Quantitative Revolution 2: The Critical (Re)Turn     

Mei-Po Kwan  Tim Schwanen 《The Professional geographer》2013,65(3):283-291

Although many have questioned the adequacy of quantitative methods for addressing issues of concern in critical geographies, such as social justice and inequality, many have argued that quantification can potentially make rich contributions to understanding and addressing these issues. In light of the recent attempts to reassert the critical potential and positive role of quantitative geography, we suggest in this introductory article for the Focus Section that the antagonism between critical and quantitative geographies is not beneficial to the discipline. We highlight some promising developments in modern quantitative geography and reflect on the ways in which the critical–quantitative binary can be at least partially eclipsed. We emphasize that knowledge in quantitative methods is essential for deciphering and challenging regressive political agendas, now often supported by numbers and quantitative analysis. Quantitative geography, when integrated with a critical sensibility and used appropriately, can be a powerful tool for fostering progressive social and political change.  相似文献   

Erratum to: Velocity attenuation of debris flows and a new momentum-based load model for rigid barriers     

R. C. H. Koo  J. S. H. Kwan  C. W. W. Ng  C. Lam  C. E. Choi  D. Song  W. K. Pun 《Landslides》2017,14(2):631-631

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Analysis of runoff in ungauged mountain watersheds in Sichuan, China using kinematic-wave-based GIUH model     

Shuyou Cao  Kwan Tun Lee  Juiyi Ho  Xingnian Liu  Er Huang  Kejun Yang 《山地科学学报》2010,7(2):157-166

Floods are one of the most common natural hazards occurring all around the world. However, the knowledge of the origins of a food and its possible magnitude in a given region remains unclear yet. This lack of understanding is particularly acute in mountainous regions with large degrees in Sichuan Province, China, where runoff is seldom measured. The nature of streamflow in a region is related to the time and spatial distribution of rainfall quantity and watershed geomorphology. The geomorphologic characteristics are the channel network and surrounding landscape which transform the rainfall input into an output hydrograph at the outlet of the watershed. With the given geomorphologic properties of the watershed, theoretically the hydrological response function can be determined hydraulically without using any recorded data of past rainfall or runoff events. In this study, a kinematic-wave-based geomorphologic instantaneous unit hydrograph (KW-GIUH) model was adopted and verified to estimate runoff in ungauged areas. Two mountain watersheds, the Yingjing River watershed and Tianquan River watershed in Sichuan were selected as study sites. The geomorphologic factors of the two watersheds were obtained by using a digital elevation model (DEM) based on the topographic database obtained from the Shuttle Radar Topography Mission of US’s NASA. The tests of the model on the two watersheds were performed both at gauged and ungauged sites. Comparison between the simulated and observed hydrographs for a number of rainstorms at the gauged sites indicated the potential of the KW-GIUH model as a useful tool for runoff analysis in these regions. Moreover, to simulate possible concentrated rainstorms that could result in serious flooding in these areas, synthetic rainfall hyetographs were adopted as input to the KW-GIUH model to obtain the flow hydrographs at two ungauged sites for different return period conditions. Hydroeconomic analysis can be performed in the future to select the optimum design return period for determining the flood control work.  相似文献   

Uncertainty and context in GIScience and geography: challenges in the era of geospatial big data     

Yongwan Chun  Mei-Po Kwan  Daniel A. Griffith 《International journal of geographical information science》2019,33(6):1131-1134

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Methods for ultimate limit state assessment of ships and ship-shaped offshore structures: Part I—Unstiffened plates     

Jeom Kee Paik  Bong Ju Kim  Jung Kwan Seo 《Ocean Engineering》2008,35(2):261-270

The present paper is Part I of a series of three papers prepared by the authors on the methods useful for ultimate limit state assessment of marine structures, that have been developed in the literature during the last few decades. It is considered that such methods are now mature enough to enter day-by-day design and strength assessment practice. The aims of the three papers are to conduct some benchmark studies of such methods on ultimate limit state assessment of (unstiffened) plates, stiffened panels, and hull girders of ships and ship-shaped offshore structures, using some candidate methods such as ANSYS nonlinear finite element analysis (FEA), DNV PULS, ALPS/ULSAP, ALPS/HULL, and IACS common structural rules (CSR) methods. As an illustrative example, an AFRAMAX-class hypothetical double hull oil tanker structure designed by CSR method is studied. In the present paper (Part I), the ultimate limit state assessment of unstiffened plates under combined biaxial compression and lateral pressure loads is emphasized using ANSYS, DNV PULS, and ALPS/ULSAP methods, and their resulting computations are compared. Part II will deal with methods for the ultimate limit state assessment of stiffened panels under combined biaxial compression and lateral pressure using ANSYS, DNV PULS, and ALPS/ULSAP methods, and Part III will treat methods for the progressive collapse analysis of the hull structure using ANSYS, ALPS/HULL, and IACS CSR methods.  相似文献   

Theory of radiation in an anisotropic plasma     

P. C. W. Fung  T. P. Kwan 《Astrophysics and Space Science》1983,93(2):281-293

We follow up the work of Fung and Young (1982) to derive explicit expressions for the power emitted and the power observed per unit solid angle along the direction of the group velocity in an anisotropic plasma. We have deduced the ratio of the time interval during which the energy is emitted and the corresponding time interval during which the energy is received in this anisotropic case. Our result obtained is consistent to the basic well-known concept of group-ray propagation in a plasma.  相似文献   

Effects of Curing Conditions on Strength Development of High Strength Concrete     

Cai Yuebo Kwan Kwok-Hung Senior Engineer 《中国海洋工程》1997,(1)

This paper presents the results of a series of studies on the influence of curing conditions onthe strength development of high strength concrete.The 1-,3-,7-,14-and 28-day strengths of four dif-ferent mixes of Grade 75～80 concrete,with or without pulverized fuel ash and/or condensed silica fume,under five different curing regimes were investigated.It is revealed that the curing conditions have signifi-cant influence on both the short term and long term strength development of the concrete and that con-crete mixes of the same grade but containing different mineral admixtures show distinct favour for a cur-ing regime.These results will be helpful for evaluating suitable curing methods for high strength concretewith different mix proportions.  相似文献   

On gas fluxes from small lakes and ponds     

Joyce Kwan  Peter A. Taylor 《Boundary-Layer Meteorology》1994,68(4):339-356

A semi-empirical model for estimating gas fluxes at the air-water interface in a neutrally stratified atmosphere is presented. Gas transfer velocity is assumed to depend on local friction velocity, whose variation with over-water fetch is estimated from Walmsleyet al.'s (1989) Guidelines. As guidance for limnologists estimating CO₂ and CH₄ fluxes from lakes and ponds in the Hudson Bay Lowlands region, we present model results of the variation of gas transfer velocity with over-water fetch,k(x), for comparison with the customary constant valuek ₀. Gas fluxes are estimated over well mixed, circular and elliptical lakes and ponds. The results of accounting for fetch dependence, wind direction, pond shapes and sizes lead to correction factors to fluxes obtained withk ₀. Recent studies of gas transfer velocity for gases of low solubility from lakes are reviewed, and the problem of time averaging on quantities determined from experimental measurements is also discussed.  相似文献   

Influence of storm magnitude and watershed size on runoff nonlinearity     

Kwan Tun Lee  Jen-Kuo Huang 《Journal of Earth System Science》2016,125(4):777-794

The inherent nonlinear characteristics of the watershed runoff process related to storm magnitude and watershed size are discussed in detail in this study. The first type of nonlinearity is referred to rainfall-runoff dynamic process and the second type is with respect to a Power-law relation between peak discharge and upstream drainage area. The dynamic nonlinearity induced by storm magnitude was first demonstrated by inspecting rainfall-runoff records at three watersheds in Taiwan. Then the derivation of the watershed unit hydrograph (UH) using two linear hydrological models shows that the peak discharge and time to peak discharge that characterize the shape of UH vary event-to-event. Hence, the intention of deriving a unique and universal UH for all rainfall-runoff simulation cases is questionable. In contrast, the UHs by the other two adopted nonlinear hydrological models were responsive to rainfall intensity without relying on linear proportion principle, and are excellent in presenting dynamic nonlinearity. Based on the two-segment regression, the scaling nonlinearity between peak discharge and drainage area was investigated by analyzing the variation of Power-law exponent. The results demonstrate that the scaling nonlinearity is particularly significant for a watershed having larger area and subjecting to a small-size of storm. For three study watersheds, a large tributary that contributes relatively great drainage area or inflow is found to cause a transition break in scaling relationship and convert the scaling relationship from linearity to nonlinearity.  相似文献   

Iranian ultrapotassic volcanism at ~11 Ma signifies the initiation of post‐collisional magmatism in the Arabia–Eurasia collision zone     

Kwan‐Nang Pang  Sun‐Lin Chung  Mohammad Hossein Zarrinkoub  Yu‐Chin Lin  Hao‐Yang Lee  Ching‐Hua Lo  Mohammad Mahdi Khatib 《地学学报》2013,25(5):405-413

Ultrapotassic rocks are a common, but volumetrically minor, hallmark of post‐collisional magmatism along the Alpine–Himalayan orogenic belt. Here, we document the occurrence of ultrapotassic volcanic rocks from the Eslamy peninsula, NW Iran in the Arabia–Eurasia collision zone. Our results indicate that magma genesis involved melting of phlogopite‐ and apatite‐bearing peridotites in the sub‐continental lithospheric mantle at ~11 Ma. These peridotites likely formed by metasomatism involving components derived from subducted sediments during Neotethyan subduction. The ~11 Ma ultrapotassic volcanism was preceded by a magmatic gap of ~11 Ma after the cessation of arc magmatism in NW Iran and Armenia, thus likely representing the initiation of post‐collisional magmatism. The age coincides with the onset of collision‐related magmatic activity and topographic uplift in the Caucasus–Iran–Anatolia region, and also with other regional geological events including the closure of the eastern Tethys gateway, the end of Arabian underthrusting and the start of escape tectonics in Anatolia.  相似文献