Preparation and characterization of carboxylated isoprene/styrene copolymer latexes

Carboxylated isoprene/styrene copolymer latexes were prepared, and the concentration of surface carboxyl groups and the freeze–thaw stability of these latexes were measured. It is clarified that the introduction method of the carboxylic monomer governs the distribution of carboxyl groups in latex particles. Introduction of the carboxylic monomer prior to the initiation of polymerization localizes only 12–13% of total carboxyl groups on the surface of particles, whereas introduction of the carboxylic monomer at the last stage of polymerization localizes more than 60% of total carboxyl groups on the surface of particles, though the percentage is strongly dependent on the conversion when the monomers are shot. These latexes show a remarkable increase in the freeze–thaw stability with the increase in the degree of neutralization of surface carboxyl groups in a fairly narrow range. There exists a linear relationship between the surface area occupied by a surface carboxyl group and the degree of neutralization of surface carboxyl groups at which the remarkable increase in the freeze–thaw stability is observed. The result suggests that the freeze–thaw stability is substantially determined by the density of carboxylate ion on the surface of particles.     

双组分无机电解质溶液的纳滤膜分离性能

纳滤膜是20世纪90年代问世的新型分离膜,具有两个显著特点：一是其截留分子量介于反渗透膜和超滤膜之间,约为2002000;另一是纳滤膜的表面分离层由聚电解质构成,一般带有负电荷,因此对无机电解质有一定的截留率．     

Mesopause-region temperature and wind measurements with pseudorandom modulation continuous-wave (PMCW) lidar at 589 nm

A study on the feasibility of using pseudorandom modulation continuous-wave (PMCW) Na lidar for mesopause-region temperature and horizontal wind measurements is presented with a number of specific geometries and associated beam-telescope overlap functions, suitable for ground-based and airborne deployments. The performance of these deployment scenarios is analyzed by scaling from the received signal and sky background and the measurement uncertainties in temperature and horizontal wind of the well-tested Colorado State University pulsed Na lidar. Using currently available high-power (~20 W) continuous-wave Na narrowband lasers, a compact PMCW bistatic Na lidar system can indeed be deployed to simultaneously measure mesopause-region temperature and horizontal winds on a 24 h continuous basis, weather permitting.     

Effect of Time Lag in Response to Switching Signal in Interrupted Electric Circuit

In this study, we analyze the characteristics of an interrupted electric circuit. In particular, we focus on a special situation where the switching action of the circuit is delayed because of a time lag in the response to the switching signal. This situation is observed in switching circuits driven by a high-frequency switching signal. However, the fundamental characteristics of this type of circuit have not yet been clarified. To address this shortfall, we assume that a time lag of the response to the switching signal occurs in simple interrupted electric circuits, and investigate how this time lag affects circuit characteristics. First, we show the model of a circuit whose switching action is the same as that of a current-mode-controlled dc/dc converter. Here by using logic circuits, we impose an artificial time lag on the response to the switching signal. Next, we define a sampled data model (i.e., a return map) that we analyze in detail. Based on the return map, we derive one- and two-parameter bifurcation diagrams. Finally, we compare the bifurcation diagrams constructed with time lag to those constructed without time lag. The results clearly show that time lag is responsible for a new structure in the return map that does not occur in circuits with ideal switching. This new return map structure is a key to understanding the essential characteristics of circuits with time lag. Furthermore, the mathematical results are verified experimentally.     

Hydrodynamic interaction between two red blood cells in simple shear flow: its impact on the rheology of a semi-dilute suspension

Blood is a suspension of red blood cells (RBCs) and its rheology is important when discussing the physiology of the cardiovascular system. In this study, we performed a numerical investigation of the rheological properties of an RBC suspension from the dilute to semi-dilute regime. RBCs were modelled as a capsule with a two-dimensional hyperelastic membrane. Large deformation of the thin membrane was calculated by a finite element method. Due to the small size of the RBC, fluid motion around the RBC was assumed to follow Stokes flow and was solved by a boundary element method. In the dilute limit, cell–cell interactions were omitted and the bulk stress of the suspension was calculated by the stresslet generated on a single RBC. Interestingly, the effective shear viscosity of the dilute suspension decreased with increasing viscosity of the internal liquid. In the semi-dilute regime, cells can be considered as showing pairwise interactions. The effective shear viscosity of the semi-dilute suspension shows a quadratic increase with respect to the volume fraction. These findings are important for understanding the complex phenomena of blood rheology.     

Status of engineering design of liquid lithium target in IFMIF-EVEDA

In International Fusion Materials Irradiation Facility (IFMIF), intense neutron flux (4.5 × 10¹⁷ n/m² s) with a peak energy of 14 MeV are produced by means of two deuteron beams with a total current of 250 mA and maximum energy of 40 MeV that strike a liquid Li target circulating in a Li loop. Major design requirement is to provide a stable Li jet at a speed of 10–20 m/s with a surface wave amplitude on the Li flow less than 1 mm for handling of an averaged heat flux of 1 GW/m² under a continuous 10 MW deuterium beam deposition. The target system consists of a target assembly, a replaceable back-plate, a Li main loop and a Li purification loop. In July 2007, Engineering Validation and Engineering Design Activities (EVEDA) started under Broader Approach. In this paper, status of the engineering design of the IFMIF Li target system performed in 2007/2008 is described. The future EVEDA tasks to develop the target system are also summarized.     

Characteristics of extracted beam from a synchrotron using a fast Q-magnet assisted by RF-knockout

Beam experiment has been carried out at the HIMAC synchrotron to study characteristics of a beam extracted with alternate operation of a fast Q-magnet (FQ) to extract and RF-knockout to diffuse a circulating beam. The FQ coil current of a chopping wave was used to find a particle density distribution after the diffusion. Two kinds of RF-knockout signal were used: a colored noise and a frequency modulation signal. The results showed that the spill structure was like an exponential wave pattern roughly and nearly constant by use of the colored noise and was varied with the frequency modulation signal. The colored noise also gave a nearly constant diffusion rate.     

Removal of aqueous organic pollutants by adsorption-catalytic process using mesoporous carbon beads loaded with metal oxides

Removal of aqueous organic pollutants using an adsorption-catalytic process was examined using metal-loaded carbon cryogel beads (CCBs) which possess numerous mesopores of controlled size. Adsorption isotherms of phenol, as a model organic pollutant, on CCBs could be interpreted based on the Langmuir model, indicating the preferable adsorption of phenol on micropores rather than on mesopores. Removal of aqueous phenol was examined using metal oxide-loaded CCBs in the presence of ozone. Due to the adsorptive-concentration effect of CCBs, it proved possible to increase the phenol removal efficiency by the simultaneous use of ozone with CCBs as compared with ozone only. Of the support materials for loading metal oxides, CCBs showed the highest removal efficiency. The enhancement effect of CCBs in the removal of aqueous phenol was examined with regard to the metal species loaded, the amount of loaded metal, the size of the mesopores, and the carbonization temperature used in the preparation of CCBs.     

Study on application of block copolymers composed of poly(vinyl alcohol) and polyacrylamide to paper sizing

Block copolymers of poly(vinyl alcohol) (PVA) and polyacrylamide (PAAm) were investigated as paper additives. The mixture of both homopolymers in aqueous solution caused phase separation, which indicated incompatibility. The block copolymers were soluble in water without macrophase separation. In the case of surface sizing to paper, PVA–b-PAAm as well as PAAm afforded stiffness to paper, whereas PVA could not. In the case of internal sizing, the block copolymers with anionically modified PAAm revealed excellent improvement in paper properties, whereas PAAm made the tearing strength worse. Brittle polymers such as PAAm appear to afford stiffness to paper, but also make the paper brittle. PVA that is a tough polymer due to high crystallinity and low glass transition temperature can afford toughness to paper, at the expense of stiffness. The block copolymers seem to retain the desirable properties of each simultaneously. © 1995 John Wiley & Sons, Inc.