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1

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

2

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

3

Stability issues in IC Low Drop Out voltage regulators  

E-print Network

Performance issues of IC Low Drop Out (LDO) voltage regulators, with specific reference to stability, are discussed in this thesis. Evaluation of existing frequency compensation schemes and their performances across operating loads is presented...

Chava, Krishna Chaitanya

2012-06-07

4

Thick Film Resistors with Improved Voltage Stability  

Microsoft Academic Search

Thick film resistors have been prepared by adding glass frits to the conductive materials of the resistors. By this method, it is found that the resistance of the glass phases in the thick film resistors decreases, with a resulting decrease of voltage drift after applying high voltage pulses to the resistors. In addition, the electrical properties and stability of these

Y. Taketa; M. Haradome

1974-01-01

5

Optimal coordinated voltage control for power system voltage stability  

Microsoft Academic Search

An optimal coordinated voltage controller (OCVC) is developed based on the spirit of model predictive control (MPC) method. The OCVC consists of three components, namely a predictor, a control candidate pool, and a selector. It has been used in secondary voltage control (SVC) to coordinate dissimilar control actions at different geographical locations in order to maintain desired voltage profiles in

J. Y. Wen; Q. H. Wu; D. R. Turner; S. J. Cheng; J. Fitch

2004-01-01

6

Voltage, Stability and Diffusion Barrier Differences between Sodium-ion and Lithium-ion Intercalation Materials  

E-print Network

To evaluate the potential of Na-ion batteries, we contrast in this work the difference between Na-ion and Li-ion based intercalation chemistries in terms of three key battery properties—voltage, phase stability and diffusion ...

Ong, Shyue Ping

7

Long term voltage stability analysis for small disturbances  

E-print Network

This dissertation attempts to establish an analytical and comprehensive framework to deal with two critical challenges associated with voltage stability analysis: 1. To study the new competitive environment appropriately and give more incentive...

Men, Kun

2009-05-15

8

Evaluating evaluation measure stability  

Microsoft Academic Search

This paper presents a novel way of examining the accuracy of the evaluation measures commonly used in information retrieval experiments. It validates several of the rules-of-thumb experimenters use, such as the number of queries needed for a good experiment is at least 25 and 50 is better, while challenging other beliefs, such as the common evaluation measures are equally reliable.

Chris Buckley; Ellen M. Voorhees

2000-01-01

9

A study on threshold voltage stability of low operating voltage organic thin-film transistors  

NASA Astrophysics Data System (ADS)

A low operating voltage (<2 V) organic field-effect transistor (OFET) using phenylhexyltrichlorosilane (PTS) self-assembled monolayer (SAM) dielectric and copper phthalocyanine (CuPc) as semiconductor with improved mobility (0.035 cm2 V-1 s-1) and threshold voltage stability was demonstrated. This device showed better performance when compared to an OFET with octyltrichlorosilane (OTS-8) SAM dielectric. The improved mobility was attributed to the 2D growth mode of CuPc on PTS SAM because of surface energy matching between the two, whereas CuPc film on OTS-8 showed a 3D growth mode with larger grain boundary density. The higher threshold voltage stability of OFETs on PTS SAM was attributed to the efficient coverage and screening of trap centres at dielectric/semiconductor interface due to stronger intermolecular linking and formation of closely packed surface by the bulky phenyl end groups. Decrease in grain boundaries offered by 2D growth of CuPc for electron and hole trapping was also found to be another reason for improved threshold voltage stability. The results indicated that the nature of the end group of SAM dielectric, surface chemistry of dielectric and initial growth mode of semiconductors are all responsible for improvement in threshold voltage stability and enhanced performance of OFET.

Padma, N.; Sen, Shaswati; Sawant, Shilpa N.; Tokas, R.

2013-08-01

10

High voltage stability performance of a gamma ray detection device  

NASA Astrophysics Data System (ADS)

An industrial grade digital radiation survey meter device is currently being developed at Malaysian Nuclear Agency. This device used a cylindrical type Geiger Mueller (GM) which acts as a detector. GM detector operates at relatively high direct current voltages depend on the type of GM tube. This thin/thick walled cylindrical type of GM tube operates at 450-650 volts range. Proper value and stability performance of high voltage are important parameters to ensure that this device give a reliable radiation dose measurement. This paper will present an assessment of the stability and performance of the high voltage supply for radiation detector. The assessment is performed using System Identification tools box in MATLAB and mathematical statistics.

Abdullah, Nor Arymaswati; Lombigit, Lojius; Rahman, Nur Aira Abd

2014-02-01

11

Application of SMES in wind farm to improve voltage stability  

NASA Astrophysics Data System (ADS)

For the wind farms introducing doubly fed induction generators (DFIGs), voltage stability is an essential issue which influences their widely integration into the power grid. This paper proposes the application of superconducting magnetic energy storage (SMES) in the power system integrated with wind farms. SMES can control the active and reactive power flow, realizing the operation in four quadrants independently. The introducing of SMES can smooth the output power flow of the wind farms, and supply dynamic voltage support. Using MATLAB/SIMULINK, the models of the DFIG, the power grid connected and the SMES are created. Simulation results show that the voltage stability of the power system integrated with wind farms can be improved considerably.

Shi, J.; Tang, Y. J.; Ren, L.; Li, J. D.; Chen, S. J.

2008-09-01

12

Global Transient Stability and Voltage Regulation for Power Systems  

Microsoft Academic Search

This paper concems the global control of power systems. It arises from the practical concem 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

Y. Guo; D. J. Hill; Y. Wang

2001-01-01

13

Global transient stability and voltage regulation for power systems  

Microsoft Academic Search

Summary form only given as follows. This paper is concerned with 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).

Yi Guo; D. J. Hill; Youyi Wang

2002-01-01

14

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

15

STABILITY OF HIGH VOLTAGE MODULATORS FOR NONLINEAR LOADS  

SciTech Connect

OAK-B135 Gyrotrons have a nonlinear voltage--current characteristic such that the small signal or ac impedance changes as operational voltage and currents are reached. The ac impedance determines the stability of a voltage or current control system. this can become particularly challenging when several gyrotron are connected in parallel to a single modulator. With all gyrotrons hooked to a common ground, large current loops can be generated as well as non-canceling currents in individual coaxial lines. These inequalities can provide the required feedback impulse to start an oscillation condition in the power system for the tubes. Recent operation of two CPI 110 GHz gyrotrons in the MN class from a single modulator on DIII-D has shown instability in the power system. An oscillation in the drive current occurs at various points in the ramp up and flat top portions of the 80 kV voltage pulse with each tube drawing 40 A at full voltage. Efforts to stabilize these instabilities are presented along with some modeling and examination of the issues for gyrotron modulators.

PAWLEY,J.C; TOOKER,J; PEAVY,J; CARY,W.P; NEREM,A; HOYT,D; LOHR,J

2003-10-01

16

Online Assessment of Voltage Stability in Power Systems with PMUs  

NASA Astrophysics Data System (ADS)

Abstract: For the assessment of voltage instability which comprises the detection of voltage instability and identification of critical buses, two indices namely, system wide Qtax, and bus-specific qtax, are proposed. The Qtax, based on the sensitivity of the reactive power injections to the loading in the system provides early detection of impending voltage instability. The computed qtax indices identify the critcal buses among the load buses in the system. The identified critical buses provided optimal lacations for the corrective control actions for averting voltage instability. Additionally, for voltage stability monitoring, determining the poing of exhaustion of the reactive reserves in system is also crucial. This is addressed by proposed Q-Monitoring Index (QMI), which is the ratio of the reactive component of the source current to the sink current that flows through the adjacent transmission line. These proposed indices together can provide early indication to impending voltage instability. This has been illustrated on IEEE-39 bus system. The reactive support on identified critical buses results in maximum increase in the loadability of the system.

Chitare, Prasad Bhagwat; Murthy Balijepalli, V. S. K.; Khaparde, S. A.

2013-05-01

17

A Novel Line Stability Index (NLSI) for Voltage Stability Assessment of Power Systems  

E-print Network

Abstract:- The management of power systems has become more difficult than earlier because power systems are operated closer to security limits, environmental constraints restrict the expansion of transmission network, the need for long distance power transfer has increased and fewer operators are engaged in the supervision and operation of power systems. Voltage stability has become a major concern in many power systems and many blackouts have been reported, where the reason has been voltage instability. This paper presents a novel line stability index (NLSI) referred to a line initiated from the voltage quadratic equation at the sending and resaving end of a representation of a 2-bus system. The line index in the interconnected system in which the value that is closed to one indicates that the line has reached its instability limit which could cause sudden voltage drop to the corresponding bus caused by the active and reactive load variation. The proposed index consider both active and reactive power to investigate the voltage stability because this index provides more precise results than those which consider only reactive power. To indicate the ability of proposed index, NEW ENGLAND 30 bus is utilized and simulation results show good conformity with the other stability index that proposed in literature. Key-Words:- Voltage stability index, Maximum permissible load, NLSI factor. 1

A. Yazdanpanah-goharrizi; R. Asghari

18

Series capacitor combined with power system stabilizer for enhancement of power-systems voltage synchronous stability  

Microsoft Academic Search

The paper presents a nonlinear dynamic controller for a combination of static series capacitor compensation and power system stabilizer, for enhancement of both voltage and transient stability of power system. The proposed controller implements speed deviation signal and generator terminal current deviation signal. The proposed scheme is validated using a sample single machine infinite bus power system loaded by a

A. M. Sharaql; M. Z. El-Sadek; F. N. Abd-Elbar; A. M. Hemeida

2000-01-01

19

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

20

A Novel Line Stability Index (NLSI) for Voltage Stability Assessment of Power Systems  

Microsoft Academic Search

The management of power systems has become more difficult than earlier because power systems are operated closer to security limits, environmental constraints restrict the expansion of transmission network, the need for long distance power transfer has increased and fewer operators are engaged in the supervision and operation of power systems. Voltage stability has become a major concern in many power

A. YAZDANPANAH-GOHARRIZI; R. ASGHARI

2007-01-01

21

Voltage and Frequency Stability of Weak Power Distribution Networks with Droop-Controlled  

E-print Network

Voltage and Frequency Stability of Weak Power Distribution Networks with Droop to improve power quality and reliability of power grids. These DG's, however, may cause voltage and frequency with rated power level (stressful). Weak networks complicate voltage stability and frequency synchronization

Lemmon, Michael

22

Voltage stability and sensitivity analysis of grid-connected photovoltaic systems  

Microsoft Academic Search

Integration of significant amount of solar power challenges the power system stability operation. This paper presents analyses on the static and transient voltage characteristics at the point of common coupling of a grid-connected photovoltaic system. The static voltage response, known as a PV curve, for the photovoltaic system is analyzed. The voltage transient behaviors caused by the disturbance of parameters

Yaosuo Xue; Madhav Manjrekar; Chenxi Lin; Maria Tamayo; John N. Jiang

2011-01-01

23

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

24

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

25

Monitoring and control of voltage stability in power systems  

SciTech Connect

This paper proposes a new technique in controlling voltage instability in power systems. This technique coordinates between the reactive power of excitation systems and that of static var compensators (SVCs). The method starts with the decomposition of system into several voltage control areas (VCAs). When a reactive power deficiency occurs in certain area, excitation systems respond first to supply the required reactive power by increasing reactive generation of synchronous generators to its upper limit. If more reactive power is needed within the specific area to recover voltage instability, a SVC will be inserted by a switching controller in order to achieve the reactive balance. This controller receives an actuating signal when the terminal voltage is still unsatisfactory. By this technique, it is possible to fully utilize the excitation systems reactive power, and to design economic size SVCs to recover voltage instability. The application of the proposed technique on the New-England 39 bus system proves its efficiency in controlling voltage instability.

Sallam, A.A.; Aboul-Ela, M.E.; Elaraby, E.E. [Suez Canal Univ., Port-Said (Egypt)

1995-12-31

26

Contribution Allocation for Voltage Stability In Deregulated Power Systems  

E-print Network

--P- controller, PI-controller and PID controller of a voltage regulator, the load flow equation of this system, control system and transmission part, etc. This paper focused on how to allocate the responsibility the contribution, and the analysis will help us design the controller and optimize the system to avoid the voltage

27

Evaluation of coupled inductor Voltage Regulators  

Microsoft Academic Search

Usually for a CPU voltage regulator (VR), there are several different coupled inductor VR setups to improve the CPU VR performance. For example, there are three different coupled inductor VR setups for a 6 phase CPU VR: 3*2 phase coupled inductor VR, 2*3 phase coupled inductor VR and 1*6 phase coupled inductor VR. Based on one industrial CPU VR demo

Yan Dong; F. C. Lee; Ming Xu

2008-01-01

28

High-voltage stability coatings in the Zeus panel  

Microsoft Academic Search

A high voltage is applied to the screen spacer of the Zeus panel to obtain high brightness and long phosphor lifetime. To prevent field emission due to high local field strength, the screen spacer is coated with a resistivity layer and a low secondary-electron-emission layer. Efficiently operating panels have been made with sputtered substoichiometric and stoichiometric silicon nitride films, and

A. R. Balkenende; G. T. Jaarsma; W. Hoogsteen; H. P. Löbl; M. Scholten

1996-01-01

29

The Voltage Stability Research of Ship Electric Power System  

Microsoft Academic Search

Ship electric power system is an independent electric power system, and is important in ships. At present, with the increasing tonnage of ships and more and more ships propelled by electric power, the capacity of generator in a marine power station is getting larger and larger. Because of electric propulsion technology applied by modern marines, the control system of voltage

Fanyinhai Zhaomin

2006-01-01

30

Bulk power system voltage phenomena -III: Voltage stability, security & control, Davos, Switzerland, August 1994 THE IRRELEVANCE OF LOAD DYNAMICS FOR THE LOADING MARGIN  

E-print Network

Bulk power system voltage phenomena - III: Voltage stability, security & control, Davos. If the loading margin is danger- ously small, then controls to steer the power system away from the fold to select controls to avoid voltage collapse. This paper justifies the use of static power models to com

Dobson, Ian

31

TCSC as a Transient Voltage Stabilizing Controller Garng Huang and Tong Zhu  

E-print Network

to enhance the voltage stability by changing the reactive power distribution in the power system. Authors of Flexible AC Transmission Systems (FACTS) in the last decade. Thyristor controlled series capacitors (TCSC and operated by some utilities [1,2]. The primary uses of TCSC are to enhance the power system angle stability

32

Influence of dump voltage and allowable temperature rise on stabilizer requirements in superconducting coils  

SciTech Connect

A superconducting winding must have enough stabilizer to satisfy two sets of criteria. During normal operation, the amount of stabilizer must be large enough either to make the coil unconditionally stable or to give a certain desired stability margin. Once a dump occurs, the amount of stabilizer must be large enough to carry the current without generating excessive dump voltages or allowing the winding to exceed a certain maximum temperature (and maximum pressure, in the case of force-cooled coils). The voltage criterion often dominates for very large coil systems, but it is frequently ignored in initial design studies. This paper gives some simple relations between the dump voltage and the stored energy, temperature rise, and coil geometry that are useful in scooping the required amount of stabilizer. Comparison with some recently proposed fusion magnet system designs indicates that excessive dump voltages could result in some cases. High-temperature superconductors may require more stabilizer than the conventional alloys. Calculations with simple model coil systems indicate how trade-offs between various coil parameters affect the dump voltage. 12 refs., 1 fig., 1 tab.

Schwenterly, S.W.

1988-01-01

33

Voltage Stability Analysis of Wind Farm Integration into Transmission Network  

Microsoft Academic Search

In some regional grids in China, wind power penetration will increase rapidly because of the abundant wind resources in those areas and the government policy impetus. However, the power system security and stability may be affected due to the higher wind power penetration. Because majority of the wind farms with higher installed capacity intends to be connected into the transmission

Yongning Chi; Yanhua Liu; Weisheng Wang; Huizhu Dai

2006-01-01

34

Self-organized synchronization and voltage stability in networks of synchronous machines  

NASA Astrophysics Data System (ADS)

The integration of renewable energy sources in the course of the energy transition is accompanied by grid decentralization and fluctuating power feed-in characteristics. This development raises novel challenges for power system stability and design. We investigate power system stability from the viewpoint of self-organized synchronization aspects. In this approach, the power grid is represented by a network of synchronous machines. We supplement the classical Kuramoto-like network model, which assumes constant voltages, with dynamical voltage equations, and thus obtain an extended model, that incorporates the coupled categories voltage stability and rotor angle synchronization. We compare disturbance scenarios in small systems simulated on the basis of both classical and extended model and we discuss resultant implications and possible applications to complex modern power grids.

Schmietendorf, Katrin; Peinke, Joachim; Friedrich, Rudolf; Kamps, Oliver

2014-06-01

35

Self-organized synchronization and voltage stability in networks of synchronous machines  

NASA Astrophysics Data System (ADS)

The integration of renewable energy sources in the course of the energy transition is accompanied by grid decentralization and fluctuating power feed-in characteristics. This development raises novel challenges for power system stability and design. We investigate power system stability from the viewpoint of self-organized synchronization aspects. In this approach, the power grid is represented by a network of synchronous machines. We supplement the classical Kuramoto-like network model, which assumes constant voltages, with dynamical voltage equations, and thus obtain an extended model, that incorporates the coupled categories voltage stability and rotor angle synchronization. We compare disturbance scenarios in small systems simulated on the basis of both classical and extended model and we discuss resultant implications and possible applications to complex modern power grids.

Schmietendorf, Katrin; Peinke, Joachim; Friedrich, Rudolf; Kamps, Oliver

2014-10-01

36

Performance Comparison of Voltage Stability Indices for Weak Bus Identification in Power Systems  

NASA Astrophysics Data System (ADS)

Voltage collapse event is identified as complex and localized in nature but its effect is extensive once occurred. The vital effect of voltage collapse would be the total system collapse or blackouts which would cost a large loss to utility companies. Eventually, on- line monitoring of power system stability has become an important factor for electric power utilities. The last utmost option to avert voltage collapse incident from occurring is by the implementation of under voltage load shedding scheme. The identification of location for load shedding is the main motivation of the study. The weakest bus in a power system is identified as the location for load shedding. This location is obtained using voltage stability index Ld. The performance and effectiveness of Ld index is compared with Fast Voltage Stability Index (FVSI) and Le Index. The results obtained indicate that Ld Index can be used to identify the weak bus in a power system and consequently for the placement of UVLS relays in a power system network.

Verayiah, R.; Mohamed, A.; Shareef, H.; Zainal Abidin, I. Hj

2013-06-01

37

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

SciTech Connect

Voltage collapse may occur in a power system due to lost 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 incidence of voltage collapse. This paper presents a new technique to determine the static voltage stability of load buses in a power system for a certain operating condition and hence identifies load buses which are close to voltage collapse. A voltage stability index with respect to a load bus is formulated from the voltage equation derived from a two bus network and it is computed using Thevenin equivalent circuit of the power system referred to a load bus. This index indicates how far the load buses from their voltage stability limits and hence identifies the critical buses. The performance of this index is tested using 9 bus radial network and the 24 bus IEEE Reliability Test System for its validity. A comparison is also made between this index and the impedance ratio used by Sterling et al. as the voltage collapse indicator. This paper also presents a new loadflow technique to compute power flow solution for radial network which found to be more superior than the Second Order Newton Raphson and Distflow since it takes less iterations to give a loadflow solution.

Abdul Rahman, T.K.; Jasmon, G.B.

1995-12-31

38

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

39

A bilevel programming approach for power system operation planning considering voltage stability and economic dispatch  

Microsoft Academic Search

This paper presents a model for power systems operation planning that aims to maximizing the voltage stability margin and also the economic dispatch, formulated as a bilevel programming problem (BPP). The objective is to obtain a solution for the network operation planning that takes into account both technical and economical aspects. The bilevel model allows system operators to define different

D. A. Arias; A. A. Mota; L. T. M. Mota; C. A. Castro

2008-01-01

40

Varying penetration ratios of wind turbine technologies for voltage and frequency stability  

Microsoft Academic Search

This paper examines the ability of a power system to accommodate wind generation with varying ratios of doubly-fed induction generator and fixed speed induction generator turbines from both static and dynamic aspects. By controlling the ratio between the two types of turbines, voltage stability is maintained for steady-state conditions for a large range of varying wind speeds. Using the ratio

Eknath Vittal; Andrew Keane; Mark O'Malley

2008-01-01

41

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

42

Dispersion Stability Evaluated by Experimental Design  

Microsoft Academic Search

The stability of paraffin and hydrocarbon oil dispersions stabilized by nonionic surfactants has been systematically evaluated. Using experimental design, the influence of the following parameters on dispersion stability was studied: surfactant concentration, shear rate, shear time and temperature of homogenisation. The experiments were evaluated with respect to particle size and particle migration velocity by a scanning optical analysis technique. This

Helena Wassenius; Magnus Nydén; Krister Holmberg

2001-01-01

43

Voltage multi-stability in distribution grids with power flow reversal  

E-print Network

High levels of penetration of distributed generation and aggressive reactive power compensation with modern power electronics may result in the reversal of active and reactive power flows in future distribution grids. The voltage stability of these operating conditions may be very different from the more traditional power consumption regime. We study the stability characteristics of distribution networks with reversed power flow. After introducing a universal algebraic approach to characterize all the solutions of the power flow equations, we show that new solutions appear in the reversed power flow regime even in the simplest three bus systems. We show that the some of these solutions are stable and the system may exhibit a phenomenon of multistability, where multiple stable equilibria co-exist at the given set of parameters, and the system may converge to an undesirable equilibrium after a disturbance. These predictions are validated with dynamic simulations of two different systems. Under certain conditions the new states are viable and may be characterized by relatively high voltages. Possible approaches towards reactive power/voltage regulation as well as permissible distributed generation capacity in future power systems are proposed and discussed in the end of the paper.

Hung D. Nguyen; Konstantin Turitsyn

2014-04-25

44

Bonneville Power Administration is investigating wide-area stability and voltage control. The control provides a flexible  

E-print Network

. There will also be synergy between wide-area control and substation automation (e.g., intelligent electronic compensation for voltage support and stabil- ity. Features include phasor measurements, digital fiber optic devices, digital control and protection). We present simulation results showing improved voltage support

Venkatasubramanian, Mani V.

45

A Sufficient Condition for Power Flow Insolvability with Applications to Voltage Stability Margins  

E-print Network

For the nonlinear power flow problem specified with standard PQ, PV, and slack bus equality constraints, we present a sufficient condition under which the specified set of nonlinear algebraic equations has no solution. This sufficient condition is constructed in a framework of an associated feasible, convex optimization problem. The objective employed in this optimization problem yields a measure of distance (in a parameter set) to the power flow solution boundary. In practical terms, this distance is closely related to quantities that previous authors have proposed as voltage stability margins. A typical margin is expressed in terms of the parameters of system loading (injected powers); here we additionally introduce a new margin in terms of the parameters of regulated bus voltages.

Molzahn, Daniel K; DeMarco, Christopher L

2012-01-01

46

On-line Collaborative Voltage Stability Control of Power Systems Integrated with Large-scale Wind Farms  

Microsoft Academic Search

Due to their unpredictable generation patterns, large-scale wind farms may affect the voltage stability of their integrated power systems negatively. This paper proposes a novel on-line collaborative voltage stability control method to eliminate the negative impact of large-scale wind farms integrated with a power system. The implementation of the proposed method is based on the on-line collaboration of existed local

Zhong Chen; Wenjuan Du; H. F. Wang; Guoqing Tang

2007-01-01

47

On-line collaborative voltage stability control of power systems intergrated with large-scale wind farms  

Microsoft Academic Search

Due to their unpredictable generation patterns, large-scale wind farms may affect the voltage stability of their integrated power systems negatively. This paper proposes a novel on-line collaborative voltage stability control method to eliminate the negative impact of large-scale wind farms integrated with a power system. The implementation of the proposed method is based on the on-line collaboration of existed local

Zhong Chen; Feng Xue; W. Du; H. F. Wang; D. Dunn

2007-01-01

48

Stability evaluation of vaccines: WHO approach.  

PubMed

The stability of vaccines has a major impact on the success of immunization programmes worldwide. In line with this, clear definition of the stability characteristics of a vaccine is of critical importance. One of the concerns at country level is whether vaccines will remain potent on its way from the manufacturer, through the distribution channels, to the final users and vaccine recipients. In response to the requests for assistance in defining stability profile of vaccines, the Expert Committee on Biological Standardization (ECBS) in October 2006 agreed that new WHO guidelines be established on stability evaluation of vaccines (http://www.who.int/biologicals/publications/trs/areas/vaccines/stability/en/index.html). This document applies to all vaccines against infectious diseases. The aim of this guideline is to provide the scientific basis and guiding principles for evaluation of vaccine stability for the purpose of clinical trial approval, licensing, and post-licensure monitoring. As part of its initiative to promote use of vaccines of assured quality, WHO emphasizes the role of National Regulatory Authorities (NRAs) and National Control Laboratories (NCLs) in overall vaccine evaluation, including stability assessment. While recognizing that manufacturers are responsible for the quality of the vaccines they produce, compliance with vaccine quality specifications is part of regulatory oversight. This article provides basic information about WHO international standards as well as key definitions and principles for stability evaluation of vaccines that are elaborated in detail in the above mentioned guidance document. PMID:19729320

Knezevic, Ivana

2009-11-01

49

Achieving Bilateralism in Electroheat Stability Evaluations  

Microsoft Academic Search

The stability criteria for controlled electroheat processes, i.e., plastic extruders, arc furnaces, induction furnaces, plasma torches, fluidized beds, etc., is studied. A previous geometric approach was unilateral, in that stability criteria could be evaluated if the electroheat gain and the controller sensitivity were known, but the reverse procedure was not possible. Subsequent experience has shown that this lack of bilateralism

William K. Roots; Cheng-Mieng Wu

1969-01-01

50

Stabilization of the Conductive Conformation of a Voltage-gated K+ (Kv) Channel  

PubMed Central

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

2013-01-01

51

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

52

The simulation and evaluation of dynamic voltage scaling algorithms  

Microsoft Academic Search

The reduction of energy consumption in microprocessors can be accomplished without impacting the peak performance through the use of dynamic voltage scaling (DVS). This approach varies the processor voltage under software control to meet dynamically varying performance requirements. This paper presents a foundation for the simulation and analysis of DVS algorithms. These algorithms are applied to a benchmark suite specifically

Trevor Pering; Thomas D. Burd; Robert W. Brodersen

1998-01-01

53

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

2012-01-01

54

Nonlinear current-voltage behavior and giant positive magnetoresistance in nonmagnetic Au/Yttria-stabilized zirconia/Si heterostructures  

NASA Astrophysics Data System (ADS)

We report on the nonlinear current-voltage (I-V) behavior and giant positive magnetoresistance (GPMR) in the Au/Yttria-stabilized zirconia/Si heterostructures. The I-V curves of the heterostructures show a rectifying property and follow the Fowler-Nordheim tunneling behavior for the larger forward bias voltages. The GPMR of the samples increases with decreasing temperature and exceeds 100 000% in a magnetic field of 7 T at 20 K with a voltage of +4 V. It also shows anisotropy with magnetoresistance for the magnetic field perpendicular to the current larger than that of the parallel case. A possible mechanism was proposed to account for the results.

Qu, T. L.; Li, J.; Zhao, Y. G.; Mei, J. W.; Liu, X.; Tian, H. F.; Shi, J. P.; Guo, S. M.; Li, J.; Zheng, D. N.; Li, J. Q.

2009-12-01

55

Application of Static VAr Compensator in Entergy System to address Voltage Stability Issues - Planning and Design Considerations  

Microsoft Academic Search

Entergy is in the process of installing SVCs at two of its major load centers. Extensive voltage stability assessment was performed to understand any operational problems and to determine the most efficient size and location of the SVCs. This paper presents planning and design aspects of one of the installations. As part of the planning consideration - problem, alternative solutions

Venkat S. Kolluri; S. Mandal; S. Datta; R. D. Powell; D. Mader; M. Claus; H. Spachtholz

2006-01-01

56

Improved control of field current heating for voltage stability machine design-PowerformerTM  

Microsoft Academic Search

The risk for voltage collapse requires that the system operator use available reactive resources in the receiving area to maintain the voltage level. There is hence a need to boost the reactive generation from synchronous machines. ABB has developed a new class of synchronous machines, PowerformerTM, which are able to deliver electric power directly at transmission voltage levels. The first

Sture Lindahl

2001-01-01

57

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...

58

Membrane bending is critical for the stability of voltage sensor segments in the membrane  

PubMed Central

The interaction between membrane proteins and the surrounding membrane is becoming increasingly appreciated for its role in regulating protein function, protein localization, and membrane morphology. In particular, recent studies have suggested that membrane deformation is needed to stably accommodate proteins harboring charged amino acids in their transmembrane (TM) region, as it is energetically prohibitive to bury charge in the hydrophobic core of the bilayer. Unfortunately, current computational methods are poorly equipped for describing such deformations, as atomistic simulations are often too short to observe large-scale membrane reorganization and most continuum approaches assume a flat membrane. Previously, we developed a method that overcomes these shortcomings by using elasticity theory to characterize equilibrium membrane distortions in the presence of a TM protein, while using traditional continuum electrostatic and nonpolar energy models to determine the energy of the protein in the membrane. Here, we linked the elastostatics, electrostatics, and nonpolar numeric solvers to permit the calculation of energies for nontrivial membrane deformations. We then coupled this procedure to a robust search algorithm that identifies optimal membrane shapes for a TM protein of arbitrary chemical composition. This advance now permits us to explore a host of biological phenomena that were beyond the scope of our original method. We show that the energy required to embed charged residues in the membrane can be highly nonadditive, and our model provides a simple mechanical explanation for this nonadditivity. Our results also predict that isolated voltage sensor segments do not insert into rigid membranes, but membrane bending dramatically stabilizes these proteins in the bilayer despite their high charge content. Additionally, we use the model to explore hydrophobic mismatch with regard to nonpolar peptides and mechanosensitive channels. Our method is in quantitative agreement with molecular dynamics simulations at a tiny fraction of the computational cost. PMID:22732310

Callenberg, Keith M.; Latorraca, Naomi R.

2012-01-01

59

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

60

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

61

Realizing Low Power FPGAs: A Design Partitioning Algorithm for Voltage Scaling and A Comparative Evaluation of Voltage Scaling Techniques for FPGAs  

E-print Network

voltage island topologies and a detailed evaluation of each fabric in terms of overheads due reliability due to excessive heat generation (due to high power) is a concern, power improvement in FPGAs in turn may affect throughput) by changing the supply and threshold voltages. In ASICs it has been shown

Kuzmanovic, Aleksandar

62

Evaluation of optimal voltage-sensitive dyes for optical monitoring of embryonic neural activity  

Microsoft Academic Search

To evaluate the suitability of a variety of fast voltage-sensitive dyes for optical recording of rapid transmembrane potential activity in the embryonic nervous system, we screened over twenty dyes, including several newly synthesized probes, in three different embryonic neural preparations: cervical vagus nerve bundle, nodose ganglion, and brainstem from 7-day old chick embryos. Measurements of voltage-related optical signals were made

Y. Momose-Sato; K. Sato; T. Sakai; A. Hirota; K. Matsutani; K. Kamino

1995-01-01

63

Shipboard Operational Evaluation of Carrier Landing Aid Stabilization System.  

National Technical Information Service (NTIS)

A prototype Carrier Landing Aid Stabilization System (CLASS) has undergone two shipboard operational evaluations. CLASS operation was compared to the current FLOLS MK6 Mod 1 Stabilization system. Review of the test data reveals CLASS provides significantl...

W. F. Davis

1971-01-01

64

Reactive power management of distribution networks with wind generation for improving voltage stability  

E-print Network

takes into account the induction motor dynamic characteristics which influence the transient voltage were generally not designed to connect power generation facilities. DG integration in these passive, furnaces, etc. The exact composition of a load is difficult to estimate as the load magnitude

Pota, Himanshu Roy

65

Study on the Static Stability of a High Voltage Cable-Wound Generator  

Microsoft Academic Search

High voltage cable-wound generator Powerformer is a new kind generator, which can be connected to the power grid directly. In this paper, the expressions of power characteristics with excitation regulator and power limit of Powerformer are deduced. Combining with the parameters of Powerformer prototype and conventional synchronous generator, the power characteristics variation of Powerformer are obtained considering the effect of

Ge Baojun; Tao Dajun; Zhang Zhiqiang; Lv Yanling

2009-01-01

66

Static bifurcations in electric power networks: Loss of steady-state stability and voltage collapse  

Microsoft Academic Search

This paper presents an analysis of static stability in electric power systems. The study is based on a model consisting of the classical swing equation characterization for generators and constant admittance, PV bus and\\/or PQ bus load representations which, in general, leads to a semi-explicit (or constrained) system of differential equations. A precise definition of static stability is given and

HARRY G. KWATNY; ARUN K. PASRIJA; LEON Y. BAHAR

1986-01-01

67

Evaluation of stability threshold analysis as a cursory method of screening potential streambank stabilization techniques  

Microsoft Academic Search

A water quality issue that is of particular concern in human-modified streams is sediment pollution. In-stream areas of sediment production have been targeted and managed using stream channelization and, more recently, biotechnical streambank stabilization. The objective of this study was to evaluate the use of stability threshold analysis as a cursory method to develop a range of potential streambank stabilization

Kelly M. Frothingham

2008-01-01

68

Evaluation of high temperature dielectric films for high voltage power electronic applications  

NASA Technical Reports Server (NTRS)

Three high temperature films, polyimide, Teflon perfluoroalkoxy and poly-P-xylene, were evaluated for possible use in high voltage power electronic applications, such as in high energy density capacitors, cables and microelectronic circuits. The dielectric properties, including permittivity and dielectric loss, were obtained in the frequency range of 50 Hz to 100 kHz at temperatures up to 200 C. The dielectric strengths at 60 Hz were determined as a function of temperature to 250 C. Confocal laser microscopy was performed to diagnose for voids and microimperfections within the film structure. The results obtained indicate that all films evaluated are capable of maintaining their high voltage properties, with minimal degradation, at temperatures up to 200 C. However, above 200 C, they lose some of their electrical properties. These films may therefore become viable candidates for high voltage power electronic applications at high temperatures.

Suthar, J. L.; Laghari, J. R.

1992-01-01

69

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. PMID:10435999

Kanevsky, Max; Aldrich, Richard W.

1999-01-01

70

A novel mechanism for fine-tuning open-state stability in a voltage-gated potassium channel  

PubMed Central

Voltage-gated potassium channels elicit membrane hyperpolarization through voltage-sensor domains that regulate the conductive status of the pore domain. To better understand the inherent basis for the open-closed equilibrium in these channels, we undertook an atomistic scan using synthetic fluorinated derivatives of aromatic residues previously implicated in the gating of Shaker potassium channels. Here we show that stepwise dispersion of the negative electrostatic surface potential of only one site, Phe481, stabilizes the channel open state. Furthermore, these data suggest that this apparent stabilization is the consequence of the amelioration of an inherently repulsive open-state interaction between the partial negative charge on the face of Phe481 and a highly co-evolved acidic side chain, Glu395, and this interaction is potentially modulated through the Tyr485 hydroxyl. We propose that the intrinsic open-state destabilization via aromatic repulsion represents a new mechanism by which ion channels, and likely other proteins, fine-tune conformational equilibria. PMID:23653196

Pless, Stephan A.; Niciforovic, Ana P.; Galpin, Jason D.; Nunez, John-Jose; Kurata, Harley T.; Ahern, Christopher A.

2013-01-01

71

Power losses evaluation of three multilevel converter topologies for direct interface with medium voltage grids  

Microsoft Academic Search

Acknowledgementsproject this report is based on was funded by E.ON as part of the E.ON International Research Initiative. Responsibility for the content of this publication lies with the author. Abstract paper presents the power losses evaluation and comparison of three different Mega Watt MW scale multilevel converter topologies proposed for interfacing energy storage systems to medium voltage grids using Medium

Mohamed Rashed; Christian Klumpner; Greg Asher

2011-01-01

72

Enhancement of Transient Stability Limit and Voltage Regulation with Dynamic Loads Using Robust Excitation Control  

NASA Astrophysics Data System (ADS)

In stressed power systems with large induction machine component, there exist undamped electromechanical modes and unstable monotonic voltage modes. This article proposes a sequential design of an excitation controller and a power system stabiliser (PSS) to stabilise the system. The operating region, with induction machines in stressed power systems, is often not captured using a linearisation around an operating point, and to alleviate this situation a robust controller is designed which guarantees stable operation in a large region of operation. A minimax linear quadratic Gaussian design is used for the design of the supplementary control to automatic voltage regulators, and a classical PSS structure is used to damp electromechanical oscillations. The novelty of this work is in proposing a method to capture the unmodelled nonlinear dynamics as uncertainty in the design of the robust controller. Tight bounds on the uncertainty are obtained using this method which enables high-performance controllers. An IEEE benchmark test system has been used to demonstrate the performance of the designed controller.

Hossain, Jahangir; Mahmud, Apel; Roy, Naruttam K.; Pota, Hemanshu R.

2013-10-01

73

The stability and pull-in voltage of electrostatic parallel-plate actuators in liquid solutions  

Microsoft Academic Search

This paper deals with parallel-plate electrostatic actuators in liquids. We study the stability conditions of such actuators and show that the pull-in effect can be shifted beyond one-third of the gap, and can even be suppressed. We demonstrate that the insulating layers of the actuator plates, which are originally designed to avoid any current leakages or short-circuits, play a major

A.-S. Rollier; B. Legrand; D. Collard; L. Buchaillot

2006-01-01

74

Low-voltage, high-mobility organic thin-film transistors with improved stability  

Microsoft Academic Search

This paper discusses organic thin-film transistors. Due to the performance degradation of pentacene based devices, this paper proposes a six-ring fused heteroarene, dinaphtho-[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT), which has a crystal structure and thin-film morphology similar to those of pentacene, but less susceptible to oxidation. This paper reports on the static and dynamic performance and on the stability of DNTT TFTs on flexible

U. Zschieschang; T. Yamamoto; K. Takimiya; H. Kuwabara; M. Ikeda; T. Sekitani; T. Someya; H. Klauk

2010-01-01

75

Sitting on stability balls: biomechanics evaluation in a workplace setting.  

PubMed

Use of a stability ball alone and stability ball chair were evaluated in the Veterans Health Administration as possible alternatives to incorporate with regular office chair use. The evaluation of stability ball use was conducted under the auspices of a work site health promotion program as a cross-over trial with participants rotating through use of the stability ball, stability ball chair, and regular office chair on a monthly basis for a total duration of 3 months. Rotations on regular office chairs served as the control. Three medical facilities participated. A total of 193 employees completed a baseline questionnaire; 159 completed at least one post-rotation questionnaire. Self-reported measures included perceived posture when sitting, perceptions of overall balance, energy levels, job performance, safety, and pain. Use was associated with improvements in perceived posture (p < 0.0001) and energy levels (p = 0.007) for stability ball users compared with the office chair control, and improvements in perceived posture (p < 0.0001) and overall balance (p = 0.05) for stability ball chair users compared with the control. Use of stability balls at work decreases the likelihood of reporting pain from regular office chair use from approximately 45% to 21%. Alternatively, a high number of participants reported pain with use of the stability ball alone and stability ball chair, 42% and 45%, respectively. The perceived risks and benefits of stability ball use should be weighed when incorporating use. PMID:23252582

Schult, Tamara M; Awosika, Ebi R; Schmunk, Sandra K; Hodgson, Michael J; Heymach, Bria L; Parker, Celestine Dent

2013-01-01

76

Contingency screening method for voltage stability analysis in the assessment of available transfer capability in deregulated power systems  

NASA Astrophysics Data System (ADS)

The electric utility industry is going through the phase of restructuring towards evolving into a competitive market. In order to facilitate that transformation, the access to the transmission network is provided on a non discriminatory basis, which is limited only by the capability of the network to transfer power. Available Transfer Capability (ATC) has become the standard tool to compute the transfer capability remaining in the network over and above already committed use. The calculation of ATC involves network limitations due to thermal and voltage stability limits. Network limitations are to be calculated not only for the current operating condition but also for a worse case that could occur due to a set of contingency cases, which require huge amount of computation. This puts constraint on ATC to be an effective tool in real time operating environment. The aim of this dissertation is to study the computational efforts involved in the computation of ATC and propose a method to minimize the computation involved in the assessment of ATC due to the voltage stability limit. The proposed method performs ranking of the contingencies using a severity index based on the incremental reactive power losses between the base case and the contingency case. Based on the ranking, a short list of contingencies is to be selected for full simulation. Since the impact of the contingencies is not known until the power flow equations are solved, the convergence of the contingency cases is not known a priori. For the purpose of identifying the base case load level for contingency screening, couple of measures of convergence of contingency cases at each load level on the base case curve are proposed, one for large correction errors and the other for divergence behavior due to load increase. The proposed method is validated with simulations on practical large power systems.

Sundhararajan, Srinivasan

2001-07-01

77

Evaluation system for camera shake and image stabilizers  

Microsoft Academic Search

Various optical image stabilizers for reducing camera shake have been developed in many camera manufacturers, however, it has not been known exactly how effective they work for cancellation of the camera shake. We developed a novel system for analyzing behavior of camera shake and evaluating effectiveness of image stabilizers quantitatively. It consists of the custom-made LED display for generating a

Kazuki Nishi; Tsubasa Onda

2010-01-01

78

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

NASA Technical Reports Server (NTRS)

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 buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV/m.

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

2012-01-01

79

Evaluation of SRAM-Core Susceptibility against Power Supply Voltage Variation  

NASA Astrophysics Data System (ADS)

The susceptibility of a static random access memory (SRAM) core against static and dynamic variation of power supply voltage is evaluated, by using on-chip diagnosis structures of memory built-in self testing (MBIST) and on-chip voltage waveform monitoring (OCM). The SRAM core of interest in this paper is a synthesizable version applicable to general systems-on-a-chip (SoC) design, and fabricated in a 90nm CMOS technology. RF power injection to power supply networks is quantified by OCM. The number of resultant erroneous bits as well as their distribution in the cell array is given by MBIST. The frequency-dependent sensitivity reflects the highly capacitive nature of densely integrated SRAM cells.

Sawada, Takuya; Toshikawa, Taku; Yoshikawa, Kumpei; Takata, Hidehiro; Nii, Koji; Nagata, Makoto

80

Design and evaluation of a preprototype hybrid fiber-optic voltage sensor for a remotely interrogated condition monitoring system  

Microsoft Academic Search

In this paper, we give details of the design and laboratory evaluation of the preprototype hybrid fiber Bragg grating piezoelectric voltage sensor for a remotely interrogated condition monitoring system, such as the measurement system used for monitoring of electrical submersible pump (ESP) motors. The proposed sensor design is directed toward the upper voltage rating (5 kV) of ESP motors.

Pawel Niewczas; Lukasz Dziuda; Grzegorz Fusiek; James R. McDonald

2005-01-01

81

Oxidative stability and sensory evaluation of microencapsulated flaxseed oil.  

PubMed

Cold pressed flaxseed oil was microencapsulated by spray drying using an emulsion containing modified starch. The fatty acid composition, moisture, water activity, wettability, water holding capacity, water solubility, crystallinity, and particle size distribution of the microcapsules were determined. The stability of the microcapsules and the crude oil were assessed. An acceptance test was used for the sensory evaluation of a powdered supplement containing the microcapsules. The fatty acid composition was not significantly affected by the microencapsulation. The moisture, water activity, wettability, water solubility and crystallinity were appropriate for dry powders. The microcapsules had no cracks and showed better oxidative stability compared with the crude oil. Storage under vacuum prevented oxidation of the microcapsules. In sensory evaluation, all quality scores of the supplement containing microcapsules were mid-range or higher. The microencapsulation improved the oxidative stability of the oil and this procedure was satisfactorily applied in powdered food. PMID:23962202

Barroso, Ana Karina Mauro; Pierucci, Anna Paola Trindade Rocha; Freitas, Suely Pereira; Torres, Alexandre Guedes; Rocha-Leão, Maria Helena Miguez da

2014-01-01

82

Evaluation of higher distribution and/or utilization voltages. First interim report (December 1978): literature search and problem definition  

SciTech Connect

A literature search has been conducted on the economics and technical problems associated with the use of higher voltages in both the primary distribution and secondary utilization systems. After a literature review and evaluation, an assessment of the state-of-the-art with regard to high voltage has been made and is presented for the primary and secondary distribution systems, end use elements, and economics and system analysis or optimization. An annotated bibliography is provided for each of the three categories. A comprehensive list of potential advantages and disadvantages of higher primary distribution and utilization voltages has also been prepared and is presented.

Not Available

1981-04-01

83

Age-Related Differences in Evaluating Developmental Stability  

ERIC Educational Resources Information Center

Two studies examined the hypothesis that the evaluation of developmental stability changes across adulthood. Results of Study 1 ("N" = 119) supported the expectation that older adults ("M"[subscript age] = 65.29 years)--compared to younger ("M"[subscript age] = 23.38 years) and middle-aged adults…

Mustafic, Maida; Freund, Alexandra M.

2013-01-01

84

Improving voltage stability of power systems by appropriate applications of Reactive Current Droop Compensation and Line Drop Compensation schemes  

Microsoft Academic Search

Voltage collapse is one of the most importance reasons leading to the catastrophic failure of power systems. Therefore, many attentions are paid to this research field in recent years. In this paper, The method to mitigate system voltage depressions is studied, which is implemented by combining Reactive Current droop Compensation scheme and Line Drop Compensation scheme. Based on a widely

Shuangping Zhang; Qing Tian; Xiangning Lin; Zhiqian Bo

2010-01-01

85

Evaluation of slope stability with respect to snowpack spatial variability  

NASA Astrophysics Data System (ADS)

The evaluation of avalanche release conditions constitutes a great challenge for risk assessment in mountainous areas. The spatial variability of snowpack properties has an important impact on snow slope stability and thus on avalanche formation, since it strongly influences failure initiation and crack propagation in weak snow layers. Hence, the determination of the link between these spatial variations and slope stability is very important, in particular, for avalanche public forecasting. In this study, a statistical-mechanical model of the slab-weak layer (WL) system relying on stochastic finite element simulations is used to investigate snowpack stability and avalanche release probability for spontaneously releasing avalanches. This model accounts, in particular, for the spatial variations of WL shear strength and stress redistribution by elasticity of the slab. We show how avalanche release probability can be computed from release depth distributions, which allows us to study the influence of WL spatial variations and slab properties on slope stability. The importance of smoothing effects by slab elasticity is verified and the crucial impact of spatial variation characteristics on the so-called knock-down effect on slope stability is revisited using this model. Finally, critical length values are computed from the simulations as a function of the various model parameters and are compared to field data obtained with propagation saw tests.

Gaume, J.; Schweizer, J.; Herwijnen, A.; Chambon, G.; Reuter, B.; Eckert, N.; Naaim, M.

2014-09-01

86

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

87

Stability evaluation of inference methods for optoelectronic fuzzy inference system  

NASA Astrophysics Data System (ADS)

System stability of various membership functions and fuzzy control methods are compared by numerical simulations to determine the feasibility of optoelectronic fuzzy inference method. An inverted pendulum is used for the destination system. A Gaussian membership function is better than a triangular one. MIN operations of grade evaluation and modification of consequent membership functions are better than other operations. SUM operation of consequent operation is better than MAX operation.

Itoh, Hideo; Yamada, Tatsuya; Houssay, Bruno; Mukal, Seiji; Uekusa, Shin-ichiro

1994-01-01

88

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

89

Epitaxial growth and capacitance-voltage characteristics of BiFeO3/CeO2/yttria-stabilized zirconia/Si(001) heterostructure  

NASA Astrophysics Data System (ADS)

We report the epitaxial growth of multiferroic BiFeO3 (BFO) film on Si(001) substrate by pulsed laser deposition using CeO2/yttria-stabilized zirconia (YSZ) as buffer layers. The epitaxial relationships of the films were BFO(001)/CeO2(001)/YSZ(001)/Si(001) for out-of-plane and [110]BFO?[100]CeO2?[100]YSZ?[100]Si for in-plane, respectively. Capacitance-voltage characteristics of a Pt/BFO/CeO2/YSZ/p-Si capacitor exhibited clockwise hysteresis loops with a large memory window of 2.5 V at sweeping voltages of ±16 V. Both the high and low capacitance values showed no obvious degradation after 104 s. The improved retention property was attributed to the use of high-k CeO2/YSZ insulating layers that effectively eliminated the charge trapping in the heterostructure.

Hu, Zhongqiang; Li, Meiya; Zhu, Yongdan; Pu, Shizhou; Liu, Xiaolian; Sebo, Bobby; Zhao, Xingzhong; Dong, Shuxiang

2012-06-01

90

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

91

Evaluating the electro-optical effect in alternating current-voltage-modulated Kerr response for multiferroic heterostructures  

NASA Astrophysics Data System (ADS)

Voltage-modified Kerr magnetometer has been widely used to measure the voltage-modulated magnetic properties in multiferroic magnetic/ferroelectric heterostructures, where the Kerr signal change is considered to be in proportion to magnetization change, i.e., the magneto-optical Kerr effect. However, the total Kerr signal changes might also incorporate contribution from the electro-optical effect of the ferroelectric layer in the multiferroic heterostructure. Here, we evaluate quantitatively, by combining analytical calculations with experimental observations, such electro-optical contribution in the total voltage-induced Kerr signal changes with comparison to those from Kerr effect via converse magnetoelectric coupling. Influences of several parameters, including the magnetic film thickness on the Kerr signal changes, are also investigated.

Shu, Li; Gao, Ya; Hu, Jia-Mian; Li, Zheng; Shen, Yang; Lin, Yuanhua; Nan, C. W.

2013-11-01

92

Rapid evaluation of a protein-based voltage probe using a field-induced membrane potential change.  

PubMed

The development of a high performance protein probe for the measurement of membrane potential will allow elucidation of spatiotemporal regulation of electrical signals within a network of excitable cells. Engineering such a probe requires a functional screen of many candidates. Although the glass-microelectrode technique generally provides an accurate measure of a given test probe, throughputs are limited. In this study, we focused on an approach that uses the membrane potential changes induced by an external electric field in a geometrically simple mammalian cell. For quantitative evaluation of membrane voltage probes that rely on the structural transition of the S1-S4 voltage sensor domain and hence have non-linear voltage dependencies, it was crucial to introduce exogenous inwardly rectifying potassium conductance to reduce cell-to-cell variability in resting membrane potentials. Importantly, the addition of the exogenous conductance drastically altered the profile of the field-induced potential. Following a site-directed random mutagenesis and the rapid screen, we identified a mutant of a voltage probe Mermaid, exhibiting positively shifted voltage sensitivity. Due to its simplicity, the current approach will be applicable under a microfluidic configuration to carry out an efficient screen. Additionally, we demonstrate another interesting aspect of the field-induced optical signals, ability to visualize electrical couplings between cells. PMID:24642225

Tsutsui, Hidekazu; Jinno, Yuka; Tomita, Akiko; Okamura, Yasushi

2014-07-01

93

Multi-objective Optimal Power Flows to Evaluate Voltage Security Costs in Power Networks  

E-print Network

of the network, the incorporation of voltage collapse criteria and tools in the operation of power systems optimization methods to determine optimal control parameters that maximize load mar- gins and thus avoid

Cañizares, Claudio A.

94

DC biased electro-optic polymer waveguide modulators with low half-wave voltage and high thermal stability  

Microsoft Academic Search

The full potential of second-order nonlinear polymers can be utilized in electro-optic polymer modulators with a DC biased operation scheme to greatly reduce the half-wave voltage. This technique makes use of the total achievable electro-optic coefficient, which can be more than three times the value that is used by the conventional devices of poled electro-optic polymer. As the result of

Antao Chen; Vadim Chuyanov; Hua Zhang; Sean M. Garner; Sang-Shin Lee; William H. Steier; Jinghong Chen; Fang Wang; Jingsong Zhu; Mingqian He; Younsoo Ra; Shane S. H. Mao; Aaron W. Harper; Larry R. Dalton; Harold R. Fetterman

1999-01-01

95

Evaluation of time stability indices for soil water storage upscaling  

NASA Astrophysics Data System (ADS)

SummaryTime stability index (TSI) is usually used to evaluate time stability of soil water storage (SWS) at point scales for SWS upscaling. The objective of this study was to evaluate seven TSIs for estimating mean SWS. Included were six indices used for indirect estimation (i.e., standard deviation of relative difference (SDRD), mean absolute bias error (MABE), width of the 90% empirical tolerance interval of relative water content (T), chi-squared statistic (?2), root-mean-squared differences (D), and temporal coefficient of variability (CVt)); and one index used for direct estimation (i.e., root mean square error (RMSE)). Five goodness-of-fit indices (GFIs), including root mean squared deviations (RMSD), Nash-Sutcliffe coefficient of efficiency (NSCE), coefficient of determination (R2), absolute mean difference (BIAS), and relative bias error (RBIAS) were selected for evaluating mean SWS estimation quality in both calibration and validation periods. The minimum number of sampling occasions needed to identify the most time-stable location was identified considering different starting dates of sampling. Evaluation of the TSIs was performed using SWS data of 0-1.0 m layer obtaining from the Canadian Prairie landscape and the Chinese Loess Plateau. The results showed that MABE, ?2, D, and CVt outperformed SDRD and T irrespective of the GFI used. If RMSD and NSCE were used, D was the best TSI. If BIAS and RBIAS were adopted, MABE was the best TSI. Mean SWS estimation by the indirect method was more accurate than that by the direct method. For both study areas, the minimum number of sampling occasions needed to identify the most time-stable location varied with starting dates of SWS measurement, and generally five to seven sampling occasions was needed to identify the most time-stable location with D and MABE.

Hu, Wei; Tallon, Lindsay K.; Si, Bing Cheng

2012-12-01

96

Robust Voltage Stabilization in an Isolated Wind-Diesel Power System using PSO based-Fixed Structure H? Loop Shaping Control  

NASA Astrophysics Data System (ADS)

It is well known that the power system controller designed by H? control is complicated, high order and impractical. In power system applications, practical structures such as proportional integral derivative (PID) etc., are widely used, because of their simple structure, less number of tuning parameters and low-order. However, tuning of controller parameters to achieve a good performance and robustness is based on designer's experiences. To overcome this problem, this paper proposes a fixed structure robust H? loop shaping control to design Static Var Compensator (SVC) and Automatic Voltage Regulator (AVR) for robust stabilization of voltage fluctuation in an isolated wind-diesel hybrid power system. The structure of the robust controller of SVC and AVR is specified by a PID controller. In the system modeling, a normalized coprime factorization is applied to represent possible unstructured uncertainties in the power system such as variation of system parameters, generating and loading conditions etc. Based on the H? loop shaping, the performance and robust stability conditions are formulated as the optimization problem. The particle swarm optimization is applied to solve for PID control parameters of SVC and AVR simultaneously. Simulation studies confirm the control effect and robustness of the proposed control.

Vachirasricirikul, Sitthidet; Ngamroo, Issarachai; Kaitwanidvilai, Somyot

97

Optical voltage reference  

SciTech Connect

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

98

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

99

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, Richard (Ammon, ID); Kotter, Dale (Bingham County, ID)

1994-01-01

100

Thin Film Transistors with High Mobility and High Threshold Voltage Stability Made Using Hot Wire Chemical Vapor Deposition  

Microsoft Academic Search

Although thin film transistors (TFT) are routinely made for commercial applications by plasma deposition, there is a need for TFTs with higher electron mobility as well as excellent stability. In this paper it is shown that hot-wire chemical vapor deposition (CVD) (Cat-CVD) can address those needs, while at the same time offering higher deposition rates and better source gas utilization.

Ruud E. I. Schropp

2006-01-01

101

Analysis and evaluation of near field noise voltage on power electronics circuits  

Microsoft Academic Search

Design procedure for power electronics circuit structures has recently been discussed for high power density circuits or thin structure converters. Then the control circuit may be connected close to the power circuit. When a pulse current flows into the power circuit, it radiates a magnetic field and it may produce a near field noise voltage in the control circuit and

Zen-nosuke Ariga; Keiji Wada

2009-01-01

102

A high-stability scanning tunneling microscope achieved by an isolated tiny scanner with low voltage imaging capability  

NASA Astrophysics Data System (ADS)

We present a novel homebuilt scanning tunneling microscope (STM) with high quality atomic resolution. It is equipped with a small but powerful GeckoDrive piezoelectric motor which drives a miniature and detachable scanning part to implement coarse approach. The scanning part is a tiny piezoelectric tube scanner (industry type: PZT-8, whose d31 coefficient is one of the lowest) housed in a slightly bigger polished sapphire tube, which is riding on and spring clamped against the knife edges of a tungsten slot. The STM so constructed shows low back-lashing and drifting and high repeatability and immunity to external vibrations. These are confirmed by its low imaging voltages, low distortions in the spiral scanned images, and high atomic resolution quality even when the STM is placed on the ground of the fifth floor without any external or internal vibration isolation devices.

Wang, Qi; Hou, Yubin; Wang, Junting; Lu, Qingyou

2013-11-01

103

A high-stability scanning tunneling microscope achieved by an isolated tiny scanner with low voltage imaging capability  

SciTech Connect

We present a novel homebuilt scanning tunneling microscope (STM) with high quality atomic resolution. It is equipped with a small but powerful GeckoDrive piezoelectric motor which drives a miniature and detachable scanning part to implement coarse approach. The scanning part is a tiny piezoelectric tube scanner (industry type: PZT-8, whose d{sub 31} coefficient is one of the lowest) housed in a slightly bigger polished sapphire tube, which is riding on and spring clamped against the knife edges of a tungsten slot. The STM so constructed shows low back-lashing and drifting and high repeatability and immunity to external vibrations. These are confirmed by its low imaging voltages, low distortions in the spiral scanned images, and high atomic resolution quality even when the STM is placed on the ground of the fifth floor without any external or internal vibration isolation devices.

Wang, Qi; Wang, Junting; Lu, Qingyou, E-mail: qxl@ustc.edu.cn [High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui 230026 (China) [High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui 230026 (China); Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Hou, Yubin [High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui 230026 (China)] [High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui 230026 (China)

2013-11-15

104

Evaluating Stability and Change in Personality and Depression  

Microsoft Academic Search

Critics have argued that personality factors believed to represent a vulnerability to depression are not stable and are therefore state dependent. However, conclusions regarding the stability of personality and the relation between personality and depression have been drawn (a) without differentiating relative stability among individual differences from absolute stability of change scores and (b) without explicitly modeling change in personality

Darcy A. Santor; R. Michael Bagby; Russell T. Joffe

1997-01-01

105

CT x-ray tube voltage optimisation and image reconstruction evaluation using visual grading analysis  

NASA Astrophysics Data System (ADS)

The purposes of this work were to find an optimal x-ray voltage for CT imaging and to determine the diagnostic effectiveness of image reconstruction techniques by using the visual grading analysis (VGA). Images of the PH-5 CT abdomen phantom (Kagaku Co, Kyoto) were acquired by the Toshiba Aquillion One 320 slices CT system with various exposures (from 10 to 580 mAs) under different tube peak voltages (80, 100 and 120 kVp). The images were reconstructed by employing the FBP and the AIDR 3D iterative reconstructions with Mild, Standard and Strong FBP blending. Image quality was assessed by measuring noise, contrast to noise ratio and human observer's VGA scores. The CT dose index CTDIv was obtained from the values displayed on the images. The best fit for the curves of the image quality VGA vs dose CTDIv is a logistic function from the SPSS estimation. A threshold dose Dt is defined as the CTDIv at the just acceptable for diagnostic image quality and a figure of merit (FOM) is defined as the slope of the standardised logistic function. The Dt and FOM were found to be 5.4, 8.1 and 9.1 mGy and 0.47, 0.51 and 0.38 under the tube voltages of 80, 100 and 120 kVp, respectively, from images reconstructed by the FBP technique. The Dt and FOM values were lower from the images reconstructed by the AIDR 3D in comparison with the FBP technique. The optimal xray peak voltage for the imaging of the PH-5 abdomen phantom by the Aquillion One CT system was found to be at 100 kVp. The images reconstructed by the FBP are more diagnostically effective than that by the AIDR 3D but with a higher dose Dt to the patients.

Zheng, Xiaoming; Kim, Ted M.; Davidson, Rob; Lee, Seongju; Shin, Cheongil; Yang, Sook

2014-03-01

106

Design and evaluation of a pre-prototype hybrid fiber-optic voltage sensor for a remotely interrogated condition monitoring system  

Microsoft Academic Search

In this paper we give details of the design and laboratory evaluation of the pre-prototype hybrid fiber Bragg grating piezoelectric voltage sensor for a remotely interrogated condition monitoring system, such as the measurement system used for monitoring of electrical submersible pump (ESP) motors. The proposed sensor design is directed towards the upper voltage rating (5 kV) of ESP motors.

P. Niewczas; L. Dzitida; G. Fusiek; J. R. McDonald

2004-01-01

107

Evaluation of voltage-sensitive fluorescence dyes for monitoring neuronal activity in the embryonic central nervous system  

PubMed Central

Using an optical imaging technique with voltage-sensitive dyes (VSDs), we have been investigating the functional organization and architecture of the central nervous system (CNS) during embryogenesis. In the embryonic nervous system, a merocyanine-rhodanine dye, NK2761, has proved to be the most useful absorption dye for detecting neuronal activity because of its high signal-to-noise ratio (S/N), low toxicity, and small dye bleaching. In the present study, we evaluated the suitability of voltage-sensitive fluorescence dyes for optical recording in the embryonic CNS. We screened eight styryl (hemicyanine) dyes in isolated brainstem-spinal cord preparations from 7-day old chick embryos. Measurements of voltage-related optical signals were made using a multiple-site optical recording system. The signal size, S/N, photobleaching, effects of perfusion, and recovery of neural responses after staining were compared. We also evaluated optical responses with various magnifications. Although the S/N was lower than with the absorption dye, clear optical responses were detected with several fluorescence dyes, including di-2-ANEPEQ, di-4-ANEPPS, di-3-ANEPPDHQ, di-4-AN(F)EPPTEA, di-2-AN(F)EPPTEA, and di-2-ANEPPTEA. Di-2-ANEPEQ showed the largest S/N, whereas its photobleaching was faster and the recovery of neural responses after staining was slower. Di-4-ANEPPS and di-3-ANEPPDHQ also exhibited a large S/N, but required a relatively long time for recovery of neural activity. Di-4-AN(F)EPPTEA, di-2-AN(F)EPPTEA, and di-2-ANEPPTEA showed smaller S/Ns than di-2-ANEPEQ, di-4-ANEPPS, and di-3-ANEPPDHQ, but the recovery of neural responses after staining was faster. This study demonstrates the potential utility of these styryl dyes in optical monitoring of voltage changes in the embryonic CNS. PMID:23975337

Mullah, Saad Habib-E-Rasul; Komuro, Ryo; Yan, Ping; Hayashi, Shihori; Inaji, Motoki; Momose-Sato, Yoko; Loew, Leslie M.; Sato, Katsushige

2014-01-01

108

Disulfide stabilization of antibody Fv: computer predictions and experimental evaluation.  

PubMed

Using molecular modeling technology we have recently identified positions in conserved framework regions of Fvs which can be used to stabilize antibody Fvs by an interchain disulfide bond engineered in between the structurally conserved framework positions of the variable domains of heavy (VH) and light (VL) immunoglobulin chains (disulfide-stabilized Fv; dsFv). The computer model indicated the existence of other potential sites in the framework regions that might be suitable for disulfide bond formation between VH and VL. The possibility of obtaining dsFvs using these positions is evaluated here experimentally by constructing dsFv immunotoxins in which the Fv moiety is fused to a truncated form of Pseudomonas exotoxin. We analyzed the extent of dsFv formation and the activity of the resulting dsFv immunotoxins, and compared various dsFv molecules with the scFv immunotoxin. Our results demonstrate that position H44-L105 is the only one which gives high production yields of active dsFv. All other positions gave either low yields and activity or completely failed to produce active dsFv. With one exception, the formation and activities of the dsFvs corresponded to the C alpha-C alpha distance between the VH and VL positions, with an optimal distance of 5.7 A producing the best dsFv. Distances of 6.0-6.9 A resulted in a low yield of protein that was still capable of binding antigen, whereas distances > 7.0 A resulted in molecules in which dsFv formation was not obtained. PMID:8869646

Reiter, Y; Brinkmann, U; Jung, S H; Pastan, I; Lee, B

1995-12-01

109

Electrodynamic stabilization conditions for high-temperature superconducting composites with different types of current-voltage characteristic nonlinearity  

NASA Astrophysics Data System (ADS)

The current instability is studied in high-temperature superconducting current-carrying elements with I- V characteristics described by power or exponential equations. Stability analysis of the macroscopic states is carried out in terms of a stationary zero-dimensional model. In linear temperature approximation criteria are derived that allow one to find the maximum allowable values of the induced current, induced electric field intensity, and overheating of the superconductor. A condition is formulated for the complete thermal stabilization of the superconducting composite with regard to the nonlinearity of its I- V characteristic. It is shown that both subcritical and supercritical stable states may arise. In the latter case, the current and electric field intensity are higher than the preset critical parameters of the superconductor. Conditions for these states depending on the properties of the matrix, superconductor's critical current, fill factor, and nonlinearity of the I- V characteristic are discussed. The obtained results considerably augment the class of allowable states for high-temperature superconductors: it is demonstrated that there exist stable resistive conditions from which superconductors cannot pass to the normal state even if the parameters of these conditions are supercritical.

Arkharov, A. M.; Lavrov, N. A.; Romanovskii, V. R.

2014-06-01

110

Thin Film Transistors with High Mobility and High Threshold Voltage Stability Made Using Hot Wire Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

Although thin film transistors (TFT) are routinely made for commercial applications by plasma deposition, there is a need for TFTs with higher electron mobility as well as excellent stability. In this paper it is shown that hot-wire chemical vapor deposition (CVD) (Cat-CVD) can address those needs, while at the same time offering higher deposition rates and better source gas utilization. Thin film transistors with the active layer deposited either from pure SiH4 or from H2-diluted silane show remarkable stability. The field-effect mobility in an inverted staggered configuration for amorphous channel material is 1.5 cm2 V-1 s-1 and in the coplanar, top gate configuration it is 1.3 cm2 V-1 s-1. For ?c-Si:H material in the top gate configuration, the as-deposited, unannealed mobility was ˜5 cm2 V-1 s-1, but recently also higher mobilities have been reported. Hot wire deposited channel layers are compatible with plasma-deposited SiNx layers, but also hot wire CVD SiNx with high density and compactness has been demonstrated. Thus it is feasible to produce all-hot-wire CVD TFTs directly on glass or polyimid.

Schropp, Ruud E. I.

2006-05-01

111

Evaluation, selection and assessment of guidelines for chemical stabilization of tropical residual soils  

Microsoft Academic Search

Soil stabilization has been widely used as an alternative to substitute the lacking of suitable materials on site. Guidelines and standards have been developed to assist practitioners in designing structures such as road by mean of stabilization. This paper presents the results of an investigation aimed at evaluating and assessing the suitable guidelines for the stabilization of tropical residual soils.

Bujang B. K. Huat; Asmidar Alias; Azlan Abdul Aziz

2008-01-01

112

Evaluation of solidification/stabilization for treating explosives contaminated soils  

SciTech Connect

The success of solidification/stabilization (S/S) for treating explosives contaminated soils was evaluated using a variety of physical, chemical, and contaminant release testing methods. The analytes of concern included explosives and their degradation products (TNT, RDX, HMX, 2, 4-Dinitrotoluene, 2,6-dinitrotoluene, 2,4,6-Trinitrotoluene, 2-Amino-4,6-Dinitrotoluene, 4-Amino-2,6-Dinitrobenzene, 2,4-Dinitrotoluene) and PAH`s (Benzo(a)anthracene, Benzo(b)fluoranthene, Benzo(k)fluoranthene, Benzo(a)pyrene, Chrysene, Dibenz(a,h) anthracene, and Ideno (1,2,3-cd)pyrene). All Toxicity Characteristic Leaching Procedure (TCLP) leachate analytes, except 2-Am-4,6-TNT was reduced approximately 97%. The release of 2,4-DNT was also significantly reduced. The results of the Sequential Batch Leach Test (SBLT) were mixed. The PAH compounds were not identified above detectable limits in the leachates from either the untreated soil or the treated soils. Release of 2,4,6-TNT was reduced to undetectable. However, other explosives related compounds (2-Am-4, 6-DNT) were identified in the leachates from the treated soils that were not identified in the untreated soil. Organic transformations in the highly alkaline environment associated with S/S or sample heterogeneity are suspected to cause this phenomena.

Cullinane, M.J. Jr.; Channell, M. [Army Engineer Waterways Experiment Station, Vicksburg, MS (United States)

1996-12-31

113

Seismic hazard evaluation for design and/or verification of a high voltage system  

SciTech Connect

The Venezuelan capital, Caracas, with a population of about 5 million, is within the area of contact of the Caribbean and South American tectonic plates. Since 1567, the valley where it lies and surroundings have been shaken by at leas six destructive events from different seismogenic sources. Electric energy is served to the city by a high voltage system consisting of 4 power stations, 20 substations (230 KV downwards) and 80 km of high voltage lines, covering an area of about 135 x 60 km{sup 2}. Given the variety of soil conditions, topographical irregularities and proximity to potentially active faults, it was decided to perform a seismic hazard study. This paper gives the results of that study synthesized by two hazard-parameter maps, which allow a conservative characterization of the acceleration on firm soils. Specific site coefficients allow for changes in soil conditions and topographical effects. Sites whose proximity to fault lines is less than about 2 km, require additional field studies in order to rule out the possibility of permanent ground displacements.

Grases, J.; Malaver, A. [Ingenieria de Consulta, Caracas (Venezuela); Lopez, S.; Rivero, P. [Electricidad de Caracas (Venezuela)

1995-12-31

114

Evaluation of higher distribution and/or utilization voltages. Fourth interim report (August 1980): assessment of optimum distribution configuration  

SciTech Connect

This interim report provides documentation on the fourth task, Assessment of Optimum Distribution Configuration, of DOE Contract No. ET-78-C-01-2866, Evaluation of Higher Distribution and/or Utilization Voltages. The work performed under this task includes the development of a computer model for assessment of life cycle costs for the distribution and utilization systems, the development of an optimization algorithm to enable distribution system configuration optimization and a net energy analysis to determine potential net energy savings. Input data for this task derive from Task 3. The major output of this task is a documented computer code.

Not Available

1981-04-01

115

Evaluation of Voltage-Sensitive Dyes for Long-Term Recording of Neural Activity in the Hippocampus  

Microsoft Academic Search

.   We searched for an optimal voltage-sensitive dye for optical measurements of neural activity in the hippocampal slice by\\u000a evaluating several merocyanine-rhodanine and oxonol dyes. The wavelength dependence (action spectra), pharmacological effects\\u000a of staining, signal size, signal-to-noise ratio, and the utility of the dyes for long-term continuous recording were examined\\u000a for four merocyanine-rhodanine dyes (NK2761, NK2776, NK3224 and NK3225), which

Y. Momose-Sato; K. Sato; Y. Arai; I. Yazawa; H. Mochida; K. Kamino

1999-01-01

116

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...

117

Evaluation of voltage-sensitive fluorescence dyes for monitoring neuronal activity in the embryonic central nervous system.  

PubMed

Using an optical imaging technique with voltage-sensitive dyes (VSDs), we investigated the functional organization and architecture of the central nervous system (CNS) during embryogenesis. In the embryonic nervous system, a merocyanine-rhodanine dye, NK2761, has proved to be the most useful absorption dye for detecting neuronal activity because of its high signal-to-noise ratio (S/N), low toxicity and small dye bleaching. In the present study, we evaluated the suitability of fluorescence VSDs for optical recording in the embryonic CNS. We screened eight styryl (hemicyanine) dyes in isolated brainstem-spinal cord preparations from 7-day-old chick embryos. Measurements of voltage-related optical signals were made using a multiple-site optical recording system. The signal size, S/N, photobleaching, effects of perfusion and recovery of neural responses after staining were compared. We also evaluated optical responses with various magnifications. Although the S/N was lower than with the absorption dye, clear optical responses were detected with several fluorescence dyes, including di-2-ANEPEQ, di-4-ANEPPS, di-3-ANEPPDHQ, di-4-AN(F)EPPTEA, di-2-AN(F)EPPTEA and di-2-ANEPPTEA. Di-2-ANEPEQ showed the largest S/N, whereas its photobleaching was faster and the recovery of neural responses after staining was slower. Di-4-ANEPPS and di-3-ANEPPDHQ also exhibited a large S/N but required a relatively long time for recovery of neural activity. Di-4-AN(F)EPPTEA, di-2-AN(F)EPPTEA and di-2-ANEPPTEA showed smaller S/Ns than di-2-ANEPEQ, di-4-ANEPPS and di-3-ANEPPDHQ; but the recovery of neural responses after staining was faster. This study demonstrates the potential utility of these styryl dyes in optical monitoring of voltage changes in the embryonic CNS. PMID:23975337

Habib-E-Rasul Mullah, Saad; Komuro, Ryo; Yan, Ping; Hayashi, Shihori; Inaji, Motoki; Momose-Sato, Yoko; Loew, Leslie M; Sato, Katsushige

2013-09-01

118

Evaluation of the electrochemical stability of graphite foams as current collectors for lead acid batteries  

Microsoft Academic Search

Graphite foams with high electrical and thermal conductivities, good mechanical strength, and low mass have been synthesized and evaluated as possible current collector materials to replace lead alloys for the development of lightweight lead acid batteries. Cyclic voltammetry and galvanostatic charge–discharge tests were performed on these foams prior to and after graphitization to evaluate their electrochemical properties. In the voltage

Young-Il. Jang; Nancy J. Dudney; Terry N. Tiegs; James William Klett

2006-01-01

119

Safety evaluation of interim stabilization of non-stabilized single-shell watch list tanks  

SciTech Connect

The report provides a summation of the status of safety issues associated with interim stabilization of Watch List SSTs (organic, ferrocyanide, and flammable gas), as extracted from recent safety analyses, including the Tank Farms Accelerated Safety Analysis efforts.

Stahl, S.M.

1994-12-30

120

Stability evaluation and system identification of flexible multibody systems  

Microsoft Academic Search

This paper is concerned with the linearized stability analysis and system identification of flexible multibody systems. Two\\u000a closely related stability analysis approaches are summarized. Next, these approaches are extended to provide robust system\\u000a identification procedures that combine least squares techniques and Kalman filters. The singular value decomposition, a numerically\\u000a stable mathematical tool, is used to improve the robustness of the

Olivier A. Bauchau; Jielong Wang

2007-01-01

121

Evaluation of Condor SS as a soil stabilizer  

E-print Network

manufacturing and coal burning lead to the production of various pozzolans such as lime kiln dust and Class C fly-ash. Reactions between pozzolanic stabilizers and soil include cation exchange, flocculation and agglomeration. Silica and alumina provided...). It is an electrochemical soil stabilizer that contains water-soluble sulfonated oils (3, 4). When inixed with water, these oils solubilize and offer an ion exchange medium. Chemically, they perform as weak organic bases and when mixed with the strong sulfuric acid...

Ahmed, Shamim

2012-06-07

122

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

PubMed Central

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

2013-01-01

123

An implementation of particle swarm optimization to evaluate optimal under-voltage load shedding in competitive electricity markets  

NASA Astrophysics Data System (ADS)

Load shedding is a crucial issue in power systems especially under restructured electricity environment. Market-driven load shedding in reregulated power systems associated with security as well as reliability is investigated in this paper. A technoeconomic multi-objective function is introduced to reveal an optimal load shedding scheme considering maximum social welfare. The proposed optimization problem includes maximum GENCOs and loads' profits as well as maximum loadability limit under normal and contingency conditions. Particle swarm optimization (PSO) as a heuristic optimization technique, is utilized to find an optimal load shedding scheme. In a market-driven structure, generators offer their bidding blocks while the dispatchable loads will bid their price-responsive demands. An independent system operator (ISO) derives a market clearing price (MCP) while rescheduling the amount of generating power in both pre-contingency and post-contingency conditions. The proposed methodology is developed on a 3-bus system and then is applied to a modified IEEE 30-bus test system. The obtained results show the effectiveness of the proposed methodology in implementing the optimal load shedding satisfying social welfare by maintaining voltage stability margin (VSM) through technoeconomic analyses.

Hosseini-Bioki, M. M.; Rashidinejad, M.; Abdollahi, A.

2013-11-01

124

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

125

TECHNOLOGY EVALUATION REPORT: SILICATE TECHNOLOGY CORPORATION - SOLIDIFICATION/STABILIZATION OF PCP AND INORGANIC CONTAMINANTS IN SOILS - SELMA, CA  

EPA Science Inventory

This Technolgy Evaluation Report evaluates the solidification/stabilization process of Silicate Technology Corporation (STC) for the on-site treatment of contaminated soil The STC immobilization technology uses a proprietary product (FMS Silicate) to chemically stabilize and ...

126

Evaluation of the effect of deforestation on slope stability and its application to watershed management  

Microsoft Academic Search

The effect of tree roots on slope stability is evaluated with the upper bound theorem. The greatest effect is indicated in mature forests where the surface soil depth is less than 100 cm. The critical soil depth is estimated as an index of instability of surface soils. All major factors affecting the stability of surface soils are discussed and summarized

YOSHINORI TSUKAMOTO; HIROHIKO MINEMATSU

127

Effects of Sample Storage on Biosolids Compost Stability and Maturity Evaluation  

E-print Network

* ABSTRACT soil storage method depends on the parameters to be analyzed. For chemical analysis, air-drying of soil sam-Compost stability and maturity are important parameters of com- ples is the most common of soil may can affect compost stability and maturity evaluation. However, sample significantly alter

Ma, Lena

128

Evaluation of Dimensional Stability of Autoclavable Elastomeric Impression Material  

Microsoft Academic Search

Impressions are important sources of cross contamination between patients and dental laboratories. As a part of infection\\u000a control impressions contaminated with variety of micro-organisms via blood and oral secretions should be cleaned and disinfected\\u000a or sterilized before being handled in dental laboratory. The purpose of this study was to determine the effect of autoclaving\\u000a on dimensional stability of elastomeric impression

G. P. Surendra; Ayesha Anjum; C. L. Satish Babu; Shilpa Shetty

2011-01-01

129

HOW TO EVALUATE THE KRAFT PULP BRIGHTNESS STABILITY?  

Microsoft Academic Search

Proper accelerated ageing methods (dry vs. humid heat) and applicability of UV-Vis reflectance spectroscopy for brightness stability studies of kraft pulps were considered. It was shown that UV-Vis reflectance spectroscopy can be used as a very sensitive and simple method to follow the degradation of HexA during thermal ageing treatments of kraft pulps. It was confirmed that the dry heat

Tiina Liitiä; Tarja Tamminen

130

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.

131

Comprehensive Stability Evaluation of Rock Slope Using the Cloud Model-Based Approach  

NASA Astrophysics Data System (ADS)

This article presents the cloud model-based approach for comprehensive stability evaluation of complicated rock slopes of hydroelectric stations in mountainous area. This approach is based on membership cloud models which can account for randomness and fuzziness in slope stability evaluation. The slope stability is affected by various factors and each of which is ranked into five grades. The ranking factors are sorted into four categories. The ranking system of slope stability is introduced and then the membership cloud models are applied to analyze each ranking factor for generating cloud memberships. Afterwards, the obtained cloud memberships are synthesized with the factor weights given by experts for comprehensive stability evaluation of rock slopes. The proposed approach is used for the stability evaluation of the left abutment slope in Jinping 1 Hydropower Station. It is shown that the cloud model-based strategy can well consider the effects of each ranking factor and therefore is feasible and reliable for comprehensive stability evaluation of rock slopes.

Liu, Zaobao; Shao, Jianfu; Xu, Weiya; Xu, Fei

2014-11-01

132

Electrical/mechanical evaluation of high voltage dielectrics for OTEC riser cables  

SciTech Connect

The unique design and test requirements for the cable dielectrics selected for evaluation for use in Ocean Thermal Energy Conversion plants are described. Specifically, the methodology of developing the test procedure is defined. The basic cable dielectrics selected for evaluation include taped/oil-impregnated insulation, and extruded solid cross-linked polyethylene insulation. These cables are designed to transmit 100 MW at 138 kV, and will be subjected to installation and operating conditions that are unprecedented for any power cable system. These conditions include ocean depths of 4000 to 5000 feet, long vertical suspension, and the motions and forces imparted by the plant and ocean. The developmental test program is designed primarily to determine the weak link in the components of the candidate cable with regard to the ability to successfully withstand the unusual OTEC conditions over a 10 to 30 year lifetime. Two basic areas of concern are the mechanical fatigue of metallic sheaths and strength members, and the electrical/mechanical ''fatigue'' of the dielectric and shielding components. The constraints and problems in such testing are addressed, and the engineering solutions are described. Finally, the scheduled plan for completion of the entire development test plan is defined.

Traut, R. T.; Kurt, J. P.; DiPietro, F. M.; Roberts, K. P.

1980-01-01

133

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 ...

134

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 ...

135

Evaluation of lime-fly ash stabilized bases and subgrades using static and dynamic deflection systems  

E-print Network

EVALUATION OF LIME-FLY ASH STABILIZED BASFS AND SUBGRADES USING STATIC AND DYNAMIC DEFLECTION SYSTEMS A Thesis GARY W. RABA Submitted to the Graduate College of Texas AIIM University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1982 Major Subject: Civil Engineering EVALUATION OF LIME-FLY ASH STABILIZED BASES AND SUBGRADES USING STATIC AND DYNAMIC DEFLECTION SYSTEMS A Thesis by Gary Nl. Raba Approved as to style and content by: !Chairman...

Raba, Gary W.

2012-06-07

136

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

137

Experimental evaluation of actual delivered dose using mega-voltage cone-beam CT and direct point dose measurement  

SciTech Connect

Radiation therapy in patients is planned by using computed tomography (CT) images acquired before start of the treatment course. Here, tumor shrinkage or weight loss or both, which are common during the treatment course for patients with head-and-neck (H and N) cancer, causes unexpected differences from the plan, as well as dose uncertainty with the daily positional error of patients. For accurate clinical evaluation, it is essential to identify these anatomical changes and daily positional errors, as well as consequent dosimetric changes. To evaluate the actual delivered dose, the authors proposed direct dose measurement and dose calculation with mega-voltage cone-beam CT (MVCBCT). The purpose of the present study was to experimentally evaluate dose calculation by MVCBCT. Furthermore, actual delivered dose was evaluated directly with accurate phantom setup. Because MVCBCT has CT-number variation, even when the analyzed object has a uniform density, a specific and simple CT-number correction method was developed and applied for the H and N site of a RANDO phantom. Dose distributions were calculated with the corrected MVCBCT images of a cylindrical polymethyl methacrylate phantom. Treatment processes from planning to beam delivery were performed for the H and N site of the RANDO phantom. The image-guided radiation therapy procedure was utilized for the phantom setup to improve measurement reliability. The calculated dose in the RANDO phantom was compared to the measured dose obtained by metal-oxide-semiconductor field-effect transistor detectors. In the polymethyl methacrylate phantom, the calculated and measured doses agreed within about +3%. In the RANDO phantom, the dose difference was less than +5%. The calculated dose based on simulation-CT agreed with the measured dose within±3%, even in the region with a high dose gradient. The actual delivered dose was successfully determined by dose calculation with MVCBCT, and the point dose measurement with the image-guided radiation therapy procedure.

Matsubara, Kana, E-mail: matsubara-kana@hs.tmu.ac.jp [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan); Kohno, Ryosuke [National Cancer Center Hospital East, Chiba (Japan); National Cancer Center Research Institute, Chiba (Japan); Nishioka, Shie; Shibuya, Toshiyuki; Ariji, Takaki; Akimoto, Tetsuo [National Cancer Center Hospital East, Chiba (Japan); Saitoh, Hidetoshi [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan)

2013-07-01

138

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

139

Real World Crash Evaluation of Vehicle Stability Control (VSC) Technology  

PubMed Central

This study quantifies the effect of Vehicle Stability Control (VSC) in reducing crash involvement rates for a subset of vehicles in the US fleet. Crash rates for a variety of impact types before and after VSC technology was implemented are compared. Police-reported crashes from six available US state files from 1998–2002 were analyzed including 13,987 crash-involved study vehicles not equipped with the technology and 5,671 crashes of vehicles equipped with VSC as a standard feature. Overall, an 11.2% (95% CI: 2.4%, 21.1%) reduction in multi-vehicle frontal crash involvement was identified for VSC-equipped vehicles. A 52.6% (95% CI: 42.5%, 62.7%) reduction in single-vehicle crash rates was found. PMID:16179137

Bahouth, G.

2005-01-01

140

Evaluation of dimensional stability of autoclavable elastomeric impression material.  

PubMed

Impressions are important sources of cross contamination between patients and dental laboratories. As a part of infection control impressions contaminated with variety of micro-organisms via blood and oral secretions should be cleaned and disinfected or sterilized before being handled in dental laboratory. The purpose of this study was to determine the effect of autoclaving on dimensional stability of elastomeric impression material (polyvinyl siloxane-Affinis). In this in vitro study standardized stainless steel die as per ADA specification number 19 was fabricated. Polyvinyl siloxane (Affinis) light body and putty viscosity elastomeric impression materials were used. A total of 40 impressions of the stainless steel die were made and numeric coding system was used to identify the samples. Measurements were made using a measuring microscope. Distance between the cross lines CD and C'D' reproduced in the impression were measured before autoclaving, immediately after autoclaving and 24 hours after autoclaving and dimensional change was calculated. The data obtained was subjected to statistical analysis. The mean difference in dimensional change between the three groups was not statistically significant (P > 0.05). However the results revealed that there was higher mean dimensional change immediately after autoclaving when compared to the other 2 time intervals. It is desirable to delay the casting of an autoclavable elastomeric impression material by about 24 hours. Though disinfection of impression is routinely followed autoclaving of impression is an effective method of sterilization. PMID:22379308

Surendra, G P; Anjum, Ayesha; Satish Babu, C L; Shetty, Shilpa

2011-03-01

141

Precision improvement for omeprazole determination through stability evaluation.  

PubMed

A new spectrofluorimetric method for the determination of omeprazole (OMP) based on its degradation reaction catalyzed by ultraviolet (UV) light is proposed. OMP in aqueous solution is very unstable, which renders a serious difficulty for controlling its quality. It does not show native fluorescence, but when exposed to UV radiation, it generates a highly fluorescent degradation product with adequate stability for indirect OMP quantification. Under the studied optimal experimental conditions (pH, temperature, exposure time to UV radiation), a specific rate constant of 2.851 min?¹--described by zero-order kinetic--was obtained for the degradation reaction. Using ?(exc) 293 nm and ?(em) 317 nm, a linear relationship was obtained (r² 0.9998) in the concentration range of 0.1 to 1.3 µg mL?¹, with a detection limit of 1.07 10?³ µg mL?¹ (S/N = 3). The methodology developed was successfully applied to OMP quality control in pure drugs and tablet dosage forms without previous treatment, with good tolerance to common excipient, and a high level of concordance between the nominal and experimental values. This work constitutes an important contribution to knowledge of the degradation mechanism of OMP. It has been shown to be appropriate for OMP quality control, to have an adequate sampling rate, low cost instrument, and to be a less polluting procedure. PMID:21287694

Peralta, Cecilia Mariana; Fernández, Liliana Patricia; Masi, Adriana Noemí

2012-01-01

142

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

143

Parametric stability evaluation in computer experiments on the mathematical model of Drosophila control gene subnetwork.  

PubMed

Using the method of generalized threshold models, the problem is formulated and solved to evaluate the parametric stability of the model of a gene subnetwork controlling the early ontogenesis of the fruit fly Drosophila melanogaster. Computer experiments have been performed to test the parametric stability of the model. Quantitative evaluations have been obtained for parametric stability of the Drosophila gene subnetwork in nuclei along the embryo's anterior-posterior axis. The results of computer experiments have been compared with the previous research data on "sensitivity" of functioning regimes to random changes of the parameters in the models of prokaryotic and eukaryotic systems, namely the system controlling the lambda-phage development and the subsystem controlling the flower morphogenesis of Arabidopsis thaliana. The obtained results confirm high parametric stability of gene networks that control the development of organisms. PMID:12762850

Tchuraev, Rustem N; Galimzyanov, Alexander V

2003-01-01

144

Evaluating Marie Byrd Land stability using an improved basal topography  

NASA Astrophysics Data System (ADS)

Prior understanding of the ice-sheet setting in Marie Byrd Land (MBL) was derived primarily from geologic and geochemical studies of the current nunataks, with very few geophysical surveys imaging the ice covered regions. The geologic context suggested that the ice rests on a broad regional high, in contrast to the deep basins and trenches that characterize the majority of West Antarctica. This assumed topography would favor long-term stability for the West Antarctic Ice Sheet (WAIS) in MBL. Airborne geophysical data collected in 2009 reveal a much deeper bed than previously estimated, including a significant trough underlying DeVicq Glacier and evidence for extensive glacial erosion. Using these data, we produce a new map of subglacial topography, with which we model the sensitivity of WAIS to a warming ocean using the ice-sheet model of Pollard and DeConto (2012b). We compare the results to estimates of ice loss during WAIS collapse using the previously defined subglacial topography, to determine the impact of the newly discovered subglacial features. Our results indicate that the topographic changes are not sufficient to destabilize the northern margin of MBL currently feeding the Getz Ice Shelf; the majority of ice loss occurs from flow toward the Siple Coast. However, despite only slight dynamic differences, using the new bed as a boundary condition results in an additional 8 cm of sea-level rise during major glacial retreat, an increase of just over 2%. Precise estimation of past and future ice retreat, as well as a complete understanding of the geologic history of the region, will require a higher resolution picture of the bed topography around the Executive Committee mountains.

Holschuh, N.; Pollard, D.; Alley, R. B.; Anandakrishnan, S.

2014-12-01

145

A perspective on coatings to stabilize high-voltage cathodes: LiMn1.5Ni0.5O4 with subnanometer Lipon cycled with LiPF6 electrolyte  

SciTech Connect

High voltage Li-ion cathodes push the limits of stability for both cathode and electrolyte. Here subnanometer coatings of an amorphous thin film electrolyte (Lipon) improved the room temperature and 60 C cycling stability of a LiMn1.5Ni0.5O4 spinel cathode when charged to 4.9V with a standard LiPF6 carbonate electrolyte. The cathodes delivered superior C-rate performances up to a 5C discharge, when compared to the uncoated cathodes. Enhanced performance extended for at least 100 cycles. Electrochemical impedance spectroscopy indicates that Lipon slows the increase of interface resistance. Thicker 1-3nm Lipon coatings are sufficiently insulating as to block electronic transport to the cathode particles. Thick coatings also slow Mn dissolution. Results suggest that Lipon may act to scavenge impurities or block active sites that promote electrolyte decomposition. While greatly improved by the Lipon coating, this cathode is not sufficiently stable for long cycle life applications. Further work is needed to assess if and what surface coatings will ultimately stabilize the high voltage cathodes. Comments include insight from other studies of Lipon coated cathodes and directions for future research.

Kim, Yoongu [ORNL; Dudney, Nancy J [ORNL; Chi, Miaofang [ORNL; Martha, Surendra K [ORNL; Nanda, Jagjit [ORNL; Veith, Gabriel M [ORNL; Liang, Chengdu [ORNL

2013-01-01

146

RESEARCH ON SPUTTERING PHENOMENA, SURFACE STABILITY AND VOLTAGE BREAKDOWN FOR ALKALI-COATED REFRACTORY ELECTRODES. Quarterly Report No. 2, August 1, 1961October 31, 1961  

Microsoft Academic Search

Studies of voltage breakdown in ion propulsion systems are described. ; Results of microscopic examinations of Cs deposited on W electrodes indicate that ; under ion propulsion conditions, Cs intercepted by the electrodes can accumulate ; and apread readily from the point of impact, thus enhancing the breakdown ; likelinood by spreading on the electrode support insulation. Plans for examining

R. L. Strayer; F. M. Charbonnier; E. C. Cooper

1963-01-01

147

Extended performance solar electric propulsion thrust system study. Volume 5. Capacitor-diode voltage multiplier: Technology evaluation  

NASA Technical Reports Server (NTRS)

A 1-kW capacitor-diode voltage multiplier (CDVM) was designed, fabricated and tested to demonstrate the power of feasibility of high power CDVM's and to verify the analytical techniques that had been used to predict the performance characteristics of a 6-kw CDVM. High efficiency (96.2%), a low ratio of component weight to power (0.55 kg/kW), and low output ripple voltage (less than 1%, peak to peak) were obtained during the operation of a 1-kW CDVM various input line, load current, and load fault conditions.

Martinelli, R. M.

1977-01-01

148

Development of a biofilm formation method for waste forms stability evaluation  

Microsoft Academic Search

The development of an accurate assessment protocol is critical for the prediction of long-term performance of waste disposal systems under field conditions. In this study, the development of a biofilm formation method for the evaluation of waste forms stability to microbially induced degradation (MID) is reported. The development process involved significant modifications to the existing Nuclear Regulatory Commission (NRC) approach.

M. A. Idachaba; K. Nyavor; N. O. Egiebor; R. D. Rogers

2000-01-01

149

EVALUATION OF THE THERMAL STABILITY POHC INCINERABILITY RANKING IN A PILOT-SCALE ROTARY KILN INCINERATOR  

EPA Science Inventory

A series of pilot-scale incineration tests was performed at EPA's Incineration Research Facility to evaluate the thermal stability-based POHC incinerability ranking. In the tests, mixtures of 12 P0HCs with predicted incinerability spanning the range af most to least difficult to ...

150

Evaluation of First Swing Stability of a Large Power System With Various FACTS Devices  

Microsoft Academic Search

This paper presents a simple method of evaluating the first swing stability of a large power system in the presence of various flexible ac transmission system (FACTS) devices. First a unified power flow controller (UPFC) and the associated transmission line are considered and represented by an equivalent pi-circuit model. The above model is then carefully interfaced to the power network

M. H. Haque

2008-01-01

151

Evaluation of acoustic attenuation as an indicator of roof stability in advancing headings  

Microsoft Academic Search

A novel acoustic technique developed to monitor roof stability in advancing headings was evaluated during a field monitoring trial at the Brunswick Mine, New Brunswick, Canada. The acoustic technique uses waveforms generated by mining activity near the active face (such as rotary-percussion drilling for the installation of support or drilling blast-holes) to identify changes in the attenuation properties of the

S. D. Butt; C. Mukherjee; G. Lebans

2000-01-01

152

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

153

TECHNOLOGY EVALUATION REPORT: SILICATE TECHNOLOGY CORPORATION, SOLIDIFICATION/STABILIZATION OF PCP AND INORGANIC CONTAMINANTS IN SOILS SELMA, CA  

EPA Science Inventory

A Superfund Innovative Technology Evaluation demonstration was conducted to evaluate the ability of the solidification/ stabilization treatment process developed by Silicate Technology Corporation (STC) to reduce the mobility and leaching potential of organic and inorganic contam...

154

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

155

Evaluation of iodine content and stability in recipes prepared with biofortified potatoes.  

PubMed

Abstract Iodine is an essential micronutrient of the human diet. Deficiency of iodine is diffused in many areas of the world and mild deficiency is present also in developed countries around Europe. Biofortification of vegetables could represent a better strategy with respect to iodized salt in order to increase iodine intake. The aim of this study was evaluating the stability of iodine, derived from biofortified potatoes, in the preparation process of three Italian typical dishes: dumplings, vegetable pie, and focaccia bread. The obtained results showed a good stability of iodine in cooking processes, in particular, during baking of focaccia bread. Significant losses of iodine were detected during boiling of dumplings and baking of vegetable pie. Although the different stability during the cooking processes, the three dishes maintained a good final content of iodine, ranging from the 33.3% to 52.7% of daily recommended intake in adults for individual serving size. PMID:24828007

Cerretani, Lorenzo; Comandini, Patrizia; Fumanelli, Davide; Scazzina, Francesca; Chiavaro, Emma

2014-11-01

156

Evaluation of the effect of cell voltage and termination current on barrier anodic AlâOâ film formation  

Microsoft Academic Search

We have observed the capacitance, breakdown voltage, and leakage current characteristics of barrier anodic films formed on 6061-T6 aluminum alloy at anodization cell potentials ranging from 600 to 950 V, and termination current densities ranging from 5% to 10% of the maximum current density (1 mA\\/cm²). We also recorded the processing times and wet leakage current characteristics. The electrolyte consisted

J. K. G. Panitz; D. J. Sharp; F. E. Martinez

1983-01-01

157

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

158

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

159

On-line detection of power system small disturbance voltage instability  

Microsoft Academic Search

Small disturbance (SD) voltage stability (or instability) deals with a system's ability to maintain satisfactory voltages following a small disturbance. For an operating condition, a system's SD voltage stability depends on the proximity of the condition to the critical point (or voltage collapse point). A Q angle and Q directional derivatives are proposed for SD voltage instability detection and weak

Liancheng Wang; A. A. Girgis

1996-01-01

160

Evaluation of Available Transfer Capability Using Transient Stability Constrained Line Flows  

NASA Astrophysics Data System (ADS)

This paper presents a methodology to evaluate transient stability constrained available transfer capability (ATC). A linear and fast line flow-based (LFB) method was adopted to optimize the ATC values. This enabled the direct determination of the system source-sink locations. This paper formulated different market transactions considering bilateral and multilateral impacts in the stability constrained ATC. The proposed method was demonstrated on the WECC 9-bus and IEEE 39-bus systems. The critical energy performance index (CEPI) enabled the direct identification of candidates for contingency screening based on ranking. This index helped to reduce the list of credible contingencies for ATC evaluation and, therefore, the computation time. The results of the proposed ATC method are consistent with the literature and can be deployed for fast assessment of the impact of transactions in an electric power system.

Uzoechi, Lazarus Okechukwu; Mahajan, Satish M.

2014-01-01

161

Field soil aggregate stability kit for soil quality and rangeland health evaluations  

USGS Publications Warehouse

Soil aggregate stability is widely recognized as a key indicator of soil quality and rangeland health. However, few standard methods exist for quantifying soil stability in the field. A stability kit is described which can be inexpensively and easily assembled with minimal tools. It permits up to 18 samples to be evaluated in less than 10 min and eliminates the need for transportation, minimizing damage to soil structure. The kit consists of two 21??10.5??3.5 cm plastic boxes divided into eighteen 3.5??3.5 cm sections, eighteen 2.5-cm diameter sieves with 1.5-mm distance openings and a small spatula used for soil sampling. Soil samples are rated on a scale from one to six based on a combination of ocular observations of slaking during the first 5 min following immersion in distilled water, and the percent remaining on a 1.5-mm sieve after five dipping cycles at the end of the 5-min period. A laboratory comparison yielded a correlation between the stability class and percent aggregate stability based on oven dry weight remaining after treatment using a mechanical sieve. We have applied the method in a wide variety of agricultural and natural ecosystems throughout western North America, including northern Mexico, and have found that it is highly sensitive to differences in management and plant community composition. Although the field kit cannot replace the careful laboratory-based measurements of soil aggregate stability, it can clearly provide valuable information when these more intensive procedures are not possible.

Herrick, J.E.; Whitford, W.G.; de Soyza, A. G.; Van Zee, J. W.; Havstad, K.M.; Seybold, C.A.; Walton, M.

2001-01-01

162

Evaluation of carrier distributions in a depletion region of semiconductor measured by a capacitance-voltage profile method  

NASA Astrophysics Data System (ADS)

It is well known that carrier depth profiles obtained by the capacitance-voltage (C-V) measurement method provide carrier information only beyond the initial semiconductor depletion region. A novel new method has been developed within the depletion approximation for obtaining carrier depth profiles inside the initial depletion region of a semiconductor through the combined use of the layer-removal technique and C-V profile measurements. This method has been successfully demonstrated through simulated C-V profile data created from a known Gaussian distribution of Si-implanted GaAs.

Yeo, Y. K.; Gainer, G. H., Jr.; Kim, Jong Hyun; Hengehold, R. L.

1990-01-01

163

Section IV.D.3 for DOE 2013 Annual Report: Novel Phosphazene-based Compounds to Enhance Safety and Stability of Cell Chemistries for High Voltage Applications (INL)  

SciTech Connect

Electrolytes play a central role in performance and aging in most electrochemical systems. As automotive and grid applications place a higher reliance on electrochemical stored energy, it becomes more urgent to have electrolyte components that enable optimal battery performance while promoting battery safety and longevity. Safety remains a foremost concern for widespread utilization of Li-ion technology in electric-drive vehicles, especially as the focus turns to higher voltage systems (5V). This work capitalizes on the long established INL expertise regarding phosphazene chemistry, aimed at battery-viable compounds for electrolytes and electrodes that are highly tolerant to abusive conditions. This report showcases our 2013 work for the DOE applied battery research (ABR) program, wherein testing results are summarized for INL electrolytes and alternative anode materials.

Kevin L. Gering; Mason K. Harrup; Eric J. Dufek; Sergiy V. Sazhin; Harry W. Rollins; David K. Jamison; Fred F. Stewart; John Burba

2013-09-01

164

Critical evaluation of the midgap-voltage-shift method for determining oxide trapped charge in irradiated MOS devices  

SciTech Connect

The validity of using midgap voltage shifts to determine radiation-induced oxide trapped charge is examined using thermally stimulated current (TSC), conductance, and C-V techniques. The assumption behind the midgap technique that all interface states are amphoteric P/sub b/ centers is shown to be not generally valid. Conductance measurements revealed a donor interface state in the upper half of the bandgap. Results obtained by combining data from TSC and high-frequency C-V measurements show the existence of three types of radiation-induced interface states: the P/sub b/ center, a donor state in the upper half of the bandgap, and an acceptor state in the lower half. No single surface potential exists that is the neutral point for N/sub it/ for all processes and radiation doses. Midgap voltage shifts do not generally correlate with oxide trapped charge determined from thermally stimulated current (TSC) measurements. The magnitude of the fractional deviation is typically less than a factor of unity but in some cases is as large as a factor of four. The significance of these errors needs to be determined for each application. Arguments and test supporting the validity of using TSC measurements for determining oxide trapped charge are presented.

Shanfield, Z.; Moriwaki, M.M.

1987-12-01

165

Saunders M., Charlier B., Bonamy J., 2005," Using evaluation to create `provisional stabilities': bridging innovation in Higher Education change processes", Evaluation, Sage Publications London,  

E-print Network

for evaluation in negotiating such periods of change. Introduction This paper will draw together the evaluationSaunders M., Charlier B., Bonamy J., 2005," Using evaluation to create `provisional stabilities': bridging innovation in Higher Education change processes", Evaluation, Sage Publications London, 2005, Vol

Paris-Sud XI, Université de

166

Evaluation of degradation kinetics for abamectin in formulations using a stability indicating method.  

PubMed

The aim of this study was to evaluate stability characteristics and kinetics behavior of abamectin (ABM) as a 1 % (m/V) topical veterinary solution. During the study, samples stressed at 55 and 70 °C were regularly analyzed for several parameters over 8 weeks on a chromatographic (HPLC) system, using a Prodigy C18, 250 x 4.6 mm, 5-?m, column eluting with 15 : 34 : 51 (V/V/V) water/methanol/ acetonitrile as mobile phase. The HPLC method was validated for precision, accuracy, linearity and specificity, and was found to be stability indicating. The results showed that degradation of ABM followed first-order kinetics and data on loss in kobs (s-1) and half life (t1/2, days) demonstrated ABM showing the maximum stability in glycerol formal. The degradation behavior of ABM varies from solvent to solvent. The effect of added alkali on pH change and loss of ABM was studied and found to be unique for all solvents and very distinct from typical hydrolysis degradation. The present study may serve as a platform to design and develop topical non-aqueous solutions of ABM for veterinary use given no such comprehensive efforts have been published to date on the stability profile of ABM in non-aqueous solvents. PMID:23482313

Awasthi, Atul; Razzak, Majid; Al-Kassas, Raida; Harvey, Joanne; Garg, Sanjay

2013-03-01

167

The idea of PGA stream computations for soil slope stability evaluation  

NASA Astrophysics Data System (ADS)

Designing and constructing of road embankments, deep excavations, landslide and snow avalanche predictions or profiling construction sites in slanting terrain need slope stability evaluations. Determination of a safety factor and the position of a potentially critical slip surface is one of the essential issues in classical and modern soil mechanics, which still remains a very important problem in engineering practice. Most of the stability evaluation methods, i.e. based on limit equilibrium assumptions, need optimization, which can be successfully realized with the assistance of a genetic algorithm. The authors propose a variational approach with a four-step technique to determination of the critical height of a slope, which can be treated as an alternative and variant method to the generally applied limit equilibrium and/or finite element methods. Some common obstacles encountered while adapting classical optimization procedures have been solved by application of a parallel genetic algorithm. Substantial acceleration of computations has been achieved by introducing SIMD stream technology, which generally relies on modern graphics processing units. Examples of the results of a slope stability analysis performed using the fast parallel computation technique are also presented.

Tran, Chi; Srokosz, Piotr

2010-09-01

168

Initial Flight Evaluation of the Army/NASA RASCAL Variable Stability Helicopter  

NASA Technical Reports Server (NTRS)

NASA Ames Research Center and the U.S. Army Aeroflightdynamics Directorate (AFDD) [will] have performed initial flight evaluations of the Research Flight Control System (RFCS) that has been integrated into the Army/NASA Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) variable stability helicopter. The RASCAL, a highly modified JUH-60A Black Hawk helicopter, is a variable-stability, in-flight simulator that is designed to support flight research programs that leverage on the flight control and handling qualities design tools developed by the Army and NASA. These tools are used in the flight control design life cycle from initial concept definition, through simulation, and ultimately into flight on-board the RASCAL helicopter. The RASCAL will be used to validate methodologies for reducing design cycle costs for new or modified aircraft, and it will serve as a base for the investigation of new rotorcraft technology.

Moralez, Ernesto, III; Hindson, William S.; Arterburn, David R.

2000-01-01

169

EVALUATING THE EFFECTIVENESS OF STREAMBANK STABILIZATION TECHNIQUES FOR REDUCING BANK EROSION ON THE UPPER CLARK FORK RIVER, WESTERN MONTANA  

Microsoft Academic Search

Lateral channel movement on the upper Clark Fork River in western Montana has resulted in loss of valuable agricultural land and delivery of sediment and mine tailings into the river. In spring 1996, we initiated a study to evaluate the effectiveness of streambank stabilization techniques to reduce bank erosion. This study examines the effectiveness of 21 different bioengineering stabilization techniques

Donna DeFrancesco; Paul L. Hansen

2000-01-01

170

EVALUATION OF TWO LEAD-BASED PAINT REMOVAL AND WASTE STABILIZATION TECHNOLOGY COMBINATIONS ON TYPICAL EXTERIOR SURFACES  

EPA Science Inventory

A study was conducted to demonstrate the effectiveness of a wet abrasive blasting technology to remove lead-based paint from exterior wood siding and brick substrates as well as to evaluate the effectiveness of two waste stabilization technologies to stabilize the resulting blast...

171

On the effect of non-carbon nanostructured supports on the stability of Pt nanoparticles during voltage cycling: A study of TiO2 nanofibres  

NASA Astrophysics Data System (ADS)

Electrospun carbon and Nb-doped TiO2 nanofibres (CNFs, TNFs) have been investigated as electrocatalyst supports for polymer electrolyte membrane fuel cells (PEMFC). The optimal Nb doping amount has been identified for TNFs, and thermal treatment of titanium oxide fibres optimised to balance the surface area and electronic conductivity requirements. The most highly conducting material is characterised by a high concentration of surface Ti3+ and Nb4+ (and oxygen vacancies). Pt nanoparticles of average diameter of 2.3 nm were loaded onto 10%at Nb doped-TiO2, retained as the best candidate for further electrochemical analysis, and on CNFs, using a microwave-assisted polyol method. Significantly higher electrochemically active surface area was retained after voltage cycling to 1.2 V for Pt supported on TNF (73%) than on CNFs, where only 8% of the original ECSA was conserved after 1000 voltammetric cycles. The mass activity was also slightly higher for the titanium oxide based electrodes in the oxygen reduction reaction.

Savych, I.; Bernard d'Arbigny, J.; Subianto, S.; Cavaliere, S.; Jones, D. J.; Rozière, J.

2014-07-01

172

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

173

Development and stability evaluation of olive oil nanoemulsion using sucrose monoester laurate  

NASA Astrophysics Data System (ADS)

Nanoemulsion is a type of emulsion that consists of fine oil-in-water dispersions, with the droplets covering the size range of 20-200 nm. It can be achieved through emulsification process. One of the processes is through low energy emulsification method. Olive oil was chosen in this study due to its efficiency in treating skin problem. Olive oil nanophase gel (NPG) formulations were performed through various ratios of olive oil, sucrose laurate and glycerin. The particle sizes and stability of the prepared olive oil nanophase gel were evaluated and the optimal formulation was then selected for the development of olive oil nanoemulsion. This study proved that the composition of oil and surfactant play an important roles in influencing the nanophase gel droplet size. Nanophase gels containing olive oil in the concentration of 50 and 60 % show good stability at 4 °C and room temperature while it was less stable at 40 °C. Olive oil nanophase gels in the concentration of 50 % and 60 % with sucrose laurate 25 % in each formulation were good candidates to prepare nanoemulsion because they have the suitable droplets size and Polydispersing Index (PDI) when compared to other formulations. A mixture of NPG 50 % and water in the ratio of 40:60 and NPG 60 % and water in the ratio of 33.3:66.7 were used to produce nanoemulsions containing 20 % of oil with negative values of zeta potential (>60) which indicate the good stability of the nanoemulsions.

Eid, Ahmad M. M.; Baie, Saringat Haji; Arafat, Osama

2012-11-01

174

Evaluation of hydrothermal treatment in enhancing rice straw compost stability and maturity.  

PubMed

In order to evaluate the hydrothermal treatment (HTT) in enhancing compost stability and maturity of lignocellulosic agricultural residues, a bin-scale (90 L) composting of rice straw with and without "HTT" was performed. The rice straw compost product with "HTT" after 6 weeks of composting can be considered stable and adequate for field application as expressed by pH of 8.4, "EC value" of 2.96 dS m(-1), C/N ratio of 12.5, microbial activity of <8.05 mg CO2 g(-1) OM d(-1), NH4(+)-N content of 93.75 mg kg(-1) DM and finally, by "GI" of >83%. However, compost may prove phytotoxic if used as growing media for EC sensitive plants. As for rice straw compost product without "HTT", the high microbial activity (>12.28 mg CO2 g(-1) OM d(-1)) even after 14 weeks of composting suggests that the residue has not stabilized yet and is far away from stability and maturity, although a higher GI (>100%) was observed. PMID:24262840

Nakhshiniev, Bakhtiyor; Biddinika, Muhammad Kunta; Gonzales, Hazel Bantolino; Sumida, Hiroaki; Yoshikawa, Kunio

2014-01-01

175

Evaluation of the color stability of two techniques for reproducing artificial irides after microwave polymerization  

PubMed Central

The use of ocular prostheses for ophthalmic patients aims to rebuild facial aesthetics and provide an artificial substitute to the visual organ. Natural intemperate conditions promote discoloration of artificial irides and many studies have attempted to produce irides with greater chromatic paint durability using different paint materials. Objectives The present study evaluated the color stability of artificial irides obtained with two techniques (oil painting and digital image) and submitted to microwave polymerization. Material and Methods Forty samples were fabricated simulating ocular prostheses. Each sample was constituted by one disc of acrylic resin N1 and one disc of colorless acrylic resin with the iris interposed between the discs. The irides in brown and blue color were obtained by oil painting or digital image. The color stability was determined by a reflection spectrophotometer and measurements were taken before and after microwave polymerization. Statistical analysis of the techniques for reproducing artificial irides was performed by applying the normal data distribution test followed by 2-way ANOVA and Tukey HSD test (?=.05). Results Chromatic alterations occurred in all specimens and statistically significant differences were observed between the oil-painted samples and those obtained by digital imaging. There was no statistical difference between the brown and blue colors. Independently of technique, all samples suffered color alterations after microwave polymerization. Conclusion The digital imaging technique for reproducing irides presented better color stability after microwave polymerization. PMID:21625733

GOIATO, Marcelo Coelho; dos SANTOS, Daniela Micheline; MORENO, Amália; GENNARI-FILHO, Humberto; PELLIZZER, Eduardo Piza

2011-01-01

176

Evaluation of bias voltage modulation sequence for nonlinear contrast agent imaging using a capacitive micromachined ultrasonic transducer array.  

PubMed

Many clinical diagnoses have now been improved thanks to the development of new techniques dedicated to contrast agent nonlinear imaging. Over the past few years, Capacitive Micromachined Ultrasonic Transducers (cMUTs) have emerged as a promising alternative to traditional piezoelectric transducers. One notable advantage of cMUTs is their wide frequency bandwidth. However, their use in nonlinear imaging approaches such as those used to detect contrast agents have been challenging due their intrinsic nonlinear character. We propose a new contrast imaging sequence, called bias voltage modulation (BVM), specifically developed for cMUTs to suppress their inherent nonlinear behavior. Theoretical and experimental results show that a complete cancellation of the nonlinear signal from the source can be reached when the BVM sequence is implemented. In-vitro validation of the sequence is performed using a cMUT probe connected to an open scanner and a flow phantom setup containing SonoVue microbubbles. Compared to the standard amplitude modulation imaging mode, a 6?dB increase of contrast-to-tissue ratio was achieved when the BVM sequence is applied. These results reveal that the problem of cMUT nonlinearity can be addressed, thus expanding the potential of this new transducer technology for nonlinear contrast agent detection and imaging. PMID:25098319

Novell, Anthony; Legros, Mathieu; Grégoire, Jean-Marc; Dayton, Paul A; Bouakaz, Ayache

2014-09-01

177

Evaluation of bias voltage modulation sequence for nonlinear contrast agent imaging using a capacitive micromachined ultrasonic transducer array  

NASA Astrophysics Data System (ADS)

Many clinical diagnoses have now been improved thanks to the development of new techniques dedicated to contrast agent nonlinear imaging. Over the past few years, Capacitive Micromachined Ultrasonic Transducers (cMUTs) have emerged as a promising alternative to traditional piezoelectric transducers. One notable advantage of cMUTs is their wide frequency bandwidth. However, their use in nonlinear imaging approaches such as those used to detect contrast agents have been challenging due their intrinsic nonlinear character. We propose a new contrast imaging sequence, called bias voltage modulation (BVM), specifically developed for cMUTs to suppress their inherent nonlinear behavior. Theoretical and experimental results show that a complete cancellation of the nonlinear signal from the source can be reached when the BVM sequence is implemented. In-vitro validation of the sequence is performed using a cMUT probe connected to an open scanner and a flow phantom setup containing SonoVue microbubbles. Compared to the standard amplitude modulation imaging mode, a 6?dB increase of contrast-to-tissue ratio was achieved when the BVM sequence is applied. These results reveal that the problem of cMUT nonlinearity can be addressed, thus expanding the potential of this new transducer technology for nonlinear contrast agent detection and imaging.

Novell, Anthony; Legros, Mathieu; Grégoire, Jean-Marc; Dayton, Paul A.; Bouakaz, Ayache

2014-09-01

178

Evaluation of stability changes in magnesium-incorporated titanium implants in the early healing period.  

PubMed

The aim of the present study was to determine the bone response to magnesium (Mg) ion-incorporated titanium (Ti) implants during the early healing period. A total of 114 patients (69 men and 45 women aged between 29 and 71 years) participated in the study. Overall, one hundred thirty-three 10-mm-long fixtures were installed, composed of 65 Mg ion-incorporated fixtures in the test group (55 participants; 30 males and 25 females) and 68 resorbable blast media (RBM) surface fixtures in the control group (59 participants; 39 males and 20 females). The bone responses were evaluated by resonance frequency analysis (RFA) at the following time points after implant insertion (ie, the healing period): 0, 2, 4, 8, and 12 weeks. Each time an RFA measurement was taken, the stability changes relating to both bone quality and implant arch location (maxilla or mandible) were recorded for further analysis. The mean stabilities were lowest at week 4 of healing for both the test and control groups. Significant differences in RFA values between the 2 groups were found at week 12 of healing. The mean percentage change in implant stability quotient (ISQ) from the baseline revealed that the implant stability of the Mg ion-incorporated test group had increased (4.55%) more than the RBM surface group (2.23%) by week 12 of healing. With respect to bone quality, the mean ISQ of Mg-incorporated Ti implants only changed significantly during the 12-week period for type 4 bone. Furthermore, at weeks 4 and 12 of healing, significant differences were found between the 2 groups for type 2 and type 4 bone. A comparison of the stability patterns of mandibular and maxillary implants revealed that the overall stability was higher in the mandible; however, no significant difference was found for Mg-incorporated Ti implants. The Mg-incorporated Ti implants exhibited a slightly better bone response with respect to ISQ than did the RBM surface implants, and the percentage change in mean ISQ from the baseline was greater for the Mg-incorporated group than for the RBM surface group at the end point of this study. PMID:24036725

Hieu, Pham Duong; Baek, Dong Heon; Park, Dong Soo; Park, Jong-Tae; Hong, Ki Seok

2013-09-01

179

Monitoring of leachate quality stored in gas ventilation pipes for evaluating the degree of landfill stabilization.  

PubMed

Monitoring of leachate quality is the essential measure in aftercare for evaluating landfill stabilization. Generally, the most common way of leachate monitoring is executed at the inlet of the leachate treatment facility. However, it does not necessarily reflect the actual state of the site. Thus, methodologies which focus on both the discharge, in order to determine when the post-closure care of the facility should terminate, and on the degree of waste stabilization in the landfill are required. In the present study, monitoring of leachate quality stored in 68 gas ventilation pipes was conducted and the degree of waste stabilization at each location in the landfill was estimated by a statistical approach using the results obtained by monitoring. Leachate characteristics varied significantly for each pipe but seemed to reflect the waste condition of the nearby location. Correlation among the analysed items was quite high. Namely, the difference of leachate quality seemed to be categorized only by the level of concentration but not by the specific characteristics. To confirm this, Euclidean distances of dissimilarity were calculated by multidimensional scaling using six items of leachate quality and temperature. Two factors (thickness of leachate and concentration of total organic carbon (TOC) and electric conductivity (EC)) that distinguish leachate characteristics appeared. To indicate the degree of stabilization by location, the spatial distribution of TOC, total nitrogen (TN), inorganic carbon (IC), and chloride ion were estimated by using the ordinary Kriging methodology. As the result, it was estimated that the concentration of leachate existing within the landfill, especially TN, was higher than the completion criteria for leachate in most parts of the investigated area. PMID:20937618

Tojo, Yasumasa; Sato, Masahiro; Matsuo, Takayuki; Matsuto, Toshihiko

2011-01-01

180

Nanoemulsion stability: experimental evaluation of the flocculation rate from turbidity measurements  

E-print Network

The coalescence of liquid drops induces a higher level of complexity compared to the classical studies about the aggregation of solid spheres. Yet, it is commonly believed that most findings on solid dispersions are directly applicable to liquid mixtures. Here, the state of the art in the evaluation of the flocculation rate of these two systems is reviewed. Special emphasis is made on the differences between suspensions and emulsions. In the case of suspensions, the stability ratio is commonly evaluated from the initial slope of the absorbance as a function of time under diffusive and reactive conditions. Puertas and de las Nieves (1997) developed a theoretical approach that allows the determination of the flocculation rate from the variation of the turbidity of a sample as a function of time. Here, suitable modifications of the experimental procedure and the referred theoretical approach are implemented in order to calculate the values of the stability ratio and the flocculation rate corresponding to a dodecane-in-water nanoemulsion stabilized with sodium dodecyl sulfate. Four analytical expressions of the turbidity are tested, basically differing in the optical cross section of the aggregates formed. The first two models consider the processes of: a) aggregation (as described by Smoluchowski) and b) the instantaneous coalescence upon flocculation. The other two models account for the simultaneous occurrence of flocculation and coalescence. The latter reproduce the temporal variation of the turbidity in all cases studied (380 \\leq [NaCl] \\leq 600 mM), providing a method of appraisal of the flocculation rate in nanoemulsions.

Kareem Rahn-Chique; Antonio M. Puertas; Manuel S. Romero-Cano; Clara Rojas; German Urbina-Villalba

2012-05-21

181

Evaluation of the probability of arrester failure in a high-voltage transmission line using a Q learning artificial neural network model  

NASA Astrophysics Data System (ADS)

One of the most popular methods of protecting high voltage transmission lines against lightning strikes and internal overvoltages is the use of arresters. The installation of arresters in high voltage transmission lines can prevent or even reduce the lines' failure rate. Several studies based on simulation tools have been presented in order to estimate the critical currents that exceed the arresters' rated energy stress and to specify the arresters' installation interval. In this work artificial intelligence, and more specifically a Q-learning artificial neural network (ANN) model, is addressed for evaluating the arresters' failure probability. The aims of the paper are to describe in detail the developed Q-learning ANN model and to compare the results obtained by its application in operating 150 kV Greek transmission lines with those produced using a simulation tool. The satisfactory and accurate results of the proposed ANN model can make it a valuable tool for designers of electrical power systems seeking more effective lightning protection, reducing operational costs and better continuity of service.

Ekonomou, L.; Karampelas, P.; Vita, V.; Chatzarakis, G. E.

2011-04-01

182

An integrated methodology to evaluate the effects of plants for slope stability  

NASA Astrophysics Data System (ADS)

The topic of eco-hydrological dynamics is fundamental in slope stability analysis on vegetated soils. The understanding of hydrological processes are based on the knowledge of the geotechnical properties of soils, on the pedological, pluviometrical and vegetational features and they are all related to the soil and roots interaction. To quantify the stability slopes effects that the root systems provide to the soil, it is important to know their spatial distribution and their tensile strength. Because of the difficulty to estimate the action of single roots, in the stability evaluation of vegetated hillslopes, only the additional root cohesion is generally taken into account depending on the spatial variability of the root area ratio RAR (the ratio between the area occupied by roots in a unit area of soil) distribution (especially with depth), even if it is not sure that all the roots in the soil actually mobilise their whole tensile strength (e.g. each root could not break at the same time due to different tortuosity and elasticity). In this paper we test some analysis and methodologies: • to value the stress-strain curve and ultimate tensile strength of the roots, we use two different testing machines normally employed for wood rheological behavior studies. • to value the cohesion contribution to rooted soil samples we use a geotechnical apparatus (the Casagrande direct shear test); • an indirect methodology to obtain the measurement of the fundamental parameters of the root apparatus; • an indirect methodology to estimate the analytical descriptors of the root apparatus based on climatic and pedological features; • a GIS survey to estimate the stability factor and its evolution with some models in different vegetation management. Mediterranean environments, particularly, where soils are shallow and water is scarce over the growing season (water controlled ecosystems), it would be more economical for plants to have the roots closer to the soil surface. This could be relevant for the abandoned slopes in the Mediterranean basin where root development has to balance the increasing infiltration capacity during re-vegetation. Such knowledge is very important for the slope stability valuation and hydrological and hydro geological dynamics understanding.

Dani, A.; Giadrossich, F.; Guastini, E.; Preti, F.; Togni, M.; Vannocci, P.

2009-04-01

183

Synthesis and evaluation of a 125I-labeled iminodihydroquinoline-derived tracer for imaging of voltage-gated sodium channels?  

PubMed Central

In vivo imaging of voltage-gated sodium channels (VGSCs) can potentially provide insights into the activation of neuronal pathways and aid the diagnosis of a number of neurological diseases. The iminodihydroquinoline WIN17317-3 is one of the most potent sodium channel blockers reported to date and binds with high affinity to VGSCs throughout the rat brain. We have synthesized a 125I-labeled analogue of WIN17317-3 and evaluated the potential of the tracer for imaging of VGSCs with SPECT. Automated patch clamp studies with CHO cells expressing the Nav1.2 isoform and displacement studies with [3H]BTX yielded comparable results for the non-radioactive iodinated iminodihydroquinoline and WIN17317-3. However, the 125I-labeled tracer was rapidly metabolized in vivo, and suffered from low brain uptake and high accumulation of radioactivity in the intestines. The results suggest that iminodihydroquinolines are poorly suited for tracer development. PMID:23910595

Perez-Medina, Carlos; Patel, Niral; Robson, Mathew; Lythgoe, Mark F.; Arstad, Erik

2013-01-01

184

Performance Evaluation and Slip Regulation Control of an Asymmetrical Parameter Type Two-Phase Induction Motor Drive Using a Three-Leg Voltage Source Inverter  

NASA Astrophysics Data System (ADS)

This paper presents a performance evaluation and a simple speed control method of an asymmetrical parameter type two-phase induction motor drive using a three-leg VSI (Voltage Source Inverter). The two-phase induction motor is adapted from an existing single-phase induction motor resulting in impedance unbalance between main and auxiliary windings. The unbalanced two-phase inverter outputs with orthogonal displacement based on a SPWM (Sinusoidal Pulse Width Modulation) method are controlled with appropriate amplitudes for improving the motor performance. Dynamic simulation of the proposed drive system is given. A simple speed controller based on a slip regulation method is designed. The overall system is implemented on a DSP (Digital Signal Processor) board. The validity of the proposed system is verified by simulation and experimental results.

Piyarat, Wekin; Kinnares, Vijit

185

Evaluation of Antioxidant Stability of Arbutin and Pyrus boissieriana Buhse Leaf Extract  

PubMed Central

With regard to the importance of antioxidants in foods, cosmetics and pharmaceutics, there are several studies on natural resources for finding rich sources of antioxidants and their role in protecting the body against oxidative stress injuries. The purpose of this study was to investigate the antioxidant stability of arbutin and the Pyrus boissieriana buhse Leaf extract and their effects on lipid oxidation in different conditions of temperature and time. Arbutin and the Pyrus boissieriana buhse Leaf extract were stored for 14 days in the different conditions of temperature including room, refrigerator and freezer. Total phenolic compounds were measured by the folin-ciocaltea method. Flavonoid compounds were evaluated by aluminum chloride method. Their total antioxidant activity was measured by FRAP (ferric reducing antioxidant power) method and their protection effect on lipid oxidation was measured by TBARS (thiobarbituric acid reactant substances) method. Also, the amount of sustainability for peroxide activities was measured by TMB (Tetra Methyl Benzedrine) method. Polyphenol formed 1.96 mg/g dry weight of Pyrus boissieriana buhse Leaf extract and the amount of flavonoid complex was 0.125 mg/g dry weight of Pyrus boissieriana buhse Leaf extract. The amount of FRAP was decreased by increasing temperature and time. The amount of lipid oxidation had increased in all samples with time (0-14). The stability of peroxide activities decreased in the different conditions of temperature and time. The results of this study show the existence of antioxidant activities with higher stability in storage time and the protective effect of arbutin and Pyrus boissieriana buhse Leaf extract on lipid oxidation. Therefore, using arbutin and Pyrus boissieriana buhse Leaf extract as a natural resource of antioxidant is suggested for substituting synthetic antioxidants. PMID:24551796

Khalilpour, Asieh; Pouramir, Mahdi; Asgharpour, Fariba

2013-01-01

186

A battery-based, low-noise voltage source.  

PubMed

A highly stable, low-noise voltage source was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess noise and ground loops, the voltage source is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of +/-15 and +/-5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented design, a relative voltage stability of 7 x 10(-7) over 6.5 h and a noise level equal or smaller than 30 nV/square root(Hz) is achieved. PMID:20590260

Wagner, Anke; Sturm, Sven; Schabinger, Birgit; Blaum, Klaus; Quint, Wolfgang

2010-06-01

187

A battery-based, low-noise voltage source  

NASA Astrophysics Data System (ADS)

A highly stable, low-noise voltage source was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess noise and ground loops, the voltage source is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of ±15 and ±5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented design, a relative voltage stability of 7×10-7 over 6.5 h and a noise level equal or smaller than 30 nV/?Hz is achieved.

Wagner, Anke; Sturm, Sven; Schabinger, Birgit; Blaum, Klaus; Quint, Wolfgang

2010-06-01

188

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

189

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

190

Evaluation of Mungbean Genotypes Based on Yield Stability and Reaction to Mungbean Yellow Mosaic Virus Disease  

PubMed Central

This work was conducted to identify mungbean genotypes showing yield stability and resistance to mungbean yellow mosaic virus (MYMV) disease. Sixteen genotypes were evaluated in a randomized complete block design with two replications for two years (2011 and 2012) at three locations (Gazipur, Ishurdi and Madaripur) of the Bangladesh Agricultural Research Institute. An analysis of variance exhibited significant effects of genotype (G), environment (E), and genotype × environment (G×E) on grain yield. Among eight agronomic characters, the principal component 1 (PC1) was always higher than the PC2. Considering G×E interaction, BM6 was the best genotype at all three locations in both years. Based on grain yield and stability performance, BM6 ranked first while the worst performing genotypes were BM1 and G10. Based on discrimination and representation, Gazipur was identified as an ideal environment for these mungbeans. Relationship between soil-plant analysis developments (SPAD) value was positive with yield but negative with MYMV severity. BM6, G1 and G2 were considered as promising sources of resistance for low disease score and stable response across the environments. The environment proved to have an influence on MYMV infection under natural infestation. A positive correlation was observed between disease score and the temperature under natural growing condition.

Alam, AKM Mahbubul; Somta, Prakit; Jompuk, Choosak; Chatwachirawong, Prasert; Srinives, Peerasak

2014-01-01

191

Evaluation of the effectiveness of various amendments on trace metals stabilization by chemical and biological methods.  

PubMed

We evaluated the effects of five different kinds of amendments on heavy metals stabilization. The five amendments were: zero valent iron, limestone, acid mine drainage treatment sludge, bone mill, and bottom ash. To determine bioavailability of the heavy metals, different chemical extraction procedures were used such as, extraction with (Ca(NO(3))(2), DTPA; toxic characteristic leaching procedure (TCLP), physiologically based extraction test (PBET) that simulates gastric juice, and sequential extraction test. Bioavailability was also determined by measuring uptake of the heavy metals by lettuce (Lactuca sativa L.) and earthworms (Eisenia fetida). In addition, dehydrogenase activity was measured to determine microbial activity in the soil with the different amendments. The addition of amendments, especially limestone and bottom ash, resulted in a significant reduction in extractable metal contents. Biological assays using lettuce, earthworm, and enzyme activity were found as appropriate indicators of available metal fraction after in situ stabilization of heavy metals. In conclusion, TCLP and sequential extraction test appear to be promising surrogate measure of metal bioavailability in soils for several environment endpoints. PMID:21333442

Lee, Sang-Hwan; Park, Hyun; Koo, Namin; Hyun, Seunghun; Hwang, Anna

2011-04-15

192

Evaluation of mungbean genotypes based on yield stability and reaction to mungbean yellow mosaic virus disease.  

PubMed

This work was conducted to identify mungbean genotypes showing yield stability and resistance to mungbean yellow mosaic virus (MYMV) disease. Sixteen genotypes were evaluated in a randomized complete block design with two replications for two years (2011 and 2012) at three locations (Gazipur, Ishurdi and Madaripur) of the Bangladesh Agricultural Research Institute. An analysis of variance exhibited significant effects of genotype (G), environment (E), and genotype × environment (G×E) on grain yield. Among eight agronomic characters, the principal component 1 (PC1) was always higher than the PC2. Considering G×E interaction, BM6 was the best genotype at all three locations in both years. Based on grain yield and stability performance, BM6 ranked first while the worst performing genotypes were BM1 and G10. Based on discrimination and representation, Gazipur was identified as an ideal environment for these mungbeans. Relationship between soil-plant analysis developments (SPAD) value was positive with yield but negative with MYMV severity. BM6, G1 and G2 were considered as promising sources of resistance for low disease score and stable response across the environments. The environment proved to have an influence on MYMV infection under natural infestation. A positive correlation was observed between disease score and the temperature under natural growing condition. PMID:25289012

Alam, Akm Mahbubul; Somta, Prakit; Jompuk, Choosak; Chatwachirawong, Prasert; Srinives, Peerasak

2014-09-01

193

Toroidal tank evaluation. [propellant tanks for spin-stabilized Pioneer spacecraft  

NASA Technical Reports Server (NTRS)

The reported study had been conducted to determine the feasibility of developing toroidal tanks for an auxiliary propulsion system that could be integrated into a Pioneer spin-stabilized spacecraft. The system evaluated consisted of two toroidal tanks equipped with surface tension devices. One tank is intended for nitrogen tetroxide, the other for monomethylhydrazine. The study included the definition of a propellant acquisition system concept that could satisfy the requirements of a spinning tank. It was found that an oxidizer tank spin rate of 76 rpm and a fuel tank spin rate of 110 rpm would be required to produce liquid loss from the acquisition system during spacecraft operation. An investigation showed that toroidal tanks can be fabricated with present technology using either titanium or aluminum alloys. The preferred material would be titanium because of its significantly higher strength.

Fester, D. A.; Anderson, J. E.

1977-01-01

194

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

195

Seedling development and evaluation of genetic stability of cryopreserved Dendrobium hybrid mature seeds.  

PubMed

Vitrification, a simple, fast, and recommended cryopreservation method for orchid germplasm conservation, was evaluated for Dendrobium hybrid "Dong Yai" mature seeds. The genetic stability of regenerated seedlings was also evaluated using flow cytometry. Mature seeds from this hybrid were submitted to plant vitrification solution (PVS2) for 0, 0.5, 1, 2, 3, 4, 5, or 6 h at 0 °C. Subsequently, they were plunged into liquid nitrogen (LN) at -196 °C for 1 h and recovered in half-strength Murashige and Skoog culture medium (1/2 MS), and seed germination was evaluated after 30 days. Seeds directly submitted to LN did not germinate after cryopreservation. Seeds treated with PVS2 between 1 and 3 h presented the best germination (between 51 and 58%), although longer exposure to PVS2 returned moderated germination (39%). Germinated seeds were further subcultured in P-723 culture medium and developed whole seedlings in vitro after 180 days, with no abnormal characteristics, diseases, or nutritional deficiencies. Seedlings were successfully acclimatized under greenhouse conditions with over 80% survival. Flow cytometry analysis revealed no chromosomal changes on vitrified seedlings, as well as seedlings germinated from the control treatment (direct exposure to LN). These findings indicate that vitrification is a feasible and safe germplasm cryopreservation method for commercial Dendrobium orchid hybrid conservation. PMID:24402568

Galdiano, Renato Fernandes; de Macedo Lemos, Eliana Gertrudes; de Faria, Ricardo Tadeu; Vendrame, Wagner Aparecido

2014-03-01

196

Development of a biofilm formation method for waste forms stability evaluation.  

PubMed

The development of an accurate assessment protocol is critical for the prediction of long-term performance of waste disposal systems under field conditions. In this study, the development of a biofilm formation method for the evaluation of waste forms stability to microbially induced degradation (MID) is reported. The development process involved significant modifications to the existing Nuclear Regulatory Commission (NRC) approach. In the biofilm formation method, the control media and fermenter broths are designed to be of similar pH to avoid overestimation of the microbe's capability to degrade the waste forms. In the NRC approach, the pH values are different. The existing one-stage process of the NRC approach is also replaced with a two-stage process in the biofilm formation method. This is to ensure full evaluation of the microbe's involvement in waste forms degradation. The first stage of the two-stage process is for biofilm formation and the second is for biofilm evaluation. The use of a two-stage process eliminates the possibility of substrate limitation, resulting in values of degradation indices that are about two times higher than those obtained using the single-stage NRC approach. Two waste forms (100% Tuskegee cement and 21% cobalt chloride/79% cement) were used in the development of the biofilm formation method. Both waste forms showed evidence of biofilm formation. The formation of biofilm on the cobalt-containing waste form indicates a lack of anti-microbial capability of cobalt. PMID:10946124

Idachaba, M A; Nyavor, K; Egiebor, N O; Rogers, R D

2000-10-01

197

Stability evaluation of a rocket engine for gaseous oxygen difluoride (OF2) and gaseous diborane (B2H6) propellants  

NASA Technical Reports Server (NTRS)

Results of an experimental evaluation of the dynamic stability of a candidate combustor for the space storable propellants gaseous OF2/B2H6 show that the combustor is unstable without supplementary damping. A computer analysis indicated that the uninhibited engine could be unstable. The experiments, conducted with O2/C2H4 substitute propellants and with 70-30 FLOX/B2H6 (OF2 simulated with FLOX), show that the uninhibited combustor has a low stability margin to starting transient perturbations, but that is relatively insensitive to bomb disturbances. Damping cavities are shown to provide stability.

Clayton, R. M.

1972-01-01

198

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. PMID:19396475

Brayda-Bruno, M.; Perona, F.; Fornari, M.; Raimondi, M. T.; Petruzzi, M.; Grava, G.; Costa, F.; Caiani, E. G.; Lamartina, C.

2009-01-01

199

Molecular MR imaging for the evaluation of the effect of dynamic stabilization on lumbar intervertebral discs.  

PubMed

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. PMID:19396475

Vaga, Stefania; Brayda-Bruno, M; Perona, F; Fornari, M; Raimondi, M T; Petruzzi, M; Grava, G; Costa, F; Caiani, E G; Lamartina, C

2009-06-01

200

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

201

Induction generator based system providing regulated voltage with constant frequency  

Microsoft Academic Search

A PWM voltage-source inverter is used in order to improve the electrical characteristics of an isolated induction generator. The electronic converter allows achievement of a better system behavior in many aspects: voltage regulation, frequeney stabilization and reactive power compensation. The PWM inverter DC voltage is the control variable of the generator speed governor, therefore the system power balance and the

E. G. Marra; J. A. Pomilio

1999-01-01

202

Investigations on the low voltage cathodoluminescence stability and surface chemical behaviour using Auger and X-ray photoelectron spectroscopy on LiSrBO{sub 3}:Sm{sup 3+} phosphor  

SciTech Connect

Highlights: {yields} Stable orange-red cathodoluminescence observed from LiSrBO{sub 3}:Sm{sup 3+} phosphor. {yields} In situ Auger electron spectroscopy, while monitoring the CL output reduction, reveals surface concentration modification of Li, Sr, B and O atoms. {yields} X-ray photoelectron spectroscopy confirms the formation of SrO{sub 2} layer due to the electron stimulated surface chemical reactions (ESSCRs). This layer is possibly contributing to the surface chemical stability and prevents further degradation. -- Abstract: Orange-red emissive LiSrBO{sub 3}:Sm{sup 3+} phosphors were synthesized through the solid-state reaction method. Under UV radiation (221 nm) and low-voltage electron beam (2 keV, 12 mA/cm{sup 2}) excitation, the Sm{sup 3+} doped LiSrBO{sub 3} phosphor shows emission corresponding to the characteristic {sup 4}G{sub 5/2}-{sup 6}H{sub 7/2} transitions of Sm{sup 3+} with the strongest emission at 601 nm. A high stability of cathodoluminescence (CL) emission during prolong electron bombardment with low-energy electrons was observed. Surface sensitive diagnostic tools such as Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used to study the surface chemistry. AES results revealed modifications in the surface concentrations of Li, Sr, B, O and C on the surface of the LiSrBO{sub 3}:Sm{sup 3+} phosphor as indicated by the changes in their Auger peak to peak heights (APPH) as a function of electron dose. Observed changes in the high resolution XPS spectra of the LiSrBO{sub 3}:Sm{sup 3+} surface irradiated with the low energy electron beam provide evidence of compositional and structural changes as a result of the electron beam stimulated surface chemical reactions (ESSCRs). Additional SrO{sub 2} was identified by XPS on the phosphor surface after it received an electron dose of 300 C/cm{sup 2} together with the increase in the concentrations of chemical species containing the B-C-O bonding. The new surface chemical species formed during electron beam bombardment are possibly responsible for the stability of the CL in the LiSrBO{sub 3}:Sm{sup 3+} phosphor.

Pitale, Shreyas S., E-mail: shreyas1234@yahoo.com [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300 (South Africa); Nagpure, I.M.; Kumar, Vinay; Ntwaeaborwa, O.M.; Terblans, J.J. [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300 (South Africa)] [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300 (South Africa); Swart, H.C., E-mail: swarthc@ufs.ac.za [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300 (South Africa)

2011-07-15

203

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

204

Evaluation of dimensional stability and accuracy of autoclavable polyvinyl siloxane impression material.  

PubMed

Dimensionally stable autoclavable impressions will be effective in controlling the cross-infection and contamination caused by patient's saliva and other oral secretions. The accuracy of newly introduced autoclavable polyvinyl siloxane impression material was assessed for its dimensional stability and accuracy. A standard metal model (Dentoform, U-501, Columbia) was customised for impression making. The impressions were made using the newly introduced polyvinyl siloxane impression materials (AFFINIS, Coltene/Whaledent AG, 9450 Alstalten, Switzerland). Fifty impressions were made and were divided into two groups A and B of 25 each. Group A was the control sample (non-autoclaved impressions) and group B was the test sample (autoclaved impressions), which was subjected to the steam autoclave procedure at 134 °C for 18 min, casts were poured in type IV gypsum products. The customised metal model, casts obtained from control and test group were subjected to laboratory evaluation with help of a travelling microscope (×10 magnification), and digital vernier calliper (0.01 mm/10 ?m accuracy). Data analysis was done using one-way ANOVA and One-Sample t test to evaluate the overall accuracy (P < 0.005). As a result, there was an average reduction of 0.016 ?m in overall dimension between the test and the control group when compared with the master model, which is not statistically or clinically significant. The newly introduced polyvinyl siloxane impression material is accurate and dimensional stable for clinical use when steam autoclaved at 134 °C for 18 min. PMID:24431790

Reddy, Subash M; Vijitha, D; Karthikeyan, S; Balasubramanian, R; Satish, A

2013-12-01

205

Low distortion automatic phase control circuit. [voltage controlled phase shifter  

NASA Technical Reports Server (NTRS)

A voltage controlled phase shifter is rendered substantially harmonic distortion free over a large dynamic input range by employing two oppositely poled, equally biased varactor diodes as the voltage controlled elements which adjust the phase shift. Control voltages which affect the bias of both diodes equally are used to adjust the phase shift without increasing distortion. A feedback stabilized phase shifter is rendered substantially frequency independent by employing a phase detector to control the phase shift of the voltage controlled phase shifter.

Hauge, G.; Pederson, C. W. (inventors)

1974-01-01

206

Does surface roughness influence the primary stability of acetabular cups? A numerical and experimental biomechanical evaluation.  

PubMed

Most acetabular cups implanted today are press-fit impacted cementless. Anchorage begins with the primary stability given by insertion of a slightly oversized cup. This primary stability is key to obtaining bone ingrowth and secondary stability. We tested the hypothesis that primary stability of the cup is related to surface roughness of the implant, using both an experimental and a numerical models to analyze how three levels of surface roughness (micro, macro and combined) affect the primary stability of the cup. We also investigated the effect of differences in diameter between the cup and its substrate, and of insertion force, on the cups' primary stability. The results of our study show that primary stability depends on the surface roughness of the cup. The presence of macro-roughness on the peripheral ring is found to decrease primary stability; there was excessive abrasion of the substrate, damaging it and leading to poor primary stability. Numerical modeling indicates that oversizing the cup compared to its substrate has an impact on primary stability, as has insertion force. PMID:25080896

Le Cann, Sophie; Galland, Alexandre; Rosa, Benoît; Le Corroller, Thomas; Pithioux, Martine; Argenson, Jean-Noël; Chabrand, Patrick; Parratte, Sébastien

2014-09-01

207

EMPIRICAL EVALUATION OF MODEL-DERIVED STABILITY LIMITS James L. Patton, Department of Biomedical Engineering, Northwestern University  

E-print Network

EMPIRICAL EVALUATION OF MODEL-DERIVED STABILITY LIMITS James L. Patton, Department of Biomedical Engineering, Northwestern University patton@nwu.edu> Yi-Chung Pai, Programs in Physical Therapy empirical trajectories in which balance is preserved. While Pai and Patton (1997) showed that some

Patton, James

208

Transient Voltage Recorder  

NASA Technical Reports Server (NTRS)

A voltage transient recorder can detect lightning induced transient voltages. The recorder detects a lightning induced transient voltage and adjusts input amplifiers to accurately record transient voltage magnitudes. The recorder stores voltage data from numerous monitored channels, or devices. The data is time stamped and can be output in real time, or stored for later retrieval. The transient recorder, in one embodiment, includes an analog-to-digital converter and a voltage threshold detector. When an input voltage exceeds a pre-determined voltage threshold, the recorder stores the incoming voltage magnitude and time of arrival. The recorder also determines if its input amplifier circuits clip the incoming signal or if the incoming signal is too low. If the input data is clipped or too low, the recorder adjusts the gain of the amplifier circuits to accurately acquire subsequent components of the lightning induced transients.

Medelius, Pedro J. (Inventor); Simpson, Howard J. (Inventor)

2002-01-01

209

A matter of quantum voltages.  

PubMed

Voltages inside matter are relevant to crystallization, materials science, biology, catalysis, and aqueous chemistry. The variation of voltages in matter can be measured by experiment, however, modern supercomputers allow the calculation of accurate quantum voltages with spatial resolutions of bulk systems well beyond what can currently be measured provided a sufficient level of theory is employed. Of particular interest is the Mean Inner Potential (Vo) - the spatial average of these quantum voltages referenced to the vacuum. Here we establish a protocol to reliably evaluate Vo from quantum calculations. Voltages are very sensitive to the distribution of electrons and provide metrics to understand interactions in condensed phases. In the present study, we find excellent agreement with measurements of Vo for vitrified water and salt crystals and demonstrate the impact of covalent and ionic bonding as well as intermolecular/atomic interactions. Certain aspects in this regard are highlighted making use of simple model systems/approximations. Furthermore, we predict Vo as well as the fluctuations of these voltages in aqueous NaCl electrolytes and characterize the changes in their behavior as the resolution increases below the size of atoms. PMID:25399199

Sellner, Bernhard; Kathmann, Shawn M

2014-11-14

210

A matter of quantum voltages  

NASA Astrophysics Data System (ADS)

Voltages inside matter are relevant to crystallization, materials science, biology, catalysis, and aqueous chemistry. The variation of voltages in matter can be measured by experiment, however, modern supercomputers allow the calculation of accurate quantum voltages with spatial resolutions of bulk systems well beyond what can currently be measured provided a sufficient level of theory is employed. Of particular interest is the Mean Inner Potential (Vo) - the spatial average of these quantum voltages referenced to the vacuum. Here we establish a protocol to reliably evaluate Vo from quantum calculations. Voltages are very sensitive to the distribution of electrons and provide metrics to understand interactions in condensed phases. In the present study, we find excellent agreement with measurements of Vo for vitrified water and salt crystals and demonstrate the impact of covalent and ionic bonding as well as intermolecular/atomic interactions. Certain aspects in this regard are highlighted making use of simple model systems/approximations. Furthermore, we predict Vo as well as the fluctuations of these voltages in aqueous NaCl electrolytes and characterize the changes in their behavior as the resolution increases below the size of atoms.

Sellner, Bernhard; Kathmann, Shawn M.

2014-11-01

211

The Transient-Energy Method of Calculating Stability  

Microsoft Academic Search

The transient-energy method is a newly developed means of checking and quantitatively evaluating the transient stability of a system of three, or possibly more synchronous machines. Each machine is represented by a constant-magnitude voltage behind a fixed reactance (usually the transient reactance) and all losses and nonsynchronous loads are assumed to be constant throughout the transient. The method is developed

P. C. Magnusson

1947-01-01

212

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

213

Stability evaluation of a cement based waste form to microbially induced degradation.  

PubMed

In this study the current Nuclear Regulatory Commission (NRC) protocol is used to evaluate the stability of Tuskegee cement/cobalt chloride waste form in the presence of Thiobacillus thiooxidans (T. thiooxidans). A critical examination of this protocol and identified limitations are reported also. Tuskegee cement/cobalt chloride waste forms were shown to exhibit considerable instability to microbial degradation as indicated by significant physical deterioration, and increased leaching of calcium and cobalt on exposure to T. thiooxidans. The instability was aggravated with higher levels of cobalt chloride content of the waste forms. The degradative capability of T. thiooxidans closely followed its ability to significantly decrease the pH of its environment. Inherent limitations in the NRC protocol were observed which could lead to serious result interpretation errors. The use of a T. thiooxidans culture that is significantly lower in pH in comparison to the control medium could lead to an overestimation of the degradative effect of T. thiooxidans, while the use of a culture that is substrate limited could result in an underestimation of T. thiooxidans capability. PMID:11720262

Idachaba, M A; Nyavor, K; Egiebor, N O; Rogers, R D

2001-08-01

214

Role of primary stability for successful osseointegration of dental implants: Factors of influence and evaluation  

PubMed Central

A secure implant primary (mechanical) stability is positively associated with a successful implant integration and long-term successful clinical outcome. Therefore, it is essential to assess the initial stability at different time-points to ensure a successful osseointegration. The present study critically reviews the factors that may play a role in achieving a successful initial stability in dental implants. Databases were searched from 1983 up to and including October 2013 using different combinations of various keywords. Bone quality and quantity, implant geometry, and surgical technique adopted may significantly influence primary stability and overall success rate of dental implants. PMID:24381734

Ahmed, Hameeda Bashir; Crespi, Roberto; Romanos, Georgios E.

2013-01-01

215

Voltage-gated sodium channels  

PubMed Central

Epilepsy is a brain disorder characterized by seizures and convulsions. The basis of epilepsy is an increase in neuronal excitability that, in some cases, may be caused by functional defects in neuronal voltage gated sodium channels, Nav1.1 and Nav1.2. The effects of antiepileptic drugs (AEDs) as effective therapies for epilepsy have been characterized by extensive research. Most of the classic AEDs targeting Nav share a common mechanism of action by stabilizing the channel’s fast-inactivated state. In contrast, novel AEDs, such as lacosamide, stabilize the slow-inactivated state in neuronal Nav1.1 and Nav1.7 isoforms. This paper reviews the different mechanisms by which this stabilization occurs to determine new methods for treatment. PMID:23531742

Abdelsayed, Mena; Sokolov, Stanislav

2013-01-01

216

Single electrode voltage clamp by iteration.  

PubMed

A technique for providing conditions of voltage clamp which differs considerably from other voltage clamp schemes has been developed. The feedback network which determines the current which will clamp the cell to the desired voltage does not operate in real time. Instead, the system uses a form of discontinuous feedback. The event to be clamped, which must be one which can be made to repeat itself without change, is elicited and allowed to run to completion without the intervention of feedback. During each repetition of the event, a current waveform is injected whose shape is based on the foregoing trials (iterations). Successive repetitions of this process develop a current waveform which ever more closely clamps the voltage to the desired value. Implementation involves a means of converting the intracellular voltage signal to digital form (a transient recorder), a means of processing the digitalized voltage signal (a digital computer), and a means of delivering the clamping current back to the preparation. The system has two advantages over other voltage clamp techniques. First, that the feedback loop is open in real time confers great stability. This advantage is exploited in the use of iterative voltage clamp in single electrode preparations. Secondly, iterative voltage clamp is essentially unlimited in the speed with which it can respond to transients. This would make the technique of interest even in preparations such as squid giant axon, where two electrodes are used and very fast responsiveness is desired. PMID:7218855

Park, M R; Leber, W; Klee, M R

1981-02-01

217

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

218

Performance Evaluation 40 (2000) 2746 A novel approach to queue stability analysis of polling models  

E-print Network

in modeling many real-world systems. For example, token-passing LAN, polling scheme, and processor sharing on stability of the whole system. This system stability analysis, however, fails to model many real-world systems for which some queues may continue to operate under an unstable system. In this paper we address

Chang, Rocky Kow-Chuen

219

Performance Evaluation of an ANFIS Based Power System Stabilizer Applied in Multi-Machine Power Systems  

Microsoft Academic Search

Power system stabilizers (PSSs) are utilized in order to make power systems stable after a large or small disturbance. Therefore PSSs must be capable of providing appropriate stabilization signal over a broad range of operational conditions and disturbances. Due to the fact that PSSs are widely used in power industry, any appropriate improvements in controlling methods of PSSs are important

A. A GHARAVEISI; A. DARABI; M. MONADI; A. KHAJEH-ZADEH; M. RASHIDI-NEJAD

220

Arthrometric evaluation of stabilizing effect of knee functional bracing at different flexion angles  

Microsoft Academic Search

Previous in-vivo investigations on the stabilizing efficacy of knee bracing for ACL reconstructed patients have been often limited to 20-30 degrees of knee flexion. In this study, the effectiveness of a uniaxial hinged functional brace to improve the knee stability was assessed at 30, 60 and 90 degrees of knee flexion. Arthrometry tests were conducted on 15 healthy subjects before

Saeedeh Seyed Mohseni; Farzam Farahmand; Hossein Karimi; Mohammad Kamali

221

AC system stability analysis and assessment for Shipboard Power Systems  

E-print Network

due to reconfiguration might cause voltage instability, such as progressive voltage decreases or voltage oscillations. SPS stability thus should be assessed to ensure the stable operation of a system during reconfiguration. In this dissertation, time...

Qi, Li

2006-04-12

222

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

223

Mixed voltage VLSI design  

NASA Technical Reports Server (NTRS)

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 overall throughput of a VLSI chip depends on the speed of the critical path(s) in the chip, it may be possible to sustain the throughput rates attained at higher voltages by operating the circuits in the critical path(s) with a high voltage while operating the other circuits with a lower voltage to minimize the power dissipation. The interface between the gates which operate at different voltages is crucial for low power dissipation since the interface may possibly have high static current dissipation thus negating the gains of the low voltage operation. The design of a voltage level translator which does the interface between the low voltage and high voltage circuits without any significant static dissipation is presented. Then, the results of the mixed voltage design using a greedy algorithm on three chips for various operating voltages are presented.

Panwar, Ramesh; Rennels, David; Alkalaj, Leon

1993-01-01

224

Study of second phase in bioabsorbable magnesium alloys: Phase stability evaluation via Dmol{sup 3} calculation  

SciTech Connect

Thermodynamical stabilities of four conventional second phases as well as magnesium matrix in bioabsorbable magnesium alloys were investigated theoretically via computer calculation method. Model of individual phase and systems including phase and four water molecular (phase-4H{sub 2}O) were established to simulate the in vitro and in vivo environment. Local orbital density functional theory approach was applied to calculate the total energy for the individual phase and phase-4H{sub 2}O system. The results demonstrated that all the second phases possessed higher phase stability compared with magnesium matrix, but the phase stability was quite different for different types of second phases or second phase-4H{sub 2}O systems. Furthermore, a schematic process of inflammation reaction caused by magnesium alloy implants was proposed for the further evaluation on biocompatibility of different second phases.

Yang, Huazhe [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Department of Biophysics, China Medical University, Shenyang 110001 (China); Liu, Chen [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Wan, Peng; Tan, Lili; Yang, Ke, E-mail: kyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

2013-11-01

225

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. PMID:22393583

Sahib, Mohanad Naji; Abdulameer, Shaymaa Abdalwahed; Darwis, Yusrida; Peh, Kok Khiang; Tan, Yvonne Tze Fung

2012-01-01

226

Interfacial degradation effects of aqueous solution-processed molybdenum trioxides on the stability of organic solar cells evaluated by a differential method  

NASA Astrophysics Data System (ADS)

The authors investigate the influence of two hole interfacial materials poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) and aqueous solution-processed MoO3 (sMoO3) on cell stability. sMoO3-based device demonstrated obviously improved stability compared to PEDOT:PSS-based one. Current-voltage characteristics analysis is carried out to investigate the effect of the hole interfacial layers on the cell stability. The formation of additional trap states at the interfaces between the hole interfacial layer and the active layer in degraded devices is verified by a differential method. Improved cell stability is attributed to a relatively stable sMoO3 interfacial layer compared to PEDOT:PSS by comparing their different trap states distributions.

Lou, Yan-Hui; Wang, Zhao-Kui; Yuan, Da-Xing; Okada, Hiroyuki; Liao, Liang-Sheng

2014-09-01

227

Biological stability evaluation of the ?2?1 receptor imaging agents: diamsar and DOTA conjugated DGEA peptide.  

PubMed

Robust chelating stability under biological condi-tions is critical for the design of copper-based radiopharmaceuticals. In this study, the stabilities of (64)Cu-DOTA and diamsar (two bifunctional Cu-64 chelators (BFCs)) conjugated DGEA peptides were evaluated. The in vitro stabilities of (64)Cu-DOTA-DGEA, (64)Cu-DOTA-Ahx-DGEA, and (64)Cu-Z-E(diamsar)-Ahx-DGEA were evaluated in PBS. A carboxyl-protected DOTA-DGEA was also synthesized to study the potential inter- and intramolecular interactions between DOTA and the carboxylate groups of DGEA peptide. microPET imaging of (64)Cu-DOTA-DGEA and (64)Cu-Z-E(diamsar)-Ahx-DGEA were performed in PC-3 prostate tumor model to further investigate the in vivo behavior of the tracers. DOTA-DGEA, DOTA-Ahx-DGEA, Z-E(diamsar)-Ahx-DGEA, and protected DOTA-DGEA peptides were readily obtained, and their identities were confirmed by MS. (64)Cu(2+) labeling was performed with high radiochemical yields (>98%) for all tracers after 1 h incubation. Stability experiments revealed that (64)Cu-DOTA-DGEA had unexpectedly high (64)Cu(2+) dissociation when incubated in PBS (>55% free (64)Cu(2+) was observed at 48 h time point). The (64)Cu(2+) dissociation was significantly reduced in the carboxyl-protected (64)Cu-DOTA-DGEA complex but not in the (64)Cu-DOTA-Ahx-DGEA complex, which suggests the presence of competitive binding for (64)Cu(2+) between DOTA and the carboxyl groups of the DGEA peptide. In contrast, no significant (64)Cu(2+) dissociation was observed for (64)Cu-Z-E(diamsar)-Ahx-DGEA in PBS. For microPET imaging, the PC-3 tumors were clearly visualized with both (64)Cu-DOTA-DGEA and (64)Cu-Z-E(diamsar)-Ahx-DGEA tracers. However, (64)Cu-DOTA-DGEA demonstrated 5× higher liver uptake than (64)Cu-Z-E(diamsar)-Ahx-DGEA. This biodistribution variance could be attributed to the chelating stability difference between these two tracers, which correlated well with the PBS stability experiments. In summary, the in vitro and in vivo evaluations of (64)Cu-Z-E(diamsar)-Ahx-DGEA and (64)Cu-DOTA-DGEA have demonstrated the significantly superior Cu-chelation stability for the diamsar derivative compared with the established DOTA chelator. The results also suggest that diamsar may be preferred for Cu chelation especially when multiple carboxylic acid groups are present. Free carboxyl groups may naturally compete with DOTA for (64)Cu(2+) binding and therefore reduce the complex stability. PMID:21244039

Huang, Chiun-Wei; Li, Zibo; Cai, Hancheng; Shahinian, Tony; Conti, Peter S

2011-02-16

228

Modular voltage source converter  

US Patent & Trademark Office Database

Voltage source converter based on a chain-link cell topology including one or more phases, each of the phases having one or more series-connected chain-link cell modules connected to each other. The output voltage of the voltage source converter is controlled by control signals applied to the series-connected chain-link cell modules. In case of failure of a chain-link cell module, that module is controlled, by the control signals, such that zero output voltage is provided at its output voltage AC terminal.

2013-08-06

229

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...

230

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...

231

A simple method for precisely evaluating the stability regions of a multi-mode laser  

NASA Astrophysics Data System (ADS)

We recently introduced a heuristic method for delimiting the stability regions of a three-mode class A laser with three freedom degrees. Here this method is extended to cover the stability conditions of a three-mode class B laser with five freedom degrees. The diagonal arrays of the stability coefficient determinant are taken equal to zero until the determinant vanishes. It then turns out that the diagonal roots correspond to the laser stability boundaries. They form the different kinds of bifurcations that segregate the above-threshold state, with three simultaneous oscillating modes, from the bistability and below-threshold states, with two and no oscillating modes, respectively. The fast optical switches and high optical memories have been designed by exploiting the bistability properties of bifurcations as reported by Perez et al (2007 Opt. Express 15 12941–8).

Jahanpanah, J.; Baiat, S.

2014-10-01

232

Economic evaluation of flying-qualities design criteria for a transport configured with relaxed static stability  

NASA Technical Reports Server (NTRS)

Direct constrained parameter optimization was used to optimally size a medium range transport for minimum direct operating cost. Several stability and control constraints were varied to study the sensitivity of the configuration to specifying the unaugmented flying qualities of transports designed to take maximum advantage of relaxed static stability augmentation systems. Additionally, a number of handling qualities related design constants were studied with respect to their impact on the design.

Sliwa, S. M.

1980-01-01

233

Evaluation of the physical properties, bulk density and aggregate stability of potential substrates in quarry restoration.  

NASA Astrophysics Data System (ADS)

Quarrying activity entails significant environmental impact affecting the soil, water, plants, landscape, etc. One of the most important impacts is the loss of the productive layer of the soil and its vegetation cover. However, mining activities are absolutely necessary for human development; keeping them sustainable implicates looking for viable solutions for the restoration of these areas to prevent degradation during and after the exploitation period. The aim of this study was to evaluate different substrates obtained from different mixes of sewage sludge and different mine spoils, to check how they are effective in quarry restoration, and to establish good practises in mining restoration. Also, the study tried to approach two refuses, one deriving from mining activity, as are the mine spoils that need to be reused for their valorisation, and the other, sewage sludge, obtained in the water depuration process to acquire a cheap substrate for soil rehabilitation. This preliminary work, which is included in a larger study, shows the results obtained from two physical properties studied, bulk density and aggregate stability, as key properties in the substrate structure for use in mining area restoration. Two doses of composted sewage sludge (30 and 90 Tm/Ha), both very rich in calcium carbonate, were applied to two different mine spoils under lab conditions. The first material, of poor quality, originated from the acquisition of arid particles in crushed limestone (Z). It is characterized by stable ''coarse elements'' predominance (up to 75% of its weight), and by the presence of elevated percentages of sand. The other waste material tested comes from limestone extraction (basically formed by the levels of interspersed non-limestone materials and the remains of stripped soils (D)). The results show that the high dose of sewage sludge applied to a mix of the two mine spoils significantly increased the percentage of stable aggregates by more than 50% than the control (the same mix without sewage sludge) and also produced an important decrease in the bulk density with respect to the control. This substrate could be a good material for use in quarry restoration.

Jordan, M.; Garcia-Orenes, F.; Mataix-Solera, J.; Garcia-Sanchez, E.

2012-04-01

234

Laboratory evaluation of the pointing stability of the ASPS Vernier System  

NASA Technical Reports Server (NTRS)

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. A simulated zero-G suspension was used to support the test payload in the laboratory. The AVS and the suspension were modelled and incorporated into a simulation of the laboratory test. Error sources were identified and pointing stability sensitivities were determined via simulation. Statistical predictions of laboratory test performance were derived and compared to actual laboratory test results. The predicted mean pointing stability during simulated shuttle disturbances was 1.22 arc seconds; the actual mean laboratory test pointing stability was 1.36 arc seconds. The successful prediction of laboratory test results provides increased confidence in the analytical understanding of the AVS magnetic bearing technology and allows confident prediction of in-flight performance. Computer simulations of ASPS, operating in the shuttle disturbance environment, predict in-flight pointing stability errors less than 0.01 arc seconds.

1980-01-01

235

Examination of Dynamic Drop Test Method for Evaluation of Hydrophobicity Stability of Polymeric Insulating Materials by CIGRE Round Robin Test  

NASA Astrophysics Data System (ADS)

To evaluate time variation of hydrophobicity of silicone rubbers used for outdoor polymeric insulators, various kinds of test methods have been suggested. CIGRE WG D1.14 conducted an international Round Robin Test (RRT) to clarify the efficiency and reproducibility of Dynamic Drop Test for the evaluation of hydrophobicity stability of the materials. Three Japanese universities were participated the RRT and had contributed much for the activity. This paper provides the outline of CIGRE RRT and typical experimental results of the Dynamic Drop test.

Homma, Hiroya; Nagao, Masayuki; Matsumoto, Takaie; Otsubo, Masahisa; Tokoro, Tetsuro

236

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...stability. (a) The frequency stability of the transmitter...ppm) of the center frequency over a temperature variation...Celsius at normal supply voltage, and over a variation...requirement to vary supply voltage. (c) It is acceptable...transmitter to meet this frequency stability...

2011-10-01

237

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2013 CFR

...stability. (a) The frequency stability of the transmitter...ppm) of the center frequency over a temperature variation...Celsius at normal supply voltage, and over a variation...requirement to vary supply voltage. (c) It is acceptable...transmitter to meet this frequency stability...

2013-10-01

238

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

...stability. (a) The frequency stability of the transmitter...ppm) of the center frequency over a temperature variation...Celsius at normal supply voltage, and over a variation...requirement to vary supply voltage. (c) It is acceptable...transmitter to meet this frequency stability...

2010-10-01

239

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...stability. (a) The frequency stability of the transmitter...ppm) of the center frequency over a temperature variation...Celsius at normal supply voltage, and over a variation...requirement to vary supply voltage. (c) It is acceptable...transmitter to meet this frequency stability...

2012-10-01

240

Evaluation of miniature vacuum ultraviolet lamps for stability and operating characteristics, Lyman-Alpha task  

NASA Technical Reports Server (NTRS)

Modifications required to change the near ultraviolet source in the Optical Contamination Monitor to a source with output at or near the Lyman-Alpha hydrogen line are discussed. The effort consisted of selecting, acquiring and testing candidate miniature ultraviolet lamps with significant output in or near 121.6 nm. The effort also included selection of a miniature dc high-voltage power supply capable of operating the lamp. The power supply was required to operate from available primary power supplied by the Optical Effect Module (DEM) and it should be flight qualified or have the ability to be qualified by the user.

Hurd, W. A.

1985-01-01

241

Technological Aspects: High Voltage  

E-print Network

This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

Faircloth, D C

2013-01-01

242

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

243

Interlimb interaction and stabilization of contralateral leg in isokinetic knee evaluation  

Microsoft Academic Search

Objective: To determine if peak torque (PT) production during isokinetic knee testing is affected by the stabilization and movement patterns of the contralateral leg.Design: Repeated measure designIntervention and Main Outcome Measure: Thirty subjects participated in comparing the force outputs in relation to the movement pattern of both legs. Another group of 45 subjects volunteered to perform five maximal isokinetic extensionflexion

Seong-Woong Kang; Young-Moo Na; Jae-Ho Moon; Sae-Il Chun; Young-Ro Yoon

1997-01-01

244

Pharmaceutical Nanotechnology Enhanced solubility and stability of PEGylated liposomal paclitaxel: In vitro and in vivo evaluation  

Microsoft Academic Search

An improved PEGylated liposomal formulation of paclitaxel has been developed with the purpose of improving the solubility of paclitaxel as well as the physicochemical stability of liposome in comparison to the current Taxol® formulation. The use of 3% (v\\/v) Tween 80 in the hydration media was able to increase the solubility of drug. The addition of sucrose as a lyoprotectant

Tao Yang; Fu-De Cui; Min-Koo Choi; Jei-Won Cho; Suk-Jae Chung; Chang-Koo Shim; Dae-Duk Kim

245

The Evaluation of Strain and Stabilization in Molecules Using Isodesmic Reactions.  

ERIC Educational Resources Information Center

Isodesmic reactions are hypothetical chemical changes in which the number of bonds of a given type are retained but change in relation to one another. Discusses use of these reactions and reaction energy to measure deviations from additivity of bond energy. Also considers relationship of enthalpies to strain and resonance stability. (JM)

Fuchs, Richard

1984-01-01

246

Evaluation of Stability of Seabed around Submarine Pipeline under Seismic Loading  

Microsoft Academic Search

The liquefaction of seabed under seismic loading is one of the main reasons that govern the overall stability of submarine pipeline. In this paper, a FEM numerical analysis method on liquefaction around a buried pipeline in sandy seabed under seismic loading is presented, the advanced soil static and dynamic universal triaxial and torsional shear apparatus is employed to perform cyclic

Xiao-ling Zhang; Mao-tian Luan; Ying Guo

247

Evaluation of Thermal Stability and Glass Transition Temperature of Different Aeronautical Polymeric Composites  

Microsoft Academic Search

In this work, the thermal stability of different polymeric composite laminates used in the aeronautical field was investigated by thermogravimetric (TGA) and dynamic mechanical thermal (DMTA) analyses. Four different types of laminates manufactured by combining two epoxy resin systems (F584 and F155) and two different types of carbon fiber fabric reinforcements were examined. The mass losses of the laminates were

Jane M. F. Paiva; Michelle L. Costa; Mirabel C. Rezende

2006-01-01

248

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...

249

Evaluation of the hok/sok Killer Locus for Enhanced Plasmid Stability  

E-print Network

into an unstable plasmid. This stability locus prevents faster-growing, plas- mid-free cells from overtaking as well as genetic means (phage techniques and complementation of host auxotrophic mark- e r of hoklsok to the expression ~ e c t o r ) , ~no need for modification of the bacterial host (so the modified

Wood, Thomas K.

250

Generalizability of the limits of stability test in the evaluation of dynamic balance among older adults  

Microsoft Academic Search

Objective: Reliability of platform posturography tests is essential for the identification and treatment of balance-related disorders. The purposes of this study were to establish the reliability of the limits of stability (LOS) test and to determine the relative variance contributions from identified sources of measurement error.Design: Generalizability theory was used to calculate (1) variance estimates and percentage of variation for

Sean Clark; Debra J. Rose; Koichiro Fujimoto

1997-01-01

251

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...

252

Superfund Innovative Technology Evaluation - Demonstration Bulletin: In-Situ Soil Stabilization  

EPA Science Inventory

In-situ stabilization technology immobilizes organics and inorganic compounds in wet or dry soils by using reagents (additives) to polymerize with the soils and sludges producing a cement-like mass. Two basic components of this technology are the Geo-Con/DSM Deep Soil Mixing Sy...

253

Improving Low Voltage Ride Through Capability of Wind Generators Using Dynamic Voltage Restorer  

NASA Astrophysics Data System (ADS)

The increasing wind power integration with power grid has forced the situation to improve the reliability of wind generators for stable operation. One important problem with induction generator based wind farm is its low ride through capability to the grid voltage disturbance. Any disturbance such as voltage dip may cause wind farm outages. Since wind power contribution is in predominant percentage, such outages may lead to stability problem. The proposed strategy is to use dynamic voltage controller (DVR) to compensate the voltage disturbance. The DVR provides the wind generator the ability to remain connected in grid and improve the reliability. The voltage dips due to symmetrical and unsymmetrical faults are considered for analysis. The vector control scheme is employed for fault compensation which uses software phase locked loop scheme and park dq0 transformation technique. Extensive simulation results are included to illustrate the control and operation of DVR.

Sivasankar, Gangatharan; Suresh Kumar, Velu

2014-08-01

254

Evaluation of Native Grasses for Highway Slope Stabilization and Salt Tolerance.  

National Technical Information Service (NTIS)

The objective of this study was to evaluate grass species native to New England for potential use on roadsides. We examined salt tolerance, rooting depth, and ability to establish and survive under roadside conditions. The grasses evaluated for all charac...

B. Maynard, R. N. Brown

2010-01-01

255

Preventing Voltage Collapse with Protection Systems that Incorporate  

E-print Network

conducting research on challenges facing the electric power industry and educating the next generation and their effects on protective schemes · to develop fast and flexible schemes for assessment of voltage stability

256

Correlation and evaluation of inplane stability characteristics for an advanced bearingless main rotor  

NASA Technical Reports Server (NTRS)

A program of experimental and analytical research was performed to demonstrate the degree of correlation achieved between measured and computed rotor inplane stability characteristics. The experimental data were obtained from hover and wind tunnel tests of a scaled bearingless main rotor model. Both isolated rotor and free-hub conditions were tested. Test parameters included blade built-in cone and sweep angles; rotor inplane structural stiffness and damping; pitch link stiffness and location; and fuselage damping, inertia, and natural frequency. Analytical results for many test conditions were obtained. In addition, the analytical and experimental results were examined to ascertain the effects of the test parameters on rotor ground and air resonance stability. The results from this program are presented herein in tabular and graphical form.

Weller, W. H.

1983-01-01

257

Superconducting dynamic synchronous condenser for improved grid voltage support  

Microsoft Academic Search

Synchronous condensers are an attractive source of dynamic VARs (both inductive and capacitive) to improve system stability and maintain voltages under varying load conditions and contingencies. A synchronous condenser is a rotating machine that runs synchronized with the grid. Its field is controlled with a voltage regulator to either generate or absorb reactive power as needed by the power system.

Swam Kalsi; David Madura; Ray Howard; G. Snitchler; Tim MacDonald; Dale Bradshaw; I. Grant; M. Ingram

2003-01-01

258

Performance evaluation of cement stabilized fly ash-GBFS mixes as a highway construction material.  

PubMed

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, unconfined compressive strength (UCS) test and California Bearing Ratio (CBR) test were conducted on cement stabilized fly ash-GBFS mixes as per the Indian Standard Code of Practice. Cement content in the mix was varied from 0% to 8% at 2% intervals, whereas the slag content was varied as 0%, 10%, 20%, 30% and 40%. Test results show that an increase of either cement or GBFS content in the mixture, results in increase of maximum dry density (MDD) and decrease of optimum moisture content (OMC) of the compacted mixture. The MDD of the cement stabilized fly ash-GBFS mixture is comparably lower than that of similarly graded natural inorganic soil of sand to silt size. This is advantageous in constructing lightweight embankments over soft, compressible soils. An increase in percentage of cement in the fly ash-GBFS mix increases enormously the CBR value. Also an increase of the amount of GBFS in the fly ash sample with fixed cement content improves the CBR value of the stabilized mix. In the present study, the maximum CBR value of compacted fly ash-GBFS-cement (52:40:8) mixture obtained was 105%, indicating its suitability for use in base and sub-base courses in highway pavements with proper combinations of raw materials. PMID:18060762

Singh, S P; Tripathy, D P; Ranjith, P G

2008-01-01

259

An eco-spatial index for evaluating stabilization state of sand dunes  

NASA Astrophysics Data System (ADS)

Geomorphologies tend to categorize dunes into three major states (mobile, semi-stabilized and stabilized) based on their shape and mobility rate. However, the ecologists try to find bio-indicators that can characterize the mobility rate and the ecological features of the various dune states. Unfortunately, there are limited numbers of significant bio-indicators, if any. The aim of our study was to develop a Dune Assemblage Index (DAI) in order to indicate the affinity of annual plants and arthropods assemblages to dune mobility. The DAI values range between 0 for stabilized dunes and 1 for bare and active dunes. The index was calculated for 10 coastal dunes in Nizzanim nature reserve, located at the southern part of the Israeli Mediterranean coast, from data that were collected in the years 2006 and 2007. Generally, the lower the vegetation cover is, the higher are DAI values for both taxon groups. Generalist species tend to mask the differences between active and stabilized dunes whereas psammophiles (sand-dwelling species) tend to increase the DAI values. Additionally, the DAI may differ among dunes with the same perennial coverage due to differences in the spatial plant distribution patterns. Likewise, the DAI depends also on the distance of the dunes from rural areas, which encourage invasion of generalist species, thus decreases the DAI value. This new defined spatial index that relies on plant and animal assemblages, rather than on individual bio-indicators, can be adapted to any taxon and dune ecosystems. The use of several taxons may support better understanding of the ecosystem state of the dune.

Rubinstein, Yehonathan; Groner, Elli; Yizhaq, Hezi; Svoray, Tal; Bar (Kutiel), Pua

2013-06-01

260

Evaluation of the drain—source voltage effect on AlGaAs/InGaAs PHEMTs thermal resistance by the structure function method  

NASA Astrophysics Data System (ADS)

The effect of drain—source voltage on AlGaAs/InGaAs PHEMTs thermal resistance is studied by experimental measuring and simulation. The result shows that AlGaAs/InGaAs PHEMTs thermal resistance presents a downward trend under the same power dissipation when the drain—source voltage (VDS) is decreased. Moreover, the relatively low VDS and large drain—source current (IDS) result in a lower thermal resistance. The chip-level and package-level thermal resistance have been extracted by the structure function method. The simulation result indicated that the high electric field occurs at the gate contact where the temperature rise occurs. A relatively low VDS leads to a relatively low electric field, which leads to the decline of the thermal resistance.

Lin, Ma; Shiwei, Feng; Yamin, Zhang; Bing, Deng; Yuan, Yue

2014-09-01

261

Ab initio evaluation of intramolecular electron transfer reactions in halobenzenes and stabilized derivatives.  

PubMed

The potential energy surfaces for the fragmentation of the radical anions of p-nitrochlorobenzene and p- and m-chloroacetophenones were explored using first principle methods. The behavior of these compounds, stabilized by pi acceptors, is compared to that shown by the unsubstituted halobenzenes (PhX, X = F, Cl, Br, I). The presence of pi and sigma radical anions was inspected as well as the intramolecular electron transfer (intra-ET) from the pi to the sigma surface, responsible for the dissociation of these intermediates. The profiles obtained with the B3LYP functional in the gas phase and in the presence of a polar solvent are in agreement with the spectroscopic evidence and with the experimentally observed reactivity of the compounds under study. The stability of the radical anion of p-nitrochlorobenzene and the adiabatic and endothermic nature of its dissociation are explained. The order of the rate constants for dissociation m-chloroacetophenone < p-chloroacetophenone is interpreted on the basis of the differences in the adiabatic character of the intra-ET of both isomers which is ascribed to the nodal properties of their SOMOs. In the halobenzene family, the electronic factors responsible for the intra-ET are analyzed. The stabilization of the sigma surface exerted by the different halogens and its effect on the rate constants for dissociation are explained. PMID:14629135

Pierini, Adriana B; Vera, D Mariano A

2003-11-28

262

Evaluation of Stability of Rotating Hinge Knee Prostheses: A Biomechanical Study  

PubMed Central

Purpose. Rotating hinge knee prostheses should provide a stable situation following reconstruction. We performed a biomechanical analysis to establish the association between design of the central rotational stem (peg) and implant's stability, in a theoretical setting. Methods. Six different rotating hinge designs were tested, and three observers performed two different measurements with a custom made biomechanical apparatus and laterally directed pressure. The aim was to assign the degree of tilting of the peg within the vertical post-in channel by extending the distraction as well as the maximum amount of distraction before the peg's dislocation. An intraclass-correlation coefficient (ICC) was calculated to determine the observer's reliability. Results. Implant designs with cylindrical pegs of different lengths were superior to implant designs with conical or other shaped pegs concerning stability and maximum amount of distraction before dislocation, showing steep rising distraction-angular displacement curves. The ICC at 15?mm and 25?mm of distraction revealed high interobserver reliability (P < 0.001). Conclusion. The biomechanical analysis showed that rotating hinge prostheses with long and cylindrical pegs have the highest stability at any given amount of distraction. Designs with shorter and markedly tapered pegs may become unstable under conditions of mild joint distraction which has to be proven in future in vivo investigations. PMID:24967114

Friesenbichler, Joerg; Leithner, Andreas; Glehr, Mathias; Sadoghi, Patrick; Maurer-Ertl, Werner; Avian, Alexander

2013-01-01

263

Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: characterization and evaluation of phase stability.  

PubMed

Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation (Delta(f)G degrees) for chukanovite is -1174.4 +/- 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs. PMID:20554346

Lee, Tony R; Wilkin, Richard T

2010-07-30

264

Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: Characterization and evaluation of phase stability  

SciTech Connect

Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation ({Delta}{sub f}G{sup o}) for chukanovite is - 1174.4 {+-} 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs.

Wilkin, Richard T.; Lee, T.R. (U.S. EPA)

2010-10-22

265

Thermal stability evaluation of microstructures and mechanical properties of tungsten vanadium alloys  

NASA Astrophysics Data System (ADS)

The thermal stability is important for tungsten based alloys as plasma facing materials to survive against high heat flux in fusion reactors. In this work, the thermal stability of W-5%V alloy fabricated following a powder metallurgy route by spark plasma sintering technique has been studied. To investigate the impact of temperature on the mechanical properties and microstructures, the alloy was subjected to heat treatment for 2 h over the temperature range 900-1500°C in a pure argon furnace. The micro-hardness values of the heat treated alloys were highly stable as compared to pure tungsten. A slight decrease flexural strength was observed with increasing annealing temperature. The maximum change flexural strength at the highest treated temperature was noted about 14% lower. The morphology analyses of the crack surfaces by scanning electron microscopy did not identify a drastic change in tungsten grain size, after heat treatment. The results indicate that the addition of vanadium in tungsten improves the overall thermal stability of microstructures and mechanical properties.

Arshad, Kameel; Zhao, Ming-Yue; Yuan, Yue; Zhang, Ying; Zhou, Zhang-Jian; Lu, Guang-Hong

2014-10-01

266

Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents.  

PubMed

Angiotensin IV (AngIV: VYIHPF)-related peptides have long been recognized as procognitive agents with potential as antidementia therapeutics. Their development as useful therapeutics, however, has been limited by physiochemical properties that make them susceptible to metabolic degradation and impermeable to gut and blood-brain barriers. A previous study demonstrated that the core structural information required to impart the procognitive activity of the AngIV analog, norleucine(1)-angiotensin IV, resides in its three N-terminal amino acids, Nle-Tyr-Ile. The goal of this project was to chemically modify this tripeptide in such a way to enhance its metabolic stability and barrier permeability to produce a drug candidate with potential clinical utility. Initial results demonstrated that several N- and C-terminal modifications lead to dramatically improved stability while maintaining the capability to reverse scopolamine-induced deficits in Morris water maze performance and augment hippocampal synaptogenesis. Subsequent chemical modifications, which were designed to increase hydrophobicity and decrease hydrogen bonding, yielded an orally active, blood-barrier permeant, metabolically stabilized analog, N-hexanoic-Tyr-Ile-(6) aminohexanoic amide (dihexa), that exhibits excellent antidementia activity in the scopolamine and aged rat models and marked synaptogenic activity. These data suggest that dihexa may have therapeutic potential as a treatment of disorders, such as Alzheimer's disease, where augmented synaptic connectivity may be beneficial. PMID:23055539

McCoy, Alene T; Benoist, Caroline C; Wright, John W; Kawas, Leen H; Bule-Ghogare, Jyote M; Zhu, Mingyan; Appleyard, Suzanne M; Wayman, Gary A; Harding, Joseph W

2013-01-01

267

Evaluation of Metabolically Stabilized Angiotensin IV Analogs as Procognitive/Antidementia Agents  

PubMed Central

Angiotensin IV (AngIV: VYIHPF)–related peptides have long been recognized as procognitive agents with potential as antidementia therapeutics. Their development as useful therapeutics, however, has been limited by physiochemical properties that make them susceptible to metabolic degradation and impermeable to gut and blood-brain barriers. A previous study demonstrated that the core structural information required to impart the procognitive activity of the AngIV analog, norleucine1-angiotensin IV, resides in its three N-terminal amino acids, Nle-Tyr-Ile. The goal of this project was to chemically modify this tripeptide in such a way to enhance its metabolic stability and barrier permeability to produce a drug candidate with potential clinical utility. Initial results demonstrated that several N- and C-terminal modifications lead to dramatically improved stability while maintaining the capability to reverse scopolamine-induced deficits in Morris water maze performance and augment hippocampal synaptogenesis. Subsequent chemical modifications, which were designed to increase hydrophobicity and decrease hydrogen bonding, yielded an orally active, blood-barrier permeant, metabolically stabilized analog, N-hexanoic-Tyr-Ile-(6) aminohexanoic amide (dihexa), that exhibits excellent antidementia activity in the scopolamine and aged rat models and marked synaptogenic activity. These data suggest that dihexa may have therapeutic potential as a treatment of disorders, such as Alzheimer’s disease, where augmented synaptic connectivity may be beneficial. PMID:23055539

McCoy, Alene T.; Benoist, Caroline C.; Wright, John W.; Kawas, Leen H.; Bule-Ghogare, Jyote M.; Zhu, Mingyan; Appleyard, Suzanne M.; Wayman, Gary A.

2013-01-01

268

Voltage-clamped soft switching PWM inverter-type DC-DC converter for microwave oven and its utility AC side harmonics evaluations  

Microsoft Academic Search

A single-ended quasi-resonant zero voltage soft-switching inverter type DC-DC converter is used to drive the magnetron for a microwave oven. This converter is simple, downsizing, high efficiency and low cost in addition to simple control scheme. However, this power conversion circuit has to control its input power under a condition of ZVS in accordance with the variable frequency regulation. The

T. Matsushige; E. Miyata; M. Ishitobi; M. Nakaoka; D. Bessyo; K. Yasui; I. Hirota; H. Omori

2000-01-01

269

Technical evaluation of the proposed design modifications and technical specification changes on grid voltage degradation (Part A) for the Rancho Seco Nuclear Generating Plant  

SciTech Connect

The Rancho Seco Nuclear Generating Plant has two 4160-volt and two 480-volt Class 1E buses. The existing undervoltage protection design uses a single undervoltage relay on each 4160-volt Class 1E bus. If the voltage drops below 3534 volts (85% of 4160 volts), the undervoltage relay will energize a set of load-shedding relays. The load-shedding relays initiate the disconnection of the emergency 4160-volt buses from the off-site source, load shed the emergency 4160-volt buses, start the emergency diesel generators, and provide an enabling signal for the load-sequencing timing circuit. When the emergency diesel generator reaches the required voltage it is connected to the emergency buses and load-sequencing will begin automatically, if a safety injection (SI) signal exists. The licensee has proposed a design change to establish an automatic degraded voltage protection circuitry. The modification consists of incorporating the existing undervoltage protection scheme will consist of 3 undervoltage relays monitoring each 4160-volt emergency bus. The 3 undervoltage relays will be arranged in a 2-out-of-3 coincident logic with a setpoint of 3771 volts +- 38 volts (90.6% of 4160 volts) with a time delay of 12 seconds +- 1.2 seconds.

White, R.L.

1980-10-01

270

Rationale, principles and experimental evaluation of the concept of soft stabilization.  

PubMed

The apparent clinical success of spinal stabilization methods that restrict rather than abolish movement in relieving mechanical back pain indicates that the concept of the aetiology of back pain should be reviewed. Further understanding of how degeneration affects disc biomechanics, and an understanding of how current soft stabilization systems alters them, may allow us to define more precisely what are the essential requirements of an ideal soft stabilization system. It appears that abnormal patterns of loading rather than abnormal movement are the reason that disc degeneration causes back pain in some patients. Abnormal load transmission is the principal cause of pain in osteoarthritic joints, and both osteotomy and, indeed, joint replacement succeed because they alter the load transmission across the joint. This concept is supported by the fact that abnormal patterns of stress distribution measured across the disc correlate with painful discs on discography. Clinically, it is often noted that back pain is primarily related to position or posture, rather than movement of the lumbar spine. Clinical success after solid fusion is unpredictable because it does not necessarily prevent painful loading across the disc, and also it may interfere with maintenance of sagittal balance in varying postures. The Graf ligament restricted flexion, and was modestly successful. It unfortunately increased the load over the posterior annulus. The Dynesys system reduces movement both in flexion and extension, and appears to be more successful. However, often it also unloads the disc to a degree that is unpredictable. The authors believe that this unloading of the disc is an important feature of a flexible stabilization system. A new a design of a flexible stabilization system has recently been described in an in vitro study, which unloads the disc by introduction of a load-sharing fulcrum near the axis of movement together with an elastic posterior ligament. This design produces maximal unloading of the disc, whilst allowing a restricted range of movement, which serves the important purpose of allowing the patient to maintain sagittal balance in varying postures. PMID:12384745

Mulholland, Robert C; Sengupta, Dilip K

2002-10-01

271

Evaluation on the stability of Hg in ABS disk CRM during measurements by wavelength dispersive X-ray fluorescence spectrometry.  

PubMed

The stability of Hg in an acrylonitrile-butadiene-styrene disk certified reference material (ABS disk CRM, NMIJ CRM 8116-a) during measurements by wavelength dispersion X-ray fluorescence (WD-XRF) analysis was evaluated in this study. The XRF intensities of Hg (L(?)) and Pb (L(?)) as well as the XRF intensity ratios of Hg (L(?))/Pb (L(?)) observed under different X-ray tube current conditions as well as their irradiation time were examined to evaluate the stability of Hg in the ABS disk CRM. The observed XRF intensities and the XRF intensity ratios for up to 32 h of measurements under 80 mA of X-ray tube current condition were constant, even though the surface of the ABS disk CRM was charred by the X-ray irradiation with high current for a long time. Moreover, the measurements on Hg and Pb in the charred disks by an energy dispersive XRF (ED-XRF) spectrometer showed constant XRF intensity ratios of Hg (L(?))/Pb (L(?)). From these results, Hg in the ABS disk CRM was evaluated to be sufficiently stable for XRF analysis. PMID:23149612

Ohata, Masaki; Kidokoro, Toshihiro; Hioki, Akiharu

2012-01-01

272

[Stability evaluation of chemical compositions of Rhizoma gastrodiae with 60Co-? irradiation by high performance liquid chromatography].  

PubMed

The main chromatographic fingerprint peaks of Rhizoma gastrodiae were established for evaluating the stability of chemical compositions of Rhizoma gastrodiae with 60Co-gamma irradiation to control the dosage of 60Co-gamma irradiation sterilization by high performance liquid chromatography (HPLC). Eight Rhizoma gastrodiae samples were analyzed. The chromatographic fingerprints of Rhizoma gastrodiae were constructed with 14 common fingerprint peaks, and its 10 main peaks were identified using the similarity evaluation system of chromatographic fingerprints of traditional Chinese medicine (version 2004 A) recommended by State Food and Drug Administration of China. The relative standard deviations of the peak areas of the 10 main peaks were used to evaluate the stability of corresponding chemical compositions of Rhizoma gastrodiae with 60Co-gamma irradiation. The results showed that the compositions of 3 of the 10 main peaks were influenced and a good relationship was obtained between the influence and 60Co-gamma irradiation doses for the eight Rhizoma gastrodiae samples. Some chemical components of Rhizoma gastrodiae weren't steady after 60Co-gamma irradiation, so a low dosage should be selected for 60Co-gamma irradiation sterilization. PMID:22500449

Yang, Xiaorong; Huang, Min; Liu, Sujun; Song, Jiuhua

2011-12-01

273

Improving voltage disturbance rejection for variable-speed wind turbines  

Microsoft Academic Search

In this paper, the effect of voltage dips on variable-speed wind turbines using voltage source converters (VSCs) is treated. Three different current controllers for the VSC are described and implemented. Their performance is evaluated when the converter is subject to different types of voltage dips. Both simulated and measured dips are used. The effect of the phase-angle jump of the

Giuseppe Saccomando; Jan Svensson; Ambra Sannino

2002-01-01

274

An evaluation of color stability of reinforced composite resin compared with dental porcelain in commonly consumed beverages.  

PubMed

The effect of tea, cola, orange juice, and distilled water on the color stability of a porcelain (VITA VMK 95) and a reinforced composite rein (GC Gradia) was evaluated. Standardized specimens for each material was prepared. Specimens from each group were immersed in staining solutions at 50 degree Celsius for 30 days. Tea caused the most significant color change. DeltaE of all of the materials was changed after the immersion in all of the staining solutions during the experimental process. PMID:18856169

Ghahramanloo, Ahmad; Madani, Azam Sadat; Sohrabi, Keyvan; Sabzevari, Saeed

2008-09-01

275

Application of maltodextrin and gum Arabic in microencapsulation of saffron petal's anthocyanins and evaluating their storage stability and color.  

PubMed

In this work, anthocyanin stability and color of encapsulated freeze-dried saffron petal's extract with various matrices consisting gum Arabic (AG) and maltodextrin (M7 and M20) were studied. Total anthocyanins of powders and color parameters (a*, b*, L*, C, H° and TCD) were measured immediately after production and during storage up to 10 weeks by pH differential method and computer vision, respectively. Different compounds of wall materials did not show any significant differences in terms of stabilizing anthocyanins (P<0.01) and no significant decrease in anthocyanin content of the powders was observed after storage. The efficiency order of wall materials considering total color differences (TCD) was AG>M20>M7. By evaluating 3D surface and Cox trace plots it was revealed that wall formulas which had the lowest amount of AG and highest amounts of M20 and M7 showed the lowest total color differences after storage (P<0.05). To conclude, microencapsulation by freeze drying could be recommended as a suitable method for stabilizing anthocyanins of saffron petal's extract. PMID:24708952

Mahdavee Khazaei, K; Jafari, S M; Ghorbani, M; Hemmati Kakhki, A

2014-05-25

276

Intervertebral disc rehydration after lumbar dynamic stabilization: magnetic resonance image evaluation with a mean followup of four years.  

PubMed

Objective. To compare the clinical and radiographic outcomes in patients of different ages who underwent the Dynesys stabilization. Methods. This retrospective study included 72 patients (mean age 61.4 years) with one- or two-level lumbar spinal stenosis who underwent laminectomy and the Dynesys (Zimmer Spine, Minneapolis) dynamic stabilization system. Thirty-seven patients were younger than 65-year old while the other 35 were older. Mean followup was 46.7 months. Pre- and postoperative radiographic and clinical evaluations were analyzed. Results. The mean calibrated disc signal (CDS) at the index level was significantly improved from 60.2 ± 25.2 preoperatively to 66.9 ± 26.0 postoperatively (P > 0.001). Screw loosening occurred in 22.2% of patients and 5.1% of screws. The improvement in CDS at index level was seen to be significant in younger patients but not in older patients. Overall, the mean visual analogue scale (VAS) of back pain, VAS of leg pain, and the Oswestry disability index (ODI) scores improved significantly after operation. There were no significant differences in pre- and postoperative VAS and ODI and screw loosening rates between the younger and older patients. Conclusions. There is significant clinical improvement after laminectomy and dynamic stabilization for symptomatic lumbar spinal stenosis. Intervertebral disc rehydration was seen in younger patients. PMID:23738082

Fay, Li-Yu; Wu, Jau-Ching; Tsai, Tzu-Yun; Tu, Tsung-Hsi; Wu, Ching-Lan; Huang, Wen-Cheng; Cheng, Henrich

2013-01-01

277

Intervertebral Disc Rehydration after Lumbar Dynamic Stabilization: Magnetic Resonance Image Evaluation with a Mean Followup of Four Years  

PubMed Central

Objective. To compare the clinical and radiographic outcomes in patients of different ages who underwent the Dynesys stabilization. Methods. This retrospective study included 72 patients (mean age 61.4 years) with one- or two-level lumbar spinal stenosis who underwent laminectomy and the Dynesys (Zimmer Spine, Minneapolis) dynamic stabilization system. Thirty-seven patients were younger than 65-year old while the other 35 were older. Mean followup was 46.7 months. Pre- and postoperative radiographic and clinical evaluations were analyzed. Results. The mean calibrated disc signal (CDS) at the index level was significantly improved from 60.2 ± 25.2 preoperatively to 66.9 ± 26.0 postoperatively (P > 0.001). Screw loosening occurred in 22.2% of patients and 5.1% of screws. The improvement in CDS at index level was seen to be significant in younger patients but not in older patients. Overall, the mean visual analogue scale (VAS) of back pain, VAS of leg pain, and the Oswestry disability index (ODI) scores improved significantly after operation. There were no significant differences in pre- and postoperative VAS and ODI and screw loosening rates between the younger and older patients. Conclusions. There is significant clinical improvement after laminectomy and dynamic stabilization for symptomatic lumbar spinal stenosis. Intervertebral disc rehydration was seen in younger patients. PMID:23738082

Fay, Li-Yu; Wu, Jau-Ching; Tsai, Tzu-Yun; Huang, Wen-Cheng; Cheng, Henrich

2013-01-01

278

Voltage balanced multilevel voltage source converter system  

DOEpatents

Disclosed is a voltage balanced multilevel converter for high power AC applications such as adjustable speed motor drives and back-to-back DC intertie of adjacent power systems. This converter provides a multilevel rectifier, a multilevel inverter, and a DC link between the rectifier and the inverter allowing voltage balancing between each of the voltage levels within the multilevel converter. The rectifier is equipped with at least one phase leg and a source input node for each of the phases. The rectifier is further equipped with a plurality of rectifier DC output nodes. The inverter is equipped with at least one phase leg and a load output node for each of the phases. The inverter is further equipped with a plurality of inverter DC input nodes. The DC link is equipped with a plurality of rectifier charging means and a plurality of inverter discharging means. The plurality of rectifier charging means are connected in series with one of the rectifier charging means disposed between and connected in an operable relationship with each adjacent pair of rectifier DC output nodes. The plurality of inverter discharging means are connected in series with one of the inverter discharging means disposed between and connected in an operable relationship with each adjacent pair of inverter DC input nodes. Each of said rectifier DC output nodes are individually electrically connected to the respective inverter DC input nodes. By this means, each of the rectifier DC output nodes and each of the inverter DC input nodes are voltage balanced by the respective charging and discharging of the rectifier charging means and the inverter discharging means. 15 figs.

Peng, F.Z.; Lai, J.S.

1997-07-01

279

Photoacoustic Evaluation of Sunscreen Stability: Wind, Water, and the Influence of the Substrates  

NASA Astrophysics Data System (ADS)

Sunscreens are designed to protect the skin against damage caused by excessive exposure to ultraviolet radiation—ranging from sunburns and premature aging to skin cancer. The photoacoustic (PA) technique can be employed to analyze topical products like sunscreens. This study aims to characterize the response of commercially available sunscreens subjected to wind and water exposure and applied in two different substrates: pig ear skin and artificial skin (Vitroskin ® ). The light source of the experimental setup was a tungsten lamp (250 W) mechanically modulated at 11 Hz. Measurements employed a double-faced, open PA cell with a sapphire window on one side; the opposite side was closed by the sample itself. Initial measurements were performed: (i) before sunscreen application in the sample, and (ii) immediately after sunscreen application. The sample was then immersed in a saline solution for 3 s and exposed to the wind under ambient temperature for 30 min; after that, a new measurement was performed. This cycle was repeated each 30 min, up to a total time of 2 h. Fitting curves (Boltzmann type) for the time evolution of the PA signal were generated with the software Origin ® . After measurements, Vitroskin ® was found to be a more adequate substrate than pig skin in the analysis of sunscreen stability. Results obtained indicate that the stability is not dependent on the sun protection factor; measurements performed in Vitroskin ® show good stability of the topically applied products for up to 2 h after sunscreen application, with a fall of less than 40 % in the PA signal amplitude even after exposure to external agents (wind and water).

Pinto, S. B.; Barja, P. R.

2012-11-01

280

Experimental Evaluation of Journal Bearing Stability and New Gas Wave Bearing Materials  

NASA Technical Reports Server (NTRS)

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 clearance. Three waves were created on the inner surface by deforming the bearing sleeve. The ratio of the wave amplitude to the radial clearance (the wave amplitude ratio) was varied from zero to 0.3.

Keith, Theo G., Jr.; Dimofte, Florin

1998-01-01

281

Organic solar cells: evaluation of the stability of P3HT using time-delayed degradation  

NASA Astrophysics Data System (ADS)

Despite the fact that the performance of organic solar cells is generally susceptible to degradation by moisture exposure, there has been suggestion that the photoactive layer (P3HT) is surprisingly resilient. This work attempts to confirm the stability of P3HT as an organic solar cell material by deliberately introducing water into the photoactive layer. A dramatic step drop in device performance during cell characterization is observed approximately one day after the device has been fabricated. The time-delayed step drop in output efficiency strongly suggests that moisture has little effect on the P3HT conducting polymer.

Poh, Chung-How; Poh, Chung-Kiak; Bryant, Glenn; Belcher, Warwick; Dastoor, Paul

2011-12-01

282

Application of matrix singular value properties for evaluating gain and phase margins of multiloop systems. [stability margins for wing flutter suppression and drone lateral attitude control  

NASA Technical Reports Server (NTRS)

A stability margin evaluation method in terms of simultaneous gain and phase changes in all loops of a multiloop system is presented. A universal gain-phase margin evaluation diagram is constructed by generalizing an existing method using matrix singular value properties. Using this diagram and computing the minimum singular value of the system return difference matrix over the operating frequency range, regions of guaranteed stability margins can be obtained. Singular values are computed for a wing flutter suppression and a drone lateral attitude control problem. The numerical results indicate that this method predicts quite conservative stability margins. In the second example if the eigenvalue magnitude is used instead of the singular value, as a measure of nearness to singularity, more realistic stability margins are obtained. However, this relaxed measure generally cannot guarantee global stability.

Mukhopadhyay, V.; Newsom, J. R.

1982-01-01

283

Homogeneity and stability of materials distributed within the wageningen evaluating programmes for analytical laboratories  

Microsoft Academic Search

Participation in laboratory evaluating programmes (Proficiency Testing schemes) is becoming increasingly important, especially for accredited laboratories. The Wageningen Agricultural University meets this need by organizing several world?wide international laboratory evaluating programmes on chemical analysis of soils (ISE), plants OPE), manure, refuses (MARSEP) and sediments (SETOC). Since 1995, the existing programmes have been placed under an umbrella organization called WEPAL: Wageningen

D. van Dijk; V. J. G. Houba

2000-01-01

284

Generating Electrical Voltage  

NSDL National Science Digital Library

Teachers' Domain presents this interactive lesson designed to help students "learn how a generator converts mechanical energy into electrical energy. Investigate the principle of magnetic induction by moving a conductor through a magnetic field to see how voltage is generated." The lesson is divided into three major sections: How Do Generators Work?, What Factors Influence Voltage Strength?, and What Determines Voltage Polarity? There are plenty of animations to help students visualize the processes at work in electricity generation. On the site, visitors will also find a supplemental background essay, discussion questions, and standards alignment from Teachers' Domain.

2010-10-06

285

Critical evaluation of the unsteady aerodynamics approach to dynamic stability at high angles of attack  

NASA Technical Reports Server (NTRS)

Bifurcation theory is used to analyze the nonlinear dynamic stability characteristics of an aircraft subject to single-degree-of-freedom. The requisite moment of the aerodynamic forces in the equations of motion is shown to be representable in a form equivalent to the response to finite amplitude oscillations. It is shown how this information can be deduced from the case of infinitesimal-amplitude oscillations. The bifurcation theory analysis reveals that when the bifurcation parameter is increased beyond a critical value at which the aerodynamic damping vanishes, new solutions representing finite amplitude periodic motions bifurcate from the previously stable steady motion. The sign of a simple criterion, cast in terms of aerodynamic properties, determines whether the bifurcating solutions are stable or unstable. For the pitching motion of flat-plate airfoils flying at supersonic/hypersonic speed and for oscillation of flaps at transonic speed, the bifurcation is subcritical, implying either the exchanges of stability between steady and periodic motion are accompanied by hysteresis phenomena, or that potentially large aperiodic departures from steady motion may develop.

Hui, W. H.

1985-01-01

286

Analysis and test evaluation of the dynamic response and stability of three advanced turboprop models  

NASA Technical Reports Server (NTRS)

Results of dynamic response and stability wind tunnel tests of three 62.2 cm (24.5 in) diameter models of the Prop-Fan, advanced turboprop, are presented. Measurements of dynamic response were made with the rotors mounted on an isolated nacelle, with varying tilt for nonuniform inflow. One model was also tested using a semi-span wing and fuselage configuration for response to realistic aircraft inflow. Stability tests were performed using tunnel turbulence or a nitrogen jet for excitation. Measurements are compared with predictions made using beam analysis methods for the model with straight blades, and finite element analysis methods for the models with swept blades. Correlations between measured and predicted rotating blade natural frequencies for all the models are very good. The IP dynamic response of the straight blade model is reasonably well predicted. The IP response of the swept blades is underpredicted and the wing induced response of the straight blade is overpredicted. Two models did not flutter, as predicted. One swept blade model encountered an instability at a higher RPM than predicted, showing predictions to be conservative.

Bansal, P. N.; Arseneaux, P. J.; Smith, A. F.; Turnberg, J. E.; Brooks, B. M.

1985-01-01

287

Preparation, characterization, stability and in vitro-in vivo evaluation of pellet-layered Simvastatin nanosuspensions.  

PubMed

The objective of the present study was to develop stable pellets-layered Simvastatin (SIM) nanosuspensions with improved dissolution and bioavailability. The nanosuspensions were prepared with 7% HPMC, antioxidant 0.03% butylated hydroxyanisole and 0.2% citric acid (m/v) by low temperature grinding. After that, SDS with SIM was in a ratio of 1:5 (m/m), was evenly dispersed in the nanosuspensions. Then, they were layered on the surface of sugar pellets. The mean particle size of the SIM nanosuspensions was 0.74 µm, and 80.6% of the particles was below 1 µm in size. The pellets could re-disperse into nanoparticle status in the dissolution medium. In 900?mL pH 7.0 phosphate solutions, the dissolution of the layered pellets was better than that of commercial tablets. Also, nearly 100% of the drug dissolved from the pellets within 5?min under sink conditions. During the stability studies, SIM pellets exhibited good physical and chemical stability. The relative bioavailability of SIM and Simvastatin ?-hydroxy acid (SIMA) for nanosuspensions layered pellets compared with commercial tablets was 117% and 173%, respectively. The bioavailability of SIMA was improved significantly (p < 0.05), confirming the improvement of bioavailability. Thus, the present study demonstrates that the pellet-layered SIM nanosuspensions improved both the dissolution and bioavailability of SIM. PMID:23046250

Luo, Yanfei; Xu, Lishuang; Tao, Xiaoguang; Xu, Ming; Feng, Jia; Tang, Xing

2013-07-01

288

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Frequency stability. 5.101 Section...Requirements § 5.101 Frequency stability. Experimental...remain within the authorized frequency band under normal operating...degrees Celsius with an input voltage variation of 85% to...

2013-10-01

289

Single Event Transients in Low Voltage Dropout (LVDO) Voltage Regulators  

NASA Technical Reports Server (NTRS)

This viewgraph presentation reviews the use of Low Voltage Dropout (LVDO) Voltage Regulators in environments where heavy ion induced Single Event Transients are a concern to the designers.Included in the presentation are results of tests of voltage regulators.

LaBel, K.; Karsh, J.; Pursley, S.; Kleyner, I.; Katz, R.; Poivey, C.; Kim, H.; Seidleck, C.

2006-01-01

290

[Evaluation of the effect of the sodium hyaluronate ophthalmic solution on tear film stability--non-contact specular microscopic evaluation].  

PubMed

Sodium hyaluronate solution is known to relieve various dry eye symptoms by suppressing the breakup of the preocular tear film. Using tear film stability as a parameter, we examined in 12 volunteers the time and concentration-dependent effects of sodium hyaluronate on their short precorneal tear film breakup time (BUT, 10 sec. or less) at a low tear volume (15 mm or less by using the phenol red thread test). Each subject underwent four separate study periods, receiving one of the following four ophthalmic solutions during each period: 0.05, 0.1, 0.3% w/v sodium hyaluronate (molecular weight, about 1,000,000) or the vehicle alone. BUT was measured non-invasively using a non-contact specular microscope before and 5, 15, 30, 60, 120, and 180 minutes after drug application. While BUT was not significantly prolonged after instilling either the vehicle or 0.05% solution, it was significantly increased at all times after applying either 0.1% or 0.3% solution, as compared to preinstillation. These results indicate that sodium hyaluronate solutions at concentrations of at least 0.1% can be effective in alleviating symptoms of dry eye. PMID:8368180

Hamano, T; Horimoto, K; Lee, M; Komemushi, S

1993-08-01

291

An evaluation of variables affecting the stability and performance of down-flow anaerobic fixed bed reactors treating piggery wastewater.  

PubMed

The influence of the most important variables on the stability and performance of down-flow anaerobic fixed bed reactors treating piggery wastewater after primary sedimentation was evaluated at HRT in the range of 1-6 d and influent substrate concentration in the range of 2 to 12 g TCOD l(-1). The effect of HRT was more pronounced compared to that of influent strength. An increase in the HRT increased the process stability and process performance at different influent strengths. TCOD, SCOD, BOD5 TSS, organic nitrogen (N) and Orthophosphate (P) removals increased with the HRT, independently of the initial substrate concentration (S0). The increase in S0 brought about an increase in the attached biomass concentration (X) at the end of the experiment. Two empirical models based on the individual effect of HRT, X and S0 were evaluated and found to be adequate to describe the influence of these variables on the process performance. The first model took all the above-mentioned variables into consideration while the second model was simplified and based on the use of HRT as the only independent variable. The results obtained by using both models were found to be similar. This demonstrated that independently of the characteristics of the operation, the behaviour and performance of the reactors were comparable. The methane yield coefficient was found to be 0.3371 methane g(-1) TCOD removed. PMID:16457178

Sánchez, E; Borja, R; Travieso, L; Martín, A; Colmenarejo, M F; Nikolaeva, S

2006-01-01

292

Electrical safety for high voltage arrays  

NASA Technical Reports Server (NTRS)

A number of key electrical safety requirements for the high voltage arrays of central station photovoltaic power systems are explored. The suitability of representative industrial DC power switchgear for control and fault protection was evaluated. Included were AC/DC circuit breakers, electromechanical contactors and relays, load interruptors, cold disconnect devices, sectionalizing switches, and high voltage DC fuses. As appropriate, steady state and transient characteristics were analyzed. Failure modes impacting upon operation and maintenance safety were also identified, as were the voltage withstand and current interruption levels.

Marshall, N. A.

1983-01-01

293

Analysis of NSTX TF Joint Voltage Measurements  

SciTech Connect

This report presents findings of analyses of recorded current and voltage data associated with 72 electrical joints operating at high current and high mechanical stress. The analysis goal was to characterize the mechanical behavior of each joint and thus evaluate its mechanical supports. The joints are part of the toroidal field (TF) magnet system of the National Spherical Torus Experiment (NSTX) pulsed plasma device operating at the Princeton Plasma Physics Laboratory (PPPL). Since there is not sufficient space near the joints for much traditional mechanical instrumentation, small voltage probes were installed on each joint and their voltage monitoring waveforms have been recorded on sampling digitizers during each NSTX ''shot''.

Woolley R

2005-10-07

294

Threshold voltage extraction circuit  

E-print Network

A novel optimally self-biasing MOSFET threshold-voltage (V[]) extractor circuit is presented. It implements the most popular industrial extraction algorithm of biasing a saturated MOSFET to the linear portion of its [] versus [] characteristic...

Hoon, Siew Kuok

2012-06-07

295

Improving membrane voltage measurements  

E-print Network

as fluorescence resonance energy transfer (FRET) donor and acceptor to develop a voltage sensor, named Mermaid activities in cultured excitable cells. Notably, Mermaid has fast on-off kinetics at warm (B33 1C

Cai, Long

296

High voltage power supply  

NASA Technical Reports Server (NTRS)

A high voltage power supply is formed by three discrete circuits energized by a battery to provide a plurality of concurrent output signals floating at a high output voltage on the order of several tens of kilovolts. In the first two circuits, the regulator stages are pulse width modulated and include adjustable ressistances for varying the duty cycles of pulse trains provided to corresponding oscillator stages while the third regulator stage includes an adjustable resistance for varying the amplitude of a steady signal provided to a third oscillator stage. In the first circuit, the oscillator, formed by a constant current drive network and a tuned resonant network included a step up transformer, is coupled to a second step up transformer which, in turn, supplies an amplified sinusoidal signal to a parallel pair of complementary poled rectifying, voltage multiplier stages to generate the high output voltage.

Ruitberg, A. P.; Young, K. M. (inventors)

1985-01-01

297

Imaging voltage in neurons  

PubMed Central

In the last decades, imaging membrane potential has become a fruitful approach to study neural circuits, especially in invertebrate preparations with large, resilient neurons. At the same time, particularly in mammalian preparations, voltage imaging methods suffer from poor signal to noise and secondary side effects, and they fall short of providing single-cell resolution when imaging of the activity of neuronal populations. As an introduction to these techniques, we briefly review different voltage imaging methods (including organic fluorophores, SHG chromophores, genetic indicators, hybrid, nanoparticles and intrinsic approaches), and illustrate some of their applications to neuronal biophysics and mammalian circuit analysis. We discuss their mechanisms of voltage sensitivity, from reorientation, electrochromic or electro-optical phenomena, to interaction among chromophores or membrane scattering, and highlight their advantages and shortcomings, commenting on the outlook for development of novel voltage imaging methods. PMID:21220095

Peterka, Darcy S.; Takahashi, Hiroto; Yuste, Rafael

2011-01-01

298

High voltage pulse generator  

NASA Technical Reports Server (NTRS)

Generator has an improved circuit for generating a controllable, high voltage spark having a constant known energy output. It can be used for testing the flash and ignition characteristics of nonmetallic materials in a controlled gas environment.

Pippen, D. L.

1969-01-01

299

Josephson voltage standards  

Microsoft Academic Search

This paper reviews the present state of modern Josephson voltage standards. The presentation focuses on conventional dc standards based on underdamped superconductor-insulator-superconductor junctions and programmable standards based on overdamped superconductor-insulator-normal conductor-insulator-superconductor junctions. The current developments of ac standards on the basis of pulse-driven arrays and single flux quantum-based voltage multipliers are briefly summarized.

Johannes Kohlmann; Ralf Behr; Torsten Funck

2003-01-01

300

CT Angiography of the Head-and-Neck Vessels Acquired with Low Tube Voltage, Low Iodine, and Iterative Image Reconstruction: Clinical Evaluation of Radiation Dose and Image Quality  

PubMed Central

Objectives We aimed to assess the effectiveness and feasibility of head-and-neck Computed Tomography Angiography (CTA) with low tube voltage and low concentration contrast media combined with iterative reconstruction algorithm. Methods 92 patients were randomly divided into group A and B: patients in group A received a conventional scan with 120 kVp and contrast media of 320 mgI/ml. Patients in group B, 80 kVp and contrast media of 270 mgI/ml were used along with iterative reconstruction algorithm techniques. Image quality, radiation dose and the effectively consumed iodine amount between two groups were analyzed and compared. Results Image quality of CTA of head-and-neck vessels obtained from patients in group B was significantly improved quantitatively and qualitatively. In addition, CT attenuation values in group B were also significantly higher than that in group A (p<0.001). Furthermore, compared with the protocol whereby 120 kVp and 320 mgI/dl were administrated, the mean radiation dose and consumed iodine amount in protocol B were also reduced by 50% and 15.6%, respectively (p<0.001). Conclusions With the help of iterative reconstruction algorithm techniques, the head-and-neck CTA with diagnostic quality can be adequately acquired with low tube voltage and low concentration contrast media. This method could be potentially extended to include any part of the body to reduce the risks related to ionizing radiation. PMID:24339936

Zhang, Wei-lan; Li, Min; Zhang, Bo; Geng, Hai-yang; Liang, Yin-qiang; Xu, Ke; Li, Song-bai

2013-01-01

301

High voltage DC power supply  

DOEpatents

A high voltage DC power supply having a first series resistor at the output for limiting current in the event of a short-circuited output, a second series resistor for sensing the magnitude of output current, and a voltage divider circuit for providing a source of feedback voltage for use in voltage regulation is disclosed. The voltage divider circuit is coupled to the second series resistor so as to compensate the feedback voltage for a voltage drop across the first series resistor. The power supply also includes a pulse-width modulated control circuit, having dual clock signals, which is responsive to both the feedback voltage and a command voltage, and also includes voltage and current measuring circuits responsive to the feedback voltage and the voltage developed across the second series resistor respectively.

Droege, Thomas F. (Batavia, IL)

1989-01-01

302

High voltage DC power supply  

DOEpatents

A high voltage DC power supply having a first series resistor at the output for limiting current in the event of a short-circuited output, a second series resistor for sensing the magnitude of output current, and a voltage divider circuit for providing a source of feedback voltage for use in voltage regulation is disclosed. The voltage divider circuit is coupled to the second series resistor so as to compensate the feedback voltage for a voltage drop across the first series resistor. The power supply also includes a pulse-width modulated control circuit, having dual clock signals, which is responsive to both the feedback voltage and a command voltage, and also includes voltage and current measuring circuits responsive to the feedback voltage and the voltage developed across the second series resistor respectively. 7 figs.

Droege, T.F.

1989-12-19

303

Low-voltage gyrotrons  

SciTech Connect

For a long time, the gyrotrons were primarily developed for electron cyclotron heating and current drive of plasmas in controlled fusion reactors where a multi-megawatt, quasi-continuous millimeter-wave power is required. In addition to this important application, there are other applications (and their number increases with time) which do not require a very high power level, but such issues as the ability to operate at low voltages and have compact devices are very important. For example, gyrotrons are of interest for a dynamic nuclear polarization, which improves the sensitivity of the nuclear magnetic resonance spectroscopy. In this paper, some issues important for operation of gyrotrons driven by low-voltage electron beams are analyzed. An emphasis is made on the efficiency of low-voltage gyrotron operation at the fundamental and higher cyclotron harmonics. These efficiencies calculated with the account for ohmic losses were, first, determined in the framework of the generalized gyrotron theory based on the cold-cavity approximation. Then, more accurate, self-consistent calculations for the fundamental and second harmonic low-voltage sub-THz gyrotron designs were carried out. Results of these calculations are presented and discussed. It is shown that operation of the fundamental and second harmonic gyrotrons with noticeable efficiencies is possible even at voltages as low as 5-10 kV. Even the third harmonic gyrotrons can operate at voltages about 15 kV, albeit with rather low efficiency (1%-2% in the submillimeter wavelength region).

Glyavin, M. Yu.; Zavolskiy, N. A.; Sedov, A. S. [Institute of Applied Physics RAS, N. Novgorod 603600 (Russian Federation); Nusinovich, G. S. [IREAP, University of Maryland, College Park, Maryland 20742-3511 (United States)

2013-03-15

304

Metastable Electrical Characteristics of Polycrystalline Thin-Film Photovoltaic Modules upon Exposure and Stabilization: Preprint  

Microsoft Academic Search

The significant features of a series of stabilization experiments conducted at the National Renewable Energy Laboratory (NREL) between May 2009 and the present are reported. These experiments evaluated a procedure to stabilize the measured performance of thin-film polycrystalline cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) thin-film photovoltaic (PV) modules. The current-voltage (I-V) characteristics of CdTe and CIGS thin-film

C. A. Deline; J. A. del Cueto; D. S. Albin; S. R. Rummel

2011-01-01

305

Understanding Skill in EVA Mass Handling. Volume 4; An Integrated Methodology for Evaluating Space Suit Mobility and Stability  

NASA Technical Reports Server (NTRS)

The empirical investigation of extravehicular activity (EVA) mass handling conducted on NASA's Precision Air-Bearing Floor led to a Phase I SBIR from JSC. The purpose of the SBIR was to design an innovative system for evaluating space suit mobility and stability in conditions that simulate EVA on the surface of the Moon or Mars. The approach we used to satisfy the Phase I objectives was based on a structured methodology for the development of human-systems technology. Accordingly the project was broken down into a number of tasks and subtasks. In sequence, the major tasks were: 1) Identify missions and tasks that will involve EVA and resulting mobility requirements in the near and long term; 2) Assess possible methods for evaluating mobility of space suits during field-based EVA tests; 3) Identify requirements for behavioral evaluation by interacting with NASA stakeholders;.4) Identify necessary and sufficient technology for implementation of a mobility evaluation system; and 5) Prioritize and select technology solutions. The work conducted in these tasks is described in this final volume of the series on EVA mass handling. While prior volumes in the series focus on novel data-analytic techniques, this volume addresses technology that is necessary for minimally intrusive data collection and near-real-time data analysis and display.

McDonald, P. Vernon; Newman, Dava

1999-01-01

306

ESR melting under constant voltage conditions  

SciTech Connect

Typical industrial ESR melting practice includes operation at a constant current. This constant current operation is achieved through the use of a power supply whose output provides this constant current characteristic. Analysis of this melting mode indicates that the ESR process under conditions of constant current is inherently unstable. Analysis also indicates that ESR melting under the condition of a constant applied voltage yields a process which is inherently stable. This paper reviews the process stability arguments for both constant current and constant voltage operation. Explanations are given as to why there is a difference between the two modes of operation. Finally, constant voltage process considerations such as melt rate control, response to electrode anomalies and impact on solidification will be discussed.

Schlienger, M.E.

1997-02-01

307

First-year evaluation of low-level waste-management stabilization techniques  

SciTech Connect

The first year of observation for effectiveness of biobarriers and herbicides in revegetation efforts demonstrated that certain practices will result in successful site stabilization: proper orientation of burial trench to reduce erosion; utilization of mulches to conserve moisture; seeding mixed perennial or annual grass species at the proper time for optimization of establishment and growth; and applying 2,4-D amine/Dicamba selective herbicide at the optimum time for enhancement of disirable grasses and reduction of competition from other species. The ultimate success or failure of a revegetation operation depends in part on the availability of equipment and manpower, weather conditions, and engineering feasibility. The data indicated that perennial grasses offered advantages over annual grasses and that the 2,4-D amine/Dicamba herbicide spray program was successful and should be expanded for next year. However, programmatic decisions should not be based on the data for 1 year, but should be based on data gathered over the full 3 years of the project.

Cox, G.R.

1981-12-01

308

Lead leachability in stabilized/solidified soil samples evaluated with different leaching tests.  

PubMed

Leaching tests and model calculations were performed to investigate the immobilization mechanisms of Pb and compare different leaching protocols. Stabilization/solidification (S/S) treatments reduced Pb concentrations in the toxicity characteristic leaching procedure (TCLP) leachate from 5.9 mg/L for untreated soil to less than 0.7 mg/L. The results of eight different leaching protocols show that: (1) the main factor controlling the Pb concentration in the leachate is the final pH; (2) the final pH is a function of the leachant acidity; and (3) for a given final pH, the type of leachant has a relatively minor effect on leachability. The diffuse layer adsorption model, aqueous and precipitation reactions were employed in the MINTEQA2 program to describe the Pb leaching behavior. Both leaching tests and model simulations indicate that the Pb leaching behavior can be divided into three stages based on the leachate pH: a high alkalinity leaching stage at pH > 12, where Pb formed soluble hydroxide anion complexes and leached out; a neutral to alkaline immobilization stage in the pH range of 6-12, which was characterized by low Pb leachability caused by adsorption and precipitation; and an acid leaching stage with pH < 6, where the acid neutralizing capacity (ANC) of the S/S materials was totally consumed and therefore free Pb-ion leached out. PMID:15511579

Jing, Chuanyong; Meng, Xiaoguang; Korfiatis, George P

2004-10-18

309

Preparation and stability evaluation of extemporaneous oral suspension of valsartan using commercially available tablets.  

PubMed

The aim of this study was to develop an extemporaneous valsartan suspension (80 mg valsartan/5 mL) starting from commercial tablets (80-mg/ tablet). A high-performance liquid chromatographic system was used for the analysis and quantification of valsartan in the samples studied. Samples of valsartan suspension for analysis were prepared as reported by the validated high-performance liquid chromatographic method and the dissolution tests were performed according to the U.S. Food and Drug Administration's method. The high-performance liquid chromatographic assay indicated that the 80-mg/5-mL valsartan suspension was stable for 30 days when stored at long-term and accelerated storage conditions. Valsartan release profile showed that approximately 85% of valsartan dissolved after 10 minutes and, accordingly, the calculation of similarity factor was not necessary. It is possible for the pharmacist to crush valsartan 80-mg tablets and prepare a suspension which has dosage flexibility that can be calculated according to body-surface area, 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:24881122

Zaid, Abdel Naser; Assali, Mohyeddin; Qaddomi, Aiman; Ghanem, Mashhour; Zaaror, Yara Abu

2014-01-01

310

Evaluation of sensory acceptability and storage stability of frozen carrot based dessert.  

PubMed

In the present study a recipe for frozen carrot based dessert (carrot halwa) was standardized on the basis of sensory characteristics such as appearance, odor, texture, taste and overall acceptability (OAA). The product was developed without addition of pure ghee to improve the storage stability under frozen conditions (-20 °C). Sensory properties of the developed product (OAA score?=?8.60) were found to be equally good as compared to the conventional carrot halwa (OAA score?=?8.75) which was prepared using pure ghee. From the physico-chemical analysis the developed product was found to have lower amount of fat (ca. 12%) than the conventional one. During the frozen storage, microbial growth in the product was found to be non-significant (P?>?0.05). The free fatty acid content, peroxide value and thiobarbituric acid content increased during frozen storage of 15 months. But the increase was insignificant. Loss in total carotenoids content of the product was found to be 60.5% from initial value at the end of 15 months frozen storage. PMID:24876657

Saxena, Tanushree Maity; Raju, P S; Bawa, A S

2014-06-01

311

Geomorphic evaluation of erosional stability at reclaimed surface mines in northwestern Colorado. Water Resources Investigation  

SciTech Connect

The report identifies geomorphic, pedologic, vegetation, and hydrologic conditions that are associated with erosion of reclaimed surface-mined lands in northwestern Colorado. The report also presents methods for determining the appropriate values of geomorphic variables that can be manipulated during reclamation to increase erosional stability. A section on geomorphic principles associated with erosion of reclaimed land surfaces is designed for use as a primer by mine personnel and reclamation planners. The areas of interest in the study were those that were reclaimed under jurisdiction of current (1988) SMCRA reclamation regulations, yet were still affected by relatively rapid erosion rates several years after reclamation activities were completed. Geomorphic, pedologic, vegetation, and hydrologic data were collected onsite and from topographic maps. Data from reclaimed areas undergoing accelerated erosion were compared with data from reclaimed areas undergoing minimal erosion to identify conditions that controlled erosion on reclaimed surface-mined lands and to identify some postmining equilibrium landform characteristics. These data also were used to develop threshold relations.

Elliott, J.G.

1990-01-01

312

Evaluation of a ventricular assist device: stability under x-rays and therapeutic beam attenuation.  

PubMed

Improved outcomes and quality of life of heart failure patients have been reported with the use of left ventricular assist devices (LVADs). However, little information exists regarding devices in patients undergoing radiation cancer treatment. Two HeartWare Ventricular Assist Device (HVAD) pumps were repeatedly irradiated with high intensity 18 MV x-rays to a dosage range of 64-75 Gy at a rate of 6 Gy/min from a radiation oncology particle accelerator to determine operational stability. Pump parameter data was collected through a data acquisition system. Second, a computerized tomography (CT) scan was taken of the device, and a treatment planning computer estimated characteristics of dose scattering and attenuation. Results were then compared with actual radiation measurements. The devices exhibited no changes in pump operation during the procedure, though the titanium components of the HVAD markedly attenuate the therapy beam. Computer modeling indicated an 11.8% dose change in the absorbed dosage that was distinctly less than the 84% dose change measured with detectors. Simulated and measured scattering processes were negligible. Computer modeling underestimates pretreatment dose to patients when the device is in the field of radiation. Future x-ray radiation dosimetry and treatment planning in HVAD patients should be carefully managed by radiation oncology specialists. PMID:22236626

Gossman, Michael S; Graham, Joel D; Tamez, Dan; Voskoboynikov, Neil; Larose, Jeffrey A

2012-01-01

313

Evaluation of load transfer characteristics of a dynamic stabilization device on disc loading under compression.  

PubMed

In the current study, finite element analyses were conducted to examine the biomechanical capability of a newly design dynamic stabilization system, FlexPLUS, to restore the load transmission of degenerated intervertebral L4-L5 lumbar motion segment spine under compression. Detailed three-dimensional FE models of L4-L5 motion segment and the FlexPLUS were developed. Compressive loading up to 1000N was applied to the intact L4-L5 model, the L4-L5 models with slight and moderate degenerated disc, and the implanted L4-L5 model. Further more, the load transmission characteristics of Dynesys and a rigid rod was also simulated for comparison. The resultant load-displacement curves and the load transferred through annulus under various conditions were compared. The predicted axial displacement of L4 top surface against applied compressive force of the intact L4-L5 model agreed well with experimental data. The predicted results showed that degenerated disc has significant effect on the lumbar segment load bearing capacity. Not only the stiffness of the segment was greatly increased, the uniform nature of the disc stress distribution was also altered. The FlexPLUS can effectively reduce the disc loading of degenerated model. Although the non-uniform load distribution pattern through annulus was not improved, the overall stress magnitude was greatly reduced to the level of intact model for grade II degeneration. PMID:19038569

Zhang, Qing Hang; Zhou, Yuan Li; Petit, Dominique; Teo, Ee Chon

2009-06-01

314

Precision evaluation of chiral capillary electrophoretic methods in the context of inter-instrumental transfer: constant current versus constant voltage application.  

PubMed

Capillary electrophoresis (CE) is an electrophoretic separation technique that was rapidly increasing in popularity some years ago and that led to high expectations. Because of their different separation mechanisms, CE and HPLC are alternative and complementary separation techniques. Chiral molecules can be directly separated with CE by simply adding a chiral selector to the running buffer solution, leading to flexible and cheap methods. Major drawbacks of capillary electrophoretic separation methods are, however, the lower precision compared to HLPC methods and a more problematic analytical method transfer. Both above stated disadvantages limit the generalized use of CE methods in the pharmaceutical industry. Multiple solutions have been suggested to improve the precision of CE methods. In this work the application of a constant current during the electrophoretic separation instead of the more commonly used application of a constant voltage was studied on two CE instruments with different cooling mechanisms. This was done in the context of optimizing method transfer conditions. A constant current may reduce the generation of heat in the capillary and the consequentially radial and axial temperature fluctuations that both negatively influence the precision of the peak areas, migration times and resolutions of a CE method. The repeatability and time-different intermediate precision of both electrophoretic separation modes were compared on two different CE instruments after a successful analytical method transfer. The chiral separations of three beta-blockers, propranolol, sotalol and betaxolol, were used as test cases. A constant current led to a general improvement of the repeatability and time-different intermediate precision of the relative Area Under the Curve of all three beta-blockers, while that of the migration times remained rather constant. It also led to more similar electropherograms than the application of a constant voltage. PMID:24680945

De Cock, Bart; Dejaegher, Bieke; Stiens, Johan; Mangelings, Debby; Vander Heyden, Yvan

2014-08-01

315

Evaluation of the stability of fluoxetine in pluronic lecithin organogel and the determination of an appropriate beyond-use date.  

PubMed

Fluoxetine is a commonly prescribed psychotropic medication for a variety of behavioral diagnoses in veterinary practice, and fluoxetine in Pluronic lecithin organogel has been used successfully in treating inappropriate urine spraying in felines. Historically, pharmacists have assigned a variety of beyond-use dates to extemporaneously compound drugs in Pluronic lecithin organogel. The objective of this study was to evaluate the stability of fluoxetine in Pluronic lecithin organogel over a period of six months and to determine an appropriate beyond-use date. A stability-indicating high-performance liquid chromatography method for fluoxetine in Pluronic lecithin organogel was validated in our laboratory. Fluoxetine-Pluronic lecithin organogel 50 mg/mL was prepared by a local compounding pharmacy and analyzed by high-performance liquid chromatograph at 0, 7, 14, 21, 28, 45, 60, 90, and 180 days. Physical stability was also assessed by visual observation. At each time point percent of initial concentration was calculated. 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 mean percent of initial concentration was 99 +/- 1.5 and, visually, the fluoxetine-Pluronic lecithin organogel retained the original color and consistency, without detectable separation of the different phases of Pluronic lecithin organogel. Since fluoxetine was physically stable and retained greater than 90 percent of initial concentration in Pluronic lecithin organogel for 180 days when stored at room temperature and protected from light, a beyond-use date of 180 days is appropriate. PMID:25306774

Peacock, Gina F; Sauvageot, Jurgita

2014-01-01

316

Evaluation of functional stability and batch-to-batch reproducibility of a Castanea sativa leaf extract with antioxidant activity.  

PubMed

A growing body of evidence suggests that free radicals are generated by UV irradiation being responsible for skin injury. In this regard, the topical use of formulations composed of plant extracts with antioxidant activity could represent a useful strategy for the prevention of photoaging and oxidative-stress-mediated diseases. The aim of this study was to assess the reproducibility of the extraction method and the functional stability of a Castanea sativa leaf extract in view of its application as topical antioxidant. Measurements of 1,1-diphenyl-2-picryl hydrazyl (DPPH) scavenging activity, total phenols (measured by the Folin Ciocalteu assay) and phenolic composition (high-performance liquid chromatography unit coupled to a UV detector) were carried out on three different batches. The influence of pH and temperature on the extract's DPPH scavenging activity was assessed in aqueous and glyceric solutions (0.025% w/v) over a 3-month period. Minor differences were found between the three extract batches for all the evaluated parameters, and therefore the reproducibility of the extraction method can be inferred. pH presented a great influence in the extract functional stability. Major antioxidant activity decrease was found at pH 7.1, while lower changes were observed at pH 5. Glyceric solutions were stable throughout the test period. At 40 degrees C and pH 5, a marked decrease of activity was observed. Again, glyceric solutions were the most stable, even at 40 degrees C. Proper selection of pH and solvent is mandatory to ensure the stability of the studied extract after being incorporated in semisolid forms. In view of these results, glycerine is proposed as the best vehicle for topical formulations incorporating C. sativa leaf extract, which should have a pH around 5. PMID:20066522

Almeida, Isabel F; Costa, Paulo C; Bahia, M Fernanda

2010-03-01

317

Device for monitoring cell voltage  

DOEpatents

A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

Doepke, Matthias (Garbsen, DE); Eisermann, Henning (Edermissen, DE)

2012-08-21

318

Dual voltage electrical system  

SciTech Connect

A dual voltage motor vehicle electrical system is described which consists of an alternating current generator having a polyphase output winding, a polyphase full-wave bridge rectifier comprised of groups of positive and negative diodes, the bridge rectifier having AC input terminals connected to the output winding and having positive and negative direct voltage output terminals, first and second storage batteries connected in series and across the direct voltage output terminals of the bridge rectifier, the negative terminal of one battery and the positive terminal of the other battery being connected to a common junction, a first switchable rectifying circuit connected between the junction and the AC input terminals, the first switchable rectifying circuit when biased conductive and one of the groups of diodes supplying charging current to one of the batteries, a second switchable rectifying circuit connected between the junction and the AC input terminals, the second switchable rectifying circuit when biased conductive and the other group of the diodes supplying charging current to the other battery, means for causing the switchable rectifying circuits to be biased alternately conductive, means for sensing the relative magnitudes of the voltages across the batteries, and means responsive to the difference in the voltages across the batteries for controlling the time periods that the switchable rectifying circuits are biased conductive.

Radomski, T.A.

1987-08-11

319

Using modeling and simulation to evaluate stability and traction performance of a track-laying robotic vehicle  

NASA Astrophysics Data System (ADS)

DOD has been involved in the research, development and acquisition of unmanned ground vehicle systems to support the troops in the field while minimizing the risks associated with supplying these troops. Engineers and scientists at TARDEC are using computer based modeling and simulation (M&S) to investigate how modifications to unmanned ground vehicles impact their mobility and stability, and to predict performance levels attainable for these types of vehicle systems. The objective of this paper will be to describe the computerbased modeling, simulation, and limited field testing effort that has been undertaken to investigate the dynamic performance of an unmanned tracked vehicle system while conducting a full matrix of tests designed to evaluate system shock, vibration, dynamic stability and off road mobility characteristics. In this paper we will describe the multi-body modeling methodology used as well as the characteristic data incorporated to define the models and their subsystems. The analysis undertaken is applying M&S to baseline the dynamic performance of the vehicle, and comparing these results with performance levels recorded for several manned vehicle systems. We will identify the virtual test matrix over which we executed the models. Finally we will describe our efforts to visualize our findings through the use of computer generated animations of the vehicle system negotiating various virtual automotive tests making up the test matrix.

Gunter, D. D.; Bylsma, W. W.; Edgar, K.; Letherwood, M. D.; Gorsich, D. J.

2005-05-01

320

Mutual compensation of mobility and threshold voltage temperature effects with applications in CMOS circuits  

Microsoft Academic Search

Mutual compensation of mobility and threshold voltage temperature variations may result in a zero temperature coefficient bias point of a MOS transistor. The conditions under which this effect occurs, and stability of this bias point are investigated. Possible applications of this effect include voltage reference circuits and temperature sensors with linear dependence of voltage versus temperature. The theory is verified

I. M. Filanovsky; Ahmed Allam

2001-01-01

321

Environmental impact of industrial sludge stabilization/solidification products: chemical or ecotoxicological hazard evaluation?  

PubMed

Nowadays, the classification of industrial solid wastes is not based on risk analysis, thus the aim of this study was to compare the toxicity classifications based on the chemical and ecotoxicological characterization of four industrial sludges submitted to a two-step stabilization/solidification (S/S) processes. To classify S/S products as hazardous or non-hazardous, values cited in Brazilian chemical waste regulations were adopted and compared to the results obtained with a battery of biotests (bacteria, alga and daphnids) which were carried out with soluble and leaching fractions. In some cases the hazardous potential of industrial sludge was underestimated, since the S/S products obtained from the metal-mechanics and automotive sludges were chemically classified as non-hazardous (but non-inert) when the ecotoxicity tests showed toxicity values for leaching and soluble fractions. In other cases, the environmental impact was overestimated, since the S/S products of the textile sludges were chemically classified as non-inert (but non-hazardous) while ecotoxicity tests did not reveal any effects on bacteria, daphnids and algae. From the results of the chemical and ecotoxicological analyses we concluded that: (i) current regulations related to solid waste classification based on leachability and solubility tests do not ensure reliable results with respect to environmental protection; (ii) the two-step process was very effective in terms of metal immobilization, even at higher metal-concentrations. Considering that S/S products will be subject to environmental conditions, it is of great interest to test the ecotoxicity potential of the contaminants release from these products with a view to avoiding environmental impact given the unreliability of ecotoxicological estimations originating from chemical analysis. PMID:21724330

Silva, Marcos A R; Testolin, Renan C; Godinho-Castro, Alcione P; Corrêa, Albertina X R; Radetski, Claudemir M

2011-09-15

322

An accurate voltage-to-frequency converter  

Microsoft Academic Search

A current- or voltage-to-frequency converter is described for converting analogue signals into a pulse form in which the pulse repetition frequency is proportional to the instantaneous signal amplitude. The conversion is linear to within 0·01% over the frequency range 0-10 kHz (or 0-1 kHz), and to within 0·1% up to 50 kHz. Thermal stability is comparable.The circuit action is based

P J Unsworth

1969-01-01

323

"Evaluation of the Effect of Ultraviolet Disinfection on Dimensional Stability of the Polyvinyl Silioxane Impressions." an in-Vitro Study  

PubMed Central

Introduction: Infection control is an important concept in the present day practice of dentistry. The prosthodontists are at an added risk of transmission because of the infection spreading through the contaminated lab equipments while working in the lab. The purpose of this study is to evaluate the effect of UV light disinfection on dimensional stability of polyvinyl siloxane impressions. Materials and Methods : Impressions were made in perforated custom tray. After polymerization of impression, half the samples were disinfected in UV light and remaining samples were not subjected to disinfection and poured in die stone which served as control group. Linear dimensions were measured on the cast with travelling microscope of 0.001accuracy. Result : The result showed that UV light disinfectant showed no significant dimensional changes on impressions. Conclusion: Hence, it can be safely used to disinfect impressions in clinical prosthodontic procedures. PMID:25386528

Godbole, Surekha R; Dahane, Trupti M; Nimonkar, Sharayu V

2014-01-01

324

Novel SiL evaluation of an optimal H? controller on the stability of a MAV in flight simulator  

NASA Astrophysics Data System (ADS)

This paper introduces a novel methodology to assist the evaluation of control algorithms for MAVs (Micro Aerial Vehicles) using Software-in-the-Loop (SiL) based flight simulation. The originality of this paper is to use © Microsoft Flight Simulator (MSFS) as the environment to embed both the dynamic and graphic models of © Ascending Technologies Pelican MAV flying robot. The resulting is a reliable model of the Pelican quadrotor. The full duplex communication between the virtual aircraft and the control algorithm is achieved by a custom C++/C software named FVMS (Flight Variables Management System), developed by Aerial Robots Team (ART), which is able to reach (read/write) a great number of flight variables from MSFS. To illustrate the effectiveness of such method, we first completely present FVMS architecture and main features. Later, the synthesis and then the application of the optimal H? robust control algorithm and its operation into the FVMS SiL context are explained. Regarding MAVs control evaluation, SiL simulation considerably contributes to save battery time, to ease control synthesis and prototyping and to prevent accidents during tests with the real robot. The final goal is to evaluate the stability of the Pelican platform in hovering tasks in flight simulation focusing on the efficiency of FVMS to properly run the optimal H? robust control algorithm. The SiL control of the MAV has proven FVMS capabilities, which may be extended to assist the design of other classes of controllers.

Sampaio, Rafael C. B.; Becker, Marcelo; Siqueira, Adriano A. G.; Freschi, Leonardo W.; Montanher, Marcelo P.

325

Voltage controlled current source  

DOEpatents

A seven decade, voltage controlled current source is described for use in testing intermediate range nuclear instruments that covers the entire test current range of from 10 picoamperes to 100 microamperes. High accuracy is obtained throughout the entire seven decades of output current with circuitry that includes a coordinated switching scheme responsive to the input signal from a hybrid computer to control the input voltage to an antilog amplifier, and to selectively connect a resistance to the antilog amplifier output to provide a continuous output current source as a function of a preset range of input voltage. An operator controlled switch provides current adjustment for operation in either a real-time simulation test mode or a time response test mode.

Casne, Gregory M. (Pittsburgh, PA)

1992-01-01

326

High voltage coaxial switch  

DOEpatents

A coaxial high voltage, high current switch having a solid cylindrical cold cathode coaxially surrounded by a thin hollow cylindrical inner electrode and a larger hollow cylindrical outer electrode. A high voltage trigger between the cathode and the inner electrode causes electrons to be emitted from the cathode and flow to the inner electrode preferably through a vacuum. Some of the electrons penetrate the inner electrode and cause a volumetric discharge in the gas (which may be merely air) between the inner and outer electrodes. The discharge provides a low impedance path between a high voltage charge placed on the outer electrode and a load (which may be a high power laser) coupled to the inner electrode. For high repetition rate the gas between the inner and outer electrodes may be continuously exchanged or refreshed under pressure. 3 figs.

Rink, J.P.

1983-07-19

327

Electron launching voltage monitor  

SciTech Connect

An electron launching voltage monitor measures MITL voltage using a relationship between anode electric field and electron current launched from a cathode-mounted perturbation. An electron launching probe extends through and is spaced from the edge of an opening in a first MITL conductor, one end of the launching probe being in the gap between the MITL conductor, the other end being adjacent a first side of the first conductor away from the second conductor. A housing surrounds the launching probe and electrically connects the first side of the first conductor to the other end of the launching probe. A detector detects the current passing through the housing to the launching probe, the detected current being representative of the voltage between the conductors.

Mendel, Clifford W. (Albuquerque, NM); Savage, Mark E. (Albuquerque, NM)

1992-01-01

328

Electron launching voltage monitor  

SciTech Connect

An electron launching voltage monitor measures MITL voltage using a relationship between anode electric field and electron current launched from a cathode-mounted perturbation. An electron launching probe extends through and is spaced from the edge of an opening in a first MITL conductor, one end of the launching probe being in the gap between the MITL conductor, the other end being adjacent a first side of the first conductor away from the second conductor. A housing surrounds the launching probe and electrically connects the first side of the first conductor to the other end of the launching probe. A detector detects the current passing through the housing to the launching probe, the detected current being representative of the voltage between the conductors. 5 figs.

Mendel, C.W.; Savage, M.E.

1992-03-17

329

High Voltage Electrostatic Pendulum  

E-print Network

A pendulum powered by high voltage electricity is described. The pendulum consists of two conducting plates(thin foil) separated by copper rods and are insulated from each other. High voltage is applied to these plates through the connecting copper rods. Another stationary aluminum plate(thin foil) is placed in front of the pendulum such that it serves to attract the pendulum plates and makes electrical contact with them enabling charge transfer between the stationary plate and the pendulum plates. The pendulum is powered by the energy stored in the capacitance between the stationary aluminum plate and the pendulum plate. Attempt has been made to obtain the time period of oscillations as a function of applied voltage and other parameters. The derived formula for the time period has been verified experimentally. This apparatus can be used to demonstrate electrical phenomena in general and in particular electrical energy stored in conductors of small dimensions.

Baddi, Raju

2012-01-01

330

Voltage regulation in distribution networks with distributed generation  

NASA Astrophysics Data System (ADS)

The paper deals with the topic of voltage regulation in distribution networks with relatively high distributed energy resources (DER) penetration. The problem of voltage rise is described and different options for voltage regulation are given. The influence of DER on voltage profile and the effectiveness of the investigated solutions are evaluated by means of simulation in DIgSILENT. The simulated network is an actual distribution network in Slovenia with a relatively high penetration of distributed generation. Recommendations for voltage control in networks with DER penetration are given at the end.

Blaži?, B.; Uljani?, B.; Papi?, I.

2012-11-01

331

Evaluation of the BD Vacutainer® RST blood collection tube for routine chemistry analytes: clinical significance of differences and stability study  

PubMed Central

Introduction: Preanalytical variables account for most of laboratory errors. There is a wide range of factors that affect the reliability of laboratory report. Most convenient sample type for routine laboratory analysis is serum. BD Vacutainer® Rapid Serum Tube (RST) (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) blood collection tube provides rapid clotting time allowing fast serum separation. Our aim was to evaluate the comparability of routine chemistry parameters in BD Vacutainer® RST blood collection tube in reference with the BD Vacutainer® Serum Separating Tubes II Advance Tube (SST) (Becton, Dickinson and Company, Franklin Lakes, NJ, USA). Materials and methods: Blood specimens were collected from 90 participants for evaluation on its results, clotting time and stability study of six routine biochemistry parameters: glucose (Glu), aspartate aminotransferase (AST), alanine aminotransferase (ALT), calcium (Ca), lactate dehidrogenase (LD) and potassium (K) measured with Olympus AU2700 analyzer (Beckman Coulter, Tokyo, Japan). The significance of the differences between samples was assessed by paired t-test or Wilcoxon Matched-Pairs Rank test after checking for normality. Results: Clotting process was significantly shorter in the RSTs compared to SSTs (2.49 min vs. 19.47 min, respectively; P < 0.001). There was a statistically significant difference between the RST and SST II tubes for glucose, calcium and LD (P < 0.001). Differences for glucose and LD were also clinically significant. Analyte stability studies showed that all analytes were stable for 24 h at 4 °C. Conclusions: Most results (except LD and glucose) from RST are comparable with those from SST. In addition, RST tube provides shorter clotting time. PMID:25351355

Kocijancic, Marija; Cargonja, Jelena; Delic-Knezevic, Alma

2014-01-01

332

Fiber-optic voltage measuring system  

NASA Astrophysics Data System (ADS)

A new fibre optic voltage measuring system has been developed based on the electrooptic effect of bismuth germanium oxide (Bi4Ge3O12)crystal. It uses the LED as the light source. The light beam emitted from the light source is transmitted to the sensor through the optic fibre and the intensity of the output beam is changed by the applied voltage. This optic signal is transmitted to the PIN detector and converted to an electric signal which is processed by the electronic circuit and 8098 single chip microcomputer the output voltage signal obtained is directly proportional to the applied voltage. This paper describes the principle the configuration and the performance parameters of the system. Test results are evaluated and discussed.

Ye, Miaoyuan; Nie, De-Xin; Li, Yan; Peng, Yu; Lin, Qi-Qing; Wang, Jing-Gang

1993-09-01

333

Lets Rock the Boat: Evaluating the Concept of Stability in Fluid Mechanics  

NSDL National Science Digital Library

As an upper level civil engineering course, Fluid Mechanics, often presents concepts that are unfamiliar to engineering students, at least to the level of understanding expected in the course. Many of these fundamentals concepts are critical to success in the course, but are frequently difficult to visualize simply with figures and equations. Additionally, many laboratory exercises for students involve a cookbook type approach which increases the chance of the attainment of reliable results, but inhibits curiosity and decreases the development of an independent engineering formation of ideas associated with problem solving. A possible solution to both issues is the incorporation of in class activities which illustrate fundamental concepts, engage students in an active learning environment, and allow for the students themselves to create a testing program. The complication lies in determining a suitable topic and in creating an activity broad enough to allow for creative testing development but narrow enough to insure at least a marginal level of reliable results. The topic chosen by the authors was that of stability, one of the basic fundamental concepts in fluid mechanics. Working in groups of four to five students, the class was asked to develop an independent testing program that addressed the qualitative effects of adjusting weight in any one, or a combination of multiple, different directions (i.e. adjustments in the x, y, and / or z plane) on a floating object. Students were given supplies to create a model barge: a Styrofoam brick, cardboard sticks, modeling clay and containers sufficiently large to allow for floatation and movement when the barge was placed inside. No restrictions were placed on the direction in which the brick was to be placed in the water, the number and location of masts, or the number, magnitude and location of weight(s). Students were told the activity was to be summarized in a one-page paper, including testing procedure, results, and conclusions and were allowed thirty minutes for experimental setup, testing, and clean-up. Determination of student comprehension was assessed through both the summary paper, as well as an exam question. Results showed a high level of understanding, both in the short term, as concluded with the paper outcomes, as well as long term retention, validated with testing results. Quantitative analysis can easily be incorporated into the program by providing measuring instruments (rulers, calipers, and a balance) if a more robust study is desired.

Bondehagen, Diane; Kunberger, Tanya

2009-09-29

334

Clustered PV inverters in LV networks: An overview of impacts and comparison of voltage control strategies  

Microsoft Academic Search

High penetration of photovoltaic (PV) inverters in low voltage (LV) distribution network challenges the voltage stability due to interaction between multiple inverters and grid. As the main objective is to provide more power injection from VSC-based PV inverters, grid stability, reliability and power quality must be maintained or improved by adding cooperative control features to the grid-connected inverters. This paper

Erhan Demirok; Dezso Sera; Remus Teodorescu; P. Rodriguez; U. Borup

2009-01-01

335

Evaluation of TEM samples of an Mg-Al alloy prepared using FIB milling at the operating voltages of 10 kV and 40 kV.  

PubMed

Transmission electron microscopy (TEM) samples of an Mg-Al alloy has been prepared using a Ga-focused ion beam (FIB) milling at two different operating voltages of 10 kV and 40 kV to investigate the influence of the FIB energy on the sample quality. The fine structures of the samples have been studied using a high resolution TEM, and the concentration of the implanted Ga was analysed using an energy dispersive X-ray (EDX) analysis. The result of the TEM observation revealed that point defects were introduced to the sample finally milled at 40 kV but not at 10 kV. However, crystal lattice images and electron diffraction patterns were clearly observed on both the samples. The typical influence of the FIB energy was indicated in the elemental analysis. The relative Ga concentration in the thin sample finally milled at 10 kV was 1.0-2.0 at% that is less than half of 4.0-6.0 at% of the Ga concentration in the sample finally milled at 40 kV. A comparison between the experimental results of the Ga concentration measurement with simulation was also discussed. PMID:15582947

Kamino, Takeo; Yaguchi, Toshie; Kuroda, Yasushi; Ohnishi, Tsuyoshi; Ishitani, Tohru; Miyahara, Yuichi; Horita, Zenji

2004-01-01

336

Evaluating the potential of natural curcumin for oxidative stability of soybean oil.  

PubMed

The active substance of turmeric rhizome (curcumin) was extracted and identified with TLC and NMR. To evaluate the antioxidant efficiency of different concentrations of curcumin (120, 160 and 200 ppm) compared with tert-butylhydroquinone (TBHQ) (120 ppm) and ?-tocopherol (200 ppm) at two different temperatures (25°C and 55°C) under dark and light conditions during 90 days, the soybean oil with no added antioxidant was used as a food model, and its fatty acids profile was determined by GC. Results indicated that increasing concentration of curcumin leads to significantly decreased oxidation rates. The soybean oil containing curcumin at 25°C in darkness with the lowest rate of increased peroxide value indicated the same antioxidant activity with ?-tocopherol and TBHQ. Moreover, the results of acid value and iodine value indicated that samples with curcumin were more effective in preventing oxidation at both temperatures compared with control. However, light did not have any significant effect. PMID:24702166

Eshghi, Naeeme; Asnaashari, Maryam; Khodaparast, Mohammad Hossein Haddad; Hosseini, Fereshteh

2014-01-01

337

Experimental Evaluation of Journal Bearing Stability and New Gas Bearing Material  

NASA Technical Reports Server (NTRS)

It has been estimated that the noise levels in aircraft engine transmissions can be reduced by as much as 10 dB through the use of journal bearings. The potential benefits of lower noise levels include reduced wear, longer gear life and enhanced comfort for passengers and crew. Based on this concept the journal-thrust wave bearing was analyzed and its performance was evaluated. Numerical codes, developed over the past 30 years by Dr. Dimofte, were used to predict the performance of the bearing. The wave bearing is a fluid film bearing and therefore was analyzed using the Reynolds pressure equation. The formulation includes turbulent flow concepts and possesses a viscosity-temperature correction. The centrifugal growth of the bearing diameter and the deformation of the bearing under gear loads were also incorporated into the code. An experimental rig was developed to test the journal-thrust wave bearing.

Keith, Theo G., Jr.; Dimofte, Florin

2001-01-01

338

Slope stability susceptibility evaluation parameter (SSEP) rating scheme - An approach for landslide hazard zonation  

NASA Astrophysics Data System (ADS)

In this paper a new slope susceptibility evaluation parameter (SSEP) rating scheme is presented which is developed as an expert evaluation approach for landslide hazard zonation. The SSEP rating scheme is developed by considering intrinsic and external triggering parameters that are responsible for slope instability. The intrinsic parameters which are considered are; slope geometry, slope material (rock or soil type), structural discontinuities, landuse and landcover and groundwater. Besides, external triggering parameters such as, seismicity, rainfall and manmade activities are also considered. For SSEP empirical technique numerical ratings are assigned to each of the intrinsic and triggering parameters on the basis of logical judgments acquired from experience of studies of intrinsic and external triggering factors and their relative impact in inducing instability to the slope. Further, the distribution of maximum SSEP ratings is based on their relative order of importance in contributing instability to the slope. Finally, summation of all ratings for intrinsic and triggering parameter based on actual observation will provide the expected degree of landslide in a given land unit. This information may be utilized to develop a landslide hazard zonation map. The SSEP technique was applied in the area around Wurgessa Kebelle of North Wollo Zonal Administration, Amhara National Regional State in northern Ethiopia, some 490 km from Addis Ababa. The results obtained indicates that 8.33% of the area fall under Moderately hazard and 83.33% fall within High hazard whereas 8.34% of the area fall under Very high hazard. Further, in order to validate the LHZ map prepared during the study, active landslide activities and potential instability areas, delineated through inventory mapping was overlain on it. All active landslide activities and potential instability areas fall within very high and high hazard zone. Thus, the satisfactory agreement confirms the rationality of considered governing parameters, the adopted SSEP technique, tools and procedures in developing the landslide hazard map of the study area.

Raghuvanshi, Tarun Kumar; Ibrahim, Jemal; Ayalew, Dereje

2014-11-01

339

AC Voltage Conversion Problems  

NSDL National Science Digital Library

This learning object, created by Terry L.M. Bartelt and John Rosz of Wisconsin Online Resource Center, focuses on AC voltage conversion problems. Aside from just the presentation, this site also contains practice problems. Overall, this is a useful presentation for a brief introduction on this topic.

Bartelt, Terry L.; Rosz, John

2010-09-24

340

Voltage-Controlled Oscillator  

NASA Technical Reports Server (NTRS)

Integrated Component Systems, Inc. incorporated information from a NASA Tech Briefs article into a voltage-controlled oscillator it designed for a customer. The company then applied the technology to its series of phase-locked loop synthesizers, which offer superior phase noise performance.

1995-01-01

341

In Vivo Evaluation of Quantitative Percussion Diagnostics for Determining Implant Stability  

PubMed Central

Purpose A percussion instrument (Periometer®, Perimetrics LLC, Newport Beach, CA, USA) and rat model were used to test the hypothesis: percussion diagnostics provides reliable, reproducible indications of osseointegration. Materials and Methods Titanium implants were placed in femurs of 36 Sprague-Dawley rats. Each animal was assigned to one of six groups of six defined by one of three time points (2, 4, or 8 weeks post-placement) and one of two treatments (MMP inhibitor or vehicle). Percussion testing was conducted three times/subject at implant placement and at one of the time points. For each time point, there was an experimental group that received daily intraperitoneal injections of GM6001, and a control group that received no MMP inhibitor. The percussion data consisted of loss coefficient (LC) values that characterize energy dissipation. Statistical analysis was performed on the LC values for two animal groups using the paired Student t test to assess differences as a function of time, and the independent t test to compare mean LC for the study groups at sacrifice (?=0.05). Histological evaluation using the osteogenic CD40 protein marker was also performed. Results A nearly significant difference in mean LC at the 2-week time point was observed between the two treatments with the GM6001 group having the higher value (p = 0.053). There was a greater difference between the mean LC values for the 4-week GM6001 and vehicle groups (p = 0.001). The histological evidence for subjects in these two groups confirmed reduction of osteogenesis at the implant interface after administration of the MMP inhibitor. Conclusions Lower vehicle LC values relative to the GM6001 therapeutic group were observed, consistent with the effect MMP inhibition has on matrix remodeling at the implant bone interface. This finding in conjunction with histological observations confirms that osseointegration can be monitored using percussion diagnostics. PMID:24066319

VanSchoiack, Lindsey R.; Shubayev, Veronica I.; Myers, Robert R.; Sheets, Cherilyn G.; Earthman, James C.

2014-01-01

342

Thermal Mechanical Stability of Single-Crystal-Oxide Refractive Concentrators Evaluated for High-Temperature Solar-Thermal Propulsion  

NASA Technical Reports Server (NTRS)

Recently, refractive secondary solar concentrator systems were developed for solar thermal power and propulsion (ref. 1). Single-crystal oxides-such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO), and sapphire (Al2O3)-are candidate refractive secondary concentrator materials. However, the refractive concentrator system will experience high-temperature thermal cycling in the solar thermal engine during the sun/shade transition of a space mission. The thermal mechanical reliability of these components in severe thermal environments is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions. In this research at the NASA Lewis Research Center, a controlled heat flux test approach was developed for investigating the thermal mechanical stability of the candidate oxide. This approach used a 3.0-kW continuous-wave (wavelength, 10.6 mm) carbon dioxide (CO2) laser (ref. 2). The CO2 laser is especially well-suited for single-crystal thermal shock tests because it can directly deliver well-characterized heat energy to the oxide surfaces. Since the oxides are opaque at the 10.6-mm wavelength of the laser beam, the light energy is absorbed at the surfaces rather than transmitting into the crystals, and thus generates the required temperature gradients within the specimens. The following figure is a schematic diagram of the test rig.

Jacobson, Nathan S.; Jacobson, Nathan S.; Miller, Robert A.

1999-01-01

343

Development of Automatic Voltage Regulator for Low Voltage Distribution Systems  

NASA Astrophysics Data System (ADS)

This paper presents the development of a new type of voltage regulator that can adequately maintain the voltage supplied to customers, dealing with the problem of voltage control along with the widespread use of photovoltaic power generation systems. The developed equipment is a pole-mounted type voltage regulator consisting of a step-down transformer that converts voltage from high to low and a series transformer for voltage compensation. The demonstration test conducted at the CRIEPI Akagi Test Center confirmed that the voltage control function of the developed voltage regulator is satisfactory based on the proposed control algorism. Also, simulation analysis, on the assumption of the clustered installation of photovoltaic power generation systems, confirmed that the introduction of the developed voltage regulator enables the system voltage to be adequately maintained and full photovoltaic power generation is possible without suppressing the output. It is anticipated that the developed voltage regulator is very effective in adequately regulating the voltage for low voltage distribution systems and gives an effective way for even more widespread photovoltaic power generation.

Matsuda, Katsuhiro; Horikoshi, Kazuhiro; Seto, Toshiyuki; Iyama, Osamu; Kobayashi, Hiromu

344

Voltage-gated sodium channel expression in mouse DRG after SNI leads to re-evaluation of projections of injured fibers  

PubMed Central

Background Dysregulation of voltage-gated sodium channels (Navs) is believed to play a major role in nerve fiber hyperexcitability associated with neuropathic pain. A complete transcriptional characterization of the different isoforms of Navs under normal and pathological conditions had never been performed on mice, despite their widespread use in pain research. Navs mRNA levels in mouse dorsal root ganglia (DRG) were studied in the spared nerve injury (SNI) and spinal nerve ligation (SNL) models of neuropathic pain. In the SNI model, injured and non-injured neurons were intermingled in lumbar DRG, which were pooled to increase the tissue available for experiments. Results A strong downregulation was observed for every Navs isoform expressed except for Nav1.2; even Nav1.3, known to be upregulated in rat neuropathic pain models, was lower in the SNI mouse model. This suggests differences between these two species. In the SNL model, where the cell bodies of injured and non-injured fibers are anatomically separated between different DRG, most Navs were observed to be downregulated in the L5 DRG receiving axotomized fibers. Transcription was then investigated independently in the L3, L4 and L5 DRG in the SNI model, and an important downregulation of many Navs isoforms was observed in the L3 DRG, suggesting the presence of numerous injured neurons there after SNI. Consequently, the proportion of axotomized neurons in the L3, L4 and L5 DRG after SNI was characterized by studying the expression of activating transcription factor 3 (ATF3). Using this marker of nerve injury confirmed that most injured fibers find their cell bodies in the L3 and L4 DRG after SNI in C57BL/6 J mice; this contrasts with their L4 and L5 DRG localization in rats. The spared sural nerve, through which pain hypersensitivity is measured in behavioral studies, mostly projects into the L4 and L5 DRG. Conclusions The complex regulation of Navs, together with the anatomical rostral shift of the DRG harboring injured fibers in C57BL/6 J mice, emphasize that caution is necessary and preliminary anatomical experiments should be carried out for gene and protein expression studies after SNI in mouse strains. PMID:24618114

2014-01-01

345

A low voltage ``railgun''  

NASA Astrophysics Data System (ADS)

Due to recent advances in solid-state switches and ultra-capacitors, it is now possible to construct a "railgun" that can operate at voltages below 20 V. Railguns typically operate above a thousand volts, generating huge currents for a few milliseconds to provide thousands of g's of acceleration to a small projectile. The low voltage railgun described herein operates for much longer time periods (tenths of seconds to seconds), has far smaller acceleration and speed, but can potentially propel a much larger object. The impetus for this development is to lay the groundwork for a possible ground-based supersonic launch track, but the resulting system may also have applications as a simple linear motor. The system would also be a useful teaching tool, requiring concepts from electrodynamics, mechanics, and electronics for its understanding, and is relatively straightforward to construct.

Starr, Stanley O.; Youngquist, Robert C.; Cox, Robert B.

2013-01-01

346

High Voltage Connector  

SciTech Connect

The originally designed high voltage connectors were to be made of brass. However, if treated like a Bellevile spring with the initially given dimensions, the stresses of the connector when crimped were calculated to be much higher than the yield stress of brass. Since the flange and outer diameters of the connector are to remain small, it was necessary to alter the other dimensions and choice of material in order to bring down the stresses applied to the connector.

Kurita, C.H.; /Fermilab

1987-03-06

347

Increased voltage photovoltaic cell  

NASA Technical Reports Server (NTRS)

A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

Ross, B.; Bickler, D. B.; Gallagher, B. D. (inventors)

1985-01-01

348

TECHNOLOGY EVALUATION REPORT, SITE PROGRAM DEMONSTRATION OF THE INTERNATIONAL WASTE TECHNOLOGIES IN SITU STABILIZATION/-SOLIDIFICATION TECHNOLOGY, HIALEAH, FL, VOLUME II  

EPA Science Inventory

A demonstration of the International Waste Technologies (IWT) process, utilizing the Geo-Con, Inc., deep-soil-mixing equipment has been performed under the Superfund Innovative Technology Evaluation (SITE) Program. his was the first field demonstration of an in situ stabilization...

349

Diagnostic stability of first-episode psychosis and predictors of diagnostic shift from non-affective psychosis to bipolar disorder: A retrospective evaluation after recurrence  

Microsoft Academic Search

Diagnostic changes during follow-up are not uncommon with a first-episode psychosis (FEP). This study aimed to evaluate the diagnostic stability of the FEP and to identify factors associated with a diagnostic shift from non-affective psychosis to bipolar disorder. Considering that the diagnosis of FEP is frequently more definite after recurrence in many clinical settings, a retrospective evaluation after recurrence was

Ji Sun Kim; Ji Hyun Baek; Ji Sun Choi; Dongsoo Lee; Jun Soo Kwon; Kyung Sue Hong

2011-01-01

350

Structural mechanism of voltage-dependent gating in an isolated voltage-sensing domain.  

PubMed

The transduction of transmembrane electric fields into protein motion has an essential role in the generation and propagation of cellular signals. Voltage-sensing domains (VSDs) carry out these functions through reorientations of positive charges in the S4 helix. Here, we determined crystal structures of the Ciona intestinalis VSD (Ci-VSD) in putatively active and resting conformations. S4 undergoes an ~5-Å displacement along its main axis, accompanied by an ~60° rotation. This movement is stabilized by an exchange in countercharge partners in helices S1 and S3 that generates an estimated net charge transfer of ~1 eo. Gating charges move relative to a ''hydrophobic gasket' that electrically divides intra- and extracellular compartments. EPR spectroscopy confirms the limited nature of S4 movement in a membrane environment. These results provide an explicit mechanism for voltage sensing and set the basis for electromechanical coupling in voltage-dependent enzymes and ion channels. PMID:24487958

Li, Qufei; Wanderling, Sherry; Paduch, Marcin; Medovoy, David; Singharoy, Abhishek; McGreevy, Ryan; Villalba-Galea, Carlos A; Hulse, Raymond E; Roux, Benoît; Schulten, Klaus; Kossiakoff, Anthony; Perozo, Eduardo

2014-03-01

351

LDEF Space Plasma-High Voltage Drainage Experiment post-flight results  

NASA Technical Reports Server (NTRS)

The Space Plasma-High Voltage Drainage Experiment (SP-HVDE) was comprised of two identical experimental trays. With one tray located on the leading (ram facing, B10) edge and the other located on the trailing (wake facing, D4) edge of the Long Duration Exposure Facility (LDEF), it was possible to directly compare the effects of ram and wake spacecraft environments on charged dielectric materials. Six arrays of Kapton dielectric samples of 2 mil, 3 mil, and 5 mil thicknesses maintained at +/- 300, +/- 500, and +/- 1000 voltage bias formed the experimental matrix of each tray. In addition, each tray carried two solar cell strings, one biased at +300 volts and the other at -300 volts, to study current leakage from High Voltage Solar Arrays (HVSA). The SP-HVDE provides the first direct, long-term, in-flight measurements of average leakage current through dielectric materials under electric stress. The experiment also yields information on the long term stability of the bulk dielectric properties of such materials. Data and findings of the SP-HVDE are an extension of those from shorter term flight experiments such as the PIX-1 (Plasma Interaction Experiment) and PIX-2 and are therefore valuable in the design and evaluation of long-lived space systems with high voltage systems exposed to the low earth orbital environment. A summary of the SP-HVDE post flight analysis final report delivered to the LDEF Project Office under contract to the National Aeronautics and Space Administration is presented.

Yaung, J. Y.; Blakkolb, B. K.; Wong, W. C.; Ryan, L. E.; Schurig, H. J.; Taylor, W. W. L.

1993-01-01

352

Efficient evaluation of process stability in milling with Spindle Speed Variation by using the Chebyshev Collocation Method  

NASA Astrophysics Data System (ADS)

Chatter is a vibrational problem affecting machining operations, which may cause bad surface quality and damages to the machining system. In recent decades, several techniques for avoiding chatter onset were developed. Among other techniques, the continuous modulation of spindle speed during the cutting process (also called Spindle Speed Variation - SSV) has been demonstrated to be very effective for reducing the chance of chatter onset. However, spindle speed modulation parameters should be adequately chosen before machining, in order to effectively increase the material removal rate. In this perspective, chatter prediction algorithms play a crucial role, since they allow a preventive evaluation of process stability for any given spindle speed regime. State of the art algorithms for chatter prediction in milling with SSV are characterized by extremely long computation times, hindering their practical application in industry. In this paper, an innovative and fast algorithm for chatter prediction in milling with SSV, based on the Chebyshev Collocation Method, is presented. The algorithm was successfully compared with a state of the art algorithm - the Semi Discretization Method - in different experimental configurations and cutting conditions. The results showed that the new method is generally more accurate and from ten to one thousand times faster than the Semi Discretization Method.

Totis, G.; Albertelli, P.; Sortino, M.; Monno, M.

2014-02-01

353

Evaluation of Solvita compost stability and maturity tests for assessment of quality of end-products from mixed latrine style compost toilets.  

PubMed

It is challenging and expensive to monitor and test decentralized composting toilet systems, yet critical to prevent the mismanagement of potentially harmful and pathogenic end-product. Recent studies indicate that mixed latrine composting toilets can be inhibited by high ammonia content, a product of urea hydrolysis. Urine-diverting vermicomposting toilets are better able to accomplish the goals of remote site human waste management by facilitating the consumption of fecal matter by earthworms, which are highly sensitive to ammonia. The reliability of Solvita compost stability and maturity tests were evaluated as a means of determining feedstock suitability for vermicomposting (ammonia) and end-product stability/completeness (carbon dioxide). A significant linear regression between Solvita ammonia and free ammonia gas was found. Solvita ranking of maturity did not correspond to ranking assigned by ammonium:nitrate standards. Solvita ammonia values 4 and 5 contained ammonia levels below earthworm toxicity limits in 80% and 100% of samples respectively indicative of their use in evaluating feedstock suitability for vermicomposting. Solvita stability tests did not correlate with carbon dioxide evolution tests nor ranking of stability by the same test, presumably due to in situ inhibition of decomposition and microbial respiration by ammonia which were reported by the Solvita CO2 test as having high stability values. PMID:23647950

Hill, Geoffrey B; Baldwin, Susan A; Vinnerås, Bjorn

2013-07-01

354

Synthesis and in vitro evaluation of 2,4-diamino-1,3,5-triazine derivatives as neuronal voltage-gated sodium channel blockers  

Microsoft Academic Search

Neuronal sodium channels blockers interfere with ion flux and have been used for managing neuropathic pain, epilepsy, and cerebral ischemic disorders. In the current study, four groups of 2,4-diamino-1,3,5-triazine derivatives were synthesized and investigated for their neuronal sodium channels binding activity. 5-Aryl-1,3,5-triazaspiro[5.5]undeca-1,3-diene-2,4-diamines (4a–4j) were found to have the best neuronal sodium binding activity among the four groups of triazines evaluated.

Xiang Ma; Thong-Yuen Poon; Peter Tsun Hon Wong; Wai-Keung Chui

2009-01-01

355

Fiber-optic voltage sensor  

Microsoft Academic Search

A fiber-optic voltage sensor is described which includes a source of light, a reference fiber for receiving a known percentage of the light and an electrostrictive element having terminals across which is applied, and a voltage to be measured. The electrostrictive element is responsive to the applied voltage to assume an altered physical state. A measuring fiber also receives a

C. B. Wood

1990-01-01

356

Atomistic Simulation and Virtual Diffraction Characterization of Alumina Interfaces: Evaluating Structure and Stability for Predictive Physical Vapor Deposition Models  

NASA Astrophysics Data System (ADS)

The objectives of this work are to investigate the structure and energetic stability of different alumina (Al2O3) phases using atomistic simulation and virtual diffraction characterization. To meet these objectives, this research performs molecular statics and molecular dynamics simulations employing the reactive force-field (ReaxFF) potential to model bulk, interface, and surface structures in the theta-, gamma-, kappa-, and ?-Al2O3 system. Simulations throughout this study are characterized using a new virtual diffraction algorithm, developed and implemented for this work, that creates both selected area electron diffraction (SAED) and x-ray diffraction (XRD) line profiles without assuming prior knowledge of the crystal system. First, the transferability of the ReaxFF potential is evaluated by modelling different alumina bulk systems. ReaxFF is shown to correctly predict the energetic stability of ?-Al2O 3 among the crystalline alumina phases, but incorrectly predicts an even lower energy amorphous phase. Virtual XRD patterns uniquely identify each phase and validate the minimum energy bulk structures through experimental comparison. Second, stable and metastable alumina surfaces are studied at 0, 300, 500, and 700 K. ReaxFF predicts minimum energy surface structures and energies in good agreement with prior studies at 0 K; however, select surface models at 500 and 700 K undergo significant reconstructions caused by the unnatural bias for a lower-energy amorphous phase. Virtual SAED analysis performed on alumina surfaces allow advanced characterization and direct experimental validation of select models. Third, ReaxFF is used to model homophase and heterophase alumina interfaces at 0 K. Predicted minimum energy structures of ?-Al2O3 interfaces show good agreement with prior works, which provides the foundation for the first atomistic study of metastable alumina grain boundaries and heterophase alumina interfaces. Virtual SAED patterns characterize select alumina interfaces and help guide the construction of low-energy heterophase alumina interfaces by providing insight into crystallographic compatibilities. Combined, the energetic data extracted from bulk, surface, and interface simulations as well as insights gained through virtual diffraction will aid the development of mesoscale predictive models of polycrystalline alumina formation during physical vapor deposition.

Coleman, Shawn

357

Intermediate state trapping of a voltage sensor  

PubMed Central

Voltage sensor domains (VSDs) regulate ion channels and enzymes by undergoing conformational changes depending on membrane electrical signals. The molecular mechanisms underlying the VSD transitions are not fully understood. Here, we show that some mutations of I241 in the S1 segment of the Shaker Kv channel positively shift the voltage dependence of the VSD movement and alter the functional coupling between VSD and pore domains. Among the I241 mutants, I241W immobilized the VSD movement during activation and deactivation, approximately halfway between the resting and active states, and drastically shifted the voltage activation of the ionic conductance. This phenotype, which is consistent with a stabilization of an intermediate VSD conformation by the I241W mutation, was diminished by the charge-conserving R2K mutation but not by the charge-neutralizing R2Q mutation. Interestingly, most of these effects were reproduced by the F244W mutation located one helical turn above I241. Electrophysiology recordings using nonnatural indole derivatives ruled out the involvement of cation-? interactions for the effects of the Trp inserted at positions I241 and F244 on the channel’s conductance, but showed that the indole nitrogen was important for the I241W phenotype. Insight into the molecular mechanisms responsible for the stabilization of the intermediate state were investigated by creating in silico the mutations I241W, I241W/R2K, and F244W in intermediate conformations obtained from a computational VSD transition pathway determined using the string method. The experimental results and computational analysis suggest that the phenotype of I241W may originate in the formation of a hydrogen bond between the indole nitrogen atom and the backbone carbonyl of R2. This work provides new information on intermediate states in voltage-gated ion channels with an approach that produces minimum chemical perturbation. PMID:23183699

Lacroix, Jerome J.; Pless, Stephan A.; Maragliano, Luca; Campos, Fabiana V.; Galpin, Jason D.; Ahern, Christopher A.; Roux, Benoit

2012-01-01

358

Evaluating factors affecting the permeability of emulsions used to stabilize radioactive contamination from a radiological dispersal device.  

PubMed

Present strategies for alleviating radioactive contamination from a radiological dispersal device (RDD) or dirty bomb involve either demolishing and removing radioactive surfaces or abandoning portions of the area near the release point. In both cases, it is imperative to eliminate or reduce migration of the radioisotopes until the cleanup is complete or until the radiation has decayed back to acceptable levels. This research investigated an alternative strategy of using emulsions to stabilize radioactive particulate contamination. Emergency response personnel would coat surfaces with emulsions consisting of asphalt or tall oil pitch to prevent migration of contamination. The site can then be evaluated and cleaned up as needed. In order for this approach to be effective, the treatment must eliminate migration of the radioactive agents in the terror device. Water application is an environmental condition that could promote migration into the external environment. This research investigated the potential for water, and correspondingly contaminant, migration through two emulsions consisting of Topein, a resinous byproduct during paper manufacture. Topein C is an asphaltic-based emulsion and Topein S is a tall oil pitch, nonionic emulsion. Experiments included water adsorption/ mobilization studies, filtration tests, and image analysis of photomicrographs from an environmental scanning electron microscope (ESEM) and a stereomicroscope. Both emulsions were effective at reducing water migration. Conductivity estimates were on the order of 10(-80) cm s(-1) for Topein C and 10(-7) cm s(-1) for Topein S. Water mobility depended on emulsion flocculation and coalescence time. Photomicrographs indicate that Topein S consisted of greater and more interconnected porosity. Dilute foams of isolated spherical gas cells formed when emulsions were applied to basic surfaces. Gas cells rose to the surface and ruptured, leaving void spaces that penetrated throughout the emulsion. These experiments indicate that emulsions may be a viable means for containing RDD residuals; however, improvements are needed for optimal performance. PMID:15952383

Fox, Garey A; Medina, Victor F

2005-05-15

359

Dynamic voltage and frequency scaling circuits with two supply voltages  

Microsoft Academic Search

Abstract—This paper presents circuits that enable dy- namic voltage and frequency scaling (DVFS) for fine- grained chip multi-processors to reduce both dynamic and leakage power dissipation. Each processor can run on either a high voltage or low voltage power supply, or disconnect from both. Switching between power supplies is performed dynamically, where scaling decisions are based on each processor’s workload,

Wayne H. Cheng; Bevan M. Baas

2008-01-01

360

A low voltage CMOS low drop-out voltage regulator  

Microsoft Academic Search

A low voltage implementation of a CMOS Low Drop-Out voltage regulator (LDO) is presented. The requirement of low voltage devices is crucial for portable devices that require extensive computations in a low power environment. The LDO is implemented in 90nm generic CMOS technology. It generates a fixed 0.8V from a 2.5V supply which on discharging goes to 1V. The buffer

Salma Ali Bakr; Tanvir Ahmad Abbasi; Mohammas Suhaib Abbasi; Mohamed Samir Aldessouky; Mohammad Usaid Abbasi

2009-01-01

361

The onset voltage of coronas on bare and coated conductors  

NASA Astrophysics Data System (ADS)

This paper concerns theoretical and experimental investigations of the effect of a conductor coating on the onset voltage of a corona on overhead transmission-line conductors. The onset voltage for a self-maintained discharge on the basis of discharge physics is evaluated. This calls first for accurate calculation of the electrical field in the vicinity of a coated conductor and its correlation to the field values near a bare conductor of the same radius. The well-known charge simulation technique is used for field calculation. The calculated electrical field values are utilized in evaluating the onset voltage of positive and negative coronas on bare and coated conductors. The onset voltage increases with a conductor coating. The calculated onset-voltage values agreed satisfactorily with those measured for laboratory models and full-scale test lines.

Abdel-Salam, M.; Turky, A. A.; Hashem, A. A.

1998-10-01

362

Stability of CIGS Solar Cells and Component Materials Evaluated by a Step-Stress Accelerated Degradation Test Method: Preprint  

SciTech Connect

A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15oC and then a 15% relative humidity (RH) increment step, beginning from 40oC/40%RH (T/RH = 40/40) to 85oC/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. The best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 ?m to 0.50 ?m on the cells. No clear 'stepwise' feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH ? 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and 'capacitor quality' factor (CPE-P), which were related to the cells? p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH ? 70/70. At T/RH = 85/70, substantial blistering of BZO layers on CIGS cell pieces was observed that was not seen on BZO/glass, and a CdS/CIGS sample displayed a small darkening and then flaking feature. Additionally, standard AlNi grid contact was less stable than thin Ni grid contact at T/RH ? 70/70. The edge sealant and moisture-blocking films were effective to block moisture ingress, as evidenced by the good stability of most CIGS solar cells and device components at T/RH = 85/70 for 704 h, and by preservation of the initial blue color on the RH indicator strips. The SSADT experiment is ongoing to be completed at T/RH = 85/85.

Pern, F. J.; Noufi, R.

2012-10-01

363

Comparison of 127I II-stabilized frequency-doubled Nd:YAG lasers and evaluation of frequency shifts caused by iodine cells  

NASA Astrophysics Data System (ADS)

We present results of measurement of purity of a set of iodine cells made at our institute. The purity was tested by improved method based on measurement of induced fluorescence and evaluation by the Stern-Volmer formula. The reproducibility of the fluorescence detection system was improved by introducing of additional compensation for the pumping laser spectral and power instabilities. Frequency-doubled Nd:YAG lasers stabilized with these cells were compared to evaluate their frequency shifts. The absolute frequencies of selected iodine hyperfine transitions were measured in direct laser frequency comparison with the reproducibility well below the kHz level. The results indicating the iodine cell purity are presented with relation to the absolute frequency shifts. This not only highlights the influence of iodine cell quality onto the stability and absolute frequency of laser etalons but also shows the way towards improvements of the iodine cell manufacturing technology.

Hrabina, Jan; Jedli?ka, Petr; ?íp, Ond?ej; Lazar, Josef

2008-04-01

364

Fiber Optic High Voltage Probe  

SciTech Connect

We developed a fiber coupled sensor to measure High Voltage directly using only light as the probe. We use the Pockles effect in lithium niobate crystal which will induce a phase shift in a laser beam that varies according to applied voltage. This can then be transformed into a modulation of beam intensity by polarizers, interferometery, or waveguide coupling. No voltage dividers are necessary, nor is any physical connection. This is accompanied by taking advantage of the structure of the power system itself, using voltage planes and dielectric insulation already present as the capacitive voltage divider. We hypothesize a bandwidth from GHz to DC. Such a system could be used in any application that calls for isolated and unobtrusive voltage sensing.

Matthew J. Heino

1999-08-01

365

Voltage analysis of distribution systems with DFIG wind turbines  

Microsoft Academic Search

Wind energy is becoming the most viable renewable energy source mainly because of the growing concerns over carbon emissions and uncertainties in fossil fuel supplies and the government policy impetus. The increasing penetration of wind power in distribution systems may significantly affect voltage stability of the systems, particularly during wind turbine cut-in and cut-off disturbances. Currently, doubly fed induction generator

Baohua Dong; Sohrab Asgarpoor; Wei Qiao

2009-01-01

366

Powerformers: A breakthrough of high-voltage power generators  

Microsoft Academic Search

This article deals with the powerformer, a new generator that can be directly connected to the transmission network without the need for a step-up transformer. Due to the powerformer's ability to generate electricity at transmission voltage levels, it offers considerable gains with respect to reactive power production and plant efficiency. Hence, a powerformer both facilitates network stability and decreases the

Ibrahim Metwally; R. M. Radwan; A. M. Abou-Elyazied

2008-01-01

367

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would...granted to use a greater frequency tolerance. Equipment...celsius with an input voltage variation of 85% to...

2012-10-01

368

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would...granted to use a greater frequency tolerance. Equipment...celsius with an input voltage variation of 85% to...

2011-10-01

369

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

...Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would...granted to use a greater frequency tolerance. Equipment...celsius with an input voltage variation of 85% to...

2010-10-01

370

A high-voltage modulator for high-power RF source research  

Microsoft Academic Search

The authors present the design, construction, and operating results of a high-voltage modulator system capable of generating 700 kV, 2.5 ?s pulses at 5 pps into a load of 900 ?. The modulator is used to energize a variety of high-power microwave devices requiring voltage stability and reproducibility. Voltage ripple is less than 0.2% during the 1.0 ?s flat top,

W. Mulligan; G. Bekefi; S. C. Chen; B. G. Danly; R. J. Temkin

1990-01-01

371

A high-voltage modulator for high-power RF source research  

Microsoft Academic Search

The design, construction, and operating results of a high-voltage modulator system capable of generating 700-kV, 2.5-?s pulses at 5 p.p.s. into a load of 900 ? are presented. The modular is used to energize a variety of high power microwave devices requiring voltage stability and reproducibility. Voltage ripple is less than 0.2% during the 1.0-?s flat top, with a shot-to-shot

William J. Mulligan; S. C. Chen; G. Bekefi; B. G. Danly; Richard J. Temkin

1991-01-01

372

Fiber optic high voltage probe  

Microsoft Academic Search

The authors developed a fiber coupled sensor to measure high voltages (~45 kV) directly using only light as the probe. They use the Pockels effect in lithium niobate crystals which induces a phase shift in a laser beam that varies according to applied voltage. This can then be transformed into a modulation of beam intensity by polarizers, interferometery or waveguide

Matthew J. Heino; Vasco Suite

1999-01-01

373

New ?-? voltage to frequency converter  

Microsoft Academic Search

The voltage to frequency converter (VFC) is an oscillator whose frequency is linearly proportional to the control voltage. There are two common VFC architectures: the current steering multivibrator and the charge-balance VFC. For higher linearity, the charge-balancing method is preferred. The charge balanced VFC may be made in asynchronous or synchronous (clocked) forms. The synchronous charge balanced VFC or \\

Milan Stork

2002-01-01

374

ABBGroup-1-High voltage lab  

E-print Network

. It is designed to protect an electrical circuit from damage caused by overload or short-circuit. A circuit©ABBGroup-1- 3-Sep-07 High voltage lab Research on high voltage gas circuit breakers Nils P. Basse-07 What is a circuit breaker? A circuit breaker is an automatically- operated electrical switch

Basse, Nils Plesner

375

ABBGroup-1-High voltage lab  

E-print Network

is designed to protect an electrical circuit from damage caused by overload or short-circuit. A circuit©ABBGroup-1- 3-Sep-07 High voltage lab Research on high voltage gas circuit breakers Nils P. Basse-07 What is a circuit breaker? A circuit breaker is an automatically- operated electrical switch which

Basse, Nils Plesner

376

Nonlinear electrokinetics at large voltages  

E-print Network

The classical theory of electrokinetic phenomena assumes a dilute solution of point-like ions in chemical equilibrium with a surface whose double-layer voltage is of order the thermal voltage, kBT/e=25 mV. In nonlinear ...

Bazant, Martin Z.

377

Strain-optic voltage monitor  

SciTech Connect

A voltage monitor which uses the shift in absorption edge of crystalline material to measure strain resulting from electric field-induced deformation of piezoelectric or electrostrictive material, providing a simple and accurate means for measuring voltage applied either by direct contact with the crystalline material or by subjecting the material to an electric field.

Weiss, J.D.

1995-12-31

378

EVALUATION OF CONTAMINANT LEACHABILITY FACTORS BY COMPARISON OF TREATABILITY STUDY DATA FOR MULTIPLE SOLIDIFIED/STABILIZED MATERIALS  

EPA Science Inventory

Solidification/stabilization (S/S) technology is widely used in the treatment of hazardous waste and contaminated soil in the US. In a project sponsored by the US Navy and the USEPA, treatability test data were compiled into a data base listing contaminant concentration and matri...

379

Comprehensive testing of 10 different ankle braces Evaluation of passive and rapidly induced stability in subjects with chronic ankle instability  

Microsoft Academic Search

Objective. The aim of the present investigation was to test the stability of 10 different ankle braces under passive and rapidly induced loading conditions in a population suffering from chronic ankle instability in order to provide objective information to choose or recommend an appropriate model for specific needs. In addition, the relationship between passive and rapidly induced testing of the

Eric Eils; Christina Demming; Guido Kollmeier; Lothar Thorwesten; Klaus V; Dieter Rosenbaum

380

Important parameters affecting the cell voltage of aqueous electrical double-layer capacitors  

NASA Astrophysics Data System (ADS)

This study discusses and demonstrates how the open-circuit potential and charges stored in the working potential window on positive and negative electrodes affect the cell voltage of carbon-based electrical double-layer capacitors (EDLCs) in aqueous electrolytes. An EDLC consisting of two activated carbon electrodes is employed as the model system for identifying these key parameters although the potential window of water decomposition can be simply determined by voltammetric methods. First, the capacitive performances of an EDLC with the same charge on positive and negative electrodes are evaluated by cyclic voltammetric, charge-discharge, electrochemical impedance spectroscopic (EIS) analyses, and inductance-capacitance-resistance meter (LCR meter). The principles for obtaining the highest acceptable cell voltage of such symmetric ECs with excellent reversibility and capacitor-like behaviour are proposed. Aqueous charge-balanced EDLCs can be operated as high as 2.0 V with high energy efficiency (about 90%) and only 4% capacitance loss after the 600-cycle stability checking. The necessity of charge balance (but not capacitance balance) for positive and negative electrodes is substantiated from the lower acceptable cell voltage of charge-unbalanced EDLCs.

Wu, Tzu-Ho; Hsu, Chun-Tsung; Hu, Chi-Chang; Hardwick, Laurence J.

2013-11-01

381

Wide-range voltage modulation  

SciTech Connect

The Superconducting Super Collider`s Medium Energy Booster Abort (MEBA) kicker modulator will supply a current pulse to the abort magnets which deflect the proton beam from the MEB ring into a designated beam stop. The abort kicker will be used extensively during testing of the Low Energy Booster (LEB) and the MEB rings. When the Collider is in full operation, the MEBA kicker modulator will abort the MEB beam in the event of a malfunction during the filling process. The modulator must generate a 14-{mu}s wide pulse with a rise time of less than 1 {mu}s, including the delay and jitter times. It must also be able to deliver a current pulse to the magnet proportional to the beam energy at any time during ramp-up of the accelerator. Tracking the beam energy, which increases from 12 GeV at injection to 200 GeV at extraction, requires the modulator to operate over a wide range of voltages (4 kV to 80 kV). A vacuum spark gap and a thyratron have been chosen for test and evaluation as candidate switches for the abort modulator. Modulator design, switching time delay, jitter and pre-fire data are presented.

Rust, K.R.; Wilson, J.M.

1992-06-01

382

3D numerical test objects for the evaluation of a software used for an automatic analysis of a linear accelerator mechanical stability  

NASA Astrophysics Data System (ADS)

Mechanical stability of a medical LINear ACcelerator (LINAC), particularly the quality of the gantry, collimator and table rotations and the accuracy of the isocenter position, are crucial for the radiation therapy process, especially in stereotactic radio surgery and in Image Guided Radiation Therapy (IGRT) where this mechanical stability is perturbed due to the additional weight the kV x-ray tube and detector. In this paper, we present a new method to evaluate a software which is used to perform an automatic measurement of the "size" (flex map) and the location of the kV and the MV isocenters of the linear accelerator. The method consists of developing a complete numerical 3D simulation of a LINAC and physical phantoms in order to produce Electronic Portal Imaging Device (EPID) images including calibrated distortions of the mechanical movement of the gantry and isocenter misalignments.

Torfeh, Tarraf; Beaumont, Stéphane; Guédon, Jeanpierre; Benhdech, Yassine

2010-04-01

383

High Current, Low Voltage Power Converter [20kA, 6V] - LHC Converter Prototype  

NASA Astrophysics Data System (ADS)

The superconducting LHC accelerator requires high currents (approximately 12.5 kA) and relatively low voltages (approximately 10 V) for its magnets. The need to install the power converters underground is the driving force for reduced volume and high efficiency. Moreover, the LHC machine will require a very high level of performance from the power converters, particularly in terms of DC stability, dynamic response and also in matters of EMC. To meet these requirements soft-switching techniques will be used. This paper describes the development of a [20kA, 6V] power converter intended as a stable high-current source for DCCT calibration and an evaluation prototype for the future LHC converters. The converter is made up using a modular concept where five current sources [4kA, 6V] are placed in parallel. The 4 kA sources are configured in plug-in modules : a diode rectifier on the AC mains with a damped L-C passive filter, a Zero Voltage Switching inverter working at 20 kHz and an output stage with high frequency transformers, Schottky rectifiers and output filters. The obtained performance (DC stability, bandwidth, efficiency, EMC,...) is presented and discussed.

Bordry, F.; Dupaquier, A.; Fernqvist, G.; Jorgensen, H. E.; Madsen, P.; Steinmann, E.

1997-05-01

384

Evaluation of the effect of elastomeric damping material on the stability of a bearingless main rotor system  

NASA Technical Reports Server (NTRS)

The considered investigation was conducted in connection with a contract to design, fabricate, and test a prototype bearingless main rotor (BMR) system. Part of the design process involved an aeroelastic stability investigation in a wind tunnel. Attention is given to a description of model testing, model test results, the description of the full scale wind tunnel configuration, full scale test results, and aspects of correlation with theory. It was found that the complex geometry of the BMR, with 12.5 degrees of nose-up prepitch at the hub and 2.5 degrees of tip-up predroop at the blade attachment clevis, is required to achieve a stable configuration. Subsequent model testing showed that a constrained layer of elastomer material could increase stability at all rotor speeds and collectives tested for a flat strap configuration.

Sheffler, M.; Staley, J.; Warmbrodt, W.

1980-01-01

385

Evaluation of modifications induced on pore network and structure of partially stabilized zirconia manufactured by hybrid plasma spray process  

Microsoft Academic Search

Thermal barrier coatings (TBCs) constituted by yttria partially stabilized zirconia (i.e. Y-PSZ, ZrO2+7wt.% Y2O3) and a metallic bond layer (i.e. usually MCrAlY where M represents a combination of Ni and Co) are extensively used to improve the performance of hot-section components of gas turbines. Air plasma spray (APS) and in-situ laser irradiation by diode laser processes are combined to modify

Guy Antou; Ghislain Montavon; Françoise Hlawka; Alain Cornet; Christian Coddet; Frédérique Machi

2004-01-01

386

Transformer regulated self-stabilizing chopper  

NASA Technical Reports Server (NTRS)

A self-stabilizing voltage regulator is described. Direct current voltage regulation employing a series transistor rendered conductive during various portions of a cycle is controlled by saturation of an autotransformer. The constant volt-second capacity of the transformer provides conduction time inverse to the input voltage whereby average output voltage is maintained constant. Conduction commenced in response to short gate signals, and resistor feedback for degenerative turn-off of the transistor was after transformer saturation. Standard output filters are also included.

Raposa, F. L. (inventor)

1969-01-01

387

Biomechanical evaluation of posterior lumbar dynamic stabilization: an in vitro comparison between Universal Clamp and Wallis systems  

PubMed Central

Treatment of chronic low back pain due to degenerative lumbar spine conditions often involves fusion of the symptomatic level. A known risk of this procedure is accelerated adjacent level degeneration. Motion preservation devices have been designed to provide stabilization to the symptomatic motion segment while preserving some physiologic motion. The aim of this study was to compare the changes in relative range of motion caused as a result of application of two non-fusion, dynamic stabilization devices: the Universal Clamp (UC) and the Wallis device. Nine fresh, frozen human lumbar spines (L1–Sacrum) were tested in flexion–extension, lateral bending, and axial rotation with a custom spine simulator. Specimens were tested in four conditions: (1) intact, (2) the Universal Clamp implanted at L3–4 (UC), (3) the UC with a transverse rod added (UCTR), and (4) the Wallis device implanted at L3–4. Total range of motion at 7.5 N-m was determined for each device and compared to intact condition. The UC device (with or without a transverse rod) restricted motion in all planes more than the Wallis. The greatest restriction was observed in flexion. The neutral position of the L3–4 motion segment shifted toward extension with the UC and UCTR. Motion at the adjacent levels remained similar to that observed in the intact spine for all three constructs. These results suggest that the UC device may be an appropriate dynamic stabilization device for degenerative lumbar disorders. PMID:21132335

Ilharreborde, Brice; Shaw, Miranda N.; Berglund, Lawrence J.; Zhao, Kristin D.; An, Kai-Nan

2010-01-01

388

Voltage tolerance testing of three-phase voltage source converters  

Microsoft Academic Search

This paper proposes a protocol for testing the immunity of three-phase self-commutated converters to voltage dips. An overview of voltage dips due to short circuits and earth faults that may affect a converter is given and their effect on the converter is demonstrated through simulation. Results confirm that the existing standard protocol given in IEC 61000-4-11 is not complete. An

Ambra Sannino; Math H. J. Bollen; Jan Svensson

2005-01-01

389

Low voltage nonprimary explosive detonator  

DOEpatents

A low voltage, electrically actuated, nonprimary explosive detonator is disclosed wherein said detonation is achieved by means of an explosive train in which a deflagration-to-detonation transition is made to occur. The explosive train is confined within a cylindrical body and positioned adjacent to low voltage ignition means have electrical leads extending outwardly from the cylindrical confining body. Application of a low voltage current to the electrical leads ignites a self-sustained deflagration in a donor portion of the explosive train which then is made to undergo a transition to detonation further down the train.

Dinegar, Robert H. (Los Alamos, NM); Kirkham, John (Newbury, GB2)

1982-01-01

390

Voltage Sensors Monitor Harmful Static  

NASA Technical Reports Server (NTRS)

A tiny sensor, small enough to be worn on clothing, now monitors voltage changes near sensitive instruments after being created to alert Agency workers to dangerous static buildup near fuel operations and avionics. San Diego s Quasar Federal Systems received a Small Business Innovation Research (SBIR) contract from Kennedy Space Center to develop its remote voltage sensor (RVS), a dime-sized electrometer designed to measure triboelectric changes in the environment. One of the unique qualities of the RVS is that it can detect static at greater distances than previous devices, measuring voltage changes from a few centimeters to a few meters away, due to its much-improved sensitivity.

2009-01-01

391

Evaluation of metal oxide and carbonate nanoparticle stability in soybean oil: Implications for controlled release of alkalinity during subsurface remediation  

NASA Astrophysics Data System (ADS)

Traditional methods for adjusting groundwater pH rely on injection of aqueous solutes and therefore, amendment distribution is reliant upon aqueous phase flow and transport. This reliance can limit mixing and sustention of amendments within the treatment zone. Oil-in-water emulsions offer an alternative for amendment delivery - one that has potential to enhance control of the distribution and release of buffering agents within the subsurface. Focus here is placed on using metal oxide and carbonate nanoparticles to release alkalinity from soybean oil, a common dispersed phase within emulsions designed to support remediation activities. Batch reactor systems were employed to examine the influence of dispersed phase composition on particle stability and solubility. The stability of uncoated MgO and CaCO3 particles in unmodified soybean oil was explored in a series of sedimentation studies conducted at solid loadings of 0.05, 0.1, and 0.2% mass. Three nominal sizes of MgO particles were examined (20, 50, and 100 nm) and one CaCO3 particle size (60 nm). Results from sedimentation studies conducted over four hours suggest that the viscosity of the soybean oil imparts a kinetic stability, for all sizes of the uncoated MgO and CaCO3 nanoparticles, which is sufficient time for particle encapsulation within oil-in-water emulsions. Based upon these results, the sedimentation of the 50 nm and 100 nm MgO, and 60 nm CaCO3 particles was assessed over longer durations (?72 hr). Results from these stability tests suggest that the 50 nm and 100 nm MgO particles have greater kinetic stability than the 60 nm CaCO3. Batch studies were also used to assess the influence of n-butanol, a co-solvent hypothesized to aid in controlling the rate of alkalinity release, on phase behavior and metal (Mg2+ and Ca2+) solubility. Phase behavior studies suggest that n-butanol has a limited region of miscibility within the soybean oil-water system. Use of n-butanol and water within this region of miscibility was found to increase the dielectric constant of the oil from 3.3 to 5.2. Results of solubility studies suggest that oil phase polarity may increase Ca2+ solubility, though effects were less discernable for Mg2+. These results are being employed to assess the distribution of carbonate and metal oxide particles between the soybean oil and aqueous phase. Subsequent studies will focus on exploring the influence of co-solvents on the rate of alkalinity release from oil-in-water emulsions.

Ramsburg, C. A.; Leach, O. I.; Sebik, J.; Muller, K.

2011-12-01

392

Voltage sensing in ion channels: Mesoscale simulations of biological devices  

NASA Astrophysics Data System (ADS)

Electrical signaling via voltage-gated ion channels depends upon the function of a voltage sensor (VS), identified with the S1-S4 domain in voltage-gated K+ channels. Here we investigate some energetic aspects of the sliding-helix model of the VS using simulations based on VS charges, linear dielectrics, and whole-body motion. Model electrostatics in voltage-clamped boundary conditions are solved using a boundary element method. The statistical mechanical consequences of the electrostatic configurational energy are computed to gain insight into the sliding-helix mechanism and to predict experimentally measured ensemble properties such as gating charge displaced by an applied voltage. Those consequences and ensemble properties are investigated for two alternate S4 configurations, ? and 310 helical. Both forms of VS are found to have an inherent electrostatic stability. Maximal charge displacement is limited by geometry, specifically the range of movement where S4 charges and countercharges overlap in the region of weak dielectric. Charge displacement responds more steeply to voltage in the ?-helical than in the 310-helical sensor. This difference is due to differences on the order of 0.1 eV in the landscapes of electrostatic energy. As a step toward integrating these VS models into a full-channel model, we include a hypothetical external load in the Hamiltonian of the system and analyze the energetic input-output relation of the VS.

Peyser, Alexander; Nonner, Wolfgang

2012-07-01

393

High voltage solar array experiments  

NASA Technical Reports Server (NTRS)

The interaction between the components of a high voltage solar array and a simulated space plasma is studied to obtain data for the design of a high voltage solar array capable of 15kW at 2 to 16kV. Testing was conducted in a vacuum chamber 1.5-m long by 1.5-m diameter having a plasma source which simulated the plasma conditions existing in earth orbit between 400 nautical miles and synchronous altitude. Test samples included solar array segments pinholes in insulation covering high voltage electrodes, and plain dielectric samples. Quantitative data are presented in the areas of plasma power losses, plasma and high voltage induced damage, and dielectric properties. Limitations of the investigation are described.

Kennerud, K. L.

1974-01-01

394

Voltage controlled metamaterial O. Reyneta)  

E-print Network

up to now, such as coupled-ring resonators,6 reso- nant coils,7 and lumped-element electronicF capacitor. The bias volt- age is applied to the diode through proper choke inductors to protect the voltage

Boyer, Edmond

395

Foreign Voltages and Frequencies Guide.  

National Technical Information Service (NTIS)

Foreign countries around the world use different electrical standards for voltage and frequency than those of the United States. Electrical equipment designed for 60 Hertz may or may not operate properly in a 50 Hertz environment. Similarly, electrical eq...

L. M. Windingland, S. A. Steele, K. K. Heyen, H. T. Maase, F. H. Holcomb

1997-01-01

396

Current Controlled Voltage Source (CCVS)  

NSDL National Science Digital Library

This interactive website from professor James A. Svoboda of Clarkson University describes a circuit that contains a Current Controlled Voltage Source (CCVS). The gain of the CCVS can be changed using the scrollbar.

Svoboda, James A.

2012-12-17

397

The voltage-sensor quartet  

PubMed Central

Decoding the workings of voltage-gated sodium channels is crucial because their mutation leads to severe disease and their activity is modulated by toxins and drugs. An innovative approach now allows such investigations. PMID:19005542

Bankston, J. R.; Kass, R. S.

2009-01-01

398

Evaluation of biomechanical strength, stability, bioactivity, and in vivo biocompatibility of a novel calcium deficient hydroxyapatite/poly(amino acid) composite cervical vertebra cage.  

PubMed

A new type of cervical vertebra cage was prepared using a novel composite, calcium deficient hydroxyapatite/poly(amino acid) (HA/PAA), and its mechanical properties, in vitro stability and bioactivity, and in vivo biocompatibility were characterized. The results showed that the axial compressive loads of the HA/PAA cage were in the range of 10058-10612 N and the lateral compressive loads were in the range of 1180-2363 N, and varied with the height of the cervical vertebra cages. After immersion in simulated body fluid (SBF) for 16 weeks, the axial compressive loads of the cage decreased from 10058 to 7131 N and the lateral compressive loads decreased from 1180 to 479 N. In addition, the weight loss decreased 6.01%, showing that HA/PAA composites had good stability during the incubation period. The pH value of SBF was also monitored during the whole soaking period; it fluctuated in the range of 6.9-7.4. Scanning electron microscope and energy dispersive spectrometer results showed the cage was bioactive with a new apatite layer attached on the surface. The histological evaluation revealed that new bone tissue bonded tightly with the surfaces of the implants, showing excellent biocompatibility. In conclusion, the HA/PAA cage showed sufficient strength, good stability, bioactivity, and biocompatibility, and has potential applications for clinical cervical vertebrae repair. PMID:25162474

Xiong, Yi; Li, Hong; Zhou, Chunguang; Yang, Xi; Song, Yueming; Qing, Yan; Yan, Yonggang

2014-11-01

399

DSC studies to evaluate the impact of bio-oil on cold flow properties and oxidation stability of bio-diesel.  

PubMed

This paper describes the use of Differential Scanning Calorimetry (DSC) to evaluate the impact of varying mix ratios of bio-oil (pyrolysis oil) and bio-diesel on the oxidation stability and on some cold flow properties of resulting blends. The bio-oils employed were produced from the semi-continuous Auger pyrolysis of pine pellets and the batch pyrolysis of pine chips. The bio-diesel studied was obtained from poultry fat. The conditions used to prepare the bio-oil/bio-diesel blends as well as some of the fuel properties of these blends are reported. The experimental results suggest that the addition of bio-oil improves the oxidation stability of the resulting blends and modifies the crystallization behavior of unsaturated compounds. Upon the addition of bio-oil an increase in the oxidation onset temperature, as determined by DSC, was observed. The increase in bio-diesel oxidation stability is likely to be due to the presence of hindered phenols abundant in bio-oils. A relatively small reduction in DSC characteristic temperatures which are associated with cold flow properties was also observed but can likely be explained by a dilution effect. PMID:20307976

Garcia-Perez, Manuel; Adams, Thomas T; Goodrum, John W; Das, K C; Geller, Daniel P

2010-08-01

400

Unlikely Combination of Experiments with a Novel High-Voltage CIGS Photovoltaic Array (Presentation)  

SciTech Connect

The goals of this study are to: (1) parameterize current-voltage (I-V) performance over a wide range of illumination and temperatures: (a) 50-1150 W/m{sup 2} irradiance, 5-65 C; (b) obtain array temperature coefficients; and (c) quantify energy production; (2) investigate high-voltage leakage currents from the CIS modules in a high-voltage array: determine dependence on moisture, temperature, and voltage bias and ascertain corrosion problems if any; and (3) study long-term power and energy production stability.

del Cueto, J. A.; Sekulic, B. R.

2006-05-01

401

Stability of Biases in Self-Evaluation and Relations to Well-Being among Elementary School Children  

ERIC Educational Resources Information Center

This paper aims to investigate to what extent a bias in self-evaluation is an enduring characteristic among children, and whether there is a relationship between the trajectory of children's self-evaluation bias over a five-year period and their psychosocial adjustment. 462 children (200 boys) in Grade 3 (mean age=8.6 years old) or Grade 4 (mean…

Bouffard, Therese; Vezeau, Carole; Roy, Mathieu; Lengele, Aurelie

2011-01-01

402

Novel bandgap-based under-voltage-lockout methods with high reliability  

NASA Astrophysics Data System (ADS)

Highly reliable bandgap-based under-voltage-lockout (UVLO) methods are presented in this paper. The proposed under-voltage state to signal conversion methods take full advantages of the high temperature stability characteristics and the enhancement low-voltage protection methods which protect the core circuit from error operation; moreover, a common-source stage amplifier method is introduced to expand the output voltage range. All of these methods are verified in a UVLO circuit fabricated with a 0.5 ?m standard BCD process technology. The experimental result shows that the proposed bandgap method exhibits a good temperature coefficient of 20 ppm/°C, which ensures that the UVLO keeps a stable output until the under-voltage state changes. Moreover, at room temperature, the high threshold voltage VTH+ generated by the UVLO is 12.3 V with maximum drift voltage of ±80 mV, and the low threshold voltage VTH- is 9.5 V with maximum drift voltage of ±70 mV. Also, the low voltage protection method used in the circuit brings a high reliability when the supply voltage is very low.

Yongrui, Zhao; Xinquan, Lai

2013-10-01

403

The Application of Droop-Control in Distributed Energy Resources to Extend the Voltage Collapse Margin  

SciTech Connect

The growth in distributed energy resources has the potential to reduce system stresses caused by transmission grid congestion by supplying power and voltage regulation closer to load centers. However, the additional voltage regulation provided by these resources can mask the onset of voltage collapse. Local voltage support flattens the slope in the upper region of the power-voltage nose curve. Coordinating voltage-regulation behavior with the droop-control scheme in distributed resources improves the observation of voltage collapse margins. Incorporating distributed resource models in the continuation power flow analysis, allows the exploration of the power transfer gains by the application of distributed resources. The analysis provides insight to the impact of droop control on the behavior of the power-voltage curve and voltage collapse. The analysis is applied to a fixed speed induction generator wind farm with separate reactive compensation and the interconnection to the local power system. Results reveal that coordinating the droop control strategy allows the distributed resource to significantly increase the voltage collapse margin without hiding the threat of voltage stability problems.

Henry, Shawn D. [Florida State University; Rizy, D Tom [ORNL; Baldwin, Thomas L [Florida State University; Kueck, John D [ORNL; Li, Fangxing [ORNL

2008-01-01

404

An Experimental Evaluation of Generalized Predictive Control for Tiltrotor Aeroelastic Stability Augmentation in Airplane Mode of Flight  

NASA Technical Reports Server (NTRS)

The results of a joint NASA/Army/Bell Helicopter Textron wind-tunnel test to assess the potential of Generalized Predictive Control (GPC) for actively controlling the swashplate of tiltrotor aircraft to enhance aeroelastic stability in the airplane mode of flight are presented. GPC is an adaptive time-domain predictive control method that uses a linear difference equation to describe the input-output relationship of the system and to design the controller. The test was conducted in the Langley Transonic Dynamics Tunnel using an unpowered 1/5-scale semispan aeroelastic model of the V-22 that was modified to incorporate a GPC-based multi-input multi-output control algorithm to individually control each of the three swashplate actuators. Wing responses were used for feedback. The GPC-based control system was highly effective in increasing the stability of the critical wing mode for all of the conditions tested, without measurable degradation of the damping in the other modes. The algorithm was also robust with respect to its performance in adjusting to rapid changes in both the rotor speed and the tunnel airspeed.

Kvaternik, Raymond G.; Piatak, David J.; Nixon, Mark W.; Langston, Chester W.; Singleton, Jeffrey D.; Bennett, Richard L.; Brown, Ross K.

2001-01-01

405

Structural Mechanism of Voltage-Dependent Gating in an Isolated Voltage-Sensing Domain  

PubMed Central

SUMMARY The transduction of transmembrane electric fields into protein motion plays an essential role in the generation and propagation of cellular signals. Voltage-sensing domains (VSD) carry out these functions through reorientations of S4 helix with discrete gating charges. Here, crystal structures of the VSD from Ci-VSP were determined in both, active (Up) and resting (Down) conformations. The S4 undergoes a ~5 Å displacement along its main axis accompanied by a ~60o rotation, consistent with the helix-screw gating mechanism. This movement is stabilized by a change in countercharge partners in helices S1 and S3, generating an estimated net charge transfer of ~1 eo. Gating charges move relative to a “hydrophobic gasket” that electrically divides intra and extracellular compartments. EPR spectroscopy confirms the limited nature of S4 movement in a membrane environment. These results provide an explicit mechanism for voltage sensing and set the basis for electromechanical coupling in voltage-dependent cellular activities. PMID:24487958

Li, Qufei; Wanderling, Sherry; Paduch, Marcin; Medovoy, David; Singharoy, Abhishek; McGreevy, Ryan; Villalba-Galea, Carlos; Hulse, Raymond E.; Roux, Benoit; Schulten, Klaus; Kossiakoff, Anthony; Perozo, Eduardo

2014-01-01

406

Comparative evaluation of different co-antioxidants on the photochemical- and functional-stability of epigallocatechin-3-gallate in topical creams exposed to simulated sunlight.  

PubMed

The catechin (-)-epigallocatechin-3-gallate (EGCG) exhibits high antioxidant activity and it has been reported to provide protection of the skin against damage induced by solar UV radiation. However, EGCG is highly unstable under sunlight. The present study aimed to compare the effectiveness of the co-antioxidant agents vitamin E, butylated hydroxytoluene, vitamin C and a-lipoic acid for their potential to protect the catechin from photochemical degradation. Model creams (oil-in-water emulsions) containing EGCG (1%, w/w) alone or combined with equimolar concentrations of co-antioxidant were exposed to a solar simulator at an irradiance corresponding to natural sunlight. Photodegradation was evaluated by HPLC-UV and HPLC-ESI-MS/MS. Addition of the co-antioxidants vitamin C and a-lipoic acid to the formulation significantly reduced the light-induced decomposition of EGCG from 76.9 ± 4.6% to 20.4 ± 2.7% and 12.6 ± 1.6%, respectively. Conversely, butylated hydroxytoluene had no effect (EGCG loss, 78.1 ± 4.6%) and vitamin E enhanced the EGCG photolysis to 84.5 ± 3.4%. The functional stability of the catechin in the creams exposed to the solar simulator was also evaluated by measuring the in vitro antioxidant activity. Following irradiation, the reduction of the EGCG formulation antioxidant power was lower (21.8%) than the extent of degradation (76.9%), suggesting the formation of photoproducts with antioxidant properties. The influence of the examined co-antioxidants on the functional stability of the catechin under simulated sunlight paralleled that measured for the EGCG photodecomposition, a-lipoic acid exerting the greatest stabilising effect (antioxidant activity decrease, 1.4%). These results demonstrated that a-lipoic acid is an effective co-antioxidant agent for the stabilization of EGCG in dermatological products for skin photoprotection. PMID:23292326

Scalia, Santo; Marchetti, Nicola; Bianchi, Anna

2013-01-01

407

Kinematic evaluation of the adjacent segments after lumbar instrumented surgery: a comparison between rigid fusion and dynamic non-fusion stabilization.  

PubMed

The aim of the current study was to evaluate changes in lumbar kinematics after lumbar monosegmental instrumented surgery with rigid fusion and dynamic non-fusion stabilization. A total of 77 lumbar spinal stenosis patients with L4 degenerative spondylolisthesis underwent L4-5 monosegmental posterior instrumented surgery. Of these, 36 patients were treated with rigid fusion (transforaminal lumbar interbody fusion) and 41 with dynamic stabilization [segmental spinal correction system (SSCS)]. Lumbar kinematics was evaluated with functional radiographs preoperatively and at final follow-up postoperatively. We defined the contribution of each segmental mobility to the total lumbar mobility as the percent segmental mobility [(sagittal angular motion of each segment in degrees)/(total sagittal angular motion in degrees) × 100]. Magnetic resonance imaging was performed on all patients preoperatively and at final follow-up postoperatively. The discs were classified into five grades based on the previously reported system. We defined the progress of disc degeneration as (grade at final follow-up) - (grade at preoperatively). No significant kinematical differences were shown at any of the lumbar segments preoperatively; however, significant differences were observed at the L2-3, L4-5, and L5-S1 segments postoperatively between the groups. At final follow-up, all of the lumbar segments with rigid fusion demonstrated significantly greater disc degeneration than those with dynamic stabilization. Our results suggest that the SSCS preserved 14% of the kinematical operations at the instrumented segment. The SSCS may prevent excessive effects on adjacent segmental kinematics and may prevent the incidence of adjacent segment disorder. PMID:21301893

Morishita, Yuichiro; Ohta, Hideki; Naito, Masatoshi; Matsumoto, Yoshiyuki; Huang, George; Tatsumi, Masato; Takemitsu, Yoshiharu; Kida, Hirotaka

2011-09-01

408

Phosphatidic acid modulation of Kv channel voltage sensor function.  

PubMed

Membrane phospholipids can function as potent regulators of ion channel function. This study uncovers and investigates the effect of phosphatidic acid on Kv channel gating. Using the method of reconstitution into planar lipid bilayers, in which protein and lipid components are defined and controlled, we characterize two effects of phosphatidic acid. The first is a non-specific electrostatic influence on activation mediated by electric charge density on the extracellular and intracellular membrane surfaces. The second is specific to the presence of a primary phosphate group, acts only through the intracellular membrane leaflet and depends on the presence of a particular arginine residue in the voltage sensor. Intracellular phosphatidic acid accounts for a nearly 50 mV shift in the midpoint of the activation curve in a direction consistent with stabilization of the voltage sensor's closed conformation. These findings support a novel mechanism of voltage sensor regulation by the signaling lipid phosphatidic acid. PMID:25285449

Hite, Richard K; Butterwick, Joel A; MacKinnon, Roderick

2014-01-01

409

Voltage-gated proton channels: what' next?  

PubMed Central

This review is an attempt to identify and place in context some of the many questions about voltage-gated proton channels that remain unsolved. As the gene was identified only 2 years ago, the situation is very different than in fields where the gene has been known for decades. For the proton channel, most of the obvious and less obvious structure–function questions are still wide open. Remarkably, the proton channel protein strongly resembles the voltage-sensing domain of many voltage-gated ion channels, and thus offers a novel approach to study gating mechanisms. Another surprise is that the proton channel appears to function as a dimer, with two separate conduction pathways. A number of significant biological questions remain in dispute, unanswered, or in some cases, not yet asked. This latter deficit is ascribable to the intrinsic difficulty in evaluating the importance of one component in a complex system, and in addition, to the lack, until recently, of a means of performing an unambiguous lesion experiment, that is, of selectively eliminating the molecule in question. We still lack a potent, selective pharmacological inhibitor, but the identification of the gene has allowed the development of powerful new tools including proton channel antibodies, siRNA and knockout mice. PMID:18801839

DeCoursey, Thomas E

2008-01-01

410

Thermal voltage noise in layered superconductors  

SciTech Connect

Thermal voltage noise in the mixed state of type-II superconductors has been calculated taking into account fluctuation modes of nonrigid vortices. It has been shown that bending of vortices leads to new effects in thermal-voltage-noise spectra at high frequencies. The power spectrum reflecting fluctuations of rigid vortices is suppressed at very low frequencies and saturates into a white spectrum at a characteristic frequency depending on the strip width. At high frequencies tilt modes of flexible vortices start to contribute to the fluctuating voltages and the power spectrum undergoes three subsequent magnitude increases, following {omega}{sup 1/2}-, {omega}{sup 2}-, and again {omega}{sup 1/2}-like behavior before becoming white again. It has been shown that for layered superconductors of a moderate anisotropy the second {omega}{sup 1/2}-like increase disappears at magnetic fields exceeding a certain threshold field corresponding to the crossover field between two-dimensional and three-dimensional vortex-lattice melting. Field dependencies of characteristic frequencies separating different regimes of spectral behavior have been evaluated and shown to be qualitatively different for low and high magnetic fields.

Ashkenazy, V.D. [Department of Physics, Bar-Ilan University, 52100, Ramat Gan (Israel)] [Department of Physics, Bar-Ilan University, 52100, Ramat Gan (Israel); Jung, G. [Department of Physics, Ben Gurion University of the Negev, 84105 Beer-Sheva (Israel)] [Department of Physics, Ben Gurion University of the Negev, 84105 Beer-Sheva (Israel); [Instytut Fizyki PAN, 02668 Warszawa (Poland); Shapiro, B.Y. [Jack and Pearl Resnick Institute of Advanced Technology, Bar-Ilan University, 52100, Ramat Gan (Israel)] [Jack and Pearl Resnick Institute of Advanced Technology, Bar-Ilan University, 52100, Ramat Gan (Israel); [Department of Physics, Bar-Ilan University, 52100, Ramat Gan (Israel)

1995-04-01

411

Next generation KATRIN high precision voltage divider for voltages up to 65kV  

NASA Astrophysics Data System (ADS)

The KATRIN (KArlsruhe TRItium Neutrino) experiment aims to determine the mass of the electron antineutrino with a sensitivity of 200 meV by precisely measuring the electron spectrum of the tritium beta decay. This will be done by the use of a retarding spectrometer of the MAC-E-Filter type. To achieve the desired sensitivity the stability of the retarding potential of -18.6 kV has to be monitored with a precision of 3 ppm over at least two months. Since this is not feasible with commercial devices, two ppm-class high voltage dividers were developed, following the concept of the standard divider for DC voltages of up to 100 kV of the Physikalisch-Technische Bundesanstalt (PTB). In order to reach such high accuracies different effects have to be considered. The two most important ones are the temperature dependence of resistance and leakage currents, caused by insulators or corona discharges. For the second divider improvements were made concerning the high-precision resistors and the thermal design of the divider. The improved resistors are the result of a cooperation with the manufacturer. The design improvements, the investigation and the selection of the resistors, the built-in ripple probe and the calibrations at PTB will be reported here. The latter demonstrated a stability of about 0.1 ppm/month over a period of two years.

Bauer, S.; Berendes, R.; Hochschulz, F.; Ortjohann, H.-W.; Rosendahl, S.; Thümmler, T.; Schmidt, M.; Weinheimer, C.

2013-10-01

412

Development of a Combined Solution Formulation of Atropine Sulfate and Obidoxime Chloride for Autoinjector and Evaluation of Its Stability  

PubMed Central

Atropine (AT) and oximes, alone or in combination, have been proven greatly valuable therapeutics in the treatment of organophosphates intoxications. An injectable mixture of AT and obidoxime (OB) was formulated for the administration by automatic self-injector. The aqueous single dose solution contained 275 mg obidoxime chloride and 2.5 mg atropine sulfate per 1 mL (220 mg and 2 mg per 0.8 effective dose, respectively). The final solution was sterilized by filtration through a 0.22 ?m pore size filter. This more concentrated solution allowed to use a smaller size and lighter weight cartridge. Quality control tests, including assay of the two major compounds were performed separately, using reversed-phase HPLC methods. Besides, the stability test was carried out according to ICH guideline for the accelerated test. The obtained results showed that the proposed formulation is stable over a period of 2 years after preparation. PMID:24250669

Ettehadi, Hossein Ali; Ghalandari, Rouhollah; Shafaati, Alireza; Foroutan, Seyed Mohsen

2013-01-01

413

Evaluation of Data Stability and Analysis of Degradation Factors of Digital Versatile Disk Recordable (DVD+R) for Archival Application  

NASA Astrophysics Data System (ADS)

Optical disks are widely used in libraries and archives as digital data media due to their archival storage stability. Nevertheless, there is relatively less focus on the understanding of physical and chemical degradation mechanism. To observe the degradation mechanism of an optical disk, the accelerated aging test was designed with high temperature and relative humidity of 85 °C and 85% in this study. After 1500 h of aging, digital versatile disk recordable (DVD+R) media resulted in a high value of over 280 in the PI sum 8 value, which means a severe data degradation in the media. From the microstructural observation of recorded marks and the chemical analysis of the reflective layer after this accelerated aging test, gradual physical deformation of recorded mark edges and chemical change of the reflective layer were observed, and they might be related to the severe increase of PI sum 8.

Lee, Kwan-Yong; Lim, Dong-Soo; Kim, Ki-Hyun; Cho, Won-Ik; Kim, Young-Joo

2012-08-01

414

[A quantitative method for evaluating the structure and conformational stability of proteins by second derivative UV-spectroscopy].  

PubMed

A quantitative method is suggested for estimating the structure and conformational stability of proteins based on the individual absorbance of Tyr residues in the second derivative UV spectra. Subtilisins Carlsberg, BPN' and 72 were chosen as the model proteins. The values of the increase of the Tyr absorption at 282.3 nm upon the total denaturation of the proteins made it possible to calculate the number of the exposed and "buried" tyrosine residues in the native proteins. A mathematical model of spectrum changes during the transition of Tyr residues from the "buried" to exposed form is suggested. The method is useful for the determination of the denaturation constants of proteins bearing "buried" tyrosine residues. PMID:8166752

Shevchenko, A A; Kost, O A; Kazanskaia, N F

1994-03-01

415

Radio frequency induced hyperthermia mediated by dextran stabilized LSMO nanoparticles: in vitro evaluation of heat shock protein response.  

PubMed

Dextran stabilized La(0.7)Sr(0.3)MnO(3) (Dex-LSMO) is an alternative cancer hyperthermia agent holding considerable promise. Here, we have carried out a comparative study on radio frequency (~264 kHz) induced Dex-LSMO mediated heating and extraneous heating (mimicking generalized hyperthermia) in terms of changes in the morphology, proliferation pattern and induction of heat shock proteins in a human melanoma cell line (A375). Our results clearly show that the cellular effects seen with extraneous heating (60 min at 43 °C) could be reproduced by just six minutes of radio frequency induced Dex-LSMO mediated heating. More importantly, the observed enhanced levels of HSP 70 and 90 (molecular markers of heat shock that trigger favorable immunological reactions) seen with Dex-LSMO mediated heating were comparable to extraneous heating. These results suggest the possible utility of Dex-LSMO as a cancer hyperthermia agent. PMID:23221040

Bhayani, K R; Rajwade, J M; Paknikar, K M

2013-01-11

416

Rheology and stability of SRC residual fuel oils - storage evaluation. SRC-1 quarterly technical report, October-December 1982. Supplement  

SciTech Connect

In Air Products ongoing study to characterize the rheology and stability of various SRC residual oils, single-phase blends of 50 wt % HSRC and TSL SRC in 1:1 mixtures of 1st- and 2nd-stage process solvents were subjected to storage stability tests at 150/sup 0/F in nitrogen and air atmospheres. Using viscosity as an indicator, it was observed that the blends studied increased in viscosity with storage time in an air atmosphere; the viscosity increase began after a 4-week storage period. The increase in HSRC blend viscosity was significantly greater than that of the TSL SRC blend. A 60-day air-stored blend will require a pumping temperature about 10/sup 0/F higher than that specified for an unaged blend in order to have the same viscosity. The viscosity increase under nitrogen storage was relatively insignificant. Nitrogen blanketing appears to be important in maintaining the specified viscosity characteristics of the blends during storage in the 150/sup 0/F storage condition tested. A loss of volatiles undoubtedly occurs during high-temperature storage under laboratory conditions. Such losses contribute to an increase in the viscosity of the blend. In commercial practice, volatile losses are expected to be significantly lower. Solvent extraction data and analysis of separated fractions suggest that during storage under the above conditions, some oxidative polymerization of pentane-soluble oil components forms higher molecular weight pentane insolubles (asphaltenes and benzene insolubles). Asphaltenes are also involved in the increase in viscosity and do chemically change. 1 reference, 8 figures, 27 tables.

Tewari, K.C.

1984-06-01

417

The evaluation of stability during the composting of different starting materials: comparison of chemical and biological parameters.  

PubMed

Three blends formed by: (i) food processing waste (CP(FP)), (ii) waste water sewage sludge (CP(WW)), and (iii) their mixture (CP(FP+WW)), blended with tree pruning as bulking agent, were composted over 3 months. During composting the blends were monitored for the main physical-chemical characteristics: temperature, oxygen saturation level (O(2)%), pH, total and volatile solids, total organic carbon, and organic nitrogen (N(org)). In addition to the main parameters, the dissolved organic carbon (DOC), the inorganic nitrogen and the Oxygen Uptake Rate (OUR) were monitored. All the mixtures easily reached a peak temperature around 70°C, related to the lowest O(2)%. After 90 d, CP(FP), CP(FP+WW), and CP(WW) showed an organic matter mineralization of 43%, 35% and 33%, respectively; CP(FP) fitted an exponential model while both CP(FP+WW), and CP(WW) fitted a logistic model. During composting an OUR reduction of 79%, 78% and 73% was registered in CP(FP), CP(FP+WW), and CP(WW), respectively; the OUR successfully fitted the adopted exponential model and well reflected the stabilization process in time. The N(org) recovery at the end of the process was positive only in CP(WW) (11.6%). The DOC significantly decreased during the composting process but did not successfully fit any model. The mineral nitrogen did not follow the typical pattern with NH(4)(+) disappearance and NO(3)(-) accumulation. Strong NO(3)(-) losses were evident in all blends, while NH(4)(+) accumulations were detectable only in CP(FP), and CP(FP+WW). The NH(4)(+)/NO(3)(-) ratio did not satisfactorily reflect the composting process over time. The comparison of the first order (exponential) and logistic (sigmoidal) models applied to the OUR and OM course highlights the role of mineral nitrogen as limiting factor during composting of the more stabilized sludge. PMID:21277001

Grigatti, Marco; Cavani, Luciano; Ciavatta, Claudio

2011-03-01

418

DC Link Capacitor Voltage Balancing in a Three-Phase Diode Clamped Inverter Controlled by a Direct Space Vector of Line-to-Line Voltages  

Microsoft Academic Search

In this paper, the direct modulation strategy of a three-level inverter with self stabilization of the dc link voltage is extended to a five-level inverter. Therefore, a new modeling and control strategy of a five-level three-phase diode-clamped inverter (DCI) is presented. The obtained modeling shows that modulated multilevel voltages are obtained by combination of eight different three-level functions, which are

O. Bouhali; B. Francois; E. M. Berkouk; C. Saudemont

2007-01-01

419

A voltage to frequency converter for astronomical photometry  

NASA Technical Reports Server (NTRS)

A voltage to frequency converter (VFC) for general use with photomultipliers is described. For high light levels, when the dead-time corrections for a photon counter would be excessive, the VFC maintains a linear response and allows the recording of data at high time resolution. Results of laboratory tests are given for the signal-to-noise characteristics, linearity, stability, and transient response of the VFC when used in conjunction with EMI 9658 and RCA C31034 photomultipliers.

Dunham, E.; Elliot, J. L.

1978-01-01

420

Modulated voltage metastable ionization detector  

NASA Technical Reports Server (NTRS)

The output current from a metastable ionization detector (MID) is applied to a modulation voltage circuit. An adjustment is made to balance out the background current, and an output current, above background, is applied to an input of a strip chart recorder. For low level concentrations, i.e., low detected output current, the ionization potential will be at a maximum and the metastable ionization detector will operate at its most sensitive level. When the detected current from the metastable ionization detector increases above a predetermined threshold level, a voltage control circuit is activated which turns on a high voltage transistor which acts to reduce the ionization potential. The ionization potential applied to the metastable ionization detector is then varied so as to maintain the detected signal level constant. The variation in ionization potential is now related to the concentration of the constituent and a representative amplitude is applied to another input of said strip chart recorder.

Carle, G. C.; Kojiro, D. R.; Humphrey, D. E. (inventors)

1985-01-01

421

Voltage-Gated Hydrophobic Nanopores  

SciTech Connect

Hydrophobicity is a fundamental property that is responsible for numerous physical and biophysical aspects of molecular interactions in water. Peculiar behavior is expected for water in the vicinity of hydrophobic structures, such as nanopores. Indeed, hydrophobic nanopores can be found in two distinct states, dry and wet, even though the latter is thermodynamically unstable. Transitions between these two states are kinetically hindered in long pores but can be much faster in shorter pores. As it is demonstrated for the first time in this paper, these transitions can be induced by applying a voltage across a membrane with a single hydrophobic nanopore. Such voltage-induced gating in single nanopores can be realized in a reversible manner through electrowetting of inner walls of the nanopores. The resulting I-V curves of such artificial hydrophobic nanopores mimic biological voltage-gated channels.

Lavrik, Nickolay V [ORNL

2011-01-01

422

RETROSPECTIVE EVALUATION OF THE EFFECTS OF SELECTED INDUSTRIAL WASTES ON MUNICIPAL SOLID WASTE STABILIZATION IN SIMULATED LANDFILLS  

EPA Science Inventory

The report is a retrospective evaluation of ten years of leachate and gas data collected from 19 simulated landfills (landfill cells) containing municipal solid waste codisposed with sewage sludge or industrial wastes. Physical and chemical parameters from each landfill cell are ...

423

Estimation of beer stability by sulphur dioxide and polyphenol determination. Evaluation of a Laccase-Sonogel-Carbon biosensor  

Microsoft Academic Search

The traditional methods used to evaluate parameters related to beer ageing have been tested, revised and criticised. With this aim, a sampling of lager beers has been carried out. Sulphur dioxide, polyphenols and antioxidant capacity have been determined in fresh and aged beer. Only sulphur dioxide concentration showed relevant differences after the ageing process. These results together with a correlation

Emiliano Martinez-Periñan; María P. Hernández-Artiga; José M. Palacios-Santander; Mohammed ElKaoutit; Ignacio Naranjo-Rodriguez; Dolores Bellido-Milla

2011-01-01

424

Low Voltage Spatial Light Modulator  

SciTech Connect

This project studied the feasibility of a Low-Voltage actuator technology that promises to reduce the switched voltage requirements and linearize the response of spatial light modulators. We created computer models that demonstrate substantial advantages offered by this technology, and fabricated and tested those devices. SLMs are electro-optic devices for modulating the phase, amplitude or angle of light beams, laser or other. Applications for arrays of SLMs include turbulence correction for high-speed optical communications, imaging through distorting media, input devices for holographic memories, optical manipulation of DNA molecules, and optical computers. Devices based on micro electro-mechanical systems (MEMS) technology have recently become of special interest because of their potential for greatly improved performance at a much lower cost than piezoelectric or liquid crystal based devices. The new MEMS-based SLM devices could have important applications in high-speed optical communication and remote optical sensing, in support of DoD and DOE missions. Virtually all previously demonstrated MEMS SLMs are based on parallel-plate capacitors where an applied voltage causes a mirror attached to a suspended electrode to move towards a fixed electrode. They require relatively high voltages, typically on the order of 100 V, resulting in (1) large transistor sizes, available only from specialized foundries at significant cost and limiting the amount/sophistication of electronics under each SLM pixel, and (2) large power dissipation/area, resulting in a heat removal issue because of the optical precision required ({approx} 1/50-th of a wavelength). The actuator described in this process uses an advanced geometry that was invented at LLNL and is currently still proprietary. The new geometry allows the application of a bias voltage. This applied bias voltage results in a reduction of the required switched voltage and a linearization of the response curve. When this advanced actuator is coupled with non-linear springs, the response curve becomes even more linear. The response curve of the springs is tailored to produce an actuator with extremely linear displacement vs. voltage characteristics.

Papavasiliou, A

2003-02-19

425

Suppression techniques of common-mode voltage generated by voltage source PWM inverter  

Microsoft Academic Search

Voltage source PWM inverters generate high frequency common-mode voltage, which induces high shaft voltage, leads to bearing current, and results in premature bearing failure. The generating mechanism of common-mode voltage of voltage source PWM inverters is discussed, which illustrates that common-mode voltage is ladder-type high dv\\/dt and high frequency step voltage, its amplitude varies with the states of switching devices.

Ma Hongfei; Xu Dianguo; Miao Lijie

2004-01-01

426

Temperature Dependence of Output Voltage Generated by Interaction of Threshold Voltage and Mobility of an NMOS Transistor  

Microsoft Academic Search

Mutual compensation of mobility andthreshold voltage temperature variations mayresult in a zero temperature coefficient (ZTC)bias point of an NMOS transistor. Theconditions under which this effect occurs,stability of this bias point, and thetemperature dependence of the output voltagefor a diode-connected transistor operating inthe vicinity of ZTC point are investigated inthis paper. Some possible applications of thiseffect include temperature sensors with lineardependence

I. M. Filanovsky; A. Allam; Su Tarn Lim

2001-01-01

427

Stability evaluation of freeze-dried Lactobacillus paracasei subsp. tolerance and Lactobacillus delbrueckii subsp. bulgaricus in oral capsules  

PubMed Central

Freeze-drying is a common preservation technology in the pharmaceutical industry. Various studies have investigated the effect of different cryoprotectants on probiotics during freeze-drying. However, information on the effect of cryoprotectants on the stability of some Lactobacillus strains during freeze-drying seems scarce. Therefore, the aim of the present study was to establish production methods for preparation of oral capsule probiotics containing Lactobacillus paracasei subsp. tolerance and Lactobacillus delbrueckii subsp. Bulgaricus. It was also of interest to examine the effect of various formulations of cryoprotectant media containing skim milk, trehalose and sodium ascorbate on the survival rate of probiotic bacteria during freeze-drying at various storage temperatures. Without any cryoprotectant, few numbers of microorganisms survived. However, microorganisms tested maintained higher viability after freeze-drying in media containing at least one of the cryoprotectants. Use of skim milk in water resulted in an increased viability after lyophilization. Media with a combination of trehalose and skim milk maintained a higher percentage of live microorganisms, up to 82%. In general, bacteria retained a higher number of viable cells in capsules containing freeze-dried bacteria with sodium ascorbate after three months of storage. After this period, a marked decline was observed in all samples stored at 23°C compared to those stored at 4°C. The maximum survival rate (about 72-76%) was observed with media containing 6% skim milk, 8% trehalose and 4% sodium ascorbate. PMID:23181077

Jalali, M.; Abedi, D.; Varshosaz, J.; Najjarzadeh, M.; Mirlohi, M.; Tavakoli, N.

2012-01-01

428

Stability evaluation of freeze-dried Lactobacillus paracasei subsp. tolerance and Lactobacillus delbrueckii subsp. bulgaricus in oral capsules.  

PubMed

Freeze-drying is a common preservation technology in the pharmaceutical industry. Various studies have investigated the effect of different cryoprotectants on probiotics during freeze-drying. However, information on the effect of cryoprotectants on the stability of some Lactobacillus strains during freeze-drying seems scarce. Therefore, the aim of the present study was to establish production methods for preparation of oral capsule probiotics containing Lactobacillus paracasei subsp. tolerance and Lactobacillus delbrueckii subsp. Bulgaricus. It was also of interest to examine the effect of various formulations of cryoprotectant media containing skim milk, trehalose and sodium ascorbate on the survival rate of probiotic bacteria during freeze-drying at various storage temperatures. Without any cryoprotectant, few numbers of microorganisms survived. However, microorganisms tested maintained higher viability after freeze-drying in media containing at least one of the cryoprotectants. Use of skim milk in water resulted in an increased viability after lyophilization. Media with a combination of trehalose and skim milk maintained a higher percentage of live microorganisms, up to 82%. In general, bacteria retained a higher number of viable cells in capsules containing freeze-dried bacteria with sodium ascorbate after three months of storage. After this period, a marked decline was observed in all samples stored at 23°C compared to those stored at 4°C. The maximum survival rate (about 72-76%) was observed with media containing 6% skim milk, 8% trehalose and 4% sodium ascorbate. PMID:23181077

Jalali, M; Abedi, D; Varshosaz, J; Najjarzadeh, M; Mirlohi, M; Tavakoli, N

2012-01-01

429

Evaluation of Saskatoon berry (Amelanchier alnifolia Nutt.) cultivars for their polyphenol content, antioxidant properties, and storage stability.  

PubMed

The polyphenol contents and antioxidant activities were assessed for 17 Saskatoon berry cultivars grown in Canada in fresh and stored fruits at -20 degrees C for 9 months. The Nelson cultivar was the richest in total polyphenol, anthocyanin, and procyanidin contents (801, 382, and 278 mg/100 g fresh weight, respectively). This cultivar was characterized also by the highest antioxidant potential measured with DPPH and ABTS radicals (2.8 and 5.0 mM/100 g FW, respectively). Cultivar-dependent changes in polyphenol content after freezer storage were observed. In the Lee 2 cultivar, significant increases in anthocyanin and flavonol contents occurred, while in the Lee 3 and Martin cultivars considerable decreases were observed. During the freezer storage, the antioxidant activity remained unchanged except for the Smokey which showed to be the most sensitive cultivar during storage. The Nelson and Lee 2 were the most stable cultivars during storage. The high polyphenol content and antioxidant activity of the Nelson cultivar and its good storage stability would make this cultivar the optimal material for fruit growers and food producers. PMID:18922015

Bakowska-Barczak, Anna M; Kolodziejczyk, Paul

2008-11-12

430

Voltage control integrated in distribution management system  

Microsoft Academic Search

The voltage control in distribution networks is established as a centralized analytical function in this paper. It is integrated in the Distribution Management System. Control devices consist of under-load and off-voltage tap changing transformers, feeder voltage regulators and buck\\/boost transformers. On the basis of areas whose voltages are influenced by these control devices and their action speeds, the voltage control

Vladimir C. Strezoski; Nenad A. Katic; Dusan S. Janjic

2001-01-01

431

Evaluation of the blood stabilizers TransFix and Cyto-Chex BCT for low-cost CD4 T-cell methodologies.  

PubMed

TransFix(TM) and Cyto-Chex((R)) BCT (blood collection tube) reagents have been shown to maintain whole blood integrity for delayed immunophenotyping by flow cytometry. We evaluated the ability of these blood-stabilizing reagents to preserve HIV-seropositive blood for delayed CD4(+) T-cell quantification utilizing the Dynal((R)) Biotech T4 Quant Kit. TransFix was added to EDTA-anticoagulated whole blood and tested at a 1:10 dilution over 7 d using the Dynal (n = 21) manual method. Compared to baseline analysis, a significant decrease in mean CD4(+) counts was observed over time. Cyto-Chex BCT-preserved samples (n = 20) were tested for CD4(+) counts by Dynal over 7 d, with storage at varying temperatures: room temperature (21 degrees C), 37 degrees C, and 37 degrees C with intermittent storage at 42 degrees C. A significant decline in mean CD4(+) counts was observed in samples at all temperatures compared to baseline (p < 0.05). Increases in temperature to and above 37 degrees C resulted in a greater decline in mean CD4(+) counts over time. Our findings indicated that neither TransFix or Cyto-Chex BCT was a suitable blood stabilizer when used for delayed CD4(+) quantification with a low-cost manual CD4(+) bead-based method. PMID:19811090

Plate, Megan M; Louzao, Raul; Steele, Pauline M; Greengrass, Vicki; Morris, Lisa M; Lewis, Jenny; Barnett, David; Warrino, Dominic; Hearps, Anna C; Denny, Thomas; Crowe, Suzanne M

2009-10-01

432

High Voltage Space Solar Arrays  

NASA Technical Reports Server (NTRS)

Recent tests performed at the NASA Glenn Research Center and elsewhere have shown promise in the design and construction of high voltage (300-1000 V) solar arrays for space applications. Preliminary results and implications for solar array design will be discussed, with application to direct-drive electric propulsion and space solar power.

Ferguson, D. C.; Hillard, G. B.; Vayner, B. V.; Galofaro, J. T.; Lyons, Valerie (Technical Monitor)

2002-01-01

433

Frequency-controlled voltage regulator  

NASA Technical Reports Server (NTRS)

Converting input ac to higher frequency reduce size and weight and makes possible unique kind of regulation. Since conversion frequency is above range of human hearing, supply generated on audible noise. It also exploits highfrequency conversion features to regulate its output voltage in novel way. Circuit is inherently short-circuit proof.

Mclyman, W. T.

1980-01-01

434

Voltage Fluctuation Compensator for Shinkansen  

NASA Astrophysics Data System (ADS)

In AC electric Railway, three-phase voltage is changed into the single-phase circuit of two circuits with the Scott-connected transformer. If it becomes large unbalancing of the load between single-phase circuits, voltage fluctuation becomes large on three-phase side. Then, Railway Static Power Conditioner (RPC) was developed for the purpose of controlling voltage fluctuation on three-phase side. An RPC is comprised of a pair of self-commutated PWM inverters. These inverters connect the main phase and teaser feeding buses, coupled with a DC side capacitor such as a Back-To-Back (BTB) converter. In this way, the two self-commutated inverters can act as a static var compensator (SVC) to compensate for the reactive power and as an active power accommodator from one feeding bus to another. 20MVA/60kV RPCs started commercial operation in 2002 at each two substations on the newly extended Tohoku Shinkansen for compensating voltage fluctuation on three-phase side caused by traction loads, absorbing harmonic current. The results of operational testing indicate that an RPC can accommodate single-phase loads such as those of PWM-controlled Shinkansen and thyristor phase-controlled Shinkansen, and handle the exciting rush current of transformers, as well as compensate for harmonics successfully.

Uzuka, Tetsuo; Ikedo, Shouji; Ueda, Keiji; Mochinaga, Yoshifumi; Funahashi, Sadao; Ide, Koiti

435

Outdoor high voltage polymeric insulators  

Microsoft Academic Search

Composite polymeric insulators are increasingly being accepted by the traditionally cautious electric utilities worldwide. They currently represent about 70% of installed new high voltage insulators in North America. The tremendous growth in the applications of non-ceramic insulators is due to their advantages over the traditional ceramic and glass insulators. However, because polymeric insulators are relatively new the expected lifetime is

R. Hackam

1998-01-01

436

Voltage Controlled Current Source (VCCS)  

NSDL National Science Digital Library

Hosted by Clarkson University, this websited contains an applet which demonstrates a circuit that contains a voltage controlled current source (VCCS). The gain of the VCCS can be changed using the scrollbar. This simple resource is a nice representation for a technical education classroom.

Dorf, Richard C.; Svoboda, James A.

2008-11-27

437

High-Voltage Droplet Dispenser  

NASA Technical Reports Server (NTRS)

An apparatus that is extremely effective in dispensing a wide range of droplets has been developed. This droplet dispenser is unique in that it utilizes a droplet bias voltage, as well as an ionization pulse, to release a droplet. Apparatuses that deploy individual droplets have been used in many applications, including, notably, study of combustion of liquid fuels. Experiments on isolated droplets are useful in that they enable the study of droplet phenomena under well-controlled and simplified conditions. In this apparatus, a syringe dispenses a known value of liquid, which emerges from, and hangs onto, the outer end of a flat-tipped, stainless steel needle. Somewhat below the needle tip and droplet is a ring electrode. A bias high voltage, followed by a high-voltage pulse, is applied so as to attract the droplet sufficiently to pull it off the needle. The voltages are such that the droplet and needle are negatively charged and the ring electrode is positively charged.

Eichenberg, Dennis J.

2003-01-01

438

High voltage MOSFET switching circuit  

DOEpatents

The problem of source lead inductance in a MOSFET switching circuit is compensated for by adding an inductor to the gate circuit. The gate circuit inductor produces an inductive spike which counters the source lead inductive drop to produce a rectangular drive voltage waveform at the internal gate-source terminals of the MOSFET. 2 figs.

McEwan, T.E.

1994-07-26

439

High voltage MOSFET switching circuit  

DOEpatents

The problem of source lead inductance in a MOSFET switching circuit is compensated for by adding an inductor to the gate circuit. The gate circuit inductor produces an inductive spike which counters the source lead inductive drop to produce a rectangular drive voltage waveform at the internal gate-source terminals of the MOSFET.

McEwan, Thomas E. (Livermore, CA)

1994-01-01

440

Saving Megawatts with Voltage Optimization  

E-print Network

In September 2008, PCS UtiliData commissioned an Industrial Voltage Optimization system at the Plum Creek Timber Medium Density Fiberboard facility in Columbia Falls, Montana. The system was based upon the AdaptiVolt(TM) Volt/VAR Optimization system...

Wilson, T.; Bell, D.

2010-01-01