Investigation of reliability of the cutoff probe by a comparison with Thomson scattering in high density processing plasmas

A “cutoff probe” uses microwaves to measure the electron density in a plasma. It is particularly attractive because it is easy to fabricate and use, its measurement is immune to surface contamination by dielectric materials, and it has a straightforward analysis to measure electron density in real time. In this work, we experimentally investigate the accuracy of the cutoff probe through a detailed comparison with Thomson scattering in a low temperature, high density processing plasma. The result shows that the electron density measured by the cutoff probe is lower than that by Thomson scattering and that the discrepancy of the two results becomes smaller as the gap between the two tips increases and/or the neutral gas pressure decreases. The underestimated electron density found by the cutoff probe can be explained by the influence of the probe holder, which becomes important as the pressure increases and the gap gets closer

Continuum understanding of twin formation near grain boundaries of FCC metals with low stacking fault energy

Deformation twinning from grain boundaries is often observed in face-centered cubic metals with low stacking fault energy. One of the possible factors that contribute to twinning origination from grain boundaries is the intergranular interactions during deformation. Nonetheless, the influence of mechanical interaction among grains on twin evolution has not been fully understood. In spite of extensive experimental and modeling efforts on correlating microstructural features with their twinning behavior, a clear relation among the large aggregate of grains is still lacking. In this work, we characterize the micromechanics of grain-to-grain interactions that contribute to twin evolution by investigating the mechanical twins near grain boundaries using a full-field crystal plasticity simulation of a twinning-induced plasticity steel deformed in uniaxial tension at room temperature. Microstructures are first observed through electron backscatter diffraction technique to obtain data to reconstruct a statistically equivalent microstructure through synthetic microstructure building. Grain-to-grain micromechanical response is analyzed to assess the collective twinning behavior of the microstructural volume element under tensile deformation. Examination of the simulated results reveal that grain interactions are capable of changing the local mechanical behavior near grain boundaries by transferring strain across grain boundary or localizing strain near grain boundary.116Ysciescopu

Efficient Index-based Methods for Processing Large Biological Databases.

Over the last few decades, advances in life sciences have generated a vast amount of biological data. To cope with the rapid increase in data volume, there is a pressing need for efficient computational methods to query large biological datasets. This thesis develops efficient and scalable querying methods for biological data. For an efficient sequence database search, we developed two q-gram index based algorithms, miBLAST and ProbeMatch. miBLAST is designed to expedite batch identification of statistically significant sequence alignments. ProbeMatch is designed for identifying sequence alignments based on a k-mismatch model. For an efficient protein structure database search, we also developed a multi-dimensional index based algorithm method called proCC, an automatic and efficient classification framework. All these algorithms result in substantial performance improvements over existing methods. When designing index-based methods, the right choice of indexing methods is essential. In addition to developing index-based methods for biological applications, we also investigated an essential database problem that reexamines the state-of-the-art indexing methods by experimental evaluation. Our experimental study provides a valuable insight for choosing the right indexing method and also motivates a careful consideration of index structures when designing index-based methods. In the long run, index-based methods can lead to new and more efficient algorithms for querying and mining biological datasets. The examples above, which include query processing on biological sequence and geometrical structure datasets, employ index-based methods very effectively. While the database research community has long recognized the need for index-based query processing algorithms, the bioinformatics community has been slow to adopt such algorithms. However, since many biological datasets are growing very rapidly, database-style index-based algorithms are likely to play a crucial role in modern bioinformatics methods. The work proposed in this thesis lays the foundation for such methods.Ph.D.Computer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/61570/1/youjkim_1.pd

Removal of Particulate Matter in a Tubular Wet Electrostatic Precipitator Using a Water Collection Electrode

As one of the effective control devices of air pollutants, the wet electrostatic precipitator (ESP) is an effective technique to eliminate acid mist and fine particles that are re-entrained in a collection electrode. However, its collection efficiency can deteriorate, as its operation is subject to water-induced corrosion of the collection electrode. To overcome this drawback, we modified the wet ESP system with the installation of a PVC dust precipitator wherein water is supplied as a replacement of the collection electrode. With this modification, we were able to construct a compact wet ESP with a small specific collection area (SCA, 0.83 m2/(m3/min)) that can acquire a high collection efficiency of fine particles (99.7%)

Clinical Characteristics of Radiation Oncology in Korea during Past 10 Years

To understand trends in the clinical characteristics of radiation oncology over the last 10 yr in Korea, annual survey questionnaires were sent to all of Korean radiation oncology facilities since 1990. Questionnaires addressed basic radiation therapy facilities and the clinical information. Responses were obtained from all facilities, and data collected from 1997 to 2006 was analyzed. The numbers of new patients that have undergone radiation therapy and the numbers of hospitals with a department of radiation oncology have steadily increased over the past 10 yr, and totaled 37,215 patients and 60 hospitals, respectively, in 2006. However, the proportion of patients irradiated among total cancer patients has remained below 30% over the last 10 yr. The numbers of prostate cancer, breast cancer, and hepatoma have increased by more than 3 fold over the past 10 yr. Moreover, the percentage of irradiated patients treated by brachytherapy was 10.3% in 1997, but this gradually fell to only 4.2% in 2006. The information collected described the role played by radiation oncology in Korea. Continuous surveys are required to enable trends to be detected

Information Content of Credit Rating Affirmations

We examine whether the reiteration of past credit ratings (i.e., credit rating affirmation) provides value-relevant information to equity analysts and stock investors. While a large body of accounting and finance research provides evidence on the informational role of credit rating downgrades and upgrades, the informational effects of credit rating affirmations remain unexplored, despite the fact that the frequency of issuing rating affirmations is 1.6 times greater than that of issuing both rating downgrades and upgrades. Using a sample of US corporate credit rating reports that reiterate the previous credit ratings over the period of April 1995-June 2018, we find that equity analysts’ earnings forecast dispersion and stock return volatility—proxies for information uncertainty—decrease within a 30-day window following the credit rating affirmation announcements. The reduction in information uncertainty after rating affirmation is mainly driven by firms with non-investment grade bonds, whereas such reduction is not statistically significant for firms with investment grade bonds. We next find that the stock market reaction to affirmations is significantly positive on average and the positive reaction is most pronounced for firms with non-investment grade bonds. Taken together, our findings suggest that credit rating affirmations reduce information uncertainty and stock market investors find it useful for their investment decisions, particularly for firms with non-investment grade bonds. This study enhances our under-standing of the non-trivial informational value of the credit rating affirmations for equity market participants