A Conversation with Alan Gelfand

Alan E. Gelfand was born April 17, 1945, in the Bronx, New York. He attended public grade schools and did his undergraduate work at what was then called City College of New York (CCNY, now CUNY), excelling at mathematics. He then surprised and saddened his mother by going all the way across the country to Stanford to graduate school, where he completed his dissertation in 1969 under the direction of Professor Herbert Solomon, making him an academic grandson of Herman Rubin and Harold Hotelling. Alan then accepted a faculty position at the University of Connecticut (UConn) where he was promoted to tenured associate professor in 1975 and to full professor in 1980. A few years later he became interested in decision theory, then empirical Bayes, which eventually led to the publication of Gelfand and Smith [J. Amer. Statist. Assoc. 85 (1990) 398-409], the paper that introduced the Gibbs sampler to most statisticians and revolutionized Bayesian computing. In the mid-1990s, Alan's interests turned strongly to spatial statistics, leading to fundamental contributions in spatially-varying coefficient models, coregionalization, and spatial boundary analysis (wombling). He spent 33 years on the faculty at UConn, retiring in 2002 to become the James B. Duke Professor of Statistics and Decision Sciences at Duke University, serving as chair from 2007-2012. At Duke, he has continued his work in spatial methodology while increasing his impact in the environmental sciences. To date, he has published over 260 papers and 6 books; he has also supervised 36 Ph.D. dissertations and 10 postdocs. This interview was done just prior to a conference of his family, academic descendants, and colleagues to celebrate his 70th birthday and his contributions to statistics which took place on April 19-22, 2015 at Duke University.Comment: Published at http://dx.doi.org/10.1214/15-STS521 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

CCD imaging instruments for planetary spacecraft applications

The development of new spacecraft camera systems to be used in conjunction with CCD sensors is reported. A brief overview of the science objectives and engineering constraints which influence the design of cameras for deep space is followed by a review of two current development programs, one leading to a line scan imager and the other to an area array frame camera. For each of these, a general description of the imager is given. It is evident that currently available CCDs fall short of requirements in some respects

A method of calculating compressible turbulent boundary layers

Equations of motion for calculating compressible turbulent boundary layer

Computer program for calculating laminar and turbulent boundary layer development in compressible flow

A computer program is described which performs a numerical integration of the equations of motion for a compressible two-dimensional boundary layer. Boundary layer calculations may be carried out for both laminar and turbulent flow for arbitrary Reynolds number and free stream Mach number distribution on planar or axisymmetric bodies with wall heating or cooling, longitudinal wall curvature, wall suction or blowing, and a rough or a smooth wall. A variety of options are available as initial conditions. The program can generate laminar initial conditions such as Falkner-Skan similarity solutions (so that initial wedge flows can be simulated including Blasius or stagnation point flow) or approximate equilibrium turbulent profiles. Alternatively, initial profile input data can be utilized

Materials processing in space: Early experiments

The characteristics of the space environment were reviewed. Potential applications of space processing are discussed and include metallurgical processing, and processing of semiconductor materials. The behavior of fluid in low gravity is described. The evolution of apparatus for materials processing in space was reviewed

Use of multiple discrete wall jets for delaying boundary layer separation

The effectiveness of a spanwise array of small discrete blowing nozzles in preventing separation of a turbulent boundary layer was investigated experimentally. The spacing, axial location, and momentum flux of the nozzles were varied in a systematic way, and overall performance was measured for each combination. Extensive mean velocity profiles were measured for one selected combination. Overall diffusion achieved before separation was correlated successfully with a momentum flux excess parameter, and in terms of this parameter discrete nozzles, when advantageously placed, were found to perform somewhat better than an optimally placed two-dimensional jet slot

Centered Partition Process: Informative Priors for Clustering

There is a very rich literature proposing Bayesian approaches for clustering starting with a prior probability distribution on partitions. Most approaches assume exchangeability, leading to simple representations in terms of Exchangeable Partition Probability Functions (EPPF). Gibbs-type priors encompass a broad class of such cases, including Dirichlet and Pitman-Yor processes. Even though there have been some proposals to relax the exchangeability assumption, allowing covariate-dependence and partial exchangeability, limited consideration has been given on how to include concrete prior knowledge on the partition. For example, we are motivated by an epidemiological application, in which we wish to cluster birth defects into groups and we have prior knowledge of an initial clustering provided by experts. As a general approach for including such prior knowledge, we propose a Centered Partition (CP) process that modifies the EPPF to favor partitions close to an initial one. Some properties of the CP prior are described, a general algorithm for posterior computation is developed, and we illustrate the methodology through simulation examples and an application to the motivating epidemiology study of birth defects

Compressive behavior of titanium alloy skin-stiffener specimens selectively reinforced with boron-aluminum composite

A method of selectively reinforcing a conventional titanium airframe structure with unidirectional boron-aluminum composite attached by brazing was successfully demonstrated in compression tests of short skin-stiffener specimens. In a comparison with all-titanium specimens, improvements in structural performance recorded for the composite-reinforced specimens exceeded 25 percent on an equivalent-weight basis over the range from room temperature to 700 K (800 F) in terms of both initial buckling and maximum strengths. Performance at room temperature was not affected by prior exposure at 588 K (600 F) for 1000 hours in air or by 400 thermal cycles between 219 K and 588 K (-65 F and 600 F). The experimental results were generally predictable from existing analytical procedures. No evidence of failure was observed in the braze between the boron-aluminum composite and the titanium alloy