Social change and fresh-food marketing in Singapore     

Lim Keak Cheng 《GeoJournal》1990,20(3):301-310

Since the turn of the 1980s, accelerated social change and government planning have resulted in changes in the patterns of food consumption, marketing behaviour, fresh food supplies and their distributing systems in singapore. Continued growing affluence, shrinking of agricultural land and in the face of planned urbanisation, urban renewal, and successful resettlement of the street hawkers are among the major factors contributing to the changes. The purpose of this paper is threefold: (a) to analyse how these factors have affected the changes; (b) to examine the major elements of the fresh-food distributing systems; and (c) to outline the problems of spatial conflict between the formal and informal sectors in fresh-food retailing and the planning implications with particular reference to markets which have hitherto been the major institutions for marketing fresh foods.  相似文献   

Use of slow-release fertilizer and biopolymers for stimulating hydrocarbon biodegradation in oil-contaminated beach sediments   总被引：4，自引：0，他引：4  

Xu R  Yong LC  Lim YG  Obbard JP 《Marine pollution bulletin》2005,51(8-12):1101-1110

Nutrient concentration and hydrocarbon bioavailability are key factors affecting biodegradation rates of oil in contaminated beach sediments. The effect of a slow-release fertilizer, Osmocote, as well as two biopolymers, chitin and chitosan, on the bioremediation of oil-spiked beach sediments was investigated using an open irrigation system over a 56-day period under laboratory conditions. Osmocote was effective in sustaining a high level of nutrients in leached sediments, as well as elevated levels of microbial activity and rates of hydrocarbon biodegradation. Chitin was more biodegradable than chitosan and gradually released nitrogen into the sediment. The addition of chitin or chitosan to the Osmocote amended sediments enhanced biodegradation rates of the alkanes relative to the presence of Osmocote alone, where chitosan was more effective than chitin due to its greater oil sorption capacity. Furthermore, chitosan significantly enhanced the biodegradation rates of all target polycyclic aromatic hydrocarbons.  相似文献   

Applying a coupled hydrometeorological simulation system to flash flood forecasting over the Korean Peninsula     

Young Ryu  Yoon-Jin Lim  Hee-Sook Ji  Hyun-Hee Park  Eun-Chul Chang  Baek-Jo Kim 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(4):421-430

In flash flood forecasting, it is necessary to consider not only traditional meteorological variables such as precipitation, evapotranspiration, and soil moisture, but also hydrological components such as streamflow. To address this challenge, the application of high resolution coupled atmospheric-hydrological models is emerging as a promising alternative. This study demonstrates the feasibility of linking a coupled atmospheric-hydrological model (WRF/WRFHydro) with 150-m horizontal grid spacing for flash flood forecasting in Korea. The study area is the Namgang Dam basin in Southern Korea, a mountainous area located downstream of Jiri Mountain (1915 m in height). Under flash flood conditions, the simulated precipitation over the entire basin is comparable to the domain-averaged precipitation, but discharge data from WRF-Hydro shows some differences in the total available water and the temporal distribution of streamflow (given by the timing of the streamflow peak following precipitation), compared to observations. On the basis of sensitivity tests, the parameters controlling the infiltration of excess precipitation and channel roughness depending on stream order are refined and their influence on temporal distribution of streamflow is addressed with intent to apply WRF-Hydro to flash flood forecasting in the Namgang Dam basin. The simulation results from the WRF-Hydro model with optimized parameters demonstrate the potential utility of a coupled atmospheric-hydrological model for forecasting heavy rain-induced flash flooding over the Korean Peninsula.  相似文献   

A distribution function calculation of the H α profiles of SNR filaments     

A. J. Lim 《Astrophysics and Space Science》1995,233(1-2):273-280

In shocked media of high preshock ionisation, the lack of thermal contact between atoms in the neutral component of the gas can prevent the formation of a thermal equilibrium independent of the ionic component. The behaviour of the neutral gas in such a shock is dominated by the atomic processes driven by the postshock ionic component.A transport equation for the velocity distribution of the neutral gas is explicitly solved under the physical conditions of a 1D ionic shock transition. The resulting distributions are used to calculate predicted H line emission from such a system.  相似文献   

Cryptotephra detection using high-resolution trace-element analysis of Holocene marine sediments, southwest Japan   总被引：1，自引：0，他引：1  

Chungwan Lim  Kazuhiro Toyoda 《Geochimica et cosmochimica acta》2008,72(20):5022-5036

Detection techniques for invisible tephra, known as cryptotephra, have been exploited to construct precise and high-resolution correlations for a broad range of sedimentary sequences. We demonstrate that continuous trace-element profiles are an effective means for detecting probable positions of distal cryptotephra in Holocene hemipelagic sediments. Instrumental neutron activation analyses were performed on specimens of bulk sediments from five piston and gravity cores (water depths: 300-1500 m) taken from the southern Japan/East Sea. The down-core variations in the Ta/Sc ratio identify the positions of one to three alkaline cryptotephra in four of these cores. The Cr/Sc profiles show the position of one rhyolitic cryptotephra in three of the cores. The existence of tephra-derived components (glass ± crystals) was confirmed by microscopic observation, SEM-EPMA analysis and refractive index measurement on grains extracted from these layers. Based on microscopic observation and the stratigraphic correlations between cores, we identified eruption ages of the cryptotephras at 6.3, 7.5 and 9.3 ¹⁴C kyr BP, and two source volcanoes around 800 and 400 km from the study area.The tephra layers visible to the naked eye contained volcanic grains coarser than 200 μm, and the alkaline and rhyolitic tephra component comprised >20% and >33% of the sediment on weight basis, respectively. In contrast, the range of particle sizes of the cryptotephras detected in this study is finer than 125 μm, and almost all of the glass shards were finer than 40 μm. The alkaline and rhyolitic cryptotephras made up only 2-17% and 22-24%, respectively, of the sediment on weigh basis. The high sensitivity of this method stems from the significant difference in trace-element contents between the tephras and enclosing hemipelagic sediments in the core. Alkaline U-Oki tephra was enriched in Ta by one order of magnitude over that of the sediment, and depleted in Sc by one order. The rhyolitic tephra, K-Ah, was depleted by about one order in Cr relative to that of enclosing the sediment. The differences in chemical composition between within-plate alkaline tephras and hemipelagic sediments are usually so large that trace-element geochemical method is likely to be useful for alkaline cryptotephra detection in other areas with similar tectonic characteristics.  相似文献   

Tephra Fallout Models: The Effect of Different Source Shapes on Isomass Maps     

Leng L. Lim  Winston L. Sweatman  Robert McKibbin  Charles B. Connor 《Mathematical Geosciences》2008,40(2):147-157

Numerous tephra dispersion and sedimentation models rely on some abstraction of the volcanic plume to simplify forecasts of tephra accumulation as a function of the distance from the volcano. Here we present solutions to the commonly used advection–dispersion equation using a variety of source shapes: a point, horizontal and vertical lines, and a circular disk. These may be related to some volcanic plume structure, such as a strong plume (vertical line), umbrella cloud (circular disk), or co-ignimbrite plume (horizontal line), or can be used to build a more complex plume structure such as a series of circular disks to represent a buoyant weak plume. Basing parameters upon eruption data, we find that depositions for the horizontal source shapes are very similar but differ from the vertical line source deposition. We also compare the deposition from a series of stacked circular disk sources of increasing radius above the volcanic vent with that from a vertical line source.  相似文献   

A superb modified new adsorbent, <Emphasis Type="Italic">Artocarpus odoratissimus</Emphasis> leaves,for removal of cationic methyl violet 2B dye     

L. B. L. Lim  N. Priyantha  N. A. H. Mohamad Zaidi 《Environmental Earth Sciences》2016,75(16):1179

  相似文献   

Point vortex dynamics for coupled surface/interior QG and propagating heton clusters in models for ocean convection     

Chjan C. Lim  Andrew J. Majda 《地球物理与天体物理流体动力学》2013,107(3-4):177-220

Abstract

The dynamic behavior of baroclinic point vortices in two-layer quasi-geostrophic flow provides a compact model for studying the transport of heat in a variety of geophysical flows including recent heton models for open ocean convection as a response to spatially localized intense surface cooling. In such heton models, the exchange of heat with the region external to the compact cooling region reaches a statistical equilibrium through the propagation of tilted heton clusters. Such tilted heton clusters are aggregates of cyclonic vortices in the upper layer and anti-cyclonic vortices in the lower layer which collectively propagate almost as an elementary tilted heton pair even though the individual vortices undergo shifts in their relative locations. One main result in this paper is a mathematical theorem demonstrating the existence of large families of long-lived propagating heton clusters for the two-layer model in a fashion compatible to a remarkable degree with the earlier numerical simulations. Two-layer quasi-geostrophic flow is an idealization of coupled surface/interior quasi-geostrophic flow. The second family of results in this paper involves the systematic development of Hamiltonian point vortex dynamics for coupled surface/interior QG with an emphasis on propagating solutions that transport heat. These are novel vortex systems of mixed species where surface heat particles interact with quasi-geostrophic point vortices. The variety of elementary two-vortex exact solutions that transport heat include two surface heat particles of opposite strength, tilted pairs of a surface heat particle coupled to an interior vortex of opposite strength and two interior tilted vortices of opposite strength at different depths. The propagation speeds of the tilted elementary hetons in the coupled surface/interior QG model are compared and contrasted with those in the simpler two-layer heton models. Finally, mathematical theorems are presented for the existence of large families of propagating long-lived tilted heton clusters for point vortex solutions in coupled surface/interior QG flow.  相似文献   

Late Quaternary glacial–interglacial variations in sediment supply in the southern Drake Passage     

Jae Il Lee  Ho Il Yoon  Kyu-Cheul Yoo  Hyoun Soo Lim  Yong Il Lee  Donghyun Kim  Young-Suk Bak  Takuya Itaki 《Quaternary Research》2012,78(1):119-129

Geochemical characteristics of marine sediment from the southern Drake Passage were analyzed to reconstruct variations in sediment provenance and transport paths during the late Quaternary. The 5.95 m gravity core used in this study records paleoenvironmental changes during the last approximately 600 ka. Down-core variations in trace element, rare earth element, and Nd and Sr isotopic compositions reveal that sediment provenance varied according to glacial cycles. During glacial periods, detrital sediments in the southern Drake Passage were mostly derived from the nearby South Shetland Islands and shelf sediments. In contrast, interglacial sediments are composed of mixed sediments, derived from both West Antarctica and East Antarctica. The East Antarctic provenance of the interglacial sediments was inferred to be the Weddell Sea region. Sediment input from the Weddell Sea was reduced during glacial periods by extensive ice sheets and weakened current from the Weddell Sea. Sediment supply from the Weddell Sea increased during interglacial periods, especially those with higher warmth such as MIS 5, 9, and 11. This suggests that the influence of deep water from the Weddell Sea increases during interglacial periods and decreases during glacial periods, with the degree of influence increasing as interglacial intensity increases.  相似文献   

A hybrid modeling approach to evaluate the groundwater flow system at the low- and intermediate-level radioactive waste disposal site in Gyeong-Ju, Korea     

Sung-Hoon Ji  Kyung Woo Park  Doo-Hyun Lim  Chunsoo Kim  Kyung Su Kim  William Dershowitz 《Hydrogeology Journal》2012,20(7):1341-1353

The development and implementation of a hybrid discrete fracture network/equivalent porous medium (DFN/EPM) approach to groundwater flow at the Gyeong-Ju low- and intermediate-level radioactive waste (LILW) disposal site in the Republic of Korea is reported. The geometrical and hydrogeological properties of fractured zones, background fractures and rock matrix were derived from site characterization data and implemented as a DFN. Several DFN realizations, including the deterministic fractured zones and the stochastic background fractures, whose statistical properties were verified by comparison with in-situ fracture and hydraulic test data, were suggested, and they were then upscaled to continuums using a fracture tensor approach for site-scale flow simulations. The upscaled models were evaluated by comparison to in-situ pressure monitoring data, and then used to simulate post-closure hydrogeology for the LILW facility. Simulation results demonstrate the importance of careful characterization and implementation of fractured zones. The study highlighted the importance of reducing uncertainty regarding the properties and variability of natural background fractures, particularly in the immediate vicinity of repository emplacement.  相似文献