Sealed End Research Articles

Effect of various configurations of swirl generator system on the hydrothermal performance of the flat-plate solar collector

This is a numerical study that analysis the heat extraction potential of solar collector tubes by assembling a couple of nozzles at the sealed end of the pipe to make swirl flow. Swirl flow intensifies the turbulence rate which augments heat transfer by ruffling the boundary layer. To this end, several decisive factors including nozzle angle (A: 30°, 45°, 60°, 90°), tube diameter (D: 20 mm, 50 mm), nozzle edge size (N: 6.25, 12.5, 25 mm (for D50) and N: 2.5, 5, 10 mm (for D20)), and mass flow rate (M: 0.1, 0.5, 1 kg/s (for D50) and M: 0.04, 0.2, 0.4 kg/s (for D20)) were considered. Results demonstrated that all of the models of class ''A…/D20/N…/M…“ had higher heat extraction potential but lower friction factor compared with ”A…/D50/N…/M…“. Maximum and minimum values of heat flux extractions are 2113390 W/m2 and 59239 W/m2 that were obtained by ”A60/D20/N2.5/M0.4″ and “A30/D50/N25/M0.1″. The created friction factor by class ”A…/D50/N…/M…“ is higher than class ''A…/D20/N…/M…”. The highest friction factor is 3.51 (''A90/D20/N2.5/M0.04″) and the lowest friction factor is 0.019 (“A30/D20/N2.5/M0.2″). Overall, for all cases, class ”A…/D50/N…/M…“ bear the higher TPF compared with class ”A…/D50/N…/M…“ so that the greatest and lowest values of TPF are 5.09 and 0.49 achieved by ”A30/D50/N6.25/M1″ and “A90/D20/N5/M0.4″, respectively.

Investigation of oversized channels in tubular fibre drawing

In a previous study, we compared experiments on drawing of axisymmetric tubular optical fibres to a mathematical model of this process. The model and experiments generally agreed closely. However, for some preforms and operational conditions, the internal channel of the drawn fibre was larger than predicted by the model. We have further investigated this phenomenon of an oversized channel with to determine the mechanism behind the size discrepancy. In particular we have explored the possibility of channel expansion similar to ‘self-pressurisation’ in fibres drawn from preforms that have been first sealed to the atmosphere, as previously described by Voyce et al. [J. Lightwave Technol. 27, 871 (2009) 10.1109/JLT.2007.916489]. For this, two pieces from each of two preforms with different inner to outer diameter ratios were drawn to fibre, one open to the atmosphere and the other with a sealed end. In addition, we have sectioned a cooled neck-down region from a previous experiment, for which the fibre had an oversized channel compared to the model prediction, and measured the cross-sectional slices. We here compare this new experimental data with the predictions of the previously derived model for drawing of an unsealed preform and a new model, developed herein, for drawing of a sealed tube. We establish that the observed oversized channels are not consistent with the self-pressurisation model for the sealed tube.

Optimum research on the temperature of the ship stern-shaft mechanical seal end faces based on finite element coupled analysis

Abstract Due to the complicated working conditions of the ship stern-shaft mechanical seals, it is very difficult to evaluate and optimize the temperature on the sealed end faces. In the paper, one FEA model of the small taper convergent stern-shaft mechanical seals was put forward, and the nonlinear end-face liquid film pressure distribution was derived from different end-face gaps based on the simplified Reynolds equation as the end-face input parameters in FEA model. To prove the correction of the FEA results, one experiment was designed and completed. At the same time, combined with a parametrically coupled FEA model and an orthogonal experimental design, one PSO-BP-GA method based on the combination of particle swarm optimization (PSO), BP neural network and genetic algorithm (GA) was proposed to optimize the temperature of the sealed end faces. The results show that aiming at the prediction accuracy of the temperature on the sealed end faces, the PSO-BP algorithm is higher than BP algorithm and GA-BP algorithm, which error interval is shortened about 40% and 29%, respectively. Subsequently, PSO-BP-GA algorithm is obviously better than BP-GA algorithm and GA-BP-GA algorithm, which validates its effectiveness and feasibility. It will help to lay a theoretical foundation for temperature evaluation on the sealed end faces.

Saccharomyces cerevisiae and S. pastorianus species and strain differentiation by direct analysis in real time time-of-flight mass spectrometry.

Seventeen different dried yeast strains, including twelve strains of Saccharomyces cerevisiae and five strains of S. pastorianus, were analyzed using direct analysis in real time (DART) time-of-flight mass spectrometry. The resulting mass spectra were used for rapid species and strain differentiation based upon small-molecule metabolomic profiles. Yeast strains purchased from local shops were suspended in a 1:1 water-methanol solution. Solutions were sampled by dipping the sealed end of a melting point capillary into each vial. Six replicates were measured in positive-ion and negative-ion mode for each strain using an automated linear rail with the DART source operated with helium gas and a gas heater temperature of 350°C. Averaged and centroided mass spectra were exported for analysis with chemometric software. Negative-ion DART mass spectra exhibited less chemical background and more distinctive components than positive-ion DART mass spectra. An on-line search of the Yeast Metabolome Database provided candidate metabolites for selection as features for chemometric analysis. Negative-ion DART mass spectra could distinguish both species and all strains. The DART analysis was also able to identify potential metabolomic differences between top-fermenting and bottom-fermenting yeast, between beer and baking yeast, and between red wine and champagne yeast. All strains could be distinguished by their negative-ion DART mass spectra with 97.7% validation accuracy. Clear differences were observed between dry and liquid forms and Saccharomyces strains with different applications to baking or beverage fermentation. Possible differences in metabolite profiles were suggested, but not confirmed, by accurate mass data.

High-fidelity Numerical Study on Air-tightness Detection System of Medicine Box

Planning an automatic detection system of the air tightness of medicine box is very necessary for growing demand for storage of pharmaceutical products. In this study, the high-fidelity CFD study is performed for the air tightness of the medicine box, using the LBM algorithm. The high-fidelity results indicate that after about 5.24 s, the stable value of the average static pressure of the ring cavity remains at about -9414 Pa. The slit flow in the early stage of micro-leakage is very complicated, especially for the initial stage. The location of the micro-leakage is concentrated in the directions of 1 o’clock, 4 o’clock, 7 o’clock and 11 o’clock along such edge of the end cap, therefore, the sealed end cover needs to be further improved. Additionally, the idea of this research work can provide a good basis and reference for the subsequent series of related airtightness studies.

Design and experimental investigation on a solar concentrating photovoltaic underwater

This paper presents a special concentrating photovoltaic that works underwater. A tri-junction GaAs solar cell and a deformable concentrator which is specially designed to converge sunlight underwater are applied to it. The concentrator is composed of a transparent membrane and a hollow cylinder with one sealed transparent end. When the membrane is perfectly cover onto the other end of the cylinder and put into water, the membrane will deform as a spherical lens due to the water pressure. A concentrator model with membrane radius of 100 mm is investigated. The effects of membrane’s deformation ratio α and length of the cylinder t on its optical characteristics were analyzed via the theoretical and simulative methods. The theoretical result indicates that f varies from about 4 m to 0.45 m when α rises from 0.05 to 0.45. The optical simulation shows that a small t is beneficial to concentrate the energy density on the focus. Finally, testing platform with a solar cell of 20∗20 mm was set up. The results illustrate that the maximum output power and efficiency can be obtained about 2 W and 15% when α is 0.3 during the normal incidence. The increase of water depth and turbidity will obviously reduce the PV efficiency.

Experiment and simulation study on convective heat transfer of all-glass evacuated tube solar collector

Solar collector with horizontal double-row all-glass evacuated tubes has been extensively implemented in the solar water heating system engineering. The temperature distribution and stratification of horizontal double-row all-glass evacuated tube collector with 24 evacuated tubes have been studied. Validation of instantaneous efficiency under different declination angle θm were studied by means of experiments. Moreover, numerical simulations are carried out for four different declination angle θm (0°/2°/4°/6°). The results showed that the declination angle θm has significant effect on energy conversion efficiency, flow patterns and stratification inside evacuated tubes. When θm > 0, with the declination angle increased, the instantaneous efficiency also increased, nevertheless, the temperature stratification weakened and the heat loss coefficient demonstrated no significant change. Declination angle 6° allowed to achieve significant higher temperatures, nevertheless, along with inactive area at the bottom of evacuated tubes appears. If declination angle θm < 0, inversion phenomenon appears. With the increase of |θm|, more heat is trapped in the sealed end of the evacuated tube, which is not conducive to the flow heat transfer in evacuated tube solar collector.

Đặc điểm dinh dưỡng của cá sửu Nibea soldado (Lacepède, 1802)

A study on the nutritional characteristics of Soldier croaker Nibea soldado (Lacepède, 1802) was conducted from January to June 2019 in coastal areas from Soc Trang to Ca Mau provinces. Fish samples were collected monthly by trawl-net (engine capacity of 70 CV) with two groups of sizes such as juvenile (total length of 114-170 mm- small fish) and adults (total length of 209-370 mm- big fish). The results showed that the fish have wide mouth, long mouth and slanting; the jaw is very developed; gill rakers were sparse, short and hard to hold feed; esophagus was short, thick wall, with many folds; stomach was greatly expanded with the posterior portion, forming as a long sac, thick wall and many folds inside; caeca has 8-9 tubes with a sealed end attached to between the stomach and intestines; intestine was short, thick wall and folded in S-shape. Relative length of the gut (RLG)

Drainage flow of a viscous compressible fluid from a small capillary with a sealed end

Volumetric expansion driven drainage flow of a viscous compressible fluid from a small capillary with a sealed end is studied in the low Mach number limit using the linearized compressible Navier–Stokes equations with no-slip condition. Density relaxation, oscillation and decay as well as the velocity field are investigated in detail. It is shown that fluid drainage is controlled by the slow decay of the standing acoustic wave inside the capillary; and the acoustic wave retards the density diffusion by reducing the diffusion coefficient of the density envelope equation by one half. Remarkably the no-slip flow exhibits a slip-like mass flow rate. The period-averaged mass flow rate at the exit (drainage rate) is found proportional to the fluid’s kinematic viscosity via the density diffusion coefficient and the average drainage speed is independent of the capillary radius. These findings are valid for arbitrarily small capillaries as long as the continuum assumption holds and they are in stark contrast to the classical lubrication based theory. Generalization to a capillary with a sound absorbing end is achieved by a simple model. The reported results offer new insights to the nature of slow viscous compressible flows in very small capillaries.

Mass Transfer and Fluid Hydrodynamics in Sealed End Hydrophobic Hollow Fiber Membrane Gas-liquid Contactors

Hollow fiber membrane modules have been extensively used as gas-liquid contactor devices to provide a high surface area within a small volume. Hollow fiber membrane contactors have been demonstrated in a wide range of application such as in gas stripping and gas absorption. In this study the performance of sealed end hydrophobic microporous hollow fiber membranes contactors were evaluated to remove dissolved oxygen from water via vacuum degassing process. Hollow fibers membranes used in the experiment were hydrophobic microporous polypropylene of 650 μm in outer diameter, 130 μm wall thickness and nominal pore size of 0.2 μm. Based on the experimentalresult the sealed end membrane contactor can remove oxygen from water as high as 3.4-gram oxygen per square meter of membrane area per hour. The oxygen flux decreases with increasing module-packing density for the same water velocity. The same effect also occurred for the mass transfer coefficient of the membrane contactors. The mass transfer coefficients were independent of fiber length within the range of study. Hydrodynamics analysis of the contactors showed that at the same Reynolds number pressure drops increase with increasing packing density due to an increase in friction between fibers and water.

Experimental study in pulmonary artery sealing with a vessel-sealing device.

The development of vessel-sealing devices will facilitate safety in video-assisted thoracoscopic surgery. Our objective was to evaluate the feasibility and safety of sealing pulmonary arteries with the Enseal tissue-sealing device. Pulmonary arteries from beagle dogs (mean body weight 13.1 kg, range 10.5-15.4 kg) were divided into 3 groups according to the in-vivo sealing method used (Enseal, ligation, and proximal ligation plus distal Enseal) and extracted to evaluate the pressure tolerance up to 75 mm Hg at the sealed end. A left lower lobectomy was performed to evaluate chronic-phase durability of the sealed stumps in a survival model. Two or three branches of the pulmonary arteries in each dog were allocated to each of the 3 groups. After the scheduled survival period, the pulmonary arteries were sampled. Pressure tolerance at the sealed end was evaluated in 91 pulmonary artery sections. All sealed ends showed pressure tolerance >75 mm Hg. A left lower lobectomy was performed in 13 dogs in which 35 pulmonary artery sections had been allocated into the 3 groups. No sealing failure was found, and pathological findings showed healing and persistent hemostasis at all sealed ends of the pulmonary arteries after 2 and 4 weeks of the survival period. Pulmonary arteries sealed invivo with the Enseal device showed pressure tolerance >75 mm Hg in the acute phase, and persistent hemostasis after 2 or 4 weeks. Pulmonary artery sealing with the Enseal device is feasible and safe in thoracic surgery settings.

Dopant-assisted direct analysis in real time mass spectrometry with argon gas.

Dopants used with Atmospheric Pressure Photoionization (APPI) were examined with the Direct Analysis in Real Time (DART® ) ion source operated with argon gas. Charge-exchange and proton transfer reactions were observed by adding toluene, anisole, chlorobenzene and acetone to the DART gas stream, complementing the information obtained by helium DART. Mass spectra were acquired with a time-of-flight mass spectrometer equipped with a DART ion source operated with argon gas. A syringe pump was used to introduce dopants directly into the DART gas stream through deactivated fused-silica capillary tubing. Samples including polycyclic aromatic hydrocarbons (PAHs), diesel fuel, trinitrotoluene and cannabinoids were deposited onto the sealed end of melting tube, allowed to dry, and the tube was then suspended in the dopant-enhanced DART gas stream. PAHs could be detected as molecular ions at concentrations in the low parts-per-billion range by using a solution of 0.5% anisole in toluene as a dopant. Argon DART analysis of a diesel fuel sample with the same dopant mixture showed a simpler mass spectrum than obtained by using helium DART. The argon DART mass spectrum was dominated by molecular ions for aromatic compounds, whereas the helium DART mass spectrum showed both molecular ions and protonated molecules. In contrast O2- attachment DART showed saturated hydrocarbons and oxygen-containing species. Mass spectra for trinitrotoluene with argon DART in negative-ion mode showed a prominent [M - H]- peak, whereas conventional helium DART showed both M- and [M - H]- . Lastly, in analogy to a report in the literature using APPI, positive ions produced by argon DART ionization for delta-9-tetrahydrocannabinol (THC) and cannabidiol showed distinctive product-ion mass spectra. Dopant-assisted argon DART operates by a mechanism that is analogous to those proposed for dopant-assisted atmospheric-pressure photoionization. Copyright © 2016 John Wiley & Sons, Ltd.

Alternative mass reference standards for direct analysis in real time mass spectrometry.

Mass spectra were acquired with the Direct Analysis in Real Time (DART®) ion source for an amine-terminated polyether used as positive-ion mass reference standards and for several fluorinated materials commonly used as negative-ion reference standards for mass spectrometry. A commercial time-of-flight mass spectrometer equipped with a DART ion source was used for all measurements. Mass reference standards deposited onto the sealed end of a glass melting point tube were suspended in the DART gas stream for analysis. A polyetheramine (Jeffamine® M-600) produced intense peaks corresponding to protonated molecules. Perfluorotributylamine (PFTBA), and perfluorotripentylamine, gave useful reference spectra for different m/z ranges. DART mass spectra of Ultramark 1621® resembled those previously reported for Fast Atom Bombardment (FAB) and Electrospray Ionization (ESI). Fomblin®Y, a fluorinated ether, was the most useful negative-ion reference standard of the materials tested. The material is commercially available, inexpensive, and provides reference peaks covering the m/z range 85 to >3000. Jeffamine-M600 was found to be a convenient alternative to polyethers such as polyethylene glycol (PEG) for DART positive-ion mass calibration. Fomblin Y was suitable for use as a negative-ion reference standard. Copyright © 2016 John Wiley & Sons, Ltd.

A Novel Membrane Process for Autotrophic Denitrification

Biological denitrification by heterotrophic bacteria is common in the wastewater industry in the U.S. and in drinking water processing in Europe.To facilitate heterotrophic denitrification, organic compounds such as methanol, ethanol and acetic acid are added to provide a carbon source for the bacteria. The resulting organic carbon residual may create problems with chlorination. The addition of these carbon compounds is expensive and results in added sludge production. This study focused on the use of autotrophic hydrogen oxidizing bacteria for denitrification. The method transfers hydrogen gas to solution via microporous hollow fiber membranes. Typically, gases are supplied to a system using conventional bubble diffusers. The conventional bubble aeration system has a low gas transfer efficiency, and, as a result, the cost of dissolving the required amount of gas is very high. In this study, microporous hollow fiber membranes were employed to supply hydrogen gas to hydrogen oxidizing autotrophic bacteria. Laboratory scale membrane modules were constructed and mass transfer studies were carried out to develop the design correlations for hydrogen gas transfer. A mixed culture was obtained and acclimated for batch denitrification studies. Both Sodium carbonate and carbon dioxide were used to deliver inorganic carbon. Bench scale continuous flow biofilm reactors containing plastic media were operated to remove nitrate from water. The required hydrogen gas was supplied at a constant rate via gas transfer modules, containing sealed end microporous hollow fiber membranes. The reactors were optimized for removal of nitrate and nitrite by varying the recycle ratios and hydraulic detention time. Experimental results indicated the presence of hydrogen oxidizing denitrifiers in wastewater sludge. Adequate pH control was possible and the pH averaged around 6.95. Gas transfer studies indicated that hydrogen transfer was primarily controlled by liquid film diffusion. Hydrogen gas was successfully delivered to the reactor via the hollow fiber membrane gas transfer module. Nitrate and hydrogen concentration measurements indicated that the system did not experience hydrogen limitations at detention times of 3.25 hours or greater. The use of hollow fiber membrane module appears to be a viable technology for transferring hydrogen gas to water. The research results in this report provide valuable information for pilot and full-scale studies for the water/wastewater community focusing on membrane processes for autotrophic denitrification. This title belongs to WERF Research Report Series ISBN: 9781843396437 (Print) ISBN: 9781780403229 (eBook)

Su2041 A Novel Dual-View Probe That Produces a Single Image and Improves Polyp Detection

Background: Colonoscopy is the procedure of choice for colon cancer screening, but is far from perfect, as lesions are missed due to lack of image contrast and due to their location behind haustral folds and at flexures. We have developed a novel dual-view optical probe that illuminates and images in the forward and omni-directional rear directions to provide a single registered video image. Objective: Evaluate the prototype dual-view probe in a standard colon model. Design: A colon model (Chamberlain Group, MA) was used for the study. Due to the stiffness of the model and the difficulty in advancing a colonoscope through it, the colon was cut into 3 sections (ascending, transverse, and descending colon) and the ends sealed to prevent leakage of light. A total of 31 red spheres and discs (to represent polyps and flat lesions) were glued to the inner surface of the model; approximately half were located in easily visible areas between folds, whereas the rest were placed in difficult to see locations proximal to folds. A research fellow advanced a standard colonoscope (Fujinon EC530-HL, Fujifilm, Wayne, NJ) with 140 degree forward view to the sealed end of each segment. The image was shown on a standard flat panel display. Each endoscopist (2 attendings, 2 fellows) examined the three colon segments with the room lights darkened. Polyps detected were called out by the endoscopist and recorded by research staff. The dual-view probe was subsequently attached to the tip of the colonoscope and the procedure repeated by each endoscopist 14 days later (so that location of polyps could not be recalled) using the dual-view probe's own light source and image display Results: Out of a total of 31 lesions a mean of 18.8 ± 2.2 lesions were visualized using standard forward-viewing colonoscope, whereas 29.3 ± 1.3 (an increase of 56%) were detected with the dual-view probe (p< 0.005, t-test). Limitations: Commercially available models made maneuverability of the colonoscope and probe difficult, necessitating the model to be cut into 3 segments. The size of this first proof of concept dual-view prototype is too large to be passed through the biopsy channel of a colonoscope and its attachment to the tip of the endoscope further limited flexion of the scope tip. Conclusions: The novel proof of concept dual-view probe is the first optical device to display both a forward and 360-degree rear-view image in the vertical plane in a single registered display. A single display allows both the forward and rear images to be viewed with ease. Imaging with the dual-view probe substantially improved polyp detection, particularly those located behind haustral folds. Ongoing work to reduce the size of the dual-view probe will allow it to be passed through a standard colonoscope for testing in patients.

Su2042 Corticotropin-Releasing Factor Changes the Phenotype and Function of Mouse Mesenteric Lymph Nodes Dendritic Cells (MLNDCs)

Background: Colonoscopy is the procedure of choice for colon cancer screening, but is far from perfect, as lesions are missed due to lack of image contrast and due to their location behind haustral folds and at flexures. We have developed a novel dual-view optical probe that illuminates and images in the forward and omni-directional rear directions to provide a single registered video image. Objective: Evaluate the prototype dual-view probe in a standard colon model. Design: A colon model (Chamberlain Group, MA) was used for the study. Due to the stiffness of the model and the difficulty in advancing a colonoscope through it, the colon was cut into 3 sections (ascending, transverse, and descending colon) and the ends sealed to prevent leakage of light. A total of 31 red spheres and discs (to represent polyps and flat lesions) were glued to the inner surface of the model; approximately half were located in easily visible areas between folds, whereas the rest were placed in difficult to see locations proximal to folds. A research fellow advanced a standard colonoscope (Fujinon EC530-HL, Fujifilm, Wayne, NJ) with 140 degree forward view to the sealed end of each segment. The image was shown on a standard flat panel display. Each endoscopist (2 attendings, 2 fellows) examined the three colon segments with the room lights darkened. Polyps detected were called out by the endoscopist and recorded by research staff. The dual-view probe was subsequently attached to the tip of the colonoscope and the procedure repeated by each endoscopist 14 days later (so that location of polyps could not be recalled) using the dual-view probe's own light source and image display Results: Out of a total of 31 lesions a mean of 18.8 ± 2.2 lesions were visualized using standard forward-viewing colonoscope, whereas 29.3 ± 1.3 (an increase of 56%) were detected with the dual-view probe (p< 0.005, t-test). Limitations: Commercially available models made maneuverability of the colonoscope and probe difficult, necessitating the model to be cut into 3 segments. The size of this first proof of concept dual-view prototype is too large to be passed through the biopsy channel of a colonoscope and its attachment to the tip of the endoscope further limited flexion of the scope tip. Conclusions: The novel proof of concept dual-view probe is the first optical device to display both a forward and 360-degree rear-view image in the vertical plane in a single registered display. A single display allows both the forward and rear images to be viewed with ease. Imaging with the dual-view probe substantially improved polyp detection, particularly those located behind haustral folds. Ongoing work to reduce the size of the dual-view probe will allow it to be passed through a standard colonoscope for testing in patients.

Oscillatory instability of the gas–liquid meniscus in a capillary under the imposed temperature difference

To understand the oscillations in the real, multi-branch pulsating heat pipe (PHP), the start-up conditions of the single branch PHP with no adiabatic section are studied theoretically and numerically. The single branch PHP is a capillary open from one end, which is connected to a reservoir at constant pressure. A gas bubble is confined between the sealed end of the capillary and the liquid. The gas is the vapor of the liquid. The gas end of the capillary is maintained at a constant temperature larger than that of the liquid end. Under certain conditions, self-sustained oscillations of the meniscus may exist in such a system. The conditions of oscillation development (i.e. of the PHP startup) are obtained via the stability analysis of an earlier proposed theoretical model. The linear instability is absent in such a system. The instability of a marginal state described by piece-wise linear equations is analyzed with the analytical averaging method. The instability boundary is presented in terms of dimensionless groups, the physical significance of which is discussed. It is found that the model describes correctly the known experimental facts. Some predictions concerning the instability threshold are formulated.

On the time dependence of countercurrent capillary imbibition

One-dimensional countercurrent capillary imbibition of the wetting phase (water) into a semibounded porous medium is considered. On a grid model for a sandstone sample the saturation and pressure profiles in the phases, as well as the change with time in the volume of the displaced nonwetting phase (oil) have been cal- culated. It has been shown that the self-similar dependence of the imbibition volume remains for some time after the imbibition front reaches the sealed end of the sample. At the end of this period the saturation profile has a form characteristic of the profile with a saturation jump in the case of the limiting initial saturation of the sample. Taking this fact into account, we propose the time dependence of the volume of displaced oil for the final period of imbibition. Introduction. The investigation of the process of spontaneous countercurrent capillary imbibition (SCCI) is of interest for elucidating the mechanism of oil displacement by water in recovering oil from cracked collectors. Because of the nonlinear process of oil replacement with water, usually one-dimensional imbibition into a semibounded porous medium (sample) is considered. In this case, two imbibition periods stand out: a long self-similar period lasting up to the moment the imbibition front reaches the sealed end of the sample and the followong non-self-similar period char- acterized by an increase in the water saturation throughout the sample. For the self-similar period, in (1-4) SCCI solutions were obtained under various constraints imposed on the relative phase permeabilities. Approximate solutions are presented in (5, 6). In (7), an exact SCCI solution constructed with the use of the notion of the rate of motion of saturation is given. The self-similar regime is characterized by the following time dependence of the imbibition inflow: q w 1 ⁄ √t . However, if we take into account the presence of the final rate of motion of saturation, such a dependence will also hold for some time after the imbibition front contacts the sealed end. For the non-self-similar regime, in (1) the dependence q w exp (−c(t − t I )) was obtained. In this case, the quadratic approximation of the saturation profile along the sample length was used. However, even the general view of the saturation profile at the beginning of this period does not comply with this approximation. To solve the above SCCI problem, in the present work the method of numerical simulation is used. Grid Model. The equations for describing the SCCI process are given in (7). The filtration flow of water q w in the sample is defined as

Transmission properties of the one-end-sealed metal–insulator–metal waveguide

The transmission properties of the one-end-sealed (OES) metal–insulator–metal (MIM) waveguide are investigated by the finite difference time domain method. The results show that the OES MIM waveguide shows a filter-like behavior. The pass bands and stop bands in the transmission spectra are resulted from the superposition of the electromagnetic fields of the surface plasmon polaritons (SPPs) reflected at the sealed end and those of the SPPs propagating towards the open end. In addition, the effects of the structural parameters of the OES MIM waveguide on the transmission properties are also studied.

A new collector for in situ pore water sampling in wetland sediment

Currently available pore water samplers generally do not allow continuous monitoring of temporal variations in pore water composition. Therefore, a new type of pore water collector was designed and constructed. These collectors were constructed of polyvinyl chloride (PVC) materials, including PVC tubing with one end sealed and another end topped with a removable PVC screw-cap. A row of holes was drilled 10 cm from the sealed end of each collector. These new collectors were deployed in different layers of the sediment in a constructed wetland in Lake Taihu, China, to reveal variations in the nutrient composition of pore water with high spatial and temporal resolution. Specifically, the collectors were driven into the sediment, and the pore water flowed into the tubing via gravity. The pore water was then sampled from the PVC tubing using a portable vacuum pump, and then was taken to the lab within 20 min for analysis of the dissolved oxygen (DO) and nutrient concentration. The DO concentration of the pore water was below the detection limit for all samples, indicating that the pore water was probably not influenced by the air and that the water in the collector tube was representative of the pore water. These findings suggest that the collector is capable of measuring the temporal and spatial variations in the nutrient concentrations in pore water. Furthermore, the inexpensive material, ease of construction, minimal disturbance to the sediment and applicability for wetland sediments are advantages of the collector presented here compared with traditional pore water sampling techniques.