Generator Insulation-Aging On-Line Monitoring Technique Based on Fiber Optic Detecting Technology

The relationship between insulation aging and generator lifespan using fiber optic sensors (FOSs) is explored to ultimately improve asset lifespan through smart choices in running conditions and maintenance. Insulation aging is a major factor that causes generator failure. FOS provides the rare opportunity of being installed up close to the insulation, monitoring degradations that are otherwise difficult to detect. FOSs, unlike purely electrical transducers, are immune to high voltage (HV) and strong electromagnetic (EM) fields. They are small and have a proven long life by their deployment in the Telecom industry. The proposed FOS is a Fabry-Perot cavity made up of two identical fiber Bragg gratings (FBGs) using light wave interference as the working principle. Such architecture delivers simultaneous vibration (10 Hz–1 kHz) and temperature (0.1°C resolution) monitoring, both helping to spot irregular vibration patterns (signatures) and hot-spots inside the generator stator slots. The signal processing unit equipped with a gateway device can help to connect the large volume of sensor data, allowing correlation with the supervisory control and data acquisition (SCADA) system data of the plant. This chapter also elaborates on the field test jointly conducted with Calpine Corporation and Oz Optics, Ltd. (Ottawa, Ontario, Canada)

The danger of vibration in power transformers

A thin fiber optics sensor, VibroFibre, has been developed to fit into a 2 mm gap in transformer windings for directly measuring the winding vibration. The new innovation is aimed to help the transformer users to safely extend service lives of their assets and to mitigate risk of unscheduled shutdown due to premature equipment failure. The optic fiber based vibration sensor can be installed inside a transformer and the resulted vibration measurement is no longer affected by various noise sources from peripheral equipment. The vibration frequency spectrum measured inside an oil-filled transformer, shows a signature of wider band ranging between 20 Hz to 1000 Hz. The new sensor has shown superior performance, especially in its response to frequencies below 100 Hz. When combined with the new Long Gauge technology, the response goes as low as 5 Hz. The sensor’s small size makes it possible to install the sensors in the winding spacers with built-in cradle-like slots, which helps avoid possible disturbance to the cooling oil flow

Optimal Property Management Strategies

This paper examines the optimal operation strategies for income properties. Specifically, the rental rate and the operating expense should be set at levels to maximize the return on investment. The results suggest that for a given demand curve of a specific rental property, there exist optimal levels of the income ratio, the operating expense ratio, and the vacancy rate. With a Cobb-Douglas demand curve, we derived closed form solutions of these optimal ratios for a given income property. The relevant local comparative statics of these ratios also are derived. These comparative statics also provide insight into the optimal building size and optimal rehabilitation decisions. An empirical case study was conducted to demonstrate how the model can be applied in real life situations.Rental Property, Vacancy Rate; Operating Strategy, Profit Optimization

Galois groups of multivariate Tutte polynomials

The multivariate Tutte polynomial $\hat Z_M$ of a matroid $M$ is a generalization of the standard two-variable version, obtained by assigning a separate variable $v_e$ to each element $e$ of the ground set $E$. It encodes the full structure of $M$. Let \bv = \{v_e\}_{e\in E}, let $K$ be an arbitrary field, and suppose $M$ is connected. We show that $\hat Z_M$ is irreducible over K(\bv), and give three self-contained proofs that the Galois group of $\hat Z_M$ over K(\bv) is the symmetric group of degree $n$, where $n$ is the rank of $M$. An immediate consequence of this result is that the Galois group of the multivariate Tutte polynomial of any matroid is a direct product of symmetric groups. Finally, we conjecture a similar result for the standard Tutte polynomial of a connected matroid.Comment: 8 pages, final version, to appear in J. Alg. Comb. Substantial revisions, including the addition of two alternative proofs of the main resul

The use of public sports facilities by the disabled in England

Disabled sports participants are a small proportion of sports participants at English public sports centres; but they are important to the social inclusion agenda. This paper aims to provide a detailed insight into the preferences and behaviour of disabled sports participants. It investigated whether there were statistical differences: first, between the disabled sports participants and the non-disabled sports participants in terms of (1) social demographics, (2) patterns of participation, (3) travel, (4) sports activities and (5) customer satisfaction; and second, between age, ethnic, socio-economic and gender groups of their subsamples, on (2), (4) and (5) again. Disability is defined as having any long term illness or health problem which limits a person's daily activities or the work that a person can do. The data collected through the National Benchmarking Service, for 458 sports centres from 2005 to 2011, revealed that about 9% of over 150,000 sports participants were disabled. Swimming, using fitness equipment and keep fit related exercises were the top three most frequently stated main sports activities by the disabled. It was also more likely for the disabled to participate in organised activities, own a leisure card and participate regularly when compared with the non-disabled participants. In addition, the disabled were also more likely than the non-disabled to travel to the centre by public transport, from home and travel a longer journey time. The industry weaknesses as identified by the disabled relate to physical evidence of the sports centres, particularly cleanliness attributes. Measures that can be taken to increase sports participation by the disabled include competent support at sports centres, promotions through discount schemes or leisure cards, and free transportation to sport centres in catchment areas with high proportions of disabled in their population.</p

A Cox Model for Biostatistics of the Future

Professor Sir David R. Cox (DRC) is widely acknowledged as among the most important scientists of the second half of the twentieth century. He inherited the mantle of statistical science from Pearson and Fisher, advanced their ideas, and translated statistical theory into practice so as to forever change the application of statistics in many fields, but especially biology and medicine. The logistic and proportional hazards models he substantially developed, are arguably among the most influential biostatistical methods in current practice. This paper looks forward over the period from DRC\u27s 80th to 90th birthdays, to speculate about the future of biostatistics, drawing lessons from DRC\u27s contributions along the way. We consider Cox\u27s model of biostatistics, an approach to statistical science that: formulates scientific questions or quantities in terms of parameters gamma in probability models f(y; gamma) that represent in a parsimonious fashion, the underlying scientific mechanisms (Cox, 1997); partition the parameters gamma = theta, eta into a subset of interest theta and other nuisance parameters eta necessary to complete the probability distribution (Cox and Hinkley, 1974); develops methods of inference about the scientific quantities that depend as little as possible upon the nuisance parameters (Barndorff-Nielsen and Cox, 1989); and thinks critically about the appropriate conditional distribution on which to base infrences. We briefly review exciting biomedical and public health challenges that are capable of driving statistical developments in the next decade. We discuss the statistical models and model-based inferences central to the CM approach, contrasting them with computationally-intensive strategies for prediction and inference advocated by Breiman and others (e.g. Breiman, 2001) and to more traditional design-based methods of inference (Fisher, 1935). We discuss the hierarchical (multi-level) model as an example of the future challanges and opportunities for model-based inference. We then consider the role of conditional inference, a second key element of the CM. Recent examples from genetics are used to illustrate these ideas. Finally, the paper examines causal inference and statistical computing, two other topics we believe will be central to biostatistics research and practice in the coming decade. Throughout the paper, we attempt to indicate how DRC\u27s work and the Cox Model have set a standard of excellence to which all can aspire in the future

Mechanical loading impacts intramuscular drug transport : impact on local drug delivery

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2008.Includes bibliographical references (leaves 152-166).Controlled-release drug-delivery systems enable efficient and defined administration of therapeutic agents to target tissues. However, ultimate drug distribution and pharmacologic effect are determined by target tissue pharmacokinetics. In muscular tissues, complex architecture that is further augmented by dynamic motion and contraction can alter the pharmacokinetics and deposition of locally delivered macromolecules. We developed a system and applied a quantitative schema to investigate the impact of controlled mechanical loads applied to skeletal and cardiac muscle tissue on intramuscular transport of locally delivered drug. In a series of studies, we examined how the interaction between architectural configuration and functional mechanics alters the transport of drugs across both physicochemical and binding properties. We correlated these pharmacokinetic effects with characteristic parameters in the physiologic range of the tissue to derive mechanistic insight into the fundamental structural and dynamic elements that underlie these effects. While previous studies have revealed the unilateral scaling of substrate uptake with mechanical influences, we elucidated an architecturally defined pharmacokinetic setpoint whereby maximal drug penetration corresponds with optimal muscle function. Our findings elucidate basic biologic design in muscle that optimizes the interface between tissue and its physical environment. The unique insights from our investigations have broad impact on current understanding of the pharmacokinetic influences of biologic form and function, and elucidate new clinical strategies for controlled release and local delivery of a wide range of therapeutic compounds to mechanically active tissues.by Peter I-Kung Wu.Ph.D

Skeletal muscle biomechanics drives intramuscular transport of locally delivered drugs

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaves 70-74).Introduction: Effective local drug delivery to contractile tissues such as skeletal muscle requires a thorough understanding of the impact of mechanical loads on intramuscular pharmacokinetics. Current preparations for studying skeletal muscle biomechanics typically use: mounting techniques that lead to mechanical disruption of the tissue, which can create drug transport artifacts. In order to accurately study mechanical influences on drug transport, experimental techniques and setups need to meet the particular design requirements of both biomechanical testing setups and local drug delivery preparations. Studies of intramuscular pharmacokinetics require anatomically physiologic and functionally viable conditions for accurate drug transport. In this study, we invent a method for the surgical isolation and mounting of whole skeletal muscles of small rodents that maintains the physiologic configuration of the tissue. We also invent a mounting assembly and dynamic loading system designed appropriately for in vitro drug transport studies. We present an effective protocol for tissue processing and visually quantifying intramuscular distribution of drug. With the primary objective of investigating muscle pharmacokinetics, we use these techniques in a study to elucidate the influence of mechanical loading on the intramuscular transport and distribution of locally delivered drug. Methods and Results: The dynamic loading system was characterized and used to investigate intramuscular transport of aqueous macromolecular drug. The loading system was designed to achieve a maximal force, velocity, and acceleration of up to 72N, 0.45m/s, and 8.5m/s2, respectively, for imposing cyclic strain on soleus muscle samples. Total compliance of the series assembly from the motor to muscle mounting blocks was less then 0.0057 ± 0.002mm/N.(cont.) Under proportional-integral-derivative (PID) control with a positional resolution of 20gpm, the loading system achieved a positional precision of +60gm or better for sinusoidal reference curves required in our studies. Tissue architectural and functional integrity as well as a technique for quantifying intramuscular fluorescent dextran were validated using the loading system. Histologic studies of rat soleus showed that interstitial porosity was consistent in tissues subjected to mechanical loading for 70 minutes, and changes in porosity were independent of the nature of imposed static (0-15% fixed strain) and cyclic (3Hz sinusoidal strain with amplitude of 2.5% oscillating about mean strains of 5-15%) loads. Permanent changes in architectural integrity depended only on the duration of time spent in vitro after isolation, in which porosity increased at the tissue edge from 11.1 + 3.3% to 21.0 + 6.1% over the course of a 70-minute incubation. The source solution used for local delivery of drug (dextran) preserved tissue functional viability, allowing muscle samples to maintain isometric twitch contractile activity at a rate of 3Hz for at least 1 hour. The active twitch force- length characteristic of soleus samples showed 0.24 + 0.06N at 0% strain, a maximum of 0.35 + 0.06N at 10% strain, and a decrease to 0.19 + 0.06N at 20% strain. Isometric twitch contractile force was at least 0.19N when measured every 15 minutes over a 2 hour period. Fractional volume of distribution for dextran was 84% of the bulk source concentration over the range of 0.1 M-lmM bulk concentrations, and demonstrated the non-binding properties of dextran. Fluorescence intensity of FITC-dextran equilibrated in soleus tissue exhibited a linear dependence on dextran concentration.(cont.) Dextran penetration and distribution in soleus muscles under either cyclic (3Hz, 0-20% peak-to- peak) or static (fixed at 0%) tensile strain for 80 minutes was quantified by fluorescent imaging. Penetration depth of 1mM 20kDa FITC-dextran at the planar surfaces of the soleus increased significantly from 0.52 + 0.09mm under static strain to 0.81 + 0.09mm under cyclic strain. Penetration at the curved margins of the soleus was significantly greater than at planar surfaces by a factor of 1.57 and 2.52 under static and cyclic strain, respectively. Penetration at curved surfaces increased to a greater extent, by a factor of 1.6, than at planar surfaces under cyclic strain. Discussion: This investigation demonstrated that dynamic, or cyclic, tensile strain impacts the penetration and distribution of aqueous drug in skeletal muscle. In the course of this study, we established an effective and robust experimental system and protocol for studying mechanical influences on intramuscular pharmacokinetics. The innovation of our surgical isolation and mounting technique allowed for the investigation of an isolated soleus muscle without disrupting the muscle, tendons, or physiologic bone attachments. The mounting device enabled muscles to be secured in a physiologic in situ configuration, to undergo more physiologically distributed tensile stresses and strains, and to be mechanically loaded while incubated in vitro in drug. Thus, the method and device eliminated the artificial tissue stresses typically introduced by current tissue handling techniques that could result in drug transport artifacts.(cont.) While effective as a standalone biomechanical testing preparation, characterization and validation of the dynamic loading system with a protocol for tissue processing and quantitative assessment of intramuscular fluorescent drug distribution demonstrated that it is a novel and robust preparation for investigating both tissue biomechanics and pharmacokinetics. With the finding from the present study that dynamic loading influences intramuscular drug transport in an architecturally dependent manner, we intend to investigate the isolated effects of different mechanical loading regimens on drug transport to establish a broader understanding of muscle pharmacokinetics. It is hoped that the insights from this work will guide the design and application of future local drug delivery strategies to mechanically active tissues.by Peter I-Kung Wu.S.M

Intrinsic Insulating Ground State in Transition Metal Dichalcogenide TiSe2

The transition metal dichalcogenide TiSe$_2$ has received significant research attention over the past four decades. Different studies have presented ways to suppress the 200~K charge density wave transition, vary low temperature resistivity by several orders of magnitude, and stabilize magnetism or superconductivity. Here we give the results of a new synthesis technique whereby samples were grown in a high pressure environment with up to 180~bar of argon gas. Above 100~K, properties are nearly unchanged from previous reports, but a hysteretic resistance region that begins around 80~K, accompanied by insulating low temperature behavior, is distinct from anything previously observed. An accompanying decrease in carrier concentration is seen in Hall effect measurements, and photoemission data show a removal of an electron pocket from the Fermi surface in an insulating sample. We conclude that high inert gas pressure synthesis accesses an underlying nonmetallic ground state in a material long speculated to be an excitonic insulator.Comment: 11 pages, 7 figure

Generators, extremals and bases of max cones

Max cones are max-algebraic analogs of convex cones. In the present paper we develop a theory of generating sets and extremals of max cones in ${{\mathbb R}}_+^n$. This theory is based on the observation that extremals are minimal elements of max cones under suitable scalings of vectors. We give new proofs of existing results suitably generalizing, restating and refining them. Of these, it is important that any set of generators may be partitioned into the set of extremals and the set of redundant elements. We include results on properties of open and closed cones, on properties of totally dependent sets and on computational bounds for the problem of finding the (essentially unique) basis of a finitely generated cone.Comment: 15 pages, 1 figure; v2: new layout, several new references, renumbering of result