Spot Model Research Articles

A Study of Service Innovation Management in the Malaysian Telecommunications Industry

To what extent does service innovation management influence performance in the telecommunications industry? That is the primary question addressed in a study of 249 managers in two leading Malaysian telecom firms. Researchers used the SPOTS model, which links five dimensions of service innovation management—strategy, process, organization, tools/technology, and system—to the three dimensions of performance—market performance, service development, and delivery process performance. Of the 15 hypotheses proposed, six were supported by the research findings. The analysis finds that the combined effect of strategy, process, organization, and system (SPOS) has an impact on service performance. © 2014 Wiley Periodicals, Inc.

PHOTOMETRIC ANALYSIS OF THE OVERCONTACT BINARY CW CAS

New CCD photometric observations of overcontact binary CWCas were carried out in 2004 and 2011. In particular, the light curve obtained in 2004 shows a remarkable O'Connell effect. Compared with light curves in different observing seasons, variations were found. These variations can be explained by dark spot activities on the surface of at least one component. Using the Wilson-Devinney code with a spot model, we find that the photometric solutions confirm CWCas is a shallow W-subtype overcontact binary with a spotted massive component. Our new determined times of minimum light together with the others published in the literature were analyzed to find a change of orbital period. From the O - C curves, the period of the system shows a cyclic period change (P-3 = 69.9 yr, A(3) = 0.03196 days) superposed on the linear increase. The cyclic variation, if explained as the light-travel time effect, reveals the presence of a tertiary companion.

Simulation of the hot core mode of arc attachment at a thoriated tungsten cathode by an emitter spot model

Recently, a constricted attachment of an atmospheric pressure low-current argon arc in the centre of the flat end face of a thoriated tungsten cathode was observed and spectroscopically analysed. Its diameter of 0.6 mm and its length of the free standing part of 10 mm are the typical dimensions of electrodes for high-intensity discharge lamps. This paper gives a physical interpretation of the axially symmetric arc spot by a simulation of its properties with a cathodic sheath model which takes into account a reduction in the work function above a critical temperature of the cathode surface by a thorium ion current.At first the optical observation and spectroscopic investigations are recapitulated. Then, an overview is given on the essential elements which are needed to simulate the cathodic arc attachment on a hot electrode. A simulation of a central cathode spot with these elements gives results which are far away from the experimental findings if a constant work function φ is used. Therefore, a temperature-dependent work function φ(T) is introduced. This φ(T) transitions from 4.55 to 3 eV above temperatures of the order of 3000 K. With this emitter spot model a constricted arc attachment is obtained by simulation in the centre of the flat end face of the cathode in accordance with experiment. For currents below iarc,max ≈ 15.5 A, two spot solutions with different cathode falls are found. They form a current–voltage–characteristic consisting of two branches which extend from a turning point at iarc,max to lower currents. For iarc > iarc,max, only a diffuse mode of cathodic arc attachment is obtained. It is shown by a comparison with measured data for iarc = 7.5, 10, 12.5 and 15 A that the solution with the lower cathode fall is observed experimentally.

CHF prediction model research for flat and hypervapotron heating surface in subcooled flow nucleate boiling

Based on fundamental nucleation boiling theory, nucleation site distribution and hot spot model, a theoretical critical heat flux (CHF) prediction model in subcooled flow boiling is presented in this paper. With the increase of heat flux, nucleation site density will finally approach the limit of site population. When the critical number of nucleation sites is reached in an area, it will cut off the supply of liquid for the central site, and then CHF emerges. In this paper, an improved hot spot model is proposed, which uses statistical bubble departure diameter and standard square shape. CHF prediction can be reasonably achieved based on fully developed boiling heat transfer curve, nucleation site density and distribution. Some related experimental data are referred and R134a subcooled flow boiling data on flat and hypervapotron test section are reported. Comparison results showed a good prediction of CHF.

Magnetic activity, differential rotation, and dynamo action in the pulsating F9IV star KIC 5955122

We present photometric spot modeling of the nearly four-year long light-curve of the Kepler target KIC 5955122 in terms of persisting dark circular surface features. With a Bayesian technique, we produced a plausible surface map that shows dozens of small spots. After some artifacts are removed, the residuals are at $\pm 0.16$\,mmag. The shortest rotational period found is $P = 16.4 \pm 0.2$ days. The equator-to-pole extrapolated differential rotation is $0.25 \pm 0.02$ rad/d. The spots are roughly half as bright as the unperturbed stellar photosphere. Spot latitudes are restricted to the zone $\pm 60^\circ$ latitude. There is no indication for any near-pole spots. In addition, the p-mode pulsations enabled us to determine the evolutionary status of the star, the extension of the convective zone, and its radius and mass. We discuss the possibility that the clear signature of active regions in the light curve of the F9IV star KIC 5955122 is produced by a flux-transport dynamo action at the base of the convection zone. In particular, we argue that this star has evolved from an active to a quiet status during the Q0--Q16 period of observation, and we predict, according to our dynamo model, that the characteristic activity cycle is of the order of the solar one.

Predictability of gun crimes: a comparison of hot spot and risk terrain modelling techniques

The current study was designed to assess the possible differences in the accuracy and precision of two methodological mapping techniques as predictors of future gun crimes in Little Rock, AR: (1) risk terrain modelling (RTM) and (2) nearest neighbour hierarchical (Nnh), a traditional hot spot technique, which relies on past crime to predict where future crime is likely to occur. Data from the Little Rock Police Department, the Little Rock Treasury Department and the 2000 census were used to examine Nnh hot spot and RTM methods of gun crime prediction. The RTM incorporated measures of crime generators and crime attractors, while Nnh hot spots were constructed from 2008 gun crime data. The two measures were compared using their predictive accuracy index (PAI) and recapture rate index (RRI) values. Six of the seven social and physical environmental measures in the RTM significantly predicted future gun crime locations and the Nnh hot spots predicted 7% of future gun crime. PAI and RRI values suggested the RTM was more precise than the Nnh hot spot technique and the Nnh hot spot technique was more accurate than the RTM technique. Relying on one spatial prediction technique may create problems with accuracy and reliability. Multiple techniques may be needed to fully assess the phenomenon. Accuracy is a potential limitation of RTM when compared to other techniques, however, RTM is more reliable than Nnh hot spots due to the inclusion of the environmental backcloth. The findings were discussed in relation to crime prediction and policing efforts.

Distinguishing black holes and wormholes with orbiting hot spots

The supermassive black hole candidates at the center of every normal galaxy might be wormholes created in the early Universe and connecting either two different regions of our Universe or two different universes in a Multiverse model. Indeed, the origin of these supermassive objects is not well understood, topological non-trivial structures like wormholes are allowed both in general relativity and in alternative theories of gravity, and current observations cannot rule out such a possibility. In a few years, the VLTI instrument GRAVITY will have the capability to image blobs of plasma orbiting near the innermost stable circular orbit of SgrA$^*$, the supermassive black hole candidate in the Milky Way. The secondary image of a hot spot orbiting around a wormhole is substantially different from that of a hot spot around a black hole, because the photon capture sphere of the wormhole is much smaller. The radius of the photon capture sphere is independent of the hot spot model, and therefore its possible detection, which is observationally challenging but not out of reach, can unambiguously test if the center of our Galaxy harbors a wormhole rather than a black hole.

Equilibrium Commodity Trading

We develop an equilibrium model of commodity spot and futures markets in which commodity production, consumption, and speculation are endogenously determined. Speculators facilitate hedging by the commodity suppliers. The entry of new speculators thus increases the supply of the commodity and decreases the expected spot prices, to the benefits of the end-users. However, this entry may be detrimental to the producers, as they do not internalize the price reduction due to greater aggregate supply. In the presence of asymmetric information, speculation on the futures market serves as a learning device. The futures price and open interest reveal different pieces of private information regarding the supply and demand side of the spot market, respectively. When the accuracy of private information is low, the entry of new speculators makes both production and spot prices more volatile. The entry of new speculators typically increases the correlation between financial and commodity markets.

Dynamical star-disk interaction in the young stellar system V354 Monocerotis

The main goal of this work is to characterize the mass accretion and ejection processes of the classical T Tauri star V354 Mon, a member of the young stellar cluster NGC 2264. In March 2008, photometric and spectroscopic observations of V354 Mon were obtained simultaneously with the CoRoT satellite, the 60 cm telescope at the Observat\'orio Pico dos Dias (LNA - Brazil) equipped with a CCD camera and Johnson/Cousins BVRI filters, and the SOPHIE \'echelle spectrograph at the Observatoire de Haute-Provence (CNRS - France). The light curve of V354 Mon shows periodical minima (P = 5.26 +/- 0.50 days) that vary in depth and width at each rotational cycle. From the analysis of the photometric and spectroscopic data, it is possible to identify correlations between the emission line variability and the light-curve modulation of the young system, such as the occurrence of pronounced redshifted absorption in the H_alpha line at the epoch of minimum flux. This is evidence that during photometric minima we see the accretion funnel projected onto the stellar photosphere in our line of sight, implying that the hot spot coincides with the light-curve minima. We applied models of cold and hot spots and a model of occultation by circumstellar material to investigate the source of the observed photometric variations. We conclude that nonuniformly distributed material in the inner part of the circumstellar disk is the main cause of the photometric modulation, which does not exclude the presence of hot and cold spots at the stellar surface. It is believed that the distortion in the inner part of the disk is created by the dynamical interaction between the stellar magnetosphere, inclined with respect to the rotation axis, and the circumstellar disk, as also observed in the classical T Tauri star AA Tau and predicted by magnetohydrodynamical numerical simulations.

On possible photometric manifestation of magnetic field in Cyg X-1

We consider the influence of the magnetic field of the O9.7Iab supergiant component in the CygX-1 X-ray binary system on its atmosphere. In the frame of the simplest model (the unipolar cylindrically symmetric circum-polar magnetic spot model in static approximation, neglecting the Lorentz force component related to the force line curvature), the magnetic pressure is found to be comparable to model-atmosphere gas and radiative pressure, exceeding them in the area around the magnetic poles. As a result, bright spots are formed on the star surface. The dipolar or quadrupolar magnetic field can create large-size bright spots which can be studied by ground-based optical photometry. In the case of magnetic field inclined to the stellar rotation axis, resulting variability may be of the order of 1%. The field of higher multipolar configuration (produced by dynamo) can form smaller spots and may be detected only by space telescopes. Besides, the spots may be revealed from spectral-line profile variability. Observations of spots can be used as an instrument of magnetic field analysis.

Development of a Model to Predict the Primary Infection Date of Bacterial Spot (Xanthomonas campestris pv. vesicatoria) on Hot Pepper.

A population model of bacterial spot caused by Xanthomonas campestris pv. vesicatoria on hot pepper was developed to predict the primary disease infection date. The model estimated the pathogen population on the surface and within the leaf of the host based on the wetness period and temperature. For successful infection, at least 5,000 cells/ml of the bacterial population were required. Also, wind and rain were necessary according to regression analyses of the monitored data. Bacterial spot on the model is initiated when the pathogen population exceeds 1015 cells/g within the leaf. The developed model was validated using 94 assessed samples from 2000 to 2007 obtained from monitored fields. Based on the validation study, the predicted initial infection dates varied based on the year rather than the location. Differences in initial infection dates between the model predictions and the monitored data in the field were minimal. For example, predicted infection dates for 7 locations were within the same month as the actual infection dates, 11 locations were within 1 month of the actual infection, and only 3 locations were more than 2 months apart from the actual infection. The predicted infection dates were mapped from 2009 to 2012; 2011 was the most severe year. Although the model was not sensitive enough to predict disease severity of less than 0.1% in the field, our model predicted bacterial spot severity of 1% or more. Therefore, this model can be applied in the field to determine when bacterial spot control is required.

Evaluating the effects of changing market parameters and policy implications in the German electricity market

In this paper the authors introduce a joint model for the electricity spot and the emission market in Germany. The model is used to simulate the effects of changing market parameters and policy implications. They propose a structural approach to connect fundamental factors, such as demand, capacity, fuel prices and emission allowances, to the price of electricity. Based on empirical bid behavior of electricity producers in day-ahead auctions they develop a novel CO2 emission rate model. In order to introduce a feedback of CO2 allowances to the actual emission of greenhouse gases, a forward-backward stochastic differential equation is used to deduce a partial differential equation to price emission allowances. The resulting equation will be solved by an alternating direction implicit finite difference scheme.

High-Tc micro and nano-constrictions modeling: hot spot approach for DC characteristics and HEB THz mixer performance

High-TC hot electron bolometers (HEB) are promising THz mixers due to their expected wide bandwidth, large mixing gain, and low intrinsic noise. We have simulated the characteristics of YBaCuO HEBs with a hot spot model usually dedicated to low-TC phonon cooled devices. With respect to e.g., NbN, the high-TC specificities are mainly arising from the large values of YBaCuO phonon thermal conductivity, and the film to MgO substrate phonon escape time. The consequent effects on the electron temperature profiles along the YBaCuO constriction and the current voltage DC characteristics are considered. The conversion gain G and noise temperature TN were computed for two constriction dimensions. For a 100 nm long × 100 nm wide × 10 nm thick constriction at 9 microwatt local oscillator (LO) power, the expected double sideband (DSB) TN = 1520 K (G = −13.7 dB). For a larger (but more realistic according to YBaCuO aging effects) 400 nm long × 400 nm wide × 35 nm thick constriction, minimum TN = 1210 K DSB at 35 microwatt LO power (G = −13.1 dB).

Analyses on the effect of hot spot density on material consumption rate

There is an observed effect of an explosive's constituent grain size and density on its performance. At the mesoscale, it is the outward burning of hot spots that controls observed performance. While statistical hot spot models can integrate the mesoscale behaviour to macroscale simulations, it is unknown what the density of created hot spots is as a function of grain size and porosity. Simulating mesoscale hot spot distributions and varying hot spot density, we discuss the resultant performance as influenced by inter-pore distance and pore distribution.

MOST detects corotating bright spots on the mid-O-type giant ξ Persei★†

We have used the MOST (Microvariability and Oscillations of STars) microsatellite to obtain four weeks of contiguous high-precision broad-band visual photometry of the O7.5III(n)((f)) star ξ Persei in 2011 November. This star is well known from previous work to show prominent DACs (discrete absorption components) on time-scales of about 2 d from UV spectroscopy and non-radial pulsation with one (l = 3) p-mode oscillation with a period of 3.5 h from optical spectroscopy. Our MOST-orbit (101.4 min) binned photometry fails to reveal any periodic light variations above the 0.1 mmag 3σ noise level for periods of a few hours, while several prominent Fourier peaks emerge at the 1 mmag level in the two-day period range. These longer period variations are unlikely due to pulsations, including gravity modes. From our simulations based upon a simple spot model, we deduce that we are seeing the photometric modulation of several corotating bright spots on the stellar surface. In our model, the starting times (random) and lifetimes (up to several rotations) vary from one spot to another yet all spots rotate at the same period of 4.18 d, the best-estimated rotation period of the star. This is the first convincing reported case of corotating bright spots on an O star, with important implications for drivers of the DACs (resulting from corotating interaction regions) with possible bright-spot generation via a breakout at the surface of a global magnetic field generated by a subsurface convection zone.

A Fuzzy Decision Making Trial and Evaluation Laboratory Analysis of SCM System Implementation

This study has two phases. The first phase constructs a comprehensi ve model of key success factors (KSFs) for supply chain network management implementation in the semiconductor industry based on both a literature review and an expert review. The model has four dimensions: strategy, process, organization, and technolog y (SPOT), and 15 KSFs. The SPOT model can be a checklist for future projects. The second phase analyzed the complicated interrelationship among KSFs with Fuzzy Decision Making Trial and Evaluation Laboratory and discussed its managerial implications. Lastly, we provide two case studies to confirm the importance of the two most important factors.

Futures pricing in electricity markets based on stable CARMA spot models

We present a new model for the electricity spot price dynamics, which is able to capture seasonality, low-frequency dynamics and extreme spikes in the market. Instead of the usual purely deterministic trend we introduce a non-stationary independent increment process for the low-frequency dynamics, and model the large fluctuations by a non-Gaussian stable CARMA process. The model allows for analytic futures prices, and we apply these to model and estimate the whole market consistently. Besides standard parameter estimation, an estimation procedure is suggested, where we fit the non-stationary trend using futures data with long time until delivery, and a robust L1-filter to find the states of the CARMA process. The procedure also involves the empirical and theoretical risk premia which – as a by-product – are also estimated. We apply this procedure to data from the German electricity exchange EEX, where we split the empirical analysis into base load and peak load prices. We find an overall negative risk premium for the base load futures contracts, except for contracts close to delivery, where a small positive risk premium is detected. Peak load contracts, on the other hand, show a clear positive risk premium, when they are close to delivery, while contracts in the longer end also have a negative premium.

Measuring stellar differential rotation with high-precision space-borne photometry

We introduce a method of measuring a lower limit to the amplitude of surface differential rotation from high-precision, evenly sampled photometric time series. It is applied to main-sequence late-type stars whose optical flux modulation is dominated by starspots. An autocorrelation of the time series was used to select stars that allow an accurate determination of starspot rotation periods. A simple two-spot model was applied together with a Bayesian information criterion to preliminarily select intervals of the time series showing evidence of differential rotation with starspots of almost constant area. Finally, the significance of the differential rotation detection and a measurement of its amplitude and uncertainty were obtained by an a posteriori Bayesian analysis based on a Monte Carlo Markov Chain approach. We applied our method to the Sun and eight other stars for which previous spot modelling had been performed to compare our results with previous ones. We find that autocorrelation is a simple method for selecting stars with a coherent rotational signal that is a prerequisite for successfully measuring differential rotation through spot modelling. For a proper Monte Carlo Markov Chain analysis, it is necessary to take the strong correlations among different parameters that exist in spot modelling into account. For the planet-hosting star Kepler-30, we derive a lower limit to the relative amplitude of the differential rotation of \Delta P / P = 0.0523 \pm 0.0016. We confirm that the Sun as a star in the optical passband is not suitable for measuring differential rotation owing to the rapid evolution of its photospheric active regions. In general, our method performs well in comparison to more sophisticated and time-consuming approaches.

Representation of Infinite-Dimensional Forward Price Models in Commodity Markets

We study the forward price dynamics in commodity markets realised as a process with values in a Hilbert space of absolutely continuous functions defined by Filipovic (Consistency problems for Heath–Jarrow–Morton interest rate models, 2001). The forward dynamics are defined as the mild solution of a certain stochastic partial differential equation driven by an infinite-dimensional Levy process. It is shown that the associated spot price dynamics can be expressed as a sum of Ornstein–Uhlenbeck processes, or more generally, as a sum of certain stationary processes. These results link the possibly infinite-dimensional forward dynamics to classical commodity spot models. We continue with a detailed analysis of multiplication and integral operators on the Hilbert spaces and show that Hilbert–Schmidt operators are essentially integral operators. The covariance operator of the Levy process driving the forward dynamics and the diffusion term can both be specified in terms of such operators, and we analyse in several examples the consequences on model dynamics and their probabilistic properties. Also, we represent the forward price for contracts delivering over a period in terms of an integral operator, a case being relevant for power and gas markets. In several examples, we reduce our general model to existing commodity spot and forward dynamics.

Convection, granulation, and period jitter in classical Cepheids

Analyses of recent observations of the sole classical Cepheid in the Kepler field, V1154 Cygni, found random changes of about 30 minutes in the pulsation period. These period changes challenge standard theories of pulsation and evolution because the period change is non-secular, and explaining this period jitter is necessary for understanding stellar evolution and the role of Cepheids as precise standard candles. We suggest that convection and convective hot spots can explain the observed period jitter. Convective hot spots alter the timing of flux maximum and minimum in the Cepheid light curve, hence change the measured pulsation period. We present a model of random hot spots that generate a localized flux excess that perturbs the Cepheid light curve and consequently the pulsation period which is consistent with the observed jitter. This result demonstrates how important understanding convection is for modeling Cepheid stellar structure and evolution, how convection determines the red edge of the instability strip, and just how sensitive Cepheid light curves are to atmospheric physics.