Development of Prediction Method for Dimensional Stability of 3D-Printed Objects

Fused deposition modeling (FDM), as one of the additive manufacturing processes, is known for strong layer adhesion suitable for prototypes and end-use items. This study used a multiple regression model and statistical analysis to explore the dimensional accuracy of FDM objects. Factors such as inclination angle, layer thickness, support space, and raster angle were examined. Machine learning models (Gaussian process regression (GPR), support vector machines (SVM), and artificial neural network (ANN)) predicted dimensions using 81 datapoints. The mean squared dimensional error (MSDE) between the measured and designed surface profiles was selected as an output for the dimensional accuracy. Support spacing, layer thickness, and raster angle were determined to be statistically significant, and all factors were confirmed as significant predictors. The coefficients of determination for multiple linear regression, GPR, SVM, and ANN models were 76%, 98%, 93%, and 99%, respectively. The mean absolute errors (MAEs)—errors between the measured and the predicted MSDEs—were 0.020 mm and 0.034 mm, respectively, for GPR and SVM models. The MAEs for ANN models were 0.0055 mm for supporting cases and 2.1468 x 10 -5 mm for non-supporting cases

Combined Tevatron upper limit on gg->H->W+W- and constraints on the Higgs boson mass in fourth-generation fermion models

Report number: FERMILAB-PUB-10-125-EWe combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg->H->W+W- in p=pbar collisions at the Fermilab Tevatron Collider at sqrt{s}=1.96 TeV. With 4.8 fb-1 of integrated luminosity analyzed at CDF and 5.4 fb-1 at D0, the 95% Confidence Level upper limit on \sigma(gg->H) x B(H->W+W-) is 1.75 pb at m_H=120 GeV, 0.38 pb at m_H=165 GeV, and 0.83 pb at m_H=200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% Confidence Level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg→H→W+W- in pp̅ collisions at the Fermilab Tevatron Collider at √s=1.96  TeV. With 4.8  fb-1 of integrated luminosity analyzed at CDF and 5.4  fb-1 at D0, the 95% confidence level upper limit on σ(gg→H)×B(H→W+W-) is 1.75 pb at mH=120  GeV, 0.38 pb at mH=165  GeV, and 0.83 pb at mH=200  GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.Peer reviewe

Effects of Steel Type and Sandblasting Pretreatment on the Solid-liquid Compound Casting Characteristics of Zinc-coated Steel/aluminum Bimetals

Effects of zinc-coated steel type and steel surface sandblasting pretreatment in the solid-liquid compound casting of layered type steel/aluminum bimetals were investigated. The Zn coating behavior and its effects on interfacial microstructure evolution and fracture mechanism were also discussed. The aluminum fluidity in thin plate type flow channels formed by the steel insert and the mold wall primarily depended on the insert surface roughness and secondarily on the wettability. As-galvanized (GI) steel/aluminum bimetal joints showed the bonding strength of 20 MPa and more, while galvannealed (GA) steels showed poor bonding. The interfacial bonding zone consisted of most Al13Fe4, Al8Fe2Si, Al4.5FeSi intermetallic phases, as well as some Si phases. A low temperature and short time of the bonding reaction coupled with a high silicon content of the aluminum alloy suppressed the formation of Al5Fe2 phase. Oxide scales on the GA steel surface prevented the molten Zn coating from mixing with the aluminum melt. The Zn coating of GI steels was rapidly disappeared from the steel surface by the chemical affinity and surface energy-driven fluid flow as well as the diffusion, resulting in the formation of Zn-free intermetallic phases. The Zn coating of GI steels played a role in retarding the onset of bonding reaction. A long time sandblasting caused an excessive growth of intermetallic layers and the formation of Kirkendall voids on the steel side, resulting in the shift of main fracture sites and a slight decrease of the bonding strength

Microstructural Refinement of As-Cast Al-Mg Alloy by Ultrasonic Melt Treatment Using a Titanium Sonotrode Under Fully Liquid Condition

The effects of ultrasonic treatment (UST) using a titanium (Ti) sonotrode in a fully liquid stage on the grain refinement and mechanical properties of as-cast Al–Mg alloy billets were investigated. To clarify the grain refinement mechanism, the grain size (GS) and dendrite arm spacing (DAS) were examined as functions of the growth restriction factor (Q) dependent on the Ti dissolution from the sonotrode, and compared to those in the as-cast and re-melted states of the samples inoculated using an Al–10 mass%Ti master alloy. In addition, the formation and dissolution behavior of Al3Ti intermetallic particles acting as a heterogeneous nuclei was indirectly observed by measuring the electrical resistivity during isochronal annealing. In comparison with the chemical refiner inoculation, the UST effectively refined not only the GS but also the DAS, both of which showed similar slightly concave upward curves with an increasing slope against 1/Q. Electrical resistivity measurement results provided indirect evidence that the dissolved Ti was present as a solute during the solidification stage. The GS, DAS, and electrical resistivity results all suggest that the dissolved Ti refined the GS primarily by solute-induced growth restriction effect rather than by providing heterogeneous nucleation sites. The UST effect on the microstructure refinement was efficient when the Ti-dissolution content was as low as less than 0.05 mass%. The refinement of grains, Al3Fe particles, dendrites, and pores by the UST significantly improved mechanical properties, especially the elongation at break

Review: Scaffold Characteristics, Fabrication Methods, and Biomaterials for the Bone Tissue Engineering

The goal of tissue engineering is to replace or regenerate damaged tissue. Scaffold fabrications and biomaterial selections are crucial factors for artificial tissue and bone tissue engineering, which are important due to the limited availability of tissue donors. This paper reviews the scaffold design considerations, manufacturing methods, and biomaterials for bone tissue engineering, and discusses current challenges and future perspectives. Scaffolds are required to have non-hazardous properties such as biocompatibility and biodegradability for the human body, and the necessary mechanical properties to support body weight, or to perform other roles, depending on the type of tissue. Moreover, scaffold structures such as porosity, pore size, and pore shape should be optimized to achieve cell viability and proliferation. Many conventional fabrication methods including thermally induced phase separation, emulsion freeze-drying, solvent casting, gas forming, and electrospinning have been studied and developed, but 3D printing is more suitable for bone tissue engineering because of its ability to manufacture complicated structures. Biomaterials can be divided into four categories: polymer, ceramic, metal, and composites. Composites blend two or more biomaterials to achieve desired properties for matching individual patient conditions. Finding a balance between fabrication method and biomaterial selection, in order to match properties between the scaffold and the target tissue, will be key to the field of bone tissue engineering in the future

Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element Vtb\bf V_{tb}

We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb$^{−1}$ per experiment. The t-channel cross section is measured to be σ$_t$=2.25$_{-0.31}^{+0.29}$ pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s+t channel cross section measurement resulting in σ$_{s+t}$=3.30$_{-0.40}^{+0.52}$ pb, without assuming the standard model value for the ratio σ$_s$/σ$_t$. The resulting value of the magnitude of the top-to-bottom quark coupling is |V$_{tb}$|=1.02$_{-0.05}^{+0.06}$, corresponding to |V$_{tb}$|>0.92 at the 95% C.L

Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron

International audienceThe CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of s=1.96  TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is AFBtt¯=0.128±0.025. The combined inclusive and differential asymmetries are consistent with recent standard model predictions

Tevatron Run II combination of the effective leptonic electroweak mixing angle

International audienceDrell-Yan lepton pairs produced in the process pp¯→ℓ+ℓ-+X through an intermediate γ*/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin2θefflept using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9–10  fb-1 of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin2θefflept=0.23148±0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin2θW, or equivalently the W-boson mass MW, using the zfitter software package yields sin2θW=0.22324±0.00033 or equivalently, MW=80.367±0.017  GeV/c2