Alan F. Karr

Bio: Alan F. Karr is an academic researcher from Research Triangle Park. The author has contributed to research in topics: Distributed database & Software system. The author has an hindex of 15, co-authored 27 publications receiving 2413 citations. Previous affiliations of Alan F. Karr include National Institutes of Health.

Does code decay? Assessing the evidence from change management data

Abstract: A central feature of the evolution of large software systems is that change-which is necessary to add new functionality, accommodate new hardware, and repair faults-becomes increasingly difficult over time. We approach this phenomenon, which we term code decay, scientifically and statistically. We define code decay and propose a number of measurements (code decay indices) on software and on the organizations that produce it, that serve as symptoms, risk factors, and predictors of decay. Using an unusually rich data set (the fifteen-plus year change history of the millions of lines of software for a telephone switching system), we find mixed, but on the whole persuasive, statistical evidence of code decay, which is corroborated by developers of the code. Suggestive indications that perfective maintenance can retard code decay are also discussed.

Permeability of cracked concrete

Abstract: The goal of the research presented here was to study the relationship between cracking and water permeability. A feedback-controlled test was used to generate width-controlled cracks. Water permeability was evaluated by a low-pressure water permeability test. The factors chosen for the experimental design were material type (paste, mortar, normal and high strength concrete), thickness of the sample and average width of the induced cracks (ranging from 50 to 350 micrometers). The water permeability test results indicated that the relationships between permeability and material type differ for uncracked and cracked material, and that there was little thickness effect. Permeability of uncracked material decreased from paste, mortar, normal strength concrete (NSC) to high strength concrete (HSC). Water permeability of cracked material significantly increased with increasing crack width. For cracks above 100 microns, NSC showed the highest permeability coefficient, where as mortar showed the lowest one.

Effect of Cracking on Water and Chloride Permeability of Concrete

Abstract: The goal of this research was to study the relationship between cracking and concrete permeability and to support accounting for permeability and cracking resistance to other factors besides strength, as criteria to be considered in mix design to achieve a durable concrete. The effect of material composition [normal-strength concrete (NSC) and high-strength concrete (HSC) with two different mix designs] and crack width (ranging from 50 to 400 μm) on water and chloride permeability were examined. Cracks of designed widths were induced in the concrete specimens using a feedback-controlled splitting tensile test. Chloride permeability of the cracked samples was evaluated using a rapid chloride permeability test and the water permeability of cracked concrete was then evaluated by a low-pressure water permeability test. Uncracked HSC was less water permeable than NSC, as expected, but cracking changed the material behavior in terms of permeability. Both NSC and HSC were affected by cracking, and the water perm...

Secure Regression on Distributed Databases

Abstract: This article presents several methods for performing linear regression on the union of distributed databases that preserve, to varying degrees, confidentiality of those databases. Such methods can be used by federal or state statistical agencies to share information from their individual databases, or to make such information available to others. Secure data integration, which provides the lowest level of protection, actually integrates the databases, but in a manner that no database owner can determine the origin of any records other than its own. Regression, associated diagnostics, or any other analysis then can be performed on the integrated data. Secure multiparty computation, based on shared local statistics effects computations necessary to compute least squares estimators of regression coefficients and error variances by means of analogous local computations that are combined additively using the secure summation protocol. We also provide two approaches to model diagnostics in this setting, one usi...

The Design and Analysis of Experiments

Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

Federated Machine Learning: Concept and Applications

Abstract: Today’s artificial intelligence still faces two major challenges. One is that, in most industries, data exists in the form of isolated islands. The other is the strengthening of data privacy and security. We propose a possible solution to these challenges: secure federated learning. Beyond the federated-learning framework first proposed by Google in 2016, we introduce a comprehensive secure federated-learning framework, which includes horizontal federated learning, vertical federated learning, and federated transfer learning. We provide definitions, architectures, and applications for the federated-learning framework, and provide a comprehensive survey of existing works on this subject. In addition, we propose building data networks among organizations based on federated mechanisms as an effective solution to allowing knowledge to be shared without compromising user privacy.

Federated Machine Learning: Concept and Applications

Abstract: Today's AI still faces two major challenges. One is that in most industries, data exists in the form of isolated islands. The other is the strengthening of data privacy and security. We propose a possible solution to these challenges: secure federated learning. Beyond the federated learning framework first proposed by Google in 2016, we introduce a comprehensive secure federated learning framework, which includes horizontal federated learning, vertical federated learning and federated transfer learning. We provide definitions, architectures and applications for the federated learning framework, and provide a comprehensive survey of existing works on this subject. In addition, we propose building data networks among organizations based on federated mechanisms as an effective solution to allow knowledge to be shared without compromising user privacy.

On Engineered Cementitious Composites (ECC)

Abstract: This article surveys the research and development of Engineered Cementitious Composites (ECC) over the last decade since its invention in the early 1990's. The importance of micromechanics in the materials design strategy is emphasized. Observations of unique characteristics of ECC based on a broad range of theoretical and experimental research are examined. The advantageous use of ECC in certain categories of structural, and repair and retrofit applications is reviewed. While reflecting on past advances, future challenges for continued development and deployment of ECC are noted. This article is based on a keynote address given at the International Workshop on Ductile Fiber Reinforced Cementitious Composites (DFRCC) - Applications and Evaluations, sponsored by the Japan Concrete Institute, and held in October 2002 at Takayama, Japan.