bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Regression Analysis to Optimize the Combination of Thermal Conductivity and Hardness in Compacted Graphite Iron
Authors: Selin Martin
Published: December 2010

In cast iron there is a contradictory relationship between thermal conductivity and strength. In many applications it is desirable to optimize the material properties to obtain both sufficiently high thermal conductivity and sufficiently high strength. The aim of this paper is to investigate how various microstructure parameters and alloying elements affect thermal conductivity and hardness in compacted graphite irons.
It was found that the fraction of ferrite, the fraction of cementite, nodularity and content of carbon and silicon are parameters that influence the thermal conductivity and hardness the most. Based on these five key parameters linear regression equations were created for calculation of thermal conductivity and hardness.
Ferrite and carbon have a positive influence on the thermal conductivity, while silicon, cementite and nodularity have a deleterious effect. All parameters except ferrite have a positive influence on the hardness. This is because the thermal conductivity is dependent on the movement of free electrons, and therefore unfavourable growth directions and grain boundaries which impede the electron movement will reduce the thermal conductivity. Ferrite has quite high thermal conductivity, while cementite has poor thermal conductivity, due to an unfavourable crystal structure. Nodular shaped graphite has a lower thermal conductivity than compacted graphite which explains the deleterious influence of nodularity.
The soft ferrite phase will reduce the hardness value, while increasing the fraction of harder graphite nodules and harder cementite phase will increase the hardness.
To investigate how these five parameters affect the combination of hardness and thermal conductivity, values for hardness and thermal conductivity were calculated for all combinations of key parameters in given intervals, using two linear regression equations. From these it is possible to predict the combination of parameters which gives a particular combination of hardness and thermal conductivity in compacted graphite iron.
Effects of Graphite Shape on Thermal Fatigue Property of Thin Wall Graphitic Cast Irons
Authors: Pan Yung Ning , Fan Chen Chi , Chang Chih Hung
Published: December 2010

The optimal alloy design and microstructure for the high temperature (around 800oC) constrained cyclic thermal fatigue applications in thin-section ductile irons have been established previously by the authors. This study intends to investigate the effect of graphite morphology on the thermal fatigue property of thin-section (2mm ~ 6mm) graphitic cast irons. The results show that to produce carbide-free spheroidal graphite irons in relatively thin sections of 2-mm or 3-mm in the as cast conditions is feasible. However, for compacted graphite cast irons, graphite particles largely in nodular form always occurs in rather thin sections, and acceptable compacted graphite structure can only be obtained when the section thickness exceeds about 6-mm. Regarding the constrained cyclic thermal fatigue property (20 ~ 800oC), cast irons with spheroidal graphite exhibit the best thermal fatigue life, which is followed by irons with compacted graphite, and then flake graphite cast irons, even though flake graphite cast irons show least swelling or distortion after cyclic thermal fatigue test. Furthermore, adding some 0.5%Mo to the irons significantly improves the thermal fatigue property, in some cases even by a factor of 2, implying that the role of Mo outweighs the influence of graphite structure in promoting thermal fatigue property.
Suppression of Elevated Temperature Brittleness in Spheroidal Graphite Cast Iron by Increasing Phosphorus Content
Authors: Iwabuchi Yoshitaka , Kobayashi Isao
Published: December 2010

Elevated temperature brittleness (ETB) of spheroidal graphite (s-g) cast iron has been referred to as reduced ductility within an elevated temperature range and has been related to grain boundary brittleness. The phenomenon of ETB has not been yet clearly understood. In this study, the factor affecting on ETB was studied in terms of strain rate and chemical composition. A study was carried out on the influence of phosphorus on ETB by using laboratory-made heats containing different phosphorus contents. ETB indicated the marked decrease in ductility at around 673K. S-g cast iron containing low phosphorus content manifested ETB at temperatures between 650K and 700K. There was a consistent correlation between the fractional increases in intergranular fracture appearance and the decrease in elongation. The increase of phosphorus suppressed ETB and s-g cast irons containing phosphorus exceeding 0.030 % were found to be immune to ETB. It was found that ETB could be suppressed by reducing the ratio of magnesium and phosphorus to less than 1.5.
Oxygen State Forms in Cast Iron and their Effect on Graphite Crystallization
Authors: Ten Edis B.
Published: December 2010

Oxygen influence on the structure and properties of cast iron is contradictory and depends on its state. It is supposed that the chemically combined oxygen exists into molten metal as Non-metallic inclusion, and it acts as a Graphite crystallization substrate and also increases graphitization degree of the cast iron. Dissolved oxygen deactivates the potential graphitization centers that are why cast iron chill tendency is increased. At the same time, according to experimental results, the more cast iron is saturated by oxygen, the higher its tendency for graphitization modification. In this study, the influence of the oxygen state on graphite forming process during the cast iron crystallization is considered and the details of its action on the graphite crystallization at different stages of casting solidification process are also represented. It is shown that oxygen, initially present in molten melt in chemically combined state, does not have a significant effect on the Cast Iron crystallization. At the same time, the dissolved oxygen in non-modified cast iron causes chill, but in modified Cast Iron the over-equilibrium dissolved Oxygen content promotes graphitizing crystallization by forming dispersed pre-crystallizing (“fresh”) non-metallic inclusions in liquid cast iron. On the basis of these concepts, the original interpretation of several well-known facts concerning graphitization modifying is presented. These facts have been widely discussed at the present time, and there is a great number of contraversal opinions on this account. Particularly, the new aspects of the damping effect of the graphitization modifying of the cast iron have been discussed. The causes of ferrosilicon graphitizing power increase by addition of the aluminum, calcium, barium, rare-earth metals and other powerful elements-deoxidizers to it are shown. The additional factors of high effectiveness of the in-mold graphitization modifying of cast iron are presented also
Analysing the Deformation Behaviour of Compacted Graphite Cast Irons Using Digital Image Correlation Techniques
Authors: Sjögren Torsten , Persson Per Eric , Vomacka Peter
Published: December 2010

During the last years the use of digital image correlation techniques (DIC) has become wide spread within different areas of research. One area in which these techniques are used is in the analysis of deformation of engineering materials. By the analysis of a set of successive images taken during a tensile test DIC makes it possible to determine how the deformation is localized. The observed local strains are often several times higher than the global strain measured by standard strain gauges.
In this study, a set of compacted graphite cast irons (CGI) with different ratios of pearlite to ferrite have been examined by the use of DIC. In contrast to the normal use of DIC, where a pattern is sprayed on the tensile test sample as a reference for the determination of deformation taking place between successive images, the materials natural microstructural pattern has been used in this study. The use of the natural microstructural pattern makes it possible to study how the macroscopic deformation is accommodated within the different phases in the CGI studied.
It is shown that the graphite phase accommodates a large portion of the strain and that the soft ferrite is strained more than the stronger, less ductile pearlite. The local strain of the observed area might be up to ten times higher than the global strain measured.
The use of DIC improves the understanding of the deformation behaviour of compacted graphite cast irons and will be a useful tool when validating future finite element analyses of the micro-mechanical properties of cast irons.
A Study on Ductile Iron Production without the Use of Feeders
Authors: Fourlakidis Vasilios
Published: December 2010

This paper investigates the effects of graphite added as a conditioner, of Lantanum containing nodulariser and of pouring temperature on the formation of shrinkage porosity in ductile iron casting with an eutectic composition. In this experiment for each heat the cooling curves were recorded by the use of Quick-Cups (thermal analysis cups) and different solidification parameters such as TElow, GRF1, GRF2 and TS were calculated and compared with the porosity which was found from the microstructure examination. The results show that there is a good correlation between the amount of the shrinkage formation and the thermal analysis values. Also this experiment confirm that by using certain treating elements and pouring temperature which was between 1340-1350°C it is possible to eliminate the shrinkage defects in ductile iron castings without using feeders.
Vibration Modal Analysis of the Active Magnetic Bearing System
Authors: Fu Hong Ya , Liu Ping Fan , Zhang Qing Chun , Wang Y.T.
Published: December 2010

Based on the principle of axial active magnetic bearing rotor-system with single degree
of freedom, magnetic rotor-system vibration mode was described. A 3D finite element model of
active magnetic bearing rotor-system was established by ANSYS11. Initial six order natural
frequencies and vibration mode were calculated by the module of modal analysis of ANSYS11, and
compared with the results of system identification. Analysis shows that there was a certain
difference between the results, but the difference was small. The analysis result indicates that it is
an effective method to apply FEA in the design of the active magnetic bearing. It provided the
foundation for structure optimal design of the system and theoretical basis for flexible system
design.
Finite Element Analysis of Inductance Sensor Structure in the Measuring System of the Grade of the Iron Concentrate
Authors: Zhou Zhen , Guan Z.H. , Luo J. , Wang L.J. , Qin Y. , Sun G.F.
Published: December 2010

According to the Biot-Savart's Law, the principle of the detecting system which measures the grade of the iron concentrate is analysed in this paper. It carries out an analysis of influence of inductance sensor coil structure parameters on the performance of sensor. The finite element model of the air core coil is established and analysis of finite element simulation is done to inductance sensors by using orthogonal method. According to different structural parameters, the relation of magnetic permeability of the iron concentrate and the inductance of the sensor coil can be established. Moreover, the effect of the sensor coil’s parameter on the linearity and the sensitivity of the sensor can also be determined. All the above provide a reference for the design of coil structure parameter of the inductance sensors.
A System Characteristic Parameters Identification Method by Wavelet Transform Image Ridge
Authors: Yue J.H. , Zhao Jian , Yu M. , Hao Yong Jiang , Wang Tai Yong
Published: December 2010

Dynamic characteristic of a system have to be obtained so as to offer the reliable data for the system dynamic modification and dynamic optimum design. The system modal parameters identification can be changed into the global optimization problem in wavelet plane because the wavelet ridges can carry much information of system characteristic parameters. Firstly, the paper will introduce the so-called PSO (Particle Swarm Optimization) technique into the modal analysis and propose the PSO wavelet ridge extraction algorithm. Furthermore, the formulas identifying modal parameters from a wavelet ridge are derived and computation steps were given. The simulation experiments are implemented in order to evaluate precision of this method and the robustness of noise. Finally, the proposed method applies to the modal parameters identification of a watermelon to explore the effectiveness. The experiment results prove the method is precision and insensitive to noise.
Algorithm for Simulator’s Road Spectrum Signal
Authors: Zhao Zhen Min , Kong Min Xiu , Du Zhi Jiang , Sun Li Ning
Published: December 2010

In response to the impossibility of directly using data of the actual road show experiment to the motion simulation of simulators, due to the limited work space of simulators, this paper begins with an attempt to extract the main frequency components of original signals by spectrum analysis and allow the input signal to meet performance requirements by adjusting the phase offset corresponding to the various frequency components. The paper proceeds with the regeneration of the signals capable of reflecting the motion characteristics of the original data and meeting the performance requirements of motion simulators by selecting these phase offsets as the design variables, selecting simulator’s displacement, velocity, and acceleration as the optimization objectives and applying Genetic Algorithm toolbox of Matlab to develop the optimization model. The paper ends with the efforts to check mechanism singularity by calculating the Jacobian matrix condition number of the regenerating signals and thus obtain the regenerating signals compatible with the work space, capable of fulfilling the performance requirements of motion simulators and free of continuous region singularity.
Finite Element Analysis of Machining Thin-Wall Parts
Authors: Izamshah R.A. R. , Mo John , Ding Song Lin
Published: December 2010

In an attempt to decrease weight, new commercial and military aircraft are designs with
unitised monolithic metal structural components which contains of thinner ribs (i.e., walls) and webs
(i.e., floors). Most of the unitised monolithic metal structural components are machined from solid
plate or forgings with the start-to-finish weight ratio of 20:1. The resulting thin-walled structure often
suffers a deformation which causes a dimensional surface error due to the action of the cutting force
generated during the machining process. To alleviate the resulting surface errors, current practices
rely on machining through repetitive feeding several times and manual calibration which resulting in
long cycle times, low productivity and high operating cost. A finite element analysis (FEA)
machining model is developed in this project to specifically predict the distortion or deflection of the
part during end milling process. The model aims to provide an input for downstream decision making
on error compensation strategy when machining a thin-wall unitised monolithic metal structural
components. A set of machining tests have been done in order to validate the accuracy of the model
and the results between simulation and experiment are found in a good agreement.
Research and Application of Data Acquisition & Processing of Standard Man-Hour in Discrete Manufacturing Process
Authors: Lv Min , Liu Yong Xin , Che Ying
Published: December 2010

In order to strengthen scientific management, a digital method of man-hour quota
calculation based on the theory of lean production was proposed and a man-hour quota management
system which is a computer-aided measurement system was researched and developed. Firstly,
machine power signals were acquired and the processing state was judged after filtering. Secondly,
the cutting processing time was gotten according to the processing status, which was integrated into
the standard man-hour. Finally, the data was stored for future use in data mining and also for
providing a reliable basis and guarantee for the accounting of product costs, the plan of production
and the allocation of resources. The accurate counting of man-hour was realized in this system, which
has the advantages of simple structure, low cost and practicality, and is suitable to be applied and
popularized in discrete manufacturing enterprises.
Simulation Study of the Temperature Field for Squashed Presetting Laser Cladding Based on ANSYS
Authors: Chen Gang , Li Xiang Feng , Zuo Dun Wen , Wang Hong Yu , Jiang Yan
Published: December 2010

In the process of modeling the squashed piece of powders for the simulation of the
temperature field of laser cladding, the metallurgical model and the pore model were proposed
separately. The effects of the organizational form, the contact resistance and the thickness of the
squashed piece of powders on the temperature were considered. Different values of physical
parameters of the squashed piece of powders were converted, different contact resistances were
calculated and the laser absorptivity for different process parameters of laser cladding was
determined. The temperature curves of six typical nodes and the temperature gradient of two nodes in
the molten pool of the substrate were discussed from different aspects.
Online Tool Life Prediction in the Machining of Titanium Alloys
Authors: Ding Song Lin , Izamshah R.A. R. , Mo John , Liu Quan Sheng
Published: December 2010

In order to reduce the risk of expensive tool failure in the machining of Titanium alloys,
the paper presents a tool life prediction approach based on the analysis of cutting forces. Regression
analysis was applied to develop the prediction model. Detailed steps of implementation are
presented. Prediction logics and criteria are introduced. Cutting tests were carried out to validate the
reliability of the proposed method. When compared with empirical methods the proposed approach
which is based on the analysis of cutting force measured in the machining process appears far more
effective in predicting tool life.
Reconstructing of Prototype Surface with Reverse Engineering and Data Process Technology
Authors: Yu Dong Man , Li Xiao Jing , Xiong Yi , Gao Zhi Hua , Wang D.
Published: December 2010

Design and manufacture of pioneer products with lower cost and shorter cycle is a major
mission for an enterprise, and reverse engineering (RE) plays an important role in accelerating
product research and borrowing ideals from other business. However, due to special structure and
complex topology relation, obtaining full surface data of a prototype is not an easy thing and should
carry out complex data process procedure to get global model. This paper describes the origin point
cloud acquisition method and the data processing steps for better point quality. Based on reverse
engineering system of a toy prototype, a fine surface reconstruction module is developed.
Measurement data are acquired by scanning the physical object using three-dimensional coordinate
measuring machine (CMM) and an optical scanning device. The model establishment and data
process of the prototype, such as noise elimination, data interpolation, data smoothing, data filtering,
data splicing and surface reconstructing are conducted subsequently. Through processing of
measurement data, the authors succeed in creating a CAD model of the prototype and gaining a good
result.
Research on Flow Field Simulation and Experiment of Numerical Control Electrochemical Machining
Authors: Fu Xiu Qing , Kang Min , Zheng Q.Y.
Published: December 2010

To design the flow field of inner-spraying ball-end cathode in NC-ECM, the numerical
model was bulit according to the physical model of the cathode flow channal, and the computational
fluid dynamics (CFD) method was applied to slove the numerical model. The velocity and pressure
distributations were obtained. The influences of the cathode internal structure and the outlet shape on
the velocity of electrolyte were analyzed on the basis of the numerical simulation. The relatively good
simulation results were obtained by means of the optimization design of the cathode. Based on the
experiment results, the accuracy of simulation was verified, and the correction number of the design
of the flow field was reduced in NC-ECM. It is indicated that the computational fluid dynamics (CFD)
method can be applied to simulate the flow field, and the optimization design of the cathode can be
guided according to the results of simulation.
Design and Study of the Initial Probe for Multi-Function Fire Helmet
Authors: Li Bin , Li Bo , Yang Hong Ze
Published: December 2010

Fire helmets are important personal protective equipment for firemen in fire-fighting and
rescue work, and the design of its function, structure, shape, etc. is directly related to the personal
safety of the firemen. The development of the fire helmet with the modernized multi-function has
very important significance. Through a study for the current research status and characteristics of fire
helmets products in domestic and abroad, and looked into the developing trends of the fire helmet.
Based on safety ergonomics and product system design method , a design program of multi-function
fire helmet is proposed, which combined with the function of infrared thermal imaging, wireless
communications conduction, emergency oxygen etc. it provided the design basis for related design
and research in future.
Magnetic Compton Profile Measurement of Thin Films
Authors: Nishino Hiroyuki , Yamaki Ryutaro , Itou Masayoshi , Sakurai Yoshiharu , Sakurai Hiroshi , Ito Masahisa
Published: December 2010

We have measured magnetic Compton profile of Co/Pd thin films sputtered on a substrate for studying the electronic structure. For the first time, a silicon nitride substrate of 100 nm thickness we used in the magnetic Compton scattering experiment. We have improved vacuum tubes of the Compton beam-line BL08W of SPring-8, and have reduced greatly the background scattering for the Compton profile. We have succeeded in measuring magnetic Compton profile of Co (0.8 nm)/Pd (1.6 nm) 400 nm multilayer.
Simple Nanoimprint Lithography with 50 nm Resolution Using Vacuum Packing
Authors: Itoh Kazuo , Hirai Hirokazu , Ando Tetsuya , Takagi Kazuya , Noguchi Katsuya
Published: December 2010

We demonstrated a simple UV nanoimprint method using vacuum packing. A glass substrate and a Si mold dropped with a photo-curable resist were vacuum-packed together in a packing sheet. They were pressed by atmospheric pressure and easily fixed without a complicated apparatus. We obtained a successful nanoimprint result for 100 nm width lines with high aspect ratio of 3.2. Further fine pattern of about 50 nm line width was also replicated using our simple method. The remaining thickness of the resist after imprint decreased with increasing the pressing pressure　whereas it saturated due to the viscosity of the resist. This saturation tendency is well explained by the balance between the pressing force and the viscous force of the resist.
Guide Pattern for Long-Range-Order Nanofabrication of Self-Assembled Block Copolymers
Authors: Akahane Takashi , Huda Miftakhul , Yin You , Hosaka Sumio
Published: December 2010

In this paper, we report two kinds of guide patterns precisely created by electron beam drawing. These guide patterns are expected to precisely control the arrangement of nanodots self-assembled from block copolymer (BCP) in order to obtain long-range-order nanofabrication. The first guide pattern is comprised only of a post lattice. The second guide pattern adds guide lines to the post lattice. The added guide lines are expected to better control the location and orientation of the BCP nanodots. We succeeded in fabricating these two kinds of guide patterns for 22-nm- and 33-nm-pitch BCP nanodots.
Proposed Phase-Change Memory with a Step-Like Channel for High-Performance Multi-State Storage
Authors: Yin You , Hosaka Sumio
Published: December 2010

Lateral rectangular (R-) and step-like (S-) channel phase-change memory (PCM) cell structures are numerically analyzed for multi-state storage based on their temperature distributions and their programming characteristics. The S-PCM cell is characterized by the sequentially melted sub-channel and step-like programming characteristics. From the viewpoint of the performance for multi-state storage, the step-like characteristics indicate high controllability for its application of multi-state storage.
Design and Fabrication of Novel Photonic Crystal Waveguide Consisting of Si-Ion Implanted SiO2 Layers
Authors: Umenyi Amarachukwu Valentine , Honmi Masashi , Kawashiri Shinya , Shinagawa Teruyoshi , Miura Kenta , Hanaizumi Osamu , Yamamoto Shunya , Inouye Aichi , Yoshikawa Masahito
Published: December 2010

In this paper, we designed and fabricated two-dimensional photonic crystal (2-D PhC) consisting of the silicon ion (Si-ion) implanted silicon dioxide (SiO2) layers. The PhC design parameters based on the telecommunication wavelength (λ=1.55 µm) were obtained using finite-difference time-domain (FDTD) method. By analyzing the samples fabricated using different fabrication approach; we found a suitable fabrication method for 2-D PhCs based on the Si-ion implanted SiO2 layers. We have analyzed the fabricated sample using atomic force microscope (AFM) and annealing temperature and time were optimized in order to recover the damage done by Si-ion implantation. The implantation of Si-ion into SiO2 with the process of 2-D PhCs structure can effectively guide light inside such structure, which can easily be integrated into the existing silicon technology for directing light from one part of the chip to the other.
Tilt Mechanism for Precision Control of Down-Slope Component of Gravitational Force for Micro Force Generation
Authors: Maru Koichi , Khunnam Wanchai , Hu Liuyan , Lu Rong Sheng , Yupapin P. Preecha , Fujii Yusaku
Published: December 2010

A simple single-axis tilt mechanism for precision control of the down-slope component of gravitational force is proposed. Precise tilt motion is realized by using a wedge shaped block and a linear actuator driven by a stepping motor. The proposed mechanism can be easily constructed by standardized aluminum frames for the skeletal structure. The measurement result indicates that the tilt angle can be controlled by adjusting the position of the linear actuator and good reproducibility of the tilt angle is achieved by using the proposed tilt mechanism.
High-Speed Data Transmission Techniques Using Raised Cosine Signaling
Authors: Yuminaka Yasushi
Published: December 2010

In this paper, we propose new pulse-shaping techniques using raised cosine signaling instead of using conventional digital signals (rectangular waves), to reduce Inter-symbol interference (ISI) and crosstalk noise. Unlike a rectangular pulse, the raised cosine pulse takes on the shape of a sinc pulse that minimizes ISI. Also, limited bandwidth of the signal can reduce crosstalk noise. We show the simulation and experimental results of the raised cosine signaling scheme to show the new signaling method plays a critical part in maintaining signal integrity in high-speed VLSI systems.
Dynamics Simulation of Microbubbles in Ultrasonic Wave Field Considering the Secondary Bjerknes Force
Authors: Miwa Takashi , Yamakoshi Yoshiki
Published: December 2010

In order to control a large number of microbubbles with a pumping ultrasonic wave, it is essential to consider a bubble-to-bubble interaction. This paper proposes a simplified microbubble dynamics simulation method considered with bubble-to-bubble interaction in ultrasonic wave field. The microbubble dynamics is solved with difference method based on the Stokes’s low and the secondary Bjerknes force between microbubbles. The laminar flow is considered in the cylindrical calculation region. The effectiveness of the frequency sweep method in laminar flow is shown with simulation results. And a usefulness of this dynamics simulation is also discussed through the experimental result.
Preparation of Anisotropic Chitosan Hydrogel with Birefringence and Analysis of Gel Formation Process
Authors: Tomita Naoko , Maki Yasuyuki , Yamamoto Takao , Dobashi Toshiaki
Published: December 2010

We have prepared an anisotropic hydrogel with birefringence by means of dialysis method and analyzed the dynamics of the gel-forming process using purified chitosan with the degree of deacetylation at 100%. The dynamics was expressed well by a theory based on “moving boundary picture”(Nobe, Dobashi and Yamamoto, Langmuir 2005).
Thermosensitive Micelles Composed of Poly(lactide)-g-Poly(NIPAM-co-HEMA) Graft Copolymers
Authors: Quynh Tran Minh , Yoneyama Masaru , Maki Yasuyuki , Nagasawa Naotsugu , Dobashi Toshiaki
Published: December 2010

Different poly(N-isopropylacrylamide-co-hydroxyethyl methacrylate) copolymers (P(NIPAM-co-HEMA)) were synthesized from N-isopropylacrylamide (NIPA) and hydroxyethyl methacrylate (HEMA) comonomers by both radical and radiation polymerizations for comparison. PLLA-g-P(NIPAM-co-HEMA) graft copolymers were synthesized from L-lactide and respective P(NIPAM-co-HEMA) copolymers by ring opening polymerization. Both NMR and FTIR analyses demonstrated the PLLA chains have been grafted on to the P(NIPAM-co-HEMA) backbone. These graft copolymers revealed the cloud point temperature higher than that of PNIPAM homopolymer as determined by optical transmittance. The graft copolymers self-assembled into micelles with regularly spherical structures as observed by atomic force microscopy (AFM). The properties of these graft copolymers are interesting for the drug delivery system.
Relationship between Dielectric Characteristic by DEP Levitation and Differentiation Activity for Stem Cells
Authors: Hirota Yusuke , Hakoda Masaru
Published: December 2010

In our previous study, we discussed the possibility of differentiation activity measurement for rat mesenchymal stem cells (RMSC) by Dielectrophoretic (DEP) levitation. Consequently, it was found that the differentiation activity of the RMSC could be evaluated by DEP levitation without the differentiation induction. Thus, we discuss the possibility of differentiation activity evaluation by DEP levitation with cells other than the RMSC. Human mesenchymal stem cells (HMSC) and human adipose tissue-derived stem cells (ASC) were used as the sample cells. The dielectric characteristics (Re[K(ω)]) measurement, the Re[K(ω)] of both the HMSC and the ASC decreased with the increasing passage number. Moreover, to evaluate the differentiation activity of the HMSC and the ASC that had performed the osteoblast differentiation induction, the amount of Alkaline Phosphatase (ALP) was measured. Consequently, the ALP activity of both the HMSC and ASC decreased with increasing the passage number. Therefore, it was found that the differentiation activity of the HMSC and the ASC could be evaluated by measuring the Re[K(ω)] due to the relationship between the Re[K(ω)] and ALP activity.
Electron and Positron Densities for Mono Vacancy in SiC
Authors: Rubaszek Anna
Published: December 2010

First principle calculations of the electron and positron band structures are performed for the SiC polytype of the 3C cubic structure. The perfect and vacancy containing elements are considered. The supercell model is incorporated Electron and positron densities as well as the positron lifetime are determined for the Si and C point defects. The resulting characteristics are studied with respect to their counterparts in the perfect crystal. Various approximations to the electron-positron correlations are applied in the calculation of the positron distribution and lifetime. Importance of non-local effects is emphasized.
The Distribution of Slowing-Down Times of Positrons Emitted from 22Na and 68Ge\68Ga Isotopes into Metals
Authors: Dryzek Jerzy , Horodek Paweł
Published: December 2010

The results of the Monte Carlo simulation, using GEANT4 codes, of the slowing-down time prior to the thermalization in metals for positrons emitted from the 22Na and 68Ge\68Ga sources are presented. Due to the energy spectrum and probabilistic processes accompanying positrons traversing a medium the slowing-down time exhibits a distribution which has a long tail. Nevertheless, the average value of the time is ranged from 0.4 ps to 8 ps depending on the density of the medium as it is for the 22Na positrons. For positrons emitted from the 68Ga nucleus the average value of the slowing-down time increases and it is ranged from 1 ps to 20 ps.
Ortho-Positronium Reactions in Water Studied by Positron Annihilation Age-Momentum Correlation
Authors: Hirade Tetsuya , Oka Toshitaka , Jae Lee Jeong
Published: December 2010

Temperature dependence on S(t), positron age dependent shape parameter of annihilation gamma-rays, in water was observed. S(t) at the ortho-Ps pick off annihilation time region were higher at higher temperatures. It is indicating that there are more reactions of ortho-Ps at higher temperature. Hence it was successfully indicated that the longest lifetime, i.e. ortho-Ps component, on positron annihilation lifetime spectra for water could be shorter at higher temperatures. The radical reactions, such as PsOH formation or ortho-Ps oxidation by hydroxyl radicals, are spin dependent reactions. The geminate pair of ortho-Ps and hydroxyl radical in water can give spin dependent reaction and the enhancement of S(t) with certain time interval, i.e. quantum beats, were expected. It was observed even for water at 11°C. It is probably indicating the hyperfine coupling constants of hydroxyl radicals in water.
Water in Montmorillonites
Authors: Sláviková Barbora , Iskrová Martina , Majerník Viktor , Šauša Ondrej , Krištiak Jozef , Jesenák K.
Published: December 2010

Positron lifetime was measured for pure and water filled montmorillonites (MMT) at room temperature. The size of free volume was correlated with interlayer distances from X-ray diffraction for different content of water in MMT. Free volume in samples with water content above 10 % (mass percentage) is smaller in comparison with bulk water. Time dependence of release of water from MMT under vacuum will be discussed.
Precise Measurement of Hyperfine Splitting of Positronium Using the Zeeman Effect
Authors: Ishida Akira , Akimoto Ginga , Sasaki Yuichi , Suehara Taikan , Namba Toshio , Asai Shoji , Kobayashi Tomio , Saito Haruo , Yoshida Mitsuhiro , Tanaka Kenichi , Yamamoto Akira
Published: December 2010

The ground state hyperfine splitting of positronium, , is sensitive to high order corrections of QED. A new calculation up to O( ) has revealed a 3.9 discrepancy between the QED prediction and the experimental results. This discrepancy might either be due to systematic problems in the previous experiments or to contributions beyond the Standard Model. We propose an experiment to measure employing new methods designed to remedy the possible systematic errors which may have affected the previous experiments. Our experiment will provide an independent check of the discrepancy. The prototype run has been performed and a result of = 203.3804 0.0022 (stat., 11 ppm) 0.0081 (sys., 40 ppm) GHz has been obtained. Compensation magnets to obtain O(ppm) magnetic field uniformity has been developed. The final run will start soon and a measurement with a precision of O(ppm) is expected within a few years.
Reconstruction of Momentum Density Distribution from 2D ACAR Data via Maximum Entropy and Cormack Methods
Authors: Pylak M. , Dobrzyński Ludwik , Kontrym-Sznajd G.
Published: December 2010

Novel application of Maximum Entropy method to the reconstruction of electron momentum density distribution from line projections is presented. Our new algorithm is applied to two dimensional angular correlation of annihilation radiation data in Gd. Reconstructed densities are in very good agreement with corresponding densities reconstructed by Cormack’s method.
Testing an Ortec Lifetime System
Authors: Karbowski Andrzej , Fidelus Janusz D. , Karwasz Grzegorz P.
Published: December 2010

We report preliminary performance tests of an ORTEC PLS lifetime system based on plastic scintillators and analog electronic system. A variety of samples was measured, from metals (Cu, stainless steel), across semiconductors (Cz-grown silicon, ZnSe) to nanostructured ceramics (ZrO2). All results obtained are compatible with literature reports and indicate the lifetime resolution of the whole system as 180 ps.
Positron Annihilation Characteristics in Superstrong Magnetic Fields
Authors: Lewicka Sylwia , Dryzek Jerzy
Published: December 2010

The recent interest in positrons distribution in the space revealed the anomalous presence of high energetic positrons. There are different possible origins of such positrons, including the decay of heavy particles in the dark matter, also pulsars or neutron stars. In our study we calculated the annihilation properties of the electron – positron bound system in superstrong magnetic fields expected for neutron stars. For this aim we use solutions of the (relativistic) Bethe-Salpeter equation derived by L.B. Leinson and A. Perez [1]. The results indicate strong dependency of the annihilation properties (rate and intensity) on the value of the magnetic field.
Structural Characterisation of Er Implanted, Ge-Rich SiO2 Layers Using Slow Positron Implantation Spectroscopy
Authors: Anwand W. , Kanjilal A. , Brauer G. , Wagner A. , Butterling M. , Cowan T.E. , Rebohle L. , Skorupa W.
Published: December 2010

Electroluminescence in SiO2 layers can be created by Ge implantation and a subsequent heat treatment, leading to the formation of Ge nano-particles inside the SiO2. An additional implantation of Er, connected with a further annealing, can lead to an improvement of the luminescent properties. However, the intensity of electroluminescence was found to decrease drastically after exceeding an optimum concentration of the Er doping. Slow positron implantation spectroscopy (SPIS), both in single (DB) and coincidence (CDB) Doppler broadening mode, was applied to probe processes at a microscopic level which might have an impact on the optical response. It shows that the increasing intensity of the electro-luminescence is connected with a crystalline structure of the SiO2 covering the nano-particles and also with the improved reverse energy transfer process between Er and Ge.
Influence of Electron-Electron Correlations and Lattice Effects on Positron-Electron Enhancement Factors
Authors: Boroński Edward
Published: December 2010

We present an approach taking into account the effect of electron-electron (e-e) correlations on electron-positron (e-p) momentum density distributions. The approach bases on the modification of the Bethe-Goldstone (B-G) equation for the positron in the electron gas due to self-energy effects. The example calculations have been performed for selected parameters corresponding to simple metals. The calculated dependencies exhibit the increase of the e-p enhancement factors below Fermi momentum, like Kahana enhancements, and a decrease above the Fermi sphere, leading to a many-body “tail” in the e-p momentum density distributions. Moreover, the influence of lattice effects on enhancement factors (EF) is taken into account. This decreases by a few percent the absolute values of the e-p momentum distributions and the corresponding annihilation rates and for real metals such as Mg or Cu evidently improve the agreement with experiment.
Studies on Radiation Defects in Tungsten Induced by W Self-Implantation
Authors: Zgardzińska Bożena , Tyburska Beata , Surowiec Zbigniew
Published: December 2010

Undamaged and damaged tungsten were investigated by means of positron spectroscopy and AFM surface images. Three different lifetimes (corresponding to dislocation loops, mono-vacancies, vacancy clusters and large size voids) were observed with different intensities. AFM shows the transition from hillocks to pinholes after W self-implantation.
Positron Annihilation in Thermally Treated Co-Zr-V Metallic Glasses
Authors: Dryzek Ewa , Jaworski Jacek , Fleury Eric , Budziak Andrzej
Published: December 2010

Positron annihilation lifetime spectroscopy (PALS) has been applied to study if the microstructure changes in Co80Zr10V10 and Co65Zr10V25 metallic glasses after heat treatment. Samples in as-quenched state were isothermally annealed at chosen temperatures in the temperature range 100°C - 580°C for 1 hour. In spite of differences of chemical composition and magnetic properties the obtained dependencies of positron lifetime on annealing temperature do not differ significantly for lower temperatures. The higher increase of positron lifetime for Co65Zr10V25 than that for Co80Zr10V10 indicates differences in crystallization in the two metallic glasses studied.
The Effect of Impact Pressure on Positron Lifetime in Ultra High Molecular Weight Polyethylene (PE-UHMW)Chirulen®1120
Authors: Pietrzak Ryszard , Szatanik Roman
Published: December 2010

The paper presents the results of investigations of the effect of impact pressure (in the range of both elastic and plastic deformations) on the parameters of the positron lifetime spectra in PE-UMHW polymer known under the trade mark Chirulen1120. The changes in the long-living component of the positron lifetime spectrum, connected with the annihilation of o-Ps in the pick-off process, are analyzed in dependence on the impact energy. The impact duration in the Charpy’s tests depending on the impact energy was measured, too. The dependencies of the radius of the volume of empty spaces in which the positronium annihilates, on the impact pressure were determined applying the Eldrup-Tao model.
Depth of Electron Traps in N-Alkanes
Authors: Pietrow Marek , Wawryszczuk J.
Published: December 2010

A systematic study of o-Ps intensity quenching by different wavelength of SWIR light was performed for a set of n-alkanes which form different crystal structures. The maximal wavelength able to quench was determined for two temperatures. The results for odd- and even-numbered alkanes were compared from this point of view. A systematic decrease in the maximal wavelength with shortening the carbon chain was found. Two kinds of traps were observed in the alkanes with chain length exceeding 30 carbon atoms, one kind only in the shorter ones. It was found that in a binary mixture of alkanes the traps are shallower than in the neat ones.
Enhanced Plasticity of Cu-Based Laminated Composites Produced by Cold Roll-Bonding
Authors: Liu H.S. , Zhang Bin , Zhang G.P.
Published: December 2010

Two different laminated composites with submicron-scale grain size and strong interface bonding toughness, Cu/Al and Cu/Cu, were fabricated by cold-roll bonding at ambient temperature, and then annealing of the laminated composites was conducted to get different interface bonding toughness. It was found that a better strength-plasticity combination for the laminated composites could be obtained through stronger interface bonding toughness, which effectively delayed the onset of plastic instability and premature local necking of the material. Uniform elongation of both Cu/Al and Cu/Cu laminated composites was enhanced compared with that of the cold-rolled Cu. At the same strength level, plasticity of the Cu/Cu laminated composite is better than that of the Cu/Al one and that of the cold-rolled Cu. Mechanisms of plasticity instability and fracture of the laminated composites were evaluated.
Influence of Dissolved Precipitated Phases on Mechanical Properties of Severely Deformed Al-4 Wt% Cu Alloys
Authors: Hu Nan , Xu Xiao Chang
Published: December 2010

Microstructural evolution and mechanical properties of Al-4.11 wt% Cu alloys subjected to multi-axial compression (MAC) and subsequent annealing were investigated. To clarify the influence of precipitated phases on mechanical properties, special samples containing only one kind of precipitated phase were prepared. During MAC at room temperature, θ"-phase-contained and θ′-phase-contained samples simultaneously showed increased strength and ductility as a function of MAC passes. This was ascribed to the considerable dissolution of precipitated phases induced by MAC that formed a supersaturated solid solution. In subsequent annealing at 393 K for 1 h, new precipitated phases appeared and the strength and ductility of deformed samples increased as precipitation proceeded. Additionally, transmission electron microscopy indicated that the MAC process accelerated the phase precipitations. Annealed mechanical properties were a function of MAC passes, annealing time, and temperature. In this study, an optimum comprehensive mechanical property was achieved in the θ"-phase-contained specimen, after eight passes of MAC and 1 h annealing at 393 K.
Fatigue Properties of Rapidly Solidified Mg-6Zn-1Y-0.6Ce-0.6Zr Alloy Processed by Reciprocating Extrusion
Authors: Zhang Zhong Ming , Xu Chun Jie , Wang Ting , Yang Lin
Published: December 2010

The ribbons of rapidly solidified Mg-6wt%Zn-1wt%Y-0.6wt%Ce-0.6wt%Zr alloy were reciprocatingly extruded and forward extruded into dense bar material. Room-temperature fatigue behavior of the alloy was tested in axial tension-tension stress condition. The fracture morphologies of the alloy after fatigue were observed by SEM. The results show that the fatigue limit is 159.2MPa with 106 cycles when the load frequency was 10Hz. The S-N curve of the alloy can be regarded as Type Ⅱ fatigue curve. The fatigue cracks originate from surface or subsurface of the fatigue specimens generally. The second phases or inclusions in these areas were prone to be the crack sources. The high fatigue properties of the alloy can be attributed to grain refinement strengthening and dispersion strengthening resulted from rapid solidification and reciprocating extrusion.
Severe Plastic Deformation by Equal Channel Angular Swaging
Authors: Bruder Enrico , Görtan Mehmet Okan , Groche Peter , Müller Clemens
Published: December 2010

Equal Channel Angular Swaging (ECAS) is a new severe plastic deformation process which combines the conventional equal channel angular pressing (ECAP) and the incremental bulk forming process rotary swaging. The tool system consists of two rotary swaging dies with an angled channel that contains four shear zones, generating severe plastic strain per pass. The crucial advantages compared to conventional ECAP are a significant reduction of friction and axial forces plus the potential to be extended to continuous processing. Thus, ECAS has high potential for a cost-efficient production of bulk UFG materials. In the present paper the principles of ECAS are introduced and first experimental results for the processing of copper are presented.
Microstructure and Mechanical Properties of an AZ31 Magnesium Alloy Processed by Accumulative Back Extrusion (ABE)
Authors: Fatemi Varzaneh Mahmood , Cabrera Jose María , Zarei-Hanzaki Abbass
Published: December 2010

A new continuous severe plastic deformation (SPD) method called accumulative back extrusion (ABE) was employed to fabricate ultra-fine grained AZ31 Mg alloy. Microstructures of AZ31 alloy processed by ABE up to four passes at a temperature of 230 °C were investigated using field emission scanning electron microscopy (FESEM). The results showed that the initial average grain size of 25 µm was reduced to about 1 µm. It was also found out that the more passes gave more homogenous microstructure. In addition, in order to ﬁnd the effect of grain size on the mechanical properties, micro-tension tests were carried out and the changes in the yield and tensile strength and fracture elongation were analyzed. The obtained tensile properties were discussed relying on the characteristics of as-processed microstructures.