Hyun-Ho Lee

Micellar-enhanced ultrafiltration for simultaneous removal of ferricyanide and nitrate

Feasibility of micellar-enhanced ultrafiltration was investigated to study simultaneous removal of ferric cyanide and nitrate with a cationic surfactant, cetylpyridinium chloride (CPC). The removal of ferricyanide and nitrate was studied as a function of surfactant to ferricyanide/nitrate molar ratios. In the ferricyanide/CPC and nitrate/CPC systems, the removal of ferricyanide and nitrate increased gradually as the molar ratio of CPC to ferricyanide or nitrate increased. With a 10 molar ratio of CPC, the removal of ferricyanide and nitrate increased to >99.9% and 93%, respectively. In the ferricyanide/nitrate/CPC system, the removal of ferricyanide increased from 62% to 72% and to 99.9%, while that of nitrate from 99.9% and 78% for ferricyanide and nitrate, respectively. Ferricyanide ions were more easily bound to CPC micelles because the binding power of ferricyanide was greater than that of nitrate. With the difference of binding power, selective removal of ferricyanide using micellar-enhanced ultrafiltration could be achieved.

Phase-shifting lateral shearing interferometer with two pairs of wedge plates

We present a compact and robust phase-shifting lateral shearing interferometer that produces shearing fringes in orthogonal directions without any mechanical rotation or precise alignment. It consists of two pairs of wedge plates, a beam splitter, and a single CCD camera. Both phase-shifting and tilt for lateral shearing are achieved with two pairs of wedge plates, which can reduce systematic errors caused by external vibration and atmospheric disturbance.

Evolution of electromagnetic interference through nano-metallic double-slit

We investigated the characteristics of the near- and far-field regions of the interference for nano-metallic double-slits using a two-dimensional finite-difference time-domain (FDTD) method. We have found that the patterns in the near-field region have a phase difference of pi with respect to those in the far-field region. A boundary, which separates the interference patterns of the two regions exists as a half circle and grows as the distance between the two slits increase. It is also found that evanescent waves can be enhanced and confined by coating the double-slit with a dielectric cladding.

Finite-difference time-domain analysis of self-focusing in a nonlinear Kerr film.

By using a finite-difference time-domain method, we analyze self-focusing effects in a nonlinear Kerr film and demonstrate that the near-field intensity distribution at the film surface can reach a stable state at only a few hundred femtoseconds after the incidence of the beam. Our simulations also show that the formation of multiple filamentations in the near-field is quite sensitive to the thickness of the nonlinear film and the power of the laser beam, strongly indicating the existence of nonlinear Fabry-Perot interference effects of the linearly polarized incident light.

Attribute-based evaluation of multiple continuous queries for filtering incoming tuples of a data stream

The filtering of incoming tuples of a data stream should be completed quickly and continuously, which requires strict time and space constraints. In order to guarantee these constraints, the selection predicates of continuous queries are grouped or indexed in most data stream management systems (DSMS). This paper proposes a new scheme called attribute selection construct (ASC). Given a set of continuous queries, an ASC divides the domain of an attribute of a data stream into a set of disjoint regions based on the selection predicates that are imposed on the attribute. Each region maintains the pre-computed matching results of the selection predicates. Consequently, an ASC can collectively evaluate all of its selection predicates at the same time. Furthermore, it can also monitor the overall evaluation statistics, such as its selectivity and tuple dropping ratio, dynamically. For those attributes that are employed to express the selection predicates of the queries, the processing order of their ASCs can significantly influence the overall performance of a multiple query evaluation. The evaluation sequence can be optimized by periodically capturing the run-time tuple dropping ratio of its current evaluation sequence. The performance of the proposed method is analyzed by a series of experiments to identify its various characteristics.

Microbial desulfurization of solubilized coal

Microbial desulfurization of low rank coal by Rhodococcus rhodochrous IGTS8 was investigated using three different pretreated coal samples. Solubilized coal was desulfurized more efficiently than hard coal and more sulfur was extracted from biologically solubilized coal than from chemically solubilized coal. Microbial desulfurization combined with biological solubilization removed 75% of the total sufur while the microbial desulfurization combined with chemical solubilization removed 63%.

Consistent collective evaluation of multiple continuous queries for filtering heterogeneous data streams

Query processing for a data stream should also be continuous and rapid. This article proposes a novel approach for consistent collective evaluation of multiple continuous queries for filtering two different types of data streams: a relational stream and an XML stream. The proposed approach commonly provides region-based selection constructs: an attribute selection construct for relational queries and a path selection construct for XPath queries. Both collectively evaluate the selection predicates of the same attribute (path), based on the precomputed matching results of the queries in each of the disjoint regions divided by the selection predicates. The performance experiments show that the proposed approach is practically more efficient and stable than other approaches at run-time.

Selectivity-sensitive shared evaluation of multiple continuous XPath queries over XML streams

One of the primary issues confronting XML message brokers is the difficulty associated with processing a large set of continuous XPath queries over incoming XML streams. This paper proposes a novel system designed to present an effective solution to this problem. The proposed system transforms multiple XPath queries before their run-time into a new data structure, called an XP-table, by sharing their common constraints. An XP-table is matched with a stream relation (SR) transformed from a target XML stream by a SAX parser. This arrangement is intended to minimize the run-time workload of continuous query processing. In addition, an early-query-termination strategy is proposed as an improved alternative to the basic approach. It optimizes query processing by arranging the evaluation sequence of the member-lists (m-lists) of an XP-table adaptively and offers increased efficiency, especially in cases of low selectivity. System performance is estimated and verified through a variety of experiments, including comparisons with previous approaches such as YFilter and LazyDFA. The proposed system is practically linear-scalable and stable for evaluating a set of XPath queries in a continuous and timely fashion.

Purification and characterization of methyl mercaptan oxidase fromThiobacillus thioparus for mercaptan detection

Methyl mercaptan oxidase was successfully induced inThiobacillus thioparus TK-m using methyl mercaptan gas, and was purified for the detection of mercaptans. The purification procedure involved a DEAE (diethylaminoethyl)-Sephacel, or Superose 12, column chromatography, with recovery yields of 47.5 and 48.5%, and specific activities of 374 and 1240.8 units/mg-protein, respectively. The molecular weight of the purified methyl mercaptan oxidase was 66.1kDa, as determined by SDS-PAGE. The extract, from gel filtration chromatography, oxidizes methyl mercaptan, producing formaldehyde, which can be easily detected by the purpald-coloring method. The optimized temperature for activity was found to be at 55°C. This enzyme was inhibited by both NH4Cl and (NH4)2SO4, but was unaffected by either KCl or NaCl at less than 200 mM. With K2SO4, the activity decreased at 20 mM, but recovered at 150 mM. In the presence of methanol, full activity was maintained, but decreased in the presence of glycerin, ethanol and acetone 43, 78 and 75%, respectively.

Simplified phase shifting Moiré interferometer using a computer generated grid pattern

A simplified phase-shifting moire interferometer for generating moire fringes from projected linear gratings and computer generated grid patterns without using a low-pass filter is presented. In particular, it is demonstrated that moire fringes can be successfully obtained even when there is no clear frequency separation between the moire fringe and the grid pattern. It is also pointed out that our proposed method produces fewer phase jumps than conventional phase-measuring profilometry, enabling us to realize more robust phase unwrapping.