Thermophysical properties data on molten semiconductors

Thermophysical properties of molten semiconductors are reviewed. Published data for viscosity, thermal conductivity, surface tension, and other properties are presented. Several measurement methods often used for molten semiconductors are described. Recommended values of thermophysical properties are tabulated for Si, Ge, GaAs, InP, InSb, GaSb, and other compounds. This review shows that further measurements of thermophysical properties of GaAs and InP in the molten state are required. It is also indicated that a very limited amount of data on emissivity is available. Space experiments relating to thermophysical property measurements are described briefly.Nomenclature Density - C _p Specific heat - Kinematic viscosity - Dynamic viscosity= - Thermal diffusivity - Thermal conductivity=C_p - Volumetric thermal expansion coefficient - Surface tension - d/dT Temperature coefficient of surface tension - g Gravitational acceleration - T Temperature - T Temperature difference - L Characteristic dimension     

Development of an epileptic seizure prediction algorithm using R–R intervals with self-attentive autoencoder

Epilepsy is a neurological disorder that may affect the autonomic nervous system (ANS) from 15 to 20 min before seizure onset, and disturbances of ANS affect R–R intervals (RRI) on an electrocardiogram (ECG). This study aims to develop a machine learning algorithm for predicting focal epileptic seizures by monitoring R–R interval (RRI) data in real time. The developed algorithm adopts a self-attentive autoencoder (SA-AE), which is a neural network for time-series data. The results of applying the developed seizure prediction algorithm to clinical data demonstrated that it functioned well in most patients; however, false positives (FPs) occurred in specific participants. In a future work, we will investigate the causes of FPs and optimize the developing seizure prediction algorithm to further improve performance using newly added clinical data.

     

Marangoni flow of molten silicon: The effects of oxygen partial pressure

Instability of the Marangoni flow of molten silicon is discussed. Time-dependent behavior of azimuthal wave numbers (m) for flow instability was investigated based on temperature oscillation measurements using a θ-t analysis, and appearance ratio of each azimuthal wave number is analyzed. The relationship between frequency and azimuthal wave numbers is deduced from an analysis of appearance ratios at a decomposed frequency band using a wavelet analysis. Oxygen partial pressure at the melt surface can be predicted using the Ratto-Ricci-Arato model. Anomalous recalescence behavior and surface oxidation of levitated molten silicon are shown. Growth striation is induced in silicon crystals grown even under high oxygen-partial pressure.     

Using ontology to improve precision of terminology extraction from documents

In this paper, we proposed a new approach using ontology to improve precision of terminology extraction from documents. Firstly, a linguistic method was used to extract the terminological patterns from documents. Then, similarity measures within the framework of ontology were employed to rank the semantic dependency of the noun words in a pattern. Finally, the patterns at a predefined proportion according to their semantic dependencies were retained and regarded as terminologies. Experiments on Retuers-21578 corpus has shown that WordNet ontology, that we adopted for the task of extracting terminologies from English documents, can improve the precision of classical linguistic method on terminology extraction significantly.     

X-ray absorption fine structure combined with fluorescence spectrometry for monitoring trace amounts of lead adsorption in the environmental conditions

The local structure of trace amounts of lead in an adsorbent matrix that contains a high concentration of iron and magnesium (Mg6Fe2(OH)16(CO3) x 3H2O) was successfully monitored by means of X-ray absorption fine structure spectroscopy combined with fluorescence spectrometry. A eutectic mixture of PbCO3 and Pb(OH)2 coagulated when Pb2+ was adsorbed from a 1.0 ppm aqueous solution, and in contrast, the major species was ion-exchanged Pb2+ in the case of adsorption from a 100 ppb aqueous solution. The difference was ascribed to the balance between the precipitation equilibrium for coagulation and the rate of the ion exchange reaction with surface hydroxyl groups.     

Effect of applied voltage frequency on swarming pulsive microdischarges in closed voids

The extinction of the partial discharge (PD) pulse has frequently been observed in an epoxy specimen with a closed void during voltage endurance tests using a CIGRE Method-II electrode. The individual discharge pulse becomes so small that the discharges cannot be detected by conventional pulse detection methods. Such discharges are known as “swarming pulsive microdischarges” (SPMD). In this paper, the SPMD characteristics are investigated by varying the frequency of the applied voltage from 0.1 to 240 Hz. As a result, the SPMD are found to occur less frequently as the frequency is lowered. To seek this cause, one-shot voltages were applied repeatedly at constant intervals. By varying the interval from 0.02 to 100 s, the PD off an electrically aged specimen was measured. It was revealed that the discharge magnitude increases as the interval becomes longer. The onset of SPMD was found to depend on the preceding discharge. The results explain the reason why swarming is harder to occur at lower frequency with a longer discharge interval. Hence, in the conventional pulse detection, it is useful to employ the very low frequency for diagnosis of machine insulation containing enclosed voids.     

Identifying rotation and oscillation in surface tension measurement using an oscillating droplet method

We proposed a new approach to identify the frequencies of droplet rotation and m=±2 oscillation that degrade the accuracy of surface tension measurement by an oscillating droplet method. Frequencies of droplet rotation and m=±2 oscillation can be identified by a phase unwrapping analysis of time dependence of the deflection angle for the maximum diameter of the droplet image observed from above. The present method was validated, using test data with given frequencies. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(7): 421–430, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20214     

Rapid erasing of wettability patterns based on TiO2-PDMS composite films

TiO₂-polydimethylsiloxane (TiO₂-PDMS) composite films are prepared using the sol–gel method from a Ti(OBu)₄–benzoylacetone solution containing PDMS. The prepared films are cured by irradiation with ultraviolet (UV) light. Structural changes in the films after UV irradiation are confirmed by UV–vis absorption experiments, which show that an absorption band characteristic of the benzoylacetonate chelate rings disappears. This finding is ascribed to structural changes associated with the dissociation of the chelate rings. The IR spectra of the thin films exhibit a broad absorption band after UV irradiation, indicating that a Ti–O–Ti network forms in the thin film. Contact angles are measured for the TiO₂-PDMS thin films, showing wettability conversion from hydrophobic to superhydrophilic states by irradiation with oxygen plasma for 1 s. This phenomenon is explained by XPS experiments which reveal that the number of carbon atoms decreases, whereas the number of oxygen atoms increases on the surface of the TiO₂-PDMS composite films. Finally, hydrophobic–superhydrophilic patterns are fabricated based on a patterned TiO₂-PDMS composite film. The film displays a rapid change to superhydrophilicity over the whole film surface upon plasma irradiation for 1 s, which means that the wettability patterns are rapidly erasable.     

A new flame retardant synthetic fiber made by an emulsion spinning process

Emulsion spinning has been discussed as a fiber forming process for a long time. At present, however, there are only a few matrix fibers commercially produced in the world. A matrix fiber composed of polyvinyl alcohol and polyvinyl chloride shows excellent flame retardancy which never goes out either by laundering or by dry cleaning and extremely low toxicity of fumes even when forced to burn. This matrix fiber is being used for home furnishings, apparel and industrial fabrics. The coming into force of regulations on children's sleepwear, carpenting, mattresses and blankets in the USA provides this fiber with a great opportunity to open a market into those fields. It has other features including a soft textural feel, moderate moisture regain and abrasion resistance. Special types of this fiber can be vacuum formed by the same manner that is used for thermoplastics molding.     

Enhancement of biofilm formation onto surface-modified hollow-fiber membranes and its application to a membrane-aerated biofilm reactor.

Surface-modified hollow-fiber membranes were prepared by radiation-induced grafting of an epoxy-group-containing monomer, glycidylmethacrylate (GMA), onto a polyethylene-based fiber (PE-fiber). The epoxy ring of GMA was opened by introduction of diethylamine (DEA). The bacterial adhesivity to this material (DEA-fiber) was tested by immersion into a nitrifying bacterial suspension. The initial adhesion rates and the amount of attached bacteria of the DEA-fiber were 6-10-fold and 3-fold greater than those of the PE fiber, respectively. A membrane-aerated biofilm reactor (MABR) composed of DEA fibers was developed for partial nitrification with nitrite accumulation. Prior to the nitrification test, it was confirmed that the oxygen supply rate (OSR) was proportional to air pressure up to 100 kPa, allowing easy control of oxygen supply. Stable nitrite accumulation was observed in the partial nitrification test at a fixed oxygen supply throughout the operation period, indicating that oxygen was consumed only by ammonia oxidizers. Furthermore, it was demonstrated that oxygen utilization efficiency (OUE) in the ammonia oxidation process was nearly 100% after 300 h incubation.