Manufacturing Metallic Parts with Designed Mesostructure via Three-Dimensional Printing of Metal Oxide Powder

Cellular materials, metallic bodies with gaseous voids, are a promising class of materials that offer high strength accompanied by a relatively low mass. In this paper, the authors investigate the use of ThreeDimensional Printing (3DP) to manufacture metallic cellular materials by selectively printing binder into a bed of metal oxide ceramic powder. The resulting green part undergoes a thermal chemical post-process in order to convert it to metal. As a result of their investigation, the authors are able to create cellular materials made of maraging steel that feature wall sizes as small as 400 µm and angled trusses and channels that are 1 mm in diameter.Mechanical Engineerin

Design Synthesis of Adaptive Mesoscopic Cellular Structures with Unit Truss Approach and Particle Swarm Optimization Algorithm

Cellular material structures have been engineered at the mesoscopic scale for high performance and multifunctional capabilities. However, the design of adaptive cellular structures - structures with cellular configurations, sizes, and shapes designed for a specific geometric and loading context - has not been sufficiently investigated. In this paper, the authors present a design synthesis method with the use of unit truss approach and particle swarm optimization algorithm to design adaptive cellular structures. A critical review is presented to show the pros and cons of the new design synthesis method and an existing homogenization method. The research extends the application of additive manufacturing in the design of new materials for high performances and benefits its long-term growth.Mechanical Engineerin

Lift Enhancement for Low-Aspect-Ratio Wings with Periodic Excitation

In an effort to enhance lift on low-aspect-ratio rectangular flat-plate wings in low-Reynolds-number post-stall flows, periodic injection of momentum is considered along the trailing edge in this numerical study. The purpose of actuation is not to reattach the flow but to change the dynamics of the wake vortices such that the resulting lift force is increased. Periodic forcing is observed to be effective in increasing lift for various aspect ratios and angles of attack, achieving a similar lift enhancement attained by steady forcing with less momentum input. Through the investigation on the influence of the actuation frequency, it is also found that there exists a frequency at which the flow locks on to a time-periodic high-lift state

Why Do Different New Ventures Internationalize Differently? A Cognitive Model of Entrepreneurs\u27 Internationalization Decisions

What makes entrepreneurs select one international opportunity while rejecting or ignoring others? Furthermore, what makes entrepreneurs decide to exploit an international opportunity earlier or later? Two theories of internationalization provide answers to these questions: the Uppsala Model and International Entrepreneurship theory. However, these two theories provide competing answers to these questions, and empirical research offers inconsistent evidence about what influences entrepreneurs to select an international opportunity – and when to exploit the opportunity. To address these issues, I develop a cognitive model that explains when and why the predictions of these theories do (and do not) explain entrepreneurs’ behavior regarding new venture internationalization. More specifically, I propose that entrepreneurs’ internationalization decision making rests, in part, on cognitive processes of similarity comparison and structural alignment. I use a multi-method / multi-study approach to answer the above questions. In the first study, I use verbal protocol techniques to analyze the cognitive processes of entrepreneurs as they ‘think out loud’ while making decisions on international opportunity selection and age at entry. In the second study, I use a survey plus secondary data to test if the actual decisions made by entrepreneurs on international opportunity selection and age at entry correspond to the dissertation’s predictions. Results show that cognitive processes of similarity comparison and structural alignment underpin entrepreneurs’ internationalization decisions. Entrepreneurs rely heavily on commonalities and look for high levels of similarity between the home and host country when deciding when to internationalize their firms. Regarding entrepreneurs’ decisions on international opportunity selection, their decisions reflect the influence of both comparable and noncomparable opportunity features. Interestingly, I observe that prior international knowledge directly impacts entrepreneurs’ internationalization decisions, but also moderates the relationship between similarity considerations and entrepreneurs’ decisions on international opportunity selection. Ultimately, I reconcile and integrate two competing internationalization theories by resolving tensions between them. I demonstrate that the different predictions of the two internationalization theories can be explained by the differential focus that entrepreneurs place on comparable and noncomparable attributes of their opportunity set. I also show the importance of taking an individual-level and cognitive view to understanding these decisions

Is the Soybean Checkoff Program Working?

The primary objective of this study is to answer two key questions regarding the U.S. soybean checkoff program over time: (1) What have been the effects of the soybean checkoff program on U.S. and world soybean and soybean product markets? (2) Has the soybean checkoff program benefited soybean producers? To answer the first key question, the effects of the soybean checkoff program on U.S. and foreign soybean, soybean meal, and soybean oil supplies, demands, prices, and trade over the 1980/81 through 2006/07 time period are measured. Those results are then used to answer the second question in a benefit-cost analysis of the soybean checkoff program to measure the overall return to producers from soybean checkoff and related expenditures over the years. In general, the study concludes that the expenditure of soybean checkoff funds to invest in production research and to promote the demand for soybeans and soybean products at home and abroad has been highly effective in enhancing the profitability, competiveness, and size of the U.S. soybean industry since at least 1980/81.Soybean, Soybean Checkoff, Crop Production/Industries, Demand and Price Analysis, Marketing, Productivity Analysis,

The Spectral Correlation Function -- A New Tool for Analyzing Spectral-Line Maps

The "spectral correlation function" analysis we introduce in this paper is a new tool for analyzing spectral-line data cubes. Our initial tests, carried out on a suite of observed and simulated data cubes, indicate that the spectral correlation function [SCF] is likely to be a more discriminating statistic than other statistical methods normally applied. The SCF is a measure of similarity between neighboring spectra in the data cube. When the SCF is used to compare a data cube consisting of spectral-line observations of the ISM with a data cube derived from MHD simulations of molecular clouds, it can find differences that are not found by other analyses. The initial results presented here suggest that the inclusion of self-gravity in numerical simulations is critical for reproducing the correlation behavior of spectra in star-forming molecular clouds.Comment: 29 pages, including 4 figures (tar file submitted as source) See also: http://cfa-www.harvard.edu/~agoodman/scf/velocity_methods.htm

Observations of Transient Active Region Heating with Hinode

We present observations of transient active region heating events observed with the Extreme Ultraviolet Imaging Spectrometer (EIS) and X-ray Telescope (XRT) on Hinode. This initial investigation focuses on NOAA active region 10940 as observed by Hinode on February 1, 2007 between 12 and 19 UT. In these observations we find numerous examples of transient heating events within the active region. The high spatial resolution and broad temperature coverage of these instruments allows us to track the evolution of coronal plasma. The evolution of the emission observed with XRT and EIS during these events is generally consistent with loops that have been heated and are cooling. We have analyzed the most energetic heating event observed during this period, a small GOES B-class flare, in some detail and present some of the spectral signatures of the event, such as relative Doppler shifts at one of the loop footpoints and enhanced line widths during the rise phase of the event. While the analysis of these transient events has the potential to yield insights into the coronal heating mechanism, these observations do not rule out the possibility that there is a strong steady heating level in the active region. Detailed statistical analysis will be required to address this question definitively

Complex trait analysis of the mouse striatum: independent QTLs modulate volume and neuron number

Background: The striatum plays a pivotal role in modulating motor activity and higher cognitive function. We analyzed variation in striatal volume and neuron number in mice and initiated a complex trait analysis to discover polymorphic genes that modulate the structure of the basal ganglia. Results: Brain weight, brain and striatal volume, neuron-packing density and number were estimated bilaterally using unbiased stereological procedures in five inbred strains (A/J, C57BL/6J, DBA/2J, BALB/cJ, and BXD5) and an F2 intercross between A/J and BXD5. Striatal volume ranged from 20 to 37 mm[super]3. Neuron-packing density ranged from approximately 50,000 to 100,000 neurons/mm[super]3, and the striatal neuron population ranged from 1.4 to 2.5 million. Inbred animals with larger brains had larger striata but lower neuron-packing density resulting in a narrow range of average neuron populations. In contrast, there was a strong positive correlation between volume and neuron number among intercross progeny. We mapped two quantitative trait loci (QTLs) with selective effects on striatal architecture. Bsc10a maps to the central region of Chr 10 (LRS of 17.5 near D10Mit186) and has intense effects on striatal volume and moderate effects on brain volume. Stnn19a maps to distal Chr 19 (LRS of 15 at D19Mit123) and is associated with differences of up to 400,000 neurons among animals. Conclusion: We have discovered remarkable numerical and volumetric variation in the mouse striatum, and we have been able to map two QTLs that modulate independent anatomic parameters