Saturation Depth Research Articles

Experimental Analysis of Glass Drilling with Ultrashort Pulse Lasers

Ultrashort pulse laser processing that facilitates high-speed and fine processing of glass materials has received considerable attention in recent years, despite mechanical processing or etching having been the mainstream methods. However, the physical mechanisms of this technique and the influence of various parameters, such as the processing conditions and physical properties of the processed material, on generated shapes are not yet fully understood. In this work, we comprehensively investigated the influence of various parameters of ultrashort pulse lasers on the processing mechanisms through experiments conducted by changing the wavelength, pulse width, repetition rate, and pulse energy over a wide range. The physical effects of the laser parameters on the reflection of light and heat generation were discussed by analyzing the experimental results, and the influence of the parameters on the generated shapes, processing speed, and saturated depth was clarified. In addition, cracks around the ablated area, which are one of the problems concerning glass processing with ultrashort pulse lasers, were observed, and the influence of the pulse energy on the cracks was evaluated. It is expected that this research will allow for a thorough understanding of the laser parameters that are suitable for glass processing and widen the range of laser processing applications.

Soil moisture causes dynamic adjustments to root reinforcement that reduce slope stability

AbstractIn steep soil‐mantled landscapes, the initiation of shallow landslides is strongly controlled by the distribution of vegetation, whose roots reinforce the soil. The magnitude of root reinforcement depends on the number, diameter distribution, orientation and the mechanical properties of roots that cross potential failure planes. Understanding how these properties vary in space and time in forests remains a significant challenge. Here we test the hypothesis that spatio‐temporal variations in root reinforcement along a hillslope occur as a function of topographic soil moisture gradients. To test this hypothesis we compared root reinforcement measurements from relatively dry, divergent noses to relatively wet, convergent hollows in the southern Appalachian Mountains, North Carolina, USA. Our initial results showed that root reinforcement decreased in areas of higher soil moisture because the tensile strength of roots decreased. A post hoc laboratory experiment further demonstrated that root tensile strength decreased as root moisture content increased. This effect is consistent with other experiments on stem woods showing that increased water content in the cell wall decreases tensile strength. Our experimental data demonstrated that roots can adjust to changes in the external root moisture conditions within hours, suggesting that root moisture content will change over the timescale of large storm events (hours–days). We assessed the effects of the dynamic changes in root tensile strength to the magnitude of apparent cohesion within the infinite slope stability model. Slopes can be considerably less stable when precipitation‐driven increases in saturated soil depth both increase pore pressures and decrease root reinforcement. Copyright © 2016 John Wiley & Sons, Ltd.

A first look at factors affecting aragonite compensation depth in the eastern Arabian Sea

Water column measurements suggest shoaling of aragonite saturation depths (ASD) throughout the world oceans, due to increase in greenhouse gas concentration. Past records of aragonite saturation state under different climatic conditions are required to assess the impact of climatic changes on shoaling/deepening of ASD. The preservation state of organisms having aragonite skeletons, is used to assess the past changes in aragonite saturation depths, with respect to the modern ASD. Here for the first time, we delineate and discuss the factors that affect the modern aragonite compensation depth (ACD) in the eastern Arabian Sea by using pteropod abundance in the surface sediments. A total of 78 spade core-top samples collected along seven latitudinal transects, covering the continental shelf, slope and abyssal region of the eastern Arabian Sea were used. Pteropods were picked from coarse fraction (≥63μm). Based on the pteropod preservation, we report that in the eastern Arabian Sea, ACD lies at a water depth of ≤525m, which matches with the chemically defined aragonite saturation depth. We further report that the ACD shoals from north to south. The zone of high pteropod abundance coincides with low %Corg. The increase in pteropod abundance in the outer shelf region coincides with the drop in dissolved oxygen concentration. The deeper limit of pteropod abundance lies in the center of the oxygen minimum zone with higher %Corg. Therefore, we suggest that the pteropod abundance in the eastern Arabian Sea is not always related with the lower dissolved oxygen, but is strongly influenced by %Corg. This first report of the pteropod based aragonite compensation depth estimates from the eastern Arabian Sea will help in assessing future changes in ACD under the influence of anthropogenic green-house gas emissions.

Numerical modelling of mechanical behaviour of partially saturated soils using coupled FEA

The effects of degree of saturation and water table depth on settlement and pore water dissipation behaviour of partially saturated soils has been analysed using coupled finite element analysis in the present study. The fundamental equations governing the fully coupled constitutive behaviour of partially saturated soils are presented. To obtain the numerical solution, a FORTRAN program has been developed. Modified cam clay model has also been implemented into a finite element code. The results are validated with available results in the literature. The behaviour of partially saturated soil under strip footing is considered as an example. Results indicate that under surface loading, consolidation behaviour of the partially saturated soils is governed by the initial degree of saturation and depth of water table.

Groundwater controls on episodic soil erosion and dust emissions in a desert ecosystem

Abstract Feedbacks between vegetation, soils, and sediment transport processes maintain arid landscapes in geomorphically active degraded states or in more biologically productive and geomorphically stable states. Landscape evolution models and resource management strategies require a detailed understanding of thresholds that limit sediment transport in deserts, but it can be difficult to quantify geomorphic responses to abrupt environmental change. Here we use measurements of fallout radionuclides and salt content in soils, horizontal sediment fluxes, vegetation cover, and saturated zone depth in Owens Valley, California (USA), to quantify the geomorphic response of a desert landscape to changes in groundwater availability. Owens Valley has a well-documented history of surface-water diversions and pumping during the A.D. 1987–1992 drought, and we studied 11 sites having a gradient of ∼0.5 m to 8 m of groundwater decline during this time. We show that short-length-scale (<50 m) sediment redistribution is active in areas with a range of environmental histories, but centimeter-scale net soil loss occurred when photosynthetic vegetation cover declined to <20% where local groundwater remained shallow enough to produce evaporite salts. Erosion and dust emissions are most severe in central Owens Valley when groundwater falls below the 2 m effective rooting depth of native meadow vegetation but remains shallow enough (<6 m) so that capillary action maintains loose erodible sediment at the surface.

Leachate flow around a well in MSW landfill: Analysis of field tests using Richards model

During the lifespan of a Municipal Solid Waste landfill, its leachate drainage system may get clogged. Then, as a consequence of rainfall, leachate generation and possibly leachate injection, the moisture content in the landfill increases to the point that a leachate mound could be created. Therefore, pumping the leachate becomes a necessary solution. This paper presents an original analysis of leachate pumping and injection in an instrumented well. The water table level around the well is monitored by nine piezometers which allow the leachate flow behaviour to be captured. A numerical model based on Richards equation and an exponential relationship between saturated hydraulic conductivity and depth is used to analyze the landfill response to pumping and injection. Decreasing permeability with depth appears to have a major influence on the behaviour of the leachate flow. It could have a drastic negative impact on the pumping efficiency with a maximum quasi-stationary pumping rate limited to approximately 1m3/h for the tested well and the radius of influence is less than 20m. The numerical model provides a reasonable description of both pumping and injection tests. However, an anomalous behaviour observed at the transition between pumping and recovery phases is observed. This could be due to a limitation of the Richards model in that it neglects the gas phase behaviour and other double porosity heterogeneous effects.

Modification of transient state analytical model under different saline groundwater depths, irrigation water salinities and deficit irrigation for quinoa

Salinization of soil is primarily caused by capillary rise from saline shallow groundwater or application of saline irrigation water. In this investigation, the transient state analytical model was modified to predict water uptake from saline shallow groundwater, actual crop evapotranspiration, soil water content, dry matter, seed yield and soil salinity under different saline groundwater depths, irrigation water salinities and deficit irrigation for quinoa. Considering the effect of salinity on soil saturated hydraulic conductivity and maximum root depth in presence of shallow saline groundwater, the model resulted in good agreement between the measured and predicted saline groundwater uptake, soil salinity increase at different groundwater depths (300-800 mm) and water salinity (10-40 dS m -1 ). Therefore, the modified model is applicable for quinoa yield and soil salinity prediction and it could be a valuable tool for soil salinity management in presence of shallow saline groundwater. Furthermore, prediction of quinoa yield by the modified model can be used for better irrigation water salinity management under different saline groundwater depths, irrigation water salinities and deficit irrigation.

Towards monitoring dysplastic progression in the oral cavity using a hybrid fiber-bundle imaging and spectroscopy probe.

Intraepithelial dysplasia of the oral mucosa typically originates in the proliferative cell layer at the basement membrane and extends to the upper epithelial layers as the disease progresses. Detection of malignancies typically occurs upon visual inspection by non-specialists at a late-stage. In this manuscript, we validate a quantitative hybrid imaging and spectroscopy microendoscope to monitor dysplastic progression within the oral cavity microenvironment in a phantom and pre-clinical study. We use an empirical model to quantify optical properties and sampling depth from sub-diffuse reflectance spectra (450–750 nm) at two source-detector separations (374 and 730 μm). Average errors in recovering reduced scattering (5–26 cm−1) and absorption coefficients (0–10 cm−1) in hemoglobin-based phantoms were approximately 2% and 6%, respectively. Next, a 300 μm-thick phantom tumor model was used to validate the probe’s ability to monitor progression of a proliferating optical heterogeneity. Finally, the technique was demonstrated on 13 healthy volunteers and volume-averaged optical coefficients, scattering exponent, hemoglobin concentration, oxygen saturation, and sampling depth are presented alongside a high-resolution microendoscopy image of oral mucosa from one volunteer. This multimodal microendoscopy approach encompasses both structural and spectroscopic reporters of perfusion within the tissue microenvironment and can potentially be used to monitor tumor response to therapy.

Effect of Supplementary Curing after Steam-Curing on Performance of Concrete

When the low strength grade of steam-curing concrete is produced, the temperature which the concrete leaves steam-curing kiln is about 20°C commonly. The temperature difference is too large between the environmental temperature and the temperature which the concrete leaves steam-curing kiln when the daily average temperature drops to 10°C. Because the steam-curing concrete is cooled rapidly, a large of crack will be produced in concrete and the internal structure of concrete will be damaged normally. Then the performance of concrete will be influenced badly. In order to improve the negative effect on concrete by steam curing, the different supplementary curing is used after steam curing. The C30 concrete is made in this research. The daily average temperature is 5°C~10°C and the minimum temperature is-6°C during the test. After the concrete is formed, it is placed in 20°C environment for 2h first. Then the concrete is heated to 55°C in 2h and maintained for 8h in the steam-curing kiln. In the end, the concrete is cooled to 20°C in 3h. After steam curing, the standard curing and covering by wet fabric or film outside are used separately for concrete. The supplementary curing time is 1d, 2d, 3d and 4d. Then the concrete is placed in natural environment to 28d. The microstructure of hydration products are observed by electron microscope. The density of concrete is analyzed by the result of the 28d saturated water content, softening factor and 28d rapid carbonation depth. The mechanical properties of concrete are researched by the result of the 28d strength. When the concrete adopts standard curing or covering by film after steam-curing, the saturated water content and 28d rapid carbonation depth of the concrete will reduce, but the softening factor and 28d strength of the concrete will increase with the time. The performance of concrete which adopts covering by wet fabric after steam-curing is worse than that adopting standard curing. At the same time, the saturated water content and softening factor of concrete change little. Covering by wet fabric is worse than no covering or similar. In the test environment, the performance of the steam-curing concrete with each supplementary curing is worse than that of the concrete with standard curing. The standard curing is the best supplementary curing in this test. But covering by film is a worthy supplementary curing from economy and practicability. Covering by film for 4d, the 28d strength of steam-curing concrete is 87 percent of that of the concrete with standard curing and exceeds Design grade. Its saturated water content is 1.50% and softening factor is 0.932. Its rapid carbonation depth is close to that of the concrete with standard curing and its microstructure of hydration products is preferable.

In vivo measurement of non-keratinized squamous epithelium using a spectroscopic microendoscope with multiple source-detector separations.

In the non-keratinized epithelia, dysplasia typically arises near the basement membrane and proliferates into the upper epithelial layers over time. We present a non-invasive, multimodal technique combining high-resolution fluorescence imaging and broadband sub-diffuse reflectance spectroscopy (sDRS) to monitor health at various tissue layers. This manuscript focuses on characterization of the sDRS modality, which contains two source-detector separations (SDSs) of 374 μm and 730 μm, so that it can be used to extract in vivo optical parameters from human oral mucosa at two tissue thicknesses. First, we present empirical lookup tables (LUTs) describing the relationship between reduced scattering (μs') and absorption coefficients (μa) and absolute reflectance. LUTS were shown to extract μs' and μa with accuracies of approximately 4% and 8%, respectively. We then present LUTs describing the relationship between μs', μa and sampling depth. Sampling depths range between 210-480 and 260-620 μm for the 374 and 730 μm SDSs, respectively. We then demonstrate the ability to extract in vivo μs', μa, hemoglobin concentration, bulk tissue oxygen saturation, scattering exponent, and sampling depth from the inner lip of thirteen healthy volunteers to elucidate the differences in the extracted optical parameters from each SDS (374 and 730 μm) within non-keratinized squamous epithelia.

Hydrogeophysical characterization of the porous and fractured media (chalk aquifer in the Beauvais, France)

This study is aimed to investigate the principal aquifer in the northern part of Paris (Beauvais region) which is materialized by the Senonian chalk deposits. This aquifer supplies water to the principal region in the north and in particular the Picardie and Artois region. In order to characterize the chalk aquifer of this area, a wide pluridisciplinary research program based on the well logging and near surface geophysics surveys (seismic refraction and electrical resistivity tomography) is in progress. These surveys were carried out within the experimental site of the LaSalle Beauvais Polytechnic Institute and its hydrogeological boreholes. The heterogeneous distribution of the seismic velocities in the complex aquifer and of the physico-chemical properties (conductivity, temperature and gamma-ray) of the chalk aquifer were revealed by the analysis and the interpretation of the seismic lines and data logging, which are linked to changes in lithology and water properties at the place of the hydrogeological wells. The fracturation investigation identified during this work makes it possible to consider the relationship between the degree of the fracturation and the variation of the hydrogeological parameters (hydraulic conductivity, porosity) and physico-chemical parameters (electrical conductivity and temperature). The interface between vadose and saturated zones was assessed by the measurement of the water conductivity, the variation of the average temperature and by the cuttings analysis in particular at the level of the capillary fringe of the chalk aquifer. The presence of the saturated depth is confirmed by the piezometric investigation. The interpretation of the well logging by using gamma-ray is consistent with the seismic and electrical analysis: the three principal layers are composed of silt and clay with cherts, soft chalk, as well as hard chalk.

Modeling of transient water table response to managed aquifer recharge: a lagoon in Muscat, Oman

Natural and anthropogenic conditions in the Gulf countries lead to substantial changes in groundwater (GW) dynamics. GW mound under a lagoon supplied by treated wastewater (TWW) from a municipal sewage treatment plant (STP) in Muscat, Oman, is studied using analytical and numerical modeling techniques. The water table mound in an unconfined aquifer, laterally bounded by the sea, receives recharge from a lagoon fed by a STP in a seasonally varying regime. The onset and duration of the filling period and, correspondingly, infiltration from the lagoon bed is dictated by the wastewater processing and TWW use. Following the period of recharge-induced growth, the GW mound decays when recharge ceases, and the void space above the water table becomes available for future injection in the next annual cycle of infiltration and TWW subsurface storage. The Green-Ampt model application illustrates that the first phase of the process (vertical infiltration with front propagating from the lagoon bed to the regional flat water table) is typically short (several hours). The second phase, when TWW gets in a direct hydraulic contact with GW, is the longest and with a mound spreading to hundreds of meters during winter months. No analytical solutions to this moving boundary-value problem are known and approximate models, based on the Boussinesq approximation and its linearizations, are utilized. The Hantush-type drawup of the water table in the vicinity of the lagoon is studied by the Watson analytical solution to the diffusion equation for a vertically averaged hydraulic head in an unbounded domain, with an instantaneous jump of the head over a disk-shaped zone. This drawup is compared with MODFLOW simulations, which take into account a finite size of the flow domain (catchment) and discharge into the sea through a constant-head segment. The Mishra-Guyonnet’s formula assumes a spatially uniform flux from the lagoon bed (disk in a model plain) into a growing mound and is used for calculation of the total discharge, which progressively decreases from the early stages of the Green-Ampt infiltration to a theoretically zero value if the second phase lasts indefinitely long. We assess characteristic times and phases of the mound dynamics during the rise and fall stages using regional hydrogeological parameters, site geometry, and typical patterns of wastewater disposal. Sensitivity analysis of the locus of the phreatic surface at a given instance and location is carried out, with storativity, hydraulic conductivity, undisturbed aquifer thickness and lagoon radius as input variables. For an example of an aquifer of saturated depth of 40 m, undisturbed vadose zone thickness of 10 m, saturated hydraulic conductivity of 10 m/day, effective porosity of 0.2, a circular lagoon size of 90 m and water depth there of 1 m we found that the infiltration front propagates to the water table in less than 0.2 days; after 40 days of a continuous mound growth in a hypothetical piezometer located 400 m from the lagoon the water table drawup was in the range of 2.0–2.7 m if the aquifer hydraulic parameters and lagoon size are varied 20 % from the average value. This approach will permit to plan more detailed site investigation, facilitate management decisions on the rate of water release to the lagoon, and foresee waterlogged areas.

An Integrated Methodology To Locate Oil Opportunities in Mature Reservoirs

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 18004, “An Integrated Methodology To Locate the Remaining-Oil Opportunities in Mature Reservoirs in Offshore Sarawak, Malaysia,” by M.J. Zulhaimi, W.M.S. Wan Ibrahim, S. Sanyal, K.A. Zamri, M.N. Mohamad, and K.N.M. Zaini, EORC; R.D. Tewari, Petronas; and A.K. Pradhan, ADCO, prepared for the 2014 International Petroleum Technology Conference, Kuala Lumpur, 10–12 December. The paper has not been peer reviewed. A matured field is currently producing with greater than 85% water cut (WC) and has significant levels of uncertainty with respect to oil/water contact (OWC), flank structure, depth of spill points, production allocation, and residual oil saturation. A robust work flow was developed to identify infill opportunities by integrating material-balance study, cased-hole-log information, water diagnostic plots, decline-curve analysis, and other information. The comprehensive locate-the-remaining-oil (LTRO) methodologies applied have been successful and have helped to estimate the potential reserves as well. Introduction The field is 20 km offshore Sarawak, Malaysia, in water depths of 100 ft. The field structure consists of a 30,000×9,000-ft elongated anticline running northeast/southwest and comprises a series of stacked reservoirs at a depth of 4,000 to 9,500 ft. The field is considered structurally simple, with a normal growth fault affecting only the deep reservoirs and no other faults visible on 2D seismic or in the wells. The field reservoirs were deposited during the Late Miocene in a lower coastal plain to the coastal environment. The depositional environment of this field is dominated by a sequence of shore-face deposits. Sands are loosely consolidated, fine- to very-fine-grained, and interbedded with layers of silts and clays. Porosity ranges from 14 to 26%, with a fieldwide mean of 20%. The permeabilities are on the order of 50 to 3,000 md. Net sand thicknesses are less than 30 ft, with most individual sands at approximately 10 ft. The reservoirs are subdivided into three categories: Shallow reservoirs at depths of 4,000 to 5,300 ft are characterized by large gas caps and mostly thin oil rims and are currently considered unfaulted. Main reservoirs at depths of 5,300 to 6,000 ft with no gas caps are also currently considered unfaulted. Deep reservoirs at depths of 6,000 to 9,500 ft can carry high pressures and are dissected by a northwestheaded growth fault with possible associated additional faulting.

Predicting Runoff Risks by Digital Soil Mapping

Digital soil mapping (DSM) permits continuous mapping soil types and properties through raster formats considering variation within soil class, in contrast to the traditional mapping that only considers spatial variation of soils at the boundaries of delineated polygons. The objective of this study was to compare the performance of SoLIM (Soil Land Inference Model) for two sets of environmental variables on digital mapping of saturated hydraulic conductivity and solum depth (A + B horizons) and to apply the best model on runoff risk evaluation. The study was done in the Posses watershed, MG, Brazil, and SoLIM was applied for the following sets of co-variables: 1) terrain attributes (AT): slope, plan curvature, elevation and topographic wetness index. 2) Geomorphons and terrain attributes (GEOM): slope, plan curvature, elevation and topographic wetness index combined with geomorphons. The most precise methodology was applied to predict runoff areas risk through the Wetness Index based on contribution area, solum depth, and saturated hydraulic conductivity. GEOM was the best set of co-variables for both properties, so this was the DSM model used to predict the runoff risk. The runoff risk showed that the critical months are from November to March. The new way to classify the landscape to use on DSM was demonstrated to be an efficient tool with which to model process that occurs on watersheds and can be used to forecast the runoff risk.

Climatic modulation of recent trends in ocean acidification in the California Current System

We reconstruct the evolution of ocean acidification in the California Current System (CalCS) from 1979 through 2012 using hindcast simulations with an eddy-resolving ocean biogeochemical model forced with observation-based variations of wind and fluxes of heat and freshwater. We find that domain-wide pH and in the top 60 m of the water column decreased significantly over these three decades by about −0.02 decade−1 and −0.12 decade−1, respectively. In the nearshore areas of northern California and Oregon, ocean acidification is reconstructed to have progressed much more rapidly, with rates up to 30% higher than the domain-wide trends. Furthermore, ocean acidification penetrated substantially into the thermocline, causing a significant domain-wide shoaling of the aragonite saturation depth of on average −33 m decade−1 and up to −50 m decade−1 in the nearshore area of northern California. This resulted in a coast-wide increase in nearly undersaturated waters and the appearance of waters with , leading to a substantial reduction of habitat suitability.Averaged over the whole domain, the main driver of these trends is the oceanic uptake of anthropogenic CO2 from the atmosphere. However, recent changes in the climatic forcing have substantially modulated these trends regionally. This is particularly evident in the nearshore regions, where the total trends in pH are up to 50% larger and trends in and in the aragonite saturation depth are even twice to three times larger than the purely atmospheric CO2-driven trends. This modulation in the nearshore regions is a result of the recent marked increase in alongshore wind stress, which brought elevated levels of dissolved inorganic carbon to the surface via upwelling. Our results demonstrate that changes in the climatic forcing need to be taken into consideration in future projections of the progression of ocean acidification in coastal upwelling regions.

Deep-water carbonate dissolution in the northern South China Sea during Marine Isotope Stage 3

The production, transportation, deposition, and dissolution of carbonate profoundly form part of the global carbon cycle and affect the amount and distribution of dissolved inorganic carbon (DIC) and alkalinity (ALK), which drive atmospheric CO2 changes during glacial/interglacial cycles. These processes may provide significant clues for better understanding of the mechanisms that control the global climate system. In this study, we calculate and analyze the foraminiferal dissolution index (FDX) and the fragmentation ratios of planktonic foraminifera for the 60–25 ka B.P. time-span, based on samples from Core 17924 and ODP Site 1144 in the northeastern South China Sea (SCS), so as to reconstruct the deep-water carbonate dissolution during Marine Isotope Stage 3 (MIS 3). Our analysis shows that the dissolution of carbonate increases gradually in Core 17924, whereas it remains stable at ODP Site 1144. This difference is caused by the deep-sea carbonate ion concentration ([CO32−]) that affected the dissolution in Core 17924 where the depth of 3440 m is below the saturation horizon. However, the depth of ODP Site 1144 is 2037 m, which is above the lysocline where the water is always saturated with calcium carbonate; the dissolution is therefore less dependent of chemical changes of the seawater. The combined effect of the productivity and the deep-water chemical evolution may decrease deep-water [CO32−] and accelerate carbonate dissolution. The fall of the sea-level increased the input of DIC and ALK to the deep ocean and deepened the carbonate saturation depth, which caused an increase of the deep-water [CO32−]. The elevated [CO32−] partially neutralized the reduced [CO32−] contributed by remineralization of organic matter and slowdown of thermohaline. These consequently are the fundamental reasons for the difference in dissolution rate between these two sites.

Effect of fibrous coalescer redispersion on W/O emulsion separation

Emulsion separation through fibrous media is a popular and complex process, and certain factors significantly affect the separation performance. This research investigates the influence of inlet droplet size distribution and redispersion on quantitative separation efficiency. The gravity settling method was developed to analyze the water droplet size distribution, and a novel grade efficiency curve was used to demonstrate the impact of redispersion. In addition, other critical factors, including specific surface area, bed permeability, degree of saturation, superficial velocity and bed depth were investigated. The results are useful for elucidating emulsion transport in fibrous media and identifying the optimum media and operating conditions.

Verification of Compton scattering spectrum of a 662 keV photon beam scattered on a cylindrical steel target using MCNP5 code

This article focuses on the possible application of a 137Cs low-radioactive source (5mCi) and a NaI(Tl) detector for measuring the saturation thickness of solid cylindrical steel targets. In order to increase the reliability of the obtained experimental results and to verify the detector response function of Compton scattering spectrum, simulation using Monte Carlo N-particle (MCNP5) code is performed. The obtained results are in good agreement with the response functions of the simulation scattering and experimental scattering spectra. On the basis of such spectra, the saturation depth of a steel cylinder is determined by experiment and simulation at about 27mm using gamma energy of 662keV (137Cs) at a scattering angle of 120°. This study aims at measuring the diameter of solid cylindrical objects by gamma-scattering technique.

A GEOTECHNICAL-HYDROLOGICAL APPROACH FOR DEFINING CRITICAL RAINFALL-INDUCED SHALLOW LANDSLIDES AND WARNING SYSTEM AT LARGE SCALE

This study proposes a novel method that combines deterministic slope stability model and hydrological approach for predicting critical rainfall-induced shallow landslides. The method first uses the slope stability model to identify “where” slope instability will occur potentially; the catchment is characterized into stability classes according to critical soil saturation index. The critical saturated soil index is calculated from local topographic components and soil attributes. Then, spatial distribution of critical rainfall is determined based on a hydrological approach under near-steady state condition as a function of local critical saturated soil depth, slope geometric, and upstream contributing drainage areas. The critical rainfall mapping is bounded by theoretically “always stable” and “always unstable” areas. To show how the method works, observed landslides (1985-2008) and a satellite-based rainfall estimates associated with a past new shallow landslide in the Upper Citarum River catchment (Indonesia) were used to validate the model. The proposed study is useful for rainfall triggered shallow landslide disaster warning at large catchment scale.
 
 Keywords: Critical rainfall, slope stability, hydrology, shallow landslide, Citarum River catchment

Experimental and Modeling Study of Solvent Diffusion in PDMS for Nanoparticle-Polymer Cosuspension Imprint Lithography.

This study is the first that focuses on solvent migration in a polydimethylsiloxane (PDMS) stamp during the imprint lithography of ZnO-poly(methyl methacrylate) (PMMA) hybrid suspensions. Using suspensions with varying solids loading levels and ZnO/PMMA ratios, the uptake of the anisole solvent in the stamp is evaluated as a function of time. Laser confocal microscopy is employed as a unique technique to measure the penetration depth of the solvent into the stamp. The suspension solids loading affects the anisole saturation depth in the PDMS stamp. For the suspensions with low solids loading, the experimental data agree with the model for non-Fickian diffusion through a rubbery-elastic polymer. For the suspensions with high solids loading, the data agree more with a sigmoidal diffusion curve, reflecting the rubbery-viscous behavior of a swelling polymer. This difference is due to the degree of swelling in the PDMS. Higher solids loadings induce more swelling because the rate of anisole diffusing into the stamp is increased, likely due to the less dense buildup of the solids as the suspension dries.