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In sweeping conversations about the impact of artificial intelligence on many sectors of the economy, healthcare has received relatively little attention. Yet it seems unlikely that an industry that represents [...]

The relationship between slack resources and innovation is complex, with the literature linking slack to both breakthrough innovations and resource misallocation. We reconcile these conflicting views by focusing on a novel mechanism: the role slack time plays in the endogenous allocation of time and effort to innovative projects. We develop a theoretical model that distinguishes between periods of high- (work weeks) versus low-(break weeks) opportunity costs of time. Low-opportunity cost time during break weeks may induce (1) lower quality ideas to be developed (a selection effect); (2) more effort to be applied for any given idea quality (an effort effect); and (3) an increase in the use of teams because scheduling is less constrained (a coordination effect). As a result, the effect of an increase in slack time on innovative outcomes is ambiguous, because the selection effect may induce more low-quality ideas, whereas the effort and coordination effect may lead to more high-quality, complex ideas. We test this framework using data on college breaks and on 165,410 Kickstarter projects across the United States. Consistent with our predictions, during university breaks, more projects are posted in the focal regions, and the increase is largest for projects of either very high or very low quality. Furthermore, projects posted during breaks are more complex, and involve larger teams with diverse skills. We discuss the implications for the design of policies on slack time. Open Access Statement: This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. You are free to download this work and share with others, but cannot change in any way or use commercially without permission, and you must attribute this work as 'Organization Science. Copyright [iD] 2018 The Author(s). https://doi.org/10.1287/orsc.2018.1215, used under a Creative Commons Attribution License: https://creativecommons.org/licenses/by-nc-nd/4.0/.' Funding: Financial support was provided by the Junior Faculty Research Assistance Program at Massachusetts Institute of Technology (MIT) Sloan, Social Sciences and Humanities Research Council, Centre for Innovation and Entrepreneurship at the University of Toronto, and the Edward B. Roberts (1957) MIT Fund Grant for Technology-Based Entrepreneurship. Supplemental Material: The online appendices are available at https://doi.org/10.1287/orsc.2018.1215. Keywords: crowdfunding * entrepreneurship * slack time * low-opportunity cost time * teamwork * internet, It's no coincidence that Microsoft and Facebook both got started in January. At Harvard that is (or was) Reading Period, when students have no classes to attend because they're supposed [...]

When firms recruit inventors, they acquire not only the use of their skills but also enhanced access to their stock of ideas. But do hiring firms actually increase their use of new recruits' prior inventions? Our estimates suggest they do, quite significantly in fact, by approximately 219% on average. However, this does not necessarily reflect widespread 'learning by hiring.' In fact, we estimate that a recruit's exploitation of her own prior ideas accounts for almost half of the above effect, with much of the diffusion to others being limited to the recruit's immediate collaborative network. Furthermore, although one might expect the recruit's role to diminish rapidly as her tacit knowledge diffuses across her new firm, our estimates indicate that her importance is surprisingly persistent over time. We base these findings on an empirical strategy that exploits the variation over time in hiring firms' citations to the recruits' premove patents. Specifically, we employ a difference-indifferences approach to compare premove versus postmove citation rates for the recruits' prior patents and corresponding matched-pair control patents. Our methodology has three benefits compared to previous studies that also examine the link between labor mobility and knowledge flow: (1) it does not suffer from the upward bias inherent in the conventional cross-sectional comparison, (2) it generates results that are robust to a more stringently matched control sample, and (3) it enables a temporal examination of knowledge flow patterns. Key words: inventor mobility; access to ideas; knowledge spillovers; learning by hiring; difference in differences; coarsened exact matching; collaborative networks; patent citations History: Received August 28, 2009; accepted August 4, 2010, by Kamalini Ramdas, entrepreneurship and innovation. Published online in Articles in Advance November 19, 2010., 1. Introduction The link between recruiting inventors and using their stock of prior ideas is important, yet we know surprisingly little about it. There is a broad consensus that innovation [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jue.2009.10.004 Byline: Ajay Agrawal (a), Iain Cockburn (b), Carlos Rosell (c) Keywords: Knowledge flows; Agglomeration; Recombination; Innovation; Entrepreneurship Abstract: We examine variation in the concentration of inventive activity across 72 of North America's most highly innovative locations. In 12 of these areas, innovation is particularly concentrated in a single, large firm; we refer to such locations as 'company towns'. We find that inventors employed by large firms in these locations tend to draw disproportionately from their firm's own prior inventions (as measured by citations to their own prior patents) relative to what would be expected given the underlying distribution of innovative activity across all inventing firms in a particular technology field. Furthermore, we find such inventors are more likely to build upon the same prior inventions year after year. However, smaller firms in company towns do not exhibit this myopic behavior; they draw upon prior inventions as broadly as their small-firm counterparts in more diverse locations. In addition, we find that inventions by large firms in company towns have less impact than those produced elsewhere, although the difference is modest, and that the impact is disproportionately appropriated by the inventing firms themselves. Finally, the geographic scope of impact realized by company town inventions is narrower, whether produced by large or small firms. Author Affiliation: (a) University of Toronto and NBER, 105 St. George St., Toronto, Ontario, Canada M5S 3E6 (b) Boston University and NBER, 595 Commonwealth Avenue, Boston, MA 02215, USA (c) Government of Canada, Department of Finance, 140 O'Connor Street, Ottawa, Ontario, Canada K1A 0G5 Article History: Received 19 June 2009; Revised 2 October 2009

Abel inverse integral to obtain local field distributions from path-integrated measurements in an axisymmetric medium is an ill-posed problem with the integrant diverging at the lower integration limit. Existing methods to evaluate this integral can be broadly categorized as numerical integration techniques, semianalytical techniques, and least-squares whole-curve-fit techniques. In this study, Simpson's 1/3rd rule (a numerical integration technique), one-point and two-point formulas (semianalytical techniques), and the Guass--Hermite product polynomial method (a least-squares whole-curve-fit technique) are compared for accuracy and error propagation in Abel inversion of deflectometric data. For data acquired at equally spaced radial intervals, the deconvolved field can be expressed as a linear combination (weighted sum) of measured data. This approach permits use of the uncertainty analysis principle to compute error propagation by the integration algorithm. Least-squares curve-fit techniques should be avoided because of poor inversion accuracy with large propagation of measurement error. The two-point formula is recommended to achieve high inversion accuracy with minimum error propagation. OCIS codes: 000.2190, 100.6950, 120.5820, 280.1740, 280.2490.

Recent increases in fuel costs, concerns for global warming, and limited supplies of fossil fuels have prompted wide spread research on renewable liquid biofuels produced domestically from agricultural feedstock. In this study, two types of biodiesels and vegetable oil (VO) are investigated as potential fuels for gas turbines to generate power. Biodiesels produced from VO and animal fat were considered in this study. The problems of high viscosity and poor volatility of VO (soybean oil) were addressed by using diesel-VO blends with up to 30% VO by volume. Gas chromatography/mass spectrometry, thermogravimetric analysis, and density, kinematic viscosity, surface tension, and water content measurements were used to characterize the fuel properties. The combustion performance of different fuels was compared experimentally in an atmospheric pressure burner with an air-assist injector and swirling primary air around it. For different fuels, the effect of the atomizing airflow rate on Sauter mean diameter was determined from a correlation for air-assist atomizers. Profiles of nitric oxides (N[O.sub.x]) and carbon monoxide (CO) emissions were obtained for different atomizing airflow rates, while the total airflow rate was kept constant. The results show that despite the compositional differences, the physical properties and emissions of the two biodiesel fuels are similar Diesel-VO fuel blends resulted in slightly higher CO emissions compared with diesel, while the N[O.sub.x] emissions correlated well with the flame temperature. The results show that the CO and N[O.sub.x] emissions are determined mainly by fuel atomization and fuel/air mixing processes, and that the fuel composition effects are of secondary importance for fuels and operating conditions of the present study. [DOI: 10.1115/1.2982137]

Understanding of the structure of complex supersonic flows requires high-resolution, nonintrusive measurements across the whole field. The measurement requirements are even more challenging when dealing with small-scale systems. In this study, we apply the miniature rainbow schlieren deflectometry system to measure the density field in underexpanded micro jets from an orifice injector of 500 [micro]m diameter. The injector is used to replicate the practical scenario of accidental leakage from a compressed gas storage facility. Experiments were conducted for a range of supply pressures [P.sub.s], although the majority of the results are presented for [P.sub.s] = 860 kPa. Experimental schlieren images were analyzed to determine the density contours in an axisymmetric domain with a field of view of 1.5 mm radius and 7.5 mm length, at a spatial resolution of 25 [micro]m. Pressure, temperature, and Mach number profiles (normalized by the values at the orifice) were also obtained along the jet centerline. Results show features similar to those observed in underexpanded macrojet from a sonic nozzle; multiple shock-cell structures with expansion and compression fans, freejet boundary, incident, normal, and reflected shock waves, subsonic slip strip, and outer shear layer. The miniature rainbow schlieren deflectometry technique is shown to provide high-quality quantitative data to explain the structural details of underexpanded microjets.

The 'unintended' knowledge flow in relation to an inventor's migration to a new country is examined. Findings show that the new country gains from the inventor's arrival, while the former country also benefits from his new country and firm due to increased knowledge flow. Details on its effect on firm strategy opportunities are discussed.

A study was conducted to investigate the effect of a decrease in collaboration costs resulting from the adoption of Bitnet on university research collaboration in engineering. The study also aimed to analyze hiw changes in collaboration costs may affect the structure of knowledge production. Findings indicate that Bitnet connection increased the collaboration rates of middle-tier schools.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jue.2008.01.003 Byline: Ajay Agrawal (a)(b), Devesh Kapur (c), John McHale (d) Keywords: Productivity; Innovation; Knowledge flows; Agglomeration; Ethnicity; Diversity Abstract: We examine how the spatial and social proximity of inventors affects access to knowledge, focusing especially on how the two forms of proximity interact. Employing patent citation data and using same-MSA and co-ethnicity as proxies for spatial and social proximity, respectively, we estimate a knowledge flow production function. Our results suggest that although spatial and social proximity both increase the probability of knowledge flows between individuals, the marginal benefit of geographic proximity is greater for inventors who are not socially close. We also report that the marginal benefit of being members of the same technical community of practice is greater in terms of access to knowledge for inventors who are not co-located. Overall, these results imply that spatial and social proximity are substitutes in their influence on access to knowledge. We discuss the implications of these findings in terms of the optimal dispersion of socially connected inventors. Author Affiliation: (a) Rotman School of Management, University of Toronto, 105 St. George Street, Toronto, ON, Canada, M5S 3E6 (b) NBER, 1050 Massachusetts Avenue, Cambridge, MA 02138, USA (c) Center for the Advance Study of India, University of Pennsylvania, 3600 Market Street Suite 560, Philadelphia, PA 19104, USA (d) Queen's School of Business, Queen's University, 143 Union Street, Kingston, ON, Canada, K7L 3N6 Article History: Received 15 March 2007; Revised 2 January 2008

Fuels produced from renewable sources offer an economically viable pathway to curtail emissions of greenhouse gases. Two such liquid fuels in common usage are biodiesel and ethanol derived from soybean, corn, or other food crops. In recent years, significant effort has been devoted to identify alternate feedstock sources and conversion techniques to diversify the biofuels porfolio. In this study, we have measured emissions from fames of diesel, biodiesel, emulsified bio-oil, and diesel-biodiesel blends. Experiments are conducted in an atmospheric pressure burner with an air-atomized injector and swirling primary air around it to replicate typical features of a gas turbine combustor. Experiments were conducted for fixed air and fuel flow rates, while the airflow split between the injector and the coflow swirler was varied. Results show a significant reduction in emissions as the fraction of total air fed into the atomizer is increased. Blue flames, reminiscent of premixed combustion, and low emissions of nitric oxides and carbon 1monoxide were observed for all fuel blends. In general, the emissions from biofuel flames were comparable or lower than those from diesel flames. [DOI: 10.1115/1.2836747]

A counter-flow annular heat recirculating burner was designed for lean prevaporized, premixed combustion. Prior to entering the combustor, the reactants are passed through a porous media-filled preheating annulus surrounding the combustor. Kerosene is dripped by gravity onto the porous media and vaporized by the heat conducted through the combustor wall. Experiments were conducted to evaluate heat transfer and combustion performance at various equivalence ratios, heat release rates, and inlet air temperatures. Results show low CO emissions over a range of equivalence ratios. N[O.sub.x] emissions were high at high heat release rates, indicating inadequate prevaporization and premixing of fuel with air. Heat recirculation and heat loss characteristics are presented at various operating conditions. [DOI: 10.1115/1.2719259]

Recent interest in small-scale flow devices has created the need for miniature instruments capable of measuring scalar flow properties with high spatial resolution. We present a miniature rainbow schlieren deflectometry system to nonintrusively obtain quantitative species concentration and temperature data across the whole field. The optical layout of the miniature system is similar to that of a macroscale system, although the field of view is smaller by an order of magnitude. Employing achromatic lenses and a CCD array together with a camera lens and extension tubes, we achieved spatial resolution down to 4 [micro]m. Quantitative measurements required a careful evaluation of the optical components. The capability of the system is demonstrated by obtaining concentration measurements in a helium microjet (diameter, d = 650 [micro]m) and temperature and concentration measurements in a hydrogen jet diffusion flame from a microinjector (d = 50 [micro]m). Further, the flow field of underexpanded nitrogen jets is visualized to reveal details of the shock structures existing downstream of the jet exit. OCIS codes: 120.0120, 120.1740, 120.4640, 120.6780.

This study deals with the computational analysis of the near-field flow structure in an isothermal helium jet injected into quiescent ambient air environment. Laminar, axisymmetric, and unsteady flow conditions were considered for the analysis. The transport equations of helium mass fraction coupled with the conservation equations of mixture mass and momentum were solved using a staggered grid finite-volume method. Jet Richardson numbers encompassing both buoyant and inertial jet flow regimes were considered. Buoyancy effects were isolated by initiating computations in Earth gravity and subsequently, reducing the gravity to simulate microgravity conditions in the 2.2 s drop tower. Computed results concur with experimental observations, i.e., a self-excited buoyant jet with periodic flow oscillations in Earth gravity becomes steady in microgravity. In an inertial jet, the flow oscillations occur at the same frequency regardless of the buoyancy, although the oscillation amplitude decreases in microgravity.

Experiments were conducted in Earth gravity and microgravity to acquire quantitative data on near-field flow structure of helium jets injected into air. Microgravity conditions were simulated in the 2.2-s drop tower at NASA John H. Glenn Research Center. The jet flow was observed by quantitative rainbow schlieren deflectometry, a nonintrusive line-of-sight measurement technique suited for the microgravity environment. The flow structure was characterized by distributions of helium mole fraction obtained from color schlieren images taken at 60 Hz. Results show that the jet in microgravity was up to 70% wider than that in Earth gravity. Experiments reveal that the global flow oscillations observed in Earth gravity are absent in microgravity. Quantitative details are provided of flow evolution as the experiment undergoes change in gravity in the drop tower.

We focus on the utility of rainbow schlieren as a tool for measuring the temperature of axisymmetric partially premixed flames (PPFs). Methane-air PPFs are established on a coannular burner. The flames involve two spatially distinct reaction zones, one in an inner premixed region that has a curved tip and a spatially planar wing portion and another that involves an outer nonpremixed zone in which intermediate species burn in air. Schlieren images are found to visualize clearly these PPF characteristics through light deflection by steep refractive-index gradients in the two reaction zone fronts. The temperature distributions of two flames established at fuel-rich mixture equivalence ratios of [[phi].sub.r] = 1.5 and 2.0, with bulk-averaged velocities, [V.sub.reac] = 60 cm [s.sup.-1] and [V.sub.air] = 50 cm [s.sup.-1], are inferred from color schlieren images, and a measurement error analysis is performed. Errors arise from two sources. One lies in the process of inferring the temperature from the refractive-index measurement by making assumptions regarding the local composition of the flame. We have shown through simulations that the average temperature deviations due to these assumptions are 1.7% for the [[phi].sub.r] = 1.5 flame and 2.3% for the [[phi].sub.r] = 2.0 flame. Another source involves the local uncertainty in the measurement of the transverse ray displacement at the filter plane that is used to determine the refractive index and thereafter the flame temperature. We have ascertained that a maximum error of 4.3% in the temperature determination can be attributed to this local measurement uncertainty. This investigation demonstrates the capability of the schlieren technique for providing not only qualitative displays of the PPFs but also full-field-of-view temperature measurements that are accurate, spatially resolved, and nonintrusive. OCIS codes: 280.1740, 120.6780, 280.2470, 120.5710.

In this paper we explore the degree to which patents are representative of the magnitude, direction, and impact of the knowledge spilling out of the university by focusing on the Massachusetts Institute of Technology (MIT), and in particular, on the Departments of Mechanical and Electrical Engineering. Drawing on both qualitative and quantitative data, we show that patenting is a minority activity: a majority of the faculty in our sample never patent, and publication rates far outstrip patenting rates. Most faculty members estimate that patents account for less than 10% of the knowledge that transfers from their labs. Our results also suggest that in two important ways patenting is not representative of the patterns of knowledge generation and transfer from MIT: patent volume does not predict publication volume, and those firms that cite MIT papers are in general not the same firms as those that cite MIT patents. However, patent volume is positively correlated with paper citations, suggesting that patent counts may be reasonable measures of research impact. We close by speculating on the implications of our results for the difficult but important question of whether, in this setting, patenting acts as a substitute or a complement to the process of fundamental research., 1. Introduction While there is a widespread belief that publicly funded research conducted at universities has a significant impact on the rate of economic growth, estimating the magnitude and describing [...]

We present an Abel-inversion algorithm to reconstruct mean and rms refractive-index profiles from spatially resolved statistical measurements of the beam-deflection angle in time-dependent, axisymmetric flows. An oscillating gas-jet diffusion flame was investigated as a test case for applying the algorithm. Experimental data were obtained across the whole field by a rainbow schlieren apparatus. Results show that simultaneous multipoint measurements are necessary to reconstruct the rms refractive index accurately.

A quantitative rainbow schlieren deflectometry (RSD) technique using computer data processing has been developed for flow prediction and design. A study was conducted to apply this method in analyzing computational fluid dynamic (CFD) calculations on non-reacting and reacting flows. Results illustrate the effectiveness of the RSD technique in providing new insights and quantitative details to validate CFD calculations.

We present quantitative rainbow schlieren deflectometry with tomography for measurements of temperature in three-dimensional gas flows. The schlieren apparatus with a continuously graded spectral filter of known transmissivity was used to create color schlieren images of the test media. These images at multiple viewing angles were used to infer beam deflection angles by the medium. The deflection data were used with a tomographic technique to reconstruct the refractive index and thus the temperature field. The temperature distributions obtained by the rainbow schlieren tomography agreed with those measured by a thermocouple probe. This research demonstrates that tomography can be used with full-field schlieren deflectometry to measure quantitatively temperature in asymmetric gas flows. The technique could be used to obtain related properties such as pressure, density, and gas composition. OCIS codes: 110.6960, 100.6890.

For inverse problems in complex flow passages, a calculation procedure based on a multizone Navier-Stokes method was developed. A heuristic approach was employed to derive wall shape corrections from the wall pressure error. Only two subdomains sharing a row of control volumes were used. The grid work in the common region was identical for both subdomains. The flow solver, inverse calculation procedure, multizone Navier-Stokes method and subdomain inverse calculation procedure were validated independently against experimental data or numerical predictions. Then, the subdomain inverse calculation method was used to determine the wall shape of the main duct of a branching flow passage. A slightly adverse pressure gradient was prescribed downstream of the sidebranch. Inverse calculations resulted in a curved wall diffuser for which the wall pressure distribution matched the design (prescribed) wall pressure distribution. The present method was illustrated for laminar, incompressible flows in branching passages. However, the method presented is flexible and can be extended for turbulent flows in multiply connected domains.

Advances in artificial intelligence (AI) highlight the potential of this technology to affect productivity, growth, inequality, market power, innovation, and employment. This volume seeks to set the agenda for economic [...]

The hypothesis that licensing strategies that directly engage the inventor increase the likelihood and degree of commercialization success is examined. Many inventors believe that licensing firms shows great insights than their size and relevant markets, including desired aspects of end product and consumer approval for payment.