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1

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

2

Voltage stability in weak connection wind farms  

Microsoft Academic Search

The total operating wind power capacity in the world increases fast, and these types of generating units also bring new opportunities and problems to the utilities and customers. It becomes necessary and important to evaluate their impact on the electrical network voltage stability, especially for weak connected systems. This paper uses the detailed wind energy conversion system and the full

Fengquan Zhou; G. Joos; C. Abbey

2005-01-01

3

A linear static voltage stability margin for radial distribution systems  

Microsoft Academic Search

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

M. H. Hauqe

2006-01-01

4

Wide-Area Stability and Voltage Control  

Microsoft Academic Search

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

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

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

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

Microsoft Academic Search

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

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

2010-01-01

7

Stability of high voltage modulators for nonlinear loads  

Microsoft Academic Search

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 gyrotrons are connected in parallel to a single modulator. With all gyrotrons hooked to a common

C. J. Pawley; J. Tooker; J. Peavy; W. P. Gary; A. Nerem; D. Hoyt; J. Lohr

2003-01-01

8

Enhancing Voltage Stability of Radial Distribution Systems by Network Reconfiguration  

Microsoft Academic Search

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

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

2005-01-01

9

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

Microsoft Academic Search

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

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

1999-01-01

10

Facts allocation for power systems voltage stability enhancement using MOPSO  

Microsoft Academic Search

Location of the static VAR compensator (SVC) and other types of FACTS devices is important for the enhancement of practical power systems voltage stability. In this paper, a Multi-objective particle swarm optimization (MOPSO) is used to solve a mixed continuous-discrete multi-objective optimization problem in order to find optimal location of FACTS. Various objectives are considered, namely voltage stability improvement, real

A. Laifa; M. Boudour

2008-01-01

11

Evaluation of pulse voltage generators  

SciTech Connect

In this paper, the electrical characteristics of the positive pulsed corona in a wire-cylinder type reactor are investigated. The injected energy and charge into the discharging volume per pulse and per unit length of corona emitting wire are adopted to evaluate the power source, electric circuits, and the corona wire. The discharging current lasts from several hundred nanoseconds to a few microseconds. The current, power peak values, and the injected energy and charge per pulse per unit length of emitting wire can reach up to 60 A/m, 5 MW/m, 480 mJ/m, and 8 {mu}C/m, respectively. The energy conversion efficiency related to the output energy from the pulse forming capacitor and the energy delivered to the discharging volume can reach up to 90%. All results are obtained at room temperature and in air. Pilot and laboratory tests have indicated significant technical and economical advantages of the cleaning processes based on pulse corona discharges compared to the traditional processes. They also put in evidence that the energy required by the process represents the largest operating cost and that the energy efficiency of the voltage pulse generator represents a key factor for the economical competitiveness of the process. The overall energy consumption needed to promote chemical oxidation is determined by the reactivity of the induced reactions and by the energy conversion efficiency from the main power source to the streamers of corona discharge. It is supposed that various physical and chemical phenomena, in addition to direct radical production, plays an important role in the simultaneous oxidation of SO{sub 2} and NO{sub x}.

Rea, M. [Univ. of Padova (Italy). Dept. of Electrical Engineering] [Univ. of Padova (Italy). Dept. of Electrical Engineering; Yan, K. [Beijing Inst. of Technology (China). Dept. of Applied Physics] [Beijing Inst. of Technology (China). Dept. of Applied Physics

1995-05-01

12

Temperature stability of components for over-voltage protection of low-voltage systems  

Microsoft Academic Search

Summary form only given. The aim of this paper is to find over-voltage component which have the best temperature stability characteristics. We examined the influence on temperature variation of characteristics on following over-voltage components: 1) transient suppresser diodes (TSD), 2) metal-oxide varistors, 3) gas filled surge arresters (GFSA) and 4) polycarbon capacitors. According to experimental results we can conclude that

B. Loncar; P. Osmokrovic; S. Stankovic

2001-01-01

13

Lyapunov stability of multimachine power systems considering the voltage regulator  

Microsoft Academic Search

A new decomposition–aggregation approach is developed, in the paper, to perform transient stability analysis of an N-machine power system. Considering the generator flux decay effect, non-uniform mechanical damping, transfer conductances and the automatic voltage regulator action, the system mathematical model is derived. It is obtained a system aggregation (square) matrix of the order (N?1)\\/2, stability of this matrix implies asymptotic

H. Shaaban

2002-01-01

14

Application of SMES in wind farm to improve voltage stability  

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

15

Economic generation direction for power system static voltage stability  

Microsoft Academic Search

This paper compares various generation direction methods in static voltage stability study in power systems. A new approach, namely economic generation direction (EGD) approach, is proposed to find the generation direction that minimizes the total operating cost. The proposed method is compared with conventional and the most recent generation direction methods, namely maximum loading margin and optimal generation direction methods,

A. Sode-Yome; N. Mithulananthan; Kwang Y. Lee

2006-01-01

16

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

17

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

18

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

19

Power flow study and voltage stability analysis for distribution systems with distributed generation  

Microsoft Academic Search

The voltage instability phenomena may occur in distribution networks. The decline of voltage stability level will restrict the increase of load served by distribution companies. Distributed generation (DG) is increasingly drawing great attention of people. The development of DGs will bring new chances to traditional power systems. DGs connected to distribution networks are potential to improve the system voltage stability.

Haiyan Chen; Jinfu Chen; Dongyuan Shi; Xianzhong Duan

2006-01-01

20

A precision CMOS voltage reference with enhanced stability for the application to advanced VLSI's  

Microsoft Academic Search

A precision CMOS voltage reference circuit is very important for the design of the stable voltage down converter of the high density VLSIs. By using the active mode operation of the component MOS transistors a CMOS bandgap type reference voltage circuit was redesigned for the enhancement of the circuit stability against the internal noises. The voltage supply independence, temperature independence

Hoi-Jun Yoo; Seung-Jun Lee; Jeong-Tae Kwon; Wi-Sik Min; Kye-Hwan Oh

1993-01-01

21

A precision CMOS voltage reference with enhanced stability for the application to advanced VLSIs  

Microsoft Academic Search

A precision CMOS voltage reference circuit is very important for the design of the stable voltage-down converter of high density VLSIs. By using the active mode operation of the component MOS transistors, a CMOS bandgap type reference voltage circuit is redesigned for the enhancement of the circuit stability against the internal noises. The voltage supply independence, temperature independence and the

Hoi-Jun Yoo; Seung-Jun Lee; Jeong-Tae Kwon; W.-S. Min; Kye-Hwan Oh

1993-01-01

22

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

23

Stability Analysis of a Three Terminal High Voltage Direct Current Power Transmission System.  

National Technical Information Service (NTIS)

The objective of this project was to investigate how individual system parameters affect the operation and stability of a three terminal HVDC (high voltage direct current) power system. In order to obtain the desired information, system stability boundary...

J. E. Teles D. P. Carroll

1975-01-01

24

Voltage stability and sensitivity analysis of grid-connected photovoltaic systems  

Microsoft Academic Search

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

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

2011-01-01

25

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

NASA Astrophysics Data System (ADS)

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

Alavian Mehr, Alireza

26

Application of an ANN based voltage stability assessment tool to restructured power systems  

Microsoft Academic Search

This paper presents an ANN based method for assessing the effect of various transactions on the voltage stability margins at the most vulnerable load buses in a restructured power system operated in a combined pool and bilateral transaction modes regime. The most vulnerable load buses of the system from voltage stability point of view are first identified by a modal

Bhavik Suthar; R. Balasubramanian

2007-01-01

27

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

Microsoft Academic Search

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

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

2006-01-01

28

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

Microsoft Academic Search

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

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

2010-01-01

29

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

Microsoft Academic Search

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

Sayonsom Chanda; Bappa Das

2011-01-01

30

Evaluation of different strategies for series voltage sag compensation  

Microsoft Academic Search

Power quality (PQ) is one of the most important issues of modern electrical distribution. Power electronics can play a very significant role in the correction of PQ problems. This paper deals with the evaluation of different control strategies applied to a dynamic voltage restorer (DVR) for the mitigation of voltage sags. The objective is to analyse the influence of the

I. Etxeberria-Otadui; U. Viscarret; S. Bacha; M. Caballero; R. Reyero

2002-01-01

31

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

32

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

Microsoft Academic Search

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

M. Arun; P. Aravindhababu

2009-01-01

33

Voltage stabilization in connection of wind farms to transmission network using VSC-HVDC  

Microsoft Academic Search

This paper investigates possible improvements of grid voltage stability in connection of 40 MW wind farm to transmission network using VSC-HVDC. The 40 MW wind farm comprises 20 individual 2 MW permanent magnet synchronous generators. The voltage at the transmission network terminal should be re-established with minimized power losses during wind speed fluctuations and after the clearance of grid side

Hanif Livani; Javad Rouhi; Hossein Karimi-Davijani

2008-01-01

34

Evaluation of epoxy based nanodielectrics for high voltage outdoor insulation  

Microsoft Academic Search

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

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

2010-01-01

35

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

Microsoft Academic Search

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

Eknath Vittal; Mark O'Malley; Andrew Keane

2010-01-01

36

Frequency stabilization of a GaAIAs semiconductor laser by voltage control.  

PubMed

A single-mode GaAlAs laser is frequency stabilized by keeping the injection current and the voltage across the laser constant. A long-term frequency stability of 7 x 10(-8) and a reproducibility of 3 x 10(-7) were obtained. PMID:20725295

Ludvigsen, H; Holmilund, C; Ikonen, E; Junttila, M L

1992-06-20

37

Stability of the Fast Voltage Control Loop in DC-DC Converters  

Microsoft Academic Search

This paper describes a method for stability analysis and design of a fast voltage loop in DC-DC converters. The method is based on the Popov criterion, which unifies tools for nonlinear system analysis with frequency domain analysis tools used in linear systems. This study establishes sufficient conditions for absolute stability of time-varying control systems. The proposed conditions extend in a

P. Dobra; L. Nagy-Kulcsar; M. Trusca; D. Moga; R. Balan

2006-01-01

38

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

39

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

NASA Astrophysics Data System (ADS)

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

Santos, Juan Santiago

40

WACS-Wide-Area Stability and Voltage Control System: R&D and Online Demonstration  

Microsoft Academic Search

As background, we describe frequently used feedforward wide-area discontinuous power system stability controls. Then we describe online demonstration of a new response-based (feedback) Wide-Area stability and voltage Control System (WACS). The control system uses powerful discontinuous actions for power system stabilization. The control system comprises phasor measurements at many substations, fiber-optic communications, real-time deterministic computers, and transfer trip output signals

CARSON W. TAYLOR; DENNIS C. ERICKSON; KENNETH E. MARTIN; ROBERT E. WILSON; VAITHIANATHAN VENKATASUBRAMANIAN

2005-01-01

41

Investigation of Voltage Stability for Residential Customers Due to High Photovoltaic Penetrations  

Microsoft Academic Search

Several studies on voltage stability analysis of electric systems with high photovoltaic (PV) penetration have been conducted at a power-transmission level, but very few have focused on small-area networks of low voltage. As a distribution system has its special characteristics—high R\\/X ratio, long tap switching delay, small PV units, and so on—PV integration impacts also need to be investigated thoroughly

Ruifeng Yan; Tapan Kumar Saha

2012-01-01

42

Improvement of Voltage stability and Critical Clearing Time for Multi-machine Power Systems Using Static VAR Compensator  

Microsoft Academic Search

The present paper studies the effect of equipping static VAR compensator, SVC in multi-machine power system to improve the voltage stability and critical clearing time CCT. of multimachine power system. Three static VAR compensators, SVCs are connected with certain power system buses to stabilize the system voltage and improve the overall power system stability subjected to different disturbances for a

Ashraf Mohamed Hemeida

43

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

44

Effect of distribution system specifications on voltage stability in presence of wind distributed generation  

Microsoft Academic Search

Increasing penetration of distributed generation and renewable energy such as wind farms due to various reasons including environmental and economic causes, decentralization and limits on fossil fuels increased the effects of DG on power systems. This paper presents a wide analysis of the effect of wind distributed generation (DG) on voltage stability of distribution networks. Wind farms with having induction

Siamak Barghi; Masoud Aliakbar Golkar; Amin Hajizadeh

2011-01-01

45

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

46

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

Microsoft Academic Search

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

Adedamola Omole

2010-01-01

47

Impacts of merit order based dispatch on transfer capability and static voltage stability  

Microsoft Academic Search

In this paper, the goal is to investigate the impacts of generation merit order based dispatch on transfer capability and static voltage stability. The concept of generation merit order can be based on traditional costs or market bids. The new merit order feature has been incorporated into the existing Continuation Method Trace Tool (CMTRACE). More specifically, the well-known continuation power

Cuong P. Nguyen; Alexander J. Flueck

2008-01-01

48

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

Microsoft Academic Search

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

N. C. Sahoo; K. Prasad

2006-01-01

49

A probabilistic nodal loading model and worst case solutions for electric power system voltage stability assessment  

Microsoft Academic Search

In this paper, a new nodal loading model for use in voltage stability assessment of electric power systems is proposed, and the formulation of worst cases based on this model, as well as related numerical methods, are described. In this nodal loading model, called the \\

Yoshihiko Kataoka

2003-01-01

50

A new advanced over excitation limiter for enhancing the voltage stability of power systems  

Microsoft Academic Search

Mitsubishi Electric has developed an advanced over excitation limiter (OEL) that not only protects the generator field winding from overheating, but also allows the generator to supply reactive power up to its maximum limitation. This in turn allows for the enhancement of voltage stability of a power system by allowing the full range of reactive power supplying ability of a

Masaru Shimomura; Yuou Xia; Masaru Wakabayashi; John Paserba

2001-01-01

51

FACTS devices allocation for congestion management considering voltage stability by means of MOPSO  

Microsoft Academic Search

This paper proposes a method for solving congestion management problem by optimally allocating FACTS devices. The problem is approached by utilizing optimization method which optimizes generation and installation costs while satisfying voltage stability index. The main contribution of this paper is to provide pareto optimal solutions which describe previous objectives during congestion and after congestion removed. Moreover, the method is

R. S. Wibowo; N. Yorino; M. Eghbal; Y. Zoka; Y. Sasaki

2009-01-01

52

Analysis of Composite Load Models on Load Margin of Voltage Stability  

Microsoft Academic Search

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

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

2006-01-01

53

Application of wavelet transformation for voltage stability in distributed power system network  

Microsoft Academic Search

By combining wavelet transform (WT) with fractal theory, a novel approach is put forward to detect early short-circuit fault and analyze voltage stability. The application of signal denoising based on the statistic rule is brought forward to determine the threshold of each order of wavelet space, and an effective method is proposed to determine the decomposition level adaptively, increasing the

Liao Wei; Han Put

2008-01-01

54

Stability and bifurcation in a voltage controlled negative-output KY Boost converter  

NASA Astrophysics Data System (ADS)

The stability and bifurcation in a voltage controlled negative-output KY Boost converter is studied in this Letter. A glimpse at the stability and bifurcation from the power electronics simulator (PSIM) software are given. And then, its mathematical model and corresponding discrete model are derived. The stability and bifurcation of the converter are determined with the help of the loci of eigenvalues of the Jacobian matrix. It is found that the Hopf bifurcation is easy to come in this converter when the value of its energy-transferring capacitor increases. Finally, the analytical results are confirmed by the circuit experiment.

Wang, Fa-Qiang; Ma, Xi-Kui

2011-03-01

55

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

SciTech Connect

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

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

2006-01-01

56

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

57

Basis for allosteric open-state stabilization of voltage-gated potassium channels by intracellular cations  

PubMed Central

The open state of voltage-gated potassium (Kv) channels is associated with an increased stability relative to the pre-open closed states and is reflected by a slowing of OFF gating currents after channel opening. The basis for this stabilization is usually assigned to intrinsic structural features of the open pore. We have studied the gating currents of Kv1.2 channels and found that the stabilization of the open state is instead conferred largely by the presence of cations occupying the inner cavity of the channel. Large impermeant intracellular cations such as N-methyl-d-glucamine (NMG+) and tetraethylammonium cause severe slowing of channel closure and gating currents, whereas the smaller cation, Cs+, displays a more moderate effect on voltage sensor return. A nonconducting mutant also displays significant open state stabilization in the presence of intracellular K+, suggesting that K+ ions in the intracellular cavity also slow pore closure. A mutation in the S6 segment used previously to enlarge the inner cavity (Kv1.2-I402C) relieves the slowing of OFF gating currents in the presence of the large NMG+ ion, suggesting that the interaction site for stabilizing ions resides within the inner cavity and creates an energetic barrier to pore closure. The physiological significance of ionic occupation of the inner cavity is underscored by the threefold slowing of ionic current deactivation in the wild-type channel compared with Kv1.2-I402C. The data suggest that internal ions, including physiological concentrations of K+, allosterically regulate the deactivation kinetics of the Kv1.2 channel by impairing pore closure and limiting the return of voltage sensors. This may represent a primary mechanism by which Kv channel deactivation kinetics is linked to ion permeation and reveals a novel role for channel inner cavity residues to indirectly regulate voltage sensor dynamics.

Goodchild, Samuel J.; Xu, Hongjian; Es-Salah-Lamoureux, Zeineb; Ahern, Christopher A.

2012-01-01

58

Evaluation of Higher Distribution and/or Utilization Voltages. Fifth Interim Report (September 1980): Assess Constraints to Higher Voltage Implementation.  

National Technical Information Service (NTIS)

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 inclu...

1981-01-01

59

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

Microsoft Academic Search

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

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

2004-01-01

60

Voltage sag and swell generator for the evaluation of custom power devices  

Microsoft Academic Search

This paper describes a new economical sag\\/swell voltage generator suitable to the evaluations of high power custom power devices such as DVR (Dynamic Voltage Restorer) and DSTATCOM (Distribution Static Compensator). Proposed system was designed to generate the several power quality disturbances in MVA power ratings - sag, swell, under voltage, over voltage and harmonic distortions. The sag and the under

Y. H. Chung; G. H. Kwon; T. B. Park; K. Y. Lim

2003-01-01

61

Stability of voltage and frequency control in distributed generation based on parallel-connected converters feeding constant power loads  

Microsoft Academic Search

In this paper stability and dynamic properties of voltage and frequency droop control of power electronic converters are investigated for a distributed generation system. Droop control is utilized to share active and reactive power among the source converters. The voltage and frequency controllers are designed so that stand-alone converter operation feeding constant power loads performs satisfactory. These controllers are adapted

P. Karlsson; J. Bjornstedt; M. Strom

2005-01-01

62

Evaluation of medium voltage enameled wire exposed to fast repetitive voltage pulses  

Microsoft Academic Search

The paper describes the investigation of the failure mechanisms of medium voltage inter-turn insulation, as a consequence of pulse aging. To study the performance and failure behaviour of enameled wires, models of inter-turn insulation are prepared with enameled wires having polyimide and nano-filled coatings. The aging of such bar samples is attained by sinusoidal (60Hz), fast repetitive unipolar voltage pulses,

Saeed Ul Haq; Shesha H. Jayaram; Edward A. Cherney

2007-01-01

63

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

64

Evaluation of EPDM rubber for high voltage insulator  

Microsoft Academic Search

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

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

1995-01-01

65

Organic photovoltaic based on copper phthalocyanine with high open circuit voltage and significant current and voltage stability  

NASA Astrophysics Data System (ADS)

Organic semiconductors are under investigation as a possible material to create low cost solar cells. We fabricated photovoltaic devices consisting of copper phthalocyanine (CuPc) modified with a sulfonated group /perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA)/ bathocuproine (BCP) A large open circuit voltage (VOC) of 0.74 V was recorded, superior to cells based on CuPc/PTCDA (VOC =0.55V). Our solar cells exhibits little change in their voltage and current for more than 7 months, superior to many organic solar cells which degrade significantly over days or weeks.

Hamam, Khalil; Al-Amar, Mohammad; Burns, Clement

2012-10-01

66

Microstructural stability of nanocrystalline LiCoO2 in lithium thin-film batteries under high-voltage cycling  

Microsoft Academic Search

The microstructural stability of nanocrystalline LiCoO2 cathodes in rechargeable thin-film batteries after high-voltage cycling was investigated by transmission electron microscopy. It was found that besides the trigonal-LiCoO2 phase, there are two other phases of LixCoO2, spinel and H1-3, that form inside the nanocrystalline cathode after electrochemical cycling (charge cutoff voltages >=4.5 V). The formation of the aforementioned secondary phases in

Chiung-Nan Li; Jenn-Ming Yang; Victor Krasnov; Jeff Arias; Kai-Wei Nieh

2007-01-01

67

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

SciTech Connect

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

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

2012-01-01

68

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.

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

2013-01-01

69

Configuration of Jacobian Matrix in Steady-State Voltage Stability Analysis Based on Rotor Flux Dynamics of Rotating Machines  

NASA Astrophysics Data System (ADS)

In the existing literatures, modal analysis for steady-state voltage stability is based on the reduced Jacobian matrix, i.e. active power equations are eliminated, and reactive power equations of the constant power/voltage buses (PV buses) are ignored in the polar coordinate expression, which is actually designed for voltage controllability, but questionable for voltage stability.In this article, power outputs of the rotating machines are newly decomposed to the steady-state and dynamic components, with the latter proportional to derivative of the rotor flux. Therefore, neither the active nor the reactive power equations of the rotating machines may be eliminated or ignored in the Jacobian matrix. Only the static buses with constant load impedance should be eliminated. Numerical results show that elimination of active power equations or ignorance of reactive power equations of the rotating machines will yield optimistic stability margins, while including power equations of static load buses yields pessimistic stability margin. It is also find that more static load component yields larger stability margin.

Li, Shenghu

2013-06-01

70

High voltage stability of nanostructured thin film catalysts for PEM fuel cells  

Microsoft Academic Search

This paper provides a comparative evaluation of electrocatalyst surface area stability in PEM fuel cells under accelerated durability testing. The two basic electrocatalyst types are conventional carbon-supported dispersed Pt catalysts (Pt\\/C), and nanostructured thin film (NSTF) catalysts. Both types of fuel cell electrocatalysts were exposed to continuous cycling between 0.6 and 1.2V, at various temperatures between 65 and 95°C, with

Mark K. Debe; Alison K. Schmoeckel; George D. Vernstrom; Radoslav Atanasoski

2006-01-01

71

Impacts of Large Scale and High Voltage Level Photovoltaic Penetration on the Security and Stability of Power System  

Microsoft Academic Search

Grid-connected photovoltaic (PV) systems are developing increasingly in recent years due to many associated economic and environmental factors and provoking control and operation problems to utilities. Most of all, it also touches the essence of management mechanism of power systems. Concerning with voltage and frequency stability, electricity quality and short-term load forecasting, the possible influences on the secure and stable

Yang Weidong; Zhou Xia; Xue Feng

2010-01-01

72

Evaluation of voltage interpolation to address process variations  

Microsoft Academic Search

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

Kevin Brownell; Gu-yeon Wei; David Brooks

2008-01-01

73

A new optimal reactive power scheduling method for loss minimization and voltage stability margin maximization using successive multi-objective fuzzy LP technique  

Microsoft Academic Search

Insufficient reactive power support in a power grid results in under voltages at load centres and also limits the real power transfer capacities of the transmission systems leading to voltage collapse. An optimal reactive power scheduling method is sought which minimizes real power transmission loss and maximizes voltage stability margin (VSM) subject to the utmost satisfaction of all the violated

B. Venkatesh; G. Sadasivam; M. Abdullah Khan

2000-01-01

74

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

Microsoft Academic Search

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

Sherif Omar Faried; Saleh Aboreshaid

2003-01-01

75

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

76

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

77

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...

78

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

PubMed

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

Callenberg, Keith M; Latorraca, Naomi R; Grabe, Michael

2012-07-01

79

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

80

MODELIZATION AND STABILITY OF AN ASYNCHRONOUS MOTOR DRIVE SUPPLIED AT CONSTANT FREQUENCY AND VOLTAGE  

Microsoft Academic Search

A new variable speed drive system is defined with a three phase cage asynchronous motor fed by normal sinusoidal supply at constant frequency and voltage through line series constant capacitors and parallel thyristor half-bridge. The variable motor voltage is controlled by the SCRs which produce zero sequence component.This very simple drive is of lower cost than inverter ones but the

A. JAMMAL; G. GRELLET

1989-01-01

81

Optimum generation direction for transmission system maximum loading margin considering static voltage stability  

Microsoft Academic Search

Owing to the difficulties in building new generators and transmission facilities to accommodate the regionally increasing load demands, it becomes vulnerable to voltage instability from over-utilization of the existing facilities or any contingency. In addition to installing FACTS devices, a good generation direction (GD) can also alleviate voltage instability and thus increase loading margin (LM) for more power transferred to

Ya-Chin Chang; Chin-Lien Su

2008-01-01

82

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

83

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

Microsoft Academic Search

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

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

1999-01-01

84

A shared mechanism for lipid- and ?-subunit-coordinated stabilization of the activated K+ channel voltage sensor  

PubMed Central

The low-dielectric plasma membrane provides an energy barrier hindering transmembrane movement of charged particles. The positively charged, voltage-sensing fourth transmembrane domain (S4) of voltage-gated ion channels must surmount this energy barrier to initiate channel activation, typically necessitating both membrane depolarization and interaction with membrane lipid phospho-head groups (MLPHGs). In contrast, and despite containing S4, the KCNQ1 K+ channel ? subunit exhibits predominantly constitutive activation when in complexes with transmembrane ? subunits, MinK-related peptide (MiRP) 1 (KCNE2) or MiRP2 (KCNE3). Here, using a 2-electrode voltage clamp and scanning mutagenesis of channels heterologously expressed in Xenopus laevis oocytes, we discovered that 2 of the 8 MiRP2 extracellular domain acidic residues (D54 and D55) are important for KCNQ1-MiRP2 constitutive activation. Double-mutant thermodynamic cycle analysis revealed energetic coupling of D54 and D55 to R237 in KCNQ1 S4 but not to 10 other native or introduced polar residues in KCNQ1 S4 and surrounding linkers. MiRP2-D54 and KCNQ1-R237 also similarly dictated susceptibility to the inhibitory effects of MLPHG hydrolysis, whereas other closely situated polar residues did not. Thus, by providing negative charge near the plasma membrane extracellular face, MiRP2 uses a lipomimetic mechanism to constitutively stabilize the activated KCNQ1 voltage sensor.—Choi, E., Abbott, G. W. A shared mechanism for lipid- and ?-subunit-coordinated stabilization of the activated K+ channel voltage sensor.

Choi, Eun; Abbott, Geoffrey W.

2010-01-01

85

Stability analysis of a voltage-temperature (V\\/T) limit circuit for satellite power system  

Microsoft Academic Search

A voltage-temperature (V\\/T) limit circuit for a satellite power system is designed and analyzed for the maximum and the minimum voltage deviations in the normal and the worst case of the EOL (end of life). The normal case is that the normal values of the V\\/T limit circuit devices are used, and the worst case is that BOL (beginning of

Youngjin Choi; Jinsuk Wang

1996-01-01

86

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

Microsoft Academic Search

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

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

1995-01-01

87

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

Microsoft Academic Search

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

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

1996-01-01

88

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

89

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

90

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

91

Evaluation of Currents and Charges in Low-Voltage Surge Arresters Due to Lightning Strikes  

Microsoft Academic Search

This paper presents an evaluation of the values of currents and charges absorbed by surge protective devices (SPD) connected in low-voltage open-wire overhead distribution networks in the case of direct lightning strikes to primary lines. Also, some information about overvoltage magnitude is included. The calculations have been performed using the Altemative Transients Program (ATP). The modeling of system components includes

W. Bassi; J. M. Janiszewski

2002-01-01

92

Evaluation of currents and charges in low-voltage surge arresters due to lightning strikes  

Microsoft Academic Search

Summary form only given, as follows. This paper presents an evaluation of the values of currents and charges absorbed by surge protective devices (SPDs) connected in low-voltage open-wire overhead distribution networks in the case of direct lightning strikes to primary lines. Also, some information about overvoltages magnitude is included. The calculations have been performed using the ATP (Alternative Transients Program).

W. Bassi; J. M. Janiszewski

2002-01-01

93

Evaluation of currents and charges in low-voltage surge arresters due to lightning strikes  

Microsoft Academic Search

This paper presents an evaluation of the values of currents and charges absorbed by surge protective devices (SPDs) connected in low-voltage open-wire overhead distribution networks in the case of direct lightning strikes to primary lines. Also, some information about overvoltages magnitude is included. The calculations have been performed using the ATP (Alternative Transients Program). The modeling of the system components

Welson Bassi; Jorge M. Janiszewski

2003-01-01

94

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

Microsoft Academic Search

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

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

2004-01-01

95

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

PubMed Central

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

Kanevsky, Max; Aldrich, Richard W.

1999-01-01

96

Determinants of voltage-dependent gating and open-state stability in the S5 segment of Shaker potassium channels.  

PubMed

The best-known Shaker allele of Drosophila with a novel gating phenotype, Sh(5), differs from the wild-type potassium channel by a point mutation in the fifth membrane-spanning segment (S5) (Gautam, M., and M.A. Tanouye. 1990. Neuron. 5:67-73; Lichtinghagen, R., M. Stocker, R. Wittka, G. Boheim, W. Stühmer, A. Ferrus, and O. Pongs. 1990. EMBO [Eur. Mol. Biol. Organ.] J. 9:4399-4407) and causes a decrease in the apparent voltage dependence of opening. A kinetic study of Sh(5) revealed that changes in the deactivation rate could account for the altered gating behavior (Zagotta, W.N., and R.W. Aldrich. 1990. J. Neurosci. 10:1799-1810), but the presence of intact fast inactivation precluded observation of the closing kinetics and steady state activation. We studied the Sh(5) mutation (F401I) in ShB channels in which fast N-type inactivation was removed, directly confirming this conclusion. Replacement of other phenylalanines in S5 did not result in substantial alterations in voltage-dependent gating. At position 401, valine and alanine substitutions, like F401I, produce currents with decreased apparent voltage dependence of the open probability and of the deactivation rates, as well as accelerated kinetics of opening and closing. A leucine residue is the exception among aliphatic mutants, with the F401L channels having a steep voltage dependence of opening and slow closing kinetics. The analysis of sigmoidal delay in channel opening, and of gating current kinetics, indicates that wild-type and F401L mutant channels possess a form of cooperativity in the gating mechanism that the F401A channels lack. The wild-type and F401L channels' entering the open state gives rise to slow decay of the OFF gating current. In F401A, rapid gating charge return persists after channels open, confirming that this mutation disrupts stabilization of the open state. We present a kinetic model that can account for these properties by postulating that the four subunits independently undergo two sequential voltage-sensitive transitions each, followed by a final concerted opening step. These channels differ primarily in the final concerted transition, which is biased in favor of the open state in F401L and the wild type, and in the opposite direction in F401A. These results are consistent with an activation scheme whereby bulky aromatic or aliphatic side chains at position 401 in S5 cooperatively stabilize the open state, possibly by interacting with residues in other helices. PMID:10435999

Kanevsky, M; Aldrich, R W

1999-08-01

97

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

PubMed Central

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

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

2013-01-01

98

Evaluation of the reverse micellar systems stability  

Microsoft Academic Search

The aim of this paper is obtaining the reverse micelle and study the stability of them. Reverse micelle systems based on AOT\\/water\\/organic solvent and CTAB\\/cyclohexane\\/hexanol\\/water, with various hydration degree, have been obtained during several experiments. Experimental data show that the AOT\\/isooctane and CTAB\\/cyclohexan\\/water\\/1-hexanol reverse micelles systems have a good time stability.

Gabriela PAUN-ROMAN; Veronica MOROEANU; Elena NEAGU

99

Evaluation of three-level rectifiers for low-voltage utility applications  

Microsoft Academic Search

This paper evaluates the benefits of three-level topologies as alternatives to two-level topologies in low-voltage converters primarily operated in rectifier mode. The main evaluation aspects are input filter size, semiconductor losses, maximum switching frequency, part count, initial cost, and life cycle cost. Semiconductor loss characteristics of various three-level topologies are discussed. A detailed converter comparison is based on a 100-kW

Ralph Teichmann; Mariusz Malinowski; Steffen Bernet

2005-01-01

100

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

PubMed

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

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

2013-01-01

101

Voltage and power swing stabilization by decoupled control with AVR and phase shifter  

Microsoft Academic Search

With the development of power system controllers, it becomes feasible to control the output power of a synchronous generator directly and quickly by some FACTS controller like a solid-state phase shifter. The authors have proposed a scheme for power system stabilization by the direct generator power control which virtually linearizes swing equations. As the proposed control is capable of controlling

Masahide Hojo; Yasunori Mitani; Kiichiro Tsuji

1998-01-01

102

Stability analysis of a medium voltage local energy system with decentralized generation  

Microsoft Academic Search

In this paper the impact of the decentralized generation provided by renewable sources, as e.g. wind parks, fuel cell power plants and photovoltaic plants, on the stability of a Local Energy System (LES) are studied. Small dimensions, small power, and the neighbourhood of generators and consumers characterize these systems. Decentralized generation in the power system is studied not only in

Peter Schegner; Piergiovanni La Seta; Sven Höpfner

2005-01-01

103

Low-voltage field emission from tungsten fiber arrays in a stabilized zirconia matrix  

Microsoft Academic Search

Field emitter array cathodes were fabricated from unidirectionally solidified composites of tungsten fibers in an insulating yttria-stabilized-zirconia (YSZ) matrix. A close-spaced molybdenum gate film (extractor) was formed utilizing e-beam evaporation of alumina as an insulator, which was overlayed by the molybdenum extractor. The high resistivity of the composite matrix coupled with the alumina insulator resulted in low leakage current and

J. K. Cochran; A. T. Chapman; D. N. Hill; K. J. Lee

1987-01-01

104

Stability and Change in Curriculum Evaluation.  

ERIC Educational Resources Information Center

Addresses the lack of congruence between different curricular and evaluation ideologies and the lack of sensitivity regarding underlying theoretical assumptions in curriculum evaluation practices from a perspective that calls for a joint ontological and epistemological view of the curriculum and curriculum evaluation. Explores curriculum as a…

Levine, Tamar

2002-01-01

105

Gap-State Distributions in Hydrogenated Amorphous Silicon-Germanium Evaluated Using Capacitance Voltage Method  

Microsoft Academic Search

The density of gap states in hydrogenated amorphous silicon-germanium (a-SiGe:H) alloys deposited at temperatures of 150 250°C has been evaluated by using a capacitance voltage (C V ) method. It was found that the gap-state distribution for a-SiGe:H deposited at 150°C has a broad bump around 0.6 eV below the conduction band edge Ec which is associated with Ge dangling

Hidenori Deki; Kouji Nakagawa; Atsushi Kohno; Seiichi Miyazaki; Masataka Hirose

1998-01-01

106

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

Microsoft Academic Search

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

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

2012-01-01

107

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

108

Evaluation of niobium as candidate electrode material for dc high voltage photoelectron guns  

NASA Astrophysics Data System (ADS)

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 mirrorlike 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 (<10pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18.7MV/m.

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

2012-08-01

109

Evaluation of the Threshold of Stability for the Human Spine  

PubMed Central

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

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

2009-01-01

110

ENVIRONMENTAL EVALUATION FOR UTILIZATION OF ASH IN SOIL STABILIZATION  

SciTech Connect

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

David J. Hassett; Loreal V. Heebink

2001-08-01

111

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

112

Investigation of low discharge voltage Hall thruster characteristics and evaluation of loss mechanisms  

NASA Astrophysics Data System (ADS)

During the early development stages of Hall thruster technology, plasma research and propulsion advancements centered primarily on 300-V, 1600-s specific impulse operation. Since the first Hall thruster firing on a Soviet satellite in 1972, extensive investigations of the plasmadynamic discharge phenomena and operating characteristics progressed the propulsion concept to a high level of performance suitable for a wide range of near-earth maneuvers and interplanetary missions. The expanded performance envelope is primarily a function of improvements in thruster lifetime, thermal margin, discharge stability, and power system capability. Advancements in Hall thruster propulsion systems enable a wider range of input parameters to the thruster, including the applied anode-to-cathode potential. Operation in the low discharge voltage regime is associated with a decline in total thruster efficiency. This dissertation is intended to investigate low-voltage Hall thruster physics, identify dominant performance loss mechanisms, and determine the discharge characteristics that drive efficiency. A systematic, experimental investigation of low-voltage Hall thruster performance and plume properties led to the conclusion that reduced electron temperature in the discharge was correlated with diminished Joule heating losses and a lower ionization cost per beam ion. However, the reduced electron temperature also decreased the ionization rate coefficient, and corresponded to an escalation of electron current to the anode to sustain ionization processes. In addition, divergence of the kinetic ion jet limited the component of axially directed thrust and reduced the total thruster efficiency. Two jet-mode Hall thruster operating regimes were discovered for low-voltage operation, corresponding to ionization instabilities in the discharge and additional electron current to the anode. These modes are methodically characterized and potential causes are hypothesized. During the course of this research, corollary studies on Faraday probe design, facility effects, and data analysis techniques improved accuracy of current density profiles and far-field plume properties. Faraday probe uncertainty is difficult to quantify, and therefore is often employed for qualitative analysis of electric propulsion plumes. The reduction in Faraday probe measurement uncertainty and the increased capability to approximate on-orbit plume expansion are significant improvements for comparison with numerical simulations and analysis of thruster performance.

Brown, Daniel Lucas

113

Oxidative stability and sensory evaluation of microencapsulated flaxseed oil.  

PubMed

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

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

2014-01-01

114

Hazards evaluation of plutonium metal opening and stabilization  

SciTech Connect

Hazards evaluation is the analysis of the significance of hazardous situations associated with an activity OK process. The HE used qualitative techniques of Hazard and Operability (HazOp) analysis and What-If analysis to identify those elements of handling and thermal stabilization processing that could lead to accidents.

JOHNSON, L.E.

1999-08-31

115

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

116

Maturity and Stability Evaluation of Composted Yard Trimmings  

Microsoft Academic Search

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

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

2003-01-01

117

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

118

Evaluation of a 125I-labelled benzazepinone derived voltage-gated sodium channel blocker for imaging with SPECT.  

PubMed

Voltage-gated sodium channels (VGSCs) are a family of transmembrane proteins that mediate fast neurotransmission, and are integral to sustain physiological conditions and higher cognitive functions. Imaging of VGSCs in vivo holds promise as a tool to elucidate operational functions in the brain and to aid the treatment of a wide range of neurological diseases. To assess the suitability of 1-benzazepin-2-one derived VGSC blockers for imaging, we have prepared a (125)I-labelled analogue of BNZA and evaluated the tracer in vivo. In an automated patch-clamp assay, a diastereomeric mixture of the non-radioactive compound blocked the Na(v)1.2 and Na(v)1.7 VGSC isoforms with IC(50) values of 4.1 ± 1.5 ?M and 0.25 ± 0.07 ?M, respectively. [(3)H]BTX displacement studies revealed a three-fold difference in affinity between the two diastereomers. Iodo-destannylation of a tin precursor with iodine-125 afforded the two diastereomerically pure tracers, which were used to assess binding to VGSCs in vivo by comparing their tissue distributions in mice. Whilst the results point to a lack of VGSC binding in vivo, SPECT imaging revealed highly localized uptake in the interscapular region, an area typically associated with brown adipose tissue, which in addition to high metabolic stability of the iodinated tracer, demonstrate the potential of 1-benzazepin-2-ones for in vivo imaging. PMID:23117159

Pérez-Medina, Carlos; Patel, Niral; Robson, Mathew; Badar, Adam; Lythgoe, Mark F; Årstad, Erik

2012-12-21

119

Investigation of power loss and voltage stability limits for large wind farm connections to a subtransmission network  

Microsoft Academic Search

Today wind farms are growing both in size and in number. Being connected at higher voltage levels, their impacts are becoming more widespread. High demand for reactive power is known as one major characteristic of large wind farms that causes voltage problems to power networks. The larger the wind farm, the more severe this effect could be. If the network

L. T. Ha; T. K. Saha

2004-01-01

120

Brush Sliding Contact Voltage Deviation Analysis Based on the Evaluation of Displacement Excited Vibration caused by Collector Ring Profile Distortion -for Turbine Generators & Traction Motors-  

Microsoft Academic Search

When commutator profile distortion in DC motors or collector ring profile distortion in AC generators or motors are caused, stabilities and reliabilities of sliding contact phenomena will be lost, causing mechanical contact instabilities and contact voltage instabilities. In this paper, how to estimate the mechanical vibration out of the ring profile distortion and how to estimate contact voltage deviation out

M. Takanezawa; H. Yanagisawa; T. Ueno; N. Morita; T. Otaka; D. Hiramatsu

2008-01-01

121

Using game theory to evaluate the stability of strategic forces  

SciTech Connect

A game theory method for evaluating the stability of various strategic force deployments in a confrontation between two parties is described. To illustrate the method future US and Soviet ICBM forces are projected. Evaluation of the results indicates that the concept of deterrence can indeed be investigated in terms of a party's incentive or disincentive to initiate a nuclear exchange and that this measure can be quantitatively determined. We suggest that this allows us to structure strategic forces to preclude either side from calculating any advantage from initiating a nuclear exchange.

Reinhardt, G.C.; Squire, R.K.

1982-02-01

122

Altus AFB Deep Soil Layer Stabilization Test Sections. Volume I. Design and Evaluation.  

National Technical Information Service (NTIS)

Information and data on stabilization of deep soil layers indicated that certain stabilization procedures should be evaluated in various field test section studies. The report describes the design, construction and evaluation of drill hole lime, pressure ...

M. R. Thompson Q. L. Robnett

1975-01-01

123

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

ERIC Educational Resources Information Center

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

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

2010-01-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

126

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

127

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

128

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

129

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

Microsoft Academic Search

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

Sibylle Dieckerhoff; Steffen Bernet; Dietmar Krug

2005-01-01

130

Nondestructive evaluation of the semiconductor interface states' density using the transverse acoustoelectric voltage  

NASA Astrophysics Data System (ADS)

Nondestructive determination of the interface states' density ( Dit) is presented. The measurement technique, utilizing the surface acoustic waves, is applied to silicon/thermal oxide structure. The detected signal is the transverse acoustoelectric voltage amplitude (TAV) which is monitored as a function of the applied bias voltage (TAV- V). Dit is measured by comparing the theoretical and experimental TAV- V curves. The calculation procedure of the Dit and the experimental example are presented.

Davari, B.; Azar, M. Tabib; Liu, T.; Das, P.

1986-01-01

131

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

132

In vivo noninvasive evaluation of hairless rat skin after high-voltage pulse exposure.  

PubMed

Short high-voltage pulses have recently been shown to dramatically increase and expedite transdermal drug transport via a mechanism hypothesized to involve electroporation. This study addresses tolerance issues of the method in vivo in hairless rat. Chromametry, transepidermal water loss (TEWL), laser Doppler flowmetry (LDF) and corneometry were jointly used for noninvasive sensing of skin biophysical parameters. Slight increases in skin redness, TEWL and LDF values followed the application of electric pulses. The changes in skin capacitance were nonsignificant. The magnitude of the alterations depended on the electrical features of the pulses. When compared to iontophoresis, high-voltage pulses did not induce stronger alterations of skin functions. This report provides the first in vivo demonstration of the safety of the high-voltage pulses proposed for transdermal delivery. PMID:9603666

Vanbever, R; Fouchard, D; Jadoul, A; De Morre, N; Préat, V; Marty, J P

1998-01-01

133

Performance evaluation of wideband bio-impedance spectroscopy using constant voltage source and constant current source  

NASA Astrophysics Data System (ADS)

Current sources are widely used in bio-impedance spectroscopy (BIS) measurement systems to maximize current injection for increased signal to noise while keeping within medical safety specifications. High-performance current sources based on the Howland current pump with optimized impedance converters are able to minimize stray capacitance of the cables and setup. This approach is limited at high frequencies primarily due to the deteriorated output impedance of the constant current source when situated in a real measurement system. For this reason, voltage sources have been suggested, but they require a current sensing resistor, and the SNR reduces at low impedance loads due to the lower current required to maintain constant voltage. In this paper, we compare the performance of a current source-based BIS and a voltage source-based BIS, which use common components. The current source BIS is based on a Howland current pump and generalized impedance converters to maintain a high output impedance of more than 1?M? at 2?MHz. The voltage source BIS is based on voltage division between an internal current sensing resistor (Rs) and an external sample. To maintain high SNR, Rs is varied so that the source voltage is divided more or less equally. In order to calibrate the systems, we measured the transfer function of the BIS systems with several known resistor and capacitor loads. From this we may estimate the resistance and capacitance of biological tissues using the least-squares method to minimize error between the measured transimpedance excluding the system transfer function and that from an impedance model. When tested on realistic loads including discrete resistors and capacitors, and saline and agar phantoms, the voltage source-based BIS system had a wider bandwidth of 10 Hz to 2.2 MHz with less than 1% deviation from the expected spectra compared to more than 10% with the current source. The voltage source also showed an SNR of at least 60 dB up to 2.2 MHz in comparison to the current source-based BIS system where the SNR drops below 40 dB for frequencies greater than 1 MHz.

Mohamadou, Youssoufa; In Oh, Tong; Wi, Hun; Sohal, Harsh; Farooq, Adnan; Woo, Eung Je; McEwan, Alistair Lee

2012-10-01

134

Experimental study on system stability evaluation in parallel running of a superconducting generator and a SMES  

Microsoft Academic Search

Parallel running operation of 100 kVA superconducting generator (SCG) with high response excitation and 0.4 MJ SMES (superconducting magnet energy storage) was carried out. The exciter capacity of the high response excitation is rather large compared with that of conventional generators. The exciter controller, that is, AVR (automatic voltage regulator) and PSS (power system stabilizer) are designed taking the exciter

Y. Shirai; T. Nitta; M. Yamada

2002-01-01

135

Evaluation of epoxy V.P.I. insulation for high voltage stator windings  

Microsoft Academic Search

Epoxy bonded high voltage mica based stator insulation systems have been produced for many years. One such system employing an epoxide\\/anhydride impregnating resin, Neccobond “E” was introduced by National Electric Coil to satisfy customer requests for an epoxy bonded insulation system. The original base materials had been successfully applied in Europe since the 1960's. However before this product was accepted

James E. Timperley; Beant S. Nindra

2000-01-01

136

Evaluation of different colling fluids for high-voltage Neutral Beam Injector grids  

Microsoft Academic Search

The Neutral Beam Injectors (NBIs) of the ITER experimental fusion reactor are designed to accelerate Deuterium negative ions with energy up to 1 MeV and current up to 40 A. The accelerator grids must be designed to operate at high voltages and to withstand high power densities (in the order of some tens of MW m-2). They must maintain a

Piero Agostinetti; Marco Boldrin; Francesca Fantini

2008-01-01

137

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

138

Evaluation of tunnel stability using integrated geophysical methods  

NASA Astrophysics Data System (ADS)

An integrated interpretation was made of data, from ground penetrating radar (GPR), seismic refraction and seismic transmission tomography, collected inside the catchment tunnels of a potable water source in central Italy. Rock fracturing and obsolescence of the concrete lining in a tunnel led a landslide that caused structural instability in the catchment work structures. To assess the stability of the rock close to the landslide, geophysical surveys were preferred to boreholes and geotechnical tests in order to avoid water pollution and the risk of further landslides. The interpretation of integrated data from seismic tomography and 200 MHz antenna GPR resulted in an evaluation of some of the elastic characteristics and the detection of discontinuities in the rock. Note also that an analysis of the back-scattered energy was required for the GPR data interpretation. The integration of seismic refraction data and 450 MHz antenna allowed us to identify the loosened zone around the tunnel and the extent of the mass involved in the cave-in, while GPR data from 225 MHz were used to evaluate the quality of contact between concrete lining and massive rock.

Cardarelli, E.; Marrone, C.; Orlando, L.

2003-02-01

139

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

140

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

NASA Astrophysics Data System (ADS)

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

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

141

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

142

Evaluation of high-voltage cable-coupler performance for mine power systems. [Ph. D. Thesis  

Microsoft Academic Search

High-voltage cable couplers are convenient and widely used accessories in modern coal-mine power distribution systems for aiding in the extension and retraction of power-feeder cables throughout a mine. Coupler design has tried to keep pace with the industry's desire to move to higher distribution levels, but the increase in recorded failures of 15-kV-class couplers, which serve the distribution levels of

Bise

1980-01-01

143

Solution-Processed Dioctylbenzothienobenzothiophene-Based Top-Gate Organic Transistors with High Mobility, Low Threshold Voltage, and High Electrical Stability  

NASA Astrophysics Data System (ADS)

Dioctylbenzothieno[2,3-b]benzothiophene (C8-BTBT)-based organic field-effect transistors (OFETs) with a top-gate configuration, having fluoropolymer gate insulators, are fabricated by means of a spin-coating technique. The device fabrication is simple, and it enables us to obtain C8-BTBT FETs having high field-effect mobility (?FET), low threshold voltage (Vth), and high electrical stability. We fabricate 116 top-gate C8-BTBT FETs having ?FET of 1.59± 0.40 cm2 V-1 s-1 and Vth of -1.48± 3.02 V, and the maximum ?FET is approximately 3 cm2 V-1 s-1. No changes in the devices characteristics are observed after applying a negative gate bias stress of -1.2 MV/cm for 104 s.

Endo, Toshiyuki; Nagase, Takashi; Kobayashi, Takashi; Takimiya, Kazuo; Ikeda, Masaaki; Naito, Hiroyoshi

2010-12-01

144

Evaluation of iris color stability in ocular prosthesis.  

PubMed

Accurate iris reproduction in the fabrication of ocular prosthesis in order to match the remaining eye is a key factor to mask the loss and achieve an esthetic outcome for anophthalmic patients. This study evaluated the stability of acrylic paints used for replicating iris color in ocular prostheses by the analysis of two factors: the temperature of the acrylic resin polymerization cycle during prosthesis fabrication and the incidence of sun light, which is the main photodegrading agent undermining the longevity of ocular prostheses. An accelerated aging assay was used for both analyses. Specimens simulating the prosthetic iris in the colors blue, yellow, black, brown and green were fabricated, and were submitted to a colorimetric reading before and after undergoing the thermal conditions of acrylic resin polymerization. Next, the specimens were submitted to an artificial accelerated aging assay with ultraviolet radiation A and weekly colorimetric readings during a 3-week period. The color change (Delta E*) values for the four specimens painted with the same color paint were averaged and the resulting values were considered for statistical analysis. Levine's test and Student's t-test were used to analyze the influence of the temperature of the polymerization cycle during prosthesis fabrication on the color stability of each acrylic resin paint. Friedman's test for three dependent samples was used for analysis of color photodegradation as function of time. Significance level was set at 0.05 for all analyses. It was observed that, after the action of the temperature of the polymerization cycle, alteration above clinically acceptable level of Delta E*> 3.3 was observed only for the yellow color. After the accelerated aging assay, there were statistically significant differences (p<0.05) as a function of time in the green, brown, black and blue colors. Changes were clinically acceptable for the brown and black colors; slightly above the clinically acceptable limit for the green color; and significantly high and impracticable from a clinical standpoint for the blue color. There was no statistically significant differences (p>0.05) for the yellow color, which presented color change only a little above the clinically acceptable limit. In conclusion: 1. Only the yellow color presented alterations above the clinically acceptable levels after the polymerization cycle; 2. After accelerated aging, there was no changes in the yellow color above the clinically acceptable levels; 3. For the green color, degradation was significant and slightly above the clinically acceptable levels; 4. The black, brown and blue colors presented significant alterations as function of time; the alterations of the brown and black colors were within acceptable clinical levels, while the blue color presented a more accentuated degradation over time. PMID:19180330

Reis, Ricardo César dos; Brito e Dias, Reinaldo; Mesquita Carvalho, Jose Carlos

2008-01-01

145

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

146

A new method to evaluate roadheader operational stability  

Microsoft Academic Search

Roadheader, one of the mechanized excavation equipments, has an exceptional place among the other excavation methods. Determination of the stability states of the roadheader is an important matter for the efficiency of excavation. For this reason, a new method has been developed to obtain numerical values that indicate stability states of such machines. The method has been developed for both

O. Acaroglu; H. Ergin

2006-01-01

147

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

Microsoft Academic Search

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

1991-01-01

148

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

149

Wide Area Voltage Regulation & Protection  

Microsoft Academic Search

A very promising wide area voltage protection (V-WAP) solution to face EHV voltage stability and system security problems is presented. Its unique ability is mainly due to an effective co-ordination with a wide area voltage regulation (V-WAR) modern system where the secondary and tertiary voltage regulations (SVR and TVR respectively) operate according with their hierarchy. Evidence is given to the

S. Corsi

2009-01-01

150

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

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

151

Evaluating competing forces constraining glacial grounding-line stability (Invited)  

NASA Astrophysics Data System (ADS)

Stability of grounding lines of marine-terminating glaciers and ice sheets is of concern due to their importance in governing rates of ice mass loss and consequent sea level rise during global warming. Although processes are similar at tidewater and floating grounding zones their relative magnitudes in terms of their influence on grounding-line stability vary between these two end members. Processes considered Important for this discussion are ice dynamics, ice surface melting and crevassing, ocean dynamics, subglacial sediment and water dynamics, and subglacial bed geometries. Models have continued to improve in their representation of these complex interactions but reliable field measurements and data continue to be hard earned and too few to properly constrain the range of boundary conditions in this complicated system. Some data will be presented covering a range of regimes from Alaska, Svalbard and Antarctica. Certainly more data are required on subglacial sediment/water dynamics and fluxes to fully represent the spectrum of glacial regimes and to assess the significance of grounding-zone sediment systems in counteracting the other processes to force grounding-line stability. Especially important here is constraining the duration of the stability that could be maintained by sediment flux - present data appear to show that it is likely to be a limited period.

Powell, R. D.

2013-12-01

152

Slope stability evaluation using Back Propagation Neural Networks  

Microsoft Academic Search

The Yudonghe landslide, located in western Hubei Province of China, consists of eastern and western subunits as well as a main landslide mass with upper and lower slip surfaces. As an important landslide close to Shuibuya Dam on the Qing River, its stability is crucial, as the slide might reactivate because of a change in ground-water level caused by filling

H. B. Wang; W. Y. Xu; R. C. Xu

2005-01-01

153

Stability evaluation of house dust mite vaccines for sublingual immunotherapy  

Microsoft Academic Search

Allergen-specific immunotherapy with house dust mite (HDM) aller- gen extracts can effectively alleviate the symptoms of allergic rhinitis and as- thma. The efficacy of the immunotherapeutic treatment is highly dependent on the quality of house dust mite vaccines. This study was performed to assess the stability of house dust mite allergen vaccines prepared for sublingual immuno- therapy. Lyophilized Dermatophagoides pteronyssinus

Lidija Burazer; Katarina Milovanovic; Tanja Cirkovic-Velickovic; Marija Gavrovic-Jankulovic

2010-01-01

154

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

155

Evaluation of Parameters Affecting Horizontal Stability of Landing Mats.  

National Technical Information Service (NTIS)

The parameters that affect the horizontal stability of airfield surfacing mats were studied by conducting a series of static full-scale buckling tests in the laboratory using various mats and lay patterns. AM2, XM18, and XM19 mats with simulated waterproo...

Y. T. Chou W. R. Barker W. P. Dawkins

1976-01-01

156

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

157

EVALUATION OF PROMISING WHEAT GENOTYPES BY THE STABILITY ANALYSIS THROUGH PARAMETRIC & NON-PARAMETRIC METHODS  

Microsoft Academic Search

Suraiya Yasmin. 2007. Evaluation of Promising Wheat Genotypes by the Stability Analysis through Parametric and Non-Parametric Methods. Int. J. Sustain. Crop Prod. 2(3): 9-16 The purpose of the present study was to compare between the application of Non Parametric Stability Analysis (NPSA) and Parametric Stability Analysis (PSA) with appropriate tests in addition to utilization of exact size -? test in

SURAIYA YASMIN

158

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

159

AMRL Evaluation of the JP-8+100 Jet Fuel Thermal Stability Additive.  

National Technical Information Service (NTIS)

An additive package designed to improve thermal stability of jet fuel by 1000 F ((caret)38 C), known as the JP8+100 additive, or more commonly as the USAF- developed JP8+1OO thermal stability additive, was evaluated to investigate its efficacy in reductio...

P. Rawson

2001-01-01

160

An atmospheric stability index based on radon progeny measurements for the evaluation of primary urban pollution  

Microsoft Academic Search

An atmospheric stability index for the evaluation of urban primary pollution, based on the elaboration of natural radioactivity data yielded by a stability monitor, has been developed. The instrument determines the atmospheric concentration of the short-lived decay products of radon, whose emanation rate can be assumed to be constant in the time and space scale of observation. The index gives

Cinzia Perrino; Adriana Pietrodangelo; Antonio Febo

2001-01-01

161

Methodologies for evaluating long-term stabilization designs of uranium mill tailings impoundments  

Microsoft Academic Search

Uranium mill tailings impoundments require long-term (200 to 1000 years) stabilization. This report reviews currently available methodologies for evaluating factors that can have a significant influence on tailings stabilization and develops methodologies in technical areas where none presently exist. Mill operators can use these methodologies to assist with (1) the selection of sites for mill tailings impoundments, (2) the design

J. D. Nelson; S. R. Abt; R. L. Volpe; D. Van Zye; N. E. Hinkle; W. P. Staub

1986-01-01

162

Flight Evaluation of a Pilot-Assist Stability Augmentation System for Light Aircraft.  

National Technical Information Service (NTIS)

The purpose of the study was to evaluate the utility of a light aircraft pilot-assist stability augmentation system in extricating the noninstrument qualified pilot from accidentally encountered instrument flight conditions. Ten noninstrument rated pilots...

R. Walchi D. Eldredge

1970-01-01

163

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 ...

164

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 ...

165

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

166

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

SciTech Connect

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

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

1980-01-01

167

Low-voltage pentacene organic field-effect transistors with high-kappa HfO2 gate dielectrics and high stability under bias stress  

Microsoft Academic Search

Low-voltage pentacene organic field-effect transistors are demonstrated (operating voltage of -3 V) with high-kappa hafnium dioxide gate dielectrics grown by atomic layer deposition at 200 °C. A high hole mobility of 0.39 cm2\\/V s with low threshold voltage (<-0.5 V) and low subthreshold slope of 120 mV\\/dec is achieved with a HfO2 dielectric layer modified with a phosphonic acid based

Xiao-Hong Zhang; Shree Prakash Tiwari; Sung-Jin Kim; Bernard Kippelen

2009-01-01

168

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

169

Piloted simulator evaluation of a relaxed static stability fighter at high angle-of-attack  

NASA Technical Reports Server (NTRS)

A piloted simulator evaluation of the stability and control characteristics of a relaxed static stability fighter aircraft was conducted using a differential maneuvering simulator. The primary purpose of the simulation was to evaluate the effectiveness of the limiters in preventing departure from controlled flight. The simulation was conducted in two phases, the first consisting of open-loop point stability evaluations over a range of subsonic flight conditions, the second concentrating on closed-loop tracking of a preprogrammed target in low speed, high angle-of-attack air combat maneuvering. The command limiters were effective in preventing departure from controlled flight while permitting competent levels of sustained maneuvering. Parametric variations during the study included the effects of pitch control power and wing-body static margin. Stability and control issues were clearly shown to impact the configuration design.

Lapins, M.; Klein, R. W.; Martorella, R. P.; Cangelosi, J.; Neely, W. R., Jr.

1982-01-01

170

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

PubMed

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&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&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&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. PMID:23266165

Matsubara, Kana; Kohno, Ryosuke; Nishioka, Shie; Shibuya, Toshiyuki; Ariji, Takaki; Akimoto, Tetsuo; Saitoh, Hidetoshi

2013-01-01

171

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

Microsoft Academic Search

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

Yogeshwar G. Bachhav; Vandana B. Patravale

2009-01-01

172

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

PubMed Central

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

Bahouth, G.

2005-01-01

173

High voltage testing  

NASA Astrophysics Data System (ADS)

The High Voltage Design Guide and High Voltage Specifications and Tests Documents referred to in this report pertain to high voltage/high power airborne equipment. A test plan was designed to evaluate and verify test parameters specified in these documents. This was done by writing detailed test procedures, obtaining representative test samples, and testing the specified parameters. In addition, a standard test fixture and corona-free 150 kV, 400 Hz power supply was specified, evaluated, and delivered for use with a partial discharge test set.

Dunbar, W. G.

1981-08-01

174

A low voltage CMOS constant current-voltage reference circuit  

Microsoft Academic Search

The proposed CMOS current-voltage reference circuit consists of a traditional bandgap circuit based on the use of PMOS transistors in weak inversion. Its current is stabilized by an on-chip resistor with positive temperature coefficient. The voltage reference is produced by compensating the positive temperature coefficient of a resistor by the negative temperature coefficient of the diode connected PMOS transistor by

Ilkka Nissinen; Juha Kostamovaara

2004-01-01

175

Voltage Sensor  

NASA Technical Reports Server (NTRS)

Under a Lewis Research Center Small Business Innovation Research contract, SRICO, Inc. developed a fiber optic voltage sensor to measure voltage in electronic systems in spacecraft. The sensor uses glass and light to sense and transmit electricity, and is relatively safe and accurate. SRICO then commercialized the sensor for measurement of electric field and voltage in applications such as electric power systems and hazardous environments, lightning detection, and fiber optic communication systems.

1996-01-01

176

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...

177

Evaluating Information Content by Factoid Analysis: Human annotation and stability  

Microsoft Academic Search

We present a new approach to intrinsic sum- mary evaluation, based on initial experiments in van Halteren and Teufel (2003), which com- bines two novel aspects: comparison of infor- mation content (rather than string similarity) in gold standard and system summary, mea- sured in shared atomic information units which we call factoids, and comparison to more than one gold standard

Simone Teufel; Hans van Halteren

2004-01-01

178

Spillover in the Academy: Marriage Stability and Faculty Evaluations.  

ERIC Educational Resources Information Center

Studied the spillover between family and work by examining the link between marital status and work performance across marriage, divorce, and remarriage. A polynomial regression model was fit to the data from 78 evaluations of an individual professor, and a cubic curve through the 3 periods was statistically significant. (SLD)

Ludlow, Larry H.; Alvarez-Salvat, Rose M.

2001-01-01

179

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.

2013-01-01

180

A High-Stability Capacitance Sensor System and Its Evaluation  

Microsoft Academic Search

A new capacitance sensor system was developed with a microcontroller, commercial humidity and temperature sensors, a capacitance-to-digital converter, and a custom-built capacitance sensor. The performance of the system was evaluated by simulation and testing of the prototype. The impact of variations of ambient conditions on the system performance was analyzed, and a model for correcting the humidity and temperature influence

Svetlana Avramov-Zamurovic; Rae Duk Lee

2009-01-01

181

Transient Stability Evaluation of a 12,000-bus Power System Data Using TEPCO-BCU  

Microsoft Academic Search

This paper describes the evaluation results of TEPCO-BCU program on a 12,000-bus power system data. TEPCO-BCU is composed of several computation modules such as improved BCU classifiers, BCU method, BCU-guided time-domain stability program and a fast time-domain pro- gram. Current version of TEPCO-BCU is able to perform accurate stability assessment and energy margin computa- tion of each contingency of large-scale

Yasuyuki Tad; Tsuyoshi Takazawa

182

Preliminary evaluation of CR Kapton(R) backed mica paper tape for high voltage coil groundwall insulation using vacuum-pressure-impregnation  

Microsoft Academic Search

Of interest, is to find a mica paper tape with higher dielectric properties than commercially available tapes. This paper presents the results of a preliminary evaluation of Corona Resistant (CR) Kapton(R) backed mica paper tape. These tapes were evaluated for possible use for high voltage coil groundwall insulation using vacuum-pressure-impregnation (VPI) with epoxy resins. CR Kapton(R) Mica Paper tape was

F. T. Emery

1998-01-01

183

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

184

Evaluation of trunk stability in the sitting position using a new device.  

PubMed

The purpose of this study was to evaluate trunk stability in seated elderly and young individuals using a new device that inclines a seat while tracking the center of pressure (CoP). We evaluated the locus of CoP, locus length, locus length per second, enveloped area, root mean square area, and locus length per unit area (LNG/AREA). LNG/AREA, which reflects postural adjustments controlled by the spinal proprioceptive reflexes of the lower limbs, was not significantly different between young and elderly individuals. Our device measured trunk stability without influence from the lower extremities, which explains why LNG/AREA did not significantly differ between young and elderly individuals. These findings indicate that the new device can be used to quantify dynamic trunk stability. PMID:24759180

Saito, Kimio; Matsunaga, Toshiki; Iwami, Takehiro; Shimada, Yoichi

2014-01-01

185

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...

186

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

Microsoft Academic Search

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

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

2000-01-01

187

PILOT-SCALE EVALUATION OF THE THERMAL STABILITY POHC INCINERABILITY RANKING  

EPA Science Inventory

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

188

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

Microsoft Academic Search

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

Mary Jo Spencer

1984-01-01

189

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

ERIC Educational Resources Information Center

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

Chen, Guo-Hai; Watkins, David

2010-01-01

190

Evaluation of Effects of Panama Canal Deepening Upon the Stability of La Pita Hill.  

National Technical Information Service (NTIS)

This report presents an analysis and evaluation of the stability, as well as provides design recommendations for La Pita Hill on the Panama Canal. The site was selected for study by the Panama Canal Company (PCC) based upon scheduled Canal deepening locat...

W. O. Miller

1979-01-01

191

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...

192

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

EPA Science Inventory

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

193

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

EPA Science Inventory

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

194

Evaluation of stability and adaptability for new spring safflower lines in different environmental conditions of Iran  

Microsoft Academic Search

The stability of seven spring safflower cultivars and lines were evaluated in five different environmental conditions of Karaj, Isfahan, Eslamabad, and Zargan, in Iran, for two years (2002- 2004). Simple analysis of variances of grain and oil yields from each experiment showed significant differences among the genotypes. After having homogeneity test for error variances combined analysis of variance was performed.

A. H. Omidi

195

Thoracolumbar fracture stabilization: comparative biomechanical evaluation of a new video-assisted implantable system.  

PubMed

Minimally invasive techniques for spinal surgery are becoming more widespread as improved technologies are developed. Stabilization plays an important role in fracture treatment, but appropriate instrumentation systems for endoscopic circumstances are lacking. Therefore a new thoracoscopically implantable stabilization system for thoracolumbar fracture treatment was developed and its biomechanical in vitro properties were compared. In a biomechanical in vitro study, burst fracture stabilization was simulated and anterior short fixation devices were tested under load with pure moments to evaluate the biomechanical stabilizing characteristics of the new system in comparison with a currently available system. With interbody graft and fixation the new system demonstrated higher stabilizing effects in flexion/extension and lateral bending and restored axial stability beyond the intact spine, as well as having comparable or improved effects compared with the current system. Because of this biomechanical characterization a clinical trial is warranted; the usefulness of the new system has already been demonstrated in 45 patients in our department and more than 300 cases in a multicenter study which is currently under way. PMID:14634854

Schultheiss, M; Hartwig, E; Kinzl, L; Claes, L; Wilke, H-J

2004-03-01

196

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

197

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

PubMed Central

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

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

2011-01-01

198

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

199

Prospective clinical evaluation of mandibular implant overdentures: Part I--Retention, stability, and tissue response.  

PubMed

Seventeen subjects with preexisting conventional complete dentures were evaluated in this prospective clinical study. Two implants were placed bilaterally in the anterior mandible. In a crossover experimental design, the conventional dentures were modified, and the retention, stability, and tissue response for conventional dentures were compared with implant overdentures that had O-ring and magnet overdenture attachments for all subjects. The study indicated statistical superiority of the implant overdenture to the conventional denture. The O-ring attachment proved significantly better than the magnet attachment for retention and stability. The soft tissue response showed a slight but significant improvement with implant overdenture therapy. PMID:7783014

Burns, D R; Unger, J W; Elswick, R K; Beck, D A

1995-04-01

200

Development and evaluation of a new product line of silicone elastomers for high voltage applications. Part 2  

Microsoft Academic Search

Silicone elastomers used for high voltage applications have proven their necessity in the areas of insulators, arresters, and cable accessories. There are many factors that make silicone materials advantageous in the insulator industry. These advantages include: long term endurance, hydrophobic recovery, and easy processing. We report on the latest results of ongoing accelerated aging studies being performed on a new

Tatyana P. Collins; Lee W. Hoffman; James L. Goudie

2000-01-01

201

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

202

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

PubMed

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

2013-08-01

203

Flight evaluation of the transonic stability and control characteristics of an airplane incorporating a supercritical wing  

NASA Technical Reports Server (NTRS)

A TF-8A airplane was equipped with a transport type supercritical wing and fuselage fairings to evaluate predicted performance improvements for cruise at transonic speeds. A comparison of aerodynamic derivatives extracted from flight and wind tunnel data showed that static longitudinal stability, effective dihedral, and aileron effectiveness, were higher than predicted. The static directional stability derivative was slower than predicted. The airplane's handling qualities were acceptable with the stability augmentation system on. The unaugmented airplane exhibited some adverse lateral directional characteristics that involved low Dutch roll damping and low roll control power at high angles of attack and roll control power that was greater than satisfactory for transport aircraft at cruise conditions. Longitudinally, the aircraft exhibited a mild pitchup tendency. Leading edge vortex generators delayed the onset of flow separation, moving the pitchup point to a higher lift coefficient and reducing its severity.

Matheny, N. W.; Gatlin, D. H.

1978-01-01

204

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

205

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.

German, Danielle; Latkin, Carl A.

2011-01-01

206

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

PubMed

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

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

2008-11-01

207

Study of second phase in bioabsorbable magnesium alloys: Phase stability evaluation via Dmol3 calculation  

NASA Astrophysics Data System (ADS)

Thermodynamical stabilities of four conventional second phases as well as magnesium matrix in bioabsorbable magnesium alloys were investigated theoretically via computer calculation method. Model of individual phase and systems including phase and four water molecular (phase-4H2O) were established to simulate the in vitro and in vivo environment. Local orbital density functional theory approach was applied to calculate the total energy for the individual phase and phase-4H2O system. The results demonstrated that all the second phases possessed higher phase stability compared with magnesium matrix, but the phase stability was quite different for different types of second phases or second phase-4H2O systems. Furthermore, a schematic process of inflammation reaction caused by magnesium alloy implants was proposed for the further evaluation on biocompatibility of different second phases.

Yang, Huazhe; Liu, Chen; Wan, Peng; Tan, Lili; Yang, Ke

2013-11-01

208

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

209

Evaluation of enzyme stability during preparation of polylactide-co-glycolide microspheres.  

PubMed

This work was aimed at studying enzyme prolidase stability and its interactions with the reagents and the process conditions involved in preparation, by an emulsification process, of prolidase loaded poly(lactide-co-glycolide) (PLGA) microparticulate systems. Enzyme stability was tested with respect to contact with methylene chloride, ethyl acetate, PLGA polymers, and several agents used as emulsifiers such as polyvinyl alcohol (PVA), polyvinyl pyrolidone (PVP), carboxymethyl cellulose (CMC) and sodium oleate (NaOl). Enzyme stability to temperature and mechanical stirring was also evaluated. Prolidase-loaded PLGA microspheres were prepared and evaluated in terms of protein activity. The results obtained showed that the prolidase-loaded PLGA microspheres can be prepared only upon enzyme stabilization by addition of both BSA and MnCl(2) into its TRIS solution. Methylene chloride was the suitable organic solvent to be used in the double emulsion process, together with PVA as dispersing agent in the outer aqueous phase. Low temperatures during the emulsification step and very short process times are recommended, in order to maintain enzyme activity at its maximum. In these conditions spherical microspheres were obtained, releasing active prolidase for up to 15 days. PMID:12433302

Perugini, P; Genta, I; Pavanetto, F; Modena, T; Maculotti, K; Conti, B

2002-01-01

210

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

211

Evaluation of frac fluid stability using a heated, pressurized flow loop  

SciTech Connect

A flow loop was used to evaluate the stability of frac fluids at high temperatures. The design provides enough pressure to prevent vaporization of water base systems up to 350/sup 0/F. The flow loop is a 25-gallon-capacity pipe viscosimeter with a 1-inch-diameter, 20-foot-long test section. Shear rates are variable, but most tests were run at values approximating the shear rates in a fracture. Shearing and heat exposure times of up to 6 hours were run. Cross-linked polymer systems from four service companies were prepared according to each supplier's recommendations and evaluated at 180/sup 0/ and 245/sup 0/F. The tests showed that cross-linked frac fluids degrade with temperature and shear, losing much of their viscosity and proppant-carrying capacity in a few hours. Thermal stability is a major factor in selecting gels for fracing deep, high-temperature reservoirs.

Lescarboura, J.A.; Sifferman, T.R.; Wahl, H.A.

1982-09-01

212

[Comparative hygienic evaluation of nonionogenic surface-active agents with regard to stability and transformation].  

PubMed

The stability of the surfactants penazoline 10-16 B, neonol AF9-CN, and perfluorodecyl alcohol on boiling, exposure to ozone, ultraviolet and electromagnetic irradiation, biota in the model water reservoir, active sludge in the model air tank was evaluated. The transformation products forming under the influence of different damaging factors were assessed. The comparative hazard of parent compounds and their transformation products on biological test objects was studied. PMID:9662879

Zholdakova, Z I; Berdina, R B; Kustova, E V

1998-01-01

213

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

NASA Astrophysics Data System (ADS)

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

Kawaguchi, Shohei; Shirai, Koji; Kanazawa, Kenji

214

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

215

[Peritrochanteric femur fractures--evaluation of distant functional outcomes of operative treatment using Dynamic Hip Stabilizer].  

PubMed

The authors make distant evaluation of functional and radiological outcomes after operative treatment of peritrochanteric femur fractures using Dynamic Hip Stabilizer (DSB). It was done basing on clinical material of 1998-2005 years. 142 patients were included into the study, 89 women (62.7%) and 53 men (37.3%), aged between 53-97 years (average 77 years). Boyd and Gryffin classification was used for evaluation of type of fracture, Harris criterions was used for evaluation of functional outcomes, and Golec's criterions was used for evaluation of radiological outcomes. Obtained outcomes confirm usefulness of DSB for treatment of type I and II according to Boyd and Griffin classification. Poor outcomes were obtained in type III and IV. PMID:18669107

Sienkiewicz, Dariusz; Golec, Edward; Nowak, Sebastian; Golec, Joanna; Szczygie?, Elzbieta; Plewa, Alicja

2008-01-01

216

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

217

Evaluation of the Effects of Different Surface Configurations on Stability of Miniscrews  

PubMed Central

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

Topcuoglu, Tolga; Bicakci, A. Altug; Avunduk, M. Cihat; Sahin Inan, Z. Deniz

2013-01-01

218

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

219

Obese elderly women exhibit low postural stability: a novel three-dimensional evaluation system  

PubMed Central

OBJECTIVE: The aim of this study was to evaluate the multisegmental static postural balance of active eutrophic and obese elderly women using a three-dimensional system under different sensory conditions. METHODS: A cross-sectional study was conducted on 31 elderly women (16 eutrophic and 15 obese) aged 65 to 75 years. The following anthropometric measurements were obtained: weight, height, waist and hip circumference, and handgrip strength. The physical activity level was evaluated using the International Physical Activity Questionnaire. Body composition was measured using the deuterium oxide dilution technique. The Polhemus® Patriot (three-dimensional) equipment was used to measure the parameters of postural balance along the anteroposterior and laterolateral axes. The data acquisition involved one trial of 60 s to test the limit of stability and four trials of 90 s each under the following conditions: (1) eyes open, stable surface; (2) eyes closed, stable surface; (3) eyes open, unstable surface; and (4) eyes closed, unstable surface. RESULTS: For the limit of stability, significant differences were observed in the maximum anteroposterior and laterolateral displacement (p<0.01) and in the parameter maximum anteroposterior displacement in the eyes closed stable surface condition (p<0.01) and maximum anteroposterior and laterolateral displacement in the eyes open unstable surface (p<0.01 and p?=?0.03) and eyes closed unstable surface (p<0.01 and p<0.01) conditions. CONCLUSIONS: Obese elderly women exhibited a lower stability limit (lower sway area) compared with eutrophic women, leaving them more vulnerable to falls.

Carneiro, Jose Ailton O.; Santos-Pontelli, Taiza E.G.; Vilaca, Karla H.C.; Pfrimer, Karina; Colafemina, Jose F.; Carneiro, Antonio Adilton O.; Ferriolli, Eduardo

2012-01-01

220

Biological and biomechanical evaluation of bone remodelling and implant stability after using an osteotome technique.  

PubMed

The influence of the osteotome technique on the osseointegration and biomechanical behaviour of cylinder implants (SLA, ITI was compared with conventional preparation of the implant site in an animal model. A total of 56 implants were placed in the cranial and caudal tibia condyle of six Gottinger minipigs. The implant site was prepared either by the conventional technique with drills (control group A) or by the osteotome technique (experimental group B). Resonance frequency measurements (RFMs) were made on each implant at the time of fixture placement and at the time of scarification. Half of the minipigs were sacrificed 7 days and 28 days after implant placement and the implants were removed with the surrounding bone. Bone tissue responses were evaluated by histological analysis and removal torque testing. For histological evaluation 30-50 microm-thick ground sections were examined. Biomechanical testing revealed a significantly higher stability of implants in the control group (A) than in the experimental group (B) (P = 0.004) at day 7. After 28 days implant stability in the control group remained significant higher (47%) than those of group B (P > 0.001). RFM demonstrated no significant difference between both groups and during the experimental course. Histological analysis demonstrated fractured trabeculae in peri-implant bone in the experimental group at day 7, while they were not posed at day 28. We conclude that the decreased implant stability by using the osteotome technique is based on microfractures in peri-implant bone. PMID:15642025

Büchter, André; Kleinheinz, Johannes; Wiesmann, Hans Peter; Kersken, Jan; Nienkemper, Manuel; Weyhrother, Hendrik von; Joos, Ulrich; Meyer, Ulrich

2005-02-01

221

Stability evaluation of thermosensitive drug carrier systems based on Pluronic F-127 polymer.  

PubMed

The aim of this study was to evaluate the stability of thermosensitive systems based on Pluronic F-127 polymer, in aspects of their possible application in novel drug technology. A formulation was prepared without any active ingredient, consisting of 16% (w/w) of polymer dissolved in aqueous medium. Such preparation was autoclaved and then subjected to 3-month conditioning at elevated (40 degrees) and reduced (5 degrees C) temperature. Rheological parameters: viscosity, consistency and sol-gel transition characteristics were studied in 1-month interval. The significance of measured changes was evaluated by proper statistical analyses. Significant changes exceeding the established criteria (+/- 10% of every initial value) were observed during the study. Furthermore, total involution of sol-gel transition phenomenon was observed in samples stored at 40 degrees C. Results indicate the lack of stability in tested formulation at both of storage conditions. However, some regularity indicates that the stability at reduced temperature could be confirmed, if only the concentration of polymer and the measurements schedule were slightly modified. PMID:24779205

Grela, Kamil P; Marciniak, Dominik M; Pluta, Janusz

2014-01-01

222

The idea of PGA stream computations for soil slope stability evaluation  

NASA Astrophysics Data System (ADS)

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

Tran, Chi; Srokosz, Piotr

2010-09-01

223

United States Environmental Protection Agency Municipal-Waste Combustion Residue Solidification/Stabilization Evaluation Program  

SciTech Connect

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 technologies to treat residues from the combustion of municipal solid waste (MSW). Solidification/Stabilization is being emphasized in the current program. The technology may enhance the environmental performance of the residues when disposed in the land, when used as road bed aggregate, as building blocks, and in the marine environment as reefs or shore erosion control barriers. The program includes four S/S process types: cement, silicate, cement kiln dust and a phosphate based process. Residue types being evaluated are fly ash, bottom ash and combined residues. An array of chemical leaching tests and physical tests are being conducted to characterize the untreated and treated residues. The S/S evaluation program is the first part of ORD's Municipal Solid Waste Innovative Technology Evaluation (MITE) program.

Wiles, C.C.; Kosson, D.S.; Holmes, T.

1990-06-01

224

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

SciTech Connect

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

Shanfield, Z.; Moriwaki, M.M.

1987-12-01

225

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

226

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

PubMed Central

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

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

2010-01-01

227

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

PubMed Central

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

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

2013-01-01

228

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...

229

Angioscopic Evaluation of Stabilizing Effects of Bezafibrate on Coronary Plaques in Patients With Coronary Artery Disease  

PubMed Central

Background Since long-term administrations of anti-hyperlipidemic agents result in reduction in % stenosis or increase in minimum lumen diameter (MLD) of stenotic coronary segments, it is generally believed that anti-hyperlipidemic agents stabilize vulnerable coronary plaques. However, recent pathologic and angioscopic studies revealed that vulnerability of coronary plaques is not related to severity of stenosis and the rims rather than top of the plaques disrupt, and therefore, angiography is not adequate for evaluation of vulnerability. Angioscopy enables macroscopic pathological evaluation of the coronary plaques. Therefore, we carried out a prospective angioscopic open trial for evaluation of the stabilizing effects of bezafibrate on coronary plaques. Methods From April, 1997 to December, 1998, 24 patients underwent coronary angioscopy of the plaques in the non-targeted vessels during coronary interventions and 6 months later. The patients were divided into control (10 patients, 14 plaques) and bezafibrat (14 patients, 21 plaques) groups. Oral administration of bezafibrate (Bezatol SR, 400mg/day) was started immediately after the interventions and was continued for 6 months. The vulnerability score was determined based on angioscopic characteristics of plaques and it was compared before and 6 months later. Results Six months later, vulnerability score was reduced (from 1.6 to 0.8;p < 0.05) in bezafibrate group and unchanged (from 1.4 to 1.3; NS) in control group. In bezafibrate group, the changes in vulnerability score was not correlated with those in % stenosis or MLD. Conclusion The results indicate that bezafibrate can stabilize coronary plaques.

Fujimori, Yoshiharu; Ohsawa, Hidefumi; Hirose, Jyunichi; Noike, Hirofumi; Tokuhiro, Keiichi; Kanai, Masahito; Yoshinuma, Masaki; Mineoka, Kazuhito; Hitsumoto, Takashi; Aoyagi, Kaneyuki; Sakurai, Takeshi; Sato, Shin; Yoshinaga, Kokushi; Ozegawa, Masaaki; Morio, Hiroshi; Yamada, Katsumi; Terasawa, Kimiko; Uchida, Yuuko; Oshima, Tomomitsu

2000-01-01

230

Angioscopic evaluation of stabilizing effects of bezafibrate on coronary plaques in patients with coronary artery disease.  

PubMed

Background Since long-term administrations of anti-hyperlipidemic agents result in reduction in % stenosis or increase in minimum lumen diameter (MLD) of stenotic coronary segments, it is generally believed that anti-hyperlipidemic agents stabilize vulnerable coronary plaques. However, recent pathologic and angioscopic studies revealed that vulnerability of coronary plaques is not related to severity of stenosis and the rims rather than top of the plaques disrupt, and therefore, angiography is not adequate for evaluation of vulnerability.Angioscopy enables macroscopic pathological evaluation of the coronary plaques. Therefore, we carried out a prospective angioscopic open trial for evaluation of the stabilizing effects of bezafibrate on coronary plaques.Methods From April, 1997 to December, 1998, 24 patients underwent coronary angioscopy of the plaques in the non-targeted vessels during coronary interventions and 6 months later. The patients were divided into control (10 patients, 14 plaques) and bezafibrat (14 patients, 21 plaques) groups. Oral administration of bezafibrate (Bezatol SR, 400mg/day) was started immediately after the interventions and was continued for 6 months. The vulnerability score was determined based on angioscopic characteristics of plaques and it was compared before and 6 months later.Results Six months later, vulnerability score was reduced (from 1.6 to 0.8;p < 0.05) in bezafibrate group and unchanged (from 1.4 to 1.3; NS) in control group. In bezafibrate group, the changes in vulnerability score was not correlated with those in % stenosis or MLD. Conclusion The results indicate that bezafibrate can stabilize coronary plaques. PMID:18493543

Uchida, Y; Fujimori, Y; Ohsawa, H; Hirose, J; Noike, H; Tokuhiro, K; Kanai, M; Yoshinuma, M; Mineoka, K; Hitsumoto, T; Aoyagi, K; Sakurai, T; Sato, S; Yoshinaga, K; Ozegawa, M; Morio, H; Yamada, K; Terasawa, K; Uchida, Y; Oshima, T

2000-01-01

231

Evaluation of Thermal Stability of Nomex® Brand Paper in Main Transformer of Shinkansen Train Series 100  

NASA Astrophysics Data System (ADS)

Nomex® brand paper has been used as wire wrapping insulation material of main transformers of Shinkansen Train Series 100 with silicone oil. After approximately 12-13 years service, 8 transformers of Series 100 were sampled to evaluate degradation of Nomex® brand paper in terms of tensile strength and intrinsic viscosity. All data were compared with initial data. The result of less degradation shows Nomex® has good thermal stability in silicone oil in the main transformer of Shinkansen Train which were used in very severe condition.

Tanaka, Hirokazu; Kondo, Chihiro; Naruse, Shinji; Ishii, Yoshitada

232

Evaluation of the stability of dye heteroassociates formed in aqueous solutions  

NASA Astrophysics Data System (ADS)

The additive tetraphenylarsonium-tetraphenylborate model of interactions was found to be applicable to the problem of “preexperimental” evaluation of the stability of associates formed by dye cations (Ct+) and anions (An-) in aqueous solutions. The possibility of predicting equilibrium association constants K as from preliminarily calculated ? G(Ct+) and ? G(An-) and of solving the inverse problem was analyzed. The invariability of the ? G(Ct+) and ? G(An-) values and the problem of bringing calculation results in consistency with the experimental K as values are discussed.

Shapovalov, S. A.

2008-09-01

233

Reliability of a New Stabilized Dynamometer System for the Evaluation of Hip Strength  

PubMed Central

Background: Hip strength is associated with numerous orthopaedic and neuromuscular injuries and/or pathologies and may be assessed with a variety of anatomic testing positions and techniques. Isokinetic dynamometers are generally too cumbersome and intricate for efficient use in mass screenings (for prognostic studies of risk for injury) as well as with special populations. The reliability of isometric testing devices has demonstrated varied reliability, generally examining only 1 or 2 motions of the hip and reporting values of force, not torque. Consequently, there is a need for an efficient hip strength-testing device to quantify torque that tests subjects in 1 anatomic position, while evaluating multiple hip motions. Hypothesis: Evaluation of supine hip abduction, adduction, flexion, and extension torque using a new stabilized dynamometer system will produce good to excellent intra- and interexaminer reliability results. Study Design: A blinded, randomized, repeated-measures study design was used in this descriptive laboratory investigation. Methods: Supine isometric hip flexion, extension, abduction, and adduction torques were evaluated with a cage-stabilized dynamometer in 19 collegiate and professional-level ice hockey athletes by 2 investigators at 3 time intervals. Inter- and intrarater reliability was assessed. Results: Supine hip flexion, extension, abduction, and adduction torque was performed with good to excellent inter- and intrarater reliability (intraclass correlation coefficients ranging from 0.74 to 0.92 and 0.78 to 0.92, respectively) for all motions tested. Conclusions: We have developed an isometric hip strength-testing device that can be assembled around an examination table to efficiently and reliably evaluate torque developed for multiple motions of the hip. Clinical Relevance: This device and testing protocol may be used to efficiently evaluate hip strength in numerous settings; it allows decreased subject burden and increased comfort (which may be important following an injury in case-control investigations); and it may be well tolerated when testing athletes as well as special populations in the clinical setting.

Tourville, Timothy W.; Smith, Helen C.; Shultz, Sandra J.; Vacek, Pamela M.; Slauterbeck, James R.; Johnson, Robert J.; Beynnon, Bruce D.

2013-01-01

234

Evaluation of the bioefficacy of a stabilized form of human growth hormone (SP-hGH).  

PubMed

Protein aggregation is a major obstacle in maintaining the stability of therapeutic proteins. In previous studies, fusion between a stabilizing peptide (SP) and human growth hormone (hGH) resulted in improved solubility and stability compared with hGH alone, although the bioactivity of the protein was not confirmed in vivo. In this study, we evaluated the bioefficacy of hGH and SP-hGH in vivo using a mouse model. Subcutaneous injections of 30 ?g of hGH or SP-hGH were administered to 8-month-old female mice, twice a week for 14 weeks. Neither hGH nor SP-hGH significantly affected body weight or blood glucose levels compared with control mice. Interestingly, abdominal fat was significantly reduced in SP-hGH-treated mice compared with hGH-treated mice. While total cholesterol, HDL, and LDL levels were slightly higher in both groups, TG levels were significantly reduced in both SP-hGH and hGH-treated mice compared with control mice. IGF-1 levels in the liver were increased in both the SP-hGH and hGH groups, thereby inducing liver cell proliferation. These results suggest that SP fusion with hGH attained similar or improved bioefficacy compared with hGH alone. PMID:23681752

Lee, S-B; Park, H; Koh, J; Lee, H; Kim, J

2013-09-01

235

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

236

Physico-mechanical and stability evaluation of carbamazepine cocrystal with nicotinamide.  

PubMed

The focus of this investigation was to prepare the cocrystal of carbamazepine (CBZ) using nicotinamide as a coformer and to compare its preformulation properties and stability profile with CBZ. The cocrystal was prepared by solution cooling crystallization, solvent evaporation, and melting and cryomilling methods. They were characterized for solubility, intrinsic dissolution rate, chemical identification by Fourier transform infrared spectroscopy, crystallinity by differential scanning calorimetry, powder X-ray diffraction, and morphology by scanning electron microscopy. Additionally, mechanical properties were evaluated by tensile strength and Heckel analysis of compacts. The cocrystal and CBZ were stored at 40°C/94% RH, 40°C/75% RH, 25°C/60% RH, and 60°C to determine their stability behavior. The cocrystals were fluffy, with a needle-shaped crystal, and were less dense than CBZ. The solubility profiles of the cocrystals were similar to CBZ, but its intrinsic dissolution rate was lower due to the high tensile strength of its compacts. Unlike CBZ, the cocrystals were resistant to hydrate transformation, as revealed by the stability studies. Plastic deformation started at a higher compression pressure in the cocrystals than CBZ, as indicated by the high yield pressure. In conclusion, the preformulation profile of the cocrystals was similar to CBZ, except that it had an advantageous resistance to hydrate transformation. PMID:21598082

Rahman, Ziyaur; Agarabi, Cyrus; Zidan, Ahmed S; Khan, Saeed R; Khan, Mansoor A

2011-06-01

237

Voltage sag and swell generator with thyristor controlled reactor  

Microsoft Academic Search

This paper describes a new economical sag\\/swell voltage generator suitable for the evaluation of high power custom power devices such as DVR (dynamic voltage restorer) and DSTATCOM (distribution static compensator). Proposed system was designed to generate the several power quality disturbances in MVA power ratings-sag, swell, under voltage, over voltage and harmonic distortions. The sag and the under voltage can

Y. H. Chung; G. H. Kwon; T. B. Park; G. Y. Lim

2002-01-01

238

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

239

Fast direct voltage controller for VSC transmission  

Microsoft Academic Search

This paper develops a controller that enables good stability and fast responses of voltage source converter (VSC) transmission. The design is challenging because the uncontrolled system is multivariable having two possible rectifier inputs and many possible rectifier outputs and similar inputs and outputs on the inverter side. It is determined that the fastest possible controller is inverter DC voltage. An

L. A. Lamont; D. Jovcic; K. Abbott

2004-01-01

240

Impact of large scale wind power on power system stability  

Microsoft Academic Search

This paper presents a detailed analysis of the impact of large scale wind power generation on both the dynamic voltage stability and the transient stability of electric power systems. The following problems have been analyzed: different penetration of wind power impact on transient stability and on voltage stability (dynamic voltage stability) following a major fault in the transmission system, determination

M. El-Shimy; M. A. L. Badr; O. M. Rassem

2008-01-01

241

Domino logic with variable threshold voltage keeper  

Microsoft Academic Search

A variable threshold voltage keeper circuit technique is proposed for simultaneous power reduction and speed enhancement of domino logic circuits. The threshold voltage of a keeper transistor is dynamically modified during circuit operation to reduce contention current without sacrificing noise immunity. The variable threshold voltage keeper circuit technique enhances circuit evaluation speed by up to 60% while reducing power dissipation

Volkan Kursun; Eby G. Friedman

2003-01-01

242

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

243

Partial discharge testing under direct voltage conditions  

NASA Technical Reports Server (NTRS)

DC partial discharge (PD) (corona) testing is performed using a multichannel analyzer for pulse storing, and data is collected during increase of voltage and at quiescent voltage levels. Thus high voltage ceramic disk capacitors were evaluated by obtaining PD data interspersed during an accelerated life test. Increased PD activity was found early in samples that later failed catastrophically. By this technique, trends of insulation behavior are revealed sensitively and nondestructively in high voltage dc components.

Bever, R. S.; Westrom, J. L.

1982-01-01

244

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

PubMed

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

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

2013-09-15

245

Use of fluorescence for the high-throughput evaluation of synergistic thermal and photo stabilizer interactions in poly (vinyl chloride)  

SciTech Connect

The selection of thermal and photo stabilizers for poly (vinyl chloride) (PVC) using conventional methods is a time-consuming process. The high-throughput screening method developed in this research demonstrates rapid and efficient ways to quantify the effectiveness of PVC stabilizers with respect to raw plastic materials, stabilizers, levels of use, and testing conditions. An experimental protocol using liquid sampling and fluorescence measurement was developed to determine the effectiveness of formulations. This was used to evaluate the performance of stabilizers based on the change of fluorescence emission at 440 nm after thermal aging or ultraviolet (UV) radiation. The performance of PVC formulations using six different types of stabilizers was successfully mapped for both PVC resin and flexible PVC.

Wu Chunyong; Wicks, Douglas A. [School of Polymers and High Performance Materials, 118 College Drive 10076, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (United States)

2005-06-15

246

Evaluation of global warming impacts for different levels of stabilization as a step toward determination of the long-term stabilization target  

Microsoft Academic Search

In order to estimate the benefit attributable to alleviating global warming for a kind of cost–benefit analysis of global\\u000a warming mitigation, global warming impacts were quantitatively evaluated for a pathway of unmitigated CO2 emissions and three pathways to stabilize the atmospheric CO2 concentration at different levels, keeping unchanged the assumed conditions on population and GDP growths, although the GDP\\u000a losses

Ayami Hayashi; Keigo Akimoto; Fuminori Sano; Shunsuke Mori; Toshimasa Tomoda

2010-01-01

247

Application of dynamic programming to evaluate the slope stability of a vertical extension to a balefill.  

PubMed

The slope-stability of a proposed vertical extension of a balefill was investigated in the present study, in an attempt to determine a geotechnically conservative design, compliant with New Jersey Department of Environmental Protection regulations, to maximize the utilization of unclaimed disposal capacity. Conventional geotechnical analytical methods are generally limited to well-defined failure modes, which may not occur in landfills or balefills due to the presence of preferential slip surfaces. In addition, these models assume an a priori stress distribution to solve essentially indeterminate problems. In this work, a different approach has been applied, which avoids several of the drawbacks of conventional methods. Specifically, the analysis was performed in a two-stage process: (a) calculation of stress distribution, and (b) application of an optimization technique to identify the most probable failure surface. The stress analysis was performed using a finite element formulation and the location of the failure surface was located by dynamic programming optimization method. A sensitivity analysis was performed to evaluate the effect of the various waste strength parameters of the underlying mathematical model on the results, namely the factor of safety of the landfill. Although this study focuses on the stability investigation of an expanded balefill, the methodology presented can easily be applied to general geotechnical investigations. PMID:20142412

Kremen, Arie; Tsompanakis, Yiannis

2010-04-01

248

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

249

Evaluation of pre-analysis loss of dependent drugs in wastewater: stability and binding assessments.  

PubMed

Wastewater analysis has the potential to provide objective and timely data on population drug consumption, but some crucial factors such as pre-analysis drug loss during sample storage and filtration could affect the accuracy and reliability of the method, and these uncertainties have yet to be fully assessed. This study was designed to evaluate analyte stability in wastewater stored under different conditions with the aim of optimizing the sample storage procedures for future studies. It also investigated whether there is significant analyte loss during filtration before sample extraction and storage after that. The studied substances and metabolites were: cotinine, cocaine and its metabolite benzoylecgonine, phenethylamines amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), opioids including codeine, methadone, 6-monoacetylmorphine (MAM) and morphine. In most situations, storing samples at 4?°C is sufficient to stabilize analytes for at least 2?weeks, and refrigeration is unnecessary during sample transportation within 3?days. However, additional measures need to be taken if unstable analytes such as cocaine and MAM are to be analyzed. No significant analyte loss was observed in the filtration process or in reconstituted extract stored at 4?°C or -20?°C for 2?weeks. By choosing stable analytes and proper storage conditions, wastewater analysis has the potential to provide accurate data for estimation of community drug use. PMID:23047767

Chen, Chang; Kostakis, Chris; Irvine, Rodney J; Felgate, Peter D; White, Jason M

2013-08-01

250

On-line transient stability screening of 14,000-bus models using TEPCO-BCU: Evaluations and methods  

Microsoft Academic Search

PJM Interconnection has successfully designed and implemented a Transient Stability Analysis & Control (TSA&C) system. This is the first on-line transient stability analysis ever performed in the control center of a large power network. TEPCO-BCU was selected as a leading fast screening tool to improve the performance of PJM's TSA system. This paper will present an evaluation of TEPCO-BCU in

Hsiao-Dong Chiang; Jianzhong Tong; Yasuyuki Tada

2010-01-01

251

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

252

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

253

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

PubMed

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

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

2014-03-01

254

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

255

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

PubMed Central

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.

de Oliveira Marreiro, Raquel; Bandeira, Maria Fulgencia Costa Lima; de Souza, Tatiane Pereira; de Almeida, Mailza Costa; Bendaham, Katiana; Venancio, Gisely Naura; Rodrigues, Isis Costa; Coelho, Cristiane Nagai; Milerio, Patricia Samea Ledo Lima; de Oliveira, Glauber Palma; de Oliveira Conde, Nikeila Chacon

2014-01-01

256

Evaluation of the stability and antioxidant activity of nanoencapsulated resveratrol during in vitro digestion.  

PubMed

Resveratrol was encapsulated in oil-in-water food-grade nanoemulsions of subcellular size, produced by high-pressure homogenization. Physicochemical stability was evaluated under accelerated aging (high temperature and UV light exposure), as well as during simulated gastrointestinal digestion. Antioxidant activity was assessed at different stages of digestion by chemical assays and by an improved cellular assay, to measure exclusively the residual activity of resveratrol that penetrated inside Caco-2 cells. Results showed that the nanoemulsions based on soy lecithin/sugar esters and Tween 20/glycerol monooleate were the most physically and chemically stable, in terms of mean droplet size (always <180 nm) and resveratrol loading, during both accelerated aging and gastrointestinal digestion. These formulations also exhibited the highest chemical and cellular antioxidant activities, which was comparable to unencapsulated resveratrol dissolved in DMSO, suggesting that nanoencapsulated resveratrol, not being metabolized in the gastrointestinal tract, can be potentially absorbed through the intestinal wall in active form. PMID:22026647

Sessa, Mariarenata; Tsao, Rong; Liu, Ronghua; Ferrari, Giovanna; Donsì, Francesco

2011-12-14

257

Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems  

NASA Astrophysics Data System (ADS)

The aim of this study was the further development of dysprosia-stabilized zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial standard thermal barrier coating. Two morphologies of ceramic top coat were studied: one using a dual-layer system and the second using a polymer to generate porosity. Evaluations were carried out using a laser flash technique to measure thermal properties. Lifetime testing was conducted using thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis was used to characterize porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

Curry, Nicholas; Markocsan, Nicolaie; Östergren, Lars; Li, Xin-Hai; Dorfman, Mitch

2013-08-01

258

Use of a general control simulation program to evaluate HVAC control stability  

NASA Astrophysics Data System (ADS)

A general process engineering simulation program for a microcomputer is used to evaluate the response of a cooling system to changes in load, set point, and controller tuning parameters to better understand the control stability of a supply air cooling system used in the Mobile Windows Thermal Test (MoWiTT) Facility. A detailed system model is built out of standard components and is used to plot the steady state performance under different operating conditions. The response of the cooling coil output depends strongly on the transport delays. For a system with a linear control valve, the process gain of the cooling coil increases rapidly as the valve flow fraction decreases. A system which is stable at mid-range is shown to become marginally unstable at the low end of the control range. The application of both an equal percentage valve and reheat are shown to improve the control response of the system under low cooling load conditions.

Zhang, Xinbang; Warren, M. L.

1987-08-01

259

Nondestructive evaluation of orthopaedic implant stability in THA using highly nonlinear solitary waves  

NASA Astrophysics Data System (ADS)

We propose a new biomedical sensing technique based on highly nonlinear solitary waves to assess orthopaedic implant stability in a nondestructive and efficient manner. We assemble a granular crystal actuator consisting of a one-dimensional tightly packed array of spherical particles, to generate acoustic solitary waves. Via direct contact with the specimen, we inject acoustic solitary waves into a biomedical prosthesis, and we nondestructively evaluate the mechanical integrity of the bone-prosthesis interface, studying the properties of the waves reflected from the contact zone between the granular crystal and the implant. The granular crystal contains a piezoelectric sensor to measure the travelling solitary waves, which allows it to function also as a sensor. We perform a feasibility study using total hip arthroplasty (THA) samples made of metallic stems implanted in artificial composite femurs using polymethylmethacrylate for fixation. We first evaluate the sensitivity of the proposed granular crystal sensor to various levels of prosthesis insertion into the composite femur. Then, we impose a sequence of harsh mechanical loading on the THA samples to degrade the mechanical integrity at the stem-cement interfaces, using a femoral load simulator that simulates aggressive, accelerated physiological loading. We investigate the implant stability via the granular crystal sensor-actuator during testing. Preliminary results suggest that the reflected waves respond sensitively to the degree of implant fixation. In particular, the granular crystal sensor-actuator successfully detects implant loosening at the stem-cement interface following violent cyclic loading. This study suggests that the granular crystal sensor and actuator has the potential to detect metal-cement defects in a nondestructive manner for orthopaedic applications.

Yang, Jinkyu; Silvestro, Claudio; Sangiorgio, Sophia N.; Borkowski, Sean L.; Ebramzadeh, Edward; De Nardo, Luigi; Daraio, Chiara

2012-01-01

260

High voltage power transistor development  

NASA Technical Reports Server (NTRS)

Design considerations, fabrication procedures, and methods of evaluation for high-voltage power-transistor development are discussed. Technique improvements such as controlling the electric field at the surface and perserving lifetimes in the collector region which have advanced the state of the art in high-voltage transistors are discussed. These improvements can be applied directly to the development of 1200 volt, 200 ampere transistors.

Hower, P. L.

1981-01-01

261

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.

2014-01-01

262

N basin stabilization project independent readiness evaluation plan for high exposure rate hardware removal.  

National Technical Information Service (NTIS)

Completion of the N Basin Stabilization Project will accomplish the following objectives: removing equipment, debris, and any suspect fuel pieces; removing water from N Basin and associated pits; and stabilizing N Basin surfaces to prevent the spread of r...

C. L. Volkman E. L. Adamson

1996-01-01

263

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

SciTech Connect

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

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

2011-07-15

264

Bioremediation of Contaminated Lake Sediments and Evaluation of Maturity Indicies as Indicators of Compost Stability  

PubMed Central

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

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

2005-01-01

265

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...

266

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...

267

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

268

Numerical simulation of ultrasonic wave propagation for the evaluation of dental implant biomechanical stability.  

PubMed

Osseointegration of dental implants remains poorly understood. The objective of this numerical study is to understand the propagation phenomena of ultrasonic waves in prototypes cylindrically shaped implants and to investigate the sensitivity of their ultrasonic response to the surrounding bone biomechanical properties. The 10 MHz ultrasonic response of the implant was calculated using a finite difference numerical simulation tool and was compared to rf signals taken from a recent experimental study by Mathieu et al. [Ultrasound Med. Biol. 37, 262-270 (2011a)]. Reflection and mode conversion phenomena were analyzed to understand the origin of the different echoes and the importance of lateral wave propagation was evidenced. The sensitivity of the ultrasonic response of the implant to changes of (i) amount of bone in contact with the implant, (ii) cortical bone thickness, and (iii) surrounding bone material properties, was compared to the reproducibility of the measurements. The results show that, either a change of 1 mm of bone in contact with the implant, or 1.1 mm of cortical thickness or 12% of trabecular bone mass density should be detectable. This study paves the way for the investigation of the use of quantitative ultrasound techniques for the evaluation of bone-implant interface properties and implant stability. PMID:21682427

Mathieu, Vincent; Anagnostou, Fani; Soffer, Emmanuel; Haiat, Guillaume

2011-06-01

269

Techniques and methodologies in modern electrocatalysis: evaluation of activity, selectivity and stability of catalytic materials.  

PubMed

The development and optimisation of materials that promote electrochemical reactions have recently attracted attention mainly due to the challenge of sustainable provision of renewable energy in the future. The need for better understanding and control of electrode-electrolyte interfaces where these reactions take place, however, implies the continuous need for development of efficient analytical techniques and methodologies capable of providing detailed information about the performance of electrocatalysts, especially in situ, under real operational conditions of electrochemical systems. During the past decade, significant efforts in the fields of electrocatalysis and (electro)analytical chemistry have resulted in the evolution of new powerful methods and approaches providing ever deeper and unique insight into complex and dynamic catalytic systems. The combination of various electrochemical and non-electrochemical methods as well as the application of quantum chemistry calculations has become a viable modern approach in the field. The focus of this critical review is primarily set on discussion of the most recent cutting-edge achievements in the development of analytical techniques and methodologies designed to evaluate three key constituents of the performance of electrocatalysts, namely, activity, selectivity and stability. Possible directions and future challenges in the design and elaboration of analytical methods for electrocatalytic research are outlined. PMID:24418971

Bandarenka, Aliaksandr S; Ventosa, Edgar; Maljusch, Artjom; Masa, Justus; Schuhmann, Wolfgang

2014-03-21

270

Evaluation of the thermal stability POHC incinerability ranking in a pilot-scale rotary kiln incinerator  

SciTech Connect

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 POHCs with predicted incinerability spanning the range of most to least difficult to incinerate class were combined with a clay-based sorbent and batch-fed to the facility's pilot-scale rotary kiln incinerator via a fiberpack drum ram feeder. Kiln operating conditions were varied to include a baseline operating condition, three modes of attempted incineration failure, and a worst case combination of the three failure modes. Kiln exit POHC DREs were in the 99.99 percent range for the volatile POHCs for the baseline, mixing failure (increased charge mass), and matrix failure (decreased feed H/C) tests. Semivolatile POHCs were not detected in the kiln exit for these tests; corresponding DREs were generally greater than 99.999 percent. The thermal failure (low kiln temperature) and worst case (combination of thermal, mixing, and matrix failure) tests resulted in substantially decreased kiln exit POHC DREs. These ranged from 99 percent or less for Freon 113 to greater than 99.999 percent for the less stable-ranked semivolatile POHCs. General agreement between relative kiln exit POHC DRE and predicted incinerability class was observed.

Lee, J.W.; Waterland, L.R.; Whitworth, W.E.; Carroll, G.J.

1991-01-01

271

Pilot-scale evaluation of the thermal-stability POHC incinerability anking  

SciTech Connect

A test series were performed at the U.S. EPA Incineration Research Facility (IRF) to evaluate the thermal-stability-based principal organic hazardous constituent (POHC) incinerability ranking. Mixtures of twelve POHCs with predicted incinerabilities spanning the range of most- to least-difficult-to-incinerate classes were combined with a clay-based sorbent matrix and fed to the facility's pilot-scale rotary kiln incinerator. Kiln operating conditions were varied to include a baseline operating condition, three modes of attempted incineration failure, and a worst-case combination of the three failure modes. Kiln-exit POHC destruction and removal efficiencies (DREs) were in the 99.99% range for the volatile POHCs during the baseline, mixing failure and matrix failure tests. Semivolatile POHCs were not detected at the kiln exit for these tests; corresponding DREs were generally greater than 99.999%. The thermal failure and worst-case tests resulted in substantially decreased kiln-exit POHC DREs, ranging from less than 99% to greater than 99.999%. General agreement between measured and predicted relative kiln-exit POHC DREs was observed for those two tests.

Lee, J.W.; Whitworth, W.E.; Waterland, L.R.

1992-04-01

272

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.

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

2010-01-01

273

Evaluation of the thermal oxidative stability of polyimides via TGA techniques  

Microsoft Academic Search

Thermogravimetric analysis (TGA) has been used for many years to eval- uate polymer thermal stability. The objective of this study is to determine if weight-loss curves from TGA and isothermal TGA (IGA) can be used to determine degradation activation energies and thus rank the thermal stability (TS) and thermooxidative stability (TOS) for selected polyimides. Two high-temperature stable addition-cured polyimides and

Mary Jo Turk; Asif S. Ansari; William B. Alston; Gloria S. Gahn; Aryeh A. Frimer; Daniel A. Scheiman

1999-01-01

274

Evaluation of Hose in Hose Transfer Line Service Life for Hanfords Interim Stabilization Program  

Microsoft Academic Search

RPP-6153, Engineering Task Plan for Hose-in-Hose Transfer System for the Interim Stabilization Program (Torres, 2000a), defines the programmatic goals, functional requirements, and technical criteria for the development and subsequent installation of waste 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 (Torres, 2000b), has been issued to

2001-01-01

275

A single-phase voltage sag generator for testing electrical equipments  

Microsoft Academic Search

This paper describes a transformer-based voltage sag generator (VSG) suitable to evaluate the susceptibility of electrical equipment to voltage sag. The built VSG utilized one auto-transformer and two solid state relays (SSRs) to provide nominal voltage and sag voltage to the load. The switch statuses of two SSRs are controlled by nominal voltage and sag voltage duration signal produced by

Yan Ma; George G. Karady

2008-01-01

276

Parenteral oil-based drospirenone microcrystal suspensions-evaluation of physicochemical stability and influence of stabilising agents.  

PubMed

Drospirenone (DRSP) is a contraceptive drug substance with challenging physicochemical properties, due to insufficient solubility in aqueous and oil-based vehicles as well as low chemical stability in aqueous fluids. Although it is one of the most popular orally used progestins, no parenteral long-acting contraceptive containing the drug substance is marketed. An oil-based DRSP microcrystal suspension (MCS) might be an attractive formulation option. The main focus of this study was to investigate the physicochemical stability of such preparations. Moreover, syringeability and injectability via autoinjector were analysed using a materials testing machine. A high chemical stability of DRSP was found in oil-based vehicles. Span(®) 83, cholesteryl oleate, lecithin, methyl cholate, Aerosil(®) R972 and 200 Pharma were tested for increasing the physical stability of DRSP dispersions. Changes in viscosity, rheological properties, and solubility were analysed. The intention was to show a stabilising effect of the excipients without increasing viscosity and solubility. To evaluate the physical stability of DRSP MCS with and without addition of stabilising agents, sedimentation and particle growth after storage were examined. Especially, the silica derivatives Aerosil(®) 200 and R972 Pharma influenced the physical stability positively. PMID:21729745

Nippe, Stefanie; General, Sascha

2011-09-15

277

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

278

Transient Voltage Recorder  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

279

Evaluation of the Pharmaceutical Quality of Docetaxel Injection Using New Stability Indicating Chromatographic Methods for Assay and Impurities  

PubMed Central

New stability indicating chromatographic methods have been developed for estimation of Assay and Impurities of Docetaxel in Docetaxel injection for evaluation of pharmaceutical quality. With this method, the process related impurities and degradants are well separated from the peaks due to placebo. The relative retention times and relative response factors of the known impurities have been established. The LOQ of the known impurities and docetaxel are found to be less than 0.2 ?g /ml and the recovery falls in the range of 90–110%. Peak purities demonstrated the stability indicating nature of the methods. The methods developed in the present study overcome the lacunae of the existing published methodologies in evaluation of the quality of Docetaxel injection. In essence, the present study provides an improved methodology for evaluation of the pharmaceutical quality of Docetaxel injection.

Malleswara Reddy, Annarapu; Banda, Nagaraju; Govind Dagdu, Shinde; Venugopala Rao, Dama; Kocherlakota, Chandra Sekhar; Krishnamurthy, Vyas

2010-01-01

280

Mass spectrometric evaluation of neuropeptidomic profiles upon heat stabilization treatment of neuroendocrine tissues in crustaceans  

PubMed Central

Tissue heat stabilization is a vital component in successful mammalian neuropeptidomic studies. Heat stabilization using focused microwave irradiation, conventional microwave irradiation, boiling, and treatment with the Denator Stabilizor T1 have all proven effective in arresting post-mortem protein degradation. Although research has reported the presence of protein fragments in crustacean hemolymph when protease inhibitors were not added to the sample, the degree to which postmortem protease activity affects neuropeptidomic tissue studies in crustacean species has not been investigated in depth. This work examines the need for Stabilizor T1 or boiling tissue stabilization methods for neuropeptide studies of Callinectes sapidus (blue crab) pericardial organ tissue. Neuropeptides in stabilized and non-stabilized tissue are extracted using acidified methanol or N,N-Dimethylformamide (DMF) and analyzed by MALDI-TOF and nanoLC-ESI-MS/MS platforms. Post-mortem fragments did not significantly affect MALDI analysis in the range m/z 650–1600, but observations in ESI MS/MS experiments suggest that putative post-mortem fragments can mask neuropeptide signal and add spectral complexity to crustacean neuropeptidomic studies. The impact of the added spectral complexity did not dramatically affect the number of detected neuropeptides between stabilized and non-stabilized tissues. However, it is prudent that neuropeptidomic studies of crustacean species include a preliminary experiment using the heat stabilization method to assess the extent of neuropeptide masking by larger, highly charged molecular species.

Sturm, Robert M.; Greer, Tyler; Woodards, Nicole; Gemperline, Erin; Li, Lingjun

2012-01-01

281

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

Microsoft Academic Search

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

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

282

Freeze-dried whole plasma: evaluating sucrose, trehalose, sorbitol, mannitol and glycine as stabilizers.  

PubMed

Several groups report stability results for freeze-dried whole plasma intended for use as a transfusion product [Hellstern P, Sachse H, Schwinn H, Oberfrank K. Manufacture and in vitro characterization of a solvent/detergent-treated human plasma. Vox Sang 1992;63:178-185; Trobisch H. Results of a quality-control study of lyophilized pooled plasmas which have been virally inactivated using a solvent detergent method (modified Horowitz procedure). Beitr Infusionsther 1991;28:92-109; Hugler P, Trobish H, Neuman H, Moller, Sirtl C, Derdak M, Laubenthal H. Quality control of three different conventional fresh-frozen plasma preparations and one new virus-inactivated lyophilized pooled plasma preparation. Klin Wochenschr 1991;69:157-161; Krutvacho T, Chuansumrit A, Isarangkura P, Pintadit P, Hathirat P, Chiewsilp P. Response of hemophilia with bleeding to fresh dry plasma. Southeast Asian J Trop Med Public Health 1993;24:169-173; Chuansumrit A, Krasaesub S, Angchaisuksiri P, Hathirat P, Isarangkura P. Survival analysis of patients with haemophilia at the International Haemophilia Training Centre, Bangkok, Thailand. Haemophilia 2004;10:542-549]. Plasma coagulation properties are substantially impaired in these freeze-dried plasmas, while pH levels are close to alkaline. In this work, plasma supplemented with 60mM sucrose, trehalose, mannitol, sorbitol or glycine was freeze-dried. The samples were subjected to forced degradation at 40 degrees C for 10 days in order to quickly evaluate the effectiveness of the different stabilizers. Initial PT, APTT and TT values were 14.4+/-0. 5s, 31.4+/-1.5s and 18.3+/-0.6s, respectively. At the end of the degradation period, PT, APTT and TT were substantially prolonged, and were 19.1+/-0. 5s, 43.1+/-0.6s and 26.1+/-1.0s, respectively. In the presence of glycine, at the end of the degradation period, PT, APTT and TT values remained close to the initial values and were 15.5+/-0. 4s, 35.7+/-0.9s and 19.4+/-0.2s, respectively. Percent activities of the coagulation factors V, VII, VIII, IX, X and the coagulation inhibitors protein C, protein S and antithrombin III were recorded. Factors V and VIII were most prone to degradation. Factor V and VIII activities, in control plasma, were approx. 44+/-3.5% and 58+/-2.3%, at the end of storage. In contrast, much higher factor V and VIII activities were maintained in the lyophilized glycine-supplemented plasma: approx. 60+/-3.5% and 74+/-7.0%, correspondingly. The most stable protein was protein C, which showed no signs of degradation under the testing conditions of this study. All tested stabilizers provided protection. Glycine, however, outperformed all tested polyols, providing superior preservation of plasma clotting properties. Thermograms of 60mM glycine in water and 60mM glycine in plasma show that, in the presence of plasma, glycine does not crystallize. The process of freeze-drying caused a complete loss of plasma pCO(2) (gas) and a substantial increase in plasma pH. Citric acid was found to be a suitable pH adjuster for lyophilized/rehydrated plasma. PMID:16962645

Bakaltcheva, Irina; O'Sullivan, Anne Marie; Hmel, Peter; Ogbu, Helen

2007-01-01

283

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.

Abdelsayed, Mena; Sokolov, Stanislav

2013-01-01

284

Stable voltage source for Penning trap experiments  

SciTech Connect

A voltage reference has been developed to bias ring electrodes of two Penning traps between -90 and 0 V. For output voltages near -90 V, the Allan deviation of the system's voltage instability is less than 1 part in 10{sup 8} over all time scales shorter than 10{sup 4} s. For averaging times longer than several seconds, the system's stability is determined almost completely by the noise, drift, and aging of the zener diodes in the array of voltage reference integrated circuits. For shorter averaging times, active filters built into the new system significantly reduce the intrinsic noise of the zener diodes. The system makes it possible to continuously adjust the ring voltages for frequency locking the axial motion in the two Penning traps. By keeping electrical noise highly correlated between the two traps, measurement uncertainty should be reduced for precision experiments such as Penning trap mass spectrometry.

Pinegar, David B.; Blaum, Klaus [Division of Stored and Cooled Ions, Max-Planck-Institut fuer Kernphysik, P.O. Box 103980, 69029 Heidelberg (Germany); Biesiadzinski, Tomasz P.; Zafonte, Steven L.; Van Dyck, Robert S. Jr. [Department of Physics, University of Washington, PAB 351560, Seattle, Washington 98195 (United States)

2009-06-15

285

Stable voltage source for Penning trap experiments.  

PubMed

A voltage reference has been developed to bias ring electrodes of two Penning traps between -90 and 0 V. For output voltages near -90 V, the Allan deviation of the system's voltage instability is less than 1 part in 10(8) over all time scales shorter than 10(4) s. For averaging times longer than several seconds, the system's stability is determined almost completely by the noise, drift, and aging of the zener diodes in the array of voltage reference integrated circuits. For shorter averaging times, active filters built into the new system significantly reduce the intrinsic noise of the zener diodes. The system makes it possible to continuously adjust the ring voltages for frequency locking the axial motion in the two Penning traps. By keeping electrical noise highly correlated between the two traps, measurement uncertainty should be reduced for precision experiments such as Penning trap mass spectrometry. PMID:19566217

Pinegar, David B; Blaum, Klaus; Biesiadzinski, Tomasz P; Zafonte, Steven L; Van Dyck, Robert S

2009-06-01

286

Newly developed voltage security monitoring system  

SciTech Connect

A new voltage security monitoring system has been developed and installed in the energy management system of the Tokyo Electric Power Co's (TEPCO) central energy control center. The system has been in operation since February 1990, running at intervals of one minute. This paper presents the background and concept of the developed system, the newly developed algorithm, the configuration of the system and results of actual operation. A PV (total demand, voltage) curve is used for estimating voltage stability. To determine the curve, a new algorithm for obtaining multiple load flow solutions is developed.

Suzuki, M.; Wada, S. (Tokyo Electric Power Co., Tokyo (JP)); Sato, M.; Asano, T.; Kudo, Y. (Toshiba Corp., Tokyo (JP))

1992-08-01

287

Optical voltage reference.  

National Technical Information Service (NTIS)

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 a...

R. Rankin D. Kotter

1992-01-01

288

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

289

TECHNOLOGY EVALUATION REPORT: SITE PROGRAM DEMONSTRATION TEST, SOLIDITECH, INC. SOLIDIFICATION/STABILIZATION PROCESS VOL II  

EPA Science Inventory

The primary objective of the Soliditech, Inc. solidification/stabilization demonstration was to develop reliable performance and cost information. he demonstration took palce at the Imperial Oil Company/Champion Chemical Company Superfund site in Morganiville, New Jersey. ontamin...

290

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...

291

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

292

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

NASA Technical Reports Server (NTRS)

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

Sliwa, S. M.

1980-01-01

293

Retrospective patient outcome evaluation after semi-rigid stabilization without fusion for degenerative lumbar instability  

Microsoft Academic Search

Postero-lateral fusion by means of rod-and-screws\\/hooks constructs is still the gold standard in the treatment of lumbar degenerative\\u000a spinal diseases. However, fusion remains fraught with a high risk of adjacent levels degeneration, sometimes leading to suboptimal\\u000a clinical outcomes. Dynamic stabilization is supposed to compensate for disadvantages associated with rigid fusion. Preliminary\\u000a results of spinal stabilization by means of dynamic devices

Jacques Benezech; Anca Mitulescu

2007-01-01

294

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

Microsoft Academic Search

The dynamic stabilization of lumbar spine is a non-fusion stabilization system that unloads the disc without the complete\\u000a loss of motion at the treated motion segment. Clinical outcomes are promising but still not definitive, and the long-term\\u000a effect on instrumented and adjacent levels is still a matter of discussion. Several experiments have been devised in order\\u000a to gain a better

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

2009-01-01

295

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

296

Vehicle mounted voltage regulator  

SciTech Connect

In a roadway vehicle having a storage battery and an engine-driven alternator, the battery voltage is controlled by a voltage regulator which has a first voltage detector for detecting when the battery voltage reduces below a higher reference level at which the battery voltage is normally controlled, and a second voltage detector for detecting when the battery voltage reduces below a lower reference level. A third voltage detector detects when the alternator voltage rises above a predetermined level. A logic gate circuit responds to outputs from the second and third voltage detectors by generating a warning signal. A semiconductor switching element is coupled in series with the field coil of the alternator to supply thereto the alternator voltage in response to a switching control which is generated in response to an output signal from the first voltage detector to cause the switching element to operate the alternator in a high output state and in response to the logic gate circuit to operate the alternator in a low output state.

Akita, Y.; Maruyama, T.; Teshima, T.; Torii, K.

1984-05-29

297

Stability of parent report on mobility and self-care item scores of the pediatric evaluation of disability inventory.  

PubMed

ABSTRACT 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

298

Design and evaluation of side slip angle-based vehicle stability control scheme on a virtual test track  

Microsoft Academic Search

This paper describes the development of side slip angle-based vehicle stability control (VSC) schemes and the evaluation of the control schemes on a virtual test track. A differential braking control law based on vehicle planar motion has been designed using a three-degree-of-freedom yaw plane vehicle model. The control threshold for the VSC is designed based on the vehicle body side

Taeyoung Chung; Kyongsu Yi

2006-01-01

299

Evaluation of low carbon Al-killed\\/Cr-stabilized steel to be used in the automobile industry  

Microsoft Academic Search

An Al-killed\\/Cr-stabilized low carbon steel was produced in the steel industry using electric arc furnace, vacuum degassing, ladle treatment and continuous casting route. The resulting slabs were then hot rolled at 1100°C, coiled at 600°C, cold rolled and annealed at 700°C. After evaluation of the microstructure, texture and mechanical properties, the fully recrystallized coils fulfilled the target properties established by

R Mendoza; M Alanis; G Aramburo; F Serrania; J. A Juárez-Islas

2004-01-01

300

Influenza vaccine powder formulation development: spray-freeze-drying and stability evaluation.  

PubMed

The purpose of this study was to develop a spray-freeze-drying (SFD) process for preparing an influenza vaccine dry powder formulation suitable for epidermal powder immunization. After preformulation of two types of flu vaccines, their dry-powder formulations were prepared by SFD. Powder properties and physical stability were determined using particle size analysis, tap density measurement, scanning electron microscopy, optical microscopy, and moisture content analysis. Chemical and biochemical stability of vaccine antigens was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, single radial immunodiffusion assay, and in vivo immunogenicity in a mouse model. We demonstrated that SFD could produce high-density particles-a critical parameter for effective skin penetration. From the stability perspective, the stress posed by SFD was mild because the antigen in the dry powder retained its stability, potency, and immunogenicity. Among several formulations screened, we noted that formulation composition has a significant role in the powder's long-term physical and biochemical stability. One formulation, in particular, containing sub-unit vaccine (45 microg of antigen in 1 mg of powder) with a tertiary mixture of trehalose, mannitol, and dextran, exhibited excellent overall stability, including acceptable biochemical stability after being exposed to a highly humid environment. After all, we have not only demonstrated the suitability of SFD to prepare powders for epidermal powder immunization but also developed a systematic formulation development strategy that allowed the optimization of an influenza vaccine dry powder formulation. More important, this study led to the selection of a formulation system that had been successfully tested in a human clinical study. PMID:15176078

Maa, Yuh-Fun; Ameri, Mahmoud; Shu, Cassandra; Payne, Lendon G; Chen, Dexiang

2004-07-01

301

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

302

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

NASA Technical Reports Server (NTRS)

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

Hurd, W. A.

1985-01-01

303

Evaluation of thermal and thermal-oxidative stability of synthetic lubricants by derivatographic method  

SciTech Connect

This work investigates the thermal and thermal-oxidative stability of various synthetic lubricating oils by means of a derivatograph of the Paulik-Paulik-Erdey system. From the relative position of the thermograms, it is established that PET and FST-5 fluids are the most thermally stable, IPMA-10 is intermediate, and DOS is least. Volatility and temperature limits are also studied. The final results rank the fluids with respect to thermal and thermal-oxidative stability as follows: FST-5, PET, IPMA, and DOS.

Nikonorov, E.M.; Irisova, K.N.; Kalinina, E.V.; Petrova, L.N.; Sazonova, N.S.

1983-11-01

304

Evaluating the stability of colistin and colistin methanesulphonate in human plasma under different conditions of storage  

PubMed Central

Objectives The purpose of this study was to assess the stability of colistin and colistin methanesulphonate (CMS) in human plasma under storage conditions typically used in clinical pharmacokinetic (PK) and PK/pharmacodynamic (PD) investigations. Methods Human plasma (pH adjusted to 7.4) containing colistin (2 mg/L) or CMS (2 or 30 mg/L) was stored at ?20, ?70 or ?80°C for 6–12 months. At periodic intervals, the concentrations of colistin in colistin-spiked samples, and of CMS and formed colistin in CMS-spiked samples, were analysed (n?=?3 replicates at each time) by HPLC. Results The time course of colistin concentrations in colistin-spiked plasma showed a substantially better stability at ?80 and ?70°C than at ?20°C. With regard to CMS-spiked plasma of 2 and 30 mg/L stored at ?80 and ?70°C, no quantifiable colistin formed over a 4 month period. However, the plasma spiked to 2 mg/L stored at ?20°C showed a substantial concentration of colistin (?0.4 mg/L) within 2 months. At all three storage temperatures, the stability of CMS was substantially better for the plasma spiked to contain 30 mg/L as compared with 2 mg/L. Conclusions The results of our long-term stability study have significant implications for those involved in conducting clinical PK and PK/PD studies with CMS/colistin.

Dudhani, Rajesh V.; Nation, Roger L.; Li, Jian

2010-01-01

305

An exonuclease I hydrolysis assay for evaluating G-quadruplex stabilization by small molecules  

Microsoft Academic Search

Telomere length homeostasis is a prerequisite for the generation and growth of cancer. In 485% cancer cells, telomere length is maintained by telomerase that add telomere repeats to the end of telomere DNA. Because the G-rich strand of telomere DNA can fold into G-quadruplex that inhibits telomerase activity, stabilizing telomere quadruplex by small molecules is emerging as a potential therapeutic

Yuan Yao; Quan Wang; Yu-hua Hao; Zheng Tan

2007-01-01

306

D050 THE USE OF XRD PATTERNS TO EVALUATE THE COMPRESSIVE STRENGTH OF STABILIZED AGGREGATES  

Microsoft Academic Search

A laboratory study was undertaken to investigate the performance of Class C fly ash-stabilized aggregate bases. Two commonly used aggregates in Oklahoma: (1) Meridian, a limestone aggregate, and (2) Hanson, a rhyolite aggregate, were utilized in this study. Cylindrical specimens were compacted and cured for 1 hour, 3, 28, and 90 days prior to unconfined compressive strength (UCS), X-ray diffraction,

Naji N. Khoury; Musharraf Zaman; Joakim G. Laguros

2003-01-01

307

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

308

AN EVALUATION OF FACTORS AFFECTING THE SOLIDIFICATION/STABILIZATION OF HEAVY METAL SLUDGE  

EPA Science Inventory

Solidification/stabilization (SIS) of hazardous waste involves mixing the waste with a binder material to enhance the physical properties of the waste and to immobilize contaminants that may be detrimental to the environment. Many hazardous wastes contain materials that are know...

309

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

310

Evaluating Stability of Vitamin C in Fortified Formula Using Water Activity and Glass Transition  

Microsoft Academic Search

Stability of vitamin C in fortified formula food at constant temperature, as affected by the water activity (aw) and glass transition (Tg), was investigated in an attempt to differentiate the effects of aw and Tg on the degradation reaction. Fortified formula samples, equilibrated at different moisture contents\\/water activity levels, were stored for more than 10 weeks at the room temperature,

Shyam S. Sablani; K. Al-Belushi; I. Al-Marhubi; R. Al-Belushi

2007-01-01

311

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

312

A thermogravimetric analysis of non-polymeric pharmaceutical plasticizers: kinetic analysis, method validation, and thermal stability evaluation.  

PubMed

Four non-polymeric plasticizers, propylene glycol, diethyl phthalate, triacetin, and glycerin have been subjected to rising temperature thermogravimetry for kinetic analysis and vaporization-based thermal stability evaluation. Since volatile loss of a substance is a function of its vapor pressure, the thermal stability of these plasticizers has been analyzed by generating vapor pressure curves using the Antoine and Langmuir equations. Unknown Antoine constants for the sample compounds, triacetin and glycerin have been derived by subjecting the vapor pressure curves to nonlinear regression. For the first time, the entire process of obtaining the unknown Antoine constants through thermogravimetry has been validated by developing an approach called the 'double reference method.' Based on this method, it has been possible to show that this technique is accurate even for structurally diverse compounds. Kinetic analysis on the volatilization of compounds revealed a predominant zero order process. The activation energy values for vaporization of propylene glycol, diethyl phthalate, triacetin, and glycerin, as deduced from the Arrhenius plots, have been determined to be 55.80, 66.45, 65.12, and 67.54 kJ/mol, respectively. The enthalpies of vaporization of the compounds have been determined from the Clausius-Clapeyron plots. Rising temperature thermogravimetry coupled with nonlinear regression analysis has been shown to be an effective and rapid technique for accurately predicting the vapor pressure behavior and thermal stability evaluation of volatile compounds. PMID:12646015

Tatavarti, Aditya S; Dollimore, David; Alexander, Kenneth S

2002-01-01

313

Evaluation of Need and Location for a Thermogravimetric Analyzer in the Plutonium Finishing Plant (PFP) Materials Stabilization  

SciTech Connect

This plan provides an analysis for locating a TGA to support PFP Thermal Stabilization processes. The scope of this document is to evaluate the need for, and location for, installation of a TGA system as a supplement to the SFE equipment for moisture measurement in pure oxides. A location assessment for the SFE equipment was previously performed (HNF 1999). Based on that assessment, co-location of the TGA system with the SFE system is the preferred option. This would enable thermally stabilized material to be analyzed for residual moisture by either the TGA system or SFE system or both This evaluation considers glovebox locations in the PFP 234-52 Building Analytical Laboratory or operating areas for the installation of the TGA system and it's supporting equipment. This evaluation considers using existing gloveboxes along with an alternative of adding a new glovebox to existing process lines. The location evaluation criteria focuses mainly on glovebox size, with qualitative consideration of relative cost and schedule impacts associated with system implementation, radiological control, and interaction with other laboratory operations and processes. In addition, the possible co-location of a TGA furnace system with the SFE system was considered.

WILLIS, H.T.

2000-01-20

314

EFFECTS OF PYRETHROIDS ON VOLTAGE-SENSITIVE CALCIUM CHANNELS: A CRITICAL EVALUATION OF STRENGTHS, WEAKNESSES, DATA NEEDS, AND RELATIONSHIP TO ASSESSMENT OF CUMULATIVE NEUROTOXICITY.  

EPA Science Inventory

A recently published review (Soderlund et al., 2002, Toxicology 171, 3-59.) of the mechanisms of acute neurotoxicity of pyrethroid compounds postulated that voltage-sensitive calcium channels (VSCC) may be a target of some pyrethroid compounds and that effects on VSCC may contrib...

315

A 24GHz Josephson array voltage standard  

Microsoft Academic Search

A Josephson array voltage standard that operates at 24 GHz has been designed and fabricated. Optimum selection of junction parameters makes possible step stability times of 20 min, which are more than adequate for calibrations at 1 V. Designs using both probe and finline microwave couplers were tested. The probe coupler was about 3 dB more efficient and allowed a

Clark A. Hamilton; Richard L. Kautz; Marilyn Stieg; Kao Chieh; William F. Avrin

1991-01-01

316

A 24 GHz Josephson array voltage standard  

Microsoft Academic Search

A Josephson array voltage standard that operates at 24 GHz has been designed and fabricated. Substantial advantages in cost and reliability are realized over more conventional devices that operate at 70-100 GHz. Typical step stability times of 20 min are more than adequate for calibrations at the 1-V level. Designs using both probe and finline microwave couplers were tested. The

C. A. Hamilton; R. L. Kautz; M. Stieg; K. Chieh; M. B. Simmonds; W. F. Avrin

1990-01-01

317

Evaluation of thermal-oxidative stability and antiglioma activity of Zanthoxylum tingoassuiba essential oil entrapped into multi- and unilamellar liposomes.  

PubMed

Zanthoxylum tinguassuiba essential oil (ZtEO) contains ?-bisabolol, a known antiglioma sesquiterpene, among other potentially active substances. Medical applications of this essential oil require advances in the design of distinctive carriers due to its low water solubility and easy degradation by heat, light, and oxygen. The aim of this work was to evaluate enhancement in oxidative stability and the ability to reduce glioblastoma cell viability of ZtEO loaded into liposomes. Multi- and unilamellar vesicles were prepared to carry ZtEO. By using thermal analysis, it was observed that thermal-oxidative stability of the liposomal ZtEO was enhanced, when compared to its free form. Liposomal ZtEO also presented significant apoptotic-inducing activity for glioma cells. These results show that liposomal systems carrying ZtEO may be a potential alternative for gliobastoma treatment. PMID:21548711

Detoni, Cassia B; de Oliveira, Diêgo Madureira; Santo, Islane E; Pedro, André São; El-Bacha, Ramon; da Silva Velozo, Eudes; Ferreira, Domingos; Sarmento, Bruno; de Magalhães Cabral-Albuquerque, Elaine C

2012-03-01

318

Evaluation of liquid fragility and thermal stability of Al-based metallic glasses by equivalent structure parameter  

NASA Astrophysics Data System (ADS)

Based on extended Ideal-Atomic-Packing model, we propose an equivalent structure parameter “ 6x+11y” to evaluate fragility and thermal stability of Al-TM-RE metallic glasses, where x and y are composition concentrations of transition metal (TM) and rare earth (RE), respectively. Experimental results show that glass forming compositions with “ 6x+11y” near 100 have the smallest fragility parameter and best structure stability. In addition, “ 6x+11y” parameter has a positive relationship with onset-crystallization temperature, T. Al-TM-RE glassy alloys with (6x+11y)?100 undergo primary crystallization of fcc-Al nanocrystals, while alloys with (6x+11y)>100 exhibit nanoglassy or glassy crystallization behavior.

Li, Xuelian; Bian, Xiufang; Hu, Lina

2010-08-01

319

Quantitative Evaluation of Colloidal Stability of Antibody Solutions using PEG-Induced Liquid-Liquid Phase Separation.  

PubMed

Colloidal stability of antibody solutions, i.e., the propensity of the folded protein to precipitate, is an important consideration in formulation development of therapeutic monoclonal antibodies. In a protein solution, different pathways including crystallization, colloidal aggregation, and liquid-liquid phase separation (LLPS) can lead to the formation of precipitates. The kinetics of crystallization and aggregation are often slow and vary from protein to protein. Due to the diverse mechanisms of these protein condensation processes, it is a challenge to develop a standardized test for an early evaluation of the colloidal stability of antibody solutions. LLPS would normally occur in antibody solutions at sufficiently low temperature, provided that it is not preempted by freezing of the solution. Poly(ethylene glycol) (PEG) can be used to induce LLPS at temperatures above the freezing point. Here, we propose a colloidal stability test based on inducing LLPS in antibody solutions and measuring the antibody concentration of the dilute phase. We demonstrate experimentally that such a PEG-induced LLPS test can be used to compare colloidal stability of different antibodies in different solution conditions and can be readily applied to high-throughput screening. We have derived an equation for the effects of PEG concentration and molecular weight on the results of the LLPS test. Finally, this equation defines a binding energy in the condensed phase, which can be determined in the PEG-induced LLPS test. This binding energy is a measure of attractive interactions between antibody molecules and can be used for quantitative characterization of the colloidal stability of antibody solutions. PMID:24679215

Wang, Ying; Latypov, Ramil F; Lomakin, Aleksey; Meyer, Julie A; Kerwin, Bruce A; Vunnum, Suresh; Benedek, George B

2014-05-01

320

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

PubMed Central

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

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

2013-01-01

321

SP Josephson Array Voltage Standard.  

National Technical Information Service (NTIS)

The SP Josephson array voltage standard has since 1993 been used to realize the Swedish unit of DC voltage. The report describes the voltage standard and how the Josephson voltage is used to determine the voltage of primary voltage standards as Weston cel...

G. Eklund H. Pajander

1995-01-01

322

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

323

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

324

Compensated Multi-Pole Mercury Trapped Ion Frequency Standard and Stability Evaluation of Systematic Effects  

NASA Astrophysics Data System (ADS)

We have developed a compensated multi-pole Linear Ion Trap Standard (LITS) that eliminates nearly all frequency sensitivity to residual ion number variations. When operated with 199Hg+, this trapped ion clock has recently demonstrated extremely good stability over a 9-month period. The short-term stability has been measured at 5 × 10-14/?1/2 and an upper limit on long-term fractional frequency deviations of < 2.7 × 10-17/day was measured in comparison to the laser-cooled primary standards and to the post-processed ultra-stable version of TAI known as TTBIPM using GPS carrier phase time transfer. We have also made a first measurement of the Hg+/Hg collision shift and place a limit of +3.8(7.2) × 10-8/Pa on the shift constant.

Burt, E. A.; Taghavi-Larigani, S.; Prestage, J. D.; Tjoelker, R. L.

2009-04-01

325

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

326

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

327

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

328

EVALUATING STABILITY OF RESTRUCTURED PORK ADDED WITH GINGER EXTRACTS BY MEANS OF CHEMICAL AND SENSORY ANALYSIS  

Microsoft Academic Search

The aim of the study was to examine the possibility to use ginger extract for stabilizing restructured pork. Ginger extracts were prepared by extraction with ethanol. The extracts were added to minced pork at concentration of 0.1%, 0.2%, 0.3% and 0.4% with regard to dry matter. The samples were then subjected to bake at 180oC and store at 4oC. During

N. M. Dang

329

Evaluation of Mechanical Effect of Vegetation on Slope Stability in Terms of Root Evolution  

NASA Astrophysics Data System (ADS)

Vegetation is planted to reduce probability of slope failure for its hydrological and mechanical effects. Root reinforcement provides additional cohesion to soil to protect slope from mass movement. The interaction between roots and soil in terms of root morphology was understood and quantified well with in situ and ex situ experiments and numerical models, especially for soil core samples. However, root morphology such as root density, root depth, root tensile strength and root orientation, which are the basis of the additional cohesion for soil, varies gradually during the life of vegetation. Furthermore, entire stand structure also changes because of individual growing that would affect root morphology within a stand. As a consequence, the mechanical effect of vegetation on slope stability should be investigated at different life stages at stand scale. The objective of this research is to understand and quantify the dynamic stabilizing mechanical effect of forest on potentially unstable slopes. To achieve this, we focus on the changes of slope stability with regard to variation in root morphology over the life cycle of stand. First, root evolutes as a result of stand density decrease with competition of bigger individual tree. Second, gaps get larger between them which could not protect soil loss. Root density, root depth and root tensile strength varies to meet the physiological demands of various growth stage of a forest stand. A spatially distributed, physical-based, dynamical model is employed to calculate the safety factor and probability of failure in a catchment on a daily time scale with root system dynamic evolution as a parameter. The results of the quantification of the mechanical effect of vegetation show there is a significantly influence by temporal and spatial distribution of stand root system and this provides reference for reliable management strategies at the scale of forest stands. Key words: slope stability, mechanical effect, root, vegetation

Meng, W.; Bogaard, T. A.

2012-04-01

330

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

NASA Astrophysics Data System (ADS)

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 (? fG°) 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.

Lee, Tony R.; Wilkin, Richard T.

2010-07-01

331

Antioxidant evaluation and oxidative stability of structured lipids from extravirgin olive oil and conjugated linoleic acid.  

PubMed

Structured lipid (SL) was synthesized from extravirgin olive oil (EVOO) and conjugated linoleic acid (CLA) via a lipase-catalyzed reaction. CLA provides a variety of health benefits, but it is not consumed in free fatty acid form. The synthesized SL olive oil contained 42.5 mol % CLA isomers, and the major isomers were cis-9,trans-11-CLA (16.9 mol %) and trans-10,cis-12-CLA (24.2 mol %). The antioxidant activity determined by the radical scavenging capacity with the 2,2-diphenyl-1-picrylhydrazyl radical was lower in SL olive oil than in EVOO. The oxidative stability was also lower in SL olive oil since it had a higher peroxide value, rho-anisidine value, and 2-thiobarbituric acid reactive substances values during 20 days of storage at 60 degrees C. This observation could be due to the reduction in the natural phenolic compounds (97%) and tocopherols (56%), and the incorporated CLA with two conjugated double bonds in the SL olive oil. The oxidative stability of SL olive oil was increased by added rosemary extracts at concentrations of 100, 200, and 300 ppm. The present study suggests that the SL olive oil may be a suitable way to incorporate or deliver CLA into human diets. However, the addition of a proper antioxidant would be required for improving its oxidative stability. PMID:16848526

Lee, Jeung Hee; Lee, Ki-teak; Akoh, Casimir C; Chung, Shin Kyo; Kim, Mee Ree

2006-07-26

332

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

PubMed

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

Ohata, Masaki; Kidokoro, Toshihiro; Hioki, Akiharu

2012-01-01

333

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

PubMed

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

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

2011-12-01

334

Wide Area Voltage Regulation in Italy and related wide area protection  

Microsoft Academic Search

A very promising Wide Area Voltage Protection (V-WAP) solution to face EHV voltage stability and system security problems is presented. Its unique ability is mainly due to an effective co-ordination with a Wide Area Voltage Regulation (V-WAR) modern system where the Secondary and Tertiary Voltage Regulations (SVR and TVR respectively) operate according with their hierarchy. Both the voltage regulating and

S. Corsi

2011-01-01

335

Snubber-Assisted Zero-Voltage and Zero-Current Transition Bilateral Buck and Boost Chopper for EV Drive Application and Test Evaluation at 25 kW  

Microsoft Academic Search

A new high-efficiency and high-power bilateral buck and boost chopper circuit for the electric-vehicle drive application is presented. The operation principle of snubber-assisted zero-voltage and zero-current transition (SAZZ) topology was applied, and a new SAZZ bilateral buck-boost chopper circuit (SAZZ-1) was created by combining two basic SAZZ circuit types. A 50-kHz 25-kW SAZZ-1 was fabricated and tested. An efficiency of

Yukinori Tsuruta; Yoshihiro Ito; Atsuo Kawamura

2009-01-01

336

Fault Current Limiter by Series Connected Voltage Source Inverter  

NASA Astrophysics Data System (ADS)

In recent years, various types of fault current limiter (FCL) have been developed, because installation of the FCL will bring a lot of benefits to power system operation. Power system controllers based on a concept of Flexible AC Transmission Systems (FACTS) can also be applicable as the FCL with growing power ratings of them. Such FCLs are expected to contribute power system stabilization or power quality enhancement in addition to fault current limitation. Authors have developed a new type of FCL, which consists of a series reactor and a self-commutated voltage source inverter connected in series with a power distribution line by a coupling transformer. In case of a system fault, the FCL will insert a sufficiently large inductance in series with the distribution line by both the series reactor and the inverter, then it will reduce the fault current. On the other hand, the inverter compensates a voltage drop across the series reactor in a standby mode. As a result, the FCL behaves like a negligible impedance in the standby mode. One of the distinctive features of the FCL is a simple configuration because its control strategy does not require an active power source. In addition, inverter voltage rating of the proposed FCL can be reduced by installing the series reactor as compared with other converter-based FCLs. The aim of this paper is to evaluate the operating characteristics of the FCL with both simulation and experimental studies.

Hojo, Masahide; Kuroe, Norihito; Ohnishi, Tokuo

337

Voltage endurance test facility for electric generator stator coils  

Microsoft Academic Search

The development of new coil designs with the use of updated materials and\\/or processes requires voltage endurance testing as one of the tests to verify the new coil design. From established voltage endurance curves, a new insulation system can be evaluated against accepted coil designs. An expanded voltage endurance test lab has been developed which has the capabilities for testing

F. T. Emery; R. F. Weddleton

1993-01-01

338

Improving voltage disturbance rejection for variable-speed wind turbines  

Microsoft Academic Search

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

Giuseppe Saccomando; Jan Svensson; Ambra Sannino

2002-01-01

339

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

PubMed

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

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

2014-05-25

340

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

PubMed Central

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

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

2013-01-01

341

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

342

An in vitro and in vivo toxicologic evaluation of a stabilized aloe vera gel supplement drink in mice.  

PubMed

Aloe vera gel is increasingly consumed as a beverage dietary supplement. The purpose of this study was to determine potential toxicity of a stabilized aloe vera gel derived from the inner gel fillet and marketed as a drink. The gel juice was assessed through assays of genotoxicity in vivo and acute and subchronic toxicity in B6C3F1 mice. Aloe vera did not increase the SOS DNA repair response in Escherichia coli and at 1× and 0.25× it did not increase mutagenesis of Salmonella TA100 resulting in histidine biosynthesis. At 3 and 14days following acute exposure, male and female mice gavaged with the stabilized aloe gel had daily appearances, total body weight gain, selected organ weights, necropsy and hematology tests similar to control mice gavaged with water. After a 13-week aloe gel feed study, male and female mice evaluated by the same criteria as the acute study plus feed consumption and serum chemistry tests were found to be equivalent to control groups. These data indicate that a commercial stabilized aloe gel consumed as a beverage was not genotoxic or toxic in vivo. These results contrast with those obtained using preparations containing aloe latex phenolic compounds such as anthraquinones. PMID:23376510

Sehgal, Inder; Winters, Wallace D; Scott, Michael; Kousoulas, Konstantine

2013-05-01

343

Variable voltage portable vaporizer  

US Patent & Trademark Office Database

A portable vaporizer having an electronic control unit electrically coupled to a power source and an atomizer. The electronic control unit utilizes a voltage regulator which allows changes in an output voltage supplied to the atomizer in response to a change in electrical resistance of a potentiometer incorporated therewith.

2014-07-15

344

Cascaded voltage collapse  

SciTech Connect

The dynamic phenomena of voltage collapse are analyzed by the method of dynamic simulation using induction motor models. From the view point of dynamic phenomena, the voltage collapse starts locally at the weakest node and spreads out to the other weak nodes.

Sekine, Y. (Tokyo Univ. (Japan)); Ohtsuki, H. (Kansai Electric Power Co., Inc., Osaka (Japan))

1990-02-01

345

High voltage engineering  

Microsoft Academic Search

This book presents a comprehensive treatment of high voltage engineering fundamentals at the introductory and intermediate levels. It covers: techniques used for generation and measurement of high direct, alternating and surge voltages for general application in industrial testing and selected special examples found in basic research; analytical and numerical calculation of electrostatic fields in simple practical insulation systems; basic ionisation

Kuffel

1984-01-01

346

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

347

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

NASA Technical Reports Server (NTRS)

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

Mukhopadhyay, V.; Newsom, J. R.

1982-01-01

348

Evaluation of enhanced thermostability and operational stability of carbonic anhydrase from Micrococcus species.  

PubMed

Carbonic anhydrase (CA) was purified from Micrococcus lylae and Micrococcus luteus with 49.90 and 53.8 % yield, respectively, isolated from calcium carbonate kilns. CA from M. lylae retained 80 % stability in the pH and temperature range of 6.0-8.0 and 35-45 °C, respectively. However, CA from M. luteus was stable in the pH and temperature range of 7.5-10.0 and 35-55 °C, respectively. Cross-linked enzyme aggregates (CLEAs) raised the transition temperature of M. lylae and M. luteus CA up to 67.5 and 74.0 °C, while the operational stability (T(1/20) of CA at 55 °C was calculated to be 7.7 and 12.0 h, respectively. CA from both the strains was found to be monomeric in nature with subunit molecular weight and molecular mass of 29 kDa. Ethoxozolamide was identified as the most potent inhibitor based on both IC(50) values and inhibitory constant measurement (K(i)). The K(m) and V(max) for M. lylae CA (2.31 mM; 769.23 ?mol/mg/min) and M. luteus CA (2.0 mM; 1,000 ?mol/mg/min) were calculated from Lineweaver-Burk plots in terms of esterase activity. Enhanced thermostability of CLEAs alleviates its role in operational stability for application at an on-site scrubber. The characteristic profile of purified CA from Micrococcus spp. advocates its effective application in biomimetic CO(2) sequestration. PMID:23609906

Bhattacharya, Abhishek; Shrivastava, Ankita; Sharma, Anjana

2013-06-01

349

Comparative evaluation of sodium hypochlorite and microwave disinfection on dimensional stability of denture bases  

PubMed Central

PURPOSE To compare the effect of sodium hypochlorite and microwave disinfection on the dimensional stability of denture bases without and with relining. MATERIALS AND METHODS A brass die was prepared by simulating an edentulous maxillary arch. It was used to fabricate 1.5 mm and 3 mm of thickness denture bases (n = 40). The 1.5 mm of thickness-specimens (n = 20) were relined with 1.5 mm of autopolymerizing relining resin. Five holes were prepared over crest of ridge of brass die with intimately fitting stainless steel pins which were transferred to the intaglio surface of specimens during fabrication of denture bases. For calculation of dimensional changes in denture bases, differences between the baseline area before and after disinfection of the specimens were used. The denture bases without and with relining were divided into 2 groups (each n = 20). Data were analyzed using student paired 't' and unpaired 't' test. RESULTS Microwave disinfection produces significant shrinkage in both denture bases without relining (t = 17.16; P<.001) and with relining (t = 14.9; P<.001). Denture bases without relining showed more shrinkage when compared with relined denture bases after microwave disinfection (t = 6.09; P<.001). The changes in dimensional stability after sodium hypochlorite disinfection were not significant for both denture bases without relining (t = 2.19; P=.056) and denture bases with relining (t = 2.17; P=.058). CONCLUSION Microwave disinfection leads to increased shrinkage of denture bases without and with relining. Chemical disinfection with sodium hypochlorite seems to be a safer method of disinfection with regards to physical properties such as changes in dimensional stability.

Thombre, Ram; Kubasad, Girish

2012-01-01

350

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

351

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

352

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

353

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

354

Voltage verification unit  

DOEpatents

A voltage verification unit and method for determining the absence of potentially dangerous potentials within a power supply enclosure without Mode 2 work is disclosed. With this device and method, a qualified worker, following a relatively simple protocol that involves a function test (hot, cold, hot) of the voltage verification unit before Lock Out/Tag Out and, and once the Lock Out/Tag Out is completed, testing or "trying" by simply reading a display on the voltage verification unit can be accomplished without exposure of the operator to the interior of the voltage supply enclosure. According to a preferred embodiment, the voltage verification unit includes test leads to allow diagnostics with other meters, without the necessity of accessing potentially dangerous bus bars or the like.

Martin, Edward J. (Virginia Beach, VA) [Virginia Beach, VA

2008-01-15

355

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

356

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

PubMed

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

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

2013-07-01

357

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

358

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

359

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

360

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

361

Release profile and stability evaluation of optimized chitosan/alginate nanoparticles as EGFR antisense vector  

PubMed Central

Chitosan/alginate nanoparticles which had been optimized in our previous study using two different N/P ratios were chosen and their ability to release epidermal growth factor receptor (EGFR) antisense was investigated. In addition, the stability of these nanoparticles in aqueous medium and after freeze-drying was investigated. In the case of both N/P ratios (5, 25), nanoparticles started releasing EGFR antisense as soon as they were exposed to the medium and the release lasted for approximately 50 hours. Nanoparticle size, shape, zeta potential, and release profile did not show any significant change after the freeze-drying process (followed by reswelling). The nanoparticles were reswellable again after freeze-drying in phosphate buffer with a pH of 7.4 over a period of six hours. Agarose gel electrophoresis of the nanoparticles with the two different N/P ratios showed that these nanoparticles could protect EGFR antisense molecules for six hours.

Azizi, Ebrahim; Namazi, Alireza; Haririan, Ismaeil; Fouladdel, Shamileh; Khoshayand, Mohammad R; Shotorbani, Parisa Y; Nomani, Alireza; Gazori, Taraneh

2010-01-01

362

Evaluation of the stability of an SR398/GroES chaperonin complex.  

PubMed

The stability of an SR398/GroES chaperonin complex was examined. As was expected, based on the finding of previous studies, the SR398/GroES complex was extremely stable in the presence of an excess amount of free adenosine 5'-[?-thio]triphosphate (ATP?S) or adenosine 5'-(?,?-imido)triphosphate (AMPPNP). However, the complex was not stable in the absence of nucleotides. These results indicate that ATP?S and AMPPNP repeatedly associated to and dissociated from the complex in a non-cooperative manner. This nucleotide exchange did not induce the dissociation of GroES and substrate from SR398, suggesting the importance of the cooperative dissociation of nucleotides from the cis-ring to release GroES and substrate proteins in the GroEL/GroES reaction cycle. PMID:24563543

Ishino, So; Kawata, Yasushi; Ikegami, Takahisa; Matsuzaki, Katsumi; Hoshino, Masaru

2014-05-01

363

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.

2014-05-01

364

Stability of trapped charges in sapphires and alumina ceramics: Evaluation by secondary electron emission  

NASA Astrophysics Data System (ADS)

The stability of trapped charges in sapphires and alumina ceramics is characterized via an experimental parameter expressing the variation of the secondary electron emission yield between two electron injections performed in a scanning electron microscope. Two types of sapphires and polycrystalline alumina, which differ mainly by their impurity content, are investigated in the temperature range 300-663 K. The stable trapping behavior in sapphires is attributed to trapping in different defects, whose nature depends on the purity level. In alumina ceramics, the ability to trap charges in a stable way is stronger in samples of high impurity content. In the low impurity samples, stable trapping is promoted when the grain diameter decreases, whereas the reverse is observed in high impurity materials. These behaviors can stem from a gettering effect occurring during sintering. The strong dependence of the variation of the secondary electron emission yield on the grain diameter and impurities enables a scaling of the stable trapping ability of alumina materials.

Zarbout, K.; Si Ahmed, A.; Moya, G.; Bernardini, J.; Goeuriot, D.; Kallel, A.

2008-03-01

365

Comparative evaluation of multi-purpose solutions in the stabilization of tear lysozyme.  

PubMed

The range and extent of tear proteins removed by various multi-purpose solutions has been investigated, but there is little information in the literature about their ability to prevent denaturation of tear proteins, particularly lysozyme. The purpose of this study was to determine the ability of Bausch+Lomb Biotrue™ multi-purpose solution and other care solutions to affect denaturation of lysozyme using a lysozyme activity assay. The test solutions used were: Biotrue multi-purpose solution, Bausch+Lomb renu(®) fresh™, formerly ReNu MultiPlus(®), Alcon OPTI-FREE RepleniSH, Alcon OPTI-FREE EXPRESS, CIBA VISION AQuify, and AMO COMPLETE Multi-Purpose Solution Easy Rub Formula. A phosphate-buffered saline (PBS) solution served as a control. The test and control solutions containing lysozyme were exposed to sodium dodecyl sulfate (SDS), a known denaturant of the enzyme. The assay was based on digestion of the cell wall of Micrococcus luteus in a suspension, a substrate sensitive to active lysozyme. Enzymatic activity against M. luteus was used to assess activity of lysozyme. The decrease in the turbidity of the cell wall suspension, a measure of relative enzyme activity, was determined by following the decrease in absorbance (at 450nm) over time using a spectrophotometer. Statistically significant greater stabilization of lysozyme was observed with Biotrue multi-purpose solution and renu fresh than with OPTI-FREE RepleniSH, OPTI-FREE EXPRESS, AQuify, COMPLETE Multi-Purpose Solution Easy Rub Formula, and a PBS control. The lysozyme activity assay revealed that Biotrue multi-purpose solution and renu fresh have the ability to stabilize lysozyme under conditions that typically denature the protein. PMID:21071258

Barniak, Vicki L; Burke, Susan E; Venkatesh, Srini

2010-12-01

366

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

367

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

368

Generating Electrical Voltage  

NSDL National Science Digital Library

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

2010-10-06

369

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

370

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.

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

2011-01-01

371

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

372

Protocol of Test Methods for Evaluating High Heat Sink Fuel Thermal Stability Additives for Aviation Jet Fuel JP-8+100.  

National Technical Information Service (NTIS)

This report describes the high heat sink fuels thermal stability additive evaluation protocol of test methods as they apply to the evaluation of additives for JP-8+100. Individual test methods are described and a standardized methodology for test operatio...

R. W. Morris D. Minus S. Zabarnick L. Balster K. E. Binns

2002-01-01

373

Seismic Stability Evaluation of Folsom Dam and Reservoir Project. Report 6. Right and Left Wing Dams.  

National Technical Information Service (NTIS)

The man-made water retaining structures at the Folsom Dam and Reservoir Project, located on the American River about 20 miles upstream of the city of Sacramento, California, have been evaluated for their seismic safety in the event of a Magnitude 6.5 eart...

D. E. Yule D. J. Elton M. E. Hynes R. E. Wahl

1989-01-01

374

Seismic Stability Evaluation of Folsom Dam and Reservoir Project. Report 3. Concrete Gravity Dam.  

National Technical Information Service (NTIS)

The man-made water retaining structures at the Folsom Dam and Reservoir Project, located on the American River about 20 miles upstream of the City of Sacramento, CA, have been evaluated for their seismic safety in the event of a magnitude 6.5 earthquake o...

J. M. Nau R. L. Hall S. C. Woodson

1989-01-01

375

Evaluation of chemical stabilizers and windscreens for wind erosion control of uranium mill tailings  

Microsoft Academic Search

Potential wind erosion of uranium mill tailings is a concern for the surface disposal of tailings at uranium mills. Wind-blown tailings may subsequently be redeposited on areas outside the impoundment. Pacific Northwest Laboratory (PNL) is investigating techniques for fugitive dust control at uranium mill tailings piles. Laboratory tests, including wind tunnel studies, were conducted to evaluate the relative effectiveness of

M. R. Elmore; J. N. Hartley

1984-01-01

376

Characterisation of Ascochyta rabiei isolates and evaluation of genotypic stability in chickpea  

Microsoft Academic Search

Ascochyta rabiei isolates were characterised for their variability using a set of host differentials following cloth chamber screening technique. Sixty chickpea genotypes were evaluated against the characterised 10 individual pathotypes separately to identify genotypes with stable resistance during 2007–2008. Twenty four genotypes showed resistance to all the pathotypes; whereas 18 genotypes were resistant to moderately resistant to these pathotypes. The

Livinder Kaur; Varinder Pal Singh; J. S. Sandhu

2012-01-01

377

Characterisation of Ascochyta rabiei isolates and evaluation of genotypic stability in chickpea  

Microsoft Academic Search

Ascochyta rabiei isolates were characterised for their variability using a set of host differentials following cloth chamber screening technique. Sixty chickpea genotypes were evaluated against the characterised 10 individual pathotypes separately to identify genotypes with stable resistance during 2007–2008. Twenty four genotypes showed resistance to all the pathotypes; whereas 18 genotypes were resistant to moderately resistant to these pathotypes. The

Livinder Kaur; Varinder Pal Singh; J. S. Sandhu

2011-01-01

378

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.

Cheng, Yen May; Claydon, Tom W.

2012-01-01

379

Evaluation of the Stability, Bioavailability, and Hypersensitivity of the Omega-3 Derived Anti-Leukemic Prostaglandin: ?12-Prostaglandin J3  

PubMed Central

Previous studies have demonstrated the ability of an eicosapentaenoic acid (EPA)-derived endogenous cyclopentenone prostaglandin (CyPG) metabolite, ?12-PGJ3, to selectively target leukemic stem cells, but not the normal hematopoietic stems cells, in in vitro and in vivo models of chronic myelogenous leukemia (CML). Here we evaluated the stability, bioavailability, and hypersensitivity of ?12-PGJ3. The stability of ?12-PGJ3 was evaluated under simulated conditions using artificial gastric and intestinal juice. The bioavailability of ?12-PGJ3 in systemic circulation was demonstrated upon intraperitoneal injection into mice by LC-MS/MS. ?12-PGJ3 being a downstream metabolite of PGD3 was tested in vitro using primary mouse bone marrow-derived mast cells (BMMCs) and in vivo mouse models for airway hypersensitivity. ZK118182, a synthetic PG analog with potent PGD2 receptor (DP)-agonist activity and a drug candidate in current clinical trials, was used for toxicological comparison. ?12-PGJ3 was relatively more stable in simulated gastric juice than in simulated intestinal juice that followed first-order kinetics of degradation. Intraperitoneal injection into mice revealed that ?12-PGJ3 was bioavailable and well absorbed into systemic circulation with a Cmax of 263 µg/L at 12 h. Treatment of BMMCs with ZK118182 for 12 h resulted in increased production of histamine, while ?12-PGJ3 did not induce degranulation in BMMCs nor increase histamine. In addition, in vivo testing for hypersensitivity in mice showed that ZK118182 induces higher airways hyperresponsiveness when compared ?12-PGJ3 and/or PBS control. Based on the stability studies, our data indicates that intraperitoneal route of administration of ?12-PGJ3 was favorable than oral administration to achieve effective pharmacological levels in the plasma against leukemia. ?12-PGJ3 failed to increase histamine and IL-4 in BMMCs, which is in agreement with reduced airway hyperresponsiveness in mice. In summary, our studies suggest ?12-PGJ3 to be a promising bioactive metabolite for further evaluation as a potential drug candidate for treating CML.

Kudva, Avinash K.; Kaushal, Naveen; Mohinta, Sonia; Kennett, Mary J.; August, Avery; Paulson, Robert F.; Prabhu, K. Sandeep

2013-01-01

380

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

381

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

SciTech Connect

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

Cox, G.R.

1981-12-01

382

Stability of influenza virus as evaluated by integrity of its RNA.  

PubMed

Various methods of handling samples of avian influenza prior to detecting influenza viruses can significantly influence both, the detection of the virus and the quantification of viral nucleic acids. The quantity of influenza viral RNA remaining in different collecting buffers and kept at temperatures of -20°C, +4°C or +22°C for various lengths of time, was determined. The quantity of viral RNA remained the same for 120 days at -20°C, but decreased when the samples were stored at either +4°C or +22°C. The quantity of RNA was influenced by the composition of the collecting buffer. The influenza virus sample that is to be used for RNA quantification can be stored at +4°C and freeze and thaw cycles should be avoided during transport. Our results clearly indicate that the quality and quantity of influenza virus nucleic acid depends on the chemical composition of used buffer and also that the samples can be protected from degradation even if they are not stored at ultra-low temperatures. However, repeated thaw and freeze cycles will damage viral RNA even if kept in stabilizing buffers. Keywords: influenza virus; degradation; RNA; buffer. PMID:22720702

Ryba, S; Tacner, J; Havlickova, M; Stopka, P

2012-01-01

383

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.

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

2014-01-01

384

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

385

Fluorescence resonance energy transfer: evaluation of the intracellular stability of polyplexes.  

PubMed

The investigation of intracellular mechanisms of non-viral nucleic acid delivery systems has provided great impetus for the improvement of their efficacy. Especially the intracellular release of the nucleic acid from the non-viral carrier system may be a relevant criterion for the high transfection efficiency of certain polymers. Therefore, we evaluated fluorescence resonance energy transfer (FRET) in combination with confocal laser scanning microscopy or flow cytometry as tool to determine the intracellular disintegration of polyplexes built with plasmid DNA and linear polyethylenimine. In microscopy, which allowed for an observation of polyplexes within single cells, sensitized emission measurement and acceptor photobleaching have been tested towards quantitative FRET analysis. In contrast, the whole cell population was analyzed by the flow cytometry-based method. We suggest that FRET is a useful tool to evaluate the intracellular disintegration of polyplexes built with various polymers. PMID:16527471

Breunig, Miriam; Lungwitz, Uta; Liebl, Renate; Goepferich, Achim

2006-06-01

386

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

387

Comparative proteomics evaluation of plasma exosome isolation techniques and assessment of the stability of exosomes in normal human blood plasma.  

PubMed

Exosomes are nanovesicles released by a variety of cells and are detected in body fluids including blood. Recent studies have highlighted the critical application of exosomes as personalized targeted drug delivery vehicles and as reservoirs of disease biomarkers. While these research applications have created significant interest and can be translated into practice, the stability of exosomes needs to be assessed and exosome isolation protocols from blood plasma need to be optimized. To optimize methods to isolate exosomes from blood plasma, we performed a comparative evaluation of three exosome isolation techniques (differential centrifugation coupled with ultracentrifugation, epithelial cell adhesion molecule immunoaffinity pull-down, and OptiPrep(TM) density gradient separation) using normal human plasma. Based on MS, Western blotting and microscopy results, we found that the OptiPrep(TM) density gradient method was superior in isolating pure exosomal populations, devoid of highly abundant plasma proteins. In addition, we assessed the stability of exosomes in plasma over 90 days under various storage conditions. Western blotting analysis using the exosomal marker, TSG101, revealed that exosomes are stable for 90 days. Interestingly, in the context of cellular uptake, the isolated exosomes were able to fuse with target cells revealing that they were indeed biologically active. PMID:24115447

Kalra, Hina; Adda, Christopher G; Liem, Michael; Ang, Ching-Seng; Mechler, Adam; Simpson, Richard J; Hulett, Mark D; Mathivanan, Suresh

2013-11-01

388

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

389

Numerical analysis for the evaluation of the stability of underground cavities in calcarenite interacting with buildings  

NASA Astrophysics Data System (ADS)

Soft and highly porous rocks such as tuffs and calcarenites are very common rocks. Due to their porous calcareous structure they are quite prone to water induced weathering mechanisms. Onshore and inland natural underground cavities are evident signs of these phenomena and of the effects in terms of failure. These materials have been largely employed in the past as building and ornamental stones and as sites to excavate underground cavities for different uses. The world famous Unesco site of "Sassi di Matera", the underground cavities in Canosa di Puglia and Gravina di Puglia , or the calcarenite cliff and natural caves of Polignano a Mare are the most representative cases. Nowadays, many of these are deteriorating because of weathering due to humidity, water infiltration, environmental pollution, and direct exposure to marine aerosols and meteoric water precipitations. In all these cases, a careful assessment of the safety of the built environment and a conscious identification of the safety measures cannot be separated from the analysis of the interaction between the cavities and the overlying buildings, and of the evolution and spatial distribution of the weathering processes. This contribute summarizes the authors' experience on the subject and suggests a methodological approach to quantitatively assess the stability of underground cavities. Starting from experimental evidences at micro and macroscale, the main debonding mechanisms have been taken into account in numerical models. The time-evolution scenarios of the weathering processes is introduced in three-dimensional numerical modelling. The intention is to provide a potentially useful tool for risk assessment in similar complex geomechanical situations.

Castellanza, Riccardo; Lollino, Piernicola; Oryem Ciantia, Matteo; di Prisco, Claudio; Crosta, Giovanni; Frigerio, Gabriele

2013-04-01

390

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.

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

2013-01-01

391

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

392

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.

393

CSER 00-003 Criticality Safety Evaluation report for PFP Magnesium Hydroxide Precipitation Process for Plutonium Stabilization Glovebox 3  

SciTech Connect

This Criticality Safety Evaluation Report analyzes the stabilization of plutonium/uranium solutions in Glovebox 3 using the magnesium hydroxide precipitation process at PFP. The process covered are the receipt of diluted plutonium solutions into three precipitation tanks, the precipitation of plutonium from the solution, the filtering of the plutonium precipitate from the solution, the scraping of the precipitate from the filter into boats, and the initial drying of the precipitated slurry on a hot plate. A batch (up to 2.5 kg) is brought into the glovebox as plutonium nitrate, processed, and is then removed in boats for further processing. This CSER establishes limits for the magnesium hydroxide precipitation process in Glovebox 3 to maintain criticality safety while handling fissionable material.

LAN, J.S.

2000-07-13

394

Community mental health centres initiated by the South-Eastern Europe Stability Pact: evaluation in seven countries.  

PubMed

Eight community mental health care centres (initiated by the South-Eastern Europe Stability Pact) in Albania, Bosnia-Herzegovina, Croatia, Macedonia, Moldova, Montenegro and Romania were evaluated. Characteristics of patients, patient reported outcomes and patient views of care were assessed in 305 psychiatric patients. Patient characteristics varied across centres, with most patients having long term psychotic disorders. Treatment satisfaction and therapeutic relationships were rated favourably. Subjective quality of life mean scores were rather low, with higher satisfaction with health and dissatisfaction with the financial and employment situation. Being unemployed was the only factor associated with poor quality of life and lower treatment satisfaction. Most developing centres target patients with persistent psychotic disorders. Care appears highly valued by the patients. The findings encourage establishing more centres in the region and call for employment schemes for people with mental illnesses. PMID:21617994

Priebe, Stefan; Matanov, Aleksandra; Demi, Neli; Blagovcanin Simic, Joka; Jovanovic, Sandra; Gajic, Milena; Radonic, Elizabeta; Bajraktarov, Stojan; Boderscova, Larisa; Konatar, Monika; Nica, Raluca; Muijen, Matthijs

2012-06-01

395

A wind-tunnel evaluation of analytical techniques for predicting static stability and control characteristics of flexible aircraft  

NASA Technical Reports Server (NTRS)

An experimental evaluation of analytical techniques for predicting certain stability and control characteristics of a large flexible aircraft is presented. Analytical methods based on both the model approach and flexibility influence coefficients are developed to predict the aerodynamic characteristics of a flexible airplane. These methods are then applied to a flexibly scaled model of a supersonic transport configuration. Comparisons of wind-tunnel data, calculations based on the model approach, and flexibility influence coefficients are presented over the Mach number range from 0.6 to 2.7. An examination of the results obtained from this study indicates that both analytical techniques predict reasonably well the effect of flexibility on the basic longitudinal characteristics and that both techniques give generally comparable results.

Abel, I.

1972-01-01

396

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

NASA Technical Reports Server (NTRS)

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 deg, 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.

McCrory, Jean L.; Lemmon, David R.; Sommer, H. Joseph; Prout, Brian; Smith, Damon; Korth, Deborah W.; Lucero, Javier; Greenisen, Michael; Moore, Jim

1999-01-01

397

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

398

DEVELOPMENT OF THE KLYSTRON MODULATOR USING A HIGH VOLTAGE INVERTER POWER SUPPLY  

Microsoft Academic Search

The existing klystron modulator in the Linac use a 60 Hz high voltage power supply and adopt traditional L-C resonant charging scheme with De-Qing circuit. The stability of the output high voltage is not satisfactory especially when the AC line voltage fluctuations. If an inverter power supply is used as a HV generator, it will just meet the demands A

Y. G. Son; S. J. Kwon; D. E. Kim; C. W. Chung

2007-01-01

399

High voltage testing. Volume 2: Specifications and procedures  

NASA Astrophysics Data System (ADS)

The High Voltage Design Guide and High Voltage Specifications and Tests Documents referred to in this report pertain to high voltage/high power airborne equipment. A test plan was designed to evaluate and verify test parameters specified in these documents. This was done by writing detailed test procedures obtaining representative test samples, and testing the specified parameters. This report is a revision of the High Voltage Specifications and Tests Document (AFAPL-TR-79-2024) which reflects the findings of the High Voltage Testing portion of the program.

Dunbar, W. G.

1982-08-01

400

Voltage regulation in distribution networks with distributed generation  

NASA Astrophysics Data System (ADS)

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

Blaži?, B.; Uljani?, B.; Papi?, I.

2012-11-01

401

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

Microsoft Academic Search

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

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

2009-01-01

402

Experimental Evaluation of Journal Bearing Stability and New Gas Bearing Material  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

403

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

PubMed

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

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

2014-09-01

404

Multi channel voltage control for fuel cells  

NASA Astrophysics Data System (ADS)

Cell voltage control is a safe method to evaluate the operation of the single cells even though large efforts are being made to stabilise the behaviour of the fuel cells over the whole operating range. For fully developed systems only voltage control of single cells is necessary, whereas in test benches it is necessary to record data of the voltages during operation. Normally, a lot of cells are combined to a stack so that higher total voltages can be reached. Higher voltages make possible a high efficient transformation from direct current of the stack to alternate current of the public network. Sometimes more than 100 cells are connected together whereby the open circuit voltage of a single cell amounts to approximately 1 V. Therefore, the signal processing chips show a high supply maximum rating or the resolution of the values has to be reduced. This paper presents an economically priced multi channel voltage control for single cells of a PEM-fuel cell in combination with a microprocessor control and was developed at the Chair for Electric Power Networks and Renewable Energy Sources. The developed system can transfer the data of up to 32 single cells in serial connection. The resolution amounts to 10 bits per channel. The module has its own microprocessor, which is responsible for the intermediate storage of the collected data and the transfer to the RS-232 interface. Optionally, the module can be equipped with an LCD-display of 20 × 4 letters where different menus of the measured and calculated values can be indicated. The module is designed for a voltage of 1 V per channel and can be supplied with a direct voltage of between 6 and 24 V from the fuel cell stack.

Heideck, G.; Purmann, M.; Styczynski, Z.

405

The sliding-helix voltage sensor  

PubMed Central

The voltage sensor (VS) domain of voltage-gated ion channels underlies electrical excitability of living cells. We simulate a mesoscale model of the VS domain to determine the functional consequences of some of its physical elements. Our mesoscale model is based on VS charges, linear dielectrics and whole-body motion, applied to an S4 ‘sliding helix’. The electrostatics under voltage-clamped boundary conditions are solved consistently using a boundary element method. Based on electrostatic configurational energy, statistical-mechanical expectations of the experimentally observable relation between displaced charge and membrane voltage are predicted. Consequences of the model are investigated for variations of: S4 configuration (?- and 310-helical), countercharge alignment with S4 charges, protein polarizability, geometry of the gating canal, screening of S4 charges by the baths, and fixed charges located at the bath interfaces. The sliding helix VS domain has an inherent electrostatic stability in the explored parameter space: countercharges present in the region of weak dielectric always retain an equivalent S4 charge in that region but allow sliding movements displacing 3 to 4 e0. That movement is sensitive to small energy variations (< 2kT) along the path dependent on a number of electrostatic parameters tested in our simulations. These simulations show how the slope of the relation between displaced charge and voltage could be tuned in a channel.

Peyser, Alexander; Nonner, Wolfgang

2012-01-01

406

High voltage coaxial switch  

DOEpatents

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

Rink, J.P.

1983-07-19

407

High voltage coaxial switch  

DOEpatents

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

Rink, John P. (Los Alamos, NM)

1983-07-19

408

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

409

Voltage Amplification using Plasma  

SciTech Connect

The purpose of this work is to present experimental results about voltage amplification using plasma produced by a simple neon lamp, series connected with a signal generator and discrete circuit elements. The main advantage of employing plasma as an amplifier is due to its ability to drive larger power and potentially to operate in a larger frequency range compared with traditional amplifiers. Our results show that both, the voltage gain and the frequency range where the gain is bigger than one, are related to the plasma density which may be adjusted by a proper control of electrical discharge conditions. The plasma produced into the neon lamp exhibits a diode characteristic that is the principal responsible by the nonlinear plasma response. The amplification occurs when the plasma shows a negative conductance. In this regime the lamp works as an active amplifier and voltage gain higher than 18 was obtained.

Farias, E. E.; Cavalcanti, G. H.; Santiago, M. A. M. [Av. Gal Milton Tavares de Souza - 24310 240 - Instituto de Fisica - Universidade Federal Fluminense (Brazil)

2006-12-04

410

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

411

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

412

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

413

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

414

Evaluation of MegaVoltage Cone Beam CT image quality with an unmodified Elekta Precise Linac and EPID: a feasibility study.  

PubMed

In order to increase the accuracy of patient positioning for complex radiotherapy treatments various 3D imaging techniques have been developed. MegaVoltage Cone Beam CT (MVCBCT) can utilise existing hardware to implement a 3D imaging modality to aid patient positioning. MVCBCT has been investigated using an unmodified Elekta Precise Linac and iView amorphous silicon electronic portal imaging device (EPID). Two methods of delivery and acquisition have been investigated for imaging an anthropomorphic head phantom and quality assurance phantom. Phantom projections were successfully acquired and CT datasets reconstructed using both acquisition methods. Bone, tissue and air were clearly resolvable in both phantoms even with low dose (22 MU) scans. The feasibility of MVCBCT was investigated using a standard linac, amorphous silicon EPID and a combination of a free open source reconstruction toolkit as well as custom in-house software written in Matlab. The resultant image quality has been assessed and presented. Although bone, tissue and air were resolvable in all scans, artifacts are present and scan doses are increased when compared with standard portal imaging. The feasibility of MVCBCT with unmodified Elekta Precise Linac and EPID has been considered as well as the identification of possible areas for future development in artifact correction techniques to further improve image quality. PMID:24609762

Markwell, Tim; Perera, Lakshal; Trapp, Jamie; Fielding, Andrew

2014-06-01

415

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

416

Immunohistochemical evaluation of the effects of paraffin section storage on biomarker stability.  

PubMed

Environmental stresses can alter immunoreactivity of biomarkers in stored tissue sections. The effect of temperature and lighting on 49 cellular or microbial antigens was evaluated in 4 serial paraffin sections, cut 12 months, 10 months, 8 months, 5 months, 3 months, 1 month, 3 days, and 1 day before immunohistochemistry. Slides were stored at room temperature (RT) in the dark, at 4°C in the dark, at RT under fluorescent light, or at RT with windowpane exposure to sunlight. Immunohistochemistry was performed simultaneously in an automated immunostainer. Immunoreactivity was compared with that in the corresponding 1-day-old section and scored as 4 (<10% reduction), 3 (10%-25% reduction), 2 (26%-60% reduction), 1(>60% reduction), or 0 (no reactivity). Any loss of immunoreactivity was proportional to the tissue section age and was least in sections stored in the dark. Immunoreactivity was only completely lost in light-exposed sections and as early as 1 month for CD45. Other markers with complete loss of immunoreactivity were bovine viral diarrhea virus, CD18 (only with fluorescent light), CD31, CD68, canine parvovirus, chromogranins, and thyroid transcription factor-1. Markers with complete loss after light exposure also had reduced immunoreactivity when stored in the dark, as early as day 3. Eight markers (Bartonella spp, CD11d, high molecular weight cytokeratins, feline coronavirus, GATA-4, insulin, p63, progesterone receptor) had minimal decrease in immunoreactivity, regardless of treatment. In conclusion, light-induced antigen decay (tissue section aging) is antigen dependent and could explain unexpectedly weak or negative immunohistochemical reactions in stored paraffin sections. PMID:23435571

Ramos-Vara, J A; Webster, J D; DuSold, D; Miller, M A

2014-01-01

417

In Vivo Evaluation of Quantitative Percussion Diagnostics for Determining Implant Stability  

PubMed Central

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

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

2014-01-01

418

Evaluation of medial meniscus tears and meniscal stability: weight-bearing MRI vs arthroscopy.  

PubMed

To assess the role of dedicated low-field standard and weight-bearing MRI in the evaluation of stable or unstable tears of medial meniscus in comparison with arthroscopy. Our series included 1750 knee MRI scans performed with a high-field MRI scanner from July 2010 to August 2011. We retrospectively reviewed and analyzed 20 MRI exams of normal knee and 57 MRI exams of knee with clinical evidence of tears of the medial meniscus. In the same session, after conventional 1.5T and "dedicated" 0.25T supine MRI exam, the patients underwent weight-bearing examination with the same dedicated MRI unit. In all cases sagittal and coronal PD-W were used. All patients underwent arthroscopy 18-25 days after the weight-bearing MRI. In the first group, no statistically significant anatomical modifications of shape, intensity and position of the medial meniscus between standard 1.5T, dedicated supine and upright MRI were observed. In group A, the images acquired in the supine position (dedicated and 1.5T MRI) documented in 21 cases a traumatic tear (group 2A) and in 36 cases a degenerative tear (group 2B). In group 2A, weight-bearing MRI showed presence of unstable tear a degenerative unstable meniscal tear only in 19 out of 36 cases. In group 2B, weight-bearing MRI showed only in 9 out 21 cases. Arthroscopy confirmed weight-bearing MRI diagnosis in all cases. This new approach to meniscus pathology gives an important contribution to a better management of a diagnostic-therapeutic approach in which standard MRI has not played a key role, so far. PMID:23199751

Barile, Antonio; Conti, Laura; Lanni, Giuseppe; Calvisi, Vittorio; Masciocchi, Carlo

2013-04-01

419

Sensitivity analysis of voltage imbalance in distribution networks with rooftop PVs  

Microsoft Academic Search

A comprehensive voltage imbalance sensitivity analysis and stochastic evaluation based on the rating and location of single-phase grid-connected rooftop photovoltaic cells (PVs) in a residential low voltage distribution network are presented. The voltage imbalance at different locations along a feeder is investigated. In addition, the sensitivity analysis is performed for voltage imbalance in one feeder when PVs are installed in

Farhad Shahnia; Ritwik Majumder; Arindam Ghosh; Gerard Ledwich; Firuz Zare

2010-01-01

420

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

421

A 10 V programmable Josephson voltage standard and its applications for voltage metrology  

NASA Astrophysics Data System (ADS)

The concept of a programmable Josephson voltage standard (PJVS) was first proposed in 1997. Since then a significant amount of research and development work has been devoted to the fabrication of the programmable Josephson junction array and its deployment in a voltage standard system. This paper reports the recent development of a 10 V PJVS system at the National Institute of Standards and Technology (NIST) and its voltage metrology applications. The superior stability of the voltage step of the new 10 V PJVS enables it to perform the same tasks as the conventional Josephson voltage standard (JVS) that uses hysteretic voltage steps and to improve the efficiency and effectiveness of a JVS direct comparison. For the first time, a comparison between a conventional JVS and the NIST 10 V PJVS was performed in order to verify the performance of the NIST 10 V PJVS. The mean difference between the two systems at 10 V was found to be -0.49 nV with a combined standard uncertainty of 1.32 nV (k = 1) or a relative combined standard uncertainty of 1.32 parts in 1010. Automatic comparisons between the 10 V PJVS and a 2.5 V PJVS at 1.018 V were performed to monitor the long term accuracy and stability of the 2.5 V PJVS and to support the NIST electronic kilogram experiment. By matching the voltages of the two PJVS systems during a comparison, the type B uncertainty can be minimized to a negligible level. The difference between the two PJVS at 1.018 V was found to be -0.38 nV with a combined standard uncertainty of 0.68 nV (k = 1) or a relative combined standard uncertainty of 6.7 parts in 1010. Issues encountered during the PJVS comparison and potential challenges for 10 V applications are also discussed.

Tang, Y.; Ojha, V. N.; Schlamminger, S.; Rüfenacht, A.; Burroughs, C. J.; Dresselhaus, P. D.; Benz, S. P.

2012-12-01

422

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

423

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

424

Using fuzzy logic power system stabilizer and static VAR compensator to improve power system transient stability  

Microsoft Academic Search

The main objectives of this paper are to improve transient stability by fuzzy logic power system stabilizer (FLPSS) and also to control voltage at the static VAR compensator (SVC) location bus. Phasor model of SVC is described and used in this paper. Necessity of using SVC to control the voltage at the middle line has been demonstrated. The paper also

Seyed Reza Moasheri; M. Alizadeh

2010-01-01

425

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

426

Evaluation of the bank stability and toe erosion model (BSTEM) for predicting lateral retreat on composite streambanks  

NASA Astrophysics Data System (ADS)

Streambank erosion is known to be a major source of sediment in streams and rivers. The Bank Stability and Toe Erosion Model (BSTEM) was developed in order to predict streambank retreat due to both fluvial erosion and geotechnical failure. However, few, if any, model evaluations using long-term streambank retreat data have been performed. The objectives of this research were to (1) monitor long-term composite streambank retreat during a hydraulically active period on a rapidly migrating stream, (2) evaluate BSTEM's ability to predict the measured streambank retreat, and (3) assess the importance of accurate geotechnical, fluvial erosion, and near-bank pore-water pressure properties. The Barren Fork Creek in northeastern Oklahoma laterally eroded 7.8 to 20.9 m along a 100-m length of stream between April and October 2009 based on regular bank location surveys. The most significant lateral retreat occurred in mid- to late-May and September due to a series of storm events, and not necessarily the most extreme events observed during the monitoring period. BSTEM (version 5.2) was not originally programmed to run multiple hydrographs iteratively, so a subroutine was written that automatically input the temporal sequence of stream stage and to lag the water table in the near-bank ground water depending on user settings. Eight BSTEM simulations of the Barren Fork Creek streambank were performed using combinations of the following input data: with and without a water table lag; default BSTEM geotechnical parameters (moderate silt loam) versus laboratory measured geotechnical parameters based on direct shear tests on saturated soil samples; and default BSTEM fluvial erosion parameters versus field measured fluvial erosion parameters from submerged jet tests. Using default BSTEM input values underestimated the actual erosion that occurred. Lagging the water table predicted more geotechnical failures resulting in greater streambank retreat. Using measured fluvial and geotechnical parameters and a water table lag also under predicted retreat (approximately 3.3 m), but did predict the appropriate timing of streambank collapses. The under prediction of retreat was hypothesized to be due to over predicting the critical shear stress of the non-cohesive gravel, under predicting the erodibility of the non-cohesive gravel, and/or under predicting the imposed shear stress acting on the streambank. Current research improving our understanding of shear stress distributions, streambank pore-water pressure dynamics, and methods for estimating excess shear stress parameters for noncohesive soils will be critical for improving BSTEM and other streambank stability models.

Midgley, Taber L.; Fox, Garey A.; Heeren, Derek M.

2012-04-01

427

Evaluating the Effect of Rainfall Infiltration on the Slope Stability of T16 tower of Taipei Mao-kong Gondola by Numerical Methods  

NASA Astrophysics Data System (ADS)

In this study, a series of rainfall-stability analyses were performed to simulate the failure mechanism and the function of remediation works of the down slope of T-16 tower pier, Mao-Kong gondola (or T-16 Slope) at the hillside of Taipei City using two-dimensional finite element method. The failure mechanism of T-16 Slope was simulated using the rainfall hyetograph of Jang-Mi typhoon in 2008 based on the field investigation data, monitoring data, soil/rock mechanical testing data and detail design plots of remediation works. Eventually, the numerical procedures and various input parameters in the analysis were verified by comparing the numerical results with the field observations. In addition, 48 hrs design rainfalls corresponding to 5, 10, 25 and 50 years return periods were prepared using the 20 years rainfall data of Mu-Zha rainfall observation station, Central Weather Bureau for the rainfall-stability analyses of T-16 Slope to inspect the effect of the compound stabilization works on the overall stability of the slope. At T-16 Slope, without considering the longitudinal and transverse drainages on the ground surface, there totally 4 types of stabilization works were installed to stabilize the slope. From the slope top to the slope toe, the stabilization works of T-16 Slope consists of RC-retaining wall with micro-pile foundation at the up-segment, earth anchor at the up-middle-segment, soil nailing at the middle-segment and retaining pile at the down-segment of the slope. The effect of each individual stabilization work on the slope stability under rainfall condition was examined and evaluated by raising field groundwater level.

RUNG, J.

2013-12-01

428

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

429

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...

430

Evaluation of an equine-optimized enzyme-linked immunosorbent assay for serum insulin measurement and stability study of equine serum insulin  

Microsoft Academic Search

This study aims to evaluate a commercially available equine-optimized insulin assay and to evaluate the stability of equine\\u000a insulin. In addition, serum insulin concentrations before and after feeding are also presented. Samples were taken before\\u000a and after feeding from 40 healthy horses and from 15 equine patients visiting the University Equine Hospital. Insulin was\\u000a analysed with the equine ELISA and

Josefine Öberg; Johan Bröjer; Owe Wattle; Inger Lilliehöök

431

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

PubMed Central

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

2014-01-01

432

High Temperature Stability of Potassium Beta Alumina  

NASA Technical Reports Server (NTRS)

None. From Objectives section: Evaluate the stability of potassium beta alumina under potassium AMTEC operating conditions. Evaluate the stability regime in which potassium beta alumina can be fabricated.

Williams, R. M.; Kisor, A.; Ryan, M. A.

1996-01-01

433

Chiral HPLC versus chiral SFC: evaluation of long-term stability and selectivity of Chiralcel OD using various eluents.  

PubMed

The long-term stability of Chiralcel OD columns under varying HPLC and SFC conditions was evaluated. Two new columns from the same supplier lot were procured, and one was installed in an HPLC system, and the other was installed in an SFC system. Enantiomeric mixtures of trans-stilbene oxide and carbobenzyloxy phenylalaninol were repeatedly injected in both systems over several days. For HPLC, hexane was the primary solvent used, along with IPA, EtOH, MeOH/IPA, or EtOH/TFA modifier. Carbon dioxide was the primary SFC solvent, together with the similar modifiers as the HPLC. Column performance was monitored by measuring resolution, theoretical plate number, and alpha between enantiomeric peaks. It was observed that, when the eluent strengths were adjusted to provide comparable retention times, the Chiralcel OD gave superior enantiomeric resolution when used in the SFC than the HPLC. Equilibration in between solvents was faster with SFC. The columns were demonstrated to be quite stable in both systems. PMID:8123734

Lynam, K G; Nicolas, E C

1993-01-01

434

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

435

Modeling of Induced Voltage of Silicon Dioxide Fiber Coupling  

NASA Astrophysics Data System (ADS)

This paper describes a new model for the breakdown voltage of SiO2 fiber coupler using the Pockel effect and empirical equation. The model is evaluated by using the coupling coefficient and the changes in the refractive index. We found that the breakdown voltage is in the order of 102 volt corresponding to coupling coefficient by the order of mm-1. Increasing the value of coupling coefficient between the electrodes leads to a reduction in the breakdown voltage.

Hanim, Nor Faridah; Saktioto; Ali, Jalil; Rahman, Rosly Abdul

436

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

437

Increased voltage photovoltaic cell  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01