Lateral bearing performance and mechanism of piles in the transition zone due to pit-in-pit excavation

Acta Geotechnica - Excavation types of foundation pits for large-scale or special-purpose urban construction have been more and more complex, and the environmental safety issues caused by pit...     

Numerical simulation and evaluation of Asian dust events observed in Mongolia in spring 2011

The Asian dust forecasting model, Mongolian Asian Dust Aerosol Model (MGLADAM), has been operated by the National Agency for Meteorology and Environmental Monitoring of Mongolia since 2010, for the forecast of Asian dust storms. In order to evaluate the performance of the dust prediction model, we simulated Asian dust events for the period of spring 2011. Simulated features were compared with observations from two sites in the dust source region of the Gobi desert in Mongolia, and in the downstream region in Korea. It was found that the simulated wind speed and friction velocity showed a good correlation with observations at the Erdene site (one of the sites in the Gobi desert). The results show that the model is proficient in the simulation of dust concentrations that are within the same order of magnitude and have similar start and end times, compared with PM₁₀ observed at two monitoring sites in the Gobi regions. Root Mean Square Error (RMSE) of the dust simulation ranges up to 200 μg m^?3 because of the high concentrations in source regions, which is three times higher than that in the downstream region. However, the spatial pattern of dust concentration matches well with dust reports from synoptic observation. In the downwind regions, it was found that the model simluated all reported dust cases successfully. It was also found that the RMSE in the downwind region increased when the model integration time increased, but that in the source regions did not show consistent change. It suggests that MGLADAM has the potential to be used as an operational dust forecasting model for predicting major dust events over the dust source regions as well as predicting transported dust concentrations over the downstream region. However, it is thought that further improvement in the emission estimation is necessary, including accurate predictions in surface and boundary layer meteorology. In the downwind regions, background PM₁₀ concentration is considerably affected by other aerosol species, suggesting that a consideration of anthropogenic pollutants will be required for accurate dust forecasting.     

Propagation of SH-waves in a layered medium

Summary. A set of recurrence relations similar to that of Kennett suitable for SH -wave generation in an ( n + l)-layered half-space is presented. The recurrence relations contain no growing terms, thus providing a stable and efficient algorithm for computing complete SH synthetic seismograms. The complete expansion of these recurrence relations gives the explicit form of the transfer function for SH -waves. The transfer function for a point source in layer s of the stratification is a series of 2 ⁿ terms in the denominator and a series of 2 ^{n−s +1} terms in the numerator. The result of Wang from ray summation is shown to be a special case of our general result. Numerical comparison of the algorithm of this paper with the propagator matrix method is also made.     

Three-dimensional subsatellite motion under air drag and oblateness perturbations

The three-dimensional relative motion of a subsatellite with respect to a reference station in an elliptical orbit is studied. A general theory based on the variation of the relative elements, i.e. the instantaneous differences between the orbital parameters of the subsatellite and those of the station, is formulated in order to incorporate arbitrary perturbing forces acting on both satellites. The loss of precision inherent in the subtraction of almost identical quantities is avoided by the consistent use of difference variables. In the absence of perturbations exact analytical representations can be obtained for the relative state parameters. The influences of air drag and Earth's oblateness on the relative motion trajectories are investigated and illustrated graphically for a number of cases.     

Detection of PAHs in seawater using surface-enhanced Raman scattering (SERS)

The laboratory characterization of a field-operable surface-enhanced Raman scattering sensor (SERS optode) is presented for the detection of aromatic hydrocarbons in seawater. The sensor has been developed for deployment with a robust underwater spectrograph. To meet the demands of the harsh seawater application, sol-gel derived SERS substrates were used. The calibration curves of six PAHs were determined to be of Langmuir adsorption isotherm type with limits of detection ranging from the microg l(-1) to ng l(-1) level. The experimentally determined adsorption constants varied strongly with the molecular weight of the analytes and correlated with their solubility. A mixture of five PAHs dissolved in seawater was investigated to demonstrate the utility of this method for screening. Emphasis was put on the interference from suspended particulate matter (SPM). The Raman measurement with backscattering configuration was shown to be immune against turbidities up to 1000 NTU. The physico-chemical interference arising from adsorption by the sediment was measured on-line by adding sediment to a PAH-spiked solution. According to the calibration curve, the PAH concentration decrease corresponded to more than 98% of the analyte being scavenged by the sediment.     

Climate change effects on tropical night days in Seoul, Korea

In Seoul (37.57°N, 126.97°E), South Korea (located at mid-latitudes), the frequency of tropical night (TN) days, which have been defined as days with a minimum temperature greater than 25°C, have shown an increase due to the effects of temperature and water vapor. It was found that TN days accounted for almost 10.2% (July) and 22.1% (August) of the total number of days in respective months during the last decade in Seoul, and these figures may be increasing with climatic change. The daytime and nighttime sky on TN days can contain water vapor when the monsoonal southwesterly flow prevails. This strong wind may induce moisture advection from the warm ocean, and consequently, there is much larger specific humidity over the city during TN days in comparison to non-TN days. The effect of climatic change on the specific humidity is related to an increase in the number of TN days, which has shown an upward trend of 13-day/100-year and is significantly modulated by both water vapor and air temperature during July and August. Moreover, the relative role of water vapor in increasing the frequency of TN days has become much more significant after the 1960s in comparison to that of air temperature, which may be attributed to urbanization in Seoul since the 1960s.     

A site evaluation campaign for a ground based atmospheric Cherenkov telescope in Romania

Around the world, several scientific projects share the interest of a global network of small Cherenkov telescopes for monitoring observations of the brightest blazars??the DWARF network. A small, ground based, imaging atmospheric Cherenkov telescope of last generation is intended to be installed and operated in Romania as a component of the DWARF network. To prepare the construction of the observatory, two support projects have been initiated. Within the framework of these projects, we have assessed a number of possible sites where to settle the observatory. In this paper we submit a brief report on the general characteristics of the best four sites selected after the local infrastructure, the nearby facilities and the social impact criteria have been applied.     

天门山震旦/寒武系界线上地外撞击事件痕迹

从湘西北天门山震旦—寒武系界线上发现的冲击砾裂、冲击角砾、冲击岩脉、微球粒撞击玻粒(microirghi-zites)、微球粒玻璃陨石(microtektites),特别是陨石碎屑残迹现象,可能表明:在震旦—寒武系界线上曾经发生过地外撞击的事件。     

地表的分形测量及其大地构造学意义

以湖北红安地区为例,采用投影覆盖法(projectivecoveringmethod)对地表进行了二维分形测量,结果表明,地表面积具有双分形(bifractal)关系,即具有小尺度的结构分形(texturalfractal)和大尺度的构造分形(structuralfractal),分叉点(breakpoint)的尺度为3610m,分维值都在2～3之间且结构分维值大于其构造分维值。可见,地表形态具有分形性质,分维值可以指示地表形态的复杂程度。构造分维值可作为构造活动强度的一个指标,可为大地构造单元的划分提供定量依据。复杂地表形态主要是由构造活动(内营力作用)和各种复杂表生地质作用(外营力作用)引起的,前者主要控制大尺度的地形起伏,后者则塑造小尺度的地表形态。地表分维值可以指示地表的发育成熟度,该地区小尺度的结构分维值大于大尺度的构造分维值表明其处于地表形态的发育晚期。此外,地表的分形尺度可以来用确定构造活动尺度,从而指导构造地质与找矿勘探研究。