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1

Wind Power Plant Voltage Stability Evaluation: Preprint  

SciTech Connect

Voltage stability refers to the ability of a power system to maintain steady voltages at all buses in the system after being subjected to a disturbance from a given initial operating condition. Voltage stability depends on a power system's ability to maintain and/or restore equilibrium between load demand and supply. Instability that may result occurs in the form of a progressive fall or rise of voltages of some buses. Possible outcomes of voltage instability are the loss of load in an area or tripped transmission lines and other elements by their protective systems, which may lead to cascading outages. The loss of synchronism of some generators may result from these outages or from operating conditions that violate a synchronous generator's field current limit, or in the case of variable speed wind turbine generator, the current limits of power switches. This paper investigates the impact of wind power plants on power system voltage stability by using synchrophasor measurements.

Muljadi, E.; Zhang, Y. C.

2014-09-01

2

Voltage stability evaluation using modal analysis  

Microsoft Academic Search

The authors discuss the voltage stability analysis of large power systems by using a modal analysis technique. The method computes, using a steady-state system model, a specified number of the smallest eigenvalues and the associated eigenvectors of a reduced Jacobian matrix. The eigenvalues, each of which is associated with a mode of voltage\\/reactive power variation, provide a relative measure of

B. Gao; G. K. Morison; P. Kundur

1992-01-01

3

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

Microsoft Academic Search

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

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

2010-01-01

4

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

5

Voltage stability analysis in the new deregulated environment  

NASA Astrophysics Data System (ADS)

Nowadays, a significant portion of the power industry is under deregulation. Under this new circumstance, network security analysis is more critical and more difficult. One of the most important issues in network security analysis is voltage stability analysis. Due to the expected higher utilization of equipment induced by competition in a power market that covers bigger power systems, this issue is increasingly acute after deregulation. In this dissertation, some selected topics of voltage stability analysis are covered. In the first part, after a brief review of general concepts of continuation power flow (CPF), investigations on various matrix analysis techniques to improve the speed of CPF calculation for large systems are reported. Based on these improvements, a new CPF algorithm is proposed. This new method is then tested by an inter-area transaction in a large inter-connected power system. In the second part, the Arnoldi algorithm, the best method to find a few minimum singular values for a large sparse matrix, is introduced into the modal analysis for the first time. This new modal analysis is applied to the estimation of the point of voltage collapse and contingency evaluation in voltage security assessment. Simulations show that the new method is very efficient. In the third part, after transient voltage stability component models are investigated systematically, a novel system model for transient voltage stability analysis, which is a logical-algebraic-differential-difference equation (LADDE), is offered. As an example, TCSC (Thyristor controlled series capacitors) is addressed as a transient voltage stabilizing controller. After a TCSC transient voltage stability model is outlined, a new TCSC controller is proposed to enhance both fault related and load increasing related transient voltage stability. Its ability is proven by the simulation.

Zhu, Tong

6

Memristor-integrated voltage-stabilizing supercapacitor system.  

PubMed

Voltage-stabilized supercapacitors: A single supercapacitor formed with PCBM/Pt/IPS nanorod-array electrodes is designed and delivers enhanced areal capacitance, capacitance retention, and excellent electrical stability under bending, while a significant voltage-decrease is observed during the discharging process. Once integrated with the memristor, the memristor-integrated supercapacitor systems deliver an extremely low voltage-drop, indicating greatly enhanced voltage-stabilizing features. PMID:24805149

Liu, Bin; Liu, Boyang; Wang, Xianfu; Wu, Xinghui; Zhao, Wenning; Xu, Zhimou; Chen, Di; Shen, Guozhen

2014-08-01

7

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

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

High voltage stability performance of a gamma ray detection device  

SciTech Connect

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 [Technical Support Division, Malaysian Nuclear Agency, 43000 Kajang, Selangor (Malaysia)

2014-02-12

10

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

11

Modal Voltage Stability Analysis of Multi-infeed HVDC System Considering its Control Systems  

NASA Astrophysics Data System (ADS)

This work presents a method for investigating the voltage stability of multi-infeed HVDC systems, which is based on the eigenvalue decomposition technique known as modal analysis. In this method, the eigenvalue of linearized steady-state system power-voltage equations are computed to evaluate the long-term voltage stability. The contributions of this work to modal analysis method are control systems of HVDC system, such as an Automatic Power Regulator (APR) and an Automatic (DC) Current Regulator (ACR) on its rectifier side and a changeover between an Automatic (DC) Voltage Regulator (AVR) and an Automatic extinction advance angle Regulator (A?R) modes on its inverter side, were taken into account, and the formularization for modal analysis considering not only these control systems of HVDC system but also generator and load characteristics was fulfilled and presented in this paper. The application results from an AC/DC model power system with dual HVDC systems verified the efficiency of the proposed method and quantitatively illustrated the influence of control systems of HVDC system on AC/DC system long-term voltage stability.

Wu, Guohong; Minakawa, Tamotsu; Hayashi, Toshiyuki

12

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

1998-12-01

13

AC loop voltages and MHD stability in RFP plasmas  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

14

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

Microsoft Academic Search

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

Nijaz Dizdarevi? S; Göran Andersson

2002-01-01

15

High voltage equipment parts evaluation tests  

Microsoft Academic Search

Airborne power supplies and equipment which supply megawatts of power at multi-kilovolts require designs of minimum weight and volume which imply compact systems with high density packaging. This is a design concern of high voltage electrical components. This paper describes high voltage tests, test parameters, and the test results of several high voltage components. In addition, the value of dielectric

W. G. Dunbar; D. L. Schweickart

1982-01-01

16

Reliability evaluation and failure analysis for high voltage ceramic capacitor  

Microsoft Academic Search

This paper presents a result of failure analysis and reliability evaluation for high voltage ceramic capacitors. The failure modes and failure mechanisms were studied in two ways in order to estimate component life and failure rate. The causes of failure mechanisms for zero resistance phenomena under withstanding voltage test in high voltage ceramic capacitors molded by epoxy resin were studied

Jin-Woo Kim; Seung-Hun Shin; Dong-Su Ryu; Seog-Weon Chang

2001-01-01

17

On the Configuration of the US Western Interconnection Voltage Stability Boundary  

SciTech Connect

Abstract—Stability limits are considered in power system planning and operations to estimate the available stability margins and, if possible, to maximize the utilization of transmission facilities. These important tasks are influenced by configuration of the stability boundary. The paper introduces a new fast approach to explore the voltage stability boundary of a large system and reveal its detailed multidimensional structure. The 17939-bus U.S. Western Interconnection planning model was used to illustrate the method. Significant peculiarities of the boundary’s configuration were identified, including its nonconvexity, discontinuity, branching and internal singularities (“holes”) that were not known before and could not been found by traditional methods. Experiments using WECC system are performed to evaluate the computation time using different methods. Our results show that the proposed methods are very promising in reducing calculation time and complexity

Makarov, Yuri V.; Vyakaranam, Bharat; Wu, Di; Hou, Zhangshuan; Elbert, Stephen T.; Huang, Zhenyu

2014-04-01

18

Strategies for Voltage Control and Transient Stability Assessment  

SciTech Connect

As wind generation grows, its influence on power system performance will becoming increasingly noticeable. Wind generation di#11;ffers from traditional forms of generation in numerous ways though, motivating the need to reconsider the usual approaches to power system assessment and performance enhancement. The project has investigated the impact of wind generation on transient stability and voltage control, identifying and addressing issues at three distinct levels of the power system: 1) at the device level, the physical characteristics of wind turbine generators (WTGs) are quite unlike those of synchronous machines, 2) at the wind-farm level, the provision of reactive support is achieved through coordination of numerous dissimilar devices, rather than straightforward generator control, and 3) from a systems perspective, the location of wind-farms on the sub-transmission network, coupled with the variability inherent in their power output, can cause complex voltage control issues. The project has sought to develop a thorough understanding of the dynamic behaviour of type-3 WTGs, and in particular the WECC generic model. The behaviour of such models is governed by interactions between the continuous dynamics of state variables and discrete events associated with limits. It was shown that these interactions can be quite complex, and may lead to switching deadlock that prevents continuation of the trajectory. Switching hysteresis was proposed for eliminating deadlock situations. Various type-3 WTG models include control blocks that duplicate integrators. It was shown that this leads to non-uniqueness in the conditions governing steady-state, and may result in pre- and post-disturbance equilibria not coinciding. It also gives rise to a zero eigenvalue in the linearized WTG model. In order to eliminate the anomalous behaviour revealed through this investigation, WECC has now released a new generic model for type-3 WTGs. Wind-farms typically incorporate a variety of voltage control equipment including tapchanging transformers, switched capacitors, SVCs, STATCOMs and the WTGs themselves. The project has considered the coordinated control of this equipment, and has addressed a range of issues that arise in wind-farm operation. The #12;first concerns the ability of WTGs to meet reactive power requirements when voltage saturation in the collector network restricts the reactive power availability of individual generators. Secondly, dynamic interactions between voltage regulating devices have been investigated. It was found that under certain realistic conditions, tap-changing transformers may exhibit instability. In order to meet cost, maintenance, fault tolerance and other requirements, it is desirable for voltage control equipment to be treated as an integrated system rather than as independent devices. The resulting high-level scheduling of wind-farm reactive support has been investigated. In addressing this control problem, several forms of future information were considered, including exact future knowledge and stochastic predictions. Deterministic and Stochastic Dynamic Programming techniques were used in the development of control algorithms. The results demonstrated that while exact future knowledge is very useful, simple prediction methods yield little bene#12;fit. The integration of inherently variable wind generation into weak grids, particularly subtransmission networks that are characterized by low X=R ratios, aff#11;ects bus voltages, regulating devices and line flows. The meshed structure of these networks adds to the complexity, especially when wind generation is distributed across multiple nodes. A range of techniques have been considered for analyzing the impact of wind variability on weak grids. Sensitivity analysis, based on the power-flow Jacobian, was used to highlight sections of a system that are most severely a#11;ffected by wind-power variations. A continuation power flow was used to determine parameter changes that reduce the impact of wind-power variability. It was also used to explore interactions betw

Hiskens, Ian A.

2013-09-25

19

Ultrasonic evaluation of high voltage circuit boards  

NASA Technical Reports Server (NTRS)

Preliminary observations indicate that an ultrasonic scanning technique may be useful as a quick, low cost, nondestructive method for judging the quality of circuit board materials for high voltage applications. Corona inception voltage tests were conducted on fiberglass-epoxy and fiberglass-polyimide high pressure laminates from 20 to 140 C. The same materials were scanned ultrasonically by utilizing the single transducer, through-transmission technique with reflector plate, and recording variations in ultrasonic energy transmitted through the board thickness. A direct relationship was observed between ultrasonic transmission level and corona inception voltage. The ultrasonic technique was subsequently used to aid selection of high quality circuit boards for the Communications Technology Satellite.

Klima, S. J.; Riley, T. J.

1976-01-01

20

A New Bifurcation Analysis for Power System Dynamic Voltage Stability Studies  

E-print Network

A New Bifurcation Analysis for Power System Dynamic Voltage Stability Studies Garng M. Huang, Senior Member, IEEE, Liang Zhao, Xuefeng Song Abstract: The dynamic of a large class of power systems can bifurcation, saddle-node and Hopf bifurcation. In this paper the dynamic voltage stability of power system

21

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

22

Design of Transformers for 60 kVA Automatic Voltage Stabilizer  

Microsoft Academic Search

This paper is a study of development of servo-controlled automatic voltage stabilizer (AVS) for application in industrial zones. These are most suitable for 24 hours continuous process plants where breakdowns due to fluctuation results in heavy financial losses occur. A stabilizer in this paper is unbalanced system because most of the industries used unbalanced load. A stabilizer in this paper

Y. Y. Pyone

2009-01-01

23

Coordinated Dynamic Voltage Stabilization based on Model Predictive Control  

E-print Network

a substation. [11] proposes a coordinated control method for ULTCs and capacitors in distribution systems tap changes and STATCOM outputs while maintaining acceptable voltage magnitudes at substation buses. Some work has also been done to design a coordinated voltage control strategy by considering dynamic

Kumar, Ratnesh

24

Design of EBW Stabilized High-Voltage Source Based on Fuzzy PID Control  

Microsoft Academic Search

A novel PWM-BOOST type EBW (electron beam welder) stabilized high-voltage source circuit system is introduced. This system consists of setting-up transformer, PWM-BOOST converter and a current limiter. PWM-BOOST converter can step up the voltage with the ratio higher than 1:5.5; as a result, the transformer's output voltage is decreased and its structure can be simplified. Due to the strongly non-linearity

He Shaojia; Mo Jinhai; Wei Shouqi; Huang Dao

2007-01-01

25

A Nonlinear Excitation Controller Design Method for Terminal Voltage Regulation and Transient Stability Enhancement  

NASA Astrophysics Data System (ADS)

This paper proposes a cascade control method to design a nonlinear excitation controller to guarantee the terminal voltage regulation and the transient stability. Firstly, a nonlinear automatic voltage regulator (NAVR) in the inner loop is designed to control the terminal voltage exactly. Secondly, the generator model including the NAVR is transformed to be a reduced one. Subsequently, based on the reduced generator model, the nonlinear power system stabilizer in the external loop is designed to enhance the transient stability of the power systems. Furthermore, a coordination strategy is presented to improve the performances of the terminal voltage regulation in the steady state and the stability in the transient state. Finally, the proposed method is verified by numerous simulation results.

Huang, Chongxin; Zhang, Kaifeng; Dai, Xianzhong; Zang, Qiang

2014-06-01

26

A new application area for fullerenes: voltage stabilizers for power cable insulation.  

PubMed

Fullerenes are shown to be efficient voltage-stabilizers for polyethylene, i.e., additives that increase the dielectric strength of the insulation material. Such compounds are highly sought-after because their use in power-cable insulation may considerably enhance the transmission efficiency of tomorrow's power grids. On a molal basis, fullerenes are the most efficient voltage stabilizers reported to date. PMID:25504254

Jarvid, Markus; Johansson, Anette; Kroon, Renee; Bjuggren, Jonas M; Wutzel, Harald; Englund, Villgot; Gubanski, Stanislaw; Andersson, Mats R; Müller, Christian

2015-02-01

27

Evaluation of resistors for transient high-voltage applications  

Microsoft Academic Search

Applications for transient, high-voltage pulsed power technologies are on the increase. High-voltage resistors are an essential component of such systems, especially in the proof-of-concept and prototype testing. The authors have recently procured and tested certain resistor samples, supplied by Kanthal Globar and HVR Advanced Power Components. Results of a detailed evaluation of the HVR resistors are presented in this paper.

J. M. Lehr; C. E. Baum; W. D. Prather; J. Hull; M. C. Skipper; M. I. Abdalla; D. V. Giri

1999-01-01

28

Fuzzy comprehensive evaluation for insulation diagnosis of high voltage cable  

Microsoft Academic Search

The insulation characteristics parameters of high voltage cable are analyzed. Fuzzy comprehensive evaluation is introduced into multiparameter diagnosis of cable insulation. The fuzzy comprehensive evaluation model is established, and the grade of membership of insulation state is judged from multiple indicators. Consulting previous division standard of insulation state, the threshold of membership function is determined by relative variation of insulation

Jiantao Sun; Guangfan Li; Keli Gao; Bo Li; Jinzhong Li; Lei Lan

2010-01-01

29

The Parameter of Automatic Voltage Regulator's Effect on Steady State Stability Limit of Turbine Generator  

Microsoft Academic Search

The steady state stability limit of turbine generator with automatic voltage regulator (AVR) extends steam turbine's safe range under exciting operation compared to generator without AVR. Therefore, Paper analyzes the parameter of AVR's effect on steady state stability limit of turbine generator, and verifies the conclusion with the simulation model in Matlab\\/Simulink environment.

Yong-Gang Li; Jun-Jie Fu; Yan-Jun Zhao; Qiang Liu

2008-01-01

30

Long term voltage stability analysis for small disturbances  

E-print Network

. This dissertation extends our new numerical scheme to stiff systems. When a system is ill-conditioned, the implicit method would be applied to achieve numerical stability. We further demonstrate the validity to combine the intelligent load adjustment technique...

Men, Kun

2009-05-15

31

Cycle versus voltage hold - Which is the better stability test for electrochemical double layer capacitors?  

NASA Astrophysics Data System (ADS)

The stability of electrochemical double layer capacitors (EDLC) utilizing an ionic liquid and tetraethylammoninium tetrafluoroborate (TEABF4) in acetonitrile electrolyte was tested by cycling and by constant voltage hold tests. It turned out that possible degradation of the EDLC is visible in the voltage hold test after a time period which is typically much shorter if compared to the cycle tests. A constant capacitance during several thousands of cycles does not necessarily indicate stability. For capacitor cells using a carbon black as active material and an ionic liquid as electrolyte constant capacitance could be demonstrated over 12,000 cycles between 0 V and 3.75 V. Clear ageing was observed, however, during the voltage hold test at 3.75 V after 300 h. For a maximum voltage of 3.5 V both the cycle and the voltage hold test indicated stable performance over 12,000 cycles or 500 h, respectively. For capacitors using an activated carbon as active material and standard electrolyte TEABF4 in acetonitrile both tests clearly demonstrated degradation for a maximum cell voltage of 3.5 V. The evolution of capacitance loss observed for the voltage hold test at 3.25 V is in good agreement with the degradation observed at 3.5 V for the voltage hold test.

Weingarth, D.; Foelske-Schmitz, A.; Kötz, R.

2013-03-01

32

Automated Evaluation of Dynamic Performance of Impulse Voltage Measurement Systems  

NASA Astrophysics Data System (ADS)

This manuscript presents and describes an automated system for the evaluation of the dynamic performance of high-voltage measurement systems, according to the requirements of the standard IEC 60060-2/2010. The system was developed in LabVIEW and controls the acquisition, measurement and analysis of step response tests of measurement systems, automatically calculating the relevant amplitude and time parameters.

Faria, L. C.; Silva, E. C.; Silva, M. T.; Barbosa, C. R. H.; Azevedo, L. C.

2015-01-01

33

Voltage stability limits for weak power systems with high wind penetration  

NASA Astrophysics Data System (ADS)

Analysis of power system voltage stability has practical value in increasing wind penetration levels. As wind penetration levels increase in power systems, voltage stability challenges arise due to locating wind resources far away from load centers. This dissertation presents several different voltage stability methods for sizing new wind farms. Power system wind penetration levels depend on the available voltage stability margins (VSMs) of the existing power system and system load characteristics. Three new iterative methods have been developed to maximize wind penetration level in weak power systems based on systems' VSMs. The first two methods use an iterative approach for increasing the size of each wind farm until reaching the collapse point. Wind farms with less negative impact on system VSMs are sized larger than others. A third wind farm sizing method has been developed using modal analysis in conjunction with the traditional voltage stability method (Q-V method). Wind farms are placed at buses in the power system which have the lowest negative impact on voltage instability modes (strong wind injection buses). By placing the wind farms at the strongest wind injection buses, higher amounts of wind power can be injected into the power system. To further increase wind penetration in weak power systems, two additional techniques are introduced and applied to the western Kansas power system. The first technique uses modes of voltage instability to place voltage support equipment like static var compensators at locations in the power system where they provide the needed reactive power support for increasing levels of wind penetration. The second technique uses the fact that wind patterns at a wind farm site may rarely allow the wind farm to produce its maximum capacity during the peak loading hours. Wind farm maximum sizes can be increased above their maximum voltage stable size limit without driving the power system into becoming voltage unstable. Preventing voltage collapse for the additional increases in wind farm sizes is accomplished by disconnecting some wind turbines inside the wind farm during critical times to reduce its power output to a voltage stable level.

Tamimi, Ala

34

Drain-bias dependence of threshold voltage stability of amorphous silicon TFTs  

Microsoft Academic Search

Amorphous silicon (a-Si:H) thin-film transistors (TFTs) used in emerging, nonswitch applications such as analog amplifiers or active loads, often have a bias at the drain terminal in addition to the gate that can alter their threshold voltage (VT) stability performance. At small gate stress voltages (0?VST?15 V) where the defect state creation instability mechanism is dominant, the presence of a

Karim S. Karim; Arokia Nathan; Michael Hack; William I. Milne

2004-01-01

35

Using D-SMES devices to improve the voltage stability of a transmission system  

Microsoft Academic Search

The D-SMES device, a combination of a superconducting magnet energy storage (SMES) system with a voltage-source IGBT converter, is capable of fast, effectively controlled, and near instantaneous injection of both real and reactive power into a transmission system. Described are results of voltage stability studies for an actual transmission system with up to seven 8 MVA D-SMES devices, each utilizing

M. Ross; M. Borodulin; Y. Kazachkov

2001-01-01

36

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

37

Evaluation of higher distribution and/or utilization voltages. Fifth interim report (September 1980): assess constraints to higher voltage implementation  

SciTech Connect

This interim report provides documentation on the fifth task, Assess Constraints to Higher Voltage Implementation, 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 list of impediments to higher voltage implementation including both technological and economic factors, an assessment of the impact of reduced costs for high voltage equipment on the selection of an optimal voltage and a set of recommendations for further work.

Not Available

1981-04-01

38

Voltage Stability Impact of Grid-Tied Photovoltaic Systems Utilizing Dynamic Reactive Power Control  

NASA Astrophysics Data System (ADS)

Photovoltaic (PV) DGs can be optimized to provide reactive power support to the grid, although this feature is currently rarely utilized as most DG systems are designed to operate with unity power factor and supply real power only to the grid. In this work, the voltage stability of a power system embedded with PV DG is examined in the context of the high reactive power requirement after a voltage sag or fault. A real-time dynamic multi-function power controller that enables renewable source PV DGs to provide the reactive power support necessary to maintain the voltage stability of the microgrid, and consequently, the wider power system is proposed. The loadability limit necessary to maintain the voltage stability of an interconnected microgrid is determined by using bifurcation analysis to test for the singularity of the network Jacobian and load differential equations with and without the contribution of the DG. The maximum and minimum real and reactive power support permissible from the DG is obtained from the loadability limit and used as the limiting factors in controlling the real and reactive power contribution from the PV source. The designed controller regulates the voltage output based on instantaneous power theory at the point-of-common coupling (PCC) while the reactive power supply is controlled by means of the power factor and reactive current droop method. The control method is implemented in a modified IEEE 13-bus test feeder system using PSCADRTM power system analysis software and is applied to the model of a Tampa ElectricRTM PV installation at Lowry Park Zoo in Tampa, FL. This dissertation accomplishes the systematic analysis of the voltage impact of a PV DG-embedded power distribution system. The method employed in this work bases the contribution of the PV resource on the voltage stability margins of the microgrid rather than the commonly used loss-of-load probability (LOLP) and effective load-carrying capability (ELCC) measures. The results of the proposed method show good improvement in the before-, during-, and post-start voltage levels at the motor terminals. The voltage stability margin approach provides the utility a more useful measure in sizing and locating PV resources to support the overall power system stability in an emerging smart grid.

Omole, Adedamola

39

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

40

Evaluation of Voltage Instability Countermeasures in Constrained Sub-transmission Power Networks.  

E-print Network

?? This paper investigates the various parameters that effect voltage stability in sub-transmission power networks. The paper first looks at contributions from equipment: generators, transmission… (more)

Jones, Peter Gibson

2012-01-01

41

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

and their sensitivities depend only on the static parts of dynamic power system models. For example, a dynamic power dynamic power system models to be properly understood, the computation of loading mar- gin and itsBulk power system voltage phenomena - III: Voltage stability, security & control, Davos

Dobson, Ian

42

Impact of Cyber Attacks on Transient Stability of Smart Grids with Voltage Support Devices  

E-print Network

Impact of Cyber Attacks on Transient Stability of Smart Grids with Voltage Support Devices Bo Chen and Computer Engineering Department University of Toronto Toronto, ON, Canada dkundur@comm.utoronto.ca Abstract--Cyber dependent on the cyber communication. Therefore, it is important to study the impact of cyber attacks

Kundur, Deepa

43

A new continfency parameterization CPF model and sensivity method for voltage stability control  

Microsoft Academic Search

A new contingency parameterization Continuation Power Flow model and the corresponding sensitivity method for static voltage stability preventive control is proposed in this paper. This proposed tool is designed to investigate the nonlinear effects of enforcing a multiple compound contingency in a large-scale power system: It can be used to investigate the existence of a power flow solution after a

Jianquan Zhao; Hsaio-Dong Ching; Hua Li

2005-01-01

44

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

45

Energy functions, transient stability and voltage behaviour in power systems with nonlinear loads  

Microsoft Academic Search

The authors present preliminary results in a computer program aimed at energy function analysis of transient behavior of power systems with nonlinear loads. The model, which preserves the network structure, is of a differential-algebraic type. This introduces some new analytical issues, but the concepts permit the establishment of a connection between transient (angle) stability, multiple stable equilibria, and voltage behavior.

I. A. Hiskens; D. J. Hill

1989-01-01

46

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

PubMed

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

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

2013-07-19

47

Online Monitoring of the Electrical Power Transfer Stability and Voltage Profile Stability Margins in Electric Power Transmission Systems Using Phasor Measurement Units Data Sets  

Microsoft Academic Search

An innovative method to monitor the electric power transfer stability on power transmission paths and the voltage profile stability at the power systems nodes in real time modus is proposed. Based on the laws of electric circuit theory, the transfer operating mode of each relevant transmission line is formulated in an active power-voltage PV characteristic. The relevant transmission line parameters

Yves Nguegan; Albert Claudi; Carsten Strunge

2009-01-01

48

Auto-zero stabilized CMOS amplifiers for very low voltage or current offset Daniel Dzahini (1), Hamid Ghazlane (2)  

E-print Network

Auto-zero stabilized CMOS amplifiers for very low voltage or current offset Daniel Dzahini (1 Rabat Principal 10001 Morocco Abstract---In this paper, we present two amplifiers designed in CMOS precision operational amplifier focusing on the voltage offset. It is a continuous time auto-zero stabilized

Boyer, Edmond

49

Abstract--This paper investigates the effect of Thyristor Controlled Series Capacitor (TCSC) on the voltage stability  

E-print Network

is to minimize power system load curtailment. Incorporating TCSC affects the topology and hence the power flow-- Load Curtailment, OPF, Voltage Stability, TCSC. I. INTRODUCTION In the deregulated power systems) on the voltage stability constrained Optimal Power Flow (OPF) formulation where the objective function

50

Gyrotron Output Power Stabilization by PID Feedback Control of Heater Current and Anode Voltage  

NASA Astrophysics Data System (ADS)

To provide stable output power of a gyrotron during long operation time the power stabilization was achieved by two schemes with PID feedback control of heater current and anode voltage. It was based on the dependence of the output power on both the anode voltage and the beam current and also on the dependence of the beam current on the gun heater current. Both schemes provided decrease of the power standard deviation to 0.3-0.5%. The comparison between parameters of both schemes is discussed in the paper.

Khutoryan, E. M.; Idehara, T.; Kuleshov, A. N.; Ueda, K.

2014-12-01

51

Surface and Structural Stabilities of Carbon Additives in High Voltage Lithium Ion Batteries  

SciTech Connect

Several different carbons have been systematically investigated in high voltage lithium ion batteries. It was founded that the higher surface area, the more parasitic reactions initiating from different onset voltages. A closer inspection reveals that for the low surface area carbon such as Super P, PF6- ions intercalate into carbon structure above 4.7 V contributing partial capacity. For high surface area carbon, in addition to the electrolyte decomposition, the oxidation of functional groups at high voltage further increases the irreversible capacities and Li+ ion consumption. Coulombic efficiency, reversible capacity and cycling stability observed by using different carbon additives are successfully correlated with their structure and surface chemistry providing information for predictive selection of carbons in different energy storage systems.

Zheng, Jianming; Xiao, Jie; Xu, Wu; Chen, Xilin; Gu, Meng; Li, Xiaohong S.; Zhang, Jiguang

2012-11-23

52

Chemical detection and laser wavelength stabilization employing spectroscopic absorption via laser compliance voltage sensing  

DOEpatents

Systems and methods are disclosed that provide a direct indication of the presence and concentration of an analyte within the external cavity of a laser device that employ the compliance voltage across the laser device. The systems can provide stabilization of the laser wavelength. The systems and methods can obviate the need for an external optical detector, an external gas cell, or other sensing region and reduce the complexity and size of the sensing configuration.

Taubman, Matthew S; Phillips, Mark C

2014-03-18

53

A low voltage and submillisecond-response polymer-stabilized blue phase liquid crystal  

NASA Astrophysics Data System (ADS)

We report a polymer-stabilized blue phase liquid crystal (BPLC) whose Kerr constant is about 2.2× larger than previous record. When filled in a 3.2-?m-thick vertical field switching cell, the on-state voltage is merely 8.4 V (at ? = 514 nm) while keeping submillisecond response time and negligible hysteresis (<1%) at the room temperature. These results imply that the dawn of BPLC era for high speed display and photonic devices has finally arrived.

Chen, Yuan; Xu, Daming; Wu, Shin-Tson; Yamamoto, Shin-ichi; Haseba, Yasuhiro

2013-04-01

54

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

2014-07-08

55

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

E-print Network

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

Venkatasubramanian, Mani V.

56

Evaluation of electromagnetic disturbances injected in high voltage networks by large electrical installations  

Microsoft Academic Search

In the actual technological context, continuous improvement of the evaluation of the electromagnetic disturbances injected by the large electrical end users and the distribution system topology into high voltage networks is highly necessary. In this case, the power quality really means the voltage quality. The disturbances phenomena occurring in the high voltage network due to some important 110 kV and

MARILENA UNGUREANU; RALUCA ROSCA

57

Evaluation of Epoxy Nanocomposites for High Voltage Insulation  

NASA Astrophysics Data System (ADS)

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

Iyer, Ganpathy

58

Effects of high voltage electrical stimulation on the rate of pH decline, meat quality and color stability in chilled beef carcasses  

PubMed Central

Objective To determine the effects of high voltage electrical stimulation (HVES, 800 Voltage) on rapid decreases in pH values and improvements in meat quality. Methods A total of 50 beef carcasses were applied, divided into two groups, one as a control and another for HVES. Meat quality was evaluated based on M. longissimus dorsi by examining pH and temperature levels at 1, 2, 5, 10 and 24 h, while color stability was examined seven days after slaughter. Results HVES decreased the pH values of the meat and accelerated rigor mortis (P<0.05). HVES caused differences in instrumental color values compared with the control groups across the ageing period at 4 °C. Conclusion the HVES had positive effects on meat quality and color stability, in contrast to undesirable consumer preferences. PMID:23998012

Mombeni, Ehsan Gharib; Mombeini, Manoochehr Gharib; Figueiredo, Lucas Chaves; Siqueira, Luciano Soares Jacintho; Dias, Debora Testoni

2013-01-01

59

Outward stabilization of the voltage sensor in domain II but not domain I speeds inactivation of voltage-gated sodium channels.  

PubMed

To determine the roles of the individual S4 segments in domains I and II to activation and inactivation kinetics of sodium current (INa) in NaV1.5, we used a tethered biotin and avidin approach after a site-directed cysteine substitution was made in the second outermost Arg in each S4 (DI-R2C and DII-R2C). We first determined the fraction of gating charge contributed by the individual S4's to maximal gating current (Qmax), and found that the outermost Arg residue in each S4 contributed ?19% to Qmax with minimal contributions by other arginines. Stabilization of the S4's in DI-R2C and DII-R2C was confirmed by measuring the expected reduction in Qmax. In DI-R2C, stabilization resulted in a decrease in peak INa of ?45%, while its peak current-voltage (I-V) and voltage-dependent Na channel availability (SSI) curves were nearly unchanged from wild type (WT). In contrast, stabilization of the DII-R2C enhanced activation with a negative shift in the peak I-V relationship by -7 mV and a larger -17 mV shift in the voltage-dependent SSI curve. Furthermore, its INa decay time constants and time-to-peak INa became more rapid than WT. An explanation for these results is that the depolarized conformation of DII-S4, but not DI-S4, affects the receptor for the inactivation particle formed by the interdomain linker between DIII and IV. In addition, the leftward shifts of both activation and inactivation and the decrease in Gmax after stabilization of the DII-S4 support previous studies that showed ?-scorpion toxins trap the voltage sensor of DII in an activated conformation. PMID:23893162

Sheets, Michael F; Chen, Tiehua; Hanck, Dorothy A

2013-10-15

60

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

61

Quantitative Evaluation of Voltage-Induced Magnetic Anisotropy Change by Magnetoresistance Measurement  

NASA Astrophysics Data System (ADS)

We investigated the voltage-induced perpendicular magnetic anisotropy change in an epitaxial magnetic tunnel junction (MTJ) with an ultrathin FeCo layer. Tunneling magnetoresistance (TMR) curves were measured under various bias voltage applications for different FeCo thicknesses. Clear changes in the shape of TMR curves were observed depending on the voltage-controlled perpendicular magnetic anisotropy. By evaluating the relative angle of two ferromagnetic layers, we could estimate the anisotropy energy change quantitatively. The realization of voltage-induced anisotropy change in the MTJ structure makes it possible to control the magnetization dynamics, leading to a new area of electric-field-based spintronics devices.

Shiota, Yoichi; Murakami, Shinichi; Bonell, Frédéric; Nozaki, Takayuki; Shinjo, Teruya; Suzuki, Yoshishige

2011-04-01

62

Evaluating plyometric exercises using time to stabilization.  

PubMed

Plyometric exercises are frequently used in strength and conditioning and rehabilitation programs because the landing phase of these exercises requires dynamic stabilization. This study examined the differences in landing stability of a variety of plyometric exercises by assessing time to stabilization (TTS), its reliability, and sex differences therein. Forty-nine men and women performed a variety of plyometric exercises thought to represent a continuum of difficulty of dynamic stabilization during landing. Plyometric exercises included line hops, cone hops, squat jumps, tuck jumps, countermovement jumps, dumbbell countermovement jumps, and single leg countermovement jumps, each performed for 3 repetitions on a force platform. A 2-way mixed analysis of covariance with repeated measures for plyometric exercise type was used to evaluate the main effects for plyometric exercise type and the interaction between plyometric exercise type and sex for TTS. Subject jumping ability was evaluated as a covariate. Results revealed significant main effects for plyometric exercise type (p < or = 0.001) and for the interaction between plyometric exercise type and sex (p = 0.002). Bonferroni adjusted post hoc analysis demonstrated differences in TTS between a number of plyometric exercises for men and women. Reliability analysis revealed intraclass correlation coefficients ranging from 0.51 to 0.86 with no significant difference between trials (p > 0.05). Practitioners who use plyometrics to train dynamic stability should create programs that progress the intensity of the exercises based on the results of this study. This study also demonstrated that TTS is moderately to highly reliable for a variety of jumping conditions for both men and women. PMID:20072070

Ebben, William P; Vanderzanden, Tyler; Wurm, Bradley J; Petushek, Erich J

2010-02-01

63

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

SciTech Connect

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

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

2010-09-29

64

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...

65

Evaluation of performance of footwear and flooring systems in combination with personnel using voltage probability analysis  

NASA Astrophysics Data System (ADS)

Evaluation of electrostatic performance of footwear and flooring in combination is necessary in applications such as electrostatic discharge (ESD) control in electronics manufacture, evaluation of equipment for avoidance of factory process electrostatic ignition risks and avoidance of electrostatic shocks to personnel in working environments. Typical standards use a walking test in which the voltage produced on a subject is evaluated by identification and measurement of the magnitude of the 5 highest "peaks" and "valleys" of the recorded voltage waveform. This method does not lend itself to effective analysis of the risk that the voltage will exceed a hazard threshold. This paper shows the advantages of voltage probability analysis and recommends that the method is adopted for use in future standards.

Smallwood, Jeremy; Swenson, David E.

2011-06-01

66

Wind Farm Stabilization by using DFIG with Current Controlled Voltage Source Converters Taking Grid Codes into Consideration  

NASA Astrophysics Data System (ADS)

Recent wind farm grid codes require wind generators to ride through voltage sags, which means that normal power production should be re-initiated once the nominal grid voltage is recovered. However, fixed speed wind turbine generator system using induction generator (IG) has the stability problem similar to the step-out phenomenon of a synchronous generator. On the other hand, doubly fed induction generator (DFIG) can control its real and reactive powers independently while being operated in variable speed mode. This paper proposes a new control strategy using DFIGs for stabilizing a wind farm composed of DFIGs and IGs, without incorporating additional FACTS devices. A new current controlled voltage source converter (CC-VSC) scheme is proposed to control the converters of DFIG and the performance is verified by comparing the results with those of voltage controlled voltage source converter (VC-VSC) scheme. Another salient feature of this study is to reduce the number of proportionate integral (PI) controllers used in the rotor side converter without degrading dynamic and transient performances. Moreover, DC-link protection scheme during grid fault can be omitted in the proposed scheme which reduces overall cost of the system. Extensive simulation analyses by using PSCAD/EMTDC are carried out to clarify the effectiveness of the proposed CC-VSC based control scheme of DFIGs.

Okedu, Kenneth Eloghene; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

67

Genetic Algorithm Used for Load Shedding Based on Sensitivity to Enhance Voltage Stability  

NASA Astrophysics Data System (ADS)

This paper presents an algorithm to calculate optimum load shedding with voltage stability consideration based on sensitivity of proximity indicator using genetic algorithm (GA). Schur's inequality based proximity indicator of load flow Jacobian has been selected, which indicates system state. Load flow Jacobian of the system is obtained using Continuation power flow method. If reactive power and active rescheduling are exhausted, load shedding is the last line of defense to maintain the operational security of the system. Load buses for load shedding have been selected on the basis of sensitivity of proximity indicator. The load bus having large sensitivity is selected for load shedding. Proposed algorithm predicts load bus rank and optimum load to be shed on load buses. The algorithm accounts inequality constraints not only in present operating conditions, but also for predicted next interval load (with load shedding). Developed algorithm has been implemented on IEEE 6-bus system. Results have been compared with those obtained using Teaching-Learning-Based Optimization (TLBO), particle swarm optimization (PSO) and its variant.

Titare, L. S.; Singh, P.; Arya, L. D.

2014-12-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

69

Evaluation of high-voltage, high-power, solid-state remote power controllers for amps  

NASA Technical Reports Server (NTRS)

The Electrical Power Branch at Marshall Space Flight Center has a Power System Development Facility where various power circuit breadboards are tested and evaluated. This project relates to the evaluation of a particular remote power controller (RPC) energizing high power loads. The Facility equipment permits the thorough testing and evaluation of high-voltage, high-power solid-state remote power controllers. The purpose is to evaluate a Type E, 30 Ampere, 200 V dc remote power controller. Three phases of the RPC evaluation are presented. The RPC is evaluated within a low-voltage, low-power circuit to check its operational capability. The RPC is then evaluated while performing switch/circuit breaker functions within a 200 V dc, 30 Ampere power circuit. The final effort of the project relates to the recommended procedures for installing these RPC's into the existing Autonomously Managed Power System (AMPS) breadboard/test facility at MSFC.

Callis, Charles P.

1987-01-01

70

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

71

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

72

Color stability evaluation of aesthetic restorative materials.  

PubMed

Color match is one of the most important characteristics of aesthetic restorative materials. Maintenance of color throughout the functional lifetime of restorations is important for the durability of treatment. This characteristic is not constant among dental materials. The purpose of this research was to assess the color stability of five aesthetic restorative materials when immersed in a coffee solution. Seventy-one 17 mm x 1 mm specimens, divided into five groups, were made using one direct composite resin (Tetric Ceram, Ivoclar/Vivadent - G1), three indirect composite resins (Targis, Ivoclar/Vivadent - G2; Resilab Master, Wilcos - G3; belleGlass HP, Kerr - G4) and one porcelain (IPS Empress 2, Ivoclar/Vivadent - G5). The specimens were immersed in a coffee staining media for 15 days and stored under a controlled temperature of 37 degrees C +/- 1 degrees C in the dark. The evaluations were made after 1, 7 and 15 days by means of reflectance spectrophotometry. The data was submitted to two-way ANOVA (p < 0.005) and post hoc tests. Statistical difference was observed between G1 / G3 and the other groups; G2 / G4 and the other groups; and G5 and all the other groups. It was concluded that G1 and G3 showed significantly higher discoloration than the other groups. G2 and G4 showed intermediary pigmentation, while G5 showed the smallest changes. PMID:18949304

Samra, Adriana Postiglione Bührer; Pereira, Stella Kossatz; Delgado, Leyla Cotrina; Borges, Christiane Phillipini

2008-01-01

73

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

74

Influence of a voltage compensation type active superconducting fault current limiter on the transient stability of power system  

NASA Astrophysics Data System (ADS)

We have proposed a voltage compensation type active superconducting fault current limiter (SFCL). In this paper, the influence of the SFCL on the transient stability of power system is investigated. For the typical one-machine infinite-bus system, the power-angle characteristics of generator with SFCL are studied in different working conditions, and the transient physical process is analyzed. Using MATLAB SIMULINK, the power-angle swing curves are simulated under different current-limiting modes, fault types and fault clearance times. The results show that the proposed SFCL can effectively reduce the transient swing amplitude of rotor and extend the critical clearance time under mode 1, compared with mode 2 and mode 3 having few effects on enhancing the transient stability.

Chen, L.; Tang, Y. J.; Shi, J.; Chen, N.; Song, M.; Cheng, S. J.; Hu, Y.; Chen, X. S.

2009-10-01

75

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

76

Power System Online Stability Assessment using Synchrophasor Data Mining  

E-print Network

, in particular the Decision Trees (DTs), for fast evaluation of power system oscillatory stability and voltage stability from synchrophasor measurements. A regression tree-based approach is proposed to predict the stability margins. Modal analysis...

Zheng, Ce

2013-04-30

77

IEEE PES WM Panel on Modeling, Simulation and Applications of FACTS Controllers in Angle and Voltage Stability Studies, Singapore, Jan. 2000 Power Flow and Transient Stability Models of FACTS Controllers  

E-print Network

IEEE PES WM Panel on Modeling, Simulation and Applications of FACTS Controllers in Angle and Voltage Stability Studies, Singapore, Jan. 2000 Power Flow and Transient Stability Models of FACTS Sourced Inverter VSI based Flex- ible AC Transmission System FACTS Controllers. Models of the Static VAr

Cañizares, Claudio A.

78

A new bifurcation analysis for power system dynamic voltage stability studies  

Microsoft Academic Search

The dynamic of a large class of power systems can be represented by parameter dependent differential-algebraic models of the form x˙ = f (x, y, p) and 0 = g(x, y, p). When the parameter p of the system (such as load of the system) changes, the stable equilibrium points may lose their dynamic stability at local bifurcation points. The

Garng M. Huang; Liang Zhao; Xuefeng Song

2002-01-01

79

A low voltage and submillisecond-response polymer-stabilized blue phase liquid crystal  

E-print Network

12 April 2013) We report a polymer-stabilized blue phase liquid crystal (BPLC) whose Kerr constant and negligible hysteresis (temperature. These results imply that the dawn of BPLC era for high), then the electrostriction effect, which causes lattice distortion would be prohibited and hysteresis be negligible (

Wu, Shin-Tson

80

Evaluating AlGaN/AlN/GaN heterostructure Schottky barrier heights with flat-band voltage from forward current-voltage characteristics  

NASA Astrophysics Data System (ADS)

Both circular and rectangular Ni Schottky contacts on AlGaN/AlN/GaN heterostructures have been fabricated. Both of the Schottky barrier heights were measured by internal photoemission. The flat-band voltage (V0) for the AlGaN/AlN/GaN heterostructure Schottky contacts was analyzed and obtained from the forward current-voltage (I-V) characteristics. Based on the forward I-V characteristics and with the obtained flat-band voltage, the Schottky barrier heights for the circular and rectangular diodes have been analyzed and calculated by self-consistently solving Schrodinger's and Poisson's equations. The evaluated Schottky barrier heights for the prepared circular and rectangular Ni Schottky diodes agree well with the photocurrent measured results.

Lv, Yuanjie; Lin, Zhaojun; Meng, Lingguo; Yu, Yingxia; Luan, Chongbiao; Cao, Zhifang; Chen, Hong; Sun, Baoquan; Wang, Zhanguo

2011-09-01

81

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

82

Low-Voltage, High-Mobility Air-Stable Ambipolar Organic Field-Effect Transistors with a Voltage-Dependent Off-Current State and Modest Operational Stability  

NASA Astrophysics Data System (ADS)

High-performance air-stable ambipolar organic field-effect transistors (OFETs) working at low voltages are demonstrated. Pentacene/N,N '-ditridecylperylene-3,4,9,10-tetracarboxylic di-imide (PTCDI-C13) and polystyrene-modified anodized Al2O3 act as the active layer and dielectric layer, respectively. A voltage-dependent off-current state and different threshold voltage shift characteristics from that of unipolar OFETs are observed, which is of great importance in practical applications such as integrated circuits. The devices have hole and electron mobilities as high as 0.5 and 0.2 cm2 V-1 s-1, respectively, with working voltages between -5 and 8 V, a high on/off ratio from 104 to 105, and a small threshold-voltage shift.

Hu, Yongsheng; Lu, Qipeng; Li, Hong; Zhang, Nan; Liu, Xingyuan

2013-05-01

83

Stabilization of polymer electrolyte fuel cell voltage with reduced-order Lyapunov exponent feedback and corrective pressure perturbations  

NASA Astrophysics Data System (ADS)

Polymer electrolyte fuel cell (PEFC) system efficiency can be decreased by instabilities resulting from the accumulation of water in the cathode as well as by excessive air delivery parasitic loads used to prevent liquid water accumulation. In this work, we present a new instability detection diagnostic tailored for the nonlinear and chaotic dynamics of PEFC operation with multi-phase flow in the gas channels. The instability statistic, the Lyapunov exponent of the reduced-order voltage return map, ?, is a measure of the exponential rate of divergence in the dynamic voltage signal measured from the fuel cell. A key advantage of this statistic for embedded control is that it is a self-referencing measure of the system stability for feedback and is not based on an a priori performance threshold. Our experiments demonstrate that the Lyapunov exponent statistic provides a warning typically 100 s in advance of significant power loss. Using this statistic as a control diagnostic, a new control scheme that detects PEFC instability in real time and mitigates it with pressure perturbations was applied experimentally to several fuel cell systems, including one that simulates stack operation. Our control scheme resulted in increased PEFC power, decreased cathode flooding leading to a lower parasitic load for air delivery, and stable PEFC performance.

Burkholder, Michael B.; Litster, Shawn

2015-02-01

84

Evaluation of stability of live attenuated camelpox vaccine stabilized with different stabilizers and reconstituted with various diluents.  

PubMed

In this study, thermostability of a Vero cell attenuated live camelpox vaccine under conventional lyophilization conditions has been evaluated. Three stabilizers were used separately for freeze-drying the vaccine and the stability of the vaccine, both in freeze-dried and reconstituted forms at different temperatures was assessed. The study revealed that the camelpox vaccine lyophilized with TAA stabilizer found superior with a shelf life of 44 months, 227 days, 22 days and 20 days at 4, 25, 37 and 45 °C, respectively followed by LS stabilizer. In terms of half-life, TAA stabilizer proved better followed by LS and BUGS stabilizers at all temperatures except at 25 °C in which LS found relatively superior. Among the four diluents viz. 1x PBS (phosphate buffered saline, pH 7.4), 0.85% NaCl, distilled water and 1 M MgSO4, PBS was a better diluent followed by 0.85% NaCl. Both the diluents maintained the infectivity titer more than the minimum effective dose (3 log10TCID50 with a maximum titre of 6.53 log10TCID50 in both the diluents) for 60 h at 37 and 45 °C. However, 1 M MgSO4 found less suitable for camelpox vaccine dilution. The study indicates that the TAA and 1× PBS are the choice of stabilizer and diluent, respectively for camelpox vaccine. PMID:24657207

Prabhu, M; Bhanuprakash, V; Venkatesan, G; Yogisharadhya, R; Bora, D P; Balamurugan, V

2014-05-01

85

On the Effect of Non-Carbon Nanostructured Supports on the Stability of Pt Nanoparticles during Voltage Cycling: a Study of TiO2 Nanofibres  

E-print Network

1 On the Effect of Non-Carbon Nanostructured Supports on the Stability of Pt Nanoparticles during Voltage Cycling: a Study of TiO2 Nanofibres I. Savych, J. Bernard d'Arbigny, S. Subianto, S. Cavaliere-mail: sara.cavaliere@univ-montp2.fr Abstract Electrospun carbon and Nb-doped TiO2 nanofibres (CNFs, TNFs

Boyer, Edmond

86

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

87

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

88

Stability evaluation of the Markel Mine at Weeks Island, Louisiana  

SciTech Connect

A three dimensional (3D) finite element analysis of the Markel Mine located on Weeks Island was performed to: (1) evaluate the stability of the mine and (2) determine the effect of mine failure on the nearby Morton Salt mine and SPR facilities. The first part of the stability evaluation investigates the effect of pillar failure on mine stability. These simulations revealed that tensile stresses and dilatant damage develop in the overlying salt as a result of pillar loss. These tensile stresses extend to the salt/overburden interface only for the case where all 45 of the pillars are assumed to fail. Tensile stresses would likely cause microfracturing of the salt, resulting in a flow path for groundwater from the overlying aquifer to enter the mine. The dilatant damage bridges between the mine and the overburden in the case where 15 or more pillars are removed from the model. Dilatant damage is attributed to microfracturing or changes in the pore structure of the salt and could also result in a flow path for groundwater to enter the mine. The second part of the Markel Mine evaluation investigates the stability of the pillars with respect to three failure mechanisms: tensile failure, compressive failure, and creep rupture. A 3D slabbing pillar model of the Markel mine was developed to investigate progressive failure of the pillars and the effect of slabbing on mine stability. Based on a strain-limiting creep rupture criterion, pillar failure is predicted to be extensive at present. The associated loss of pillar strength should be equivalent to removing all pillars from the model as was done in the first part of this stability analysis, resulting in the possibility of ground water intrusion. Since creep rupture is not a well understood phenomenon, further development and validation of this criterion is recommended.

Hoffman, E.L.

1994-06-01

89

Evaluation of Self-Driven Schemes for a 12-V Self-Driven Voltage Regulator  

Microsoft Academic Search

Compared to the conventional multiphase buck converter, the 12-V zero-voltage switching self-driven nonisolated full-bridge converter has many advantages for voltage regulator (VR) module applications. The employment of the synchronous rectifier (SR) self-driven technology in VRs leads to lower SR drive loss and body diode conduction loss. However, the SR drive voltage is fixed at the input voltage, which is too

Ke Jin; D. Sterk; F. C. Lee; Ming Xu; Yi Sun

2009-01-01

90

Equipment Failure Probability Evaluation Due to Voltage Sag Using Cloud Model  

Microsoft Academic Search

The sensitivity of sensitive equipment to voltage sags depends on the characteristics of voltage sag on the power supply site and the voltage tolerance of equipment. It is multi-uncertain including stochastic and fuzzy. Cloud model is used to present the sensitivity of equipment in this paper. The direct normal cloud generator was used to translate the qualitative distribution of VTC

Sun Xiao-Lu; Li Yuan-Bo; Wang Ying; Xiao Xian-Yong

2010-01-01

91

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

92

Photo stability of solution-processed low-voltage high mobility zinc-tin-oxide/ZrO2 thin-film transistors for transparent display applications  

NASA Astrophysics Data System (ADS)

We report solution-processed low-voltage zinc-tin-oxide (ZTO)/zirconium-oxide thin-film transistors (TFTs) possessing a field-effect mobility of ˜10 cm2/Vs, a threshold voltage of 0.1 V, and an on-off current ratio of ˜1 × 109. These TFTs exhibit very small hysteresis windows in both dark and illuminated conditions. We also investigate the photo stability combined with prolong negative bias in these devices. Large threshold voltage shifts and sub-threshold swing degradation typically observed in ZTO TFTs are not present in our devices. We believe that these device characteristics, which stem from the electronically clean semiconductor-dielectric interface, satisfy the requirement for high quality and low power-consuming transparent displays.

Ha, Tae-Jun; Dodabalapur, Ananth

2013-03-01

93

Dielectric stress tests and capacitance-voltage analysis to evaluate the effect of post deposition annealing on Al2O3 films deposited on GaN  

NASA Astrophysics Data System (ADS)

Systematic stress tests that help to evaluate the stability and dielectric performance of Al2O3 films under DC bias conditions are reported. Capacitance-voltage (C-V) curves were monitored for changes after subjecting the dielectric film to constant forward and reverse bias stress. Stress tests, along with C-V analysis, are used to evaluate the effect of post deposition annealing on Metal-Organic Chemical Vapor Deposition) Al2O3 films deposited on GaN. The individual benefits and drawbacks of each film and anneal condition were identified. These suggest that the anneals can be tailored to the unannealed film characteristics to achieve desired improvements in performance. It is found that post deposition annealing in forming gas improves performance under reverse bias stress by reducing the fixed charge and the field in the oxide but does not improve performance under forward bias.

Yeluri, Ramya; Liu, Xiang; Guidry, Matthew; Koksaldi, Onur S.; Lal, Shalini; Kim, Jeonghee; Lu, Jing; Keller, Stacia; Mishra, Umesh K.

2014-12-01

94

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

SciTech Connect

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

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

2012-01-01

95

Evaluation of Insulation Systems for the Optimal Design of High Voltage Pulse Transformers  

E-print Network

This paper presents a study for the design of the insulation systems of high voltage pulse transformer based on experimental tests and numerical simulations. Data of high voltage tests on solid and liquid insulation materials are presented and discussed. The understanding of each part of the insulation is supported by electrostatic fields simulations.

Sylvain, Candolfi; Davide, Aguglia; Philippe, Viarouge; Jürgen, Biela; Jerome, Cros

2015-01-01

96

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

97

Voltage Divider  

NSDL National Science Digital Library

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

98

Evaluation of motor-gasoline stability. Interim report  

SciTech Connect

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

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

1990-12-01

99

A Study on the Innovation Cost and Effectiveness Evaluation of Compensation Devices for Voltage Sags  

NASA Astrophysics Data System (ADS)

Due to the advancement of information technology and widespread use of power electronic devices in recent years, many customers in various fields have suffered from the voltage sag problem. In order to compensate voltage sags, sensitive loads have been primarily equipped with uninterruptible power supplies (UPS) by each consumer individually. Because consumers have many individual needs, this topic becomes an important problem to be considered by quality consultants in the electric utility industry. Based on this situation, we present the applications of UPS and dynamic voltage restorer (DVR) as compensation devices of voltage sags. By considering the need for power quality, we examine the cost-efficiency of both devices quantitatively. Simulations are carried out and the results are shown in this paper.

Lang, Xuhui; Hara, Ryoichi; Kita, Hiroyuki; Tanaka, Eiichi; Hasegawa, Jun; Kubo, Hiroshi; Yonaga, Shigeru

100

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

101

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

102

A comprehensive study to evaluate the effect of constant low voltage iontophoresis on transungual delivery.  

PubMed

Treatment of nail diseases by topical drug delivery continues to draw much attention in the recent days. This study aims to systematically investigate the effect of constant voltage iontophoresis in the transungual drug delivery, using ciclopirox as a model drug. Preliminary permeation studies were carried out by applying constant voltage (6 V for 24 h) using a gel formulation across the human nail plate in a Franz diffusion cell. Different protocols have been studied to authenticate the potential of the proposed technique. Antifungal studies were carried out to assess the pharmacodynamic effect of drug depot formed in the nail plate. Initial studies revealed that application of constant voltage iontophoresis enhanced the permeation by an order of magnitude (p = 0.019) and delivered significant amount of drug into the deeper nail layers. Noticeably higher permeation was observed during the active phase in on-off studies. Excellent correlation was observed in permeation (r(2) = 0.98) and drug load (r(2) = 0.97) with the increase in applied voltage (3-12 V), indicating that the current technique is predictable. The data observed suggest that any further increase in voltage could eventually lead to increase in the permeation and drug load, as the saturation level is very distant. Furthermore, the enhancement in permeation with the applied voltage (3-12 V) was found to be 6-20 folds, compared to the passive process. Results of step up and step down studies substantiated the viability of the current technique. Zone of inhibition measured during the antifungal studies demonstrated that the drug molecules loaded into the nail plate by low voltage iontophoresis is active and releases over an extended period of time (~32 days). Given the excellent results, the current technique could be used as an effective approach for the delivery of antimycotics, which would localize the drug at the infection site and potentially offer higher patient compliance. PMID:23057692

Nair, Anroop B; Singh, Kishan; Shinu, Pottathil; Harsha, Sree; Al-Dhubiab, Bandar E

2013-05-01

103

Global Stability of Banking Networks Against Financial Contagion: Measures, Evaluations and  

E-print Network

To investigate financial networks, one must first settle questions of the following type: What is the modelGlobal Stability of Banking Networks Against Financial Contagion: Measures, Evaluations stability of financial system Theoretical (computational complexity and algorithmic) results Empirical

DasGupta, Bhaskar

104

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

SciTech Connect

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

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

2011-01-01

105

Evaluation of higher distribution and/or utilization voltages. Final report  

SciTech Connect

An electric energy distribution/utilization system cost analysis model is presented for exploring cost tradeoffs (capital innvestment, operation and maintenance and cost of losses) and optimizing system configuration. The model focuses on the treatment of residential and light commercial service areas with time-varying load characteristics, including customer load profile changes, per customer load growth and service area population growth. Applications of the model are discussed. These include providing insight on: the selection of primary and secondary voltages; conductor sizing; distribution transformer sizing, change out policies and copper-to-core-loss ratio; and limits on allowable voltage variation at the service entrance. Examples are provided to illustrate model capabilities.

Hazelrigg, Jr, George A.

1981-01-01

106

Preliminary safety evaluation for the plutonium stabilization and packaging system  

SciTech Connect

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

Shapley, J.E., Fluor Daniel Hanford

1997-03-14

107

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

108

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

109

Implementation and Evaluation of a Stator and Rotor Flux Linkage-Based Dead-Beat, Direct Torque Control of Induction Machines at the Operational Voltage Limits  

Microsoft Academic Search

Dead-beat, direct torque (and flux) control of an induction machine is experimentally achieved at a 10 kHz sampling frequency. The inverse solution utilized lends itself to a very insightful graphical representation. This allows for an objective experimental evaluation of voltage vector choices in the operational voltage limits. The parameter sensitivity of the control algorithm is also investigated.

N. T. West; R. D. Lorenz

2007-01-01

110

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

111

The Switched-Capacitor step-down DC-DC converter with improved voltage stability and load range  

Microsoft Academic Search

A 5V to 1.1V Switched-Capacitor (SC) DC-DC converter with a novel PFM control is proposed here to achieve a steady output voltage with wide load range. The advantage is through PFM control, the duty cycle of the converter can be fixed to obtain the optimum efficiency even in wide load condition. For the novel PFM control, it uses an error

Yie-Tone Chen; Kun-Jing Liu

2010-01-01

112

Demonstration and Field Evaluation of Streambank Stabilization with Submerged Vanes  

USGS Publications Warehouse

The effectiveness of submerged vanes for reducing bank erosion and improving aquatic habitat is being evaluated at a site on North Fish Creek, a Lake Superior tributary. Increased runoff from agricultural areas with clayey soils has increased flood magnitudes and the erosion potential/transport capacity of the stream. Most of the creek's sediment load originates from the erosion of 17 large bluffs. This creek contains important recreational fisheries that are potentially limited by the loss of aquatic habitat from deposition of sediment on spawning beds. Submerged vanes are a cost effective and environmentally less intrusive alternative to traditional structural stabilization measures. Submerged vanes protrude from a channel bed, are oriented at an angle to the local velocity, and are distributed along a portion of channel. They induce a transverse force and torque on the flow along with longitudinal vortexes that alter the cross sectional shape and alignment of the channel. Submerged vanes were installed at a bluff/bend site in summer and fall 2000. The number, size, and layout of the vanes were based upon the channel morphology under estimated bankfull conditions. The effectiveness of the vanes will be evaluated by comparing surveys of the bluff face, streamflow, and channel conditions for several years after installation of the submerged vanes with surveys before and immediately after their installation.

Whitman, H.; Hoopes, J.; Poggi, D.; Fitzpatrick, F.; Walz, K.

2001-01-01

113

Interference Evaluation of Overhead Medium-Voltage Broadband Power Line Systems  

Microsoft Academic Search

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

Song Liu; Larry J. Greenstein

2010-01-01

114

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

Microsoft Academic Search

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

Song Liu; Larry J. Greenstein

2007-01-01

115

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

116

Modelling of illuminated current-voltage characteristics to evaluate leakage currents in long wavelength infrared mercury cadmium telluride photovoltaic detectors  

NASA Astrophysics Data System (ADS)

The current-voltage characteristics of long wavelength mercury cadmium telluride infrared detectors have been studied using a recently suggested method for modelling of illuminated photovoltaic detectors. Diodes fabricated on in-house grown arsenic and vacancy doped epitaxial layers were evaluated for their leakage currents. The thermal diffusion, generation-recombination (g-r), and ohmic currents were found as principal components of diode current besides a component of photocurrent due to illumination. In addition, both types of diodes exhibited an excess current component whose growth with the applied bias voltage did not match the expected growth of trap-assisted-tunnelling current. Instead, it was found to be the best described by an exponential function of the type, Iexcess = Ir0 + K1 exp (K2 V), where Ir0, K1, and K2 are fitting parameters and V is the applied bias voltage. A study of the temperature dependence of the diode current components and the excess current provided the useful clues about the source of origin of excess current. It was found that the excess current in diodes fabricated on arsenic doped epitaxial layers has its origin in the source of ohmic shunt currents. Whereas, the source of excess current in diodes fabricated on vacancy doped epitaxial layers appeared to be the avalanche multiplication of photocurrent. The difference in the behaviour of two types of diodes has been attributed to the difference in the quality of epitaxial layers.

Gopal, Vishnu; Qiu, WeiCheng; Hu, Weida

2014-11-01

117

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...

118

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

119

Predictions of tumour morphological stability and evaluation against experimental observations  

PubMed Central

The hallmark of malignant tumours is their spread into neighbouring tissue and metastasis to distant organs, which can lead to life threatening consequences. One of the defining characteristics of aggressive tumours is an unstable morphology, including the formation of invasive fingers and protrusions observed both in vitro and in vivo. In spite of extensive biological, clinical and modelling study and research at physical scales ranging from the molecular to the tissue, the driving dynamics of tumour invasiveness are not completely understood, partly because it is challenging to observe and study cancer as a multi-scale system. Mathematical modelling has been applied to provide further insights into these complex invasive and metastatic behaviours. Modelling a solid tumour as an incompressible fluid, we consider three possible constitutive relations to describe tumour growth, namely Darcy's law, Stokes' law and the combined Darcy–Stokes law. We study the tumour morphological stability described by each model and evaluate the consistency between theoretical model predictions and experimental data from in vitro three-dimensional multicellular tumour spheroids. The analysis reveals that the Stokes model is the most consistent with the experimental observations, and that it predicts our experimental tumour growth is marginally stable. We further show that it is feasible to extract parameter values from a limited set of data and create a self-consistent modelling framework that can be extended to the multi-scale study of cancer. PMID:20519213

Pham, Kara; Frieboes, Hermann B.; Cristini, Vittorio; Lowengrub, John

2011-01-01

120

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

121

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

122

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

123

Evaluating alternative models for power system dynamic stability studies  

Microsoft Academic Search

A dynamic stability model for detailed stability studies on synchronous power systems is presented in such a form that it can be systematically reduced to models of reduced complexity. The complete model includes representation of stator and network transient effects as well as shaft torsional oscillation effects. The family of models of reduced cemplexity span the range of models found

R. T. H. Alden; P. J. Nolan

1976-01-01

124

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

1995-01-01

125

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

126

Evaluation of STMicroelectronics RH-L49 1 3 positive hardened low drop voltage regulator  

NASA Astrophysics Data System (ADS)

An evaluation of the RH-L4913 from the manufacturer STMicroelectronics, total dose radiation hardened, has been done. This evaluation has consisted of an electrical characterization, a physical analysis, endurance tests (silicon & package) and radiations tests, in order to assess the specific failure modes and the reliability of this regulator in space environment. The results are presented in this paper and demonstrate the RH-L4913 regulator ability to be used in space applications.

Briand, P.; Vadrot, J.-F.; Belasic, M.

2002-12-01

127

Evaluation of a Programmable Voltage-Controlled MEMS Oscillator, Type SiT3701, Over a Wide Temperature Range  

NASA Technical Reports Server (NTRS)

Semiconductor chips based on MEMS (Micro-Electro-Mechanical Systems) technology, such as sensors, transducers, and actuators, are becoming widely used in today s electronics due to their high performance, low power consumption, tolerance to shock and vibration, and immunity to electro-static discharge. In addition, the MEMS fabrication process allows for the miniaturization of individual chips as well as the integration of various electronic circuits into one module, such as system-on-a-chip. These measures would simplify overall system design, reduce parts count and interface, improve reliability, and reduce cost; and they would meet requirements of systems destined for use in space exploration missions. In this work, the performance of a recently-developed MEMS voltage-controlled oscillator was evaluated under a wide temperature range. Operation of this new commercial-off-the-shelf (COTS) device was also assessed under thermal cycling to address some operational conditions of the space environment

Patterson, Richard; Hammoud, Ahmad

2009-01-01

128

Evaluation of modulating field of photoreflectance of surface-intrinsic-n+ type doped GaAs by using photoinduced voltage  

NASA Astrophysics Data System (ADS)

Photoreflectance (PR) of surface-intrinsic-n+ type doped GaAs has been measured for various power densities of pump laser. The spectra exhibited many Franz-Keldysh oscillations, whereby the strength of electric field F in the undoped layer can be determined. The thus obtained Fs are subject to photovoltaic effect and are less than built-in field Fbi. In the previous work we have obtained the relation F?Fbi-?F/2 when ?F?Fbi by using electroreflectance to simulate PR, where ?F is the modulating field of the pump beam. In this work a method was devised to evaluate ?F by using photoinduced voltages Vs and, hence, the relation can be verified by PR itself. The ?Fs obtained by Vs are also consistent with those of using imaginary part of fast Fourier transform of PR spectra.

Lee, W. Y.; Chien, J. Y.; Wang, D. P.; Huang, K. F.; Huang, T. C.

2002-04-01

129

Effects of Sample Storage on Biosolids Compost Stability and Maturity Evaluation  

E-print Network

Effects of Sample Storage on Biosolids Compost Stability and Maturity Evaluation L. Wu and L. Q. Ma-drying of soil sam-Compost stability and maturity are important parameters of com- ples is the most common practice (Bates, 1993), despitepost quality. To date, nearly all compost characterization has been

Ma, Lena

130

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

Microsoft Academic Search

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

Wilker Altidor; Taghi M. Khoshgoftaar; Amri Napolitano

2011-01-01

131

Rapid evaluation and optimization of machine tools with position-dependent stability  

E-print Network

Rapid evaluation and optimization of machine tools with position-dependent stability Mohit Law Available online 21 February 2013 Keywords: Machine tool Model reduction Stability Optimization a b s t r a c t Machine tool's productivity is a function of the dynamic response between the spindle nose

Phani, A. Srikantha

132

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

133

Archaerhodopsin voltage imaging: synaptic calcium and BK channels stabilize action potential repolarization at the Drosophila neuromuscular junction.  

PubMed

The strength and dynamics of synaptic transmission are determined, in part, by the presynaptic action potential (AP) waveform at the nerve terminal. The ion channels that shape the synaptic AP waveform remain essentially unknown for all but a few large synapses amenable to electrophysiological interrogation. The Drosophila neuromuscular junction (NMJ) is a powerful system for studying synaptic biology, but it is not amenable to presynaptic electrophysiology. Here, we demonstrate that Archaerhodopsin can be used to quantitatively image AP waveforms at the Drosophila NMJ without disrupting baseline synaptic transmission or neuromuscular development. It is established that Shaker mutations cause a dramatic increase in neurotransmitter release, suggesting that Shaker is predominantly responsible for AP repolarization. Here we demonstrate that this effect is caused by a concomitant loss of both Shaker and slowpoke (slo) channel activity because of the low extracellular calcium concentrations (0.2-0.5 mM) used typically to assess synaptic transmission in Shaker. In contrast, at physiological extracellular calcium (1.5 mM), the role of Shaker during AP repolarization is limited. We then provide evidence that calcium influx through synaptic CaV2.1 channels and subsequent recruitment of Slo channel activity is important, in concert with Shaker, to ensure proper AP repolarization. Finally, we show that Slo assumes a dominant repolarizing role during repetitive nerve stimulation. During repetitive stimulation, Slo effectively compensates for Shaker channel inactivation, stabilizing AP repolarization and limiting neurotransmitter release. Thus, we have defined an essential role for Slo channels during synaptic AP repolarization and have revised our understanding of Shaker channels at this model synapse. PMID:25355206

Ford, Kevin J; Davis, Graeme W

2014-10-29

134

Evaluation of the stability of gas hydrates in Northern Alaska  

USGS Publications Warehouse

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

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

1987-01-01

135

Toxicological evaluation of the chemical oxidation methods for landfill stabilization.  

PubMed

As the stabilization criteria for landfill sites, only chemical criteria for the leachate discharges from the landfill sites have been used in Japan and many other countries. Recently, chemical oxidation has been developed as a method for the early-stabilization of landfills. However, by-products that are difficult to detect by chemical analysis can be produced by this method. Therefore, toxicity tests are useful tools for detecting the changes of leachate quality after application of this method. The heat source in the A landfill was analyzed by organic position inquiry technology, and ozone-treated leachate was sprayed back to the heat source in the landfill. Toxicity changes of the leachate after the spray were monitored using Microtoxtrade mark, ToxScreen-II, and DaphTox tests. The hardly-degradable organic matter was efficiently removed and toxicities of the leachate in the heat source decreased after the application. These toxicity results were significantly related to chemical oxygen demand (COD) changes. Thus, it was concluded that the toxicity tests were effective for monitoring the leachate quality after applying the chemical oxidation method for landfill stabilization, and its incorporation to establish the criteria for early-stabilization of landfill sites needs to be considered. PMID:18838260

Cho, Eun-ah; Tameda, Kazuo; Hanashima, Masataka; Yamada, Tatsuyoshi; Higuchi, Sotaro

2009-03-01

136

Evaluation of HAN-TEAN Stabilizers using Microcalorimetry  

NASA Technical Reports Server (NTRS)

HAN-TEAN (hydroxylammonium nitrate - triethanolammonium nitrate - in water) is being considered for various propellant applications. This propellant has advantages in terms of insensitivity to impact and fire, low vapor pressure and environmentally benign reaction products. One office concerns with HAN-TEAN is its stability and shelf-life, especially when contaminated with trace metals. Stabilizer systems, consisting of anti-oxidants and/or chealating agents were investigated for their ability to control the decomposition of HAN-TEAN. Isothermal microcalorimetry, an ultrasensitive heat measurement technique, was used to monitor the decomposition of HANTEAN at near ambient temperatures. Isothermal microcalorimetry measures the heat flow from a reaction vessel into a surrounding heat sink. Microcalorimetry is approximately 1,000 times more sensitive than accelerating rate calorimetry (ARC) or differential scanning calorimetry (DSC) for measuring heat flow. Samples of HAN-TEAN containing the stabilizers were spiked with 50 ppm iron and the heat evolution monitored for a period of at least 30 days. Ten stabilizer combinations were tested and the rates of HAN-TEAN decomposition were lowered by 74 to 95 percent in the presence of iron.

Hornung, Steven D.; Davis, Dennis D.; Chang, Craig H.; Baker, David L.

1997-01-01

137

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 ...

138

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 ...

139

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

140

Evaluation and testing of low-voltage bituminous coal at New England Power  

SciTech Connect

Steam coals used by eastern United States electric utilities are traditionally high volatile, moderate to high sulfur, high ash content bituminous coals. Increasingly stringent regulations on sulfur emissions have caused an emphasis on beneficiated coals. Recent changes in the economics of steel-making and the decline of steel plants has released large quantities of metallurgical or coking coals to the open market. This is low volatile, low sulfur, low ash bituminous coal and is commonly beneficiated prior to sale. The decline in the market for coking coals has caused them to be priced competitively with steam coals. The authors of this paper are involved in a series of laboratory studies and full scale utility boiler demonstration test burns which have shown conclusively that these coking coals can be successfully substituted for conventional medium and high volatile coals in existing pulverized, coal-fired utility boilers. These coals can be used with no changes in plant operating procedures and with no changes in equipment settings. This work has led to the development of a coal specification model that NEP used to further develop their coal specifications when procuring coals of this type. The coal specification model parameters are: the higher heating value of the volatiles on a pound of coal basis (HHV{sub vol}) derived from coal calorimetry; the Bimaceral Reflectance Index (BRI) derived from the petrographic analysis (coal fingerprint) and the Coal Stability Index (CSI) derived from the HHV{sub vol} and the BRI.

Afonso, R.F.; Dyas, B. (New England Electric System, Westborough, MA (United States)); Dusatko, G.C.; Schrecengost, R.A. (Energy Systems Associates, Pittsburgh, PA (US)); Hatt, R.M. (Island Creek Corp., Lexington, KY (United States))

1991-01-01

141

Evaluation of the numerical stability and sensitivity to material parameter variations for several unified constitutive models  

E-print Network

EVALUATION OF THE NUMERICAL STABILITY AND SENSITIVITY TO MATERIAL PARAMETER VARIATIONS FOR SEVERAL UNIFIED CONSTITUTIVE MODELS A Thesis By PETER KENNETH IMBRIE Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE May 1985 Major Subject: Aerospace Engineering EVALUATION OF THE NUMERICAL STABILITY AND SENSITIVITY TO MATERIAL PARAMETER VARIATIONS FOR SEVERAL UNIFIED CONSTITUTIVE MODELS A Thesis By PETER KENNETH...

Imbrie, Peter Kenneth

1985-01-01

142

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

SciTech Connect

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

Zimmerman, R.A.

1991-01-01

143

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

144

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

145

Measurement and protocol for evaluating video and still stabilization systems  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

146

RESULTS FROM THE STABILIZATION TECHNOLOGIES EVALUATED BY THE SITE PROGRAM  

EPA Science Inventory

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

147

Interpretation of battery response to pulse loads: Evaluation of the relation between the internal resistance of the battery and the instantaneous voltage drop  

NASA Astrophysics Data System (ADS)

The restrictions which govern the measurement of the internal resistance of batteries using a pulse loading technique are derived and evaluated. The voltage response of a battery may be used to measure the internal resistance of that battery when the response is measured during a time interval much smaller than the faradaic relaxation time constant and circuit relaxation time constant.

Delnick, F. M.

1982-01-01

148

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

EPA Science Inventory

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

149

Evaluation of multiple management objectives for northeast Atlantic flatfish stocks: sustainability vs. stability of yield  

Microsoft Academic Search

This paper describes a simulation study that evaluated the ICES scientific advisory process used to recommend total allowable catches (TACs) for flatfish stocks. Particular emphasis is given to examining the effects on stock biomass, yield and stability of constraining interannual variation in TACs. A ¿management strategy evaluation¿ approach is used where an operating model is used to represent the underlying

L. T. Kell; M. A. Pastoors; R. D. Scott; M. T. Smith; Beek van F. A; C. M. O'Brien; G. M. Pilling

2005-01-01

150

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.

151

Myopia Stabilization and Associated Factors Among Participants in the Correction of Myopia Evaluation Trial (COMET)  

PubMed Central

Purpose. To use the Gompertz function to estimate the age and the amount of myopia at stabilization and to evaluate associated factors in the Correction of Myopia Evaluation Trial (COMET) cohort, a large ethnically diverse group of myopic children. Methods. The COMET enrolled 469 ethnically diverse children aged 6 to younger than 12 years with spherical equivalent refraction between ?1.25 and ?4.50 diopters (D). Noncycloplegic refraction was measured semiannually for 4 years and annually thereafter. Right eye data were fit to individual Gompertz functions in participants with at least 6 years of follow-up and at least seven refraction measurements over 11 years. Function parameters were estimated using a nonlinear least squares procedure. Associated factors were evaluated using linear regression. Results. In total, 426 participants (91%) had valid Gompertz curve fits. The mean (SD) age at myopia stabilization was 15.61 (4.17) years, and the mean (SD) amount of myopia at stabilization was ?4.87 (2.01) D. Ethnicity (P < 0.0001) but not sex or the number of myopic parents was associated with the age at stabilization. Ethnicity (P = 0.02) and the number of myopic parents (P = 0.01) but not sex were associated with myopia magnitude at stabilization. At stabilization, African Americans were youngest (mean age, 13.82 years) and had the least myopia (mean, ?4.36 D). Participants with two versus no myopic parents had approximately 1.00 D more myopia at stabilization. The age and the amount of myopia at stabilization were correlated (r = ?0.60, P < 0.0001). Conclusions. The Gompertz function provides estimates of the age and the amount of myopia at stabilization in an ethnically diverse cohort. These findings should provide guidance on the time course of myopia and on decisions regarding the type and timing of interventions. PMID:24159085

2013-01-01

152

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

SciTech Connect

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

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

2012-01-01

153

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

154

Design and evaluation of single nozzle with a non-conductive tip for reducing applied voltage and pattern width in electrohydrodynamic jet printing (EHDP)  

NASA Astrophysics Data System (ADS)

We investigated the effect of a non-conductive tip inserted into a capillary nozzle (inner diameter of 860 µm) on jet formation and pattern width in electrohydrodynamic jet printing. Simulated and experimental results showed that the non-conductive tip stabilized the jet, and reduced the effective nozzle diameter and the onset voltage needed for the cone-jet mode, by eliminating the backflow near the apex of the liquid cone while a tiny backflow away from the apex of the liquid cone still remained. Silver nanocolloid patterns with an average width of 18.5 µm (standard deviation: 1.5 µm) were obtained with an applied voltage of 2.7 kV, a flow rate of 3 µl min-1 and a stage velocity of 200 mm s-1.

Kim, Sang-Yoon; Kim, Yong; Park, Jaehong; Hwang, Jungho

2010-05-01

155

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

156

Dynamic simulation of voltage collapses  

SciTech Connect

Most of the time the voltage collapse phenomena are studied by means of computer programs designed for the calculation of steady state conditions. But in the real world, the simultaneous occurrences of losses of synchronism, of AVR dynamics or of transformer tap changes call for a full dynamic simulation of voltage phenomena. The present paper shows some examples of dynamic simulations of voltage phenomena using a new general purpose stability program (EUROSTAG), covering in a continuous way the classical fields of transient, mid-term and long-term stability, and also the quasi steady state conditions of a power system.

Deuse, J.; Stubbe, M. (Tractebel, Brussels (Belgium))

1993-08-01

157

An intelligent on line voltage regulation in power distribution system  

Microsoft Academic Search

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

Shrabani Pal; Sudipta Nath

2010-01-01

158

Development of automatic voltage regulator for synchronous generator  

Microsoft Academic Search

This paper presents the development of an automatic voltage regulator (AVR) for synchronous generator in industries applications. The AVR operates as a voltage stabilizer and controller because the output voltage is controlled and regulated through a power electronic system. It is observed that the automatic voltage regulator managed to achieve up to 2% voltage regulation at full load operation of

C. S. Hoong; T. Taib; K. S. Rao; I. Daut

2004-01-01

159

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

PubMed

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

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

2003-01-01

160

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.

161

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY MUNICIPAL WASTE COMBUSTION RESIDUE SOLIDIFICATION/STABILIZATION EVALUATION PROGRAM  

EPA Science Inventory

Vendors of solidification/stabilization (S/S) and other technologies are cooperating with the U.S. Environmental Protection Agency's (U.S. EPA's) Office of Research and Development (ORD), Risk Reduction Engineering Laboratory to demonstrate and evaluate the performance of the tec...

162

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

EPA Science Inventory

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

163

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 ...

164

Analysing the stability of series-shunt circuits based on voltage- and current- feedback OpAmps through SPICE AC simulations  

Microsoft Academic Search

Two methods for determining the loop gain of OpAmp-based circuits with series-shunt feedback through simulations are analyzed and compared: the standard method — that involves breaking the feedback loop by inserting an independent voltage source with DC=0 and AC=1 — and a more precise method, based on the Rosenstark theorem. Only the cases for the traditional (voltage-feedback) and the current-feedback

Marius Neag; Raul Onet; Robert Groza; Marina Topa

2010-01-01

165

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...

166

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

167

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

168

High Voltage TAL Performance  

NASA Technical Reports Server (NTRS)

The performance of a two-stage, anode layer Hall thruster was evaluated. Experiments were conducted in single and two-stage configurations. In single-stage configuration, the thruster was operated with discharge voltages ranging from 300 to 1700 V. Discharge specific impulses ranged from 1630 to 4140 sec. Thruster investigations were conducted with input power ranging from 1 to 8.7 kW, corresponding to power throttling of nearly 9: 1. An extensive two-stage performance map was generated. Data taken with total voltage (sum of discharge and accelerating voltage) constant revealed a decrease in thruster efficiency as the discharge voltage was increased. Anode specific impulse values were comparable in the single and two-stage configurations showing no strong advantage for two-stage operation.

Jacobson, David T.; Jankovsky, Robert S.; Rawlin, Vincent K.; Manzella, David H.

2001-01-01

169

Proposal for using Sine With Dwell on low friction for the evaluation of yaw stability for heavy vehicle combinations  

Microsoft Academic Search

This paper proposes how the test case Sine With Dwell could be modified for the evaluation of yaw stability of heavy vehicles. The test case was originally proposed by the National Highway Traffic Safety Administration (NHTSA) for evaluation of Electronic Stability Programs (ESP) performance during an oversteer situation on high friction. The modified test case presented here accounts for the

Leo Laine; Sogol Kharrazi; Nicolas Dela

2008-01-01

170

Operating stability of a self-breakdown spark-gap frequency switch rated at a voltage of 300 kV and a switched power of up to 450 J  

NASA Astrophysics Data System (ADS)

A test bench for studying two-electrode spark gaps rated at a voltage of 300 kV and a pulse repetition rate of up to 10 Hz and operating in air at elevated pressure. The typical time of pulse charging of a capacitive storage in the bench equals about 100 ?s. The object of investigation is a spark gap the operating stability of which at a level of 10% of the rate voltage is achieved by initiating a corona discharge at the prebreakdown stage. It is shown that unstable operation is due to the accumulation of nitrogen oxides in the gap. To maintain the oxide content at an acceptable level, continuous gas purging is applied and necessary gas flow rates are estimated.

Koval'chuk, B. M.; Korolev, Yu. D.; Kumpyak, E. V.; Frants, O. B.; Shemyakin, I. A.

2014-12-01

171

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

172

[Evaluation of electrocardiographic left ventricular hypertrophy with both QRS voltage and ST-T change using echocardiography].  

PubMed

The purpose of the present study is to determine whether electrocardiographic QRS voltage criteria with ST-T change is useful in the diagnosis of left ventricular hypertrophy (LVH) using echocardiography. One hundred men including 59 with hypertension (HT), 9 with hypertrophic cardiomyopathy (HCM), and 32 without any cardiovascular disease were enrolled in this study. All of them had the electrocardiographic evidence of LVH by Sokolow-Lyon voltage criteria (RV5 or RV6 > 2.6 mV, SV1+RV5 or SV1+RV6 > or = 3.5 mV). They were classified into three groups based on ST-T pattern as follows: Normal ST-T (group N): normal ST-T in twelve leads; Early strain ST-T (group ES): ST depression, flat T (T/R < 1/10), diphasic T or T wave inversion < 0.1 mV in V5 or V6; and Strain ST-T (group S): inverted T wave in V5 and V6. Echocardiographic LVH was determined when either interventricular septal thickness (IVST) or left ventricular posterior wall thickness (LVPWT) > or = 12 mm was present. According to this echocardiographic evidence, 31.7%(20/63) of group N, 75.0% (12/16) of group ES, and 100% (21/21) of group S were diagnosed. There were significant correlations between QRS voltage indices (RV5, RV6, SV1+RV5 and SV1+RV6) and IVST, (IVST+LVPWT)/2, and LV mass in group S(r = 0.650 to 0.858, p < 0.05) but not in group N. Values for IVST and LV mass were significantly greater in group S than in group ES or N. The electrocardiographic diagnosis of LVH with both QRS voltage and ST-T change thus appeared to be more useful than that with QRS voltage criteria alone. PMID:9283227

Yagi, T; Noda, A; Itoh, R; Yamada, H; Nakashima, N; Yokota, M

1997-08-01

173

SOCIAL STABILITY AND HIV RISK BEHAVIOR: EVALUATING THE ROLE OF ACCUMULATED VULNERABILITY  

PubMed Central

This study evaluated a cumulative and syndromic relationship among commonly co-occurring vulnerabilites (homelessness, incarceration, low-income, residential transition) in association with HIV-related risk behaviors among 635 low-income women in Baltimore. Analysis included descriptive statistics, logistic regression, latent class analysis and latent class regression. Both methods of assessing multidimensional instability showed significant associations with risk indicators. Risk of multiple partners, sex exchange, and drug use decreased significantly with each additional domain. Higher stability class membership (77%) was associated with decreased likelihood of multiple partners, exchange partners, recent drug use, and recent STI. Multidimensional social vulnerabilities were cumulatively and synergistically linked to HIV risk behavior. Independent instability measures may miss important contextual determinants of risk. Social stability offers a useful framework to understand the synergy of social vulnerabilities that shape sexual risk behavior. Social policies and programs aiming to enhance housing and overall social stability are likely to be beneficial for HIV prevention. PMID:21259043

German, Danielle; Latkin, Carl A.

2011-01-01

174

Macrocyclic biphenyl tetraoxazoles: Synthesis, evaluation as G-quadruplex stabilizers and cytotoxic activity  

PubMed Central

A series of macrocyclic biphenyl tetraoxazoles was synthesized. The latter stages of the synthetic approach allowed for the addition of varied N-protected ?-amino acids, which were subsequently deprotected and condensed to provide the desired macrocycles. Improved yields could be realized in the macrocyclization step of their synthesis relative to other macrocyclic G-quadruplex stabilizers. These 24-membered macrocycles were evaluated for their ability to stabilize G-quadruplex DNA and for their relative cytotoxicity against human tumor cells. These biphenyl tetraoxazoles were not strong ligands for G-quadruplex DNA relative to other macrocyclic polyoxazoles. This reduced stabilizing potential did correlate with their comparatively lower cytotoxic activity as observed in the human tumor cell lines, RPMI 8402 and KB3-1. These studies provide useful insights into the conformational requirements for the development of selective and more potent G-quadruplex ligands. PMID:23787291

Blankson, Gifty A.; Pilch, Daniel S.; Liu, Angela A.; Liu, Leroy F.; Rice, Joseph E.; LaVoie, Edmond J.

2014-01-01

175

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

SciTech Connect

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

Turner, J.P.

1991-01-01

176

Evaluation of higher distribution and/or utilization voltages. Third interim report (October 1979): analysis of individual component cost and/or energy efficiencies  

SciTech Connect

This interim report provides documentation on the third task, Analysis of Individual Component Cost and/or Energy Efficiencies, 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 both cost and energy loss models for the distribution and customer utilization system elements as well as the analysis of critical performance variables for the types of motors in end use elements, as a function of voltage level. The purpose of this task is to provide individual component cost and energy models which will be incorporated in the global system optimization program under Task 4. A major output of this task is a mathematical model for each component's cost and/or energy losses and a graphical representation of each model.

Not Available

1981-04-01

177

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

178

Voltage stability constrained risk-based TTC evaluation of a power system with large integration of renewable energy  

Microsoft Academic Search

A future power grid should allow all types of generation including renewable energy, e.g. wind power and photovoltaic (PV). Over recent years, it has been witnessed a fast-growing renewable energy development throughout the world. Japan also pushes toward the renewable energy development setting out a target of 6610 MW wind power and 53 GW PV by 2030. This large penetration

Nattawut Paensuwan; Akihiko Yokoyama; S. C. Verma; Nakachi Yoshiki

2010-01-01

179

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

SciTech Connect

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

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

2000-09-28

180

Fabrication and evaluation of an OSO-1 type baseplate. [dimensional stability testing  

NASA Technical Reports Server (NTRS)

An OSO-1 type baseplate of a low thermal-expansion glass-ceramic material was evaluated for its dimensional stability after exposure to thermal cycling and mechanical vibration. The results indicate that baseplates of relatively simple design can be successfully cast and machined, although the demonstration article produced deviated somewhat from design specifications. It is likely that baseplates of more sophisticated designs and improved structural efficiency also can be prepared from low thermal expansion material.

Marschall, C. W.

1975-01-01

181

Mechanism and CHARM2 Evaluation of P-Channel Metal Oxide Semiconductor Threshold Voltage Drop during High Density Plasma Heat-up Process  

NASA Astrophysics Data System (ADS)

Plasma damage during the plasma deposition process is one of the most critical device characteristic issues facing complementary metal oxide semiconductor field effect transistor (CMOSFET) technology. In this paper, the CHARM2 monitoring system is used to evaluate UV damage and plasma charging damage during a high density plasma chemical vapor deposition (HDP-CVD) heat-up process. As a result, the amount of UV damage and negative charging damage is increased as the HDP-CVD heat-up process source power is increased. The main cause of P-channel metal oxide semiconductor field effect transistor (PMOSFET) threshold voltage drop is UV photon facilitated gate oxide electron trapping at the gate oxide and substrate P-channel interface during the HDP-CVD heat-up process. In N-channel metal oxide semiconductor field effect transistor (NMOSFET), when negative gate voltage stress is increased, gate oxide energy bend is flattened. Electrons cannot be trapped at the gate oxide and substrate N-channel interface. Therefore, the NMOSFET threshold voltage is constant during the HDP-CVD heat-up plasma process.

Kim, Dong-Hwan; Lee, Jeongyun; Kim, Min-Sung; Tokashiki, Ken; Shin, Kyoungsub; Han, Woosung; Kang, Hyun-Il; Kim, Eung-Kwon; Song, Joon-Tae

2009-08-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

183

Evaluation of initial stability and crestal bone loss in immediate implant placement: An in vivo study  

PubMed Central

Objectives: (1) To measure the crestal bone levels around implants immediately, and one month, three months, and six months after immediate implant placement, to evaluate the amount of bone level changes in six months. (2) To measure the initial stability in immediate implant placement. Materials and Methods: Ten patients were selected and a total of ten implants were placed in the immediate extraction sites. The change in the level of crestal bone was measured on standardized digital periapical radiographs taken at baseline, first month, third month, and sixth months for each patient, using the SOPRO imaging software. The initial stability of implants was measured with resonance frequency analysis (RFA) and an engine-driven torque. The measurements were statistically analyzed. The student's t-test was used, to identify the significance of the study parameters. Results: When mesial and distal bone losses were averaged, the radiographic evaluation with the SOPRO imaging software showed an average of 0.80 mm, with a standard deviation of ± 0.18 mm bone loss at the first month, followed by 1.03 mm with a standard deviation of ± 0.19 mm at the third month, and 1.23 mm with standard deviation of ± 0.6 mm at the sixth month. The initial stability with the RFA instrument showed a mean of 55 implant stability quotient (ISQ) values and the torque showed a value of 36.50 Nm. Conclusions: The implant has to be placed 2 mm below the crestal bone level to compensate the crestal bone loss. The initial stability is achieved by apical preparation of the socket wall and use of straight screw implants. When the defect is more than 2 mm, autogenous grafts with membranes are the best choice. PMID:25374829

Tadi, Durga Prasad; Pinisetti, Soujanya; Gujjalapudi, Mahalakshmi; Kakaraparthi, Sampath; Kolasani, Balaram; Vadapalli, Sri Harsha Babu

2014-01-01

184

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

185

Stress wave communication in concrete: II. Evaluation of low voltage concrete stress wave communications utilizing spectrally efficient modulation schemes with PZT transducers  

NASA Astrophysics Data System (ADS)

Piezoelectric materials, traditionally used for structural health monitoring, have recently been used to implement stress wave communications. Within a protective encasing we fabricate a smart aggregate which enables transmission and reception of modulated stress waves for digital communication within concrete. Our research focuses on building a high efficiency stress wave communication system and comparing the performance of phase shift keying (PSK) with quadrature amplitude modulation (QAM). Our experiments evaluate the performance of QPSK and 16QAM implemented with our stress wave communication system at a transmit voltage ranging from 32 dBV to 37 dBV. We also demonstrate the increase in spectral efficiency of 16QAM compared to QPSK.

Siu, Sam; Qing, Ji; Wang, Kun; Song, Gangbing; Ding, Zhi

2014-12-01

186

Stability of trimethyl phosphate non-flammable based electrolyte on the high voltage cathode (LiNi0.5Mn1.5O4)  

NASA Astrophysics Data System (ADS)

Trimethyl phosphate (TMP) which is a non-flammable solvent is a good candidate to replace flammable carbonates in battery electrolytes. In the case of Li-ion battery using high voltage cathode such as LiNi0.5Mn1.5O4 (LNM), the use of TMP based electrolyte leads to high cycle performance (96% capacity retention after 50 cycles). Also gas generation drastically decreased. According to careful observation of the LNM surface by scanning electron microscopy (SEM) after cycles, it has been found that TMP decomposes itself and forms polymer based film on the electrode surface suppressing further electrolyte decomposition. This work leads us to propose new electrolytes for Li-ion batteries using high voltage cathode.

Matsumoto, Kazuaki; Martinez, Mathieu; Gutel, Thibaut; Mailley, Sophie; De vito, Eric; Patoux, Sébastien; Inoue, Kazuhiko; Utsugi, Koji

2015-01-01

187

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

PubMed Central

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

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

2010-01-01

188

Application of a validated stability-indicating chromatographic method to evaluate the reproducibility between batches of small peptides in solution  

Microsoft Academic Search

A stability-indicating reversed-phase high-performance liquid chromatographic method was developed and validated as per the International Conference on Harmonization (ICH) guidelines to evaluate the reproducibility of batches of synthetic peptides included in a stability program, in particular cholecystokinin (CCK-4) peptide.Both isothermal and nonisothermal approaches were used to determine stability under experimental conditions and the resulting degradation products were identified by liquid

Alexis Oliva; Matías Llabrés; José B. Fariña

2010-01-01

189

Development and flight evaluation of an augmented stability active controls concept with a small horizontal tail  

NASA Technical Reports Server (NTRS)

A limited authority pitch active control system (PACS) was developed for a wide body jet transport (L-1011) with a flying horizontal stabilizer. Two dual channel digital computers and the associated software provide command signals to a dual channel series servo which controls the stabilizer power actuators. Input sensor signals to the computer are pitch rate, column-trim position, and dynamic pressure. Control laws are given for the PACS and the system architecture is defined. The piloted flight simulation and vehicle system simulation tests performed to verify control laws and system operation prior to installation on the aircraft are discussed. Modifications to the basic aircraft are described. Flying qualities of the aircraft with the PACS on and off were evaluated. Handling qualities for cruise and high speed flight conditions with the c.g. at 39% mac ( + 1% stability margin) and PACS operating were judged to be as good as the handling qualities with the c.g. at 25% (+15% stability margin) and PACS off.

Rising, J. J.; Kairys, A. A.; Maass, C. A.; Siegart, C. D.; Rakness, W. L.; Mijares, R. D.; King, R. W.; Peterson, R. S.; Hurley, S. R.; Wickson, D.

1982-01-01

190

Evaluation of stability of titanium and hydroxyapatite-coated osseointegrated dental implants: a pilot study.  

PubMed

An endosseous implant is described as osseointegrated when it is immobile in function. Objective measures of stability testing have been described. The Periotest is a commercially available device that is used for this purpose. This study was designed to measure stability of endosseous implants placed in the mandible. Implants were placed in the mandibular canine or first premolar area to support an overdenture prosthesis. Stability was evaluated through the use of a Periotest device at the time of implant placement and following one year of functional loading. Implant designs were either a screw-shaped titanium alloy or a hydroxyapatite-coated cylinder. A total of 54 implants were placed, 37 were titanium screw-shaped implants, while the remaining 17 were hydroxyapatite cylinders. Initial measurements of stability showed no difference due to implant type. Following one year of functional loading, titanium screw-shaped implants were more stable than hydroxyapatite implants (P < 0.05). The difference in implant rigidity following a period of functional loading may be an indication of a difference in osseointegration between the two implants used in this study. PMID:12005148

Simunek, Antonin; Vokurkova, Jarmila; Kopecka, Dana; Celko, Martin; Mounajjed, Radek; Krulichova, Iva; Skrabkova, Zuzana

2002-02-01

191

How to measure ecosystem stability? An evaluation of the reliability of stability metrics based on remote sensing time series across the major global ecosystems.  

PubMed

Increasing frequency of extreme climate events is likely to impose increased stress on ecosystems and to jeopardize the services that ecosystems provide. Therefore, it is of major importance to assess the effects of extreme climate events on the temporal stability (i.e., the resistance, the resilience, and the variance) of ecosystem properties. Most time series of ecosystem properties are, however, affected by varying data characteristics, uncertainties, and noise, which complicate the comparison of ecosystem stability metrics (ESMs) between locations. Therefore, there is a strong need for a more comprehensive understanding regarding the reliability of stability metrics and how they can be used to compare ecosystem stability globally. The objective of this study was to evaluate the performance of temporal ESMs based on time series of the Moderate Resolution Imaging Spectroradiometer derived Normalized Difference Vegetation Index of 15 global land-cover types. We provide a framework (i) to assess the reliability of ESMs in function of data characteristics, uncertainties and noise and (ii) to integrate reliability estimates in future global ecosystem stability studies against climate disturbances. The performance of our framework was tested through (i) a global ecosystem comparison and (ii) an comparison of ecosystem stability in response to the 2003 drought. The results show the influence of data quality on the accuracy of ecosystem stability. White noise, biased noise, and trends have a stronger effect on the accuracy of stability metrics than the length of the time series, temporal resolution, or amount of missing values. Moreover, we demonstrate the importance of integrating reliability estimates to interpret stability metrics within confidence limits. Based on these confidence limits, other studies dealing with specific ecosystem types or locations can be put into context, and a more reliable assessment of ecosystem stability against environmental disturbances can be obtained. PMID:24777443

De Keersmaecker, Wanda; Lhermitte, Stef; Honnay, Olivier; Farifteh, Jamshid; Somers, Ben; Coppin, Pol

2014-07-01

192

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...

193

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

194

Evaluation of the geological relationships to gas hydrate formation and stability  

SciTech Connect

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

Not Available

1986-01-01

195

Simultaneous and multisite measure of micromotion, subsidence and gap to evaluate femoral stem stability.  

PubMed

The initial stability of cementless femoral components is crucial for the long-term success of total hip arthroplasty. This has been reported in animal and clinical studies. Until now, the stability was evaluated by the measurement of relative micromotion on a few simultaneous locations around the stem in cadaveric experiments. This paper presents an extended experimental setup to measure simultaneously local micromotion, subsidence and gap on hundreds of points at the bone-stem interface. This technique we applied to anatomical and straight stems in three pairs of cadaveric femurs. Measurements were in agreement with typically reported values. Conversely to other methods, which measure micromotion between implant and bone anchoring points of the measuring device, our method provides local micromotion between stem surface and adjacent bone surface. The observed variation of micromotion at the peri-implant surface confirms the importance of this simultaneous measure on a lot of points around the implant. PMID:22356845

Gortchacow, Michael; Wettstein, Michael; Pioletti, Dominique P; Müller-Gerbl, Magdalena; Terrier, Alexandre

2012-04-30

196

An empirical evaluation of the insurance hypothesis in diversity-stability models.  

PubMed

An important stabilizing mechanism in most diversity stability models is the insurance hypothesis, which involves correlation/covariance relationships among species. These models require that species do not fluctuate synchronously over time: that is, the correlation between pairs of species does not equal 1.0. However, the strength of this stabilizing mechanism increases as correlations decline away from 1.0, especially as they become more negative and also as the summed covariance across all species pairs becomes more negative. We evaluated the importance of the insurance hypothesis as a stabilizing mechanism by examining a variety of terrestrial assemblages using long-term data from the Global Population Dynamics Database, the Breeding Bird Survey, and a long-term site in southeastern Arizona, USA. We identified co-occurring assemblages of species and calculated the Spearman rank correlations of all pairs of species and the summed covariance of the entire assemblage. We found that, in most assemblages, positive correlations were two to three times more common than negative and that the magnitude of the positive correlations tended to be stronger than the negative correlations. For all but three assemblages, the summed covariance was positive. Data from larger spatial scales tended to exhibit more positive correlations, but even at the smallest spatial scales, positive correlations outnumbered negative. We suggest that species often covary positively because coexisting species respond similarly to fluctuations in their resource base driven by climatic fluctuations. As such, our review suggests that the insurance hypothesis may not be a strong mechanism stabilizing fluctuations in natural terrestrial communities. PMID:18409441

Valone, Thomas J; Barber, Nicholas A

2008-02-01

197

The Dynamic Evaluation of Rock Slope Stability Considering the Effects of Microseismic Damage  

NASA Astrophysics Data System (ADS)

A state-of-the-art microseismic monitoring system has been implemented at the left bank slope of the Jinping first stage hydropower station since June 2009. The main objectives are to ensure slope safety under continuous excavation at the left slope, and, very recently, the safety of the concrete arch dam. The safety of the excavated slope is investigated through the development of fast and accurate real-time event location techniques aimed at assessing the evolution and migration of the seismic activity, as well as through the development of prediction capabilities for rock slope instability. Myriads of seismic events at the slope have been recorded by the microseismic monitoring system. Regions of damaged rock mass have been identified and delineated on the basis of the tempo-spatial distribution analysis of microseismic activity during the periods of excavation and consolidation grouting. However, how to effectively utilize the abundant microseismic data in order to quantify the stability of the slope remains a challenge. In this paper, a rock mass damage evolutional model based on microseismic data is proposed, combined with a 3D finite element method (FEM) model for feedback analysis of the left bank slope stability. The model elements with microseismic damage are interrogated and the deteriorated mechanical parameters determined accordingly. The relationship between microseismic activities induced by rock mass damage during slope instability, strength degradation, and dynamic instability of the slope are explored, and the slope stability is quantitatively evaluated. The results indicate that a constitutive relation considering microseismic damage is concordant with the simulation results and the influence of rock mass damage can be allowed for its feedback analysis of 3D slope stability. In addition, the safety coefficient of the rock slope considering microseismic damage is reduced by a value of 0.11, in comparison to the virgin rock slope model. Our results demonstrate that microseismic activity induced by construction disturbance only slightly affects the stability of the slope. The proposed feedback analysis technique provides a novel method for dynamically assessing rock slope stability and can be used to assess the slope stability of other similar rock slopes.

Xu, N. W.; Dai, F.; Liang, Z. Z.; Zhou, Z.; Sha, C.; Tang, C. A.

2014-03-01

198

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

199

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

200

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

SciTech Connect

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

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

2012-01-01

201

Long Term Stability Evaluation of Prostacyclin Released from Biomedical Device through Turbiscan Lab Expert.  

PubMed

Therapeutic guidelines indicate prostacyclin as the first line of treatment in inflammation and vascular diseases. Prostacyclins prevent formation of the platelet plug involved in primary hemostasis by inhibiting platelet activation and, combined with thromboxane, are effective vasodilators in vascular damage. Trans-Atlantic Inter-Society Consensus Document on Management of Peripheral Arterial Disease II guidelines indicates prostacyclins; in particular, Iloprost, as the first therapeutic option for treating peripheral arterial disease. However, therapeutic efficacy of Iloprost has witnessed several drawbacks that have occurred in patients receiving repeated weekly administration of the drug by intravenous infusions. Adverse reactions arose under perfusion with Iloprost for 6 h and patient compliance was drastically decreased. Biomedical devices could provide a suitable alternative to overcome these drawbacks. In particular, elastomeric pumps, filled with Iloprost isotonic solution, could slowly release the drug, thus decreasing its side effects, representing a valid alternative to hospitalization of patients affected by peripheral arterial disease. However, the home therapy treatment of patients requires long-term stability of Iloprost in solution-loaded elastomeric pumps. The aim of this work was to investigate the long-term stability of Iloprost isotonic solution in biomedical devices using Turbiscan technology. Turbiscan Lab Expert (L'Union, France) predicts the long-term stability of suspensions, emulsions and colloidal formulations by measuring back scattering and transmission of particulates dispersed in solution. The formulations were evaluated by measuring the variation of physicochemical properties of colloids and suspensions as a function of back scattering and transmission modifications. In addition, the release profile of Iloprost isotonic solution from the biomedical device was evaluated. PMID:25381994

Celia, Christian; Locatelli, Marcello; Cilurzo, Felisa; Cosco, Donato; Gentile, Emanuela; Scalise, Daniela; Carafa, Maria; Ventura, Cinzia Anna; Fleury, Mathias; Tisserand, Christelle; Barbacane, Renato C; Fresta, Massimo; Marzio, Luisa Di; Paolino, Donatella

2014-11-10

202

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

203

Health-hazard evaluation report HETA 86-339-1741, EMCO High Voltage Company, Sutter Creek, California  

SciTech Connect

Possible exposure to several chemical substances during the fabrication of power-supply modules was investigated at the EMCO High Voltage Company, Sutter Creek, California, at the request of an employee. Environmental air samples were collected during the coating and developing process and during the epoxy potting operation. Samples were analyzed for chlorobenzene and xylenes; no overexposures were registered. No overexposure was observed to butyl-glycidyl-ether and no detectable levels of epichlorohydrin, cyclohexanone, 2-methoxyethanol, or 2-ethoxyethanol were found. During the pot soldering operation there was a potential for exposure to the fluxing agent, 3% hydrochloric-acid, and the operator had complained of throat and nose irritation. The author recommends that the fabrication operator wear protective gloves during coating and developing of copper boards. Gloves and goggles should be worn when weighing out the sodium-persulfate and when removing panels from the bench top etcher. Local exhaust ventilation with a movable duct should be used during the pot soldering operation.

Belanger, P.L.

1986-10-01

204

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

205

Evaluation of interface shear strength of composite liner system and stability analysis for a landfill lining system in Thailand  

Microsoft Academic Search

The paper presents the case history of laboratory evaluation of the interface shear strength properties of various interfaces encountered in a modern day landfill with emphasis on proper simulation of field conditions and subsequent use of these results in the stability analyses of liner system. Over 70 large direct shear tests were systematically conducted to evaluate the interface shear strength

D. T. Bergado; G. V. Ramana; H. I. Sia; Varun

2006-01-01

206

Evaluation of solidification/stabilization technology for Buffalo River sediment. Final report  

SciTech Connect

The Buffalo River drains a 446-square-mile (1,155-sq-km) watershed in western New York State and discharges into Lake Erie at the city of Buffalo. The Buffalo River has been classified by the State of New York as a fishing and fish survival stream, but municipal and industrial discharges have degraded the water quality and resulted in a fish advisory for the river. Under the Assessment and Remediation of Contaminated Sediment Program, the US Environmental Protection Agency asked the US Army Corps of Engineers to evaluate solidification/stabilization (S/S) for potential treatment of the contaminated sediments in the Buffalo River. An evaluation of S/S technology was conducted on the bench-scale level on Buffalo River sediment to determine whether physical and chemical properties of the sediment would be improved. Based on analyses of the untreated sediment, five metals were selected for evaluation: chromium, copper, lead, nickel, and zinc. Initial screening tests (ISTs) were conducted on the sediments to narrow the range of binder-to-soil ratios (BSRs) to be prepared in the detailed evaluation.

Fleming, E.C.; Averett, D.E.; Channell, M.G.; Perry, B.D.

1991-05-01

207

Design and flight performance evaluation of the Mariners 6, 7, and 9 short-circuit current, open-circuit voltage transducers  

NASA Technical Reports Server (NTRS)

The purpose of the short-circuit voltage transducer is to provide engineering data to aid the evaluation of array performance during flight. The design, fabrication, calibration, and in-flight performance of the transducers onboard the Mariner 6, 7 and 9 spacecrafts are described. No significant differences were observed in the in-flight electrical performance of the three transducers. The transducers did experience significant losses due to coverslides or adhesive darkening, increased surface reflection, or spectral shifts within coverslide assembly. Mariner 6, 7 and 9 transducers showed non-cell current degradations of 3-1/2%, 3%, and 4%, respectively at Mars encounter and 6%, 3%, and 4-12%, respectively at end of mission. Mariner 9 solar Array Test 2 showed 3-12% current degradation while the transducer showed 4-12% degradation.

Patterson, R. E.

1973-01-01

208

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

209

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

210

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

PubMed

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

211

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

212

Landslides and slope stability evaluation in the historical town of Kruja, Albania  

NASA Astrophysics Data System (ADS)

This paper describes the landslides and slope stability evaluation in the urban area of Kruja town, Albania. Kruja is a~historical and heritage center, due to the existence of many important cultural monuments including Skanderbeg castle and Bazaar square etc. The urban area of Kruja town has been affected from the Landslides effects, in the past and also present. From this phenomenon many engineering objects such as buildings, roads etc. are damaged and demolished. From the engineering geological mapping at scale 1 : 5000 it is observed that many active landslides have dramatically increased in activity after 1980s. The landslide types found in the studied area are earth slides, debris flow, as well as rock fall and rock rolling. Also, from field works and laboratory analysis, the slope stability of whole urban areas has been determined; for this purpose the studied zone is divided into the stable and unstable areas, which helps to better understand the mass movement's activity as one of the most harmful hazards of the geodynamics' phenomena.

Muceku, Y.; Korini, O.

2013-07-01

213

Landslide and slope stability evaluation in the historical town of Kruja, Albania  

NASA Astrophysics Data System (ADS)

This paper describes landslides and slope stability evaluation in the urban area of Kruja, Albania. Kruja is a historical and heritage center, due to the existence of many important cultural monuments, including "Skanderbeg" castle and Bazaar square, etc. The urban area of Kruja has been affected by landslide effects, in the past and also the present. From this phenomenon many engineering objects such as buildings, roads, etc., are damaged and demolished. From engineering geological mapping at scale 1:5000 it is observed that many active landslides have dramatically increased in activity since the 1980s. The landslide types found in the studied area are earthslides, debris flow, as well as rockfall and rock rolling. Also, from field works and laboratory analysis, the slope stability of the whole urban area has been determined; for this purpose the studied zone is divided into stable and unstable areas, which helps to better understand mass movement activity as one of the most harmful hazards of geodynamic phenomena.

Muceku, Y.; Korini, O.

2014-03-01

214

A Preliminary Evaluation of Using Fill Materials to Stabilize Used Nuclear Fuel During Storage and Transportation  

SciTech Connect

This report contains a preliminary evaluation of potential fill materials that could be used to fill void spaces in and around used nuclear fuel contained in dry storage canisters in order to stabilize the geometry and mechanical structure of the used nuclear fuel during extended storage and transportation after extended storage. Previous work is summarized, conceptual descriptions of how canisters might be filled were developed, and requirements for potential fill materials were developed. Elements of the requirements included criticality avoidance, heat transfer or thermodynamic properties, homogeneity and rheological properties, retrievability, material availability and cost, weight and radiation shielding, and operational considerations. Potential fill materials were grouped into 5 categories and their properties, advantages, disadvantages, and requirements for future testing were discussed. The categories were molten materials, which included molten metals and paraffin; particulates and beads; resins; foams; and grout. Based on this analysis, further development of fill materials to stabilize used nuclear fuel during storage and transportation is not recommended unless options such as showing that the fuel remains intact or canning of used nuclear fuel do not prove to be feasible.

Maheras, Steven J.; Best, Ralph; Ross, Steven B.; Lahti, Erik A.; Richmond, David J.

2012-08-01

215

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

216

Evaluation of the stability and antimicrobial activity of an ethanolic extract of Libidibia ferrea.  

PubMed

Biofilm is a dense, whitish, noncalcified aggregate of bacteria, with desquamated epithelial cells and food debris creating conditions for an imbalance of resident oral microflora and favoring the destruction of hard and soft tissues by development of caries and gingivitis. The aim of this study was to obtain and characterize an extract of Libidibia ferrea, ex Caesalpinia ferrea L. and to evaluate its feasibility for formulation as a mouthwash, according to current legislation. For this purpose, pH, sedimentation, density, and stability were evaluated, along with microbiological testing of the extract. The microbiological test was used to verify the presence of Staphylococcus aureus, Pseudomonas aeruginosa, fungi, yeasts, coliforms, and minimum inhibitory concentrations of Streptococcus mutans and Streptococcus oralis strains. Characterization, microbiological evaluation, and minimum inhibitory concentration results were tabulated and described using descriptive statistics. The L. ferrea extract showed stable characteristics, product quality, and antibacterial activity against the microorganisms tested irrespective of experimental time intervals. According to these results, it can be concluded that formulation of a mouthwash containing L. ferrea extract to control biofilm is feasible, but further studies are needed. PMID:24501546

de Oliveira Marreiro, Raquel; Bandeira, Maria Fulgência Costa Lima; de Souza, Tatiane Pereira; de Almeida, Mailza Costa; Bendaham, Katiana; Venâncio, Gisely Naura; Rodrigues, Isis Costa; Coelho, Cristiane Nagai; Milério, Patrícia Sâmea Lêdo Lima; de Oliveira, Glauber Palma; de Oliveira Conde, Nikeila Chacon

2014-01-01

217

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

218

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

219

A novel photometric method for evaluation of the oxidative stability of virgin olive oils.  

PubMed

The Oxitester method, a novel, simple, and fast photometric method for the evaluation of the antioxidant capacity of olive oils, was validated and compared to the official oil stability index (Rancimat) method. The Oxitester method appeared to be a good alternative to the Rancimat method with adequate correlation for a wide range of virgin olive oil samples, including extrissima virgin olive oils (correlation coefficient 0.88), and extra virgin olive oils of increased acidity (free fatty acids >0.45%, correlation coefficient 0.89). Other quality factors (flavor, free fatty acids content, specific absorbance at 270 and 232 nm, peroxide value, and content of oleic, linoleic, and linolenic acids) were also measured and correlated to the antioxidant capacity values of the Oxitester and Rancimat methods. The Oxitester method, in contrast to the Rancimat method, was indicative of the flavor characteristics of the olive oils and the content of linolenic acid. PMID:18727539

Kamvissis, Vassilis N; Barbounis, Emmanouil G; Megoulas, Nikolaos C; Koupparis, Michael A

2008-01-01

220

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

221

Clinical evaluation of accommodation and ocular surface stability relavant to visual asthenopia with 3D displays  

PubMed Central

Background To validate the association between accommodation and visual asthenopia by measuring objective accommodative amplitude with the Optical Quality Analysis System (OQAS®, Visiometrics, Terrassa, Spain), and to investigate associations among accommodation, ocular surface instability, and visual asthenopia while viewing 3D displays. Methods Fifteen normal adults without any ocular disease or surgical history watched the same 3D and 2D displays for 30 minutes. Accommodative ability, ocular protection index (OPI), and total ocular symptom scores were evaluated before and after viewing the 3D and 2D displays. Accommodative ability was evaluated by the near point of accommodation (NPA) and OQAS to ensure reliability. The OPI was calculated by dividing the tear breakup time (TBUT) by the interblink interval (IBI). The changes in accommodative ability, OPI, and total ocular symptom scores after viewing 3D and 2D displays were evaluated. Results Accommodative ability evaluated by NPA and OQAS, OPI, and total ocular symptom scores changed significantly after 3D viewing (p?=?0.005, 0.003, 0.006, and 0.003, respectively), but yielded no difference after 2D viewing. The objective measurement by OQAS verified the decrease of accommodative ability while viewing 3D displays. The change of NPA, OPI, and total ocular symptom scores after 3D viewing had a significant correlation (p?stability may be causative factors of visual asthenopia in individuals viewing 3D displays. PMID:24612686

2014-01-01

222

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

223

Voltage Breakdown Mechanisms in High Voltage Rated, Surface Mount MLCCs  

Microsoft Academic Search

Multilayer ceramic capacitors (MLCCs) exposed to high voltages, around 1000VDC in air, are prone to both surface-arc- over and internal breakdown. In either event failures will result at the instance of surface-arc-over as the circuit is de- stabilized which may cause damage to surrounding components even if the capacitor remains temporarily functional. The performance of HVArc GuardTM X7R capacitors, that

J. Bultitude; P. Gormally; J. Rogers; J. Jiang

224

Formulation and stability evaluation of extemporaneously prepared atenolol capsules from crushed atenolol tablets.  

PubMed

The purpose of this study was to formulate a 25-mg atenolol capsule starting from a commercial 100-mg atenolol tablet, given the fact that this strength is not available in Palestine and also because 50-mg atenolol tablets failed the splitting uniformity test of the European Pharmacopoeia, and to evaluate the chemical stability and dissolution behavior of the obtained capsules so as to ensure a high-quality product. A high-performance liquid chromatographic system was used for the analysis and quantification of atenolol in the samples studied. Samples of atenoIol for analysis were prepared as reported by the United States Pharmacopeia monograph. Disintegration and dissolution tests were performed according to the United States Pharmacopeia. The high-performance liquid chromatography assay indicated that the 25-mg atenolol capsules were stable for four months when stored at ambient temperature conditions. The disintegration time for all atenolol capsules was within the United States Pharmacopeia limits of 15 minutes. Atenolol release profile showed that approximately 90% of atenolol dissolved after 10 minutes. This study is important for patients who need to take one half of a 50-mg tablet, but for whom the splitting process doesn't give equal halves, and also for modifying the dose for patients with renal or hepatic problems. Therefore, it is possible for the community pharmacist to crush atenolol 100-mg tablets and refill them in new capsules with each containing a precise amount of atenolol, calculated according to body surface area and kidney and liver functions without affecting the chemical stability of the active ingredient nor its dissolution profile and also have a cost effective dosage form. PMID:23050394

Zaid, Abdel Naser; Malkieh, Numan; Kharoaf, Maher; Abu Ghoush, Abeer; Al-Ramahi, Rowa'

2012-01-01

225

Evaluation of liver tissue damage and grasp stability using finite element analysis.  

PubMed

Minimizing tissue damage and maintaining grasp stability are essential considerations in surgical grasper design. Most past and current research analyzing graspers used for tissue manipulation in minimally invasive surgery is based on in vitro experiments. Most previous work assessed tissue injury and grasp security by visual inspection; only a few studies have quantified it. The goal of the present work is to develop a methodology with which to compute tissue damage magnitude and grasp quality that is appropriate for a wide range of grasper-tissue interaction. Using finite element analysis (FEA), four graspers with varying radii of curvature and four graspers with different tooth sizes were analyzed while squeezing and pulling liver tissue. All graspers were treated as surgical steel with linear elastic material properties. Nonlinear material properties of tissue used in the FEA as well as damage evaluation were derived from previously reported in vivo experiments. Computed peak stress, integrated stress, and tissue damage were compared. Applied displacement is vertical and then horizontal to the tissue surface to represent grasp and retraction. A close examination of the contact status of each node within the grasper-tissue interaction surface was carried out to investigate grasp stability. The results indicate less tissue damage with increasing radius of curvature. A smooth wave pattern reduced tissue damage at the cost of inducing higher percentage of slipping area. This methodology may be useful for researchers to develop and test various designs of graspers. Also it could improve surgical simulator performance by reflecting more realistic tissue material properties and predicting tissue damage for the student. PMID:25408249

Cheng, Lei; Hannaford, Blake

2014-11-19

226

Analysis and Design of a 60 GHz Wideband Voltage-Voltage Transformer Feedback LNA  

Microsoft Academic Search

To cope with the problem of instability and imperfect reverse isolation, a millimeter-wave voltage-voltage transformer feedback low noise amplifier has been analyzed, designed, and measured in CMOS 65 nm technology. Analytical formulae are derived for describing the stability, gain, and noise in this circuit topology. An analogy with the classic concept of Masons's invariant is used to illustrate how the

Pooyan Sakian; Erwin Janssen; Arthur H. M. van Roermund; Reza Mahmoudi

2012-01-01

227

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

EPA Science Inventory

NRMRL-CIN-1624 Daniels*, A., Kominsky, J.R., and Clark*, P.J. Evaluation of Two Lead-Based Paint Removal and Waste Stabilization Technology Combinations on Typical Exterior Surfaces. Published in: Journal of Hazardous Materials 87 (1-3):117-126 (2001). 10/04/2001 A study was co...

228

INTERNATIONAL WASTE TECHNOLOGIES EVALUATION REPORT SITE PROGRAM DEMONSTRATION, IN-SITU STABILIZATION/SOLIDIFICATION, HIALEAH, FL, VOLUME I  

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...

229

Bioremediation of contaminated lake sediments and evaluation of maturity indicies as indicators of compost stability.  

PubMed

Land contamination is one of the widely addressed problems, which is gaining importance in many developed and developing countries. International efforts are actively envisaged to remediate contaminated sites as a response to adverse health effects. Popular conventional methodologies only transfer the phase of the contaminant involving cost intensive liabilities besides handling risk of the hazardous waste. Physico-chemical methods are effective for specific wastes, but are technically complex and lack public acceptance for land remediation. iBioremediatio nî, is one of the emerging low-cost technologies that offer the possibility to destroy various contaminants using natural biological activities. Resultant non-toxic end products due to the microbial activity and insitu applicability of this technology is gaining huge public acceptance. In the present study, composting is demonstrated as a bioremediation methodology for the stabilization of contaminated lake sediments of Hyderabad, A.P, India. Lake sediment contaminated with organics is collected from two stratums--upper (0.25 m) and lower (0.5m) to set up as Pile I (Upper) and Pile II (Lower) in the laboratory. Lime as a pretreatment to the lake sediments is carried out to ensure metal precipitation. The pretreated sediment is then mixed with organic and inorganic fertilizers like cow dung, poultry manure, urea and super phosphate as initial seeding amendments. Bulking agents like sawdust and other micronutrients are provided. Continuous monitoring of process control parameters like pH, moisture content, electrical conductivity, total volatile solids and various forms of nitrogen were carried out during the entire course of the study. The stability of the compost was evaluated by assessing maturity indices like C/N, Cw (water soluble carbon), CNw (Cw/Nw), nitrification index (NH4/NO-3), Cation Exchange Capacity (CEC), germination index, humification ratio, compost mineralization index (ash content/oxidizable carbon), sorption capacity index (CEC/oxidizable carbon). Enzyme activities of agricultural interest like urease, phosphatase, P-glucosidase, dehydrogenase and BAA-hydrolyzing protease, which are involved in the nitrogen, phosphorus and carbon cycles, were also assessed. Total content of macro and micronutrients in the final compost was also determined to assess the fertilizer value. The studies revealed that composting could be applied as a remediation technology after removing the top sediment. The maturity indices that are evaluated from the present study can be used to validate the success of the remediation technology. PMID:16705825

Rekha, P; Suman Raj, D S; Aparna, C; Hima Bindu, V; Anjaneyulu, Y

2005-08-01

230

Liquid meniscus oscillation and drop ejection by ac voltage, pulsed dc voltage, and superimposing dc to ac voltages  

NASA Astrophysics Data System (ADS)

The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and the meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Based on this in-depth study of the meniscus behavior under various signals, the optimal signal is implemented to an EHD inkjet head for drop-on-demand operation. For applied ac voltage and ac voltage superimposed on dc voltage, the jetting phenomenon is a dynamic process due to sequential opposite sign signals. The jetting occurs at the end of the oscillation cycle, where the meniscus oscillates upward and arrives at its highest position.

Tran, Si Bui Quang; Byun, Doyoung; Nguyen, Vu Dat; Kang, Tae Sam

2009-08-01

231

Liquid meniscus oscillation and drop ejection by ac voltage, pulsed dc voltage, and superimposing dc to ac voltages.  

PubMed

The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and the meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Based on this in-depth study of the meniscus behavior under various signals, the optimal signal is implemented to an EHD inkjet head for drop-on-demand operation. For applied ac voltage and ac voltage superimposed on dc voltage, the jetting phenomenon is a dynamic process due to sequential opposite sign signals. The jetting occurs at the end of the oscillation cycle, where the meniscus oscillates upward and arrives at its highest position. PMID:19792260

Tran, Si Bui Quang; Byun, Doyoung; Nguyen, Vu Dat; Kang, Tae Sam

2009-08-01

232

Automatic voltage regulator using an AC voltage-voltage converter  

Microsoft Academic Search

Voltage sags and extended undervoltages are one of the main concerns of industry today. These voltage sags could cause high negative impact on productivity, which is certainly an undesirable aspect in industrial and commercial applications. Current tap-changing transformers used in distribution systems have proven to be inadequate in solving these problems related to line regulation. A solution to these problems

Steven M. Hietpas; Mark Naden

2000-01-01

233

Automatic voltage regulator using an AC voltage-voltage converter  

Microsoft Academic Search

Voltage sags and extended undervoltages are one of the main concerns of industries today. These voltage sags could cause high negative impact on productivity, which is certainly an undesirable aspect in industrial and commercial applications. Current tap-changing transformers used in distribution systems have proven to be inadequate in solving these problems related to line regulation. A solution to these problems

Steven M. Hietpas; Mark Naden

1999-01-01

234

Preparation of Sterically Stabilized Chitin Nanowhisker Dispersions by Grafting of Poly(ethylene glycol) and Evaluation of Their Dispersion Stability.  

PubMed

Sterically stabilized chitin nanowhiskers (ChNWs) were prepared by surface grafting monomethoxy poly(ethylene glycol) (mPEG) via reductive amination of primary amino groups on ChNWs and terminal aldehydes on mPEG. The amount of grafted mPEG was determined to be 0.2-0.3 g/g ChNWs, by conductometric titration, from the decrease in amino groups after grafting. ChNWs with controlled amounts of surface amino groups were obtained by deacetylation; however, this did not cause a drastic change in the amount of grafted mPEG. Grafting was confirmed by Fourier-transform infrared spectroscopy; however, X-ray diffractometry indicated no sign of mPEG. Thermogravimetry indicated a higher amount of mPEG than that from titration, suggesting an overestimation due to the facilitated combustion of grafted samples. In contrast to ungrafted samples, all grafted samples were stable in the presence of electrolytes. However, liquid-crystalline phase separation of grafted ChNWs was not observed, possibly owing to the high viscosity of the concentrated sample. PMID:25455958

Araki, Jun; Kurihara, Mari

2015-01-12

235

In Vitro Evaluation of Dimensional Stability of Alginate Impressions after Disinfection by Spray and Immersion Methods  

PubMed Central

Background and aims The most common method for alginate impression disinfection is spraying it with disinfecting agents, but some studies have shown that these impressions can be immersed, too. The aim of this study was to evaluate the dimensional stability of alginate impressions following disinfecting by spray and immersion methods. Materials and methods Four common disinfecting agents (Sodium Hypochlorite, Micro 10, Glutaraldehyde and De-conex) were selected and the impressions (n=108) were divided into four groups (n=24) and eight subgroups (n=12) for disinfecting by any of the four above-mentioned agents by spray or immersion methods. The control group (n=12) was not disinfected. Then the impressions were poured by type III Dental Stone Plaster in a standard method. The results were ana-lyzed by descriptive methods (mean and standard deviation), t-test, two-way analysis of variance (ANOVA) and Duncan test, using SPSS 14.0 software for windows. Results The mean changes of length and height were significant between the various groups and disinfecting methods. Regarding the length, the greatest and the least amounts were related to Deconex and Micro 10 in the immersion method, respectively. Regarding height, the greatest and the least amounts were related to Glutaraldehyde and Deconex in the im-mersion method, respectively. Conclusion Disinfecting alginate impressions by Sodium Hypochlorite, Deconex and Glutaraldehyde by immersion method is not recommended and it is better to disinfect alginate impressions by spraying of Micro 10, Sodium Hypochlorite, Glutaraldehyde and immersion in Micro 10. PMID:23346340

Hamedi Rad, Fahimeh; Ghaffari, Tahereh; Safavi, Sayed Hamed

2010-01-01

236

Stability evaluation of the Panel 1 rooms and the E140 drift at WIPP  

SciTech Connect

WIPP, intended for underground permanent disposal of defense transuranic waste, is located 40 km east of Carlsbad at a depth of 655 m in the salt beds of the 600-m thick Permian Salado Formation. It will consist of 56 ``rooms`` each 91.5 m long, 10 m wide, and 4 m high, grouped in 8 ``panels`` of 7 rooms each. About 7.5 km of access drifts will also be provided. Excavation began in 1982 and surface/access/test facilities and one panel were completed by 1988, many years before it could be used. Current plans are to start emplacing waste in WIPP in 1998 and continue for 35 years. The north- south drift E140 is the widest (25 ft) of the four main north-south drifts and is the main north-south passage. Plans to conduct experiments with waste in 1993 were abandoned, and the plan now is to use panel 1 for permanent disposal of waste starting in 1998. The stability evaluation resulted in the conclusion that, while it would be possible to safely use portions of panel 1 for waste emplacement, it would be best to abandon panel 1 and mine a new panel after the decision has been made to use WIPP as a repository and the necessary permits obtained.

Maleki, H. [Maleki Technologies, Inc. (United States); Chaturvedi, L. [Environmental Evaluation Group, Albuquerque, NM (United States)

1996-08-01

237

Precision voltage regulator  

NASA Technical Reports Server (NTRS)

Balanced positive and negative voltage output circuit, in which error voltage for control is developed from difference in absolute value of positive and negative voltages referenced to a common point, regulates voltage for use with inertial reference unit. Fast-acting, temperature-compensated, high-gain operational amplifier circuits maintain common point.

Hand, P. J.; Crawford, R. A.

1972-01-01

238

Evaluating network analysis and agent based modeling for investigating the stability of commercial air carrier schedules  

NASA Astrophysics Data System (ADS)

For a number of years, the United States Federal Government has been formulating the Next Generation Air Transportation System plans for National Airspace System improvement. These improvements attempt to address air transportation holistically, but often address individual improvements in one arena such as ground or in-flight equipment. In fact, air transportation system designers have had only limited success using traditional Operations Research and parametric modeling approaches in their analyses of innovative operations. They need a systemic methodology for modeling of safety-critical infrastructure that is comprehensive, objective, and sufficiently concrete, yet simple enough to be deployed with reasonable investment. The methodology must also be amenable to quantitative analysis so issues of system safety and stability can be rigorously addressed. The literature suggests that both agent-based models and network analysis techniques may be useful for complex system development and analysis. The purpose of this research is to evaluate these two techniques as applied to analysis of commercial air carrier schedule (route) stability in daily operations, an important component of air transportation. Airline-like routing strategies are used to educe essential elements of applying the method. Two main models are developed, one investigating the network properties of the route structure, the other an Agent-based approach. The two methods are used to predict system properties at a macro-level. These findings are compared to observed route network performance measured by adherence to a schedule to provide validation of the results. Those interested in complex system modeling are provided some indication as to when either or both of the techniques would be applicable. For aviation policy makers, the results point to a toolset capable of providing insight into the system behavior during the formative phases of development and transformation with relatively low investment. Both Agent-Based Modeling and Network Analysis were found to be useful in this context, particularly when applied with an eye towards the system context, and concentrated effort on capturing the salient features of the system of interest.

Conway, Sheila Ruth

239

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 (V(o))--the spatial average of these quantum voltages referenced to the vacuum. Here we establish a protocol to reliably evaluate V(o) 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 V(o) 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 V(o) 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

240

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

241

Evaluation of stabilization/solidification of fluidized-bed incinerator ash (K048 and K051). Final report  

SciTech Connect

This report presents the results of testing performed on a stabilized/solidified (S/S) incinerator ash. This study was conducted in support of the US Environmental Protection Agency, Best Demonstrated Available Technology program. The ash samples evaluated in the study were residuals resulting from the incineration of a mixture of dissolved air-flotation float (K048), API separator oily sludge (K051), and a biological sludge. Three S/S processes were evaluated. They included: (1) a cement process; (2) a kiln-dust process; and (3) a lime/fly ash process. Physical and leaching characteristics of the S/S waste-ash materials were evaluated. Physical characteristics were evaluated using the unconfined compressive-strength test. The waste-leaching characteristics were evaluated using the toxicity characteristic leaching procedure.

Bricka, R.M.; Holmes, T.; Cullinane, M.J.

1988-12-01

242

Approach to evaluating dried blood spot sample stability during drying process and discovery of a treated card to maintain analyte stability by rapid on-card pH modification.  

PubMed

Unstable drug candidates often lead to complexity for both sample collection and bioanalysis. Dried blood spot (DBS) technology is believed to be a viable solution to address this problem. However, it is currently a challenge to evaluate compound stability on DBS due to its solid format. The observed compound loss on a DBS card could be degradation and/or incomplete recovery. Therefore, a reliable bioanalytical method which can differentiate recovery loss from degradation is necessary for such stability evaluation. In this paper, the stability of an unstable drug candidate (KAI-9803) in human blood was evaluated using DBS. A reliable approach to evaluating analyte stability on DBS was developed with an appropriate time-zero sample, a consistent DBS sample processing method, and a suitable positive control. Commercially available DBS cards were evaluated, and it was found that KAI-9803 degraded during the drying process. An in-house modified DBS card was developed and demonstrated to be able to stabilize KAI-9803 during the drying process by rapidly lowering the pH of the spotted blood sample. The storage stability of KAI-9803 in human blood on this new card has been established for at least 48 days at room temperature. This in-house modified DBS card could provide a generic approach for other compounds which require stabilization at a low pH. PMID:21995953

Liu, Guowen; Ji, Qin C; Jemal, Mohammed; Tymiak, Adrienne A; Arnold, Mark E

2011-12-01

243

Stability of parent report on Mobility and Self-Care item scores of the Pediatric Evaluation of Disability Inventory.  

PubMed

Secondary analysis using data from a clinical trial was performed to evaluate the stability of individual items of the Mobility and Self-Care functional skills scales of the Pediatric Evaluation of Disability Inventory (PEDI). Parents of 113 children aged 1-6 years old with cerebral palsy completed the PEDI twice by questionnaire 6 months apart. An item was classified "unstable" if the score changed from capable to unable. The number of children with more than five unstable items and the number of items with more than five children having unstable scoring patterns were calculated. Nineteen children (17%) and 13 items had unstable scoring patterns. The majority of PEDI items demonstrated stability of parent scoring. Examination of unstable items suggests that parents may need assistance in understanding the difference between "usual" and "best" performance, interpreting descriptors such as "thoroughly," and maintaining the same context reference for outdoor mobility items. PMID:23931334

Worth, Melanie; Darrah, Johanna; Magill-Evans, Joyce; Wiart, Lesley; Law, Mary

2014-08-01

244

Evaluation of stabilization\\/solidification of fluidized-bed incinerator ash (K048 and K051). Final report  

Microsoft Academic Search

This report presents the results of testing performed on a stabilized\\/solidified (S\\/S) incinerator ash. This study was conducted in support of the US Environmental Protection Agency, Best Demonstrated Available Technology program. The ash samples evaluated in the study were residuals resulting from the incineration of a mixture of dissolved air-flotation float (K048), API separator oily sludge (K051), and a biological

R. M. Bricka; T. Holmes; M. J. Cullinane

1988-01-01

245

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...

246

Evaluation of the positive biased temperature stress stability in HfSiON gate dielectrics  

Microsoft Academic Search

Electrical instability due to charge trapping in high-k materials is a primary concern for the usefulness of these films in future CMOS devices. This paper reports the effect of charge trapping on the threshold voltage and transistor drive current of devices made with HfSiON gate dielectric. Our results show that the physics of the charge trapping in HfSiON is unique

A. Shanware; M. R. Visokay; J. J. Chambers; A. L. P. Rotondaro; H. Bu; M. J. Bevan; R. Khamankar; S. Aur; P. E. Nicollian; J. McPherson; L. Colombo

2003-01-01

247

Stability evaluation of aqueous alumina–zircon–silicon carbide suspensions by application of DLVO theory  

Microsoft Academic Search

The colloidal stability of alumina–zircon–silicon carbide suspensions has been investigated by measuring particle size distribution, sedimentation height and zeta potential. A polyelectrolyte (Dolapix CE-64) was used as a dispersant in different concentrations. Silicon carbide (SiC) particles lowered the zeta potential of suspensions, sedimentation height and also average particle size of resultant powders. It was concluded that the stability of alumina–zircon

H. Majidian; T. Ebadzadeh; E. Salahi

2011-01-01

248

Evaluation of retained austenite stability in heat treated cold work tool steel  

Microsoft Academic Search

In the paper interdependence between retained austenite volume fraction and external tensile stresses as well as temperature and tempering time have been observed. On the basis of the obtained research a parameter characterising mechanical stability of retained austenite has been introduced. Low mechanical stability of retained austenite has been observed in the structure of the researched 70MnCrMoV9-2-4-2 steel which was

A. Kokosza; J. Pacyna

2005-01-01

249

Generating Electrical Voltage  

NSDL National Science Digital Library

This interactive resource adapted from the Wisconsin Online Resource Center illustrates how electrical voltage is generated through a process called magnetic induction and describes some of the factors that affect the magnitude of the voltage produced.

2009-12-08

250

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

251

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

252

In vitro evaluation of the acetabular cup primary stability by impact analysis.  

PubMed

The implant primary stability of the acetabular cup (AC) is an important parameter for the surgical success of press-fit procedures used for the insertion of cementless hip prostheses. In previous studies by our group (Mathieu, V., Michel, A., Lachaniette, C. H. F., Poignard, A., Hernigou, P., Allain, J., and Haiat, G., 2013, "Variation of the Impact Duration During the in vitro Insertion of Acetabular Cup Implants," Med. Eng. Phys., 35(11), pp. 1558-1563) and (Michel, A., Bosc, R., Mathieu, V., Hernigou, P., and Haiat, G., 2014, "Monitoring the Press-Fit Insertion of an Acetabular Cup by Impact Measurements: Influence of Bone Abrasion," Proc. Inst. Mech. Eng., Part H, 228(10), pp. 1027-1034), the impact momentum and duration were shown to carry information on the press-fit insertion of the AC within bone tissue. The aim of the present study is to relate the impact momentum recorded during the AC insertion to the AC biomechanical primary stability. The experimental protocol consisted in testing 13 bovine bone samples that underwent successively series of 15 reproducible mass falls impacts (5 kg, 5 cm) followed by tangential stability testing. Each bone sample was tested with different hole sizes in order to obtain different stability configurations. The impact momentum and the tangential primary stability reach a maximum value for an interference fit equal to around 1 mm. Moreover, a correlation between the impact momentum and the stability was obtained with all samples and all configuration (R2?=?0.65). The implant primary stability can be assessed through the measurement of the impact force signal analysis. This study opens new paths for the development of a medical device which could be used as a decision support system to assist the surgeon during the insertion of the AC implant. PMID:25565382

Michel, Adrien; Bosc, Romain; Vayron, Romain; Haiat, Guillaume

2015-03-01

253

Comprehensive evaluation of etanercept stability in various concentrations with biophysical assessment.  

PubMed

The effect of protein concentration on biophysical stability of etanercept was investigated to monitor its effect on protein formulation development. The conformational and accelerated storage stability of etanercept (marketed as Enbrel(®)) was examined by biophysical analyses including CD, FTIR, DSC, and DLS together with size-exclusion chromatography (SEC). As concentration of etanercept decreased, conformational stability (Tm) decreased with increasing hydrodynamic size and zeta potential. Decreasing secondary structural stability was also observed for relative helix and ?-sheet contents. Further investigation examined the accelerated storage stability at different incubation temperatures. Low protein concentration (0.25 and 0.5mg/mL) at 4°C and 30°C exhibited fast monomer loss compared to high concentration (25 and 50mg/mL). The lowest etanercept concentration of 0.25mg/mL displayed the fastest monomer loss and increased fragments since it had lowest Tm values. However, at 50°C, a marked increase in aggregation was observed at high concentrations, as well as accelerated monomer loss into multimers and insoluble aggregates. Induced insoluble aggregation of etanercept was dependent on its concentration and no significant aggregation issues were found at low concentrations such as 0.25 and 0.5mg/mL. The results indicated that the conformational stability of protein solution involved steric repulsion of neighboring protein molecules. Electrostatic circumstances and structural interactions resulted in low stability at low concentrations of etanercept under heat stress. Therefore, it might be recommended to be less diluted during protein formulation development, even in the earlier stages of investigation, to avoid undesirable results. PMID:24269208

Kim, Nam Ah; Lim, Dae Gon; Lim, Jun Yeul; Kim, Ki Hyun; Jeong, Seong Hoon

2014-01-01

254

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

255

Voltage monitoring system  

NASA Technical Reports Server (NTRS)

A description is given of a system for monitoring the voltage at a remote location and determining when the voltage exceeds upper and lower levels. The system includes transmission lines for transmitting the voltage back to a central station and applying such to an amplifier having a pair of outputs. One of the outputs of the amplifier is applied to an oscillograph. The other output is fed through an isolation transformer, a full wave rectifier, to a pair of unijunctional transistor circuits for producing pulses when the voltage exceeds or drops below a predetermined level. These pulses, in turn, energize a relay which turns on the oscillograph for recording the voltages being monitored.

Canicatti, C. L. (inventor)

1975-01-01

256

High Voltage SPT Performance  

NASA Technical Reports Server (NTRS)

A 2.3 kW stationary plasma thruster designed to operate at high voltage was tested at discharge voltages between 300 and 1250 V. Discharge specific impulses between 1600 and 3700 sec were demonstrated with thrust between 40 and 145 mN. Test data indicated that discharge voltage can be optimized for maximum discharge efficiency. The optimum discharge voltage was between 500 and 700 V for the various anode mass flow rates considered. The effect of operating voltage on optimal magnet field strength was investigated. The effect of cathode flow rate on thruster efficiency was considered for an 800 V discharge.

Manzella, David; Jacobson, David; Jankovsky, Robert

2001-01-01

257

Quantitative evaluation of transient heat transfer on axial flow compressor stability  

NASA Astrophysics Data System (ADS)

An essential factor for acceptable engine performance and safety in the case of an aircraft gas turbine engine is the stable operation of the compression system. A number of basic research programs were conducted to investigate the influence of transient heat transfer effects on axial flow compressor stability. The results of these programs led to the conclusion that sound theoretical models predict a significant influence of transient heat transfer on compressor stability. However, no transient turbine engine data were available to validate model predictions. The present investigation utilizes high quality transient turbine engine data to quantify and support the reported conclusion. Attention is given to core compressor thermal energy storage, standard stability tests for gas turbine engines, transient mass flow calculations, transient heat transfer calculations, blade heat transfer flux, heat transfer results, and a comparison.

Crawford, R. A.; Burwell, A. E.

1985-07-01

258

Statistical method for evaluation of dissolution stability in the formulation development of solid dosage forms: tablets of amonafide.  

PubMed

A statistical method for the evaluation of the dissolution stability results and for selecting the most stable formulation within a solid dosage form development is discussed. Three types of tablets of an antineoplastic drug, amonafide, stored at a relative humidities (RH), 45% and 75%, were used. The drug release from tablets was tested before and after storage. The experimental data were statistically fitted to empirical model equations. Furthermore, the best mathematical fit was the statistical comparison of the residuals. From the selected model equation, time-dependent dissolution (Q45 and DE45) and dissolved quantity-dependent parameters (t70, t100 and MDT) were calculated. A useful parameter to present and evaluate the results obtained in comparative stability studies was defined: the Modification Factor (MF). It allowed the selection of the most stable formulation in the easiest and fastest way: the most stable formulation should present the smallest modification of the studied characteristics, in other words, the smallest MF value. In this way, tablets II (manufactured by wet granulation and with Emcompress as main excipient) showed the greater dissolution stability of the three types of tablets studied. Amonafide tablets must be packaged in impermeable containers, since the environmental relative humidity strongly modifies their dissolution characteristics. PMID:15296092

Gil-Alegre, M E; Bernabeu, J A; Camacho, M A; Torres-Suarez, A I

2004-07-01

259

An Evaluation of the Relative Influence of Habitat Complexity and Habitat Stability on Fish Assemblage Structure in Unregulated and Regulated Reaches of a Large Southeastern Warmwater Stream  

Microsoft Academic Search

River regulation and development are the foremost problems threatening lotic fishes and other aquatic biota in the United States. The operation of hydroelectric facilities can influence both habitat availability and environmental stability in downstream reaches. We evaluated the relative influence of habitat complexity and environmental stability on fish assemblage structure at unregulated and hydropower-regulated reaches of the Flint River in

Colin P. Shea; James T. Peterson

2007-01-01

260

Influence of Input Parameters on Dynamic Orbital Stability of Walking: In-Silico and Experimental Evaluation  

PubMed Central

Many measures aiming to assess the stability of human motion have been proposed in the literature, but still there is no commonly accepted way to define or quantify locomotor stability. Among these measures, orbital stability analysis via Floquet multipliers is still under debate. Some of the controversies concerning the use of this technique could lie in the absence of a standard implementation. The aim of this study was to analyse the influence of i) experimental measurement noise, ii) variables selected for the construction of the state space, and iii) number of analysed cycles on the outputs of orbital stability applied to walking. The analysis was performed on a 2-dimensional 5-link walking model and on a sample of 10 subjects performing long over-ground walks. Noise resulting from stereophotogrammetric and accelerometric measurement systems was simulated in the in-silico analysis. Maximum Floquet multipliers resulted to be affected by both number of analysed strides and state space composition. The effect of experimental noise was found to be slightly more potentially critical when analysing stereophotogrammetric data then when dealing with acceleration data. Experimental and model results were comparable in terms of overall trend, but a difference was found in the influence of the number of analysed cycles. PMID:24260498

Riva, Federico; Bisi, Maria Cristina; Stagni, Rita

2013-01-01

261

Influence of input parameters on dynamic orbital stability of walking: in-silico and experimental evaluation.  

PubMed

Many measures aiming to assess the stability of human motion have been proposed in the literature, but still there is no commonly accepted way to define or quantify locomotor stability. Among these measures, orbital stability analysis via Floquet multipliers is still under debate. Some of the controversies concerning the use of this technique could lie in the absence of a standard implementation. The aim of this study was to analyse the influence of i) experimental measurement noise, ii) variables selected for the construction of the state space, and iii) number of analysed cycles on the outputs of orbital stability applied to walking. The analysis was performed on a 2-dimensional 5-link walking model and on a sample of 10 subjects performing long over-ground walks. Noise resulting from stereophotogrammetric and accelerometric measurement systems was simulated in the in-silico analysis. Maximum Floquet multipliers resulted to be affected by both number of analysed strides and state space composition. The effect of experimental noise was found to be slightly more potentially critical when analysing stereophotogrammetric data then when dealing with acceleration data. Experimental and model results were comparable in terms of overall trend, but a difference was found in the influence of the number of analysed cycles. PMID:24260498

Riva, Federico; Bisi, Maria Cristina; Stagni, Rita

2013-01-01

262

Evaluation of roots mechanical contribution to slope stability by finite element modelling  

Microsoft Academic Search

The paper deals with the assessment of vegetation contribution to slope stability, with particular emphasis on the mechanical effects provided by the root apparatus. As it is well known, the presence of a root system within the soil increases, with respect to the case of soil without vegetation, the material effective cohesion with no significant change in its friction angle.

F. Gentile; G. Elia; R. Elia

2009-01-01

263

EVALUATION OF A MODEL THAT DETERMINES THE STABILITY LIMITS OF DYNAMIC BALANCE  

Microsoft Academic Search

A recent model of balance control has revealed two types of boundaries describing stability limits for center of mass (CM) dynamics: torque boundaries and state boundaries. The purpose of this study was to determine if these boundaries correctly characterize empirical data. We analyzed 2367 trials from 10 subjects who recovered their balance after they voluntarily pulled on a handle. We

James L. Patton; Yi-Chung Pai; Wynne A. Lee

264

Evaluation of a model that determines the stability limits of dynamic balance  

Microsoft Academic Search

A recent model of balance control has revealed two types of boundaries describing stability limits for center of mass (CM) dynamics: torque boundaries and state boundaries. The purpose of this study was to determine if these boundaries correctly characterize empirical data. We analyzed 2367 trials from 10 subjects who recovered their balance after they voluntarily pulled on a handle. We

James L Patton; Yi-Chung Pai; Wynne A Lee

1999-01-01

265

The evaluation of stability and maturity during the composting of cattle manure.  

PubMed

We examined chemical, microbiological and biochemical parameters in order to assess their effectiveness as stability and maturity indicators during the composting process of cattle manure. The composting material obtained after 15 d in trenches and at different times during the maturation phase (i.e. 80, 180 and 270 d) were analyzed. We found that the material collected at the end of the active phase was inadequate to be applied to soil as organic amendment due to its high content of NH4+, its high level of phytotoxicity and the low degree of organic matter stability. After a maturation period of 80 d, the stability of the sample increased. This was shown by a reduction in the dissolved organic carbon (DOC) content and NH4+ concentration and also by a reduction in the microbial activity and biomass; however, 180 d of composting were not sufficient to reduce the phytotoxicity to levels consistent for a safe soil application. Among the various parameters studied, the change in DOC with composting time gave a good indication of stability. PMID:17689588

Gómez-Brandón, María; Lazcano, Cristina; Domínguez, Jorge

2008-01-01

266

Safety evaluation for the interim stabilization of Tank 241-C-103  

SciTech Connect

This document provides the basis for interim stabilization of tank 241-C-103. The document covers the removal of the organic liquid layer and the aqueous supernatant from tank 241-C-103. Hazards are identified, consequences are calculated and controls to mitigate or prevent potential accidents are developed.

Geschke, G.R.

1995-03-01

267

Development and flight evaluation of an augmented stability active controls concept: Executive summary  

NASA Technical Reports Server (NTRS)

A pitch active control system (PACS) was developed and flight tested on a wide body jet transport (L-1011) with a flying horizontal stabilizer. Two dual channel digital computers and the associated software provide command signals to a dual channel series servo which controls the stabilizer power actuators. Input sensor signals to the computer are pitch rate, column trim position, and dynamic pressure. Control laws are given for the PACS and the system architecture is defined. Discussions are given regarding piloted flight simulation and vehicle system simulation and vehicle system simulation tests that are performed to verify control laws and system operation prior to installation on the aircraft. Modifications to the basic aircraft included installation of the PACS, addition of a c.g. management system to provide a c.g. range from 25 to 39% mac, and downrigging of the geared elevator to provide the required nose down control authority for aft c.g. flight test conditions. Three pilots used the Cooper-Harper Rating Scale to judge flying qualities of the aircraft with PACS on and off. The handling qualities with the c.g. at 39% mac (41% stability margin) and PACS operating were judged to be as good as the handling qualities with the c.g. at 25% mac (+15% stability margin) and PACS off.

Guinn, W. A.

1982-01-01

268

EVALUATION OF SOLIDIFICATION/STABILIZATION FOR TREATING HAZADOUS WASTE IN THE UNITED STATES  

EPA Science Inventory

In hazardous waste management, solidification/stabilization (S/S) is a term normally used to designate technology employing additives to alter hazardous waste to reduce the mobility of pollutants, thereby making it acceptable for land disposal or other uses. The use of the techno...

269

An Outcome Evaluation of an Inpatient Crisis Stabilization and Assessment Program for Youth  

ERIC Educational Resources Information Center

Objective: To describe characteristics and outcomes of youth aged 7 to 17 who received inpatient psychiatric and mental health services along different clinical pathways of a new service delivery model. Method: Participants included 211 admissions to an inpatient crisis stabilization and assessment program over a one-year period. Standardized…

Greenham, Stephanie L.; Bisnaire, Lise

2008-01-01

270

Evaluation of stability constants of metal complexes with sulphonated azo-ligands.  

PubMed

An ion-exchange procedure is described for the determination of the stability constants for cadmium, copper, nickel and manganese complexes with three sulphonated azo ligands: calmagite, alizarin violet N and palatine chrome black. The results, log K values, show a good agreement with those obtained by a spectrophotometric technique. PMID:18966044

Abollino, O; Sarzanini, C; Mentasti, E; Liberatori, A

1994-07-01

271

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

272

Evaluation of the correlation between insertion torque and primary stability of dental implants using a block bone test  

PubMed Central

Purpose Implant stability at the time of surgery is crucial for the long-term success of dental implants. Primary stability is considered of paramount importance to achieve osseointegration. The purpose of the present study was to investigate the correlation between the insertion torque and primary stability of dental implants using artificial bone blocks with different bone densities and compositions to mimic different circumstances that are encountered in routine daily clinical settings. Methods In order to validate the objectives, various sized holes were made in bone blocks with different bone densities (#10, #20, #30, #40, and #50) using a surgical drill and insertion torque together with implant stability quotient (ISQ) values that were measured using the Osstell Mentor. The experimental groups under evaluation were subdivided into 5 subgroups according to the circumstances. Results In group 1, the mean insertion torque and ISQ values increased as the density of the bone blocks increased. For group 2, the mean insertion torque values decreased as the final drill size expanded, but this was not the case for the ISQ values. The mean insertion torque values in group 3 increased with the thickness of the cortical bone, and the same was true for the ISQ values. For group 4, the mean insertion torque values increased as the cancellous bone density increased, but the correlation with the ISQ values was weak. Finally, in group 5, the mean insertion torque decreased as the final drill size increased, but the correlation with the ISQ value was weak. Conclusions Within the limitations of the study, it was concluded that primary stability does not simply depend on the insertion torque, but also on the bone quality. PMID:23508040

Bayarchimeg, Dorjpalam; Namgoong, Hee; Kim, Byung Kook; Kim, Myung Duk; Kim, Sungtae; Kim, Tae-Il; Seol, Yang Jo; Lee, Yong Moo; Ku, Young; Rhyu, In-Chul; Lee, Eun Hee

2013-01-01

273

Synthesis of Macrocyclic Hexaoxazole (6OTD) Dimers, Containing Guanidine and Amine Functionalized Side Chains, and an Evaluation of Their Telomeric G4 Stabilizing Properties  

PubMed Central

Structure-activity relationship studies were carried out on macrocyclic hexaoxazole (6OTD) dimers, whose core structure stabilizes telomeric G-quadruplexes (G4). Two new 6OTD dimers having side chain amine and guanidine functional groups were synthesized and evaluated for their stabilizing ability against a telomeric G4 DNA sequence. The results show that the 6OTD dimers interact with the DNA to form 1:1 complexes and stabilize the antiparallel G4 structure of DNA in the presence of potassium cation. The guanidine functionalized dimer displays a potent stabilizing ability of the G4 structure, as determined by using a FRET melting assay (?Tm = 14°C). PMID:20700415

Iida, Keisuke; Tera, Masayuki; Hirokawa, Takatsugu; Shin-ya, Kazuo; Nagasawa, Kazuo

2010-01-01

274

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

275

In-Well Sediment Incubators to Evaluate Microbial Community Stability and Dynamics following Bioimmobilization of Uranium  

SciTech Connect

An in-situ incubation device (ISI) was developed in order to investigate the stability and dynamics of sediment associated microbial communities to prevailing subsurface oxidizing or reducing conditions. Here we describe the use of these devices at the Old Rifle Uranium Mill Tailings Remedial Action (UMTRA) site. During the 7 month deployment oxidized Rifle aquifer background sediments (RABS) were deployed in previously biostimulated wells under iron reducing conditions, cell densities of known iron reducing bacteria including Geobacteraceae increased significantly showing the microbial community response to local subsurface conditions. PLFA profiles of RABS following in situ deployment were strikingly similar to those of adjacent sediment cores suggesting ISI results could be extrapolated to the native material of the test plots. Results for ISI deployed reduced sediments showed only slight changes in community composition and pointed toward the ability of the ISIs to monitor microbial community stability and response to subsurface conditions.

Baldwin, Brett R.; Peacock, Aaron D.; Gan, M.; Resch, Charles T.; Arntzen, Evan V.; Smithgall, A. N.; Pfiffner, S.; Freifeld, Barry M.; White, D. C.; Long, Philip E.

2009-09-23

276

Evaluation of H2RG stability for infrared Earth-observing systems  

NASA Astrophysics Data System (ADS)

Although originally developed for astronomical applications, the space qualification and availability of the Teledyne HAWAII detector make it appealing for high-precision Earth-observing systems such as the carbon monoxide correlation radiometer required for GEO-CAPE. In this shot noise-limited application, the signal-to-noise ratio of a co-averaged measurement is driven by the detector's temporal stability. To assess the stability, we operated the H2RG under monitored blackbody illumination. The Teledyne SIDECAR ASIC provided 16-bit digitization and clocking for integration times faster than the frame conversion time. With proper application of reference signals, the co-averaging of hundreds of frames is possible. Integrations of one-quarter of the full well depth can attain precision to the 200 ppm level in the co-averaged result. For integrations above three-quarters the well depth, the precision reaches 111 ppm.

Sullivan, P. W.; Edens, W. K.; Darlington, E. H.; Neil, D. O.

2011-10-01

277

Evaluating Arctic Lower Tropospheric Stability in CAM4 and CAM5  

NASA Astrophysics Data System (ADS)

Previous research has shown that the CMIP3 models have an Arctic lower troposphere that is more stable than reanalysis products, and that this bias may lead to an unrealistic Arctic feedback. Basic questions of why these models drift toward a more stable lower troposphere in the Arctic have not been thoroughly investigated. What season is the bias more likely? What atmospheric level or levels is causing the bias? In this analysis, we examine the lower tropospheric stability in CAM4 and CAM5. The models run in forecast and AMIP mode. The lower tropospheric stability is examined across the Arctic domain with analysis products, and in more detail using in-situ data at the North Slope of Alaska. We show that CAM4's and CAM5's Arctic lower tropospheric stability bias is greater during the winter months, and that the bias is largely due to models' surface temperature drifting lower than observations. Reasons why the models' surface temperatures are lower are investigated. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.iases in lower-tropospheric stability (top), potential temperature at 700 hPa (middle), and potential temperature (bottom) at the lowest model level (LML) for CAM4 (left) and CAM5 (right). The biases are averaged poleward of 60°N and are measured with respect to ECMWF analysis. The x-axis indicates month and the y-axis indicates the hindcast day in which models were analyzed with the top row illustrating the bias in AMIP mode

Barton, N. P.; Klein, S. A.; Boyle, J. S.

2012-12-01

278

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

279

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

280

Impaction grafted bone chip size effect on initial stability in an acetabular model: Mechanical evaluation  

PubMed Central

Introduction Acetabular bone defect reconstruction is an increasing problem for surgeons with patients undergoing complex primary or revision total hip replacement surgery. Impaction bone grafting is one technique that has favourable long-term clinical outcome results for patients who undergo this reconstruction method for acetabular bone defects. Creating initial mechanical stability of the impaction bone graft in this technique is known to be the key factor in achieving a favourable implant survival rate. Different sizes of bone chips were used in this technique to investigate if the size of bone chips used affected initial mechanical stability of a reconstructed acetabulum. Methodology Twenty acetabular models were created in total. Five control models were created with a cemented cup in a normal acetabulum. Then five models in three different groups of bone chip size were constructed. The three groups had an acetabular protrusion defect reconstructed using either; 2–4 mm3, 10 mm3 or 20 mm3 bone chip size for impaction grafting reconstruction. The models underwent compression loading up to 9500 N and displacement within the acetabular model was measured indicating the initial mechanical stability. Results This study reveals that, although not statistically significant, the largest (20 mm3) bone chip size grafted models have an inferior maximum stiffness compared to the medium (10 mm3) bone chip size. Interpretations Our study suggests that 10 mm3 size of bone chips provide better initial mechanical stability compared to smaller or larger bone chips. We dismissed the previously held opinion that the biggest practically possible graft is best for acetabular bone graft impaction. PMID:24396238

Holton, Colin; Bobak, Peter; Wilcox, Ruth; Jin, Zhongmin

2013-01-01

281

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

282

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

283

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

284

Utilization of phosphogypsum in tannery sludge stabilization and evaluation of the radiological impact.  

PubMed

The current global trend towards increasingly stringent environmental standards and efforts for efficient utilization and re-use of available by-products and/or wastes, favors the use of low-cost sorbent materials for the treatment of heavy metal-contaminated solid wastes. In this study, the stabilization of tannery sludge, produced from the physicochemical and biological treatment of tannery wastewaters, was examined by the addition of phosphogypsum (PG) at a ratio of 1:1. Characterization of the tannery sludge leachates showed high amounts of chromium which exceeded the acceptable level for disposal in non-hazardous waste landfills, while the dissolved organic carbon (DOC) concentrations exceeded the limits for disposal in landfills for hazardous wastes, according to the EU Decision 2003/33/EC. Leachates of the waste stabilized with PG presented chromium and DOC concentrations below the regulation limits for disposal in landfills for non-hazardous wastes. Moreover, mixing PG with tannery sludge resulted in a stabilized waste with reduced radioactivity. PMID:25432294

Pantazopoulou, E; Zebiliadou, O; Noli, F; Mitrakas, M; Samaras, P; Zouboulis, A

2015-03-01

285

Optimization of microwave-assisted extraction of cottonseed oil and evaluation of its oxidative stability and physicochemical properties.  

PubMed

Microwave assisted extraction (MAE) is a novel method, which can reduce the extraction time and solvent consumption. This study aimed to evaluate the influence of MAE on oxidative stability and physicochemical properties of cottonseed oil. We found that the optimum extraction conditions were: irradiation time 3.57 min; cottonseed moisture content 14% and cottonseed to solvent ratio 1:4, which resulted in an extraction efficiency of 32.6%, 46 ppm total phenolic content, 0.7% free fatty acids, peroxide value of 0.2 and 11.5 h of Rancimat oxidative stability at 110 °C. GC analysis for MAE cottonseed oil determined palmitic acid (23.6%), stearic acid (2.3%), oleic acid (15.6%) and linoleic acid (55.1%), which were not significant different (P>0.05) than conventionally-extracted (control) cottonseed oil. MAE oil samples from whole cottonseed (without dehulling) had the greatest long-term stability, more than oil samples containing BHT. PMID:24799213

Taghvaei, Mostafa; Jafari, Seid Mahdi; Assadpoor, Elham; Nowrouzieh, Shahram; Alishah, Omran

2014-10-01

286

Neural network controlled voltage disturbance detector and output voltage regulator for Dynamic Voltage Restorer  

Microsoft Academic Search

This paper describes the high power DVR (Dynamic Voltage Restorer) with the neural network controlled voltage disturbance detector and output voltage regulator. Two essential parts of DVR control are how to detect the voltage disturbance such as voltage sag and how to compensate it as fast as possible respectively. The new voltage disturbance detector was implemented by using the delta

Y. H. Chung; H. J. Kim; G. H. Kwon; T. B. Park; S. H. Kim; K. S. Kim; J. W. Choe

2007-01-01

287

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

288

Off-set stabilizer for comparator output  

DOEpatents

A stabilized off-set voltage is input as the reference voltage to a comparator. In application to a time-interval meter, the comparator output generates a timing interval which is independent of drift in the initial voltage across the timing capacitor. A precision resistor and operational amplifier charge a capacitor to a voltage which is precisely offset from the initial voltage. The capacitance of the reference capacitor is selected so that substantially no voltage drop is obtained in the reference voltage applied to the comparator during the interval to be measured.

Lunsford, James S. (Los Alamos, NM)

1991-01-01

289

Evaluation of methane oxidation activity in waste biocover soil during landfill stabilization.  

PubMed

Biocover soil has been demonstrated to have high CH(4) oxidation capacity and is considered as a good alternative cover material to mitigate CH(4) emission from landfills, yet the response of CH(4) oxidation activity of biocover soils to the variation of CH(4) loading during landfill stabilization is poorly understood. Compared with a landfill cover soil (LCS) collected from Hangzhou Tianziling landfill cell, the development of CH(4) oxidation activity of waste biocover soil (WBS) was investigated using simulated landfill systems in this study. Although a fluctuation of influent CH(4) flux occurred during landfill stabilization, the WBS covers showed a high CH(4) removal efficiency of 94-96% during the entire experiment. In the LCS covers, the CH(4) removal efficiencies varied with the fluctuation of CH(4) influent flux, even negative ones occurred due to the storage of CH(4) in the soil porosities after the high CH(4) influent flux of ~137 gm(-2) d(-1). The lower concentrations of O(2) and CH(4) as well as the higher concentration of CO(2) were observed in the WBS covers than those in the LCS covers. The highest CH(4) oxidation rates of the two types of soil covers both occurred in the bottom layer (20-30 cm). Compared to the LCS, the WBS showed higher CH(4) oxidation activity and methane monooxygenase activity over the course of the experiment. Overall, this study indicated the WBS worked well for the fluctuation of CH(4) influent flux during landfill stabilization. PMID:22776254

He, Ruo; Wang, Jing; Xia, Fang-Fang; Mao, Li-Juan; Shen, Dong-Sheng

2012-10-01

290

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

291

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

292

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

SciTech Connect

Highlights: • Solvita® stability and maturity tests used on composting toilet end-product. • Solvita® ammonia better suited in evaluation of feedstock suitability for vermicomposting. • No clear value of Solvita® stability test due to prevalent inhibition of decomposition by ammonia. - Abstract: 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® CO{sub 2} test as having high stability values.

Hill, Geoffrey B., E-mail: geoff.hill@geog.ubc.ca [University of British Columbia, Department of Geography, 1984 West Mall, Vancouver, Canada V6T 1Z2 (Canada); Baldwin, Susan A. [Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, B.C., Canada V6T 1Z3 (Canada); Vinnerås, Bjorn [Swedish University of Agricultural Sciences, Box 7032, SE-750 07 Uppsala (Sweden)

2013-07-15

293

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

294

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

295

Stability evaluation of the PUMA-560 robot arm under model mismatch  

NASA Astrophysics Data System (ADS)

This paper summarizes the stability of the PUMA - 560 robot manipulator under dynamic model mismatch resulting from incomplete knowledge of the link masses centers of mass and radii of gyration. PD and PID controllers are used. PAPER SUMMARY Model based control of robotic manipulators eliminates the nonlinearities in the manipulator equations under perfect knowledge of dynamic model parameters. When this is the case the manipulator model matches completely the real robot arm. However robot manipulators are in general extremely complicated to even approximately model. Moreover to keep the system model within practical and acceptable limits one has to accept (and control) unmodeled dynamics. Model mismatch may also result from incomplete knowledge of manipulator hardware parameters. This paper summarizes the stability of the PUMA - 560 manipulator under model mismatch using PD and PID controllers. Craig''s method [3] is directly applied when a PD controller is used. However it is also extended and modified to incorporate PID controllers [12]. The PUMA-560 robot arm has been selected because of our knowledge related to its real-time behavior [6 7 10 11]. All desired trajectories are achievable in real-time do not violate arm speed acceleration structural and hardware limits and have been repeatedly tested and used for real-time control of the PUMA robot arm. A software package (robot simulation package) has been built on top of the original software given to us by Dr.

Larsson, Thomas; Perev, K.; Valavanis, Kimon P.; Gardner, S.

1991-02-01

296

Voltage correction power flow  

SciTech Connect

A method for power flow solution of weakly meshed distribution and transmission networks is presented. It is based on oriented ordering of network elements. That allows an efficient construction of the loop impedance matrix and rational organization of the processes such as: power summation (backward sweep), current summation (backward sweep) and node voltage calculation (forward sweep). The first step of the algorithm is calculation of node voltages on the radial part of the network. The second step is calculation of the breakpoint currents. Then, the procedure continues with the first step, which is preceded by voltage correction. It is illustrated that using voltage correction approach, the iterative process of weakly meshed network voltage calculation is faster and more reliable.

Rajicic, D.; Ackovski, R.; Taleski, R. (Univ. Sv. Kiril i Metodij'', Skopje, Macedonia (Greece). Dept. of Electrical Engineering)

1994-04-01

297

An evaluation of growth and stability in untreated and treated subjects  

Microsoft Academic Search

This retrospective longitudinal study compared skeletal and dental changes in orthodontically treated patients with changes in a comparable untreated group to evaluate the relationship between skeletal changes and mandibular incisor crowding. Cephalograms and models of 44 untreated subjects from the Broadbent-Bolton Growth Study and 43 treated patients were evaluated at “posttreatment” (14.3 ± 1.5 and 15.2 ± 1.1 years, respectively)

Jean Driscoll-Gilliland; Peter H. Buschang; Rolf G. Behrents

2001-01-01

298

Evaluation of the thermal stability of a novel strain of live-attenuated mumps vaccine (RS-12 strain) lyophilized in different stabilizers.  

PubMed

The stability of live-attenuated viral vaccines is important for immunization efficacy. Here, the thermostabilities of lyophilized live-attenuated mumps vaccine formulations in two different stabilizers, a trehalose dihydrate-based stabilizer and a stabilizer containing sucrose, human serum albumin and sorbitol were investigated using accelerated stability tests at 4°C, 25°C and 37°C at time points between 4h (every 4h for the first 24h) and 1 week. Even under the harshest storage conditions of 37°C for 1 week, the 50% cell culture infective dose (CCID50) determined from titrations in Vero cells dropped by less than 10-fold using each stabilizer formulation and thus complied with the World Health Organization's requirements for the potency of live-attenuated mumps vaccines. However, as the half-life of the RS-12 strain mumps virus infectivity was lengthened substantially at elevated temperatures using the trehalose dihydrate (TD)-based stabilizer, this stabilizer is recommended for vaccine use. PMID:24462846

Jamil, Razieh Kamali; Taqavian, Mohammad; Sadigh, Zohreh-Azita; Shahkarami, Mohammad-Kazem; Esna-Ashari, Fatemeh; Hamkar, Rasool; Hosseini, Seyedeh-Marzieh; Hatami, Alireza

2014-04-01

299

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

300

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

301

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

302

Physicochemical stability of papaverine hydrochloride-phentolamine mesylate mixtures used for intracavernous injection: a preliminary evaluation.  

PubMed

Physicochemical stability of intracavernous injections of 30 mg. per ml. papaverine hydrochloride with 0.5 or 1.0 mg. per ml. phentolamine mesylate used to induce erection in patients with impotence was examined. The samples were stored at room temperature, in the refrigerator at 4C and in the freezer at -20C for 6 months. The examination consisted of visual observation for change in color or evidence of precipitation, measurement of pH and thin layer chromatography at different intervals. During the 6 months of storage no change had occurred in pH, color development, precipitation or formation of new moieties. Therefore, the aforementioned injection solutions of papaverine hydrochloride with phentolamine mesylate can be dispensed safely with instruction to patients for adequate storage and manipulation. PMID:2454330

Hadzija, B W; Mattocks, A M; Stahl, G M

1988-07-01

303

Evaluation of western coal fly ashes for stabilization of low-volume roads  

SciTech Connect

A laboratory study is described in which the engineering properties of subgrade soils were modified by treatment with fly ash derived from low-sulfur western coal. A wide range of soil types including gravel-sand, silty sand, sandy silt, and highly plastic clay exhibited substantial improvements in compressive strength, resilient modulus, and wet-dry and freeze-thaw durability when treated with fly ash from several Wyoming power plants. Application of the test results to design of aggregate-surfaced secondary roads indicates that use of fly ash stabilization can decrease the required aggregate thickness substantially. Currently there are no standards which specify minimum required improvements in the engineering properties of fly ash treated soils.

Turner, J.P. [Univ. of Wyoming, Laramie, WY (United States). Dept. of Civil and Archeological Engineering

1997-12-31

304

Study on process development and property evaluation of sol-gel derived magnesia stabilized zirconia minispheres  

NASA Astrophysics Data System (ADS)

In order to overcome limitations in the processing parameters of powder compaction method, a novel processing technique based on sol-gel route has been developed to produce near-net-shaped prototype fine zirconia minispheres with required properties that could potentially be used as grinding media. Impact of magnesia concentration and sintering temperature on the final product has been analyzed in detail. Zirconia minispheres have been characterized to establish a correlation between physical, structural and mechanical properties. Sintering temperature, soaking period, heating rate and viscosity of the sol apparently influence the characteristics of the magnesia stabilized zirconia minispheres. The phase identification, density variation, chemical decomposition, functional group specification, surface area, porosity, shrinkage and microstructural features of the dried and sintered final product have been studied. It has been observed that magnesia content, sintering temperature, density and the grain size of the sintered minispheres have a significant impact on the mechanical properties of the final product.

Judes, J.; Kamaraj, V.

2014-06-01

305

Low voltage to high voltage level shifter and related methods  

NASA Technical Reports Server (NTRS)

A shifter circuit comprises a high and low voltage buffer stages and an output buffer stage. The high voltage buffer stage comprises multiple transistors arranged in a transistor stack having a plurality of intermediate nodes connecting individual transistors along the stack. The transistor stack is connected between a voltage level being shifted to and an input voltage. An inverter of this stage comprises multiple inputs and an output. Inverter inputs are connected to a respective intermediate node of the transistor stack. The low voltage buffer stage has an input connected to the input voltage and an output, and is operably connected to the high voltage buffer stage. The low voltage buffer stage is connected between a voltage level being shifted away from and a lower voltage. The output buffer stage is driven by the outputs of the high voltage buffer stage inverter and the low voltage buffer stage.

Mentze, Erik J. (Inventor); Hess, Herbert L. (Inventor); Buck, Kevin M. (Inventor); Cox, David F. (Inventor)

2006-01-01

306

Voltage balanced multilevel voltage source converter system  

DOEpatents

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.

Peng, Fang Zheng (Oak Ridge, TN); Lai, Jih-Sheng (Knoxville, TN)

1997-01-01

307

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

308

An evaluation of biomass yield stability of switchgrass ( Panicum virgatum L.) cultivars  

Microsoft Academic Search

The present work deals with evaluation of the adaptation and biomass production of various switchgrass cultivars (upland and lowland type) in Southern Italy. A field trial was established in 1998 with 15 switchgrass varieties in ENEA Trisaia (Matera). The experiment was conducted for four years (1998–2001). During each growing period, a series of measurements were taken. At the end of

N Sharma; I Piscioneri; V Pignatelli

2003-01-01

309

Stability of Repeated Student Evaluations of Teaching in the Second Preclinical Year of a Medical Curriculum  

ERIC Educational Resources Information Center

The second preclinical year of the medical curriculum at the Medical Faculty of the University of Lausanne in Switzerland includes nine multidisciplinary organ-system-oriented modules consisting of lectures and problem-based-learning tutorials. This study reports the experience accumulated with the evaluation of lectures during the academic years…

Krantz-Girod, Catherine; Bonvin, Raphael; Lanares, Jacques; Cueanot, Seagoleine; Feihl, Francois; Bosman, Fred; Waeber, Bernard

2004-01-01

310

Stability evaluation and track life of the PDAF for tracking in clutter  

Microsoft Academic Search

The authors present an effective approach of a hybrid nature to the nonsimulation performance evaluation of the probabilistic data association filtering (PDAF) method for tracking in clutter. In this approach, a continuous-valued covariance, which is a function of a discrete-valued random variable (the number of validated measurements), is used to characterize the tracking errors in an average sense. This covariance

X. Rong Li; Yaakov Bar-Shalom

1991-01-01

311

Evaluation of antioxidant activity of green tea extract and its effect on the biscuits lipid fraction oxidative stability.  

PubMed

This article investigates the effect of green tea extract (GTE) on biscuits lipid fraction oxidative stability. The antioxidant activity of GTE was compared with commonly used synthetic antioxidant butylated hydroxyanisole (BHA). Biscuits were prepared in 3 variations. Control samples were prepared without addition of antioxidants. The other variations were prepared by adding BHA (0.02%) and GTE at 3 different levels: 0.02%, 0.1%, and 1%. Biscuits were subjected to sensory studies and instrumental and chemical analysis. Phenolic compounds of GTE characterized powerful antioxidant activities evaluated using free radical, 2,2-diphenyl-1-picrylhydrazyl method, compared with gallic acid and significantly better than BHA. Antioxidants added to the samples clearly slowed down the process of oxidation of fatty acids, inhibiting the monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) decomposition. Addition of GTE at the level of 1% gave an excellent antioxidant effect on the biscuits lipid stability, inhibiting hydroperoxides formation by about 47% to 73% compared with BHA, which showed about 16% to 60% inhibition. However, GTE did not improve significantly lipid stability, measured by anisidine value (p-AV), and inhibited formation of secondary oxidation products only by 3.5%. After accelerated storage time, insensitivity of oxidized-like flavor was about 2 times higher for control samples compared to samples with addition of antioxidants. Moreover, after storage biscuits treated with natural antioxidant received a higher panel score of overall acceptance compared to samples with BHA. Using volatile compound formation as a marker of lipid oxidation, both GTE and BHA were effective inhibitors of the decomposition of hydroperoxides. PMID:19799681

Mildner-Szkudlarz, S; Zawirska-Wojtasiak, R; Obuchowski, W; Go?li?ski, M

2009-10-01

312

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

313

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.

314

Voltage-Dependent Gating of hERG Potassium Channels  

PubMed Central

The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv) channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4–S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-à-go-go related gene, hERG), which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure–function relationships underlying activation and deactivation gating in Shaker and hERG channels, with a focus on the roles of the voltage-sensing domain and the S4–S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter-charge interactions. More recent data suggest that key amino acid differences in the hERG voltage-sensing unit and S4–S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor. PMID:22586397

Cheng, Yen May; Claydon, Tom W.

2012-01-01

315

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

SciTech Connect

The long-term stability of nuclear waste form borosilicate glasses can be evaluated by understanding the processes that effect the long-term alteration of glass and by comparing laboratory alteration of synthetic basalt and borosilicate glasses with the observed stability of naturally occurring basaltic glasses in diverse geologic environments. This paper presents detailed electron microprobe analyses of naturally altered basaltic glasses (with maximum ages of 10,000 to 20 million years) from low-temperature environments. These results are compared to laboratory data on the corrosion of a synthetic basaltic glass in MCC-1 tests (90/sup 0/C, a SA/V of 0.1 cm/sup -1/ and time periods up to 182 days), MCC-2 tests (190/sup 0/C, a SA/V of 0.1 cm/sup -1/ and time periods up to 210 days) and hydration tests in saturated water vapor (240/sup 0/C, an estimated SA/V of approx. 10/sup 6/ cm/sup -1/ and time periods up to 63 days). Additionally, laboratory-induced hydration alteration of synthetic basalt and borosilicate glasses is compared. These preliminary experiments provide evidence that the alteration processes observed for natural basalt glasses are relevant to understanding the alteration of nuclear waste glass, as both appear to react via similar processes. 12 references, 6 figures, 1 table.

Byers, C.D.; Jercinovic, M.J.; Ewing, R.C.; Keil, K.

1984-01-01

316

Benchtop MRI for pharmacokinetic evaluation of two aqueous-based nano-scaled formulations of oleic acid stabilized magnetite nanocrystals.  

PubMed

Abstract Background: The interplay between numerous factors, including the size, shape, coating, surface charge and composition of particles is known to affect the pharmacokinetics and biodistribution of superparamagnetic iron oxides (SPIOs). This makes understanding the role of each factor independently quite challenging. Methods: In the present study, the in vivo magnetic resonance imaging (MRI), biodistribution and hepatic clearance evaluations of two SPIOs Formulations A and B developed from ?13.5?nm hydrophobic oleic acid stabilized monodisperse magnetite nanocrystals core and lipid-based amphiphilic stabilizers were performed using a prototype benchtop MR imager (22?MHz) and pulsed nuclear magnetic resonance (NMR) system (20?MHz), respectively. Formulation A was composed of mPEG-2000-DSPE and Formulation B was composed of Phospholipon-100H, sucrose ester M-1695 and Cremophor RH-40. Results: The in vivo MRI investigations showed that both formulations were safe and effective as potential liver MR contrast agents with sustained liver contrast for at least seven days. In addition, ex vivo relaxometric investigations revealed that the formulations predominantly distribute to the liver and spleen following I.V. injection. The hepatic clearance kinetics determined based on the relaxometric quantification method indicated that both formulations exhibited a biphasic clearance process with a slow terminal clearance half-life of 11.5 and 12.7 days, respectively, for Formulations A and B. Conclusions: The results of this study showed the potential biomedical applications of the investigated magnetopharmaceutical formulations as MRI contrast agents. PMID:24354323

Belete, Anteneh; Metz, Hendrik; Mueller, Thomas; Maeder, Karsten

2013-12-20

317

Evaluation of disulfide bond position to enhance the thermal stability of a highly stable single domain antibody.  

PubMed

Single domain antibodies are the small recombinant variable domains derived from camelid heavy-chain-only antibodies. They are renowned for their stability, in large part due to their ability to refold following thermal or chemical denaturation. In addition to refolding after heat denaturation, A3, a high affinity anti-Staphylococcal Enterotoxin B single domain antibody, possesses a melting temperature of ?84°C, among the highest reported for a single domain antibody. In this work we utilized the recently described crystal structure of A3 to select locations for the insertion of a second disulfide bond and evaluated the impact that the addition of this second bond had on the melting temperature. Four double-disulfide versions of A3 were constructed and each was found to improve the melting temperature relative to the native structure without reducing affinity. Placement of the disulfide bond at a previously published position between framework regions 2 and 3 yielded the largest improvement (>6°C), suggesting this location is optimal, and seemingly provides a universal route to raise the melting temperature of single domain antibodies. This study further demonstrates that even single domain antibodies with extremely high melting points can be further stabilized by addition of disulfide bonds. PMID:25526640

Zabetakis, Dan; Olson, Mark A; Anderson, George P; Legler, Patricia M; Goldman, Ellen R

2014-01-01

318

Evaluation of Disulfide Bond Position to Enhance the Thermal Stability of a Highly Stable Single Domain Antibody  

PubMed Central

Single domain antibodies are the small recombinant variable domains derived from camelid heavy-chain-only antibodies. They are renowned for their stability, in large part due to their ability to refold following thermal or chemical denaturation. In addition to refolding after heat denaturation, A3, a high affinity anti-Staphylococcal Enterotoxin B single domain antibody, possesses a melting temperature of ?84°C, among the highest reported for a single domain antibody. In this work we utilized the recently described crystal structure of A3 to select locations for the insertion of a second disulfide bond and evaluated the impact that the addition of this second bond had on the melting temperature. Four double-disulfide versions of A3 were constructed and each was found to improve the melting temperature relative to the native structure without reducing affinity. Placement of the disulfide bond at a previously published position between framework regions 2 and 3 yielded the largest improvement (>6°C), suggesting this location is optimal, and seemingly provides a universal route to raise the melting temperature of single domain antibodies. This study further demonstrates that even single domain antibodies with extremely high melting points can be further stabilized by addition of disulfide bonds. PMID:25526640

Zabetakis, Dan; Olson, Mark A.; Anderson, George P.; Legler, Patricia M.; Goldman, Ellen R.

2014-01-01

319

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.

320

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

321

Evaluation of the geological relationships to gas hydrate formation and stability  

SciTech Connect

The summaries of regional basin analyses document that potentially economic accumulations of gas hydrates can be formed in both active and passive margin settings. The principal requirement for gas hydrate formation in either setting is abundant methane. Passive margin sediments with high sedimentation rates and sufficient sedimentary organic carbon can generate large quantities of biogenic methane for hydrate formation. Similarly, active margin locations near a terrigenous sediment source can also have high methane generation potential due to rapid burial of adequate amounts of sedimentary organic matter. Many active margins with evidence of gas hydrate presence correspond to areas subject to upwelling. Upwelling currents can enhance methane generation by increasing primary productivity and thus sedimentary organic carbon. Structural deformation of the marginal sediments at both active and passive sites can enhance gas hydrate formation by providing pathways for migration of both biogenic and thermogenic gas to the shallow gas hydrate stability zone. Additionally, conventional hydrocarbon traps may initially concentrate sufficient amounts of hydrocarbons for subsequent gas hydrate formation.

Krason, J.; Finley, P.

1988-01-01

322

Evaluation of stability of surface-treated mini-implants in diabetic rabbits.  

PubMed

Introduction. The purpose of this study was to investigate effects of surface treatment of mini-implants in diabetes-induced rabbits by comparing osseointegration around mini-implants. Methods. Twelve New Zealand white rabbits were divided into two groups (alloxan-induced diabetic group and control group). A total of 48 mini-implants were placed after four weeks of diabetic induction. 24 mini-implants were surface-treated with SLA (sandblasted with large grit, and acid etched) and the remaining 24 mini-implants had smooth surfaces. Four weeks after placement, 32 mini-implants were removed from 4 control and 4 diabetic rabbits. Insertion and removal torques were measured. The remaining 16 mini-implants from the two groups were histomorphometrically analyzed. Results. Maximum insertion torque showed no difference between diabetic and control groups, but total insertion energy was higher in control group. In surface-treated mini-implants, maximum removal torque was higher in both diabetic and control groups. Bone-implant contact (BIC) was increased in the control group when compared to the diabetic group. Surface-treated group had higher BIC than smooth surface group in both control and diabetic groups. However, there was no significantly statistical difference. Conclusions. Type 1 diabetes mellitus and surface treatment method of mini-implant affected primary stability of mini-implants. In addition, the use of orthodontic mini-implants in a diabetic patient is likely to show results similar to the healthy patient. PMID:24971093

Oh, Nam-Hee; Kim, Eun-Young; Paek, Janghyun; Kook, Yoon-Ah; Jeong, Do-Min; Cho, Il-Sik; Nelson, Gerald

2014-01-01

323

Oxidative stability and shelf-life evaluation of selected culinary oils.  

PubMed

Four out of eight 'healthier' oils-namely, almond oil, avocado oil, hazelnut oil and macadamia nut oil-studied were rich sources of monounsaturated fatty acids like olive oil. Grape seed oil, rice barn oil (marketed recently), toasted sesame oil and walnut oil contained high levels of essential fatty acids. The order of oxidative stability determined by Rancimat measuring of the induction period at four temperatures (90 degrees C, 100 degrees C, 110 degrees C, and 120 degrees C) was found to be macadamia oil > rice bran oil approximately toasted sesame oil > avocado oil > almond oil > hazelnut oil > grape seed oil > walnut oil. High-level monounsaturated fatty acid oils gave a linear relationship between 100 times the reciprocal of the induction period against the total unsaturated fatty acid content obtained as %C18:2 + 0.08 x C18:1 + 2.08 x %C18:3, while the polyunsaturated fatty acid oils gave an exponential relationship. In the case of rice bran and hazelnut oils, shelf-life prediction from the extrapolation of the Arrhenius plots and the Q(10) factors was compared well with that of storage time given by the oil producers. In the cases of the other oils (with an exception of macadamia nut oil), the predicted shelf-lives were significantly lower than that of the storage times; especially, walnut oil (very prone to oxidation) gave 15-20 times lower shelf-life than the best-before storage life. PMID:19634067

Kochhar, S Parkash; Henry, C Jeya K

2009-01-01

324

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

325

Evaluation of Stability of Surface-Treated Mini-Implants in Diabetic Rabbits  

PubMed Central

Introduction. The purpose of this study was to investigate effects of surface treatment of mini-implants in diabetes-induced rabbits by comparing osseointegration around mini-implants. Methods. Twelve New Zealand white rabbits were divided into two groups (alloxan-induced diabetic group and control group). A total of 48 mini-implants were placed after four weeks of diabetic induction. 24 mini-implants were surface-treated with SLA (sandblasted with large grit, and acid etched) and the remaining 24 mini-implants had smooth surfaces. Four weeks after placement, 32 mini-implants were removed from 4 control and 4 diabetic rabbits. Insertion and removal torques were measured. The remaining 16 mini-implants from the two groups were histomorphometrically analyzed. Results. Maximum insertion torque showed no difference between diabetic and control groups, but total insertion energy was higher in control group. In surface-treated mini-implants, maximum removal torque was higher in both diabetic and control groups. Bone-implant contact (BIC) was increased in the control group when compared to the diabetic group. Surface-treated group had higher BIC than smooth surface group in both control and diabetic groups. However, there was no significantly statistical difference. Conclusions. Type 1 diabetes mellitus and surface treatment method of mini-implant affected primary stability of mini-implants. In addition, the use of orthodontic mini-implants in a diabetic patient is likely to show results similar to the healthy patient. PMID:24971093

Oh, Nam-Hee; Kim, Eun-Young; Paek, Janghyun; Kook, Yoon-Ah; Jeong, Do-Min; Cho, Il-Sik; Nelson, Gerald

2014-01-01

326

Epoxidized Soybean Oil: Evaluation of Oxidative Stabilization and Metal Quenching/Heat Transfer Performance  

NASA Astrophysics Data System (ADS)

Vegetable and animal oils as a class of fluids have been used for hundreds of years, if not longer, as quenchants for hardening steel. However, when petroleum oils became available in the late 1800s and early 1900s, the use of these fluids as quenchants, in addition to their use in other industrial oil applications, quickly diminished. This was primarily, but not exclusively, due to their generally very poor thermal-oxidative instability and the difficulty for formulating fluid analogs with varying viscosity properties. Interest in the use of renewable fluids, such as vegetable oils, has increased dramatically in recent years as alternatives to the use of relatively non-biodegradable and toxic petroleum oils. However, the relatively poor thermal-oxidative stability has continued to be a significant reason for their general non-acceptance in the marketplace. Soybean oil (SO) is one of the most highly produced vegetable oils in Brazil. Currently, there are commercially produced epoxidized versions of SO which are available. The objective of this paper is to discuss the potential use of epoxidized SO and its heat transfer properties as a viable alternative to petroleum oils for hardening steel.

Simencio Otero, Rosa L.; Canale, Lauralice C. F.; Said Schicchi, Diego; Agaliotis, Eliana; Totten, George E.; Sánchez Sarmiento, Gustavo

2013-07-01

327

Nanocarriers for antioxidant resveratrol: formulation approach, vesicle self-assembly and stability evaluation.  

PubMed

In this work we studied various nanoformulations of resveratrol in phospholipid vesicles. Conventional phophatidylcholine liposomes were prepared and characterized in parallel with PEVs (Penetration Enhancer-containing Vesicles) obtained by adding one of eight selected amphiphilic penetration enhancers (PEs; 0.2% w/v; HLB range 1-16) to the composition. All vesicles were around 100 nm, negatively charged (?-30 mV) and able to incorporate resveratrol in good yields (>74%). The structure and the lamellar self-organization of the vesicles were investigated by Transmission Electron Microscopy (TEM) and Small and Wide Angle X-ray Scattering (SWAXS). These analyses showed that the lamellarity of the vesicles depended on the formulation composition. This work also addressed the stability of our colloidal dispersions, which was measured by means of the analytical centrifuge LUMiSizer(®): this procedure disclosed the absence of any demixing phenomena and estimated a 3- to 6-month shelf-life. Moreover, the antioxidant activity of resveratrol was determined by assessing its ability to scavenge free radicals (DPPH assay), and showed that it was not affected by the vesicular formulation. PMID:23838200

Caddeo, Carla; Manconi, Maria; Fadda, Anna Maria; Lai, Francesco; Lampis, Sandrina; Diez-Sales, Octavio; Sinico, Chiara

2013-11-01

328

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

329

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

330

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

331

Evaluation of a Treadmill with Vibration Isolation and Stabilization (TVIS) for use on the International Space Station.  

PubMed

A treadmill with vibration isolation and stabilization designed for the International Space Station (ISS) was evaluated during Shuttle mission STS-81. Three crew members ran and walked on the device, which floats freely in zero gravity. For the majority of the more than 2 hours of locomotion studied, the treadmill showed peak to peak linear and angular displacements of less than 2.5 cm and 2.5 degrees, respectively. Vibration transmitted to the vehicle was within the microgravity allocation limits that are defined for the ISS. Refinements to the treadmill and harness system are discussed. This approach to treadmill design offers the possibility of generating 1G-like loads on the lower extremities while preserving the microgravity environment of the ISS for structural safety and vibration free experimental conditions. PMID:11541844

McCrory, J L; Lemmon, D R; Sommer, H J; Prout, B; Smith, D; Korth, D W; Lucero, J; Greenisen, M; Moore, J; Kozlovskaya, I; Pestov, I; Stepansov, V; Miyakinchenko, Y; Cavanagh, P R

1999-08-01

332

Active Filter Based On-Chip Step-Down DC-DC Switching Voltage Regulator  

Microsoft Academic Search

Switching type step-down voltage regulators are commonly used as the power source for the IC circuit loads. To ensure that the voltage stability is well maintained, the switching type voltage regulator usually uses LC low-pass filter in the output terminal. However, the inductor size and cost are two of the major concerns in the circuit design of this kind of

Chun-Hsun Wu; Le-Ren Chang-Chien; Lih-Yih Chiou

2005-01-01

333

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

334

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

335

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

336

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

337

Low-voltage gyrotrons  

NASA Astrophysics Data System (ADS)

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.; Nusinovich, G. S.

2013-03-01

338

Self micro-emulsifying drug delivery system of tacrolimus: Formulation, in vitro evaluation and stability studies  

PubMed Central

Background: Tacrolimus has poor solubility in water ranging from 4 to 12 ?g/mL. The oral bio availabilities of tacrolimus is poor and exhibits high intra and inter-subject variability (4-89%, average 25%) in the liver and the kidney transplant recipients and in patients with renal impairment. Aim: The present study deals with the development and characterization of self-micro-emulsifying drug delivery system to improve the oral bioavailability of poorly soluble drug tacrolimus. Materials and Methods: Solubility of the tacrolimus was estimated in various oils, surfactants, and co-surfactants. Various in vitro tests such as percentage transmittance, emulsification time, cloud point, precipitation, and thermodynamic stabilities were used to find out optimized formulations. Optimized liquid self micro-emulsifying (SMEDDS) were characterized by particle size analysis and converted in solid by using the Florite RE as an adsorbent, which is further characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and particle size analysis. Results: The optimized liquid SMEDDS formulation contained 10% Lauroglycol FCC as an oil, 60% Cremophor RH, and 30% PEG (polyethylene glycol) 400 as a surfactant and co-surfactant respectively. The optimized liquid and solid SMEDDS showed higher drug release than the marketed capsule and pure API (active pharmaceutical ingredient) powder. For optimized liquid SMEDDS and solid SMEDDS, the globule sizes were found 113 nm and 209 nm respectively. The solid state characterization of solid-SMEDDS by SEM, DSC, FTIR, and XRD revealed the absence of crystalline tacrolimus in the solid-SMEDDS. Shelf-lives for liquid SMEDDS and solid SMEDDS were found to be 1.84 and 2.25 year respectively. Conclusions: The results indicate that liquid SMEDDS and solid SMEDDS of tacrolimus, owing to nano-sized, have potential to enhance the absorption of the drug. PMID:24015381

Patel, Pranav V; Patel, Hitesh K; Panchal, Shital S; Mehta, Tejal A

2013-01-01

339

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

340

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

341

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

342

Contributions of Intracellular Ions to Kv Channel Voltage Sensor Dynamics  

PubMed Central

Voltage-sensing domains (VSDs) of Kv channels control ionic conductance through coupling of the movement of charged residues in the S4 segment to conformational changes at the cytoplasmic region of the pore domain, that allow K+ ions to flow. Conformational transitions within the VSD are induced by changes in the applied voltage across the membrane field. However, several other factors not directly linked to the voltage-dependent movement of charged residues within the voltage sensor impact the dynamics of the voltage sensor, such as inactivation, ionic conductance, intracellular ion identity, and block of the channel by intracellular ligands. The effect of intracellular ions on voltage sensor dynamics is of importance in the interpretation of gating current measurements and the physiology of pore/voltage sensor coupling. There is a significant amount of variability in the reported kinetics of voltage sensor deactivation kinetics of Kv channels attributed to different mechanisms such as open state stabilization, immobilization, and relaxation processes of the voltage sensor. Here we separate these factors and focus on the causal role that intracellular ions can play in allosterically modulating the dynamics of Kv voltage sensor deactivation kinetics. These considerations are of critical importance in understanding the molecular determinants of the complete channel gating cycle from activation to deactivation. PMID:22719727

Goodchild, Samuel J.; Fedida, David

2012-01-01

343

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

344

Synthesis of saxitoxin derivatives bearing guanidine and urea groups at C13 and evaluation of their inhibitory activity on voltage-gated sodium channels.  

PubMed

Here, we describe the synthesis of the first C13-N-substituted STX derivatives 4, 5, and 6 bearing a guanidine, a urea group, and an acetamide, respectively, via the fully protected saxitoxinol derivative 8. These compounds are of interest because a previous docking study of saxitoxin (STX) with voltage-gated sodium channels (NaVCh) suggested that the C13 carbamoyl group of STX interacts with residue E403 in the pore region of NaVCh. In a cell-based assay with Neuro-2a cells, the NaVCh-inhibitory activities of 4 and 5 were more than 20- to 50-fold weaker than that of decarbamoyl-STX (3), which is 10-fold less potent than STX. On the other hand, 6 was 1000 times less potent than 3. The electrostatic analysis of C13 in STX and its analogs 4-6 using EON calculations suggested that the NaVCh-inhibitory activity of these derivatives is influenced by both the hydrophilicity and the charge balance of the substituent at C13. PMID:23989458

Akimoto, Takafumi; Masuda, Asako; Yotsu-Yamashita, Mari; Hirokawa, Takatsugu; Nagasawa, Kazuo

2013-10-14

345

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

346

Evaluation of structure and material properties of RF magnetron sputter-deposited yttria-stabilized zirconia thin films  

NASA Astrophysics Data System (ADS)

Over the past several decades, research has focused on utilizing ceramic materials in new technological applications. Their uses have been primarily in applications that involve high temperatures or corrosive environments. Unfortunately, ceramic materials have been limited especially since they can be brittle, failing in a sudden and catastrophic manner. A strong emphasis on understanding mechanical properties of ceramics and ways to improving their strength and toughness, has led to many new technologies. The present work is part of a larger research initiative that is aimed at using RF magnetron sputter deposition of yttria-stabilized zirconia to improve the fracture toughness of brittle substrates (more specifically dental ceramics). Partially-stabilized zirconia (PSZ) has been studied extensively, due to its high temperature stability and stress-induced tetragonal to monoclinic (T?M) martensitic phase transformation. RF magnetron sputtering was chosen as the deposition method because of its versatility, especially the ability to deposit oxides at low temperatures. Initial investigations focused on the development of process-structure-properties of YSZ sputtered deposited thin films. The YSZ thin films were deposited over a range of temperatures (22--300°C), pressures (5--25 mTorr), and gas compositions (Ar:O2 ratio). Initial studies characterized a select set of properties in relation to deposition parameters including: refractive index, structure, and film stress. X-ray Diffraction (XRD) showed that the films are comprised of mainly monoclinic and tetragonal crystal phases. The film refractive index determined by prism coupling, depends strongly on deposition conditions and ranged from 1.959 to 2.223. Wafer bow measurements indicate that the sputtered YSZ films can have initial stress ranging from 86 MPa tensile to 192 MPa compressive, depending on the deposition parameters. Exposure to ambient conditions (25°C, 75% relative humidity) led to large increase (˜ 100 MPa) in the compressive stress of the films. Environmental aging suggests the change in compressive stress was related to water vapor absorption. These effects were then evaluated for films formed under different deposition parameters with varying density (calculated packing density) and crystal structure (XRD). Based on the above results, it was determined to evaluate stress as a function of substrate bias. It was shown that increasing substrate bias power disrupted columnar grain growth and reduced the percent change in compressive stress when exposed to ambient environments. TEM confirmed a reduction in inter-granular porosity for substrate bias depositions, but an increase in lateral defects. It was hypothesized that substrate bias would increase the film's density, but after inspection of SEM and TEM micrographs, it appeared that as bias was increased the density decreased. This T?M phase transformation has been well documented for bulk PSZ, but limited data exists for PSZ thin films. Data is presented that supports a stress-induced T=>M transformation mechanism that occurs during sputter-deposition in the presence of a substrate bias. Substrate bias (0--50W) was originally applied to increase film density, modify microstructure, and vary film stress. The films were deposited using rf magnetron sputtering from a sintered yttria-stabilized zirconia (YSZ) target and subsequently characterized using scanning (SEM) and transmission electron microscopy (TEM), x-ray diffraction (XRD), and wafer bow measurement (for stress analysis). With no substrate bias the films exhibited a columnar grain structure consistent with sputter-deposited films, with a majority tetragonal phase as determined by XRD. Under higher substrate bias, wafer bow measurements indicated a steady increase in compressive stress as substrate bias increased (max. 310MPa at 50W bias), while XRD indicated a corresponding increase in the percentage of monoclinic phase. Both SEM and TEM analyses revealed a shift from a defect-free columnar structure to one consisting of lateral intra-c

Piascik, Jeffrey Robert

347

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

348

High voltage variable diameter insulator  

DOEpatents

A high voltage feedthrough assembly having a tubular insulator extending between the ground plane ring and the high voltage ring. The insulator is made of Pyrex and decreases in diameter from the ground plane ring to the high voltage ring, producing equipotential lines almost perpendicular to the wall of the insulator to optimize the voltage-holding capability of the feedthrough assembly.

Vanacek, D.L.; Pike, C.D.

1982-07-13

349

A fast ac voltage regulator  

Microsoft Academic Search

The study and implementation of an AC voltage regulator is presented in this paper. Traditionally an AC voltage regulator is made with a transformer tap changer or with an AC-AC converter based on buck topologies, recently the developments in ac-ac converter makes feasible the implementation of voltage regulator with other topologies. In this paper is analyzed an ac voltage regulator

N. Vazquez; A. Velazquez; C. Hernandez; E. Rodriguez; R. Orosco

2008-01-01

350

Electron launching voltage monitor  

DOEpatents

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

351

Electron launching voltage monitor  

DOEpatents

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

352

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

353

High frequency breakdown voltage  

SciTech Connect

This report contains information about the effect of frequency on the breakdown voltage of an air gap at standard pressure and temperature, 76 mm Hg and O{degrees}C, respectively. The frequencies of interest are 47 MHz and 60 MHz. Additionally, the breakdown in vacuum is briefly considered. The breakdown mechanism is explained on the basis of collision and ionization. The presence of the positive ions produced by ionization enhances the field in the gap, and thus determines the breakdown. When a low-frequency voltage is applied across the gap, the breakdown mechanism is the same as that caused by the DC or static voltage. However, when the frequency exceeds the first critical value f{sub c}, the positive ions are trapped in the gap, increasing the field considerably. This makes the breakdown occur earlier; in other words, the breakdown voltage is lowered. As the frequency increases two decades or more, the second critical frequency, f{sub ce}, is reached. This time the electrons start being trapped in the gap. Those electrons that travel multiple times across the gap before reaching the positive electrode result in an enormous number of electrons and positive ions being present in the gap. The result is a further decrease of the breakdown voltage. However, increasing the frequency does not decrease the breakdown voltage correspondingly. In fact, the associated breakdown field intensity is almost constant (about 29 kV/cm).The reason is that the recombination rate increases and counterbalances the production rate, thus reducing the effect of the positive ions` concentration in the gap. The theory of collision and ionization does not apply to the breakdown in vacuum. It seems that the breakdown in vacuum is primarily determined by the irregularities on the surfaces of the electrodes. Therefore, the effect of frequency on the breakdown, if any, is of secondary importance.

Chu, Thanh Duy

1992-03-01

354

Surface voltage gradient role in high voltage solar array-plasma interaction: Center Director's discretionary fund  

NASA Technical Reports Server (NTRS)

A large amount of experimental and analytical effort has been directed toward understanding the plasma sheath growth and discharge phenomena which lead to high voltage solar array-space plasma interactions. An important question which has not been addressed is how the surface voltage gradient on such an array may affect these interactions. The results of this study indicate that under certain conditions, the voltage gradient should be taken into account when evaluating the effect on a solar array operating in a plasma environment.

Carruth, M. R., Jr.

1985-01-01

355

Evaluation of the threshold of stability for the human spine Martin L. Tanaka a,b,d,, Maury A. Nussbaum b,c  

E-print Network

Evaluation of the threshold of stability for the human spine Martin L. Tanaka a,b,d,Ã?, Maury A in which minimal instrumentation is needed. Its simplicity, sensitivity, and low cost suggest that the To of the spine, paraspinal ligaments, core musculature, and neuro- muscular control system to maintain an upright

Ross, Shane

356

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...

357

Stability and Feedback Stabilization 1639 Stability and Feedback Stabilization  

E-print Network

Stability and Feedback Stabilization 1639 Stability and Feedback Stabilization EDUARDO D. SONTAG Sensitivity to Small Measurement Errors Future Directions Bibliography Glossary Stability A globally, with no large excursions. Stabilization A system is stabilizable (with respect to a given state

Sontag, Eduardo

358

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

359

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. M.

360

Measuring Breakdown Voltage.  

ERIC Educational Resources Information Center

The article discusses an aspect of conductivity, one of the electrical properties subdivisions, and describes a tester that can be shop-built. Breakdown voltage of an insulation material is specifically examined. Test procedures, parts lists, diagrams, and test data form are included. (MF)

Auer, Herbert J.

1978-01-01

361

Geomagnetism and Induced Voltage  

ERIC Educational Resources Information Center

Introductory physics laboratories have seen an influx of "conceptual integrated science" over time in their classrooms with elements of other sciences such as chemistry, biology, Earth science, and astronomy. We describe a laboratory to introduce this development, as it attracts attention to the voltage induced in the human brain as it is…

Abdul-Razzaq, W.; Biller, R. D.

2010-01-01

362

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

363

Evaluation of protein stability and in vitro permeation of lyophilized polysaccharides-based microparticles for intranasal protein delivery.  

PubMed

Biocompatible microparticles prepared by lyophilization were developed for intranasal protein delivery. To test for the feasibility of this formulation, stability of the incorporated protein and enhancement of in vitro permeation across the nasal epithelium were evaluated. Lyophilization was processed with hydroxypropylmethylcellulose (HPMC) or water soluble chitosan (WCS) as biocompatible polymers, hydroxypropyl-?-cyclodextrin (HP-?-CD) and d-alpha-tocopheryl poly(ethylene glycol 1000) succinate (TPGS 1000) as permeation enhancers, sugars as cryoprotectants and lysozyme as the model protein. As a result, microparticles ranging from 6 to 12?m were developed where the maintenance of the protein conformation was verified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism and fluorescence intensity detection. Moreover, in vitro bioassay showed that the lysozyme activity was preserved during the preparation process while exhibiting less cytotoxicity in primary human nasal epithelial (HNE) cells. Results of the in vitro release study revealed slower release rate in these microparticles compared to that of the lysozyme itself. On the other hand, the in vitro permeation study exhibited a 9-fold increase in absorption of lysozyme when prepared in lyophilized microparticles with HPMC, HP-?-CD and TPGS 1000 (F4-2). These microparticles could serve as efficient intranasal delivery systems for therapeutic proteins. PMID:21703339

Cho, Hyun-Jong; Balakrishnan, Prabagar; Chung, Suk-Jae; Shim, Chang-Koo; Kim, Dae-Duk

2011-09-15

364

Evaluating the suitability of highly cross-linked and remelted materials for use in posterior stabilized knees.  

PubMed

Posterior stabilized (PS) knee designs are a popular choice for cruciate sacrificing knee arthroplasty procedures. The introduction of PS inserts fabricated from highly cross-linked and remelted Ultra High Molecular Weight Polyethylene (UHMWPE) has recently generated concern as these materials have been shown to possess reduced mechanical properties. This study investigated whether highly cross-linked and remelted UHMWPE material (referred to as XRP) can be expected to perform similarly to historical gamma-air polyethylene, which has suffered few reported incidences of tibial post failure. Never-implanted gamma-air PS tibial inserts shelf-aged 14 years were examined and compared to XRP materials. Evaluation of oxidation levels, impact toughness, and fatigue strength demonstrated never-implanted gamma-air PS tibial inserts to possess nonuniform mechanical properties. Despite severe oxidation along the exterior of gamma-air tibial posts, comparatively low oxidation levels at the center of the tibial posts corresponded to sufficiently high mechanical properties. XRP material (75 kGy) showed superior impact toughness over shelf aged gamma-air material; however, tibial post fatigue testing demonstrated XRP material (100 kGy) to be less resistant to fatigue failure than historical gamma-air material. Results from this study indicate that XRP materials (100 kGy) may demonstrate an inferior resistance to tibial post failure than historical polyethylene. PMID:20845487

Huot, J Caitlin; Van Citters, Douglas W; Currier, John H; Currier, Barbara H; Mayor, Michael B; Collier, John P

2010-11-01

365

Mechanism and CHARM2 Evaluation of P-Channel Metal Oxide Semiconductor Threshold Voltage Drop during High Density Plasma Heat-up Process  

Microsoft Academic Search

Plasma damage during the plasma deposition process is one of the most critical device characteristic issues facing complementary metal oxide semiconductor field effect transistor (CMOSFET) technology. In this paper, the CHARM2 monitoring system is used to evaluate UV damage and plasma charging damage during a high density plasma chemical vapor deposition (HDP-CVD) heat-up process. As a result, the amount of

Dong-Hwan Kim; Jeongyun Lee; Min-Sung Kim; Ken Tokashiki; Kyoungsub Shin; Woosung Han; Hyun-Il Kang; Eung-Kwon Kim; Joon-Tae Song

2009-01-01

366

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

367

Development of an in vitro liquid chromatography-mass spectrometry method to evaluate stereo and chemical stability of new drug candidates employing immobilized artificial membrane column.  

PubMed

A stopped-flow HPLC method was developed to evaluate configurational and chemical stability of pharmaceutical compounds employing immobilized artificial membranes (IAM) column to simulate conditions that pharmaceutical compounds will meet in vivo. The method was applied to recent developed chiral 5-arylbenzothiadiazine derivatives possessing high positive allosteric modulatory (PAM) activity on AMPA receptor. In particular the stopped-flow HPLC method developed used a chiral column to separate single enantiomer of the compounds that are forced into an IAM column where configurational and chemical stability was evaluated in simulated gastrointestinal fluids (pH 1.2 and 6.8 at 37.5 °C) to simulate in vivo conditions. The results were compared to those obtained by dynamic and off-column methods to evaluate the effects of stationary phases on kinetic constant of enantiomerization and hydrolysis. The results suggested that the phospholipids environment of IAM stationary phases, which mimes biological membrane, greatly influence the hydrolysis process increasing the chemical stability of tested compounds while no influence on enantiomerization kinetic was observed. Therefore it is possible to suppose that 5-arylbenzothiadiazine derivatives should not hydrolysed in vivo while they should rapidly racemized in aqueous solvents. The method could represents a rapid and value tool to predict chemical and configurational stability of new chemical entities to decrease the number of animal studies. PMID:24935265

Cannazza, Giuseppe; Battisti, Umberto M; Carrozzo, Marina M; Cazzato, Addolorata S; Braghiroli, Daniela; Parenti, Carlo; Troisi, Luigino

2014-10-10

368

How membrane proteins sense voltage.  

PubMed

The ionic gradients across cell membranes generate a transmembrane voltage that regulates the function of numerous membrane proteins such as ion channels, transporters, pumps and enzymes. The mechanisms by which proteins sense voltage is diverse: ion channels have a conserved, positively charged transmembrane region that moves in response to changes in membrane potential, some G-protein coupled receptors possess a specific voltage-sensing motif and some membrane pumps and transporters use the ions that they transport across membranes to sense membrane voltage. Characterizing the general features of voltage sensors might lead to the discovery of further membrane proteins that are voltage regulated. PMID:18354422

Bezanilla, Francisco

2008-04-01

369

Evaluation of Colloidal Stability and Ecotoxicity of Metal-based Nanoparticles in the Aquatic and Terrestrial Systems  

NASA Astrophysics Data System (ADS)

Intrinsic to the many nano-enabled products are atomic-size multifunctional engineered nanomaterials, which upon release contaminate the environments, raising considerable health and safety concerns. This Ph.D. dissertation is designed to investigate (i) whether metals or oxide nanoparticles are more toxic than ions, and if MetPLATE(TM) bioassay is applicable as a rapid nanotoxicity screening tool; (ii) how variable water chemistry (dissolved organic carbon (DOC), pH, and hardness) and organic compounds (cysteine, humic acid, and trolox) modulate colloidal stability, ion release, and aquatic toxicity of silver nanoparticles (AgNP); and (iii) the developmental responses of crop plants exposed to Ag- or ZnO- (zinc oxide) nanoparticles. Results suggest that the MetPLATE can be considered a high-throughput screening tool for rapid nanotoxicity evaluation. Detectable changes in the colloidal diameter, surface charge, and plasmonic resonance revealed modulating effects of variable water chemistry and organic ligands on the particle stability, dissolution, and toxicity of AgNPs against Escherichia coli or Daphnia magna. Silver dissolution increased as a function of DOC concentrations but decreased with increasing hardness, pH, cysteine, or trolox levels. Notably, the dissociated Ag+ was inadequate to explain AgNP toxicity, and that the combined effect of AgNPs and dissolved Ag+ under each ligand treatment was lower than of AgNO 3. Significant attenuation by trolox signifies an oxidative stress-mediated AgNP toxicity; its inability to attenuate AgNO3 toxicity, however, negates oxidative stress as Ag+ toxicity mechanism, and that cysteine could effectively quench free Ag+ to alleviate AgNO 3 toxicity in D. magna. Surprisingly, DOC-AgNPs complex that apparently formed at higher DOC levels might have led daphnids filter-feed on aggregates, potentially elevating internal dose, and thus higher mortality. Maize root anatomy showed differential alterations upon exposure to AgNPs, ZnONPs, or their ions. Overall, various metal-based nanoparticles revealed lower toxicity than their ions against multiple organisms. This study showed that particle size, surface properties, and ion release kinetics of AgNPs modify following release into aquatic environment, suggesting potential implications to ecosystem health and functions, and that caution be applied when extending one species toxicity results to another because obvious differences in organism biology---supporting species sensitivity paradigm---can significantly alter nanoparticle or ionic toxicity.

Pokhrel, Lok Raj

370

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

371

Evaluation of stability and size distribution of sunflower oil-coated micro bubbles for localized drug delivery  

PubMed Central

Background Micro bubbles were initially introduced as contrast agents for ultrasound examinations as they are able to modify the signal-to-noise ratio in imaging, thus improving the assessment of clinical information on human tissue. Recent developments have demonstrated the feasibility of using these bubbles as drug carriers in localized delivery. In micro fluidics devices for generation of micro bubbles, the bubbles are formed at interface of liquid gas through a strangulation process. A device that uses these features can produce micro bubbles with small size dispersion in a single step. Methods A T-junction micro fluidic device constructed using 3D prototyping was made for the production of mono dispersed micro bubbles. These micro bubbles use sunflower oil as a lipid layer. Stability studies for micro bubbles with diameters different generated from a liquid phase of the same viscosity were conducted to evaluate whether micro bubbles can be used as drug carriers. The biocompatibility of coating layer, the ability to withstand environmental pressure variations combined with echogenicity, are key factors that they can safely play the role of drug transporters. Results The normal distribution curve with small dispersion of the diameter of bubbles validates the process of generating micro bubbles with low value of variation coefficient, i.e., 0.381 at 1.90%. The results also showed the feasibility of using sunflower oil as the lipid matrix with stable population of bubbles over 217 minutes for micro bubbles with an average diameter of 313.04 ?m and 121 minutes for micro bubbles with an average diameter of 73.74 ?m, considering bubbles with air as gaseous phase. Conclusion The results indicate that the micro fluidic device designed can be used for producing micro bubbles with low variation coefficient using sunflower oil as a coating of micro bubbles. These carriers were stable for periods of time that are long enough for clinical applications even when regular air is used as the gas phase. Improved stability can be achieved when biocompatible gas with lower permeability is used. PMID:22995578

2012-01-01

372

Modulation of BK channel voltage gating by different auxiliary ? subunits  

PubMed Central

Calcium- and voltage-activated potassium channels (BK) are regulated by a multiplicity of signals. The prevailing view is that different BK gating mechanisms converge to determine channel opening and that these gating mechanisms are allosterically coupled. In most instances the pore forming ? subunit of BK is associated with one of four alternative ? subunits that appear to target specific gating mechanisms to regulate the channel activity. In particular, ?1 stabilizes the active configuration of the BK voltage sensor having a large effect on BK Ca2+ sensitivity. To determine the extent to which ? subunits regulate the BK voltage sensor, we measured gating currents induced by the pore-forming BK ? subunit alone and with the different ? subunits expressed in Xenopus oocytes (?1, ?2IR, ?3b, and ?4). We found that ?1, ?2, and ?4 stabilize the BK voltage sensor in the active conformation. ?3 has no effect on voltage sensor equilibrium. In addition, ?4 decreases the apparent number of charges per voltage sensor. The decrease in the charge associated with the voltage sensor in ? ?4 channels explains most of their biophysical properties. For channels composed of the ? subunit alone, gating charge increases slowly with pulse duration as expected if a significant fraction of this charge develops with a time course comparable to that of K+ current activation. In the presence of ?1, ?2, and ?4 this slow component develops in advance of and much more rapidly than ion current activation, suggesting that BK channel opening proceeds in two steps. PMID:23112204

Contreras, Gustavo F.; Neely, Alan; Alvarez, Osvaldo; Gonzalez, Carlos; Latorre, Ramon

2012-01-01

373

Modulation of BK channel voltage gating by different auxiliary ? subunits.  

PubMed

Calcium- and voltage-activated potassium channels (BK) are regulated by a multiplicity of signals. The prevailing view is that different BK gating mechanisms converge to determine channel opening and that these gating mechanisms are allosterically coupled. In most instances the pore forming ? subunit of BK is associated with one of four alternative ? subunits that appear to target specific gating mechanisms to regulate the channel activity. In particular, ?1 stabilizes the active configuration of the BK voltage sensor having a large effect on BK Ca(2+) sensitivity. To determine the extent to which ? subunits regulate the BK voltage sensor, we measured gating currents induced by the pore-forming BK ? subunit alone and with the different ? subunits expressed in Xenopus oocytes (?1, ?2IR, ?3b, and ?4). We found that ?1, ?2, and ?4 stabilize the BK voltage sensor in the active conformation. ?3 has no effect on voltage sensor equilibrium. In addition, ?4 decreases the apparent number of charges per voltage sensor. The decrease in the charge associated with the voltage sensor in ? ?4 channels explains most of their biophysical properties. For channels composed of the ? subunit alone, gating charge increases slowly with pulse duration as expected if a significant fraction of this charge develops with a time course comparable to that of K(+) current activation. In the presence of ?1, ?2, and ?4 this slow component develops in advance of and much more rapidly than ion current activation, suggesting that BK channel opening proceeds in two steps. PMID:23112204

Contreras, Gustavo F; Neely, Alan; Alvarez, Osvaldo; Gonzalez, Carlos; Latorre, Ramon

2012-11-13

374

Arrester Protection of High-Voltage Stations Against Lightning  

Microsoft Academic Search

1. A graphical method for evaluating the effect of nonstandard lightning surge voltages on equipment insulation has been presented and applied in the course of the study. The method is considered to be sufficiently accurate in measuring the relative effect of surge voltages to be extremely useful in such a study. The method is simple to understand and very easy

G. D. Breuer; R. H. Hopkinson; I. B. Johnson; A. J. Schultz

1960-01-01

375

Voltage regulation using dynamic voltage restorer for large frequency variations  

Microsoft Academic Search

The paper discusses the voltage regulation of a critical load bus using a dynamic voltage restorer (DVR) in a distribution system. The critical load cannot tolerate any power quality (PQ) disturbance including large frequency variations occurring in the system. The DVR is operated such that it holds the voltage across the critical load bus terminals constant at system nominal frequency

Amit Kumar Jindal; Arindam Ghosh; Avinash Joshi

2005-01-01

376

Stable voltage reference sources  

Microsoft Academic Search

A family of well-regulated voltage references are shown, which are readily integrable for use with emitter-coupled logic, threshold logic, or linear circuit arrays. By relying on the relatively well-matched characteristics and the temperature tracking of integrated transistors and resistor ratios, the circuit can provide a large range of output fractions of the power supply. The relationships of the circuit components

D. Hampel

1972-01-01

377

The voltage-dependent step of the chloride transporter of Valonia utricularis encounters a Nernst-Planck and not an Eyring type of potential energy barrier.  

PubMed

Voltage-clamp experiments were performed on cells of the giant marine alga Valonia utricularis to study the voltage dependence of the previously postulated chloride transporter (Wang, J., G. Wehner, R. Benz, and U. Zimmermann. 1991. Biophys. J. 59:235-248). Only one exponential current relaxation (apart from the capacitive spike) could be resolved up to a clamp voltage of approximately 120 mV within the time resolution of our experimental instrumentation (100 mus). This means that the rate constants of the heterogeneous complexation, k(R) (association) and k(D) (dissociation), were too fast to be resolved. Therefore, the "Läuger" model for carrier-mediated ion transport with equilibrium heterogeneous surface reaction was used to fit the experimental results. The voltage dependence of the initial membrane conductance was used for the evaluation of the voltage dependence of the translocation rate constant of the complexed carriers, k(AS). The initial conductance was found to be independent on the clamp voltage, which means that the translocation rate constant k(AS) is a linear function of the applied voltage and that the voltage dependence of the translocation of charged carriers through the plasmalemma could be explained by a square-type Nernst-Planck barrier. The movement of the complexed form of the carrier through the membrane may be explained by a diffusion process rather than by simple first-order kinetic jump across an Eyring-type potential well. The current relaxation after a voltage clamp was studied as a function of the external chloride concentration. The results allowed an estimation of the stability constant, K, of the heterogeneous complexation reaction and a calculation of the translocation rate constants of the free and the complexed carriers, k(s) and k(AS), respectively. PMID:19431881

Wang, J; Zimmermann, U; Benz, R

1993-04-01

378

The voltage-dependent step of the chloride transporter of Valonia utricularis encounters a Nernst-Planck and not an Eyring type of potential energy barrier  

PubMed Central

Voltage-clamp experiments were performed on cells of the giant marine alga Valonia utricularis to study the voltage dependence of the previously postulated chloride transporter (Wang, J., G. Wehner, R. Benz, and U. Zimmermann. 1991. Biophys. J. 59:235-248). Only one exponential current relaxation (apart from the capacitive spike) could be resolved up to a clamp voltage of ?120 mV within the time resolution of our experimental instrumentation (100 ?s). This means that the rate constants of the heterogeneous complexation, kR (association) and kD (dissociation), were too fast to be resolved. Therefore, the “Läuger” model for carrier-mediated ion transport with equilibrium heterogeneous surface reaction was used to fit the experimental results. The voltage dependence of the initial membrane conductance was used for the evaluation of the voltage dependence of the translocation rate constant of the complexed carriers, kAS. The initial conductance was found to be independent on the clamp voltage, which means that the translocation rate constant kAS is a linear function of the applied voltage and that the voltage dependence of the translocation of charged carriers through the plasmalemma could be explained by a square-type Nernst-Planck barrier. The movement of the complexed form of the carrier through the membrane may be explained by a diffusion process rather than by simple first-order kinetic jump across an Eyring-type potential well. The current relaxation after a voltage clamp was studied as a function of the external chloride concentration. The results allowed an estimation of the stability constant, K, of the heterogeneous complexation reaction and a calculation of the translocation rate constants of the free and the complexed carriers, ks and kAS, respectively. PMID:19431881

Wang, Jianning; Zimmermann, Ulrich; Benz, Roland

1993-01-01

379

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

380

Planned Variation in Preanalytical Conditions to Evaluate Biospecimen Stability in the National Children’s Study (NCS)  

PubMed Central

BACKGROUND Preanalytical conditions encountered during collection, processing, and storage of biospecimens may influence laboratory results. The National Children’s Study (NCS) is a planned prospective cohort study of 100,000 families to examine the influence of a wide variety of exposures on child health. In developing biospecimen collection, processing, and storage procedures for the NCS, we identified several analytes of different biochemical categories for which it was unclear to what extent deviations from NCS procedures could influence measurement results. METHODS A pilot study was performed to examine effects of preanalytic sample handling conditions (delays in centrifugation, freezing delays, delays in separation from cells, additive delay, and tube type) on concentrations of eight different analytes. 2,825 measurements were made to assess 15 unique combinations of analyte and handling conditions in blood collected from 151 women of childbearing age (?20 individuals per handling condition). RESULTS The majority of analytes were stable under the conditions evaluated. However, levels of plasma interleukin-6 and serum insulin were decreased in response to sample centrifugation delays of up to 5.5 hours post collection (P<0.0001). In addition, delays in freezing centrifuged plasma samples (comparing 24, 48 and 72 hours to immediate freezing) resulted in increased levels of adrenocorticotropic hormone (P=0.0014). CONCLUSIONS Determining stability of proposed analytes in response to preanalytical conditions and handling helps to ensure high-quality specimens for study now and in the future. The results inform development of procedures, plans for measurement of analytes, and interpretation of laboratory results. PMID:23924524

Mechanic, Leah; Mendez, Armando; Merrill, Lori; Rogers, John; Layton, Marnie; Todd, Deborah; Varanasi, Arti; O’Brien, Barbara; Meyer, William A.; Zhang, Ming; Schleicher, Rosemary L.; Moye, Jack

2014-01-01

381

High voltage variable diameter insulator  

DOEpatents

A high voltage feedthrough assembly (10) having a tubular insulator (15) extending between the ground plane ring (16) and the high voltage ring (30). The insulator (15) is made of Pyrex and decreases in diameter from the ground plane ring (16) to the high voltage ring (30), producing equipotential lines almost perpendicular to the wall (27) of the insulator (15) to optimize the voltage-holding capability of the feedthrough assembly (10).

Vanecek, David L. (Martinez, CA); Pike, Chester D. (Pinole, CA)

1984-01-01

382

Automatic voltage-imbalance detector  

SciTech Connect

A device is described 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, R.E.; McCormick, J.B.; Kerwin, W.J.

1981-05-20

383

Charge-pump voltage converter  

DOEpatents

A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

Brainard, John P. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2009-11-03

384

Voltage-gated ion channels  

Microsoft Academic Search

Voltage-dependent ion channels are membrane proteins that conduct ions at high rates regulated by the voltage across the membrane. They play a fundamental role in the generation and propagation of the nerve impulse and in cell homeostasis. The voltage sensor is a region of the protein bearing charged amino acids that relocate upon changes in the membrane electric field. The

Francisco Bezanilla

2005-01-01

385

Intermediate state trapping of a voltage sensor.  

PubMed

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, Jérôme J; Pless, Stephan A; Maragliano, Luca; Campos, Fabiana V; Galpin, Jason D; Ahern, Christopher A; Roux, Benoît; Bezanilla, Francisco

2012-12-01

386

Evaluation of the effects of selected plant-derived nutraceuticals on the quality and shelf-life stability of raw and cooked pork sausages  

Microsoft Academic Search

The effect of lutein (200?g\\/g meat), sesamol (250?g\\/g meat), ellagic acid (300?g\\/g meat) and olive leaf extract (200?g\\/g meat) on total viable counts (TVC), pH, water holding capacity (WHC), cooking loss, lipid oxidation (thiobarbituric acid-reactive substances, TBARs), colour stability, texture and sensory evaluation of fresh and cooked pork sausages stored in aerobic or modified atmosphere packs (MAP) was investigated. Addition

J. E. Hayes; V. Stepanyan; P. Allen; M. N. O’Grady; J. P. Kerry

2011-01-01

387

Evaluating Chemical Reactivity And Mechanical Stability Of Nano Palladized Iron Embedded In Activated Carbon On Dechlorination Of Polychlorinated Biphenyls  

EPA Science Inventory

Remediation of contaminated sites with hydrophobic organic compounds such as polychlorinated biphenyls (PCBs) remains a scientific and technical challenge. The high stability, low aqueous solubility, and high organic affinity of PCBs make them difficult to treat. Many physical,...

388

Evaluation of efficacy of stabilizers on the thermostability of live attenuated thermo-adapted Peste des petits ruminants vaccines.  

PubMed

In this study, thermo-adapted (Ta) PPR vaccines were assessed for their stability at 25, 37, 40, 42 and 45°C in lyophilized form using two extrinsic stabilizers {lactalbumin hydrolysate-sucrose (LS) and stabilizer E} and in reconstituted form with the diluents (1 mol/L MgSO(4) or 0.85% NaCl). The lyophilized vaccines showed an expiry period of 24-26 days at 25°C, 7-8 days at 37°C and 3-4 days at 40°C. LS stabilizer was superior at 42°C with a shelf-life of 44 h, whereas in stabilizer E, a 40 h shelf-life with a comparable half-life was observed. At 45°C, the half-life in stabilizer E was better than LS and lasted for 1 day. Furthermore, the reconstituted vaccine maintained the titre for 48 h both at 4°C and 25°C and for 24-30 h at 37°C. As both the stabilizers performed equally well with regard to shelf-life and half-life, the present study suggests LS as stabilizer as a choice for lyophilization with 0.85% NaCl diluent, because it has better performance at higher temperature. These Ta vaccines can be used as alternatives to existing vaccines for the control of the disease in tropical countries as they are effective in avoiding vaccination failure due to the breakdown in cold-chain maintenance, as this vaccine is considerably more stable at ambient temperatures. PMID:21979572

Riyesh, Thachamvally; Balamurugan, Vinayagamurthy; Sen, Arnab; Bhanuprakash, Veerakyathappa; Venkatesan, Gnanavel; Yadav, Vinita; Singh, Raj Kumar

2011-10-01

389

Stability of CIGS solar cells and component materials evaluated by a step-stress accelerated degradation test method  

NASA Astrophysics Data System (ADS)

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 15°C and then a 15% relative humidity (RH) increment step, beginning from 40°C/40%RH (T/RH = 40/40) to 85°C/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

390

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

391

Chemical stabilization of medical waste fly ash using chelating agent and phosphates: Heavy metals and ecotoxicity evaluation.  

PubMed

Chemical stabilization of heavy metals in medical waste fly ash has been carried out using the following compounds: a chelating agent (Ashnite S803), a commercial acidic phosphoric acid solution (Ashnite R303) as well as basic one (Ashnite R201). In order to predict the leachability of heavy metals, Japanese Leaching Test (JLT-13) procedure was applied to the stabilized fly ash products. An ecotoxicity assessment of the stabilized fly ash products leachate and the unstabilized fly ash leachate was conducted using a battery of bioassays based on lettuce root elongation inhibition, Daphnia magna mortality and Vibrio fischeri photoinhibition. The results showed that the three stabilizing agents were able to significantly decrease (ANOVA, P < 0.05) the concentration of heavy metals in the leachates. Although the leachate from both stabilized and unstabilized fly ash were very toxic to lettuce and daphnids, the incorporation of these stabilizing agents diminished significantly (ANOVA, P < 0.05) the toxicity of the leachates towards the three tested organisms. Pearson correlation analysis was used to analyze the strength of the relationship between chemical elements concentration in the leachate and bioassays results. Most of the heavy metals in the leachate were significantly correlated (ANOVA, P < 0.05) with the toxicity values of the bioassays. However, the correlation was not found between the concentration of dissolved organic carbon (DOC) and the toxicity effect of the leachate to the tested organisms. PMID:19356916

Sukandar; Padmi, Tri; Tanaka, Masaru; Aoyama, Isao

2009-07-01

392

In vitro evaluation of 9-(2-phosphonylmethoxyethyl)adenine ester analogues, a series of anti-HBV structures with improved plasma stability and liver release.  

PubMed

Chronic hepatitis B virus (HBV) infection may lead to liver cirrhosis and hepatocellular carcinoma, but few drugs are available for its treatment. Acyclic nucleoside phosphonates (ANPs) have remarkable antivirus activities but are not easily absorbed from the gastrointestinal tract and accumulate in the kidneys, resulting in nephrotoxicity. Therefore, there is a need to find effective liver site-specific prodrugs. The dipivaloyloxymethyl ester of 9-(2-phosphonylmethoxyethyl)adenine (PMEA)-adefovir dipivoxil (ADV)-is a first-line therapy drug for chronic hepatitis B with a low therapeutic index because of renal toxicity and low hepatic uptake. In this study, a series of PMEA derivatives were synthesized to enhance plasma stability and liver release. The metabolic stability of ADV (Chemical I) and its two analogues (Chemicals II and III) was evaluated in rat plasma and liver homogenate in vitro. An ion-pair reverse-phase HPLC-UV method and a hybrid ion trap and high-resolution time-of-flight mass spectrometry (LC-IT-TOF-MS) were used to evaluate the degradation rate of the analogues and to identify their intermediate metabolites, respectively. Chemicals I and II were hydrolyzed by cleavage of the C-O bond to give monoesters. Sufficient enzymatic activation in the liver homogenate through a relatively simple metabolic pathway, in addition to a favorable stability profile in rat plasma, made Chemical II an optimal candidate. Next, six analogues based on the structure of Chemical II were synthesized and evaluated in plasma and liver homogenate. Compared to Chemical II, these compounds generated less active PMEA levels in rat liver homogenate. Therefore, chemical modification of Chemical II may lead to new promising PMEA derivatives with enhanced plasma stability and liver activation. PMID:24338503

Liao, Sha; Fan, Shi-Yong; Liu, Qin; Li, Chang-Kun; Chen, Jia; Li, Jing-Lai; Zhang, Zhi-Wei; Zhang, Zhen-Qing; Zhong, Bo-Hua; Xie, Jian-Wei

2014-11-01

393

A Study on a Centralized Under-Voltage Load Shedding Scheme Considering the Load Characteristics  

NASA Astrophysics Data System (ADS)

Under-voltage load shedding is an important measure for maintaining voltage stability.Aiming at the optimal load shedding problem considering the load characteristics,firstly,the traditional under-voltage load shedding scheme based on a static load model may cause the analysis inaccurate is pointed out on the equivalent Thevenin circuit.Then,the dynamic voltage stability margin indicator is derived through local measurement.The derived indicator can reflect the voltage change of the key area in a myopia linear way.Dimensions of the optimal problem will be greatly simplified using this indicator.In the end,mathematical model of the centralized load shedding scheme is built with the indicator considering load characteristics.HSPPSO is introduced to slove the optimal problem.Simulation results on IEEE-39 system show that the proposed scheme display a good adaptability in solving the under-voltage load shedding considering dynamic load characteristics.

Deng, Jiyu; Liu, Junyong

394

Series-stacked medium voltage electronic voltage regulator  

Microsoft Academic Search

This paper discusses the development of a series- stacked medium-voltage electronic voltage regulator for the pur- pose of regulating the voltage on a 22 kV three-phase transmission line. The three-phase regulator consists of three independent 12.75 kV regulator cells, connected in a star configuration. Each regulator cell consists of an autotransformer with one common and two series windings. An AC-to-AC

Males Tomlinson; Dewald Abrie; Toit Mouton

2011-01-01

395

Study on Non Contact Automatic on-Load Voltage Regulating Distributing Transformer Based on Solid State Relay  

Microsoft Academic Search

Automatic on-load voltage regulation of transformer is an effective method to stabilize load voltage. Mechanic contact tap changing switch is not adequate for distributing transformer because of its high cost and low capability. The paper presents the structure and automatic on-load voltage regulating principle of distributing transformer, which employs solid state relay as non contact automatic on-load voltage regulating tap

Zhao-Yulin; Dong-Shoutian; Li-Jiahui; Yao-Xin; Zheng-Na; Liu-Xueli

2006-01-01

396

"Flogging dead horses": evaluating when have clinical trials achieved sufficiency and stability? A case study in cardiac rehabilitation  

PubMed Central

Background Most systematic reviews conclude that another clinical trial is needed. Measures of sufficiency and stability may indicate whether this is true. Objectives: To show how evidence accumulated on centre-based versus home-based cardiac rehabilitation, including estimates of sufficiency and stability Methods Systematic reviews of clinical trials of home versus centre-based cardiac rehabilitation were used to develop a cumulative meta-analysis over time. We calculated the standardised mean difference (SMD) in effect, confidence intervals and indicators of sufficiency and stability. Sufficiency refers to whether the meta-analytic database adequately demonstrates that an intervention works - is statistically superior to another. It does this by assessing the number of studies with null results that would be required to make the meta-analytic effect non-statistically significant. Stability refers to whether the direction and size of the effect is stable as new studies are added to the meta-analysis. Results The standardised mean effect difference reduced over fourteen comparisons from a non-significant difference favouring home-based cardiac rehabilitation to a very small difference favouring hospital (SMD -0.10, 95% CI -0.32 to 0.13). This difference did not reach the sufficiency threshold (failsafe ratio 0.039 < 1) but did achieve the criteria for stability (cumulative slope 0.003 < 0.005). Conclusions The evidence points to a relatively small effect difference which was stable but not sufficient in terms of the suggested thresholds. Sufficiency should arguably be based on substantive significance and decided by patients. Research on patient preferences should be the priority. Sufficiency and stability measures are useful tools that need to be tested in further case studies. PMID:21418648

2011-01-01

397

Evaluation of colour stability of provisional restorative materials exposed to different mouth rinses at varying time intervals: an in vitro study.  

PubMed

The most important factor affecting esthetics is colour. Whether a definitive prosthesis or a provisional restoration, maintenance of esthetics is of prime concern along with restoration of function. Colour stability of provisional prosthesis is affected by various factors and various studies are documented in the literature on this. The purpose of this study was to evaluate the colour stability of provisional restorative materials exposed to different mouth rinses at varying time intervals. 120 discs, each of self cure tooth moulding material, Protemp 4 and Revotek LC were prepared and immersed in two mouth rinses, hexidine and periogard and evaluated for their colour stability after 1 week, 1 and 3 months. The data obtained was statistically analysed using ANOVA and Tukey's post hoc analysis. The results indicate that there is a significant difference in the colour variation of various materials in two different mouth rinses at different time intervals. Revotek LC was found to be the most colour stable material and periogard had the least staining potential at varying time intervals. PMID:24605003

Prasad, D Krishna; Alva, Harshitha; Shetty, Manoj

2014-03-01

398

Evaluation by step response tests of prototype relief valves designed for YF-12 inlet stability bleed system  

NASA Technical Reports Server (NTRS)

Two stability bleed system relief valves were tested in a special dynamic test facility. These poppet valves are prototypes for a stability bleed system designed for use in a YF-12 flight inlet. One valve is unshielded, while the other has a special shield to eliminate the flow effect pressures on the piston. The tests determined the size of a damping orifice to be used during wind tunnel tests of the bleed system and verified an analog simulation of the valves. The effects of initial pressure level, pressure step size, and spring rate were investigated.

Dustin, M. O.; Neiner, G. H.

1975-01-01

399

Analytical investigation of the pull-in voltage in capacitive mechanical sensors  

Microsoft Academic Search

A MEMS capacitive sensor is basically an electrostatic transducer and an analytical approach to evaluate the pull-in voltage associated with a clamped circular plate or a circular membrane due to a bias voltage is presented. The approach is based on a linearized uniform approximation of the nonlinear electrostatic force due to a bias voltage and the use of a 2D

J. Lardiès; M. Berthillier; F. M. L. Bellaredj

2011-01-01

400

System voltage potential-induced degradation mechanisms in PV modules and methods for test  

Microsoft Academic Search

Over the past decade, degradation and power loss have been observed in PV modules resulting from the stress exerted by system voltage bias. This is due in part to qualification tests and standards that do not adequately evaluate for the durability of modules to the long-term effects of high voltage bias experienced in fielded arrays. High voltage can lead to

Peter Hacke; Kent Terwilliger; Ryan Smith; Stephen Glick; Joel Pankow; Michael Kempe; Sarah Kurtz Ian Bennett; Mario Kloos

2011-01-01

401

Fuzzy Based Digital Automatic Voltage Regulator of a Synchronous Generator with Unbalanced Loads  

Microsoft Academic Search

Voltage stability and power quality of the electrical systems depend on proper operation of the Automatic Voltage Regulators (AVR) of generators. Nowadays, design technology of the AVRs is being broadly improved. According to wide range operating conditions of the generators and loads, the fuzzy AVRs are going to be the modern type of regulators, particularly, for the genset alternators operating

A. Darabi; S. A. Soleamani; A. Hassannia

2008-01-01

402

High voltage feedthrough bushing  

DOEpatents

A feedthrough bushing for a high voltage diode provides for using compression sealing for all sealing surfaces. A diode assembly includes a central conductor extending through the bushing and a grading ring assembly circumferentially surrounding and coaxial with the central conductor. A flexible conductive plate extends between and compressively seals against the central conductor and the grading ring assembly, wherein the flexibility of the plate allows inner and outer portions of the plate to axially translate for compression sealing against the central conductor and the grading ring assembly, respectively. The inner portion of the plate is bolted to the central conductor for affecting sealing. A compression beam is also bolted to the central conductor and engages the outer portion of the plate to urge the outer portion toward the grading ring assembly to obtain compression sealing therebetween.

Brucker, John P. (Espanola, NM)

1993-01-01

403

Substation voltage upgrading  

SciTech Connect

This report addresses specific issues to support sound yet not unduly conservative uprating practices for substations. The main parts of the report cover the insulation withstand and overvoltage protection aspects, environmental measurements, reliability criteria, and industry experience. First the insulation design concerns are addressed. Substation stress by a backflashover of the line insulation due to lightning in the vicinity of the substation is recognized as a critical stress. A representative part of a 550 kV BIL substation was erected at the EPRI High Voltage Transmission Research Center, where also a special test circuit was assembled to produce a fast front, slow tail (0.2/200 {mu}s) wave. The substation as well as some special configurations were tested for line-to-ground and line-to-line withstand. Computer studies were performed to complement the test results. A number of important conclusions was reached. The most prominent result in that the high frequency oscillations, as caused by reflections within the substation, do not effect the Critical Flashover Voltage (CFO). The present practice, based on the highest peak is therefore very conservative. The slow tail of the wave appears to dictate the CFO. An arrester model for computer studies to represent very fast as well as slow phenomena was derived. It is based on full scale arrester test data, made available in this project. The computer program to calculate arrester model parameters is also a part of the report. The electric environmental measurements are reported for the tested substation at the HVTRC and for the uprated substation of Public Service Company of Colorado, both before and after the uprating. The performance is satisfactory when corona free hardware is used. Insulation design criteria are analyzed based on substation reliability, the system viewpoint and consequences of the failure. Utility experience with uprated substations is reviewed.

Panek, J.; Elahi, H.; Lux, A.; Imece, A.F. (General Electric Co., Schenectady, NY (United States). Power Systems Engineering Dept.); LaPanse, R.A.; Stewart, J.R. (Public Service Co. of Colorado, Denver, CO (United States))

1992-04-01

404

Evaluation of the geological relationships to gas hydrate formation and stability. Second annual technical progress report, October 1, 1985--September 30, 1986  

SciTech Connect

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

Not Available

1986-12-31

405

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...

406

Effects of stabilizing agents on the development of myricetin nanosuspension and its characterization: An in vitro and in vivo evaluation.  

PubMed

Although myricetin has various pharmacological applications, it shows low oral bioavailability (<10%) in rats due to its poor aqueous solubility. To overcome this issue, myricetin nanosuspensions were developed and the effects of stabilizers were investigated. Based on the particle size and zeta potential, stabilizers soya lecithin, TPGS, HP-?-CD, and/or a combination thereof were used. The prepared nanosuspensions were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray powder diffraction (XRD). The resulting myricetin nanosuspensions contained particles in the size range of 300-500nm and were physically stable. Myricetin was partially transformed from crystalline to amorphous forms in the presence of different excipients after the nanosizing process. The solubility and in vitro dissolution of all myricetin nanosuspensions were greatly increased compared with those of the myricetin powder. Consequently, the relative bioavailability in rats were 2.44, 3.57, 1.61, and 2.96 for nanosuspensions stabilized with TPGS, soya lecithin, soya lecithin+TPGS, and HP-?-CD+TPGS, respectively, relative to that of the coarse myricetin. This research demonstrated that nanosuspension is a promising strategy for delivering poor water-soluble drugs such as myricetin and that stabilizers played a critical role in the formulation design of myricetin nanosuspensions. PMID:25445518

Hong, Chao; Dang, Yang; Lin, Guobei; Yao, Yashu; Li, Guowen; Ji, Guang; Shen, Hongyi; Xie, Yan

2014-12-30

407

Voltage-gated ion channels.  

PubMed

Voltage-dependent ion channels are membrane proteins that conduct ions at high rates regulated by the voltage across the membrane. They play a fundamental role in the generation and propagation of the nerve impulse and in cell homeostasis. The voltage sensor is a region of the protein bearing charged amino acids that relocate upon changes in the membrane electric field. The movement of the sensor initiates a conformational change in the gate of the conducting pathway thus controlling the flow of ions. Major advances in molecular biology, spectroscopy, and structural techniques are delineating the main features and possible structural changes that account for the function of voltage-dependent channels. PMID:15816170

Bezanilla, Francisco

2005-03-01

408

High-and Extra-High-Voltage Substation Design and Economic Comparisons  

Microsoft Academic Search

Analytical techniques for comparing high-and extra-high-voltage substation schemes for 161 kv, 230 kv, 345 kv, and 500 kv are evaluated, not only between voltages, but also between a series of layouts at any given voltage. Detailed cost data voltages are listed. Analyses showing the effects on costs of varying one or several en gineering parameters provide additional guides for such

G. E. Hertig

1962-01-01

409

The number of feedbacks needed for reliable evaluation. A multilevel analysis of the reliability, stability and generalisability of students’ evaluation of teaching  

Microsoft Academic Search

A multilevel analysis approach was used to analyse students’ evaluation of teaching (SET). The low value of inter-rater reliability stresses that any solid conclusions on teaching cannot be made on the basis of single feedbacks. To assess a teacher’s general teaching effectiveness, one needs to evaluate four randomly chosen course implementations. Two implementations are needed when one course is evaluated,

Pekka Rantanen

2012-01-01

410

Evaluation of Sample Stability and Automated DNA Extraction for Fetal Sex Determination Using Cell-Free Fetal DNA in Maternal Plasma  

PubMed Central

Objective. The detection of paternally inherited sequences in maternal plasma, such as the SRY gene for fetal sexing or RHD for fetal blood group genotyping, is becoming part of daily routine in diagnostic laboratories. Due to the low percentage of fetal DNA, it is crucial to ensure sample stability and the efficiency of DNA extraction. We evaluated blood stability at 4°C for at least 24 hours and automated DNA extraction, for fetal sex determination in maternal plasma. Methods. A total of 158 blood samples were collected, using EDTA-K tubes, from women in their 1st trimester of pregnancy. Samples were kept at 4°C for at least 24 hours before processing. An automated DNA extraction was evaluated, and its efficiency was compared with a standard manual procedure. The SRY marker was used to quantify cfDNA by real-time PCR. Results. Although lower cfDNA amounts were obtained by automated DNA extraction (mean 107,35?GE/mL versus 259,43?GE/mL), the SRY sequence was successfully detected in all 108 samples from pregnancies with male fetuses. Conclusion. We successfully evaluated the suitability of standard blood tubes for the collection of maternal blood and assessed samples to be suitable for analysis at least 24 hours later. This would allow shipping to a central reference laboratory almost from anywhere in Europe. PMID:24222898

Ordoñez, Elena; Rueda, Laura; Cañadas, M. Paz; Fuster, Carme; Cirigliano, Vincenzo

2013-01-01

411

Current vs. Voltage Feedback Amplifiers  

E-print Network

Current vs. Voltage Feedback Amplifiers One question continuously troubles the analog design engi- neer: 'Which amplifier topology is better for my application, current feedback or voltage feedback) are not apparent. Today's CFB and VFB amplifiers have comparable performance, but there are cer- tain unique

Lanterman, Aaron

412

Temperature controlled high voltage regulator  

DOEpatents

A temperature controlled high voltage regulator for automatically adjusting the high voltage applied to a radiation detector is described. The regulator is a solid state device that is independent of the attached radiation detector, enabling the regulator to be used by various models of radiation detectors, such as gas flow proportional radiation detectors.

Chiaro, Jr., Peter J. (Clinton, TN); Schulze, Gerald K. (Knoxville, TN)

2004-04-20

413

How membrane proteins sense voltage  

Microsoft Academic Search

The ionic gradients across cell membranes generate a transmembrane voltage that regulates the function of numerous membrane proteins such as ion channels, transporters, pumps and enzymes. The mechanisms by which proteins sense voltage is diverse: ion channels have a conserved, positively charged transmembrane region that moves in response to changes in membrane potential, some G-protein coupled receptors possess a specific

Francisco Bezanilla

2008-01-01

414

Predicting Therapeutic Template by Evaluating the Structural Stability of Anti-Cancer Peptides—A Computational Approach  

Microsoft Academic Search

Clinically significant antibiotic resistance has evolved against virtually every antibiotic deployed. Yet the development\\u000a of new classes of antibiotics has lagged far behind our growing need for such drugs. Antimicrobial peptides (AMPs) have emerged\\u000a as novel therapeutics hailed for their bactericidal and immunomodulatory properties. However, the process of optimizing antimicrobial\\u000a peptide stability, using large peptide libraries is both tedious and

K. Ramanathan; V. Shanthi; R. Rajasekaran; C. Sudandiradoss; C. George Priya Doss; Rao Sethumadhavan

2011-01-01

415

Thermal stability of GaAs heteroface solar cells with differing contact materials  

NASA Technical Reports Server (NTRS)

GaAlAs/GaAs heteroface solar cells used in space offer advantages of higher operating temperatures and recovery from radiation damage using thermal annealing. Elevated temperature experiments were conducted to evaluate the electrical stability of cells with different contact materials. These experiments indicate that for operation of GaAs heteroface solar cells at elevated temperatures, front contact metals must be carefully chosen. The short circuit current varied by only about 3% for cells with Pd/Ag contacts that were heated to 240 C for a total of 500 hours. However, a total decrease in the open circuit voltage of about 20% was observed for these cells. After heating cells to 400 C, large changes in open circuit voltage were observed for cells with Pd/Ag, Pd/Au, Pd, Ag, and Ti contacts; however, preliminary results indicate more stable open circuit voltages for cells with Au, Cr, Zn, and Cr/Au contacts.

Friesen, W. J.; Walker, G. H.; Conway, E. J.

1981-01-01

416

Evaluation of sulfidic mine tailings solidified/stabilized with cement kiln dust and fly ash to control acid mine drainage  

SciTech Connect

In the present research, industrial byproducts, namely, cement kiln dust (CKD) and Class C fly ash (FAC) have been used as candidate materials along with the partial addition of sulfate-resistant cement (SRC) in the Stabilization/solidification of polymetallic sulfidic mine tailings (MT). The effectiveness of S/S was assessed by comparing laboratory experimental values obtained from unconfined compressive strength, hydraulic conductivity and leaching propensity tests of S/S samples with regulatory standards for safe surface disposal of such wastes. Despite general regulatory compliance of compressive strength and hydraulic conductivity, some solidified/stabilized-cured matrices were found unable to provide the required immobilization of pollutants. Solidified/stabilized and 90-day cured mine tailings specimens made with composite binders containing (10% CKD + 10% FAC), (5% SRC + 15% FAC) and (5% SRC + 5% CKD + 10% FAC) significantly impaired the solubility of all contaminants investigated and proved successful in fixing metals within the matrix, in addition to achieving adequate unconfined compressive strength and hydraulic conductivity values, thus satisfying USEPA regulations. Laboratory investigations revealed that, for polymetallic mining waste, leachate concentrations are the most critical factor in assessing the effectiveness of S/S technology.

Nehdi, M.; Tariq, A. [University of Western Ontario, London, ON (Canada). Dept. of Civil & Environmental Engineering

2008-11-15

417

Comparative evaluation of rumen-protected fat, coconut oil and various oilseeds supplemented to fattening bulls. 2. Effects on composition and oxidative stability of adipose tissues.  

PubMed

The effects of five different dietary fat supplements on fatty acid composition and oxidative stability of subcutaneous and kidney fat were evaluated in 36 Brown Swiss bulls and compared to a low fat diet in a monofactorial design. The following fat supplements were provided as additional fat at 30 g per kg feed dry matter: crystalline rumen-protected fat, coconut oil, and three types of crushed whole oilseeds (rapeseed, sunflower seed and linseed). Adipose tissues reflected differences (P < 0.05) in dietary fatty acid composition although to a lower extent. Using protected fat, which contained elevated levels of trans fatty acids, and sunflower seed, containing a high proportion of linoleic acid, significantly increased C18:1 trans fatty acid proportion in the adipose tissues. The use of sunflower seed increased conjugated linoleic acid. The oilseeds resulted in lower amounts of C16:0 in favour of C18:0. Except for linseed, all fat supplemented groups improved oxidative stability of adipose tissues as compared with control. This was explained by lower proportions of unsaturated fatty acids in adipose tissue (protected fat), by elevated alpha-tocopherol contents (rapeseed, sunflower seed) or by a combination of both (coconut oil). Fat colour remained unaffected by treatments. Compared to other fat supplements oilseeds, especially sunflower seed and rapeseed, can therefore be recommended to be fed to bulls in order to increase the proportions of C18 unsaturated fatty acids in adipose tissues and to maintain or improve oxidative stability. PMID:10836256

Casutt, M M; Scheeder, M R; Ossowski, D A; Sutter, F; Sliwinski, B J; Danilo, A A; Kreuzer, M

2000-01-01

418

Application of an asymmetric finite element model of the C2-T1 cervical spine for evaluating the role of soft tissues in stability.  

PubMed

Different finite element models of the cervical spine have been suggested for evaluating the roles of ligaments, facet joints, and disks in the stability of cervical spine under sagittal moments. However, no comprehensive study on the response of the full cervical spine that has used a detailed finite element (FE) model (C2-T1) that considers the asymmetry about the mid-sagittal plane has been reported. The aims of this study were to consider asymmetry in a FE model of the full cervical spine and to investigate the influences of ligaments, facet joints, and disk nucleus on the stability of the asymmetric model during flexion and extension. The model was validated against various published in vitro studies and FE studies for the three main loading planes. Next, the C4-C5 level was modified to simulate different cases to investigate the role of the soft tissues in segmental stability. The FE model predicted that excluding the interspinous ligament (ISL) from the index level would cause excessive instability during flexion and that excluding the posterior longitudinal ligament (PLL) or the ligamentum flavum (LF) would not affect segmental rotation. During extension, motion increased when the facet joints were excluded. The model without disk nucleus was unstable compared to the intact model at lower loads and exhibited a similar rotation response at higher loads. PMID:24641811

Erbulut, D U; Zafarparandeh, I; Lazoglu, I; Ozer, A F

2014-07-01

419

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

420

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

421

The Number of Feedbacks Needed for Reliable Evaluation. A Multilevel Analysis of the Reliability, Stability and Generalisability of Students' Evaluation of Teaching  

ERIC Educational Resources Information Center

A multilevel analysis approach was used to analyse students' evaluation of teaching (SET). The low value of inter-rater reliability stresses that any solid conclusions on teaching cannot be made on the basis of single feedbacks. To assess a teacher's general teaching effectiveness, one needs to evaluate four randomly chosen course implementations.…

Rantanen, Pekka

2013-01-01

422

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

423

Synthesis and evaluation of novel lipidated neuromedin U analogs with increased stability and effects on food intake.  

PubMed

Neuromedin U (NMU) is a 25 amino acid peptide expressed and secreted in the brain and gastrointestinal tract. Data have shown that peripheral administration of human NMU decreases food intake and body weight and improves glucose tolerance in mice, suggesting that NMU receptors constitute a possible anti-diabetic and anti-obesity drug target. However, the clinical use of native NMU is hampered by a poor pharmacokinetic profile. In the current study, we report in vitro and in vivo data from a series of novel lipidated NMU analogs. In vitro plasma stability studies of native NMU were performed to investigate the proteolytic stability and cleavage sites using LC-MS. Native NMU was found to be rapidly cleaved at the C-terminus between Arg(24) and Asn(25) , followed by cleavage between Arg(16) and Gly(17) . Lipidated NMU analogs were generated using solid-phase peptide synthesis, and in vitro potency was investigated using a human embryonic kidney 293-based inositol phosphate accumulation assay. All lipidated analogs had preserved in vitro activity on both NMU receptors with potency improving as the lipidation site was moved away from the receptor-interacting C-terminal octapeptide segment. In vivo efficacy was assessed in lean mice as reduction in food intake after acute subcutaneous administration of 1, 0.3, 0.1, and 0.03?µmol/kg. These lipidated NMU analogs prolonged the anorectic effect of NMU in a dose-dependent manner. This was likely an effect of improved pharmacokinetic properties because of improved vitro plasma stability. Accordingly, the data demonstrate that lipidated NMU analogs may represent drug candidates for the treatment of obesity. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd. PMID:25521062

Dalbøge, Louise S; Pedersen, Søren L; van Witteloostuijn, Søren B; Rasmussen, Jakob E; Rigbolt, Kristoffer T G; Jensen, Knud J; Holst, Birgitte; Vrang, Niels; Jelsing, Jacob

2015-02-01

424

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

425

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

426

Physical modeling of river spanning rock structures: Evaluating interstitial flow, local hydraulics, downstream scour development, and structure stability  

USGS Publications Warehouse

Rock weir and ramp structures uniquely serve a necessary role in river management: to meet water deliveries in an ecologically sound manner. Uses include functioning as low head diversion dams, permitting fish passage, creating habitat diversity, and stabilizing stream banks and profiles. Existing information on design and performance of in-stream rock structures does not provide the guidance necessary to implement repeatable and sustainable construction and retrofit techniques. As widespread use of rock structures increases, the need for reliable design methods with a broad range of applicability at individual sites grows as well. Rigorous laboratory testing programs were implemented at the U.S. Bureau of Reclamation (Reclamation) and at Colorado State University (CSU) as part of a multifaceted research project focused on expanding the current knowledge base and developing design methods to improve the success rate of river spanning rock structures in meeting project goals. Physical modeling at Reclamation is being used to measure, predict, and reduce interstitial flow through rock ramps. CSU is using physical testing to quantify and predict scour development downstream of rock weirs and its impact on the stability of rock structures. ?? 2009 ASCE.

Collins, K.L.; Thornton, C.I.; Mefford, B.; Holmquist-Johnson, C. L.

2009-01-01

427

Evaluation of cholecystokinin (CCK-8) peptide thermal stability for use as radiopharmaceutical by means isothermal and nonisothermal approaches.  

PubMed

The purpose of this research was to study the thermal stability of cholecystokinin octapeptide (CCK-8) in aqueous solution at pH 12 and ionic strength 0.01 M, which were kept as constants, by using isothermal and nonisothermal methods. The isothermal decomposition of CCK-8 was investigated as a function of temperature (40 degrees C to 70 degrees C). Nonisothermal stability studies were performed using a linear increasing temperature program. Two different nonisothermal studies were carried out at 0.25 degrees K and 0.5 degrees K per hour, and the temperature interval varied from 40 degrees C to 82 degrees C. The degradation of CCK-8 followed first-order kinetics, obeying the Arrhenius equation in the experimental temperature range. This indicated that the degradation mechanism of CCK-8 could be the equal within the temperature range studied. The nonisothermal approach resulted in activation energy (Ea) and shelf-life (t90%) values that agree well with those obtained by the isothermal method. The level of uncertainty in the estimates of t90% and Ea values is determined mainly by the extent of drug degradation and temperature change during the experiment. Therefore, nonisothermal experiments save time, labor and materials (i.e. the amount of drugs necessary to conduct the experiment) compared to the classic isothermal experiments, if they are performed using a suitable experimental design and a precise analytical method. PMID:16954107

Oliva, A; Hidalgo, M; Alvarez, C; Llabrés, M; Fariña, J B

2006-09-01

428

76 FR 70721 - Voltage Coordination on High Voltage Grids; Notice of Staff Workshop  

Federal Register 2010, 2011, 2012, 2013, 2014

...Regulatory Commission [Docket No. AD12-5-000] Voltage Coordination on High Voltage Grids; Notice of Staff Workshop Take notice...will hold a Workshop on Voltage Coordination on High Voltage Grids on Thursday, December 1, 2011 from...

2011-11-15

429

Coordination of Voltage and Frequency Feedback in Load-Frequency Control Capability of Wind Turbine  

E-print Network

role and the importance of the rotor angle stability as a key criterion in power system stability/reactive power balance and subsequently participation in frequency/voltage regulation is assigned to VSWTs [2 energy stored in spinning rotor proportional to grid frequency gradient for primary frequency control

Silva, Filipe Faria Da

430

Stability, Boundedness, and Lagrange Stability of Fractional Differential Equations with Initial Time Difference  

PubMed Central

Differential inequalities, comparison results, and sufficient conditions on initial time difference stability, boundedness, and Lagrange stability for fractional differential systems have been evaluated. PMID:24693255

Çiçek, Muhammed; Yakar, Co?kun; O?ur, Bülent

2014-01-01

431

Voltage-Gated K Channels  

NSDL National Science Digital Library

This STKE review discusses the structural basis for the selectivity and voltage-dependent gating of the voltage-gated K channel. Ion channels and the electrical properties they confer on cells are involved in every human characteristic that distinguishes us from the stones in a field. Every perception, thought, movement, and heartbeat depends on electrical signals generated by the activity of ion channels. These membrane proteins must show specificity for particular ionic species, facilitate the rapid movement of the selected ions across the cell membrane, and open and shut (gate) in response to appropriate signals. Such gating signals may include changes in the voltage across the cell membrane, mechanical deformation of the membrane, and various chemicals. This review, which focuses on voltage-gated K channels, goes from early views of the relationship between ion channel structure and function to our current picture of how selectivity, conduction, and gating are achieved. This review has eight figures and 56 references.

Clay M. Armstrong (University of Pennsylvania; Department of Physiology REV)

2003-06-24

432

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

433

Saving Megawatts with Voltage Optimization  

E-print Network

that had been installed at several electric utility distribution substations in the U.S. and Canada. These systems, being operated in Conservation Voltage Regulation mode, have provided significant energy conservation where they have been installed...

Wilson, T.; Bell, D.

2010-01-01

434

Voltage tunable microwave ferrite resonator  

E-print Network

A novel method of implementing a tunable resonator using an applied voltage is presented. Stress is used to tune a microstrip resonator fabricated on a polycrystalline ferrite substrate. The stress was applied either ...

Oates, Daniel E.

435

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

436

High voltage lightning grounding device  

NASA Technical Reports Server (NTRS)

Grounding device insertion in wire termination cabinets and terminal block modification prevent lightning-induced high voltage transients from reaching inputs or outputs of solid state instruments and control systems. Installation minimizes wiring confusion and achieves 100 percent protection.

Hoffman, R. G.; Peterson, V. S.

1971-01-01

437

Radio frequency induced hyperthermia mediated by dextran stabilized LSMO nanoparticles: in vitro evaluation of heat shock protein response  

NASA Astrophysics Data System (ADS)

Dextran stabilized La0.7Sr0.3MnO3 (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.

Bhayani, K. R.; Rajwade, J. M.; Paknikar, K. M.

2013-01-01

438

Monitoring and evaluating the stability of soil slopes: A review on various available methods and feasibility of acoustic emission technique  

NASA Astrophysics Data System (ADS)

Landslide is considered as one of the major natural hazards that cause enormous social and economic losses. Some techniques have been introduced to monitor the stability of slopes, such as the global positioning system (GPS), the geographic information system (GIS), aerial photography, and inclinometers. Each one of these offers advantages against others, but at the same time also possesses different limitations. Acoustic emission (AE) has recently been recognized as one of the feasible techniques to monitor soil slope. This article addresses issues involved in application of AE techniques for soil slope monitoring. If it is properly instrumented, AE could provide effective solutions for detecting early activities related to landslide development and giving early warning to such failures.

Zaki, Ahmad; Chai, Hwa Kian; Razak, Hashim Abdul; Shiotani, Tomoki

2014-09-01

439

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