Algorithms for Constructing Overlay Networks For Live Streaming

We present a polynomial time approximation algorithm for constructing an overlay multicast network for streaming live media events over the Internet. The class of overlay networks constructed by our algorithm include networks used by Akamai Technologies to deliver live media events to a global audience with high fidelity. We construct networks consisting of three stages of nodes. The nodes in the first stage are the entry points that act as sources for the live streams. Each source forwards each of its streams to one or more nodes in the second stage that are called reflectors. A reflector can split an incoming stream into multiple identical outgoing streams, which are then sent on to nodes in the third and final stage that act as sinks and are located in edge networks near end-users. As the packets in a stream travel from one stage to the next, some of them may be lost. A sink combines the packets from multiple instances of the same stream (by reordering packets and discarding duplicates) to form a single instance of the stream with minimal loss. Our primary contribution is an algorithm that constructs an overlay network that provably satisfies capacity and reliability constraints to within a constant factor of optimal, and minimizes cost to within a logarithmic factor of optimal. Further in the common case where only the transmission costs are minimized, we show that our algorithm produces a solution that has cost within a factor of 2 of optimal. We also implement our algorithm and evaluate it on realistic traces derived from Akamai's live streaming network. Our empirical results show that our algorithm can be used to efficiently construct large-scale overlay networks in practice with near-optimal cost

Dynamic Single-Photon Emission Computed Tomography Data Analysis: Capabilities for Determining Functional Significance of Coronary Artery Atherosclerosis

The aim of the study was to develop the method for collecting and processing scintigraphic data to determine myocardial flow reserve by using gamma-camera with a new type detector based on Cadmium Zinc Telluride (CZT). Sixteen coronary artery disease patients and nine healthy volunteers received cardiac dynamic single-photon emission computed tomography with technetium 99m methoxyisobutylisonitrile ({99m}Tc-MIBI) at rest and during pharmacologic stress test. Data processing involved a formation of regions of interest from the left ventricular (LV) cavity and myocardial walls to build activity-time curves. Myocardial flow reserve index was determined as a quotient of two ratios of mean myocardial counts to area under a curve peak from LV cavity during stress test and at rest. Mean values of myocardial flow reserve index were 1.86 (1.59; 2.2) in group of healthy volunteers and 1.39 (1.12; 1.69) in patients with multivessel coronary artery disease. When the value of this index was less than 1.77, the method allowed for identification of multivessel disease with sensitivity and specificity of 81.8% and 66.7%, respectively. Standard myocardial perfusion scintigraphy in combination with the method of myocardial flow reserve index determination allows for increasing diagnostic significance of the scintigraphic approach for assessment of coronary microcirculation lesions in multivessel coronary artery disease

Quality of Enterprise Management During Ramp-Up Preparation and Launch: Concept and Evaluation Method

AbstractCurrent economic conditions are forcing market players to bring new products to consumers rapidly, maintaining the high quality and providing the reasonable price. The concept of ramp-up management is designed to meet this request. The implementation of this concept in practice, in particular for Russian industrial enterprises, causes certain challenges. Correspondingly the quality of enterprise management becomes a factor that appreciably influences the ramp-up execution. In this regard, the study designed to develop the theoretical provision and methodological approach towards the assessment of the management quality is viewed as relevant to the practical needs of enterprises during the ramp-up and technological re-equipment.In the present article we propose a conceptual approach to assess the quality of enterprise management on the basis of value chain methodology which is relevant to the conditions of ramp-up preparation and implementation. By the “quality of management” notion in the study it is proposed to understand the totality of objectively existing properties and characteristics of enterprise management system which adequately reflects all aspects of its activities and contributes to the efficiency of enterprises development and competitiveness

Optical rectification and down-conversion of fs pulses into mid-IR and THz range in GaSe1-xSx

Design of top S-doped GaSe growth technology is completed. New methods for characterization of high optical quality crystals are proposed that allowed selection optimally doped crystals. Frequency conversion of fs pulses into 6.5–35 μm and into 0.2–4.5 THz is realized. S-doped crystals demonstrated advantages from 50–70% in the first experiments up to 8.5–15 times in the following experiments depending on experimental conditions. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only