Distortion Of Curve Research Articles

Rest-Stress Limb Perfusion Imaging in Humans with Contrast Ultrasound Using Intermediate-Power Imaging and Microbubbles Resistant to Inertial Cavitation

Contrast-enhanced ultrasound (CEU) limb perfusion imaging is a promising approach for evaluating peripheral artery disease (PAD). However, low signal enhancement in skeletal muscle has necessitated high-power intermittent imaging algorithms, which are not clinically feasible. We hypothesized that CEU using a combination of intermediate power and a contrast agent resistant to inertial cavitation would allow real-time limb stress perfusion imaging. In normal volunteers, CEU of the calf skeletal muscle was performed on separate days with Sonazoid,Optison, or Definity. Progressive reduction in the ultrasound pulsing interval was used to assess the balance between signal enhancement and agent destruction at escalating mechanical indices (MI, 0.1-0.4). Real-time perfusion imaging at MI 0.1-0.4 using postdestructive replenishment kinetics was performedat rest and during 25W plantar flexion contractile exercise. For Optison, limb perfusion imaging was unreliable at rest due to very low signal enhancement generated at all MIs and was possible during exercise-induced hyperemia only at MI 0.1 due to agent destruction at higher MIs. For Definity, signal intensity progressively increased with MI but was offset by microbubble destruction, which resulted in modest signal enhancement during CEU perfusion imaging and distortion of replenishment curves at MI≥0.2. For Sonazoid, there strong signal enhancement at MI≥0.2, with little destruction detected only at MI 0.4. Accordingly, high signal intensity and nondistorted perfusion imaging was possible at MI 0.2-0.3 and detected an 8.0- ± 5.7-fold flow reserve. Rest-stress limb perfusion imaging in humans with real-time CEU, which requires only seconds to perform, is possible using microbubbles with viscoelastic properties that produce strong nonlinear signal generation without destruction at intermediate acoustic pressures.

A Kind of Neither Keynesian Nor Neoclassical Model (4): The Nature of Philips Curve

Officials always want to use the replacement relationship between the unemployment rate and the price of the Phillips curve to reduce the unemployment rate, but things go crisscross. The reason is that there is no causal relationship between price and unemployment. In this paper, it demonstrates the Phillips curve is derived from the unemployment cycle equation and the inflation equation. And then, it discusses the influence of core variables and fluctuating variables on Phillips curve and the cause of distortion or complete disappearance of Phillips curve. Finally, this paper discusses monetary neutrality and related monetary policy issues. The policy that is conducive to the smooth operation of the system is consistent with the constant money supply of the economic cycle, rather than counter-cyclical regulation.

Extending the concept of energy-based pushover analysis to assess seismic demands of asymmetric-plan buildings

The energy-based pushover analysis was developed in previous studies to address the issues regarding the distortion of capacity curve in conventional pushover procedures. Despite the conceptual superiority of an energy-based approach, its application is currently restricted to 2D structures. This study aims to extend the concept of this approach to asymmetric-plan buildings and bidirectional seismic excitation. For this purpose, a new energy-based multimode pushover analysis is developed. The overall procedure is quite similar to the well-known Modal Pushover Analysis (MPA). In contrast, however, the work done by lateral loads and torques here is used in preference to displacement of the roof center as an index to establish capacity curves. The efficiency of the proposed procedure is evaluated through seismic assessment of a set of one-way asymmetric (asymmetric around one axis) RC shear wall buildings. The results are compared with those of the MPA, ASCE41-13 pushover procedure, and the nonlinear response history analysis as a benchmark solution. Findings show that the proposed procedure can provide more accurate results than the MPA and ASCE41-13 procedures, in estimating the structural demands such as wall-hinge rotations and drift ratios.

Field emission characteristics of nano-diamond cathode surface by graphitization pretreatment

Cathode samples of nano-diamond by graphitization pretreatment with different temperatures were fabricated by electrophoresis, then the structures and morphologies of the cathode samples were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), and the field emission tests were conducted. The effects of graphitization pretreatment on the field emission characteristics of nano-diamond cathode surface on titanium substrate are studied. The results indicate that the surface morphologies of nano-diamond cathode samples after graphitization pretreatment change a lot, and the field emission characteristics in low-voltage area are improved obviously. However, in high-voltage area, the curve distortion happens, and it doesn’t conform the mechanism of field emission characteristics.

Towards high performance Cd-free CZTSe solar cells with a ZnS(O,OH) buffer layer: the influence of thiourea concentration on chemical bath deposition

High-performance kesterite- (CZTSe-)based solar cell devices usually employ an absorber/buffer heterostructure using toxic CdS deposited by chemical bath deposition (CBD) as a buffer layer. This is due to the favourable spike-like conduction band alignment of the CdS buffer and CZTSe absorber. ZnS(O,OH) buffer layers provide a promising nontoxic alternative. Here, variation of the thiourea concentration in the CBD of ZnS(O,OH) buffer layers and its influence on device performances of pure selenide CZTSe heterostructure solar cells is presented. Furthermore, the influence of buffer layer deposition conditions on light-induced metastabilities is discussed. A ZnS(O,OH) buffer layer deposited with a high thiourea concentration leads to distorted illuminated J–V curves as expected for devices with unfavourably high spike-like conduction band alignment between the buffer and CZTSe absorber. By adjusting the thiourea concentration J–V curve distortions can be reduced. An optimized CBD process leads to a device efficiency of up to 6.5% after light soaking, which is comparable to the efficiency of a reference device that employs CdS as the buffer layer (6.9%).

Isoconversional analysis of copper recrystallization

Recrystallization of Cu deformed under compression has been monitored by differential scanning calorimetry (DSC) with experiments carried out at constant heating rate. From these experiments, an isothermal crystallization process has been predicted by the classical Kolmogorov–Johnson–Mehl–Avrami (KJMA) kinetics and by model-free isoconversional analysis. Whereas prediction by KJMA does not match the experimental curve, the isoconversional prediction is successful. The paper also highlights the need to correct the raw DSC curves to obtain the actual sample temperature and to avoid curve distortion due to thermal inertia.

Observations and light curve solutions of the eclipsing binaries USNO-B1.0 1395-0370184 and USNO-B1.0 1395-0370731

We present follow-up photometric observations in Sloan filters g', i' of the newly discovered eclipsing stars USNO-B1.0 1395-0370184 and USNO-B1.0 1395-0370731. Our data revealed that their orbital periods are considerably bigger than the previous values. This result changed the classification of USNO-B1.0 1395-0370184 from ultrashort-period binary (P=0.197 d) to short-period system (P=0.251 d). The light curve solutions of our observations revealed that USNOB1.0 1395-0370184 and USNO-B1.0 1395-0370731 are overcontact binaries in which components are K dwarfs, close in masses and radii. The light curve distortions were reproduced by cool spots with angular radius of around 20?.

Research of Non-Sinusoidal Voltage in Frequency Converter of Medium Power Operation

The article presents the comparative analysis of influence frequency regulated electric drive and current electric drive to harmonic structure of voltage of power grid. There was obtained the dependence of total harmonic distortion (THD) of curve on loading power for 2 types of valve converters. The effectiveness is shown in use of filter compensating device, connected at low side of converting transformer. There were defined the ranges of filter adjusting for improving THD of voltage curve. The described solutions are performed by the structural modeling method of Simulink packet in Matlab environment.

Problems of network simplification by edge bundling

Node occlusion and edge congestion problems,which are caused by the increment of network scale and complexity,had become a hot spot in network visualization research. To solve the visual clutter problem in network,edges close to each other in network were bundled by curving them. The bundling started from node position and group division,laying emphasis on edge bundling technique through edge convergence,edges bundled close to each other in network to reduce visual complexity. A segmental forced directed algorithm( FDA) simplification model and a group based consistent edge bundling network model were proposed and improved. In segmental FDA bundling model,quadratic spline was used to display line in network,control points of spline were produced by iteration to implement edge bundling. To solve the problem of excessive bending of some edges in segmental FDA bundling model,network was divided into different groups by CNM cluster algorithm. Lines in the same group were applied with edge consistent principle on basement of network group structure,and bundling level was calculated by the matching coefficient of edges. After edge bundling,the phenomena of curve's distortion decreased and curves became smoother. Domestic airline network data was chosen as experimental subject,and the network was simplified by two bundling models,and then the simplification result was analyzed. Experimental result shows that positions of nodes in the same group stand close to each other,and airline network shows distinct crossing skeleton. Airlines have north-south and westeast orientation bundle independently,which reveals the whole trends of airline network construction in these two directions. The bundling simplification algorithm introduced mentioned above has a wide applicability,and network visualized by this algorithm has good visual effect and readability.

Study on the distortion of apparent resistivity curves caused by the ‘infinite’ electrode space of a Pole–Pole array and its correction

The Pole–Pole (PP) array is widely used for measurements that incorporate two-dimensional (2-D) and three-dimensional (3-D) multi-electrode electrical resistivity surveys, although an effective equilibrium has not yet been achieved between two factors, the location of ‘infinite’ electrodes and the data utilisation of the effective resistivity, which affects the detection accuracy; thus, the data collected under the conditions of ‘infinite’ electrodes that are as finite as possible are maximally effective. Studies have shown that the optimum ‘infinite’ electrode distance must be greater than 20 times the current-potential electrode distance AM; this value is much greater than the currently used value of 5 to 10 times AM. However, limitations imposed by landforms and topographic conditions, such as mountainous areas and coal mine roadways, often prevent the ‘infinite’ condition from being satisfied. In this study, a field test was designed and performed by adopting a particular PP array to collect sounding data under different ‘infinite’ electrode distances, and the differences were analysed in the apparent resistivity curves calculated with different geometric coefficients. The results reveal that when the ‘infinite’ electrode space is finite relative to AM, significant distortion may occur, and a minimum inflection point may appear in the sounding curve of apparent resistivity that is calculated with the geometric coefficient Kpp. Although the data past the minimum inflection point of ρs-mpp curve lose their value for the sounding application, a portion of the first segment of the distorted curve can be used, therefore, a correction formula under the condition of non-infinite electrode (Bing and Greenhalgh, 1998) space in a PP array is derived based on traditional electric field theories and formulas of apparent resistivity under different electrode arrays. The error analysis after correction indicates that the data utilisation ratio in the corrected effective apparent resistivity is significantly improved, and all the data that appear before the minimum inflection point can be effectively corrected. Additionally, the error between the corrected apparent resistivity and the value under an ideal state (when BM is at least 20 times AM) is less than 5%. Engineering application cases are conducted to validate the effectiveness of this correction formula, and the results indicate that this formula can be applied to process the resistivity sounding data affected by the ‘infinite’ electrodes.

Laser Tuning Performance Testing and Optimization in TDLAS Oxygen Measuring Systems

TDLAS (tunable diode laser absorption spectroscopy) technology, with its unmatched advantages such as high selectivity molecular spectra, fast response, high sensitivity, non-contact measuring, become the preferred scheme for combustion process diagnosis, and can be effectively used for oxygen measuring. DFB (distributed feedback) laser diode with its small size, low power consumption, long service life, narrow linewidth, tunable wavelength has become the main choice of the TDLAS system. Performance of laser tuning characteristics is a key factor restricting TDLAS's measuring performance. According to TDLAS oxygen measuring system's working requirements, a simple experimental method was used to test and analyze tuning characteristics such as wavelength current, power current and wavelength temperature of a 764 nm DFB laser diode in the system. Nonlinear distortion of tuning curves was obvious, which affects oxygen measuring accuracy. The laser spectra's characteristics such as narrow linewidth, high side mode suppression ratio and wide wavelength tuning range are obvious, while its wavelength-current tuning curve with a tuning rate of about 0.023 nm x mA(-1) is not strictly linear. The higher the temperature the greater the threshold current, the PI curve is not strictly linear either. Temperature tuning curve is of good linearity, temperature-wave-length tuning rate keeps constant of about 0.056 nm/DEG C. Temperature tuning nonlinearity can be improved by high temperature control accuracy, and current power nonlinearity can be improved by setting the reference light path. In order to solve the wavelength current tuning nonlinear problems, the method of DA controlling injection current was considered to compensate for non-linear wavelength current tuning according to DFB laser diode tuning mechanism and polynomial fitting of test results. In view of different type of lasers, this method needs only one polynomial fitting process before the system's initial work. The compensation scheme is reasonable and the realization is simple, what's more, it does not affect the measuring process. The experiments prove that XI curve's linear fit residuals are less than 1 μm after compensation, far less than those of before compensation 22 pm, the compensation effect is obvious, which provided a basis for various oxygen parameters' TDLAS measuring and inversion.

Analysis of double-probe characteristics in low-frequency gas discharges and its improvement.

The double-probe has been used successfully in radio-frequency discharges. However, in low-frequency discharges, the double-probe I-V curve is so much seriously distorted by the strong plasma potential fluctuations that the I-V curve may lead to a large estimate error of plasma parameters. To suppress the distortion, we investigate the double-probe characteristics in low-frequency gas discharge based on an equivalent circuit model, taking both the plasma sheath and probe circuit into account. We discovered that there are two primary interferences to the I-V curve distortion: the voltage fluctuation between two probe tips caused by the filter difference voltage and the current peak at the negative edge of the plasma potential. Consequently, we propose a modified passive filter to reduce the two types of interference simultaneously. Experiments are conducted in a glow-discharge plasma (f = 30 kHz) to test the performance of the improved double probe. The results show that the electron density error is reduced from more than 100% to less than 10%. The proposed improved method is also suitable in cases where intensive potential fluctuations exist.

PHOTOMETRIC PROPERTIES FOR SELECTED ALGOL-TYPE BINARIES. VII. V404 AND WITH MAGNETIC ACTIVITY

We present new CCD light curves of the short-period Algol-type eclipsing binary V404 And obtained in 2009-2011. The time-resolving multiple BVRI color light curves of the year 2011 with full phase coverage were analyzed simultaneously using the latest Wilson-Devinney program. We concluded that the configuration of two starspots on the primary is the most reliable explanation for the light curve distortions observed in 2011. Based on the new photometric solution, we further applied the spot model to explain the other light curves, including the previously published R-band light curves. We revealed that the starspots changed on a long timescale in terms of the spot parameters and the differences between Max. I and Max. II. Moreover, the O - C diagram spanning about 15 yr shows an upward parabola, which indicates a secular increase in the orbital period of V404 And. The orbital period increases at a rate of dP/dt = 5.3(0.3) x 10(-7) days yr(-1), which might be interpreted by the angular momentum exchange via magnetic activity.

MAGNETIC ACTIVITY AND ORBITAL PERIOD VARIATION OF THE SHORT-PERIOD ECLIPSING BINARY DV Psc

We present six new BVRcIc CCD light curves of a short-period RS CVn binary DV Psc obtained in 2010-2012. The light curve distortions change on both short and long timescales, which is explained by two starspots on the primary component. Moreover, five new flare events were detected and the flare ratio of DV Psc is about 0.082 flares per hour. There is a possible relation between the phases (longitude) of the flares and starspots for all of the available data of late-type binaries, which implies a correlation of the stellar activity of the spots and flares. The cyclic oscillation, with a period of 4.9 +/- 0.4 yr, may result from the magnetic activity cycle, identified by the variability of Max. I-Max. II. Until now, there were no spectroscopic studies of chromospheric activity indicators of the H-beta and H-gamma lines for DV Psc. Our observations of these indicators show that DV Psc is active, with excess emissions. The updated O - C diagram with an observing time span of about 15 yr shows an upward parabola, which indicates a secular increase in the orbital period of DV Psc. The orbital period secularly increases at a rate of dP/dt = 2.0x10(-7) days yr(-1), which might be explained by the angular momentum exchanges or mass transfer from the secondary to primary component.

Design of Servo Stamping Motion Considering Constraints of Different Orders and Actuation Capability

The design of stamping motion is one of the key technologies to make the servo press performing stamping operation perfectly. An interpolation method considering constraints of different orders is proposed based on NURBS motion curve that any one or all constraints of position, velocity and acceleration can be defined at desired key points of the stamping motion in order to satisfy both accuracy and flexibility requirements. An algorithm is presented to generate the dwell section of stamping motion curve with given time span quickly. A reasonable solution is given to define the derivative magnitudes in construction of the interpolation equation to avoid stamping motion curve's distortion. A method to amend proper velocity or acceleration constraint is proposed to improve the performance of stamping motion curve. Following above discussion, a general process of servo stamping motion design is proposed and an interactive stamping motion design software is developed considering constraints from metal forming operation and actuation capability of the servomotors. Finally, the proposed stamping motion design method is demonstrated by a forming case of automobile wing workpiece.

Application of the Methods of Mechanical Resonance for the Detection of Defects in Steels of Steam Pipelines After Operation

We use linear and nonlinear methods of mechanical resonance to detect defects in steels after operation for ~7 · 104 − 2.45 · 105 h in steam pipelines of a thermoelectric plant. We determine the sound velocity, vibration decrement, its dependence on the amplitude of maximum cyclic stresses, and the dependence of the resonance frequency of a cantilevered rod specimen on the strain amplitude. It is shown that the vibration decrement of materials after operation is higher than in the as-delivered state and its dependence on the stress amplitude becomes stronger. It is found that the material after operation is characterized by the nonlinear elastic behavior, which manifests itself as a distortion of the resonance curve and in the form of dependence of the resonance frequency on the amplitude. We establish a linear dependence of the resonance frequency on the strain amplitude, which is in good agreement with a similar dependence of the vibration decrement. We confirm that the nonlinear methods are promising for the detection of defects in steam pipelines.

Факторы риска возникновения психических нарушений в отдаленном периоде черепно-мозговой травмы

У 437 больных, которые перенесли черепно-мозговую травму (ЧМТ) и имеют определенную психопатологию, с помощью клинических обследований, психометрических шкал, лабораторных методов, включавших проточную цитометрию и определение уровня мелатонина, а также инструментальных методов (КТ, МРТ, ЭЭГ, РЭГ) выявлены факторы риска неблагоприятного прогноза в отдаленном периоде черепно-мозговой травмы, что приводит к тяжелым психическим расстройствам. Установлено, что важнейшими из них могут считаться следующие: выраженная астения, нарушение регуляции апоптоза, биологических ритмов, а именно — извращение температурной кривой, обмена мелатонина, инсомнии. Характерно, что вышеуказанные нарушения достигали большой выраженности даже у лиц, перенесших легкую ЧМТ. При этом наиболее распространенными неблагоприятными последствиями ЧМТ были такие психопатологические проявления, как когнитивные, шизофреноподобные и аффективные расстройства. Функциональные расстройства, возникшие у лиц, перенесших легкую ЧМТ, с течением времени приводили к стойкому нарушению адаптационной системы всего организма.

P.102: Improvement of Gamma Curve Distortion in VA LCD by using Optical Film Patterned Retarder

AbstractIn this paper, we improved the γ‐curve distortion at off‐axis direction in a 4‐domain (4‐D) patterned vertical alignment (PVA) liquid crystal (LC) cell by applying a pair of the film patterned retarder (FPR) system with the A‐film property at the conventional wide‐view (WV) PVA LC cell. In order to achieve the excellent γ‐curve in the 4‐domain LC cell, we optimized the parameter of the pair of the patterned A‐film by using the two‐dimensional parameter space method, which calculates the polarization difference between the normal direction and the all viewing directions under voltage applied state. As a result, we confirmed that the gamma distortion index (GDI) of the proposed optical structure is reduced to over 80% without any loss of the optical luminance and the contrast ratio in the dark state.

Consequences of choosing samples in hypothesis testing to ensure homogeneity of variance

The two-sample Student t test of location was performed on random samples of scores and on rank-transformed scores from normal and non-normal population distributions with unequal variances. The same test also was performed on scores that had been explicitly selected to have nearly equal sample variances. The desired homogeneity of variance was brought about by repeatedly rejecting pairs of samples having a ratio of standard deviations that exceeded a predetermined cut-off value of 1.1, 1.2, or 1.3, while retaining pairs with ratios less than the cut-off value. Despite this forced conformity with the assumption of equal variances, the tests on the selected samples were no more robust than tests on unselected samples, and in most cases substantially less robust. Under conditions where sample sizes were unequal, so that Type I error rates were inflated and power curves were atypical, the selection procedure produced still greater inflation and distortion of the power curves.

An assessment of the impact of reduced averaging time on small wind turbine power curves, energy capture predictions and turbulence intensity measurements

The effect of varying the averaging time of measured data used to calculate wind turbine power curves is examined. The effects of reducing the averaging time from 10 minutes to 1 minute, as recommended for small wind turbines are investigated using power performance data recorded using a 15kW wind turbine. Test site data have been processed according to IEC 61400-12-1 to provide power curves and annual energy yield predictions [1]. A number of issues are explored: the systematic distortion of the power curve that occurs as averaging time is decreased, the errors introduced by the use of one minute averaged power curves to calculate energy yield and the reduction of turbulence intensity as averaging time is reduced. Recommendations for improved small wind turbine testing and energy yield calculation are given.