• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.6
• /
• pp.860-873
• /
• 1998

In a low speed open-type wind tunnel, a group of parallel wakes downstream of two dimensional grid model consisting of several circular cylinders were experimentally investigated to study the response of the wake flows to the acoustic excitation, in hoping to promote the understanding of the underlying mechanism behind the gross flow change due to artificial excitation. In the unexcited wake flows, the development of the individual wakes behind cylinders was almost uniform for the ratio of the spacing to the cylinder diameter of s/d.geq.1.5. For smaller s/d, however, the jet streams issued through the gaps between the cylinders became biased in one side and the cylinders had wakes of different sizes. At s/d=1.25, the gap flow directions change in time, leading to unstable wake patterns. Further reduction in s/d made this unstable flip-flopping of the jets stable. The most effective excitation frequency was found to be in the Strouhal number range of St=0.5-0.6. This frequency was related to the vortex shedding. At s/d=1.75, the excitation frequency was 2 or 4 times the vortex shedding frequency. When the flow was excited at this frequency, the vortex sheddings were energized, and pairings between neighboring vortices were generated. Also, the merging process between individual wakes was accelerated. The unstable and unbalanced wake patterns at s/d=2.15 were made stable and balanced. The unstable and unbalanced wake patterns at s/d=2.15 were made stable and balanced. For smaller spacing of s/d .leq,1.0, the acoustic excitation became less effective in controlling the flow.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2003.05a
• /
• pp.474-479
• /
• 2003

This paper addresses the problem of B-spline surface interpolation to serial contours, where the number of points varies from contour to contour. A traditional lofting approach creates a set of B-spline curves via B-spline curve interpolation to each contour, makes them compatible via degree elevation and knot insertion, and performs B-spline surface lofting to get a B-spline surface interpolating them. The approach tends to result in an astonishing number of control points in the resulting B-spline surface. This situation arises mainly from the inevitable process of progressively merging different knot vectors to make the B-spline curves compatible. This paper presents a new approach for avoiding this troublesome situation. The approach includes a novel process of getting a set of compatible B-spline curves from the given contours. The process is based on the universal parameterization [1,2] allowing the knots to be selected freely but leading to a more stable linear system for B-spline curve interpolation. Since the number of control points in each compatible B-spline curve is equal to the highest number of contour points, the proposed approach can realize efficient data reduction and provide a compact representation of a B-spline surface while keeping the desired surface shape. Some experimental results demonstrate its usefulness and quality.

• Korean Journal of Plant Taxonomy
• /
• v.46 no.2
• /
• pp.129-148
• /
• 2016

Plant species on oceanic islands comprise nearly 25% of described vascular plants on only 5% of the Earth's land surface yet are among the most rare and endangered plants. Conservation of plant biodiversity on islands poses particular challenges because many species occur in a few and/or small populations, and their habitats on islands are often disturbed by the activity of humans or by natural processes such as landslides and volcanoes. In addition to described species, evidence is accumulating that there are likely significant numbers of "cryptic" species in oceanic archipelagos. Plant systematists, in collaboration with others in the botanical disciplines, are critical to the discovery of the subtle diversity in oceanic island floras. Molecular data will play an ever increasing role in revealing variation in island lineages. However, the input from plant systematists and other organismal biologists will continue to be important in calling attention to morphological and ecological variation in natural populations and in the discovery of "new" populations that can inform sampling for molecular analyses. Conversely, organismal biologists can provide basic information necessary for understanding the biology of the molecular variants, including diagnostic morphological characters, reproductive biology, habitat, etc. Such basic information is important when describing new species and arguing for their protection. Hybridization presents one of the most challenging problems in the conservation of insular plant diversity, with the process having the potential to decrease diversity in several ways including the merging of species into hybrid swarms or conversely hybridization may generate stable novel recombinants that merit recognition as new species. These processes are often operative in recent radiations in which intrinsic barriers to gene flow have not evolved. The knowledge and continued monitoring of plant populations in the dynamic landscapes on oceanic islands are critical to the preservation of their plant diversity.

• Journal of Technologic Dentistry
• /
• v.38 no.2
• /
• pp.63-68
• /
• 2016

Purpose: The purpose of this study was to assess the internal fitness of the PMMA 3-unit bridge that was fabricated with 5-axis milling machine and to verify the clinically allowable values. Methods: For fabrication of the crown bridge in this study, 25-27 abutment teeth were used. The prepare abutment teeth were scanned with a scanner and 3-unit bridge was designed by using design software. Upon the completion of the design, the 3-unit bridge was fabricated by using a PMMA block with 5-axis milling machine. The internal surface of the fabricated 3-unit bridge was scanned by using a scanner and the difference between the 3-unit bridge and the abutment teeth was assessed by merging them together. Results: $RMS{\pm}SD$ values for PRE group, MOL group, and BRI group were $51.2{\pm}18.2$, $44.8{\pm}10.0$, and $52.1{\pm}8.3{\mu}m$, respectively. The mean of the PRE group was bigger than that of the MOL and BRI group; however, statistically significant difference was not found (p>0.05). Conclusion: The PMMA 3-unit bridge that was fabricated with 5-axis milling machine presented stable internal values for each crown and overall internal values were within the range of clinically allowable values.

• Korean Journal of Plant Taxonomy
• /
• v.41 no.4
• /
• pp.345-352
• /
• 2011

The morphological characters of Scrophularia kakudensis Franch. and its relatives were examined. The major features of S. kakudensis were determined to resolve the taxonomic confusion with the closely related taxa of S. kakudensis var. microphylla, S. pilosa and S. cephalantha. S. kakudensis is characterized by its flowering in Jul. to Sep., the node numbers on a stem, the size of the leaves, the development of inflorescences and the presence of glandular trichomes on its stems and leaves. S. cephalantha is distinct from S. kakudensis by the earlier flowering season, fewer node numbers on a stem, and fewer numbers of flowers on shorter rachis. Smaller sizes of S. kakudensis var. microphylla, considered to be a problematic character previously, are stable and distinctive from other taxa in the natural habitats of the multiple populations investigated in the study. Therefore, the taxon should remain as a variety of S. kakudensis. An examination of the diagnostic characteristics of S. pilosa, such as its inflorescence type and the presence of a stem with pubescence, does not provide sufficient distinction from S. kakudensis. A type specimen and habitat survey also support the merging of the two taxa. S. pilosa should be treated as a synonym of S. kakudensis, because it is considered to be a misidentification of S. kakudensis.