Detecting temporal changes in the extent of annual flooding within the Cambodia and the Vietnamese Mekong Delta from MODIS time-series imagery

This paper presents the methodology used to detect temporal changes in the extent of annual flooding within the Cambodia and the Vietnamese Mekong Delta (VMD) based on MODIS time-series imagery (Wavelet-based Filter for detecting spatio-temporal changes in Flood Inundation; WFFI). This methodology involves the use of a wavelet-based filter to interpolate missing information and reduce the noise component in the time-series data, as proposed in a previous study. The smoothed time profiles of Enhanced Vegetation Index (EVI), Land Surface Water Index (LSWI), and the Difference Value between EVI and LSWI (DVEL) are obtained from MOD09 8-day composite time-series data (resolution: 500 m; time period: 2000-2005). The proposed algorithm was applied to produce time-series inundation maps (WFFI products) for the five annual flood seasons over the period from 2000 to 2004. The WFFI products were validated via comparisons with Landsat-derived results and inundation maps based on RADARSAT images, hydrological data, and digital elevation model data. Compared with the RADARSAT-derived inundation maps at the province level, the obtained RMSE range from 364 to 443 km² and the determination coefficients [R²] range from 0.89 to 0.92. Compared with Landsat-derived results at the 10-km grid level, the obtained RMSE range from 6.8 to 15.2 km² and the determination coefficients [R²] range from 0.77 to 0.97. The inundated area of flooded forests/marsh to the northeast of Tonle Sap Lake were underestimated, probably because of extensive vegetation cover in this area. The spatial characteristics of the estimated start dates, end dates, and duration of inundation cycles were also determined for the period from 2000 to 2004. There are clear contrasts in the distribution of the estimated end dates and duration of inundation cycles between large-scale floods (2000-2002) and medium- and small-scale floods (2003 and 2004). At the regional scale, the estimated start dates for the southern part of An Giang Province during 2003 and 2004 was distinctly later than that for surrounding areas. The results indicate that these triple-cropping areas enclosed by dikes increased in extent from 2003 to 2004. In contrast, the estimated end dates of inundation at the Co Do and Song Hau State Farms were clearly earlier than those for surrounding areas, although the estimated start dates were similar. Temporal changes in the inundation area of Flood pixels in the Dong Thap and Long An Provinces are in excellent agreement with daily water-level data recorded at Tan Chau Station. The estimated area of Long-term water body increased in size from 2000 to 2004, especially in coastal areas of the Ca Mau and Bac Lieu Provinces. Statistical data for Vietnam indicate that this trend may reflect the expansion of shrimp-farming areas. The WFFI products enable an understanding of seasonal and annual changes in the water distribution and environment of the Cambodia and the VMD from a global viewpoint.     

Measurement of ion and electron temperatures in plasma blobs by using an improved ion sensitive probe system and statistical analysis methods

We have measured ion temperature as well as electron temperature in plasma blobs observed in a linear plasma device by using an improved ion sensitive probe. Current-voltage characteristics of the ion sensitive probe inside and outside plasma blobs were re-constructed with a conditional sampling method. It is clearly found that both ion and electron temperatures in plasma blobs decrease more slowly in a cross-field direction than those in a bulk plasma without plasma blobs.     

Ad-Molecule Orientation and Thermo- and Photo-Induced Surface-Aligned Desorption

Two-directional N₂ desorption was found in N₂O decomposition on Pd(110) at 100–160 K. It collimated ±43° off the surface normal in the (001) plane. A hot-atom-assisted model is proposed for N₂ desorption. Inclined O₂ desorption was simulated by hot atoms emitted from aligned oxygen molecules on stepped Pt(112) at 308 nm irradiation.     

Alloy Casting by the Horizontal Ohno Continuous Casting System

Abstract

Sn-Pb alloys in the compositional range 2.5–22.5% Pb have been continuously cast using the horizontal Ohno Continuous Casting (OCC) process. The effects of alloy composition and process variables on the location and size of the liquid-solid zone were investigated and information obtained was examined in order to establish the breakout point. It was found that the liquid-solid zone existed partly or entirely within the mould during casting, depending on casting conditions. The liquid-solid zone expanded with increasing mould-cooler distance and also with decreasing mould exit temperature, whereas it remained constant with the casting speed within the range investigated. As the composition approaches the eutectic point, the L+S zone shifted into the mould, and existed entirely within the mould at 22.5% Pb. It was also found that breakout occurred when the rod temperature at the mould exit exceeded a critical temperature which can be expressed as Tc=228–2A, where Tc is the critical rod temperature in Celsius and A is wt% Pb (<22.5% Pb). It was confirmed that the mould exit temperature must be kept above the liquidus temperature of the alloy to be cast in order to obtained unidirectional or single crystal materials.     

Direct visualization of hetero-enzyme co-encapsulated in mesoporous silicas

In this study, a direct visualization technique was applied to the determination of a hetero-enzyme co-encapsulated in pores of mesoporous silicas in solution. Lipase and trypsin modified with fluorescent dyes, used as model enzymes, were co-encapsulated at the same instant in two kinds of mesoporous silicas – FSM-22 and SBA-15 – with pore diameters of 4.2 and 7.1 nm, respectively. A direct observation of composite materials of a hetero-enzyme and a mesoporous silica by a combination of differential interference contrast and fluorescence microscopy revealed that the enzymes were uniformly dispersed throughout the particles of the mesoporous silicas, because of the successful incorporation of the two enzymes. Moreover, lipase and trypsin co-encapsulated in the mesopores maintained their enzymatic activities in hydrolysis reactions of their substrates (triglyceride and casein, respectively), without loss of their enzymatic activities due to structural degradation.     

Warm Spray Forming of Ti-6Al-4V

Warm spray (WS) is a modification of high-velocity oxy-fuel spraying, in which the temperature of the supersonic gas flow generated by the combustion of kerosene and oxygen is controlled by diluting the combustion flame with an inert gas such as nitrogen. The inert gas is injected into the mixing chamber placed between the combustion chamber and the powder feed ports, thus the temperature of the propellant gas can be controlled from ~700 to 2,000 K. Since WS allows for higher particle temperatures in comparison to cold spray, warm sprayed particles are more softened upon impact, thus resulting in greater deformation facilitating the formation of shear instability for bonding. Recently, the combustion pressure of WS has been increased from 1 (low-pressure warm spray) to 4 MPa (high-pressure warm spray) in order to increase the velocity of sprayed particles. Effects of spray parameters on microstructure, mechanical properties, and splats formation of Ti-6Al-4V were systematically studied. Obtained coatings were examined by analyzing the coating cross-section images, microhardness as well as oxygen content. In addition, flattening ratio of splats was calculated as a function of nitrogen flow rate. It was found that the increased particle velocity caused by the increased combustion pressure had significant beneficial effects in terms of improving density and controlling the oxygen level in the sprayed Ti-6Al-4V coatings.     

Performance analysis of a time diversity ARQ in land mobile radio

A time diversity automatic repeat-request (ARQ) scheme with a finite number of transmissions is investigated for a digital FM mobile radio with frequency demodulation (FD). It processes all the retransmissions of a single data block using postdetection diversity combining. The analysis of the signal energy per bit required for a given bit error rate (BER) and the spectral efficiency in a cellular mobile radio system are presented. The results obtained from the numerical calculations show that this ARQ scheme offers a performance superior to both the basic ARQ scheme and the time-diversity scheme