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Certain Limits (certain + limit)
Selected AbstractsDynamic COI-tracking concept for the control of generators in multi-machine power systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2008Zhou Lan Abstract In the conventional excitation control concept, the power angle and frequency of a generator are driven to a pre-designed operation point after the fault occurs. It is named as Constant Point Stabilization (CPS) concept in this paper. A novel concept, called dynamic Center of Inertia (COI)-tracking concept is proposed in this paper. In the concept, the power angle and frequency of each generator track the dynamic COI of the power system. Compared to CPS concept, a salient feature the suggested dynamic COI-tracking concept has is that the generators are not restricted to constant angle point or frequency any longer but track the dynamic COI trajectory of the system to keep synchronous in rotor angle and frequency. Wide area measurement system (WAMS) will be used to transform COI signals to each generator. The time delay within a certain limit of WAMS signals is permitted. To make comparison between the two concepts, the control system models based on the two concepts are first established. Then, using the back-stepping method, two robust controllers are designed to achieve the control objectives of the two concepts. At last, dynamic simulations are carried out based on a 2-area-4-machine test power system, and the control effects of the two controllers, together with that of the conventional AVR,+,PSS excitation system, are compared. Copyright © 2007 John Wiley & Sons, Ltd. [source] Batch kinetics and modelling of ethanolic fermentation of wheyINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2005Salman Zafar Summary The fermentation of whey by Kluyveromyces marxianus strain MTCC 1288 was studied using varying lactose concentrations at constant temperature and pH. The increase in substrate concentration up to a certain limit was accompanied by an increase in ethanol formation, for example, at a substrate concentration of 10 g L,1, the production of ethanol was 0.618 g L,1 whereas at 50 g L,1 it was 3.98 g L,1. However, an increase in lactose concentration to 100 g L,1 led to a drastic decrease in product formation and substrate utilization. The maximum ethanol yield was obtained with an initial lactose concentration of 50 g L,1. A method of batch kinetics was utilized to formulate a mathematical model using substrate and product inhibition constants. The model successfully simulated the batch kinetics observed at S0 = 10 and 50 g L,1 but failed in case of S0 = 100 g L,1 because of strong substrate inhibition. [source] Control of GaAs-MESFET breakdown voltage by Shannon implantationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2007Y. Kumar Abstract The dependence of GaAs-MESFET gate-drain breakdown voltage on gate-Schottky barrier enhancement by Shannon-implantation is analyzed. The analytical results show that the breakdown voltage can be increased by increasing the Shannon-implant dose. However, the tolerable limit of hole accumulation under the gate does not allow the breakdown voltage to be increased beyond a certain limit. The breakdown voltage limit is higher for a channel of lighter doping. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Words from Nowhere , Limits of CriticismPHILOSOPHICAL INVESTIGATIONS, Issue 2 2008Steinar Bøyum In the present essay, I aim to accentuate an analogy between the patterns of thought articulated by Berkeley's Hylas and those of Nagel in his philosophy of bats and aliens. The comparison has a critical purpose, with Philonous playing a role similar to that of Wittgenstein. I argue that Nagel's central claim comes down to statements that are marked by a peculiar form of emptiness. Towards the end, though, I will concede that this kind of Wittgensteinian criticism runs up against certain limits. The fantasies produced by Hylas or Nagel have as counterparts genuine philosophical expressions of experience, which are not vulnerable to the charges levelled at their theoretical parallels. [source] Addressing conflicts in research ethics: consent and risk of harmPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 2 2010Julius Sim Abstract This paper explores some ethical conflicts that may arise in physiotherapy-related research, focusing particularly on the issues of informed consent and avoidance of harm. These central issues in research ethics are defined and related to fundamental moral principles such as respect for autonomy, respect for persons and non-maleficence, and their implications are examined through a set of hypothetical case studies, encompassing both quantitative and qualitative research approaches. It is argued that these ethical requirements may legitimately be traded off against each other, so that a prima facie need to gain informed consent or to avoid a risk of harm to participants may , within certain limits , be outweighed by other ethical requirements. Copyright © 2010 John Wiley & Sons, Ltd. [source] Random dense bipartite graphs and directed graphs with specified degreesRANDOM STRUCTURES AND ALGORITHMS, Issue 2 2009Catherine Greenhill Abstract Let s and t be vectors of positive integers with the same sum. We study the uniform distribution on the space of simple bipartite graphs with degree sequence s in one part and t in the other; equivalently, binary matrices with row sums s and column sums t. In particular, we find precise formulae for the probabilities that a given bipartite graph is edge-disjoint from, a subgraph of, or an induced subgraph of a random graph in the class. We also give similar formulae for the uniform distribution on the set of simple directed graphs with out-degrees s and in-degrees t. In each case, the graphs or digraphs are required to be sufficiently dense, with the degrees varying within certain limits, and the subgraphs are required to be sufficiently sparse. Previous results were restricted to spaces of sparse graphs. Our theorems are based on an enumeration of bipartite graphs avoiding a given set of edges, proved by multidimensional complex integration. As a sample application, we determine the expected permanent of a random binary matrix with row sums s and column sums t. © 2009 Wiley Periodicals, Inc. Random Struct. Alg., 2009 [source] Single-crystal neutron diffraction investigation on crystals belonging to the langasite family: a comparative studyACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2010R. Chitra Crystals of the langasite family are of interest as they are piezoelectric in different devices. The properties of these classes of crystals can be modified within certain limits by isomorphous substitution. Single-crystal neutron diffraction studies were carried out for LGT (La3Ga5.5Ta0.5O14), LGST (La3Ga5.25Ta0.25Si0.5O14) and LGZrT (La3Ga5.25Ta0.25Zr0.5O14) as the neutron study gives a better average picture of the crystal properties over a macroscopic region of the grown crystal. The effect of small substitutions at various sites on the piezoelectric properties of the crystal was studied. [source] IgE-Mediated Asthma and Rhinitis I: A Role of Allergen Exposure?BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 5 2002Gunnar D. Nielsen The IgE antibodies and associated cellular responses are responsible for the allergic airway diseases, allergic rhinitis and allergic asthma, which are increasing in societies with Western life style. Aeroallergens may have different potential to sensitize exposed subjects. Thus, there are only a limited number of important groups of aeroallergens, which are those from house dust mites, cockroaches, pets, pollens, and moulds. Allergy follows to a certain extent the pharmacological/toxicological paradigm of dose-response relationship. Unlike effects of pharmacologically and toxicologically active substances, allergens elicit their adverse effects in a two-stage process. In the first stage the immunologically naïve individual is sensitized to the allergen. In the second stage renewed exposure to the allergen elicits the disease response. Also, high concentrations of aeroallergens may induce immunological tolerance. The scientific literature suggests that many environmental factors contribute to the increase in sensitization and development of airway allergies. Nevertheless, the dose-response relationships apply (within certain limits) both to the sensitization itself and to the exacerbation of the diseases. This suggest that exposure reduction may be one of the methods for reduction of risk, in relation to control of the allergic airway diseases. [source] Estimating Mean Response as a Function of Treatment Duration in an Observational Study, Where Duration May Be Informatively CensoredBIOMETRICS, Issue 2 2004Brent A. Johnson Summary. After a treatment is found to be effective in a clinical study, attention often focuses on the effect of treatment duration on outcome. Such an analysis facilitates recommendations on the most beneficial treatment duration. In many studies, the treatment duration, within certain limits, is left to the discretion of the investigators. It is often the case that treatment must be terminated prematurely due to an adverse event, in which case a recommended treatment duration is part of a policy that treats patients for a specified length of time or until a treatment-censoring event occurs, whichever comes first. Evaluating mean response for a particular treatment-duration policy from observational data is difficult due to censoring and the fact that it may not be reasonable to assume patients are prognostically similar across all treatment strategies. We propose an estimator for mean response as a function of treatment-duration policy under these conditions. The method uses potential outcomes and embodies assumptions that allow consistent estimation of the mean response. The estimator is evaluated through simulation studies and demonstrated by application to the ESPRIT infusion trial coordinated at Duke University Medical Center. [source] | ||||||||||||||||