bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Sulphate Concentration on the Community Structure and Activity of Sulphate Reducing Bacteria
Authors: Oyekola Oluwaseun O. , van Hille Robert P. , Harrison Susan T.L.
Published: March 2009

This study investigated the effect of sulphate concentration and residence time on the
performance of anaerobic sulphate reduction by a mixed sulphate reducing bacteria (SRB) culture
using lactate as the sole carbon source and electron donor. The process performance is related to the
population structure of the microbial consortia and dominant metabolic reactions. Laboratory scale
chemostat cultures at different residence times (1-4 d) and sulphate concentrations (1.0-10.0 g/L)
were employed. Lactate oxidation was prevalent at feed sulphate concentrations of 1.0 to 5.0 g/L. A
corresponding increase in the volumetric sulphate reduction rate with increasing volumetric loading
rate was also observed at this range. However, at the higher feed sulphate concentration range
(10.0-15.0 g/L), sulphate inhibition, lactate fermentation and an increased microbial diversity were
evident. At each feed concentration of sulphate in the range 5.0 to 15.0 g/L, varying dilution rates
resulted in significant shifts in dominant metabolic reactions. Sulphate concentration and residence
time have significant effects on both the structure of the microbial population and kinetics of
biological sulphate reduction.
Discovery of Small Regulatory RNAs Extends Our Understanding of Gene Regulation in the Acidithiobacillus Genus
Authors: Shmaryahu Amir , Holmes David S.
Published: March 2009

Small regulatory RNAs (srRNAs) control gene expression in Bacteria, usually at the posttranscriptional
level, by acting as antisense RNAs that bind targeted mRNAs or by interacting with
regulatory proteins. srRNAs are involved in the regulation of a large variety of processes such as
plasmid replication, transposition and global genetic circuits that respond to environmental changes.
Since their discovery a few years ago, it has become apparent that they are prolific and widespread. In
this study, we describe bioinformatic approaches to srRNA discovery in the biomining microorganisms
Acidithiobacillus ferrooxidans, A. caldus and A. thiooxidans. Intergenic regions of the annotated
genomes were extracted and computationally searched for srRNAs. Candidate srRNAs that were
associated with predicted sigma 70 promoters and/or rho-independent terminators were chosen for
further study. The resulting potential srRNAs include known examples from other microorganisms and
some novel candidates and reveal interesting underlying biology of the Acidithiobacillus genus.
C-di-GMP Pathway in Acidithiobacillus ferrooxidans: Analysis of Putative Diguanylate Cyclases (DGCs) and Phosphodiesterases (PDEs) Bifunctional Proteins
Authors: Ruíz Lina María , Sand Wolfgang , Jerez Carlos A. , Guiliani Nicolas
Published: March 2009

Acidithiobacillus ferrooxidans, an acidophilic, chemolithotrophic, γ-proteobacterium, is
involved in the bioleaching of metal sulfides. For this process, bacterial attachment to mineral
surface and biofilm development play a pivotal role. Generally, biofilm formation and production of
exopolysaccharides is regulated by the second messenger cyclic diguanylic acid (c-di-GMP) whose
cellular level depends on the synthesis and degradation activities of diguanylate cyclase (DGCs,
with GGDEF domain) and phosphodiesterase (PDE, with EAL or HD-GYP domains), respectively.
The analysis of the genomic sequence of A. ferrooxidans ATCC 23270 allowed us to identify 5
putative orfs encoding DGC and/or PDE-like proteins. Four of them encode for bifunctional
putative proteins with GGDEF and EAL domains and are named AFE_0053, AFE_1360,
AFE_1373 and AFE_1379. The fifth one named AFE_1852 has an EAL domain. The putative
proteins also include PAS and GAF domains involved in signal transduction. These features suggest
an involvement in signalling transduction through the metabolism of c-di-GMP. The amino acid
sequences of these putative proteins were aligned with known DGCs and PDEs. Alignments
indicate that AFE_1360 and AFE_1373 share more consensus sequences with active PDEs, whereas
AFE_0053 and AFE_1379 do with active DGCs. On the other hand, in AFE_1852 some conserved
residues of known active PDEs are changed. RT-PCR-experiments revealed that the genes that
encode for these putative DGCs and/or PDEs are expressed by growth on two different substrates.
These preliminary results suggest that A. ferrooxidans possesses a c-di-GMP pathway that should be
involved in biofilm formation, as it occurs in many bacteria.
Searching for Useful Bacteria on Chalcopyrite Leaching from Japanese Abandoned Mines
Authors: Joe Seong Jin , Sakoda Masatoshi , Chida Tadashi , Kida Yoshiharu , Nakamura Hidekatsu , Tamura Muneyuki
Published: March 2009

Bioleaching studies have been conducted to obtain bacteria having a high ability to dissolve copper from chalcopyrite. For these studies, samples of mine drainage water which contain high concentrations of copper or iron ions in several abandoned mines in Japan were used to inoculate enrichment cultures on 0.16 M ferrous iron in the absence of chalcopyrite concentrate. Afterwards, these were accumulated and supplied to shaking-flask bioleaching tests on chalcopyrite concentrate. Copper dissolution rates were measured in chalcopyrite leaching experiments and compared with those using cell-free ferrous/ferric media. The copper dissolution rate in ferrous sulphate medium was higher than that in ferric sulphate medium. Moreover, tests in the presence of bacteria showed even an higher copper dissolution rate.
Continuous Bioleaching of a Cobaltiferous Pyrite in Stirred Reactors: Population Dynamics and EPS Production vs. Bioleaching Performances
Authors: D'Hugues P. , Joulian Catherine , Spolaore P. , Michel C. , Garrido F. , Morin Dominique H.R.
Published: March 2009

In the frame of a European project (BioMinE - FP6), a continuous bioleaching operation
was carried out in a laboratory-scale unit using a cobaltiferous pyrite. The objective of the work was
to use this system to investigate mechanisms of microbial activity and mineral oxidation in
continuous stirred bioreactors (1x50L - 3x20L). A combination of scientific and technical
approaches (molecular ecology, biochemistry and microscopy) was used and various key operating
parameters were tested (temperature, nitrogen source, CO2 availability, designed consortia).
An increase of temperature of 10°C (35°C to 45°C) had no major influence on the bioleaching
efficiency. When the ammonium source was limiting, there was a negative influence on both
bacterial growth and bioleaching efficiency. This result was related to a combination of factors such
as less bacterial attachment to the pyrite surface and less precipitate formation. CO2 limitation had a
very significant negative effect on the bacterial productivity and consequently on the bioleaching
efficiency. Nevertheless, the population composition remained unchanged. An important decrease
of EPS (sugar) production was also observed.
The bacterial strains, that dominate the culture, originated from the deposit in Uganda. It seems that
their bioleaching ability was improved over the time when cultured in continuous mode. The culture
composition was very stable. The iron-oxidizer L. ferriphilum was the dominant organism in
standard (not limiting) conditions, and was always very well represented during the first 3-4 days of
residence time. Sulfobacillus sp. BRGM2 also played an important role in the process.
This study gives new insights for the application of this technology, and more specifically on the
influence of key operating parameters on bioleaching performances, population dynamics and
attachment of bacteria to the solid surfaces.
Heavy Metal Tolerance and Copper Uptake in Yeast Isolated from Patagonia/ Argentina
Authors: Lavalle L. , Portillo M. , Chiacchiarini P. , Donati Edgardo R.
Published: March 2009

In recent years the use of microbial methods for decontamination or recovery of heavy metals from environment has increased. Microorganisms such as yeasts are potential bioremediators, removing metals via active or passive uptake. Pink-coloured and pigment-less yeast strains isolated from Agrio River, Patagonia Argentina, were tested for copper, nickel, cadmium and zinc tolerance. An agar-plate qualitative screening method using YNB-glucose agar at different metal concentrations was employed. The tolerance to the metals varied depending on the strain tested. A pigmented yeast strain (Agrio 16) was selected by its tolerance. The ability of this strain to copper uptake was investigated. The kinetics of bioaccumulation/biosorption with increasing copper concentrations up to 622.8 mg l-1 were carried out using viable and nonviable biomass. The values of constants k and n obtained for the Freundlich model are 0.0418 and 0.7430, respectively. The maximun sorption uptake capacity (q) for viable biomass was 81.6 mg of copper/g of biomass.
Three-Dimensional Optical Measurement with Locally Adapted Projection
Authors: Denkena Berend , Acker W.
Published: March 2009

This paper deals with the measurement and the detection of errors in the threedimensional
geometry of high-strength structure components. Firstly different geometrical
measuring systems and their usability for the measurement of high-strength structure components
are discussed. An optimized solution is suggested, an adaptive projection method based on pattern
projection is introduced. The technique takes care of the special properties of high-strength structure
components within the production process. The measurement procedure is divided into two steps.
Within the adaptation-step the luminescence and the resolution of the projected pattern is adapted
on the measured object. The actual picture is taken and calculated in a second step in order to avoid
vibrations. The paper concludes with a description of the data processing procedures necessary in
order to evaluate the correctness of the measured structure and describes how a 100% geometrical
quality control can be achieved using the described methods.
Fatigue Life Calculation Concepts for Structures with Inhomogenous Strength Properties
Authors: Esderts Alfons , Masendorf Rainer , Medhurst Tim
Published: March 2009

A fast transfer of new manufacturing- and material technologies to actual design use is
only to be expected if calculation concepts exist, which allow an easy estimation of the parts’
strength properties. This Collaborative Research Project (CRP) will develop new manufacturing and
joining techniques to create high strength structures by adjusting the local strength properties of
parts. These types of structures are usually loaded dynamically. To specifically optimise the fatigue
behaviour, stiffness and weight of a structure, the influences of locally strengthening manufacturing
processes must be considered in the fatigue life calculation concept. It is the goal of this project to
include a simulation of the fatigue behaviour in the process simulation of manufacturing.
Recently research on the influence of local strengthening by cold forming on fatigue life was
undertaken in cooperation within another research project. The fatigue life calculation of sheet
metal structures can be based on a calculation concept developed in CRP 362, subproject C5, which
takes into account the influence of forming, [1,2,3,4]. This concept shall be extended to incorporate
the effects of local martensite forming in the cold formed areas.
New Developments in Powder Technology
Authors: Torralba José M. , Gordo Elena , Jiménez-Morales Antonia , Ruiz-Navas E.M. , Campos Mónica , Rabanal M.E. , Ruiz-Amador D.
Published: March 2009

In this paper we try to summarize the research activities of the PM group in the
University Carlos III of Madrid. This research group is highly devoted to PM activities covering
different fields (both under the point of view of the materials and the processes). In the PM lab
powders can be produced by spray pyrolysis, mechanical alloying and water/gas atomization. These
powders can be processed by pressing and sintering, powder injection moulding, isostatic
pressing,… Sintering facilities cover vacuum and gas controlled sintering. Regarding the materials,
in the group we have different research lines covering low alloyed steels, stainless steels, HSS,
ferrites, metal matrix composite (Al and Fe base), Ti, intermetallics, ceramics with functional and
structural propierties, … In this paper we describe slightly some of the recent developments
produced in the group which is not exhaustive (are there a few more) but representative about we
are doing at present.
On the Mechanical Properties of Cooper–Al2O3 Cermets of a Low Reinforcing Level, Processed by Powder Metallurgy
Authors: Mîtcă Luisa N. , Orban Radu L.
Published: March 2009

There is investigated the influence of Al2O3 content on the density and mechanical
properties of Cu-Al2O3 (2.0 ÷ 10.0 [vol.%] Al2O3) cermets processed by classical routes of powder
metallurgy. The obtained results show that the cermets relative density remains quite constant, at a
value of over 95 [%], up to a content of ~4 [vol.%] Al2O3. Together with reinforcing effect of the
hard Al2O3 particles, proved by the apparition of an elastic zone on the Stress-Strain curve of tensile
test, determine a notable increasing of ultimate tensile strength (UTS) and hardness with a small
variation of elongation. Over about 4÷5 [vol.%] Al2O3, a decrease in UTS and also in toughness,
proved by the Fracture energy decreasing, occurs. Consequently, from the considered points of
view, is not recommended to adopt higher reinforcing levels. For electrical applications, the relative
density of the processed cermets can be further increased with 3 ÷ 4 [%] by die cold repressing.
Increase of the Mechanical Properties of Low Alloyed Steels through Complementary Alloying
Authors: Mátyás Cornelia , Domşa Şerban , Brânduşan Liviu
Published: March 2009

The mechanical properties of sintered steels are mainly dependent on the material
microstructure determined by the matrix composition. The paper presents the mechanical properties
of some sintered steels obtained from mixtures of Distaloy AB, Astaloy Mo and graphite powders.
The aim of this paper is to investigate the performances increasing of the materials obtained by
sintering some mixed compositions of Distaloy AB and Astaloy Mo steel powders with graphite
additions.
The Influence of Feedstock’s Composition on Rheological Behaviour at Forming by Metallic Powder Injection
Authors: Brânduşan Liviu
Published: March 2009

Forming process developed by injection is influenced by rheological characteristics of the feedstock. Because the feedstock is a mixture formed by a powder and a binder, in the performed research it was pursued establishing of binder composition influence. Rheological characteristics establishing was realised with the help of a rotational rheometer RHEOTEST 2, which can be used at the establishing of some properties of Newtonian and non-Newtonian fluids in different temperature circumstances. Utilised binders were formed of different proportions of wax, low density polyethylene, and stearic acid. Obtained results show that wax has a great influence on rheological characteristics of the binder. As it contains increases the dynamic viscosity decreases pronouncedly.
Characterization and Sinterability Study of P.M. High-Speed Steel Obtained by Water Atomization
Authors: Covaciu Manuela , Canta Traian , Gordo Elena
Published: March 2009

The paper presents studies about reducing the sintering temperature of PM High-Speed
Steel obtained by water atomization. The powder was characterized to proceed with compaction and
sintering at different temperatures between 1140-1220°C in different atmospheres: nitrogen (N2),
nitrogen-hydrogen-methane (N2/H2/CH4) and vacuum. It is described the experiment in able to
increase hardness by a quenching and tempering heat treatment that was carried out on sintered
samples at 1140°C in vacuum atmosphere at 1200°C in N2/H2/CH4.
Practical Aspects Regarding to Thixoforming Process Applied to Aluminum Alloys
Authors: Zaharia I.I. , Geamăn Virgil
Published: March 2009

The paper presents some experimental data about the thixoforming process applied to
different aluminum alloys very used in the Romanian machine building industry.
From many procedures for obtaining the semisolid slurry described in the paper, based on
specialized literature [2, 3, 4] in particular, the accent is given to choose the mechanical mixture in
the overheated mould until it reached the liquid alloy temperature. The main results are based on
reducing of stirring time for increasing the benefits of the new technology.
All procedures and results are described in the paper and also some specific conclusions are given.
The experimental data of the research, were obtained in the specific testing laboratory from
Transilvania University of Brasov.
Strengthening Mechanisms of 1H18N9T Austenitic Steel Buildups Created with Cold Forming Processes
Authors: Presz W. , Kaczorowski M.
Published: March 2009

In metal forming processes in the tool-workpiece contact area occur high pressure,
surface expansion and elevated temperature. It makes ideal circumstances for braking of the
lubricant film that causes a direct contact between metallic surfaces. Such a contact usually leads to
buildups creation on the tool surface. These phenomena mainly result product surface damage.
Damages can also refer to tool surface since the hardness of buildups can be comparable with the
tool hardness. The cause of this investigation was finding the answer of the question what was the
reason of extreme hardness of buildups created during bulk metal forming processes of 1H18N9T
austenitic stainless steel. The studies were conducted using transmission electron microscopy
(TEM). On the basis of analysis structural and electron diffraction pattern it was suggested that
simultaneously to very well known strengthening mechanism like grain refinement, the additional
mechanism can not be excluded. Based mostly on the electron diffraction pattern (appearance of
forbidden reflexes for FCC) it is suggested that this additional mechanism could be the marthensitic
transformation caused by very high plastic deformation.
Modeling of Geometry Design in Wire Drawing Using Cassette Roller Die
Authors: Nistor Liviu , Tintelecan M.
Published: March 2009

The most important activity of wire drawing technology is the correct design of stages
geometry. The wire drawing within a roller die is described by an irregular deformation on wire
width, strongly connected by the gauge shape between the rollers and cross section wire surface.
Free lateral wire surface that has no contact with the roller on the deformation zone obstructs the
wire elongation. There is a biunique correspondence between the shape and dimension of wire that
enters between the rollers, and the free space between the rollers, corresponding to a specific stage
of drawing. This has a great effect on dimensional accuracy of final wire. A drawing zone feature
based model, allowed the examination of interaction evolution between wire and rolls geometry.
This analysis helps the user of this technology to make a proper change in the arrangement and
position of wire entering between rolls, or in the rolls configuration.
Studies Concerning the Hardening Capacity of Aluminium Alloys through Heat Treatment in Electromagnetic Field
Authors: Stoicănescu Maria , Giacomelli I. , Pantelimon Maria Simona
Published: March 2009

It is well known that the aluminum alloys containing Cu and/or Mg lead to soluble compounds which themselves allow the hardening during the process of strengthening and ageing. At the same time, the hardening process during ageing takes a relatively long period of time, and the registered rises are generally not too high. There are presented studies regarding to alloy AlCu4Mg1,5Mn which was tested in several heat treatment conditions. These alloy, after final heat treatment of hardness by and ageing, suffers a sensitive hardening – the ageing is recommended for pieces used under medium and intense mechanical stresses Using the alternative electromagnetic fields is more efficient by 10 to 12% than stationary one, not only regarding to the period of ageing, but also regarding to the highest values of hardness; Also other specific results are given in the paper.
Study of the Hydride Morphology in the CANDU Reactor Pressure Tube Modified by Heat Treatment
Authors: Velciu L. , Meleg T. , Mihalache M.
Published: March 2009

The aim of this study is to discuss the morphology (the shape and orientation) of the
hydride platelets in the pressure tube material (Zr-2.5%Nb alloy) in function of the modified
microstructure by heat treatment.The different microstructures were obtained by annealing and
hydrides by hydrogenation (using the electrolytic deposition and the diffusion of the hydrides in the
block of samples by a thermal treatment of ageing). The microstructures and hydride morphology
were characterised by microscopic analysis, hydrogen content measurements, hydride orientation
factor, microhardness Vickers measurements.Based on the results obtained, the increased
recrystallization degree involves changes in the hydride distribution. This fact is reflected in the
increase of the orientation factor of hydrides and in micro-hardness diminution.
Influence of the Casting Process on the Properties of Al Based Automotive Components
Authors: Rosso Mario , Grande Marco Actis
Published: March 2009

This work concerns the study of the fatigue properties of A319, A 356 and A357 Aluminum alloys, produced by means of permament mould casting, sand casting and loast foam. Smooth plane or cylindrical samples were cut out from supension arms, engine blocks and cylinder heads and then they were subjected to axial fatigue testing at room temperature. Some castings were subjected to LHIP (Liquid Hot Isostatic Pressing) and also the effect of this process has been evaluated regarding the improvement of fatigue properties. Optical microscopy and scanning electron microscopy (SEM) were used to document the elimination of porosity after LHIP and to show the different nucleation sites of fatigue cracks on the fracture surfaces in no-LHIP and LHIP conditions.
Silicon Influence on Corrosion Properties of Austenitic Stainless Steels
Authors: Ghiban Brandusa
Published: March 2009

In the present paper there are presented results concerning comparative corrosion
resistance of some austenitic stainless steels, with or without silicon content. The silicon content is
varying in the range of 1-5 %, in a matrix of alloyed austenite, containing 20% Cr and 15-18%Ni
and with very low carbon contents (lower than 0,03% C). There are investigated different types of
corrosion resistance: intergranular corrosion in nitrogen media, stress corrosion resistance in
chloride media, and transpassive behaviour in sulphuric media. The testing media contained
nitrogen, as it follows: Huey test (65% HNO3, at boiling temperature, 244 hours maintain), and 5N
HNO3 +1g/l Cr6+ (144 h, at boiling temperature). The media containing chloride is 45% MgCl2 at
boiling temperature, with a period of 1000 hours. The transpassive behaviour is tested in 10%
HSO4. The investigations were made by optic and electronic microscope, and the corroded surfaces
were examined by scanning electron microscopy.
Structure of Composite Layers Reinforced with SiC Particles Obtained by Electrochemical Deposition
Authors: Vida-Simiti I. , Jumate Nicolae , Guzun M. , Ajder V. , Bobanova J.
Published: March 2009

The paper reports on a study regarding the structure of composite layers obtained by electrochemical deposition. The depositions were achieved in a bath formed of a mixture of aqueous solutions of iron salts (iron chloride), cobalt (cobalt sulphate) and solid particles of silicon carbide (SiC) in suspension. Following the electrochemical deposition on composite structures are formed as a thin layer with a metallic matrix (FeCo alloy), reinforced with hard particles of SiC. The structure of the composite layer is uniform and very fine, with crystalline granules under 500 nm. The electrochemically deposited FeCo alloy representing the metallic matrix of the composite layer has a high micro-hardness (864 HV), superior to the same alloy obtained by casting.
Influence of Ion Nitriding Process Parameters on the Microstructure, Hardness and Thermal Shock Behaviour of X3CrNiMo17-13-3 Stainless Steel
Authors: Rus Vasile , Negrea Gavril , Arghir George , Jumate Nicolae
Published: March 2009

The experimental researches was made on X3CrNiMo17-13-3 stainless steel samples ion nitrided at different temperatures, duration and work atmospheres. The analysis of superficial layers was made in order to identify the microstructure of the ion nitrided layer using X-ray diffraction, and also the determination of the superficial hardness and hardness gradient. The nitrided samples were subjected to two thermal shock regimes, one in the range of 500-20°C and the other in the range 600-20°C. The crack and crack networks initiation process as a result of thermal fatigue was analyzed quantitatively and qualitatively using optical microscopy. The study of the cracking process highlighted the fact that thermal shock resistance is influenced by the characteristics of the superficial layer and also by the maximum temperature of the thermal stress cycle.
Inoculating Influence of Re-Carburizers in Grey Cast Iron
Authors: Riposan Iulian , Chisamera Mihai , Stan Stelian , Toboc P.
Published: March 2009

In laboratory experiments Thermal Analysis data were recorded and different
solidification parameters were identified to characterize the inoculation effect of the carbon
materials (amorphous and crystalline structure) in low sulphur (<0.025 %S) grey cast iron. These
parameters are linked to graphite morphology as well as chill formation in carburized cast irons. In
low sulphur base iron the difference in inoculation efficiency between crystalline and amorphous
carbon materials is limited. Secondary granular carbon materials, previously used as conductive or
resistive media in electric graphitizing furnaces were found to be potential carbon raisers with
visible inoculation effects in grey irons, especially those from a petroleum coke origin. A controlled
presence of a low amount of SiC (2-3%) is effective, including low sulphur grey irons.
Titanium Dioxide Thin Film for Photodegradation of Methyl Orange
Authors: Andronic Luminita , Duta Anca
Published: March 2009

The photocatalytic activity of the titanium dioxide thin film has been investigated
towards the degradation of methyl orange in aqueous solutions. Porous TiO2 thin films were
deposited on glass substrate by doctor blade technique. The thickness of the film prepared by doctor
blade was also evaluated from de UV spectrum and the average value corresponds to 5 μm. The
photocatalytic efficiency was evaluated as the percentage of pollutant bleaching, after 6h of UV
illumination. The influence of the operational parameters (dye concentration, pH) on the
degradation rate of the dye on TiO2 was examined. The catalytic activity of the films towards
photodegradation of methyl orange pollutant was examined and their photocatalytic efficiency was
calculated.
Products of Ethylene-Propylene Terpolymer Rubber (EPDM) Obtained by an Environmentally Friendly Process
Authors: Zuga M.D. , Miu Lucretia , Crudu M. , Bratulescu V. , Iovu H. , Manaila E.
Published: March 2009

In the research work some thermoplastic elastomers have been obtained by compounding
the ethylene-propylene terpolymer (EPDM) rubber with melt platicized PVC. The influence of
every constituent level on the polymer compound characteristics was measured. The two polymers
are incompatible, for the improvement of the EPDM/ PVC blends two methods of compatibility
improvement have been used: 1) using compatibilizing agents (CPE was the selected
compatibilizing agent); 2) electron beam irradiation (the optimum irradiation dose determined was 5
Mrad). The resulted products showed specific elastomer characteristics and can be processed by
commonly used techniques for thermoplastic materials like as injection and injection molding.
Numerical Simulation of the Flame Stabilization inside an Aeroderivative Combustor to be Operated with Waste Bio-Gas
Authors: Prisecaru Tudor , Dinescu D.C. , Mihaescu L. , Prisecaru Malina , Darie G. , Necula H.
Published: March 2009

This paper investigates the methods to stabilize a bio-gas flame inside a combustor. A procedure a modelling by dividing the combustor in 8 identical sections, each sections having 343,000 volume cells have been used. Bio-gas composition has been assumed to be 50% methane, 40% carbon dioxide and all the rest to be assimilated with hydrogen in volumetric participation. Due to the different values of ignition time delay, some gas flames already observed to be unstable can be transformed into stable ones by using by-product supplementary fuels
Mechanical Alloying of Fe30Cu70
Authors: Prică Virgiliu Călin , Arghir George
Published: March 2009

Fe-Cu system is a binary alloys system, nevertheless very difficult. This paper presented
the milling duration influence on ball-milled Fe30Cu70 alloys. After 16 hour of milling it has been
concluded that true alloying at atomic level occurs during milling. The average grain size depends
by milling time. Varying the milling time changes the powder morphology, their size and structure.
We found that the complete fcc Fe –Cu solid solution is formed when the grain size of Fe-bcc reach
a value about 10 nm, because at this value of crystallite the free energy for interface become less
than interfaces energy. The milling duration have a strongly influence on solid solubility and phases
form in Fe-Cu system. The phase formation for Fe30Cu70 (mass %) has been investigated by X-ray
diffraction (XRD). The mixing enthalpy (positive in this system) also depends on alloy
composition.
EDM with USM Combination Process of Sintered NdFeB Permanent Magnet
Authors: Li Li , Wang Dong , Niu Zong Wei , Li Zhi Yong
Published: March 2009

Sintered NdFeB permanent magnet is widely used because of its excellent magnet
property. But there is few report of machinbility of it. This paper presents an experimental
investigation of the machining characteristics of sintered NdFeB permanent magnet using a
combination process of electro-discharge machining (EDM) with ultrasonic machining (USM). The
EDM / USM machining mechanisms are integrated to improve the machining efficiency. During the
experiments, concentration of abrasive in the dielectric fluid is changed to explore its effect on the
material removal rate (MRR). MRR of EDM /USM, conventional EDM and tool vibration aided
EDM are compared, REWR and machined surface characteristics are also compared between them.
From the experimental results, it is concluded that the combination EDM/USM process can increase
the MRR and decrease the thickness of the recast layer. In the combination process, an appropriate
abrasive concentration can improve its machining efficiency.
Study on Building and Simulation of the Polishing Path of Mold Based on MasterCAM
Authors: Ding Jin Fu , Mei Guang Yi , Zhang Ke Hua , Yu Fu Jin
Published: March 2009

In order to improve the surface quality and machining efficiency for mold polishing.
Digital automatic Polishing is a good method, MasterCAM is the software that often is used for
CAM machining, path layout and building method are emphasized according to the MasterCam’s
curved surface processing path setting method, and aimed at the different curved surface use different
polishing path building method, at last, the rationality of the polishing path building was validated.
Flows Field Simulation of Two-Phase Swirling Flows Finishing
Authors: Yang Sheng Qiang , Li Wen Hui , Yang Shi Chun
Published: March 2009

Two-phase swirling flows finishing is put forward mainly for hole surface. By theoretic
analysis and experimental research, the characteristics of flows field will directly affect finishing
quality and efficiency. On the basic premise of defining Renault stress model on swirling flows field,
numerical simulation of velocity vector graph, turbulent kinetic energy graph, turbulent dissipation
ratio graph, pressure distribution graph, vorticity magnitude distribution graph etc. are made, and
vorticity magnitude and tangential velocity in different mediums are contrasted, which provide
theoretic basis for thorough research.
A Study on Erosion Mechanisms of Quartz Crystals Polished by Micro Abrasive Waterjet
Authors: Li Quan Lai , Huang Chuan Zhen , Wang Jun , Zhu Hong Tao , Che Cui Lian
Published: March 2009

The potential of abrasive waterjet technology was investigated as a method to polish
Z-blocks of synthetic quartz crystals. The polished surfaces were characterized by surface
roughometer and scanning electron microscopy. The main factors affecting the surface roughness and
the erosion mechanisms related to material removal were analysed. It is found that abrasive mesh,
water pressure and jet incidence angle are the main factors affecting the surface roughness. By
contrast, the influence of traverse speed on the surface roughness is small. Under certain controlled
conditions, the erosion mechanisms of synthetic quartz crystals are plastic flow, leaving a crack-free
surface by low-middle pressure micro abrasive waterjet.
Theory and Experiment Study on the Grinding Force
Authors: Zhang Jian Hua , Ge Pei Qi , Zhang L.
Published: March 2009

The grinding force was one of the most important parameters, almost related with all the parameters in grinding. In this paper, the grinding force model was established by a new method. The abrasive grains were analyzed using the statistical probability method. The abrasive grains were divided into two types, one was the cutting abrasive grain, and the other was contacting abrasive grain. The force analysis of a single abrasive grain was done. The grinding force model was established on the basis of the statistical probability method and the force analysis of a single abrasive grain. Theoretical analysis was verified by the experiment. The results indicated, the experimental results agree well with the theoretical prediction. The model can accurately predict the grinding force.
Research on Stock Removal Uniformity for Double Sided Polishing Process
Authors: Li Wei , Yu Tian Ming , Hu Xiao Zhen , Zhang B. , Zhang Y.H.
Published: March 2009

Based on the kinematic analysis of the double sided polishing process, the equation of
relative velocity (the workpiece to the polishing plate) is established. According to the Preston’s
equation, the function of stock removal uniformity is presented. By computer simulations of the
machining process, the effects of rotating speed ratios (the carrier revolution speed to plate rotating
speed, carrier rotating speed to plate speed) on the stock removal uniformity are discussed in this
paper. At last, some experiments have been done for validating the theoretical study of stock
removal uniformity. The results show that, the computer simulation can estimate and conduct the
experiment result in double-sided polishing process.
Experimental Research on Grindability of Aluminum Alloy
Authors: Yuan Suo Xian , Ding Hui , Wang Wan Shan
Published: March 2009

The grinding process of aluminum alloy is introduced in the paper and carried out
experiment. The material is removed from the workpiece by fixed abrasives and scratching the
surface to be finished in grinding process. In order to increase machining accuracy and efficiency, it is
necessary to analyze the machining parameters of grinding process. The emphasis is the effect of
machining parameters on roughness of surface and mass loss of workpiece by a set of experiments in
this paper.
Precision Grinding of SUS304 Using Metal Bonded CBN Wheel
Authors: Hasuda Y. , Suzuki Y. , Tadokoro Y. , Kinebuchi S. , Ohashi T. , Furusawa T.
Published: March 2009

The fundamental experiment of the grinding of the stainless steel using the metal bonded CBN wheel which was excellent in wear resistance was conducted. The most appropriate grinding conditions were obtained by clarifying wear process of grinding wheel and finished ground surface quality. When grinding was carried out up to stock removal 7000mm3/mm, radial wear of grinding wheel %R is 3μm and surface roughness Rz was 0.5μm or less. The grinding ratio Gr becomes about 3000, and long life grinding with little change of surface roughness was possible.
Innovation of Widening Grinding and Avoiding Dressing Grinding by Using Planet-Abrasivetool
Authors: Yao Bin , Mao F.P.
Published: March 2009

A planet diamond abrasivetool can achieve the purpose of widening grinding area,
improving the use efficiency of abrasives and reducing the cost, which doesn’t need any dressing
techniques and tools. It could solve some problems of diamond abrasivetool, such as inefficiency of
abrasive use, deficiency of cooling, repetitiousness of dressing and so on. This paper describes the
characteristics of the planet-abrasivetool and presents an equation for grinding a curving face by the
new tool on five-axis grinding machine. At last, the developmental potential of the
planet-abrasivetool is predicted.
Study on Hardness Depth Variation of Different Grinding Zone in Grind-Hardening
Authors: Zhang L. , Ge Pei Qi , Zhang Jian Hua , Zhang Q.
Published: March 2009

The experiments are performed to study the hardness layer depth at work piece different
surface zone in grinding. The result is that hardness layer depth is various at work piece different
surface zone. The hardness layer depth is thinner at cutting-in grinding zone, deeper at middle
grinding zone and deepest at cutting-off grinding zone. In order to analyze the cause of hardness depth
variation, the grinding temperature field is simulated by means of finite element method. From the
temperature field and heat flux simulation, the cause of the hardness depth variation is that the
grinding heat flux is variable at different grinding zone along the work piece surface in
grind-hardening. At cutting-in zone, most of grinding heat flows into the front-below work piece part
inverse to table speed, the depth that temperature of surface layer higher than austenite temperature is
thin and there is slim martensite transformation layer. At middle zone, the temperature of surface
layer is higher than austenite temperature because of grinding heat accumulated in the surface layer,
and martensite transformation takes place after cooling. At cutting-off zone, most of grinding heat
flows into the below work piece part because of work piece boundary, and hardness depth is deeper
than that at middle zone.
Edge Quality and Evaluation of Workpiece in Precision Machining
Authors: Li Qin Feng , Wang Gui Cheng , Qu Hai Jun , Fan Shu Tian , Zhu Yun Ming
Published: March 2009

With the development of machine manufacture science and technology toward precise, quality evaluation of precision parts has put forward higher request. Problems are pointed out in this paper based on comparison and analysis of burr standard at home and abroad. This study suggests the viewpoint of edge quality of precision parts and provides the fundamentals for enhancing edge (burr) quality according to items such as economic cost, technology level, manufacture level, personnel technological capability and production management level. These have important theoretical value and applied prospects for further enriching and perfecting burr standard, promoting precision machining and automatic machining technology.
Surface Damage Analyse of KDP Crystal Grinding
Authors: Wu Dong Jiang , Cao Xian Suo , Gao Hang , Kang Ren Ke
Published: March 2009

The functional crystal material Potassium dihydrogen phosphate KH2PO4 (KDP for short) is widely used in navigate, spaceflight, national defenses, energy sources and information technology fields because of its excellent non-linear optical property. However, KDP crystal has some disadvantages such as soft, fragile, hygroscopic, anisotropy, thermally sensitive and low rigidity, which make it a most difficult processing material. In this paper, KDP crystal was machined by the wheel grinding. Some equipment, such as Optic microscope, SEM, ZYGO and Raman spectroscope were used to observe and analysis the KDP crystal surface which was damaged during grinding. The results shows that serious nicks, crashes and the press stress appeared on the surface of the KDP crystal after grinding.
Surface Quality of Finishing Cut by WEDM in Gas
Authors: Wang Tong , Zhang Xin Fu , Zhao Xue Fang , Kunieda M.
Published: March 2009

This paper studies on a newly developed method, WEDM in gas, and discribes the features of finishing dry-WEDMed surface, such as narrower discharge gap length, higher surface straightness accuracy and no electrochemical etching actions. Low-speed WEDM removal rate in gas can be improved by increasing the wire winding speed. High-speed WEDM in gas has a significant advantage as high removal rate beyond the abovementioned good points, which is available for improving conventional high-speed WEDM quality.
Numerical Analysis on Flow Stress of AZ61B Magnesium Alloy during Hot Compression Simulation Testing
Authors: Peng Jian , Pan Fu Sheng , Song Cheng Meng
Published: March 2009

The flow stress-strain curves and other information during hot compression testing of
AZ61B magnesium alloy was investigated by simulated test on Gleeble-1500D thermal-mechanical
simulator. The relations between Z and other characteristic value, including peak stress, peak strain
and grain size, was calculated by regression analysis. The mathematical model of flow stress was
introduced to predict the flow stress. The predicting values is close to the experimental values with
not more than 10% error.
Structure Stability and Electronic Structure of Semiconducting Rhenium Silicide with Doping
Authors: Qiu An Ning , Zhang Lan Ting , Wu Jian Sheng
Published: March 2009

Full-potential linearized augmented plane-wave (FP-LAPW) method within the local
density approximation plus self-interaction correction (LDA+USIC) has been applied to study the
structure stability and electronic structure of ReSi1.75 and its doped systems with Al and Mo.
Structural relaxation results show that the vacancy prefers to occupy the Si3 and Si4 site in the
lattice with little ordering. For doping systems, Al prefers to substitute for Si at the Si3 site and Mo
prefers to substitute for Re at the Re1 site. ReSi1.75 shows narrow gap semiconductor behavior with
an indirect gap of 0.12 eV and a direct gap of 0.36 eV. Al doping compound remains semiconductor
while Mo doping compound has a tendency to change into semimetals or metals. The Fermi level of
doped systems moves into the valence band resulting in an increase of density of state at the Fermi
level. It will enhance the thermoelectric properties and agrees well with the experiment results.
Characterization of Dynamic Globularization Behavior during Hot Working of Ti-6Al-4V Alloy
Authors: Yeom Jong Taek , Kim Jeoung Han , Kim Nam Yong , Park Nho Kwang , Lee Chong Soo
Published: March 2009

The dynamic globularization behavior during hot working of Ti-6Al-4V alloy was
investigated by high temperature torsion tests. The torsion tests were carried out to investigate
microstructure evolution occurring during dynamic globularization in Ti-6Al-4V alloy. The torsion
tests were performed under a wide range of temperatures and strain rates with true strain up to 2. The
flow curves revealed that the amount of flow softening for the fine alpha-lamellae structure was
higher than that for the coarse alpha-lamellae structure under the temperature of 900oC. The effects of
hot deformation parameters and initial microstructures on the dynamic globularization were analyzed.
Pulse Electroplating of Ni-P-Nano TiO2 and ZrO2 for Steam Generator Tube Repair
Authors: Urm Kee Won , Lee Seon Ho , Kim Woo Sung , Cho Chang Yeol , Lee Jong Ho
Published: March 2009

Steam generator tubes provide the pressure boundary between the primary and
secondary regions of a nuclear power plant. Alloy 600 is a tube material with good corrosion
resistance; however, tubes of this material have experienced damage, particularly as Stress
Corrosion Cracking, under the elevated temperature and pressure environment of a nuclear power
plant. These damaged tubes must be repaired to prevent leakage of radioactive material from the
primary to the second regions in the nuclear steam generator. In this study, Ni-P-Nano TiO2 and
ZrO2 layers were produced by pulse electroplating for steam generator tube repair. These
electroplate layers were obtained from Ni sulfamate bath with an added small quantity of H3PO3
and Nano TiO2 and ZrO2 particles with an average size of 20-80nm. Results of TEM analysis in
these layers show that Nano TiO2 and ZrO2 particles were uniformly distributed into the
electroplated Ni matrix and the tensile strength of these layers at 800-1000MPa was higher than that
of alloy 600 with a conventional pure Ni electroplate layer.
Homogeneity of Grain Refinement of Aluminum Alloy with Compressive Torsion Processing
Authors: Kume Yuji , Kobashi Makoto , Kanetake Naoyuki
Published: March 2009

Compressive torsion combined loading that uses relatively low compressive pressure has a
great advantage of microstructure refinement of cylindrical metal blocks without changing their
shape while processing. In the present work, effects of processing temperature and rotation times on
homogeneity of the refined microstructure were investigated for Al-5%Mg alloy. Although lower
processing temperature was effective to obtain fine grains, it was difficult to obtain homogeneous
refinement at lower temperature. Higher processing temperature was favorable to obtain
homogeneous microstructure, for instance, in the cylindrical specimen of φ25×10 mm the
homogeneous refinement could be obtained at higher temperatures than 373K. Increasing rotation
times was also effective to obtain homogeneous refined microstructure for thicker specimens.
Natural Photo-Oxidation Degradation of Polypropylene Containing Nucleating Agent
Authors: Li Ji Fang , Yang Rui , Yu Jian
Published: March 2009

The natural photo-oxidation of PP bars containing nucleating agent (TMB-5) were studied
by using infrared microscope (IM), differential scanning calorimetry (DSC), scanning electron
microscope (SEM) and polarizing optical microscope (POM). The results indicated that nucleating
agent accelerated the oxidation of PP significantly. The oxidation began from the surface and
developed into the interior with time. There is a transition region near the surface, caused by the fast
cooling during the injection moulding. This region is prior to be oxidized because of the low density.
Therefore, it corresponded to the surface oxidation layer in PP and PP/TMB-5 bars. The nucleating
agent helped to reduce the spherulite size of PP and broaden the transition region greatly – from about
25 μm to more than 200μm, covering the morphology of amorphous, fine crystals to relatively perfect
crystals. More crystal boundaries, i.e. low density, and broad transition region led to higher oxidation
degree and further oxidation along the depth. However, the thickness of the surface oxidation layer
maintained nearly constant till the fragments dropped from the seriously damaged surface.
Dislocations in Phase-Change Ge2Sb2Te5 Alloy
Authors: Zhang Wei , Song Se Ahn , Jeong Hong Sik , Kim Jin Gyu , Kim Youn Joong
Published: March 2009

Characteristic 60° dislocations occurred in hexagonal phase of Ge2Sb2Te5 thin foil cooled
from 500°C to room temperature in a high voltage transmission electron microscope. The Burgers
vector of dislocation was identified as 1/ 24 < 9902 > which is the edge component of 1 3 < 2110 >
projected on the (1120) lattice plane. The dislocation resulted from the cooling-induced stress/strain
in the Ge2Sb2Te5 alloy.