bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of Aspergillus niger Cellulase Inhibition by Reducing Sugar Produced by the Hydrolysis of Carboxymethylcellulose
Authors: Al-Zuhair Sulaiman , Fan Yu Ling , Chui Kit Soon , Rizwan Sarmad
Published: March 2007

Hydrolysis of two types of cellulose, namely, totally amorphous Carboxymethylcellulose (CMC) and highly crystalline wood shavings, by Aspergillus niger cellulase was studied in a stirred batch reactor at 50oC. Two kinetic models were devised to predict the rate of reducing sugar production assuming competitive and non-competitive product inhibition of the enzyme. The applicability of the models was tested by comparing experimental results with those predicted by the models. Both models followed the experimental data fairly well, giving standard deviation of 13.3 and 7.9 for the competitive and the non-competitive inhibition models, respectively. However the non-competitive inhibition model showed more realistic behaviour than the non-competitive model and represented better the experimental data. The significance of crystallinity was determined by comparing the production of reducing sugar from wood shavings to the production from CMC. At same initial substrate concentration, it was found that the production of reducing sugar ceased at much shorter times for wood shavings in comparison to that for CMC.
In-Situ CO2-Absorption in a Dual Fluidized Bed Biomass Steam Gasifier to Produce a Hydrogen Rich Syngas
Authors: Pfeifer Christoph , Puchner Bernhard , Hofbauer Hermann
Published: March 2007

Within the last years renewable energy sources came more and more into the public focus. Steam gasification of solid biomass yields high quality producer gases that can be used for efficient combined heat and power production (CHP) and as a renewable resource for chemical syntheses. The dual fluidized bed steam gasification technology provides the necessary heat for steam gasification by circulating hot bed material that is heated in a second fluidized bed reactor by combustion of residual biomass char. The hydrogen content in producer gas of such gasifiers is about 40vol% (dry basis). Addition of carbonates to the bed material and adequate adjustment of operation conditions in the reactors allow selective transport of CO2 from gasification to combustion zone (Absorption Enhanced Reforming  AER concept). An 8MW (fuel power) CHP plant successfully demonstrates gasification in Guessing, Austria since 2002. A process development unit (100 kW fuel power) has been recently operated to investigate the potential of the selective CO2 transport achieving a H2 content of up to 75vol% (dry basis) in the producer gas. No significant increase in tar formation occurs despite the low gasification temperatures (600-700°C). It can be shown, that the selective transport of CO2 yields high hydrogen contents in the producer gas and the possibility of operating at lower temperatures increases the efficiency of energy conversion.
Accounting for Dependence in Similarity Data from DNA Fingerprinting
Authors: Hepworth Graham , Gordon Ian R , McCullough Michael J
Published: March 2007

Differentiating strains of a pathogen is often central to investigating its epidemiological aspects. The genetic similarity of a group of strains can be assessed by calculating a matrix of dissimilarities from their DNA fingerprinting profiles. The mean dissimilarity for each strain across other strains within the group is then used as an observation in a statistical analysis. These observations are not independent of each other, and so standard analysis techniques such as the t-test are inappropriate, because they underestimate the variance of the group means, and hence overstate the statistical significance of any differences. By examining the correlation between elements of the dissimilarity matrix, it is shown that the variance is underestimated by a factor of between about 2 and 4. Permutation tests are proposed as a way of addressing the problem of dependence, and are applied to a study of fluconazole resistance in Candida albicans.
A Generalized Sidak-Holm Procedure and Control of Generalized Error Rates under Independence
Authors: Guo Wenge , Romano Joseph
Published: March 2007

For testing multiple null hypotheses, the classical approach to dealing with the multiplicity problem is to restrict attention to procedures that control the familywise error rate (FWER), the probability of even one false rejection. In many applications, one might be willing to tolerate more than one false rejection provided the number of such cases is controlled, thereby increasing the ability of the procedure to detect false null hypotheses. This suggests replacing control of the FWER by controlling the probability of k or more false rejections, which is called the k-FWER. In Hommel and Hoffmann (1987) and Lehmann and Romano (2005a), single step and stepdown procedures are derived that control the k-FWER, without making any assumptions concerning the dependence structure of the p-values of the individual tests. However, if the p-values are mutually independent, one can improve the procedures. In fact, Sarkar (2005) provided such an improvement. However, we show other improvements are possible which appear to be generally much better, and are sometimes unimprovable. When k=1, the procedure reduces to the classical method of Sidak, and the stepdown procedure is unimprovable and strictly dominates that of Sarkar. Under a monotonicity condition, an unimprovable procedure is obtained. In the case k=2, the monotonicity condition is satisfied, and the condition can be checked numerically in general. We then develop a stepdown method that controls the false discovery proportion. Except for the case of k-FWER control with k=1, the gains are surprisingly dramatic, and theoretical and numerical evidence is given.
Sparse Logistic Regression with Lp Penalty for Biomarker Identification
Authors: Liu Zhenqiu , Jiang Feng , Tian Guoliang , Wang Suna , Sato Fumiaki , Meltzer Stephen J. , Tan Ming
Published: March 2007

In this paper, we propose a novel method for sparse logistic regression with non-convex regularization Lp (p <1). Based on smooth approximation, we develop several fast algorithms for learning the classifier that is applicable to high dimensional dataset such as gene expression. To the best of our knowledge, these are the first algorithms to perform sparse logistic regression with an Lp and elastic net (Le) penalty. The regularization parameters are decided through maximizing the area under the ROC curve (AUC) of the test data. Experimental results on methylation and microarray data attest the accuracy, sparsity, and efficiency of the proposed algorithms. Biomarkers identified with our methods are compared with that in the literature. Our computational results show that Lp Logistic regression (p <1) outperforms the L1 logistic regression and SCAD SVM. Software is available upon request from the first author.
Accurate Ranking of Differentially Expressed Genes by a Distribution-Free Shrinkage Approach
Authors: Opgen-Rhein Rainer , Strimmer Korbinian
Published: March 2007

High-dimensional case-control analysis is encountered in many different settings in genomics. In order to rank genes accordingly, many different scores have been proposed, ranging from ad hoc modifications of the ordinary t statistic to complicated hierarchical Bayesian models.Here, we introduce the shrinkage t statistic that is based on a novel and model-free shrinkage estimate of the variance vector across genes. This is derived in a quasi-empirical Bayes setting. The new rank score is fully automatic and requires no specification of parameters or distributions. It is computationally inexpensive and can be written analytically in closed form.Using a series of synthetic and three real expression data we studied the quality of gene rankings produced by the shrinkage t statistic. The new score consistently leads to highly accurate rankings for the complete range of investigated data sets and all considered scenarios for across-gene variance structures.
Statistical Inference for Quantitative Polymerase Chain Reaction Using a Hidden Markov Model: A Bayesian Approach
Authors: Lalam Nadia
Published: March 2007

Quantitative Polymerase Chain Reaction (Q-PCR) aims at determining the initial quantity of specific nucleic acids from the observation of the number of amplified DNA molecules. The most widely used technology to monitor the number of DNA molecules as they replicate is based on fluorescence chemistry. Considering this measurement technique, the observation of DNA amplification by PCR contains intrinsically two kinds of variability. On the one hand, the number of replicated DNA molecules is random, and on the other hand, the measurement of the fluorescence emitted by the DNA molecules is collected with some random error. Relying on a stochastic model of these two types of variability, we aim at providing estimators of the parameters arising in the proposed model, and, more specifically, of the initial amount of molecules. The theory of branching processes is classically used to model the evolution of the number of DNA molecules at each replication cycle. The model is a binary splitting Galton-Watson branching process. Its unknown parameters are the initial number of DNA molecules and the reaction efficiency of PCR, which is defined as the probability of replication of a DNA molecule. The number of DNA molecules is indirectly observed through noisy fluorescence measurements resulting in a so-called Hidden Markov Model. We aim at inference of the parameters of the underlying branching process, and the parameters of the noise from the fluorescence measurements in a Bayesian framework. Using simulations and experimental data, we investigate the performance of the Bayesian estimators obtained by Markov Chain Monte Carlo methods.
Supervised Detection of Conserved Motifs in DNA Sequences with Cosmo
Authors: Bembom Oliver , Keles Sunduz , van der Laan Mark J.
Published: March 2007

A number of computational methods have been proposed for identifying transcription factor binding sites from a set of unaligned sequences that are thought to share the motif in question. We here introduce an algorithm, called cosmo, that allows this search to be supervised by specifying a set of constraints that the position weight matrix of the unknown motif must satisfy. Such constraints may be formulated, for example, on the basis of prior knowledge about the structure of the transcription factor in question. The algorithm is based on the same two-component multinomial mixture model used by MEME, with stronger reliance, however, on the likelihood principle instead of more ad-hoc criteria like the E-value. The intensity parameter in the ZOOPS and TCM models, for instance, is estimated based on a profile-likelihood approach, and the width of the unknown motif is selected based on BIC. These changes allow cosmo to outperform MEME even in the absence of any constraints, as evidenced by 2- to 3-fold greater sensitivity in some simulation studies. Additional improvements in performance can be achieved by selecting the model type (OOPS, ZOOPS, or TCM) data-adaptively or by supplying correctly specified constraints, especially if the motif appears only as a weak signal in the data. The algorithm can data-adaptively choose between working in a given constrained model or in the completely unconstrained model, guarding against the risk of supplying mis-specified constraints. Simulation studies suggest that this approach can offer 3 to 3.5 times greater sensitivity than MEME. The algorithm has been implemented in the form of a stand-alone C program as well as a web application that can be accessed at http://cosmoweb.berkeley.edu. An R package is available through Bioconductor (http://bioconductor.org).
Active Learning Strategies...Not for the Birds!
Authors: Bowles Donna J.
Published: March 2007

Nursing students historically have struggled to learn a large amount of content in a short period of time. Reliance on intense memorization of endless facts from multiple textbook chapters is ineffective, exhausting, and generally does not result in knowledge retention. Nursing educators face the challenge of facilitating learning that promotes critical thinking through the use of strategies that actively engage the students. Creating an environment of learning where students come prepared to class and use the textbook material to enhance understanding and knowledge acquisition is imperative. This article presents active learning strategies that are flexible for varying class sizes, time availability, and topics. Classroom assessment techniques support the value of this teaching-learning approach.
Self-Esteem, Parent-Child Interaction, Emotional Support, and Self-Perception among Thai Undergraduate Nursing Students
Authors: Ross Ratchneewan , Zeller Richard , Srisaeng Pakvilai , Yimmee Suchawadee , Sawatphanit Wilaiphan , Somchid Sujidra
Published: March 2007

The purpose of this study was to examine the effect of parent-child interaction on self-esteem as mediated by emotional support and self-perception among undergraduate nursing students in Thailand. This study recruited 307 Thai baccalaureate nursing students who completed the Rosenberg Self-Esteem Scale, Ross Parent-Child Interaction Questionnaire, Emotional Support instrument, and Self-Perception questionnaire. Results revealed that the students reported relatively high self-esteem. A path model demonstrated the positive effect of parent-child interaction on emotional support and self-perception, and the positive effects of emotional support and self-perception on self-esteem. Self esteem was powerfully predicted from emotional support and moderately predicted from self-perception. These variables account for 37% of the variance in self esteem.
Reusable Learning Units: An Innovative Teaching Strategy for Online Nursing Education
Authors: Jesse D. Elizabeth , Taleff Janice , Payne Patricia , Cox Ruth , Steele Linda L.
Published: March 2007

Constructivist and adult learning theory provided the theoretical framework for reusable learning units (RLUs) developed for a Southeastern University's family nurse-practitioner and nurse-midwifery distance educational programs. Reusable learning units are an organized series of learning events that satisfy one or more interrelated learning objectives that cannot be broken down to component parts without losing semantic and pragmatic meaning. This paper describes the conceptual framework, background and history of RLUs, and collaborative efforts for development and implementation.
Perceptions of Nursing Student Clinical Placement Experiences
Authors: Leners Debra , Sitzman Kathleen , Hessler Karen L.
Published: March 2007

There is an unprecedented shortage of registered nurses (RNs) in the United States of America. Efforts to educate more RNs have been limited by a shortage of both clinical placements and preceptors for nursing students. The purpose of this study was to examine nursing education issues associated with student clinical placement as experienced by hospital personnel who coordinate the placements with various schools of nursing. A qualitative study involving 15 state-wide participants directly associated with clinical placement of nursing students was conducted. Emergent themes from the data included lack of consistent terminology and definition of student and preceptor roles, preference of clinical scholars, process of site placements, rewards for supervision of students, dis-satisfiers to the supervision of students and suggested strategies for change. Recommendations which developed from the research are summarized and discussed.
Teaching Professional Values in a BSN Program
Authors: Vezeau Toni M.
Published: March 2007

Values are core to the practice of nursing, determining priorities in healthcare and forming the foundation of relationships with clients. Specific values have been recognized as essential to professional nursing practice and are considered central content within a baccalaureate nursing program. While these professional values are identified and defined, there is little guidance in nursing pedagogical literature as to teaching approaches, range and depth of content, and evaluative methods in this area. Clear discussion of an effective educational approach to professional values would be a significant contribution to the discipline of nursing.The paper expands on the brief summary of the five professional values identified by AACN as essential to professional nursing practice. It is easy to understand these values on a superficial level, but these values have many layers and are very difficult to live out in nursing practice. The discussion moves beyond definition and gives specific examples to lend clarity and depth to the topic. The discussion includes common areas in which students have difficulty, noting the inherent challenges for each of the values.
Nursing Graduates' Perceptions of Their Undergraduate Clinical Placement
Authors: Hartigan-Rogers Jackie A , Cobbett Shelley L , Amirault Mardi A , Muise-Davis Martha E
Published: March 2007

Student clinical practice is a significant and essential part of nursing education. Accordingly, clinical placements need to be positive and valuable. The purpose of this study was to describe newly-graduated nurses' perceptions of their student clinical intersession placements and how these placements impacted their functioning as graduate nurses. Inductive semantic analysis of the data revealed four themes: developing nursing skills and knowledge; preparing for future employment; experiencing supportive relationships; and experiencing realities of work-life. Educators must ensure that clinical placements are in an environment that is conducive to learning and promotes the personal and professional development of nursing students. Positive clinical experiences are more likely related to how valued and supported students feel than the physical aspects of a placement; thus, it is imperative educators assess and focus on providing placements that offer a supportive learning environment.
Career Intentions of Nursing Students and New Nurse Graduates: A Review of the Literature
Authors: Hayes Laureen J , Orchard Carole A , McGillis Hall Linda , Nincic Vera , O'Brien-Pallas Linda , Andrews Gavin
Published: March 2007

This paper highlights findings from a literature search to examine the role of nursing education in preparing nurses to meet healthcare demands. The review focused on nursing students perceptions of nursing and whether these views change during their nursing studies and impact workplace preferences. Nursing students often enter their program with preconceived ideas of where they want to work following graduation. Large urban hospitals were favored over community care because of the perceived opportunities for support. Of particular importance were the negative views relating to care of elderly patients. Unless attitudes are changed during their nursing studies, they may affect initial job selection. Implications for nursing education include provision of educational experiences that foster an optimistic career outlook in areas where there is a growing need for nursing services. More research is needed to determine how to enable appropriate learning experiences when there are limited resources and practice placements.
Practicing What We Preach: Balancing Teaching and Clinical Practice Competencies
Authors: Little Maureen A , Milliken P. Jane
Published: March 2007

Most nurse educators fulfill dual roles of clinical practitioner and teacher and thus have to achieve a balance between these two challenging sets of competencies. The authors discuss the obligation and expectation that nurse educators are concurrently experts in clinical practice and education. Is this dual competence a feasible and sustainable goal? To begin to explore this issue, the meanings of 'expert practice' and 'practice competence,' derived from the nursing education literature, are reviewed. Current professional practice competency requirements related to the nurse educator role are discussed. Questions are raised regarding support for and barriers to achieving these competencies. The potential challenges and rewards of this endeavour are presented and illustrated by two nurse educators who share their stories of achieving a balance in teaching and clinical practice competence. Finally, implications for nurse educators and directions for future research into this issue are proposed.
When West Meets East: A Short-Term Immersion Experience in South Korea
Authors: Wallace Linda S
Published: March 2007

The purpose of this study was to explore American student perceptions of caring for Korean patients during a 2 week exchange program. Perceptions of Korea/Koreans focused on five areas: respect, hospitality and gift giving, ability to speak English, hierarchal relationships, and being protective. Their perceptions of personal change focused in four areas: valuing personal cultural experiences, increasing cultural awareness and compassion, seeing people from other ethnic groups as individuals and developing interest in oriental medicine. Four areas of importance identified when caring for Korean patients included showing respect, importance of family, food, and care for post-partum mothers. Differences were experienced between an individualistic, low-context society (United States) and a collectivistic, high context society (Korea) where the influence of Confucianism is pervasive.
Locating Carper's Aesthetic Pattern of Knowing within Contemporary Nursing Evidence, Praxis and Theory
Authors: Duff Cloutier Julie , Duncan Craig , Hill Bailey Patricia
Published: March 2007

Carper's (1978) seminal work has been used in nursing education for many years as a method for introducing students to the multitude of ways of knowing that support nursing practice. This manuscript focuses on the aesthetic pattern of knowing and the ongoing debate in nursing literature surrounding aesthetics, evidence and nursing practice. Writers will describe and critique a strategy used to introduce first year undergraduate nursing students to this pattern of knowing. The implications of the critique of the project and the ongoing debate in relation to Carper's (1978) work, evidenced based practice and nursing praxis are discussed.
Bringing Theory to Life: Engaging Nursing Students in a Collaborative Population-Based Screening Project
Authors: Arbuthnot Elsa , Hansen-Ketchum Patti A , Jewers Heather , Moseley Jane , Wilson Christopher
Published: March 2007

A collaborative population-based project for bowel cancer prevention provided an ideal opportunity to involve nursing students in applying theory to practice. In this article, described is how the engagement of students and subsequent application of a population health template contributed to a community-based bowel cancer education and screening campaign. The campaign was a valuable teaching-learning experience for students and contributed to the goal of reducing and reporting on the number of bowel cancer deaths in the local area. Project evaluation data provide insight into student learning outcomes and reveal ways to strengthen the population health initiative for future years. Originally, a scholarly pursuit of discovery and application developed in response to growing rates of bowel cancer and advances in effective screening programs, the project has evolved into the domain of teaching and learning. This evolution has benefited students, project organizers and community members.
Teaching Psychomotor Skills to Beginning Nursing Students Using a Web-Enhanced Approach: A Quasi-Experimental Study
Authors: Salyers Vincent L
Published: March 2007

To begin to address the problem of psychomotor skills deficiencies observed in many new graduate nurses, a skills laboratory course was developed using a web-enhanced approach. In this quasi-experimental study, the control group attended weekly lectures, observed skill demonstrations by faculty, practiced skills, and were evaluated on skill performance. The experimental group learned course content using a web-enhanced approach. This allowed students to learn course material outside of class at times convenient for them, thus they had more time during class to perfect psychomotor skills. The experimental group performed better on the final cognitive examination. Students in the traditional sections were more satisfied with the course, however. It was concluded that a web-enhanced approach for teaching psychomotor skills can provide a valid alternative to traditional skills laboratory formats.
The Case for Public Funding and Public Oversight of Clinical Trials
Authors: Lewis Tracy R. , Reichman Jerome H. , So Anthony D.
Published: March 2007

Clinical drug trials are public goods and should be publicly funded to avoid undersupply, the suppression of adverse results and other problems, according to Tracy R. Lewis, Jerome H. Reichman and Anthony D. So.
Do Economists Agree on Anything? Yes!
Authors: Whaples Robert
Published: March 2007

Despite the appearances to the contrary, survey evidence by Robert Whaples suggests that economists agree on a wide range of policy issues from free trade to educational vouchers. Climate change and Social Security remain areas of disagreement.
Dirty Money: What the Underworld Understands that Economists Do Not
Authors: Baker Raymond W. , Nordin Jennifer
Published: March 2007

Economists have overlooked and misunderstood the impact of illegal financial flows  "dirty money"  on the global economy, according to Raymond Baker and Jennifer Nordin. Estimated at $1 trillion annually, dirty money renders economic analysis inaccurate and undermines development in poor countries.
Letter: Replacing Payroll with Sales Taxes Shifts Risks from Firms to Governments
Authors: Pope Robin E
Published: March 2007

Robin Pope argues that Kotlikoff is right to favor shifting payroll taxes to sales taxes only Kotlikoff fails to mention all the benefits that would be obtained by the shift. One of these benefits would be aiding employment by shifting the burden of risk bearing from firms to governments that can shoulder the risk burden at a lower cost than most firms can because of their risk pooling abilities.
The Estate Tax Compromise
Authors: Rakowski Eric
Published: March 2007

In 2011 the federal estate tax is scheduled to revert to its pre-2001 form, with a $1 million exemption and a 55% rate on large estates. Several compromise bills are now under discussion that would raise the exempt amount and lower rates. Although many arguments bear on this decision, the choice ultimately turns on the relative force of two opposing moral principles: a principle of autonomy with respect to the use of one's justly acquired property and a principle of equality with respect to unmerited advantages. We should worry much less about raising the exempt amount than lowering rates.
Letter: What Will Stiglitz's Global Warming Remedy Really Cost?
Authors: Saunders Harry D.
Published: March 2007

Harry Saunders argues that we owe it to the public, as well as to the economics profession, to be realistic about the level of pain required to combat global warming.
The Discretion of Judges and Corporate Executives: An Insider's View of the Disney Case
Authors: Donohue John
Published: March 2007

John Donohue wonders if the Disney case means that the courts of Delaware will cleverly find the facts they need to allow managers to waste corporate assets however they please.
Letter: Believe It or Not, What We Need Now Are Higher Gas Prices
Authors: Casey James F
Published: March 2007

Despite current high gasoline prices, what we need now is to increase gas taxes.
Freak-Freakonomics
Authors: Rubinstein Ariel
Published: March 2007

Ariel Rubinstein gives his answer to Freakonomics.
Needed: A New Empiricism
Authors: Bergmann Barbara R
Published: March 2007

How do economists know what they know? In a call for a new empiricism Barbara Bergmann asserts that economists mainly make it up.
If Voters Won't Go for Taxing Oil to Conserve Energy, How Do We Do It?
Authors: Edlin Aaron S.
Published: March 2007

Proposition 87 reemphasized that Americans don't want the cost of driving to increase: Aaron Edlin suggests a way to reduce driving that may be more politically palatable.
Letter: Is Professor Quigley Too Cynical?
Authors: Pope-Handy Mary E
Published: March 2007

According to Mary Pope-Handy, the residents of Silicon Valley oppose urban sprawl for many reasons, but not, contrary to what John M. Quigley asserts, to keep housing scarce and prices high.
Letter: Current Insurance Pricing Unduly Limits Car Ownership
Authors: Butler Patrick
Published: March 2007

Patrick Butler argues that Aaron Edlin's case for converting auto insurance to cents-per-odometer-mile prices would be made more compelling if he developed Vickrey's further assessment that current insurance pricing limits car ownership, particularly among the poor.
Deconstructing the China Price
Authors: Navarro Peter
Published: March 2007

Peter Navarro and the China Price project explore how China has become the world's "factory floor" in just a few short decades.
Housing Collapse? Bring It On!
Authors: Edlin Aaron S.
Published: March 2007

Aaron Edlin confesses his selfish reasons to root for a collapse of housing prices and explains why many who worry should not.
The President's New Executive Order on Regulation
Authors: Hahn Robert W. , Litan Robert E.
Published: March 2007

Robert Hahn and Robert Litan defend President Bush's recent executive order on government regulation.
Protective Effects of Silymarin against Free Radical-Induced Erythrocyte Lysis
Authors: Karimi Gholamreza , Hassanzadeh Mohammad , Mehri Soghra
Published: March 2007

The oxidative hemolysis of rat erythrocytes induced by 2,2-azobis(2-amidinopropane) (AAPH) and its inhibition by silymarin studied. Different concentrations of silymarin showed no significant hemolysis compared with phosphate buffer solution. AAPH (25 mM and 50 mM) induced hemolysis in a time-dependent manner. Silymarin inhibited AAPH (25 mM)-induced hemolysis concentration-dependently. However, in the presence of 50 mM of AAPH, only the two higher concentrations of silymarin inhibited hemolysis. Addition of silymarin 3h after incubation with AAPH (25 mM), had no significant effects on the time course of cell lysis. It is concluded that, in addition to its well-established antioxidant effects, silymarin displays cytoprotective properties.
Optimal Allocation of FACTS Devices by Using Multi-Objective Optimal Power Flow and Genetic Algorithms
Authors: Ippolito Lucio , La Cortiglia Antonio , Petrocelli Michele
Published: March 2007

The increases in power flows and environmental constraints are forcing electricity utilities to install new equipment to enhance network operation. Some application of Flexible AC Transmission System (FACTS) technologies to existing high-voltage power systems has proved the use of FACTS technology may be a cost-effective option for power delivery system enhancements. Amongst various power electronic devices, the unified power flow controller (UPFC) device has captured the interest of researchers for its capability of regulating the power flow and minimizing the power losses simultaneously. Since for a cost-effective application of FACTS technology a proper selection of the number and placement of these devices is required, the scope of this paper is to propose a methodology, based on a genetic algorithm, able to identify the optimal number and location of UPFC devices in an assigned power system network for maximizing system capabilities, social welfare and to satisfy contractual requirements in an open market power.In order to validate the usefulness of the approach suggested herein, a case study using a IEEE 30-bus power system is presented and discussed.
A Three Gate Neural Network Based Approach for Automatic Control of Small Hydro Power Plants
Authors: Goyal Himani
Published: March 2007

This paper presents a flow control approach for the speed control of hydro turbines. Power can be controlled by controlling the rotary motion of the spear valve. In this paper, a flow control based model is proposed for the automatic control of small hydro power plants. In the proposed model, a servomotor is used to control the flow of water by controlling the rotational motion of the spear valve. The spear valve causes a 'continuous' control of the flow of water. `Discrete' flow control is achieved by the use of butterfly gates which are activated by DC motors. The suitability of servomotors for the control of small hydro power plants is discussed and PI controllers are used to further enhance their governing capability. State space representation is used to mathematically model the proposed model. Extensive simulations are performed to analyze the behaviour of the proposed model. Parameter optimization is performed using Artificial Neural Networks.
A Rule Based Expert System for Identification of Harmonics Originating from Single Phase Nonlinear Loads
Authors: Mohamed Azah , Umeh Kingsley Chidi , Hussain Aini , Mohamed Ramizi
Published: March 2007

Presently, there is still a critical shortage of experts to interpret and diagnose problems associated with power system harmonics. Thus, the use of a rule based expert system is proposed for the identification of harmonic sources originating from various single phase nonlinear loads such as uninterruptible power supply, personal computer, fluorescent lamp with magnetic and electronic ballasts, PC monitor and oscilloscope. Identification of harmonics originating from single phase nonlinear loads is implemented by first analyzing the harmonic current waveforms using fractal and fast Fourier transform analyses so as to characterize the harmonic signatures of the different types of nonlinear loads. Then, a rule-based expert system is developed in which the system identifies and classifies the different types of nonlinear loads from the input current waveforms. The expert system with its user interface has been developed in MATLAB and it has been verified with real current measurements. The results obtained prove that the system enables accurate identification of nonlinear loads.
Transient Behavior Analysis of Induction Generator at Three-Phase Fault Condition
Authors: Senju Tomonobu , Kuninaka Ryo , Kaneko Toshiaki , Miyazato Yoshitaka , Yona Atsushi , Urasaki Naomitsu , Funabashi Toshihisa , Sekine Hideomi
Published: March 2007

In recent years, renewable energy generation has been coming up for effective use of natural energy, such as wind energy. Induction generators consisting squirrel-cage rotors are widely used as wind generators because of their salient features like robust rotor design, simplicity in the construction, maintenance free operation, etc. In this paper, it is derived that the transient current, electromechanical torque, and active power taking into account rotor speed change of induction generators at three-phase fault conditions. The output equations of the induction generator has nonlinearity, and the speed-time characteristic in a fault period is also expressed by the nonlinear equation. The approximation to derive analytical formulas for transient conditions is proposed, and the transient behavior of the induction generator is analyzed by the developed equations. The simulation block diagram in MATLAB/SIMULINK is constituted using the system equation in consideration of the nonlinearity of the induction generator. The simulation results obtained from each theoretical analysis are in close agreement with that of results obtained using MATLAB/SIMULINK simulation. Furthermore, theoretical discussion also developed to determine the fault phase angle and the time at which maximum transient currents flow in the system.
Analysis of a Saturated Multi-Phase (Six-Phase) Self-Excited Induction Generator
Authors: Singh G. K. , Yadav K. B. , Saini R. P.
Published: March 2007

The present paper is concerned with the application of the equations of a saturated smooth air-gap machine to the analysis of the transient behavior of a multi-phase (six-phase) self-excited induction generator (SEIG). In the analytical model (d-q axis model), the effects of common mutual leakage inductance between the two three-phase winding sets have been included. A detailed experimental investigation of self-excitation process, loss of excitation and re-excitation, switching-in of pure resistive load without, and with series compensation (short shunt) is also included in this paper.
Radial System Reconfiguration to Minimize Operating Costs in Markets
Authors: Chandramohan S. , Devi R. P. Kumudini , Venkatesh Bala
Published: March 2007

The operating cost of a radial distribution system may be minimized by reducing the amount of real power and reactive power drawn from the transmission system. Presently, real power is being priced through a market clearing scheme all over North America. Reactive power is an ancillary service and its supply would be priced appropriately in the near future through a clearing market structure. A recent US Federal Energy Regulatory Commission staff report [1] has initiated a discussion on the formulation of a reactive power market. When such a market is designed and operated, large customers (distribution corporations) will have to purchase reactive power along with real power from the transmission corporation through an independent system operator. Envisaging such a prospect, this paper proposes a new method of reconfiguring radial systems considering costs of real and reactive power while maintaining an appropriate voltage profile and level of reliable power supply. The proposed method is tested on sample test systems and reported.
A New Definition of Non-Active Power
Authors: Khalsa Harnaak , Zhang Jingxin
Published: March 2007

There is no unique definition of non-active power for nonsinusoidal systems. A new definition of non-active power is proposed in this paper. This definition is based on energy transfer and provides a unique solution for non-active power of single-phase systems under both sinusoidal and non-sinusoidal conditions. An example is used to illustrate the use of this new definition. Energy transfer calculated using the new definition provides the same energy transfer determined from the non-sinusoidal non-active instantaneous power. This is consistent with the existing definition of active power that is also based on energy transfer.
Impacts of Multiple Distributed Generations on a Weak Distribution Network - A Case Study
Authors: Limpananwadi Watthana , Tayati Worawit
Published: March 2007

It is well known to electricity authority worldwide of difficulty in meeting an ever increasing demand of a rural load center tens to hundred kilometers away from the interconnected grid. In many cases, upgrading sub-transmission system seemed appropriate in technical, economic and environmental aspects. Nevertheless, there are cases where addition of local generation is the only means to meet the increasing demand. For more than ten years, Thailand's Provincial Electricity Authority has been tackling complications of adding more and more local generations until exceeding the local off peak demand. These generations consist of four small hydro, one geothermal and one fuel oil power plants. Unfortunately, the unplanned attempts made to resolve problem concerning provision of electricity supply to meet the demand without conducting any pre-engineering study had proved ineffective and sustainable solution could not be attained. This paper described, analyzed and discussed in details the development of PEA's distribution system planning to supply quality and reliable electricity to a small rural and remote community in the country Northern province. Extensive field surveys and technical analyses were carried out to investigate impacts of distributed generation on the performance of the network. Finally, recommendations were given as guideline for further study in search of feasible and sustainable solutions.
Application of Random Search Technique in Directional Overcurrent Relay Coordination
Authors: Birla Dinesh , Maheshwari Rudra Prakash , Gupta Hari Om , Deep Kusum , Thakur Manoj
Published: March 2007

Recently, using a non-linear programming method authors have demonstrated that based on certain criteria if some non-significant selectivity constraints are relaxed, all remaining constraints happen to be feasible but the solution of coordination problem is not possible with the conventional objective function as optimization procedure leaves the solution space [20]. In coordination studies solution with the conventional objective function provides minimum relay operating times. The present paper describes an additional criterion so that the solution with the conventional objective function can be achieved. This paper also achieves the acceptable speed of the primary protection while attempting to coordinate the maximum relay pairs. Complete results are presented in this paper in this regard. This paper uses the non-linear Random Search Technique to solve the coordination problem, which has been successfully applied in many problem areas.
Energy Planning with Air Pollution Constraints
Authors: Lauria Davide , Mottola Fabio , Verde Paola
Published: March 2007

Electrical energy planning of modern electric power system requires great attention for the air pollution problem. This is in accordance to the increasing tendency to optimise the production processes in the respect of their sustainability. Moreover, the advent of the deregulation in the electric energy market has involved substantial modifications of philosophy in planning and managing the electrical power system. These aspects together offer new challenge in defining proper system study methodologies and suitable planning strategies. One of the most complex problems in the planning strategies is the data management uncertainty related to load forecasting and environmental modelling. In this paper a robust optimal planning procedure is formalized, taking adequately into account the problem of stochastic variables presence, allowing to satisfy the air quality and load demand forecast constraints in spite of uncertainties. The proposed approach addresses generation planning, where the various aspects have been integrated to solve the problem in a feasible and realistic way. A numerical application to an electrical power system with respect to a regional area is reported in the final part of the paper, showing the applicability of the proposed methodology.
Life Cycle Impact Assessment of Fuel Procuring and Electricity Generating Processes in Japan by Using an 'LCA-NETS' Scheme
Authors: Sadamichi Yucho , Kato Seizo
Published: March 2007

Japan imports almost all of the energy resources with 40% of them used for electricity generation. Electricity is generated mainly by five types of power plants (LNG-fired, LNG-CC, oil-fired, coal-fired, and nuclear), which have various environmental impacts, for example, fossil fuel depletion, global warming, acid rain, etc.The purpose of this paper is to make a life cycle assessment (LCA) of the electricity generating processes of power plants in Japan and to suggest some concrete measures to reduce the environmental impacts.Our study proceeds as follows. We focus on the fuel procuring process reflecting Japan's import of fuel resources and then the whole electricity generating process of the different types of power plants. Firstly, we quantify the environmental loads resulting from each type of plant by Life Cycle Inventory (LCI) analysis. Secondly, Life Cycle Impact Assessment (LCIA) method is applied to evaluate the total impacts of each type of plant. Thirdly, we make some concluding remarks on reduction of the environmental impacts. LCI analysis and LCIA evaluation are done with use of the 'LCA-NETS' scheme we have developed.Our LCIA evaluation shows that in the fuel procuring process nuclear plants rank top, coal-fired plants second, oil-fired plants third, and LNG-fired plants bottom in the ascending (better) order of the `NETS/MJ' values, and that in the whole electricity generating process LNG-CC plants rank top, LNG-fired and coal-fired plants second, oil-fired plants third and nuclear plants last in the ascending (better) order of the `NETS/kWh' values.Our findings about the fuel procuring process imply that if LNG-fired plants can find an effective usage of their byproduct of cold energy or import natural gas without liquefaction directly from nearby countries, they will rank up next to nuclear plants and that if any legal regulations of desulfurization are imposed on sea transportation the impacts of crude oil and coal will be reduced a great deal.It follows from the total evaluation of the whole electricity generating process that if coal-fired plants can reduce the total impacts by 20% by introducing a technology of coal gasification they will be superior to LNG-CC plants and that if nuclear plants can adopt a technology of recycling uranium to reduce the total impacts by 50% they will be as good as LNG-CC plants.
Harmonic Reducing ANN Controller for a SVC Compensating Unbalanced Fluctuating Loads
Authors: Rajapakse A. , Puangpairoj Anawat
Published: March 2007

This paper presents the development of an artificial neural network (ANN) controller for a Static Var Compensator (SVC) system compensating unbalanced fluctuating loads. The proposed controller can balance and reduce the reactive power drawn from the source under unbalanced loads while keeping harmonic injection to the system due to SVC operation low. The first stage of controller development is a fuzzy logic based control algorithm. This algorithm determines a number of possible operating states of SVC for a given load condition and calculates corresponding harmonics injections. Then a fuzzy logic system is used to rank those operating states in terms of the magnitude of the reactive power drawn from the source and the harmonic injection level indicated by Total Demand Distortion (TDD). The best operating state is selected based on the ranking score assigned by the fuzzy logic ranking system. Finally, computational speed of the controller is improved by replacing the analytical and fuzzy computations by a set of neural networks trained with data generated with fuzzy logic based controller.
An Experimental Study on the Electrical Properties of Fly Ash in the Grounding System
Authors: Chen Shin-Der , Chen Li-Hsiung , Cheng Chih-Kun , Chen Jiann-Fuh
Published: March 2007

A good grounding system is the fundamental insurance to keep the safe operation of power systems. The grounding resistance reduction additive-fly ash is proposed in this study. Fly ash is the byproduct of coal-fired power plants. A pulverized coal boiler generates approximately 80% fly ash and only 20% bottom ash. Furthermore, the study of these materials will assume greater importance. Waste utilization is an attractive alternative to disposal in that disposal cost and potential pollution problems are reduced. Extensively used as an additive in Portland cement or as a mineral admixture in concrete in recent years, we have found that fly ash has a low resistivity, and so can be used as an agent for reducing resistance to grounding. Also, an effort is made to investigate the effect of water-to-cement(W/C) and temperature on the resistivity of the test specimens. The grounding resistance reduction agent was determined by considering various proportions of water, cement and salt. Experimental results demonstrate that the proposed approach can effectively reduce the grounding resistance.