Investigations of Free Turbulent Mixing

A discussion of the integral relations for the flow of the boundary-layer type is presented. It is shown that the characteristic laws of spread of jets, wakes, and so forth, can be obtained directly for the laminar case and, with the help of dimensional reasoning, for the turbulent case as well. Measurements of the mean velocity, the intensity and scale of the turbulent fluctuations, and of the turbulent shear in a two-dimensional mixing zone are presented. The results of these measurements are compared with the mixing-length theories. It is shown that both mixing length and exchange coefficient vary across the mixing zone. The theories based on the assumption of constant mixing length or exchange coefficient are thus in error. A discussion of the energy balance of the fluctuating motion is given and the triple point correlation is estimated

Game theoretic aspects of distributed spectral coordination with application to DSL networks

In this paper we use game theoretic techniques to study the value of cooperation in distributed spectrum management problems. We show that the celebrated iterative water-filling algorithm is subject to the prisoner's dilemma and therefore can lead to severe degradation of the achievable rate region in an interference channel environment. We also provide thorough analysis of a simple two bands near-far situation where we are able to provide closed form tight bounds on the rate region of both fixed margin iterative water filling (FM-IWF) and dynamic frequency division multiplexing (DFDM) methods. This is the only case where such analytic expressions are known and all previous studies included only simulated results of the rate region. We then propose an alternative algorithm that alleviates some of the drawbacks of the IWF algorithm in near-far scenarios relevant to DSL access networks. We also provide experimental analysis based on measured DSL channels of both algorithms as well as the centralized optimum spectrum management

Assurance of learning standards and scaling strategies to enable expansion of experiential learning courses in management education

In today’s dynamic globalized business environment, management educators must develop pedagogies that support students to manage and lead in rapidly changing business contexts. An increasing number of institutions use experiential learning as a component of their curriculum to address this challenge. Initially, a response to industry criticism that graduates were unable effectively apply skills needed to be successful, experiential learning has become a baseline expectation in management education programs. Students increasingly expect opportunities to practice and demonstrate competency in the theories they learn in the classroom by applying them in real-world projects. However, expanding such opportunities for students is limited by a unique set of complex administrative challenges inherent in this approach. To expand opportunities for students, institutions must overcome scalability obstacles resulting from the customized nature of the offerings. Business challenges where student teams work with external partners provide a real world learning experience. But they also pose difficulty in applying a standardized approach to assurance of learning. Course content must be redeveloped each time the course is offered, as external projects must be sourced, leading to input and output variation. Advising, monitoring, and assessing students is resource intensive, because at many schools each team is assigned a different business challenge. This article offers a set of assurance of learning standards that institutions can apply to project-based experiential learning courses and posits that greater cross-departmental integration in sourcing projects and better use of technology can increase the efficacy and efficiency of the courses to address the scalability issue.Educatio

Semi-Supervised Sound Source Localization Based on Manifold Regularization

Conventional speaker localization algorithms, based merely on the received microphone signals, are often sensitive to adverse conditions, such as: high reverberation or low signal to noise ratio (SNR). In some scenarios, e.g. in meeting rooms or cars, it can be assumed that the source position is confined to a predefined area, and the acoustic parameters of the environment are approximately fixed. Such scenarios give rise to the assumption that the acoustic samples from the region of interest have a distinct geometrical structure. In this paper, we show that the high dimensional acoustic samples indeed lie on a low dimensional manifold and can be embedded into a low dimensional space. Motivated by this result, we propose a semi-supervised source localization algorithm which recovers the inverse mapping between the acoustic samples and their corresponding locations. The idea is to use an optimization framework based on manifold regularization, that involves smoothness constraints of possible solutions with respect to the manifold. The proposed algorithm, termed Manifold Regularization for Localization (MRL), is implemented in an adaptive manner. The initialization is conducted with only few labelled samples attached with their respective source locations, and then the system is gradually adapted as new unlabelled samples (with unknown source locations) are received. Experimental results show superior localization performance when compared with a recently presented algorithm based on a manifold learning approach and with the generalized cross-correlation (GCC) algorithm as a baseline

On the Spectrum of Isotropic Turbulence

Measurements of the spectrum and correlation functions at large Reynolds number (RN ~ 10^5 based on the grid mesh) have been made, as well as a series of accurate spectrum measurements at lower Reynolds number (RN ~ 10^4). The results are compared with the theoretical laws proposed in recent years. It is found that the measurements at large Reynolds numbers exhibit a range of frequencies where the spectrum is nearly of the form n^- 5/3. The largest part of the spectrum in the initial stage of decay at the lower Reynolds number was found to follow closely the simple spectrum A/[B + n^2] , where A and B are constants and n is the frequency of fluctuation. At x/M = 1000 (where x is the distance behind the grid and M is the mesh size) the spectrum approaches a Gaussian distribution. The second, fourth, and sixth moments of the spectrum have been computed from the measurements and are discussed In relation to theoretical results. The significance of the number of zeros of the fluctuating velocity u(t) is discussed and examples of measurements for the determination of the microscale of turbulence [lambda] from zero counts are given