Direct numerical study of hypersonic flow about a swept parabolic body

Direct numerical simulations (DNS) of hypersonic flow about a swept parabolic body have been performed to study the global stability of flow in the leading-edge region of a swept blunt body. Previous stability investigations have been based on local models but have not fully succeeded in reproducing the established experimental findings. The current flow configuration represents a more realistic model and is thus expected to resolve some of the remaining questions. However, novel approaches like DNS-based global stability theory are necessary for such flow models and are employed in this study. As a result, boundary-layer modes have been identified by different but complementary techniques as the dominant instability mechanism. The DNS starting with small-amplitude white noise provide further evidence for the presence of non-modal effects which may be important in the subcritical regime. From a methodological point of view, the potential for quantitative flow analysis by combining numerical simulations with advanced iterative techniques represents a promising direction for investigating the governing physical processes of complex flows.     

Comments on “Robust optimal design and convergence properties analysis of iterative learning control approaches” and “On the P-type and Newton-type ILC schemes for dynamic systems with non-affine input factors”

The papers by Xu and Tan [Robust optimal design and convergence properties analysis of iterative learning control approaches, Automatica 38 (2002) 1867-1880], and Xu and Tan [On the P-type and Newton-type ILC schemes for dynamic systems with non-affine input factors, Automatica 38 (2002) 1237-1242], give a convergence analysis for several iterative learning control approaches. Unfortunately, these papers contains several mathematical errors that render the proofs of the claimed results invalid. As there are no obvious ways to correct these errors, the results presented in these papers are questionable.     

Beneficial and harmful explanatory machine learning

Machine Learning - Given the recent successes of Deep Learning in AI there has been increased interest in the role and need for explanations in machine learned theories. A distinct notion in this...     

Automated identification of different lead users regarding the innovation process

Lead users are often established in an organizational innovation process to attenuate the difficulties a company faces, such as high costs or the obscurity of customers’ needs. But to benefit from these lead users a major challenge is to characterize and identify them especially in the fast-moving world of social media. Therefore, we aim to design a tool to identify lead users automatically for the two innovation phases (“Idea generation” and “Development”) by combining different approaches such as social network analysis, topic modeling and sentiment analysis. Thus, we consulted the design science approach and applied our artifact to 11,481 contributions of an online digital platform. The technical realization of the six different characteristics and their respective weighting according to the different phases of the innovation process resulted in different lead users and showed the necessity of distinguishing between them. Our results were evaluated and confirmed by the identified lead users and an expert. Hence, our investigation contributes to both practice and theory (kernel theories and design theory) alike.

     

Evaluating the reduced flight deck crew concept using cognitive work analysis and social network analysis: comparing normal and data-link outage scenarios

Cognition, Technology & Work - The aim of the present paper is to demonstrate how a subset of methods from Cognitive Work Analysis (CWA) in combination with Social Network Analysis (SNA) can be...     

On techniques for angle compensation in nonideal iris recognition.

The popularity of the iris biometric has grown considerably over the past two to three years. Most research has been focused on the development of new iris processing and recognition algorithms for frontal view iris images. However, a few challenging directions in iris research have been identified, including processing of a nonideal iris and iris at a distance. In this paper, we describe two nonideal iris recognition systems and analyze their performance. The word "nonideal" is used in the sense of compensating for off-angle occluded iris images. The system is designed to process nonideal iris images in two steps: 1) compensation for off-angle gaze direction and 2) processing and encoding of the rotated iris image. Two approaches are presented to account for angular variations in the iris images. In the first approach, we use Daugman's integrodifferential operator as an objective function to estimate the gaze direction. After the angle is estimated, the off-angle iris image undergoes geometric transformations involving the estimated angle and is further processed as if it were a frontal view image. The encoding technique developed for a frontal image is based on the application of the global independent component analysis. The second approach uses an angular deformation calibration model. The angular deformations are modeled, and calibration parameters are calculated. The proposed method consists of a closed-form solution, followed by an iterative optimization procedure. The images are projected on the plane closest to the base calibrated plane. Biorthogonal wavelets are used for encoding to perform iris recognition. We use a special dataset of the off-angle iris images to quantify the performance of the designed systems. A series of receiver operating characteristics demonstrate various effects on the performance of the nonideal-iris-based recognition system.     

Analysis of the human immune response to vaccinia by use of a novel protein microarray suggests that antibodies recognize less than 10% of the total viral proteome

Control of smallpox by mass vaccination was one of the most effective public health measures ever employed for eradicating a devastating infectious disease. However, new methods are needed for monitoring smallpox immunity within current vulnerable populations, and for the development of replacement vaccines for use by immunocompromized or low-responding individuals. As a measure for achieving this goal, we developed a protein microarray of the vaccinia virus proteome by using high-throughput baculovirus expression and purification of individual elements. The array was validated with therapeutic-grade, human hyperimmune sera, and these data were compared to results obtained from individuals vaccinated against smallpox using Dryvax. A high level of reproducibility with a very low background were apparent in repetitive assays that confirmed previously reported antigens and identified new proteins that may be important for neutralizing viral infection. Our results suggest that proteins recognized by antibodies from all vaccinees constituted <10% of the total vaccinia proteome.     

Reconciling fault-tolerant distributed computing and systems-on-chip

Classic distributed computing abstractions do not match well the reality of digital logic gates, which are the elementary building blocks of Systems-on-Chip (SoCs) and other Very Large Scale Integrated (VLSI) circuits: Massively concurrent, continuous computations undermine the concept of sequential processes executing sequences of atomic zero-time computing steps, and very limited computational resources at gate-level make even simple operations prohibitively costly. In this paper, we introduce a modeling and analysis framework based on continuous computations and zero-bit message channels, and employ this framework for the correctness & performance analysis of a distributed fault-tolerant clocking approach for Systems-on-Chip (SoCs). Starting out from a “classic” distributed Byzantine fault-tolerant tick generation algorithm, we show how to adapt it for direct implementation in clockless digital logic, and rigorously prove its correctness and derive analytic expressions for worst case performance metrics like synchronization precision and clock frequency. Rather than on absolute delay values, both the algorithm’s correctness and the achievable synchronization precision depend solely on the ratio of certain path delays. Since these ratios can be mapped directly to placement & routing constraints, there is typically no need for changing the algorithm when migrating to a faster implementation technology and/or when using a slightly different layout in an SoC.