bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Visual and Audiovisual Competition on the Auditory N1-P2 Evoked Potential
Authors: Weihing Jeffrey , Daniels Shannon , Musiek Frank E.
Published: December 2009

Background: Use of a competition stimuli (e.g., video) in clinical settings is a widespread practice, yet the effects of these stimuli on evoked potentials are not well understood. Purpose: The present investigation acquired the click evoked auditory N1-P2 in quiet and
in two types of competition: during presentation of an unrelated visual stimulus or audiovisual stimulus. Responses were acquired in each of these conditions at two click stimulus levels (i.e., 35 and 65 dBnHL) to determine if the effect of competition was greater closer to threshold. An attempt
was made to quantify effect robustness by examining within- and between-session reliability. Research Design: Repeated measures ANOVA. Study Sample: 17 normal hearing female subjects. Results: Findings indicated a significant effect of audiovisual competition on the amplitude
of the N1-P2, and a borderline significant effect of visual competition on this index. The extent of visual competition was better conveyed when examined on a case-by-case basis, in which was revealed a subgroup of the sample that was negatively affected by visual competition. There was no
interaction between competition and click stimulus level. Conclusions: Although competition stimuli can negatively affect the amplitude of the N1-P2, consideration should be given to subjects on a case-by-case basis to warrant if removal of this stimulus is necessary.
Effects of a Cell Phone Conversation on Cognitive Processing Performances
Authors: Kemker Brett E. , Stierwalt Julie A.G. , LaPointe Leonard L. , Heald Gary R.
Published: December 2009

Background: The ability to apportion cognitive resources to process multiple visual and auditory stimuli is essential for human communication in competing conditions. Purpose: The purpose of the current research was to examine the effects of a cell phone conversation on
a battery of cognitive tests, using both timing (RT) and accuracy (A′) as dependent measures. Research Design: A repeated measures ANOVA was conducted. Study Sample: Forty-two college-age (mean 22 yr) adult females with normal hearing and cognitive function participated
in the study. Data Collection and Analysis: In one condition (quiet), a standardized cognitive assessment battery was administered to participants in a quiet room. In the (cell phone) condition, subjects were formulating and responding to specific questions about their travel experiences
during administration of the same cognitive assessment battery. The computer automatically records subject performance. Post-hoc pairwise comparisons were conducted using the Bonferroni approach. The alpha level was set at .05 for all data analysis. This method of analysis was repeated for
each of the dependent measures, RT, and A′. Results: The results revealed a consistent, significant effect on reaction time between the two conditions. The same analysis was also conducted to examine the effect of participation in a cell phone discussion on accuracy. As with RT,
results revealed a consistent, significant affect on A′ between the two conditions. Conclusions: Our study supports the notion that there are differential effects of auditory distracters across cognitive spheres. For simple automatic type visual cognitive tasks, the effect is
minimal. However, as visual tasks increase in difficulty, the effect of the auditory distraction is magnified, particularly when the task requires extensive division of language resources.
Incidence and Risk Factors of HIV-Related Non-Hodgkin's Lymphoma in the era of Combination Antiretroviral Therapy: A European Multicohort Study
Authors:   The Collaboration of Observational HIV Epidemiological Research Europe (COHERE) Study Group, Bohlius Julia , Schmidlin Kurt , Costagliola Dominique , Fätkenheuer Gerd , May Margaret , Caro-Murillo Ana Maria , Mocroft Amanda , Bonnet Fabrice , Clifford Gary , Karafoulidou Anastasia , Miro Jose M , Lundgren Jens , Chene Genevieve , Egger Matthias
Published: December 2009

Background

Incidence and risk factors of HIV-associated non-Hodgkin's lymphoma (NHL) are not well defined in the era of combination antiretroviral therapy (cART).

Methods

A total of 56,305 adult HIV type-1 (HIV-1)-infected patients who started cART in 1 of 22 prospective studies in Europe were included. Weibull random effects models were used to estimate hazard ratios (HRs) for developing systemic NHL and included CD4+ T-cell counts and viral load as time-updated variables.

Results

During the 212,042 person-years of follow-up, 521 patients were diagnosed with systemic NHL and 62 with primary brain lymphoma (PBL). The incidence rate of systemic NHL was 463 per 100,000 person-years not on cART and 205 per 100,000 person-years in treated patients for a rate ratio of 0.44 (95% confidence interval [CI] 0.37–0.53). The corresponding incidence rates of PBL were 57 and 24 per 100,000 person-years (rate ratio 0.43, 95% CI 0.25-0.73). Suppression of HIV-1 replication on cART (HR 0.60, 95% CI 0.44-0.81, comparing ≤500 with 10,000-99,999 copies/ml) and increases in CD4+ T-cell counts (HR 0.30, 0.22-0.42, comparing ≥350 with 100-199 cells/pl) were protective; a history of Kaposi's sarcoma (HR 1.70, 1.08-2.68, compared to no history of AIDS), transmission through sex between men (HR 1.57, 1.19-2.08, compared with heterosexual transmission) and older age (HR 3.71, 2.37-5.80, comparing ≥50 with 16-29 years) were risk factors for systemic NHL.

Conclusions

The incidence rates of both systemic NHL and PBL were substantially reduced in patients on cART. Timely initiation of therapy is key to the prevention of NHL in the era of cART.
Optimal Length of Antiviral Therapy in Patients with Hepatitis C virus Genotypes 2 and 3: A Meta-Analysis
Authors: Slavenburg Serena , Weggelaar Ines , van Oijen Martijn GH , Drenth Joost PH
Published: December 2009

Background

Current guidelines recommend a duration of 24 weeks of treatment with pegylated interferon and ribavirin for patients infected with chronic hepatitis C virus (HCV) genotypes 2 and 3. Several trials investigated whether shorter treatment duration is equally effective in achieving sustained virological response (SVR). Our aim was to determine the optimal length of treatment in patients with HCV genotypes 2 and 3.

Methods

Systematic literature identified eight randomized controlled trials (RCTs). Meta-analyses were carried out on SVR data from three studies randomized at baseline and five studies randomized at rapid virological response (RVR) to either 12–16 weeks or a 24-week course.

Results

Pooled SVR data were higher in standard treatment in RCTs that randomized at baseline, with a relative risk (RR) of 0.88 (95% confidence interval [CI] 0.76–1.01). The pooled proportion of SVR rates of RCTs that randomized at RVR were similar in the short treatment group (82%) as in the standard treatment (83%), with the pooled effect given by a RR of 1.00 (95% CI 0.92–1.09).

Conclusions

A shorter course (12–16 weeks) of combination therapy does not impair efficacy compared with a 24-week course in HCV genotypes 2 and 3 patients who achieve an RVR. HCV patients without RVR should consider 24 weeks of treatment.
Pretreatment with Pegylated Interferon Prevents Emergence of Lamivudine Mutants in Lamivudine-Naive Patients: A Pilot Study
Authors: Villa Erica , Lei Barbara , Taliani Gloria , Graziosi Amalia , Critelli Rosina , Luongo Monica , Gennari William , Bianchini Marcello , Ferretti Ilva
Published: December 2009

Background

In patients with advanced fibrosis, primary end points of long-term or possibly indefinite antiviral therapy are sustained inhibition of viral replication and avoidance of emergence of resistance. In lamivudine-treated patients, the strongest predictor of emergence of YMDD mutations is baseline hepatitis B virus (HBV) DNA viral load. We aimed to verify whether abatement of viraemia by a short course of pegylated interferon (PEG-IFN-α2a) treatment before lamivudine treatment could prevent the emergence of lamivudine-associated mutations during long-term therapy.

Methods

A total of 14 patients with hepatitis B e antigen (HBeAg)-negative infection (3 lamivudine- experienced and 11 lamivudine-naive), with moderate/high viraemia (>106 copies/ml) and with Ishak stage 4-6 at liver biopsy were sequentially treated with 180 mg PEG-IFN-α2a for a period long enough to reach HBV DNA levels ≤103 copies/ ml or have a decrease of 3 log10 copies/ml from baseline. Lamivudine was then added to PEG-IFN-α2a treatment for 1 month and finally continued as monotherapy for 2 years or until viral breakthrough.

Results

Baseline HBV DNA (mean ±se 2.3x107 ±7.2x107 copies/ml) decreased with PEG-IFN-α2a treatment to target value in mean ±se 3.7 ±1.3 months. None of the 11 lamivudine-naive patients developed genotypic resistance and were still HBV-DNA-negative after a mean ±se observation period of 23 ±2 months, whereas the three lamivudine-experienced patients developed YMDD mutations after 6, 9 and 12 months of lamivudine monotherapy ( P=0.003, Fisher's exact test).

Conclusions

In lamivudine-naive patients, abatement of HBV DNA<103 copies/ml by pretreatment with PEG-IFN-α2a completely prevents the emergence of YMDD mutants after 24 months of lamivudine monotherapy. This sequential schedule can optimize the use of a well tolerated, effective and inexpensive drug, such as lamivudine, in highly viraemic HBV patients.
Herpesviridaeand novel inhibitors
Authors: Siakallis George , Spandidos Demetrios A , Sourvinos George
Published: December 2009

Herpesviridae comprises a large family of double-stranded DNA viruses that infect both animals and humans. Eight herpseviruses are known to infect humans: herpes simplex virus type-1 and -2, varicella zoster virus, human cytomegalovirus, Epstein–Barr virus, human herpesvirus 6 type-A and -B, human herpesvirus type-7 and -8 or Kaposi's sarcoma virus.

Despite the fact that the past two decades have been evolutionary in the development of antiviral agents, therapeutic choices are restricted by limited efficacy and toxicity. Viral infections remain the cause of significant mortality worldwide, thus indicating the high medical need for the introduction of novel promising compounds in the antiviral chemotherapy era.

This review focuses on recent data regarding several novel groups of agents that have proved to be effective as antiherpetic drugs. The agents mentioned are those considered to be the most likely candidates for entering clinical trials and those in the process of being granted approval by the US Food and Drug Administration. The diversity in their molecular mechanism of action highlights the different perspectives currently encountered in the era of antiviral therapy.
Los determinantes socioeconómicos de la desigualdad económica. Datos de Portugal
Authors: Budría Santiago
Published: December 2009

Este artículo utiliza el Panel de Hogares de la Unión Europea (1994-2001) para investigar cuáles son los determinantes socioeconómicos de la desigualdad. el artículo se centra en Portugal, el país de la Unión Europea con mayores niveles de desigualdad, para documentar hechos relevantes sobre las distribuciones de la renta, salarios y rentas de capital. se muestra cómo estas distribuciones están relacionadas con características familiares tales como edad, educación, estado civil y estado laboral. Por último, se emplea un modelo Probit ordenado generalizado para investigar cómo y en qué medida las diferentes características socio-económicas de las familias determinan su estatus económico y su movilidad a lo largo de las distribuciones. el artículo concluye que la educación es, con diferencia, la dimensión socioeconómica más determinante en relación con la desigualdad.
Friction and Bitten Condition in Cold Ring Rolling
Authors: Zuo Z.J. , Yang J.J. , Yu W.X.
Published: December 2009

Analytic calculation and Finite Element Method simulation are used to research the relationship between friction and bitten condition in cold ring rolling. It is found: if the ring can’t be bitten in groove, rolling process will be stopped. The rolling force will increase rapidly, which will cause the breakage of rolls and equipment. When the feed velocity and other technical parameters are kept unchanged, the bitten condition will be disappeared with the process of ring rolling even if the ring can be bitten at the beginning stage.
Measuring out of Flatness of a Rough Quartz Surface and Correction by Mist-Abrasion Machining
Authors: Shakeri Mohsen , Amirabadi Hossein , Horiuchi Osamu
Published: December 2009

In this research, Air mist-abrasion machining method for corrective figuring of a rough isotropic quartz surface before polishing process has been proposed. By this method, not only the next polishing time decreases, but also figuring efficiency increases through the possibility of using bigger abrasive grain size. Since the restrictions of laser interferometer measuring devices, capacitor probe has been used for measuring “out of flatness” of a rough isotropic quartz surface and creating error map for corrective figuring. By the proposed Air mist-abrasion figuring method, flatness of a rough isotropic quartz surface improved from PV= 0.4μm to PV=0.1μm without any change in surface roughness value.
Development of Nitrided Layer during Nitriding of Steel
Authors: Ratajski Jerzy , Olik Roman
Published: December 2009

The present work is devoted to research the influence of micro-structural evolution of the compound zone (iron (carbo)nitrides zone) upon development of hardness profiles in diffusion zone.
A different phase structure of iron (carbo)nitrides zone on steel as compared to iron, further changing with the process, may result in upsetting the quasi-equilibrium of nitrogen concentration in the iron (carbo)nitrides zone/diffusion zone interface and may as a result have impact on the kinetics of this layer’s growth. Aimed at solving this problem there was a research carried out to evaluate influence of (carbo)nitrides zone, with intentionally created diametrically different phase composition, on hardness profiles in the diffusion zone.
Based on the research conducted, it was shown that the evolution of phase structure of the compound zone contributes significantly, regardless of nitrogen potential and temperature, to the formation of the diffusion zone and in particular to its effective thickness. It makes this complex picture of nitrided case development on steel even more intricated.
Investigation of Dry Plasma Etching of Silicon
Authors: Morshed Muhammad M. , Daniels Stephen M.
Published: December 2009

Meso-scale structures are formed on a silicon surface using a sulphur hexafluoride (SF6) based dry etching process. Etched feature parameters, including etch rate, trench profile, and selectivity are explored using an optical emission spectroscopy and a resonance hairpin probe. With increasing process power, the etch rate was observed to increase, which was correlated with an observed increase in intensity of fluorine emission. Damage of the photoresist with increasing power was observed and a marked increase in hydrogen (H) emission was found to indicate this fault. The electron density and the sidewall roughness were also found to increase with higher reactor power. The e-SF6 collisions contribute to the production of atomic fluorine, which etches the silicon by the dissociative ionization (SF+5 and F or SF+3 and F) and electron impact dissociation (SF5 and F).
Optimization of Short Stroke Control Curve in Hot Strip Mill by FEM Modelling
Authors: Du Xiao Zhong , Yang Quan , Lu Cheng , Zhu Hong Tao , Tieu A. Kiet
Published: December 2009

The slab edge rolling has been widely used in the roughing stand of hot strip mill to control the width of the slab. However, the slab edge rolling and consequent horizontal rolling will cause a significant width change in the head part and tail part of the slab, which have to be trimmed before the finishing stands. The short stroke control (SSC) technology has been developed to overcome this problem. In this paper, the finite element method (FEM) has been used to simulate the unsteady edge rolling process. Three SSC control curves have been compared in order to obtain the best width control result. The optimized SSC control curve has been applied to the industrial rolling mill.
A New Die Design for Sheet Hydroforming of Complex Industrial Parts
Authors: Bakhshi M. , Gorji A. , Hosseinzade M. , Jamshidi M. , Mohammad-Alinejad G.
Published: December 2009

Some new sheet hydroforming processes have been introduced during the last few years to increase the application and to overcome some of the limitations in conventional deep drawing. In recent years, the applications of sheet hydroforming have become increased. Nowadays, this technology has been largely accepted by industries for the production of different components with specific characteristics. Despite the advantages of the sheet hydroforming techniques, they have their own disadvantages.
In this paper, a new sheet hydroforming technique is presented that improves the applications of the current sheet hydroforming processes. The proposed technique is applied to two complex non-symmetrical industrial parts. It is shown that the new technique can produce the products very well. In addition, it is shown that the forming pressure and load are very low compared with those of other hydrofoming methods.
A New Punch Profile Design for Orbital Forging of a Bevel Gear Part
Authors: Sheu Jinn Jong , He M.S.
Published: December 2009

The difficulty in forging of bevel gear with an outside diameter larger than 75mm is due to the high forming load requirement. In this paper, a new intuitive method for the punch and preform design of the bevel gear warm orbital forging is proposed to lower the forging load and improve the die filling. The geometry of the forged bevel gear are divided into characteristic features and mapped to the main dimensions of the preform design. The exact dimensions of the preform are determined utilizing constraints of the volume constancy and the section centroid balance. The surface of punch tip is designed using the section profile described by a Bezier curve with five control points which are related to the preform and the forged part geometry simultaneously. The forming process was analyzed via the FEM simulation. The die stress was also calculated to prevent die failure and improve tool life. A PXW-200 orbital forging press was adopted for the experimental tests of the proposed designs. The unfilled area at the teeth faces were examined via the laser scanner. The experimental results of the maximum unfilled distances were varied from 0.3 mm to 0.8mm depending on the different punch tip profile design. The predicted tooth profiles were in good agreement with the experimental measurements.
Grain Refinement in Ferritic Stainless Steel Welds: The Journey so Far
Authors: Amuda M.O.H. , Mridha S.
Published: December 2009

The ferritic stainless steel is a low cost alternative to the most often adopted austenitic stainless steel due to its higher strength, better ductility and superior corrosion resistance in caustic and chloride environments. However, the application of ferritic steel is limited because of poor ductility and notch impact toughness of its weld section with differential grain structures. Several techniques have been explored to control the grain features of the weld to minimize these problems. In the present effort, a review of these options in relation to the degree of grain refinement in ferritic stainless steel weld is conducted in order to have a better understanding about the grain refining phenomenon in the weld microstructure. So far, the most effective technique is found to be the pulse AC TIG welding which can produce weld with mechanical properties equivalent to 65% to those of the base metal. The refinement in this process occurred through dendrite fragmentation and grain detachment in the weld pool producing small-grained microstructures with a large fraction of equiaxed grains. However, in friction welding process where heat input and heat transfer are effectively controlled, the strength can be as high as 95% of the parent metal. This suggests that the total energy input for welding and heat transfer phenomenon mainly control the development of microstructural feature in the weld pool and hence the strength.
Near Net Shape Forging of CV Joint Outer Race
Authors: Mohammadi M.M. , Sadeghi M.H.
Published: December 2009

A CV joint outer race is an important load-supporting part in cars. Its geometry is very
complicated. Traditional hot and cold forging methods have their own limitations to produce such a
complex shaped part. Therefore, multistage forging may be advantageous to produce this part.
The key point of outer race is performing the geometry of ball grooves with negative slope angle.
Traditional methods form the ball groove by machining that takes long time and waste many
portions of the material. Thus near net shape forging is an attractive option for producing of outer
race. In this study, the process sequence in the multistage forging of a CV joint outer race has been
investigated by using the rigid plastic finite volume method and forging process sequence is
designed which can produce a near net-shape housing without defects within a given press capacity.
Finally physical modelling with commercial lead is used to verify the reliability of numerical
simulation results.
Inverse Method Based on Modal Vibration Testing for Characterizing the Elastic Properties
Authors: Lin Yu Hua , Chang Chia Lung
Published: December 2009

This paper presents a inverse method to derive the material properties from the resonance frequencies of a free-edge test specimen based on modal vibration test. A mixed numerical experimental identification procedure is used for this purpose. Finite element models of the test plate is simultaneously updating and reproduces the updating frequencies, then optimal procedure is running. The sum of the squared differences between the experimental and the finite element method numerical resonance frquencies is the objective function. To seek practical solutions, here presents a global optimization method--simulated annealing method for the determination of the elastic properties. The inverse method is applied to determine the elastic constants of aluminum , carbon/epoxy , Glass/PP composite material and double coated steel plate. The results indicate that the method can obtain very accurate elastic constants for aluminum , Glass/PP , carbon/epoxy composite material ,but for double coated steel plate , if the individual layer of the three different layers is as isotroptic material having six elastic constants , the method can obtain very accurate results , but if it is as transversely isotropic material having twelve elastic constants, the evaluating elastic constants are bad.
A Study on Distributions of Electromagnetic Force of the Dissimilar Metal Joining in MPW Using a FEM
Authors: Shim J.Y. , Kang B.Y. , Kim Ill Soo , Kang M.J. , Park D.H. , Kim I.J.
Published: December 2009

Recent trends of welding system have been focused on the development of new process in order to achieve better quality, higher productivity and friendly to the environmentally in welding process. The Magnetic Pulse Welding(MPW) process is based on the principle of a tremendous amount of energy compressed and discharged for an extremely short period of time. The purpose of this paper is to investigate welding characteristics according to the distributions of an electromagnetic force on the weldment using a finite element method and to find the optimal process parameters such as input current and frequency. To successfully accomplish this objective, a 2-dimensional axisymmetric electromagnetic numerical model has firstly been developed. The equation was solved using a general electromagnetic mechanics computer program, ANSYS code. The comparison between the calculated and measured results has been carried out to verify the developed system.
Heuristics for Direct Slicing of Point Clouds for Layered Manufacturing
Authors: Percoco G.
Published: December 2009

Reverse Engineering and Rapid Prototyping are integrated mostly using the tessellated STL (Solid-to-Layer) file. If copies of 3D scanned products are needed in a few time, the polygonization task is normally performed on the point cloud, often generating errors, requiring high computational effort, and heavy human intervention. In this paper it is proposed to overcome the limitations of polygonization by using direct slicing of point clouds, modelling the problem as a travelling salesman problem (TSP), solved basing on the heuristic technique called cheapest insertion. The point cloud is decomposed into elementary voxels, then, considering each Z level of the voxelized point cloud, the external non-void voxels are linked together, using the above mentioned heuristics, to generate the contour of the object with an automatic process. The contour of the object can be easily converted into commercial slice files suitable for Rapid Prototyping machines. The approach is applied to several complex shaped models to prove its robustness and efficiency.
Prediction of Machining Force and Surface Roughness in Ultrasonic Vibration-Assisted Turning Using Neural Networks
Authors: Soleimanimehr H. , Nategh Mohammad Javad , Amini Saeed
Published: December 2009

In present study, neural networks have been employed for studying the ultrasonic vibration-assisted turning (UAT) process and for predicting the machining force and workpiece's surface roughness. Extensive experiments were carried out using different values of UAT parameters such as vibration amplitude, depth of cut, feed rate and cutting speed. The tests were implemented on the basis of full factorial design of experiments for three different levels of each UAT parameter. The machining force and workpiece's surface roughness were measured as the responses of the experiments and were subsequently modeled with the aid of back propagation multilayer perceptron neural network for 1.1191 steel. The nonlinear relation existing between the aforementioned UAT parameters and the machining force and workpiec's surface roughness could effectively be modeled by the developed networks and the responses error could be kept less than ten percent. This was verified by further experiments different from those carried out for developing the network.
ECAP Processing of High Si Bainitic Steel, Microstructure and Mechanical Properties
Authors: Nili-Ahmadabadi Mahmoud , Haji-Akbari F. , Rad F. , Iranpour M. , Shahirnia M. , Poorganji Behrang , Furuhara Tadashi
Published: December 2009

Microstructure and mechanical properties of high Si bainitic steel, before and after two passes of equal channel angular pressing (ECAP) at room temperature were investigated. SEM and TEM microscopy were used for microstructural study. Shear punch test and Vickers hardness test of as received and ECAPed samples were carried out to measure the influence of ECAP process on the mechanical properties of the samples. The results showed that tensile strength and shear strain were increased as a consequence of ECAP processing.
Evaluation of the AZ31 Formability According to Temperature Using a Constant Strain Rate Test
Authors: Palumbo G. , Sorgente Donato , Tricarico Luigi
Published: December 2009

The present paper is focused on the Finite Element modeling of the Marciniak stretch-forming test in warm condition. Such a test was proposed by the authors for evaluating the warm formability of the Mg alloy AZ31 according to the most important parameters: the temperature and the strain rate. Tensile tests confirmed the large influence of the strain rate on the deformation of the AZ31, especially when the test temperature is over 200°C. Three dimensional FE simulations were thus carried out in order to analyze the strain and strain rate evolutions during the formability test at the temperature of 200°C. In particular, simulations were aimed at investigating the effect of the specimen’s geometry on the strain rate evolution in the central region, where failure occurs during the Marciniak stretch-forming test. An equation for calculating the punch speed profile able to keep a constant equivalent strain rate in the central region of the specimen has been furnished according to the geometry of the specimen. Its efficiency was validated by means of additional simulations implementing the punch speed profile calculated using the proposed approach.
Effect of Magnesium and Artificial Aging on the Microstructure and Mechanical Properties of Al-Si-Mn-Mg Alloys
Authors: Shabestari S.G. , Hejazi M.M. , Bahramifar M.
Published: December 2009

The effect of magnesium addition up to 0.9 wt.% on the microstructure and mechanical properties of Al-9Si-0.35Mn alloy has been investigated in both as-cast and heat treated conditions. Generally, Mg addition increases the heat treatability and strength of the alloys at the expense of the lower ductility. High levels of magnesium addition, causes the formation of large and brittle intermetallics, a slight increase in porosity and hence, a decrease in ultimate tensile strength and ductility of the cast alloys. T6 heat treatment increases the strength of the alloys up to 80 percent compared to as-cast samples. Among the studied compositions, heat treated Al-9Si-0.35Mn-0.25Mg alloy, has the maximum value of quality index and can be regarded as a promising material with the optimum mechanical properties for industrial applications.
Microstructure and Mechanical Properties of Dissimilar Ferritic and Austenitic Steel Joints with an Intermediate Inconel-182 Buttering Layer
Authors: Shariatpanahi A.M. , Farhangi Hassan
Published: December 2009

In this study, microstructure and mechanical properties of dissimilar weld joints between 2.25Cr-1Mo ferritic steel and 316L austenitic stainless steel, with and without an Inconel-182 buttering layer, have been investigated. The buttering layer widths produced on the machined edges of the ferritic steel plate were 3 and 5 mm. The dissimilar weld joints were butt-welded using a SMAW process with Inconel-182 electrodes. The results indicate that the ferritic base metal dilution effects are minimized due to buttering and a more uniform distribution of Fe, Ni, Cr and Nb contents is established over a broad region within the fusion zone. Moreover, a microstructure consisting of combined columnar and equiaxed dendrite with interdendritic Nb-rich particles is developed within the fusion zone as a result of buttering. Mechanical tests show that the average hardness, tensile ductility and impact energy of the weld metal were enhanced with increasing width of the buttering, while tensile strength properties were unaffected. It is observed that fracture surfaces of tensile specimens exhibit ductile features composed of ductile tear ridges with numerous interspersed dimples. However, the dominant fracture mode is noted to change from interdendritic to transdendritic with the use of a buttering layer.
Milling of Carbon Fiber Reinforced Plastics
Authors: López de Lacalle Luis Norberto , Lamikiz Aitzol
Published: December 2009

This work presents the main results of several tests carried out to define the best milling tools for routing carbon fiber reinforcement plastics, mainly in use for airframes. The new milling tools are shaped by multiple left-hand and right-hand helical edges, which form small pyramidal edges along the cutting length. Several carbide substrates and coatings were tested. After the analysis of tests and modifications on the tool prototypes, the final results allow the definition of routing endmills optimized for carbon fiber composites.
Microstructural Investigation of Gamma-Irradiated Ultra High Molecular Weight Polyethylene in Nitrogen Atmosphere
Authors: Al-Ma'adeed Mariam , Al-Thani N.J. , Bader M.
Published: December 2009

In this paper the results of structural changes in ultra high molecular
polyethylene (UHMWPE) upon gamma irradiation and storage in nitrogen environment
are reported. Based on differential scanning calorimetry (DSC), wide angle x-ray
scattering (WAXS), gel content, fourier transform infrared spectroscopy (FTIR), and
scanning electron microscope (SEM), we show that upon gamma irradiation crystallinity
percentage increases by 20% at high doses due to aging, at low doses up to 50 kGy there
is no significant changes. Lamellar thickness increases with the dose, possibly due to
chain scission and the addition of new molecular segments to the lamellae. Upon storage
in nitrogen DSC data confirmed the appearance of new smaller lamellae.
Crosslinking was achieved by irradiation but the ratio of scission to crosslinking is higher
after aging. This was confirmed by the increase in the oxidation index and the high brittle
behavior of the polymer after aging where fibrous surface was noticed.
Preheating in End Milling of AISI D2 Hardened Steel with Coated Carbide Inserts
Authors: Lajis Mohd Amri , Nurul Amin A.K.M. , Karim A.N. Mustafizul , Hafiz A.M.K.
Published: December 2009

This study was conducted to investigate the effect of preheating through inductive heating mechanism in end milling of AISI D2 hardened steel (60-62 HRC) by using coated carbide tool inserts. Apart from preheating, two other machining parameters such as cutting speed and feed were varied while the depth of cut constant was kept constant. Tool wear phenomenon and machined surface finish were found to be significantly affected by preheating temperature and other two variables. End milling operation was performed on a Vertical Machining Centre (VMC). Preheating of the work material to a higher temperature range resulted in a noticeable reduction in tool wear rate leading to a longer tool life. In addition, improved surface finish was obtained with surface roughness values lower than 0.4 μm, leaving a possibility of skipping the grinding and polishing operations for certain applications.
Aluminum Recycling - Challenges and Opportunities
Authors: Mahfoud Musbah , Emadi Daryoush
Published: December 2009

Aluminum has experienced significant growth in several sectors over the last decade as a result of its properties and performance attributes. Aluminum is being recognized by different sectors such as automotive, construction, aerospace, etc. as a one of the best candidate material for various applications. Increasing demand for aluminum-based products and further globalization of the aluminum industry have contributed significantly to the higher consumption of aluminum scrap for re-production of aluminum alloys. In automotive applications, for example, the opportunities for continued growth in powertrain and suspension applications plus lightweighting of body structures offer the potential for considerable further growth. Today, a large amount of the aluminum going into new products is coming from recycled products. This represents a growing "energy bank" of aluminum that will become available for recycling at the end of vehicles' lives, and thus recycling is becoming a major issue, and it is essential to tackle this problem before it is too late. The future growth offers opportunity for new recycling technologies and practices to maximize scrap quality, improve efficiency and reduce cost. The present paper highlights some of the current development work in recycling, the challenges facing the implementation of recycling technologies and the future prospective of the idea.
Metallurgical and Numerical Correlation of Mold Vibration with the Refinement of Al-Si Alloy
Authors: Abu-Dheir Numan
Published: December 2009

Applying mechanical vibration with subsonic frequencies during permanent mold casting enhances nucleation and improves mold-casting heat transfer. Despite the several published papers in this field, little attention was given to correlating the vibration parameters of frequency and amplitude with the casting microstructure. In this paper microstructure examination and numerical simulation are used to explain the microstructure refinement using mold-vibration. A 1-D numerical model is used to explain the different mechanisms that mold-vibration has at different frequencies of 100 Hz, 500 Hz, and 2000 Hz. Microstructure examination for samples of Al-12.6wt%Si are presented and a correlation with the numerical results using inverse heat conduction method is attempted. Results show that increasing the value of the apparent thermal diffusivity of the casting is as a result of vibration is a major factor in achieving the desired refinement. Improving the mold-casting heat transfer coefficient showed significant influence on the process only at high frequency of 2 kHz due to the low vibration amplitude used.
Investigation of the Formability of Flanged Parts of Magnesium Alloy under Hot Forging Process
Authors: Ho Huey Lin , Hsiang Su Hai , Huang Zun Yao
Published: December 2009

This study investigated the mechanical properties and forming characteristics of flanged parts made of AZ61 magnesium alloys via hot working. The bearing cover of the gearbox in cars was selected as a carrier in hot forging to probe into the formability of magnesium alloys. A high-speed metal test machine was used for compression tests under different forming temperatures and strain rates to obtain stress-strain curves. The stress-strain data are applied to the Finite Element Method to analyze the formability of the bearing cover.
Finally, based on the comparison of simulation and experimental results, we conclude that under the same billet heating temperature and low strain rate, the forming load was small and no cracks developed on the flanges of forged parts. However, under the same condition, the microstructure of the part was coarse. This study also attempted to identify a method for manufacturing a bearing cover with a low forging load, and determined how temperature influences hardness and microstructure of the bearing cover.
Reducing Electrode Wear Using Cryogenic Cooling during Electrical Discharge Machining
Authors: Abdulkareem Suleiman , Khan Ahsan Ali , Konneh Mohamed
Published: December 2009

In electrical discharge machining (EDM), material is removed by a series of electrical discharge between the electrode (tool) and the workpiece that develops a temperature of about 8,0000C to 12,0000C. Due to high temperature of the sparks, work material is melted and vapourized, at the same time the electrode material is also eroded by melting and vapourization. Electrodes wear (EW) process is quite similar to the material removal mechanism as the electrode and the workpiece are considered as a set of electrode in EDM. In the present study effort has been made to reduce EW by cooling, using liquid nitrogen during the EDM of titanium alloy. Investigation on the effect of cooling on electrode wear (EW), material removal rate (MRR) and surface roughness (Ra) of the workpiece was carried out. Current (I), pulse on-time (ton), pause off-time (toff) and voltage (v) were considered as the machining parameters. Design of experiment (DOE) was used to design the experimental works. Cooling of electrode by this technique reduced the melting and vapourization of electrode material and enhances electrode life. It was possible to reduce EW up to 27% by applying this technique while MRR and Ra were improved by 18% and 8% respectively.
Surface Integrity and Residual Stresses Analysis by Strain Gages after Hard Turning Process of Case Hardened Steel AISI 8620
Authors: Farias A. , Delijaicov S. , de Mello José Daniel Biasoli , Stipkovic Filho M. , Batalha G. F.
Published: December 2009

This work aims an analysis on the functional surface integrity resulting from turning mechanical components manufactured from case hardened steel AISI 8620 with 1 millimeter average layer depth and hardness of 58-62HRC. A cBN tool with PVD coat and Wiper geometry-edge was used for continuous turning of hardened steel, the cutting conditions (Vc [m/min] and f in [mm/rev]) used were concerned to reflect large running production of mechanical components.
Parametric Approach Model for Determining Electrical Discharge Machining (EDM) Conditions: Effect of Cutting Parameters on the Surface Integrity
Authors: Tebni Wissem , Boujelbene M. , Bayraktar E.
Published: December 2009

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes. EDM process is based on thermoelectric energy between the work piece and an electrode. There are various types of products which can be produced by using the EDM such as dies and moulds. Today many parts used in aerospace and automotive industry and also final processes of surgical components can be finished by EDM process.
A simple and easily understandable model was proposed for predicting the relative importance of different factors (composition of the steels and Electro Discharge Machining processing conditions) in order to obtain an efficient pieces. A detail application on the tool steels machined by EDM was given in this study. This model is based on thermal, metallurgical and mechanical and also in situ test conditions. It gives detail information on the effect of electrochemical parameters on the surface integrity and sub-surface damage of the material (Heat Affected Zone, HAZ), the level of residual stresses, and the surface texture. This approach is an efficient way to separate the responsibilities of the steel maker and machining process designer for increasing the reliability of the machined structures.
Prediction by Genetic Algorithm and Measurement by Center Hole Drilling of Residual Stresses of MAG Weldment
Authors: Farrahi G.H. , Majzoobi G.H. , Fadaee A.
Published: December 2009

In the present work, specimens were cut out from St-37 plates with 19 mm thickness. The thickness of plates was reduced to 12.5 mm by milling and grinding operations. Then a standard V-shaped fillet was made on one edge of the plates. Two plates were butt-welded by standard metal arc gas (MAG) welding process. Residual stresses induced by welding were measured on 20 specimens by centre hole drilling. Load controlled axial fatigue tests were carried out to determine the fatigue life of specimens. Crack growth rates were obtained from experiment. Fractography of specimens was performed. Genetic Algorithm (GA) was employed for prediction of residual stress value in weldments using the crack growth rates obtained from experiments. The results show that, by using the measured crack growth rates and GA model, residual stresses can be estimated with a good approximation.
Performance Investigation for Precision Mold Turning by PCBN Tool
Authors: Lin Shen Yung , Tang C.C. , Shih J.C. , Chi S.S.
Published: December 2009

In order to ascertain the superior characteristics of PCBN tool for hardened material machining, to promote the cutting performance and efficiency of a mold manufacturing, to investigate the wear mechanism of the cutting tool, and to investigate the dimensional accuracy and surface finish of the machined molds, SKD11 die steel and the polycrystalline cubic boron nitride are used as the workpiece and tool materials, respectively, in this study for turning experiments. After some proper surface layers removed from the workpiece in the experiment, the tool wear was measured through the toolmaker’s microscope and the roughness of the machined surface was measured by the roughness measuring instruments. So that, the associated sampling data prepared for training pattern of a neural network can be obtained. Besides, the noise-mediator was used to detect cutting noise during each surface layer removal for the cutting performance judgment in the machining processes additionally. An assessment model of cutting process is thus developed using a neural network system if the reliable and sufficient data is taken from the experiments. Based on the developed neural network, the complicated relationships between the cutting parameters (cutting speed, depth of cut and feed rate) and the cutting performance (surface roughness, tool wear and cutting temperature) can be clearly clarified. The best surface roughness of 0.29μm Ra is obtained from these experiments under the cutting conditions of d =0.2mm, f =0.05mm/rev and V=120m/min. This surface quality is equivalent to the manufacturing process of chemical-mechanical polishing (CMP), and the surface roughness of 0.2~0.5μm Ra may be attained by CMP. The CMP is always applied to high precision surface processing such as the valve piping and connector components in semiconductor/LED manufacturing.
Molding Analysis of Multi-Cavity Aspheric Lens and Mold Designing
Authors: Lin Jui Cheng , Lee King Sun
Published: December 2009

The key of qualities of optical lens created by injection molding are geometric errors and distribution of residual stress. This study analyses a mobile phone camera lens with aspheric optical lens created by one mold and 16 cavities. Mold flow analysis was used to simulate geometric shapes of different gates and design cooling systems to control mold temperatures. Mold temperature was controlled during the actual injection process and simulation results were used as the basis for mold design. The effects of cold-wall-mold on lens residual stress are discussed. The experiment result showed that higher mold temperatures are helpful to reduce residual stress. An aspheric mould measurement system was used to measure both the mold and the product. The results showed that the replicating capacity is satisfactory with a molding error of 3.604μm.
Influence of Billet Quality on Hot Extrusion Die Life and its Relationship with Process Parameters
Authors: Akhtar S.S. , Arif Abul Fazal M. , Sheikh A.K.
Published: December 2009

Apart from other factors such as die design and manufacturing, heat treatment, working conditions etc, performance of hot extrusion die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die life based on microstructural and statistical analyses. In microstructural investigation, secondary (remelt) billet cast in-house at local extrusion plant is compared with primary (smelter) billet by applying different material characterization techniques including optical microscopy, hardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). The statistical study is based on the failure history of some 53 hollow-profile dies in which the effect of billet quality on various measurable process parameters including extrusion ratio, billet temperature, exit temperature and repeated nitriding is analysed and related with useful die service life. Comparatively coarse grain structure, non-homogeneous distribution of secondary phases, and high hardness in the case of secondary billet were found responsible for poor die performance as observed in statistical investigation of failed dies. Two types of regression models are also proposed for prediction of die life in terms of secondary billets’ usage and measurable influencing parameters. Using current results, some suggestions during in-house billet preparation of secondary billets have been devised for improved die life.
Warm-Forming of Light-Weight Alloys under Multi-Stage Forming Process
Authors: Lai Chi Ping , Chan Luen Chow , Chow Chi Loong , Yu Kai Ming
Published: December 2009

This paper aims at presenting an experimental investigation to obtain the optimum formability of light-weight alloys under the multi-stage forming process. Titanium alloy sheets (Ti-6Al-4V) and aluminium alloy sheets (AA5052) are selected as forming specimens. The special fixture with heating device is applied in order to carry out the prestraining process. The swift forming test at warm-forming condition is performed for measuring the limit dome heights after the multi-stage formign process. The outcomes of this investigation are valuable for engineers to design and fabricate high-quality light-weight components efficiently.