Nyquist Frequency in Sequentially Sampled Data

This paper studies the sequential sampling scheme as a solution to the problem of aliasing, where the sampling interval is restricted to a minimum allowable value. Sequential sampling is analyzed and it is proved that when the sampling ratio is an integral number, the associated spectral estimates give a Nyquist frequency . This sampling scheme can, therefore, be employed to yield a required cut- off frequency.Nyquist Freqency; cut-off frequency; Sequential Sampling; Spectral Density Function

On the Economic Value and Price-Responsiveness of Ramp-Constrained Storage

The primary concerns of this paper are twofold: to understand the economic value of storage in the presence of ramp constraints and exogenous electricity prices, and to understand the implications of the associated optimal storage management policy on qualitative and quantitative characteristics of storage response to real-time prices. We present an analytic characterization of the optimal policy, along with the associated finite-horizon time-averaged value of storage. We also derive an analytical upperbound on the infinite-horizon time-averaged value of storage. This bound is valid for any achievable realization of prices when the support of the distribution is fixed, and highlights the dependence of the value of storage on ramp constraints and storage capacity. While the value of storage is a non-decreasing function of price volatility, due to the finite ramp rate, the value of storage saturates quickly as the capacity increases, regardless of volatility. To study the implications of the optimal policy, we first present computational experiments that suggest that optimal utilization of storage can, in expectation, induce a considerable amount of price elasticity near the average price, but little or no elasticity far from it. We then present a computational framework for understanding the behavior of storage as a function of price and the amount of stored energy, and for characterization of the buy/sell phase transition region in the price-state plane. Finally, we study the impact of market-based operation of storage on the required reserves, and show that the reserves may need to be expanded to accommodate market-based storage

Dependent Nonparametric Bayesian Group Dictionary Learning for online reconstruction of Dynamic MR images

In this paper, we introduce a dictionary learning based approach applied to the problem of real-time reconstruction of MR image sequences that are highly undersampled in k-space. Unlike traditional dictionary learning, our method integrates both global and patch-wise (local) sparsity information and incorporates some priori information into the reconstruction process. Moreover, we use a Dependent Hierarchical Beta-process as the prior for the group-based dictionary learning, which adaptively infers the dictionary size and the sparsity of each patch; and also ensures that similar patches are manifested in terms of similar dictionary atoms. An efficient numerical algorithm based on the alternating direction method of multipliers (ADMM) is also presented. Through extensive experimental results we show that our proposed method achieves superior reconstruction quality, compared to the other state-of-the- art DL-based methods

Automated Synthesis of Distributed Self-Stabilizing Protocols

In this paper, we introduce an SMT-based method that automatically synthesizes a distributed self-stabilizing protocol from a given high-level specification and network topology. Unlike existing approaches, where synthesis algorithms require the explicit description of the set of legitimate states, our technique only needs the temporal behavior of the protocol. We extend our approach to synthesize ideal-stabilizing protocols, where every state is legitimate. We also extend our technique to synthesize monotonic-stabilizing protocols, where during recovery, each process can execute an most once one action. Our proposed methods are fully implemented and we report successful synthesis of well-known protocols such as Dijkstra's token ring, a self-stabilizing version of Raymond's mutual exclusion algorithm, ideal-stabilizing leader election and local mutual exclusion, as well as monotonic-stabilizing maximal independent set and distributed Grundy coloring

Effects Of Road Geometry And Roadside Trees On Urban Road Thermal Performance In Penang

Penyelidikan ini merupakan kajian tentang kesan sifat fizikal jalan dan pokok bersebelahan jalan terhadap perilaku termal jalan di Pulau Pinang Malaysia; iaitu di kawasan tropika dengan keamatan radiasi solar yang tinggi. This research investigates the effects of the physical road characteristics and roadside tree features on the road thermal performance in Penang, Malaysia; located in tropical region where there is high solar radiation intensity

Improving flow-induced hemolysis prediction models.

Partial or complete failure of red blood cell membrane, also known as hemolysis, is a persistent issue with almost all blood contacting devices. Many experimental and theoretical contributions over the last few decades have increased insight into the mechanisms of mechanical hemolysis in both laminar and turbulent flow regimes, with the ultimate goal of developing a comprehensive, mechanistic and universal hemolysis prediction model. My research is broadly divided into two sections: theoretical/analytical/Computational Fluid Dynamics (CFD) analyses and experimental tests. The first part of my research revolved entirely around analyzing the simplest and most popular hemolysis model, commonly called as the power-law model. This model was developed only for laminar pure shear flow within a limited range of exposure time. Subsequently, modified versions of this model have been developed to be used for more complex flows. Many of these modified models assume that hemolysis scales with a resultant, scalar stress representing all components of the fluid stress tensor. The most common representative stress used in the power-law model is a von-Mises-like stress. However, using membrane tension models for pure shear and pure extension in both laminar and turbulent flows, for some simple example cases, we have shown that scalar stress alone is inadequate for scaling hemolysis. Alternatively, the rate of viscous energy dissipation rate has also been proposed as the parameter to scale hemolysis with. Applying the same order-of-magnitude estimate as vi mentioned above, we have found that dissipation rate even behaves worse than the resultant scalar stress for hemolysis prediction. It is therefore concluded that energy dissipation rate alone is also not sufficient to universally scale blood damage across complex flows. These show that a realistic model of hemolysis must take into account different responses of the viscoelastic cell membrane to different stress type. Various discretized version of the power-law model has also been introduced for post-processing of the CFD results. The power law can be either discretized in space, Eulerian treatment, or in time, Lagrangian treatment. Our study on the Eulerian approach revealed that the current equations used in the literature has a missing term, and thus incorrect. We also examined the mathematical stability of the discretized power-law model, and found that it may introduce significant error in red cell damage prediction for certain pathlines with specific stress history. Experimental results on deformation of red cell in pure shear flow is present for a relatively wide range of shear rates. However, red cell deformation/elongation in pure laminar extensional flow is scarce, with only one publication reporting their results on red cell deformation for only up to stress level of 10 Pa. For the experimental part of my research, we conducted experiments to observe the difference in deformation of red cell in pure shear and pure extensional flows, for stresses beyond what has already been reported in the literature. This dissertation is composed of three chapters. Chapter I is the literature survey and introductory materials. Chapter II contains the discussion and results for the theoretical/analytical/CFD part of the research. Finally, discussion and results for the experimental tests are presented in Chapter III