Design and Fabrication of Components with Optimized Lattice Microstructures

The design and fabrication of components with optimized lattice microstructures is a new approach to creating lightweight high-performance objects. This paper introduces a unique and complete integration of design and fabrication leading to the creation of structural components with complex composite microstructures. Rather than a solid cast component with optimized outer shape this new approach leads to a component with an inner skeleton or microstructure maximizing one or more properties such as the stiffness-to-weight ratio. Three dimensional gradient materials are a natural outcome of this approach. An introduction to the design optimization and hybrid fabrication approach will be provided in addition to research progress and challenges through Spring 2004.Mechanical Engineerin

Geometry and Procedure for Benchmarking SFF and Hybrid Fabrication Process Resolution

Since the advent of SFF and RP a number of SFF benchmarking geometries and methodologies have been developed and employed with some similarities but limited standardization. Minimal information has been published in regard to a standard method of measuring the resolution limits or capabilities of SFF and SFF-based hybrid processes. In an effort to benchmark resolution limits of SFF and Hybrid Fabrication processes, several benchmarking geometries were developed to capture the resolution capabilities, specifically hole size and rod size range, of multiple hybrid fabrication path steps and a hybrid path as a whole. These useful geometries are shared with the SFF community and procedures for their use are described in this paper.Mechanical Engineerin

Statistical Process Control For Solid Freeform Fabrication Processes

Statistical prpcess control (SPC) has not been widely used for solid freeform fabrication (SFF) pr~cesses, primarily due to the wide diversity ofgeometries in builds. In addition, typical parts created on SFF platforms are not ofsimple, nor easy-to- measure geometries, which fVrther complicates the application ofSPC. A study is currently in progress to establisq a method to apply SPC to SFF. Three SPC test parts were studied to determine the addedIbuild cost and accuracy improvement when SPC is applied to stereolithography. In this study, SPC was applied to X & Y shrinkage, and line-widthcompensation facto~s over a period oftime. IfSPC can be effectively applied, it will alert the operator to othe~seunnoticed system changes before valuable build-time is lost.Mechanical Engineerin

Indirect Rapid Molds for Prototype Lost-Foam Pattern Production 506

Lost-foam (also known as Expendable Pattern Casting, EPC) is an ever-growing metalmcasting technique, capable of producing complex metal components without parting lines. Mold preparation for lost-foam casting is typically accurate, but expensive and slow. The goal of this research was to develop a new approach for producing rapid lost-foam molds. With this new approach, patterns generated by SFF technology are used to form indirect composite lost-foam molds. Ultimately, our objective is to produce these molds quickly, accurately, and inexpensively. This new approach to lost-foam mold-making will be explained as well as the results of one trial.Mechanical Engineerin

Synthesis of a Compact Tetralattice Heat Exchanger using Solid Freeform Fabrication and Comparison Testing Against a Tube Heat Exchanger

The challenge for Solid Freeform Fabrication (SFF) lies in fabricating complex parts that are not possible by conventional manufacturing means. The goal was to apply SFF techniques to complex geometry heat exchangers. The heat exchanger structure is modeled after the covalently bonded carbon atoms of a diamond. The tetrahedron diamond lattice, or Tetralattice, is a repeating lattice unit that forms a network of channels to form the heat exchanger. Electroforming methods creating Tetralattice were applied to synthesize an air-oil compact heat exchanger. After production, the heat exchanger was tested and compared with an industry standard heat exchanger for performance evaluation.Mechanical Engineerin

Cost-effectiveness analysis of alectinib versus crizotinib in first-line treatment of anaplastic lymphoma kinase-positive advanced non-small cell lung cancer:

In the randomized, active-controlled, multicenter Phase III open-label ALEX trial, alectinib showed superior efficacy and lower toxicity compared with crizotinib in the primary treatment of anaplastic lymphoma kinase-positive non-small cell lung cancer (ALK-positive NSCLC). The aim of this economic evaluation was to assess the cost-utility of alectinib versus crizotinib from the perspective of the Italian National Health Service (INHS). A partitioned survival model with three health states (progression-free, post-progression, and death) was used. The clinical data (progression-free survival, overall survival and time to progression) was based on the ALEX trial. Utility values were derived from EQ-5D scores evaluated in the ALEX trial and literature. Costs included drug treatments, progression-free, post-progression and supportive care. Direct medical costs and benefits (quality-adjusted life-years, QALYs) were discounted at a 3.0% annual rate. Uncertainty was assessed using deterministic and probabilistic sensitivity analyses. Treatment with alectinib versus crizotinib led to a gain of 2.82 life-years, 1.86 QALYs, and incremental costs of €58,276, resulting in an incremental cost-utility ratio of €31,353 per QALY. The deterministic analysis showed that the most critical parameters in the model were the cost of post-progression and utility scores. From the probabilistic sensitivity analysis, alectinib had a 64.5% probability of being cost-effective at a willingness-to-pay threshold of €40,000 per QALY. Compared with crizotinib, alectinib increased the length of the progression-free state and the QALYs. The incremental overall cost increase was reflective of longer treatment durations in the progression-free state. Compared with crizotinib, alectinib can be considered a valid cost-utility option in the treatment of naive patients with ALK-positive NSCLC

Impact of Surface Treatment on the Corrosion Resistance of ASTM F138-F139 Stainless Steel for Biomedical Applications

AbstractAISI 316 LVM stainless steel type considered in ASTM F138 and F139 standards for implant devices is widely used, in particular for orthopedic surgery, because it combines good biofunctionality and acceptable biocompatibility at low costs. Adequate interaction of these materials with the human body and its capability to reach the desired service level are determined by the surface preparation. The goal of the present work is to relate the surface roughness parameters with the localized corrosion resistance of AISI 316 LVM stainless steel grit blasted for different times and passivated with nitric acid. At intermediate blasting times the roughness parameters attain an extreme value and this surface condition corresponds with the maximum pitting corrosion resistance

TRIS I: Absolute Measurements of the Sky Brightness Temperature at 0.6, 0.82 and 2.5 GHz

At frequencies close to 1 GHz the sky diffuse radiation is a superposition of radiation of Galactic origin, the 3 K Relic or Cosmic Microwave Background Radiation, and the signal produced by unresolved extragalactic sources. Because of their different origin and space distribution the relative importance of the three components varies with frequency and depends on the direction of observation. With the aim of disentangling the components we built TRIS, a system of three radiometers, and studied the temperature of the sky at $\nu =0.6$, $\nu = 0.82$ and $\nu = 2.5$ GHz using geometrically scaled antennas with identical beams (HPBW = $18^{\circ} \times 23^{\circ}$). Observations included drift scans along a circle at constant declination $\delta=+42^{\circ}$ which provided the dependence of the sky signal on the Right Ascension, and absolute measurement of the sky temperature at selected points along the same scan circle. TRIS was installed at Campo Imperatore (lat. = $42^{\circ}~26'$ N, long.= $13^{\circ}~33'$, elevation = 2000 m a.s.l.) in Central Italy, close to the Gran Sasso Laboratory.Comment: Accepted for publication in The Astrophysical Journa

TRIS III: the diffuse galactic radio emission at δ=+42∘\delta=+42^{\circ}

We present values of temperature and spectral index of the galactic diffuse radiation measured at 600 and 820 MHz along a 24 hours right ascension circle at declination $\delta = +42^{\circ}$. They have been obtained from a subset of absolute measurements of the sky temperature made with TRIS, an experiment devoted to the measurement of the Cosmic Microwave Background temperature at decimetric-wavelengths with an angular resolution of about $20^{\circ}$. Our analysis confirms the preexisting picture of the galactic diffuse emission at decimetric wavelength and improves the accuracy of the measurable quantities. In particular, the signal coming from the halo has a spectral index in the range $2.9-3.1$ above 600 MHz, depending on the sky position. In the disk, at TRIS angular resolution, the free-free emission accounts for the 11% of the overall signal at 600 MHz and 21% at 1420 MHz. The polarized component of the galactic emission, evaluated from the survey by Brouw and Spoelstra, affects the observations at TRIS angular resolution by less than 3% at 820 MHz and less than 2% at 600 MHz. Within the uncertainties, our determination of the galactic spectral index is practically unaffected by the correction for polarization. Since the overall error budget of the sky temperatures measured by TRIS at 600 MHz, that is 66 mK(systematic)$+$18 mK (statistical), is definitely smaller than those reported in previous measurements at the same frequency, our data have been used to discuss the zero levels of the sky maps at 150, 408, 820 and 1420 MHz in literature. Concerning the 408 MHz survey, limiting our attention to the patch of sky corresponding to the region observed by TRIS, we suggest a correction of the base-level of $(+3.9\pm 0.6)$K.Comment: Accepted for publication in the Astrophysical Journa