• Wind and Structures
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• v.38 no.2
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• pp.129-146
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• 2024

Aiming at the problem of non-stationary wind field simulation of downbursts, a non-stationary down-burst generation system was designed by adding a nozzle and program control valve to the inlet of the original wall jet model. The computational fluid dynamics (CFD) method was used to simulate the downburst. Firstly, the two-dimensional (2D) model was used to study the outflow situation, and the database of working conditions was formed. Then the combined superposition of working conditions was carried out to simulate the full-scale measured downburst. The three-dimensional (3D) large eddy simulation (LES) was used for further verification based on this superposition condition. Finally, the wind tunnel test is used to further verify. The results show that after the valve is opened, the wind ve-locity at low altitude increases rapidly, then stays stable, and the wind velocity at each point fluctuates. The velocity of the 2D model matches the wind velocity trend of the measured downburst well. The 3D model matches the measured downburst flow in terms of wind velocity and pulsation characteris-tics. The time-varying mean wind velocity of the wind tunnel test is in better agreement with the meas-ured time-varying mean wind velocity of the downburst. The power spectrum of fluctuating wind ve-locity at different vertical heights for the test condition also agrees well with the von Karman spectrum, and conforms to the "-5/3" law. The vertical profile of the maximum time-varying average wind veloci-ty obtained from the test shows the basic characteristics of the typical wind profile of the downburst. The effectiveness of the downburst generation system is verified.

• Journal of the Korean Society of Radiology
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• v.85 no.2
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• pp.308-326
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• 2024

A comprehensive evaluation of cardiac function includes information in relation to cardiac output and systemic venous return. The heart is composed of four chambers: two atria and two ventricles, each with its own unique mechanical function. These four cardiac chambers, their valves, and the pulmonary circulation system are inter-related as they preload or afterload on each other. Cardiac dysfunction is a failure of global cardiac function, resulting in typical clinical manifestations. To investigate the underlying cause of cardiac dysfunction, a step-by-step evaluation of cardiac blood flow tracks is necessary. In this context, imaging markers showing details of the cardiac structures have an important role in assessing cardiac function. An image-based evaluation allows for investigation of function in terms of individual cardiac components. Evaluation of cardiac function using cardiac CT has recently been validated. This review aimed to discuss cardiac CT-based imaging markers for comprehensive and detailed cardiac function assessment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.2
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• pp.183-193
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• 1995

Assuming that fishing nets are porous structures to suck water into their mouth and then filtrate water out of them, the flow resistance N of nets with wall area S under the velicity v was taken by $R=kSv^2$, and the coefficient k was derived as $$k=c\;Re^{-m}(\frac{S_n}{S_m})n(\frac{S_n}{S})$$ where $R_e$ is the Reynolds' number, $S_m$ the area of net mouth, $S_n$ the total area of net projected to the plane perpendicular to the water flow. Then, the propriety of the above equation and the values of c, m and n were investigated by the experimental results on plane nettings carried out hitherto. The value of c and m were fixed respectively by $240(kg\cdot sec^2/m^4)$ and 0.1 when the representative size on $R_e$ was taken by the ratio k of the volume of bars to the area of meshes, i. e., $$\lambda={\frac{\pi\;d^2}{21\;sin\;2\varphi}$$ where d is the diameter of bars, 21 the mesh size, and 2n the angle between two adjacent bars. The value of n was larger than 1.0 as 1.2 because the wakes occurring at the knots and bars increased the resistance by obstructing the filtration of water through the meshes. In case in which the influence of $R_e$ was negligible, the value of $cR_e\;^{-m}$ became a constant distinguished by the regions of the attack angle $ \theta$ of nettings to the water flow, i. e., 100$(kg\cdot sec^2/m^4)\;in\;45^{\circ}<\theta \leq90^{\circ}\;and\;100(S_m/S)^{0.6}\;(kg\cdot sec^2/m^4)\;in\;0^{\circ}<\theta \leq45^{\circ}$. Thus, the coefficient $k(kg\cdot sec^2/m^4)$ of plane nettings could be obtained by utilizing the above values with $S_m\;and\;S_n$ given respectively by $$S_m=S\;sin\theta$$ and $$S_n=\frac{d}{I}\;\cdot\;\frac{\sqrt{1-cos^2\varphi cos^2\theta}} {sin\varphi\;cos\varphi} \cdot S$$ But, on the occasion of $\theta=0^{\circ}$ k was decided by the roughness of netting surface and so expressed as $$k=9(\frac{d}{I\;cos\varphi})^{0.8}$$ In these results, however, the values of c and m were regarded to be not sufficiently exact because they were obtained from insufficient data and the actual nets had no use for k at $\theta=0^{\circ}$. Therefore, the exact expression of $k(kg\cdotsec^2/m^4)$, for actual nets could De made in the case of no influence of $R_e$ as follows; $$k=100(\frac{S_n}{S_m})^{1.2}\;(\frac{S_m}{S})\;.\;for\;45^{\circ}<\theta \leq90^{\circ}$$, $$k=100(\frac{S_n}{S_m})^{1.2}\;(\frac{S_m}{S})^{1.6}\;.\;for\;0^{\circ}<\theta \leq45^{\circ}$$

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.1
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• pp.34-44
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• 1998

Analysis of gravity, magnetic, and seismic reflection data from the Ulleung Basin, East Sea has provided some insights into the opening mechanism and crustal type of the basin. Free-air gravity anomaly data show positive anomalies of about 40~60 mgal near the Korea Plateau and Oki Bank and of about -20~20 mgal in the central basin. Bouguer gravity anomaly data exhibit NE-SW trending positive anomalies of about 150 mgal in the central basin which is interpreted to be related to high-density crustal material. Abrupt changes in both Free-air and Bouguer gravity anomaly profiles across the basin margins may be due to transition between continental and oceanic crusts. Magnetic anomalies in the basin are generally less than -400 nT. No stripe pattern is evident in the magnetic anomaly map but a NW-SE trending symmetric pattern is seen in some magnetic profiles. The symmetric pattern is probably associated with the high-density crustal material in the central basin suggested by Bouguer gravity anomaly. The acoustic basement in the deep part of the basin has only a small amount of local relief. No graben or half-graben structures are seen in the acoustic basement from which mechanical extension might be inferred. The lack of high-relief structures in the acoustic basement may suggest that the basin is underlain by oceanic crust or that the basement is overlain by thick volcanic layer which obscures the structures and relief of the basement. High-density crust in the central basin inferred from gravity data, abrupt changes in gravity anomalies across the basin margins, symmetric pattern seen in some magnetic anomaly profiles, and lack of relief in the acoustic basement may suggest sea-floor spreading origin of the Ulleung Basin.

• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.452-458
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• 1989

The crystal structures of vacuum-dehydrated $Ag^+\;and\;Ca^{2+}$ exchanged zeolite A, Ag_7Ca_{2.5}-A(a = 12.310(1){\AA})$ and $Ag_2Ca_5-A(a = 12.287(2){\AA})$ have been determined by single-crystal X-ray diffraction methods in the cubic space group Pm3m at $21(1)^{\circ}C$. The crystals of $A_7Ca_{2.5}-A\;and\;Ag_2Ca_5-A$ were prepared by flow method using exchange solutions in which mole ratios of $AgNO_3\;and\;Ca(NO_3)_2$ were 1:50 and 1:1000, respectively, with total concentration of 0.05 M. Full-matrix least-squares refinement converged to the final error indices of R1 = 0.056 and R2 = 0.059 for $Ag7Ca2.5-A$, and R1 = 0.054 and R2 = 0.082 for $Ag2Ca5-A$ using 306 and 348 reflections, respectively, for which I >3 {\sigma}$ (I). 5.5 $Ag^+$ ions and 2.5 Ca^{2+}$ ions for $Ag_7Ca_{2.5}-A\;and\;2\;Ag^+$ ions and 5 $Ca^{2+}$ ions for $Ag_2Ca_5-A$ lie on two crystallographically nonequivalent threefold axes on the 6-rings. Both structures indicate that smaller Ca2+ ions preferentially occupy 6-ring sites and larger $Ag+$ ions occupy 8-ring sites when total number of cations per unit cell is more than 8.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.2
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• pp.63-75
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• 2013

The Inner Port Phase 2 area of the Pyeongtaek-Dangjin Port is enclosed by a total of three permeable sea-walls, and the disposal site to the east of the Inner Port Phase 2 is also enclosed by two permeable sea-walls. The maximum tidal range measured in the Inner Port Phase 2 and in the disposal site in May 2010 is 4.70 and 2.32 m, respectively. It reaches up to 54 and 27%, respectively of 8.74 m measured simultaneously in the exterior. Regression formulas between the difference of hydraulic head and the rate of interior water volume change, are induced. A three-dimensional numerical hydrodynamic model for the Asan Bay is constructed incorporating a module to compute water discharge through the permeable sea-walls at each computation time step by employing the formulas. Hydrodynamics for the period from 13th to 27th May, 2010 is simulated by driving forces of real-time reconstructed tide with major five constituents($M_2$, $S_2$, $K_1$, $O_1$ and $N_2$) and freshwater discharges from Asan, Sapkyo, Namyang and Seokmoon Sea dikes. The skill scores of modeled mean high waters, mean sea levels and mean low waters are excellent to be 96 to 100% in the interior of permeable sea-walls. Compared with the results of simulation to obstruct the flow through the permeable sea-walls, the maximum current speed increases by 0.05 to 0.10 m/s along the main channel and by 0.1 to 0.2 m/s locally in the exterior of the Outer Sea-wall of Inner Port. The maximum bottom shear stress is also intensified by 0.1 to 0.4 $N/m^2$ in the main channel and by more than 0.4 $N/m^2$ locally around the arched Outer Sea-wall. The module developed to compute the flow through impermeable seawalls can be practically applied to simulate and predict the advection and dispersion of materials, the erosion or deposion of sediments, and the local scouring around coastal structures where large-scale permeable sea-walls are maintained.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1034-1042
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• 2012

This study was performed by using an LFR (laminar flow reactor), which can be used to carry out different types of research on coal. In this study, an LFR was used to analyze coal flames, tar and soot yields, and structures of chars for two coals depending on their volatile content. The results show that the volatile content and oxygen concentration have a significant effect on the length and width of the soot cloud and that the length and width of the cloud under combustion conditions are less than those under a pyrolysis atmosphere. At sampling heights until 50 mm, the tar and soot yields of Berau (sub-bituminous) coal, which contains a large amount of volatile matter, are less than those of Glencore A.P. (bituminous) coal because tar is oxidized by the intrinsic oxygen component of coal and by radicals such as OH-. On the other hand, at sampling heights above 50 mm, the tar and soot yields of Berau coal are higher than those of Glencore A.P. coal by reacted residual volatile matter, tar and light gas in char and flame. With above results, it is confirmed that the volatile matter content and the intrinsic oxygen component in a coal are significant parameters for length and width of the soot cloud and yields of the soot. In addition, the B.E.T. results and the images of samples (SEM) obtained from the particle separation system of the sampling probe support the above results pertaining to the yields; the results also confirm the pore development on the char surface caused by devolatilization.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.726-734
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• 2019

To understand the relationship between water velocity in a fishway and fish morphology, the fineness ratio of fish, expressed as the standard length to the body depth, was measured. The fineness ratios of fish groups belonging to Cyprinidae, Acheilognathinae, Centropomidae, and Centrachidae were relatively low. The FRs of other groups, excluding eel-shaped types of fish, were over 4.5, indicating streamlined structures. The fineness ratios of Korean fish were classified into three different types: type I was Bitterling-Carp group that favored a slow-flowing pool habitat(FRs ranged from 2.1 to 3.3), type II was the Chub group representing streamlined types (FRs FRs ranged from 3.7 to 5.2), and type III was the Smelt-Barbel fish group that preferred riffle-run habitats with high velocity (FRs is over 5.2). Fish abundance analysis of fish using the fishway during the experimental periods showed a relatively high abundance of both type II and III compared to type I. The FRs of the fish passing through fishway(velocity 0.5-1.0 m s^-1) ranged from 4.5 to 5.0, indicating that the fish using the fishway were mainly the streamlined type. As one of the standard fishways in Korea, the flow rate of the ice harbor type ranged from 0.2 to 2.6 m s^-1. The FR values of the fish groups using the fishway ranged from 4.3 to 5.0. In contrast, the flow rate measured in an artificial channel type of fishway (same as a natural type of fishway) ranged from 0.1 to 1.9 m s^-1 and the FR values for the fish groups using a natural type of fishway ranged from 3.3 to 5.3. The low FR values in natural fish are considered to be due to differences in the flow rates between the two types of fishways.

• Sim-seong Yeon-gu
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• v.26 no.1
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• pp.67-88
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• 2011

Pungsu is an ancient logic that systemizes geography based on the Yin-Yang and The Five Elements Principle. It is defined as the unique and highly systemized ancient Eastern art of selecting auspicious sites and arranging harmonious structures such as graves, houses, and cities on them by evaluating the surrounding landscape and cosmological directions. Pungsu helps allegedly one improve life by receiving vital energy(Shengqi, 生氣)-energy flow that flows under the ground. It is traditional belief that the living lead their lives on the ground, indirectly receiving the energy coming out of the ground, whereas the dead are buried under the ground, allowing them to directly absorb energy from the ground, which makes Shengqi the dead receive bigger and more obvious than that the living receive. This energy absorbed by the dead from the ground was believed to be passed on to their descendants. This phenomenon is called "Induction of vital energy between Ancestors and Descendants". People searched for the sites which were believed to contain rich and positive vital energy flow. They also tried to bury their ancestors under such sites hoping to receive the Shengqi coming from underground which they believed would help them thrive and prosper. The efforts to locate the sites which have the most vital energy, auspicious sites or "Bright Yard(明堂)", are easily observed in Asia including China and Korea. The ultimate goal of searching for auspicious sites lies in human(whether alive or dead) receiving vital energy from the nature to enjoy happy lives. In choosing a place to live or to bury their dead ancestors, people tried to understand the energy flow of the site considering the factors related with mountain, water, and direction. If we take a closer look into the methods of finding auspicious sites, we can see that people have tried to see the outer conditions of lands, mountains and waters within the perfect harmony if possible. Auspicious site or Bright Yard is the site with those elements in perfect order and harmony, that is, it is the place which derives the most vital energy from the best order and harmony of nature. As this shows, an auspicious site symbolizes totality-the Self, and it seems to be projected to the land. It is believed to be an attempt that the reason why we try to find auspicious sites to internalize the totality that we projected to the outer world. Therefore, this auspicious site is what our foremost values, symbol of the Self, such as harmony, equilibrium, perfection, and uniqueness are reflected to the land. Through the process of finding such a site, we try to gain totality of psyche.

• Economic and Environmental Geology
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• v.30 no.6
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• pp.613-624
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• 1997

A study of anisotropy of magnetic susceptibility (AMS) was conducted on the Ordovician-Eocene strata in the Taebaek area. The study area is a northeastern part of the Okchon belt, sometimes called as Paegunsan Synclinal Area. A total of 600 independently oriented samples were collected from 60 sites covering the whole area. With a few exception of late Cretaceous-Eocene volcanic rocks, all the sampled strata are nonmetamorphosed sedimentary rocks, mainly sandstones. Among the 60 sites, 5 sites showed flow lineation lying on the bedding plane, 11 sites showed load foliation parallel to the bedding plane, and 21 sites showed tectonic foliation unrelated to the bedding plane. The tectonic foliations are defined by $k_1-k_2$ ($k_{max}-k_{int}$) anisotropy plane, and are considered as a result of tectonic forces acted perpendicularly to the foliation plane in the geologic past. Regardless of sample-site locations, tectonic force directions defined by $k_3$ ($k_{min}$) axis perpendicular to the tectonic foliation are consistent among the strata of the same geologic age. In the course of geologic time, however, the tectonic force directions showed a clockwise rotation: approximately E-W in the Ordovician sites, NW-SE in the Permian sites, N-S in the Triassic sites, and lastly NE-SW in the late Cretaceous-Eocene sites. The pre-Permian directions showed better clustering in the in-situ (geographic) coordinates, while the younger directions become better clustered after the bedding-tilt correction. It is interpreted that the major tectonic structures of the Taebaek area were controlled by the above-mentioned tectonic forces: The Paegunsan Syncline and the Hambaeksan Fault must have been generated by the NW-SE force of late Permian-early Triassic time. It was then reactivated in the reverse (dextral) sense by the N-S force of Triassic time. The Osipchon Fault in the eastern part of the study area was either generated or reactivated by the NE-SW force of late Cretaceous-Eocene time. The Permo-Triassic NW-SE force should be an expression of the Songnim Disturbance in the Korean peninsula, which is in turn related with the SCB/NCB collision in China.