ショウトツ フンリュウ ニヨル コウオンメン ノ キュウソク レイキャクチュウ ノ ヒテイジョウ デンネツ トクセイ

Transient heat transfer has been investigated experimentally with a subcooled water jet during quenching of hot cylindrical blocks made of copper, brass and steel for initial surface temperatures from 250 to 600 oC. The jet velocity was from 3 to 15 m/s and jet subcooling was from 5 to 80 K with a jet diameter of 2 mm. When the jet first struck the hot surface, the visible leading edge of the moving liquid (wetting front) became stagnant for a certain period of time in the small impinged region and splashed out from that region before wetting the entire surface. This wetting delay may be described as resident time which is a strong function of block material and jet subcooling and also a function of block initial temperature and jet velocity. New correlations for the resident time and the surface temperature at resident time at wetting front position have been proposed in this study which agree well with the experimental data. During the movement of the wetting front, the surface temperature at the wetting front drops to 120-200 oC and the surface heat flux reaches its maximum value due to forced convection nucleation boiling. The maximum heat flux is a strong function of the position on the hot surface, jet velocity, block material properties and jet subcooling. A new correlation for maximum heat flux is also proposed. When the resident time is short, the rate of movement of the maximum heat flux position increases with the increase of jet velocity and subcooling and decreases with the increase of block initial temperature. These trends are opposite for long resident time. During the movement of the wetting front over the hot surface, a darker moving vigorous boiling region is observed at the leading area of moving liquid. The width of this vigorous boiling region is described as the ‘boiling width’. Boiling width affects the heat flux estimation and distribution in jet impingement quenching. Boiling width increases with radial position. Higher conductivity of the test section material results in the higher v

Natural Disaster and Sickness Shocks: Evidence of Informal Social Insurance from Bangladesh

Bangladesh is prone to large scale natural disasters with consequent impacts on human health and survival. In 1998, Bangladesh experienced the flood of the century\u27. Households exposed to flooding had major crop failure, suffered from various water-borne diseases, lost shelter, assets and ability to meet their basic needs. Based on multiple rounds of household survey data from rural Bangladesh collected after the 1998 flooding, this article investigate the factors that contribute to reduce sickness shocks after a massive natural disaster. Results indicate that social cohesion built on group-based microfinance programs may provide an informal social insurance mechanism to reduce sickness shocks. Simply put, households with stronger social bonds built on microfinance programs spend less for medical expenses in recovering from post-flood sickness shocks. Policy implications are explored in a developing country context, where sickness significantly impacts household welfare and no formal health insurance exists.\u2

Impacts of pumping on the distribution of arsenic in Bangladesh groundwater

Chronic exposure to naturally occurring arsenic (As) in groundwater threatens the health of >150 million villagers in S/SE Asia. In Bangladesh, low As aquifers offer the best hope of reducing the exposure of 35-40 million remain exposed to elevated levels of As in drinking water (>10 μg/L). These low As aquifers could be affected, however, by massive pumping from shallow (<30 m) depths for growing rice and overexploitation of deeper aquifer for municipal water supply. The goal of this dissertation is to assess the impacts of groundwater pumping on the distribution in groundwater of dissolved As, reactive carbon, and redox-sensitive elements in anoxic aquifers of Bangladesh based on long-term hydrologic measurements, geochemical analyses, and numerical flow modeling. In the second chapter, changes in the well-water As concentrations within a 25 sq. km area over a 10+ year timespan are assessed on the basis of continuous time series for 18 monitoring wells, a set of 271 wells resampled three times, and a large dataset obtained from blanket surveys of several thousand wells in the region. The two larger data sets both show a 10% decline in the initial areal mean As of 100 μg/L. This decline can be explained by flushing of As in the shallow aquifer by low-As recharge water, evidently compensated to some extent by the desorption of sediment-bound As. The presence of a large exchangeable pool of As in the sediment therefore seems to buffer changes in the distribution of As in the face of large perturbation in groundwater flow, albeit not enough to prevent some trends indicated by the detailed time series. The third chapter provides a complementary perspective on groundwater-sediment interactions by quantifying the rates of adsorption and desorption of As with column experiments conducted in the field for two different types of sediments: grey reduced Holocene sands and orange oxidized Pleistocene sands. The data show that, contrary to widely held beliefs, retardation of As transport by adsorption is quite similar in Holocene and Pleistocene sediments, even if Holocene sands initially contain a much larger pool of easily mobilizable As. The field column experiments also showed significant changes in solid phase speciation that affected As retention within a timespan of only a few weeks. Detailed field observations and flow modeling in the fourth chapter examine how perturbed flow paths can draw either As or reactive carbon into a Pleistocene aquifer. A groundwater flow model, constrained by head measurements and isotopic tracer data shows that certain portions of the aquifer are becoming increasingly contaminated with As as a result of municipal pumping, but against a background of redox transformation in the aquifer that probably preceded this perturbation. Overall, the research conducted for this thesis shows that alteration of the hydrological system due to local and regional forcing is affecting the distribution of As in groundwater. These changes do not affect all wells yet and, if they do, the increase in As concentrations observed so far are gradual because of the buffering capacity of the sediment. Lowering exposure by targeting low As aquifer should therefore definitely continue in Bangladesh, with particular attention paid to regular monitoring using vulnerability criteria this research has helped to identify

Revisiting variance gamma pricing : an application to S&P500 index options

We reformulate the Lévy-Kintchine formula to make it suitable for modelling the stochastic time-changing effects of Lévy processes. Using Variance-Gamma (VG) process as an example, it illustrates the dynamic properties of a Lévy process and revisits the earlier work of Geman (2002). It also shows how the model can be calibrated to price options under a Lévy VG process, and calibrates the model on recent S&P500 index options data. It then compares the pricing performance of Fast Fourier Transform (FFT) and Fractional Fourier Transform (FRFT) approaches to model calibration and investigates the trade-off between calibration performance and required calculation time

Applications of Ultrafine Powder Coatings

Powder coatings have emerged as an alternative to the conventional liquid coatings when environmental regulations become stricter every year. The advantage of powder coatings mainly renders to their solvent-free formulations, because solvent(s) used in liquid coatings are to be evaporated to environment contributing to the total volatile organic compounds (VOCs) emissions. Although advantageous, until recently, powder coating was not able to provide surface finishes comparable to the liquid coatings. However, when ultrafine powders (particularly, in the size range of 15-25 µm) becomes flowable with the aid of nano-additive(s), ultrafine powder coatings (UPCs) came into business with its thinner and smoother films well-comparable to the liquid coatings. Thus UPC offers environmentally friendly alternative to the coating industries having applied to develop many functional coatings. Ultrafine powder coating (UPC) technology has been utilized to develop superhydrophobic powder coatings that mimic lotus leaf surfaces and exhibit water contact angles (CAs) of over 160° and sliding angle (SA) of less than 5° on the coated substrates. Water droplets tend to be very unstable on these surfaces so that they run away from the superhydrophobic surfaces even with the slightest inclination. This unique phenomenon is attributed to the double-scale micro-/nano hierarchical structures that have been successfully fabricated on such surfaces just by incorporating nano-sized hydrophobic additive(s) in the coating formulations. Thus the solvent-free UPC technique has offered simple but environmentally friendly solution in developing superhydrophobic surfaces that could be used as self-cleaning surfaces. Ultrafine powder coating (UPC) technique has been employed to develop polymeric biocompatible powder coatings enriched with nano-Ti02 with varying degree of nanoroughness ranging from -37 nm to -260 nm. The developed coatings have been assessed for their biocompatibility when human mesenchymal cells were cultured on them. Cells attached spread and expressed Runx2 and Collagen Type Ion these biocompati ble coatings. Interestingly, they performed even better than commercially pure titanium (cpTi) when their nanoroughness could be maintained below -50 nm. UPC has been able to tune up the nanoroughness of the developed coatings without changing anything in the existing processes, rather by changing amount of the constituents in the coating formulations. Thus UPC could possibly replace the traditional techniques (plasma treatment, sputter-coating or vapour deposition) to develop bioactive coatings for medical devices with offering simple and inexpensive coating method. Ultrafine powder coating (UPC) technique has also been used to apply flow-modified glass ionomer cement (GIC) powders onto exposed dentine surfaces to occlude exposed dentinal tubules that could effectively treat dentine hypersensitivity. Proprietary ultrafine GIC powders, (Ketac-Cem® and Fuji I® ) have been processed with appropriate amounts of nano-sized Ah03 to improve their flowability before applying them to the dentine sections by using UPC process employing Corona spraying gun. With this powder spraying technique, dentinal tubules have been occluded as deep as -1 mm µm, in some instances. Such deeper dentinal tubule occlusion renders superiority over any other existing technique (i.e., highest penetration depth was revealed in the literatures is -270 µm). Moreover, UPC technique showed a higher proportion of tubules filled. Thus, UPC could enter into the treatment of dentine hypersensitivity

Building-level adaptation analysis under uncertain sea-level rise

Recent studies show climate-induced sea-level rise (SLR) will accelerate storm surge impacts in many coastal areas around the world. The decision-making of building-level adaptation strategies is a challenging task due to uncertain climate impacts. This study evaluates building-level adaptation strategies through a dynamic programming-based cost-benefit analysis approach to incorporate the latest information of SLR in adaptation decision-making. The adaptation outcomes are estimated by applying a Monte-Carlo method with stochastic flood damage of buildings under four SLR projections. Based on a case study in Bay County, Florida (USA), results indicate that single-family and multi-family buildings are the most vulnerable buildings in Bay County. Mobile homes have a lower flood risk, while they are more sensitive to SLR. The long-term flood damage shows SLR could exponentially increase the average annual flood damage in the community from $17.7 million to$204 million. Investing in adaptive measures can substantially mitigate building-level flood risk, where the adapted average annual damage ranges from $9.57 million to$38.2 million in the county. The proposed adaptation method could facilitate more effective risk communications between the public and private sectors and improvise community adaptation planning under uncertain SLR

Evaluation of temporal moments and Fourier transformed data in time-domain diffuse optical tomography

Time-domain diffuse optical tomography (TD-DOT) uses near-infrared pulsed lasers as light sources to measure time-varying exitance on the boundary of the target. These are used to estimate optical properties of the imaged target. Several integral-transform-based moments of the time-resolved data have been utilized in TD-DOT, the most common being the mean time of flight and variance. Recently, it has been shown that Fourier transforming the time-domain data to frequency domain enables utilization of these data at one or several frequencies, producing equally as good estimates as the whole time-domain data. In this work, we present a systematic comparison of the usage of the temporal moments and Fourier transformed data in TD-DOT. Both absolute and difference imaging are evaluated using numerical simulations. The simulations show that utilizing temporal moments and Fourier transformed data in TD-DOT provides good quality reconstructions with a good estimation accuracy. These estimates are improved if more than one data type is used. Furthermore, the simulations show that the frequency-domain computations enable computationally cheaper and straightforward implementation of the inverse solver when compared to the temporal moments