A Measure of Magnetic Field Discontinuity     

Moon  Y.-J.  Yun  H.S.  Lee  S.W.  Kim  J.-H.  Choe  G.S.  Park  Y.D.  Ai  G.  Zhang  H.Q.  Fang  C. 《Solar physics》1999,184(2):323-338

In this paper we introduce a measure of magnetic field discontinuity, MAD, defined as Maximum Angular Difference between two adjacent magnetic field vectors. To examine the characteristics of the MAD, we have considered several active region models having a quadrupolar field configuration and computed MADs over these active regions by approximating the 3-D magnetic fields as an ensemble of charge potential fields or linear force-free fields. The computed MAD fields are studied in comparison with other flare activity indicators such as separators. It is found that (1) the region of high level MAD corresponds well with the separator, or practically the intersection of the separator with the plane of measurement, (2) it singles out local discontinuities of magnetic fields, and (3) the MAD can also be a measure of the evolutionary status of an active region.An observational test has been made for 2-D MADs, using the Yohkoh SXT observation of a flare in AR 6919 and the vector magnetogram taken at the Mees Solar Observatory during this flare activity. The high level contours of 2-D MAD are found to trace well the observed soft X-ray bright points, which indicates that the MAD could serve as a good flare activity indicator.  相似文献   

An additional application of the Space Interferometry Mission to gravitational microlensing experiments     

Cheongho Han  Tu-Whan Kim 《Monthly notices of the Royal Astronomical Society》1999,305(4):795-801

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Probabilistic corrosion rate estimation model for longitudinal strength members of bulk carriers     

Jeom Kee Paik  Sung Kyu Kim  Sang Kon Lee 《Ocean Engineering》1998,25(10):837-860

Many bulk carrier losses have been reported of late, and one of the possible causes of such casualties is thought to be the structural failure of aging hulls in rough weather. Clearly, in such cases, vessels that start out being adequate somehow become marginal later in life. Fatigue and corrosion-related potential problems may be the most important factors affecting such age related vessel damage. With respect to fatigue, extensive studies have been done worldwide both experimentally and theoretically, and the results have been applied to some extent. However, in the case of corrosion effects, additional research is still needed to better understand, clarify and address the various strength uncertainties and their effects on structural behaviour. This paper develops a probabilistic corrosion rate estimation model for the longitudinal strength members of bulk carriers. The model is based on available statistical data for corrosion of existing bulk carriers. The corrosion data collected are documented for future use.  相似文献   

3‐D hydrodynamic simulations of the solar chromosphere     

S. Wedemeyer  B. Freytag  M. Steffen  H.‐G. Ludwig  H. Holweger 《Astronomische Nachrichten》2003,324(4):410-411

We present first results of three‐dimensional numerical simulations of the non‐magnetic solar chromosphere, computed with the radiation hydrodynamics code CO⁵BOLD. Acoustic waves which are excited at the top of the convection zone propagate upwards into the chromosphere where the waves steepen into shocks. The interaction of the waves leads to the formation of complex structures which evolve on short time scales. Consequently, the model chromosphere is highly dynamical, inhomogeneous, and thermally bifurcated.  相似文献   

A mass ratio limit for primordial black holes     

P. Brosche  F.‐Th. Lentes  L. J. Tassie 《Astronomische Nachrichten》2003,324(6):556-559

We augment our scenario for the formation of astronomical objects from macroscopic superstrings by the assumption that the central matter keeps its identity in the fragmentation. From the condition that the angular momentum per mass squared of this matter should be less than the Kerr limit G/c, we obtain upper limits for the ratio of the mass of central black holes M(BH) to the mass M of the host object. This limit is M(BH)/M ≈ 0.001, and, expressed in observed quantities, approximately M(BH)/M ≈ σ²/(v · c) where σ is the r.m.s. velocity, v the rotational velocity and c the velocity of light. The valuesM(BH) agree with the observed behaviour both in order of magnitude and in the variation with velocity dispersion. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The impact of incorrectly estimating factor productivity in agriculture on the environment and human health   总被引：3，自引：0，他引：3  

C. S. Kim  C. Sandretto  N. D. Uri 《Environmental Geology》1999,37(1-2):47-53

 This paper explores the implications of a misspecification of the production function on the use of factor inputs in the context of the adoption of an alternative production practice (a technological innovation) designed to mitigate the impact of agricultural production on human health and the environment. It is demonstrated that if the level of the use of some inputs is considered rather than their consumptive use (i.e., the actual amount used by a plant), the productivity of the input is inaccurately measured. It is also demonstrated that an aggregate production function approach can lead to overestimation of the value of the marginal product of an input due to the frequently implicit assumptions that the output supply, output demand, and fertilizer demand are infinitely price elastic. The implications of the results are important for determining the optimal use of inputs such as fertilizer and pesticides which have known adverse impacts on the environment and human health. Received: 22 November 1996 · Accepted: 4 May 1998  相似文献   

Identification of the Hualien soil-structure interaction system     

C. -B. Yun  J. -S. Choi  J. -M. Kim 《Soil Dynamics and Earthquake Engineering》1999,18(6):689

This article demonstrates how system identification techniques can be successfully applied to a soil-structure interaction system in conjunction with the results of the forced vibration tests on the Hualien large-scale seismic test structure which was recently built in Taiwan for an international joint research. The parameters identified are the shear moduli of several near-field soil regions as well as Young's moduli of the shell sections of the structure. The soil-structure interaction system is represented by the finite element method combined with infinite element formulation for the unbounded layered soil medium. Preliminary investigations are carried out on the results of the static stress analysis for the soil medium and the results of the in-situ tests to divide the soil-structure system into several regions with homogeneous properties and to determine the lower and upper bounds of the parameters for the purpose of identification. Then two sets of parameters are identified for two principal directions based on the forced vibration test data by minimizing the estimation error using the constrained steepest descent method. The simulated responses for the forced vibration tests using the identified parameters show excellent agreement with the test data. The present estimated parameters are also found to be well compared with the average value of those by other researchers in the joint project.  相似文献   

Morphology and kinematics in thick box‐peanut bulge galaxies     

D. Vergani  R.‐J. Dettmar 《Astronomische Nachrichten》2004,325(2):96-99

Both, observational and theoretical results support the close connection between bars and box/peanut‐shaped bulges in spiral galaxies. However, for the sub‐class of thick box/peanut‐shaped bulges, an environmental process instead of an internal mechanism is suggested to account for the prominence of the box/peanut component. In this paper a multiwavelength study of the morphology and the kinematics of a sample of thick box/peanut‐shaped bulges is presented. The results suggest a scenario in which interaction events play a significant role in the history of thick box/peanut‐shaped bulge galaxies. Most likely these sources have experienced a mass infall. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The Euro3D data format: A common FITS data format for integral field spectrographs     

M. Kissler‐Patig  Y. Copin  P. Ferruit  A. Pcontal‐Rousset  M.M. Roth 《Astronomische Nachrichten》2004,325(2):159-162

As integral field spectrographs have become more common around the world and in Europe in particular, the need for a common data format has been recognized. Here, we present the Euro3D format that is adapted as a post‐instrumentalsignature‐removal format for all instruments within the Euro3D network. It follows the FITS standard, and includes several extensions, all of them being binary FITS tables. This article is intended to give a comprehensive overview, but does not attempt to serve as a full definition document. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Assessment of the potential for groundwater contamination using the DRASTIC/EGIS technique, Cheongju area, South Korea     

Youn Jong Kim  Se-Yeong Hamm 《Hydrogeology Journal》1999,7(2):227-235

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