Statistical Studies of Fading in Underwater Wireless Optical Channels in the Presence of Air Bubble, Temperature, and Salinity Random Variations (Long Version)

Optical signal propagation through underwater channels is affected by three main degrading phenomena, namely absorption, scattering, and fading. In this paper, we experimentally study the statistical distribution of intensity fluctuations in underwater wireless optical channels with random temperature and salinity variations as well as the presence of air bubbles. In particular, we define different scenarios to produce random fluctuations on the water refractive index across the propagation path, and then examine the accuracy of various statistical distributions in terms of their goodness of fit to the experimental data. We also obtain the channel coherence time to address the average period of fading temporal variations. The scenarios under consideration cover a wide range of scintillation index from weak to strong turbulence. Moreover, the effects of beam-collimator at the transmitter side and aperture averaging lens at the receiver side are experimentally investigated. We show that the use of a transmitter beam-collimator and/or a receiver aperture averaging lens suits single-lobe distributions such that the generalized Gamma and exponential Weibull distributions can excellently match the histograms of the acquired data. Our experimental results further reveal that the channel coherence time is on the order of $10^{-3}$ seconds and larger which implies to the slow fading turbulent channels

Modeling Flood Perils and Flood Insurance Program in Taiwan

Taiwan had approximately 3,000 buildings damaged by floods with an economic loss of NT$12.8 billion annually, a figure 4.5 times more than economic losses due to fire damages. Many insurers become extremely cautious when underwriting their flood policies for people living in areas that are frequently struck by floods. The rising damages also trigger the demand for a mandatory national flood insurance program. This paper describes the development of an integrated flood risk assessment model for Taiwan which contains of a hazard, vulnerability and financial analysis module. We take the perspective that the mandatory program will be provided to fire policyholders as part of building and content insurance to mitigate the financial losses. The issue of a long-term balance between fund accumulations and its claim payouts will be addressed along with policy recommendations based on the modeling results.Risk Assessment, Typhoon, Flood Insurance, Financial Analysis, Resource /Energy Economics and Policy, Risk and Uncertainty,

Ontology-based patterns for the integration of business processes and enterprise application architectures

Increasingly, enterprises are using Service-Oriented Architecture (SOA) as an approach to Enterprise Application Integration (EAI). SOA has the potential to bridge the gap between business and technology and to improve the reuse of existing applications and the interoperability with new ones. In addition to service architecture descriptions, architecture abstractions like patterns and styles capture design knowledge and allow the reuse of successfully applied designs, thus improving the quality of software. Knowledge gained from integration projects can be captured to build a repository of semantically enriched, experience-based solutions. Business patterns identify the interaction and structure between users, business processes, and data. Specific integration and composition patterns at a more technical level address enterprise application integration and capture reliable architecture solutions. We use an ontology-based approach to capture architecture and process patterns. Ontology techniques for pattern definition, extension and composition are developed and their applicability in business process-driven application integration is demonstrated

Inverz szóráselméleti kutatások = Problems of inverse scattering theory

Kifejlesztettünk egy új fix-energiás inverz kvantum szórás módszert. Szórási adatok invertálására alkalmassá tettük a Cox-Thompson inverz kvantum szórás eljárást. Bose-kondenzátumok ütközéséből származó fázistolás adatokból határoztunk meg effektív Rb-Rb atomi potenciálokat. Kétkomponensű Bose-Einstein kondenzátumok stabilitását vizsgáltuk. Megbecsültük a különző specimenek közti szóráshosszak azon tartományát, amely esetében szoliton gerjesztések létrejöhetnek a kondenzátumban. Kifejelesztettünk és numerikusan teszteltünk egy csatolt Gross-Pitaevskii egyenlet megoldó programot. A kutatási munkatervben vállalt 7 publikáció és 4 konferencia előadást jelentősen túl teljestettük, amennyiben 3 disszertáció, 3 konferenciakiadvány és 25 publiáció született az egy évvel meghosszabbított, 5 éves 4 résztvevős kutatás alatt. Ezen kívül egy nemzetközi inverz kvantum szórás konferenciát is rendeztünk (www.math.bme.hu/~hirvath/iqs). | New fix-energy inverse quantum scattering method has been developed. The Cox-Thompson inverse quantum scattering procedure has been made appropriate to invert scattering data. We have determined Rb-Rb atomic scattering potential from data extracted from Bose condensate collisions. Stability of two-component Bose-Einstein condensates has been inversigated. Assessments have been given to values of interspecies scattering length at which soliton excitations are to be expected to exist inside the condensate. We have developed and numerically tested an evolution code which simulate the time evolution of a two-component Bose-Einstein condensate accoring to the Gross-Pitaevskii equation. The original undertaking has been well overcompleted in that 3 theses (1 Phd and 2 DSc), 3 conference contribution and 25 publications in journals of high international reputation have been delivered ba the 4 participants during the 5 years research. Besides also an international inverse quantum scattering conference has been held (www.math.bme.hu/~hirvath/iqs)

Reliability analysis and fault-tolerant system development for a redundant strapdown inertial measurement unit

A methodology is developed and applied for quantitatively analyzing the reliability of a dual, fail-operational redundant strapdown inertial measurement unit (RSDIMU). A Markov evaluation model is defined in terms of the operational states of the RSDIMU to predict system reliability. A 27 state model is defined based upon a candidate redundancy management system which can detect and isolate a spectrum of failure magnitudes. The results of parametric studies are presented which show the effect on reliability of the gyro failure rate, both the gyro and accelerometer failure rates together, false alarms, probability of failure detection, probability of failure isolation, and probability of damage effects and mission time. A technique is developed and evaluated for generating dynamic thresholds for detecting and isolating failures of the dual, separated IMU. Special emphasis is given to the detection of multiple, nonconcurrent failures. Digital simulation time histories are presented which show the thresholds obtained and their effectiveness in detecting and isolating sensor failures

Investigations of simulated aircraft flight through thunderstorm outflows

The effects of wind shear on aircraft flying through thunderstorm gust fronts were investigated. A computer program was developed to solve the two dimensional, nonlinear equations of aircraft motion, including wind shear. The procedure described and documented accounts for spatial and temporal variations of the aircraft within the flow regime. Analysis of flight paths and control inputs necessary to maintain specified trajectories for aircraft having characteristics of DC-8, B-747, augmentor wing STOL, and DHC-6 aircraft was recorded. From the analysis an attempt was made to find criteria for reduction of the hazards associated with landing through thunderstorm gust fronts