamiltonian to transitional nulcei. The primary concern is to understand the advantages and limitations inherent to the basic model and its many variants. (author).

Energy Technology Data Exchange (ETDEWEB)

We argue that the tachyons which exist in some string models are a signal of deconfinement. We compare the deconfinement temperature obtained from Monte Carlo calculations with some string models. (orig.).

Science.gov (United States)

... kinematic model for the robots and designed ... theoretic approach for modeling mobile robot teamn formations". ... "UUV teams, control from a biological ...

UK PubMed Central (United Kingdom)

BackgroundPreclinical models of pediatric cancers are essential for testing new chemotherapeutic combinations for clinical trials. The most widely used ...Full Text Available

Science.gov (United States)

... Those functions are fundamental routines to build a power model for more complex circuits or functional blocks. ... 21 of 54 6. Memory Power Model ...

Energy Technology Data Exchange (ETDEWEB)

This dissertation is devoted to the study of the phenomenological consequences of the three-generation heterotic string models based on the Calabi-Yau compactifications and the N = 2 superconformal constructions.