Note: This page contains sample records for the topic voltage stability evaluation from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Probabilistic evaluation of voltage stability  

Microsoft Academic Search

This paper presents a contingency enumeration based approach to evaluate the voltage stability of a power system. The proposed approach, includes the selection and evaluation of contingencies, the classification of contingencies according to selected failure criteria and the accumulation of voltage stability indices. Voltage stability is quantified in the form of indices such as the probability and frequency of voltage

S. Aboreshaid; R. Billinton

1999-01-01

2

Performance Evaluation of Voltage Stability Indices for Dynamic Voltage Collapse Prediction  

Microsoft Academic Search

The research presents a study in evaluating the performance of several voltage stability indices used for dynamic voltage collapse prediction in power systems. A new voltage stability index has been proposed and it is named as the power transfer stability index. The proposed index is then compared with other known voltage stability indices such as the voltage collapse prediction index,

Muhammad Nizam; Azah Mohamed; Aini Hussain

2006-01-01

3

Voltage stability considerations in composite power system reliability evaluation  

Microsoft Academic Search

This paper presents an approach which includes voltage stability considerations in the adequacy assessment of a composite power system. A fast technique for the probabilistic assessment of voltage stability is presented which can be used in conjunction with detailed contingency evaluation in a composite system adequacy assessment. Voltage stability is quantified using an indicator that can be easily included in

Roy Billinton; Saleh Aboreshaid

1998-01-01

4

Real-time voltage stability monitoring and evaluation using synchorophasors  

Microsoft Academic Search

This paper focuses on evaluating online voltage stability indices for an interconnected power system. The voltage stability indices are measured during the operation of the power system when the dynamic changes take places. The evaluation of the stability and security indices were performed by simulation and measurement of real-time data using Phasor Measurement Units (PMUs). The evaluation of the dynamic

Vahid Salehi; O. Mohammed

2011-01-01

5

Voltage stability constrained load curtailment procedure to evaluate power system reliability measures  

Microsoft Academic Search

This paper reports a method to evaluate composite power system reliability indices incorporating the voltage stability margin criteria. To compute the load curtailment evaluation, an optimal power flow (OPF) computation algorithm, considering the steady state voltage stability margin constraint is developed. A steady state voltage stability indicator is first discussed for its applicability as a suitable indicator for representing stability

G. M. Huang; Nirmal-Kumar C Nair

2002-01-01

6

Evaluation of voltage stability indices (VSI) using genetic algorithm  

Microsoft Academic Search

In this paper, three voltage stability indices (VSIs) have been assessed. The voltage stability problem has been formulated as an optimization problem. Genetic algorithm (GA) has been employed to solve this optimization problem. Wale & Hale 6 bus system was used in this paper study.

Muhammad Tami Al-Hajri; M. A. Abido

2010-01-01

7

Evaluation of some indices for voltage stability assessment  

Microsoft Academic Search

The liberalization of the electricity markets causes power systems to work closer and closer to their limits. The online assessment of system security becomes a topic of paramount importance in control centers. In this context fast indices to quickly assess system security are fundamental in an on-line DSA session. This paper considers three voltage stability indices recently proposed in literature

S. Massucco; S. Grillo; A. Pitto; F. Silvestro

2009-01-01

8

A New Voltage Stability Index Considering Voltage Limits  

Microsoft Academic Search

Recently, concerns over voltage instability phenomena have been increasing, because significant voltage drops are regarded crucial in stable operations. Thus, effective voltage control schemes using voltage stability indices have been brought to attention in a considerable number of studies. The conventional voltage stability indices are mainly based on evaluating voltage stability margins to a critical point. The operator usually determines

Y. Kataoka; M. Watanabe; S. Iwamoto

2006-01-01

9

Small disturbance voltage stability evaluation of power systems  

Microsoft Academic Search

Loading of today power systems continuously increases especially in the developed countries and liberalized electricity markets. On the other hand, operating points of a power system are acceptable in the feasible region usually surrounded by the borders of different stabilities. Power system instability is critical for all participants of the electricity market. Determination of different stability margins can result in

Nima Amjady; Mohammad Reza Ansari

2008-01-01

10

Study of STATCOM and UPFC Controllers for Voltage Stability Evaluated by Saddle-Node Bifurcation Analysis  

Microsoft Academic Search

One of the major causes of voltage instability is the reactive power limit of the system. Improving the system's reactive power handling capacity via flexible AC transmission system (FACTS) devices is a remedy for prevention of voltage instability and hence voltage collapse. In this paper, the effects of two FACTS controllers, STATCOM and UPFC, on voltage stability will be studied.

A. Kazemi; V. Vahidinasab; A. Mosallanejad

2006-01-01

11

Voltage Stability Evaluation of The Khouzestan Power System in Iran Using CPF Method and Modal Analysis  

Microsoft Academic Search

Voltage stability is an important factor that needs to be taken into consideration during the planning and operation of power systems in order to avoid voltage collapse and subsequently partial or full system blackout. The study of the voltage collapse phenomenon can provide a way to prevent this event from happening. There have been many methods developed to study the

Farbod Larki; Mahmood Joorabian; H. M. Kelk; M. Pishvaei

2010-01-01

12

Comparison of SVC, STATCOM, TCSC, and UPFC controllers for Static Voltage Stability evaluated by continuation power flow method  

Microsoft Academic Search

One of the major causes of voltage instability is the reactive power limit of the system. Improving the systempsilas reactive power handling capacity via flexible AC transmission system (FACTS) devices is a remedy for prevention of voltage instability and hence voltage collapse. In this paper, the effects of four FACTS controllers, SVC, STATCOM, TCSC, and UPFC, on voltage stability will

M. A. Kamarposhti; M. Alinezhad; H. Lesani; N. Talebi

2008-01-01

13

Line voltage stability calculations in power systems  

Microsoft Academic Search

Voltage instability and voltage collapses are increasingly attracting worldwide interest. Operating power system closer to its stability limits, transferring large amounts of powers from long distance and an inadequate supply of reactive power contribute to system voltage instability and eventually to voltage collapse. Accurate calculations of voltage stability, precise prediction of voltage collapse points and low time consumption of procedures

F. A. Althowibi; M. W. Mustafa

2010-01-01

14

Voltage Stability Analysis of Radial Distribution Networks  

Microsoft Academic Search

The paper presents voltage stability analysis of radial distribution networks. A new stability index is proposed to identify the nodes that are on the verge of voltage collapse. The value of the proposed voltage stability index is calculated at each node of the network. A modified load flow method is used for voltage stability analysis. The modified load flow method

R. RANJAN; D. DAS

2003-01-01

15

Accuracy analysis of fixed voltage setpoint indices for voltage stability  

Microsoft Academic Search

There are many voltage stability indices for voltage security assessment and calculating stable margins from operating points to voltage instability at each load bus. Among them, one type of indices based on fixed voltage setpoint is applied in practice. Previous research has proved inaccuracy of these indices with the P-V curve method. This paper aims to verify the accuracy of

Sun Huadong; Tang Yong; Bu Guangquan

2010-01-01

16

Line stability indices for voltage collapse prediction  

Microsoft Academic Search

Voltage collapse is a problem that occurs in heavily stressed systems. This paper compares the effectiveness of line stability indices in providing information about the proximity of voltage instability of a electrical power system. Line voltage stability indices can provide an accurate information of the stability condition of the lines of the system and can also determine the weakest bus

C. Reis; A. Andrade; F. P. Maciel

2009-01-01

17

An optimized fast voltage stability indicator  

Microsoft Academic Search

This paper proposes a simulated annealing optimization technique for optimal voltage stability profile throughout the whole power network. The technique is applied to control the power elements of major influence on the voltage stability profile. Elements such as generator reactive generation, adjustable shunt compensation devices and transformer tap settings are optimally adjusted to reach the objective of minimizing the voltage

C. A. Belhadj; M. A. Abido

1999-01-01

18

A linear static voltage stability margin for radial distribution systems  

Microsoft Academic Search

A new static voltage stability margin (VSM) of a radial distribution system is proposed to faithfully determine the distance to voltage collapse. The proposed VSM varies almost linearly with system load and it requires only the complex bus voltages to evaluate. By knowing the values of the proposed VSM at two different operating points, the system critical load or distance

M. H. Hauqe

2006-01-01

19

Wide-Area Stability and Voltage Control  

Microsoft Academic Search

Bonneville Power Administration is investigating wide-area stability and voltage control. The control provides a flexible platform for rapid implementation of generator tripping and reactive power compensation for voltage support and stabil-ity. Features include phasor measurements, digital fiber optic communications, and fuzzy logic control. The control includes both fast and slow subsystems. The controls are being developed in close collaboration between

Carson W. Taylor; Mani V. Venkatasubramanian; Chen Yonghong

20

Voltage stability indices for stressed power systems  

Microsoft Academic Search

The use of static voltage stability indices based on a singular value decomposition of the power flow Jacobian matrix and matrices derived from the Jacobian matrix is discussed. It is shown that such indices, together with the singular vectors, contain substantial and important information about the proximity to voltage instability and also about critical buses and disturbances from a voltage

P. A. Loef; G. Andersson; D. J. Hill

1993-01-01

21

Threshold voltage stabilization in radiation environments  

SciTech Connect

CMOS circuit hardness to total ionizing dose is improved by a circuit technique that dynamically adjusts well and/or substrate voltages to maintain constant device threshold voltages. Threshold voltage excursions below a reference value activate an oscillator driving a charge pump. Stabilization is demonstrated experimentally. Techniques for optimizing the circuitry for various CMOS technology implementations are provided and supported with simulations.

Kerns, D.V. Jr.; Barnaby, H.J.; Kerns, S.E. [Vanderbilt Univ., Nashville, TN (United States). Dept. of Electrical and Computer Engineering

1998-12-01

22

Technique for voltage stability assessment using newly developed line voltage stability index  

Microsoft Academic Search

This paper presents an efficient technique for voltage stability assessment using a newly developed line voltage stability index that becomes half at a collapse point. Power flow equations have been used to identify critical lines, which may be vulnerable during an increased loading condition. Further, based on the line voltage stability index, a reliable scheme is proposed for protection against

L. D. Arya; S. C. Choube; M. Shrivastava

2008-01-01

23

Fast calculation of a voltage stability index  

Microsoft Academic Search

The minimum singular value of the power flow Jacobian matrix has been used as a static voltage stability index, indicating the distance between the studied operating point and the steady-state voltage stability limit. A fast method to calculate the minimum singular value and the corresponding (left and right) singular vectors is presented. The main advantages of the algorithm are the

P. A. Loef; T. Smed; G. Andersson; D. J. Hill

1992-01-01

24

A comparison of voltage stability indices  

Microsoft Academic Search

Voltage stability has become a very important issue of power systems analysis. This paper discusses some important aspects related to voltage stability indices in electric power systems. Some techniques previously studied in the literature are analyzed and a comparison of the performance of several indices is presented. The effectiveness of the analyzed methods are demonstrated through numerical studies in IEEE

Claudia Reis; F. P. Maciel Barbosa

2006-01-01

25

Line indices for voltage stability assessment  

Microsoft Academic Search

Voltage stability has become one of the most important issues in electrical power systems. The power system ability to maintain acceptable bus voltage is a very important characteristic of a network. This paper analyzes the performance of line stability indices. These indices were tested in IEEE 14 and IEEE 57 busbar test systems, with satisfactory results. Simulation results show that

F. P. M. Barbosa

2009-01-01

26

Voltage stability based weak area clustering technique in power system  

Microsoft Academic Search

This paper presents the voltage stability based weak area clustering technique in power system. The technique employed voltage stability and line outage contingency analyses. From the voltage stability analysis, the sensitive lines in a system during stressed condition are identified, while line outage contingency analysis identified the critical line outages. A pre-developed voltage stability index was utilised as an indicator

Ismail Musirin; Titik Khawa Abdul Rahman

2004-01-01

27

Line outage contingency screening and ranking for voltage stability assessment  

Microsoft Academic Search

This paper presents the voltage stability based weak area clustering techniques in power system. The techniques employed voltage stability analysis (VSA) and Line outage contingency analysis (LOCA). From the VSA and LOCA, the most critical lines in a system during stressed condition are identified. A predeveloped voltage stability index was utilized as an indicator to voltage stability condition of the

C. Subramani; S. S. Dash; M. Arun Bhaskar; M. Jagadeeshkumar; K. Sureshkumar; R. Parthipan

2009-01-01

28

Incorporation of dynamic voltage stability constraints in the ATC determination of power system  

Microsoft Academic Search

The evaluation of available transfer capability (ATC) in deregulated power system should take into account thermal limits, transient, steady-state and dynamic angle stability as well as the voltage stability limits. The consideration of voltage stability in the determination of ATC, however, was usually neglected. On the other hand, under the power market environment, voltage instability becomes a more important consideration

Y. Cheng; T. S. Chung; C. Y. Chung; C. W. Yu

2004-01-01

29

An improved voltage stability index and its application  

Microsoft Academic Search

After some damaging blackouts, voltage stability and collapse have become worldwide concerned problems. In this paper, we focus on the aspect of voltage stability. An improved voltage stability index named LI is presented, which can give an accurate indication to power system voltage instability with considering the influence of the load model. Its calculating speed is very fast, so it

Jia Hongjie; Yu Xiaodan; Yu Yixin

2005-01-01

30

Novel fast voltage stability index (FVSI) for voltage stability analysis in power transmission system  

Microsoft Academic Search

Since a couple of decades ago, voltage stability assessment has received increasing attention due to the complexity of power systems. With the increase in power demand and limited power sources has caused the system to operate at its maximum capacity. Therefore, a study that is able to determine the maximum capacity limit before voltage collapse must be carried out so

Ismail Musirin; Titik Khawa Abdul Rahman

2002-01-01

31

Simple and efficient method for steady-state voltage stability assessment of radial distribution systems  

Microsoft Academic Search

A new static voltage stability index of a radial distribution system is proposed to faithfully evaluate the severity of the loading situation, thereby predicting for voltage instability at definite load value. The proposed index includes different parameters which affect the steady-state voltage stability of distribution systems, therefore it gives accurate results. The maximum value of 1 of that index denotes

Mohamed M. Hamada; Mohamed. A. A. Wahab; Nasser. G. A. Hemdan

2010-01-01

32

Distribution system modelling for voltage stability studies  

Microsoft Academic Search

This paper presents a method to include a radial distribution system, with cascaded tap-changers, in voltage stability studies. A rural distribution system, including the 50 kV, 20 kV, 10 kV and 0.4 kV levels, has been studied. A detailed model of the network down to the customer level, with all lines and transformers explicitly represented, has been compared with a

Rikard Lind; D. Karlsson

1996-01-01

33

Three terminal voltage regulators. An evaluation of fixed 5V positive voltage regulators. Reliability and stability under various environmental and load conditions  

NASA Astrophysics Data System (ADS)

The capability of IC regulators to withstand thermal cycling over a wide range of operating conditions was determined. The dependence of thermal fatigue, as a failure mechanism, on the quality of the die-mounting is verified. Components from four manufacturers, including seven variants, were tested for different properties, i.e., change in power dissipation (power cycling), high temperature reverse bias, high temperature storage life, temperature cycling (zero voltage), and steady state operating life. Power cycling was for 24,000 cycles while test duration for the remaining tests was 1000 hr each. A total of 450 devices (five types of encapsulation) were tested, resulting in 12 failures. Four of the seven variants, including two low current ones, have no failures. All variants except one appear to have reasonable or even excellent performance. The weak variant shows poor power cycling performance as well as failures during temperature cycling and poor steady state operating life.

Hansen, C.; Schneider, B.

1980-09-01

34

Voltage stability calculations in power transmission lines: Indications and allocations  

Microsoft Academic Search

In recent years, voltage stability problems have been increasing since power systems operate close to stability limits and large amounts of power are being transferred from long distance. Accurate determination of voltage collapse points with rapid line voltage stability analysis, indications and allocations, allows operators to take necessary action to prevent such collapse incidents. Although several methods have been used

F. A. Althowibi; M. W. Mustafa

2010-01-01

35

Application of artificial neural networks in voltage stability assessment  

Microsoft Academic Search

Voltage stability problems have been one of the major concerns for electric utilities as a result of system heavy loading. This paper reports on an investigation on the application of ANNs in voltage stability assessment. A multilayer feedforward artificial neural network (ANN) with error backpropagation learning is proposed for calculation of voltage stability margins (VSM). Based on the energy method,

A. A. El-Keib; X. Ma

1995-01-01

36

Dynamical voltage stability analysis using Lyapunov function method  

Microsoft Academic Search

This paper presents a method to analyze small perturbation voltage stability for power systems with varying load by mean of a quadratic Lyapunov function. By using the quadratic Lyapunov function, the voltage stability is analyzed algebraically. In this paper, voltage stability proximity indices are also proposed. Numerical tests are carried out on a three-bus power system and a single machine

Abdul Halim; Kazuhiro Takahashi; Bahman Kermanshahi

1998-01-01

37

Phasor measurement application for power system voltage stability monitoring  

Microsoft Academic Search

Monitoring voltage stability is an important task for ensuring secure operation of electrical power networks. In this paper, a phasor measurement based voltage stability monitoring scheme is proposed. By using phasor measurement units and transformer tap position changes, voltage stability indices can be computed at load supply points in the operational time scale. Because this scheme is only based on

Le Fu; Bikash C. Pal; Brian J. Cory

2008-01-01

38

Analysis of voltage stability enhancement via unified power flow controller  

Microsoft Academic Search

This paper discusses the control of the unified power flow controller (UPFC) to improve power system voltage stability. A dynamical UPFC model is presented. The impact of the UPC model on voltage stability is clarified through bifurcation analysis. Robust techniques are employed for the series and shunt branches control and the DC capacitor voltage control. Only local measurements are required

H. Chen; Y. Wang; R. Zhou

2000-01-01

39

Voltage stability and controllability indices for multimachine power systems  

Microsoft Academic Search

This paper presents a voltage stability index (VSI) and a voltage controllability index (VCI), related to the eigenvalues of m x m matrices in a multimachine power system made up of m synchronous generators and a number of infinite buses. System loads can have an arbitrary voltage sensitivity described by generalized voltage exponents. These nonlinear loads are linearized around an

C. D. Vournas

1995-01-01

40

Development of voltage stability constrained optimal power flow (VSCOPF)  

Microsoft Academic Search

This paper presents an application of optimization techniques incorporating voltage stability constraints. L-index that indicates voltage collapse proximity is adapted into the OPF formulation. This paper shows the impact of incorporation of voltage security constraint into optimal power flow formulation in which the active power dispatch problem is associated with guaranteeing adequate voltage security levels in power systems. It provides

S. Kim; T.-Y. Song; M.-H. Jeong; B. Lee; Y.-H. Moon; J.-Y. Namkung; G. Jang

2001-01-01

41

Application of distributed superconducting magnetic energy storage system (D-SMES) in the entergy system to improve voltage stability  

Microsoft Academic Search

The Western Region of the Entergy System (USA) is limited in both generation and transmission. Past events as well as extensive steady state and dynamic voltage stability analysis have indicated that the region can be subjected to potential voltage stability problems under certain contingency conditions. In order to improve voltage stability in the area, Entergy evaluated several shunt reactive reinforcement

S. Kolluri

2002-01-01

42

Design of secondary voltage and stability controls with multiple control objectives  

NASA Astrophysics Data System (ADS)

The purpose of the proposed research is to design a Decentralized Voltage/Stability Monitoring and Control System to counteract voltage violations and the impact of disturbances/contingencies on power system voltage stability. A decentralized voltage and stability control system is designed to coordinate the controls of the local secondary voltage control devices and necessary load shedding without requiring information about the rest of the system. A brief review of the voltage stability monitoring and control applications in power systems is presented. The existing secondary voltage control applications rely on the automatic/manual control of individual secondary voltage control devices whose time constants are approximately three minutes in length. The design of a fast secondary voltage/stability control system is important to mitigate the impact of disturbances on system stability. A literature survey of the applications in the Wide Area Measurement System (WAMS) is performed. Based on the infrastructure of the WAMS, upgrades in voltage and stability controls are one of the most important options. The voltage/stability control can be formulated as a multi-objective optimization problem. The control objectives include, but are not limited to: minimization of system active/reactive losses; maximization of the system stability margin; and minimization of the control actions. The constraints of the optimization problem depend on the specifications of the actual system components. For the first time, margin sensitivities of the control actions are included in the control formulation. The concept of using margin sensitivity to evaluate the post-control load margin is presented as a fast and accurate way to assess potential voltage and stability control options. A system decomposition procedure is designed to define the disturbance-affected zone as an independent control subsystem. A normal constraint algorithm is adopted to identify the most suitable control solution in a shorter timeline than the typical utility voltage-control practice. Both steady-state and dynamic simulations are performed to compare the proposed system with typical utility control practices.

Song, Yang

43

A Voltage Stability Contingency Ranking Method Including Unstable Contingencies  

NASA Astrophysics Data System (ADS)

In this paper, the fast voltage stability contingency ranking method including unstable contingency cases is proposed. The proposed method provides the following three advantages at once: i) Reduction of the computation time for voltage stability contingencies using the concept of the power flow compensation, ii) Calculation of the voltage stability index for all load buses and assessment of the voltage stability for each N-1 contingency, iii) Estimation of the necessary amount of load shedding ?Pcut on condition that stabilizing the unstable load buses is required. The proposed method makes it possible to arrange contingency cases in descending order according to the severity of voltage stability index and the amount of load shedding, although unstable load buses are included in contingency cases. The performance of the method is validated using simple a 6-node test system and a modified IEEE 30 bus system.

Su, Su; Tanaka, Kazuyuki

44

Power system voltage stability analysis using Modified Differential Evolution  

Microsoft Academic Search

The problem of voltage stability is one of the main concerns in the operation of power systems. Many approaches have been used to estimate the voltage stability limit. One of the approaches is determining the maximum loading point of the system. In this approach, the margin from the current operating point to the maximum loading point of the system is

C. Muthamil Selvi; K. Gnanambal

2011-01-01

45

Online voltage stability monitoring using Artificial Neural Network  

Microsoft Academic Search

This paper presents an application of Artificial Neural Network (ANN) for monitoring power system voltage stability. The training of ANN is accomplished by adapting information received from local and remote measurements as inputs and fast indicators providing voltage stability information of the whole power system and one at each particular bus as outputs. The use of feature reduction techniques can

Worawat Nakawiro; I. Erlich

2008-01-01

46

Power system voltage stability assessment employing phasor measurement units  

Microsoft Academic Search

Employing Phasor Measurement Units in wide area monitoring and control of power systems and the availability of phase angles, a new look at the voltage stability indices is performed in this paper. A systematic approach for comparing these indices is presented, where the behavior of different indices to a step load change, for studying long term voltage stability, is compared.

H. Mesgarnejad; S. M. Shahrtash

2010-01-01

47

Induction motor loads and voltage stability assessment using PV curves  

Microsoft Academic Search

Knowledge of the load composition and characteristics, such as corresponding PV curves, are necessary tools for the voltage stability analysis. This paper investigates small industrial induction motors that are operated under different mechanical load conditions. Experimental tests were performed to determine the system's PV characteristics and assess the voltage stability under different loading composition. The load characteristics of induction motor

León Max Vargas; Juri Jatskevich; José R. Martí

2009-01-01

48

Enhancing Voltage Stability of Radial Distribution Systems by Network Reconfiguration  

Microsoft Academic Search

Network reconfiguration is performed by altering the topological structure of distribution feeders. By reconfiguring the network, voltage stability can be maximized for a particular set of loads in distribution systems. A simple algorithm is formulated for enhancement of voltage stability by network reconfiguration through loss reduction method. In network reconfiguration for loss reduction, the solution involves a search over relevant

S. SIVANAGARAJU; N. VISALI; V. SANKAR; T. RAMANA

2005-01-01

49

Global transient stability and voltage regulation for multimachine power systems  

Microsoft Academic Search

This paper addresses simultaneously the major fundamental and difficult issues of nonlinearity, uncertainty, dimensionality and globality to derive performance enhancing power system stability control. The main focus is on simultaneous enhancement of transient stability and voltage regulation of power systems. This problem arises from the practical concern that both frequency and voltage control are important indices of power system control

Mark Gordon; David J. Hill

2008-01-01

50

MATLAB BASED ARTIFICIAL NEURAL NETWORK ALGORITHM FOR VOLTAGE STABILITY ASSESSMENT  

Microsoft Academic Search

This paper presents an analysis and selection of various techniques\\/parameters in developing a suitable feed forward neural network for performing static voltage stability analysis using MATLAB 5.2 NEURAL NETWORK TOOLBOX. Initially, an approach based on the input-output relation of real\\/reactive power and voltage vectors for generator as well as load buses with the voltage stability Index-L is used to train

D. Thukaram; Sukumar Kamalasadan; Adel A. Ghandakly

51

Iterative congestion management considering voltage stability under multicontingency  

Microsoft Academic Search

This paper presents an iterative congestion management method considering voltage stability under multi-contingency for day-ahead electricity markets. Load margins constraints under multi-contingency as well as normal conditions are incorporated into VSC-OPF (voltage stability constrained OPF). Based on sensitivity of the loading margin with respect to active power of generators and loads, an allocation method of congestion costs related to voltage

Xiaosong Zou; Xianjue Luo; Zhiwei Peng

2008-01-01

52

Large scale voltage stability constrained optimal VAr planning and voltage stability applications using existing OPF\\/optimal VAr planning tools  

Microsoft Academic Search

Traditionally in optimal VAr planning, the feasible operation has been translated as observing voltage profile criteria ensuring that the system voltage profile is acceptable for system normal and post contingency conditions. This feasibility definition is not sufficient when considering the VAr planning practice of the utilities concerned with voltage stability problems. Presently, these utilities use two reinforcement criteria for VAr

Ebrahim Vaahedi; J. Tamby; Y. Mansour; Wenyuan Li; D. Sun

1999-01-01

53

Modeling and Simulation of Voltage Source Converter–Medium-voltage DC System for Stability Analysis  

Microsoft Academic Search

This article presents the modeling and simulation of a simple two-terminal and a multi-terminal voltage source converter based medium-voltage DC system, representing a simplified shipboard distribution network, for angular stability analysis. The control modes considered for the voltage source converter include the voltage control mode and the active and reactive power control schemes. The impact of these control modes on

Seetharama Rudraraju; Suresh C. Srivastava; Anurag K. Srivastava; Noel N. Schulz

2011-01-01

54

On-line voltage stability based contingency ranking using fast voltage stability index (FVSI)  

Microsoft Academic Search

Voltage instability is one phenomenon that could happen in a power system due to its stressed condition. The result would be the occurrence of voltage collapse which leads to total blackout to the whole system. Therefore voltage collapse prediction is important in power system planning and operation so that the occurrence of voltage collapse due to voltage instability could be

Ismail Musirin; Titik Khawa Abdul Rahman

2002-01-01

55

Application of artificial neural networks in voltage stability assessment  

SciTech Connect

Voltage stability problems have been one of the major concerns for electric utilities as a result of system heavy loading. This paper reports on an investigation on the application of ANNs in voltage stability assessment. A multi-layer feed-forward artificial neural network (ANN) with error back-propagation learning is proposed for calculation of voltage stability margins (VSM). Based on the energy method, a direct mapping relation between system loading conditions and the VSMs is set up via the ANN. A systematic method for selecting the ANN`s input variables was developed using sensitivity analysis. The effects of ANN`s training pattern sensitivity problems were also studied by dividing system operating conditions into several loading levels based on sensitivity analysis. Extensive testing of the proposed ANN-based approach indicate its viability for power system voltage stability assessment. Simulation results on five test systems are reported in the paper.

El-Keib, A.A.; Ma, X. [Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Electrical Engineering

1995-11-01

56

Comparison of load margin analysis for steady state voltage stability  

Microsoft Academic Search

Voltage stability becomes an increasing severe problem as the power systems become more complex and heavily loaded. Voltage problems have been a subject of great concern during planning and operation of power systems due to the significant number of serious failures believed to have been caused by this phenomenon. Therefore, how to develop an efficient research technique is one of

Yue Yuan; Xuehong Wen; Chengke Zhou

2007-01-01

57

Voltage Stability Study of the PJM System Following Extreme Disturbances  

Microsoft Academic Search

This paper presents results from an analysis of voltage stability following severe contingencies in the PJM system. The analyses involved the use of steady-state (OPF) and short- and long-term simulation tools. The results highlight the importance of adequate load modeling in assessing the performance of and solutions to voltage instability. Undervoltage load shedding (UVLS) is shown to be beneficial in

Rodolfo J. Koessler; Wenzheng Qiu; Mahendra Patel; Harrison K. Clark

2007-01-01

58

Neural-network representation of Voltage Stability Indices at the voltage collapse  

Microsoft Academic Search

Representing system security in power flow based system models by the scalar magnitude of a Voltage Stability Index (VSI) may be a very difficult task, which may even render the applicability of such models impractical. VSIs at voltage collapse points are difficult to predict when reactive power generation limits are taken into account in system modeling. Therefore, this paper proposes

Guilherme G. Lage; Ricardo A. S. Fernandes; Geraldo R. M. da Costa

2011-01-01

59

Voltage stability analysis of multi-infeed HVDC systems using small-signal stability assessment  

Microsoft Academic Search

This paper presents an analysis of multi-infeed HVDC systems voltage stability using small-signal analysis techniques (eigen-structure analysis). A correlation ratio relating to voltage stability is put forward. A small test system with two HVDC infeeds is built to study the voltage stability of the multi-infeed HVDC system. Then the detailed dynamic models of the HVDC system including DC system control

Y. Shao; Y. Tang

2010-01-01

60

STATCOM Modeling for Voltage and Angle Stability Studies  

Microsoft Academic Search

This paper proposes and validates models to accurately represent STATic Syn- chronous Shunt COMpensators (STATCOM) in voltage and angle stability studies of powers systems. The proposed STATCOM stability models are justified based on the basic operational characteristics of this Flexible AC Transmission System (FACTS) controller for both phase and PWM control strategies. These models are first validated by means of

Claudio A. Canizares; Massimo Pozzi; Sandro Corsi; Edvina Uzunovic

2003-01-01

61

Voltage Stability Probabilistic Assessment in Composite Systems: Modeling Unsolvability and Controllability Loss  

Microsoft Academic Search

Several papers have recognized the effect of uncertainties in voltage stability analysis through probabilistic methods. In these papers, the unstable states are generally identified by the unsolvability of the power flow equations or by violations in the voltage stability margin limit. However, voltage stability problems may also be associated with a loss in voltage controllability, when a voltage control action

Anselmo Barbosa Rodrigues; Ricardo B. Prada; Maria Da Guia da Silva

2010-01-01

62

Online Monitoring of Wide-Area Voltage Stability Based on Short Circuit Capacity  

Microsoft Academic Search

Short circuit capacity is an effective indicator of voltage stability. In this study, an online monitoring system of wide-area voltage stability based on short circuit capacity is proposed. Firstly, the relation of short circuit capacity and voltage stability is briefly illustrated, and the voltage stability index based on short circuit capacity (VSISCC) containing the impact of both the load side

Lei Huang; Jian Xu; Yuanzhang Sun; Ting Cui; Fei Dai

2011-01-01

63

Estimating of loadability margin of a power system by comparing Voltage Stability Indices  

Microsoft Academic Search

Estimating the margin in the loadability of the power system is essential in the real time voltage stability assessment. Voltage stability is currently one of the most important research areas in the field of electrical power system. The condition of voltage stability in a power system can be known using voltage stability indices (VSI). The loading margin is one of

M. V. Suganyadevia; C. K. Babulal

2009-01-01

64

Capacitance–voltage, current–voltage, and thermal stability of copper alloyed with aluminium or magnesium  

Microsoft Academic Search

Copper alloyed with small amounts of aluminium or magnesium has recently been suggested as a promising material for interconnect applications in silicon integrated circuits. This work reports the results of the investigation of the electrical (capacitance–voltage and current–voltage) stability of the metal–oxide–semiconductor capacitor made with copper–0.5 at.% aluminium and copper–2 at.% magnesium as metal, deposited on thermally oxidized silicon substrates.

T Suwwan de Felipe; S. P Murarka; S Bedell; W. A Lanford

1998-01-01

65

Impact of wind turbine systems on power system voltage stability  

Microsoft Academic Search

This paper investigates the effect of fixed speed and variable speed grid-connected wind generators on the voltage stability of a power system network. The wind generators considered are the squirrel cage induction generator (SCIG), which is a fixed speed, the doubly-fed induction generator (DFIG) and the direct driven synchronous generator (DDSG) which are variable speed. Studies were conducted on a

D. Devaraj; R. Jeevajyothi

2011-01-01

66

Development of a Versatile Voltage Stability Index Algorithm  

Microsoft Academic Search

Power system experts have shown interest in the development of methods for predicting system status in the form of voltage stability indices. These indices performed well because they were primarily used for system planning as utilities then were either highly localized and regulated by the state or owned and operated by big electricity consumers. However, the situation changed drastically with

D. O. Dike; S. M. Mahajan; G. Radman

2007-01-01

67

A comprehensive analysis of mid-term voltage stability  

Microsoft Academic Search

This paper proposes a comprehensive approach to mid-term voltage stability, combining fast simulation, instability diagnosis and corrective control determination. The fast simulation approximates the mid-term evolution by a succession of equilibrium points, thereby offering a good compromise between efficiency and accuracy. The instability diagnosis and corrective control determination consist of fast sensitivity analyses at some points of the simulated system

T. Van Cutsem; Y. Jacquemart; J.-N. Marquet; P. Pruvot

1995-01-01

68

A practical voltage-stability-constrained optimal power flow  

Microsoft Academic Search

This paper proposes a novel and practical method to enforce a voltage stability constraint (VSC) in an optimal power flow (OPF) auction model, based on the minimum singular value and minimum singular vectors of the power flow Jacobian. The proposed technique is based on a singular value decomposition of the power flow Jacobian at a given solution point, plus an

Rafael J. Avalos; Claudio A. Canizares; Miguel F. Anjos

2008-01-01

69

Effects of STATCOM, SSSC and UPFC on voltage stability  

Microsoft Academic Search

The purpose of this paper is to study the effects of three FACTS controllers: STATCOM, SSSC and UPFC on voltage stability in power systems. Continuation power flow, with accurate model of these controllers, is used for this study. Applying saddle node bifurcation theory with the use of power system analysis toolbox (PSAT), the optimal location of these controllers are determined.

R. Natesan; G. Radman

2004-01-01

70

Global transient stability and voltage regulation for power systems  

Microsoft Academic Search

This paper concerns the global control of power systems. It arises from the practical concern that transient stability and voltage regulation are both important properties of power system control, but they are ascribed to different model descriptions and relate to different stages of system operation (i.e., transient period and post-transient period respectively). Earlier control results deal with the two problems

Yi Guo; David J. Hill; Youyi Wang

2001-01-01

71

Dynamic Voltage Stability Improvement using coordinated control of dynamic VAR-sources  

Microsoft Academic Search

Fast voltage collapse is a new phenomenon in today's stressed power system. To prevent fast voltage collapse sufficient amount of compensation from dynamic reactive sources such as generator, condenser, SVC and STATCOM are needed. This paper presents a new controller (called power system voltage stabilizer or PSVS) for dynamic voltage stability enhancement of power systems and\\/or prevention of fast voltage

Ghadir Radman; Alex Pama; Jeff Powell; David Gao

2007-01-01

72

Determination of static voltage stability-margin of the power system prior to voltage collapse  

Microsoft Academic Search

adequate increase in the reactive power. Frequently, both power industry engineers and academic researchers study Voltage instability problems in power system are an system stability and planning by utilizing static load important issue that should be taken into consideration models (i.e. constant impedance, constant current, during the planning and operation stages of modem constant power, and combinations of these models)

M. K. Jalboub; A. M. Ihbal; H. S. Rajamtani; R. A. Abd-Alhameed

2011-01-01

73

Neural-network-based load modeling and its use in voltage stability analysis  

Microsoft Academic Search

Voltage stability analysis is very important for predicting potential voltage instability. Load modeling plays a key role in voltage stability assessment. In the literature, most available approaches to the voltage stability problem are either static or quasistatic, which do not take load dynamics into account. First, this paper presents a survey of those approaches, makes a comparison between them, and

Dingguo Chen; Ronald R. Mohler

2003-01-01

74

Probabilistic Assessment of Voltage Stability in composite generation and transmission systems  

Microsoft Academic Search

Several papers have recognized the effect of uncertainties in system parameters on voltage stability analysis through probabilistic methods. In these papers, the unstable states are identified by the unsolvability of the power flow equations or the violation in the Voltage Stability Margin (VSM) minimum limit. However, voltage stability problems may also be associated with the loss of voltage controllability, when

A. B. Rodrigues; R. B. Prada; M. G. da Silva

2010-01-01

75

Fast voltage stability assessment and reinforcement in an interconnected power system  

Microsoft Academic Search

It is believed that voltage stability analysis will be more difficult due to the full utilization of transmission systems and the growth of inter-utility power transfer. An online voltage stability analyzing system which can be incorporated into the EMS to deal with the threats of suddenly arising voltage collapses is presented. Operating margin prediction, voltage stability assessment and reinforcement are

Wen-Ta Hsiao

1998-01-01

76

Improved branch-based voltage stability proximity indices. Part I: Theoretical background  

Microsoft Academic Search

In this paper improved branch-based voltage stability proximity indices are proposed. Their computation does not require the use of equivalents nor matrix handling, being straightforward and fast. They can be a very useful tool for power systems operators and planners both to evaluate systems operating conditions, and to determine system reinforcement actions. Also, the indices can be used to compare

Adriana S. Quintela; Carlos A. Castro

2002-01-01

77

MVAr management on the pre-dispatch problem for improving voltage stability margin  

Microsoft Academic Search

This paper presents a methodology that includes at the power system pre-dispatch problem the evaluation and improvement of voltage stability margin by optimizing generators and synchronous condensers reactive power injections. From modal participation. factors it is defined penalty indices for all generators, which are added to the optimal power flow objective function. The purpose is to obtain the most adequate

Taciana Menezes; L. C. P. da Silva; C. Affonso; V. F. da Costa; S. Soares

2002-01-01

78

AVC system based on on-line voltage stability monitoring system  

Microsoft Academic Search

This paper presents that when power\\/voltage automatic control system (AVC) is being applied in provincial dispatching centre, in order to implement reactive power\\/voltage optimization control on condition of ensuring limited on-line voltage stability margin, monitoring module of on-line voltage stability should be introduced to realize the coordinated closed loop control of on-line voltage stability monitoring and AVC system. It defines

Xiaoqun Ding; Ling Zhou; Liu Hongliang

2008-01-01

79

A comparative study of voltage stability for long distance HVAC and HVDC interconnections  

Microsoft Academic Search

This paper presents a comparative study of voltage stability indices for three different long transmission technologies. High Voltage AC (HVAC), hybrid High Voltage DC (HVDC) and bipolar HVDC lines are compared in terms of voltage stability and point of collapse. Each scenario is analyzed with different lengths of transmission lines and in different contingency conditions. The impacts of HVDC control

Mai H. Nguyen; Tapan K. Saha; Mehdi Eghbal

2010-01-01

80

Power Transmission Path Analysis of Voltage Stability in Shandong Power System  

Microsoft Academic Search

Voltage stability of Shandong power system is analyzed by power transmission path analysis. Weak buses are decided by local voltage stability index. Voltage stability indices of both active power transmission paths from the west to the east and local reactive power transmission paths are computed with load increasing. The reactive power reserve indicator is also calculated and key factors that

Liang Wang; Yutian Liu

2006-01-01

81

Deterministic and probabilistic analysis of static voltage stability in power systems  

Microsoft Academic Search

The mechanism of static voltage stability was examined by a visual explanation, in that way, the static voltage stability criterion was obtained. It was indicated that the static voltage stability is determined by both characteristics in generation side and characteristics in load side. Then each kind of two-dimensional plane analysis can be unified in three-dimensional space. It is pointed that

X. Hou; P. Ju

2009-01-01

82

Artificial neural network approach in determining voltage stability in power system networks  

Microsoft Academic Search

Voltage stability problems have been one of the major concerns for electric utilities as a result of system heavy loading. As electric power systems are operated under increasingly stressed conditions, the ability to maintain voltage stability becomes a growing concern. This paper reports on an investigation on the application of artificial neural networks (ANNs) in voltage stability assessment. A multilayer

A. Arunagiri; B. Venkatesh; Stella Morris

2002-01-01

83

Voltage Stability Assessment of Multi-Machine Power Systems Using Energy Function and Neural Networks Techniques  

Microsoft Academic Search

Voltage stability problems have been one of the major concerns for electric utilities as a result of heavy loading of power system. Steady state voltage stability analysis is effectively used to determine a stability margin that shows how close the current operating point of a power system to the voltage collapse point. This article presents a generalized energy function for

A. Y. Abdelaziz; M. M. Abu-Elnaga; M. A. Elsharkawy; K. M. Elbahrawy

2006-01-01

84

Voltage stability of transmission network with different penetration levels of wind generation  

Microsoft Academic Search

Voltage stability problem is an emerging phenomenon in planning and operation of modern power systems with high penetration levels of wind generation. The level of voltage stability\\/instability depends, amongst other factors, on the degree of penetration of wind generations and on their connected locations. The objective of this paper is to investigate the impact of wind generation on voltage stability

I. S. Naser; A. Garba; O. Anaya-Lara; K. L. Lo

2010-01-01

85

Reactive reserve-based contingency constrained optimal power flow (RCCOPF) for enhancement of voltage stability margins  

Microsoft Academic Search

This paper presents a new concept of reactive reserve-based contingency constrained optimal power flow (RCCOPF) for voltage stability enhancement. This concept is based on the fact that increase in reactive reserves is effective for enhancement of voltage stability margins of post-contingent states. In this paper, the proposed algorithm is applied to voltage stability margin of interface flow. Interface flow limit,

Hwachang Song; Byongjun Lee; Sae-Hyuk Kwon; Venkataramana Ajjarapu

2003-01-01

86

AC loop voltages and MHD stability in RFP plasmas  

NASA Astrophysics Data System (ADS)

Applied AC loop voltages provide a means to study and control the dynamics of MHD activity in RFP plasmas. In MST experiments with a new programmable power supply, applying a poloidal loop voltage oscillation of sufficient amplitude is observed to tightly entrain the ambient quasiperiodic sawtooth magnetic-relaxation cycle in the RFP, making it almost strictly periodic. The RFP's limit-cycle trajectory in (F, ?) space, where F and ? are the equilibrium reversal and pinch parameters, is drastically modified and suggests a fundamentally different relaxation regime. Applying both poloidal and toroidal AC loop voltages, as in oscillating-field current drive (OFCD), changes the limit cycle and can reduce MHD fluctuation amplitudes. The MHD response in OFCD experiments with varying source amplitudes and phase lags is examined in terms of linear stability and nonlinear mode coupling. Linear stability for MHD current-driven modes is calculated in cylindrical geometry, including the effect of conducting-wall proximity, and preliminary results indicate the presence of a stable region in (F, ?) space, consistent with past results for the RFP. By using OFCD to control the RFP's positioning in (F, ?) space, it might be possible to control or suppress MHD activity while driving steady-state plasma current.

McCollam, K. J.; Holly, D. J.; Mirnov, V. V.; Sarff, J. S.; Stone, D. R.

2012-10-01

87

Optical stabilization of voltage fluctuations in half-Josephson lasers  

NASA Astrophysics Data System (ADS)

A recently proposed device, dubbed half-Josephson laser, provides a phase-lock between the optical phase and the superconducting phase difference between the leads of the device. In this paper we propose to utilize this phase-lock for the stabilization of voltage fluctuations, by two optical feedback schemes. The first scheme involves a single half-Josephson laser and allows to significantly decrease the diffusion coefficient of the superconducting phase difference. The second scheme involves a stable optical source and a fluctuating half-Josephson laser and permits quenching of the diffusion of the relative phase of the lasers. This opens up perspectives of the optical control of the superconducting phase and voltage fluctuations.

Godschalk, Frans; Nazarov, Yuli V.

2013-07-01

88

Fast voltage stability assessment and reinforcement in an interconnected power system  

NASA Astrophysics Data System (ADS)

It is believed that voltage stability analysis will be more difficult due to the full utilization of transmission systems and the growth of inter-utility power transfer. An online voltage stability analyzing system which can be incorporated into the EMS to deal with the threats of suddenly arising voltage collapses is presented. Operating margin prediction, voltage stability assessment and reinforcement are three major functions. Two predicting methods are proposed to calculate the operating margin according to current operating condition and the anticipative system state. A fast risk indicator based on the saddle-node bifurcation theory is designed to predict the proximity of a system to voltage collapse. A novel CPF method which can trace the power flow solution path through the nose point without notorious numerical difficulties is presented. Speed is the advantage of former method, while accuracy is the important feature of latter one. Voltage stability assessment is required to predict steady-state conditions of a system following a large number of anticipated transmission branch or generator outages. An efficient and simple method based on voltage sensitivity changing rates is proposed for quickly identify the weak buses in a large-scale system. An effective contingency selection function relying on search algorithms built into power flow solutions is designed to filter out most of harmless contingencies for system operators who are working with rapidly changing load/generation patterns and a wide variety of operating conditions. A contingency evaluation function having the ability to deal with real-time numerous contingencies in a very short period of time is utilized to find high-severity contingencies. Var compensation and load shedding are two remedial measures of reinforcement function. Suitable var compensation scheme has three contributions: extending operating margin to avoid voltage collapses, fully utilizing the transmission infrastructure to earn economic benefits, and reducing the number of must-run units to eliminate monopoly profits. A load shedding method is designed to provide protection from fatal voltage collapses occurring outside of prior planning and operating studies. Two practical large-scale power systems and their interconnections are used to study voltage stability throughout this dissertation.

Hsiao, Wen-Ta

89

COMPOSITE LOAD SENSITIVITY IN VOLTAGE STABILITY PROBLEM SOLVED BY UNIFIED POWER FLOW CONTROLLER  

Microsoft Academic Search

Alleviation of voltage stability problem by using Unified Power Flow Controller (UPFC) represents main concern of this paper. The UPFC is analysed as the device capable of giving voltage support and\\/or co- ordinating power flow control action. Voltage stability problem is viewed from longer-term time domain response of a composite load model. Sensitivity analysis is applied with respect to parameters

Nijaz Dizdarevi? S; Göran Andersson

2002-01-01

90

Multi-criteria integrated voltage stability index for weak buses identification  

Microsoft Academic Search

How to identify the weak buses comprehensively and practically in power system voltage stability analysis is an important issue, and is posing great interests to the power engineers. In this paper, a multi-criteria integrated voltage stability index was proposed for weak buses identification. Firstly, the bus voltage change index and reactive power margins, which were determined by P-V curve and

Peng Gao; Libao Shi; Liangzhong Yao; Yixin Ni; M. Bazargan

2009-01-01

91

Identification of weak locations in bulk transmission systems using voltage stability margin index  

Microsoft Academic Search

PV analysis is widely used in the industry for investigating voltage stability problems. However, PV analysis doesn't provide any information about weak facilities with potential voltage problems in the system. This paper presents a new method of finding the weak locations in a large scale power system. The new method is based on the relationship between voltage stability and the

Tao He; Shma Kolluri; Sujit Mandal; F. Galvan; P. Rastgoufard

2004-01-01

92

Soft Computing for Voltage Stability Analysis and Contingency Ranking in Power System  

Microsoft Academic Search

Voltage stability has recently become a challenging problem for many power systems. Voltage instability is one phenomenon that could happen in power system due to its stressed condition. The result would be the occurrence of voltage collapse which leads to total blackout to the whole system Investigation and online monitoring of power system stability have become vital factors to electric

C. Subramani; S. S. Dash; M. Arun Bhaskar; M. Jagadeeshkumar; K. Balaji

2009-01-01

93

Maximizing radial voltage stability and load balancing via loss minimization in distribution networks  

Microsoft Academic Search

Distribution networks have to be operated under minimized loss condition due to economic reasons. Besides economic considerations, a reconfigured distribution network operating at a minimum loss condition has some added advantages in the form of increased voltage stability and load balancing. This paper presents the relationship between voltage stability and loss minimization in which it can be shown that voltage

M. A. Kashem; Mahmoud Moghavvemi

1998-01-01

94

Identification of weak locations in bulk transmission systems using voltage stability margin index  

Microsoft Academic Search

PV analysis is widely used in the industry for investigating voltage stability problems. However, PV analysis doesn't provide any information about weak facilities with potential voltage problems in the system. This work presents a new method of finding the weak locations in a large scale power system. The new method is based on the relationship between voltage stability and the

Tao He; Sharma Kolluri; Sujit Mandal; Floyd Galvan; P. Rasigoufard

2004-01-01

95

Accuracy Analysis of Static Voltage Stability Indices Based On Power Flow Model  

Microsoft Academic Search

There are some voltage stability indices for voltage security assessment and calculating stable margin from operating point to voltage instability at each load bus. Most of those indices are based on static analyses using power flow model. This paper aims to verifying the accuracy of representative power flow model based indices by small signal stability analysis and dynamic time domain

Huadong Sun; Xiaoxin Zhou; Ruomei Li

2005-01-01

96

Identification of Weak Locations in Bulk Transmission Systems Using Voltage Stability Margin Index  

Microsoft Academic Search

PV curve analysis is widely used in the industry for investigating voltage stability problems. However, PV curve analysis does not provide any information about weak facilities with potential voltage problems in the system. This paper presents a new method of finding the weak locations in a large-scale power system. The new method is based on the relationship between voltage stability

Tao He; Sharma Kolluri; Sujit Mandal; Floyd Galvan; Parviz Rastgoufard

97

The use of voltage stability indices and proposed instability prediction to coordinate with protection systems  

Microsoft Academic Search

This paper proposes a methodology for mitigating the occurrence of cascading failure in stressed power systems. The methodology is essentially based on predicting voltage instability in the power system using a voltage stability index and then devising a corrective action in order to increase the voltage stability margin. The paper starts with a brief description of the cascading failure mechanism

R. Leelaruji; V. Knazkins

2009-01-01

98

Investigation of various generator reactive power reserve (GRPR) definitions for online voltage stability\\/security assessment  

Microsoft Academic Search

Voltage stability in power system is influenced by reactive support at various locations. It is desirable to monitor the reactive power reserves as system conditions change. There is a need to find a relationship between the reactive power reserves and system security with respect to voltage stability margin and voltage violations. In this paper we have investigated how different approaches

B. Leonardi; V. Ajjarapu

2008-01-01

99

A comparative study of voltage stability indices in a power system  

Microsoft Academic Search

The paper compares the effectiveness of voltage stability indices in providing information about the proximity of voltage instability of a power system. Three simple voltage stability indices are proposed and their effectiveness is compared with some of the recently proposed indices. The comparison is carried out over a wide range of system operating conditions by changing the load power factor

A. K. Sinha; D. Hazarika

2000-01-01

100

Test Evaluation of a Reduced-Voltage Induction Motor Controller.  

SciTech Connect

This project was designed to test the performance of a motor controller called the ``Electro Guard`` that was distributed by Conservation Products Manufacturing. This motor controller was marketed as a new generation motor controller that saves electric energy by reducing voltage to match motor load and to improve power factor. This project included laboratory testing and had the option of field demonstrations to evaluate energy savings and cost effectiveness, equipment stability and reliability, appropriate applications, level of induced harmonic currents, maintenance soft start benefits, and potential regional electrical energy savings.

Portland General Energy Systems.

1994-07-01

101

A novel static voltage stability index based on equilibrium solution region of branch power flow  

Microsoft Academic Search

This paper proposes a novel online real-time assessment method based on equilibrium solution region of branch power flow. This method demonstrates the use of line stability index in order to determine the voltage stability limits in a power system. Line voltage stability indices presented in the literatures are reviewed and discussed. The shortcomings of these methods are pointed out in

Liu Baozhu; Li Bolong

2008-01-01

102

Optimal static voltage stability improvement using a numerically stable SLP algorithm, for real time applications  

Microsoft Academic Search

A numerically stable sequential Primal–Dual LP algorithm for the reactive power optimisation (RPO) is presented in this article. The algorithm minimises the voltage stability index C 2 [1] of all the load buses to improve the system static voltage stability. Real time requirements such as numerical stability, identification of the most effective subset of controllers for curtailing the number of

R Raghunatha; R Ramanujam; K Parthasarathy; D Thukaram

1999-01-01

103

Screening of xenobiotics by ultra-performance liquid chromatography-mass spectrometry using in-source fragmentation at increasing cone voltages: library constitution and an evaluation of spectral stability.  

PubMed

In clinical and forensic toxicology, general unknown screening is used to detect and identify exogenous compounds. In this study, we aimed to develop a fast (15 min) comprehensive screening method for 500 toxicologically relevant analytes based on ultra-performance liquid chromatography (UPLC) coupled with a quadrupole mass spectrometer (MS) system operated in full scan mode. Data were acquired using both positive and negative electrospray ionization by scanning across the range m/z 80-650. For each ionization mode, data were also collected under multiple fragmentation conditions (i.e., at six different cone voltages). Consequently, each molecule could be characterized by a combination of retention time and up to a maximum of 12 individual spectra. Investigation of the 500 analytes resulted in the compilation of a library containing 2975 spectra. An assessment of the stability of these spectra was evaluated under various conditions, that is, the impact of increasing drug concentration and the presence of biological matrix. In addition, the transferability of the spectral library was assessed by comparison with data acquired using several other instruments of same model and from the same manufacturer. These data are presented in addition to the utility of the method for the analysis of routine clinical and forensic samples. Following extraction, identified compounds were compared to those found with two other techniques, one based on immunoassay and the other, on high-performance liquid chromatography-photodiode-array. PMID:21073810

Humbert, Luc; Grisel, Frederic; Richeval, Camille; Lhermitte, Michel

2010-11-01

104

Optimal Power Flow with steady-state voltage stability consideration using Improved Evolutionary Programming  

Microsoft Academic Search

This paper presents an Improved Evolutionary Programming (IEP) algorithm for the Optimal Power Flow (OPF) with steady-state voltage stability consideration. The objective function is formulated as a trade-off between an economic concern, i.e. fuel cost and a system security issue, i.e. voltage stability margin. The indicator L is adopted to estimate the steady-state voltage stability margin in this paper. The

Kritsana Tangpatiphan; Akihiko Yokoyama

2009-01-01

105

Market-clearing for pricing system security based on voltage stability criteria  

Microsoft Academic Search

This paper presents a novel technique for representing system security in the operation of decentralized electricity markets, with special emphasis on voltage stability. The market-clearing algorithm is modeled as voltage stability constrained-optimal power flow (VSC-OPF) problem for providing market solutions by means of a function of complying with the required voltage stability criteria. Benders’ decomposition is applied for solving the

M. K. Kim; J. K. Park; Y. W. Nam

2011-01-01

106

A novel index for online voltage stability assessment based on correlation characteristic of voltage profiles  

Microsoft Academic Search

Voltage instability is a major threat for security of power systems. Preserving voltage security margin at a certain limit is a vital requirement for today's power systems. Assessment of voltage security margin is a challenging task demanding sophisticated indices. In this paper, a new index based on the correlation characteristic of network voltage profile is proposed for the purpose of

M. R. Aghamohammadi; S. Hashemi; M. S. Ghazizadeh

2010-01-01

107

A new technique for voltage stability analysis in a power system and improved loadflow algorithm for distribution network  

Microsoft Academic Search

Voltage collapse may occur in a power system due to loss in voltage stability in the system. Therefore voltage stability analysis is important in order to identify critical buses in a power system, i.e. buses which are closed to their voltage stability limits and thus enable certain measures to be taken by the control engineer in order to avoid any

T. K. Abdul Rah; G. B. Jasmon

1995-01-01

108

Neural network method based on PMU data for voltage stability assessment and visualization  

Microsoft Academic Search

Voltage phase angle measurement between two points provides the indicator of the system state. This parameter as well as voltage magnitude have been used to identify how stress the system while load increased. In this paper we proposed a new technique for voltage stability assessment based on the Phasor Measurement Units (PMU) data. Firstly, a new method to visualized the

Herbert Innah; Takashi Hiyama

2011-01-01

109

Effect of semiconductor-controlled voltage injection by UPFC and ULTC on power system stability  

NASA Astrophysics Data System (ADS)

Commercial availability of various power semiconductor switches indicates proliferation of power electronic based apparatus in utility power systems. Furthermore, existing power system apparatus, e.g. mechanical phase shifters and mechanical tap changing transformers, will be retrofitted to utilize higher switching speed of semiconductor switches. A group of these apparatus, i.e., unified power flow controller (UPFC), static phase shifter (SPS), under-load tap-changing (ULTC) transformer and static series capacitor (SSC), perform their respective functions by means of injecting series controlled voltages in power systems. This thesis demonstrates that fast series voltage injection, for dynamic power flow regulation, can result in voltage dynamics and even voltage instability. This indicates that fast voltage injection by means of power electronic based apparatus can couple voltage stability and angle stability phenomena. To investigate this coupling phenomena, the voltage dependency of the load must be adequately represented in the load model. The reported studies in this work are based on representing the load by a combination of static and dynamic loads. This thesis primarily investigates impacts of UPFC and semiconductor-controlled ULTC on voltage stability and angle stability phenomena. An eigen analysis approach is used for the studies. The eigen analysis results are validated by digital time-domain simulations using a transient stability software. Both the eigen analysis and the transient stability software tools are tailored to account for angle and voltage stability phenomena.

Alavian Mehr, Alireza

110

Contingency Ranking for Voltage Stability Analysis of Large-Scale Power Systems  

Microsoft Academic Search

In this paper we propose a screening method and suitable software program to analyze contingencies and their impact on static voltage stability in large power systems. The program substantially reduces the number of load flow simulation for contingency analysis and voltage stability studies and is based on the impact of the contingency on the load, and the available Mega Watt

Majid Poshtan; Parviz Rastgoufard; Brij Singh

2004-01-01

111

Voltage stability margin improvement using shunt capacitors and active and reactive power management  

Microsoft Academic Search

Improvement of the power system economical dispatch from voltage stability margin viewpoint is studied in this paper and for that a methodology is proposed. The considered time interval is short term operation. Active and reactive power (generation) re-dispatch injection is the basis of proposed method and voltage stability will be achieved using generated reactive power by shunt capacitors in power

H. Omidi; B. Mozafari; A. Parastar; M. A. Khaburi

2009-01-01

112

Artificial Neural Network Modeling Technique for Voltage Stability Assessment of Radial Distribution Systems  

Microsoft Academic Search

This paper presents an artificial neural network (ANN) based modeling technique for predicting the voltage stability of radial distribution systems. The modeling technique is based on a new voltage stability index for assessment of radial distribution systems Lv . The index is implemented to investigate a 33-bus distribution system. An ANN model which has an input layer with two input

M. M. Hamada; M. A. A. Wahab; N. G. A. Hemdan

2006-01-01

113

A Comparison of Voltage Stability Indices for Placing Shunt FACTS Controllers  

Microsoft Academic Search

Location of shunt compensation devices is important for the enhancement of the voltage stability for practical power systems. This paper presents a comparison of several voltage stability indices in electric power system to identify the weakest bus\\/ area of the system. Shunt FACTS controller is introduced at the weakest bus in IEEE 14-bus test system and its effectiveness is assessed

A. R. Phadke; S. K. Bansal; K. R. Niazi

2008-01-01

114

Development of voltage stability index using synchro-phasor based data  

Microsoft Academic Search

Through the development of phasor measurement units (PMU), various aspects of power system dynamic behavior could be monitored and diagnosed. Monitoring dynamic voltage stability becomes one of achievements we can obtain from PMUs. It is very important to select the method appropriate to the KEPCO system since there are many voltage stability indices. In the paper, we propose an advanced

Sangwook Han; B. Lee; S. Kim; Y. Moon

2009-01-01

115

OPF based voltage stability assessment of a multi-bus power system using network equivalencing technique  

Microsoft Academic Search

In this paper a unique methodology for assessment of voltage stability is proposed considering economic criteria using the concept of equivalencing the multi-bus system to a two bus radial system and by studying the necessary parameters of the equivalent system. Hence, a generalized global voltage stability indicator being developed, it has been applied to a typical 6-bus system and a

Palukuru Nagendra; S. H. nee Dey; Subrata Paul

2009-01-01

116

Estimation of voltage stability index for power system employing artificial neural network technique and TCSC placement  

Microsoft Academic Search

This paper proposes a scheme for online voltage stability monitoring for various load conditions using feed forward back propagation network (FFBPN). A single FFBPN with minimal number of neurons is used to estimate the line voltage stability index for various load conditions. A sequential learning strategy is used to design the FFBPN and the weights in the output layer are

V. Jayasankar; N. Kamaraj; N. Vanaja

2010-01-01

117

Voltage Stability Monitoring Based on the Concept of Coupled Single-Port Circuit  

Microsoft Academic Search

This paper reveals that the impedance match (or the Thevenin circuit) based voltage stability monitoring techniques have problems to predict voltage stability limits when applied to multi-load power systems. Power system loads are nonlinear and dynamic. They cannot be simply represented as Thevenin circuit parameters for impedance match analysis. To overcome these difficulties, a new concept called \\

Yunfei Wang; Iraj Rahimi Pordanjani; Weixing Li; Wilsun Xu; Tongwen Chen; Ebrahim Vaahedi; Jim Gurney

2011-01-01

118

Improved branch-based voltage stability proximity indices. II. Application in security analysis  

Microsoft Academic Search

In this paper, a method for contingency ranking for voltage stability is proposed. Contingencies are ranked according to a performance index defined in terms of branch-based voltage stability proximity indices. Simulation results show that the most critical contingencies can be correctly identified.

Adriana S. Quintela; Carlos A. Castro

2002-01-01

119

A new approach to improve voltage stability in a network with fixed speed wind turbines  

Microsoft Academic Search

In this paper, fixed speed wind turbines problems has been studied from the short term voltage stability point of view and a new approach is presented to improve voltage stability of networks with this kind of turbines without using of FACTS devices. A full converter wind turbine next to the induction generators can inject reactive power, to improve their transient

Yasser Ashkhane

2011-01-01

120

Experimental investigation on voltage stability in vehicle power nets for power distribution management  

Microsoft Academic Search

The power demand and the complexity of vehicle power nets has increased continuously during the last years. Especially the high demands of chassis control systems can cause voltage drops that endanger the power net's stability. A power net test bench that enables experimental research on voltage stability in vehicular power nets is presented in this paper. Thereby the relevance of

Tom P. Kohler; Thomas Wagner; Andreas Thanheiser; Christiane Bertram; Dominik Buecherl; Hans-Georg Herzog; Joachim Froeschl; Rainer Gehring

2010-01-01

121

Design of an Adaptive Artificial Neural Network for Online Voltage Stability Assessment  

Microsoft Academic Search

\\u000a Voltage instability has become a major concern in many power systems and blackouts have been reported, where the reason has\\u000a been voltage instability. Voltage stability is concerned with the ability of a power system to maintain acceptable voltages\\u000a at all buses in the system under normal condition and after being subjected to a disturbance. It is an important consideration\\u000a in

Mehran Rashidi; Farzan Rashidi

2004-01-01

122

Identification of weak buses in a power network using novel voltage stability indicator in radial distribution system  

Microsoft Academic Search

A unique and novel voltage stability indicator derived from voltage equation of radial distribution system has been proposed in this paper. The voltage stability indicator (VSI) can identify the condition of load buses in the voltage collapse point of view. The developed VSI has been tested on a standard 32-bus radial distribution system for reliability test. A comparative study between

Sayonsom Chanda; Bappa Das

2011-01-01

123

A new reconfiguration scheme for voltage stability enhancement of radial distribution systems  

Microsoft Academic Search

Network reconfiguration is an operation problem, which entails altering the topological structure of the distribution feeders by rearranging the status of switches in order to obtain an optimal configuration in order to minimise the system losses. This paper presents a new reconfiguration algorithm that enhances voltage stability and improves the voltage profile besides minimising losses without incurring any additional cost

M. Arun; P. Aravindhababu

2009-01-01

124

Voltage stability modelling and real-time monitoring using expert system for operation assistance  

Microsoft Academic Search

This paper describes a prototype expert system to determine a viable power system voltage stability control scheme. A new model for generator buses reaching their limits of reactive power output is presented. This expert system is designed to assist the power system operator in taking the most appropriate VAr control action in a timely fashion. Sensitivity of a fast voltage

Chokri Belhadj; R. Mohamedi; Serge Lefebvre; P.-J. Lagace; Xuan-Dai Do

1996-01-01

125

Pulse-type voltage stabilizer with integral pulse-width modulation  

Microsoft Academic Search

A voltage stabilizer with integral pulse width modulation consists of a power amplifier followed by a low pass filter for the line voltage, a reference oscillator and a variable ratio frequency divider, and a pulse phase detector which performs the integral control by comparing the two incoming signals from the reference oscillator and the frequency divider respectively, and feeds the

I. A. Fedorova; A. P. Kuznetsov; L. Y. Shilin

1985-01-01

126

A novel method to assess global voltage stability of a multi-bus power system  

Microsoft Academic Search

This paper presents a methodology to obtain an equivalent two bus network from a multi-bus network to assess critical loadability in terms of voltage stability. The weakest bus of the system being diagnosed, maximum loadability of the system is obtained for different operating condition. The methodology has also been applied to a six bus power system to assess global voltage

S. Dey; Ranjita Chowdhury; Priyanath Das

2009-01-01

127

Optimal placement of distributed generation with sensitivity factors considering voltage stability and losses indices  

Microsoft Academic Search

Loss minimization in distribution networks has considered as great significance recently since the trend to the distribution generation will require the most efficient operating scenario for economic viability variations. Furthermore, voltage instability phenomena can occur in distribution systems and caused a major blackout in the network. The decline of voltage stability level will restrict the increase of load served by

A. Parizad; A. Khazali; M. Kalantar

2010-01-01

128

Novel algorithm for online voltage stability assessment based on feed forward neural network  

Microsoft Academic Search

This paper presents an artificial feed forward neural network (FFNN) approach for the assessment of power system voltage stability. A novel approach based on the input-output relation between real and reactive power, as well as voltage vectors for generators and load buses is used to train the neural net (NN). The input properties of the feed forward network are generated

S. Kamalasadan; A. K. Srivastava; D. Thukaram

2006-01-01

129

Fuzzy logic controlled particle swarm for reactive power optimization considering voltage stability  

Microsoft Academic Search

This paper presents the application of a fuzzy logic controlled particle swarm optimization (FLCPSO) to reactive power and voltage control (Volt\\/VAR control or VVC) considering voltage stability. An improved particle swarm optimization with three fuzzy controllers based on some heuristics is proposed to adaptively adjust the parameters of PSO, such as the inertia weight and learning factors, during the optimization

W. Zhang; Y. Liu

2005-01-01

130

Using bus impedance and bus PQ curve for voltage stability control  

Microsoft Academic Search

Voltage control and voltage stability problems are not new in the operation of electric power networks but are now receiving special attention in many countries because of a greater need for improving efficiency of usage of transmission capacity in the competitive electric energy market. Practically, the idea of P-V and Q-V curves is used to determine the maximal reactive margin

M. Sobierajski; K. Wilkosz; J. Bertsch; M. Fulczyk

2001-01-01

131

Large-scale wind power integration and voltage stability limits in regional networks  

Microsoft Academic Search

When planning and developing large-scale wind power plants in areas distant from the main power transmission system, voltage control assessments and reactive power compensation are increasingly important. Voltage stability of the regional network may be a main limitation with respect to maximum rating and operation of the wind power plant Technical constraints in relation to wind power integration in weak

M. P. Palsson; T. Toftevaag; K. Uhlen; J. O. G. Tande

2002-01-01

132

Voltage stabilization and reactive compensation using a novel FACTS STATCOM scheme  

Microsoft Academic Search

This paper presents the use of a new full 48 pulse GTO model of voltage source converter FACTS-STATCOM (static synchronous compensator) for reactive power compensation and voltage stabilization on electric grid network. The device is a power electronic GTO converter connected in parallel with the power system bus and is controlled by a novel controller. The complete digital simulation of

M. S. ElMoursi; A. M. Sharaf

2005-01-01

133

Visualization and Analysis of Voltage Stability Using Self-Organizing Neural Networks  

Microsoft Academic Search

On the basis of a compelling mathematical description of voltage stability in electrical power systems and its indication using the minimum singular value of the load flow Jacobian the application of a self-organizing Kohonen-Neural-Network (KNN) is presented for a fast and secure indication and visualization of voltage stability. The advantage of the structural representation of the system condition by the

Edmund Handschin; Dietmar Kuhlmann; Christian Rehtanz

1997-01-01

134

A Novel Voltage Stabilization Control Scheme for Stand-alone Wind Energy Conversion Systems  

Microsoft Academic Search

This paper proposes a novel low cost FACTS based voltage stabilization scheme for a stand-alone wind energy conversion systems using self excited squirrel-cage induction generator (SEIG) driven by a wind turbine and interfaced to electric load. The new control scheme is designed not only to ensure bus voltage stabilization, but also to improve energy utilization using a low-cost PWM-switched modulated

A. M. Sharaf; A. Aljankawey; I. H. Altas

2007-01-01

135

A New Circuit Topology for the Realization of Very Low Noise, High Stability Voltage Sources  

Microsoft Academic Search

A new topology for the realization of high-stability very low noise voltage references is presented. The topology relies on a self-biasing circuit configuration based on a low-noise operational amplifier (OA). The series connection of a number of forward-biased low-noise diodes is used as an internal reference for generating any desired output voltage. The circuit may include a temperature stabilization system

Carmine Ciofi; Graziella Scandurra; Gianluca Cannata

2010-01-01

136

New Fuzzy Excitation Controller Design Based on Coordination of Voltage Regulation and Dynamic Stability  

Microsoft Academic Search

Taking advantages of proportional-integral-differential (PID) control in voltage regulation, and those of linear optimal control in dynamic stability, a new excitation control scheme based on fuzzy logic control is proposed. The method adjusts the weights of voltage regulation tunnel and auxiliary stabilizing tunnel on-line according to different operating conditions by a fuzzy controller, aiming to improve the performance of excitation

Hengxu Zhang; Chunyi Wang; Ning Zhang; Jian Zuo; Dawei Fan

2007-01-01

137

A Steady-State Voltage Stability Analysis of Power Systems With High Penetrations of Wind  

Microsoft Academic Search

As wind generation begins to contribute significantly to power systems, the need arises to assess the impact of this new source of variable generation on the stability of the system. This work provides a detailed methodology to assess the impact of wind generation on the voltage stability of a power system. It will also demonstrate the value of using time-series

Eknath Vittal; Mark O'Malley; Andrew Keane

2010-01-01

138

Evaluation of epoxy based nanodielectrics for high voltage outdoor insulation  

Microsoft Academic Search

Nano and micro based epoxy samples have been evaluated for predicting their electrical performance in outdoor high voltage insulation applications. Scanning electron microscopy (SEM) is used to evaluate the shape and the dispersion of the filler material. Space charge characterization and the role of the interface in these materials is evaluated using dielectric spectroscopy on these samples. The results of

G. Iyer; R. S. Gorur; R. Richert; A. Krivda; L. E. Schmidt

2010-01-01

139

Modeling of the effect of distributive generation on voltage stability on a large metropolitan district  

NASA Astrophysics Data System (ADS)

A theoretical foundation for modeling, analysis, and evaluation of large-scale application of distributive generation (DG) technologies connected to the bulk transmission grid is developed to answer questions concerning DG penetration levels as they affect system voltage. This work examines the penetration of DG on a dense metropolitan area by developing a non-specific distribution feeder model. There is significant detail to measure the effects of the feeder and DG penetration. The modeling approach replaces the existing aggregate load with an approximated model of the feeder, distribution transformers, and load in order to study the effects of these devices on voltage stability. To capture the effects of increased DG, a non-specific (not based on technologies) inverter device is modeled on the end of each feeder. This inverter model allows for depiction of commutation failure due to low voltage on the feeder to be captured, and is used to develop the effects of the distribution feeder from a bulk transmission perspective. A case study, using the methods developed in this research, demonstrated that a distributive generation penetration level of between 20% to 27% could be used to meet the electrical demands of a large metropolitan area. Following this level of DG penetration, the test system under single-outage conditions experienced rapid voltage decay similar to voltage collapse. Contributions of this research are predominately in the field of electrical engineering and are focused on numerical modeling of power systems. Major contributions include: (1) Data collection and modeling of DG exceeds any previous attempts, due to at least in part to the availability of data and to computer limitations. (2) Development of an aggregated Universal Distributed Generation Feeder (UDGF) model for the distribution system is a new approach. Previous studies examined single distribution feeders as opposed to modeling the entire distribution and transmission system together. (3) Numerical valuation methods utilized in this research have not been previously used in this manner and represent a novel approach. This research used the point at which the load-flow Jacobian is singular to represent an undesirable operating point where system voltages collapse. Groups interested in this research are bulk system planning engineers, power system operators, power system researchers, regulatory bodies and transmission system owners.

Santos, Juan Santiago

140

Quantitative evaluation of nation stability  

Microsoft Academic Search

This paper quantitatively evaluates nation stability, defined as the state of a country's social and economic system as measured by multiple evaluation indicators, and observes its transitions. Data Envelopment Analysis\\/Malmquist Index (DEA\\/MI) methodology is applied to the panel data for 97 countries for the period 1981–2004, although the DEA application is totally different from the DEA efficiency\\/productivity analysis. This analysis

Takao Tsuneyoshi; Akihiro Hashimoto; Shoko Haneda

141

Estabilizacao de Osciladores Controlados Por Tensao Atraves de Cavidades Ressonantes (Stabilization of Voltage-Controlled Oscillators Through Resonant Cavities).  

National Technical Information Service (NTIS)

Described is a design procedure for cavity stabilization of voltage-controlled oscillators. The procedure is applied to the design of a voltage controlled oscillator, mechanically tuned in the 0.95 GHz to 1.35 GHz frequency band.

P. M. Marshall C. E. Santana

1986-01-01

142

Transient stability and voltage regulation in power systems with renewable distributed energy resources  

Microsoft Academic Search

In this paper, energy storage used to enhance the transient stability of an electrical power system with renewable power generation is investigated. The passivity-based control design method (IDA-PBC) is used to achieve power angle stability and frequency and voltage regulation after the occurrence of a large disturbance (a symmetrical three-phase short circuit transmission line fault). The performance of the control

Adirak Kanchanaharuthai; Vira Chankong; Kenneth Loparo

2011-01-01

143

Evaluating software architectures: development, stability, and evolution  

Microsoft Academic Search

Summary form only given. We survey seminal work on software architecture evaluation methods. We then look at an emerging class of methods that explicates evaluating software architectures for stability and evolution. We define architectural stability and formulate the problem of evaluating software architectures for stability and evolution. We draw attention to the use of Architectures Description Languages (ADLs) for supporting

Rami Bahsoon; Wolfgang Emmerich

2003-01-01

144

A fuzzy genetic approach for network reconfiguration to enhance voltage stability in radial distribution systems  

Microsoft Academic Search

This paper presents a fuzzy genetic approach for reconfiguration of radial distribution systems (RDS) so as to maximize the voltage stability of the network for a specific set of loads. The network reconfiguration involves a mechanism for selection of the best set of branches to be opened, one from each loop, such that the reconfigured RDS possesses desired performance characteristics.

N. C. Sahoo; K. Prasad

2006-01-01

145

Behavior of Loads During Voltage Dips Encountered in Stability Studies Field and Laboratory Tests  

Microsoft Academic Search

The lack of knowledge of the behavior of loads during the voltage depressions caused by faults in HV grids has been emphasized on many occasions. Field and laboratory tests were advocated for more realistic representation of loads in transient stability studies.

F. Illicico; A. Ceyhan; G. Ruckstuhl

1972-01-01

146

Decision fusion of voltage stability indicators for small sized power systems  

Microsoft Academic Search

In this paper, the authors consider a probabilistic approach to at the issue of voltage stability of a small power system. They do this via a data fusion technique using the Bayesian rule, which is well suited for such applications. They use three proximity indicators in this study. On their own, each of these indicators have some amount of probability

Derek Sam; Chika Nwankpa; Dagmar Niebur

2001-01-01

147

Analysis of Composite Load Models on Load Margin of Voltage Stability  

Microsoft Academic Search

While it has been widely accepted that the constant P-Q leads to conservative load margin calculation of voltage stability, lately the studies show that induction motor loads can lead to an even more conservative load margin calculation. This paper analyzes the impacts of the composite load model (the composite of ZIP and induction motor load models) on the load margin

Shao-Hua Li; Hsiao-Dong Chiang; Sheng Liu

2006-01-01

148

Influence of a wind farm in the dynamic voltage stability of a power network  

Microsoft Academic Search

The electrical power production from dispersed energy sources or distributed generation is playing an increasing role in the supply of electricity in the liberalized electricity markets. Distributed generation can have a significant impact on the power flow, voltage profile, stability and the power quality for both customers and electricity suppliers. In this paper it is studied and analysed the influence

R. M. Monteiro Pereira; C. M. Machado Ferreira; F. P. Maciel Barbosa

2009-01-01

149

Flexible low-voltage organic transistors with high thermal stability at 250 °C.  

PubMed

Low-operating-voltage flexible organic thin-film transistors with high thermal stability using DPh-DNTT and SAM gate dielectrics are reported. The mobility of the transistors are decreased by 23% after heating to 250 °C for 30 min. Furthermore, flexible organic pseudo-CMOS inverter circuits, which are functional after heating to 200 °C, are demonstrated. PMID:23616376

Yokota, Tomoyuki; Kuribara, Kazunori; Tokuhara, Takeyoshi; Zschieschang, Ute; Klauk, Hagen; Takimiya, Kazuo; Sadamitsu, Yuji; Hamada, Masahiro; Sekitani, Tsuyoshi; Someya, Takao

2013-04-25

150

Investigating the impact of Powerformer on voltage stability by dynamic simulation  

Microsoft Academic Search

This paper provides an overview of a dynamic analysis carried out on a modified Nordic test system to determine the impact of the Powerformer on voltage stability. The unique aspects of the Powerformer are highlighted and the modeling of long-term dynamic elements, especially those pertinent to the study of the Powerformer are discussed. Overexcitation limiter models created for use in

Craig Anthony Aumuller; Tapan Kumar Saha

2003-01-01

151

Organic thin film devices with stabilized threshold voltage and mobility, and method for preparing the devices  

DOEpatents

Organic thin film devices that included an organic thin film subjected to a selected dose of a selected energy of ions exhibited a stabilized mobility (.mu.) and threshold voltage (VT), a decrease in contact resistance R.sub.C, and an extended operational lifetime that did not degrade after 2000 hours of operation in the air.

Nastasi, Michael Anthony; Wang, Yongqiang; Fraboni, Beatrice; Cosseddu, Piero; Bonfiglio, Annalisa

2013-06-11

152

Short-term voltage stability of fixed-speed wind turbines: Comparison of single and double cage  

Microsoft Academic Search

This paper studies the short-term grid voltage stability of double cage induction generators in fixed speed wind turbines. The performed analysis shows that for voltage stability studies of fixed speed wind turbines with induction generators (either single or double cage), the mechanical rotor turbine model is preferable as a detailed aerodynamic model. Simulations of the suggested modeling approaches are presented,

Andreas Sumper; Oriol Gomis-Belmunt; A. Sudria-Andreu; Roberto Villafafila-Robles; Joan Rull-Duran

2010-01-01

153

A Novel Voltage Stability Sensitivity Index Incorporating the Slip of the Wind Generator and the Stochastic Wind Speed and Load  

Microsoft Academic Search

This paper presents a novel voltage stability sensitivity index incorporating the slip of wind generator and stochastic wind speed and load. Tradition studies are insufficient to inquire the impact of the slip of asynchronous wind generators and stochastic wind speed and load on voltage stability index. Firstly, the slip of asynchronous generator is introduced as a new state variable, and

Si Zheng; Rui Ma; Junying Song; Huihua Chen; Zhiwen Shen

2011-01-01

154

Stabilization of turbulent lifted jet flames assisted by pulsed high voltage discharge  

SciTech Connect

To reduce fuel consumption or the pollutant emissions of combustion (furnaces, aircraft engines, turbo-reactors, etc.), attempts are made to obtain lean mixture combustion regimes. These lead to poor stability of the flame. Thus, it is particularly interesting to find new systems providing more flexibility in aiding flame stabilization than the usual processes (bluff-body, stabilizer, quarl, swirl, etc.). The objective is to enlarge the stability domain of flames while offering flexibility at a low energy cost. Evidence is presented that the stabilization of a turbulent partially premixed flame of more than 10 kW can be enhanced by pulsed high-voltage discharges with power consumption less than 0.1% of the power of the flame. The originality of this work is to demonstrate that very effective stabilization of turbulent flames is obtained when high-voltage pulses with very short rise times are used (a decrease by 300% in terms of liftoff height for a given exit jet velocity can be reached) and to provide measurements of minimum liftoff height obtained with discharge over a large range of the stability domain of the lifted jet flame.

Criner, K.; Cessou, A.; Louiche, J.; Vervisch, P. [CORIA UMR 6614 CNRS-Universite et INSA de Rouen, University of Rouen, 76801 Saint Etienne du Rouvray (France)

2006-01-01

155

A new approach to the assessment of steady-state voltage stability margins using the P– Q– V curve  

Microsoft Academic Search

Voltage stability margin is represented by a measurement associated with the maximum real and reactive power demands for a specified node, area or overall system that can sustain an adequate corresponding minimum voltage magnitude. With this perspective, a new approach to the assessment of voltage stability margins based on the P–Q–V curve technique is proposed. A P–Q–V curve shows the

Ching-Yin Lee; Shao-Hong Tsai; Yuan-Kang Wu

2010-01-01

156

All low voltage lateral junction scanning tunneling microscope with very high precision and stability.  

PubMed

We describe the first lateral junction and fully low voltage scanning tunneling microscope, featuring very high precision, stability, compactness, and image quality (highly oriented pyrolytic graphite atomic resolution images). In its core, the tip and sample each sit on one of two parallel-mounted piezoelectric tube scanners so that the tip-sample gap is regulated along the scanners' pairing direction. The scanner's large lateral deflection provides a large gap regulation range even under low voltages, allowing exclusively using only low voltage (less than +/-15 V) operational amplifiers to precisely implement the coarse (inertial slider) and fine approach, feedback control, and hence the entire electronics. Because the scanners are identical and adjacent, thermal drifts are minimal. PMID:19045895

Hou, Yubin; Wang, Jihui; Lu, Qingyou

2008-11-01

157

MW and MVar management on supply and demand side for meeting voltage stability margin criteria  

Microsoft Academic Search

This paper presents a methodology to improve the power system economical dispatch from a voltage stability margin perspective. The time horizon under discussion is the short-term operation planning. The proposed method is based on active\\/reactive power re-dispatch for normal operation, and also minimum load shedding strategies in case of critical contingencies. The actions are taken in the direction provided by

Carolina M. Affonso; L. C. P. da Silva; F. G. M. Lima; S. Soares

2004-01-01

158

Adaptive Scheme for Minimal Load Shedding Utilizing Synchrophasor Measurements to Ensure Frequency and Voltage Stability  

Microsoft Academic Search

This article presents a new scheme for load curtailment in the power system under critical contingencies that may pose a threat to the frequency and voltage stability of the system. The proposed scheme is based on a two-stage load-shedding strategy. In the first stage, disturbances have been classified based on the computed value of the disturbance power, and the load-shedding

K. Seethalekshmi; S. N. Singh; S. C. Srivastava

2010-01-01

159

Improvement of Plasma Spray Torch Stability by Controlling Pressure and Voltage Dynamic Coupling  

Microsoft Academic Search

The development of coating formation processes involving electric arcs depends on process stability and the capacity to ensure\\u000a a constant reproducibility of coating properties. This is particularly important when considering suspension plasma spraying\\u000a or solution precursor plasma spraying. Submicron particles closely follow plasma instabilities and have nonhomogeneous plasma\\u000a treatment. Recently, it has been shown that arc voltage fluctuations in direct-current

V. Rat; J. F. Coudert

2011-01-01

160

The continuation power flow: a tool for steady state voltage stability analysis  

Microsoft Academic Search

The authors present a method of finding a continuum of power flow solutions starting at some base load and leading to the steady-state voltage stability limit (critical point) of the system. A salient feature of the so-called continuation power flow is that it remains well-conditioned at and around the critical point. As a consequence, divergence due to ill-conditioning is not

Venkataramana Ajjarapu; Colin Christy

1992-01-01

161

Multi-objective optimization by reinforcement learning for power system dispatch and voltage stability  

Microsoft Academic Search

This paper presents a new method called Multi-objective Optimization by Reinforcement Learning (MORL), to solve the optimal power system dispatch and voltage stability problem. In MORL, the search is undertaken on individual dimension in a high-dimensional space via a path selected by an estimated path value which represents the potential of finding a better solution. MORL is compared with multi-objective

H. L. Liao; Q. H. Wu; L. Jiang

2010-01-01

162

Voltage stability of the Puget Sound system under abnormally cold weather conditions  

SciTech Connect

The potential for voltage collapse in the Puget Sound area is analyzed. Shunt and series compensation schemes, as well as undervoltage load shedding, are evaluated. Twenty-five minute time simulations of the Puget Sound area system are presented, showing interaction of load dynamics with LTCs, switched compensation and protective equipment. Results and analysis are relevant to utilities worldwide which must address similar concerns.

Jimma, K.M.; Sheehan, M.T. (Puget Sound Power and Light, Bellevue, WA (United States)); Comegys, G.L. (Bonneville Power Administration, Portland, OR (United States)); Miller, N.W.; D'Aquila, R.

1993-08-01

163

Evaluation of fast voltage discriminators in the picosecond time range  

SciTech Connect

An automated system for the evaluation of fast risetime voltage discriminators is described. A high-performance time digitizer is used to determine the elapsed time between the generation of a test pulse and the response of the discriminator under test. The measurement is repeated for a series of discriminator threshold levels generated by a digital-to-analog converter and the results compared to a photograph of the leading edge of the pulse obtained with a sampling socilloscope. To obtain high accuracy, an average of several thousand individual digitizations is used in each measurement to reduce the uncertainty to a maximum of +-3 ps. The measurement system is used with a test fixture to evaluate the performance of a number of tunnel diodes and in preliminary measurements of a prototype discriminator of new design.

Kolbe, W.F.; Turko, B.; Smith, C.

1989-02-01

164

Evaluation of fast voltage discriminators in the picosecond time range  

SciTech Connect

An automated system for the evaluation of fast risetime voltage discriminators is described. A high-performance time digitizer is used to determine the elapsed time between the generation of a test pulse and the response of the discriminator under test. The measurement is repeated for a series of discriminator threshold levels generated by a digital-to-analog converter and the results compared to a photograph of the leading edge of the pulse obtained with a sampling oscilloscope. To obtain high accuracy, an average of several thousand individual digitizations is used in each measurement to reduce the uncertainty to a maximum of +-3 ps. The measurement system is used with a test fixture to evaluate the performance of a number of tunnel diodes and in preliminary measurements of a prototype discriminator of new design. 2 refs., 9 figs.

Kolbe, W.F.; Turko, B.T.; Smith, R.C.

1988-04-01

165

Determination of the weakest branch in a radial distribution network using local voltage stability indicator at the proximity of the voltage collapse point  

Microsoft Academic Search

This paper presents a unique method to determine the weakest branch or the overstressed branch in a distribution network. This radial feature of the network has been fully exploited to establish the concept of local voltage stability indicator in terms of reactive power. The effectiveness of the proposed method has been successfully tested in 12 bus radial distribution system and

Sumit Banerjee; C. K. Chanda; S. C. Konar

2009-01-01

166

Stabilization of the conductive conformation of a voltage-gated K+ (Kv) channel: the lid mechanism.  

PubMed

Voltage-gated K(+) (Kv) channels are molecular switches that sense membrane potential and in response open to allow K(+) ions to diffuse out of the cell. In these proteins, sensor and pore belong to two distinct structural modules. We previously showed that the pore module alone is a robust yet dynamic structural unit in lipid membranes and that it senses potential and gates open to conduct K(+) with unchanged fidelity. The implication is that the voltage sensitivity of K(+) channels is not solely encoded in the sensor. Given that the coupling between sensor and pore remains elusive, we asked whether it is then possible to convert a pore module characterized by brief openings into a conductor with a prolonged lifetime in the open state. The strategy involves selected probes targeted to the filter gate of the channel aiming to modulate the probability of the channel being open assayed by single channel recordings from the sensorless pore module reconstituted in lipid bilayers. Here we show that the premature closing of the pore is bypassed by association of the filter gate with two novel open conformation stabilizers: an antidepressant and a peptide toxin known to act selectively on Kv channels. Such stabilization of the conductive conformation of the channel is faithfully mimicked by the covalent attachment of fluorescein at a cysteine residue selectively introduced near the filter gate. This modulation prolongs the occupancy of permeant ions at the gate. It is this longer embrace between ion and gate that we conjecture underlies the observed stabilization of the conductive conformation. This study provides a new way of thinking about gating. PMID:23609443

Santos, Jose S; Syeda, Ruhma; Montal, Mauricio

2013-04-22

167

Power system voltage stability and agent based distribution automation in smart grid  

NASA Astrophysics Data System (ADS)

Our interconnected electric power system is presently facing many challenges that it was not originally designed and engineered to handle. The increased inter-area power transfers, aging infrastructure, and old technologies, have caused many problems including voltage instability, widespread blackouts, slow control response, among others. These problems have created an urgent need to transform the present electric power system to a highly stable, reliable, efficient, and self-healing electric power system of the future, which has been termed "smart grid". This dissertation begins with an investigation of voltage stability in bulk transmission networks. A new continuation power flow tool for studying the impacts of generator merit order based dispatch on inter-area transfer capability and static voltage stability is presented. The load demands are represented by lumped load models on the transmission system. While this representation is acceptable in traditional power system analysis, it may not be valid in the future smart grid where the distribution system will be integrated with intelligent and quick control capabilities to mitigate voltage problems before they propagate into the entire system. Therefore, before analyzing the operation of the whole smart grid, it is important to understand the distribution system first. The second part of this dissertation presents a new platform for studying and testing emerging technologies in advanced Distribution Automation (DA) within smart grids. Due to the key benefits over the traditional centralized approach, namely flexible deployment, scalability, and avoidance of single-point-of-failure, a new distributed approach is employed to design and develop all elements of the platform. A multi-agent system (MAS), which has the three key characteristics of autonomy, local view, and decentralization, is selected to implement the advanced DA functions. The intelligent agents utilize a communication network for cooperation and negotiation. Communication latency is modeled using a user-defined probability density function. Failure-tolerant communication strategies are developed for agent communications. Major elements of advanced DA are developed in a completely distributed way and successfully tested for several IEEE standard systems, including: Fault Detection, Location, Isolation, and Service Restoration (FLISR); Coordination of Distributed Energy Storage Systems (DES); Distributed Power Flow (DPF); Volt-VAR Control (VVC); and Loss Reduction (LR).

Nguyen, Cuong Phuc

168

Voltage Stability Constrained Distributed Generation Planning using Modified Bare Bones Particle Swarm Optimization  

NASA Astrophysics Data System (ADS)

A procedure for selection of buses have been developed in this paper for sub transmission system for locations of distributed generation (DG). The buses have been selected based on incremental voltage (dV/dP) sensitivities. Optimal capacity of DG at these locations for minimum transmission losses have been evaluated. A modified version of Bare Bones Particle Swarm Optimization (BBPSO) known as BBExp has been used to evaluate the optimum DG capacity. The developed algorithm has been implemented on standard 14-bus and 39-bus test systems.

Koshti, A.; Arya, L. D.; Choube, S. C.

2013-08-01

169

Voltage Stability Constrained Distributed Generation Planning using Modified Bare Bones Particle Swarm Optimization  

NASA Astrophysics Data System (ADS)

A procedure for selection of buses have been developed in this paper for sub transmission system for locations of distributed generation (DG). The buses have been selected based on incremental voltage (d V/d P) sensitivities. Optimal capacity of DG at these locations for minimum transmission losses have been evaluated. A modified version of Bare Bones Particle Swarm Optimization (BBPSO) known as BBExp has been used to evaluate the optimum DG capacity. The developed algorithm has been implemented on standard 14-bus and 39-bus test systems.

Koshti, A.; Arya, L. D.; Choube, S. C.

2013-06-01

170

Evaluation of EPDM rubber for high voltage insulator  

Microsoft Academic Search

This paper describes the fundamental characteristics of EPDM (ethylene propylene rubber) which is applied as a high voltage insulation material. Also recently, polymer compounds have been applied as high voltage insulation materials. EPDM rubber is inferior in weather resistance to silicone rubber. However, we found that the addition of carbon black results in an excellent weathering property of EPDM rubber

Y. Kurata; K. Takano; K. Sakuraba; M. Hayashi

1995-01-01

171

On the choice of voltage regulators for droop-controlled voltage source converters in microgrids to ensure stability  

Microsoft Academic Search

Microgrids are emerging to be an attractive means to cluster various distributed generation systems with local loads while operating either in a grid-connected mode or in an islanded mode in a semi-autonomous fashion. Voltage source converter (VSC) based distributed generation devices are often an essential component in such microgrids, particularly in interfacing dc energy storage devices. While system level control

Sandeep Bala; Giri Venkataramanan

2010-01-01

172

Real Power and Reactive Power Control of a Three-Phase Single-Stage-PV System and PV voltage Stability  

SciTech Connect

Grid-connected photovoltaic (PV) systems with power electronic interfaces can provide both real and reactive power to meet power system needs with appropriate control algorithms. This paper presents the control algorithm design for a three-phase single-stage grid-connected PV inverter to achieve either maximum power point tracking (MPPT) or a certain amount of real power injection, as well as the voltage/var control. The switching between MPPT control mode and a certain amount of real power control mode is automatic and seamless. Without the DC-to-DC booster stage, PV DC voltage stability is an important issue in the control design especially when the PV inverter is operating at maximum power point (MPP) with voltage/var control. The PV DC voltage collapse phenomenon and its reason are discussed. The method based on dynamic correction of the PV inverter output is proposed to ensure PV DC voltage stability. Simulation results of the single-stage PV system during system disturbances and fast solar irradiation changes confirm that the proposed control algorithm for single-stage PV inverters can provide appropriate real and reactive power services and ensure PV DC voltage stability during dynamic system operation and atmospheric conditions.

Li, Huijuan [ORNL; Xu, Yan [ORNL; Adhikari, Sarina [ORNL; Rizy, D Tom [ORNL; Li, Fangxing [ORNL; Irminger, Philip [ORNL

2012-01-01

173

Evaluation of Epoxy Nanocomposites for High Voltage Insulation  

NASA Astrophysics Data System (ADS)

Polymeric materials containing nanometer (nm) size particles are being introduced to provide compact shapes for low and medium voltage insulation equipment. The nanocomposites may provide superior electrical performance when compared with those available currently, such as lower dielectric losses and increased dielectric strength, tracking and erosion resistance, and surface hydrophobicity. All of the above mentioned benefits can be achieved at a lower filler concentration (< 10%) than conventional microfillers (40-60%). Also, the uniform shapes of nanofillers provide a better electrical stress distribution as compared to irregular shaped microcomposites which can have high internal electric stress, which could be a problem for devices with active electrical parts. Improvement in electrical performance due to addition of nanofillers in an epoxy matrix has been evaluated in this work. Scanning Electron Microscopy (SEM) was done on the epoxy samples to confirm uniform dispersion of nano-sized fillers as good filler dispersion is essential to realize the above stated benefits. Dielectric spectroscopy experiments were conducted over a wide range of frequencies as a function of temperature to understand the role of space charge and interfaces in these materials. The experiment results demonstrate significant reduction in dielectric losses in samples containing nanofillers. High voltage experiments such as corona resistance tests were conducted over 500 hours to monitor degradation in the samples due to corona. These tests revealed improvements in partial discharge endurance of nanocomposite samples. These improvements could not be adequately explained using a macroscopic quantity such as thermal conductivity. Thermo gravimetric analysis (TGA) showed higher weight loss initiation temperatures for nanofilled samples which is in agreement with the corona resistance experimental results. Theoretical models have also been developed in this work to complement the results of the corona resistance experiment and the TGA analysis. Degradation model was developed to map the erosion path using Dijkstra's shortest path algorithm. A thermal model was developed to calculate the localized temperature distribution in the micro and nano-filled samples using the PDE toolbox in MATLAB. Both the models highlight the fact that improvement in nanocomposites is not limited to the filler concentrations that were tested experimentally.

Iyer, Ganpathy

174

Wind turbine mechanical characteristics and grid parameters influence on the transient voltage stability of a fixed speed wind turbine  

Microsoft Academic Search

This paper describes the effect of wind turbine mechanical characteristic of construction and grid parameters on the transient voltage stability of a fixed speed wind turbine (FSWT) connected to a simple grid. The model of FSWT has been developed in Matlab\\/Simulink. Using this model, a three-phase fault is applied close to the wind turbine (WT) and cleared by disconnecting the

L. Dusonchet; F. Massaro; E. Telaretti

2008-01-01

175

Effects of electrical parameters of induction generator on the transient voltage stability of a fixed speed wind turbine  

Microsoft Academic Search

This paper describes the effect of electrical parameters of the induction generator on the transient voltage stability of a fixed speed wind turbine connected to a simple grid; the dynamic behavior of a wind turbine connected to the grid is examined. The model of the fixed speed wind turbine has been developed in the simulation tool Matlab\\/Simulink. Itpsilas composed by

L. Dusonchet; F. Massaro; E. Telaretti

2008-01-01

176

Application of a multivariable feedback linearization scheme for rotor angle stability and voltage regulation of power systems  

Microsoft Academic Search

This paper investigates the application of a nonlinear controller to the multi-input multi-output model of a system consisting of a hydraulic turbine and a synchronous generator. The controller proposed is based on a feedback linearization scheme. Its main goal is to control the rotor angle as well as the terminal voltage, to improve the system's stability and damping properties under

Ouassima AKHRIF; F.-A. Okou; L.-A. Dessaint; R. Champagne

1999-01-01

177

Stochastic evaluation of voltage sags in series capacitor compensated radial distribution systems  

Microsoft Academic Search

Voltage sags, also known as dips, are important to industrial reliability. This paper presents a Monte Carlo-based approach to evaluate the maximum voltage sag magnitudes in series capacitor compensated radial distribution systems. In this context, investigations have been conducted on a sample distribution system model taking into consideration the uncertainty of several factors associated with the practical operation of a

Sherif Omar Faried; Saleh Aboreshaid

2003-01-01

178

Wall-shaped electrodes for reducing the operation voltage of polymer-stabilized blue phase liquid crystal displays  

NASA Astrophysics Data System (ADS)

Polymer-stabilized blue phase liquid crystal displays based on the Kerr effect are emerging due to their submillisecond response time, wide view and simple fabrication process. However, the conventional in-plane switching device exhibits a relatively high operating voltage because the electric fields are restricted in the vicinity of the electrode surface. To overcome this technical barrier, we propose a partitioned wall-shaped electrode configuration so that the induced birefringence is uniform between electrodes throughout the entire cell gap. Consequently, the operating voltage is reduced by ~ 2.8× with two transistors. The responsible physical mechanisms are explained.

Kim, Miyoung; Kim, Min Su; Kang, Byeong Gyun; Kim, Mi-Kyung; Yoon, Sukin; Lee, Seung Hee; Ge, Zhibing; Rao, Linghui; Gauza, Sebastian; Wu, Shin-Tson

2009-12-01

179

Evaluation of Conservation Voltage Reduction (CVR) on a National Level  

SciTech Connect

Conservation Voltage Reduction (CVR) is a reduction of energy consumption resulting from a reduction of feeder voltage. While there have been numerous CVR systems deployed in North America there has been little substantive analytic analysis of the effect; the majority of the published results are based on empirical field measurements. Since these results are based on empirical measurements it is difficult to extrapolate how this technology will behave on the various types of distribution feeders found throughout the nation. This report has utilized the Taxonomy of Prototypical feeder developed under the Modern Grid Initiative (MGI), now the Modern Grid Strategy (MGS), in order to estimate the benefits of CVR on multiple distribution feeder types. This information will then be used to determine an estimate of the national benefits of a wide scale deployment of CVR.

Schneider, Kevin P.; Fuller, Jason C.; Tuffner, Francis K.; Singh, Ruchi

2010-09-29

180

Evaluation of voltage interpolation to address process variations  

Microsoft Academic Search

Post-fabrication tuning provides a promising design approach to mitigate the performance and power overheads of process variation in advanced fabrication technologies. This paper explores design considerations and VLSI-CAD support for a recently proposed post-fabrication tuning knob called voltage interpolation. The paper discusses design tradeoffs between circuit tuning range and static power overheads that can be performed within the synthesis flow

Kevin Brownell; Gu-Yeon Wei; David Brooks

2008-01-01

181

Stability in high-output-voltage push-pull current-fed converters  

SciTech Connect

This paper studies the relationship between the magnetizing inductances of a transformer and of a choke coil in high-voltage power supplies. This analysis defines the conditions for high switching frequency and stable operation of high-voltage power supplies without the power loss increase. This approach is confirmed by the implementation of a high-voltage power supply operating at 200 kHz with a high efficiency of 86%.

Ohtsu, Satoshi; Yamashita, Takashi; Yamamoto, Katsuhiko; Sugiura, Toshiyuki (NTT Interdisciplinary Research Lab., Tokyo (Japan))

1993-04-01

182

Symmetrical and unsymmetrical voltage sag effects on the three-phase synchronous machine stability  

Microsoft Academic Search

This paper focuses on the effects of voltage sags, both symmetrical and unsymmetrical, on the three-phase synchronous machine (SM). Voltage sags on SM cause speed variations, current and torque peaks and hence may cause tripping and equipment damage. The consequences of voltage sags on the machine behaviour depend on different factors such as sag's magnitude (or depth), duration, initial point-on-wave

Daniel Aguilar; Alejandro Rolán; Gerardo Vázquez; Felipe Córcoles; Pedro Rodríguez

2009-01-01

183

HIGH VOLTAGE ENVIRONMENTAL APPLICATIONS, INC.ELECTRON BEAM TECHNOLOGY - INNOVATIVE TECHNOLOGY EVALUATION REPORT  

EPA Science Inventory

This report evaluates a high-voltage electron beam (E-beam) technology's ability to destroy volatile organic compounds (VOCs) and other contaminants present in liquid wastes. Specifically, this report discusses performance and economic data from a Superfund Innovative Technology...

184

Evaluation of Niobium as Candidate Electrode Material for DC High Voltage Photoelectron Guns.  

National Technical Information Service (NTIS)

The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to...

A. Mohamed A. A. Elmustafa C. Hernandez-Garcia J. Clark J. Hansknecht K. Surles-Law M. BastaniNejad M. Poelker P. Adderley P. Williams R. Mammei S. Covert

2012-01-01

185

Operational stability enhancement of low-voltage organic field-effect transistors based on bilayer polymer dielectrics  

NASA Astrophysics Data System (ADS)

Bilayer polymer dielectrics consisting of hydrophobic thin layers on high-k polyvinylalcohol (PVA) are utilized to realize p-type and n-type low-voltage organic field-effect transistors (OFETs), which show superior mobility and operational stability compared with the devices with PVA single-layer dielectric. The OFETs with top layers containing discrete ?-groups, such as polystyrene (PS) and poly(2-vinyl naphthalene) (PVN), show stronger bias stress instability than those with ?-group free polymethylmethacrylate (PMMA), and it is ascribed to slow charge trapping into the ?-groups under bias stress. By integrating p-type and n-type low-voltage OFETs based on PMMA/PVA bilayer dielectric, a low-power high-stability complementary inverter is achieved.

She, Xiao-Jian; Liu, Jie; Zhang, Jing-Yu; Gao, Xu; Wang, Sui-Dong

2013-09-01

186

Effectiveness of Current-controlled Voltage Source Converter Excited Doubly Fed Induction Generator for Wind Farm Stabilization  

Microsoft Academic Search

In this article, stabilization methods of wind farms composed of fixed-speed wind turbines and variable-speed wind turbines are analyzed. A current-controlled voltage source converter scheme for a variable-speed wind turbine driving doubly fed induction generator is proposed. The proposed scheme is then compared with two other doubly fed induction generator control schemes to show the effectiveness of the proposed controller.

K. E. Okedu; S. M. Muyeen; Rion Takahashi; Junji Tamura

2012-01-01

187

System for Stabilizing the Magnitude and Frequency of Voltages in a Micro Hydroelectric Power Plant with Asymmetric Ballast Regulation  

Microsoft Academic Search

Regulation of the electric power generated by an autonomous electric-supply system fed from a micro hydroelectric plant (microHEP) using an additional ballast load is an effective means of stabilizing the magnitude and frequency of its voltages.Power that can be diffused in ballast can be regulated using thyristor phase-regulating devices or thyristor keys that commutate a set of ballast resistances in

B. V. Lukutin; E. B. Shandarova

2001-01-01

188

Effect of detailed power system models in traditional and voltage-stability-constrained optimal power-flow problems  

Microsoft Academic Search

In this paper, detailed generator, exponential load, and static volt-ampere-reactive (VAr) compensator models are incorporated into traditional and voltage-stability-constrained optimal power-flow problems to study the effect that the different models have on costs and system-loadability. The proposed models are compared to typical models by means of a detailed analysis of the results obtained for two IEEE test systems; interior point

William D. Rosehart; Claudio A. Cañizares; Victor H. Quintana

2003-01-01

189

Asynchronized Turbogenerators as a Means of Improving the Stability and Voltage Control in Electric Networks  

Microsoft Academic Search

Voltage level normalization in networks of voltage class 220 – 500 kV is a long-standing problem for power pool systems in Russia. In recent years, this was due mainly to reduced power consumption and, as a consequence, the generation of reactive power by underloaded power transmission lines. At present, because of the limited means for reactive power compensation, synchronous turbo

I. A. Labunets; P. V. Sokur; N. D. Pinchuk; I. A. Kadi-Ogly; A. G. Loginov; A. V. Fadeev; V. T. Zinakov; E. V. Chernyshev; P. A. Sheiko

2004-01-01

190

Voltage collapse precipitated by the immediate change in stability when generator reactive power limits are encountered  

Microsoft Academic Search

When a generator of a heavily loaded electric power system reaches a reactive power limit, the system can become immediately unstable and a dynamic voltage collapse leading to blackout may follow. The statics and dynamics of this mechanism for voltage collapse are studied by example and by the generic theory of saddle node and transcritical bifurcations. It is shown that

I. Dobson; L. Lu

1992-01-01

191

Effect of voltage sags on adjustable speed drives-a critical evaluation and an approach to improve its performance  

Microsoft Academic Search

In this paper, a critical evaluation of the effect of voltage sags on adjustable speed drives (ASDs) is presented. In particular the DC-link voltage variation under voltage sag and its dependence on source impedance, DC-link inductance and output load is computed. It is shown that for larger source impedance, the DC-link voltage variation under a voltage sag is also large

J. L. Duran-Gomez; Prasad N. Enjeti; Byeong Ok Woo

1999-01-01

192

Effect of voltage sags on adjustable-speed drives: a critical evaluation and an approach to improve performance  

Microsoft Academic Search

In this paper, a critical evaluation of the effect of voltage sags on adjustable-speed drives (ASDs) is presented. In particular, the DC-link voltage variation under voltage sag and its dependence on source impedance, DC-link inductance and output load is computed. It is shown that, for larger source impedance, the DC-link voltage variation under a voltage sag is also large and

J. L. Duran-Gomez; P. N. Enjeti; Byeong Ok Woo

1999-01-01

193

Modeling of the automotive 14 V power net for voltage stability analysis  

Microsoft Academic Search

The number of electrical components in cars has steadily increased in recent years. Furthermore, systems with high peak loads like engine-start-stop systems and x-by-wire systems will be employed in the near future. These peak loads lead to voltage fluctuations within the power net. To guarantee the proper functioning of all electrical components, a stable voltage supply is necessary. This paper

Rainer Gehring; J. Froschl; T. P. Kohler; H.-G. Herzog

2009-01-01

194

Development of a drive cycle based evaluation method for Variable Voltage Converter in vehicle electrification applications  

Microsoft Academic Search

In this work, an innovative and feasible evaluation method is proposed to fully verify the Variable Voltage Converter (VVC) functionality for vehicle electrification applications. With the proposed method, the VVC can be fully tested for all four operation modes which can occur during vehicle real driving conditions. The proposed method provides a solution which allows hardware self-evaluation with HEV drive

Lihua Chen; Liwen Xu; Nagaraj Narayanachar; Shahram Zarei

2011-01-01

195

Computational Evaluation of Quiet Tunnel Hypersonic Boundary Layer Stability Experiments.  

National Technical Information Service (NTIS)

A computational evaluation of two stability experiments conducted in the NASA Langley Mach 6 axisymmetric quiet nozzle test chamber facility is conducted. Navier- Stokes analysis of the mean flow and linear stability theory analysis of boundary layer dist...

M. L. Manning

2000-01-01

196

Voltage dependence and stability of the gating kinetics of the fast chloride channel from rat skeletal muscle.  

PubMed

1. The voltage dependence and stability of the gating kinetics of the fast Cl-channel in excised patches of membrane from cultured rat skeletal muscle were studied with the patch clamp technique. Up to 10(6) open and shut intervals were analysed from each of five different patches containing a single fast Cl-channel. 2. To test for kinetic stability, plots of the mean durations of consecutive groups of 5-500 open and shut intervals were examined at each voltage. After excluding infrequent entries into both an apparent subconductance state and a long-lived (inactive) shut state, there were no abrupt and sustained changes in the moving means, indicating the absence of obvious shifts to other kinetic modes. The moving means did, however, fluctuate about the overall mean. 3. A comparison of experimental and simulated data indicated that most, but not all, of the fluctuation in the moving means was due to the stochastic variation inherent in the gating process. The fluctuation not accounted for by stochastic variation was mainly expressed as a slow, low-amplitude, component of drift about the mean. This slow component was unlikely to have arisen from measurement errors. 4. To examine whether the slow drift reflected detectable changes in kinetic modes, the data were divided into consecutive groups of 50,000 intervals. The exponential components describing the distributions were remarkably similar among the different groups, with stochastic variation accounting for most of the observed differences. This finding implies a single kinetic mode throughout the experiment. Thus, any changes in channel activity associated with the slow drift would have little effect on the analysis of gating kinetics presented here. 5. Depolarization increased channel open probability, Popen, for all five channels. This increase had a voltage sensitivity of 17 +/- 4 mV per e-fold change (effective gating charge of 1.6 +/- 0.32 electronic charges at 23 degrees C). Popen was 0.5 at -31 +/- 4 mV. 6. The depolarization-induced increase in Popen typically arose from a decrease in the mean shut time (19 +/- 4 mV per e-fold change; effective gating charge of 1.3 +/- 0.3 at 23 degrees C) and an increase in the mean open time (109 +/- 61 mV per e-fold change; effective gating charge of -0.24 +/- 0.13). 7. Neither plots of Popen versus voltage nor plots of the mean open and mean shut time versus voltage were completely described by a single Boltzmann distribution, suggesting multiple voltage-sensitive steps in channel gating.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1700104

Weiss, D S; Magleby, K L

1990-07-01

197

The study of countrate stability of photomultiplier tube with different types of voltage dividers  

Microsoft Academic Search

In the recent experiments for high energy physics (HEP), luminosity of beams has been increased to achieve the precise measurement. This leads to high countrate environment for photodetectors like photomultiplier tubes (PMTs). Even under such a condition, PMTs are required to be operated stably. To do that, it's important to choose a suitable divider from several kinds of high voltage

Y. Yoshizawa; H. Yamaguchi; N. Ooishi; H. Suzuki; S. Suzuki

1995-01-01

198

The study of countrate stability of photomultiplier tube with different types of voltage dividers  

Microsoft Academic Search

In the recent experiments for high energy physics (HEP) luminosity of beams has been increased to achieve the precise measurement. This leads to high countrate environment for photodetectors like photomultiplier tubes (PMTs). Even under such a condition, PMTs are required to be operated stably. To do that, ifs important to choose a suitable divider from several kinds of high voltage

Y. Yoshizawa; H. Yamaguchi; N. Ooishi; H. Suzuki; S. Suzuki

1996-01-01

199

Small disturbance voltage stability assessment of power systems by modal analysis and dynamic simulation  

Microsoft Academic Search

The introduction of liberalized electricity markets in many countries has resulted in more highly stressed power systems. On the other hand, operating points of a power system are acceptable in the feasible region, which is surrounded by the borders of different stabilities. Power system instability is critical for all participants of the electricity market. Determination of different stability margins can

Nima Amjady; Mohammad Reza Ansari

2008-01-01

200

Comparative performance evaluations of IGBTs and MCT in single-ended quasi-resonant zero voltage soft switching inverter  

Microsoft Academic Search

The simple and low-cost operation at zero voltage soft commutation voltage-fed quasi-resonant PFM inverter is widely used, which is more suitable and cost effective for consumer induction heated cooking appliances. This paper presents feasible performance evaluations of each generation IGBT developed and MOS controlled thyristor (MCT) incorporated into the simplest voltage source type quasi-resonant PFM inverter operating in zero voltage

Haruo Terai; Izuo Hirota; Takahiro Miyauchi; Hideki Omori; K. Ogura; Y. Hirota; M. Nakaoka

2001-01-01

201

Optimal Location of STATCOM and SVC Based on Contingency Voltage Stability by Using Continuation Power Flow: Case Studies of Khouzestan Power Networks in Iran  

Microsoft Academic Search

This paper presents a new approach for identification of optimal locations of STATCOM and SVC. The power system operates in stability boundary and system probably loses its stability by occurring disturbance, so considering contingency outage and recognition of voltage instability in allocation of shunt FACTS devices has importance. This paper by considering of power system contingencies based on the effects

Farbod Larki; Homayoun Meshgin Kelk; M. Pishvaei; A. Johar; M. Joorabian

2009-01-01

202

Determinants of Voltage-Dependent Gating and Open-State Stability in the S5 Segment of Shaker Potassium Channels  

PubMed Central

The best-known Shaker allele of Drosophila with a novel gating phenotype, Sh5, differs from the wild-type potassium channel by a point mutation in the fifth membrane-spanning segment (S5) (Gautam, M., and M.A. Tanouye. 1990. Neuron. 5:67–73; Lichtinghagen, R., M. Stocker, R. Wittka, G. Boheim, W. Stühmer, A. Ferrus, and O. Pongs. 1990. EMBO [Eur. Mol. Biol. Organ.] J. 9:4399–4407) and causes a decrease in the apparent voltage dependence of opening. A kinetic study of Sh5 revealed that changes in the deactivation rate could account for the altered gating behavior (Zagotta, W.N., and R.W. Aldrich. 1990. J. Neurosci. 10:1799–1810), but the presence of intact fast inactivation precluded observation of the closing kinetics and steady state activation. We studied the Sh5 mutation (F401I) in ShB channels in which fast N-type inactivation was removed, directly confirming this conclusion. Replacement of other phenylalanines in S5 did not result in substantial alterations in voltage-dependent gating. At position 401, valine and alanine substitutions, like F401I, produce currents with decreased apparent voltage dependence of the open probability and of the deactivation rates, as well as accelerated kinetics of opening and closing. A leucine residue is the exception among aliphatic mutants, with the F401L channels having a steep voltage dependence of opening and slow closing kinetics. The analysis of sigmoidal delay in channel opening, and of gating current kinetics, indicates that wild-type and F401L mutant channels possess a form of cooperativity in the gating mechanism that the F401A channels lack. The wild-type and F401L channels' entering the open state gives rise to slow decay of the OFF gating current. In F401A, rapid gating charge return persists after channels open, confirming that this mutation disrupts stabilization of the open state. We present a kinetic model that can account for these properties by postulating that the four subunits independently undergo two sequential voltage-sensitive transitions each, followed by a final concerted opening step. These channels differ primarily in the final concerted transition, which is biased in favor of the open state in F401L and the wild type, and in the opposite direction in F401A. These results are consistent with an activation scheme whereby bulky aromatic or aliphatic side chains at position 401 in S5 cooperatively stabilize the open state, possibly by interacting with residues in other helices.

Kanevsky, Max; Aldrich, Richard W.

1999-01-01

203

Reliability evaluation of radial distribution systems considering voltage drop constraints in the restoration process  

Microsoft Academic Search

Predictive reliability evaluation in distribution networks consists of the estimation of the system continuity indices based on the network topology and components' fault data. Traditionally, the proposed models to estimate these indices consider only the feeder's loading constraints along the restoration process. The system charge points may suffer voltage violations during the restoration process. Those violations can cause supply interruptions

C. L. C. de Castro; A. B. Rodrigues; M. G. Silva

2004-01-01

204

Evaluation and reduction of harmonic distortion caused by solid state voltage controllers of induction motors  

SciTech Connect

The harmonic distortion caused by a solid state AC voltage controller of an induction motor drive is evaluated. A conventional shunt harmonic filter (SHF) for harmonic reduction for a group of such drives is compared with a harmonic blocking compensator (HBC). It is shown that the HBC is more efficient in harmonic reduction than the SHF, especially, with distorted supply voltage. Moreover, the designer has more control over the HBC than the SHF performance. The HBC, however, has a higher power rating than the SHF.

Czarnecki, L.S.; Tan, O.T. (Louisiana State Univ., Baton Rouge, LA (United States))

1994-09-01

205

Using Game Theory to Evaluate the Stability of Strategic Forces.  

National Technical Information Service (NTIS)

A game theory method for evaluating the stability of various strategic force deployments in a confrontation between two parties is described. To illustrate the method future US and Soviet ICBM forces are projected. Evaluation of the results indicates that...

G. C. Reinhardt R. K. Squire

1982-01-01

206

Wide area measurement and protection system for emergency voltage stability control  

Microsoft Academic Search

When a major power system disturbance occurs, protection and control systems have to limit the impact, stop the degradation and restore the system to a normal state by appropriate remedial actions. Wide area measurement and protection systems limit the severity of disturbances by early recognition as well as proposition and execution of coordinated stabilizing actions. These systems complement classical protection

Christian Rehtanz; Joachim Bertsch

2002-01-01

207

Evaluation of Stone Column Stabilized Embankment Foundation.  

National Technical Information Service (NTIS)

The report documents construction procedures, monitors field performance, and make recommendations concerning the effectiveness and future use of a foundation improvement procedure using stone columns for stabilization. The effort was executed by use of f...

B. W. Meade D. L. Allen

1985-01-01

208

An Approach to Determine a Pair of Power-Flow Solutions Related to the Voltage Stability of Unbalanced Three-Phase Networks  

Microsoft Academic Search

This paper proposes an approach to determine a pair of power-flow solutions associated with the voltage stability of unbalanced three-phase networks. The approach is derived from the observations of the multiple three-phase power-flow solutions of a two-bus network. It is found that there are two pairs of solutions at the load bus. The plot of the voltage magnitude of each

Mamdouh Abdel-Akher; Mahrous E. Ahmad; Rabindra N. Mahanty; Khalid Mohamed Nor

2008-01-01

209

Online fuzzy voltage collapse risk quantification  

Microsoft Academic Search

Many voltage stability indicators have been proposed in the past for the voltage collapse assessment. Almost all of them are determined through quite complex analytical tools; therefore, it is difficult for system operators to give them a physical meaning. In order to perform a simple and reliable evaluation of the security margins, it is necessary to make a synthesis of

A. Berizzi; C. Bovo; D. Cirio; M. Delfanti; M. Merlo; M. Pozzi

2009-01-01

210

Stability of Measurement of Heterojunction Bipolar Transistors Current-Voltage Characteristics with Thermal Effect  

NASA Astrophysics Data System (ADS)

To obtain a reliable design, a careful determination of model parameters is needed. In this study, the thermally stable time of collector current (IC) of heterojunction bipolar transistors (HBTs) operated at different biasing points is observed. It is observed that the stable time of IC is different with different biasing points. The maximum thermally stable time is about 72 ms in this study. For the conventional measurement method, the default biasing time of current-voltage (IC-VCE) curves at each bias point is about 20 ms. The calculated thermal resistance and junction temperature obtained by the conventional measurement are quite different from those obtained by thermally stable measurement. In this work, we found that the thermal resistance obtained by thermally stable measurement (i.e. sufficiently long biasing time) is smaller than that obtained by conventional measurement. Moreover, the junction temperature estimated from the former is smaller than that from the latter. It is obvious that the biasing time of every measurement point must be ascertained by using the curve of IC versus biasing time with the operation VCE.

Wei, Sun-Chin; Su, Yan-Kuin; Wang, Ruey-Lue

2002-12-01

211

Evaluation of Niobium as Candidate Electrode Material for DC High Voltage Photoelectron Guns  

Microsoft Academic Search

The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain and two fine-grain) that were chemically polished using a

M. BastaniNejad; A. A Elmustafa; P. Adderley; J. Clark; S. Covert; J. Hansknecht; C. Hernandez--Garcia; M. Poelker; R. Mammei; K. Surles-Law; P. Williams

2012-01-01

212

Goals of stability evaluation throughout the vaccine life cycle.  

PubMed

Stability studies play a critical role in assuring product quality at all points in the vaccine life cycle. At and after licensure, stability studies on quality attributes (including potency) provide a critical link between marketed and clinically evaluated vaccine product, addressing important regulatory concerns by assuring that product quality is maintained throughout the dating period. During development, stability studies are done to assure product quality and to obtain the data needed to support licensure. Stability studies may also be performed after licensure to assure that product continues to perform as it did pre-licensure, as well as to evaluate the effect on product quality of deliberately introduced manufacturing changes. At each phase in the product life cycle, it is important to consider the goals of stability evaluation and to perform appropriate statistical analyses in order to assure and reach appropriate conclusions about product quality. PMID:19775911

Krause, Philip R

2009-09-22

213

Evaluation of the 1960-1963 Corvair Handling and Stability.  

National Technical Information Service (NTIS)

The National Highway Traffic Safety Administration (NHTSA), Department of Transportation, began an evaluation of the handling and stability characteristics of the 1960-1963 Corvair vehicle, beginning with review of General Motors Corporation documents and...

1972-01-01

214

Evaluation of the Threshold of Stability for the Human Spine  

PubMed Central

0. Abstract The threshold of stability (ToS) is introduced as a new tool for evaluating spinal stability. Current methods have evaluated the magnitude of spinal kinematic variability, stability diffusion, or Lyapunov exponents. This present method differs by modifying task difficulty to obtain a critical value delineating regions of stability and instability. Conceptually, as task difficulty increases, kinematic variability of the system increases and the basin of stability decreases. When kinematic variability exceeds the basin of stability, stability cannot be maintained over time. This concept is first illustrated using a mathematical model, from which an effective potential function was calculated to show the relationships among kinematic variability, the basin of stability, and task difficulty. In addition, an experiment was performed to evaluate the sensitivity of the ToS to changes in postural control using visual feedback as a control variable. The ToS was found to be more sensitive than the Lyapunov exponent to removal of visual feedback, suggesting it may have use as a diagnostic indicator (e.g. for low back pain). Furthermore, this new method has an additional advantage in that minimal instrumentation is needed. Its simplicity, sensitivity, and low cost suggest that the ToS has potential as a diagnostic or prognostic tool in a clinical setting.

Tanaka, Martin L.; Nussbaum, Maury A.; Ross, Shane D.

2009-01-01

215

DEVELOPMENT OF STABILITY EVALUATION METHOD OF RAILWAY LEANING RETAINING WALLS  

NASA Astrophysics Data System (ADS)

Conventionally, an inspection method to evaluate stability of railway retaining walls is basically visual inspection. This is because there is no quantitative inspection method. Therefore, a percussion test which is commonly applied to bridge substructures to check its stability was applied to the leaning retaining walls for investigation of their frequency characteristics. Subsequently, to indentify the relationships between the integrity and frequency characteristics of the retaining walls, a series of model tests was conducted. Consequently, a newly developed stability inspection and evaluation methods were presented, and successfully verified to apply to existing leaning retaining walls.

Shinoda, Masahiro; Nakajima, Susumu; Abe, Keita

216

ENVIRONMENTAL EVALUATION FOR UTILIZATION OF ASH IN SOIL STABILIZATION  

SciTech Connect

The Minnesota Pollution Control Agency (MPCA) approved the use of coal ash in soil stabilization, indicating that environmental data needed to be generated. The overall project goal is to evaluate the potential for release of constituents into the environment from ash used in soil stabilization projects. Supporting objectives are: (1) To ensure sample integrity through implementation of a sample collection, preservation, and storage protocol to avoid analyte concentration or loss. (2) To evaluate the potential of each component (ash, soil, water) of the stabilized soil to contribute to environmental release of analytes of interest. (3) To use laboratory leaching methods to evaluate the potential for release of constituents to the environment. (4) To facilitate collection of and to evaluate samples from a field runoff demonstration effort. The results of this study indicated limited mobility of the coal combustion fly ash constituents in laboratory tests and the field runoff samples. The results presented support previous work showing little to negligible impact on water quality. This and past work indicates that soil stabilization is an environmentally beneficial CCB utilization application as encouraged by the U.S. Environmental Protection Agency. This project addressed the regulatory-driven environmental aspect of fly ash use for soil stabilization, but the demonstrated engineering performance and economic advantages also indicate that the use of CCBs in soil stabilization can and should become an accepted engineering option.

David J. Hassett; Loreal V. Heebink

2001-08-01

217

Effect of energy and voltage ratings of ZnO protective systems of series capacitors on transient stability and transient torques  

SciTech Connect

The effect of voltage and energy ratings of ZnO protective systems of series capacitors on the transient stability and the transient torque phenomenon is investigated. The Bonneville Power Adminstration's Electromagnetic Transients Program (EMTP) is used for the studies. The stability studies are also carried out by a stability program and the results are compared with the EMTP results. The capacitor-varistor linear model is included in the stability program. The investigations show that the system switching strategy, the frequency of the inertial mode and the systems susceptability to SSR, are also important factors in proper determination of voltage and energy ratings of ZnO protective systems. As compared with the EMTP results, the stability program results are erroneous, if the effect of ZnO protective systems of series capacitors are not considered in the analysis. Inclusion of capacitor-varistor linear model(s) in a stability program, results in optimistic stability margins, however, the results can be accepted with a fair degree of confidence.

Iravani, M.R. (Univ. of Toronto, Toronto, Ontario M5S 1A4 (CA))

1988-11-01

218

Effect of energy and voltage ratings of ZnO protective systems of series capacitors on transient stability and transient torques  

SciTech Connect

The effect of voltage and energy ratings of ZnO protective systems of series capacitors on the transient stability and the transient torque phenomenon is investigated. The Bonneville Power Administration's Electromagnetic Transients Program (EMTP) is used for the studies. The stability studies are also carried out by a stability program and the results are compared with the EMTP results. The capacitor-varistor linear model is included in the stability program. The investigations show that the system switching strategy, the frequency of the inertial mode and the systems susceptability to SSR, are also important factors in proper determination of voltage and energy ratings of ZnO protective systems. As compared with the EMTP results, the stability program results are erroneous, if the effect of ZnO protective systems of series capacitors are not considered in the analysis. Inclusion of capacitor-varistor linear model(s) in a stability program, results in optimistic stability margins, however, the results can be accepted with a fair degree of confidence.

Iravani, M.R.

1988-01-01

219

Technical evaluation of the adequacy of station electric-distribution-system voltages for the Duane Arnold Energy Center  

SciTech Connect

The technical evaluation of the adequacy of the station electric distribution system voltages for the Duane Arnold Energy Center is documented. The evaluation is to determine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analyses submitted demonstrate that the offsite power sources in conjunction with the onsite distribution system has sufficient capacity and capability to supply adequate voltages to the Class 1E equipment under worst case conditions.

Selan, J.C.

1981-10-12

220

Technical evaluation of the adequacy of station electric distribution system voltages for the Haddam Neck Nuclear Power Plant  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Haddam Neck Nuclear Power Plant. The evaluation is to determine if the onsite distribution system, in conjunction with the offsite power sources, has sufficient capacity to automatically start and operate all class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analysis shows that the electric distribution system has the capacity and capability to supply adequate voltage to the class 1E equipment, provided that the grid is maintained at or above the administrative minimum limits.

Selan, J.C.

1982-02-01

221

Technical evaluation of the adequacy of station electric-distribution-system voltages for the Arkansas Nuclear One, Unit 2  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Arkansas Nuclear One, Unit 2. The evaluation is to determine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analyses submitted demonstrate that the station's electric distribution system supplies adequate voltage to the Class 1E equipment under the worst case conditions analyzed.

Selan, J.C.

1982-03-10

222

Technical evaluation of the adequacy of station electric distribution system voltages for the Arkansas Nuclear One, Unit 1  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Arkansas Nuclear One, Unit 1. The evaluation is to determine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analyses submitted demonstrate that the station's electric distribution system supplies adequate voltage to the Class 1E equipment under the worst case conditions analyzed.

Selan, J.C.

1981-12-16

223

Technical evaluation of the adequacy of station electric distribution system voltages for the San Onofre Nuclear Generating Station, Unit 1  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the San Onofre Nuclear Generating Station, Unit. The evaluation is to determine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analysis submitted demonstrates that acceptable voltages will be supplied to the Class 1E equipment under worst-case conditions.

Selan, J.C.

1982-01-14

224

Technical evaluation of the adequacy of station electric-distribution-system voltages for the Pilgrim Nuclear Power Station, Unit 1  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Pilgrim Nuclear Power Station, Unit 1. The evaluation is to determine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analyses demonstrated that for the worst case conditions established, the Class 1E equipment will automatically start and continue to operate within the equiment design voltage rating.

Selan, J.C.

1981-12-28

225

Technical evaluation of the adequacy of station electric distribution system voltages for the Yankee Rowe Nuclear Power Station  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Yankee Rowe Nuclear Power Station. The evaluation is to determine if the onsite distribution system, in conjunction with the offsite power sources, has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analysis shows that the station electric distribution system has the capacity and capability to supply voltage to the Class 1E equipment with their design ratings for the worst case loading condition.

Selan, J.C.

1981-05-29

226

Numerical evaluation of long-term stability  

SciTech Connect

The problem of predicting long-term particle loss in 4D betatronic motion is considered. A phenomenological scenario is derived through numerical tools based on tracking and frequency analysis. A three-parameter formula to interpolate the dynamic aperture versus the number of turns is proposed. The agreement with tracking data is excellent, and the extrapolation for very high number of turns agrees with the onset of chaos evaluated through the Lyapunov method.

Giovannozzi, M.; Todesco, E. [University of Bologna, Department of Physics, Via Irnerio 46, 40126, Bologna (Italy); Scandale, W. [CERN, SL. Division, CH 1211 Geneva (Switzerland)

1997-04-10

227

Low Voltage and High Transmittance Polymer-Stabilized Blue-Phase Liquid Crystal Device by Combined In-Plane and Oblique Electric Field along the Horizontal Direction  

NASA Astrophysics Data System (ADS)

We propose a polymer-stabilized blue-phase liquid crystal (PS-BPLC) device with high transmittance and low driving voltage by designing the electrode structure. The electrodes are comprised with two interdigitated bottom pixel electrodes with opposite polarities and a top common electrode with 0 V, which is placed in the middle of the two bottom electrodes. Since these electrode structures could generate a strong horizontal electric field and induce a high Kerr effect, we could realize a lower driving voltage (30 V) and higher transmittance characteristics (20%) than those of conventional PS-BPLC cells with an in-plane switching electrode structure.

Bae, Kwang-Soo; Lee, You-Jin; Yu, Chang-Jae; Lee, Hyeokjin; Park, Jae-Hong; Kim, Jae-Hoon

2012-07-01

228

Evaluation of Silicone Rubber Insulators used in High-Voltage Transmission Lines  

NASA Astrophysics Data System (ADS)

Three long-rod silicone rubber composite insulators used in 230 kV power transmission lines were evaluated for aging affects. The insulators were obtained from various outdoor desert locations within Saudi Arabia where they had been in service for 6 years. Surface degradation associated with the aging process was analyzed by using Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infra-Red Spectroscopy (FTIR), and Electron Spectroscopy for Chemical Analysis (ESCA). Electrical performance of insulators was evaluated by Rapid Flashover Voltage Tests (RFVT) and Pollution Severity Measurement Tests. Depending on their locations of service, the samples exhibited various types of pollutants at their surfaces. The analysis indicated that the insulator material showed localized surface degradation while there was no evidence of micro-cracking. Furthermore, it was noted that the electrical performance of the insulators was not significantly affected by exposure during the in-service period.

Ul-Hamid, Anwar; Soufi, Khaled Y.; Al-Hamoudi, Ibrahim

2008-04-01

229

Maturity and Stability Evaluation of Composted Yard Trimmings  

Microsoft Academic Search

The objective of this research was to evaluate a variety of stability and maturity in- dices for yard trimmings compost produced in the Puget Sound region of western Washington State. Compost samples were collected periodically during a 133-d com- posting cycle at a commercial composting facility, showing that indices of compost respiration rate were sensitive indicators of compost quality. All

Linda J. Brewer; Dan M. Sullivan; Oregon Corvallis

2003-01-01

230

Evaluation of ankle instability using the Biodex Stability System.  

PubMed

Ten patients with chronic unilateral functional lateral instability of the ankle were evaluated using the Biodex Stability System. This system uses a multiaxial testing platform which can be set at variable degrees of instability. Patients are then tested for their ability to "balance" the platform during single-limb stance, and a stability index is electronically generated. This stability index is believed to be an objective measurement that correlates with proprioceptive status of the ankle. Instability of the ankle was confirmed in all 10 patients, using stress radiographs. Two levels of platform stability were tested. With the platform in its most stable configuration, there was minimal difference between the previously injured and the uninjured ankle. With the platform set to permit up to 20 degrees of tilt in any plane, 6 of 10 patients had more difficulty balancing the platform with their injured ankle (higher stability index). This preliminary study suggests that the Biodex Stability System may be a useful tool in trying to objectively measure proprioceptive function. PMID:10353771

Testerman, C; Vander Griend, R

1999-05-01

231

Evaluation of capacitance-voltage characteristic and memory window of metal-ferroelectric-insulator-silicon capacitors  

NASA Astrophysics Data System (ADS)

It is recognized that the conventional model for metal-ferroelectric-insulator-silicon (MFIS) capacitor is always not consistent with the experimental observation very well due to negligence of the history-dependent electric field effect. In this letter, combining the switching physics of ferroelectric with silicon physics, an improved model is proposed to investigate the capacitance-voltage (C-V) characteristic and memory window. For two MFIS capacitors with SrBi2Ta2O9 and Bi3.25La0.75Ti3O12 ferroelectric layers, C-V characteristic and memory window were evaluated, and the results are more consistent with the previous experiments than that of the Lue model. The improved model could be extendedly applied to MFIS structure devices.

Zheng, X. J.; Sun, J.; Zhang, J. J.; Tang, M. H.; Li, W.

2008-11-01

232

Quantitative Evaluation of the Stability of Engineered Water Soluble Nanoparticles  

NASA Astrophysics Data System (ADS)

Stability of nanoparticle solutions is a key factor dictating the bioavailability and transport characteristics of nanoparticles (NPs) in the environment. The synthesis of materials with dimensions less than 100 nm relies on the ability to stabilize surfaces. If the stabilization of the material is disrupted by aggregation, precipitation, or dissolution, the chemical and physical properties often revert to the properties of the bulk material or molecular constituents. We synthesized CdSe and gold NPs, and studied their aggregation rate and the critical coagulation concentration (CCC) using Dynamic Light Scattering (DLS). The chemical and physical properties of our NPs have been characterized by Transmission Electron Microscopy (TEM), UV-VIS spectroscopy, IR spectroscopy, Zeta potential measurements, and Nuclear Magnetic Resonance (NMR) measurements. This comprehensive approach to synthesis and characterization enables the isolation of design parameters with greater precision that can be obtained using commercially available NPs. This research evaluates NP design parameters including composition, size, and surface coating, as a function of concentration, pH, and ionic strength, to determine which factors most affect NP stability. The aggregation characteristics of both gold NPs and cadmium selinide NPs, which are between 2-12 nm in diameter, and have been capped with various ligands, have been studied. While previous work demonstrates that these variables influence stability, it does not systematically compare their relative significance. Our results indicate that changing the ligand shell radically affects the stability of NP as a function of both pH and ionic strength, while changing the material from CdSe to gold has only a moderate influence on the stability and aggregation characteristics of our particles. Additionally, the ligand charge, length, and binding affinity all significantly effect NP stability. Funding was provided by the U.S. Department of Energy, the joint BER-EPA-NSF nanoparticulate research program. Aggregation behavior of gold and CdSe nanoparticles both capped with mercaptoundecanoic acid as a function of ionic strength.

Mulvihill, M. J.; Habas, S.; Mokari, T.; Wan, J.

2009-12-01

233

The impact of new generation pre-dressing medium-voltage electrical stimulation on tenderness and colour stability in lamb meat.  

PubMed

Previous work identified that a large number of domestic lamb carcases processed in Australia do not meet the recommended pH/temperature window during chilling. New medium voltage electrical stimulation technology has been developed to alleviate this problem. This study used an optimised setting (800mA with a pulse width 0.5ms) to evaluate the effects on meat quality with a focus on tenderness and meat colour. In total 40 (electrically stimulated) and 40 (non electrically stimulated) lambs from 11 lots killed over 2 days were evaluated. There was a significant difference (P<0.05) between stimulation treatments for initial pH, rate of pH decline and the predicted temperature at pH 6.0. There was also a large difference in the number of carcases that met the recommended window (pH of 6.0, between 18 and 25°C), with an average 67.5% of stimulated carcases and 25% of unstimulated carcases meeting or falling just above the recommended window. The stimulation treatment had no significant (P>0.05) effect on sarcomere length or myofibrillar fragmentation index (MFI) of the m. longissimus (LL). After 1day of ageing LL samples from stimulated carcases had a significantly lower (P<0.05) shear force than non stimulated samples, but there was no difference between stimulation treatments after 5 days ageing. However, ageing period did have a significant effect (P<0.001) on both MFI and shear force, such that 5days aged product had higher MFI and lower shear force values. There were minimal effects of stimulation on colour stability. PMID:22063030

Toohey, E S; Hopkins, D L; Stanley, D F; Nielsen, S G

2007-11-07

234

Evaluation of Triplet Aromaticity by the Isomerization Stabilization Energy.  

PubMed

The many manifestations of aromaticity have long fascinated both experimentalists and theoreticians. Due to their degenerate half-filled MOs, triplet [n]annulenes with 4n ?-electrons are also aromatic, but the degree of their stabilization has been difficult to quantify. The isomerization stabilization energy (ISE) method has been applied to evaluate the triplet aromaticity. The reliability of this approach is indicated by the strong correlation of the ISE results with NICS(1)zz, a magnetic indicator of triplet state aromaticity. PMID:23638944

Zhu, Jun; An, Ke; Schleyer, Paul von Ragué

2013-05-01

235

A novel neutral point potential stabilization technique using the information of output current polarities and voltage vector  

Microsoft Academic Search

This paper proposes a new neutral point potential control technique for the neutral-point-clamped three-level inverter. Utilizing the phase current polarity information, this technique distributes the redundant voltage vectors in a manner to obtain stable neutral point voltage under all operating conditions including the zero-power-factor condition. Detailed analysis and computer simulations show the superiority of the proposed method. The feasibility of

Katsutoshi Yamanaka; Ahmet M. Hava; Hiroshi Kirino; Yoshiyuki Tanaka; Noritaka Koga; Tsuneo Kume

2002-01-01

236

Radio frequency glow discharge source with integrated voltage and current probes used for evaluation of discharge parameters  

NASA Astrophysics Data System (ADS)

A radio frequency (rf) Grimm-type glow discharge source for the chemical analysis of solid samples, with integrated voltage and current probes, was developed. All elements of a plasma equivalent circuit are determined from the measured current-voltage characteristics. The procedure is based on the independent evaluation of the ion current and electron current region. The physical meaning of the parameters is investigated by comparisons with measurements from dc glow discharges. We found that the reduced rf current of the powered electrode is comparable to the reduced current in dc discharges. A formula is developed that corrects the reduced current due to gas heating. The sheath thickness at the powered rf electrode is evaluated and is between 75 and 1100 ?m. The voltage of the bulk plasma is in the range 2-15 V, and the resistance is between 30 and 400 ?. The bulk plasma consumes about 3% of the total power, and the reduced voltage is comparable to the reduced electrical field in the positive column of direct current discharges. The sheath voltage at the grounded electrode is in the range 25-100 V, the capacities are between 10 and 400 pF, and the resistances are in the range 100 ?-5000 ?. We also found invariants for the evaluated sheath parameters.

Wilken, L.; Hoffmann, V.; Wetzig, K.

2006-03-01

237

Voltage Divider  

NSDL National Science Digital Library

This voltage divider produces an output voltage, Vo, that is proportional to the input voltage, Vs. The output voltage is measured using a voltmeter. The input voltage is the voltage of the voltage source. The constant of proportionality is called the gain of the voltage divider. The value of the gain of the voltage divider is determined by the resistances, R1 and R2, of the two resistors that comprise the voltage divider.

2008-11-24

238

A vertical-field-driven polymer-stabilized blue phase liquid crystal mode to obtain a higher transmittance and lower driving voltage.  

PubMed

We demonstrate a vertical-field-driven polymer-stabilized blue phase liquid crystal (PS-BPLC) mode for solving low transmittance and high driving voltage problems in conventional in-plane-switching (IPS) PS-BPLC modes. By controlling the ray directions of incident beams by means of two prism sheets attached to the top and bottom substrates, continuous grayscale properties can be achieved with a vertical field, where the transmittance of the proposed structure can be increased to become twice as high as that of a IPS PS-BPLC cell, and its driving voltage can also be lowered by about 20 V. With the vertical-field-driven PS-BPLC mode, the hysteresis problem of the IPS PS-BPLC mode can also be solved due to a reduction of the electric field required to achieve sufficient field-induced retardation. PMID:21935109

Kim, Yong-Hun; Hur, Sung-Taek; Park, Chang-Sub; Park, Kyung-Woo; Choi, Suk-Won; Kang, Shin-Won; Kim, Hak-Rin

2011-08-29

239

Method for locating and evaluating geothermal sources of energy by sensing electrostatic voltage gradients  

Microsoft Academic Search

A method of locating subterranean sources of geothermal energy is devised wherein electrostatic voltage gradients are present at the earth's surface which correspond to the heat emanating from said geothermal sources. The method comprises traversing an area on the surface of the earth to be examined for geothermal sources, during such traversal sensing the magnitudes of the electrostatic voltage gradients

W. L. Sayer; P. Wright

1973-01-01

240

Evaluation Methods of Contamination Flashover Voltage Performance of Cylindrical Type Semi-conducting Glaze Porcelain Insulators  

NASA Astrophysics Data System (ADS)

Higher contamination flashover voltage of a semi-conducting glaze (SG) insulator owes primarily to the drying effect by leakage current flowing in the glaze. Significant reduction in contamination flashover voltage was confirmed on a cylindrical SG insulator when fog density was increased from 0.5g/m3 to 13g/m3 in clean fog test. The effect of de-energized duration between trip-out and re-energization on the contamination flashover voltage of a cylindrical SG insulator under cold-wet switch-on conditions was investigated. As the de-energized duration becomes shorter, the flashover voltage of a cylindrical SG insulator becomes higher. Higher contamination design voltages may be adopted even under cold-wet switch-on conditions.

Yamada, Kazuma; Hayashi, Akio; Saka, Chiharu; Sakanishi, Kenji; Matsuoka, Ryosuke; Ito, Susumu; Fujii, Osamu

241

Estimation of interruption performance in high-voltage circuit breakers with a modified method for arc parameter evaluation  

Microsoft Academic Search

Interruption performance of high-voltage circuit breakers has been quantitatively evaluated through current zero measurements during interruption tests. The interruption capabilities of the circuit breakers are able to be estimated by means of an arc model calculation. The parameters of the arc model are determined through the current zero measurements. In order to simulate more precisely the success or failure of

Hajime Urai; Youichi Ooshita; Makoto Koizumi; Noriyuki Yaginuma; Masanori Tsukushi

2011-01-01

242

An Improved Network-Equivalent Method of Reliability Evaluation for Complex Medium-Voltage Distribution System Based on Feeder Partition  

Microsoft Academic Search

A method of reliability evaluation for complex medium-voltage distribution system based on simplified network model and network-equivalent is proposed in this paper. According to the topology of distribution system and the function of the protection device and the switch, a distribution network is divided into different zones, the distribution network based on electrical components is changed into a simplified network

Huijia Liu; Hanmei Hu

2009-01-01

243

Evaluating the Performance of a Battery Using Temperature and Voltage Profiles and a Battery-Resistor Circuit Module  

ERIC Educational Resources Information Center

|An experimental learning module has been developed to study the mass and energy balance involved with operation of an AA Alkaline battery under a load current. An extension of the module allows evaluation of laboratory-assembled batteries using granular anodic/cathodic materials. The system allows load resistance to be varied and measures voltage

Sawyer, Bryan; Ji, Michelle; Gordon, Michael J.; Suppes, Galen J.

2010-01-01

244

High voltage stability of LiCoO2 particles with a nano-scale Lipon coating  

SciTech Connect

For high-voltage cycling of rechargeable Li batteries, a nano-scale amorphous Li-ion conductor, lithium phosphorus oxynitride (Lipon), has been coated on surfaces of LiCoO{sub 2} particles by combining a RF-magnetron sputtering technique and mechanical agitation of LiCoO{sub 2} powders. LiCoO{sub 2} particles coated with 0.36 wt% ({approx}1 nm thick) of the amorphous Lipon, retain 90% of their original capacity compared to non-coated cathode materials that retain only 65% of their original capacity after more than 40 cycles in the 3.0-4.4 V range with a standard carbonate electrolyte. The reason for the better high-voltage cycling behavior is attributed to reduction in the side reactions that cause increase of the cell resistance during cycling. Further, Lipon coated particles are not damaged, whereas uncoated particles are badly cracked after cycling. Extending the charge of Lipon-coated LiCoO{sub 2} to higher voltage enhances the specific capacity, but more importantly the Lipon-coated material is also more stable and tolerant of high voltage excursions. A drawback of Lipon coating, particularly as thicker films are applied to cathode powders, is the increased electronic resistance that reduces the power performance.

Kim, Yoongu [ORNL; Veith, Gabriel M [ORNL; Nanda, Jagjit [ORNL; Unocic, Raymond R [ORNL; Dudney, Nancy J [ORNL

2011-01-01

245

Technical-evaluation report on the adequacy of station electric-distribution-system voltages for the Vermont Yankee Nuclear Power Station. Document No. 50-271  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Vermont Yankee Nuclear Power Station. The evaluation is to determine if the onsite distribution system, in conjunction with the offsite power sources, has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The evaluation finds that the voltage analyses submitted demonstrate that adequate voltage will be supplied to the Class 1E equipment under worst case conditions.

Selan, J.C.

1982-09-03

246

Health Hazard Evaluation Report HETA 86-339-1741, EMCO High Voltage Company, Sutter Creek, California.  

National Technical Information Service (NTIS)

Possible exposure to several chemical substances during the fabrication of power supply modules was investigated at the EMCO High Voltage Company (SIC3679), Sutter Creek, California, at the request of an employee. Environmental air samples were collected ...

P. L. Belanger

1986-01-01

247

Power loss-oriented evaluation of high voltage IGBTs and multilevel converters in transformerless traction applications  

Microsoft Academic Search

The low-frequency line transformer in todays ac rail vehicles suffers from poor efficiency and a substantial weight. Future traction drives may operate directly from the mains without this transformer. A feasible concept for a transformerless drive system consists of series connected medium voltage converters applying modern high-voltage insulated gate bipolar transistors (HV-IGBTs). In a first design step, the switching characteristics

Sibylle Dieckerhoff; Steffen Bernet; Dietmar Krug

2005-01-01

248

Analysis and performance evaluation of a distribution STATCOM for compensating voltage fluctuations  

Microsoft Academic Search

Controller design of a STATCOM-based voltage compensator requires a valid analytical model of the system. If phasor algebra is used for modeling, it is difficult to accurately describe the STATCOM behavior during compensation of subcycle transients in the PCC voltage. In this paper, a small-signal model of the system, with a distribution line, is derived. Predictions based on frequency-domain analysis

P. S. Sensarma; K. R. Padiyar; V. Ramanarayanan

2001-01-01

249

Evaluation of motor-gasoline stability. Interim report  

SciTech Connect

This report covers results of a storage program whose primary goal was the development of improved methods for evaluating motor gasoline stability. Several existing and potential predictive tests were applied to individual refinery components of gasoline, selected laboratory blends, and commercial gasolines for which ASTM D 525 induction periods ranged from 75 to 5000 minutes. Darkroom storage was conducted at 43 C, 54 C, and ambient temperatures, for various time periods with ambient storage ultimately reaching 4 years for most of the samples. Results confirm the findings of earlier researchers that ASTM D 525 is not viable as a predictive device by virtue of a low coefficient of determination between induction period and gum formed in storage at 43 C for periods up to 1 year. It is recognized, however, and ASTM D 525 is not likely to be abandoned as a specification stability test. Based upon the data generated under the four phases of this storage stability of commercial/military motor gasoline (produced for long term storage) is the ASTM D 873 Method using a 6-hour aging existent gum maximum limit of 5 mg/100 mL.

Stavinoha, L.L.; Bowden, J.N.; LePera, M.E.

1990-12-01

250

Optical voltage reference  

DOEpatents

An optical voltage reference for providing an alternative to a battery source is described. The optical reference apparatus provides a temperature stable, high precision, isolated voltage reference through the use of optical isolation techniques to eliminate current and impedance coupling errors. Pulse rate frequency modulation is employed to eliminate errors in the optical transmission link while phase-lock feedback is employed to stabilize the frequency to voltage transfer function. 2 figures.

Rankin, R.; Kotter, D.

1994-04-26

251

Optical voltage reference  

DOEpatents

An optical voltage reference for providing an alternative to a battery source. The optical reference apparatus provides a temperature stable, high precision, isolated voltage reference through the use of optical isolation techniques to eliminate current and impedance coupling errors. Pulse rate frequency modulation is employed to eliminate errors in the optical transmission link while phase-lock feedback is employed to stabilize the frequency to voltage transfer function.

Rankin, R.; Kotter, D.

1992-12-31

252

Technical evaluation of the adequacy of station electric-distribution-system voltages for the St. Lucie Nuclear Power Plant, Unit 1  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the St. Lucie Nuclear Power Plant, Unit 1. The evaluation is to determine if the onsite distribution system, in conjunction with the offsite power sources, has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The voltage analysis submitted has adequately demonstrated the capacity and capability of the electrical distribution system to supply adequate voltage to the Class 1E equipment under worst case operating conditions.

Selan, J.C.

1981-10-05

253

Technical Evaluation Report on the Adequacy of Station Electric Distribution System Voltages for the Peach Bottom Atomic Power Station. Units 2 and 3.  

National Technical Information Service (NTIS)

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Peach Bottom Atomic Power Station, Units 2 and 3. The evaluation is to determine if the onsite distribution system, in conjunction ...

R. L. White

1982-01-01

254

Technical-Evaluation Report on the Adequacy of Station Electric-Distribution-System Voltages for the Nine Mile Point Nuclear Station, Unit 1, (Docket No. 50-220).  

National Technical Information Service (NTIS)

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Nine Mile Point Nuclear Station, Unit 1. The evaluation is to determine if the onsite distribution system in conjunction with the o...

J. C. Selan

1983-01-01

255

Biomechanical evaluation of immediate stability with rectangular versus cylindrical interbody cages in stabilization of the lumbar spine  

Microsoft Academic Search

BACKGROUND: Recent cadaver studies show stability against axial rotation with a cylindrical cage is marginally superior to a rectangular cage. The purpose of this biomechanical study in cadaver spine was to evaluate the stability of a new rectangular titanium cage design, which has teeth similar to the threads of cylindrical cages to engage the endplates. METHODS: Ten motion segments (five

Dilip K Sengupta; SMH Mehdian; Robert C Mulholland; John K Webb; Donna D Ohnmeiss

2002-01-01

256

Service-life evaluations of low-voltage power circuit breakers and molded-case circuit breakers  

Microsoft Academic Search

This paper summarizes the methods that are typically used in industry to evaluate the service-life of low-voltage power circuit breakers and molded-case circuit breakers. It reviews the electrical ratings and endurance requirements set forth in manufacturing standards, the ways that these endurance requirements can be used to develop expectations of circuit breaker life, the methods of maintenance inspections and the

M. J. Sprague

2000-01-01

257

Light flicker evaluation of power systems based on frequency spectrum of voltage waveforms  

Microsoft Academic Search

In this paper, a frequency domain approach is proposed to measure the light flicker of the electricity transmission systems. Analytical expressions of the instantaneous light flicker sensation are obtained beginning from the voltage waveform and these expressions are used to obtain a flicker estimation method based on the IEC flickermeter. In the proposed method, the leakage effect of the FFT

N. Kose; O. Salor; I. Cadirci

2009-01-01

258

A method for the evaluation of insulation systems for high voltage rotating machines  

Microsoft Academic Search

Partial Discharge Pattern of three important types of defects in insulation systems of high voltage rotating machines (the internal defect, the damaged semi-conductive screen and the defect on grading coating) were studied. As test object, model stator bars with artificial defects similar to practical ones on the ground wall and end-winding of bars were used. The internal defect in insulation

M. Farahani; E. Gockenbach; H. Borsi; M. Kaufhold

2003-01-01

259

Comparing and evaluating the voltage regulation of a UPFC and STATCOM  

Microsoft Academic Search

In recent years it has been illustrated that the installation position of a Unified power flow controller (UPFC) has an important effect on its overall performance. A pulse width modulation (PWM) based UPFC used as a voltage regulator is modeled and analyzed to investigate its optimal position in the transmission line. This is compared with STATic COMpensator (STATCOM) device. This

S. A Al-Mawsawi

2003-01-01

260

Evaluation of Dynamic Voltage and Frequency Scaling as a Differential Power Analysis Countermeasure  

Microsoft Academic Search

Differential power analysis (DPA) attack is a major concern for secure embedded devices (Ravi et al., 2004)-(Ors et al., 2004). Currently proposed countermeasures (Pramstaller, 2005)-(Tin and Verbauwhede, 2004) to prevent DPA imposes significant area, power and performance overheads. In addition they either require special standard cell library and design flows or algorithmic modifications. Recently, random dynamic voltage and frequency scaling

Karthik Baddam; Mark Zwolinski

2007-01-01

261

Multiobjective optimal power flows to evaluate voltage security costs in power networks  

Microsoft Academic Search

In this paper, new optimal power flow (OPF) techniques are proposed based on multiobjective methodologies to optimize active and reactive power dispatch while maximizing voltage security in power systems. The use of interior point methods together with goal programming and linearly combined objective functions as the basic optimization techniques are explained in detail. The effects of minimizing operating costs, minimizing

William D. Rosehart; Claudio A. Cañizares; Victor H. Quintana

2003-01-01

262

Preliminary safety evaluation for the plutonium stabilization and packaging system  

SciTech Connect

This Preliminary Safety Evaluation (PSE) describes and analyzes the installation and operation of the Plutonium Stabilization and Packaging System (SPS) at the Plutonium Finishing Plant (PFP). The SPS is a combination of components required to expedite the safe and timely storage of Plutonium (Pu) oxide. The SPS program will receive site Pu packages, process the Pu for storage, package the Pu into metallic containers, and safely store the containers in a specially modified storage vault. The location of the SPS will be in the 2736- ZB building and the storage vaults will be in the 2736-Z building of the PFP, as shown in Figure 1-1. The SPS will produce storage canisters that are larger than those currently used for Pu storage at the PFP. Therefore, the existing storage areas within the PFP secure vaults will require modification. Other modifications will be performed on the 2736-ZB building complex to facilitate the installation and operation of the SPS.

Shapley, J.E., Fluor Daniel Hanford

1997-03-14

263

Asymmetric synthesis and evaluation of a hydroxyphenylamide voltage-gated sodium channel blocker in human prostate cancer xenografts.  

PubMed

Voltage-gated sodium channels are known to be expressed in neurons and other excitable cells. Recently, voltage-gated sodium channels have been found to be expressed in human prostate cancer cells. ?-Hydroxy-?-phenylamides are a new class of small molecules that have demonstrated potent inhibition of voltage-gated sodium channels. The hydroxyamide motif, an isostere of a hydantoin ring, provides an active scaffold from which several potent racemic sodium channel blockers have been derived. With little known about chiral preferences, the development of chiral syntheses to obtain each pure enantiomer for evaluation as sodium channel blockers is important. Using Seebach and Frater's chiral template, cyclocondensation of (R)-3-chloromandelic acid with pivaldehyde furnished both the cis- and trans-2,5-disubsituted dioxolanones. Using this chiral template, we synthesized both enantiomers of 2-(3-chlorophenyl)-2-hydroxynonanamide, and evaluated their ability to functionally inhibit hNa(v) isoforms, human prostate cancer cells and xenograft. Enantiomers of lead demonstrated significant ability to reduce prostate cancer in vivo. PMID:22364743

Davis, Gary C; Kong, Yali; Paige, Mikell; Li, Zhang; Merrick, Ellen C; Hansen, Todd; Suy, Simeng; Wang, Kan; Dakshanamurthy, Sivanesan; Cordova, Antoinette; McManus, Owen B; Williams, Brande S; Chruszcz, Maksymilian; Minor, Wladek; Patel, Manoj K; Brown, Milton L

2011-09-01

264

Evaluation of Interconnect-Complexity-Aware Low-Power VLSI Design Using Multiple Supply and Threshold Voltages  

NASA Astrophysics Data System (ADS)

This paper presents a high-level synthesis approach to minimize the total power consumption in behavioral synthesis under time and area constraints. The proposed method has two stages, functional unit (FU) energy optimization and interconnect energy optimization. In the first stage, active and inactive energies of the FUs are optimized using a multiple supply and threshold voltage scheme. Genetic algorithm (GA) based simultaneous assignment of supply and threshold voltages and module selection is proposed. The proposed GA based searching method can be used in large size problems to find a near-optimal solution in a reasonable time. In the second stage, interconnects are simplified by increasing their sharing. This is done by exploiting similar data transfer patterns among FUs. The proposed method is evaluated for several benchmarks under 90nm CMOS technology. The experimental results show that more than 40% of energy savings can be achieved by our proposed method.

Waidyasooriya, Hasitha Muthumala; Hariyama, Masanori; Kameyama, Michitaka

265

Evaluation of Digital Crosstalk Noise on Differential Input Voltage Controlled Oscillator  

Microsoft Academic Search

With an increase in the operation frequency of complimentary metal oxide semiconductor (CMOS) circuits, a radio-frequency system-on-a-chip (RF-SOC) that integrates GHz-RF and large-scale digital circuits becomes a key device for wireless systems and high-speed networks. To develop high-performance RF-SOCs, high quality voltage controlled oscillators (VCOs) are required as local oscillators or clock generators, which operate in noisy environments suffering from

Akihiro Toya; Yoshitaka Murasaka; Takafumi Ohmoto; Atsushi Iwata

2008-01-01

266

Analysis and Performance Evaluation of Triac-Voltage Controlled Capacitor Run Induction Motor  

Microsoft Academic Search

This article presents steady-state analysis and simulation of triac-voltage controlled capacitor run single-phase induction motor driving a domestic fan load. Two schemes of circuits, namely, line controlled and branch controlled configurations, suitable for speed control are considered and simulation results are presented. Also, the two schemes are compared in terms of motor efficiency, line current pollution, and input power factor,

K. SUNDARESWARAN; P. S. MANUJITH

2004-01-01

267

Modeling and Interference Evaluation of Overhead Medium-Voltage Broadband Power Line (BPL) Systems  

Microsoft Academic Search

We analyze the radio interference from a Broadband Power Line (BPL) system operating between 2 MHz and several tens of MHz. The overhead medium-voltage (MV) power line is modeled as a 3-phase set of parallel wires above a lossy earth. A near-exact solution, based on previous approaches for infinitely long lines, is presented for the fields from arbitrarily long lines.

Song Liu; Larry J. Greenstein

2007-01-01

268

An evaluation of mitigation techniques for bearing currents, EMI and over-voltages in ASD applications  

Microsoft Academic Search

With the increased application of adjustable speed drives (ASDs) for the efficient speed control of AC motors, there has been a growing number of costly motor-drive related process failures. The popular ASDs consist of a pulse-width modulated (PWM) inverter switching insulated gate bipolar transistors (IGBTs) at 2 to 20 kHz, with rates of voltage rise (dv\\/dt) of 6000 V\\/?s. The

Annette von Jouanne; Haoran Zhang; Alan Wallace

1997-01-01

269

Evaluation of Surge Suppression Resistors in High-Voltage Circuit Breakers  

Microsoft Academic Search

The switching surge insulation level of steel tower and wood pole transmission lines operating at system voltage levels of 115 through 500 kV are compared with the switching surge magnitudes that can occur on these systems. High-side and low-side switching with and without surge suppression resistors is considered. The results indicate that at 345 kV and above surge suppression resistors

Charles Wagner; J. W. Bankoske

1967-01-01

270

Evaluation of capacitance-voltage characteristic and memory window of metal-ferroelectric-insulator-silicon capacitors  

Microsoft Academic Search

It is recognized that the conventional model for metal-ferroelectric-insulator-silicon (MFIS) capacitor is always not consistent with the experimental observation very well due to negligence of the history-dependent electric field effect. In this letter, combining the switching physics of ferroelectric with silicon physics, an improved model is proposed to investigate the capacitance-voltage (C-V) characteristic and memory window. For two MFIS capacitors

X. J. Zheng; J. Sun; J. J. Zhang; M. H. Tang; W. Li

2008-01-01

271

High voltage considerations with MLCs  

Microsoft Academic Search

Mica and film capacitors dominate most of the high voltage applications. The combination of high voltage withstanding characteristics and their stability under most electrical and environmental stress conditions have favored these types of capacitors in many designs. Over the years, ceramic capacitors have been developed for high voltage applications that have been proven very reliable in these applications, but the

M. Prevallet; S. Bagdy; J. Prymak; M. Randall

2004-01-01

272

Preparation of [In-111]-labeled-DTPA-bombesin conjugates at high specific activity and stability: evaluation of labeling parameters and potential stabilizers.  

PubMed

The aim of the present work was to obtain stabilized high specific activity (HSA) (111)In-labeled bombesin conjugates for preclinical evaluations. Parameters influencing the kinetics of labeling were investigated and the effect of stabilizers on HSA radiopeptides stability at room temperature were systematically categorized applying chromatography techniques. A SA of 174 GBq/?mol was achieved with high radiochemical purity, but the labeled compounds exhibited low stability. The addition of stabilizers avoided their radiolysis and significantly increased their stability. PMID:22405643

Pujatti, P B; Massicano, A V F; Mengatti, J; de Araújo, E B

2012-02-25

273

Technical-evaluation report on the adequacy of station electric-distribution-system voltages for the San Onofre Nuclear Generating Station, Unit 1. Document No. 50-206  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the San Onofre Nuclear Generating Station, Unit 1. The evaluation is to determine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analysis submitted demonstrates that acceptable voltages will be supplied to the Class 1E equipment under worstcase conditions.

Selan, J.C.

1982-09-08

274

Technical evaluation report on the proposed design modifications and technical-specification changes on grid voltage degradation for the San Onofre Nuclear Genetating Station, Unit 1  

SciTech Connect

This report documents the technical evaluation of the proposed design modifications and Technical Specification changes for protection of Class 1E equipment from grid voltage degradation for the San Onofre Nuclear Generating Station, Unit 1. The review criteria are based on several IEEE standards and the Code of Federal Regulations. The evaluation finds that the proposed design modifications and Technical Specification changes will ensure that the Class 1E equipment will be protected from sustained voltage degradation.

Selan, J.C.

1982-05-26

275

Voltage sag analysis case studies  

Microsoft Academic Search

This paper summarizes the results from a number of different voltage sag investigations. These investigations involve characterizing the voltage sag performance at a customer facility and evaluating equipment sensitivity to different voltage sag magnitudes and durations. Possible solutions to voltage sag sensitivity problems are also described

J. Lamoree; D. Mueller; P. Vinett; W. Jones; M. Samotyj

1994-01-01

276

Evaluation of approaches to active compressor surge stabilization  

Microsoft Academic Search

Recent work has shown that compression systems can be actively stabilized against the instability known as surge, thereby realizing a significant gain in system mass flow range. Ideally, this surge stabilization requires only a single sensor and a single actuator connected by a suitable control law. Almost all research to date has been aimed at proof of concept studies of

J. S. Simon; L. Valavani; A. H. Epstein; E. M. Greitzer

1993-01-01

277

A framework for the analysis of voltage collapse in electric power systems  

SciTech Connect

The phenomenon of voltage collapse in a power system is manifested as a progressive decline (i.e., sagging) in bus voltages, notably load bus voltages, over a relatively long time frame (i.e., seconds to minutes). At present, the voltage collapse problem is not fully understood; which makes its prevention, assessment and control difficult. Further complicating this problem is the confusion over whether voltage collapse is steady-state or dynamic in nature. The main contribution of this thesis is the formulation of a decision support framework to evaluate the accuracy of Performance Indices (PI's) used to assess voltage instability phenomena, such as voltage collapse, in electric power systems. It is shown that many of the criteria proposed in the literature to assess voltage stability can be rewritten in terms of scalar PI's and corresponding threshold values of the PI's. Based on this framework, criteria to assess voltage stability are reformulated as decision rules; so that, the misclassification errors incurred in using the criteria can be expressed in terms of (i) the probability of missing a voltage unstable event and (ii) the probability of false alarm. It is shown that the key to quantifying these misclassification errors are the definitions and characterizations of a Voltage Stability (VS) Region, which is based on the power system model and signifies the universal set of possible impacts on the system, and an Approximate Voltage Stability (AVS) Region, which is defined by the voltage stability criterion. Moreover, based on this framework, an optimization problem is formulated whose solution provides an accurate criterion to predict static mechanisms of voltage instability which satisfies a given trade-off in the number of misses and false alarms by the operator.

Mercede, F.J.

1989-01-01

278

EVALUATION OF SOLIDIFICATION/STABILIZATION AS A BEST DEMONSTRATED AVAILABLE TECHNOLOGY FOR CONTAMINATED SOILS  

EPA Science Inventory

This project involved the evaluation of solidification/stabilization technology as a BDAT for contaminated soil. Three binding agents were used on four different synthetically contaminated soils. Performance evaluation data included unconfined compressive strength (UCS) and the T...

279

Stability evaluation and treatment of a deformable rockmass in the Three Gorge Reservoir Area, China  

Microsoft Academic Search

The stability evaluation and control design of a deformable rockmass body was one of the most challenging problems encountered during the construction of the Three Gorge Reservoir in China. Part of the rockmass body appeared to be deforming where as the whole rockmass remained stable. The evaluation and improvement of the stability of a landslide appeared to be different for

XINLI HU; HUIMING TANG; YUANHUA LUO

280

Evaluation of accelerated stability test conditions for medicated chewing gums.  

PubMed

The overall stability of medicated chewing gums is investigated under different storage conditions. Active substances with different chemical stabilities in solid state are chosen as model drugs. The dosage form is a three layer tablet obtained by direct compression. The gum core contains the active ingredient while the external layers are formulated to prevent gum adhesion to the punches of the tableting machine. Two accelerated test conditions (40°C/75% RH and 30°C/65% RH) are performed for 6 months. Furthermore, a long-term stability test at room conditions is conducted to verify the predictability of the results obtained from the stress tests. Some drugs are stable in all the conditions tested, but other drugs, generally considered stable in solid dosage forms, have shown relevant stability problems particularly when stress test conditions are applied to this particular semi-solid dosage forms. For less stable drugs, the stress conditions of 40°C/75% RH are not always predictable of chewing gum stability at room temperature and may produce false negative; intermediate conditions, 30°C/65% RH, are more predictive for this purpose, the results of drug content found after 6 months at intermediate stress conditions and 12 months at room conditions are generally comparable. But the results obtained show that only long-term conditions stability tests gave consistent results. During aging, the semi solid nature of the gum base itself, may also influence the drug delivery rate during chewing and great attention should be given also to the dissolution stability. PMID:22794248

Maggi, Lauretta; Conte, Ubaldo; Nhamias, Alain; Grenier, Pascal; Vergnault, Guy

2012-07-16

281

Modulation of Human Mitochondrial Voltage-dependent Anion Channel 2 (hVDAC-2) Structural Stability by Cysteine-assisted Barrel-lipid Interactions.  

PubMed

Human mitochondrial voltage-dependent anion channel 2 (hVDAC-2), the most predominant isoform seen in brain mitochondria, is not only crucial for cell survival but is also implicated in Alzheimer disease. The abundance of cysteines in this isoform is particularly fascinating, as hVDAC-1 cysteines have no associated functional role. We report a detailed biophysical examination of a Cys-less mutant of hVDAC-2, and its behavioral comparison with the wild type protein. Our findings suggest that cysteine mutation results in the formation of a better barrel at the expense of weakened protein-lipid interactions. The wild type protein displays stronger lipid association, despite being less structured. A reversal in behavior of both proteins is observed in the case of chemical denaturation, with the Cys-less mutant exhibiting lowered unfolding free energies. In bicellar systems comprising 14-C phosphocholines, we observe that protein-lipid interactions are weakened in both constructs, resulting in barrel structure destabilization. Our biochemical and biophysical studies together reveal key structural roles for the cysteine residues. We find that minor conformational variations in local residues are sufficient to define the membrane protein dynamics in hVDAC-2. Such subtle sequence variations contribute to differential stability of VDACs and may have implications in their in vivo regulation and recycling. PMID:23873934

Maurya, Svetlana Rajkumar; Mahalakshmi, Radhakrishnan

2013-07-19

282

Evaluation of malonanilides as new stabilizers for double-base propellants.  

PubMed

Five malonanilide derivatives (M1-M5) were prepared by the reaction of ethyl malonate with aniline derivatives. These compounds were investigated as new stabilizers for double-base propellants (DBPs). The evaluation process has been performed through thermal stability tests, thermal analyses measurements (TGA and DSC) and kinetic parameters calculations (E(a)). The results of the new stabilizers were compared with the results of the classical stabilizer N, N-diethyldiphenyl urea. It has been found that o- and p-dinitromalonanilides, in particular, showed better stability effect for DBPs than the classical one. PMID:10751694

Zayed, M A; Soliman, A A; Hassan, M A

2000-04-28

283

Design Principle of the Precision Digital Control Reference Voltage Source  

Microsoft Academic Search

Reference voltage source is a high stabilization voltage source as a sort of voltage standard, used abroad in digital instrument, intelligent instrument and test system at present. At the auto-control domain, often need one output voltage adjustable precision reference voltage source to control the action of the execute machine. The characteristic of the digital control reference voltage is precision setting

Meng Zhiyong; Sha Zhanyou; Xu Yunfeng

2007-01-01

284

PBS performance evaluation under a high-accelerating-voltage e-beam exposure  

NASA Astrophysics Data System (ADS)

Advanced reticle fabrication, including phase-shifting mask (PSM) and optical proximity correction (OPC) reticle, has created a growing needs for a resist system with wider process latitude, superior linearity and fidelity, which lead to better CD uniformity. Some of aqueous-based DNQ-novolak resist systems, including chemical amplified one, have been proposed, however, their feasibility has not reached a practical level yet. Accordingly there seem to be many activities, in the industry at present, in re-establishing a new process technique and condition with conventional high-molecular polymer resists such as PBSTM particularly in utilizing a 'thin resist' coated blanks. Figure 1a shows e-beam resist trend of leading-edge 6' square and 250 mils thick (6025TM) photomask blanks shipment in '96 world-wide from our photomask blanks factory. High molecular polymer resist is still the major, and the top five resists have roughly 90% share, which are PBS, EBR-9TM, EBR-9 HS31TM, ZEP810TM and ZEP7000TM. Figure 1b shows 6025 PBS blanks shipment per coating thickness in '96. Thin PBS was started utilizing from '91, and had 17% share out of all 6025 PBS blanks shipment in '96. In order to reduce reticle CD error sources due to blanks, we have been doing exploratory study to determine the optimal resist process conditions in coating thickness and post-spin baking (PSB), exposure, dose as well, which enables us to appreciate real advantages of 'thin resist.' And we reported the results and its efficacy in patterning performance at Photomask Japan '97. In the report, 250 nm thick was selected particularly for PBS since it was a kind of standard as thin PBS already in the industry, while 300 nm thick was selected for the other four resists as our investigation results. Our study also resulted that only PBS had an inferiority in CD linearity as compared with the other four resists, but, exposure was done at 10 kV for PBS and 20 kV for the others. Then, we looked for an optimal PBS coating thickness again for suitable pattern resolution and risk of clear defect quality. We also tried to see an impact of e-beam accelerating voltage especially for PBS linearity and fidelity improvement this time. This paper describes our investigation results on optimum conditions in coating thickness, post-spin baking and exposure dose, as well as comparison results on patterning performance of thin resist coating between the top five conventional resists, PBS, EBR-9, EBR-9 HS31, ZEP-810 and ZEP-7000, for advanced e-beam reticle fabrication. An impact of e-beam accelerating voltage up on PBS patterning performance is also reported in this paper.

Kobayashi, Hideo; Higuchi, Takao; Asakawa, Keishi; Yokoya, Yasunori

1997-02-01

285

Evaluation of the mechanical stability of a megavoltage imaging system using a new flat panel positioner  

NASA Astrophysics Data System (ADS)

Mega-Voltage systems are used in radiation oncology both for external radiation delivery and patient positioning prior to treatment. A pair of portal images compared with digitally reconstructed radiographs is currently the gold standard for positioning but new developments have made possible the use of Mega-Voltage Cone Beam CT for better 3D setup. The non-ideal imaging geometry of the treatment unit has a direct impact on both methods. It led to the use of a reticule attachment as reference for the scale and the isocenter position on the portal images. The reticule has limited precision and occasionally super-imposes anatomical information. As for Cone Beam, the image quality crucially depends on the knowledge of the scan geometry during the acquisition. The reproducibility of the detector position at each angle will affect the image reconstruction and determine how frequently geometrical calibration must be performed. The objectives of this study are to measure the flex of the detector and evaluate its reproducibility. A RID 1640 Perkin Elmer a-Si Flat Panel is installed on a Siemens Primus linear accelerator with a positioner similar the the one used in the Oncor product. Three original methods are used to investigate the behavior in space and time of the imaging system. A reticule and a Plumb Bob tip are placed along the line formed by the isocenter and the source. Their positions projected on the flat panel for different gantry positions are used to calculate the mechanical flex. Projection matrices obtained in a geometrical Cone Beam calibration are also used to quantify the flat panel sagging. Six full sets of data were acquired over a period of 5 months and recorded overall mechanical flexes of 1 and 3 mm for the transversal and longitudinal directions respectively. The absolute magnitude of the flat panel displacement varies slightly with the method used but the discrepancy stays within the laser precision used for alignment. The small standard deviations of the flat panel displacement (< 1 mm) suggest great stability over time and permits the clinical implementation of patient positioning without the reticule. More experiments on the positioner with the complete set of projection matrices need to be performed to characterize the long-term behavior of the system and to determinate how frequently the Cone Beam calibration needs to be done to conserve image quality. Future work will develop a daily QA protocol to detect possible collisions that would bring the Cone Beam imaging system out of geometrical calibration.

Morin, O.; Chen, J.; Aubin, M.; Pouliot, J.

2005-04-01

286

Technical evaluation report on the proposed design modifications and technical specification changes on grid voltage degradation for the Millstone Nuclear Power Station, Unit 1  

Microsoft Academic Search

This report documents the technical evaluation of the proposed design modifications and Technical Specification change for protection of Class 1E equipment from grid voltage degradation for the Millstone Nuclear Power Station, Unit 1. The review criteria are based on several IEEE standards and the Code of Federal Regulations. The evaluation finds that the licensee has not provided sufficient information on

Selan

1982-01-01

287

Technical evaluation report on the proposed design modifications and technical-specification changes on grid voltage degradation for the San Onofre Nuclear Genetating Station, Unit 1  

Microsoft Academic Search

This report documents the technical evaluation of the proposed design modifications and Technical Specification changes for protection of Class 1E equipment from grid voltage degradation for the San Onofre Nuclear Generating Station, Unit 1. The review criteria are based on several IEEE standards and the Code of Federal Regulations. The evaluation finds that the proposed design modifications and Technical Specification

Selan

1982-01-01

288

Evaluation of a Jet Fuel Thermal Stability Rig  

Microsoft Academic Search

Current and planned gas turbine engines use fuel as their primary heat sink. When jet fuel is thermally stressed it will form gums and deposits. These deposits can block engine fuel nozzles, causing damage to the engine hot sections, especially the combustor region. The fuel's thermal stability is a critical fuel property with respect to optimum performance of modern military

Paul Rawson

289

Evaluation of Techniques for Algae Removal from Wastewater Stabilization Ponds.  

National Technical Information Service (NTIS)

The removal of algae from stabilization pond effluent can be accomplished by many methods, and under certain conditions each process can be shown to be economical and operational. A discussion of the most promising procedures proposed as a means of polish...

D. B. Porcella E. J. Middlebrooks G. R. Marshall J. H. Reynolds R. A. Gearheart

1974-01-01

290

Evaluation of the stability of gas hydrates in Northern Alaska  

USGS Publications Warehouse

The factors which control the distribution of in situ gas hydrate deposits in colder regions such as Northern Alaska include; mean annual surface temperatures (MAST), geothermal gradients above and below the base of permafrost, subsurface pressures, gas composition, pore-fluid salinity and the soil condition. Currently existing data on the above parameters for the forty-six wells located in Northern Alaska were critically examined and used in calculations of depths and thicknesses of gas hydrate stability zones. To illustrate the effect of gas hydrate stability zones, calculations were done for a variable gas composition using the thermodynamic model of Holder and John (1982). The hydrostatic pressure gradient of 9.84 kPa/m (0.435 lbf/in2ft), the salinity of 10 parts per thousand (ppt) and the coarse-grained soil conditions were assumed. An error analysis was performed for the above parameters and the effect of these parameters on hydrate stability zone calculations were determined. After projecting the hydrate stability zones for the forty-six wells, well logs were used to identify and to obtain values for the depth and thickness of hydrate zones. Of the forty-six wells, only ten wells showed definite evidence of the presence of gas hydrates. ?? 1987.

Kamath, A.; Godbole, S. P.; Ostermann, R. D.; Collett, T. S.

1987-01-01

291

Evaluation of malonanilides as new stabilizers for double-base propellants. (I)  

Microsoft Academic Search

Five malonanilide derivatives (M1–M5) were prepared by the reaction of ethyl malonate with aniline derivatives. These compounds were investigated as new stabilizers for double-base propellants (DBPs). The evaluation process has been performed through thermal stability tests, thermal analyses measurements (TGA and DSC) and kinetic parameters calculations (Ea). The results of the new stabilizers were compared with the results of the

M. A Zayed; A. A.-W Soliman; M. A Hassan

2000-01-01

292

Voltage Drop  

NSDL National Science Digital Library

The first site with information on voltage drop is provided by Power and System Innovations on their Frequently Asked Questions: Voltage Drop (1) page. Visitors can read what voltage drop is, what causes it, what happens as a result of it, and what the maximum recommended voltage drop is. The second site, Basics of Electricity (2), is part of General Electric's Lighting for Business Web site. Through descriptions and illustrations, the site explains what voltage drop is and gives examples of how it is calculated using Ohm's law. The next site is a lab worksheet that is part of a class from the Electrical and Computer Engineering Department of Montana State University called Voltage Drop in Cables (3). The objective of the lesson is to determine the internal resistance of an extension cord and choose the proper wire size for a particular application. Students are given an explanation of the procedure and a number of questions to answer related to the exercise. The Oregon Building Congress offers the Lesson Plans (4) Web site and the downloadable Voltage Drop educational activity. The lesson, which is suggested to be contained within a unit on formulas and solving literal equations, explores the concept of voltage drop that is encountered in basic wiring. The fifth site entitled Explanation of Voltage Drop in a Series Circuit (5) is offered by the Horizons Electronic Lesson Plan Resource. The page describes voltage drop as an electronic concept, gives a formula determining voltage drop, provides a schematic that helps illustrate the concept, and offers a quiz and answer sheet. Next, from electrician.com, is the online Voltage Drop Calculator (6). Users input the type and size of wire being used, the voltage and phase, circuit length, and amp load to calculate voltage drop and several other parameters. The seventh site, entitled The Hazards of Voltage Drop (7), is provided within the Electrical Construction Maintenance Web site. The page describes how electrical equipment can overheat or even power down if it operates below its voltage rating. It also provides a thorough explanation of how to determine the load's operating voltage. The last site, maintained by Williamson Labs (8), is a comprehensive learning site called Elementary Electricity. Visitors will find a wealth of information here, including fun descriptions, graphics, and animations on all aspects of electricity including voltage drop.

293

A noise-based stability evaluation of threshold-based feature selection techniques  

Microsoft Academic Search

This paper presents a noise-based stability performance evaluation approach for feature selection techniques. For the stability assessment, a similarity-based measure is used to quantify the degree of agreement between a filter's output on a clean dataset and its outputs on the same dataset corrupted with different combinations of noise level and noise distribution. Experiments are conducted with 11 threshold- based

Wilker Altidor; Taghi M. Khoshgoftaar; Amri Napolitano

2011-01-01

294

Evaluation of feature representation and machine learning methods in grasp stability learning  

Microsoft Academic Search

This paper addresses the problem of sensor-based grasping under uncertainty, specifically, the on-line estimation of grasp stability. We show that machine learning approaches can to some extent detect grasp stability from haptic pressure and finger joint information. Using data from both simulations and two real robotic hands, the paper compares different feature representations and machine learning methods to evaluate their

Janne Laaksonen; Ville Kyrki; Danica Kragic

2010-01-01

295

Modeling synchronous voltage source converters in transmission system planning studies  

Microsoft Academic Search

A Voltage Source Converter (VSC) can be beneficial to power utilities in many ways. To evaluate the VSC performance in potential applications, the device has to be represented appropriately in planning studies. This paper addresses VSC modeling for EMTP, powerflow, and transient stability studies. First, the VSC operating principles are overviewed, and the device model for EMTP studies is presented.

D. N. Kosterev

1997-01-01

296

Evaluation of three waterborne polymers as stabilizers for sandy soil  

Microsoft Academic Search

This study reports on waterborne polymer emulsion systems that were used for structural modification of sandy soils. The first\\u000a emulsion used was a styrene-acrylic, copolymer emulsion; the second and third were vinyl-acrylic, copolymer-based emulsions.\\u000a Specimens were prepared by adding different polymer emulsions to the sand and water in prescribed amounts. The performance\\u000a of the different emulsion systems as sand stabilizers

Abdullah Al-Khanbashi; Shihab W. Abdalla

2006-01-01

297

Intrinsic Surface Stability in LiMn{sub 2-x}Ni{sub x}O{sub 4-?} (x = 0.45, 0.5) High Voltage Spinel Materials for Lithium Ion Batteries  

SciTech Connect

This work reports the surface stability of the high voltage Li ion cathode LiMn{sub 2–x}Ni{sub x}O{sub 4–?} (x = 0.5, 0.45) by comparing thin film and powder composite electrodes after cycling using X-ray photoelectron spectroscopy. The thin film electrodes offer the ability to probe the surface of the material without the need of a conductive agent and polymer binder typically used in composite electrodes. The results suggest that neither oxidation of PF{sub 6} to POF{sub 3} nor the decomposition of ethylene carbonate or dimethylene carbonate occurs on the surface of the spinel material. These results confirm the enhanced cycling stability and rate capability associated with the high voltage spinel material and suggests that the SEI layer forms due to the reaction of electrochemically inactive components in composite electrodes with the electrolyte.

Carroll, Kyler J.; Yang, Ming-Che; Veith, G. M.; Dudney, N. J.; Meng, Ying Shirley

2012-01-01

298

Intrinsic Surface Stability in LiMn2-xNixO4-d (x=0.45, 0.5) High Volt-age Spinel Materials for Lithium Ion Batteries  

SciTech Connect

This work reports the surface stability of the high voltage Li ion cathode LiMn2-xNixO4- (x= 0.5, 0.45) by comparing thin film and powder composite electrodes after cycling using X-ray photoelectron spectroscopy. The thin film electrodes offer the ability to probe the surface of the material without the need of a conductive agent and polymer binder typically used in composite electrodes. The results suggest that neither oxidation of PF6 to POF5 nor the decomposition of ethylene carbonate or dimethylene carbonate occurs on the surface of the spinel material. These results confirm the enhanced cycling stability and rate capability associated with the high voltage spinel material and suggests that the SEI layer forms due to the reaction of electrochemically inactive components in composite electrodes with the electrolyte.

Carroll, Kyler J [University of California, San Diego; Yang, Ming-Che [University of Florida, Gainesville; Veith, Gabriel M [ORNL; Dudney, Nancy J [ORNL; Meng, Ying Shirley [University of California, San Diego

2012-01-01

299

EVALUATION OF CHEMICALLY BONDED PHOSPHATE CERAMICS FOR MERCURY STABILIZATION OF A MIXED SYNTHETIC WASTE  

EPA Science Inventory

This experimental study was conducted to evaluate the stabilization and encapsulation technique developed by Argonne National Laboratory, called the Chemically Bonded Phosphate Ceramics technology for Hg- and HgCl2-contaminated synthetic waste materials. Leachability ...

300

Panel Evaluation of the NHTSA Approach to the 1960-1963 Corvair Handling and Stability.  

National Technical Information Service (NTIS)

A three-man advisory panel was engaged by the National Highway Traffic Safety Administration to independently and objectively evaluate all of the information presented to them concerning the handling and stability performance of the 1960-1963 Corvair and ...

E. L. Resler P. H. Wright R. W. Caldwell

1972-01-01

301

EVALUATION USING AN ORGANOPHILIC CLAY TO CHEMICALLY STABILIZE WASTE CONTAINING ORGANIC COMPOUNDS  

EPA Science Inventory

A modified clay (organophilic) was utilized to evaluate the potential for chemically stabilizing a waste containing organic compounds. hemical bonding between the binder and the contaminants was indicated. eachate testing also indicated strong binding. Copy available at NTIS as ...

302

Evaluation of first swing stability of power system with doubly fed induction generator wind farms  

Microsoft Academic Search

For evaluating the first swing stability (FSS) of power systems in the presence of doubly fed induction generator (DFIG) wind farms, a simple and unified model of DFIG is proposed in this paper. In addition the proposed DFIG model is carefully incorporated into the power system for fast FSS evaluation. The evaluation algorithm is also presented in details in the

Gang Zheng; Ghadir Radman

2011-01-01

303

Intrinsic Surface Stability in LiMn2-xNixO4-d (x=0.45, 0.5) High Voltage Spinel Materials for Lithium Ion Batteries  

Microsoft Academic Search

This work reports the surface stability of the high voltage Li ion cathode LiMn{sub 2-x}NiâO{sub 4-δ} (x = 0.5, 0.45) by comparing thin film and powder composite electrodes after cycling using X-ray photoelectron spectroscopy. The thin film electrodes offer the ability to probe the surface of the material without the need of a conductive agent and polymer binder typically used

Kyler J Carroll; Ming-Che Yang; Gabriel M Veith; Nancy J Dudney; Ying Shirley Meng

2012-01-01

304

AN EVALUATION OF CONDITION MONITORING TECHNIQUES FOR LOW-VOLTAGE ELECTRIC CABLES  

SciTech Connect

Aging of systems and components in nuclear power plants is a well known occurrence that must be managed to ensure the continued safe operation of these plants. Much of the degradation due to aging is controlled through periodic maintenance and/or component replacement. However, there are components that do not receive periodic maintenance or monitoring once they are installed; electric cables are such a component. To provide a means of monitoring the condition of electric cables, research is ongoing to evaluate promising condition monitoring (CM) techniques that can be used in situ to monitor cable condition and predict remaining life. While several techniques are promising, each has limitations that must be considered in its application. This paper discusses the theory behind several of the promising cable CM techniques being studied, along with their effectiveness for monitoring aging degradation in typical cable insulation materials, such as cross-linked polyethylene and ethylene propylene rubber. Successes and limitations of each technique are also presented.

LOFARO,R.J.; GROVE,E.; SOO,P.

2000-07-23

305

Voltage and frequency stabilizer based on Fuzzy logic control for three-level NPC converters in stand-alone wind energy systems  

Microsoft Academic Search

The paper proposes a Fuzzy logic approach for controlling three-level NPC converters in stand alone wind energy systems. A key function of this controller is to maintain constant voltage and frequency for customers while maintaining smooth voltage waveform with less filtering requirements. The principle of the proposed Fuzzy controller is based on a modified PI approach in which the error

Ameen Gargoom; Abu Mohammad Osman Haruni; M. E. Haque; M. Negnevitsky

2010-01-01

306

Evaluation of oxygen utilization as an indicator of municipal solid-waste compost stability  

SciTech Connect

This research evaluated oxygen utilization parameters as indicators of MSW compost stability. Parameters evaluated were the oxygen utilization rate (OUR), specific oxygen uptake rate (SOUR), five-day biochemical oxygen demand, and chemical oxygen demand. In addition, other suggested indicators of stability were investigated including percent volatile solids, volatile solids reduction, nitrogen content, carbon: nitrogen ratio, and reheating potential (RP). OUR is a measure of the rate of oxygen utilization by the microorganisms in the decomposition of organic matter in compost. OUR was observed to be sensitive to the degree of stabilization and decreased with increasing compost age and stability. OUR values near zero indicate that the compost microorganisms are in a state of endogenous respiration, which is characteristic of a stable compost. Therefore, OUR is an excellent indicator of stability. A number of disadvantages are associated with OUR for practical application. Therefore, other parameters were evaluated as indicators of stability based on their statistical correlation to OUR. RP exhibited the strongest correlation to OUR. In combination, RP and SOUR were the two parameters which exhibited the strongest correlation to OUR. OUR, RP, and SOUR are all measures of microbial activity which reflect the degree of organic decomposition, and therefore, stability. Based on the results of this research; OUR, RP, and SOUR are useful parameters in assessing compost stability.

Zimmerman, R.A.

1991-01-01

307

Evaluation of uncertainty in the inductive measurement of critical current densities of superconducting films using third-harmonic voltages  

NASA Astrophysics Data System (ADS)

Several techniques can be used for inductive measurement of the critical current density Jc of large-area superconducting thin films used in microwave devices and fault-current limiters. The most popular of these methods employs the third-harmonic voltages V3. We have proposed a standard method using V3 for determining Jc under a criterion of electric field E. Here, the uncertainty in the standard method is evaluated. Since the measured Jc is directly proportional to the magnetic field at the upper surface of the superconducting film, the most significant systematic effect is the deviation of the coil-to-film distance Z1 from the prescribed value. The principal origins of this deviation of Z1 are (1) inadequate pressing of the coil onto the film and (2) ice layers occasionally forming between the coil and the protective polyimide film. If these effects are eliminated, uncertainty of Jc originates mainly from (a) uncertainty of the experimental coil coefficient k?, which is dominated by uncertainty of the transport Jc, and (b) underestimation of the induced electric field E when using a simple Bean model. For a typical DyBa2Cu3O7 film specimen, the relative combined standard uncertainty in the standard method was evaluated as ˜5%. The effect of the film edge on Jc measurements is also described.

Yamasaki, H.; Mawatari, Y.; Nakagawa, Y.; Yamada, H.

2012-10-01

308

Measurement and protocol for evaluating video and still stabilization systems  

NASA Astrophysics Data System (ADS)

This article presents a system and a protocol to characterize image stabilization systems both for still images and videos. It uses a six axes platform, three being used for camera rotation and three for camera positioning. The platform is programmable and can reproduce complex motions that have been typically recorded by a gyroscope mounted on different types of cameras in different use cases. The measurement uses a single chart for still image and videos, the texture dead leaves chart. Although the proposed implementation of the protocol uses a motion platform, the measurement itself does not rely on any specific hardware. For still images, a modulation transfer function is measured in different directions and is weighted by a contrast sensitivity function (simulating the human visual system accuracy) to obtain an acutance. The sharpness improvement due to the image stabilization system is a good measurement of performance as recommended by a CIPA standard draft. For video, four markers on the chart are detected with sub-pixel accuracy to determine a homographic deformation between the current frame and a reference position. This model describes well the apparent global motion as translations, but also rotations along the optical axis and distortion due to the electronic rolling shutter equipping most CMOS sensors. The protocol is applied to all types of cameras such as DSC, DSLR and smartphones.

Cormier, Etienne; Cao, Frédéric; Guichard, Frédéric; Viard, Clément

2013-01-01

309

RESULTS FROM THE STABILIZATION TECHNOLOGIES EVALUATED BY THE SITE PROGRAM  

EPA Science Inventory

The Superfund Innovative Technology Evaluation (SITE) Program was developed to assist the development of hazardous waste treatment technologies necessary to implement new cleanup standards which require greater reliance on permanent remedies. s part of the SITE program, four stab...

310

SMEDDS of Glyburide: Formulation, In Vitro Evaluation, and Stability Studies  

Microsoft Academic Search

The objective of the present investigation was to develop and evaluate self-microemulsifying drug delivery system (SMEDDS)\\u000a for improving the delivery of a BCS class II antidiabetic agent, glyburide (GLY). The solubility of GLY in oils, cosurfactants,\\u000a and surfactants was evaluated to identify the components of the microemulsion. The ternary diagram was plotted to identify\\u000a the area of microemulsion existence. The

Yogeshwar G. Bachhav; Vandana B. Patravale

2009-01-01

311

A method of reliability evaluation for complex medium-voltage distribution system based on simplified network model and network-equivalent  

Microsoft Academic Search

A method of reliability evaluation for complex medium-voltage distribution system based on simplified network model and network-equivalent is proposed in this paper. According to the topology of distribution system and the function of the protection device and the switch, a distribution network is divided into different zones, the distribution network based on electrical components is changed into a simplified network

Huijia Liu; Hanmei Hu; Jingguang Huang

2008-01-01

312

Voltage Controlled Voltage Source (VCVS)  

NSDL National Science Digital Library

Hosted by Clarkson University, this applet demonstrates a circuit that contains a voltage controlled voltage source (VCVS). The gain may be modified using the scroll bar. Even though brief, this resource can be used in a variety of different technical education classrooms.

Dorf, Richard C.; Svoboda, James A.

2008-11-27

313

An intelligent on line voltage regulation in power distribution system  

Microsoft Academic Search

In a reliable power system one of the most important requirements is to maintain the voltage at consumer premises within permissible ranges to ensure high quality of customer service. Since the voltage profile is consistently varied by load fluctuations hence it should be controlled by voltage regulators. Voltage stability and power quality of electrical systems depend on the proper voltage

Shrabani Pal; Sudipta Nath

2010-01-01

314

Probabilistic Stability Evaluation of Oppstadhornet Rock Slope, Norway  

NASA Astrophysics Data System (ADS)

Probabilistic analyses provide rational means to treat the uncertainties associated with underlying parameters in a systematic manner. The stability of a 734-m-high jointed rock slope in the west of Norway, the Oppstadhornet rock slope, is investigated by using a probabilistic method. The first-order reliability method (FORM) is used for probabilistic modeling of the plane failure problem in the rock slope. The Barton-Bandis (BB) shear strength criterion is used for the limit state equation. The statistical distributions of the BB criterion parameters, for which comprehensive data were collected and statistically analyzed, are determined by using distribution fitting algorithms. The sensitivity of the FORM model for the BB criterion is also investigated. It is found that the model is most sensitive to the mean value of the residual friction angle ( ? r) and least sensitive to the mean value of the slope angle ( ? f). It is also found that the standard deviation of joint compressive strength (JCS) causes the greatest difference in the reliability index, which has the least sensitivity to the change in the mean and standard deviation of joint roughness coefficient (JRC).

Duzgun, H. S. B.; Bhasin, R. K.

2009-10-01

315

Bench-Scale Evaluation Of Chemically Bonded Phosphate Ceramic Technology To Stabilize Mercury Waste Mixtures  

EPA Science Inventory

This bench-scale study was conducted to evaluate the stabilization of mercury (Hg) and mercuric chloride-containing surrogate test materials by the chemically bonded phosphate ceramics technology. This study was performed as part of a U.S. EPA program to evaluate treatment and d...

316

Yield Performance and Stability Evaluation of Peanut Breeding Lines with the CSM-CROPGRO-Peanut Model  

Microsoft Academic Search

Multienvironment trials of crop breeding lines consume many resources. Crop models have a potential to assist in this process. The goal of this study was to evaluate the potential of the CSM- CROPGRO-Peanut model in assisting with yield performance and stability evaluation of peanut (Arachis hypogaea L.) breeding lines. Seventeen peanut lines were tested in 11 environments in Thailand during

B. Suriharn; A. Patanothai; K. Pannangpetch; S. Jogloy; G. Hoogenboom

2008-01-01

317

Evaluation of stability of arsenic species in rice.  

PubMed

Although most edible vegetables do not accumulate As at a high rate, rice, carrots and certain others are exceptions. In addition to nutritional or toxicological considerations, the relatively high level and variety of As species present in rice make it a very suitable matrix for a candidate reference material representative of terrestrial biological samples.An analytical procedure was developed for As speciation in rice based on the use of a 1:1 methanol-water mixture for species extraction, an anion Hamilton PRPX-100 column (at pH 6, and phosphate mobile phase 10 mM), and a cation Hamilton PRP-X200 column (at pH 2.8 in pyridine formiate 4 mM) for species separation and final determination by HPLC-ICP-MS. The detection limits for dry flour rice expressed as As were 2 and 3 ng g(-1) for As(III) and AsB on the cation column and 3, 6 and 5 ng g(-1) for As(V), MMA and DMA, respectively, on the anion column. The methodology developed was applied to check the stability of As species in the water-methanol extract and also under different processing steps and storage time and temperature conditions. It was demonstrated that the As species in the water-methanol extracts stored at +4 degrees C remained stable for at least one month. Once the rice grains are ground, the MMA and As(V) species are not stable under any storage conditions probably due to microbiological activity. When ground rice is gamma-irradiated species remain stable although the AsB does not appear. PMID:12734624

Pizarro, Isabel; Gómez, Milagros; Palacios, Maria Antonia; Cámara, Carmen

2003-03-29

318

Multistate Structural Modeling and Voltage-Clamp Analysis of Epilepsy/Autism Mutation Kv10.2-R327H Demonstrate the Role of This Residue in Stabilizing the Channel Closed State.  

PubMed

Voltage-gated potassium channel Kv10.2 (KCNH5) is expressed in the nervous system, but its functions and involvement in human disease are poorly understood. We studied a human Kv10.2 channel mutation (R327H) recently identified in a child with epileptic encephalopathy and autistic features. Using multistate structural modeling, we demonstrate that the Arg327 residue in the S4 helix of voltage-sensing domain has strong ionic interactions with negatively charged residues within the S1-S3 helices in the resting (closed) and early-activation state but not in the late-activation and fully-activated (open) state. The R327H mutation weakens ionic interactions between residue 327 and these negatively charged residues, thus favoring channel opening. Voltage-clamp analysis showed a strong hyperpolarizing (?70 mV) shift of voltage dependence of activation and an acceleration of activation. Our results demonstrate the critical role of the Arg327 residue in stabilizing the channel closed state and explicate for the first time the structural and functional change of a Kv10.2 channel mutation associated with neurological disease. PMID:24133262

Yang, Yang; Vasylyev, Dmytro V; Dib-Hajj, Fadia; Veeramah, Krishna R; Hammer, Michael F; Dib-Hajj, Sulayman D; Waxman, Stephen G

2013-10-16

319

Evaluation of the Cell Voltage of Electrolytic HI Concentration for Thermochemical Water-Splitting Iodine-Sulfur Process  

SciTech Connect

Breakdown of the cell voltage in the electro-dialysis process for concentrating HIx solution (HI-H{sub 2}O-I{sub 2} mixture) was preliminarily examined in an effort to clarify the optimal operation condition as well as to optimize the cell design for the application to the thermochemical water-splitting IS process for large-scale hydrogen production. Basic data such as electric resistance of HIx solution, overvoltage of the iodine-iodide ion redox reaction at graphite electrode, and the membrane voltage drop, were measured using HIx solution with composition of interest. Also, a methodology for estimating the cell voltage was discussed. The calculated cell voltage agreed well with the experimental one indicating the validity of the procedure adopted. (authors)

Tanaka, Nobuyuki; Yoshida, Mitsunori; Okuda, Hiroyuki; Sato, Hiroyuki; Kubo, Shinji; Onuki, Kaoru [Japan Atomic Energy Agency, 4002 Narita-cho, Oarai-machi, Higash-iibaraki-gun Ibaraki 311-1393 (Japan)

2007-07-01

320

Evaluation, repair and stabilization of the boling sinkhole  

NASA Astrophysics Data System (ADS)

Abrupt ground subsidence occurred along FM 442, approximately 3 miles east of Boling, in Wharton County, Texas, in August 1983 The subsidence created a depression of approximately 250 feet in diameter with a maximum depth of about 25 feet. Roadway collapse, pavement breakage, and inundation of the sinkhole by subsurface waters forced the closure of FM 442 to thru-traffic The vicinity of the sinkhole is underlain, by alluvial deposits of the Colorado River drainage basin and unconsolidated Miocene, Pliocene, and Pleistocene sediments to a depth of about 500 feet. The sediments consist largely of sand, silts, clays, and gravels. The Boling Salt Dome and its associated caprock occur directly beneath the section of unconsolidated sediments Major and minor axes of the dome are about 5 miles and 35 miles, respectively, and the sinkhole occurred approximately 1 mile east-northeast of the dome's center An investigation was conducted in the immediate area of the sinkhole to determine the cause of the subsidence and also to determine the feasibility of dewatering the sinkhole Four monitoring wells were installed around the perimeter to evaluate the potential recharge from shallow sand units Two 300-foot holes were drilled and geophysically logged to determine the stratigraphy adjacent to the sinkhole, and two slope indicators were installed in order to evaluate further earth movements A total of six million gallons of saline water were removed and disposed of from the sinkhole Based on information provided by the geologic and dewatering investigation, the Texas State Department of Highways and Public Transportation elected to fill the existing sinkhole and reconstruct the roadway A total of 3,500 cubic yards of rock borrow and 26,000 cubic yards of soil borrow were placed in the depression Construction began in February 1984, and the roadway was completed in May A monitoring program to evaluate subsequent earth movements will continue into 1985

Dreyer, Boyd V.; Schulz, Clyde E.

1986-03-01

321

Optimal power flow incorporating voltage collapse constraints  

Microsoft Academic Search

The paper presents applications of optimization techniques to voltage collapse studies. First a “maximum distance to voltage collapse” algorithm that incorporates constraints on the current operating conditions is presented. Second, an optimal power flow formulation that incorporates voltage-stability criteria is proposed. The algorithms are tested on a 30-bus system using a standard power flow model, where the effect of limits

William Rosehart; C. Canizares; Victor Quintana

1999-01-01

322

Technical-Evaluation Report on the Tests Conducted to Verify the Analyses Performed on the Adequacy of Station Electric Distribution-System Voltages for the Arkansas Nuclear One, Unit 1 (Docket No. 50-313).  

National Technical Information Service (NTIS)

This report supplements the technical evaluation documented in a separate report dated December 16, 1981 (UCID-19118) on the adequacy of station electric distribution system voltages for the Arkansas Nuclear One, Unit 1. The evaluation is to determine the...

J. C. Selan

1983-01-01

323

Technical Evaluation Report on the Adequacy of Station Electric Distribution System Voltages for the Turkey Point Nuclear Generating Plant, Units 3 and 4. Docket Nos. 50-250, 50-251.  

National Technical Information Service (NTIS)

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Turkey Point Nuclear Generating Plant, Units 3 and 4. The evaluation is to determine if the onsite distribution system in conjuncti...

J. C. Selan

1982-01-01

324

First-strike stability: A methodology for evaluating strategic forces. Interim report  

SciTech Connect

This report presents a logical and transparent methodology for evaluating strategic offensive forces on the basis of first-strike stability, which the authors define as a condition that exists when neither superpower perceives the other as motivated by the strategic force posture to launch the first nuclear strike in a crisis. The methodology underlines that (1) first-strike stability under current conditions is relatively robust, (2) postures of U.S. and Soviet strategic nuclear forces become increasingly important under an arms reduction regime if the current level of first-strike stability is desired, (3) enlarging U.S. and Soviet strategic nuclear weapons inventories does not necessarily erode first-strike stability, (4) the superpowers should realize the importance of both sides generating forces early in a crisis to render these forces nontargetable.

Kent, G.A.; Thaler, D.E.

1989-08-01

325

Evaluation of factors affecting the solidification/stabilization of heavy metal sludge. Final report  

SciTech Connect

Solidification/stabilization of hazardous waste involves mixing the waste with a binder material to enhance the physical properties of the waste and to immobilize contaminants that may be detrimental to the environment. Many hazardous wastes contain materials that are known to inhibit the setting and strength development properties of cement and pozzolan binding agents commonly used in solidification/stabilization processes. This study presents the results of an evaluation into the effects of ten interfering substances (oil, grease, lead, copper, zinc, sodium hydroxide, sodium sulfate, phenol, trichloroethylene, and hexachlorobenzene) on the physical and contaminant mobility properties of a solidified/stabilized heavy metal sludge. Three binder materials (Portland cement, lime/fly ash, and cement/fly ash) were used to solidify/stabilize a synthetic metal plating waste sludge containing substantial concentrations of four metals (cadmium, chromium, nickel, and mercury). The effects of these interfering materials were evaluated using five physical tests: unconfined compressive strength (UCS), cone index, bulk density, wet/dry cycling, and permeability. Contaminant leaching properties were evaluated using the US Environmental Protection Agency's Extraction Procedure test. Microchemical/micromorphological analyses were also performed on the treated sludges.... Cement, Metals, Fixation, Pozzolan, Hazardous waste, Solidification, Heavy metals, Stabilization, Interferences.

Bricka, R.M.; Jones, L.W.

1993-03-01

326

An integrated chemical, thermal, and microbiological approach to compost stability evaluation.  

PubMed

The evaluation of compost stability is of the utmost importance for the reliability of composting as a recycling strategy. To date there is no single parameter that can give a sure indication of the stability of composts from different starting materials. This paper investigates different methods of evaluating the dynamics of transformation of materials and the stability level of the end products in a composting process. The following parameters were determined on compost samples of different ages from cotton (Gossypium herbaceum L.) cardings and yard wastes: humification index (HI), degree of humification (DH), thermogravimetry (TG) microbial biomass C (B(C)), and ninhydrin-reactive N (B(NIN)). Finally, from TG, derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) thermal stability parameters were deduced. Humification parameters in the end products (0.2 and 81% for HI and DH, respectively) showed the effective stability reached by the organic matter (OM). Thermal analysis evidenced the presence of two main organic pools with different thermal stability. During composting a relative increase in the more stable organic pool was indicated by the variation of the thermostability index R1 from 0.41 to 0.74. The parameter R1 was significantly correlated with both HI (r = -0.94; P < 0.05) and DH (r = 0.97; P < 0.05). Microbial biomass content dynamics reflected the availability of readily decomposable substrates. The ratio between B(NIN) and total N in the end product was 0.96%, indicating a good stability level. The simultaneous application of different approaches, considering different properties of composting materials, provides a more complete description of the stability and quality reached by the organic materials. PMID:14674563

Mondini, Claudio; Dell'Abate, Maria Teresa; Leita, Liviana; Benedetti, Anna

327

Stability and Correlates of Student Evaluations of Teaching at a Chinese University  

ERIC Educational Resources Information Center

|This paper examines the stability and validity of a student evaluations of teaching (SET) instrument used by the administration at a university in the PR China. The SET scores for two semesters of courses taught by 435 teachers were collected. Total 388 teachers (170 males and 218 females) were also invited to fill out the 60-item NEO Five-Factor…

Chen, Guo-Hai; Watkins, David

2010-01-01

328

PILOT-SCALE EVALUATION OF THE THERMAL STABILITY POHC INCINERABILITY RANKING  

EPA Science Inventory

A test series were performed at the U.S. EPA Incineration Research Facility (IRF) to evaluate the thermal-stability-based principal organic hazardous constituent (POHC) incinerability ranking. ixtures of twelve POHCs with predicted incinerabilities spanning the range of most- to ...

329

TECHNOLOGY EVALUATION REPORT: CHEMFIX TECHNOLOGIES, INC. - SOLIDIFICATION/STABILIZATION PROCESS - CLACKAMAS, OREGON - VOLUME II  

EPA Science Inventory

The CHEMFIX solidification/stabilization process was evaluated in the U.S. Environmental Protection Agency's SITE program. Waste from an uncontrolled hazardous waste site was treated by the CHEMFIX process and subjected to a variety of physical and chemical test methods. Physical...

330

TECHNOLOGY EVALUATION REPORT: CHEMFIX TECHNOLOGIES, INC. - SOLIDIFICATION/STABILIZATION PROCESS - CLACKAMAS, OREGON - VOLUME I  

EPA Science Inventory

The CHEMFIX solidification/stabilization process was evaluated in the U.S. Environment Protection Agency's SITE program. Waste from an uncontrolled hazardous waste site was treated by the CHEMFIX process and subjected to a variety of physical and chemical test methods. Physical t...

331

Evaluation of maturity and stability parameters of composts prepared from agro-industrial wastes  

Microsoft Academic Search

The objective of this study was to evaluate changes in physical, chemical and biological parameters to assess the maturity and stability of composts prepared from mixture of different farm and agro-industrial wastes over a period of 150days. All the composts appeared granular, dark grey in color without foul odor and attained an ambient temperature at 120days of composting indicating the

Dev Raj; R. S. Antil

2011-01-01

332

Mine stability evaluation of panel 1 during waste emplacement operations at WIPP.  

National Technical Information Service (NTIS)

The specific objectives of the work were defined by the Environmental Evaluation Group (EEG) as follows: (1) assess the stability of panel 1 during the proposed operation of waste emplacement; (2) estimate the amount of time before room closure would be e...

H. Maleki

1998-01-01

333

Bench?scale evaluation of asphalt emulsion stabilization of contaminated soils  

Microsoft Academic Search

The application of ambient temperature asphalt emulsion stabilization technology to the environmental fixation of soils contaminated by organic contaminants, primarily hydrocarbons, was pioneered in 1987. Since that time, the process has seen many applications in recycling contaminated soils into an environmentally stable, structurally enhanced, paving base material. A bench?scale demonstration was undertaken to evaluate and demonstrate the effectiveness of the

Michael F. Conway P. E

1993-01-01

334

Laboratory and Field Evaluation of Soil Stabilization Using Cement Kiln Dust.  

National Technical Information Service (NTIS)

A field and laboratory study was undertaken to evaluate Cement Kiln Dust (CKD) as a soil stabilizer. The performance of CKD from three different sources, Holnam of Ada, Blue Circle Cement of Tulsa, and Lone Star Industries, Inc. of Pryor was compared to t...

G. A. Miller M. M. Zaman J. Rahman N. K. Tan

2003-01-01

335

Trace Metals In Seawater: Chelation Capacities, Conditional Stability Constants, And Water Sampler Evaluations (copper, Zinc, Lead)  

Microsoft Academic Search

In this study, the use of anodic stripping voltammetry and copper titrations for the determination of complexation capacity and conditional stability constants for copper-organic complexes in seawater has been evaluated. Pseudopolarogram studies showed that there were two separate polarographic waves corresponding to the reduction of inorganic copper complexes and to the reduction of organic forms of copper. An equation for

Mary Jo Spencer

1984-01-01

336

Montezuma Creek Stability Evaluation at Site of Former Monticello Tailings Pile  

Microsoft Academic Search

This report documents the results of an evaluation of stream stability for Montezuma Creek downstream of the former uranium and vanadium millsite at Monticello, Utah. The work was performed by personnel from Oak Ridge National Laboratory's (ORNL's) Environmental Technology Section (ETS). ORNL\\/ETS was the Independent Verification Contractor (IVC) for the Monticello projects, and it established independent verification strategies that provided

Korte

2001-01-01

337

EVALUATION OF SOLIDIFICATION/STABILIZATION TREATMENT PROCESSES FOR MUNICIPAL WASTE COMBUSTION RESIDUES  

EPA Science Inventory

Investigations were carried out to compare and evaluate solidification/stabilization (S/S) processes to treat residues from combustion (MWC). ull factorial experimental design was used to processes to treat bottom ash, air pollution control (APC) residue, The 5 S/S processes incl...

338

High-level waste-form-product performance evaluation. [Leaching; waste loading; mechanical stability  

SciTech Connect

Seven candidate waste forms were evaluated for immobilization and geologic disposal of high-level radioactive wastes. The waste forms were compared on the basis of leach resistance, mechanical stability, and waste loading. All forms performed well at leaching temperatures of 40, 90, and 150/sup 0/C. Ceramic forms ranked highest, followed by glasses, a metal matrix form, and concrete. 11 tables.

Bernadzikowski, T A; Allender, J S; Stone, J A; Gordon, D E; Gould, Jr, T H; Westberry, III, C F

1982-01-01

339

Evaluation of Stability Changes in Tapered and Parallel Wall Implants: A Human Clinical Trial  

PubMed Central

Objective To determine the pattern of stability changes as a reflection of early healing around single-stage roughened-surface implants in humans utilizing resonance frequency analysis (RFA). Materials and Methods Hundred twenty-five patients who demanded dental implants were treated with two different implant (Nobel Biocare Replace™ and Strumman™ ITI) systems. Bone type was classified into four groups. RFA was used for direct measurement of implant stability on the day of implant placement and consecutively at 14, 30 and 60 days after placement. The data were analyzed with Student t test and regression analysis. Results Three-hundred four roughened surface implants placed in the maxilla and mandible were evaluated. In Replace™ implants the lowest mean stability measurement was at 30 days for all bone types and the stability did not change significantly in any of the bone types (p>0.05). ITI™ implants demonstrated the lowest stability at 60 days for type 1 and 30 days and baseline for type 2, 3 and 4 bones. In addition, there was significant differences in implant stability between bone types 1 and 4 (P<0.001), 2 and 3 (p<0.05), and bone types 3 and 4 (P=0.07) at all aforementioned times in ITI™ implants. In Replace™ implants, regarding the implant diameter, contrary to ITI implants, no significant stability changes were detected (p>0.05). No significant difference was observed regarding gender, age and lengths in both systems. Conclusion In comparison to ITI™ implants, Replace™ implants revealed no significant difference in the pattern of stability changes among different bone types.

Rokn, AR.; Ghahroudi, AAR. Rasouli; Mesgarzadeh, A.; Miremadi, AA.; Yaghoobi, S.

2011-01-01

340

Evaluation of Hose in Hose Transfer Line Service Life for Hanford's Interim Stabilization Program  

SciTech Connect

RPP-6153, Engineering Task Plan for Hose-in-Hose Transfer System for the Interim Stabilization Program, defines the programmatic goals, functional requirements, and technical criteria for the development and subsequent installation of transfer line equipment to support Hanford's Interim Stabilization Program. RPP-6028, Specification for Hose in Hose Transfer Lines for Hanford's Interim Stabilization Program, has been issued to define the specific requirements for the design, manufacture, and verification of transfer line assemblies for specific waste transfer applications. Included in RPP-6028 are tables defining the chemical constituents of concern to which transfer lines will be exposed. Current Interim Stabilization Program planning forecasts that the at-grade transfer lines will be required to convey pumpable waste for as much as three years after commissioning. Prudent engineering dictates that the equipment placed in service have a working life in excess of this forecasted time period, with some margin to allow for future adjustments to the planned schedule. This document evaluates the effective service life of the Hose-in-Hose Transfer Lines, based on information submitted by the manufacturer and published literature. The effective service life of transfer line assemblies is a function of several factors. Foremost among these are process fluid characteristics, ambient environmental conditions, and the manufacturer's stated shelf life. This evaluation examines the manufacturer's certification of shelf life, the manufacturer's certifications of chemical compatibility with waste, and published literature on the effects of exposure to ionizing radiation on the mechanical properties of elastomeric materials to evaluate transfer line service life.

TORRES, T.D.

2000-08-24

341

A desensitized controller for voltage regulation of power systems  

Microsoft Academic Search

In this paper, a robust linear voltage controller is proposed to improve power system stability and performance under varying operating conditions. This controller includes an automatic voltage regulator and power system stabilizer. It limits the variations of the terminal voltage, damps electromechanical oscillations and increases the excitation during and after a short circuit in all operating points. The design method

A. Heiiiche; H. Bourles; M. P. Houry

1995-01-01

342

Soil stabilization using oil shale solid wastes: Laboratory evaluation of engineering properties  

SciTech Connect

Oil shale solid wastes were evaluated for possible use as soil stabilizers. A laboratory study was conducted and consisted of the following tests on compacted samples of soil treated with water and spent oil shale: unconfined compressive strength, moisture-density relationships, wet-dry and freeze-thaw durability, and resilient modulus. Significant increases in strength, durability, and resilient modulus were obtained by treating a silty sand with combusted western oil shale. Moderate increases in strength, durability, and resilient modulus were obtained by treating a highly plastic clay with combusted western oil shale. Solid waste from eastern shale can be used for soil stabilization if limestone is added during combustion. Without limestone, eastern oil shale waste exhibits little or no cementation. The testing methods, results, and recommendations for mix design of spent shale-stabilized pavement subgrades are presented. 11 refs., 3 figs., 10 tabs.

Turner, J.P.

1991-01-01

343

Evaluation of the stability of gentamicin in different antibiotic carriers using a validated MEKC method.  

PubMed

The quality control of gentamicin in different antibiotic carriers, using MEKC as stability-indicating method is described. Baseline separations of gentamicin C1, C1a, C2, C2a and C2b and, furthermore the impurities and degradation products garamin (GARA), 2-deoxy-streptamine (DSA) and sisomicin (SISO) were achieved with a background electrolyte containing 20mM deoxycholic acid, 15 mM beta-cyclodextrin and 100mM tetraborate (pH 10.0). After derivatization with o-phthaldialdehyde reagent (OPA), UV detection at 340 nm was possible. The method was validated with respect to selectivity, limit of detection (LOD) and quantification (LOQ) of the impurities, linearity, accuracy, precision and robustness. Evaluation of four different antibiotic carriers stored under stability conditions according to the International Conference on Harmonization (ICH) guidelines and older pharmaceutical formulations disclosed good stability. PMID:18639995

Kühn, K-D; Weber, C; Kreis, S; Holzgrabe, U

2008-06-18

344

Evaluation of the Long-Term Stability and Temperature Coefficient of Dew-Point Hygrometers  

NASA Astrophysics Data System (ADS)

The continuous quest for improved specifications of optical dew-point hygrometers has raised customer expectations on the performance of these devices. In the absence of a long calibration history, users with a limited prior experience in the measurement of humidity, place reliance on manufacturer specifications to estimate long-term stability. While this might be reasonable in the case of measurement of electrical quantities, in humidity it can lead to optimistic estimations of uncertainty. This article reports a study of the long-term stability of some hygrometers and the analysis of their performance as monitored through regular calibration. The results of the investigations provide some typical, realistic uncertainties associated with the long-term stability of instruments used in calibration and testing laboratories. Together, these uncertainties can help in establishing initial contributions in uncertainty budgets, as well as in setting the minimum calibration requirements, based on the evaluation of dominant influence quantities.

Benyon, R.; Vicente, T.; Hernández, P.; De Rivas, L.; Conde, F.

2012-09-01

345

Analysis and Performance Evaluation of Interleaved DCM\\/CCM Boundary Boost PFC Converters Around Zero-Crossing of Line Voltage  

Microsoft Academic Search

In this paper, causes of improper interleaving of two DCM\\/CCM boundary boost PFC converters around zero crossing of the line voltage are analyzed. The converters have a master-slave relationship. The slave is synchronized to the turn-on instant of the master by using an open-loop interleaving method. It is shown that phase shifting the gate drive signals of the two stages

Claudio Adragna; Laszlo Huber; Brian T. Irving; M. M. Jovanovic

2009-01-01

346

pH stability and comparative evaluation of ranaspumin-2 foam for application in biochemical reactors  

NASA Astrophysics Data System (ADS)

Aqueous channels of foam represent a simplified, natural bioreactor on the micro-/nano-scale. Previous studies have demonstrated the feasibility and potential application of foams in replicating cellular process in vitro, but no research has been performed to establish a basis for designing stable and biocompatible foam formulations. Our research has been directed specifically to the evaluation of ranaspumin-2 (RSN-2), a frog foam nest protein. The strong surfactant activity of RSN-2 enabled us to produce foams using low protein concentration (1 mg ml-1) over a wide pH range (pH ? 3). Importantly, the RSN-2 formulation exhibited the best foam stability at a near neutral pH condition, which shows a potential for application to various biosynthesis applications. Model cellular systems such as liposomes and inactivated A/PR/8/34 influenza virus maintained their physicochemical stability and full hemagglutination activity, indicating biocompatibility of RSN-2 with both cellular membranes and proteins both in bulk solution and in foam. Moreover, the addition of RSN-2 did not exert any deteriorative effects on bacterial cell growth kinetics. In contrast, Tween 20, Triton X-100, and BSA did not show satisfactory performance in terms of foamability, foam stability, physicochemcial stability, and biochemical stability. Although our study has been limited to representative formulations composed of only surfactant molecules, a number of unique advantages make RSN-2 a promising candidate for in vitro foam biosynthesis.

Choi, Hyo-Jick; Ebersbacher, Charles F.; Quan, Fu-Shi; Montemagno, Carlo D.

2013-02-01

347

Evaluation of Rotordynamic Stability of a Steam Turbine Due to Labyrinth Seal Force  

NASA Astrophysics Data System (ADS)

This paper describes the evaluation of unstable vibration caused by the seal force, which is known as "Steam Whirl" in a steam turbine. Stability of a steam turbine is evaluated by complex eigenvalue analysis of rotordynamics model considering the dynamics of seals, rotor, bearings and pedestals. A commercial CFD program is employed to estimate the dynamic coefficients of labyrinth seal. The labyrinth seal of a large scales steam turbine is taken as an object of analysis and a 3D model with eccentric rotor is solved to obtain the rotordynamic force components. The rotordynamic force is derived by integrating the pressure on the rotor surface. Evaluation formula is formed from the results of numerical calculation, which is used to predict the dynamic coefficient of each seal in a steam turbine. Then rotordynamics model of total system including seal is constructed and stability is evaluated by complex eigenvalue analysis. This procedure is applied to the design of steam turbines and enables the optimization of the turbine structure considering the efficiency and stability.

Hirano, Toshio; Sasaki, Takashi; Sakakida, Hitoshi; Uchida, Tatsuro; Tsutsui, Masaji; Ikeda, Kazunori

348

Template-free self-assembling fullerene and lipopeptide conjugates of alamethicin form voltage-dependent ion channels of remarkable stability and activity.  

PubMed

N- and C-terminally modified with fullerene or lipopeptide alamethicin molecules were designed for the formation of template-free, self-assembling, voltage-dependent ion conducting channels. The automated solid phase synthesis of the alamethicin-F30 sequence was performed by in situ fluoride activation on 2-chlorotritylchloride-polystyrene resin and the conjugation with fullerenes-C60 and -C70 was carried out in solution. Voltage-dependent bilayer experiments revealed preferred channel sizes for C-terminal alamethicin F30-fullerene-C60 and -C70 conjugates and higher activity compared with native alamethicin, whereas N-terminally linked fullerene balls destabilize pore formation. C-terminal alamethicin F30-fullerene-C70 conjugates show pore states with remarkably long lifetimes of seconds. C-terminal lipopeptide conjugates of alamethicin were prepared by coupling via short peptide spacers with synthetic tripalmitoyl-S-glyceryl-cysteine. which represents the strong membrane anchoring N-terminus of bacterial lipoprotein. Alamethicin-lipopeptide conjugates exhibit high channel forming activities, whereby they self-assemble and adopt preferred pore states with extremely long lifetimes. The novel membrane modifying peptaibol constructs are valuable lead compounds for developments in sensorics related to transmembrane ion conductance. PMID:14658798

Jung, Günther; Redemann, Thomas; Kroll, Karsten; Meder, Sabine; Hirsch, Andreas; Boheim, Günther

349

Evaluation of the Magnesium Hydroxide Treatment Process for Stabilizing PFP Plutonium/Nitric Acid Solutions  

SciTech Connect

This document summarizes an evaluation of the magnesium hydroxide [Mg(OH)2] process to be used at the Hanford Plutonium Finishing Plant (PFP) for stabilizing plutonium/nitric acid solutions to meet the goal of stabilizing the plutonium in an oxide form suitable for storage under DOE-STD-3013-99. During the treatment process, nitric acid solutions bearing plutonium nitrate are neutralized with Mg(OH)2 in an air sparge reactor. The resulting slurry, containing plutonium hydroxide, is filtered and calcined. The process evaluation included a literature review and extensive laboratory- and bench-scale testing. The testing was conducted using cerium as a surrogate for plutonium to identify and quantify the effects of key processing variables on processing time (primarily neutralization and filtration time) and calcined product properties.

Gerber, Mark A.; Schmidt, Andrew J.; Delegard, Calvin H.; Silvers, Kurt L.; Baker, Aaron B.; Gano, Susan R.; Thornton, Brenda M.

2000-09-28

350

Evaluating the reliability and sensitivity of the Kerr electro-optic field mapping measurements with high-voltage pulsed transformer oil  

NASA Astrophysics Data System (ADS)

Transformer oil is the most widely used dielectric liquid for high voltage insulation. Measurements of the electric field distribution in high voltage pulsed transformer oil are of both practical and theoretical interests. Due to its low Kerr constant, previous electro-optic measurements with transformer oil rely on a technique called ac modulation, which works only for dc steady-state electric field mapping. With the help of a high-sensitivity charge-coupled device, we directly measure the Kerr electro-optic effect between parallel electrodes in transformer oil stressed by high voltage pulses. This work aims at demonstrating the reliability and evaluating the sensitivity of the measurements for three cases with identical electrodes: space-charge free, uniform electric field in the mid-region of the gap; space-charge free, non-uniform fringing electric field; and space charge distorted electric field in the mid-region of the gap. Future directions to improve accuracy by identifying and handling various sources of error and noise are suggested.

Zhang, X.; Nowocin, J. K.; Zahn, M.

2013-08-01

351

Molecular mechanism of allosteric modification of voltage-dependent sodium channels by local anesthetics.  

PubMed

The hallmark of many intracellular pore blockers such as tetra-alkylammonium compounds and local anesthetics is their ability to allosterically modify the movement of the voltage sensors in voltage-dependent ion channels. For instance, the voltage sensor of domain III is specifically stabilized in the activated state when sodium currents are blocked by local anesthetics. The molecular mechanism underlying this long-range interaction between the blocker-binding site in the pore and voltage sensors remains poorly understood. Here, using scanning mutagenesis in combination with voltage clamp fluorimetry, we systematically evaluate the role of the internal gating interface of domain III of the sodium channel. We find that several mutations in the S4-S5 linker and S5 and S6 helices dramatically reduce the stabilizing effect of lidocaine on the activation of domain III voltage sensor without significantly altering use-dependent block at saturating drug concentrations. In the wild-type skeletal muscle sodium channel, local anesthetic block is accompanied by a 21% reduction in the total gating charge. In contrast, point mutations in this critical intracellular region reduce this charge modification by local anesthetics. Our analysis of a simple model suggests that these mutations in the gating interface are likely to disrupt the various coupling interactions between the voltage sensor and the pore of the sodium channel. These findings provide a molecular framework for understanding the mechanisms underlying allosteric interactions between a drug-binding site and voltage sensors. PMID:20937693

Arcisio-Miranda, Manoel; Muroi, Yukiko; Chowdhury, Sandipan; Chanda, Baron

2010-10-11

352

Purity evaluation and influence of carbon nanotube on carbon nanotube\\/graphite thermal stability  

Microsoft Academic Search

High resolution thermogravimetry has been used to evaluate the carbonaceous content in a commercial sample of single-walled\\u000a carbon nanotube (SWNT). The content of SWNTs in the sample was found to be at least 77 mass% which was supported by images\\u000a obtained with scanning and transmission electron microscopies (SEM and TEM). Furthermore, the influence of SWNT addition on\\u000a the thermal stability

Aline M. F. Lima; Anthony W. Musumeci; Hong-Wei Liu; Eric R. Waclawik; Glaura G. Silva

2009-01-01

353

Closed-loop simulation and evaluation of vehicle handling stability on the basis of SIMPACK  

Microsoft Academic Search

Using a new multi-body simulation software SIMPACK as platform, a whole mini-car model is built, and a PID controller with time-delay transfer function is adopted to set up the driver control model. A closed-loop simulation of severe double-lane change test is carried out. And according to the human-vehicle-road closed-loop maneuverability evaluation, the handling stability of the model is graded. The

Haobin Jiang; Tao Wang; Jiaojiao Li

2010-01-01

354

Evaluation of the thermal stability of biodiesel blends of castor oil and passion fruit  

Microsoft Academic Search

The diversity of raw materials and technological routes employed in the biodiesel production has resulted in products with\\u000a different chemical properties. This non-uniformity in the biodiesel composition may influence to the fuel quality. The aim\\u000a of this study was to evaluate biodiesel blends of passion fruit and castor oil in different proportions and their thermal\\u000a stability. Biodiesel blends of passion

Rosiane M. C. Farias; Marta M. Conceição; Roberlúcia A. Candeia; Marta C. D. Silva; Valter J. Fernandes; Antonio G. Souza

355

Technical Evaluation of the Proposed Design Modifications and Technical Specification Changes on Grid Voltage Degradation (Part A) for the Peach Bottom Atomic Power Station, Units 2 and 3: Selected Issues Program (Docket Nos. 50-277, 50-278).  

National Technical Information Service (NTIS)

This report documents the technical evaluation of the proposed design modification and Technical Specification changes for protection of Class 1E equipment from grid voltage degradation for the Peach Bottom Atomic Power Station, Units 2 and 3. The review ...

R. L. White

1981-01-01

356

Technical Evaluation Report on the Proposed Design Modifications and Technical-Specification Changes on Grid-Voltage Degradation for the Turkey Point Nuclear Generating Plant, Units 3 and 4. Docket Nos. 50-250, 50-251.  

National Technical Information Service (NTIS)

This report documents the technical evaluation of the proposed design modification and Technical Specification changes for protection of Class 1E equipment from grid voltage degradation for the Turkey Point Nuclear Generating Plant, Units 3 and 4. The rev...

J. C. Selan

1982-01-01

357

Technical evaluation of the adequacy of station electric distribution systems voltages for the Calvert Cliffs Nuclear Power Plant, Units 1 and 2. Docket Nos. 50-317, 50-318  

SciTech Connect

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the Calvert Cliffs Nuclear Power Plant, Units 1 and 2. The evaluation is to determine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity to automatically start and operate all Class 1E loads within the equipment voltage ratings under certain conditions established by the Nuclear Regulatory Commission. The analyses submitted demonstrate that adequate voltage will be supplied to the Class 1E equipment under worst case conditions.

Selan, J. C.

1982-04-09

358

Prediction of the location of stationary steady-state zone positions in counterflow isotachophoresis performed under constant voltage in a vortex-stabilized annular column  

PubMed Central

A theoretical model is presented and an analytical expression derived to predict the locations of stationary steady-state zone positions in ITP as a function of current for a straight channel under a constant applied voltage. Stationary zones may form in the presence of a countercurrent flow whose average velocity falls between that of a pure leader zone and of a pure trailer zone. A comparison of model predictions with experimental data from an anionic system shows that the model is able to predict the location of protein zones with reasonable accuracy once the ITP stack has formed. This result implies that an UP stack can be precisely directed by the operator to specific positions in a channel whence portions of the stack can be removed or redirected for further processing or analysis.

Harrison, Schurie L. M.; Ivory, Cornelius F.

2010-01-01

359

STABILITY EVALUATION OF METAL CASK ATTACHED TO A TRANSFER PALLET DURING LONG-PERIOD SEISMIC MOTIONS  

NASA Astrophysics Data System (ADS)

Rocking behavior of unfixed body is affected by center of mass, material coefficient of restitution and so on. 2/5 scale metal cask model considering these parameter was used for seismic test to evaluate stability of grounding metal cask attached to a transfer pallet under the influence of long-period earthquake motion. The newest knowledge from seismic test indicates seismic motion with high velocity over 100 kine not always cause the raise of response velocity of metal cask because of energy consumption by cask sliding and impact deformation of concrete. And new estimation method (called "Window energy spectrum method") of earthquake response spectrum gives suitable evaluation of response energy.

Kawaguchi, Shohei; Shirai, Koji; Kanazawa, Kenji

360

Intrinsic Surface Stability in LiMn2-xNix04-s (x = 0.45, 0.5) High Voltage Spinel Materials for Lithium Ion Batteries  

SciTech Connect

This work reports the surface stability of the high vollage Li ion cathode LiMn2_,Ni,Ooh\\ (x = 0.5, 0.45) by comparing thin fi lm and powder composite electrodes after cycling using X-ray photoelectron spectroscopy. The thin film electrodes offer the abili ty to probe the surface of the material without the need of a conductive agent and polymer binder typically used in composite electrodes. The resulls suggest that neither oxidation of PP6 to POF3 nor the decomposition of ethylene carbonate or dimethylene carbonate occurs on the surface of the spinel material. These resulls confirm the enhanced cycling stability and rate capability associated with the high vollage spinel material and suggests that the SE!IIayer fonns due to the reaction of electrochemically inactive components in composite electrodes with the electrolyte.

Carroll, Kyler J [University of California, San Diego; Yang, Ming-Che [University of Florida, Gainesville; Veith, Gabriel M [ORNL; Dudney, Nancy J [ORNL; Meng, Ying Shirley [University of California, San Diego

2012-01-01

361

Evaluation of the effects of different surface configurations on stability of miniscrews.  

PubMed

Introduction. The aim of this study was to analyze the effects of screw design and force application on the stability of miniscrews, using RTT, SEM, and histomorphometric analyses. Materials and Methods. Eighty cylindrical, self-drilling, and Ti6Al4V alloy miniscrews (1,6?×?6?mm) were used. Four mini-screws were inserted in fibulas of each rabbit, and 115?G of force was immediately applied. Four miniscrews were inserted in the other fibula, on which no force was applied. Eight weeks after insertion, osseointegration between miniscrew and the surrounding bone was evaluated by the histomorphometric analyses, SEM, and RTT. Kruskal-Wallis and the paired t-tests were used for statistical analysis. Results. Values obtained from Group I were significantly higher than those of the other loaded groups (P < .05). There were no differences in RTT scores among Groups II, III, and IV. Similar findings were also observed for unloaded mini-screws. There was no significant difference between Groups I and IC, while the differences between loaded and unloaded controls for each miniscrew were statistically significant. Conclusions. Immediate loading of miniscrews does not impair screw stability. Also, the diameter of miniscrew and more frequent thread pitches have a positive effect on stability; however, length of miniscrews does not have a significant effect on the stability. PMID:23935417

Topcuoglu, Tolga; Bicakci, A Altu?; Avunduk, M Cihat; Sahin Inan, Z Deniz

2013-07-01

362

Evaluation of the effectiveness of olive cake residue as an expansive soil stabilizer  

NASA Astrophysics Data System (ADS)

The quantity of the by-product olive cake residue generated in most parts of the Mediterranean countries continues to increase and expected to double in amount within 10 15 years. This increase intensifies the problems associated with the disposal of this by-product. Olive cake residue has a potential for use as a soil stabilizer and large volumes can be beneficially used. This study is directed toward determining if olive cake residue can be utilized to increase the strength and stability of expansive soils which constitute a costly natural hazard to lightweight structures on shallow foundations. A series of laboratory tests using engineering properties, such as Atterberg limits, moisture-density relationship (compaction), swell, unconfined compressive strength were undertaken to evaluate the effectiveness and performance of the olive cake residue as a soil stabilizer. Test results indicate that an addition of only 3% burned olive waste into the soil causes a reduction in plasticity, volume change and an increase in the unconfined compressive strength. However, it was observed that the presence of burned olive waste in the soil greater than 3% caused an increase in the compressibility and a decrease in the unconfined compressive strength. Test results indicate that the use of olive waste in soil stabilization gives greater benefits to the environment than simply disposing of the by-product, olive cake residue.

Nalbantoglu, Zalihe; Tawfiq, Salma

2006-08-01

363

Development of an extemporaneous oral liquid formulation of oxandrolone and its stability evaluation.  

PubMed

Many references exist in the literature identifying the usefulness of oxandrolone in treating muscle wasting due to various conditions including severe burns. However, there is an absence of dosage form alternatives as it is only available as tablets. The dose for children is weight based (0.1 mg/kg) which is difficult to achieve with the currently available tablets of 2.5 mg and 10 mg. The literature provides ample evidence of clinical importance but little guidance on extemporaneous oral liquid formulation of oxandrolone. In order to develop and validate an extemporaneous liquid formulation, suspensions of oxandrolone were developed using locally available (New Zealand) vehicles. Combinations of these vehicles with ethanol, as advised in some articles were also tried. Assay method was developed for oxandrolone using High Performance Liquid Chromatography (HPLC) and Mass Spectroscopy (LC-MS). The formulations were evaluated for stability as per the International Conference on Harmonization (ICH) stability guidelines. They were observed for physical and chemical stability at different time points over a period of 28 days. A stable and validated liquid formulation of oxandrolone has been developed which can be made under the hospital and community pharmacy conditions. The formula utilises commercially available oxandrolone tablets, crushed and dispersed in Simple Syrup BP or Orablend(®) vehicle. The formulation has confirmed stability for 21 days and can be easily made with locally available vehicles. PMID:21764219

Garg, Alka; Garg, Sanjay; She, Richard Wong

2011-07-20

364

Tools for voltage collapse assessment  

Microsoft Academic Search

A variety of tools and techniques used for voltage stability analysis in power systems are discussed in this paper, with particular emphasis on their application to electricity markets. Thus, the computation of transfer capability limits, which are directly associated with the security constraints used in energy auction systems, by means of continuation power flows (CPF) as well as maximum loadability

Claudio A. Canizares; Sameh K. M. Kodsi

2006-01-01

365

Selection of food and chewing side for evaluating masticatory path stability.  

PubMed

In order to find the most suitable food and chewing side for evaluating the stability of masticatory movement, three types of food with varying textures, as well as both free chewing and unilateral chewing, were utilized in analyzing the masticatory path during mastication. A piece of chewing gum, one peanut, and a slice of crispy bread were used as test foods. For 20 healthy subjects, movement of the incisal point while masticating a test food for 10 s on the free side and the habitual side was recorded. Indicators representing movement path stability were calculated and compared among the foods and between the chewing sides. Masticatory movement was most stable when masticating chewing gum, and less stable for the peanut, and most unstable for the crispy bread. There was a statistically significant difference between each pair of foods for almost all of the indicators. The indicators for peanut were approximately 1.5 times larger than those for masticating chewing gum and the indicators for crispy bread were double those for the chewing gum. When comparing free chewing with unilateral chewing, the masticatory movement of unilateral chewing was significantly more stable than that of free chewing for all test foods. From these results it was suggested that, for evaluating masticatory movement path stability, the most suitable type of food was softened chewing gum and the most suitable chewing method was unilateral chewing on the habitual chewing side. PMID:14505186

Shiga, Hiroshi; Kobayashi, Yoshinori; Arakawa, Ichiro; Shonai, Yasuharu

2003-09-01

366

[Evaluation of reports on environmental measurements of electromagnetic fields generated by high voltage transmission lines and substations].  

PubMed

This paper presents some situations, in which measurements of electromagnetic fields generated by transmission lines and substations should be performed. The range of measurements may differ, but maximum values of electric and magnetic fields and flux density must be identified in all situations. The area with electric field exceeding 1 kV/m should be identified as well. The author also presents basic requirements to be met by the measurement technique. These requirements are specified according to the national standard. Special attention should be paid to the identification of the spatial distribution of electric field and flux density generated in the vicinity of high voltage transmission lines. To verify the measurement results, it is necessary to calculate the distribution of both aforesaid field components. For environmental protection purposes, it is also proposed that the report should include measurements of electromagnetic fields of 50 Hz along with calculated results presented in tables and diagrams. PMID:17926507

Szuba, Marek

2007-01-01

367

Enhanced low voltage cycling stability of LiMn 2O 4 cathode by ZnO coating for lithium ion batteries  

Microsoft Academic Search

Aluminium doped spinel, LiAl0.04Mn1.96O4, was modified by melting impregnation using Zn(NO3)2. High-resolution transmission electron microscopy observations indicated that ZnO was coated on the surface of LiAl0.04Mn1.96O4 particles. Cycling tests between 2.60 and 4.35V showed that the surface modification stabilizes the spinel structure and leads to a steady discharge capacity without Jahn–Teller distortion, which could be significant for LiMn2O4 based spinels

J. Tu; X. B. Zhao; J. Xie; G. S. Cao; D. G. Zhuang; T. J. Zhu

2007-01-01

368

Output Impedance Oriented Design for Voltage Regulator wvith High Repetitive Rate Transient  

Microsoft Academic Search

Modern microprocessors can rapidly shift between a sleep state and full load operation, placing a heavy requirement on the voltage regulator to stabilize its output voltage. High repetitive rate transient poses new challenges for voltage regulator design. The old \\

Wenkai Wu; George Schuellein

2007-01-01

369

Implant stability evaluation by resonance frequency analysis in the fit lock technique. A clinical study.  

PubMed

Surgical procedures for the application of implants in the lateral-superior sectors are affected by the availability of the residual bone. When this condition is lower than 5 mm it is recommended that techniques involving two therapeutic phases, a reconstructive and an applicative one, as reported in the international literature, are adopted. The authors propose here a new method with the potential to apply implants simultaneously with the reconstructive phase. The aim of this longitudinal retrospective study was to evaluate the stability of implants applied with the fit lock technique in the upper maxillarys in us with bone availability lower than 4 mm by measuring resonance frequency at different follow-up periods The seme as urements, carried out on 30 implants, were analysed with specific statistical procedures. The results indicate that the stability of the implants inserted with the fit lock method increases progressively over time in a statistically significant manner. The stability recorded after one year from the insertion (ISQ T2) is significantly higher than that recorded after six months (ISQ T1), and this is significantly higher than that recorded at the time of implant placement (ISQ T0). The implants inserted in the maxillary zones with scarce bone availability and applied with this technique showed a similar stability as reported with other techniques. In light of the results, the authors confirm that the primary stability represents the basic requirement to guarantee a correct healing of the implant and demonstrate that the fit lock technique also all ows reaching this condition when bone availability is minimal. PMID:23991271

Falisi, Giovanni; Galli, Massimo; Velasquez, Pedro Vittorini; Rivera, Juan Carlos Gallegos; Di Paolo, Carlo

2013-06-25

370

Implant stability evaluation by resonance frequency analysis in the fit lock technique. A clinical study  

PubMed Central

Summary Surgical procedures for the application of implants in the lateral-superior sectors are affected by the availability of the residual bone. When this condition is lower than 5 mm it is recommended that techniques involving two therapeutic phases, a reconstructive and an applicative one, as reported in the international literature, are adopted. The authors propose here a new method with the potential to apply implants simultaneously with the reconstructive phase. The aim of this longitudinal retrospective study was to evaluate the stability of implants applied with the fit lock technique in the upper maxillarys in us with bone availability lower than 4 mm by measuring resonance frequency at different follow-up periods The seme as urements, carried out on 30 implants, were analysed with specific statistical procedures. The results indicate that the stability of the implants inserted with the fit lock method increases progressively over time in a statistically significant manner. The stability recorded after one year from the insertion (ISQ T2) is significantly higher than that recorded after six months (ISQ T1), and this is significantly higher than that recorded at the time of implant placement (ISQ T0). The implants inserted in the maxillary zones with scarce bone availability and applied with this technique showed a similar stability as reported with other techniques. In light of the results, the authors confirm that the primary stability represents the basic requirement to guarantee a correct healing of the implant and demonstrate that the fit lock technique also all ows reaching this condition when bone availability is minimal.

Falisi, Giovanni; Galli, Massimo; Velasquez, Pedro Vittorini; Rivera, Juan Carlos Gallegos; Di Paolo, Carlo

2013-01-01

371

Effects of sample storage on biosolids compost stability and maturity evaluation.  

PubMed

Compost stability and maturity are important parameters of compost quality. To date, nearly all compost characterization has been performed using samples freshly collected because sample storage can affect compost stability and maturity evaluation. However, sample preservation is sometimes necessary, especially for scientific research purposes. There is little information available on the effects of sample storage on compost stability and maturity. Samples of biosolids compost with different levels of stability and maturity were collected from four compost facilities in Florida (referred to as Register, Winslow, Sunset, and Meadow). Comparisons of CO2 evolution, seed germination rate, and water-soluble organic carbon (WSOC) were made between fresh samples with short storage at 4 degrees C for less than 1 wk and air-dried or frozen compost samples stored for 1 yr. The effects of storage (air-dry or frozen) on the measured parameters depended on compost stability and maturity and on the compost material source. Frozen storage reduced the peak CO2 evolution of Register samples by 12 to 29%, while accumulated CO2 evolution was reduced by 43 to 64% and 110 to 277% with air-dry and frozen storage, respectively. The storage effect on CO2 evolution with more stable compost was inconsistent. Storage did not affect compost phytotoxicity, except for samples from the Sunset facility. Air-drying reduced the WSOC by up to 35%, and freezing increased it by up to 34%, while both storage methods had no significant effect on samples of low WSOC. Despite all these variations, WSOC had a significant and consistent relation to CO2 evolution and seed germination rates with R2 of 0.78 and 0.57, respectively, regardless of storage methods. PMID:11215657

Wu, L; Ma, L Q

372

Evaluation of the geological relationships to gas hydrate formation and stability  

SciTech Connect

Although there are many publications pertaining to gas hydrates, their formation and stability in various geological conditions are poorly known. Therefore, for the same reasons and because of the very broad scope of our research, limited amount and extremely dispersed information, the study regions are very large. Moreover, almost without exception the geological environments controlling gas hydrates formation and stability of the studied regions are very complex. The regions studied (completed and partially completed - total 17 locations) during the reporting period, particularly the Gulf of Mexico and the Middle America Trench, are the most important in this entire research project. In the past, both of these regions have been extensively studied, the presence of gas hydrates confirmed and samples recovered. In our investigation it was necessary not only to review all previous data and interpretations, but to do a thorough analysis of the basins, and a critical evaluation of an previously reported and publicly available but not published information.

Not Available

1986-01-01

373

STABILITY EVALUATION OF AMBIENT CONCENTRATIONS OF SULFUR DIOXIDE, NITRIC OXIDE, AND NITROGEN DIOXIDE CONTAINED IN COMPRESSED GAS CYLINDERS  

EPA Science Inventory

Compressed gas samples of sub-part per million concentrations of sulfur dioxide, nitric oxide, and nitrogen dioxide were evaluated for long and short term stability. Except for several stainless steel tanks, the samples were contained in aluminum cylinders. A degree of stability ...

374

Basalt glass: an analogue for the evaluation of the long-term stability of nuclear waste form borosilicate glasses  

Microsoft Academic Search

The long-term stability of nuclear waste form borosilicate glasses can be evaluated by understanding the processes that effect the long-term alteration of glass and by comparing laboratory alteration of synthetic basalt and borosilicate glasses with the observed stability of naturally occurring basaltic glasses in diverse geologic environments. This paper presents detailed electron microprobe analyses of naturally altered basaltic glasses (with

C. D. Byers; M. J. Jercinovic; R. C. Ewing; K. Keil

1984-01-01

375

Modeling synchronous voltage source converters in transmission system planning studies  

SciTech Connect

A Voltage Source Converter (VSC) can be beneficial to power utilities in many ways. To evaluate the VSC performance in potential applications, the device has to be represented appropriately in planning studies. This paper addresses VSC modeling for EMTP, powerflow, and transient stability studies. First, the VSC operating principles are overviewed, and the device model for EMTP studies is presented. The ratings of VSC components are discussed, and the device operating characteristics are derived based on these ratings. A powerflow model is presented and various control modes are proposed. A detailed stability model is developed, and its step-by-step initialization procedure is described. A simplified stability model is also derived under stated assumptions. Finally, validation studies are performed to demonstrate performance of developed stability models and to compare it with EMTP simulations.

Kosterev, D.N. [Oregon State Univ., Corvallis, OR (United States)

1997-04-01

376

Magnetic fields dispersed by high-voltage power lines: an advanced evaluation method based on 3-D models of electrical lines and the territory.  

PubMed

An advanced numerical evaluation tool is proposed for calculating the magnetic flux density dispersed by high-voltage power lines. When compared to existing software packages based on the application of standardized methods, this tool turned out to be particularly suitable for making accurate evaluations on vast portions of the territory, especially when the contribution of numerous aerial and/or underground lines must be taken into account. The aspects of the tool of greatest interest are (1) the interaction with an electronic archive of power lines, from which all the information necessary for the calculation is obtained; (2) the use of three-dimensional models of both the power lines and the territory crossed by these; (3) the direct interfacing with electronic cartography; and finally (4) the use of a representation procedure for the results that is based on contour maps. The tool had proven to be very useful especially for Environmental Impact Assessment procedures relative to new power lines. PMID:15550699

Andreuccetti, D; Zoppetti, N

2004-01-01

377

SLOPE STABILITY EVALUATION AND EQUIPMENT SETBACK DISTANCES FOR BURIAL GROUND EXCAVATIONS  

SciTech Connect

After 1970 Transuranic (TRU) and suspect TRU waste was buried in the ground with the intention that at some later date the waste would be retrieved and processed into a configuration for long term storage. To retrieve this waste the soil must be removed (excavated). Sloping the bank of the excavation is the method used to keep the excavation from collapsing and to provide protection for workers retrieving the waste. The purpose of this paper is to document the minimum distance (setback) that equipment must stay from the edge of the excavation to maintain a stable slope. This evaluation examines the equipment setback distance by dividing the equipment into two categories, (1) equipment used for excavation and (2) equipment used for retrieval. The section on excavation equipment will also discuss techniques used for excavation including the process of benching. Calculations 122633-C-004, 'Slope Stability Analysis' (Attachment A), and 300013-C-001, 'Crane Stability Analysis' (Attachment B), have been prepared to support this evaluation. As shown in the calculations the soil has the following properties: Unit weight 110 pounds per cubic foot; and Friction Angle (natural angle of repose) 38{sup o} or 1.28 horizontal to 1 vertical. Setback distances are measured from the top edge of the slope to the wheels/tracks of the vehicles and heavy equipment being utilized. The computer program utilized in the calculation uses the center of the wheel or track load for the analysis and this difference is accounted for in this evaluation.

MCSHANE DS

2010-03-25

378

An approach to mitigate the risk of voltage collapse accounting uncertainties using improved particle swarm optimization  

Microsoft Academic Search

This paper describes a new viewpoint for static voltage stability enhancement based on an improved particle swarm optimization technique. The objective function is selected for maximization of reactive power reserve subjected to usual operating constraints at an operating point. Probabilistic risk of voltage collapse has been used for maintaining desired level of voltage stability margin. This risk of voltage collapse

L. D. Arya; L. S. Titare; D. P. Kothari

2009-01-01

379

An Evaluation of SMES Control Logics for Power System Stabilization Based on Analogue Simulation  

NASA Astrophysics Data System (ADS)

Focusing on control that can be used to efficiently regulate SMES, unique control logics for power system stabilization were devised by combining the popularly used power deviation (?P) of a generator with the angular velocity deviation (??) of a generator or the phase correction. In the previous paper, we analyzed the performance and characteristics of the new control logics (?P + ?? control logic, ?P + ?? + phase correction control logic) on both one-and multi-machine infinite-bus systems using the Y-method power system dynamics analysis program, and suggested that the new logics could improve the stability of power systems in comparison to the conventional ?P control logic. For the next phase of research, we have evaluated the performance and characteristics of the control logics mentioned above based on analogue simulation. As a result, the logics have showed the same tendency as the case of the digital simulation and it have been confirmed that the logics, especially ?P + ??+ phase correction control logic, have the superior effect on the improvement of the stability of power system.

Taguchi, Akira; Imayoshi, Tadakazu; Hayashi, Hidemi; Ishii, Toshinori

380

Evaluation of PFP Furnace Systems for Thermal Stabilization of Washed High Chloride Plutonium Oxide Items  

SciTech Connect

High chloride content plutonium (HCP) oxides are impure plutonium oxide scrap which contains NaCl, KCl, MgCl2 and/or CaCl2 salts at potentially high concentrations and must be stabilized at 950 C per the DOE Standard, DOE-STD-3013-2000. The chlorides pose challenges to stabilization because volatile chloride salts and decomposition products can corrode furnace heating elements and downstream ventilation components. A high-temperature furnace (same make and model as used at the RMC at Plutonium Finishing Plant) and the associated offgas system were set up at PNNL to identify system vulnerabilities and to investigate alternative materials and operating conditions that would mitigate any corrosion and plugging of furnace and offgas components. The key areas of interest for this testing were the furnace heating elements, the offgas line located inside the furnace, the offgas line between the furnace and the filter/knockout pot, the filter/knockout pot, the sample boat, and corrosion coupons to evaluate alternative materials of construction. The evaluation was conducted by charging the furnace with CeO2 that had been impregnated with a mixture of chloride salts (selected to represent the expected residual chloride salt level in washed high chloride items) and heated in the furnace in accordance with the temperature ramp rates and hold times used at PFP.

Fischer, Christopher M.; Elmore, Monte R.; Schmidt, Andrew J.; Gerber, Mark A.; Muzatko, Danielle S.; Gano, Susan R.; Thornton, Brenda M.

2002-12-17

381

Technical-Evaluation Report on the Adequacy of Station Electric-Distribution-System Voltages for the H.B. Robinson Steam Electric Plant, Unit 2 (Docket No. 50-261).  

National Technical Information Service (NTIS)

This report documents the technical evaluation of the adequacy of the station electric distribution system voltages for the H.B. Robinson Steam Electric Plant, Unit 2. The evaluation is to determine if the onsite distribution system in conjunction with th...

J. C. Selan

1983-01-01

382

30 CFR - Voltage Longwalls  

Code of Federal Regulations, 2010 CFR

...STANDARDS-UNDERGROUND COAL MINES Underground High-Voltage Distribution § 75.812-2 High-voltage power centers and transformers; record...in a book approved by the Secretary. High-Voltage Longwalls Source: 67 FR 11001,...

2010-07-01

383

Evaluation of dynamic postural balance using the Biodex Stability System in rheumatoid arthritis patients.  

PubMed

The aim of this study was to investigate dynamic postural balance in patients with rheumatoid arthritis (RA) in relation to the disease characteristics. Seventy-four patients with RA and 42 controls of the same age group were tested using the Biodex Stability System (Biodex Medical Systems, Shirley, NY, USA). Anterior/posterior (AP), medial/lateral (ML), and overall (OA) indices were obtained with bilateral stance at platform stabilities of 2 and 8. Subjects were tested with "eyes open" at all times. At the same time, Disease Activity Score, functional disability [Health Assessment Questionnaire, (HAQ)], and Steinbrocker Functional Class (SFC) were assessed. Both the AP and OA indices in the RA group were significantly higher than in the control group for level 8. For OA index, the results were 2.7+/-0.9 in RA and 2.2+/-0.7 in the control group (p=0.006), and for AP index, the results were 2.1+/-0.7 in RA and 1.7+/-0.6 in the control group (p=0.002). Eleven patients (15.9%) and three controls (7.1%) could not complete the test at level 2. When the patients and controls who completed the test were compared, a significant difference was found only in the ML index. The results were 4.6+/-2.4 in RA and 3.8+/-1.6 in the control group (p=0.047). A positive correlation between HAQ and postural balance for all three stability indices at level 8 was detected. A positive correlation between SFC and postural balance for OA and ML at level 8 was also found. Multiple linear regression analyses revealed age and body mass index (BMI) to be the most important factors influencing postural dynamic balance at both levels in the RA group and in healthy controls. RA has a negative effect on dynamic postural stability. The functional status affects dynamic balance more than disease activity. Age and BMI were the most important factors influencing postural dynamic balance in the RA group and in healthy controls. Level 2 does not appear to be an appropriate level for evaluating postural stability in RA. PMID:16247584

Aydo?, Ece; Bal, Ajda; Aydo?, Sedat Tolga; Cakci, Aytül

2005-10-25

384

Mine stability evaluation of panel 1 during waste emplacement operations at WIPP  

SciTech Connect

The specific objectives of the work were defined by the Environmental Evaluation Group (EEG) as follows: (1) assess the stability of panel 1 during the proposed operation of waste emplacement; (2) estimate the amount of time before room closure would be expected to transfer rock loads to the waste packages. The work consisted of (1) an analysis of geotechnical data and a review of the Department of Energy`s (DOE) plans for waste emplacement in panel 1, (2) an evaluation of ground conditions based on data analysis and observations of changes in ground conditions since the first evaluation in 1993 (USBM 1993), and (3) preparation of a report and presentation of the results to EEG staff. Excluded from this study are radiological safety issues and policies. The study is based on data provided by DOE and Westinghouse Electric Corporation (operator of the site) and conversations with DOE and Westinghouse personnel. MTI cannot independently verify the accuracy of the data within the scope of this study and recommends independent evaluations of data gathering, quality assurance procedures, and structural designs. The operator has the ultimate responsibility for structural designs and has expressed a strong commitment to ensuring worker safety.

Maleki, H. [Maleki Technologies Inc., Spokane, WA (United States)

1998-07-01

385

Evaluation of solidification/stabilization technology for Buffalo River sediment. Final report  

SciTech Connect

The Buffalo River drains a 446-square-mile (1,155-sq-km) watershed in western New York State and discharges into Lake Erie at the city of Buffalo. The Buffalo River has been classified by the State of New York as a fishing and fish survival stream, but municipal and industrial discharges have degraded the water quality and resulted in a fish advisory for the river. Under the Assessment and Remediation of Contaminated Sediment Program, the US Environmental Protection Agency asked the US Army Corps of Engineers to evaluate solidification/stabilization (S/S) for potential treatment of the contaminated sediments in the Buffalo River. An evaluation of S/S technology was conducted on the bench-scale level on Buffalo River sediment to determine whether physical and chemical properties of the sediment would be improved. Based on analyses of the untreated sediment, five metals were selected for evaluation: chromium, copper, lead, nickel, and zinc. Initial screening tests (ISTs) were conducted on the sediments to narrow the range of binder-to-soil ratios (BSRs) to be prepared in the detailed evaluation.

Fleming, E.C.; Averett, D.E.; Channell, M.G.; Perry, B.D.

1991-05-01

386

Voltage Breakdown Mechanisms in High Voltage Rated, Surface Mount MLCCs  

Microsoft Academic Search

Multilayer ceramic capacitors (MLCCs) exposed to high voltages, around 1000VDC in air, are prone to both surface-arc- over and internal breakdown. In either event failures will result at the instance of surface-arc-over as the circuit is de- stabilized which may cause damage to surrounding components even if the capacitor remains temporarily functional. The performance of HVArc GuardTM X7R capacitors, that

J. Bultitude; P. Gormally; J. Rogers; J. Jiang

387

Voltage Collapse Operating Margin Analysis Using Sensitivity Techniques  

Microsoft Academic Search

In this paper, we describe the basic formulation, voltage collapse and plan operations under such implementation and application of a computer model, conditions, PG&E has developed a computer called VCMARGIN, for determining the s teady-state model called VCMARGIN (Voltage Collapse Operating operating margin of a potver system based on voltage Margin Calculation Program). stability considerations. The determination of the operating

C. Rajagopalan; S. Hao; D. Shirmohammadi; M. K. Celik

1993-01-01

388

Use of fluorescence for the high-throughput evaluation of synergistic thermal and photo stabilizer interactions in poly (vinyl chloride)  

SciTech Connect

The selection of thermal and photo stabilizers for poly (vinyl chloride) (PVC) using conventional methods is a time-consuming process. The high-throughput screening method developed in this research demonstrates rapid and efficient ways to quantify the effectiveness of PVC stabilizers with respect to raw plastic materials, stabilizers, levels of use, and testing conditions. An experimental protocol using liquid sampling and fluorescence measurement was developed to determine the effectiveness of formulations. This was used to evaluate the performance of stabilizers based on the change of fluorescence emission at 440 nm after thermal aging or ultraviolet (UV) radiation. The performance of PVC formulations using six different types of stabilizers was successfully mapped for both PVC resin and flexible PVC.

Wu Chunyong; Wicks, Douglas A. [School of Polymers and High Performance Materials, 118 College Drive 10076, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (United States)

2005-06-15

389

Evaluation of global warming impacts for different levels of stabilization as a step toward determination of the long-term stabilization target  

Microsoft Academic Search

In order to estimate the benefit attributable to alleviating global warming for a kind of cost–benefit analysis of global\\u000a warming mitigation, global warming impacts were quantitatively evaluated for a pathway of unmitigated CO2 emissions and three pathways to stabilize the atmospheric CO2 concentration at different levels, keeping unchanged the assumed conditions on population and GDP growths, although the GDP\\u000a losses

Ayami Hayashi; Keigo Akimoto; Fuminori Sano; Shunsuke Mori; Toshimasa Tomoda

2010-01-01

390

An energy efficient rate selection algorithm for voltage quantized dynamic voltage scaling  

Microsoft Academic Search

This paper presents a highly energy efficient alternative algorithm to the conventional workload averaging technique for voltage quantized dynamic voltage scaling. This algorithm incorporates the strengths of the conventional workload averaging technique and our previously proposed Rate Selection Algorithm, resulting in higher energy savings while minimizing the buffer size requirement and improving the overall system stability by minimizing the number

Lama H. Chandrasena; Priyadarshana Chandrasena; Michael J. Liebelt

2001-01-01

391

Seismic stability evaluation of Alben Barkley Lock and Dam Project. Volume 1. Summary report. Final report  

SciTech Connect

This report summarizes the results of seismological, geological, laboratory, field, and analytical investigations conducted to evaluate the seismic stability of two earth embankment sections of the Alben Barkley Lock and Dam Project, Kentucky. These represent typical sections of the powerhouse/switch-yard area and the main embankment. Detailed documentation of each of the major topical areas of this study are contained in Volumes 2 through 5 of this series of reports. The design earthquake, from the New Madrid Seismic Zone, had a body-wave magnitude of 7.5. Of particular interest in this study, was the seismic performance of silty sands in the foundation and their overall effect on the stability of these embankment sections. The results of this study indicate that large scale deformations and/or slope failure which would result in the loss of reservoir are not deformations on the order of 2 to 3 ft are expected. These deformations are relatively small in light of the fact that 28 ft of freeboard are expected to be available during the design earthquake.

Wahl, R.E.; Bluhm, P.F.

1992-09-01

392

Evaluation of pre-analysis loss of dependent drugs in wastewater: stability and binding assessments.  

PubMed

Wastewater analysis has the potential to provide objective and timely data on population drug consumption, but some crucial factors such as pre-analysis drug loss during sample storage and filtration could affect the accuracy and reliability of the method, and these uncertainties have yet to be fully assessed. This study was designed to evaluate analyte stability in wastewater stored under different conditions with the aim of optimizing the sample storage procedures for future studies. It also investigated whether there is significant analyte loss during filtration before sample extraction and storage after that. The studied substances and metabolites were: cotinine, cocaine and its metabolite benzoylecgonine, phenethylamines amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), opioids including codeine, methadone, 6-monoacetylmorphine (MAM) and morphine. In most situations, storing samples at 4?°C is sufficient to stabilize analytes for at least 2?weeks, and refrigeration is unnecessary during sample transportation within 3?days. However, additional measures need to be taken if unstable analytes such as cocaine and MAM are to be analyzed. No significant analyte loss was observed in the filtration process or in reconstituted extract stored at 4?°C or -20?°C for 2?weeks. By choosing stable analytes and proper storage conditions, wastewater analysis has the potential to provide accurate data for estimation of community drug use. Copyright © 2012 John Wiley & Sons, Ltd. PMID:23047767

Chen, Chang; Kostakis, Chris; Irvine, Rodney J; Felgate, Peter D; White, Jason M

2012-10-09

393

A Preliminary Evaluation of Using Fill Materials to Stabilize Used Nuclear Fuel During Storage and Transportation  

SciTech Connect

This report contains a preliminary evaluation of potential fill materials that could be used to fill void spaces in and around used nuclear fuel contained in dry storage canisters in order to stabilize the geometry and mechanical structure of the used nuclear fuel during extended storage and transportation after extended storage. Previous work is summarized, conceptual descriptions of how canisters might be filled were developed, and requirements for potential fill materials were developed. Elements of the requirements included criticality avoidance, heat transfer or thermodynamic properties, homogeneity and rheological properties, retrievability, material availability and cost, weight and radiation shielding, and operational considerations. Potential fill materials were grouped into 5 categories and their properties, advantages, disadvantages, and requirements for future testing were discussed. The categories were molten materials, which included molten metals and paraffin; particulates and beads; resins; foams; and grout. Based on this analysis, further development of fill materials to stabilize used nuclear fuel during storage and transportation is not recommended unless options such as showing that the fuel remains intact or canning of used nuclear fuel do not prove to be feasible.

Maheras, Steven J.; Best, Ralph; Ross, Steven B.; Lahti, Erik A.; Richmond, David J.

2012-08-01

394

Molecular MR imaging for the evaluation of the effect of dynamic stabilization on lumbar intervertebral discs  

PubMed Central

The dynamic stabilization of lumbar spine is a non-fusion stabilization system that unloads the disc without the complete loss of motion at the treated motion segment. Clinical outcomes are promising but still not definitive, and the long-term effect on instrumented and adjacent levels is still a matter of discussion. Several experiments have been devised in order to gain a better understanding of the effect of the device on the intervertebral disc. One of the hypotheses was that while instrumented levels are partially relieved from loading, adjacent levels suffer from the increased stress. But this has not been proved yet. The aim of this study was to investigate the long-term effect of dynamic stabilization in vivo, through the quantification of glycosaminoglycans (GAG) concentration within instrumented and adjacent levels by means of the delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) protocol. Ten patients with low back pain, unresponsive to conservative treatment and scheduled for Dynesys implantation at one to three lumbar spine levels, underwent the dGEMRIC protocol to quantify GAG concentration before and 6 months after surgery. Each patient was also evaluated with visual analog scale (VAS), Oswestry, Prolo, Modic and Pfirrmann scales, both at pre-surgery and at follow-up. Six months after implantation, VAS, Prolo and Oswestry scales had improved in all patients. Pfirrmann scale could not detect any change, while dGEMRIC data already showed a general improvement in the instrumented levels: GAG was increased in 61% of the instrumented levels, while 68% of the non-instrumented levels showed a decrease in GAG, mainly in the posterior disc portion. In particular, seriously GAG-depleted discs seemed to have the greatest benefit from the Dynesys implantation, whereas less degenerated discs underwent a GAG depletion. dGEMRIC was able to visualize changes in both instrumented and non-instrumented levels. Our results suggest that the dynamic stabilization of lumbar spine is able to stop and partially reverse the disc degeneration, especially in seriously degenerated discs, while incrementing the stress on the adjacent levels, where it induces a matrix suffering and an early degeneration.

Brayda-Bruno, M.; Perona, F.; Fornari, M.; Raimondi, M. T.; Petruzzi, M.; Grava, G.; Costa, F.; Caiani, E. G.; Lamartina, C.

2009-01-01

395

Stability evaluation of selected polyphenols and triterpene glycosides in black cohosh.  

PubMed

Black cohosh ( Actaea racemosa L., syn. Cimicifuga racemosa L.) is rich in both triterpene glycosides and polyphenols, which have various biological activities that may be important to its medical use. To evaluate the stability of the polyphenolic constituents and triterpene glycosides of black cohosh, experiments were conducted using three sample types: plant material, extracts of black cohosh, and encapsulated commercial extract. The samples were stored at various temperatures and humidity conditions. Three triterpene glycosides and six major polyphenols in black cohosh were quantitatively measured with an HPLC-PDA method at 0, 3, 6, and 9 weeks. The triterpene glycosides were stable at the tested conditions, whereas the polyphenols were stable only at room temperature and low humidity and not stable at higher temperature and/or humidity due to hydrolysis and/or oxidation. The rate of compound decomposition depended upon the chemical structure of the individual polyphenols. Polyphenols in the extracts decomposed more readily than those in plant material. PMID:18817410

Jiang, Bei; Lyles, James T; Reynertson, Kurt A; Kronenberg, Fredi; Kennelly, Edward J

2008-09-26

396

Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems  

NASA Astrophysics Data System (ADS)

The aim of this study was the further development of dysprosia-stabilized zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial standard thermal barrier coating. Two morphologies of ceramic top coat were studied: one using a dual-layer system and the second using a polymer to generate porosity. Evaluations were carried out using a laser flash technique to measure thermal properties. Lifetime testing was conducted using thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis was used to characterize porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

Curry, Nicholas; Markocsan, Nicolaie; Östergren, Lars; Li, Xin-Hai; Dorfman, Mitch

2013-04-01

397

Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems  

NASA Astrophysics Data System (ADS)

The aim of this study was the further development of dysprosia-stabilized zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial standard thermal barrier coating. Two morphologies of ceramic top coat were studied: one using a dual-layer system and the second using a polymer to generate porosity. Evaluations were carried out using a laser flash technique to measure thermal properties. Lifetime testing was conducted using thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis was used to characterize porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

Curry, Nicholas; Markocsan, Nicolaie; Östergren, Lars; Li, Xin-Hai; Dorfman, Mitch

2013-08-01

398

Nondestructive evaluation of orthopaedic implant stability in THA using highly nonlinear solitary waves  

NASA Astrophysics Data System (ADS)

We propose a new biomedical sensing technique based on highly nonlinear solitary waves to assess orthopaedic implant stability in a nondestructive and efficient manner. We assemble a granular crystal actuator consisting of a one-dimensional tightly packed array of spherical particles, to generate acoustic solitary waves. Via direct contact with the specimen, we inject acoustic solitary waves into a biomedical prosthesis, and we nondestructively evaluate the mechanical integrity of the bone-prosthesis interface, studying the properties of the waves reflected from the contact zone between the granular crystal and the implant. The granular crystal contains a piezoelectric sensor to measure the travelling solitary waves, which allows it to function also as a sensor. We perform a feasibility study using total hip arthroplasty (THA) samples made of metallic stems implanted in artificial composite femurs using polymethylmethacrylate for fixation. We first evaluate the sensitivity of the proposed granular crystal sensor to various levels of prosthesis insertion into the composite femur. Then, we impose a sequence of harsh mechanical loading on the THA samples to degrade the mechanical integrity at the stem-cement interfaces, using a femoral load simulator that simulates aggressive, accelerated physiological loading. We investigate the implant stability via the granular crystal sensor-actuator during testing. Preliminary results suggest that the reflected waves respond sensitively to the degree of implant fixation. In particular, the granular crystal sensor-actuator successfully detects implant loosening at the stem-cement interface following violent cyclic loading. This study suggests that the granular crystal sensor and actuator has the potential to detect metal-cement defects in a nondestructive manner for orthopaedic applications.

Yang, Jinkyu; Silvestro, Claudio; Sangiorgio, Sophia N.; Borkowski, Sean L.; Ebramzadeh, Edward; De Nardo, Luigi; Daraio, Chiara

2012-01-01

399

High voltage pulse test plan  

NASA Astrophysics Data System (ADS)

The purpose of this program is to prepare a high voltage pulse test plan for three types of test articles to interrelate the findings of the High Voltage Pulse Survey and High Voltage Testing: Volume 1, Test Program Report, and Volume 2, Specifications and Test Procedures, AFWAL-TR-82-2057. This test plan will be developed from the baseline of test procedures established in Volume 2 which utilize a 1.2 X 50 microsecond waveform. The test plan will detail other pulse waveform parameters, voltage magnitudes, and number of pulses required to evaluate the component under test in conjunction with the results of the Pulse Test Survey already completed (AFWAL-TR-85-2079).

Dunbar, William G.

1987-04-01

400

HIGH VOLTAGE POWER SUPPLIES FOR ION BEAMS ELECTRON COOLERS  

Microsoft Academic Search

High voltage power supplies, developed for feeding the electron coolers EC-35 and EC-300, are described in this report. Stabilized voltage power supplies with output voltages 35 kV and 300 kV with the current up to 5mA and stability up to 10 -5 are used for electron cooling of heavy ion beam. Under high potential of these power supplies there are

V. M. Veremeenko; R. V. Voskoboynikov; A. D. Goncharov; A. Evtushenko; V. V. Kolmogorov; M. N. Kondaurov; G. S. Kraynov; A. M. Kryuchkov; A. S. Medvedko; V. V. Parkhomchuk; S. P. Petrov; V. B. Reva; M. A. Tiunov; B. R. Karymov

401

Evaluation of the mechanical stability of a megavoltage imaging system using a new flat panel positioner  

Microsoft Academic Search

Mega-Voltage systems are used in radiation oncology both for external radiation delivery and patient positioning prior to treatment. A pair of portal images compared with digitally reconstructed radiographs is currently the gold standard for positioning but new developments have made possible the use of Mega-Voltage Cone Beam CT for better 3D setup. The non-ideal imaging geometry of the treatment unit

O. Morin; J. Chen; M. Aubin; J. Pouliot

2005-01-01

402

Evaluation of Deep-Seated Slope Stability of Embankments over Deep Mixed Foundations  

Microsoft Academic Search

When embankments are constructed over soft foundations, deep-seated slope stability often becomes one of the controlling factors in design. Deep mixing methods have been commonly used as an alternative to solve the deep-seated slope stability problem. Bishop's modified method is a commonly adopted approach for analyzing the slope stability of embankments on deep mixed foundations. Bishop's modified method assumed slopes

Jie Han; Jin-Chun Chai; Dov Leshchinsky; Shui-Long Shen

403

Evaluation in vitro of the tensile strength of crimpable hooks used for stabilization in orthognathic surgery.  

PubMed

OBJECTIVE: The aim of this study was to evaluate the tensile strength of crimpable hooks used for arch stabilization in orthognatic surgery. STUDY DESIGN: Ninety stainless steel wire (0.019" × 0.026") segments, each measuring 6 cm long, were used and attached to crimpable hooks of different commercial brands. Six groups were formed (n = 10) denominated as follows: control, in which the wire segments were perpendicularly welded by spot welding machine; and the hooks groups M (Morelli), MS (Morelli with weld), TP (TP Ortho), TPS (TP with weld), TPTg (TP-tungsten), TPTgS (TP-tungsten with weld), AO (American Orthodontics), and AOS (American Orthodontics with weld). The test specimen topography was evaluated by scanning electron microscopy before and after the tensile strength tests. After obtaining the results, the analysis of variance and Kruskal-Wallis multiple-comparison tests were applied. RESULTS: Compared with the control group, the AOS ball hooks and those from TPS required a greater amount of force to be displaced along the rectangular arch. The hooks in group M were significantly easier to displace, followed by those from AO. CONCLUSIONS: The best ball hooks for clinical application are those from AOS and TPS. PMID:21664150

Andrade Gomes, Nascimento Leonard Euller; Melo, Pithon Matheus; Lacerda, Santos Rogério; D'Albuquerque, Medeiros Paulo Jose

2011-06-01

404

Formulation and stability evaluation of extemporaneously prepared atenolol capsules from crushed atenolol tablets.  

PubMed

The purpose of this study was to formulate a 25-mg atenolol capsule starting from a commercial 100-mg atenolol tablet, given the fact that this strength is not available in Palestine and also because 50-mg atenolol tablets failed the splitting uniformity test of the European Pharmacopoeia, and to evaluate the chemical stability and dissolution behavior of the obtained capsules so as to ensure a high-quality product. A high-performance liquid chromatographic system was used for the analysis and quantification of atenolol in the samples studied. Samples of atenoIol for analysis were prepared as reported by the United States Pharmacopeia monograph. Disintegration and dissolution tests were performed according to the United States Pharmacopeia. The high-performance liquid chromatography assay indicated that the 25-mg atenolol capsules were stable for four months when stored at ambient temperature conditions. The disintegration time for all atenolol capsules was within the United States Pharmacopeia limits of 15 minutes. Atenolol release profile showed that approximately 90% of atenolol dissolved after 10 minutes. This study is important for patients who need to take one half of a 50-mg tablet, but for whom the splitting process doesn't give equal halves, and also for modifying the dose for patients with renal or hepatic problems. Therefore, it is possible for the community pharmacist to crush atenolol 100-mg tablets and refill them in new capsules with each containing a precise amount of atenolol, calculated according to body surface area and kidney and liver functions without affecting the chemical stability of the active ingredient nor its dissolution profile and also have a cost effective dosage form. PMID:23050394

Zaid, Abdel Naser; Malkieh, Numan; Kharoaf, Maher; Abu Ghoush, Abeer; Al-Ramahi, Rowa'

405

Static var compensators stabilize power voltages  

SciTech Connect

This article discusses the operation of a static var compensator as installed by Alabama Power near a steel mill with a large arc furnace load. This is expected to result in a number of benefits, including flicker reduction, dynamic power factor correction, harmonics filtering and a reduction in system losses.

Burch, R.

1996-06-01

406

Technical evaluation report (Revision 1) on the proposed design modifications and technical specification changes on grid voltage degradation for the Peach Bottom Atomic Power Station, Units 2 and 3  

Microsoft Academic Search

This report is a revision of the technical evaluation documented in a separate report dated November 3, 1981 (UCID-19115) on the proposed design modification and Technical Specification changes for the protection of the Class 1E equipment from grid voltage degradation for the Peach Bottom Atomic Power Station, Units 2 and 3. The review criteria are based on several IEEE standards

Selan

1983-01-01

407

Adaptive voltage position design for voltage regulators  

Microsoft Academic Search

This paper proposes a general design guideline for the voltage regulator (VR) to achieve adaptive voltage position (AVP). All existing control methods are covered for different kinds of output filter capacitors. Based on the small-signal model analysis, the output impedance and system control bandwidth are discussed. Following the proposed design guidelines, simulation and experimental results demonstrate very good VR transient

Kaiwei Yao; Yuancheng Ren; Julu Sun; Kisun Lee; Ming Xu; Jinghai Zhou; Fred C. Lee

2004-01-01

408

Bioremediation of Contaminated Lake Sediments and Evaluation of Maturity Indicies as Indicators of Compost Stability  

PubMed Central

Land contamination is one of the widely addressed problems, which is gaining importance in many developed and developing countries. International efforts are actively envisaged to remediate contaminated sites as a response to adverse health effects. Popular conventional methodologies only transfer the phase of the contaminant involving cost intensive liabilities besides handling risk of the hazardous waste. Physico-chemical methods are effective for specific wastes, but are technically complex and lack public acceptance for land remediation. “Bioremediation”, is one of the emerging low-cost technologies that offer the possibility to destroy various contaminants using natural biological activities. Resultant non -toxic end products due to the microbial activity and insitu applicability of this technology is gaining huge public acceptance. In the present study, composting is demonstrated as a bioremediation methodology for the stabilization of contaminated lake sediments of Hyderabad, A.P, India. Lake sediment contaminated with organics is collected from two stratums – upper (0.25 m) and lower (0.5m) to set up as Pile I (Upper) and Pile II (Lower) in the laboratory. Lime as a pretreatment to the lake sediments is carried out to ensure metal precipitation. The pretreated sediment is then mixed with organic and inorganic fertilizers like cow dung, poultry manure, urea and super phosphate as initial seeding amendments. Bulking agents like sawdust and other micronutrients are provided. Continuous monitoring of process control parameters like pH, moisture content, electrical conductivity, total volatile solids and various forms of nitrogen were carried out during the entire course of the study. The stability of the compost was evaluated by assessing maturity indices like C/N, Cw (water soluble carbon), CNw (Cw/Nw), nitrification index (NH4/NO?3), Cation Exchange Capacity (CEC), germination index, humification ratio, compost mineralization index (ash content/oxidizable carbon), sorption capacity index (CEC/oxidizable carbon). Enzyme activities of agricultural interest like urease, phosphatase, ?-glucosidase, dehydrogenase and BAA-hydrolyzing protease, which are involved in the nitrogen, phosphorus and carbon cycles, were also assessed. Total content of macro and micronutrients in the final compost was also determined to assess the fertilizer value. The studies revealed that composting could be applied as a remediation technology after removing the top sediment. The maturity indices that are evaluated from the present study can be used to validate the success of the remediation technology.

Rekha, P.; Suman Raj, D. S.; Aparna, C.; Bindu, V. Hima; Anjaneyulu, Y.

2005-01-01

409

Bioremediation of contaminated lake sediments and evaluation of maturity indicies as indicators of compost stability.  

PubMed

Land contamination is one of the widely addressed problems, which is gaining importance in many developed and developing countries. International efforts are actively envisaged to remediate contaminated sites as a response to adverse health effects. Popular conventional methodologies only transfer the phase of the contaminant involving cost intensive liabilities besides handling risk of the hazardous waste. Physico-chemical methods are effective for specific wastes, but are technically complex and lack public acceptance for land remediation. iBioremediatio nî, is one of the emerging low-cost technologies that offer the possibility to destroy various contaminants using natural biological activities. Resultant non-toxic end products due to the microbial activity and insitu applicability of this technology is gaining huge public acceptance. In the present study, composting is demonstrated as a bioremediation methodology for the stabilization of contaminated lake sediments of Hyderabad, A.P, India. Lake sediment contaminated with organics is collected from two stratums--upper (0.25 m) and lower (0.5m) to set up as Pile I (Upper) and Pile II (Lower) in the laboratory. Lime as a pretreatment to the lake sediments is carried out to ensure metal precipitation. The pretreated sediment is then mixed with organic and inorganic fertilizers like cow dung, poultry manure, urea and super phosphate as initial seeding amendments. Bulking agents like sawdust and other micronutrients are provided. Continuous monitoring of process control parameters like pH, moisture content, electrical conductivity, total volatile solids and various forms of nitrogen were carried out during the entire course of the study. The stability of the compost was evaluated by assessing maturity indices like C/N, Cw (water soluble carbon), CNw (Cw/Nw), nitrification index (NH4/NO-3), Cation Exchange Capacity (CEC), germination index, humification ratio, compost mineralization index (ash content/oxidizable carbon), sorption capacity index (CEC/oxidizable carbon). Enzyme activities of agricultural interest like urease, phosphatase, P-glucosidase, dehydrogenase and BAA-hydrolyzing protease, which are involved in the nitrogen, phosphorus and carbon cycles, were also assessed. Total content of macro and micronutrients in the final compost was also determined to assess the fertilizer value. The studies revealed that composting could be applied as a remediation technology after removing the top sediment. The maturity indices that are evaluated from the present study can be used to validate the success of the remediation technology. PMID:16705825

Rekha, P; Suman Raj, D S; Aparna, C; Hima Bindu, V; Anjaneyulu, Y

2005-08-01

410

Mechanism of voltage gating in potassium channels.  

PubMed

The mechanism of ion channel voltage gating-how channels open and close in response to voltage changes-has been debated since Hodgkin and Huxley's seminal discovery that the crux of nerve conduction is ion flow across cellular membranes. Using all-atom molecular dynamics simulations, we show how a voltage-gated potassium channel (KV) switches between activated and deactivated states. On deactivation, pore hydrophobic collapse rapidly halts ion flow. Subsequent voltage-sensing domain (VSD) relaxation, including inward, 15-angstrom S4-helix motion, completes the transition. On activation, outward S4 motion tightens the VSD-pore linker, perturbing linker-S6-helix packing. Fluctuations allow water, then potassium ions, to reenter the pore; linker-S6 repacking stabilizes the open pore. We propose a mechanistic model for the sodium/potassium/calcium voltage-gated ion channel superfamily that reconciles apparently conflicting experimental data. PMID:22499946

Jensen, Morten Ø; Jogini, Vishwanath; Borhani, David W; Leffler, Abba E; Dror, Ron O; Shaw, David E

2012-04-13

411

Systematic Evaluation of Hardware and Animal Stability for High-Resolution Layer-Specific MRI of the Retina  

Microsoft Academic Search

Purpose: To examine animal and hardware instability in phantoms and in vivo rat retinas, and to implement solu- tions to improve stability for structural and functional MRI of the retina. Materials and Methods: Anatomical (25 25 m) and perfusion-based functional (90 90 m) MRI protocols were evaluated on phantoms and in vivo rat retinas at 7 Tesla. Temporal phase drift

Timothy Q. Duong; Xiaodong Zhang; Yingxia Li

2009-01-01

412

SEDIMENT STABILITY ASSESSMENT TO EVALUATE NATURAL RECOVERY AS A VIABLE REMEDY FOR CONTAMINATED SEDIMENTS WORKING DRAFT, JUNE 2004  

Microsoft Academic Search

Natural recovery processes have been shown at some contaminated sediment sites to provide sustained reductions in contaminant bioavailability over time as indicated by contaminant trends in biota tissue, sediment and water column samples. Evaluation of the future effectiveness of monitored natural recovery (MNR) as a potential long-term remedy requires an assessment of sediment stability, especially when long-term burial of contaminated

Michael J. Erickson; John W. Davis; Clay Patmont; Michael Swindoll

2004-01-01

413

Stability Analysis for Evaluating the Influence of Environment on Chemical and Biological Control of White Mold ( Sclerotinia sclerotiorum) of Bean  

Microsoft Academic Search

Fungicide and biological control treatments were evaluated for efficacy in suppressing white mold of bean in six field trials. In all trials, treatment with the fungicide benomyl significantly suppressed disease. In almost all trials, at least one biological control treatment significantly suppressed disease but no biological control treatments provided significant suppression in more than two trials. Stability analyses of the

G. J. Boland

1997-01-01

414

Tracking the longitudinal stability of medical students' perceptions using the AAMC graduation questionnaire and serial evaluation surveys  

Microsoft Academic Search

BACKGROUND: This study examined the longitudinal stability of students' perceptions by comparing ratings on similar survey items in three sequential evaluations: end-of-clerkship (EOC), AAMC graduation questionnaire (GQ), and a postgraduate survey (PGY1).\\u000aMETHOD: For the classes of 2000 and 2001, ratings were compiled from EOC evaluations and comparable items from the GQ. For both cohorts, selected GQ items were included

Michele P. Pugnaire; Mary L. Zanetti; Michele M. Carlin

2004-01-01

415

Experimental evaluation of Harrington rod fixation supplemented with sublaminar wires in stabilizing thoracolumbar fracture-dislocations.  

PubMed

Segments of the spinal column of calves were instrumented with Harrington rods with and without sublaminar wires. Grossly unstable lesions were created by resecting a 2-cm segment from the central spinal segment. Testing on an Instron tester documented the improvement in stability provided by the sublaminar wires in this grossly unstable experimental fracture. Improved stability was seen in resisting axial loading, lateral bending, and forward flexion loading. Rotational stability was particularly improved. PMID:6478708

Munson, G; Satterlee, C; Hammond, S; Betten, R; Gaines, R W

1984-10-01

416

Stability Evaluation Of Previous Volcanic Edifice Collapse At Pico De Orizaba Volcano, Mexico, Using Geotechnical Techniques  

NASA Astrophysics Data System (ADS)

Pico de Orizaba volcano has collapsed twice during its geologic evolution (Carrasco-Nuñez, 1997). The initial stage of evolution for this volcano is known as the Torrecillas cone that collapsed 0.21 Ma b.p., and the related deposits formed the Jamapa avalanche which traveled eastward 75 km. A second, superimposed constructional stage is the Espolón de Oro cone that also ended with a collapse 20 000 years b.p., forming the Tetelzingo avalanche-lahar that traveled 85 km. Samples from the remains of old summit cores and their corresponding collapse deposits were collected and tested in order to obtain strength parameters of altered rock from old volcanic edifices. Hydrothermal alteration and variations of strength of the two avalanche deposits were correlated with the strength values and alterations from the in situ corresponding sources. Strength values: Hoek and Brown's parameters, Uniaxial Compressive Strength (50-300 kPa), cohesion (480-2000 kPa), angle of friction (6° - 35° ); and degree of alteration give insights of rock mass quality and maximum intact rock strengths of the edifice rock mass. These values provide the upper limits for numerical model input parameter values for evaluation of flank stability. Rock strength from numerical model of previous failures can be compared with those obtained for the rock mass and intact rock of the actual edifice. This would permit the assessment of future avalanche hazards.

Concha-Dimas, A.; Watters, R. J.

2001-12-01

417

Evaluation of maturity and stability parameters of composts prepared from agro-industrial wastes.  

PubMed

The objective of this study was to evaluate changes in physical, chemical and biological parameters to assess the maturity and stability of composts prepared from mixture of different farm and agro-industrial wastes over a period of 150 days. All the composts appeared granular, dark grey in color without foul odor and attained an ambient temperature at 120 days of composting indicating the stable nature of composts. Correlation analysis showed that the optimal values of the selected parameters for our experimental conditions are as follows: organic matter loss >42%, C:N ratio <15, water soluble organic carbon (C(w)):organic N (N(org)) ratio <0.55, humic acid (HA):fulvic acid (FA) ratio >1.9, humification index (HI) >30%, cation exchange capacity (CEC):total organic carbon (TOC) ratio >1.7 and germination index (GI) >70%. Compost enriched with sewage sludge, pressmud and poultry waste matured earlier compared to composts either enriched with distillery effluent or un-enriched. PMID:21075622

Raj, Dev; Antil, R S

2010-10-23

418

Evaluation of crystallinity and film stress in yttria-stabilized zirconia thin films  

SciTech Connect

Yttria (3 mol %)-stabilized zirconia (YSZ) thin films were deposited using radio frequency (rf) magnetron sputtering. The YSZ thin films were deposited over a range of temperatures (22-300 deg. C), pressures (5-25 mTorr), and gas compositions (Ar/O ratio). Initial studies characterized a select set of properties in relation to deposition parameters including: refractive index, structure, and film stress. X-ray diffraction (XRD) showed that the films are comprised of mainly monoclinic and tetragonal crystal phases. The film refractive index determined by prism coupling, depends strongly on deposition conditions and ranged from 1.959 to 2.223. Wafer bow measurements indicate that the sputtered YSZ films can have initial stress ranging from 86 MPa tensile to 192 MPa compressive, depending on the deposition parameters. Exposure to ambient conditions (25 deg. C, 75% relative humidity) led to large increase ({approx}100 MPa) in the compressive stress of the films. Environmental aging suggests the change in compressive stress was related to water vapor absorption. These effects were then evaluated for films formed under different deposition parameters with varying density (calculated packing density) and crystal structure (XRD)

Piascik, Jeffrey R.; Thompson, Jeffrey Y.; Bower, Christopher A.; Stoner, Brian R. [Curriculum of Applied and Material Science, University of North Carolina, Chapel Hill, North Carolina 27599 and RTI International, Center for Materials and Electronic Technologies, Research Triangle Park, North Carolina 27709 (United States); Curriculum of Applied and Material Science, and School of Dentistry, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); RTI International, Center for Materials and Electronic Technologies, Research Triangle Park, North Carolina 27709 (United States); RTI International, Center for Materials and Electronic Technologies, Research Triangle Park, North Carolina, 27709 and Curriculum of Applied and Material Science, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)

2005-09-15

419

Stability evaluation of the Panel 1 rooms and the E140 drift at WIPP  

SciTech Connect

WIPP, intended for underground permanent disposal of defense transuranic waste, is located 40 km east of Carlsbad at a depth of 655 m in the salt beds of the 600-m thick Permian Salado Formation. It will consist of 56 ``rooms`` each 91.5 m long, 10 m wide, and 4 m high, grouped in 8 ``panels`` of 7 rooms each. About 7.5 km of access drifts will also be provided. Excavation began in 1982 and surface/access/test facilities and one panel were completed by 1988, many years before it could be used. Current plans are to start emplacing waste in WIPP in 1998 and continue for 35 years. The north- south drift E140 is the widest (25 ft) of the four main north-south drifts and is the main north-south passage. Plans to conduct experiments with waste in 1993 were abandoned, and the plan now is to use panel 1 for permanent disposal of waste starting in 1998. The stability evaluation resulted in the conclusion that, while it would be possible to safely use portions of panel 1 for waste emplacement, it would be best to abandon panel 1 and mine a new panel after the decision has been made to use WIPP as a repository and the necessary permits obtained.

Maleki, H. [Maleki Technologies, Inc. (United States); Chaturvedi, L. [Environmental Evaluation Group, Albuquerque, NM (United States)

1996-08-01

420

Evaluation of crystallinity and film stress in yttria-stabilized zirconia thin films  

NASA Astrophysics Data System (ADS)

Yttria (3 mol %)-stabilized zirconia (YSZ) thin films were deposited using radio frequency (rf) magnetron sputtering. The YSZ thin films were deposited over a range of temperatures (22-300 °C), pressures (5-25 mTorr), and gas compositions (Ar/O ratio). Initial studies characterized a select set of properties in relation to deposition parameters including: refractive index, structure, and film stress. X-ray diffraction (XRD) showed that the films are comprised of mainly monoclinic and tetragonal crystal phases. The film refractive index determined by prism coupling, depends strongly on deposition conditions and ranged from 1.959 to 2.223. Wafer bow measurements indicate that the sputtered YSZ films can have initial stress ranging from 86 MPa tensile to 192 MPa compressive, depending on the deposition parameters. Exposure to ambient conditions (25 °C, 75% relative humidity) led to large increase (~100 MPa) in the compressive stress of the films. Environmental aging suggests the change in compressive stress was related to water vapor absorption. These effects were then evaluated for films formed under different deposition parameters with varying density (calculated packing density) and crystal structure (XRD).

Piascik, Jeffrey R.; Thompson, Jeffrey Y.; Bower, Christopher A.; Stoner, Brian R.

2005-09-01

421

Evaluation of stabilization energies in ?-? and cation-? interactions involved in biological macromolecules by ab initio calculations  

NASA Astrophysics Data System (ADS)

Non-covalent interactions involving aromatic rings contribute significantly to the stability of three-dimensional structures of biological macromolecules. Therefore, accurate descriptions of such interactions are crucial in understanding the functional mechanisms of biological molecules. However, it is also well known that, for some cases where van der Waals interactions make a dominant contribution, conventional ab initio electronic structure calculations, such as density functional theory, do not produce accurate interaction energies. In this study, we evaluated molecular mechanics (MM) calculations for two types of interactions involving aromatic rings, ?-? interactions and cation-? interactions, by comparing our results with those obtained by advanced ab initio calculations at the coupled-cluster with singles, doubles and perturbative triples level. In structures with stacked aromatic rings, interaction energies obtained by MM calculations are overestimated. On the other hand, for cation-? interactions, the energies in MM calculations are significantly underestimated. In both cases, addition of an induction energy based on polarization effects also fails to improve the estimate given by MM calculations. The results indicate that current effective pairwise potentials are inappropriate to represent ?-? and cation-? interactions.

Tateno, Masaru; Hagiwara, Yohsuke

2009-02-01

422

Two examples of using physical mechanics approach to evaluate colloidal stability  

NASA Astrophysics Data System (ADS)

Since Mr. Tsien brought up his idea of physical mechanics, as a new field in engineering science, to public attention in the early 50's of the 20th century, innumerable application examples of physical mechanics approach in diverse fields have manifested its strong vitality increasingly. One of important aspects in applications of physical mechanics is to appropriately choose the microscopic quantity for the system in consideration and build a bridge to connect its relevant microscopic information to its desired macroscopic properties. We present two unique cases of using the physical mechanics approach to study colloidal stability. In the first case we measured the outcomes from artificially induced collisions at individual particle levels, by means of directly observing artificially induced collisions with the aid of optical tweezers. In the second case, by using T-matrix method, the microscopic quantity extinction cross section of the doublet can be accurately evaluated and therefore the measurement range and accuracy of the turbidity methodology for determining the CRC are greatly improved.

Sun, ZhiWei; Xu, ShengHua

2012-06-01

423

Clotrimazole nanoemulsion for malaria chemotherapy. Part II: stability assessment, in vivo pharmacodynamic evaluations and toxicological studies.  

PubMed

The aim of present investigation was to evaluate the potential of clotrimazole as antimalarial drug. Due to poor aqueous solubility and high lipophilicity, it was previously formulated in a nanoemulsion based system. The intrinsic effects of nanoemulsion on improvement of antimalarial activity of clotrimazole were assessed in mice infected with Plasmodium berghei and compared to its suspension formulation. In four-day suppressive test, mice treated with 10mg/kg clotrimazole nanoemulsion showed the highest suppression of parasitemia and; parasitemia was significantly lower than that of 10mg/kg clotrimazole suspension. In onset of activity and recrudescence test, percent reduction of parasitemia was significantly higher in 10 and 15 mg/kg clotrimazole nanoemulsion groups compared to 15 mg/kg suspension group. In both murine models, survival of mice treated with nanoemulsion was significantly prolonged compared to suspension at equivalent doses. The inhibition of parasite growth by clotrimazole in the nanoemulsion was dose dependent as determined by test for linear trend. In repeated dose oral toxicity, levels of serum liver enzymes and biomarkers of hepatotoxicity did not vary significantly from control. Six-month stability testing of the clotrimazole nanoemulsion exhibited no changes in various physiochemical attributes of drug product compared to initial analysis. PMID:22265913

Borhade, Vivek; Pathak, Sulabha; Sharma, Shobhona; Patravale, Vandana

2012-01-14

424

Effect of alternative preservatives on the microbial quality, lipid stability and sensory evaluation of boerewors.  

PubMed

Boerewors is a South African fresh sausage preserved with 450mg/kg sulphur dioxide (SO(2)). The preservative effects of rosemary (Ros; 260mg/kg) and chitosan (Chi; 10g/kg) were compared to SO(2). Eight boerewors models were formulated. Microbial, colour, lipid and sensory characteristics were evaluated. Chi and Chi in combination with other preservatives had a significant effect on reducing total bacterial, coliform and Enterobacteriaceae counts, comparable to SO(2). Chi, however, had a better effect on decreasing yeasts and mould counts than SO(2). Chi showed good colour properties comparable to SO(2). Ros showed comparable lipid stability to SO(2) but better when compared to Chi. Ros had a better effect on the sensory taste when compared to Chi, but SO(2) was still preferred. Reduced levels of 100mg/kg SO(2) showed good antimicrobial and colour effects in combination with Chi and in combination with Ros as antioxidant and improving the sensory properties. Alternative preservatives can be used to reduce the SO(2) content of boerewors. PMID:22326060

Mathenjwa, S A; Hugo, C J; Bothma, C; Hugo, A

2012-01-25

425

Mixed Voltage VLSI Design.  

National Technical Information Service (NTIS)

A technique for minimizing the power dissipated in a Very Large Scale Integration (VLSI) chip by lowering the operating voltage without any significant penalty in the chip throughput even though low voltage operation results in slower circuits. Since the ...

R. Panwar D. Rennels L. Alkalaj

1993-01-01

426

Automatic voltage imbalance detector  

DOEpatents

A device for indicating and preventing damage to voltage cells such as galvanic cells and fuel cells connected in series by detecting sequential voltages and comparing these voltages to adjacent voltage cells. The device is implemented by using operational amplifiers and switching circuitry is provided by transistors. The device can be utilized in battery powered electric vehicles to prevent galvanic cell damage and also in series connected fuel cells to prevent fuel cell damage.

Bobbett, Ronald E. (Los Alamos, NM); McCormick, J. Byron (Los Alamos, NM); Kerwin, William J. (Tucson, AZ)

1984-01-01

427

Ultrasonic test application for evaluation of improvement of marl soil stabilized by lime  

NASA Astrophysics Data System (ADS)

Ultrasonic test has been accepted for non-destructive, fast, and accurate measurement of elastic constants, longitudinal and shear wave velocities, in rock and soil materials in the geotechnical engineering. The ultrasonic test is valid for the measurement of compression and shear wave velocities in the both anisotropic and isotropic samples. There is a direct relation between the elastic constants and elastic waves velocities. The velocity of elastic waves varies with the variation of compression and tensile strengths of materials. In this research, using ultrasonic velocity-meter, propagation velocity of high frequency pulses, according to ISRM (International Society for Rock Mechanics), and ASTM D2845 standards, was measured in samples from an unstable telecommunication station site located in Ahvaz city in Iran. The geological materials of the site were composed of marl soils, and the sequences of sandstone, and marlstone. The test results showed that longitudinal and shear wave velocities, Young's and shear modulus are higher in the sandstone samples obtained from the site than the marlstone samples. Some engineering tests showed that the marl soils due to high clay minerals content and high swelling potential are the cause of instability in the form of crack in the site. Chemical stabilization with lime was selected as a way for reduction of the swelling potential and enhancement of the strength characteristics of the marl soils. Several samples of the marl soils were mixed and cured with different (1, 3, 6, 9, 12, and15) percents of lime. Longitudinal wave velocity, according to the standards mentioned above, was measured in the prepared samples. The test results showed that longitudinal wave velocity increases in the samples with the increase of lime content from 1 up to 9 percent, and decreases after 9 percent lime. The uniaxial compression test results showed that the uniaxial strength value of the prepared samples increases with the increase of lime content from 1 up to 9 percent, and decreases after 9 percents. Also, other geotechnical tests showed that 9 percent lime in the marl soil samples, is the optimum content for the improvement of the marl soils in the site. With comparison of the results from these tests, it can be inferred that the ultrasonic testing can be used as a fast method for the evaluation of improvement of marl soils stabilized by lime.

Jamshidi, H.; Sheshpari, M.

2011-12-01

428

A VME Board Prototype of High Voltage Power Supply Incorporating Piezoelectric Ceramic Transformer  

Microsoft Academic Search

A high voltage power supply channel produces a stabilized direct current high voltage, utilizing a piezoelectric ceramic transformer to generate high voltage. With the intention of developing a 16-channel VME board, a single channel VME board was prototyped, where a high voltage power supply was implemented on a VME board so that a computer could control the power supply. The

Masatosi Imori; Takashi Taniguchi; Toshiyuki Kimura; Satoru Imada

429

A novel method to achieve zero-voltage regulation in buck converter  

Microsoft Academic Search

The function control law for a buck converter is derived to achieve zero voltage regulation of the output voltage. A new method to retrieve the low frequency component of the inductor voltage is proposed and analyzed. The stability of the closed loop system using a proportional and differential controller is analyzed. The effect of the supply voltage and load current

Yan-Fei Liu; Paresh C. Sen

1995-01-01

430

Using a single-board computer to maintain constant voltage, current sources  

Microsoft Academic Search

Constant voltage sources and constant current sources, especially high voltage power supplies going from several tens of thousands of volts to several hundreds of thousands of volts, in some special equipment or special situations, when increasing power, require rising slowly from zero to a predetermined voltage or current and then stabilizing at that point. When load changes or input voltage

L. Zigang; Y. Yongzhi

1985-01-01

431

SHORT REPORT: EVALUATION OF THE POTENCY AND STABILITY OF A CANDIDATE VACCINE AGAINST AMERICAN CUTANEOUS LEISHMANIASIS  

Microsoft Academic Search

Availability of a safe, immunogenic, and affordable vaccine would represent the best strategy for control of cutaneous leishmaniasis (CL). Stability in field conditions is a essential property for any candidate vaccine. The stability and immunogenicity of three different preparations (thimerosal-preserved, autoclaved, and lyophilized) of a killed Leishmania amazonensis vaccine were assessed using fresh products and after 12 months of storage

WILSON MAYRINK; JORGE PINTO; CARLOS DA COSTA; VICENTE TOLEDO; TANIA GUIMARAES; ODAIR GENARO; LUCIANO VILELA

432

Technical evaluation report (Revision 1) on the proposed design modifications and technical specification changes on grid voltage degradation for the Peach Bottom Atomic Power Station, Units 2 and 3  

SciTech Connect

This report is a revision of the technical evaluation documented in a separate report dated November 3, 1981 (UCID-19115) on the proposed design modification and Technical Specification changes for the protection of the Class 1E equipment from grid voltage degradation for the Peach Bottom Atomic Power Station, Units 2 and 3. The review criteria are based on several IEEE standards and The Code of Federal Regulations. The evaluation compares the submittals made by the plant with the NRC staff positions and the review criteria. The evaluation finds that the proposed design modifications and the required changes to the Technical Specifications will ensure that the Class 1E equipment will be protected from sustained voltage degradation.

Selan, J.C.

1983-03-11

433

Acoustoelectric Voltage Measurements for Semiconductor Material Characterization  

Microsoft Academic Search

Transverse Acoustoelectric Voltage (TAV) measurements were used to characterize the electrical and optical properties of semiconducting materials. A modified theoretical expression for the acoustoelectric voltage was obtained and utilized to evaluate the change of TAV as a function of external perturbations, such as applied bias, incident photon energy, temperature and SAW power. The change in TAV due to applied bias

Agostino Abbate

1993-01-01

434

Use of factorial design for evaluation of factors affecting the chemical stability of sirolimus (rapamycin) in solid dosage form.  

PubMed

Effects of four process and formulation parameters (spraying rate of ethanol solution, drying and tablet hardness and hydroxypropyl methyl cellulose (HPMC) content) were evaluated in terms of initial quality of tablets using factorial design approach. For determination of stability of final drug product, the tablets were exposed to stress testing conditions and the three most significant factors were investigated (spraying rate of ethanol solution, drying and HPMC content). Considering the chemical stability of Sirolimus, the following responses were found to be most important: total sum of degradation products, levels of impurity I and assay of isomer C. Investigated factors and their interactions most significantly affected the assay of isomer C in initial and in stressed stability testing samples. The factorial design approach is a very economic way of obtaining the maximum amount of information in a short period of time, which is especially important in studies that include a variety of different factors and their interactions. PMID:24061185

Petelin, Petra; Homar, Miha; Bajc, Aleksander; Ker?, Janez; Simona, Bohanec

2012-03-01

435

Evaluation of physical stability and leachability of Portland pozzolona cement (PPC) solidified chemical sludge generated from textile wastewater treatment plants.  

PubMed

The chemical sludge generated from the treatment of textile dyeing wastewater is a hazardous waste as per Indian Hazardous Waste Management rules. In this paper, stabilization/solidification of chemical sludge was carried out to explore its reuse potential in the construction materials. Portland pozzolona cement (PPC) was selected as the binder system which is commercially available cement with 10-25% fly ash interground in it. The stabilized/solidified blocks were evaluated in terms of unconfined compressive strength, block density and leaching of heavy metals. The compressive strength (3.62-33.62 MPa) and block density (1222.17-1688.72 kg/m3) values as well as the negligible leaching of heavy metals from the stabilized/solidified blocks indicate that there is a potential of its use for structural and non-structural applications. PMID:21724323

Patel, Hema; Pandey, Suneel

2011-06-02

436

Gemifloxacin mesylate (GFM) stability evaluation applying a validated bioassay method and in vitro cytotoxic study.  

PubMed

The validation of a microbiological assay applying the cylinder-plate method to determine the quinolone gemifloxacin mesylate (GFM) content is described. Using a strain of Staphylococcus epidermidis ATCC 12228 as the test organism, the GFM content in tablets at concentrations ranging from 0.5 to 4.5 ?g mL(-1) could be determined. A standard curve was obtained by plotting three values derived from the diameters of the growth inhibition zone. A prospective validation showed that the method developed is linear (r=0.9966), precise (repeatability and intermediate precision), accurate (100.63%), specific and robust. GFM solutions (from the drug product) exposed to direct UVA radiation (352 nm), alkaline hydrolysis, acid hydrolysis, thermal stress, hydrogen peroxide causing oxidation, and a synthetic impurity were used to evaluate the specificity of the bioassay. The bioassay and the previously validated high performance liquid chromatographic (HPLC) method were compared using Student's t test, which indicated that there was no statistically significant difference between these two validated methods. These studies demonstrate the validity of the proposed bioassay, which allows reliable quantification of GFM in tablets and can be used as a useful alternative methodology for GFM analysis in stability studies and routine quality control. The GFM reference standard (RS), photodegraded GFM RS, and synthetic impurity samples were also studied in order to determine the preliminary in vitro cytotoxicity to peripheral blood mononuclear cells. The results indicated that the GFM RS and photodegraded GFM RS were potentially more cytotoxic than the synthetic impurity under the conditions of analysis applied. PMID:21238783

Paim, Clésio S; Führ, Fernanda; Barth, Aline B; Gonçalves, Carlos E I; Nardi, Nance; Steppe, Martin; Schapoval, Elfrides E S

2010-12-04

437

Development and evaluation of suspension plasma sprayed yttria stabilized zirconia coatings as thermal barriers  

NASA Astrophysics Data System (ADS)

The insulating effects from thermal barrier coatings (TBCs) in gas turbine engines allow for increased operational efficiencies and longer service lifetimes. Consequently, improving TBCs can lead to enhanced gas turbine engine performance. This study was conducted to investigate if yttria-stabilized zirconia (YSZ) coatings, the standard industrial choice for TBCs, produced from nano-sized powder could provide better thermal insulation than current commericial YSZ coatings generated using micron-sized powders. The coatings for this research were made via the recently developed suspension plasma spraying (SPS) process. With SPS, powders are suspended in a solvent containing dispersing agents; the suspension is then injected directly into a plasma flow that evaporates the solvent and melts the powder while transporting it to the substrate. Although related to the industrial TBC production method of air plasma spraying (APS), SPS has two important differences---the ability to spray sub-micron diameter ceramic particles, and the ability to alloy the particles with chemicals dissolved in the solvent. These aspects of SPS were employed to generate a series of coatings from suspensions containing ˜100 nm diameter YSZ powder particles, some of which were alloyed with neodymium and ytterbium ions from the solvent. The SPS coatings contained columnar structures not observed in APS TBCs; thus, a theory was developed to explain the formation of these features. The thermal conductivity of the coatings was tested to evaluate the effects of these unique microstructures and the effects of the alloying process. The results for samples in the as-sprayed and heat-treated conditions were compared to conventional YSZ TBCs. This comparison showed that, relative to APS YSZ coatings, the unalloyed SPS samples typically exhibited higher as-sprayed and lower heat-treated thermal conductivities. All thermal conductivity values for the alloyed samples were lower than conventional YSZ TBCs. The different thermal conduction behaviors were linked to the porosity and compositional properties of the coatings using immersion density, SEM, and synchrotron radiation characterization techniques.

van Every, Kent J.

438

Solubilization of beclomethasone dipropionate in sterically stabilized phospholipid nanomicelles (SSMs): physicochemical and in vitro evaluations  

PubMed Central

Background The local treatment of lung disorders such as asthma and chronic obstructive pulmonary disease via pulmonary drug delivery offers many advantages over oral or intravenous routes of administration. This is because direct deposition of a drug at the diseased site increases local drug concentrations, which improves the pulmonary receptor occupancy and reduces the overall dose required, therefore reducing the side effects that result from high drug doses. From a clinical point of view, although jet nebulizers have been used for aerosol delivery of water-soluble compounds and micronized suspensions, their use with hydrophobic drugs has been inadequate. Aim: To evaluate the feasibility of sterically stabilized phospholipid nanomicelles (SSMs) loaded with beclomethasone dipropionate (BDP) as a carrier for pulmonary delivery. Methods 1,2-Distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy-poly(ethylene glycol 5000) polymeric micelles containing BDP (BDP-SSMs) were prepared by the coprecipitation and reconstitution method, and the physicochemical and in vitro characteristics of BDP-SSMs were investigated. Results BDP-SSMs were successfully prepared with a content uniformity and reproducibility suitable for pulmonary administration. The maximum solubility of BDP in SSMs was approximately 1300 times its actual solubility. The particle size and zeta potential of BDP-SSMs were 19.89 ± 0.67 nm and ?28.03 ± 2.05 mV, respectively. The SSMs system slowed down the release of BDP and all of the aerodynamic values of the aerosolized rehydrated BDP-SSMs were not only acceptable but indicated a significant level of deposition in the lungs. Conclusion The SSM system might be an effective way of improving the therapeutic index of nebulized, poorly soluble corticosteroids.

Sahib, Mohanad Naji; Abdulameer, Shaymaa Abdalwahed; Darwis, Yusrida; Peh, Kok Khiang; Tan, Yvonne Tze Fung

2012-01-01

439

Evaluation of Solar Selective Coating Stability. Final Report, September 1, 1978-May 31, 1980.  

National Technical Information Service (NTIS)

Methods were investigated for increasing the cost effectiveness of evacuated tubular collectors through the use of antireflective (AR) coatings and by increasing the high temperature stability. Both surfaces of the cover tube were successfully AR treated ...

L. Spanoudis

1982-01-01

440

Wear and related evaluations of partially stabilized ZrO2  

SciTech Connect

Pin-on-disk (POD) tests show partially stabilized ZrO2 (PSZ) crystals to have about the same wear as fully stabilized ZrO2 crystals, until stabilizer contents are low enough (e.g., 4.5 wt pct Y2O3) so that some monoclinic ZrO2 is present. Then wear increases substantially, as stabilizer content is further reduced, and monoclinic content increases. Tests of PSZ-crystal cutting tools have not proved particularly successful, and rolling-contact fatigue tests of various PSZ materials showed them to be poor candidates for rolling-element bearings, with the latter results indicating a Petch-type dependence. Possible reasons for such limited or poor performance of PSZ, despite its good toughness, are discussed. Poor performance with concentrated loads is noted in particular, indicating limitations due to plastic flow. 9 references.

Rice, R.W.; Wu, C.CM.

1985-08-01

441

TECHNOLOGY EVALUATION REPORT: SITE PROGRAM DEMONSTRATION TEST, SOLIDITECH, INC. SOLIDIFICATION/STABILIZATION PROCESS VOL I  

EPA Science Inventory

The primary objective of the Soliditech, Inc. solidification/stabilization demonstration was to develop reliable performance and cost information. he demonstration took palce at the Imperial Oil Company/Champion Chemical Company Superfund site in Morganiville, New Jersey. Contami...

442

TECHNOLOGY EVALUATION REPORT: SITE PROGRAM DEMONSTRATION TEST, SOLIDITECH, INC. SOLIDIFICATION/STABILIZATION PROCESS VOL II  

EPA Science Inventory

The primary objective of the Soliditech, Inc. solidification/stabilization demonstration was to develop reliable performance and cost information. he demonstration took palce at the Imperial Oil Company/Champion Chemical Company Superfund site in Morganiville, New Jersey. ontamin...

443

Laboratory Evaluation of the Pointing Stability of the ASPS Vernier System.  

National Technical Information Service (NTIS)

The annular suspension and pointing system (ASPS) is an end-mount experiment pointing system designed for use in the space shuttle. The results of the ASPS Vernier System (AVS) pointing stability tests conducted in a laboratory environment are documented....

1980-01-01

444

Evaluation of Factors Affecting the Solidification/Stabilization of Heavy Metal Sludge.  

National Technical Information Service (NTIS)

Solidification/stabilization of hazardous waste involves mixing the waste with a binder material to enhance the physical properties of the waste and to immobilize contaminants that may be detrimental to the environment. Many hazardous wastes contain mater...

R. M. Bricka L. W. Jones

1993-01-01

445

Evaluation of retained austenite stability in heat treated cold work tool steel  

Microsoft Academic Search

In the paper interdependence between retained austenite volume fraction and external tensile stresses as well as temperature and tempering time have been observed. On the basis of the obtained research a parameter characterising mechanical stability of retained austenite has been introduced. Low mechanical stability of retained austenite has been observed in the structure of the researched 70MnCrMoV9-2-4-2 steel which was

A. Kokosza; J. Pacyna

2005-01-01

446

The production of anti-Vibrio harveyi egg yolk immunoglobulin and evaluation of its stability and neutralisation efficacy  

Microsoft Academic Search

In order to replace the antibiotic treatment for control of Vibrio harveyi, a causal agent of luminous disease in Black tiger shrimp, anti-V. harveyi IgY was produced and showed its potential in our preliminary study. However, for further use as feed additive, the IgY stability should be evaluated. The titre of specific IgY was enhanced with an immunostimulant, C-phosphate guanosine

Kawin Punyokun; Ratchanee Hongprayoon; Prapansak Srisapoome; Theerapol Sirinarumitr

2012-01-01

447

Influenza vaccine powder formulation development: spray-freeze-drying and stability evaluation.  

PubMed

The purpose of this study was to develop a spray-freeze-drying (SFD) process for preparing an influenza vaccine dry powder formulation suitable for epidermal powder immunization. After preformulation of two types of flu vaccines, their dry-powder formulations were prepared by SFD. Powder properties and physical stability were determined using particle size analysis, tap density measurement, scanning electron microscopy, optical microscopy, and moisture content analysis. Chemical and biochemical stability of vaccine antigens was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, single radial immunodiffusion assay, and in vivo immunogenicity in a mouse model. We demonstrated that SFD could produce high-density particles-a critical parameter for effective skin penetration. From the stability perspective, the stress posed by SFD was mild because the antigen in the dry powder retained its stability, potency, and immunogenicity. Among several formulations screened, we noted that formulation composition has a significant role in the powder's long-term physical and biochemical stability. One formulation, in particular, containing sub-unit vaccine (45 microg of antigen in 1 mg of powder) with a tertiary mixture of trehalose, mannitol, and dextran, exhibited excellent overall stability, including acceptable biochemical stability after being exposed to a highly humid environment. After all, we have not only demonstrated the suitability of SFD to prepare powders for epidermal powder immunization but also developed a systematic formulation development strategy that allowed the optimization of an influenza vaccine dry powder formulation. More important, this study led to the selection of a formulation system that had been successfully tested in a human clinical study. PMID:15176078

Maa, Yuh-Fun; Ameri, Mahmoud; Shu, Cassandra; Payne, Lendon G; Chen, Dexiang

2004-07-01

448

Stability and coking of direct-methane solid oxide fuel cells: Effect of CO 2 and air additions  

Microsoft Academic Search

This paper concerns the stability of anode-supported solid oxide fuel cells (SOFCs), operated with fuel mixtures of methane–CO2 and methane–air. Stability, which was evaluated in terms of voltage decrease at constant current density, was affected by coke deposits. Chemically inert anode barrier layers were shown to enhance stability and to slow catalytic endothermic reforming reactions within the Ni–YSZ anode that

Manoj Pillai; Yuanbo Lin; Huayang Zhu; Robert J. Kee; Scott A. Barnett

2010-01-01

449

Evaluation of extracted organic carbon and microbial biomass as stability parameters in ligno-cellulosic waste composts.  

PubMed

Extracted organic C and microbial biomass were evaluated as stability parameters in 3 different ligno-cellulosic waste composts. Organic C was extracted by both water and alkali and further separated in humic-like carbon (HLC) and nonhumic carbon (NHC). Conventional humification parameters, such as humification index and degree of humification were calculated from NHC and HLC. Microbial biomass carbon (B(C)) was determined as an indicator of the degree of biochemical transformation, whereas ninhydrin reactive N (B(NIN)) was measured to obtain the stability parameter B(NIN)/N(TOT) (N(TOT), total N). The water-extracted organic C did not provide reliable information on the transformations underwent by the ligno-cellulosic wastes during composting, since its content remained almost unaltered during the whole process. In contrast, parameters based on the alkali-extracted organic C and microbial biomass clearly reflected organic matter (OM) changes during the process. There was an increase in the net amount of HLC in the alkali extracts throughout composting, especially in the first 7 to 12 wk of the process, as well as a relative enrichment of HLC with respect to NHC. Values of humification index and degree of humification in end products were consistent with an adequate level of compost stability. The stability parameter B(NIN)/N(TOT) showed to be a reliable indicator of stability in ligno-cellulosic wastes. Parameters based on the alkali-extracted C and microbial biomass clearly reflected the transformation of the OM during composting and can be used as stability parameters in ligno-cellulosic waste composts. PMID:17071902

Mondini, Claudio; Sánchez-Monedero, Miguel A; Sinicco, Tania; Leita, Liviana

2006-10-27

450

Direct subnanosecond voltage monitors  

SciTech Connect

Advanced system development in the subnanosecond time frame increasingly demands high-resolution voltage measurements for both single-shot and repetitive operation. Voltage monitors having capabilities up to the hundred kilovolt level have been developed for direct measurements in discrete and transmission line geometries. Resolutions of 100 ps at 100 kV to 30 ps at 20 kV have been achieved. Detailed test data is presented and ultimate voltage scaling limits are discussed.

Barth, J.E.; Sajeant, W.J.

1981-01-01

451

Threshold voltage instabilities in high-? gate dielectric stacks  

Microsoft Academic Search

Over recent years, there has been increasing research and development efforts to replace SiO2 with high dielectric constant (high-?) materials such as HfO2, HfSiO, and Al2O3. An important transistor reliability issue is the threshold voltage stability under prolonged stressing. In these materials, threshold voltage is observed to shift with stressing time and conditions, thereby giving rise to threshold voltage instabilities.

Sufi Zafar; Arvind Kumar; Evgeni Gusev; E. Cartier

2005-01-01

452

Relationships between analytical methods utilized as tools in the evaluation of landfill waste stability.  

PubMed

In this study, the refuse from 12 landfills of various ages ranging from fresh refuse to material 11 years old was collected, and changes in the bio-stability parameters were determined. The parameters measured included cellulose, lignin, biochemical methane potential (BMP) and volatile solids, along with plastics. These parameters, along with the cellulose to lignin ratio were compared to determine which were most indicative of the bio-stability of the refuse. Lignin and volatile solids measurements were affected by plastics in refuse samples. Plastics increased both lignin and volatile solids measurements by approximately 10%. Cellulose and volatile solids measurements correlated well with age, each other, and with BMP measurements and were therefore considered the best parameters to determine stability. Data for the Riverbend landfill, a landfill with a moisture content of 48%, which is similar to that of bioreactor landfills, showed that degradation was nearly complete after 5 years as indicated by low values for cellulose and BMP. PMID:16427774

Kelly, Ryan J; Shearer, Bradley D; Kim, Jongmin; Goldsmith, C Douglas; Hater, Gary R; Novak, John T

2006-01-20

453

Evaluation of the stability of acetaminophen in pluronic lecithin organogel and the determination of an appropriate beyond-use date.  

PubMed

Transdermal acetaminophen in Pluronic lecithin organogel (APAP-PLO) has been anecdotally reported as beneficial when used in cancer patients in the hospice setting. However, there is currently no published information regarding the stability of APAP-PLO. The objective of this study was to identify an appropriate formulation of APAP-PLO and to evaluate the stability of that formulation in order to determine an appropriate beyond-use date. APAP-PLO 50% was prepared by a local compounding pharmacy and analyzed at 0, 7, 14, 28, 45, 60, 90, and 180 days using a stability-indicating high-performance liquid chromatographic method. The mean concentrations and standard deviations were determined for each time point. Physical stability was also assessed by visual observation at each time point. The beyond-use date was determined as the time period that the samples maintained at least 90 percent of the initial concentration. At 180 days, the APAP-PLO was physically stable as noted by visual observation, and the concentration was 102 +/- 4.8 percent of initial concentration indicating that a beyond-use date of 180 days would be appropriate for this formulation. PMID:23072202

Peacock, Gina F; Sauvageot, Jurgita

454

Evaluation of roots mechanical contribution to slope stability by finite element modelling  

Microsoft Academic Search

The paper deals with the assessment of vegetation contribution to slope stability, with particular emphasis on the mechanical effects provided by the root apparatus. As it is well known, the presence of a root system within the soil increases, with respect to the case of soil without vegetation, the material effective cohesion with no significant change in its friction angle.

F. Gentile; G. Elia; R. Elia

2009-01-01

455

Relationships between analytical methods utilized as tools in the evaluation of landfill waste stability  

Microsoft Academic Search

In this study, the refuse from 12 landfills of various ages ranging from fresh refuse to material 11 years old was collected, and changes in the bio-stability parameters were determined. The parameters measured included cellulose, lignin, biochemical methane potential (BMP) and volatile solids, along with plastics. These parameters, along with the cellulose to lignin ratio were compared to determine which

Ryan J. Kelly; Bradley D. Shearer; Jongmin Kim; C. Douglas Goldsmith; Gary R. Hater; John T. Novak

2006-01-01

456

EVALUATION OF SOLIDIFICATION/STABILIZATION FOR TREATING HAZADOUS WASTE IN THE UNITED STATES  

EPA Science Inventory

In hazardous waste management, solidification/stabilization (S/S) is a term normally used to designate technology employing additives to alter hazardous waste to reduce the mobility of pollutants, thereby making it acceptable for land disposal or other uses. The use of the techno...

457

Experimental Evaluation of Journal Bearing Stability and New Gas Wave Bearing Materials.  

National Technical Information Service (NTIS)

A gas journal bearing, with a wavy surfaces was tested in a range of speeds up to 18,000 RPM to determine its stability in an unloaded condition as a function of the wave amplitude. The bearing, was 50 mm in diameter, 58 mm long and had 0.01 65 mm radial ...

T. G. Keith F. Dimofte

1998-01-01

458

Development and evaluation of suspension plasma sprayed yttria stabilized zirconia coatings as thermal barriers  

Microsoft Academic Search

The insulating effects from thermal barrier coatings (TBCs) in gas turbine engines allow for increased operational efficiencies and longer service lifetimes. Consequently, improving TBCs can lead to enhanced gas turbine engine performance. This study was conducted to investigate if yttria-stabilized zirconia (YSZ) coatings, the standard industrial choice for TBCs, produced from nano-sized powder could provide better thermal insulation than current

Kent J. van Every

2009-01-01

459

Yield stability evaluation of peanut lines: A comparison of an experimental versus a simulation approach  

Microsoft Academic Search

The assessment of yield stability of crop breeding lines requires data from multi-locations in order to be able to represent a sufficient number of different environments. In addition, the variation in yield of the test lines not only reflects the differential responses of the genotypes to different soil and climatic conditions, which are of primary concern to breeders, but also

P. Banterng; A. Patanothai; K. Pannangpetch; S. Jogloy; G. Hoogenboom

2006-01-01

460

AN EVALUATION OF FACTORS AFFECTING THE SOLIDIFICATION/STABILIZATION OF HEAVY METAL SLUDGE  

EPA Science Inventory

Solidification/stabilization (SIS) of hazardous waste involves mixing the waste with a binder material to enhance the physical properties of the waste and to immobilize contaminants that may be detrimental to the environment. Many hazardous wastes contain materials that are know...

461

Evaluation of Stabilization/Solidification of a K088 Spent Potliner Waste.  

National Technical Information Service (NTIS)

This report presents the results of testing performed on a stabilized/solidified (S/S) spent potliner waste. The waste is an ash from the incineration of wastes produced from the primary reduction of aluminum from the smelting industry. The contaminants f...

M. G. Channell T. T. Kosson

1993-01-01

462

DEVELOPMENT AND APPLICATION OF AN EXPERT SYSTEM FOR EVALUATION OF SCOUR AND STREAM STABILITY  

Microsoft Academic Search

This paper describes a field-deployable decision support system that assists state highway department bridge inspectors in recognizing potential scour hazards and assessing the vulnerability of bridge sites in a cost effective manner. Scour and stream stability is an extremely important problem related to bridge safety as approximately 75% of all bridge failures are related to scour. The purpose of the

PAUL HARMSEN; RICHARD PALMER; GEORGE TURKIYYAH

2001-01-01

463

STABILITY EVALUATION OF SULFUR DIOXIDE, NITRIC OXIDE AND CARBON MONOXIDE GASES IN CYLINDERS  

EPA Science Inventory

The US EPA recommends in their EPA Traceability Protocol 1 and 2 that reactive gases be reanalyzed every six months. The purpose of this study was to assess the stability of selected reactive gases as a function of time to determine the feasibility of extending the recertificatio...

464

An exonuclease I hydrolysis assay for evaluating G-quadruplex stabilization by small molecules  

Microsoft Academic Search

Telomere length homeostasis is a prerequisite for the generation and growth of cancer. In 485% cancer cells, telomere length is maintained by telomerase that add telomere repeats to the end of telomere DNA. Because the G-rich strand of telomere DNA can fold into G-quadruplex that inhibits telomerase activity, stabilizing telomere quadruplex by small molecules is emerging as a potential therapeutic

Yuan Yao; Quan Wang; Yu-hua Hao; Zheng Tan

2007-01-01

465

Attachment of antibodies to sterically stabilized liposomes: evaluation, comparison and optimization of coupling procedures  

Microsoft Academic Search

Several coupling methods for binding antibodies (Ab) to liposomes have previously been developed. We were interested in examining if some of these methods would be suitable for attaching Ab to long-circulating formulations of liposomes (SL), sterically stabilized with poly(ethylene glycol) (PEG). We studied three ‘classical’ coupling methods in which Ab was attached at the bilayer surface of SL, and two

Christian B. Hansen; Grace Y. Kao; Elaine H. Moase; Samuel Zalipsky; Theresa M. Allen

1995-01-01

466

Predictions of stability in pharmaceutical preparations XIX: Stability evaluation and bioanalysis of clofibric acid esters by high-pressure liquid chromatography.  

PubMed

Specific, sensitive, reversed-phase high-pressure liquid chromatographic assays of clofibric acid esters, clofibrate and etofibrate, and their hydrolysis products, clofibric acid and its monoglycolate and nicotinic acid and its monoglycolate, have been developed in aqueous solution and in biological fluids. Sensitivities of 100 ng/ml of injected mobile phase, a 10-fold increase over existing methods, are reported. Plasma concentrations as low as 200 ng/ml can be analyzed easily in the miscible phase after acetonitrile denaturation. The compounds and their products can be extracted with haloalkane solvents. The extracts were evaporated, reconstituted, and assayed in minimal amounts of mobile phase, resulting in sensitivities of 10 ng/ml of plasma. Conditions are presented that minimize interferences with plasma components. The assay was used to determine the stability of the clofibric acid esters in aqueous solutions, to establish log k-pH profiles at various temperatures, and to evaluate Arrhenius parameters. Hydrolysis was by specific acid-base catalysis. The initial product of etofibrate solvolysis at pH greater than 6 is the monoglycol ester of clofibric acid; at pH less than 3, it is the monoglycol ester of nicotinic acid. Clofibric acid esters are highly unstable to mild alkali (1-3 hr at pH 10 and 30 degrees); even in the estimated pH range of maximum stability, they have half-lives of 100-200 days at 30 degrees. They have half-lives of 4-7 min at 37.5 degrees in fresh dog plasma, and data presented indicate that clofibric acid monoglycolate is an initial product of etofibrate solvolysis. PMID:7057373

Garrett, E R; Gardner, M R

1982-01-01

467

Off-set stabilizer for comparator output  

DOEpatents

A stabilized off-set voltage is input as the reference voltage to a comparator. In application to a time-interval meter, the comparator output generates a timing interval which is independent of drift in the initial voltage across the timing capacitor. A precision resistor and operational amplifier charge a capacitor to a voltage which is precisely offset from the initial voltage. The capacitance of the reference capacitor is selected so that substantially no voltage drop is obtained in the reference voltage applied to the comparator during the interval to be measured. 3 figs.

Lunsford, J.S.

1990-02-26

468

Fault Current Limiter by Series Connected Voltage Source Inverter  

NASA Astrophysics Data System (ADS)

In recent years, various types of fault current limiter (FCL) have been developed, because installation of the FCL will bring a lot of benefits to power system operation. Power system controllers based on a concept of Flexible AC Transmission Systems (FACTS) can also be applicable as the FCL with growing power ratings of them. Such FCLs are expected to contribute power system stabilization or power quality enhancement in addition to fault current limitation. Authors have developed a new type of FCL, which consists of a series reactor and a self-commutated voltage source inverter connected in series with a power distribution line by a coupling transformer. In case of a system fault, the FCL will insert a sufficiently large inductance in series with the distribution line by both the series reactor and the inverter, then it will reduce the fault current. On the other hand, the inverter compensates a voltage drop across the series reactor in a standby mode. As a result, the FCL behaves like a negligible impedance in the standby mode. One of the distinctive features of the FCL is a simple configuration because its control strategy does not require an active power source. In addition, inverter voltage rating of the proposed FCL can be reduced by installing the series reactor as compared with other converter-based FCLs. The aim of this paper is to evaluate the operating characteristics of the FCL with both simulation and experimental studies.

Hojo, Masahide; Kuroe, Norihito; Ohnishi, Tokuo

469

High Voltage Testing. Volume II. Specifications and Procedures.  

National Technical Information Service (NTIS)

The High Voltage Design Guide and High Voltage Specifications and Tests Documents referred to in this report pertain to high voltage/high power airborne equipment. A test plan was designed to evaluate and verify test parameters specified in these document...

W. G. Dunbar

1982-01-01

470

Evaluation of Need and Location for a Thermogravimetric Analyzer in the Plutonium Finishing Plant (PFP) Materials Stabilization  

SciTech Connect

This plan provides an analysis for locating a TGA to support PFP Thermal Stabilization processes. The scope of this document is to evaluate the need for, and location for, installation of a TGA system as a supplement to the SFE equipment for moisture measurement in pure oxides. A location assessment for the SFE equipment was previously performed (HNF 1999). Based on that assessment, co-location of the TGA system with the SFE system is the preferred option. This would enable thermally stabilized material to be analyzed for residual moisture by either the TGA system or SFE system or both This evaluation considers glovebox locations in the PFP 234-52 Building Analytical Laboratory or operating areas for the installation of the TGA system and it's supporting equipment. This evaluation considers using existing gloveboxes along with an alternative of adding a new glovebox to existing process lines. The location evaluation criteria focuses mainly on glovebox size, with qualitative consideration of relative cost and schedule impacts associated with system implementation, radiological control, and interaction with other laboratory operations and processes. In addition, the possible co-location of a TGA furnace system with the SFE system was considered.

WILLIS, H.T.

2000-01-20

471

Evaluation of the correlation between insertion torque and primary stability of dental implants using a block bone test  

PubMed Central

Purpose Implant stability at the time of surgery is crucial for the long-term success of dental implants. Primary stability is considered of paramount importance to achieve osseointegration. The purpose of the present study was to investigate the correlation between the insertion torque and primary stability of dental implants using artificial bone blocks with different bone densities and compositions to mimic different circumstances that are encountered in routine daily clinical settings. Methods In order to validate the objectives, various sized holes were made in bone blocks with different bone densities (#10, #20, #30, #40, and #50) using a surgical drill and insertion torque together with implant stability quotient (ISQ) values that were measured using the Osstell Mentor. The experimental groups under evaluation were subdivided into 5 subgroups according to the circumstances. Results In group 1, the mean insertion torque and ISQ values increased as the density of the bone blocks increased. For group 2, the mean insertion torque values decreased as the final drill size expanded, but this was not the case for the ISQ values. The mean insertion torque values in group 3 increased with the thickness of the cortical bone, and the same was true for the ISQ values. For group 4, the mean insertion torque values increased as the cancellous bone density increased, but the correlation with the ISQ values was weak. Finally, in group 5, the mean insertion torque decreased as the final drill size increased, but the correlation with the ISQ value was weak. Conclusions Within the limitations of the study, it was concluded that primary stability does not simply depend on the insertion torque, but also on the bone quality.

Bayarchimeg, Dorjpalam; Namgoong, Hee; Kim, Byung Kook; Kim, Myung Duk; Kim, Sungtae; Kim, Tae-Il; Seol, Yang Jo; Lee, Yong Moo; Ku, Young; Rhyu, In-Chul; Lee, Eun Hee

2013-01-01

472

Validation of uv derivative spectrophotometric method for determination of benazepril hydrochloride in tablets and evaluation of its stability.  

PubMed

The absorbance and first-, second- and third-order derivative UV spectroscopic methods were applied for the determination of benazepril hydrochloride (BEN) in model solutions and tablets, as well as the estimation of its stability in solid phase. Derivative UV spectroscopy and HPLC methods were tested for: precision, linearity, accuracy and repeatability. HPLC was used as a reference method. The study presents that derivative UV spectroscopy (the first and second derivative only) and HPLC can be successfully applied for the quantitative analysis of benazepril hydrochloride both pure and in pharmaceutical formulations. Although, the first and second derivative spectrophotometric methods are fast, precise and accurate, but they cannot be used for evaluation of purity and stability of BEN in pharmaceutical formulations (due to a lack of selectivity). PMID:19702164

Stanisz, Beata; Paszun, Sylwia; Le?niak, Marcin

473

Evaluation of the stability of pin configuration in K-wire fixation of displaced supracondylar fractures in children.  

PubMed

Precutaneous Kirschner wire fixation of displaced Gartlands types II and III supracondylar fractures with image guidance remains a preferred procedure for most orthopaedic units. Various K-wire configurations have been in use, but recent objective evaluation of pin stability has favoured two techniques; the 2 crossed pins placed from the medial and lateral epicondyles, and 2 parallel lateral pins when the former technique is impracticable because of swelling. We reviewed patients who had K-wire fixation precutaneously over a 2-year period (Feb 1996 to Feb 1998). There were 44 children, 30 males, 14 females, ages between 1-15 years. 19 patients had (medial and lateral pins) 15, (2 parallel lateral) and 10 patients (2 lateral crossed) precutaneous pin placement respectively. Their postoperative course indicated that maximum stability was obtained with two opposite crossed pins, followed by the 2 paralleled pin method. These observation determined the choice of technique by the surgeons who operated on these patients. PMID:9870790

Onwuanyi, O N; Nwobi, D G

474

Rotor heating as an indicator of system voltage instability  

SciTech Connect

Voltage stability hinges on the continuing control of the total system`s supply and demand of reactive power within the overall transmission, subtransmission and distribution networks which connects the power stations to the consumers. This is complicated by the elements interspersed within this extensive network that both supply and consume reactive power. Extensive collapses have followed disturbances more severe than considered at the planning stages, but there is a puzzling delay of minutes between the disturbance and collapse. By simulating the physical process, the critical factor has been found to be the action of rotor overcurrent protection in curtailing rotating unit reactive power output. The puzzling delay has been solved by the mathematical modeling of the generator rotor`s thermal response which shows that above rated rotor current would take minutes to reach the rotor`s temperature limit. The paper describes the heat run tests from which the parameters for mathematical rotor thermal models for 500 MW and 660 MW generators have been obtained. The algorithm that has been devised is both simple and reliable and allows computer evaluation, in a fraction of a second, of the time for rotor temperature limit to be reached. When integrated into SCADA, this information would give an early warming and so provide a valuable tool for the control system voltage stability.

Lachs, W.R.; Sutanto, D. [Univ. of New South Wales, Kensington (Australia). School of Electrical Engineering

1995-02-01

475

Evaluation of H2RG stability for infrared Earth-observing systems  

NASA Astrophysics Data System (ADS)

Although originally developed for astronomical applications, the space qualification and availability of the Teledyne HAWAII detector make it appealing for high-precision Earth-observing systems such as the carbon monoxide correlation radiometer required for GEO-CAPE. In this shot noise-limited application, the signal-to-noise ratio of a co-averaged measurement is driven by the detector's temporal stability. To assess the stability, we operated the H2RG under monitored blackbody illumination. The Teledyne SIDECAR ASIC provided 16-bit digitization and clocking for integration times faster than the frame conversion time. With proper application of reference signals, the co-averaging of hundreds of frames is possible. Integrations of one-quarter of the full well depth can attain precision to the 200 ppm level in the co-averaged result. For integrations above three-quarters the well depth, the precision reaches 111 ppm.

Sullivan, P. W.; Edens, W. K.; Darlington, E. H.; Neil, D. O.

2011-09-01

476

Optical S-ALOHA/CDMA Systems for Multirate Applications: Architecture, Performance Evaluation, and System Stability  

NASA Astrophysics Data System (ADS)

In this paper, a new multirate optical network based on a hybrid slotted-ALOHA (S-ALOHA)/overlapped code division multiple access (O-CDMA) system is proposed as an effective way of integrating multiclass traffic. The key issue in this proposal is to exploit the potential of the optical O-CDMA using fiber Bragg gratings when jointly used with the S-ALOHA protocol in a link layer. The newly proposed system is modeled using a general Markov chain from which both the system throughput and the average packet delay are derived. The system stability passing through a general finite user model is also envisaged. The system is then compared to the classical S-ALOHA/variable processing gain (VPG) CDMA system. Numerical results show that the proposed system outperforms the latter one, especially at high transmission rates. In addition, stability measures demonstrate that the overlapped system tends to be more stable than the VPG system.

Raad, Robert; Inaty, Elie; Fortier, Paul; Shalaby, Hossam M. H.

2006-05-01

477

In-Well Sediment Incubators to Evaluate Microbial Community Stability and Dynamics following Bioimmobilization of Uranium  

SciTech Connect

An in-situ incubation device (ISI) was developed in order to investigate the stability and dynamics of sediment associated microbial communities to prevailing subsurface oxidizing or reducing conditions. Here we describe the use of these devices at the Old Rifle Uranium Mill Tailings Remedial Action (UMTRA) site. During the 7 month deployment oxidized Rifle aquifer background sediments (RABS) were deployed in previously biostimulated wells under iron reducing conditions, cell densities of known iron reducing bacteria including Geobacteraceae increased significantly showing the microbial community response to local subsurface conditions. PLFA profiles of RABS following in situ deployment were strikingly similar to those of adjacent sediment cores suggesting ISI results could be extrapolated to the native material of the test plots. Results for ISI deployed reduced sediments showed only slight changes in community composition and pointed toward the ability of the ISIs to monitor microbial community stability and response to subsurface conditions.

Baldwin, Brett R.; Peacock, Aaron D.; Gan, M.; Resch, Charles T.; Arntzen, Evan V.; Smithgall, A. N.; Pfiffner, S.; Freifeld, Barry M.; White, D. C.; Long, Philip E.

2009-09-23

478

Performance evaluation of cement stabilized fly ash–GBFS mixes as a highway construction material  

Microsoft Academic Search

Fly ash and granulated blast furnace slag (GBFS) are major by-products of thermal and steel plants, respectively. These materials often cause disposal problems and environmental pollution. Detailed laboratory investigations were carried out on cement stabilized fly ash–(GBFS) mixes in order to find out its suitability for road embankments, and for base and sub-base courses of highway pavements. Proctor compaction test,

S. P. Singh; D. P. Tripathy; P. G. Ranjith

2008-01-01

479

Spray-dried indomethacin-loaded polyester nanocapsules and nanospheres: development, stability evaluation and nanostructure models  

Microsoft Academic Search

The industrial development of polymeric nanoparticle suspensions, as drug delivery systems, is limited due to the problems in maintaining stability of suspensions. In this work, a spray-drying technique was applied to dry nanocapsule and nanosphere suspensions prepared by nanoprecipitation of polyesters using SiO2 as adjuvant. Powders obtained from nanocapsules presented stable drug recoveries and morphological characteristics after 5 months. For

Adriana Raffin Pohlmann; Valeria Weiss; Omar Mertins; Nádya Pesce da Silveira; S??lvia Stanisçuaski Guterres

2002-01-01

480

Infiltration analysis to evaluate the surficial stability of two-layered slopes considering rainfall characteristics  

Microsoft Academic Search

Shallow slope failures in residual soil during periods of prolonged infiltration are common throughout the world. Using a one-dimensional infiltration model and an infinite slope analysis, this study examines an approximate method of determining how infiltration influences the surficial stability of two-layered slopes. The method extends Moore's infiltration model, which is based on the Green–Ampt model, to cover more general

Sung Eun Cho

2009-01-01