Minute Air Research Articles

Development of New Electrode System for High Field Dielectric Properties Measurement Using Evaporated Polypropylene Thin Guard Film

Non-polar polymers such as polyethylene (PE) and polypropylene (PP) are widely used as very important electrical insulating and dielectric materials. They are used in the increasingly high AC electric field strength region approaching to the limit of electrical breakdown strength of the materials. Therefore the study of high-field dielectric property is very important in terms of understanding the AC breakdown mechanism of materials. A three-terminals electrode system with a guard film (new type electrode system) was developed in our laboratory for the precise measurement of high-field tanδ, where the guard film was used to reduce the disturbance of electric field around the edge of a main electrode.However, minute air sometimes steals between a sample film and the guard film. The air sometimes generates partial discharge in the high electric field region. Therefore, when the sample had minute air, the new type electrode system was limited under 100kVrms/mm application that didn't reach to an intrinsic breakdown strength of the 30μm-thick sample. We tried to improve the new electrode system without minute air between a sample film and the guard film. We also tried to make very thin guard film to reduce the field disturbance at the edge of main electrode. In this paper a PP-guard film on a biaxially oriented polypropylene (BOPP) film was made by evaporation. This improvement of the electrode system using the evaporated PP-guard film was in success so that high-field dielectric properties of BOPP film could be measured up to near the intrinsic breakdown field of the sample.

Dynamics of the oil-air interface in hard disk drive bearings

Practically all hard disk drives (HDD) built today contain disks supported on fluid dynamic bearings (FDB) because they offer quiet operation and unmatched non-repeatable run-out (NRRO). To operate FDBs with reliability and robustness one must control an exceedingly small amount of oil over a wide range of operating conditions. In particular, the behavior of the oil-air interface (OAI) must be predictable and consistent. This paper presents a linearized analysis of the OAI valid when the flow in the fluid film obeys Reynolds equation and the kinematic boundary conditions at the free surface. It suggests that more grooves reduce the instability. The results establish the occurrence of air intrusion into the oil, which in its late stages may lead to tip streaming, a capillary instability in which minute air bubbles are released into the oil.

The fouling characterization and control in the high concentration PAC membrane bioreactor HCPAC-MBR

This study focuses on the experimental investigation to identify the effect of PAC at high concentrations on the fouling of membranes. A pilot-scale experimental apparatus was installed at a water treatment plant located downstream of Nakdong river basin, Korea. Effluent of rapid sand filter was used as influent of the system, which consists of PAC bio-reactor, submerged membrane module (hollow fiber with pore size 0.1 m) and air supply facility. PAC was dosed at 40 g/L initially and it was not replaced during the operation period. Suction type filtration was carried out at intervals of 12 min. suction and 3 min. idling. At the initial flux 0.36 m/d, the system could be operated stably for around 90 days at target trans-membrane pressure (TMP) of 40 kPa. Among total resistance of membrane filtration, cake and gel layer resistance, Rc+Rg, was the dominant fraction (more than 90% of the total) to increase the filtration pressure, which means that the filtration resistance could be controlled by the PAC cake layer and then irreversible membrane fouling could be prevented. Three minutes air backwashing every 3 days could extend the operation period to 127 days. Organics were analyzed in terms of molecular weight structure. The influent of the system consists of 15.0% and 74.4% of hydrophobic and hydrophilic natural organic matter (NOM), respectively. Hydrophobic and hydrophilic (electrostatic) interaction was the main factor on fouling of the membrane in the reactor. Hydrophobic fraction decreased slightly in the effluent, which means hydrophobic NOM removal in the reactor by adsorption. Organics accumulated in the membrane were extracted for analysis after a certain period of operation. The fraction of hydrophobic and hydrophilic organics was 41.4% and 38.9%, respectively. On the basis of the experimental results, the hydrophobic organics were the major materials causing the fouling of the membrane, which should be changed to other types of material.

Thermodynamic Limits of Electrical Efficiency in Hydrocarbon Fueled SOFC Using Internal Reforming

This paper examines the behavior of a miniature tubular anode-supported SOFC at the limits of complete fuel utilization. Fuels include H 2 , CO and a 3:1.H 2 :CO mixture, selected to represent syngas. Construction of the NiO/8YSZ anode support, 8YSZ electrolyte, cathode and experimental apparatus are described. Current vs. voltage plots for fuel flow rates ranging from 0.6 to 6 seem show the affects of fuel depletion near limiting currents. I-V plots are also used to investigate air leak rates and oxidation of Ni metal in the anode support. Measured electrical efficiencies are found to depend strongly on the operating conditions of the fuel cell and minute air leaks into anode channel. These leaks are quantified from open circuit voltages. Fuel composition, fuel flow, and operating voltage are found to influence the overall electrical efficiency. Because of air diffusing into the anode channel and the water gas shift reaction (CO + H 2 O ↔ CO 2 + H 2 ), syngas yields higher efficiencies than pure H 2 . Experimental results are compared with results of a thermodynamic model, which predicts the maximum theoretical electrical efficiency as a function of operating voltage.

Filtering Efficiency of N95- and R95-Type Facepiece Respirators, Dust-Mist Facepiece Respirators, and Surgical Masks Operating in Unipolarly Ionized Indoor Air Environments

The emission of unipolar air ions in the vicinity of a filtering facepiece respirator has been recently shown to considerably enhance its respiratory protection efficiency. The effect is driven by the electric repelling forces that develop between the unipolarly charged mask and the aerosol particles, thus creating a shield for the incoming particles and consequently decreasing the penetration efficiency through the filter. The manikin-based preliminary evaluation of this concept has been performed with a very limited number of variables. In this study, four types of half-mask facepiece filtering devices (N95, R95, and dust-mist respirators, as well as surgical masks), operating at two different breathing flow rates, were tested with unipolar air ion emitters exhibiting different emission rates and polarities. The particle penetration efficiency through the facepiece filter was determined in a room-size indoor test chamber by a real-time particle size selective aerosol monitoring performed inside and outside of the mask, which was face-sealed onto a manikin. Three commercially available ionic air purifiers were utilized as air ion emitters. For the targeted particle size range of ~0.04 – 1.3 μm, a 12- minute air ionization in the vicinity of a manikin enhanced the respiratory mask performance by a factor ranging from 1.61 to 3,250, depending on the respirator type, breathing flow rate, and the ion emission rate. The effect was achieved primarily within the first 3 minutes.

1003 超音波を用いた血流中の栓子と気泡の識別法の開発(GS-2,5 キャビテーション・気泡,研究発表講演)

In an artificial valve substitution operation and the example of assisted artificial heart wearing, embolism is concurred with in high rate. Although minute air bubbles are generated with opening and closing of an artificial valve in such a patient's blood, it is difficult to discriminate air bubbles from emboli by the method of discriminating emboli using the present ultrasonic wave. By modeled emboli, the density of air bubbles and the difference in characteristic acoustic impedance, the difference in movement of both at the time of an ultrasonic wave hitting a particle arises. In this research, it tried to discriminate both from the difference in movement by measuring the move speed of the direction of an ultrasonic beam of the particle produced according to an ultrasonic wave using ultrasonic measurement equipment. The movement caused because the ultrasound was irradiated in pulsatile flow confirmed the difference in air bubbles and modeled emboli.

Synthesis of a 1,3-diphosphacyclobutane-2,4-diyl from Mes*C[triple bond]P.

A very stable biradical, 2, was prepared from 1 (see picture). The deep-blue/violet biradical was stable in the air for several minutes. The sp2-hybridized carbon radical centers of 2 were confirmed by X-ray crystallography and its reversible oxidation was characterized by cyclic voltammetry. Mes*=2,4,6-tBu3C6H2.

A New Method for Designing Vortical Aerators

The oxygen saturation of water for various uses — water treatment for communal and industrial needs, waste effluent treatment, biological self-cleaning in reservoirs and in streams, etc. — is an important step in water improvement technology. For that purpose, various methods and variously designed mechanical and pneumatic aerators are used in practice. A high-efficiency vortical aerator has been designed at the MGSU [1]. Operation of this aerator is based on the interaction of two coaxial circular flows rotating in opposite directions (Fig. 1). The flow swirling is effected by means of tangential inlet ducts 1. The inner circular flow develops a flow discontinuity cavity in the central part, conventionally called the air-vapor core 2. Because of the centrifugal effect, the air-vapor core pressure is lower than the atmospheric pressure, owing to which the atmospheric air is automatically drawn in the air-vapor core through air inlet pipe 3. In mixing chamber 4, the circular water flows and the central air flow converge. Owing to the intense turbulent agitation, the convergent flows in the mixing chamber mingle in an axial flow saturated with a vast number of uniformly distributed minute air bubbles, which creates a large air–water contact surface. Owing to this, the process of saturation of water with dissolved oxygen intensifies appreciably under vortical aerator conditions. The familiar methods for analysis of vortical aerators [5] fail to reflect in full measure the complicated hydraulic events involved that can be accounted for only using adequate experimental data. Viewed from a hydraulic standpoint, one can draw an analogy with the swirling flows in vortical aerators and hydraulic turbines. In both cases, the flow channel represents a kind of hydraulic resistance which is difficult (if possible at all) to take account of theoretically. For this reason, in a hydraulic-turbine analysis a common procedure is to determine experimentally the characteristics of a model hydraulic turbine and then to scale them up to life-size analogs. In our case, one may also assume that the fluid flows in geometrically similar vortical aerators differing in absolute dimensions are mechanically similar. If so, one can use the same principle of analysis as that for hydraulic turbines. An analogy between swirling spillways (equipped with vortical gates) and hydraulic turbines was earlier noted in [3].

Sensitive detection of voids in solid materials by refraction-enhanced synchrotron radiation imaging

Voids in opaque materials (minute air bubbles) were imaged with synchrotron radiation in a refraction enhancement mode. The voids are imaged by an enhanced x-ray intensity inside the bubble, surrounded by a border region with decreased x-ray intensity, thus allowing sensitive detection of air bubbles in plastic materials. As those “impurities” could not be depicted with conventional radiography, and optical inspection is not useful if the matrix is opaque, this in-situ imaging technique offers the potential to obtain information of air inclusions, voids, and cracking that appear inadvertently in opaque plastics and possibly in metals as well.

Pneumatically bidirectional microfluidic regulation using Venturi pumps by deep RIE and bonding technology

A novel design for bidirectional fluidic motion has been demonstrated which is widely used in the biochip or microfluidic component. Two miniaturized Venturi pumps as well as pneumatic servo system are designed to easily control the bidirectional fluidic motion by simple fabrication. The pumping velocity is 0.86 μl/min at a 2.75 slpm (standard liter per minute) air flow read from mass flow controller (MFC) for totally 4.3 μl blue ink in a 300 μm wide by 300 μm deep channel. The higher airflow, the faster fluidic pumping speed. Numerical simulation is performed to correlate the experimental data of fluidic speed and air flow in microchannel. The test chip with two Venturi pumps and channel was batchedly fabricated by silicon deep reactive ion etching (RIE) and glass anodic bonding. The ICP LIGA process is also investigated after deep RIE followed the electroforming and hot embossing.

Use of glucose feeding to produce concentrated yeast cells.

A defined medium and fed-batch feeding process for the production of a yeast biocatalyst, developed at the 23-L scale, was scaled up to the 600-L pilot scale. Presterilized 100-L-vol plastic bags were implemented for the pilot-scale nutrient feeding. Medium of increased concentration Oqs implemented at the pilot scale, and equivalent dry cell weights were reached with a medium 80% more concentrated than that used at the laboratory scale. The higher medium concentration was believed to be necessary at the pilot scale owing to the additional heat stresses on key components (e.g., complexing of magnesium sulfate with phosphate), increased dilution during sterilization, lower evaporation rate owing to the lower vessel volume per minute air flow rate, and increased dilution owing to nutrient feeding or shot additions. Peak cell density was found to be somewhat insensitive to variations in residual glucose levels. These results suggest that defined medium developed at the laboratory scale may need to be further optimized at the pilot scale for equivalent performance.

Photooxidation study of polymer light-emitting devices

In this paper, the photooxidation effect on the organic electroluminescent devices based on a π-conjugated polymer, poly(2-methoxy-5-dodecyloxy- p-phenylene vinylene) (MDOPPV) is reported. The devices used have a semitransparent Al cathode, which enables atmospheric oxygen to penetrate into the polymer layer in the device, and therefore extensive photooxidation takes place upon photoirradiation in air. It was confirmed that when the Al cathode is sufficiently thin (with an optical transmittance of ∼30% at λ=500 nm), the photooxidation rate of the polymer is independent of whether the Al film exists or not. Therefore, the electroluminescence (EL) data obtained from such a device irradiated for a period of time can be directly compared with the photoluminescence (PL) data obtained from a naked polymer film irradiated for a similar period. We have found that the external quantum efficiency of EL for the device based on MDOPPV does not change on photooxidation in air for a few minutes, while the quantum efficiency of PL rapidly decreases upon such photooxidation. This means that the optically generated luminescent species are efficiently quenched by photooxidized defects, but the electrically generated luminescent species are not, suggesting that the recombination zone for the electroluminescent process is spatially separated from the photooxidized defects, or excitons ‘dodge’ the defects.

Stable free radicals as ubiquitous components of red wines

A stable ESR signal, centred at g = 2.0037 ± 0.0002, characterised by a single resonance and assignable to a free radical, was found in all the bottled red wines, both commercial and experimental, that we have examined. The radical concentration was calculated to be in the range of 5–82 nM. After exposure of the wines to air for a few minutes a two fold increase of the ESR signal, followed by a slow decrease with time, was observed. The intensity of ESR signal in experimental red wines, was found to increase with the ageing of the wines and was strictly correlated to the total content of polyphenols. The formation of semiquinone radicals of polyphenols is suggested as one possible mechanism leading to the presence of stable free radicals in red wines.

CHROMOTROPIC CHANGES OF Cu(II) AND Ni(II) COMPLEXES WITH N2O2 AND N3O2 SCHIFF-BASE LIGANDS IN THE SOLID PHASE

Four new Schiff-base ligands have been prepared from the condensation of 3-formyl-4-hy-droxy-1,8-naphthyridin-2-one with different diamines and a triamine, H2La-H2Ld. Two series of Ni(II) and Cu(II) complexes with the four ligands were also prepared. The ligands and their metal complexes were characterized by chemical analyses, IR, Far-IR, electronic, ESR and mass spectra as well as magnetic measurements and X-ray diffraction patterns. Different products for Ni(II) and Cu(II) were obtained in similar reactions with the same metal salt, depending on the nature of the ligand. Different geometries were also obtained depending on the counter anion of metal salt. Thus, violet square-planar Cu(II) complexes were obtained with Cu(OAc)2. H2O and green octahedral ones with CuCl2. 2H2O, except the reaction with ligand H2Ld which gave only an octahedral product whether the anion was acetate, chloride or perchlorate. Electronic and ESR spectra were used to differentiate between the two geometries of the Cu(II) complexes. The green octahedral Cu(II) complexes undergo irreversible thermochromism to the violet square-planar complexes except the copper complex of the ligand H2Ld which did not not show any color change and retained its octahedral geometry. Based on the magnetic moments and thermal analyses, only one Ni(II) complex of the Schiffbase ligand H2Lc undergoes reversible thermochromism from green (octahedral) to red (squareplanar). The reverse change of the thermal product (red) to the parent complex (green) proceeded on exposure to atmospheric air for a few minutes. On the other hand, Ni(II) complexes of ligands H2La and H2Lb have stable square-planar geometry and all efforts to add other ligands such as H2O or pyridine to these complexes failed to yield other products. The corresponding Cu(II) complexes were easily transformed to their octahedral geometry by adding H2O or pyridine and heating.

BRONCHIAL CASTS OF HUMAN LUNGS USING NEGATIVE PRESSURE INJECTION

Negative-pressure casting techniques have been used for obtaining silicone rubber casts of the avian respiratory system, which contains minute air capillaries, noncompressible hollow bones, and highly flexible air sacs. The possibilities of this technique for the study of human airway diseases, which present technical difficulties similar to those of avian lungs, are investigated here. Left lungs from patients with various obstructive lung diseases or with normal lungs were fixed at autopsy under 25 cm H2O airway pressure with 2.5% phosphate-buffered glutaraldehyde. Cannulated, isolated lobes were placed in a vacuum chamber, and Dow Corning 734 RTV silicone elastomer, diluted with 10% low viscosity silicone oil, was introduced into the airways at -10 kPa. Following complete polymerization, the tissue was microdissected to reveal the lung cast in situ, and histological sections were obtained for correlative studies. The tissue was then macerated in 5.25% sodium hypochlorite. The total time from fixation to finished cast was 3-4 days. Linear shrinkage of the elastomer was less than 1% in glutaraldehyde or water and between 1 and 2% in bleach. The negative-pressure injection technique enabled complete and accurate filling of airways to the alveolar duct level at physiological pressures and provided good delineation of blind cavities such as obstructed airways or ectatic mucous gland ducts. The technique proved useful for the study of obstructive lung disease and should also prove useful for modelling aerosol deposition in diseased lungs.

Identification in TLC of fructose and fructosyl derivatives in levan and sugar mixtures with resorcinol and thiourea

Fructose and fructosyl derivatives were detected on TLC plates using a modification of the Roe-Papadopoulos method. A large increase in sensitivity was obtained using H2SO4 in the TLC assay. Fructose and fructosyl groups (sucrose, raffinose, and levan) appeared as purple spots after spraying the modified Roe-Papadopoulus reagent onto the plate and then heating with hot air for a few minutes. Reducing sugars, such as glucose and xylose, and nonreducing sugar trehalose were not detectable by this technique.

余剰汚泥の減圧浮上濃縮に関する基礎的検討

A vacuum flotation of waste activated sludge was investigated experimentally. The results showed almost equal or higher flotation efficiency compared with usual dissolved-air flotation. The growth rate of separated liquor zone was approximated by the equation that was similar to Roberts' equation of batch settling. Some additional treatments, such as, thermal treatment, mixing with water and/or dissolution of carbon dioxide enhanced the flotation rate. In addition, the small amount of air was sufficient to raise the sludge, since minute air bubbles were made under a partial vacuum condition. Furthermore, the small space in the flotation cell saved a great amount of energy to obtain the vacuum pressure. These results show that the vacuum flotation is promising process for practical use.

Thermal properties of capacitively coupled electrodes in interstitial hyperthermia

The multi-electrode current source (MECS) interstitial hyperthermia system, which is used for treatment of cancer, employs segmented electrodes inserted in plastic tubes implanted in the treatment volume. The mean power deposition of the individual electrodes is controlled by varying the duty cycle of the RF signal applied to the electrodes, using thermocouples inside the electrodes for thermometry. A non-zero loss angle results in self-heating of the catheter. The thermal influence of self-heating was investigated and an analysis of the measurement of temperatures inside the catheter during and after heating is presented. Analytical models and a high-resolution numerical model were used for the calculation of steady state and transient distributions, respectively. The model results are compared with experimental data obtained in a muscle equivalent phantom. Results indicate that there is no difference between temperature inside and outside the catheter when using lossless catheter materials (e.g. PE and PTFE). Self-heating in the catheter wall has an adverse effect on the uniformity of the stationary temperature distribution and the reliability of temperature measurement with internal thermometry. These problems remain within acceptable limits for mildly lossy materials; the difference between the temperature inside and outside is only 6% when using low-loss Nylon. Analysis of the thermal decay after power-off shows that low-loss materials allow more time to obtain an accurate estimate of the tissue temperature at the catheter wall during power-on. This effect is enhanced by the presence of minute air layers in the applicator. Distortion of temperature gradients along the catheter was also investigated. Key factors are the thermal conduction across the catheter wall, and especially the presence of minute layers of air between consecutive layers of the probe. The distortion extends less than two millimetres, which is acceptable. The simulation results are compatible with measurements in phantoms and show that, if the proper choice of materials is made, the MECS applicator answers our expectations and that the temperature measurement inside the catheter can be used for direct feedback treatment control.

Application of air backflushing technique in membrane bioreactor

The optimum air backflushing and filtration cycle was investigated for a 0.1 μm hollow fiber membrane module immersed in an activated sludge aeration tank. It was found that 15 minutes filtration and 15 minutes air backflushing gave the best result both in terms of flux stability and net cumulative permeate volume. Although this cyclic operation could not completely remove the clogging, this process improved the flux by up to 371% compared to the continuous operation. During the long term runs, three different hydraulic retention times (HRT) of 12, 6 and 3 hours, corresponding to 0.16, 0.32 and 0.64 m3/m2.d of permeate flux respectively, were investigated. Stable operation was obtained at the HRT of 12 hours. Decrease in HRT led to rapid formation of a compact cake layer on the membrane surface thus increasing the transmembrane pressure. It was also noted that filtration pressure increases with increase in bioreactor MLSS concentration. With operation time, the MLVSS/MLSS value decreased without significant effect on the process performance, indicating that inorganic mass constantly accumulated in the bioreactor. All the experimental runs produced more than 90% removal of COD, and TKN. In terms of physical, chemical, biological and bacteriological parameters, the membrane bioreactor effluent was superior to the conventional activated sludge process.

Generation and evaluation of test gas mixtures for the Gas‐Phase Sulfur Intercomparison Experiment

The automated sulfur gas dilution system (ASGDS) was used during the Gas‐Phase Sulfur Intercomparison Experiment (GASIE) to generate and analyze test gas mixtures containing pptv levels of SO2 in the presence of various suites of potential measurement interferent gases. These test gas mixtures were provided in a 100 standard liters per minute air matrix manifold, allowing simultaneous sampling by all seven intercomparison participants. The test gas mixtures were homogeneous within the 90‐min test periods of the synthetic air phases of GASIE, allowing rigorous intercomparison of any two or more data points obtained during a given test period. A number of delivered SO2 concentrations were successfully replicated throughout the experiment, permitting the collection of a sufficient amount of data for statistical evaluation. The SO2 concentrations measured by the ASGDS quality control instrumentation agreed with values obtained by the intercomparison participants but were different from the set point values.