Prediction of surface potential temperature over complex terrain     

H. N. Lee  W. S. Kau 《Boundary-Layer Meteorology》1984,28(1-2):79-87

Based on a statistical approach, the surface potential temperature at seven observing stations in complex terrain has been examined. It is shown that the surface potential temperature depends primarily on the rate of change of slope wind and on the geostrophic-level potential temperature.  相似文献   

Neutron and electromagnetic emissions during the 1990 May 24 solar flare     

L. G. Kocharov  Jeongwoo W. Lee  H. Zirin  G. A. Kovaltsov  I. G. Usoskin  K. R. Pyle  M. A. Shea  D. F. Smart 《Solar physics》1994,155(1):149-170

In this paper, we are primarily concerned with the solar neutron emission during the 1990 May 24 flare, utilizing the counting rate of the Climax neutron monitor and the time profiles of hard X-rays and γ-rays obtained with the GRANAT satellite (Pelaezet al., 1992; Talonet al., 1993; Terekhovet al., 1993). We compare the derived neutron injection function with macroscopic parameters of the flare region as obtained from theHα and microwave observations made at the Big Bear Solar Observatory and the Owens Valley Radio Observatory, respectively. Our results are summarized as follows: (1) to explain the neutron monitor counting rate and 57.5–110 MeV and 2.2 MeV γ-ray time profiles, we consider a two-component neutron injection function,Q(E, t), with the form $$Q(E,t) = N_f {\text{ exp[}} - E/E_f - t/T_f ] + N_s {\text{ exp[}} - E/E_s - t/T_s ],$$ whereN _f(s),E _f(s), andT _f(s) denote number, energy, and decay time of the fast (slow) injection component, respectively. By comparing the calculated neutron counting rate with the observations from the Climax neutron monitor we derive the best-fit parameters asT _f ≈ 20 s,E _f ≈ 310 MeV,T _s ≈ 260 s,E _s ≈ 80 MeV, andN _f (E > 100 MeV)/N _s (E > 100 MeV) ≈ 0.2. (2) From the Hα observations, we find a relatively small loop of length ≈ 2 × 10⁴ km, which may be regarded as the source for the fast-decaying component of γ-rays (57.5–110 MeV) and for the fast component of neutron emission. From microwave visibility and the microwave total power spectrum we postulate the presence of a rather big loop (≈ 2 × 10⁵ km), which we regard as being responsible for the slow-decaying component of the high-energy emission. We show how the neutron and γ-ray emission data can be explained in terms of the macroscopic parameters derived from the Hα and microwave observations. (3) The Hα observations also reveal the presence of a fast mode MHD shock (the Moreton wave) which precedes the microwave peak by 20–30 s and the peak of γ-ray intensity by 40–50 s. From this relative timing and the single-pulsed time profiles of both radiations, we can attribute the whole event as due to a prompt acceleration of both electrons and protons by the shock and subsequent deceleration of the trapped particles while they propagate inside the magnetic loops.  相似文献   

Influence of rainfall-induced wetting on the stability of slopes in weathered soils   总被引：13，自引：0，他引：13  

Jaehong Kim  Sangseom Jeong  Seongwan Park  Jitendra Sharma 《Engineering Geology》2004,75(3-4):251-262

Shallow failures of slopes in weathered soil are caused by infiltration due to prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in matric suction induced by the water infiltration. This paper reports trends of rainfall-induced wetting band depth in two types of weathered soils that are commonly found in Korea. Both theoretical and numerical analyses for wetting band depth are presented based on the soil–water characteristic curve obtained using filter paper as well as tensiometer tests. It is found that the magnitude of wetting front suction plays a key role in the stability of slopes in weathered soils. Theoretical analysis based on modified Green and Ampt model tends to underestimate the wetting band depth for typical Korean weathered soils. It was also deduced that for Korean weathered soils, the factor of safety drops rapidly once the wetting band depth of 1.2 m reached.  相似文献   

Geostatistical integration of MT and borehole data for RMR evaluation     

Seokhoon Oh  Hojoon Chung  Duk Kee Lee 《Environmental Geology》2004,46(8):1070-1078

The geostatistical approach was applied to integrate MT (Magneto-telluric) resistivity data and borehole information for the spatial RMR (Rock Mass Rating) evaluation. Generally, resistivity of the subsurface is believed to be positively related to the RMR, thus the resistivity and borehole RMR information was combined in a geostatistical approach. To relate the two different sets of data, the MT resistivity data were used as secondary information and the RMR mean values were estimated at unsampled points by identification of the resistivity to the borehole data. Two types of approach are performed for the estimation of RMR mean values. Then the residuals of the RMR values around the borehole sites are geostatistically modeled to infer the spatial structure of difference between real RMR values and estimated mean values. Finally, this geostatistical estimation is added to the previous means. The result applied to a real situation shows prominent improvements to reflect the subsurface structure and spatial resolution of RMR information.  相似文献   

Capacity evaluation of statnamic tested long piles     

San-Shyan Lin  J. L. Hong  Wei F. Lee  Y. H. Chang 《Soil Dynamics and Earthquake Engineering》2004,24(11):829-838

A procedure that uses the structural damping (SD) concept for estimating the capacity of a pile based on the Statnamic (STN) pile load test results, formerly used by the authors for short piles, is extended in this paper for the STN tested long piles. Similar to segmental unloading point method procedures for long piles, the shaft length is divided into several segments and each segment is assumed to behave as a mass of a single degree of freedom. The SD concept is then applied to each segment to consider the displacement related soil damping instead of the velocity dependent damping. Instrumented strain gauge data at different levels of the shaft are required for the interpretation method. Three case studies are presented in this paper to study the validity and applicability of the present method. The predicted results are also compared to the available test or analytical data.  相似文献   

Principal axes of M-DOF structures Part Ⅱ: Dynamic loading     

Zach Liang  George C.Lee 《地震工程与工程振动(英文版)》2003,2(1)

This paper is the second in a two-part series that discusses the principal axes of M-DOF structures subjected to static and dynamic loads. The primary purpose of this series is to understand the magnitude of the dynamic response of structures to enable better design of structures and response modification devices/systems. Under idealized design conditions, the structural responses are obtained by using single direction input ground motions in the direction of the intended response modification devices/systems, and by assuming that the responses of the structure is decoupleable in three mutually perpendicular directions. This standard practice has been applied to both new and retrofitted structures using various seismic protective systems. Very limited information is available on the effects of neglecting the impact of directional couplings (cross effects of which torsion is a component) of the dynamic response of structures. In order to quantify such effects, it is necessary to examine the principal axes of structures under both static and dynamic loading. In this two-part series, the first paper is concerned with static loading, which provides definitions and fundamental formulations, with the conclusion that cross effects of a statically loaded M-DOF structure resulting from the lack of principal axes are of insignificant magnitude. However, under dynamic or earthquake loading, a relatively small amount of energy transferred across perpendicular directions is accumulated, which may result in significant enlargement of the structural response. This paper deals with a formulation to define the principal axes of M-DOF structures under dynamic loading and develops quantitative measures to identify cross effects resulting from the non-existence of principal axes.  相似文献   

Radiaxial fibrous calcites as low-magnesian calcite cement precipitated in a marine-meteoric mixing zone   总被引：1，自引：0，他引：1  

Yongin Kim  Yong Il Lee 《Sedimentology》2003,50(4):731-742

Abstract Radiaxial fibrous calcite (RFC) has previously been interpreted as a marine or replacive cement. Study of the Dongjeom Formation (Early Ordovician), Korea, shows that RFC can form in marine‐meteoric mixing zones as a low‐magnesian calcite (LMC) cement. RFC in the shallow‐marine Dongjeom Formation occurs in arenaceous limestones at the top of a transgressive facies overlying a regressive facies. It shows well‐developed growth zonation, and lighter oxygen isotope values and more radiogenic strontium isotope ratios than those of Early Ordovician marine calcite. Such petrographic and chemical evidence indicates that the RFC was precipitated as a primary LMC cement in a marine and meteoric mixing zone. Owing to the unique environment of formation, the Dongjeom RFC is characterized by growth zonal fabric comprising alternating subzones, which may indicate precipitation from varying fluids. In addition, this study documents the importance of substrate for development of RFC. Early ‘nucleation’ for RFC occurred mainly on microcrystalline skeletal grains and internal sediments, whereas on homogeneously altered substrates, thin‐coated banding structure developed, ultimately forming coarse crystalline spar. This suggests that microcrystalline substrates are preferred sites for nucleation of RFC.  相似文献   

Ground-penetrating radar investigation of active faults along the Dead Sea Transform and implications for seismic hazards within the city of Aqaba, Jordan   总被引：1，自引：0，他引：1  

Lee Slater  Tina M. Niemi   《Tectonophysics》2003,368(1-4):33

Ground-penetrating radar (GPR) was used in an effort to locate a major active fault that traverses Aqaba City, Jordan. Measurements over an exposed (trenched) cross fault outside of the city identify a radar signature consisting of linear events and horizontal offset/flexured reflectors both showing a geometric correlation with two known faults at a control site. The asymmetric linear events are consistent with dipping planar reflectors matching the known direction of dip of the faults. However, other observations regarding this radar signature render the mechanism generating these events more complex and uncertain.GPR measurements in Aqaba City were limited to vacant lots. Seven GPR profiles were conducted approximately perpendicular to the assumed strike of the fault zone, based on regional geological evidence. A radar response very similar to that obtained over the cross fault was observed on five of the profiles in Aqaba City, although the response is weaker than that obtained at the control site. The positions of the identified responses form a near straight line with a strike of 45°. Although subsurface verification of the fault by trenching within the city is needed, the geophysical evidence for fault zone location is strong. The location of the interpreted fault zone relative to emergency services, military bases, commercial properties, and residential areas is defined to within a few meters. This study has significant implications for seismic hazard analysis in this tectonically active and heavily populated region.  相似文献   

Interaction between groundwater quality and hydraulic head in an area around an underground LPG storage cavern,Korea     

Jeongho Lee  Rak-Hyun Kim  Ho-Wan Chang 《Environmental Geology》2003,43(8):901-912

The interactive influence between groundwater flow and salinization that occurs in an underground LPG cavern site in Korea was investigated using chemical analysis data and cross-correlation analysis between hydraulic head and operating pressure data. The concentration of the major cations and anions showed a large difference between rainy and dry seasons due to the seasonal intrusion of highly saline water into the cavern area. However, the Cl/Br ratio and '¹⁸O-Cl relationship showed that two types of saline water (seawater and halite-dissolved solution) influenced the groundwater salinization of the study area. The cross-correlation results revealed that a positive relationship between hydraulic head and cavern operating pressure was far more conspicuous in the propane cavern area (89-91% of correlation coefficients), and tidal change influenced the head variation in the butane cavern area. That is, continuous intrusion of seawater near the South Sea could bring about a high concentration of major cations and anions in the butane seepage waters and groundwaters near the coastal area, and seasonal variation in the operating pressure at the propane cavern played an important driving force in fast infiltration of halite-dissolved solution from surface halite stock and a subsequent increase in Na and Cl concentration during the dry season.  相似文献   

孔隙水压力对岩石裂纹扩展影响的数值模拟   总被引：1，自引：0，他引：1  

唐春安  杨天鸿  李连崇  梁正召  ThamL.G.  LeeK.K.  TsuiY. 《岩土力学》2003,(Z2)

应用岩石破坏过程渗流-应力-损伤(FSD)耦合分析软件F-RFPA2D,通过对孔隙水压作用下岩石试件加载破坏过程的数值模拟,对孔隙水压力大小和梯度对岩石试样中裂纹的萌生和扩展进行了数值模拟研究。模拟结果再现了孔隙水压力作用下裂纹萌生扩展的全过程,表明孔隙水压力大小和梯度对岩石中裂纹的萌生和扩展模式都有很大的影响。  相似文献