• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.4
• /
• pp.347-354
• /
• 2012

Using a single-line pulsed laser beam is well known as a useful noncontact method to generate a directional surface acoustic wave. In this method, different laser beam energy profiles produce different waveforms and frequency characteristics. In this paper, we considered two typical kinds of laser beam energy profiles, Gaussian and square-like, to find out a difference in the frequency characteristics. To achieve this, mathematical models were proposed first for Gaussian laser beam profile and square-like respectively, both of which depended on the laser beam width. To verify the theoretical models, experimental setups with a cylindrical lens and a line-slit mask were respectively designed to produce a line laser beam with Gaussian spatial energy profile and square-like. The frequency responses of the theoretical models showed good agreement with experimental results in terms of the existence of harmonic frequency components and the shift of the first peak frequencies to low.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.10a
• /
• pp.188-197
• /
• 2005

Square patterned jet grouting technique is the soil improvement method that shakes the special end monitor left and right like as tail fin and mixing the soil and cement paste after cutting the soil in square shape by injecting the cement paste from installed two nozzles. The structure shape by jet grouting technique can be constructed in various shapes and sizes like as square, circle, and sector form designed by an engineer. Also, it can be constructed without waste material and reduced a construction time of work economically. In this study, the applicability of Square Jet Grouting to reduce permeability is estimated by FEM analysis and in-situ test in many cases which are various coefficient of permeability and breadth of grouting structure.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.33 no.3
• /
• pp.257-263
• /
• 2013

Acoustic nonlinearity of surface waves is an effective method to evaluate the micro damage on the surface of materials. In this method, the $A_1$ (magnitude of the fundamental wave) and $A_2$ (magnitude of the second-order harmonic wave) are measured for evaluation of acoustic nonlinearity. However, if there is another source of second-order harmonic wave other than the material itself, the linear relationship between $A_1{^2}$ and $A_2$ will not be guaranteed. Therefore, the second-order harmonic generation by another source should be fully suppressed. In this paper, we investigated the initial second-order harmonic generation in narrowband surface waves by multi-line laser beams. The spatial profile of laser beam was considered in the cases of Gaussian and square-like. The temporal profile was assumed to be Gaussian. In case of Gaussian spatial profile, the generation of the initial second-order harmonic wave was inevitable. However, when the spatial profile was square-like, the generation of the initial second-order harmonic wave was able to be fully suppressed at specific duty ratio. These results mean that the multi-line laser beams of square-like profile with a proper duty ratio are useful to evaluate the acoustic nonlinearity of the generated surface waves.

• Journal of Integrative Natural Science
• /
• v.14 no.3
• /
• pp.123-129
• /
• 2021

This research examines the effect of positively skewed population distribution on the two sample t-test through simulation. For simulation work, two independent samples were selected from the same chi-square distributions with 3, 5, 10, 15, 20, 30 degrees of freedom and sample sizes 3, 5, 10, 15, 20, 30, respectively. Chi-square distribution is largely skewed to the right at small degrees of freedom and getting symmetric as the degrees of freedom increase. Simulation results show that the sampled populations are distributed positively skewed like chi-square distribution with small degrees of freedom, the F-test for the equality of variances shows poor performances even at the relatively large degrees of freedom and sample sizes like 30 for both, and so it is recommended to avoid using F-test. When two population variances are equal, the skewness of population distribution does not affect on the t-test in terms of the confidence level. However even though for the highly positively skewed distribution and small sample sizes like three or five the t-test achieved the nominal confidence level, the error limits are very large at small sample size. Therefore, if the sampled population is expected to be highly skewed to the right, it will be recommended to use relatively large sample size, at least 20.

• Journal of Power System Engineering
• /
• v.10 no.3
• /
• pp.17-22
• /
• 2006

Surface modifications like rib-roughening and displaced insert devices like the twisted tape are commonly used in applications such as compact heat exchangers and cooling systems. In this paper, regionally averaged heat transfer distributions in square channels with twisted tape inserts and with twisted tape inserts plus interrupted ribs are respectively investigated. The square ribs are arranged to follow the trace of the twisted tape and along the flow direction defined as axial interrupted ribs. Each wall of the square channel is composed of isolated aluminum sections. Regionally averaged Nusselt number and channel averaged Nusselt number in turbulent air flows are presented for Reynold numbers from 8,900 to 29,000. We have obtained the following conclusions from the experimental study: 1) The local Nusselt number in the two-sided heated case is higher than that in the four-sided heated condition. 2) In the 4 heating wall channel with twisted tape inserts, Nusselt number based on bottom wall temperature is enhanced by 1.2 - 1.6 times if adding the axial interrupted ribs on the bottom wall only. 3) The twisted tape with interrupted ribs under the two-sided heating condition produces the highest heat transfer coefficient.

• Archives of Plastic Surgery
• /
• v.51 no.1
• /
• pp.126-129
• /
• 2024

The square flap method has been successful in releasing contracture bands at various body regions. However, the original square flap method alone may not be efficient in releasing long contracture bands. We, therefore, proposed an extended design to the traditional design, which is called the "square-plus flap." A 4-year-old girl presented with a postburn web-like contracture band over the right axilla. We marked a square flap technique at the center of the contracture band and then two additional Z-plasties were placed on both edges of the flap. After the release and securing of the square flap, the adjacent distal Z-plasty was then transposed and sutured in their new locations. We do not need to incise the proximal Z-plasty as we could achieve complete relaxation of the contracture band. This novel modification can be added to the plastic surgeon's armamentarium for releasing long postburn contracture bands involving distinct body regions.

• Journal of the Korean Home Economics Association
• /
• v.44 no.1 s.215
• /
• pp.151-157
• /
• 2006

Ten types of male headgear-Kwonwoonkwan, crown-like headgear, hats with a square flap, hats with feathers, crowns with plumes, Ballip, hats with flat crowns, Somo, turban, and fur hats-were described in Jip-Sah, which was published in the 14th century. Mongolian people used summer headgear, winter hats, and crown ornaments, which had been used until the Ch'ing dynasty of China. From the late 12th century to 1304, the headgear styles remained the same, suggesting that the Mongolian people kept their tradition. Kwonwoonkwan, crown-like headgear, and Somo, presented in Jip-Sah, were also described in U. Yadamsuren's album, a pictorial depiction of the 20th century Mongolian headgear.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.1061-1064
• /
• 1997

Micro injection molding technology is very important fiw mass product of micro structures or micro parts. And, it is so difficult that the molding technology of micro pole or thin wall(barrier rib) structures with high aspect ratio. In this stud). \vc intend to research on the basic technology of micro wall structure part:< with high aspect ratio by the inject~on moldins method. The mold for esperimenrs with micro multi-square structures was made by L, I(;A process. One square polc's size is 157 157pm. height 50011111. And the distance of each poles is 5011n1. 7'hus. molding products will be for~nctl like as the net structure with thin wall of about 50pn thickness.(aspect ratio 10) Ihrough the e~lxriment. \be obtained the prociuctr of micro multi-square slructure with bout 37.000 cell per a piece. 'Ihe micro injection molding process technolog for thin wall by multi-square structure mold was analy~cd.

• School Mathematics
• /
• v.4 no.1
• /
• pp.97-109
• /
• 2002

In this paper, tangram-like puzzles which are made by dissecting square are introduced. Especially, tangram-like puzzles which are consists of five pieces, six pieces, seven pieces, eight pieces, nine pieces, ten pieces, twelve pieces, fourteen pieces are introduced. But, This Introduction is very superficial. It means introduction is focused on each piece's geometrical shape, relative area when each tangram-like puzzles' area is one. With this introduction, six tangram-like puzzles' implication in mathematics education are suggested as followings. (1) Tangram-like puzzles may help fostering spatial senses. (2) Tangram-like puzzles may help teaching polygons, and its properties, congruences, similarities, etc. (3)Tangram-like puzzles may help teaching additions of fractions. (4) Tangram-like puzzles may help fostering mathematical thinking. (5) Tangram-like puzzles may serve as topics for supplement or reinforcement in teaching and learning tangram. (6) Tangram-like puzzles may serve as topics for problem posing in teaching and learning tangram.

• Proceedings of the KIEE Conference
• /
• 2006.10c
• /
• pp.585-587
• /
• 2006

Generally, LPF(low pass filter) circuits are used for converting square wave to average value, but these are not used necessary for average value of square wave in real time because of time constant of LPF. This paper deals with acquiring method for average value of square wave in real tine in case of frequency of output voltage is fixed, waveform of output voltage is square wave and duty of output voltage is varied like as 1 quadrant or 4 quadrant chopper.