Line-of-sight indoor radio communication using circular polarizedwaves

This paper presents an anti-multipath fading scheme employing a circular polarized wave for line-of-sight (LOS) indoor radio communications. The circular polarized wave transmission/reception significantly mitigates the multipath fading caused by reflections from walls, ceiling, and floor since the energies of single-bounce reflected waves do not appear at the receiver, thereby resulting in significant amplitude fade and delay spread reduction. The received signal intensity variations and delay spread are investigated numerically using a 14-path propagation model and the usefulness is confirmed by comparing with a linear polarized wave transmission/reception under a same LOS condition     

Molecular characteristics and gelling properties of carrageenan family 2. Tri-sulfated and tetra-sulfated carrageenans

Summary New series of tri-sulfated (τ-carrageenan) and tetra-sulfated (ρ-carrageenan) carrageenans were prepared by the sulfating reaction from ι-carrageenan. The chain conformations of new carrageenans in aqueous solutions were investigated in the presence of various metal salts by means of static/dynamic light scattering and small-angle X-ray scattering, and their conformational characteristics were discussed with respect to the gelation behaviour. Although the overall conformation of newly prepared carrageenans is specified as a random coil, the local chain retains a rigid-rod-like structure by forming a helical conformation. The sulfate groups on C2 of (1→3)-linked β-D-galactoses were found primarily responsible to prevent gelation. Received: 28 August 2001/Accepted: 17 September 2001     

Viscoelastic simulation of film casting process for a polymer melt

Numerical simulations of the film casting process were performed using a finite element method for Newtonian and viscoelasttc fluids. We simplified the governing equations by the assumption that the stress and velocity gradients in the thickness direction were negligible, and obtained the film thickness and mean value of stress and velocity components in the thickness direction as variables. Viscoelasticity was described by the Larson model with multiple relaxation times. Non‐isothermal conditions were considered by applying the time‐temperature superposition law. The simulation results for the several kinds of commercial low‐density polyethylenes wore compared to the experimental data for a laboratory‐scale process at l90°C and a commercial‐scale process at 310°C. The film width and film thickness distribution at chill roll, and the change of film width were in good agreement for the laboratory‐scale process, but the agreement for the commercial‐scale process was; not as good. In the simulation of the commercial‐scale process at high temperature, the value predicted by the use of the Viscoelasticity for the original pellet showed poor agreement owing to the change of Viscoelasticity in the process. The agreement was improved by the use of the Viscoelasticity for the processed resin, which was changed from the original one. Next, viscoelastic effects on neck‐in and edge bead phenomena were investigated. The neck‐in and edge bead phenomena were considered to be affected by both the uniaxial elongational viscosity and planar elongational viscosity.     

Oxygen gas permeability and the mechanical properties of poly (n-butylamino)-(di-n-hexyamino) phosphazene Membranes

Poly (n-butylamino)-(di-n-hexylamino)-phosphazene was prepared by the reaction of poly (dichlorophosphazene), di-n-hexylamine and n-butylamine using tetrahydrofuran (THF) solvent and triethylamine at room temperature. To increase the mechanical properties of polymer films, cross-linking agents, such as neopentyl glycidyl diether and trimethylol propane triglycidyl diether, were added to the original polymer. The original and agent-added polymer films were prepared by a casting method. The films with cross-linking agents were heated at 60 and 120 °C, and then transparent films were prepared. The oxygen gas permeability and the mechanical properties of the original and the cross-linked films were determined. It was found that the oxygen gas permeability and the mechanical properties, such as Young's modulus, of the cross-linked films were greater than for the original film.     

Transient hydrocephalus due to movement of a clot plugging the aqueduct

The study of a modified minilaparotomy technique of interval female sterilization is reported. The modified minilaparotomy technique of interval female sterilization is performed under local anesthesia using the Ramathibodi uterine manipulator, bivalve speculum, and a low midline incision. Sixty cases were treated with this technique. From the study, it was revealed that the mean age of patients +/- SD was 31.2 +/- 5.6 years, the mean body weight +/- SD was 43.3 +/- 5.1 kg, and the mean height +/- SD was 152.1 +/- 8.2 cm. The mean operating time was 24.3 +/- 5.5 min with a range from 15 to 35 min. All patients recovered and were allowed home within 2 h after operation. No immediate or late complications were observed. It was concluded that this technique is quick, safe, inexpensive, and easy to perform as an outpatient procedure.