Kim Model Research Articles

Analysis of Critical Current Density in Bi2Sr2CaCu2O8+x Round Wire with Filament Fracture

Bi2Sr2CaCu2O8+x (Bi-2212) round wires have outstanding electromagnetic behaviors in a high magnetic field. However, the filaments’ fracture or gas bubble is difficult to avoid during the fabrication and application of Bi-2212 round wire, which would affect the critical current density seriously. In this paper, the engineering current density is studied based on Kim model for 7-bundle and 18-bundle wires with filament fracture by considering the effect of bridges between filaments. The distributions of critical current density of filaments are also investigated for different external fields. Finally, we present the relation between the number of cracked filaments and the applied strain.

Influence of Parameters on the Simulation of HTS Bulks Magnetized by Pulsed Field Magnetization

High-temperature superconducting (HTS) bulks can be magnetized to become powerful trapped field magnets (TFMs), which are promising for high-performance electrical applications. To magnetize such TFMs, pulsed field magnetization (PFM) is supposed to substitute field cooling (FC) to provide in situ magnetization. However, the heat generation during PFM, which reduces the trapped field, has always been an issue; thus, numerical simulation of the process is important to provide optimal magnetization strategies. In this paper, HTS bulks magnetized by PFM are simulated with an axisymmetric electromagnetic-thermal coupled model based on the H-formulation. Influences of important yet difficult-to-characterize parameters of HTS bulks, including n values in the E-J power law and B 0 in the Kim model, are investigated to show the influences of parameters on the modeling of HTS by PFM.

Cosmologically Safe QCD Axion without Fine-Tuning.

Although QCD axion models are widely studied as solutions to the strong CP problem, they generically confront severe fine-tuning problems to guarantee the anomalous Peccei-Quinn (PQ) symmetry. In this Letter, we propose a simple QCD axion model without any fine-tunings. We introduce an extra dimension and a pair of extra quarks living on two branes separately, which is also charged under a bulk Abelian gauge symmetry. We assume a monopole condensation on our brane at an intermediate scale, which implies that the extra quarks develop chiral symmetry breaking and the PQ symmetry is broken. In contrast to Kim's original model, our model explains the origin of the PQ symmetry thanks to the extra dimension and avoids the cosmological domain wall problem because of chiral symmetry breaking in Abelian gauge theory.

1.5 μm能见度激光雷达的波长修正模型比较

大气能见度在大气污染监测和保障航空、航海及陆上交通安全等方面具有重要作用。1.5 μm能见度激光雷达具有人眼允许最大曝光功率大,易于实现眼安全，可实现小型化和模块化等优点，适用于人员密集的场所。大气能见度定义为当550 nm准直激光经大气衰减到出射功率的2%或5%时所传输的大气距离，因此当采用1.5 μm激光时，需要进行波长修正。本文总结了现有的几种波长修正模型，并对它们之间的差异进行了分析。为了比较各种模型，研制了1.5 μm能见度激光雷达，并在2014年10月份于安徽合肥进行了连续24小时的能见度观测。通过与前向散射能见度仪进行比较，确认Kim模型与合肥实际情况最为吻合，平均相对误差小于7.8%。 Visibility has a great effect on air pollution monitoring and all kinds of traffic operations. 1.5 μm visibility lidar has many advantages, such as eye-safe, miniaturization and modularity. Therefore 1.5 μm visibility lidar is suitable for crowded places. Visibility is defined as the atmospheric dis-tance of transmission when 550 nm collimated laser’s output power attenuates to 2% or 5%. Thus, when using 1.5 μm visibility lidar, the wavelength correction must be done. Several models have been summarized in this work, and the differences of these models have been analyzed. To have a comparison of these models, a 1.5 μm visibility lidar has been constructed. And a 24-hour continuous visibility observation is carried out in Hefei, Anhui Province in October, 2014. By comparing the data of lidar with the forward visibility meter, the Kim model is confirmed as the most suitable model for visibility measurement in Hefei and the average relative error is less than 7.8%.

A choice of pure steam vertical in-tube condensation model for simulating a passive residual heat removal system

The steam generator secondary passive residual heat removal system (SGSPRHRS) is designed with three natural circulation loops. Its thermal-hydraulic characteristics are often simulated using the RELAP5 code. A test facility is simulated with the same size as one type of SGSPRHRS using RELAP5/MOD3.2 code and it is found that in some conditions, due to the limitation of the default pure steam vertical in-tube condensation model (PSVCM) in RELAP5/MOD3.2 code, the simulation results signify cantly under-estimate the experimental data of heat exchanger (HX) water level while over-estimate the experimental data of HX outlet condensed water temperature and ascending pipe (AP) steam volumetric flow rate. To find out the PSVCM simulating condensation heat transfer for this type of SGSPRHRS more accurately, the solutions of three PSVCMs (modified UCB, Oh and Lee models) for laminar conditions and two PSVCMs (Shah and Kim models) for turbulent conditions are presented in detail and six different PSVCMs are formed from the combinations of selected PSVCMs for laminar and turbulent conditions. The six different PSVCMs are implemented into the RELAP5/MOD3.2 code and simulations of the test facility are performed using the modified RELAP5/MOD3.2 codes. By the comparisons of simulation results with the experimental data, a PSVCM (Oh model for laminar conditions and Kim model for turbulent conditions) is favored due to its most accuracy of simulating condensation heat transfer for the test facility of this type of SGSPRHRS in the six different PSVCMs.

A stratified Tracy and Osahan's two-stage randomized response model

ABSTRACTThis paper proposes an alternative two-stage stratified randomized response model based on Tracy and Osahan (1999) model that has an optimal allocation and large gain in precision. It is also shown that the proposed model is more efficient than Kim and Warde (2004) and Kim and Elam (2005) stratified randomized response models under the conditions presented in both the cases of completely truthful reporting and that of not completely truthful reporting by the respondents. Numerical illustrations and graphs are also given in support of the present study.

Statistical analysis for HTS coil considering inhomogeneous Icdistribution of HTS tape

Abstract Critical current of high-temperature superconducting (HTS) coil is influenced by its own self magnetic field. Direction and density distribution of the magnetic field around the coil are fixed after the shape of the coil is decided. If the entire part of the HTS tape has homogeneous I c distribution characteristic, quench would be initiatedin fixed location on the coil. However, the actual HTS tape has in homogeneous I c distribution along the length. If the I c distribution of the HTS tape is known, we can expect the spot within the HTS coil that has the highest probability to initiate the quench. In this paper, I c distribution within the HTS coil under self-field effect is simulated by MATLAB. In the simulation procedure, I c distribution of the entire part of the HTS tape is assumed to follow Gaussian-distribution by central limit theorem. The HTS coil model is divided into several segments, and the critical current of each segment is calculated based on the-generalized Kim model. Single pancake model is simulated and self-field of HTS coil is calculated by Biot-Savart’s law. As a result of simulation, quench-initiating spot in the actual HTS coil can be predicted statistically. And that statistical analysis can help detect or protect the quench of the HTS coil.

The Role of Tourism Marketing in Crisis Management in Egypt

The purpose of this study is to analyze the marketing role of both the officials and private tourism marketing bodies during the crisis in the last period in Egypt. The study depended on semi-structured interviews with a purposeful sample of tourism marketing body’s officials and responsible to tourism marketing and managers in tourism companies. The study concluded that there is no crisis management department in the official and private tourism marketing bodies. Furthermore, the Internet is the only distribution means for tourism companies during the travel ban to Egypt. In addition, the reducing prices’ policy is considered wrong. Finally, media and public relation are considered the most important tourism promotional elements during crises. The presence of other reservations related to the nature of the list of competitiveness determinants has been observed especially (Qualitative) and the possibility of including it within the criteria for measuring the competitiveness in general, because of the importance of integrating the determinants of quantity and Qualitative in one frame (which was clearly evident in Dwyer & Kim model. It was found that the practical application of the models needs many complementary and composite actions, while there are a number of models of which the integrative (Dwyer & Kim), which is an integrated project to measure the competitiveness of the tourist destinations through the submission of a full list of competitiveness determinants applicable on the tourist destinations, prompting its usage as a tool to measure the Alexandrian tourist destination competitiveness.

A Strategic Vision for the Management of Tourist Destinations through maximizing the competitiveness (Application to the City of Alexandria)

The evolution of destination management could be considered as a result of the increased competition, which is reflected in the existence of an increasing interest in measuring the tourist destination competitiveness on the global level, therefore, many of the research studies appeared which have been translated in the form of international models for measuring destination competitiveness to be used by governments and administrative entities so as to maximize the value and impact of tourist destinations. Theories related to the competitiveness of the tourist destination have included three directions, the first theory is concerned with how to identify the competitiveness status of a certain tourist destination, the second focuses on certain aspects of the tourist destination competitiveness, and finally, the theory of providing a range of general models and theories for the study of tourist destination competitiveness. So it becomes necessary that the destination determines the nature of the products offered and their compatibility with the requirements of tourists, which requires the development of a strategic framework for its management in an integrated manner in order to effectuate the competitiveness advantages, targeting an optimal utilization of its resources. The presence of other reservations related to the nature of the list of competitiveness determinants has been observed especially (Qualitative) and the possibility of including it within the criteria for measuring the competitiveness in general, because of the importance of integrating the determinants of quantity and Qualitative in one frame (which was clearly evident in Dwyer & Kim model. It was found that the practical application of the models needs many complementary and composite actions, while there are a number of models of which the integrative (Dwyer & Kim), which is an integrated project to measure the competitiveness of the tourist destinations through the submission of a full list of competitiveness determinants applicable on the tourist destinations, prompting its usage as a tool to measure the Alexandrian tourist destination competitiveness.

Role of weights in improving the efficiency of Kim and Warde's mixed randomized response model

ABSTARCTIn this paper we have suggested a class of unbiased estimators of πS, the proportion of respondents possessing a sensitive attribute A using mixed randomized response model. The variance of the proposed class of estimators has been obtained. In addition to Kim and Warde's (2005) estimator, several other acceptable estimators of πS have been identified from the proposed class for suitable weights. It has been shown that the newly identified estimators are more efficient than the Kim and Warde's (2005) estimator. Numerical illustrations and graphs are also given in support of the present study.

Magnetization in a Finite Superconducting Hollow Cylinder in the Presence of the Radial and Azimuthal Transport Currents

The main aim of this study is to investigate the magnetization of a finite superconducting hollow cylinder in an axial applied magnetic field and in presence of different values of the radial and azimuthal transport currents in the framework of the three critical states models, namely, Bean, Kim, and exponential models. A set of self-consistency coupled-integral equations for the magnetization hysteresis loops have been solved by using Newton’s numerical method. Throughout the calculations, it has been assumed that the flux penetration starts from the inner lateral surface of the sample. A comparison has been made between the magnetic responses of the sample in applying the radial and azimuthal transport currents. It was found that when the transport current increases, the saturation value, enclosed area of the hysteresis loops, and the initial slopes in the virgin curve decreases. However, given that the flux penetration and demagnetizing effect did not affect by the azimuthal angle, the rate of the mentioned changes as the transport current is in azimuthal direction was slower than when that is in the radial direction. In addition, the radial transport current destroyed the azimuthal symmetry of the shielding current distribution and induced the nonuniform magnetic field in the finite sample. The obtained results have shown the importance of the magnetic field dependence of the critical current density on the magnetic response of the finite superconducting hollow cylinder.

Reanalysis of Uranus’ cloud scattering properties from IRTF/SpeX observations using a self-consistent scattering cloud retrieval scheme

We have developed a new retrieval approach to modelling near-infrared spectra of Uranus that represents a significant improvement over previous modelling methods. We reanalysed IRTF/SpeX observations of Uranus observed in 2009 covering the wavelength range 0.8–1.8μm and reported by Tice et al. (Tice, D.S., Irwin, P.G.J., Fletcher, L.N., Teanby, N.A., Hurley, J., Orton, G.S., Davis, G.R. [2013]. Icarus 223, 684–698). By retrieving the imaginary refractive index spectra of cloud particles we are able to consistently define the real part of the refractive index spectra, through a Kramers–Kronig analysis, and thus determine self-consistent extinction cross-section, single-scattering and phase-function spectra for the clouds and hazes in Uranus’ atmosphere. We tested two different cloud-modelling schemes used in conjunction with the temperature/methane profile of Baines et al. (Baines, K.H., Mickelson, M.E., Larson, L.E., Ferguson, D.W. [1995]. Icarus 114, 328–340), a reanalysis of the Voyager-2 radio-occultation observations performed by Sromovsky, Fry and Kim (Sromovsky, L.A., Fry, P.M., Kim, J.H. [2011]. Icarus 215, 292–312), and a recent determination from Spitzer (Orton, G.S., Fletcher, L.N., Moses, J.I., Mainzer, A.K., Hines, D., Hammel, H.B., Martin-Torres, F.J., Burgdorf, M., Merlet, C., Line, M.R. [2014]. Icarus 243, 494–513). We find that both cloud-modelling schemes represent the observed centre-of-disc spectrum of Uranus well, and both require similar cloud scattering properties of the main cloud residing at ∼2bars. However, a modified version of the Sromovsky, Fry and Kim (2011) model, with revised spectral properties of the lowest cloud layer, fits slightly better at shorter wavelengths and is more consistent with the expected vertical position of Uranus’ methane cloud.We find that the bulk of the reflected radiance from Uranus arises from a thick cloud at approximately the 2bar level, composed of particles that are significantly more absorbing at wavelengths λ>1.0μm than they are at shorter wavelengths λ<1.0μm. This spectral information provides a possible constraint on the identity of the main particle type, although we find that the scattering properties required are not consistent with any of the available laboratory data for pure NH3, NH4SH, or CH4 ice (all suspected of condensing in the upper troposphere). It is possible that the observed clouds are mixtures of tropospheric condensate mixed with photochemical products diffusing down from above, which masks their pure scattering features. Because there is no available laboratory data for pure H2S or PH3 ice (both of which might be present as well), they cannot be excluded as the cloud-forming species. We note, however, that their absorptive properties would have to be two orders of magnitude greater than the other measured ices at wavelengths greater than 1μm to be consistent with our retrieval, which suggests that mixing with photochemical products may still be important.

Comments on information erasure in black hole

We analyze the Kim, Lee and Lee model of information erasure by black holes and find contradictions with standard physical laws. We demonstrate that the erasure model leads to arbitrarily fast information erasure; the proposed physical interpretation of information freezing at the event horizon as observed by an asymptotic observer is problematic; and information erasure, whatever the process may be, near the black hole horizon leads to contradictions with quantum mechanics if Landauer's principle is assumed. The later part of the work demonstrates the significance of the "erasure entropy". We show that the erasure entropy is the mutual information between two subsystems.

Two-stage stratified partial randomized response strategies

This article proposes two – stage stratified partial randomized response models based on Tracy and Osahan (1995) model and have large gain in precision. It is also shown that the proposed models are more efficient than Kim and Warde (2004) and Kim and Elam (2005) stratified randomized response models under the conditions presented in the case of completely truthful reporting and less than completely truthful reporting by the respondents. Numerical illustrations and graphs are also given in support of the present study.

Identification of DSGE Models - The Effect of Higher-Order Approximation and Pruning

Several formal methods have been proposed to check local identification in linearized DSGE models using rank criteria. Recently there has been huge progress in the estimation of non-linear DSGE models, yet formal identification criteria are missing. The contribution of the paper is threefold: First, we extend the existent methods to higher-order approximations and establish rank criteria for local identification given the pruned state-space representation. It is shown that this may improve overall identification of a DSGE model via imposing additional restrictions on the moments and spectrum. Second, we derive analytical derivatives of the reduced-form matrices, unconditional moments and spectral density for the pruned state-space system. Third, using a second-order approximation, we are able to identify previously non-identifiable parameters: namely the parameters governing the investment adjustment costs in the Kim (2003) model and all parameters in the An and Schorfheide (2007) model, including the coefficients of the Taylor-rule.

Numerical Study of the Influence of Material Properties on Pulsed-Field Magnetization for HTS Bulk Magnets

To optimize pulse field magnetization processes for high-temperature superconducting (HTS) bulk magnets, it is important to control the magnetic field amplitude and the driving temperature. Many publications have reported on the experimental and numerical results of the pulsed-field magnetization method. In the numerical method, the HTS bulk properties are modeled to simplify the calculations, examples being the Bean model and the Kim model, etc. During pulsed-field magnetization the critical current density in the HTS bulk changes dramatically due to the magnetic field and temperature rise induced by the ac losses. For these reasons these properties are key to the analysis of the pulsed-field magnetization process, which is calculated using the measured practical HTS bulk properties, and these results show different temperature rise and trapped magnetic field characteristics. We assumed that HTS bulk has intrinsic deterioration in practice. Therefore, we recalculated using the adjusted parameters, and these analytic results correspond with the experimental results.

Analysis of critical current reduction in self-field in stacked twisted 2G HTS tapes

Twisted stacked-tape cable (TSTC) is one of the methods to produce flexible current carrying elements (CCE) with high current density made of 2G coated conductors. The critical current of CCE in self-field is less than the sum of critical currents of all tapes used to make CCE. This critical current reduction is attributed to self-field influence of critical currents of tapes. To describe the current reduction accurately in TSTC it is necessary to take into account current and field distribution in a stack cross-section using dependencies of critical current on magnetic field for each tape. In other words one has to make self-consistent calculations of current and magnetic field distribution in a stack. In this paper we present the self-consistent analysis of magnetic field and current distribution in TSTC with different number of tapes using the generalized Kim model. We also measured current degradation in TSTC made of from two to ten 2G tapes and compared it with calculations. We found good coincidence of calculated and measured current degradation that confirm the validity of our approach.

The modelling of an SF6 arc in a supersonic nozzle: I. Cold flow features and dc arc characteristics

The cold flow and the arc, under direct currents burning in the nozzle of the arcing device used in Benenson (1980 Final Report General Electric Co. (Schenectady, NY) Project 246–2) with fixed stagnation pressure, have been investigated computationally using five flow models; the laminar flow model, the Prandtl mixing length model, the standard k-epsilon model and its two variants, the Chen–Kim model and the renormalization group model. For the cold flow, the computational results are almost the same for the different flow models apart from in the regions close to the two electrodes. There is a bow shock in front of the downstream hollow electrode and a wake near the tip of the upstream electrode. The size of the wake and the strength and the structure of the shock differ greatly amongst the flow models. With a dc arc in the nozzle, derived voltage–current characteristics are negative for currents of less than 600 A but for higher currents the arc voltage is nearly constant.

A STRATIFIED MANGAT AND SINGH'S OPTIONAL RANDOMIZED RESPONSE MODEL USING PROPORTIONAL AND OPTIMAL ALLOCATION

This paper suggests a stratified optional randomized response model based on Mangat and Singh (1994) model that has proportional and optimal allocation and larger gain in efficiency. Numerically it is found that the suggested model is more efficient than Kim and Warde (2004) stratified randomized response model and Mangat and Singh (1994) model. Graphical representations are also given in support of the present study.

Flux-Pinning-Induced Stress Behaviors in a Long Rectangular Superconducting Slab With a Central Rectangular Hole

In this paper, the rectangular hole problem is investigated for a long high-temperature superconducting slab under electromagnetic forces. The effects of rectangular hole on the magnetic flux density distribution in the slab are considered in either the Bean model or the Kim critical state model in the case of the descending field both for the zero-field cooling (ZFC) and the field cooling (FC) magnetization processes. Based on the finite element method, both the corresponding stress concentration factors near the corners and the distributions of nonzero principle stress along the hole edge are numerically calculated and discussed. Numerical results obtained show that the ZFC activation process has more significant influence on the stress concentration factors than the FC activation process. For every activation process, the peak values of stress concentration factors in the Bean model are larger than the corresponding ones in the Kim model. In addition, in the Kim model, the peak values of stress concentration factors generally decrease with the increasing of the introduced dimensionless parameter p. Additionally, the stress concentration factors usually increase with the increasing of the ratio of length and width of the hole. The present study should be helpful to the design and application of high-temperature superconductors.