Spot Parameters Research Articles

Abstract W P247: Dynamic Characterization of CT Angiographic Spot Sign

Background and purpose: Standard (static) CT angiography is used to identify the intracerebral hemorrhage (ICH) spot sign. We used dynamic CT-angiography to describe spot sign characteristics and measurement parameters over 60-seconds of image acquisition. Methods: We prospectively collected consecutive patients with acute ICH presenting within 6 hours of symptom onset who underwent whole brain dynamic CT-angiography (dCTA). Spot parameters (earliest appearance, duration, Maximum Hounsfield unit (HU), time to maximum HU, time to spot diagnosis (based on HU>100 or >120) and spot volume) and hematoma volumes were measured using volumetric analysis software. Result: We enrolled 34 patients: three were excluded due to secondary causes of ICH. In the 31 patients with primary ICH, there were 13 males with median age 70 and baseline hematoma volume 33 ml. In our series, 13 patients (42 %) had positive dCTA spot sign. The spot was visualized as an expanding 3-dimensional structure that temporally evolved in its morphology over the scanning period. Median time to spot appearance was 21s (range 15-35 seconds). This method allowed tracking spots where they continued until end of venous phase (persistent leak) with median duration of 39s (range 25-45 seconds). The median maximum HU was 204, and median time to maximum HU was 30.8s. Median time to spot diagnosis was 20.8s using either the HU 100 or 120 definitions. Conclusion: Dynamic CT Angiography allows a 3-dimensional assessment of spot sign formation during acute ICH; this is the first study to quantitatively describe spot sign formation and morphology using dCTA.

Radial velocity variations in the young eruptive star EX Lupi

EX Lup-type objects (EXors) are low-mass pre-main sequence objects characterized by outbursts attributed to highly enhanced disk accretion. The trigger mechanism of EXor outbursts is still debated. One theory requires a close (sub)stellar companion that perturbs the inner disk and triggers the onset of the outburst. Here, we study the radial velocity (RV) variations of EX Lup, the prototype of EXors. We conducted a 5-year RV survey with HARPS and FEROS. We analyzed the activity of EX Lup by checking the bisector and several other activity indicators. We complemented the RV data with photometric monitoring to look for signatures of activity or varying accretion. We found that the RV of EX Lup is periodic, with stable period, semi-amplitude, and phase over at least four years of observations. This period is not present in any of the activity indicators. However, the RV of narrow metallic emission lines suggest the same period, but with an anti-correlating phase. The observed absorption line RVs can be fitted with a Keplerian solution around a 0.6 M_Sun central star with M2 sin i = (14.7 +/- 0.7) M_Jup and eccentricity of e = 0.24. Alternatively, we attempted to model the observations with a cold/hot stellar spot as well, but the spot parameters needed to reproduce the RV semi-amplitude are in contradiction with the photometric variability, making the spot scenario unlikely. We discuss two possibilities to explain the RV data: a geometry with two accretion columns rotating with the star, and a single accretion flow synchronized with the orbital motion of the hypothetical companion. In the companion scenario, the companion's mass would fall into the brown dwarf desert, which, together with the unusually small separation would make EX Lup a unique binary system, with interesting implications on the physical mechanisms responsible for triggering the outburst.

Investigation on Laser Direct Welding of Quad Flat Pack Components

The feasibility of laser direct welding quad flat pack (QFP) device without solder is analyzed and practiced. The relations between the tensile strength of QFP joints and laser welding parameters are investigated, and the optimized parameters are obtained. Further study of weld microstructure under the optimum parameters indicates the dependable metallurgical bonding has been formed. In accordance with the experimental parameters, the finite-element method is employed to simulate the temperature field of the welding process. The simulation results at optimum parameters of the welding spot's temperature distribution are discussed. The temperature rises linearly with the increment of loaded laser heating time, and the center temperature is rising much faster than other locations. The temperature is similar with actual measured highest temperature in this circumstance. It demonstrates the established model is satisfied, and the simulation result is reliable, which is significant to guide practical application.

Ortho-Rectification of SPOT 6 Satellite Images Based on RPC Models

In this paper, the technical parameters of SPOT 6 are simply introduced, and the definition and error compensation scheme of the RPC model are discussed in detail. A SPOT 6 image of Beijing area was picked up to test the correction accuracy of SPOT 6 based on the RPC model by using ten schemes. Results show that the accuracy of ortho-rectification can reach 6 pixels (9 meters) without control point. And the RPC model base on affine transformation is the most adaptive for processing SPOT6 image.

Near-Cathode Plasma Layer on CuCr Contacts of Vacuum Arcs

A model of near-cathode layers in vacuum arcs is developed. The model relies on a numerical solution of the problem of near-cathode space-charge sheath with ionization of atoms emitted by the cathode surface, and allows the self-consistent determination of all parameters of the near-cathode layer, including the ion backflow coefficient. The dependence of the density of energy flux from the plasma to the cathode surface on the local surface temperature is nonmonotonic with a maximum, a feature that plays an important role in the physics of plasma–cathode interaction. The developed model may be used for a variety of purposes, including as a module of complex nonstationary multidimensional numerical models of plasma–cathode interaction in vacuum arcs. As a simple example, an analytical evaluation of parameters of stationary spots on copper and chromium is given. In the case of composite CuCr contacts with large grains, spots with current of several tens of amperes burning on the copper matrix coexist with spots with currents of the order of 1 A burning on the chromium grains.

SIGNS OF ACCRETION IN THE ABUNDANCE PATTERNS OF THE COMPONENTS OF THE RS CVn-TYPE ECLIPSING BINARY STAR LX PERSEI

We present spectroscopic observations of LX Per carried out using the Korean Bohyunsan Observatory Echelle Spectrograph (BOES) with spectral resolving power R = 80, 000. The spectrograph was attached to the 1.8 m telescope. The fit of synthetic spectra to the observed spectrum of the system allowed us to find the component parameters and the abundances of chemical elements in the atmospheres of the components. The strong Ca II H and K emissions are confirmed; we also found emission lines in the Ca II reversals' triplet absorptions at the wavelengths of 8498, 8542, and 8662 A in the spectrum of the cooler component of LX Per. A unique photometric solution using the distorted light curves of three different epochs was made. The spot model light curves were fitted to the 1981, 1982, and 1983 observations successfully by adjusting only spot parameters. We could infer that the variation of spot location and size was the main reason for the changing shape of light curves. The main feature of the abundance patterns of both components was the apparent deficiency of heavy (Z > 30) elements. Only elements with strong lines, namely Y and Ba, were detected. Correlations of relative abundances of chemicalmore » elements with condensation temperatures and second ionization potentials of these elements, which can be explained by the accretion of dust and gas, were found.« less

THE INFORMATION CONTENT IN ANALYTIC SPOT MODELS OF BROADBAND PRECISION LIGHT CURVES

We present the results of numerical experiments to assess degeneracies in lightcurve models of starspots. Using synthetic lightcurves generated with the Cheetah starspot modeling code, we explore the extent to which photometric light curves constrain spot model parameters, including spot latitudes and stellar inclination. We also investigate the effects of spot parameters and differential rotation on one's ability to correctly recover rotation periods and differential rotation in the Kepler lightcurves. We confirm that in the absence of additional constraints on the stellar inclination, such as spectroscopic measurements of vsini or occultations of starspots by planetary transits, the spot latitude and stellar inclination are difficult to determine uniquely from the photometry alone. We find that for models with no differential rotation, spots that appear on opposite hemispheres of the star may cause one to interpret the rotation period to be half of the true period. When differential rotation is included, the changing longitude separation between spots breaks the symmetry of the hemispheres and the correct rotation period is more likely to be found. The dominant period found via periodogram analysis is typically that of the largest spot. Even when multiple spots with periods representative of the star's differential rotation exist, if one spot dominates the lightcurve the signal of differential rotation may not be detectable from the periodogram alone. Starspot modeling is applicable to stars with a wider range of rotation rates than other surface imaging techniques (such as Doppler imaging), allows subtle signatures of differential rotation to be measured, and may provide valuable information on the distribution of stellar spots. However, given the inherent degeneracies and uncertainty present in starspot models, caution should be exercised in their interpretation.

Research of Intelligent Control System for Fish-Farming

Used Atmega 8 microcontroller as the control center, with the temperature sensor DS18B20, feeding control system, combined with radio frequency technology, intelligent control system for fish-farming was designed. The system has the whole process of intelligent automatic control and testing for feeding, supplemental oxygen, and PID temperature regulation; PC and the host processor connect each other through the RS-485 to greatly improve the transmission distance, using CRC cyclic redundancy check code ensure the accuracy of data. The machine is mainly responsible for collecting the spot parameters such as temperature and transmitting the data to the host processor, and send data to PC by the host processor through the serial port to display. Using GSM short message service directly sends the relevant data to the console or the owner of the mobile phone, so as to realize the entire fish process automation management. The system can be widely used in families, and pond pisciculture, and provides the owners efficient and convenient services.

Optimization on Parameters of Resistance Spot Welding Process for Galvanized Steel Plate

In order to research welding technology of DX51D+Z cold rolled galvanized steel, using multivariate nonlinear regression orthogonal combination design method, adopted the shear load as quality indicators, counted welding current, electrode force, welding time, squeeze time and the interaction of them as factors, to built the nonlinear regression models, by adopting this model to forecast shearing load. The result shows that this model has high forecast precision.

Determining thermodynamic parameters of aluminum X-pinch plasma

Experiments on a compact pulsed power generator with an amplitude of 200 kA and a 180-ns front width loaded on an X-pinch consisting of four aluminum wires with a diameter of 35 μm have been carried out. Experimental data and the results of calculations performed in the framework of an impact-radiation model have been used to determine parameters (temperature, density, linear mass) of the X-pinch hot spot at the moment of maximum compression. It is established that (i) a pulse of soft X-ray emission from the X-pinch is generated upon almost complete ejection of substance from the hot spot and (ii) hot-spot formation in the X-pinch proceeds under conditions close to the Bennett equilibrium.

Mathematical estimation of melt depth in conduction mode of laser spot remelting process

A one-dimensional mathematical model based on the front tracking method was developed to predict the melt depth as a function of internal and external parameters of laser spot remelting process in conduction mode. Power density, pulse duration, and thermophysical properties of material including thermal diffusivity, melting point, latent heat, and absorption coefficient have been taken into account in the model of this article. By comparing the theoretical results and experimental welding data of commercial pure nickel and titanium plates, the validity of the developed model was examined. Comparison shows a reasonably good agreement between the theory and experiment. For the sake of simplicity, a graphical technique was presented to obtain the melt depth of various materials at any arbitrary amount of power density and pulse duration. In the graphical technique, two dimensionless constants including the Stefan number (Ste) and an introduced constant named laser power factor (LPF) are used. Indeed, all of the internal and external parameters have been gathered in LPF. The effect of power density and pulse duration on the variation of melt depth for different materials such as aluminum, copper, and stainless steel were investigated. Additionally, appropriate expressions were extracted to describe the minimum power density and time to reach melting point in terms of process parameters. A simple expression is also extracted to estimate the thickness of mushy zone for alloys.

PHYSICAL PROPERTIES OF THE LOW-MASS ECLIPSING BINARY NSVS 02502726

NSVS 02502726 has been known as a double-lined, detached eclipsing binary that consists of two low-mass stars. We obtained $BVRI$ photometric follow-up observations in 2009 and 2011 to measure improved physical properties of the binary star. Each set of light curves, including the 2008 data given by \cCakirli et al., was simultaneously analyzed with the previously published radial-velocity curves using the Wilson-Devinney binary code. The conspicuous seasonal light variations of the system are satisfactorily modelled by a two-spot model with one starspot on each component and by changes of the spot parameters with time. Based on 23 eclipse timings calculated from the synthetic model and one ephemeris epoch, an orbital period study of NSVS 02502726 reveals that the period has experienced a continuous decrease of $-5.9\times10^{-7}$ d yr$^{-1}$ or a sinusoidal variation with a period and semi-amplitude of 2.51 yrs and 0.0011 d, respectively. The timing variations could be interpreted as either the light-travel-time effect due to the presence of an unseen third body, or as the combination of this effect and angular momentum loss via magnetic stellar wind braking. Individual masses and radii of both components are determined to be $M_1$=0.689$\pm$0.016 M$_\odot$, $M_2$=0.341$\pm$0.009 M$_\odot$, $R_1$=0.707$\pm$0.007 R$_\odot$, and $R_2$=0.657$\pm$0.008 R$_\odot$. The results are very different from those of \cCakirli et al. with the primary's radius (0.674$\pm$0.006 R$_\odot$) smaller the secondary's (0.763$\pm$0.007 R$_\odot$). We compared the physical parameters presented in this paper with current low-mass stellar models and found that the measured values of the primary star are best fitted to a 79-Myr isochrone. The primary is in good agreement with the empirical mass-radius relation from low-mass binaries, but the secondary is oversized by about 85%.

The Development and Application of Slug Test in Hydrogeology

The slug test is a field-testing method to evaluate hydrogeological parameters by recording the instantaneous change of the underground water level. Basing on abroad development of slug test, this paper tried to measure some parameters of aquifer with middle and high permeability using high accuracy testing. According to field tests and existing pumping data, discussed difference of several theoretic model, analyzed and computed the hydrogeological parameters of a certain spot in Chang Chun, China by classical Cooper Model. At last, comparing with pumping test, the accuracy of the test was verified, which supplied the theory foundation for its application and generalization.

Starspot detection and properties

AbstractI review the currently available techniques for the starspots detection including the one-dimensional spot modelling of photometric light curves. Special attention will be paid to the modelling of photospheric activity based on the high-precision light curves obtained with space missions MOST, CoRoT, and Kepler. Physical spot parameters (temperature, sizes and variability time scales including short-term activity cycles) are discussed.

TS형 박강판 용접 구조물의 자동화설계를 위한 피로특성에 관한 연구

Cold-rolled carbon steel sheets are commonly used in railroad car or commercial vehicles such as the automobile. These are mainly fabricated by spot welding which is a kind of electric resistance welding. But fatigue strength of spot welding joint is lower than that of base metal due to high stress concentration at nugget edge of the spot welded part. And fatigue strength of them is especially influenced by not only geometrical and mechanical factors but also welding conditions of the spot welded joint. So for fatigue design of gas welded joints such as TS-type joints, it is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of spot welded joints. And also, the influence of the geometrical parameters of spot welded joints on stress distribution and fatigue strength must be evaluated. And analysis approach for fatigue test using design of experiment are evaluated optimum factor in TS-type welded joint and geometrical parameters of materials. Using these results, that factors applied to fundamental information for automation of fatigue design.

Dynamic Breast Magnetic Resonance Imaging: Pretreatment Prediction of Tumor Response to Neoadjuvant Chemotherapy

BackgroundDynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) may have the potential of predicting response to neoadjuvant chemotherapy for patients with breast cancer. However, most of these studies focused on evaluating hot-spot characteristics. To thoroughly reflect tumor status, the cold spot and heterogeneity characteristics should also be evaluated. Patients and MethodsDCE-MRIs from 60 patients newly diagnosed with primary invasive breast cancer were reviewed. Kinetic parameters (including cold spot, hot spot, and heterogeneity parameters) derived from DCE-MRI data were used to describe cold spot, hot spot, and heterogeneity features. Patients with a pathologic complete response (pCR) or a ductal carcinoma in situ with microinvasion after chemotherapy were categorized into the pCR group. Pretreatment kinetic parameters in the pCR and non-pCR groups were compared by using univariate tests. Binary logistic regression analysis was used to identify the independent predictors for pCR. The best cutoff value of the independent predictor at pretreatment, with which to differentiate between patients who had a pCR and a non-pCR, was calculated by using receiver operating characteristic curve analysis. ResultsAfter chemotherapy, 10 (16.7%) patients were categorized into the pCR group and 50 (83.3%) into non-pCR group. Multivariate analysis showed that pretreatment washout slope at a cold spot (washoutC) was the only significant and independent predictor of pCR (β = 26.128; P = .005). The best pretreatment washoutC cutoff value with which to differentiate between patients who had pCR and those with non-pCR was 0.0277, which yielded a sensitivity of 80.0% (95% CI, 44.4%-97.5%) and a specificity of 74.0% (95% CI, 59.7%-85.4%). ConclusionWashoutC may be used as a predictor for pCR in patients with breast cancer who undergo neoadjuvant chemotherapy.

Some studies on weld bead geometries for laser spot welding process using finite element analysis

Nd:YAG laser beam welding is a high power density welding process which has the capability to focus the beam to a very small spot diameter of about 0.4 mm. It has favorable characteristics namely, low heat input, narrow heat affected zone and lower distortions, as compared to conventional welding processes. In this study, finite element method (FEM) is applied for predicting the weld bead geometry i.e. bead length (BL), bead width (BW) and depth of penetration (DP) in laser spot welding of AISI 304 stainless steel sheet of thickness 2.5 mm. The input parameters of laser spot welding such as beam power, incident angle of the beam and beam exposure time are varied for conducting experimental trials and numerical simulations. Temperature-dependent thermal properties of AISI 304 stainless steel, the effect of latent heat of fusion, and the convective and radiative aspects of boundary conditions are considered while developing the finite element model. The heat input to the developed model is assumed to be a three-dimensional conical Gaussian heat source. Finite-element simulations of laser spot welding were carried out by using Ansys Parametric Design Language (APDL) available in finite-element code, ANSYS. The results of the numerical analysis provide the shape of the weld beads for different ranges of laser input parameters that are subsequently compared with the results obtained through experimentation and it is found that they are in good agreement.

Continuous Transient Cathode Spot Operation on a Microprotrusion: Transient Cathode Potential Drop

Time-dependent cathode potential drop (CPD) is studied for a transient cathode spot on a Cu cathode protrusion when the spot operates continuously. A transient heat model was self-consistently developed, taking into account the kinetics of cathode vapor flow in a Knudsen layer, considering the momentum and energy conservation in the sheath, the electron relaxation zone, and the hydrodynamic region of the expanding plasma. The difference between evaporated and return fluxes of heavy particles determines the protrusion erosion rate and, hence, the decrease of its size during transient spot operation. It is shown that the spot parameters (e.g., CPD, temperature, and density) change from an initial to a steady-state value with time. Thus, for continuous spot operation on a Cu protrusion with a 5-μm radius, the CPD is about 90 V when the spot originates from initial plasma with a time duration of less than 50 ns and decreases to 13 V when spot operation continues up to 1 μs. This result explains the relatively large power supply voltage (~100 V) needed for arc ignition (after triggering the initial plasma at the cathode in a low-voltage electrode gap) compared to the low CPD appearing during steady-state arc operation. The calculated potential drop in the plasma expansion region at steady state is about 5 V, and the sum of this value with the CPD agrees well with the measured Cu arc voltage. The spot initiation and development can be consistently described as a vaporization mechanism by the gasdynamic model without involving any phenomena of explosion of irregularities at the cathode surface.

光斑环围参量阵列测试法的测量不确定度

光斑环围参量阵列测试法的测量不确定度

The zoo of starspots

AbstractStarspots are being observed with many different techniques but not always with coherent results. In particular not if model-dependent data analysis must be employed, e.g. through two-dimensional spot modelling of one-dimensional photometric light curves. I review the zoo of currently available physical spot parameters, i.e. their size, temperature and variability time scales, and also compare results from different techniques. Most of the current values come from Doppler imaging and multi-color photometry. I also list a few cases where starspot detections turned out to be very different to the solar analog.