Novel anion exchange membranes having fluorocarbon backbone: Preparation and stability

Anion exchange membranes with excellent durability were prepared by chemical modification of Nafion. The modification was achieved by transformation of the sulfonic acid group into quaternary ammonium group. Namely, Nafion membrane was first converted into an amide-type membrane. Reduction of the carbonxyl group to methylene followed by quaternarization with alkyl iodide resulted in the formation of an anion exchange membrane. The electric resistance of the resulting membranes depends on the equivalent weight of the starting membranes (4.4–6.0 Ω cm² in 0.5N NaCl). The characteristics of the membranes are the excellent stability toward chemical substances such as organic solvents, oxidizing agents, acids, etc. For example, the membranes are stable in aqueous saturated chlorine solution at 60°C for 1000 hr.     

Preparation of Pt-PtOx thin films as electrode for memory capacitors

Pt-PtO_x thin films were prepared on Si(100) substrates at temperatures from 30 to 700°C by reactive r.f. magnetron sputtering with platinum target. Deposition atmosphere was varied with O₂/Ar flow ratio. The deposited films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. Resistively of the deposited films was measured by d.c. four probe method. The films mainly consisted of amorphous PtO and Pt₃O₄ (or Pt₂O₃) below 400°C, and amorphous Pt was increased in the film as a deposition temperature increased to 600°C. When deposition temperature was thoroughly increased, (111) oriented pure Pt films were formed at 700°C. Compounds included in the films strongly depended on substrate temperature rather than O₂/Ar flow ratio. Electrical resistivity of Pt-PtO_x films was measured to be from the order of 10⁻¹ Ω cm to 10⁻⁵ Ω cm, which was related to the amount of Pt phase included in the deposited films.     

Variability in salt flux and water circulation in Ota River Estuary,Japan

In this study the sub-tidal and intra-tidal variations of salt fluxes in the upstream section of a shallow estuary (with a water depth of less than 3 m) were investigated. The salt fluxes were estimated based on the cross-sectional average salinity and velocity measured by the fluvial acoustic tomography system (FATS). The results indicate that the magnitude of seaward fluxes is approximately two times greater than that of landward fluxes under normal conditions. The results of short-term observation in the study area indicate that there is a phase lag of the bottom and surface salinities between the regions with the largest and smallest depths. The vertical shear flux with a peak value of ?0.7 m2/s during the ebb tide indicated an important contribution to the total salt flux compared with the advective flux. A phase lag occurred between the vertical shear terms in the regions with the largest and smallest depths, which resulted from the correlation between the vertical variations of the salinity and velocity and the existence of transversal velocity circulations.     

Turbulent Effects on the Settling Velocity of Suspended Sediment

The mean settling velocities of suspended sediments in turbulence have been examined. The settling velocities in a flume are directly measured by using an acoustic Doppler velocimeter. The results indicate the same trend as previous work in homogeneous isotropic turbulence. In addition to the flume experiment, the numerical experiments were conducted in the velocity field of homogeneous isotropic turbulence simulated by Kraichnan’s technique. The experimental and numerical results show that at high turbulence intensity the relative settling velocity increases with the increasing relative turbulence intensity regardless of the Stokes number. At intermediate turbulence intensity, it seems that the settling data bifurcate, i.e., the particles at the large Stokes number tend to be slowed, whereas the settling velocity of particles is increased at the small Stokes number.     

Investigation of stage-discharge model performance for streamflow estimating: A case study of the Gono River,Japan

In water resource studies, long-term measurements of river streamflow are essential. They allow us to observe trends and natural cycles and are prerequisites for hydraulic and hydrology models. This paper presents a new application of the stage-discharge rating curve model introduced by Maghrebi et al. (2016) to estimate continuous streamflow along the Gono River, Japan. The proposed method, named single stage-discharge (SSD) method, needs only one observed data to estimate the continuous streamflow. However, other similar methods require more than one observational data to fit the curve. The results of the discharge estimation by the SSD are compared with the improved fluvial acoustic tomography system (FATS), conventional rating curve (RC), and flow-area rating curve (FARC). Some statistical indicators, such as the coefficient of determination (R²), root mean square error (RMSE), percent bias (PBAIS), mean absolute error (MAE), and Kling-Gupta efficiency (KGE), are used to assess the performance of the proposed model. ADCP data are used as a benchmark for comparing four studied models. As a result of the comparison, the SSD method outperformed of FATS method. Also, the three studied RC methods were highly accurate at estimating streamflow if all observed data were used in calibration. However, if the observed data in calibration was reduced, the SSD method by R² = 0.99, RMSE = 2.83 (m³/s), PBIAS = 0.715(%), MAE = 2.30 (m³/s), and KGE = 0.972 showed the best performance compared to other methods. It can be summarized that the SSD method is the feasible method in the data-scarce region and delivers a strong potential for streamflow estimation.     

Monitoring Inflow Dynamics in a Multipurpose Dam Based on Travel-time Principle

Understanding inflow dynamics in a dam lake forms the basis for optimal dam operation and management practices. However, methods pertaining to adequately determining negative inflows and addressing them, as well as quantifying uncertainties in dam inflow, have been scarcely investigated. In this study, the inflow was observed using two pairs of fluvial acoustic tomography (FAT) systems placed diagonally in a dam lake, forming a crossed-shaped pattern. The “travel-time” principle is the primary approach for measuring the inflow by FAT. The novelty of this study is in discussing the inflow characteristics within a slow water-flow environment monitored by FAT. Based on the reciprocal sound transmission, we upgraded an equation to estimate the flow direction; this newly proposed generalized equation can be used in a fluctuating flow environment. We also discussed the sound propagation characteristics for slow flow velocities. Finally, we demonstrated that a small inaccuracy in the acoustic signal, even by a sub-millisecond, can cause significant errors in measurements. One of the novel findings of this study is the detection of internal waves using the improved flow direction equation and acoustic travel-time records. Overall, this study presents a promising approach for inflow measurements under extremely slow flow conditions.

     

A proposed method for the polarographic determination of Mo(IV) in the presence of glycolic,lactic or malic acid

It was found that the polarographic reduction of molybdate(VI) was possible in the presence of glycolic, lactic and malic acids in neutral borate-phosphate solution. The polarographic wave was precisely proportional to the concentration (<10^?2M) of molybdate, and hence the straight line was useful as a calibration curve in quantitative analysis of molybdate. It was suggested that a reducible species on a mercury electrode was molybdate complex produced through hydrogen (glycolic, lactic or malic acid)-oxygen (molybdate) bond.     

Incorporation of exogenous docosahexaenoic acid into various bacterial phospholipids

Incorporation of exogenous docosahexaenoic acid (DHA) into bacterial phospholipids was examined as a method for DHA-linked phospholipid production. The cultivation of 23 bacterial strains in medium with DHA showed that an eicosapentaenoic acid-producing bacteriumShewanella sp. strain SCRC-2738 (strain SCRC-2738),Bacillus subtilis W23,B. cereus, an Antarctic marine bacterium strain S-7 (strain S-7), photosynthesis bacterium (PSB)Rhodopseudomonas capsulatus utilized for the production of larval marine fish,Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens andEscherichia coli K12 all incorporated DHA into their polar lipids. The polar lipids of the strain SCRC-2738, strain S-7, PSB andE. coli K12 were identified to be phospholipids. DHA was localized at thesn-2 position in the phospholipids of the four strains. Incorporation of exogenous DHA into their phospholipids produced an increase in saturated fatty acids and a decrease in monounsaturated fatty acids exceptE. coli K12. The strain SCRC-2738 incorporated the largest amount of DHA into their phospholipids among the tested bacterial strains in this study: DHA was 16% of the total fatty acids in the phosphatidylethanolamine (PE) and 29% in the phosphatidylglycerol (PG). In the PSB, incorporated DHA was 12% of the total fatty acids in the PE, 10% in the PG and phosophatidylcholine so that the PSB was nutritionally fortified.     

New acoustic system for continuous measurement of river discharge and water temperature

In many cases,river discharge is indirectly estimated from water level or streamflow velocity near the water surface.However,these methods have limited applicability.In this study,an innovative system,the fluvial acoustic tomography system(FATS),was used for continuous discharge measurement.Transducers with a central frequency of 30 kHz were installed diagonally across the river.The system's significant functions include accurate measurement of the travel time of the transmission signal using a GPS clock and the attainment of a high signal-to-noise ratio as a result of modulation of the signal by the 10th order M-sequence.In addition,FATS is small and lightweight,and its power consumption is low.Operating in unsteady streamflow,FATS successfully measured the cross-sectional average velocity.The agreement between FATS and acoustic Doppler current profilers(ADCPs)on water discharge was satisfactory.Moreover,the temporal variation of the cross-sectional average temperature deduced from the sound speed of FATS was similar to that measured by a temperature sensor near the bank.     

Electrical conductivity of carbon-polymer composites as a function of carbon content

The electrical conductivity of carbon particle-filled polymers was measured as a function of carbon content to find a break point of the relationships between the carbon content and the conductivity. The conductivity jumps by as much as ten orders of magnitude at the break point. The critical carbon content corresponding to the break point varies depending on the polymer species and tends to increase with the increase in the surface tension of polymer. In order to explain the dependency of the critical carbon content on the polymer species, a simple equation was derived under some assumptions, the most important of which was that when the interfacial excess energy introduced by carbon particles into the polymer matrix reaches a universal value, g ^*, the carbon particles begin to coagulate so as to avoid any further increase of the energy and to form networks which facilitate electrical conduction. The equation well explains the dependency through surface tension, as long as the difference of the surface tensions between the carbon particles and the polymer is not very small.