Studies on syntheses and permeabilities of special polymer membranes: 41. Finger-like cavities in cellulose nitrate membranes from binary organic solvents

The formation of finger-like cavities in asymmetric cellulose nitrate membranes was investigated by changing the composition of binary mixed casting solvent and the evaporation period during the membrane formation process. The nature of the casting mixture, during the solvent evaporation process, was of coacervated droplets with absorbed water molecules from the atmosphere. Changes in the concentration of cellulose nitrate and the dissolution state of the cellulose nitrate molecules in the evaporation loss of the casting solvent, were clearly related to the formation of the finger-like cavity in the back sponge layer in asymmetric cellulose nitrate membranes.     

Metal-assisted chemical etching of Ge(100) surfaces in water toward nanoscale patterning

We propose the metal-assisted chemical etching of Ge surfaces in water mediated by dissolved oxygen molecules (O₂). First, we demonstrate that Ge surfaces around deposited metallic particles (Ag and Pt) are preferentially etched in water. When a Ge(100) surface is used, most etch pits are in the shape of inverted pyramids. The mechanism of this anisotropic etching is proposed to be the enhanced formation of soluble oxide (GeO₂) around metals by the catalytic activity of metallic particles, reducing dissolved O₂ in water to H₂O molecules. Secondly, we apply this metal-assisted chemical etching to the nanoscale patterning of Ge in water using a cantilever probe in an atomic force microscopy setup. We investigate the dependences of probe material, dissolved oxygen concentration, and pressing force in water on the etched depth of Ge(100) surfaces. We find that the enhanced etching of Ge surfaces occurs only when both a metal-coated probe and saturated-dissolved-oxygen water are used. In this study, we present the possibility of a novel lithography method for Ge in which neither chemical solutions nor resist resins are needed.     

Task-board task for assembling a belt drive unit

ABSTRACT

A task board is a board for assembling parts, developed to test the abilities of a robot system to perform assembly operations associated with a manufacturing process. This study describes a task board that can serve as a basis for developing program modules for assembling a specific product. A properly designed task board can serve as a preliminary template for a specific assembly and can promote robotic assembly. This study analyzes the design of a Task-board task performed at the World Robot Summit 2018 (WRS 2018). The main competitive task at the WRS 2018 was the assembly of a belt drive unit. Analyses showed that the directions of assembly, especially the horizontal direction, were common difficulties in both Task-board and Assembly task competitions. Development of a task board for a specific assembly product requires an increase of its relevance to the assembly product, such as using the same workpieces or using similar assembly orientations.     

Studies on syntheses and permeabilities of special polymer membranes: 33. Permeation behaviour of aqueous alcohol solution through cellulose membranes

The permeabilities of various aqueous alcohol solutions through cellulose membranes were investigated by changing the preparation conditions of membranes, the feed concentration, and the feed solute, etc. The permeation rates for aqueous solutions of alcohols, glycols, glycerol, trihydroxyl benzene were greater than for pure water. This permeation phenomenon could be explained by some permeation models considering water cluster, activation of water molecules (second bound water-like) attached weakly to the bound water in cellulose membrane, and the surface of cellulose membrane, and plasticization of cellulose molecules.     

Effects of mildly heated,slightly acidic electrolyzed water on the disinfection and physicochemical properties of sliced carrot

The efficacy of mildly heated, slightly acidic electrolyzed water (mildly heated SlAEW) at 45 °C for disinfection and maintenance of sliced carrot quality was studied. Mildly heated SlAEW (23 mg/L available chlorine, pH at 5.5) was used to treat the carrots, followed by rinsing with tap water (TW) for 2 min at 4 °C, and its effectiveness as a disinfectant was evaluated. The physicochemical properties of the carrots were determined and a comparison was made between treatments with SlAEW at room temperature (18 °C), TW at 18 °C and mildly heated TW at 45 °C. Results show that total aerobic bacteria, mold and yeast populations were significantly lower after mildly heated SlAEW treatment. Mildly heated SlAEW treatment reduced the total aerobic bacteria by 2.2 log₁₀ CFU/g and molds and yeasts by >1.9 log₁₀ CFU/g compared with TW treatment. Color indices of hue and chroma of sample surfaces were not affected by mildly heated SlAEW treatment and there were insignificant differences in hardness or the ascorbic acid and β-carotene contents of sliced carrots. The use of mildly heated SlAEW is suggested as an effective disinfection method for fresh cut carrots with low available chlorine.     

Studies on syntheses and permeabilities of special polymer membranes.: 15. Permeation characteristics of nylon-12 cellulose acetate blends

The permeation characteristics of nylon-12-cellulose acetate polymer blend membranes in the separation of polymers, poly(vinyl alcohols), from their aqueous solutions were investigated under various conditions. The permeation characteristics were influenced markedly by the ratio of nylon-12-cellulose acetate, the feed concentration, the operating pressure and temperature. It was found that the changes of polymer ratio and the concentration of blended polymer were related to the change of microporous structure of the resulting membranes. When the cellulose acetate content was higher a significant compaction of the membrane occurred under pressure. It was found that there was a concentration polarization of poly(vinyl alcohol) molecules on the membrane surface, whose thickness increased with increase in molecular weight of poly(vinyl alcohol) and in feed concentration. The bursting strength of the polymer blend membranes swollen with water increased considerably as the cellulose acetate content in the blended polymer increased.     

Studies on syntheses and permeabilities of special polymer membranes. IV. Permeation characteristics of improved cellulose nitrate membranes

For the purpose of the application of cellulose nitrate membranes for artificial kidneys, the permeation characteristics and the bursting strength of three types of membranes, which were prepared from a system of cellulose nitrate/methyl alcohol/1,4-dioxane/barium perchlorate (CN-1), from a system of cellulose nitrate/methyl alcohol/formamide (CN-2), and a poly(ethylene terephthalate) cloth coated with the casting solution of CN-2 (CN-3), were investigated under various conditions. It was found that permeabilities of these membranes were influenced significantly by the preparation methods of the membranes and the permeation conditions, and they depended upon the structure of the resulting membranes and the interaction between the polymer in the membrane and the feed. In blood filtrations, the permeation rates of our three types of membranes had about four-fold values than a cuprophane membrane, and moreover no protein was found in the blood filtrate. The bursting strength of the membranes swollen with water was in the order CN-3 > cuprophane > CN-2 > CN-1, and this ratio was calculated to be about 5.9:1.0:0.5:0.3     

Reduction of vibration level in rotordynamics by design optimization

We focus on the reduction of the vibration level of rotors by optimizing the shape of the body. The target is to reduce rotor weight and rotor vibrations leading to higher efficiency and less noise. We consider a finite element discretization of the rotor using a Rayleigh beam model which includes rotary inertia and gyroscopic moments leading to nonself-adjoint systems. We present a general algebraic framework for this case. The mass function is the objective function of the optimization problem and constraints are set on the nonlinear and nonconvex functions of critical speed and unbalanced response. For the numerical solution, algorithms belonging to the class of sequential convex programming are applied for the example of a turbocharger. A remarkable reduction of mass of an initially given prototype could be achieved while significantly reducing the unbalanced response and raising the critical speeds.