• Journal of Distribution Science
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• v.13 no.8
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• pp.61-71
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• 2015

Purpose - Before the year 2000, the housing prices in Korea were increasing every decade. After 2000, for the first time, Korea experienced a decrease in housing prices, and the repetitive cycle of price fluctuation started. Such a "boom and bust cycle" is a worldwide phenomenon. The current study proposes a mathematical model to explain price fluctuation cycles based on the theory of consumer psychology. Specifically, the model incorporates the effects of buyer expectations of future prices on actual price changes. Based on the model, this study investigates various independent variables affecting the amplitude of price fluctuations in housing markets. Research design, data, and methodology - The study provides theoretical analyses based on a mathematical model. The proposed model uses the following assumptions of the pricing mechanism in housing markets. First, the price of a house at a certain time is affected not only by its current price but also by its expected future price. Second, house investors or buyers cannot predict the exact future price but make a subjective prediction based on observed price changes up to the present. Third, the price is determined by demand changes made in previous time periods. The current study tries to explain the boom-bust cycle in housing markets with a mathematical model and several numerical examples. The model illustrates the effects of consumer price elasticity, consumer sensitivity to price changes, and the sensitivity of prices to demand changes on price fluctuation. Results - The analytical results imply that even without external effects, the boom-bust cycle can occur endogenously due to buyer psychological factors. The model supports the expectation of future price direction as the most important variable causing price fluctuation in housing market. Consumer tendency for making choices based on both the current and expected future price causes repetitive boom-bust cycles in housing markets. Such consumers who respond more sensitively to price changes are shown to make the market more volatile. Consumer price elasticity is shown to be irrelevant to price fluctuations. Conclusions - The mechanism of price fluctuation in the proposed model can be summarized as follows. If a certain external shock causes an initial price increase, consumers perceive it as an ongoing increasing price trend. If the demand increases due to the higher expected price, the price goes up further. However, too high a price cannot be sustained for long, thus the increasing price trend ceases at some point. Once the market loses the momentum of a price increase, the price starts to drop. A price decrease signals a further decrease in a future price, thus the demand decreases further. When the price is perceived as low enough, the direction of the price change is reversed again. Policy makers should be cognizant that the current increase in housing prices due to increased liquidity can pose a serious threat of a sudden price decrease in housing markets.

• Korea-Australia Rheology Journal
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• v.17 no.3
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• pp.131-140
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• 2005

In this work we show the results of our most recent Direct Numerical Simulations (DNS) of turbulent viscoelastic channel flow using spectral spatial approximations and a stabilizing artificial diffusion in the viscoelastic constitutive model. The Finite-Elasticity Non-Linear Elastic Dumbbell model with the Peterlin approximation (FENE-P) is used to represent the effect of polymer molecules in solution, The corresponding rheological parameters are chosen so that to get closer to the conditions corresponding to maximum drag reduction: A high extensibility parameter (60) and a moderate solvent viscosity ratio (0.8) are used with two different friction Weissenberg numbers (50 and 100). We then first find that the corresponding achieved drag reduction, in the range of friction Reynolds numbers used in this work (180-590), is insensitive to the Reynolds number (in accordance to previous work). The obtained drag reduction is at the level of $49\%\;and\;63\%$, for the friction Weissenberg numbers 50 and 100, respectively. The largest value is substantially higher than any of our previous simulations, performed at more moderate levels of viscoelasticity (i.e. higher viscosity ratio and smaller extensibility parameter values). Therefore, the maximum extensional viscosity exhibited by the modeled system and the friction Weissenberg number can still be considered as the dominant factors determining the levels of drag reduction. These can reach high values, even for of dilute polymer solution (the system modeled by the FENE-P model), provided the flow viscoelasticity is high, corresponding to a high polymer molecular weight (which translates to a high extensibility parameter) and a high friction Weissenberg number. Based on that and the changes observed in the turbulent structure and in the most prevalent statistics, as presented in this work, we can still rationalize for an increasing extensional resistance-based drag reduction mechanism as the most prevalent mechanism for drag reduction, the same one evidenced in our previous work: As the polymer elasticity increases, so does the resistance offered to extensional deformation. That, in turn, changes the structure of the most energy-containing turbulent eddies (they become wider, more well correlated, and weaker in intensity) so that they become less efficient in transferring momentum, thus leading to drag reduction. Such a continuum, rheology-based, mechanism has first been proposed in the early 70s independently by Metzner and Lamley and is to be contrasted against any molecularly based explanations.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.568-576
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• 2015

In this study, scenarios based on the leakage of highly compressed air and fire occurrence turned out to be high risks in an operation stage of CAES facility were constructed and estimated. By combining Bernoulli equation with momentum equation, an expression to calculate an impact force of a jet flow of compressed air was derived. An impact force was found to be proportional to the square of diameter of fracture and the pressure of compressed air. Four types of fire scenarios were composed to evaluate an effects that seasonal change and location of fire source have on the spread behavior of smoke. Smoke from the fire ignited in the vicinity of CAES opening descended more quickly below the limit line of breathing than one from the fire occurred 10 m away from CAES opening, which is expected to occur due to a propagation of wave front of smoke. It was shown that a rate of smoke spread of the winter fire is faster than one of the summer fire and smoke from the winter fire spreads farther than one of the summer fire, which are dependent on the direction of air flow into access opening. Evacuation simulation indicated that the required safe evacuation time(RSET) of the summer and winter fires are 262, 670 s each.

• The Journal of Korean Medical History
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• v.25 no.1
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• pp.53-60
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• 2012

In recent times, a medical book called "WooJam JabJeo" has been published in complete Korean version. Not a few cases where the vivid appearance of the place for medical treatment are included intact in this medical book. This study is attempting to analyze one symptom of a disease by choosing it among the diseases our ancient sages treated in the light of the fact that there are only a few models which are applied to today's clinical treatment by our ancient sages appearance of medical service. This study believes that such an analysis of ancient medicine could be a part of the efforts to increase the applicable models to today's clinical treatment one by one. This paper is aimed at introducing and analyzing the three cases of Ganwul which are found in "WooJam JabJeo". It's because this study thinks that Ganwul is a symptom over which oriental medicine can not only establish dominance over western medicine it its diagnosis and prescription but Ganwul will also have high applicability to today's clinical treatment. Through this research, this study was able to perceive that the author. Jang, Tae-kyeong of "WooJam JabJeo" had vast knowledge of medical theories, especially in author's understanding diseases and composing prescription based on "Donguibogam". Up to the present time, domestic medical circles have understood the emergence of "Jejungshinpyeon(濟衆新編)"(1799) or "Bangyakhappyeon(方藥合編)"(1885) as an outlining work at most for overcoming such a limit of "DonguiBogam" superficially. However, by looking into Jang Tae-kyeong's understanding of "Dongui Bogam". this study was able to know the fact that the emergence of such medical books was possible because the medical knowledge included in "Dongui Bogam" was fully understood and digested in society of the Josen Dynasty. Conclusively, such a fact reminds us that it serves as a momentum to confirm once more that "Dongui Bogam" could be a good model for even today's clinical treatment.

• Fire Science and Engineering
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• v.13 no.1
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• pp.37-47
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• 1999

The spreading fire of very small floating particles after they are ignited is fast and t therefore dangerous. The research on this area has been limited to experiments and global simulations which treat them as dusts or gaseous fuel with certain concentration well m mixed with air. This research attempted micro-scale analysis of ignition of those particles modeling them as liquid droplets. For the beginning, the in-line array of fuel droplets is modeled by two-dimensional, unsteady conservation equations for mass, momentum, energy and species transport in the gas phase and an unsteady energy equation in the liquid phase. They are solved numerically in a generalized non-orthogonal coordinate. The single step chemical reaction with reaction rate controlled by Arrhenius’ law is assumed to a assess chemical reaction numerically. The calculated results show the variation of temperature and the concentration profile with time during evaporation and ignition process. Surrounding oxygen starts to mix with evaporating fuel vapor from the droplet. When the ignition condition is met, the exothermic reactions of the premixed gas initiate a and burn intensely. The maximum temperature position gradually approaches the droplet surface and maximum temperature increases rapidly following the ignition. The fuel and oxygen concentration distributions have minimum points near the peak temperature position. Therefore the moment of ignition seems to have a premixed-flame aspect. After this very short transient period minimum points are observed in the oxygen and fuel d distributions and the diffusion flame is established. The distance between droplets is an important parameter. Starting from far-away apart, when the distance between droplets decreases, the ignition-delay time decreases meaning faster ignition. When they are close and after the ignition, the maximum temperature moves away from the center line of the in-line array. It means that the oxygen at the center line is consumed rapidly and further supply is blocked by the flame. The study helped the understanding of the ignition of d droplet array and opened the possibility of further research.

• Journal of Korea Water Resources Association
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• v.41 no.2
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• pp.197-212
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• 2008

Recently, stream flow analysis has been accomplished by one or two dimensional equations and was applied by simple momentum equations and fixed energy conservations which contain many condition limits. In this study, FLOW-3D using CFD (Computational Fluid Dynamics) was applied to stream flow analysis which can solve three dimensional RANS (Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behaviors and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as ${\kappa}-{\varepsilon}$, RNG (Renormalized Group) ${\kappa}-{\varepsilon}$ and LES (Large Eddy Simulation). Numerical analysis results have been illustrated by the turbulence energy effects, velocity of flow, water level pressure and eddy flows around the piers and transverse overflow type structures. These results will be able to used by basis data that catch hold of effects on long-term bed elevation changes, sediment accumulations, scours and water aggravations by removal of obsolete transverse over flow type structures in urban stream.

• Korean Journal of Agricultural and Forest Meteorology
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• v.12 no.1
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• pp.45-62
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• 2010

Zero plane displacement (d) is the elevated height of the apparent momentum sink exerted by the vegetation on the air. For a vegetative canopy, d depends on the roughness structure of a plant canopy such as leaf area index, canopy height and canopy density, and thus is critical for the analysis of canopy turbulence and the calculation of surface scalar fluxes. In this research note, we estimated d at the Gwangneung coniferous forest by employing two independent methods of Rotach (1994) and Martano (2000), which require only a single-level eddy-covariance measurement. In general, these two methods provided comparable estimates of $d/h_c$ (where $h_c$ is the canopy height, i.e., ~23m), which ranged from 0.51 to 0.97 depending on wind directions. These estimates of $d/h_c$ were within the ranges (i.e., 0.64~0.94) reported from other forests in the literature but were sensitive to the forms of the nondimensional functions for atmospheric stability. Our finding indicates that one should be careful in interepreation of zero plane displacement estimated from a single-level eddy covariance measurement that is conductaed within the roughness sublayer.

• Journal of the Korean association of regional geographers
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• v.19 no.3
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• pp.454-475
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• 2013

In 2011, Daegu hosted the International Association of Athletics Federation Championships and attempted to use this event strengthen its global profile. Organizers hoped Daegu 2011 would strengthen knowledge about Daegu internationally and help the city overcome recent economic stagnation by bolstering tourism and investment on the global scale. Written from the perspective of a foreigner living in Korea, this interpretive article uses mixed-method cultural geographic analysis to evaluate the momentum Daegu 2011 produced in these directions. The article draws on a tripartite "territorialisation" approach to mega-event tourism's production of space, focusing on representational efforts during the approach to the championships and the event itself. Promotional materials receive particular attention. Interviews with international tourists during 2011 strengthen conclusions drawn from analysis of promotional materials. After reviewing relevant conceptual literature, Daegu's history, and the background of Daegu 2011, the article devotes three subsections to analysis. The first uses critical discourse analysis of a key promotional video to argue that Daegu's self-promotions betrayed insecurity about the city's place within the global tourism market. A second analysis subbsection finds that additional promotional materials did not fully overcome that problem. These materials also produced an overload of Daegu images and aspirations. The third subsection further develops these arguments, pointing to a partial mismatch between images emphasized by promotions and experiences available in the tourism landscape. This subsection also argues that while Daegu 2011 undoubtedly produced positive effects for the city, key challenges remain if Daegu will be placed on the map of globally acknowledged cities.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.4
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• pp.419-424
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• 1983

Tensile strength and shattering losses of rice grains in a binder harvest and in a free falling test were examined. Indica$\times$Japonica varieties, Milyang 23, Hangangchal, and Taebaek, and a Japonica variety, Jinheung were used for this study. The average tensile strength varied with varieties, showing 0.743N (Newton) in Milyang 23, 1.078N in Hangangchal, 1.573 N in Taebaek, and 1.775 N in Jinheung. Extrapolation of the average tensile strength for the zero field loss of grain indicated about 1.7 N. Moisture content of straw at the cutting position in a binder harvest was 76.0 to 86.7% in culm and 76.7 to 77.8% in leaf sheath. The percent loss of grains occurring in binder barvest in the field was equivalent to the degree of shattering in the panicle-falling test onto the concrete floor at the height of about 40cm. The grain shattering (Y) was closely related to the impulse (X), the change in momentum: Y=-25.73+4958.4X, ($r^2$=0.987) for Milyang 23, Y=-12.97+2258.3X, ($r^2$=0.979) for Hanagangchal, Y=-5.24+840.4X, ($r^2$ =0.976) for Taebaek. The tensile strengths of grains and their variance varied singnificantly yearly even in the same variety. The magnitude of year-variance was somewhat smaller for the easily shattering variety.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.23-30
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• 2009

Crash cushions are protective devices that prevent errant vehicles from impacting on fixed objects. This function is accomplished by gradually decelerating a vehicle to a safe stop in a relatively short distance. Commonly used crash cushions generally employ one of two concepts to accomplish this function. The first concept involves the absorption of the kinetic energy of a moving vehicle by crushable or plastically deformable materials and the other one involves the transfer of the momentum of a moving vehicle to an expendable mass of material located in the vehicle's path. Crash cushions using the first concept are generally referred to as compression crash cushions and crash cushions using the other concept are generally referred to as inertial crash cushion. The objective of this research is the development of a compression-type crash cushion by employing the two concepts simultaneously. To minimize the number of full-scale crash tests for the development of the crash cushion, preliminary design guide considering inertial and frictional energy absorption was constructed and computer simulation was performed. LS-DYNA program, which is most widely used to analyze roadside safety features, was used for the computer simulation. The developed crash cushion satisfied the safety evaluation criteria for various impact conditions of CC2 performance level in the Korean design guide.