• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.370-374
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• 2016

We investigated the three dimensional turbulent flow characteristic around a sidewall-mounted rectangular block using a laboratory flume experiment. The experiment was conducted in the flume which is 18m long and 0.9m wide, and a rectangular block that is 0.3m wide and a height of 0.4m and 0.004m thick is mounted on a sidewall of the flume. Velocity data were collected using Acoustic Doppler Velocimeter(ADV) for the flow rate conditions : $0.0528m^3/s$. The time-averaged velocity and water depth data were analyzed to examine the three-dimensional flow patterns downstream of the rectangular block.

• Journal of the Korea Society for Simulation
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• v.8 no.3
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• pp.39-48
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• 1999

A finite element model of geared rotor system with flexible bearings were used to simulate the critical speeds and to investigate the effects of bearing coefficients on the dynamic behaviors of the systems. The finite element model includes the effects of tooth mesh stiffness, gyroscopic moment, rotary inertia, shear, and torque of the shaft. The gear mesh was modelled as a pair of rigid disks connected by a spring of time varying stiffness. The time varying mesh stiffness results in the abrupt change of the critical speeds of spur geared systems. As the bearing stiffness increases, critical speeds increase rapidly in case of stiff shafts, compared with flexible shafts.

• Journal of Species Research
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• v.8 no.3
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• pp.283-287
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• 2019

Pardosa pseudolaevitarsis n. sp. and Hygrolycosa umidicola Tanaka, 1978 belonging to Lycosidae are described from Korea. To date, fourteen species in the genus Pardosa C. L. Koch, 1847 have been described from Korea. H. umidicola belongs to Hygrolycosa Dahl, 1908 was once described from Korea, but the previous description of this species could not provide adequate scientific evidence for adding H. umidicola to the Korean spider fauna. Pardosa pseudolaevitarsis n. sp. is similar to P. laevitarsis Tanaka & Suwa, 1986 in the shape of its epigyne and palp, but can be distinguished by the followings: epigynal atrium small; spermathecae extending to the end of atrium; shape, location and orientation of fertilization duct in epigyne and internal genitalia; blunt basal spur of median apophysis in palp; number, shape and arrangement cheliceral teeth on both margins. Both species were collected using pitfall traps on a ridge between rice fields and seem to prefer habitats with relatively high humidity.

• Korean Journal of Plant Taxonomy
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• v.51 no.2
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• pp.166-170
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• 2021

Distribution of Viola inconspicua is newly discovered in Korea. This species was collected from grassy fields and roadsides in Jeju-si and Seogwipo-si, Jejudo Island. V. inconspicua shares several characteristics (i.e., purple or pale purple flowers, triangular leaf blades, winged petioles, and a linear-lanceolate stipules) with the related species V. mandshurica and V. yedoensis. However, V. inconspicua can be easily distinguished from other species by the following characteristics: leaf base (cordate vs. truncate to attenuate), and spur (short, 2-4 mm long vs. longer, 5-8 mm long). Here, we describe and illustrate of V. inconspicua. In addition, the identification key to allied species, photographs in its habitat, distribution, ecology, and phenology are provided as well. The Korean name for the species is given as 'Hwa-sal-ip-je-bi-kkot', considering the shape of its leaves.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.235.1-235.1
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• 2003

With an aim of obtaining high efficacy in cartilage regeneration, implantable polymeric rods were fabricated. These rod-type matrices were anticipated to perform structural tissue supporting activity and enhance extracellular matrix (ECM) formation by releasing specific agent, DHEA-S, in controlled manner. It is expected that application for the drilling operation on the articular cartilage of OA patients as the implants may promote regeneration of their cartilage. Osteoarthritis (OA) is a degenerative joint disease characterized by progressive loss of articular cartilage, subchondral bone remodeling, spur formation, and synovial inflammation. (omitted)

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.516-516
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• 2023

하천 만곡부 외곽 하안부의 빠른 유속은 침식을 유발하고 내측의 느린 유속은 토사 퇴적의 원인이 된다. 이는 하천 지형을 지속적으로 변화시키는 원인이 되고 나아가 하천 주변의 환경뿐만 아니라 안정성에도 문제를 일으킨다. 하천의 안정성과 수생태계 보존을 위해서는 수제와 같은 인공 구조물을 설치하여 하도의 안정을 유지할 수 있다. 수제는 후류에 느린 유속을 발생시켜 침식을 예방하고 제방과 하안을 보호한다. 그러나 수제 주변에서 발생하는 강한 와류는 국부 세굴을 유발하여 구조물의 안정성을 저해하기도 한다. 본 연구에서는 이동상 수리실험을 통해 수제 주변에서 발생하는 국부 세굴 및 후류에서의 하상 변동을 측정하였다. 수리실험은 길이 10 m, 폭 0.44 m, 높이 0.59 m인 수로에서 D50 = 2.98 mm인 모래를 사용하였고 하상변동은 하상이 평형상태에 이르렀을 때 물의 흐름을 멈추고 측정하였다. 실험 결과를 바탕으로 평형상태의 하상변동과 시간 변화에 따른 세굴심 변화를 도출하였다.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.29-35
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• 1996

For semi-solid forging with aluminuim alloys, it is required to develope the globular grain structure. It was studide that cold upsetting ration in SIMA process has effect on the globularization of grain structure. Globular microstructure was generated without cold upsettings for commercial aluminium alloys. In the case of A12024, the range of grain size was 40 .approx. 50 .mu. m. The grain growth in growth in globular microstructure depend on heating time. Spur gear was forged in semi-solid state to investigate the forging condition for A12024 with hydraulic press.

• Korean Journal of Radiology
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• v.1 no.3
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• pp.169-171
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• 2000

In order to relieve mechanical obstruction caused by rectal carcinoma, a bare rectal stent was inserted in the sigmoid colon of a 70-year-old female. The procedure was successful, and for one month the patient made good progress. She then complained of abdominal pain, however, and plain radiographs of the chest and abdomen revealed the presence of free gas in the subdiaphragmatic area. Surgical findings showed that a spur at the proximal end of the bare rectal stent had penetrated the rectal mucosal wall. After placing a bare rectal stent for the palliative treatment of colorectal carcinoma, close follow-up to detect possible perforation of the bowel wall is necessary.

• Applied Microscopy
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• v.31 no.4
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• pp.333-345
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• 2001

The mature sperms of three species of cephalopods (Octopus minar, Octopus ocellatus, Todarodes pacificus) were observed by electron microscopy. The results obtained are as follows: The sperm lengths of Octopus minor and Octopus ocellatus of octopods are long and they are about $390{\mu}m$ and $125\sim130{\mu}m$, respectively, but the sperm length of Todarodes pacificus is short and about $35{\mu}m$. The sperm of Octopus minor has a helical acrosome and a head bent a little like a banana while Octopus ocellatus of octopod has a twisted acrosome and a long rod-shaped head. A number of horizontal stripes are observed as a periodic structure in their subacrosome cavities and dense plugs are formed in the cavities of their heads. On the other hand, the acrosome of Todarodes pacificus is circular cap-shaped, and its head is long and oval. It is notable that two small cavities were observed in its basal acrosome. Juxtanuclear acrosomal materials of high electron density filled the subacrosomal cavity. In the middle piece of mature sperms of Octopus minor and Octopus ocellatus, the mitochondria form the mitochondrial sleeve, but the numbers of mitochondria differ between the species so that they are $11\sim12$ and $8\sim9$, respectively. Meanwhile, in the middle piece of mature sperms of Todarodes pacificus, the mitochondria are separated from the axoneme, forming a mitochondrial spur in which $10\sim13$ mitochondria and some electron dense materials concentrate. The axoneme of Octopus minor, Octopus ocellatus and Todarodes pacificus are of 9+2 type in common, surrounded by 9 coarse fibres. A number of glycogen were observed only in the axoneme of Todarodes pacificus. The coarse fibres were found as far as the main piece of sperm tail in Octopks minor and Todarodes pacificus, while to the end piece of sperm tail in Octopus ocellatus.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.7 s.337
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• pp.35-40
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• 2005

This paper proposes a fractional-N phase-locked loop (PLL) frequency synthesizer using the 3rd order ${\Delta}{\sum}$ modulator for 900MHz medium speed wireless link. The LC voltage-controlled oscillator (VCO) is used for the good phase noise property. To reduce the lock-in time, a charge pump has been developed to control the pumping current according to the frequency steps and the reference frequency is increased up to 3MHz. A 36/37 fractional-N divider is used to increase the reference frequency of the phase frequency detector (PFD) and to reduce the minimum frequency step simultaneously. A 3rd order ${\Delta}{\sum}$ modulator has been developed to reduce the fractional spur VCO, Divider by 8 Prescaler, PFD and Charge pump have been developed with 0.25um CMOS, and the fractional-N divider and the third order ${\Delta}{\sum}$ modulator have been designed with the VHDL code, and they are implemented through the FPGA board of the Xilinx Spartan2E. The measured results show that the output power of the PLL is about -lldBm and the phase noise is -77.75dBc/Hz at 100kHz offset frequency. The minimum frequency step and the maximum lock-in time are 10kHz and around 800us for the maximum frequency change of 10MHz, respectively.